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https://arxiv.org/abs/1001.3182 | math.OA
(what is this?)
# Title: The structure of an isometric tuple
Abstract: An $n$-tuple of operators $(V_1,...,V_n)$ acting on a Hilbert space $H$ is said to be isometric if the operator $[V_1\...\ V_n]:H^n\to H$ is an isometry. We prove a decomposition for an isometric tuple of operators that generalizes the classical Lebesgue-von Neumann-Wold decomposition of an isometry into the direct sum of a unilateral shift, an absolutely continuous unitary and a singular unitary. We show that, as in the classical case, this decomposition determines the weakly closed algebra and the von Neumann algebra generated by the tuple.
Comments: 30 pages; significant changes Subjects: Operator Algebras (math.OA); Functional Analysis (math.FA) MSC classes: 47L55, 46L35, 47A13 Journal reference: Proceedings of the London Mathematical Society 106 (2013), 1157-1177 DOI: 10.1112/plms/pds065 Cite as: arXiv:1001.3182 [math.OA] (or arXiv:1001.3182v2 [math.OA] for this version)
## Submission history
From: Matthew Kennedy [view email]
[v1] Tue, 19 Jan 2010 02:45:16 GMT (11kb)
[v2] Tue, 12 Jul 2011 05:05:34 GMT (19kb) | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.5013640522956848, "perplexity": 1190.7943901849226}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.3, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2018-17/segments/1524125945111.79/warc/CC-MAIN-20180421090739-20180421110739-00500.warc.gz"} |
https://datascience.stackexchange.com/questions/23690/fractions-or-probabilities-as-training-labels | # Fractions or probabilities as training labels
This it a problem that has come on my path a few times now and I don't have a satisfying solution yet. The goal is to predict probabilities or fractions based on some $x$ where our training $y$ has these probabilties or fractions and thus is in the domain $[0,1]$ as opposed to $\{0,1\}$. My question is with regards to my loss function. In the case of fractions, if the error between 0.4 and 0.5 and the error between 0.89 and 0.99 is the same I can just use MSE if I want to predict the expected value.
In case of probabilities where we want to approach it similarly as classification problems, where the difference between 0.89 and 0.99 is much bigger than that of 0.4 and 0.5, we want to put this in our loss function. Does cross entropy still work properly if I feed it fractions in $y$?
$\mathcal{L}(y,\hat{y})=-y\log(\hat{y}) - (1-y)\log(1-\hat{y})$
Let's say our $y=0.5$ and our current prediction is $\hat{y}=0.6$ we would get:
$\mathcal{L}(0.5,0.6)=-0.5\log(0.6) - 0.5\log(0.4)$
I don't really see why this would go wrong? The function is still convex. Everywhere it says that the target should be in $\{0, 1\}$ however. Maybe my math is lacking or I'm missing something obvious, why is this a bad idea?
Cross-entropy loss still works with probabilities in $[0,1]$ as well as $\{0,1\}$. Most importantly, $\hat{y} = y$ is still a stationary point (although it will not equal $0$).
It is also the case that the possible improvement in loss (and immediate gradient) is larger for $\hat{y} = 0.99, y = 0.89$ than for $\hat{y} = 0.4, y = 0.5$. If you use a sigmoid output, then the gradient at the logit $\hat{y} - y$ still applies - the larger gradient of the loss function scales inversely to the lower gradient of the sigmoid at that point.
So, in short, yes use binary cross-entropy loss for single-class probabilities, even when they are not strictly in $\{0,1\}$. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.941820502281189, "perplexity": 211.53655240629803}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2022-40/segments/1664030336978.73/warc/CC-MAIN-20221001230322-20221002020322-00613.warc.gz"} |
https://en.wiktionary.org/wiki/logarithm | # logarithm
## English
Wikipedia has an article on:
Wikipedia
### Etymology
From New Latin logarithmus, term coined by Scot mathematician John Napier from Ancient Greek λόγος (lógos, word, reason) and ἀριθμός (arithmós, number); compare rational number, from analogous Latin.
### Pronunciation
• (US) IPA(key): /ˈlɑ.ɡə.ɹɪ.ð(ə)m/, /ˈlɑɡəɹ.ɹɪ.ðəm/, /ˈlɑɡ.ə.ɹɪðm/, /ˈlɑɡ.əɹ.ɹɪðm/
• Hyphenation: log‧a‧ri‧thm
### Noun
logarithm (plural logarithms)
1. (mathematics) For a number ${\displaystyle x}$, the power to which a given base number must be raised in order to obtain ${\displaystyle x}$. Written ${\displaystyle \log _{b}x}$. For example, ${\displaystyle \log _{10}1000=3}$ because ${\displaystyle 10^{3}=1000}$ and ${\displaystyle \log _{2}16=4}$ because ${\displaystyle 2^{4}=16}$.
For a currency which uses denominations of 1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, etc., each jump in the base-10 logarithm from one denomination to the next higher is either 0.3010 or 0.3979. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 7, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8890751600265503, "perplexity": 4105.97882387396}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2018-09/segments/1518891814538.66/warc/CC-MAIN-20180223075134-20180223095134-00271.warc.gz"} |
https://www.newton.ac.uk/seminar/20170124143015301 | # W$^*$-Bundles and Continuous Families of Subfactors
Presented by:
Sam Evington University of Glasgow
Date:
Tuesday 24th January 2017 - 14:30 to 15:30
Venue:
INI Seminar Room 1
Abstract:
W$^*$-bundles were first introduced by Ozawa, motivated by work on the Toms-Winter Conjecture and, more generally, the classification of C$^*$-algebras.
I will begin with a brief introduction to W$^*$-bundles, explaining how they combine the measure theoretic nature of tracial von Neumann algebras with the topological nature of C$^*$-algebras. I will then discuss the relationship between the triviality problem for W$^*$-bundles and the Toms-Winter Conjecture. Finally, I will present my work with Ulrich Pennig on locally trivial W$^*$-bundles and my ongoing work on expected subbundles of W$^*$-bundles inspired by subfactor theory.
The video for this talk should appear here if JavaScript is enabled.
If it doesn't, something may have gone wrong with our embedded player.
We'll get it fixed as soon as possible. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.3277580142021179, "perplexity": 1417.4405273848172}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-30/segments/1563195529737.79/warc/CC-MAIN-20190723215340-20190724001340-00074.warc.gz"} |
http://mathhelpforum.com/new-users/209928-hello-taking-calculus.html | ## Hello, taking Calculus
I normally don't say my names on forums. So, hi. I'm taking IB Calculus this year and let's just say, I will probably need help. | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9701468348503113, "perplexity": 5687.065917194488}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-43/segments/1508187824931.84/warc/CC-MAIN-20171022003552-20171022023552-00365.warc.gz"} |
http://genealogy.math.ndsu.nodak.edu/id.php?id=140011 | ## David Olson
Ph.D. University of Oregon 1984
Dissertation: The Reliability of Analytic and Holistic Methods in Rating Students' Computer Programs | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8005830645561218, "perplexity": 17172.32699649791}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2015-18/segments/1430460074863.26/warc/CC-MAIN-20150501060114-00003-ip-10-235-10-82.ec2.internal.warc.gz"} |
http://physics.stackexchange.com/questions/31474/higgs-field-requires-a-large-cosmological-constant-does-the-zero-point-field/31495 | # Higgs field requires a large cosmological constant — does the Zero Point Field balance it?
I just read Wolfram's blog post on the Higgs discovery.
Still, there’s another problem. To get the observed particle masses, the background Higgs field that exists throughout the universe has to have an incredibly high density of energy and mass. Which one might expect would have a huge gravitational effect—in fact, enough of an effect to cause the universe to roll up into a tiny ball. Well, to avoid this, one has to assume that there’s a parameter (a “cosmological constant”) built right into the fundamental equations of gravity that cancels to incredibly high precision the effects of the energy and mass density associated with the background Higgs field.
Then I recalled that one of the great unsolved problems in physics is why the zero-point energy of the vacuum predicts a very large cosmological constant which is not observed.
The language used to describe these two effects confuses me, but as far as I can tell, Higgs->contraction and ZPF->expansion
Any chance these two effects are in balance?
- | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.886253297328949, "perplexity": 142.02915030714217}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2015-18/segments/1429246651873.94/warc/CC-MAIN-20150417045731-00260-ip-10-235-10-82.ec2.internal.warc.gz"} |
https://gmatclub.com/forum/eight-litres-are-drawn-off-from-a-vessel-full-of-water-and-s-95749.html?fl=similar | Eight litres are drawn off from a vessel full of water and s : GMAT Problem Solving (PS)
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# Eight litres are drawn off from a vessel full of water and s
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Eight litres are drawn off from a vessel full of water and substituted by pure milk. Again eight litres of the mixture are drawn off and substituted by pure milk. If the vessel now contains water and milk in the ratio 9:40, find the capacity of the vessel.
A. 21 liters
B. 22 liters
C. 20 liters
D. 14 liters
E. 28 liters
[Reveal] Spoiler: OA
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12 Jun 2010, 18:42
the equation you'd get once 8 lts are drawn the second time is: (w-16)/16 = 9/40 where w is the capacity of the vessel.
Solving for w, w = 19.6. So, its C
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12 Jun 2010, 21:37
iambroke wrote:
the equation you'd get once 8 lts are drawn the second time is: (w-16)/16 = 9/40 where w is the capacity of the vessel.
Solving for w, w = 19.6. So, its C
Ya but second time 8 liters are removed from the mixture of milk and water not only water.
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virupaksh2010 wrote:
Eight litres are drawn off from a vessel full of water and substituted by pure milk. Again eight litres of the mixture are drawn off and substituted by pure milk.If the vessel now contains water and milk in the ratio 9:40, find the capacity of the vessel.
A. 21 liters
B. 22 liters
C. 20 liters
D. 14 liters
E. 28 liters
Let the capacity of the vessel be $$x$$.
After the first removal there would be $$x-8$$ liters of water left in the vessel. Note that the share of the water would be $$\frac{x-8}{x}$$;
After the second removal, the removed mixture of 8 liters will contain $$8*\frac{x-8}{x}$$ liters of water, so there will be $$(x-8)-8*\frac{x-8}{x}=\frac{(x-8)^2}{x}$$ liters of water left.
As the ratio of water to milk after that is $$\frac{9}{40}$$, then the ratio of water to the capacity of the vessel would be $$\frac{9}{40+9}=\frac{9}{49}$$.
So $$\frac{\frac{(x-8)^2}{x}}{x}=\frac{9}{49}$$ --> $$\frac{(x-8)^2}{x^2}=\frac{9}{49}$$ --> $$\frac{x-8}{x}=\frac{3}{7}$$ --> $$x=14$$.
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13 Jun 2010, 08:44
Oops, should've read the question better..sorry abt that....thanks Bunuel...
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Re: Eight litres are drawn off from a vessel full of water and s [#permalink]
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13 Jun 2010, 21:39
After the second removal, the removed mixture of 8 liters will contain 8 * (x-8)/x liters of water, so there will be x-8-8 * (x-8)/8 = (x-8)^2/x liters of water left.
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14 Jun 2010, 05:49
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bibha wrote:
After the second removal, the removed mixture of 8 liters will contain 8 * (x-8)/x liters of water, so there will be x-8-8 * (x-8)/8 = (x-8)^2/x liters of water left.
Step1 :-
Water in vessel = x
8 liters is removed and replaced with milk
so now,
Water = x-8
Milk = 8
Step 2 :-
Now again 8 liters of mixture is removes , so water in that mixture is w = (x-8/x) * 8
So Total water removed = x-8-w = x-8-(x-8/x)*8 = (x^2-8x-8x-64)/x = (x^2-16x-64)/x
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Re: Eight litres are drawn off from a vessel full of water and s [#permalink]
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12 Jul 2010, 05:45
Is this a real GMAT question? Would be very tough to solve it in 3 minutes.
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Re: Eight litres are drawn off from a vessel full of water and s [#permalink]
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16 Jul 2010, 00:25
one more way:
Vessel capacity be 20litre:
8litre water removed and milk added: W=12litre, M=8litre
8litre mixture removed, (removed proportionately) : W= 12-4.8 = 7.2litre, M= 8-3.2 = 4.8 litre
8litre milk added ; W=7.2 litre, M=12.8 litre
Ratio will be 72/128 = 18/32 = 9/16
As we can see that milk is less so we have to select the ratio even less than 20,
Vessel capcity be 14 litre
8litre water removed and milk added: W=6 litre, M=8 litre
8litre mixture removed, (removed proportionately) : W= 6-3.4 = 2.6 litre, M= 8-4.6 = 3.4 litre
8litre milk added ; W=2.6 litre, M=11.4 litre
Ratio will be 26/114 = 8.66/38 (approx) very close to 9/40
So correct option is D
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Re: Eight litres are drawn off from a vessel full of water and s [#permalink]
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16 Jul 2010, 22:47
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I solved it 2:28 mins in reverse way.
Then another 8 litre milk added.
so total is milk < 16 (as some milk is removed)
since final ratio of water is 9:40
water shud be < 16*9/40 i.e < 3....
so total must be less than 19...
in the given options it is clear that 14 is the answer.
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05 Sep 2010, 02:00
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virupaksh2010 wrote:
Eight litres are drawn off from a vessel full of water and substituted by pure milk. Again eight litres of the mixture are drawn off and substituted by pure milk.If the vessel now contains water and milk in the ratio 9:40, find the capacity of the vessel.
A. 21 litrers
B. 22 litres
C. 20 litres
D. 14 litres
E. 28 litres
Using Wine formula:
{ (P-8) / P }^2 = 9/49
P solves to 14 - Ans - D
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Re: Eight litres are drawn off from a vessel full of water and s [#permalink]
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13 Feb 2012, 12:23
Bunuel, could you please pin point to a mistake in my reasoning?
Let T = total capacity of vessel
1.) the concentration of milk after the first round is 8/T
2.) After the second round the concentration of milk is $$40/49$$
$$8/T$$ * (T-8) + 8 = $$40/49$$ T
Now, I can't solve this equation. And even substituting answer choices won't help.
Where's the mistake?
Thank you very much.
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13 Feb 2012, 13:12
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nonameee wrote:
Bunuel, could you please pin point to a mistake in my reasoning?
Let T = total capacity of vessel
1.) the concentration of milk after the first round is 8/T
2.) After the second round the concentration of milk is $$40/49$$
$$8/T$$ * (T-8) + 8 = $$40/49$$ T
Now, I can't solve this equation. And even substituting answer choices won't help.
Where's the mistake?
Thank you very much.
Equation is correct.
$$\frac{8}{t}(t-8)+8=\frac{40}{49}t$$ --> $$\frac{t-8}{t}+1=\frac{5t}{49}$$. Now, if you substitute t=14 you'll see that it'll hold true.
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Re: Eight litres are drawn off from a vessel full of water and s [#permalink]
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13 Feb 2012, 13:19
Bunuel, thanks a lot. I must have made some miscalculation.
Conceptually the question is interesting. However the numbers are quite "difficult" to work with. Do you think that a real GMAT question would have better numbers?
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13 Feb 2012, 13:25
nonameee wrote:
Bunuel, thanks a lot. I must have made some miscalculation.
Conceptually the question is interesting. However the numbers are quite "difficult" to work with. Do you think that a real GMAT question would have better numbers?
If you and up with an equation shown in my post above then it won't be that difficult to solve it, for your equation it's better to plug numbers of course. So I think that the question, though tough, is still a GMAT type.
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15 Feb 2012, 00:58
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nonameee wrote:
Bunuel, thanks a lot. I must have made some miscalculation.
Conceptually the question is interesting. However the numbers are quite "difficult" to work with. Do you think that a real GMAT question would have better numbers?
Actually, the numbers are quite suitable for a very efficient, quick and oral solution. This is what I thought of when I came up with the answer in 20 secs. Mind you, you need to go through the link provided below to understand this theory. Else the 20 sec solution will probably not make sense to you.
We are substituting milk so we should work with water.
Final concentration of water = 9/49
There were two iterations. So, 9/49 = (100%)*(Vi/Vf)^2
Vi/Vf = 3/7
Since we are putting 8 liters of water but difference between Vi and Vf is 4, final volume (which is also equal to volume of the vessel) must be twice too i.e. 7*2 = 14 liters.
http://www.veritasprep.com/blog/2012/01 ... -mixtures/
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nonameee wrote:
Bunuel, thanks a lot. I must have made some miscalculation.
Conceptually the question is interesting. However the numbers are quite "difficult" to work with. Do you think that a real GMAT question would have better numbers?
This is not a GMAT like question. Answers in gmat are usually sorted. as for as calculation is concerned it is easy. See below
Following formulae works in such scenario. More about its derivation later: If out of x, y is taken repeatedly after nth trial amount left is x(1-y/x)^n
Here asuming x ltr for water water left after two attempts is : x(1-8/x)^2
=> (x(1-8/x)^2)/x = 9/(9+40) => 1-8/x = 3/7 => 8/x = 4/7 or x = (7/4)*8 = 14ltr
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Re: Eight litres are drawn off from a vessel full of water and s [#permalink]
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25 May 2013, 10:28
Bunuel wrote:
virupaksh2010 wrote:
Eight litres are drawn off from a vessel full of water and substituted by pure milk. Again eight litres of the mixture are drawn off and substituted by pure milk.If the vessel now contains water and milk in the ratio 9:40, find the capacity of the vessel.
A. 21 litrers
B. 22 litres
C. 20 litres
D. 14 litres
E. 28 litres
Let the capacity of the vessel be $$x$$.
After the first removal there would be $$x-8$$ liters of water left in the vessel. Note that the share of the water would be $$\frac{x-8}{x}$$;
After the second removal, the removed mixture of 8 liters will contain $$8*\frac{x-8}{x}$$ liters of water, so there will be $$x-8-8*\frac{x-8}{x}=\frac{(x-8)^2}{x}$$ liters of water left.
As the ratio of water to milk after that is $$\frac{9}{40}$$, then the ratio of water to the capacity of the vessel would be $$\frac{9}{40+9}=\frac{9}{49}$$.
So $$\frac{\frac{(x-8)^2}{x}}{x}=\frac{9}{49}$$ --> $$\frac{(x-8)^2}{x^2}=\frac{9}{49}$$ --> $$\frac{x-8}{x}=\frac{3}{7}$$ --> $$x=14$$.
if we are removing 8 litres of mixture,does that mean we are removing water share ?? because in mixture,how can we remove water now,as it contains milk too now. why do we use 8*water share??Pls clarify..
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26 May 2013, 03:59
up4gmat wrote:
Bunuel wrote:
virupaksh2010 wrote:
Eight litres are drawn off from a vessel full of water and substituted by pure milk. Again eight litres of the mixture are drawn off and substituted by pure milk.If the vessel now contains water and milk in the ratio 9:40, find the capacity of the vessel.
A. 21 litrers
B. 22 litres
C. 20 litres
D. 14 litres
E. 28 litres
Let the capacity of the vessel be $$x$$.
After the first removal there would be $$x-8$$ liters of water left in the vessel. Note that the share of the water would be $$\frac{x-8}{x}$$;
After the second removal, the removed mixture of 8 liters will contain $$8*\frac{x-8}{x}$$ liters of water, so there will be $$x-8-8*\frac{x-8}{x}=\frac{(x-8)^2}{x}$$ liters of water left.
As the ratio of water to milk after that is $$\frac{9}{40}$$, then the ratio of water to the capacity of the vessel would be $$\frac{9}{40+9}=\frac{9}{49}$$.
So $$\frac{\frac{(x-8)^2}{x}}{x}=\frac{9}{49}$$ --> $$\frac{(x-8)^2}{x^2}=\frac{9}{49}$$ --> $$\frac{x-8}{x}=\frac{3}{7}$$ --> $$x=14$$.
if we are removing 8 litres of mixture,does that mean we are removing water share ?? because in mixture,how can we remove water now,as it contains milk too now. why do we use 8*water share??Pls clarify..
We are calculating how much water is left in the vessel after two removals.
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Re: Eight litres are drawn off from a vessel full of water and s [#permalink]
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03 Jun 2013, 12:24
VeritasPrepKarishma wrote:
nonameee wrote:
Bunuel, thanks a lot. I must have made some miscalculation.
Conceptually the question is interesting. However the numbers are quite "difficult" to work with. Do you think that a real GMAT question would have better numbers?
Actually, the numbers are quite suitable for a very efficient, quick and oral solution. This is what I thought of when I came up with the answer in 20 secs. Mind you, you need to go through the link provided below to understand this theory. Else the 20 sec solution will probably not make sense to you.
We are substituting milk so we should work with water.
Final concentration of water = 9/49
There were two iterations. So, 9/49 = (100%)*(Vi/Vf)^2
Vi/Vf = 3/7
Since we are putting 8 liters of water but difference between Vi and Vf is 4, final volume (which is also equal to volume of the vessel) must be twice too i.e. 7*2 = 14 liters.
http://www.veritasprep.com/blog/2012/01 ... -mixtures/
Hi Karishma , Could you please elaborate the highlighted portion ? I am unable to grasp the last part of the solution . Thanks in advance .
Re: Eight litres are drawn off from a vessel full of water and s [#permalink] 03 Jun 2013, 12:24
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https://cstheory.stackexchange.com/questions/1257/properties-of-random-directed-graphs-with-fixed-out-degree | # Properties of Random Directed Graphs with Fixed Out-Degree
I am interested in properties of random directed graphs with fixed out-degree $d$. I am imagining a random graph model where each vertex chooses d neighbors (say, with replacement) u.a.r.
Question: Is anything known about the stationary distribution and mixing times of random walks on these random graphs (for various values of $d$)?
I am particularly interested in the case where $d = 2$, which corresponds to a model of random automata over a Boolean alphabet. (Yes, I realize these graphs are often not connected, but what happens in a given component?) I am happy with partial results and results about other properties of these graphs.
It seems most of the literature on random graphs focuses on the Erdős–Rényi model, which has very different properties than the model I am thinking about.
• I can offer this: if you search on the phrase "clustering coefficient" you might find more literature that relates. I decided I was interested in other things, so I don't remember specifics. Sep 13 '10 at 15:30
• you should hunt for models of web graphs (start with the Aiello/Chung paper (projecteuclid.org/…) and work forward). It's possible you'll find interesting models of web graphs. Also look at Christos Faloutsos' recent work Sep 13 '10 at 16:04
• thanks for the pointer - I've looked at Chung's work and this paper - while they do consider interesting models, they unfortunately don't consider mine... Sep 13 '10 at 17:32
• You suggest that the process occurs with replacement. Does this mean that you allow multidigraphs (with possibly multiple arcs from s to t)? Sep 13 '10 at 20:14
• That's right - in the random walk you take each edge equiprobably, and with multiple arcs, you increase the probability of a given transition (and we allow self loops too). However, if you wish to answer the question for choosing edges without replacement, that's fine too. Sep 13 '10 at 20:25
In the undirected case random $d$-regular graphs are expanders with high probability (not for $d=2$, but I think $d \ge 3$ suffices), which implies that the mixing time of random walks is $O(\log n)$. I don't remember enough about these proofs to know whether everything goes through in the directed case (certainly some properties are different: the uniform distribution is no longer stationary), but it may be worth looking into. Good references for expander graphs are Expander Graphs and their Applications by Hoory, Linial, and Wigderson and Pseudorandomness by Vadhan.
• Thanks - this is a good reference. I had seen this work before but forgot about it. It's certainly worth going through their proof. Sep 14 '10 at 13:53
Do you know about the following work (and references therein)? (It's also available on arXiv.)
Bohman, T. and Frieze, A. (2009), Hamilton cycles in 3-out. Random Structures & Algorithms, 35: 393–417. doi: 10.1002/rsa.20272
• thanks - it's an interesting result, but having a Hamiltonian cycle is far from the type of property I am thinking about. Sep 13 '10 at 19:11
• Hm, perhaps I was taking "I am happy with partial results and results about other properties of these graphs" too literally. To me, it seems as if the k-out model is very close to the model you are interested in and investigating past results on k-out would be fruitful, especially considering that both Hamiltonicity and rapid mixing can be considered strengthened forms of connectivity in random graph models.
– RJK
Sep 14 '10 at 15:44
• you are right - it is indeed a result about a property of these graphs, and possibly a useful one. I can't give you the accepted answer, but certainly an upvote :) Sep 14 '10 at 16:54
Are you still looking into the problem? This paper is actually a bit relevant: Alan Frieze, Páll Melsted and Michael Mitzenmacher, "An Analysis of Random-Walk Cuckoo Hashing", 2009.
• do you have a link for it ? Jan 5 '11 at 0:51 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.6484105587005615, "perplexity": 416.02271848383793}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-49/segments/1637964358705.61/warc/CC-MAIN-20211129104236-20211129134236-00458.warc.gz"} |
https://projecteuclid.org/euclid.aoms/1177706898 | The Annals of Mathematical Statistics
Estimates of the Mean and Standard Deviation of a Normal Population
W. J. Dixon
Abstract
Several simple estimates of the mean and standard deviation of a normal population are discussed. The efficiencies of these estimates are compared to the sample mean and sample standard deviation and to the best linear unbiased estimates. Little efficiency is lost when simple rather than optimum weights are used. Since moments of the order statistics are now available for samples of sizes $N \leqq 20$ from normal populations [3] it is a simple matter to find the variances of linear combinations of order statistics. The sample values are denoted $X_1 \leqq X_2 \leqq X_3 \leqq \cdots \leqq X_N$.
Article information
Source
Ann. Math. Statist., Volume 28, Number 3 (1957), 806-809.
Dates
First available in Project Euclid: 27 April 2007
https://projecteuclid.org/euclid.aoms/1177706898
Digital Object Identifier
doi:10.1214/aoms/1177706898
Mathematical Reviews number (MathSciNet)
MR91590
Zentralblatt MATH identifier
0082.13605
JSTOR | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8460453748703003, "perplexity": 522.9407840435074}, "config": {"markdown_headings": false, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-09/segments/1550247481624.10/warc/CC-MAIN-20190217051250-20190217073250-00119.warc.gz"} |
https://math.eretrandre.org/tetrationforum/showthread.php?tid=424&pid=7869 | • 1 Vote(s) - 5 Average
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using sinh(x) ? tommy1729 Ultimate Fellow Posts: 1,358 Threads: 330 Joined: Feb 2009 11/28/2012, 08:07 PM (This post was last modified: 11/28/2012, 08:11 PM by tommy1729.) Another thing I would like to talk about is the following property. I will start with an example. Let x be a real. Consider $f(n,x)=sin(n^2 x)/n$. If n goes to oo the limit gives $f(oo,x)=f(x)=0$. Now intuitively one would expect about the derivative with respect to x that $D f(x) dx =$ lim n-> oo $D f(n,x) dx = 0.$ Clearly $D f(x) dx = D 0 dx = 0.$ However $D sin(n^2 x)/n = n cos(n^2 x)$ so lim n-> oo $D f(n,x) dx$ =/= 0 ! This is an important and classic lesson in math. So many of our iterations used here require formal and carefull analysis. If you are not convinced notice F(n,x) = g^[n](Q(n,x)) IS something that occurs in the majority of limits related to tetration including e.g. tommysexp , basechange , interpolation methods , matrix methods , iterations to improve on riemann mappings , ... ! I do not know if $D^m F(n,x) dx = D^m F(x) dx$ has been proven here for any method ? Also note that I took x to be a real. So this is about Coo functions defined over the reals but for analytic functions defined over the complex number the issue is even bigger. Also note that in my example both f(n,x) and f(x) were Coo , in fact even analytic. So being analytic or Coo does not solve this issue. I think we need to work on this. --- For those clueness on how to such things , I point out that putting boundaries on values or signs and using the intermediate value theorem frequently does miracles. tommy1729 Ultimate Fellow Posts: 1,358 Threads: 330 Joined: Feb 2009 12/17/2012, 04:34 PM I was wondering about the following conjectured uniqueness criterion for real-analytic half iterates ( easily generalized to all iterates btw) : (based upon my sinh method) for all real x: (D is the derivative operator) D exp^[1/2](x) > 0 D^2 exp^[1/2](x) > 0 exp^[1/2](x) - ln(ln(2sinh^[1/2](exp(exp(x))))) > 0. It seems intuitive , especially considering how the sinh method works. However tetration is sometimes (or often) counterintuitive. A stronger conjecture would be : D exp^[1/2](x) > 0 D^2 exp^[1/2](x) > 0 ln(ln(2cosh^[1/2](exp(exp(x))))) > exp^[1/2](x) > ln(ln(2sinh^[1/2](exp(exp(x))))) Although this requires some concept of cosh^[1/2]. ( I once considered a method based upon cosh but made a mistake ) Im not even sure about the uniqueness of these uniqueness criterions. For instance how this might be related to D^n exp^[1/2](x) > 0 for integer n with n>1 and/or curvature and/or length conditions. Intuitively it seems like f(x) = exp^[1/2](x) computed by the sinh method gives the shortest path/length between f(a) and f(b) for sufficiently large real a and b but im not even sure if that is a selfconsistant statement for ANY exp^[1/2](x). Also clearly shortest length and smallest curvature relate alot. Recently I posted a new thread that involved the point w := f ' (w) = 1 which might relate to uniqueness. Clearly there is still work. And I must admit its not all clear to me yet. Tetration is calculus on drugs regards tommy1729 tommy1729 Ultimate Fellow Posts: 1,358 Threads: 330 Joined: Feb 2009 02/10/2015, 12:02 AM To extend the idea to smaller bases see this link : http://math.eretrandre.org/tetrationforu...21#pid7621 regards tommy1729 tommy1729 Ultimate Fellow Posts: 1,358 Threads: 330 Joined: Feb 2009 04/22/2015, 12:27 PM Numerical test Use the Taylor expansions at 3,4,5 and see if they agree on the values of f(3),f(4),f(5) for say f= semi-exp. Regards Tommy1729 tommy1729 Ultimate Fellow Posts: 1,358 Threads: 330 Joined: Feb 2009 04/23/2015, 04:49 PM Recently i started 2 threads about analytic like 2sinh type functions. Regards Tommy1729 tommy1729 Ultimate Fellow Posts: 1,358 Threads: 330 Joined: Feb 2009 10/26/2015, 12:56 AM The 2sinh method is for bases larger than exp(1/2). There are easy analogues for bases > eta. For instance replace 2sinh with t(x) = exp(x) - 1/2 [ exp(-x) + exp( (3 - 2e) x) ]. Notice t(x) is close to 2sinh , is bijective from R to R and has Taylor t(x) = 0 + e x + O(x^2). Regards Tommy1729 tommy1729 Ultimate Fellow Posts: 1,358 Threads: 330 Joined: Feb 2009 11/26/2015, 11:56 PM There are many ways to solve f(f(x)) = exp(x) or g(g(x)) = 2sinh(x). If g < f then g is uniquely so. Also using the 2sinh method on g gives us f. NOTICE it is impossible to directly solve for g in the 2sinh method. So we must use g < f. This implies a bijection between g and f , by the 2sinh or equivalently the inequality. Since there exist both analytic half iterates for both 2sinh and exp , for Every f there is a g and vice versa , we get the next BIG conclusion ; There MUST exist analytic solution of type 2sinh method. --- That is nice. But one wonders if f and g related as above must 1) both be analytic or both not. ? In other words is the bijection actually univalent ? I kinda repeat myself , but I assumed it belongs here better , and it was not understood by most. Regards tommy1729 sheldonison Long Time Fellow Posts: 626 Threads: 22 Joined: Oct 2008 11/27/2015, 03:41 PM (This post was last modified: 11/27/2015, 07:34 PM by sheldonison.) (11/26/2015, 11:56 PM)tommy1729 Wrote: There are many ways to solve f(f(x)) = exp(x) or g(g(x)) = 2sinh(x). If g < f then g is uniquely so. Also using the 2sinh method on g gives us f. .... But one wonders if f and g related as above must 1) both be analytic or both not. If g=2sinh(z), and f=exp(z), One can start with the analytic Abel function $\alpha_g(z)\;\;$ and the superfunction for g. $\alpha^{-1}_g(z)$. For example, the abel and superfunction for 2sinh(z) can be developed using Koenig's method. Now this gives us $g^{[0.5]}(z) = \alpha_g^{-1}(\alpha_g(z)+0.5)$ We wish to generate the superfunction for f(z) from $\alpha_g\;\alpha_g^{-1}$, with the equation below. In the case at hand this limit for the superfunction of f converges at the real axis, but it is not analytic; it does not converge in the complex plane. So far, this seems always be the case for arbitrary exponentially growing functions, f and g. $\alpha^{-1}_f(x)\; = \; \lim_{n \to \infty} \; f^{[-n]}( \alpha^{-1}_g(x+n))\;\;\;$the superfunction for f(z) So the resulting half iterate of f developed in this way is not analytic either, even thought it converges at the real axis $f^{[0.5]}(z) = \alpha_f^{-1}(\alpha_f(z)+0.5)$ - Sheldon tommy1729 Ultimate Fellow Posts: 1,358 Threads: 330 Joined: Feb 2009 11/28/2015, 01:21 PM I think you are confused. Sorry. But it seems you are not agreeing with what I said ... For dubious reasons. Again the 2sinh starts at real x > 0. Then we take the Limit of the continuations of the n th step iteration. NOT the continuation of the Limit of the n th step iteration. Afterwards we can take analytic continuation of THAT limit. Depending on the super/Abel you use for 2sinh this works infinitely AND fails infinitely often. AND .. Not or. Regards Tommy1729 sheldonison Long Time Fellow Posts: 626 Threads: 22 Joined: Oct 2008 11/29/2015, 03:03 PM (This post was last modified: 11/29/2015, 03:03 PM by sheldonison.) Given half iterates, f(f(x))=exp(x), and g(g(x))=2sinh(x), which uniquely satisfy the Op's relationship, then the obvious conjecture from my post would be that only one of the two (f,g) can be analytic. If one of them is analytic, then the other is infinitely differentiable and nowhere analytic, so that the other does not converge to its Taylor series anywhere. This is kind of an interesting conjecture; that Tommy might be inclined to agree with based on earlier posts in this thread (see Tommy's post#61 for example). As far as "dubious reasons" go, I was merely answering Tommy's question, "both be analytic or both not.", as well as searching for cool mathematical truths. - Sheldon « Next Oldest | Next Newest »
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Users browsing this thread: 2 Guest(s) | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 14, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9014895558357239, "perplexity": 2253.5919946653767}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.3, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-39/segments/1568514575515.93/warc/CC-MAIN-20190922135356-20190922161356-00109.warc.gz"} |
http://hal.in2p3.fr/in2p3-00110708 | # Study of the Interaction of $SeO_3^{2-}$, $I^-$, $Cs^+$ AND $Ni^{2+}$ on Consolidated Bentonite
Document type :
Conference papers
Domain :
http://hal.in2p3.fr/in2p3-00110708
Contributor : Dominique Girod <>
Submitted on : Tuesday, October 31, 2006 - 3:23:58 PM
Last modification on : Wednesday, October 30, 2019 - 4:50:02 PM
### Identifiers
• HAL Id : in2p3-00110708, version 1
### Citation
E. Alhajji, Gilles Montavon, Bernd Grambow. Study of the Interaction of $SeO_3^{2-}$, $I^-$, $Cs^+$ AND $Ni^{2+}$ on Consolidated Bentonite. Clays in Natural & Engineering Barriers for Radioactive Waste Confinement, Tours, France. ⟨in2p3-00110708⟩
Record views | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.5626993179321289, "perplexity": 24616.69247006072}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-47/segments/1573496670770.21/warc/CC-MAIN-20191121101711-20191121125711-00197.warc.gz"} |
https://tex.stackexchange.com/questions/51757/how-can-i-use-tikz-to-make-standalone-svg-graphics/71648 | # How can I use TikZ to make standalone (SVG) graphics?
I would like to use TikZ in other settings than TeX and I'd especially like to use the drawings on websites where the text should be searchable and selectable. However, I'm unsure of the best way to convert my drawings to SVG.
How do I best take some TikZ code, render the drawing and turn the output into SVG?
You can use the standalone class to produce tight PDF files for one or multiple TikZ pictures. I originally wrote it to simplify the creation of the many pictures of my thesis. Since v1.0 it includes a convert option which can convert the produced PDF into a graphics file automatically (using external software, which requires the -shell-escape compiler option).
This is very similar to Compile a LaTeX document into a PNG image that's as short as possible, but SVG needs some extra care.
You can write your TikZ pictures the following way:
\documentclass[tikz,convert={outfile=\jobname.svg}]{standalone}
\begin{document}
\begin{tikzpicture}% Example:
\draw (0,0) -- (10,10); % ...
\draw (10,0) -- (0,10); % ...
\node at (5,5) {Lorem ipsum at domine standalonus};
\end{tikzpicture}
\end{document}
Then either you compile the file as usual with pdflatex or another latex and convert the PDF to a SVG manually or compile it with the -shell-escape option and let standalone convert it for you.
Manual conversion can be done with a number of tools. It is simpler under Linux, because these tools are easily available there, but should be possible under Windows as well. (The convert options isn't really tested under Windows, btw.) By default standalone uses Image Magick's convert, which can do PDF to SVG but will not always give you good results. The pdf2svg tool seems to be better suited, but isn't supported out-of-the-box by standalone yet. It can of course be used manually as shown in Exporting all equations from a document as individual svg files.
You can configure standalone to use pdf2svg directly by using the command key of the convert option. Unfortunately, there is a small bug in standalone preventing it. I just fixed that and will upload the new version today.
With this you can write:
\documentclass[crop,tikz,convert={outext=.svg,command=\unexpanded{pdf2svg \infile\space\outfile}},multi=false]{standalone}[2012/04/13]
\makeatletter
\begin{document}
\begin{tikzpicture}
\draw (0,0) -- (10,10); % ...
\draw (10,0) -- (0,10); % ...
\draw (5,0) -- (0,10); % ...
\node at (5,5) {Lorem ipsum at domine standalonus};
\end{tikzpicture}
\end{document}
The \unexpanded is required because LaTeX expands class options. You can also add \noexpand before every macro instead.
If you need this more often you can also use a standalone.cfg file which enables this for all (local) standalone files. Simply create this file as follows in the same directory:
% Local standalone.cfg file
\standaloneconfig{convert={command={pdf2svg \infile\space\outfile}}}
I might add a special pdf2svg key in the next version as well, so you only need to write the following then:
\documentclass[crop,tikz,convert=pdf2svg]{standalone}[2012/04/13]
% ...
• The new version v1.0b is now in CTAN. Mirrors might need up to 24 hours to sync. TeXLive should have it inside the next few days. – Martin Scharrer Apr 13 '12 at 13:01
• Escaping some special characters in the command key seems to be too complicated. That is why I prefer to invoke the conversion outside the standalone. – kiss my armpit Mar 9 '13 at 21:33
• I am sorry, but ImageMagick produces raster images only, see Avoid using ImageMagick for 'Vector Image' to 'Vector Image' conversions EG: converting between formats like: PDF, PS, SVG imagemagick.org/Usage/formats/#vector pdf2svg is the only way to go – escalator Feb 18 '15 at 7:35
• @escalator: Thanks for the link. I actually didn't know that. Note that standalone uses ghostscript on Linux by default (ImageMagick by defauly only on Windows), which should be able to create true vector graphics. That is also the reason I didn't noted the issue with IM, I'm a Linux user ;-) – Martin Scharrer Feb 18 '15 at 20:48
• I tried to compile your latex file with pdflatex -shell-escape filename.tex. It generated an svg image. But the size was horrible: 17 MB. pdf was 13 KB. So, this method of conversion seems useless. Or I did something wrong? – user4035 Sep 3 '15 at 12:38
I use tex4ht and set the PGF output format to SVG. This solution comes from page 110 of the pgfmanual http://mirrors.ctan.org/graphics/pgf/base/doc/generic/pgf/pgfmanual.pdf.
I've only used it to create SVG of a TikZ picture in an otherwise empty \documentclass{article} but it looks like you could use this to make html with SVG graphics of a large document.
The advantage of this approach is that the SVG is produced by PGF and you know you're getting vector graphics. Also you get the result in a single step. It won't do functional shading or matricies and text in the pictures can be a problem but there's more on fixing that in the pgfmanual.
• In the TeX or LaTeX document preamble before you load the TikZ package, e.g. with \usepackage{tikz} in LaTeX type:
\def\pgfsysdriver{pgfsys-tex4ht.def}
• Then process the TeX or LaTeX with httex or htlatex as appropriate. You may need to add tex4ht to your tex installation; it's at http://www.tug.org/applications/tex4ht/. For example to process my file called logoname.tex I do
htlatex logoname.tex
• The following output files are created in the current directory
logoname.html
logoname.css
logoname-1.svg
If you have more TikZ pictures in the document I assume they would become logoname-2.svg and so on.
I'm able to look at the SVG output in firefox and inkscape so it seems to produce good results.
• This things works for me (with $htlatex file.tex, not with pdflatex)! (Cf. the same solution suggested in this answer and a not on using htlatex) As I had some problems with installing pdf2svg (I am on OS X), this answer solves my problem whereas the most upvoted/accepted - does not. – Piotr Migdal Apr 22 '14 at 15:55 • This generally works, but one needs to be aware of a bug in the tex4ht driver of pgf 3.0.0. See sourceforge.net/p/pgf/bugs/327 There's also a thread on tex.SE about this, but I can't remember where it is. – Fizz Aug 12 '14 at 19:56 On linux, you can use pdf2svg (an opensource tool). All glyphs are converted to paths, thus you can't edit your text. But it is the only tool that seems to give good results for images mixing drawings and texts. In your MWE, to get smooth result, I add the smooth option to plot. Here is a snapshot of the svg file rendered by Firefox (click on the image to download the SVG file): Here the two commands used to convert TEX to SVG: pdflatex file.tex pdf2svg file.pdf file.svg Your MWE with my changes: \documentclass{standalone} \usepackage{tikz} \usepackage{lmodern} \usepackage[T1]{fontenc} \begin{document} \begin{tikzpicture}[domain=-2:2,samples=100,scale=1.0,>=latex] \tikzset{bgrid/.style={help lines,color=blue!10,very thin}} \draw[bgrid] (-1.5,-3.5) grid (7.5,3.5); \draw[<->, color=black] (-1.5,0) -- (7.5,0) node[right] {$x$}; \draw[<->, color=black] (0,-3.5) -- (0,3.5) node[above] {$y$}; \foreach \x/\xtext in {-1,1,2,3,4,5,6,7} \draw (\x cm,1pt) -- (\x cm,-1pt) node[anchor=north] {$\xtext$}; \foreach \y/\ytext in {-3,-2,-1,1,2,3} \draw (1pt,\y cm) -- (-1pt,\y cm) node[anchor=east] {$\ytext$}; \draw[thick,color=black,domain=0:7.5,smooth] plot (\x,{sqrt(\x)}) node[anchor=south] {$y = \sqrt{x}$}; \draw[dashed,color=black,domain=0:7.5,smooth] plot (\x,{(-1)*(sqrt(\x))}) node[anchor=north] {$y = -\sqrt{x}$}; \draw[thick,color=black,domain=-1.5:5.5,samples=3] plot (\x,{(\x)-2}) node[anchor=south] {$y = x - 2$}; \filldraw[black] (4,2) circle(2pt) node[anchor=south east] {$(4, 2)$}; \filldraw[red] (1,-1) circle(2pt); \draw[red] (1.5,-1) node[anchor=west] {$(1, -1)\$};
\end{tikzpicture}
\end{document}
• I have tried to implement your suggestion, but this doesn't work for me in MiKTeX in Windows. I can produce a pdf file as usual, but when I use the command pdf2svg file.pdf file.svg I get the following error message: 'pdf2svg' is not recognized as an internal or external command, operable program or batch file. Using the commands htlatex or mzlatex produce html files that do not have the graphics in them, and do not produce svg files. – Santo D'Agostino Sep 16 '12 at 19:29
• @SantoD'Agostino: To my knowledge, opensource pdf2svg exists only for linux. – Paul Gaborit Sep 16 '12 at 21:27
• Sorry to hear this, Paul, but thanks very much for your time anyway. I now face the question of whether I should transfer my latex operation from my Windows machine to my Linux machine; if I do this (which seems inevitable, the only question being when), then your answer will be relevant, and I will store it for use at that time. Thanks again! – Santo D'Agostino Sep 16 '12 at 22:51
• @SantoD'Agostino here is a cross-compiled version, that works under windows for me. Just download, unzip and add the location to the Path system environment variable. – Carsten Aug 24 '18 at 10:42
You can use dvisvgm, which is a built-in tool of some TeX distributions (e.g. MiKTeX).
The basic usage:
latex testsvg.tex
dvisvgm testsvg.dvi
Then the SVG file will be saved in the current directory.
If you converted a simple math formula but get garbage when displaying the SVG, you can run dvisvgm with option --no-fonts to replace the fonts with path elements.
dvisvgm --no-fonts testsvg.dvi
As of version 2.0, you can call dvisvgm with option --font-format=woff, you should get SVG files that render correctly in almost all recent web browsers.
dvisvgm --font-format=woff testsvg.dvi
If you use TeXstudio, you can edit the texstudio.ini file (located in AppData\Roaming\TeXstudio for Windows) and add the following line below [texmaker].
Tools\Commands\dvi2svg="txs:///latex | dvisvgm --font-format=woff %.dvi"
Restart TeXstudio and you can find your custom command at Tools->User->dvi2svg.
• The --font-format=woffis a great hint which is missing from the dvisvgm FAQ. It enabled me to get sensible output in Chrome, Firefox, IE and Edge, while keeping all text as text. – DaveP Apr 27 '18 at 1:38
If I run dvisvgm with option -n and the evaluation of PostScript specials is enabled, I get the expected result:
Since MiKTeX doesn't provide a dvisvgm binary through its repositories, you have to install it manually. Recent builds for MiKTeX are available from the dvisvgm website. Simply extract dvisvgm.exe to the MiKTeX subfolder miktex\bin, or even better, install it in a local texmf tree.
• This doesn't work for me in MiKTeX (Windows). I get a one-line mash up of symbols, and no graph. I placed the dvisvgm.exe in the miktex\bin folder (I'm using MiKTeX 2.8). How do I enable the evaluation of PostScript specials? – Santo D'Agostino Sep 16 '12 at 19:39
• In order to enable the processing of PS specials, you have to install a recent version of Ghostscript, and add the directory containing gsdll32.dll to the PATH environment variable. You can check the availability of PS processing with dvisvgm -l. If the ps entry is present, everything should work as expected. – Martin Sep 17 '12 at 6:09
• This works! Thank-you very much, Martin! All the best! – Santo D'Agostino Sep 17 '12 at 13:18
• You're welcome. I'm glad to hear that you've got it working now. – Martin Sep 17 '12 at 13:34
• Hi Martin, I think I spoke a little too soon. The program works if I use the example file, but if I try to use standalone with the following first line <br /><br /> \documentclass[tikz,crop=true,border=0.5cm]{standalone} <br /><br /> then I get an error message <br /><br /> DVI error: no font selected <br /><br /> and no svg file is produced. Any advice? (Using dvisvgm -l shows that the ps entry is present, so that is not the problem.) – Santo D'Agostino Sep 17 '12 at 19:14
You might want to check out a tool I just wrote: tikz2svg.
Given in.tikz (or stdin):
> cat in.tikz
\begin{tikzpicture}
\fill[red!90!black] ( 90:.6) circle (1);
\fill[green!80!black] (210:.6) circle (1);
\fill[blue!90!black] (330:.6) circle (1);
\end{tikzpicture}
It outputs:
> cat tikz2svg < in.tikz
<?xml version="1.0" encoding="UTF-8"?> | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9123871326446533, "perplexity": 3476.337085414384}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-51/segments/1575540542644.69/warc/CC-MAIN-20191212074623-20191212102623-00359.warc.gz"} |
https://www.mathdoubts.com/algebraic-binomials/ | # Binomials
An algebraic expression that contains two terms is called a binomial.
## Introduction
The meaning of binomial is defined from a prefix “Bi” and a Latin term “Nomial”.
1. The meaning of Prefix “Bi” is two.
2. The meaning of “Nomial” is a term.
Combining the meanings of both terms, the term binomial is defined in algebra as an algebraic expression with two terms. A binomial is actually expressed in terms of two unlike algebraic terms for representing a quantity mathematically. In a binomial, the two unlike algebraic terms are connected by plus ($+$) or minus sign ($-$) to form an algebraic expression.
A binomial is also known as a polynomial of two terms. It is possibly formed in two different forms.
### A term and a Number
The binomials are formed by two unlike terms but in some cases, one term is an algebraic term and other term is a number.
#### Examples
$(1) \,\,\,\,\,\,$ $2b+5$
$(2) \,\,\,\,\,\,$ $x-7$
$(3) \,\,\,\,\,\,$ $-\dfrac{3}{2}+0.75xy^2$
$(4) \,\,\,\,\,\,$ $-pqr-8$
$(5) \,\,\,\,\,\,$ $r^3+7\sqrt{6}$
### Two Unlike Algebraic terms
Similarly, the binomials are also formed purely by two unlike algebraic terms.
#### Examples
$(1) \,\,\,\,\,\,$ $a+b$
$(2) \,\,\,\,\,\,$ $x-2y$
$(3) \,\,\,\,\,\,$ $-\dfrac{p}{7}-\sqrt{3}pq^2r^3$
$(4) \,\,\,\,\,\,$ $-0.8m+m^2n^2$
$(5) \,\,\,\,\,\,$ $ut+\dfrac{1}{2}gt^2$
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Do intensive properties depend upon the amount of matter present? no heat is defined as an _____ physical property because it is the sum total of the kinetic energy of the sample of matter. extensive The SI unit of heat is the ____ (J) or _______ (KJ) Joule/kilojoule 1 cal= 4.148 J 1 kcal is the same as the Calorie which both= 1000 calories heat energy changes are measured eperimentally in a device called a calorimeter Every substance has a physical property known as specific heat capacity, abbreviated as C Specific heat capactiy for water= 4.184 J/g x c or 1.00 cal/g x c how to calculate heat (lost or gained) q=m x T x c q=m x T x c q=? heat (energy) q=m x T x c m=? mass q=m x T x c T=? temperature change q=m x T x c c=? specific heat capacity acids have a ____ taste. sour _____ can conduct electricity in aqueous solution. acids acids on litmus indicator= color turns to red acids on Phenolphthalein= turns colorless active metals react with acid to release _____ gas. hydrogen acids react with bases to produce salt+water acids reacting with bases is called neutralization acids contain hydronium ions (formula ____) which are hydrated H+ H30 Bases have a _____ taste bitter Bases feel slippery bases can conduct electricity in _____ solutions aqueous bases in litmus indicator= color turns to blue bases in phenophthalein turns pink bases contain _____ ions Hydroxide (OH) bases react with acids to produce salt+water The theory of ionization was developed by Arrhenius molecular compounds dissolve in polar solvents to form ____ ions no ions existed in the _____ compound undissolved molecular compounds are covalent ionization refers to ______ substances molecular dissociation refers to _______ substances ionization Strong electrolytes may ionize or dissociate _____ in aqueous solutions completely Weak electrolytes may ionize or dissociate _____ in aqueous solution slightly Arrhenius (traditional theory) acids are substances that produce ____ in water solutions H+ Arrhenius (traditional theory) bases produce ____ in water solution OH- Bronsted-Lowry Theory: acids are proton ____ donors (give up H+) Bronsted-Lowry Theory: bases are proton ___ acceptors (recieve H+) Bronsted-Lowry Theory: When a Bronsted-Lowry acid donates a H ion, a _____ is formed. conjugate base Bronsted-Lowry Theory: When a Bronsted-Lowry base accepts a H ion, a ________ is formed conjugate acid Bronsted-Lowry Theory: Two substances related to each other by the acid and conjugate of a H ion are a conjugate acid-base pair acids that have more than one ionizable proton (H+) are polyprotic during a ____ change use q=mass x heat of fusion phase | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9118474721908569, "perplexity": 22282.883806516213}, "config": {"markdown_headings": true, "markdown_code": false, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": false}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2014-35/segments/1408500831565.57/warc/CC-MAIN-20140820021351-00091-ip-10-180-136-8.ec2.internal.warc.gz"} |
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# In the table above is shown the percent reduction in the
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In the table above is shown the percent reduction in the [#permalink]
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23 Jul 2011, 21:12
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Date of Purchase
Percent Reduction
July 1 through July 7
5%
July 8 through July 14
30%
July 15 through July 21
55%
July 22 through July 28
70%
In the table above is shown the percent reduction in the price of every item in a store off the original price of that item on June 30 of that year. The table is for the 28 days immediately after June 30 of that year. If on July n of that year, Bill bought a suit that originally cost $450, what is the value of n? (1) Bill paid$112.50 less than he would have if he had bought it the day before.
(2) Bill paid $202.50 for the suit. [Reveal] Spoiler: OA Senior Manager Joined: 24 Mar 2011 Posts: 457 Location: Texas Followers: 5 Kudos [?]: 126 [0], given: 20 Re: DS - 700 level - Suit [#permalink] ### Show Tags 23 Jul 2011, 21:27 interesting question.. i think i will choose A for this... only statement 1 is sufficient... how i solved? B - of course is sufficient..$202.50 .. falls under 3rd category BUT i dont know which day in 3rd category.. it can be any from july 15th through 21st...
now for A to be correct there is hint... to see if 55% of 450 - 30% of 450 = 112.50 and i think it is.
so it is the 15th day of july
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Re: DS - 700 level - Suit [#permalink]
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23 Jul 2011, 21:40
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bschool83 wrote:
Date of Purchase
Percent Reduction
July 1 through July 7
5%
July 8 through July 14
30%
July 15 through July 21
55%
July 22 through July 28
70%
In the table above is shown the percent reduction in the price of every item in a store off the original price of that item on June 30 of that year. The table is for the 28 days immediately after June 30 of that year. If on July n of that year, Bill bought a suit that originally cost $450, what is the value of n? (1) Bill paid$112.50 less than he would have if he had bought it the day before.
From 2) if Bill paid $202.5 for the suit, you can figure out the week that particular sale price was on, but not the exact date. Hence, eliminate B. If both are true, it is easy to just pick the date which falls within the week from 2). Hence, C is correct. No math is required except 112.5/450 which is easy 25%. Hope this helps you. GMAT Club Legend Joined: 09 Sep 2013 Posts: 10580 Followers: 495 Kudos [?]: 129 [0], given: 0 Re: In the table above is shown the percent reduction in the [#permalink] ### Show Tags 17 Oct 2013, 07:34 Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email. _________________ GMAT Club Legend Joined: 09 Sep 2013 Posts: 10580 Followers: 495 Kudos [?]: 129 [0], given: 0 Re: In the table above is shown the percent reduction in the [#permalink] ### Show Tags 17 Apr 2015, 21:09 Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email. _________________ Manager Joined: 05 Mar 2015 Posts: 231 Followers: 1 Kudos [?]: 24 [0], given: 23 Re: In the table above is shown the percent reduction in the [#permalink] ### Show Tags 15 Jun 2016, 10:09 bschool83 wrote: Date of Purchase Percent Reduction July 1 through July 7 5% July 8 through July 14 30% July 15 through July 21 55% July 22 through July 28 70% In the table above is shown the percent reduction in the price of every item in a store off the original price of that item on June 30 of that year. The table is for the 28 days immediately after June 30 of that year. If on July n of that year, Bill bought a suit that originally cost$450, what is the value of n?
(1) Bill paid $112.50 less than he would have if he had bought it the day before. (2) Bill paid$202.50 for the suit.
(1) insuff..because we don't know the discounted price/any price for which he would have paid $112.5. (2)202.5 is what percent less of 450... 450(1-x/100)=202.5 x=55% date "n" could be anything between july15-july21...not suff.... Combining both Bill paid$112.50 less than he would have if he had bought it the day before
means bill paid (202.5+112.5=\$315) if he bought with any previous discount a day before.
315 is 30% less than 450.
So he must bought on july 15
Ans C
Re: In the table above is shown the percent reduction in the [#permalink] 15 Jun 2016, 10:09
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https://scipost.org/submissions/2103.06115v2/ | # Symmetry meets AI
### Submission summary
As Contributors: Veronica Sanz Arxiv Link: https://arxiv.org/abs/2103.06115v2 (pdf) Code repository: https://github.com/johanneshirn/symmetry_meets_AI Date accepted: 2021-07-07 Date submitted: 2021-06-30 10:09 Submitted by: Sanz, Veronica Submitted to: SciPost Physics Academic field: Physics Specialties: Artificial Intelligence
### Abstract
We explore whether Neural Networks (NNs) can {\it discover} the presence of symmetries as they learn to perform a task. For this, we train hundreds of NNs on a {\it decoy task} based on well-controlled Physics templates, where no information on symmetry is provided. We use the output from the last hidden layer of all these NNs, projected to fewer dimensions, as the input for a symmetry classification task, and show that information on symmetry had indeed been identified by the original NN without guidance. As an interdisciplinary application of this procedure, we identify the presence and level of symmetry in artistic paintings from different styles such as those of Picasso, Pollock and Van Gogh.
Published as SciPost Phys. 11, 014 (2021)
We would like to thank the referees for their careful reading of the manuscript and suggestions for improving and clarifying its content. Below we list the comments and answers:
*It would useful to specify clearly in the manuscript what is the *exact input* and what is the output of the FCNN used for the decoy task. What are the details of the training? is there a training set and a validation set?.
*In section II.1, the authors are designing a decoy task procedure using FCNN where after a step of preprocessing the template images (fig 2), they are given to an FCNN. This requires a particular procedure of flattening the image. If a large enough network has been given, the flattening procedure should not affect the outcome. I was wondering if the authors have investigated different flattening options or their effects on the outcome. Since this will affect the relationship between neighbouring pixels, I wonder if it affects learning the underlying symmetries.
*Please avoid this request in case if I missed it in the manuscript. For reproducibility purposes, can authors clarify the specification of the FCNN that has been used? Such as the activation functions, loss functions, if any etc.
At this point, it is important to remember that we are not teaching a CNN to recognize shapes in a full image, but training an FCNN on individual points to be classified in either of two classes: we are feeding the FCNN individual lines of a table of coordinates in no particular order, and asking it to perform a binary classification for each of these pairs of coordinates, i.e. to predict whether a given point or pixel belongs to the contour or to the background. In practice, the pairs of coordinates are fed by batches in random order without regard to their respective positions in the 2D space of the original image, i.e. a random flattening procedure. Only after a whole epoch has the FCNN seen all the points (coordinate pairs) that were selected from the image.
We use {\tt fastai} \cite{fastai} {\tt TabularLearner} with a one-cycle policy~\cite{leslie_smith}, maximum learning rate of $5 \times 10^{-3}$, batch size of 8,000 (or less if there are fewer points in the input data) using a training/validation split of $80\%/20\%$ for 300 epochs, at which point the FCNN has typically reached a validation accuracy of $99.9\%$.
*As usual with these kind of studies, it would be good to have some reassurance about the potential systematic errors in the procedure. How strongly do the results depend on tuning some of the hyper-parameters? There are currently a few comments at the end of section II in the manuscript, but it would be useful to expand and provide some more quantitative information. For instance when saying that 'the CNN [...] does not manage to reach the same accuracy...', can this be quantified with a few examples? This point in particular could be important, since the authors suggest that a 'less-perfect' learning would rely on symmetries to encode the image more than a perfect reproduction. This is obviously a very interesting suggestion, which deserves more detailed scrutiny. Surely, if the training is relaxed too much, then informations about the image will be lost. There must be an ideal window where the system works best. Is it possible to explore this feature quantitatively?
We checked how our results were affected by varying the hyperparameters of the FCNN, in particular as they allow a more precise or looser fit. The most obvious issue is when the FCNNs do not perform so well at their binary classification task: the CNN then has a hard time reaching a good accuracy. For instance, with the same hyperparameters, but only 100 epochs instead of 300, the FCNNs typically reach an accuracy below 99.8\% on the whole training plus validation dataset. CNNs trained on the resulting PCAs barely reach 60\% accuracy on the 5-class task.
Perhaps less obvious is the fact that it is counterproductive to train the FCNNs until they learn their task perfectly: we have tested this by training FCNNs with the same hyperparameters (including in particular 300 epochs), but without defining a validation set. The best model is then selected by minimizing the (training) loss instead of the validation error as was the case before. Such models typically reach an average error rate below 1/10,000 on the whole dataset, i.e. so small that most of them did not make a single mistake in their binary classification task (involving several thousands of points). Here again, the CNNs trained on the resulting PCAs barely reach 60\% accuracy on the 5-class task, possibly because the FCNN has overfit to the location of the individual pixels that have been selected in the random-ssampling process instead of relying on simplifying assumptions such as the symmetry.
*In section II.2, the authors are using ResNet18 for the classification of the symmetries. I wondered if smaller network options have been investigated and if the reason for choosing such an extensive network is purely for increasing accuracy.
Looking for a good accuracy in our image classification task, we perform transfer learning using a Resnet network, but select the smallest one (i.e. ResNet18~\cite{resnet18}) for speed, as implemented in the {\tt fastai} package~\cite{fastai}. From a training sample of 1240 PCAs, we achieve a validation accuracy of $73\%$ on the 5-class problem, and an 80\%-95\% accuracy for each of the four different binary problems of identifying the presence or absence of each symmetry separately.
image.gif
*Can the authors clarify the origin of the error bars of the symmetry bins in figures 4 to 8? Does it appear as a result of running the algorithm many times, as described on page 5? Please correct me if I am missing something, but a neural network will result with the same output every time unless it has a Bayesian layer. Is this because the authors are using multiple distorted template images to classify one symmetry; hence, a class is decided by the statistical significance of this collection?
For each painting, we train the same FCNN architecture several times with the same hyperparameters but using different random initializations of the parameters, yielding different outputs from the hidden layer, and thus different PCAs. We then feed each of these PCAs from the same paintings to the same CNN model we trained on the PCAs of potentials. For each painting, we depict the predicted likelihood for all five symmetries (none $\emptyset$, rotation $O(2)$, continuous translation $T$, discrete translation $T_n$ and reflection $Z_2$) and draw a 68\% confidence interval computed via a non-parametric bootstrap on the predictions obtained from running the same CNN on the PCAs resulting from multiple FCNN runs on the same painting.
*I'm aware that it is hard to release a public code, but if it is possible, can authors also release the analysis code that has been used for this study. I'm sure that the community will appreciate and further develop related studies using their code.
We will be placing our code on Github at the following URL: https://github.com/johanneshirn/symmetry_meets_AI
### List of changes
Some text has been added and modified following the reviewers' suggestions. The details are given above, in the 'Author comments'. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.6830830574035645, "perplexity": 794.0021804173342}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-39/segments/1631780057366.40/warc/CC-MAIN-20210922132653-20210922162653-00424.warc.gz"} |
https://www.physicsforums.com/threads/what-energy-density-expected-at-lhc-point-of-collision.171170/ | # What energy density expected at LHC point of collision?
1. May 21, 2007
### marcus
I'm more used to seeing colliders rated by the kinetic energy of the colliding particles, but just recently I've been seeing estimates of the ENERGY DENSITY to be expected right at the point of collision.
This raises doubts about exactly what is meant. what is the nominal area of collision? what nominal volume is the kinetic energy spread out in?
but there should be some way to give a plausible rough figure for the energy density. experimental physicists are good at that kind of guesstimation.
So what do our experts in this department say?
Would you say it is closer to 10 GeV per cubic fermi
or to, say, 1016 GeV per cubic fermi?
Can you offer guidance or do you also need help?
Draft saved Draft deleted
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https://www.physicsforums.com/threads/coefficient-of-restitution-problem.907173/ | # Homework Help: Coefficient of Restitution problem
1. Mar 10, 2017
### CCC1212
Hello, I have this simple COR problem that I seem to be a bit stuck on.
1. The problem statement, all variables and given/known data
A 1.25 kg squash racquet swung at 37 m/s contacts a ball moving at 42 m/s in the opposite direction. Immediately after impact the racquet has a velocity of 25 m/s and the ball has a velocity of 50 m/s. What is the coefficient of restitution associated with the impact?
2. Relevant equations
I've been using e= (V1-V2)/(U1-U2)
3. The attempt at a solution
When I use this equation I get 5, but obviously that's wrong since it shouldn't be greater than 1.
Can anyone point me in the right direction? Thanks so much
2. Mar 10, 2017
### PeroK
The operative word is direction!
3. Mar 10, 2017
### CCC1212
I sort of had a feeling this may be the case. Should I be using "U1+U2" instead of "U2-U1". Or am I way off?
4. Mar 10, 2017
### PeroK
Then depends on the direction of $U_1$ and $U_2$. Are you using speeds or velocities?
5. Mar 10, 2017
### CCC1212
Velocities since it says 'in the opposite direction' I'm assuming.
6. Mar 10, 2017
### PeroK
So, what are the initial velocities of the racket and ball?
7. Mar 10, 2017
### CCC1212
They are 37 m/s (racket) and 42 m/s (ball)
Ahhh I think I see what you may be getting at. Because it says the ball is moving in the opposite direction, should I be writing the equation like...
50-25/37- -42
8. Mar 10, 2017
### PeroK
No, for velocities that can't be correct if they are in opposite directions.
Only if you know why!
9. Mar 10, 2017
### CCC1212
Could you explain that statement. I thought the difference between speed and velocity is that velocity considers direction?
10. Mar 10, 2017
### PeroK
When you have a problem in 1D it's up to you to decide what direction is positive and what direction is negative. In this case I might decide that the racket is moving in the positive direction, which means that the velocity of the racket is $37m/s$.
The ball is moving in the opposite direction, so its velocity must be $-42 m/s$.
11. Mar 10, 2017
### CCC1212
Ahhh of course. Thanks so much! | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9139354228973389, "perplexity": 855.9292222578765}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2018-30/segments/1531676590046.11/warc/CC-MAIN-20180718021906-20180718041906-00194.warc.gz"} |
https://byjus.com/question-answer/reaction-a-2b-c-rightarrow-product-follows-the-rate-law-displaystyle-frac-d-left-c/ | Question
Reaction $$\:A+2B+C\rightarrow product$$, follows the rate law$$\displaystyle-\frac{d\left[C\right]}{d\,t}\,=\,k\left[A\right]^2$$False statement regarding the above reaction is :
A
On doubling the conc. of B and C the rate of the reaction remains unaffected
B
Reducing the conc. of A to half, the rate becomes one-fourth
C
Half life period of the reaction depends upon the conc. of B
D
Half life period of the reaction is inversely proportional to the first power conc. of A
Solution
The correct option is C Half life period of the reaction depends upon the conc. of BHalf life period of the reaction depends upon the concentration of A and is independent of the concentration of B. ChemistryNCERTStandard XII
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http://www.cs.cornell.edu/courses/cs3110/2018sp/l/10-afri/notes.html | # Abstraction Functions and Representation Invariants * * * <i> Topics: * module specifications * abstraction functions * representation invariants </i> * * * ## Module specifications Let us now consider the use of specification in module *implementations*. The first question we must ask ourselves is who is going to read the comments written in module implementations. Because we are going to work hard to allow module clients to program against the module while reading only its interface, clearly clients are not the intended audience. Rather, the purpose of implementation comments is to explain the implementation to other implementers or maintainers of the module. This is done by writing comments that convince the reader that the implementation correctly implements its interface. It is inappropriate to copy the specifications of functions found in the module interface into the module implementation. Copying runs the risk of introducing inconsistency as the program evolves, because programmers don't keep the copies in sync. Copying code and specifications is a major source (if not *the* major source) of program bugs. In any case, implementers can always look at the interface for the specification. Implementation comments fall into two categories. The first category arises because a module implementation may define new types and functions that are purely internal to the module. If their significance is not obvious, these types and functions should be documented in much the same style that we have suggested for documenting interfaces. Often, as the code is written, it becomes apparent that the new types and functions defined in the module form an internal data abstraction or at least a collection of functionality that makes sense as a module in its own right. This is a signal that the internal data abstraction might be moved to a separate module and manipulated only through its operations. The second category of implementation comments is associated with the use of *data abstraction*. Suppose we are implementing an abstraction for a set of items of type 'a. The interface might look something like this: (* A set is an unordered collection in which multiplicity is ignored. *) module type Set = sig (* the type representing a set whose elements are type ['a] *) type 'a set (* the set containing no elements *) val empty : 'a set (* [mem x s] is whether [x] is a member of set [s] *) val mem : 'a -> 'a set -> bool (* [add x s] is the set containing all the elements of [s] * as well as [x]. *) val add : 'a -> 'a set -> 'a set (* [rem x s] is the set containing all the elements of [s], * minus [x]. *) val rem : 'a -> 'a set -> 'a set (* [size s] is the cardinality of [s] *) val size: 'a set -> int (* [union s1 s2] is the set containing all the elements that * are in either [s1] or [s2]. *) val union: 'a set -> 'a set -> 'a set (* [inter s1 s2] is the set containing all the elements that * are in both [s1] and [s2]. *) val inter: 'a set -> 'a set -> 'a set end In a real signature for sets, we'd want operations such as map and fold as well, but let's omit these for now for simplicity. There are many ways to implement this abstraction. One easy way is as a list: (* Implementation of sets as lists with duplicates *) module ListSetDups : Set = struct type 'a set = 'a list let empty = [] let mem = List.mem let add x l = x :: l let rem x = List.filter ((<>) x) let rec size = function | [] -> 0 | h :: t -> size t + (if mem h t then 0 else 1) let union l1 l2 = l1 @ l2 let inter l1 l2 = List.filter (fun h -> mem h l2) l1 end This implementation has the advantage of simplicity. For small sets that tend not to have duplicate elements, it will be a fine choice. Its performance will be poor for large sets or applications with many duplicates but for some applications that's not an issue. Notice that the types of the functions do not need to be written down in the implementation. They aren't needed because they're already present in the signature, just like the specifications that are also in the signature don't need to be replicated in the structure. Here is another implementation of Set that also uses 'a list but requires the lists to contain no duplicates. This implementation is also correct (and also slow for large sets). Notice that we are using the same representation type, yet some important aspects of the implementation are quite different. (* Implementation of sets as lists without duplicates *) module ListSetNoDups : Set = struct type 'a set = 'a list let empty = [] let mem = List.mem (* add checks if already a member *) let add x l = if mem x l then l else x :: l let rem x = List.filter ((<>) x) let size = List.length (* size is just length if no duplicates *) let union l1 l2 = (* check if already in other set *) List.fold_left (fun a x -> if mem x l2 then a else x :: a) l2 l1 let inter l1 l2 = List.filter (fun h -> mem h l2) l1 end An important reason why we introduced the writing of function specifications was to enable *local reasoning*: once a function has a spec, we can judge whether the function does what it is supposed to without looking at the rest of the program. We can also judge whether the rest of the program works without looking at the code of the function. However, we cannot reason locally about the individual functions in the three module implementations just given. The problem is that we don't have enough information about the relationship between the concrete type (int list) and the corresponding abstract type (set). This lack of information can be addressed by adding two new kinds of comments to the implementation: the *abstraction function* and the *representation invariant* for the abstract data type. ## Abstraction functions The client of any Set implementation should not be able to distinguish it from any other implementation based on its functional behavior. As far as the client can tell, the operations act like operations on the mathematical ideal of a set. In the first implementation, the lists [3; 1], [1; 3], and [1; 1; 3] are distinguishable to the implementer, but not to the client. To the client, they all represent the abstract set {1, 3} and cannot be distinguished by any of the operations of the Set signature. From the point of view of the client, the abstract data type describes a set of abstract values and associated operations. The implementers knows that these abstract values are represented by concrete values that may contain additional information invisible from the client's view. This loss of information is described by the *abstraction function*, which is a mapping from the space of concrete values to the abstract space. The abstraction function for the implementation ListSetDups looks like this:  Notice that several concrete values may map to a single abstract value; that is, the abstraction function may be *many-to-one*. It is also possible that some concrete values do not map to any abstract value; the abstraction function may be *partial*. That is not the case with ListSetDups, but it might be with other implementations. The abstraction function is important for deciding whether an implementation is correct, therefore it belongs as a comment in the implementation of any abstract data type. For example, in the ListSetDups module, we could document the abstraction function as follows: module ListSetDups : Set = struct (* Abstraction function: the list [a1; ...; an] represents the * smallest set containing all the elements a1, ..., an. * The list may contain duplicates. * [] represents the empty set. *) type 'a set = 'a list ... This comment explicitly points out that the list may contain duplicates, which is helpful as a reinforcement of the first sentence. Similarly, the case of an empty list is mentioned explicitly for clarity, although it is redundant. The abstraction function for the second implementation, which does not allow duplicates, hints at an important difference: we can write the abstraction function for this second representation a bit more simply because we know that the elements are distinct. module ListSetNoDups : Set = struct (* Abstraction function: the list [a1; ...; an] represents the set * {a1, ..., an}. [] represents the empty set. *) type 'a set = 'a list ... ## Commutative diagrams Using the abstraction function, we can now talk about what it means for an implementation of an abstraction to be *correct*. It is correct exactly when every operation that takes place in the concrete space makes sense when mapped by the abstraction function into the abstract space. This can be visualized as a *commutative diagram*:  A commutative diagram means that if we take the two paths around the diagram, we have to get to the same place. Suppose that we start from a concrete value and apply the actual implementation of some operation to it to obtain a new concrete value or values. When viewed abstractly, a concrete result should be an abstract value that is a possible result of applying the function *as described in its specification* to the abstract view of the actual inputs. For example, consider the union function from the implementation of sets as lists with repeated elements covered last time. When this function is applied to the concrete pair [1; 3], [2; 2], it corresponds to the lower-left corner of the diagram. The result of this operation is the list [2; 2; 1; 3], whose corresponding abstract value is the list {1, 2, 3}. Note that if we apply the abstraction function AF to the input lists [1; 3] and [2; 2], we have the sets {1, 3} and {2}. The commutative diagram requires that in this instance the union of {1, 3} and {2} is {1, 2, 3}, which is of course true. ## Representation invariants The abstraction function explains how information within the module is viewed abstractly by module clients. However, this is not all we need to know to ensure correctness of the implementation. Consider the size function in each of the two implementations. For ListSetNoDups, in which the lists of integers have no duplicates, the size is just the length of the list: let size = List.length But for ListSetDups, which allows duplicates, we need to be sure not to double-count duplicate elements: let rec size = function | [] -> 0 | h :: t -> size t + (if mem h t then 0 else 1) How we know that we don't need to do this check in ListSetNoDups? Since the code does not explicitly say that there are no duplicates, implementers will not be able to reason locally about whether functions like size are implemented correctly. The issue here is that in the ListSetNoDups representation, not all concrete data items represent abstract data items. That is, the *domain* of the abstraction function does not include all possible lists. There are some lists, such as [1; 1; 2], that contain duplicates and must never occur in the representation of a set in the ListSetNoDups implementation; the abstraction function is undefined on such lists. We need to include a second piece of information, the *representation invariant* (or *rep invariant*, or *RI*), to determine which concrete data items are valid representations of abstract data items. For sets represented as lists without duplicates, we write this as part of the comment together with the abstraction function: module ListSetNoDups : Set = struct (* Abstraction function: the list [a1; ...; an] represents the set * {a1, ..., an}. [] represents the empty set. * * Representation invariant: the list contains no duplicates. *) type 'a set = 'a list ... If we think about this issue in terms of the commutative diagram, we see that there is a crucial property that is necessary to ensure correctness: namely, that all concrete operations preserve the representation invariant. If this constraint is broken, functions such as size will not return the correct answer. The relationship between the representation invariant and the abstraction function is depicted in this figure:  We can use the rep invariant and abstraction function to judge whether the implementation of a single operation is correct *in isolation from the rest of the module*. It is correct if, assuming that: 1. the function's preconditions hold of the argument values 2. the concrete representations of the arguments satisfy the rep invariant we can show that 1. all new representation values created satisfy the rep invariant, and 2. the commutative diagram holds. The rep invariant makes it easier to write code that is provably correct, because it means that we don't have to write code that works for all possible incoming concrete representations—only those that satisfy the rep invariant. For example, in the implementation ListSetNoDups, we do not care what the code does on lists that contain duplicate elements. However, we do need to be concerned that on return, we only produce values that satisfy the rep invariant. As suggested in the figure above, if the rep invariant holds for the input values, then it should hold for the output values, which is why we call it an *invariant*. ## Implementing the rep invariant When implementing a complex abstract data type, it is often helpful to write an internal function that can be used to check that the rep invariant holds of a given data item. By convention we will call this function rep_ok. If the module accepts values of the abstract type that are created outside the module, say by exposing the implementation of the type in the signature, then rep_ok should be applied to these to ensure the representation invariant is satisfied. In addition, if the implementation creates any new values of the abstract type, rep_ok can be applied to them as a sanity check. With this approach, bugs are caught early, and a bug in one function is less likely to create the appearance of a bug in another. A convenient way to write rep_ok is to make it an identity function that just returns the input value if the rep invariant holds and raises an exception if it fails. (* Checks whether x satisfies the representation invariant. *) let rep_ok (x : int list) : int list = ... Here is an implementation of Set that uses the same data representation as ListSetNoDups, but includes copious rep_ok checks. Note that rep_ok is applied to all input sets and to any set that is ever created. This ensures that if a bad set representation is created, it will be detected immediately. In case we somehow missed a check on creation, we also apply rep_ok to incoming set arguments. If there is a bug, these checks will help us quickly figure out where the rep invariant is being broken. (* Implementation of sets as lists without duplicates. * Includes rep_ok checks. *) module ListSetNoDupsRepOk : Set = struct (* Abstraction function: the list [a1; ...; an] represents the * set {a1, ..., an}. [] represents the empty set {}. * * Representation invariant: the list contains no duplicates. *) type 'a set = 'a list let rep_ok (l : 'a set) : 'a set = List.fold_right (fun x t -> assert (not (List.mem x t)); x :: t) l [] let empty = [] let mem x l = List.mem x (rep_ok l) let add x l = rep_ok (if mem x (rep_ok l) then l else x :: l) let rem x l = rep_ok (List.filter ((<>) x) (rep_ok l)) let size l = List.length (rep_ok l) let union l1 l2 = rep_ok (List.fold_left (fun a x -> if mem x l2 then a else x :: a) (rep_ok l2) (rep_ok l1)) let inter l1 l2 = rep_ok (List.filter (fun h -> mem h l2) (rep_ok l1)) end Calling rep_ok on every argument can be too expensive for the production version of a program. The rep_ok above is quite expensive (though it could be implemented more cheaply). For production code, it may be more appropriate to use a version of rep_ok that only checks the parts of the rep invariant that are cheap to check. When there is a requirement that there be no run-time cost, rep_ok can be changed to an identity function (or macro) so the compiler optimizes away the calls to it. However, it is a good idea to keep around the full code of rep_ok (perhaps in a comment) so it can be easily reinstated during future debugging. Some languages provide support for conditional compilation. These constructs are ideal for checking representation invariants and other types of sanity checks. There is a compiler option that allows such assertions to be turned on during development and turned off for the final production version. For example, the ocaml compiler supports a flag noassert that disables assertion checking. ## Terms and concepts * abstract value * abstraction function * commutative diagram * conditional compilation * concrete value * data abstraction * many to one * partial * rep ok * representation invariant * representation type ## Further reading * [*Program Development in Java: Abstraction, Specification, and Object-Oriented Design*][liskov-guttag], chapter 5, by Barbara Liskov with John Guttag. [liskov-guttag]: https://newcatalog.library.cornell.edu/catalog/9494027 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.575695812702179, "perplexity": 853.4081936114778}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 5, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2018-47/segments/1542039742666.36/warc/CC-MAIN-20181115095814-20181115121814-00306.warc.gz"} |
http://tex.stackexchange.com/questions/64459/overfull-vbox-warning-disable?answertab=active | # overfull vbox warning disable [duplicate]
Possible Duplicate:
How to suppress overfull hbox warnings up to some maximum?
I get many warnings like
Overfull \vbox (13.88728pt too high) detected at line 250
How can I remove/disable the warnings? I don't care about 13pt's of overfull. I believe it has to do with how I use mdframed and page breaks. It's not a big deal to have 13pts over. I'd like to either completely remove the warning or allow around 30pts of overfull for vbox before the warning occurs.
I've tried various things like
\pretolerance=10000
\tolerance=10000
\emergencystretch=30pt
But none have any effect.
-
## marked as duplicate by Gonzalo Medina, Martin Schröder, Marco Daniel, clemens, percusseAug 22 '12 at 3:09
You can change the value of \vfuzz in the preamble:
\vfuzz=30pt
\vfuzz controls the maximum overrun before overfull vbox messages occur. However, in my opinion, admitting 30pt overfull might be excessive. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.4598521590232849, "perplexity": 12540.54277621434}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2015-11/segments/1424936463420.52/warc/CC-MAIN-20150226074103-00036-ip-10-28-5-156.ec2.internal.warc.gz"} |
https://msdn.microsoft.com/en-us/library/windows/desktop/aa381041(v=vs.85).aspx | Renaming the Compiled Resource File
# Renaming the Compiled Resource File
By default, when compiling resources, RC names the compiled resource (.res) file with the base name of the .rc file and places it in the same directory as the .rc file. CVTRES must then be invoked to convert the .res file to a binary resource (.rbj) format which can be understood by the linker. The following example compiles MyApp.rc and creates a compiled resource file named MyApp.res in the same directory as MyApp.rc:
rc myapp.rc
The /fo option gives the resulting .res file a name that differs from the name of the corresponding .rc file. For example, to name the resulting .res file NewFile.res, use the following command:
rc -fo newfile.res myapp.rc
The /fo option can also place the .res file in a different directory. For example, the following command places the compiled resource file MyApp.res in the directory C:\Source\Resource:
rc -fo c:\source\resource\myapp.res myapp.rc | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8125725388526917, "perplexity": 10149.237965882234}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2016-30/segments/1469257824337.54/warc/CC-MAIN-20160723071024-00314-ip-10-185-27-174.ec2.internal.warc.gz"} |
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# m03 Q 32
Author Message
SVP
Joined: 16 Nov 2010
Posts: 1672
Location: United States (IN)
Concentration: Strategy, Technology
Followers: 33
Kudos [?]: 522 [1] , given: 36
### Show Tags
02 Apr 2011, 18:35
1
KUDOS
A car dealership sold two cars: the first car at a 10% profit and the second car at a 10% loss, which gave them an overall profit margin of 5% from these two sales. If the dealership's total profit was $1000, what was the sale price of each car?$5,000 and $1,000$9,000 and $5,000$11,000 and $9,000$15,000 and $5,000$20,000 and $10,000 x - Cost of car 1 y - Cost of car 2 1.1x + 0.9y - x - y = 1000 0.1x - 0.1y = 1000 x - y = 10000 1.1x + 0.9y = 1.05(x + y) 0.05x - 0.15y = 0 x - 3y = 0 => 2y = 10000, y = 5000 x = 15000 I think the question should ask "Cost Price" instead of "sale price". Could someone please advise on this ? Regards, Subhash _________________ Formula of Life -> Achievement/Potential = k * Happiness (where k is a constant) GMAT Club Premium Membership - big benefits and savings Director Status: Impossible is not a fact. It's an opinion. It's a dare. Impossible is nothing. Affiliations: University of Chicago Booth School of Business Joined: 03 Feb 2011 Posts: 920 Followers: 14 Kudos [?]: 346 [0], given: 123 Re: m03 Q 32 [#permalink] ### Show Tags 02 Apr 2011, 20:16 I think the question should ask "Cost Price" instead of "sale price". Could someone please advise on this ? Yes you are correct! I think elimination is the strategy here. Start from C and if the profit is less move down the options and if profit is more, move up the options. The overall profit is$1000
Option C
Profit from first car = 11k * 0.1=1100
loss from the second car 9k * 0.1= 900
overall profit =1100-900=$200 Option D Profit from first car= 15k * 0.1= 1500 loss from the second car= 5k * 0.1=500 overall profit = 1500-500=$1000
I am done. Hence D
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Re: m03 Q 32 [#permalink] 02 Apr 2011, 20:16
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http://mathhelpforum.com/geometry/139148-vectors-question.html | Math Help - Vectors question
1. Vectors question
I can't finish this attached vectors question.
Attached Thumbnails
2. Originally Posted by Stuck Man
I can't finish this attached vectors question.
Dear Stuck Man,
There is a calculation error in your result for $\overline{PQ}$. It must be, $\overline{PQ}=\frac{1}{2}\underline{b}-\frac{3}{10}\underline{a}$.
After you correct this you can equate the two results you obtained for $\overline{QR}$. Then considering the coefficients of $\underline{a}~and~\underline{b}$ you can find k and n.
3. I thought that might be wrong earlier. I still don't know how to find n and k.
4. Originally Posted by Stuck Man
I thought that might be wrong earlier. I still don't know how to find n and k.
Dear Stuck Man,
$\overline{QR}=\frac{n}{10}(5\underline{b}-3\underline{a})=\frac{1}{2}(1+2k)\underline{b}-\frac{1}{2}\underline{a}$
Now, you can equate the coefficients of $\underline{a}~and~\underline{b}$.
5. I have done it now. My mistake earlier did not help. I originally made an equation from the two expressions fo r the vector QR. Thanks. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 6, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.948655366897583, "perplexity": 877.7692922426554}, "config": {"markdown_headings": false, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2015-48/segments/1448398449793.41/warc/CC-MAIN-20151124205409-00008-ip-10-71-132-137.ec2.internal.warc.gz"} |
https://naturalismathematica.wordpress.com/2017/08/26/the-last-digit-of-powers-of-2/ | The Last Digit of Powers
Previously, I had published a post about a general method of finding the last digit of enormous numbers, specifically those of some large number to a large power (e.g. $2016^{2016}$) which you can check out here.
In this post we shall be looking at a problem which at first glance, seems easier to determine but in reality requires a bit more work on the previous post. This time, we choose to ask:
What is the last digit of $2^{500}$?
To recapitulate, this is the method by which we solved the previous problem:
1. Use the ‘trick’ to reduce the base down (i.e the last digit of $2016^{2016}$ was the same as $6^{2016}$
2. Continually multiply 6 by itself and observe any patterns with the last digit (we noticed that when you multiply 6 by itself, it produces another number ending with a 6)
Also, to freshen up your memory, we had a handy, short hand version of writing things $52\equiv 2(mod10)$ which was equivalent to saying “2 is the remainder you get when you remove as many 10s as you can from the number 50”.
Knowing all of this, we can begin tackling $2^{500}$. Notice that in this case, we cannot use our little trick of simplifying the base any further since 2 is already less than 10. In other words, $2\equiv 2 (mod 10)$.
This immediately leads us to the next step, which is to multiply 2 by itself and observing whether any patterns occur with the last digit. Let us try to see what happens:
$\begin{array}{rcl} 2^1=\mathbf{2} &\equiv & \mathbf{2} (mod 10) \\ 2^2=\mathbf{4} &\equiv & \mathbf{4} (mod 10) \\ 2^3=\mathbf{8} &\equiv & \mathbf{8} (mod 10) \\ 2^4 =1\mathbf{6}&\equiv& \mathbf{6} (mod 10) \\ 2^5 =3\mathbf{2}&\equiv& \mathbf{2} (mod 10) \\ 2^6 =6\mathbf{4}&\equiv& \mathbf{4} (mod 10) \\ 2^7 =12\mathbf{8}&\equiv& \mathbf{8} (mod 10)\\ 2^8=25\mathbf{6} &\equiv& \mathbf{6} (mod 10) \end{array}$
Do you see the pattern in the last digit when we increase the power?
It appears that the last digit seems to follow the cycle $2,4,8,6$ whereby after 6, it wraps back to 2 and repeats indefinitely!
This is great, as it means that any power of 2, no matter how large, will always end in either a 2,4,8 or 6. We already saw that 5th power of 2 (i.e. $2^5$) lands on a 2 as its last digit. This can also be obtained by counting the cycle:
1. 2
2. 4
3. 8
4. 6
5. 2
A question we might also ask is with regards to our question is: where does 500 fit into this cycle? Clearly we can’t count 500 numbers by hand to check where we land on the cycle as we did before. We therefore need to find a more elegant and easier way of determining this position.
The powers of 2 that have a last digit of are $2^1,2^5,2^9,\cdots$. What do the numbers $1,5,9, \cdots$ have in common? They are obtained by adding 4 to the previous number. This can be written as:
$\begin{array}{rcl} 1 &=& 1 \\ 5 &=& 1+4 \\ 9 &=& 1+4+4\\13&=&1+4+4+4 \\ \cdots \end{array}$
Which can be written in short as $4k+1$ where $k$ may take the values $0,1,2,3,\cdots$.
We can check that this indeed matches:
$\begin{array}{rcl} 4(0)+1 &=& 1 \\ 4(1)+1 &=& 5 \\ 4(2)+1 &=& 9 \\4(3)+1 &=& 13 \\ \cdots \end{array}$
Similarly, we can have that for numbers that have a last digit of 4, we have the sequence $2,6,10,\cdots$ which can be written as $4k+2$ etc.
Thus we can categorize the last digit in terms of these groups as
Has last digit 2 if can be represented as $4k+1$
Has last digit 4 if can be represented as $4k+2$
Has last digit 8 if can be represented as $4k+3$
Has last digit 6 if can be represented as $4k$
Luckily for us, 500 is an exact multiple of 4 since $4(125)=500$. This means that in the cycle $2,4,8,6$ it lands exactly on 6! This means that the last digit of $2^{500}$ is 6 or $2^{500} \equiv 6 (mod 10)$.
We have seen how continually multiplying 2 by itself produces last digits which form a cycle $2,4,8,6$. What would happen to the last digit of other numbers like 3 or 7 to some power? Would they form cycles and if so, what would their cycles be?
These kind of extra investigations would also not only solve what the last digit of any number from 1-9 to any power would be such as $8^{156} \text{or} 3^{109}$. In conjunction with the ‘trick’ from the previous post, this would also solve what the last digit of $1208^{346} \text{or} 1040243^{5345}$ or similar, without ever needing to work out what that number actually is!
The method by which this is done is very similar to what we have done already, so I shall leave it to you, the readers to make your own discoveries. I shall conclude this post by giving the respective cycles of last digits for each of the numbers 1-9 in case anyone wanted to compare 🙂 I have also included some exercises.
• Last digit of any power of 1 cycles: 1
• Last digit of any power of 2 cycles: 2,4,8,6
• Last digit of any power of 3 cycles: 3,9,7,1
• Last digit of any power of 4 cycles: 4,6
• Last digit of any power of 5 cycles: 5
• Last digit of any power of 6 cycles: 6
• Last digit of any power of 7 cycles: 7,9,3,1
• Last digit of any power of 8 cycles: 8,4,2,6
• Last digit of any power of 9 cycles: 9,1
Exercise 1: What is the last digit of $7^{210}$?
Exercise 2: What is the last digit of $4^{1201}$?
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-Sinthorel | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 32, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.4785584807395935, "perplexity": 295.8003783845121}, "config": {"markdown_headings": false, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 5, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2018-51/segments/1544376823710.44/warc/CC-MAIN-20181212000955-20181212022455-00270.warc.gz"} |
https://mathoverflow.net/questions/243490/how-do-these-primes-jump | # How do these primes jump?
Update 2017.08.28: I am still looking for references. I have posted a request to https://cs.stackexchange.com/q/79971 which includes some literature references I found which are of interest but still miss the mark for this question. End Update.
Edit 2018.08.08 This answer https://mathoverflow.net/a/307881 will be updated to give recent information about S, especially a forthcoming preprint. End Edit 2018.08.08
I have several questions regarding the analysis, behaviour, and expression of a simple sieving algorithm which uses associative arrays. The pseudocode below assumes integer addition, string concatenation, checking that an index (key) exists in an array (so at the beginning, (n in c) is false for all n, but when c[m]=p is carried out, then (m in c) returns true), and sufficient memory. (Or set LIM to 100.)
for n = 2 to LIM
p = n
if (n in c) p = c[n]
m = n + p
while (m in c) m = m + p
c[m] = p
t[p] = t[p] "," m
(Compare a similar algorithm which in part computes the list of distinct prime factors for each n, found here: https://mathoverflow.net/a/50691 .) When this loop is run, at the end c[m] contains a prime factor p of m for each composite number m at most LIM, as well as for some composite m greater than LIM. t contains for each p a comma-delimited string of indices m for which c[m] gets p. It is a nice exercise to show that (at the end of the loop body) p is a prime, that c has only composite indices m, that c[m] when defined is always a prime dividing m, and that t[p] encodes an increasing sequence of some multiples of p. When I simulate this by hand, I imagine the primes p jumping over occupied slots in c until they find an empty slot c[m] and land there.
Question 1: Does this sieve implementation (perhaps slightly modified) exist in the computer science or number theory literature?
I am aware of wheel sieving which is faster, but this algorithm is not too shabby, even if you have to write your own data structure to perform (n in c).
Question 2: What does t[2] look like? Calling the $j$th member $m_j$, how good an approximation can we get to $m_j$ in terms of $j$?
Here are the first few terms of t[2] and of t[3]:
4 8 12 16 24 30 32 40 50 64 78 90 104 108 128 140 156 176 192 208
6 9 15 18 27 36 48 54 63 72 81 96 105 126 144 162 180 189 210 231
I will make a different post with other questions related to this algorithm and variants. If you want to play with it, here is an (untested) version which saves memory by removing c[n] after it is used, and by not storing p values larger than LIM:
BEGIN{ LIM = 100; LIM2 = LIM*LIM
for ( n=1; LIM2 > n++; ) {
if ((m=n) in c) { m += (p=c[n]); delete c[n]
while ( m in c ) m += p }
else m += (p=n)
if (p < LIM ) { c[m] = p; t[p] = t[p] "," m }
}
for ( p=1; p < LIM; p++ ) if (p in t) print t[p]
}
Question 3: How much slower does t[2] grow ( as a function of LIM ) than the sequence above where all primes are "jumped"?
Gerhard "Is Awed By Elegant Simplicity" Paseman, 2016.07.01.
• One key aspect which should be mentioned is that every prime $p$ jumping from $n$ to $n+kp$ must pick $k$ so that the greatest prime factor of $n+kp$ is less than $kp$. This along with good bounds on $kp$ gives a degree of smoothness to the trajectory, and may help with other aspects related to distribution of primes. Gerhard "Could Be Something Really Wide" Paseman, 2016.08.24. – Gerhard Paseman Aug 24 '16 at 18:52
• Yes, those agree with my output as well as the test that the next entry is "jump-length" smooth: The largest prime factor of the next entry is no bigger than the length of the jump from the previous entry. Gerhard "Hopes To Use At Length" Paseman, 2017.03.13. – Gerhard Paseman Mar 14 '17 at 1:07
• I've looked you up on LinkedIn. – user114263 Mar 6 at 16:55
• @user Thanks! I need to finish my current write-up and post a link to it from my profiles. Gerhard "Many Paths To Jumping Primes" Paseman, 2020.03.06. – Gerhard Paseman Mar 6 at 19:07
Just to confirm your list of $t[2]$ and extend it a bit, here is what those terms look like:
$t[2]=$ $$4,8,12,16,24,30,32,40,50,64,78,90,104,108,128,140,156,176,192,208,216,234,250,256,280,304,320,338,350,374,392,420,440,468,486,500,512,540,570,598,630,648,676,704,726,750,768,800,832,858,882,910,950,972,1008,1024,1056,1088,1122,1150,1176,1210,1248,1280,1296,1344,1372,1426,1458,1500,1536,1568,1584,1600,1632,1672,1694,1728,1760,1792,1824,1856,1904,1936,1976,2016 \;.$$
• This looks good! It suggests a subquadratic growth, and in fact I hope to prove that going from t[j] to t[j+1] involves a jump proportional to $\pi(\sqrt{}$t[j] $)$, or about proportional to the number of primes less than the square root of the origin of the jump. Gerhard "Will Square Off With This" Paseman, 2017.03.13. – Gerhard Paseman Mar 14 '17 at 1:16
Here is some information on how the primes jump. It seems the trajectories are somewhat smooth. Skipping numbers seems to be a topic which is a tempting if not low-hanging fruit.
As a prime traverses through its multiples according to the algorithm, it will skip over some multiples because a different prime got there first. For a prime $p$ I define skip($p$) to be the smallest positive multiple of $p$ not in the trajectory of $p$. I will use aliases of $sk(p)$ or $sk$ when $p$ is understood. One can simulate the first few steps to note skip($2$) is $6$, skip($3$) is $12$, skip($5$) is $15$, and skip($7$) is $35$.
Tracking the value of skip($p$) for many primes $p$, I note that $p^2 \lt 3sk(p) \lt 39p^2/11$ for $11 \lt p \lt 4000$. How close can we get to proving such equalities for all primes $p$?
One approach is to show for a fixed integer $k$ which primes $p$ that have $kp$ in their trajectory also have $(k+1)p$ in that trajectory, or which $p$ jump from $k$ to $k+1$. For $k=1$, there are two simple proofs: a) note that $2$ jumps from $1$ to $2$, and note for an odd prime $p$ that there are more even numbers between $p$ and $2p$ than odd primes less than $p$, so there is an even number between $p$ and $2p$ to be part of the trajectory of $2$, giving $p$ a chance to jump to $2p$ before $2$ does, and b) between $p$ and $2p$ is a power of $2$, so $2$ must land somewhere above $p$ and less than or equal to that power of $2$, again leaving $2p$ available for odd $p$.
For $k=2$, jumping from $2$ to $3$ is straightforward if there is a power of $3$ between $2p$ and $3p$. When there isn't, one can use $3$-smooth numbers (numbers whose distinct prime factors are at most $3$) for sufficiently large $p$. In particular, if $r$ is the largest $3$-smooth number less than $2p$ and $r$ is a multiple of $6$, then $2p \lt 4r/3 \lt 3r/2 \lt 3p$ and so there is a place for both $2$ and $3$ to land strictly below $3p$. If $r$ is a power of $2$ at least $8$, then one can use $9r/8$ and $3r/2$ in a similar way, and if $r$ is a power of $3$ at least $27$ then one can use $32r/27$ and $4r/3$. So for all $p$ with $2p \gt 12$, we get a pair of places (which are $3$-smooth numbers) less than $3p$ for both $2$ and $3$ to land. This takes care of $p \gt 7$, while $p=3$ can be settled by hand, leaving $p=2$ and $5$ missing out on jumping from $2$ to $3$, which they do.
In general, jumping from $k$ to $k+1$ involves the set of distinct prime divisors of $k+1$, and one may have to throw in a few more small primes to pull the argument through. Namely, find a nice set $Q$ of primes such that $k+1$ is a $Q$-smooth number (all the prime divisors come from $Q$), and so that if $Q$ has $t$ distinct primes, then find those $p$ such that the interval $(kp, (k+1)p)$ contains at least $t$ $Q$-smooth numbers. Then when $kp$ is processed, all the primes in $Q$ are guaranteed a place to land above $kp$ and below $(k+1)p$, leaving the latter available for $p$.
A problem with this approach is that I don't know an estimate for $Q$-smooth numbers in an interval that has small enough error. A rough estimate, given that there are $t$ many primes $q$ in $Q$ , and involving logarithms to different prime bases $q$, is $$\big[\prod_{q \in Q} (1 + \lfloor\log_q((k+1)p)\rfloor) - \prod_{q \in Q} (1 + \lfloor\log_q(kp) \rfloor)\big]/t!,$$ but I think this is a bad approximation when $k$ and $p$ are close to the same size.
A different approach is to consider what primes would jump to a number between $kp$ and $(k+1)p$. Using the statistics above as a guide, this interval has labels from all the primes in the interval $(kp/2,(k+1)p/2)$, and in general from $(kp/i,(k+1)p/i)$ for $i$ up to some integer hopefully close to $k$. Again, I am unsure that the error in such an estimate is easy to control.
Suppose we are able to determine $G(k)$, a non-decreasing function so that for all $p \geq G(k)$ that $p$ jumps from $k$ to $k+1$. Then define $F(p)$ to be the largest $k$ such that $p \geq G(k)$, and we now have that $F(p)=k$ means the multiples $2p$ up to $(k+1)p$, or skip($p$) $\gt F(p)$. Now the goal is to show something like $G(k)=3k+1$.
In any case, we can give a rough description now of how the labels p are arranged in c. When $n$ is processed with label $p$ dividing $n$ (so c[n] has the value p), we have all the primes $q$ from $n/2$ up to $n$ have jumped to $2q$, and for many small $t$ each prime $q$ from $n/(t+1)$ up to $n/t$ has landed on $(t+1)q$, up to about $t \in O(\sqrt{n})$. This just leaves about $O(\sqrt{n})$ many primes whose location above $n$ is unknown, but are likely below $n + K{\sqrt{n}}^{1+\epsilon}$ for some given value of $\epsilon$ and some small value of $K$ depending only on $\epsilon$. This suggests that the trajectory for a prime grows irregularly but somewhat quadratically. (Since there are at most $O(n/\log(n))$ obstructions for a given prime, we should expect strictly subquadratic growth.) Also suggested is that if $n$ has label $p$ and $p$ is not the largest prime factor of $n$, then the largest prime factor of $n$ is not much bigger than $\sqrt{3n}$, which I suggest as a conjecture.
Additional question: does it make sense to define skip($n$) for composite $n$, and will that help in the trajectory analysis? (I can see the definition depending on the prime assigned to $n$ as well as depending on the set of distinct prime factors.)
Gerhard "More Answers Gives More Questions" Paseman, 2016.08.22.
• We have skip(11)=143 and skip(89)=8277, and many instances where skip(p) is larger than p^2, but not by much. There are fewer instance where skip(p) is less than p^2, with the sample showing that for most remaining primes skip(p) is between (p^2)/2 and 2(p^2)/3. There is probably a combinatorial explanation for this, which I would like to see. Gerhard "Analytic Number Theorems Needn't Apply" Paseman, 2016.08.22. – Gerhard Paseman Aug 22 '16 at 20:28
I've made some headway on Question 3. It is related to my studies of Jacobsthal's function. Although a theory for general square free numbers $Q$ can be developed, I will take $Q=P_n$, the product of the first $n$ primes, for this post. Of course, $2$ can only make a jump of size at most $2n$, but it will rarely make a jump of that size for large $n$.
If I restrict the algorithm to primes dividing $Q$, the union of the trajectories are those numbers not coprime to $Q$, and as the system can be modeled as a finite state automaton, the trajectory of each prime will be periodic with a period related to a multiple of $Q$. More precisely, for a given prime $p$ dividing $Q$, one has that a positive number $m$ is in the trajectory if and only if $m+Q$ is in the trajectory. (Temporarily, I include $p$ in its own trajectory, contrary to the post above.)
To see this, note that $\gcd(Q,Q+p)=p$ for every prime divisor $p$ (and also every divisor) of $Q$. Thus, modulo $Q$, there is only one way to arrange the $n$ primes at the start ( the pattern of primes assigned to the indices in $[mQ+2, mQ+p_n]$ is independent of $m$), and thus the pattern of primes assigned to c repeats modulo $Q$ as well.
It is tempting to conjecture that c[$m$]$=$c[$Q-m$] for positive $m$ less than and not coprime to $Q$, but when $Q=30$ one has c[$12$]$=2$ and c[$18$]$=3$ (and similar examples exist for some larger $Q$). It is also tempting to conjecture that each prime $p$ does slightly less than $Q/p$ jumps in a range of length $Q$, with the difference related to inclusion-exclusion. Simulations show much smaller numbers than this prediction. Note that the longest jump is bounded above by the sum of the $n$ primes, and is likely to be much less. For small values of $n$ $(n\leq 9)$ I see the largest jump as less than $3p_n$. I would not be surprised if the largest jump were of the same order as $g(Q)$, the Jacobsthal function applied to $Q$, which would be conjectured at or near $p_n(\log p_n)^2$ but I would settle for strictly less than $O(n^2)$. In any case, it is apparent that the set of primes stay in a rather tight cluster not much larger than the largest prime as they jump according to the restricted version of the algorithm. How tight is hopefully less hard than various open questions regarding the distribution of prime numbers.
Gerhard "More Jumping Means More Excitement" Paseman, 2016.09.11.
I've decided to bust through my writer's block and post a partial result.
Of course when a prime $p$ jumps, it skims over multiples of $p$ occupied by other primes, and one question is how far a prime can jump from its location at $n$. The brief answer is that $p \cdot f_0(n/p)$ is a strict upper bound, and I am trying to tighten that to $f_0(n/p)$, maybe multiplied by a fractional power of $p$. Here $f_0(n)$ relates to the number $w$ of distinct prime factors of the product of integers in the interval $[n+1,n+k]$, and is the largest integer $k$ for which $w\geq k$. $f_0()$ (and also $f_2()$ which relates to Grimm's conjecture in another post) comes from a 1971 paper of Erdos and Selfridge.
The proof of this upper bound is clear: for each of the multiples of $p$ above $n$ which have a different prime divisor occupying that multiple, we run out of (a non repetitive pattern of) possible prime divisors when we hit $f_0(n/p)$ many such multiples. (Indeed we run out before encountering $1+f_2(n/p)$ many such multiples.) However, some of the primes $q$ involved may actually not be on a multiple of $p$, but occur on a smaller multiple of $q$ above $n$, and it is reasonable (but not well supported) to assume that about $1/p$ of these primes $q$ reside on multiples of $p$.
The nice thing is that the 1971 paper has a proof that $f_0(n)$ is $O(\sqrt{n/\log n})$, and $f_2(n)$ seems not much smaller. I hope to make a proof with explicit constants, and add it to a write-up. I also hope to get an inspiring idea for a lower bound on the length of a jump of $p$ from a large multiple of $p$. However, I find it interesting already that a trajectory of any prime is eventually smoother than somewhat smooth, and hope to use this in further analysis. Also, intriguing is how small the ratio skip(p)/p gets as p gets large.
Gerhard "Going For Block Busting Results" Paseman, 2017.07.05. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 1, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.895319938659668, "perplexity": 257.5656906280442}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2020-29/segments/1593655886121.45/warc/CC-MAIN-20200704104352-20200704134352-00445.warc.gz"} |
http://community.wolfram.com/groups/-/m/t/1024987 | # Solve an elementary quadratic equation?
GROUPS:
Valeriu Ungureanu 1 Vote Dear All,May someone explain what is wrong with the functions Solve[] and Reduce[] applications when they solve a very simple quadratic equation: $x^2+x+1=0$This equation has two complex solutions: $\frac{-1 +\sqrt{3} i}{2}$ and $\frac{-1 -\sqrt{3} i}{2}.$Both the functions Solve[] and Reduce[] give other solutions: In[1]:= Solve[x^2 + x + 1 == 0] Out[1]= {{x -> -(-1)^(1/3)}, {x -> (-1)^(2/3)}} In[2]:= Reduce[x^2 + x + 1 == 0] Out[2]= x == -(-1)^(1/3) || x == (-1)^(2/3) The function NSolve[] gives correct solutions: In[3]:= NSolve[x^2 + x + 1 == 0] Out[3]= {{x -> -0.5 - 0.866025 I}, {x -> -0.5 + 0.866025 I}}
7 months ago
10 Replies
Frank Kampas 1 Vote The solutions from Solve and Reduce are correct. In[1]:= Solve[x^2 + x + 1 == 0] Out[1]= {{x -> -(-1)^(1/3)}, {x -> (-1)^(2/3)}} In[2]:= N[%] Out[2]= {{x -> -0.5 - 0.866025 I}, {x -> -0.5 + 0.866025 I}}
7 months ago
Thank you, Frank! It's somewhat unusual solution presentation!
7 months ago
Frank Kampas 4 Votes In[1]:= Solve[x^2 + x + 1 == 0] Out[1]= {{x -> -(-1)^(1/3)}, {x -> (-1)^(2/3)}} In[2]:= N[%] Out[2]= {{x -> -0.5 - 0.866025 I}, {x -> -0.5 + 0.866025 I}} In[3]:= ComplexExpand[%%] Out[3]= {{x -> -(1/2) - (I Sqrt[3])/2}, {x -> -(1/2) + (I Sqrt[3])/2}}
7 months ago
O Mirza 1 Vote Both Solve[] and Reduce[] give the exact solutions in using rational numbers. NSolve[] gives a numerical approximation to the solution.To see this use the functions N and ComplexExpand. In[1]:= Map[N, {{x -> -(-1)^(1/3)}, {x -> (-1)^(2/3)}}, {2}] In[2]:=Map[ComplexExpand, {{x -> -(-1)^(1/3)}, {x -> (-1)^(2/3)}}, {2}] Out[1]= {{x -> -0.5 - 0.866025 I}, {x -> -0.5 + 0.866025 I}} Out[2]= {{x -> {{x -> -(1/2) - (I Sqrt[3])/2}, {x -> -(1/2) + (I Sqrt[3])/2}}
7 months ago
Sam Carrettie 2 Votes You don't really have to map ComplexExpand, this will gave you the same result: ComplexExpand[x/.Solve[x^2 + x + 1 == 0]] $$\left\{-\frac{1}{2}-\frac{i \sqrt{3}}{2},-\frac{1}{2}+\frac{i \sqrt{3}}{2}\right\}$$ ComplexExpand[Reduce[x^2 + x + 1 == 0]] $$x=-\frac{1}{2}-\frac{i \sqrt{3}}{2}\lor x=-\frac{1}{2}+\frac{i \sqrt{3}}{2}$$
7 months ago
Valeriu Ungureanu 1 Vote Wolfram Alpha finds the same solutions:But, I used Step-by-step solution and found solution with the well known formula in the traditional form:After that I used other variant of Step-by-step solution procedure and found the solution in the traditional form, too: So, it's not clear why the result is presented in "non-traditional" form? In[2]:= {{x -> -(-1)^(1/3)}, {x -> (-1)^(2/3)}} // FullForm Out[2]//FullForm= \!$$TagBox[StyleBox[RowBox[{"List", "[", RowBox[{RowBox[{"List", "[", RowBox[{"Rule", "[", RowBox[{"x", ",", RowBox[{"Times", "[", RowBox[{RowBox[{"-", "1"}], ",", RowBox[{"Power", "[", RowBox[{RowBox[{"-", "1"}], ",", RowBox[{"Rational", "[", RowBox[{"1", ",", "3"}], "]"}]}], "]"}]}], "]"}]}], "]"}], "]"}], ",", RowBox[{"List", "[", RowBox[{"Rule", "[", RowBox[{"x", ",", RowBox[{"Power", "[", RowBox[{RowBox[{"-", "1"}], ",", RowBox[{"Rational", "[", RowBox[{"2", ",", "3"}], "]"}]}], "]"}]}], "]"}], "]"}]}], "]"}],ShowSpecialCharacters->False,ShowStringCharacters->True,\NumberMarks->True], FullForm]$$ What is the reason to present solutions in an unusual "rational" form?
7 months ago
Todd Rowland 3 Votes While I don't know why it is designed like this, here are a few possible reasons:1) The solving algorithms have to be as general as possible (not just quadratic).2) It would be possible to add an extra layer of code checking for cases where there is a more elementary presentation that is also small, but this would slow things down. That could be problematical for someone doing a large calculation. Often the right design decision is to have the calculation do the fastest thing and then let the user decide if he wants a different presentation.3) It is a matter of perspective of what is unusual. I say this because the roots of unity (which includes the roots of -1) is a classical topic in mathematics.
First two reasons are clear, correct and acceptable! But the last one is somewhat confusing, because cubic root of $-1$ in traditional interpretation is $-1$. So, in such interpretations solutions of this equation are: $1$ and $1$. In my opinion, this is a serious confusion for a lot of people...
Thank you, Daniel! I found an exhaustive explanation on the $Wolfram MathWorld$ page: The schoolbook definition of the cube root of a negative number is (-x)^(1/3)=-(x^(1/3)). However, extension of the cube root into the complex plane gives a branch cut along the negative real axis for the principal value of the cube root as illustrated above. By convention, "the" (principal) cube root is therefore a complex number with positive imaginary part. As a result, the Wolfram Language and other symbolic algebra languages and programs that return results valid over the entire complex plane therefore return complex results for (-x)^(1/3). For example, in the Wolfram Language, ComplexExpand[(-1)^(1/3)] gives the result 1/2+isqrt(3)/2. When considering a positive real number x, the Wolfram Language function CubeRoot[x], which is equivalent to Surd[x, 3], may be used to return the real cube root. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 2, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.5489558577537537, "perplexity": 1857.6053862139988}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-39/segments/1505818688966.39/warc/CC-MAIN-20170922130934-20170922150934-00339.warc.gz"} |
http://dasonk.com/r/2013/02/09/Using-the-delta-method | This was originally posted at Point Mass Prior and features MathML. If you’re viewing from StatsBlogs the math probably won’t show up properly and it would be beneficial to view the post here
Somebody recently asked me about the delta method and specifically the deltamethod function in the msm package. I thought I would write about that and so to motivate this we’ll look at an example. The example we’ll consider is a simple case where we fit a quadratic regression to some data. This means our model has the form
where $\epsilon_i$ are independent and identically distributed normal random variables with mean 0 and a variance of $\sigma^2$.
To start we’ll generate some data such that we have roots at x=0 and x=10 and the quadratic is such that we have a maximum instead of a minimum.
We can plot the data to get a feel for it:
Now it might be that what we’re really interested in is the input value that gives us the maximum value for the response (on average). Let’s call that value $x_\text{max}$. Now if we knew the true parameters for this data we could figure out exactly where that maximum occurs. We know that for a quadratic function $y = \beta_0 + \beta_1x + \beta_2x^2$ the maximum value occurs at $x = \frac{-\beta_1}{2\beta_2}$. In our specific case we have $y = 0 + 10x -x^2$ so the maximum occurs at $x = 5$. Just eyeballing our plot it doesn’t look like the quadratic that will be fit will give us a maximum that occurs exactly at $x=5$. Let’s actually fit the quadratic regression and see what we get for the estimated value of $x_\text{max}$ which I will call $\hat{x}_\text{max}$.
So our estimate of the value where the maximum occurs is $\hat{x}_\text{max} =$ 5.1903. This is pretty close but it would still be nice to have some sort of interval to go along with our estimate. This is where the delta method can help us out. The delta method can be thought of as a way to get an estimated standard error for a transformation of estimated parameter values. In our case we’re interested in applying the function
to our estimated parameters.
To perform the delta method we need to know a little bit of calculus. The method requires taking derivatives of our function of interest. Now this isn’t too bad to do in practice but not everybody that wants to perform an analysis will know how to take derivatives (or at least it might have been a long time since they’ve taken a derivative).
Luckily for us we don’t have to do the delta method by hand though as long as we know the transformation of interest. The deltamethod function in the msm package provides a convenient way to get the estimated standard error of the transformation as long as we can provide
1. The transformation of interest
2. The estimated parameter values
3. The covariance matrix of the estimated parameters
We already know (1) but we have to make sure it write it in the proper syntax for deltamethod. We can easily obtain (2) by using coef on our fitted model and we can also easily obtain (3) by using vcov on the estimated model.
When writing the syntax for the transformation when using the deltamethod function you need to refer to the first parameter as x1, the second parameter as x2, and so on. So if I wanted to find the standard error for the sum of two parameters I would write that as ~ x1 + x2. In our case our estimated parameters are from the output of coef(o) so let’s sneak a peak at them to remind ourselves the output order.
So in this case when writing our transformation we would refer to $\hat{\beta_0}$ as x1, $\hat{\beta_1}$ as x2, and $\hat{\beta_2}$ as x3. As a reminder the transformation we applied was $\frac{-\hat{\beta_1}}{2\hat{\beta_2}}$ so the formula we want is ~ -x2 / (2 * x3).
So we see that our confidence interval does contain the true value. We could also do a hypothesis test if we wanted to test against a certain value. Here we’ll test using a null hypothesis that the true $x_\text{max} = 5$.
Our p-value of 0.473 doesn’t allow us to reject the null hypothesis in this situation.
So we can see that it’s fairly easy to implement the delta method in R. Now this isn’t necessarily my favorite way to get intervals for transformations of parameters but if you’re a frequentist then it can be quite useful.
09 February 2013
R | {"extraction_info": {"found_math": true, "script_math_tex": 16, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.7492964863777161, "perplexity": 209.82826283450754}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.3, "absolute_threshold": 20, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2018-39/segments/1537267159160.59/warc/CC-MAIN-20180923055928-20180923080328-00289.warc.gz"} |
https://www.physicsforums.com/threads/difficult-polynomial-and-determinant-formula.273000/ | # Difficult polynomial and determinant formula
1. Nov 18, 2008
### jostpuur
Anyone having any ideas about how this formula could be proved?
$$\underset{k<l}{\prod_{k,l=1}^n} (x_k - x_l) = (-1)^{n(n-1)/2} \left|\begin{array}{ccc} 1 & \cdots & 1 \\ x_1 & \cdots & x_n \\ \vdots & & \vdots \\ x_1^{n-1} & \cdots & x_n^{n-1} \\ \end{array}\right|$$
I tried induction without success. The induction step seems to only require other difficult formulas.
2. Nov 19, 2008
### morphism
Look up the Vandermonde determinant.
3. Dec 10, 2008
### jostpuur
I have now seen this Vandermonde determinant been mentioned in several places, but I've still not encountered the proof. It seems that most authors prefer mentioning the result instead of proving it.
4. Dec 10, 2008
### Anthony
What can you say about the ith and jth columns if $$x_i=x_j$$? Can you see how to construct a proof from there?
5. Dec 10, 2008
### jostpuur
I can see that in the equation I wrote, both sides are zero precisely when $x_i=x_j$ for some $i\neq j$, but I don't see how this remark would help with a proof yet.
6. Dec 10, 2008
### Anthony
Do you agree that the determinant is a polynomial in the variables $$x_i$$?
7. Dec 10, 2008
### jostpuur
Yes.
8. Dec 11, 2008
### Anthony
What order will the polynomial be in each of the $$x_i$$?
9. Dec 11, 2008
### jostpuur
n-1.
10. Dec 11, 2008
### epenguin
Subtract x1 (or if you prefer xn) times each row from the next row. You'll then find you get a factor in each column which you can take out and is (x2-x1)(x3-x1)...(xn-x1) and the other factor is the next smallest Vandermonde determinant on x2, x3,... xn. You can also formulate the above as matrix multiplication.
The fiddly may be is getting the expression for sign right. Actually I am not sure you have.
11. Dec 11, 2008
### jostpuur
This seems to imply that there exists some constant $C\in\mathbb{R}$ so that
$$\underset{k<l}{\prod_{k,l=1}^n} (x_k-x_l) = C \left|\begin{array}{ccc} 1 & \cdots & 1 \\ x_1 & \cdots & x_n \\ \vdots & & \vdots \\ x_1^{n-1} & \cdots & x_n^{n-1} \\ \end{array}\right|$$
I'll continue thinking.
12. Dec 11, 2008
### jostpuur
By using the formula
$$x_k^m - x_l^m = (x_k - x_l)(x_k^{m-1} + x_k^{m-2}x_l + \cdots + x_k x_l^{m-2} + x_l^{m-1})$$
I managed to do this:
$$\left|\begin{array}{ccc} 1 & \cdots & 1 \\ x_1 & \cdots & x_n \\ \vdots & & \vdots \\ x_1^{n-1} & \cdots & x_n^{n-1} \\ \end{array}\right| = (x_2 - x_1)\left|\begin{array}{ccccc} 1 & 0 & 1 & \cdots & 1 \\ x_1 & 1 & x_3 & \cdots & x_n \\ x_1^2 & x_2+x_1 & x_3^2 & \cdots & x_n^2 \\ \vdots & \vdots & \vdots & & \vdots \\ x_1^{n-1} & x_2^{n-2} + x_2^{n-3}x_1 + \cdots + x_1^{n-2} & x_3^{n-1} & \cdots & x_n^{n-1} \\ \end{array}\right| = \cdots$$
$$\cdots = (-1)^{n-2}\Big(\prod_{k=2}^n (x_1 - x_k)\Big)\left|\begin{array}{cccc} 1 & 0 & \cdots & 0 \\ x_1 & 1 & \cdots & 1 \\ x_1^2 & x_2 + x_1 & \cdots & x_n + x_1 \\ \vdots & \vdots & & \vdots \\ x_1^{n-1} & x_2^{n-2} + \cdots + x_1^{n-2} & \cdots & x_n^{n-2} + \cdots + x_1^{n-2} \\ \end{array}\right|$$
It looks like difficult to proceed. If I subtract the second column from the third column, the three first rows will become this
$$0 - 0 = 0$$
$$1 - 1 = 0$$
$$(x_3+x_1) - (x_2+x_1) = x_3 - x_2$$
but what about the rows below these? It becomes an algebraic mess.
13. Dec 11, 2008
### Anthony
Hurrah! So all you need do is find the constant $$C$$. Can you do that?
14. Dec 11, 2008
### jostpuur
The fourth row will be
$$(x_3^2 + x_3x_1 + x_1^2) - (x_2^2 + x_2x_1 + x_1^2) = (x_3-x_2)(x_3 + x_2 + x_1).$$
This looks good, and most obviously $x_3-x_2$ will become a common factor, but it is a mystery to me how one proves this. When one proceeds like this, the algebraic expressions at some arbitrary step seem to be complicated.
15. Dec 11, 2008
### jostpuur
Maybe. I'll try induction with choice $x_n=0$, and see what happens.
16. Dec 11, 2008
### jostpuur
Yes, it seems that a recursion formula
$$C_n = (-1)^{n+1} C_{n-1}$$
holds, and by checking the case $n=2$ first, the constants
$$C_n = (-1)^{n(n-1)/2}$$
follow.
Good job Anthony
17. Dec 11, 2008
### Anthony
Glad to be of service.
18. Dec 11, 2008
### jostpuur
I must admit I suspected that you had underestimated the problem at the time of your first post. You made it sound too simple.
19. Dec 11, 2008
### jostpuur
Actually this is not all clear to me yet. There was one result that I considered trivial earlier, but which turned out to be more difficult. How does on prove that if the vectors
$$\left(\begin{array}{c} 1 \\ x_1 \\ \vdots \\ x_1^{n-1} \\ \end{array}\right), \left(\begin{array}{c} 1 \\ x_2 \\ \vdots \\ x_2^{n-1} \\ \end{array}\right),\cdots, \left(\begin{array}{c} 1 \\ x_n \\ \vdots \\ x_n^{n-1} \\ \end{array}\right)$$
are linearly dependent, then $x_i=x_j$ with some $i\neq j$?
20. Dec 11, 2008
### epenguin
I can't do tex determinants, but if you subtract x1 X (penultimate row) from last row,..., x1 X first row from second row, then don't you get for first column {1, 0, 0, ...}, for second column {1, (x2-x1), x2(x2-x1), x22(x2-x1), ... ?
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http://www.phy.duke.edu/~rgb/Class/phy51/phy51/node23.html | Next: Damped Oscillation Up: The Pendulum Previous: The Pendulum Contents
### The Physical Pendulum
In the treatment of the ordinary pendulum above, we just used Newton's Second Law directly to get the equation of motion. This was possible only because we could neglect the mass of the string and because we could treat the mass like a point mass at its end.
However, real grandfather clocks often have a large, massive pendulum like the one above - a long massive rod (of length and mass ) with a large round disk (of radius and mass ) at the end. The round weight rotates through an angle of in each oscillation, so it has angular momemtum. Newton's Law for forces no longer suffices. We must use torque and the moment of inertia to obtain the frequency of the oscillator.
To do this we go through the same steps (more or less) that we did for the regular pendulum. First we compute the net gravitational torque on the system at an arbitrary (small) angle :
(76)
(The - sign is there because the torque opposes the angular displacement from equilibrium.)
Next we set this equal to , where is the total moment of inertia for the system about the pivot of the pendulum and simplify:
(77)
(78)
and make the small angle approximation to get:
(79)
Note that for this problem:
(80)
(the moment of inertia of the rod plus the moment of inertial of the disk rotating about a parallel axis a distance away from its center of mass). From this we can read off the angular frequency:
(81)
With in hand, we know everything. For example:
(82)
gives us the angular trajectory. We can easily solve for the period , the frequency , the spatial or angular velocity, or whatever we like.
Note that the energy of this sort of pendulum can be tricky. Obviously its potential energy is easy enough - it depends on the elevation of the center of masses of the rod and the disk. The kinetic energy, however, is:
(83)
where I do not write as usual because it confuses (the angular frequency of the oscillator, roughly contant) and (the angular velocity of the pendulum bob, which varies between 0 and some maximum value in every cycle).
Next: Damped Oscillation Up: The Pendulum Previous: The Pendulum Contents
Robert G. Brown 2004-04-12 | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9781979322433472, "perplexity": 436.1781005458815}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.3, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2014-42/segments/1414637900248.22/warc/CC-MAIN-20141030025820-00102-ip-10-16-133-185.ec2.internal.warc.gz"} |
https://www.hepdata.net/search/?q=&reactions=DEUT+C+--%3E+P+X&sort_order=&page=1&sort_by=latest | Showing 12 of 12 results
#### MEASUREMENT OF THE SPECTATOR PROTON YIELD AT 0 ANGLE IN THE DEUTERON STRIPPING REACTION ON CARBON AT 8.9-GeV/c. (IN RUSSIAN)
Ableev, V.g. ; Vorobev, G.g. ; Zaporozhets, S.a. ; et al.
Inspire Record 192436
The invariant cross section of the reaction of deuteron stripping on carbon target has been measured at a deuteron momentum of 8.9 GeV/c. The cross section is obtained at a zero detection angle of the stripping proton: E/p2xd2σ/dpdΩ=(281+-9)xbxGeV/srx(GeV/c)3. This value is consistent with the one calculated in the framework of the Bertocci-Treleani model of deuteron fragmentation. When the method of Nissen-Meyer is used for orthogonalization of the wave functions of primary deuteron and the (np) system, resulting from its disintegration, a similar calculation gives the result, which is 1.4 times larger than the measured value. Distribution in the cosine of angle of proton yield at the fixed proton momentum p turned out to be near to isotropy one and distribution in p at the fixed cos theta has the maximum at p=50 MeV/c
3 data tables
#### Investigation of the breakup of a target nucleus in nucleus-nucleus collisions at an incident momentum of 4.2 GeV/c per nucleon
Bondarenko, A.I. ; Bondarenko, R.A. ; Kladnitskaya, E.N. ;
Phys.Atom.Nucl. 60 (1997) 1833-1842, 1997.
Inspire Record 1392946
6 data tables
No description provided.
No description provided.
No description provided.
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#### Analyzing the features of pi- mesons and protons from A C interactions at a momentum of p = 4.2-GeV/c per projectile nucleon on the basis of the FRITIOF model
Baatar, T. ; Bondarenko, A.I. ; Bondarenko, R.A. ; et al.
Phys.Atom.Nucl. 63 (2000) 839-844, 2000.
Inspire Record 533011
16 data tables
No description provided.
No description provided.
No description provided.
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#### Measurement of the tensor analyzing power T(20) in inclusive deuteron breakup at 9-GeV/c on hydrogen and carbon
Azhgirei, L.S. ; Afanasev, S.V. ; Chernykh, E.V. ; et al.
Phys.Lett. B387 (1996) 37-42, 1996.
Inspire Record 328522
2 data tables
No description provided.
No description provided.
#### Measurement of the tensor analyzing power T(20) for d (polarized) + C-12 ---> p (0-degrees) + X in the region of internal momenta in the deuteron up to 1-GeV/c
Aono, T. ; Chernykh, E.V. ; Dzikowski, T. ; et al.
Phys.Rev.Lett. 74 (1995) 4997-5000, 1995.
Inspire Record 379428
1 data table
The momentum K, called momentum in light-cone dynamics, is expressed by thefollowing formula k**2=mt**2/(4*alpha*(1-alpha))-m**2,with mt**2=kt**2+m**2 wh ere kt is the proton transverse momentum.The light-cone variable alpha is the p art of the deuteron momentum carried by the proton in the infinite momentum frameand is expressed by the formula alpha=(Ep+Pp)/(Ed+Pd).
#### Rapidity distributions of protons in (p, d, alpha, C) C interactions at 4.2-GeV/c per nucleon
Bekmirzaev, R.N. ; Kladnitskaya, E.N. ; Muminov, M.M. ; et al.
Phys.Atom.Nucl. 58 (1995) 1548-1554, 1995.
Inspire Record 382325
7 data tables
ASYM is defined as follows: ASYM = (SIG(YRAP(P=3,RF=LAB)<1.1) - (SIG(YRAP(P=3,RF=LAB)>1.1)) / (SIG(YRAP(P=3,RF=LAB)<1.1)+ SIG(YRAP(P=3,RF=LAB)>1.1)).
ASYM is defined as follows: ASYM = (SIG(YRAP(P=3,RF=LAB)<1.1) - (SIG(YRAP( P=3,RF=LAB)>1.1)) / (SIG(YRAP(P=3,RF=LAB)<1.1)+SIG(YRAP(P=3,RF=LAB)>1.1)).
ASYM is defined as follows: ASYM = (SIG(YRAP(P=3,RF=LAB)<1.1) - (SIG(YRAP( P=3,RF=LAB)>1.1)) / (SIG(YRAP(P=3,RF=LAB)<1.1)+SIG(YRAP(P=3,RF=LAB)>1.1)).
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#### Dependence of spectra and cross-sections yield of proton at the energy more than 0.4-GeV at fixed angles on atomic weights of colliding nuclei in nucleus-nucleus interactions
Agakishiev, G.N. ; Bekmirzaev, R. ; Kanarek, T. ; et al.
Phys.Atom.Nucl. 56 (1993) 1397-1405, 1993.
Inspire Record 345328
3 data tables
No description provided.
No description provided.
No description provided.
#### Analyzing power in d (polarized) C ---> p X and d (polarized) C ---> p p (d) X reactions for fast protons scattered at large angles
Beznogikh, G.G. ; Budilov, V.A. ; Filipkowski, A. ; et al.
Sov.J.Nucl.Phys. 54 (1991) 812-818, 1991.
Inspire Record 324762
14 data tables
No description provided.
No description provided.
No description provided.
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#### MEASUREMENT OF INELASTIC AND TOPOLOGICAL CROSS-SECTIONS OF INTERACTION OF DEUTERONS WITH CARBON NUCLEI AT ENERGY 1-GeV PER NUCLEON
Gulkanian, G.R. ; Kakoian, V.G. ; Kanetsian, A.R. ; et al.
No Journal Information, 1989.
Inspire Record 281772
5 data tables
No description provided.
No description provided.
No description provided.
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#### INCLUSIVE AND MULTIPLE CHARACTERISTICS OF CUMULATIVE PROTONS IN NUCLEUS-NUCLEUS INTERACTIONS AT 4.2-GeV/c PER NUCLEON
Gulkanian, G.R. ; Ravinovich, I.M. ; Cheplakov, A.P. ;
Sov.J.Nucl.Phys. 50 (1989) 259, 1989.
Inspire Record 267866
11 data tables
No description provided.
No description provided.
No description provided.
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#### INVESTIGATION OF MOMENTUM AND ANGULAR CHARACTERISTICS OF PROTONS PRODUCED IN n C AND n Ta INTERACTIONS AT 4.2-GeV/c MOMENTUM
Bekmirzaev, R.N. ; Ivanovskaya, I.A. ; Muminov, M.M. ; et al.
Sov.J.Nucl.Phys. 49 (1989) 305, 1989.
Inspire Record 263768
12 data tables
No description provided.
No description provided.
No description provided.
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#### A Study of the Proton Momentum Spectrum From Deuteron Fragmentation at 8.9 GeV/$c$ and an Estimate of Admixture Parameters for the Six Quark State in Deuteron
Ableev, V.G. ; Abdushukurov, D.A. ; Avramenko, S.A. ; et al.
Nucl.Phys. A393 (1983) 491, 1983.
Inspire Record 179179
The momentum spectrum of protons emitted at small angles in the stripping reaction d + 12 C → p + X has been measured at a deuteron momentum of 8.9 GeV/ c . The data are described in the framework of the Glauber-Sitenko theory using the hybrid model of the deuteron wave function which includes a six-quark state. The parameters of this state are determined. A shoulder in the spectrum has been observed in the proton momenta region which kinematically corresponds to the production of a dibaryon resonance with a mass from 2.0 to 2.2 GeV.
1 data table
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http://elib.mi.sanu.ac.rs/pages/browse_issue.php?db=kjm&rbr=13 | eLibrary of Mathematical Instituteof the Serbian Academy of Sciences and Arts
> Home / All Journals / Journal /
Kragujevac Journal of MathematicsPublisher: Prirodno-matematički fakultet Kragujevac, KragujevacISSN: 1450-9628Issue: 34Date: 2010Journal Homepage
A geometrical description of visual sensation II 5 - 24 Bart Ons and Paul Verstraelen
AbstractKeywords: Sensation, Perception, Brightness illusion, Helmholtz's illusion, Human vision, Plateau's irradiation phenomenon, Kitaoka's bulge illusion, Psychophysics, Casorati curvature.MSC: 91E30 91E99 92C20 53B25
Some geometrical properties of marginally trapped surfaces in Minkowski space $M^4$ 25 - 30 Bernard Rouxel
AbstractKeywords: Trapped surfaces, Mean curvature vectorMSC: 53A35 53B30
Nonimmersion results for the real flag manifolds $\mathbb{R} F(1,1,1,n-3)$ 31 - 38 Deborah Olayide A. Ajayi
AbstractKeywords: Immersions, Embeddings, Real flag manifold, Stiefel-Whitney class, Fibre bundleMSC: 57R42 57R20 57R40
Affine Invariant $L$-systems 39 - 49 Ljubiša Kocić and Marija Rafajlović
AbstractKeywords: $L$-system, Fractal attractor, Affine invarianceMSC: 28A80
Biminimal general helix in the Heisenberg group $Heis^{3}$ 51 - 60 Essin Turhan and Talat Körpinar
AbstractKeywords: Heisenberg group, Biminimal curve, General helixMSC: 58A10 58E20
On some $n$-starlike integral operators 61 - 71 Kunle Oladeji Babalola
AbstractKeywords: Analytic and univalent functions, $n$-starlikeness, Starlike, Convex functions, Integral operators, Salagean derivativesMSC: 30C45 30C50 30C55
Descriptions of zero sets and parametric representations of certain analytic area Nevanlinna type classes in the unit disk 73 - 89 Romi Shamoyan and Haiying Li
AbstractKeywords: Djrbashian products, Area Nevanlinna spaces, Nevanlinna characteristic, Parametric representations, Zero sets.MSC: 30D45
On the continuous dependence of the fixed points for $(\varphi,~\psi)$-contractive-type operators 91 - 102 Memudu Olaposi Olatinwo
AbstractKeywords: Continuous dependence, General contractive conditions, Banach space settingMSC: 47H06 47H10
Sharp function estimate for multilinear commutator of Littlewood-Paley operator 103 - 112 Peng Meijun and Liu Lanzhe
AbstractKeywords: Multilinear commutator, Littlewood-Paley operator, BMO, Sharp inequalityMSC: 42B20 42B25
On the existence of (196,91,42) Hadamard difference sets 113 - 130 Adegoke S. A. Osifodunrin
AbstractKeywords: Representation, Idempotents, Menon-Hadamard difference Sets, Intersection numbersMSC: 05B10 05B20
Article page: 12>>
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https://www.gradesaver.com/textbooks/math/algebra/intermediate-algebra-12th-edition/chapter-7-section-7-2-rational-exponents-7-2-exercises-page-449/67 | ## Intermediate Algebra (12th Edition)
$x^{5/12}$
$\bf{\text{Solution Outline:}}$ Use the laws of exponents to simplify the given expression, $x^{2/3}\cdot x^{-1/4} .$ $\bf{\text{Solution Details:}}$ Using the Product Rule of the laws of exponents which is given by $x^m\cdot x^n=x^{m+n},$ the expression above is equivalent to \begin{array}{l}\require{cancel} x^{\frac{2}{3}+\left(-\frac{1}{4}\right)} \\\\= x^{\frac{2}{3}-\frac{1}{4}} .\end{array} To simplify the expression, $\dfrac{2}{3}-\dfrac{1}{4} ,$ find the $LCD$ of the denominators $\left\{ 3,4 \right\}.$ The $LCD$ is $12$ since it is the lowest number that can be exactly divided by the denominators. Multiplying both the numerator and denominator of each terms by the constant that will make the denominators equal to the $LCD$ results to \begin{array}{l}\require{cancel} x^{\frac{2}{3}\cdot\frac{4}{4}-\frac{1}{4}\cdot\frac{3}{3}} \\\\= x^{\frac{8}{12}-\frac{3}{12}} \\\\= x^{\frac{5}{12}} \\\\= x^{5/12} .\end{array} | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9988040924072266, "perplexity": 505.63744563334683}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2018-43/segments/1539583508988.18/warc/CC-MAIN-20181015080248-20181015101748-00254.warc.gz"} |
http://www.denizyuret.com/2015/05/what-is-wrong-with-p-values.html | ## May 27, 2015
### What is wrong with p-values?
Earlier this year, editors of the journal Basic and Applied Social Psychology announced that the journal would no longer publish papers containing p-values. The latest American Psychological Association Publication Manual states that researchers should "wherever possible, base discussion and interpretation of results on point and interval estimates," i.e. not p-values. FDA has been encouraging Bayesian analysis. What is wrong with p-values?
What is a p-value? In the classical statistical procedure known as "significance testing", we have a default hypothesis, usually called the null hypothesis and denoted by H0, and we wish to determine whether or not to reject H0 based on some observations X. We choose a statistic S=f(X) (a scalar function of X) that summarizes our data. The p-value is the probability of observing a value at least as extreme as S under H0. We reject H0 if the p-value is below some specified small threshold like α=0.05 and we say something like "H0 is rejected at 0.05 significance level." This threshold or significance level (α) upper bounds the probability of false rejection, i.e. rejecting H0 when it is correct.
Example: We toss a coin 1000 times and observe 532 heads, 468 tails. Is this a fair coin? In this example the null hypothesis H0 is that the coin is fair, observation X is the sequence of heads and tails, and the statistic S is the number of heads. The p-value, or probability of S ∉ [469,531] under H0, can be calculated as: $1 - \sum_{k=469}^{531} {1000 \choose k} \left(\frac{1}{2}\right)^{1000} = 0.04629$ We can reject the null hypothesis at 0.05 significance level and decide the coin is biased. But should we?
Objection 1: (MacKay 2003, pp.63) What we would actually like to know is the probability of H0 given that we observed 532 heads. Unfortunately the p-value 0.04629 is not that probability (although this is a common confusion). We can't calculate a probability for H0 unless we specify some alternatives. Come to think of it, how can we reject a hypothesis if we don't look at what the alternatives are? What if the alternatives are worse? So let's specify a "biased coin" alternative (H1) which assumes that the head probability of the coin (θ) is distributed uniformly between 0 and 1 (other ways of specifying H1 are possible and do not effect the conclusion). We have: $P(S=532 \mid H_0) = {1000 \choose 532} \left(\frac{1}{2}\right)^{1000} = 0.003256$ $P(S=532 \mid H_1) = \int_0^1 {1000 \choose 532} \theta^{532} (1-\theta)^{468} d\theta = 0.001$ So H0 makes our data 3.2 times more likely than H1! And here the p-value almost made us think the data was 1:20 in favor of the "biased" hypothesis.
Objection 2: (Berger 1982, pp.13) Well, now that we understand p-value is not the probability of H0, does it tell us anything useful? According to the definition it limits the false rejection rate, i.e. if we always use significance tests with a p-value threshold α=0.01, we can be assured of incorrectly rejecting only 1% of correct hypotheses in the long run. So does that mean when I reject a null hypothesis I am only mistaken 1% of the time? Of course not! P(reject|correct) is 1%, P(correct|reject) can be anything! Here is an example:
X=1 X=2 H0 .01 .99 H1 .01001 .98999
The table gives the probabilities the two hypotheses H0 and H1 assign to different outcomes X=1 or X=2. Say we observe X=1. We reject H0 at α=0.01 significance level. But there is very little evidence against H0, the likelihood ratio P(X|H1)/P(X|H0) is very close to 1, so the chance of being in error is about 1/2 (assuming H0 and H1 are a-priori equally likely). Thus α=0.01 is providing a very misleading and false sense of security when rejection actually occurs.
Objection 3: (Murphy 2013, pp.213) Consider two experiments. In the first one we toss a coin 1000 times and observe 474 tails. Using T=474 as our statistic the one sided p-value is P(T≤474|H0): $\sum_{k=0}^{474} {1000 \choose k} \left(\frac{1}{2}\right)^{1000} = 0.05337$ So at a significance level of α=0.05 we do not reject the null hypothesis of an unbiased coin.
In the second experiment we toss the coin until we observe 474 tails, and it happens to take us 1000 trials. Different intention, same data. This time N=1000 is the natural test statistic and the one sided p-value is P(N≥1000|H0): $\sum_{n=1000}^\infty {n-1 \choose 473} \left(\frac{1}{2}\right)^n = 0.04994$ Suddenly we are below the magical α=0.05 threshold and we can reject the null hypothesis. The observed data, thus the likelihoods of any hypotheses for this data have not changed. The p-value is based not just on what actually happened, but what could have happened. This is clearly absurd.
Objection 4: (Cumming 2012) If we base the fate of our hypotheses on p-values computed from experiments, at the very least we should expect the p-values (thus our critical decisions) to change very little when we replicate the experiments. Unfortunately p-values do not even give us stability, as this wonderful video "Dance of the p values" by Geoff Cumming illustrates:
Conclusion: (Jaynes 2003, pp.524) expressed the absurdity of significance testing best:
In order to argue for an hypothesis H1 that some effect exists, one does it indirectly: invent a "null hypothesis" H0 that denies any such effect, then argue against H0 in a way that makes no reference to H1 at all (that is, using only probabilities conditional on H0). To see how far this procedure takes us from elementary logic, suppose we decide that the effect exists; that is, we reject H0. Surely, we must also reject probabilities conditional on H0; but then what was the logical justification for the decision? Orthodox logic saws off its own limb.
Harold Jeffreys (1939, p. 316) expressed his astonishment at such limb-sawing reasoning by looking at a different side of it: "An hypothesis that may be true is rejected because it has failed to predict observable results that have not occurred. This seems a remarkable procedure. On the face of it, the evidence might more reasonably be taken as evidence for the hypothesis, not against it." | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8699479699134827, "perplexity": 921.9959729496144}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-31/segments/1627046154175.76/warc/CC-MAIN-20210801092716-20210801122716-00327.warc.gz"} |
https://www.advanceduninstaller.com/NVIDIA-3D-Vision-Driver-296_43-da55bd7b7383e32f3733eca3faabc739-application.htm | # NVIDIA 3D Vision Driver 296.43
## A way to uninstall NVIDIA 3D Vision Driver 296.43 from your system
NVIDIA 3D Vision Driver 296.43 is a Windows program. Read more about how to remove it from your computer. It is produced by NVIDIA Corporation. More information on NVIDIA Corporation can be seen here. The program is usually placed in the C:\Program Files\NVIDIA Corporation\3D Vision folder. Take into account that this location can vary depending on the user's decision. C:\Windows\system32\RunDll32.EXE is the full command line if you want to uninstall NVIDIA 3D Vision Driver 296.43. NVIDIA 3D Vision Driver 296.43's main file takes about 1.57 MB (1643328 bytes) and is called nvstview.exe.
The executables below are part of NVIDIA 3D Vision Driver 296.43. They occupy an average of 14.07 MB (14749696 bytes) on disk.
• nvSCPAPISvr.exe (373.31 KB)
• NvStereoUtilityOGL.exe (868.81 KB)
• nvStInst.exe (576.81 KB)
• nvstlink.exe (890.31 KB)
• nvstreg.exe (420.31 KB)
• nvsttest.exe (2.25 MB)
• nvstview.exe (1.57 MB)
• nvstwiz.exe (7.20 MB)
...click to view all...
The information on this page is only about version 296.43 of NVIDIA 3D Vision Driver 296.43. After the uninstall process, the application leaves some files behind on the computer. Some of these are shown below.
Folders left behind when you uninstall NVIDIA 3D Vision Driver 296.43:
• C:\Program Files\NVIDIA Corporation\3D Vision
Generally, the following files remain on disk:
• C:\Program Files\NVIDIA Corporation\3D Vision\npnv3dv.dll
• C:\Program Files\NVIDIA Corporation\3D Vision\npnv3dvstreaming.dll
• C:\Program Files\NVIDIA Corporation\3D Vision\Nv3DVisionIePlugin.dll
• C:\Program Files\NVIDIA Corporation\3D Vision\Nv3DVisionIePlugin64.dll
• C:\Program Files\NVIDIA Corporation\3D Vision\Nv3DVStreaming.dll
• C:\Program Files\NVIDIA Corporation\3D Vision\Nv3DVStreaming64.dll
• C:\Program Files\NVIDIA Corporation\3D Vision\Nv3DVStreamingIePlugin.dll
• C:\Program Files\NVIDIA Corporation\3D Vision\Nv3DVStreamingIePlugin64.dll
• C:\Program Files\NVIDIA Corporation\3D Vision\nvimage.dll
• C:\Program Files\NVIDIA Corporation\3D Vision\nvimage64.dll
• C:\Program Files\NVIDIA Corporation\3D Vision\nvSCPAPI.dll
• C:\Program Files\NVIDIA Corporation\3D Vision\nvSCPAPI64.dll
• C:\Program Files\NVIDIA Corporation\3D Vision\nvSCPAPISvr.exe
• C:\Program Files\NVIDIA Corporation\3D Vision\nvstdef.reg
• C:\Program Files\NVIDIA Corporation\3D Vision\nvStereoApiI.dll
• C:\Program Files\NVIDIA Corporation\3D Vision\nvStereoApiI64.dll
• C:\Program Files\NVIDIA Corporation\3D Vision\NvStereoUtilityOGL.exe
• C:\Program Files\NVIDIA Corporation\3D Vision\nvStInst.exe
• C:\Program Files\NVIDIA Corporation\3D Vision\nvstlink.exe
• C:\Program Files\NVIDIA Corporation\3D Vision\nvstreg.exe
• C:\Program Files\NVIDIA Corporation\3D Vision\nvstres.dll
• C:\Program Files\NVIDIA Corporation\3D Vision\nvsttest.exe
• C:\Program Files\NVIDIA Corporation\3D Vision\nvstview.exe
• C:\Program Files\NVIDIA Corporation\3D Vision\nvstwiz.exe
• C:\Program Files\NVIDIA Corporation\3D Vision\nvtimings.ini
• C:\Program Files\NVIDIA Corporation\3D Vision\nvwl.dll
• C:\Program Files\NVIDIA Corporation\3D Vision\oglstreg.reg
Registry keys:
• HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Uninstall\{B2FE1952-0186-46C3-BAEC-A80AA35AC5B8}_Display.3DVision
Additional registry values that you should clean:
• HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Stereo Service\ImagePath
## How to remove NVIDIA 3D Vision Driver 296.43 from your computer with the help of Advanced Uninstaller PRO
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## Disclaimer
This page is not a piece of advice to uninstall NVIDIA 3D Vision Driver 296.43 by NVIDIA Corporation from your computer, nor are we saying that NVIDIA 3D Vision Driver 296.43 by NVIDIA Corporation is not a good application for your PC. This page only contains detailed info on how to uninstall NVIDIA 3D Vision Driver 296.43 supposing you want to. Here you can find registry and disk entries that Advanced Uninstaller PRO stumbled upon and classified as "leftovers" on other users' PCs.
2016-06-20 / Written by Dan Armano for Advanced Uninstaller PRO
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Last update on: 2016-06-20 19:34:49.417 | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9601238965988159, "perplexity": 25611.841305675396}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": false}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-18/segments/1555578531994.14/warc/CC-MAIN-20190421160020-20190421182020-00417.warc.gz"} |
http://mathhelpforum.com/advanced-algebra/95818-algebraic-geometry-elliptic-quartic-curve.html | ## Algebraic Geometry: Elliptic Quartic Curve
This is a problem about an elliptic quartic in $P^{3}$
$Y$ is defined by
$x^{2} - xz - yw = 0$ and
$yz - xw -zw = 0$
Let $P$ be the point $(0,0,0,1)$
Let $f$ be the projection from $P$ to the plane $w=0$.
I need to show that $f$ induces an isomorphism of $Y - P$ with the plane cubic curve $K$ defined by:
$zy^{2} - x^{3} + xz^{2}=0$
minus the point $Q:=(1,0,-1)$
The point of the exercise is to prove that $Y$ is irreducible and nonsingular. This follows after showing that $f$ is an isomorphism since then we can show that $K$ is irreducible and nonsingular which is straightforward.
I have been trying to show that $f(Y)$ is contained in $K$ and vice versa.
Am I correct to right the $f(Y)$ as the equations that define $Y$ with $w==0$?
if so $f(Y)= x^{2} - xz = 0 = yz$ (excluding the point $(0,0,0)$)
But the algebra is not working out for me. Is there another approach? | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 24, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9831420183181763, "perplexity": 90.60384691816633}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 20, "end_threshold": 5, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2015-11/segments/1424936462762.87/warc/CC-MAIN-20150226074102-00234-ip-10-28-5-156.ec2.internal.warc.gz"} |
http://mathhelpforum.com/calculus/22650-integral-problem.html | 1. ## Integral problem
Find f(x) if f(1) = -1 and the tangent line at (x, f(x)) has slope 2e^x + 1
This is a problem that was thrown into my indefinite integral homework, and I'm kinda stuck.
any help appreciated.
2. Originally Posted by leviathanwave
Find f(x) if f(1) = -1 and the tangent line at (x, f(x)) has slope 2e^x + 1
This is a problem that was thrown into my indefinite integral homework, and I'm kinda stuck.
any help appreciated.
the derivative gives the slope. thus if the slope at any $x$ is $2e^x + 1$ it means that:
$f'(x) = 2e^x + 1$
$\Rightarrow f(x) = \int f'(x)~dx$
and use the fact that $f(1) = -1$ to solve for the arbitrary constant of integration | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 5, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9943254590034485, "perplexity": 534.0216032262972}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 20, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368696382360/warc/CC-MAIN-20130516092622-00071-ip-10-60-113-184.ec2.internal.warc.gz"} |
https://openstax.org/books/intermediate-algebra-2e/pages/6-5-polynomial-equations | Intermediate Algebra 2e
# 6.5Polynomial Equations
Intermediate Algebra 2e6.5 Polynomial Equations
### Learning Objectives
By the end of this section, you will be able to:
• Use the Zero Product Property
• Solve quadratic equations by factoring
• Solve equations with polynomial functions
• Solve applications modeled by polynomial equations
Be Prepared 6.10
Before you get started, take this readiness quiz.
Solve: $5y−3=0.5y−3=0.$
If you missed this problem, review Example 2.2.
Be Prepared 6.11
Factor completely: $n3−9n2−22n.n3−9n2−22n.$
If you missed this problem, review Example 3.48.
Be Prepared 6.12
If $f(x)=8x−16,f(x)=8x−16,$ find $f(3)f(3)$ and solve $f(x)=0.f(x)=0.$
If you missed this problem, review Example 3.59.
We have spent considerable time learning how to factor polynomials. We will now look at polynomial equations and solve them using factoring, if possible.
A polynomial equation is an equation that contains a polynomial expression. The degree of the polynomial equation is the degree of the polynomial.
### Polynomial Equation
A polynomial equation is an equation that contains a polynomial expression.
The degree of the polynomial equation is the degree of the polynomial.
We have already solved polynomial equations of degree one. Polynomial equations of degree one are linear equations are of the form $ax+b=c.ax+b=c.$
We are now going to solve polynomial equations of degree two. A polynomial equation of degree two is called a quadratic equation. Listed below are some examples of quadratic equations:
$x2+5x+6=03y2+4y=1064u2−81=0n(n+1)=42x2+5x+6=03y2+4y=1064u2−81=0n(n+1)=42$
The last equation doesn’t appear to have the variable squared, but when we simplify the expression on the left we will get $n2+n.n2+n.$
The general form of a quadratic equation is $ax2+bx+c=0,ax2+bx+c=0,$ with $a≠0.a≠0.$ (If $a=0,a=0,$ then $0·x2=00·x2=0$ and we are left with no quadratic term.)
An equation of the form $ax2+bx+c=0ax2+bx+c=0$ is called a quadratic equation.
$a,b,andcare real numbers anda≠0a,b,andcare real numbers anda≠0$
To solve quadratic equations we need methods different from the ones we used in solving linear equations. We will look at one method here and then several others in a later chapter.
### Use the Zero Product Property
We will first solve some quadratic equations by using the Zero Product Property. The Zero Product Property says that if the product of two quantities is zero, then at least one of the quantities is zero. The only way to get a product equal to zero is to multiply by zero itself.
### Zero Product Property
If $a·b=0,a·b=0,$ then either $a=0a=0$ or $b=0b=0$ or both.
We will now use the Zero Product Property, to solve a quadratic equation.
### Example 6.44
#### How to Solve a Quadratic Equation Using the Zero Product Property
Solve: $(5n−2)(6n−1)=0.(5n−2)(6n−1)=0.$
Try It 6.87
Solve: $(3m−2)(2m+1)=0.(3m−2)(2m+1)=0.$
Try It 6.88
Solve: $(4p+3)(4p−3)=0.(4p+3)(4p−3)=0.$
### How To
#### Use the Zero Product Property.
1. Step 1. Set each factor equal to zero.
2. Step 2. Solve the linear equations.
3. Step 3. Check.
### Solve Quadratic Equations by Factoring
The Zero Product Property works very nicely to solve quadratic equations. The quadratic equation must be factored, with zero isolated on one side. So we must be sure to start with the quadratic equation in standard form, $ax2+bx+c=0.ax2+bx+c=0.$ Then we must factor the expression on the left.
### Example 6.45
#### How to Solve a Quadratic Equation by Factoring
Solve: $2y2=13y+45.2y2=13y+45.$
Try It 6.89
Solve: $3c2=10c−8.3c2=10c−8.$
Try It 6.90
Solve: $2d2−5d=3.2d2−5d=3.$
### How To
#### Solve a quadratic equation by factoring.
1. Step 1. Write the quadratic equation in standard form, $ax2+bx+c=0.ax2+bx+c=0.$
2. Step 2. Factor the quadratic expression.
3. Step 3. Use the Zero Product Property.
4. Step 4. Solve the linear equations.
5. Step 5. Check. Substitute each solution separately into the original equation.
Before we factor, we must make sure the quadratic equation is in standard form.
Solving quadratic equations by factoring will make use of all the factoring techniques you have learned in this chapter! Do you recognize the special product pattern in the next example?
### Example 6.46
Solve: $169q2=49.169q2=49.$
Try It 6.91
Solve: $25p2=49.25p2=49.$
Try It 6.92
Solve: $36x2=121.36x2=121.$
In the next example, the left side of the equation is factored, but the right side is not zero. In order to use the Zero Product Property, one side of the equation must be zero. We’ll multiply the factors and then write the equation in standard form.
### Example 6.47
Solve: $(3x−8)(x−1)=3x.(3x−8)(x−1)=3x.$
Try It 6.93
Solve: $(2m+1)(m+3)=12m.(2m+1)(m+3)=12m.$
Try It 6.94
Solve: $(k+1)(k−1)=8.(k+1)(k−1)=8.$
In the next example, when we factor the quadratic equation we will get three factors. However the first factor is a constant. We know that factor cannot equal 0.
### Example 6.48
Solve: $3x2=12x+63.3x2=12x+63.$
Try It 6.95
Solve: $18a2−30=−33a.18a2−30=−33a.$
Try It 6.96
Solve: $123b=−6−60b2.123b=−6−60b2.$
The Zero Product Property also applies to the product of three or more factors. If the product is zero, at least one of the factors must be zero. We can solve some equations of degree greater than two by using the Zero Product Property, just like we solved quadratic equations.
### Example 6.49
Solve: $9m3+100m=60m2.9m3+100m=60m2.$
Try It 6.97
Solve: $8x3=24x2−18x.8x3=24x2−18x.$
Try It 6.98
Solve: $16y2=32y3+2y.16y2=32y3+2y.$
### Solve Equations with Polynomial Functions
As our study of polynomial functions continues, it will often be important to know when the function will have a certain value or what points lie on the graph of the function. Our work with the Zero Product Property will be help us find these answers.
### Example 6.50
For the function $f(x)=x2+2x−2,f(x)=x2+2x−2,$
find x when $f(x)=6f(x)=6$ find two points that lie on the graph of the function.
Try It 6.99
For the function $f(x)=x2−2x−8,f(x)=x2−2x−8,$
find x when $f(x)=7f(x)=7$ Find two points that lie on the graph of the function.
Try It 6.100
For the function $f(x)=x2−8x+3,f(x)=x2−8x+3,$
find x when $f(x)=−4f(x)=−4$ Find two points that lie on the graph of the function.
The Zero Product Property also helps us determine where the function is zero. A value of x where the function is 0, is called a zero of the function.
### Zero of a Function
For any function f, if $f(x)=0,f(x)=0,$ then x is a zero of the function.
When $f(x)=0,f(x)=0,$ the point $(x,0)(x,0)$ is a point on the graph. This point is an x-intercept of the graph. It is often important to know where the graph of a function crosses the axes. We will see some examples later.
### Example 6.51
For the function $f(x)=3x2+10x−8,f(x)=3x2+10x−8,$ find
the zeros of the function, any x-intercepts of the graph of the function, any y-intercepts of the graph of the function
Try It 6.101
For the function $f(x)=2x2−7x+5,f(x)=2x2−7x+5,$ find
the zeros of the function, any x-intercepts of the graph of the function, any y-intercepts of the graph of the function.
Try It 6.102
For the function $f(x)=6x2+13x−15,f(x)=6x2+13x−15,$ find
the zeros of the function, any x-intercepts of the graph of the function, any y-intercepts of the graph of the function.
### Solve Applications Modeled by Polynomial Equations
The problem-solving strategy we used earlier for applications that translate to linear equations will work just as well for applications that translate to polynomial equations. We will copy the problem-solving strategy here so we can use it for reference.
### How To
#### Use a problem solving strategy to solve word problems.
1. Step 1. Read the problem. Make sure all the words and ideas are understood.
2. Step 2. Identify what we are looking for.
3. Step 3. Name what we are looking for. Choose a variable to represent that quantity.
4. Step 4. Translate into an equation. It may be helpful to restate the problem in one sentence with all the important information. Then, translate the English sentence into an algebraic equation.
5. Step 5. Solve the equation using appropriate algebra techniques.
6. Step 6. Check the answer in the problem and make sure it makes sense.
7. Step 7. Answer the question with a complete sentence.
We will start with a number problem to get practice translating words into a polynomial equation.
### Example 6.52
The product of two consecutive odd integers is 323. Find the integers.
Try It 6.103
The product of two consecutive odd integers is 255. Find the integers.
Try It 6.104
The product of two consecutive odd integers is 483 Find the integers.
Were you surprised by the pair of negative integers that is one of the solutions to the previous example? The product of the two positive integers and the product of the two negative integers both give positive results.
In some applications, negative solutions will result from the algebra, but will not be realistic for the situation.
### Example 6.53
A rectangular bedroom has an area 117 square feet. The length of the bedroom is four feet more than the width. Find the length and width of the bedroom.
Try It 6.105
A rectangular sign has an area of 30 square feet. The length of the sign is one foot more than the width. Find the length and width of the sign.
Try It 6.106
A rectangular patio has an area of 180 square feet. The width of the patio is three feet less than the length. Find the length and width of the patio.
In the next example, we will use the Pythagorean Theorem $(a2+b2=c2).(a2+b2=c2).$ This formula gives the relation between the legs and the hypotenuse of a right triangle.
We will use this formula to in the next example.
### Example 6.54
A boat’s sail is in the shape of a right triangle as shown. The hypotenuse will be 17 feet long. The length of one side will be 7 feet less than the length of the other side. Find the lengths of the sides of the sail.
Try It 6.107
Justine wants to put a deck in the corner of her backyard in the shape of a right triangle. The length of one side of the deck is 7 feet more than the other side. The hypotenuse is 13. Find the lengths of the two sides of the deck.
Try It 6.108
A meditation garden is in the shape of a right triangle, with one leg 7 feet. The length of the hypotenuse is one more than the length of the other leg. Find the lengths of the hypotenuse and the other leg.
The next example uses the function that gives the height of an object as a function of time when it is thrown from 80 feet above the ground.
### Example 6.55
Dennis is going to throw his rubber band ball upward from the top of a campus building. When he throws the rubber band ball from 80 feet above the ground, the function $h(t)=−16t2+64t+80h(t)=−16t2+64t+80$ models the height, h, of the ball above the ground as a function of time, t. Find:
the zeros of this function which tell us when the ball hits the ground, when the ball will be 80 feet above the ground, the height of the ball at $t=2t=2$ seconds.
Try It 6.109
Genevieve is going to throw a rock from the top a trail overlooking the ocean. When she throws the rock upward from 160 feet above the ocean, the function $h(t)=−16t2+48t+160h(t)=−16t2+48t+160$ models the height, h, of the rock above the ocean as a function of time, t. Find:
the zeros of this function which tell us when the rock will hit the ocean, when the rock will be 160 feet above the ocean, the height of the rock at $t=1.5t=1.5$ seconds.
Try It 6.110
Calib is going to throw his lucky penny from his balcony on a cruise ship. When he throws the penny upward from 128 feet above the ground, the function $h(t)=−16t2+32t+128h(t)=−16t2+32t+128$ models the height, h, of the penny above the ocean as a function of time, t. Find:
the zeros of this function which is when the penny will hit the ocean, when the penny will be 128 feet above the ocean, the height the penny will be at $t=1t=1$ seconds which is when the penny will be at its highest point.
### Media
Access this online resource for additional instruction and practice with quadratic equations.
### Section 6.5 Exercises
#### Practice Makes Perfect
Use the Zero Product Property
In the following exercises, solve.
277.
$(3a−10)(2a−7)=0(3a−10)(2a−7)=0$
278.
$(5b+1)(6b+1)=0(5b+1)(6b+1)=0$
279.
$6m(12m−5)=06m(12m−5)=0$
280.
$2x(6x−3)=02x(6x−3)=0$
281.
$(2x−1)2=0(2x−1)2=0$
282.
$(3y+5)2=0(3y+5)2=0$
In the following exercises, solve.
283.
$5a2−26a=245a2−26a=24$
284.
$4b2+7b=−34b2+7b=−3$
285.
$4m2=17m−154m2=17m−15$
286.
$n2=5n−6n2=5n−6$
287.
$7a2+14a=7a7a2+14a=7a$
288.
$12b2−15b=−9b12b2−15b=−9b$
289.
$49m2=14449m2=144$
290.
$625=x2625=x2$
291.
$16y2=8116y2=81$
292.
$64p2=22564p2=225$
293.
$121n2=36121n2=36$
294.
$100y2=9100y2=9$
295.
$(x+6)(x−3)=−8(x+6)(x−3)=−8$
296.
$(p−5)(p+3)=−7(p−5)(p+3)=−7$
297.
$(2x+1)(x−3)=−4x(2x+1)(x−3)=−4x$
298.
$(y−3)(y+2)=4y(y−3)(y+2)=4y$
299.
$(3x−2)(x+4)=12x(3x−2)(x+4)=12x$
300.
$(2y−3)(3y−1)=8y(2y−3)(3y−1)=8y$
301.
$20x2−60x=−4520x2−60x=−45$
302.
$3y2−18y=−273y2−18y=−27$
303.
$15x2−10x=4015x2−10x=40$
304.
$14y2−77y=−3514y2−77y=−35$
305.
$18x2−9=−21x18x2−9=−21x$
306.
$16y2+12=−32y16y2+12=−32y$
307.
$16p3=24p2–9p16p3=24p2–9p$
308.
$m3−2m2=−mm3−2m2=−m$
309.
$2x3+72x=24x22x3+72x=24x2$
310.
$3y3+48y=24y23y3+48y=24y2$
311.
$36x3+24x2=−4x36x3+24x2=−4x$
312.
$2y3+2y2=12y2y3+2y2=12y$
Solve Equations with Polynomial Functions
In the following exercises, solve.
313.
For the function, $f(x)=x2−8x+8,f(x)=x2−8x+8,$ find when $f(x)=−4f(x)=−4$ Use this information to find two points that lie on the graph of the function.
314.
For the function, $f(x)=x2+11x+20,f(x)=x2+11x+20,$ find when $f(x)=−8f(x)=−8$ Use this information to find two points that lie on the graph of the function.
315.
For the function, $f(x)=8x2−18x+5,f(x)=8x2−18x+5,$ find when $f(x)=−4f(x)=−4$ Use this information to find two points that lie on the graph of the function.
316.
For the function, $f(x)=18x2+15x−10,f(x)=18x2+15x−10,$ find when $f(x)=15f(x)=15$ Use this information to find two points that lie on the graph of the function.
In the following exercises, for each function, find: the zeros of the function the x-intercepts of the graph of the function the y-intercept of the graph of the function.
317.
$f(x)=9x2−4f(x)=9x2−4$
318.
$f(x)=25x2−49f(x)=25x2−49$
319.
$f(x)=6x2−7x−5f(x)=6x2−7x−5$
320.
$f(x)=12x2−11x+2f(x)=12x2−11x+2$
Solve Applications Modeled by Quadratic Equations
In the following exercises, solve.
321.
The product of two consecutive odd integers is 143. Find the integers.
322.
The product of two consecutive odd integers is 195. Find the integers.
323.
The product of two consecutive even integers is 168. Find the integers.
324.
The product of two consecutive even integers is 288. Find the integers.
325.
The area of a rectangular carpet is 28 square feet. The length is three feet more than the width. Find the length and the width of the carpet.
326.
A rectangular retaining wall has area 15 square feet. The height of the wall is two feet less than its length. Find the height and the length of the wall.
327.
The area of a bulletin board is 55 square feet. The length is four feet less than three times the width. Find the length and the width of the a bulletin board.
328.
A rectangular carport has area 150 square feet. The width of the carport is five feet less than twice its length. Find the width and the length of the carport.
329.
A pennant is shaped like a right triangle, with hypotenuse 10 feet. The length of one side of the pennant is two feet longer than the length of the other side. Find the length of the two sides of the pennant.
330.
A stained glass window is shaped like a right triangle. The hypotenuse is 15 feet. One leg is three more than the other. Find the lengths of the legs.
331.
A reflecting pool is shaped like a right triangle, with one leg along the wall of a building. The hypotenuse is 9 feet longer than the side along the building. The third side is 7 feet longer than the side along the building. Find the lengths of all three sides of the reflecting pool.
332.
A goat enclosure is in the shape of a right triangle. One leg of the enclosure is built against the side of the barn. The other leg is 4 feet more than the leg against the barn. The hypotenuse is 8 feet more than the leg along the barn. Find the three sides of the goat enclosure.
333.
Juli is going to launch a model rocket in her back yard. When she launches the rocket, the function $h(t)=−16t2+32th(t)=−16t2+32t$ models the height, h, of the rocket above the ground as a function of time, t. Find:
the zeros of this function, which tell us when the rocket will be on the ground. the time the rocket will be 16 feet above the ground.
334.
Gianna is going to throw a ball from the top floor of her middle school. When she throws the ball from 48 feet above the ground, the function $h(t)=−16t2+32t+48h(t)=−16t2+32t+48$ models the height, h, of the ball above the ground as a function of time, t. Find:
the zeros of this function which tells us when the ball will hit the ground. the time(s) the ball will be 48 feet above the ground. the height the ball will be at $t=1t=1$ seconds which is when the ball will be at its highest point.
#### Writing Exercises
335.
Explain how you solve a quadratic equation. How many answers do you expect to get for a quadratic equation?
336.
Give an example of a quadratic equation that has a GCF and none of the solutions to the equation is zero.
#### Self Check
After completing the exercises, use this checklist to evaluate your mastery of the objectives of this section.
Overall, after looking at the checklist, do you think you are well-prepared for the next section? Why or why not?
Order a print copy
As an Amazon Associate we earn from qualifying purchases. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 230, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.6292291283607483, "perplexity": 375.44339033427707}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 20, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-31/segments/1627046154897.82/warc/CC-MAIN-20210804174229-20210804204229-00599.warc.gz"} |
https://tvim.info/en/node/776 | # Стационарные характеристики однолинейной системы обслуживания с потерями и ненадежным прибором
Authors:
Semi-Markov model of operation of a single-server queue system with losses and unreliable server has been built. All the random values appearing in the problem definition are supposed to have general distribution functions. An explicit form of system stationary characteristics has been defined.
UDC:
519.873 | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8463340401649475, "perplexity": 5077.455841148129}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-21/segments/1620243989012.26/warc/CC-MAIN-20210509183309-20210509213309-00262.warc.gz"} |
https://worldwidescience.org/topicpages/a/acoustic+scattering.html | #### Sample records for acoustic scattering
1. Scattering Of Nonplanar Acoustic Waves
Science.gov (United States)
Gillman, Judith M.; Farassat, F.; Myers, M. K.
1995-01-01
Report presents theoretical study of scattering of nonplanar acoustic waves by rigid bodies. Study performed as part of effort to develop means of predicting scattering, from aircraft fuselages, of noise made by rotating blades. Basic approach was to model acoustic scattering by use of boundary integral equation to solve equation by the Galerkin method.
2. Scattering of Acoustic Waves from Ocean Boundaries
Science.gov (United States)
2015-09-30
at the Target and Reverberation Experiment 2013 (TREX13),” in Proc. IEEE/OES Acoustics in Underwater Geosciences Symposium, Rio de Janeiro , Brazil...a Sandy Seabed at the Target and Reverberation Experiment 2013 (TREX13),” in Proc. IEEE/OES Acoustics in Underwater Geosciences Symposium, Rio de ... Janeiro , Brazil, July 2015. PRESENTATIONS Presenter: Isakson, M.J., Chotiros, N.P., Piper, J.N. and McNeese, A. “Acoustic Scattering from a Sandy Seabed
3. Inverse acoustic problem of N homogeneous scatterers
DEFF Research Database (Denmark)
Berntsen, Svend
2002-01-01
The three-dimensional inverse acoustic medium problem of N homogeneous objects with known geometry and location is considered. It is proven that one scattering experiment is sufficient for the unique determination of the complex wavenumbers of the objects. The mapping from the scattered fields...
4. Acoustic scattering on spheroidal shapes near boundaries
Science.gov (United States)
Miloh, Touvia
2016-11-01
A new expression for the Lamé product of prolate spheroidal wave functions is presented in terms of a distribution of multipoles along the axis of the spheroid between its foci (generalizing a corresponding theorem for spheroidal harmonics). Such an "ultimate" singularity system can be effectively used for solving various linear boundary-value problems governed by the Helmholtz equation involving prolate spheroidal bodies near planar or other boundaries. The general methodology is formally demonstrated for the axisymmetric acoustic scattering problem of a rigid (hard) spheroid placed near a hard/soft wall or inside a cylindrical duct under an axial incidence of a plane acoustic wave.
5. Support minimized inversion of acoustic and elastic wave scattering
International Nuclear Information System (INIS)
Safaeinili, A.
1994-01-01
This report discusses the following topics on support minimized inversion of acoustic and elastic wave scattering: Minimum support inversion; forward modelling of elastodynamic wave scattering; minimum support linearized acoustic inversion; support minimized nonlinear acoustic inversion without absolute phase; and support minimized nonlinear elastic inversion
6. Acoustic scattering by multiple elliptical cylinders using collocation multipole method
International Nuclear Information System (INIS)
Lee, Wei-Ming
2012-01-01
This paper presents the collocation multipole method for the acoustic scattering induced by multiple elliptical cylinders subjected to an incident plane sound wave. To satisfy the Helmholtz equation in the elliptical coordinate system, the scattered acoustic field is formulated in terms of angular and radial Mathieu functions which also satisfy the radiation condition at infinity. The sound-soft or sound-hard boundary condition is satisfied by uniformly collocating points on the boundaries. For the sound-hard or Neumann conditions, the normal derivative of the acoustic pressure is determined by using the appropriate directional derivative without requiring the addition theorem of Mathieu functions. By truncating the multipole expansion, a finite linear algebraic system is derived and the scattered field can then be determined according to the given incident acoustic wave. Once the total field is calculated as the sum of the incident field and the scattered field, the near field acoustic pressure along the scatterers and the far field scattering pattern can be determined. For the acoustic scattering of one elliptical cylinder, the proposed results match well with the analytical solutions. The proposed scattered fields induced by two and three elliptical–cylindrical scatterers are critically compared with those provided by the boundary element method to validate the present method. Finally, the effects of the convexity of an elliptical scatterer, the separation between scatterers and the incident wave number and angle on the acoustic scattering are investigated.
7. High frequency and pulse scattering physical acoustics
CERN Document Server
Pierce, Allan D
1992-01-01
High Frequency and Pulse Scattering investigates high frequency and pulse scattering, with emphasis on the phenomenon of echoes from objects. Geometrical and catastrophe optics methods in scattering are discussed, along with the scattering of sound pulses and the ringing of target resonances. Caustics and associated diffraction catastrophes are also examined.Comprised of two chapters, this volume begins with a detailed account of geometrically based approximation methods in scattering theory, focusing on waves transmitted through fluid and elastic scatterers and glory scattering; surface ray r
8. Scattering of acoustic waves by small crustaceans
Science.gov (United States)
Andreeva, I. B.; Tarasov, L. L.
2003-03-01
Features of underwater sound scattering by small crustaceans are considered. The scattering data are obtained with the use of unique instrumentation that allows one to measure quantitative scattering characteristics (backscattering cross sections and angular scattering patterns) for crustaceans of different sizes, at different frequencies (20 200 kHz) and different insonification aspects. A computational model of crustaceans is considered with allowance for both the soft tissues of the main massive part of the animal's body and the stiff armour. The model proves to be advantageous for explaining some scattering features observed in the experiments. The scattering cross sections of crustaceans measured by other researchers are presented in a unified form appropriate for comparison. Based on such a quantitative comparison, relatively simple approximate empirical formulas are proposed for estimating the backscattering cross sections of small (within several centimeters) marine crustaceans in a broad frequency range.
9. Scattering from objects and surfaces in room acoustical simulations
DEFF Research Database (Denmark)
Marbjerg, Gerd Høy; Brunskog, Jonas; Jeong, Cheol-Ho
2016-01-01
been implemented in the simulation tool PARISM (Phased Acoustical Radiosity and Image Source Method). Scattering from objects and surfaces is likely to be strongly frequency dependent and the frequency dependence can depend on their sizes, shapes and structure. The importance of the frequency...
10. Sound field reproduction as an equivalent acoustical scattering problem.
Science.gov (United States)
Fazi, Filippo Maria; Nelson, Philip A
2013-11-01
Given a continuous distribution of acoustic sources, the determination of the source strength that ensures the synthesis of a desired sound field is shown to be identical to the solution of an equivalent acoustic scattering problem. The paper begins with the presentation of the general theory that underpins sound field reproduction with secondary sources continuously arranged on the boundary of the reproduction region. The process of reproduction by a continuous source distribution is modeled by means of an integral operator (the single layer potential). It is then shown how the solution of the sound reproduction problem corresponds to that of an equivalent scattering problem. Analytical solutions are computed for two specific instances of this problem, involving, respectively, the use of a secondary source distribution in spherical and planar geometries. The results are shown to be the same as those obtained with analyses based on High Order Ambisonics and Wave Field Synthesis, respectively, thus bringing to light a fundamental analogy between these two methods of sound reproduction. Finally, it is shown how the physical optics (Kirchhoff) approximation enables the derivation of a high-frequency simplification for the problem under consideration, this in turn being related to the secondary source selection criterion reported in the literature on Wave Field Synthesis.
11. Coherent scattering of CO2 light from ion-acoustic waves
International Nuclear Information System (INIS)
Peratt, A.L.; Watterson, R.L.; Derfler, H.
1977-01-01
Scattering of laser radiation from ion-acoustic waves in a plasma is investigated analytically and experimentally. The formulation predicts a coherent component of the scattered power on a largely incoherent background spectrum when the acoustic analog of Bragg's law and Doppler shift conditions are satisfied. The experiment consists of a hybrid CO 2 laser system capable of either low power continuous wave or high power pulsed mode operation. A heterodyne light mixing scheme is used to detect the scattered power. The proportionality predicted by the theory is verified by scattering from externally excited acoustic and ion-acoustic waves; continuous wave and pulsed modes in each case. Measurement of the ion-acoustic dispersion relation by continuous wave scattering is also presented
12. Support Minimized Inversion of Acoustic and Elastic Wave Scattering
Science.gov (United States)
Safaeinili, Ali
Inversion of limited data is common in many areas of NDE such as X-ray Computed Tomography (CT), Ultrasonic and eddy current flaw characterization and imaging. In many applications, it is common to have a bias toward a solution with minimum (L^2)^2 norm without any physical justification. When it is a priori known that objects are compact as, say, with cracks and voids, by choosing "Minimum Support" functional instead of the minimum (L^2)^2 norm, an image can be obtained that is equally in agreement with the available data, while it is more consistent with what is most probably seen in the real world. We have utilized a minimum support functional to find a solution with the smallest volume. This inversion algorithm is most successful in reconstructing objects that are compact like voids and cracks. To verify this idea, we first performed a variational nonlinear inversion of acoustic backscatter data using minimum support objective function. A full nonlinear forward model was used to accurately study the effectiveness of the minimized support inversion without error due to the linear (Born) approximation. After successful inversions using a full nonlinear forward model, a linearized acoustic inversion was developed to increase speed and efficiency in imaging process. The results indicate that by using minimum support functional, we can accurately size and characterize voids and/or cracks which otherwise might be uncharacterizable. An extremely important feature of support minimized inversion is its ability to compensate for unknown absolute phase (zero-of-time). Zero-of-time ambiguity is a serious problem in the inversion of the pulse-echo data. The minimum support inversion was successfully used for the inversion of acoustic backscatter data due to compact scatterers without the knowledge of the zero-of-time. The main drawback to this type of inversion is its computer intensiveness. In order to make this type of constrained inversion available for common use, work
13. Acoustic characteristics of urban streets in relation to scattering caused by building facades
DEFF Research Database (Denmark)
Onaga, Hiroshi; Rindel, Jens Holger
2007-01-01
The relationship between scattering and the acoustic characteristics of urban streets is examined by computer simulation. The simulation method is a combination of the image method for specular reflection and the radiosity method for scattering reflection. The findings are as follows: (1) the eff......The relationship between scattering and the acoustic characteristics of urban streets is examined by computer simulation. The simulation method is a combination of the image method for specular reflection and the radiosity method for scattering reflection. The findings are as follows: (1...
14. RAMAN SCATTERING BY ACOUSTIC PHONONS AND STRUCTURAL PROPERTIES OF FIBONACCI, THUE-MORSE AND RANDOM SUPERLATTICES
OpenAIRE
Merlin , R.; Bajema , K.; Nagle , J.; Ploog , K.
1987-01-01
We report structural studies of incommensurate and random GaAs-AlAs superlattices using Raman scattering by acoustic phonons. Properties of the structure factor of Fibonacci and Thue-Morse superlattices are discussed in some detail.
15. Global effects of moon phase on nocturnal acoustic scattering layers
KAUST Repository
Prihartato, PK
2016-01-18
© Inter-Research 2016. The impact of moon phase on the global nocturnal vertical distribution of acoustic scattering layers (SLs) in the upper 200 m was studied during the Malaspina expedition that circumnavigated the world. We assessed the nocturnal weighted mean depths and the vertical extension of the SL (the range between the upper 25th percentile and lower 75th percentile of the backscatter) and used a generalized additive model to reveal the relationship between the nocturnal vertical distribution of the SL and moon phase, as well as other environmental factors. Moon phase significantly affected the SL distribution on a global scale, in contrast to other factors such as dissolved oxygen, temperature and fluorescence, which each correlated with nocturnal SL distribution during the large geographic coverage. Full moon caused a deepening effect on the nocturnal SL. Contrary to expectations, the shallowest distribution was not observed during the darkest nights (new moon) and there was no difference in vertical distribution between new moon and intermediate moon phases. We conclude that the trend of deepening SL during approximately full moon (bright nights) is a global phenomenon related to anti-predator behavior.
16. Global effects of moon phase on nocturnal acoustic scattering layers
KAUST Repository
Prihartato, Perdana; Irigoien, Xabier; Genton, Marc G.; Kaartvedt, Stein
2016-01-01
© Inter-Research 2016. The impact of moon phase on the global nocturnal vertical distribution of acoustic scattering layers (SLs) in the upper 200 m was studied during the Malaspina expedition that circumnavigated the world. We assessed the nocturnal weighted mean depths and the vertical extension of the SL (the range between the upper 25th percentile and lower 75th percentile of the backscatter) and used a generalized additive model to reveal the relationship between the nocturnal vertical distribution of the SL and moon phase, as well as other environmental factors. Moon phase significantly affected the SL distribution on a global scale, in contrast to other factors such as dissolved oxygen, temperature and fluorescence, which each correlated with nocturnal SL distribution during the large geographic coverage. Full moon caused a deepening effect on the nocturnal SL. Contrary to expectations, the shallowest distribution was not observed during the darkest nights (new moon) and there was no difference in vertical distribution between new moon and intermediate moon phases. We conclude that the trend of deepening SL during approximately full moon (bright nights) is a global phenomenon related to anti-predator behavior.
17. Guided Acoustic and Optical Waves in Silicon-on-Insulator for Brillouin Scattering and Optomechanics
Science.gov (United States)
2016-08-01
APL PHOTONICS 1, 071301 (2016) Guided acoustic and optical waves in silicon-on- insulator for Brillouin scattering and optomechanics Christopher J...is possible to simultaneously guide optical and acoustic waves in the technologically important silicon on insulator (SOI) material system. Thin...high sound velocity — makes guiding acoustic waves difficult, motivating the use of soft chalcogenide glasses and partial or complete releases (removal
18. Axisymmetric scattering of an acoustical Bessel beam by a rigid fixed spheroid
OpenAIRE
Mitri, F. G.
2015-01-01
Based on the partial-wave series expansion (PWSE) method in spherical coordinates, a formal analytical solution for the acoustic scattering of a zeroth-order Bessel acoustic beam centered on a rigid fixed (oblate or prolate) spheroid is provided. The unknown scattering coefficients of the spheroid are determined by solving a system of linear equations derived for the Neumann boundary condition. Numerical results for the modulus of the backscattered pressure (\\theta = \\pi) in the near-field an...
19. Evanescent Acoustic Wave Scattering by Targets and Diffraction by Ripples Graduate Traineeship Award in Ocean Acoustics
National Research Council Canada - National Science Library
Osterhoudt, Curtis F; Marston, Philip L
2007-01-01
.... The purpose of his research was to improve the understanding of the way that acoustic evanescent waves interact with targets buried in sediments in situations encountered in underwater acoustics...
20. Acoustic Estimates of Distribution and Biomass of Different Acoustic Scattering Types Between the New England Shelf Break and Slope Waters
KAUST Repository
McLaren, Alexander
2011-11-01
Due to their great ecological significance, mesopelagic fishes are attracting a wider audience on account of the large biomass they represent. Data from the National Marine Fisheries Service (NMFS) provided the opportunity to explore an unknown region of the North-West Atlantic, adjacent to one of the most productive fisheries in the world. Acoustic data collected during the cruise required the identification of acoustically distinct scattering types to make inferences on the migrations, distributions and biomass of mesopelagic scattering layers. Six scattering types were identified by the proposed method in our data and traces their migrations and distributions in the top 200m of the water column. This method was able to detect and trace the movements of three scattering types to 1000m depth, two of which can be further subdivided. This process of identification enabled the development of three physically-derived target-strength models adapted to traceable acoustic scattering types for the analysis of biomass and length distribution to 1000m depth. The abundance and distribution of acoustic targets varied closely in relation to varying physical environments associated with a warm core ring in the New England continental Shelf break region. The continental shelf break produces biomass density estimates that are twice as high as the warm core ring and the surrounding continental slope waters are an order of magnitude lower than either estimate. Biomass associated with distinct layers is assessed and any benefits brought about by upwelling at the edge of the warm core ring are shown not to result in higher abundance of deepwater species. Finally, asymmetric diurnal migrations in shelf break waters contrasts markedly with the symmetry of migrating layers within the warm ring, both in structure and density estimates, supporting a theory of predatorial and nutritional constraints to migrating pelagic species.
1. Acoustical Scattering, Propagation, and Attenuation Caused by Two Abundant Pacific Schooling Species: Humboldt Squid and Hake
Science.gov (United States)
2015-09-30
an area important for acoustical testing and tactical exercises, the most abundant species by biomass is Pacific hake, Merluccius productus, a fish...scattering characteristics of the animal especially if the animal has eaten hard- shelled mollusc prey. Figure 7. A dorsal scan (similar to an x-ray) of a...kHz echogram. 11 In order to generate abundance and biomass estimates for organisms using active acoustics, one assumption that can be made is
2. Arbitrary scattering of an acoustical Bessel beam by a rigid spheroid with large aspect-ratio
Science.gov (United States)
Gong, Zhixiong; Li, Wei; Mitri, Farid G.; Chai, Yingbin; Zhao, Yao
2016-11-01
In this paper, the T-matrix (null-field) method is applied to investigate the acoustic scattering by a large-aspect-ratio rigid spheroid immersed in a non-viscous fluid under the illumination of an unbounded zeroth-order Bessel beam with arbitrary orientation. Based on the proposed method, a MATLAB software package is constructed accordingly, and then verified and validated to compute the acoustic scattering by a rigid oblate or prolate spheroid in the Bessel beam. Several numerical examples are carried out to investigate the novel phenomenon of acoustic scattering by spheroids in Bessel beams with arbitrary incidence, with particular emphasis on the aspect ratio (i.e. the ratio of the polar radius over the equatorial radius of the spheroid), the half-cone angle of Bessel beam, the dimensionless frequency, as well as the angle of incidence. The quasi-periodic oscillations are observed in the plots of the far-field backscattering form function modulus versus the dimensionless frequency, owing to the interference between the specular reflection and the Franz wave circumnavigating the spheroid in the surrounding fluid. Furthermore, the 3D far-field scattering directivity patterns at end-on incidence and 2D polar plots at arbitrary angles of incidence are exhibited, which could provide new insights into the physical mechanisms of Bessel beam scattering by flat or elongated spheroid. This research work may provide an impetus for the application of acoustic Bessel beam in engineering practices.
3. Acoustic Wave Dispersion and Scattering in Complex Marine Sediment Structures
Science.gov (United States)
2018-03-21
slides) versus scattering from discrete particles (e.g., rocks, shells, or bubbles). Measurements are needed to 1) exploit the volume scattering theory...Developed theory and methodology to distinguish between the two major classes of volume heterogeneities, discrete particles or a fluctuation...reflection to obtain a quasi -three-dimensional map of sediment sound speed. The sound speed is obtained over a 2 km x 2 km area of high variability
4. Plasma characterization using ultraviolet Thomson scattering from ion-acoustic and electron plasma waves (invited)
Energy Technology Data Exchange (ETDEWEB)
Follett, R. K., E-mail: [email protected]; Delettrez, J. A.; Edgell, D. H.; Henchen, R. J.; Katz, J.; Myatt, J. F.; Froula, D. H. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States)
2016-11-15
Collective Thomson scattering is a technique for measuring the plasma conditions in laser-plasma experiments. Simultaneous measurements of ion-acoustic and electron plasma-wave spectra were obtained using a 263.25-nm Thomson-scattering probe beam. A fully reflective collection system was used to record light scattered from electron plasma waves at electron densities greater than 10{sup 21} cm{sup −3}, which produced scattering peaks near 200 nm. An accurate analysis of the experimental Thomson-scattering spectra required accounting for plasma gradients, instrument sensitivity, optical effects, and background radiation. Practical techniques for including these effects when fitting Thomson-scattering spectra are presented and applied to the measured spectra to show the improvements in plasma characterization.
5. Interior and exterior resonances in acoustic scattering. pt. 1 - spherical targets
International Nuclear Information System (INIS)
Gaunaurd, G.C.; Tanglis, E.; Uberall, H.; Brill, D.
1983-01-01
In acoustic scattering from elastic objects, resonance features appear in the returned echo at frequencies at which the object's eigenfrequencies are located, which are explained by the excitation of 'interior' creeping waves. Corresponding resonance terms may be split off from the total scattering amplitude, leaving behind an apparently nonresonant background amplitude. This is demonstrated here for scatterers of spherical geometry and in a companion paper also for scatterers of arbitrary geometry, by using the T-matrix approach. For the case of near-impenetrable spheres, it is subsequently shown that the background amplitude can be split further into specularly reflected contributions, plus highly attenuated resonance terms which are explained by the excitation of 'exterior' (Franz-type) creeping waves. The singularity structure of the scattering function is shown mathematically, by using the R-matrix approach of the nuclear-scattering theory, as that of a meromorphic function 'without' any additional 'entire function' (as had been postulated by the singularity expansion method)
6. Quality factor due to roughness scattering of shear horizontal surface acoustic waves in nanoresonators
NARCIS (Netherlands)
Palasantzas, G.
2008-01-01
In this work we study the quality factor associated with dissipation due to scattering of shear horizontal surface acoustic waves by random self-affine roughness. It is shown that the quality factor is strongly influenced by both the surface roughness exponent H and the roughness amplitude w to
7. Temperature dependence of Brillouin light scattering spectra of acoustic phonons in silicon
International Nuclear Information System (INIS)
Olsson, Kevin S.; Klimovich, Nikita; An, Kyongmo; Sullivan, Sean; Weathers, Annie; Shi, Li; Li, Xiaoqin
2015-01-01
Electrons, optical phonons, and acoustic phonons are often driven out of local equilibrium in electronic devices or during laser-material interaction processes. The need for a better understanding of such non-equilibrium transport processes has motivated the development of Raman spectroscopy as a local temperature sensor of optical phonons and intermediate frequency acoustic phonons, whereas Brillouin light scattering (BLS) has recently been explored as a temperature sensor of low-frequency acoustic phonons. Here, we report the measured BLS spectra of silicon at different temperatures. The origins of the observed temperature dependence of the BLS peak position, linewidth, and intensity are examined in order to evaluate their potential use as temperature sensors for acoustic phonons
8. Physics of the ion acoustic wave driven by the stimulated Brillouin scattering instability
International Nuclear Information System (INIS)
Clayton, C.E.
1984-01-01
The ion acoustic wave excited in the stimulated Brillouin scattering (SBS) instability is probed via collective ruby-laser Thomson scattering in order to understand the low saturation level observed in the instability. Many of the features observed in the Brillouin backscattered CO 2 laser light from the underdense gas-target plasma are also observed in the Thomson scattered ruby light - from which it is learned that the ion acoustic wave grows exponentially and then saturates as the CO 2 pump power is increased. The primary advantage of the ruby Thomson scattering diagnostic is in its capability of providing simultaneous space and time resolved measurements of the ion wave amplitude. From these first such detailed measurements, it was found that the ion wave grows exponentially in space at a rate that agrees with the linear convective SBS theory. However, at higher pump powers, the ion wave saturates at an inferred amplitude of anti-n/n 0 approx. = 5 to 10%. Further increases in the pump power appear to result in an increase in the length over which the ion wave is saturated. A nearly constant SBS reflectivity in this saturated regime, however, suggests that the saturated ion wave does not contribute as much to the scattered power as would be expected from Bragg scattering theory. This apparent contradiction can be resolved if ion trapping is responsible for the saturation of the ion wave
9. Acoustic scattering by arbitrary distributions of disjoint, homogeneous cylinders or spheres.
Science.gov (United States)
Hesford, Andrew J; Astheimer, Jeffrey P; Waag, Robert C
2010-05-01
A T-matrix formulation is presented to compute acoustic scattering from arbitrary, disjoint distributions of cylinders or spheres, each with arbitrary, uniform acoustic properties. The generalized approach exploits the similarities in these scattering problems to present a single system of equations that is easily specialized to cylindrical or spherical scatterers. By employing field expansions based on orthogonal harmonic functions, continuity of pressure and normal particle velocity are directly enforced at each scatterer using diagonal, analytic expressions to eliminate the need for integral equations. The effect of a cylinder or sphere that encloses all other scatterers is simulated with an outer iterative procedure that decouples the inner-object solution from the effect of the enclosing object to improve computational efficiency when interactions among the interior objects are significant. Numerical results establish the validity and efficiency of the outer iteration procedure for nested objects. Two- and three-dimensional methods that employ this outer iteration are used to measure and characterize the accuracy of two-dimensional approximations to three-dimensional scattering of elevation-focused beams.
10. Guided acoustic and optical waves in silicon-on-insulator for Brillouin scattering and optomechanics
Directory of Open Access Journals (Sweden)
Christopher J. Sarabalis
2016-10-01
Full Text Available We numerically study silicon waveguides on silica showing that it is possible to simultaneously guide optical and acoustic waves in the technologically important silicon on insulator (SOI material system. Thin waveguides, or fins, exhibit geometrically softened mechanical modes at gigahertz frequencies with phase velocities below the Rayleigh velocity in glass, eliminating acoustic radiation losses. We propose slot waveguides on glass with telecom optical frequencies and strong radiation pressure forces resulting in Brillouin gains on the order of 500 and 50 000 W−1m−1 for backward and forward Brillouin scattering, respectively.
11. Axisymmetric scattering of an acoustical Bessel beam by a rigid fixed spheroid.
Science.gov (United States)
Mitri, Farid G
2015-10-01
Based on the partial-wave series expansion (PWSE) method in spherical coordinates, a formal analytical solution for the acoustic scattering of a zeroth-order Bessel acoustic beam centered on a rigid fixed (oblate or prolate) spheroid is provided. The unknown scattering coefficients of the spheroid are determined by solving a system of linear equations derived for the Neumann boundary condition. Numerical results for the modulus of the backscattered pressure (θ = π) in the near field and the backscattering form function in the far field for both prolate and oblate spheroids are presented and discussed, with particular emphasis on the aspect ratio (i.e., the ratio of the major axis over the minor axis of the spheroid), the half-cone angle of the Bessel beam, and the dimensionless frequency. The plots display periodic oscillations (versus the dimensionless frequency) because of the interference of specularly reflected waves in the backscattering direction with circumferential Franz' waves circumnavigating the surface of the spheroid in the surrounding fluid. Moreover, the 3-D directivity patterns illustrate the near- and far-field axisymmetric scattering. Investigations in underwater acoustics, particle levitation, scattering, and the detection of submerged elongated objects and other related applications utilizing Bessel waves would benefit from the results of the present study.
12. Tunneling effects in resonant acoustic scattering of an air bubble in unbounded water
Directory of Open Access Journals (Sweden)
ANDRÉ G. SIMÃO
2016-06-01
Full Text Available Abstract The problem of acoustic scattering of a gaseous spherical bubble immersed within unbounded liquid surrounding is considered in this work. The theory of partial wave expansion related to this problem is revisited. A physical model based on the analogy between acoustic scattering and potential scattering in quantum mechanics is proposed to describe and interpret the acoustical natural oscillation modes of the bubble, namely, the resonances. In this context, a physical model is devised in order to describe the air water interface and the implications of the high density contrast on the various regimes of the scattering resonances. The main results are presented in terms of resonance lifetime periods and quality factors. The explicit numerical calculations are undertaken through an asymptotic analysis considering typical bubble dimensions and underwater sound wavelengths. It is shown that the resonance periods are scaled according to the Minnaert’s period, which is the short lived resonance mode, called breathing mode of the bubble. As expected, resonances with longer lifetimes lead to impressive cavity quality Q-factor ranging from 1010 to 105. The present theoretical findings lead to a better understanding of the energy storage mechanism in a bubbly medium.
13. Classification of underwater targets from autonomous underwater vehicle sampled bistatic acoustic scattered fields.
Science.gov (United States)
Fischell, Erin M; Schmidt, Henrik
2015-12-01
One of the long term goals of autonomous underwater vehicle (AUV) minehunting is to have multiple inexpensive AUVs in a harbor autonomously classify hazards. Existing acoustic methods for target classification using AUV-based sensing, such as sidescan and synthetic aperture sonar, require an expensive payload on each outfitted vehicle and post-processing and/or image interpretation. A vehicle payload and machine learning classification methodology using bistatic angle dependence of target scattering amplitudes between a fixed acoustic source and target has been developed for onboard, fully autonomous classification with lower cost-per-vehicle. To achieve the high-quality, densely sampled three-dimensional (3D) bistatic scattering data required by this research, vehicle sampling behaviors and an acoustic payload for precision timed data acquisition with a 16 element nose array were demonstrated. 3D bistatic scattered field data were collected by an AUV around spherical and cylindrical targets insonified by a 7-9 kHz fixed source. The collected data were compared to simulated scattering models. Classification and confidence estimation were shown for the sphere versus cylinder case on the resulting real and simulated bistatic amplitude data. The final models were used for classification of simulated targets in real time in the LAMSS MOOS-IvP simulation package [M. Benjamin, H. Schmidt, P. Newman, and J. Leonard, J. Field Rob. 27, 834-875 (2010)].
14. Feasibility of Ocean Acoustic Waveguide Remote Sensing (OAWRS of Atlantic Cod with Seafloor Scattering Limitations
Directory of Open Access Journals (Sweden)
Ankita D. Jain
2013-12-01
Full Text Available Recently reported declines in the population of Atlantic cod have led to calls for additional survey methods for stock assessments. In combination with conventional line-transect methods that may have ambiguities in sampling fish populations, Ocean Acoustic Waveguide Remote Sensing (OAWRS has been shown to have a potential for providing accurate stock assessments (Makris N.C., et al. Science 2009, 323, 1,734–1,737; 54th Northeast Regional Stock Assessment Workshop (54th SAW US Department of Commerce, Northeast Fisheries Science Center, 2012. The use of OAWRS technology enables instantaneous wide-area sensing of fish aggregations over thousands of square kilometers. The ratio of the intensity of scattered returns from fish versus the seafloor in any resolution cell typically determines the maximum fish detection range of OAWRS, which then is a function of fish population density, scattering amplitude and depth distribution, as well as the level of seafloor scattering. With the knowledge of oceanographic parameters, such as bathymetry, sound speed structure and attenuation, we find that a Rayleigh–Born volume scattering approach can be used to efficiently and accurately estimate seafloor scattering over wide areas. From hundreds of OAWRS measurements of seafloor scattering, we determine the Rayleigh–Born scattering amplitude of the seafloor, which we find has a ƒ2,4 frequency dependence below roughly 2 kHz in typical continental shelf environments along the US northeast coast. We then find that it is possible to robustly detect cod aggregations across frequencies at and near swim bladder resonance for observed spawningconfigurations along the U.S. northeast coast, roughly the two octave range 150–600 Hzfor water depths up to roughly 100 m. This frequency range is also optimal for long-rangeocean acoustic waveguide propagation, because it enables multimodal acoustic waveguidepropagation with minimal acoustic absorption and forward
15. Multiple scattering formulation of two-dimensional acoustic and electromagnetic metamaterials
Energy Technology Data Exchange (ETDEWEB)
Torrent, Daniel; Sanchez-Dehesa, Jose, E-mail: [email protected], E-mail: [email protected] [Grupo de Fenomenos Ondulatorios, Departamento de IngenierIa Electronica, Universitat Politecnica de Valencia, Camino de Vera s/n (Edificio 7F), ES-46022 Valencia (Spain)
2011-09-15
A multiple scattering formulation of two-dimensional (2D) acoustic metamaterials is presented. This approach is comprehensive and can lead to frequency-dependent effective parameters (scalar bulk modulus and tensorial mass density), as it is possible to have not only positive or negative ellipsoidal refractive index, but also positive or negative hyperbolic refractive index. The correction due to multiple scattering interactions is included in the theory and it is demonstrated that its contribution is important only for lattices with high filling fractions. Since the surface fields on the scatterers are mainly responsible for the anomalous behavior of the resulting effective medium, complex scatterers can be used to engineer the frequency response. Anisotropic effects are also discussed within this formulation and some numerical examples are reported. A homogenization theory is also extended to electromagnetic wave propagation in 2D lattices of dielectric structures, where Mie resonances are found to be responsible for the metamaterial behavior.
16. Vertical distribution, composition and migratory patterns of acoustic scattering layers in the Canary Islands
KAUST Repository
Ariza, A.
2016-01-21
Diel vertical migration (DVM) facilitates biogeochemical exchanges between shallow waters and the deep ocean. An effective way of monitoring the migrant biota is by acoustic observations although the interpretation of the scattering layers poses challenges. Here we combine results from acoustic observations at 18 and 38 kHz with limited net sampling in order to unveil the origin of acoustic phenomena around the Canary Islands, subtropical northeast Atlantic Ocean. Trawling data revealed a high diversity of fishes, decapods and cephalopods (152 species), although few dominant species likely were responsible for most of the sound scattering in the region. We identified four different acoustic scattering layers in the mesopelagic realm: (1) at 400–500 m depth, a swimbladder resonance phenomenon at 18 kHz produced by gas-bearing migrant fish such as Vinciguerria spp. and Lobianchia dofleini, (2) at 500–600 m depth, a dense 38 kHz layer resulting primarily from the gas-bearing and non-migrant fish Cyclothone braueri, and to a lesser extent, from fluid-like migrant fauna also inhabiting these depths, (3) between 600 and 800 m depth, a weak signal at both 18 and 38 kHz ascribed either to migrant fish or decapods, and (4) below 800 m depth, a weak non-migrant layer at 18 kHz which was not sampled. All the dielly migrating layers reached the epipelagic zone at night, with the shorter-range migrations moving at 4.6 ± 2.6 cm s − 1 and the long-range ones at 11.5 ± 3.8 cm s − 1. This work reduces uncertainties interpreting standard frequencies in mesopelagic studies, while enhances the potential of acoustics for future research and monitoring of the deep pelagic fauna in the Canary Islands.
17. Vertical distribution, composition and migratory patterns of acoustic scattering layers in the Canary Islands
KAUST Repository
Ariza, A.; Landeira, J.M.; Escá nez, A.; Wienerroither, R.; Aguilar de Soto, N.; Rø stad, Anders; Kaartvedt, S.; Herná ndez-Leó n, S.
2016-01-01
Diel vertical migration (DVM) facilitates biogeochemical exchanges between shallow waters and the deep ocean. An effective way of monitoring the migrant biota is by acoustic observations although the interpretation of the scattering layers poses challenges. Here we combine results from acoustic observations at 18 and 38 kHz with limited net sampling in order to unveil the origin of acoustic phenomena around the Canary Islands, subtropical northeast Atlantic Ocean. Trawling data revealed a high diversity of fishes, decapods and cephalopods (152 species), although few dominant species likely were responsible for most of the sound scattering in the region. We identified four different acoustic scattering layers in the mesopelagic realm: (1) at 400–500 m depth, a swimbladder resonance phenomenon at 18 kHz produced by gas-bearing migrant fish such as Vinciguerria spp. and Lobianchia dofleini, (2) at 500–600 m depth, a dense 38 kHz layer resulting primarily from the gas-bearing and non-migrant fish Cyclothone braueri, and to a lesser extent, from fluid-like migrant fauna also inhabiting these depths, (3) between 600 and 800 m depth, a weak signal at both 18 and 38 kHz ascribed either to migrant fish or decapods, and (4) below 800 m depth, a weak non-migrant layer at 18 kHz which was not sampled. All the dielly migrating layers reached the epipelagic zone at night, with the shorter-range migrations moving at 4.6 ± 2.6 cm s − 1 and the long-range ones at 11.5 ± 3.8 cm s − 1. This work reduces uncertainties interpreting standard frequencies in mesopelagic studies, while enhances the potential of acoustics for future research and monitoring of the deep pelagic fauna in the Canary Islands.
18. Angular characteristics of the stimulated-Brillouin-scattering spectrum from a laser plasma with strong acoustic-wave damping
International Nuclear Information System (INIS)
Saikia, P.
1981-01-01
The spectrum of stimulated Brillouin scattering from an inhomogeneous moving laser plasma is analyzed. The damping of acoustic waves and scattered electromagnetic waves is taken into account. Spectra are derived for various scattering angles and for various radii of the laser beam. For all observation angles the center of the spectral line is at an unshifted frequency. As the observation angle increases, the width of the red wing in the spectrum increases. The intensity of the scattered light is very anisotropic
19. A Comprehensive Review of Boundary Integral Formulations of Acoustic Scattering Problems
Directory of Open Access Journals (Sweden)
S.I. Zaman
2000-12-01
Full Text Available This is a review presenting an overview of the developments in boundary integral formulations of the acoustic scattering problems. Generally, the problem is formulated in one of two ways viz. Green’s representation formula, and the Layer-theoretic formulation utilizing either a simple-layer or a double-layer potential. The review presents and expounds the major contributions in this area over the last four decades. The need for a robust and improved formulation of the exterior scattering problem (Neumann or Dirichlet arose due to the fact that the classical formulation failed to yield a unique solution at (acoustic wave-numbers which correspond to eigenvalues (eigenfrequencies of the corresponding interior scattering problem. Moreover, this correlation becomes more pronounced as the wave-numbers become larger i.e. as the (acoustic frequency increases. The robust integral formulations which are discussed here yield Fredholms integral equations of the second kind which are more amenable to computation than the first kind. However, the integral equation involves a hypersingular kernel which creates ill-conditioning in the final matrix representation. This is circumvented by a regularisation technique. An extensive useful list of references is also presented here for researchers in this area.
20. Acoustic scattering of a Bessel vortex beam by a rigid fixed spheroid
Science.gov (United States)
Mitri, F. G.
2015-12-01
Partial-wave series representation of the acoustic scattering field of high-order Bessel vortex beams by rigid oblate and prolate spheroids using the modal matching method is developed. The method, which is applicable to slightly elongated objects at low-to-moderate frequencies, requires solving a system of linear equations which depends on the partial-wave index n and the order of the Bessel vortex beam m using truncated partial-wave series expansions (PWSEs), and satisfying the Neumann boundary condition for a rigid immovable surface in the least-squares sense. This original semi-analytical approach developed for Bessel vortex beams is demonstrated for finite oblate and prolate spheroids, where the mathematical functions describing the spheroidal geometry are written in a form involving single angular (polar) integrals that are numerically computed. The transverse (θ = π / 2) and 3D scattering directivity patterns are evaluated in the far-field for both prolate and oblate spheroids, with particular emphasis on the aspect ratio (i.e., the ratio of the major axis over the minor axis of the spheroid) not exceeding 3:1, the half-cone angle β and order m of the Bessel vortex beam, as well as the dimensionless size parameter kr0. Periodic oscillations in the magnitude plots of the far-field scattering form function are observed, which result from the interference of the reflected waves with the circumferential (Franz') waves circumnavigating the surface of the spheroid in the surrounding fluid. Moreover, the 3D directivity patterns illustrate the far-field scattering from the spheroid, that vanishes in the forward (θ = 0) and backward (θ = π) directions. Particular applications in underwater acoustics and scattering, acoustic levitation and the detection of submerged elongated objects using Bessel vortex waves to name a few, would benefit from the results of the present investigation.
1. Characterizing riverbed sediment using high-frequency acoustics 1: spectral properties of scattering
Science.gov (United States)
Buscombe, Daniel D.; Grams, Paul E.; Kaplinski, Matt A.
2014-01-01
Bed-sediment classification using high-frequency hydro-acoustic instruments is challenging when sediments are spatially heterogeneous, which is often the case in rivers. The use of acoustic backscatter to classify sediments is an attractive alternative to analysis of topography because it is potentially sensitive to grain-scale roughness. Here, a new method is presented which uses high-frequency acoustic backscatter from multibeam sonar to classify heterogeneous riverbed sediments by type (sand, gravel,rock) continuously in space and at small spatial resolution. In this, the first of a pair of papers that examine the scattering signatures from a heterogeneous riverbed, methods are presented to construct spatially explicit maps of spectral properties from geo-referenced point clouds of geometrically and radiometrically corrected echoes. Backscatter power spectra are computed to produce scale and amplitude metrics that collectively characterize the length scales of stochastic measures of riverbed scattering, termed ‘stochastic geometries’. Backscatter aggregated over small spatial scales have spectra that obey a power-law. This apparently self-affine behavior could instead arise from morphological- and grain-scale roughnesses over multiple overlapping scales, or riverbed scattering being transitional between Rayleigh and geometric regimes. Relationships exist between stochastic geometries of backscatter and areas of rough and smooth sediments. However, no one parameter can uniquely characterize a particular substrate, nor definitively separate the relative contributions of roughness and acoustic impedance (hardness). Combinations of spectral quantities do, however, have the potential to delineate riverbed sediment patchiness, in a data-driven approach comparing backscatter with bed-sediment observations (which is the subject of part two of this manuscript).
2. Electron-longitudinal-acoustic-phonon scattering in double-quantum-dot based quantum gates
International Nuclear Information System (INIS)
Zhao Peiji; Woolard, Dwight L.
2008-01-01
We propose a nanostructure design which can significantly suppress longitudinal-acoustic-phonon-electron scattering in double-quantum-dot based quantum gates for quantum computing. The calculated relaxation rates vs. bias voltage exhibit a double-peak feature with a minimum approaching 10 5 s -1 . In this matter, the energy conservation law prohibits scattering contributions from phonons with large momenta; furthermore, increasing the barrier height between the double quantum dots reduces coupling strength between the dots. Hence, the joint action of the energy conservation law and the decoupling greatly reduces the scattering rates. The degrading effects of temperatures can be reduced simply by increasing the height of the barrier between the dots
3. An exploration in acoustic radiation force experienced by cylindrical shells via resonance scattering theory.
Science.gov (United States)
2014-04-01
4. Surface acoustic waves and elastic constants of InN epilayers determined by Brillouin scattering
Energy Technology Data Exchange (ETDEWEB)
Jimenez-Rioboo, R.J.; Prieto, C. [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, Madrid (Spain); Cusco, R.; Domenech-Amador, N.; Artus, L. [Institut Jaume Almera, Consell Superior d' Investigacions Cientifiques (CSIC), Lluis Sole i Sabaris s.n., Barcelona, Catalonia (Spain); Yamaguchi, T.; Nanishi, Y. [Faculty of Science and Engineering, Ritsumeikan University, Noji-Higashi, Kusatsu, Shiga (Japan)
2012-06-15
The surface acoustic wave velocity in InN has been experimentally determined by means of Brillouin scattering experiments on c - and m -face epilayers. From simulations based on the Green's function formalism we determine the shear elastic constants c{sub 66} and c{sub 44} and propose a complete set of elastic constants for wurtzite InN. The analysis of the sagittal and azimuthal dependence of the surface acoustic wave velocity indicates a slightly different elastic behavior of the m -face sample that basically affects the c{sub 44} elastic constant. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
5. Light penetration structures the deep acoustic scattering layers in the global ocean
DEFF Research Database (Denmark)
Aksnes, Dag L.; Rostad, Anders; Kaartvedt, Stein
2017-01-01
The deep scattering layer (DSL) is a ubiquitous acoustic signature found across all oceans and arguably the dominant feature structuring the pelagic open ocean ecosystem. It is formed by mesopelagic fishes and pelagic invertebrates. The DSL animals are an important food source for marine megafauna...... distributions with hypoxic waters. In enhancing understanding of this phenomenon, our results should improve the ability to predict and model the dynamics of one of the largest animal biomass components on earth, with key roles in the oceanic biological carbon pump and food web....
6. Acoustic resonance scattering by a system of concentrically multilayered shells: the inherent background and resonance coefficients
CERN Document Server
Choi, M S; Lee, S H
1999-01-01
The inherent background coefficients that exactly describe the background amplitudes in the scattered field have been presented for the scattering of plane acoustic waves by a system of concentrically multilayered solid and/or fluid shells submerged in a fluid. The coefficients have been obtained by replacing the mechanical surface admittance function with the zero-frequency limit of the admittance function for the analogous fluid system, where the shear wave speeds in the solid layers are set to zero. By taking advantage of the concept of incoming and outgoing waves, we find the surface admittance function for the fluid system in such a form that the analytical generalization for any number of layers and the physical interpretation are very easy. The background coefficients obtained are independent of the bulk wave speeds in the system: they depend on the mass densities and the thickness of the shells. With increasing frequency, the inherent background undergoes a transition from the soft to the rigid backgr...
7. Analysis of a Cartesian PML approximation to acoustic scattering problems in and
KAUST Repository
Bramble, James H.
2013-08-01
We consider the application of a perfectly matched layer (PML) technique applied in Cartesian geometry to approximate solutions of the acoustic scattering problem in the frequency domain. The PML is viewed as a complex coordinate shift ("stretching") and leads to a variable complex coefficient equation for the acoustic wave posed on an infinite domain, the complement of the bounded scatterer. The use of Cartesian geometry leads to a PML operator with simple coefficients, although, still complex symmetric (non-Hermitian). The PML reformulation results in a problem whose solution coincides with the original solution inside the PML layer while decaying exponentially outside. The rapid decay of the PML solution suggests truncation to a bounded domain with a convenient outer boundary condition and subsequent finite element approximation (for the truncated problem). This paper provides new stability estimates for the Cartesian PML approximations both on the infinite and the truncated domain. We first investigate the stability of the infinite PML approximation as a function of the PML strength σ0. This is done for PML methods which involve continuous piecewise smooth stretching as well as piecewise constant stretching functions. We next introduce a truncation parameter M which determines the size of the PML layer. Our analysis shows that the truncated PML problem is stable provided that the product of Mσ0 is sufficiently large, in which case the solution of the problem on the truncated domain converges exponentially to that of the original problem in the domain of interest near the scatterer. This justifies the simple computational strategy of selecting a fixed PML layer and increasing σ0 to obtain the desired accuracy. The results of numerical experiments varying M and σ0 are given which illustrate the theoretically predicted behavior. © 2013 Elsevier B.V. All rights reserved.
8. The factorization method for inverse acoustic scattering in a layered medium
International Nuclear Information System (INIS)
Bondarenko, Oleksandr; Kirsch, Andreas; Liu, Xiaodong
2013-01-01
In this paper, we consider a problem of inverse acoustic scattering by an impenetrable obstacle embedded in a layered medium. We will show that the factorization method can be applied to recover the embedded obstacle; that is, the equation F-tilde g =φ z is solvable if and only if the sampling point z is in the interior of the unknown obstacle. Here, F-tilde is a self-adjoint operator related to the far field operator and ϕ z is the far field pattern of the Green function with respect to the problem of scattering by the background medium for point z. The validity of the factorization method is proven with the help of a mixed reciprocity principle and an application of the scattering operator. Due to the established mixed reciprocity principle, knowledge of the Green function for the background medium is no longer required, which makes the method attractive from the computational point of view. The paper is only concerned with sound-soft obstacles, but the analysis can be easily extended for sound-hard obstacles, or obstacles with separated sound-soft and sound-hard parts. Finally, we provide an explicit example for a radially symmetric case and present some numerical examples. (paper)
9. Analysis of the spectrum of a Cartesian Perfectly Matched Layer (PML) approximation to acoustic scattering problems
KAUST Repository
Kim, Seungil
2010-01-01
In this paper, we study the spectrum of the operator which results when the Perfectly Matched Layer (PML) is applied in Cartesian geometry to the Laplacian on an unbounded domain. This is often thought of as a complex change of variables or "complex stretching." The reason that such an operator is of interest is that it can be used to provide a very effective domain truncation approach for approximating acoustic scattering problems posed on unbounded domains. Stretching associated with polar or spherical geometry lead to constant coefficient operators outside of a bounded transition layer and so even though they are on unbounded domains, they (and their numerical approximations) can be analyzed by more standard compact perturbation arguments. In contrast, operators associated with Cartesian stretching are non-constant in unbounded regions and hence cannot be analyzed via a compact perturbation approach. Alternatively, to show that the scattering problem PML operator associated with Cartesian geometry is stable for real nonzero wave numbers, we show that the essential spectrum of the higher order part only intersects the real axis at the origin. This enables us to conclude stability of the PML scattering problem from a uniqueness result given in a subsequent publication. © 2009 Elsevier Inc. All rights reserved.
10. Intrinsic acoustical cross sections in the multiple scattering by a pair of rigid cylindrical particles in 2D
Science.gov (United States)
Mitri, F. G.
2017-08-01
The multiple scattering effects occurring between two scatterers are described based upon the multipole expansion formalism as well as the addition theorem of cylindrical wave functions. An original approach is presented in which an effective incident acoustic field on a particular object, which includes both the primary and re-scattered waves from the other particle is determined first, and then used with the scattered field to derive closed-form analytical expressions for the inherent (i.e. intrinsic) cross-sections based on the far-field scattering. This method does not introduce any approximation in the calculation of the intrinsic cross-sections since the procedure is reduced to the one-body problem. The mathematical expressions for the intrinsic cross-sections are formulated in partial-wave series expansions (PWSEs) in cylindrical coordinates involving the angle of incidence, the addition theorem for the cylindrical wave functions, and the expansion coefficients of the scatterers. Numerical examples illustrate the analysis for two rigid circular cylindrical cross-sections with different radii immersed in a non-viscous fluid. Computations for the dimensionless extrinsic and intrinsic extinction cross-section factors are evaluated with particular emphasis on varying the angle of incidence, the interparticle distance, as well as the sizes of the particles. A symmetric behavior is observed for the dimensionless extrinsic extinction cross-section, while asymmetry arises for the intrinsic extinction cross-section of each particle with respect to the angle of incidence. The present analysis provides a complete analytical and computational method for the prediction of the intrinsic (local) scattering, absorption and extinction cross-sections in the multiple acoustic scatterings of plane progressive waves of arbitrary incidence by a pair of scatterers. The results and computational analyses can be used as a priori information for future applications to guide the
11. Intrinsic acoustical cross sections in the multiple scattering by a pair of rigid cylindrical particles in 2D
International Nuclear Information System (INIS)
Mitri, F G
2017-01-01
The multiple scattering effects occurring between two scatterers are described based upon the multipole expansion formalism as well as the addition theorem of cylindrical wave functions. An original approach is presented in which an effective incident acoustic field on a particular object, which includes both the primary and re-scattered waves from the other particle is determined first, and then used with the scattered field to derive closed-form analytical expressions for the inherent (i.e. intrinsic) cross-sections based on the far-field scattering. This method does not introduce any approximation in the calculation of the intrinsic cross-sections since the procedure is reduced to the one-body problem. The mathematical expressions for the intrinsic cross-sections are formulated in partial-wave series expansions (PWSEs) in cylindrical coordinates involving the angle of incidence, the addition theorem for the cylindrical wave functions, and the expansion coefficients of the scatterers. Numerical examples illustrate the analysis for two rigid circular cylindrical cross-sections with different radii immersed in a non-viscous fluid. Computations for the dimensionless extrinsic and intrinsic extinction cross-section factors are evaluated with particular emphasis on varying the angle of incidence, the interparticle distance, as well as the sizes of the particles. A symmetric behavior is observed for the dimensionless extrinsic extinction cross-section, while asymmetry arises for the intrinsic extinction cross-section of each particle with respect to the angle of incidence. The present analysis provides a complete analytical and computational method for the prediction of the intrinsic (local) scattering, absorption and extinction cross-sections in the multiple acoustic scatterings of plane progressive waves of arbitrary incidence by a pair of scatterers. The results and computational analyses can be used as a priori information for future applications to guide the
12. The fast multipole method and Fourier convolution for the solution of acoustic scattering on regular volumetric grids
Science.gov (United States)
Hesford, Andrew J.; Waag, Robert C.
2010-10-01
The fast multipole method (FMM) is applied to the solution of large-scale, three-dimensional acoustic scattering problems involving inhomogeneous objects defined on a regular grid. The grid arrangement is especially well suited to applications in which the scattering geometry is not known a priori and is reconstructed on a regular grid using iterative inverse scattering algorithms or other imaging techniques. The regular structure of unknown scattering elements facilitates a dramatic reduction in the amount of storage and computation required for the FMM, both of which scale linearly with the number of scattering elements. In particular, the use of fast Fourier transforms to compute Green's function convolutions required for neighboring interactions lowers the often-significant cost of finest-level FMM computations and helps mitigate the dependence of FMM cost on finest-level box size. Numerical results demonstrate the efficiency of the composite method as the number of scattering elements in each finest-level box is increased.
13. Relationship between the Amplitude and Phase of a Signal Scattered by a Point-Like Acoustic Inhomogeneity
Science.gov (United States)
Burov, V. A.; Morozov, S. A.
2001-11-01
Wave scattering by a point-like inhomogeneity, i.e., a strong inhomogeneity with infinitesimal dimensions, is described. This type of inhomogeneity model is used in investigating the point-spread functions of different algorithms and systems. Two approaches are used to derive the rigorous relationship between the amplitude and phase of a signal scattered by a point-like acoustic inhomogeneity. The first approach is based on a Marchenko-type equation. The second approach uses the scattering by a scatterer whose size decreases simultaneously with an increase in its contrast. It is shown that the retarded and advanced waves are scattered differently despite the relationship between the phases of the corresponding scattered waves.
14. Acoustic resonance scattering from a multilayered cylindrical shell with imperfect bonding.
Science.gov (United States)
2009-12-01
The method of wave function expansion is adopted to study the three dimensional scattering of a time-harmonic plane progressive sound field obliquely incident upon a multi-layered hollow cylinder with interlaminar bonding imperfection. For the generality of solution, each layer is assumed to be cylindrically orthotropic. An approximate laminate model in the context of the modal state equations with variable coefficients along with the classical T-matrix solution technique is set up for each layer to solve for the unknown modal scattering and transmission coefficients. A linear spring model is used to describe the interlaminar adhesive bonding whose effects are incorporated into the global transfer matrix by introduction of proper interfacial transfer matrices. Following the classic acoustic resonance scattering theory (RST), the scattered field and response to surface waves are determined by constructing the partial waves and obtaining the non-resonance (backgrounds) and resonance components. The solution is first used to investigate the effect of interlayer imperfection of an air-filled and water submerged bilaminate aluminium cylindrical shell on the resonances associated with various modes of wave propagation (i.e., symmetric/asymmetric Lamb waves, fluid-borne A-type waves, Rayleigh and Whispering Gallery waves) appearing in the backscattered spectrum, according to their polarization and state of stress. An illustrative numerical example is also given for a multi-layered (five-layered) cylindrical shell for which the stiffness of the adhesive interlayers is artificially varied. The sensitivity of resonance frequencies associated with higher mode numbers to the stiffness coefficients is demonstrated to be a good measure of the bonding strength. Limiting cases are considered and fair agreements with solutions available in the literature are established.
15. Neutron scattering investigation of the acoustic-mode Grüneisen parameters in RbBr
DEFF Research Database (Denmark)
Ernst, G.; Krexner, G.; Quittner, G.
1984-01-01
The microscopic Grüneisen parameters in RbBr have been determined for 44 acoustic modes in the main symmetry directions Δ, Σ, and Λ by inelastic neutron scattering under hydrostatic pressure. The experimental data are well described within the framework of a breathing-shell model, which includes...
16. Soliton generation via continuous stokes acoustic self-scattering of hypersonic waves in a paramagnetic crystal
International Nuclear Information System (INIS)
Bugay, A. N.; Sazonov, S. V.
2008-01-01
A new mechanism is proposed for continuous frequency down-conversion of acoustic waves propagating in a paramagnetic crystal at a low temperature in an applied magnetic field. A transverse hypersonic pulse generating a carrier-free longitudinal strain pulse via nonlinear effects is scattered by the generated pulse. This leads to a Stokes shift in the transverse hypersonic wave proportional to its intensity, and both pulses continue to propagate in the form of a mode-locked soliton. As the transverse-pulse frequency is Stokes shifted, its spectrum becomes narrower. This process can be effectively implemented only if the linear group velocity of the transverse hypersonic pulse equals the phase velocity of the longitudinal strain wave. These velocities are renormalized by spin-phonon coupling and can be made equal by adjusting the magnitude of the applied magnetic field. The transverse structure of the soliton depends on the sign of the group velocity dispersion of the transverse component. When the dispersion is positive, planar solitons can develop whose transverse component has a topological defect of dark vortex type and longitudinal component has a hole. In the opposite case, the formation of two-component acoustic 'bullets' or vortices localized in all directions is possible
17. Interior and exterior resonances in acoustic scattering. pt. 2 - Targets of arbitrary shape (T-matrix approach)
International Nuclear Information System (INIS)
Uberall, H.; Gaunaurd, G.C.; Tanglis, E.
1983-01-01
The T-matrix approach, which describes the scattering of acoustic waves (or of other waves) from objects of arbitrary shape and geometry, is here 'married' to the resonance scattering theory in order to obtain the (complex) resonance frequencies of an arbitrary shaped target. For the case of nearly impenetrable targets the partial-wave scattering amplitudes are splitted into terms corresponding to 'internal' resonances, plus an apparently nonresonant background amplitude which, however, contains the broad resonances caused by 'external' diffracted (or Franz-type, creeping) waves, in addition to geometrically reflected and refracted (ray) contributions
18. Time reversal invariance for a nonlinear scatterer exhibiting contact acoustic nonlinearity
Science.gov (United States)
Blanloeuil, Philippe; Rose, L. R. Francis; Veidt, Martin; Wang, Chun H.
2018-03-01
The time reversal invariance of an ultrasonic plane wave interacting with a contact interface characterized by a unilateral contact law is investigated analytically and numerically. It is shown analytically that despite the contact nonlinearity, the re-emission of a time reversed version of the reflected and transmitted waves can perfectly recover the original pulse shape, thereby demonstrating time reversal invariance for this type of contact acoustic nonlinearity. With the aid of finite element modelling, the time-reversal analysis is extended to finite-size nonlinear scatterers such as closed cracks. The results show that time reversal invariance holds provided that all the additional frequencies generated during the forward propagation, such as higher harmonics, sub-harmonics and zero-frequency component, are fully included in the retro-propagation. If the scattered waves are frequency filtered during receiving or transmitting, such as through the use of narrowband transducers, the recombination of the time-reversed waves will not exactly recover the original incident wave. This discrepancy due to incomplete time invariance can be exploited as a new method for characterizing damage by defining damage indices that quantify the departure from time reversal invariance. The sensitivity of these damage indices for various crack lengths and contact stress levels is investigated computationally, indicating some advantages of this narrowband approach relative to the more conventional measurement of higher harmonic amplitude, which requires broadband transducers.
19. Acoustic Scattering from Munitions in the Underwater Environment: Measurements and Modeling
Science.gov (United States)
Williams, K.; Kargl, S. G.; Espana, A.
2017-12-01
Acoustical scattering from elastic targets has been a subject of research for several decades. However, the introduction of those targets into the ocean environment brings new complexities to quantitative prediction of that scattering. The goal of our work has been to retain as much of the target physics as possible while also handling the propagation to and from the target in the multi-path ocean environment. Testing of the resulting predictions has been carried out via ocean experiments in which munitions are deployed on and within the sediment. We will present the overall philosophy used in the modeling and then compare model results to measurements. A 60 cm long 30 cd diameter aluminum cylinder will be used as a canonical example and then a sample of results for a variety of munitions will be shown. Finally, we will discuss the use of both the models and measurements in assessing the ability of sonar to discriminate munitions from other man-made targets. The difficulty of this challenge will be made apparent via results from a recent experiment in which both munitions and man-made "clutter" were deployed on a rippled sand interface.
20. MEASUREMENTS OF THE ABSORPTION AND SCATTERING CROSS SECTIONS FOR THE INTERACTION OF SOLAR ACOUSTIC WAVES WITH SUNSPOTS
International Nuclear Information System (INIS)
Zhao, Hui; Chou, Dean-Yi
2016-01-01
The solar acoustic waves are modified by the interaction with sunspots. The interaction can be treated as a scattering problem: an incident wave propagating toward a sunspot is scattered by the sunspot into different modes. The absorption cross section and scattering cross section are two important parameters in the scattering problem. In this study, we use the wavefunction of the scattered wave, measured with a deconvolution method, to compute the absorption cross section σ ab and the scattering cross section σ sc for the radial order n = 0–5 for two sunspots, NOAA 11084 and NOAA 11092. In the computation of the cross sections, the random noise and dissipation in the measured acoustic power are corrected. For both σ ab and σ sc , the value of NOAA 11092 is greater than that of NOAA 11084, but their overall n dependence is similar: decreasing with n . The ratio of σ ab of NOAA 11092 to that of NOAA 11084 approximately equals the ratio of sunspot radii for all n , while the ratio of σ sc of the two sunspots is greater than the ratio of sunspot radii and increases with n . This suggests that σ ab is approximately proportional to the sunspot radius, while the dependence of σ sc on radius is faster than the linear increase.
1. MEASUREMENTS OF THE ABSORPTION AND SCATTERING CROSS SECTIONS FOR THE INTERACTION OF SOLAR ACOUSTIC WAVES WITH SUNSPOTS
Energy Technology Data Exchange (ETDEWEB)
Zhao, Hui [National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 200012 (China); Chou, Dean-Yi, E-mail: [email protected] [Physics Department, National Tsing Hua University, Hsinchu, Taiwan (China)
2016-05-01
The solar acoustic waves are modified by the interaction with sunspots. The interaction can be treated as a scattering problem: an incident wave propagating toward a sunspot is scattered by the sunspot into different modes. The absorption cross section and scattering cross section are two important parameters in the scattering problem. In this study, we use the wavefunction of the scattered wave, measured with a deconvolution method, to compute the absorption cross section σ {sub ab} and the scattering cross section σ {sub sc} for the radial order n = 0–5 for two sunspots, NOAA 11084 and NOAA 11092. In the computation of the cross sections, the random noise and dissipation in the measured acoustic power are corrected. For both σ {sub ab} and σ {sub sc}, the value of NOAA 11092 is greater than that of NOAA 11084, but their overall n dependence is similar: decreasing with n . The ratio of σ {sub ab} of NOAA 11092 to that of NOAA 11084 approximately equals the ratio of sunspot radii for all n , while the ratio of σ {sub sc} of the two sunspots is greater than the ratio of sunspot radii and increases with n . This suggests that σ {sub ab} is approximately proportional to the sunspot radius, while the dependence of σ {sub sc} on radius is faster than the linear increase.
2. Scattering of acoustic and electromagnetic waves by small impedance bodies of arbitrary shapes applications to creating new engineered materials
CERN Document Server
Ramm, Alexander G
2013-01-01
The behavior of acoustic or electromagnetic waves reflecting off, and scattering from, intercepted bodies of any size and kind can make determinations about the materials of those bodies and help in better understanding how to manipulate such materials for desired characteristics. This book offers analytical formulas which allow you to calculate acoustic and electromagnetic waves, scattered by one and many small bodies of an arbitrary shape under various boundary conditions. Equations for the effective (self-consistent) field in media consisting of many small bodies are derived. These results and formulas are new and not available in the works of other authors. In particular, the theory developed in this book is different from the classical work of Rayleigh on scattering by small bodies: not only analytical formulas are derived for the waves scattered by small bodies of an arbitrary shape, but the amplitude of the scattered waves is much larger, of the order O(a 2-k), than in Rayleigh scattering, where the or...
3. Experimental observation of spontaneous depolarized guided acoustic-wave Brillouin scattering in side cores of a multicore fiber
Science.gov (United States)
Hayashi, Neisei; Mizuno, Yosuke; Nakamura, Kentaro; Set, Sze Yun; Yamashita, Shinji
2018-06-01
Spontaneous depolarized guided acoustic-wave Brillouin scattering (GAWBS) was experimentally observed in one of the side cores of an uncoated multicore fiber (MCF). The frequency bandwidth in the side core was up to ∼400 MHz, which is 0.5 times that in the central core. The GAWBS spectrum of the side core of the MCF included intrinsic peaks, which had different acoustic resonance frequencies from those of the central core. In addition, the spontaneous depolarized GAWBS in the central/side core was unaffected by that in the other core. These results will lead to the development of polarization/phase modulators using an MCF.
4. Risk of a second cancer from scattered radiation in acoustic neuroma treatment
Science.gov (United States)
Yoon, Myonggeun; Lee, Hyunho; Sung, Jiwon; Shin, Dongoh; Park, Sungho; Chung, Weon Kuu; Jahng, Geon-Ho; Kim, Dong Wook
2014-06-01
5. Risk of a second cancer from scattered radiation in acoustic neuroma treatment
Energy Technology Data Exchange (ETDEWEB)
Yoon, Myonggeun; Lee, Hyunho; Sung, Jiwon [Korea University, Seoul (Korea, Republic of); Shin, Dongoh [Kyung Hee University Medical Center, Seoul (Korea, Republic of); Park, Sungho [Ulsan University Hospital, Ulsan (Korea, Republic of); Chung, Weonkuu; Jahng, Geonho; Kim, Dongwook [Kyung Hee University Hospital at Gangdong, Seoul (Korea, Republic of)
2014-06-15
6. Estimation of biological parameters of marine organisms using linear and nonlinear acoustic scattering model-based inversion methods.
Science.gov (United States)
Chu, Dezhang; Lawson, Gareth L; Wiebe, Peter H
2016-05-01
The linear inversion commonly used in fisheries and zooplankton acoustics assumes a constant inversion kernel and ignores the uncertainties associated with the shape and behavior of the scattering targets, as well as other relevant animal parameters. Here, errors of the linear inversion due to uncertainty associated with the inversion kernel are quantified. A scattering model-based nonlinear inversion method is presented that takes into account the nonlinearity of the inverse problem and is able to estimate simultaneously animal abundance and the parameters associated with the scattering model inherent to the kernel. It uses sophisticated scattering models to estimate first, the abundance, and second, the relevant shape and behavioral parameters of the target organisms. Numerical simulations demonstrate that the abundance, size, and behavior (tilt angle) parameters of marine animals (fish or zooplankton) can be accurately inferred from the inversion by using multi-frequency acoustic data. The influence of the singularity and uncertainty in the inversion kernel on the inversion results can be mitigated by examining the singular values for linear inverse problems and employing a non-linear inversion involving a scattering model-based kernel.
7. Iterative solution of multiple radiation and scattering problems in structural acoustics using the BL-QMR algorithm
Energy Technology Data Exchange (ETDEWEB)
Malhotra, M. [Stanford Univ., CA (United States)
1996-12-31
Finite-element discretizations of time-harmonic acoustic wave problems in exterior domains result in large sparse systems of linear equations with complex symmetric coefficient matrices. In many situations, these matrix problems need to be solved repeatedly for different right-hand sides, but with the same coefficient matrix. For instance, multiple right-hand sides arise in radiation problems due to multiple load cases, and also in scattering problems when multiple angles of incidence of an incoming plane wave need to be considered. In this talk, we discuss the iterative solution of multiple linear systems arising in radiation and scattering problems in structural acoustics by means of a complex symmetric variant of the BL-QMR method. First, we summarize the governing partial differential equations for time-harmonic structural acoustics, the finite-element discretization of these equations, and the resulting complex symmetric matrix problem. Next, we sketch the special version of BL-QMR method that exploits complex symmetry, and we describe the preconditioners we have used in conjunction with BL-QMR. Finally, we report some typical results of our extensive numerical tests to illustrate the typical convergence behavior of BL-QMR method for multiple radiation and scattering problems in structural acoustics, to identify appropriate preconditioners for these problems, and to demonstrate the importance of deflation in block Krylov-subspace methods. Our numerical results show that the multiple systems arising in structural acoustics can be solved very efficiently with the preconditioned BL-QMR method. In fact, for multiple systems with up to 40 and more different right-hand sides we get consistent and significant speed-ups over solving the systems individually.
8. Light penetration structures the deep acoustic scattering layers in the global ocean.
KAUST Repository
Aksnes, Dag L.
2017-05-01
The deep scattering layer (DSL) is a ubiquitous acoustic signature found across all oceans and arguably the dominant feature structuring the pelagic open ocean ecosystem. It is formed by mesopelagic fishes and pelagic invertebrates. The DSL animals are an important food source for marine megafauna and contribute to the biological carbon pump through the active flux of organic carbon transported in their daily vertical migrations. They occupy depths from 200 to 1000 m at daytime and migrate to a varying degree into surface waters at nighttime. Their daytime depth, which determines the migration amplitude, varies across the global ocean in concert with water mass properties, in particular the oxygen regime, but the causal underpinning of these correlations has been unclear. We present evidence that the broad variability in the oceanic DSL daytime depth observed during the Malaspina 2010 Circumnavigation Expedition is governed by variation in light penetration. We find that the DSL depth distribution conforms to a common optical depth layer across the global ocean and that a correlation between dissolved oxygen and light penetration provides a parsimonious explanation for the association of shallow DSL distributions with hypoxic waters. In enhancing understanding of this phenomenon, our results should improve the ability to predict and model the dynamics of one of the largest animal biomass components on earth, with key roles in the oceanic biological carbon pump and food web.
9. Light penetration structures the deep acoustic scattering layers in the global ocean.
KAUST Repository
Aksnes, Dag L.; Rø stad, Anders; Kaartvedt, Stein; Martinez, Udane; Duarte, Carlos M.; Irigoien, Xabier
2017-01-01
The deep scattering layer (DSL) is a ubiquitous acoustic signature found across all oceans and arguably the dominant feature structuring the pelagic open ocean ecosystem. It is formed by mesopelagic fishes and pelagic invertebrates. The DSL animals are an important food source for marine megafauna and contribute to the biological carbon pump through the active flux of organic carbon transported in their daily vertical migrations. They occupy depths from 200 to 1000 m at daytime and migrate to a varying degree into surface waters at nighttime. Their daytime depth, which determines the migration amplitude, varies across the global ocean in concert with water mass properties, in particular the oxygen regime, but the causal underpinning of these correlations has been unclear. We present evidence that the broad variability in the oceanic DSL daytime depth observed during the Malaspina 2010 Circumnavigation Expedition is governed by variation in light penetration. We find that the DSL depth distribution conforms to a common optical depth layer across the global ocean and that a correlation between dissolved oxygen and light penetration provides a parsimonious explanation for the association of shallow DSL distributions with hypoxic waters. In enhancing understanding of this phenomenon, our results should improve the ability to predict and model the dynamics of one of the largest animal biomass components on earth, with key roles in the oceanic biological carbon pump and food web.
10. Blind source separation based on time-frequency morphological characteristics for rigid acoustic scattering by underwater objects
Science.gov (United States)
Yang, Yang; Li, Xiukun
2016-06-01
Separation of the components of rigid acoustic scattering by underwater objects is essential in obtaining the structural characteristics of such objects. To overcome the problem of rigid structures appearing to have the same spectral structure in the time domain, time-frequency Blind Source Separation (BSS) can be used in combination with image morphology to separate the rigid scattering components of different objects. Based on a highlight model, the separation of the rigid scattering structure of objects with time-frequency distribution is deduced. Using a morphological filter, different characteristics in a Wigner-Ville Distribution (WVD) observed for single auto term and cross terms can be simplified to remove any cross-term interference. By selecting time and frequency points of the auto terms signal, the accuracy of BSS can be improved. An experimental simulation has been used, with changes in the pulse width of the transmitted signal, the relative amplitude and the time delay parameter, in order to analyzing the feasibility of this new method. Simulation results show that the new method is not only able to separate rigid scattering components, but can also separate the components when elastic scattering and rigid scattering exist at the same time. Experimental results confirm that the new method can be used in separating the rigid scattering structure of underwater objects.
11. Stimulated Brillouin scattering phase-locking using a transient acoustic standing wave excited through an optical interference field
International Nuclear Information System (INIS)
Ondrej Slezak; Milan Kalal; Hon Jin Kong
2010-01-01
Complete text of publication follows. Analytical description of an experimentally verified scheme leading to a phase-locked stimulated Brillouin scattering (SBS), used in a laser beam combination systems, is presented. The essential condition for the phase-locking effect for SBS is the fixation of the starting position and time of the acoustic Brillouin wave. It is shown that the starting position fixation of this acoustic wave may have its origin in a transient acoustic standing wave initiated by an arising optical interference field produced by the back-seeding concave mirror. This interference field leads to a stationary density modulation of the medium. However, the way to the formation of this density modulation leads via the acoustic standing wave. An appropriate solution, in the form of the standing wave, was obtained from solving the acoustic wave-equation using the electrostriction as a driving force. As a consequence of the damping term included in this equation the acoustic standing wave becomes gradually attenuated and contrary to the undamped solution published earlier, thus constitutes a truly transient phenomenon. Using a mathematical formalism similar to that which is used for the SBS description in the case of a random phase, the coupled equations describing the phase-locked SBS were derived. Contrary to the case without the back-seeding mirror, where the wave chosen from the thermal noise background subsequently plays the role of a trigger of the stimulated process, in this case it is replaced by the transient standing wave produced as a consequence of the presence of an optical interference field arisen in the focal region of the back-seeding concave mirror.
12. A boundary integral equation method using auxiliary interior surface approach for acoustic radiation and scattering in two dimensions.
Science.gov (United States)
Yang, S A
2002-10-01
This paper presents an effective solution method for predicting acoustic radiation and scattering fields in two dimensions. The difficulty of the fictitious characteristic frequency is overcome by incorporating an auxiliary interior surface that satisfies certain boundary condition into the body surface. This process gives rise to a set of uniquely solvable boundary integral equations. Distributing monopoles with unknown strengths over the body and interior surfaces yields the simple source formulation. The modified boundary integral equations are further transformed to ordinary ones that contain nonsingular kernels only. This implementation allows direct application of standard quadrature formulas over the entire integration domain; that is, the collocation points are exactly the positions at which the integration points are located. Selecting the interior surface is an easy task. Moreover, only a few corresponding interior nodal points are sufficient for the computation. Numerical calculations consist of the acoustic radiation and scattering by acoustically hard elliptic and rectangular cylinders. Comparisons with analytical solutions are made. Numerical results demonstrate the efficiency and accuracy of the current solution method.
13. Practical methods to define scattering coefficients in a room acoustics computer model
DEFF Research Database (Denmark)
Zeng, Xiangyang; Christensen, Claus Lynge; Rindel, Jens Holger
2006-01-01
of obtaining the data becomes quite time consuming thus increasing the cost of design. In this paper, practical methods to define scattering coefficients, which is based on an approach of modeling surface scattering and scattering caused by limited size of surface as well as edge diffraction are presented...
14. Elastic Characterization of Transparent and Opaque Films, Multilayers and Acoustic Resonators by Surface Brillouin Scattering: A Review
Directory of Open Access Journals (Sweden)
Giovanni Carlotti
2018-01-01
Full Text Available There is currently a renewed interest in the development of experimental methods to achieve the elastic characterization of thin films, multilayers and acoustic resonators operating in the GHz range of frequencies. The potentialities of surface Brillouin light scattering (surf-BLS for this aim are reviewed in this paper, addressing the various situations that may occur for the different types of structures. In particular, the experimental methodology and the amount of information that can be obtained depending on the transparency or opacity of the film material, as well as on the ratio between the film thickness and the light wavelength, are discussed. A generalization to the case of multilayered samples is also provided, together with an outlook on the capability of the recently developed micro-focused scanning version of the surf-BLS technique, which opens new opportunities for the imaging of the spatial profile of the acoustic field in acoustic resonators and in artificially patterned metamaterials, such as phononic crystals.
15. Acoustic Phonons and Mechanical Properties of Ultra-Thin Porous Low-k Films: A Surface Brillouin Scattering Study
Science.gov (United States)
Zizka, J.; King, S.; Every, A.; Sooryakumar, R.
2018-04-01
To reduce the RC (resistance-capacitance) time delay of interconnects, a key development of the past 20 years has been the introduction of porous low-k dielectrics to replace the traditional use of SiO2. Moreover, in keeping pace with concomitant reduction in technology nodes, these low-k materials have reached thicknesses below 100 nm wherein the porosity becomes a significant fraction of the film volume. The large degree of porosity not only reduces mechanical strength of the dielectric layer but also renders a need for non-destructive approaches to measure the mechanical properties of such ultra-thin films within device configurations. In this study, surface Brillouin scattering (SBS) is utilized to determine the elastic constants, Poisson's ratio, and Young's modulus of these porous low-k SiOC:H films (˜ 25-250 nm thick) grown on Si substrates by probing surface acoustic phonons and their dispersions.
16. Investigation into the bistatic evolution of the acoustic scattering from a cylindrical shell using time-frequency analysis
Science.gov (United States)
Agounad, Said; Aassif, El Houcein; Khandouch, Younes; Maze, Gérard; Décultot, Dominique
2018-01-01
The time and frequency analyses of the acoustic scattering by an elastic cylindrical shell in bistatic method show that the arrival times of the echoes and the resonance frequencies of the elastic waves propagating in and around the cylindrical shell are a function of the bistatic angle, β, between the emitter and receiver transducers. The aim of this work is to explain the observed results in time and frequency domains using time-frequency analysis and graphical interpretations. The performance of four widely used time-frequency representations, the Smoothed Pseudo Wigner-Ville (SPWV), the Spectrogram (SP), the reassignment SPWV, and the reassignment SP, are studied. The investigation into the evolution of the time-frequency plane as a function of the bistatic angle β shows that there are the waves propagating in counter-clockwise direction (labeled wave+) and the waves which propagate in clockwise direction (labeled waves-). In this paper the A, S0, and A1 circumferential waves are investigated. The graphical interpretations are used to explain the formation mechanism of these waves and the acoustic scattering in monostatic and bistatic configurations. The delay between the echoes of the waves+ and those of the waves- is expressed in the case of the circumnavigating wave (Scholte-Stoneley wave). This study shows that the observed waves at β = 0 ° and β = 18 0 ° are the result of the constructive interferences between the waves+ and the waves-. A comparative study of the physical properties (group velocity dispersion and cut-off frequency) of the waves+, the waves- and the waves observed in monostatic configuration is conducted. Furthermore, it is shown that the ability of the time-frequency representation to highlight the waves+ and the waves- is very useful, for example, for the detection and the localization of defaults, the classification purposes, etc.
17. Analysis of the spectrum of a Cartesian Perfectly Matched Layer (PML) approximation to acoustic scattering problems
KAUST Repository
Kim, Seungil; Pasciak, Joseph E.
2010-01-01
is stable for real nonzero wave numbers, we show that the essential spectrum of the higher order part only intersects the real axis at the origin. This enables us to conclude stability of the PML scattering problem from a uniqueness result given in a
18. Analysis of a Cartesian PML approximation to acoustic scattering problems in and
KAUST Repository
Bramble, James H.; Pasciak, Joseph E.
2013-01-01
to that of the original problem in the domain of interest near the scatterer. This justifies the simple computational strategy of selecting a fixed PML layer and increasing σ0 to obtain the desired accuracy. The results of numerical experiments varying M and σ0 are given
19. Acoustic scattering from a contrast agent microbubble near an elastic wall of finite thickness
International Nuclear Information System (INIS)
Doinikov, Alexander A; Aired, Leila; Bouakaz, Ayache
2011-01-01
Interest in the problem under consideration in this study is motivated by targeted ultrasound imaging where one has to deal with microbubble contrast agents pulsating near blood vessel walls. A modified Rayleigh–Plesset equation is derived that describes the oscillation of a contrast agent microbubble near an elastic wall of finite thickness. It is assumed that the medium behind the wall is a fluid but it is shown that the equation obtained is easily transformable to the case that the medium behind the wall is an elastic solid. In contrast to the model of a rigid wall, which predicts decreasing natural frequency of a bubble near the wall, the elastic wall model reveals that the bubble natural frequency can both decrease and increase, and in cases of interest for medical applications, the bubble natural frequency usually increases. It is found that the influence of an elastic wall on the acoustic response of a bubble is determined by the ratio between a cumulative parameter, which integrally characterizes the mechanical properties of the wall and has the dimension of density, and the density of the liquid surrounding the bubble. It is shown that the acoustic influence of the arterial wall on the bubble is weak and apparently cannot be used to recognize the moment when the bubble approaches the wall. However, in experiments where the behavior of bubbles near various plastic walls is observed, changes in the bubble response, such as increasing natural frequency and decreasing oscillation amplitude, are detectable.
20. Modelling of the acoustic field of a multi-element HIFU array scattered by human ribs
Science.gov (United States)
Gélat, Pierre; ter Haar, Gail; Saffari, Nader
2011-09-01
The efficacy of high-intensity focused ultrasound (HIFU) for the treatment of a range of different cancers, including those of the liver, prostate and breast, has been demonstrated. As a non-invasive focused therapy, HIFU offers considerable advantages over techniques such as chemotherapy and surgical resection in terms of reduced risk of harmful side effects. Despite this, there are a number of significant challenges which currently hinder its widespread clinical application. One of these challenges is the need to transmit sufficient energy through the rib cage to induce tissue necrosis in the required volume whilst minimizing the formation of side lobes. Multi-element random-phased arrays are currently showing great promise in overcoming the limitations of single-element transducers. Nevertheless, successful treatment of a patient with liver tumours requires a thorough understanding of the way in which the ultrasonic pressure field from a HIFU array is scattered by the rib cage. In order to address this, a boundary element approach based on a generalized minimal residual (GMRES) implementation of the Burton-Miller formulation was used in conjunction with phase conjugation techniques to focus the field of a 256-element random HIFU array behind human ribs at locations requiring intercostal and transcostal treatment. Simulations were carried out on a 3D mesh of quadratic pressure patches generated using CT scan anatomical data for adult ribs 9-12 on the right side. The methodology was validated on spherical and cylindrical scatterers. Field calculations were also carried out for idealized ribs, consisting of arrays of strip-like scatterers, demonstrating effects of splitting at the focus. This method has the advantage of fully accounting for the effect of scattering and diffraction in 3D under continuous wave excitation.
1. Modelling of the acoustic field of a multi-element HIFU array scattered by human ribs
Energy Technology Data Exchange (ETDEWEB)
Gelat, Pierre [National Physical Laboratory, Hampton Road, Teddington TW11 0LW (United Kingdom); Ter Haar, Gail [Therapeutic Ultrasound Group, Physics Department, Institute of Cancer Research, Sutton SM2 5NG (United Kingdom); Saffari, Nader, E-mail: [email protected] [Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom)
2011-09-07
The efficacy of high-intensity focused ultrasound (HIFU) for the treatment of a range of different cancers, including those of the liver, prostate and breast, has been demonstrated. As a non-invasive focused therapy, HIFU offers considerable advantages over techniques such as chemotherapy and surgical resection in terms of reduced risk of harmful side effects. Despite this, there are a number of significant challenges which currently hinder its widespread clinical application. One of these challenges is the need to transmit sufficient energy through the rib cage to induce tissue necrosis in the required volume whilst minimizing the formation of side lobes. Multi-element random-phased arrays are currently showing great promise in overcoming the limitations of single-element transducers. Nevertheless, successful treatment of a patient with liver tumours requires a thorough understanding of the way in which the ultrasonic pressure field from a HIFU array is scattered by the rib cage. In order to address this, a boundary element approach based on a generalized minimal residual (GMRES) implementation of the Burton-Miller formulation was used in conjunction with phase conjugation techniques to focus the field of a 256-element random HIFU array behind human ribs at locations requiring intercostal and transcostal treatment. Simulations were carried out on a 3D mesh of quadratic pressure patches generated using CT scan anatomical data for adult ribs 9-12 on the right side. The methodology was validated on spherical and cylindrical scatterers. Field calculations were also carried out for idealized ribs, consisting of arrays of strip-like scatterers, demonstrating effects of splitting at the focus. This method has the advantage of fully accounting for the effect of scattering and diffraction in 3D under continuous wave excitation.
2. Light comfort zones of mesopelagic acoustic scattering layers in two contrasting optical environments
KAUST Repository
2016-03-31
We make a comparison of the mesopelagic sound scattering layers (SLs) in two contrasting optical environments; the clear Red Sea and in murkier coastal waters of Norway (Masfjorden). The depth distributions of the SL in Masfjorden are shallower and narrower than those of the Red Sea. This difference in depth distribution is consistent with the hypothesis that the organisms of the SL distribute according to similar light comfort zones (LCZ) in the two environments. Our study suggest that surface and underwater light measurements ranging more than10 orders of magnitude is required to assess the controlling effects of light on SL structure and dynamics.
3. Low and high frequency asymptotics acoustic, electromagnetic and elastic wave scattering
CERN Document Server
2013-01-01
This volume focuses on asymptotic methods in the low and high frequency limits for the solution of scattering and propagation problems. Each chapter is pedagogical in nature, starting with the basic foundations and ending with practical applications. For example, using the Geometrical Theory of Diffraction, the canonical problem of edge diffraction is first solved and then used in solving the problem of diffraction by a finite crack. In recent times, the crack problem has been of much interest for its applications to Non-Destructive Evaluation (NDE) of flaws in structural materials.
4. Light comfort zones of mesopelagic acoustic scattering layers in two contrasting optical environments
KAUST Repository
Rø stad, Anders; Kaartvedt, Stein; Aksnes, Dag L.
2016-01-01
We make a comparison of the mesopelagic sound scattering layers (SLs) in two contrasting optical environments; the clear Red Sea and in murkier coastal waters of Norway (Masfjorden). The depth distributions of the SL in Masfjorden are shallower and narrower than those of the Red Sea. This difference in depth distribution is consistent with the hypothesis that the organisms of the SL distribute according to similar light comfort zones (LCZ) in the two environments. Our study suggest that surface and underwater light measurements ranging more than10 orders of magnitude is required to assess the controlling effects of light on SL structure and dynamics.
5. SCATTER
International Nuclear Information System (INIS)
Broome, J.
1965-11-01
The programme SCATTER is a KDF9 programme in the Egtran dialect of Fortran to generate normalized angular distributions for elastically scattered neutrons from data input as the coefficients of a Legendre polynomial series, or from differential cross-section data. Also, differential cross-section data may be analysed to produce Legendre polynomial coefficients. Output on cards punched in the format of the U.K. A. E. A. Nuclear Data Library is optional. (author)
6. Method of interior boundaries in a mixed problem of acoustic scattering
Directory of Open Access Journals (Sweden)
P. A. Krutitskii
1999-01-01
Full Text Available The mixed problem for the Helmholtz equation in the exterior of several bodies (obstacles is studied in 2 and 3 dimensions. The Dirichlet boundary condition is given on some obstacles and the impedance boundary condition is specified on the rest. The problem is investigated by a special modification of the boundary integral equation method. This modification can be called ‘Method of interior boundaries’, because additional boundaries are introduced inside scattering bodies, where impedance boundary condition is given. The solution of the problem is obtained in the form of potentials on the whole boundary. The density in the potentials satisfies the uniquely solvable Fredholm equation of the second kind and can be computed by standard codes. In fact our method holds for any positive wave numbers. The Neumann, Dirichlet, impedance problems and mixed Dirichlet–Neumann problem are particular cases of our problem.
7. Development of the ion-acoustic turbulence in a magnetoactive plasma following induced ls-scattering near the lower hybrid resonance
International Nuclear Information System (INIS)
Batanov, G.M.; Kolik, L.V.; Sapozhnikov, A.V.; Sarksyan, K.A.; Skvortsova, N.N.
1984-01-01
The development and nonlinear saturation of ion-acoustic turbulent oscillat tions excited in a plasma by high frequency pumping wave have been experimentall investigated. As a result of investigations into the interaction between obliqu ue Langmuir waves and a magnetoactive plasma near the lower hybrid resonance performed under the regime of HF-pumping wave pulse generation the following c conclusions are drawn: 1) dynamic characteristics of the development of ion-acou tic turbulent oscillations point to the induced ls-scattering process and the de ependence of the rate of this process on the level of initial superthermal ion-acoustic noises, 2) a nonlinear process limiting the of ion-acoustic turbule ence intensity growth is probably the process of induced sound wave scattering on ions followed by the unstable wave energy transfer over the spectrum into the e lower frequency region. Various mechanisms are responsible for excitation of on acoustic waves and HF-waves near the pumping wave frequency (red satellite)
8. Shallow Water Acoustic Laboratory
Data.gov (United States)
Federal Laboratory Consortium — FUNCTION: Supports experimental research where high-frequency acoustic scattering and surface vibration measurements of fluid-loaded and non-fluid-loaded structures...
9. Laboratory for Structural Acoustics
Data.gov (United States)
Federal Laboratory Consortium — FUNCTION: Supports experimental research where acoustic radiation, scattering, and surface vibration measurements of fluid-loaded and non-fluid-loaded structures are...
10. Problems in nonlinear acoustics: Scattering of sound by sound, parametric receiving arrays, nonlinear effects in asymmetric sound beams and pulsed finite amplitude sound beams
Science.gov (United States)
Hamilton, Mark F.
1989-08-01
Four projects are discussed in this annual summary report, all of which involve basic research in nonlinear acoustics: Scattering of Sound by Sound, a theoretical study of two nonconlinear Gaussian beams which interact to produce sum and difference frequency sound; Parametric Receiving Arrays, a theoretical study of parametric reception in a reverberant environment; Nonlinear Effects in Asymmetric Sound Beams, a numerical study of two dimensional finite amplitude sound fields; and Pulsed Finite Amplitude Sound Beams, a numerical time domain solution of the KZK equation.
11. A mesh-free approach to acoustic scattering from multiple spheres nested inside a large sphere by using diagonal translation operators.
Science.gov (United States)
Hesford, Andrew J; Astheimer, Jeffrey P; Greengard, Leslie F; Waag, Robert C
2010-02-01
A multiple-scattering approach is presented to compute the solution of the Helmholtz equation when a number of spherical scatterers are nested in the interior of an acoustically large enclosing sphere. The solution is represented in terms of partial-wave expansions, and a linear system of equations is derived to enforce continuity of pressure and normal particle velocity across all material interfaces. This approach yields high-order accuracy and avoids some of the difficulties encountered when using integral equations that apply to surfaces of arbitrary shape. Calculations are accelerated by using diagonal translation operators to compute the interactions between spheres when the operators are numerically stable. Numerical results are presented to demonstrate the accuracy and efficiency of the method.
12. Turbule Ensemble Model of Atmospheric Turbulence: Progress in its Development and Use in Acoustical-Scattering Investigations
National Research Council Canada - National Science Library
Auvermann, Harry
2001-01-01
The objective of one portion of the Army Research Laboratory program on acoustic propagation on the battlefield is to develop an advanced method of accounting for the effects of anisotropic inhomogeneous turbulence...
13. TRANSFORMATION AND SCATTERING OF SURFACE WAVES ON THE ACOUSTIC LOAD TO ULTRASONIC EVALUATION AND MEASUREMENTS. Part 1. The boundary of acoustic contact is sliding
Directory of Open Access Journals (Sweden)
A. R. Baev
2018-01-01
Full Text Available for the enhancement and improvement of ultrasonic methods evaluation and measurements. The purpose of this work is to determine the influence of the geometric parameters of the acoustic load body and its position on the coefficients of reflection and propagation of the Stoneley and Rayleigh waves and to identify the possibility of using the results of the study for practical applications.Based on the analysis of the acoustic path and the experimental data, the relationship between the measured amplitude parameters and the coefficients of the propagation and reflection of surface waves, as well as the reflectivity of the contact region of the load body in the form of a prism through the sliding boundary, which reaches up to ≈ 32–34 дБ, is established. For the first time, the dependence of these coefficients on the inclination angle of one of the prism lateral faces in the range of 0 ± 45°, dimensionless thickness of the contact layer (0–0,05 and its orientation relative to the acoustic axis.It is established that these coefficients are mainly maximal when the prism is rectangular. The coefficient of reflectivity in the hard contact of bodies is more than an order of magnitude less, and the coefficients of wave propagation – comparable in magnitude. The prospects of using the results of the study to evaluate the quality of adhesion of materials during welding, soldering, gluing, detection of defects in hardto-reach places, as well as to determine the physical and mechanical properties of metals by the proposed method of creating a reference signal are shown.
14. Combination of acoustic levitation with small angle scattering techniques and synchrotron radiation circular dichroism. Application to the study of protein solutions.
Science.gov (United States)
Cristiglio, Viviana; Grillo, Isabelle; Fomina, Margarita; Wien, Frank; Shalaev, Evgenyi; Novikov, Alexey; Brassamin, Séverine; Réfrégiers, Matthieu; Pérez, Javier; Hennet, Louis
2017-01-01
15. Acoustic inverse scattering using topological derivative of far-field measurements-based L2 cost functionals
International Nuclear Information System (INIS)
Bellis, Cédric; Bonnet, Marc; Cakoni, Fioralba
2013-01-01
Originally formulated in the context of topology optimization, the concept of topological derivative has also proved effective as a qualitative inversion tool for a wave-based identification of finite-sized objects. This approach remains, however, largely based on a heuristic interpretation of the topological derivative, whereas most other qualitative approaches to inverse scattering are backed by a mathematical justification. As an effort toward bridging this gap, this study focuses on a topological derivative approach applied to the L 2 -norm of the misfit between far-field measurements. Either an inhomogeneous medium or a finite number of point-like scatterers are considered, using either the Born approximation or a full-scattering model. Topological derivative-based imaging functionals are analyzed using a suitable factorization of the far-field operator, for each of the considered cases, in order to characterize their behavior and assess their ability to reconstruct the unknown scatterer(s). Results include the justification of the usual sign heuristic underpinning the method for (i) the Born approximation and (ii) full-scattering models limited to moderately strong scatterers. Semi-analytical and numerical examples are presented. Within the chosen framework, the topological derivative approach is finally discussed and compared to other well-known qualitative methods. (paper)
16. A single-sided homogeneous Green's function representation for holographic imaging, inverse scattering, time-reversal acoustics and interferometric Green's function retrieval
Science.gov (United States)
Wapenaar, Kees; Thorbecke, Jan; van der Neut, Joost
2016-04-01
Green's theorem plays a fundamental role in a diverse range of wavefield imaging applications, such as holographic imaging, inverse scattering, time-reversal acoustics and interferometric Green's function retrieval. In many of those applications, the homogeneous Green's function (i.e. the Green's function of the wave equation without a singularity on the right-hand side) is represented by a closed boundary integral. In practical applications, sources and/or receivers are usually present only on an open surface, which implies that a significant part of the closed boundary integral is by necessity ignored. Here we derive a homogeneous Green's function representation for the common situation that sources and/or receivers are present on an open surface only. We modify the integrand in such a way that it vanishes on the part of the boundary where no sources and receivers are present. As a consequence, the remaining integral along the open surface is an accurate single-sided representation of the homogeneous Green's function. This single-sided representation accounts for all orders of multiple scattering. The new representation significantly improves the aforementioned wavefield imaging applications, particularly in situations where the first-order scattering approximation breaks down.
17. Acoustic integrated extinction
OpenAIRE
Norris, Andrew N.
2015-01-01
The integrated extinction (IE) is defined as the integral of the scattering cross section as a function of wavelength. Sohl et al. (2007 J. Acoust. Soc. Am. 122, 3206–3210. (doi:10.1121/1.2801546)) derived an IE expression for acoustic scattering that is causal, i.e. the scattered wavefront in the forward direction arrives later than the incident plane wave in the background medium. The IE formula was based on electromagnetic results, for which scattering is causal by default. Here, we der...
18. Characterizing riverbed sediment using high-frequency acoustics 2: scattering signatures of Colorado River bed sediment in Marble and Grand Canyons
Science.gov (United States)
Buscombe, Daniel D.; Grams, Paul E.; Kaplinski, Matt A.
2014-01-01
In this, the second of a pair of papers on the statistical signatures of riverbed sediment in high-frequency acoustic backscatter, spatially explicit maps of the stochastic geometries (length- and amplitude-scales) of backscatter are related to patches of riverbed surfaces composed of known sediment types, as determined by geo-referenced underwater video observations. Statistics of backscatter magnitudes alone are found to be poor discriminators between sediment types. However, the variance of the power spectrum, and the intercept and slope from a power-law spectral form (termed the spectral strength and exponent, respectively) successfully discriminate between sediment types. A decision-tree approach was able to classify spatially heterogeneous patches of homogeneous sands, gravels (and sand-gravel mixtures), and cobbles/boulders with 95, 88, and 91% accuracy, respectively. Application to sites outside the calibration, and surveys made at calibration sites at different times, were plausible based on observations from underwater video. Analysis of decision trees built with different training data sets suggested that the spectral exponent was consistently the most important variable in the classification. In the absence of theory concerning how spatially variable sediment surfaces scatter high-frequency sound, the primary advantage of this data-driven approach to classify bed sediment over alternatives is that spectral methods have well understood properties and make no assumptions about the distributional form of the fluctuating component of backscatter over small spatial scales.
19. Stimulated scattering of space-charge waves in a relativistic electron beam by the ion acoustic wave of a plasma waveguide
International Nuclear Information System (INIS)
Balakirev, V.A.; Buts, V.A.
1982-01-01
The interaction of a relativistic electron beam with a plasma waveguide whose density is modulated by an ion acoustic wave leads to the emission of electromagnetic radiation. The wavelength of the radiation is 2#betta# 2 times shorter than the ion acoustic wavelength. The emission is accompanied by the amplification of the ion acoustic wave. The maximum amplitudes of the excited waves are found
20. Localized Acoustic Surface Modes
KAUST Repository
Farhat, Mohamed
2015-08-04
We introduce the concept of localized acoustic surface modes (ASMs). We demonstrate that they are induced on a two-dimensional cylindrical rigid surface with subwavelength corrugations under excitation by an incident acoustic plane wave. Our results show that the corrugated rigid surface is acoustically equivalent to a cylindrical scatterer with uniform mass density that can be represented using a Drude-like model. This, indeed, suggests that plasmonic-like acoustic materials can be engineered with potential applications in various areas including sensing, imaging, and cloaking.
1. Experimental analysis of thermo-acoustic instabilities in a generic gas turbine combustor by phase-correlated PIV, chemiluminescence, and laser Raman scattering measurements
Science.gov (United States)
Arndt, Christoph M.; Severin, Michael; Dem, Claudiu; Stöhr, Michael; Steinberg, Adam M.; Meier, Wolfgang
2015-04-01
A gas turbine model combustor for partially premixed swirl flames was equipped with an optical combustion chamber and operated with CH4 and air at atmospheric pressure. The burner consisted of two concentric nozzles for separately controlled air flows and a ring of holes 12 mm upstream of the nozzle exits for fuel injection. The flame described here had a thermal power of 25 kW, a global equivalence ratio of 0.7, and exhibited thermo-acoustic instabilities at a frequency of approximately 400 Hz. The phase-dependent variations in the flame shape and relative heat release rate were determined by OH* chemiluminescence imaging; the flow velocities by stereoscopic particle image velocimetry (PIV); and the major species concentrations, mixture fraction, and temperature by laser Raman scattering. The PIV measurements showed that the flow field performed a "pumping" mode with varying inflow velocities and extent of the inner recirculation zone, triggered by the pressure variations in the combustion chamber. The flow field oscillations were accompanied by variations in the mixture fraction in the inflow region and at the flame root, which in turn were mainly caused by the variations in the CH4 concentration. The mean phase-dependent changes in the fluxes of CH4 and N2 through cross-sectional planes of the combustion chamber at different heights above the nozzle were estimated by combining the PIV and Raman data. The results revealed a periodic variation in the CH4 flux by more than 150 % in relation to the mean value, due to the combined influence of the oscillating flow velocity, density variations, and CH4 concentration. Based on the experimental results, the feedback mechanism of the thermo-acoustic pulsations could be identified as a periodic fluctuation of the equivalence ratio and fuel mass flow together with a convective delay for the transport of fuel from the fuel injector to the flame zone. The combustor and the measured data are well suited for the validation of
2. Ion-acoustic plasma turbulence
International Nuclear Information System (INIS)
Bychenkov, V.Y.; Silin, V.P.
1982-01-01
A theory is developed of the nonlinear state that is established in a plasma as a result of development of ion-acoustic instability. Account is taken simultaneously of the linear induced scattering of the waves by the ions and of the quasilinear relaxation of the electrons by the ion-acoustic pulsations. The distribution of the ion-acoustic turbulence in frequency and in angle is obtained. An Ohm's law is established and expressions are obtained for the electronic heat flux and for the relaxation time of the electron temperature in a turbulent plasma. Anomalously large absorption and scattering of the electromagnetic waves by the ion-acoustic pulsations is predicted
3. Modelling Hyperboloid Sound Scattering
DEFF Research Database (Denmark)
Burry, Jane; Davis, Daniel; Peters, Brady
2011-01-01
The Responsive Acoustic Surfaces workshop project described here sought new understandings about the interaction between geometry and sound in the arena of sound scattering. This paper reports on the challenges associated with modelling, simulating, fabricating and measuring this phenomenon using...... both physical and digital models at three distinct scales. The results suggest hyperboloid geometry, while difficult to fabricate, facilitates sound scattering....
4. High-Frequency Seafloor Acoustics
CERN Document Server
Jackson, Darrell R
2007-01-01
High-Frequency Seafloor Acoustics is the first book in a new series sponsored by the Office of Naval Research on the latest research in underwater acoustics. This exciting new title provides ready access to experimental data, theory, and models relevant to high-frequency seafloor acoustics and will be of interest to sonar engineers and researchers working in underwater acoustics. The physical characteristics of the seafloor affecting acoustic propagation and scattering are covered, including physical and geoacoustic properties and surface roughness. Current theories for acoustic propagation in sediments are presented along with corresponding models for reflection, scattering, and seafloor penetration. The main text is backed up by an extensive bibliography and technical appendices.
5. Fundamentals of Shallow Water Acoustics
CERN Document Server
Katsnelson, Boris; Lynch, James
2012-01-01
Shallow water acoustics (SWA), the study of how low and medium frequency sound propagates and scatters on the continental shelves of the world's oceans, has both technical interest and a large number of practical applications. Technically, shallow water poses an interesting medium for the study of acoustic scattering, inverse theory, and propagation physics in a complicated oceanic waveguide. Practically, shallow water acoustics has interest for geophysical exploration, marine mammal studies, and naval applications. Additionally, one notes the very interdisciplinary nature of shallow water acoustics, including acoustical physics, physical oceanography, marine geology, and marine biology. In this specialized volume, the authors, all of whom have extensive at-sea experience in U.S. and Russian research efforts, have tried to summarize the main experimental, theoretical, and computational results in shallow water acoustics, with an emphasis on providing physical insight into the topics presented.
6. Architectural acoustics
National Research Council Canada - National Science Library
Long, Marshall
2014-01-01
.... Beginning with a brief history, it reviews the fundamentals of acoustics, human perception and reaction to sound, acoustic noise measurements, noise metrics, and environmental noise characterization...
7. Acoustic emission
International Nuclear Information System (INIS)
Nichols, R.W.
1976-01-01
The volume contains six papers which together provide an overall review of the inspection technique known as acoustic emission or stress wave emission. The titles are: a welder's introduction to acoustic emission technology; use of acoustic emission for detection of defects as they arise during fabrication; examples of laboratory application and assessment of acoustic emission in the United Kingdom; (Part I: acoustic emission behaviour of low alloy steels; Part II: fatigue crack assessment from proof testing and continuous monitoring); inspection of selected areas of engineering structures by acoustic emission; Japanese experience in laboratory and practical applications of acoustic emission to welded structures; and ASME acoustic emission code status. (U.K.)
8. Acoustic holograms of active regions
International Nuclear Information System (INIS)
Chou, Dean-Yi
2008-01-01
We propose a method to study solar magnetic regions in the solar interior with the principle of optical holography. A magnetic region in the solar interior scatters the solar background acoustic waves. The scattered waves and background waves could form an interference pattern on the solar surface. We investigate the feasibility of detecting this interference pattern on the solar surface, and using it to construct the three-dimensional scattered wave from the magnetic region with the principle of optical holography. In solar acoustic holography, the background acoustic waves play the role of reference wave; the magnetic region plays the role of the target object; the interference pattern, acoustic power map, on the solar surface plays the role of the hologram.
9. Acoustic holograms of active regions
Energy Technology Data Exchange (ETDEWEB)
Chou, Dean-Yi [Physics Department, National Tsing Hua University, Hsinchu, 30013, Taiwan (China)], E-mail: [email protected]
2008-10-15
We propose a method to study solar magnetic regions in the solar interior with the principle of optical holography. A magnetic region in the solar interior scatters the solar background acoustic waves. The scattered waves and background waves could form an interference pattern on the solar surface. We investigate the feasibility of detecting this interference pattern on the solar surface, and using it to construct the three-dimensional scattered wave from the magnetic region with the principle of optical holography. In solar acoustic holography, the background acoustic waves play the role of reference wave; the magnetic region plays the role of the target object; the interference pattern, acoustic power map, on the solar surface plays the role of the hologram.
10. Electrostatic ion acoustic waves
International Nuclear Information System (INIS)
Hasegawa, A.
1983-01-01
In this paper, certain aspects of plasma physics are illustrated through a study of electrostatic ion acoustic waves. The paper consists of three Sections. Section II deals with linear properties of the ion acoustic wave including derivation of the dispersions relation with the effect of Landau damping and of an ambient magnetic field. The section also introduces the excitation processes of the ion acoustic wave due to an electron drift or to a stimulated Brillouin scattering. The nonlinear properties are introduced in Section III and IV. In Section III, incoherent nonlinear effects such as quasilinear and mode-coupling saturations of the instability are discussed. The coherent nonlinear effects such as the generation of ion acoustic solitons, shocks and weak double layers are presented in Section IV. (Auth.)
11. Scattering from black holes
International Nuclear Information System (INIS)
Futterman, J.A.H.; Handler, F.A.; Matzner, R.A.
1987-01-01
This book provides a comprehensive treatment of the propagation of waves in the presence of black holes. While emphasizing intuitive physical thinking in their treatment of the techniques of analysis of scattering, the authors also include chapters on the rigorous mathematical development of the subject. Introducing the concepts of scattering by considering the simplest, scalar wave case of scattering by a spherical (Schwarzschild) black hole, the book then develops the formalism of spin weighted spheroidal harmonics and of plane wave representations for neutrino, electromagnetic, and gravitational scattering. Details and results of numerical computations are given. The techniques involved have important applications (references are given) in acoustical and radar imaging
12. Communication Acoustics
DEFF Research Database (Denmark)
Blauert, Jens
Communication Acoustics deals with the fundamentals of those areas of acoustics which are related to modern communication technologies. Due to the advent of digital signal processing and recording in acoustics, these areas have enjoyed an enormous upswing during the last 4 decades. The book...... the book a source of valuable information for those who want to improve or refresh their knowledge in the field of communication acoustics - and to work their way deeper into it. Due to its interdisciplinary character Communication Acoustics is bound to attract readers from many different areas, such as......: acoustics, cognitive science, speech science, and communication technology....
13. Concentric layered Hermite scatterers
Science.gov (United States)
Astheimer, Jeffrey P.; Parker, Kevin J.
2018-05-01
The long wavelength limit of scattering from spheres has a rich history in optics, electromagnetics, and acoustics. Recently it was shown that a common integral kernel pertains to formulations of weak spherical scatterers in both acoustics and electromagnetic regimes. Furthermore, the relationship between backscattered amplitude and wavenumber k was shown to follow power laws higher than the Rayleigh scattering k2 power law, when the inhomogeneity had a material composition that conformed to a Gaussian weighted Hermite polynomial. Although this class of scatterers, called Hermite scatterers, are plausible, it may be simpler to manufacture scatterers with a core surrounded by one or more layers. In this case the inhomogeneous material property conforms to a piecewise continuous constant function. We demonstrate that the necessary and sufficient conditions for supra-Rayleigh scattering power laws in this case can be stated simply by considering moments of the inhomogeneous function and its spatial transform. This development opens an additional path for construction of, and use of scatterers with unique power law behavior.
14. Acoustic Neuroma
Science.gov (United States)
An acoustic neuroma is a benign tumor that develops on the nerve that connects the ear to the brain. ... can press against the brain, becoming life-threatening. Acoustic neuroma can be difficult to diagnose, because the ...
15. Acoustic cloaking and transformation acoustics
International Nuclear Information System (INIS)
Chen Huanyang; Chan, C T
2010-01-01
In this review, we give a brief introduction to the application of the new technique of transformation acoustics, which draws on a correspondence between coordinate transformation and material properties. The technique is formulated for both acoustic waves and linear liquid surface waves. Some interesting conceptual devices can be designed for manipulating acoustic waves. For example, we can design acoustic cloaks that make an object invisible to acoustic waves, and the cloak can either encompass or lie outside the object to be concealed. Transformation acoustics, as an analog of transformation optics, can go beyond invisibility cloaking. As an illustration for manipulating linear liquid surface waves, we show that a liquid wave rotator can be designed and fabricated to rotate the wave front. The acoustic transformation media require acoustic materials which are anisotropic and inhomogeneous. Such materials are difficult to find in nature. However, composite materials with embedded sub-wavelength resonators can in principle be made and such 'acoustic metamaterials' can exhibit nearly arbitrary values of effective density and modulus tensors to satisfy the demanding material requirements in transformation acoustics. We introduce resonant sonic materials and Helmholtz resonators as examples of acoustic metamaterials that exhibit resonant behaviour in effective density and effective modulus. (topical review)
16. Design of the Coordinate Transformation Function for Cylindrical Acoustic Cloaks with a Quantity of Discrete Layers
International Nuclear Information System (INIS)
Cai Li; Wen Ji-Hong; Yu Dian-Long; Lu Zhi-Miao; Wen Xi-Sen
2014-01-01
Acoustic cloak based on coordinate transformation is of great topical interest and has promise in potential applications such as sound transparency and insulation. The frequency response of acoustic cloaks with a quantity of discrete homogeneous layers is analyzed by the acoustic scattering theory. The effect of coordinate transformation function on the acoustic total scattering cross section is discussed to achieve low scattering with only a few layers of anisotropic metamaterials. Also, the physics of acoustic wave interaction with the interfaces between the discrete layers inside the cloak shell is discussed. These results provide a better way of designing a multilayered acoustic cloak with fewer layers. (fundamental areas of phenomenology(including applications))
17. Design of the Coordinate Transformation Function for Cylindrical Acoustic Cloaks with a Quantity of Discrete Layers
Science.gov (United States)
Cai, Li; Wen, Ji-Hong; Yu, Dian-Long; Lu, Zhi-Miao; Wen, Xi-Sen
2014-09-01
Acoustic cloak based on coordinate transformation is of great topical interest and has promise in potential applications such as sound transparency and insulation. The frequency response of acoustic cloaks with a quantity of discrete homogeneous layers is analyzed by the acoustic scattering theory. The effect of coordinate transformation function on the acoustic total scattering cross section is discussed to achieve low scattering with only a few layers of anisotropic metamaterials. Also, the physics of acoustic wave interaction with the interfaces between the discrete layers inside the cloak shell is discussed. These results provide a better way of designing a multilayered acoustic cloak with fewer layers.
18. Topological Acoustics
Science.gov (United States)
Yang, Zhaoju; Gao, Fei; Shi, Xihang; Lin, Xiao; Gao, Zhen; Chong, Yidong; Zhang, Baile
2015-03-01
The manipulation of acoustic wave propagation in fluids has numerous applications, including some in everyday life. Acoustic technologies frequently develop in tandem with optics, using shared concepts such as waveguiding and metamedia. It is thus noteworthy that an entirely novel class of electromagnetic waves, known as "topological edge states," has recently been demonstrated. These are inspired by the electronic edge states occurring in topological insulators, and possess a striking and technologically promising property: the ability to travel in a single direction along a surface without backscattering, regardless of the existence of defects or disorder. Here, we develop an analogous theory of topological fluid acoustics, and propose a scheme for realizing topological edge states in an acoustic structure containing circulating fluids. The phenomenon of disorder-free one-way sound propagation, which does not occur in ordinary acoustic devices, may have novel applications for acoustic isolators, modulators, and transducers.
19. Acoustical Imaging
CERN Document Server
Litniewski, Jerzy; Kujawska, Tamara; 31st International Symposium on Acoustical Imaging
2012-01-01
The International Symposium on Acoustical Imaging is a unique forum for advanced research, covering new technologies, developments, methods and theories in all areas of acoustics. This interdisciplinary Symposium has been taking place continuously since 1968. In the course of the years the proceedings volumes in the Acoustical Imaging Series have become a reference for cutting-edge research in the field. In 2011 the 31st International Symposium on Acoustical Imaging was held in Warsaw, Poland, April 10-13. Offering both a broad perspective on the state-of-the-art as well as in-depth research contributions by the specialists in the field, this Volume 31 in the Series contains an excellent collection of papers in six major categories: Biological and Medical Imaging Physics and Mathematics of Acoustical Imaging Acoustic Microscopy Transducers and Arrays Nondestructive Evaluation and Industrial Applications Underwater Imaging
20. Acoustic textiles
CERN Document Server
Nayak, Rajkishore
2016-01-01
This book highlights the manufacturing and applications of acoustic textiles in various industries. It also includes examples from different industries in which acoustic textiles can be used to absorb noise and help reduce the impact of noise at the workplace. Given the importance of noise reduction in the working environment in several industries, the book offers a valuable guide for companies, educators and researchers involved with acoustic materials.
1. Saturation of ion-acoustic turbulence
International Nuclear Information System (INIS)
1985-01-01
The time evolution of ion-acoustic turbulence is investigated taking into consideration both the scattering of electrons and the induced scattering of waves by the ions. The growth rate of the ion-acoustic turbulence is studied as the function of the wave number, including the long-wave ion sound excitations. It is shown that the relaxation of the ion-acoustic turbulence leads to the quasistationary noise distributions, which are the products of distributions according to the wave number and to the angle. The spectra conform to the stationary theory. (D.Gy.)
2. Bursting behaviours in cascaded stimulated Brillouin scattering
International Nuclear Information System (INIS)
Liu Zhan-Jun; He Xian-Tu; Zheng Chun-Yang; Wang Yu-Gang
2012-01-01
Stimulated Brillouin scattering is studied by numerically solving the Vlasov—Maxwell system. A cascade of stimulated Brillouin scattering can occur when a linearly polarized laser pulse propagates in a plasma. It is found that a stimulated Brillouin scattering cascade can reduce the scattering and increase the transmission of light, as well as introduce a bursting behaviour in the evolution of the laser-plasma interaction. The bursting time in the reflectivity is found to be less than half the ion acoustic period. The ion temperature can affect the stimulated Brillouin scattering cascade, which can repeat several times at low ion temperatures and can be completely eliminated at high ion temperatures. For stimulated Brillouin scattering saturation, higher-harmonic generation and wave—wave interaction of the excited ion acoustic waves can restrict the amplitude of the latter. In addition, stimulated Brillouin scattering cascade can restrict the amplitude of the scattered light. (physics of gases, plasmas, and electric discharges)
3. Acoustic interaction forces between small particles in an ideal fluid
DEFF Research Database (Denmark)
Silva, Glauber T.; Bruus, Henrik
2014-01-01
We present a theoretical expression for the acoustic interaction force between small spherical particles suspended in an ideal fluid exposed to an external acoustic wave. The acoustic interaction force is the part of the acoustic radiation force on one given particle involving the scattered waves...... from the other particles. The particles, either compressible liquid droplets or elastic microspheres, are considered to be much smaller than the acoustic wavelength. In this so-called Rayleigh limit, the acoustic interaction forces between the particles are well approximated by gradients of pair...
4. Acoustic transparency in two-dimensional sonic crystals
Energy Technology Data Exchange (ETDEWEB)
Sanchez-Dehesa, Jose; Torrent, Daniel [Wave Phenomena Group, Department of Electronic Engineering, Polytechnic University of Valencia, C/ Camino de Vera s/n, E-46022 Valencia (Spain); Cai Liangwu [Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States)], E-mail: [email protected]
2009-01-15
Acoustic transparency is studied in two-dimensional sonic crystals consisting of hexagonal distributions of cylinders with continuously varying properties. The transparency condition is achieved by selectively closing the acoustic bandgaps, which are governed by the structure factor of the cylindrical scatterers. It is shown here that cylindrical scatterers with the proposed continuously varying properties are physically realizable by using metafluids based on sonic crystals. The feasibility of this proposal is analyzed by a numerical experiment based on multiple scattering theory.
5. Modeling of acoustic wave propagation and scattering for telemetry of complex structures; Modelisation de la propagation et de l'interaction d'une onde acoustique pour la telemetrie de structures complexes
Energy Technology Data Exchange (ETDEWEB)
LU, B.
2011-11-07
This study takes place in the framework of tools development for the telemetry simulation. Telemetry is a possible technology applied to monitoring the sodium-cooled fast reactors (SFR) and consists in positioning in the reactor core a transducer to generate an ultrasonic beam. This beam propagates through an inhomogeneous random medium since temperature fluctuations occur in the liquid sodium and consequently the sound velocity fluctuates as well, which modifies the bream propagation. Then the beam interacts with a reactor structure immersed in sodium. By measuring the time of flight of the backscattered echo received by the same transducer, one can determine the precise location of the structure. The telemetry simulation therefore requires modeling of both the acoustic wave propagation in an inhomogeneous random medium and the interaction of this wave with structures of various shapes; this is the objective of this work. A stochastic model based on a Monte Carlo algorithm is developed in order to take into account the random fluctuations of the acoustic field. The acoustic field through an inhomogeneous random medium is finally modeled from the field calculated in a mean homogeneous medium by modifying the travel times of rays in the homogeneous medium, using a correction provided by the stochastic model. This stochastic propagation model has been validated by comparison with a deterministic model and is much simpler to integrate in the CIVA software platform for non destructive evaluation simulation and less time consuming than the deterministic model. In order to model the interaction between the acoustic wave and the immersed structures, classical diffraction models have been evaluated for rigid structures, including the geometrical theory of diffraction (GTD) and the Kirchhoff approximation (KA). These two approaches appear to be complementary. Combining them so as to retain only their advantages, we have developed a hybrid model (the so-called refined KA
6. Anomalous acoustic dispersion in architected microlattice metamaterials
Science.gov (United States)
KröDel, Sebastian; Palermo, Antonio; Daraio, Chiara
The ability to control dispersion in acoustic metamaterials is crucial to realize acoustic filtering and rectification devices as well as perfect imaging using negative refractive index materials. Architected microlattice metamaterials immersed in fluid constitute a versatile platform for achieving such control. We investigate architected microlattice materials able to exploit locally resonant modes of their fundamental building blocks that couple with propagating acoustic waves. Using analytical, numerical and experimental methods we find that such lattice materials show a hybrid dispersion behavior governed by Biot's theory for long wavelengths and multiple scattering theory when wave frequency is close to the resonances of the building block. We identify the relevant geometric parameters to alter and control the group and phase velocities in this class of acoustic metamaterials. Furthermore, we fabricate small-scale acoustic metamaterial samples using high precision SLA additive manufacturing and test the resulting materials experimentally using a customized ultrasonic setup. This work paves the way for new acoustic devices based on microlattice metamaterials.
7. Lecture Notes On Acoustics
International Nuclear Information System (INIS)
Kim, Yang Han
2005-09-01
This book mentions string vibration and wave, one-dimension wave and wave equation, characteristic impedance, governing equation of string, and wave energy from string, wave equation of wave and basic physical quantity like one-dimension wave equation, sound unit, sound intensity and energy, sound movement in a surface of discontinuity with transmission loss of sound by partition, and Snell's law, radiation, scatter and diffraction and sound in closed space with Sabine's theory, sound characteristic of closed space and duct acoustics.
8. Battlefield acoustics
CERN Document Server
Damarla, Thyagaraju
2015-01-01
This book presents all aspects of situational awareness in a battlefield using acoustic signals. It starts by presenting the science behind understanding and interpretation of sound signals. The book then goes on to provide various signal processing techniques used in acoustics to find the direction of sound source, localize gunfire, track vehicles, and detect people. The necessary mathematical background and various classification and fusion techniques are presented. The book contains majority of the things one would need to process acoustic signals for all aspects of situational awareness in one location. The book also presents array theory, which is pivotal in finding the direction of arrival of acoustic signals. In addition, the book presents techniques to fuse the information from multiple homogeneous/heterogeneous sensors for better detection. MATLAB code is provided for majority of the real application, which is a valuable resource in not only understanding the theory but readers, can also use the code...
9. Acoustics Research
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — Fisheries acoustics data are collected from more than 200 sea-days each year aboard the FRV DELAWARE II and FRV ALBATROSS IV (decommissioned) and the FSV Henry B....
10. Acoustical Imaging
CERN Document Server
Akiyama, Iwaki
2009-01-01
The 29th International Symposium on Acoustical Imaging was held in Shonan Village, Kanagawa, Japan, April 15-18, 2007. This interdisciplinary Symposium has been taking place every two years since 1968 and forms a unique forum for advanced research, covering new technologies, developments, methods and theories in all areas of acoustics. In the course of the years the volumes in the Acoustical Imaging Series have developed and become well-known and appreciated reference works. Offering both a broad perspective on the state-of-the-art in the field as well as an in-depth look at its leading edge research, this Volume 29 in the Series contains again an excellent collection of seventy papers presented in nine major categories: Strain Imaging Biological and Medical Applications Acoustic Microscopy Non-Destructive Evaluation and Industrial Applications Components and Systems Geophysics and Underwater Imaging Physics and Mathematics Medical Image Analysis FDTD method and Other Numerical Simulations Audience Researcher...
11. Room Acoustics
Science.gov (United States)
Kuttruff, Heinrich; Mommertz, Eckard
The traditional task of room acoustics is to create or formulate conditions which ensure the best possible propagation of sound in a room from a sound source to a listener. Thus, objects of room acoustics are in particular assembly halls of all kinds, such as auditoria and lecture halls, conference rooms, theaters, concert halls or churches. Already at this point, it has to be pointed out that these conditions essentially depend on the question if speech or music should be transmitted; in the first case, the criterion for transmission quality is good speech intelligibility, in the other case, however, the success of room-acoustical efforts depends on other factors that cannot be quantified that easily, not least it also depends on the hearing habits of the listeners. In any case, absolutely "good acoustics" of a room do not exist.
12. Acoustic Tomography in the Canary Basin: Meddies and Tides
Science.gov (United States)
Dushaw, Brian D.; Gaillard, Fabienne; Terre, Thierry
2017-11-01
An acoustic propagation experiment over 308 km range conducted in the Canary Basin in 1997-1998 was used to assess the ability of ocean acoustic tomography to measure the flux of Mediterranean water and Meddies. Instruments on a mooring adjacent to the acoustic path measured the southwestward passage of a strong Meddy in temperature, salinity, and current. Over 9 months of transmissions, the acoustic arrival pattern was an initial broad stochastic pulse varying in duration by 250-500 ms, followed eight stable, identified-ray arrivals. Small-scale sound speed fluctuations from Mediterranean water parcels littered around the sound channel axis caused acoustic scattering. Internal waves contributed more modest acoustic scattering. Based on simulations, the main effect of a Meddy passing across the acoustic path is the formation of many early-arriving, near-axis rays, but these rays are thoroughly scattered by the small-scale Mediterranean-water fluctuations. A Meddy decreases the deep-turning ray travel times by 10-30 ms. The dominant acoustic signature of a Meddy is therefore the expansion of the width of the initial stochastic pulse. While this signature appears inseparable from the other effects of Mediterranean water in this region, the acoustic time series indicates the steady passage of Mediterranean water across the acoustic path. Tidal variations caused by the mode-1 internal tides were measured by the acoustic travel times. The observed internal tides were partly predicted using a recent global model for such tides derived from satellite altimetry.
13. Measurement of sound velocity on metal surfaces by impulsive stimulated Brillouin scattering
International Nuclear Information System (INIS)
Shimada, Yukihiro; Murakami, Hiroshi; Nishimura, Akihiko
2005-01-01
Impulsive stimulated Brillouin Scattering (ISBS) experiment was performed in order to measure acoustic waves on metal surfaces. The ISBS technique offers robust method of obtaining acoustic velocities without physical contact. The generation and detection mechanism were discussed. (author)
14. Momentum transfer in a Brillouin surface scattering
International Nuclear Information System (INIS)
Khater, A.F.
1980-01-01
The theory of acoustic excitation scattering in the surface of Brilloiun of opaque materials, is related to the question of momentum transfexed from radiation fields to the material when the incident eight is scattered in a measurable spectrum. (A.C.A.S.) [pt
15. Omnidirectional ventilated acoustic barrier
Science.gov (United States)
Zhang, Hai-long; Zhu, Yi-fan; Liang, Bin; Yang, Jing; Yang, Jun; Cheng, Jian-chun
2017-11-01
As an important problem in acoustics, sound insulation finds applications in a great variety of situations. In the existing schemes, however, there has always been a trade-off between the thinness of sound-insulating devices and their ventilating capabilities, limiting their potentials in the control of low-frequency sound in high ventilation environments. Here, we design and experimentally implement an omnidirectional acoustic barrier with a planar profile, subwavelength thickness ( 0.18 λ ), yet high ventilation. The proposed mechanism is based on the interference between the resonant scattering of discrete states and the background scattering of continuous states which induces a Fano-like asymmetric transmission profile. Benefitting from the binary-structured design of the coiled unit and hollow pipe, it maximally simplifies the design and fabrication while ensuring the ventilation for all the non-resonant units with open tubes. The simulated and measured results agree well, showing the effectiveness of our proposed mechanism to block low frequency sound coming from various directions while allowing 63% of the air flow to pass. We anticipate our design to open routes to design sound insulators and to enable applications in traditionally unattainable cases such as those calling for noise reduction and cooling simultaneously.
16. Acoustic biosensors.
Science.gov (United States)
Fogel, Ronen; Limson, Janice; Seshia, Ashwin A
2016-06-30
Resonant and acoustic wave devices have been researched for several decades for application in the gravimetric sensing of a variety of biological and chemical analytes. These devices operate by coupling the measurand (e.g. analyte adsorption) as a modulation in the physical properties of the acoustic wave (e.g. resonant frequency, acoustic velocity, dissipation) that can then be correlated with the amount of adsorbed analyte. These devices can also be miniaturized with advantages in terms of cost, size and scalability, as well as potential additional features including integration with microfluidics and electronics, scaled sensitivities associated with smaller dimensions and higher operational frequencies, the ability to multiplex detection across arrays of hundreds of devices embedded in a single chip, increased throughput and the ability to interrogate a wider range of modes including within the same device. Additionally, device fabrication is often compatible with semiconductor volume batch manufacturing techniques enabling cost scalability and a high degree of precision and reproducibility in the manufacturing process. Integration with microfluidics handling also enables suitable sample pre-processing/separation/purification/amplification steps that could improve selectivity and the overall signal-to-noise ratio. Three device types are reviewed here: (i) bulk acoustic wave sensors, (ii) surface acoustic wave sensors, and (iii) micro/nano-electromechanical system (MEMS/NEMS) sensors. © 2016 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.
17. Acoustic Parametric Array for Identifying Standoff Targets
Science.gov (United States)
Hinders, M. K.; Rudd, K. E.
2010-02-01
An integrated simulation method for investigating nonlinear sound beams and 3D acoustic scattering from any combination of complicated objects is presented. A standard finite-difference simulation method is used to model pulsed nonlinear sound propagation from a source to a scattering target via the KZK equation. Then, a parallel 3D acoustic simulation method based on the finite integration technique is used to model the acoustic wave interaction with the target. Any combination of objects and material layers can be placed into the 3D simulation space to study the resulting interaction. Several example simulations are presented to demonstrate the simulation method and 3D visualization techniques. The combined simulation method is validated by comparing experimental and simulation data and a demonstration of how this combined simulation method assisted in the development of a nonlinear acoustic concealed weapons detector is also presented.
18. Hidden acoustic information revealed by intentional nonlinearity
Science.gov (United States)
Dowling, David R.
2017-11-01
Acoustic waves are omnipresent in modern life and are well described by the linearized equations of fluid dynamics. Once generated, acoustic waves carry and collect information about their source and the environment through which they propagate, respectively, and this information may be retrieved by analyzing recordings of these waves. Because of this, acoustics is the primary means for observation, surveillance, reconnaissance, and remote sensing in otherwise opaque environments, such as the Earth's oceans and crust, and the interior of the human body. For such information-retrieval tasks, acoustic fields are nearly always interrogated within their recorded frequency range or bandwidth. However, this frequency-range restriction is not general; acoustic fields may also carry (hidden) information at frequencies outside their bandwidth. Although such a claim may seem counter intuitive, hidden acoustic-field information can be revealed by re-introducing a marquee trait of fluid dynamics: nonlinearity. In particular, an intentional quadratic nonlinearity - a form of intra-signal heterodyning - can be used to obtain acoustic field information at frequencies outside a recorded acoustic field's bandwidth. This quadratic nonlinearity enables a variety of acoustic remote sensing applications that were long thought to be impossible. In particular, it allows the detrimental effects of sparse recordings and random scattering to be suppressed when the original acoustic field has sufficient bandwidth. In this presentation, the topic is developed heuristically, with a just brief exposition of the relevant mathematics. Hidden acoustic field information is then revealed from simulated and measured acoustic fields in simple and complicated acoustic environments involving frequencies from a few Hertz to more than 100 kHz, and propagation distances from tens of centimeters to hundreds of kilometers. Sponsored by ONR, NAVSEA, and NSF.
19. Acoustic emission
International Nuclear Information System (INIS)
Straus, A.; Lopez Pumarega, M.I.; Di Gaetano, J.O.; D'Atellis, C.E.; Ruzzante, J.E.
1990-01-01
This paper is related to our activities on acoustic emission (A.E.). The work is made with different materials: metals and fibre reinforced plastics. At present, acoustic emission transducers are being developed for low and high temperature. A test to detect electrical discharges in electrical transformers was performed. Our experience in industrial tests to detect cracks or failures in tanks or tubes is also described. The use of A.E. for leak detection is considered. Works on pattern recognition of A.E. signals are also being performed. (Author)
20. Building Acoustics
Science.gov (United States)
Cowan, James
This chapter summarizes and explains key concepts of building acoustics. These issues include the behavior of sound waves in rooms, the most commonly used rating systems for sound and sound control in buildings, the most common noise sources found in buildings, practical noise control methods for these sources, and the specific topic of office acoustics. Common noise issues for multi-dwelling units can be derived from most of the sections of this chapter. Books can be and have been written on each of these topics, so the purpose of this chapter is to summarize this information and provide appropriate resources for further exploration of each topic.
1. The acoustics of snoring.
Science.gov (United States)
Pevernagie, Dirk; Aarts, Ronald M; De Meyer, Micheline
2010-04-01
Snoring is a prevalent disorder affecting 20-40% of the general population. The mechanism of snoring is vibration of anatomical structures in the pharyngeal airway. Flutter of the soft palate accounts for the harsh aspect of the snoring sound. Natural or drug-induced sleep is required for its appearance. Snoring is subject to many influences such as body position, sleep stage, route of breathing and the presence or absence of sleep-disordered breathing. Its presentation may be variable within or between nights. While snoring is generally perceived as a social nuisance, rating of its noisiness is subjective and, therefore, inconsistent. Objective assessment of snoring is important to evaluate the effect of treatment interventions. Moreover, snoring carries information relating to the site and degree of obstruction of the upper airway. If evidence for monolevel snoring at the site of the soft palate is provided, the patient may benefit from palatal surgery. These considerations have inspired researchers to scrutinize the acoustic characteristics of snoring events. Similarly to speech, snoring is produced in the vocal tract. Because of this analogy, existing techniques for speech analysis have been applied to evaluate snoring sounds. It appears that the pitch of the snoring sound is in the low-frequency range (noise-like', and has scattered energy content in the higher spectral sub-bands (>500 Hz). To evaluate acoustic properties of snoring, sleep nasendoscopy is often performed. Recent evidence suggests that the acoustic quality of snoring is markedly different in drug-induced sleep as compared with natural sleep. Most often, palatal surgery alters sound characteristics of snoring, but is no cure for this disorder. It is uncertain whether the perceived improvement after palatal surgery, as judged by the bed partner, is due to an altered sound spectrum. Whether some acoustic aspects of snoring, such as changes in pitch, have predictive value for the presence of
2. Nonlinear Acoustics: Periodic Waveguide, Scattering of Sound by Sound, Three-Layer Fluid, Finite Amplitude Sound in a Medium Having a Distribution of Relaxation Processes, and Production of an Isolated Negative Pulse in Water
Science.gov (United States)
1993-06-03
propagation and shape of the waveform," Conference on Lithotripsy (Extra-Corporeal Shock Wave Applications - Technical and Clinical Problems), Univer- sity of...Blackstock, "Physical aspects of lithotripsy ," Paper GG1, 115th Meeting, Acoustical Society of America, Seattle, 16-20 May 1988. ABSTRACT: J. Acoust...Am. 90, 2244(A) (1991). kAlso supported in part by Grant NAG-1-1204 and University of Southampton , Eng- land. 49 1992 ONR Contract Code 1109 JS 1. F
3. Surface Wave Focusing and Acoustic Communications in the Surf Zone
National Research Council Canada - National Science Library
Preisig, James
2004-01-01
The forward scattering of acoustic signals off of shoaling surface gravity waves in the surf zone results in a time-varying channel impulse response that is characterized by intense, rapidly fluctuating arrivals...
4. Acoustic properties of a porous glass (vycor) at hypersonic frequencies
International Nuclear Information System (INIS)
Levelut, C; Pelous, J
2007-01-01
Brillouin scattering experiments have been performed from 5 to 1600 K in vycor, a porous silica glass. The acoustic velocity and attenuation at hypersonic frequencies are compared to those of bulk silica and others porous silica samples. The experimental evidence for the influence of porosity on the scattering by acoustic waves is compared to calculations. The correlation between internal friction and thermal conductivity at low temperature is discussed
5. Integrating Sound Scattering Measurements in the Design of Complex Architectural Surfaces
DEFF Research Database (Denmark)
2010-01-01
Digital tools present the opportunity for incorporating performance analysis into the architectural design process. Acoustic performance is an important criterion for architectural design. There is much known about sound absorption but little about sound scattering, even though scattering is reco...
6. Time reversal transfer: Exploring the robustness of time reversed acoustics in media with geometry perturbations
Czech Academy of Sciences Publication Activity Database
Kober, Jan; Dvořáková, Zuzana; Převorovský, Zdeněk; Krofta, Josef
2015-01-01
Roč. 138, č. 1 (2015), EL49-EL53 ISSN 0001-4966 Institutional support: RVO:61388998 Keywords : acoustic waves * boundary value problems * elastic waves * green's function methods * acoustic scattering Subject RIV: BI - Acoustics Impact factor: 1.572, year: 2015 http://scitation.aip.org/content/asa/journal/jasa/138/1/10.1121/1.4922623
7. Acoustic Territoriality
DEFF Research Database (Denmark)
Kreutzfeldt, Jacob
2011-01-01
Under the heading of "Gang i København" a number of initiatives was presented by the Lord Mayer and the Technical and Environmental Mayer of Copenhagen in May 2006. The aim of the initiative, which roughly translates to Lively Copenhagen, was both to make Copenhagen a livelier city in terms of city...... this article outline a few approaches to a theory of acoustic territoriality....
8. Acoustic lenses
International Nuclear Information System (INIS)
Kittmer, C.A.
1983-03-01
Acoustic lenses focus ultrasound to produce pencil-like beams with reduced near fields. When fitted to conventional (flat-faced) transducers, such lenses greatly improve the ability to detect and size defects. This paper describes a program developed to design acoustic lenses for use in immersion or contact inspection, using normal or angle beam mode with flat or curved targets. Lens surfaces are circular in geometry to facilitate machining. For normal beam inspection of flat plate, spherical or cylindrical lenses are used. For angle beam or curved surface inspections, a compound lens is required to correct for the extra induced aberration. Such a lens is aspherical with one radius of curvature in the plane of incidence, and a different radius of curvature in the plane perpendicular to the incident plane. The resultant beam profile (i.e., location of the acoustic focus, beam diameter, 6 dB working range) depends on the degree of focusing and the transducer used. The operating frequency and bandwidth can be affected by the instrumentation used. Theoretical and measured beam profiles are in good agreement. Various applications, from zone focusing used for defect sizing in thick plate, to line focusing for pipe weld inspection, are discussed
9. Acoustic Neuroma Association
Science.gov (United States)
... EVENTS DONATE NEWS Home Learn Back Learn about acoustic neuroma AN Facts What is acoustic neuroma? Diagnosing ... Brain Freeze ? READ MORE Read More What is acoustic neuroma? Identifying an AN Learn More Get Info ...
10. Panel acoustic contribution analysis.
Science.gov (United States)
Wu, Sean F; Natarajan, Logesh Kumar
2013-02-01
Formulations are derived to analyze the relative panel acoustic contributions of a vibrating structure. The essence of this analysis is to correlate the acoustic power flow from each panel to the radiated acoustic pressure at any field point. The acoustic power is obtained by integrating the normal component of the surface acoustic intensity, which is the product of the surface acoustic pressure and normal surface velocity reconstructed by using the Helmholtz equation least squares based nearfield acoustical holography, over each panel. The significance of this methodology is that it enables one to analyze and rank relative acoustic contributions of individual panels of a complex vibrating structure to acoustic radiation anywhere in the field based on a single set of the acoustic pressures measured in the near field. Moreover, this approach is valid for both interior and exterior regions. Examples of using this method to analyze and rank the relative acoustic contributions of a scaled vehicle cabin are demonstrated.
11. Time-domain Brillouin scattering assisted by diffraction gratings
Science.gov (United States)
Matsuda, Osamu; Pezeril, Thomas; Chaban, Ievgeniia; Fujita, Kentaro; Gusev, Vitalyi
2018-02-01
Absorption of ultrashort laser pulses in a metallic grating deposited on a transparent sample launches coherent compression/dilatation acoustic pulses in directions of different orders of acoustic diffraction. Their propagation is detected by delayed laser pulses, which are also diffracted by the metallic grating, through the measurement of the transient intensity change of the first-order diffracted light. The obtained data contain multiple frequency components, which are interpreted by considering all possible angles for the Brillouin scattering of light achieved through multiplexing of the propagation directions of light and coherent sound by the metallic grating. The emitted acoustic field can be equivalently presented as a superposition of plane inhomogeneous acoustic waves, which constitute an acoustic diffraction grating for the probe light. Thus the obtained results can also be interpreted as a consequence of probe light diffraction by both metallic and acoustic gratings. The realized scheme of time-domain Brillouin scattering with metallic gratings operating in reflection mode provides access to wide range of acoustic frequencies from minimal to maximal possible values in a single experimental optical configuration for the directions of probe light incidence and scattered light detection. This is achieved by monitoring the backward and forward Brillouin scattering processes in parallel. Potential applications include measurements of the acoustic dispersion, simultaneous determination of sound velocity and optical refractive index, and evaluation of samples with a single direction of possible optical access.
12. NORSTAR Project: Norfolk public schools student team for acoustical research
Science.gov (United States)
Fortunato, Ronald C.
1987-01-01
Development of the NORSTAR (Norfolk Public Student Team for Acoustical Research) Project includes the definition, design, fabrication, testing, analysis, and publishing the results of an acoustical experiment. The student-run program is based on a space flight organization similar to the Viking Project. The experiment will measure the scattering transfer of momentum from a sound field to spheres in a liquid medium. It is hoped that the experimental results will shed light on a difficult physics problem - the difference in scattering cross section (the overall effect of the sound wave scattering) for solid spheres and hollow spheres of differing wall thicknesses.
13. Acoustic transducer
Science.gov (United States)
Drumheller, Douglas S.
2000-01-01
An active acoustic transducer tool for use down-hole applications. The tool includes a single cylindrical mandrel including a shoulder defining the boundary of a narrowed portion over which is placed a sandwich-style piezoelectric tranducer assembly. The piezoelectric transducer assembly is prestressed by being placed in a thermal interference fit between the shoulder of the mandrel and the base of an anvil which is likewise positioned over the narrower portion of the mandrel. In the preferred embodiment, assembly of the tool is accomplished using a hydraulic jack to stretch the mandrel prior to emplacement of the cylindrical sandwich-style piezoelectric transducer assembly and anvil. After those elements are positioned and secured, the stretched mandrel is allowed to return substantially to its original (pre-stretch) dimensions with the result that the piezoelectric transducer elements are compressed between the anvil and the shoulder of the mandrel.
14. Acoustic cryocooler
International Nuclear Information System (INIS)
Swift, G.W.; Martin, R.A.; Radebaugh, R.
1990-01-01
This patent describes an acoustic cryocooler with no moving parts is formed from a thermoacoustic driver (TAD) driving a pulse tube refrigerator (PTR) through a standing wave tube. Thermoacoustic elements in the TAD are spaced apart a distance effect to accommodate the increased thermal penetration length arising from the relatively low TAD operating frequency in the range of 15--60 Hz. At these low operating frequencies, a long tube is required to support the standing wave. The tube may be coiled to reduce the overall length of the cryocooler. One or two PTR's are located on the standing wave tube adjacent antinodes in the standing wave to be driven by the standing wave pressure oscillations. It is predicted that a heat input of 1000 W at 1000 K will maintain a cooling load of 5 W at 80 K
15. Use of acoustic vortices in acoustic levitation
DEFF Research Database (Denmark)
Cutanda Henriquez, Vicente; Santillan, Arturo Orozco; Juhl, Peter Møller
2009-01-01
Acoustic fields are known to exert forces on the surfaces of objects. These forces are noticeable if the sound pressure is sufficiently high. Two phenomena where acoustic forces are relevant are: i) acoustic levitation, where strong standing waves can hold small objects at certain positions......, counterbalancing their weight, and ii) acoustic vortices, spinning sound fields that can impinge angular momentum and cause rotation of objects. In this contribution, both force-creating sound fields are studied by means of numerical simulations. The Boundary Element Method is employed to this end. The simulation...... of acoustical vortices uses an efficient numerical implementation based on the superposition of two orthogonal sound fields with a delay of 90° between them. It is shown that acoustic levitation and the use of acoustic vortices can be combined to manipulate objects in an efficient and controlled manner without...
16. Interior acoustic cloak
OpenAIRE
Wael Akl; A. Baz
2014-01-01
Acoustic cloaks have traditionally been intended to externally surround critical objects to render these objects acoustically invisible. However, in this paper, the emphasis is placed on investigating the application of the acoustic cloaks to the interior walls of acoustic cavities in an attempt to minimize the noise levels inside these cavities. In this manner, the acoustic cloaks can serve as a viable and efficient alternative to the conventional passive noise attenuation treatments which a...
17. Quasiresonant scattering
International Nuclear Information System (INIS)
Hategan, Cornel; Comisel, Horia; Ionescu, Remus A.
2004-01-01
The quasiresonant scattering consists from a single channel resonance coupled by direct interaction transitions to some competing reaction channels. A description of quasiresonant Scattering, in terms of generalized reduced K-, R- and S- Matrix, is developed in this work. The quasiresonance's decay width is, due to channels coupling, smaller than the width of the ancestral single channel resonance (resonance's direct compression). (author)
18. Thomson Scattering
NARCIS (Netherlands)
Donne, A. J. H.
1994-01-01
Thomson scattering is a very powerful diagnostic which is applied at nearly every magnetic confinement device. Depending on the experimental conditions different plasma parameters can be diagnosed. When the wave vector is much larger than the plasma Debye length, the total scattered power is
19. A numerical study of super-resolution through fast 3D wideband algorithm for scattering in highly-heterogeneous media
KAUST Repository
Lé tourneau, Pierre-David; Wu, Ying; Papanicolaou, George; Garnier, Josselin; Darve, Eric
2016-01-01
We present a wideband fast algorithm capable of accurately computing the full numerical solution of the problem of acoustic scattering of waves by multiple finite-sized bodies such as spherical scatterers in three dimensions. By full solution, we
20. Acoustic discrimination of Southern Ocean zooplankton
Science.gov (United States)
Brierley, Andrew S.; Ward, Peter; Watkins, Jonathan L.; Goss, Catherine
Acoustic surveys in the vicinity of the sub-Antarctic island of South Georgia during a period of exceptionally calm weather revealed the existence of a number of horizontally extensive yet vertically discrete scattering layers in the upper 250 m of the water column. These layers were fished with a Longhurst-Hardy plankton recorder (LHPR) and a multiple-opening 8 m 2 rectangular mid-water trawl (RMT8). Analysis of catches suggested that each scattering layer was composed predominantly of a single species (biovolume>95%) of either the euphausiids Euphausia frigida or Thysanöessa macrura, the hyperiid amphipod Themisto gaudichaudii, or the eucalaniid copepod Rhincalanus gigas. Instrumentation on the nets allowed their trajectories to be reconstructed precisely, and thus catch data to be related directly to the corresponding acoustic signals. Discriminant function analysis of differences between mean volume backscattering strength at 38, 120 and 200 kHz separated echoes originating from each of the dominant scattering layers, and other signals identified as originating from Antarctic krill ( Euphausia superba), with an overall correct classification rate of 77%. Using echo intensity data alone, gathered using hardware commonly employed for fishery acoustics, it is therefore possible to discriminate in situ between several zooplanktonic taxa, taxa which in some instances exhibit similar gross morphological characteristics and have overlapping length- frequency distributions. Acoustic signals from the mysid Antarctomysis maxima could also be discriminated once information on target distribution was considered, highlighting the value of incorporating multiple descriptors of echo characteristics into signal identification procedures. The ability to discriminate acoustically between zooplankton taxa could be applied to provide improved acoustic estimates of species abundance, and to enhance field studies of zooplankton ecology, distribution and species interactions.
1. Study on the scattering law and scattering kernel of hydrogen in zirconium hydride
International Nuclear Information System (INIS)
Jiang Xinbiao; Chen Wei; Chen Da; Yin Banghua; Xie Zhongsheng
1999-01-01
The nuclear analytical model of calculating scattering law and scattering kernel for the uranium zirconium hybrid reactor is described. In the light of the acoustic and optic model of zirconium hydride, its frequency distribution function f(ω) is given and the scattering law of hydrogen in zirconium hydride is obtained by GASKET. The scattering kernel σ l (E 0 →E) of hydrogen bound in zirconium hydride is provided by the SMP code in the standard WIMS cross section library. Along with this library, WIMS is used to calculate the thermal neutron energy spectrum of fuel cell. The results are satisfied
2. Springer Handbook of Acoustics
CERN Document Server
Rossing, Thomas D
2007-01-01
Acoustics, the science of sound, has developed into a broad interdisciplinary field encompassing the academic disciplines of physics, engineering, psychology, speech, audiology, music, architecture, physiology, neuroscience, and others. The Springer Handbook of Acoustics is an unparalleled modern handbook reflecting this richly interdisciplinary nature edited by one of the acknowledged masters in the field, Thomas Rossing. Researchers and students benefit from the comprehensive contents spanning: animal acoustics including infrasound and ultrasound, environmental noise control, music and human speech and singing, physiological and psychological acoustics, architectural acoustics, physical and engineering acoustics, signal processing, medical acoustics, and ocean acoustics. This handbook reviews the most important areas of acoustics, with emphasis on current research. The authors of the various chapters are all experts in their fields. Each chapter is richly illustrated with figures and tables. The latest rese...
3. Responsive acoustic surfaces
DEFF Research Database (Denmark)
Peters, Brady; Tamke, Martin; Nielsen, Stig Anton
2011-01-01
Acoustic performance is defined by the parameter of reverberation time; however, this does not capture the acoustic experience in some types of open plan spaces. As many working and learning activities now take place in open plan spaces, it is important to be able to understand and design...... for the acoustic conditions of these spaces. This paper describes an experimental research project that studied the design processes necessary to design for sound. A responsive acoustic surface was designed, fabricated and tested. This acoustic surface was designed to create specific sonic effects. The design...... was simulated using custom integrated acoustic software and also using Odeon acoustic analysis software. The research demonstrates a method for designing space- and sound-defining surfaces, defines the concept of acoustic subspace, and suggests some new parameters for defining acoustic subspaces....
4. Scattering theory
International Nuclear Information System (INIS)
Sitenko, A.
1991-01-01
This book emerged out of graduate lectures given by the author at the University of Kiev and is intended as a graduate text. The fundamentals of non-relativistic quantum scattering theory are covered, including some topics, such as the phase-function formalism, separable potentials, and inverse scattering, which are not always coverded in textbooks on scattering theory. Criticisms of the text are minor, but the reviewer feels an inadequate index is provided and the citing of references in the Russian language is a hindrance in a graduate text
5. NEUTRON-SCATTERING STUDY OF DCN
DEFF Research Database (Denmark)
Mackenzie, Gordon A.; Pawley, G. S.
1979-01-01
Phonons in deuterium cyanide have been measured by neutron coherent inelastic scattering. The main subject of study was the transverse acoustic mode in the (110) direction polarised along (110) which is associated with the first-order structural phase transition at 160K. Measurements have shown...
6. Long-Wavelength Phonon Scattering in Nonpolar Semiconductors
DEFF Research Database (Denmark)
Lawætz, Peter
1969-01-01
The long-wavelength acoustic- and optical-phonon scattering of carriers in nonpolar semiconductors is considered from a general point of view. The deformation-potential approximation is defined and it is shown that long-range electrostatic forces give a nontrivial correction to the scattering...... of the very-short-range nature of interactions in a covalent semiconductor....
7. Light scattering by surface phonons in crystals
International Nuclear Information System (INIS)
Albuquerque, E.L. de
1981-01-01
A theory of inelastic light scattering by surface acoustic phonons in homogeneous crystals is presented. The Green functions are determined by the use of a classical linear response method and used to evaluate the Brillouin cross section. The acoustic modes are found from solutions to the acoustical-wave equation and boundary conditions appropriated. Two light-scattering mechanisms, namely the surface corrugation and bulk elasto-optic effect are analyzed by deriving optical fields which satisfy both the acousto-optically driven wave equation and the electromagnetic boundary conditions. No restrictions are imposed concerning the angle of incidence of the light. Some representative computed Brillouin lineshapes are also presented and their features discussed. (Author) [pt
8. Light scattering by surface phonons in crystals
International Nuclear Information System (INIS)
Albuquerque, D.L.
1980-01-01
Theory of inelastic light scattering by surface acoustic phonons homogeneous crystals is presented. The Green functions are determined by the use of a classical linear response method and used to evaluate the Brillouin cross section. The acoustic modes are found from solutions to the acoustical-wave equation and boundary conditions appropriated. Two light-scattering mechanisms, amely the surface corrugation and bulk elasto-optic effect are analyzed by deriving optical fields which satisfy both the acousto-optically driven wave equation and the electromagnetic boundary conditions. No restrictions are imposed concerning the angle of incidence of the light. Some representative computed Brillouin ineshapes are also presented and their features discussed. (author) [pt
9. Acoustics an introduction
CERN Document Server
Kuttruff, Heinrich
2006-01-01
This definitive textbook provides students with a comprehensive introduction to acoustics. Beginning with the basic physical ideas, Acoustics balances the fundamentals with engineering aspects, applications and electroacoustics, also covering music, speech and the properties of human hearing. The concepts of acoustics are exposed and applied in:room acousticssound insulation in buildingsnoise controlunderwater sound and ultrasoundScientifically thorough, but with mathematics kept to a minimum, Acoustics is the perfect introduction to acoustics for students at any level of mechanical, electrical or civil engineering courses and an accessible resource for architects, musicians or sound engineers requiring a technical understanding of acoustics and their applications.
10. Acoustic source for generating an acoustic beam
Science.gov (United States)
Vu, Cung Khac; Sinha, Dipen N.; Pantea, Cristian
2016-05-31
An acoustic source for generating an acoustic beam includes a housing; a plurality of spaced apart piezo-electric layers disposed within the housing; and a non-linear medium filling between the plurality of layers. Each of the plurality of piezoelectric layers is configured to generate an acoustic wave. The non-linear medium and the plurality of piezo-electric material layers have a matching impedance so as to enhance a transmission of the acoustic wave generated by each of plurality of layers through the remaining plurality of layers.
11. Critical scattering
International Nuclear Information System (INIS)
Stirling, W.G.; Perry, S.C.
1996-01-01
We outline the theoretical and experimental background to neutron scattering studies of critical phenomena at magnetic and structural phase transitions. The displacive phase transition of SrTiO 3 is discussed, along with examples from recent work on magnetic materials from the rare-earth (Ho, Dy) and actinide (NpAs, NpSb, USb) classes. The impact of synchrotron X-ray scattering is discussed in conclusion. (author) 13 figs., 18 refs
12. Interior acoustic cloak
Directory of Open Access Journals (Sweden)
Wael Akl
2014-12-01
Full Text Available Acoustic cloaks have traditionally been intended to externally surround critical objects to render these objects acoustically invisible. However, in this paper, the emphasis is placed on investigating the application of the acoustic cloaks to the interior walls of acoustic cavities in an attempt to minimize the noise levels inside these cavities. In this manner, the acoustic cloaks can serve as a viable and efficient alternative to the conventional passive noise attenuation treatments which are invariably heavy and bulky. The transformation acoustics relationships that govern the operation of this class of interior acoustic cloaks are presented. Physical insights are given to relate these relationships to the reasons behind the effectiveness of the proposed interior acoustic cloaks. Finite element models are presented to demonstrate the characteristics of interior acoustic cloaks used in treating the interior walls of circular and square cavities both in the time and frequency domains. The obtained results emphasize the effectiveness of the proposed interior cloaks in eliminating the reflections of the acoustic waves from the walls of the treated cavities and thereby rendering these cavities acoustically quiet. It is important to note here that the proposed interior acoustic cloaks can find applications in acoustic cavities such as aircraft cabins and auditoriums as well as many other critical applications.
13. Numerical modelling of multiple scattering between two elastical particles
DEFF Research Database (Denmark)
Bjørnø, Irina; Jensen, Leif Bjørnø
1998-01-01
in suspension have been studied extensively since Foldy's formulation of his theory for isotropic scattering by randomly distributed scatterers. However, a number of important problems related to multiple scattering are still far from finding their solutions. A particular, but still unsolved, problem......Multiple acoustical signal interactions with sediment particles in the vicinity of the seabed may significantly change the course of sediment concentration profiles determined by inversion from acoustical backscattering measurements. The scattering properties of high concentrations of sediments...... is the question of proximity thresholds for influence of multiple scattering in terms of particle properties like volume fraction, average distance between particles or other related parameters. A few available experimental data indicate a significance of multiple scattering in suspensions where the concentration...
14. Acoustic Neuroma Educational Video
Medline Plus
Full Text Available ... Facts What is acoustic neuroma? Diagnosing Symptoms Side Effects Keywords Questions to ask Choosing a healthcare provider ... Surgery What is acoustic neuroma Diagnosing Symptoms Side effects Question To Ask Treatment Options Back Overview Observation ...
15. Acoustic Neuroma Educational Video
Medline Plus
Full Text Available ... Facts What is acoustic neuroma? Diagnosing Symptoms Side Effects Keywords World Language Videos Questions to ask Choosing ... Surgery What is acoustic neuroma Diagnosing Symptoms Side effects Question To Ask Treatment Options Back Overview Observation ...
16. Atlantic Herring Acoustic Surveys
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — The NEFSC Advanced Sampling Technologies Research Group conducts annual fisheries acoustic surveys using state-of-the-art acoustic, midwater trawling, and underwater...
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — The Tethys database houses the metadata associated with the acoustic data collection efforts by the Passive Acoustic Group. These metadata include dates, locations...
18. A neutron scattering study of DCN
International Nuclear Information System (INIS)
Mackenzie, G.A.; Pawley, G.S.
1979-01-01
Phonons in deuterium cyanide have been measured by neutron coherent inelastic scattering. The main subject of study was the transverse acoustic mode in the (110) direction polarised along (110) which is associated with the first-order structural phase transition at 160 K. Measurements have shown that the frequency decreases by about 25% between about 225 and 160 K as the transition temperature is approached. The other acoustic modes observable in the a*b* scattering plane have been measured and show no anomalous temperature dependence. Optic modes were unobservable because of the small size of the single-crystal sample which gave insufficient scattered intensity. Apart from the 'soft' mode, the measured frequencies are in good agreement with lattice dynamics calculations. (author)
19. Tutorial on architectural acoustics
Science.gov (United States)
Shaw, Neil; Talaske, Rick; Bistafa, Sylvio
2002-11-01
This tutorial is intended to provide an overview of current knowledge and practice in architectural acoustics. Topics covered will include basic concepts and history, acoustics of small rooms (small rooms for speech such as classrooms and meeting rooms, music studios, small critical listening spaces such as home theatres) and the acoustics of large rooms (larger assembly halls, auditoria, and performance halls).
20. Visualization of acoustic particle interaction and agglomeration: Theory evaluation
International Nuclear Information System (INIS)
Hoffmann, T.L.; Koopmann, G.H.
1997-01-01
In this paper experimentally observed trajectories of particles undergoing acoustically induced interaction and agglomeration processes are compared to and validated with numerically generated trajectories based on existing agglomeration theories. Models for orthokinetic, scattering, mutual radiation pressure, and hydrodynamic particle interaction are considered in the analysis. The characteristic features of the classical orthokinetic agglomeration hypothesis, such as collision processes and agglomerations due to the relative entrainment motion, are not observed in the digital images. The measured entrainment rates of the particles are found to be consistently lower than the theoretically predicted values. Some of the experiments reveal certain characteristics which may possibly be related to mutual scattering interaction. The study's most significant discovery is the so-called tuning fork agglomeration [T. L. Hoffmann and G. H. Koopmann, J. Acoust. Soc. Am. 99, 2130 endash 2141 (1996)]. It is shown that this phenomenon contradicts the theories for mutual scattering interaction and mutual radiation pressure interaction, but agrees with the acoustic wake effect model in its intrinsic feature of attraction between particles aligned along the acoustic axis. A model by Dianov et al. [Sov. Phys. Acoust. 13 (3), 314 endash 319 (1968)] is used to describe this effect based on asymmetric flow fields around particles under Oseen flow conditions. It is concluded that this model is consistent with the general characteristics of the tuning fork agglomerations, but lacks certain refinements with respect to accurate quantification of the effect. copyright 1997 Acoustical Society of America
1. Hybrid CFD/CAA Modeling for Liftoff Acoustic Predictions
Science.gov (United States)
Strutzenberg, Louise L.; Liever, Peter A.
2011-01-01
This paper presents development efforts at the NASA Marshall Space flight Center to establish a hybrid Computational Fluid Dynamics and Computational Aero-Acoustics (CFD/CAA) simulation system for launch vehicle liftoff acoustics environment analysis. Acoustic prediction engineering tools based on empirical jet acoustic strength and directivity models or scaled historical measurements are of limited value in efforts to proactively design and optimize launch vehicles and launch facility configurations for liftoff acoustics. CFD based modeling approaches are now able to capture the important details of vehicle specific plume flow environment, identifY the noise generation sources, and allow assessment of the influence of launch pad geometric details and sound mitigation measures such as water injection. However, CFD methodologies are numerically too dissipative to accurately capture the propagation of the acoustic waves in the large CFD models. The hybrid CFD/CAA approach combines the high-fidelity CFD analysis capable of identifYing the acoustic sources with a fast and efficient Boundary Element Method (BEM) that accurately propagates the acoustic field from the source locations. The BEM approach was chosen for its ability to properly account for reflections and scattering of acoustic waves from launch pad structures. The paper will present an overview of the technology components of the CFD/CAA framework and discuss plans for demonstration and validation against test data.
2. Interaction of electromagnetic and acoustic waves in a stochastic atmosphere
Science.gov (United States)
Bhatnagar, N.; Peterson, A. M.
1979-01-01
In the Stanford radio acoustic sounding system (RASS) an electromagnetic signal is made to scatter from a moving acoustic pulse train. Under a Bragg-scatter condition maximum electromagnetic scattering occurs. The scattered radio signal contains temperature and wind information as a function of the acoustic-pulse position. In this investigation RASS performance is assessed in an atmosphere characterized by the presence of turbulence and mean atmospheric parameters. The only assumption made is that the electromagnetic wave is not affected by stochastic perturbations in the atmosphere. It is concluded that the received radio signal depends strongly on the intensity of turbulence for altitudes of the acoustic pulse greater than the coherence length of propagation. The effect of mean vertical wind and mean temperature on the strength of the received signal is also demonstrated to be insignificant. Mean horizontal winds, however, shift the focus of the reflected electromagnetic energy from its origin, resulting in a decrease in received signal level when a monostatic radio-frequency (RF) system is used. For a bistatic radar configuration with space diversified receiving antennas, the shifting of the acoustic pulse makes possible the remote measurement of the horizontal wind component.
3. Controllable asymmetric transmission via gap-tunable acoustic metasurface
Science.gov (United States)
Liu, Bingyi; Jiang, Yongyuan
2018-04-01
In this work, we utilize the acoustic gradient metasurface (AGM) of a bilayer configuration to realize the controllable asymmetric transmission. Relying on the adjustable gap between the two composing layers, the metasurface could switch from symmetric transmission to asymmetric transmission at a certain gap value. The underlying mechanism is attributed to the interference between the forward diffracted waves scattered by the surface bound waves at two air-AGM interfaces, which is apparently influenced by the interlayer distance. We further utilize the hybrid acoustic elements to construct the desired gradient metasurface with a tunable gap and validate the controllable asymmetric transmission with full-wave simulations. Our work provides the solution for actively controlling the transmission property of an acoustic element, which shows potential application in acoustic communication as a dynamic tunable acoustic diode.
4. Compton scattering
International Nuclear Information System (INIS)
Botto, D.J.; Pratt, R.H.
1979-05-01
The current status of Compton scattering, both experimental observations and the theoretical predictions, is examined. Classes of experiments are distinguished and the results obtained are summarized. The validity of the incoherent scattering function approximation and the impulse approximation is discussed. These simple theoretical approaches are compared with predictions of the nonrelativistic dipole formula of Gavrila and with the relativistic results of Whittingham. It is noted that the A -2 based approximations fail to predict resonances and an infrared divergence, both of which have been observed. It appears that at present the various available theoretical approaches differ significantly in their predictions and that further and more systematic work is required
5. Compton scattering
Energy Technology Data Exchange (ETDEWEB)
Botto, D.J.; Pratt, R.H.
1979-05-01
The current status of Compton scattering, both experimental observations and the theoretical predictions, is examined. Classes of experiments are distinguished and the results obtained are summarized. The validity of the incoherent scattering function approximation and the impulse approximation is discussed. These simple theoretical approaches are compared with predictions of the nonrelativistic dipole formula of Gavrila and with the relativistic results of Whittingham. It is noted that the A/sup -2/ based approximations fail to predict resonances and an infrared divergence, both of which have been observed. It appears that at present the various available theoretical approaches differ significantly in their predictions and that further and more systematic work is required.
6. Spatial Processing of Urban Acoustic Wave Fields from High-Performance Computations
National Research Council Canada - National Science Library
Ketcham, Stephen A; Wilson, D. K; Cudney, Harley H; Parker, Michael W
2007-01-01
.... The objective of this work is to develop spatial processing techniques for acoustic wave propagation data from three-dimensional high-performance computations to quantify scattering due to urban...
7. Parametric Room Acoustic Workflows
DEFF Research Database (Denmark)
Parigi, Dario; Svidt, Kjeld; Molin, Erik
2017-01-01
The paper investigates and assesses different room acoustics software and the opportunities they offer to engage in parametric acoustics workflow and to influence architectural designs. The first step consists in the testing and benchmarking of different tools on the basis of accuracy, speed...... and interoperability with Grasshopper 3d. The focus will be placed to the benchmarking of three different acoustic analysis tools based on raytracing. To compare the accuracy and speed of the acoustic evaluation across different tools, a homogeneous set of acoustic parameters is chosen. The room acoustics parameters...... included in the set are reverberation time (EDT, RT30), clarity (C50), loudness (G), and definition (D50). Scenarios are discussed for determining at different design stages the most suitable acoustic tool. Those scenarios are characterized, by the use of less accurate but fast evaluation tools to be used...
8. Homogenization scheme for acoustic metamaterials
KAUST Repository
Yang, Min
2014-02-26
We present a homogenization scheme for acoustic metamaterials that is based on reproducing the lowest orders of scattering amplitudes from a finite volume of metamaterials. This approach is noted to differ significantly from that of coherent potential approximation, which is based on adjusting the effective-medium parameters to minimize scatterings in the long-wavelength limit. With the aid of metamaterials’ eigenstates, the effective parameters, such as mass density and elastic modulus can be obtained by matching the surface responses of a metamaterial\\'s structural unit cell with a piece of homogenized material. From the Green\\'s theorem applied to the exterior domain problem, matching the surface responses is noted to be the same as reproducing the scattering amplitudes. We verify our scheme by applying it to three different examples: a layered lattice, a two-dimensional hexagonal lattice, and a decorated-membrane system. It is shown that the predicted characteristics and wave fields agree almost exactly with numerical simulations and experiments and the scheme\\'s validity is constrained by the number of dominant surface multipoles instead of the usual long-wavelength assumption. In particular, the validity extends to the full band in one dimension and to regimes near the boundaries of the Brillouin zone in two dimensions.
9. Simulation of an Underwater Acoustic Communication Channel Characterized by Wind-Generated Surface Waves and Bubbles
NARCIS (Netherlands)
Dol, H.S.; Colin, M.E.G.D.; Ainslie, M.A.; Walree, P.A. van; Janmaat, J.
2012-01-01
Sea surface scattering by wind-generated waves and bubbles is regarded to be the main non-platform related cause of the time variability of shallow acoustic communication channels. Simulations for predicting the quality of acoustic communication links in such channels thus require adequate modeling
10. Methods And Systems For Using Reference Images In Acoustic Image Processing
Science.gov (United States)
Moore, Thomas L.; Barter, Robert Henry
2005-01-04
A method and system of examining tissue are provided in which a field, including at least a portion of the tissue and one or more registration fiducials, is insonified. Scattered acoustic information, including both transmitted and reflected waves, is received from the field. A representation of the field, including both the tissue and the registration fiducials, is then derived from the received acoustic radiation.
11. Acoustic Metamaterials in Aeronautics
Directory of Open Access Journals (Sweden)
Giorgio Palma
2018-06-01
Full Text Available Metamaterials, man-made composites that are scaled smaller than the wavelength, have demonstrated a huge potential for application in acoustics, allowing the production of sub-wavelength acoustic absorbers, acoustic invisibility, perfect acoustic mirrors and acoustic lenses for hyper focusing, and acoustic illusions and enabling new degrees of freedom in the control of the acoustic field. The zero, or even negative, refractive sound index of metamaterials offers possibilities for the control of acoustic patterns and sound at sub-wavelength scales. Despite the tremendous growth in research on acoustic metamaterials during the last decade, the potential of metamaterial-based technologies in aeronautics has still not been fully explored, and its utilization is still in its infancy. Thus, the principal concepts mentioned above could very well provide a means to develop devices that allow the mitigation of the impact of civil aviation noise on the community. This paper gives a review of the most relevant works on acoustic metamaterials, analyzing them for their potential applicability in aeronautics, and, in this process, identifying possible implementation areas and interesting metabehaviors. It also identifies some technical challenges and possible future directions for research with the goal of unveiling the potential of metamaterials technology in aeronautics.
12. Elastic scattering
International Nuclear Information System (INIS)
1991-01-01
With very few unexplained results to challenge conventional ideas, physicists have to look hard to search for gaps in understanding. An area of physics which offers a lot more than meets the eye is elastic and diffractive scattering where particles either 'bounce' off each other, emerging unscathed, or just graze past, emerging relatively unscathed. The 'Blois' workshops provide a regular focus for this unspectacular, but compelling physics, attracting highly motivated devotees
13. Neutron scattering
International Nuclear Information System (INIS)
1991-02-01
The annual report on hand gives an overview of the research work carried out in the Laboratory for Neutron Scattering (LNS) of the ETH Zuerich in 1990. Using the method of neutron scattering, it is possible to examine in detail the static and dynamic properties of the condensed material. In accordance with the multidisciplined character of the method, the LNS has for years maintained a system of intensive co-operation with numerous institutes in the areas of biology, chemistry, solid-state physics, crystallography and materials research. In 1990 over 100 scientists from more than 40 research groups both at home and abroad took part in the experiments. It was again a pleasure to see the number of graduate students present, who were studying for a doctorate and who could be introduced into the neutron scattering during their stay at the LNS and thus were in the position to touch on central ways of looking at a problem in their dissertation using this modern experimental method of solid-state research. In addition to the numerous and interesting ways of formulating the questions to explain the structure, nowadays the scientific programme increasingly includes particularly topical studies in connection with high temperature-supraconductors and materials research
14. Scattering theory
CERN Document Server
Friedrich, Harald
2016-01-01
This corrected and updated second edition of "Scattering Theory" presents a concise and modern coverage of the subject. In the present treatment, special attention is given to the role played by the long-range behaviour of the projectile-target interaction, and a theory is developed, which is well suited to describe near-threshold bound and continuum states in realistic binary systems such as diatomic molecules or molecular ions. It is motivated by the fact that experimental advances have shifted and broadened the scope of applications where concepts from scattering theory are used, e.g. to the field of ultracold atoms and molecules, which has been experiencing enormous growth in recent years, largely triggered by the successful realization of Bose-Einstein condensates of dilute atomic gases in 1995. The book contains sections on special topics such as near-threshold quantization, quantum reflection, Feshbach resonances and the quantum description of scattering in two dimensions. The level of abstraction is k...
15. Springer handbook of acoustics
CERN Document Server
2014-01-01
Acoustics, the science of sound, has developed into a broad interdisciplinary field encompassing the academic disciplines of physics, engineering, psychology, speech, audiology, music, architecture, physiology, neuroscience, and electronics. The Springer Handbook of Acoustics is also in his 2nd edition an unparalleled modern handbook reflecting this richly interdisciplinary nature edited by one of the acknowledged masters in the field, Thomas Rossing. Researchers and students benefit from the comprehensive contents. This new edition of the Handbook features over 11 revised and expanded chapters, new illustrations, and 2 new chapters covering microphone arrays and acoustic emission. Updated chapters contain the latest research and applications in, e.g. sound propagation in the atmosphere, nonlinear acoustics in fluids, building and concert hall acoustics, signal processing, psychoacoustics, computer music, animal bioacousics, sound intensity, modal acoustics as well as new chapters on microphone arrays an...
16. Vibro-acoustics
CERN Document Server
Nilsson, Anders
2015-01-01
This three-volume book gives a thorough and comprehensive presentation of vibration and acoustic theories. Different from traditional textbooks which typically deal with some aspects of either acoustic or vibration problems, it is unique of this book to combine those two correlated subjects together. Moreover, it provides fundamental analysis and mathematical descriptions for several crucial phenomena of Vibro-Acoustics which are quite useful in noise reduction, including how structures are excited, energy flows from an excitation point to a sound radiating surface, and finally how a structure radiates noise to a surrounding fluid. Many measurement results included in the text make the reading interesting and informative. Problems/questions are listed at the end of each chapter and the solutions are provided. This will help the readers to understand the topics of Vibro-Acoustics more deeply. The book should be of interest to anyone interested in sound and vibration, vehicle acoustics, ship acoustics and inter...
17. Handbook of Engineering Acoustics
CERN Document Server
Möser, Michael
2013-01-01
This book examines the physical background of engineering acoustics, focusing on empirically obtained engineering experience as well as on measurement techniques and engineering methods for prognostics. Its goal is not only to describe the state of art of engineering acoustics but also to give practical help to engineers in order to solve acoustic problems. It deals with the origin, the transmission and the methods of the abating different kinds of air-borne and structure-borne sounds caused by various mechanisms – from traffic to machinery and flow-induced sound. In addition the modern aspects of room and building acoustics, as well as psychoacoustics and active noise control, are covered.
18. Acoustic Technology Laboratory
Data.gov (United States)
Federal Laboratory Consortium — This laboratory contains an electro-magnetic worldwide data collection and field measurement capability in the area of acoustic technology. Outfitted by NASA Langley...
19. Ultrasonic trap for light scattering measurement
Science.gov (United States)
Barton, Petr; Pavlu, Jiri
2017-04-01
Light scattering is complex phenomenon occurring widely in space environments, including the dense dusty clouds, nebulas or even the upper atmosphere of the Earth. However, when the size of the dust (or of other scattering center) is close to the incident light wavelength, theoretical determination is difficult. In such case, Mie theory is to be used but there is a lack of the material constants for most space-related materials. For experimental measurement of light scattering, we designed unique apparatus, based on ultrasonic trap. Using acoustic levitation we are able to capture the dust grain in midair, irradiate it with laser, and observe scattering directly with goniometer-mounted photodiode. Advantage of this approach is ability to measure directly in the air (thus, no need for the carrier medium) and possibility to study non-spherical particles. Since the trap development is nearly finished and initial experiments are carried out, the paper presents first tests on water droplets.
20. Hermite scatterers in an ultraviolet sky
Science.gov (United States)
Parker, Kevin J.
2017-12-01
The scattering from spherical inhomogeneities has been a major historical topic in acoustics, optics, and electromagnetics and the phenomenon shapes our perception of the world including the blue sky. The long wavelength limit of ;Rayleigh scattering; is characterized by intensity proportional to k4 (or λ-4) where k is the wavenumber and λ is the wavelength. With the advance of nanotechnology, it is possible to produce scatterers that are inhomogeneous with material properties that are functions of radius r, such as concentric shells. We demonstrate that with proper choice of material properties linked to the Hermite polynomials in r, scatterers can have long wavelength scattering behavior of higher powers: k8, k16, and higher. These ;Hermite scatterers; could be useful in providing unique signatures (or colors) to regions where they are present. If suspended in air under white light, the back-scattered spectrum would be shifted from blue towards violet and then ultraviolet as the higher order Hermite scatterers were illuminated.
1. Acoustic Levitation With Less Equipment
Science.gov (United States)
Barmatz, M. B.; Jacobi, N.
1983-01-01
Certain chamber shapes require fewer than three acoustic drivers. Levitation at center of spherical chamber attained using only one acoustic driver. Exitation of lowest spherical mode produces asymmetric acoustic potential well.
2. What Is an Acoustic Neuroma
Science.gov (United States)
... CALENDAR DONATE NEWS Home Learn Back Learn about acoustic neuroma AN Facts What is acoustic neuroma? Diagnosing ... Italian Japanese Korean Portuguese Romanian Spanish What is Acoustic Neuroma? Each heading slides to reveal information. Important ...
3. Scattering of electromagnetic waves by anomalous fluctuations of a magnetized plasma
Science.gov (United States)
Pavlenko, V. N.; Panchenko, V. G.
1990-04-01
Fluctuations and scattering of transverse electromagnetic waves by density fluctuations in a magnetized plasma in the presence of parametric decay of the pump wave are investigated. The spectral density of electron-density fluctuations is calculated. It is shown that the differential scattering cross-section has sharp maxima at the ion-acoustic and lower-hybrid frequencies when parametric decay of the lower-hybrid pump wave occurs. We note that scattering at the ion-acoustic frequency is dominant. When the pump-wave amplitude tends to the threshold strength of the electric field the scattering cross-section increases anomalously, i.e. there is critical opalescence.
4. Acoustic coupling of two parallel shells in compressible fluid
International Nuclear Information System (INIS)
Gerges, S.N.Y.
1982-01-01
Modifications are done in the acoustic impedance for a vibrating shell, due to the pressure of another similar shell. The multi-analysis method of scattering is used. The results of the impedance in function of the shell radius, the wave length, the distance between the shell axis and its vibration models are presented. (E.G.) [pt
5. Sound Scattering and Its Reduction by a Janus Sphere Type
Directory of Open Access Journals (Sweden)
Deliya Kim
2014-01-01
Full Text Available Sound scattering by a Janus sphere type is considered. The sphere has two surface zones: a soft surface of zero acoustic impedance and a hard surface of infinite acoustic impedance. The zones are arranged such that axisymmetry of the sound field is preserved. The equivalent source method is used to compute the sound field. It is shown that, by varying the sizes of the soft and hard zones on the sphere, a significant reduction can be achieved in the scattered acoustic power and upstream directivity when the sphere is near a free surface and its soft zone faces the incoming wave and vice versa for a hard ground. In both cases the size of the sphere’s hard zone is much larger than that of its soft zone. The boundary location between the two zones coincides with the location of a zero pressure line of the incoming standing sound wave, thus masking the sphere within the sound field reflected by the free surface or the hard ground. The reduction in the scattered acoustic power diminishes when the sphere is placed in free space. Variations of the scattered acoustic power and directivity with the sound frequency are also given and discussed.
6. Diffractive scattering
CERN Document Server
De Wolf, E.A.
2002-01-01
We discuss basic concepts and properties of diffractive phenomena in soft hadron collisions and in deep-inelastic scattering at low Bjorken-x. The paper is not a review of the rapidly developing field but presents an attempt to show in simple terms the close inter-relationship between the dynamics of high-energy hadronic and deep-inelastic diffraction. Using the saturation model of Golec-Biernat and Wusthoff as an example, a simple explanation of geometrical scaling is presented. The relation between the QCD anomalous multiplicity dimension and the Pomeron intercept is discussed.
7. Diffractive Scattering
International Nuclear Information System (INIS)
Wolf, E.A. de
2002-01-01
We discuss basic concepts and properties of diffractive phenomena in soft hadron collisions and in deep-inelastic scattering at low Bjorken - x. The paper is not a review of the rapidly developing field but presents an attempt to show in simple terms the close inter-relationship between the dynamics of high-energy hadronic and deep-inelastic diffraction. Using the saturation model of Golec-Biernat and Wuesthoff as an example, a simple explanation of geometrical scaling is presented. The relation between the QCD anomalous multiplicity dimension and the Pomeron intercept is discussed. (author)
8. Acoustic measuring techniques for suspended sediment
Science.gov (United States)
Gruber, P.; Felix, D.; Storti, G.; Lattuada, M.; Fleckenstein, P.; Deschwanden, F.
2016-11-01
Acoustic signals can be used in various ways for suspended sediment monitoring. One possibility which lends itself particularly well in the context of hydropower plants (HPPs), is to use installations for acoustic discharge measurement (ADM). Such installations already exist at waterways of many HPPs. Similar to certain turbidimeters, the attenuation of the forward scattered signal travelling through the water-sediment mixture is correlated with suspended sediment concentration (SSC). This correlation can be based on reference SSCs, e.g. from gravimetric analyses of bottle samples. Without the need of additional sensors and practically maintenance-free, this method is used successfully in the HPP Fieschertal to warn the HPP operator of high SSC to prevent excessive turbine abrasion. Acoustic methods and systems that allow for estimating both SSC and particle size distribution (PSD) are under development. The simultaneous determination of SSC and PSD is not possible using a single frequency. Therefore, multi-frequency approaches are investigated for generally scattered signals. When backscattered signals are used, a stronger frequency dependency can be exploited. However, the reliable simultaneous determination of particle size (and distribution) and concentration is still a major challenge due to a low signal-to-noise ratio and an ill- posed problem of estimating concentration and size from recorded signals. The optimal setup configuration (angles, frequencies) for such a system is not unique and further investigations are recommended.
9. Scattering and/or diffusing elements in a variety of recently completed music auditoria
Science.gov (United States)
McKay, Ronald L.
2002-11-01
Architectural elements which provide effective acoustic scattering and/or diffusion in a variety of recently completed auditoria for music performance will be presented. Color slides depicting the various elements will be shown. Each will be discussed with respect to its acoustic performance and architectural logic. Measured time-energy reflection patterns will be presented in many cases.
10. Acoustic Neuroma Educational Video
Medline Plus
Full Text Available ... 30041 770-205-8211 [email protected] The world’s #1 acoustic neuroma resource Click to learn more... ... is acoustic neuroma? Diagnosing Symptoms Side Effects Keywords World Language Videos Questions to ask Choosing a healthcare ...
Science.gov (United States)
Ballard, Kenny
2010-01-01
This presentation reviews the status of the acoustic equipment from the medical operations perspective. Included is information about the acoustic dosimeters, sound level meter, and headphones that are planned for use while on orbit. Finally there is information about on-orbit hearing assessments.
12. Broadband and flexible acoustic focusing by metafiber bundles
Science.gov (United States)
Sun, Hong-Xiang; Chen, Jia-He; Ge, Yong; Yuan, Shou-Qi; Liu, Xiao-Jun
2018-06-01
We report a broadband and flexible acoustic focusing through metafiber bundles in air, in which each metafiber consists of eight circular and narrow rectangular cavities. The fractional bandwidth of the acoustic focusing could reach about 0.2, which arises from the eigenmodes of the metafiber structure. Besides, owing to the flexible characteristic of the metafibers, the focus position can be manipulated by bending the metafiber bundles, and the metafiber bundles could bypass rigid scatterers inside the lens structure. More interestingly, the acoustic propagation and focusing directions can be changed by using a designed right-angled direction converter fabricated by the metafibers, and a waveform converter and a focusing lens of the cylindrical acoustic source are realized based on the metafiber bundles. The proposed focusing lens has the advantages of broad bandwidth, flexible structure, and high focusing performance, showing great potentials in versatile applications.
13. Acoustic Signals and Systems
DEFF Research Database (Denmark)
2008-01-01
The Handbook of Signal Processing in Acoustics will compile the techniques and applications of signal processing as they are used in the many varied areas of Acoustics. The Handbook will emphasize the interdisciplinary nature of signal processing in acoustics. Each Section of the Handbook...... will present topics on signal processing which are important in a specific area of acoustics. These will be of interest to specialists in these areas because they will be presented from their technical perspective, rather than a generic engineering approach to signal processing. Non-specialists, or specialists...... from different areas, will find the self-contained chapters accessible and will be interested in the similarities and differences between the approaches and techniques used in different areas of acoustics....
14. Computational Ocean Acoustics
CERN Document Server
Jensen, Finn B; Porter, Michael B; Schmidt, Henrik
2011-01-01
Since the mid-1970s, the computer has played an increasingly pivotal role in the field of ocean acoustics. Faster and less expensive than actual ocean experiments, and capable of accommodating the full complexity of the acoustic problem, numerical models are now standard research tools in ocean laboratories. The progress made in computational ocean acoustics over the last thirty years is summed up in this authoritative and innovatively illustrated new text. Written by some of the field's pioneers, all Fellows of the Acoustical Society of America, Computational Ocean Acoustics presents the latest numerical techniques for solving the wave equation in heterogeneous fluid–solid media. The authors discuss various computational schemes in detail, emphasizing the importance of theoretical foundations that lead directly to numerical implementations for real ocean environments. To further clarify the presentation, the fundamental propagation features of the techniques are illustrated in color. Computational Ocean A...
15. Acoustic simulations of Mudejar-Gothic churches.
Science.gov (United States)
Galindo, Miguel; Zamarreño, Teófilo; Girón, Sara
2009-09-01
In this paper, an iterative process is used in order to estimate the values of absorption coefficients of those materials of which little is known in the literature, so that an acoustic simulation can be carried out in Mudejar-Gothic churches. The estimation of the scattering coefficients, which is even less developed, is based on the size of the irregularities. This methodology implemented is applied to six Mudejar-Gothic churches of Seville (southern Spain). The simulated monophonic acoustic parameters, both in the frequency domain and as a function of source-receiver distance (spatial distribution), are analyzed and compared with the in situ measures. Good agreement has been found between these sets of values, whereby each parameter is discussed in terms of the just noticeable difference. This procedure for existing buildings, especially for those which are rich in heritage, enables a reliable evaluation of the effect on the maintenance, restoration, and conditioning for new uses, as well as the recreation of the acoustic environment of ancient times. Along these lines, the acoustic influence of the timber roof and the presence of the public in these churches have also been studied.
16. Calibration of acoustic emission transducers
International Nuclear Information System (INIS)
Leschek, W.C.
1976-01-01
A method is described for calibrating an acoustic emission transducer to be used in a pre-set frequency range. The absolute reception sensitivity of a reference transducer is determined at frequencies selected within the frequency range. The reference transducer and the acoustic emission transducer are put into acoustic communication with the surface of a limited acoustic medium representing an equivalent acoustic load appreciably identical to that of the medium in which the use of the acoustic emission transducer is intended. A blank random acoustic noise is emitted in the acoustic medium in order to establish a diffuse and reverberating sound field, after which the output responses of the reference transducer and of the acoustic emission transducer are obtained with respect to the diffuse and reverberating field, for selected frequencies. The output response of the acoustic emission transducer is compared with that of the reference transducer for the selected frequencies, so as to determine the reception sensitivity of the acoustic emission transducer [fr
17. Parametric Room Acoustic workflows with real-time acoustic simulation
DEFF Research Database (Denmark)
Parigi, Dario
2017-01-01
The paper investigates and assesses the opportunities that real-time acoustic simulation offer to engage in parametric acoustics workflow and to influence architectural designs from early design stages......The paper investigates and assesses the opportunities that real-time acoustic simulation offer to engage in parametric acoustics workflow and to influence architectural designs from early design stages...
18. Electrical circuit modeling and analysis of microwave acoustic interaction with biological tissues.
Science.gov (United States)
Gao, Fei; Zheng, Qian; Zheng, Yuanjin
2014-05-01
Numerical study of microwave imaging and microwave-induced thermoacoustic imaging utilizes finite difference time domain (FDTD) analysis for simulation of microwave and acoustic interaction with biological tissues, which is time consuming due to complex grid-segmentation and numerous calculations, not straightforward due to no analytical solution and physical explanation, and incompatible with hardware development requiring circuit simulator such as SPICE. In this paper, instead of conventional FDTD numerical simulation, an equivalent electrical circuit model is proposed to model the microwave acoustic interaction with biological tissues for fast simulation and quantitative analysis in both one and two dimensions (2D). The equivalent circuit of ideal point-like tissue for microwave-acoustic interaction is proposed including transmission line, voltage-controlled current source, envelop detector, and resistor-inductor-capacitor (RLC) network, to model the microwave scattering, thermal expansion, and acoustic generation. Based on which, two-port network of the point-like tissue is built and characterized using pseudo S-parameters and transducer gain. Two dimensional circuit network including acoustic scatterer and acoustic channel is also constructed to model the 2D spatial information and acoustic scattering effect in heterogeneous medium. Both FDTD simulation, circuit simulation, and experimental measurement are performed to compare the results in terms of time domain, frequency domain, and pseudo S-parameters characterization. 2D circuit network simulation is also performed under different scenarios including different sizes of tumors and the effect of acoustic scatterer. The proposed circuit model of microwave acoustic interaction with biological tissue could give good agreement with FDTD simulated and experimental measured results. The pseudo S-parameters and characteristic gain could globally evaluate the performance of tumor detection. The 2D circuit network
19. What does See the Impulse Acoustic Microscopy inside Nanocomposites?
Science.gov (United States)
Levin, V. M.; Petronyuk, Y. S.; Morokov, E. S.; Celzard, A.; Bellucci, S.; Kuzhir, P. P.
The paper presents results of studying bulk microstructure in carbon nanocomposites by impulse acoustic microscopy technique. Nanocomposite materials are in the focus of interest because of their outstanding properties in minimal nanofiller content. Large surface area and high superficial activity cause strong interaction between nanoparticles that can result in formation of fractal conglomerates. This paper involves results of the first direct observation of nanoparticle conglomerates inside the bulk of epoxy-carbon nanocomposites. Diverse types of carbon nanofiller have been under investigation. The impulse acoustic microscope SIAM-1 (Acoustic Microscopy Lab, IBCP RAS) has been employed for 3D imaging bulk microstructure and measuring elastic properties of the nanocomposite specimens. The range of 50-200 MHz allows observing microstructure inside the entire specimen bulk. Acoustic images are obtained in the ultramicroscopic regime; they are formed by the Rayleigh type scattered radiation. It has been found the high-resolution acoustic vision (impulse acoustic microscopy) is an efficient technique to observe mesostructure formed by fractal cluster inside nanocomposites. The clusterization takes its utmost form in nanocomposites with graphite nanoplatelets as nanofiller. The nanoparticles agglomerate into micron-sized conglomerates distributed randomly over the material. Mesostructure in nanocomposites filled with carbon nanotubes is alternation of regions with diverse density of nanotube packing. Regions with alternative density of CNT packing are clearly seen in acoustical images as neighboring pixels of various brightness.
20. Transmission acoustic microscopy investigation
Science.gov (United States)
Maev, Roman; Kolosov, Oleg; Levin, Vadim; Lobkis, Oleg
The nature of acoustic contrast, i.e. the connection of the amplitude and phase of the output signal of the acoustic microscope with the local values of the acoustic parameters of the sample (density, elasticity, viscosity) is a central problem of acoustic microscopy. A considerable number of studies have been devoted to the formation of the output signal of the reflection scanning acoustic microscope. For the transmission acoustic microscope (TAM) this problem has remained almost unstudied. Experimental investigation of the confocal system of the TAM was carried out on an independently manufactured laboratory mockup of the TAM with the working frequency of the 420 MHz. Acoustic lenses with the radius of curvature of about 500 microns and aperture angle of 45 deg were polished out in the end faces of two cylindrical sound conductors made from Al2O3 single crystals with an axis parallel to the axis C of the crystal (the length of the sound conductor is 20 mm; diameter, 6 mm). At the end faces of the sound conductor, opposite to the lenses, CdS transducers with a diameter of 2 mm were disposed. The electric channel of the TAM provided a possibility for registering the amplitude of the microscope output signal in the case of the dynamic range of the 50 dB.
1. The accidental (acoustical) tourist
Science.gov (United States)
Van Kirk, Wayne
2002-11-01
The acoustical phenomenon observed at an ancient temple in the Great Ball Court at Chichen Itza was described as ''little short of amazing--an ancient whispering gallery'' by Silvanus G. Morley, leader of the Carnegie Institute's archaeological team that excavated and restored these structures in the 1920s. Since then, many others have experienced the extraordinary acoustics at Chichen Itza and other Maya sites. Despite these reports, archaeologists and acousticians have until recently shown little interest in understanding these phenomena. After experiencing Chichen Itza's remarkable acoustics as a tourist in 1994, the author commenced collecting and disseminating information about acoustical phenomena there and at other Mayan sites, hoping to stimulate interest among archaeologists and acousticians. Were these designs accidental or intentional? If intentional, how was the knowledge obtained? How were acoustical features used? This paper highlights the author's collection of anecdotal reports of mysterious Mayan acoustics (http://http://www.ianlawton.com/pa1.htm), recommended reading for scientists and engineers who wish to pursue this fascinating study. Also recounted are some of the reactions of archaeologists-ranging from curious, helpful, and insightful to humorous and appalling--to outsiders' efforts to bring serious scientific attention to the new field of acoustical archaeology.
2. Enhanced ion acoustic fluctuations and ion outflows
Directory of Open Access Journals (Sweden)
F. R. E. Forme
1999-02-01
Full Text Available A number of observations showing enhanced ion acoustic echoes observed by means of incoherent scatter radars have been reported in the literature. The received power is extremely enhanced by up to 1 or 2 orders of magnitude above usual values, and it is mostly contained in one of the two ion acoustic lines. This spectral asymmetry and the intensity of the received signal cannot be resolved by the standard analysis procedure and often causes its failure. As a result, and in spite of a very clear spectral signature, the analysis is unable to fit the plasma parameters inside the regions of ion acoustic turbulence. We present European Incoherent Scatter radar (EISCAT observations of large ion outflows associated with the simultaneous occurrence of enhanced ion acoustic echoes. The ion fluxes can reach 1014 m-2 s-1 at 800 km altitude. From the very clear spectral signatures of these echoes, a method is presented to extract estimates of the electron temperature and the ion drift within the turbulent regions. It is shown that the electron gas is strongly heated up to 11 000 K. Also electron temperature gradients of about 0.02 K/m exist. Finally, the estimates of the electron temperature and of the ion drift are used to study the possible implications for the plasma transport inside turbulent regions. It is shown that strong electron temperature gradients cause enhancement of the ambipolar electric field and can account for the observed ion outflows.Key words. Ionosphere (auroral ionosphere; ionosphere · magnetosphere interactions; plasma waves and instabilities.
3. Translational illusion of acoustic sources by transformation acoustics.
Science.gov (United States)
Sun, Fei; Li, Shichao; He, Sailing
2017-09-01
An acoustic illusion of creating a translated acoustic source is designed by utilizing transformation acoustics. An acoustic source shifter (ASS) composed of layered acoustic metamaterials is designed to achieve such an illusion. A practical example where the ASS is made with naturally available materials is also given. Numerical simulations verify the performance of the proposed device. The designed ASS may have some applications in, e.g., anti-sonar detection.
4. Acoustic building infiltration measurement system
Science.gov (United States)
Muehleisen, Ralph T.; Raman, Ganesh
2018-04-10
Systems and methods of detecting and identifying a leak from a container or building. Acoustic pressure and velocity are measured. Acoustic properties are acquired from the measured values. The acoustic properties are converted to infiltration/leakage information. Nearfield Acoustic Holography (NAH) may be one method to detect the leakages from a container by locating the noise sources.
5. Neutron scattering. Lectures
International Nuclear Information System (INIS)
Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner
2012-01-01
The following topics are dealt with: Neutron scattering in contemporary research, neutron sources, symmetry of crystals, diffraction, nanostructures investigated by small-angle neutron scattering, the structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic scattering, strongly correlated electrons, dynamics of macromolecules, applications of neutron scattering. (HSI)
6. Acoustical heat pumping engine
Science.gov (United States)
Wheatley, J.C.; Swift, G.W.; Migliori, A.
1983-08-16
The disclosure is directed to an acoustical heat pumping engine without moving seals. A tubular housing holds a compressible fluid capable of supporting an acoustical standing wave. An acoustical driver is disposed at one end of the housing and the other end is capped. A second thermodynamic medium is disposed in the housing near to but spaced from the capped end. Heat is pumped along the second thermodynamic medium toward the capped end as a consequence both of the pressure oscillation due to the driver and imperfect thermal contact between the fluid and the second thermodynamic medium. 2 figs.
7. Deep Water Acoustics
Science.gov (United States)
2016-06-28
the Deep Water project and participate in the NPAL Workshops, including Art Baggeroer (MIT), J. Beron- Vera (UMiami), M. Brown (UMiami), T...Kathleen E . Wage. The North Pacific Acoustic Laboratory deep-water acoustic propagation experiments in the Philippine Sea. J. Acoust. Soc. Am., 134(4...estimate of the angle α during PhilSea09, made from ADCP measurements at the site of the DVLA. Sim. A B1 B2 B3 C D E F Prof. # 0 4 4 4 5 10 16 20 α
8. Radiation acoustics and its applications
International Nuclear Information System (INIS)
Lyamshev, L.M.
1992-01-01
Radiation acoustics is a new branch of acoustics, developing on the boundary of acoustics, nuclear physics, elementary particles and high-energy physics. Its fundamentals are laying in the research of acoustical effects due to the interaction of penetrating radiation with matter. The study of radiation-acoustical effects leads to the new opportunities in the penetration radiation research (acoustical detection, radiation-acoustical dosimetry), study of the physical parameters of matter, in a solution of some applied problems of nondestructive testing, and also for the radiation-acoustical influence on physical and chemical structure of the matter. Results of theoretical and experimental investigations are given. Different mechanisms of the sound generation by penetrating radiation of liquids and solids are considered. Some applications - the radiation acoustical microscopy and visualisation, the acoustical detection of high energy X-ray particles and possibility of using of high energy neutrino beams in geoacoustics - are discussed
9. Particle levitation and laboratory scattering
International Nuclear Information System (INIS)
Reid, Jonathan P.
2009-01-01
Measurements of light scattering from aerosol particles can provide a non-intrusive in situ method for characterising particle size distributions, composition, refractive index, phase and morphology. When coupled with techniques for isolating single particles, considerable information on the evolution of the properties of a single particle can be gained during changes in environmental conditions or chemical processing. Electrostatic, acoustic and optical techniques have been developed over many decades for capturing and levitating single particles. In this review, we will focus on studies of particles in the Mie size regime and consider the complimentarity of electrostatic and optical techniques for levitating particles and elastic and inelastic light scattering methods for characterising particles. In particular, we will review the specific advantages of establishing a single-beam gradient force optical trap (optical tweezers) for manipulating single particles or arrays of particles. Recent developments in characterising the nature of the optical trap, in applying elastic and inelastic light scattering measurements for characterising trapped particles, and in manipulating particles will be considered.
10. Point sources and multipoles in inverse scattering theory
CERN Document Server
Potthast, Roland
2001-01-01
Over the last twenty years, the growing availability of computing power has had an enormous impact on the classical fields of direct and inverse scattering. The study of inverse scattering, in particular, has developed rapidly with the ability to perform computational simulations of scattering processes and led to remarkable advances in a range of applications, from medical imaging and radar to remote sensing and seismic exploration. Point Sources and Multipoles in Inverse Scattering Theory provides a survey of recent developments in inverse acoustic and electromagnetic scattering theory. Focusing on methods developed over the last six years by Colton, Kirsch, and the author, this treatment uses point sources combined with several far-reaching techniques to obtain qualitative reconstruction methods. The author addresses questions of uniqueness, stability, and reconstructions for both two-and three-dimensional problems.With interest in extracting information about an object through scattered waves at an all-ti...
11. Design of a broadband ultra-large area acoustic cloak based on a fluid medium
Science.gov (United States)
Zhu, Jian; Chen, Tianning; Liang, Qingxuan; Wang, Xiaopeng; Jiang, Ping
2014-10-01
A broadband ultra-large area acoustic cloak based on fluid medium was designed and numerically implemented with homogeneous metamaterials according to the transformation acoustics. In the present work, fluid medium as the body of the inclusion could be tuned by changing the fluid to satisfy the variant acoustic parameters instead of redesign the whole cloak. The effective density and bulk modulus of the composite materials were designed to agree with the parameters calculated from the coordinate transformation methodology by using the effective medium theory. Numerical simulation results showed that the sound propagation and scattering signature could be controlled in the broadband ultra-large area acoustic invisibility cloak, and good cloaking performance has been achieved and physically realized with homogeneous materials. The broadband ultra-large area acoustic cloaking properties have demonstrated great potentials in the promotion of the practical applications of acoustic cloak.
12. Diffraction and diffusion in room acoustics
DEFF Research Database (Denmark)
Rindel, Jens Holger; Rasmussen, Birgit
1996-01-01
Diffraction and diffusion are two phenomena that are both related to the wave nature of sound. Diffraction due to the finite size of reflecting surfaces and the design of single reflectors and reflector arrays are discussed. Diffusion is the result of scattering of sound reflected from surfaces...... that are not plane but curved or irregular. The importance of diffusion has been demonstrated in concert halls. Methods for the design of diffusing surfaces and the development of new types of diffusers are reviewed. Finally, the importance of diffraction and diffusion in room acoustic computer models is discussed....
13. Physical Acoustics in the Solid State
CERN Document Server
Lüthi, B
2006-01-01
Suitable for researchers and graduate students in physics and material science, "Physical Acoustics in the Solid State" reviews the modern aspects in the field, including many experimental results, especially those involving ultrasonics. Practically all fields of solid-state physics are covered: metals, semiconductors, magnetism, superconductivity, different kinds of phase transitions, low-dimensional systems, and the quantum Hall effect. After a review of the relevant experimental techniques and an introduction to the theory of elasticity, emphasizing the symmetry aspects, applications in the various fields of condensed matter physics are presented. Also treated are Brillouin-scattering results and results from thermodynamic investigations, such as thermal expansion and specific heat.
14. Physical Acoustics in the Solid State
CERN Document Server
Lüthi, Bruno
2007-01-01
Suitable for researchers and graduate students in physics and material science, "Physical Acoustics in the Solid State" reviews the modern aspects in the field, including many experimental results, especially those involving ultrasonics. Practically all fields of solid-state physics are covered: metals, semiconductors, magnetism, superconductivity, different kinds of phase transitions, low-dimensional systems, and the quantum Hall effect. After a review of the relevant experimental techniques and an introduction to the theory of elasticity, emphasizing the symmetry aspects, applications in the various fields of condensed matter physics are presented. Also treated are Brillouin-scattering results and results from thermodynamic investigations, such as thermal expansion and specific heat.
15. A numerical study of microparticle acoustophoresis driven by acoustic radiation forces and streaming-induced drag forces
DEFF Research Database (Denmark)
Muller, Peter Barkholt; Barnkob, Rune; Jensen, Mads Jakob Herring
2012-01-01
We present a numerical study of the transient acoustophoretic motion of microparticles suspended in a liquid-filled microchannel and driven by the acoustic forces arising from an imposed standing ultrasound wave: the acoustic radiation force from the scattering of sound waves on the particles...
16. Acoustic Neuroma Educational Video
Medline Plus
Full Text Available ... a healthcare provider Request a patient kit Treatment Options Overview Observation Radiation Surgery What is acoustic neuroma Diagnosing Symptoms Side effects Question To Ask Treatment Options Back Overview Observation Radiation Surgery Choosing a healthcare ...
17. Acoustic-Levitation Chamber
Science.gov (United States)
Barmatz, M. B.; Granett, D.; Lee, M. C.
1984-01-01
Uncontaminated environments for highly-pure material processing provided within completely sealed levitation chamber that suspends particles by acoustic excitation. Technique ideally suited for material processing in low gravity environment of space.
18. Acoustic Casimir Effect
National Research Council Canada - National Science Library
Homes, Christopher
1997-01-01
...). When the indirect manifestations of the ZPF are interpreted as due to radiation pressure, acoustic noise can provide an excellent analog to investigate the Casimir effect as well as other effects due to the ZPF...
19. Acoustic Neuroma Educational Video
Medline Plus
Full Text Available ... a patient kit Treatment Options Overview Observation Radiation Surgery What is acoustic neuroma Diagnosing Symptoms Side effects ... To Ask Treatment Options Back Overview Observation Radiation Surgery Choosing a healthcare provider Request a patient kit ...
20. Acoustic Neuroma Educational Video
Medline Plus
Full Text Available ... Choosing a healthcare provider Request a patient kit Treatment Options Overview Observation Radiation Surgery What is acoustic neuroma Diagnosing Symptoms Side effects Question To Ask Treatment Options Back Overview Observation Radiation Surgery Choosing a ...
1. Acoustic ambient noise recorder
Digital Repository Service at National Institute of Oceanography (India)
Saran, A.K.; Navelkar, G.S.; Almeida, A.M.; More, S.R.; Chodankar, P.V.; Murty, C.S.
with a robust outfit that can withstand high pressures and chemically corrosion resistant materials. Keeping these considerations in view, a CMOS micro-controller-based marine acoustic ambient noise recorder has been developed with a real time clock...
2. Acoustic Neuroma Educational Video
Medline Plus
Full Text Available ... Learn more about ANA About ANA Mission, Vision & Values Shop ANA Leadership & Staff Annual Reports Acoustic Neuroma ... 8211 [email protected] About ANA Mission, Vision & Values Leadership & Staff Annual Reports Shop ANA Home Learn ...
3. Acoustic Neuroma Educational Video
Medline Plus
Full Text Available ... ANA About ANA Mission, Vision & Values Shop ANA Leadership & Staff Annual Reports Acoustic Neuroma Association 600 Peachtree ... [email protected] About ANA Mission, Vision & Values Leadership & Staff Annual Reports Shop ANA Home Learn Educational ...
4. Acoustic Neuroma Educational Video
Medline Plus
Full Text Available ... patient kit Treatment Options Overview Observation Radiation Surgery What is acoustic neuroma Diagnosing ... Back Community Patient Stories Share Your Story Video Stories Caregivers Milestones Gallery Submit Your Milestone Team ANA Volunteer ...
5. Acoustic Neuroma Educational Video
Medline Plus
Full Text Available ... Connections Overview Find a Meeting Host a Meeting Volunteer Become a Volunteer Opportunities Support Overview Patient Events ... ANA About ANA Mission, Vision & Values Shop ANA Leadership & Staff Annual Reports Acoustic Neuroma Association 600 Peachtree ...
Data.gov (United States)
Federal Laboratory Consortium — FUNCTION: Collects underwater acoustic data and oceanographic data. Data are recorded onboard an ocean buoy and can be telemetered to a remote ship or shore station...
7. Acoustic MIMO signal processing
CERN Document Server
Huang, Yiteng; Chen, Jingdong
2006-01-01
A timely and important book addressing a variety of acoustic signal processing problems under multiple-input multiple-output (MIMO) scenarios. It uniquely investigates these problems within a unified framework offering a novel and penetrating analysis.
8. Acoustic Neuroma Educational Video
Medline Plus
Full Text Available ... Back Learn more about ANA About ANA Mission, Vision & Values Shop ANA Leadership & Staff Annual Reports Acoustic ... 205-8211 [email protected] About ANA Mission, Vision & Values Leadership & Staff Annual Reports Shop ANA Home ...
9. Thermal Acoustic Fatigue Apparatus
Data.gov (United States)
Federal Laboratory Consortium — The Thermal Acoustic Fatigue Apparatus (TAFA) is a progressive wave tube test facility that is used to test structures for dynamic response and sonic fatigue due to...
10. Acoustic Neuroma Educational Video
Medline Plus
Full Text Available ... Spanish Washington Support Group Leslie of Stone Mountain, ... Providers Acoustic Neuroma Association Donate Now Newly Diagnosed What is AN? Request a Patient Kit Treatment Options Get Support Find a Provider Discussion Forum ...
11. Acoustic Neuroma Educational Video
Medline Plus
Full Text Available ... Mission, Vision & Values Shop ANA Leadership & Staff Annual Reports Acoustic Neuroma Association 600 Peachtree Parkway Suite 108 ... About ANA Mission, Vision & Values Leadership & Staff Annual Reports Shop ANA Home Learn Educational Video English English ...
12. Acoustic Igniter, Phase I
Data.gov (United States)
National Aeronautics and Space Administration — An acoustic igniter eliminates the need to use electrical energy to drive spark systems to initiate combustion in liquid-propellant rockets. It does not involve the...
13. Department of Cybernetic Acoustics
Science.gov (United States)
The development of the theory, instrumentation and applications of methods and systems for the measurement, analysis, processing and synthesis of acoustic signals within the audio frequency range, particularly of the speech signal and the vibro-acoustic signal emitted by technical and industrial equipments treated as noise and vibration sources was discussed. The research work, both theoretical and experimental, aims at applications in various branches of science, and medicine, such as: acoustical diagnostics and phoniatric rehabilitation of pathological and postoperative states of the speech organ; bilateral ""man-machine'' speech communication based on the analysis, recognition and synthesis of the speech signal; vibro-acoustical diagnostics and continuous monitoring of the state of machines, technical equipments and technological processes.
14. Acoustic Neuroma Educational Video
Medline Plus
Full Text Available ... 1 acoustic neuroma resource Click to learn more... LOGIN CALENDAR DONATE NEWS Home Learn Back Learn about ... Webinar Library Newsletter Library Patient Info Booklets Member Login Research ANA Survey/Registry AN Research Patient Registry ...
15. Acoustic Neuroma Educational Video
Medline Plus
Full Text Available ... About ANA Mission, Vision & Values Shop ANA Leadership & Staff Annual Reports Acoustic Neuroma Association 600 Peachtree Parkway ... ANAUSA.org About ANA Mission, Vision & Values Leadership & Staff Annual Reports Shop ANA Home Learn Educational Video ...
16. Acoustic Neuroma Educational Video
Medline Plus
Full Text Available ... Click to learn more... LOGIN CALENDAR DONATE NEWS Home Learn Back Learn about acoustic neuroma AN Facts ... Vision & Values Leadership & Staff Annual Reports Shop ANA Home Learn Educational Video English English Arabic Catalan Chinese ( ...
17. Acoustic imaging system
Science.gov (United States)
Smith, Richard W.
1979-01-01
An acoustic imaging system for displaying an object viewed by a moving array of transducers as the array is pivoted about a fixed point within a given plane. A plurality of transducers are fixedly positioned and equally spaced within a laterally extending array and operatively directed to transmit and receive acoustic signals along substantially parallel transmission paths. The transducers are sequentially activated along the array to transmit and receive acoustic signals according to a preestablished sequence. Means are provided for generating output voltages for each reception of an acoustic signal, corresponding to the coordinate position of the object viewed as the array is pivoted. Receptions from each of the transducers are presented on the same display at coordinates corresponding to the actual position of the object viewed to form a plane view of the object scanned.
18. Principles of musical acoustics
CERN Document Server
Hartmann, William M
2013-01-01
Principles of Musical Acoustics focuses on the basic principles in the science and technology of music. Musical examples and specific musical instruments demonstrate the principles. The book begins with a study of vibrations and waves, in that order. These topics constitute the basic physical properties of sound, one of two pillars supporting the science of musical acoustics. The second pillar is the human element, the physiological and psychological aspects of acoustical science. The perceptual topics include loudness, pitch, tone color, and localization of sound. With these two pillars in place, it is possible to go in a variety of directions. The book treats in turn, the topics of room acoustics, audio both analog and digital, broadcasting, and speech. It ends with chapters on the traditional musical instruments, organized by family. The mathematical level of this book assumes that the reader is familiar with elementary algebra. Trigonometric functions, logarithms and powers also appear in the book, but co...
19. Anal acoustic reflectometry
DEFF Research Database (Denmark)
Mitchell, Peter J; Klarskov, Niels; Telford, Karen J
2011-01-01
Anal acoustic reflectometry is a new technique of assessing anal sphincter function. Five new variables reflecting anal canal function are measured: the opening and closing pressure, the opening and closing elastance, and hysteresis.......Anal acoustic reflectometry is a new technique of assessing anal sphincter function. Five new variables reflecting anal canal function are measured: the opening and closing pressure, the opening and closing elastance, and hysteresis....
20. Bidirectional optical scattering facility
Data.gov (United States)
Federal Laboratory Consortium — Goniometric optical scatter instrument (GOSI)The bidirectional reflectance distribution function (BRDF) quantifies the angular distribution of light scattered from a...
1. Crystal-like nature of acoustic excitations in glassy ethanol
International Nuclear Information System (INIS)
Matic, A.; Engberg, D.; Boerjesson, L.; Masciovecchio, C.; Santucci, S.C.; Monaco, G.; Verbeni, R.
2004-01-01
We report on inelastic x-ray scattering experiments on crystalline and glassy phases of ethanol in order to directly compare the influence of disorder on high frequency acoustic excitations. We find that both the dispersion and the line-width of the longitudinal acoustic excitations in the glass are the same as in the polycrystal in the reciprocal space portion covering the 1st and 2nd Brillouin zones. The structural disorder is found to play little role apart from an intrinsic angular averaging, and the nature of these excitations must essentially be the same in both glass and poly crystal
2. Acoustic calibration apparatus for calibrating plethysmographic acoustic pressure sensors
Science.gov (United States)
Zuckerwar, Allan J. (Inventor); Davis, David C. (Inventor)
1995-01-01
An apparatus for calibrating an acoustic sensor is described. The apparatus includes a transmission material having an acoustic impedance approximately matching the acoustic impedance of the actual acoustic medium existing when the acoustic sensor is applied in actual in-service conditions. An elastic container holds the transmission material. A first sensor is coupled to the container at a first location on the container and a second sensor coupled to the container at a second location on the container, the second location being different from the first location. A sound producing device is coupled to the container and transmits acoustic signals inside the container.
3. Three forms of omnidirectional acoustic invisibility engineered using fast elastodynamic transfer-matrix method
International Nuclear Information System (INIS)
Bowen, Patrick T; Urzhumov, Yaroslav A
2016-01-01
Acoustic metamaterial structures with discrete and continuous rotational symmetries attract interest of theorists and engineers due to the relative simplicity of their design and fabrication. They are also likely candidates for omnidirectional acoustic cloaking and other transformation-acoustical novelties. In this paper, we employ a stratified description of such structures, and develop the theory and an efficient symbolic/numerical algorithm for analyzing the scattering properties of such structures immersed in homogeneous fluid environments. The algorithm calculates the partial scattering amplitudes and the related scattering phases for an arbitrary layered distribution of acoustic material properties. The efficiency of the algorithm enables us to find approximate solutions to certain inverse scattering problems through quasi-global optimization. The scattering problems addressed here are the three forms of cloaking: (1) extinction cross-section suppression, the canonical form of cloaking, (2) monostatic sonar invisibility (backscattering suppression), and (3) acoustic force cloaking (transport cross-section suppression). We also address the efficiency-bandwidth tradeoff and design approximate cloaks with wider bandwidth using a new optimization formulation. (paper)
4. Three forms of omnidirectional acoustic invisibility engineered using fast elastodynamic transfer-matrix method
Science.gov (United States)
Bowen, Patrick T.; Urzhumov, Yaroslav A.
2016-04-01
Acoustic metamaterial structures with discrete and continuous rotational symmetries attract interest of theorists and engineers due to the relative simplicity of their design and fabrication. They are also likely candidates for omnidirectional acoustic cloaking and other transformation-acoustical novelties. In this paper, we employ a stratified description of such structures, and develop the theory and an efficient symbolic/numerical algorithm for analyzing the scattering properties of such structures immersed in homogeneous fluid environments. The algorithm calculates the partial scattering amplitudes and the related scattering phases for an arbitrary layered distribution of acoustic material properties. The efficiency of the algorithm enables us to find approximate solutions to certain inverse scattering problems through quasi-global optimization. The scattering problems addressed here are the three forms of cloaking: (1) extinction cross-section suppression, the canonical form of cloaking, (2) monostatic sonar invisibility (backscattering suppression), and (3) acoustic force cloaking (transport cross-section suppression). We also address the efficiency-bandwidth tradeoff and design approximate cloaks with wider bandwidth using a new optimization formulation.
5. Ultrasonic superlensing jets and acoustic-fork sheets
Energy Technology Data Exchange (ETDEWEB)
Mitri, F.G., E-mail: [email protected]
2017-05-18
Focusing acoustical (and optical) beams beyond the diffraction limit has remained a major challenge in imaging instruments and systems, until recent advances on “hyper” or “super” lensing and higher-resolution imaging techniques have shown the counterintuitive violation of this rule under certain circumstances. Nonetheless, the proposed technologies of super-resolution acoustical focusing beyond the diffraction barrier require complex tools such as artificially engineered metamaterials, and other hardware equipment that may not be easily synthesized or manufactured. The present contribution therefore suggests a simple and reliable method of using a sound-penetrable circular cylinder lens illuminated by a nonparaxial Gaussian acoustical sheet (i.e. finite beam in 2D) to produce non-evanescent ultrasonic superlensing jets (or bullets) and acoustical ‘snail-fork’ shaped wavefronts with limited diffraction. The generalized (near-field) scattering theory for acoustical sheets of arbitrary wavefronts and incidence is utilized to synthesize the incident beam based upon the angular spectrum decomposition method and the multipole expansion method in cylindrical wave functions to compute the scattered pressure around the cylinder with particular emphasis on its physical properties. The results show that depending on the beam and lens parameters, a tight focusing (with dimensions much smaller than the beam waist) can be achieved. Subwavelength resolution can be also achieved by selecting a lens material with a speed of sound exceeding that of the host fluid medium. The ultrasonic superlensing jets provide the impetus to develop improved subwavelength microscopy and acoustical image-slicing systems, cell lysis and surgery, and photoacoustic imaging to name a few examples. Moreover, an acoustical fork-sheet generation may open innovative avenues in reconfigurable on-chip micro/nanoparticle tweezers and surface acoustic waves devices. - Highlights: • Ultrasonic
6. Photoacoustic imaging in scattering media by combining a correlation matrix filter with a time reversal operator.
Science.gov (United States)
Rui, Wei; Tao, Chao; Liu, Xiaojun
2017-09-18
Acoustic scattering medium is a fundamental challenge for photoacoustic imaging. In this study, we reveal the different coherent properties of the scattering photoacoustic waves and the direct photoacoustic waves in a matrix form. Direct waves show a particular coherence on the antidiagonals of the matrix, whereas scattering waves do not. Based on this property, a correlation matrix filter combining with a time reversal operator is proposed to preserve the direct waves and recover the image behind a scattering layer. Both numerical simulations and photoacoustic imaging experiments demonstrate that the proposed approach effectively increases the image contrast and decreases the background speckles in a scattering medium. This study might improve the quality of photoacoustic imaging in an acoustic scattering environment and extend its applications.
7. Internal tides and deep diel fades in acoustic intensity.
Science.gov (United States)
White, Andrew W; Henyey, Frank S; Andrew, Rex K; Mercer, James A; Worcester, Peter F; Dzieciuch, Matthew A; Colosi, John A
2016-11-01
A mechanism is presented by which the observed acoustic intensity is made to vary due to changes in the acoustic path that are caused by internal-tide vertical fluid displacements. The position in range and depth of large-scale caustic structure is determined by the background sound-speed profile. Internal tides cause a deformation of the background profile, changing the positions of the caustic structures-which can introduce intensity changes at a distant receiver. Gradual fades in the acoustic intensity occurring over timescales similar to those of the tides were measured during a low-frequency (284-Hz) acoustic scattering experiment in the Philippine Sea in 2009 [White et al., J. Acoust. Soc. Am. 134(4), 3347-3358 (2013)]. Parabolic equation and Hamiltonian ray-tracing calculations of acoustic propagation through a plane-wave internal tide environmental model employing sound-speed profiles taken during the experiment indicate that internal tides could cause significant gradual changes in the received intensity. Furthermore, the calculations demonstrate how large-scale perturbations to the index of refraction can result in variation in the received intensity.
8. Acoustic wave spread in superconducting-normal-superconducting sandwich
International Nuclear Information System (INIS)
2004-01-01
The acoustic wave spread, perpendicular to the boundaries between superconducting and normal metals in superconducting-normal-superconducting (SNS) sandwich has been considered. The alternate current flow sound induced by the Green function method has been found and the coefficient of the acoustic wave transmission through the junction γ=(S 1 -S 2 )/S 1 , (where S 1 and S 2 are average energy flows formed on the first and second boundaries) as a function of the phase difference between superconductors has been investigated. It is shown that while the SNS sandwich is almost transparent for acoustic waves (γ 0 /τ), n=0,1,2, ... (where τ 0 /τ is the ratio of the broadening of the quasiparticle energy levels in impurity normal metal as a result of scattering of the carriers by impurities 1/τ to the spacing between energy levels 1/τ 0 ), γ=2, (S 2 =-S 1 ), which corresponds to the full reflection of the acoustic wave from SNS sandwich. This result is valid for the limit of a pure normal metal but in the main impurity case there are two amplification and reflection regions for acoustic waves. The result obtained shows promise for the SNS sandwich as an ideal mirror for acoustic wave reflection
9. Acoustic comfort in eating establishments
DEFF Research Database (Denmark)
Svensson, David; Jeong, Cheol-Ho; Brunskog, Jonas
2014-01-01
The subjective concept of acoustic comfort in eating establishments has been investigated in this study. The goal was to develop a predictive model for the acoustic comfort, by means of simple objective parameters, while also examining which other subjective acoustic parameters could help explain...... the feeling of acoustic comfort. Through several layers of anal ysis, acoustic comfort was found to be rather complex, and could not be explained entirely by common subjective parameters such as annoyance, intelligibility or privacy. A predictive model for the mean acoustic comfort for an eating establishment...
10. Sound Scattering by a Flexible Plate Embedded on Free Surface
Directory of Open Access Journals (Sweden)
2012-01-01
Full Text Available Sound wave scattering by a flexible plate embedded on water surface is considered. Linear acoustics and plate elasticity are assumed. The aim is to assess the effect of the plate’s flexibility on sound scattering and the potential in using that flexibility for this purpose. A combined sound-structure solution is used, which is based on a Fourier transform of the sound field and a finite-difference numerical-solution of the plate’s dynamics. The solution is implemented for a circular plate subject to a perpendicular incoming monochromatic sound wave. A very good agreement is achieved with a finite-difference solution of the sound field. It is shown that the flexibility of the plate dampens its scattered sound wave regardless of the type of the plate’s edge support. A hole in the plate is shown to further scatter the sound wave to form maxima in the near sound field. It is suggested that applying an external oscillatory pressure on the plate can reduce significantly and even eliminate its scattered wave, thus making the plate close to acoustically invisible. A uniformly distributed external pressure is found capable of achieving that aim as long as the plate is free edged or is not highly acoustically noncompact.
11. Neutron scattering. Lectures
Energy Technology Data Exchange (ETDEWEB)
Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner [eds.
2010-07-01
The following topics are dealt with: Neutron sources, symmetry of crystals, diffraction, nanostructures investigated by small-angle neutron scattering, the structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic scattering, strongly correlated electrons, dynamics of macromolecules, applications of neutron scattering. (HSI)
12. Neutron scattering. Lectures
International Nuclear Information System (INIS)
Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner
2013-01-01
The following topics are dealt with: Neutron sources, symmetry of crystals, nanostructures investigated by small-angle neutron scattering, structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic neutron scattering, strongly correlated electrons, polymer dynamics, applications of neutron scattering. (HSI)
13. Neutron scattering. Lectures
International Nuclear Information System (INIS)
Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner
2010-01-01
The following topics are dealt with: Neutron sources, symmetry of crystals, diffraction, nanostructures investigated by small-angle neutron scattering, the structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic scattering, strongly correlated electrons, dynamics of macromolecules, applications of neutron scattering. (HSI)
14. Dynamics of acoustically levitated disk samples.
Science.gov (United States)
Xie, W J; Wei, B
2004-10-01
The acoustic levitation force on disk samples and the dynamics of large water drops in a planar standing wave are studied by solving the acoustic scattering problem through incorporating the boundary element method. The dependence of levitation force amplitude on the equivalent radius R of disks deviates seriously from the R3 law predicted by King's theory, and a larger force can be obtained for thin disks. When the disk aspect ratio gamma is larger than a critical value gamma(*) ( approximately 1.9 ) and the disk radius a is smaller than the critical value a(*) (gamma) , the levitation force per unit volume of the sample will increase with the enlargement of the disk. The acoustic levitation force on thin-disk samples ( gammaacoustic field for stable levitation of a large water drop is to adjust the reflector-emitter interval H slightly above the resonant interval H(n) . The simulation shows that the drop is flattened and the central parts of its top and bottom surface become concave with the increase of sound pressure level, which agrees with the experimental observation. The main frequencies of the shape oscillation under different sound pressures are slightly larger than the Rayleigh frequency because of the large shape deformation. The simulated translational frequencies of the vertical vibration under normal gravity condition agree with the theoretical analysis.
15. Airborne chemistry: acoustic levitation in chemical analysis.
Science.gov (United States)
Santesson, Sabina; Nilsson, Staffan
2004-04-01
This review with 60 references describes a unique path to miniaturisation, that is, the use of acoustic levitation in analytical and bioanalytical chemistry applications. Levitation of small volumes of sample by means of a levitation technique can be used as a way to avoid solid walls around the sample, thus circumventing the main problem of miniaturisation, the unfavourable surface-to-volume ratio. Different techniques for sample levitation have been developed and improved. Of the levitation techniques described, acoustic or ultrasonic levitation fulfils all requirements for analytical chemistry applications. This technique has previously been used to study properties of molten materials and the equilibrium shape()and stability of liquid drops. Temperature and mass transfer in levitated drops have also been described, as have crystallisation and microgravity applications. The airborne analytical system described here is equipped with different and exchangeable remote detection systems. The levitated drops are normally in the 100 nL-2 microL volume range and additions to the levitated drop can be made in the pL-volume range. The use of levitated drops in analytical and bioanalytical chemistry offers several benefits. Several remote detection systems are compatible with acoustic levitation, including fluorescence imaging detection, right angle light scattering, Raman spectroscopy, and X-ray diffraction. Applications include liquid/liquid extractions, solvent exchange, analyte enrichment, single-cell analysis, cell-cell communication studies, precipitation screening of proteins to establish nucleation conditions, and crystallisation of proteins and pharmaceuticals.
16. Localization of a small change in a multiple scattering environment without modeling of the actual medium
OpenAIRE
Rakotonarivo , Sandrine; Walker , S.C.; Kuperman , W. A.; Roux , Philippe
2011-01-01
International audience; A method to actively localize a small perturbation in a multiple scattering medium using a collection of remote acoustic sensors is presented. The approach requires only minimal modeling and no knowledge of the scatterer distribution and properties of the scattering medium and the perturbation. The medium is ensonified before and after a perturbation is introduced. The coherent difference between the measured signals then reveals all field components that have interact...
17. Spectral estimation for characterization of acoustic aberration.
Science.gov (United States)
Varslot, Trond; Angelsen, Bjørn; Waag, Robert C
2004-07-01
Spectral estimation based on acoustic backscatter from a motionless stochastic medium is described for characterization of aberration in ultrasonic imaging. The underlying assumptions for the estimation are: The correlation length of the medium is short compared to the length of the transmitted acoustic pulse, an isoplanatic region of sufficient size exists around the focal point, and the backscatter can be modeled as an ergodic stochastic process. The motivation for this work is ultrasonic imaging with aberration correction. Measurements were performed using a two-dimensional array system with 80 x 80 transducer elements and an element pitch of 0.6 mm. The f number for the measurements was 1.2 and the center frequency was 3.0 MHz with a 53% bandwidth. Relative phase of aberration was extracted from estimated cross spectra using a robust least-mean-square-error method based on an orthogonal expansion of the phase differences of neighboring wave forms as a function of frequency. Estimates of cross-spectrum phase from measurements of random scattering through a tissue-mimicking aberrator have confidence bands approximately +/- 5 degrees wide. Both phase and magnitude are in good agreement with a reference characterization obtained from a point scatterer.
18. Magnetoactive Acoustic Metamaterials.
Science.gov (United States)
Yu, Kunhao; Fang, Nicholas X; Huang, Guoliang; Wang, Qiming
2018-04-11
Acoustic metamaterials with negative constitutive parameters (modulus and/or mass density) have shown great potential in diverse applications ranging from sonic cloaking, abnormal refraction and superlensing, to noise canceling. In conventional acoustic metamaterials, the negative constitutive parameters are engineered via tailored structures with fixed geometries; therefore, the relationships between constitutive parameters and acoustic frequencies are typically fixed to form a 2D phase space once the structures are fabricated. Here, by means of a model system of magnetoactive lattice structures, stimuli-responsive acoustic metamaterials are demonstrated to be able to extend the 2D phase space to 3D through rapidly and repeatedly switching signs of constitutive parameters with remote magnetic fields. It is shown for the first time that effective modulus can be reversibly switched between positive and negative within controlled frequency regimes through lattice buckling modulated by theoretically predicted magnetic fields. The magnetically triggered negative-modulus and cavity-induced negative density are integrated to achieve flexible switching between single-negative and double-negative. This strategy opens promising avenues for remote, rapid, and reversible modulation of acoustic transportation, refraction, imaging, and focusing in subwavelength regimes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
19. Stimulated brillouin scattering of electromagnetic waves in a dusty plasma
International Nuclear Information System (INIS)
Salimullah, M.; Sen, A.
1991-08-01
The stimulated Brilluoin scattering of electromagnetic waves in a homogeneous, unmagnetized and collisionless dusty plasma has been investigated theoretically. The Vlasov equation has been solved perturbatively to find the nonlinear response of the plasma particles. The presence of the dust particles introduces a background inhomogeneous electric field which significantly influences the dispersive properties of the plasma. At the ion acoustic branch we find the usual scattering slightly modified by the charged dust grains. However, at the frequency lower than the ion acoustic branch we find a new mode of the plasma arising from the oscillations of the ions in the static structure of the dust distribution. This low frequency branch causes enhanced stimulated Brillouin scattering of electromagnetic waves in a dusty plasma. (author). 15 refs
20. Neutron scattering. Lectures
Energy Technology Data Exchange (ETDEWEB)
Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)
2010-07-01
The following topics are dealt with: Neutron sources, neutron properties and elastic scattering, correlation functions measured by scattering experiments, symmetry of crystals, applications of neutron scattering, polarized-neutron scattering and polarization analysis, structural analysis, magnetic and lattice excitation studied by inelastic neutron scattering, macromolecules and self-assembly, dynamics of macromolecules, correlated electrons in complex transition-metal oxides, surfaces, interfaces, and thin films investigated by neutron reflectometry, nanomagnetism. (HSI)
1. Neutron scattering. Lectures
International Nuclear Information System (INIS)
Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner
2010-01-01
The following topics are dealt with: Neutron sources, neutron properties and elastic scattering, correlation functions measured by scattering experiments, symmetry of crystals, applications of neutron scattering, polarized-neutron scattering and polarization analysis, structural analysis, magnetic and lattice excitation studied by inelastic neutron scattering, macromolecules and self-assembly, dynamics of macromolecules, correlated electrons in complex transition-metal oxides, surfaces, interfaces, and thin films investigated by neutron reflectometry, nanomagnetism. (HSI)
2. Advanced Active Acoustics Lab (AAAL)
Data.gov (United States)
Federal Laboratory Consortium — The Advanced Active Acoustics Lab (AAAL) is a state-of-the-art Undersea Warfare (USW) acoustic data analysis facility capable of both active and passive underwater...
3. Sea Turtle Acoustic Telemetry Data
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — Acoustic transmitters attached to sea turtles captured in various fishing gear enable the animals to be passively tracked. Acoustic receivers set up in an array...
4. Perspective: Acoustic metamaterials in transition
KAUST Repository
Wu, Ying; Yang, Min; Sheng, Ping
2017-01-01
Acoustic metamaterials derive their novel characteristics from the interaction between acoustic waves with designed structures. Since its inception seventeen years ago, the field has been driven by fundamental geometric and physical principles
5. A Century of Acoustic Metrology
DEFF Research Database (Denmark)
Rasmussen, Knud
1998-01-01
The development in acoustic measurement technique over the last century is reviewed with special emphasis on the metrological aspect.......The development in acoustic measurement technique over the last century is reviewed with special emphasis on the metrological aspect....
6. Acoustic Levitation Containerless Processing
Science.gov (United States)
Whymark, R. R.; Rey, C. A.
1985-01-01
This research program consists of the development of acoustic containerless processing systems with applications in the areas of research in material sciences, as well as the production of new materials, solid forms with novel and unusual microstructures, fusion target spheres, and improved optical fibers. Efforts have been focused on the containerless processing at high temperatures for producing new kinds of glasses. Also, some development has occurred in the areas of containerlessly supporting liquids at room temperature, with applications in studies of fluid dynamics, potential undercooling of liquids, etc. The high temperature area holds the greatest promise for producing new kinds of glasses and ceramics, new alloys, and possibly unusual structural shapes, such as very uniform hollow glass shells for fusion target applications. High temperature acoustic levitation required for containerless processing has been demonstrated in low-g environments as well as in ground-based experiments. Future activities include continued development of the signals axis acoustic levitator.
7. Practical acoustic emission testing
CERN Document Server
2016-01-01
This book is intended for non-destructive testing (NDT) technicians who want to learn practical acoustic emission testing based on level 1 of ISO 9712 (Non-destructive testing – Qualification and certification of personnel) criteria. The essential aspects of ISO/DIS 18436-6 (Condition monitoring and diagnostics of machines – Requirements for training and certification of personnel, Part 6: Acoustic Emission) are explained, and readers can deepen their understanding with the help of practice exercises. This work presents the guiding principles of acoustic emission measurement, signal processing, algorithms for source location, measurement devices, applicability of testing methods, and measurement cases to support not only researchers in this field but also and especially NDT technicians.
8. Topological Acoustic Delay Line
Science.gov (United States)
Zhang, Zhiwang; Tian, Ye; Cheng, Ying; Wei, Qi; Liu, Xiaojun; Christensen, Johan
2018-03-01
Topological protected wave engineering in artificially structured media is at the frontier of ongoing metamaterials research that is inspired by quantum mechanics. Acoustic analogues of electronic topological insulators have recently led to a wealth of new opportunities in manipulating sound propagation with strikingly unconventional acoustic edge modes immune to backscattering. Earlier fabrications of topological insulators are characterized by an unreconfigurable geometry and a very narrow frequency response, which severely hinders the exploration and design of useful devices. Here we establish topologically protected sound in reconfigurable phononic crystals that can be switched on and off simply by rotating its three-legged "atoms" without altering the lattice structure. In particular, we engineer robust phase delay defects that take advantage of the ultrabroadband reflection-free sound propagation. Such topological delay lines serve as a paradigm in compact acoustic devices, interconnects, and electroacoustic integrated circuits.
9. Acoustic detection of pneumothorax
Science.gov (United States)
Mansy, Hansen A.; Royston, Thomas J.; Balk, Robert A.; Sandler, Richard H.
2003-04-01
This study aims at investigating the feasibility of using low-frequency (pneumothorax detection were tested in dogs. In the first approach, broadband acoustic signals were introduced into the trachea during end-expiration and transmitted waves were measured at the chest surface. Pneumothorax was found to consistently decrease pulmonary acoustic transmission in the 200-1200-Hz frequency band, while less change was observed at lower frequencies (ppneumothorax states (pPneumothorax was found to be associated with a preferential reduction of sound amplitude in the 200- to 700-Hz range, and a decrease of sound amplitude variation (in the 300 to 600-Hz band) during the respiration cycle (pPneumothorax changed the frequency and decay rate of percussive sounds. These results imply that certain medical conditions may be reliably detected using appropriate acoustic measurements and analysis. [Work supported by NIH/NHLBI #R44HL61108.
10. Acoustics waves and oscillations
CERN Document Server
Sen, S.N.
2013-01-01
Parameters of acoustics presented in a logical and lucid style Physical principles discussed with mathematical formulations Importance of ultrasonic waves highlighted Dispersion of ultrasonic waves in viscous liquids explained This book presents the theory of waves and oscillations and various applications of acoustics in a logical and simple form. The physical principles have been explained with necessary mathematical formulation and supported by experimental layout wherever possible. Incorporating the classical view point all aspects of acoustic waves and oscillations have been discussed together with detailed elaboration of modern technological applications of sound. A separate chapter on ultrasonics emphasizes the importance of this branch of science in fundamental and applied research. In this edition a new chapter ''Hypersonic Velocity in Viscous Liquids as revealed from Brillouin Spectra'' has been added. The book is expected to present to its readers a comprehensive presentation of the subject matter...
11. Acoustic Liners for Turbine Engines
Science.gov (United States)
Jones, Michael G (Inventor); Grady, Joseph E (Inventor); Kiser, James D. (Inventor); Miller, Christopher (Inventor); Heidmann, James D. (Inventor)
2016-01-01
An improved acoustic liner for turbine engines is disclosed. The acoustic liner may include a straight cell section including a plurality of cells with straight chambers. The acoustic liner may also include a bent cell section including one or more cells that are bent to extend chamber length without increasing the overall height of the acoustic liner by the entire chamber length. In some cases, holes are placed between cell chambers in addition to bending the cells, or instead of bending the cells.
12. Spatial filtering of audible sound with acoustic landscapes
Science.gov (United States)
Wang, Shuping; Tao, Jiancheng; Qiu, Xiaojun; Cheng, Jianchun
2017-07-01
Acoustic metasurfaces manipulate waves with specially designed structures and achieve properties that natural materials cannot offer. Similar surfaces work in audio frequency range as well and lead to marvelous acoustic phenomena that can be perceived by human ears. Being intrigued by the famous Maoshan Bugle phenomenon, we investigate large scale metasurfaces consisting of periodic steps of sizes comparable to the wavelength of audio frequency in both time and space domains. We propose a theoretical method to calculate the scattered sound field and find that periodic corrugated surfaces work as spatial filters and the frequency selective character can only be observed at the same side as the incident wave. The Maoshan Bugle phenomenon can be well explained with the method. Finally, we demonstrate that the proposed method can be used to design acoustical landscapes, which transform impulsive sound into famous trumpet solos or other melodious sound.
13. Uncertainty of input data for room acoustic simulations
DEFF Research Database (Denmark)
Jeong, Cheol-Ho; Marbjerg, Gerd; Brunskog, Jonas
2016-01-01
Although many room acoustic simulation models have been well established, simulation results will never be accurate with inaccurate and uncertain input data. This study addresses inappropriateness and uncertainty of input data for room acoustic simulations. Firstly, the random incidence absorption...... and scattering coefficients are insufficient when simulating highly non-diffuse rooms. More detailed information, such as the phase and angle dependence, can greatly improve the simulation results of pressure-based geometrical and wave-based models at frequencies well below the Schroeder frequency. Phase...... summarizes potential advanced absorption measurement techniques that can improve the quality of input data for room acoustic simulations. Lastly, plenty of uncertain input data are copied from unreliable sources. Software developers and users should be careful when spreading such uncertain input data. More...
14. INTERFERENCE FRINGES OF SOLAR ACOUSTIC WAVES AROUND SUNSPOTS
Energy Technology Data Exchange (ETDEWEB)
Chou, Dean-Yi; Zhao Hui; Yang, Ming-Hsu; Liang, Zhi-Chao, E-mail: [email protected] [Physics Department, National Tsing Hua University, Hsinchu, Taiwan (China)
2012-10-20
Solar acoustic waves are scattered by a sunspot due to the interaction between the acoustic waves and the sunspot. The sunspot, excited by the incident wave, generates the scattered wave. The scattered wave is added to the incident wave to form the total wave around the sunspot. The interference fringes between the scattered wave and the incident wave are visible in the intensity of the total wave because the coherent time of the incident wave is of the order of a wave period. The strength of the interference fringes anti-correlates with the width of temporal spectra of the incident wave. The separation between neighboring fringes increases with the incident wavelength and the sunspot size. The strength of the fringes increases with the radial order n of the incident wave from n = 0 to n = 2, and then decreases from n = 2 to n = 5. The interference fringes play a role analogous to holograms in optics. This study suggests the feasibility of using the interference fringes to reconstruct the scattered wavefields of the sunspot, although the quality of the reconstructed wavefields is sensitive to the noise and errors in the interference fringes.
15. Densitometry By Acoustic Levitation
Science.gov (United States)
Trinh, Eugene H.
1989-01-01
"Static" and "dynamic" methods developed for measuring mass density of acoustically levitated solid particle or liquid drop. "Static" method, unknown density of sample found by comparison with another sample of known density. "Dynamic" method practiced with or without gravitational field. Advantages over conventional density-measuring techniques: sample does not have to make contact with container or other solid surface, size and shape of samples do not affect measurement significantly, sound field does not have to be know in detail, and sample can be smaller than microliter. Detailed knowledge of acoustic field not necessary.
16. Acoustic phenomena during boiling
International Nuclear Information System (INIS)
Dorofeev, B.M.
1985-01-01
Applied and theoretical significance of investigation into acoustic phenomena on boiling is discussed. Effect of spatial and time conditions on pressure vapour bubble has been elucidated. Collective effects were considered: acoustic interaction of bubbles, noise formation ion developed boiling, resonance and hydrodynamic autooscillations. Different methods for predicting heat transfer crisis using changes of accompanying noise characteristics were analysed. Principle peculiarities of generation mechanism of thermoacoustic autooscillations were analysed as well: formation of standing waves; change of two-phase medium contraction in a channel; relation of alternating pressure with boiling process as well as with instantaneous and local temperatures of heat transfer surface and liquid in a boundary layer
17. Shallow Water Acoustics Studies
Science.gov (United States)
2017-11-19
LE O CEAN RAPHIC I TITUTI Appli d Oc:ean Physics and E11gi1i,ering Depar1111,11t vember 9, 2017 Dr. Robert Headrick ffice of Naval Resear h, ode...UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT Applied Ocean Physics and Engineering Department...2015). [3] J.F. Lynch and A.E. Newhall, "Shallow water acoustics", book chapter in "Practical Underwater Acoustics," L. Bjorno, T. Neighbors, and D
18. Acoustic emission intrusion detector
International Nuclear Information System (INIS)
Carver, D.W.; Whittaker, J.W.
1980-01-01
An intrusion detector is provided for detecting a forcible entry into a secured structure while minimizing false alarms. The detector uses a piezoelectric crystal transducer to sense acoustic emissions. The transducer output is amplified by a selectable gain amplifier to control the sensitivity. The rectified output of the amplifier is applied to a Schmitt trigger circuit having a preselected threshold level to provide amplitude discrimination. Timing circuitry is provided which is activated by successive pulses from the Schmitt trigger which lie within a selected time frame for frequency discrimination. Detected signals having proper amplitude and frequency trigger an alarm within the first complete cycle time of a detected acoustical disturbance signal
19. Acoustic emission intrusion detector
International Nuclear Information System (INIS)
Carver, D.W.
1978-01-01
In order to improve the security of handling special nuclear materials at the Oak Ridge Y-12 Plant, a sensitive acoustic emission detector has been developed that will detect forcible entry through block or tile walls, concrete floors, or concrete/steel vault walls. A small, low-powered processor was designed to convert the output from a sensitive, crystal-type acoustic transducer to an alarm relay signal for use with a supervised alarm loop. The unit may be used to detect forcible entry through concrete, steel, block, tile, and/or glass
20. Room Acoustical Fields
CERN Document Server
Mechel, Fridolin
2013-01-01
This book presents the theory of room acoustical fields and revises the Mirror Source Methods for practical computational use, emphasizing the wave character of acoustical fields. The presented higher methods include the concepts of “Mirror Point Sources” and “Corner sources which allow for an excellent approximation of complex room geometries and even equipped rooms. In contrast to classical description, this book extends the theory of sound fields describing them by their complex sound pressure and the particle velocity. This approach enables accurate descriptions of interference and absorption phenomena.
1. Acoustically Induced Vibration of Structures: Reverberant Vs. Direct Acoustic Testing
Science.gov (United States)
Kolaini, Ali R.; O'Connell, Michael R.; Tsoi, Wan B.
2009-01-01
Large reverberant chambers have been used for several decades in the aerospace industry to test larger structures such as solar arrays and reflectors to qualify and to detect faults in the design and fabrication of spacecraft and satellites. In the past decade some companies have begun using direct near field acoustic testing, employing speakers, for qualifying larger structures. A limited test data set obtained from recent acoustic tests of the same hardware exposed to both direct and reverberant acoustic field testing has indicated some differences in the resulting structural responses. In reverberant acoustic testing, higher vibration responses were observed at lower frequencies when compared with the direct acoustic testing. In the case of direct near field acoustic testing higher vibration responses appeared to occur at higher frequencies as well. In reverberant chamber testing and direct acoustic testing, standing acoustic modes of the reverberant chamber or the speakers and spacecraft parallel surfaces can strongly couple with the fundamental structural modes of the test hardware. In this paper data from recent acoustic testing of flight hardware, that yielded evidence of acoustic standing wave coupling with structural responses, are discussed in some detail. Convincing evidence of the acoustic standing wave/structural coupling phenomenon will be discussed, citing observations from acoustic testing of a simple aluminum plate. The implications of such acoustic coupling to testing of sensitive flight hardware will be discussed. The results discussed in this paper reveal issues with over or under testing of flight hardware that could pose unanticipated structural and flight qualification issues. Therefore, it is of paramount importance to understand the structural modal coupling with standing acoustic waves that has been observed in both methods of acoustic testing. This study will assist the community to choose an appropriate testing method and test setup in
2. Variable-Position Acoustic Levitation
Science.gov (United States)
Barmatz, M. B.; Stoneburner, J. D.; Jacobi, N.; Wang, T. G.
1983-01-01
Method of acoustic levitation supports objects at positions other than acoustic nodes. Acoustic force is varied so it balances gravitational (or other) force, thereby maintaining object at any position within equilibrium range. Levitation method applicable to containerless processing. Such objects as table-tennis balls, hollow plastic spheres, and balsa-wood spheres levitated in laboratory by new method.
3. Fundamentals of Acoustics. Psychoacoustics and Hearing. Acoustical Measurements
Science.gov (United States)
Begault, Durand R.; Ahumada, Al (Technical Monitor)
1997-01-01
These are 3 chapters that will appear in a book titled "Building Acoustical Design", edited by Charles Salter. They are designed to introduce the reader to fundamental concepts of acoustics, particularly as they relate to the built environment. "Fundamentals of Acoustics" reviews basic concepts of sound waveform frequency, pressure, and phase. "Psychoacoustics and Hearing" discusses the human interpretation sound pressure as loudness, particularly as a function of frequency. "Acoustic Measurements" gives a simple overview of the time and frequency weightings for sound pressure measurements that are used in acoustical work.
4. The geometrical acoustic method for calculating the echo of targets submerged in a shallow water waveguide
Institute of Scientific and Technical Information of China (English)
CHEN Yan; TANG Weilin; FAN Wei; FAN Jun
2012-01-01
A geometrical acoustic method based on image-source method and physicM acoustic method was developed to calculate the echo of targets submerged in the shallow water waveguide. The incident rays and the scattering rays are reflected by two boundaries for many times, and then the back rays become countless. The total backscattering field is obtained through summing up the scattering field produced by each combination of incident rays and back rays. The echo of the 10m-radius pressure release sphere in Pekeris waveguide with the range is calculated by the geometrical acoustic method. Compared with the results calculated by the wave acoustic method in the available literature, it shows that both are in accordance on average value and descend trend. The following results indicate that the difference between Effective Target Strength （ETS） in shallow water and the Target Strength （TS） in free space for spheres and certain other rounded objects is small. However, the ETS of some targets such as cone-shaped is quite different from TS in free space, which can lead to large errors in estimating a target＇s scattering property using traditional sonar equation. Compared with the method of wave acoustics, the geometrical acoustic method not only has the definite physical meaning but also can calculate the echo of complex objects in shallow water waveguide.
5. Acoustic phonon dispersion of CoSi2
International Nuclear Information System (INIS)
Weiss, L.; Rumyantsev, A.Yu.; Ivanov, A.S.
1985-01-01
The acoustical phonon dispersion curves of CoSi 2 are measured at room temperature along the main symmetry directions by means of coherent one-phonon scattering of thermal neutrons. The dispersion curves are compared with those of Ge, Si, and the fluorite structure types as CaF 2 and UO 2 . From the slope of the phonon dispersion curves at the GAMMA-point the elastic constants have been obtained
6. Acoustic study of YBa2Cu3Ox thin films
International Nuclear Information System (INIS)
Lee, S.; Chi, C.; Koren, G.; Gupta, A.
1991-01-01
The attenuation of surface acoustic waves by epitaxial YBa 2 Cu 3 O x films has been studied for x congruent 6 to 7. For fully oxygenated samples, the acoustic attenuation as a function of temperature shows two broad peaks at about 135 and 240 K, and decreases monotonically below the lower peak temperature. The cause of attenuation peaks is attributed to scattering by optical phonons. Our data do not show any gap structure at T c due to relatively weak electron-phonon interactions at the acoustic frequencies. As the oxygen deficiency increases, the temperature dependence of the dc resistance changes from metallic to semiconducting and finally to insulating behavior. Acoustic attenuation data correspondingly show a drastic change due to different attenuation mechanisms: from the phonon scattering loss in the metallic regime to the electric-field coupling loss in the semiconducting and insulating regimes. In the latter regimes, the temperature dependence of low-frequency resistance calculated from the attenuation data can be fitted to a three-dimensional Mott variable-range-hopping model
7. Electron - polar acoustical phonon interactions in nitride based diluted magnetic semiconductor quantum well via hot electron magnetotransport
International Nuclear Information System (INIS)
Pandya, Ankur; Shinde, Satyam; Jha, Prafulla K.
2015-01-01
In this paper the hot electron transport properties like carrier energy and momentum scattering rates and electron energy loss rates are calculated via interactions of electrons with polar acoustical phonons for Mn doped BN quantum well in BN nanosheets via piezoelectric scattering and deformation potential mechanisms at low temperatures with high electric field. Electron energy loss rate increases with the electric field. It is observed that at low temperatures and for low electric field the phonon absorption is taking place whereas, for sufficient large electric field, phonon emission takes place. Under the piezoelectric (polar acoustical phonon) scattering mechanism, the carrier scattering rate decreases with the reduction of electric field at low temperatures wherein, the scattering rate variation with electric field is limited by a specific temperature beyond which there is no any impact of electric field on such scattering
8. Practical way to avoid spurious geometrical contributions in Brillouin light scattering experiments at variable scattering angles.
Science.gov (United States)
Battistoni, Andrea; Bencivenga, Filippo; Fioretto, Daniele; Masciovecchio, Claudio
2014-10-15
In this Letter, we present a simple method to avoid the well-known spurious contributions in the Brillouin light scattering (BLS) spectrum arising from the finite aperture of collection optics. The method relies on the use of special spatial filters able to select the scattered light with arbitrary precision around a given value of the momentum transfer (Q). We demonstrate the effectiveness of such filters by analyzing the BLS spectra of a reference sample as a function of scattering angle. This practical and inexpensive method could be an extremely useful tool to fully exploit the potentiality of Brillouin acoustic spectroscopy, as it will easily allow for effective Q-variable experiments with unparalleled luminosity and resolution.
9. Topological Creation of Acoustic Pseudospin Multipoles in a Flow-Free Symmetry-Broken Metamaterial Lattice
Science.gov (United States)
Zhang, Zhiwang; Wei, Qi; Cheng, Ying; Zhang, Ting; Wu, Dajian; Liu, Xiaojun
2017-02-01
The discovery of topological acoustics has revolutionized fundamental concepts of sound propagation, giving rise to strikingly unconventional acoustic edge modes immune to scattering. Because of the spinless nature of sound, the "spinlike" degree of freedom crucial to topological states in acoustic systems is commonly realized with circulating background flow or preset coupled resonator ring waveguides, which drastically increases the engineering complexity. Here we realize the acoustic pseudospin multipolar states in a simple flow-free symmetry-broken metamaterial lattice, where the clockwise (anticlockwise) sound propagation within each metamolecule emulates pseudospin down (pseudospin up). We demonstrate that tuning the strength of intermolecular coupling by simply contracting or expanding the metamolecule can induce the band inversion effect between the pseudospin dipole and quadrupole, which leads to a topological phase transition. Topologically protected edge states and reconfigurable topological one-way transmission for sound are further demonstrated. These results provide diverse routes to construct novel acoustic topological insulators with versatile applications.
10. Precipitate Contribution to the Acoustic Nonlinearity in Nickel-Based Superalloy
Institute of Scientific and Technical Information of China (English)
Chung-Seok KIM; Cliff J.LISSENDEN
2009-01-01
The influence of γ' precipitate on the acoustic nonlinearity is investigated for a nickel-based superalloy,which is subjected to creep deformation.During creep deformation,the cuboidal γ' precipitate is preferentially coarsened in a direction perpendicular to the applied stress axis.The length and shape factor of the γ' precipitate increase with creep time.The increase of relative acoustic nonlinearity with increasing fraction of creep life is discussed in relation to the rafting of γ' precipitate,which is closely related to the scattering and distortion of the acoustic wave.
11. Improved acoustic levitation apparatus
Science.gov (United States)
Berge, L. H.; Johnson, J. L.; Oran, W. A.; Reiss, D. A.
1980-01-01
Concave driver and reflector enhance and shape levitation forces in acoustic resonance system. Single-mode standing-wave pattern is focused by ring element situated between driver and reflector. Concave surfaces increase levitating forces up to factor of 6 as opposed to conventional flat surfaces, making it possible to suspend heavier objects.
12. Acoustic cavitation studies
Science.gov (United States)
Crum, L. A.
1981-09-01
The primary thrust of this study was toward a more complete understanding of general aspects of acoustic cavitation. The effect of long-chain polymer additives on the cavitation threshold was investigated to determine if they reduced the acoustic cavitation threshold in a similar manner to the observed reduction in the cavitation index in hydrodynamic cavitation. Measurements were made of the acoustic cavitation threshold as a function of polymer concentration for additives such as guar gum and polyethelene oxide. The measurements were also made as a function of dissolved gas concentration, surface tension and viscosity. It was determined that there was a significant increase in the acoustic cavitation threshold for increased concentrations of the polymer additives (measurable effects could be obtained for concentrations as low as a few parts per million). One would normally expect that an additive that reduces surface tension to decrease the pressure required to cause a cavity to grow and thus these additives, at first thought, should reduce the threshold. However, even in the hydrodynamic case, the threshold was increased. In both of the hydrodynamic cases considered, the explanation for the increased threshold was given in terms of changed fluid dynamics rather than changed physical properties of the fluid.
13. Acoustic Neuroma Educational Video
Medline Plus
Full Text Available ... Cumming, GA 30041 770-205-8211 [email protected] The world’s #1 acoustic neuroma resource Click to ... Cumming, GA 30041 770-205-8211 [email protected] About ANA Mission, Vision & Values Leadership & Staff Annual ...
14. Evoked acoustic emission
DEFF Research Database (Denmark)
Elberling, C; Parbo, J; Johnsen, N J
1985-01-01
Stimulated acoustic emissions were recorded in response to tonal stimuli at 60 dB p.e. SPL in a small group of normal-hearing adults. Power spectral analysis reveals that the evoked activity from each ear contains energy in preferential frequency bands and the change of stimulus frequency has only...
15. Portable acoustic myography
DEFF Research Database (Denmark)
Harrison, Adrian Paul; Danneskiold-Samsøe, Bente; Bartels, Else Marie
2013-01-01
Muscle sound gives a local picture of muscles involved in a particular movement and is independent of electrical signals between nerve and muscle. Sound recording (acoustic myography) is a well-known noninvasive technique that has suffered from not being easily applicable, as well as not being able...
16. Surface Acoustic Wave Devices
DEFF Research Database (Denmark)
Dühring, Maria Bayard
The work of this project is concerned with the simulation of surface acoustic waves (SAW) and topology optimization of SAW devices. SAWs are elastic vibrations that propagate along a material surface and are extensively used in electromechanical filters and resonators in telecommunication. A new...
17. Acoustic force spectroscopy
NARCIS (Netherlands)
Sitters, G.; Kamsma, D.; Thalhammer, G.; Ritsch-Marte, M.; Peterman, E.J.G.; Wuite, G.J.L.
2015-01-01
Force spectroscopy has become an indispensable tool to unravel the structural and mechanochemical properties of biomolecules. Here we extend the force spectroscopy toolbox with an acoustic manipulation device that can exert forces from subpiconewtons to hundreds of piconewtons on thousands of
18. Underwater Acoustic Networking Techniques
CERN Document Server
Otnes, Roald; Casari, Paolo; Goetz, Michael; Husøy, Thor; Nissen, Ivor; Rimstad, Knut; van Walree, Paul; Zorzi, Michele
2012-01-01
This literature study presents an overview of underwater acoustic networking. It provides a background and describes the state of the art of all networking facets that are relevant for underwater applications. This report serves both as an introduction to the subject and as a summary of existing protocols, providing support and inspiration for the development of network architectures.
19. Acoustic Surface Cavitation
NARCIS (Netherlands)
Zijlstra, A.G.
2011-01-01
Merely the presence of compressible entities, known as bubbles, greatly enriches the physical phenomena encountered when introducing ultrasound in a liquid. Mediated by the response of these bubbles, the otherwise diffuse and relatively low energy density of the acoustic field can induce strong,
20. Non-Invasive Acoustic-Based Monitoring of Heavy Water and Uranium Process Solutions
Energy Technology Data Exchange (ETDEWEB)
Pantea, Cristian [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sinha, Dipen N. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lakis, Rollin Evan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Beedle, Christopher Craig [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Davis, Eric Sean [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-10-20
This presentation includes slides on Project Goals; Heavy Water Production Monitoring: A New Challenge for the IAEA; Noninvasive Measurements in SFAI Cell; Large Scatter in Literature Values; Large Scatter in Literature Values; Highest Precision Sound Speed Data Available: New Standard in H/D; ~400 pts of data; Noninvasive Measurements in SFAI Cell; New funding from NA241 SGTech; Uranium Solution Monitoring: Inspired by IAEA Challenge in Kazakhstan; Non-Invasive Acoustic-Based Monitoring of Uranium in Solutions; Non-Invasive Acoustic-Based Monitoring of Uranium in Solutions; and finally a summary.
1. Select Internet Resources on Acoustics
Directory of Open Access Journals (Sweden)
Angela R. Davis
2016-12-01
Full Text Available Merriam-Webster (2016 defines acoustics as, “a science that deals with the production, control, transmission, reception, and effects of sounds.” According to Rossing (2014, the study of acoustics began in ancient Greece with Pythagoras’ study of vibrating strings on musical instruments. Since those early beginnings, famous scientists including Rayleigh, Alexander Graham Bell, and Thomas Edison, have helped expand the field of acoustics to include architectural, physical, engineering, structural, underwater, physiological and psychological, musical acoustics, and speech. Acoustics is a highly interdisciplinary field and researchers may need resources from physics, medicine, and engineering to understand all aspects of their research.
2. Scattering and multiple scattering in disordered materials
International Nuclear Information System (INIS)
Weaver, R.L.; Butler, W.H.
1992-01-01
The papers in this section were presented at a joint session of symposium V on Applications of Multiple Scattering Theory and of Symposium P on Disordered Systems. They show that the ideas of scattering theory can help us to understand a very broad class of phenomena
3. Wave scattering from statistically rough surfaces
CERN Document Server
Bass, F G; ter Haar, D
2013-01-01
Wave Scattering from Statistically Rough Surfaces discusses the complications in radio physics and hydro-acoustics in relation to wave transmission under settings seen in nature. Some of the topics that are covered include radar and sonar, the effect of variations in topographic relief or ocean waves on the transmission of radio and sound waves, the reproduction of radio waves from the lower layers of the ionosphere, and the oscillations of signals within the earth-ionosphere waveguide. The book begins with some fundamental idea of wave transmission theory and the theory of random processes a
4. Holograms for acoustics.
Science.gov (United States)
Melde, Kai; Mark, Andrew G; Qiu, Tian; Fischer, Peer
2016-09-22
Holographic techniques are fundamental to applications such as volumetric displays, high-density data storage and optical tweezers that require spatial control of intricate optical or acoustic fields within a three-dimensional volume. The basis of holography is spatial storage of the phase and/or amplitude profile of the desired wavefront in a manner that allows that wavefront to be reconstructed by interference when the hologram is illuminated with a suitable coherent source. Modern computer-generated holography skips the process of recording a hologram from a physical scene, and instead calculates the required phase profile before rendering it for reconstruction. In ultrasound applications, the phase profile is typically generated by discrete and independently driven ultrasound sources; however, these can only be used in small numbers, which limits the complexity or degrees of freedom that can be attained in the wavefront. Here we introduce monolithic acoustic holograms, which can reconstruct diffraction-limited acoustic pressure fields and thus arbitrary ultrasound beams. We use rapid fabrication to craft the holograms and achieve reconstruction degrees of freedom two orders of magnitude higher than commercial phased array sources. The technique is inexpensive, appropriate for both transmission and reflection elements, and scales well to higher information content, larger aperture size and higher power. The complex three-dimensional pressure and phase distributions produced by these acoustic holograms allow us to demonstrate new approaches to controlled ultrasonic manipulation of solids in water, and of liquids and solids in air. We expect that acoustic holograms will enable new capabilities in beam-steering and the contactless transfer of power, improve medical imaging, and drive new applications of ultrasound.
5. Acoustic field modulation in regenerators
Science.gov (United States)
Hu, J. Y.; Wang, W.; Luo, E. C.; Chen, Y. Y.
2016-12-01
The regenerator is a key component that transfers energy between heat and work. The conversion efficiency is significantly influenced by the acoustic field in the regenerator. Much effort has been spent to quantitatively determine this influence, but few comprehensive experimental verifications have been performed because of difficulties in modulating and measuring the acoustic field. In this paper, a method requiring two compressors is introduced and theoretically investigated that achieves acoustic field modulation in the regenerator. One compressor outputs the acoustic power for the regenerator; the other acts as a phase shifter. A RC load dissipates the acoustic power out of both the regenerator and the latter compressor. The acoustic field can be modulated by adjusting the current in the two compressors and opening the RC load. The acoustic field is measured with pressure sensors instead of flow-field imaging equipment, thereby greatly simplifying the experiment.
6. Controlling sound with acoustic metamaterials
DEFF Research Database (Denmark)
Cummer, Steven A. ; Christensen, Johan; Alù, Andrea
2016-01-01
Acoustic metamaterials can manipulate and control sound waves in ways that are not possible in conventional materials. Metamaterials with zero, or even negative, refractive index for sound offer new possibilities for acoustic imaging and for the control of sound at subwavelength scales....... The combination of transformation acoustics theory and highly anisotropic acoustic metamaterials enables precise control over the deformation of sound fields, which can be used, for example, to hide or cloak objects from incident acoustic energy. Active acoustic metamaterials use external control to create......-scale metamaterial structures and converting laboratory experiments into useful devices. In this Review, we outline the designs and properties of materials with unusual acoustic parameters (for example, negative refractive index), discuss examples of extreme manipulation of sound and, finally, provide an overview...
7. Flexural-Phonon Scattering Induced by Electrostatic Gating in Graphene
DEFF Research Database (Denmark)
Gunst, Tue; Kaasbjerg, Kristen; Brandbyge, Mads
2017-01-01
Graphene has an extremely high carrier mobility partly due to its planar mirror symmetry inhibiting scattering by the highly occupied acoustic flexural phonons. Electrostatic gating of a graphene device can break the planar mirror symmetry, yielding a coupling mechanism to the flexural phonons......-limiting factor, and show how the carrier density and temperature scaling of the mobility depends on the electrostatic environment. Our findings may explain the high deformation potential for in-plane acoustic phonons extracted from experiments and, furthermore, suggest a direct relation between device symmetry...
8. Low-Field Mobility and Galvanomagnetic Properties of Holes in Germanium with Phonon Scattering
DEFF Research Database (Denmark)
Lawætz, Peter
1968-01-01
acoustic scattering, no overall consistency is found between available galvanomagnetic data and deformation potentials derived directly from experiments on strained Ge. The discrepancies may be ascribed to ionized-impurity scattering, but at higher temperatures where optical phonon scattering is operative......A theoretical calculation of the low-field galvanomagnetic properties of holes in Ge has been carried out incorporating all relevant details of the band structure. The scattering is limited to acoustic and optical phonons and is described by the deformation potentials a, b, d, and d0. For pure......, the deviations are still appreciable. We are led to conclude that the deformation-potential theory of phonon scattering needs reconsideration, and a nontrivial correction is pointed out....
9. Neutron scattering from fractals
DEFF Research Database (Denmark)
Kjems, Jørgen; Freltoft, T.; Richter, D.
1986-01-01
The scattering formalism for fractal structures is presented. Volume fractals are exemplified by silica particle clusters formed either from colloidal suspensions or by flame hydrolysis. The determination of the fractional dimensionality through scattering experiments is reviewed, and recent small...
10. Scatter from optical components
International Nuclear Information System (INIS)
Stover, J.C.
1989-01-01
This book is covered under the following topics: measurement and analysis techniques; BRDF standards, comparisons, and anomalies; scatter measurement of several materials; scatter from contaminations; and optical system contamination: effects, measurement, and control
11. Four-jet impingement: Noise characteristics and simplified acoustic model
International Nuclear Information System (INIS)
Brehm, C.; Housman, J.A.; Kiris, C.C.; Barad, M.F.; Hutcheson, F.V.
2017-01-01
Highlights: • Large eddy simulation of unique four jet impingement configuration. • Characterization of flow features using POD, FFT, and wavelet decomposition. • Noise source identification utilizing causality method. • Development of simplified acoustic model utilizing equivalent source method. • Comparison with experimental data from BENS experiment. - Abstract: The noise generation mechanisms for four directly impinging supersonic jets are investigated employing implicit large eddy simulations with a higher-order weighted essentially non-oscillatory scheme. Although these types of impinging jet configurations have been used in many experiments, a detailed investigation of the noise generation mechanisms has not been conducted before. The flow field is highly complex and contains a wide range of temporal and spatial scales relevant for noise generation. Proper orthogonal decomposition is utilized to characterize the unsteady nature of the flow field involving unsteady shock oscillations, large coherent turbulent flow structures, and the sporadic appearance of vortical flow structures in the center of the four-jet impingement region. The causality method based on Lighthills acoustic analogy is applied to link fluctuations of flow quantities inside the source region to the acoustic pressure in the far field. It will be demonstrated that the entropy fluctuation term plays a vital role in the noise generation process. Consequently, the understanding of the noise generation mechanisms is employed to develop a simplified acoustic model of the four-jet impingement device by utilizing the equivalent source method. Finally, three linear acoustic four-jet impingement models of the four-jet impingement device are used as broadband noise sources inside an engine nacelle and the acoustic scattering results are validated against far-field acoustic experimental data.
12. Electron scattering from tetrahydrofuran
International Nuclear Information System (INIS)
Fuss, M C; Sanz, A G; García, G; Muñoz, A; Oller, J C; Blanco, F; Do, T P T; Brunger, M J; Almeida, D; Limão-Vieira, P
2012-01-01
Electron scattering from Tetrahydrofuran (C 4 H 8 O) was investigated over a wide range of energies. Following a mixed experimental and theoretical approach, total scattering, elastic scattering and ionization cross sections as well as electron energy loss distributions were obtained.
13. Neutron-proton scattering
International Nuclear Information System (INIS)
Doll, P.
1990-02-01
Neutron-proton scattering as fundamental interaction process below and above hundred MeV is discussed. Quark model inspired interactions and phenomenological potential models are described. The seminar also indicates the experimental improvements for achieving new precise scattering data. Concluding remarks indicate the relevance of nucleon-nucleon scattering results to finite nuclei. (orig.) [de
14. Neutron Scattering Software
Science.gov (United States)
Home Page | Facilities | Reference | Software | Conferences | Announcements | Mailing Lists Neutron Scattering Banner Neutron Scattering Software A new portal for neutron scattering has just been established sets KUPLOT: data plotting and fitting software ILL/TAS: Matlab probrams for analyzing triple axis data
15. Magnetic photon scattering
International Nuclear Information System (INIS)
Lovesey, S.W.
1987-05-01
The report reviews, at an introductory level, the theory of photon scattering from condensed matter. Magnetic scattering, which arises from first-order relativistic corrections to the Thomson scattering amplitude, is treated in detail and related to the corresponding interaction in the magnetic neutron diffraction amplitude. (author)
16. Polarized Neutron Scattering
OpenAIRE
Roessli, B.; Böni, P.
2000-01-01
The technique of polarized neutron scattering is reviewed with emphasis on applications. Many examples of the usefulness of the method in various fields of physics are given like the determination of spin density maps, measurement of complex magnetic structures with spherical neutron polarimetry, inelastic neutron scattering and separation of coherent and incoherent scattering with help of the generalized XYZ method.
17. Bubble nonlinear dynamics and stimulated scattering process
Science.gov (United States)
Jie, Shi; De-Sen, Yang; Sheng-Guo, Shi; Bo, Hu; Hao-Yang, Zhang; Shi-Yong, Hu
2016-02-01
A complete understanding of the bubble dynamics is deemed necessary in order to achieve their full potential applications in industry and medicine. For this purpose it is first needed to expand our knowledge of a single bubble behavior under different possible conditions including the frequency and pressure variations of the sound field. In addition, stimulated scattering of sound on a bubble is a special effect in sound field, and its characteristics are associated with bubble oscillation mode. A bubble in liquid can be considered as a representative example of nonlinear dynamical system theory with its resonance, and its dynamics characteristics can be described by the Keller-Miksis equation. The nonlinear dynamics of an acoustically excited gas bubble in water is investigated by using theoretical and numerical analysis methods. Our results show its strongly nonlinear behavior with respect to the pressure amplitude and excitation frequency as the control parameters, and give an intuitive insight into stimulated sound scattering on a bubble. It is seen that the stimulated sound scattering is different from common dynamical behaviors, such as bifurcation and chaos, which is the result of the nonlinear resonance of a bubble under the excitation of a high amplitude acoustic sound wave essentially. The numerical analysis results show that the threshold of stimulated sound scattering is smaller than those of bifurcation and chaos in the common condition. Project supported by the Program for Changjiang Scholars and Innovative Research Team in University, China (Grant No. IRT1228) and the Young Scientists Fund of the National Natural Science Foundation of China (Grant Nos. 11204050 and 11204049).
18. Enhanced creation of dispersive monolayer phonons in Xe/Pt(111) by inelastic helium atom scattering at low energies
DEFF Research Database (Denmark)
Hansen, Flemming Yssing; Bruch, Ludwig Walter
2007-01-01
Conditions likely to lead to enhanced inelastic atomic scattering that creates shear horizontal (SH) and longitudinal acoustic (LA) monolayer phonons are identified, specifically examining the inelastic scattering of He-4 atoms by a monolayer solid of Xe/Pt(111) at incident energies of 2-25 meV. ...
19. Education in acoustics in Argentina
Science.gov (United States)
Miyara, Federico
2002-11-01
Over the last decades, education in acoustics (EA) in Argentina has experienced ups and downs due to economic and political issues interfering with long term projects. Unlike other countries, like Chile, where EA has reached maturity in spite of the acoustical industry having shown little development, Argentina has several well-established manufacturers of acoustic materials and equipment but no specific career with a major in acoustics. At the university level, acoustics is taught as a complementary--often elective--course for careers such as architecture, communication engineering, or music. In spite of this there are several research centers with programs covering environmental and community noise, effects of noise on man, acoustic signal processing, musical acoustics and acoustic emission, and several national and international meetings are held each year in which results are communicated and discussed. Several books on a variety of topics such as sound system, architectural acoustics, and noise control have been published as well. Another chapter in EA is technical and vocational education, ranging between secondary and postsecondary levels, with technical training on sound system operation or design. Over the last years there have been several attempts to implement master degrees in acoustics or audio engineering, with little or no success.
20. Acoustic energy harvesting based on a planar acoustic metamaterial
Science.gov (United States)
2016-06-01
We theoretically report on an innovative and practical acoustic energy harvester based on a defected acoustic metamaterial (AMM) with piezoelectric material. The idea is to create suitable resonant defects in an AMM to confine the strain energy originating from an acoustic incidence. This scavenged energy is converted into electrical energy by attaching a structured piezoelectric material into the defect area of the AMM. We show an acoustic energy harvester based on a meta-structure capable of producing electrical power from an acoustic pressure. Numerical simulations are provided to analyze and elucidate the principles and the performances of the proposed system. A maximum output voltage of 1.3 V and a power density of 0.54 μW/cm3 are obtained at a frequency of 2257.5 Hz. The proposed concept should have broad applications on energy harvesting as well as on low-frequency sound isolation, since this system acts as both acoustic insulator and energy harvester.
1. Flat acoustic lens by acoustic grating with curled slits
KAUST Repository
Peng, Pai
2014-10-01
We design a flat sub-wavelength lens that can focus acoustic wave. We analytically study the transmission through an acoustic grating with curled slits, which can serve as a material with tunable impedance and refractive index for acoustic waves. The effective parameters rely on the geometry of the slits and are independent of frequency. A flat acoustic focusing lens by such acoustic grating with gradient effective refractive index is designed. The focusing effect is clearly observed in simulations and well predicted by the theory. We demonstrate that despite the large impedance mismatch between the acoustic lens and the matrix, the intensity at the focal point is still high due to Fabry-Perot resonance.
2. Sound extinction by fish schools: forward scattering theory and data analysis.
Science.gov (United States)
2015-02-01
A model used previously to study collective back scattering from fish schools [Feuillade et al., J. Acoust. Soc. Am. 99(1), 196-208 (1996)], is used to analyze the forward scattering properties of these objects. There is an essential physical difference between back and forward scattering from fish schools. Strong frequency dependent interference effects, which affect the back scattered field amplitude, are absent in the forward scattering case. This is critically important for data analysis. There is interest in using back scattering and transmission data from fish schools to study their size, the species and abundance of fish, and fish behavior. Transmission data can be processed to determine the extinction of the field by a school. The extinction of sound depends on the forward scattering characteristics of the school, and data inversion to provide information about the fish should be based upon a forward scattering paradigm. Results are presented of an analysis of transmission data obtained in September 1995 during an experiment performed in the Gulf of Lion in the Mediterranean Sea [Diachok, J. Acoust. Soc. Am. 105(4), 2107-2128 (1999)]. The analysis shows that using forward scattering leads to significantly larger estimates of fish abundance than previous analysis based upon back scattering approaches.
3. An acoustic prion assay
Directory of Open Access Journals (Sweden)
Gordon Hayward
2016-12-01
Full Text Available An acoustic prion assay has been demonstrated for sheep brain samples. Only five false positives and no false negatives were observed in a test of 45 positive and 45 negative samples. The acoustic prion sensor was constructed using a thickness shear mode quartz resonator coated with a covalently bound recombinant prion protein. The characteristic indicator of a scrapie infected sheep brain sample was an observed shoulder in the frequency decrease in response to a sample.The response of the sensor aligns with a conformational shift in the surface protein and with the propagation mechanism of the disease. This alignment is evident in the response timing and shape, dependence on concentration, cross species behaviour and impact of blood plasma. This alignment is far from sufficient to prove the mechanism of the sensor but it does offer the possibility of a rapid and inexpensive additional tool to explore prion disease. Keywords: Prions, Thickness shear mode quartz sensor
4. Osmotic Acoustic Source
Science.gov (United States)
2017-09-25
Technology Transfer at (401) 832-1511. DISTRIBUTION STATEMENT Approved for Public Release Distribution is unlimited Attorney Docket No...in the enclosure through osmosis. Valves open at a specified time after the liquid injection to free flood between the enclosure and the...the timing of the salt jets and the free-flooding valves enables a repeatable Attorney Docket No. 300070 4 of 14 acoustic pulse at low
5. Ocean acoustic tomography
International Nuclear Information System (INIS)
Cornuelle, Bruce D; Worcester, Peter F; Dzieciuch, Matthew A
2008-01-01
Ocean acoustic tomography (OAT) was proposed in 1979 by Walter Munk and Carl Wunsch as an analogue to x-ray computed axial tomography for the oceans. The oceans are opaque to most electromagnetic radiation, but there is a strong acoustic waveguide, and sound can propagate for 10 Mm and more with distinct multiply-refracted ray paths. Transmitting broadband pulses in the ocean leads to a set of impulsive arrivals at the receiver which characterize the impulse response of the sound channel. The peaks observed at the receiver are assumed to represent the arrival of energy traveling along geometric ray paths. These paths can be distinguished by arrival time, and by arrival angle when a vertical array of receivers is available. Changes in ray arrival time can be used to infer changes in ocean structure. Ray travel time measurements have been a mainstay of long-range acoustic measurements, but the strong sensitivity of ray paths to range-dependent sound speed perturbations makes the ray sampling functions uncertain in real cases. In the ray approximation travel times are sensitive to medium changes only along the corresponding eigenrays. Ray theory is an infinite-frequency approximation, and its eikonal equation has nonlinearities not found in the acoustic wave equation. We build on recent seismology results (kernels for body wave arrivals in the earth) to characterize the kernel for converting sound speed change in the ocean to travel time changes using more complete propagation physics. Wave-theoretic finite frequency kernels may show less sensitivity to small-scale sound speed structure.
6. Anisotropy of acoustic properties in paratellurite
International Nuclear Information System (INIS)
1996-01-01
One of the peculiarities of the TeO 2 crystal consists of its strong acoustic anisotropy. This anisotropy demonstrates itself by acoustic energy walk-off and anisotropic distortion of an acoustic beam. Four constants completely characterise the acoustic anisotropy of the medium. In this paper these constants are calculated for various directions of the acoustic beam in crystal. (authors)
7. Canada Basin Acoustic Propagation Experiment (CANAPE)
Science.gov (United States)
2015-09-30
acoustic communications, acoustic navigation, or acoustic remote sensing of the ocean interior . RELATED PROJECTS The 2015 CANAPE pilot study was a...1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Canada Basin Acoustic Propagation Experiment (CANAPE...ocean structure. Changes in sea ice and the water column affect both acoustic propagation and ambient noise. This implies that what was learned
8. Acoustically enhanced heat transport
Energy Technology Data Exchange (ETDEWEB)
Ang, Kar M.; Hung, Yew Mun; Tan, Ming K., E-mail: [email protected] [School of Engineering, Monash University Malaysia, 47500 Bandar Sunway, Selangor (Malaysia); Yeo, Leslie Y. [Micro/Nanophysics Research Laboratory, RMIT University, Melbourne, VIC 3001 (Australia); Friend, James R. [Department of Mechanical and Aerospace Engineering, University of California, San Diego, California 92093 (United States)
2016-01-15
We investigate the enhancement of heat transfer in the nucleate boiling regime by inducing high frequency acoustic waves (f ∼ 10{sup 6} Hz) on the heated surface. In the experiments, liquid droplets (deionized water) are dispensed directly onto a heated, vibrating substrate. At lower vibration amplitudes (ξ{sub s} ∼ 10{sup −9} m), the improved heat transfer is mainly due to the detachment of vapor bubbles from the heated surface and the induced thermal mixing. Upon increasing the vibration amplitude (ξ{sub s} ∼ 10{sup −8} m), the heat transfer becomes more substantial due to the rapid bursting of vapor bubbles happening at the liquid-air interface as a consequence of capillary waves travelling in the thin liquid film between the vapor bubble and the air. Further increases then lead to rapid atomization that continues to enhance the heat transfer. An acoustic wave displacement amplitude on the order of 10{sup −8} m with 10{sup 6} Hz order frequencies is observed to produce an improvement of up to 50% reduction in the surface temperature over the case without acoustic excitation.
9. Bilateral acoustic neuromas.
Science.gov (United States)
Anand, V T; Byrnes, D P; Walby, A P; Kerr, A G
1993-10-01
This article reviews 12 patients with bilateral acoustic neuromas. The sex incidence was equal and the mean age at diagnosis was 26.2 years. The family history was positive in nine of the patients. Five patients have had incomplete surgical removal of acoustic neuromas on both sides. Two of them are completely deaf and the other three have severe sensorineural hearing loss in one ear and no hearing in the other ear. In five patients the tumour on one side has been operated on and the other side is being observed with at least short-term preservation of good hearing. The remaining two patients died of intra-cranial complications, one of them post-operatively. Four patients developed facial palsy immediately following surgery and one developed facial weakness 6 months after surgery. Guidelines are discussed for the care of these patients including the timing of surgery and alternative treatment options (observation, radio-surgery and chemotherapy). This is essentially a group of young individuals who have had multiple operations for bilateral acoustic tumours and associated manifestations and for whom the disease and the sequelae of treatment can be tragic.
10. Magnon and phonon thermometry with inelastic light scattering
Science.gov (United States)
Olsson, Kevin S.; An, Kyongmo; Li, Xiaoqin
2018-04-01
Spin caloritronics investigates the interplay between the transport of spin and heat. In the spin Seebeck effect, a thermal gradient across a magnetic material generates a spin current. A temperature difference between the energy carriers of the spin and lattice subsystems, namely the magnons and phonons, is necessary for such thermal nonequilibrium generation of spin current. Inelastic light scattering is a powerful method that can resolve the individual temperatures of magnons and phonons. In this review, we discuss the thermometry capabilities of inelastic light scattering for measuring optical and acoustic phonons, as well as magnons. A scattering spectrum offers three temperature sensitive parameters: frequency shift, linewidth, and integrated intensity. We discuss the temperatures measured via each of these parameters for both phonon and magnons. Finally, we discuss inelastic light scattering experiments that have examined the magnon and phonon temperatures in thermal nonequilibrium which are particularly relevant to spin caloritronic phenomena.
11. Acoustic Studies on Nanodroplets, Microbubbles and Liposomes
Science.gov (United States)
Kumar, Krishna Nandan
Microbubbles and droplets are nanometer to micron size biocompatible particles which are primarily used for drug delivery and contrast imaging. Our aim is to broaden the use of microbubbles from contrast imaging to other applications such as measuring blood pressure. The other goal is to develop in situ contrast agents (phase shift droplets) which can be used for applications such as cancer tumor imaging. Therefore, the focus is on developing and validating the concept using experimental and theoretical methods. Below is an overview of each of the projects performed on droplets and microbubbles. Phase shift droplets vaporizable by acoustic stimulation offer many advantages over microbubbles as contrast agents due to their higher stability and possibility of smaller sizes. In this study, the acoustic droplet vaporization (ADV) threshold of a suspension of PFP droplets (400-3000nm) was acoustically measured as a function of the excitation frequency by examining the scattered signals, fundamental, sub- and second-harmonic. This work presents the experimental methodology to determine ADV threshold. The threshold increases with frequency: 1.25 MPa at 2.25 MHz, 2.0 MPa at 5 MHz and 2.5 MPa at 10 MHz. The scattered response from droplets was also found to match well with that of independently prepared lipid-coated microbubble suspension in magnitude as well as trends above the threshold value. Additionally, we have employed classical nucleation theory (CNT) to investigate the ADV, specifically the threshold value of the peak negative pressure required for vaporization. The theoretical analysis predicts that the ADV threshold increases with increasing surface tension of the droplet core and frequency of excitation, while it decreases with increasing temperature and droplet size. The predictions are in qualitative agreement with experimental observations. A technique to measure the ambient pressure using microbubbles was developed. Here we are presenting the results of an
12. Interaction of a high-order Bessel beam with a submerged spherical ultrasound contrast agent shell - Scattering theory.
Science.gov (United States)
Mitri, F G
2010-03-01
Acoustic scattering properties of ultrasound contrast agents are useful in extending existing or developing new techniques for biomedical imaging applications. A useful first step in this direction is to investigate the acoustic scattering of a new class of acoustic beams, known as helicoidal high-order Bessel beams, to improve the understanding of their scattering characteristics by an ultrasound contrast agent, which at present is very limited. The transverse acoustic scattering of a commercially available albuminoidal ultrasound contrast agent shell filled with air or a denser gas such as perfluoropropane and placed in a helicoidal Bessel beam of any order is examined numerically. The shell is assumed to possess an outer radius a=3.5 microns and a thickness of approximately 105 nm. Moduli of the total and resonance transverse acoustic scattering form functions are numerically evaluated in the bandwidth 0scattering of a helicoidal Bessel beam of order m1 so that the dynamics of contrast agents would be significantly altered. The main finding of the present theory is the suppression or enhancement for a particular resonance that may be used to advantage in imaging with ultrasound contrast agents for clinical applications. 2009 Elsevier B.V. All rights reserved.
13. The inside–outside duality for inverse scattering problems with near field data
International Nuclear Information System (INIS)
Lechleiter, Armin; Peters, Stefan
2015-01-01
We derive an inside–outside duality for near field scattering data generated by time-harmonic scattering of acoustic point sources from a sound-soft scatterer. This duality in particular rigorously characterizes interior Dirichlet eigenvalues of the scattering object by near field operators for an interval of wave numbers. As a crucial new concept to prove this duality we exploit the numerical ranges of certain modifications of these near field operators. We also show that our theoretical results can be numerically used to approximate interior Dirichlet eigenvalues from multi-frequency near field measurements. (paper)
14. Electron-electron scattering and mobilities in semiconductors and quantum wells
International Nuclear Information System (INIS)
Lyo, S.K.
1986-01-01
The effect of electron-electron scattering on the mobility in semiconductors and semiconductor quantum wells is examined. A general exact formula is derived for the mobility, when the electron-electron collision rate is much faster than other scattering rates such as those by ionized impurities and phonons. In this limit, the transport relaxation rate is independent of the carrier's energy and contributions to the inverse mobility from individual scattering mechanism add up. The mobility becomes significantly reduced from its value in the absence of electron-electron scattering. When the collision rates are not necessarily dominated by electron-electron scattering, the mobility is calculated by the Kohler-Sondheimer variational method in the presence of ionized-impurity scattering and acoustic-phonon scattering in a nondegenerate two-dimensional quantum well
15. Shallow-Water Mud Acoustics
Science.gov (United States)
2015-09-30
1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Shallow-Water Mud Acoustics William L. Siegmann...models and methods that explain observed material and acoustic properties of different physical types of shallow-ocean mud sediments. Other goals...are to assess prior data relating to the acoustic properties of mud and to provide guidance in the development and interpretation of experiments. A
16. Coupled Acoustic-Mechanical Bandgaps
DEFF Research Database (Denmark)
Jensen, Jakob Søndergaard; Kook, Junghwan
2016-01-01
medium and the presence of acoustic resonances. It is demonstrated that corrugation of the plate structure can introduce bending wave bandgaps and bandgaps in the acoustic domain in overlapping and audible frequency ranges. This effect is preserved also when taking the physical coupling between the two...... domains into account. Additionally, the coupling is shown to introduce extra gaps in the band structure due to modal interaction and the appearance of a cut-on frequency for the fundamental acoustic mode....
17. Collective hypersonic excitations in strongly multiple scattering colloids.
Science.gov (United States)
Still, T; Gantzounis, G; Kiefer, D; Hellmann, G; Sainidou, R; Fytas, G; Stefanou, N
2011-04-29
Unprecedented low-dispersion high-frequency acoustic excitations are observed in dense suspensions of elastically hard colloids. The experimental phononic band structure for SiO(2) particles with different sizes and volume fractions is well represented by rigorous full-elastodynamic multiple-scattering calculations. The slow phonons, which do not relate to particle resonances, are localized in the surrounding liquid medium and stem from coherent multiple scattering that becomes strong in the close-packing regime. Such rich phonon-matter interactions in nanostructures, being still unexplored, can open new opportunities in phononics.
18. Acoustic Communications Measurement Systems (ACOMMS)
Data.gov (United States)
Federal Laboratory Consortium — FUNCTION: Design and develop adaptive signal processing techniques to improve underwater acoustic communications and networking. Phase coherent and incoherent signal...
19. Sinusoidal Representation of Acoustic Signals
Science.gov (United States)
Honda, Masaaki
Sinusoidal representation of acoustic signals has been an important tool in speech and music processing like signal analysis, synthesis and time scale or pitch modifications. It can be applicable to arbitrary signals, which is an important advantage over other signal representations like physical modeling of acoustic signals. In sinusoidal representation, acoustic signals are composed as sums of sinusoid (sine wave) with different amplitudes, frequencies and phases, which is based on the timedependent short-time Fourier transform (STFT). This article describes the principles of acoustic signal analysis/synthesis based on a sinusoid representation with focus on sine waves with rapidly varying frequency.
20. Guided acoustic wave inspection system
Science.gov (United States)
Chinn, Diane J.
2004-10-05
A system for inspecting a conduit for undesirable characteristics. A transducer system induces guided acoustic waves onto said conduit. The transducer system detects the undesirable characteristics of the conduit by receiving guided acoustic waves that contain information about the undesirable characteristics. The conduit has at least two sides and the transducer system utilizes flexural modes of propagation to provide inspection using access from only the one side of the conduit. Cracking is detected with pulse-echo testing using one transducer to both send and receive the guided acoustic waves. Thinning is detected in through-transmission testing where one transducer sends and another transducer receives the guided acoustic waves.
1. Tunable coupled surface acoustic cavities
Science.gov (United States)
de Lima, M. M.; Santos, P. V.; Kosevich, Yu. A.; Cantarero, A.
2012-06-01
We demonstrate the electric tuning of the acoustic field in acoustic microcavities (MCs) defined by a periodic arrangement of metal stripes within a surface acoustic delay line on LiNbO3 substrate. Interferometric measurements show the enhancement of the acoustic field distribution within a single MC, the presence of a "bonding" and "anti-bonding" modes for two strongly coupled MCs, as well as the positive dispersion of the "mini-bands" formed by five coupled MCs. The frequency and amplitude of the resonances can be controlled by the potential applied to the metal stripes.
2. Transition section for acoustic waveguides
International Nuclear Information System (INIS)
Karplus, H.H.B.
1975-01-01
A means of facilitating the transmission of acoustic waves with minimal reflection between two regions having different specific acoustic impedances is described comprising a region exhibiting a constant product of cross-sectional area and specific acoustic impedance at each cross-sectional plane along the axis of the transition region. A variety of structures that exhibit this feature is disclosed, the preferred embodiment comprising a nested structure of doubly reentrant cones. This structure is useful for monitoring the operation of nuclear reactors in which random acoustic signals are generated in the course of operation
3. Combined Environment Acoustic Chamber (CEAC)
Data.gov (United States)
Federal Laboratory Consortium — Purpose: The CEAC imposes combined acoustic, thermal and mechanical loads on aerospace structures. The CEAC is employed to measure structural response and determine...
4. NDE Acoustic Microscopy Research Laboratory
Data.gov (United States)
Federal Laboratory Consortium — The purpose is to develop advanced, more effective high-resolution micro-NDE materials characterization methods using scanning acoustic microscopy. The laboratory's...
5. Mössbauer forward scattering: time-domain spectra
Energy Technology Data Exchange (ETDEWEB)
Sadykov, E. K., E-mail: [email protected]; Yurichuk, A. A.; Gainov, R. R.; Vagizov, F. G. [Kazan (Volga Region) Federal University (Russian Federation)
2016-12-15
The transmission of the Mössbauer radiation through an absorber being in the acoustic oscillation mode under forward scattering (FS) conditions has been analyzed. The modification of the existing models of the FS spectra (frequency and time) formation to the case of the arbitrary phase correlation of nuclear oscillations in the sample has been proposed. An adequate description of the time delayed experiments with the {sup 57}Fe Mössbauer resonance using the modulation of the single-photon wave packet by acoustic field has been obtained. One has been done in the frame of the Raman scattering of Mössbauer photons. The models extended this way can be used to control the degree of phase correlation of nuclear oscillations (or other processes) induced in the sample by external fields.
6. Wave scattering theory a series approach based on the Fourier transformation
CERN Document Server
Eom, Hyo J
2001-01-01
The book provides a unified technique of Fourier transform to solve the wave scattering, diffraction, penetration, and radiation problems where the technique of separation of variables is applicable. The book discusses wave scattering from waveguide discontinuities, various apertures, and coupling structures, often encountered in electromagnetic, electrostatic, magnetostatic, and acoustic problems. A system of simultaneous equations for the modal coefficients is formulated and the rapidly-convergent series solutions amenable to numerical computation are presented. The series solutions find practical applications in the design of microwave/acoustic transmission lines, waveguide filters, antennas, and electromagnetic interference/compatibilty-related problems.
7. Raman scattering from epitaxial HfN layers grown on MgO(001)
International Nuclear Information System (INIS)
Stoehr, M.; Seo, H.-S.; Petrov, I.; Greene, J.E.
2006-01-01
Stoichiometric single-crystal HfN layers grown on MgO(001) are analyzed by Raman spectroscopy. Second-order Raman scattering predominates, but first-order modes in the acoustic and optical ranges are also visible. The latter indicates that the O h symmetry of NaCl-structure HfN is broken. The large mass difference between Hf and N leads to a correspondingly large separation, 250 cm -1 , between the first-order acoustic and optical bands. Within this gap, four Raman lines are clearly observed. The first three are the second-order transverse acoustic mode (240 cm -1 ), the sum of the first-order transverse and longitudinal acoustic modes (280 cm -1 ), and the second-order longitudinal acoustic mode (325 cm -1 ). The fourth line at 380 cm -1 is identified as the difference between the first-order optical and acoustic modes. The observed first-order Raman scattering, as well as the width of the gap between the first-order acoustic and optical modes, is in good agreement with previously calculated HfN phonon density of states
8. Evaluation of performance of Son Tek Argonaut acoustic doppler velocity log in tow tank and sea
Digital Repository Service at National Institute of Oceanography (India)
Joseph, A; Madhan, R.; Mascarenhas, A.A; Desai, R.G.P.; VijayKumar, K.; Dias, M.; Tengali, S.; Methar, A
Performance of a 500-kHz, 3-beam downward-looking Sontex Argonaut acoustic Doppler velocity log (DVL) based on measurements at tow-tank and sea is addressed. Its accuracy and linearity under tow-tank measurements were largely scattered...
9. Acoustic transparency and slow sound using detuned acoustic resonators
DEFF Research Database (Denmark)
Santillan, Arturo Orozco; Bozhevolnyi, Sergey I.
2011-01-01
We demonstrate that the phenomenon of acoustic transparency and slowsound propagation can be realized with detuned acoustic resonators (DAR), mimicking thereby the effect of electromagnetically induced transparency (EIT) in atomic physics. Sound propagation in a pipe with a series of side...
10. Acoustical radiation torque and force for spheres and Bessel beam extinction efficiency
Science.gov (United States)
Marston, Philip L.; Zhang, Likun
2014-11-01
The scattering of optical and acoustical beams is relevant to the levitation and manipulation of drops. Here we examine theoretical developments in the acoustical case. We previously showed how the optical theorem for extinction can be extended to invariant beams. The example of a sphere in a Bessel beam facilitates the direct comparison with a circular disc computed using Babinet's principle and the Kirchhoff approximation. In related work, by considering traveling or standing wave first-order vortex beams we previously showed that the radiation torque is the ratio of the absorbed power and the radian acoustic frequency. By modifying the scattering to account for the viscosity of the surrounding fluid in the analysis of the absorbed power, approximations for radiation torque and force are obtained at long wavelengths in special cases and these can be compared with results published elsewhere.
11. Scattering with polarized neutrons
International Nuclear Information System (INIS)
Schweizer, J.
2007-01-01
In the history of neutron scattering, it was shown very soon that the use of polarized neutron beams brings much more information than usual scattering with unpolarized neutrons. We shall develop here the different scattering methods that imply polarized neutrons: 1) polarized beams without polarization analysis, the flipping ratio method; 2) polarized beams with a uniaxial polarization analysis; 3) polarized beams with a spherical polarization analysis. For all these scattering methods, we shall give examples of the physical problems which can been solved by these methods, particularly in the field of magnetism: investigation of complex magnetic structures, investigation of spin or magnetization densities in metals, insulators and molecular compounds, separation of magnetic and nuclear scattering, investigation of magnetic properties of liquids and amorphous materials and even, for non magnetic material, separation between coherent and incoherent scattering. (author)
12. Neutron scattering and magnetism
International Nuclear Information System (INIS)
Mackintosh, A.R.
1983-01-01
Those properties of the neutron which make it a unique tool for the study of magnetism are described. The scattering of neutrons by magnetic solids is briefly reviewed, with emphasis on the information on the magnetic structure and dynamics which is inherent in the scattering cross-section. The contribution of neutron scattering to our understanding of magnetic ordering, excitations and phase transitions is illustrated by experimental results on a variety of magnetic crystals. (author)
13. Stationary theory of scattering
International Nuclear Information System (INIS)
Kato, T.
1977-01-01
A variant of the stationary methods is described, and it is shown that it is useful in a wide range of problems, including scattering, by long-range potentials, two-space scattering, and multichannel scattering. The method is based on the notion of spectral forms. The paper is restricted to the simplest case of continuous spectral forms defined on a Banach space embedded in the basic Hilbert space. (P.D.)
14. Introduction to neutron scattering
Energy Technology Data Exchange (ETDEWEB)
Fischer, W E [Paul Scherrer Inst. (PSI), Villigen (Switzerland)
1996-11-01
We give here an introduction to the theoretical principles of neutron scattering. The relationship between scattering- and correlation-functions is particularly emphasized. Within the framework of linear response theory (justified by the weakness of the basic interaction) the relation between fluctuation and dissipation is discussed. This general framework explains the particular power of neutron scattering as an experimental method. (author) 4 figs., 4 refs.
15. Acoustic Mechanical Feedthroughs
Science.gov (United States)
Sherrit, Stewart; Walkemeyer, Phillip; Bao, Xiaoqi; Bar-Cohen, Yoseph; Badescu, Mircea
2013-01-01
Electromagnetic motors can have problems when operating in extreme environments. In addition, if one needs to do mechanical work outside a structure, electrical feedthroughs are required to transport the electric power to drive the motor. In this paper, we present designs for driving rotary and linear motors by pumping stress waves across a structure or barrier. We accomplish this by designing a piezoelectric actuator on one side of the structure and a resonance structure that is matched to the piezoelectric resonance of the actuator on the other side. Typically, piezoelectric motors can be designed with high torques and lower speeds without the need for gears. One can also use other actuation materials such as electrostrictive, or magnetostrictive materials in a benign environment and transmit the power in acoustic form as a stress wave and actuate mechanisms that are external to the benign environment. This technology removes the need to perforate a structure and allows work to be done directly on the other side of a structure without the use of electrical feedthroughs, which can weaken the structure, pipe, or vessel. Acoustic energy is pumped as a stress wave at a set frequency or range of frequencies to produce rotary or linear motion in a structure. This method of transferring useful mechanical work across solid barriers by pumping acoustic energy through a resonant structure features the ability to transfer work (rotary or linear motion) across pressure or thermal barriers, or in a sterile environment, without generating contaminants. Reflectors in the wall of barriers can be designed to enhance the efficiency of the energy/power transmission. The method features the ability to produce a bi-directional driving mechanism using higher-mode resonances. There are a variety of applications where the presence of a motor is complicated by thermal or chemical environments that would be hostile to the motor components and reduce life and, in some instances, not be
16. MRI of acoustic neurinoma
International Nuclear Information System (INIS)
Matsumoto, Kunihiko; Niitsu, Mamoru; Yoshioka, Hiroshi; Tanaka, Yumiko; Anno, Izumi; Kuramoto, Kenmei; Itai, Yuji
1994-01-01
Thirty six patients were studied with a 1.5 T superconductive magnetic resonance imager. Small neurinomas appeared as homogenous intensities, large neurinomas as heterogenous intensities in T 1 and T 2 weighted images. Dural tail representing reactive change of the meninges was seen in our three acoustic neurinomas. High resolution, thin slice, MR imaging was particularly useful for intracanalicular tumor to see the relationship between the tumor and facial nerve. Total or near-total removal of tumor was performed in thirteen cases, in which functional preservation of the cochlear nerve was achieved in only three cases. (author)
17. Oscillating acoustic streaming jet
International Nuclear Information System (INIS)
Moudjed, Brahim; Botton, Valery; Henry, Daniel; Millet, Severine; Ben Hadid, Hamda; Garandet, Jean-Paul
2014-01-01
The present paper provides the first experimental investigation of an oscillating acoustic streaming jet. The observations are performed in the far field of a 2 MHz circular plane ultrasound transducer introduced in a rectangular cavity filled with water. Measurements are made by Particle Image Velocimetry (PIV) in horizontal and vertical planes near the end of the cavity. Oscillations of the jet appear in this zone, for a sufficiently high Reynolds number, as an intermittent phenomenon on an otherwise straight jet fluctuating in intensity. The observed perturbation pattern is similar to that of former theoretical studies. This intermittently oscillatory behavior is the first step to the transition to turbulence. (authors)
18. Acoustic classification of dwellings
DEFF Research Database (Denmark)
Berardi, Umberto; Rasmussen, Birgit
2014-01-01
insulation performance, national schemes for sound classification of dwellings have been developed in several European countries. These schemes define acoustic classes according to different levels of sound insulation. Due to the lack of coordination among countries, a significant diversity in terms...... exchanging experiences about constructions fulfilling different classes, reducing trade barriers, and finally increasing the sound insulation of dwellings.......Schemes for the classification of dwellings according to different building performances have been proposed in the last years worldwide. The general idea behind these schemes relates to the positive impact a higher label, and thus a better performance, should have. In particular, focusing on sound...
19. Quantum theory of scattering
CERN Document Server
Wu Ta You
1962-01-01
This volume addresses the broad formal aspects and applications of the quantum theory of scattering in atomic and nuclear collisions. An encyclopedic source of pioneering work, it serves as a text for students and a reference for professionals in the fields of chemistry, physics, and astrophysics. The self-contained treatment begins with the general theory of scattering of a particle by a central field. Subsequent chapters explore particle scattering by a non-central field, collisions between composite particles, the time-dependent theory of scattering, and nuclear reactions. An examinati
20. Cross plane scattering correction
International Nuclear Information System (INIS)
Shao, L.; Karp, J.S.
1990-01-01
Most previous scattering correction techniques for PET are based on assumptions made for a single transaxial plane and are independent of axial variations. These techniques will incorrectly estimate the scattering fraction for volumetric PET imaging systems since they do not take the cross-plane scattering into account. In this paper, the authors propose a new point source scattering deconvolution method (2-D). The cross-plane scattering is incorporated into the algorithm by modeling a scattering point source function. In the model, the scattering dependence both on axial and transaxial directions is reflected in the exponential fitting parameters and these parameters are directly estimated from a limited number of measured point response functions. The authors' results comparing the standard in-plane point source deconvolution to the authors' cross-plane source deconvolution show that for a small source, the former technique overestimates the scatter fraction in the plane of the source and underestimate the scatter fraction in adjacent planes. In addition, the authors also propose a simple approximation technique for deconvolution
1. A numerical study on acoustic behavior in gas turbine combustor with acoustic resonator
International Nuclear Information System (INIS)
Park, I Sun; Sohn, Chae Hoon
2005-01-01
Acoustic behavior in gas turbine combustor with acoustic resonator is investigated numerically by adopting linear acoustic analysis. Helmholtz-type resonator is employed as acoustic resonator to suppress acoustic instability passively. The tuning frequency of acoustic resonator is adjusted by varying its length. Through harmonic analysis, acoustic-pressure responses of chamber to acoustic excitation are obtained and the resonant acoustic modes are identified. Acoustic damping effect of acoustic resonator is quantified by damping factor. As the tuning frequency of acoustic resonator approaches the target frequency of the resonant mode to be suppressed, mode split from the original resonant mode to lower and upper modes appears and thereby complex patterns of acoustic responses show up. Considering mode split and damping effect as a function of tuning frequency, it is desirable to make acoustic resonator tuned to broad-band frequencies near the maximum frequency of those of the possible upper modes
2. Acoustic Levitation With One Driver
Science.gov (United States)
Wang, T. G.; Rudnick, I.; Elleman, D. D.; Stoneburner, J. D.
1985-01-01
Report discusses acoustic levitation in rectangular chamber using one driver mounted at corner. Placement of driver at corner enables it to couple effectively to acoustic modes along all three axes. Use of single driver reduces cost, complexity and weight of levitation system below those of three driver system.
3. Acoustic Levitation With One Transducer
Science.gov (United States)
Barmatz, Martin B.
1987-01-01
Higher resonator modes enables simplification of equipment. Experimental acoustic levitator for high-temperature containerless processing has round cylindrical levitation chamber and only one acoustic transducer. Stable levitation of solid particle or liquid drop achieved by exciting sound in chamber to higher-order resonant mode that makes potential well for levitated particle or drop at some point within chamber.
4. Digital Controller For Acoustic Levitation
Science.gov (United States)
Tarver, D. Kent
1989-01-01
Acoustic driver digitally controls sound fields along three axes. Allows computerized acoustic levitation and manipulation of small objects for such purposes as containerless processing and nuclear-fusion power experiments. Also used for controlling motion of vibration-testing tables in three dimensions.
5. Acoustic engineering and technology '90
International Nuclear Information System (INIS)
1990-01-01
Acoustic monitoring, testing and diagnosis in machines, production processes and products enhance the uptimes and profitability of machinery and plants. 18 papers discuss the current state of the art of acoustic monitoring systems including integrated factory planning as well as industrial health, and noise protection. (DG) [de
6. Acoustical Properties of Contemporary Mosques
OpenAIRE
Karaman Özgül Yılmaz; Güzel Neslihan Onat
2017-01-01
Religious buildings are important for many communities because of their representation of different beliefs. In such structures, the sense of individuality or unity & togetherness are created according to variable worship activities; these different uses have also different acoustical requirements. In order to create the desired feeling in the space at the required time, rooms should be evaluated in terms of acoustical conditions.
7. Acoustic Center or Time Origin?
DEFF Research Database (Denmark)
Staffeldt, Henrik
1999-01-01
The paper discusses the acoustic center in relation to measurements of loudspeaker polar data. Also, it presents the related concept time origin and discusses the deviation that appears between positions of the acoustic center found by wavefront based and time based measuring methods....
8. Propagation of Ion Acoustic Perturbations
DEFF Research Database (Denmark)
Pécseli, Hans
1975-01-01
Equations describing the propagation of ion acoustic perturbations are considered, using the assumption that the electrons are Boltzman distributed and isothermal at all times. Quasi-neutrality is also considered.......Equations describing the propagation of ion acoustic perturbations are considered, using the assumption that the electrons are Boltzman distributed and isothermal at all times. Quasi-neutrality is also considered....
9. Acoustic Emission Technology and Application
International Nuclear Information System (INIS)
Joo, Y. S.; Lim, S. H.; Eom, H. S.; Kim, J. H.; Jung, H. K.
2003-10-01
Acoustic emission is the elastic wave that is generated by the rapid release of energy from the localized sources within a material. After the observation of acoustic emission phenomenon in 1950, the research and further investigation had been performed. Acoustic emission examination becomes a rapidly matured nondestructive testing method with demonstrated capabilities for characterizing material behavior and for detecting the defect. It is of interest as a possible passive monitoring technique for detecting, locating and characterizing the defects in component and structure. Acoustic emission technology has recently strengthened the on-line monitoring application for the detection of incipient failures and the assurance of structural integrity. The field of acoustic emission testing is still growing vigorously and presents many challenges. Especially, acoustic emission has been successfully applied in the leak detection of primary pressure boundary of nuclear power plants. In this state-of-art report, the principle, measurement and field applications of acoustic emission technique is reviewed and summarized. Acoustic emission technology will contribute to the assurance of nuclear safety as the on-line monitoring technique of structural integrity of NSSS components and structures
10. The nonlinear propagation of acoustic waves in a viscoelastic medium containing cylindrical micropores
International Nuclear Information System (INIS)
Yu-Lin, Feng; Xiao-Zhou, Liu; Jie-Hui, Liu; Li, Ma
2009-01-01
Based on an equivalent medium approach, this paper presents a model describing the nonlinear propagation of acoustic waves in a viscoelastic medium containing cylindrical micropores. The influences of pores' nonlinear oscillations on sound attenuation, sound dispersion and an equivalent acoustic nonlinearity parameter are discussed. The calculated results show that the attenuation increases with an increasing volume fraction of micropores. The peak of sound velocity and attenuation occurs at the resonant frequency of the micropores while the peak of the equivalent acoustic nonlinearity parameter occurs at the half of the resonant frequency of the micropores. Furthermore, multiple scattering has been taken into account, which leads to a modification to the effective wave number in the equivalent medium approach. We find that these linear and nonlinear acoustic parameters need to be corrected when the volume fraction of micropores is larger than 0.1%
11. Electron/electron acoustic instability
International Nuclear Information System (INIS)
Gary, S.P.
1987-01-01
The electron acoustic wave becomes a normal mode of an unmagnetized collisionless plasma in the presence of two electron components with similar densities, but strongly disparate temperatures. The characteristic frequency of this mode is the plasma frequency of the cooler electron component. If these two electron components have a relative drift speed several times the thermal speed of the cooler component, the electron/electron acoustic instability may arise. This paper describes the parametric dependences of the threshold drift speed and maximum growth rate of this instability, and compares these with the same properties of the electron/ion acoustic instability. Under the condition of zero current, the electron/ion acoustic instability typically has the lower threshold drift speed, so that observation of the electron/electron acoustic instability is a strong indication of the presence of an electrical current in the plasma
12. Acoustic emission linear pulse holography
Science.gov (United States)
Collins, H.D.; Busse, L.J.; Lemon, D.K.
1983-10-25
This device relates to the concept of and means for performing Acoustic Emission Linear Pulse Holography, which combines the advantages of linear holographic imaging and Acoustic Emission into a single non-destructive inspection system. This unique system produces a chronological, linear holographic image of a flaw by utilizing the acoustic energy emitted during crack growth. The innovation is the concept of utilizing the crack-generated acoustic emission energy to generate a chronological series of images of a growing crack by applying linear, pulse holographic processing to the acoustic emission data. The process is implemented by placing on a structure an array of piezoelectric sensors (typically 16 or 32 of them) near the defect location. A reference sensor is placed between the defect and the array.
13. Acoustics and Hearing
CERN Document Server
2008-01-01
When one listens to music at home, one would like to have an acoustic impression close to that of being in the concert hall. Until recently this meant elaborate multi-channelled sound systems with 5 or more speakers. But head-related stereophony achieves the surround-sound effect in living rooms with only two loudspeakers. By virtue of their slight directivity as well as an electronic filter the limitations previously common to two-speaker systems can be overcome and this holds for any arbitrary two-channel recording. The book also investigates the question of how a wide and diffuse sound image can arise in concert halls and shows that the quality of concert halls decisively depends on diffuse sound images arising in the onset of reverberation. For this purpose a strong onset of reverberation is modified in an anechoic chamber by electroacoustic means. Acoustics and Hearing proposes ideas concerning signal processing in the auditory system that explain the measured results and the resultant sound effects plea...
14. [Acoustical parameters of toys].
Science.gov (United States)
Harazin, Barbara
2010-01-01
Toys play an important role in the development of the sight and hearing concentration in children. They also support the development of manipulation, gently influence a child and excite its emotional activities. A lot of toys emit various sounds. The aim of the study was to assess sound levels produced by sound-emitting toys used by young children. Acoustical parameters of noise were evaluated for 16 sound-emitting plastic toys in laboratory conditions. The noise level was recorded at four different distances, 10, 20, 25 and 30 cm, from the toy. Measurements of A-weighted sound pressure levels and noise levels in octave band in the frequency range from 31.5 Hz to 16 kHz were performed at each distance. Taking into consideration the highest equivalent A-weighted sound levels produced by tested toys, they can be divided into four groups: below 70 dB (6 toys), from 70 to 74 dB (4 toys), from 75 to 84 dB (3 toys) and from 85 to 94 dB (3 toys). The majority of toys (81%) emitted dominant sound levels in octave band at the frequency range from 2 kHz to 4 kHz. Sound-emitting toys produce the highest acoustic energy at the frequency range of the highest susceptibility of the auditory system. Noise levels produced by some toys can be dangerous to children's hearing.
15. Review of Progress in Acoustic Levitation
Science.gov (United States)
2018-04-01
Acoustic levitation uses acoustic radiation forces to counteract gravity and suspend objects in mid-air. Although acoustic levitation was first demonstrated almost a century ago, for a long time, it was limited to objects much smaller than the acoustic wavelength levitating at fixed positions in space. Recent advances in acoustic levitation now allow not only suspending but also rotating and translating objects in three dimensions. Acoustic levitation is also no longer restricted to small objects and can now be employed to levitate objects larger than the acoustic wavelength. This article reviews the progress of acoustic levitation, focusing on the working mechanism of different types of acoustic levitation devices developed to date. We start with a brief review of the theory. Then, we review the acoustic levitation methods to suspend objects at fixed positions, followed by the techniques that allow the manipulation of objects. Finally, we present a brief summary and offer some future perspectives for acoustic levitation.
16. Riemann–Hilbert problem approach for two-dimensional flow inverse scattering
Energy Technology Data Exchange (ETDEWEB)
Agaltsov, A. D., E-mail: [email protected] [Faculty of Computational Mathematics and Cybernetics, Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Novikov, R. G., E-mail: [email protected] [CNRS (UMR 7641), Centre de Mathématiques Appliquées, Ecole Polytechnique, 91128 Palaiseau (France); IEPT RAS, 117997 Moscow (Russian Federation); Moscow Institute of Physics and Technology, Dolgoprudny (Russian Federation)
2014-10-15
We consider inverse scattering for the time-harmonic wave equation with first-order perturbation in two dimensions. This problem arises in particular in the acoustic tomography of moving fluid. We consider linearized and nonlinearized reconstruction algorithms for this problem of inverse scattering. Our nonlinearized reconstruction algorithm is based on the non-local Riemann–Hilbert problem approach. Comparisons with preceding results are given.
17. Riemann–Hilbert problem approach for two-dimensional flow inverse scattering
International Nuclear Information System (INIS)
Agaltsov, A. D.; Novikov, R. G.
2014-01-01
We consider inverse scattering for the time-harmonic wave equation with first-order perturbation in two dimensions. This problem arises in particular in the acoustic tomography of moving fluid. We consider linearized and nonlinearized reconstruction algorithms for this problem of inverse scattering. Our nonlinearized reconstruction algorithm is based on the non-local Riemann–Hilbert problem approach. Comparisons with preceding results are given
18. Investigation of the Stimulated Brillouin Scattering (SBS) Gain Enhancement in Silicon Nano-Waveguides and Applications
OpenAIRE
Al-Taiy, Hassanain Majeed
2017-01-01
Stimulated Brillouin scattering is a third order non-linear effect with the lowest power threshold in standard single mode optical fiber, by which an interaction between optical and acoustic modes takes place. During the Brillouin scattering process, part of the pump wave power will be transferred to a counter propagating wave (Stokes), with a frequency shift of about 11 GHz for a telecommunication wavelength of 1550 nm in a standard single mode fiber. The frequency shift effective parameters...
19. An assessment of the DORT method on simple scatterers using boundary element modelling.
Science.gov (United States)
Gélat, P; Ter Haar, G; Saffari, N
2015-05-07
The ability to focus through ribs overcomes an important limitation of a high-intensity focused ultrasound (HIFU) system for the treatment of liver tumours. Whilst it is important to generate high enough acoustic pressures at the treatment location for tissue lesioning, it is also paramount to ensure that the resulting ultrasonic dose on the ribs remains below a specified threshold, since ribs both strongly absorb and reflect ultrasound. The DORT (décomposition de l'opérateur de retournement temporel) method has the ability to focus on and through scatterers immersed in an acoustic medium selectively without requiring prior knowledge of their location or geometry. The method requires a multi-element transducer and is implemented via a singular value decomposition of the measured matrix of inter-element transfer functions. The efficacy of a method of focusing through scatterers is often assessed by comparing the specific absorption rate (SAR) at the surface of the scatterer, and at the focal region. The SAR can be obtained from a knowledge of the acoustic pressure magnitude and the acoustic properties of the medium and scatterer. It is well known that measuring acoustic pressures with a calibrated hydrophone at or near a hard surface presents experimental challenges, potentially resulting in increased measurement uncertainties. Hence, the DORT method is usually assessed experimentally by measuring the SAR at locations on the surface of the scatterer after the latter has been removed from the acoustic medium. This is also likely to generate uncertainties in the acoustic pressure measurement. There is therefore a strong case for assessing the efficacy of the DORT method through a validated theoretical model. The boundary element method (BEM) applied to exterior acoustic scattering problems is well-suited for such an assessment. In this study, BEM was used to implement the DORT method theoretically on locally reacting spherical scatterers, and to assess its focusing
20. Pion-pion scattering
International Nuclear Information System (INIS)
Kuehnelt, H.
1975-01-01
We discuss a few properties of scattering amplitudes proved within the framework of the field theory and their significance in the derivation of quantitative statements. The state of the boundaries for the scattering lengths is to be especially discussed as well as the question as to how far it is possible to exclude various solutions from phase displacement analyses. (orig./LH) [de
1. Incoherent Thomson scattering
NARCIS (Netherlands)
Donne, A. J. H.
1996-01-01
Thomson scattering is a very powerful diagnostic which is applied at nearly every magnetic confinement device. Depending on the experimental conditions different plasma parameters can be diagnosed. When the wave vector is much larger than the plasma Debye length, the total scattered power is
2. Dynamics of beam-driven Langmuir and ion-acoustic waves including electrostatic decay
International Nuclear Information System (INIS)
Li, B.; Willes, A.J.; Robinson, P.A.; Cairns, I.H.
2003-01-01
The evolution of Langmuir waves and ion-acoustic waves stimulated by a hot electron beam in an initially homogeneous plasma is investigated numerically in time, position, and wave number space. Quasilinear interactions between the beam particles and Langmuir waves, nonlinear interactions between the Langmuir and ion-acoustic waves through Langmuir decay processes, and spontaneous emission are taken into account in the kinetic theory employed. For illustrative parameters of those in the solar wind near 1 a.u., nonlinear Langmuir decays are observed to transfer the beam-driven Langmuir waves rapidly out of resonance. The scattered Langmuir waves then undergo further decays, moving sequentially toward small wave numbers, until decay is kinematically prohibited. The main features of the evolution of Langmuir and ion-acoustic waves are spatially inhomogeneous. The scattered Langmuir spectra increase and eventually reach or exceed the beam-driven Langmuir spectra at a given spatial location (except in regions where further decays proceed). The ion-acoustic waves are relatively weak and subject to damping at the later stages of their evolution. The development of fine structures in the product Langmuir and ion-acoustic waves are observed, due to depletion of their energy by decay and dominant damping effects, respectively. The propagation of the beam is essentially unaffected by the operation of the decay process. The decay process is thus slaved to the primary beam-plasma evolution, as assumed in previous studies. A variation of the ratio of electron temperature to ion temperature is found to affect not only the ion-acoustic wave levels through effects on the damping rate, but also the dynamics of decay via effects on the decay rate. The latter was not addressed in previous studies. Furthermore, spontaneous emission of ion-acoustic waves is found to affect the dynamics of decay, thus its inclusion is necessary to correctly model the Langmuir and ion-acoustic spectra
3. Introductory theory of neutron scattering
International Nuclear Information System (INIS)
Gunn, J.M.F.
1986-12-01
The paper comprises a set of six lecture notes which were delivered to the summer school on 'Neutron Scattering at a pulsed source', Rutherford Laboratory, United Kingdom, 1986. The lectures concern the physical principles of neutron scattering. The topics of the lectures include: diffraction, incoherent inelastic scattering, connection with the Schroedinger equation, magnetic scattering, coherent inelastic scattering, and surfaces and neutron optics. (UK)
4. Diffuse scattering of neutrons
International Nuclear Information System (INIS)
Novion, C.H. de.
1981-02-01
The use of neutron scattering to study atomic disorder in metals and alloys is described. The diffuse elastic scattering of neutrons by a perfect crystal lattice leads to a diffraction spectrum with only Bragg spreads. the existence of disorder in the crystal results in intensity and position modifications to these spreads, and above all, to the appearance of a low intensity scatter between Bragg peaks. The elastic scattering of neutrons is treated in this text, i.e. by measuring the number of scattered neutrons having the same energy as the incident neutrons. Such measurements yield information on the static disorder in the crystal and time average fluctuations in composition and atomic displacements [fr
5. Acoustic metamaterials for new two-dimensional sonic devices
Energy Technology Data Exchange (ETDEWEB)
Torrent, Daniel; Sanchez-Dehesa, Jose [Wave Phenomena Group, Department of Electronic Engineering, Polytechnic University of Valencia, C/Camino de Vera sn, E-46022 Valencia (Spain)
2007-09-15
It has been shown that two-dimensional arrays of rigid or fluidlike cylinders in a fluid or a gas define, in the limit of large wavelengths, a class of acoustic metamaterials whose effective parameters (sound velocity and density) can be tailored up to a certain limit. This work goes a step further by considering arrays of solid cylinders in which the elastic properties of cylinders are taken into account. We have also treated mixtures of two different elastic cylinders. It is shown that both effects broaden the range of acoustic parameters available for designing metamaterials. For example, it is predicted that metamaterials with perfect matching of impedance with air are now possible by using aerogel and rigid cylinders equally distributed in a square lattice. As a potential application of the proposed metamaterial, we present a gradient index lens for airborne sound (i.e. a sonic Wood lens) whose functionality is demonstrated by multiple scattering simulations.
6. Acoustic analog of monolayer graphene and edge states
International Nuclear Information System (INIS)
Zhong, Wei; Zhang, Xiangdong
2011-01-01
Acoustic analog of monolayer graphene has been designed by using silicone rubber spheres of honeycomb lattices embedded in water. The dispersion of the structure has been studied theoretically using the rigorous multiple-scattering method. The energy spectra with the Dirac point have been verified and zigzag edge states have been found in ribbons of the structure, which are analogous to the electronic ones in graphene nanoribbons. The guided modes along the zigzag edge excited by a point source have been numerically demonstrated. The open cavity and 'Z' type edge waveguide with 60 o corners have also been realized by using such edge states. -- Highlights: → Acoustic analog of monolayer graphene has been designed. → The energy spectra with the Dirac point have been verified. → The zigzag edge states have been found in ribbons of the structure. → The guided modes excited by a point source have been demonstrated. → The open cavity and 'Z' type edge waveguide have been realized.
7. Generalized theory of resonance scattering (GTRS) using the translational addition theorem for spherical wave functions.
Science.gov (United States)
Mitri, Farid
2014-11-01
The generalized theory of resonance scattering (GTRS) by an elastic spherical target in acoustics is extended to describe the arbitrary scattering of a finite beam using the addition theorem for the spherical wave functions of the first kind under a translation of the coordinate origin. The advantage of the proposed method over the standard discrete spherical harmonics transform previously used in the GTRS formalism is the computation of the off-axial beam-shape coefficients (BSCs) stemming from a closed-form partial-wave series expansion representing the axial BSCs in spherical coordinates. With this general method, the arbitrary acoustical scattering can be evaluated for any particle shape and size, whether the particle is partially or completely illuminated by the incident beam. Numerical examples for the axial and off-axial resonance scattering from an elastic sphere placed arbitrarily in the field of a finite circular piston transducer with uniform vibration are provided. Moreover, the 3-D resonance directivity patterns illustrate the theory and reveal some properties of the scattering. Numerous applications involving the scattering phenomenon in imaging, particle manipulation, and the characterization of multiphase flows can benefit from the present analysis because all physically realizable beams radiate acoustical waves from finite transducers as opposed to waves of infinite extent.
8. Inelastic Light Scattering Processes
Science.gov (United States)
Fouche, Daniel G.; Chang, Richard K.
1973-01-01
Five different inelastic light scattering processes will be denoted by, ordinary Raman scattering (ORS), resonance Raman scattering (RRS), off-resonance fluorescence (ORF), resonance fluorescence (RF), and broad fluorescence (BF). A distinction between fluorescence (including ORF and RF) and Raman scattering (including ORS and RRS) will be made in terms of the number of intermediate molecular states which contribute significantly to the scattered amplitude, and not in terms of excited state lifetimes or virtual versus real processes. The theory of these processes will be reviewed, including the effects of pressure, laser wavelength, and laser spectral distribution on the scattered intensity. The application of these processes to the remote sensing of atmospheric pollutants will be discussed briefly. It will be pointed out that the poor sensitivity of the ORS technique cannot be increased by going toward resonance without also compromising the advantages it has over the RF technique. Experimental results on inelastic light scattering from I(sub 2) vapor will be presented. As a single longitudinal mode 5145 A argon-ion laser line was tuned away from an I(sub 2) absorption line, the scattering was observed to change from RF to ORF. The basis, of the distinction is the different pressure dependence of the scattered intensity. Nearly three orders of magnitude enhancement of the scattered intensity was measured in going from ORF to RF. Forty-seven overtones were observed and their relative intensities measured. The ORF cross section of I(sub 2) compared to the ORS cross section of N2 was found to be 3 x 10(exp 6), with I(sub 2) at its room temperature vapor pressure.
9. Specularity of longitudinal acoustic phonons at rough surfaces
Science.gov (United States)
Gelda, Dhruv; Ghossoub, Marc G.; Valavala, Krishna; Ma, Jun; Rajagopal, Manjunath C.; Sinha, Sanjiv
2018-01-01
The specularity of phonons at crystal surfaces is of direct importance to thermal transport in nanostructures and to dissipation in nanomechanical resonators. Wave scattering theory provides a framework for estimating wavelength-dependent specularity, but experimental validation remains elusive. Widely available thermal conductivity data presents poor validation since the involvement of the infinitude of phonon wavelengths in thermal transport presents an underconstrained test for specularity theory. Here, we report phonon specularity by measuring the lifetimes of individual coherent longitudinal acoustic phonon modes excited in ultrathin (36-205 nm) suspended silicon membranes at room temperature over the frequency range ˜20 -118 GHz. Phonon surface scattering dominates intrinsic Akhiezer damping at frequencies ≳60 GHz, enabling measurements of phonon boundary scattering time over wavelengths ˜72 -140 nm . We obtain detailed statistics of the surface roughness at the top and bottom surfaces of membranes using HRTEM imaging. We find that the specularity of the excited modes are in good agreement with solutions of wave scattering only when the TEM statistics are corrected for projection errors. The often-cited Ziman formula for phonon specularity also appears in good agreement with the data, contradicting previous results. This work helps to advance the fundamental understanding of phonon scattering at the surfaces of nanostructures.
10. In-situ optical and acoustical measurements of the buoyant cyanobacterium p. Rubescens: spatial and temporal distribution patterns.
Directory of Open Access Journals (Sweden)
Hilmar Hofmann
Full Text Available Optical (fluorescence and acoustic in-situ techniques were tested in their ability to measure the spatial and temporal distribution of plankton in freshwater ecosystems with special emphasis on the harmful and buoyant cyanobacterium P. rubescens. Fluorescence was measured with the multi-spectral FluoroProbe (Moldaenke FluoroProbe, MFP and a Seapoint Chlorophyll Fluorometer (SCF. In-situ measurements of the acoustic backscatter strength (ABS were conducted with three different acoustic devices covering multiple acoustic frequencies (614 kHz ADCP, 2 MHz ADP, and 6 MHz ADV. The MFP provides a fast and reliable technique to measure fluorescence at different wavelengths in situ, which allows discriminating between P. rubescens and other phytoplankton species. All three acoustic devices are sensitive to P. rubescens even if other scatterers, e.g., zooplankton or suspended sediment, are present in the water column, because P. rubescens containing gas vesicles has a strong density difference and hence acoustic contrast to the ambient water and other scatterers. After calibration, the combination of optical and acoustical measurements not only allows qualitative and quantitative observation of P. rubescens, but also distinction between P. rubescens, other phytoplankton, and zooplankton. As the measuring devices can sample in situ at high rates they enable assessment of plankton distributions at high temporal (minutes and spatial (decimeters resolution or covering large temporal (seasonal and spatial (basin scale scales.
11. Relaxation time of acoustically disturbed plasma
International Nuclear Information System (INIS)
Mkrtchyan, K.S.; Abrahamyan, A.S.
2005-01-01
The conservation time of an acoustic structure in plasma after relieving of external acoustic influence is investigated. Dependences of the conservation time on discharge parameters are presented. It is asserted that the plasma becomes an anisotropic uniaxial medium with an acoustic superlattice under the acoustic influence
12. MR of acoustic neuromas
International Nuclear Information System (INIS)
Suzuki, Masayuki; Takashima, Tsutomu; Kadoya, Masumi; Takahashi, Shiroh; Miyayama, Shiroh; Taira, Sakae; Kashihara, Kengo; Yamashima, Tetsumori; Itoh, Haruhide
1989-01-01
In this report, the relationship of acoustic neuromas to the adjacent cranial nerves is discussed. On T 1 -weighted images, the trigeminal nerve was detected in all 13 cases. Mild to marked compression of these nerves by the tumors was observed in eight cases. The extent of compression did not always correspond to the clinical symptoms. In four cases with a maximum tumor diameter of 2 cm or less, the 7th and 8th cranial nerves were identified. There was no facial palsy in these patients. Two patients with a tumor diameter of more than 2 cm also had no facial palsy. All patients, including those with small tumors, complained of hearing loss and/or tinnitus. While MR imaging has some limitations, it is an effective imaging modality for showing the relationship between tumors and nerves. (author)
13. Light scattering studies at UNICAMP
International Nuclear Information System (INIS)
Luzzi, R.; Cerdeira, H.A.; Salzberg, J.; Vasconcellos, A.R.; Frota Pessoa, S.; Reis, F.G. dos; Ferrari, C.A.; Algarte, C.A.S.; Tenan, M.A.
1975-01-01
Current theoretical studies on light scattering spectroscopy at UNICAMP is presented briefly, such as: inelastic scattering of radiation from a solid state plasma; resonant Ramman scattering; high excitation effects; saturated semiconductors and glasses
14. Acoustics of friction
Science.gov (United States)
2002-04-01
This article presents an overview of the acoustics of friction by covering friction sounds, friction-induced vibrations and waves in solids, and descriptions of other frictional phenomena related to acoustics. Friction, resulting from the sliding contact of solids, often gives rise to diverse forms of waves and oscillations within solids which frequently lead to radiation of sound to the surrounding media. Among the many everyday examples of friction sounds, violin music and brake noise in automobiles represent the two extremes in terms of the sounds they produce and the mechanisms by which they are generated. Of the multiple examples of friction sounds in nature, insect sounds are prominent. Friction also provides a means by which energy dissipation takes place at the interface of solids. Friction damping that develops between surfaces, such as joints and connections, in some cases requires only microscopic motion to dissipate energy. Modeling of friction-induced vibrations and friction damping in mechanical systems requires an accurate description of friction for which only approximations exist. While many of the components that contribute to friction can be modeled, computational requirements become prohibitive for their contemporaneous calculation. Furthermore, quantification of friction at the atomic scale still remains elusive. At the atomic scale, friction becomes a mechanism that converts the kinetic energy associated with the relative motion of surfaces to thermal energy. However, the description of the conversion to thermal energy represented by a disordered state of oscillations of atoms in a solid is still not well understood. At the macroscopic level, friction interacts with the vibrations and waves that it causes. Such interaction sets up a feedback between the friction force and waves at the surfaces, thereby making friction and surface motion interdependent. Such interdependence forms the basis for friction-induced motion as in the case of
15. Anti-sound and Acoustical Cloaks
Directory of Open Access Journals (Sweden)
Veturia CHIROIU
2016-12-01
Full Text Available The principles by which the acoustics can be mimicked in order to reduce or cancel the vibrational field are based on anti-sound concept which can be materialized by acoustic cloaks. Geometric transformations open an elegant way towards the unconstrained control of sound through acoustic metamaterials. Acoustic cloaks can be achieved through geometric transformations which bring exotic metamaterial properties into the acoustic equations. Our paper brings new ideas concerning the technological keys for manufacturing of novel metamaterials based on the spatial compression of Cantor structures, and the architecture of 3D acoustic cloaks in a given frequency band, with application to architectural acoustics.
16. Acoustic of monolithic dome structures
Directory of Open Access Journals (Sweden)
Mostafa Refat Ismail
2018-03-01
The interior of monolithic domes have perfect, concave shapes to ensure that sound travels through the dome and perfectly collected at different vocal points. These dome structures are utilized for domestic use because the scale allows the focal points to be positioned across daily life activities, thereby affecting the sonic comfort of the internal space. This study examines the various acoustic treatments and parametric configurations of monolithic dome sizes. A geometric relationship of acoustic treatment and dome radius is established to provide architects guidelines on the correct selection of absorption needed to maintain the acoustic comfort of these special spaces.
17. Perspective: Acoustic metamaterials in transition
KAUST Repository
Wu, Ying
2017-12-15
Acoustic metamaterials derive their novel characteristics from the interaction between acoustic waves with designed structures. Since its inception seventeen years ago, the field has been driven by fundamental geometric and physical principles that guide the structure design rules as well as provide the basis for wave functionalities. Recent examples include resonance-based acoustic metasurfaces that offer flexible control of acoustic wave propagation such as focusing and re-direction; parity-time (PT)-symmetric acoustics that utilizes the general concept of pairing loss and gain to achieve perfect absorption at a single frequency; and topological phononics that can provide one-way edge state propagation. However, such novel functionalities are not without constraints. Metasurface elements rely on resonances to enhance their coupling to the incident wave; hence, its functionality is limited to a narrow frequency band. Topological phononics is the result of the special lattice symmetry that must be fixed at the fabrication stage. Overcoming such constraints naturally forms the basis for further developments. We identify two emergent directions: Integration of acoustic metamaterial elements for achieving broadband characteristics as well as acoustic wave manipulation tasks more complex than the single demonstrative functionality; and active acoustic metamaterials that can adapt to environment as well as to go beyond the constraints on the passive acoustic metamaterials. Examples of a successful recent integration of multi-resonators in achieving broadband sound absorption can be found in optimal sound-absorbing structures, which utilize causality constraint as a design tool in realizing the target-set absorption spectrum with a minimal sample thickness. Active acoustic metamaterials have also demonstrated the capability to tune bandgaps as well as to alter property of resonances in real time through stiffening of the spring constants, in addition to the PT symmetric
18. Industrial installation surveillance acoustic device
International Nuclear Information System (INIS)
Marini, Jean; Audenard, Bernard.
1981-01-01
The purpose of this invention is the detection of possible impacts of bodies migrating inside the installation, using acoustic sensors of the waves emitted at the time of impact of the migrating bodies. This device makes it possible to take into account only those acoustic signals relating to the impacts of bodies migrating in the area under surveillance, to the exclusion of any other acoustic or electric perturbing phenomenon. The invention has a preferential use in the case of a linear shape installation in which a fluid flows at high rate, such as a section of the primary system of a pressurized water nuclear reactor [fr
19. Flat acoustic lens by acoustic grating with curled slits
KAUST Repository
Peng, Pai; Xiao, Bingmu; Wu, Ying
2014-01-01
and well predicted by the theory. We demonstrate that despite the large impedance mismatch between the acoustic lens and the matrix, the intensity at the focal point is still high due to Fabry-Perot resonance.
20. Focusing of Acoustic Waves through Acoustic Materials with Subwavelength Structures
KAUST Repository
Xiao, Bingmu
2013-01-01
-domain (FDTD) method for the two-dimensional acoustic wave equation. The theory provides the effective impedance and refractive index functions for the equivalent medium, which can reproduce the transmission and reflection spectral responses of the original
1. Scattering and; Delay, Scale, and Sum Migration
Energy Technology Data Exchange (ETDEWEB)
Lehman, S K
2011-07-06
How do we see? What is the mechanism? Consider standing in an open field on a clear sunny day. In the field are a yellow dog and a blue ball. From a wave-based remote sensing point of view the sun is a source of radiation. It is a broadband electromagnetic source which, for the purposes of this introduction, only the visible spectrum is considered (approximately 390 to 750 nanometers or 400 to 769 TeraHertz). The source emits an incident field into the known background environment which, for this example, is free space. The incident field propagates until it strikes an object or target, either the yellow dog or the blue ball. The interaction of the incident field with an object results in a scattered field. The scattered field arises from a mis-match between the background refractive index, considered to be unity, and the scattering object refractive index ('yellow' for the case of the dog, and 'blue' for the ball). This is also known as an impedance mis-match. The scattering objects are referred to as secondary sources of radiation, that radiation being the scattered field which propagates until it is measured by the two receivers known as 'eyes'. The eyes focus the measured scattered field to form images which are processed by the 'wetware' of the brain for detection, identification, and localization. When time series representations of the measured scattered field are available, the image forming focusing process can be mathematically modeled by delayed, scaled, and summed migration. This concept of optical propagation, scattering, and focusing have one-to-one equivalents in the acoustic realm. This document is intended to present the basic concepts of scalar scattering and migration used in wide band wave-based remote sensing and imaging. The terms beamforming and (delayed, scaled, and summed) migration are used interchangeably but are to be distinguished from the narrow band (frequency domain) beamforming to determine
2. Underwater object classification using scattering transform of sonar signals
Science.gov (United States)
Saito, Naoki; Weber, David S.
2017-08-01
In this paper, we apply the scattering transform (ST)-a nonlinear map based off of a convolutional neural network (CNN)-to classification of underwater objects using sonar signals. The ST formalizes the observation that the filters learned by a CNN have wavelet-like structure. We achieve effective binary classification both on a real dataset of Unexploded Ordinance (UXOs), as well as synthetically generated examples. We also explore the effects on the waveforms with respect to changes in the object domain (e.g., translation, rotation, and acoustic impedance, etc.), and examine the consequences coming from theoretical results for the scattering transform. We show that the scattering transform is capable of excellent classification on both the synthetic and real problems, thanks to having more quasi-invariance properties that are well-suited to translation and rotation of the object.
3. Incoherent neutron scattering in acetanilide and three deuterated derivatives
Science.gov (United States)
Barthes, Mariette; Almairac, Robert; Sauvajol, Jean-Louis; Moret, Jacques; Currat, Roland; Dianoux, José
1991-03-01
Incoherent-neutron-scattering measurements of the vibrational density of states of acetanilide and three deuterated derivatives are presented. These data allow one to identify an intense maximum, assigned to the N-H out-of-plane bending mode. The data display the specific behavior of the methyl torsional modes: large isotopic shift and strong low-temperature intensity; confirm our previous inelastic-neutron-scattering studies, indicating no obvious anomalies in the range of frequency of the acoustic phonons. In addition, the data show the existence of thermally activated quasielastic scattering above 100 K, assigned to the random diffusive motion of the methyl protons. These results are discussed in the light of recent theoretical models proposed to explain the anomalous optical properties of this crystal.
4. Effects of the ohmic current on collective scattering spectra
International Nuclear Information System (INIS)
Castiglioni, S.; Lontano, M.; Tartari, U.
1993-01-01
A numerical and analytical study of the modifications induced in the collective scattering spectra by the ohmic current governing the equilibrium magnetic configuration in toroidal plasmas is presented. The spectral density function is calculated assuming equilibrium distributions for the (bulk and impurity) ion species and a Spitzer-like distribution to describe the response of the electrons to the applied DC electric field. As expected, the spectral asymmetries can be non-negligibly enhanced in the region of the ion-acoustic frequency. They reach their maxima for tangential scattering geometries, where the magnetic effects on the spectra are negligible. This justifies the assumption of the non-magnetized spectra. A theoretically motivated potential is shown to exist for a more detailed experimental investigation of the feasibility of current-density measurements in ohmic plasmas, based on collective scattering. (author)
5. X-ray scattering at liquid surfaces and interfaces
International Nuclear Information System (INIS)
Daillant, Jean
2000-01-01
X-ray and neutron reflectivity techniques have become quite popular for the analysis of surfaces and interfaces over the last ten years. In this review, we discuss the specific aspects of both specular and diffuse x-ray reflectivity at liquid interfaces. We start from a model liquid surface for which the scattering cross-section can be calculated in terms of thermally excited capillary and acoustic waves, and we examine in detail the experimental consequences of the large bulk scattering and of the low q divergence of the surface scattering. Deviations from the simple calculated behaviour point to interesting phenomena which can be studied in detail, like the appearance of a bending stiffness. The method is illustrated through the discussion of representative studies of liquid surfaces, of surfactant monolayers, of liquid-liquid interfaces and of microemulsions. (author)
6. Virtual neutron scattering experiments
DEFF Research Database (Denmark)
Overgaard, Julie Hougaard; Bruun, Jesper; May, Michael
2017-01-01
. In the last week of the course, students travel to a large-scale neutron scattering facility to perform real neutron scattering experiments. Through student interviews and survey answers, we argue, that the virtual training prepares the students to engage more fruitfully with experiments by letting them focus......We describe how virtual experiments can be utilized in a learning design that prepares students for hands-on experiments at large-scale facilities. We illustrate the design by showing how virtual experiments are used at the Niels Bohr Institute in a master level course on neutron scattering...
7. Scattering on magnetic monopoles
International Nuclear Information System (INIS)
Petry, H.R.
1980-01-01
The time-dependent scattering theory of charged particles on magnetic monopoles is investigated within a mathematical frame-work, which duely pays attention to the fact that the wavefunctions of the scattered particles are sections in a non-trivial complex line-bundle. It is found that Moeller operators have to be defined in a way which takes into account the peculiar long-range behaviour of the monopole field. Formulas for the scattering matrix and the differential cross-section are derived, and, as a by-product, a momentum space picture for particles, which are described by sections in the underlying complex line-bundle, is presented. (orig.)
8. Deep inelastic neutron scattering
International Nuclear Information System (INIS)
Mayers, J.
1989-03-01
The report is based on an invited talk given at a conference on ''Neutron Scattering at ISIS: Recent Highlights in Condensed Matter Research'', which was held in Rome, 1988, and is intended as an introduction to the techniques of Deep Inelastic Neutron Scattering. The subject is discussed under the following topic headings:- the impulse approximation I.A., scaling behaviour, kinematical consequences of energy and momentum conservation, examples of measurements, derivation of the I.A., the I.A. in a harmonic system, and validity of the I.A. in neutron scattering. (U.K.)
9. A Neutron Scattering Study of Phonons in Per-Deuterated S-Triazine
DEFF Research Database (Denmark)
Doue, M. T.; Heilmann, I. U.; Kjems, Jørgen
1983-01-01
The lattice dynamics of a fully-deuterated single crystal of s-triazine is investigated using the technique of coherent inelastic neutron scattering. Detailed measurements of the temperature dependence of the dispersion of the soft acoustic mode associated with the ferroelastic phase transition...
10. A Literature Survey on Inverse Scattering for Electron Density Profile Determination. Volume II.
Science.gov (United States)
1981-09-24
THE INVERSE SCATTERING PROBLEM4 FOR THE EQUAT ION Of ACOUSTIC\$ AVILA, G.S.S. DEPT. DE MATEMATICA . INST. DE CIENCIAS EXATAS. UNIV. Of BRASILIA...of Colict support Portinari. Joao C. Departamento do Matematica . Pontificia Universidade Catolica do Rio de Janeiro, Rio do Janeiro. Brasil J. Math
11. Effects of subsampling of passive acoustic recordings on acoustic metrics.
Science.gov (United States)
Thomisch, Karolin; Boebel, Olaf; Zitterbart, Daniel P; Samaran, Flore; Van Parijs, Sofie; Van Opzeeland, Ilse
2015-07-01
Passive acoustic monitoring is an important tool in marine mammal studies. However, logistics and finances frequently constrain the number and servicing schedules of acoustic recorders, requiring a trade-off between deployment periods and sampling continuity, i.e., the implementation of a subsampling scheme. Optimizing such schemes to each project's specific research questions is desirable. This study investigates the impact of subsampling on the accuracy of two common metrics, acoustic presence and call rate, for different vocalization patterns (regimes) of baleen whales: (1) variable vocal activity, (2) vocalizations organized in song bouts, and (3) vocal activity with diel patterns. To this end, above metrics are compared for continuous and subsampled data subject to different sampling strategies, covering duty cycles between 50% and 2%. The results show that a reduction of the duty cycle impacts negatively on the accuracy of both acoustic presence and call rate estimates. For a given duty cycle, frequent short listening periods improve accuracy of daily acoustic presence estimates over few long listening periods. Overall, subsampling effects are most pronounced for low and/or temporally clustered vocal activity. These findings illustrate the importance of informed decisions when applying subsampling strategies to passive acoustic recordings or analyses for a given target species.
12. Anisotropic mass density by two-dimensional acoustic metamaterials
Energy Technology Data Exchange (ETDEWEB)
Torrent, Daniel; Sanchez-Dehesa, Jose [Wave Phenomena Group, Department of Electronic Engineering, Polytechnic University of Valencia, C/Camino de Vera s/n, E-46022 Valencia (Spain)], E-mail: [email protected]
2008-02-15
We show that specially designed two-dimensional arrangements of full elastic cylinders embedded in a nonviscous fluid or gas define (in the homogenization limit) a new class of acoustic metamaterials characterized by a dynamical effective mass density that is anisotropic. Here, analytic expressions for the dynamical mass density and the effective sound velocity tensors are derived in the long wavelength limit. Both show an explicit dependence on the lattice filling fraction, the elastic properties of cylinders relative to the background, their positions in the unit cell, and their multiple scattering interactions. Several examples of these metamaterials are reported and discussed.
13. Measurements of acoustic pressure at high amplitudes and intensities
International Nuclear Information System (INIS)
Crum, L A; Bailey, M R; Kaczkowski, P; McAteer, J A; Pishchalnikov, Y A; Sapozhnikov, O A
2004-01-01
In our research group, we desire measurements of the large pressure amplitudes generated by the shock waves used in shock wave lithotripsy (SWL) and the large acoustic intensities used in High Intensity Focused Ultrasound (HIFU). Conventional piezoelectric or PVDF hydrophones can not be used for such measurements as they are damaged either by cavitation, in SWL applications, or heat, in HIFU applications. In order to circumvent these difficulties, we have utilized optical fiber hydrophones in SWL that do not cavitate, and small glass probes and a scattering technique for measurements of large HIFU intensities. Descriptions of these techniques will be given as well as some typical data
14. Strong spectral variation of biomass smoke light absorption and single scattering albedo observed with a novel dual-wavelength photoacoustic instrument
Science.gov (United States)
Kristin Lewis; William P. Arnott; Hans Moosmuller; Cyle E. Wold
2008-01-01
A dual-wavelength photoacoustic instrument operating at 405 and 870 nm was used during the 2006 Fire Lab at Missoula Experiment to measure light scattering and absorption by smoke from the combustion of a variety of biomass fuels. Simultaneous measurements of aerosol light scattering by reciprocal nephelometry within the instrument's acoustic resonator accompany...
15. An Experimental Introduction to Acoustics
Science.gov (United States)
Black, Andy Nicholas; Magruder, Robert H.
2017-11-01
Learning and understanding physics requires more than studying physics texts. It requires doing physics. Doing research is a key opportunity for students to connect physical principles with their everyday experience. A powerful way to introduce students to research and technique is through subjects in which they might find interest. Presented is an experiment that serves to introduce an advanced undergraduate or high school student to conducting research in acoustics via an experiment involving a standard dreadnought acoustic guitar, recording industry-related equipment, and relevant industrial analysis software. This experimental process is applicable to a wide range of acoustical topics including both acoustic and electric instruments. Also, the student has a hands-on experience with relevant audio engineering technology to study physical principles.
16. Reverberant Acoustic Test Facility (RATF)
Data.gov (United States)
Federal Laboratory Consortium — The very large Reverberant Acoustic Test Facility (RATF) at the NASA Glenn Research Center (GRC), Plum Brook Station, is currently under construction and is due to...
17. Physical acoustics principles and methods
CERN Document Server
Mason, Warren P
2012-01-01
Physical Acoustics: Principles and Methods, Volume IV, Part B: Applications to Quantum and Solid State Physics provides an introduction to the various applications of quantum mechanics to acoustics by describing several processes for which such considerations are essential. This book discusses the transmission of sound waves in molten metals. Comprised of seven chapters, this volume starts with an overview of the interactions that can happen between electrons and acoustic waves when magnetic fields are present. This text then describes acoustic and plasma waves in ionized gases wherein oscillations are subject to hydrodynamic as well as electromagnetic forces. Other chapters examine the resonances and relaxations that can take place in polymer systems. This book discusses as well the general theory of the interaction of a weak sinusoidal field with matter. The final chapter describes the sound velocities in the rocks composing the Earth. This book is a valuable resource for physicists and engineers.
18. PVT Degradation Studies: Acoustic Diagnostics
Energy Technology Data Exchange (ETDEWEB)
Dib, Gerges [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Tucker, Brian J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kouzes, Richard T. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Smith, Philip J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2017-04-01
Under certain environmental conditions, polyvinyl toluene (PVT) plastic scintillator has been observed to undergo internal fogging. This document reports on a study of acoustic techniques to determine whether they can provide a diagnostic for the fogging of PVT. Different ultrasound techniques were employed for detecting the level of internal fogging in PVT, including wave velocity measurements, attenuation, nonlinear acoustics, and acoustic microscopy. The results indicate that there are linear relations between the wave velocity and wave attenuation with the level of internal fogging. The effects of fogging on ultrasound wave attenuation is further verified by acoustic microscopy imaging, where regions with fog in the specimen demonstration higher levels of attenuation compared to clear regions. Results from the nonlinear ultrasound measurements were inconclusive due to high sensitivities to transducer coupling and fixture variabilities.
19. Acoustic Characterization of Mesoscale Objects
Energy Technology Data Exchange (ETDEWEB)
Chinn, D; Huber, R; Chambers, D; Cole, G; Balogun, O; Spicer, J; Murray, T
2007-03-13
This report describes the science and engineering performed to provide state-of-the-art acoustic capabilities for nondestructively characterizing mesoscale (millimeter-sized) objects--allowing micrometer resolution over the objects entire volume. Materials and structures used in mesoscale objects necessitate the use of (1) GHz acoustic frequencies and (2) non-contacting laser generation and detection of acoustic waves. This effort demonstrated that acoustic methods at gigahertz frequencies have the necessary penetration depth and spatial resolution to effectively detect density discontinuities, gaps, and delaminations. A prototype laser-based ultrasonic system was designed and built. The system uses a micro-chip laser for excitation of broadband ultrasonic waves with frequency components reaching 1.0 GHz, and a path-stabilized Michelson interferometer for detection. The proof-of-concept for mesoscale characterization is demonstrated by imaging a micro-fabricated etched pattern in a 70 {micro}m thick silicon wafer.
20. Acoustic agglomeration methods and apparatus
Science.gov (United States)
Barmatz, M. B. (Inventor)
1984-01-01
Methods are described for using acoustic energy to agglomerate fine particles on the order of one micron diameter that are suspended in gas, to provide agglomerates large enough for efficient removal by other techniques. The gas with suspended particles, is passed through the length of a chamber while acoustic energy at a resonant chamber mode is applied to set up one or more acoustic standing wave patterns that vibrate the suspended particles to bring them together so they agglomerate. Several widely different frequencies can be applied to efficiently vibrate particles of widely differing sizes. The standing wave pattern can be applied along directions transversed to the flow of the gas. The particles can be made to move in circles by applying acoustic energy in perpendicular directions with the energy in both directions being of the same wavelength but 90 deg out of phase.
1. A programmable nonlinear acoustic metamaterial
Directory of Open Access Journals (Sweden)
Tianzhi Yang
2017-09-01
Full Text Available Acoustic metamaterials with specifically designed lattices can manipulate acoustic/elastic waves in unprecedented ways. Whereas there are many studies that focus on passive linear lattice, with non-reconfigurable structures. In this letter, we present the design, theory and experimental demonstration of an active nonlinear acoustic metamaterial, the dynamic properties of which can be modified instantaneously with reversibility. By incorporating active and nonlinear elements in a single unit cell, a real-time tunability and switchability of the band gap is achieved. In addition, we demonstrate a dynamic “editing” capability for shaping transmission spectra, which can be used to create the desired band gap and resonance. This feature is impossible to achieve in passive metamaterials. These advantages demonstrate the versatility of the proposed device, paving the way toward smart acoustic devices, such as logic elements, diode and transistor.
2. Electron scattering from pyrimidine
International Nuclear Information System (INIS)
Colmenares, Rafael; Fuss, Martina C; García, Gustavo; Oller, Juan C; Muñoz, Antonio; Blanco, Francisco; Almeida, Diogo; Limão-Vieira, Paulo
2014-01-01
Electron scattering from pyrimidine (C 4 H 4 N 2 ) was investigated over a wide range of energies. Following different experimental and theoretical approaches, total, elastic and ionization cross sections as well as electron energy loss distributions were obtained.
3. Gravitational Bhabha scattering
International Nuclear Information System (INIS)
Santos, A F; Khanna, Faqir C
2017-01-01
Gravitoelectromagnetism (GEM) as a theory for gravity has been developed similar to the electromagnetic field theory. A weak field approximation of Einstein theory of relativity is similar to GEM. This theory has been quantized. Traditional Bhabha scattering, electron–positron scattering, is based on quantized electrodynamics theory. Usually the amplitude is written in terms of one photon exchange process. With the development of quantized GEM theory, the scattering amplitude will have an additional component based on an exchange of one graviton at the lowest order of perturbation theory. An analysis will provide the relative importance of the two amplitudes for Bhabha scattering. This will allow an analysis of the relative importance of the two amplitudes as the energy of the exchanged particles increases. (paper)
4. Applied electromagnetic scattering theory
CERN Document Server
Osipov, Andrey A
2017-01-01
Besides classical applications (radar and stealth, antennas, microwave engineering), scattering and diffraction are enabling phenomena for some emerging research fields (artificial electromagnetic materials or metamaterials, terahertz technologies, electromagnetic aspects of nano-science). This book is a tutorial for advanced students who need to study diffraction theory. The textbook gives fundamental knowledge about scattering and diffraction of electromagnetic waves and provides some working examples of solutions for practical high-frequency scattering and diffraction problems. The book focuses on the most important diffraction effects and mechanisms influencing the scattering process and describes efficient and physically justified simulation methods - physical optics (PO) and the physical theory of diffraction (PTD) - applicable in typical remote sensing scenarios. The material is presented in a comprehensible and logical form, which relates the presented results to the basic principles of electromag...
5. Scattering by bound nucleons
International Nuclear Information System (INIS)
Tezuka, Hirokazu.
1984-10-01
Scattering of a particle by bound nucleons is discussed. Effects of nucleons that are bound in a nucleus are taken as a structure function. The way how to calculate the structure function is given. (author)
6. LIDAR Thomson scattering
International Nuclear Information System (INIS)
1991-07-01
This collection contains 21 papers on the application and development of LIDAR (Light Detection and Ranging) Thomson scattering techniques for the determination of spatially resolved electron temperature and density in magnetic confinement experiments, particularly tokamaks. Refs, figs and tabs
7. Magnetic electron scattering
International Nuclear Information System (INIS)
Peterson, G.A.
1989-01-01
We briefly review some of the motivations, early results, and techniques of magnetic elastic and inelastic electron-nucleus scattering. We then discuss recent results, especially those acquired at high momentum transfers. 50 refs., 19 figs
8. Deep inelastic lepton scattering
International Nuclear Information System (INIS)
Nachtmann, O.
1977-01-01
Deep inelastic electron (muon) nucleon and neutrino nucleon scattering as well as electron positron annihilation into hadrons are reviewed from a theoretical point of view. The emphasis is placed on comparisons of quantum chromodynamics with the data. (orig.) [de
9. A Brillouin scattering study of the effect of chemical passivation on the elastic properties of porous silicon
Science.gov (United States)
Fan, H. J.; Kuok, M. H.; Ng, S. C.; Boukherroub, R.; Lockwood, D. J.
2002-07-01
Brillouin scattering has been performed to probe acoustic waves in porous silicon films that have been chemically modified with either 1-decene, decyl aldehyde, undecylenic acid, or ethyl undecylenate. The shift in the frequencies of acoustic modes in the passivated porous silicon samples, relative to those in freshly prepared porous silicon, is different for different chemical modifiers. The magnitude of the frequency shift is qualitatively correlated with the change, caused by the passivation, in the average densities and elastic constants of the samples.
10. A frequency domain linearized Navier-Stokes method including acoustic damping by eddy viscosity using RANS
Science.gov (United States)
Holmberg, Andreas; Kierkegaard, Axel; Weng, Chenyang
2015-06-01
In this paper, a method for including damping of acoustic energy in regions of strong turbulence is derived for a linearized Navier-Stokes method in the frequency domain. The proposed method is validated and analyzed in 2D only, although the formulation is fully presented in 3D. The result is applied in a study of the linear interaction between the acoustic and the hydrodynamic field in a 2D T-junction, subject to grazing flow at Mach 0.1. Part of the acoustic energy at the upstream edge of the junction is shed as harmonically oscillating disturbances, which are conveyed across the shear layer over the junction, where they interact with the acoustic field. As the acoustic waves travel in regions of strong shear, there is a need to include the interaction between the background turbulence and the acoustic field. For this purpose, the oscillation of the background turbulence Reynold's stress, due to the acoustic field, is modeled using an eddy Newtonian model assumption. The time averaged flow is first solved for using RANS along with a k-ε turbulence model. The spatially varying turbulent eddy viscosity is then added to the spatially invariant kinematic viscosity in the acoustic set of equations. The response of the 2D T-junction to an incident acoustic field is analyzed via a plane wave scattering matrix model, and the result is compared to experimental data for a T-junction of rectangular ducts. A strong improvement in the agreement between calculation and experimental data is found when the modification proposed in this paper is implemented. Discrepancies remaining are likely due to inaccuracies in the selected turbulence model, which is known to produce large errors e.g. for flows with significant rotation, which the grazing flow across the T-junction certainly is. A natural next step is therefore to test the proposed methodology together with more sophisticated turbulence models.
11. Stable And Oscillating Acoustic Levitation
Science.gov (United States)
Barmatz, Martin B.; Garrett, Steven L.
1988-01-01
Sample stability or instability determined by levitating frequency. Degree of oscillation of acoustically levitated object along axis of levitation chamber controlled by varying frequency of acoustic driver for axis above or below frequency of corresponding chamber resonance. Stabilization/oscillation technique applied in normal Earth gravity, or in absence of gravity to bring object quickly to rest at nominal levitation position or make object oscillate in desired range about that position.
12. Simplified Rotation In Acoustic Levitation
Science.gov (United States)
Barmatz, M. B.; Gaspar, M. S.; Trinh, E. H.
1989-01-01
New technique based on old discovery used to control orientation of object levitated acoustically in axisymmetric chamber. Method does not require expensive equipment like additional acoustic drivers of precisely adjustable amplitude, phase, and frequency. Reflecting object acts as second source of sound. If reflecting object large enough, close enough to levitated object, or focuses reflected sound sufficiently, Rayleigh torque exerted on levitated object by reflected sound controls orientation of object.
13. Acoustical Properties of Contemporary Mosques
Directory of Open Access Journals (Sweden)
Karaman Özgül Yılmaz
2017-04-01
Full Text Available Religious buildings are important for many communities because of their representation of different beliefs. In such structures, the sense of individuality or unity & togetherness are created according to variable worship activities; these different uses have also different acoustical requirements. In order to create the desired feeling in the space at the required time, rooms should be evaluated in terms of acoustical conditions.
14. Acoustic techniques in nuclear safeguards
International Nuclear Information System (INIS)
Olinger, C.T.; Sinha, D.N.
1995-01-01
Acoustic techniques can be employed to address many questions relevant to current nuclear technology needs. These include establishing and monitoring intrinsic tags and seals, locating holdup in areas where conventional radiation-based measurements have limited capability, process monitoring, monitoring containers for corrosion or changes in pressure, and facility design verification. These acoustics applications are in their infancy with respect to safeguards and nuclear material management, but proof-of-principle has been demonstrated in many of the areas listed
15. Acoustic Multipurpose Cargo Transfer Bag
Science.gov (United States)
Baccus, Shelley
2015-01-01
The Logistics Reduction (LR) project within the Advanced Exploration Systems (AES) program is tasked with reducing logistical mass and repurposing logistical items. Multipurpose Cargo Transfer Bags (MCTB) are designed to be the same external volume as a regular cargo transfer bag, the common logistics carrier for the International Space Station. After use as a cargo bag, the MCTB can be unzipped and unfolded to be reused. This Acoustic MCTBs transform into acoustic blankets after the initial logistics carrying objective is complete.
16. Small angle neutron scattering
International Nuclear Information System (INIS)
Bernardini, G.; Cherubini, G.; Fioravanti, A.; Olivi, A.
1976-09-01
A method for the analysis of the data derived from neutron small angle scattering measurements has been accomplished in the case of homogeneous particles, starting from the basic theory without making any assumption on the form of particle size distribution function. The experimental scattering curves are interpreted with the aid the computer by means of a proper routine. The parameters obtained are compared with the corresponding ones derived from observations at the transmission electron microscope
17. Pp scattering at SIN
International Nuclear Information System (INIS)
Aprile-Giboni, E.; Cantale, G.; Hausammann, R.
1983-01-01
Using the PM1 polarized proton beam at SIN and a polarized target, the elastic pp scattering as well as the inelastic channel pp → π + d have been studied between 400 and 600 MeV. For the elastic reaction, a sufficient number of spin dependent parameters has been measured in order to do a direct reconstruction of the scattering matrix between 38 0 /sub cm/ and 90 0 /sub cm/. 10 references, 6 figures
18. Development of acoustic particle detector
International Nuclear Information System (INIS)
Matsuyama, Tadayoshi; Hinode, Fujio; Konno, Osamu
1999-01-01
To detect acoustic sign from electron, determination of acoustic radiation from high energy electron and detector were studied. When charge particles pass through medium, energy loss generates local expansion and contraction of medium and pressure compression wave. We need caustic element with 10 -5 Pa the minimum acoustic receive sensitivity and from 10 to 100 kHz frequency sensitivity characteristic. Elements were made by Low-Q materials, piezoelectric materials (PZT). Various sharp of elements were constructed and measured. 50 mm spherical element showed 38 m V/Pa, the best sensitivity. Our developed acoustic element could detect acoustic radiation generated by electron beam from accelerator. The wave sharp detected proved the same as bipolar wave, which was given theoretically. The pressure generated by beam was proportional to the energy loss E. 200 MeV electron beam existed about 95% particles on the incident axis. So that acoustic detector on the axis proved to detect sound wave generated on the beam axis. (S.Y.)
19. Ultrasonic characterization of three animal mammary tumors from three-dimensional acoustic tissue models
Science.gov (United States)
Mamou, Jonathan M.
This dissertation investigated how three-dimensional (3D) tissue models can be used to improve ultrasonic tissue characterization (UTC) techniques. Anatomic sites in tissue responsible for ultrasonic scattering are unknown, which limits the potential applications of ultrasound for tumor diagnosis. Accurate 3D models of tumor tissues may help identify the scattering sites. Three mammary tumors were investigated: a rat fibroadenoma, a mouse carcinoma, and a mouse sarcoma. A 3D acoustic tissue model, termed 3D impedance map (3DZM), was carefully constructed from consecutive histologic sections for each tumor. Spectral estimates (scatterer size and acoustic concentration) were obtained from the 3DZMs and compared to the same estimates obtained with ultrasound. Scatterer size estimates for three tumors were found to be similar (within 10%). The 3DZMs were also used to extract tissue-specific scattering models. The scattering models were found to allow clear distinction between the three tumors. This distinction demonstrated that UTC techniques may be helpful for noninvasive clinical tumor diagnosis.
20. On the interplay between phonon-boundary scattering and phonon-point-defect scattering in SiGe thin films
Science.gov (United States)
Iskandar, A.; Abou-Khalil, A.; Kazan, M.; Kassem, W.; Volz, S.
2015-03-01
This paper provides theoretical understanding of the interplay between the scattering of phonons by the boundaries and point-defects in SiGe thin films. It also provides a tool for the design of SiGe-based high-efficiency thermoelectric devices. The contributions of the alloy composition, grain size, and film thickness to the phonon scattering rate are described by a model for the thermal conductivity based on the single-mode relaxation time approximation. The exact Boltzmann equation including spatial dependence of phonon distribution function is solved to yield an expression for the rate at which phonons scatter by the thin film boundaries in the presence of the other phonon scattering mechanisms. The rates at which phonons scatter via normal and resistive three-phonon processes are calculated by using perturbation theories with taking into account dispersion of confined acoustic phonons in a two dimensional structure. The vibrational parameters of the model are deduced from the dispersion of confined acoustic phonons as functions of temperature and crystallographic direction. The accuracy of the model is demonstrated with reference to recent experimental investigations regarding the thermal conductivity of single-crystal and polycrystalline SiGe films. The paper describes the strength of each of the phonon scattering mechanisms in the full temperature range. Furthermore, it predicts the alloy composition and film thickness that lead to minimum thermal conductivity in a single-crystal SiGe film, and the alloy composition and grain size that lead to minimum thermal conductivity in a polycrystalline SiGe film.
1. Near field acoustic holography with microphones mounted on a rigid sphere
DEFF Research Database (Denmark)
Jacobsen, Finn; Moreno, Guillermo; Fernandez Grande, Efren
2008-01-01
Spherical near field acoustic holography (spherical NAH) is a technique that makes it pos-sible to reconstruct the sound field inside and just outside an acoustically transparent spherical surface on which the sound pressure is measured with an array of microphones with negligible scattering...... is only valid if it can be assumed that the sphere has a negligible in-fluence on the incident sound field, and this is not necessarily a good assumption when the sphere is very close to a radiating surface. This paper describes the modified spherical NAH theory and examines the matter through simulations...
2. Spherical near field acoustic holography with microphones on a rigid sphere
DEFF Research Database (Denmark)
Jacobsen, Finn; Hald, Jørgen; Fernandez Grande, Efren
2008-01-01
Spherical near field acoustic holography (SNAH) is a recently developed technique that makes it possible to reconstruct the sound field inside and just outside an acoustically transparent spherical surface on which the sound pressure is measured with an array of microphones with negligible...... with an array of microphones flush-mounted on a rigid sphere. However, this approach is only valid if it can be assumed that the sphere has a negligible influence on the incident sound field, in other words if multiple scattering can be ignored, and this is not necessarily a good assumption when the sphere...
3. Acoustic and thermal anomalies in a liquid-glass transition of racemic S(+)-R(-) ketoprofen
Science.gov (United States)
Shibata, Tomohiko; Takayama, Haruki; Kim, Tae Hyun; Kojima, Seiji
2014-01-01
Acoustic and thermal properties of pharmaceutical racemic S(+)-R(-) ketoprofen were investigated in wide temperature range including glassy, supercooled liquid and liquid states by Brillouin scattering and temperature modulated DSC. Sound velocity and acoustic attenuation exhibited clear changes at 265 K indicating a liquid-glass transition and showed the typical structural relaxation above Tg. The high value of the fragility index m = 71 was determined by the dispersion of the complex heat capacity. New relaxation map was suggested in combination with previous study of dielectric measurement.
4. A numerical study of super-resolution through fast 3D wideband algorithm for scattering in highly-heterogeneous media
KAUST Repository
Létourneau, Pierre-David
2016-09-19
We present a wideband fast algorithm capable of accurately computing the full numerical solution of the problem of acoustic scattering of waves by multiple finite-sized bodies such as spherical scatterers in three dimensions. By full solution, we mean that no assumption (e.g. Rayleigh scattering, geometrical optics, weak scattering, Born single scattering, etc.) is necessary regarding the properties of the scatterers, their distribution or the background medium. The algorithm is also fast in the sense that it scales linearly with the number of unknowns. We use this algorithm to study the phenomenon of super-resolution in time-reversal refocusing in highly-scattering media recently observed experimentally (Lemoult et al., 2011), and provide numerical arguments towards the fact that such a phenomenon can be explained through a homogenization theory.
5. A manifestly reciprocal theory of scattering in the presence of elastic media
International Nuclear Information System (INIS)
Wurmser, D.
1996-01-01
The role of elastic waves in the scattering problem is examined in the context of modern field theory. This effort builds upon a previously published, and since successfully applied formalism for solving the acoustic and electromagnetic scattering problems. It specifically addresses the scattering of acoustic waves from a fluid-solid interface, as well as the scattering of elastodynamic waves from surfaces satisfying the zero-displacement, stress-free, and solid endash solid boundary conditions. Expressions for the change in the scattering amplitude due to a perturbation in the scattering surface are derived directly from the requirement of time reversal symmetry (also known as reciprocity). These results constitute formal statements of the composite (or two-scale) model. In a typical application, the perturbation usually corresponds to Bragg scattering and is treated statistically, while the reference surface provides tilt, shadowing, and multiple scattering, and is usually treated deterministically. Used in this way, the new formalism effectively allows existing numerical and operator expansion methods to be used to calculate the scattering from rougher and/or higher dimensional surfaces than would otherwise be possible. An alternate application of the formalism is illustrated using the fluid-solid boundary as an example. A new manifestly reciprocal expression for the scattering amplitude is presented, as are the small slope and open-quote open-quote local close-quote close-quote two-scale approximations for this problem. (By local, it is meant that only local phenomena such as the tilt of the reference surface are automatically included. However, since the result is manifestly reciprocal, it is fairly straightforward to incorporate a non-local effect such as shadowing.) During the course of the discussion, the classical scattering problem is reexamined from an entirely new perspective
6. Acoustics of the Intonarumori
Science.gov (United States)
Serafin, Stefania
2005-04-01
The Intonarumori were a family of musical instruments invented by the Italian futurist composer and painter Luigi Russolo. Each Intonarumori was made of a wooden parallelepiped sound box, inside which a wheel of different sizes and materials was setting into vibration a catgut or metal string. The pitch of the string was varied by using a lever, while the speed of the wheel was controlled by the performer using a crank. At one end of the string there was a drumhead that transmitted vibrations to the speaker. Unfortunately, all the original Intonarumori were destroyed after a fire during World War II. Since then, researchers have tried to understand the sound production mechanism of such instruments, especially by consulting the patents compiled by Russolo or by reading his book The art of noise.'' In this paper we describe the acoustics of the Intonarumori. Based on such description, we propose physical models that simulate such instruments. The intonarumori's string is modeled using a one dimensional waveguide, which is excited either by an impact or a friction model. The body of the instrument is modeled using a 3-D rectangular mesh, while the horn is considered as an omnidirectional radiator.
7. Introduction to nonlinear acoustics
Science.gov (United States)
Bjørnø, Leif
2010-01-01
A brief review of the basic principles of fluid mechanics needed for development of linear and nonlinear ultrasonic concepts will be given. The fundamental equations of nonlinear ultrasonics will be derived and their physical properties explained. It will be shown how an originally monochromatic finite-amplitude ultrasonic wave, due to nonlinear effects, will distort during its propagation in time and space to form higher harmonics to its fundamental frequency. The concepts of shock formation will be presented. The material nonlinearity, described by the nonlinearity parameter B/A of the material, and the convective nonlinearity, described by the ultrasonic Mach Number, will be explained. Two procedures for determination of B/A will briefly be described and some B/A-values characterizing biological materials will be presented. Shock formation, described by use of the Goldberg Number,and Ultrasonic Saturation will be discussed.. An introduction to focused ultrasonic fields will be given and it will be shown how the ultrasonic intensity will vary axially and laterally in and near the focal region and how the field parameters of interest to biomedical applications may be described by use of the KZK-Model. Finally, an introduction will be given to the parametric acoustic array formed by mixing and interaction of two monochromatic, finite-amplitude ultrasonic waves in a liquid and the potentials of this mixing process in biomedical ultrasound will briefly be mentioned.
8. Localization of a small change in a multiple scattering environment without modeling of the actual medium.
Science.gov (United States)
Rakotonarivo, S T; Walker, S C; Kuperman, W A; Roux, P
2011-12-01
A method to actively localize a small perturbation in a multiple scattering medium using a collection of remote acoustic sensors is presented. The approach requires only minimal modeling and no knowledge of the scatterer distribution and properties of the scattering medium and the perturbation. The medium is ensonified before and after a perturbation is introduced. The coherent difference between the measured signals then reveals all field components that have interacted with the perturbation. A simple single scatter filter (that ignores the presence of the medium scatterers) is matched to the earliest change of the coherent difference to localize the perturbation. Using a multi-source/receiver laboratory setup in air, the technique has been successfully tested with experimental data at frequencies varying from 30 to 60 kHz (wavelength ranging from 0.5 to 1 cm) for cm-scale scatterers in a scattering medium with a size two to five times bigger than its transport mean free path. © 2011 Acoustical Society of America
9. Influence of KF substitution on the ferroelectric phase transition of lead titanate single crystals studied by Brillouin light scattering
Directory of Open Access Journals (Sweden)
Seonhyeop Shin
2015-06-01
Full Text Available The elastic properties of KF-substituted perovskite lead titanate (PbTiO3 were investigated by dielectric measurements and Brillouin light scattering. The ferroelectric phase transition occurred at substantially lower temperature due to KF substitution, which was attributed to the modification of the covalency in Pb–O and Ti–O bonds. The longitudinal acoustic (LA mode of KF-substituted PbTiO3 showed a frequency softening in the paraelectric phase, which was accompanied by increasing acoustic damping. This indicated that polarization fluctuations responsible for the acoustic anomalies were enhanced by KF substitution.
10. Focusing of Acoustic Waves through Acoustic Materials with Subwavelength Structures
KAUST Repository
Xiao, Bingmu
2013-05-01
In this thesis, wave propagation through acoustic materials with subwavelength slits structures is studied. Guided by the findings, acoustic wave focusing is achieved with a specific material design. By using a parameter retrieving method, an effective medium theory for a slab with periodic subwavelength cut-through slits is successfully derived. The theory is based on eigenfunction solutions to the acoustic wave equation. Numerical simulations are implemented by the finite-difference time-domain (FDTD) method for the two-dimensional acoustic wave equation. The theory provides the effective impedance and refractive index functions for the equivalent medium, which can reproduce the transmission and reflection spectral responses of the original structure. I analytically and numerically investigate both the validity and limitations of the theory, and the influences of material and geometry on the effective spectral responses are studied. Results show that large contrasts in impedance and density are conditions that validate the effective medium theory, and this approximation displays a better accuracy for a thick slab with narrow slits in it. Based on the effective medium theory developed, a design of a at slab with a snake shaped" subwavelength structure is proposed as a means of achieving acoustic focusing. The property of focusing is demonstrated by FDTD simulations. Good agreement is observed between the proposed structure and the equivalent lens pre- dicted by the theory, which leads to robust broadband focusing by a thin at slab.
11. Effect of pressure on the second-order Raman scattering intensities of zincblende semiconductors
Energy Technology Data Exchange (ETDEWEB)
Trallero-Giner, C.; Syassen, K. [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, 70569 Stuttgart (Germany)
2010-01-15
A microscopic description of the two-phonon scattering intensities in direct-gap zincblende-type semiconductors as a function of hydrostatic pressure and for non-resonant excitation is presented. The calculations were performed according to the electron-two-phonon deformation potential interaction for the {gamma}{sub 1} and {gamma}{sub 15} components of the Raman tensor. It is shown that the effect of pressure on the Raman scattering cross-section exhibits a complex behavior according to the contribution of the acoustical or optical phonons to the overtones and combinations. Second-order scattering intensities via acoustical modes could decrease or increase with increasing hydrostatic pressure, while for combinations or overtones of optical phonons a decreasing intensity is obtained. Calculations of the effect of pressure on second-order Raman intensities are compared to experimental results for ZnTe. (Abstract Copyright [2010], Wiley Periodicals, Inc.)
12. Density and Shape Effects in the Acoustic Propulsion of Bimetallic Nanorod Motors.
Science.gov (United States)
Ahmed, Suzanne; Wang, Wei; Bai, Lanjun; Gentekos, Dillon T; Hoyos, Mauricio; Mallouk, Thomas E
2016-04-26
Bimetallic nanorods are propelled without chemical fuels in megahertz (MHz) acoustic fields, and exhibit similar behaviors to single-metal rods, including autonomous axial propulsion and organization into spinning chains. Shape asymmetry determines the direction of axial movement of bimetallic rods when there is a small difference in density between the two metals. Movement toward the concave end of these rods is inconsistent with a scattering mechanism that we proposed earlier for acoustic propulsion, but is consistent with an acoustic streaming model developed more recently by Nadal and Lauga ( Phys. Fluids 2014 , 26 , 082001 ). Longer rods were slower at constant power, and their speed was proportional to the square of the power density, in agreement with the acoustic streaming model. The streaming model was further supported by a correlation between the disassembly of spinning chains of rods and a sharp decrease in the axial speed of autonomously moving motors within the levitation plane of the cylindrical acoustic cell. However, with bimetallic rods containing metals of different densities, a consistent polarity of motion was observed with the lighter metal end leading. Speed comparisons between single-metal rods of different densities showed that those of lower density are propelled faster. So far, these density effects are not explained in the streaming model. The directionality of bimetallic rods in acoustic fields is intriguing and offers some new possibilities for designing motors in which shape, material, and chemical asymmetry might be combined for enhanced functionality.
13. Acoustic radiation force on a multilayered sphere in a Gaussian standing field
Science.gov (United States)
Wang, Haibin; Liu, Xiaozhou; Gao, Sha; Cui, Jun; Liu, Jiehui; He, Aijun; Zhang, Gutian
2018-03-01
We develop a model for calculating the radiation force on spherically symmetric multilayered particles based on the acoustic scattering approach. An expression is derived for the radiation force on a multilayered sphere centered on the axis of a Gaussian standing wave propagating in an ideal fluid. The effects of the sound absorption of the materials and sound wave on acoustic radiation force of a multilayered sphere immersed in water are analyzed, with particular emphasis on the shell thickness of every layer, and the width of the Gaussian beam. The results reveal that the existence of particle trapping behavior depends on the choice of the non-dimensional frequency ka, as well as the shell thickness of each layer. This study provides a theoretical basis for the development of acoustical tweezers in a Gaussian standing wave, which may benefit the improvement and development of acoustic control technology, such as trapping, sorting, and assembling a cell, and drug delivery applications. Project supported by National Key R&D Program (Grant No. 2016YFF0203000), the National Natural Science Foundation of China (Grant Nos. 11774167 and 61571222), the Fundamental Research Funds for the Central Universities of China (Grant No. 020414380001), the Key Laboratory of Underwater Acoustic Environment, Institute of Acoustics, Chinese Academy of Sciences (Grant No. SSHJ-KFKT-1701), and the AQSIQ Technology R&D Program of China (Grant No. 2017QK125).
14. Reverberant acoustic energy in auditoria that comprise systems of coupled rooms
Science.gov (United States)
Summers, Jason E.
2003-11-01
A frequency-dependent model for reverberant energy in coupled rooms is developed and compared with measurements for a 1:10 scale model and for Bass Hall, Ft. Worth, TX. At high frequencies, prior statistical-acoustics models are improved by geometrical-acoustics corrections for decay within sub-rooms and for energy transfer between sub-rooms. Comparisons of computational geometrical acoustics predictions based on beam-axis tracing with scale model measurements indicate errors resulting from tail-correction assuming constant quadratic growth of reflection density. Using ray tracing in the late part corrects this error. For mid-frequencies, the models are modified to account for wave effects at coupling apertures by including power transmission coefficients. Similarly, statical-acoustics models are improved through more accurate estimates of power transmission measurements. Scale model measurements are in accord with the predicted behavior. The edge-diffraction model is adapted to study transmission through apertures. Multiple-order scattering is theoretically and experimentally shown inaccurate due to neglect of slope diffraction. At low frequencies, perturbation models qualitatively explain scale model measurements. Measurements confirm relation of coupling strength to unperturbed pressure distribution on coupling surfaces. Measurements in Bass Hall exhibit effects of the coupled stage house. High frequency predictions of statistical acoustics and geometrical acoustics models and predictions of coupling apertures all agree with measurements.
15. PORTABLE ACOUSTIC MONITORING PACKAGE (PAMP)
Energy Technology Data Exchange (ETDEWEB)
John l. Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Deepak Mehra
2003-07-01
The 1st generation acoustic monitoring package was designed to detect and analyze weak acoustic signals inside natural gas transmission lines. Besides a microphone it housed a three-inch diameter aerodynamic acoustic signal amplifier to maximize sensitivity to leak induced {Delta}p type signals. The theory and test results of this aerodynamic signal amplifier was described in the master's degree thesis of our Research Assistant Deepak Mehra who is about to graduate. To house such a large three-inch diameter sensor required the use of a steel 300-psi rated 4 inch weld neck flange, which itself weighed already 29 pounds. The completed 1st generation Acoustic Monitoring Package weighed almost 100 pounds. This was too cumbersome to mount in the field, on an access port at a pipeline shut-off valve. Therefore a 2nd generation and truly Portable Acoustic Monitor was built. It incorporated a fully self-contained {Delta}p type signal sensor, rated for line pressures up to 1000 psi with a base weight of only 6 pounds. This is the Rosemont Inc. Model 3051CD-Range 0, software driven sensor, which is believed to have industries best total performance. Its most sensitive unit was purchased with a {Delta}p range from 0 to 3 inch water. This resulted in the herein described 2nd generation: Portable Acoustic Monitoring Package (PAMP) for pipelines up to 1000 psi. Its 32-pound total weight includes an 18-volt battery. Together with a 3 pound laptop with its 4-channel data acquisition card, completes the equipment needed for field acoustic monitoring of natural gas transmission pipelines.
International Nuclear Information System (INIS)
Lin, W.H.
1980-01-01
An analytical study of the interaction between an infinite acoustic medium and a cluster of circular rods is described. The acoustic field due to oscillating rods and the acoustic loading on the rods are first solved in a closed form. The acoustic loading is then used as a forcing function for rod responses, and the acousto-elastic couplings are solved simultaneously. Numerical examples are presented for several cases to illustrate the effects of various system parameters on the acoustic reaction force coefficients. The effect of the acoustic loading on the coupled eigenfrequencies are discussed
17. Problems in nonlinear acoustics: Pulsed finite amplitude sound beams, nonlinear acoustic wave propagation in a liquid layer, nonlinear effects in asymmetric cylindrical sound beams, effects of absorption on the interaction of sound beams, and parametric receiving arrays
Science.gov (United States)
Hamilton, Mark F.
1990-12-01
This report discusses five projects all of which involve basic theoretical research in nonlinear acoustics: (1) pulsed finite amplitude sound beams are studied with a recently developed time domain computer algorithm that solves the KZK nonlinear parabolic wave equation; (2) nonlinear acoustic wave propagation in a liquid layer is a study of harmonic generation and acoustic soliton information in a liquid between a rigid and a free surface; (3) nonlinear effects in asymmetric cylindrical sound beams is a study of source asymmetries and scattering of sound by sound at high intensity; (4) effects of absorption on the interaction of sound beams is a completed study of the role of absorption in second harmonic generation and scattering of sound by sound; and (5) parametric receiving arrays is a completed study of parametric reception in a reverberant environment.
18. Observation of the low-frequency ion acoustic instability in the turbulently heated TRIAM-1 tokamak plasma
Energy Technology Data Exchange (ETDEWEB)
Mitarai, O; Watanabe, T; Nakamura, Y; Nakamura, K; Hiraki, N; Toi, K; Kawai, Y; Itoh, S [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics
1980-12-01
Density fluctuations in the frequency range of several MHz are observed in the turbulently heated TRIAM-1 tokamak plasma by means of a 4 mm microwave scattering method. It is found from the measurement of the dispersion relation that this instability is considered to be the low-frequency ion acoustic instability propagating nearly perpendicular to the toroidal magnetic field.
19. Acoustic constituents of prosodic typology
Science.gov (United States)
Komatsu, Masahiko
Different languages sound different, and considerable part of it derives from the typological difference of prosody. Although such difference is often referred to as lexical accent types (stress accent, pitch accent, and tone; e.g. English, Japanese, and Chinese respectively) and rhythm types (stress-, syllable-, and mora-timed rhythms; e.g. English, Spanish, and Japanese respectively), it is unclear whether these types are determined in terms of acoustic properties, The thesis intends to provide a potential basis for the description of prosody in terms of acoustics. It argues for the hypothesis that the source component of the source-filter model (acoustic features) approximately corresponds to prosody (linguistic features) through several experimental-phonetic studies. The study consists of four parts. (1) Preliminary experiment: Perceptual language identification tests were performed using English and Japanese speech samples whose frequency spectral information (i.e. non-source component) is heavily reduced. The results indicated that humans can discriminate languages with such signals. (2) Discussion on the linguistic information that the source component contains: This part constitutes the foundation of the argument of the thesis. Perception tests of consonants with the source signal indicated that the source component carries the information on broad categories of phonemes that contributes to the creation of rhythm. (3) Acoustic analysis: The speech samples of Chinese, English, Japanese, and Spanish, differing in prosodic types, were analyzed. These languages showed difference in acoustic characteristics of the source component. (4) Perceptual experiment: A language identification test for the above four languages was performed using the source signal with its acoustic features parameterized. It revealed that humans can discriminate prosodic types solely with the source features and that the discrimination is easier as acoustic information increases. The
20. Radiological evaluation of acoustic neurinoma
Energy Technology Data Exchange (ETDEWEB)
Lee, Jong Tae; Park, Chang Yun; Choi, Byung So [Yonsei University College of Medicine, Seoul (Korea, Republic of)
1974-04-15
All 25 patients surgically proven acoustic neurinoma was analysed clinically, radiographically at Severance Hospital of Yonsei Univ. The patients not proved surgically in spite of clinical diagnosis of acoustic neurinoma was excluded from this study. The results are summarized as follows; The clinical findings are; 1. The incidence of tumor in female was twice more frequent than in male and the range of age was 20-50 years peak of age at onset of symptom. 2. The clinical symptoms were variable from unilateral hearing impairment or less (100%), headache (84%) to tinnitus (60%) in order of frequency. 3. The tumor growth in the left cerebellopontine angle was twice more than in the right side with the radio of 16:8. However, in one case bilateral simultaneous growth of acoustic neurinoma was noted. The radiological findings are: The best radiographic method to study the shape and size of internal acoustic canal to demonstrate erosion or destruction of petrous pyramida was considered to be straight frontal view and tomography of the skull in our series. 1. The shape of internal acoustic canal in tumors were straight (in 2 cases), bulbous (in 12 cases), and flared (in 11 cases). Particularly there was erosion or destruction of petrous bone in all of the flared cases of canal. 2. The acoustic meatal erosion was mainly suprameatal in 14 cases of 17 which was noted definite erosion radiographically. 3. The difference of height (vertical diameter) of both side of acoustic canal were follows; 6 cases among 25 was in the range of 0-2 mm measurement, remainder was more than 2 mm. Hence the variation in greater than 1 mm in between both sides of canal in same patient should be regard as abnormal as of acoustic neurinoma. 4. The carotid angiogram shows hydrocephalic pattern in 12 cases among 17. 5. In the vertebral angiogram of 8 cases, anterolateral displacement of basilar artery (in 6 caes), the upward displacement of superior cerebellar artery (in 4 cases) was common findings
1. Radiological evaluation of acoustic neurinoma
International Nuclear Information System (INIS)
Lee, Jong Tae; Park, Chang Yun; Choi, Byung So
1974-01-01
All 25 patients surgically proven acoustic neurinoma was analysed clinically, radiographically at Severance Hospital of Yonsei Univ. The patients not proved surgically in spite of clinical diagnosis of acoustic neurinoma was excluded from this study. The results are summarized as follows; The clinical findings are; 1. The incidence of tumor in female was twice more frequent than in male and the range of age was 20-50 years peak of age at onset of symptom. 2. The clinical symptoms were variable from unilateral hearing impairment or less (100%), headache (84%) to tinnitus (60%) in order of frequency. 3. The tumor growth in the left cerebellopontine angle was twice more than in the right side with the radio of 16:8. However, in one case bilateral simultaneous growth of acoustic neurinoma was noted. The radiological findings are: The best radiographic method to study the shape and size of internal acoustic canal to demonstrate erosion or destruction of petrous pyramida was considered to be straight frontal view and tomography of the skull in our series. 1. The shape of internal acoustic canal in tumors were straight (in 2 cases), bulbous (in 12 cases), and flared (in 11 cases). Particularly there was erosion or destruction of petrous bone in all of the flared cases of canal. 2. The acoustic meatal erosion was mainly suprameatal in 14 cases of 17 which was noted definite erosion radiographically. 3. The difference of height (vertical diameter) of both side of acoustic canal were follows; 6 cases among 25 was in the range of 0-2 mm measurement, remainder was more than 2 mm. Hence the variation in greater than 1 mm in between both sides of canal in same patient should be regard as abnormal as of acoustic neurinoma. 4. The carotid angiogram shows hydrocephalic pattern in 12 cases among 17. 5. In the vertebral angiogram of 8 cases, anterolateral displacement of basilar artery (in 6 caes), the upward displacement of superior cerebellar artery (in 4 cases) was common findings
2. Acoustic backscatter at a Red Sea whale shark aggregation site
KAUST Repository
Hozumi, Aya; Kaartvedt, Stein; Rø stad, Anders; Berumen, Michael L.; Cochran, Jesse E.M.; Jones, Burton
2018-01-01
An aggregation of sexually immature whale sharks occurs at a coastal submerged reef near the Saudi Arabian Red Sea coast each spring. We tested the hypothesis that these megaplanktivores become attracted to a prey biomass peak coinciding with their aggregation. Acoustic backscatter of the water column at 120 kHz and 333 kHz –a proxy for potential prey biomass –was continuously measured spanning the period prior to, during, and subsequent to the seasonal whale shark aggregations. No peak in acoustic backscatter was observed at the time of the aggregation. However, we observed a decrease in acoustic backscatter in the last days of deployment, which coincided the trailing end of whale shark season. Organisms forming the main scattering layer performed inverse diel vertical migration, with backscatter peaking at mid-depths during the day and in the deeper half of the water column at night. Target strength analyses suggested the backscatter was likely composed of fish larvae. Subsurface foraging behavior of the whale sharks within this aggregation has not been described, yet this study does not support the hypothesis that seasonal peaks in local whale shark abundance correspond to similar peaks in prey availability.
3. Dynamics of metastable breathers in nonlinear chains in acoustic vacuum
Science.gov (United States)
Sen, Surajit; Mohan, T. R. Krishna
2009-03-01
The study of the dynamics of one-dimensional chains with both harmonic and nonlinear interactions, as in the Fermi-Pasta-Ulam and related problems, has played a central role in efforts to identify the broad consequences of nonlinearity in these systems. Nevertheless, little is known about the dynamical behavior of purely nonlinear chains where there is a complete absence of the harmonic term, and hence sound propagation is not admissible, i.e., under conditions of “acoustic vacuum.” Here we study the dynamics of highly localized excitations, or breathers, which are known to be initiated by the quasistatic stretching of the bonds between adjacent particles. We show via detailed particle-dynamics-based studies that many low-energy pulses also form in the vicinity of the perturbation, and the breathers that form are “fragile” in the sense that they can be easily delocalized by scattering events in the system. We show that the localized excitations eventually disperse, allowing the system to attain an equilibrium-like state that is realizable in acoustic vacuum. We conclude with a discussion of how the dynamics is affected by the presence of acoustic oscillations.
4. Acoustic backscatter at a Red Sea whale shark aggregation site
KAUST Repository
Hozumi, Aya
2018-03-28
An aggregation of sexually immature whale sharks occurs at a coastal submerged reef near the Saudi Arabian Red Sea coast each spring. We tested the hypothesis that these megaplanktivores become attracted to a prey biomass peak coinciding with their aggregation. Acoustic backscatter of the water column at 120 kHz and 333 kHz –a proxy for potential prey biomass –was continuously measured spanning the period prior to, during, and subsequent to the seasonal whale shark aggregations. No peak in acoustic backscatter was observed at the time of the aggregation. However, we observed a decrease in acoustic backscatter in the last days of deployment, which coincided the trailing end of whale shark season. Organisms forming the main scattering layer performed inverse diel vertical migration, with backscatter peaking at mid-depths during the day and in the deeper half of the water column at night. Target strength analyses suggested the backscatter was likely composed of fish larvae. Subsurface foraging behavior of the whale sharks within this aggregation has not been described, yet this study does not support the hypothesis that seasonal peaks in local whale shark abundance correspond to similar peaks in prey availability.
5. A study on the dimensioning of flaws by acoustical holography
International Nuclear Information System (INIS)
Yamamoto, Michio; Ando, Tomozumi; Enami, Koji; Yajima, Minoru; Fukui, Shigetaka.
1978-01-01
As a means of evaluating the safety of flawed pressure vessels and other structures against fracture, fracture mechanics has come to be applied. For the application of fracture mechanics it is necessary to get information concerning the sizes and shapes of flaws. The ultrasonic flaw detection method that is widely used as a nondestructive inspection method cannot measure the sizes and shapes of flaws accurately. Considering that acoustical holography is an useful means for the dimensioning of flaws, we performed basic tests on this method and obtained the following results: (1) The measured values of artificial flaws (flat bottom drilled holes: 5 - 36 mm) made on a steel plate of 150 mm thick showed a good linear relation with their actual sizes and scatter in the measured values was +-3 - 6 mm. (2) The measured values of fatigue cracks (length: 5 - 57 mm) introduced into a steel plate of 150 mm thick also showed a good linear relation with their actual sizes and scatter in the measured values was +-3 mm. (3) It was found that acoustical holography can also be applied to heavy section cast steels. (4) The method of correcting distortion caused by curved surface was investigated by computer-aided simulation and it was considered that such distortion can be corrected by radial scanning of a transducer. (author)
Science.gov (United States)
Cantrell, John H.
2018-01-01
The theoretical foundation of acoustic radiation pressure in plane wave beams is reexamined. It is shown from finite deformation theory and the Boltzmann-Ehrenfest Adiabatic Principle that the Brillouin stress tensor (BST) is the radiation stress in Lagrangian coordinates (not Eulerian coordinates) and that the terms in the BST are not the momentum flux density and mean excess Eulerian stress but are simply contributions to the variation in the wave oscillation period resulting from changes in path length and true wave velocity, respectively, from virtual variations in the strain. It is shown that the radiation stress in Eulerian coordinates is the mean Cauchy stress (not the momentum flux density, as commonly assumed) and that Langevin's second relation does not yield an assessment of the mean Eulerian pressure, since the enthalpy used in the traditional derivations is a function of the thermodynamic tensions - not the Eulerian pressure. It is shown that the transformation between Lagrangian and Eulerian quantities cannot be obtained from the commonly-used expansion of one of the quantities in terms of the particle displacement, since the expansion provides only the difference between the value of the quantity at two different points in Cartesian space separated by the displacement. The proper transformation is obtained only by employing the transformation coefficients of finite deformation theory, which are defined in terms of the displacement gradients. Finite deformation theory leads to the result that for laterally unconfined, plane waves the Lagrangian and Eulerian radiation pressures are equal with the value (1/4)(2K) along the direction of wave propagation, where (K) is the mean kinetic energy density, and zero in directions normal to the propagation direction. This is contrary to the Langevin result that the Lagrangian radiation pressure in the propagation direction is equal to (2K) and the BST result that the Eulerian radiation pressure in that direction
7. CALCULATION OF ACOUSTIC EFFICIENCY OF PORTABLE ACOUSTIC SCREEN
Directory of Open Access Journals (Sweden)
Aleksandr Skvortsov
2016-03-01
Full Text Available The research of influence of life environment adverse factors on physical development and health of population is an actual problem of ecology. The aspects of the most actual problems of the modern world, namely environmental industrial noise pollution are considered in the article. Industrial facilities everywhere have noisy equipment. Noise is a significant factors of negative influenceon people and environment. Combined effects of noise and of other physical pollutions on people may cause amplification of their negative impact. If the noise pollution level from the object in a residential area exceeds the permissible levels (MPL, noise protection measures can be initiated. Today, the most common design decisions for noise protection are sound absorbing construction, noise screens and barriers, acousting housings, soundproff cabins. Many of them are popular, others are less known. The article deals with one of the most wide spread means of noise protection – a portable acoustic screen. The aim of the research is to determine the efficiency of portable acoustic screens. It is shown that the installation of such structures can reduce the average value of the sound level. The authors analyzed acoustic screens as device to reduce noise pollution. The authors offer a potable acoustic screen differing from the used easyness, mobility, minimum price and good sound protective properties. Effectiveness, a sound absorption coefficient and sound conductivity coefficient of a portable acoustic screen are evaluated. The descriptions of the algorithm calculations and the combination of technical solutions have practical originality. The results of the research demonstrate the advantages of the proposed solutions for reducing noise levels in the agro-industrial complex.
8. Acoustic emission from polycrystalline graphites
International Nuclear Information System (INIS)
Ioka, I.; Yoda, S.; Oku, T.; Miyamoto, Y.
1987-01-01
9. Virtual neutron scattering experiments
DEFF Research Database (Denmark)
Overgaard, Julie Hougaard; Bruun, Jesper; May, Michael
2016-01-01
We describe how virtual experiments can be utilized in a learning design that prepares students for hands-on experiments at large-scale facilities. We illustrate the design by showing how virtual experiments are used at the Niels Bohr Institute in a master level course on neutron scattering....... In the last week of the course, students travel to a large-scale neutron scattering facility to perform real neutron scattering experiments. Through student interviews and survey answers, we argue, that the virtual training prepares the students to engage more fruitfully with experiments by letting them focus...... on physics and data rather than the overwhelming instrumentation. We argue that this is because they can transfer their virtual experimental experience to the real-life situation. However, we also find that learning is still situated in the sense that only knowledge of particular experiments is transferred...
10. Electron scattering off nuclei
International Nuclear Information System (INIS)
Gattone, A.O.
1989-01-01
Two recently developed aspects related to the scattering of electrons off nuclei are presented. On the one hand, a model is introduced which emphasizes the relativistic aspects of the problem in the impulse approximation, by demanding strict maintenance of the algebra of the Poincare group. On the other hand, the second model aims at a more sophisticated description of the nuclear response in the case of collective excitations. Basically, it utilizes the RPA formalism with a new development which enables a more careful treatment of the states in the continuum as is the case for the giant resonances. Applications of both models to the description of elastic scattering, inelastic scattering to discrete levels, giant resonances and the quasi-elastic region are discussed. (Author) [es
11. Cold moderator scattering kernels
International Nuclear Information System (INIS)
MacFarlane, R.E.
1989-01-01
New thermal-scattering-law files in ENDF format have been developed for solid methane, liquid methane liquid ortho- and para-hydrogen, and liquid ortho- and para-deuterium using up-to-date models that include such effects as incoherent elastic scattering in the solid, diffusion and hindered vibration and rotations in the liquids, and spin correlations for the hydrogen and deuterium. These files were generated with the new LEAPR module of the NJOY Nuclear Data Processing System. Other modules of this system were used to produce cross sections for these moderators in the correct format for the continuous-energy Monte Carlo code (MCNP) being used for cold-moderator-design calculations at the Los Alamos Neutron Scattering Center (LANSCE). 20 refs., 14 figs
12. Quantum Optical Multiple Scattering
DEFF Research Database (Denmark)
Ott, Johan Raunkjær
. In the first part we use a scattering-matrix formalism combined with results from random-matrix theory to investigate the interference of quantum optical states on a multiple scattering medium. We investigate a single realization of a scattering medium thereby showing that it is possible to create entangled...... states by interference of squeezed beams. Mixing photon states on the single realization also shows that quantum interference naturally arises by interfering quantum states. We further investigate the ensemble averaged transmission properties of the quantized light and see that the induced quantum...... interference survives even after disorder averaging. The quantum interference manifests itself through increased photon correlations. Furthermore, the theoretical description of a measurement procedure is presented. In this work we relate the noise power spectrum of the total transmitted or reflected light...
13. MAGNETIC NEUTRON SCATTERING
Energy Technology Data Exchange (ETDEWEB)
ZALIZNYAK,I.A.; LEE,S.H.
2004-07-30
Much of our understanding of the atomic-scale magnetic structure and the dynamical properties of solids and liquids was gained from neutron-scattering studies. Elastic and inelastic neutron spectroscopy provided physicists with an unprecedented, detailed access to spin structures, magnetic-excitation spectra, soft-modes and critical dynamics at magnetic-phase transitions, which is unrivaled by other experimental techniques. Because the neutron has no electric charge, it is an ideal weakly interacting and highly penetrating probe of matter's inner structure and dynamics. Unlike techniques using photon electric fields or charged particles (e.g., electrons, muons) that significantly modify the local electronic environment, neutron spectroscopy allows determination of a material's intrinsic, unperturbed physical properties. The method is not sensitive to extraneous charges, electric fields, and the imperfection of surface layers. Because the neutron is a highly penetrating and non-destructive probe, neutron spectroscopy can probe the microscopic properties of bulk materials (not just their surface layers) and study samples embedded in complex environments, such as cryostats, magnets, and pressure cells, which are essential for understanding the physical origins of magnetic phenomena. Neutron scattering is arguably the most powerful and versatile experimental tool for studying the microscopic properties of the magnetic materials. The magnitude of the cross-section of the neutron magnetic scattering is similar to the cross-section of nuclear scattering by short-range nuclear forces, and is large enough to provide measurable scattering by the ordered magnetic structures and electron spin fluctuations. In the half-a-century or so that has passed since neutron beams with sufficient intensity for scattering applications became available with the advent of the nuclear reactors, they have became indispensable tools for studying a variety of important areas of modern
14. Λ scattering equations
Science.gov (United States)
Gomez, Humberto
2016-06-01
The CHY representation of scattering amplitudes is based on integrals over the moduli space of a punctured sphere. We replace the punctured sphere by a double-cover version. The resulting scattering equations depend on a parameter Λ controlling the opening of a branch cut. The new representation of scattering amplitudes possesses an enhanced redundancy which can be used to fix, modulo branches, the location of four punctures while promoting Λ to a variable. Via residue theorems we show how CHY formulas break up into sums of products of smaller (off-shell) ones times a propagator. This leads to a powerful way of evaluating CHY integrals of generic rational functions, which we call the Λ algorithm.
15. Electromagnetic scattering theory
Science.gov (United States)
Bird, J. F.; Farrell, R. A.
1986-01-01
Electromagnetic scattering theory is discussed with emphasis on the general stochastic variational principle (SVP) and its applications. The stochastic version of the Schwinger-type variational principle is presented, and explicit expressions for its integrals are considered. Results are summarized for scalar wave scattering from a classic rough-surface model and for vector wave scattering from a random dielectric-body model. Also considered are the selection of trial functions and the variational improvement of the Kirchhoff short-wave approximation appropriate to large size-parameters. Other applications of vector field theory discussed include a general vision theory and the analysis of hydromagnetism induced by ocean motion across the geomagnetic field. Levitational force-torque in the magnetic suspension of the disturbance compensation system (DISCOS), now deployed in NOVA satellites, is also analyzed using the developed theory.
16. A Treatise on Acoustic Radiation. Volume 2. Acoustic Transducers
Science.gov (United States)
1983-01-01
Newton) V (meter/sec) acoustical p (Newton/meter2 ) U (meter 3/sec) To display Eq. 1.53.1 in simple form we take time to be given by exp(- iot ) and choose...if all the C-component edges and e-drivers are in the tree, all the L-component "A edges and idrivers are in the cotree, all the algebraic equations...momentum and mass of the elastic field then become, (a) Al - V -T + F 278 W-4. ,-,- * * * 4 % • *.• Design of Acoustic Transducers IOT (b) I + VV-s
17. Scattering from Artificial Piezoelectriclike Meta-Atoms and Molecules
Science.gov (United States)
2018-01-01
Inspired by natural piezoelectricity, we introduce hybrid-wave electromechanical meta-atoms and metamolecules that consist of coupled electrical and mechanical oscillators with similar resonance frequencies. We explore the linearized electromechanical scattering process and demonstrate that by exploiting the hybrid-wave interaction one may enable functionalities that are forbidden otherwise. For example, we study a dimer metamolecule that is highly directional for electromagnetic waves, although it is electrically deep subwavelength. This unique behavior is a consequence of the fact that, while the metamolecule is electrically small, it is acoustically large. This idea opens vistas for a plethora of exciting dynamics and phenomena in electromagnetics and acoustics, with implications for miniaturized sensors, superresolution imaging, compact nonreciprocal antennas, and more.
18. Neutron scattering. Experiment manuals
Energy Technology Data Exchange (ETDEWEB)
Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)
2010-07-01
The following topics are dealt with: The thermal triple axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot single-crystal diffractometer HEiDi for structure analysis with neutrons, the backscattering spectrometer SPHERES, neutron polarization analysis with tht time-of-flight spectrometer DNS, the neutron spin-echo spectrometer J-NSE, small-angle neutron scattering with the KWS-1 and KWS-2 diffractometers, the very-small-angle neutron scattering diffractrometer with focusing mirror KWS-3, the resonance spin-echo spectrometer RESEDA, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)
19. Nuclear Compton scattering
International Nuclear Information System (INIS)
Christillin, P.
1986-01-01
The theory of nuclear Compton scattering is reformulated with explicit consideration of both virtual and real pionic degrees of freedom. The effects due to low-lying nuclear states, to seagull terms, to pion condensation and to the Δ dynamics in the nucleus and their interplay in the different energy regions are examined. It is shown that all corrections to the one-body terms, of diffractive behaviour determined by the nuclear form factor, have an effective two-body character. The possibility of using Compton scattering as a complementary source of information about nuclear dynamics is restressed. (author)
20. Diffraction in nuclear scattering
International Nuclear Information System (INIS)
Wojciechowski, H.
1986-01-01
The elastic scattering amplitudes for charged and neutral particles have been decomposed into diffractive and refractive parts by splitting the nuclear elastic scattering matrix elements into components responsible for these effects. It has been shown that the pure geometrical diffractive effect which carries no information about the nuclear interaction is always predominant at forward angle of elastic angular distributions. This fact suggests that for strongly absorbed particles only elastic cross section at backward angles, i.e. the refractive cross section, can give us basic information about the central nuclear potential. 12 refs., 4 figs., 1 tab. (author) | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.78361976146698, "perplexity": 2622.2424080628757}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-39/segments/1631780056974.30/warc/CC-MAIN-20210920010331-20210920040331-00059.warc.gz"} |
https://crypto.stackexchange.com/questions/75777/rsa-exercises-example/75779 | # RSA exercises example
Consider the following textbook RSA example. Let be p = 7, q = 11 and e = 3. Give a general algorithm for calculating d and run such algorithm with the above inputs. What is the max integer that can be encrypted? Is there any changes in the answers, if we swap the values of p and q?
I tried to apply RSA in this way:
$$p=7$$ and $$q = 11$$ so $$n=(pq)$$ and $$n=77$$, therefore $$\phi(pq) = (p-1)(q-1) = (7-1)(11-1)= 60$$
Pick $$e$$ that is $$<60$$ and isn't coprime (which means I can't use $$2,3$$ and $$5$$)
So after that, I'm blocked, and my solution is to choose another coprime, for example $$e=7$$ in order to have public-key: $$(n,e)= (77,7)$$
But I'm wrong somewhere, because if I use $$7$$ (or another coprime like $$11$$) I can't compute $$d$$. In fact, for all numbers that I used, for example with $$e=7$$, if I pick $$d=9$$ I have $$63$$ that if I divided for $$60$$ I have $$1$$ with rest $$3$$.
So my questions are these :
• Am I wronging? (where?)
• As a request , can I pick 3, even if it isn't coprime? (because as I saw on theory, I need at least a coprime).
• pick $$e= p$$ or $$q$$ seams wrong.right?
• You find the inverse of $e$ according to $\phi(n)$ not according to $n$. The inverse can be calculated with ext-GCD. – kelalaka Nov 15 '19 at 18:50
• $7^{-1} = 43 \bmod 60$ see at Wolfram. You cannot choose 3 since the setup will not be a permutation. An example here – kelalaka Nov 15 '19 at 19:16
• is this homework? – kelalaka Nov 16 '19 at 8:18
• I'm studying computer security, I have an exam in a few months and I want to understand these topics before the exam (so I'm studying now). This question has already been asked in an old exam task (in 2015). @kelalaka – theantomc Nov 16 '19 at 9:01
Am I wrong? (where?)
Yes, there is a small mistake in the way you are computing $$d$$: you need to compute $$d$$ as being the inverse of $$e$$ modulo $$\phi(n) = (p-1)(q-1) = 60$$. So, if you pick $$e= 7$$ (since you cannot pick $$e = 3$$ because it would be coprime with $$\phi(n)$$), you need to compute its inverse modulo (which is typically done using Euclid's algorithm). As said in the comment, the modular inverse of $$7 \bmod{60}$$ is $$7^{-1} = 43 \bmod{60}$$.
As a request , can I pick 3, even if it isn't coprime? (because as I saw on theory, I need at least a coprime).
No, picking a value $$e$$ that is not coprime with $$\phi(n)$$ does not allow to guarantee unique decryption of ciphertexts.
Since this is not desirable, it is required that $$e$$ is coprime with $$\phi(n)$$, which in turn implies that $$\gcd(e,p-1)=1=\gcd(e, q-1)$$ when using RSA with $$n=pq$$ for $$p,q$$ two primes.
Picking $$e=p$$ or $$q$$ seems wrong, right?
Yes, because then you are literally giving away your private key, since anybody can see that $$n \bmod e \equiv 0$$, which means that $$e$$ divides $$n$$! And, let's say you set $$e=p$$, then it is easy to recover $$q$$ as well by computing $$\frac{n}{e}=q$$ and so anybody knowing your public key $$(n,e)$$ would be able to recover your private key $$(p,q,d)$$.
• My problem continues to be that calculation of d ... I'm trying to understand The Euclidean Algorithm – theantomc Nov 16 '19 at 9:09
• @theantomc: you want to understand the Extended Euclidean Algorithm. See there for a more efficient and easier to implement variant. – fgrieu Nov 16 '19 at 9:19
• @fgrieu Ups, indeed, missing a "not". – Lery Nov 18 '19 at 15:14
if I use $$e=7$$ (or another coprime like $$11$$) I can't compute $$d$$
You can use $$e=7$$. When $$n$$ is squarefree, a private exponent $$d$$ will work if (not: only if) $$e\;d\equiv1\pmod{\phi(n)}$$, that is by definition when $$e\;d-1$$ is divisible by $$\phi(n)$$. There are solutions to that if and only if $$e$$ is coprime with $$\phi(n)$$. The textbook systematic way to find such $$d$$ is the Extended Euclidean Algorithm. See there for a more efficient and easier to implement variant; or there for a "binary" variant.
Note: When $$n$$ is squarefree, the necessary and sufficient condition for $$d$$ to work in RSA is: $$e\;d\equiv1\pmod{\lambda(n)}$$ (where $$\lambda$$ is the Carmichael function). That simplifies computation of $$d$$, and typically leads to a smaller one. $$d=e^{-1}\bmod\lambda(n)$$ is required by some RSA standards including FIPS 186-4. When $$n$$ is the product of distinct primes $$p$$ and $$q$$, $$\lambda(n)$$ can be computed as \begin{align}\lambda(n)&=\operatorname{lcm}(p-1,q-1)\\&=\frac{(p-1)(q-1)}{\gcd(p-1,q-1)}\end{align}
Can I pick $$e=3$$, even if it isn't coprime with $$\phi(n)$$?
No. It is required that $$e$$ is coprime with $$\phi(n)$$ [equivalently: that $$\gcd(e,p-1)=1=\gcd(e,q-1)$$ ] in order to insure unique decryption of ciphertexts. Otherwise, there will be multiple plaintexts $$m\in[0,n)$$ leading to the same ciphertext $$m^e\bmod n$$. In your case $$(n,e)=(77,3)$$, for example, $$m=4$$ and $$m=15$$ would lead to the same ciphertext $$64$$.
Picking $$e=p$$ or $$q$$ seams wrong
For large $$n$$, it would be bad to choose $$e$$ equal to a factor of $$n$$ (or with any other approximate relation between $$e$$ and a factor of $$n$$) since that would allow factoring $$n$$. But when one deliberately illustrates RSA with a toy $$n$$ such as $$n=77$$ which is trivial to factor, choosing $$e$$ equal to one of the factors is a non-issue. Still, one could use $$e=13$$ to avoid that special case.
What is the largest integer that can be encrypted?
In textbook RSA, plaintext and ciphertext space is the integer interval $$[0,n)$$. The largest integer that can be encrypted (and decrypts correctly) is thus $$n-1$$. Notice that it is always encrypted to itself, thus trivial to decipher. More generally, textbook RSA is insecure when directly used to encipher data. It is conjectured secure when $$p$$ and $$q$$ are large random secret primes, and a random $$x$$ in the plaintext space $$[0,n)$$ is enciphered.
• What is the max integer that can be encrypted? is m<n (in my case 77)? – theantomc Nov 16 '19 at 13:25 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 100, "wp-katex-eq": 0, "align": 1, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9117564558982849, "perplexity": 309.8969217746375}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2020-40/segments/1600402131986.91/warc/CC-MAIN-20201001174918-20201001204918-00529.warc.gz"} |
https://cms.math.ca/cmb/msc/46 | Canadian Mathematical Society www.cms.math.ca
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1. CMB Online first
Cruz-Uribe, David; Rodney, Scott; Rosta, Emily
Poincaré Inequalities and Neumann Problems for the $p$-Laplacian We prove an equivalence between weighted Poincaré inequalities and the existence of weak solutions to a Neumann problem related to a degenerate $p$-Laplacian. The Poincaré inequalities are formulated in the context of degenerate Sobolev spaces defined in terms of a quadratic form, and the associated matrix is the source of the degeneracy in the $p$-Laplacian. Keywords:degenerate Sobolev space, $p$-Laplacian, Poincaré inequalitiesCategories:30C65, 35B65, 35J70, 42B35, 42B37, 46E35
2. CMB Online first
Loring, Terry A.; Schulz-Baldes, Hermann
Spectral flow argument localizing an odd index pairing An odd Fredholm module for a given invertible operator on a Hilbert space is specified by an unbounded so-called Dirac operator with compact resolvent and bounded commutator with the given invertible. Associated to this is an index pairing in terms of a Fredholm operator with Noether index. Here it is shown by a spectral flow argument how this index can be calculated as the signature of a finite dimensional matrix called the spectral localizer. Keywords:index pairing, spectral flow, topological materialsCategories:19K56, 46L80
3. CMB Online first
Banica, Teodor
Tannakian duality for affine homogeneous spaces Associated to any closed quantum subgroup $G\subset U_N^+$ and any index set $I\subset\{1,\dots,N\}$ is a certain homogeneous space $X_{G,I}\subset S^{N-1}_{\mathbb C,+}$, called affine homogeneous space. We discuss here the abstract axiomatization of the algebraic manifolds $X\subset S^{N-1}_{\mathbb C,+}$ which can appear in this way, by using Tannakian duality methods. Keywords:quantum isometry, noncommutative manifoldCategories:46L65, 46L89
4. CMB Online first
Schmidt, Simon; Weber, Moritz
Quantum symmetries of graph $C^*$-algebras The study of graph $C^*$-algebras has a long history in operator algebras. Surprisingly, their quantum symmetries have never been computed so far. We close this gap by proving that the quantum automorphism group of a finite, directed graph without multiple edges acts maximally on the corresponding graph $C^*$-algebra. This shows that the quantum symmetry of a graph coincides with the quantum symmetry of the graph $C^*$-algebra. In our result, we use the definition of quantum automorphism groups of graphs as given by Banica in 2005. Note that Bichon gave a different definition in 2003; our action is inspired from his work. We review and compare these two definitions and we give a complete table of quantum automorphism groups (with respect to either of the two definitions) for undirected graphs on four vertices. Keywords:finite graph, graph automorphism, automorphism group, quantum automorphism, graph C*-algebra, quantum group, quantum symmetryCategories:46LXX, 05CXX, 20B25
5. CMB 2018 (vol 61 pp. 236)
Boutonnet, Remi; Roydor, Jean
A Note on Uniformly Bounded Cocycles into Finite von Neumann Algebras We give a short proof of a result of T. Bates and T. Giordano stating that any uniformly bounded Borel cocycle into a finite von Neumann algebra is cohomologous to a unitary cocycle. We also point out a separability issue in their proof. Our approach is based on the existence of a non-positive curvature metric on the positive cone of a finite von Neumann algebra. Keywords:Borel cocycle, von Neumann algebraCategories:46L55, 46L40, 22D40
6. CMB Online first
Bénéteau, Catherine Anne; Fleeman, Matthew C.; Khavinson, Dmitry S.; Seco, Daniel; Sola, Alan
Remarks on inner functions and optimal approximants We discuss the concept of inner function in reproducing kernel Hilbert spaces with an orthogonal basis of monomials and examine connections between inner functions and optimal polynomial approximants to $1/f$, where $f$ is a function in the space. We revisit some classical examples from this perspective, and show how a construction of Shapiro and Shields can be modified to produce inner functions. Keywords:inner function, reproducing Kernel Hilbert Space, operator-theoretic function theoryCategories:46E22, 30J05
7. CMB Online first
Abrahamsen, Trond A.; Hájek, Petr; Nygaard, Olav; Troyanski, Stanimir L.
Strongly extreme points and approximation properties We show that if $x$ is a strongly extreme point of a bounded closed convex subset of a Banach space and the identity has a geometrically and topologically good enough local approximation at $x$, then $x$ is already a denting point. It turns out that such an approximation of the identity exists at any strongly extreme point of the unit ball of a Banach space with the unconditional compact approximation property. We also prove that every Banach space with a Schauder basis can be equivalently renormed to satisfy the sufficient conditions mentioned. Keywords:denting point, strongly extreme point, unconditional compact approximation propertyCategories:46B20, 46B04
8. CMB 2017 (vol 60 pp. 855)
Suárez de la Fuente, Jesús
The Kottman Constant for $\alpha$-Hölder Maps We investigate the role of the Kottman constant of a Banach space $X$ in the extension of $\alpha$-Hölder continuous maps for every $\alpha\in (0,1]$. Keywords:Kottman constant, $\alpha$-Hölder mapCategories:46B60, 46B80
9. CMB 2017 (vol 60 pp. 673)
Abtahi, Fatemeh; Azizi, Mohsen; Rejali, Ali
Character Amenability of the Intersection of Lipschitz Algebras Let $(X,d)$ be a metric space and $J\subseteq [0,\infty)$ be nonempty. We study the structure of the arbitrary intersections of Lipschitz algebras, and define a special Banach subalgebra of $\bigcap_{\gamma\in J}\operatorname{Lip}_\gamma X$, denoted by $\operatorname{ILip}_J X$. Mainly, we investigate $C$-character amenability of $\operatorname{ILip}_J X$, in particular Lipschitz algebras. We address a gap in the proof of a recent result in this field. Then we remove this gap, and obtain a necessary and sufficient condition for $C$-character amenability of $\operatorname{ILip}_J X$, specially Lipschitz algebras, under an additional assumption. Keywords:amenability, character amenability, Lipschitz algebra, metric spaceCategories:46H05, 46J10, 11J83
10. CMB 2017 (vol 61 pp. 225)
Bichon, Julien; Kyed, David; Raum, Sven
Higher $\ell^2$-Betti Numbers of Universal Quantum Groups We calculate all $\ell^2$-Betti numbers of the universal discrete Kac quantum groups $\hat{\mathrm U}^+_n$ as well as their half-liberated counterparts $\hat{\mathrm U}^*_n$. Keywords:$\ell^2$-Betti number, free unitary quantum group, half-liberated unitary quantum group, free product formula, extensionCategories:16T05, 46L65, 20G42
11. CMB Online first
Figiel, Tadeusz; Johnson, William
Quotients of Essentially Euclidean Spaces A precise quantitative version of the following qualitative statement is proved: If a finite dimensional normed space contains approximately Euclidean subspaces of all proportional dimensions, then every proportional dimensional quotient space has the same property. Keywords:essentially euclidean spaceCategories:46B20, 46B07, 46B99
12. CMB 2017 (vol 60 pp. 402)
Shravan Kumar, N.
Invariant Means on a Class of von Neumann Algebras Related to Ultraspherical Hypergroups II Let $K$ be an ultraspherical hypergroup associated to a locally compact group $G$ and a spherical projector $\pi$ and let $VN(K)$ denote the dual of the Fourier algebra $A(K)$ corresponding to $K.$ In this note, we show that the set of invariant means on $VN(K)$ is singleton if and only if $K$ is discrete. Here $K$ need not be second countable. We also study invariant means on the dual of the Fourier algebra $A_0(K),$ the closure of $A(K)$ in the $cb$-multiplier norm. Finally, we consider generalized translations and generalized invariant means. Keywords:ultraspherical hypergroup, Fourier algebra, Fourier-Stieltjes algebra, invariant mean, generalized translation, generalized invariant meanCategories:43A62, 46J10, 43A30, 20N20
13. CMB 2017 (vol 61 pp. 301)
Józiak, Paweł
Remarks on Hopf Images and Quantum Permutation Groups $S_n^+$ Motivated by a question of A. Skalski and P.M. SoÅtan (2016) about inner faithfulness of the S. Curran's map of extending a quantum increasing sequence to a quantum permutation, we revisit the results and techniques of T. Banica and J. Bichon (2009) and study some group-theoretic properties of the quantum permutation group on $4$ points. This enables us not only to answer the aforementioned question in positive in case $n=4, k=2$, but also to classify the automorphisms of $S_4^+$, describe all the embeddings $O_{-1}(2)\subset S_4^+$ and show that all the copies of $O_{-1}(2)$ inside $S_4^+$ are conjugate. We then use these results to show that the converse to the criterion we applied to answer the aforementioned question is not valid. Keywords:Hopf image, quantum permutation group, compact quantum groupCategories:20G42, 81R50, 46L89, 16W35
14. CMB 2017 (vol 61 pp. 114)
Haralampidou, Marina; Oudadess, Mohamed; Palacios, Lourdes; Signoret, Carlos
A characterization of $C^{\ast}$-normed algebras via positive functionals We give a characterization of $C^{\ast}$-normed algebras, among certain involutive normed ones. This is done through the existence of enough specific positive functionals. The same question is also examined in some non normed (topological) algebras. Keywords:$C^{\ast}$-normed algebra, $C^*$-algebra, (pre-)locally $C^*$-algebra, pre-$C^*$-bornological algebra, positive functional, locally uniformly $A$-convex algebra, perfect locally $m$-convex algebra, $C^*$-(resp. $^*$-) subnormable algebraCategories:46H05, 46K05
15. CMB 2017 (vol 60 pp. 449)
Alaghmandan, Mahmood; Crann, Jason
Character Density in Central Subalgebras of Compact Quantum Groups We investigate quantum group generalizations of various density results from Fourier analysis on compact groups. In particular, we establish the density of characters in the space of fixed points of the conjugation action on $L^2(\mathbb{G})$, and use this result to show the weak* density and norm density of characters in $ZL^\infty(\mathbb{G})$ and $ZC(\mathbb{G})$, respectively. As a corollary, we partially answer an open question of Woronowicz. At the level of $L^1(\mathbb{G})$, we show that the center $\mathcal{Z}(L^1(\mathbb{G}))$ is precisely the closed linear span of the quantum characters for a large class of compact quantum groups, including arbitrary compact Kac algebras. In the latter setting, we show, in addition, that $\mathcal{Z}(L^1(\mathbb{G}))$ is a completely complemented $\mathcal{Z}(L^1(\mathbb{G}))$-submodule of $L^1(\mathbb{G})$. Keywords:compact quantum group, irreducible characterCategories:43A20, 43A40, 46J40
16. CMB 2017 (vol 60 pp. 791)
Jiang, Chunlan
Reduction to Dimension Two of Local Spectrum for $AH$ Algebra with Ideal Property A $C^{*}$-algebra $A$ has the ideal property if any ideal $I$ of $A$ is generated as a closed two sided ideal by the projections inside the ideal. Suppose that the limit $C^{*}$-algebra $A$ of inductive limit of direct sums of matrix algebras over spaces with uniformly bounded dimension has ideal property. In this paper we will prove that $A$ can be written as an inductive limit of certain very special subhomogeneous algebras, namely, direct sum of dimension drop interval algebras and matrix algebras over 2-dimensional spaces with torsion $H^{2}$ groups. Keywords:AH algebra, reduction, local spectrum, ideal propertyCategory:46L35
17. CMB 2017 (vol 60 pp. 690)
Bao, Guanlong; Göğüş, Nıhat Gökhan; Pouliasis, Stamatis
$\mathcal{Q}_p$ Spaces and Dirichlet Type Spaces In this paper, we show that the Möbius invariant function space $\mathcal {Q}_p$ can be generated by variant Dirichlet type spaces $\mathcal{D}_{\mu, p}$ induced by finite positive Borel measures $\mu$ on the open unit disk. A criterion for the equality between the space $\mathcal{D}_{\mu, p}$ and the usual Dirichlet type space $\mathcal {D}_p$ is given. We obtain a sufficient condition to construct different $\mathcal{D}_{\mu, p}$ spaces and we provide examples. We establish decomposition theorems for $\mathcal{D}_{\mu, p}$ spaces, and prove that the non-Hilbert space $\mathcal {Q}_p$ is equal to the intersection of Hilbert spaces $\mathcal{D}_{\mu, p}$. As an application of the relation between $\mathcal {Q}_p$ and $\mathcal{D}_{\mu, p}$ spaces, we also obtain that there exist different $\mathcal{D}_{\mu, p}$ spaces; this is a trick to prove the existence without constructing examples. Keywords:$\mathcal {Q}_p$ space, Dirichlet type space, Möbius invariant function spaceCategories:30H25, 31C25, 46E15
18. CMB 2017 (vol 60 pp. 816)
Moslehian, Mohammad Sal; Zamani, Ali
Characterizations of Operator Birkhoff--James Orthogonality In this paper, we obtain some characterizations of the (strong) Birkhoff--James orthogonality for elements of Hilbert $C^*$-modules and certain elements of $\mathbb{B}(\mathscr{H})$. Moreover, we obtain a kind of Pythagorean relation for bounded linear operators. In addition, for $T\in \mathbb{B}(\mathscr{H})$ we prove that if the norm attaining set $\mathbb{M}_T$ is a unit sphere of some finite dimensional subspace $\mathscr{H}_0$ of $\mathscr{H}$ and $\|T\|_{{{\mathscr{H}}_0}^\perp} \lt \|T\|$, then for every $S\in\mathbb{B}(\mathscr{H})$, $T$ is the strong Birkhoff--James orthogonal to $S$ if and only if there exists a unit vector $\xi\in {\mathscr{H}}_0$ such that $\|T\|\xi = |T|\xi$ and $S^*T\xi = 0$. Finally, we introduce a new type of approximate orthogonality and investigate this notion in the setting of inner product $C^*$-modules. Keywords:Hilbert $C^*$-module, Birkhoff--James orthogonality, strong Birkhoff--James orthogonality, approximate orthogonalityCategories:46L05, 46L08, 46B20
19. CMB 2016 (vol 60 pp. 655)
Zhuo, Ciqiang; Sickel, Winfried; Yang, Dachun; Yuan, Wen
Characterizations of Besov-Type and Triebel-Lizorkin-Type Spaces via Averages on Balls Let $\ell\in\mathbb N$ and $\alpha\in (0,2\ell)$. In this article, the authors establish equivalent characterizations of Besov-type spaces, Triebel-Lizorkin-type spaces and Besov-Morrey spaces via the sequence $\{f-B_{\ell,2^{-k}}f\}_{k}$ consisting of the difference between $f$ and the ball average $B_{\ell,2^{-k}}f$. These results give a way to introduce Besov-type spaces, Triebel-Lizorkin-type spaces and Besov-Morrey spaces with any smoothness order on metric measure spaces. As special cases, the authors obtain a new characterization of Morrey-Sobolev spaces and $Q_\alpha$ spaces with $\alpha\in(0,1)$, which are of independent interest. Keywords:Besov space, Triebel-Lizorkin space, ball average, Calderón reproducing formulaCategories:42B25, 46E35, 42B35
20. CMB 2016 (vol 60 pp. 350)
Ma, Yumei
Isometry on Linear $n$-G-quasi Normed Spaces This paper generalizes the Aleksandrov problem: the Mazur-Ulam theorem on $n$-G-quasi normed spaces. It proves that a one-$n$-distance preserving mapping is an $n$-isometry if and only if it has the zero-$n$-G-quasi preserving property, and two kinds of $n$-isometries on $n$-G-quasi normed space are equivalent; we generalize the Benz theorem to n-normed spaces with no restrictions on the dimension of spaces. Keywords:$n$-G-quasi norm, Mazur-Ulam theorem, Aleksandrov problem, $n$-isometry, $n$-0-distanceCategories:46B20, 46B04, 51K05
21. CMB 2016 (vol 60 pp. 217)
Wang, Yuanyi
Condition $C'_{\wedge}$ of Operator Spaces In this paper, we study condition $C'_{\wedge}$ which is a projective tensor product analogue of condition $C'$. We show that the finite-dimensional OLLP operator spaces have condition $C'_{\wedge}$ and $M_{n}$ $(n\gt 2)$ does not have that property. Keywords:operator space, local theory, tensor productCategory:46L07
22. CMB 2016 (vol 60 pp. 104)
Diestel, Geoff
An Extension of Nikishin's Factorization Theorem A Nikishin-Maurey characterization is given for bounded subsets of weak-type Lebesgue spaces. New factorizations for linear and multilinear operators are shown to follow. Keywords:factorization, type, cotype, Banach spacesCategories:46E30, 28A25
23. CMB 2016 (vol 60 pp. 122)
Ghanei, Mohammad Reza; Nasr-Isfahani, Rasoul; Nemati, Mehdi
A Homological Property and Arens Regularity of Locally Compact Quantum Groups We characterize two important notions of amenability and compactness of a locally compact quantum group ${\mathbb G}$ in terms of certain homological properties. For this, we show that ${\mathbb G}$ is character amenable if and only if it is both amenable and co-amenable. We finally apply our results to Arens regularity problems of the quantum group algebra $L^1({\mathbb G})$; in particular, we improve an interesting result by Hu, Neufang and Ruan. Keywords:amenability, Arens regularity, co-amenability, locally compact quantum group, homological propertyCategories:46L89, 43A07, 46H20, 46M10, 58B32
24. CMB 2016 (vol 60 pp. 173)
Oubbi, Lahbib
On Ulam Stability of a Functional Equation in Banach Modules Let $X$ and $Y$ be Banach spaces and $f : X \to Y$ an odd mapping. For any rational number $r \ne 2$, C. Baak, D. H. Boo, and Th. M. Rassias have proved the Hyers-Ulam stability of the following functional equation: \begin{align*} r f \left(\frac{\sum_{j=1}^d x_j}{r} \right) & + \sum_{\substack{i(j) \in \{0,1\} \\ \sum_{j=1}^d i(j)=\ell}} r f \left( \frac{\sum_{j=1}^d (-1)^{i(j)}x_j}{r} \right) = (C^\ell_{d-1} - C^{\ell -1}_{d-1} + 1) \sum_{j=1}^d f(x_j) \end{align*} where $d$ and $\ell$ are positive integers so that $1 \lt \ell \lt \frac{d}{2}$, and $C^p_q := \frac{q!}{(q-p)!p!}$, $p, q \in \mathbb{N}$ with $p \le q$. In this note we solve this equation for arbitrary nonzero scalar $r$ and show that it is actually Hyers-Ulam stable. We thus extend and generalize Baak et al.'s result. Different questions concerning the *-homomorphisms and the multipliers between C*-algebras are also considered. Keywords:linear functional equation, Hyers-Ulam stability, Banach modules, C*-algebra homomorphisms.Categories:39A30, 39B10, 39A06, 46Hxx
25. CMB 2016 (vol 60 pp. 586)
Liu, Feng; Wu, Huoxiong
Endpoint Regularity of Multisublinear Fractional Maximal Functions In this paper we investigate the endpoint regularity properties of the multisublinear fractional maximal operators, which include the multisublinear Hardy-Littlewood maximal operator. We obtain some new bounds for the derivative of the one-dimensional multisublinear fractional maximal operators acting on vector-valued function $\vec{f}=(f_1,\dots,f_m)$ with all $f_j$ being $BV$-functions. Keywords:multisublinear fractional maximal operators, Sobolev spaces, bounded variationCategories:42B25, 46E35
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© Canadian Mathematical Society, 2018 : https://cms.math.ca/ | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9677823185920715, "perplexity": 994.3632319268808}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": false}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2018-17/segments/1524125945459.17/warc/CC-MAIN-20180421223015-20180422003015-00267.warc.gz"} |
http://mathoverflow.net/users/78/theo-johnson-freyd?tab=reputation | Theo Johnson-Freyd
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10 Feb 29 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.5893987417221069, "perplexity": 28579.694270326258}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2016-18/segments/1461860125524.70/warc/CC-MAIN-20160428161525-00159-ip-10-239-7-51.ec2.internal.warc.gz"} |
http://www.physicsforums.com/showthread.php?p=3855005 | # Inviscid flow around cylinder in presence of wall
by Armin1986
Tags: cylinder, flow, inviscid, presence, wall
P: 1 Hi there, Is there someone who would know how to solve the following potential flow theory problem: How to find the flow field and resulting force on a cylinder moving at a constant velocity through a stagnant fluid in the presence of a wall. The motion of the cylinder is parallel to the wall. Without the wall it can be found that there is no force due to the inviscid nature of the flow. However, due to the wall, "ground effect" occurs and therefore there will be a lift force. I have two questions: - How to find the flow field (e.g. streamlines or vector field) - How to find the force as a function of the distance from the wall I would be very thankfull if someone could help me with this problem.
Related Discussions General Physics 4 Mechanical Engineering 7 Engineering, Comp Sci, & Technology Homework 2 Engineering, Comp Sci, & Technology Homework 1 Mechanical Engineering 2 | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8826754689216614, "perplexity": 319.6879277705075}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2014-15/segments/1397609539447.23/warc/CC-MAIN-20140416005219-00160-ip-10-147-4-33.ec2.internal.warc.gz"} |
http://stats.stackexchange.com/questions/13301/assuming-u-sim-n0-sigma2-when-y-is-highly-skewed | # Assuming $u\sim N(0,\sigma^2)$ when y is highly skewed
does it make sense to assume $u\sim N(0,\sigma^2)$ when I know from a histogram that $y$ is highly skewed. Because from the assumption $u\sim N(0,\sigma^2)$ it follows that $y\sim N(x\beta,\sigma^2)$ and I'm absoluteley not sure if the assumption $u\sim N(0,\sigma^2)$ makes sense in a case where I know that the distribution of $y$ is not bell shaped. The alternative would be just to make OLS without any assumption about the error term, but in this case I can't analyze outliers and leverages (what I'd really like to do, because otherwise I can't present much more than a line which minimizes the sqaured sum of the residuals). [addendum: I can't make an outlier analysis because I can not define "outlier" in a context where I don't assume a normal distribution, because there is no outlying without a distribution] Besides your answers I'd really like to have a recommendation for a good book, where I can find some thoughts about what assumptions should we make when y is obviously not normal distributed.
Regards
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There is Taleb's book, although it will merely point the risk of this assumption. – wok Jul 20 '11 at 15:41
You need to put some more background into this. In the linear model $y_i = \alpha + \beta x_i + \epsilon_i$, it is not unusual to assume the $\epsilon_i$ are iid with a normal distribution of mean $0$, but there is no requirement for the $x_i$ or $y_i$ to be normally distributed. – Henry Jul 20 '11 at 15:41
Well, just because $y|x \sim N(x \beta, \sigma^2)$ doesn't mean that a histogram of the marginal distribution of $y$ will look bell shaped; I believe that will only happen if $x$ is also normally distributed. – Macro Jul 20 '11 at 16:37
@Henry For background you could read the almost identical series of questions here, here, and here. "What we've got here is failure to communicate." – whuber Jul 20 '11 at 17:17
@Mark Pick any $\beta$ and $\sigma$, generate 10 iid draws $\epsilon_1$, ..., $\epsilon_{10}$ from a normal(0, $\sigma$) distribution, and create the dataset $((2^i, \beta 2^i + \epsilon_i), i=1,\ldots,10)$. When $|\beta|$ and $\sigma$ are near $1$, the y's will be highly positively skewed but the data are perfectly linear with beautifully normal errors. In short, the skewness of the y's comes from the skewness of the x's but (of itself) reveals nothing at all about the distribution of the residuals. You check distributional assumptions by studying the residuals, not the y's. – whuber Jul 20 '11 at 19:44
If u is the residual from a regression of y on some other variable x, then I think this is a variant of an earlier question. The residuals of u can be Gaussian even if the distribution of y is highly skewed as it may simply be that the distribution of x is highly skewed.
Consider an example of estimating temperature (y) as a function of lattitude (x); here u represents the measurment error of the thermometer (and is Gaussian). The distribution of y values in our sample will depend on where we choose to site out weather stations. If we place them all either at the poles or the equator, then we will have a bimodal distribution. If we place them on a regular equal area grid, we will get a unimodal distribution of y values, even though the physics of climate is the same for both samples and the measurement uncertainty u is normal.
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Thanks for the answer! Do you have some good references in this context for me? A good book or a paper. – MarkDollar Jul 21 '11 at 5:41 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.951729953289032, "perplexity": 349.9692632532123}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 5, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2013-48/segments/1386163052912/warc/CC-MAIN-20131204131732-00024-ip-10-33-133-15.ec2.internal.warc.gz"} |
https://www.varsitytutors.com/gre_subject_test_math-help/infinite-sequences | # GRE Subject Test: Math : Infinite Sequences
## Example Questions
### Example Question #2 : Sequences & Series
Which of the following are not infinite sequences?
Explanation:
Step 1: Define what an infinite sequence is...
An infinite sequence is a sequence that is non-terminating.
Step 2: Determine if each sequence above is infinite...
For , the sequence is always infinite because the set of factorials is infinite. Also, the set of values by raising two factorial powers together is also infinite, it never has an ending term.
For , this sequence is FINITE!
For , this sequence is FINITE! | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9951685070991516, "perplexity": 1508.5994584628324}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2018-22/segments/1526794865456.57/warc/CC-MAIN-20180523063435-20180523083435-00211.warc.gz"} |
https://astarmathsandphysics.com/a-level-physics-notes/electricity/2590-the-double-beam-tube.html?tmpl=component&print=1&page= | ## The Double Beam Tube
The double beam tube consists of a set of Helmholtz coils surrounding a bulb of helium gas at low pressure.
Inside the bulb there are two electron guns. One emits electrons straight into the glass bulb (the radial electron gun), and the other shoots electrons tangentially to the coil. Using the radial electron gun, the range of the electrons is show to be proportional to the accelerating voltage and the energy of the electrons. When a current is passed through the Helmholtz coils, the magnetic field generated acts on the electron. The tangential beam can be bent into a circle.
For a field of flux densityfor the electrons to travel in a circle of radiuswe have(1)
The kinetic energy of the electron is equal toand this is equal to the potential energy gained,whereis the voltage difference between anode and cathode, so(2)
From (2)
cancelfrom both sides to givethen | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8552136421203613, "perplexity": 804.4173985508844}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-34/segments/1502886110578.17/warc/CC-MAIN-20170822104509-20170822124509-00392.warc.gz"} |
https://dsp.stackexchange.com/questions/61257/is-maximizing-hamming-distance-the-same-as-minimizing-correlation/61264#61264 | # Is maximizing hamming distance the same as minimizing correlation?
For the design of an error correcting code, I might wish to maximize the distance between the codewords $$\sum a_i \oplus b_i$$.
For spreading sequences I'd like to minimize the cross-correlation at $$t=0$$ of $$\sum \sigma(a_i)\sigma(b_i)$$ where $$\sigma(\cdot)$$ maps binary $$0\to1$$ and $$1 \to (-1)$$ (i.e. what you'd get out of a BPSK matched filter when $$E_b$$ is normalized and there is no noise).
Are these criteria the same? It seems to me that since $$\sigma$$ acts as an isomorphism that turns cyclic$$\pmod 2$$ addition into cyclic complex multiplication, they are equivalent statements. Can you verify this and let me know where I can read more about it?
• hey, what's "minimally correlated" in terms of correlation coefficient to you? Zero? -1? Oct 14 '19 at 20:43
• I did mean the numerical minimum, so I thought of large (magnitude) negative values to be minimal for the purpose of the comparison with the hamming distance. I graphed both functions for a bunch of vectors and noticed that one measurement is a linear transformation of the other. Oct 14 '19 at 20:54
• ah, ok, yeah, in that case, your approach is right: since by normalization no value below -1 can occur, the vector that is -1 the other is the one with the minimum cross-correlation (in your definition). Whether that definition is useful is a different question, though! Oct 14 '19 at 21:21
## 2 Answers
Well, as you can easily verify, these two criteria aren't the same if you define "minimum correlation" to mean that the absolute value of the correlation coefficient is minimized (i.e. 0):
• In $$\mathbb F_2^N$$, the vector that's the farthest away from any given vector $$v$$ is its bit-wise inverse $$\overline v$$ (using Hamming distance)
• Using your mapping, the BPSK symbol vector mapping to $$\overline v$$ is the $$-1$$ times the one mapping to $$v$$: $$\sigma(v) =-\sigma(\overline v)$$. That's maximal correlation, not minimal.
In short, the hamming distance defined over your finite field isn't a compatible norm to the $$\mathcal L_2$$ norm that gives a correlation coefficient over fields over the real or complex numbers, given your $$\sigma$$. There's not much to say here – they are simply not the same.
If you, however, define the minimum correlation to be found when the correlation coefficient takes the smallest possible value (not: absolute value), then yes, due to normalization, the minimum possible correlation coefficient is -1, and as shown above, your method is one to find the matching BPSK representation.
• Marcus, I also suspect that they're not the same, but I'm not sure about your example. Let's say a codeword is $1,1,1$, then the codeword at largest distance is $-1,-1,-1$; the correlation is -3, which is the minimum possible given 3 elements restricted to $\pm 1$.
– MBaz
Oct 14 '19 at 19:36
• @MBaz ah, it's the minimum correlation coefficient, but maximally correlated, I'd say; I'd say "correlation" is a measure on the absolute of the correlation coefficient, because, from a purely practical point of view, two signals that are linked by a factor (like -1) are very correlated. Doesn't get any more correlated :) Oct 14 '19 at 19:51
• Marcus, I agree that a very large negative correlation coefficient means that the signals are highly correlated. In the context of this problem, though, it might prove interesting to interpret "minimize the correlation" as "obtaining the actual smallest correlation coefficient", without taking absolute values.
– MBaz
Oct 14 '19 at 20:15
• good point, let's ask OP, maybe I also just misunderstood him or her Oct 14 '19 at 20:43
Two codewords $$c_1$$ and $$c_2$$ of length $$n$$, with elements in $$\lbrace +1, -1 \rbrace$$, and Hamming distance $$d$$, have a cross-correlation given by $$(n-d) -d = n-2d.$$ The reason is that there are $$n-d$$ bits that are equal and their product is $$1$$, and $$d$$ bits that are different and their product is $$-1$$.
Note that:
• The larger the distance $$d$$, the smaller the correlation.
• The correlation by itself does not tell you anything about the distance, since you also need to know $$n$$. For example, $$1,1,1$$ and $$-1,-1,-1$$ have correlation $$-3$$ but $$1,1,1,1,1,1$$ and $$1,1,1,-1,-1,-1$$ have correlation $$0$$. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 36, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8947585225105286, "perplexity": 379.08454910233036}, "config": {"markdown_headings": true, "markdown_code": false, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": false}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-43/segments/1634323587767.18/warc/CC-MAIN-20211025185311-20211025215311-00373.warc.gz"} |
http://math.stackexchange.com/questions/339621/surface-area-of-an-elliptic-paraboloid | # Surface area of an elliptic paraboloid
The elliptic paraboloid has height h, and two semiaxes a, b. How to find its surface area? Does it possible to use a direct formula without integrals?
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## 2 Answers
The elliptic paraboloid is represented parametrically as follows:
$$x=a \sqrt{u} \cos{v}$$ $$y=b \sqrt{u} \sin{v}$$ $$z=u$$
The surface area of this object is given by
$$\int_0^h du \: \int_0^{2 \pi} dv \: \sqrt{E \,G - F^2}$$
where the 1st fundamental form is given by
$$E=1+\frac{a^2 \cos^2{v} + b^2 \sin^2{v}}{4 u}$$ $$F=\frac{1}{4} (b^2-a^2) \sin{2 v}$$ $$G = (a^2 \sin^2{v}+b^2 \cos^2{v}) u$$
The integral simplifies to
$$\int_0^h du \: \left [\sqrt{b^2 \left(a^2+4 u\right)} E\left(\frac{4 \left(b^2-a^2\right) u}{b^2 \left(a^2+4 u\right)}\right)+\sqrt{a^2 \left(b^2+4 u\right)} E\left(\frac{4 (a-b) (a+b) u}{a^2 \left(b^2+4 u\right)}\right)\right ]$$
where $E$ is the elliptic integral defined as
$$E(m) = \int_0^{\pi/2} dx \sqrt{1-m \sin^2{x}}$$
This is about the best you'll do as far as I can see.
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The best but still very complex :) – Ivan Bunin Mar 24 '13 at 15:51
@IvanBunin: surface area is a very complex topic in general. I didn't do SA calculations for surfaces other than figures of revolution (and simple objects like cubes and prisms) until I took differential geometry. – Ron Gordon Mar 24 '13 at 15:54
@IvanBunin: you should at this point accept one of the solutions if you found it useful. I know you think mine is complex, but I challenge you to find something simpler. (Arc length and surface area of the ellipse are the reason the elliptic integrals have their names.) – Ron Gordon Apr 2 '13 at 13:19
When one takes the parameter $m$ as argument, you usually don't square it before multiplying by $\sin^2$; similarly, one uses the square if one is taking the modulus $k$ as the argument for the complete elliptic integral. See this for instance. – Ｊ. Ｍ. Apr 3 '13 at 6:20
At the very least, @Ron, Mathematica and A&S both use the parameter convention (which also happens to be my preference), while Maple and the DLMF use the modulus convention. So yes, care ought to be taken... :) – Ｊ. Ｍ. Apr 3 '13 at 9:51
The function in question is $z=\frac{x^2}{a^2}+\frac{y^2}{b^2}$.
It is more convenient to work in polar coordinates, so that $x=a r \cos \theta,y=b r\sin \theta,z=r^2$, and the parameters vary like so: $0\leq \theta \leq 2\pi,0 \leq r \leq \sqrt{h}$.
You can find the surfrace area according the the formula $A=\int_0^{2 \pi} d \theta \int_0^\sqrt{h} dr \| {\bf x}_r \times {\bf x}_\theta \|$, where ${\bf x}=(x,y,z)$. I couldn't evaluate this integral analytically.
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What does $\| {\bf x}_r \times {\bf x}_\theta \|$ means? – Ivan Bunin Mar 24 '13 at 15:48
It is the norm (length) of the cross product of $\frac{\partial {\bf x}}{\partial r}$ and $\frac{\partial {\bf x}}{\partial \theta}$ – user1337 Mar 24 '13 at 16:15 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 1, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9381604194641113, "perplexity": 776.0557499235797}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": false}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2015-18/segments/1429246649234.62/warc/CC-MAIN-20150417045729-00075-ip-10-235-10-82.ec2.internal.warc.gz"} |
http://science.sciencemag.org/content/33/851/629 | ArticlesSpecial Article
# THE RELATION OF PERMEABILITY CHANGE TO CLEAVAGE, IN THE FROG'S EGG
+ See all authors and affiliations
Science 21 Apr 1911:
Vol. 33, Issue 851, pp. 629-630
DOI: 10.1126/science.33.851.629
This is a PDF-only article. The first page of the PDF of this article appears below. | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.892850399017334, "perplexity": 8779.63293600216}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-26/segments/1498128321306.65/warc/CC-MAIN-20170627083142-20170627103142-00200.warc.gz"} |
https://www.physicsforums.com/threads/holomorphic-function-reduces-to-a-polynomial.432094/ | # Homework Help: Holomorphic function reduces to a polynomial
1. Sep 25, 2010
### snipez90
1. The problem statement, all variables and given/known data
Let f: C -> C be a holomorphic function such that there is a constant R such that |z| >
R implies |f(z)| > R. Show that f is a polynomial.
2. Relevant equations
Not sure, I pulled this randomly from a complex analysis qualifying exam.
3. The attempt at a solution
So from experience a typical way to show that a holomorphic function is a polynomial is to apply Cauchy estimates (e.g. the immediate estimates from the Cauchy integral formula). However that approach doesn't seem to work here, since we usually have to let the boundary circle in the Cauchy integral formula either get larger and larger or smaller and smaller. To me it's not clear how the given growth condition gives estimates.
I've also thought about the maximum modulus principle, but I don't how to use it well, even if it does apply here. Can someone provide a hint? Thanks in advance.
2. Sep 25, 2010
### Office_Shredder
Staff Emeritus
You might want to look at 1/f(z). It's bounded, except for the possibility of poles inside |z|<R. Try to make a new holomorphic function from this
3. Sep 25, 2010
### snipez90
All right thanks. I did consider 1/f, but erroneously thought of Liouville. I'll try your suggestion.
4. Sep 25, 2010
### Office_Shredder
Staff Emeritus
Well, Liouville will come into play. But first you need to find a slightly different function that's actually bounded | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9818541407585144, "perplexity": 527.213029511971}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2018-13/segments/1521257651780.99/warc/CC-MAIN-20180325025050-20180325045050-00235.warc.gz"} |
http://mathhelpforum.com/calculus/25475-integration-one-right-i-m-confused.html | # Math Help - Integration, which one is right? (I'm confused)
1. ## Integration, which one is right? (I'm confused)
I'm now little bit confused. I have textbook that says:
$\int \! x \left( {x}^{2}+1 \right) ^{2}{dx}\$
$=\frac{1}{6}\left(x ^{2}+1\right)^{3}\$
Ok, I'll do it my way and Integrate function by expand polynom first:
$\int \! x \left( {x}^{2}+1 \right) ^{2}{dx}\$
$=\mathop{\rm }\int \left(x ^{5}+2\mathop{\rm }x ^{3}+x \right)\mathop{\rm } dx$
$=\mathop{\rm }\frac{x ^{6}}{6}+\frac{x ^{4}}{2}+\frac{x ^{2}}{2}$
I get different integral function. let x=3 then first integral function gives result: 500/3=166,6666666... but seconds gives 333/2 = 166,5.
So, which one is right?
2. They differ by a constant C=1/6
$\frac{(x^{2}+1)^{3}}{6}=\frac{x^{6}}{6}+\frac{x^{4 }}{2}+\frac{x^{2}}{2}+\frac{1}{6}$
3. Originally Posted by tabularasa
I'm now little bit confused. I have textbook that says:
$\int \! x \left( {x}^{2}+1 \right) ^{2}{dx}\$
$=\frac{1}{6}\left(x ^{2}+1\right)^{3}\$
Never miss the constant of integration!
If you want to know how the book did it, try the substitution $u = x^2$
4. Oh, clever. Thanks guys!
5. Originally Posted by Isomorphism
Never miss the constant of integration!
If you want to know how the book did it, try the substitution $u = x^2$
Ok, I try to substitute u = x^2 Therefore I get:
u = x^2
x = u^(1/2)
du = 2x
dx = du/2
ok, then function looks like:
$
\int \! x \left( u+1 \right) ^{2}\frac{du}{2}\
$
or should it be:
$
\int \! u^{\frac{1}{2}} \left( u+1 \right) ^{2}\frac{du}{2}\
$
Could you help me little bit on this..what next or is it already wrong?
6. Originally Posted by tabularasa
I'm now little bit confused. I have textbook that says:
$\int \! x \left( {x}^{2}+1 \right) ^{2}{dx}\$
Let $u = x^2+1$
$\,du = 2x\,dx\Rightarrow \,dx = \frac{\,du}{2x}$
So the integral becomes
$\int x\cdot u^2 \cdot \frac{\,du}{2x}$
$=\int u^2 \cdot \frac{\,du}{2}$
$=\frac{1}{2}\int u^2 \,du$
$=\frac{1}{2} \left(\frac{u^3}{3}\right)+C$
$=\frac{1}{2}\frac{(x^2+1)^3}{3}+C$
$=\frac{1}{6}(x^2+1)^3+C$
7. Originally Posted by DivideBy0
$\,du = 2x\,dx\Rightarrow \,dx = \frac{\,du}{2x}$
So the integral becomes
$\int x\cdot u^2 \cdot \frac{\,du}{2x}$
Thank you! This was the part i've totally forgot with substitution. X to the bottom Now I see the light too.
8. I have one more question.
I want to integrate function x*(x+1)^3 with substitution u = (x+1)^3
How it continues?
9. Originally Posted by tabularasa
I have one more question.
I want to integrate function x*(x+1)^3 with substitution u = (x+1)^3
How it continues?
Substitute: $u = x+1$. The integrand then becomes $(u-1)u^3$ which simplifies to $u^4 - u^3$. I think you can handle it from here. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 26, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9929925203323364, "perplexity": 2222.3866901737397}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2014-10/segments/1394011064849/warc/CC-MAIN-20140305091744-00085-ip-10-183-142-35.ec2.internal.warc.gz"} |
https://www.degruyter.com/view/j/phys.2016.14.issue-1/phys-2016-0040/phys-2016-0040.xml?format=INT | Show Summary Details
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# Open Physics
### formerly Central European Journal of Physics
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Volume 14, Issue 1
# Self-healing phenomena of graphene: potential and applications
K. VijayaSekhar
/ Swati Ghosh Acharyya
/ Sanghamitra Debroy
/ V. Pavan Kumar Miriyala
/ Amit Acharyya
Published Online: 2016-10-17 | DOI: https://doi.org/10.1515/phys-2016-0040
## Abstract
The present study investigates the self healing behavior of both pristine and defected single layer graphene using a molecular dynamic simulation. Single layer graphene containing various defects such as preexisting vacancies and differently oriented pre-existing cracks were subjected to uniaxial tensile loading till fracture occurred. Once the load was relaxed, the graphene was found to undergo self healing. It was observed that this self healing behaviour of cracks holds irrespective of the nature of pre-existing defects in the graphene sheet. Cracks of any length were found to heal provided the critical crack opening distance lies within 0.3-0.5 nm for a pristine sheet and also for a sheet with pre-existing defects. Detailed bond length analysis of the graphene sheet was done to understand the mechanism of self healing of graphene. The paper also discusses the immense potential of the self healing phenomena of graphene in the field of graphene based sub-nano sensors for crack sensing.
PACS: 81.05.ue
## 1 Introduction
Graphene, a two-dimensional material system, is the building block of fullerenes, carbon nanotubes and graphite. Since Andre Geim et al. [1] discovered a modest but novel method to isolate single atomic layers of graphene from graphite in 2004, graphene has attracted significant interest and has become the focus of widespread research due to its unique mechanical, electronic, thermal, and optical properties [1-9]. The exceptional band structure of graphene bestows it with extraordinary electrical transport properties, owing to which it is believed to be an immensely potential candidate for next generation electronics [10-17].
Defects in graphene, especially cracks have been shown to affect both the mechanical and electrical properties of graphene significantly [18]. This has led to numerous studies on understanding the failure behaviour of graphene [19-24]. Understanding the mechanical behaviour of graphene in presence of defects is crucial in the design and key to predicting the ultimate mechanical behaviour of nano-graphene based structural (nano-composites) and nano-electromechanical systems (NEMS).
It has previously been reported both from experimental studies and also by molecular dynamics simulations that graphene can heal its vacancy defects and other topological defects with the aid of metal doping [25-32]. The authors of this paper have reported for the first time that the self-healing phenomena takes place for single layer graphene without any external aid [33]. The authors had shown in their work that cracks nucleated ‘in-situ’ in a graphene sheet due to the application of tensile load self-heals within pico seconds of load relaxation. The phenomenon of self-healing was found to be independent of crack length. However, a critical crack opening displacement range of 0.3-0.5 nm was required for self healing to occur. If the crack opening displacement exceeds this limit no healing was observed to occur.
This paper presents the effects of pre-existing defects on the self-healing phenomenon of cracks in graphene using a molecular dynamics (MD) simulation. With the concept of self-healing of cracks, we envisage a sub-nano sensor design using graphene that can sense cracks as soon as it starts nucleation or even if it had propagated a certain distance the crack then heals making it a potential candidate for next generation electronics applications.
The remaining paper is organized as follows. Section 2 discusses the simulation methodology, Section 3 represents the phenomena of crack healing, while section 4 discusses the effect of different imperfections on crack healing and section 5 discusses the importance of the critical crack opening displacement. Finally, Section 6 presents the envisaged scenario of sub-nano crack sensing in the presence of different cracks and Section 7 concludes the discussion.
## 2 Simulation methodology
The MD simulations were performed using LAMMPS [34] (Large-scale Atomic/Molecular Massively parallel simula-tor). We used AIREBO (Adaptive inter-molecular reactive Bond order potential) to define force fields in our simulation model which originated from the Tersoff-Berner potential. This defines bond-bond interactions, bond breaking, bond reforming, inter molecular interactions between non-bonded atoms, as well as torsion angles formed by the sequence of three bonds [35,36].
We implemented a quantized fracture mechanics (QFM) modified Griffith’s model. Based on QFM modelling, the fracture strength is largely related to crack tip radius and crack length and is accurate in studying the fracture behaviour, previously proved by [37, 38]. The quantised fracture strength is given by the following equation: $σf(l,ρ)=σc1+ρ/2L01+2l/L0$(1)
where σcis fracture strength of pristine sheet, p is crack tip radius, l is crack length and L0is the minimum propagation distance of the crack.
The simulations were performed on a (5 x 5 nm) graphene sheet which contained 1008 carbon atoms with PBC boundary conditions in two in-plane directions and a vacuum space of 100 nm was considered along the z-direction to avoid edge effects. All simulations were performed at a room temperature by Nose-Hoover thermostat. The velocity-verlet time integrating scheme was applied with a time step of 0.0005 ps and held at equilibrium for 30 ps. After equilibrium was attained, the tensile test had been carried out by deformation control method by applying strain loading with an increment of 0.001/ps until the ultimate tensile strength of the material was reached. In order to study self-healing phenomenon, all the forces acting on the deformed graphene sheet were removed and the sheet was allowed to relax for a period of 150 ps.
## 3 Tensile testing of graphene sheet & observation of self-healing of cracks
Tensile testing of a graphene sheet (5 x 5 nm) was carried out for pristine condition in longitudinal loading direction. The simulations have been carried out at constant room temperature T=300 K, in the canonical ensemble (NVT), where the amount of substance is (N), volume (V) and temperature (T). Periodic Boundary Conditions were imposed on the system and allowed to relax for a period of 30 ps. The cracks were formed and it propagated in the pristine sheets after the load exceeded the ultimate tensile strength during uniaxial loading.
Once all the forces acting on the deformed graphene sheet were removed and the sheet was relaxed, the cracks were found to heal provided the critical crack opening displacement of 0.3-0.5 nm was met. The phenomenon of self-healing of cracks in pristine graphene was earlier reported by the authors [33]. Figure 1(A-D) shows the different stages of self-healing for a pristine sheet in longitudinal mode.
Figure 1
(A-D). Shows the different stages of self-healing for pristine sheet after relaxation for the case of loading in longitudinal mode.
In case of a pristine graphene sheet loaded in a longitudinal direction at relaxation time t=0 ps the carbon atoms in the defected region have dangling bonds which were unsaturated and were energetically unstable [39]. If the crack opening length was less than or equal to 0.5 nm the chemical binding energy was found to be negative, ensuring attractive forces were present in between the nearest neighbouring carbon atoms. The detailed calculations based on chemical binding energy has been explained in section V.
At t = 0 ps, i.e. at the point of relaxation of the sheet, 91% of the carbon bond lengths were found to be elongated in the range of 1.43-1.78 Å as compared to the bond length of 1.42 Å. At t = 0.1ps, it was observed that the carbon atoms started reconstructing through dangling bond saturation, forming non-hexagonal rings i.e. pentagonheptagons (5-T-7-5) structure on the graphene sheet. This pentagon-heptagon rings are known as Stone-Wales construction, which can be seen as the result of a C-C bond rotation by 90° that transforms four hexagons into two pentagons and two heptagons. This type of defect has been investigated previously [40, 41]. In the present study, the Stone-Wales construction acts as a spontaneous topological change for the repair of the defective sheet. The defective graphene started healing, through the formation of Stone-Wales (SW) construction which is energetically preferred in self-healing processes [42] while only 41% bonds remained elongated (1.43-1.48 Å) in the entire sheet at t=0.1 ps. Finally at t=0.2 ps, it was found that the carbon atom coalesced due to atomic rearrangements leading to healing of the broken bonds. At this point of time 33% of the bonds still remained elongated within a range of 1.431.52 Å and the rest (67%) fell into the equilibrium bond length of 1.42 Å.
Therefore at t=0.2 ps, self healing of the cracks took place and the resultant sheet was still left with some vacancies and Stone-Wales defects. Terrones et al. [43] had also observed that the presence of Stone-Wales structures can result in coalescence of defective SWCNTs in both armchair and zigzag chiralities leading to self-healing in SWCNT. Figure 2 shows the stages of self-healing through bond length analysis.
Figure 2
Shows different stages of self healing through bond length analysis.
In order to determine the strength of the healed graphene sheet, tensile testing of the healed graphene sheet was carried out, and the fracture strength observed was about 16% less as compared to the pristine graphene sheet. The reduction in the value of fracture stress is owing to the formation of Stone Wales-defect in the healed sheet. This proves that the graphene sheet can be reused repetitively but with certain degradation in the strength of the sheet.
## 4 Effect of varying defect morphology on crack-healing behavior
Effect of different type of imperfections & defects on the self-healing of cracks were studied with the help of MD simulations. The density of defects were varied by varying the concentration of missing atoms as follows 0.09%, 0.2%, 0.4%, 0.6%, 2% and 5% in the graphene sheet, with pre-existing defects (like single vacancy, multiple vacancies, cracks etc.) in longitudinal as well as transverse mode and were tested in tensile loading. Once the crack formed in-situ and propagated after reaching the ultimate tensile strength, the sheet was relaxed by removing all the forces acting on the sheet. It was observed that in all the cases self-healing was evident though the defects created initially existed as shown in Figure 3. The reason for this was that the atoms initially deleted cannot heal as the simulation box does not contain any extra atom to fill in the defect. It is evident that crack healing takes place (in span of pico seconds) in each case whenever the critical gap between the two separated graphene segments is less than or equals 0.5 nm. Interestingly, it was observed that as the length of the defect increases, e.g, from single to multiple vacancies to cracks, the time to heal the crack also in-creased.
## 5 Critical crack opening displacement
In all of the cases discussed above, the study was repeated with different values of crack length and crack opening displacement so as to arrive at the critical crack length and crack opening displacement required for self healing to occur. The results indicated that the phenomenon of selfhealing was independent of the length of the crack. Hence cracks of any length would be healed once the load was relaxed and thus defining critical crack length is not needed. However, the MD simulation indicated that the critical crack opening displacement is required to be within 0.3-0.5 nm for the cracks to be healed. If the crack opening exceeded 0.5 nm, self healing of the cracks would not take place.
Figure 3
Effect of Defects on Self-healing phenomena.
The critical crack opening of ~0.5 nm was arrived at from the interatomic interaction forces. Chemical binding energy Ebbetween the atoms is given by [44]: $Eb=∑i∑j>iVRrij−bijVArij.$(2)
The functions VR (r) and VA (r) are pair-additive interactions that represent all interatomic repulsions (corecore) and attraction from valence electrons, respectively. The quantity rijis the distance between pairs of nearest- neighbour atoms i and j, and bijis a bond order between atoms iand jthat is derivable from Huckel or similar level electronic structure theory. The terms VR(r) and VA(r) for carbon-carbon bonds system are defined by [45] as $VR(r)=fc(r)(1+Q/r)Ae−αr$(3) $VA(r)=fc(r)∑n=1,3Bne−βnr.$(4)
The subscript n refers to the sum in equation (4), and r is the scalar distance between atoms. The function fc(r) limits the range of the covalent interactions. The parameter fitting for carbon discussed below assumes a value of one for fc(r) for nearest neighbours and zero for all other interatomic distances. The variables A, Q, α, B1, B2, B3, β1, β2 and β3 are defined in [45].
Inserting equation (3) and (4) in equation (2) and the variable values from ref [45], the chemical binding energy vs. the interatomic distance plot has been determined as shown alongside Figure 4. From Figure 4, it was observed that after 0.5 nm the binding energy nearly tends to 0.
Figure 4
Plot shows the attractive and repulsive pair terms as a function of interatomic distance indicating the importance of critical crack opening displacement.
## 6 Potential application of self healing phenomena of graphene
With the unique property of self healing in graphene, we have envisaged an idea of a sub-nano sensor design using graphene that can sense crack as soon as it starts nucleation or even if it had propagated a certain distance and then healing of the crack making it a potential candidate for next generation electronics. The working process of the sensor is applicable only for graphene sheet loaded in longitudinal direction. The reason for this is that in a sensor application, we need the sheet to tear totally in order to have an open circuit. From Figure 3 we observe that for pristine and defective sheet in transverse mode, the sheets do not tear apart totally with uniaxial loading, though self-healing can be observed.
As illustrated in Figure 5a, a voltage source is connected to the graphene sheet. This voltage source generates current passing through the graphene sheet which is loaded in the horizontal direction. Cracks were generated in the graphene sheet by application of a tensile loading up to its ultimate tensile strength at room temperature. The recent research of Yu et al. found that transferred graphene on PDMS grown by CVD has a higher gauge factor of 151 [46]. This shows that there will be change in resistivity of the graphene with a change in mechanical strain. When there is no crack, voltage output will be nearly equal to the input voltage because it acts like closed loop circuitry. As the strain increases, though the resistivity of graphene increases [47], some output voltage can be still obtained. But as the propagating crack leads to a total tear of a sheet the voltage output will equal to 0, and the open circuit will be obtained as shown in Figure 5b. An installed microcontroller shall receive the zero voltage signal and act simultaneously to send the signal so as to release the load or stop further mechanical stretching or bending activity. Instantaneously, the graphene sheet will heal back again (if crack opening displacement is less than 0.5 nm) and the sensor becomes ready to measure any further surge in deforming load.
Figure 5
Schematic view of nano graphene sensor- (A) Without crack, (B) With Crack.
As discussed in the previous section, when the critical crack opening displacement is less than 0.3-0.5 nm, graphene tends to heal its crack by itself. Hence even if a crack nucleates it can be tracked as well as healed. Figure 5 represents the self-healing phenomenon in graphene leading to crack curing. This will allow to sense current same as input due to healing, if the loadings are removed from the system. Healing occurs at a very fast rate of approximately 0.2 ps within the critical range of 0.3-0.5 nm as shown in Figure 6. Even a crack opening displacement above 0.5 nm can be detected but healing in the process cannot be achieved leading to an open circuit as shown in Figure 7. Hence if the microcontroller can send the signal for release of the deforming load or pressure, crack opening displacement can be controlled & thus the graphene sheet can be healed, ensuring perennial use of the sensor. This technology can be extended to various other critical equipment like relief valves in pressure vessels, boilers, cranes etc.
Figure 6
Graphene sheet loaded leading to detection of crack as well healing of crack. Sub-nano sensing of the crack by applying voltage and measuring the output current.
Figure 7
Graphene sheet loaded leading to detection of crack but voltage output is 0 V.
It is also evident that crack healing takes place irrespective of the original defect nature in the sheet. Thus, sub-nano sensing may be demonstrated equally efficiently with a pristine or defective parent graphene sheet loaded in a longitudinal direction.
These findings are believed to be significant in the field of next-generation electronics e.g. artificial skin. The skin is the largest organ in the human body. It is mechanically self-healing, but if such behavior can be developed in artificial skin, then it shall prove to be the future for robots used by humans in daily life for numerous applications [48-50]. Due to unprecedented stretching or bending, rupture of this electronic artificial skin can occur in robots. Using the above concept sub-nano crack sensing methodology for graphene based artificial skin could be one of the potential electronic applications in near future.
## 7 Conclusions
The self healing nature of single layer graphene has been studied both in case of pristine and in the presence of pre-existing defects like vacancies (single and multiple) and cracks of different orientation. The results obtained are summarised as follows:
• a)
Self healing phenomena of graphene was observed irrespective of the nature of defects pre-existing in the sheet though the time to self-heal increased with increasing defect density.
• b)
MD simulations showed that cracks underwent selfhealing within pico-seconds of load relaxation when the distance between crack surfaces was ≤ 0.5 nm both in presence and in absence of a pre-existing defect.
• c)
A potential application of the self healing phenomena of graphene has been proposed for artificial skin in fu-ture robots etc. which makes graphene a next generation’s electronic sensor for sub nano sensing applications.
• d)
The timescales for the working of the sensor at present is in picoseconds and future research efforts would aim at achieving increased timescale for the realistic implementation of this sensor.
## Acknowledgement
The authors would like to acknowledge the following for supporting this work: The School of Engineering Science and Technology University of Hyderabad, India and Indian Institute of Technology (IIT) Hyder-abad, India. Department of Science and Technology (DST), Government of India for Innovation in Science Pursuit for Inspired Research (INSPIRE) PhD fellowship to Sanghamitra Debroy (Grant: IF131049); University Grants Commission (UGC), Government of India, Rajiv Gandhi National Fellowship (grant RGNF201517SCAND26105) PhD fellowship to K. Vijaya Sekhar, and Department of Electronics and Information Technology (DEITY), Government of India under Internet Of Things (IOT) for Smarter Healthcare under Grant No: 13(7)/2012-CC&BT, Dated 25th February, 2013.
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Accepted: 2016-02-08
Published Online: 2016-10-17
Published in Print: 2016-01-01
Citation Information: Open Physics, Volume 14, Issue 1, Pages 364–370, ISSN (Online) 2391-5471,
Export Citation
## Citing Articles
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[3]
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Journal of Physics: Conference Series, 2017, Volume 901, Page 012150 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 4, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.6180023550987244, "perplexity": 4699.711918757026}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2020-10/segments/1581875149238.97/warc/CC-MAIN-20200229114448-20200229144448-00065.warc.gz"} |
http://mathhelpforum.com/trigonometry/116970-trig-graphing-i-think.html | # Math Help - Trig graphing(I think)
1. ## Trig graphing(I think)
I think I'm suppose to graph these but I don't know how
1) Y=5sin1/3x
2) Y=Sin2x-4
3) Y=1/2Sin2(X-90degrees)+1
4) Y=Sin(3x-120)+1
5) Y=4Sin(1/2x+30degrees)-1
Can anyone help me?
2. Originally Posted by Draft
I think I'm suppose to graph these but I don't know how
1) Y=5sin1/3x
2) Y=Sin2x-4
3) Y=1/2Sin2(X-90degrees)+1
4) Y=Sin(3x-120)+1
5) Y=4Sin(1/2x+30degrees)-1
Can anyone help me?
HI
There are too many questions here . I will do 1 and 2 and you will try the rest . Ok ?
For (1) , always refer to the original sin graph , $y=\sin \theta$ . Note that For all sin graph here , it will start from 0 and end at 360 .
One cycle here is $360^o$ . 1/3 of the cycle would be $120^o$ so your graph should stop at $120^o$ . Then label this $120^o$ as $360^o$ . Notice that the amplitude is 5.
For (2) , sin 2x : this will go 2 rounds . -4 : shift the graph downwards for 4 .
HI
There are too many questions here . I will do 1 and 2 and you will try the rest . Ok ?
For (1) , always refer to the original sin graph , $y=\sin \theta$ . Note that For all sin graph here , it will start from 0 and end at 360 .
One cycle here is $360^o$ . 1/3 of the cycle would be $120^o$ so your graph should stop at $120^o$ . Then label this $120^o$ as $360^o$ . Notice that the amplitude is 5.
For (2) , sin 2x : this will go 2 rounds . -4 : shift the graph downwards for 4 . | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 12, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.917064368724823, "perplexity": 896.8730223476099}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2014-41/segments/1410665301782.61/warc/CC-MAIN-20140914032821-00107-ip-10-234-18-248.ec2.internal.warc.gz"} |
https://brilliant.org/problems/evening-square/ | # Collapsing Angle
Geometry Level 2
In the square above, $E$, $F$ and $G$ are midpoints of $\overline{DC}$, $\overline{BC}$ and $\overline{FE}$, respectively.
If $\angle EGD=x$, find the value of $\tan x$.
× | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 8, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9687637090682983, "perplexity": 486.48606682813323}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-43/segments/1570987836295.98/warc/CC-MAIN-20191023201520-20191023225020-00260.warc.gz"} |
https://api.projectchrono.org/classchrono_1_1_ch_variables.html | chrono::ChVariables Class Referenceabstract
## Description
Base class for representing objects that introduce 'variables' (also referred as 'v') and their associated mass submatrices for a sparse representation of the problem.
Each ChVariables object must be able to compute a mass submatrix, that will be assembled directly inside the global matrix Z, (in particular inside the block H or M). Because of this there is no need for ChVariables and derived classes to actually store their mass submatrix in memory: they just need to be able to compute it!
Moreover, in some cases, the mass submatrix is not even needed. In fact, some Chrono solvers are matrix-free. This means that each ChVariables (and derived) object can be asked not to assemble its mass submatrix, but instead to provide operation related to it. E.g. M*x, M\x, +=M*x, and so on... Each derived class must implement these methods!
Because of this, the ChVariables class does not include any mass submatrix by default
#include <ChVariables.h>
Inheritance diagram for chrono::ChVariables:
## Public Member Functions
ChVariables (int m_ndof)
ChVariablesoperator= (const ChVariables &other)
Assignment operator: copy from other object.
void SetDisabled (bool mdis)
Deactivates/freezes the variable (these variables won't be modified by the system solver).
bool IsDisabled () const
Check if the variables have been deactivated (these variables won't be modified by the system solver).
bool IsActive () const
Check if these variables are currently active. More...
virtual int Get_ndof () const
The number of scalar variables in the vector qb (dof=degrees of freedom) *** This function MUST BE OVERRIDDEN by specialized inherited classes.
ChVectorRef Get_qb ()
Returns reference to qb, body-relative part of degrees of freedom q in system: More...
virtual void Compute_fb ()
Compute fb, body-relative part of known vector f in system. More...
ChVectorRef Get_fb ()
Returns reference to fb, body-relative part of known vector f in system. More...
virtual void Compute_invMb_v (ChVectorRef result, ChVectorConstRef vect) const =0
Computes the product of the inverse mass matrix by a vector, and store in result: result = [invMb]*vect.
virtual void Compute_inc_invMb_v (ChVectorRef result, ChVectorConstRef vect) const =0
Computes the product of the inverse mass matrix by a vector, and increment result: result += [invMb]*vect.
virtual void Compute_inc_Mb_v (ChVectorRef result, ChVectorConstRef vect) const =0
Computes the product of the mass matrix by a vector, and increment result: result = [Mb]*vect.
virtual void MultiplyAndAdd (ChVectorRef result, ChVectorConstRef vect, const double c_a) const =0
Computes the product of the corresponding block in the system matrix (ie. More...
virtual void DiagonalAdd (ChVectorRef result, const double c_a) const =0
Add the diagonal of the mass matrix scaled by c_a, to 'result', as a vector. More...
virtual void Build_M (ChSparseMatrix &storage, int insrow, int inscol, const double c_a)=0
Build the mass submatrix (for these variables) multiplied by c_a, storing it in 'storage' sparse matrix, at given column/row offset. More...
void SetOffset (int moff)
Set offset in global q vector (set automatically by ChSystemDescriptor)
int GetOffset () const
Get offset in global q vector.
virtual void ArchiveOUT (ChArchiveOut &marchive)
virtual void ArchiveIN (ChArchiveIn &marchive)
## Protected Attributes
int offset
offset in global q state vector (needed by some solvers)
## ◆ Build_M()
virtual void chrono::ChVariables::Build_M ( ChSparseMatrix & storage, int insrow, int inscol, const double c_a )
pure virtual
Build the mass submatrix (for these variables) multiplied by c_a, storing it in 'storage' sparse matrix, at given column/row offset.
Most iterative solvers don't need to know this matrix explicitly. *** This function MUST BE OVERRIDDEN by specialized inherited classes
## ◆ Compute_fb()
virtual void chrono::ChVariables::Compute_fb ( )
inlinevirtual
Compute fb, body-relative part of known vector f in system.
*** This function MAY BE OVERRIDDEN by specialized inherited classes (e.g., for impulsive multibody simulation, this may be fb = dt*Forces+[M]*previous_v ). Another option is to set values into fb vectors, accessing them by Get_fb() from an external procedure, for each body, before starting the solver.
virtual void chrono::ChVariables::DiagonalAdd ( ChVectorRef result, const double c_a ) const
pure virtual
Add the diagonal of the mass matrix scaled by c_a, to 'result', as a vector.
NOTE: the 'result' vector must already have the size of system unknowns, ie the size of the total variables & constraints in the system; the procedure will use the ChVariable offset (that must be already updated) as index.
## ◆ Get_fb()
ChVectorRef chrono::ChVariables::Get_fb ( )
inline
Returns reference to fb, body-relative part of known vector f in system.
| M -Cq'|*|q|- | f|= |0| , c>0, l>0, l*r=0;
| Cq 0 | |l| |-b| |c|
This function can be used to set values of fb vector before starting the solver.
## ◆ Get_qb()
ChVectorRef chrono::ChVariables::Get_qb ( )
inline
Returns reference to qb, body-relative part of degrees of freedom q in system:
| M -Cq'|*|q|- | f|= |0| , c>0, l>0, l*r=0;
| Cq 0 | |l| |-b| |c|
## ◆ IsActive()
bool chrono::ChVariables::IsActive ( ) const
inline
Check if these variables are currently active.
In general, tells if they must be included into the system solver or not. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.5659928321838379, "perplexity": 9553.58739114316}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-21/segments/1620243991801.49/warc/CC-MAIN-20210515100825-20210515130825-00027.warc.gz"} |
https://www.chemicalforums.com/index.php?topic=105510.msg372122 | November 27, 2020, 03:47:14 AM
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### Topic: Can piperazine form van-der-Waals interactions? (Read 244 times)
0 Members and 1 Guest are viewing this topic.
#### MDL
• Very New Member
• Posts: 2
• Mole Snacks: +0/-0
##### Can piperazine form van-der-Waals interactions?
« on: September 30, 2020, 06:12:24 AM »
Hi everyone,
I was wondering what's your opinion about the ability of molecules containing polar atoms to form van-der-Waals interactions.
For example piperazine. Each carbon atom is connected to a heteroatom (N), causing partial dipoles. Can it then form attractive van-der-Waals interactions with, for example, a phenyl ring (given a favourable distance)?
To my knowledge, the methyl part of a methoxy group can, at least according to literature.
Any help is greatly appreciated! Thanks
#### chenbeier
• Sr. Member
• Posts: 1204
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• Gender:
##### Re: Can piperazine form van-der-Waals interactions?
« Reply #1 on: September 30, 2020, 06:28:35 AM »
It will be more as van de Waals, Hetereoatoms have polar behavior. So the more negative atom attract to more positive areas.
#### MDL
• Very New Member
• Posts: 2
• Mole Snacks: +0/-0
##### Re: Can piperazine form van-der-Waals interactions?
« Reply #2 on: September 30, 2020, 12:40:05 PM »
Thanks, I agree, but what if the molecule interacting with piperazine is completely apolar? Will they form van-der-Waals interactions?
#### wildfyr
• Global Moderator
• Sr. Member
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• Mole Snacks: +166/-10
##### Re: Can piperazine form van-der-Waals interactions?
« Reply #3 on: September 30, 2020, 02:34:00 PM »
All organic molecules experience van der waals interactions, its more a matter of degree. Usually "surface area" is a decent stand in for how strong the interaction will be. | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8136999011039734, "perplexity": 24915.884001877115}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2020-50/segments/1606141191511.46/warc/CC-MAIN-20201127073750-20201127103750-00246.warc.gz"} |
https://asmedigitalcollection.asme.org/pressurevesseltech/article-abstract/128/3/467/444192/The-Effect-of-Pressure-Relief-Valve-Blowdown-and?redirectedFrom=fulltext | In the summers of 2000 and 2001, a series of controlled fire tests were conducted on horizontal $1890liter$ (500 US gallon) propane pressure vessels. The test vessels were instrumented with pressure transducers, liquid space, vapor space, and wall thermocouples, and an instrumented flow nozzle in place of a pressure relief valve (PRV). A computer controlled PRV was used to control pressure. The vessels were heated using high momentum, liquid propane utility torches. Open pool fires were not used for the testing because they are strongly affected by wind. These wind effects make it almost impossible to have repeatable test conditions. The fire conditions used were calibrated to give heat inputs similar to a luminous hydrocarbon pool fire with an effective blackbody temperature in the range of $850°C±50°C$. PRV blowdown (i.e., $blowdown=poppressure−reclosepressure$) and fire conditions were varied in this test series while all other input parameters were held constant. The fire conditions were varied by changing the number of burners applied to the vessel wall areas wetted by liquid and vapor. It was found that the vessel content’s response and energy storage varied according to the fire conditions and the PRV operation. The location and quantity of the burners affected the thermal stratification within the liquid, and the liquid swelling (due to vapor generation in the liquid) at the liquid∕vapor interface. The blowdown of the PRV affected the average vessel pressure, average liquid temperature, and time to temperature destratification in the liquid. Large blowdown also delayed thermal rupture.
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AIChE
, 1994,
Guidelines for Evaluating theCharacteristics of Vapor Cloud Explosions, Flash Fires and BLEVEs
, AIChE Centre for Chemical Process Safety, New York. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 3, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.4305126368999481, "perplexity": 14248.471882267759}, "config": {"markdown_headings": true, "markdown_code": false, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-43/segments/1570986710773.68/warc/CC-MAIN-20191020132840-20191020160340-00160.warc.gz"} |
http://mathoverflow.net/questions/98438/does-there-exist-a-curve-of-degree-11-having-15-triple-points/98439 | # Does there exist a curve of degree 11 having 15 triple points?
Does there exist an irreducible curve of degree 11 in the projective plane which would have 15 triple points?
For information, such a curve would be rational, if it exists, and would be smooth at all other points (compute the genus with the classical formula: $(d-1)(d-2)/2-\sum a_i(a_i-1)/2=45-3\cdot 15=0$)
-
if we start from three lines with a common point, then add two lines through some point of that triad, we have degree 5 and only two triple points, so adding 6 more lines gives only 14 triple points. thus even if we can smooth the extraneous double points we lose. maybe one should pass some conics through more nodes. we could pass one conic through all 4 nodes at step 3 above, getting a degree 7 curve with 6 triple points, and 4 nodes. passing another conic through all 4 gives a degree 9 curve with 10 triple points, and 10 nodes. so we get a reducible one, then try to smooth it. / – roy smith May 31 '12 at 2:24
This seems to be study in this paper by O. Dumitrescu (which I did not read in detail, but it seems quite algorithmic).
-
According to the paper, the virtual dimension of the linear system is $78-90-1<0$ since the degree of the equation is at least $5$. So it looks like the answer is no. – Will Sawin May 31 '12 at 3:00
Dumitrescu's paper deals with points in general position (even if that may not be clear in the intro). The singular points of that rational curve would certainly not be in general position; that can happen. For instance, there are indeed curves of degree 10 with 12 double points. These two papers by Gradolato-Mezzetti are more relevant: "Families of curves with ordinary singular points on regular surfaces". Ann. Mat. Pura Appl. (4) 150 (1988), 281–298. and "Curves with nodes, cusps and ordinary triple points", Ann. Univ. Ferrara Sez. VII (N.S.) 31 (1985), 23–47 (1986). It's Roy's approach. – quim May 31 '12 at 15:22
I ment 12 triple points! – quim Jun 1 '12 at 6:03
Yes, the points could be in special position, of course. The simplest example is sextic with 10 double points. A lot of such curves exist, but the points are not in general position. I will try to find the articles you mention. They seem to be very interesting. – Jérémy Blanc Jun 13 '12 at 16:55
I found the articles and some rough bounds which give existence of curves with triple points, but the bounds seem to be too far from my explicit question. – Jérémy Blanc Jun 25 '12 at 14:57 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.7216644883155823, "perplexity": 509.88410832319295}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 5, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2014-15/segments/1397609535095.9/warc/CC-MAIN-20140416005215-00028-ip-10-147-4-33.ec2.internal.warc.gz"} |
http://www.lofoya.com/Solved/483/we-can-coax-physical-nature-into-many-of-our-wishes-but-we | # Easy Sentence Completion Solved QuestionVerbal Ability Discussion
Q. We can coax physical nature into ________ many of our wishes but we cannot ________ authority over it or make it change its ways one jot.
✖ A. granting, empower ✖ B. satiating, display ✔ C. satisfying, exercise ✖ D. stimulating, exercise
Solution:
Option(C) is correct
We can satisfy the wishes and exercise authority over someone or something. | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9141778349876404, "perplexity": 15821.246043715246}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 5, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-13/segments/1490218191396.90/warc/CC-MAIN-20170322212951-00472-ip-10-233-31-227.ec2.internal.warc.gz"} |
https://par.nsf.gov/search/author:%22Olmschenk,%20Greg%22 | # Search for:All records
Creators/Authors contains: "Olmschenk, Greg"
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1. Gatherings of thousands to millions of people frequently occur for an enormous variety of educational, social, sporting, and political events, and automated counting of these high-density crowds is useful for safety, management, and measuring significance of an event. In this work, we show that the regularly accepted labeling scheme of crowd density maps for training deep neural networks may not be the most effective one. We propose an alternative inverse k-nearest neighbor (i[Formula: see text]NN) map mechanism that, even when used directly in existing state-of-the-art network structures, shows superior performance. We also provide new network architecture mechanisms that we demonstrate in our own MUD-i[Formula: see text]NN network architecture, which uses multi-scale drop-in replacement upsampling via transposed convolutions to take full advantage of the provided i[Formula: see text]NN labeling. This upsampling combined with the i[Formula: see text]NN maps further improves crowd counting accuracy. We further analyze several variations of the i[Formula: see text]NN labeling mechanism, which apply transformations on the [Formula: see text]NN measure before generating the map, in order to consider the impact of camera perspective views, image resolutions, and the changing rates of the mapping functions. To alleviate the effects of crowd density changes in each image, we alsomore »
Free, publicly-accessible full text available December 30, 2022
2. Abstract This supplement provides supporting material for Lam et al. We briefly summarize past gravitational microlensing searches for black holes (BHs) and present details of the observations, analysis, and modeling of five BH candidates observed with both ground-based photometric microlensing surveys and Hubble Space Telescope astrometry and photometry. We present detailed results for four of the five candidates that show no or low probability for the lens to be a BH. In these cases, the lens masses are <2 M ⊙ , and two of the four are likely white dwarfs or neutron stars. We also present detailed methods for comparing the full sample of five candidates to theoretical expectations of the number of BHs in the Milky Way (∼10 8 ).
Free, publicly-accessible full text available June 1, 2023
3. Aims. With the aim of finding short-term planetary signals, we investigated the data collected from current high-cadence microlensing surveys. Methods. From this investigation, we found four planetary systems with low planet-to-host mass ratios, including OGLE-2017-BLG-1691L, KMT-2021-BLG-0320L, KMT-2021-BLG-1303L, and KMT-2021-BLG-1554L. Despite the short durations, ranging from a few hours to a couple of days, the planetary signals were clearly detected by the combined data of the lensing surveys. We found that three of the planetary systems have mass ratios on the order of 10 −4 and the other has a mass ratio that is slightly greater than 10 −3 . Results. The estimated masses indicate that all discovered planets have sub-Jovian masses. The planet masses of KMT-2021-BLG-0320Lb, KMT-2021-BLG-1303Lb, and KMT-2021-BLG-1554Lb correspond to ~0.10, ~0.38, and ~0.12 times the mass of the Jupiter, and the mass of OGLE-2017-BLG-1691Lb corresponds to that of the Uranus. The estimated mass of the planet host KMT-2021-BLG-1554L, M host ~ 0.08 M ⊙ , corresponds to the boundary between a star and a brown dwarf. Besides this system, the host stars of the other planetary systems are low-mass stars with masses in the range of ~[0.3–0.6] M ⊙ . The discoveries of the planets fully demonstrate themore »
Free, publicly-accessible full text available August 1, 2023
4. This paper describes the interface and testing of an indoor navigation app - ASSIST - that guides blind & visually impaired (BVI) individuals through an indoor environment with high accuracy while augmenting their understanding of the surrounding environment. ASSIST features personalized interfaces by considering the unique experiences that BVI individuals have in indoor wayfinding and offers multiple levels of multimodal feedback. After an overview of the technical approach and implementation of the first prototype of the ASSIST system, the results of two pilot studies performed with BVI individuals are presented – a performance study to collect data on mobility (walking speed, collisions, and navigation errors) while using the app, and a usability study to collect user evaluation data on the perceived helpfulness, safety, ease-of-use, and overall experience while using the app. Our studies show that ASSIST is useful in providing users with navigational guidance, improving their efficiency and (more significantly) their safety and accuracy in wayfinding indoors. Findings and user feed-back from the studies confirm some of the previous results, while also providing some new insights into the creation of such an app, including the use of customized user interfaces and expanding the types of information provided.
5. Aims. The high-magnification microlensing event KMT-2021-BLG-1077 exhibits a subtle and complex anomaly pattern in the region around the peak. We analyze the lensing light curve of the event with the aim of revealing the nature of the anomaly. Methods. We test various models in combination with several interpretations: that the lens is a binary (2L1S), the source is a binary (1L2S), both the lens and source are binaries (2L2S), or the lens is a triple system (3L1S). We search for the best-fit models under the individual interpretations of the lens and source systems. Results. We find that the anomaly cannot be explained by the usual three-body (2L1S and 1L2S) models. The 2L2S model improves the fit compared to the three-body models, but it still leaves noticeable residuals. On the other hand, the 3L1S interpretation yields a model explaining all the major anomalous features in the lensing light curve. According to the 3L1S interpretation, the estimated mass ratios of the lens companions to the primary are ~1.56 × 10 −3 and ~1.75 × 10 −3 , which correspond to ~1.6 and ~1.8 times the Jupiter/Sun mass ratio, respectively, and therefore the lens is a multiplanetary system containing two giant planets. Withmore »
Free, publicly-accessible full text available June 1, 2023
6. We complete the analysis of all 2018 prime-field microlensing planets identified by the Korea Microlensing Telescope Network (KMTNet) Anomaly Finder. Among the ten previously unpublished events with clear planetary solutions, eight are either unambiguously planetary or are very likely to be planetary in nature: OGLE-2018-BLG-1126, KMT-2018-BLG-2004, OGLE-2018-BLG-1647, OGLE-2018-BLG-1367, OGLE-2018-BLG-1544, OGLE-2018-BLG-0932, OGLE-2018-BLG-1212, and KMT-2018-BLG-2718. Combined with the four previously published new Anomaly Finder events and 12 previously published (or in preparation) planets that were discovered by eye, this makes a total of 24 2018 prime-field planets discovered or recovered by Anomaly Finder. Together with a paper in preparation on 2018 subprime planets, this work lays the basis for the first statistical analysis of the planet mass-ratio function based on planets identified in KMTNet data. By systematically applying the heuristic analysis to each event, we identified the small modification in their formalism that is needed to unify the so-called close-wide and inner-outer degeneracies.
Free, publicly-accessible full text available August 1, 2023
7. Abstract
We present the analysis of five black hole candidates identified from gravitational microlensing surveys. Hubble Space Telescope astrometric data and densely sampled light curves from ground-based microlensing surveys are fit with a single-source, single-lens microlensing model in order to measure the mass and luminosity of each lens and determine if it is a black hole. One of the five targets (OGLE-2011-BLG-0462/MOA-2011-BLG-191 or OB110462 for short) shows a significant >1 mas coherent astrometric shift, little to no lens flux, and has an inferred lens mass of 1.6–4.4M. This makes OB110462 the first definitive discovery of a compact object through astrometric microlensing and it is most likely either a neutron star or a low-mass black hole. This compact-object lens is relatively nearby (0.70–1.92 kpc) and has a slow transverse motion of <30 km s−1. OB110462 shows significant tension between models well fit to photometry versus astrometry, making it currently difficult to distinguish between a neutron star and a black hole. Additional observations and modeling with more complex system geometries, such as binary sources, are needed to resolve the puzzling nature of this object. For the remaining four candidates, the lens masses are <2M, and they are unlikely to be black holes;more »
8. Abstract We report on the observations, analysis and interpretation of the microlensing event MOA-2019-BLG-008. The observed anomaly in the photometric light curve is best described through a binary lens model. In this model, the source did not cross caustics and no finite-source effects were observed. Therefore, the angular Einstein ring radius θ E cannot be measured from the light curve alone. However, the large event duration, t E ∼ 80 days, allows a precise measurement of the microlensing parallax π E . In addition to the constraints on the angular radius θ * and the apparent brightness I s of the source, we employ the Besançon and GalMod galactic models to estimate the physical properties of the lens. We find excellent agreement between the predictions of the two galactic models: the companion is likely a resident of the brown dwarf desert with a mass M p ∼ 30 M Jup , and the host is a main-sequence dwarf star. The lens lies along the line of sight to the Galactic bulge, at a distance of ≤4 kpc. We estimate that in about 10 yr the lens and source will be separated by ∼55 mas, and it will be possible tomore »
Free, publicly-accessible full text available August 2, 2023
9. ABSTRACT
Follow-up observations of high-magnification gravitational microlensing events can fully exploit their intrinsic sensitivity to detect extrasolar planets, especially those with small mass ratios. To make followup observations more uniform and efficient, we develop a system, HighMagFinder, to automatically alert possible ongoing high-magnification events based on the real-time data from the Korea Microlensing Telescope Network (KMTNet). We started a new phase of follow-up observations with the help of HighMagFinder in 2021. Here we report the discovery of two planets in high-magnification microlensing events, KMT-2021-BLG-0171 and KMT-2021-BLG-1689, which were identified by the HighMagFinder. We find that both events suffer the ‘central-resonant’ caustic degeneracy. The planet-host mass-ratio is q ∼ 4.7 × 10−5 or q ∼ 2.2 × 10−5 for KMT-2021-BLG-0171, and q ∼ 2.5 × 10−4 or q ∼ 1.8 × 10−4 for KMT-2021-BLG-1689. Together with two other events, four cases that suffer such degeneracy have been discovered in the 2021 season alone, indicating that the degenerate solutions may have been missed in some previous studies. We also propose a quantitative factor to weight the probability of each solution from the phase space. The resonant interpretations for the two events are disfavoured under this consideration. This factor can be included in future statistical studies to weight degenerate solutions.
10. Gatherings of thousands to millions of people frequently occur for an enormous variety of events, and automated counting of these high-density crowds is useful for safety, management, and measuring significance of an event. In this work, we show that the regularly accepted labeling scheme of crowd density maps for training deep neural networks is less effective than our alternative inverse k-nearest neighbor (i$k$NN) maps, even when used directly in existing state-of-the-art network structures. We also provide a new network architecture MUD-i$k$NN, which uses multi-scale upsampling via transposed convolutions to take full advantage of the provided i$k$NN labeling. This upsampling combined with the i$k$NN maps further improves crowd counting accuracy. Our new network architecture performs favorably in comparison with the state-of-the-art. However, our labeling and upsampling techniques are generally applicable to existing crowd counting architectures. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.7060344815254211, "perplexity": 1996.5129741987746}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2022-49/segments/1669446710801.42/warc/CC-MAIN-20221201053355-20221201083355-00105.warc.gz"} |
https://chatgrape.com/doc/deployment/activedirectory.html | # Active Directory / LDAP¶
## Security Risks¶
By using AD/LDAP for authentication, you need to be aware that passwords are sent to the grape server in clear text and transmitted to the LDAP server. This means, if the Grape server is compromised, the attacker could log passwords of users at the login and compromise other systems with those credentials.
We therefore recommend to use our SSO feature for authentication because passwords never reach the Grape server but only the SSO IDP. This is recommended for any software in a company to keep user passwords secure.
## Prerequisites¶
1. You need to be admin or owner of the Organization, in order to manage LDAP
2. You need an Active Directory that can be reached from the Grape instance
3. You need a AD User to use for binding via LDAP with sufficient privileges
4. Pagination has to be enabled (we use a page size of 100 by default)
5. The bind user must be able to see Users you want to import and get the following attributes:
• memberOf
• cn
• name
• sAMAccountName
• mail
• userAccountControl
• accountExpires
• member
and be able to read the groups that are specified by the memberOf of the user. Grape will only read the groups’ name by querying each group’s DN individually. This is especially relevant for the CIFS integration which will crawl through the groups recursively in order to determine file access permissions.
## Enable LDAP for an Organization¶
2. Click on “Organizations”
3. Click on the organization that needs LDAP
4. Scroll down to “Features”
5. Select “Active Directory” From the drop-down menu
6. Scroll down to the bottom
7. Press “Save”
## Configure LDAP¶
In the Web Client or in your Desktop Client:
1. Click the cogwheel
2. Click “Organization Settings”
3. Click on “LDAP Settings” in the menu on the left (this option is only available after you enabled LDAP in the admin site!)
4. When you enter this page for the first time, you will be redirected to the LDAP Connection creation page Enter the LDAP bind credentials there. The form will only save if a connection could be established successfully.
It’s important that you proper configure the field “Default action for removed user” ad this action will be taken when removing users from AD. See remove user documentation for more details.
Please make sure to use a read-only service user for this connection. This user’s credentials will be stored in recoverable encrypted form for later background synchronization.
## Importing Users and Groups¶
Click the users icon
You can add as many AD user sources as you want (OUs or AD Groups), by adding their DNs respectively. For each Import source you get to chose if the user import should be recursive or just flatly in the specified DN.
## Implementation Details¶
### OUs¶
We get all objects that are of objectClass=person within the specified OU (and all underlying OUs if you chose recursive).
First we get the single object of the group and read all DNs in the member attribute. From this we find the biggest common denominator (bcd) that all members in the Group share. Next we make a LDAP query asking for all Users that have the memberOf relation to that AD Group and limit the search to the bcd . If recursive is turned on for the AD Group, we will also find groups that have that memberOf attribute and repeat the operation.
### Locked users¶
Users that are locked in the AD (either ACCOUNTLOCKED flag or account expire date timestamp in the past) will not be initially imported. If users are already imported and are flagged locked at a later synchronization, will be disabled in the organization.
Unlocking works the same way: Users that where locked and are unlocked in AD will become unlocked in grape right after the next synchronization.
### Syncronisation time and status¶
The synchronization of user and group data via LDAP happens asynchronously in the background. Depending on what other background processes are running, the synchronization can be queued for some time.
You can see the “sync status” and the last time a source was successfully synced for each import. If a sync failed, the sync status usually reveals an error message. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.2573951780796051, "perplexity": 4059.8597761252536}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-18/segments/1555578526904.20/warc/CC-MAIN-20190418221425-20190419003425-00236.warc.gz"} |
https://math.stackexchange.com/questions/4363699/projective-line-construction-of-exceptional-steiner-system | # Projective line construction of exceptional Steiner system.
Wikipedia gives a beautiful construction of the $$S(5,6,12)$$ Steiner system; take as blocks the subset of the projective line over the field with $$11$$ elements consisting of $$\{\infty,1,3,4,5,9\}$$ and all its images under the natural action of $$PSL_2(11)$$.
I am hoping to find a slick verification that this does indeed form such a Steiner system, that is, that any $$5$$ elements are contained in a unique one of the above blocks. Here are my thoughts so far: note that the 6 elements in our starter block are just the non zero squares and $$\infty$$, so that it is stabilized in $$PSL_2(11)$$ by at multiplication by squares. As $$PSL_2(11)$$ has order $$660$$, this shows there are at most $$660/5 = 132$$ blocks. In fact the stabilizer of a block has size only $$5$$, which I can verify but in a slightly computational way. If one does that, it suffices to show no two distinct blocks intersect in $$5$$. Another helpful fact is that $$PGL_2(11)$$ acts $$3$$ transitively on the $$12$$ points of the projective line, and $$PSL_2(11)$$ can at least map any ordered $$3$$ to any other unordered $$3$$ (in $$3$$ ways), which seems helpful, but I can't quite show what I want from this. Wikipedia gives a reference to this statement, but it doesn't contain a proof.
I care about this result as I know a handful of constructions of $$S(5,6,12)$$ already, as well as its uniqueness, thus understanding result will further shed light on this Steiner system's symmetries, which form the sporadic group $$M_{12}$$. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 21, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9562234282493591, "perplexity": 170.87677886145644}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2022-27/segments/1656103360935.27/warc/CC-MAIN-20220628081102-20220628111102-00604.warc.gz"} |
https://mathoverflow.net/questions/293942/configuration-spaces-ran-spaces-free-semilattices-vietoris-spaces-and-power-o | # Configuration spaces, Ran spaces, free semilattices, Vietoris spaces and power objects
These are five important constructions and I would like to know how they are related.
The $n$th unordered configuration space of a space $X$ is $$\operatorname{UConf}_n(X):=\{\text{embeddings of \{1,...,n\} into X}\}/(\text{nth symmetric group}),$$ topologized as a subquotient of $X^n$.
The Ran space of $X$ is the set $\operatorname{Ran}(X)$ of finite subsets of $X$ with the topology generated by sets $$\nabla_{U_1,...,U_n}:=\{S\in\operatorname{Ran}(U_1\cup\cdots\cup U_n)\mid S\cap U_i\ne\varnothing, i=1,...,n\}$$ where $U_i$ are disjoint open subsets of $X$.
The free topological semilattice $\operatorname{Sl}(X)$ on $X$ is the value on $X$ of the left adjoint to the forgetful functor from topological semilattices to topological spaces.
The Vietoris space $\mathscr VX$ of $X$ is the set of some (depending on the context) subsets of $X$ topologized by the same kind of $\nabla_{U_1,...,U_n}$ except that they are not required to be disjoint.
Finally, one may choose some nice embedding $I$ of some subcategory of spaces that contains $X$ into a topos in various ways, and consider there the power object $\Omega^{IX}$. Usually it is not in the image of $I$. There are versions like $\operatorname{Sub}_{\mathrm{fin}}(IX)\rightarrowtail\Omega^{IX}$ of objects of finite (say, Kuratowski finite) subobjects of $IX$ which might be. (Note that $\operatorname{Sub}_{\mathrm{fin}}$, with Kuratowski finiteness, is the free internal semilattice functor on any topos whatsoever.)
As a variation on the latter - say, $X$ is a simplicial set; since simplicial sets readily form a topos we have simplicial sets $\operatorname{Sub}_{\mathrm{fin}}(X)\rightarrowtail\Omega^X$.
Questions:
1. Is $\operatorname{UConf}_n(X)$ (homeomorphic to) a subspace of $\operatorname{Ran}(X)$?
2. There is a topology on $\bigcup_n\operatorname{UConf}_n(X)$ with $\{x_1,...,x_n,x_{n+1}\}$ close to $\{x_1,...,x_n\}$ when $x_{n+1}$ is close to $x_n$ in $X$. Is this homeomorphic to $\operatorname{Ran}(X)$?
3. The same two questions with $\operatorname{Sl}$ in place of $\operatorname{Ran}$.
4. Is $\operatorname{Ran}(X)$ homeomorphic to $\operatorname{Sl}(X)$?
5. Are $\operatorname{Ran}(X)$, $\operatorname{UConf}_n(X)$ or $\operatorname{Sl}(X)$ subspaces in $\mathscr VX$ for some nice spaces $X$?
6. Are there known embeddings of some categories of spaces into toposes such that the image of the embedding is closed under taking $\operatorname{Sub}_{\mathrm{fin}}$? In particular, can $\operatorname{Sub}_{\mathrm{fin}}(IX)$ be isomorphic to $I(\operatorname{Sl}(X))$ for some such $I$?
7. How does the geometric realization of $\operatorname{Sub}_{\mathrm{fin}}(X)$ relate to $\operatorname{Ran}$, $\operatorname{UConf}_n$, $\operatorname{Sl}$ and $\mathscr V$ of the geometric realization of $X$ for a simplicial set $X$?
$\ \ \,$0.$\$Are these considered together and compared somewhere in the literature?
Too long for a comment but it is essentially a comment:
It is easy to see that for a Hausdorff space $X$ the topology on the Ran space coincides with the Vietoris topology and for a non-Hausdorff space $X$ the Ran topology is strictly weaker than the Vietoris topology.
The topology of the free topological semilattice is stronger than the Vietoris topology. For example, for an infinite compact metrizable space $K$ the space $SL(K)$ is a non-metrizable $k_\omega$-space whereas the Vietoris topology is metrizable. So, $SL(K)$ even topologically does not embed into $\mathcal V X$.
By the way, the hyperspace $\mathcal V X$ of non-empty finite subsets of a topological space $X$ endowed with the Vietoris topology coincides with the free Lawson topological semilattice of $X$.
For a Hausdorff space $X$ the configuration space $\mathrm{UConf}_n(X)$ naturally embeds into the free (Lawson) topological semilattice. For the free Lawson semilattice $\mathcal V X$ this can be shown by comparing the Vietoris (or Ran) topology with the quotient topology on $\mathrm{UConf}_n(X)$. Then combining this with the continuity of the natural maps $\mathrm{UConf}_n(X)\to SL(X)\to \mathcal V X$, we can conclude that $\mathrm{UConf}_n(X)\to SL(X)$ is an embedding, too.
Concerning the literature on the free (locally convex) topological semilattices (at least), you can look at the following papers and references therein:
Banakh and Sakai - Free topological semilattices homeomorphic to $\mathbb R^\infty$ or $\mathbb Q^\infty$
Banakh, Guran, and Gutik - Free topological inverse semigroups
As I understand in question (2) on the space $\bigcup_{n\in\mathbb N}\mathrm{UConf}_n(X)$ it is considered the topology of direct limit of the tower $exp_n(X)$ where $exp_n(X)$ is the family of all at most $n$-element subsets of $X$ endowed with the Vietoris (or Ran) topology. This topology is stronger than the topology of $SL(X)$ and I am afraid that two topologies coincide only for $k_\omega$-spaces. For general spaces the operation of taking union is discontinuous with respect to this direct limit topology, so it is not a topological semilattice. This follows from Proposition 4, p. 35, of Banakh, Guran, and Gutik - Free topological inverse semigroups. This proposition says that if for a functionally Hausdorff space $X$ the free topological semilattice $SL(X)$ is a $k$-space, then each closed metrizable subspace of $X$ is locally compact.
• If this is essentially a comment, it is a very essential one! – მამუკა ჯიბლაძე Feb 27 '18 at 9:32
• @მამუკაჯიბლაძე Thank you. By the way, I looked at (en.wikipedia.org/wiki/Ran_space) for the Ran space and found there mentionong the Beilinson-Drinfeld Theorem on the weak contractibility of the Ran space. It should be mentined that the weak contractibility (= triviality of all homotopy groups) of topological semilattices is a well-known and old fact. So, what was actually proved by Beilinson and Drinfeld? Only non-Hausdorff case (important in Algebraic Geometry)? – Taras Banakh Feb 27 '18 at 9:38
• Concerning Beilinson-Drinfeld Theorem on weak contractibiliy of the Ran space of a connected manifold. This theorem follows (trivially) from the known fact that any path-connected topological semilattice has trivial homotopy groups. And this fact follows from the known fact that the circle is an $exp_3$-valued retract of the disk. I do not remember who first noticed the existence of such retraction but Dranishnikov applied it in 80-ies in his papers devoted to functors. So, what was actually proved by Beilinson and Drinfeld? – Taras Banakh Feb 27 '18 at 10:08
• Trying to find more information on the Ran space, I looked at the paper (arxiv.org/pdf/1608.07472.pdf) and already on page 3 found a topological gap. The author writes that the Ran space of any topological space is a topological semilattice with respect to the topology of the direct limit, but this contradicts Proposition 4 in the paper of Banakh-Guran-Gutik. It is interesting how many such misbeliefs there are in Algebraic Geometry (in topologycal algebra also there was some time when people believed that the free topological group carries the topology of dircet limit). – Taras Banakh Feb 27 '18 at 10:52
• Sorry I am confused by your fifth paragraph. Do you want to say that the free topological semilattice carries Lawson topology, but is smaller than the value of the left adjoint to the forgetful functor from Lawson semilattices to spaces? Btw is it known that this adjoint exists? – მამუკა ჯიბლაძე Feb 27 '18 at 11:13 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 1, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9238756895065308, "perplexity": 245.6777715733718}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-43/segments/1570986666959.47/warc/CC-MAIN-20191016090425-20191016113925-00121.warc.gz"} |
http://cerco.cs.unibo.it/changeset/3207/Deliverables | Changeset 3207 for Deliverables
Ignore:
Timestamp:
Apr 29, 2013, 3:31:04 PM (7 years ago)
Message:
Final version up to spellchecking.
File:
1 edited
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Unmodified
r3126 \begin{document} \title{??????} \author{??????} \date{dd/mm/yy} \title{Dependent labelling applied to stateful hardware components} \author{G. Pulcini$^*$, C. Sacerdoti Coen\footnote{The project CerCo acknowledges the financial support of the Future and Emerging Technologies (FET) programme within the Seventh Framework Programme for Research of the European Commission, under FET-Open grant number: 243881}\\~\\ \texttt{\{pulcini,sacerdot\}@cs.unibo.it}\\~ \\Dipartimento di Informatica - Scienza ed Ingegneria\\ Universit\`a di Bologna} \date{03/04/2013} \maketitle \section{Middle and Long Term Improvements} In order to identify the middle and long term improvements, we briefly review \abstract{The Certified Complexity (CerCo) EU Project~\cite{cerco} aims at integrating and unifying the functional and non functional analyses of safety and time critical software by performing both of them together on the source code. It is based on the labelling approach~\cite{labelling} that allows to write compilers that induce on the source code a sound and precise cost model for basic blocks. The cost model is computed on object code blocks and then transferred to the source code by reversing the optimizations to the control flow~\cite{paolo}. In this technical report we address the important issue of stateful hardware whose instructions cost is a function of the internal state. Typical examples are pipelines and caches. In order to avoid loss of precision, the cost model must be parametric on the state, which has no correspondent one at the source level. We show how to enrich the source code with the minimal amount of information that allows to compute costs precisely. We also briefly argue in favour of probabilistic static time analysis and we examine how it is already supported by the labelling approach. } \section{Introduction} The labelling approach~\cite{labelling,paolo} is a new technique to implement compilers that induce on the source code a sound and precise cost model for basic blocks. The cost model is computed on object code blocks and then transferred to the source code by reversing the optimizations to the control flow~\cite{paolo}. In the rest of this technical report we assume reader's knowledge on the labelling approach. At the end of the CerCo project, we are convinced that the labelling approach can support most optimizations currently supported by real world compilers. Moreover, we have formally certified the code of a compiler that transfers cost models according to the labelling approach, greatly reducing the trusted code base of time analysis. The main issue that is left is to identify the classes of cost models that can be expressed at the source level and that we can automatically reason on. In particular, we know that cost models for modern hardware are complex objects that assign to each instruction a cost which also depends on the internal state of stateful hardware components that are designed to optimize the average case. Pipelines, caches, branch predictors are tipical examples of components that have no impact on the functional behavior of the code, but that greatly augment the code performance. Ignorance on the internal state of these components during a WCET analysis forces to assume the worst case, leading to useless time bounds. Therefore, standard WCET tools tend to statically execute code fragments as much as possible, to minimize the ignorance on the state. For loops, for example, are totally unrolled. In CerCo we could do the same, departing from the labelling approach. However, what is more natural is to stay closer to the labelling approach and avoid loosing precision by computing parametric exact costs. This is the topic of this research report. In Section~\ref{premises} we briefly review the premises and goals of the CerCo approach in order to compare the CerCo approach to the traditional WCET one, which is able to deal with modern hardware. In Section~\ref{controlflow} we compare the control flow analyses performed in CerCo and in traditional WCET, arguing that our approach is winning. In Section~\ref{static} we compare the static analyses performed in CerCo and in traditional WCET. Only the latter can deal with modern hardware. Section~\ref{static2} contains the new material. We revise our static analysis and the labelling approach in general to accomodate modern hardware. Temporary conclusions are found in Section~\ref{conclusions}. \section{\label{premises}CerCo: premises and goals} We briefly review here the premises and goals of the CerCo approach to resource analysis. \begin{itemize} choose the cost model in such a way that the cost bounds are high enough to bound the cost of every produced code. This was attempted for instance in the EmBounded project with good success. However, we believe that bounds in the EMBounded project~\cite{embounded} with good success. However, we believe that bounds obtained in this way have few possibilities of being tight. \item Therefore our approach consists in having the compiler generate the techniques need to estimate the cost of control blocks of instructions. \subsection{Control flow analysis} \section{Control flow analysis\label{controlflow}} The first main difference is in the control flow analysis. Traditional WCET techniques. \subsection{Static analysis of costs of basic blocks} \section{Static analysis of costs of basic blocks\label{static}} At the beginning of the project we have deliberately decided to focus our attention on the control flow preservation, the cost model propagation and unlikely that our methodology could contribute to the solution of the problem. \subsubsection{Static analysis of costs of basic blocks revisited} \section{Static analysis of costs of basic blocks revisited\label{static2}} We will now describe what currently seems to be the most interesting technique for the static analysis of the cost of basic blocks in presence of complex Nevertheless, operand insensitivity is an important property for the labelling approach. In~\cite{tranquilli} we introduced \emph{dependent labels} and approach. In~\cite{paolo} we introduced \emph{dependent labels} and \emph{dependent costs}, which are the possibility of assigning costs to basic blocks of instructions which are also dependent on the state of the high level independent cost functions), we need to review the behaviour of probabilistic caches as proposed by PROARTIS. The interested reader can consult~\cite{proartis2-articolo30} for further informations. consult~\cite{proartis2} for further informations. In a randomized cache, the probability of evicting a given line on every access pipelines. \paragraph{Conclusions} \section{Conclusions\label{conclusions}} At the current state of the art functional properties of programs are better proved high level languages, but the non functional ones are proved on the size of the views can be tamed in practice without ruining the whole approach. \begin{thebibliography}{} \bibitem{cerco} \textbf{Certified Complexity}, R. Amadio, A. Asperti, N. Ayache, B. Campbell, D. Mulligan, R. Pollack, Y. Regis-Gianas, C. Sacerdoti Coen, I. Stark, in Procedia Computer Science, Volume 7, 2011, Proceedings of the 2 nd European Future Technologies Conference and Exhibition 2011 (FET 11), 175-177. \bibitem{labelling} \textbf{Certifying and Reasoning on Cost Annotations in C Programs}, N. Ayache, R.M. Amadio, Y.Régis-Gianas, in Proc. FMICS, Springer LNCS 7437: 32-46, 2012, DOI:10.1007/978-3-642-32469-7\_3. \bibitem{paolo} \textbf{Indexed Labels for Loop Iteration Dependent Costs}, P. Tranquilli, in Proceedings of the 11th International Workshop on Quantitative Aspects of Programming Languages and Systems (QAPL 2013), Rome, 23rd-24th March 2013, Electronic Proceedings in Theoretical Computer Science, to appear in 2013. \bibitem{embounded} \textbf{The EmBounded project (project paper)}, K. Hammond, R. Dyckhoff, C. Ferdinand, R. Heckmann, M. Hofmann, H. Loidl, G. Michaelson, J. Serot, A. Wallace, in Trends in Functional Programming, Volume 6, Intellect Press, 2006. \bibitem{proartis} \textbf{PROARTIS: Probabilistically Analysable Real-Time Systems}, F.J. Cazorla, E. Qui˜nones, T. Vardanega, L. Cucu, B. Triquet, G. Bernat, E. Berger, J. Abella, F. Wartel, M. Houston, et al., in ACM Transactions on Embedded Computing Systems, 2012. \bibitem{proartis2} \textbf{A Cache Design for Probabilistic Real-Time Systems}, L. Kosmidis, J. Abella, E. Quinones, and F. Cazorla, in Design, Automation, and Test in Europe (DATE), Grenoble, France, 03/2013. \end{thebibliography} \end{document} | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.3855441212654114, "perplexity": 2465.8708623511347}, "config": {"markdown_headings": false, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-47/segments/1573496668416.11/warc/CC-MAIN-20191114104329-20191114132329-00264.warc.gz"} |
https://en.khanacademy.org/math/integral-calculus/ic-series/ic-lagrange-error-bound/v/lagrange-error-bound-for-sine-function | If you're seeing this message, it means we're having trouble loading external resources on our website.
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## Integral Calculus
### Course: Integral Calculus>Unit 5
Lesson 12: Lagrange error bound
# Worked example: estimating sin(0.4) using Lagrange error bound
AP.CALC:
LIM‑8 (EU)
,
LIM‑8.C (LO)
,
LIM‑8.C.1 (EK)
Lagrange error bound (also called Taylor remainder theorem) can help us determine the degree of Taylor/Maclaurin polynomial to use to approximate a function to a given error bound. See how it's done when approximating the sine function.
## Want to join the conversation?
• The MacLaurin expansion of sin(x) is x - x^3/3! + x^5/5! - x^7/7! + x^9/9! ...
The polynomial of degree 4 is actually identical to the the polynomial of degree 3 because the coefficient of x^4 is 0. Shouldn't the answer to the exercise be 3 instead of 4?
• While what you said is technically true, what Sal is doing in the is using the error function to evaluate the absolute maximum error bound of the function. You are not supposed to know before hand that the coefficient fourth degree polynomial is 0, the error function is basically just telling you to what degree polynomial you need to take Maclaurin polynomial to be completely sure that the error is within certain bounds. It is always gonna be an overestimate since it is taking the absolute maximum that the error could be, not what actually is.
• I agree with Sal that no matter how many times we take the derivative of sin, it's absolute value will always be between 0 and 1 and so the value of "M" will be 1 but isn't Sal ignoring the fact that we have to only consider an open interval containing 0 and 0.4, in that case if the n+1'th derivative of sinx is (+or-)sinx again depending on value of 'n' then if we look in the interval of 0 and 0.4 then the absolute value of sinx will not lie between 0 and 1 but it will lie between 0 and sin(0.4)..........
So isn't something WRONG here??
• SIn(0.4 ) = 0.389..(the range of M is from 0 to 0.389) and cos(0.4) = 0.921...(the range is from 1 to 0.921). The (n+1)th derivative of f(x) could be either (+or-)cosx or (+or-)sinx. But we are sure that the value of M is always less than 1.
*Edit:*
What we have to take for M is the maximum possible value in the interval (x=0 to x=0.4). But we are not sure if its cosx or sinx in the n+1 th derivative. So we take M=1. It is gonna be less precise if it is sinx and more precise if it is cosx.
• We know that sin x is < or = to 1 over the whole domain, but might one find a smaller M for the open interval between -0.0001 and 0.40001? If we use an M larger than necessary, could it cause us to specify a higher degree polynomial than necessary?
• That's right. I solved the problem for this specific interval and the minimal degree is 3 and not 4.
• how do we solve the final inequality Sal arrives at (at ) without trial and error?
do we just take log on both sides and solve for n?
• Because of the factorial and there being "n" both as an exponent and outside of the exponent, I do not think there is a way to solve it without trial and error.
• wait so i am confusion
why is the M equal to one in this particular situation?
i know that the graph of sine is bounded by 1, so does that make M always equal to 1 in these kind of problems?
• Because whatever x is, sin(x) and cos(x) is always bounded by 1, yes, it would make M equals 1 in this kind of problems. You might think sin(x) on (0, 0.4) much less than 1 but the derivative of sin(x) is ccos(x) which has quite close value to 1 in the above interval. Whereas this is not really precise, it's good enough
• In the previous video "Taylor polynomial remainder (part 2)" the right hand side of the remainder equation is without the absolute value, while in @ the right hand side is with the absolute value. Why?
• In the previous video the remainder theorem formula is shown to have (x-a) and not just x over an interval between a and b. I am assuming it is just x because the interval is between 0 and 0.4, hence, a is 0?
• Actually, it's because we're using the Maclaurin polynomial
• Where does the condition that n+1th derivative of f(x) has to be less than or equal to M for an open interval including 0 and x come from? Why won't this work for other intervals?
• Te open interval including 0 and x comes from just wanting to make sure the function is differentiable in that range. say you had 1/x as the function, or some other rational expression. You wouldn't be able to use any portion that has a vertical asymptote.
Anyway, in the intro videos to the error/ remainder Sal goes through to show where that entire term comes from. Specifically in this video. https://www.khanacademy.org/math/ap-calculus-bc/bc-series-new/bc-10-12/v/proof-bounding-the-error-or-remainder-of-a-taylor-polynomial-approximation If that doesn't make sense though I can try to explain. I reccomend watching through both parts though. | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8202081918716431, "perplexity": 406.98120118864887}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.3, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2023-14/segments/1679296945168.36/warc/CC-MAIN-20230323132026-20230323162026-00640.warc.gz"} |
https://worldwidescience.org/topicpages/s/shocks+lacked+type.html | #### Sample records for shocks lacked type
1. Analytical solutions of hypersonic type IV shock - shock interactions
Science.gov (United States)
Frame, Michael John
An analytical model has been developed to predict the effects of a type IV shock interaction at high Mach numbers. This interaction occurs when an impinging oblique shock wave intersects the most normal portion of a detached bow shock. The flowfield which develops is complicated and contains an embedded jet of supersonic flow, which may be unsteady. The jet impinges on the blunt body surface causing very high pressure and heating loads. Understanding this type of interaction is vital to the designers of cowl lips and leading edges on air- breathing hypersonic vehicles. This analytical model represents the first known attempt at predicting the geometry of the interaction explicitly, without knowing beforehand the jet dimensions, including the length of the transmitted shock where the jet originates. The model uses a hyperbolic equation for the bow shock and by matching mass continuity, flow directions and pressure throughout the flowfield, a prediction of the interaction geometry can be derived. The model has been shown to agree well with the flowfield patterns and properties of experiments and CFD, but the prediction for where the peak pressure is located, and its value, can be significantly in error due to a lack of sophistication in the model of the jet fluid stagnation region. Therefore it is recommended that this region of the flowfield be modeled in more detail and more accurate experimental and CFD measurements be used for validation. However, the analytical model has been shown to be a fast and economic prediction tool, suitable for preliminary design, or for understanding the interactions effects, including the basic physics of the interaction, such as the jet unsteadiness. The model has been used to examine a wide parametric space of possible interactions, including different Mach number, impinging shock strength and location, and cylinder radius. It has also been used to examine the interaction on power-law shaped blunt bodies, a possible candidate for
2. Coronal mass ejection shock fronts containing the two types of intermediate shocks
International Nuclear Information System (INIS)
Steinolfson, R.S.; Hundhausen, A.J.
1990-01-01
Numerical solutions of the time-dependent, magnetohydrodynamic (MHD) equations in two dimensions are used to demonstrate the formation of both types of intermediate shocks in a single shock front for physical conditions that are an idealization of those expected to occur in some observed coronal mass ejections. The key to producing such a shock configuration in the simulations is the use of an initial atmosphere containing a magnetic field representative of that in a coronal streamer with open field lines overlying a region of closed field lines. Previous attempts using just open field lines (perpendicular to the surface) produced shock configurations containing just one of the two intermediate shock types. A schematic of such a shock front containing both intermediate shock types has been constructed previously based solely on the known properties of MHD shocks from the Rankine-Hugoniot equations and specific requirements placed on the shock solution at points along the front where the shock normal and upstream magnetic field are aligned. The shock front also contains, at various locations along the front, a hydrodynamic (nonmagnetic) shock, a switch-on shock, and a fast shock in addition to the intermediate shocks. This particular configuration occurs when the shock front speed exceeds the upstream (preshock) intermediate wave speed but is less than a critical speed defined in the paper (equation 1) along at least some portion of the shock front. A distinctive feature of the front is that it is concave upward (away from the surface) near the region where the field in the preshock plasma is normal to the front of near the central portion of the shock front
3. SHOCK BREAKOUT FROM TYPE Ia SUPERNOVA
International Nuclear Information System (INIS)
Piro, Anthony L.; Chang, Philip; Weinberg, Nevin N.
2010-01-01
The mode of explosive burning in Type Ia supernovae (SNe Ia) remains an outstanding problem. It is generally thought to begin as a subsonic deflagration, but this may transition into a supersonic detonation (the delayed detonation transition, DDT). We argue that this transition leads to a breakout shock, which would provide the first unambiguous evidence that DDTs occur. Its main features are a hard X-ray flash (∼20 keV) lasting ∼10 -2 s with a total radiated energy of ∼10 40 erg, followed by a cooling tail. This creates a distinct feature in the visual light curve, which is separate from the nickel decay. This cooling tail has a maximum absolute visual magnitude of M V ∼ -9 to -10 at ∼1 day, which depends most sensitively on the white dwarf radius at the time of the DDT. As the thermal diffusion wave moves in, the composition of these surface layers may be imprinted as spectral features, which would help to discern between SN Ia progenitor models. Since this feature should accompany every SNe Ia, future deep surveys (e.g., m = 24) will see it out to a distance of ∼80 Mpc, giving a maximum rate of ∼60 yr -1 . Archival data sets can also be used to study the early rise dictated by the shock heating (at ∼20 days before maximum B-band light). A similar and slightly brighter event may also accompany core bounce during the accretion-induced collapse to a neutron star, but with a lower occurrence rate.
4. Shock waves in luminous early-type stars
International Nuclear Information System (INIS)
Castor, J.I.
1986-01-01
Shock waves that occur in stellar atmospheres have their origin in some hydrodynamic instability of the atmosphere itself or of the stellar interior. In luminous early-type stars these two possibilities are represented by shocks due to an unstable radiatively-accelerated wind, and to shocks generated by the non-radial pulsations known to be present in many or most OB stars. This review is concerned with the structure and development of the shocks in these two cases, and especially with the mass loss that may be due specifically to the shocks. Pulsation-produced shocks are found to be very unfavorable for causing mass loss, owing to the great radiation efficiency that allows them to remain isothermal. The situation regarding radiatively-driven shocks remains unclear, awaiting detailed hydrodynamics calculations. 20 refs., 2 figs
5. Multiple sleep alterations in mice lacking cannabinoid type 1 receptors.
Directory of Open Access Journals (Sweden)
Alessandro Silvani
Full Text Available Cannabinoid type 1 (CB1 receptors are highly expressed in the brain and play a role in behavior control. Endogenous cannabinoid signaling is modulated by high-fat diet (HFD. We investigated the consequences of congenital lack of CB1 receptors on sleep in mice fed standard diet (SD and HFD. CB1 cannabinoid receptor knock-out (KO and wild-type (WT mice were fed SD or HFD for 4 months (n = 9-10 per group. Mice were instrumented with electroencephalographic (EEG and electromyographic electrodes. Recordings were performed during baseline (48 hours, sleep deprivation (gentle handling, 6 hours, sleep recovery (18 hours, and after cage switch (insomnia model paradigm, 6 hours. We found multiple significant effects of genotype on sleep. In particular, KO spent more time awake and less time in non-rapid-eye-movement sleep (NREMS and rapid-eye-movement sleep (REMS than WT during the dark (active period but not during the light (rest period, enhancing the day-night variation of wake-sleep amounts. KO had slower EEG theta rhythm during REMS. REMS homeostasis after sleep deprivation was less effective in KO than in WT. Finally, KO habituated more rapidly to the arousing effect of the cage-switch test than WT. We did not find any significant effects of diet or of diet x genotype interaction on sleep. The occurrence of multiple sleep alterations in KO indicates important roles of CB1 cannabinoid receptors in limiting arousal during the active period of the day, in sleep regulation, and in sleep EEG in mice.
6. Central venous pressure and shock index predict lack of hemodynamic response to volume expansion in septic shock: a prospective, observational study.
Science.gov (United States)
Lanspa, Michael J; Brown, Samuel M; Hirshberg, Eliotte L; Jones, Jason P; Grissom, Colin K
2012-12-01
Volume expansion is a common therapeutic intervention in septic shock, although patient response to the intervention is difficult to predict. Central venous pressure (CVP) and shock index have been used independently to guide volume expansion, although their use is questionable. We hypothesize that a combination of these measurements will be useful. In a prospective, observational study, patients with early septic shock received 10-mL/kg volume expansion at their treating physician's discretion after brief initial resuscitation in the emergency department. Central venous pressure and shock index were measured before volume expansion interventions. Cardiac index was measured immediately before and after the volume expansion using transthoracic echocardiography. Hemodynamic response was defined as an increase in a cardiac index of 15% or greater. Thirty-four volume expansions were observed in 25 patients. A CVP of 8 mm Hg or greater and a shock index of 1 beat min(-1) mm Hg(-1) or less individually had a good negative predictive value (83% and 88%, respectively). Of 34 volume expansions, the combination of both a high CVP and a low shock index was extremely unlikely to elicit hemodynamic response (negative predictive value, 93%; P = .02). Volume expansion in patients with early septic shock with a CVP of 8 mm Hg or greater and a shock index of 1 beat min(-1) mm Hg(-1) or less is unlikely to lead to an increase in cardiac index. Copyright © 2012 Elsevier Inc. All rights reserved.
7. Design and testing of a shock absorber for a type I container
International Nuclear Information System (INIS)
Sappok, M.; Beine, B.; Rittscher, D.; Jais, M.
1994-01-01
A simple method of designing a shock absorber to protect a type B cast-iron container is developed. The results of deformation tests of the structural material (steel pipes) used for the shock absorber are presented. The accelerations and strains measured during the 9m drop tests of the container with the shock absorber are compared with the theoretical results of the calculations for the shock absorber design. ((orig.))
8. The lack of theoretical support for using person trade-offs in QALY-type models
DEFF Research Database (Denmark)
Østerdal, Lars Peter Raahave
2009-01-01
-adjusted life years (DALYs). This paper discusses the theoretical support for the use of person trade-offs in QALY-type measurement of (changes in) population health. It argues that measures of this type based on such quality-adjustment factors almost always violate the Pareto principle, and so lack normative...
9. H2 profiles of C-type bow shocks
International Nuclear Information System (INIS)
Smith, M.D.; Brand, P.W.J.L.
1990-01-01
We present emission-line profiles of molecular hydrogen from curved C-shocks within molecular clouds. Shock configurations arising from the supersonic motion of jets and bullets within a dense cloud are chosen. Bow shock speeds in the range υ w = 40-200 km s -1 are investigated. Breakdown through dissociation and self-ionization restricts the C-shock section to the bow tail. We find that profiles are essentially single-peaked and narrow with full widths (at 10 per cent maximum intensity, deconvolved) of up to about 50, 40 and 30 km s -1 for cones, hemispherical caps and paraboloids, respectively. Exceptional field alignments can produce lines as wide as 75 km s -1 in the conical shock model. (author)
10. Shock modon: a new type of coherent structure in rotating shallow water.
Science.gov (United States)
2012-01-27
We show that a new type of coherent structure, a shock modon, exists in a rotating shallow water model at large Rossby numbers. It is a combination of an asymmetric vortex dipole with a stationary hydraulic jump. The structure is long living, despite the energy dissipation by the hydraulic jump, and moving along a circular path. Collisions of shock modons can be elastic, or lead to formation of shock tripoles.
11. Chemical-Petrographic Types and Shock Metamorphism of 184 Grove Mountains Equilibrated Ordinary Chondrites
Directory of Open Access Journals (Sweden)
Deqiu Dai
2018-06-01
Full Text Available We reported the petrography and mineral chemistry of 184 equilibrated ordinary chondrites collected from Grove Mountains, Antarctica. The chemical-petrographic types and shock metamorphism degrees of these chondrites were assigned. They were classified into 46 H groups (22 H4, 20 H5, and four H6, 133 L groups (eight L4, 75 L5, and 50 L6, and five LL groups (four LL4 and one LL5. Some of these chondrites could be paired; however, both H and L group meteorites were affected. Further studies such as terrestrial ages and thermal luminescence are required in order to confirm the pairings. The relative abundances of H, L, and LL are different in Grove Mountain meteorites, when compared to those in Transcontinental Ridge meteorites. Based on the shock effects, the shock metamorphism degrees of these chondrites were assigned. Compared to previous studies, the heavily shocked samples of S4 and S5 have a higher fraction (59 out of 184 in Grove Mountain ordinary chondrites. The L group (54 out of 59 is the dominant chemical group in the heavily shocked chondrites, except for five meteorites which belong to the H group. The shock metamorphism degrees of the H and L groups are distinct, which may indicate different surface properties in their parent bodies. In addition, the petrologic types and shock degrees are probably closely related, with the most heavily shocked chondrites observed in types 5 and 6.
12. Characteristics of coronal shock waves and solar type 2 radio bursts
Science.gov (United States)
Mann, G.; Classen, H.-T.
1995-01-01
In the solar corona shock waves generated by flares and/or coronal mass ejections can be observed by radio astronomical methods in terms of solar type 2 radio bursts. In dynamic radio spectra they appear as emission stripes slowly drifting from high to low frequencies. A sample of 25 solar type 2 radio bursts observed in the range of 40 - 170 MHz with a time resolution of 0.1 s by the new radiospectrograph of the Astrophvsikalisches Institut Potsdam in Tremsdorf is statistically investigated concerning their spectral features, i.e, drift rate, instantaneous bandwidth, and fundamental harmonic ratio. In-situ plasma wave measurements at interplanetary shocks provide the assumption that type 2 radio radiation is emitted in the vicinity of the transition region of shock waves. Thus, the instantaneous bandwidth of a solar type 2 radio burst would reflect the density jump across the associated shock wave. Comparing the inspection of the Rankine-Hugoniot relations of shock waves under coronal circumstances with those obtained from the observational study, solar type 2 radio bursts should be regarded to be generated by weak supercritical, quasi-parallel, fast magnetosonic shock waves in the corona.
13. Solar radio bursts of spectral type II, coronal shocks, and optical coronal transients
Science.gov (United States)
Maxwell, A.; Dryer, M.
1981-01-01
An examination is presented of the association of solar radio bursts of spectral type II and coronal shocks with solar flare ejecta observed in H-alpha, the green coronal line, and white-light coronagraphs. It is suggested that fast-moving optical coronal transients should for the most part be identified with piston-type phenomena well behind the outward-traveling shock waves that generate type II radio bursts. A general model is presented which relates type II radio bursts and coronal shocks to optically observed ejecta and consists of three main velocity regimes: (1) a quasi-hemispherical shock wave moving outward from the flare at speeds of 1000-2000 km/sec and Alfven Mach number of about 1.5; (2) the velocity of the piston driving the shock, on the order of 0.8 that of the shock; and (3) the regime of the slower-moving H-alpha ejecta, with velocities of 300-500 km/sec.
14. Research on Shock Responses of Three Types of Honeycomb Cores
Science.gov (United States)
Peng, Fei; Yang, Zhiguang; Jiang, Liangliang; Ren, Yanting
2018-03-01
The shock responses of three kinds of honeycomb cores have been investigated and analyzed based on explicit dynamics analysis. According to the real geometric configuration and the current main manufacturing methods of aluminum alloy honeycomb cores, the finite element models of honeycomb cores with three different cellular configurations (conventional hexagon honeycomb core, rectangle honeycomb core and auxetic honeycomb core with negative Poisson’s ratio) have been established through FEM parametric modeling method based on Python and Abaqus. In order to highlight the impact response characteristics of the above three honeycomb cores, a 5 mm thick panel with the same mass and material was taken as contrast. The analysis results showed that the peak values of longitudinal acceleration history curves of the three honeycomb cores were lower than those of the aluminum alloy panel in all three reference points under the loading of a longitudinal pulse pressure load with the peak value of 1 MPa and the pulse width of 1 μs. It could be concluded that due to the complex reflection and diffraction of stress wave induced by shock in honeycomb structures, the impact energy was redistributed which led to a decrease in the peak values of the longitudinal acceleration at the measuring points of honeycomb cores relative to the panel.
15. Design and testing of a shock absorber for a type 1 container
International Nuclear Information System (INIS)
Sappok, M.; Beine, B.; Rittscher, D.
1993-01-01
A shock-absorber will be required for a rad. waste 'Konrad' type 1 container made of ductile cast iron whenever it will be used as a type B container according to the IAEA-Regulations for the Safe Transport of Radioactive materials. The shock-absorber has to protect the type B container during shipping such as to withstand the accident scenarios that are covered by the IAEA-Regulation tests without substantial loss of its shielding and tightness functions. The designation as type 1 container originates from German regulations for the intermediate storage site Gorleben and the final depository Konrad-mine. These regulations call for the limits on outside dimensions of 1700 mm in length, 1600 mm in width and 1450 mm in height as well as for a limit of 20 Mg on total weight without shock-absorber. The relatively simple design method for the shock-absorber has been validated by the test results. It can be extended to other materials and designs for shock-absorbers if reliable force-displacement-diagrams are available for the structural elements from which the absorbed energy and the displacements can be calculated by integration. In order to account for the dynamic effects, the better approximation of the true duration of the impact would be helpful. The present limit of 0.5 R p0,2 on the nominal stresses should be discussed because the large number of tests on containers made of ductile cast iron that have been performed up to now have shown a substantial level of conservatism on this respect. The sharply tapered pipes on edge Kl of the shock-absorbers should be replaced by pipe bends. This will result in smaller accelerations and in an even higher level of protection of the container than effected by the tested shock-absorber
16. Heat Shock Response Associated with Hepatocarcinogenesis in a Murine Model of Hereditary Tyrosinemia Type I
International Nuclear Information System (INIS)
Angileri, Francesca; Morrow, Geneviève; Roy, Vincent; Orejuela, Diana; Tanguay, Robert M.
2014-01-01
Hereditary Tyrosinemia type 1 (HT1) is a metabolic liver disease caused by genetic defects of fumarylacetoacetate hydrolase (FAH), an enzyme necessary to complete the breakdown of tyrosine. The severe hepatic dysfunction caused by the lack of this enzyme is prevented by the therapeutic use of NTBC (2-[2-nitro-4-(trifluoromethyl)benzoyl]cyclohexane-1,3-dione). However despite the treatment, chronic hepatopathy and development of hepatocellular carcinoma (HCC) are still observed in some HT1 patients. Growing evidence show the important role of heat shock proteins (HSPs) in many cellular processes and their involvement in pathological diseases including cancer. Their survival-promoting effect by modulation of the apoptotic machinery is often correlated with poor prognosis and resistance to therapy in a number of cancers. Here, we sought to gain insight into the pathophysiological mechanisms associated with liver dysfunction and tumor development in a murine model of HT1. Differential gene expression patterns in livers of mice under HT1 stress, induced by drug retrieval, have shown deregulation of stress and cell death resistance genes. Among them, genes coding for HSPB and HSPA members, and for anti-apoptotic BCL-2 related mitochondrial proteins were associated with the hepatocarcinogenetic process. Our data highlight the variation of stress pathways related to HT1 hepatocarcinogenesis suggesting the role of HSPs in rendering tyrosinemia-affected liver susceptible to the development of HCC
17. Heat Shock Response Associated with Hepatocarcinogenesis in a Murine Model of Hereditary Tyrosinemia Type I
Directory of Open Access Journals (Sweden)
Francesca Angileri
2014-04-01
Full Text Available Hereditary Tyrosinemia type 1 (HT1 is a metabolic liver disease caused by genetic defects of fumarylacetoacetate hydrolase (FAH, an enzyme necessary to complete the breakdown of tyrosine. The severe hepatic dysfunction caused by the lack of this enzyme is prevented by the therapeutic use of NTBC (2-[2-nitro-4-(trifluoromethylbenzoyl] cyclohexane-1,3-dione. However despite the treatment, chronic hepatopathy and development of hepatocellular carcinoma (HCC are still observed in some HT1 patients. Growing evidence show the important role of heat shock proteins (HSPs in many cellular processes and their involvement in pathological diseases including cancer. Their survival-promoting effect by modulation of the apoptotic machinery is often correlated with poor prognosis and resistance to therapy in a number of cancers. Here, we sought to gain insight into the pathophysiological mechanisms associated with liver dysfunction and tumor development in a murine model of HT1. Differential gene expression patterns in livers of mice under HT1 stress, induced by drug retrieval, have shown deregulation of stress and cell death resistance genes. Among them, genes coding for HSPB and HSPA members, and for anti-apoptotic BCL-2 related mitochondrial proteins were associated with the hepatocarcinogenetic process. Our data highlight the variation of stress pathways related to HT1 hepatocarcinogenesis suggesting the role of HSPs in rendering tyrosinemia-affected liver susceptible to the development of HCC.
18. Heat Shock Response Associated with Hepatocarcinogenesis in a Murine Model of Hereditary Tyrosinemia Type I
Energy Technology Data Exchange (ETDEWEB)
Angileri, Francesca; Morrow, Geneviève; Roy, Vincent; Orejuela, Diana; Tanguay, Robert M., E-mail: [email protected] [Laboratory of Cell and Developmental Genetics, Department of Molecular Biology, Medical Biochemistry and Pathology, Institut de Biologie Intégrative et des Systèmes (IBIS) and PROTEO, 1030 avenue de la médecine, Université Laval, Québec G1V 0A6 (Canada)
2014-04-23
Hereditary Tyrosinemia type 1 (HT1) is a metabolic liver disease caused by genetic defects of fumarylacetoacetate hydrolase (FAH), an enzyme necessary to complete the breakdown of tyrosine. The severe hepatic dysfunction caused by the lack of this enzyme is prevented by the therapeutic use of NTBC (2-[2-nitro-4-(trifluoromethyl)benzoyl]cyclohexane-1,3-dione). However despite the treatment, chronic hepatopathy and development of hepatocellular carcinoma (HCC) are still observed in some HT1 patients. Growing evidence show the important role of heat shock proteins (HSPs) in many cellular processes and their involvement in pathological diseases including cancer. Their survival-promoting effect by modulation of the apoptotic machinery is often correlated with poor prognosis and resistance to therapy in a number of cancers. Here, we sought to gain insight into the pathophysiological mechanisms associated with liver dysfunction and tumor development in a murine model of HT1. Differential gene expression patterns in livers of mice under HT1 stress, induced by drug retrieval, have shown deregulation of stress and cell death resistance genes. Among them, genes coding for HSPB and HSPA members, and for anti-apoptotic BCL-2 related mitochondrial proteins were associated with the hepatocarcinogenetic process. Our data highlight the variation of stress pathways related to HT1 hepatocarcinogenesis suggesting the role of HSPs in rendering tyrosinemia-affected liver susceptible to the development of HCC.
19. Transonic buffet control research with two types of shock control bump based on RAE2822 airfoil
Directory of Open Access Journals (Sweden)
Yun TIAN
2017-10-01
Full Text Available Current research shows that the traditional shock control bump (SCB can weaken the intensity of shock and better the transonic buffet performance. The author finds that when SCB is placed downstream of the shock, it can decrease the adverse pressure gradient. This may prevent the shock foot separation bubble to merge with the trailing edge separation and finally improve the buffet performance. Based on RAE2822 airfoil, two types of SCB are designed according to the two different mechanisms. By using Reynolds-averaged Navier-Stokes (RANS and unsteady Reynolds-averaged Navier-Stokes (URANS methods to analyze the properties of RAE2822 airfoil with and without SCB, the results show that the downstream SCB can better the buffet performance under a wide range of freestream Mach number and the steady aerodynamics characteristic is similar to that of RAE2822 airfoil. The traditional SCB can only weaken the intensity of the shock under the design condition. Under the off-design conditions, the SCB does not do much to or even worsen the buffet performance. Indeed, the use of backward bump can flatten the leeward side of the airfoil, and this is similar to the mechanism that supercritical airfoil can weaken the recompression of shock wave.
20. SHOCK BREAKOUT IN TYPE II PLATEAU SUPERNOVAE: PROSPECTS FOR HIGH-REDSHIFT SUPERNOVA SURVEYS
International Nuclear Information System (INIS)
Tominaga, N.; Morokuma, T.; Blinnikov, S. I.; Nomoto, K.; Baklanov, P.; Sorokina, E. I.
2011-01-01
Shock breakout is the brightest radiative phenomenon in a supernova (SN) but is difficult to be observed owing to the short duration and X-ray/ultraviolet (UV)-peaked spectra. After the first observation from the rising phase reported in 2008, its observability at high redshift is attracting enormous attention. We perform multigroup radiation hydrodynamics calculations of explosions for evolutionary presupernova models with various main-sequence masses M MS , metallicities Z, and explosion energies E. We present multicolor light curves of shock breakouts in Type II plateau SNe, being the most frequent core-collapse SNe, and predict apparent multicolor light curves of shock breakout at various redshifts z. We derive the observable SN rate and reachable redshift as functions of filter x and limiting magnitude m x,lim by taking into account an initial mass function, cosmic star formation history, intergalactic absorption, and host galaxy extinction. We propose a realistic survey strategy optimized for shock breakout. For example, the g'-band observable SN rate for m g',lim = 27.5 mag is 3.3 SNe deg -2 day -1 and half of them are located at z ≥ 1.2. It is clear that the shock breakout is a beneficial clue for probing high-z core-collapse SNe. We also establish ways to identify shock breakout and constrain SN properties from the observations of shock breakout, brightness, timescale, and color. We emphasize that the multicolor observations in blue optical bands with ∼hour intervals, preferably over ≥2 continuous nights, are essential to efficiently detect, identify, and interpret shock breakout.
1. Propagation of interplanetary shock waves by observations of type II solar radio bursts on IMP-6
International Nuclear Information System (INIS)
Chertok, I.M.; Fomichev, V.V.
1976-01-01
A new interpretation of the low frequency type II solar radio bursts of 30 June 1971, and 7-8 August 1972 observed with IMP-6 satellite (Malitson, H.H., Fainberg, J. and Stone, R.G., 1973, Astrophys. Lett., vol. 14, 111; Astrophys. J., vol. 183, L35) is suggested. The analysis is carried out for two models of the electron density distribution in the interplanetary medium taking into account that N approximately 3.5 cm -3 at a distance of 1 a.u. It is assumed that the frequency of the radio emission corresponds to the average electron density behind the shock front which exceeds the undisturbed electron density by the factor of 3. The radio data indicate essential deceleration of the shock waves during propagation from the Sun up to 1 a.u. The characteristics of the shock waves obtained from the type II bursts agree with the results of the in situ observations. (author)
2. Type II solar radio bursts, interplanetary shocks, and energetic particle events
International Nuclear Information System (INIS)
Cane, H.V.; Stone, R.G.
1984-01-01
Using the ISEE 3 radio astronomy experiment data we have identified 37 interplanetary type II bursts in the period 1978 September to 1981 December. We lists these events and the associated phenomena. The events are preceded by intense, soft X-ray events with long decay times and type II or type IV bursts, or both, at meter wavelengths. The meter wavelength type II bursts are usually intense and exhibit herringbone structure. The extension of the herringbone structure into the kilometer wavelength range appears as a fast drift radio feature which we refer to as a shock associated radio event. The shock associated event is an important diagnostic for the presence of a strong shock and particle acceleration. The majority of the interplanetary type II bursts are associated with energetic particle events. Our results support other studies which indicate that energetic soalr particles detected at 1 A.U. are generatd by shock acceleration. From a preliminary analysis of the available data there appears to be a high correlation with white light coronal transients. The transients are fast: i.e., velocities greater than 500 km s -1
3. Increased anxiety and fear memory in adult mice lacking type 2 deiodinase.
Science.gov (United States)
2017-10-01
A euthyroid state in the brain is crucial for its adequate development and function. Impairments in thyroid hormones (THs; T3 or 3,5,3'-triiodothyronine and T4 or thyroxine) levels and availability in brain can lead to neurological alterations and to psychiatric disorders, particularly mood disorders. The thyroid gland synthetizes mainly T4, which is secreted to circulating blood, however, most actions of THs are mediated by T3, the transcriptionally active form. In the brain, intracellular concentrations of T3 are modulated by the activity of type 2 (D2) and type 3 (D3) deiodinases. In the present work, we evaluated learning and memory capabilities and anxiety-like behavior at adult stages in mice lacking D2 (D2KO) and we analyzed the impact of D2-deficiency on TH content and on the expression of T3-dependent genes in the amygdala and the hippocampus. We found that D2KO mice do not present impairments in spatial learning and memory, but they display emotional alterations with increased anxiety-like behavior as well as enhanced auditory-cued fear memory and spontaneous recovery of fear memory following extinction. D2KO mice also presented reduced T3 content in the hippocampus and decreased expression of the T3-dependent gene Dio3 in the amygdala suggesting a hypothyroid status in this structure. We propose that the emotional dysfunctions found in D2KO mice can arise from the reduced T3 content in their brain, which consequently leads to alterations in gene expression with functional consequences. We found a downregulation in the gene encoding for the calcium-binding protein calretinin (Calb2) in the amygdala of D2KO mice that could affect the GABAergic transmission. The current findings in D2KO mice can provide insight into emotional disorders present in humans with DIO2 polymorphisms. Copyright © 2017 Elsevier Ltd. All rights reserved.
4. Development of a toroidal shell-type shock absorber for an irradiated fuel shipping cask
International Nuclear Information System (INIS)
Sugita, Y.; Mochizuki, S.
1983-01-01
This study described the design method of a toroidal shell-type shock absorber and the dynamic responses of the cask body, the internal structure and water when this shock absorber was used. Conclusions are: the calculated results on the basis of the master curves of non-dimensionalized force-deflection relations by static compression tests show a close agreement with the experimental results; the internal structure moves together with the cask body in every position; and the maximum water pressure is larger by a factor of 1.2 than the static pressure multiplied by the maximum deceleration in every direction due to the low-frequency wave propagation
5. Toxic shock syndrome
Science.gov (United States)
Staphylococcal toxic shock syndrome; Toxic shock-like syndrome; TSLS ... Toxic shock syndrome is caused by a toxin produced by some types of staphylococcus bacteria. A similar problem, called toxic shock- ...
6. Heights of Coronal Mass Ejections and Shocks Inferred from Metric and DH Type II Radio Bursts
Science.gov (United States)
Shanmugaraju, A.; Bendict Lawrance, M.; Moon, Y. J.; Lee, Jae-Ok; Suresh, K.
2017-09-01
A set of 27 continuous events that showed extension of metric Type-II radio bursts (m-Type IIs) into the deca-hectometric (DH) domain is considered. The coronal mass ejections (CMEs) associated with this type of continuous event supply more energy to produce space-weather effects than the CMEs that produce Type-II bursts in any one region. Since the heights of shock formation at the start of m-Type IIs were not available from observations, they were estimated using kinematic modeling in previous studies. In the present study, the heights of shock formation during metric and DH Type-II bursts are determined using two methods: i) the CME leading-edge method and ii) a method employing known electron-density models and start/end frequencies. In the first method, assuming that the shocks are generated by the associated CMEs at the leading edge, the height of the CME leading edge (LE) is calculated at the onset and end of m-Type IIs using the kinematic equation with constant acceleration or constant speed. The LE heights of CMEs that are assumed to be the heights of shock formation/end of nearly 79% of m-Type IIs are found to be within the acceptable range of 1 - 3 R_{⊙}. For other events, the heights are beyond this range, for which the shocks might either have been generated at the CME flanks/flare-blast waves, or the initial CME height might have been different. The CME/shock height at the onset and end of 17 DH Type IIs are found to be in the range of 2 - 6 R_{⊙} and within 30 R_{⊙}, respectively. In addition, the CME LE heights from observations at the onset and end of metric/DH Type IIs are compared with the heights corresponding to the observed frequency that is determined using the known electron-density models, and they are in agreement with the model results. The heights are also estimated using the space speed available for 15 halo CMEs, and it is found that the difference is smaller at the m-Type II start/end (0.02 to 0.66 R_{⊙}) and slightly greater
7. Development and performance evaluation of an electromagnetic-type shock wave generator for lipolysis
Energy Technology Data Exchange (ETDEWEB)
Liang, S. M., E-mail: [email protected]; Yang, Z. Y. [Department of Industrial Design, Far East University, No. 49, Zhonghua Road, Xinshi District, Tainan City 744, Taiwan (China); Chang, M. H. [Department of Aeronautics and Astronautics, National Cheng Kung University, No. 1, University Road, East District, Tainan City 701, Taiwan (China)
2014-01-15
This study aims at the design and development of electromagnetic-type intermittent shock wave generation in a liquid. The shock wave generated is focused at a focal point through an acoustic lens. This hardware device mainly consists of a full-wave bridge rectifier, 6 capacitors, a spark gap, and a flat coil. A metal disk is mounted in a liquid-filled tube and is placed in close proximity to the flat coil. Due to the repulsive force existing between the coil and disk shock waves are generated, while an eddy current is induced in the metal disk. Some components and materials associated with the device are also described. By increasing the capacitance content to enhance electric energy level, a highly focused pressure can be achieved at the focal point through an acoustic lens in order to lyse fat tissue. Focused pressures were measured at the focal point and its vicinity for different operation voltages. The designed shock wave generator with an energy intensity of 0.0016 mJ/mm{sup 2} (at 4 kV) and 2000 firings or higher energy intensities with 1000 firings is found to be able to disrupt pig fat tissue.
8. Development and performance evaluation of an electromagnetic-type shock wave generator for lipolysis.
Science.gov (United States)
Liang, S M; Chang, M H; Yang, Z Y
2014-01-01
This study aims at the design and development of electromagnetic-type intermittent shock wave generation in a liquid. The shock wave generated is focused at a focal point through an acoustic lens. This hardware device mainly consists of a full-wave bridge rectifier, 6 capacitors, a spark gap, and a flat coil. A metal disk is mounted in a liquid-filled tube and is placed in close proximity to the flat coil. Due to the repulsive force existing between the coil and disk shock waves are generated, while an eddy current is induced in the metal disk. Some components and materials associated with the device are also described. By increasing the capacitance content to enhance electric energy level, a highly focused pressure can be achieved at the focal point through an acoustic lens in order to lyse fat tissue. Focused pressures were measured at the focal point and its vicinity for different operation voltages. The designed shock wave generator with an energy intensity of 0.0016 mJ/mm(2) (at 4 kV) and 2000 firings or higher energy intensities with 1000 firings is found to be able to disrupt pig fat tissue.
9. Type II successful supernovae, the anatomy of shocks: neutrino emission and the adiabatic index
International Nuclear Information System (INIS)
Kahana, S.; Baron, E.; Cooperstein, J.
1983-01-01
Hydrodynamic calculations of stellar collapse in Type II Supernova are described using a variable stiffness and compressibility for the nuclear equation of state at high density. Initial models employing a relatively small mass core with low central entropy are necessary to achieve viable shocks; near success the models are sensitive to both neutrino emission and the high density equation of state. The treatment of neutrino production and transport is sketched and recent results reported
10. Lack of association of PTPN1 gene polymorphisms with type 2 ...
2011-08-19
Aug 19, 2011 ... Details of methods used for estimating fasting plasma glu- cose, serum insulin, serum ... Data for continuous variables were expressed as mean±SD. ..... bility gene for type 2 diabetes mellitus or obesity among Pima. Indians.
11. Dependent Neyman type A processes based on common shock Poisson approach
Science.gov (United States)
2016-04-01
The Neyman type A process is used for describing clustered data since the Poisson process is insufficient for clustering of events. In a multivariate setting, there may be dependencies between multivarite Neyman type A processes. In this study, dependent form of the Neyman type A process is considered under common shock approach. Then, the joint probability function are derived for the dependent Neyman type A Poisson processes. Then, an application based on forest fires in Turkey are given. The results show that the joint probability function of the dependent Neyman type A processes, which is obtained in this study, can be a good tool for the probabilistic fitness for the total number of burned trees in Turkey.
12. EVALUATION OF SERUM LACTATE LEVELS AS A PROGNOSTIC INDICATOR IN VARIOUS TYPES OF SHOCK
Directory of Open Access Journals (Sweden)
Siddaraj Wali
2017-08-01
Full Text Available BACKGROUND Sepsis is a lethal disease that has a complex pathophysiology including a dysregulated inflammatory response, endothelial injury, microvascular thrombosis, vasoplegia and myocardial depression leading to multiorgan failure. Prompt recognition of sepsis, early initiation of antibiotics, source control, optimal fluid and vasopressor therapy are of utmost importance. Early diagnosis of sepsis is very critical for the timely and efficient use of treatment modalities, however, there are no reliable, specific biomarkers that can guide the diagnosis of sepsis. Cardiopulmonary failure, sepsis, trauma, oncologic pathology and so can lead to lactic acidosis. The aim of the study is to evaluate the serum lactic acid levels as a prognostic marker in various type of shock. MATERIALS AND METHODS It is a prospective clinical study with 50 patients studied for 1 year. To study the values of serum lactate levels in shock patients. Statistical analysis- Chi-square test 2. Student’s t-test (two tailed, independent. RESULTS Out of the 50 patients included in the study, the incidence of shock was found to be high in the 21-30 years age group, 13 (26%. This study of ours revealed the most common focus of sepsis as respiratory tract (60%, followed by urinary tract (25%, skin and soft tissue (15%. Out of the 18 patients who died, it was noted that mortality rates were highest 10 (55.5% in patients with initial (0 hours high positive serum lactate levels (>4 mmol/L. Out of the 32 patients who recovered, majority 21 (65.6% had low positive serum lactate levels (0-2.5 mmol/L on admission (0 hours. Serum lactate level is significantly reduced in recovered patients. CONCLUSION Approximately, 30% to 45% of patients with septic shock and 60% to 90% of patients with cardiogenic shock die within 1 month of presentation. Lactate was chosen because it is used as a prognostic marker of global hypoxia. Serial lactate values followed over a period of time can be used to
13. Abnormal motor phenotype at adult stages in mice lacking type 2 deiodinase.
Science.gov (United States)
Bárez-López, Soledad; Bosch-García, Daniel; Gómez-Andrés, David; Pulido-Valdeolivas, Irene; Montero-Pedrazuela, Ana; Obregon, Maria Jesus; Guadaño-Ferraz, Ana
2014-01-01
Thyroid hormones have a key role in both the developing and adult central nervous system and skeletal muscle. The thyroid gland produces mainly thyroxine (T4) but the intracellular concentrations of 3,5,3'-triiodothyronine (T3; the transcriptionally active hormone) in the central nervous system and skeletal muscle are modulated by the activity of type 2 deiodinase (D2). To date no neurological syndrome has been associated with mutations in the DIO2 gene and previous studies in young and juvenile D2-knockout mice (D2KO) did not find gross neurological alterations, possibly due to compensatory mechanisms. This study aims to analyze the motor phenotype of 3-and-6-month-old D2KO mice to evaluate the role of D2 on the motor system at adult stages in which compensatory mechanisms could have failed. Motor abilities were explored by validated tests. In the footprint test, D2KO showed an altered global gait pattern (mice walked slower, with shorter strides and with a hindlimb wider base of support than wild-type mice). No differences were detected in the balance beam test. However, a reduced latency to fall was found in the rotarod, coat-hanger and four limb hanging wire tests indicating impairment on coordination and prehensile reflex and a reduction of muscle strength. In histological analyses of cerebellum and skeletal muscle, D2KO mice did not present gross structural abnormalities. Thyroid hormones levels and deiodinases activities were also determined. In D2KO mice, despite euthyroid T3 and high T4 plasma levels, T3 levels were significantly reduced in cerebral cortex (48% reduction) and skeletal muscle (33% reduction), but not in the cerebellum where other deiodinase (type 1) is expressed. The motor alterations observed in D2KO mice indicate an important role for D2 in T3 availability to maintain motor function and muscle strength. Our results suggest a possible implication of D2 in motor disorders.
14. SHOCK BREAKOUT AND EARLY LIGHT CURVES OF TYPE II-P SUPERNOVAE OBSERVED WITH KEPLER
International Nuclear Information System (INIS)
Garnavich, P. M.; Tucker, B. E.; Rest, A.; Shaya, E. J.; Olling, R. P.; Kasen, D; Villar, A.
2016-01-01
We discovered two transient events in the Kepler field with light curves that strongly suggest they are type II-P supernovae (SNe II-P). Using the fast cadence of the Kepler observations we precisely estimate the rise time to maximum for KSN2011a and KSN2011d as 10.5 ± 0.4 and 13.3 ± 0.4 rest-frame days, respectively. Based on fits to idealized analytic models, we find the progenitor radius of KSN2011a (280 ± 20 R ⊙ ) to be significantly smaller than that for KSN2011d (490 ± 20 R ⊙ ), but both have similar explosion energies of 2.0 ± 0.3 × 10 51 erg. The rising light curve of KSN2011d is an excellent match to that predicted by simple models of exploding red supergiants (RSG). However, the early rise of KSN2011a is faster than the models predict, possibly due to the supernova shock wave moving into pre-existing wind or mass-loss from the RSG. A mass-loss rate of 10 −4 M ⊙ yr −1 from the RSG can explain the fast rise without impacting the optical flux at maximum light or the shape of the post-maximum light curve. No shock breakout emission is seen in KSN2011a, but this is likely due to the circumstellar interaction suspected in the fast rising light curve. The early light curve of KSN2011d does show excess emission consistent with model predictions of a shock breakout. This is the first optical detection of a shock breakout from a SNe II-P
15. Abnormal motor phenotype at adult stages in mice lacking type 2 deiodinase.
Directory of Open Access Journals (Sweden)
Full Text Available BACKGROUND: Thyroid hormones have a key role in both the developing and adult central nervous system and skeletal muscle. The thyroid gland produces mainly thyroxine (T4 but the intracellular concentrations of 3,5,3'-triiodothyronine (T3; the transcriptionally active hormone in the central nervous system and skeletal muscle are modulated by the activity of type 2 deiodinase (D2. To date no neurological syndrome has been associated with mutations in the DIO2 gene and previous studies in young and juvenile D2-knockout mice (D2KO did not find gross neurological alterations, possibly due to compensatory mechanisms. AIM: This study aims to analyze the motor phenotype of 3-and-6-month-old D2KO mice to evaluate the role of D2 on the motor system at adult stages in which compensatory mechanisms could have failed. RESULTS: Motor abilities were explored by validated tests. In the footprint test, D2KO showed an altered global gait pattern (mice walked slower, with shorter strides and with a hindlimb wider base of support than wild-type mice. No differences were detected in the balance beam test. However, a reduced latency to fall was found in the rotarod, coat-hanger and four limb hanging wire tests indicating impairment on coordination and prehensile reflex and a reduction of muscle strength. In histological analyses of cerebellum and skeletal muscle, D2KO mice did not present gross structural abnormalities. Thyroid hormones levels and deiodinases activities were also determined. In D2KO mice, despite euthyroid T3 and high T4 plasma levels, T3 levels were significantly reduced in cerebral cortex (48% reduction and skeletal muscle (33% reduction, but not in the cerebellum where other deiodinase (type 1 is expressed. CONCLUSIONS: The motor alterations observed in D2KO mice indicate an important role for D2 in T3 availability to maintain motor function and muscle strength. Our results suggest a possible implication of D2 in motor disorders.
16. Phenylbutyrate Sensitizes Human Glioblastoma Cells Lacking Wild-Type P53 Function to Ionizing Radiation
International Nuclear Information System (INIS)
Lopez, Carlos A.; Feng, Felix Y.; Herman, Joseph M.; Nyati, Mukesh K.; Lawrence, Theodore S.; Ljungman, Mats
2007-01-01
Purpose: Histone deacetylase (HDAC) inhibitors induce growth arrest, differentiation, and apoptosis in cancer cells. Phenylbutyrate (PB) is a HDAC inhibitor used clinically for treatment of urea cycle disorders. Because of its low cytotoxicity, cerebrospinal fluid penetration, and high oral bioavailability, we investigated PB as a potential radiation sensitizer in human glioblastoma cell lines. Methods and Materials: Four glioblastoma cell lines were selected for this study. Phenylbutyrate was used at a concentration of 2 mM, which is achievable in humans. Western blots were used to assess levels of acetylated histone H3 in tumor cells after treatment with PB. Flow cytometry was used for cell cycle analysis. Clonogenic assays were performed to assess the effect of PB on radiation sensitivity. We used shRNA against p53 to study the role of p53 in radiosensitization. Results: Treatment with PB alone resulted in hyperacetylation of histones, confirmed by Western blot analysis. The PB alone resulted in cytostatic effects in three cell lines. There was no evidence of G 1 arrest, increase in sub-G 1 fraction or p21 protein induction. Clonogenic assays showed radiosensitization in two lines harboring p53 mutations, with enhancement ratios (± SE) of 1.5 (± 0.2) and 1.3 (± 0.1), respectively. There was no radiopotentiating effect in two cell lines with wild-type p53, but knockdown of wild-type p53 resulted in radiosensitization by PB. Conclusions: Phenylbutyrate can produce p21-independent cytostasis, and enhances radiation sensitivity in p53 mutant human glioblastoma cells in vitro. This suggests the potential application of combined PB and radiotherapy in glioblastoma harboring mutant p53
17. Dwarfism and early death in mice lacking C-type natriuretic peptide
Science.gov (United States)
Chusho, Hideki; Tamura, Naohisa; Ogawa, Yoshihiro; Yasoda, Akihiro; Suda, Michio; Miyazawa, Takashi; Nakamura, Kenji; Nakao, Kazuki; Kurihara, Tatsuya; Komatsu, Yasato; Itoh, Hiroshi; Tanaka, Kiyoshi; Saito, Yoshihiko; Katsuki, Motoya; Nakao, Kazuwa
2001-01-01
Longitudinal bone growth is determined by endochondral ossification that occurs as chondrocytes in the cartilaginous growth plate undergo proliferation, hypertrophy, cell death, and osteoblastic replacement. The natriuretic peptide family consists of three structurally related endogenous ligands, atrial, brain, and C-type natriuretic peptides (ANP, BNP, and CNP), and is thought to be involved in a variety of homeostatic processes. To investigate the physiological significance of CNP in vivo, we generated mice with targeted disruption of CNP (Nppc−/− mice). The Nppc−/− mice show severe dwarfism as a result of impaired endochondral ossification. They are all viable perinatally, but less than half can survive during postnatal development. The skeletal phenotypes are histologically similar to those seen in patients with achondroplasia, the most common genetic form of human dwarfism. Targeted expression of CNP in the growth plate chondrocytes can rescue the skeletal defect of Nppc−/− mice and allow their prolonged survival. This study demonstrates that CNP acts locally as a positive regulator of endochondral ossification in vivo and suggests its pathophysiological and therapeutic implication in some forms of skeletal dysplasia. PMID:11259675
18. Flare-induced MHD disturbances in the corona--Moreton waves and type II shocks
International Nuclear Information System (INIS)
Uchida, Y.
1972-01-01
The propagation in the corona of the magnetohydrodynamic (MHD) disturbance possibly emitted at the explosive stage in the initial phase of a flare is considered. The behavior of the MHD fast-mode wavefront, whose source is located at the flare, is calculated by using eiconal-characteristic method in the High Altitude Observatory (HAO) realistic models of coronal magnetic field and density for the days of some particular flare events. It is shown as the result that the peculiar behavior of Moreton' s surface wave and the peculiar appearance in the shape and position of the type II burst sources can be consistently understood by considering the refraction, focussing, and fermation of shocks of MHD fast-mode disturbance in the actual distribution of Alfven velocity in the corona. Based on some comparison of the positions of low-Alfven-velocity regions in the corona with observed positions of type II burst sources, it is proposed that the type II burst sources may be identified with such low-Alfven-velocity regions ''illuminated'' by thus enhanced shocks. (U.S.)
19. Intification and modelling of flight characteristics for self-build shock flyer type UAV
Science.gov (United States)
Rashid., Z. A.; Dardin, A. S. F. Syed.; Azid, A. A.; Ahmad, K. A.
2018-02-01
The development of an autonomous Unmanned Aerial Vehicle (UAV) requires a fundamentals studies of the UAV's flight characteristic. The aim of this study is to identify and model the flight characteristic of a conventional fixed-wing type UAV. Subsequence to this, the mode of flight of the UAV can be investigated. One technique to identify the characteristic of a UAV is a flight test where it required specific maneuvering to be executed while measuring the attitude sensor. In this study, a simple shock flyer type UAV was used as the aircraft. The result shows that the modeled flight characteristic has a significant relation with actual values but the fitting value is rather small. It is suggested that the future study is conducted with an improvement of the physical UAV, data filtering and better system identification methods.
20. Lack of immunogenicity of ice structuring protein type III HPLC12 preparation administered by the oral route to human volunteers
DEFF Research Database (Denmark)
Crevel, R W R; Cooper, K J; Poulsen, Lars K.
2007-01-01
Before a novel protein can be used in foods, its potential allergenicity must be assessed. In this study, healthy volunteers consumed ice structuring protein (ISP) Type III preparation or a control material 5 days a week for a total of 8 weeks. General measures of health were recorded during...... background against which to interpret the results. Nevertheless, the absence of an immune response using a protocol which could have been expected to result in a response with a strongly immunogenic protein, confirms the conclusions of earlier published work, and attests to the lack of allergenicity of ISP...
1. Fast magnetic reconnection supported by sporadic small-scale Petschek-type shocks
International Nuclear Information System (INIS)
Shibayama, Takuya; Nakabou, Takashi; Kusano, Kanya; Miyoshi, Takahiro; Vekstein, Grigory
2015-01-01
Standard magnetohydrodynamic (MHD) theory predicts reconnection rate that is far too slow to account for a wide variety of reconnection events observed in space and laboratory plasmas. Therefore, it was commonly accepted that some non-MHD (kinetic) effects play a crucial role in fast reconnection. A recently renewed interest in simple MHD models is associated with the so-called plasmoid instability of reconnecting current sheets. Although it is now evident that this effect can significantly enhance the rate of reconnection, many details of the underlying multiple-plasmoid process still remain controversial. Here, we report results of a high-resolution computer simulation which demonstrate that fast albeit intermittent magnetic reconnection is sustained by numerous small-scale Petschek-type shocks spontaneously formed in the current sheet due to its plasmoid instability
2. Fast magnetic reconnection supported by sporadic small-scale Petschek-type shocks
Energy Technology Data Exchange (ETDEWEB)
Shibayama, Takuya, E-mail: [email protected]; Nakabou, Takashi [Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601 (Japan); Kusano, Kanya [Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601 (Japan); Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Kanazawa-ku, Yokohama, Kanagawa 236-0001 (Japan); Miyoshi, Takahiro [Department of Physical Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan); Vekstein, Grigory [Jodrell Bank Centre for Astrophysics, University of Manchester, Manchester M13 9PL (United Kingdom)
2015-10-15
Standard magnetohydrodynamic (MHD) theory predicts reconnection rate that is far too slow to account for a wide variety of reconnection events observed in space and laboratory plasmas. Therefore, it was commonly accepted that some non-MHD (kinetic) effects play a crucial role in fast reconnection. A recently renewed interest in simple MHD models is associated with the so-called plasmoid instability of reconnecting current sheets. Although it is now evident that this effect can significantly enhance the rate of reconnection, many details of the underlying multiple-plasmoid process still remain controversial. Here, we report results of a high-resolution computer simulation which demonstrate that fast albeit intermittent magnetic reconnection is sustained by numerous small-scale Petschek-type shocks spontaneously formed in the current sheet due to its plasmoid instability.
3. δ- and δ'-shock wave types of singular solutions of systems of conservation laws and transport and concentration processes
International Nuclear Information System (INIS)
Shelkovich, V M
2008-01-01
This is a survey of some results and problems connected with the theory of generalized solutions of quasi-linear conservation law systems which can admit delta-shaped singularities. They are the so-called δ-shock wave type solutions and the recently introduced δ (n) -shock wave type solutions, n=1,2,..., which cannot be included in the classical Lax-Glimm theory. The case of δ- and δ'-shock waves is analyzed in detail. A specific analytical technique is developed to deal with such solutions. In order to define them, some special integral identities are introduced which extend the concept of weak solution, and the Rankine-Hugoniot conditions are derived. Solutions of Cauchy problems are constructed for some typical systems of conservation laws. Also investigated are multidimensional systems of conservation laws (in particular, zero-pressure gas dynamics systems) which admit δ-shock wave type solutions. A geometric aspect of such solutions is considered: they are connected with transport and concentration processes, and the balance laws of transport of 'volume' and 'area' to δ- and δ'-shock fronts are derived for them. For a 'zero-pressure gas dynamics' system these laws are the mass and momentum transport laws. An algebraic aspect of these solutions is also considered: flux-functions are constructed for them which, being non-linear, are nevertheless uniquely defined Schwartz distributions. Thus, a singular solution of the Cauchy problem generates algebraic relations between its components (distributions).
4. Dispersive shock waves in systems with nonlocal dispersion of Benjamin-Ono type
Science.gov (United States)
El, G. A.; Nguyen, L. T. K.; Smyth, N. F.
2018-04-01
We develop a general approach to the description of dispersive shock waves (DSWs) for a class of nonlinear wave equations with a nonlocal Benjamin-Ono type dispersion term involving the Hilbert transform. Integrability of the governing equation is not a pre-requisite for the application of this method which represents a modification of the DSW fitting method previously developed for dispersive-hydrodynamic systems of Korteweg-de Vries (KdV) type (i.e. reducible to the KdV equation in the weakly nonlinear, long wave, unidirectional approximation). The developed method is applied to the Calogero-Sutherland dispersive hydrodynamics for which the classification of all solution types arising from the Riemann step problem is constructed and the key physical parameters (DSW edge speeds, lead soliton amplitude, intermediate shelf level) of all but one solution type are obtained in terms of the initial step data. The analytical results are shown to be in excellent agreement with results of direct numerical simulations.
5. Lack of the nucleoside transporter ENT1 results in the Augustine-null blood type and ectopic mineralization.
Science.gov (United States)
Daniels, Geoff; Ballif, Bryan A; Helias, Virginie; Saison, Carole; Grimsley, Shane; Mannessier, Lucienne; Hustinx, Hein; Lee, Edmond; Cartron, Jean-Pierre; Peyrard, Thierry; Arnaud, Lionel
2015-06-04
The Augustine-negative alias At(a-) blood type, which seems to be restricted to people of African ancestry, was identified half a century ago but remains one of the last blood types with no known genetic basis. Here we report that a nonsynonymous single nucleotide polymorphism in SLC29A1 (rs45458701) is responsible for the At(a-) blood type. The resulting p.Glu391Lys variation in the last extracellular loop of the equilibrative nucleoside transporter 1 (ENT1; also called SLC29a1) is known not to alter its ability to transport nucleosides and nucleoside analog drugs. Furthermore, we identified 3 individuals of European ancestry who are homozygous for a null mutation in SLC29A1 (c.589+1G>C) and thus have the Augustine-null blood type. These individuals lacking ENT1 exhibit periarticular and ectopic mineralization, which confirms an important role for ENT1/SLC29A1 in human bone homeostasis as recently suggested by the skeletal phenotype of aging Slc29a1(-/-) mice. Our results establish Augustine as a new blood group system and place SLC29A1 as a new candidate gene for idiopathic disorders characterized with ectopic calcification/mineralization. © 2015 by The American Society of Hematology.
6. Proteasome-mediated degradation of integral inner nuclear membrane protein emerin in fibroblasts lacking A-type lamins
International Nuclear Information System (INIS)
Muchir, Antoine; Massart, Catherine; Engelen, Baziel G. van; Lammens, Martin; Bonne, Gisele; Worman, Howard J.
2006-01-01
We previously identified and characterized a homozygous LMNA nonsense mutation leading to the absence of A-type lamins in a premature neonate who died at birth. We show here that the absence of A-type lamins is due to degradation of the aberrant mRNA transcript with a premature termination codon. In cultured fibroblasts from the subject with the homozygous LMNA nonsense mutation, there was a decreased steady-state expression of the integral inner nuclear membrane proteins emerin and nesprin-1α associated with their mislocalization to the bulk endoplasmic reticulum and a hyperphosphorylation of emerin. To determine if decreased emerin expression occurred post-translationally, we treated cells with a selective proteasome inhibitor and observed an increase in expression. Our results show that mislocalization of integral inner nuclear membrane proteins to the endoplasmic reticulum in human cells lacking A-type lamins leads to their degradation and provides the first evidence that their degradation is mediated by the proteasome
7. Alterations in gene expression in mutant amyloid precursor protein transgenic mice lacking Niemann-Pick type C1 protein.
Directory of Open Access Journals (Sweden)
Mahua Maulik
Full Text Available Niemann-Pick type C (NPC disease, a rare autosomal recessive disorder caused mostly by mutation in NPC1 gene, is pathologically characterized by the accumulation of free cholesterol in brain and other tissues. This is accompanied by gliosis and loss of neurons in selected brain regions, including the cerebellum. Recent studies have shown that NPC disease exhibits intriguing parallels with Alzheimer's disease, including the presence of neurofibrillary tangles and increased levels of amyloid precursor protein (APP-derived β-amyloid (Aβ peptides in vulnerable brain neurons. To evaluate the role of Aβ in NPC disease, we determined the gene expression profile in selected brain regions of our recently developed bigenic ANPC mice, generated by crossing APP transgenic (Tg mice with heterozygous Npc1-deficient mice. The ANPC mice exhibited exacerbated neuronal and glial pathology compared to other genotypes [i.e., APP-Tg, double heterozygous (Dhet, Npc1-null and wild-type mice]. Analysis of expression profiles of 86 selected genes using real-time RT-PCR arrays showed a wide-spectrum of alterations in the four genotypes compared to wild-type controls. The changes observed in APP-Tg and Dhet mice are limited to only few genes involved mostly in the regulation of cholesterol metabolism, whereas Npc1-null and ANPC mice showed alterations in the expression profiles of a number of genes regulating cholesterol homeostasis, APP metabolism, vesicular trafficking and cell death mechanism in both hippocampus and cerebellum compared to wild-type mice. Intriguingly, ANPC and Npc1-null mice, with some exceptions, exhibited similar changes, although more genes were differentially expressed in the affected cerebellum than the relatively spared hippocampus. The altered gene profiles were found to match with the corresponding protein levels. These results suggest that lack of Npc1 protein can alter the expression profile of selected transcripts as well as proteins, and
8. Lack of Association between SLC30A8 Variants and Type 2 Diabetes in Mexican American Families
Directory of Open Access Journals (Sweden)
Hemant Kulkarni
2016-01-01
Full Text Available SLC30A8 encodes zinc transporter 8 which is involved in packaging and release of insulin. Evidence for the association of SLC30A8 variants with type 2 diabetes (T2D is inconclusive. We interrogated single nucleotide polymorphisms (SNPs around SLC30A8 for association with T2D in high-risk, pedigreed individuals from extended Mexican American families. This study of 118 SNPs within 50 kb of the SLC30A8 locus tested the association with eight T2D-related traits at four levels: (i each SNP using measured genotype approach (MGA; (ii interaction of SNPs with age and sex; (iii combinations of SNPs using Bayesian Quantitative Trait Nucleotide (BQTN analyses; and (iv entire gene locus using the gene burden test. Only one SNP (rs7817754 was significantly associated with incident T2D but a summary statistic based on all T2D-related traits identified 11 novel SNPs. Three SNPs and one SNP were weakly but interactively associated with age and sex, respectively. BQTN analyses could not demonstrate any informative combination of SNPs over MGA. Lastly, gene burden test results showed that at best the SLC30A8 locus could account for only 1-2% of the variability in T2D-related traits. Our results indicate a lack of association of the SLC30A8 SNPs with T2D in Mexican American families.
9. The stress protein heat shock cognate 70 (Hsc70) inhibits the Transient Receptor Potential Vanilloid type 1 (TRPV1) channel.
Science.gov (United States)
Iftinca, Mircea; Flynn, Robyn; Basso, Lilian; Melo, Helvira; Aboushousha, Reem; Taylor, Lauren; Altier, Christophe
2016-01-01
Specialized cellular defense mechanisms prevent damage from chemical, biological, and physical hazards. The heat shock proteins have been recognized as key chaperones that maintain cell survival against a variety of exogenous and endogenous stress signals including noxious temperature. However, the role of heat shock proteins in nociception remains poorly understood. We carried out an expression analysis of the constitutively expressed 70 kDa heat-shock cognate protein, a member of the stress-induced HSP70 family in lumbar dorsal root ganglia from a mouse model of Complete Freund's Adjuvant-induced chronic inflammatory pain. We used immunolabeling of dorsal root ganglion neurons, behavioral analysis and patch clamp electrophysiology in both dorsal root ganglion neurons and HEK cells transfected with Hsc70 and Transient Receptor Potential Channels to examine their functional interaction in heat shock stress condition. We report an increase in protein levels of Hsc70 in mouse dorsal root ganglia, 3 days post Complete Freund's Adjuvant injection in the hind paw. Immunostaining of Hsc70 was observed in most of the dorsal root ganglion neurons, including the small size nociceptors immunoreactive to the TRPV1 channel. Standard whole-cell patch-clamp technique was used to record Transient Receptor Potential Vanilloid type 1 current after exposure to heat shock. We found that capsaicin-evoked currents are inhibited by heat shock in dorsal root ganglion neurons and transfected HEK cells expressing Hsc70 and TRPV1. Blocking Hsc70 with matrine or spergualin compounds prevented heat shock-induced inhibition of the channel. We also found that, in contrast to TRPV1, both the cold sensor channels TRPA1 and TRPM8 were unresponsive to heat shock stress. Finally, we show that inhibition of TRPV1 depends on the ATPase activity of Hsc70 and involves the rho-associated protein kinase. Our work identified Hsc70 and its ATPase activity as a central cofactor of TRPV1 channel function
10. Investigation on Mie-Grüneisen type shock Hugoniot equation of state for concrete
Directory of Open Access Journals (Sweden)
M Katayama
2017-09-01
Full Text Available This paper ascertains that the bilinear shock Hugoniot equation of state (EOS can model the plasticizing process of the porous media like concrete material for high-velocity impact problems successfully. The negative slope of the bilinear Hugoniot for low particle velocity regime can simulate the process that the porosity of concrete may be compressed to form shock wave in concrete, through a series of numerical analyses over the investigation on the physical phenomena. The results of particle velocity for the concrete material are also discussed to be compared with those of non-porous aluminum alloy for 100 and 1000 m/s impact velocities. All the numerical simulations were carried out by applying the bilinear shock Hugoniot EOS to concrete which was linked to the binary object of a hydrocode: ANSYS Autodyn®[1−3] through a user’s subroutine.
11. Low Intensity Extracorporeal Shock Wave Therapy Improves Erectile Function in a Model of Type II Diabetes Independently of NO/cGMP Pathway.
Science.gov (United States)
Assaly-Kaddoum, Rana; Giuliano, François; Laurin, Miguel; Gorny, Diane; Kergoat, Micheline; Bernabé, Jacques; Vardi, Yoram; Alexandre, Laurent; Behr-Roussel, Delphine
2016-09-01
Erectile dysfunction is highly prevalent in type II diabetes mellitus. Low intensity extracorporeal shock wave therapy improves erectile function in patients with erectile dysfunction of vasculogenic origin, including diabetes. However, its mode of action remains unknown. We investigated the effects of low intensity extracorporeal shock wave therapy compared to or combined with sildenafil on erectile dysfunction in a type II diabetes mellitus model. Our purpose was to test our hypothesis of a mode of action targeting the cavernous nitric oxide/cyclic guanosine monophosphate pathway. GK rats, a validated model of type II diabetes mellitus, and age matched Wistar rats were treated with low intensity extracorporeal shock wave therapy twice weekly for 3 weeks. Treatment was repeated after a 3-week no-treatment interval. The penis was stretched and dipped in a specifically designed water-filled cage. Shock waves were delivered by a calibrated probe yielding a controlled energy flux density (0.09 mJ/mm(2)). The probe was attached to an electrohydraulic unit with a focused shock wave source, allowing for accurate extrapolation to humans. Following a 4-week washout period erectile function was assessed as well as endothelium dependent and independent, and nitrergic relaxations of the corpus cavernosum of GK rats. Low intensity extracorporeal shock wave therapy significantly improved erectile function in GK rats to the same extent as sildenafil. Treatment effects were potentiated when combined with sildenafil. Shock wave effects were not associated with improved cavernous endothelium dependent or independent, or nitrergic reactivity. Low intensity extracorporeal shock wave therapy improved erectile function in GK rats. Unexpectedly, this was not mediated by a nitric oxide/cyclic guanosine monophosphate dependent mechanism. Sildenafil increased shock wave efficacy. This preclinical paradigm to deliver low intensity extracorporeal shock wave therapy to the rat penis should
12. Lack of effect of intermittently administered sodium fusidate in patients with newly diagnosed type 1 diabetes mellitus: the FUSIDM trial
DEFF Research Database (Denmark)
Conget, I; Aguilera, E; Pellitero, S
2005-01-01
We evaluated in a double-blind study the effect of early treatment with the immunomodulatory drug fusidin in patients with newly diagnosed type 1 diabetes mellitus.......We evaluated in a double-blind study the effect of early treatment with the immunomodulatory drug fusidin in patients with newly diagnosed type 1 diabetes mellitus....
13. Serious clopidogrel associated renal hematoma in a type 2 diabetic patient with primary hyperparathyroidism after extracorporeal shock wave lithotripsy
International Nuclear Information System (INIS)
Bahceci, Mithat; Tuzcu, Alpaslan; Agil, Cuneyt; Akay, Ferruh; Akay, Hatice
2005-01-01
Renal hematoma after extracorporeal shock wave lithotripsy SWL is a rare complication. We report a case of a large renal hematoma following SWL that resulted in nephrectomy in a type 2 diabetic patient with primary hyperparathyroidism using clopidogrel due to coronary heart disease CHD. Although it was claimed that preoperative use of clopidogrel was not associated with increased bleeding, all patients who are scheduled for SWL should be interrogated in terms of using of platelet aggregation inhibitors such as clopidogrel, and these drugs should be interrupted appropriately before undergoing SWL. (author)
14. NRC Information No. 89-86: Type HK circuit breakers missing close latch anti-shock springs
International Nuclear Information System (INIS)
Rossi, C.E.
1992-01-01
During the recent refueling outage at Fermi Unit 2, the licensee inspected both safety-related and non-safety-related Type HK circuit breakers. The close latch anti-shock springs were observed to be missing in approximately 40 safety-related Type HK circuit breakers that had been manufactured outside of the previously identified timeframes. (The identified circuit breakers were manufactured in 1974.) Thus, the timeframes previously identified by the manufacturer (prior to 1973 and from June 1975 to June 1977) may not be totally inclusive. In addition, because of changes in corporate name, mergers, etc., Type HK circuit breakers may indicate manufacture by ITE, ITE Imperial, Gould, Brown Boveri, or a combination thereof. The current name of the manufacturer is ASEA Brown Boveri. Recipients may need to be cognizant of this when determining whether they utilize potentially affected equipment
15. Lack of an association of miR-938 SNP in IDDM10 with human type 1 diabetes
Directory of Open Access Journals (Sweden)
Mi Xiaofan
2011-10-01
Full Text Available Abstract MicroRNAs (miRNAs are a newly discovered type of small non-protein coding RNA that function in the inhibition of effective mRNA translation, and may serve as susceptibility genes for various disease developments. The SNP rs12416605, located in human type 1 diabetes IDDM10 locus, changes the seeding sequence (UGU[G/A]CCC of miRNA miR-938 and potentially alters miR-938 targets, including IL-16 and IL-17A. In an attempt to test whether miR-938 may be a susceptibility gene for IDDM10, we assessed the possible association of the miR-938 SNP with T1D in an American Caucasian cohort of 622 patients and 723 healthy controls by TaqMan assay. Our current data do not support the association between the SNP in miR-938 and type 1 diabetes.
16. Magnetite Compensates for the Lack of a Pilin-Associated c-Type Cytochrome in Extracellular Electron Exchange
DEFF Research Database (Denmark)
Liu, Fanghua; Rotaru, Amelia-Elena; Shrestha, Pravin
2015-01-01
investigation revealed that magnetite attached to the electrically conductive pili of Geobacter species in a manner reminiscent of the association of the multi-heme c-type cytochrome OmcS with the pili of Geobacter sulfurreducens. Magnetite conferred extracellular electron capabilities on an Omc...
17. Normal viability and altered pharmacokinetics in mice lacking mdr1-type (drug-transporting) P-glycoproteins
NARCIS (Netherlands)
Schinkel, A. H.; Mayer, U.; Wagenaar, E.; Mol, C. A.; van Deemter, L.; Smit, J. J.; van der Valk, M. A.; Voordouw, A. C.; Spits, H.; van Tellingen, O.; Zijlmans, J. M.; Fibbe, W. E.; Borst, P.
1997-01-01
The mdr1-type P-glycoproteins (P-gps) confer multidrug resistance to cancer cells by active extrusion of a wide range of drugs from the cell. To study their physiological roles, we have generated mice genetically deficient in the mdr1b gene [mdr1b (-/-) mice] and in both the mdr1a and mdr1b genes
18. Vitamin B-12 deficiency and the lack of its consequences in type 2 diabetes patients using metformin
NARCIS (Netherlands)
de Groot-Kamphuis, D. M.; van Dijk, P. R.; Groenier, K. H.; Houweling, Sebastiaan; Bilo, H. J. G.; Kleefstra, N.
Objectives: To study vitamin B-12 concentrations in patients with type 2 diabetes with and without metformin use and to identify risk factors and consequences of low vitamin B-12 concentrations. Research design and methods: This study had a cross-sectional design. During eight weeks all patients
19. Vitamin B12 deficiency and the lack of its consequences in type 2 diabetes patients using metformin
NARCIS (Netherlands)
de Groot-Kamphuis, D M; van Dijk, P R; Groenier, K H; Houweling, S T; Bilo, H J G; Kleefstra, N
OBJECTIVES: To study vitamin B12 concentrations in patients with type 2 diabetes with and without metformin use and to identify risk factors and consequences of low vitamin B12 concentrations. RESEARCH DESIGN AND METHODS: This study had a cross-sectional design. During eight weeks all patients with
20. FLARE-GENERATED SHOCK WAVE PROPAGATION THROUGH SOLAR CORONAL ARCADE LOOPS AND AN ASSOCIATED TYPE II RADIO BURST
Energy Technology Data Exchange (ETDEWEB)
Kumar, Pankaj; Cho, Kyung-Suk [Korea Astronomy and Space Science Institute (KASI), Daejeon, 305-348 (Korea, Republic of); Innes, D. E., E-mail: [email protected] [Max-Planck Institut für Sonnensystemforschung, D-37077 Göttingen (Germany)
2016-09-01
This paper presents multiwavelength observations of a flare-generated type II radio burst. The kinematics of the shock derived from the type II burst closely match a fast extreme ultraviolet (EUV) wave seen propagating through coronal arcade loops. The EUV wave was closely associated with an impulsive M1.0 flare without a related coronal mass ejection, and was triggered at one of the footpoints of the arcade loops in active region NOAA 12035. It was initially observed in the 335 Å images from the Atmospheric Image Assembly with a speed of ∼800 km s{sup −1} and it accelerated to ∼1490 km s{sup −1} after passing through the arcade loops. A fan–spine magnetic topology was revealed at the flare site. A small, confined filament eruption (∼340 km s{sup −1}) was also observed moving in the opposite direction to the EUV wave. We suggest that breakout reconnection in the fan–spine topology triggered the flare and associated EUV wave that propagated as a fast shock through the arcade loops.
1. FLARE-GENERATED SHOCK WAVE PROPAGATION THROUGH SOLAR CORONAL ARCADE LOOPS AND AN ASSOCIATED TYPE II RADIO BURST
International Nuclear Information System (INIS)
Kumar, Pankaj; Cho, Kyung-Suk; Innes, D. E.
2016-01-01
This paper presents multiwavelength observations of a flare-generated type II radio burst. The kinematics of the shock derived from the type II burst closely match a fast extreme ultraviolet (EUV) wave seen propagating through coronal arcade loops. The EUV wave was closely associated with an impulsive M1.0 flare without a related coronal mass ejection, and was triggered at one of the footpoints of the arcade loops in active region NOAA 12035. It was initially observed in the 335 Å images from the Atmospheric Image Assembly with a speed of ∼800 km s −1 and it accelerated to ∼1490 km s −1 after passing through the arcade loops. A fan–spine magnetic topology was revealed at the flare site. A small, confined filament eruption (∼340 km s −1 ) was also observed moving in the opposite direction to the EUV wave. We suggest that breakout reconnection in the fan–spine topology triggered the flare and associated EUV wave that propagated as a fast shock through the arcade loops.
2. Mice deficient in 11beta-hydroxysteroid dehydrogenase type 1 lack bone marrow adipocytes, but maintain normal bone formation
DEFF Research Database (Denmark)
Justesen, Jeannette; Mosekilde, Lis; Holmes, Megan
2004-01-01
Glucocorticoids (GCs) exert potent, but poorly characterized, effects on the skeleton. The cellular activity of GCs is regulated at a prereceptor level by 11beta-hydroxysteroid dehydrogenases (11betaHSDs). The type 1 isoform, which predominates in bone, functions as a reductase in intact cells...... and regenerates active cortisol (corticosterone) from circulating inert 11-keto forms. The aim of the present study was to investigate the role of this intracrine activation of GCs on normal bone physiology in vivo using mice deficient in 11betaHSD1 (HSD1(-/-)). The HSD1(-/-) mice exhibited no significant changes...... in cortical or trabecular bone mass compared with wild-type (Wt) mice. Aged HSD1(-/-) mice showed age-related bone loss similar to that observed in Wt mice. Histomorphometric analysis showed similar bone formation and bone resorption parameters in HSD1(-/-) and Wt mice. However, examination of bone marrow...
3. Lack of association of colonic epithelium telomere length and oxidative DNA damage in Type 2 diabetes under good metabolic control
Directory of Open Access Journals (Sweden)
Kennedy Hugh
2008-10-01
Full Text Available Abstract Background Telomeres are DNA repeat sequences necessary for DNA replication which shorten at cell division at a rate directly related to levels of oxidative stress. Critical telomere shortening predisposes to cell senescence and to epithelial malignancies. Type 2 diabetes is characterised by increased oxidative DNA damage, telomere attrition, and an increased risk of colonic malignancy. We hypothesised that the colonic mucosa in Type 2 diabetes would be characterised by increased DNA damage and telomere shortening. Methods We examined telomere length (by flow fluorescent in situ hybridization and oxidative DNA damage (flow cytometry of 8 – oxoguanosine in the colonic mucosal cells of subjects with type 2 diabetes (n = 10; mean age 62.2 years, mean HbA1c 6.9% and 22 matched control subjects. No colonic pathology was apparent in these subjects at routine gastrointestinal investigations. Results Mean colonic epithelial telomere length in the diabetes group was not significantly different from controls (10.6 [3.6] vs. 12.1 [3.4] Molecular Equivalent of Soluble Fluorochrome Units [MESF]; P = 0.5. Levels of oxidative DNA damage were similar in both T2DM and control groups (2.6 [0.6] vs. 2.5 [0.6] Mean Fluorescent Intensity [MFI]; P = 0.7. There was no significant relationship between oxidative DNA damage and telomere length in either group (both p > 0.1. Conclusion Colonic epithelium in Type 2 diabetes does not differ significantly from control colonic epithelium in oxidative DNA damage or telomere length. There is no evidence in this study for increased oxidative DNA damage or significant telomere attrition in colonic mucosa as a carcinogenic mechanism.
4. Lack of evidence for intertypic recombinants in the pathogenesis of recurrent genital infections with herpes simplex virus type 1.
Science.gov (United States)
Fife, K H; Boggs, D
1986-01-01
Clinical observations indicate that herpes simplex virus type 1 (HSV-1) is significantly less likely than herpes simplex virus type 2 (HSV-2) to establish latency in (or reactivate from) sacral ganglionic tissue. In an effort to identify viral functions associated with latency, we analyzed HSV-1 isolates from three patients with established recurrent genital herpes and sought evidence of DNA sequences and proteins similar to those found in HSV-2. By restriction endonuclease cleavage patterns and by DNA hybridization analysis using either whole HSV-2 DNA or several cloned segments of HSV-2 DNA as probes, we found that the three HSV-1 isolates from patients with recurrent genital herpes showed no unusual homology to HSV-2 as compared with other HSV-1 isolates. Similarly, the proteins of these isolates could not be distinguished from those of other HSV-1 isolates and were distinct from those of HSV-2. At this level of resolution, there was no evidence to suggest that these recurrent genital HSV-1 isolates were intertypic recombinants, nor did they show any other unusual similarity to HSV-2.
5. Lack of significant metabolic abnormalities in mice with liver-specific disruption of 11β-hydroxysteroid dehydrogenase type 1.
LENUS (Irish Health Repository)
Lavery, Gareth G
2012-07-01
Glucocorticoids (GC) are implicated in the development of metabolic syndrome, and patients with GC excess share many clinical features, such as central obesity and glucose intolerance. In patients with obesity or type 2 diabetes, systemic GC concentrations seem to be invariably normal. Tissue GC concentrations determined by the hypothalamic-pituitary-adrenal (HPA) axis and local cortisol (corticosterone in mice) regeneration from cortisone (11-dehydrocorticosterone in mice) by the 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) enzyme, principally expressed in the liver. Transgenic mice have demonstrated the importance of 11β-HSD1 in mediating aspects of the metabolic syndrome, as well as HPA axis control. In order to address the primacy of hepatic 11β-HSD1 in regulating metabolism and the HPA axis, we have generated liver-specific 11β-HSD1 knockout (LKO) mice, assessed biomarkers of GC metabolism, and examined responses to high-fat feeding. LKO mice were able to regenerate cortisol from cortisone to 40% of control and had no discernible difference in a urinary metabolite marker of 11β-HSD1 activity. Although circulating corticosterone was unaltered, adrenal size was increased, indicative of chronic HPA stimulation. There was a mild improvement in glucose tolerance but with insulin sensitivity largely unaffected. Adiposity and body weight were unaffected as were aspects of hepatic lipid homeostasis, triglyceride accumulation, and serum lipids. Additionally, no changes in the expression of genes involved in glucose or lipid homeostasis were observed. Liver-specific deletion of 11β-HSD1 reduces corticosterone regeneration and may be important for setting aspects of HPA axis tone, without impacting upon urinary steroid metabolite profile. These discordant data have significant implications for the use of these biomarkers of 11β-HSD1 activity in clinical studies. The paucity of metabolic abnormalities in LKO points to important compensatory effects by HPA
6. Lack of impact of low-dose acetylsalicylic acid on kidney function in type 1 diabetic patients with microalbuminuria
DEFF Research Database (Denmark)
Hansen, H P; Gaede, P H; Jensen, B R
2000-01-01
to be elucidated. RESEARCH DESIGN AND METHODS: We performed a randomized double-blind crossover trial in 17 type 1 diabetic patients with microalbuminuria (urinary AER 30-300 mg/24 h). Patients were given ASA (150 mg/daily) for 4 weeks followed by placebo for 4 weeks with at least a 2-week washout period in random...... order. At the end of each treatment period, AER (enzyme-linked immunosorbent assay), glomerular filtration rate (GFR) (plasma clearance of 51Cr-EDTA), blood pressure (BP) (Hawksley), and HbA1c (by high-performance liquid chromatography) were measured. Patients were advised to follow a normal diabetes...... diet without sodium restriction and received their usual antihypertensive treatment during the investigation. RESULTS: During the study (ASA vs. placebo), urinary AER (geometric mean 64 [95% CI 39-105] vs. 59 [40-87] mg/24 h), GFR (mean 106 [93-118] vs. 104 [90-117] ml x min(-1) x 1.73 m(-2)), systolic...
7. Alfven shock trains
International Nuclear Information System (INIS)
Malkov, M.A.; Kennel, C.F.; Wu, C.C.; Pellat, R.; Shapiro, V.D.
1991-01-01
The Cohen--Kulsrud--Burgers equation (CKB) is used to consider the nonlinear evolution of resistive, quasiparallel Alfven waves subject to a long-wavelength, plane-polarized, monochromatic instability. The instability saturates by nonlinear steepening, which proceeds until the periodic waveform develops an interior scale length comparable to the dissipation length; a fast or an intermediate shock then forms. The result is a periodic train of Alfven shocks of one or the other type. For propagation strictly parallel to the magnetic field, there will be two shocks per instability wavelength. Numerical integration of the time-dependent CKB equation shows that an initial, small-amplitude growing wave asymptotes to a stable, periodic stationary wave whose analytic solution specifies how the type of shock embedded in the shock train, and the amplitude and speed of the shock train, depend on the strength and phase of the instability. Waveforms observed upstream of the Earth's bowshock and cometary shocks resemble those calculated here
8. THE POSSIBLE ROLE OF CORONAL STREAMERS AS MAGNETICALLY CLOSED STRUCTURES IN SHOCK-INDUCED ENERGETIC ELECTRONS AND METRIC TYPE II RADIO BURSTS
Energy Technology Data Exchange (ETDEWEB)
Kong, Xiangliang; Chen, Yao; Feng, Shiwei; Wang, Bing; Du, Guohui [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, and Institute of Space Sciences, Shandong University, Weihai, Shandong 264209 (China); Guo, Fan [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Li, Gang, E-mail: [email protected] [Department of Space Science and CSPAR, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)
2015-01-10
Two solar type II radio bursts, separated by ∼24 hr in time, are examined together. Both events are associated with coronal mass ejections (CMEs) erupting from the same active region (NOAA 11176) beneath a well-observed helmet streamer. We find that the type II emissions in both events ended once the CME/shock fronts passed the white-light streamer tip, which is presumably the magnetic cusp of the streamer. This leads us to conjecture that the closed magnetic arcades of the streamer may play a role in electron acceleration and type II excitation at coronal shocks. To examine such a conjecture, we conduct a test-particle simulation for electron dynamics within a large-scale partially closed streamer magnetic configuration swept by a coronal shock. We find that the closed field lines play the role of an electron trap via which the electrons are sent back to the shock front multiple times and therefore accelerated to high energies by the shock. Electrons with an initial energy of 300 eV can be accelerated to tens of keV concentrating at the loop apex close to the shock front with a counter-streaming distribution at most locations. These electrons are energetic enough to excite Langmuir waves and radio bursts. Considering the fact that most solar eruptions originate from closed field regions, we suggest that the scenario may be important for the generation of more metric type IIs. This study also provides an explanation of the general ending frequencies of metric type IIs at or above 20-30 MHz and the disconnection issue between metric and interplanetary type IIs.
9. Alpha-crystallin-type heat shock proteins: socializing minichaperones in the context of a multichaperone network.
Science.gov (United States)
Narberhaus, Franz
2002-03-01
Alpha-crystallins were originally recognized as proteins contributing to the transparency of the mammalian eye lens. Subsequently, they have been found in many, but not all, members of the Archaea, Bacteria, and Eucarya. Most members of the diverse alpha-crystallin family have four common structural and functional features: (i) a small monomeric molecular mass between 12 and 43 kDa; (ii) the formation of large oligomeric complexes; (iii) the presence of a moderately conserved central region, the so-called alpha-crystallin domain; and (iv) molecular chaperone activity. Since alpha-crystallins are induced by a temperature upshift in many organisms, they are often referred to as small heat shock proteins (sHsps) or, more accurately, alpha-Hsps. Alpha-crystallins are integrated into a highly flexible and synergistic multichaperone network evolved to secure protein quality control in the cell. Their chaperone activity is limited to the binding of unfolding intermediates in order to protect them from irreversible aggregation. Productive release and refolding of captured proteins into the native state requires close cooperation with other cellular chaperones. In addition, alpha-Hsps seem to play an important role in membrane stabilization. The review compiles information on the abundance, sequence conservation, regulation, structure, and function of alpha-Hsps with an emphasis on the microbial members of this chaperone family.
10. R5 strains of human immunodeficiency virus type 1 from rapid progressors lacking X4 strains do not possess X4-type pathogenicity in human thymus
NARCIS (Netherlands)
Berkowitz, R. D.; van't Wout, A. B.; Kootstra, N. A.; Moreno, M. E.; Linquist-Stepps, V. D.; Bare, C.; Stoddart, C. A.; Schuitemaker, H.; McCune, J. M.
1999-01-01
Some individuals infected with only R5 strains of human immunodeficiency virus type 1 progress to AIDS as quickly as individuals harboring X4 strains. We determined that three R5 viruses were much less pathogenic than an X4 virus in SCID-hu Thy/Liv mice, suggesting that R5 virus-mediated rapid
11. Deletion of the Thyroid Hormone-Activating Type 2 Deiodinase Rescues Cone Photoreceptor Degeneration but Not Deafness in Mice Lacking Type 3 Deiodinase.
Science.gov (United States)
Ng, Lily; Liu, Hong; St Germain, Donald L; Hernandez, Arturo; Forrest, Douglas
2017-06-01
Type 2 deiodinase amplifies and type 3 deiodinase depletes levels of the active form of thyroid hormone, triiodothyronine. Given the opposing activities of these enzymes, we tested the hypothesis that they counteract each other's developmental functions by investigating whether deletion of type 2 deiodinase (encoded by Dio2) modifies sensory phenotypes in type 3 deiodinase-deficient (Dio3-/-) mice. Dio3-/- mice display degeneration of retinal cones, the photoreceptors that mediate daylight and color vision. In Dio2-/- mice, cone function was largely normal but deletion of Dio2 in Dio3-/- mice markedly recovered cone numbers and electroretinogram responses, suggesting counterbalancing roles for both enzymes in cone survival. Both Dio3-/- and Dio2-/- strains exhibit deafness with cochlear abnormalities. In Dio3-/-;Dio2-/- mice, deafness was exacerbated rather than alleviated, suggesting unevenly balanced actions by these enzymes during auditory development. Dio3-/- mice also exhibit an atrophic thyroid gland, low thyroxine, and high triiodothyronine levels, but this phenotype was ameliorated in Dio3-/-;Dio2-/- mice, indicating counterbalancing roles for the enzymes in determining the thyroid hormone status. The results suggest that the composite action of these two enzymes is a critical determinant in visual and auditory development and in setting the systemic thyroid hormone status.
12. Shock stability in systems that change type. Final grant report to the Department of Energy
International Nuclear Information System (INIS)
Keyfitz, B.L.
1995-01-01
The aim of the original project was to investigate systems of conservation laws that change type. Progress was made on this problem. During the last period of the grant, the author began an investigation of a multidimensional system related to Mach reflection which goes beyond the original work proposed. This has been fruitful direction in which to apply expertise on change of type. Some basic theoretical results have been found
13. Effect of Geranylgeranylacetone on Ultraviolet Radiation Type B-Induced Cataract in Heat-Shock Transcription Factor 1 Heterozygous Mouse.
Science.gov (United States)
Ogasawara, Satoshi; Hashizume, Kouhei; Okuno, Takashi; Imaizumi, Toshiyasu; Inomata, Yui; Tezuka, Yu; Sanbe, Atushi; Kurosaka, Daijiro
2017-05-01
We investigated whether heat-shock transcription factor 1 (HSF1) was involved in ultraviolet radiation type B (UVR-B)-induced lens opacity (cataract) using HSF1 heterozygous mice. We also examined the effects of geranylgeranylacetone (GGA), an inducer of heat-shock proteins via activation of HSF, on the UVR-B-induced cataract. Male HSF1 +/- and WT mice were unilaterally exposed to UVR-B (total: 1200mJ) at 16 weeks of age. At 48 h after the last UVR-B irradiation, the lens was isolated and the induction of the cataract was quantified as the cataract area ratio (opacity area/anterior capsule). GGA was orally administered at a dosage of 500 mg/kg once a day for two days before the first UVR-B exposure until the end of the experiment (21days in total). The HSF1 expression was more greatly decreased in the lens from HSF1 +/- mice than in that from WT mice (p B exposure could mainly induce cataracts in the anterior capsule in both HSF1 +/- and WT mice, while the opacity of the lens was markedly enhanced in HSF 1+/- mice compared to that in WT mice(p (0.01). GGA treatment could prevent the induction of lens opacity by UVR-B exposure in both WT and HSF1 +/- mice as compared with the non-administration group (p B radiation was seen in lens protein levels of αA-crystallin, αB-crystallin, or γ-crystallin with or without GGA administration among all groups of mice. In contrast to the crystallins, the lens protein level of HSP25 was decreased by UVR-B exposure in both HSF1 +/- and WT mice, and was significantly recovered in WT mice by the GGA treatment (p B-induced cataracts, possibly via regulation of HSPs such as HSP25.
14. Shock and patient preimplantation type D personality are associated with poor health status in patients with implantable cardioverter-defibrillator
DEFF Research Database (Denmark)
Pedersen, Susanne S.; Tekle, Fetene B; Hoogwegt, Madelein T
2012-01-01
Implantable cardioverter-defibrillator (ICD) shock is a critical event to patients associated with well-being after implantation, although other factors may play an equally important role. We compared the association of shock and the patient's preimplantation personality with health status, using...
15. Conversion of piston-driven shocks from powerful solar flares to blast wave shocks in the solar wind
International Nuclear Information System (INIS)
Pinter, S.
1990-01-01
It was suggested by Smart and Shea (1985) that the time of arrival of solar-flare-generated shock waves at any point in space may be predicted by assuming that they are first driven from the Sun after which they decay into blast shocks. Their study was extended by using the duration of the Type IV radio emission as a phenomenological symptom of the piston-driven phase of these shocks. Using a sample of 39 cases of combined Type II/Type IV observations from 1972 to 1982 solar flares, it was found that the average predicted times-of-arrival of these shocks to Earth (and elsewhere) deviate from the actual times by 1.40 hr with a standard deviation of 1.25 hr. On the average, a representative shock from this sample is emitted from a powerful flare with a velocity of 1,560 km sec -1 ; moves at a constant inertial velocity to a distance of 0.12 AU after which it begins to decelerate as a classical (Sedov-type) blast shock that is convected by the ambient solar wind as suggested by Smart and Shea; and arrives to Earth 45.8 hr after its initiation in the Sun. Shocks that appear to deviate from this phenomenological scenario by virtue of lack of detection on Earth are assumed to decay into fast mode MHD waves. (author). 7 figs., 1 tab., 53 refs
16. The formation of shocks and fundamental solution of a fourth-order quasilinear Boussinesq-type equation
Science.gov (United States)
Galaktionov, Victor A.
2009-02-01
As a basic higher-order model, the fourth-order Boussinesq-type quasilinear wave equation (the QWE-4) \$\\begin{equation*}\\fl u_{tt} = -(|u|^n u)_{xxxx} \\tqs in\\ \\mathbb{R} \\times \\mathbb{R}_+, \\quad with\\ exponent\\ n > 0,\\end{equation*} \$ is considered. Self-similar blow-up solutions \$\\begin{eqnarray*}\\tqs\\tqs u_-(x,t)=g(z), \\quad\\, z=\\frac x{\\sqrt{T-t}},\\\\ where\\ g\\ solved\\ the\\ ODE\\ \\frac 14 g'' z^2 + \\frac 34 g'z = -(|g|^n g)^{(4)},\\end{eqnarray*} \$ are shown to exist that generate as t → T- discontinuous shock waves. The QWE-4 is also shown to admit a smooth (for t > 0) global 'fundamental solution' \$\\begin{eqnarray*}\\fl b_n(x,t)= t^{\\frac{2}{n+4}} F_n(y),\\ y = x/t^{\\frac{n+2}{n+4}},\\ such\\ that\\ b_{n}(x,0)= 0,\\ b_{nt}(x,0)= {\\delta}(x),\\end{eqnarray*} \$ i.e. having a measure as initial data. A 'homotopic' limit n → 0 is used to get b_0(x,t)= \\sqrt t \\, F_0(x/\\sqrt t) being the classic fundamental solution of the 1D linear beam equation \\[ \\begin{equation*}u_{tt} = -u_{xxxx} \\tqs in\\ \\mathbb{R} \\times \\mathbb{R}_+.\\end{equation*} \\
17. Lack of association of the HMGA1 IVS5-13insC variant with type 2 diabetes in an ethnically diverse hypertensive case control cohort
Directory of Open Access Journals (Sweden)
Karnes Jason H
2013-01-01
Full Text Available Abstract Background Recently, the high-mobility group A1 gene (HMGA1 variant IVS5-13insC has been associated with type 2 diabetes, but reported associations are inconsistent and data are lacking in Hispanic and African American populations. We sought to investigate the HMGA1-diabetes association and to characterize IVS5-13insC allele frequencies and linkage disequilibrium (LD in 3,070 Caucasian, Hispanic, and African American patients from the INternational VErapamil SR-Trandolapril STudy (INVEST. Methods INVEST was a randomized, multicenter trial comparing two antihypertensive treatment strategies in an ethnically diverse cohort of hypertensive, coronary artery disease patients. Controls, who were diabetes-free throughout the study, and type 2 diabetes cases, either prevalent or incident, were genotyped for IVS5-13insC using Taqman®, confirmed with Pyrosequencing and Sanger sequencing. For LD analysis, genotyping for eight additional HMGA1 single nucleotide polymorphisms (SNPs was performed using the Illumina® HumanCVD BeadChip. We used logistic regression to test association of the HMGA1 IVS5-13insC and diabetes, adjusted for age, gender, body mass index, and percentage European, African, and Native American ancestry. Results We observed IVS5-13insC minor allele frequencies consistent with previous literature in Caucasians and African Americans (0.03 in cases and 0.04 in controls for both race/ethnic groups, and higher frequencies in Hispanics (0.07 in cases and 0.07 in controls. The IVS5-13insC was not associated with type 2 diabetes overall (odds ratio 0.98 [0.76-1.26], p=0.88 or in any race/ethnic group. Pairwise LD (r2 of IVS5-13insC and rs9394200, a SNP previously used as a tag SNP for IVS5-13insC, was low (r2=0.47 in Caucasians, r2=0.25 in Hispanics, and r2=0.06 in African Americans. Furthermore, in silico analysis suggested a lack of functional consequences for the IVS5-13insC variant. Conclusions Our results suggest that IVS5-13ins
18. Reactive oxygen species and transcript analysis upon excess light treatment in wild-type Arabidopsis thaliana vs a photosensitive mutant lacking zeaxanthin and lutein
Directory of Open Access Journals (Sweden)
Roncaglia Enrica
2011-04-01
Full Text Available Abstract Background Reactive oxygen species (ROS are unavoidable by-products of oxygenic photosynthesis, causing progressive oxidative damage and ultimately cell death. Despite their destructive activity they are also signalling molecules, priming the acclimatory response to stress stimuli. Results To investigate this role further, we exposed wild type Arabidopsis thaliana plants and the double mutant npq1lut2 to excess light. The mutant does not produce the xanthophylls lutein and zeaxanthin, whose key roles include ROS scavenging and prevention of ROS synthesis. Biochemical analysis revealed that singlet oxygen (1O2 accumulated to higher levels in the mutant while other ROS were unaffected, allowing to define the transcriptomic signature of the acclimatory response mediated by 1O2 which is enhanced by the lack of these xanthophylls species. The group of genes differentially regulated in npq1lut2 is enriched in sequences encoding chloroplast proteins involved in cell protection against the damaging effect of ROS. Among the early fine-tuned components, are proteins involved in tetrapyrrole biosynthesis, chlorophyll catabolism, protein import, folding and turnover, synthesis and membrane insertion of photosynthetic subunits. Up to now, the flu mutant was the only biological system adopted to define the regulation of gene expression by 1O2. In this work, we propose the use of mutants accumulating 1O2 by mechanisms different from those activated in flu to better identify ROS signalling. Conclusions We propose that the lack of zeaxanthin and lutein leads to 1O2 accumulation and this represents a signalling pathway in the early stages of stress acclimation, beside the response to ADP/ATP ratio and to the redox state of both plastoquinone pool. Chloroplasts respond to 1O2 accumulation by undergoing a significant change in composition and function towards a fast acclimatory response. The physiological implications of this signalling specificity are
19. Reactive oxygen species and transcript analysis upon excess light treatment in wild-type Arabidopsis thaliana vs a photosensitive mutant lacking zeaxanthin and lutein
Science.gov (United States)
2011-01-01
Background Reactive oxygen species (ROS) are unavoidable by-products of oxygenic photosynthesis, causing progressive oxidative damage and ultimately cell death. Despite their destructive activity they are also signalling molecules, priming the acclimatory response to stress stimuli. Results To investigate this role further, we exposed wild type Arabidopsis thaliana plants and the double mutant npq1lut2 to excess light. The mutant does not produce the xanthophylls lutein and zeaxanthin, whose key roles include ROS scavenging and prevention of ROS synthesis. Biochemical analysis revealed that singlet oxygen (1O2) accumulated to higher levels in the mutant while other ROS were unaffected, allowing to define the transcriptomic signature of the acclimatory response mediated by 1O2 which is enhanced by the lack of these xanthophylls species. The group of genes differentially regulated in npq1lut2 is enriched in sequences encoding chloroplast proteins involved in cell protection against the damaging effect of ROS. Among the early fine-tuned components, are proteins involved in tetrapyrrole biosynthesis, chlorophyll catabolism, protein import, folding and turnover, synthesis and membrane insertion of photosynthetic subunits. Up to now, the flu mutant was the only biological system adopted to define the regulation of gene expression by 1O2. In this work, we propose the use of mutants accumulating 1O2 by mechanisms different from those activated in flu to better identify ROS signalling. Conclusions We propose that the lack of zeaxanthin and lutein leads to 1O2 accumulation and this represents a signalling pathway in the early stages of stress acclimation, beside the response to ADP/ATP ratio and to the redox state of both plastoquinone pool. Chloroplasts respond to 1O2 accumulation by undergoing a significant change in composition and function towards a fast acclimatory response. The physiological implications of this signalling specificity are discussed. PMID:21481232
20. Grain destruction in interstellar shocks
International Nuclear Information System (INIS)
Seab, C.G.; Shull, J.M.
1984-01-01
One of the principal methods for removing grains from the Interstellar Medium is to destroy them in shock waves. Previous theoretical studies of shock destruction have generally assumed only a single size and type of grain; most do not account for the effect of the grain destruction on the structure of the shock. Earlier calculations have been improved in three ways: first, by using a ''complete'' grain model including a distribution of sizes and types of grains; second, by using a self-consistent shock structure that incorporates the changing elemental depletions as the grains are destroyed; and third, by calculating the shock-processed ultraviolet extinction curves for comparison with observations. (author)
1. INTERFERENCE OF UNIDIRECTIONAL SHOCK WAVES
Directory of Open Access Journals (Sweden)
P. V. Bulat
2015-05-01
Full Text Available Subject of study.We consider interference of unidirectional shock waves or, as they are called, catching up shock waves. The scope of work is to give a classification of the shock-wave structures that arise in this type of interaction of shock waves, and the area of their existence. Intersection of unidirectional shock waves results in arising of a shock-wave structure at the intersection point, which contains the main shock wave, tangential discontinuity and one more reflected gas-dynamic discontinuity of unknown beforehand type. The problem of determining the type of reflected discontinuity is the main problem that one has to solve in the study of catching shock waves interference. Main results.The paper presents the pictures of shock-wave structures arising at the interaction of catching up shock waves. The areas with a regular and irregular unidirectional interaction of shocks are described. Characteristic shock-wave structures are of greatest interest, where reflected gas-dynamic discontinuity degenerates into discontinuous characteristics. Such structures have a number of extreme properties. We have found the areas of existence for such shock-wave structures. There are also areas in which the steady-state solution is not available. The latter has determined revival of interest for the theoretical study of the problem, because the facts of sudden shock-wave structure destruction inside the air intake of supersonic aircrafts at high Mach numbers have been discovered. Practical significance.The theory of interference for unidirectional shock waves and design procedure are usable in the design of supersonic air intakes. It is also relevant for application possibility investigation of catching up oblique shock waves to create overcompressed detonation in perspective detonation air-jet and rocket engines.
2. Lack of Association Between Maternal or Neonatal Vitamin D Status and Risk of Childhood Type 1 Diabetes: A Scandinavian Case-Cohort Study.
Science.gov (United States)
Thorsen, Steffen U; Mårild, Karl; Olsen, Sjurdur F; Holst, Klaus K; Tapia, German; Granström, Charlotta; Halldorsson, Thorhallur I; Cohen, Arieh S; Haugen, Margaretha; Lundqvist, Marika; Skrivarhaug, Torild; Njølstad, Pål R; Joner, Geir; Magnus, Per; Størdal, Ketil; Svensson, Jannet; Stene, Lars C
2018-06-01
Studies on vitamin D status during pregnancy and risk of type 1 diabetes mellitus (T1D) lack consistency and are limited by small sample sizes or single measures of 25-hydroxyvitamin D (25(OH)D). We investigated whether average maternal 25(OH)D plasma concentrations during pregnancy are associated with risk of childhood T1D. In a case-cohort design, we identified 459 children with T1D and a random sample (n = 1,561) from the Danish National Birth Cohort (n = 97,127) and Norwegian Mother and Child Cohort Study (n = 113,053). Participants were born between 1996 and 2009. The primary exposure was the estimated average 25(OH)D concentration, based on serial samples from the first trimester until delivery and on umbilical cord plasma. We estimated hazard ratios using weighted Cox regression adjusting for multiple confounders. The adjusted hazard ratio for T1D per 10-nmol/L increase in the estimated average 25(OH)D concentration was 1.00 (95% confidence interval: 0.90, 1.10). Results were consistent in both cohorts, in multiple sensitivity analyses, and when we analyzed mid-pregnancy or cord blood separately. In conclusion, our large study demonstrated that normal variation in maternal or neonatal 25(OH)D is unlikely to have a clinically important effect on risk of childhood T1D.
3. Shock Prevention
Science.gov (United States)
1978-01-01
The electrician pictured is installing a General Electric Ground Fault Interrupter (GFI), a device which provides protection against electrical shock in the home or in industrial facilities. Shocks due to defective wiring in home appliances or other electrical equipment can cause severe burns, even death. As a result, the National Electrical Code now requires GFIs in all new homes constructed. This particular type of GFI employs a sensing element which derives from technology acquired in space projects by SCI Systems, Inc., Huntsville, Alabama, producer of sensors for GE and other manufacturers of GFI equipment. The sensor is based on the company's experience in developing miniaturized circuitry for space telemetry and other spacecraft electrical systems; this experience enabled SCI to package interruptor circuitry in the extremely limited space available and to produce sensory devices at practicable cost. The tiny sensor measures the strength of the electrical current and detects current differentials that indicate a fault in the functioning of an electrical system. The sensing element then triggers a signal to a disconnect mechanism in the GFI, which cuts off the current in the faulty circuit.
4. Wind Magnetic Clouds for the Period 2013 - 2015: Model Fitting, Types, Associated Shock Waves, and Comparisons to Other Periods
Science.gov (United States)
Lepping, R. P.; Wu, C.-C.; Berdichevsky, D. B.; Szabo, A.
2018-04-01
We give the results of parameter fitting of the magnetic clouds (MCs) observed by the Wind spacecraft for the three-year period 2013 to the end of 2015 (called the "Present" period) using the MC model of Lepping, Jones, and Burlaga ( J. Geophys. Res. 95, 11957, 1990). The Present period is almost coincident with the solar maximum of the sunspot number, which has a broad peak starting in about 2012 and extending to almost 2015. There were 49 MCs identified in the Present period. The modeling gives MC quantities such as size, axial attitude, field handedness, axial magnetic-field strength, center time, and closest-approach vector. Derived quantities are also estimated, such as axial magnetic flux, axial current density, and total axial current. Quality estimates are assigned representing excellent, fair/good, and poor. We provide error estimates on the specific fit parameters for the individual MCs, where the poor cases are excluded. Model-fitting results that are based on the Present period are compared to the results of the full Wind mission from 1995 to the end of 2015 (Long-term period), and compared to the results of two other recent studies that encompassed the periods 2007 - 2009 and 2010 - 2012, inclusive. We see that during the Present period, the MCs are, on average, slightly slower, slightly weaker in axial magnetic field (by 8.7%), and larger in diameter (by 6.5%) than those in the Long-term period. However, in most respects, the MCs in the Present period are significantly closer in characteristics to those of the Long-term period than to those of the two recent three-year periods. However, the rate of occurrence of MCs for the Long-term period is 10.3 year^{-1}, whereas this rate for the Present period is 16.3 year^{-1}, similar to that of the period 2010 - 2012. Hence, the MC occurrence rate has increased appreciably in the last six years. MC Type (N-S, S-N, All N, All S, etc.) is assigned to each MC; there is an inordinately large percentage of All S
5. Upregulation of adipose 11-beta-hydroxysteroid dehydrogenase type 1 expression in ovariectomized rats is due to obesity rather than lack of estrogen.
Science.gov (United States)
Paulsen, Søren K; Nielsen, Maria P; Richelsen, Bjørn; Bruun, Jens M; Flyvbjerg, Allan; Pedersen, Steen B
2008-04-01
Increased tissue activity of cortisol induced by the activation of inert cortisone to active cortisol through 11-beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) may play a role in the metabolic syndrome. We recently found that 11beta-HSD1 in subcutaneous adipose tissue (AT) was lower in lean women compared with lean men. Estrogen suppresses hepatic and renal 11beta-HSD1 in rats; hence we investigated the in vitro effect of estrogen on human and rat AT, and the in vivo effects on rat AT 11beta-HSD1 expression. Wistar rats were divided into four groups of eight animals. One group was sham-operated (controls) and others were ovariectomized (OVX). One OVX group was left untreated (OVX-E), another (OVX+E) received estrogen treatment, and one received a hypo-caloric diet (OVX-E+D), matching the weight gain of the control group. AT from women undergoing liposuction or surgery and from killed male and female rats were incubated with estrogen alone or in the presence of IL-1beta. Gene expressions were determined by real-time reverse transcriptase PCR. Ovariectomy resulted in a 280% increase in adipose 11beta-HSD1 expression P < 0.05). 11beta-HSD1 expression in the (OVX+E)-group was significantly reduced compared with the nonsubstituted group (P < 0.05). 11beta-HSD1 expression in the (OVX-E+D)-group was reduced significantly (P < 0.05) when compared with the level of the estrogen-substituted group. No significant differences between the control group, the (OVX+E)-group, and the (OVX-E+D)-group were found. In the in vitro studies, no direct effect of estrogen on adipose 11beta-HSD1 was found. The upregulation of 11beta-HSD1 in ovariectomized rats was most likely due to changes in body composition rather than lack of estrogen.
6. Altered thalamocortical rhythmicity and connectivity in mice lacking CaV3.1 T-type Ca2+ channels in unconsciousness
Science.gov (United States)
Choi, Soonwook; Yu, Eunah; Lee, Seongwon; Llinás, Rodolfo R.
2015-01-01
In unconscious status (e.g., deep sleep and anesthetic unconsciousness) where cognitive functions are not generated there is still a significant level of brain activity present. Indeed, the electrophysiology of the unconscious brain is characterized by well-defined thalamocortical rhythmicity. Here we address the ionic basis for such thalamocortical rhythms during unconsciousness. In particular, we address the role of CaV3.1 T-type Ca2+ channels, which are richly expressed in thalamic neurons. Toward this aim, we examined the electrophysiological and behavioral phenotypes of mice lacking CaV3.1 channels (CaV3.1 knockout) during unconsciousness induced by ketamine or ethanol administration. Our findings indicate that CaV3.1 KO mice displayed attenuated low-frequency oscillations in thalamocortical loops, especially in the 1- to 4-Hz delta band, compared with control mice (CaV3.1 WT). Intriguingly, we also found that CaV3.1 KO mice exhibited augmented high-frequency oscillations during unconsciousness. In a behavioral measure of unconsciousness dynamics, CaV3.1 KO mice took longer to fall into the unconscious state than controls. In addition, such unconscious events had a shorter duration than those of control mice. The thalamocortical interaction level between mediodorsal thalamus and frontal cortex in CaV3.1 KO mice was significantly lower, especially for delta band oscillations, compared with that of CaV3.1 WT mice, during unconsciousness. These results suggest that the CaV3.1 channel is required for the generation of a given set of thalamocortical rhythms during unconsciousness. Further, that thalamocortical resonant neuronal activity supported by this channel is important for the control of vigilance states. PMID:26056284
7. Exploring the Efficacy and Limitations of Shock-cooling Models: New Analysis of Type II Supernovae Observed by the Kepler Mission
Science.gov (United States)
2017-10-01
Modern transient surveys have begun discovering and following supernovae (SNe) shortly after first light—providing systematic measurements of the rise of Type II SNe. We explore how analytic models of early shock-cooling emission from core-collapse SNe can constrain the progenitor’s radius, explosion velocity, and local host extinction. We simulate synthetic photometry in several realistic observing scenarios; assuming the models describe the typical explosions well, we find that ultraviolet observations can constrain the progenitor’s radius to a statistical uncertainty of ±10%-15%, with a systematic uncertainty of ±20%. With these observations the local host extinction (A V ) can be constrained to a factor of two and the shock velocity to ±5% with a systematic uncertainty of ±10%. We also reanalyze the SN light curves presented by Garnavich et al. (2016) and find that KSN 2011a can be fit by a blue supergiant model with a progenitor radius of {R}sred supergiant model with a progenitor radius of {R}s={111}-21({stat)-1({sys})}+89({stat)+49({sys})} {R}⊙ . Our results do not agree with those of Garnavich et al. Moreover, we re-evaluate their claims and find that there is no statistically significant evidence for a shock-breakout flare in the light curve of KSN 2011d.
8. Variations of L- and D-amino acid levels in the brain of wild-type and mutant mice lacking D-amino acid oxidase activity.
Science.gov (United States)
Du, Siqi; Wang, Yadi; Weatherly, Choyce A; Holden, Kylie; Armstrong, Daniel W
2018-05-01
D-amino acids are now recognized to be widely present in organisms and play essential roles in biological processes. Some D-amino acids are metabolized by D-amino acid oxidase (DAO), while D-Asp and D-Glu are metabolized by D-aspartate oxidase (DDO). In this study, levels of 22 amino acids and the enantiomeric compositions of the 19 chiral proteogenic entities have been determined in the whole brain of wild-type ddY mice (ddY/DAO +/+ ), mutant mice lacking DAO activity (ddY/DAO -/- ), and the heterozygous mice (ddY/DAO +/- ) using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). No significant differences were observed for L-amino acid levels among the three strains except for L-Trp which was markedly elevated in the DAO +/- and DAO -/- mice. The question arises as to whether this is an unknown effect of DAO inactivity. The three highest levels of L-amino acids were L-Glu, L-Asp, and L-Gln in all the three strains. The lowest L-amino acid level was L-Cys in ddY/DAO +/- and ddY/DAO -/- mice, while L-Trp showed the lowest level in ddY/DAO +/+ mice. The highest concentration of D-amino acid was found to be D-Ser, which also had the highest % D value (~ 25%). D-Glu had the lowest % D value (~ 0.01%) in all the three strains. Significant differences of D-Leu, D-Ala, D-Ser, D-Arg, and D-Ile were observed in ddY/DAO +/- and ddY/DAO -/- mice compared to ddY/DAO +/+ mice. This work provides the most complete baseline analysis of L- and D-amino acids in the brains of ddY/DAO +/+ , ddY/DAO +/- , and ddY/DAO -/- mice yet reported. It also provides the most effective and efficient analytical approach for measuring these analytes in biological samples. This study provides fundamental information on the role of DAO in the brain and may be relevant for future development involving novel drugs for DAO regulation.
9. Shock absorber
International Nuclear Information System (INIS)
Nemeth, J.D.
1981-01-01
A shock absorber for the support of piping and components in a nuclear power plant is described. It combines a high degree of stiffness under sudden shocks, e.g. seismic disturbances, with the ability to allow for thermal expansion without resistance when so required. (JIW)
10. demystifying the shock of shocking
African Journals Online (AJOL)
(with a pulse), atrial fibrillation and atrial flutter. The energy dose in cardioversion is less (0.5. - 2 J/kg) than in defibrillation (2 - 4 J/kg). In cardioversion the shock is discharged synchronously with the native R wave of the patient. Without synchronisation,. VF can be induced if a shock is delivered during the refractory period ...
11. Cardiogenic shock following blunt chest trauma
Directory of Open Access Journals (Sweden)
Rodríguez-González Fayna
2010-01-01
Full Text Available Cardiac contusion, usually caused by blunt chest trauma, has been recognized with increased frequency over the past decades. Traffic accidents are the most frequent cause of cardiac contusions resulting from a direct blow to the chest. Other causes of blunt cardiac injury are numerous and include violent fall impacts, interpersonal aggression, explosions, and various types of high-risk sports. Myocardial contusion is difficult to diagnose; clinical presentation varies greatly, ranging from lack of symptoms to cardiogenic shock and arrhythmia. Although death is rare, cardiac contusion can be fatal. We present a case of cardiac contusion due to blunt chest trauma secondary to a fall impact, which manifested as cardiogenic shock.
12. Hypovolemic shock
Science.gov (United States)
... the person's position unless they are in immediate danger. Do not give fluids by mouth. If person ... the patient with shock. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine . 25th ed. Philadelphia, PA: ...
13. Shock absorber
International Nuclear Information System (INIS)
Housman, J.J.
1978-01-01
A shock absorber is described for use in a hostile environment at the end of a blind passage for absorbing impact loads. The shock absorber includes at least one element which occupies the passage and which is comprised of a porous brittle material which is substantially non-degradable in the hostile environment. A void volume is provided in the element to enable the element to absorb a predetermined level of energy upon being crushed due to impact loading
14. A lack of association between vitamin D-binding protein and 25-hydroxyvitamin D concentrations in pediatric type 1 diabetes without microalbuminuria
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Hwa Young Kim
2017-12-01
Full Text Available Purpose Vitamin D deficiency is reported to be more common in type 1 diabetes patients and might be associated with the increased urinary loss of vitamin D binding protein (VDBP consequent to impaired 25-hydroxyvitamin D (25(OHD circulation. We aimed to evaluate the possible increased urinary loss of VDBP, a correlation between VDBP and circulating 25(OHD level, and risk factors influencing low vitamin D level in pediatric type 1 diabetes patients without microalbuminuria. Methods This is a cross-sectional study of subjects who visited Seoul National University Children’s Hospital between January and March 2013. Forty-two type 1 diabetes patients and 29 healthy controls were included. Biochemical parameters including serum and urine VDBP concentrations were analyzed. Results There was no significant difference in the frequency of vitamin D deficiency or serum 25(OHD level between the 2 groups. The serum and urine VDBP concentrations did not show any difference between the 2 groups. Serum 25(OH D level did not correlate with serum or urine VDBP. Multivariate regression analysis revealed that daylight outdoor hours (β=2.948, P=0.003 and vitamin D intake (β=2.865, P=0.003 affected the 25(OHD level; the presence of type 1 diabetes or urinary VDBP excretion was not significant. Conclusions In pediatric type 1 diabetes patients, urinary VDBP excretion did not contribute to low serum 25(OHD level in the setting of normoalbuminuria. The factors associated with 25(OHD level during winter periods were daylight outdoor hours and vitamin D intake. Further studies including both micro- and macroalbuminuria patients with type 1 diabetes are warranted.
15. MHD intermediate shock discontinuities: Pt. 1
International Nuclear Information System (INIS)
Kennel, C.F.; Blandford, R.D.; Coppi, P.
1989-01-01
Recent numerical investigations have focused attention once more on the role of intermediate shocks in MHD. Four types of intermediate shock are identified using a graphical representation of the MHD Rankine-Hugoniot conditions. This same representation can be used to exhibit the close relationship of intermediate shocks to switch-on shocks and rotational discontinuities. The conditions under which intermediate discontinuities can be found are elucidated. The variations in velocity, pressure, entropy and magnetic-field jumps with upstream parameters in intermediate shocks are exhibited graphically. The evolutionary arguments traditionally advanced against intermediate shocks may fail because the equations of classical MHD are not strictly hyperbolic. (author)
16. Differential Distribution of Type II CRISPR-Cas Systems in Agricultural and Nonagricultural Campylobacter coli and Campylobacter jejuni Isolates Correlates with Lack of Shared Environments.
Science.gov (United States)
Pearson, Bruce M; Louwen, Rogier; van Baarlen, Peter; van Vliet, Arnoud H M
2015-09-02
CRISPR (clustered regularly interspaced palindromic repeats)-Cas (CRISPR-associated) systems are sequence-specific adaptive defenses against phages and plasmids which are widespread in prokaryotes. Here we have studied whether phylogenetic relatedness or sharing of environmental niches affects the distribution and dissemination of Type II CRISPR-Cas systems, first in 132 bacterial genomes from 15 phylogenetic classes, ranging from Proteobacteria to Actinobacteria. There was clustering of distinct Type II CRISPR-Cas systems in phylogenetically distinct genera with varying G+C%, which share environmental niches. The distribution of CRISPR-Cas within a genus was studied using a large collection of genome sequences of the closely related Campylobacter species Campylobacter jejuni (N = 3,746) and Campylobacter coli (N = 486). The Cas gene cas9 and CRISPR-repeat are almost universally present in C. jejuni genomes (98.0% positive) but relatively rare in C. coli genomes (9.6% positive). Campylobacter jejuni and agricultural C. coli isolates share the C. jejuni CRISPR-Cas system, which is closely related to, but distinct from the C. coli CRISPR-Cas system found in C. coli isolates from nonagricultural sources. Analysis of the genomic position of CRISPR-Cas insertion suggests that the C. jejuni-type CRISPR-Cas has been transferred to agricultural C. coli. Conversely, the absence of the C. coli-type CRISPR-Cas in agricultural C. coli isolates may be due to these isolates not sharing the same environmental niche, and may be affected by farm hygiene and biosecurity practices in the agricultural sector. Finally, many CRISPR spacer alleles were linked with specific multilocus sequence types, suggesting that these can assist molecular epidemiology applications for C. jejuni and C. coli. © The Author(s) 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.
17. Decreased expression of heat shock proteins may lead to compromised wound healing in type 2 diabetes mellitus patients.
Science.gov (United States)
Singh, Kanhaiya; Agrawal, Neeraj K; Gupta, Sanjeev K; Mohan, Gyanendra; Chaturvedi, Sunanda; Singh, Kiran
2015-01-01
Heat shock proteins (HSPs) are inducible stress proteins expressed in cells exposed to stress. HSPs promote wound healing by recruitment of dermal fibroblasts to the site of injury and bring about protein homeostasis. Diabetic wounds are hard to heal and inadequate HSPs may be important contributors in the etiology of diabetic foot ulcers (DFU). To analyze the differential expression of HSPs and their downstream molecules in human diabetic wounds compared to control wounds. Expressional levels of HSP27, HSP47 and HSP70 and their downstream molecules like TLR4, p38-MAPK were seen in biopsies from 101 human diabetic wounds compared to 8 control subjects without diabetes using RT-PCR, western blot and immunohistochemistry. Our study suggested a significant down regulation of HSP70, HSP47 and HSP27 (p value=diabetic wounds. Our study demonstrates that the down regulation of HSPs in diabetic wounds is associated with wound healing impairment in T2DM subjects. Copyright © 2015 Elsevier Inc. All rights reserved.
18. Lack of association between KCNJ11 (rs5219 and ABCC8 (rs757110 polymorphisms and sulphonylurea treatment response in type 2 diabetes patients in Novosibirsk region
Directory of Open Access Journals (Sweden)
2015-03-01
Full Text Available Aim. Sulfonylureas (SU are widely used in everyday clinical practice in treatment of patients with type 2 diabetes mellitus (T2DM. There is a considerable variability in SU effects, which may be caused by psychological, social, biological and genetic factors. The aim of the study was to investigate the association between rs5219 KCNJ11 gene and rs757110 ABCC8 gene polymorphism and long-term response to SU-drugs of second and third generation in the Novosibirsk region. Materials and Methods. 326 patients with type 2 diabetes in the Novosibirsk region were examined. Patients were divided into 2 groups, depending on HbA1c level. The first group included patients with target HbA1c levels on SU monotherapy. The second group included patients who did not reach target HbA1c levels on the highest dose of SU. Genotyping of KCNJ11 (rs5219 and ABCC8 (rs757110 was performed by TaqMan real-time PCR (ICBFM SB RAS, Novosibirsk, Russia. Results. Patients with type 2 diabetes with a good response to SU-therapy compared to the group of patients with a poor response to SU-therapy were older (65.8?9.1 years vs. 61.6?7.9 years, p
19. Hepatitis C as a risk factor for diabetes type 2: lack of evidence in a hospital in central-west Brazil
Directory of Open Access Journals (Sweden)
Luce Marina Freires Corrêa da Costa
Full Text Available In order to assess the importance of HCV infection as a possible risk factor for type 2 diabetes mellitus, a case-control study was conducted, comparing the prevalence of HCV infection among diabetic and non-diabetic patients. Diabetic outpatients attending to a University Hospital in Central-West Brazil were evaluated between April and October 2005. A control group composed by patients from the same institution was matched by gender and age. Candidates to control group were included only if fasting glucose measures were under 100 mg/dL. Diabetics and controls had blood samples taken in order to test for antibodies against HCV (anti-HCV by enzyme-immunoassay. Polymerase chain reaction and immunoblot were performed to confirm the anti-HCV status. Each group included 206 participants. Despite of the groups were in general comparable. The diabetics had a greater body mass average and smaller family income. The prevalence of confirmed anti-HCV in the diabetic group was of 1.4%, which was similar to the controls (1%. Finding statistical difference may have been hampered by the low frequency of HCV infection in both groups. It was not possible to demonstrate a role of HCV as an etiologic factor in type 2 diabetes, since HCV infected patients represented a small portion of the overall diabetes cases. This finding does not allow to recommend regular screening for HCV infection in type 2 diabetics in this region.
20. Pirfenidone inhibits TGF-β1-induced over-expression of collagen type I and heat shock protein 47 in A549 cells
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Hisatomi Keiko
2012-06-01
Full Text Available Abstract Background Pirfenidone is a novel anti-fibrotic and anti-inflammatory agent that inhibits the progression of fibrosis in animal models and in patients with idiopathic pulmonary fibrosis (IPF. We previously showed that pirfenidone inhibits the over-expression of collagen type I and of heat shock protein (HSP 47, a collagen-specific molecular chaperone, in human lung fibroblasts stimulated with transforming growth factor (TGF-β1 in vitro. The increased numbers of HSP47-positive type II pneumocytes as well as fibroblasts were also diminished by pirfenidone in an animal model of pulmonary fibrosis induced by bleomycin. The present study evaluates the effects of pirfenidone on collagen type I and HSP47 expression in the human alveolar epithelial cell line, A549 cells in vitro. Methods The expression of collagen type I, HSP47 and E-cadherin mRNAs in A549 cells stimulated with TGF-β1 was evaluated by Northern blotting or real-time PCR. The expression of collagen type I, HSP47 and fibronectin proteins was assessed by immunocytochemical staining. Results TGF-β1 stimulated collagen type I and HSP47 mRNA and protein expression in A549 cells, and pirfenidone significantly inhibited this process. Pirfenidone also inhibited over-expression of the fibroblast phenotypic marker fibronectin in A549 cells induced by TGF-β1. Conclusion We concluded that the anti-fibrotic effects of pirfenidone might be mediated not only through the direct inhibition of collagen type I expression but also through the inhibition of HSP47 expression in alveolar epithelial cells, which results in reduced collagen synthesis in lung fibrosis. Furthermore, pirfenidone might partially inhibit the epithelial-mesenchymal transition.
1. Lack of association between the Pro12Ala polymorphism of the PPAR-gamma 2 gene and type 2 diabetes mellitus in the Qatari consanguineous population.
Science.gov (United States)
Badii, Ramin; Bener, Abdulbari; Zirie, Mahmoud; Al-Rikabi, Ammar; Simsek, Mehmet; Al-Hamaq, Abdulla O A A; Ghoussaini, Maya; Froguel, Philippe; Wareham, Nick J
2008-03-01
Peroxisome proliferators-activated receptor gamma (PPAR gamma) is a nuclear hormone receptor that serves as a master regulator for adipocytes-specific genes contributing to adipocytes differentiation, insulin sensitivity and lipid metabolism. The substitution of proline to alanine at codon 12 of the PPAR gamma 2 gene (Pro12Ala polymorphism) is most widely studied, and the associations with diabetes, obesity, and other clinical parameters have been reported and discussed in several ethnic groups. Among native Qatar ethnicity, however, there is no report about this polymorphism. The aim of this study was to estimate the allele frequency of the Pro12Ala polymorphism of PPAR gamma 2 gene among Qatari population and investigate the association between this polymorphism and obesity or type 2 diabetes. This is a matched case-control study. It was carried out among diabetic patients and healthy subjects at the Primary Healthcare Clinics, and the survey was conducted from February 2003 to March 2006 in Qatari male and female nationals aged 35 to 60 years. The study was based on matched age, sex, and ethnicity of 400 cases (with diabetes) and 450 controls (without diabetes). Face-to-face interviews were based on a questionnaire that included variables such as age, sex, sociodemographic status, body mass index (BMI), and obesity. Their health status was assessed by medical conditions, family history, and blood pressure measurements. The allele frequency of Pro12Ala polymorphism in PPAR gamma 2 gene among Qataris is lower than that in many Caucasian ethnic groups. No association is seen between the Pro12Ala and type 2 Diabetes (0.055 vs 0.059, OR = 1.1311, P = 0.669). Nearly half of the diabetic type 2 patients (48.5%) were obese (BMI > 30) compared to nondiabetic subjects (29.8%) (P Qatar.
2. Lack of association of genetic variation in chromosome region 15q14-22.1 with type 2 diabetes in a Japanese population
Directory of Open Access Journals (Sweden)
Ichiishi Eiichiro
2008-03-01
Full Text Available Abstract Background Chromosome 15q14-22.1 has been linked to type 2 diabetes (T2D and its related traits in Japanese and other populations. The presence of T2D disease susceptibility variant(s was assessed in the 21.8 Mb region between D15S118 and D15S117 in a Japanese population using a region-wide case-control association test. Methods A two-stage association test was performed using Japanese subjects: The discovery panel (Stage 1 used 372 cases and 360 controls, while an independent replication panel (Stage 2 used 532 cases and 530 controls. A total of 1,317 evenly-spaced, common SNP markers with minor allele frequencies > 0.10 were typed for each stage. Captured genetic variation was examined in HapMap JPT SNPs, and a haplotype-based association test was performed. Results SNP2140 (rs2412747 (C/T in intron 33 of the ubiquitin protein ligase E3 component n-recognin 1 (UBR1 gene was selected as a landmark SNP based on repeated significant associations in Stage 1 and Stage 2. However, the marginal p value (p = 0.0043 in the allelic test, OR = 1.26, 95% CI = 1.07–1.48 for combined samples was weak in a single locus or haplotype-based association test. We failed to find any significant SNPs after correcting for multiple testing. Conclusion The two-stage association test did not reveal a strong association between T2D and any common variants on chromosome 15q14-22.1 in 1,794 Japanese subjects. A further association test with a larger sample size and denser SNP markers is required to confirm these observations.
3. Possible pressurized thermal shock events during large primary to secondary leakage. The Hungarian AGNES project and PRISE accident scenarios in VVER-440/V213 type reactor
Energy Technology Data Exchange (ETDEWEB)
Perneczky, L. [KFKI Atomic Energy Research Inst., Budabest (Hungary)
1997-12-31
Nuclear power plants of WWER-440/213-type have several special features. Consequently, the transient behaviour of such a reactor system should be different from the behaviour of the PWRs of western design. The opening of the steam generator (SG) collector cover, as a specific primary to secondary circuit leakage (PRISE) occurring in WWER-type reactors happened first time in Rovno NPP Unit I on January 22, 1982. Similar accident was studied in the framework of IAEA project RER/9/004 in 1987-88 using the RELAP4/mod6 code. The Hungarian AGNES (Advanced General and New Evaluation of Safety) project was performed in the period 1991-94 with the aim to reassess the safety of the Paks NPP using state-of-the-art techniques. The project comprised three type of analyses for the primary to secondary circuit leakages: Design Basis Accident (DBA) analyses, Pressurized Thermal Shock (PTS) study and deterministic analyses for Probabilistic Safety Analysis (PSA). Major part of the thermohydraulic analyses has been performed by the RELAP5/mod2.5/V251 code version with two input models. 32 refs.
4. Possible pressurized thermal shock events during large primary to secondary leakage. The Hungarian AGNES project and PRISE accident scenarios in VVER-440/V213 type reactor
Energy Technology Data Exchange (ETDEWEB)
Perneczky, L [KFKI Atomic Energy Research Inst., Budabest (Hungary)
1998-12-31
Nuclear power plants of WWER-440/213-type have several special features. Consequently, the transient behaviour of such a reactor system should be different from the behaviour of the PWRs of western design. The opening of the steam generator (SG) collector cover, as a specific primary to secondary circuit leakage (PRISE) occurring in WWER-type reactors happened first time in Rovno NPP Unit I on January 22, 1982. Similar accident was studied in the framework of IAEA project RER/9/004 in 1987-88 using the RELAP4/mod6 code. The Hungarian AGNES (Advanced General and New Evaluation of Safety) project was performed in the period 1991-94 with the aim to reassess the safety of the Paks NPP using state-of-the-art techniques. The project comprised three type of analyses for the primary to secondary circuit leakages: Design Basis Accident (DBA) analyses, Pressurized Thermal Shock (PTS) study and deterministic analyses for Probabilistic Safety Analysis (PSA). Major part of the thermohydraulic analyses has been performed by the RELAP5/mod2.5/V251 code version with two input models. 32 refs.
5. Lack of viral selection in human immunodeficiency virus type 1 mother-to-child transmission with primary infection during late pregnancy and/or breastfeeding.
Science.gov (United States)
Ceballos, Ana; Andreani, Guadalupe; Ripamonti, Chiara; Dilernia, Dario; Mendez, Ramiro; Rabinovich, Roberto D; Cárdenas, Patricia Coll; Zala, Carlos; Cahn, Pedro; Scarlatti, Gabriella; Martínez Peralta, Liliana
2008-11-01
Mother-to-child transmission (MTCT) of human immunodeficiency virus type 1 (HIV-1) as described for women with an established infection is, in most cases, associated with the transmission of few maternal variants. This study analysed virus variability in four cases of maternal primary infection occurring during pregnancy and/or breastfeeding. Estimated time of seroconversion was at 4 months of pregnancy for one woman (early seroconversion) and during the last months of pregnancy and/or breastfeeding for the remaining three (late seroconversion). The C2V3 envelope region was analysed in samples of mother-child pairs by molecular cloning and sequencing. Comparisons of nucleotide and amino acid sequences as well as phylogenetic analysis were performed. The results showed low variability in the virus population of both mother and child. Maximum-likelihood analysis showed that, in the early pregnancy seroconversion case, a minor viral variant with further evolution in the child was transmitted, which could indicate a selection event in MTCT or a stochastic event, whereas in the late seroconversion cases, the mother's and child's sequences were intermingled, which is compatible with the transmission of multiple viral variants from the mother's major population. These results could be explained by the less pronounced selective pressure exerted by the immune system in the early stages of the mother's infection, which could play a role in MTCT of HIV-1.
6. Lack of Association between Serum Vitamin B₆, Vitamin B12, and Vitamin D Levels with Different Types of Glaucoma: A Systematic Review and Meta-Analysis.
Science.gov (United States)
Li, Shengjie; Li, Danhui; Shao, Mingxi; Cao, Wenjun; Sun, Xinghuai
2017-06-21
Although vitamins play a major role in health, and their deficiency may be linked to symptoms of optic-nerve dysfunction, the association between serum vitamin levels and glaucoma in humans remains controversial. In this study, articles in the PubMed, Web of Science, and EMBASE databases were searched up to 25March 2017. Nine studies on primary open-angle glaucoma (POAG), four studies on normal tension glaucoma (NTG), and six studies on exfoliative glaucoma (EXG) were retrieved. The combined results showed no differences in the levels of serum vitamin B₆ between POAG ( p = 0.406) and EXG ( p = 0.139) patients and controls. The weighted mean differences (WMDs) with 95% confidence intervals (CIs) were 2.792 ng/mL (-3.793 to 9.377) and 1.342 ng/mL (-3.120 to 0.436), respectively. There was no difference between POAG ( p = 0.952), NTG ( p = 0.757), or EXG ( p = 0.064) patients and controls in terms of serum vitamin B 12 . The WMDs with 95% CIs were 0.933 pg/mL (-31.116 to 29.249), 6.652 pg/mL (-35.473 to 48.777), and 49.946 pg/mL (-102.892 to 3.001), respectively. The serum vitamin D levels exhibited no differences ( p = 0.064) between POAG patients and controls; the WMD with 95% CI was 2.488 ng/mL (-5.120 to 0.145). In conclusion, there was no association found between serum vitamin B₆, vitamin B 12 , or vitamin D levels and the different types of glaucoma.
7. Lack of evidence from studies of soluble protein fragments that Knops blood group polymorphisms in complement receptor-type 1 are driven by malaria.
Directory of Open Access Journals (Sweden)
Patience B Tetteh-Quarcoo
Full Text Available Complement receptor-type 1 (CR1, CD35 is the immune-adherence receptor, a complement regulator, and an erythroid receptor for Plasmodium falciparum during merozoite invasion and subsequent rosette formation involving parasitized and non-infected erythrocytes. The non-uniform geographical distribution of Knops blood group CR1 alleles Sl1/2 and McC(a/b may result from selective pressures exerted by differential exposure to infectious hazards. Here, four variant short recombinant versions of CR1 were produced and analyzed, focusing on complement control protein modules (CCPs 15-25 of its ectodomain. These eleven modules encompass a region (CCPs 15-17 key to rosetting, opsonin recognition and complement regulation, as well as the Knops blood group polymorphisms in CCPs 24-25. All four CR1 15-25 variants were monomeric and had similar axial ratios. Modules 21 and 22, despite their double-length inter-modular linker, did not lie side-by-side so as to stabilize a bent-back architecture that would facilitate cooperation between key functional modules and Knops blood group antigens. Indeed, the four CR1 15-25 variants had virtually indistinguishable affinities for immobilized complement fragments C3b (K(D = 0.8-1.1 µM and C4b (K(D = 5.0-5.3 µM. They were all equally good co-factors for factor I-catalysed cleavage of C3b and C4b, and they bound equally within a narrow affinity range, to immobilized C1q. No differences between the variants were observed in assays for inhibition of erythrocyte invasion by P. falciparum or for rosette disruption. Neither differences in complement-regulatory functionality, nor interactions with P. falciparum proteins tested here, appear to have driven the non-uniform geographic distribution of these alleles.
8. Lack of regulation of 11β-hydroxysteroid dehydrogenase type 1 during short-term manipulation of GH in patients with hypopituitarism
Science.gov (United States)
Sigurjonsdottir, Helga A; Andrew, Ruth; Stimson, Roland H; Johannsson, Gudmundur; Walker, Brian R
2009-01-01
Objective Evidence from long-term clinical studies measuring urinary steroid ratios, and from in vitro studies, suggests that GH administered for longer than 2 months down-regulates 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), thereby reducing cortisol regeneration in liver and adipose tissue. We aimed to measure acute effects of GH on 11β-HSD1 in liver and adipose tissue in vivo, including using a stable isotope tracer. Design Observational studies of GH withdrawal and reintroduction in patients with hypopituitarism. Methods Twelve men with benign pituitary disease causing GH and ACTH deficiency on stable replacement therapy for >6 months were studied after GH withdrawal for 3 weeks, and after either placebo or GH injections were reintroduced for another 3 weeks. We measured cortisol kinetics during 9,11,12,12-2H4-cortisol (d4-cortisol) infusion, urinary cortisol/cortisone metabolite ratios, liver 11β-HSD1 by appearance of plasma cortisol after oral cortisone, and 11β-HSD1 mRNA levels in subcutaneous adipose biopsies. Results GH withdrawal and reintroduction had no effect on 9,12,12-[2H]3-cortisol (d3-cortisol) appearance, urinary cortisol/cortisone metabolite ratios, initial appearance of cortisol after oral cortisone, or adipose 11β-HSD1 mRNA. GH withdrawal increased plasma cortisol 30–180 min after oral cortisone, increased d4-cortisol clearance, and decreased relative excretion of 5α-reduced cortisol metabolites. Conclusions In this setting, GH did not regulate 11β-HSD1 rapidly in vivo in humans. Altered cortisol metabolism with longer term changes in GH may reflect indirect effects on 11β-HSD1. These data do not suggest that glucocorticoid replacement doses need to be increased immediately after introducing GH therapy to compensate for reduced 11β-HSD1 activity, although dose adjustment may be required in the longer term. PMID:19549748
9. The Broad-Lined Type Ic SN 2012ap and the Nature of Relativistic Supernovae Lacking a Gamma-Ray Burst Detection
Science.gov (United States)
Milisavljevic, D.; Margutti, R.; Parrent, J. T.; Soderberg, A. M.; Fesen, R. A.; Mazzali, P.; Maeda, K.; Sanders, N. E.; Cenko, S. B.; Silverman, J. M.
2014-01-01
We present ultraviolet, optical, and near-infrared observations of SN2012ap, a broad-lined Type Ic supernova in the galaxy NGC 1729 that produced a relativistic and rapidly decelerating outflow without a gamma-ray burst signature. Photometry and spectroscopy follow the flux evolution from -13 to +272 days past the B-band maximum of -17.4 +/- 0.5 mag. The spectra are dominated by Fe II, O I, and Ca II absorption lines at ejecta velocities of v approx. 20,000 km s(exp. -1) that change slowly over time. Other spectral absorption lines are consistent with contributions from photospheric He I, and hydrogen may also be present at higher velocities (v approx. greater than 27,000 km s(exp. -1)). We use these observations to estimate explosion properties and derive a total ejecta mass of 2.7 Solar mass, a kinetic energy of 1.0×1052 erg, and a (56)Ni mass of 0.1-0.2 Solar mass. Nebular spectra (t > 200 d) exhibit an asymmetric double-peaked [O I] lambda lambda 6300, 6364 emission profile that we associate with absorption in the supernova interior, although toroidal ejecta geometry is an alternative explanation. SN2012ap joins SN2009bb as another exceptional supernova that shows evidence for a central engine (e.g., black-hole accretion or magnetar) capable of launching a non-negligible portion of ejecta to relativistic velocities without a coincident gamma-ray burst detection. Defining attributes of their progenitor systems may be related to notable properties including above-average environmental metallicities of Z approx. greater than Solar Z, moderate to high levels of host-galaxy extinction (E(B -V ) > 0.4 mag), detection of high-velocity helium at early epochs, and a high relative flux ratio of [Ca II]/[O I] > 1 at nebular epochs. These events support the notion that jet activity at various energy scales may be present in a wide range of supernovae.
10. Lack of independent effect of type 2 diabetes beyond characteristic comorbidities and medications on small muscle mass exercising muscle blood flow and exercise tolerance.
Science.gov (United States)
Poitras, Veronica J; Bentley, Robert F; Hopkins-Rosseel, Diana H; LaHaye, Stephen A; Tschakovsky, Michael E
2015-08-01
Persons with type 2 diabetes (T2D) are believed to have reduced exercise tolerance; this may be partly due to impaired exercising muscle blood flow (MBF). Whether there is an impact of T2D on exercising MBF within the typical constellation of comorbidities (hypertension, dyslipidemia, obesity) and their associated medications has not been investigated. We tested the hypothesis that small muscle mass exercise tolerance is reduced in persons with T2D versus Controls (matched for age, body mass index, fitness, comorbidities, non-T2D medications) and that this is related to blunted MBF. Eight persons with T2D and eight controls completed a forearm critical force (fCFimpulse) test as a measure of exercise tolerance (10-min intermittent maximal effort forearm contractions; the average contraction impulse in the last 30 sec quantified fCFimpulse). Forearm blood flow (FBF; ultrasound) and mean arterial pressure (MAP; finger photoplethysmography) were measured; forearm vascular conductance (FVK) was calculated. Data are means ± SD, T2D versus Control. fCFimpulse was not different between groups (136.9 ± 47.3 N·sec vs. 163.1 ± 49.7 N·sec, P = 0.371) nor was the ∆FBF from rest to during exercise at fCFimpulse (502.9 ± 144.6 vs. 709.1 ± 289.2 mL/min, P = 0.092), or its determinants ∆FVK and ∆MAP (both P > 0.05), although there was considerable interindividual variability. ∆FBF was strongly related to fCFimpulse (r = 0.727, P = 0.002), providing support for the relationship between oxygen delivery and exercise tolerance. We conclude that small muscle mass exercising MBF and exercise tolerance are not impaired in representative persons with T2D versus appropriately matched controls. This suggests that peripheral vascular control impairment does not contribute to reduced exercise tolerance in this population. © 2015 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and
11. THE BROAD-LINED Type Ic SN 2012ap AND THE NATURE OF RELATIVISTIC SUPERNOVAE LACKING A GAMMA-RAY BURST DETECTION
Energy Technology Data Exchange (ETDEWEB)
Milisavljevic, D.; Margutti, R.; Parrent, J. T.; Soderberg, A. M.; Sanders, N. E.; Kamble, A.; Chakraborti, S.; Drout, M. R.; Kirshner, R. P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Fesen, R. A. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States); Mazzali, P. [Astrophysics Research Institute, Liverpool John Moores University, Liverpool L3 5RF (United Kingdom); Maeda, K. [Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); Cenko, S. B. [Astrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771 (United States); Silverman, J. M. [University of Texas at Austin, 1 University Station C1400, Austin, TX 78712-0259 (United States); Filippenko, A. V. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Pickering, T. E. [Southern African Large Telescope, P.O. Box 9, Observatory 7935, Cape Town (South Africa); Kawabata, K. [Hiroshima Astrophysical Science Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Hattori, T. [Subaru Telescope, National Astronomical Observatory of Japan, Hilo, HI 96720 (United States); Hsiao, E. Y. [Carnegie Observatories, Las Campanas Observatory, Colina El Pino, Casilla 601 (Chile); Stritzinger, M. D., E-mail: [email protected] [Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C (Denmark); and others
2015-01-20
We present ultraviolet, optical, and near-infrared observations of SN 2012ap, a broad-lined Type Ic supernova in the galaxy NGC 1729 that produced a relativistic and rapidly decelerating outflow without a gamma-ray burst signature. Photometry and spectroscopy follow the flux evolution from –13 to +272 days past the B-band maximum of –17.4 ± 0.5 mag. The spectra are dominated by Fe II, O I, and Ca II absorption lines at ejecta velocities of v ≈ 20,000 km s{sup –1} that change slowly over time. Other spectral absorption lines are consistent with contributions from photospheric He I, and hydrogen may also be present at higher velocities (v ≳ 27,000 km s{sup –1}). We use these observations to estimate explosion properties and derive a total ejecta mass of ∼2.7 M {sub ☉}, a kinetic energy of ∼1.0 × 10{sup 52} erg, and a {sup 56}Ni mass of 0.1-0.2 M {sub ☉}. Nebular spectra (t > 200 days) exhibit an asymmetric double-peaked [O I] λλ6300, 6364 emission profile that we associate with absorption in the supernova interior, although toroidal ejecta geometry is an alternative explanation. SN 2012ap joins SN 2009bb as another exceptional supernova that shows evidence for a central engine (e.g., black hole accretion or magnetar) capable of launching a non-negligible portion of ejecta to relativistic velocities without a coincident gamma-ray burst detection. Defining attributes of their progenitor systems may be related to notable observed properties including environmental metallicities of Z ≳ Z {sub ☉}, moderate to high levels of host galaxy extinction (E(B – V) > 0.4 mag), detection of high-velocity helium at early epochs, and a high relative flux ratio of [Ca II]/[O I] >1 at nebular epochs. These events support the notion that jet activity at various energy scales may be present in a wide range of supernovae.
12. Inferior vena cava obstruction and shock
Directory of Open Access Journals (Sweden)
Megri Mohammed
2018-01-01
Full Text Available Shock is one of the most challenging life-threatening conditions with high mortality and morbidity; the outcomes are highly dependent on the early detection and management of the condition. Septic shock is the most common type of shock in the Intensive Care Unit. While not as common as other subsets of shock, obstructive shock is a significant subtype due to well defined mechanical and pathological causes, including tension pneumothorax, massive pulmonary embolism, and cardiac tamponade. We are presenting a patient with obstructive shock due to inferior vena cava obstruction secondary to extensive deep venous thrombosis. Chance of survival from obstructive shock in our patient was small; however, there was complete and immediate recovery after treatment of the obstruction on recognizing the affected vessels. This case alerts the practicing intensivist and the emergency medicine physician to consider occlusion of the great vessels other than the pulmonary artery or aorta as causes of obstructive shock.
13. SN 2016X: a type II-P supernova with a signature of shock breakout from explosion of a massive red supergiant
Science.gov (United States)
Huang, F.; Wang, X.-F.; Hosseinzadeh, G.; Brown, P. J.; Mo, J.; Zhang, J.-J.; Zhang, K.-C.; Zhang, T.-M.; Howell, D.-A.; Arcavi, I.; McCully, C.; Valenti, S.; Rui, L.-M.; Song, H.; Xiang, D.-F.; Li, W.-X.; Lin, H.; Wang, L.-F.
2018-04-01
We present extensive ultraviolet (UV) and optical photometry, as well as dense optical spectroscopy, for type II Plateau (IIP) supernova SN 2016X that exploded in the nearby (˜15 Mpc) spiral galaxy UGC 08041. The observations span the period from 2 to 180 d after the explosion; in particular, the Swift UV data probably captured the signature of shock breakout associated with the explosion of SN 2016X. It shows very strong UV emission during the first week after explosion, with a contribution of ˜20-30 per cent to the bolometric luminosity (versus ≲15 per cent for normal SNe IIP). Moreover, we found that this supernova has an unusually long rise time of about 12.6 ± 0.5 d in the R band (versus ˜7.0 d for typical SNe IIP). The optical light curves and spectral evolution are quite similar to the fast-declining type IIP object SN 2013ej, except that SN 2016X has a relatively brighter tail. Based on the evolution of photospheric temperature as inferred from the Swift data in the early phase, we derive that the progenitor of SN 2016X has a radius of about 930 ± 70 R⊙. This large-size star is expected to be a red supergiant star with an initial mass of ≳19-20 M⊙ based on the mass-radius relation of the Galactic red supergiants, and it represents one of the most largest and massive progenitors found for SNe IIP.
14. Heat Shock Protein Beta-1 Modifies Anterior to Posterior Purkinje Cell Vulnerability in a Mouse Model of Niemann-Pick Type C Disease.
Directory of Open Access Journals (Sweden)
Chan Chung
2016-05-01
Full Text Available Selective neuronal vulnerability is characteristic of most degenerative disorders of the CNS, yet mechanisms underlying this phenomenon remain poorly characterized. Many forms of cerebellar degeneration exhibit an anterior-to-posterior gradient of Purkinje cell loss including Niemann-Pick type C1 (NPC disease, a lysosomal storage disorder characterized by progressive neurological deficits that often begin in childhood. Here, we sought to identify candidate genes underlying vulnerability of Purkinje cells in anterior cerebellar lobules using data freely available in the Allen Brain Atlas. This approach led to the identification of 16 candidate neuroprotective or susceptibility genes. We demonstrate that one candidate gene, heat shock protein beta-1 (HSPB1, promoted neuronal survival in cellular models of NPC disease through a mechanism that involved inhibition of apoptosis. Additionally, we show that over-expression of wild type HSPB1 or a phosphomimetic mutant in NPC mice slowed the progression of motor impairment and diminished cerebellar Purkinje cell loss. We confirmed the modulatory effect of Hspb1 on Purkinje cell degeneration in vivo, as knockdown by Hspb1 shRNA significantly enhanced neuron loss. These results suggest that strategies to promote HSPB1 activity may slow the rate of cerebellar degeneration in NPC disease and highlight the use of bioinformatics tools to uncover pathways leading to neuronal protection in neurodegenerative disorders.
15. Identification of Heat Shock Protein families and J-protein types by incorporating Dipeptide Composition into Chou's general PseAAC.
Science.gov (United States)
2015-11-01
Heat Shock Proteins (HSPs) are the substantial ingredients for cell growth and viability, which are found in all living organisms. HSPs manage the process of folding and unfolding of proteins, the quality of newly synthesized proteins and protecting cellular homeostatic processes from environmental stress. On the basis of functionality, HSPs are categorized into six major families namely: (i) HSP20 or sHSP (ii) HSP40 or J-proteins types (iii) HSP60 or GroEL/ES (iv) HSP70 (v) HSP90 and (vi) HSP100. Identification of HSPs family and sub-family through conventional approaches is expensive and laborious. It is therefore, highly desired to establish an automatic, robust and accurate computational method for prediction of HSPs quickly and reliably. Regard, a computational model is developed for the prediction of HSPs family. In this model, protein sequences are formulated using three discrete methods namely: Split Amino Acid Composition, Pseudo Amino Acid Composition, and Dipeptide Composition. Several learning algorithms are utilized to choice the best one for high throughput computational model. Leave one out test is applied to assess the performance of the proposed model. The empirical results showed that support vector machine achieved quite promising results using Dipeptide Composition feature space. The predicted outcomes of proposed model are 90.7% accuracy for HSPs dataset and 97.04% accuracy for J-protein types, which are higher than existing methods in the literature so far. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
16. Shock waves in gas and plasma
International Nuclear Information System (INIS)
Niu, K.
1996-01-01
A shock wave is a discontinuous surface that connects supersonic flow with subsonic flow. After a shock wave, flow velocity is reduced, and pressure and temperature increase; entropy especially increases across a shock wave. Therefore, flow is in nonequilibrium, and irreversible processes occur inside the shock layer. The thickness of a shock wave in neutral gas is of the order of the mean free path of the fluid particle. A shock wave also appears in magnetized plasma. Provided that when the plasma flow is parallel to the magnetic field, a shock wave appears if the governing equation for velocity potential is in hyperbolic type in relation with the Mach number and the Alfven number. When the flow is perpendicular to the magnetic field, the Maxwell stress, in addition to the pressure, plays a role in the shock wave in plasma. When the plasma temperature is so high, as the plasma becomes collision-free, another type of shock wave appears. In a collision-free shock wave, gyromotions of electrons around the magnetic field lines cause the shock formation instead of collisions in a collision-dominant plasma or neutral gas. Regardless of a collision-dominant or collision-free shock wave, the fluid that passes through the shock wave is heated in addition to being compressed. In inertial confinement fusion, the fuel must be compressed. Really, implosion motion performs fuel compression. A shock wave, appearing in the process of implosion, compresses the fuel. The shock wave, however, heats the fuel more intensively, and it makes it difficult to compress the fuel further because high temperatures invite high pressure. Adiabatic compression of the fuel is the desired result during the implosion, without the formation of a shock wave. (Author)
17. Shock Waves
CERN Document Server
Jiang, Z
2005-01-01
The International Symposium on Shock Waves (ISSW) is a well established series of conferences held every two years in a different location. A unique feature of the ISSW is the emphasis on bridging the gap between physicists and engineers working in fields as different as gas dynamics, fluid mechanics and materials sciences. The main results presented at these meetings constitute valuable proceedings that offer anyone working in this field an authoritative and comprehensive source of reference.
18. Particle acceleration in modified shocks
International Nuclear Information System (INIS)
Drury, L.O'C.; Axford, W.I.; Summers, D.
1982-01-01
Efficient particle acceleration in shocks must modify the shock structure with consequent changes in the particle acceleration. This effect is studied and analytic solutions are found describing the diffusive acceleration of particles with momentum independent diffusion coefficients in hyperbolic tangent type velocity transitions. If the input particle spectrum is a delta function, the shock smoothing replaces the truncated power-law downstream particle spectrum by a more complicated form, but one which has a power-law tail at high momenta. For a cold plasma this solution can be made completely self-consistent. Some problems associated with momentum dependent diffusion coefficients are discussed. (author)
19. Particle acceleration in modified shocks
Energy Technology Data Exchange (ETDEWEB)
Drury, L.O' C. (Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany, F.R.)); Axford, W.I. (Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau (Germany, F.R.)); Summers, D. (Memorial Univ. of Newfoundland, St. John' s (Canada))
1982-03-01
Efficient particle acceleration in shocks must modify the shock structure with consequent changes in the particle acceleration. This effect is studied and analytic solutions are found describing the diffusive acceleration of particles with momentum independent diffusion coefficients in hyperbolic tangent type velocity transitions. If the input particle spectrum is a delta function, the shock smoothing replaces the truncated power-law downstream particle spectrum by a more complicated form, but one which has a power-law tail at high momenta. For a cold plasma this solution can be made completely self-consistent. Some problems associated with momentum dependent diffusion coefficients are discussed.
20. The source of real and nominal exchange rate fluctuations in Thailand: Real shock or nominal shock
OpenAIRE
Le Thanh, Binh
2015-01-01
This paper examines the source of exchange rate fluctuations in Thailand. We employed a structural vector auto-regression (SVAR) model with the long-run neutrality restriction of Blanchard and Quah (1989) to investigate the changes in real and nominal exchange rates from 1994 to 2015. In this paper, we assume that there are two types of shocks which related to exchange rate movements: real shocks and nominal shocks. The empirical analysis indicates that real shocks are the fundamental compon...
1. On Modeling Risk Shocks
OpenAIRE
Dorofeenko, Victor; Lee, Gabriel; Salyer, Kevin; Strobel, Johannes
2016-01-01
Within the context of a financial accelerator model, we model time-varying uncertainty (i.e. risk shocks) through the use of a mixture Normal model with time variation in the weights applied to the underlying distributions characterizing entrepreneur productivity. Specifically, we model capital producers (i.e. the entrepreneurs) as either low-risk (relatively small second moment for productivity) and high-risk (relatively large second moment for productivity) and the fraction of both types is...
2. Converging cylindrical shocks in ideal magnetohydrodynamics
International Nuclear Information System (INIS)
Pullin, D. I.; Mostert, W.; Wheatley, V.; Samtaney, R.
2014-01-01
We consider a cylindrically symmetrical shock converging onto an axis within the framework of ideal, compressible-gas non-dissipative magnetohydrodynamics (MHD). In cylindrical polar co-ordinates we restrict attention to either constant axial magnetic field or to the azimuthal but singular magnetic field produced by a line current on the axis. Under the constraint of zero normal magnetic field and zero tangential fluid speed at the shock, a set of restricted shock-jump conditions are obtained as functions of the shock Mach number, defined as the ratio of the local shock speed to the unique magnetohydrodynamic wave speed ahead of the shock, and also of a parameter measuring the local strength of the magnetic field. For the line current case, two approaches are explored and the results compared in detail. The first is geometrical shock-dynamics where the restricted shock-jump conditions are applied directly to the equation on the characteristic entering the shock from behind. This gives an ordinary-differential equation for the shock Mach number as a function of radius which is integrated numerically to provide profiles of the shock implosion. Also, analytic, asymptotic results are obtained for the shock trajectory at small radius. The second approach is direct numerical solution of the radially symmetric MHD equations using a shock-capturing method. For the axial magnetic field case the shock implosion is of the Guderley power-law type with exponent that is not affected by the presence of a finite magnetic field. For the axial current case, however, the presence of a tangential magnetic field ahead of the shock with strength inversely proportional to radius introduces a length scale R=√(μ 0 /p 0 ) I/(2 π) where I is the current, μ 0 is the permeability, and p 0 is the pressure ahead of the shock. For shocks initiated at r ≫ R, shock convergence is first accompanied by shock strengthening as for the strictly gas-dynamic implosion. The diverging magnetic field
3. Converging cylindrical shocks in ideal magnetohydrodynamics
KAUST Repository
Pullin, D. I.
2014-09-01
We consider a cylindrically symmetrical shock converging onto an axis within the framework of ideal, compressible-gas non-dissipative magnetohydrodynamics (MHD). In cylindrical polar co-ordinates we restrict attention to either constant axial magnetic field or to the azimuthal but singular magnetic field produced by a line current on the axis. Under the constraint of zero normal magnetic field and zero tangential fluid speed at the shock, a set of restricted shock-jump conditions are obtained as functions of the shock Mach number, defined as the ratio of the local shock speed to the unique magnetohydrodynamic wave speed ahead of the shock, and also of a parameter measuring the local strength of the magnetic field. For the line current case, two approaches are explored and the results compared in detail. The first is geometrical shock-dynamics where the restricted shock-jump conditions are applied directly to the equation on the characteristic entering the shock from behind. This gives an ordinary-differential equation for the shock Mach number as a function of radius which is integrated numerically to provide profiles of the shock implosion. Also, analytic, asymptotic results are obtained for the shock trajectory at small radius. The second approach is direct numerical solution of the radially symmetric MHD equations using a shock-capturing method. For the axial magnetic field case the shock implosion is of the Guderley power-law type with exponent that is not affected by the presence of a finite magnetic field. For the axial current case, however, the presence of a tangential magnetic field ahead of the shock with strength inversely proportional to radius introduces a length scale R = √μ0/p0 I/(2π) where I is the current, μ0 is the permeability, and p0 is the pressure ahead of the shock. For shocks initiated at r ≫ R, shock convergence is first accompanied by shock strengthening as for the strictly gas-dynamic implosion. The diverging magnetic field then
4. Converging cylindrical shocks in ideal magnetohydrodynamics
KAUST Repository
Pullin, D. I.; Mostert, W.; Wheatley, V.; Samtaney, Ravi
2014-01-01
We consider a cylindrically symmetrical shock converging onto an axis within the framework of ideal, compressible-gas non-dissipative magnetohydrodynamics (MHD). In cylindrical polar co-ordinates we restrict attention to either constant axial magnetic field or to the azimuthal but singular magnetic field produced by a line current on the axis. Under the constraint of zero normal magnetic field and zero tangential fluid speed at the shock, a set of restricted shock-jump conditions are obtained as functions of the shock Mach number, defined as the ratio of the local shock speed to the unique magnetohydrodynamic wave speed ahead of the shock, and also of a parameter measuring the local strength of the magnetic field. For the line current case, two approaches are explored and the results compared in detail. The first is geometrical shock-dynamics where the restricted shock-jump conditions are applied directly to the equation on the characteristic entering the shock from behind. This gives an ordinary-differential equation for the shock Mach number as a function of radius which is integrated numerically to provide profiles of the shock implosion. Also, analytic, asymptotic results are obtained for the shock trajectory at small radius. The second approach is direct numerical solution of the radially symmetric MHD equations using a shock-capturing method. For the axial magnetic field case the shock implosion is of the Guderley power-law type with exponent that is not affected by the presence of a finite magnetic field. For the axial current case, however, the presence of a tangential magnetic field ahead of the shock with strength inversely proportional to radius introduces a length scale R = √μ0/p0 I/(2π) where I is the current, μ0 is the permeability, and p0 is the pressure ahead of the shock. For shocks initiated at r ≫ R, shock convergence is first accompanied by shock strengthening as for the strictly gas-dynamic implosion. The diverging magnetic field then
5. Converging cylindrical shocks in ideal magnetohydrodynamics
Energy Technology Data Exchange (ETDEWEB)
Pullin, D. I. [Graduate Aerospace Laboratories, California Institute of Technology, Pasadena, California 91125 (United States); Mostert, W.; Wheatley, V. [School of Mechanical and Mining Engineering, University of Queensland, Queensland 4072 (Australia); Samtaney, R. [Mechanical Engineering, Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal (Saudi Arabia)
2014-09-15
We consider a cylindrically symmetrical shock converging onto an axis within the framework of ideal, compressible-gas non-dissipative magnetohydrodynamics (MHD). In cylindrical polar co-ordinates we restrict attention to either constant axial magnetic field or to the azimuthal but singular magnetic field produced by a line current on the axis. Under the constraint of zero normal magnetic field and zero tangential fluid speed at the shock, a set of restricted shock-jump conditions are obtained as functions of the shock Mach number, defined as the ratio of the local shock speed to the unique magnetohydrodynamic wave speed ahead of the shock, and also of a parameter measuring the local strength of the magnetic field. For the line current case, two approaches are explored and the results compared in detail. The first is geometrical shock-dynamics where the restricted shock-jump conditions are applied directly to the equation on the characteristic entering the shock from behind. This gives an ordinary-differential equation for the shock Mach number as a function of radius which is integrated numerically to provide profiles of the shock implosion. Also, analytic, asymptotic results are obtained for the shock trajectory at small radius. The second approach is direct numerical solution of the radially symmetric MHD equations using a shock-capturing method. For the axial magnetic field case the shock implosion is of the Guderley power-law type with exponent that is not affected by the presence of a finite magnetic field. For the axial current case, however, the presence of a tangential magnetic field ahead of the shock with strength inversely proportional to radius introduces a length scale R=√(μ{sub 0}/p{sub 0}) I/(2 π) where I is the current, μ{sub 0} is the permeability, and p{sub 0} is the pressure ahead of the shock. For shocks initiated at r ≫ R, shock convergence is first accompanied by shock strengthening as for the strictly gas-dynamic implosion. The
6. Sepsis and Septic Shock Strategies.
Science.gov (United States)
Armstrong, Bracken A; Betzold, Richard D; May, Addison K
2017-12-01
Three therapeutic principles most substantially improve organ dysfunction and survival in sepsis: early, appropriate antimicrobial therapy; restoration of adequate cellular perfusion; timely source control. The new definitions of sepsis and septic shock reflect the inadequate sensitivity, specify, and lack of prognostication of systemic inflammatory response syndrome criteria. Sequential (sepsis-related) organ failure assessment more effectively prognosticates in sepsis and critical illness. Inadequate cellular perfusion accelerates injury and reestablishing perfusion limits injury. Multiple organ systems are affected by sepsis and septic shock and an evidence-based multipronged approach to systems-based therapy in critical illness results in improve outcomes. Copyright © 2017 Elsevier Inc. All rights reserved.
7. Energy brands lack vitality
International Nuclear Information System (INIS)
Godri, S.; Wilders, E.
2004-01-01
The three Dutch energy companies (Nuon, Essent and Eneco Energie) have relatively little brand strength. The brands are not perceived to be sufficiently different from one another and are not valued by consumers. With liberalisation imminent, this is hardly a strong starting point. How can you win over consumers if it is not clear what is on offer? In the business market, decision-makers are better placed to distinguish between brands. However, the brands lack vitality in this sector of the market too. The only consolation is that the situation is by no means exclusive to the Netherlands [nl
8. Radio emission from coronal and interplanetary shocks
International Nuclear Information System (INIS)
Cane, H.V.
1987-01-01
Observational data on coronal and interplanetary (IP) type II burst events associated with shock-wave propagation are reviewed, with a focus on the past and potential future contributions of space-based observatories. The evidence presented by Cane (1983 and 1984) in support of the hypothesis that the coronal (metric) and IP (kilometric) bursts are due to different shocks is summarized, and the fast-drift kilometric events seen at the same time as metric type II bursts (and designated shock-accelerated or shock-associated events) are characterized. The need for further observations at 0.5-20 MHz is indicated. 20 references
9. Enhanced Molecular Typing of Treponema pallidum subspecies pallidum Strains From 4 Italian Hospitals Shows Geographical Differences in Strain Type Heterogeneity, Widespread Resistance to Macrolides, and Lack of Mutations Associated With Doxycycline Resistance.
Science.gov (United States)
Giacani, Lorenzo; Ciccarese, Giulia; Puga-Salazar, Christian; Dal Conte, Ivano; Colli, Laura; Cusini, Marco; Ramoni, Stefano; Delmonte, Sergio; DʼAntuono, Antonietta; Gaspari, Valeria; Drago, Francesco
2018-04-01
Although syphilis rates have been relatively high in Italy for more than 15 years, no data on the molecular types of Treponema pallidum subspecies pallidum circulating in this country are yet available. Likewise, no data on how widespread is resistance to macrolide or tetracycline antibiotics in these strains exist. Such data would, however, promote comprehensive studies on the molecular epidemiology of syphilis infections in Italy and inform future interventions aiming at syphilis control in this and other European countries. Swabs from oral, genital, cutaneous, or anal lesions were obtained from 60 syphilis patients attending dermatology clinics in Milan, Turin, Genoa, and Bologna. Molecular typing of T. pallidum DNA was performed to provide a snapshot of the genetic diversity of strains circulating in Northern Italy. Samples were also screened for mutations conferring resistance to macrolides and tetracyclines. T. pallidum DNA was detected in 88.3% (53/60) of the specimens analyzed. Complete and partial T. pallidum typing data were obtained for 77.3% (41/53) and 15.0% (8/53) of samples, respectively, whereas 4 samples could not be typed despite T. pallidum DNA being detected. The highest strain type heterogeneity was seen in samples from Bologna and Milan, followed by Genoa. Minimal diversity was detected in samples from Turin, despite the highest number of typeable samples collected there. Resistance to macrolides was detected in 94.3% (50/53) of the strains, but no known mutations associated with tetracycline resistance were found. Genetic diversity among T. pallidum strains circulating in Northern Italy varies significantly among geographical areas regardless of physical distance. Resistance to macrolides is widespread.
10. INTERFERENCE OF COUNTERPROPAGATING SHOCK WAVES
Directory of Open Access Journals (Sweden)
P. V. Bulat
2015-03-01
Full Text Available The subject of study. We examined the interaction of counterpropagating shock waves. The necessity of counterpropagating shock waves studying occurs at designing of high Mach number modern internal compression air intakes, Ramjets with subsonic and supersonic combustion, in asymmetrical supersonic nozzles and in some other cases. In a sense, this problem is a generalization of the case of an oblique shock reflection from the wall or from the plane of symmetry. With the renewed vigor, the interest to this problem emerged at the end of the 90s. This was due to the start of the programs for flight study at hypersonic speeds. The first experiments performed with air intakes, which realized the interaction of counterpropagating shock waves have shown that the change in flow velocity is accompanied by abrupt alteration of shock-wave structure, the occurrence of nonstationary and oscillatory phenomena. With an increase of flow velocity these phenomena undesirable for aircraft structure became more marked. The reason is that there are two fundamentally different modes of interaction of counterpropagating shock waves: a four-wave regular and a five-wave irregular. The transition from one mode to another can be nonstationary abrupt or gradual, it can also be accompanied by hysteresis. Main results. Criteria for the transition from regular reflection of counterpropagating shock waves to irregular are described: the criterion of von Neumann and the stationary Mach configuration criterion. We described areas in which the transition from one reflection type to another is possible only in abrupt way, as well as areas of possible gradual transition. Intensity dependences of the reflected shock waves from the intensity of interacting counterpropagating shocks were given. Qualitative pictures of shock-wave structures arising from the interaction of counterpropagating shock waves were shown. Calculation results of the intensity of outgoing gas
11. Influence of shock wave propagation on dielectric barrier discharge plasma actuator performance
International Nuclear Information System (INIS)
Erfani, Rasool; Zare-Behtash, Hossein; Kontis, Konstantinos
2012-01-01
Interest in plasma actuators as active flow control devices is growing rapidly due to their lack of mechanical parts, light weight and high response frequency. Although the flow induced by these actuators has received much attention, the effect that the external flow has on the performance of the actuator itself must also be considered, especially the influence of unsteady high-speed flows which are fast becoming a norm in the operating flight envelopes. The primary objective of this study is to examine the characteristics of a dielectric barrier discharge (DBD) plasma actuator when exposed to an unsteady flow generated by a shock tube. This type of flow, which is often used in different studies, contains a range of flow regimes from sudden pressure and density changes to relatively uniform high-speed flow regions. A small circular shock tube is employed along with the schlieren photography technique to visualize the flow. The voltage and current traces of the plasma actuator are monitored throughout, and using the well-established shock tube theory the change in the actuator characteristics are related to the physical processes which occur inside the shock tube. The results show that not only is the shear layer outside of the shock tube affected by the plasma but the passage of the shock front and high-speed flow behind it also greatly influences the properties of the plasma. (paper)
12. Focusing of Shear Shock Waves
Science.gov (United States)
Giammarinaro, Bruno; Espíndola, David; Coulouvrat, François; Pinton, Gianmarco
2018-01-01
Focusing is a ubiquitous way to transform waves. Recently, a new type of shock wave has been observed experimentally with high-frame-rate ultrasound: shear shock waves in soft solids. These strongly nonlinear waves are characterized by a high Mach number, because the shear wave velocity is much slower, by 3 orders of magnitude, than the longitudinal wave velocity. Furthermore, these waves have a unique cubic nonlinearity which generates only odd harmonics. Unlike longitudinal waves for which only compressional shocks are possible, shear waves exhibit cubic nonlinearities which can generate positive and negative shocks. Here we present the experimental observation of shear shock wave focusing, generated by the vertical motion of a solid cylinder section embedded in a soft gelatin-graphite phantom to induce linearly vertically polarized motion. Raw ultrasound data from high-frame-rate (7692 images per second) acquisitions in combination with algorithms that are tuned to detect small displacements (approximately 1 μ m ) are used to generate quantitative movies of gel motion. The features of shear shock wave focusing are analyzed by comparing experimental observations with numerical simulations of a retarded-time elastodynamic equation with cubic nonlinearities and empirical attenuation laws for soft solids.
13. Collisionless electrostatic shocks
DEFF Research Database (Denmark)
Andersen, H.K.; Andersen, S.A.; Jensen, Vagn Orla
1970-01-01
An attempt was made in the laboratory to observe the standing collisionless electrostatic shocks in connection with the bow shock of the earth......An attempt was made in the laboratory to observe the standing collisionless electrostatic shocks in connection with the bow shock of the earth...
14. Macroeconomic impacts of oil price shocks in Asian economies
International Nuclear Information System (INIS)
Cunado, Juncal; Jo, Soojin; Perez de Gracia, Fernando
2015-01-01
This paper analyzes the macroeconomic impact of structural oil shocks in four of the top oil-consuming Asian economies, using a VAR model. We identify three different structural oil shocks via sign restrictions: an oil supply shock, an oil demand shock driven by global economic activity and an oil-specific demand shock. The main results suggest that economic activity and prices respond very differently to oil price shocks depending on their types. In particular, an oil supply shock has a limited impact, while a demand shock driven by global economic activity has a significant positive effect in all four Asian countries examined. Our finding also includes that policy tools such as interest rates and exchange rates help mitigating the effects of supply shocks in Japan and Korea; however, they can be more actively used in response to demands shocks. - Highlights: • We analyze the effects of three structural oil price shocks on Asian economies. • Supply shocks have limited impact on the economic activity of Asian economies examined. • Demand shocks due to economic activity boosts GDP of all economies. • CPIs in India and Indonesia were only marginally affected by oil price shocks. • Monetary and exchange rate tools help mitigating supply shocks in Korea and Japan.
15. Geomorphology: the Shock of the Familiar
Science.gov (United States)
Dietrich, W. E.
2008-12-01
Everyone experiences landscapes and has a sense about how they work: water runs down hill, it erodes and carries sediments, and that's about it, right? Introductory earth science text books are uniformly qualitative about the field, and leave one with little sense of wonder, and certainly not "shock". But four shocks occur if one peels away the first impressions. First, landscapes are surprisingly similar: the same forms are repeated in virtually all environments, including under the ocean and on other planets. Second, we lack theory and mechanistic observations to answer many simple first-order questions, e.g. what controls the width of a river, how does rock type control hillslope form and erosion rate, or, is there a topographic signature of life. Third, there are unexpected connections between surface erosion, deep earth processes, and climate. And fourth, the field itself, despite having been a subject of study for well over 100 years, is currently experiencing a revolution of ideas and discoveries through new tools, observatories, centers, journals, books, contributions of researchers from other disciplines, and from a significant hiring of young researchers in geomorphology. Deep messages await discovery in the simple landforms surrounding us.
16. Geometrical shock dynamics for magnetohydrodynamic fast shocks
KAUST Repository
Mostert, W.; Pullin, D. I.; Samtaney, Ravi; Wheatley, V.
2016-01-01
We describe a formulation of two-dimensional geometrical shock dynamics (GSD) suitable for ideal magnetohydrodynamic (MHD) fast shocks under magnetic fields of general strength and orientation. The resulting area–Mach-number–shock-angle relation is then incorporated into a numerical method using pseudospectral differentiation. The MHD-GSD model is verified by comparison with results from nonlinear finite-volume solution of the complete ideal MHD equations applied to a shock implosion flow in the presence of an oblique and spatially varying magnetic field ahead of the shock. Results from application of the MHD-GSD equations to the stability of fast MHD shocks in two dimensions are presented. It is shown that the time to formation of triple points for both perturbed MHD and gas-dynamic shocks increases as (Formula presented.), where (Formula presented.) is a measure of the initial Mach-number perturbation. Symmetry breaking in the MHD case is demonstrated. In cylindrical converging geometry, in the presence of an azimuthal field produced by a line current, the MHD shock behaves in the mean as in Pullin et al. (Phys. Fluids, vol. 26, 2014, 097103), but suffers a greater relative pressure fluctuation along the shock than the gas-dynamic shock. © 2016 Cambridge University Press
17. Geometrical shock dynamics for magnetohydrodynamic fast shocks
KAUST Repository
Mostert, W.
2016-12-12
We describe a formulation of two-dimensional geometrical shock dynamics (GSD) suitable for ideal magnetohydrodynamic (MHD) fast shocks under magnetic fields of general strength and orientation. The resulting area–Mach-number–shock-angle relation is then incorporated into a numerical method using pseudospectral differentiation. The MHD-GSD model is verified by comparison with results from nonlinear finite-volume solution of the complete ideal MHD equations applied to a shock implosion flow in the presence of an oblique and spatially varying magnetic field ahead of the shock. Results from application of the MHD-GSD equations to the stability of fast MHD shocks in two dimensions are presented. It is shown that the time to formation of triple points for both perturbed MHD and gas-dynamic shocks increases as (Formula presented.), where (Formula presented.) is a measure of the initial Mach-number perturbation. Symmetry breaking in the MHD case is demonstrated. In cylindrical converging geometry, in the presence of an azimuthal field produced by a line current, the MHD shock behaves in the mean as in Pullin et al. (Phys. Fluids, vol. 26, 2014, 097103), but suffers a greater relative pressure fluctuation along the shock than the gas-dynamic shock. © 2016 Cambridge University Press
18. Shock Incarceration: Rehabilitation or Retribution?
Science.gov (United States)
MacKenzie, Doris Layton; And Others
1989-01-01
Reviews Louisiana's shock incarceration program used as alternative to standard prison incarceration. Program involves short period of imprisonment in a "boot camp" type atmosphere followed by three phases of intensive parole supervision. Examines the program in regard to its rehabilitative potential and compares program elements to…
19. Acceleration mechanisms flares, magnetic reconnection and shock waves
International Nuclear Information System (INIS)
Colgate, S.A.
1979-01-01
Several mechanisms are briefly discussed for the acceleration of particles in the astrophysical environment. Included are hydrodynamic acceleration, spherically convergent shocks, shock and a density gradient, coherent electromagnetic acceleration, the flux tube origin, symmetries and instabilities, reconnection, galactic flares, intergalactic acceleration, stochastic acceleration, and astrophysical shocks. It is noted that the supernova shock wave models still depend critically on the presupernova star structure and the assumption of highly compact presupernova models for type I supernovae. 37 references
20. Elastic moduli, damping and modulus of rupture changes in a high alumina refractory castable due to different types of thermal shock
Directory of Open Access Journals (Sweden)
Pereira, A. H. A.
2012-06-01
Full Text Available The work herein verifies the changes of the elastic moduli, damping and modulus of rupture (MOR of a high alumina refractory castable due to heating, cooling and heating-cooling thermal shock damage. Twelve prismatic specimens were prepared for the tests and divided into four groups. The thermal shocks were performed on three groups, each containing three specimens having abrupt temperature changes of 1100°C during heating in the first group, during cooling in the second and during heating followed by cooling in the third group. The fourth group, which was taken as a reference did not receive any thermal shock. The elastic moduli were measured after each thermal shock cycle. After 10 cycles, the MOR, the damping and the damping dependence on excitation amplitude were measured at room temperature for all specimens. The elastic moduli showed a similar decrease and the damping a similar increase due to the cooling and heating-cooling thermal shocks. The heating thermal shocks caused no significant changes on the elastic moduli and damping. However, the MOR appeared to be sensitive to the heating thermal shock. This work also shows that the damping for the studied refractory castable is non-linear (i.e., amplitude of excitation sensitive and that this non-linearity increases when the damage level rises.
En este trabajo se investigaron las alteraciones de los módulos elásticos dinámicos, del amortiguamiento y del módulo de rotura (MOR de un material refractario moldeable de alta alúmina después de recibir choques térmicos de calentamiento, enfriamiento y calentamiento seguido de enfriamiento (calentamiento-enfriamiento. Para ello se prepararon doce cuerpos prismáticos dividiéndolos en cuatro grupos. Los choques térmicos se le aplicaron a sólo tres grupos, cada uno con tres muestras. Al primer grupo se le aplicó un cambio brusco de temperatura de 1100 °C en calentamiento, en enfriamiento al segundo grupo y calentamiento seguido
1. SPECIAL PURPOSE SHOCK TUBE for BLAST ASSESSMENT
Data.gov (United States)
Federal Laboratory Consortium — This device is a specially designed shock tube for testing fabric samples in a controlled environment. The device determines the appropriate types of sensors to be...
2. Miniature shock tube for laser driven shocks.
Science.gov (United States)
Busquet, Michel; Barroso, Patrice; Melse, Thierry; Bauduin, Daniel
2010-02-01
We describe in this paper the design of a miniature shock tube (smaller than 1 cm(3)) that can be placed in a vacuum vessel and allows transverse optical probing and longitudinal backside extreme ultraviolet emission spectroscopy in the 100-500 A range. Typical application is the study of laser launched radiative shocks, in the framework of what is called "laboratory astrophysics."
3. Are Credit Shocks Supply or Demand Shocks?
OpenAIRE
Bijapur, Mohan
2013-01-01
This paper provides new insights into the relationship between the supply of credit and the macroeconomy. We present evidence that credit shocks constitute shocks to aggregate supply in that they have a permanent effect on output and cause inflation to rise in the short term. Our results also suggest that the effects on aggregate supply have grown stronger in recent decades.
4. Shock absorbing structure
International Nuclear Information System (INIS)
Kojima, Naoki; Matsushita, Kazuo.
1992-01-01
Small pieces of shock absorbers are filled in a space of a shock absorbing vessel which is divided into a plurality of sections by partitioning members. These sections function to prevent excess deformation or replacement of the fillers upon occurrence of falling accident. Since the shock absorbing small pieces in the shock absorbing vessel are filled irregularly, shock absorbing characteristics such as compression strength is not varied depending on the direction, but they exhibit excellent shock absorbing performance. They surely absorb shocks exerted on a transportation vessel upon falling or the like. If existing artificial fillers such as pole rings made of metal or ceramic and cut pieces such as alumium extrusion molding products are used as the shock absorbing pieces, they have excellent fire-proofness and cold resistance since the small pieces are inflammable and do not contain water. (T.M.)
5. Melting under shock compression
International Nuclear Information System (INIS)
Bennett, B.I.
1980-10-01
A simple model, using experimentally measured shock and particle velocities, is applied to the Lindemann melting formula to predict the density, temperature, and pressure at which a material will melt when shocked from room temperature and zero pressure initial conditions
6. Effects of Atwood number on shock focusing in shock-cylinder interaction
Science.gov (United States)
Ou, Junfeng; Ding, Juchun; Luo, Xisheng; Zhai, Zhigang
2018-02-01
The evolution of shock-accelerated heavy-gas cylinder surrounded by the air with different Atwood numbers (A_t=0.28, 0.50, 0.63) is investigated, concentrating on shock focusing and jet formation. Experimentally, a soap film technique is used to generate an ideal two-dimensional discontinuous gas cylinder with a clear surface, which can guarantee the observation of shock wave movements inside the cylinder. Different Atwood numbers are realized by different mixing ratios of SF_6 and air inside the cylinder. A high-speed schlieren system is adopted to capture the shock motions and jet morphology. Numerical simulations are also performed to provide more information. The results indicate that an inward jet is formed for low Atwood numbers, while an outward jet is generated for high Atwood numbers. Different Atwood numbers will lead to the differences in the relative velocities between the incident shock and the refraction shock, which ultimately results in the differences in shock competition near the downstream pole. The morphology and feature of the jet are closely associated with the position and intensity of shock focusing. The pressure and vorticity contours indicate that the jet formation should be attributed to the pressure pulsation caused by shock focusing, and the jet development is ascribed to the vorticity induction. Finally, a time ratio proposed in the previous work for determining the shock-focusing type is verified by experiments.
7. Biomass shock pretreatment
Science.gov (United States)
Holtzapple, Mark T.; Madison, Maxine Jones; Ramirez, Rocio Sierra; Deimund, Mark A.; Falls, Matthew; Dunkelman, John J.
2014-07-01
Methods and apparatus for treating biomass that may include introducing a biomass to a chamber; exposing the biomass in the chamber to a shock event to produce a shocked biomass; and transferring the shocked biomass from the chamber. In some aspects, the method may include pretreating the biomass with a chemical before introducing the biomass to the chamber and/or after transferring shocked biomass from the chamber.
8. Acute Systemic Infection with Dengue Virus Leads to Vascular Leakage and Death through Tumor Necrosis Factor-α and Tie2/Angiopoietin Signaling in Mice Lacking Type I and II Interferon Receptors.
Science.gov (United States)
Phanthanawiboon, Supranee; Limkittikul, Kriengsak; Sakai, Yusuke; Takakura, Nobuyuki; Saijo, Masayuki; Kurosu, Takeshi
2016-01-01
Severe dengue is caused by host responses to viral infection, but the pathogenesis remains unknown. This is, in part, due to the lack of suitable animal models. Here, we report a non-mouse-adapted low-passage DENV-3 clinical isolate, DV3P12/08, derived from recently infected patients. DV3P12/08 caused a lethal systemic infection in type I and II IFN receptor KO mice (IFN-α/β/γR KO mice), which have the C57/BL6 background. Infection with DV3P12/08 induced a cytokine storm, resulting in severe vascular leakage (mainly in the liver, kidney and intestine) and organ damage, leading to extensive hemorrhage and rapid death. DV3P12/08 infection triggered the release of large amounts of TNF-α, IL-6, and MCP-1. Treatment with a neutralizing anti-TNF-α antibody (Ab) extended survival and reduced liver damage without affecting virus production. Anti-IL-6 neutralizing Ab partly prolonged mouse survival. The anti-TNF-α Ab suppressed IL-6, MCP-1, and IFN-γ levels, suggesting that the severe response to infection was triggered by TNF-α. High levels of TNF-α mRNA were expressed in the liver and kidneys, but not in the small intestine, of infected mice. Conversely, high levels of IL-6 mRNA were expressed in the intestine. Importantly, treatment with Angiopoietin-1, which is known to stabilize blood vessels, prolonged the survival of DV3P12/08-infected mice. Taken together, the results suggest that an increased level of TNF-α together with concomitant upregulation of Tie2/Angiopoietin signaling have critical roles in severe dengue infection.
9. Relativistic Shock Acceleration
International Nuclear Information System (INIS)
Duffy, P.; Downes, T.P.; Gallant, Y.A.; Kirk, J.G.
1999-01-01
In this paper we briefly review the basic theory of shock waves in relativistic hydrodynamics and magneto-hydrodynamics, emphasising some astrophysically interesting cases. We then present an overview of the theory of particle acceleration at such shocks describing the methods used to calculate the spectral indices of energetic particles. Recent results on acceleration at ultra-relativistic shocks are discussed. (author)
10. Collisionless shocks in space plasmas structure and accelerated particles
CERN Document Server
Burgess, David
2015-01-01
Shock waves are an important feature of solar system plasmas, from the solar corona out to the edge of the heliosphere. This engaging introduction to collisionless shocks in space plasmas presents a comprehensive review of the physics governing different types of shocks and processes of particle acceleration, from fundamental principles to current research. Motivated by observations of planetary bow shocks, interplanetary shocks and the solar wind termination shock, it emphasises the physical theory underlying these shock waves. Readers will develop an understanding of the complex interplay between particle dynamics and the electric and magnetic fields that explains the observations of in situ spacecraft. Written by renowned experts in the field, this up-to-date text is the ideal companion for both graduate students new to heliospheric physics and researchers in astrophysics who wish to apply the lessons of solar system shocks to different astrophysical environments.
11. Standing shocks in adiabatic black hole accretion of rotating matter
International Nuclear Information System (INIS)
Abramowicz, M.A.; Chakrabarti, S.K.
1988-08-01
We present all the solutions for stationary, axially symmetric, transonic, adiabatic flows with polytropic, rotating fluid configurations of small transverse thickness, in an arbitrarily chosen potential. Special attention is paid to the formation of the standing shocks in the case of black hole accretion and winds. We point out the possibility of three types of shocks depending upon three extreme physical conditions at the shocks. These are: Rankine-Hugoniot shocks, isentropic compression waves, and isothermal shocks. We write down the shock conditions for these three cases and discuss briefly the physical situations under which these shocks may form. A complete discussion on the properties of these shocks will be presented elsewhere. (author). 21 refs, 4 figs
12. Converging shocks in elastic-plastic solids.
Science.gov (United States)
Ortega, A López; Lombardini, M; Hill, D J
2011-11-01
We present an approximate description of the behavior of an elastic-plastic material processed by a cylindrically or spherically symmetric converging shock, following Whitham's shock dynamics theory. Originally applied with success to various gas dynamics problems, this theory is presently derived for solid media, in both elastic and plastic regimes. The exact solutions of the shock dynamics equations obtained reproduce well the results obtained by high-resolution numerical simulations. The examined constitutive laws share a compressible neo-Hookean structure for the internal energy e=e(s)(I(1))+e(h)(ρ,ς), where e(s) accounts for shear through the first invariant of the Cauchy-Green tensor, and e(h) represents the hydrostatic contribution as a function of the density ρ and entropy ς. In the strong-shock limit, reached as the shock approaches the axis or origin r=0, we show that compression effects are dominant over shear deformations. For an isothermal constitutive law, i.e., e(h)=e(h)(ρ), with a power-law dependence e(h) is proportional to ρ(α), shock dynamics predicts that for a converging shock located at r=R(t) at time t, the Mach number increases as M is proportional to [log(1/R)](α), independently of the space index s, where s=2 in cylindrical geometry and 3 in spherical geometry. An alternative isothermal constitutive law with p(ρ) of the arctanh type, which enforces a finite density in the strong-shock limit, leads to M is proportional to R(-(s-1)) for strong shocks. A nonisothermal constitutive law, whose hydrostatic part e(h) is that of an ideal gas, is also tested, recovering the strong-shock limit M is proportional to R(-(s-1)/n(γ)) originally derived by Whitham for perfect gases, where γ is inherently related to the maximum compression ratio that the material can reach, (γ+1)/(γ-1). From these strong-shock limits, we also estimate analytically the density, radial velocity, pressure, and sound speed immediately behind the shock. While the
13. System Shock: The Archetype of Operational Shock
Science.gov (United States)
2017-05-25
the battle space. They can also facilitate a much greater understanding of the variables involved in each party’s decision - making process. However...system shock nests within current US Army Unified Land Operations doctrine. In order to test the utility of system shock theory to Gray Zone...23 Neil E. Harrison, “Thinking about the World We Make ” in Chaos Theory in the Social Sciences: Foundations and Applications
14. Surface instabilities in shock loaded granular media
Science.gov (United States)
Kandan, K.; Khaderi, S. N.; Wadley, H. N. G.; Deshpande, V. S.
2017-12-01
The initiation and growth of instabilities in granular materials loaded by air shock waves are investigated via shock-tube experiments and numerical calculations. Three types of granular media, dry sand, water-saturated sand and a granular solid comprising PTFE spheres were experimentally investigated by air shock loading slugs of these materials in a transparent shock tube. Under all shock pressures considered here, the free-standing dry sand slugs remained stable while the shock loaded surface of the water-saturated sand slug became unstable resulting in mixing of the shocked air and the granular material. By contrast, the PTFE slugs were stable at low pressures but displayed instabilities similar to the water-saturated sand slugs at higher shock pressures. The distal surfaces of the slugs remained stable under all conditions considered here. Eulerian fluid/solid interaction calculations, with the granular material modelled as a Drucker-Prager solid, reproduced the onset of the instabilities as seen in the experiments to a high level of accuracy. These calculations showed that the shock pressures to initiate instabilities increased with increasing material friction and decreasing yield strain. Moreover, the high Atwood number for this problem implied that fluid/solid interaction effects were small, and the initiation of the instability is adequately captured by directly applying a pressure on the slug surface. Lagrangian calculations with the directly applied pressures demonstrated that the instability was caused by spatial pressure gradients created by initial surface perturbations. Surface instabilities are also shown to exist in shock loaded rear-supported granular slugs: these experiments and calculations are used to infer the velocity that free-standing slugs need to acquire to initiate instabilities on their front surfaces. The results presented here, while in an idealised one-dimensional setting, provide physical understanding of the conditions required to
15. Impact of Shock Front Rippling and Self-reformation on the Electron Dynamics at Low-Mach-number Shocks
Science.gov (United States)
Yang, Zhongwei; Lu, Quanming; Liu, Ying D.; Wang, Rui
2018-04-01
Electron dynamics at low-Mach-number collisionless shocks are investigated by using two-dimensional electromagnetic particle-in-cell simulations with various shock normal angles. We found: (1) The reflected ions and incident electrons at the shock front provide an effective mechanism for the quasi-electrostatic wave generation due to the charge-separation. A fraction of incident electrons can be effectively trapped and accelerated at the leading edge of the shock foot. (2) At quasi-perpendicular shocks, the electron trapping and reflection is nonuniform due to the shock rippling along the shock surface and is more likely to take place at some locations accompanied by intense reflected ion-beams. The electron trapping process has a periodical evolution over time due to the shock front self-reformation, which is controlled by ion dynamics. Thus, this is a cross-scale coupling phenomenon. (3) At quasi-parallel shocks, reflected ions can travel far back upstream. Consequently, quasi-electrostatic waves can be excited in the shock transition and the foreshock region. The electron trajectory analysis shows these waves can trap electrons at the foot region and reflect a fraction of them far back upstream. Simulation runs in this paper indicate that the micro-turbulence at the shock foot can provide a possible scenario for producing the reflected electron beam, which is a basic condition for the type II radio burst emission at low-Mach-number interplanetary shocks driven by Coronal Mass Ejections (CMEs).
16. Formation, structure, and stability of MHD intermediate shocks
International Nuclear Information System (INIS)
Wu, C.C.
1990-01-01
Contrary to the usual belief that MHD intermediate shocks are extraneous, the author has recently shown by numerical solutions of dissipative MHD equations that intermediate shocks are admissible and can be formed through nonlinear wave steepening from continuous waves. In this paper, the formation, structure and stability of intermediate shocks in dissipative MHD are considered in detail. The differences between the conventional theory and his are pointed out and clarified. He shows that all four types of intermediate shocks can be formed from smooth waves. He also shows that there are free parameters in the structure of the intermediate shocks, and that these parameters are related to the shock stability. In addition, he shows that a rotational discontinuity can not exist with finite width, indicate how this is related to the existence of time-dependent intermediate shocks, and show why the conventional theory is not a good approximation to dissipative MHD solutions whenever there is rotation in magnetic field
17. Hydraulic shock absorbers
International Nuclear Information System (INIS)
Thatcher, G.; Davidson, D. F.
1984-01-01
A hydraulic shock absorber of the dash pot kind for use with electrically conducting liquid such as sodium, has magnet means for electro magnetically braking a stream of liquid discharged from the cylinder. The shock absorber finds use in a liquid metal cooled nuclear reactor for arresting control rods
18. Our Favorite Film Shocks
DEFF Research Database (Denmark)
Willerslev, Rane; Suhr, Christian
2014-01-01
The modern medium of film has long been hailed for its capacity for producing shocks of an entertaining, thought-provoking, or even politically emancipative nature. But what is a shock, how and when does it occur, how long does it last, and are there particular techniques for producing cinematic...
19. Climate shocks and conflict
NARCIS (Netherlands)
2016-01-01
This paper offers a historical micro-level analysis of the impact of climate shocks on the incidence of civil conflict in colonial Nigeria (1912-1945). Primary historical sources on court cases, prisoners and homicides are used to capture conflict. To measure climate shocks we use the deviation
20. MHD shocks in the ISM
Science.gov (United States)
Chernoff, D. F.; Hollenbach, David J.; Mckee, Christopher F.
1990-01-01
Researchers survey shock solutions of a partially ionized gas with a magnetic field. The gas is modeled by interacting neutral, ion, electron and charged grain components. They employ a small neutral-ion chemical network to follow the dissociation and ionization of the major species. Cooling by molecular hydrogen (rotational, vibrational and dissociation), grains and dipole molecules is included. There are three basic types of solutions (C, C asterisk, and J) and some more complicated flows involving combinations of the basic types. The initial preshock conditions cover hydrogen nuclei densities of 1 less than n less than 10(exp 10) cm(-3) and shock velocities of 5 less than v(sub s) less than 60 km/s. The magnetic field is varied over 5 decades and the sensitivity of the results to grain parameters, UV and cosmic ray fluxes is ascertained. The parameter space is quite complicated, but there exist some simple divisions. When the initial ionization fraction is small (chi sub i less than 10(-5)), there is a sharp transition between fully C solutions at low velocity and strong J solutions at high velocity. When the initial ionization fraction is larger, C asterisk and/or very weak J shocks are present at low velocities in addition to the C solutions. The flow again changes to strong J shocks at high velocities. When the ionization fraction is large and the flow is only slightly greater than the bulk Alfven velocity, there is a complicated mixture of C, C asterisk and J solutions.
1. Lack of synergism between long-term poor glycaemic control and three gene polymorphisms of the renin angiotensin system on risk of developing diabetic nephropathy in type I diabetic patients
DEFF Research Database (Denmark)
Tarnow, L; Kjeld, T; Knudsen, E
2000-01-01
AIMS/HYPOTHESIS: Reports on a putative synergism between poor glycaemic control and carriage of the angiotensin II type 1 receptor (AGTR1) C1166-allele and risk of diabetic nephropathy have been conflicting. Therefore, we investigated the interaction between long-term glycaemic control and three...... studied Caucasian patients with Type I (insulin-dependent) diabetes mellitus and nephropathy (120 men 74 women, age 41.1 +/- 9.6 years, diabetes duration 28 +/- 8 years) and long-standing Type I diabetic patients with persistent normoalbuminuria (112 men 69 women, age 42.5 +/- 10.0 years, diabetes...... duration 27 +/- 9 years). Genotyping was PCR-based and metabolic control estimated from all measurements of HbA1c done in each patient [average (range) n = 31 (6-74)]. The median observation time (range) was 13.5 (2-14) years. RESULTS: Type I diabetic patients with a history of poor glycaemic control (HbA1...
2. Magnetic field amplification in interstellar collisionless shock waves
International Nuclear Information System (INIS)
Chevalier, R.A.
1977-01-01
It is stated that it is commonly assumed that a simple compression of the magnetic field occurs in interstellar shock waves. Recent space observations of the Earth's bow shock have shown that turbulent amplification of the magnetic field can occur in a collisionless shock. It is shown here that radio observations of Tycho's supernova remnant indicate the presence of a shock wave with such magnetic field amplification. There is at present no theory for the microinstabilities that give rise to turbulent amplification of the magnetic field. Despite the lack of theoretical understanding the possibility of field amplification in interstellar shock waves is here considered. In Tycho's supernova remnant there is evidence for the presence of a collisionless shock, and this is discussed. On the basis of observations of the Earth's bow shock, it is expected that turbulent magnetic field amplification occurs in the shock wave of this remnant, and this is supported by radio observations of the remnant. Consideration is given as to what extent the magnetic field is amplified in the shock wave on the basis of the non-thermal radio flux. (U.K.)
3. Collisionless shock waves
International Nuclear Information System (INIS)
Sagdeev, R.Z.; Kennel, C.F.
1991-01-01
Collisionless shocks cannot occur naturally on the earth, because nearly all matter here consists of electrically neutral atoms and molecules. In space, however, high temperatures and ultraviolet radiation from hot stars decompose atoms into their constituent nuclei and electrons, producing a soup of electrically charged particles known as a plasma. Plasma physicists proposed that the collective electrical and magnetic properties of plasmas could produce interactions that take the place of collisions and permit shocks to form. In 1964 the theoretical work found its first experimental confirmation. Norman F. Ness and his colleagues at the Goddard Space Flight Center, using data collected from the iMP-1 spacecraft, detected clear signs that a collisionless shock exists where the solar wind encounters the earth's magnetic field. More recent research has demonstrated that collisionless shocks appear in a dazzling array of astronomical settings. For example, shocks have been found in the solar wind upstream (sunward) of all the planet and comets that have been visited by spacecraft. Violent flares on the sun generate shocks that propagate to the far reaches of the solar system; tremendous galactic outbursts create disruptions in the intergalactic medium that are trillions of times larger. In addition, many astrophysicists think that shocks from supernova explosions in our galaxy accelerate cosmic rays, a class of extraordinarily energetic elementary particles and atomic nuclei that rain down on the earth from all directions
4. Pediatric Toxic Shock Syndrome
Directory of Open Access Journals (Sweden)
Jennifer Yee
2017-09-01
Full Text Available Audience: This scenario was developed to educate emergency medicine residents on the diagnosis and management of a pediatric patient with toxic shock syndrome. The case is also appropriate for teaching of medical students and advanced practice providers, as well as a review of the principles of crisis resource management, teamwork, and communication. Introduction: Toxic shock syndrome is a low-frequency, high-acuity scenario requiring timely identification and aggressive management. If patients suffering from this condition are managed incorrectly, they may progress into multi-organ dysfunction and potentially death. Toxic shock syndrome has been associated with Streptococcus and Staphylococcus aureus (Staph. Approximately half of Staph cases are associated with menstruation, which was first described in the 1970s-1980s and was associated with the use of absorbent tampons.1 Group A Streptococcus may cause complications such as necrotizing fasciitis and gangrenous myositis.2 Pediatric patients may present critically ill from toxic shock syndrome. Providers need to perform a thorough history and physical exam to discern the source of infection. Management requires aggressive care with antibiotics and IV fluids. Objectives: By the end of this simulation session, the learner will be able to: 1 Recognize toxic shock syndrome. 2 Review the importance of a thorough physical exam. 3 Discuss management of toxic shock syndrome, including supportive care and the difference in antibiotic choices for streptococcal and staphylococcal toxic shock syndrome. 4 Appropriately disposition a patient suffering from toxic shock syndrome. 5 Communicate effectively with team members and nursing staff during a resuscitation of a critically ill patient. Method: This session was conducted using high-fidelity simulation, followed by a debriefing session and lecture on toxic shock syndrome.
5. Lack of support for a role of the insulin gene variable number of tandem repeats minisatellite (INS-VNTR) locus in fetal growth or type 2 diabetes-related intermediate traits in United Kingdom populations.
Science.gov (United States)
Mitchell, Simon M S; Hattersley, Andrew T; Knight, Beatrice; Turner, Tina; Metcalf, Bradley S; Voss, Linda D; Davies, David; McCarthy, Anne; Wilkin, Terence J; Smith, George Davey; Ben-Shlomo, Yoav; Frayling, Timothy M
2004-01-01
The insulin gene variable number of tandem repeats minisatellite (INS-VNTR) class III allele is associated with altered fetal growth, type 2 diabetes risk (especially when paternally inherited), and insulin and IGF2 gene expression. Further studies are needed to establish the role of the INS-VNTR in fetal growth and assess whether its effects depend on the parent of origin. We analyzed the INS-VNTR-linked -23 Hph1 polymorphism in 2283 subjects, comprising 1184 children and 1099 parents. There were no differences (P VNTR was nominally associated (P VNTR in fetal growth and nominal association with type 2 diabetes-related intermediate traits.
6. Shocks near Jamming
Science.gov (United States)
Gómez, Leopoldo R.; Turner, Ari M.; van Hecke, Martin; Vitelli, Vincenzo
2012-02-01
Nonlinear sound is an extreme phenomenon typically observed in solids after violent explosions. But granular media are different. Right when they jam, these fragile and disordered solids exhibit a vanishing rigidity and sound speed, so that even tiny mechanical perturbations form supersonic shocks. Here, we perform simulations in which two-dimensional jammed granular packings are dynamically compressed and demonstrate that the elementary excitations are strongly nonlinear shocks, rather than ordinary phonons. We capture the full dependence of the shock speed on pressure and impact intensity by a surprisingly simple analytical model.
7. Mechanical shock absorber
International Nuclear Information System (INIS)
Vrillon, Bernard.
1973-01-01
The mechanical shock absorber described is made of a constant thickness plate pierced with circular holes regularly distributed in such a manner that for all the directions along which the strain is applied during the shock, the same section of the substance forming the plate is achieved. The shock absorber is made in a metal standing up to extensive deformation before breaking, selected from a group comprising mild steels and austenitic stainless steels. This apparatus is used for handling pots of fast neutron reactor fuel elements [fr
8. Shock formation of HCO+
International Nuclear Information System (INIS)
Elitzur, M.
1983-01-01
It is shown that shocks propagating in dense molecular regions will lead to a decrease in HCO + relative abundance, in agreement with previous results by Iglesias and Silk. The shock enhancement of HCO + detected in the supernova remnant IC 443 by Dickenson et al. is due to enhanced ionization in the shocked material. This is the result of the material penetrating the remnant cavity where it becomes exposed to the trapped cosmic rays. A similar enhancement appears to have been detected by Wootten in W28 and is explained by the same model
9. Lack of relationship between 11 beta-hydroxysteroid dehydrogenase setpoint and insulin sensitivity in the basal state and after 24h of insulin infusion in healthy subjects and type 2 diabetic patients
NARCIS (Netherlands)
Kerstens, MN; Riemens, SC; Sluiter, WJ; Pratt, JJ; Wolthers, BG; Dullaart, RPF
OBJECTIVES To test whether insulin resistance in type 2 diabetes mellitus is associated with an altered overall setpoint of the 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) mediated cortisol to cortisone interconversion towards cortisol, and to evaluate whether changes in insulin sensitivity
10. Lack of association between PKLR rs3020781 and NOS1AP rs7538490 and type 2 diabetes, overweight, obesity and related metabolic phenotypes in a Danish large-scale study: case-control studies and analyses of quantitative traits
Directory of Open Access Journals (Sweden)
Almind Katrine
2008-12-01
Full Text Available Abstract Background Several studies in multiple ethnicities have reported linkage to type 2 diabetes on chromosome 1q21-25. Both PKLR encoding the liver pyruvate kinase and NOS1AP encoding the nitric oxide synthase 1 (neuronal adaptor protein (CAPON are positioned within this chromosomal region and are thus positional candidates for the observed linkage peak. The C-allele of PKLR rs3020781 and the T-allele of NOS1AP rs7538490 are reported to strongly associate with type 2 diabetes in various European-descent populations comprising a total of 2,198 individuals with a combined odds ratio (OR of 1.33 [1.16–1.54] and 1.53 [1.28–1.81], respectively. Our aim was to validate these findings by investigating the impact of the two variants on type 2 diabetes and related quantitative metabolic phenotypes in a large study sample of Danes. Further, we intended to expand the analyses by examining the effect of the variants in relation to overweight and obesity. Methods PKLR rs3020781 and NOS1AP rs7538490 were genotyped, using TaqMan allelic discrimination, in a combined study sample comprising a total of 16,801 and 16,913 individuals, respectively. The participants were ascertained from four different study groups; the population-based Inter99 cohort (nPKLR = 5,962, nNOS1AP = 6,008, a type 2 diabetic patient group (nPKLR = 1,873, nNOS1AP = 1,874 from Steno Diabetes Center, a population-based study sample (nPKLR = 599, nNOS1AP = 596 from Steno Diabetes Center and the ADDITION Denmark screening study cohort (nPKLR = 8,367, nNOS1AP = 8,435. Results In case-control studies we evaluated the potential association between rs3020781 and rs7538490 and type 2 diabetes and obesity. No significant associations were observed for type 2 diabetes (rs3020781: pAF = 0.49, OR = 1.02 [0.96–1.10]; rs7538490: pAF = 0.84, OR = 0.99 [0.93–1.06]. Neither did we show association with overweight or obesity. Additionally, the PKLR and the NOS1AP genotypes were demonstrated not
11. Shock Isolation Elements Testing for High Input Loadings. Volume II. Foam Shock Isolation Elements.
Science.gov (United States)
SHOCK ABSORBERS ), (*GUIDED MISSILE SILOS, SHOCK ABSORBERS ), (*EXPANDED PLASTICS, (*SHOCK(MECHANICS), REDUCTION), TEST METHODS, SHOCK WAVES, STRAIN(MECHANICS), LOADS(FORCES), MATHEMATICAL MODELS, NUCLEAR EXPLOSIONS, HARDENING.
12. Counseling For Future Shock
Science.gov (United States)
Morgan, Lewis B.
1974-01-01
In this article the author looks at some of the searing prophecies made by Alvin Toffler in his book Future Shock and relates them to the world of the professional counselor and the clientele the counselor attempts to serve. (Author)
13. Life shocks and homelessness.
Science.gov (United States)
Curtis, Marah A; Corman, Hope; Noonan, Kelly; Reichman, Nancy E
2013-12-01
We exploited an exogenous health shock-namely, the birth of a child with a severe health condition-to investigate the effect of a life shock on homelessness in large cities in the United States as well as the interactive effects of the shock with housing market characteristics. We considered a traditional measure of homelessness, two measures of housing instability thought to be precursors to homelessness, and a combined measure that approximates the broadened conceptualization of homelessness under the 2009 Homeless Emergency Assistance and Rapid Transition to Housing Act (2010). We found that the shock substantially increases the likelihood of family homelessness, particularly in cities with high housing costs. The findings are consistent with the economic theory of homelessness, which posits that homelessness results from a conjunction of adverse circumstances in which housing markets and individual characteristics collide.
14. Unlimited Relativistic Shock Surfing Acceleration
International Nuclear Information System (INIS)
Ucer, D.; Shapiro, V. D.
2001-01-01
Nonrelativistic shock surfing acceleration at quasiperpendicular shocks is usually considered to be a preacceleration mechanism for slow pickup ions to initiate diffusive shock acceleration. In shock surfing, the particle accelerates along the shock front under the action of the convective electric field of the plasma flow. However, the particle also gains kinetic energy normal to the shock and eventually escapes downstream. We consider the case when ions are accelerated to relativistic velocities. In this case, the ions are likely to be trapped for infinitely long times, because the energy of bounce oscillations tends to decrease during acceleration. This suggests the possibility of unlimited acceleration by shock surfing
International Nuclear Information System (INIS)
Song, S.G.; Gray, G.T. III, and; Lopez, M.F.
1996-01-01
The post-shock stress-strain response and microstructural evolution of Zr shock-loaded to 7 GPa were investigated. A Bauschinger effect in the room temperature reload stress-strain behavior due to shock-loading has been observed following yielding. Deformation twinning is shown to play a more important role than slip during post-shock plastic deformation and work hardening. The work hardening rate of the shock-prestrained specimens is less temperature sensitive than that of annealed Zr. The underlying microstructures responsible for the Bauschinger effect and the differences in work hardening behavior are characterized. A new type of dense dislocation arrangement occurring during the shock-wave deformation of Zr is discussed. copyright 1996 American Institute of Physics
16. Shock wave focusing in water inside convergent structures
Directory of Open Access Journals (Sweden)
C Wang
2016-09-01
Full Text Available Experiments on shock focusing in water-filled convergent structures have been performed. A shock wave in water is generated by means of a projectile, launched from a gas gun, which impacts a water-filled convergent structure. Two types of structures have been tested; a bulk material and a thin shell structure. The geometric shape of the convergent structures is given by a logarithmic spiral, and this particular shape is chosen because it maximizes the amount of energy reaching the focal region. High-speed schlieren photography is used to visualize the shock dynamics during the focusing event. Results show that the fluid-structure interaction between the thin shell structure and the shock wave in the water is different from that of a bulk structure; multiple reflections of the shock wave inside the thin shell are reflected back into the water, thus creating a wave train, which is not observed for shock focusing in a bulk material.
17. Transient shock waves in heliosphere and Sun-Earth relations
International Nuclear Information System (INIS)
Voeroes, Z.
1990-01-01
The problem of shock waves, caused by solar activity in the Earth's magnetosphere and its magnetic field, is discussed. All types of shock waves have their origin either in solar corona effects or in solar eruptions. Ionospheric and magnetospheric effects, such as X and gamma radiation, particle production, geomagnetic storms and shock waves, caused by solar activity, are dealt with and attempts are made to explain their interdependence. The origin and propagation of coronal shock waves, interplanetary shock waves and geomagnetic field disorders are described and their relations discussed. The understanding of the solar corona and wind phenomena seems to allow prediction of geomagnetic storms. The measurement and analysis of solar activity and its effects could yield useful information about shock waves physics, geomagnetosphere structure and relations between the Earth and the Sun. (J.J.). 7 figs., 1 tab., 37 refs
18. Shock modification and chemistry and planetary geologic processes
International Nuclear Information System (INIS)
Boslough, M.S.
1991-01-01
This paper brings the rapid advances on shock processing of materials to the attention of Earth scientists, and to put these advances in the context of planetary geologic processes. Most of the recent research in this area has been directed at materials modification an synthesis, and the information gained has direct relevance to shock effects in nature. Research on various types of shock modification and chemistry in both naturally and experimentally shocked rocks and minerals is reviewed, and where appropriate their significance to planetary processes is indicated. As a case study, the surface of Mars is suggested as a place where conditions are optimal for shock processing to be a dominant factor. The various mechanisms of shock modification, activation, synthesis and decomposition are all proposed as major contributors to the evolution of chemical, mineralogical, and physical properties of the Martian regolith
19. Thermal shock considerations for the TFCX limiter and first wall
International Nuclear Information System (INIS)
Haines, J.R.; Fuller, G.M.
1983-01-01
Resistance to thermal shock fracture of limiter and first wall surface material candidates during plasma disruption heating conditions is evaluated. A simple, figure-of-merit type thermal shock parameter which provides a mechanism to rank material candidates is derived. Combining this figure-of-merit parameter with the parameters defining specific heating conditions yields a non-dimensional thermal shock parameter. For values of this parameter below a critical value, a given material is expected to undergo thermal shock damage. Prediction of thermal shock damage with this parameter is shown to exhibit good agreement with test data. Applying this critical parameter value approach, all materials examined in this study are expected to experience thermal shock damage for nominal TFCX plasma disruption conditions. Since the extent of this damage is not clear, tests which explore the range of expected conditions for TFCX are recommended
20. Experimental study of micro-shock tube flow
Energy Technology Data Exchange (ETDEWEB)
Park, Jin Ouk; Kim, Gyu Wan; Rasel, Md. Alim Iftakhar [Dept. of Mechanical Engineering, Andong National University, Andong (Korea, Republic of); Kim, Heuy Dong [Fire Research Center, Korea Institute of Civil Engineering and Building Technology, Hwasung (Korea, Republic of)
2015-03-15
The flow characteristics in micro shock tube are investigated experimentally. Studies were carried out using a stainless steel micro shock tube. Shock and expansion wave was measured using 8 pressure sensors. The initial pressure ratio was varied from 4.3 to 30.5, and the diameter of tube was also changed from 3 mm to 6 mm. Diaphragm conditions were varied using two types of diaphragms. The results obtained show that the shock strength in the tube becomes stronger for an increase in the initial pressure ratio and diameter of tube. For the thinner diaphragm, the highest shock strength was found among varied diaphragm condition. Shock attenuation was highly influenced by the diameter of tube.
1. Dynamic testing of adhesive joints using a shock testing machine
NARCIS (Netherlands)
Aanhold, J.E. van; Weersink, A.F.J.; Ludolphy, J.W.L.
1998-01-01
A light-weight shock testing machine, designed for type approval testing of naval equipment up to 300 kg mass, has been modified into a dynamic tensile test rig. This enables to test structural details for high rate dynamic tensile loadings such as occur during underwater shock. The maximum capacity
2. out-of-n systems with shock model
African Journals Online (AJOL)
distributed. Sarhan, A.M. and Abouammoh (2000) used the shock model to derive the re- liability function of k-out-of-n systems with nonindependent and nonidentical components. They assumed that a system is subjected to n + m independent types of shocks. Liu et al. (2008) proposed a model to evaluate the reliability ...
3. Dust acoustic solitary and shock waves in strongly coupled dusty ...
between nonlinear and dispersion effects can result in the formation of symmetrical solitary waves. Also shock ... et al have studied the effect of nonadiabatic dust charge variation on the nonlinear dust acoustic wave with ..... Figure 5 presents the border between oscillatory- and monotonic-type shock waves as functions of ...
4. Laura: Soybean variety lacking Kunitz trypsin inhibitor
Directory of Open Access Journals (Sweden)
Srebrić Mirjana
2010-01-01
Full Text Available Grain of conventional soybean varieties requires heat processing to break down trypsin inhibitor's activity before using as food or animal feed. At the same time, protein denaturation and other qualitative changes occur in soybean grain, especially if the temperature of heating is not controlled. Two types of trypsin inhibitor were found in soybean grain the Kunitz trypsin inhibitor and the Bowman-Birk inhibitor. Mature grain of soybean Laura is lacking Kunitz trypsin inhibitor. Grain yield of variety Laura is equal to high yielding varieties from the maturity group I, where it belongs. Lacking of Kunitz-trypsin inhibitor makes soybean grain suitable for direct feeding in adult non ruminant animals without previous thermal processing. Grain of variety Laura can be processed for a shorter period of time than conventional soybeans. This way we save energy, and preserve valuable nutritional composition of soybean grain, which is of interest in industrial processing.
5. Technology shocks matter
OpenAIRE
Jonas D. M. Fisher
2002-01-01
This paper uses the neoclassical growth model to identify the effects of technological change on the US business cycle. In the model there are two sources of technological change: neutral, which effects the production of all goods homogeneously, and investment-specific. Investment-specific shocks are the unique source of the secular trend in the real price of investment goods, while shocks to both kinds of technology are the only factors which affect labor productivity in the long run. Consis...
6. The Heliospheric Termination Shock
Science.gov (United States)
Jokipii, J. R.
2013-06-01
The heliospheric termination shock is a vast, spheroidal shock wave marking the transition from the supersonic solar wind to the slower flow in the heliosheath, in response to the pressure of the interstellar medium. It is one of the most-important boundaries in the outer heliosphere. It affects energetic particles strongly and for this reason is a significant factor in the effects of the Sun on Galactic cosmic rays. This paper summarizes the general properties and overall large-scale structure and motions of the termination shock. Observations over the past several years, both in situ and remote, have dramatically revised our understanding of the shock. The consensus now is that the shock is quite blunt, is with the front, blunt side canted at an angle to the flow direction of the local interstellar plasma relative to the Sun, and is dynamical and turbulent. Much of this new understanding has come from remote observations of energetic charged particles interacting with the shock, radio waves and radiation backscattered from interstellar neutral atoms. The observations and the implications are discussed.
7. Lack of TNF-alpha receptor type 2 protects motor neurons in a cellular model of amyotrophic lateral sclerosis and in mutant SOD1 mice but does not affect disease progression.
Science.gov (United States)
Tortarolo, Massimo; Vallarola, Antonio; Lidonnici, Dario; Battaglia, Elisa; Gensano, Francesco; Spaltro, Gabriella; Fiordaliso, Fabio; Corbelli, Alessandro; Garetto, Stefano; Martini, Elisa; Pasetto, Laura; Kallikourdis, Marinos; Bonetto, Valentina; Bendotti, Caterina
2015-10-01
Changes in the homeostasis of tumor necrosis factor α (TNFα) have been demonstrated in patients and experimental models of amyotrophic lateral sclerosis (ALS). However, the contribution of TNFα to the development of ALS is still debated. TNFα is expressed by glia and neurons and acts through the membrane receptors TNFR1 and TNFR2, which may have opposite effects in neurodegeneration. We investigated the role of TNFα and its receptors in the selective motor neuron death in ALS in vitro and in vivo. TNFR2 expressed by astrocytes and neurons, but not TNFR1, was implicated in motor neuron loss in primary SOD1-G93A co-cultures. Deleting TNFR2 from SOD1-G93A mice, there was partial but significant protection of spinal motor neurons, sciatic nerves, and tibialis muscles. However, no improvement of motor impairment or survival was observed. Since the sciatic nerves of SOD1-G93A/TNFR2-/- mice showed high phospho-TAR DNA-binding protein 43 (TDP-43) accumulation and low levels of acetyl-tubulin, two indices of axonal dysfunction, the lack of symptom improvement in these mice might be due to impaired function of rescued motor neurons. These results indicate the interaction between TNFR2 and membrane-bound TNFα as an innovative pathway involved in motor neuron death. Nevertheless, its inhibition is not sufficient to stop disease progression in ALS mice, underlining the complexity of this pathology. We show evidence of the involvement of neuronal and astroglial TNFR2 in the motor neuron degeneration in ALS. Both concur to cause motor neuron death in primary astrocyte/spinal neuron co-cultures. TNFR2 deletion partially protects motor neurons and sciatic nerves in SOD1-G93A mice but does not improve their symptoms and survival. However, TNFR2 could be a new target for multi-intervention therapies. © 2015 International Society for Neurochemistry.
8. GLP-1 and Calcitonin Concentration in Humans: Lack of Evidence of Calcitonin Release from Sequential Screening in over 5000 Subjects with Type 2 Diabetes or Nondiabetic Obese Subjects Treated with the Human GLP-1 Analog, Liraglutide
DEFF Research Database (Denmark)
Hegedüs, Laszlo; Moses, Alan C; Zdravkovic, Milan
2011-01-01
to the GLP-1 receptor agonist liraglutide in subjects with type 2 diabetes mellitus or nondiabetic obese subjects. Methods: Unstimulated serum CT concentrations were measured at 3-month intervals for no more than 2 yr in a series of trials in over 5000 subjects receiving liraglutide or control therapy....... Results: Basal mean CT concentrations were at the low end of normal range in all treatment groups and remained low throughout the trials. At 2 yr, estimated geometric mean values were no greater than 1.0 ng/liter, well below upper normal ranges for males and females. Proportions of subjects whose CT...
9. Lack of Correlation of the Serum 25(OH Vitamin D Levels with the Glycated Hemoglobin A1c and the Lipid Profile in Type 2 Diabetes Patients on Oral Antidiabetic Drugs – Preliminary Data
Directory of Open Access Journals (Sweden)
Bakalov D.
2014-12-01
Full Text Available Data from different studies correlating the serum 25(OHD levels with the metabolic and glycemic parameters in type 2 diabetes patients are still varying. The objective if this study was to describe the correlation between serum 25(OHD levels and some metabolic parameters in Bulgarian type 2 diabetes patients on oral antidiabetic drugs. One hundred type 2 diabetes patients participated - 56 men and 44 women. The mean age and diabetes duration of the women was 59.0 and 9.8 years, of the men - 58.0 and 7.7 years respectively. Complete patient history was taken and physical examination was performed (body weight and height, waist circumference. Body composition was measured on a leg-to-leg body impedance analyzer (TBF-215, Tanita Corp., Tokyo, Japan. Serum levels of vitamin D were measured by electro-hemi-luminescent detection as 25-(ОН D Total (ECLIA, Elecsys 2010, Roche Diagnostics, Switzerland. Glycated hemoglobin A1c was measured on a NycoCard reader (Alere™. Total, HDL-cholesterol (direct and triglycerides were analyzed on a Cobas Integra 400+ analyzer. Correlation analysis was performed on a SPSS 13.0 for Windows platform and included 10 curves. The data were first analyzed for the group as a whole and then separately for men and women as well as in the different vitamin D tertiles. The mean serum 25-OH-vitamin D levels were 23.8 ± 12.1 nmol/l in women and 33.3 ± 20.0 nmol/l in men. We were unable to find any statistically significant correlation between serum 25(OH vitaminand the serum lipids (cholesterol profile and triglycerides. On the contrary, there was a weak correlation with the glycated hemoglobin A1c (cubic model, R2 = 0.178, p = 0.05 and the BMI (inverse model, R2 = 0.101, p = 0.038. The sub-analyses (men versus women or according to tertiles of vitamin D did not produce any additional information. The influence of vitamin D on the parameters of the metabolic control in type 2 diabetes is very weak on an individual level. It
10. Differentially regulated protein kinase A (PKA) activity in adipose tissue and liver is associated with resistance to diet-induced obesity and glucose intolerance in mice that lack PKA regulatory subunit type IIα.
Science.gov (United States)
London, Edra; Nesterova, Maria; Sinaii, Ninet; Szarek, Eva; Chanturiya, Tatyana; Mastroyannis, Spyridon A; Gavrilova, Oksana; Stratakis, Constantine A
2014-09-01
The cAMP-dependent protein kinase A (PKA) signaling system is widely expressed and has a central role in regulating cellular metabolism in all organ systems affected by obesity. PKA has four regulatory (RIα, RIIα, RIβ, RIIβ) and four catalytic (Cα, Cβ, Cγ, Prkx) subunit isoforms that have tissue-specific expression profiles. In mice, knockout (KO) of RIIβ, the primary PKA regulatory subunit in adipose tissue or knockout of the catalytic subunit Cβ resulted in a lean phenotype that resists diet-induced obesity and associated metabolic complications. Here we report that the disruption of the ubiquitously expressed PKA RIIα subunit in mice (RIIαKO) confers resistance to diet-induced obesity, glucose intolerance, and hepatic steatosis. After 2-week high-fat diet exposure, RIIαKO mice weighed less than wild-type littermates. Over time this effect was more pronounced in female mice that were also leaner than their wild-type counterparts, regardless of the diet. Decreased intake of a high-fat diet contributed to the attenuated weight gain in RIIαKO mice. Additionally, RIIα deficiency caused differential regulation of PKA in key metabolic organs: cAMP-stimulated PKA activity was decreased in liver and increased in gonadal adipose tissue. We conclude that RIIα represents a potential target for therapeutic interventions in obesity, glucose intolerance, and nonalcoholic fatty liver disease.
11. Oral administration of Lactococcus lactis-expressing heat shock protein 65 and tandemly repeated IA2P2 prevents type 1 diabetes in NOD mice.
Science.gov (United States)
Liu, Kun-Feng; Liu, Xiao-Rui; Li, Guo-Liang; Lu, Shi-Ping; Jin, Liang; Wu, Jie
2016-06-01
12. A model for radio emission from solar coronal shocks
Energy Technology Data Exchange (ETDEWEB)
Zhao, G. Q.; Chen, L.; Wu, D. J., E-mail: [email protected] [Purple Mountain Observatory, CAS, Nanjing 210008 (China)
2014-05-01
Solar coronal shocks are very common phenomena in the solar atmosphere and are believed to be the drivers of solar type II radio bursts. However, the microphysical nature of these emissions is still an open question. This paper proposes that electron cyclotron maser (ECM) emission is responsible for the generation of radiation from the coronal shocks. In the present model, an energetic ion beam accelerated by the shock first excites the Alfvén wave (AW), then the excited AW leads to the formation of a density-depleted duct along the foreshock boundary of the shock. In this density-depleted duct, the energetic electron beam produced via the shock acceleration can effectively excite radio emission by ECM instability. Our results show that this model may potentially be applied to solar type II radio bursts.
13. A model for radio emission from solar coronal shocks
International Nuclear Information System (INIS)
Zhao, G. Q.; Chen, L.; Wu, D. J.
2014-01-01
Solar coronal shocks are very common phenomena in the solar atmosphere and are believed to be the drivers of solar type II radio bursts. However, the microphysical nature of these emissions is still an open question. This paper proposes that electron cyclotron maser (ECM) emission is responsible for the generation of radiation from the coronal shocks. In the present model, an energetic ion beam accelerated by the shock first excites the Alfvén wave (AW), then the excited AW leads to the formation of a density-depleted duct along the foreshock boundary of the shock. In this density-depleted duct, the energetic electron beam produced via the shock acceleration can effectively excite radio emission by ECM instability. Our results show that this model may potentially be applied to solar type II radio bursts.
14. Lack of association of C282Y and H63D mutations in the hemochromatosis (HFE) gene with diabetes mellitus type 2 in a case-control study of women in Brazil.
Science.gov (United States)
Gomes, K B; Carvalho, M G; Coelho, F F; Rodrigues, I F; Soares, A L; Guimarães, D A; Fernandes, A P
2009-10-27
Hereditary hemochromatosis is one of the most common autosomal recessive diseases; it is characterized by excess absorption of iron. Clinically, the major challenge is to diagnose increased iron deposition before irreversible tissue damage has occurred. C282Y and H63D are the main mutations related to hereditary hemochromatosis; these mutations have been reported to be associated with increased risk of developing diabetes mellitus type 2 (DM2). We investigated whether these mutations are associated with increased risk for the development of DM2 in women in Brazil. Seventy-two women with clinical diagnosis of DM2 under treatment with hypoglycemic agents and a control group composed of 72 women with no clinical history of diabetes were studied. The C282Y and H63D mutations were determined by PCR-RFLP. Significant differences were not observed for C282Y and H63D, when we compared diabetic and non-diabetic women. We suggest that mutations C282Y and H63D in the HFE gene are not significant risk factors for the development of DM2 in Brazilian women.
15. Shocks in fragile matter
Science.gov (United States)
Vitelli, Vincenzo
2012-02-01
Non-linear sound is an extreme phenomenon typically observed in solids after violent explosions. But granular media are different. Right when they unjam, these fragile and disordered solids exhibit vanishing elastic moduli and sound speed, so that even tiny mechanical perturbations form supersonic shocks. Here, we perform simulations in which two-dimensional jammed granular packings are continuously compressed, and demonstrate that the resulting excitations are strongly nonlinear shocks, rather than linear waves. We capture the full dependence of the shock speed on pressure and compression speed by a surprisingly simple analytical model. We also treat shear shocks within a simplified viscoelastic model of nearly-isostatic random networks comprised of harmonic springs. In this case, anharmonicity does not originate locally from nonlinear interactions between particles, as in granular media; instead, it emerges from the global architecture of the network. As a result, the diverging width of the shear shocks bears a nonlinear signature of the diverging isostatic length associated with the loss of rigidity in these floppy networks.
16. Lack of evidence for a harmful effect of sodium-glucose co-transporter 2 (SGLT2) inhibitors on fracture risk among type 2 diabetes patients: a network and cumulative meta-analysis of randomized controlled trials.
Science.gov (United States)
Tang, H L; Li, D D; Zhang, J J; Hsu, Y H; Wang, T S; Zhai, S D; Song, Y Q
2016-12-01
To evaluate the comparative effects of sodium-glucose co-transporter 2 (SGLT2) inhibitors on risk of bone fracture in patients with type 2 diabetes mellitus (T2DM). PubMed, EMBASE, CENTRAL and ClinicalTrials.gov were systematically searched from inception to 27 January 2016 to identify randomized controlled trials (RCTs) reporting the outcome of fracture in patients with T2DM treated with SGLT2 inhibitors. Pairwise and network meta-analyses, as well as a cumulative meta-analysis, were performed to calculate odds ratios (ORs) and 95% confidence intervals (CIs). A total of 38 eligible RCTs (10 canagliflozin, 15 dapagliflozin and 13 empagliflozin) involving 30 384 patients, with follow-ups ranging from 24 to 160 weeks, were included. The fracture event rates were 1.59% in the SGLT2 inhibitor groups and 1.56% in the control groups. The incidence of fracture events was similar among these three SGLT2 inhibitor groups. Compared with placebo, canagliflozin (OR 1.15; 95% CI 0.71-1.88), dapagliflozin (OR 0.68; 95% CI 0.37-1.25) and empagliflozin (OR 0.93; 95% CI 0.74-1.18) were not significantly associated with an increased risk of fracture. Our cumulative meta-analysis indicated the robustness of the null findings with regard to SGLT2 inhibitors. Our meta-analysis based on available RCT data does not support the harmful effect of SGLT2 inhibitors on fractures, although future safety monitoring from RCTs and real-world data with detailed information on bone health is warranted. © 2016 John Wiley & Sons Ltd.
17. Mechanical vibration and shock analysis, sinusoidal vibration
CERN Document Server
Lalanne, Christian
2014-01-01
Everything engineers need to know about mechanical vibration and shock...in one authoritative reference work! This fully updated and revised 3rd edition addresses the entire field of mechanical vibration and shock as one of the most important types of load and stress applied to structures, machines and components in the real world. Examples include everything from the regular and predictable loads applied to turbines, motors or helicopters by the spinning of their constituent parts to the ability of buildings to withstand damage from wind loads or explosions, and the need for cars to m
18. Vulnerability to shocks in the global seafood trade network
Science.gov (United States)
Gephart, Jessica A.; Rovenskaya, Elena; Dieckmann, Ulf; Pace, Michael L.; Brännström, Åke
2016-03-01
19. Characteristics of shocks in the solar corona, as inferred from radio, optical, and theoretical investigations
Science.gov (United States)
Maxwell, A.; Dryer, M.
1982-01-01
Solar radio bursts of spectral type II provide one of the chief diagnostics for the propagation of shocks through the solar corona. Radio data on the shocks are compared with computer models for propagation of fast-mode MHD shocks through the solar corona. Data on coronal shocks and high-velocity ejecta from solar flares are then discussed in terms of a general model consisting of three main velocity regimes.
20. Reduced alcohol consumption in mice lacking preprodynorphin.
Science.gov (United States)
Blednov, Yuri A; Walker, Danielle; Martinez, Marni; Harris, R Adron
2006-10-01
Many studies suggest a role for endogenous opioid peptides and their receptors in regulation of ethanol intake. It is commonly accepted that the kappa-opioid receptors and their endogenous ligands, dynorphins, produce a dysphoric state and therefore may be responsible for avoidance of alcohol. We used mutant mice lacking preprodynorphin in a variety of behavioral tests of alcohol actions. Null mutant female, but not male, mice showed significantly lower preference for alcohol and consumed lower amounts of alcohol in a two-bottle choice test as compared with wild-type littermates. In the same test, knockout mice of both sexes showed a strong reduction of preference for saccharin compared to control mice. In contrast, under conditions of limited (4 h) access (light phase of the light/dark cycle), null mutant mice did not show any differences in consumption of saccharin, but they showed significantly reduced intake of sucrose. To determine the possible cause for reduction of ethanol preference and intake, we studied other ethanol-related behaviors in mice lacking the preprodynorphin gene. There were no differences between null mutant and wild-type mice in ethanol-induced loss of righting reflex, acute ethanol withdrawal, ethanol-induced conditioned place preference, or conditioned taste aversion to ethanol. These results indicate that deletion of preprodynorphin leads to substantial reduction of alcohol intake in female mice, and suggest that this is caused by decreased orosensory reward of alcohol (sweet taste and/or palatability).
1. H2 emission from non-stationary magnetized bow shocks
Science.gov (United States)
Tram, L. N.; Lesaffre, P.; Cabrit, S.; Gusdorf, A.; Nhung, P. T.
2018-01-01
When a fast moving star or a protostellar jet hits an interstellar cloud, the surrounding gas gets heated and illuminated: a bow shock is born that delineates the wake of the impact. In such a process, the new molecules that are formed and excited in the gas phase become accessible to observations. In this paper, we revisit models of H2 emission in these bow shocks. We approximate the bow shock by a statistical distribution of planar shocks computed with a magnetized shock model. We improve on previous works by considering arbitrary bow shapes, a finite irradiation field and by including the age effect of non-stationary C-type shocks on the excitation diagram and line profiles of H2. We also examine the dependence of the line profiles on the shock velocity and on the viewing angle: we suggest that spectrally resolved observations may greatly help to probe the dynamics inside the bow shock. For reasonable bow shapes, our analysis shows that low-velocity shocks largely contribute to H2 excitation diagram. This can result in an observational bias towards low velocities when planar shocks are used to interpret H2 emission from an unresolved bow. We also report a large magnetization bias when the velocity of the planar model is set independently. Our 3D models reproduce excitation diagrams in BHR 71 and Orion bow shocks better than previous 1D models. Our 3D model is also able to reproduce the shape and width of the broad H2 1-0S(1) line profile in an Orion bow shock (Brand et al. 1989).
2. Physics of Collisionless Shocks Space Plasma Shock Waves
CERN Document Server
Balogh, André
2013-01-01
The present book provides a contemporary systematic treatment of shock waves in high-temperature collisionless plasmas as are encountered in near Earth space and in Astrophysics. It consists of two parts. Part I develops the complete theory of shocks in dilute hot plasmas under the assumption of absence of collisions among the charged particles when the interaction is mediated solely by the self-consistent electromagnetic fields. Such shocks are naturally magnetised implying that the magnetic field plays an important role in their evolution and dynamics. This part treats both subcritical shocks, which dissipate flow energy by generating anomalous resistance or viscosity, and supercritical shocks. The main emphasis is, however, on super-critical shocks where the anomalous dissipation is insufficient to retard the upstream flow. These shocks, depending on the direction of the upstream magnetic field, are distinguished as quasi-perpendicular and quasi-parallel shocks which exhibit different behaviours, reflecti...
3. Life Shocks and Homelessness
Science.gov (United States)
Corman, Hope; Noonan, Kelly; Reichman, Nancy E.
2014-01-01
We exploited an exogenous health shock—namely, the birth of a child with a severe health condition—to investigate the effect of a life shock on homelessness in large cities in the United States as well as the interactive effects of the shock with housing market characteristics. We considered a traditional measure of homelessness, two measures of housing instability thought to be precursors to homelessness, and a combined measure that approximates the broadened conceptualization of homelessness under the 2009 Homeless Emergency Assistance and Rapid Transition to Housing Act (2010). We found that the shock substantially increases the likelihood of family homelessness, particularly in cities with high housing costs. The findings are consistent with the economic theory of homelessness, which posits that homelessness results from a conjunction of adverse circumstances in which housing markets and individual characteristics collide. PMID:23868747
4. Health Shocks and Retirement:
DEFF Research Database (Denmark)
Datta Gupta, Nabanita; Larsen, Mona
We investigate the effect of an acute health shock on retirement among elderly male workers in Denmark, 1991-1999, and in particular whether various welfare state programs and institutions impinge on the retirement effect. The results show that an acute health event increases the retirement chances...... significant. For the most part, the retirement effect following a health shock seems to be immune to the availability of a multitude of government programs for older workers in Denmark....... benefits in Denmark nor by the promotion of corporate social responsibility initiatives since the mid-1990s. In the late 1990s, however, the retirement rate following a health shock is reduced to 3% with the introduction of the subsidized employment program (fleksjob) but this effect is not strongly...
5. Pressurized thermal shock (PTS)
International Nuclear Information System (INIS)
Rosso, Ricardo D.; Ventura, Mirta A.
2006-01-01
In the present work, a description of Thermal Shock in Pressurized conditions (PTS), and its influence in the treatment of the integrity of the pressure vessel (RPV) of a Pressurized Water Reactor (PWR) and/or of a Heavy water Pressurized water Reactor (PHWR) is made. Generally, the analysis of PTS involves a process of three stages: a-) Modeling with a System Code of relevant thermohydraulics transients in reference with the thermal shock; b-) The local distribution of temperatures in the downcomer and the heat transference coefficients from the RPV wall to the fluid, are determined; c-) The fracture mechanical analysis. These three stages are included in this work: Results with the thermohydraulics code Relap5/mod.3, are obtained, for a LOCA scenario in the hot leg of the cooling System of the Primary System of the CAN-I reactor. The method used in obtaining results is described. A study on the basis of lumped parameters of the local evolutions of the temperature of the flow is made, in the downcomer of the reactor pressure vessel. The purpose of this study is to determine how the intensification of the stress coefficient, varies in function of the emergency injected water during the thermohydraulic transients that take place under the imposed conditions in the postulated scene. Specially, it is considered a 50 cm 2 break, located in the neighborhoods of the pressurized with the corresponding hot leg connection. This size is considered like the most critical. The method used to obtain the results is described. The fracture mechanical analysis is made. From the obtained results we confirmed that we have a simple tool of easy application in order to analyze phenomena of the type PTS in the postulated scenes by break in the cold and hot legs of the primary system. This methodology of calculus is completely independent of the used ones by the Nucleoelectrica Argentina S.A. (NASA) in the analysis of the PTS phenomena in the CAN-I. The results obtained with the adopted
6. The Shock Routine
DEFF Research Database (Denmark)
van Hooren, Franca; Kaasch, Alexandra; Starke, Peter
2014-01-01
in Australia, Belgium, the Netherlands and Sweden over the course of four global economic shocks, we ask whether the notion of critical junctures is useful in understanding the nature of change triggered by crisis. The main empirical finding is that fundamental change in the aftermath of an exogenous shock...... is the exception rather than the rule. Instead, incremental ‘crisis routines’ based on existing policy instruments are overwhelmingly used to deal with economic hardship. We discuss these findings in the light of the psychological ‘threat-rigidity’ effect and reflect on their consequences for theories...
7. Particle acceleration by coronal and interplanetary shock waves
International Nuclear Information System (INIS)
Pesses, M.E.
1982-01-01
Utilizing many years of observation from deep space and near-earth spacecraft a theoretical understanding has evolved on how ions and electrons are accelerated in interplanetary shock waves. This understanding is now being applied to solar flare-induced shock waves propagating through the solar atmosphere. Such solar flare phenomena as gamma-ray line and neutron emissions, interplanetary energetic electron and ion events, and Type II and moving Type IV radio bursts appear understandable in terms of particle acceleration in shock waves
8. Shock absorber in Ignalina NPP
International Nuclear Information System (INIS)
Bulavas, A.; Muralis, J.
1996-09-01
Theoretical calculation and experimental analysis of models of shock absorber in Ignalina NPP is presented. The results obtained from the investigation with model of shock absorber coincide with the theoretical calculation. (author). 2 figs., 3 refs
9. Shock Response of Boron Carbide
National Research Council Canada - National Science Library
Dandekar, D. P. (Dattatraya Purushottam)
2001-01-01
.... The present work was undertaken to determine tensile/spall strength of boron carbide under plane shock wave loading and to analyze all available shock compression data on boron carbide materials...
10. Fascinating World of Shock Waves
Srimath
travelling at supersonic speeds (more than the sound speed at ... actual earth- quake, travel at supersonic speeds. .... The time scale of the shock wave is also important ..... real lithotripsy where a shock wave is used shatter the kidney stones!
11. Structure of fast shocks in the presence of heat conduction
International Nuclear Information System (INIS)
Tsai, C. L.; Chen, H. H.; Wu, B. H.; Lee, L. C.
2007-01-01
There are three types of magnetohydrodynamic (MHD) shocks: the fast shock, intermediate shock, and slow shock. The structure of slow shocks and intermediate shocks in the presence of heat conduction has been studied earlier [C. L. Tsai, R. H. Tsai, B. H. Wu, and L. C. Lee, Phys. Plasmas 9, 1185 (2002); C. L. Tsai, B. H. Wu, and L. C. Lee, Phys. Plasmas 12, 82501 (2005)]. Based on one-dimensional MHD numerical simulations with a heat conduction term, the evolution and structure of fast shocks are studied. The fast shock will form a foreshock in the presence of heat conduction. The foreshock is formed due to the heat flow from downstream to upstream and located in the immediate upstream of the main shock. In the steady state, the value of diffusion velocity V d in the foreshock is found to nearly equal the upstream convection velocity in the fast shock frame. It is found that the density jump across the main shock in high Mach number case can be much larger than 4 in the early simulation time. However the density jump will gradually evolve to a value smaller than 4 at steady state. By using the modified Rankine-Hugoniot relations with heat flux, the density jump across the fast shock is examined for various upstream parameters. The results show that the calculated density jump with heat flux is very close to the simulation value and the density jump can far exceed the maximum value of 4 without heat conduction. The structure of foreshock and main shock is also studied under different plasma parameters, such as the heat conductivity K 0 , the ratio of upstream plasma pressure to magnetic pressure β 1 , Alfven Mach number M A1 , and the angle θ 1 between shock normal and magnetic field. It is found that as the upstream shock parameters K 0 , β 1 , and M A1 increase or θ 1 decreases, the width of foreshock L d increases. The present results can be applied to fast shocks in the solar corona, solar wind, and magnetosphere, in which the heat conduction effects are
12. Shock tube Multiphase Experiments
Science.gov (United States)
Middlebrooks, John; Allen, Roy; Paudel, Manoj; Young, Calvin; Musick, Ben; McFarland, Jacob
2017-11-01
Shock driven multiphase instabilities (SDMI) are unique physical phenomena that have far-reaching practical applications in engineering and science. The instability is present in high energy explosions, scramjet combustors, and supernovae events. The SDMI arises when a multiphase interface is impulsively accelerated by the passage of a shockwave. It is similar in development to the Richtmyer-Meshkov (RM) instability however, particle-to-gas coupling is the driving mechanism of the SDMI. As particle effects such as lag and phase change become more prominent, the SDMI's development begins to significantly deviate from the RM instability. We have developed an experiment for studying the SDMI in our shock tube facility. In our experiments, a multiphase interface is created using a laminar jet and flowed into the shock tube where it is accelerated by the passage of a planar shockwave. The interface development is captured using CCD cameras synchronized with planar laser illumination. This talk will give an overview of new experiments conducted to examine the development of a shocked cylindrical multiphase interface. The effects of Atwood number, particle size, and a second acceleration (reshock) of the interface will be discussed.
13. Teleconnected food supply shocks
Science.gov (United States)
Bren d'Amour, Christopher; Wenz, Leonie; Kalkuhl, Matthias; Steckel, Jan Christoph; Creutzig, Felix
2016-03-01
The 2008-2010 food crisis might have been a harbinger of fundamental climate-induced food crises with geopolitical implications. Heat-wave-induced yield losses in Russia and resulting export restrictions led to increases in market prices for wheat across the Middle East, likely contributing to the Arab Spring. With ongoing climate change, temperatures and temperature variability will rise, leading to higher uncertainty in yields for major nutritional crops. Here we investigate which countries are most vulnerable to teleconnected supply-shocks, i.e. where diets strongly rely on the import of wheat, maize, or rice, and where a large share of the population is living in poverty. We find that the Middle East is most sensitive to teleconnected supply shocks in wheat, Central America to supply shocks in maize, and Western Africa to supply shocks in rice. Weighing with poverty levels, Sub-Saharan Africa is most affected. Altogether, a simultaneous 10% reduction in exports of wheat, rice, and maize would reduce caloric intake of 55 million people living in poverty by about 5%. Export bans in major producing regions would put up to 200 million people below the poverty line at risk, 90% of which live in Sub-Saharan Africa. Our results suggest that a region-specific combination of national increases in agricultural productivity and diversification of trade partners and diets can effectively decrease future food security risks.
14. STEREO interplanetary shocks and foreshocks
International Nuclear Information System (INIS)
Blanco-Cano, X.; Kajdič, P.; Aguilar-Rodríguez, E.; Russell, C. T.; Jian, L. K.; Luhmann, J. G.
2013-01-01
We use STEREO data to study shocks driven by stream interactions and the waves associated with them. During the years of the extended solar minimum 2007-2010, stream interaction shocks have Mach numbers between 1.1-3.8 and θ Bn ∼20-86°. We find a variety of waves, including whistlers and low frequency fluctuations. Upstream whistler waves may be generated at the shock and upstream ultra low frequency (ULF) waves can be driven locally by ion instabilities. The downstream wave spectra can be formed by both, locally generated perturbations, and shock transmitted waves. We find that many quasiperpendicular shocks can be accompanied by ULF wave and ion foreshocks, which is in contrast to Earth's bow shock. Fluctuations downstream of quasi-parallel shocks tend to have larger amplitudes than waves downstream of quasi-perpendicular shocks. Proton foreshocks of shocks driven by stream interactions have extensions dr ≤0.05 AU. This is smaller than foreshock extensions for ICME driven shocks. The difference in foreshock extensions is related to the fact that ICME driven shocks are formed closer to the Sun and therefore begin to accelerate particles very early in their existence, while stream interaction shocks form at ∼1 AU and have been producing suprathermal particles for a shorter time.
15. STEREO interplanetary shocks and foreshocks
Energy Technology Data Exchange (ETDEWEB)
Blanco-Cano, X. [Instituto de Geofisica, UNAM, CU, Coyoacan 04510 DF (Mexico); Kajdic, P. [IRAP-University of Toulouse, CNRS, Toulouse (France); Aguilar-Rodriguez, E. [Instituto de Geofisica, UNAM, Morelia (Mexico); Russell, C. T. [ESS and IGPP, University of California, Los Angeles, 603 Charles Young Drive, Los Angeles, CA 90095 (United States); Jian, L. K. [NASA Goddard Space Flight Center, Greenbelt, MD and University of Maryland, College Park, MD (United States); Luhmann, J. G. [SSL, University of California Berkeley (United States)
2013-06-13
We use STEREO data to study shocks driven by stream interactions and the waves associated with them. During the years of the extended solar minimum 2007-2010, stream interaction shocks have Mach numbers between 1.1-3.8 and {theta}{sub Bn}{approx}20-86 Degree-Sign . We find a variety of waves, including whistlers and low frequency fluctuations. Upstream whistler waves may be generated at the shock and upstream ultra low frequency (ULF) waves can be driven locally by ion instabilities. The downstream wave spectra can be formed by both, locally generated perturbations, and shock transmitted waves. We find that many quasiperpendicular shocks can be accompanied by ULF wave and ion foreshocks, which is in contrast to Earth's bow shock. Fluctuations downstream of quasi-parallel shocks tend to have larger amplitudes than waves downstream of quasi-perpendicular shocks. Proton foreshocks of shocks driven by stream interactions have extensions dr {<=}0.05 AU. This is smaller than foreshock extensions for ICME driven shocks. The difference in foreshock extensions is related to the fact that ICME driven shocks are formed closer to the Sun and therefore begin to accelerate particles very early in their existence, while stream interaction shocks form at {approx}1 AU and have been producing suprathermal particles for a shorter time.
16. Heat shock transcription factors regulate heat induced cell death in a ...
2007-03-29
Mar 29, 2007 ... Heat shock transcription factors regulate heat induced cell death in a rat ... the synthesis of heat shock proteins (Hsps) which is strictly regulated by ... The lack of Hsp synthesis in these cells was due to a failure in HSF1 DNA ...
17. Accidents in radiotherapy: Lack of quality assurance?
International Nuclear Information System (INIS)
Novotny, J.
1997-01-01
About 150 radiological accidents, involving more than 3000 patients with adverse effects, 15 patient's fatalities and about 5000 staff and public exposures have been collected and analysed. Out of 67 analysed accidents in external beam therapy 22% has been caused by wrong calculation of the exposure time or monitor units, 13% by inadequate review of patient's chart, 12% by mistakes in the anatomical area to be treated. The remaining 35% can be attributed to 17 different causes. The most common mistakes in brachytherapy were wrong activities of sources used for treatment (20%), inadequate procedures for placement of sources applicators (14%), mistakes in calculating the treatment time (12%), etc. The direct and contributing causes of radiological accidents have been deduced from each event, when it was possible and categorized into 9 categories: mistakes in procedures (30%), professional mistakes (17%), communication mistakes (15%), lack of training (8.5%), interpretation mistakes (7%), lack of supervision (6%), mistakes in judgement (6%), hardware failures (5%), software and other mistakes (5.5%). Three types of direct and contributing causes responsible for almost 62% of all accidents are directly connected to the quality assurance of treatment. The lessons learnt from the accidents are related to frequencies of direct and contributing factors and show that most of the accident are caused by lack, non-application of quality assurance (QA) procedures or by underestimating of QA procedures. The international system for collection of accidents and dissemination of lessons learnt from the different accidents, proposed by IAEA, can contribute to better practice in many radiotherapy departments. Most of the accidents could have been avoided, had a comprehensive QA programme been established and properly applied in all radiotherapy departments, whatever the size. (author)
18. Advanced Computational Modeling Approaches for Shock Response Prediction
Science.gov (United States)
Derkevorkian, Armen; Kolaini, Ali R.; Peterson, Lee
2015-01-01
Motivation: (1) The activation of pyroshock devices such as explosives, separation nuts, pin-pullers, etc. produces high frequency transient structural response, typically from few tens of Hz to several hundreds of kHz. (2) Lack of reliable analytical tools makes the prediction of appropriate design and qualification test levels a challenge. (3) In the past few decades, several attempts have been made to develop methodologies that predict the structural responses to shock environments. (4) Currently, there is no validated approach that is viable to predict shock environments overt the full frequency range (i.e., 100 Hz to 10 kHz). Scope: (1) Model, analyze, and interpret space structural systems with complex interfaces and discontinuities, subjected to shock loads. (2) Assess the viability of a suite of numerical tools to simulate transient, non-linear solid mechanics and structural dynamics problems, such as shock wave propagation.
19. MONETARY SHOCKS AND REAL EXCHANGE RATE FLUCTUATIONS IN CEE COUNTRIES
Directory of Open Access Journals (Sweden)
Nataša Erjavec
2012-12-01
Full Text Available The aim of this paper is to investigate the role of the exchange rate regime in absorbing macroeconomic shocks for a group of Central and East European countries (CEE. Whether the flexible exchange rate regime is beneficial for an economy depends on the capacity of the exchange rate to act as a shock absorber. An appropriate framework for assessing the role of the exchange rate is a structural vector autoregressive (SVAR model. Impact of two types of macroeconomic shocks is estimated: nominal and real. The shocks are identified on the basis of Blanchard-Quah long run identification scheme which means that the restrictions are imposed on the long run responses while the short run dynamics is kept unrestricted. The importance of nominal and real shocks is assessed using the variance decomposition and the impulse response functions.
20. Langmuir waveforms at interplanetary shocks: STEREO statistical analysis
Science.gov (United States)
Briand, C.
2016-12-01
Wave-particle interactions and particle acceleration are the two main processes allowing energy dissipation at non collisional shocks. Ion acceleration has been deeply studied for many years, also for their central role in the shock front reformation. Electron dynamics is also important in the shock dynamics through the instabilities they can generate which may impact the ion dynamics.Particle measurements can be efficiently completed by wave measurements to determine the characteristics of the electron beams and study the turbulence of the medium. Electric waveforms obtained from the S/WAVES instrument of the STEREO mission between 2007 to 2014 are analyzed. Thus, clear signature of Langmuir waves are observed on 41 interplanetary shocks. These data enable a statistical analysis and to deduce some characteristics of the electron dynamics on different shocks sources (SIR or ICME) and types (quasi-perpendicular or quasi-parallel). The conversion process between electrostatic to electromagnetic waves has also been tested in several cases.
1. Shock Dynamics in Stellar Outbursts. I. Shock Formation
Energy Technology Data Exchange (ETDEWEB)
Ro, Stephen; Matzner, Christopher D., E-mail: [email protected] [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada)
2017-05-20
Wave-driven outflows and non-disruptive explosions have been implicated in pre-supernova outbursts, supernova impostors, luminous blue variable eruptions, and some narrow-line and superluminous supernovae. To model these events, we investigate the dynamics of stars set in motion by strong acoustic pulses and wave trains, focusing on nonlinear wave propagation, shock formation, and an early phase of the development of a weak shock. We identify the shock formation radius, showing that a heuristic estimate based on crossing characteristics matches an exact expansion around the wave front and verifying both with numerical experiments. Our general analytical condition for shock formation applies to one-dimensional motions within any static environment, including both eruptions and implosions. We also consider the early phase of shock energy dissipation. We find that waves of super-Eddington acoustic luminosity always create shocks, rather than damping by radiative diffusion. Therefore, shock formation is integral to super-Eddington outbursts.
2. Introduction to Shock Waves and Shock Wave Research
Energy Technology Data Exchange (ETDEWEB)
Anderson, William Wyatt [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-02-02
M-9 and a number of other organizations at LANL and elsewhere study materials in dynamic processes. Often, this is described as “shock wave research,” but in reality is broader than is implied by that term. Most of our work is focused on dynamic compression and associated phenomena, but you will find a wide variety of things we do that, while related, are not simple compression of materials, but involve a much richer variety of phenomena. This tutorial will introduce some of the underlying physics involved in this work, some of the more common types of phenomena we study, and common techniques. However, the list will not be exhaustive by any means.
3. Curved Radio Spectra of Weak Cluster Shocks
Science.gov (United States)
Kang, Hyesung; Ryu, Dongsu
2015-08-01
In order to understand certain observed features of arc-like giant radio relics such as the rareness, uniform surface brightness, and curved integrated spectra, we explore a diffusive shock acceleration (DSA) model for radio relics in which a spherical shock impinges on a magnetized cloud containing fossil relativistic electrons. Toward this end, we perform DSA simulations of spherical shocks with the parameters relevant for the Sausage radio relic in cluster CIZA J2242.8+5301, and calculate the ensuing radio synchrotron emission from re-accelerated electrons. Three types of fossil electron populations are considered: a delta-function like population with the shock injection momentum, a power-law distribution, and a power law with an exponential cutoff. The surface brightness profile of the radio-emitting postshock region and the volume-integrated radio spectrum are calculated and compared with observations. We find that the observed width of the Sausage relic can be explained reasonably well by shocks with speed {u}{{s}}˜ 3× {10}3 {km} {{{s}}}-1 and sonic Mach number {M}{{s}}˜ 3. These shocks produce curved radio spectra that steepen gradually over (0.1-10){ν }{br} with a break frequency {ν }{br}˜ 1 GHz if the duration of electron acceleration is ˜60-80 Myr. However, the abrupt increase in the spectral index above ˜1.5 GHz observed in the Sausage relic seems to indicate that additional physical processes, other than radiative losses, operate for electrons with {γ }{{e}}≳ {10}4.
4. Shocked molecular gas and the origin of cosmic rays
Science.gov (United States)
Reach, William; Gusdorf, Antoine; Richter, Matthew
2018-06-01
When massive stars reach the end of their ability to remain stable with core nuclear fusion, they explode in supernovae that drive powerful shocks into their surroundings. Because massive stars form in and remain close to molecular clouds they often drive shocks into dense gas, which is now believed to be the origin of a significant fraction of galactic cosmic rays. The nature of the supernova-molecular cloud interaction is not well understood, though observations are gradually elucidating their nature. The range of interstellar densities, and the inclusion of circumstellar matter from the late-phase mass-loss of the stars before their explosions, leads to a wide range of possible appearances and outcomes. In particular, it is not even clear what speed or physical type of shocks are present: are they dense, magnetically-mediated shocks where H2 is not dissociated, or are they faster shocks that dissociate molecules and destroy some of the grains? SOFIA is observing some of the most significant (in terms of cosmic ray production potential and infrared energy output) supernova-molecular cloud interactions for measurement of the line widths of key molecular shocks tracers: H2, [OI], and CO. The presence of gas at speeds 100 km/s or greater would indicate dissociative shocks, while speeds 30 km/s and slower retain most molecules. The shock velocity is a key ingredient in modeling the interaction between supernovae and molecular clouds including the potential for formation of cosmic rays.
5. Success and failure of the defibrillation shock: insights from a simulation study.
Science.gov (United States)
Skouibine, K; Trayanova, N; Moore, P
2000-07-01
This simulation study presents a further inquiry into the mechanisms by which a strong electric shock fails to halt life-threatening cardiac arrhythmias. The research uses a model of the defibrillation process that represents a sheet of myocardium as a bidomain. The tissue consists of nonuniformly curved fibers in which spiral wave reentry is initiated. Monophasic defibrillation shocks are delivered via two line electrodes that occupy opposite tissue boundaries. In some simulation experiments, the polarity of the shock is reversed. Electrical activity in the sheet is compared for failed and successful shocks under controlled conditions. The maps of transmembrane potential and activation times calculated during and after the shock demonstrate that weak shocks fail to terminate the reentrant activity via two major mechanisms. As compared with strong shocks, weak shocks result in (1) smaller extension of refractoriness in the areas depolarized by the shock, and (2) slower or incomplete activation of the excitable gap created by deexcitation of the negatively polarized areas. In its turn, mechanism 2 is associated with one or more of the following events: (a) lack of some break excitations, (b) latency in the occurrence of the break excitations, and (c) slower propagation through deexcited areas. Reversal of shock polarity results in a change of the extent of the regions of deexcitation, and thus, in a change in defibrillation threshold. The results of this study indicate the paramount importance of shock-induced deexcitation in both defibrillation and postshock arrhythmogenesis.
6. Bubble Dynamics and Shock Waves
CERN Document Server
2013-01-01
This volume of the Shock Wave Science and Technology Reference Library is concerned with the interplay between bubble dynamics and shock waves. It is divided into four parts containing twelve chapters written by eminent scientists. Topics discussed include shock wave emission by laser generated bubbles (W Lauterborn, A Vogel), pulsating bubbles near boundaries (DM Leppinen, QX Wang, JR Blake), interaction of shock waves with bubble clouds (CD Ohl, SW Ohl), shock propagation in polydispersed bubbly liquids by model equations (K Ando, T Colonius, CE Brennen. T Yano, T Kanagawa, M Watanabe, S Fujikawa) and by DNS (G Tryggvason, S Dabiri), shocks in cavitating flows (NA Adams, SJ Schmidt, CF Delale, GH Schnerr, S Pasinlioglu) together with applications involving encapsulated bubble dynamics in imaging (AA Doinikov, A Novell, JM Escoffre, A Bouakaz), shock wave lithotripsy (P Zhong), sterilization of ships’ ballast water (A Abe, H Mimura) and bubbly flow model of volcano eruptions ((VK Kedrinskii, K Takayama...
OpenAIRE
2012-01-01
Bakalářská práce obsahuje přehled používaných tlumičů osobních automobilů, závodních automobilů a motocyklů. Jsou zde popsány systémy t lumením, konstrukce tlumičů a vidlic používaných u motocyklů. Dále je zde přehled prvků používaných u podvozků automobilů. This bachelor´s thesis contains the survey of the shock absorbers of passenger cars, racing cars and motorcycles. Are described damping systems, the design used shock absorbers and forks for motorcycles. Then there is the list of the e...
International Nuclear Information System (INIS)
1997-01-01
The influences of thermal radiation on the state equation of shock waves, derived in the previous paper [L. N. Tsintsadze, Phys. Plasmas 2, 4462 (1995)], are studied and a series of relations of thermodynamic quantities that hold for shock waves are derived. It is shown that the presence of radiation can strongly change the compressibility of the plasma. It is well known that for polytropic gases the compressibility cannot change more than four times the initial value in the case of nonrelativistic temperatures. The numerical calculations show that there are no such restrictions, when the radiation energy exceeds the kinetic energy of the plasma. The ultrarelativistic temperature range is also covered in our numerical calculations. Also studied are the influences of the radiation on the PT and the TV diagrams. A significant modification due to radiation is found in every case studied. copyright 1997 American Institute of Physics
9. POSTURAL SHOCK IN PREGNANCY
Science.gov (United States)
Wilkening, Ralph L.; Knauer, John; Larson, Roger K.
1955-01-01
Signs and symptoms of shock may be produced in some patients in late pregnancy by putting them in the dorsal recumbent posture. Change from this position will relieve the condition. The features of the supine hypotensive syndrome can be duplicated by applying pressure to the abdomen with the patient in a lateral position. The postural variations of venous pressure, blood pressure, and pulse appear to be due to obstruction of venous return from the lower portion of the body caused by the large uterus of late pregnancy compressing the vena cava. When shock is observed in a woman in late pregnancy, she should be turned to a lateral position before more active measures of treatment are begun. ImagesFigure 1. PMID:14351983
10. Bow shock data analysis
Science.gov (United States)
Zipf, Edward C.; Erdman, Peeter W.
1994-08-01
The University of Pittsburgh Space Physics Group in collaboration with the Army Research Office (ARO) modeling team has completed a systematic organization of the shock and plume spectral data and the electron temperature and density measurements obtained during the BowShock I and II rocket flights which have been submitted to the AEDC Data Center, has verified the presence of CO Cameron band emission during the Antares engine burn and for an extended period of time in the post-burn plume, and have adapted 3-D radiation entrapment codes developed by the University of Pittsburgh to study aurora and other atmospheric phenomena that involve significant spatial effects to investigate the vacuum ultraviolet (VUV) and extreme ultraviolet (EUV) envelope surrounding the re-entry that create an extensive plasma cloud by photoionization.
11. Riemann solvers and undercompressive shocks of convex FPU chains
International Nuclear Information System (INIS)
Herrmann, Michael; Rademacher, Jens D M
2010-01-01
We consider FPU-type atomic chains with general convex potentials. The naive continuum limit in the hyperbolic space–time scaling is the p-system of mass and momentum conservation. We systematically compare Riemann solutions to the p-system with numerical solutions to discrete Riemann problems in FPU chains, and argue that the latter can be described by modified p-system Riemann solvers. We allow the flux to have a turning point, and observe a third type of elementary wave (conservative shocks) in the atomistic simulations. These waves are heteroclinic travelling waves and correspond to non-classical, undercompressive shocks of the p-system. We analyse such shocks for fluxes with one or more turning points. Depending on the convexity properties of the flux we propose FPU-Riemann solvers. Our numerical simulations confirm that Lax shocks are replaced by so-called dispersive shocks. For convex–concave flux we provide numerical evidence that convex FPU chains follow the p-system in generating conservative shocks that are supersonic. For concave–convex flux, however, the conservative shocks of the p-system are subsonic and do not appear in FPU-Riemann solutions
12. Shock Isolation Elements Testing for High Input Loadings. Volume III. Mechanical Shock Isolation Elements.
Science.gov (United States)
SHOCK ABSORBERS ), (*GUIDED MISSILE SILOS, SHOCK ABSORBERS ), (*SPRINGS, (*SHOCK(MECHANICS), REDUCTION), TORSION BARS, ELASTOMERS, DAMPING, EQUATIONS OF MOTION, MODEL TESTS, TEST METHODS, NUCLEAR EXPLOSIONS, HARDENING.
13. Shock resistance testing
International Nuclear Information System (INIS)
Pouard, M.
1984-03-01
In the framework of mechanical tests and to answer the different requests for tests, the T.C.R (Transport Conditionnement et Retraitement) laboratory got test facilities. These installations allow to carry out tests of resistance to shocks, mainly at the safety level of components of nuclear power plants, mockups of transport casks for fuel elements and transport containers for radioactive materials. They include a tower and a catapult. This paper give a decription of the facilities and explain their operation way [fr
14. The Shock Doctrine
OpenAIRE
Dionysios K. Solomos; Dimitrios N. Koumparoulis
2011-01-01
Naomi Klein attempts to redefine the economic history discovering the historical continuities and to reveal the neoliberal theory which functions via the utilization of specific “tools”. The state of shock is the key for the opponents of Chicago School and Milton Friedman in order for them to establish neoliberal policies and to promote the deregulated capitalism which includes less welfare state, less public sector, less regulation, weakened labor unions, privatizations and laissez-faire. Th...
15. Characterization of shocked beryllium
Directory of Open Access Journals (Sweden)
Papin P.A.
2012-08-01
Full Text Available While numerous studies have investigated the low-strain-rate constitutive response of beryllium, the combined influence of high strain rate and temperature on the mechanical behavior and microstructure of beryllium has received limited attention over the last 40 years. In the current work, high strain rate tests were conducted using both explosive drive and a gas gun to accelerate the material. Prior studies have focused on tensile loading behavior, or limited conditions of dynamic strain rate and/or temperature. Two constitutive strength (plasticity models, the Preston-Tonks-Wallace (PTW and Mechanical Threshold Stress (MTS models, were calibrated using common quasi-static and Hopkinson bar data. However, simulations with the two models give noticeably different results when compared with the measured experimental wave profiles. The experimental results indicate that, even if fractured by the initial shock loading, the Be remains sufficiently intact to support a shear stress following partial release and subsequent shock re-loading. Additional “arrested” drive shots were designed and tested to minimize the reflected tensile pulse in the sample. These tests were done to both validate the model and to put large shock induced compressive loads into the beryllium sample.
16. Electron beams by shock waves in the solar corona
International Nuclear Information System (INIS)
Mann, G.; Klassen, A.
2005-07-01
Beams of energetic electrons can be generated by shock waves in the solar corona. At the Sun shock waves are produced either by flares and/or by coronal mass ejections (CMEs). They can be observed as type II bursts in the solar radio radiation. Shock accelerated electron beams appear as rapidly drifting emission stripes (so-called ''herringbones'') in dynamic radio spectra of type II bursts. A large sample of type II bursts showing ''herringbones'' was statistically analysed with respect to their properties in dynamic radio spectra. The electron beams associated with the ''herringbones'' are considered to be generated by shock drift acceleration. Then, the accelerated electrons establish a shifted loss-cone distribution in the upstream region of the associated shock wave. Such a distribution causes plasma instabilities leading to the emission of radio waves observed as ''herringbones''. Consequences of a shifted loss-cone distribution of the shock accelerated electrons are discussed in comparison with the observations of ''herringbones'' within solar type II radio bursts. (orig.)
17. Air box shock absorber for a nuclear reactor
International Nuclear Information System (INIS)
1977-01-01
Disclosed is an air box type shock absorber primarily for use in an ice condenser compartment of a nuclear reactor. The shock absorber includes a back plate member and sheet metal top, bottom, and front members. The front member is prefolded, and controlled clearances are provided among the members for predetermined escape of air under impact and compression. Prefolded internal sheet metal stiffeners also absorb a portion of the kinetic energy imparted to the shock absorber, and limit rebound. An external restraining rod guided by restraining straps insures that the sheet metal front member compresses inward upon impact. 6 claims, 11 figures
18. Regional employment growth, shocks and regional industrial resilience
DEFF Research Database (Denmark)
Holm, Jacob Rubæk; Østergaard, Christian Richter
2013-01-01
The resilience of regional industries to economic shocks has gained a lot of attention in evolutionary economic geography recently. This paper uses a novel quantitative approach to investigate the regional industrial resilience of the Danish ICT sector to the shock following the burst of the dot......-com bubble. It is shown that regions characterised by small and young ICT service companies were more adaptable and grew more than others, while diversity and urbanisation increased the sensitivity to the business cycle after the shock. Different types of resilient regions are found: adaptively resilient......, rigidly resilient, entrepreneurially resilient and non-resilient regions....
19. Regional Employment Growth, Shocks and Regional Industrial Resilience
DEFF Research Database (Denmark)
Holm, J.R.; Østergaard, Christian Richter
2015-01-01
The resilience of regional industries to economic shocks has gained a lot of attention in evolutionary economic geography recently. This paper uses a novel quantitative approach to investigate the regional industrial resilience of the Danish information and communication technology (ICT) sector...... to the shock following the burst of the dot.com bubble. It is shown that regions characterized by small and young ICT service companies were more adaptable and grew more than others, while diversity and urbanization increased the sensitivity to the business cycle after the shock. Different types of resilient...... regions are found: adaptively resilient, rigidly resilient, entrepreneurially resilient and non-resilient regions....
20. On Poor Separation in Magnetically Driven Shock Tube
DEFF Research Database (Denmark)
Chang, C.T.
1973-01-01
Observations made at steady-state running conditions in a magnetically driven shock tube, with parallel-plate electrodes, showed that for a given discharge voltage, sufficient separation between the shock and the current-sheet occurred only at relatively high discharge pressures. As a comparison......, poor separations were also noted in conventional diaphragm-type shock tubes running at low initial pressures. It is demonstrated that the observed poor separation can be explained by a mass leakage, instead of through the wall boundary layer, but through the current-sheet itself....
1. Selfsimilar time dependent shock structures
International Nuclear Information System (INIS)
Beck, R.; Drury, L.O.
1985-01-01
Diffusive shock acceleration as an astrophysical mechanism for accelerating charged particles has the advantage of being highly efficient. This means however that the theory is of necessity nonlinear; the reaction of the accelerated particles on the shock structure and the acceleration process must be self-consistently included in any attempt to develop a complete theory of diffusive shock acceleration. Considerable effort has been invested in attempting, at least partially, to do this and it has become clear that in general either the maximum particle energy must be restricted by introducing additional loss processes into the problem or the acceleration must be treated as a time dependent problem (Drury, 1984). It is concluded that stationary modified shock structures can only exist for strong shocks if additional loss processes limit the maximum energy a particle can attain. This is certainly possible and if it occurs the energy loss from the shock will lead to much greater shock compressions. It is however equally possible that no such processes exist and we must then ask what sort of nonstationary shock structure develops. The same argument which excludes stationary structures also rules out periodic solutions and indeed any solution where the width of the shock remains bounded. It follows that the width of the shock must increase secularly with time and it is natural to examine the possibility of selfsimilar time dependent solutions
2. Selfsimilar time dependent shock structures
Science.gov (United States)
Beck, R.; Drury, L. O.
1985-01-01
Diffusive shock acceleration as an astrophysical mechanism for accelerating charged particles has the advantage of being highly efficient. This means however that the theory is of necessity nonlinear; the reaction of the accelerated particles on the shock structure and the acceleration process must be self-consistently included in any attempt to develop a complete theory of diffusive shock acceleration. Considerable effort has been invested in attempting, at least partially, to do this and it has become clear that in general either the maximum particle energy must be restricted by introducing additional loss processes into the problem or the acceleration must be treated as a time dependent problem (Drury, 1984). It is concluded that stationary modified shock structures can only exist for strong shocks if additional loss processes limit the maximum energy a particle can attain. This is certainly possible and if it occurs the energy loss from the shock will lead to much greater shock compressions. It is however equally possible that no such processes exist and we must then ask what sort of nonstationary shock structure develops. The ame argument which excludes stationary structures also rules out periodic solutions and indeed any solution where the width of the shock remains bounded. It follows that the width of the shock must increase secularly with time and it is natural to examine the possibility of selfsimilar time dependent solutions.
3. SELF-REGULATED SHOCKS IN MASSIVE STAR BINARY SYSTEMS
Energy Technology Data Exchange (ETDEWEB)
Parkin, E. R.; Sim, S. A., E-mail: [email protected], E-mail: [email protected] [Research School of Astronomy and Astrophysics, Australian National University, ACT 2611 (Australia)
2013-04-20
In an early-type, massive star binary system, X-ray bright shocks result from the powerful collision of stellar winds driven by radiation pressure on spectral line transitions. We examine the influence of the X-rays from the wind-wind collision shocks on the radiative driving of the stellar winds using steady-state models that include a parameterized line force with X-ray ionization dependence. Our primary result is that X-ray radiation from the shocks inhibits wind acceleration and can lead to a lower pre-shock velocity, and a correspondingly lower shocked plasma temperature, yet the intrinsic X-ray luminosity of the shocks, L{sub X}, remains largely unaltered, with the exception of a modest increase at small binary separations. Due to the feedback loop between the ionizing X-rays from the shocks and the wind driving, we term this scenario as self-regulated shocks. This effect is found to greatly increase the range of binary separations at which a wind-photosphere collision is likely to occur in systems where the momenta of the two winds are significantly different. Furthermore, the excessive levels of X-ray ionization close to the shocks completely suppress the line force, and we suggest that this may render radiative braking less effective. Comparisons of model results against observations reveal reasonable agreement in terms of log (L{sub X}/L{sub bol}). The inclusion of self-regulated shocks improves the match for kT values in roughly equal wind momenta systems, but there is a systematic offset for systems with unequal wind momenta (if considered to be a wind-photosphere collision).
4. SELF-REGULATED SHOCKS IN MASSIVE STAR BINARY SYSTEMS
International Nuclear Information System (INIS)
Parkin, E. R.; Sim, S. A.
2013-01-01
In an early-type, massive star binary system, X-ray bright shocks result from the powerful collision of stellar winds driven by radiation pressure on spectral line transitions. We examine the influence of the X-rays from the wind-wind collision shocks on the radiative driving of the stellar winds using steady-state models that include a parameterized line force with X-ray ionization dependence. Our primary result is that X-ray radiation from the shocks inhibits wind acceleration and can lead to a lower pre-shock velocity, and a correspondingly lower shocked plasma temperature, yet the intrinsic X-ray luminosity of the shocks, L X , remains largely unaltered, with the exception of a modest increase at small binary separations. Due to the feedback loop between the ionizing X-rays from the shocks and the wind driving, we term this scenario as self-regulated shocks. This effect is found to greatly increase the range of binary separations at which a wind-photosphere collision is likely to occur in systems where the momenta of the two winds are significantly different. Furthermore, the excessive levels of X-ray ionization close to the shocks completely suppress the line force, and we suggest that this may render radiative braking less effective. Comparisons of model results against observations reveal reasonable agreement in terms of log (L X /L bol ). The inclusion of self-regulated shocks improves the match for kT values in roughly equal wind momenta systems, but there is a systematic offset for systems with unequal wind momenta (if considered to be a wind-photosphere collision).
5. Shock Hugoniot and equations of states of water, castor oil, and aqueous solutions of sodium chloride, sucrose and gelatin
Science.gov (United States)
Gojani, A. B.; Ohtani, K.; Takayama, K.; Hosseini, S. H. R.
2016-01-01
This paper reports a result of experiments for the determination of reliable shock Hugoniot curves of liquids, in particular, at relatively low pressure region, which are needed to perform precise numerical simulations of shock wave/tissue interaction prior to the development of shock wave related therapeutic devices. Underwater shock waves were generated by explosions of laser ignited 10 mg silver azide pellets, which were temporally and spatially well controlled. Measuring temporal variation of shock velocities and over-pressures in caster oil, aqueous solutions of sodium chloride, sucrose and gelatin with various concentrations, we succeeded to determine shock Hugoniot curves of these liquids and hence parameters describing Tait type equations of state.
6. Reliability for systems of degrading components with distinct component shock sets
International Nuclear Information System (INIS)
Song, Sanling; Coit, David W.; Feng, Qianmei
2014-01-01
This paper studies reliability for multi-component systems subject to dependent competing risks of degradation wear and random shocks, with distinct shock sets. In practice, many systems are exposed to distinct and different types of shocks that can be categorized according to their sizes, function, affected components, etc. Previous research primarily focuses on simple systems with independent failure processes, systems with independent component time-to-failure, or components that share the same shock set or type of shocks. In our new model, we classify random shocks into different sets based on their sizes or function. Shocks with specific sizes or function can selectively affect one or more components in the system but not necessarily all components. Additionally the shocks from the different shock sets can arrive at different rates and have different relative magnitudes. Preventive maintenance (PM) optimization is conducted for the system with different component shock sets. Decision variables for two different maintenance scheduling problems, the PM replacement time interval, and the PM inspection time interval, are determined by minimizing a defined system cost rate. Sensitivity analysis is performed to provide insight into the behavior of the proposed maintenance policies. These models can be applied directly or customized for many complex systems that experience dependent competing failure processes with different component shock sets. A MEMS (Micro-electro mechanical systems) oscillator is a typical system subject to dependent and competing failure processes, and it is used as a numerical example to illustrate our new reliability and maintenance models
7. Thermal Shielding Effects of a Damaged Shock Absorber and an Intact Shock Absorber
Energy Technology Data Exchange (ETDEWEB)
Bang, K. S.; Lee, J. C.; Kim, K. Y.; Seo, C. S.; Seo, K. S. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2011-05-15
In order to safely transport the radioactive waste arising from the hot test of an ACP(Advanced Spent Fuel Conditioning Process) a shipping package is required. Therefore, KAERI is developing a shipping package to transport the radioactive waste arising from the ACPF during a hot test. The regulatory requirements for a Type B package are specified in the Korea Most Act 2009-37, IAEA Safety Standard Series No. TS-R-1, and US 10 CFR Part. These regulatory guidelines classify the hot cell cask as a Type B package, and state that the Type B package for transporting radioactive materials should be able to withstand a test sequence consisting of a 9 m drop onto an unyielding surface, a 1 m drop onto a puncture bar, and a 30 minute fully engulfing fire. Greiner et al. investigated the thermal protection provided by shock absorbers by using the CAFE computer code. To evaluate the thermal shielding effect of the shock absorber, the thermal test was performed by using a 1/2 scale model with a shock absorber which was damaged by both a 9 m drop test and a 1 m puncture test. For the purpose of comparison, the thermal test was also carried out by using a 1/2 scale model with the intact shock absorber
8. Two-state ion heating at quasi-parallel shocks
International Nuclear Information System (INIS)
Thomsen, M.F.; Gosling, J.T.; Bame, S.J.; Onsager, T.G.; Russell, C.T.
1990-01-01
In a previous study of ion heating at quasi-parallel shocks, the authors showed a case in which the ion distributions downstream from the shock alternated between a cooler, denser, core/shoulder type and a hotter, less dense, more Maxwellian type. In this paper they further document the alternating occurrence of two different ion states downstream from several quasi-parallel shocks. Three separate lines of evidence are presented to show that the two states are not related in an evolutionary sense, but rather both are produced alternately at the shock: (1) the asymptotic downstream plasma parameters (density, ion temperature, and flow speed) are intermediate between those characterizing the two different states closer to the shock, suggesting that the asymptotic state is produced by a mixing of the two initial states; (2) examples of apparently interpenetrating (i.e., mixing) distributions can be found during transitions from one state to the other; and (3) examples of both types of distributions can be found at actual crossings of the shock ramp. The alternation between the two different types of ion distribution provides direct observational support for the idea that the dissipative dynamics of at least some quasi-parallel shocks is non-stationary and cyclic in nature, as demonstrated by recent numerical simulations. Typical cycle times between intervals of similar ion heating states are ∼2 upstream ion gyroperiods. Both the simulations and the in situ observations indicate that a process of coherent ion reflection is commonly an important part of the dissipation at quasi-parallel shocks
9. Risk shocks and housing markets
OpenAIRE
Dorofeenko, Viktor; Lee, Gabriel S.; Salyer, Kevin D.
2010-01-01
Abstract: This paper analyzes the role of uncertainty in a multi-sector housing model with financial frictions. We include time varying uncertainty (i.e. risk shocks) in the technology shocks that affect housing production. The analysis demonstratesthat risk shocks to the housing production sector are a quantitatively important impulse mechanism for the business cycle. Also, we demonstrate that bankruptcy costs act as an endogenous markup factor in housing prices; as a consequence, the volati...
10. Shocks to Bank Lending, Risk-Taking, Securitization, and Their Role for U.S. Business Cycle Fluctuations
NARCIS (Netherlands)
Peersman, G.; Wagner, W.B.
2014-01-01
Abstract: Shocks to bank lending, risk-taking and securitization activities that are orthogonal to real economy and monetary policy innovations account for more than 30 percent of U.S. output variation. The dynamic effects, however, depend on the type of shock. Expansionary securitization shocks
11. Health shocks and risk aversion.
Science.gov (United States)
Decker, Simon; Schmitz, Hendrik
2016-12-01
We empirically assess whether a health shock influences individual risk aversion. We use grip strength data to obtain an objective health shock indicator. In order to account for the non-random nature of our data regression-adjusted matching is employed. Risk preferences are traditionally assumed to be constant. However, we find that a health shock increases individual risk aversion. The finding is robust to a series of sensitivity analyses and persists for at least four years after the shock. Income changes do not seem to be the driving mechanism. Copyright © 2016 Elsevier B.V. All rights reserved.
12. Shock in the emergency department
DEFF Research Database (Denmark)
Holler, Jon Gitz; Henriksen, Daniel Pilsgaard; Mikkelsen, Søren
2016-01-01
BACKGROUND: The knowledge of the frequency and associated mortality of shock in the emergency department (ED) is limited. The aim of this study was to describe the incidence, all-cause mortality and factors associated with death among patients suffering shock in the ED. METHODS: Population...... failures. Outcomes were annual incidence per 100,000 person-years at risk (pyar), all-cause mortality at 0-7, and 8-90 days and risk factors associated with death. RESULTS: We identified 1646 of 438,191 (0.4 %) ED patients with shock at arrival. Incidence of shock increased from 53.8 to 80.6 cases per 100...
13. Shock compression of diamond crystal
OpenAIRE
Kondo, Ken-ichi; Ahrens, Thomas J.
1983-01-01
Two shock wave experiments employing inclined mirrors have been carried out to determine the Hugoniot elastic limit (HEL), final shock state at 191 and 217 GPa, and the post-shock state of diamond crystal, which is shock-compressed along the intermediate direction between the and crystallographic axes. The HEL wave has a velocity of 19.9 ± 0.3 mm/µsec and an amplitude of 63 ± 28 GPa. An alternate interpretation of the inclined wedge mirror streak record suggests a ramp precursor wave and th...
14. Phase velocity enhancement of linear explosive shock tubes
Science.gov (United States)
Loiseau, Jason; Serge, Matthew; Szirti, Daniel; Higgins, Andrew; Tanguay, Vincent
2011-06-01
Strong, high density shocks can be generated by sequentially detonating a hollow cylinder of explosives surrounding a thin-walled, pressurized tube. Implosion of the tube results in a pinch that travels at the detonation velocity of the explosive and acts like a piston to drive a shock into the gas ahead of it. In order to increase the maximum shock velocities that can be obtained, a phase velocity generator can be used to drag an oblique detonation wave along the gas tube at a velocity much higher than the base detonation velocity of the explosive. Since yielding and failure of the gas tube is the primary limitation of these devices, it is desirable to retain the dynamic confinement effects of a heavy-walled tamper without interfering with operation of the phase velocity generator. This was accomplished by cutting a slit into the tamper and introducing a phased detonation wave such that it asymmetrically wraps around the gas tube. This type of configuration has been previously experimentally verified to produce very strong shocks but the post-shock pressure and shock velocity limits have not been investigated. This study measured the shock trajectory for various fill pressures and phase velocities to ascertain the limiting effects of tube yield, detonation obliquity and pinch aspect ratio.
15. A Shocking Solar Nebula?
OpenAIRE
Liffman, Kurt
2009-01-01
It has been suggested that shock waves in the solar nebula formed the high temperature materials observed in meteorites and comets. It is shown that the temperatures at the inner rim of the solar nebula could have been high enough over a sufficient length of time to produce chondrules, CAIs, refractory dust grains and other high-temperature materials observed in comets and meteorites. The solar bipolar jet flow may have produced an enrichment of 16O in the solar nebula over time and the chond...
16. Myths of "shock therapy".
Science.gov (United States)
Fink, M
1977-09-01
The author discusses the myths of the ECT process--that shock and the convulsion are essential, memory loss and brain damage are inescapable, and little is known of the process--and assesses the fallacies in these ideas. Present views of the ECT process suggest that its mode of action in depression may best be described as a prolonged form of diencephalic stimulation, particularly useful to affect the hypothalamic dysfunctions that characterize depressive illness. The author emphasizes the need for further study of this treatment modality and for self-regulation by the profession.
17. Gravitational shock waves and extreme magnetomaterial shock waves
International Nuclear Information System (INIS)
Lichnerowicz, Andre.
1975-01-01
Within an astrophysical context corresponding to high densities, a self-gravitating model is studied, which is the set of an extreme material medium of infinite conductivity and of a magnetic field. Corresponding shock waves generate necessarily, in general, gravitational shock waves [fr
18. Shock Producers and Shock Absorbers in the Crisis
OpenAIRE
Sinn, Hans-Werner
2009-01-01
It is not surprising that the U.S. has been by far the world’s largest shock producer in this crisis. The big shock absorbers on the other hand were Japan, Russia and Germany, whose exports shrank more than their imports.
19. Simulations of Converging Shock Collisions for Shock Ignition
Science.gov (United States)
Sauppe, Joshua; Dodd, Evan; Loomis, Eric
2016-10-01
Shock ignition (SI) has been proposed as an alternative to achieving high gain in inertial confinement fusion (ICF) targets. A central hot spot below the ignition threshold is created by an initial compression pulse, and a second laser pulse drives a strong converging shock into the fuel. The collision between the rebounding shock from the compression pulse and the converging shock results in amplification of the converging shock and increases the hot spot pressure above the ignition threshold. We investigate shock collision in SI drive schemes for cylindrical targets with a polystyrene foam interior using radiation-hydrodynamics simulations with the RAGE code. The configuration is similar to previous targets fielded on the Omega laser. The CH interior results in a lower convergence ratio and the cylindrical geometry facilitates visualization of the shock transit using an axial X-ray backlighter, both of which are important for comparison to potential experimental measurements. One-dimensional simulations are used to determine shock timing, and the effects of low mode asymmetries in 2D computations are also quantified. LA-UR-16-24773.
20. 30th International Symposium on Shock Waves
CERN Document Server
2017-01-01
These proceedings collect the papers presented at the 30th International Symposium on Shock Waves (ISSW30), which was held in Tel-Aviv Israel from July 19 to July 24, 2015. The Symposium was organized by Ortra Ltd. The ISSW30 focused on the state of knowledge of the following areas: Nozzle Flow, Supersonic and Hypersonic Flows with Shocks, Supersonic Jets, Chemical Kinetics, Chemical Reacting Flows, Detonation, Combustion, Ignition, Shock Wave Reflection and Interaction, Shock Wave Interaction with Obstacles, Shock Wave Interaction with Porous Media, Shock Wave Interaction with Granular Media, Shock Wave Interaction with Dusty Media, Plasma, Magnetohyrdrodynamics, Re-entry to Earth Atmosphere, Shock Waves in Rarefied Gases, Shock Waves in Condensed Matter (Solids and Liquids), Shock Waves in Dense Gases, Shock Wave Focusing, Richtmyer-Meshkov Instability, Shock Boundary Layer Interaction, Multiphase Flow, Blast Waves, Facilities, Flow Visualization, and Numerical Methods. The two volumes serve as a reference ...
1. High pressure multiple shock response of aluminum
International Nuclear Information System (INIS)
Lawrence, R.J.; Asay, J.R.
1977-01-01
It is well known that both dynamic yield strength and rate-dependent material response exert direct influence on the development of surface and interface instabilities under conditions of strong shock loading. A detailed understanding of these phenomena is therefore an important aspect of the analysis of dynamic inertial confinement techniques which are being used in such applications as the generation of controlled thermonuclear fusion. In these types of applications the surfaces and interfaces under consideration can be subjected to cyclic loading characterized by shock pressures on the order of 100 GPa or more. It thus becomes important to understand how rate effects and material strength differ from the values observed in the low pressure regime where they are usually measured, as well as how they are altered by the loading history
2. On numerical considerations for modeling reactive astrophysical shocks
International Nuclear Information System (INIS)
Papatheodore, Thomas L.; Messer, O. E. Bronson
2014-01-01
Simulating detonations in astrophysical environments is often complicated by numerical approximations to shock structure. A common prescription to ensure correct detonation speeds and associated quantities is to prohibit burning inside the numerically broadened shock. We have performed a series of simulations to verify the efficacy of this approximation and to understand how resolution and dimensionality might affect its use. Our results show that in one dimension, prohibiting burning in the shock is important wherever the carbon burning length is not resolved, in keeping with the results of Fryxell et al. In two dimensions, we find that the prohibition of shock burning effectively inhibits the development of cellular structure for all but the most highly resolved cases. We discuss the possible impacts this outcome may have on sub-grid models and detonation propagation in models of Type Ia supernovae, including potential impacts on observables.
3. Ultrafast dynamic ellipsometry and spectroscopy of laser shocked materials
Energy Technology Data Exchange (ETDEWEB)
Mcgrane, Shawn David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bolme, Cindy B [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Whitley, Von H [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Moore, David S [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2010-01-01
Shock waves create extreme states of matter with very high pressures, temperatures, and volumetric compressions, at an exceedingly rapid rate of change. We review how to use a beamsplitter and a note card to turn a typical chirp pulse amplified femtosecond laser system into an ultrafast shock dynamics machine. Open scientific questions that can be addressed with such an apparatus are described. We report on the development of several single shot time resolved diagnostics needed to answer these questions. These single shot diagnostics are expected to be broadly applicable to other types of laser ablation experiments. Experimental results measured from shocked material dynamics of several systems are detailed. Finally, we report on progress towards using transient absorption as a measure of electronic excitation and coherent Raman as a picosecond probe of temperature in shock compressed condensed matter.
4. Molecular diagnostics of interstellar shocks
International Nuclear Information System (INIS)
Hartquist, T.W.; Oppenheimer, M.; Dalgarno, A.
1980-01-01
The chemistry of molecules in shocked regions of the interstellar gas is considered and calculations are carried out for a region subjected to a shock at a velocity of 8 km s -1 Substantial enhancements are predicted in the concentrations of the molecules H 2 S, SO, and SiO compared to those anticipated in cold interstellar clouds
5. Molecular diagnostics of interstellar shocks
Science.gov (United States)
Hartquist, T. W.; Dalgarno, A.; Oppenheimer, M.
1980-02-01
The chemistry of molecules in shocked regions of the interstellar gas is considered and calculations are carried out for a region subjected to a shock at a velocity of 8 km/sec. Substantial enhancements are predicted in the concentrations of the molecules H2S, SO, and SiO compared to those anticipated in cold interstellar clouds.
6. How Culture Shock Affects Communication.
Science.gov (United States)
Barna, LaRay M.
The paper defines the term "culture shock" and discusses the changes that this state can make in a person's behavior. Culture shock refers to the emotional and physiological reaction of high activation that is brought about by sudden immersion in a new culture. Because one's own culture shields one from the unknown and reduces the need to make…
7. Molecular diagnostics of interstellar shocks
Science.gov (United States)
Hartquist, T. W.; Dalgarno, A.; Oppenheimer, M.
1980-01-01
The chemistry of molecules in shocked regions of the interstellar gas is considered and calculations are carried out for a region subjected to a shock at a velocity of 8 km/sec. Substantial enhancements are predicted in the concentrations of the molecules H2S, SO, and SiO compared to those anticipated in cold interstellar clouds.
8. Shock wave treatment in medicine
Home; Journals; Journal of Biosciences; Volume 30; Issue 2 ... In the present paper we discuss the basic theory and application of shock waves and its history in medicine. The idea behind using shock wave therapy for orthopedic diseases is the stimulation of healing in tendons, surrounding tissue and bones. This is a ...
9. Shock wave treatment in medicine
Unknown
to open surgery, the cost of the ESWT is very reasonable. But nevertheless it is necessary to improve the basic un ... In second group, shock waves are used to measure distances because of the low energy loss over large distances ... pared to a piezoelectric hydrophone. The rise time of an electrohydraulic generated shock ...
10. Numerical modeling of slow shocks
International Nuclear Information System (INIS)
Winske, D.
1987-01-01
This paper reviews previous attempt and the present status of efforts to understand the structure of slow shocks by means of time dependent numerical calculations. Studies carried out using MHD or hybrid-kinetic codes have demonstrated qualitative agreement with theory. A number of unresolved issues related to hybrid simulations of the internal shock structure are discussed in some detail. 43 refs., 8 figs
11. Dynamic shock wave: hammer blow
International Nuclear Information System (INIS)
Lackme, Claude
1978-01-01
The general properties of shocks, their generation and the conditions of reflexion to an interface are dealt with in turn. By then applying these concepts to a liquid column and its environment (wall, free area, closing devices) the hammer blow is presented as being a relatively weak shock [fr
12. Slow shocks and their transition to fast shocks in the inner solar wind
International Nuclear Information System (INIS)
Wang, Y.C.
1987-01-01
The jump conditions of MHD shocks may be directly calculated as functions of three upstream conditions: the shock Alfven number based on the normal component of the relative shock speed, the shock angle, and the plasma β value. The shock Alfven number is less than 1 for a slow shock and greater than 1 for a fast shock. A traveling, forward shock can be a slow shock in coronal space, where the Alfven speed is of the order of 1000 km/s. The surface of a forward slow shock has a bow-shaped geometry with its nose facing toward the sun. The decrease in the Alfven speed at increasing heliocentric distance causes the shock Alfven number of a forward slow shock to become greater than 1, and the shock eventually evolves from a slow shock into a fast shock. During the transition the shock system consists of a slow shock, a fast shock, and a rotational discontinuity. They intersect along a closed transition line. As the system moves outward from the sun, the area enclosed by the transition line expands, the fast shock grows stronger, and the slow shock becomes weaker. Eventually, the slow shock diminishes, and the entire shock system evolves into a forward fast shock. copyrightAmerican Geophysical Union 1987
13. Shocking matter to extreme conditions
International Nuclear Information System (INIS)
Gupta, Y.M.; Sharma, S.M.
1997-01-01
A good understanding of the thermodynamic response of matter at high compression and high energy densities is important to several areas of physics. Shock-wave experiments are uniquely suited for obtaining data at extreme conditions, and a shock-compressed matter can be viewed as a condensed system with or without dissociation or as a strongly coupled plasma. This article reviews work by Da Silva et al. in which irradiances ranging from 5x10 superscript 12 to 2x10 superscript 14 W/cm 2 were used to generate 8- to 10-ns square pulses in liquid deuterium. The authors demonstrated negligible pre-heating of the sample, steady propagation of the shock wave, and direct determination of the shock wave velocity along with particle velocity and density in the shocked state. Da Silva et al. results are compared with models and other experimental information, and the usefulness of the data in other areas is assessed. 11 refs., 1 fig
14. Electron transport and shock ignition
Energy Technology Data Exchange (ETDEWEB)
Bell, A R; Tzoufras, M, E-mail: [email protected] [Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom)
2011-04-15
Inertial fusion energy (IFE) offers one possible route to commercial energy generation. In the proposed 'shock ignition' route to fusion, the target is compressed at a relatively low temperature and then ignited using high intensity laser irradiation which drives a strong converging shock into the centre of the fuel. With a series of idealized calculations we analyse the electron transport of energy into the target, which produces the pressure responsible for driving the shock. We show that transport in shock ignition lies near the boundary between ablative and heat front regimes. Moreover, simulations indicate that non-local effects are significant in the heat front regime and might lead to increased efficiency by driving the shock more effectively and reducing heat losses to the plasma corona.
15. Oscillating nonlinear acoustic shock waves
DEFF Research Database (Denmark)
Gaididei, Yuri; Rasmussen, Anders Rønne; Christiansen, Peter Leth
2016-01-01
We investigate oscillating shock waves in a tube using a higher order weakly nonlinear acoustic model. The model includes thermoviscous effects and is non isentropic. The oscillating shock waves are generated at one end of the tube by a sinusoidal driver. Numerical simulations show that at resona......We investigate oscillating shock waves in a tube using a higher order weakly nonlinear acoustic model. The model includes thermoviscous effects and is non isentropic. The oscillating shock waves are generated at one end of the tube by a sinusoidal driver. Numerical simulations show...... polynomial in the space and time variables, we find analytical approximations to the observed single shock waves in an infinitely long tube. Using perturbation theory for the driven acoustic system approximative analytical solutions for the off resonant case are determined....
16. The effects of oil price shocks on output and inflation in China
International Nuclear Information System (INIS)
Zhao, Lin; Zhang, Xun; Wang, Shouyang; Xu, Shanying
2016-01-01
Crude oil price shocks derive from many sources, each of which may bring about different effects on macro-economy variables and require completely different designs in macro-economic policy; thus, distinguishing the sources of oil price fluctuations is crucial when evaluating these effects. This paper establishes an open-economy dynamic stochastic general equilibrium (DSGE) model with two economies: China and the rest of the world. To assess the effects of oil price shocks, the CES production function is extended by adding oil as an input. Based on the model, the effects of four types of oil price fluctuations are evaluated. The four types of oil price shocks are supply shocks driven by political events in OPEC countries, other oil supply shocks, aggregate shocks to the demand for industrial commodities, and demand shocks that are specific to the crude oil market. Simulation results indicate the following: Oil supply shocks driven by political events mainly produce short-term effects on China's output and inflation, while the other three shocks produce relatively long-term effects; in addition, demand shocks that are specific to the crude oil market contribute the most to the fluctuations in China's output and inflation.
17. The Curious Events Leading to the Theory of Shock Waves
Science.gov (United States)
Salas, Manuel D.
2006-01-01
We review the history of the development of the modern theory of shock waves. Several attempts at an early-theory quickly collapsed for lack of foundations in mathematics and thermodynamics. It is not until the works of Rankine and later Hugoniot that a full theory is established. Rankine is the first to show that within the shock a non-adiabatic process must occur. Hugoniot showed that in the absence of viscosity and heat conduction conservation of energy implies conservation of entropy in smooth regions and a jump in entropy across a shock. Even after the theory is fully developed, old notions continue to pervade the literature well into the early part of the 20th Century.
18. Lack of RNase L attenuates macrophage functions.
Directory of Open Access Journals (Sweden)
Xin Yi
Full Text Available Macrophages are one of the major cell types in innate immunity against microbial infection. It is believed that the expression of proinflammatory genes such as tumor necrosis factor-α (TNF-α, interleukin (IL-1β, IL-6, and cyclooxygenase-2 (Cox-2 by macrophages is also crucial for activation of both innate and adaptive immunities. RNase L is an interferon (IFN inducible enzyme which is highly expressed in macrophages. It has been demonstrated that RNase L regulates the expression of certain inflammatory genes. However, its role in macrophage function is largely unknown.Bone marrow-derived macrophages (BMMs were generated from RNase L(+/+and (-/- mice. The migration of BMMs was analyzed by using Transwell migration assays. Endocytosis and phagocytosis of macrophages were assessed by using fluorescein isothiocyanate (FITC-Dextran 40,000 and FITC-E. coli bacteria, respectively. The expression of inflammatory genes was determined by Western Blot and ELISA. The promoter activity of Cox-2 was measured by luciferase reporter assays.Lack of RNase L significantly decreased the migration of BMMs induced by M-CSF, but at a less extent by GM-CSF and chemokine C-C motif ligand-2 (CCL2. Interestingly, RNase L deficient BMMs showed a significant reduction of endocytic activity to FITC-Dextran 40,000, but no any obvious effect on their phagocytic activity to FITC-bacteria under the same condition. RNase L impacts the expression of certain genes related to cell migration and inflammation such as transforming growth factor (TGF-β, IL-1β, IL-10, CCL2 and Cox-2. Furthermore, the functional analysis of the Cox-2 promoter revealed that RNase L regulated the expression of Cox-2 in macrophages at its transcriptional level. Taken together, our findings provide direct evidence showing that RNase L contributes to innate immunity through regulating macrophage functions.
19. Shock interaction with a two-gas interface in a novel dual-driver shock tube
Science.gov (United States)
Labenski, John R.
Fluid instabilities exist at the interface between two fluids having different densities if the flow velocity and density gradient are anti-parallel or if a shock wave crosses the boundary. The former case is called the Rayleigh-Taylor (R-T) instability and the latter, the Richtmyer-Meshkov (R-M) instability. Small initial perturbations on the interface destabilize and grow into larger amplitude structures leading to turbulent mixing. Instabilities of this type are seen in inertial confinement fusion (ICF) experiments, laser produced plasmas, supernova explosions, and detonations. A novel dual-driver shock tube was used to investigate the growth rate of the R-M instability. One driver is used to create an argon-refrigerant interface, and the other at the opposite end of the driven section generates a shock to force the interface with compressible flows behind the shock. The refrigerant gas in the first driver is seeded with sub-micron oil droplets for visualization of the interface. The interface travels down the driven section past the test section for a fixed amount of time. A stronger shock of Mach 1.1 to 1.3 drives the interface back past the test section where flow diagnostics are positioned. Two schlieren systems record the density fluctuations while light scattering detectors record the density of the refrigerant as a function of position over the interface. A pair of digital cameras take stereo images of the interface, as mapped out by the tracer particles under illumination by a Q-switched ruby laser. The amount of time that the interface is allowed to travel up the driven section determines the interaction time as a control. Comparisons made between the schlieren signals, light scattering detector outputs, and the images quantify the fingered characteristics of the interface and its growth due to shock forcing. The results show that the interface has a distribution of thickness and that the interaction with a shock further broadens the interface. The
20. Shock Wave Propagation in Layered Planetary Interiors: Revisited
Science.gov (United States)
Arkani-Hamed, J.; Monteux, J.
2017-12-01
The end of the terrestrial planet accretion is characterized by numerous large impacts. About 90% of the mass of a large planet is accreted while the core mantle separation is occurring, because of the accretionary and the short-lived radio-isotope heating. The characteristics of the shockwave propagation, hence the existing scaling laws are poorly known within the layered planets. Here, we use iSALE-2D hydrocode simulations to calculate shock pressure in a differentiated Mars type body for impact velocities of 5-20 km/s, and impactor sizes of 100-400 km. We use two different rheologies for the target interior, an inviscid model ("no-stress model") and a pressure and damage-dependent strength model ("elaborated model"). To better characterize the shock pressure within the whole mantle as a function of distance from the impact site, we propose the following distribution: (1) a near field zone larger than the isobaric core that extends to 7-15 times the projectile radius into the target, where the peak shock pressure decays exponentially with increasing distance, (2) a far field zone where the pressure decays with distance following a power law. The shock pressure decreases more rapidly with distance in the near field for the elaborated model than for the no-stress model because of the influence of acoustic fluidization and damage. However to better illustrate the influence of the rheology on the shock propagation, we use the same expressions to fit the shock pressure with distance for both models. At the core-mantle boundary, CMB, the peak shock pressure jumps as the shock wave enters the core. We derived the boundary condition at CMB for the peak shock pressure. It is less sensitive to the impact velocity or the impactor size, but strongly depends on the rheology of the planet's mantle. Because of the lower shock wave velocity in the core compared to that in the mantle, the refracted shockwave propagates toward the symmetry axis of the planet, and the shock
1. Shock waves & explosions
CERN Document Server
Sachdev, PL
2004-01-01
Understanding the causes and effects of explosions is important to experts in a broad range of disciplines, including the military, industrial and environmental research, aeronautic engineering, and applied mathematics. Offering an introductory review of historic research, Shock Waves and Explosions brings analytic and computational methods to a wide audience in a clear and thorough way. Beginning with an overview of the research on combustion and gas dynamics in the 1970s and 1980s, the author brings you up to date by covering modeling techniques and asymptotic and perturbative methods and ending with a chapter on computational methods.Most of the book deals with the mathematical analysis of explosions, but computational results are also included wherever they are available. Historical perspectives are provided on the advent of nonlinear science, as well as on the mathematical study of the blast wave phenomenon, both when visualized as a point explosion and when simulated as the expansion of a high-pressure ...
2. Analysis of shock implosion
Energy Technology Data Exchange (ETDEWEB)
Mishkin, E.A.; Alejaldre, C. (Polytechnic Inst. of New York, Brooklyn (USA))
1984-06-01
An imploding shock wave, coming from infinity, moves through an ideal gas with the adiabatic constant ..gamma... To define a single-valued self-similar coefficient over the whole classical interval 1<..gamma..
3. The cosmic-ray shock structure problem for relativistic shocks
Science.gov (United States)
Webb, G. M.
1985-01-01
The time asymptotic behaviour of a relativistic (parallel) shock wave significantly modified by the diffusive acceleration of cosmic-rays is investigated by means of relativistic hydrodynamical equations for both the cosmic-rays and thermal gas. The form of the shock structure equation and the dispersion relation for both long and short wavelength waves in the system are obtained. The dependence of the shock acceleration efficiency on the upstream fluid spped, long wavelength Mach number and the ratio N = P sub co/cP sub co+P sub go)(Psub co and P sub go are the upstream cosmic-ray and thermal gas pressures respectively) are studied.
4. Cosmic-ray shock acceleration in oblique MHD shocks
Science.gov (United States)
Webb, G. M.; Drury, L. OC.; Volk, H. J.
1986-01-01
A one-dimensional, steady-state hydrodynamical model of cosmic-ray acceleration at oblique MHD shocks is presented. Upstream of the shock the incoming thermal plasma is subject to the adverse pressure gradient of the accelerated particles, the J x B force, as well as the thermal gas pressure gradient. The efficiency of the acceleration of cosmic-rays at the shock as a function of the upstream magnetic field obliquity and upstream plasma beta is investigated. Astrophysical applications of the results are briefly discussed.
5. Antigenicity of Leishmania-Activated C-Kinase Antigen (LACK in Human Peripheral Blood Mononuclear Cells, and Protective Effect of Prime-Boost Vaccination With pCI-neo-LACK Plus Attenuated LACK-Expressing Vaccinia Viruses in Hamsters
Directory of Open Access Journals (Sweden)
Laura Fernández
2018-04-01
Full Text Available Leishmania-activated C-kinase antigen (LACK is a highly conserved protein among Leishmania species and is considered a viable vaccine candidate for human leishmaniasis. In animal models, prime-boost vaccination with LACK-expressing plasmids plus attenuated vaccinia viruses (modified vaccinia Ankara [MVA] and mutant M65 expressing LACK, has been shown to protect against cutaneous leishmaniasis (CL. Further, LACK demonstrated to induce the production of protective cytokines in patients with active CL or cured visceral leishmaniasis, as well as in asymptomatic individuals from endemic areas. However, whether LACK is capable to trigger cytokine release by peripheral blood mononuclear cells from patients cured of CL due to Leishmania infantum (L. infantum or induce protection in L. infantum-infected hamsters [visceral leishmaniasis (VL model], has not yet been analyzed. The present work examines the ex vivo immunogenicity of LACK in cured VL and CL patients, and asymptomatic subjects from an L. infantum area. It also evaluates the vaccine potential of LACK against L. infantum infection in hamsters, in a protocol of priming with plasmid pCI-neo-LACK (DNA-LACK followed by a booster with the poxvirus vectors MVA-LACK or M65-LACK. LACK-stimulated PBMC from both asymptomatic and cured subjects responded by producing IFN-γ, TNF-α, and granzyme B (Th1-type response. Further, 78% of PBMC samples that responded to soluble Leishmania antigen showed IFN-γ secretion following stimulation with LACK. In hamsters, the protocol of DNA-LACK prime/MVA-LACK or M65-LACK virus boost vaccination significantly reduced the amount of Leishmania DNA in the liver and bone marrow, with no differences recorded between the use of MVA or M65 virus vector options. In summary, the Th1-type and cytotoxic responses elicited by LACK in PBMC from human subjects infected with L. infantum, and the parasite protective effect of prime/boost vaccination in hamsters with DNA-LACK/MVA-LACK
6. Chondrule destruction in nebular shocks
Energy Technology Data Exchange (ETDEWEB)
Jacquet, Emmanuel; Thompson, Christopher, E-mail: [email protected] [Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St George Street, Toronto, ON M5S 3H8 (Canada)
2014-12-10
Chondrules are millimeter-sized silicate spherules ubiquitous in primitive meteorites, but whose origin remains mysterious. One of the main proposed mechanisms for producing them is melting of solids in shock waves in the gaseous protoplanetary disk. However, evidence is mounting that chondrule-forming regions were enriched in solids well above solar abundances. Given the high velocities involved in shock models, destructive collisions would be expected between differently sized grains after passage of the shock front as a result of differential drag. We investigate the probability and outcome of collisions of particles behind a one-dimensional shock using analytic methods as well as a full integration of the coupled mass, momentum, energy, and radiation equations. Destruction of protochondrules seems unavoidable for solid/gas ratios ε ≳ 0.1, and possibly even for solar abundances because of 'sandblasting' by finer dust. A flow with ε ≳ 10 requires much smaller shock velocities (∼2 versus 8 km s{sup –1}) in order to achieve chondrule-melting temperatures, and radiation trapping allows slow cooling of the shocked fragments. Initial destruction would still be extensive; although re-assembly of millimeter-sized particles would naturally occur by grain sticking afterward, the compositional heterogeneity of chondrules may be difficult to reproduce. We finally note that solids passing through small-scale bow shocks around few kilometer-sized planetesimals might experience partial melting and yet escape fragmentation.
7. TG2 regulates the heat-shock response by the post-translational modification of HSF1.
Science.gov (United States)
Rossin, Federica; Villella, Valeria Rachela; D'Eletto, Manuela; Farrace, Maria Grazia; Esposito, Speranza; Ferrari, Eleonora; Monzani, Romina; Occhigrossi, Luca; Pagliarini, Vittoria; Sette, Claudio; Cozza, Giorgio; Barlev, Nikolai A; Falasca, Laura; Fimia, Gian Maria; Kroemer, Guido; Raia, Valeria; Maiuri, Luigi; Piacentini, Mauro
2018-05-11
Heat-shock factor 1 (HSF1) is the master transcription factor that regulates the response to proteotoxic stress by controlling the transcription of many stress-responsive genes including the heat-shock proteins. Here, we show a novel molecular mechanism controlling the activation of HSF1. We demonstrate that transglutaminase type 2 (TG2), dependent on its protein disulphide isomerase activity, triggers the trimerization and activation of HSF1 regulating adaptation to stress and proteostasis impairment. In particular, we find that TG2 loss of function correlates with a defect in the nuclear translocation of HSF1 and in its DNA-binding ability to the HSP70 promoter. We show that the inhibition of TG2 restores the unbalance in HSF1-HSP70 pathway in cystic fibrosis (CF), a human disorder characterized by deregulation of proteostasis. The absence of TG2 leads to an increase of about 40% in CFTR function in a new experimental CF mouse model lacking TG2. Altogether, these results indicate that TG2 plays a key role in the regulation of cellular proteostasis under stressful cellular conditions through the modulation of the heat-shock response. © 2018 The Authors.
8. Shock fabrics in fine-grained micrometeorites
Science.gov (United States)
Suttle, M. D.; Genge, M. J.; Russell, S. S.
2017-10-01
The orientations of dehydration cracks and fracture networks in fine-grained, unmelted micrometeorites were analyzed using rose diagrams and entropy calculations. As cracks exploit pre-existing anisotropies, analysis of their orientation provides a mechanism with which to study the subtle petrofabrics preserved within fine-grained and amorphous materials. Both uniaxial and biaxial fabrics are discovered, often with a relatively wide spread in orientations (40°-60°). Brittle deformation cataclasis and rotated olivine grains are reported from a single micrometeorite. This paper provides the first evidence for impact-induced shock deformation in fine-grained micrometeorites. The presence of pervasive, low-grade shock features in CM chondrites and CM-like dust, anomalously low-density measurements for C-type asteroids, and impact experiments which suggest CM chondrites are highly prone to disruption all imply that CM parent bodies are unlikely to have remained intact and instead exist as a collection of loosely aggregated rubble-pile asteroids, composed of primitive shocked clasts.
9. Simulation of mechanical shock environments
International Nuclear Information System (INIS)
Lalanne, Christian.
1975-07-01
Shocks can produce a severe mechanical environment which must be taken into account when designing and developing new equipments. After some mathematical (Laplace and Fourier transforms) and mechanical recalls (response of a one degree freedom system to a sinusoidal excitation), different analysis methods are compared, these methods being the most used now to compare relative severities of tests and establish specifications. A few chapter deal with the different properties of simple, easy to produce, shock shapes. Then some now-in-use programmators or shock-machines specifications are shown. A final chapter concerns acceleration transducers [fr
10. Shocks in the Early Universe.
Science.gov (United States)
Pen, Ue-Li; Turok, Neil
2016-09-23
We point out a surprising consequence of the usually assumed initial conditions for cosmological perturbations. Namely, a spectrum of Gaussian, linear, adiabatic, scalar, growing mode perturbations not only creates acoustic oscillations of the kind observed on very large scales today, it also leads to the production of shocks in the radiation fluid of the very early Universe. Shocks cause departures from local thermal equilibrium as well as create vorticity and gravitational waves. For a scale-invariant spectrum and standard model physics, shocks form for temperatures 1 GeVUniverse as early as 10^{-30} sec after the big bang.
11. A New Method to Comprehensively Diagnose Shock Waves in the Solar Atmosphere Based on Simultaneous Spectroscopic and Imaging Observations
Science.gov (United States)
Ruan, Wenzhi; Yan, Limei; He, Jiansen; Zhang, Lei; Wang, Linghua; Wei, Yong
2018-06-01
Shock waves are believed to play an important role in plasma heating. The shock-like temporal jumps in radiation intensity and Doppler shift have been identified in the solar atmosphere. However, a quantitative diagnosis of the shocks in the solar atmosphere is still lacking, seriously hindering the understanding of shock dissipative heating of the solar atmosphere. Here, we propose a new method to realize the goal of the shock quantitative diagnosis, based on Rankine–Hugoniot equations and taking the advantages of simultaneous imaging and spectroscopic observations from, e.g., IRIS (Interface Region Imaging Spectrograph). Because of this method, the key parameters of shock candidates can be derived, such as the bulk velocity and temperature of the plasma in the upstream and downstream, the propagation speed and direction. The method is applied to the shock candidates observed by IRIS, and the overall characteristics of the shocks are revealed quantitatively for the first time. This method is also tested with the help of forward modeling, i.e., virtual observations of simulated shocks. The parameters obtained from the method are consistent with the parameters of the shock formed in the model and are independent of the viewing direction. Therefore, the method we proposed here is applicable to the quantitative and comprehensive diagnosis of the observed shocks in the solar atmosphere.
12. Factors influencing flow steadiness in laminar boundary layer shock interactions
Science.gov (United States)
Tumuklu, Ozgur; Levin, Deborah A.; Gimelshein, Sergey F.; Austin, Joanna M.
2016-11-01
The Direct Simulation Monte Carlo method has been used to model laminar shock wave boundary interactions of hypersonic flow over a 30/55-deg double-wedge and "tick-shaped" model configurations studied in the Hypervelocity Expansion Tube facility and T-ADFA free-piston shock tunnel, respectively. The impact of thermochemical effects on these interactions by changing the chemical composition from nitrogen to air as well as argon for a stagnation enthalpy of 8.0 MJ/kg flow are investigated using the 2-D wedge model. The simulations are found to reproduce many of the classic features related to Edney Type V strong shock interactions that include the attached, oblique shock formed over the first wedge, the detached bow shock from the second wedge, the separation zone, and the separation and reattachment shocks that cause complex features such as the triple point for both cases. However, results of a reacting air flow case indicate that the size of the separation length, and the movement of the triple point toward to the leading edge is much less than the nitrogen case.
13. PROMINENCE ACTIVATION BY CORONAL FAST MODE SHOCK
Energy Technology Data Exchange (ETDEWEB)
Takahashi, Takuya [Department of Astronomy, Kyoto University, Sakyo, Kyoto, 606-8502 (Japan); Asai, Ayumi [Unit of Synergetic Studies for Space, Kyoto University, Yamashina, Kyoto 607-8471 (Japan); Shibata, Kazunari, E-mail: [email protected] [Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto 607-8471 (Japan)
2015-03-01
An X5.4 class flare occurred in active region NOAA11429 on 2012 March 7. The flare was associated with a very fast coronal mass ejection (CME) with a velocity of over 2500 km s{sup −1}. In the images taken with the Solar Terrestrial Relations Observatory-B/COR1, a dome-like disturbance was seen to detach from an expanding CME bubble and propagated further. A Type-II radio burst was also observed at the same time. On the other hand, in extreme ultraviolet images obtained by the Solar Dynamic Observatory/Atmospheric Imaging Assembly (AIA), the expanding dome-like structure and its footprint propagating to the north were observed. The footprint propagated with an average speed of about 670 km s{sup −1} and hit a prominence located at the north pole and activated it. During the activation, the prominence was strongly brightened. On the basis of some observational evidence, we concluded that the footprint in AIA images and the ones in COR1 images are the same, that is, the MHD fast mode shock front. With the help of a linear theory, the fast mode Mach number of the coronal shock is estimated to be between 1.11 and 1.29 using the initial velocity of the activated prominence. Also, the plasma compression ratio of the shock is enhanced to be between 1.18 and 2.11 in the prominence material, which we consider to be the reason for the strong brightening of the activated prominence. The applicability of linear theory to the shock problem is tested with a nonlinear MHD simulation.
14. Investigation of Shock-Induced Reactions in a Ni+Al Powder Mixture
International Nuclear Information System (INIS)
Eakins, D. E.; Thadhani, N. N.
2006-01-01
The shock-compression and reaction response of equi-volumetric micron-scale (∼50-60% dense) spherical nickel and aluminum powder mixtures is investigated in the range of the calculated crush-up pressure (P = 0.4 GPa) and up to 6 GPa. Time resolved stress measurements (using PVDF gauges) coupled with VISAR data is used to determine the shock states. Evidence of reaction or lack thereof is inferred by comparing the measured states with calculated Hugoniot state of reaction products based on the ballotechnic model proposed by Bennett and Horie, (Shock Waves 4:127-136). Post-impact micro-structural analysis of recovered material and comparison of calculated and measured product states is used to establish the criterion for reaction occurring in the shock or post-shock states
15. Shock parameter calculations at weak interplanetary shock waves
Directory of Open Access Journals (Sweden)
J. M. Gloag
2005-02-01
Full Text Available A large set of interplanetary shock waves observed using the Ulysses spacecraft is analysed in order to determine their local parameters. For the first time a detailed analysis is extended to the thermodynamic properties of a large number of events. The intention is to relate the shock parameters to the requirements set by MHD shock theory. A uniform approach is adopted in the selection of up and downstream regions for this analysis and applied to all the shock waves. Initially, the general case of a 3 component adiabatic plasma is considered. However, the calculation of magnetosonic and Alfvénic Mach numbers and the ratio of downstream to upstream entropy produce some unexpected results. In some cases there is no clear increase in entropy across the shock and also the magnetosonic Mach number can be less than 1. It is found that a more discerning use of data along with an empirical value for the polytropic index can raise the distribution of downstream to upstream entropy ratios to a more acceptable level. However, it is also realised that many of these shocks are at the very weakest end of the spectrum and associated phenomena may also contribute to the explanation of these results.
16. Quasilinear simulations of interplanetary shocks and Earth's bow shock
Science.gov (United States)
Afanasiev, Alexandr; Battarbee, Markus; Ganse, Urs; Vainio, Rami; Palmroth, Minna; Pfau-Kempf, Yann; Hoilijoki, Sanni; von Alfthan, Sebastian
2016-04-01
We have developed a new self-consistent Monte Carlo simulation model for particle acceleration in shocks. The model includes a prescribed large-scale magnetic field and plasma density, temperature and velocity profiles and a self-consistently computed incompressible ULF foreshock under the quasilinear approximation. Unlike previous analytical treatments, our model is time dependent and takes full account of the anisotropic particle distributions and scattering in the wave-particle interaction process. We apply the model to the problem of particle acceleration at traveling interplanetary (IP) shocks and Earth's bow shock and compare the results with hybrid-Vlasov simulations and spacecraft observations. A qualitative agreement in terms of spectral shape of the magnetic fluctuations and the polarization of the unstable mode is found between the models and the observations. We will quantify the differences of the models and explore the region of validity of the quasilinear approach in terms of shock parameters. We will also compare the modeled IP shocks and the bow shock, identifying the similarities and differences in the spectrum of accelerated particles and waves in these scenarios. The work has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 637324 (HESPERIA). The Academy of Finland is thanked for financial support. We acknowledge the computational resources provided by CSC - IT Centre for Science Ltd., Espoo.
17. Diaphragmless shock wave generators for industrial applications of shock waves
Science.gov (United States)
Hariharan, M. S.; Janardhanraj, S.; Saravanan, S.; Jagadeesh, G.
2011-06-01
The prime focus of this study is to design a 50 mm internal diameter diaphragmless shock tube that can be used in an industrial facility for repeated loading of shock waves. The instantaneous rise in pressure and temperature of a medium can be used in a variety of industrial applications. We designed, fabricated and tested three different shock wave generators of which one system employs a highly elastic rubber membrane and the other systems use a fast acting pneumatic valve instead of conventional metal diaphragms. The valve opening speed is obtained with the help of a high speed camera. For shock generation systems with a pneumatic cylinder, it ranges from 0.325 to 1.15 m/s while it is around 8.3 m/s for the rubber membrane. Experiments are conducted using the three diaphragmless systems and the results obtained are analyzed carefully to obtain a relation between the opening speed of the valve and the amount of gas that is actually utilized in the generation of the shock wave for each system. The rubber membrane is not suitable for industrial applications because it needs to be replaced regularly and cannot withstand high driver pressures. The maximum shock Mach number obtained using the new diaphragmless system that uses the pneumatic valve is 2.125 ± 0.2%. This system shows much promise for automation in an industrial environment.
18. IRC -10414: a bow-shock-producing red supergiant star
Science.gov (United States)
Gvaramadze, V. V.; Menten, K. M.; Kniazev, A. Y.; Langer, N.; Mackey, J.; Kraus, A.; Meyer, D. M.-A.; Kamiński, T.
2014-01-01
Most runaway OB stars, like the majority of massive stars residing in their parent clusters, go through the red supergiant (RSG) phase during their lifetimes. Nonetheless, although many dozens of massive runaways were found to be associated with bow shocks, only two RSG bow-shock-producing stars, Betelgeuse and μ Cep, are known to date. In this paper, we report the discovery of an arc-like nebula around the late M-type star IRC -10414 using the SuperCOSMOS H-alpha Survey. Our spectroscopic follow-up of IRC -10414 with the Southern African Large Telescope (SALT) showed that it is a M7 supergiant, which supports previous claims on the RSG nature of this star based on observations of its maser emission. This was reinforced by our new radio- and (sub)millimetre-wavelength molecular line observations made with the Atacama Pathfinder Experiment 12-m telescope and the Effelsberg 100-m radio telescope, respectively. The SALT spectrum of the nebula indicates that its emission is the result of shock excitation. This finding along with the arc-like shape of the nebula and an estimate of the space velocity of IRC -10414 (≈70 ± 20 km s-1) imply the bow shock interpretation for the nebula. Thus, IRC -10414 represents the third case of a bow-shock-producing RSG and the first one with a bow shock visible at optical wavelengths. We discuss the smooth appearance of the bow shocks around IRC -10414 and Betelgeuse and propose that one of the necessary conditions for stability of bow shocks generated by RSGs is the ionization of the stellar wind. Possible ionization sources of the wind of IRC -10414 are proposed and discussed.
19. Motor hypertonia and lack of locomotor coordination in mutant mice lacking DSCAM.
Science.gov (United States)
Lemieux, Maxime; Laflamme, Olivier D; Thiry, Louise; Boulanger-Piette, Antoine; Frenette, Jérôme; Bretzner, Frédéric
2016-03-01
Down syndrome cell adherence molecule (DSCAM) contributes to the normal establishment and maintenance of neural circuits. Whereas there is abundant literature regarding the role of DSCAM in the neural patterning of the mammalian retina, less is known about motor circuits. Recently, DSCAM mutation has been shown to impair bilateral motor coordination during respiration, thus causing death at birth. DSCAM mutants that survive through adulthood display a lack of locomotor endurance and coordination in the rotarod test, thus suggesting that the DSCAM mutation impairs motor control. We investigated the motor and locomotor functions of DSCAM(2J) mutant mice through a combination of anatomical, kinematic, force, and electromyographic recordings. With respect to wild-type mice, DSCAM(2J) mice displayed a longer swing phase with a limb hyperflexion at the expense of a shorter stance phase during locomotion. Furthermore, electromyographic activity in the flexor and extensor muscles was increased and coactivated over 20% of the step cycle over a wide range of walking speeds. In contrast to wild-type mice, which used lateral walk and trot at walking speed, DSCAM(2J) mice used preferentially less coordinated gaits, such as out-of-phase walk and pace. The neuromuscular junction and the contractile properties of muscles, as well as their muscle spindles, were normal, and no signs of motor rigidity or spasticity were observed during passive limb movements. Our study demonstrates that the DSCAM mutation induces dystonic hypertonia and a disruption of locomotor gaits. Copyright © 2016 the American Physiological Society.
20. Shock wave dynamics derivatives and related topics
CERN Document Server
Emanuel, George
2012-01-01
"...this monograph develops an esoteric niche within shock wave theory. …treats shock waves from an analytical approach assuming perfect gas. Emanuel has made significant contributions to the theory of shock waves and has selected a number of topics that reflect those contributions."-Shock Waves, 2013.
1. Experimental Study of the Information Signal of Combined Shock, Tilt, and Motion Sensor Based on the 3-Axis MEMS-Accelerometer
Directory of Open Access Journals (Sweden)
S. A. Vasyukov
2014-01-01
Full Text Available Modern car alarm systems are equipped with smart sensors implemented using various physical principles. These sensors have to ensure high reliability and validity of monitored parameters with a lack of false operations. First of all, shock sensor, which is a part of, essentially, entire alarm systems, as well as tilt and motion sensors are referred to the smart sensors.Shock sensors with the sensitive elements (SE of piezoelectric, microphone, and electromagnetic types possess a number of the essential shortcomings caused by the type of SE. It is, first of all, a narrow band of the sensitive elements, which does not allow true differentiation of shocks to the autobody from false actions, as well as a various sensitivity of sensors depending on the SE axis orientation.Tilt sensors of electromagnetic type implemented as separate devices were seldom used because of their high cost and imperfect characteristics. Though there is still a need for such sensors. The specified shortcomings can be hardly overcome through improvement of sensitive element hangers of considered sensors. The use of the three-axial accelerometers made by MEMS technology seems to be the most perspective here.The article presents results of pilot studies of the accelerations reached when auto-body is under shock and a car is inclined and runs. When measuring, the test board STM32F3DISCOVERY with the MEMS accelerometer LSM303DLHS is used. A level of noise and vibrations has been analysed when mounting a board on the plastic panel of the car and when operating the engine in the range from 700 to 4000 rpm. The article presents accelerations implemented under the following conditions: light shocks in different parts of the auto-body (wing, trunk, hood; strong shock (closing a door; slow and fast acceleration to the speed of 20 km/h with the subsequent braking and passage of obstacles such as "sleeping policemen".Research results enabled us to make justification for selecting the
2. Agricultural Commodity Price Shocks and their Effect on Growth in Sub-Saharan Africa
OpenAIRE
2014-01-01
Commodity price shocks are an important type of external shock and are often cited as a problem for economic growth in sub-Saharan Africa. This paper quantifies the impact of agricultural commodity price shocks using a near vector autoregressive model. The novel aspect of this model is that we define an auxiliary variable that can potentially capture the definition of a price shock that allows us to determine whether the response of per capita Gross domestic product (GDP) growth in sub-Sahara...
3. Nonlinearity, Conservation Law and Shocks
Almost all natural phenomena, and social and economic changes, .... reference moving with velocity c also by the same symbol x and ... abstract as can be seen from the publication of the book Shock Waves and Reaction Diffusion Equation.
4. Shock Thermodynamic Applied Research Facility
Data.gov (United States)
Federal Laboratory Consortium — The Shock Thermodynamic Applied Research Facility (STAR) facility, within Sandia’s Solid Dynamic Physics Department, is one of a few institutions in the world with a...
5. Target design for shock ignition
International Nuclear Information System (INIS)
Schurtz, G; Ribeyre, X; Lafon, M
2010-01-01
The conventional approach of laser driven inertial fusion involves the implosion of cryogenic shells of deuterium-tritium ice. At sufficiently high implosion velocities, the fuel ignites by itself from a central hot spot. In order to reduce the risks of hydrodynamic instabilities inherent to large implosion velocities, it was proposed to compress the fuel at low velocity, and ignite the compressed fuel by means of a convergent shock wave driven by an intense spike at the end of the laser pulse. This scheme, known as shock ignition, reduces the risks of shell break-up during the acceleration phase, but it may be impeded by a low coupling efficiency of the laser pulse with plasma at high intensities. This work provides a relationship between the implosion velocity and the laser intensity required to ignite the target by a shock. The operating domain of shock ignition at different energies is described.
6. Undercuts by Laser Shock Forming
International Nuclear Information System (INIS)
Wielage, Hanna; Vollertsen, Frank
2011-01-01
In laser shock forming TEA-CO 2 -laser induced shock waves are used to form metal foils, such as aluminum or copper. The process utilizes an initiated plasma shock wave on the target surface, which leads to a forming of the foil. A challenge in forming technologies is the manufacturing of undercuts. By conventional forming methods these special forms are not feasible. In this article, it is presented that undercuts in the micro range can be produced by laser shock deep drawing. Different drawing die diameters, drawing die depths and the material aluminum in the thicknesses 20 and 50 μm were investigated. It will be presented that smaller die diameters facilitate undercuts compared to bigger die diameters. The phenomena can be explained by Barlow's formula. Furthermore, it is shown which maximum undercut depth at different die diameters can be reached. To this end, cross-sections of the different parameter combinations are displayed.
7. Electric Shock Injuries in Children
Science.gov (United States)
... Issues Listen Español Text Size Email Print Share Electric Shock Injuries in Children Page Content When the ... comes into direct contact with a source of electricity, the current passes through it, producing what's called ...
8. Relativistic shocks and particle acceleration
International Nuclear Information System (INIS)
Heavens, A.F.
1988-01-01
In this paper, we investigate the fluid dynamics of relativistic shock waves, and use the results to calculate the spectral index of particles accelerated by the Fermi process in such shocks. We have calculated the distributions of Fermi-accelerated particles at shocks propagating into cold proton-electron plasma and also cold electron-positron plasma. We have considered two different power spectra for the scattering waves, and find, in contrast to the non-relativistic case, that the spectral index of the accelerated particles depends on the wave power spectrum. On the assumption of thermal equilibrium both upstream and downstream, we present some useful fits for the compression ratio of shocks propagating at arbitrary speeds into gas of any temperature. (author)
9. Shock wave interaction with turbulence: Pseudospectral simulations
International Nuclear Information System (INIS)
Buckingham, A.C.
1986-01-01
Shock waves amplify pre-existing turbulence. Shock tube and shock wave boundary layer interaction experiments provide qualitative confirmation. However, shock pressure, temperature, and rapid transit complicate direct measurement. Computational simulations supplement the experimental data base and help isolate the mechanisms responsible. Simulations and experiments, particularly under reflected shock wave conditions, significantly influence material mixing. In these pseudospectral Navier-Stokes simulations the shock wave is treated as either a moving (tracked or fitted) domain boundary. The simulations assist development of code mix models. Shock Mach number and pre-existing turbulence intensity initially emerge as key parameters. 20 refs., 8 figs
10. Impact shock frequency components and attenuation in rearfoot and forefoot running
Directory of Open Access Journals (Sweden)
Allison H. Gruber
2014-06-01
Conclusion: The difference in impact shock frequency content between footfall patterns suggests that the primary mechanisms for attenuation may differ. The relationship between shock attenuation mechanisms and injury is not clear but given the differences in impact frequency content, neither footfall pattern may be more beneficial for injury, rather the type of injury sustained may vary with footfall pattern preference.
11. Unemployment dynamics, and propagation of aggregate and reallocation shocks in the Netherlands
NARCIS (Netherlands)
van Montfort, C.A.G.M.; den Butter, F.A.G.; Weitenberg, G.
2003-01-01
This paper models the propagation at the macro level of four types of shocks using the SVAR approach. Time series data for the Netherlands on job creation, job destruction, the number of vacancies and labour supply are used to identify aggregate demand and supply shocks, and reallocation demand and
12. The Efficacy of Cognitive Shock
Science.gov (United States)
2015-05-21
way, causing dissonance or cognitive conflict, so that the mental model has to be ‘accommodated’ to the new data. Categories and knowledge have to...The Efficacy of Cognitive Shock A Monograph by MAJ Anthony L. Marston United States Army School of Advanced Military Studies...DATES COVERED (From - To) JUN 2014 – MAY 2015 4. TITLE AND SUBTITLE The Efficacy of Cognitive Shock 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c
13. Pressurized Thermal Shock, Pts
International Nuclear Information System (INIS)
Boyd, C.
2008-01-01
Pressurized Thermal Shock (Pts) refers to a condition that challenges the integrity of the reactor pressure vessel. The root cause of this problem is the radiation embrittlement of the reactor vessel. This embrittlement leads to an increase in the reference temperature for nil ductility transition (RTNDT). RTNDT can increase to the point where the reactor vessel material can loose fracture toughness during overcooling events. The analysis of the risk of having a Pts for a specific plant is a multi-disciplinary problem involving probabilistic risk analysis (PRA), thermal-hydraulic analysis, and ultimately a structural and fracture analysis of the vessel wall. The PRA effort involves the postulation of overcooling events and ultimately leads to an integrated risk analysis. The thermal-hydraulic effort involves the difficult task of predicting the system behavior during a postulated overcooling scenario with a special emphasis on predicting the thermal and mechanic loadings on the reactor pressure vessel wall. The structural and fracture analysis of the reactor vessel wall relies on the thermal-hydraulic conditions as boundary conditions. The US experience has indicated that medium and large diameter primary system breaks dominate the risk of Pts along with scenarios that involve a stuck open valve (and associated system cooldown) that recloses resulting in system re-pressurization while the vessel wall is cool.
14. Sepsis and septic shock
Science.gov (United States)
Hotchkiss, Richard S.; Moldawer, Lyle L.; Opal, Steven M.; Reinhart, Konrad; Turnbull, Isaiah R.; Vincent, Jean-Louis
2017-01-01
For more than two decades, sepsis was defined as a microbial infection that produces fever (or hypothermia), tachycardia, tachypnoea and blood leukocyte changes. Sepsis is now increasingly being considered a dysregulated systemic inflammatory and immune response to microbial invasion that produces organ injury for which mortality rates are declining to 15–25%. Septic shock remains defined as sepsis with hyperlactataemia and concurrent hypotension requiring vasopressor therapy, with in-hospital mortality rates approaching 30–50%. With earlier recognition and more compliance to best practices, sepsis has become less of an immediate life-threatening disorder and more of a long-term chronic critical illness, often associated with prolonged inflammation, immune suppression, organ injury and lean tissue wasting. Furthermore, patients who survive sepsis have continuing risk of mortality after discharge, as well as long-term cognitive and functional deficits. Earlier recognition and improved implementation of best practices have reduced in-hospital mortality, but results from the use of immunomodulatory agents to date have been disappointing. Similarly, no biomarker can definitely diagnose sepsis or predict its clinical outcome. Because of its complexity, improvements in sepsis outcomes are likely to continue to be slow and incremental. PMID:28117397
15. Shock Wave Diffraction Phenomena around Slotted Splitters
Directory of Open Access Journals (Sweden)
Francesca Gnani
2015-01-01
Full Text Available In the field of aerospace engineering, the study of the characteristics of vortical flows and their unsteady phenomena finds numerous engineering applications related to improvements in the design of tip devices, enhancement of combustor performance, and control of noise generation. A large amount of work has been carried out in the analysis of the shock wave diffraction around conventional geometries such as sharp and rounded corners, but the employment of splitters with lateral variation has hardly attracted the attention of researchers. The investigation of this phenomenon around two-dimensional wedges has allowed the understanding of the basic physical principles of the flow features. On the other hand, important aspects that appear in the third dimension due to the turbulent nature of the vortices are omitted. The lack of studies that use three-dimensional geometries has motivated the current work to experimentally investigate the evolution of the shock wave diffraction around two splitters with spike-shaped structures for Mach numbers of 1.31 and 1.59. Schlieren photography was used to obtain an insight into the sequential diffraction processes that take place in different planes. Interacting among them, these phenomena generate a complicated turbulent cloud with a vortical arrangement.
16. Thermoluminescence of annealed and shock-loaded feldspar
International Nuclear Information System (INIS)
Hartmetz, C.P.
1988-01-01
Samples of oligoclase and bytownite were shock-loaded to a variety of pressures, and annealed for a variety of temperatures and times. The effect of Mrad doses of gamma-rays on oligoclase TL were also studied. After these treatments, thermoluminescence (TL) and X-ray diffraction (XRD) measurements were made to: (1) determine the effects of shock on terrestrial feldspar and compare with variations in the TL emission of ordinary chondrites (OCs); (2) determine if disordering in feldspar was responsible for any related changes in TL properties of OCs; (3) determine if the combined effect of shock plus annealing causes the changes in TL properties; (4) see if radiation damage from cosmic ray exposure plays a role in the TL variations; (5) examine the implications of this work to the thermal and shock histories of OCs. The lightly shock-loaded and annealed oligoclase samples have a dominant peak temperature of 120-140 C, identical to type 3.3-3.5 OCs. The heavily shocked samples dominant peak is at 230C, similar to type > 3.5 OCs . While the heavily annealed/disordered oligoclase samples have a peak at 280C, this peak is rarely observed in OCs. Radiation damage from Mrad doses of gamma-rays produced no change in peak temperature, but facilitated the shift to higher peak temperatures. The TL sensitivity of the shocked samples decreased by a factor of 25. Samples annealed at low temperatures (438-533C) showed a factor of 2 decrease in TL, but at the highest temperatures, the TL was a factor of 8 higher
17. Shock compression of synthetic opal
International Nuclear Information System (INIS)
Inoue, A; Okuno, M; Okudera, H; Mashimo, T; Omurzak, E; Katayama, S; Koyano, M
2010-01-01
Structural change of synthetic opal by shock-wave compression up to 38.1 GPa has been investigated by using SEM, X-ray diffraction method (XRD), Infrared (IR) and Raman spectroscopies. Obtained information may indicate that the dehydration and polymerization of surface silanole due to high shock and residual temperature are very important factors in the structural evolution of synthetic opal by shock compression. Synthetic opal loses opalescence by 10.9 and 18.4 GPa of shock pressures. At 18.4 GPa, dehydration and polymerization of surface silanole and transformation of network structure may occur simultaneously. The 4-membered ring of TO 4 tetrahedrons in as synthetic opal may be relaxed to larger ring such as 6-membered ring by high residual temperature. Therefore, the residual temperature may be significantly high at even 18.4 GPa of shock compression. At 23.9 GPa, opal sample recovered the opalescence. Origin of this opalescence may be its layer structure by shock compression. Finally, sample fuse by very high residual temperature at 38.1 GPa and the structure closes to that of fused SiO 2 glass. However, internal silanole groups still remain even at 38.1 GPa.
18. Computations of slowly moving shocks
International Nuclear Information System (INIS)
Karni, S.; Canic, S.
1997-01-01
Computations of slowly moving shocks by shock capturing schemes may generate oscillations are generated already by first-order schemes, but become more pronounced in higher-order schemes which seem to exhibit different behaviors: (i) the first-order upwind (UW) scheme which generates strong oscillations and (ii) the Lax-Friedrichs scheme which appears not to generate any disturbances at all. A key observation is that in the UW case, the numerical viscosity in the shock family vanishes inside the slow shock layer. Simple scaling arguments show the third-order effects on the solution may no longer be neglected. We derive the third-order modified equation for the UW scheme and regard the oscillatory solution as a traveling wave solution of the parabolic modified equation for the perturbation. We then look at the governing equation for the perturbation, which points to a plausible mechanism by which postshock oscillations are generated. It contains a third-order source term that becomes significant inside the shock layer, and a nonlinear coupling term which projects the perturbation on all characteristic fields, including those not associated with the shock family. 5 refs., 8 figs
19. Shock compression of synthetic opal
Science.gov (United States)
Inoue, A.; Okuno, M.; Okudera, H.; Mashimo, T.; Omurzak, E.; Katayama, S.; Koyano, M.
2010-03-01
Structural change of synthetic opal by shock-wave compression up to 38.1 GPa has been investigated by using SEM, X-ray diffraction method (XRD), Infrared (IR) and Raman spectroscopies. Obtained information may indicate that the dehydration and polymerization of surface silanole due to high shock and residual temperature are very important factors in the structural evolution of synthetic opal by shock compression. Synthetic opal loses opalescence by 10.9 and 18.4 GPa of shock pressures. At 18.4 GPa, dehydration and polymerization of surface silanole and transformation of network structure may occur simultaneously. The 4-membered ring of TO4 tetrahedrons in as synthetic opal may be relaxed to larger ring such as 6-membered ring by high residual temperature. Therefore, the residual temperature may be significantly high at even 18.4 GPa of shock compression. At 23.9 GPa, opal sample recovered the opalescence. Origin of this opalescence may be its layer structure by shock compression. Finally, sample fuse by very high residual temperature at 38.1 GPa and the structure closes to that of fused SiO2 glass. However, internal silanole groups still remain even at 38.1 GPa.
20. Shock compression of synthetic opal
Energy Technology Data Exchange (ETDEWEB)
Inoue, A; Okuno, M; Okudera, H [Department of Earth Sciences, Kanazawa University Kanazawa, Ishikawa, 920-1192 (Japan); Mashimo, T; Omurzak, E [Shock Wave and Condensed Matter Research Center, Kumamoto University, Kumamoto, 860-8555 (Japan); Katayama, S; Koyano, M, E-mail: [email protected] [JAIST, Nomi, Ishikawa, 923-1297 (Japan)
2010-03-01
Structural change of synthetic opal by shock-wave compression up to 38.1 GPa has been investigated by using SEM, X-ray diffraction method (XRD), Infrared (IR) and Raman spectroscopies. Obtained information may indicate that the dehydration and polymerization of surface silanole due to high shock and residual temperature are very important factors in the structural evolution of synthetic opal by shock compression. Synthetic opal loses opalescence by 10.9 and 18.4 GPa of shock pressures. At 18.4 GPa, dehydration and polymerization of surface silanole and transformation of network structure may occur simultaneously. The 4-membered ring of TO{sub 4} tetrahedrons in as synthetic opal may be relaxed to larger ring such as 6-membered ring by high residual temperature. Therefore, the residual temperature may be significantly high at even 18.4 GPa of shock compression. At 23.9 GPa, opal sample recovered the opalescence. Origin of this opalescence may be its layer structure by shock compression. Finally, sample fuse by very high residual temperature at 38.1 GPa and the structure closes to that of fused SiO{sub 2} glass. However, internal silanole groups still remain even at 38.1 GPa.
1. Electromagnetically driven radiative shocks and their measurements
International Nuclear Information System (INIS)
Kondo, K.; Watanabe, M.; Nakajima, M.; Kawamura, T.; Horioka, K.
2005-01-01
Experimental results on a generation of strong shocks in a compact pulse power device are reported. The characteristics of strong shocks are different from hydrodynamical shocks' because they depend on not only collisions but radiation processes. Radiative shocks are relevant to high energy density phenomena such as the explosions of supernovae. When initial pressure is lower than about 50 mtorr, an interesting structure is confirmed at the shock front, which might indicate a phenomenon proceeded by the radiative process. (author)
2. Report of 22nd International Symposium on Shock Waves; Dai 22 kai kokusai shogekiha symposium shusseki hokoku
Energy Technology Data Exchange (ETDEWEB)
Takayama, K. [Tohoku Univ., Sendai (Japan). Inst. of Fluid Science
1999-11-05
Outlined herein are the topics at the 22nd. International Symposium on Shock Waves, held in July 1999 in London. Prof. Takayama of Tohoku University gave an invited lecture on application of shock waves to medical area, stressing significance of shock waves on a human body. A total of 81 papers were presented from Japan. Number of Japanese papers and number of Japanese attendees both accounted for approximately 25%. The themes of these papers are centered by behavior of shock waves (e.g., propagation, reflection, and diffraction), extreme supersonic flows, interference between shock wave and boundary layer, aerodynamics (e.g., interference between vortex and shock wave), numerical simulation of shock wave phenomena, development of a new shock wave tube and measurement method, researches on elementary steps in chemical reactions, shock wave phenomena in condensed media and multi-phase media, shock wave noise produced while a high-speed train is running in a tunnel, and application of shock waves to industrial and medical areas. Japan contributes much to the application to medical area, and a method dispensing with injection is reported. Japan's aerospace-related researches include interference between shock wave and boundary layer, in which the real gas effect is taken into consideration, designs for protection from heat during the re-entry into the atmosphere, and construction of the world largest free-piston type wind tunnel. (NEDO)
3. Importance of CME Radial Expansion on the Ability of Slow CMEs to Drive Shocks
Energy Technology Data Exchange (ETDEWEB)
Lugaz, Noé; Farrugia, Charles J.; Winslow, Reka M. [Space Science Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH (United States); Small, Colin R.; Manion, Thomas [Department of Physics, University of New Hampshire, Durham, NH (United States); Savani, Neel P. [NASA/GSFC and University of Maryland Baltimore County, Greenbelt, MD (United States)
2017-10-20
Coronal mass ejections (CMEs) may disturb the solar wind by overtaking it or expanding into it, or both. CMEs whose front moves faster in the solar wind frame than the fast magnetosonic speed drive shocks. Such shocks are important contributors to space weather, by triggering substorms, compressing the magnetosphere, and accelerating particles. In general, near 1 au, CMEs with speed greater than about 500 km s{sup −1} drive shocks, whereas slower CMEs do not. However, CMEs as slow as 350 km s{sup −1} may sometimes, although rarely, drive shocks. Here we study these slow CMEs with shocks and investigate the importance of CME expansion in contributing to their ability to drive shocks and in enhancing shock strength. Our focus is on CMEs with average speeds under 375 km s{sup −1}. From Wind measurements from 1996 to 2016, we find 22 cases of such shock-driving slow CMEs, and for about half of them (11 out of the 22), the existence of the shock appears to be strongly related to CME expansion. We also investigate the proportion of all CMEs with speeds under 500 km s{sup −1} with and without shocks in solar cycles 23 and 24, depending on their speed. We find no systematic difference, as might have been expected on the basis of the lower solar wind and Alfvén speeds reported for solar cycle 24 versus 23. The slower expansion speed of CMEs in solar cycle 24 might be an explanation for this lack of increased frequency of shocks, but further studies are required.
4. Slow shock characteristics as a function of distance from the X-line in the magnetotail
International Nuclear Information System (INIS)
Lee, L.C.; Lin, Y.; Shi, Y.; Tsurutani, B.T.
1989-01-01
Both particle and MHD simulations are performed to study the characteristics of slow shocks in the magnetotail. The particle simulations indicate that switch-off shocks exhibit large amplitude rotational wave trains, while magnetotail slow shocks with an intermediate Mach number M An c congruent 0.98 do not display such rotational wave trains. The MHD simulations show that the spontaneous reconnection process in the near-earth plasma sheet leads to the formation of a pair of slow shocks tailward of the reconnection line (X-line). The properties of slow shocks are found to vary as a function of the distance from X-line due to the fomation of plasmoid. Slow shocks in most regions of the magnetotail are found to be non-switch-off shocks with M An <0.98. The present results are used to discuss the lack of large amplitude rotational wave trains at slow shocks in the deep magnetotail. copyright American Geophysical Union 1989
5. A Phenomenological Study on Lack of Motivation
Science.gov (United States)
Educational Research and Reviews, 2013
2013-01-01
The aim of this research is to point out the underlying reasons about the lack of motivation at academic activities concerning Attribution Theory. Attribution Theory trys to understand how the people answer "why" question and how they do casual explanations. This research is a qualitative based research. It used the phenomenological…
6. Time-place learning and memory persist in mice lacking functional Per1 and Per2 clock genes.
Science.gov (United States)
Mulder, C; Van Der Zee, E A; Hut, R A; Gerkema, M P
2013-12-01
With time-place learning, animals link a stimulus with the location and the time of day. This ability may optimize resource localization and predator avoidance in daily changing environments. Time-place learning is a suitable task to study the interaction of the circadian system and memory. Previously, we showed that time-place learning in mice depends on the circadian system and Cry1 and/or Cry2 clock genes. We questioned whether time-place learning is Cry specific or also depends on other core molecular clock genes. Here, we show that Per1/Per2 double mutant mice, despite their arrhythmic phenotype, acquire time-place learning similar to wild-type mice. As well as an established role in circadian rhythms, Per genes have also been implicated in the formation and storage of memory. We found no deficiencies in short-term spatial working memory in Per mutant mice compared to wild-type mice. Moreover, both Per mutant and wild-type mice showed similar long-term memory for contextual features of a paradigm (a mild foot shock), measured in trained mice after a 2-month nontesting interval. In contrast, time-place associations were lost in both wild-type and mutant mice after these 2 months, suggesting a lack of maintained long-term memory storage for this type of information. Taken together, Cry-dependent time-place learning does not require Per genes, and Per mutant mice showed no PER-specific short-term or long-term memory deficiencies. These results limit the functional role of Per clock genes in the circadian regulation of time-place learning and memory.
7. Corticosteroids in the treatment of dengue shock syndrome
Directory of Open Access Journals (Sweden)
Rajapakse S
2014-05-01
Full Text Available Senaka Rajapakse,1 Chaturaka Rodrigo,1 Sachith Maduranga,1 Anoja Chamarie Rajapakse21Department of Clinical Medicine, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka; 2Kings Mill Hospital, Sherwood Forest NHS Foundation Trust, Sutton-in-Ashfield, Nottinghamshire, UKAbstract: Dengue infection causes significant morbidity and mortality in over 100 countries worldwide, and its incidence is on the rise. The pathophysiological basis for the development of severe dengue, characterized by plasma leakage and the “shock syndrome” are poorly understood. No specific treatment or vaccine is available, and careful monitoring and judicious administration of fluids forms the mainstay of management at present. It is postulated that vascular endothelial dysfunction, induced by cytokine and chemical mediators, is an important mechanism of plasma leakage. Although corticosteroids are potent modulators of the immune system, their role in pharmacological doses in modulating the purported immunological effects that take place in severe dengue has been a subject of controversy. The key evidence related to the role of corticosteroids for various manifestations of dengue are reviewed here. In summary, there is currently no high-quality evidence supporting the beneficial effects of corticosteroids for treatment of shock, prevention of serious complications, or increasing platelet counts. Non-randomized trials of corticosteroids given as rescue medication for severe shock have shown possible benefit. Nonetheless, the evidence base is small, and good-quality trials are lacking. We reiterate the need for well-designed and adequately powered randomized controlled trials of corticosteroids for the treatment of dengue shock.Keywords: dengue, dengue shock, shock, corticosteroids, vascular leak, thrombocytopenia
8. Shock wave structure in an ideal dissociating gas
Science.gov (United States)
Liu, K. H.
1975-01-01
Composition changes within the shock layer due to chemical reactions are considered. The Lighthill ideal dissociating gas model was used in an effort to describe the oxygen type molecule. First, the two limiting cases, when the chemical reaction rates are very slow and very fast in comparison to local convective rates, are investigated. Then, the problem is solved for arbitrary chemical reaction rates.
9. Early Identification of Circulatory Shock in Critical Care Transport
Science.gov (United States)
2008-09-30
disclosure and community consultation. Early Identification of Circulatory Shock in Critical Care Transport 2 Community consultation for this...in two aircraft types (Eurocopter EC 135 and EC 145), in IFR weather conditions, and during both day and night operations. We calculated the
Science.gov (United States)
Lyutikov, Maxim
2018-06-01
We consider the structure of mildly relativistic shocks in dense media, taking into account the radiation and pair loading, and diffusive radiation energy transfer within the flow. For increasing shock velocity (increasing post-shock temperature), the first important effect is the efficient energy redistribution by radiation within the shock that leads to the appearance of an isothermal jump, whereby the flow reaches the final state through a discontinuous isothermal transition. The isothermal jump, on scales much smaller than the photon diffusion length, consists of a weak shock and a quick relaxation to the isothermal conditions. Highly radiation-dominated shocks do not form isothermal jump. Pair production can mildly increase the overall shock compression ratio to ≈10 (4 for matter-dominated shocks and 7 of the radiation-dominated shocks).
11. Prediction of massive bleeding. Shock index and modified shock index.
Science.gov (United States)
Terceros-Almanza, L J; García-Fuentes, C; Bermejo-Aznárez, S; Prieto-Del Portillo, I J; Mudarra-Reche, C; Sáez-de la Fuente, I; Chico-Fernández, M
2017-12-01
To determine the predictive value of the Shock Index and Modified Shock Index in patients with massive bleeding due to severe trauma. Retrospective cohort. Severe trauma patient's initial attention at the intensive care unit of a tertiary hospital. Patients older than 14 years that were admitted to the hospital with severe trauma (Injury Severity Score >15) form January 2014 to December 2015. We studied the sensitivity (Se), specificity (Sp), positive and negative predictive value (PV+ and PV-), positive and negative likelihood ratio (LR+ and LR-), ROC curves (Receiver Operating Characteristics) and the area under the same (AUROC) for prediction of massive hemorrhage. 287 patients were included, 76.31% (219) were male, mean age was 43,36 (±17.71) years and ISS was 26 (interquartile range [IQR]: 21-34). The overall frequency of massive bleeding was 8.71% (25). For Shock Index: AUROC was 0.89 (95% confidence intervals [CI] 0.84 to 0.94), with an optimal cutoff at 1.11, Se was 91.3% (95% CI: 73.2 to 97.58) and Sp was 79.69% (95% CI: 74.34 to 84.16). For the Modified Shock Index: AUROC was 0.90 (95% CI: 0.86 to 0.95), with an optimal cutoff at 1.46, Se was 95.65% (95% CI: 79.01 to 99.23) and Sp was 75.78% (95% CI: 70.18 to 80.62). Shock Index and Modified Shock Index are good predictors of massive bleeding and could be easily incorporated to the initial workup of patients with severe trauma. Copyright © 2017 Elsevier España, S.L.U. y SEMICYUC. All rights reserved.
12. Optimum Shock Isolation
National Research Council Canada - National Science Library
Bolotnik, Nikolai
2001-01-01
.... Several types of performance criteria for isolation are considered, the most important of which are the peak force transmitted to the body to be isolated and the maximum displacement of the body relative to the base...
13. Shock diffraction in alumina powder
International Nuclear Information System (INIS)
Venz, G.; Killen, P.D.; Page, N.W.
1996-01-01
In order to produce complex shaped components by dynamic compaction of ceramic powders detailed knowledge of their response under shock loading conditions is required. This work attempts to provide data on release effects and shock attenuation in 1 μm and 5 μm α-alumina powders which were compacted to between 85 % and 95 % of the solid phase density by the impact of high velocity steel projectiles. As in previous work, the powder was loaded into large cylindrical dies with horizontal marker layers of a contrasting coloured powder to provide a record of powder displacement in the recovered specimens. After recovery and infiltration with a thermosetting resin the specimens were sectioned and polished to reveal the structure formed by the passage of the projectile and shock wave. Results indicate that the shock pressures generated were of the order of 0.5 to 1.4 GPa and higher, with shock velocities and sound speeds in the ranges 650 to 800 m/s and 350 to 400 m/s respectively
14. Transient shocks beyond the heliopause
International Nuclear Information System (INIS)
Fermo, R L; Pogorelov, N V; Burlaga, L F
2015-01-01
The heliopause is a rich, dynamic surface affected by the time-dependent solar wind. Stream interactions due to coronal mass ejections (CMEs), corotating interaction regions (CIRs), and other transient phenomena are known to merge producing global merged interaction regions (GMIRs). Numerical simulations of the solar wind interaction with the local interstellar medium (LISM) show that GMIRs, as well other time-dependent structures in the solar wind, may produce compression/rarefaction waves and shocks in the LISM behind the heliopause. These shocks may initiate wave activity observed by the Voyager spacecraft. The magnetometer onboard Voyager 1 indeed observed a few structures that may be interpreted as shocks. We present numerical simulations of such shocks in the year of 2000, when both Voyager spacecraft were in the supersonic solar wind region, and in 2012, when Voyager 1 observed traveling shocks. In the former case, Voyager observations themselves provide time- dependent boundary conditions in the solar wind. In the latter case, we use OMNI data at 1 AU to analyze the plasma and magnetic field behavior after Voyager 1 crossed the heliospheric boundary. Numerical results are compared with spacecraft observations. (paper)
15. Dispersive shock waves in nonlinear and atomic optics
Directory of Open Access Journals (Sweden)
Kamchatnov Anatoly
2017-01-01
Full Text Available A brief review is given of dispersive shock waves observed in nonlinear optics and dynamics of Bose-Einstein condensates. The theory of dispersive shock waves is developed on the basis of Whitham modulation theory for various situations taking place in these two fields. In particular, the full classification is established for types of wave structures evolving from initial discontinuities for propagation of long light pulses in fibers with account of steepening effect and for dynamics of the polarization mode in two-component Bose-Einstein condensates.
16. A primary standard for low-g shock calibration by laser interferometry
Science.gov (United States)
Sun, Qiao; Wang, Jian-lin; Hu, Hong-bo
2014-07-01
This paper presents a novel implementation of a primary standard for low-g shock acceleration calibration by laser interferometry based on rigid body collision at National Institute of Metrology, China. The mechanical structure of the standard device and working principles involved in the shock acceleration exciter, laser interferometers and virtual instruments are described. The novel combination of an electromagnetic exciter and a pneumatic exciter as the mechanical power supply of the standard device can deliver a wide range of shock acceleration levels. In addition to polyurethane rubber, two other types of material are investigated to ensure a wide selection of cushioning pads for shock pulse generation, with pulse shapes and data displayed. A heterodyne He-Ne laser interferometer is preferred for its precise and reliable measurement of shock acceleration while a homodyne one serves as a check standard. Some calibration results of a standard acceleration measuring chain are shown in company with the uncertainty evaluation budget. The expanded calibration uncertainty of shock sensitivity of the acceleration measuring chain is 0.8%, k = 2, with the peak acceleration range from 20 to 10 000 m s-2 and pulse duration from 0.5 to 10 ms. This primary shock standard can meet the traceability requirements of shock acceleration from various applications of industries from automobile to civil engineering and therefore is used for piloting the ongoing shock comparison of Technical Committee of Acoustics, Ultrasound and Vibration (TCAUV) of Asia Pacific Metrology Program (APMP), coded as APMP.AUV.V-P1.
17. Energetic ion acceleration at collisionless shocks
Science.gov (United States)
Decker, R. B.; Vlahos, L.
1985-01-01
An example is presented from a test particle simulation designed to study ion acceleration at oblique turbulent shocks. For conditions appropriate at interplanetary shocks near 1 AU, it is found that a shock with theta sub B n = 60 deg is capable of producing an energy spectrum extending from 10 keV to approx. 1 MeV in approx 1 hour. In this case total energy gains result primarily from several separate episodes of shock drift acceleration, each of which occurs when particles are scattered back to the shock by magnetic fluctuations in the shock vicinity.
18. Energetic ion acceleration at collisionless shocks
International Nuclear Information System (INIS)
Decker, R.B.; Vlahos, L.
1985-01-01
An example is presented from a test particle simulation designed to study ion acceleration at oblique turbulent shocks. For conditions appropriate at interplanetary shocks near 1 AU, it is found that a shock with theta sub B n = 60 deg is capable of producing an energy spectrum extending from 10 keV to approx 1 MeV in approx 1 hour. In this case total energy gains result primarily from several separate episodes of shock drift acceleration, each of which occurs when particles are scattered back to the shock by magnetic fluctuations in the shock vicinity
19. Why the Nature of Oil Shocks Matters
International Nuclear Information System (INIS)
Archanskaia, Elizaveta; Hubert, Paul; Creel, Jerome
2009-03-01
This article studies the impact of oil shocks on the macro-economy in two ways insofar unexploited in the literature. The analysis is conducted at the global level, and it explicitly accounts for the potentially changing nature of oil shocks. Based on an original world GDP series and a grouping of oil shocks according to their nature, we find that oil supply shocks negatively impact world growth, contrary to oil demand shocks, pro-cyclical in their nature. This result is robust at the national level for the US. Furthermore, endogenous monetary policy is shown to have no counter-cyclical effects in the context of an oil demand shock. (authors)
20. Shock waves in weakly compressed granular media.
Science.gov (United States)
van den Wildenberg, Siet; van Loo, Rogier; van Hecke, Martin
2013-11-22
We experimentally probe nonlinear wave propagation in weakly compressed granular media and observe a crossover from quasilinear sound waves at low impact to shock waves at high impact. We show that this crossover impact grows with the confining pressure P0, whereas the shock wave speed is independent of P0-two hallmarks of granular shocks predicted recently. The shocks exhibit surprising power law attenuation, which we model with a logarithmic law implying that shock dissipation is weak and qualitatively different from other granular dissipation mechanisms. We show that elastic and potential energy balance in the leading part of the shocks.
1. Conceptualising the lack of health insurance coverage.
Science.gov (United States)
Davis, J B
2000-01-01
This paper examines the lack of health insurance coverage in the US as a public policy issue. It first compares the problem of health insurance coverage to the problem of unemployment to show that in terms of the numbers of individuals affected lack of health insurance is a problem comparable in importance to the problem of unemployment. Secondly, the paper discusses the methodology involved in measuring health insurance coverage, and argues that the current method of estimation of the uninsured underestimates the extent that individuals go without health insurance. Third, the paper briefly introduces Amartya Sen's functioning and capabilities framework to suggest a way of representing the extent to which individuals are uninsured. Fourth, the paper sketches a means of operationalizing the Sen representation of the uninsured in terms of the disability-adjusted life year (DALY) measure.
2. Acidic pH shock induces the expressions of a wide range of stress-response genes
Directory of Open Access Journals (Sweden)
Hong Soon-Kwang
2008-12-01
Full Text Available Abstract Background Environmental signals usually enhance secondary metabolite production in Streptomycetes by initiating complex signal transduction system. It is known that different sigma factors respond to different types of stresses, respectively in Streptomyces strains, which have a number of unique signal transduction mechanisms depending on the types of environmental shock. In this study, we wanted to know how a pH shock would affect the expression of various sigma factors and shock-related proteins in S. coelicolor A3(2. Results According to the results of transcriptional and proteomic analyses, the major number of sigma factor genes were upregulated by an acidic pH shock. Well-studied sigma factor genes of sigH (heat shock, sigR (oxidative stress, sigB (osmotic shock, and hrdD that play a major role in the secondary metabolism, were all strongly upregulated by the pH shock. A number of heat shock proteins including the DnaK family and chaperones such as GroEL2 were also observed to be upregulated by the pH shock, while their repressor of hspR was strongly downregulated. Oxidative stress-related proteins such as thioredoxin, catalase, superoxide dismutase, peroxidase, and osmotic shock-related protein such as vesicle synthases were also upregulated in overall. Conclusion From these observations, an acidic pH shock was considered to be one of the strongest stresses to influence a wide range of sigma factors and shock-related proteins including general stress response proteins. The upregulation of the sigma factors and shock proteins already found to be related to actinorhodin biosynthesis was considered to have contributed to enhanced actinorhodin productivity by mediating the pH shock signal to regulators or biosynthesis genes for actinorhodin production.
3. Shock, diaschisis and von Monakow
Directory of Open Access Journals (Sweden)
Eliasz Engelhardt
2013-07-01
Full Text Available The concept of shock apparently emerged in the middle of the 18th century (Whyett as an occurrence observed experimentally after spinal cord transection, and identified as "shock" phenomenon one century later (Hall. The concept was extended (Brown-Séquard and it was suggested that brain lesions caused functional rupture in regions distant from the injured one ("action à distance". The term "diaschisis" (von Monakow, proposed as a new modality of shock, had its concept broadened, underpinned by observations of patients, aiming at distinguishing between symptoms of focal brain lesions and transitory effects they produced, attributable to depression of distant parts of the brain connected to the injured area. Presently, diaschisis is related mainly to cerebrovascular lesions and classified according to the connection fibers involved, as proposed by von Monakow. Depression of metabolism and blood flow in regions anatomically separated, but related by connections with the lesion, allows observing diaschisis with neuroimaging.
4. Shock compression of geological materials
International Nuclear Information System (INIS)
Kirk, S; Braithwaite, C; Williamson, D; Jardine, A
2014-01-01
Understanding the shock compression of geological materials is important for many applications, and is particularly important to the mining industry. During blast mining the response to shock loading determines the wave propagation speed and resulting fragmentation of the rock. The present work has studied the Hugoniot of two geological materials; Lake Quarry Granite and Gosford Sandstone. For samples of these materials, the composition was characterised in detail. The Hugoniot of Lake Quarry Granite was predicted from this information as the material is fully dense and was found to be in good agreement with the measured Hugoniot. Gosford Sandstone is porous and undergoes compaction during shock loading. Such behaviour is similar to other granular material and we show how it can be described using a P-a compaction model.
5. Shock compression of simulated adobe
Science.gov (United States)
Braithwaite, C. H.; Church, P. D.; Gould, P. J.; Stewart, B.; Jardine, A. P.
2017-01-01
A series of plate impact experiments were conducted to investigate the shock response of a simulant for adobe, a traditional form of building material widely used around the world. Air dried bricks were sourced from the London brick company, dry machined and impacted at a range of velocities in a single stage gas gun. The shock Hugoniot was determined (Us =2.26up+0.37) as well as release information. The material was found to behave in a manner which was similar to that of loose sand and considerably less stiff than a weak porous sandstone. The effect of any cementing of the grains was examined by shocking powdered samples contained within a cell arrangement.
6. Shock compression of a recrystallized anorthositic rock from Apollo 15
Science.gov (United States)
Ahrens, T. J.; Gibbons, R. V.; O'Keefe, J. D.
1973-01-01
Hugoniot measurements on 15,418, a recrystallized and brecciated gabbroic anorthosite, yield a value of the Hugoniot elastic limit (HEL) varying from 45 to 70 kbar as the final shock pressure is varied from 70 to 280 kbar. Above the HEL and to 150 kbar, the pressure-density Hugoniot is closely described by a hydrostatic equation of state constructed from ultrasonic data for single-crystal plagioclase and pyroxene. Above 150 kbar, the Hugoniot states indicate that a series of one or more shock-induced phase changes are occurring in the plagioclase and pyroxene. From Hugoniot data for both the single-crystal minerals and the Frederick diabase, we infer that the shock-induced high-pressure phases in 15,418 probably consists of a 3.71 g/cu cm density, high-pressure structure for plagioclase and a 4.70 g/cu cm perovskite-type structure for pyroxene.
7. Electrostatic shock structures in dissipative multi-ion dusty plasmas
Science.gov (United States)
Elkamash, I. S.; Kourakis, I.
2018-06-01
A comprehensive analytical model is introduced for shock excitations in dusty bi-ion plasma mixtures, taking into account collisionality and kinematic (fluid) viscosity. A multicomponent plasma configuration is considered, consisting of positive ions, negative ions, electrons, and a massive charged component in the background (dust). The ionic dynamical scale is focused upon; thus, electrons are assumed to be thermalized, while the dust is stationary. A dissipative hybrid Korteweg-de Vries/Burgers equation is derived. An analytical solution is obtained, in the form of a shock structure (a step-shaped function for the electrostatic potential, or an electric field pulse) whose maximum amplitude in the far downstream region decays in time. The effect of relevant plasma configuration parameters, in addition to dissipation, is investigated. Our work extends earlier studies of ion-acoustic type shock waves in pure (two-component) bi-ion plasma mixtures.
8. Interaction of Energetic Particles with Discontinuities Upstream of Strong Shocks
Science.gov (United States)
Malkov, Mikhail; Diamond, Patrick
2008-11-01
Acceleration of particles in strong astrophysical shocks is known to be accompanied and promoted by a number of instabilities which are driven by the particles themselves. One of them is an acoustic (also known as Drury's) instability driven by the pressure gradient of accelerated particles upstream. The generated sound waves naturally steepen into shocks thus forming a shocktrain. Similar magnetoacoustic or Alfven type structures may be driven by pick-up ions, for example. We consider the solutions of kinetic equation for accelerated particles within the shocktrain. The accelerated particles are assumed to be coupled to the flow by an intensive pitch-angle scattering on the self-generated Alfven waves. The implications for acceleration and confinement of cosmic rays in this shock environment will be discussed.
9. Corticosteroids in the treatment of dengue shock syndrome.
Science.gov (United States)
Rajapakse, Senaka; Rodrigo, Chaturaka; Maduranga, Sachith; Rajapakse, Anoja Chamarie
2014-01-01
Dengue infection causes significant morbidity and mortality in over 100 countries worldwide, and its incidence is on the rise. The pathophysiological basis for the development of severe dengue, characterized by plasma leakage and the "shock syndrome" are poorly understood. No specific treatment or vaccine is available, and careful monitoring and judicious administration of fluids forms the mainstay of management at present. It is postulated that vascular endothelial dysfunction, induced by cytokine and chemical mediators, is an important mechanism of plasma leakage. Although corticosteroids are potent modulators of the immune system, their role in pharmacological doses in modulating the purported immunological effects that take place in severe dengue has been a subject of controversy. The key evidence related to the role of corticosteroids for various manifestations of dengue are reviewed here. In summary, there is currently no high-quality evidence supporting the beneficial effects of corticosteroids for treatment of shock, prevention of serious complications, or increasing platelet counts. Non-randomized trials of corticosteroids given as rescue medication for severe shock have shown possible benefit. Nonetheless, the evidence base is small, and good-quality trials are lacking. We reiterate the need for well-designed and adequately powered randomized controlled trials of corticosteroids for the treatment of dengue shock.
10. Relativistic electron dropout echoes induced by interplanetary shocks
Science.gov (United States)
Schiller, Q.; Kanekal, S. G.; Boyd, A. J.; Baker, D. N.; Blake, J. B.; Spence, H. E.
2017-12-01
Interplanetary shocks that impact Earth's magnetosphere can produce immediate and dramatic responses in the trapped relativistic electron population. One well-studied response is a prompt injection capable of transporting relativistic electrons deep into the magnetosphere and accelerating them to multi-MeV energies. The converse effect, electron dropout echoes, are observations of a sudden dropout of electron fluxes observed after the interplanetary shock arrival. Like the injection echo signatures, dropout echoes can also show clear energy dispersion signals. They are of particular interest because they have only recently been observed and their causal mechanism is not well understood. In the analysis presented here, we show observations of electron drift echo signatures from the Relativistic Electron-Proton Telescope (REPT) and Magnetic Electron and Ion Sensors (MagEIS) onboard NASA's Van Allen Probes mission, which show simultaneous prompt enhancements and dropouts within minutes of the associated with shock impact. We show that the observations associated with both enhancements and dropouts are explained by the inward motion caused by the electric field impulse induced by the interplanetary shock, and either energization to cause the enhancement, or lack of a seed population to cause the dropout.
11. Electric foot shock stress adaptation: Does it exist or not?
Science.gov (United States)
Bali, Anjana; Jaggi, Amteshwar Singh
2015-06-01
12. Shock Initiation of Damaged Explosives
Energy Technology Data Exchange (ETDEWEB)
Chidester, S K; Vandersall, K S; Tarver, C M
2009-10-22
Explosive and propellant charges are subjected to various mechanical and thermal insults that can increase their sensitivity over the course of their lifetimes. To quantify this effect, shock initiation experiments were performed on mechanically and thermally damaged LX-04 (85% HMX, 15% Viton by weight) and PBX 9502 (95% TATB, 5% Kel-F by weight) to obtain in-situ manganin pressure gauge data and run distances to detonation at various shock pressures. We report the behavior of the HMX-based explosive LX-04 that was damaged mechanically by applying a compressive load of 600 psi for 20,000 cycles, thus creating many small narrow cracks, or by cutting wedge shaped parts that were then loosely reassembled, thus creating a few large cracks. The thermally damaged LX-04 charges were heated to 190 C for long enough for the beta to delta solid - solid phase transition to occur, and then cooled to ambient temperature. Mechanically damaged LX-04 exhibited only slightly increased shock sensitivity, while thermally damaged LX-04 was much more shock sensitive. Similarly, the insensitive explosive PBX 9502 was mechanically damaged using the same two techniques. Since PBX 9502 does not undergo a solid - solid phase transition but does undergo irreversible or 'rachet' growth when thermally cycled, thermal damage to PBX 9502 was induced by this procedure. As for LX-04, the thermally damaged PBX 9502 demonstrated a greater shock sensitivity than mechanically damaged PBX 9502. The Ignition and Growth reactive flow model calculated the increased sensitivities by igniting more damaged LX-04 and PBX 9502 near the shock front based on the measured densities (porosities) of the damaged charges.
13. Control coordination abilities in shock combat sports
Directory of Open Access Journals (Sweden)
Natalya Boychenko
2014-12-01
Full Text Available Purpose: optimize the process control level of coordination abilities in martial arts. Material and Methods: analysis and compilation of scientific and methodological literature, interviews with coaches of drum martial arts, video analysis techniques, teacher observations. Results: identified specific types of coordination abilities in shock combat sports. Pod branny and offered specific and nonspecific tests to monitor the level of species athletes coordination abilities. Conclusion: it is determined that in order to achieve victory in the fight martial artists to navigate the space to be able to assess and manage dynamic and spatio-temporal parameters of movements, maintain balance, have a high coordination of movements. The proposed tests to monitor species coordination abilities athletes allow an objective assessment of not only the overall level of coordination, and the level of specific types of manifestations of this ability.
14. Shock compaction of molybdenum powder
Science.gov (United States)
Ahrens, T. J.; Kostka, D.; Vreeland, T., Jr.; Schwarz, R. B.; Kasiraj, P.
1983-01-01
Shock recovery experiments which were carried out in the 9 to 12 GPa range on 1.4 distension Mo and appear adequate to compact to full density ( 45 (SIGMA)m) powders were examined. The stress levels, however, are below those calculated to be from 100 to approx. 22 GPa which a frictional heating model predicts are required to consolidate approx. 10 to 50 (SIGMA)m particles. The model predicts that powders that have a distension of m=1.6 shock pressures of 14 to 72 GPa are required to consolidate Mo powders in the 50 to 10 (SIGMA)m range.
15. Cation disorder in shocked orthopyroxene.
Science.gov (United States)
Dundon, R. W.; Hafner, S. S.
1971-01-01
The study of cation distributions over nonequivalent lattice sites in minerals may reveal information on the history of temperature and pressure in rocks. Chemically homogeneous orthopyroxene specimens were shocked under well-controlled conditions in the laboratory in order to provide a basis for the interpretation of more complex natural materials. As a result of the investigation it is concluded that the distribution of magnesium and iron over the M1 and M2 positions in Bamle enstatite shocked at 1 megabar is highly disordered. It corresponds to an equilibrium distribution of at least 1000 C.
16. Shock/shock interactions between bodies and wings
Directory of Open Access Journals (Sweden)
Gaoxiang XIANG
2018-02-01
Full Text Available This paper examines the Shock/Shock Interactions (SSI between the body and wing of aircraft in supersonic flows. The body is simplified to a flat wedge and the wing is assumed to be a sharp wing. The theoretical spatial dimension reduction method, which transforms the 3D problem into a 2D one, is used to analyze the SSI between the body and wing. The temperature and pressure behind the Mach stem induced by the wing and body are obtained, and the wave configurations in the corner are determined. Numerical validations are conducted by solving the inviscid Euler equations in 3D with a Non-oscillatory and Non-free-parameters Dissipative (NND finite difference scheme. Good agreements between the theoretical and numerical results are obtained. Additionally, the effects of the wedge angle and sweep angle on wave configurations and flow field are considered numerically and theoretically. The influences of wedge angle are significant, whereas the effects of sweep angle on wave configurations are negligible. This paper provides useful information for the design and thermal protection of aircraft in supersonic and hypersonic flows. Keywords: Body and wing, Flow field, Hypersonic flow, Shock/shock interaction, Wave configurations
17. Transcriptome modulation by hydrocortisone in severe burn shock: ancillary analysis of a prospective randomized trial.
Science.gov (United States)
Plassais, Jonathan; Venet, Fabienne; Cazalis, Marie-Angélique; Le Quang, Diane; Pachot, Alexandre; Monneret, Guillaume; Tissot, Sylvie; Textoris, Julien
2017-06-16
Despite shortening vasopressor use in shock, hydrocortisone administration remains controversial, with potential harm to the immune system. Few studies have assessed the impact of hydrocortisone on the transcriptional response in shock, and we are lacking data on burn shock. Our objective was to assess the hydrocortisone-induced transcriptional modulation in severe burn shock, particularly modulation of the immune response. We collected whole blood samples during a randomized controlled trial assessing the efficacy of hydrocortisone administration in burn shock. Using whole genome microarrays, we first compared burn patients (n = 32) from the placebo group to healthy volunteers to describe the transcriptional modulation induced by burn shock over the first week. Then we compared burn patients randomized for either hydrocortisone administration or placebo, to assess hydrocortisone-induced modulation. Study groups were similar in terms of severity and major outcomes, but shock duration was significantly reduced in the hydrocortisone group. Many genes (n = 1687) were differentially expressed between burn patients and healthy volunteers, with 85% of them exhibiting a profound and persistent modulation over seven days. Interestingly, we showed that hydrocortisone enhanced the shock-associated repression of adaptive, but also innate immunity. We found that the initial host response to burn shock encompasses wide and persistent modulation of gene expression, with profound modulation of pathways associated with metabolism and immunity. Importantly, hydrocortisone administration may worsen the immunosuppression associated with severe injury. These data should be taken into account in the risk ratio of hydrocortisone administration in patients with inflammatory shock. ClinicalTrials.gov, NCT00149123 . Registered on 6 September 2005.
18. The ways for increasing the technical capabilities of antiseismic hydraulic shock absorbers
International Nuclear Information System (INIS)
Kaznovskij, S.P.; Lenskij, V.S.; Plyaskov, A.S.
1986-01-01
Basic achievements in a sphere of production of a new type of atomic power equipment-hydraulic shock absorbers-intended for NPP antiseismic fixation of pipelines are considered in short. In designing the new shock absorbers emphasis is placed on maximum unification of the most labor-consuming units, introduction of promising technological processes for mechanical treatment, optimization of the type and dimensional series, impovement of operational characteristics and simplification of assemblying and preparation for putting into operation
19. "Driverless" Shocks in the Interplanetary Medium
Science.gov (United States)
Gopalswamy, N.; Kaiser, M. L.; Lara, A.
1999-01-01
Many interplanetary shocks have been detected without an obvious driver behind them. These shocks have been thought to be either blast waves from solar flares or shocks due to sudden increase in solar wind speed caused by interactions between large scale open and closed field lines of the Sun. We investigated this problem using a set of interplanetary shock detected {\\it in situ} by the Wind space craft and tracing their solar origins using low frequency radio data obtained by the Wind/WAVES experiment. For each of these "driverless shocks" we could find a unique coronal mass ejections (CME) event observed by the SOHO (Solar and Heliospheric Observatory) coronagraphs. We also found that these CMEs were ejected at large angles from the Sun-Earth line. It appears that the "driverless shocks" are actually driver shocks, but the drivers were not intercepted by the spacecraft. We conclude that the interplanetary shocks are much more extended than the driving CMEs.
20. Shock and Vibration. Volume 1, Issue 1
National Research Council Canada - National Science Library
Pilkey, Walter D
1994-01-01
..., and earthquake engineering. Among the specific areas to be covered are vibration testing and control, vibration condition monitoring and diagnostics, shock hardenings, modal technology, shock testing, data acquisition, fluid...
1. Initial ISEE magnetometer results: shock observation
International Nuclear Information System (INIS)
Russell, C.T.
1979-01-01
ISEE-1 and -2 magnetic field profiles across 6 terrestrial bow shock and one interplanetary shock are examined. The inteplanetary shock illustrates the behavior of a low Mach number shock. Three examples of low or moderate β, high Mach number, quasi-perpendicular shocks are examined. These did not have upstream waves, but rather had waves growing in the field gradient. Two examples of high β shocks showed little coherence in field variation even though the two vehicles were only a few hundred kilometers apart. The authors present the joint behavior of wave, particle and field data across some of these shocks to show some of the myriad of shock features whose behavior they are now beginning to investigate. (Auth.)
2. 29th International Symposium on Shock Waves
CERN Document Server
Ranjan, Devesh
2015-01-01
This proceedings present the results of the 29th International Symposium on Shock Waves (ISSW29) which was held in Madison, Wisconsin, U.S.A., from July 14 to July 19, 2013. It was organized by the Wisconsin Shock Tube Laboratory, which is part of the College of Engineering of the University of Wisconsin-Madison. The ISSW29 focused on the following areas: Blast Waves, Chemically Reactive Flows, Detonation and Combustion, Facilities, Flow Visualization, Hypersonic Flow, Ignition, Impact and Compaction, Industrial Applications, Magnetohydrodynamics, Medical and Biological Applications, Nozzle Flow, Numerical Methods, Plasmas, Propulsion, Richtmyer-Meshkov Instability, Shock-Boundary Layer Interaction, Shock Propagation and Reflection, Shock Vortex Interaction, Shock Waves in Condensed Matter, Shock Waves in Multiphase Flow, as well as Shock Waves in Rarefield Flow. The two Volumes contain the papers presented at the symposium and serve as a reference for the participants of the ISSW 29 and individuals interes...
3. Shock dynamics in layered periodic media
KAUST Repository
Ketcheson, David I.
2012-01-01
Solutions of constant-coeffcient nonlinear hyperbolic PDEs generically develop shocks, even if the initial data is smooth. Solutions of hyperbolic PDEs with variable coeffcients can behave very differently. We investigate formation and stability of shock waves in a one-dimensional periodic layered medium by a computational study of time-reversibility and entropy evolution. We find that periodic layered media tend to inhibit shock formation. For small initial conditions and large impedance variation, no shock formation is detected even after times much greater than the time of shock formation in a homogeneous medium. Furthermore, weak shocks are observed to be dynamically unstable in the sense that they do not lead to significant long-term entropy decay. We propose a characteristic condition for admissibility of shocks in heterogeneous media that generalizes the classical Lax entropy condition and accurately predicts the formation or absence of shocks in these media.
4. Proteomic analysis reveals differential accumulation of small heat shock proteins and late embryogenesis abundant proteins between ABA-deficient mutant vp5 seeds and wild-type Vp5 seeds in maize
Directory of Open Access Journals (Sweden)
Xiaolin eWu
2015-01-01
Full Text Available ABA is a major plant hormone that plays important roles during many phases of plant life cycle, including seed development, maturity and dormancy, and especially the acquisition of desiccation tolerance. Understanding of the molecular basis of ABA-mediated plant response to stress is of interest not only in basic research on plant adaptation but also in applied research on plant productivity. Maize mutant viviparous-5 (vp5, deficient in ABA biosynthesis in seeds, is a useful material for studying ABA-mediated response in maize. Due to carotenoid deficiency, vp5 endosperm is white, compared to yellow Vp5 endosperm. However, the background difference at proteome level between vp5 and Vp5 seeds is unclear. This study aimed to characterize proteome alterations of maize vp5 seeds and to identify ABA-dependent proteins during seed maturation. We compared the embryo and endosperm proteomes of vp5 and Vp5 seeds by gel-based proteomics. Up to 46 protein spots, most in embryos, were found to be differentially accumulated between vp5 and Vp5. The identified proteins included small heat shock proteins (sHSPs, late embryogenesis abundant (LEA proteins, stress proteins, storage proteins and enzymes among others. However, EMB564, the most abundant LEA protein in maize embryo, accumulated in comparable levels between vp5 and Vp5 embryos, which contrasted to previously characterized, greatly lowered expression of emb564 mRNA in vp5 embryos. Moreover, LEA proteins and sHSPs displayed differential accumulations in vp5 embryos: six out of eight identified LEA proteins decreased while nine sHSPs increased in abundance. Finally, we discussed the possible causes of global proteome alterations, especially the observed differential accumulation of identified LEA proteins and sHSPs in vp5 embryos. The data derived from this study provides new insight into ABA-dependent proteins and ABA-mediated response during maize seed maturation.
5. Why does Colombia lack agricultural commodity futures?
Directory of Open Access Journals (Sweden)
Pablo Moreno-Alemay
2015-11-01
Full Text Available This article explores the reasons why futures contracts are not traded as an alternative to price hedging for agricultural goods in Colombia. Based on surveys, interviews and statistical analysis, this study identified that conceptual gaps in contract negotiation, lack of consensus in the agricultural sector regarding the use of financial mechanisms and the sector’s infrequent contact with Colombia’s financial institutions, are the main reasons why a futures contracts market has not emerged.
6. Entropy jump across an inviscid shock wave
Science.gov (United States)
Salas, Manuel D.; Iollo, Angelo
1995-01-01
The shock jump conditions for the Euler equations in their primitive form are derived by using generalized functions. The shock profiles for specific volume, speed, and pressure are shown to be the same, however density has a different shock profile. Careful study of the equations that govern the entropy shows that the inviscid entropy profile has a local maximum within the shock layer. We demonstrate that because of this phenomenon, the entropy, propagation equation cannot be used as a conservation law.
7. Collisionless Electrostatic Shock Modeling and Simulation
Science.gov (United States)
2016-10-21
equations with piston -like boundary conditions gives a solution for the shock behavior. • Assumes cold upstream ions, therefore neglecting shock...temperature ratio (>10) – Wave Train Wavelength – Shock-Front Mach Number – Reflected Ion Beam Velocity Gathering Experiment Data – Double Plasma Device...experimental shock data. • Inconsistencies in published 1969 double -plasma device data hampered validation. Future Work: Extension to Moderately
8. Electric shock and electrical fire specialty
International Nuclear Information System (INIS)
2011-02-01
This book deals with electric shock and electrical fire, which is made up seven chapters. It describes of special measurement for electric shock and electrical fire. It mentions concretely about electrical fire analysis and precautionary measurement, electrical shock analysis cases, occurrence of static electricity and measurement, gas accident, analysis of equipment accident and precautionary measurement. The book is published to educate the measurement on electric shock and electrical fire by electrical safety technology education center in Korea Electrical Safety Corporation.
9. Prenatal temperature shocks reduce cooperation
NARCIS (Netherlands)
Duchoslav, Jan
2017-01-01
Climate change has not only led to a sustained rise in mean global temperature over the past decades, but also increased the frequency of extreme weather events. This paper explores the effect of temperature shocks in utero on later-life taste for cooperation. Using historical climate data combined
10. Shock Mounting for Heavy Machines
Science.gov (United States)
Thompson, A. R.
1984-01-01
Elastomeric bearings eliminate extraneous forces. Rocket thrust transmitted from motor to load cells via support that absorbs extraneous forces so they do not affect accuracy of thrust measurements. Adapter spoked cone fits over forward end of rocket motor. Shock mounting developed for rocket engines under test used as support for heavy machines, bridges, or towers.
11. 2-Shock layered tuning campaign
Science.gov (United States)
Masse, Laurent; Dittrich, T.; Khan, S.; Kyrala, G.; Ma, T.; MacLaren, S.; Ralph, J.; Salmonson, J.; Tipton, R.; Los Alamos Natl Lab Team; Lawrence Livermore Natl Lab Team
2016-10-01
The 2-Shock platform has been developed to maintain shell sphericity throughout the compression phase of an indirect-drive target implosion and produce a stagnating hot spot in a quasi 1D-like manner. A sub-scale, 1700 _m outer diameter, and thick, 200 _m, uniformly Silicon doped, gas-filled plastic capsule is driven inside a nominal size 5750 _m diameter ignition hohlraum. The hohlraum fill is near vacuum to reduce back-scatter and improve laser/drive coupling. A two-shock pulse of about 1 MJ of laser energy drives the capsule. The thick capsule prevents ablation front feed-through to the imploded core. This platform has demonstrated its efficiency to tune a predictable and reproducible 1-D implosion with a nearly round shape. It has been shown that the high foot performance was dominated by the local defect growth due to the ablation front instability and by the hohlraum radiation asymmetries. The idea here is to take advantage of this 2-Shock platform to design a 1D-like layered implosion and eliminates the deleterious effects of radiation asymmetries and ablation front instability growth. We present the design work and our first experimental results of this near one-dimensional 2-Shock layered design. This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344.
12. Interstellar turbulence and shock waves
International Nuclear Information System (INIS)
Bykov, A.M.
1982-01-01
Random deflections of shock fronts propagated through the turbulent interstellar medium can produce the strong electro-density fluctuations on scales l> or approx. =10 13 cm inferred from pulsar radio scintillations. The development of turbulence in the hot-phase ISM is discussed
13. Nonlinearity, Conservation Law and Shocks
However, genuine nonlinearity is always present in an ideal gas. The conservation form of the equation (25) brings in shocks which cut off the growing part of the amplitUde as shown in. Figure 15. Acknowledgements. The author sincerely thanks the two referees whose valuable comments led to an improvement of the ...
14. Model for Shock Wave Chaos
KAUST Repository
Kasimov, Aslan R.
2013-03-08
We propose the following model equation, ut+1/2(u2−uus)x=f(x,us) that predicts chaotic shock waves, similar to those in detonations in chemically reacting mixtures. The equation is given on the half line, x<0, and the shock is located at x=0 for any t≥0. Here, us(t) is the shock state and the source term f is taken to mimic the chemical energy release in detonations. This equation retains the essential physics needed to reproduce many properties of detonations in gaseous reactive mixtures: steady traveling wave solutions, instability of such solutions, and the onset of chaos. Our model is the first (to our knowledge) to describe chaos in shock waves by a scalar first-order partial differential equation. The chaos arises in the equation thanks to an interplay between the nonlinearity of the inviscid Burgers equation and a novel forcing term that is nonlocal in nature and has deep physical roots in reactive Euler equations.
15. EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY AS ...
African Journals Online (AJOL)
Objective To evaluate extracorporeal shock wave lithotripsy (ESWL) as a monotherapy for urolithiasis in patients with solitary kidney and to determine the factors that may affect its results. Patients and Methods Using the Dornier MFL 5000 lithotriptor, 106 patients with solitary kidney (80 men and 26 women) were treated for ...
16. Shock formation within sonoluminescence bubbles
International Nuclear Information System (INIS)
Vuong, V.Q.; Szeri, A.J.; Young, D.A.
1999-01-01
A strong case has been made by several authors that sharp, spherically symmetric shocks converging on the center of a spherical bubble driven by a strong acoustic field give rise to rapid compression and heating that produces the brief flash of light known as sonoluminescence. The formation of such shocks is considered. It is found that, although at the main collapse the bubble wall does indeed launch an inwardly-traveling compression wave, and although the subsequent reflection of the wave at the bubble center produces a very rapid temperature peak, the wave is prevented from steepening into a sharp shock by an adverse gradient in the sound speed caused by heat transfer. It is shown that the mathematical characteristics of the flow can be prevented from accumulating into a shock front by this adverse sound speed gradient. A range of results is presented for a variety of bubble ambient radii and sound field amplitudes suggested by experiments. The time scale of the peak temperature in the bubble is set by the dynamics of the compression wave: this is typically in the range 100 - 300 ps (FWHM) in concert with recent measurements of the sonoluminescence pulse width. copyright 1999 American Institute of Physics
17. Model for Shock Wave Chaos
KAUST Repository
Kasimov, Aslan R.; Faria, Luiz; Rosales, Rodolfo R.
2013-01-01
: steady traveling wave solutions, instability of such solutions, and the onset of chaos. Our model is the first (to our knowledge) to describe chaos in shock waves by a scalar first-order partial differential equation. The chaos arises in the equation
18. Studying shocks in model astrophysical flows
International Nuclear Information System (INIS)
Chakrabarti, S.K.
1989-01-01
We briefly discuss some properties of the shocks in the existing models for quasi two-dimensional astrophysical flows. All of these models which allow the study of shock analytically have some unphysical characteristics due to inherent assumptions made. We propose a hybrid model for a thin flow which has fewer unpleasant features and is suitable for the study of shocks. (author). 5 refs
19. Shock waves in relativistic nuclear matter, I
International Nuclear Information System (INIS)
Gleeson, A.M.; Raha, S.
1979-02-01
The relativistic Rankine-Hugoniot relations are developed for a 3-dimensional plane shock and a 3-dimensional oblique shock. Using these discontinuity relations together with various equations of state for nuclear matter, the temperatures and the compressibilities attainable by shock compression for a wide range of laboratory kinetic energy of the projectile are calculated. 12 references
20. The microphysics of collisionless shock waves
DEFF Research Database (Denmark)
Marcowith, Alexandre; Bret, Antoine; Bykov, Andrei
2016-01-01
Collisionless shocks, that is shocks mediated by electromagnetic processes, are customary in space physics and in astrophysics. They are to be found in a great variety of objects and environments: magnetospheric and heliospheric shocks, supernova remnants, pulsar winds and their nebulæ, active ga...
1. Shock wave and flame front induced detonation in a rapid compression machine
Science.gov (United States)
Wang, Y.; Qi, Y.; Xiang, S.; Mével, R.; Wang, Z.
2018-05-01
The present study focuses on one mode of detonation initiation observed in a rapid compression machine (RCM). This mode is referred to as shock wave and flame front-induced detonation (SWFID). Experimental high-speed imaging and two-dimensional numerical simulations with skeletal chemistry are combined to unravel the dominant steps of detonation initiation under SWFID conditions. It is shown that the interaction between the shock wave generated by the end-gas auto-ignition and the spherical flame creates a region of high pressure and temperature which enables the acceleration of the flame front and the detonation onset. The experimental observation lacks adequate spatial and temporal resolution despite good reproducibility of the detonation onset. Based on the numerical results, phenomenological interpretation of the event within the framework of shock wave refraction indicates that the formation of a free-precursor shock wave at the transition between regular and irregular refraction may be responsible for detonation onset. The present results along with previous findings on shock wave reflection-induced detonation in the RCM indicate that super-knock occurs after the interaction of the shock wave generated by end-gas auto-ignition with the RCM walls, preignition flame, or another shock wave.
2. Permeability enhancement by shock cooling
Science.gov (United States)
Griffiths, Luke; Heap, Michael; Reuschlé, Thierry; Baud, Patrick; Schmittbuhl, Jean
2015-04-01
The permeability of an efficient reservoir, e.g. a geothermal reservoir, should be sufficient to permit the circulation of fluids. Generally speaking, permeability decreases over the life cycle of the geothermal system. As a result, is usually necessary to artificially maintain and enhance the natural permeability of these systems. One of the methods of enhancement -- studied here -- is thermal stimulation (injecting cold water at low pressure). This goal of this method is to encourage new thermal cracks within the reservoir host rocks, thereby increasing reservoir permeability. To investigate the development of thermal microcracking in the laboratory we selected two granites: a fine-grained (Garibaldi Grey granite, grain size = 0.5 mm) and a course-grained granite (Lanhelin granite, grain size = 2 mm). Both granites have an initial porosity of about 1%. Our samples were heated to a range of temperatures (100-1000 °C) and were either cooled slowly (1 °C/min) or shock cooled (100 °C/s). A systematic microstructural (2D crack area density, using standard stereological techniques, and 3D BET specific surface area measurements) and rock physical property (porosity, P-wave velocity, uniaxial compressive strength, and permeability) analysis was undertaken to understand the influence of slow and shock cooling on our reservoir granites. Microstructurally, we observe that the 2D crack surface area per unit volume and the specific surface area increase as a result of thermal stressing, and, for the same maximum temperature, crack surface area is higher in the shock cooled samples. This observation is echoed by our rock physical property measurements: we see greater changes for the shock cooled samples. We can conclude that shock cooling is an extremely efficient method of generating thermal microcracks and modifying rock physical properties. Our study highlights that thermal treatments are likely to be an efficient method for the "matrix" permeability enhancement of
3. A Comprehensive Review of the Techniques on Regenerative Shock Absorber Systems
Directory of Open Access Journals (Sweden)
Ran Zhang
2018-05-01
Full Text Available In this paper, the current technologies of the regenerative shock absorber systems have been categorized and evaluated. Three drive modes of the regenerative shock absorber systems, namely the direct drive mode, the indirect drive mode and hybrid drive mode are reviewed for their readiness to be implemented. The damping performances of the three different modes are listed and compared. Electrical circuit and control algorithms have also been evaluated to maximize the power output and to deliver the premium ride comfort and handling performance. Different types of parameterized road excitations have been applied to vehicle suspension systems to investigate the performance of the regenerative shock absorbers. The potential of incorporating nonlinearity into the regenerative shock absorber design analysis is discussed. The research gaps for the comparison of the different drive modes and the nonlinearity analysis of the regenerative shock absorbers are identified and, the corresponding research questions have been proposed for future work.
4. Evaluation of thermal shock strengths for graphite materials using a laser irradiation method
International Nuclear Information System (INIS)
Kim, Jae Hoon; Lee, Young Shin; Kim, Duck Hoi; Park, No Seok; Suh, Jeong; Kim, Jeng O.; Il Moon, Soon
2004-01-01
Thermal shock is a physical phenomenon that occurs during the exposure to rapidly high temperature and pressure changes or during quenching of a material. The rocket nozzle throat is exposed to combustion gas of high temperature. Therefore, it is important to select suitable materials having the appropriate thermal shock resistance and to evaluate these materials for rocket nozzle design. The material of this study is ATJ graphite, which is the candidate material for rocket nozzle throat. This study presents an experimental method to evaluate the thermal shock resistance and thermal shock fracture toughness of ATJ graphite using laser irradiation. In particular, thermal shock resistance tests are conducted with changes of specimen thickness, with laser source irradiated at the center of the specimen. Temperature distributions on the specimen surface are detected using type K and C thermocouples. Scanning electron microscope (SEM) is used to observe the thermal cracks on specimen surface
5. Effect of target-fixture geometry on shock-wave compacted copper powders
Science.gov (United States)
Kim, Wooyeol; Ahn, Dong-Hyun; Yoon, Jae Ik; Park, Lee Ju; Kim, Hyoung Seop
2018-01-01
In shock compaction with a single gas gun system, a target fixture is used to safely recover a powder compact processed by shock-wave dynamic impact. However, no standard fixture geometry exists, and its effect on the processed compact is not well studied. In this study, two types of fixture are used for the dynamic compaction of hydrogen-reduced copper powders, and the mechanical properties and microstructures are investigated using the Vickers microhardness test and electron backscatter diffraction, respectively. With the assistance of finite element method simulations, we analyze several shock parameters that are experimentally hard to control. The results of the simulations indicate that the target geometry clearly affects the characteristics of incident and reflected shock waves. The hardness distribution and the microstructure of the compacts also show their dependence on the geometry. With the results of the simulations and the experiment, it is concluded that the target geometry affects the shock wave propagation and wave interaction in the specimen.
6. Effects of arm elevation on radial artery pressure: a new method to distinguish hypovolemic shock and septic shock from hypotension.
Science.gov (United States)
Xie, Zhiyi; Zhang, Zhenyu; Xu, Yuan; Zhou, Hua; Wu, Sheng; Wang, Zhong
2018-06-01
In this prospective observational study, we investigated the variability in radial artery invasive blood pressure associated with arm elevation in patients with different hemodynamic types. We carried out a prospective observational study using data from 73 general anesthesia hepatobiliary postoperative adult patients admitted to an ICU over a 1-year period. A standard procedure was used for the arm elevation test. The value of invasive radial arterial pressure was recorded at baseline, and 30 and 60 s after the arm had been raised from 0° to 90°. We compared the blood pressure before versus after arm elevation, and between hemodynamically stable, hypovolemic shock, and septic shock patient groups. In all 73 patients, systolic arterial pressure (SAP) decreased, diastolic arterial pressure (DAP) increased, and pulse pressure (PP) decreased at 30 and 60 s after arm elevation (Ppressure (MAP) was unchanged (P>0.05). On comparing 30 and 60 s, there was no significant difference in SAP, DAP, PP, or MAP (P>0.05). In 40 hemodynamically stable patients, SAP and PP decreased, and DAP and MAP increased significantly at 30 and 60 s after arm elevation compared with baseline (P0.05). In 17 patients with septic shock, SAP, PP, and MAP decreased significantly versus baseline at 30 and 60 s (P0.05). Comparison of the absolute value of pressure change of septic shock patients at 30 s after raising the arm showed that SAP, DAP, and MAP changes were significantly lower compared with those in hypovolemic shock and hemodynamically stable patients (Parm elevation of SAP. The best cut-off point for the SAP change value was -5 mmHg or less, with a sensitivity of 94.12%, a specificity of 80.36%, a positive likelihood ratio of 4.79 (95% CI: 2.8-8.2), and a negative likelihood ratio of 0.073 (95% CI: 0.01-0.5). Our study shows that hypovolemic shock and septic shock patients have significantly different radial artery invasive blood pressure changes in an arm elevation test
7. Lack of consensus in social systems
Science.gov (United States)
Benczik, I. J.; Benczik, S. Z.; Schmittmann, B.; Zia, R. K. P.
2008-05-01
We propose an exactly solvable model for the dynamics of voters in a two-party system. The opinion formation process is modeled on a random network of agents. The dynamical nature of interpersonal relations is also reflected in the model, as the connections in the network evolve with the dynamics of the voters. In the infinite time limit, an exact solution predicts the emergence of consensus, for arbitrary initial conditions. However, before consensus is reached, two different metastable states can persist for exponentially long times. One state reflects a perfect balancing of opinions, the other reflects a completely static situation. An estimate of the associated lifetimes suggests that lack of consensus is typical for large systems.
8. Inappropriate shocks in the subcutaneous ICD
DEFF Research Database (Denmark)
Olde Nordkamp, Louise R A; Brouwer, Tom F; Barr, Craig
2015-01-01
shocks have been reported. METHODS: We analyzed the incidence, predictors and management of inappropriate shocks in the EFFORTLESS S-ICD Registry, which collects S-ICD implantation information and follow-up data from clinical centers in Europe and New Zealand. RESULTS: During a follow-up of 21 ± 13...... xyphoid to V6) reduced the risk. Reprogramming or optimization of SVT treatment after the first clinical event of inappropriate shock was successful in preventing further inappropriate shocks for cardiac oversensing and SVT events. CONCLUSIONS: Inappropriate shocks, mainly due to cardiac oversensing...
9. Shock reliability analysis and improvement of MEMS electret-based vibration energy harvesters
International Nuclear Information System (INIS)
Renaud, M; Goedbloed, M; De Nooijer, C; Van Schaijk, R; Fujita, T
2015-01-01
Vibration energy harvesters can serve as a replacement solution to batteries for powering tire pressure monitoring systems (TPMS). Autonomous wireless TPMS powered by microelectromechanical system (MEMS) electret-based vibration energy harvester have been demonstrated. The mechanical reliability of the MEMS harvester still has to be assessed in order to bring the harvester to the requirements of the consumer market. It should survive the mechanical shocks occurring in the tire environment. A testing procedure to quantify the shock resilience of harvesters is described in this article. Our first generation of harvesters has a shock resilience of 400 g, which is far from being sufficient for the targeted application. In order to improve this aspect, the first important aspect is to understand the failure mechanism. Failure is found to occur in the form of fracture of the device’s springs. It results from impacts between the anchors of the springs when the harvester undergoes a shock. The shock resilience of the harvesters can be improved by redirecting these impacts to nonvital parts of the device. With this philosophy in mind, we design three types of shock absorbing structures and test their effect on the shock resilience of our MEMS harvesters. The solution leading to the best results consists of rigid silicon stoppers covered by a layer of Parylene. The shock resilience of the harvesters is brought above 2500 g. Results in the same range are also obtained with flexible silicon bumpers, which are simpler to manufacture. (paper)
10. Shock reliability analysis and improvement of MEMS electret-based vibration energy harvesters
Science.gov (United States)
Renaud, M.; Fujita, T.; Goedbloed, M.; de Nooijer, C.; van Schaijk, R.
2015-10-01
Vibration energy harvesters can serve as a replacement solution to batteries for powering tire pressure monitoring systems (TPMS). Autonomous wireless TPMS powered by microelectromechanical system (MEMS) electret-based vibration energy harvester have been demonstrated. The mechanical reliability of the MEMS harvester still has to be assessed in order to bring the harvester to the requirements of the consumer market. It should survive the mechanical shocks occurring in the tire environment. A testing procedure to quantify the shock resilience of harvesters is described in this article. Our first generation of harvesters has a shock resilience of 400 g, which is far from being sufficient for the targeted application. In order to improve this aspect, the first important aspect is to understand the failure mechanism. Failure is found to occur in the form of fracture of the device’s springs. It results from impacts between the anchors of the springs when the harvester undergoes a shock. The shock resilience of the harvesters can be improved by redirecting these impacts to nonvital parts of the device. With this philosophy in mind, we design three types of shock absorbing structures and test their effect on the shock resilience of our MEMS harvesters. The solution leading to the best results consists of rigid silicon stoppers covered by a layer of Parylene. The shock resilience of the harvesters is brought above 2500 g. Results in the same range are also obtained with flexible silicon bumpers, which are simpler to manufacture.
11. MMS observations of the Earth bow shock during magnetosphere compression and expansion: comparison of whistler wave properties around the shock ramp
Science.gov (United States)
Russell, C. T.; Strangeway, R. J.; Schwartz, S. J.
2017-12-01
The Magnetospheric Multiscale (MMS) spacecraft, with their state-of-the-art plasma and field instruments onboard, allow us to investigate electromagnetic waves at the bow shock and their association with small-scale disturbances in the shocked plasmas. Understanding these waves could improve our knowledge on the heating of electrons and ions across the shock ramp and the energy dissipation of supercritical shocks. We have found broad-band and narrow band waves across the shock ramp and slightly downstream. The broad-band waves propagate obliquely to the magnetic field direction and have frequencies up to the electron cyclotron frequency, while the narrow-band waves have frequencies of a few hundred Hertz, durations under a second, and are right-handed circularly polarized and propagate along the magnetic field lines. Both wave types are likely to be whistler mode with different generation mechanisms. When the solar wind pressure changes, MMS occasionally observed a pair of bow shocks when the magnetosphere was compressed and then expanded. We compare the wave observations under these two situations to understand their roles in the shock ramp as well as the upstream and downstream plasmas.
12. Perpendicular relativistic shocks in magnetized pair plasma
Science.gov (United States)
Plotnikov, Illya; Grassi, Anna; Grech, Mickael
2018-04-01
Perpendicular relativistic (γ0 = 10) shocks in magnetized pair plasmas are investigated using two dimensional Particle-in-Cell simulations. A systematic survey, from unmagnetized to strongly magnetized shocks, is presented accurately capturing the transition from Weibel-mediated to magnetic-reflection-shaped shocks. This transition is found to occur for upstream flow magnetizations 10-3 10-2, it leaves place to a purely electromagnetic precursor following from the strong emission of electromagnetic waves at the shock front. Particle acceleration is found to be efficient in weakly magnetized perpendicular shocks in agreement with previous works, and is fully suppressed for σ > 10-2. Diffusive Shock Acceleration is observed only in weakly magnetized shocks, while a dominant contribution of Shock Drift Acceleration is evidenced at intermediate magnetizations. The spatial diffusion coefficients are extracted from the simulations allowing for a deeper insight into the self-consistent particle kinematics and scale with the square of the particle energy in weakly magnetized shocks. These results have implications for particle acceleration in the internal shocks of AGN jets and in the termination shocks of Pulsar Wind Nebulae.
13. Initial conditions of radiative shock experiments
International Nuclear Information System (INIS)
Kuranz, C. C.; Drake, R. P.; Krauland, C. M.; Marion, D. C.; Grosskopf, M. J.; Rutter, E.; Torralva, B.; Holloway, J. P.; Bingham, D.; Goh, J.; Boehly, T. R.; Sorce, A. T.
2013-01-01
We performed experiments at the Omega Laser Facility to characterize the initial, laser-driven state of a radiative shock experiment. These experiments aimed to measure the shock breakout time from a thin, laser-irradiated Be disk. The data are then used to inform a range of valid model parameters, such as electron flux limiter and polytropic γ, used when simulating radiative shock experiments using radiation hydrodynamics codes. The characterization experiment and the radiative shock experiment use a laser irradiance of ∼7 × 10 14 W cm −2 to launch a shock in the Be disk. A velocity interferometer and a streaked optical pyrometer were used to infer the amount of time for the shock to move through the Be disk. The experimental results were compared with simulation results from the Hyades code, which can be used to model the initial conditions of a radiative shock system using the CRASH code
14. Exploratory laser-driven shock wave studies
International Nuclear Information System (INIS)
Solem, J.C.; Veeser, L.R.
1977-11-01
We show the results of a feasibility study for investigating shock structure and for measuring equation-of-state parameters using high-energy, short-pulse lasers. We discuss the temporal and spatial structure of the luminosity from laser-driven shock unloading in aluminum foils. We demonstrate that shock velocity can be measured by observing the time interval between shock emergence across two thicknesses and show data for shocks of 1.3 and 2.1 Mbar. The fact that we observe shock fronts cleanly breaking through steps as small as 3 μm indicates that the shock front thickness is very small in the few megabar region; this is the first experimental verification that these fronts are not more than a few micrometers thick. We present approximate measurements of free-surface velocity. Finally, we speculate on the use of these techniques to obtain detailed equation-of-state data
15. Shock-induced chemistry in organic materials
Energy Technology Data Exchange (ETDEWEB)
Dattelbaum, Dana M [Los Alamos National Laboratory; Sheffield, Steve [Los Alamos National Laboratory; Engelke, Ray [Los Alamos National Laboratory; Manner, Virginia [Los Alamos National Laboratory; Chellappa, Raja [Los Alamos National Laboratory; Yoo, Choong - Shik [WASHINGTON STATE UNIV
2011-01-20
The combined 'extreme' environments of high pressure, temperature, and strain rates, encountered under shock loading, offer enormous potential for the discovery of new paradigms in chemical reactivity not possible under more benign conditions. All organic materials are expected to react under these conditions, yet we currently understand very little about the first bond-breaking steps behind the shock front, such as in the shock initiation of explosives, or shock-induced reactivity of other relevant materials. Here, I will present recent experimental results of shock-induced chemistry in a variety of organic materials under sustained shock conditions. A comparison between the reactivity of different structures is given, and a perspective on the kinetics of reaction completion under shock drives.
16. Experimental methods of shock wave research
CERN Document Server
Seiler, Friedrich
2016-01-01
This comprehensive and carefully edited volume presents a variety of experimental methods used in Shock Waves research. In 14 self contained chapters this 9th volume of the “Shock Wave Science and Technology Reference Library” presents the experimental methods used in Shock Tubes, Shock Tunnels and Expansion Tubes facilities. Also described is their set-up and operation. The uses of an arc heated wind tunnel and a gun tunnel are also contained in this volume. Whenever possible, in addition to the technical description some typical scientific results obtained using such facilities are described. Additionally, this authoritative book includes techniques for measuring physical properties of blast waves and laser generated shock waves. Information about active shock wave laboratories at different locations around the world that are not described in the chapters herein is given in the Appendix, making this book useful for every researcher involved in shock/blast wave phenomena.
17. Motion of shocks through interplanetary streams
International Nuclear Information System (INIS)
Burlaga, L.F.; Scudder, J.D.
1975-01-01
A model for the motion of flare-generated shocks through interplanetary streams is presented, illustrating the effects of a stream-shock interaction on the shock strength and geometry. It is a gas dynamic calculation based on Whitham's method and on an empirical approximation for the relevant characteristics of streams. The results show that the Mach number of a shock can decrease appreciably to near unity in the interaction region ahead of streams and that the interaction of a spherically symmetric shock with a spiral-shaped corotating stream can cause significant distortions of the initial shock front geometry. The geometry of the February 15--16, 1967, shock discussed by Lepping and Chao (1972) is qualitatively explained by this model
18. Do oil shocks predict economic policy uncertainty?
Science.gov (United States)
Rehman, Mobeen Ur
2018-05-01
Oil price fluctuations have influential role in global economic policies for developed as well as emerging countries. I investigate the role of international oil prices disintegrated into structural (i) oil supply shock, (ii) aggregate demand shock and (iii) oil market specific demand shocks, based on the work of Kilian (2009) using structural VAR framework on economic policies uncertainty of sampled markets. Economic policy uncertainty, due to its non-linear behavior is modeled in a regime switching framework with disintegrated structural oil shocks. Our results highlight that Indian, Spain and Japanese economic policy uncertainty responds to the global oil price shocks, however aggregate demand shocks fail to induce any change. Oil specific demand shocks are significant only for China and India in high volatility state.
19. Shock Wave Dynamics in Weakly Ionized Plasmas
Science.gov (United States)
Johnson, Joseph A., III
1999-01-01
An investigation of the dynamics of shock waves in weakly ionized argon plasmas has been performed using a pressure ruptured shock tube. The velocity of the shock is observed to increase when the shock traverses the plasma. The observed increases cannot be accounted for by thermal effects alone. Possible mechanisms that could explain the anomalous behavior include a vibrational/translational relaxation in the nonequilibrium plasma, electron diffusion across the shock front resulting from high electron mobility, and the propagation of ion-acoustic waves generated at the shock front. Using a turbulence model based on reduced kinetic theory, analysis of the observed results suggest a role for turbulence in anomalous shock dynamics in weakly ionized media and plasma-induced hypersonic drag reduction.
20. Lucky in Life, Unlucky in Love? The Effect of Random Income Shocks on Marriage and Divorce
Science.gov (United States)
Hankins, Scott; Hoekstra, Mark
2011-01-01
Economists have long been interested in the extent to which economic resources affect decisions to marry and divorce. However, this issue has been difficult to address empirically due to a lack of exogenous income shocks. We overcome this problem by exploiting the randomness of the Florida Lottery and comparing recipients of large prizes to those…
1. [Analysis of the protective effect of shock-absorbing shoes for patients treated with hip and knee endoprostheses].
Science.gov (United States)
Gebauer, D; Cziuk, N
1988-01-01
Biomechanical loading of total knee and hip replacement is one of the essential factors which limit the longterm-function of the implant components. A simple and cheap safety provision to avoid mechanical overload seems to be wearing of shock-absorbing shoes. The performed study analyzes the effect of that type of shoe. For judgement the parameters: energy absorption while slow shock, damping while hard shock and safety against sliding were taken. The experiments showed the shock-absorbing shoe is an easy, inexpensive, but very efficient protection measure to improve the longterm-stability of endoprosthesis of the lower extremity.
2. Study on Reflected Shock Wave/Boundary Layer Interaction in a Shock Tube
Energy Technology Data Exchange (ETDEWEB)
Kim, Dong Wook; Kim, Tae Ho; Kim, Heuy Dong [Andong Nat’l Univ., Andong (Korea, Republic of)
2017-07-15
The interaction between a shock wave and a boundary layer causes boundary layer separation, shock train, and in some cases, strong unsteadiness in the flow field. Such a situation is also observed in a shock tube, where the reflected shock wave interacts with the unsteady boundary layer. However, only a few studies have been conducted to investigate the shock train phenomenon in a shock tube. In the present study, numerical studies were conducted using the two-dimensional axisymmetric domain of a shock tube, and compressible Navier-Stokes equations were solved to clarify the flow characteristics of shock train phenomenon inside a shock tube. A detailed wave diagram was developed based on the present computational results, which were validated with existing experimental data.
3. Insight into magnetorheological shock absorbers
CERN Document Server
Gołdasz, Janusz
2015-01-01
This book deals with magnetorheological fluid theory, modeling and applications of automotive magnetorheological dampers. On the theoretical side a review of MR fluid compositions and key factors affecting the characteristics of these fluids is followed by a description of existing applications in the area of vibration isolation and flow-mode shock absorbers in particular. As a majority of existing magnetorheological devices operates in a so-called flow mode a critical review is carried out in that regard. Specifically, the authors highlight common configurations of flow-mode magnetorheological shock absorbers, or so-called MR dampers that have been considered by the automotive industry for controlled chassis applications. The authors focus on single-tube dampers utilizing a piston assembly with one coil or multiple coils and at least one annular flow channel in the piston.
4. Magnetohydrodynamic shocks in molecular clouds
International Nuclear Information System (INIS)
Chernoff, D.F.
1985-01-01
Part one develops the mathematical and physical theory of one-dimensional, time-independent subalfvenic flow in partially ionized gas with magnetic fields, for application to shocks in molecular clouds. Unlike normal gas-dynamic shocks, the neutral flow may be continuous and cool if the gas radiates efficiently and does not self-ionize. Analytic solutions are given in the limit that the neutral gas is either adiabatic or isothermal (cold). Numerical techniques are developed and applied to find the neutral flow under general circumstances. Part two extends the theory and results of part one in three ways: (1) to faster, superalfvenic flow, (2) to complex gases containing heavy charged particles (grains) in addition to ions, containing heavy charged particles (grains) in addition to ions, electrons and neutrals, and (3) to the entire range in (Omega tau), the ratio of charged particle damping time to gyroperiod, expected in gas flows in molecular clouds
5. Measuring resilience to energy shocks
OpenAIRE
Molyneaux, Lynette; Brown, Colin; Foster, John; Wagner, Liam
2015-01-01
Measuring energy security or resilience in energy is, in the main, confined to indicators which are used for comparative purposes or to show trends rather than provide empirical evidence of resilience to unpredicted crises. In this paper, the electricity systems of the individual states within the United States of America are analysed for their response to the 1973-1982 and the 2003-2012 oil price shocks. Empirical evidence is sought for elements which are present in systems that experience r...
6. Experimental investigation of shock wave - bubble interaction
Energy Technology Data Exchange (ETDEWEB)
2010-04-09
In this work, the dynamics of laser-generated single cavitation bubbles exposed to lithotripter shock waves has been investigated experimentally. The energy of the impinging shock wave is varied in several steps. High-speed photography and pressure field measurements simultaneously with image acquisition provide the possibility of capturing the fast bubble dynamics under the effect of the shock wave impact. The pressure measurement is performed using a fiber optic probe hydrophone (FOPH) which operates based on optical diagnostics of the shock wave propagating medium. After a short introduction in chapter 1 an overview of the previous studies in chapter 2 is presented. The reported literatures include theoretical and experimental investigations of several configurations of physical problems in the field of bubble dynamics. In chapter 3 a theoretical description of propagation of a shock wave in a liquid like water has been discussed. Different kinds of reflection of a shock wave at an interface are taken into account. Undisturbed bubble dynamics as well as interaction between a planar shock wave and an initially spherical bubble are explored theoretically. Some physical parameters which are important in this issue such as the velocity of the shock-induced liquid jet, Kelvin impulse and kinetic energy are explained. The shock waves are generated in a water filled container by a focusing piezoelectric generator. The shock wave profile has a positive part with pulse duration of ∼1 μs followed by a longer tension tail (i.e. ∼3 μs). In chapter 4 high-speed images depict the propagation of a shock wave in the water filled tank. The maximum pressure is also derived for different intensity levels of the shock wave generator. The measurement is performed in the free field (i.e. in the absence of laser-generated single bubbles). In chapter 5 the interaction between lithotripter shock waves and laserinduced single cavitation bubbles is investigated experimentally. An
7. The effect of long and short time oil shocks on economic growth in Iran
OpenAIRE
2012-01-01
Oil is one of the strategic good so that price fluctuations and shocks of it have major effects on economic growth and recession in depended countries to revenues of it. In this study, it is tried that the effect of oil price shocks investigated in two types (short and long time) on Economic growth in Iran. Its Period is from 1974 to 2006. According it, oil price uncertainty is quantized by GARCH model and is determined the effects of oil price shocks on economic growth in Iran during a short...
8. Replacement policy in a system under shocks following a Markovian arrival process
International Nuclear Information System (INIS)
Montoro-Cazorla, Delia; Perez-Ocon, Rafael; Carmen Segovia, Maria del
2009-01-01
We present a system subject to shocks that arrive following a Markovian arrival process. The system is minimally repaired. It is replaced when a certain number of shocks arrive. A general model where the replacements are governed by a discrete phase-type distribution is studied. For this system, the Markov process governing the system is constructed, and the interarrival times between replacements and the number of replacements are calculated. A special case of this system is when it can stand a prefixed number of shocks. For this new system, the same performance measures are calculated. The systems are considered in transient and stationary regime
9. Replacement policy in a system under shocks following a Markovian arrival process
Energy Technology Data Exchange (ETDEWEB)
Montoro-Cazorla, Delia [Department of Statistics and Operational Research, University of Jaen (Spain); Perez-Ocon, Rafael [Department of Statistics and Operational Research, University of Granada, Granada (Spain)], E-mail: [email protected]; Carmen Segovia, Maria del [Departamento de Estadistica e I.O., University of Granada, Granada (Spain)
2009-02-15
We present a system subject to shocks that arrive following a Markovian arrival process. The system is minimally repaired. It is replaced when a certain number of shocks arrive. A general model where the replacements are governed by a discrete phase-type distribution is studied. For this system, the Markov process governing the system is constructed, and the interarrival times between replacements and the number of replacements are calculated. A special case of this system is when it can stand a prefixed number of shocks. For this new system, the same performance measures are calculated. The systems are considered in transient and stationary regime.
10. Prediction of CMEs and Type II Bursts from Sun to Earth
Science.gov (United States)
Cairns, I. H.; Schmidt, J. M.; Gopalswamy, N.; van der Holst, B.
2017-12-01
Most major space weather events are due to fast CMEs and their shocks interacting with Earth's magnetosphere. SImilarly, type II solar radio bursts are well-known signatures of CMEs and their shocks moving through the corona and solar wind. The properties of the space weather events and the type II radio bursts depend sensitively on the CME velocity, shape, and evolution as functions of position and time, as well as on the magnetic field vector in the coronal and solar wind plasma, downstream of the CME shock, and inside the CME. We report simulations of CMEs and type II bursts from the Sun to Earth with the Space Weather Modelling Framework (2015 and 2016 versions), set up carefully using relevant data, and a kinetic radio emission theory. Excellent agreement between observations, simulations, and theory are found for the coronal (metric) type II burst of 7 September 2014 and associated CME, including the lack of radio emission in the solar wind beyond about 10 solar radii. Similarly, simulation of a CME and type II burst from the Sun to 1 AU over the period 29 November - 1 December 2013 yield excellent agreement for the radio burst from 10 MHz to 30 kHz for STEREO A and B and Wind, arrival of the CME at STEREO A within 1 hour reported time, deceleration of the CME in agreement with the Gopalswamy et al. [2011] observational analyses, and Bz rotations at STEREO A from upstream of the CME shock to within the CME. These results provide strong support for the type II theory and also that the Space WeatherModeling Framework can accurately predict the properties and evolution of CMEs and the interplanetary magnetic field and plasma from the Sun to 1 AU when sufficiently carefully initialized.
11. Particle Acceleration in Two Converging Shocks
Energy Technology Data Exchange (ETDEWEB)
Wang, Xin; Wang, Na; Shan, Hao [Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi 830011 (China); Giacalone, Joe [Lunar and Planetary Laboratory, University of Arizona, Tucson AZ 85721 (United States); Yan, Yihua [CAS Key Laboratory of Solar Activity, National Astronomical Observatories, Beijing 100012 (China); Ding, Mingde, E-mail: [email protected] [Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University) Ministry of Education, Nanjing 210093 (China)
2017-06-20
Observations by spacecraft such as ACE , STEREO , and others show that there are proton spectral “breaks” with energy E {sub br} at 1–10 MeV in some large CME-driven shocks. Generally, a single shock with the diffusive acceleration mechanism would not predict the “broken” energy spectrum. The present paper focuses on two converging shocks to identify this energy spectral feature. In this case, the converging shocks comprise one forward CME-driven shock on 2006 December 13 and another backward Earth bow shock. We simulate the detailed particle acceleration processes in the region of the converging shocks using the Monte Carlo method. As a result, we not only obtain an extended energy spectrum with an energy “tail” up to a few 10 MeV higher than that in previous single shock model, but also we find an energy spectral “break” occurring on ∼5.5 MeV. The predicted energy spectral shape is consistent with observations from multiple spacecraft. The spectral “break,” then, in this case is caused by the interaction between the CME shock and Earth’s bow shock, and otherwise would not be present if Earth were not in the path of the CME.
12. Simulation of turbulent flows containing strong shocks
International Nuclear Information System (INIS)
Fryxell, Bruce; Menon, Suresh
2008-01-01
Simulation of turbulent flows with strong shocks is a computationally challenging problem. The requirements for a method to produce accurate results for turbulence are orthogonal to those needed to treat shocks properly. In order to prevent an unphysical rate of decay of turbulent structures, it is necessary to use a method with very low numerical dissipation. Because of this, central difference schemes are widely used. However, computing strong shocks with a central difference scheme can produce unphysical post-shock oscillations that corrupt the entire flow unless additional dissipation is added. This dissipation can be difficult to localize to the area near the shock and can lead to inaccurate treatment of the turbulence. Modern high-resolution shock-capturing methods usually use upwind algorithms to provide the dissipation necessary to stabilize shocks. However, this upwind dissipation can also lead to an unphysical rate of decay of the turbulence. This paper discusses a hybrid method for simulating turbulent flows with strong shocks that couples a high-order central difference scheme with a high-resolution shock-capturing method. The shock-capturing method is used only in the vicinity of discontinuities in the flow, whereas the central difference scheme is used in the remainder of the computational domain. Results of this new method will be shown for a variety of test problems. Preliminary results for a realistic application involving detonation in gas-particle flows will also be presented.
13. Electron velocity distributions near collisionless shocks
International Nuclear Information System (INIS)
Feldman, W.C.
1984-01-01
Recent studies of the amount of electron heating and of the shapes of electron velocity distributions across shocks near the earth are reviewed. It is found that electron heating increases with increasing shock strength but is always less than the ion heating. The scale length of electron heating is also less than that for the ions. Electron velocity distributions show characteristic shapes which depend on the strength of the shocks. At the weaker shocks, electron heating is mostly perpendicular to the ambient magnetic field, bar B, and results in Gaussian-shaped velocity distributions at low-to-moderate energies. At the stronger shocks, parallel heating predominates resulting in flat-topped velocity distributions. A reasonable interpretation of these results indicates that at the weaker shocks electron heating is dominated by a tendency toward conservation of the magnetic moment. At the stronger fast-mode shocks, this heating is thought to be dominated by an acceleration parallel to bar B produced by the macroscopic shock electric field followed by beam driven plasma instabilities. Some contribution to the heating at the stronger shocks from conservation of the magnetic moment and cross-field current-driven instabilities cannot be ruled out. Although the heating at slow-mode shocks is also dominated by instabilities driven by magnetic field-aligned electron beams, their acceleration mechanism is not yet established
14. The Basic Research for Pulverization of Rice Using Underwater Shock Wave by Electric Discharge
Directory of Open Access Journals (Sweden)
M Ide
2016-09-01
Full Text Available In recent years, the food self-support rate of Japan is 40%, and this value is the lowest level in major developed countries. This reason includes decreasing of diverting rice consumption in Japan and increasing abandonment of cultivation. Therefore, these problems are solved by using rice powder instead of expensive flour, and we manage to increase the food selfsupport rate. Previously, the rice powder is manufactured by two methods. One is dry type, and the other is wet type. The former is the method getting rice powder by running dried rice to rotating metal, and has a problem which that starch is damaged by heat when processing was performed. The latter is performed same method against wet rice, and has a problem which a large quantity of water is used. As a method to solve these problems, an underwater shock wave is used. Shock wave is the pressure wave which is over speed of sound by discharging high energy in short time. Propagating shock wave in water is underwater shock wave. The characters of underwater shock wave are long duration of shock wave because water density is uniform, water is low price and easy to get and not heat processing. Thinking of industrialization, the electric discharge is used as the generating source of underwater shock wave in the experiment. As the results, the efficiency of obtaining enough grain size, 100ìm, of rice powder was too bad only using the simple processing using underwater shock wave. Therefore, in Okinawa National College of Technology collaborating with us, obtaining rice powder with higher efficiency by using converged underwater shock wave is the goal of this research. In this research, the underwater shock wave with equal energy of the experimental device of underwater shock wave is measured by the optical observation. In addition, the appearance converging underwater shock wave is simulated by numerical analysis, and the pressure appreciation rate between the first wave and converged
15. Lack of efficacy of ergocalciferol repletion
Directory of Open Access Journals (Sweden)
Thomas Wasser
2012-04-01
Full Text Available Introduction: Vitamin D has become an area of intensive scrutiny, both in medical and lay literature. However, there are limited data to suggest proper repletion regimens for those patients who have hypovitaminosis D. Consequently, various methods are used in clinical practice. The aim of this study was to assess the efficacy of various treatment strategies for hypovitaminosis D in an ambulatory internal medicine practice. Methods: A retrospective chart review between October 2005 and June 2010 of a suburban internal medicine practice was performed via query of the electronic medical record (Centricity, General Electric Healthcare, UK. Patients with a 25-hydroxyvitamin D concentration less than 32 mg/dl were identified and treated. Treatment success was defined as 25-hydroxyvitamin D concentrations greater than 32 mg/dl. Statistical analysis to assess changes in vitamin D level controlling for season, comorbidities, and demographics were used. Results: A total of 607 treatment episodes were identified, with 395 excluded due to lack of follow-up vitamin D level within 16 weeks, no treatment documented, topical treatment, doxercalciferol treatment, or non-compliance. Of the remaining patients, there were 212 treatment instances on 178 patients. Ergocalciferol 50,000 international units (IU was used most frequently (71.4% of the time.. A higher initial vitamin D level was positively associated with treatment success (adjusted odds ratio = 1.11, p=0.002. Increased doses of ergocalciferol increased the likelihood of treatment success (p=0.0011. Seasonal variation was related to posttreatment 25-hydroxyvitamin D concentration as was body mass index (BMI (p=0.003 and p=0.044. Conclusion: Pretreatment levels of 25-hydroxyvitamin D, BMI, season, and vitamin D dose are predictors of successful hypovitaminosis D treatment. Our data suggest that patients with initial 25-hydroxyvitamin D concentrations of <20 should be treated with a higher total dose of
16. Macroeconomic Evolution after a Production Shock: the Role for Financial Intermediation
OpenAIRE
2006-01-01
Financial intermediaries may increase economic efficiency through intertemporal risk smoothing. However without an adequate regulation, intermediation may fail to do this. This paper studies the effects of a production shock in a closed economy and compares abilities of market-based and bank-based financial systems in processing the shock. Unregulated banking system may collapse in absence of a proper regulation. The paper studies several types of regulatory interventions, which may improve t...
17. Stationary Shock Waves with Oscillating Front in Dislocation Systems of Semiconductors
Science.gov (United States)
Gestrin, S. G.; Shchukina, E. V.
2018-05-01
The paper presents a study of weakly nonlinear wave processes in the cylindrical region of a hole gas surrounding a negatively charged dislocation in an n-type semiconductor crystal. It is shown that shock waves propagating along the dislocation are the solutions of the Korteweg-de Vries-Burgers equation when the dispersion and dissipation of medium are taken into account. Estimates are obtained for the basic physical parameters characterizing the shock wave and the region inside the Reed cylinder.
18. Computer simulations of collisionless shock waves
International Nuclear Information System (INIS)
Leroy, M.M.
1984-01-01
A review of the contributions of particle computer simulations to the understanding of the physics of magnetic shock waves in collisionless plasmas is presented. The emphasis is on the relation between the computer simulation results, spacecraft observations of shocks in space, and related theories, rather than on technical aspects of the numerics. It is shown that much has been learned from the comparison of ISEE spacecraft observations of the terrestrial bow shock and particle computer simulations concerning the quasi-perpendicular, supercritical shock (ion scale structure, ion reflection mechanism and ultimate dissipation processes). Particle computer simulations have also had an appreciable prospective role in the investigation of the physics of quasi-parallel shocks, about which still little is known observationally. Moreover, these numerical techniques have helped to clarify the process of suprathermal ion rejection by the shock into the foreshock, and the subsequent evolution of the ions in the foreshock. 95 references
19. Molecular dynamics simulation of laser shock phenomena
Energy Technology Data Exchange (ETDEWEB)
Fukumoto, Ichirou [Japan Atomic Energy Research Inst., Kansai Research Establishment, Advanced Photon Research Center, Neyagawa, Osaka (Japan).
2001-10-01
Recently, ultrashort-pulse lasers with high peak power have been developed, and their application to materials processing is expected as a tool of precision microfabrication. When a high power laser irradiates, a shock wave propagates into the material and dislocations are generated. In this paper, laser shock phenomena of the metal were analyzed using the modified molecular dynamics method, which has been developed by Ohmura and Fukumoto. The main results obtained are summarized as follows: (1) The shock wave induced by the Gaussian beam irradiation propagates radially from the surface to the interior. (2) A lot of dislocations are generated at the solid-liquid interface by the propagation of a shock wave. (3) Some dislocations are moved instantaneously with the velocity of the longitudinal wave when the shock wave passes, and their velocity is not larger than the transverse velocity after the shock wave has passed. (author)
20. Entropy Generation Across Earth's Bow Shock
Science.gov (United States)
Parks, George K.; McCarthy, Michael; Fu, Suiyan; Lee E. s; Cao, Jinbin; Goldstein, Melvyn L.; Canu, Patrick; Dandouras, Iannis S.; Reme, Henri; Fazakerley, Andrew;
2011-01-01
Earth's bow shock is a transition layer that causes an irreversible change in the state of plasma that is stationary in time. Theories predict entropy increases across the bow shock but entropy has never been directly measured. Cluster and Double Star plasma experiments measure 3D plasma distributions upstream and downstream of the bow shock that allow calculation of Boltzmann's entropy function H and his famous H-theorem, dH/dt O. We present the first direct measurements of entropy density changes across Earth's bow shock. We will show that this entropy generation may be part of the processes that produce the non-thermal plasma distributions is consistent with a kinetic entropy flux model derived from the collisionless Boltzmann equation, giving strong support that solar wind's total entropy across the bow shock remains unchanged. As far as we know, our results are not explained by any existing shock models and should be of interests to theorists.
1. Remote shock sensing and notification system
Science.gov (United States)
Muralidharan, Govindarajan; Britton, Charles L.; Pearce, James; Jagadish, Usha; Sikka, Vinod K.
2008-11-11
A low-power shock sensing system includes at least one shock sensor physically coupled to a chemical storage tank to be monitored for impacts, and an RF transmitter which is in a low-power idle state in the absence of a triggering signal. The system includes interference circuitry including or activated by the shock sensor, wherein an output of the interface circuitry is coupled to an input of the RF transmitter. The interface circuitry triggers the RF transmitting with the triggering signal to transmit an alarm message to at least one remote location when the sensor senses a shock greater than a predetermined threshold. In one embodiment the shock sensor is a shock switch which provides an open and a closed state, the open state being a low power idle state.
2. Role of echocardiography in reducing shock reversal time in pediatric septic shock: a randomized controlled trial
Directory of Open Access Journals (Sweden)
Ahmed A. EL‐Nawawy
2018-01-01
Conclusion: Serial echocardiography provided crucial data for early recognition of septic myocardial dysfunction and hypovolemia that was not apparent on clinical assessment, allowing a timely management and resulting in shock reversal time reduction among children with septic shock.
3. The earth's foreshock, bow shock, and magnetosheath
Science.gov (United States)
Onsager, T. G.; Thomsen, M. F.
1991-01-01
Studies directly pertaining to the earth's foreshock, bow shock, and magnetosheath are reviewed, and some comparisons are made with data on other planets. Topics considered in detail include the electron foreshock, the ion foreshock, the quasi-parallel shock, the quasi-perpendicular shock, and the magnetosheath. Information discussed spans a broad range of disciplines, from large-scale macroscopic plasma phenomena to small-scale microphysical interactions.
4. The earth's foreshock, bow shock, and magnetosheath
International Nuclear Information System (INIS)
Onsager, T.G.; Thomsen, M.F.
1991-01-01
Studies directly pertaining to the earth's foreshock, bow shock, and magnetosheath are reviewed, and some comparisons are made with data on other planets. Topics considered in detail include the electron foreshock, the ion foreshock, the quasi-parallel shock, the quasi-perpendicular shock, and the magnetosheath. Information discussed spans a broad range of disciplines, from large-scale macroscopic plasma phenomena to small-scale microphysical interactions. 184 refs
5. Nonequilibrium chemistry in shocked molecular clouds
International Nuclear Information System (INIS)
Iglesias, E.R.; Silk, J.
1978-01-01
The gas phase chemistry is studied behind a 10 km s -1 shock propagating into a dense molecular cloud. Our principal conclusions are that the concentrations of certain molecules (CO, NH 3 , HCN, N 2 ) are unperturbed by the shock; other molecules (H 2 CO, CN, HCO + ) are greatly decreased in abundance; and substantial amounts of H 2 O, HCO, and CH 4 are produced. Approximately 10 6 yr (independent of the density) must elapse after shock passage before chemical equilibrium is attained
6. Reaction effects in diffusive shock acceleration
International Nuclear Information System (INIS)
Drury, L.Oc.
1984-01-01
The effects of the reaction of accelerated particles back on the shock wave in the diffusive-shock-acceleration model of cosmic-ray generation are investigated theoretically. Effects examined include changes in the shock structure, modifications of the input and output spectra, scattering effects, and possible instabilities in the small-scale structure. It is pointed out that the latter two effects are applicable to any spatially localized acceleration mechanism. 14 references
7. PIV tracer behavior on propagating shock fronts
International Nuclear Information System (INIS)
Glazyrin, Fyodor N; Mursenkova, Irina V; Znamenskaya, Irina A
2016-01-01
The present work was aimed at the quantitative particle image velocimetry (PIV) measurement of a velocity field near the front of a propagating shock wave and the study of the dynamics of liquid tracers crossing the shock front. For this goal, a shock tube with a rectangular cross-section (48 × 24 mm) was used. The flat shock wave with Mach numbers M = 1.4–2.0 propagating inside the tube channel was studied as well as an expanding shock wave propagating outside the channel with M = 1.2–1.8 at its main axis. The PIV imaging of the shock fronts was carried out with an aerosol of dioctyl sebacate (DEHS) as tracer particles. The pressures of the gas in front of the shock waves studied ranged from 0.013 Mpa to 0.1 MPa in the series of experiments. The processed PIV data, compared to the 1D normal shock theory, yielded consistent values of wake velocity immediately behind the plain shock wave. Special attention was paid to the blurring of the velocity jump on the shock front due to the inertial particle lag and peculiarities of the PIV technique. A numerical algorithm was developed for analysis and correction of the PIV data on the shock fronts, based on equations of particle-flow interaction. By application of this algorithm, the effective particle diameter of the DEHS aerosol tracers was estimated as 1.03 ± 0.12 μm. A number of different formulations for particle drag were tested with this algorithm, with varying success. The results show consistency with previously reported experimental data obtained for cases of stationary shock waves. (paper)
8. Condensed matter at high shock pressures
International Nuclear Information System (INIS)
Nellis, W.J.; Holmes, N.C.; Mitchell, A.C.; Radousky, H.B.; Hamilton, D.
1985-01-01
Experimental techniques are described for shock waves in liquids: Hugoniot equation-of-state, shock temperature and emission spectroscopy, electrical conductivity, and Raman spectroscopy. Experimental data are reviewed and presented in terms of phenomena that occur at high densities and temperatures in shocked He, Ar, N 2 , CO, SiO 2 -aerogel, H 2 O, and C 6 H 6 . The superconducting properties of Nb metal shocked to 100 GPa (1 Mbar) and recovered intact are discussed in terms of prospects for synthesizing novel, metastable materials. Ultrahigh pressure data for Cu is reviewed in the range 0.3 to 6TPa (3 to 60 Mbar). 56 refs., 9 figs., 1 tab
9. Advanced and Exploratory Shock Sensing Mechanisms.
Energy Technology Data Exchange (ETDEWEB)
Nelsen, Nicholas H. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Kolb, James D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Kulkarni, Akshay G. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sorscher, Zachary [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Habing, Clayton D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Mathis, Allen [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Beller, Zachary J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2017-09-01
Mechanical component response to shock environments must be predictable in order to ensure reliability and safety. Whether the shock input results from accidental drops during transportation to projectile impact scenarios, the system must irreversibly transition into a safe state that is incapable of triggering the component . With this critical need in mind, the 2017 Nuclear Weapons Summer Product Realization Institute (NW SPRINT) program objective sought the design of a passive shock failsafe with emphasis on additively manufactured (AM) components. Team Advanced and Exploratory (A&E) responded to the challenge by designing and delivering multiple passive shock sensing mech anisms that activate within a prescribed mechanical shock threshold. These AM failsafe designs were tuned and validated using analytical and computational techniques including the shock response spectrum (SRS) and finite element analysis (FEA). After rapid prototyping, the devices experienced physical shock tests conducted on Sandia drop tables to experimentally verify performance. Keywords: Additive manufacturing, dynamic system, failsafe, finite element analysis, mechanical shock, NW SPRINT, shock respon se spectrum
10. Irreversible thermodynamics of overdriven shocks in solids
International Nuclear Information System (INIS)
Wallace, D.C.
1981-01-01
An isotropic solid capable of transporting heat and of undergoing dissipative plastic flow, is treated. The shock is assumed to be a steady wave, and any phase changes or macroscopic inhomogeneities which might be induced by the shock are neglected. Under these conditions it is established that for an overdriven shock, no solution is possible without heat transport, and when the heat transport is governed by the steady conduction equation, no solution is possible without plastic dissipation as well. Upper and lower bounds are established for the thermodynamic variables, namely the shear stress, temperature, entropy, plastic strain, and heat flux, as functions of compression through the shock
11. Towards an understanding of resilience: responding to health systems shocks.
Science.gov (United States)
Hanefeld, Johanna; Mayhew, Susannah; Legido-Quigley, Helena; Martineau, Frederick; Karanikolos, Marina; Blanchet, Karl; Liverani, Marco; Yei Mokuwa, Esther; McKay, Gillian; Balabanova, Dina
2018-04-01
The recent outbreak of Ebola Virus Disease (EVD) in West Africa has drawn attention to the role and responsiveness of health systems in the face of shock. It brought into sharp focus the idea that health systems need not only to be stronger but also more 'resilient'. In this article, we argue that responding to shocks is an important aspect of resilience, examining the health system behaviour in the face of four types of contemporary shocks: the financial crisis in Europe from 2008 onwards; climate change disasters; the EVD outbreak in West Africa 2013-16; and the recent refugee and migration crisis in Europe. Based on this analysis, we identify '3 plus 2' critical dimensions of particular relevance to health systems' ability to adapt and respond to shocks; actions in all of these will determine the extent to which a response is successful. These are three core dimensions corresponding to three health systems functions: 'health information systems' (having the information and the knowledge to make a decision on what needs to be done); 'funding/financing mechanisms' (investing or mobilising resources to fund a response); and 'health workforce' (who should plan and implement it and how). These intersect with two cross-cutting aspects: 'governance', as a fundamental function affecting all other system dimensions; and predominant 'values' shaping the response, and how it is experienced at individual and community levels. Moreover, across the crises examined here, integration within the health system contributed to resilience, as does connecting with local communities, evidenced by successful community responses to Ebola and social movements responding to the financial crisis. In all crises, inequalities grew, yet our evidence also highlights that the impact of shocks is amenable to government action. All these factors are shaped by context. We argue that the '3 plus 2' dimensions can inform pragmatic policies seeking to increase health systems resilience.
12. Nonlinear Monte Carlo model of superdiffusive shock acceleration with magnetic field amplification
Science.gov (United States)
Bykov, Andrei M.; Ellison, Donald C.; Osipov, Sergei M.
2017-03-01
Fast collisionless shocks in cosmic plasmas convert their kinetic energy flow into the hot downstream thermal plasma with a substantial fraction of energy going into a broad spectrum of superthermal charged particles and magnetic fluctuations. The superthermal particles can penetrate into the shock upstream region producing an extended shock precursor. The cold upstream plasma flow is decelerated by the force provided by the superthermal particle pressure gradient. In high Mach number collisionless shocks, efficient particle acceleration is likely coupled with turbulent magnetic field amplification (MFA) generated by the anisotropic distribution of accelerated particles. This anisotropy is determined by fast particle transport, making the problem strongly nonlinear and multiscale. Here, we present a nonlinear Monte Carlo model of collisionless shock structure with superdiffusive propagation of high-energy Fermi accelerated particles coupled to particle acceleration and MFA, which affords a consistent description of strong shocks. A distinctive feature of the Monte Carlo technique is that it includes the full angular anisotropy of the particle distribution at all precursor positions. The model reveals that the superdiffusive transport of energetic particles (i.e., Lévy-walk propagation) generates a strong quadruple anisotropy in the precursor particle distribution. The resultant pressure anisotropy of the high-energy particles produces a nonresonant mirror-type instability that amplifies compressible wave modes with wavelengths longer than the gyroradii of the highest-energy protons produced by the shock.
13. Model for shock wave chaos.
Science.gov (United States)
Kasimov, Aslan R; Faria, Luiz M; Rosales, Rodolfo R
2013-03-08
We propose the following model equation, u(t) + 1/2(u(2)-uu(s))x = f(x,u(s)) that predicts chaotic shock waves, similar to those in detonations in chemically reacting mixtures. The equation is given on the half line, xorder partial differential equation. The chaos arises in the equation thanks to an interplay between the nonlinearity of the inviscid Burgers equation and a novel forcing term that is nonlocal in nature and has deep physical roots in reactive Euler equations.
International Nuclear Information System (INIS)
Faraj, Rami; Holnicki-Szulc, Jan; Knap, Lech; Seńko, Jarosław
2016-01-01
This paper introduces and discusses a new concept of impact absorption by means of impact energy management and storage in dedicated rotating inertial discs. The effectiveness of the concept is demonstrated in a selected case-study involving spinning management, a recently developed novel impact-absorber. A specific control technique performed on this device is demonstrated to be the main source of significant improvement in the overall efficiency of impact damping process. The influence of various parameters on the performance of the shock-absorber is investigated. Design and manufacturing challenges and directions of further research are formulated. (paper)
15. Barcoding heat shock proteins to human diseases: looking beyond the heat shock response.
Science.gov (United States)
Kakkar, Vaishali; Meister-Broekema, Melanie; Minoia, Melania; Carra, Serena; Kampinga, Harm H
2014-04-01
There are numerous human diseases that are associated with protein misfolding and the formation of toxic protein aggregates. Activating the heat shock response (HSR)--and thus generally restoring the disturbed protein homeostasis associated with such diseases--has often been suggested as a therapeutic strategy. However, most data on activating the HSR or its downstream targets in mouse models of diseases associated with aggregate formation have been rather disappointing. The human chaperonome consists of many more heat shock proteins (HSPs) that are not regulated by the HSR, however, and researchers are now focusing on these as potential therapeutic targets. In this Review, we summarize the existing literature on a set of aggregation diseases and propose that each of them can be characterized or 'barcoded' by a different set of HSPs that can rescue specific types of aggregation. Some of these 'non-canonical' HSPs have demonstrated effectiveness in vivo, in mouse models of protein-aggregation disease. Interestingly, several of these HSPs also cause diseases when mutated--so-called chaperonopathies--which are also discussed in this Review.
16. The application of front tracking to the simulation of shock refractions and shock accelerated interface mixing
International Nuclear Information System (INIS)
Sharp, D.H.; Grove, J.W.; Yang, Y.; Boston, B.; Holmes, R.; Zhang, Q.; Glimm, J.
1993-01-01
The mixing behavior of two or more fluids plays an important role in a number of physical processes and technological applications. The authors consider two basic types of mechanical (i.e., non-diffusive) fluid mixing. If a heavy fluid is suspended above a lighter fluid in the presence of a gravitational field, small perturbations at the fluid interface will grow. This process is known as the Rayleigh-Taylor instability. One can visualize this instability in terms of bubbles of the light fluid rising into the heavy fluid, and fingers (spikes) of the heavy fluid falling into the light fluid. A similar process, called the Richtmyer-Meshkov instability occurs when an interface is accelerated by a shock wave. These instabilities have several common features. Indeed, Richtmyer's approach to understanding the shock induced instability was to view that process as resulting from an acceleration of the two fluids by a strong gravitational field acting for a short time. Here, the authors report new results on the Rayleigh-Taylor and Richtmyer-Meshkov instabilities. Highlights include calculations of Richtmyer-Meshkov instabilities in curved geometries without grid orientation effects, improved agreement between computations and experiments in the case of Richtmyer-Meshkov instabilities at a plane interface, and a demonstration of an increase in the Rayleigh-Taylor mixing layer growth rate with increasing compressibility, along with a loss of universality of this growth rate. The principal computational tool used in obtaining these results was a code based on the front tracking method
17. Effect of the dynamic pressure on the shock wave structure in a rarefied polyatomic gas
Energy Technology Data Exchange (ETDEWEB)
Taniguchi, Shigeru, E-mail: [email protected]; Sugiyama, Masaru, E-mail: [email protected] [Graduate School of Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Arima, Takashi, E-mail: [email protected] [Center for Social Contribution and Collaboration, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Ruggeri, Tommaso, E-mail: [email protected] [Department of Mathematics and Research Center of Applied Mathematics (CIRAM), University of Bologna, Bologna (Italy)
2014-01-15
We study the shock wave structure in a rarefied polyatomic gas based on a simplified model of extended thermodynamics in which the dissipation is due only to the dynamic pressure. In this case the differential system is very simple because it is a variant of Euler system with a new scalar equation for the dynamic pressure [T. Arima, S. Taniguchi, T. Ruggeri, and M. Sugiyama, Phys. Lett. A 376, 2799–2803 (2012)]. It is shown that this theory is able to describe the three types of the shock wave structure observed in experiments: the nearly symmetric shock wave structure (Type A, small Mach number), the asymmetric structure (Type B, moderate Mach number), and the structure composed of thin and thick layers (Type C, large Mach number)
18. TRIGGERING COLLAPSE OF THE PRESOLAR DENSE CLOUD CORE AND INJECTING SHORT-LIVED RADIOISOTOPES WITH A SHOCK WAVE. II. VARIED SHOCK WAVE AND CLOUD CORE PARAMETERS
Energy Technology Data Exchange (ETDEWEB)
Boss, Alan P.; Keiser, Sandra A., E-mail: [email protected], E-mail: [email protected] [Department of Terrestrial Magnetism, Carnegie Institution, 5241 Broad Branch Road, NW, Washington, DC 20015-1305 (United States)
2013-06-10
A variety of stellar sources have been proposed for the origin of the short-lived radioisotopes that existed at the time of the formation of the earliest solar system solids, including Type II supernovae (SNe), asymptotic giant branch (AGB) and super-AGB stars, and Wolf-Rayet star winds. Our previous adaptive mesh hydrodynamics models with the FLASH2.5 code have shown which combinations of shock wave parameters are able to simultaneously trigger the gravitational collapse of a target dense cloud core and inject significant amounts of shock wave gas and dust, showing that thin SN shocks may be uniquely suited for the task. However, recent meteoritical studies have weakened the case for a direct SN injection to the presolar cloud, motivating us to re-examine a wider range of shock wave and cloud core parameters, including rotation, in order to better estimate the injection efficiencies for a variety of stellar sources. We find that SN shocks remain as the most promising stellar source, though planetary nebulae resulting from AGB star evolution cannot be conclusively ruled out. Wolf-Rayet (WR) star winds, however, are likely to lead to cloud core shredding, rather than to collapse. Injection efficiencies can be increased when the cloud is rotating about an axis aligned with the direction of the shock wave, by as much as a factor of {approx}10. The amount of gas and dust accreted from the post-shock wind can exceed that injected from the shock wave, with implications for the isotopic abundances expected for a SN source.
19. Shock compression profiles in ceramics
Energy Technology Data Exchange (ETDEWEB)
1996-03-01
An investigation of the shock compression properties of high-strength ceramics has been performed using controlled planar impact techniques. In a typical experimental configuration, a ceramic target disc is held stationary, and it is struck by plates of either a similar ceramic or by plates of a well-characterized metal. All tests were performed using either a single-stage propellant gun or a two-stage light-gas gun. Particle velocity histories were measured with laser velocity interferometry (VISAR) at the interface between the back of the target ceramic and a calibrated VISAR window material. Peak impact stresses achieved in these experiments range from about 3 to 70 GPa. Ceramics tested under shock impact loading include: Al{sub 2}O{sub 3}, AlN, B{sub 4}C, SiC, Si{sub 3}N{sub 4}, TiB{sub 2}, WC and ZrO{sub 2}. This report compiles the VISAR wave profiles and experimental impact parameters within a database-useful for response model development, computational model validation studies, and independent assessment of the physics of dynamic deformation on high-strength, brittle solids.
20. Shock-resistant scintillation detector
International Nuclear Information System (INIS)
Novak, W.P.
1979-01-01
A unique scintillation detector unit is disclosed which employs a special light transfer and reflector means that encases and protects the scintillator crystal against high g forces. The light transfer means comprises a flexible silicon rubber optical material bonded between the crystal and the optical window and having an axial thickness sufficient to allow the scintillator to move axially inside the container under high g forces without destroying the bonds. The reflector means comprises a soft elastic silicone rubber sleeve having a multiplicity of closely arranged tapered protrusions radiating toward and engaging the periphery of the scintillator crystal to cushion shocks effectively and having a reflective material, such as aluminum oxide powder, in the spaces between the protrusions. The reflector means provides improved shock absorption because of the uniform support and cushioning action of the protrusions and also provides the detector with high efficiency. The silicon rubber composition is specially compounded to include a large amount of aluminum oxide which enables the rubber to function effectively as a light reflector
1. Shock Absorbers Multi-Modeling and Suspension Optimization
Directory of Open Access Journals (Sweden)
LUPU Ciprian
2013-05-01
Full Text Available The standard dampers used by more 90% of vehicles have damping coefficients constant along stroke, so they can’t solve simultaneous all of them, situation solving practically using a relative dampingcoefficient able to made compromise between them. This paper design and simulation testing multi-models of two types of Damp (DSA and VZN. To compare the two types of suspension they are simulated in various road and load conditions. Analysis of simulation results is presente a new VZN shock absorber. This is an invention of the Institute of Mechanics of the Romanian Academy, and patented at European and U.S. [1], [2]. This is Called VZN shock absorber, iscoming from Variable Zeta Necessary acronym, for well moving in all road and load Conditions, Where zeta Represents the relative damping, Which is Adjusted automatically, stepwise, According to the piston positions [3,4,5]. Suspension systems are used in all air and ground transportation to protect that building transportation and cargo transported around against shocks and vibrations induced in the systemfrom the road Modifying damping coefficients (Zeta function piston position, being correlated with vehicle load and road unevenness.
2. Significance of Environmental Density in Shocked Poststarburst Galaxy Evolution
Science.gov (United States)
Jaliff, Laura
2018-01-01
The Shocked POstarbusrt Galaxy Survey (SPOGS) comprises 1,066 galaxies undergoing the transformation from blue cloud late-type spirals to red sequence non-star-forming early-type ellipticals and lenticulars. They are selected via spectral analysis of ionized gas line ratios, which indicate shocked objects, and Balmer H-δ equivalent width, which select recently formed stars, but not active star formation. E+A galaxies (Zabludoff et al. 1996), like SPOGs, contain young stars but, unlike SPOGs, no emission lines consistent with star formation. They differ in that the quality used to discern SPOGs, their shocks, produces H-α lines that prevent them from being found via the same criteria as E+As. Thus, SPOGs can be found before being entirely stripped of their gas, and, while E+As are largely red and dead, found leaving the green valley, SPOGS are mostly entering it. The environmental density data for SPOGs was retrieved via the NASA Extragalactic Database (NED) radial velocity constrained cone tool, which provides counts and densities within spheres of radii 1, 5, and 10 Mpc from the center of search as well as relative positions and redshifts of objects. The kinematic morphology-density relation (Cappellari et al. 2011) is employed as a point of comparison for how SPOGs’ environmental densities might relate to morphological and spectroscopic factors, including tidal features, asymmetry, and color, in order to fully understand the role of environmental factors in SPOGS object evolution.
3. A primary standard for low-g shock calibration by laser interferometry
International Nuclear Information System (INIS)
Sun, Qiao; Wang, Jian-lin; Hu, Hong-bo
2014-01-01
This paper presents a novel implementation of a primary standard for low-g shock acceleration calibration by laser interferometry based on rigid body collision at National Institute of Metrology, China. The mechanical structure of the standard device and working principles involved in the shock acceleration exciter, laser interferometers and virtual instruments are described. The novel combination of an electromagnetic exciter and a pneumatic exciter as the mechanical power supply of the standard device can deliver a wide range of shock acceleration levels. In addition to polyurethane rubber, two other types of material are investigated to ensure a wide selection of cushioning pads for shock pulse generation, with pulse shapes and data displayed. A heterodyne He–Ne laser interferometer is preferred for its precise and reliable measurement of shock acceleration while a homodyne one serves as a check standard. Some calibration results of a standard acceleration measuring chain are shown in company with the uncertainty evaluation budget. The expanded calibration uncertainty of shock sensitivity of the acceleration measuring chain is 0.8%, k = 2, with the peak acceleration range from 20 to 10 000 m s −2 and pulse duration from 0.5 to 10 ms. This primary shock standard can meet the traceability requirements of shock acceleration from various applications of industries from automobile to civil engineering and therefore is used for piloting the ongoing shock comparison of Technical Committee of Acoustics, Ultrasound and Vibration (TCAUV) of Asia Pacific Metrology Program (APMP), coded as APMP.AUV.V-P1. (paper)
4. Experimental study of radiative shocks at PALS facility
Czech Academy of Sciences Publication Activity Database
Stehlé, C.; Gonzalez, M.; Kozlová, Michaela; Rus, Bedřich; Mocek, Tomáš; Acef, O.; Colombier, J.P.; Lanz, T.; Champion, N.; Jakubczak, Krzysztof; Polan, Jiří; Barroso, P.; Baudin, D.; Audit, E.; Dostál, Jan; Stupka, Michal
2010-01-01
Roč. 28, č. 2 (2010), s. 253-261 ISSN 0263-0346 R&D Projects: GA MŠk(CZ) LC528 Institutional research plan: CEZ:AV0Z10100523 Keywords : laboratory astrophysics * hydrodynamics * laser plasmas * shocks * stellar formation Subject RIV: BH - Optics, Masers, Lasers Impact factor: 3.656, year: 2010 http://journals.cambridge.org/action/displayFulltext?type=6&fid=7807203&jid=LPB&volumeId=28&issueId=02&aid=7807202&fulltextType=RA&fileId=S02630346100
5. Efficient OCT Image Enhancement Based on Collaborative Shock Filtering.
Science.gov (United States)
Liu, Guohua; Wang, Ziyu; Mu, Guoying; Li, Peijin
2018-01-01
Efficient enhancement of noisy optical coherence tomography (OCT) images is a key task for interpreting them correctly. In this paper, to better enhance details and layered structures of a human retina image, we propose a collaborative shock filtering for OCT image denoising and enhancement. Noisy OCT image is first denoised by a collaborative filtering method with new similarity measure, and then the denoised image is sharpened by a shock-type filtering for edge and detail enhancement. For dim OCT images, in order to improve image contrast for the detection of tiny lesions, a gamma transformation is first used to enhance the images within proper gray levels. The proposed method integrating image smoothing and sharpening simultaneously obtains better visual results in experiments.
6. Shock-wave structure formation in a dusty plasma
International Nuclear Information System (INIS)
Popel', S.I.; Golub', A.P.; Loseva, T.V.; Bingkhem, R.; Benkadda, S.
2001-01-01
Nonstationary problem on evolution perturbation and its transformation into nonlinear wave structure is considered. The method developed permits finding solution to the system of nonlinear evolution equations describing dust particles with variable charge, Boltzmann electron and inertia ions. An accurate stationary solution as ion-sonic wave structures explained by anomalous dissipation due to electric discharge of dust particles was found. Evolution of two types of initial perturbations was studied, i.e.: soliton and immobile region with increased density of ions - a step. Soliton evolution in plasma with variable charge of dust particles results in the appearance on nonstationary shock-wave structure, whereas the step evolution gives rise to appearance of a shock wave similar to the stationary one along with rarefaction wave [ru
7. Observation of a flare-generated shock wave at 9.7 AU by Pioneer 10
International Nuclear Information System (INIS)
Dryer, M.; Shea, M.A.; Smart, D.F.; Collard, H.R.; Mihalov, J.D.; Wolfe, J.H.; Warwick, J.W.
1978-01-01
The period March 15 to May 15, 1976, was declared in advance to be the internationally recognized Study of Traveling Interplanetary Phenomena Interval II. A variety of ground- and space-based equipment was requested to make coordinated studies during this part of the minimum of solar cycle 20. Following an absence of solar activity for a long period, several type II radio bursts on March 20, 1976, produced by two solar flares behind the east limb heralded a series of solar interplanetary, and terrestrial events. These solar radio astronomical observations were followed by non-Io-associated radio emission from Jupiter and solar wind plasma detection at Pioneer 10 at 9.7 AU of an apparent shock wave on March 30 and April 9, 1976, respectively. In view of the fact that the solar flares on March 20 were essentially at central meridian with respect to Jupiter and Pioneer 10 and also that the sun was extremely inactive prior to that date we consider the circumstantial evidence that at least one solar-flare-generated shock wave propagated to the position of Pioneer 10. The average velocities of this shock wave, together with the inferred type II velocity, support previous observations and theory concerning the rapid deceleration and survival of interplanetary shock waves to distances at least as large as approx.10 AU. It is therefore believed that dissipation (other than that within shocks themselves) plays an insignificant role in shock wave dynamics within the solar wind
8. Constraining the magnitude of the largest event in a foreshock-main shock-aftershock sequence
Science.gov (United States)
Shcherbakov, Robert; Zhuang, Jiancang; Ogata, Yosihiko
2018-01-01
Extreme value statistics and Bayesian methods are used to constrain the magnitudes of the largest expected earthquakes in a sequence governed by the parametric time-dependent occurrence rate and frequency-magnitude statistics. The Bayesian predictive distribution for the magnitude of the largest event in a sequence is derived. Two types of sequences are considered, that is, the classical aftershock sequences generated by large main shocks and the aftershocks generated by large foreshocks preceding a main shock. For the former sequences, the early aftershocks during a training time interval are used to constrain the magnitude of the future extreme event during the forecasting time interval. For the latter sequences, the earthquakes preceding the main shock are used to constrain the magnitudes of the subsequent extreme events including the main shock. The analysis is applied retrospectively to past prominent earthquake sequences.
9. Ion acceleration at the earth's bow shock: A review of observations in the upstream region
International Nuclear Information System (INIS)
Gosling, J.T.; Asbridge, J.R.; Bame, S.J.; Feldman, W.C.
1979-01-01
Positive ions are accelerated at or near the earth's bow shock and propagate into the upstream region. Two distinctly different population of these ions, distinguished by their greatly different spectral and angular widths, can be identified there. The type of ion population observed in the upstream region is strongly correlated with the presence or absence of long-period compresive waves in the solar wind. Very few ions are accelerated in the vicinity of the shock to energies much above about 100 keV. It is not yet clear whether the most energetic ions (i.e. those near 100 keV) are accelerated at the shock or in the broad disturbed region upstream from the shock. In either case stochastic acceleration by turbulent electrostatic fields seems to be the most viable candidate for the acceleration of the most energetic particles
10. Low-frequency electrostatic shock excitations in a multi-component dusty plasma
Energy Technology Data Exchange (ETDEWEB)
Ferdousi, M.; Miah, M.R.; Sultana, S.; Mamun, A.A., E-mail: [email protected] [Department of Physics, Jahangirnagar University, Savar (Bangladesh)
2015-10-01
Dust-acoustic shock waves are investigated in a four-component plasma consisting of arbitrarily charged inertial dusts, Boltzmann distributed negatively charged heavy ions, positively charged light ions, and electrons. The reductive perturbation technique is employed in order to derive the nonlinear time evolution Burgers-type equation. The properties of dust-acoustic shock waves are analysed via the solution of Burgers equation. It is observed that the basic features of dust-acoustic shock waves are significantly modified due to the influence of arbitrarily charged dusts, Maxwellian electrons, number density and temperatures of heavier and lighter ions, and dust kinematic viscosity. Both polarity (positive and negative potential) shock waves are also found to exists in the plasma under consideration in this manuscript. The findings of this investigation may be used in understanding the dust-acoustic wave properties in both laboratory and space plasmas. (author)
11. Low-frequency electrostatic shock excitations in a multi-component dusty plasma
International Nuclear Information System (INIS)
Ferdousi, M.; Miah, M.R.; Sultana, S.; Mamun, A.A.
2015-01-01
Dust-acoustic shock waves are investigated in a four-component plasma consisting of arbitrarily charged inertial dusts, Boltzmann distributed negatively charged heavy ions, positively charged light ions, and electrons. The reductive perturbation technique is employed in order to derive the nonlinear time evolution Burgers-type equation. The properties of dust-acoustic shock waves are analysed via the solution of Burgers equation. It is observed that the basic features of dust-acoustic shock waves are significantly modified due to the influence of arbitrarily charged dusts, Maxwellian electrons, number density and temperatures of heavier and lighter ions, and dust kinematic viscosity. Both polarity (positive and negative potential) shock waves are also found to exists in the plasma under consideration in this manuscript. The findings of this investigation may be used in understanding the dust-acoustic wave properties in both laboratory and space plasmas. (author)
12. Fluid Replacement in Treatment of Hypovolemia and Shock: Crystalloids and Colloids
Directory of Open Access Journals (Sweden)
Fatih Yildiz
2013-06-01
Full Text Available Shock is a pathologic state with high mortality rate and characterized by a reduction of systemic tissue perfusion and decresead oxygen delivery. Absolute or relative hypovolemia is a common pathology of most shock types. Correction of hypovolemia might reverse the disturbance and increase the tissue perfusion. Fluid resuscitation with crystalloid and colloid solutions can carry the risk of increasing morbidity and mortality if not used properly. Although crystalloid and colloid solutions are considered to have equal efficacy and safety profile, recent studies showed that this assumption may not be correct. Early and effective management of hypovolemia is the cornerstone of shock resuscitation. Initial management of patients with septic shock and hypovolemia should be done with 30ml/kg of crystalloids. Proper fluid replacement and resuscitation algoritms might increase the survival rate. [Archives Medical Review Journal 2013; 22(3.000: 347-361
13. Ion acceleration at the earth's bow shock: a review of observations in the upstream region
International Nuclear Information System (INIS)
Gosling, J.T.; Asbridge, J.R.; Bame, S.J.; Feldman, W.C.
1979-01-01
Positive ions are accelerated at or near the earth's bow shock and propagate into the upstream region. Two distinctly different populations of these ions, distinguished by their greatly different spectral and angular widths, can be identified there. The type of ion population observed in the upstream region is strongly correlated with the presence or absence of long-period compressive waves in the solar wind. Very few ions are accelerated in the vicinity of the shock to energies much above about 100 keV. It is not yet clear whether the most energetic ions (i.e., those near 100 keV) are accelerated at the shock or in broad disturbed region upstream from the shock. In either case stochastic acceleration by turbulent electrostatic fields seems to be the most viable candidate for the acceleration of the most energetic particles
14. The ''injection problem'' for quasiparallel shocks
International Nuclear Information System (INIS)
Zank, G. P.; Rice, W. K. M.; le Roux, J. A.; Cairns, I. H.; Webb, G. M.
2001-01-01
For a particle to be accelerated diffusively at a shock by the first-order Fermi acceleration mechanism, the particle must be sufficiently energetic that it can scatter across all the micro- and macrostructure of the shock, experiencing compression between the converging upstream and downstream states. This is the well-known ''injection problem.'' Here the interaction of ions with the ramp of a quasiparallel shock is investigated. Some ions incident on the shock experience specular reflection, caused either by the cross-shock electrostatic potential or by mirroring as the magnetic field is bent and compressed through the ramp. Scattering of reflected ions by self-generated and pre-existing turbulence in the region upstream of the shock then acts to trap backstreaming ions and return them to the ramp, where some experience further reflections. Such repeated reflections and scattering energize a subpopulation of ions up to energies sufficiently large that they can be diffusively shock accelerated. Two ion distributions are considered: pickup ions which are assumed to be described by a shell distribution, are thermal solar wind ions which may be described by a kappa distribution. Injection efficiencies are found analytically to be very high for pickup ions and much lower for thermal solar wind ions, suggesting that this injection mechanism, stochastic reflected ion or SRI acceleration, is a natural precursor for the acceleration of the anomalous cosmic ray component at a quasiparallel shock. While significantly less efficient, SRI acceleration is also viable for thermal solar wind ions described by a kappa distribution
15. PRECURSORS TO INTERSTELLAR SHOCKS OF SOLAR ORIGIN
Energy Technology Data Exchange (ETDEWEB)
Gurnett, D. A.; Kurth, W. S. [University of Iowa, Department of Physics and Astronomy, Iowa City, IA 52242 (United States); Stone, E. C.; Cummings, A. C. [California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Krimigis, S. M.; Decker, R. B. [Applied Physics Laboratory/JHU, 11100 Johns Hopkins Road, Laurel, MD 20723 (United States); Ness, N. F. [Catholic University of America, 620 Michigan Avenue NE, Washington, DC 20064 (United States); Burlaga, L. F., E-mail: [email protected] [NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States)
2015-08-20
On or about 2012 August 25, the Voyager 1 spacecraft crossed the heliopause into the nearby interstellar plasma. In the nearly three years that the spacecraft has been in interstellar space, three notable particle and field disturbances have been observed, each apparently associated with a shock wave propagating outward from the Sun. Here, we present a detailed analysis of the third and most impressive of these disturbances, with brief comparisons to the two previous events, both of which have been previously reported. The shock responsible for the third event was first detected on 2014 February 17 by the onset of narrowband radio emissions from the approaching shock, followed on 2014 May 13 by the abrupt appearance of intense electron plasma oscillations generated by electrons streaming outward ahead of the shock. Finally, the shock arrived on 2014 August 25, as indicated by a jump in the magnetic field strength and the plasma density. Various disturbances in the intensity and anisotropy of galactic cosmic rays were also observed ahead of the shock, some of which are believed to be caused by the reflection and acceleration of cosmic rays by the magnetic field jump at the shock, and/or by interactions with upstream plasma waves. Comparisons to the two previous weaker events show somewhat similar precursor effects, although differing in certain details. Many of these effects are very similar to those observed in the region called the “foreshock” that occurs upstream of planetary bow shocks, only on a vastly larger spatial scale.
16. Corporate Policies with Permanent and Transitory Shocks
NARCIS (Netherlands)
J-P. Decamps (Jean-Paul); S. Gryglewicz (Sebastian); E. Morellec (Erwan); S. Villeneuve (Stephane)
2016-01-01
textabstractWe model the financing, cash holdings, and hedging policies of a firm facing financing frictions and subject to permanent and transitory cash flow shocks. We show that permanent and transitory shocks generate distinct, sometimes opposite, effects on corporate policies and use the model
17. Shock dynamics in layered periodic media
KAUST Repository
Ketcheson, David I.; Leveque, Randall J.
2012-01-01
of shock waves in a one-dimensional periodic layered medium by a computational study of time-reversibility and entropy evolution. We find that periodic layered media tend to inhibit shock formation. For small initial conditions and large impedance variation
18. Particle acceleration and shock wave structure
International Nuclear Information System (INIS)
DRURY, L.O'C.
1989-01-01
A significant determinant in the large-scale structure and evolution of strong collisionless shocks under astrophysical conditions is probably the acceleration of charged particles. The reaction of these particles on the dynamical structure of the shock wave is discussed both theoretically and in the light of recent numerical calculations. Astrophysical implications for the evolution of supernova remnants, are considered. (author). 15 refs
19. Laser shock wave and its applications
Science.gov (United States)
Yang, Chaojun; Zhang, Yongkang; Zhou, Jianzhong; Zhang, Fang; Feng, Aixin
2007-12-01
The technology of laser shock wave is used to not only surface modification but also metal forming. It can be divided into three parts: laser shock processing, laser shock forming (LSF) and laser peenforming(LPF). Laser shock processing as a surface treatment to metals can make engineering components have a residual compressive stress so that it obviously improves their fatigue strength and stress corrosion performances, while laser shock forming (LSF) is a novel technique that is used in plastic deformation of sheet metal recently and Laser peen forming (LPF) is another new sheet metal forming process presented in recent years. They all can be carried out by a high-power and repetition pulse Nd:Glass laser device made by Jiangsu University. Laser shock technology has characterized of ultrahigh pressure and high strain rate (10 6 - 10 7s -1). Now, for different materials, we are able to form different metals to contours and shapes and simultaneity leave their surfaces in crack-resistant compressive stress state. The results show that the technology of laser shock wave can strengthen surface property and prolong fatigue life and especially can deform metals to shapes that could not be adequately made using conventional methods. With the development of the technology of laser shock wave, the applied fields of laser will become greater and greater.
20. Shock loading predictions from application of indicial theory to shock-turbulence interactions
Science.gov (United States)
Keefe, Laurence R.; Nixon, David
1991-01-01
A sequence of steps that permits prediction of some of the characteristics of the pressure field beneath a fluctuating shock wave from knowledge of the oncoming turbulent boundary layer is presented. The theory first predicts the power spectrum and pdf of the position and velocity of the shock wave, which are then used to obtain the shock frequency distribution, and the pdf of the pressure field, as a function of position within the interaction region. To test the validity of the crucial assumption of linearity, the indicial response of a normal shock is calculated from numerical simulation. This indicial response, after being fit by a simple relaxation model, is used to predict the shock position and velocity spectra, along with the shock passage frequency distribution. The low frequency portion of the shock spectra, where most of the energy is concentrated, is satisfactorily predicted by this method.
1. Shock-induced devolatilization of calcite
Science.gov (United States)
Boslough, M. B.; Ahrens, T. J.; Vizgirda, J.; Becker, R. H.; Epstein, S.
1982-01-01
Experimental measurements of the release adiabats by Vizgirda (1981) indicate that substantial vaporization takes place upon release from shock pressures of 37 GPa for calcite and 14 GPa for aragonite. The present investigation includes the first controlled partial vaporization experiments on calcite. The experiments were conducted to test the predictions of the release adiabat experiments. The quantities of the gaseous species produced from shocked calcite and their carbon and oxygen isotopic compositions were determined, and the shock-induced effect on the Mn(2+) electron spin resonance spectrum in the shock-recovered calcite was observed. On the basis of the obtained results, it is concluded that shock stresses at the 17-18 GPa level give rise to volatilization of 0.03-0.3 (mole) percent of calcite to CO2 and CO. The devolatilization of calcite occurs at low pressure at significantly lower entropy densities than predicted on the basis of thermodynamic continuum models.
2. Shock waves in helium at low temperatures
International Nuclear Information System (INIS)
Liepmann, H.W.; Torczynski, J.R.
1986-01-01
Results are reported from studies of the properties of low temperature He-4 using shock waves as a probe. Ideal shock tube theory is used to show that sonic speeds of Mach 40 are attainable in He at 300 K. Viscosity reductions at lower temperatures minimize boundary layer effects at the side walls. A two-fluid model is described to account for the phase transition which He undergoes at temperatures below 2.2 K, after which the quantum fluid (He II) and the normal compressed superfluid (He I) coexist. Analytic models are provided for pressure-induced shocks in He I and temperature-induced shock waves (called second sound) which appear in He II. The vapor-fluid interface of He I is capable of reflecting second and gasdynamic sound shocks, which can therefore be used as probes for studying phase transitions between He I and He II. 17 references
3. Analytical extension of curved shock theory
Science.gov (United States)
Emanuel, G.
2018-03-01
Curved shock theory (CST) is limited to shock waves in a steady, two-dimensional or axisymmetric (2-Ax) flow of a perfect gas. A unique feature of CST is its use of intrinsic coordinates that result in an elegant and useful formulation for flow properties just downstream of a shock. For instance, the downstream effect of upstream vorticity, shock wave curvature, and the upstream pressure gradient along a streamline is established. There have been several attempts to extend CST, as mentioned in the text. Removal of the steady, 2-Ax, and perfect gas limitations, singly or in combination, requires an appropriate formulation of the shock wave's jump relations and the intrinsic coordinate Euler equations. Issues discussed include flow plane versus osculating plane, unsteady flow, vorticity, an imperfect gas, etc. The extension of CST utilizes concepts from differential geometry, such as the osculating plane, streamline torsion, and the Serret-Frenet equations.
4. 28th International Symposium on Shock Waves
CERN Document Server
2012-01-01
The University of Manchester hosted the 28th International Symposium on Shock Waves between 17 and 22 July 2011. The International Symposium on Shock Waves first took place in 1957 in Boston and has since become an internationally acclaimed series of meetings for the wider Shock Wave Community. The ISSW28 focused on the following areas: Blast Waves, Chemically Reacting Flows, Dense Gases and Rarefied Flows, Detonation and Combustion, Diagnostics, Facilities, Flow Visualisation, Hypersonic Flow, Ignition, Impact and Compaction, Multiphase Flow, Nozzle Flow, Numerical Methods, Propulsion, Richtmyer-Meshkov, Shockwave Boundary Layer Interaction, Shock Propagation and Reflection, Shock Vortex Interaction, Shockwave Phenomena and Applications, as well as Medical and Biological Applications. The two Volumes contain the papers presented at the symposium and serve as a reference for the participants of the ISSW 28 and individuals interested in these fields.
Energy Technology Data Exchange (ETDEWEB)
Menikoff, Ralph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-01-12
The barrier experiments are a variant of the gap test; a detonation wave in a donor HE impacts a barrier and drives a shock wave into an acceptor HE. The question we ask is: What is the trade-off between the barrier material and threshold barrier thickness to prevent the acceptor from detonating. This can be viewed from the perspective of shock initiation of the acceptor subject to a complex pressure drive condition. Here we consider key factors which affect whether or not the acceptor undergoes a shock-to-detonation transition. These include the following: shock impedance matches for the donor detonation wave into the barrier and then the barrier shock into the acceptor, the pressure gradient behind the donor detonation wave, and the curvature of detonation front in the donor. Numerical simulations are used to illustrate how these factors affect the reaction in the acceptor.
6. Counseling Centers Lack Resources to Help Troubled Students
Science.gov (United States)
Farrell, Elizabeth F.
2008-01-01
The fatal shootings at Northern Illinois University this month were shocking yet familiar. For the second time in 10 months, a student with a record of mental-health problems went on a killing spree at a large public university. Ever since a disturbed student fatally shot 32 students and professors at Virginia Tech last April, college…
7. Small-Scale Shock Testing of Propellants and Ingredients
National Research Council Canada - National Science Library
Dawley, S
2004-01-01
.... The use of small-scale gap testing to evaluate the shock sensitivity of individual propellant ingredients and propellant formulations is a valuable method for experimentally establishing shock...
8. Thermal shock analysis of liquid-mercury spallation target
CERN Document Server
Ishikura, S; Futakawa, M; Hino, R; Date, H
2002-01-01
The developments of the neutron scattering facilities are carried out under the high-intensity proton accelerator project promoted by JAERI and KEK. To estimate the structural integrity of the heavy liquid-metal (Hg) target used as a spallation neutron source in a MW-class neutron scattering facility, dynamic stress behavior due to the incident of a 1 MW-pulsed proton beam was analyzed by using FEM code. Two-type target containers with semi-cylindrical type and flat-plate type window were used as models for analyses. As a result, it is confirmed that the stress (pressure wave) generated by dynamic thermal shock becomes the largest at the center of window, and the flat-plate type window is more advantageous from the structural viewpoint than the semi-cylindrical type window. It has been understood that the stress generated in the window by the pressure wave can be treated as the secondary stress. (author)
9. Application of 133Xe encephalography in lack blood diseases
International Nuclear Information System (INIS)
Xie Zhiyuan; Guo Huiying
1993-01-01
The determination of local blood flow in brain gray matter (rCBF) using the type CGEM 2000 133 Xe encephalography is a reliable indication for judging the degree of lack blood disease. For all the inspected patients the scalp analogy localization is used. 28 probes are applied to some regions of the forehead, the vertex, the temporal folium and the occipital folium. The localization is accurate and repeatable. The result of rCBF determination is similar to XCT, but its range is rather wider than XCT. Therefore, the rCBF determination in clinic diagnosis is reliable and can give the rCBF value qualitatively. It can be used not only for diagnosing the decease in brain, but also for the predication before apoplexy, especially for vertigo disease to be inspected. For the vertigo disease of middle age and old man, the first consideration should be the decreasing of rCBF value. For the inspection of thrombus of neck artery system, it can reflect the real range of pathological changes correctly. The method is superior to XCT for treatment planning, estimating the results, supervising the effect treatment, and the diagnosis of acute cerebral embolism. In China, the morbidity rate, the sickness rate, the disability rate and recurrent rate of cerebrovascular disease are very high, especially for the old man. Satisfactory results for 1010 cases altogether are obtained by using type CGEM 2000 cerebral angiography technique for the screening
10. An interferometric and numerical study of pseudo-stationary oblique-shock-wave reflections in sulfur hexafluoride (SF6)
Science.gov (United States)
Hu, T. C. J.; Glass, I. I.
Results are reported from experimental and analytical investigations of real-gas effects in the propagation of shock waves through SF6, a gas with 15 vibrational degrees of freedom. Shock waves with speeds ranging from Mach 1.25-8 were directed toward sharp steel wedges in a hypervelocity shock tube. Mach-Zehnder interferometry was used to obtain shock shape and geometry, isopycnic and density field data. Frozen-gas and equilibrium-gas (EQM) analyses modeling were performed for comparisons with experimental data, which depicted four types of reflection and transitions among them. Transition boundaries were best predicted with EQM treatment. A new criterion was derived for transition between single-Mach and complex-Mach reflection. Regular reflection continued past the boundary line defined by the transition criterion because of boundary layer growth produced on the wedge surface by passage of the shock wave.
11. Kinetic instabilities in plasmas: from electromagnetic fluctuations to collisionless shocks
International Nuclear Information System (INIS)
Ruyer, Charles
2014-01-01
Collisionless shocks play a major role in powerful astrophysical objects (e.g., gamma-ray bursts, supernova remnants, pulsar winds, etc.), where they are thought to be responsible for non-thermal particle acceleration and radiation. Numerical simulations have shown that, in the absence of an external magnetic field, these self-organizing structures originate from electromagnetic instabilities triggered by high-velocity colliding flows. These Weibel-like instabilities are indeed capable of producing the magnetic turbulence required for both efficient scattering and Fermi-type acceleration. Along with rapid advances in their theoretical understanding, intense effort is now underway to generate collisionless shocks in the laboratory using energetic lasers. In a first part we study the (w,k)-resolved electromagnetic thermal spectrum sustained by a drifting relativistic plasma. In particular, we obtain analytical formulae for the fluctuation spectra, the latter serving as seeds for growing magnetic modes in counterstreaming plasmas. Distinguishing between sub-luminal and supra-luminal thermal fluctuations, we derived analytical formulae of their respective spectral contributions. Comparisons with particle-in-cell (PIC) simulations are made, showing close agreement in the sub-luminal regime along with some discrepancy in the supra-luminal regime. Our formulae are then used to estimate the saturation time of the Weibel instability of relativistic pair plasmas. Our predictions are shown to match 2-D particle-in-cell (PIC) simulations over a three-decade range in flow energy. We then develop a predictive kinetic model of the nonlinear phase of the Weibel instability induced by two counter-streaming, symmetric and non-relativistic ion beams. This self consistent, fully analytical model allows us to follow the evolution of the beams' properties up to a stage close to complete isotropization and thus to shock formation. Its predictions are supported by 2D and 3D particle
12. Shock Mechanism Analysis and Simulation of High-Power Hydraulic Shock Wave Simulator
Directory of Open Access Journals (Sweden)
Xiaoqiu Xu
2017-01-01
Full Text Available The simulation of regular shock wave (e.g., half-sine can be achieved by the traditional rubber shock simulator, but the practical high-power shock wave characterized by steep prepeak and gentle postpeak is hard to be realized by the same. To tackle this disadvantage, a novel high-power hydraulic shock wave simulator based on the live firing muzzle shock principle was proposed in the current work. The influence of the typical shock characteristic parameters on the shock force wave was investigated via both theoretical deduction and software simulation. According to the obtained data compared with the results, in fact, it can be concluded that the developed hydraulic shock wave simulator can be applied to simulate the real condition of the shocking system. Further, the similarity evaluation of shock wave simulation was achieved based on the curvature distance, and the results stated that the simulation method was reasonable and the structural optimization based on software simulation is also beneficial to the increase of efficiency. Finally, the combination of theoretical analysis and simulation for the development of artillery recoil tester is a comprehensive approach in the design and structure optimization of the recoil system.
13. A Prognostic Model for Development of Profound Shock among Children Presenting with Dengue Shock Syndrome.
Directory of Open Access Journals (Sweden)
Phung Khanh Lam
Full Text Available To identify risk factors and develop a prediction model for the development of profound and recurrent shock amongst children presenting with dengue shock syndrome (DSS.We analyzed data from a prospective cohort of children with DSS recruited at the Paediatric Intensive Care Unit of the Hospital for Tropical Disease in Ho Chi Minh City, Vietnam. The primary endpoint was "profound DSS", defined as ≥2 recurrent shock episodes (for subjects presenting in compensated shock, or ≥1 recurrent shock episodes (for subjects presenting initially with decompensated/hypotensive shock, and/or requirement for inotropic support. Recurrent shock was evaluated as a secondary endpoint. Risk factors were pre-defined clinical and laboratory variables collected at the time of presentation with shock. Prognostic model development was based on logistic regression and compared to several alternative approaches.The analysis population included 1207 children of whom 222 (18% progressed to "profound DSS" and 433 (36% had recurrent shock. Independent risk factors for both endpoints included younger age, earlier presentation, higher pulse rate, higher temperature, higher haematocrit and, for females, worse hemodynamic status at presentation. The final prognostic model for "profound DSS" showed acceptable discrimination (AUC=0.69 for internal validation and calibration and is presented as a simple score-chart.Several risk factors for development of profound or recurrent shock among children presenting with DSS were identified. The score-chart derived from the prognostic models should improve triage and management of children presenting with DSS in dengue-endemic areas.
14. Inflammatory stress of pancreatic beta cells drives release of extracellular heat-shock protein 90α.
Science.gov (United States)
Ocaña, Gail J; Pérez, Liliana; Guindon, Lynette; Deffit, Sarah N; Evans-Molina, Carmella; Thurmond, Debbie C; Blum, Janice S
2017-06-01
A major obstacle in predicting and preventing the development of autoimmune type 1 diabetes (T1D) in at-risk individuals is the lack of well-established early biomarkers indicative of ongoing beta cell stress during the pre-clinical phase of disease. Recently, serum levels of the α cytoplasmic isoform of heat-shock protein 90 (hsp90) were shown to be elevated in individuals with new-onset T1D. We therefore hypothesized that hsp90α could be released from beta cells in response to cellular stress and inflammation associated with the earliest stages of T1D. Here, human beta cell lines and cadaveric islets released hsp90α in response to stress induced by treatment with a combination of pro-inflammatory cytokines including interleukin-1β, tumour necrosis factor-α and interferon-γ. Mechanistically, hsp90α release was found to be driven by cytokine-induced endoplasmic reticulum stress mediated by c-Jun N-terminal kinase (JNK), a pathway that can eventually lead to beta cell apoptosis. Cytokine-induced beta cell hsp90α release and JNK activation were significantly reduced by pre-treating cells with the endoplasmic reticulum stress-mitigating chemical chaperone tauroursodeoxycholic acid. The hsp90α release by cells may therefore be a sensitive indicator of stress during inflammation and a useful tool in assessing therapeutic mitigation of cytokine-induced cell damage linked to autoimmunity. © 2017 John Wiley & Sons Ltd.
15. Heat shock proteins of higher plants
International Nuclear Information System (INIS)
Key, J.L.; Lin, C.Y.; Chen, Y.M.
1981-01-01
The pattern of protein synthesis changes rapidly and dramatically when the growth temperture of soybean seedling tissue is increased from 28 0 C (normal) to about 40 0 C (heat shock). The synthesis of normal proteins is greatly decreased and a new set of proteins, heat shock proteins, is induced. The heat shock proteins of soybean consist of 10 new bands on one-dimensional NaDodSO 4 gels; a more complex pattern is observed on two-dimensional gels. when the tissue is returned to 28 0 C after 4 hr at 40 0 C, there is progressive decline in the synthesis of heat shock proteins and reappearance of a normal pattern of synthesis by 3 or 4 hr. In vitro translation of poly(A) + RNAs isolated from tissued grown at 28 and 40 0 C shows that the heat shock proteins are translated from a ndw set of mRNAs induced at 40 0 C; furthermore, the abundant class mRNAs for many of the normal proteins persist even though they are translated weakly (or not at all) in vivo at 40 or 42.5 0 C. The heat shock response in soybean appears similar to the much-studied heat shock phenomenon in Drosophila
16. Overview of shock waves in medicine
Science.gov (United States)
Cleveland, Robin O.
2003-10-01
A brief overview of three applications of shock waves is presented. Shock wave lithotripsy (SWL) has been in clinical use for more than 20 years. In the United States it is used to treat more than 80% of kidney stone cases and has wide acceptance with patients because it is a noninvasive procedure. Despite SWLs enormous success there is no agreement on how shock waves comminute stones. There is also a general acceptance that shock waves lead to trauma to the soft tissue of the kidney. Yet there has been little forward progress in developing lithotripters which provide comminution with less side-effects, indeed the original machine is still considered the gold standard. The last decade has seen the advent of new shock wave devices for treating principally musculoskeletal indications, such as plantar fasciitis, tennis elbow, and bone fractures that do not heal. This is referred to as shock wave therapy (SWT). The mechanisms by which SWT works are even less well understood than SWL and the consequences of bioeffects have also not been studied in detail. Shock waves have also been shown to be effective at enhancing drug delivery into cells and assisting with gene transfection. [Work partially supported by NIH.
17. Structure of Energetic Particle Mediated Shocks Revisited
International Nuclear Information System (INIS)
Mostafavi, P.; Zank, G. P.; Webb, G. M.
2017-01-01
The structure of collisionless shock waves is often modified by the presence of energetic particles that are not equilibrated with the thermal plasma (such as pickup ions [PUIs] and solar energetic particles [SEPs]). This is relevant to the inner and outer heliosphere and the Very Local Interstellar Medium (VLISM), where observations of shock waves (e.g., in the inner heliosphere) show that both the magnetic field and thermal gas pressure are less than the energetic particle component pressures. Voyager 2 observations revealed that the heliospheric termination shock (HTS) is very broad and mediated by energetic particles. PUIs and SEPs contribute both a collisionless heat flux and a higher-order viscosity. We show that the incorporation of both effects can completely determine the structure of collisionless shocks mediated by energetic ions. Since the reduced form of the PUI-mediated plasma model is structurally identical to the classical cosmic ray two-fluid model, we note that the presence of viscosity, at least formally, eliminates the need for a gas sub-shock in the classical two-fluid model, including in that regime where three are possible. By considering parameters upstream of the HTS, we show that the thermal gas remains relatively cold and the shock is mediated by PUIs. We determine the structure of the weak interstellar shock observed by Voyager 1 . We consider the inclusion of the thermal heat flux and viscosity to address the most general form of an energetic particle-thermal plasma two-fluid model.
18. Impaired Fracture Healing after Hemorrhagic Shock
Directory of Open Access Journals (Sweden)
Philipp Lichte
2015-01-01
Full Text Available Impaired fracture healing can occur in severely injured patients with hemorrhagic shock due to decreased soft tissue perfusion after trauma. We investigated the effects of fracture healing in a standardized pressure controlled hemorrhagic shock model in mice, to test the hypothesis that bleeding is relevant in the bone healing response. Male C57/BL6 mice were subjected to a closed femoral shaft fracture stabilized by intramedullary nailing. One group was additionally subjected to pressure controlled hemorrhagic shock (HS, mean arterial pressure (MAP of 35 mmHg for 90 minutes. Serum cytokines (IL-6, KC, MCP-1, and TNF-α were analyzed 6 hours after shock. Fracture healing was assessed 21 days after fracture. Hemorrhagic shock is associated with a significant increase in serum inflammatory cytokines in the early phase. Histologic analysis demonstrated a significantly decreased number of osteoclasts, a decrease in bone quality, and more cartilage islands after hemorrhagic shock. μCT analysis showed a trend towards decreased bone tissue mineral density in the HS group. Mechanical testing revealed no difference in tensile failure. Our results suggest a delay in fracture healing after hemorrhagic shock. This may be due to significantly diminished osteoclast recruitment. The exact mechanisms should be studied further, particularly during earlier stages of fracture healing.
19. Structure of Energetic Particle Mediated Shocks Revisited
Energy Technology Data Exchange (ETDEWEB)
Mostafavi, P.; Zank, G. P. [Department of Space Science, University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Webb, G. M. [Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899 (United States)
2017-05-20
The structure of collisionless shock waves is often modified by the presence of energetic particles that are not equilibrated with the thermal plasma (such as pickup ions [PUIs] and solar energetic particles [SEPs]). This is relevant to the inner and outer heliosphere and the Very Local Interstellar Medium (VLISM), where observations of shock waves (e.g., in the inner heliosphere) show that both the magnetic field and thermal gas pressure are less than the energetic particle component pressures. Voyager 2 observations revealed that the heliospheric termination shock (HTS) is very broad and mediated by energetic particles. PUIs and SEPs contribute both a collisionless heat flux and a higher-order viscosity. We show that the incorporation of both effects can completely determine the structure of collisionless shocks mediated by energetic ions. Since the reduced form of the PUI-mediated plasma model is structurally identical to the classical cosmic ray two-fluid model, we note that the presence of viscosity, at least formally, eliminates the need for a gas sub-shock in the classical two-fluid model, including in that regime where three are possible. By considering parameters upstream of the HTS, we show that the thermal gas remains relatively cold and the shock is mediated by PUIs. We determine the structure of the weak interstellar shock observed by Voyager 1 . We consider the inclusion of the thermal heat flux and viscosity to address the most general form of an energetic particle-thermal plasma two-fluid model.
20. Shock propagation in a heterogeneous medium
International Nuclear Information System (INIS)
Elbaz, D.
2011-01-01
In the frame of the inertial confinement fusion in direct drive, the use of foams as ablator allows the reduction of hydrodynamic instabilities created on the target by the direct laser irradiation. The foam is made up of carbon (CH) fibers impregnated of cryogenic deuterium-tritium (DT). In the past, studies have been carried out considering this foam to be a homogeneous medium. Yet, the foam presents heterogeneous features. We study the effects of this heterogeneity on the shock velocity when the laser irradiates the target. Thanks to experimental and numerical studies, we show that the shock propagates faster in the heterogeneous medium than in the homogeneous one with the same averaged density. This velocity gap depends on the presence rate of the CH fibers in the foam, the density ratio, the adiabatic coefficient and the foam geometry. We model the foam by different ways, more and more complex. The shock velocity modification is due to the baroclinicity which, during the interaction between the shock front and the interface, creates a vorticity deposition, responsible for the shock acceleration. Accordingly, an interface, which is plane and perpendicular to the front shock, maximizes the vorticity deposition and increases the velocity gaps between heterogeneous and homogeneous media. We found a correlation between the kinetic energy behind the shock front and the velocities relative difference. We compared our results with two analytical models. However, the system is not closed, so we can't for the moment develop a predictive model. (author) [fr
1. Energetics of the terrestrial bow shock
Science.gov (United States)
Hamrin, Maria; Gunell, Herbert; Norqvist, Patrik
2017-04-01
The solar wind is the primary energy source for the magnetospheric energy budget. Energy can enter through the magnetopause both as kinetic energy (plasma entering via e.g. magnetic reconnection and impulsive penetration) and as electromagnetic energy (e.g. by the conversion of solar wind kinetic energy into electromagnetic energy in magnetopause generators). However, energy is extracted from the solar wind already at the bow shock, before it encounters the terrestrial magnetopause. At the bow shock the supersonic solar wind is slowed down and heated, and the region near the bow shock is known to host many complex processes, including the accelerating of particles and the generation of waves. The processes at and near the bow shock can be discussed in terms of energetics: In a generator (load) process kinetic energy is converted to (from) electromagnetic energy. Bow shock regions where the solar wind is decelerated correspond to generators, while regions where particles are energized (accelerated and heated) correspond to loads. Recently, it has been suggested that currents from the bow shock generator should flow across the magnetosheath and connect to the magnetospause current systems [Siebert and Siscoe, 2002; Lopez et al., 2011]. In this study we use data from the Magnetospheric MultiScale (MMS) mission to investigate the energetics of the bow shock and the current closure, and we compare with the MHD simulations of Lopez et al., 2011.
2. PHYSICAL CONDITIONS OF CORONAL PLASMA AT THE TRANSIT OF A SHOCK DRIVEN BY A CORONAL MASS EJECTION
Energy Technology Data Exchange (ETDEWEB)
Susino, R.; Bemporad, A.; Mancuso, S., E-mail: [email protected] [INAF–Turin Astrophysical Observatory, via Osservatorio 20, I-10025 Pino Torinese (Italy)
2015-10-20
We report here on the determination of plasma physical parameters across a shock driven by a coronal mass ejection using white light (WL) coronagraphic images and radio dynamic spectra (RDS). The event analyzed here is the spectacular eruption that occurred on 2011 June 7, a fast CME followed by the ejection of columns of chromospheric plasma, part of them falling back to the solar surface, associated with a M2.5 flare and a type-II radio burst. Images acquired by the Solar and Heliospheric Observatory/LASCO coronagraphs (C2 and C3) were employed to track the CME-driven shock in the corona between 2–12 R{sub ⊙} in an angular interval of about 110°. In this interval we derived two-dimensional (2D) maps of electron density, shock velocity, and shock compression ratio, and we measured the shock inclination angle with respect to the radial direction. Under plausible assumptions, these quantities were used to infer 2D maps of shock Mach number M{sub A} and strength of coronal magnetic fields at the shock's heights. We found that in the early phases (2–4 R{sub ⊙}) the whole shock surface is super-Alfvénic, while later on (i.e., higher up) it becomes super-Alfvénic only at the nose. This is in agreement with the location for the source of the observed type-II burst, as inferred from RDS combined with the shock kinematic and coronal densities derived from WL. For the first time, a coronal shock is used to derive a 2D map of the coronal magnetic field strength over intervals of 10 R{sub ⊙} altitude and ∼110° latitude.
3. Radiative shocks with electron thermal conduction
International Nuclear Information System (INIS)
Borkowski, Kazimierz.
1988-01-01
The authors studies the influence of electron thermal conduction on radiative shock structure for both one- and two-temperature plasmas. The dimensionless ratio of the conductive length to the cooling length determines whether or not conduction is important, and shock jump conditions with conduction are established for a collisionless shock front. He obtains approximate solutions with the assumptions that the ionization state of the gas is constant and the cooling rate is a function of temperature alone. In the absence of magnetic fields, these solutions indicate that conduction noticeably influences normal-abundance interstellar shocks with velocities 50-100 km s -1 and dramatically affects metal-dominated shocks over a wide range of shock velocities. Magnetic fields inhibit conduction, but the conductive energy flux and the corresponding decrease in the post-shock electron temperature may still be appreciable. He calculates detailed steady-state radiative shock models in gas composed entirely of oxygen, with the purpose of explaining observations of fast-moving knots in Cas A and other oxygen-rich supernova remnants (SNRs). The O III ion, whose forbidden emission usually dominates the observed spectra, is present over a wide range of shock velocities, from 100 to 170 kms -1 . All models with conduction have extensive warm photoionization zones, which provides better agreement with observed optical (O I) line strengths. However, the temperatures in these zones could be lowered by (Si II) 34.8 μm and (Ne II) 12.8 μm cooling if Si and Ne are present in appreciable abundance relative to O. Such low temperatures would be inconsistent with the observed (O I) emission in oxygen-rich SNRs
4. Underwater hydraulic shock shovel control system
Science.gov (United States)
Liu, He-Ping; Luo, A.-Ni; Xiao, Hai-Yan
2008-06-01
The control system determines the effectiveness of an underwater hydraulic shock shovel. This paper begins by analyzing the working principles of these shovels and explains the importance of their control systems. A new type of control system’s mathematical model was built and analyzed according to those principles. Since the initial control system’s response time could not fulfill the design requirements, a PID controller was added to the control system. System response time was still slower than required, so a neural network was added to nonlinearly regulate the proportional element, integral element and derivative element coefficients of the PID controller. After these improvements to the control system, system parameters fulfilled the design requirements. The working performance of electrically-controlled parts such as the rapidly moving high speed switch valve is largely determined by the control system. Normal control methods generally can’t satisfy a shovel’s requirements, so advanced and normal control methods were combined to improve the control system, bringing good results.
5. Nonthermal Radiation from Supernova Remnant Shocks
Directory of Open Access Journals (Sweden)
Hyesung Kang
2013-09-01
Full Text Available Most of high energy cosmic rays (CRs are thought to be produced by diffusive shock acceleration (DSA at supernova remnants (SNRs within the Galaxy. Fortunately, nonthermal emissions from CR protons and electrons can provide direct observational evidence for such a model and place strong constraints on the complex nonlinear plasma processes in DSA theory. In this study we calculate the energy spectra of CR protons and electrons in Type Ia SNRs, using time-dependent DSA simulations that incorporate phenomenological models for some wave-particle interactions. We demonstrate that the timedependent evolution of the self-amplified magnetic fields, Alfvénic drift, and escape of the highest energy particles affect the energy spectra of accelerated protons and electrons, and so resulting nonthermal radiation spectrum. Especially, the spectral cutoffs in X-ray and γ-ray emission spectra are regulated by the evolution of the highest energy particles, which are injected at the early phase of SNRs. Thus detailed understandings of nonlinear wave-particle interactions and time-dependent DSA simulations of SNRs are crucial in testing the SNR hypothesis for the origin of Galactic cosmic rays.
6. Laser shock peening on a 6056-T4 aluminium alloy for airframe applications
CSIR Research Space (South Africa)
Glaser, D
2014-03-01
Full Text Available stream_source_info Pityana1_2014_ABSTRACT ONLY.pdf.txt stream_content_type text/plain stream_size 1356 Content-Encoding ISO-8859-1 stream_name Pityana1_2014_ABSTRACT ONLY.pdf.txt Content-Type text/plain; charset=ISO-8859-1... Laser Shock Peening on a 6056-T4 Aluminium Alloy for Airframe Applications Daniel Glaser, Claudia Polese, Rachana D. Bedekar, Jasper Plaisier,Sisa Pityana, Bathusile Masina, Tebogo Mathebula, and Enrico Troiani Keywords: Laser Shock Peening...
7. DSMC Computations for Regions of Shock/Shock and Shock/Boundary Layer Interaction
Science.gov (United States)
Moss, James N.
2001-01-01
This paper presents the results of a numerical study of hypersonic interacting flows at flow conditions that include those for which experiments have been conducted in the Calspan-University of Buffalo Research Center (CUBRC) Large Energy National Shock (LENS) tunnel and the ONERA R5Ch low-density wind tunnel. The computations are made with the direct simulation Monte Carlo (DSMC) method of Bird. The focus is on Mach 9.3 to 11.4 flows about flared axisymmetric configurations, both hollow cylinder flares and double cones. The results presented highlight the sensitivity of the calculations to grid resolution, provide results concerning the conditions for incipient separation, and provide information concerning the flow structure and surface results for the extent of separation, heating, pressure, and skin friction.
8. Metabolic Response of Maize Roots to Hyperosmotic Shock 1
Science.gov (United States)
Spickett, Corinne M.; Smirnoff, Nicholas; Ratcliffe, R. George
1992-01-01
31P nuclear magnetic resonance spectroscopy was used to study the response of maize (Zea mays L.) root tips to hyperosmotic shock. The aim was to identify changes in metabolism that might be relevant to the perception of low soil water potential and the subsequent adaptation of the tissue to these conditions. Osmotic shock was found to result in two different types of response: changes in metabolite levels and changes in intracellular pH. The most notable metabolic changes, which were produced by all the osmotica tested, were increases in phosphocholine and vacuolar phosphate, with a transient increase in cytoplasmic phosphate. It was observed that treatment with ionic and nonionic osmotica produced different effects on the concentrations of bioenergetically important metabolites. It is postulated that these changes are the result of hydrolysis of phosphatidylcholine and other membrane phospholipids, due to differential activation of specific membrane-associated phospholipases by changes in the surface tension of the plasmalemma. These events may be important in the detection of osmotic shock and subsequent acclimatization. A cytoplasmic alkalinization was also observed during hyperosmotic treatment, and this response, which is consistent with the activation of the plasmalemma H+-ATPase, together with the other metabolic changes, may suggest the existence of a complex and integrated mechanism of osmoregulation. PMID:16669012
9. Shock Fluctuations in Flat TASEP Under Critical Scaling
Science.gov (United States)
Ferrari, Patrik L.; Nejjar, Peter
2015-08-01
We consider TASEP with two types of particles starting at every second site. Particles to the left of the origin have jump rate , while particles to the right have jump rate . When there is a formation of a shock where the density jumps to . For fixed, the statistics of the associated height functions around the shock is asymptotically (as time ) a maximum of two independent random variables as shown in Ferrari and Nejjar (Probab Theory Rel Fields 161:61-109, 2015). In this paper we consider the critical scaling when , where is the observation time. In that case the decoupling does not occur anymore. We determine the limiting distributions of the shock and numerically study its convergence as a function of . We see that the convergence to occurs quite rapidly as increases. The critical scaling is analogue to the one used in the last passage percolation to obtain the BBP transition processes (Baik et al. in Ann Probab 33:1643-1697, 2006).
10. Laser shock wave consolidation of nanodiamond powders on aluminum 319
Energy Technology Data Exchange (ETDEWEB)
Molian, Pal [Laboratory for Lasers, MEMS, and Nanotechnology, Department of Mechanical Engineering, Iowa State University, Ames, IA 50011-2161 (United States)], E-mail: [email protected]; Molian, Raathai; Nair, Rajeev [Laboratory for Lasers, MEMS, and Nanotechnology, Department of Mechanical Engineering, Iowa State University, Ames, IA 50011-2161 (United States)
2009-01-01
A novel coating approach, based on laser shock wave generation, was employed to induce compressive pressures up to 5 GPa and compact nanodiamond (ND) powders (4-8 nm) on aluminum 319 substrate. Raman scattering indicated that the coating consisted of amorphous carbon and nanocrystalline graphite with peaks at 1360 cm{sup -1} and 1600 cm{sup -1} respectively. Scanning electron microscopy revealed a wavy, non-uniform coating with an average thickness of 40 {mu}m and absence of thermal effect on the surrounding material. The phase transition from nanodiamond to other phases of carbon is responsible for the increased coating thickness. Vicker's microhardness test showed hardness in excess of 1000 kg{sub f}/mm{sup 2} (10 GPa) while nanoindentation test indicated much lower hardness in the range of 20 MPa to 2 GPa. Optical surface profilometry traces displayed slightly uneven surfaces compared to the bare aluminum with an average surface roughness (R{sub a}) in the range of 1.5-4 {mu}m depending on the shock wave pressure and type of confining medium. Ball-on-disc tribometer tests showed that the coefficient of friction and wear rate were substantially lower than the smoother, bare aluminum sample. Laser shock wave process has thus aided in the generation of a strong, wear resistant, durable carbon composite coating on aluminum 319 substrate.
11. A new method for testing thermal shock resistance properties of soapstone – Effects of microstructures and mineralogical variables
Directory of Open Access Journals (Sweden)
A. Huhta
2016-09-01
Full Text Available Soapstone industry utilizes different types of soapstone mainly as a construction material for fireplaces. In this application soapstone has to meet different temperature requirements in different parts of fireplaces. Mineralogical and structural information is needed for placing an appropriate type of soapstone in an appropriate position in the fireplace construction. This allows employment of higher temperatures resulting in more particulate-free combustion, which makes it possible for soapstone industry to develop more efficient and environmentally friendly fireplaces. Of many soapstone types, which differ from each other in their chemical composition and thermal properties, carbonate soapstone and its microstructural variations were investigated in this study. A new method was developed to measure thermal shock resistant of natural stones. By exposing carbonate soapstone samples of different textural types to rapid temperature changes, it was possible to determine the parameters that affect the capacity of the rock to resist thermal shock. The results indicate that the type of microtexture is an important factor in controlling the thermal shock resistance of carbonate soapstone. The soapstone samples with a high thermal shock resistance show deformation textures, such as crenulation cleavage and S/C mylonite. A strong negative correlation was observed between the thermal shock resistance and length of cleavage domains in foliated rocks. Also a slight elevation in the iron concentration of talc and magnesite was discovered to improve the thermal shock resistance of carbonate soapstone. Attention should especially be paid to the length and planarity of cleavage domains of spaced foliation.
12. Comparison of accelerated ion populations observed upstream of the bow shocks at Venus and Mars
Directory of Open Access Journals (Sweden)
M. Yamauchi
2011-03-01
Full Text Available Foreshock ions are compared between Venus and Mars at energies of 0.6~20 keV using the same ion instrument, the Ion Mass Analyser, on board both Venus Express and Mars Express. Venus Express often observes accelerated protons (2~6 times the solar wind energy that travel away from the Venus bow shock when the spacecraft location is magnetically connected to the bow shock. The observed ions have a large field-aligned velocity compared to the perpendicular velocity in the solar wind frame, and are similar to the field-aligned beams and intermediate gyrating component of the foreshock ions in the terrestrial upstream region. Mars Express does not observe similar foreshock ions as does Venus Express, indicating that the Martian foreshock does not possess the intermediate gyrating component in the upstream region on the dayside of the planet. Instead, two types of gyrating protons in the solar wind frame are observed very close to the Martian quasi-perpendicular bow shock within a proton gyroradius distance. The first type is observed only within the region which is about 400 km from the bow shock and flows tailward nearly along the bow shock with a similar velocity as the solar wind. The second type is observed up to about 700 km from the bow shock and has a bundled structure in the energy domain. A traversal on 12 July 2005, in which the energy-bunching came from bundling in the magnetic field direction, is further examined. The observed velocities of the latter population are consistent with multiple specular reflections of the solar wind at the bow shock, and the ions after the second reflection have a field-aligned velocity larger than that of the de Hoffman-Teller velocity frame, i.e., their guiding center has moved toward interplanetary space out from the bow shock. To account for the observed peculiarity of the Martian upstream region, finite gyroradius effects of the solar wind protons compared to the radius of the bow shock curvature and
13. Matrix stochastic analysis of the maintainability of a machine under shocks
International Nuclear Information System (INIS)
Montoro-Cazorla, Delia; Pérez-Ocón, Rafael
2014-01-01
We study the maintenance of a machine operating under environmental conditions producing shocks affecting the lifetime of the machine. The shocks cause different types of damage depending on their strength and eventually the total failure. The maintenance of the machine is performed by repairs and replacement. The interarrival times of shocks are dependent. We introduce a multidimensional stochastic model for simulating the evolution of the lifetime of the machine. This model implies the application of the matrix-analytic methods, that are being used in stochastic modelling with interesting results. Under this methodology, the availability, the reliability, and the rates of occurrence of the different types of failures and of the replacements are calculated, obtaining mathematically tractable expressions. The results are applied to a numerical example. - Highlights: • A machine under random environmental conditions producing shocks and wear is studied under matrix-analytic methods. • There is dependence in the interarrival times of shocks. • Different types of failure producing damage in the internal and external structure of the machine are considered. • Maintenance is performed by repair and replacement. • Explicit expressions for the main reliability performance measures are given
14. THE EFFECT OF LARGE-SCALE MAGNETIC TURBULENCE ON THE ACCELERATION OF ELECTRONS BY PERPENDICULAR COLLISIONLESS SHOCKS
International Nuclear Information System (INIS)
Guo Fan; Giacalone, Joe
2010-01-01
We study the physics of electron acceleration at collisionless shocks that move through a plasma containing large-scale magnetic fluctuations. We numerically integrate the trajectories of a large number of electrons, which are treated as test particles moving in the time-dependent electric and magnetic fields determined from two-dimensional hybrid simulations (kinetic ions and fluid electron). The large-scale magnetic fluctuations effect the electrons in a number of ways and lead to efficient and rapid energization at the shock front. Since the electrons mainly follow along magnetic lines of force, the large-scale braiding of field lines in space allows the fast-moving electrons to cross the shock front several times, leading to efficient acceleration. Ripples in the shock front occurring at various scales will also contribute to the acceleration by mirroring the electrons. Our calculation shows that this process favors electron acceleration at perpendicular shocks. The current study is also helpful in understanding the injection problem for electron acceleration by collisionless shocks. It is also shown that the spatial distribution of energetic electrons is similar to in situ observations. The process may be important to our understanding of energetic electrons in planetary bow shocks and interplanetary shocks, and explaining herringbone structures seen in some type II solar radio bursts.
15. Temperature measurements of shock-compressed deuterium
International Nuclear Information System (INIS)
Holmes, N.C.; Ross, M.; Nellis, W.J.
1994-11-01
The authors measured the temperatures of single and double-shocked D 2 and H 2 up to 85 GPa (0.85 Mbar) and 5,200 K. While single shock temperatures, at pressures to 23 GPa, agree well with previous models, the double shock temperatures are as much as 40% lower than predicted. This is believed to be caused by molecular dissociation, and a new model of the hydrogen EOS at extreme conditions has been developed which correctly predicts their observations. These data and model have important implications for programs which use condensed-phase hydrogen in implosion systems
16. Recent oil price shock and Tunisian economy
International Nuclear Information System (INIS)
Jbir, Rafik; Zouari-Ghorbel, Sonia
2009-01-01
The objective of this paper is to study the oil prices-macroeconomy relationship by the analysis of the role of subsidy policy. The vector autoregression (VAR) method was employed to analyze the data over the period 1993 Q1 - 2007 Q3. The results of the model using both linear and non-linear specifications indicate that there is no direct impact of oil price shock on the economic activity. The shock of oil prices affects economic activity indirectly. The most significant channel by which the effects of the shock are transmitted is the government's spending. (author)
17. Delayed Failure in a Shock Loaded Alumina
International Nuclear Information System (INIS)
Cooper, G. A.; Millett, J. C. F.; Bourne, N. K.; Dandekar, D. P.
2006-01-01
Manganin stress gauges have been used to measure the lateral stress in a shock-loaded alumina. In combination with known longitudinal stresses, these have been used to determine the shear strength of this material, behind the shock front. The two-step nature of the lateral stress traces shows a slow moving front behind the main shock, behind which shear strength undergoes a significant decrease. Results also show that this front decreases markedly in velocity as the HEL is crossed, suggesting that limited plasticity occurs during inelastic deformation. Finally, comparison of measured shear strengths with other aluminas shows a high degree of agreement
18. Turbulent energy generated by accelerations and shocks
International Nuclear Information System (INIS)
Mikaelian, K.O.
1986-01-01
The turbulent energy generated at the interface between two fluids undergoing a constant acceleration or a shock is calculated. Assuming linear density profiles in the mixed region we find E/sub turbulent//E/sub directed/ = 2.3A 2 % (constant acceleration) and 9.3A 2 % (shock), where A is the Atwood number. Diffusion models predict somewhat less turbulent energy and a density profile with a tail extending into the lower density fluid. Eddy sizes are approximately 27% (constant acceleration) and 17% (shock) of the mixing depth into the heavier fluid. 6 refs., 3 figs
19. Demonstration of a viable quantitative theory for interplanetary type II radio bursts
Energy Technology Data Exchange (ETDEWEB)
Schmidt, J. M., E-mail: [email protected]; Cairns, Iver H. [School of Physics, Physics Road, Building A28, University of Sydney, NSW 2006 (Australia)
2016-03-25
Between 29 November and 1 December 2013 the two widely separated spacecraft STEREO A and B observed a long lasting, intermittent, type II radio burst for the extended frequency range ≈ 4 MHz to 30 kHz, including an intensification when the shock wave of the associated coronal mass ejection (CME) reached STEREO A. We demonstrate for the first time our ability to quantitatively and accurately simulate the fundamental (F) and harmonic (H) emission of type II bursts from the higher corona (near 11 solar radii) to 1 AU. Our modeling requires the combination of data-driven three-dimensional magnetohydrodynamic simulations for the CME and plasma background, carried out with the BATS-R-US code, with an analytic quantitative kinetic model for both F and H radio emission, including the electron reflection at the shock, growth of Langmuir waves and radio waves, and the radiations propagation to an arbitrary observer. The intensities and frequencies of the observed radio emissions vary hugely by factors ≈ 10{sup 6} and ≈ 10{sup 3}, respectively; the theoretical predictions are impressively accurate, being typically in error by less than a factor of 10 and 20 %, for both STEREO A and B. We also obtain accurate predictions for the timing and characteristics of the shock and local radio onsets at STEREO A, the lack of such onsets at STEREO B, and the z-component of the magnetic field at STEREO A ahead of the shock, and in the sheath. Very strong support is provided by these multiple agreements for the theory, the efficacy of the BATS-R-US code, and the vision of using type IIs and associated data-theory iterations to predict whether a CME will impact Earth’s magnetosphere and drive space weather events.
20. Switch-shock wave structure in a magnetized partly-ionized gas
International Nuclear Information System (INIS)
Cramer, N.F.
1975-01-01
The effect of the interaction of plasma and neutral gas on the structure of switch-type shock waves propagating in a partly-ionized gas is studied. These shocks, in which the magnetic field is perpendicular to the shock front either upstream or downstream, exhibit a spiralling behaviour of the magnetic field in the shock transition region, if the Hall term is important in the Ohm's law. Observations of this behaviour for shocks propagating into a plasma with a residual neutral content of about 15% has implied an anomalously high resistivity of the plasma. We show that this can be partly explained by considering the collisions of ions with the neutral atoms in a magnetic field. We show that the extra dissipation due to the increase in resistivity goes primarily to the ions and neutrals. Thus even in the absence of viscous dissipation within each species, the heavy particles can be appreciably heated in a shock propagating into a partly-ionized gas in a magnetic field. (author) | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.717221200466156, "perplexity": 4459.09068804366}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-43/segments/1570986675598.53/warc/CC-MAIN-20191017172920-20191017200420-00206.warc.gz"} |
https://techutils.in/blog/tag/salsa20/ | ## #StackBounty: #stream-cipher #authenticated-encryption #chacha #salsa20 #poly1305 Append data to authenticated ciphertext encrypted usi…
### Bounty: 50
Say we have xSalsa20 authenticated using Poly1305. If $$X$$ is the ciphertext, $$N$$ is the nonce value, and $$H$$ is the authentication tag such that the final ciphertext is $$N || X || H$$, then given the key $$K$$, is it possible to extend $$X$$ with more data, without decrypting it, updating $$N$$ and $$Y$$ as needed? (I’m not sure if $$N$$ would need to be changed.)
Salsa20 is a stream cipher so it produces a CSPR key-stream, $$S$$, and then then ciphertext becomes $$X = S oplus P$$, where $$P$$ is the plaintext. So I intuitively feel as though this should be a lot easier to do than with a block cipher. Perhaps by generating the same key-stream up until the size of the ciphertext and encrypting the new data with the part of the key-stream past that point. If the authentication tag is generated from the ciphertext then decryption wouldn’t be necessary for that either. Also the nonce would not really be reused in a scheme like this as far as I can see.
How well would this translate to other stream ciphers like XChaCha20-Poly1305?
Get this bounty!!! | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 12, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.6510148048400879, "perplexity": 1047.888968973354}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2020-10/segments/1581875147054.34/warc/CC-MAIN-20200228043124-20200228073124-00240.warc.gz"} |
https://www.physicsforums.com/threads/a-force-question.234637/ | # A Force Question
1. May 12, 2008
### inflames829
1. The problem statement, all variables and given/known data
A force F=-4.3i+2.0j+1.5k Newtons exerts a displacement of d=-0.8i+1.8j+-3.6k metres upon a small (ie mass is negligible) object. If the friction force is equal to Ffr=-0.2,, then what is the net work done upon the object?
2. Relevant equations
3. The attempt at a solution
I know the net work is the sum of all the individual work and the work equation is W=F.D. So i tried to work out the work of the initial force stated by multiplying the force and displacement stated which i got 1.64J. I think the only other work is caused by the friction force but when i try to work that out (because the mass is negligable) i get 0. Can someone please help?
2. May 12, 2008
### Tedjn
Mass is negligible only affects calculating the friction force using $\mu N$, but you already have the friction force. What can you do with it?
3. May 12, 2008
### inflames829
could i put it as the force in the work equation and put the distance as the displacement thats stated in the question?
4. May 12, 2008
### Phlogistonian
Yes.
5. May 12, 2008
### inflames829
so i have 1.64 from the first force i worked out and if i put the friction force into the work equation w= -0.2 x D i get -0.82. If I add the two works i have i get 0.82, but the answer is 1.3.... can you give me hints on what ive done wrong??
6. May 12, 2008
### Tedjn
I get that also. From where did you get this problem?
Similar Discussions: A Force Question | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9851386547088623, "perplexity": 792.9350883687313}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-22/segments/1495463608984.81/warc/CC-MAIN-20170527171852-20170527191852-00190.warc.gz"} |
https://forum.bebac.at/forum_entry.php?id=17014&view=forum | ## Denmark Curiosa (1 in 90% CI in 0.8-1.25) [Power / Sample Size]
Hi everybody and nobody.
It was mentioned here several times that Danish Medicines Agency has one more requirement for BE:
"In the opinion of the Danish Medicines Agency, the 90 % confidence intervals for the ratio of the test and reference products should include 100 %, regardless that the acceptance limits are within 80.00-125.00 % or a narrower interval. Deviations are usually only accepted if it can be adequately proved that the deviation has no clinically relevant impact on the efficacy and safety of the medicinal product." source (bolded by me)
Btw. FDA document (Guidance for Industry: Bioavailability and Bioequivalence Studies for Orally Administered Drug Products - General Considerations) states in section II. BACKGROUND:
C. Bioequivalence
Bioequivalence is defined in § 320.1 as:
the absence of a significant difference in the rate and extent to which the active ingredient or active moiety in pharmaceutical equivalents or pharmaceutical alternatives becomes available at the site of drug action when administered at the same molar dose under similar conditions in an appropriately designed study.
When value 1 is outside of 90% CI of GMR then there is a significant difference (maybe except for some border cases). - End of fun, of course this statistically significant difference is not relevant for FDA according to other statements requiring the confidence interval in the BE limits.
On the other hand, if some new regulatory reader is suprised with the significant difference between IMPs (acc. to ANOVA p value) and ask for justification. He would be probably shocked by the answer: "It is not possible to plan the BE study with assumention of GMR=0.95, CV=x%, 90% CI in 0.8-1.25 and not significant treatment effect for power at least 80%."
Maybe, Denmark has the requirement as a way to keep "Forced BE" away.
(Sounds good, until the problems appear and it can filter not only "Forced BE" as everyone knows.)
Nevertheless the EMA's statement "The number of subjects to be included in the study should be based on an appropriate sample size calculation." should be sufficient (to keep "Forced BE" away), if controlled correctly.
(Many of regulatory authorities think that sample size is issue of ethical committees. Many of ethical committees are not able to assess the sample size estimation.)
Back to the future:
Should be the requirement of the inclusion of 100% in 90% CI included in the sample size estimation? (I would bet it has never been used.) ... It's quite problematic task.
(So this post is only for interest to know. - I can not imagine the actual use after I made some power analysis.)
One issue is that with increasing sample size we will get 100% out of 90% CI (Helmut the Hero showed it graphically here).
Another issue is that test and reference products can differ (eg. the assayed content can differ up to 5%, even if the difference is zero (according to CoAs), there is some analytical accuracy, etc.), so it is usual to use null ratio 0.95 for sample size estimation (and possible worse ratio to 0.9 as option - discussed here).
(Null ratio 0.90 would be unlucky coin flipping for Denmark.)
I performed some simulations for power (with added condition of 1 in 90% CI to the condition of 90% CI in 0.8-1.25 (in counting step)).
So I can share my figures (more accurately levelplots) for different null ratio (expected GMR used for power estimation via simulations):
GMR = 0.95 GMR = 0.96
For GMR = 0.95 (left side) the maximum simulated power is 0.7809. (For n 12-80 and CV 1-50 maximum simulated power for GMR=0.95 is 0.7888.)
Nice to know that with all these requirements+assumptions the power is below 80%. (Or at least seems to be acc. to simulations.)
GMR = 0.97 GMR = 0.98
GMR = 0.99 GMR = 1
For GMR = 1 (right side) the maximum simulated power is 0.9016.
Green columns are little defect due to I decided to move set.seed function into loops (so same seed was used for each combination of n and intra-subject CV, which looks better for smooth color transitions. And I decided to use only 20 colors for easy to see which value is over 80% and which over 90%. So I prepare two additional figures.)
The darker green columns are saying that values are in 0.9-0.95, but the values are close to 0.9, and similar issue in the lighter green category 0.85-0.9 - almost in whole green region all values are really close to 0.9.)
And columns appeared because n+2 makes little bit more change than CV+1 (with the same seed used).
GMR = 1 (additional 1) GMR = 1 (additional 2)
GMR = 1 - additional 1 (left side): Function set.seed is still in loops so there is trend in coloring. (Green color is close to 0.9 in the scale.)
GMR = 1 - additional 2 (right side): Function set.seed moved before loops so values are over 90% randomly - it's the same as using of different seed for each combo of n and CV. (Actually there are many of values around 90% power - simulated values are sometimes little bit over 90% - because it is not exact method of course.)
For GMR = 1 (right side, with set.seed before loops) the maximum simulated power is 0.9073.
Null GMR 1, max power 0.90 with alpha 0.05. The simulations confirm what I never thought about but what everyone can expect.
Really scary when sponsor wants to plan the BE study with power 90%. You must expect the GMR value equal to 1 and anyway power 90% is just a theoretical maximum, in practice the power is always lower than 90%. Moreover I ignore that this should be valid for two PK metrics (AUC and Cmax).
GMR = 0.9
For GMR = 0.9 the maximum simulated power is 0.4757.
Little bit going to extreme n and CV (presented twice - 1) on the left to easy see categories; 2) on the right as presentable;)
GMR = 0.95 (20 colors) GMR = 0.95 (200 colors)
For GMR = 0.95 the maximum simulated power is 0.8012 (n=12-480 and CV=1-300%). It can be over 0.8 only due to lucky number as a seed used in simulations, etc..
With comparison to EMA: (I used the same simulations as for Denmark requirement "1 in 90% CI in 0.8-1.25", although exact method exist for standard "90% CI in 0.8-1.25").
GMR = 1:
Green area: For Denmark almost 90% power, standardly almost 100% power. It's a big difference!
GMR = 0.95:
No green area for Denmark at all!
GMR = 0.9:
No comment!
Coded (with the use of function provided by Hero d_labes here) as:
power.sim2x2 <- function(CV, GMR, n, nsims=1E4, alpha=0.05, lBEL=0.8, uBEL=1.25, details=FALSE) { ptm <- proc.time() # n is total if given as simple number # to be correct n must then be even! if (length(n)==1) { nsum <- n fact <- 2/n } if (length(n)==2) { nsum <- sum(n) fact <- 0.5*sum(1/n) } mse <- log(1.0 + CV^2) df <- nsum-2 tval <- qt(1-alpha,df) # Attention! With nsims=1E8 memory of my machine (4 GB) is too low # Thus work in chunks of 1E6 if nsims>1E6. chunks <- 1 ns <- nsims if (nsims>1e6) { chunks <- trunc(nsims/1E6) ns <- 1E6 if (chunks*1e6!=nsims){ nsims <- chunks*1e6 warning("nsims truncated to", nsims) } } BEcount <- 0 sdm <- sqrt(fact*mse) mlog <- log(GMR) for (i in 1:chunks) { # simulate sample mean via its normal distribution means <- rnorm(ns, mean=mlog, sd=sdm) # simulate sample mse via chi-square distribution of df*mses/mse mses <- mse*rchisq(ns,df)/df hw <- tval*sqrt(fact*mses) lCL <- means - hw uCL <- means + hw # point <- exp(means) lCL <- exp(lCL) uCL <- exp(uCL) #BE <- (lBEL<=lCL & uCL<=uBEL) # standard check if 90% CI of GMR is in 0.8-1.25 (without rounding CI limits) BE <- lBEL<=lCL & uCL<=uBEL & lCL<=1 & 1<=uCL # change for Denmark BEcount <- BEcount + sum(BE) } if (details) { cat(nsims,"sims. Time elapsed (sec):\n") print(proc.time()-ptm) } BEcount/nsims } n=seq(12,48,2) CV=seq(1,30,1) power_sim=matrix(0,nrow=length(CV),ncol=length(n)) for (i in 1:length(CV)){ for (j in 1:length(n)){ set.seed(12345) # if set.seed is done before the "for loop", it generate differ set for each n and CV combination power_sim[i,j]=power.sim2x2(CV=CV[ i ]/100,GMR=0.95,n=n[j],nsims=1E4, alpha=0.05, lBEL=0.8, uBEL=1.25) # I have it without rounding 90% confinfidence limits and with added condition of 1 in 90% CI } } max(power_sim) # I know, someone can do it better (eg. in 3D like this kind of figure). # But not me. x) library(lattice) x <- n y <- CV z <- t(power_sim) rownames(z) <- x colnames(z) <- paste(as.character(y),"%") ck=list(at=seq(0,1,0.05),labels=c("0 %","5 %","10 %","15 %","20 %","25 %","30 %","35 %","40 %","45 %","50 %","55 %","60 %","65 %","70 %","75 %","80 %","85 %","90 %","95 %","100 %")) levelplot(z, at=seq(0,1,length=21), colorkey=ck, col.regions=colorRampPalette(c("black","brown","red","orange","yellow","green")), xlab="n", ylab="CV (%)", main=list(c(" 1 in 90% CI in 0.8000-1.2500"," Power"),cex=c(1.2,0.8))) # or below is better looking #levelplot(z, col.regions=colorRampPalette(c("black","brown","red","orange","yellow","green")), at=seq(0,1,length=201), xlab="n", ylab="CV (%)", main=list(c(" 1 in 90% CI in 0.8000-1.2500"," Power"),cex=c(1.2,0.8))) # ----- # for levelplot of extreme n and CV: n=seq(12,480,2); CV=seq(1,300,1); #x_ticks=c(1,20,45,70,95,120,145,170,195,220,235) #y_ticks=c(1,10,20,30,40,50,75,100,150,200,250,300) #levelplot(z, at=seq(0,1,length=21), colorkey=ck, col.regions=colorRampPalette(c("black","brown","red","orange","yellow","green")), scales=list(x=list(at=x_ticks,labels=n[x_ticks]),y=list(at=y_ticks,labels=sprintf("%s %%",y_ticks))), xlab="n", ylab="CV (%)", main=list(c(" 1 in 90% CI in 0.8000-1.2500"," Power"),cex=c(1.2,0.8))) # or below is better looking #levelplot(z, col.regions=colorRampPalette(c("black","brown","red","orange","yellow","green")), at=seq(0,1,length=201), scales=list(x=list(at=x_ticks,labels=n[x_ticks]),y=list(at=y_ticks,labels=sprintf("%s %%",y_ticks))), xlab="n", ylab="CV (%)", main=list(c(" 1 in 90% CI in 0.8000-1.2500"," Power"),cex=c(1.2,0.8)))
In this case, it's more than true to say:
Power. That which statisticians are always calculating
but never have. Stephen Senn internal source
Wingardium Leviosa,
zizou | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.705696702003479, "perplexity": 19794.764136959726}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-47/segments/1573496671239.99/warc/CC-MAIN-20191122042047-20191122070047-00145.warc.gz"} |
https://mathshistory.st-andrews.ac.uk/Biographies/Ringrose/ | # John Robert Ringrose
Born
21 December 1932
### Biography
John Ringrose was educated at Buckhurst Hill County High School in Chigwell in the Epping Forest district of Essex, England. The school is on the northeastern perimeter of the metropolitan area of London. After leaving the school, Ringrose entered St John's College, Cambridge and he received an M.A., then later a Ph.D. from Cambridge in 1957.
After completing his Ph.D., Ringrose was appointed a lecturer in mathematics at King's College of the University of Newcastle-upon-Tyne in 1957. He remained in Newcastle until 1961 when he returned to Cambridge as a lecturer in mathematics. He was also elected a fellow of his old College, St John's College, Cambridge. He remained at Cambridge for two years then, in 1963, Ringrose returned to Newcastle where he was appointed a senior lecturer in mathematics.
In 1964 he was appointed to the chair of Pure Mathematics at the University of Newcastle-upon-Tyne and he held this post until he retired in 1993. On his retiral he became professor emeritus at Newcastle. He also served as Pro-Vice-Chancellor at the University of Newcastle-upon-Tyne from 1983 until 1988.
Ringrose is a leading world expert on non-self-adjoint operators and operator algebras. He has written on operators of Volterra-type, compact linear operators, the Neumann series of integral operators, algebras of operators, automorphisms and derivations of operator algebras, and the cohomology of operator algebras.
He has written a number of influential texts including Compact non-self-adjoint operators (1971) and, with R V Kadison, Fundamentals of the theory of operator algebras in four volumes published in 1983, 1986, 1991 and 1992. The first of these volumes is an elementary approach to the theory of $C^{*}$-algebras and von Neumann algebras. The authors state in the preface that their:-
... primary goal is to teach the subject and lead the reader to the point where the vast recent literature, both in the subject proper and in its many applications, becomes accessible.
The second volume treats advanced topics which Ringrose and Kadison consider to be fundamental for an understanding of current research in operator algebras. R S Doran, a reviewer of the text, writes that:-
The book [is] written by two eminent mathematicians each of whom has made major contributions to the theory of operator algebras.
He concludes the review saying that:-
...the authors have presented [the material] in a fresh and attractive way which conveys the spirit and beauty of the subject. They are to be commended for writing a beautiful book which, in the reviewer's opinion, fulfills all of the promises made in the preface.
These two volumes contain an outstanding collection of exercises which in many cases lead the reader to prove some further major results by skillfully breaking them down into manageable parts. The third and fourth volumes contain the solutions to the exercises. R S Doran says the authors' solutions:-
... which were developed from scratch specifically for this volume, are models of clarity and efficiency, reflecting their vast experience and insight into the subject.
The Royal Society of London elected Ringrose as a fellow in 1977 and he has also been elected a fellow of the Royal Society of Edinburgh. He has served the London Mathematical Society in many different ways including holding the position of president of the Society from 1992 to 1994. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 1, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.4902842044830322, "perplexity": 1259.6666834023272}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2020-24/segments/1590348517506.81/warc/CC-MAIN-20200606155701-20200606185701-00294.warc.gz"} |
https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=14&t=34010 | ## Mnemonic for em spectrum
$c=\lambda v$
gabbym
Posts: 76
Joined: Wed Apr 11, 2018 3:00 am
### Mnemonic for em spectrum
Hey guys! My PLF taught me a really cool mnemonic that I thought I would share with you. It goes like this: "Really Man I See U X Genius." R=radio waves, M=microwaves, I=Infrared, See=Visible Light, U=UV Light, and G=Gamma Rays.
I hope this helps!
Mayaal_Khan_4H
Posts: 41
Joined: Fri Sep 28, 2018 12:28 am
### Re: Mnemonic for em spectrum
Thank you so much for posting this!!
Hanniel U 2B
Posts: 76
Joined: Fri Sep 28, 2018 12:16 am
Thanks! | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 1, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.6656411290168762, "perplexity": 26490.969785468656}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2020-29/segments/1593657138718.61/warc/CC-MAIN-20200712113546-20200712143546-00058.warc.gz"} |
http://bayesianthink.blogspot.com/2012/11/fun-with-uniform-random-numbers.html | ## Friday, November 16, 2012
### Fun with Uniform Random Numbers
Q: You have two uniformly random numbers x and y (meaning they can take any value between 0 and 1 with equal probability). What distribution does the sum of these two random numbers follow? What is the probability that their product is less than 0.5.
The Probability Tutoring Book: An Intuitive Course for Engineers and Scientists
A: Let z = x + y be the random variable whose distribution we want. Clearly z runs from 0 to 2. Let 'f' denote the uniform random distribution between [0,1]. An important point to understand is that f has a fixed value of 1 when x runs from 0 to 1 and its 0 otherwise.
So the probability density for z, call it P(z) at any point is the product of f(y) and f(z-y), where y runs from 0 to 1.
However in that range f(y) is equal to 1. So the above equation becomes
From here on, it gets a bit tricky. Notice that the integral is a function of z. Let us take a look at how else we can simply the above integral.
It is easy to see that f(z-y) = 1 when (z-y) is between [0,1]. This is the same as saying
Likewise, f(z-y) = 1 when y is lesser than z and greater than 0. ie
Combining the two cases above results in a discontinuous function as
which is a triangular function.
Now that we done with the sum, what about the product xy? A quick way to go about it is to visualize a 2 dimensional plane. All the points (x,y) within the square [0,1]x[0,1] fall in the candidate space. The case when xy = 0.5 makes a curve
The area under the curve would represent the cases for which xy <= 0.5 (shown shaded below). Since the area for the square is 1, that area is the sought probability.
The curve intersects the square at [0.5,1] and [1,0.5]. The area under the curve would the be sum of the 2 quadrants (1/4 each) along with the integral of y = 0.5/x under the range 0.5 to 1 yielding
\begin{align*} P(xy\lt 0.5) &= \frac{1}{2} + \int_{0.5}^{1}\frac{0.5}{x}dx \\ &= \frac{1}{2} + \frac{1}{2}ln2 \approx 0.85 \end{align*}
If you are looking to buy some books in probability here are some of the best books to learn the art of Probability
Here are a few
Fifty Challenging Problems in Probability with Solutions (Dover Books on Mathematics)
This book is a great compilation that covers quite a bit of puzzles. What I like about these puzzles are that they are all tractable and don't require too much advanced mathematics to solve.
Introduction to Algorithms
This is a book on algorithms, some of them are probabilistic. But the book is a must have for students, job candidates even full time engineers & data scientists
Introduction to Probability Theory
An Introduction to Probability Theory and Its Applications, Vol. 1, 3rd Edition
The Probability Tutoring Book: An Intuitive Course for Engineers and Scientists (and Everyone Else!)
Introduction to Probability, 2nd Edition
The Mathematics of Poker
Good read. Overall Poker/Blackjack type card games are a good way to get introduced to probability theory
Let There Be Range!: Crushing SSNL/MSNL No-Limit Hold'em Games
Easily the most expensive book out there. So if the item above piques your interest and you want to go pro, go for it.
Quantum Poker
Well written and easy to read mathematics. For the Poker beginner.
Bundle of Algorithms in Java, Third Edition, Parts 1-5: Fundamentals, Data Structures, Sorting, Searching, and Graph Algorithms (3rd Edition) (Pts. 1-5)
An excellent resource (students/engineers/entrepreneurs) if you are looking for some code that you can take and implement directly on the job.
Understanding Probability: Chance Rules in Everyday Life A bit pricy when compared to the first one, but I like the look and feel of the text used. It is simple to read and understand which is vital especially if you are trying to get into the subject
Data Mining: Practical Machine Learning Tools and Techniques, Third Edition (The Morgan Kaufmann Series in Data Management Systems) This one is a must have if you want to learn machine learning. The book is beautifully written and ideal for the engineer/student who doesn't want to get too much into the details of a machine learned approach but wants a working knowledge of it. There are some great examples and test data in the text book too.
Discovering Statistics Using R
This is a good book if you are new to statistics & probability while simultaneously getting started with a programming language. The book supports R and is written in a casual humorous way making it an easy read. Great for beginners. Some of the data on the companion website could be missing. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 1, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8161534667015076, "perplexity": 569.6860427639293}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2014-42/segments/1414119647914.3/warc/CC-MAIN-20141024030047-00277-ip-10-16-133-185.ec2.internal.warc.gz"} |
http://dynamicsystems.asmedigitalcollection.asme.org/article.aspx?articleID=2648286 | 0
Research Papers
# Design of Robust Double-Fuzzy-Summation Nonparallel Distributed Compensation Controller for Chaotic Power Systems
[+] Author and Article Information
Navid Vafamand
School of Electrical and Computer Engineering,
Shiraz University,
Shiraz 71886-97476, Fars, Iran
e-mail: [email protected]
Department of Energy Technology,
Aalborg University,
Aalborg 71886-97476, Denmark
e-mail: [email protected]
Alireza Khayatian
School of Electrical and Computer Engineering,
Shiraz University,
Shiraz 71348-51154, Fars, Iran
e-mail: [email protected]
Frede Blabbjerg
Department of Energy Technology,
Aalborg University,
Aalborg 71886-97476, Denmark
e-mail: [email protected]
1Corresponding author.
Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL. Manuscript received October 30, 2016; final manuscript received June 18, 2017; published online November 8, 2017. Assoc. Editor: Heikki Handroos.
J. Dyn. Sys., Meas., Control 140(3), 031004 (Nov 08, 2017) (8 pages) Paper No: DS-16-1523; doi: 10.1115/1.4037527 History: Received October 30, 2016; Revised June 18, 2017
## Abstract
This paper studies a systematic linear matrix inequality (LMI) approach for controller design of nonlinear chaotic power systems. The presented method is based on a Takagi–Sugeno (TS) fuzzy model, a double-fuzzy-summation nonparallel distributed compensation (non-PDC) controller, and a double-fuzzy-summation nonquadratic Lyapunov function (NQLF). Since time derivatives of fuzzy membership functions (MFs) appear in the NQLF-based controller design conditions, local controller design criteria is considered, and sufficient conditions are formulated in terms of LMIs. Compared with the existing works in hand, the proposed LMI conditions provide less conservative results due to the special structure of the NQLF and the non-PDC controller in which two fuzzy summations are employed. To evaluate the effectiveness of the presented approach, two practical benchmark power systems, which exhibit chaotic behavior, are considered. Simulation results and hardware-in-the-loop illustrate the advantages of the proposed method compared with the recently published works.
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Vanfretti, L. , Chenine, M. , Almas, M. S. , Leelaruji, R. , Angquist, L. , and Nordstrom, L. , 2012, “ SmarTS Lab—A Laboratory for Developing Applications for WAMPAC Systems,” IEEE Power and Energy Society General Meeting (PESGM), San Diego, CA, July 22–26, pp. 1–8.
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## Figures
Fig. 1
CODOPS system states (Theorem 2 “—,” Ref. [5] “····,” and Ref. [23] “-·-”): (a) The state x1 and (b) the state x2
Fig. 2
PMSM system states (Theorem 2 “—” and Ref. [33] “····”): (a) The state x1, (b) the state x2, and (c) the state x3
Fig. 3
PMSM system control input (Theorem 2 “—” and Ref. [33] “····”)
Fig. 4
Liu system states (Theorem 2 “—” and Ref. [30] “····”): (a) The state x1, (b) the state x2, (c) the state x3, and (d) the statex4
Fig. 5
Liu system control input (Theorem 2 “—” and Ref. [33] “····”): (a) the state x1, (b) the state x2, (c) the state x3, and (d) the state x4
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https://zbmath.org/?q=an:1168.14030 | ×
# zbMATH — the first resource for mathematics
Nondense subsets of varieties in a power of an elliptic curve. (English) Zbl 1168.14030
Let $$A$$ be a $$g$$-dimensional abelian variety over $$\bar{\mathbb{Q}}$$, and $$V$$ be its proper $$d$$-dimensional irreducible algebraic subvariety. $$V$$ is said to be transverse (resp. weak-transverse) if $$V$$ is not contained in any translate of a proper algebraic subgroup of $$A$$ (resp. in any proper algebraic subgroup of $$A$$). Consider the sets $$S_r(V,F)=V\cap\bigcup_{\mathrm{cod} B \geq r}(B+F)$$, where $$B$$ runs over all abelian subvarieties of $$A$$ of codimension at least $$r$$, $$1 \leq r \leq g$$, and $$F$$ is a subset of $$A$$. The author considers the case where $$A = E^g$$ is a power of an elliptic curve $$E$$. Set $$\mathcal{O}_\varepsilon = \{\xi \in E^g \; : \; \|\xi\| \leq \varepsilon\}$$, where $$\varepsilon \geq 0$$, $$\| \cdot \|$$ is a fixed semi-norm on $$E^g$$ induced by the Néron-Tate height on $$E$$, $$\Gamma_\varepsilon = \Gamma + \mathcal{O}_\varepsilon$$, where $$\Gamma$$ is a subgroup of finite rank in $$E^g$$. Let $$V \subset E^g$$ be an irreducible algebraic subvariety of $$E^g$$, and $$V_K = V \cap \mathcal{O}_K$$. With this notation the main result of the paper asserts: for every $$K \geq 0$$ there exists an effective $$\varepsilon \geq 0$$ such that: (i) if $$V$$ is weak-transverse, then $$S_{d+1}(V_K, \mathcal{O}_\varepsilon)$$ is Zariski nondense in $$V$$; (ii) if $$V$$ is transverse, then $$S_{d+1}(V_K, \Gamma_\varepsilon)$$ is Zariski nondense in $$V$$.
The author proves firstly that the assertions (i) and (ii) are equivalent. Then the proof of (ii) consists of three steps. The first two steps allow to avoid $$\Gamma$$ and to approximate an algebraic subgroup with a subgroup of bounded degree. The third step shows that certain special sets are Zariski nondense in $$V \times \gamma$$, where $$\gamma$$ is a maximal free set of the division group of $$\Gamma$$. Here the proof is based on an essentially optimal Bogomolov-type bound for the normalized height of a transverse subvariety in $$E^g$$. There is a conjecture asserting that there exist $$\varepsilon>0$$ and a nonempty Zariski open subset $$V^u$$ of $$V$$ such that if $$V$$ is weak-transverse (resp. transverse), then $$S_{d+1}(V^u, \mathcal{O}_\varepsilon)$$ (resp. $$S_{d+1}(V^u,\Gamma_\varepsilon)$$) has bounded height. The paper concludes with the proof of a special case of this conjecture.
##### MSC:
14K12 Subvarieties of abelian varieties 11G05 Elliptic curves over global fields 11G50 Heights 14H25 Arithmetic ground fields for curves
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http://math.stackexchange.com/questions/73456/after-saw-this-piece-of-discussion-i-ask-myself-what-is-the-most-rigorous-defin | # After saw this piece of discussion, i ask myself what is the most rigorous definition of the circle, but i can't figure it out
Discussion: Is value of $\pi$ = 4?
so what is the "real definition" of a circle?
i think the original solution from wikipedia is too ambigous, i couldn't find why the circumference of the circle is 2*r*pi=3.14...
if we really use the method that i provide from the link how are we able to get an infinite series of pi and find the circumference of an ellipse?
-
Is en.wikipedia.org/wiki/Circle not clear? To quote: "a circle is the set of points in a plane that are a given distance from a given point, the centre". – lhf Oct 17 '11 at 21:21
The standard notion of a circle is a set of all points in a plane equidistant from some fixed point in that plane (its center).
By distance we mean standard Euclidean distance. So a circle in $\mathbb{R}^2$ is a set $\{ (x,y) \in \mathbb{R}^2 \,|\ \mathrm{distance}((x,y),(a,b))=r \}$ for some fixed point $(a,b) \in \mathbb{R}^2$ (the center of the circle) and some fixed (positive) distance $r \in \mathbb{R}$, $r>0$ (the radius).
Euclidean distance is given by the formula: $\mathrm{distance}((x,y),(a,b)) = \sqrt{(x-a)^2+(y-b)^2}$. Thus squaring both sides of the equation "$\mathrm{distance}((x,y),(a,b))=r$" gives us
$$\{ (x,y) \in \mathbb{R}^2 \,|\ (x-a)^2+(y-b)^2=r^2 \}$$
This is the circle with radius $r$ and center $(a,b)$.
If we wish to discuss a circle in $\mathbb{R}^n$, then we need to specify the plane in which it lies. The circle with center ${\bf c}$ and radius $r>0$ which lies in the plane $({\bf x} - {\bf p}) {\bf \cdot} {\bf n}=0$ (the plane through the point ${\bf p}$ with normal vector ${\bf n}$) is given by $\{ {\bf x} \in \mathbb{R}^n \,|\ ({\bf x}-{\bf p}){\bf \cdot}{\bf n}=0 \mbox{ and } |{\bf x}-{\bf c}|=r \}$. Again $|{\bf x}-{\bf c}|$ is the standard Euclidean norm.
If you mess with the definition of distance, then you can still call the corresponding set a "circle", but it's not a circle is the standard "classical" sense.
-
That discussion had nothing to do with the definition of "circle", and everything to do with the definitions of "length" and "limit". But at any rate, the definition of a circle (in the plane, $\mathbb{R}^2$) is a subset of the form $$\{(x,y)\in\mathbb{R}^2\mid (x-h)^2+(y-k)^2=r\}$$ where $r\in\mathbb{R}$, $r>0$ and $(h,k)\in\mathbb{R}^2$ is any point.
The circumference of a circle of radius $r$ is $2\pi r$ essentially by the definition of $\pi$ (so unless your circle has radius $\frac{1}{2}$, it doesn't have circumference $\pi$...). See here or here for an explanation of why this actually defines a single number $\pi$ for all circles.
-
Here's a totally rigorous definition.
Definition. For all $C \subseteq \mathbb{R}^2,$ we call $C$ a circle iff there exists $r>0$ and $c \in \mathbb{R}^2$ such that the following holds. $$\forall x \in \mathbb{R}^2(x \in C \leftrightarrow d(x,c)=r)$$
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https://homework.cpm.org/category/ACC/textbook/ccaa8/chapter/9%20Unit%2010/lesson/CCA:%209.4.1/problem/9-99 | ### Home > CCAA8 > Chapter 9 Unit 10 > Lesson CCA: 9.4.1 > Problem9-99
9-99.
$x^2−6x+3=0$
Subtract 3 from both sides of the equation. Then add a constant to both sides to make $\left(x-3\right)^2$on the left side. | {"extraction_info": {"found_math": true, "script_math_tex": 2, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8780133724212646, "perplexity": 1899.8076389698967}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2020-50/segments/1606141674082.61/warc/CC-MAIN-20201201104718-20201201134718-00473.warc.gz"} |
http://www.elke.ntua.gr/en/research_project/a-study-of-heavy-quark-production-with-the-h1-experiment-at-hera/ | A STUDY OF HEAVY QUARK PRODUCTION WITH THE H1 EXPERIMENT AT HERA
Ref.No: 65120000 Start date: 01.01.2002 End date: 30.06.2004 Approval date: 15.11.2002 Department: APPLIED MATHEMATICAL & PHYSICAL SCIENCES Sector: PHYSICS Financier: ΒΑΣΙΚΗ ΕΡΕΥΝΑ, E.M.P. EID.LOG.EREUNAS PD 432/ Budget: 11.738,80 € Scientific Responsible: Assoc. Prof. GEORGIOS TSIPOLITIS Email: [email protected] Description: THE STUDY OF ELECTRON PROTON COLLISIONS WHERE AMONG THE PRODUCTS ARE HARDONS THAT INCLUDE ONE OF THE HEAVY QUARKS IS ONE OF THE BASIC TESTS OF THE QUANTUM CHROMODYNAMICS. THE MEASUREMENTS OF THE PRODUCTION OF THE C-QUARK ARE IN A REASONABLE AGREEMENT...
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http://www.graphoilogy.com/2006_04_01_archive.html | ## Thursday, April 20, 2006
### Status of the US Gasoline Stockpiles
This is a quick post about the spectacular drop in gasoline stock that have been reported by the EIA this week:
Fig 1. US gasoline stocks (EIA, 14th April 2006).
I was wondering how significant is this drop in terms of equivalent Number of Day of Forward Consumption (NDFC). The NDFC is a convenient way to take into account the current level of gasoline consumption which is rising every year. I used the data from the spreadsheet available on the EIA website that gives the historical stock and demand levels for gasoline since February 1991. The NDFC values are simply computed by dividing each stock volume by the gasoline demand at each available point int time. Because the EIA produces data only on a weekly basis, I interpolated the data for the remaining days of the year (spline interpolation). Then, for each day of the year, I computed the observed NDFC value distribution (i.e. the frequency of each NDFC value for a given day). The resulting probability map is shown in the background of Fig. 2, the darkest areas indicate the more probable NDFC values from the available historic data (1991-2006).
Fig 2. Observed NDFC values: the shaded gray values are the observed distribution of NDFC values for each day of the year from all the available years (1991 to 2006) (dark means high probability, white means low probability). The lines are for the last 5 years.
Clearly, we can observe that the current stock levels, as well as for the last five years, are in the lower range of what have been observed over the past 15 years. However, this week NDFC value is still near the most probable NDFC value for this days of the year (around 23 days).
For more discussion, there is also a thread on theoildrum and interesting graphs by Oil CEO.
## Tuesday, April 18, 2006
### What the mainstream media is not telling you about the recent run up in oil prices
by Jeffrey J. Brown
Following is an excerpt from a recent Reuters article on oil prices:
"Oil prices have risen more than 20 percent since mid-February, despite sizable U.S. crude inventories, as geo-political fears compounded fundamental worries that refiners might struggle to make enough gasoline for the summer driving season."
Guess what also happened in mid-February? Total net US petroleum imports started falling.
The following numbers are weekly, not four week running averages. The week ending 2/10/06 showed average daily net petroleum imports of 13,396,000 bpd. Seven of the subsequent eight weeks have shown declines. The most current weekly data (through 4/7/06) show average weekly total net US petroleum imports of 11,634,000 bpd. This is a decline of 13.2%. (The same period last year showed about a 3.7% decline.)
Looking at a slightly bigger picture, 12/30/05 to 4/7/06 (four week running average) we saw a decline of 8.7% (versus an increase in imports for the same time period last year).
In the article that "Khebab" and I coauthored that was published on March 6, 2006, "M. King Hubbert's Lower 48 Prediction Revisited", we had the following statements:
"A critical point to keep in mind is that an exporter can only export what is left after domestic consumption is satisfied. Consider a simple example, a country producing 2.0 mbpd, consuming 1.0 mbpd and therefore exporting 1.0 mbpd. Let's assume a 25% drop in production over a six year period (which we have seen in the North Sea, which by the way peaked at 52% of Qt) and let's assume a 10% increase in domestic consumption. Production would be 1.5 mbpd. Consumption would be 1.1 mbpd. Net exports would be production (1.5 mbpd) less consumption (1.1 mbpd) = 0.4 mbpd. Therefore, because of a 25% drop in production and because of a 10% increase in domestic consumption, net oil exports from our hypothetical net exporter dropped by 60%, from 1.0 mbpd to 0.4 mbpd, over a six year period.
" We are deeply concerned that the world is probably facing an imminent and catastrophic collapse in net oil export capacity because of declining production and increasing domestic consumption in the top exporting countries.
Again, from 2/10/06 to 4/7/06, total net petroleum imports into the US dropped 13.2%, which corresponded to a 20% increase in light, sweet crude oil prices. There is one market for light, sweet crude oil (at least when the US government is not putting oil into the strategic petroleum reserve): refineries. If refiners don't need the imports, why are they bidding up the price of light, sweet crude oil?
Consider the simple math. If Deffeyes is correct that the world oil production peaked in December, 2005, then at current rates of consumption, by the time that a first grader, entering the first grade this September, 2006, is ready for the fifth grade in September, 2010, we will have used more than 10% of all remaining conventional crude + condensate reserves.
The two "cleanest" HL (Hubbert Linearization) case histories we have are the Lower 48 and the North Sea (see link below for more information). The two principal constraints on production were: (1) they would not produce oil at a loss and (2) fields were generally produced at a rate which would not damage the reservoirs. There were no substantial political problems or constraints on production.
The Lower 48 peaked at slightly less than 50% (at 49%) and the North Sea peaked at slightly over 50% (52%). In other words, slightly less than 50% to slightly more than 50%. These were both for crude + condensate Deffeyes estimated that we hit the crude + condensate 50% of Qt mark worldwide in mid-December. The highest crude + condensate EIA number on record was for December, 2005, followed promptly by about a 500,000 bpd drop in January, 2006.
It is true that we have relatively high crude oil inventories, but note that we don't know what percentage of crude oil inventories consists of heavy, sour crude, which can't be used in light, sweet crude oil refineries. Also, total product inventories are only up 2.9% year over year. But fundamentally, what does one expect to see at peak production? I expect to see peak everything, followed by a permanent and irreversible decline in conventional oil production.
The interesting question is why the Mainstream Media (MSM) is not fully reporting the oil story.
I think that we are seeing an "Iron Triangle" of sorts defending the status quo: (1) most housing/auto/financing companies and related companies; (2) Most MSM companies that are selling advertising to Group #1 and (3) some major oil companies, major oil exporters and energy analysts that are working for the major oil companies and exporters.
In my opinion, Group #3 is afraid of punitive taxation (major oil companies) and military takeovers (exporters). Group #1 wants to keep selling and financing large homes and SUV's. Group #2 wants to keep selling advertising to Group #1. Group #3 provides the arguments for Groups #1 and #2, i.e., we have trillions and trillions of barrels of remaining reserves.
One important exception to Group #1: Mike Jackson, the CEO of AutoNation, is calling for a much higher gasoline tax. While this is a start, I recommend a much higher energy tax, offset by tax cuts elsewhere.
## Monday, April 03, 2006
### An Open Letter to the Publishers of the Fort Worth Star Telegram and the Dallas Morning News
April 2, 2006
Mr. Wesley R. Turner, President & Publisher
Fort Worth Star Telegram
Mr. James H. Moroney , III, Publisher & CEO
The Dallas Morning News
Subject: What Are Two Texas Billionaires,
Richard Rainwater & T. Boone Pickens,
Saying About Peak Oil & Why Aren’t You Listening?
Gentlemen:
I realize that I don’t have to introduce Richard Rainwater and Boone Pickens to you two gentlemen, but for the benefit of those who may not be familiar with Messrs. Rainwater and Pickens, following are brief introductions.
Richard Rainwater is the Texas based businessman who was chiefly responsible for turning the Bass Family’s inheritance of $50 into a$5 billion dollar fortune. Mr. Rainwater was therefore indirectly responsible for the remarkable urban renaissance of downtown Fort Worth, as a result of the Bass family’s massive investments. Mr. Rainwater also had a material role in George W. Bush’s selection as Managing Partner of the Texas Rangers Baseball Team, which launched Mr. Bush on his way to the Governor’s Mansion and then to the White House.
Mr. Pickens, now based in Dallas, has had a long and storied career in the oil and gas industry. Like most Texas oilmen, Mr. Pickens has had his ups and downs. Most recently he has been on an up cycle, via his investment firm, BP Capital.
These two gentlemen share an uncanny and proven ability to accurately predict future trends. The only real mistake that I am aware of is Mr. Pickens’ timing regarding natural gas prices some years ago. He was right about the price move, but he was just a little early.
Mr. Rainwater was profiled in the 12/14/05 issue of Fortune Magazine, “The Rainwater Prophecy.” Mr. Rainwater is deeply concerned about Peak Oil. In the article, Mr. Rainwater said, “This is the first scenario I’ve seen where I question the survivability of mankind.” Mr. Rainwater first became concerned about Peak Oil after reading “The Long Emergency” by James Howard Kunstler.
According to Bill McKenzie, with the Dallas Morning News, the primary reason that President Bush used the “Addicted to OIl” phrase in his state of the Union Speech was the Fortune article about Richard Rainwater, and again Mr. Rainwater became concerned about Peak Oil after reading Mr. Kunstler’s book.
On November 1, 2005 the Greater Dallas Planning Council and the Southern Methodist University Environmental Sciences Department cosponsored a symposium featuring Mr. Kunstler and Matthew R. Simmons entitled “The Unfolding Energy Crisis and its Impact on Development Patterns.”
Mr. Pickens, via BP Capital, was one of the lead underwriters of the event.
Mr. Pickens, several of his associates, and several other notable Dallas businessmen such as Herbert Hunt were at the Simmons/Kunstler symposium, but no one from your respective editorial and news departments were able to make the event--despite multiple notices of the event.
In any case, Mr. Pickens has publicly stated that he believes that the world is at peak oil production. Mr. Pickens has publicly suggested increasing the gasoline tax, in an attempt to reduce oil consumption, with offsetting tax cuts elsewhere.
I certainly don’t speak for either Richard Rainwater or Boone Pickens, but my impression of these two gentlemen--along with Matt Simmons and Jim Kunstler--is that they are American patriots, in the truest sense of the word, who are trying to warn their fellow Americans about the dangers posed by Peak Oil.
In the Fortune interview, Mr. Rainwater was quoted as follows, “I believe in Hubbert’s Peak. I came out of Texas. I watched oil fields reach peak and go over, and I’ve watched how people would do all they could, put whatever amount of money into the field, and they couldn’t do anything about it.”
Much of the Peak Oil debate is based on pioneering work done by a famous Texas born geoscientist, M. King Hubbert. My coauthor, “Khebab,” and I wrote an article that was published on the Energy Bulletin website, “M. King Hubbert's Lower 48 Prediction Revisited: What can 1970 and Earlier Lower 48 Oil Production Data Tell Us About Post-1970 Lower 48 Oil Production?” Following is an excerpt from that article.
"Fifty years ago this week, on March 8, 1956, at a meeting of the American Petroleum Institute in San Antonio, Texas, M. King Hubbert, in the preprinted version of his prepared remarks, had the following statement, "According to the best currently available information, the production of petroleum and natural gas on a world scale will probably pass its climax within the order of a half century (i.e., by 2006), while for both the United States and for Texas, the peaks of production may be expected to occur with the next 10 or 15 years (i.e., 1966 to 1971)." As more and more people are learning, Lower 48 oil production, as predicted by Dr. Hubbert, peaked in 1970, and it has fallen fairly steadily since 1970.
Kenneth Deffeyes, in Chapter Three of his recent book, "Beyond Oil: The View From Hubbert's Peak," described a simplified way of predicting the production peaks for various regions and for their subsequent declines. One simply plots annual production (P) divided by cumulative production to date (Q) on the vertical axis, or P/Q, versus Q on the horizontal axis. Stuart Staniford, on The Oil Drum Blog, has described this technique as "Hubbert Linearization" or HL.
With time, a HL data set starts to show a linear progression, and one can extrapolate the data down to where P is effectively zero, which gives one Qt, or ultimate recoverable reserves for the region. Based on the assumption that production tends to peak at about 50% of Qt, one can generate a predicted production profile for the region. The Lower 48 peaked at 48.5% of Qt.
Using the HL technique, Dr. Deffeyes, an associate of Dr. Hubbert, predicted that the world crossed the mathematical 50% of Qt mark on December 16, 2005. In other words, Dr. Deffeyes believes that the world is now where the Lower 48 was at in the early Seventies."
We used the HL method to predict post-1970 Lower 48 cumulative oil production, using only 1970 and earlier production data. Our work indicated that the HL method was 98.7% accurate in predicting post-1970 Lower 48 cumulative oil production.
We need to differentiate between conventional and nonconventional oil. Perhaps the best way to differentiate the two types of oil is to classify it the following way. Conventional--the oil will move to a wellbore on its own. Nonconventional--the oil and oil-like solids have to be surface mined or heated in order to move to a wellbore (or synthesized from lighter hydrocarbons).
Dr. Deffeyes estimates that we have two trillion barrels of recoverable conventional oil reserves worldwide and that we have used half of this amount.
Fossil fuels can be viewed as a continuum, from natural gas, to natural gas liquids, to condensate, to light sweet crude oil to heavy sour crude oil to bitumen to coal. (Kerogen, a precursor to bitumen, can also be processed to yield oil.) This list is a progression from gas, to liquid to solid. It is also a progression from cleanest, natural gas, to dirtiest, coal.
The world wants Liquid Transportation Fuels (LTF’s)--gasoline, diesel and jet fuel. LTF’s can be obtained for the least expenditures of energy and capital from light sweet crude. It only makes sense that light sweet crude will peak before heavy sour, and based on the current historically high spreads between light sweet crude and heavy sour crude, that appears to be the case.
The world is increasingly turning toward the endpoints--natural gas/natural gas liquids on the light end and bitumen/coal on the heavy end--in an attempt to maintain and increase our supply of LTF’s. There are several problems. These are hugely capital intensive programs that tend to produce liquids at very low rates compared to conventional oil sources, and on the heavy end there are some fairly severe environmental consequences. Another point that is often overlooked is that every fossil fuel resource, except for kerogen, is currently being commercially exploited. In other words, we are simply talking about increasing our rate of extraction of our finite fossil fuel resource base in a desperate attempt to maintain the current American way of life of driving $50,000 SUV’s on 50 mile roundtrips to and from$500,000 mortgages.
Currently, the most significant source of nonconventional oil is the tar sands play in Alberta, Canada, where bitumen is being extracted via surface mining or via the injection of steam into deeper beds.
From fossil fuel and nuclear sources, the world currently uses the energy equivalent of a billion barrels of oil (Gb) every five days. The mighty East Texas Oil Field, the foundation of so many Dallas fortunes, the largest oil field in the Lower 48, and the field that was largely responsible for providing the oil to power the Allies victory over the Axis powers in World War II, made about 5.5 Gb. The field is currently producing 1.2 million barrels of water per day, with a 1% oil cut. It took about 75 years to pretty much fully deplete the East Texas Field. In terms of oil equivalent, the Barnett Shale Gas Play in North Texas should ultimately produce, over several decades, on the order of 4-5 Gbe.
The world uses, from nuclear and fossil fuel sources, the energy equivalent of the recoverable reserves in the East Texas oil Field or the Barnett Shale Play in less than 30 days.
In the 4/2/06 Star Telegram, Automotive Journalist Ed Wallace, in the classified advertising section, wrote a rebuttal to the Peak Oil theories. Mr. Wallace’s two basic points: (1) improved technology will increase recoverable conventional reserves by 50% to 3,000 Gb and (2) nonconventional oil sources will add another 3,000 Gb. Therefore, based on Mr. Wallace’s estimates, we have used 1,000 Gb out of a 6,000 Gb resource base.
In the Viewpoints (Op-Ed) section of the Dallas Morning News, similar “cornucopian” energy abundance articles were published last year making basically the same points that Mr. Wallace made.
In regard to the technology issue, this assertion is directly contradicted by our experience in Texas (peaked at 54% of Qt), the overall Lower 48 (peaked at 49% of Qt) and the North Sea (peaked at 52% of Qt). Nothing the industry has tried in these regions has reversed the production declines once about half of the oil reserves were consumed. The reason is best illustrated by the East Texas field, now producing water with a 1% oil cut. What can better technology do to help a field that has watered out?
In regard to the nonconventional sources of oil, Mr. Wallace is primarily focused on the Canadian tar sands and shale oil (kerogen). The tar sands play is a proven commercial success, that is however hugely energy intensive and that is also yielding vast amounts of contaminated waste water. Mr. Wallace cites the most widely used estimate of 175 Gb in recoverable reserves (note that this should be discounted by about 35% to 50% to get net energy equivalent). He also cited a vague estimate by a Shell executive of 2,000 Gb, that can’t be currently recovered. There is one interesting research program testing some new shale oil technologies, but there is nothing commercial yet.
In any case, let’s look at past and current estimates of Canadian tar sands production. In 2003, the US Energy Information Agency (EIA) estimated that total Canadian oil production--driven by increasing tar sands production--would increase by 700,000 BOPD from 2003 to 2005. The reality? Total Canadian oil production fell from 2003 to 2005. The tar sands production fell short of estimates, and the increasing tar sands production the Canadians had could not make up for the decline in conventional Canadian oil production.
The Canadians themselves are estimating that tar sands production will only increase to about three million BOPD (mbpd) in 2016 from one mbpd today. Note that we will probably start losing a net two mbpd to four mbpd in conventional oil production per year, starting this year. Again, note that you have to discount the tar sands production by 35% to 50% to get net energy.
In effect, Mr. Wallace, and the other energy cornucopians see no problem with the $50,000 Hummer,$500,000 mortgage way of life.
Messrs. Rainwater and Pickens disagree. I can’t speak for them, but I assume that they believe that while nonconventional oil will help, it will only serve to slow the rate of decline of total oil production.
Some types of ethanol production (not from corn sources) appear have some possibilities, but there are a number of problems. Among the problems is a basic conflict between land devoted to food production and land devoted to fuel production. By the way, the US is probably now a net food importer. Currently, the US uses up to 10 calories of fossil fuels to produce one calorie of food. Ponder the impact on our food supply of a declining oil supply.
I realize that US media companies are facing severe economic pressures, and I realize that you are heavily dependent on advertising revenues from the housing/auto industries and from related companies. However, in my opinion we have hit the iceberg. The US media can lash themselves to the sinking ship, by failing to face reality, or you can face the reality of finite energy resources and start heading for the lifeboats.
I am supporting a proposal to abolish the Payroll (Social Security + Medicare) Tax and to replace it with an energy tax, principally a tax on liquid transportation fuels. This would unleash powerful economic forces against profligate energy use. Since it is in effect a consumption tax, it would tax those who currently don’t pay the Payroll Tax, by using cash. Instead of taxing payrolls to fund the Social Security and Medicare systems, we would instead tax energy consumption.
Alan Drake, a consulting engineer, has written a compelling article advocating a crash program of electrifying our transportation system, with special emphasis on Urban Rail.
I am working with a small group regarding the possibility of a Fall symposium on the Energy Tax and Urban Rail proposals, and we would be delighted to have support from The Fort Worth Star Telegram and/or The Dallas Morning News.
Note that these two proposals would address: the Social Security/Medicare crisis; the Peak Oil crisis; the loss of farmland due to suburban sprawl and Global Warming issues. We would replace “dumb growth” with “smart growth,” New Urbanism projects along mass transit lines.
In addition, I would at least ask you to give your readers a balanced report on the Peak Oil issue. Two leading citizens of your respective cities--Richard Rainwater and T. Boone Pickens--are deeply concerned about Peak Oil. The stated mission of the Fort Worth Star Telegram is: “Earning the People’s Trust Daily.” I assume that the Dallas Morning New concurs with this mission statement.
In my opinion, the US media have two choices regarding the Peak Oil issue. To paraphrase Winston Churchill, you can now have either your honor or the status quo. If you do nothing regarding Peak Oil, you will soon have neither the status quo nor your honor.
Sincerely,
Jeffrey J. Brown
Jeffrey J. Brown is an independent petroleum geologist in the Dallas area.
[email protected]
Fortune: The Rainwater Prophecy
Brown & Khebab: M. King Hubbert's Lower 48 Prediction Revisited
Wallace: A Theory Like Y2K, But For Cars...
Drake: Electrification of transportation as a response to peaking of world oil production | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.3176182508468628, "perplexity": 3952.271548192109}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 20, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2016-26/segments/1466783402516.86/warc/CC-MAIN-20160624155002-00060-ip-10-164-35-72.ec2.internal.warc.gz"} |
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The Algebraic Theory of Semigroups, Volume I
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Electronic ISBN: 978-1-4704-1234-0
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AMS Member Price: $39.20 Click above image for expanded view The Algebraic Theory of Semigroups, Volume I Available Formats: Electronic ISBN: 978-1-4704-1234-0 Product Code: SURV/7.1.E List Price:$49.00 MAA Member Price: $44.10 AMS Member Price:$39.20
• Book Details
Mathematical Surveys and Monographs
Volume: 71961; 224 pp
MSC: Primary 20;
The material in this volume was presented in a second-year graduate course at Tulane University, during the academic year 1958–1959. The book aims at being largely self-contained, but it is assumed that the reader has some familiarity with sets, mappings, groups, and lattices. Only in Chapter 5 will more preliminary knowledge be required, and even there the classical definitions and theorems on the matrix representations of algebras and groups are summarized.
• Table of Contents
• Chapters
• 1. Elementary concepts
• 2. Ideals and related concepts
• 3. Representation by matrices over a group with zero
• 4. Decompositions and extensions
• 5. Representation by matrices over a field
• Requests
Review Copy – for reviewers who would like to review an AMS book
Permission – for use of book, eBook, or Journal content
Accessibility – to request an alternate format of an AMS title
Volume: 71961; 224 pp
MSC: Primary 20;
The material in this volume was presented in a second-year graduate course at Tulane University, during the academic year 1958–1959. The book aims at being largely self-contained, but it is assumed that the reader has some familiarity with sets, mappings, groups, and lattices. Only in Chapter 5 will more preliminary knowledge be required, and even there the classical definitions and theorems on the matrix representations of algebras and groups are summarized.
• Chapters
• 1. Elementary concepts
• 2. Ideals and related concepts
• 3. Representation by matrices over a group with zero
• 4. Decompositions and extensions
• 5. Representation by matrices over a field
Review Copy – for reviewers who would like to review an AMS book
Permission – for use of book, eBook, or Journal content
Accessibility – to request an alternate format of an AMS title
Please select which format for which you are requesting permissions. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.28961479663848877, "perplexity": 2802.600769201623}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 20, "end_threshold": 15, "enable": false}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2023-14/segments/1679296949025.18/warc/CC-MAIN-20230329182643-20230329212643-00109.warc.gz"} |
https://en.wikipedia.org/wiki/Parameter_identification_problem | # Parameter identification problem
For a more technical treatment, see Identifiability.
In statistics and econometrics, the parameter identification problem is the inability in principle to identify a best estimate of the value(s) of one or more parameters in a regression. This problem can occur in the estimation of multiple-equation econometric models where the equations have variables in common.
More generally, the term can be used to refer to any situation where a statistical model will invariably have more than one set of parameters that generate the same distribution of observations, meaning that multiple parametrizations are observationally equivalent.
## Standard example, with two equations
Consider a linear model for the supply and demand of some specific good. The quantity demanded varies negatively with the price: a higher price decreases the quantity demanded. The quantity supplied varies directly with the price: a higher price increases the quantity supplied.
Assume that, say for several years, we have data on both the price and the traded quantity of this good. Unfortunately this is not enough to identify the two equations (demand and supply) using regression analysis on observations of Q and P: one cannot estimate a downward slope and an upward slope with one linear regression line involving only two variables. Additional variables can make it possible to identify the individual relations.
In the graph shown here, the supply curve (red line, upward sloping) shows the quantity supplied depending positively on the price, while the demand curve (black lines, downward sloping) shows quantity depending negatively on the price and also on some additional variable Z, which affects the location of the demand curve in quantity-price space. This Z might be consumers' income, with a rise in income shifting the demand curve outwards. This is symbolically indicated with the values 1, 2 and 3 for Z.
With the quantities supplied and demanded being equal, the observations on quantity and price are the three white points in the graph: they reveal the supply curve. Hence the effect of Z on demand makes it possible to identify the (positive) slope of the supply equation. The (negative) slope parameter of the demand equation cannot be identified in this case. In other words, the parameters of an equation can be identified if it is known that some variable does not enter into the equation, while it does enter the other equation.
A situation in which both the supply and the demand equation are identified arises if there is not only a variable Z entering the demand equation but not the supply equation, but also a variable X entering the supply equation but not the demand equation:
supply: ${\displaystyle Q=a_{S}+b_{S}P+cX\,}$
demand: ${\displaystyle Q=a_{D}+b_{D}P+dZ\,}$
with positive bS and negative bD. Here both equations are identified if c and d are nonzero.
Note that this is the structural form of the model, showing the relations between the Q and P. The reduced form however can be identified easily.
## Estimation methods and disturbances
"It is important to note that the problem is not one of the appropriateness of a particular estimation technique. In the situation described [without the Z variable], there clearly exists no way using any technique whatsoever in which the true demand (or supply) curve can be estimated. Nor, indeed, is the problem here one of statistical inference—of separating out the effects of random disturbance. There is no disturbance in this model [...] It is the logic of the supply-demand equilibrium itself which leads to the difficulty." (Fisher 1966, p. 5)
## More equations
More generally, consider a linear system of M equations, with M > 1.
An equation cannot be identified from the data if less than M − 1 variables are excluded from that equation. This is a particular form of the order condition for identification. (The general form of the order condition deals also with restrictions other than exclusions.) The order condition is necessary but not sufficient for identification.
The rank condition is a necessary and sufficient condition for identification. In the case of only exclusion restrictions, it must "be possible to form at least one nonvanishing determinant of order M − 1 from the columns of A corresponding to the variables excluded a priori from that equation" (Fisher 1966, p. 40), where A is the matrix of coefficients of the equations. This is the generalization in matrix algebra of the requirement "while it does enter the other equation" mentioned above (in the line above the formulas).
## Related use of the term
In engineering language, the term "parameter identification" is used to indicate a more general subject, which is roughly the same as estimation in statistics. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 2, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8758203983306885, "perplexity": 604.4528847985853}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.3, "absolute_threshold": 10, "end_threshold": 5, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2018-30/segments/1531676590329.62/warc/CC-MAIN-20180718213135-20180718233135-00492.warc.gz"} |
https://assertnotmagic.com/2017/05/30/unwrapping-decorators-1/ | # Preface
I promised in an earlier post to talk about Python decorators. A note for the smarty-pantses reading this: there is apparently something called the Decorator Pattern. While you can use Python “lowercase d” decorators to implement the Decorator Pattern, that is only one possible use for them. For a longer and more detailed discussion of the naming issues here, the Type A people should read the relevant PEP. For the rest of this post, when I say decorator, I mean the Python decorator language feature. Now. Onward!
# Prerequisites
I have to lay a baseline so that everybody is on the same page. If you’re comfortable with functional concepts like functions as variables, parameters, returned objects, and functions within functions – and you don’t want to hear me yammer about it – you can skip to the good stuff.
## Functions as Variables
For those of you still with me, God bless you. If you didn’t know, in the same way you assign a literal value to a variable, you can assign a function without calling it.
## Functions as Parameters and Return Values
Cool, right? Now, as a direct result of that, you can pass functions around in and out of other functions, just like any other variable.
## Defining Functions within Other Functions
You can even define functions within other functions! This can be super powerful. Which leads to one of my favorite coding puzzles of all time: make the following test pass.
assert five(plus(three())) == 8
Like I said, that one’s a puzzle, so if you don’t get it the first time, try writing in out on paper, and doing the substitutions like a math problem. Anyways, long story short, functions are neat little objects that you can sling around and define pretty much anywhere you could use literals. A function doesn’t get called until you slap some () on the end. Now, the main event.
# Decorators
Decorators are used to wrap other functions to add separate functionality without polluting the function in question. This helps each function retain a Single Responsibility™. I believe in learning the crappy way to do something first, so you appreciate the beauty of the pretty way, so let’s look at how we would do that…
## The Crappy Way
Imagine we have a function that barked everytime its inner function was called. Why? Because examples are hard.
In order to wrap hello in the woofing functionality, we’d have to do this:
Do you see what happens? We replace hello with inner, which prints “Woof!” before calling the original hello function. Not beautiful. Not beautiful because you have to wrap hello after it is defined. Someone could possibly glance at the function definition before calling it, blithely expecting Hello! but getting an unexpected Woof!. The path of least surprise is usually the best one. What if it looked more like this:
## The Pretty Way
You would be able to quickly see what the function did and that it was slightly modified by something called pre_bark. Now we’re talking. And then there was evening, and there was morning – your first decorator. And it was good.
## But What About My Arguments?
In order to snag any arguments passed to your function, the inner function will accept those arguments in the form of *args, **kwargs. I won’t go into that now, but this has a pretty good explanation if you are not familiar. Short version: think of *args as a list of all the positional arguments passed and **kwargs as a dictionary of all of the keyword arguments passed. That’s not quite accurate, but it’s close enough for government work.
# Conclusion of Part 1
I was going to go on, because we still have to talk about passing arguments to decorators, stacking decorators, and we haven’t even begun to cover what you can do with decorators and classes! But then I looked at my word-count-o-meter which informed me that I was well beyond even the bravest of attention spans. I’ll finish up with the rest of this next week. I’m sure everyone will be mashing their refresh button, anxiously waiting for the dramatic conclusion.
Author: Ryan Palo | Tags: python pythonic functional |
Like my stuff? Have questions or feedback for me? Want to mentor me or get my help with something? Get in touch! To stay updated, subscribe via RSS | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.267179012298584, "perplexity": 1410.3486115664061}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2018-47/segments/1542039741628.8/warc/CC-MAIN-20181114041344-20181114063344-00226.warc.gz"} |
https://brilliant.org/problems/polynomial-equation-3/ | Polynomial equation
Algebra Level 5
Find the number of polynomials $$P(x)$$ with integer coefficients such that $$\deg P(x)\leq 2014$$ and
$P(x)^2-2=P(x^2-2)$
This problem is not original
× | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 1, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.7831078171730042, "perplexity": 500.2578986063051}, "config": {"markdown_headings": false, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-30/segments/1500549426234.82/warc/CC-MAIN-20170726162158-20170726182158-00045.warc.gz"} |
https://www.physicsforums.com/threads/torque-req-for-fixed-rot-acc.124725/ | # Torque Req. for Fixed Rot. Acc.
1. Jun 26, 2006
### Beyond Aphelion
I'm having difficulty with this question:
A day-care worker pushes tangentially on a small hand-driven merry-go-round and is able to accelerate it from rest to a spinning rate of 18.0 rpm in 10.1s. Assume the merry-go-round is a disk of radius 2.30m and has a mass of 830kg, and two children (each with a mass of 25.4kg) sit opposite each other on the edge. Calculate the torque required to produce the acceleration, neglecting frictional torque.
Alright, this is my process; although, I know my end result is wrong:
I used the angular kinematic equation to solve for the angular acceleration.
f = ωi + αΔt)
I got α = 0.186629 rad/s² (approx.) after converting from rpm's.
The equation I have for torque is:
τ = mr²α
But, since we're working with a disk, I = ½MR².
Therefore, I solved for torque using the equation:
τ = ½MR²α
I'm moderately confident with myself at this point, although I realize I can be completely off, but I think I'm screwing up what to use for mass.
I plugged in the mass of the merry-go-round plus the mass of the two children.
M = 880.8 kg
Most likely, this is where my reasoning is flawed. I've just recently been introduced to torque, and it is honestly confusing me.
τ = ½MR²α = τ = ½(880.8 kg)(2.3)²(0.186629 rad/s²) =
434.79 N*m
This is the wrong answer, I know. But it is the best I could come up with based on the information my textbook is giving me. Any advice would be helpful.
2. Jun 26, 2006
### nrqed
For a point mass, I is MR^2 (where R is the distance from the point mass to the axis of rotation). For a disk, the moment of inertia is 1/2 MR^2. What you have to do here is to calculate the total moment of inertia, with is $I_{total}=I_{child#1} + I_{child#2} + I_{disk}$
Use this for the total moment of inertia. barring any algebra mistake, this should work.
Patrick
Similar Discussions: Torque Req. for Fixed Rot. Acc. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9126288294792175, "perplexity": 1154.8846736858404}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-17/segments/1492917120881.99/warc/CC-MAIN-20170423031200-00358-ip-10-145-167-34.ec2.internal.warc.gz"} |
http://mathhelpforum.com/statistics/72423-question-probability.html | # Math Help - Question on Probability!
1. ## Question on Probability!
49. On a multiple choice test of 10 questions, each question has 5 possible answers. A student is certain of the answers to 4 questions but is totally baffled by 6 questions. If the student randomly guesses the answer to those 6 questions, what is the probability that the student will get a score of 5 or more on the test? Express your answer correct to two decimal places. out of 4 marks
2. Originally Posted by cnmath16
49. On a multiple choice test of 10 questions, each question has 5 possible answers. A student is certain of the answers to 4 questions but is totally baffled by 6 questions. If the student randomly guesses the answer to those 6 questions, what is the probability that the student will get a score of 5 or more on the test? Express your answer correct to two decimal places. out of 4 marks
Since the student is certain to get at least 4 of the questions correct, he is getting at least a 4 on the exam, then. Thus, it is equivalent to having a 6 (10 questions - 4 guarantees) question test and asking about the probability of getting 1 or more on the exam.
We observe that the chances of him getting any one question correct is 1/5, or 20% and of course, the chance of him getting it wrong would be 4/5, or 80%. Find the probability that he gets all 6 questions wrong first. By independent, we can simply multiple and get $0.8^6$. So that chance that he gets at least 1 question right is the complement of the previous probability, or $1-0.8^6$. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 2, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.7098814249038696, "perplexity": 166.75752091513556}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2016-22/segments/1464049278389.62/warc/CC-MAIN-20160524002118-00129-ip-10-185-217-139.ec2.internal.warc.gz"} |
https://www.physicsforums.com/threads/tension-of-string-holding-one-mass-to-a-wall-on-top-of-another-moving-mass.300050/ | # Tension of string holding one mass to a wall, on top of another moving mass?
#### finniusmorgan
1
0
Hello!
This is my first post, I am taking an introductory physics course during my second semester of college and having some trouble with this problem. I hope I have followed the correct format, I appreciate any help that can be offered!
1. The problem statement, all variables and given/known data
A 4.82 kg block is placed on top of a 10.7 kg
block. A horizontal force of F = 69.7 N is
applied to the 10.7 kg block, and the 4.82 kg
block is tied to the wall. The coefficient of
kinetic friction between all moving surfaces
is 0.197. There is friction both between the
masses and between the 10.7 kg block and the
ground.
The acceleration of gravity is 9.8 m/s2 .
2. Relevant equations
F=ma
f= [coefficient of friction]*Fn
3. The attempt at a solution
I really don't know how to find the normal forces that are used in finding the frictional force, but after that I would subtract the friction from the horizontal force to find the net force on the bottom (10.7kg) object, but I do not understand how to relate that to the tension in the string holding the second object.
Thank you!
#### sArGe99
133
0
Hint : The frictional force between the blocks acts in different directions for the bodies. Tension can be calculated from it..
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• Solo and co-op problem solving | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8564910888671875, "perplexity": 743.2844048884025}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-13/segments/1552912204857.82/warc/CC-MAIN-20190326054828-20190326080828-00550.warc.gz"} |
https://www.bartleby.com/questions-and-answers/find-the-standard-deviation-step-by-step.-that-is-find-the-deviation-of-each-observation-from-the-me/e21d97c7-4364-41e3-966d-6d422da94b73 | # find the standard deviation step by step. that is find the deviation of each observation from the mean, square the deviations then obtain the variance and the standard deviation.i found the mean : 10.05i need help finding the standard deviation and the variance
Question
3 views
find the standard deviation step by step. that is find the deviation of each observation from the mean, square the deviations then obtain the variance and the standard deviation.
i found the mean : 10.05
i need help finding the standard deviation and the variance
check_circle
Step 1
To find standard deviation we need to do following steps.
FInd the mean.
For each data point, find the square of its distance to the mean.
Sum the values from Step 2.
Divide by the number of data points-1.
Take the square root.
The formula for standard deviation (sd) is,
Step 2
Step 3
Lets take one example.
Suppose data set contains of si...
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Tagged in | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9475874900817871, "perplexity": 905.8006048267254}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2020-10/segments/1581875143784.14/warc/CC-MAIN-20200218150621-20200218180621-00531.warc.gz"} |
http://cs.stackexchange.com/questions/6781/difference-between-reductions-in-algebraic-problems-versus-reductions-in-computa | # Difference between reductions in algebraic problems versus reductions in computational intractability
When I read about NP-completeness for the first time, I really wondered why is the concept of reductions given such high emphasis, after all we have been looking at concepts such as reductions and 'special case of one another problem' in mathematics since elementary algebra. What I mean by reductions in algebra is the following.
Problem 1: Find value of x such that $x^2+ax+b=0$
Problem 2: Find value of x such that $(x+m/n)^2=0$
We can go on proving both the problems are same and one solution can be translated to another.
My question is that "Is the concept of reductions in computational intractability same as that in above algebraic theory?" If not, how are the reductions in CI theory different?
-
Cross-posted on CSTheory cstheory.stackexchange.com/q/14395/77. Please don't do that. – Dave Clarke Nov 20 '12 at 15:05
Suppose that you knew how to solve $(x+m/n)^2 = 0$, but had no idea how to solve $x^2+ax+b=0$. Then you'd be very interested in knowing whether the two were equivalent and how to convert from one to the other! Similarly, suppose you're trying to solve $x^2+ax+b=0$. If you knew that $(x + m/n)^2=0$ could not be solved by any possible algorithm, you would again be very interested to find out that $x^2+ax+b=0$ is equivalent to it. Then you could give up on your problem because you know it can't be done. – usul Dec 4 '12 at 22:37
Reductions in computational complexity are similar to the reduction you described, but are usually given with bounds on the time or space. To be useful, these bounds are usually inconsequential (ie. the same or smaller) to the bounds of solving the problem.
Reductions in computational complexity are about converting one problem to another equivalent one. Usually one would also give bounds on how hard (how much time/space) a reduction takes as well. For example, all NP-complete problems have reductions to each-other, and their reductions are polynomially bounded. Since algorithms solving NP-complete problems are suspected to take exponential time on a deterministic Turing machine, the polynomial time reductions are inconsequential (compared with the time of actually solving the reduced problem), and thus these reductions make all of the NP-complete problems essentially equivalent. There can reductions between problems in other classes of complexity as well, and to be useful they would likely be bounded by something considered inconsequential to solving them.
-
Reductions are useful in studying computability not so much to prove that problems are computable (although that is also done), but to prove that problems are not computable.
Used to prove incomputability, a reduction proof is a particular kind of proof by contradiction. You take your problem P and a known incomputable problem X, and you show that if you had an algorithm that computed solutions to P you could use it to compute solutions to X. Since we already know that there there does not exist a method for computing solutions to X this proves that there cannot exist a method for computing solutions to P.
This isn't really "different" from the kind of reduction you're talking about in algebra; if you have an algebraic problem P and you show that a solution to P could be used to find a solution to X, and you already know that X has no solutions, then this would show that P has no solutions either. But you usually think about the notion of "problem" slightly differently in algebra, as well as about the way you use "reductions".
My experience in mathematics was that you're usually aiming to turn an equation you don't know how to solve in to a form that you do know how to solve, in order to find a particular solution (possibly with unknown constants). Whereas a "problem" in computer science is a specification for producing an output (usually yes/no) on instances of an infinite family of inputs.1 And for computability purposes you're interested not in finding any particular solution, but in showing whether or not there exists an algorithm that can compute the solution for any input.
Basically it has turned out that a large number of computational problems have been difficult to directly prove incomputable, but are relatively easy to reduce to known incomputable problems. Variants on the Halting Problem are particularly rich sources of undergraduate-level incomputability proofs. I'm not aware that this is done nearly so much in mathematics, hence the difference in emphasis.
1 Any problem that only has one instance (e.g. one specific algebraic formula, like 2x^8 - 9 = 83) is completely uninteresting from the point of view of computability theory, because finite problem series are all trivially computable by a stupid algorithm that simply has all the solutions hard-coded and immediately prints the one corresponding to its input.
My Theory of Computation lecturer liked to joke that the problem "does God exist?" is computable; the program that computes the solution is either a single-state DFA that immediately accepts, or a single-state DFA that immediately rejects. We just don't know which one it is!
-
For example, say you give me a problem to solve. After spending time on it, I am unable to come up with an efficient algorithm for it. Maybe I'm too dumb to come up with an algorithm, or maybe a (fast) algorithm doesn't exist. I would like to back up my excuse somehow. If I can reduce a known hard problem $X$ to the problem you gave me, I'm showing that $X$ is at least as hard the problem you gave me. That means that maybe I'm not that dumb; other people have not been able to solve the problem either. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8545082211494446, "perplexity": 324.0341267721226}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2014-10/segments/1394010795590/warc/CC-MAIN-20140305091315-00044-ip-10-183-142-35.ec2.internal.warc.gz"} |
https://tex.stackexchange.com/questions/414599/how-to-detect-empty-elements-inside-a-tikz-foreach-statement | # How to detect “empty” elements inside a tikz \foreach statement
I want to define a macro that feeds its contents into a tikz \foreach statement, for example:
\newcommand\Macro[1]{ \foreach \x in {#1} {x=\x.} }
which is then used as \Macro{1,2,3,4}. Sometimes, I want to give it "empty" arguments, such as \Macro{,,,4,5,5}. I'd like to be able to detect the "empty" arguments and do something different in such cases. I thought that something like the following would work:
\newcommand\Macro[1]{%
\foreach \x in {#1} {
\if\relax\detokenize{\x}\relax Empty!
\else x=\x.
\fi
}
}
but for some reason this does not detect the empty arguments and instead produces:
I have tried many other things, such as expanding \x first, but I am yet to find anything that works.
Can any one see a way of doing this?
[My real code is generating a tikzpicture environment so I really want to use \foreach from tikz.]
Something like this?
\documentclass{article}
\usepackage{tikz}
\newcommand\Macro[1]{%
\foreach \x in {#1} {
\ifx\x\empty\relax Empty!
\else x=\x.
\fi
}
}
\begin{document}
\Macro{,,,4,5,5}
\end{document}
• Thanks marmot! I thought that I was probably being stupid and missing something obvious! – Andrew Feb 10 '18 at 3:50
The problem in the macro from the question:
\newcommand\Macro[1]{%
\foreach \x in {#1} {
\if\relax\detokenize{\x}\relax Empty!
\else x=\x.
\fi
}
}
is that \detokenize does not expand its argument and returns the two tokens \ and x. This is cured by adding an \expandafter:
\detokenize\expandafter{\x}
The full macro:
\newcommand\Macro[1]{%
\foreach \x in {#1} {
\if\relax\detokenize\expandafter{\x}\relax Empty!
\else x=\x.
\fi
}
}
The mandatory expl3 answer (after noting that \detokenize\expandafter{\x} would be the solution):
\documentclass{article}
\usepackage{tikz}
\usepackage{xparse}
\ExplSyntaxOn
\NewExpandableDocumentCommand{\blankTF}{mmm}
{% #1 = text to test, #2 = blank case, #3 = non blank case
\str_if_eq_x:nnTF { #1 } { } { #2 } { #3 }
}
\NewDocumentCommand{\lforeach}{O{,}mm}
{% #1 = delimiter, #2 = list, #3 = code
\seq_set_split:Nnn \l_andrew_foreach_seq { #1 } { #2 }
\seq_map_inline:Nn \l_andrew_foreach_seq { #3 }
}
\ExplSyntaxOff
\newcommand\Macro[1]{%
\lforeach{#1}{%
\blankTF{##1}{Empty!}{$|$##1$|$.}
}
}
\begin{document}
\lforeach[-]{a-b--\texttt{c}}{%
\blankTF{#1}{Empty!}{$|$#1$|$.}
}
\lforeach{, ,,4, 5 ,5}{%
\blankTF{#1}{Empty!}{$|$#1$|$.}
}
\Macro{, ,,4, 5 ,5}
\end{document}
The current item in the cycle is denoted by #1 (which has to become ##1 in the definition of \Macro`). | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9680665731430054, "perplexity": 4374.945929827382}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 5, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2020-10/segments/1581875143635.54/warc/CC-MAIN-20200218055414-20200218085414-00310.warc.gz"} |
http://tex.stackexchange.com/questions/106514/hyperlink-with-number-sign | # Hyperlink with # (number sign)
\documentclass{article}
\usepackage{hyperref}
\begin{document}
\href{http://de.wikipedia.org/wiki/Hybridorbital#Beispiele}
{http://de.wikipedia.org/wiki/Hybridorbital#Beispiele}
\end{document}
which has a # in the link, however if I enter it as \# Beispiele it won't open the link in the PDF and only if I leave the section after # will it open the page. However, I want it to open at a specific section in the webpage, which is coded by the # part.
-
Welcome to TeX.sx! Please note that you can mark inline code with back ticks like code. Furthermore I made a minimal working example (MWE) of your code but adding a documentclass. – Tobi Apr 2 '13 at 11:10
Do you really mean \\# Beispiele and not \# Beispiele (single backslash)? – Tobi Apr 2 '13 at 11:11
You have to prefix the hash with a backslash:
\href{http://de.wikipedia.org/wiki/Hybridorbital#Beispiele}
{http://de.wikipedia.org/wiki/Hybridorbital\#Beispiele}
Now it should work ;)
-
Note that the prefixed backslash is only necessary in the second argument which is the on to be typset by the TeX engin and therefore must respect TeX special symbols (which # is one of). The first argument is the verbatim link an though doesn’t need special cares on symbols. – Tobi Apr 2 '13 at 11:05
I got it now! My mistake was that I wrote \# Beispiel instead of \#Beispiel (without space in between) because I thought it wouldn't recognise the second command. – gasserv Apr 2 '13 at 11:11
use \url instead:
\documentclass{article}
\usepackage{hyperref}
\begin{document}
\url{http://de.wikipedia.org/wiki/Hybridorbital#Beispiele}
\end{document}
-
Didn't think of that :) Note that \url typesets the url in typewriter font by default. – ralfix Apr 2 '13 at 11:04
Just use \urlstyle{same} to change this behaviour. @Micha may like to add this to the answer. – Tobi Apr 2 '13 at 11:06 | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9745509624481201, "perplexity": 4124.546963070828}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 5, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2014-23/segments/1406510267075.55/warc/CC-MAIN-20140728011747-00156-ip-10-146-231-18.ec2.internal.warc.gz"} |
https://www.physicsforums.com/threads/electric-circuit-to-solve-with-nodal-analysis.275198/ | # Electric Circuit to solve with nodal analysis
1. Nov 26, 2008
Can someone solve this circuit
Find v and i in the circuit.
I know that we have to make somethng with supernode, but where the supernode is here? How to develop this problem? Please help me :)
Btw it is nice forum, today i have found that. I hope I will be able to help you in other engeenering topics. Greets
2. Nov 26, 2008
### Redbelly98
Staff Emeritus
Welcome to PF!
For homework problems, we like for students to:
1. Show any relevent equations or principles, and show your attempt at solving it before getting help.
and
2. Post homework problems in the homework area:
https://www.physicsforums.com/forumdisplay.php?f=152 | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8607749342918396, "perplexity": 2868.9500154179973}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2018-26/segments/1529267864943.28/warc/CC-MAIN-20180623054721-20180623074721-00423.warc.gz"} |
http://wias-berlin.de/publications/wias-publ/run.jsp?template=abstract&type=Preprint&year=2003&number=831 | WIAS Preprint No. 831, (2003)
# Stochastic models and Monte Carlo algorithms for Boltzmann type equations
Authors
• Wagner, Wolfgang
2010 Mathematics Subject Classification
• 65C05 76P05 82C80
Keywords
• Boltzmann equation, stochastic models, Monte Carlo algorithms
Abstract
In this paper we are concerned with three typical aspects of the Monte Carlo approach. First there is a certain field of application, namely physical systems described by the Boltzmann equation. Then some class of stochastic models is introduced and its relation to the equation is studied using probability theory. Finally Monte Carlo algorithms based on those models are constructed. Here numerical issues like efficiency and error estimates are taken into account. In Section 1 we recall some basic facts from the kinetic theory of gases, introduce the Boltzmann equation and discuss some applications. Section 2 is devoted to the study of stochastic particle systems related to the Boltzmann equation. The main interest is in the convergence of the system (when the number of particles increases) to the solution of the equation in an appropriate sense. In Section 3 we introduce a modification of the standard direct simulation Monte Carlo'' method, which allows us to tackle the problem of variance reduction. Results of some numerical experiments are presented. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9652292132377625, "perplexity": 303.7569933349164}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-04/segments/1547583730728.68/warc/CC-MAIN-20190120184253-20190120210253-00385.warc.gz"} |
http://mathhelpforum.com/differential-equations/176823-need-help-how-solve-certain-type-differential-equation-print.html | # Need help with how to solve a certain type of differential equation
• April 4th 2011, 06:07 PM
iPod
Need help with how to solve a certain type of differential equation
I would really appreciate it if someone could show me the steps to how to solve such a differential equation.
$\dot{x}=32x-64y$
$\dot{y}=-3x+48y$
$x(0)=-64$
$y(0)=4$
Thank you very much.
• April 4th 2011, 06:45 PM
Ackbeet
There are at least a couple of options:
1. Use the eigenvalue/eigenvector diagonalization approach.
2. Eliminate one variable to get a second-order DE.
You can check those out at Chris's DE tutorial. Is a method specified for this problem, or can you use any method?
• April 4th 2011, 07:17 PM
iPod
its through the method of finding eigenvalues/vectors however i have no idea how to do so - if theres a tutorial online, id be very greatful
• April 4th 2011, 07:24 PM
Prove It
$\displaystyle \frac{dx}{dt} = 32x - 64y$
$\displaystyle \frac{dy}{dt} = -3x + 48y$.
$\displaystyle \frac{dy}{dx} = \frac{\frac{dy}{dt}}{\frac{dx}{dt}}$
$\displaystyle \frac{dy}{dx} = \frac{-3x + 48y}{32x - 64y}$
$\displaystyle (32x - 64y)\,dy = (-3x + 48y)\,dx$
$\displaystyle (32x - 64y)\,dy + (3x - 48y)\,dx = 0$.
Now you can probably find an integrating factor to turn this into an exact equation.
• April 4th 2011, 07:29 PM
iPod
:| you are amazing
but ive forgotten how to find the integrating factor for exact equations, could you please remind me :)
• April 4th 2011, 08:00 PM
Prove It
• April 4th 2011, 08:21 PM
TheEmptySet
Quote:
Originally Posted by iPod
I would really appreciate it if someone could show me the steps to how to solve such a differential equation.
$\dot{x}=32x-64y$
$\dot{y}=-3x+48y$
$x(0)=-64$
$y(0)=4$
Thank you very much.
First write the system as a matrix.
Let $\mathbf{X}=\begin{pmatrix} x(t) \\ y(t) \end{pmatrix}$
And $A=\begin{pmatrix} 32 & -64 \\ -3 & 48 \end{pmatrix}$
Now we have $\dot{\mathbf{X}}=A\mathbf{X}$
Here is a link on how to solve a matrix system ODE. Scroll down a bit to find the computation of eigenvalues and eigenvectors section. They also have examples of this type of problem.
Eigenvalues and Eigenvectors Technique | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 17, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.6260267496109009, "perplexity": 705.3632788440675}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2015-48/segments/1448398468971.92/warc/CC-MAIN-20151124205428-00011-ip-10-71-132-137.ec2.internal.warc.gz"} |
http://logiciansdoitwithmodels.com/ | February 24, 2013
It’s a fun story about the early search for mathematical foundations involving figures like Bertrand Russell, George Cantor, Ludwig Wittgenstein, Gottlob Frege, Kurt Gödel and Alan Turing.
http://www.scribd.com/doc/98921232/Bertrand-Russell-Logicomix
And for those interested, here’s a review of Logicomix by noted philosopher of mathematics, Paolo Mancosu:
https://philosophy.berkeley.edu/file/509/logicomix-review-january-2010.pdf
The Nonsense Math Effect
December 28, 2012
An article suggesting that non-math academics are impressed by equations even if the equations are nonsense:
http://journal.sjdm.org/12/12810/jdm12810.pdf
Well Ordering Infinite Sets, the Axiom of Choice and the Continuum Hypothesis
December 17, 2012
We’re trying to understand the relationship between $\aleph_{0}$, and other infinite cardinal numbers. We’ve reviewed two ways (here and here) to generate infinite cardinals greater than $\aleph_{0}$. The first way is by considering the set of all subsets of positive integers, the power set $\mathcal{P}(\mathbb{N})$ of $\mathbb{N}$ with cardinality $2^{\aleph_{0}}$. The second way is by considering the set of countably infinite ordinals, $\omega_{1}$ and its cardinality, $\aleph_{1}$.
We begin by introducing the axiom of choice. The axiom of choice (AC) is an axiom of set theory that says, informally, that for any collection of bins, each containing at least one element, it’s possible to make a selection of at least one element from each bin. It was first set forth by Zermelo in 1904 and was controversial for a time (early 20th century) due to its being highly non-constructive.
For example, AC is equivalent to the well ordering theorem (WOT) stating that every set can be well ordered, and it can be proven using AC/WOT that there are non-Lebesgue measurable sets of real numbers. Nevertheless, this result is consistent with the result that no such set of reals is definable! And use of the AC to achieve unintuitive mathematical results, like paradoxical decompositions in geometry in the spirit of the Banach-Tarski paradox, have also fueled skepticism and mistrust of the axiom. But contemporary mathematicians make free use of the axiom and hardly mind that it was ever controversial.
Formally, the axiom of choice says the following:
For each family $(X_{i})_{i \in I}$ of non-empty sets $X_{i}$, the product set $\prod_{i \in I}{(X_{i})}$ is non-empty.
The elements of $\prod_{i \in I}{(X_{i})}$ are actually “choice functions”
$(x_{i})_{i \in I}$, $I \rightarrow \bigcup_{i \in I}{(x_{i})}$, satisfying $x(i) = x_{i}$ for each $i \in I$.
AC is important when thinking about infinite cardinals in part because of its equivalence to the WOT. Because WOT says that every set can be well ordered, it follows that each cardinal (any set really) can be associated with an ordinal number and you can count them via the ordinals. For instance, $\aleph_{0}$ can be represented by $\omega$, $\aleph_{1}$ by $\omega_{1}$ and in general AC/WOT enables us to give the von Neumann definition of cardinal numbers where the cardinality of a set $X$ is the least ordinal $\alpha$ such that there is a bijection between $X$ and $\alpha$.
AC and WOT do a lot of other work as well in terms of ordering infinities. We say that an $aleph$ is the cardinal number of a well ordered infinite set. Because every set is well order able, all infinite cardinals are $alephs$. It was shown by Friedrich Hartogs in 1915 that trichotomy, which is a property of an order relation on a set $A$ such that for any $x, y \in A$, $x < y, x = y$, or $x > y$, is equivalent to AC.
So with AC we can list, in (a total) order, the infinite cardinals and compare them. Thus we can set up the following infinite list of $alephs$, $\aleph_{0}, \aleph_{1}, \aleph_{2}, \cdots, \aleph_{\alpha}, \cdots$. We know that $\aleph_{1}$ is greater than and distinct from $\aleph_{0}$. The cardinal $\aleph_{1}$ is the cardinality of the ordinal $\omega_{1}$ which is larger than all countable ordinals, so $\aleph_{1}$ is distinguished from $\aleph_{0}$. What about $2^{\aleph_{0}}$?
It’s unclear where $2^{\aleph_{0}}$ fits in in the list $\aleph_{0}, \aleph_{1}, \aleph_{2}, \cdots, \aleph_{\alpha}, \cdots$. The infinite cardinal $2^{\aleph_{0}}$ is the cardinality of the set of subsets of $\mathbb{N}$, but it’s also the cardinality of the set, $\mathbb{R}$, of real numbers or the set of points on a line, known as the continuum. (This equality is provable using the Cantor-Schröder-Bernstein theorem and follows from the proof of the uncountability of $\mathbb{R}$.)
George Cantor, the inventor of set theory, conjectured in 1878 that there is no set whose cardinality is strictly between the cardinality of the integers ($\aleph_{0}$) and the cardinality of the continuum ($2^{\aleph_{0}}$). Since we’re assuming AC, that means that $2^{\aleph_{0}} = \aleph_{1}$.
This conjecture is famously known as the Continuum Hypothesis (CH) and was the first of 23 problems in David Hilbert’s famous 1900 list of open problems in mathematics. The problem of whether or not CH is true remains open to this day although Kurt Gödel (in 1940) and Paul Cohen (in 1963) showed that CH is independent of the axioms of Zermelo-Fraenkel set theory, if these axioms are consistent.
There is much of philosophical interest surrounding the mathematics of the continuum hypothesis and I hope to be able to turn my attention to those topics in the future.
Priest, Beall and Armour-Garb’s “The Law of Non-Contradiction” Available Online via Scribd
November 5, 2012
Priest, Beall and Armour-Garb’s “The Law of Non-Contradiction”, (link below) is a great collection of essays on the philosophy and logic of dialetheism, the belief that that there are sentences A, such that both A and its negation, ¬A are true. Non-classical, paraconsistent logics may be necessary for formalizing and understanding physical and social systems.
http://www.scribd.com/doc/62132941/3/Letters-to-Beall-and-Priest
Paul Cohen Reflects on the Nature of Mathematics
November 5, 2012
Reflections on the nature of mathematics from Paul Cohen’s “Comments on the foundations of set theory” in Scott and Jech, Axiomatic Set Theory, Vol.1, p. 15.
A Mathematician’s Survival Guide, by Pete Casazza
April 29, 2012
“All My Imaginary Friends Like Me” -Nikolas Bourbaki
From §2 of “A Mathematician’s Survival Guide“, a good read for all, not just mathematical people.
The Cardinality of Uncountable Sets II
March 6, 2012
We can get at another infinite cardinal that is greater than $\aleph_{0}$ by thinking about the ordinal numbers. Think of the natural, or counting numbers $\textup{N} = (1, 2, 3, \cdots)$. These numbers double as the finite cardinal numbers. Cardinal numbers, we have seen, express the size of a set or the number of objects in a collection (e.g., as in “24 is the number of hours in a day”). But they also double as the finite ordinal numbers, which indicate a place in an ordering or in a sequence (e.g., as in ” the letter ‘x’ is the 24th letter in the English alphabet”). In the case of finite collections, the finite ordinal numbers are the same as the finite cardinals.
But when we start thinking of infinite collections the similarities diverge. In order to see the differences in the infinite case we should get clear on what an ordinal number is. Say that a set $x$ is transitive if, and only if, every element of $x$ is a subset of $x$, where $x$ is not a urelement (something that is not a set). Now say that a set $x$ is well-ordered by the membership relation, $\in$, if $\{\langle y, z\rangle \in x \times x : y \in z\}$. What this does is simply order the elements of $x$ in terms of membership. We can do this type of thing with transitive sets. Combining these two definitions we get the definition of an ordinal number: a set $x$ is an ordinal if, and only if, $x$ is transitive and well-ordered by $\in$.
Now, let $\omega = \{1, 2, 3, \cdots\}$ (i.e., the set $\textup{N}$ of natural numbers). $\omega$ is an ordinal because when we think of the natural numbers as constructed by letting $0 = 0$ and letting $1 = \{0\}$, the singleton set of $0$, $2 = \{0, \{0\}\}$, and so on and so forth it satisfies the definition above of an ordinal number as a transitive set well-ordered by $\in$. So we can set up the sequence $1, 2, 3, \cdots, \omega$ with all ordinals less than $\omega$ either equal to $0$ or one of its successors.
Suppose that you take the natural numbers and re-arrange (re-order) them so that $0$ is the last element. This is weird because the regular ordering of the natural numbers has no last element. But still, you can think of there being a countable infinity of natural numbers $1, 2, 3, \cdots$ prior to the appearance of $0$. So we have the standard order of $\textup{N}$ and we have added another element, $0$. If we let $\omega$ be the standard order of $\textup{N}$, then we have just described $\omega + 1$. We can do the same thing by now setting $1$ as the last element of $\omega + 1$ and thus get $\omega + 2$. Note that addition (and multiplication below) does not commute; e.g., $1 + \omega = \omega$ and not $\omega + 1$. This process can be generalized (e.g., $n, n +1, \cdots, 0, 1, \cdots, n -1$) to get $\omega + n$.
Again, doing something weird: take the natural numbers and put all the even numbers first, followed by the odd numbers. It’ll look like this, $0, 2, 4, \cdots, 2n, \cdots, 1, 2, 3, \cdots 2n+1, \cdots$. Here we have taken $\omega$ (the evens) and appended it to $\omega$ (the odds) so we have $\omega + \omega$. In each case, $\omega$, $\omega + n$ and $\omega + \omega$, we are dealing with the same cardinality, the cardinality of $\textup{N}$.
We’ve created a variety of different ordinal numbers here, and, as they represent different orderings of the natural numbers, they are all countable. There are many more countably infinite ordinals. For example, the ordinal $\omega \cdot 2 = \{ 0, 1, 2, \cdots, \omega, \cdots, \omega+1, \omega+2, \cdots \}, \omega \cdot 2+1, \cdots \omega^{2}, \omega^{3}, \omega^{4}, \cdots \omega^{\omega}, \cdots \omega^{\omega^{\omega}} \cdots$.
Taking the countable ordinals and laying them out (kind of like in the previous sentence but starting with $1, 2, 3, \cdots, \omega, \cdots, \omega + 1, \omega + 2, \cdots$) we end up with a a set that is itself an ordinal. In order to see this let $\alpha$ be the set of countable ordinals. If $\beta \in \alpha$ then $\beta \subset \alpha$ since the members of $\beta$ are countable ordinals. Therefore $\alpha$ is an ordinal.
It is in fact the first uncountable ordinal because if it were countable, then $\alpha$ would be a member of itself and there would be an infinitely descending sequence of ordinals. But because the ordinals are transitive sets (see definition above), this cannot be the case. So the set of countable ordinals is uncountable. (It is also the smallest such set because the ordinals are well ordered by $\in$, so every ordinal in $\alpha$ is a member of $\alpha$ and countable.) This uncountable set goes by the name $\omega_{1}$.
Here we see how the similarities between the ordinal numbers and the cardinal numbers in the finite case diverge in the infinite case. Whereas there is only one countably infinite cardinal, $\aleph_{0}$, there are uncountably many countably infinite ordinals, namely all countably infinite ordinals less than $\omega_{1}$.
It is natural to wonder about the cardinality of the set $\omega_{1}$ of countable ordinals. Its cardinality is transfinite and is denoted by the uncountable cardinal number, $\aleph_{1}$.
So far we’ve talked about $\aleph_{0}, 2^{\aleph_{0}}$ (see here, and here, respectively), and have generated $\aleph_{1}$ by considering the uncountable set of countably infinite ordinals, $\omega_{1}$. In the next update we’ll talk more about the relationship between these cardinal numbers as well as the celebrated axiom of choice.
Cantor’s Attic
January 15, 2012
Cantor’s Attic: a resource on mathematical infinity. Philosophically rich mathematics is the best mathematics.
FOM Posting on A. Kiselev’s claim that “There are no weakly inaccessible cardinals” in ZF
August 17, 2011
Alex Kiselev claims to have shown “There are no weakly inaccessible cardinals” in Zermelo-Fraenkel set theory (ZF). This would have the consequence that strongly inaccessible cardinals don’t exist either and so on for all the other large cardinals. Martin Davis on the FOM list cautions that the claim is “highly dubious”.
Here are links to Kiselev’s papers:
Link to the FOM list entry: http://www.cs.nyu.edu/pipermail/fom/2011-August/015694.html
The Cardinality of Uncountable Sets I
August 11, 2011
We saw earlier that $\aleph_{0}$ can accommodate a countable infinity of countable infinities. Now we’re going to produce an infinite cardinal number that is bigger than $\aleph_{0}$. Cardinal numbers express the size of, or number of elements of a set. Countably infinite sets have cardinality $\aleph_{0}$. We know that countably infinite sets can be matched up (by way of a one-to-one and onto function) to the set of positive integers. So if we can find a cardinal number greater than $\aleph_{0}$, we can find a set greater than the set of positive integers, or an uncountably infinite set.
We’re going to begin with an infinite list of subsets of the set of positive integers:$S_{1}, S_{2}, S_{3} \cdots$ And we’re going to represent each of these sets by a function of positive integers:
$s_{n}(x)= \begin{cases} 1, &\text{if } x \in S_{n};\\ 0, &\text{if } x\notin S_{n}. \end{cases}$
For example, if the third set in our list, $S_{3}$ is the set of positive even integers, then the values of the function $s_{3}(x)$ are $s_{3}(1) = 0, s_{3}(2) = 1, s_{3}(3) = 0 \cdots$ And if the fourth set in our list, $S_{4}$ is the set of squares, then the values of the function $s_{4}(x)$ are $s_{4}(1) = 1, s_{4}(2) = 0, s_{4}(3) = 0 \cdots$ and so on.
Imagine now that we set up an infinite table like this. The top row will be our header row, or our x-axis and will contain, in the first position the label “Sets of positive integers”. To the right of this label we list out the positive integers, $1, 2, 3, \cdots$ These are our columns. Immediately below the label “Sets of positive integers” we list the names of the each subset of positive integers, $S_{1}, S_{2}, S_{3} \cdots$ This is our y-axis and extends infinitely downwards. We now fill out the values of each coordinate using the values of the functions $s_{1}, s_{2}, s_{3} \cdots$ extending to the right of each set name on the y-axis. Basically the rows of the infinite table contain the 0-1 representation of each of the sets.
It looks like this:
You may have noticed that the diagonal values of the table are in bold. The bold values form a sequence, $s_{1}(1), s_{2}(2), s_{3}(3), \cdots$ called the diagonal sequence. We’ll return to the diagonal sequence in a moment. But first we want to ask: does our list (along the y-axis) contain all of the sets (subsets) of positive integers? It doesn’t if we can always produce a set different from each of the sets on the list.
Here is where the diagonal comes in. The diagonal sequence is just a sequence of 0′s and 1′s and and may very well encode a set of positive integers appearing in our list. But we’re trying to find a set that does not appear on the list. It’s easy to find one if we think of a sequence that contains positive integers that do not appear in the diagonal sequence. So we can take the diagonal sequence and create the antidiagonal by changing 1′s to 0′s and 0′s to 1′s in the the diagonal sequence. So let the antidiagonal be given by subtracting each element of the diagonal sequence from 1. The antidiagonal is $1 - s_{1}(1), 1 - s_{2}(2), 1 - s_{3}(3), \dots$ and does not appear anywhere as a row in our table.
But suppose that the antidiagonal did appear as, say, the kth row in our table, thus representing the kth subset of positive integers. It would look like this: $s_{k}(1) = 1 - s_{1}(1), s_{k}(2) = 1 - s_{2}(2), s_{k}(3) = 1 - s_{3}(3), \cdots s_{k}(k) = 1 - s_{k}(k), \cdots$ But $s_{k}(k) = 1 - s_{k}(k)$ can never obtain because $s_{k}(k)$ has to either be 0 or 1. If it’s a 0, then we have $0 = 1 - 0 = 1$. But if it’s a 1 then we have $1 = 1 - 1 = 0$. In either case, it is absurd, so the antidiagonal, whatever it may be, must be different from any set appearing in the list $S_{1}, S_{2}, S_{3} \cdots$ of subsets of positive integers. If we take the antidiagonal and append it to our list of subsets of positive integers all we have to do is repeat the argument and we will end up with another distinct antidiagonal sequence that does not appear on our list.
The set of all subsets of the positive integers is called the power set of the set of positive integers. If the set of positive integers is denoted by $\textup{N}$ then the power set of $\textup{N}$ is $\mathcal{P}(\textup{N})$.
What can we say about the cardinality of $\mathcal{P}(\textup{N})$? Well, for any one of the sequences given by our list of subsets of positive integers, the first digit can be either 0 or 1, and the same is true for the second and third digits, and so on for all $\aleph_{0}$ digits in the sequence. This means that there are $2 \times 2 \times 2 \times \cdots$ (for $\aleph_{0}$ factors) possible sequences of 0′s and 1′s and so there are $2^{\aleph_{0}}$ sets of positive integers. And we have just shown by means of the antidiagonal that $2^{\aleph_{0}} > \aleph_{0}$.
So $2^{\aleph_{0}}$ is an infinite cardinal number that is greater than $\aleph_{0}$ and the power set, $\mathcal{P}(\textup{N})$, of the positive integers is an uncountably infinite set.
In the next update we’ll produce anothe cardinal number, $\aleph_{1}$ greater than $\aleph_{0}$. | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 150, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9265945553779602, "perplexity": 222.93093512093967}, "config": {"markdown_headings": false, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368696383218/warc/CC-MAIN-20130516092623-00000-ip-10-60-113-184.ec2.internal.warc.gz"} |
http://forum.coppeliarobotics.com/viewtopic.php?t=7926 | ## Simulate multiple steps
Typically: "How do I... ", "How can I... " questions
Phlogiston90
Posts: 5
Joined: 12 Jun 2019, 16:37
### Simulate multiple steps
Hi,
I would like to simulate exactly 20 timesteps, using the legacy remote API. If I write a for loop around vrep.simxSynchronousTrigger, it takes quite long, probably because I have to send the trigger command 20 times to the V-rep server.
Therefore, I would like to write the for loop in a lua (child/customization)-script. However, there is no lua function like vrep.simxSynchronousTrigger.
I then found the simulation_stepper model in the model folder after it was suggested in a forum thread, but for me this only works if I press the UI button, but not if called from Python via vrep.simxCallScriptFunction (it returns, but doesn't move the objects in the GUI).
Any help would be much appreciated!
coppelia
Posts: 7543
Joined: 14 Dec 2012, 00:25
### Re: Simulate multiple steps
Hello,
if you want to step a simulation from within V-REP, then you will have to loop into the callback function sysCall_beforeMainScript used inside of a customization script, as was done in the simulation stepper tool.
That function will basically be called at the beginning of every simulationstep. If you return {doNotRunMainScript=true}, then the main script won't be called this time. THis is how you control the stepping.
So simply do something like:
Code: Select all
function stepSimulation(inInts,inFloats,inStrings,inBuffer)
runOneStep=true;
return {},{},{},''
end
function sysCall_beforeMainScript()
local retValue={doNotRunMainScript=runOneStep}
runOneStep=false
return retValue
end
and call stepSimulation from your remote API client.
Cheers
Phlogiston90
Posts: 5
Joined: 12 Jun 2019, 16:37
### Re: Simulate multiple steps
Thanks for your answer! But it doesn't work or I don't understand it.
So I have a Python program that does something like:
Code: Select all
for _ in range(20):
vrep.simxSynchronousTrigger(client_id)
return_code, ping_time = vrep.simxGetPingTime(client_id)
This is slow (~240ms), so I want to speed it up by calling a lua script function, where I can give 20 as a parameter and then it performs 20 steps. It does not have to be 20 steps but e.g. 20ms - I just want to have it deterministic.
So what I did now was to copy paste your code into a) my previously used remote_api customization script and b) as a new customization script attached to a dummy object 'Dummy'.
Both did not work, i.e. if I call
Code: Select all
return_code, _,_,_,_ = vrep.simxCallScriptFunction(client_id, 'Dummy', vrep.sim_scripttype_customizationscript,
'stepSimulation', [], [], [], bytearray(), vrep.simx_opmode_blocking)
it does not run any step: If I start the simulation with
Code: Select all
return_code = vrep.simxSynchronous(client_id, enable=True)
return_code = vrep.simxStartSimulation(client_id, vrep.simx_opmode_blocking)
it doesn't do anything and if I start it without vrep.simxSynchronous then the simulation runs without any halt.
Furthermore, I would like to have a for-loop in the customization script as written before, but I don't know how to add it to your example code.
Best regards,
Mark
coppelia
Posts: 7543
Joined: 14 Dec 2012, 00:25
### Re: Simulate multiple steps
With following in your customization script, you can run 20 simulation steps at a time:
Code: Select all
function sysCall_init()
stepsToRun=0
end
function start20StepRun()
stepsToRun=20
end
function sysCall_beforeMainScript()
return {doNotRunMainScript=(stepsToRun==0)}
end
function sysCall_actuation()
stepsToRun=stepsToRun-1
end
you just need to call start20StepRun to trigger the 20 steps. Since a customization script runs non-threaded, you can't make a for-loop to step through simulation steps.
Also, do not mix the remote API synchronous mode, an any synchronous mode you might create yourself (like in above example), otherwise you'll have two mechanisms blocking (and you'll have to activate two different triggers).
Cheers
Phlogiston90
Posts: 5
Joined: 12 Jun 2019, 16:37
### Re: Simulate multiple steps
Thank you a lot! This worked for me, and reduced the time needed to simulate 20 steps from 210ms to 10ms!
Best,
Mark | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.5349886417388916, "perplexity": 3860.6324495680947}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 20, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2020-05/segments/1579251789055.93/warc/CC-MAIN-20200129071944-20200129101944-00366.warc.gz"} |
https://sunlimingbit.wordpress.com/category/pde/elliptic-pde/ | ## Category Archives: Elliptic PDE
32519989
### Bach flat four dimensional manifold and sigma2 functional
We want to find the necessary condition of being the critical points of ${\int\sigma_2}$ on four dimensional manifold.
1. Preliminary
Suppose ${(M^n,g)}$ is a Riemannian manifold with ${n=4}$. ${P_g}$ is the Schouten tensor
$\displaystyle P_g=\frac{1}{n-2}\left(Ric-\frac{R}{2(n-1)}g\right)$
and denote ${J=\text{\,Tr\,} P_g}$. Define
$\displaystyle \sigma_2(g)=\frac{1}{2}[(\text{\,Tr\,} P_g)^2-|P_g|_g^2]$
$\displaystyle I_2(g)=\int_M \sigma_2(g)d\mu_g$
where ${|P|_g^2=\langle P,P\rangle_g}$. It is well known that ${I_2(g)}$ is conformally invariant.
Suppose ${g(t)=g+th}$ where ${h}$ is a symmetric 2-tensor. We want to calculate the first derivative of ${I_2(g(t))}$ at ${t=0}$. To that end, let us list some basic facts (see the book of Toppings). Firstly denote ${(\delta h)_j=-\nabla^i{h_{ij}}}$ the divergence operator and
$\displaystyle G(h)=h-\frac{1}{2}(\text{\,Tr\,} h) g$
$\displaystyle (\Delta_L h)_{ij}=(\Delta h)_{ij}-h_{ik}Ric_{jl}g^{kl}-h_{jk}Ric_{il}g^{kl}+2R_{ikjl}h^{kl}$
where ${\Delta_L}$ is the Lichnerowicz Laplacian. Then the first variation of Ricci curvature and scalar curvature are
$\displaystyle \dot{R}=\delta^2h-\Delta(\text{\,Tr\,} h)-\langle h,Ric\rangle \ \ \ \ \ (1)$
$\displaystyle \dot{Ric}=-\frac{1}{2}\Delta_Lh-\frac{1}{2}L_{(\delta G(h))^\sharp}g=-\frac{1}{2}\Delta_Lh-\frac{1}{2}L_{(\delta h)^\sharp}g-\frac{1}{2}Hess(\text{\,Tr\,} h)$
$\displaystyle =-\frac{1}{2}\Delta_Lh-d(\delta h)-\frac{1}{2}Hess(\text{\,Tr\,} h)$
where we were using upper dot to denote the derivative with respect to ${t}$.
2. First variation of the sigma2 functional
Lemma 1 ${(M^4,g)}$ is a critical point of ${I_2(g)}$ if and only if
$\displaystyle \Delta P-Hess(J)+2\mathring{Rm}(P)-2JP-|P|_g^2g=0 \ \ \ \ \ (2)$
where ${(\mathring{Rm}(P))_{ij}=R_{ikjl}P^{kl}}$.
Proof:
$\displaystyle \frac{d}{dt}\big|_{t=0} I_2(g(t))=\int_M J\dot J-\langle\dot P,P\rangle+\langle h,P\wedge P\rangle+\frac{1}{2}\sigma_2\text{\,Tr\,} h \,d\mu_g$
where ${(P\wedge P)_{ij}=P_{ik}P_{jl}g^{kl}}$. Since we have
$\displaystyle \int_M\langle P,\dot P\rangle\\ =\frac{1}{n-2}\int_M\langle P, \dot Ric-\dot Jg-Jh\rangle =\frac{1}{n-2}[\langle P, \dot Ric\rangle-\dot J J-J\langle h,P\rangle]$
$\displaystyle =\frac{1}{n-2}[-\frac{1}{2}\langle h,\Delta_L P\rangle+\langle h,Hess(J)\rangle-\frac{1}{2}\Delta J \text{\,Tr\,} h-\dot J J-J\langle h,P\rangle]$
Plugging this into the derivative of ${I_2}$ to get
$\displaystyle (n-2)\frac{d}{dt}\big|_{t=0} I_2(g(t))\\ =\int_M\frac{1}{2}\langle h,\Delta_L P\rangle-\langle h,Hess(J)\rangle+\frac{1}{2}\Delta J \text{\,Tr\,} h\\$
$\displaystyle \quad +(n-1)\dot J J+J\langle h,P\rangle+(n-2)\langle h,P\wedge P\rangle+\frac{n-2}{2}\sigma_2\text{\,Tr\,} h d\mu_g$
In order to simplify the above equation, we recall the definition of Lichnerowicz Laplacian ${\Delta_L}$
$\displaystyle (\Delta_LP)_{ij}=(\Delta P)_{ij}-2P_{ik}Ric_{jl}g^{kl}+2R_{ikjl}P^{kl}$
$\displaystyle =(\Delta P)_{ij}-2(n-2)P_{ik}P_{jl}g^{kl}-2JP_{ij}+2R_{ikjl}P^{kl}$
Apply (1) to get
$(n-1)\dot J J=\frac12J\dot R=\frac12J[\delta^2h-\Delta(\text{\,Tr\,} h)-\langle h,Ric\rangle]$
$=\frac{1}{2}[\langle h, Hess(J)\rangle-\text{\,Tr\,} h\Delta J-(n-2)J\langle h, P\rangle-J^2\text{\,Tr\,} h]$
Therefore we can simplify it to be
$\displaystyle (n-2)\frac{d}{dt}\big|_{t=0} I_2(g(t)) =\int_M\frac{1}{2}\langle h,\Delta P\rangle-\frac{1}{2}\langle h, Hess(J)\rangle+h^{ij}R_{ikjl}P^{kl}$
$\displaystyle -\frac{n-2}{2}J\langle h,P\rangle-\frac{1}{2} J^2 \text{\,Tr\,} h+\frac{n-2}{2}\sigma_2\text{\,Tr\,} h d\mu_g$
Let us denote ${(\mathring{Rm}(P))_{ij}=R_{ikjl}P^{kl}}$. Using the fact ${n=4}$ and the definition of ${\sigma_2}$,
$\displaystyle \frac{d}{dt}\big|_{t=0} I_2(g(t))=\frac{1}{4}\int_M\langle h,Q\rangle d\mu_g$
where
$\displaystyle Q=\Delta P-Hess(J)+2\mathring{Rm}(P)-2JP-|P|_g^2g$
$\Box$
Remark 1 It is easy to verify ${\text{\,Tr\,} Q=0}$, this is equivalent to say ${I_2}$ is invariant under conformal change. More precisely, letting ${h=2ug}$, then
$\displaystyle \frac{d}{dt}\big|_{t=0} I_2(g(t))=\frac{1}{4}\int_M\langle h,Q\rangle d\mu_g=\frac{1}{2}\int_M u\text{\,Tr\,} Q d\mu_g=0.$
Remark 2 If ${g}$ is an Einstein metric with ${Ric=2(n-1)\lambda g}$, then ${P=\lambda g}$, ${J=n\lambda}$ and
$\displaystyle \mathring{Rm}(P)=\lambda Ric=2(n-1)\lambda^2 g$
It is easy to verify that ${Q=0}$. In other words, Einstein metrics are critical points of ${I_2}$.
Are there any non Einstein metric which are critical points of ${I_2}$?
Here is one example. Suppose ${M=\mathbb{S}^2\times N}$, where ${\mathbb{S}^2}$ is the sphere with standard round metric and ${(N,g_N)}$ is a two dimensional compact manifolds with sectional curvature ${-1}$. ${M}$ is endowed with the product metric. We can prove ${Ric=g_{S^2}-g_N}$, ${P=\frac{1}{2}g_{S^2}-\frac{1}{2}g_N}$, ${J=0}$, ${\mathring{Rm}(P)=g_{prod}}$ and consequently ${Q=0}$.
Note that the above example is a locally conformally flat manifold. For this type of manifold, we have the following lemma which can say
Lemma 2 Suppose ${g}$ is locally conformally flat and ${Q=0}$, then
Proof: When ${g}$ is locally conformally flat,
$\displaystyle \mathring{Rm}(g)=JP+|P|_g^2g-2P\wedge P$
${Q=0}$ is equivalent to
$\displaystyle \Delta P-Hess(J)+|P|_g^2g-4P\wedge P=0$
Actually this is equivalent to the Bach tensor ${B}$ is zero. $\Box$
3. Another point of view
We have the Euler Characteristic formula for four dimensional manifolds
$\displaystyle 8\pi^2\chi(M)=\int_M (|W|_g^2+\sigma_2) d\mu_g$
therefore the critical points for ${\int_M \sigma_2d\mu_g}$ will be the same as the critical points of ${\int_M |W|_g^2d\mu_g}$. However, the functional
$\displaystyle g\rightarrow \int_M |W|_g^2d\mu_g$
is well studied by Bach. The critical points of this functional satisfy Bach tensor equal to 0.
$\displaystyle B_{ij}=\nabla^k\nabla^l W_{likj}+\frac{1}{2}Ric^{kl}W_{likj}$
Obviously, ${B=0}$ for Einstein metric, but not all Bach flat metrics are Einstein. For example ${B=0}$ for any locally conformally flat manifolds.
### Unique continuation property on the boundary
I am writing a theorem proved by Jin Zhiren in his thesis.
Suppose $\Omega$ is a smooth domain in $\mathbb{R}^n$, $x_0\in \partial \Omega$ and $u$ is a harmonic function in $\Omega$. If there exists $A, b>0$ such that
$\displaystyle |u(x)|\leq Ae^{-\frac{b}{|x-x_0|}}\quad x\in \Omega$
for $|x-x_0|$ small, then $u=0$. If $n=2$, the same conclusion holds for the solutions of a general second order linear elliptic equation.
A borderline example for this theorem is $u$ be the real part of $e^{-1/z^\alpha}$, $\alpha\in (0,1)$. $u$ is harmonic in the right half plane and $u\leq Ae^{-1/|x|^\alpha}$ and consequently $D^\beta u(0)=0$.
### Interior estimate for Monge Ampere equation
Suppose we have $u$ is a generalized solution of the Monge-Ampere equation
$\det(\nabla^2 u)=1 \text{ in } B_1\subset\mathbb{R}^n$
when $n=2$, Heinz proved
$|\nabla^2 u|_{B_{1/2}}\leq \sup_{B_1}u$
when $n\geq 3$, Pogorelov has a counter example. One can have a solution $u\in C^1(B_1)$, but $u\in C^{1,\beta}(B_1)$ for some $\beta\in (0,1)$. See his book The Minkowski Multidimensional Problem, on page 83.
### Newton tensor
Suppose ${A:V\rightarrow V}$ is a symmetric endomorphism of vector space ${V}$, ${\sigma_k}$ is the ${k-}$th elementary symmetric function of the eigenvalue of ${A}$. Then
$\displaystyle \det(A+tI)=\sum_{k=0}^n \sigma_k t^{n-k}$
One can define the ${k-}$th Newton transformation as the following
$\displaystyle \det(A+tI)(A+tI)^{-1}=\sum_{k=0}^{n-1}T_k(A)t^{n-k-1}$
This means
$\displaystyle \det(A+tI)=\sum_{k=0}^{n-1}T_k(A+tI)t^{n-k-1}$
$\displaystyle =T_0 t^n+\sum_{k=0}^{n-2}(A\cdot T_k(A)+T_{k+1}(A))t^{n-k-1}+T_{n-1}(A)$
By comparing coefficients of ${t}$, we get the relations of ${T_k}$
$\displaystyle T_0=1,\quad A\cdot T_k(A)+T_{k+1}(A)=\sigma_{k+1}I,\, 0\leq k\leq n-2\quad T_{n-1}(A)=\sigma_n$
Induction shows
$\displaystyle T_{k}(A)=\sigma_kI-\sigma_{k-1}A+\cdots+(-1)^kA^k$
For example
$\displaystyle T_1(A)=\sigma_1I-A$
$\displaystyle T_2(A)=\sigma_2-\sigma_1A+A^2$
One of the important property of Newton transformation is that: Suppose ${F(A)=\sigma_k(A)}$, then
$\displaystyle F^{ij}=\frac{\partial F}{\partial A_{ij}}=T_{k-1}^{ij}(A)$
The is because
$\displaystyle \frac{\partial }{\partial A_{ij}}\det(A+tI)=\det(A+tI)((A+tI)^{-1})_{ij}.$
If ${A\in \Gamma_k}$, then ${T_{k-1}(A)}$ is positive definite and therefore ${F}$ is elliptic.
Remark: Hu, Z., Li, H. and Simon, U. . Schouten curvature functions on locally conformally flat Riemannian manifolds. Journal of Geometry, 88(1${-}$2), (2008), 75${-}$100.
### Some calculations of sigma_2
On four-manifold ${(M^4,g_0)}$, we define Shouten tensor
$\displaystyle A = Ric-\frac 16 Rg$
and Einstein tensor and gravitational tensor
$\displaystyle E=Ric - \frac 14 Rg\quad S=-Ric+\frac{1}{2}Rg$
Suppose ${\sigma_2}$ is the elemantary symmetric function
$\displaystyle \sigma_2(\lambda)=\sum_{i
Thinking of ${A}$ as a tensor of type ${(1,1)}$. ${\sigma_2(A)}$ is defined as ${\sigma_2}$ applied to eigenvalues of ${A}$. Then
$\displaystyle \sigma_2(A)= \frac{1}{2}[(tr_g A)^2-\langle A, A\rangle_g] \ \ \ \ \ (1)$
Notice ${A=E+\frac{1}{12}Rg}$. Easy calculation reveals that
$\displaystyle \sigma_2(A)=-\frac{1}{2}|E|^2+\frac{1}{24}R^2 \ \ \ \ \ (2)$
Under conformal change of metric ${g=e^{2w}g_0}$, we have
$\displaystyle R= e^{-2w}(R_0-6\Delta_0 w-6|\nabla_0 w|^2) \ \ \ \ \ (3)$
$\displaystyle A=A_0-2\nabla^2_0 w+2dw\otimes dw-|\nabla_0w|^2g_0 \ \ \ \ \ (4)$
$\displaystyle S=S_0+2\nabla_0^2w-2\Delta_0wg_0-2dw\otimes dw-|\nabla_0 w|^2g_0 \ \ \ \ \ (5)$
We want to solve the equation ${\sigma_2(A)=f>0}$, which is equivalent to solve
$\displaystyle \sigma_2(A_0-2\nabla^2_0w+2dw\otimes dw-|\nabla_0w|^2g_0)=f$
This is an fully nonlinear equation of Monge-Ampere type. Under local coordinates, the above equation can be treated as
$\displaystyle F(\partial_i\partial_j w,\partial_kw,w,x)=f$
where ${F(p_{ij},v_k,s,x):\mathbb{R}^{n\times n}\times\mathbb{R}^n\times\mathbb{R}\times\mathbb{R}^n\rightarrow \mathbb{R}}$. This equation is elliptic if the matrix ${\left(\frac{\partial F}{\partial p_{ij}}\right)}$ is positive definite. In order to find that matrix, we need the linearized operator
$\displaystyle L[\phi]=\frac{\partial F}{\partial p_{ij}}(\nabla_0^2\phi)_{ij}=\frac{d}{dt}|_{t=0}F(\partial_i\partial_j w+t\partial_i\partial_j\phi,\partial_kw,w,x) \ \ \ \ \ (6)$
Using the elementary identity
$\displaystyle \frac{d}{dt}\rvert_{t=0}\sigma_2(H+tG)=tr_gH\cdot tr_gG-\langle H, G\rangle_g. \ \ \ \ \ (7)$
for any fixed matrix ${H}$ and ${G}$. Now plug in ${H=A}$ is Schouten tensor and ${B=-2\nabla_0^2\phi}$. One can calculate them as
$\displaystyle tr_g H\cdot tr_g G=\langle \frac{1}{3}Rg, G\rangle_g \ \ \ \ \ (8)$
Then we get
$\displaystyle L[\phi]=\langle S,G\rangle_g=-2\langle S,\nabla^2_0\phi\rangle_g$
### f-extremal disk
In the last nonlinear analysis seminar, Professor Espinar talked about the overdetermined elliptic problem(OEP) which looks like the following
$\Delta u+f(u)=0\quad\text{ in }\Omega$
$u>0\quad \text{ in }\Omega$
$u=0 \quad \text{on }\partial \Omega$
$\frac{\partial u}{\partial\eta}=cst\quad\text{on }\partial \Omega$
There is a BCN conjecture related to this
BCN: If $f$ is Lipschitz, $\Omega\subset \mathbb{R}^n$ is a smooth(in fact, Lipschitz) connected domain with $\mathbb{R}^n\backslash\Omega$ connected where OEP admits a bounded solution, then $\Omega$ must be either a ball, a half space, a generalized cylinder or the complement of one of them.
BCN is false in $n\geq 3$. Epsinar wih Mazet proved BCN when $n=2$. This implies the Shiffer conjecture in dimension 2. In higher dimension of Shiffer conjecture, if we know the domain is contained in one hemisphere of $\mathbb{S}^n$, then one can use the equator or the great circle to perform the moving plane.
### Compensated compactness
Suppose $T$ is a vector field and $\nabla\cdot T = 0$. $E= \nabla \psi$ and $\psi$ is a scalar function. We have following theorem(Coifman-Lions-Meyers-Semmes)
Theorem: If $T\in L^2(\mathbb{R}^n)$ and $T\in L^2(\mathbb{R}^n)$, then $E\cdot T\in \mathcal{H}^1(\mathbb{R}^n)$, which is the hardy space.
Given $f(x)\in L^1(\mathbb{R}^n)$, it has harmonic extension $\mathbb{R}^{n+1}_+=\{(x,t)|x\in\mathbb{R}^n, t>0\}$
$\tilde{f}(x,t)=c_n\int_{\mathbb{R}^n}\frac{ f(x-y)t}{(t^2+|x|^2)^{\frac{n+1}{2}}}dy$
Definition: the non-tangential maximal function
$N(f)=\sup_{(\xi,t)\in \Gamma(x)}|\tilde f(\xi, t)|$
It is easy to prove that $N(f)\leq c_n f^*(x)$ the Hardy-Littlewood maximal function. From this we can Hardy norm as
$||f||_{\mathcal{H}^1}=||f||_{L^1}+||N(f)||_{L^1}$
Hardy space consists of all $f$ having finite hardy norm. There is well know fact that the dual space of $\mathcal{H}^1$ is BMO, which is defined as the following.
Define $f\in L^1_{loc}(\mathbb{R}^n)$, if for any cube $Q$,
$\sup_Q\frac{1}{|Q|}\int_Q|f-f_Q|<\infty,\quad \text{where }f_Q=\frac{1}{|Q|}\int_Qf$
then $f\in BMO$. $L^\infty \subset BMO$ and $\log|x|\in BMO$ but not in $L^\infty$.
Let us see how do we use the main theorem. Suppose on $\mathbb{R}^2$, $u$ is the solution of the following elliptic equation
$\displaystyle\frac{\partial}{\partial x_i}\left(a_{ij}(x)\frac{\partial u}{\partial x_j}\right)=\frac{\partial f}{\partial x_1}\frac{\partial g}{\partial x_2}-\frac{\partial f}{\partial x_2}\frac{\partial f}{\partial x_2}$
where $||\nabla f||_{L^2}<\infty$, $||\nabla g||_{L^2}<\infty$ and $(a_{ij})$ is uniform elliptic. YanYan Li and Sagun Chanillo proved that the green function of this elliptic operator belongs to BMO. The right hand side of this equation can be rewritten as $T\cdot E$, where
$T=\left(\frac{\partial f}{\partial x_2}, -\frac{\partial f}{\partial x_1}\right),\quad E=\left(\frac{\partial g}{\partial x_1},\frac{\partial g}{\partial x_a}\right)$
therefore the right hand side belong to $\mathcal{H}^1$. Since
$u(x)=\int G_x(y)T\cdot E(y)dy$
therefore from the theorem we stated at the beginning, we get
$||u||_\infty\leq C||\nabla f||_{L^2}||\nabla g||_{L^2}$
### Subcriticality and supercriticality
Consider the equation
$\displaystyle \Delta u=u^p\text{ on }\mathbb{R}^n$
usually we call the equation is subcritical when ${p<\frac{n+2}{n-2}}$, supercritical when ${p>\frac{n+2}{n-2}}$. The reason comes from the scalling the solution. Suppose ${u(x)}$ is a solution of the equation, then ${u^\lambda(x)=\lambda^{\frac{2}{p-1}}u(\lambda x)}$ is another solution. Consider the energy possessed by ${u}$ around any point ${x_0}$ of radius ${{\lambda}}$ can be bounded
$\displaystyle \int_{B_{\lambda}(x_0)}|\nabla u(x)|^2dx\leq E$
when ${\lambda\rightarrow 0}$, we scale ${B_\lambda(x_0)}$ to ${B_1(x_0)}$, then ${u}$ will become ${u^\lambda}$ in order to be a solution and ${u^\lambda}$ lives on ${B_1(x_0)}$. While the energy will be
$\displaystyle \int_{B_{1}(x_0)}|\nabla u^\lambda(x)|^2dx=\lambda^{\frac{4}{p-1}+2-n}\int_{B_{\lambda}(x_0)}|\nabla u(y)|^2dy$
If the ${\delta=\frac{4}{p-1}+2-n<0}$, which is ${p> \frac{n+2}{n-2}}$, the energy bound of ${u^\lambda}$ will become ${\lambda^\delta E}$. Since ${\lambda\rightarrow 0}$, the bound deteriorates by ‘zooming in’. In this case, we call the equation is supercritical. The solution looks more singular at this time.
Remark: The energy should include ${\int_{B_{\lambda}(x_0)}u^2dx}$, but somehow this term scale differently with ${\int_{B_{\lambda}(x_0)}|\nabla u(x)|^2dx}$ and can not give one the critical exponent exactly.
### Approriate scalling in Yamabe equation
Suppose ${(M,g)}$ is a Riemannian manifold, and ${L_g=\Delta_g -\frac{n-2}{4(n-1)}R_g}$ is the conformal Laplacian. Assume ${u>0}$ satisfies
$\displaystyle L_gu+Ku^p=0$
where ${K}$ is some fixed constant, ${1. Suppose near a point ${x_0\in M}$, there is a coordinates ${x^1,x^2,\cdots, x^n}$. We want to scale the coordinates to ${x^i=\lambda y^i}$,
$\displaystyle g(x)=g_{ij}(x)dx^idx^j=\lambda^2 g_{ij}(\lambda y)dy^idy^j=\lambda^2 \hat{g}(y)$
By the conformal invariance of ${L}$, for any ${\phi}$, we get
$\displaystyle L_{g}(\lambda^{-\frac{n-2}{2}}\phi)=\lambda^{-\frac{n+2}{2}}L_{\hat{g}}(\phi)$
We want to choose ${\phi(y)=\lambda^{\alpha}u(\lambda y)}$ such that
$\displaystyle L_{\hat{g}}(\phi)+K\phi^p=0$
which means
$\displaystyle L_{\hat{g}}(\lambda^{\alpha}u(\lambda y))=\lambda^{\frac{n+2}{2}}L_g (\lambda^{\alpha-\frac{n-2}{2}}u(\lambda y))=-K\lambda^{\alpha+2} (u(\lambda y))^p$
Letting
$\displaystyle \alpha+2=\alpha p$
we get ${\alpha=\frac{2}{p-1}}$.
The above proof may not be right.
Or we should look it more directly
$\displaystyle L_g(u(x))=\lambda^2 L_{\hat{g}}(u(\lambda y))=\lambda^2 Ku(\lambda y)^p$
then
$\displaystyle L_{\hat{g}}(\lambda^\alpha u(\lambda y))=K(\lambda^\alpha u(\lambda y))^p$
with ${\alpha=\frac{2}{p-1}}$.
### Harnack inequality under scaling
Thm: Suppose ${\Omega}$ is domain in ${\mathbb{R}^n}$. ${u}$ is a harmonic function in ${\Omega}$, ${u\geq 0}$. For any subdomain ${\Omega'\subset\subset \Omega}$, there exists a constant ${C}$ such that
$\displaystyle \sup_{\Omega'}u\leq C(n,\Omega,\Omega')\inf_{\Omega'}u$
To prove this Harnack inequality, there is an intermediate step
$\displaystyle \sup_{B_R}u\leq 3^n\inf_{B_R}u$
whenever ${B_{4R}\subset\Omega}$.
Here the constant is independent of ${R}$, actually the constant ${3^n}$ is not so important. We can use the above Thm to give another proof.
Suppose ${v(x)=u(Rx)}$ for ${x\in B_1}$. Let ${\Omega=B_2}$ and ${\Omega'=B_1}$, applying the thm
$\displaystyle \sup_{B_1}v\leq C(n)\inf_{B_1}v$
convert back to ${u}$
$\displaystyle \sup_{B_R}u\leq C(n)\inf_{B_R}u$ | {"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 269, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.9969982504844666, "perplexity": 944.3242364473734}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 20, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2017-43/segments/1508187823478.54/warc/CC-MAIN-20171019212946-20171019232946-00596.warc.gz"} |
https://hotinfonow.com/physicists-have-just-discovered-a-very-strange-particle-that-is-not-a-particle-at-all/ | Breaking News
Home https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Science https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Physicists have just discovered a very strange particle that is not a particle at all
# Physicists have just discovered a very strange particle that is not a particle at all
Sounds like the beginning of a very bad physics riddle: I'm a particle that is not really; I disappear before I can be discovered, but it can still be seen. I interrupt your understanding of physics, but I do not review your knowledge. Who am I?
This is Odderon, a particle that is even stranger than its name suggests, and it could have been discovered in the Large Hadron Accelerator, the most powerful atom that breaks particles close to the speed of light. 17-mile (27 km) ring near Geneva, Switzerland
First, the dentron is not really a particle. What we think of particles is usually very stable: electrons, protons, quarks, neutrinos, and so on. You can hold them in your hand and carry them with you. Hell, your hand is literally made by them. And your hand does not disappear very soon, so we can probably assume that its main particles are in the long run. [7 Strange Facts About Quarks]
There are other particles that do not last long, but are still called particles. Despite their short life, they remain particles. They are free, independent and capable of living independently, apart from any interaction ̵
1; these are the hallmarks of a real particle.
And then there is the so-called quasi-part, which is just one step above and is not a-particles in everything. Quasi-particles are not just particles, but they are not a fiction. Just … complicated. [The 18 Biggest Unsolved Mysteries in Physics]
As in, literally complicated. In particular, particle interactions at ultra-high velocities are complicated. When two protons break at almost the speed of light, it's not like two billiard balls that break apart together. This is more like two drops of jellyfish that swing to each other, pulling out of their guts, and rearranging everything before returning to the jump.
In all this complicated confusion, sometimes strange patterns appear. Small particles enter and go out of existence in an instant of an eye, just to be followed by another minor particle – and another. Sometimes these flashes of particles appear in a certain sequence or pattern. Sometimes, it does not even blink particles, just vibrations in the soup from the mixture of collision – vibrations that suggest the presence of a transient particle. Physicists here face a mathematical dilemma. They may either try to fully describe the complex mess that leads to these effervescent models, or they can pretend – purely for convenience – that these patterns are "particles" by themselves but with strange properties such as negative masses and spins that change over time. [5 Seriously Mind-Boggling Math Facts]
Physicists choose the last option and thus a quasi-part is born. Quasi-particles are short, effervescent models or waves of energy that appear in the midst of collision with high-energy particles. But as much work is needed to fully describe this situation in mathematics, physicists take some shortcuts and pretend that these patterns are their own particles. This is done only to make math easier to manage. So, quasi particles are treated as particles, although they are definitely not.
It's like pretending your uncle's jokes are really fun. It is quasi-bound for convenience only.
A particular type of quasi-part is called the oderon, which is supposed to exist in the 1970s. It is believed that this occurs when an odd number of quarks – the heavy particles that are the building blocks of matter – briefly light up and disappear during the collisions of proton and antiproton. If the oderones are present in this collapsing scenario, there will be little cross-sectional difference (physical jargon of how easily one particle strikes another) of collisions between particles with themselves and their antiparticles. So, if we put a bunch of protons together, for example, we can calculate a cross section for this interaction. Then we can repeat this exercise for proton-antiproton collisions. In a world without hypersons these two cross sections must be identical. But the echoes change the picture – these short patterns, which we call the oderones, appear more favorably in particle-particles than collisions with antiparticle antiparticles that will slightly modify cross-sections. , so you will need many events or collisions before you can claim a discovery.
Now, only if we had a giant particle accelerator that regularly breaks protons and antiprotons together and did so with such high energies and so often we can get reliable statistics. Oh, right: Great Hadron Accelerator.
In a recent article published on March 26 at the arXiv prescription server, TOTEM Collaboration (in the lively jargon acronym of high energy physics, TOTEM stands for the "TOTal cross" section, Elastic Scattering and Differential Dissociation Measurement in LHC) for significant differences between the cross sections of the protons that break other protons against protons that are closed to antiprotons, and the only way to explain the difference is to revive this decade an old idea for oderone. another word and other forms of exotic particles), but the odd people, however strange they seem, seem the best candidate
Totem has discovered something new and fun for the universe, for sure, did TOTEM find a brand new particle? No, because the kerosene are quasi-particles and not particles It still helps us overcome the boundaries of the known physics, for sure, does it break the familiar physics? No, because it was supposed that the Odderones exist in our present understanding.
Does all this look a little weird for you? Ask the cosmonaut and Cosmical Radio and Author of Your Place in the Universe . Originally posted on Live Science . | {"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8116864562034607, "perplexity": 1050.2264516861217}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-39/segments/1568514573439.64/warc/CC-MAIN-20190919040032-20190919062032-00449.warc.gz"} |
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