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S0022407319307368
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Droplets are often attached to glass during the target optical detection process . This causes light to hit the droplets along the transmission path . The direction of transmission and amount of energy changes after the light passes through the droplets such that the energy that finally enters the detector varies affecting the target detection . The energy distribution model of the receiving surface affected by the droplets attached to the glass is established based on the basic principle of light radiation transmission . The Monte Carlo ray tracing method was used to calculate the effect of the droplets attached to the inner and outer sides of the glass on the transmission of light . The effect of the distance between the glass containing the droplets and the receiving surface and the effect of the contact angle of the droplets on the image seen are analyzed . The contact angle between the droplets and the glass affects the transmittance of light . When the contact angle is an obtuse angle the effect of the droplets on imaging is greater than that for an acute contact angle . The energy corresponding to the droplets on the receiving surface gradually converges to a particular distance and then gradually diverges as the distance between the receiving surface and the rear surface of the glass increases for the case in which the droplets adhere to the inner side of the glass . This study provides new ideas and methods for obtaining the influence of droplets attached to glass on the energy distribution of the receiving surface in target optical detection .
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Energy distribution model of the receiving surface affected by glass with droplets attached is established. The Monte Carlo ray tracing method is used to calculate the transmission of light through glass with droplets attached. Contact angle between the droplets and glass affects the transmittance and energy distribution of the receiving surface. Energy corresponding to the droplets on the receiving surface gradually converges to a distance and then gradually diverges.
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S0022407319307393
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Cloud phase detection via satellites is essential in the accurate estimation of cloud radiative forcing at global and regional scales . The difference in polarized reflectance features between liquid and ice clouds can be used for detecting the cloud phase . The directional polarimetric camera onboard the Chinese GaoFen 5 satellite was launched in May 2018 . The multidirectional multispectral and multipolarization capabilities of the DPC provide essential measurements to better understand the distribution of clouds and their physical properties . Numerous studies have demonstrated that the angular polarization signatures of ice crystals and liquid cloud droplets are effective in the detection of liquid and ice clouds . This study uses cloud phase profiles from Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations to select reliable liquid and ice cloud pixels via the DPC and analyzes the angular polarization signatures of ice and cloud clouds . These extracted angular polarization signatures are compared with the simulated results . Then based on the earlier POLDER cloud phase algorithm we propose a cloud phase detection method for DPC using multiple tests developed based on the extracted angular polarization signatures . Finally P CP algorithm is applied to the measurements of DPC and POLDER on 1 June 2008 and the analysis indicates that our cloud phase detection results agree well with the MODIS and POLDER cloud phase products .
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The polarized cloud phase P CP algorithm is developed for DPC. CALIPSO is used to reliably select DPC pixels containing liquid or ice clouds. Validation of P CP against POLDER and MODIS global products are shown.
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S0022407319307411
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It is not feasible to use the Geiger mode avalanche photodiode detection model to guide detection quantitatively during daytime because of the incompletely built echo intensity model . In this study because the background noise and the signal light are both modulated by the target s optical scattering characteristics a hybrid light scattering model model is substituted in the laser detection and ranging ranging equation . In such a BRDF model the Li Liang BRDF model is taken as the kernel and the background noise equivalent intensity coefficient is employed to link the background noise part to the laser echo part . According to the results of a Gm APD outdoor experiment the proposed LADAR ranging equation is applicable to detection during daytime and the noise scaling factor
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A modified kernel based BRDF model is introduced in the LADAR ranging equation. The proposed LADAR ranging equation is completely suitable for the daytime detection. The signal intensity between the theory and the experiment is only a difference of 5 . The echo SNR and triggering probability are firstly analyzed based on the LADAR ranging equation. A theoretical method is proposed to calculate maximum detection range in the daytime.
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S0022407319307423
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The dual focus property of focused circularly polarized ring Airy beam under the action of tightly focused lens is demonstrated in this paper . The radiation forces at two foci of tightly focused RAB are calculated the numerical results show that the particle could be longitudinally and transversely trapped at the two foci . By varying corresponding parameters we could control the property of two traps . The trapping force increases with NA and the scaling parameter
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Dual focus property of ring Airy beams RAB is demonstrated under the action of high NA lens. The particle could be trapped at the two foci of RAB and the radiation forces are investigated. The modulation methods with different corresponding parameters for the dual optical trap created by RAB are proposed.
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S0022407319307435
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Pursuing a study concerning the evaluation of Beam Shape Coefficients of Laguerre Gauss beams after having dealt with the case of beams freely propagating the present paper establishes finite series expressions to evaluate the BSCs of Laguerre Gauss beams focused by a lens which have the known advantage of speeding up computations with respect to the use of numerical quadrature techniques and which may deal with the limitations of localized approximations in the case of beams exhibiting topological charges and or axicon angles .
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Beam shape coefficients for Laguerre Gauss beams focused by a lens are discussed. The method used is the finite series techniques and expressions within this framework are established. Expressions rely on recurrence equations which are solved.
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S0022407319307484
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The small angle approximation is used in solving the radiative transfer equation when the single scattering phase function has a strong forward peak . The original vector radiative transfer equation is decomposed into three equations the forward the regular and the correction ones . The forward equation can be efficiently solved using the small angle approximation . The solution of the regular equation is given by the adding doubling method in this study . The correction equation including cross terms between the forward and the regular quantities is given and analyzed . The combined model associated with the forward and regular equations is further verified in the forward radiative transfer model where the molecular absorptions with respect to the standard atmospheric profiles are taken into consideration using the line by line method . Great agreements are given between the combined model and the model using the straight adding doubling method .
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The correction vector radiative transfer equation is explicitly given to evaluate the cross terms associated with decomposition and the second order approximated solution is obtained. The equation can be used in any radiative transfer method. The radiative transfer equation associated with particle scattering is solved by combining the small angle approximation SAA and the adding doubling method ADM . The line by line method LBLRTM is used to compute the molecular optical depth and corresponding Rayleigh extinction. The LBLRTM SAA ADM are combined together as the forward radiative transfer model. The combined model is verified using the line by line method LBLRTM and the straightforward adding doubling method SAD . Six standard atmospheric models are used as the atmospheric profiles and great agreement is reached between the LBLRTM SAA ADM and the LBLRTM SAD.
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S0022407319307575
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When dealing with light scattering theories such as the T matrix methods for structured laser beams e.g . Generalized Lorenz Mie Theory or the Extended Boundary Condition Method EM fields are expanded over a set of Vector Spherical Wave Functions involving spherical Bessel functions with expansion coefficients expressed in terms of Beam Shape Coefficients . Although spherical Bessel functions are orthogonal over the range
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Non orthogonal spherical Bessel functions may be used in the framework of generalized Lorenz Mie theory. This implies the existence of an infinite number of quadratures for evaluating the beam shape coefficients BSCs . This infinite number of quadratures nevertheless implies the uniqueness of BSCs i.e. the uniqueness of the decomposition of EM fields over VSWFs.
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S0022407319307629
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Anthropogenic skyglow dominates views of the natural night sky in most urban settings and the associated emission of artificial light at night into the environment of cities involves a number of known and suspected negative externalities . One approach to lowering consumption of ALAN in cities is dimming or extinguishing publicly owned outdoor lighting during overnight hours however there are few reports in the literature about the efficacy of these programs . Here we report the results of one of the largest municipal lighting dimming experiments to date involving 20 000 roadway luminaires owned and operated by the City of Tucson Arizona U.S. We analyzed both single channel and spatially resolved ground based measurements of broadband night sky radiance obtained during the tests determining that the zenith sky brightness during the tests decreased by
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An experiment was conducted involving the dimming of nearly 20 000 municipally owned street lights in a U.S. city of half a million inhabitants over ten nights in the spring of 2019. The signal of the dimming tests was successfully observed in measurements of zenith night sky radiance obtained at various radii from the city center. Observedzenith radiance changes of. during the tests imply that known street lights account for 264. The results can be used to inform future optimization of the citys street lighting system to further reductions in skyglow while preserving public safety.
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S0022407319307678
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A new model to account for turbulence radiation interaction on the radiation emission in the framework of Reynolds Averaged Navier Stokes simulations is proposed and tested . The models development is based on Reynolds decompositions of the temperature
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A new model for turbulence radiation interaction TRI is developed. The development is based on transient data numerically generated for pool fires. The model allows for the consideration of emission TRI in RANS simulations. An approximation for the mean Planck mean absorption coefficient is also proposed. Errors of the model are significantly smaller than those of existing models.
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S0022407319307708
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In this paper we present two methods for deriving the transition matrix of a nonspherical particle in the non local optical response theory which is important for particles of size below about 10nm . The key point in our analysis is the separation of the internal field into a transverse and a longitudinal component . The first method for
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The transition matrix in the non local optical response theory has been derived. The null field equation for the longitudinal field outside the particle was applied. A projection scheme for the additional boundary condition was used for the derivation.
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S0022407319307757
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We have developed a model within the relativistic framework to calculate the photoionization process of highly charged ions in the presence of a strongly coupled plasma environment . The ion sphere potential including the screening on nuclear charge and the effect of confinement due to the neighbouring ions is used to incorporate the plasma effects . Energies and wave functions of the continuum states are determined by solving the modified Dirac equations . As an application we determine the bound and continuum state wave functions energy levels and transition parameters for plasma density ranges of
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We have developed a model to calculate the photoionization process of highly charged ions in a strongly coupled plasma. Comparison of our calculated data with the results of other authors when available is made. Some interesting behaviors of the respective properties concerning the screening strength are noted.
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S0022407319307939
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The modeling of radiative properties of soot particles can be addressed by a number of methods . Among them the canonical Rayleigh Debye Gans theory and the Superposition T Matrix Method are particularly well adapted to the task . Here both RDG and STMM are used to model the radiative properties of two types of fractal aggregates indicative of soot relevant to lidar sensing . One type a canonical aggregate with a chain like morphology corresponds to low sooting flames and is well characterized by a single fractal dimension . The other type a superaggregate exhibits multiple fractal dimensions and is seen in heavily sooting flames . Radiative properties such as the differential scattering cross section total scattering cross sections backscattering cross sections and linear depolarization ratio are calculated for a range of wavelengths from
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The superposition T matrix method STMM is used to simulate light scattering from soot. The simulations cover a wide range of wavelength and several scattering observables. Comparisons between the STMM and Rayleigh Debye Gans approximation are made. The linear depolarization ratio is roughly 10 times larger for superaggregates than chain like.
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S0022407319307964
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A Symbolic Monte Carlo method is applied to the identification of radiative properties of a heterogeneous semitransparent insulating material from measurements of directional hemispherical transmittance and reflectance at room temperature . The polynomials obtained with SMC allow the development of a complete inverse analysis which determines if the inverse problem solution exists is unique and stable . Moreover the numerical efficiency of the absorption and scattering coefficients identification is improved since the radiative transfer equation is only solved once in the overall inverse iterative procedure .
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Symbolic Monte Carlo method is applied for the identification of radiative properties of an insulating material. An inverse analysis based on SMC polynomials determines if the inverse problem is well or ill posed. SMC polynomials allows to decrease significantly the computational cost of the inverse method.
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S0022407319308003
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Kirchhoff s law relates the emittance and absorptance of an object and has played an important role in radiative heat transfer calculations for many engineering applications . Along with the advancement of metamaterials two dimensional materials and micro nanoscale thermal radiation Kirchhoff s law has been revisited by several groups . Some studies also questioned the derivations and applicability of the statement of Kirchhoff s law that appears in prevalent radiative heat transfer textbooks . The present study begins with a short review of Kirchhoff s law for isotropic objects and its validity for both hemispherical emittance and directional emittance . Then this study formulates Kirchhoff s law for opaque anisotropic materials considering both co polarization and cross polarization and then for semitransparent films . It is shown that for macroscopic objects as long as the Helmholtz reciprocity can be established conventional expressions of Kirchhoff s law can be applied for engineering thermal analysis and design even with anisotropic media and metamaterials . Numerical examples and results are provided based on a natural hyperbolic material and a magneto optical material to illustrate the reciprocity and applicability of Kirchhoff s law .
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Investigated Kirchhoff s law for anisotropic materials. Investigated Kirchhoff s law for semitransparent metamaterial films. Kirchhoff s law is valid for individual polarization if Helmholtz reciprocity holds. Kirchhoff s law breaks down for nonreciprocal materials.
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S0022407319308015
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Based on the generalized LorenzMie theory and the angular spectrum decomposition method we calculate the optical radiation force exerted on a lossless dielectric sphere of arbitrary size illuminated by an Airy light sheet . The beam shape coefficients of the Airy light sheet are calculated using the vector angular spectrum decomposition and vector spherical wave functions methods . The optical radiation force acting on the spherical particle is obtained by the integral of Maxwells stress tensor . The transverse
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Optical force on a sphere of arbitrary size illuminated by an Airy lightsheet is investigated using GLMT. The BSCs of the Airy light sheet are calculated using ASDM and VSWFs. The negative longitudinal optical force is particularly emphasized. The two kinds of polarizations TE and TM of Airy light sheet are discussed. The influences of the transverse scale parameter. and attenuation parameter. of the Airy light sheet are discussed.
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S0022407319308027
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Imprisonment of resonance radiation in the spherical barium plasma rotating around its symmetry axis is numerically studied . Photoexcitation of barium ions at resonance transition with the wavelength
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Rotation of plasma leads to a broadening and a shift of the emission spectrum from the line center of the static medium to either red or blue spectral region. At strong broadening of the spectral line resonant photons that would be locked in static plasma owing to reabsorption processes can now easily diffuse toward the plasma surface and escape the plasma. The phenomenon of bandwidth expansion for resonant photons leads to escape of photons and to a decrease in effective lifetime of the excited level. The presence of a velocity gradient dependent on the radius of the sphere leads to a spreading of the spectral line over a wider frequency range compared to the static emission spectrum.
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S0022407319308039
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In chains of closely spaced nanoparticles supporting surface polaritons near field electromagnetic coupling leads to collective effects and super Planckian thermal radiation exchange . Researchers have primarily used two analytical approaches to calculate radiative heat transfer in these systems fluctuational electrodynamics which directly incorporates fluctuating thermal currents into Maxwell s equations and a kinetic approach where the dispersion relation provides modes and propagation lengths for the Boltzmann transport equation . Here we compare results from the two approaches in the isotropic dipole limit in order to identify regimes in which kinetic theory is valid and to explain differing results in the literature on its validity . Using both methods we calculate the diffusive radiative thermal conductivity of nanoparticle chains . We show that kinetic theory is valid and matches predictions by fluctuational electrodynamics if both the surface polariton propagation lengths are greater than the particle spacing and surface polaritons are the dominant contributors to radiative heat transfer .
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Compared approaches to near field radiative heat transfer in nanoparticle chains. Calculated radiative thermal conductivity for different materials and spacings. Showed that kinetic theory is valid for strong coupling by surface polaritons. Fluctuational electrodynamics is needed when kinetic theory assumptions fail.
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S0022407319308076
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Metallic nanoparticles scatter sun light efficiently at resonance wavelength where the scattering and absorption in the nanoparticles are highly influenced by shape size material composition host medium and volume fraction of the nanoparticles in the host medium . We present transfer matrix method and Mie theory based a modified analytical model to optimize the scattering property of nanoparticles and to simulate power transfer from the metallic nanoparticles layer into an absorber layer
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Light scattering and absorption in metallic nanoparticles are studied with Mie theory. A TMM based analytical model for power transfer from nanoparticle layer into a solar cell absorber is developed. Metal nanoparticles with an absorber layer is studied. Al nanoparticles based proposed structure demonstrates higher power transfer than Ag Au and Cu nanoparticles. Au and Cu nanoparticles show high backscattering in visible region.
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S0022407319308118
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A simple model to account for subgrid scale turbulence radiation interaction in the filtered radiative emission is evaluated for coupled and uncoupled simulations of a scaled up version of the Sandia flame D. The model is assessed based on comparisons with a reference solution that accounts for SGS TRI by employing the Eulerian Monte Carlo stochastic field method . While SGS TRI effects are in general marginal for the studied flame results of the uncoupled calculations show that the model consistently gives a better approximation of the filtered emission than what is obtained by fully neglecting SGS fluctuations . However this improvement is small due to a significant underprediction of the SGS temperature variance
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A subgrid scale SGS turbulence radiation interaction models accuracy is assessed. The configuration under study is a scaled version of the Sandia flame D. The reference solution is given by the Eulerian Monte Carlo stochastic field method. The model performs slightly better than an approach that neglects SGS fluctuations. A major inaccuracy of the model is in its estimate of the SGS temperature variance.
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S0022407319308143
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In this study the capabilities of the Dynamic Radiative Transfer System are shown both for expressing the temporal and spatial behavior of photon propagation and most importantly for imaging through optically complex turbid media . A light beam with linear shaped source profile was employed and pulse durations ranging from the continuous down to the ultra fast regime were studied . By further applying simple intensity normalization processing clean images of the embedded objects can be extracted . The pulse evolution through the medium can be traced and displayed in time frame sequence depicting the gradual image formation and fading . It is demonstrated that illumination from scattered photons in the medium is advantageous yielding clean full frame images without need for beam scanning . Additionally image retrieval is significantly enhanced by registering directionally selected photons revealing 3 D objects embedded deeper in the medium . In contrast with the accepted notion that early photons are the sole means for image formation DRTS proves that there exists a capability for image formation using the scattered photons . The forward problem simulation results can be directly applicable in a variety of scientific and technological fields .
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DRTS addresses in its general form the solution of the time dependent problem of photon propagation in absorbing and diffusive media. New general dynamic system language is introduced for the modeling description and solution of the physical problem. DRTS capabilities are shown both for expressing the temporal spatial photon propagation and for imaging through a 3D medium. Numerical experiments are performed in the widest possible light source time profile from continuous to ultrafast pulse. Employing single directional information has yielded cleaner more accurate and higher quality images of embedded bodies.
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S0022407319308167
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The hyperfine structure of neutral holmium was studied using a hollow cathode discharge lamp and laser induced fluorescence spectroscopy or optogalvanic spectroscopy respectively . Altogether 42 spectral lines in the wavelength range from 780nm to 830nm were investigated . Magnetic dipole hyperfine structure constants
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New hyperfine structure constants of atomic Holmium. Improved hyperfine structure constants of atomic Holmium. New energy level of atomic Holmium.
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S0022407319308180
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The scattering of a non paraxial Bessel light sheet by a sphere of arbitrary size is studied in framework of generalized Lorenz Mie theory . The electrical fields of the Bessel light sheet are expanded using the vector angular spectrum decomposition method and the beam shape coefficients of the Bessel light sheet are derived using the method of multipole expansion and vector spherical wave functions . The internal and near surface fields and absorption and extinction efficiency factors are numerically calculated when a Bessel light sheet is incident and the effects of beams order and half cone angle are mainly discussed . Numerical results show that there is strong point convergence in the forward scattering region under the incident of a Bessel light sheet and the internal and near surface fields of Bessel light sheet are very sensitive to the beams order half cone angle etc . Such results have potential applications in the super resolution imaging using a light sheet microscopy .
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The scattering of a non paraxial Bessel light sheet by a sphere of arbitrary size is investigated using GLMT. The BSCs of the Bessel light sheet are calculated using ASDM and VSWFs. The incident internal and near surface fields are numerically calculated. The absorption and extinction efficiencies are analyzed. The influences of the order and half cone angle of the Bessel light sheet are discussed.
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S0022407319308192
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Highly anisotropic phase functions are often approximated by simpler ones given by the sum of a Dirac delta function and a smooth function . However if both forward and backward scattering are important two Dirac delta functions are needed . In problems without collimated radiation those phase functions can be easily handled using the discrete ordinates method . However when collimated irradiation is present the DOM can not be applied using the decomposition of the radiation intensity into a diffuse and a collimated component . A new formulation of the DOM to solve radiative transfer problems with collimated irradiation in anisotropically scattering media with such approximate phase functions is described in this work . The proposed method is based on a decomposition of the radiation intensity into three components namely a collimated a backscattered collimated and a diffuse component . The method is applied to problems without and with collimated radiation and its accuracy is assessed through comparison with results obtained from Monte Carlo simulations . When a linear approximate phase function is used the new formulation of the DOM yields accurate results without collimated irradiation but does not perform so well with collimated irradiation particularly for media with an optical thickness of the order of unity or lower . However if the linear approximation is replaced by a quadratic one the results are significantly improved .
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Scattering media with a phase function that involves two Dirac deltas are considered. The discrete ordinates method cannot be applied to these media if there is collimated radiation. A decomposition of the radiation intensity into three components is introduced. The new decomposition overcomes this limitation of the discrete ordinates method.
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S0022407319308209
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Heritage atmospheric correction and ocean inherent optical property retrieval algorithms such as those implemented in NASAs SeaDAS platform often produce questionable results in complex environments such as in turbid coastal and inland waters and for heavy aerosol loadings . We present new AC and ocean IOP retrieval algorithms for the Medium Resolution Spectral Imager II onboard the FengYun 3D satellite that solve these problems . The algorithm development is based on extensive radiative transfer simulations for a coupled atmosphere ocean system in conjunction with machine learning techniques to retrieve ocean color products from MERSI II sensor data . The final ocean color products include spectral remote sensing reflectances
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New AC and ocean IOP algorithms developed for YF 3D MERSI II sensor. First ocean color products from FY 3D MERSI II sensor are demonstrated. Algorithm based on machine learning method driven by coupled atmosphere ocean RT simulations. Completely resolved negative water leaving signal issue plagues heritage algorithms. Algorithm is globally applicable reliable robust and efficient.
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S0022407319308246
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Relations are discussed which provide a solution of the problem of the precise abundance determination of isotopologues in a gas mixture . Numerical values of necessary coefficients of these relations are obtained for some polyatomic asymmetric top molecules H
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General method for determination of partial pressure of isotopologue in a gaseous mixture is presented. Simple relation is derived which allows to predict with a high accuracy effective dipole moment parameters of different species. Quantitative values of parameters in this relation are determined for a number of isotopologues of different asymmetric top molecules.
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S002240731930826X
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Fractal aggregate model has shown significant superiority in simulating integral optical properties of soot aerosol . In this study angular distributions of scattering matrices for soot samples were measured at 532nm wavelength . Experiments were conducted over scattering angles from 5 to 175 using an improved and validated apparatus . Soot particles emitted from burning of toluene and n heptane were collected and re aerosolized for matrix measurements . Electrical mobility diameter distributions of soot aggregates were measured and converted to volume equivalent diameter distributions according to various conversion factors . Size distributions of soot monomers and fractal parameters were obtained through statistical analyses of transmission electron microscope images . Fractal aggregate models were generated by a tunable particle cluster algorithm using measured size distributions of aggregates and statistically obtained morphological parameters . Multiple sphere
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Scattering matrices for soot samples were measured from 5 to 175 scattering angles. Size distributions and morphological parameters of soot samples were characterized. Ideal fractal aggregates were generated and their scattering matrices were calculated. Measured scattering matrices cannot be totally reproduced by ideal fractal aggregates.
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S0022407319308271
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The low lying electronic states of thallium fluoride are investigated using the multi reference configuration interaction method including the core valence and the spin orbit coupling effects . Based on the calculated potential energy curves the spectroscopic constants of the bound states of TlF are determined which are in accordance with available theoretical and experimental results in the literature . The transition dipole moments Franck Condon factors and the radiative lifetimes of the a
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Accurate electronic state properties of TlF are calculated with MRCI Q method. Spectroscopic constants for bound states of TlF are obtained. The radiative lifetimes of the transitions a. None. X. None. and a. None. X. None. are computed.
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S0022407319308295
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The influence of dielectronic recombination of projectile ions on characteristics of fast heavy ion beams passing through cold plasmas is studied on the basis of fully relativistic multi configuration calculations of DR rate coefficients . Present results are compared with the first results for DR rates of 1.5 MeV u iodine ions penetrating fully ionized hydrogen plasma with the electron temperature
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Dielectronic recombination influences the characteristics of fast heavy ion beams passing through cold plasmas. Dielectronic recombination rates of projectiles are large strongly increase the total recombination rate and decrease the mean equilibrium charge of the ion beam. A knowledge of correct dielectronic recombination rate values allows one to predict the charge state distributions of ions moving in a plasma and to find the optimal conditions beam energy plasma density and temperature to obtain ions with required charge state and density.
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S0022407319308337
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Significant increase of plasmonic surface enhancement has been observed in gold coated micron sized inverse pyramids entrapping a gold nanoparticle . The amplification of both surface enhanced Raman and fluorescence signals was found and it was dependent on the size of the trapped gold nanoparticle . The enhancement was found to be 50 times higher for the 250nm diameter nanosphere compared to the 50nm one . Finite differential time domain simulations were performed to determine the near field distribution in the structure and showed that when the nanoparticle protrudes into the hotspot zone of the void coupling of the electromagnetic field occurs and the plasmon related near field enhancement is concentrated into the close vicinity of the nanoparticle mainly into the gaps around the contact points of the curved sphere and the flat pyramid surfaces .
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Giant plasmonic surface enhancement has been observed in gold coated micron sized inverse pyramids entrapping a gold nanoparticle. The amplification of both surface enhanced Raman and photoluminescence signals was found. Near field enhancement hotspots of the structure were determined using FDTD simulations. The plasmon related near field enhancement is concentrated into the close gaps around the tangential points of the curved sphere and the flat pyramid surface
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S0022407319308428
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The generalized multi particle Mie equation and electromagnetic momentum theory are applied to investigate the stability and dynamics of chiral nanoparticles in lateral optical binding induced by a high order Bessel beam . Such non diffracting light suppressed the influence of the axial intensity profile of the illuminating beams on the self organization process which then depended critically upon the inter particles interactions . The illuminating HOBB is described in terms of beam shape coefficients within the framework of generalized LorenzMie theories . Utilizing the addition theorem of the vector spherical wave functions the interactive scattering coefficients are derived through the continuous boundary conditions on which the interaction of the chiral nanoparticles is considered . The observed lateral binding force dependence of the separation of optically bound particles on the incidence of HOBB is in agreement with earlier theoretical prediction when the chiral spheres degenerate into isotropic spheres . We discuss the influence of the different parameters of the incident Bessel beam and of the chiral body on lateral BF in detail . Linearly and circularly polarized incident Bessel beams are considered and the corresponding lateral BFs are compared and analyzed . The polarizations of incident HOBB considerably influence the lateral BF of chiral nanoparticles . In binding chiral nanoparticles the polarization of incident beams should be chosen in accordance with the chirality . This finding may provide a recipe to understand the light interaction with multiple chiral particles of arbitrary shapes with the aid of the analytical approach . It could be a promising avenue in controlling the optical micromanipulation on chiral structures self arrangement .
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The lateral binding force exerted on chiral bi sphere induced by a high order Bessel beam with arbitrary polarization states is studied analytically. The accuracy of the theory and codes is verified. Numerical effects of various parameters and different properties are numerically analyzed in detail. Even more so in hindsight of these parameters with respect to optical binding clearly shows that in what case optical binding exists as a fine balance between those parameters.
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S0022407319308465
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High resolution laboratory spectra of several lines from the oxygen B band R branch measured with cavity ring down spectroscopy were fitted with advanced line shape functions . We show that for the low intensity transitions in the range from 10
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B band transitions with quantum number. up to 38 were measured by PDH locked FS CRDS linked to the optical frequency comb. Multispectrum fit performed for the Voigt speed dependent Voigt and speed dependent NelkinGhatak profiles compatible with the HartmannTran profile. Intensities and other line shape parameters determined with subpercent accuracy. Spectroscopic parameters of the. and. states of. determined from Dunham fit.
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S0022407319308489
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The metallic nanoparticle dimer is a fundamental model system for enhancing and tuning localized surface plasmon resonances . In the past it had been found that the far and near field optical properties of dimer antennas can be regulated by many parameters . In recent years the quantum mechanical effects such as nonlocal screening and electron tunneling have been achieved when the gap distance in a dimer approaches 1nm and subnanometer . In this communication both the near field enhancement and optical force in dimer are fully investigated and compared between classical and nonlocal models . Compared with classical theory we found that both the resonant wavelength and peak intensity have smaller changes in nonlocal model when geometrical or material parameters changes . Besides the extent of parameter induced spectral changes is slightly different between near field enhancement and optical force . These results make possible the quantitative analysis of nonlocal effects in surface enhanced spectroscopy nanoantennas refractive index sensing surface enhanced optical force and quantum plasmonics .
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The local analogue model LAM for nonlocal effects is integrated into the generalized Mie theory GMT for simulating strongly coupled plasmonic nanoparticle dimer. Both the near field enhancement and optical force in the dimer nanoantenna are calculated. The influence of some geometrical and material parameters are investigated and compared between classical and nonlocal models.
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S0022407319308507
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Laser spectroscopy methods were used in investigations of the Zeeman hf structure of 17 lines of atomic vanadium in the visible green red region 568.3 648.1 nm . We used two methods of laser spectroscopy the laser induced fluorescence and fluorescence depletion spectroscopy . A hollow cathode discharge tube was the source of vanadium atoms . Zeeman structure measurements were carried out using a permanent neodymium magnet generating a field of approximately 800 G. We determined
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Laser spectroscopy methods LIF and FDS were used in measurements of the Zeeman hf structure of atomic vanadium. New experimental gJ factors have been determined for 10 energy levels of V I. New experimental hfs constants were determined for 7 levels of V I. Hfs and gJ data for many other levels of V I have been tested and verified. In the computer analysis of the spectra the saturation effect was taken into account.
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S0022407319308520
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Metal nanoparticles have attracted intense attention due to their unique optical and thermal properties for applications such as micro nano electronics and photonics . Relative orientation interparticle spacing and particle size strongly impact the optical behavior of the nanoparticle assemblies . The near field confinement of electromagnetic fields between closely packed metal nanoparticles which is enhanced due to their plasmonic behavior creates high thermal energy densities under visible to near infrared wavelength laser irradiation . As metal nanoparticles tend to be oxidized or change shape under laser illumination resulting in non linear optical and thermal behavior surrounding each metal nanoparticle with a dielectric shell could be a potential way to mitigate these effects as well as to engineer their plasmonic behavior . In this study we use numerical simulations to analyze the plasmonic behavior of gold nanoparticles surrounded with dielectric shell by investigating nanoparticle s various configurations to each other as well as their relative orientation to incoming light source under laser irradiation in dielectric media . Such geometries are of particular interest for applications such as photonic integrated circuits photonic sintering and nanophotonic cooling .
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The characteristics of optical electromagnetic energy propagation in au nanoparticle dimers and chains with various nanoparticle radii and configuration surrounded with dielectric material and suspended in different media under various wavelengths are determined. Very large increases in field intensity up to 1500 fold can be obtained at 25nm radius au nanoparticle dimer having no dielectric shell with particles having 30 relative angle to the electric field in dielectric medium. 1.33 under 532nm TM polarized light. It is observed that using 2nm thick dielectric shell can enhance the plasmonic behavior of the au nanoparticles such dielectric shells may also be beneficial in controlling oxidation and agglomeration. Dimer configuration is observed to yield about 25 larger maximum poynting vector ratio than 4 particle configuration chain when the nanoparticles are suspended into dielectric medium where. 2. Au nanoparticles surrounded with dielectric shell and suspended in various media exhibit different plasmonic effects within investigated particle configurations and also exhibit different extinction cross section or efficiency such that extinction efficiency of 8.6 and 11.5 are observed for 4 nanoparticle configuration chain and nanoparticle dimer respectively at the maximum extinction cross section resonant conditions.
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S0022407319308544
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Development of robust and easy to implement methods for quantitative turbidity characterization by inherent properties of absorption and scattering can have wide applications . We report a new method for multiparameter characterization of turbid samples with three photodiodes based on the radiative transfer theory . Instead of acquiring collimated transmittance by spatial filtering and scattered light signals by integrating spheres the method determines RT parameters from forward transmittance dominated by light of single scattering and non hemispherical diffuse reflectance and transmittance dominated by light of multiple scattering . A Monte Carlo based inverse algorithm has been developed to rapidly obtain absorption coefficient
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A new and robust method for determination of absorption coefficient. scattering coefficient. and anisotropy factor g has been developed without integrating spheres based on the radiative transfer RT theory. The RT parameters are determined from the measured signals of forward transmittance dominated by light of single scattering and non hemispherical diffuse reflectance and transmittance dominated by light of multiple scattering. An inverse algorithm based on GPU executed Monte Carlo simulations has been developed to rapidly obtain the RT parameters from the measured signals. The new method has been validated against the Mie theory with different sphere suspension samples in a spectral region of 4601000nm. Uniqueness of the inverse solutions has been proved at selected wavelengths.
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S002240731930857X
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The Chebyshev collocation spectral method is developed for solving the vector radiative transfer equation in participating media and then extended to polarized radiative transfer problems in two layered media . The derivation of the CCSM discretization for the VRTE is presented and the numerical performance of the CCSM is investigated . The accuracy of the CCSM for solving the VRTE is first verified by comparing the CCSM solutions for the polarized radiative transfer in a plane parallel medium with published results . Afterward the CCSM is applied to polarized radiative transfer problems in inhomogeneous media including two layered media with different scattering characteristics and two layered media with different refractive indices . Finally taking both effects of different medium properties and reflective refractive interface into account we investigated the polarized radiative transfer in a realistic atmosphere ocean system via the CCSM and discussed the distributions of the Stokes vector components . Results show that the CCSM is accurate and efficient for solving the VRTE and the distributions of Stokes vector for a realistic atmosphere ocean system are presented in detail .
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Chebyshev collocation spectral method CCSM is developed for solving the vector radiative transfer equation VRTE . The CCSM is accurate and efficient for solving the VRTE. The CCSM is extended to polarized radiative transfer problems in inhomogeneous media. The Stokes vector distributions for a realistic atmosphere ocean system are presented and analyzed.
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S002240731930860X
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The optical resonance scattering of a dielectric sphere of arbitrary size illuminated by a polarized Airy beam is studied using the generalized LorenzMie theory . The electric field is derived using the vector angular spectrum decomposition method . The beam shape coefficients are obtained using the multipole expansion method involving vector spherical wave functions . The resonance scattering characteristics are calculated using the GLMT by subtracting a non resonant background of a perfectly conducting impenetrable sphere . The effects of beam polarization the attenuation parameter
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The optical resonance scattering of a dielectric lossless sphere of arbitrary size illuminated by a polarized Airy beam is studied using the GLMT. The BSCs of the polarized Airy beams are calculated using VASDM and VSWFs. The influences of beam polarization attenuation parameter. and transverse scale. of the incident Airy beam are discussed. The scattering and extinction resonance and interference efficiencies are examined under different parameters. The scattering efficiency for a perfectly conducting sphere the normalized far field scattering intensity and its resonance counterpart are calculated and plotted.
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S0022407319308635
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Optical non invasive techniques for temperature and mole fraction measurements in flames and other reactive flows are often limited to applications under well defined laboratory environments . These limitations mainly arise from various prerequisites of the techniques e.g . regarding the optical accessibility of the systems under investigation its environmental conditions such as vibrations and temperature or the need of tracers inside the flow . In order to weaken these constrains we present a robust fiber based sensor system utilizing tracer free spontaneous rotational Raman spectroscopy with tunable near infrared continuous wave laser excitation capable of a simultaneous point wise determination of gas temperature and mole fractions in laminar spatially uniform non sooting reactive flows . Benefits and limits of this method are evaluated investigating a laminar premixed methane air flat flame of a McKenna type burner . In that case the main rotational Raman active and therefore detectable compounds are nitrogen oxygen and carbon dioxide . For the subtraction of flame luminosity two different techniques were used simple background subtraction and shifted excitation Raman difference spectroscopy . For both methods the corrected spectra are matched to simulated spectra via a least square fit algorithm in order to extract the quantities of interest . Hereby Bayesian inference enables the determination of the uncertainties of the results . The consideration of the covariance within the multi variate analysis allows for the combination of the BGS and SERDS method to establish a more advanced analysis routine .
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Multiparameter Raman measurements for reactive flows. Bayesian analysis for parameter uncertainty estimation. Comparison of different background correction methods.
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S0022407319308659
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Magnetic polaritons which refer to the couplings between incident electromagnetic waves with magnetic excitation inside the structures play an important role in tailoring thermal radiative properties . Many researchers devote themselves to studying the geometric effects of the micro nanostructures based on magnetic polaritons and many wavelength selective devices are designed . However the links between different structures on thermal radiative properties based on structural transformation are not investigated yet . In this work the idea that deep slit arrays and deep gratings can be equivalent conversion approximately when studying the radiative properties is proposed . Magnetic polariton resonant conditions of deep metal gratings and slit arrays are investigated . Considering the symmetry of the structures when gratings and slit arrays have same geometry parameters except that the slit heights are twice that of the grating depths the phenomena that they have almost identical magnetic polariton resonant frequencies are observed . The reason for almost identical magnetic polariton resonant conditions is attributed to that the symmetry of the structures leads to the similar electromagnetic field distributions . Moreover equivalent inductor capacitor circuit model is also used to analytically illuminate and confirm almost same MP resonant frequencies . The idea provided in this paper may benefit design of the wavelength selective devices based on magnetic polaritons and further studies on tailoring radiative properties from perspective of structural transformation .
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The idea that slit arrays and gratings can be equivalent conversion based on structural transformation when studying the radiative properties is proposed. The symmetry of structures leads to the similarity of the electromagnetic field distributions between gratings and half slits. MLC circuit model shows good description and prediction on MP in gratings and LC circuit model is used to analytically illuminate why MPn of gratings and MP 2n 1 of slit arrays have almost same MP resonant frequencies.
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S0022407319308672
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We present measurements of the scattered light intensity by aerosolized hematite aggregate particles . The measurements were made at a wavelength of 532nm in the scattering angle range from 0.32 to 157 . Hematite has high values of the real and imaginary parts of the refractive index m n i 3 i0.5 at the studied wavelength . Scanning electron micrographs indicated that the particles were aggregates whereas the optical microscope pictures showed that the aerosol had a bimodal distribution with effective mean diameters of roughly 1 and 10m . This is consistent with the light scattering results which displayed two Guinier regimes . The aggregates were composed of smaller grains with an approximate size of 200nm . Ultra Small Angle X ray Scattering indicate that the aggregates were uniform and non fractal . Mie calculations for a sphere equivalent to the aggregate size were compared to the experimentally observed results . The observed results showed an enhanced backscattering whereas the Mie calculations did not due to the large imaginary part of the refractive index . Hematite aggregates were simulated by assuming they were composed of spherical monomers inside a spherical volume . Then the light scattering was calculated using the T matrix method for these simulated aggregates . The calculated results show an enhanced backscattering . We present a dimensional analysis to estimate the extent of multiple scattering within the aggregate and find a correlation between the average number of scattering events within the aggregate and the enhancement in the backscattering .
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The scattered light was enhanced in the backscattering regime despite large imaginary refractive index. Enhancement backscattering for the aggregate is due to internal multiple scattering between the grains within the aggregate. Bimodal size distribution causes an extended Guinier regime. Highly refractive particles displays two dimensional diffraction properties.
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S0022407319308696
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Scattering by aerosols and gases cause a certain fraction of artificial light emitted upwards is redirected to the ground . Of all atmospheric constituents just the aerosols are most important modulators of night sky brightness under cloudless conditions . Unlike most of the previous we highlight a crucial role of solar radiometry for determining the atmospheric optical depth before night time observation is to be made . Aerosol optical depth at visible wavelengths extracted from the data measured provides then the information on size distribution or mean refractive index of aerosol particles that in turn are both necessary to make night sky brightness prediction more accurate . Therefore combining daytime and night time radiometry we can achieve accuracy much higher than ever before . This is due to significantly reduced uncertainty in aerosol properties .
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More accurate night sky brightness predictions requires information on aerosols. A portable turbidity analyzer is developed for in situ aerosol characterization. Multi wavelength radiometry provides information on AOD and size distribution. An experiment was performed to test the system and the method under limit conditions.
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S0022407319308726
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Clouds are a kind of atmospheric factor that most effectively scatters the artificial light coming from the ground . Therefore they have the most significant impact on the brightness of the night sky . The paper analyses the influence of both the level of cloudiness as well as the genera of clouds and altitude of its base on amplifying of the light pollution . The impact of cloudiness on the brightness of the night sky in places with different levels of light pollution was researched . Measurements of meteorological elements were used together with clouds genera assessments . The introduction of an innovative method of identifying some genera of clouds on the base of the all night continuous measurements of the sky s brightness allowed for a similar analysis in the absence of observational data specifying the genera of clouds .
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Clouds are the main factor of ecological light pollution. There is a clear linear dependence of the night sky brightness and the cloudiness. There are three groups of light polluted areas connected to the population density. Night sky brightness depends on the clouds genus. Brightness of the night sky depends on the altitude of clouds base.
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S0022407319308738
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An optical model has been developed for analyzing the coherent transmittance of a polymer dispersed liquid crystal films doped with carbon nanotubes at uniform normal droplet polymer interface anchoring . It is based on the FoldyTwersky and anomalous diffraction approximations Maxwell Garnett equations and the order parameters concept . The model allows one to analyze the electro optical response of films depending on their thickness the refractive indices of the liquid crystal and polymer matrix size and concentration of the LC droplets concentration of nanotubes conductivities of the LC and the polymer . Experimental verification of the model is performed .
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A model to describe the electro optical response of PDLC. CNT films is developed. Experimental verification of the model is performed. The model is applied for the films with uniform normal interface anchoring. A technique connecting the mass and volume filling factors of the films is created.
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S0022407319308775
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Recent progress is reported on the assignment and fitting of a rotational spectrum of methylamine in the ground vibrational state and first and second torsional states . The high resolution infrared spectrum has been analyzed in the 40 to 360 cm
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Assignment of the rotational IR spectrum of methylamine. Rotational transitions in the ground first and second torsional states. A global fit of each set of rotational transitions carried out. A model based on the group theoretical formalism of Hougen and Ohashi.
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S0022407319308817
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Following previous theoretical development based on the assumption of a rank correlated comonotonic spectrum the Locally Correlated SLW method is outlined . The relationship between the LC SLW method and the Reference Approach SLW method and the Rank Correlated SLW method is established . Further the relationship between these SLW model variants and other global models including the Full Spectrum Correlated
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The Locally Correlated SLW LC SLW model is outlined theoretically. The LC SLW model s relationship to other SLW models and to other global models ADF FSCK is clearly identified. The LC SLW model s accuracy is assessed over a broad range of conditions. It is shown that the LC SLW model may prove more accurate in regions of high temperature dominant gas emission but suffers in situations of dominant gas absorption. It is shown that the LC SLW cannot claim universal improvement relative to RC SLW model in predictive accuracy at all conditions.
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S0022407319308969
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Particle shapes can be distinguished by the properties of optical light scattering patterns . We investigate the feasibility of convolutional neural networks for shape based classification using light scattering patterns by mimicking a real application scenario of shape classification of micro sized phytoplankton . Six different particle shapes were chosen . The volume equivalent size parameter ranged from 2.98 to 14.89 . The real part of refractive index was
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Six representative shapes of phytoplankton in the low size range were modeled including sphere ellipsoid cylinder box cone half sphere and prolate spheroid 2 cylinders. The volume equivalent size parameter ranged from 2.98 to 14.89. The real part of refractive index was. 1.060.04. The particles were random oriented with respect to the direction of propagation of the incident light. The angular range of the scattering pattern in the data set was limited to 89152 for the scattering angle and 063 for the azimuthal angle which is close to the real use case. Convolutional neural network achieves an average of 97 particle shape classification accuracy.
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S0022407319309082
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The effect of impurities on spectral absorption coefficient of snow snow absorptance and albedo is modeled and analyzed for the practically important case of soot particles . A combination of physical processes of snow formation in the atmosphere and periodic partial melting of snow cover can lead to various morphologies of contaminated snow . Therefore both the internal mixing of soot in ice grains and the external mixing when soot is between the grains are considered . The geometrical optics approximation for large semi transparent particles the Rayleigh theory for small soot particles the Maxwell Garnett theory for the effective optical constants of ice containing soot and the Mie theory generalized for absorption and scattering of light by two layered spherical particles are employed . Calculations showed that a possible uneven distribution of soot in ice grains can lead to significant differences in the values of the absorption coefficient of snow cover in the visible region of the spectrum .
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The spectral absorption coefficient of polluted snow is calculated. The external and nonuniform internal mixing of soot are considered. The maximum effect of a central pollution of ice grains is obtained. The spectral absorptance and albedo of polluted snow are calculated.
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S0022407319309094
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The accuracy of absorption based measurement is directly linked to the fidelity of the pressure and temperature dependent reference absorption cross sections used for fitting and data interpretation . For large complex molecules or species for which line by line absorption databases do not exist cross sections are often measured in the laboratory at a particular set of known temperature and pressure conditions and published for use as reference spectra . For subsequent simulations or measurements at conditions between or outside of the reference conditions no exact reference cross sections exist . We propose a technique which enables the scaling of reference absorption cross sections to different pressures . Pressure influences the shape of the cross section through collisional broadening . We modify the collisional broadening of the cross section by performing an inverse Fourier transform on the dataset to view the free induction decay of the molecule and then computationally adjusting the decay rate of the FID . This effectively pressure scales the broadening parameters of the multitude of contributing molecular resonances . The technique is validated here against reference absorption cross sections and can yield residuals between modified and measured reference spectra below one percent . The approach is simple to apply and allows users to generate reference cross sections at any pressure above the pressure condition of the reference dataset . It therefore also significantly reduces the need to measure reference absorption cross sections at many pressures .
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Technique to broaden absorption cross section datasets to higher pressure conditions without knowledge of individual line parameters. Based on scaling the exponential decay envelope of the molecular free induction decay formed from the inverse fourier transform of an absorption cross section at a particular pressure. Validated for three complex molecules using published absorption cross section data at different pressure conditions.
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S0022407319309100
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Independent scattering refers to situations when particles are sufficiently distant that some of the radiation characteristics of particle systems can be determined by adding the contributions of each particle . When particles are in close proximity however dependent scattering prevails and is affected by near field interactions and far field interferences among scattered waves from nearby particles . The dimensionless parameters governing the scattering cross section and asymmetry factor of non absorbing bispheres disordered and ordered suspensions and aggregates with up to 8 spherical particles were found to be the particle size parameter
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Scattering by non absorbing bispheres and particle suspensions and aggregates was studied systematically. A wide range of size parameter refractive index and interparticle distance to wavelength ratio was explored. New transition criteria between independent dependent scattering regimes were established. The scattering cross section and asymmetry factor feature different transition criteria. Criteria for bispheres cannot be extended to suspensions and aggregates of small particles.
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S0022407319309203
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This paper analyses the impact of various types of aerosols both of natural and anthropogenic origin on the brightness of the night sky glow in southern Poland . The particles of particulate matter related to the combustion of solid fuels in the winter the volcanic or desert dust as well as mists and haze are considered as the artificial light scattering sources . Measurements of the brightness of the cloudless and moonless night sky were done in 20092016 both within the city of Krakow and in suburban areas as well as in mountainous ones . The strong linear correlation between the brightness of such sky and the concentration of particulate matter is shown . The acoustic sounding of the atmosphere has indicated the possibility of a relationship between the brightness of the night sky and the amount of such particulates which accumulate in atmospheric boundary layers . The usefulness of the theoretical model of horizontal transport of dust in the atmosphere for forecasting the brightness of the night sky glow is also pointed out . A clear effect of the Saharan origin dust clouds on the brightness of the night sky glow is shown . This brightness in the conditions of a low level of light pollution is associated with the forecasted optical density of such clouds . It is also demonstrated that with the thickening of mist the impact of distant light sources on the brightness of the night sky decreases but the one of a nearby sources becomes more significant . The conclusion states that anthropogenic particulate matter has the greatest impact on the brightness of the cloudless night sky glow in winter . In areas heavily polluted with light fogs and mist are particularly important . In areas with low levels of light pollution the clear impact of desert dust is visible .
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Aerosols are the main light scattering factor in the cloudless sky. Particulate matter PM plays a special role in the sky glow over the residential areas. There is a linear relationship between PM concentration and brightness of the sky glow. Particulate matter accumulates at the boundaries of atmospheric layers. Desert dust seasonally plays a special role in the sky glow over the protected areas.
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S0022407319309264
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The presence of the oxide coatings on conducting metal particles is often ignored in the calculations of microwave absorption . However we find that the optical properties of the coatings play a significant role in enhancing or suppressing the absorption of electromagnetic energy . Here we solve the Mie scattering equations numerically to separate and quantify the role of electric and magnetic field absorption from microwaves at 2.45GHz by small metal spheres coated with dielectric or semi conducting materials . The range of size and conductivities of the metal particles and the optical properties of the coatings are chosen for their practical importance . We also provide simple approximate expressions for the absorption per unit volume by coated spheres in the small particle limit which agrees very well with the exact Mie solution . We have demonstrated that for highly conducting particles coated with a material of low conductivity the electric field absorption depends
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High loss coatings significantly enhance microwave absorption in metal particles. Only a very thin layer of coating is required to maximize absorption. Coatings are dominant absorbers of the electric field. Magnetic field absorption depends only on the properties of the core.
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S0022407319309276
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This work presents the possibility of using the extremely popular compact digital cameras of smartphones or action cameras to perform sky photometry . The newest generation of these devices allows to save raw images . They are not as good as digital single lens reflex camera in particular in terms of sensitivity noise and pixel depth but they have the advantage of being extremely widespread on the population and relatively cheap . These economical digital compact cameras work with an electronic shutter it overcomes the consumption of mechanics and allows to gather images for long time . The work uses a simple calibration method to transfer raw data from the proprietary RGB color space to the standard CIE 1931 color space . It allows the measurement of sky luminance in cdm
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Use of smartphone cameras to perform sky photometry. A calibration allows to transfer data from the proprietary RGB color space to a standard color space. Measurement of sky luminance according SI has an uncertainty of about 20 . The colorimetric calibration allows to measure the correlated color temperature of the sky. Calibrated smartphone cameras can be a worldwide distributed tool for sky quality measurements and citizen science activities.
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S0022407319309306
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A numerical model is presented for spectral characteristics of radiation coming from a pool fire flame . The case studies are 1.75
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LES CFD model of large pool fire is developed using FDS. Transient CFD profiles are taken for a line of sight LoS of a sensor. The LBL spectral calculation along the LoS is performed and validated. The intensity peak of hot CO2 is identified as the signature of fire spectra. A sensitivity analysis carried out for size of the pools air relative humidity and distance from the pools.
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S0022407319309331
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This paper presents the ongoing research of the lighting laboratory to develop a standardized method for the measurement of several types of lighting installations using unmanned aircraft systems . The technology of unmanned aircraft systems can incorporate multiple types of sensors and can be programmed to fly in predefined areas and routes in order to perform complex measurements with limited human intervention . This technology provides the freedom of measurements from several angular positions and altitudes in a fast easy accurate and repeatable way . The overall aim of this work is to assess the lighting installations not only against the applicable lighting standards but also to investigate and reveal issues related to light pollution and obtrusive lighting . The latter are issues that in most cases are neglected due to the lack of standardized methods of calculation and measurement . Current assessment methods require illuminance or luminance measurements of horizontal and vertical surfaces generally from the ground . The proposed approach provides a holistic three dimensional evaluation of the lighting installations beyond the common methods and geometries and opens the discussion for future update of the relevant standards on outdoor lighting . In the scope of this paper several proof of concept cases are presented .
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A new proposed method for the measurement and assessment of the obtrusive light and the light pollution. Introduction of the concept of the Drone Gonio PhotoMeter DGPM. Proposed lighting measurement geometries for aerial platforms. Assessment of lighting installations fast and easily from the air. Presentation of preliminary test cases.
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S0022407319309343
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In quantitative photoacoustic tomography the aim is to reconstruct distributions of optical parameters of an imaged target from an initial pressure distribution obtained from ultrasound measurements . In order to obtain accurate and quantitative information on the optical parameters modeling light transport in the target is required . Utilizing an approximative model for light transport would be favorable to reduce the computational cost but the modeling errors of the approximative model can result in significant errors in the reconstructions . In this work we approach the image reconstruction problem of quantitative photoacoustic tomography in the Bayesian framework . We utilize the Bayesian approximation error method to compensate for the modeling errors between the diffusion approximation and Monte Carlo model for light transport . The approach is studied with two dimensional numerical simulations with varying optical parameters and noise levels . The results show that Bayesian approximation error method can be used to reduce the effects of the modeling errors in quantitative photoacoustic tomography in a wide range of optical parameters .
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Bayesian framework enables accurate estimates and reliability assessment. Modeling errors can be compensated using Bayesian methods. Modeling of the errors improves the reliability of the credibility estimates.
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S0022407319309355
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This article aims to determine the most relevant engineering global method for gas radiative property modeling to be applied in the simulations of combustion problems . Two versions of the full spectrum correlated k model the Rank Correlated full spectrum
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Engineering global methods for gas radiation are considered. Comparisons are performed in several axisymmetric jet diffusion flames at high pressure. WSGG model is found to provide acceptable accuracy for engineering predictions. FSCK II and RC SLW are found to be the most mature gas radiative property models to be implemented in CFD codes.
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S0022407319309379
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A reliable control of current orientation of a spacecraft is a very important task in aerospace engineering . This makes important to elaborate a backup or replacement system which can be used for the verification or correction of the orientation . It seems natural to use various conditions of radiative heating of the design elements of different orientations with respect of the Sun and strongly radiating or reflecting planets of the Solar system . In the case of an ordinary slow variation of the vehicle orientation in space the temperature measurements can be used to distinguish different integral radiative flux to various surfaces of a specially designed thermal sensor with several facets . An analysis of a possibility of such an engineering solution is a subject of the present study . The mathematical problem to be solved is one of the so called inverse heat transfer problems and its solution is not a simple task . Therefore the main efforts of the authors are focused on solution of this ill posed problem . The known methods of the inverse problem regularization are modified to take into account special features of the heat transfer problem under consideration . The resulting algorithm is verified using the typical case problems . It was shown that one can obtain sufficiently accurate results on the bases of a limiting set of relatively simple temperature measurements . The latter enables us to consider the method suggested as a promising way to elaborate a series simple backup replacement system of an approximate retrieval of a spacecraft current orientation . This statement is confirmed by calculation for one of the typical trajectory of a vehicle in the Solar system .
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An approach to solve Inverse Heat Transfer Problem for distributed and lumped parameter systems is suggested. A new technology to estimate the orientation of spacecraft is proposed. Experimental approving of suggested approach was executed.
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S0022407319309392
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Artificial skyglow is a form of light pollution with wide ranging implications on the environment . The extent intensity and color of skyglow depends on the artificial light sources and weather conditions . Skyglow can be best determined with ground based instruments . We mapped the skyglow of Berlin Germany for clear sky and overcast sky conditions inside and outside of the city limits . We conducted observations using a transect from the city center of Berlin towards a rural place more than 58km south of Berlin using all sky photometry with a calibrated commercial digital camera and a fisheye lens . From the multispectral imaging data we processed luminance and correlated color temperature maps . We extracted the night sky brightness and correlated color temperature at zenith as well as horizontal and scalar illuminance simultaneously . We calculated cloud amplification factors at each site and investigated the changes of brightness and color with distance particularly showing differences inside and outside of the city limits . We found high values for illuminance above full moon light levels and amplification factors as high as 25 in the city center and a gradient towards the city limit and outside of the city limit . We further observed that clouds decrease the correlated color temperature in almost all cases . We discuss advantages and weaknesses of our method compare the results with modeled night sky brightness data and provide recommendations for future work .
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The brightness and color of skyglow was mapped inside and outside of a city for clear and overcast skies. High luminance values and illuminance values were obtained within the city for overcast conditions. Cloud amplification is highest in city center. Clouds shift the color of the night sky towards the red.
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S0022407319309409
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Four laminar non premixed methane air flames with increasing Reynolds numbers are investigated using a newly developed conjugate combustion radiation laminar flame solver . The baseline model includes a forward Monte Carlo ray tracing solver coupled with a line by line spectral model a 16 species skeletal chemical mechanism and no soot model . A backward Monte Carlo solver is developed for the nongray inhomogeneous combustion mixtures and verified using the forward Monte Carlo solver . A 25 species skeletal chemical mechanism is adopted for parametric studies . Effects of soot radiation on unsteady flames are investigated using a two equation soot model . Good agreement with experiments in radiative flux and radiant fraction is observed for all flames using the baseline model . The radiative heat flux predicted by the backward Monte Carlo solver agrees well with that obtained from the forward Monte Carlo solver with well controlled standard deviations . Contours of radiation related scalars indicate that the laminar flames are within the optically thin limit . Results obtained from conjugate combustion radiation simulations with various radiation solvers and spectral models show minor differences for the two smaller flames . For the two unsteady flames radiative re absorption has a more significant impact on the overall flame structure especially when soot is considered . Parametric studies using the longest flickering flame suggest that the choice of chemical mechanism the consideration of radiation and the inclusion of soot radiation affect the prediction of the instantaneous flame height . The prediction of flame puffing frequency is insensitive to the variations in chemistry soot and radiation models . The radiative heat flux prediction is sensitive to the thermal boundary condition of the fuel nozzle the inclusion of soot and its radiation with re absorption . It is recommended that soot should be considered for future studies when assessing radiation models using this set of target flames .
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A conjugate combustion radiation solver is developed and applied to simulate laminar non premixed methane flames with good agreement. Radiative re absorption has a more significant impact on the flame structures of unsteady flames especially when soot is considered. The choice of chemical model radiation consideration and the inclusion of soot radiation affect flame height prediction for unsteady flames. The radiative heat flux of the unsteady flames is sensitive to the thermal boundary conditions of fuel nozzles and the inclusion of soot radiation. A backward Monte Carlo solver is developed for nongray combustion mixtures and shows good performance with well controlled standard deviations.
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S0022407319309410
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The in orbit performance of the Microwave Temperature Sounder onboard the Fengyun 3D satellite is evaluated using the Community Radiative Transfer Model and the Radiative Transfer for the Television Infrared Observation Satellite Operational Vertical Sounder model . Both radio occultation data from the Constellation Observing System for Meteorology Ionosphere and Climate Data Analysis and Archive Center and ERA Interim analysis data from the European centre for Medium Range Weather Forecasts are taken as inputs to the two fast radiative transfer models . The radio occultation data are quality controlled and the collocation criterion between the radio occultation data and the MWTS measurements is defined such that the spatial and temporal difference is 50km and 3h respectively . The biases of MWTS channels 510 produced by both CRTM and RTTOV agree well over the oceans under clear sky conditions between 60 S and 60 N from July to December 2018 . The mean biases simulated by the radio occultation and ERA Interim data are negative and the absolute values of the biases are 0.6 and 1.5K for channels 510 of the MWTS respectively . The biases at channels 4 and 11 between the CRTM and RTTOV simulations are inconsistent and require further investigation of the transmittance difference between the fast models . The standard deviation of the biases from the radio occultation and ERA Interim data are 0.5 and 1.8K for the limited amount of collocated radio occultation data . Asymmetrical patterns are detected for the MWTS through the scan angle dependent bias . The long term mean MWTS bias shows only a weak dependence on latitude which suggests that biases do not vary systematically with brightness temperature .
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The mean biases simulated by the radio occultation and ERA Interim data are within 0.6 0 and 1.5 0 k for channels 510 of the MWTS. Asymmetrical patterns are detected for the MWTS through the scan angle dependent bias. The MWTS bias shows a weak dependence on latitude.
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S0022407319309434
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Heat treatment processes have a major impact on the mechanical and structural properties of the end products . Accurate control of the material temperatures during the heating and cooling regimes is very crucial for the quality of a given production . However especially in continuous heat treatment furnaces the products inside the furnace are rarely in thermal equilibrium with the furnace and monitoring the air temperature inside the furnace provides a very indirect information about the solid temperatures of the products . In this study the solid temperatures of the products inside a continuous glassware annealing furnace model is solved numerically . The continuous furnace model is divided into heating and cooling sections each filled with rows of goblets and they are treated separately using a segregated modeling approach . In this approach the convective heat transfer inside the furnace is modelled using a steady state convection solver in stationary frame of reference . The transient heat conduction inside the moving goblets is calculated using a separate transient heat conduction solver in moving frame of reference . Thermal radiation exchange between the surfaces is treated using a new backward Monte Carlo based surface to surface radiation model and the calculated radiative heat fluxes are added as heat flux boundary conditions on the goblet outer walls . Similarly the convective heat fluxes calculated with the convection solver are also imposed as heat flux boundary conditions . This iterative solution approach showed a fast convergence behavior requiring only 4 iterations to converge both for the heating and cooling sections of the furnace . The overall computational cost of the simulation is measured as 10h and 20h for the heating and cooling sections respectively . Among all the three heat transfer modes convection is found to be by far computationally the most expensive followed by the thermal radiation and conduction being the computationally least expensive one . Overall the approach enables to conduct high fidelity analysis of the heat treatment processes with acceptable computational cost .
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A segregated numerical approach has been proposed for the modeling of the multi mode heat transfer to the moving glasses inside a continuous glassware annealing furnace. Segregated numerical approach showed a fast convergence behavior requiring only 4 iterations to converge both for the heating and cooling sections of the furnace. Radiation heat transfer is found to be dominant compared to convective heat transfer in the considered glass annealing furnace. Among all the three heat transfer modes convection is found to be by far computationally the most expensive followed by the thermal radiation and conduction being the computationally least expensive one.
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S0022407319309446
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Based on the future measured temperature the Rauch Tung Striebel smoothing technique coupled with unscented Kalman filter is introduced to resolve the nonlinear inverse radiation conduction heat transfer problem which is nonlinear because of specific heat and thermal conductivity with temperature and existence of the radiative heat transfer . For the direct process the finite volume method is applied to calculate the energy equation and radiative transfer equation is computed by the discrete ordinate method . Based on the measurement temperature signals of the right surface the left surface time dependent heat flux and interior temperature in absorbing and scattering medium are retrieved in near real time by using the proposed method . The different number of the future measured temperature measurement noise and process noise covariance are applied to examine the feasibility and reliability of the present algorithm . All retrieval results show that the Rauch Tung Striebel smoothing technique coupled with unscented Kalman filter is accurate and stable . Compared to the unscented Kalman filter the accuracy of the retrieval temperature distribution is improved significantly the deviation and oscillation of the retrieval time dependent heat flux are also decreased substantially .
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The boundary heat flux and temperature field can be retrieved in near real time. Compared with UKF the time delay of estimated heat flux is reduced greatly. When UKS is empolyed the deviation between the retrieval temperature field and exact one reduces. The UKS technique is more robust comparing to the UKF.
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S002240731930946X
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Light pollution is an environmental problem produced by an unjustified escalation of upward propagated artificial lighting from inaccurately situated or designed artificial night lighting systems . The radiative transfer of the nocturnal artificial lighting in cities spreads spatio temporally with a certain randomness where the modelling through network theory allows to describe invariants of this phenomenon . A critical part of light pollution studies is to quantify how spatial heterogeneity relates to the lighting system . Since satellite images are the visual representation of the information captured by a sensor they can be used to obtain information data on artificial night radiation . In this sense the utilization of such images must be justified with the correct use algorithms for data calibration and noise reduction in order to establish the baseline of the data to be used . In this work we analyse satellite images that represent light pollution in a specific time frame . Using these images we propose to represent the change in light pollution as a network . We calculated some classical network measurements to characterize the networks . In doing so we demonstrate the utility of this representation as an urban construct with respect to radiative transfer of artificial light . The results indicate that largest cliques and transitivity are a good interpretive structural modelling based approach to determine aspects of light pollution that may be related to urban processes . Therefore we hope this document will motivate future research that links urban processes with the increase of nocturnal artificial lighting .
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Trends in light pollution and urban sprawl can be monitored based on nighttime satellite imagery. Thresholding methods are useful in a brightness domain for background foreground extraction in cases with good light and contrast. Various physical processes are involved in the radiative transfer of the light projected from the cities. With a correct method based on background subtraction any nocturnal image can be useful in detecting urban sprawl.
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S0022407319309483
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Oxy fuel combustion is a modern carbon capture and storage technique that improves the combustion process and reduces the environmental penalty of many combustion systems . Evidently the accurate radiative calculation of oxy fuel combustion is very important to obtain more improved combustion system designs with less environmental drawbacks . In the present study a small scale unconfined turbulent bluff body flame is numerically simulated to calculate the gas radiative properties using three different approaches of ignoring radiation applying a modified version of the weighted sum of gray gases model and employing the spectral line based weighted sum of gray gases model . First the selected bluff body flame is validated against experimental data . The early outcome is that the simulation results of three chosen approaches are very close if there is no oxygen enrichment . Next the effect of oxygen enrichment is carefully investigated imposing the aforementioned spectral radiation approaches . The achieved results indicate that the predicted gas temperature becomes more sensitive to the implemented radiative approach as the oxygen concentration in the oxidizer increases . In very high oxygen enrichment condition the gas temperature predicted by SLW model shows up to 155K differences with that of ignoring radiation approach . The simulation results also show that the oxygen enrichment would raise the CO
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Heat and mass flow in a unconfined bluff body flow is modelled. Three different spectral models are studied in oxy fired combustion scenario. The WSGG model SLW and no radiation cases are compared. The effect of spectral radiation in small scale oxy fired combustion is found to be marginal. Effect of oxygen level in importance of non gray modeling is investigated.
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S0022407319309501
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Lunar sun reflected light can be effectively measured through a low light band or a day night band implemented on space based optical sensors . Based on moonlight nocturnal observations for artificial light sources at night can be achieved . However to date an open sourced and mature Low Light Radiative Transfer Model for the further understanding of the radiative transfer problem at night is still unavailable . Therefore this study develops a new LLRTM at night with the correction of the lunar and active surface light sources . First the radiative transfer equations with an active surface light source are derived for the calculation based on the lunar spectral irradiance model . The simulation from this new LLRTM shows a minimal bias when compared with the discrete ordinates radiative transfer model . The simulated results of radiance and reflectance at the top of the atmosphere also show that the surface light source has a remarkable impact on the radiative transfer process . In contrast the change in the lunar phase angle has minimal influence . Also comparing with space based DNB radiance observations LLRTM shows the potential to simulate space based low light imager observations under an effective surface light source condition during the night .
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New Low Light Radiative Transfer Model with active surface light sources is developed. The simulation of the new model has a minimal bias compared with the DISORT model. The new model shows potential to simulate space based low light imager observations.
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S0022407319309525
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In this work laser spectroscopic investigations of selected electronic levels in the holmium atom are performed in the context of possible second stage laser cooling transitions which can be considered in a magneto optical trap . Five transitions were directly recorded by the method of laser induced fluorescence in a hollow cathode discharge . The hyperfine structure constants
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Hyperfine structure hfs of 5 possible second stage narrow band laser cooling transitions in atomic holmium was recorded by laser induced fluorescence in a hollow cathode discharge lamp this allowed direct determination of the intervals between the relevant hfs components. Hyperfine structure Zeeman patterns of the same transitions was investigated and the Land. factors for the upper even parity levels were determined for the first time. A good consistency was found between the. values experimentally obtained in this work and predicted by the earlier semi empirical fits. Preliminary semi empirical analysis of the oscillatorsstrengths was performed allowing estimation of the lifetimes of the upper even parity levels involved in the cooling transitions considered.
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S0022407319309549
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Modulating the photon tunneling probability is the key to control the near field radiative heat transfer between two objects . It has been found that nanoparticle doping technology can enable plentiful resonance modes which significantly adjust photon emission spectra . In this work we theoretically analyze the performance of a near field negative electroluminescent refrigeration system consisting a Mie metamaterial emitter and mercury cadmium telluride receiver with spacing between them less than the thermal wavelength . The emitter consists of graphene SiC core shell nanoparticle embedded thin film of Si deposited on bulk Si . We show that with the inclusion of GSCS nanoparticles the thin layer of Mie metamaterial acts like an effective medium that excites radiative heat transfer for the photons above the band gap of MCT . We analyze NFNELR performance for various bias voltages various cryogenic temperatures various volume fractions and various chemical potentials of GSCS nanoparticles . We also would like to emphasize that in order to improve the performance of the NFNELR system the host matrix materials chosen are not necessarily stationary . These results provide a powerful way to rouse and regulate the NFRHT meanwhile in turn open up a way to explore actual development and present some guidance for optimal design of NFRHT .
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Mie metamaterial is modeled as effective medium with ClausiusMossotti equation of dielectric function. Mie metamaterial layer provides more surface modes at high frequency. Presence of GSCS nanoparticles in a host material gives rise to an appearance of new SPhP resonance peaks above the band gap frequency providing a good refrigeration potential. Significant enhancement in performance of the near field negative electroluminescent refrigeration system is achieved.
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S0022407319309550
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The optical properties of atmospheric black carbon aerosols are needed to model the direct radiative forcing of the climate system as well as for interpreting and assimilating remote sensing observations from satellites . Modelling efforts during the past decade have predominantly been based on using morphologically highly realistic representations of the particle geometry in conjunction with numerically exact methods for solving the light scattering problem . We review the present state of knowledge about the morphological dielectric and compositional properties of BC aerosols the state of the art in numerical light scattering methods frequently applied to black carbon and the recent literature on modelling optical properties of BC aggregates both bare and internally mixed with liquid phase material . From this review we formulate some key lessons learned regarding those morphological properties that have a dominant impact on the optical properties . These morphological key features can form the basis for devising simplified model particles that can be used in large scale applications . We illustrate this approach with one example appropriate for climate modelling and one example relevant to the interpretation of lidar remote sensing data .
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Review of physical compositional dielectric and morphological properties of soot. Review of numerical light scattering methods applicable to soot. Review of modelling optical properties of bare and coated atmospheric soot. Discussion of morphological properties that dominate the optical properties. Construction of simple models that focus on the dominant morphological features.
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S0022407319309562
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Radiation transport through particle clouds plays a major role in many engineering applications . In this paper we study this problem by means of solving the radiative transport equation on a Eulerian continuous domain . The particle clouds are generated through direct numerical simulation of Navier Stokes equations coupled with Lagrangian particle transport at different Stokes numbers . We confirm the earlier observation noted in the literature that the solution to the RTE on Eulerian mesh diverges when the Eulerian mesh size is of the order of the particle diameter . This observation is often called the homogenization error stemming from relegation of number density onto the Eulerian domain . In order to circumvent this divergence problem we propose a filtering strategy that spreads the information of the particles to the neighboring cells in a way that the representation of the particles remains the same even when the mesh size is smaller than that of the particle size . We show through our simulations that our filtering strategy solves the issue of homogenization error for the cases where the Beer Bouger law is valid .
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We confirm the non verifiability of the radiation transport equation RTE on a Eulerian domain for particle clouds. We develop a novel filtering strategy for the computation of number density to circumvent the issue of homogenization error. We test the dependency of filter width on the transmission profiles for radiation transport through particle clouds. We demonstrate that the solution of RTE converges to the gold standard for the cases that satisfy the BB law assumptions. We apply our methodology to turbulent particle clouds to study the influence of Stokes number on the transmission profiles.
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S0022407319309616
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We present a general technique to select optimal filters for a multispectral midwavelength infrared camera to quantify multiple components of a gas mixture . Filter sets are ranked in terms of the ratio of quantity of interest variance to noise variance which is minimized by the optimal filter set . The suitability of this criterion is demonstrated using a numerical experiment in which we estimate the combustion efficiency of a gas flare from MWIR images of the flare . Synthetic hyperspectral intensity data are generated using the spatially resolved thermochemical state of a simulated flare in crosswind . We then compute multispectral images for commercially available filter sets and estimate the concentration of key species CH
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A technique to select a filter set for a multispectral midwavelength infrared MWIR camera using uncertainty propagation is presented. The optimal filter set is found by minimizing the ratio of the quantity of interest variance to the measurement noise variance. The procedure can be used to select bands of different applications involving quantitative optical gas imaging. The filter sets rank found by the error propagation technique agrees with the results found by more expensive computationally Monte Carlo simulation.
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S0022407319309653
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Multi spectral imaging radiometry of the night sky provides essential information on light pollution and sky quality . However due to the different spectral sensitivity of the devices used for light pollution measurement the comparison of different surveys is not always trivial . In addition to the differences between measurement approaches there is a strong variation in natural sky radiance due to the changes of airglow . Thus especially at dark locations the classical measurement methods fail to provide consistent results . In this paper we show how to make better use of the multi spectral capabilities of commercial digital cameras and show their application for airglow analysis . We further recommend a novel sky quality metric the Dark Sky Unit based on an easily usable and SI traceable unit . This unit is a natural choice for consistent digital camera based measurements . We also present our camera system calibration methodology for use with the introduced metrics .
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We present a new recommendation for a metric and its unit for dark sky quality measurements. The system is SI traceable and can be implemented by using digital cameras. It is recommended to use band averaged radiance as a primary measure of night sky quality. The natural unit is nW m. sr nm. Digital camera based three colour radiance measurements give an optimal way for sky brightness measurements.
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S0022407319309677
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Asbestos refers to silicate minerals belonging to the serpentine group and the amphibole group . Such materials have strong effect on health and real time instrumentation is on demand to detect asbestos . The current real time techniques use only some aspects of the optical properties of asbestos since the scattering properties of the various natures of asbestos has not been yet fully determined . We present here the brightness and linear polarization scattering functions for 6 natures of asbestos in the 425 1650nm spectral domain obtained with the PROGRA2 instrument . Although the samples exhibit different shapes the linear polarization values remain low bell shaped as usual for irregular particles and close to those of mineral particles previously studied with PROGRA2 . On the opposite asbestos brightness curves present strong differences for the different samples . The chrysotile is darker than the other samples in the 80 150 angle range probably due to its tubular shape that can act as a light trap for scattering angles greater than a few tens of degrees . Other asbestos particles can be distinguished from building materials such as glass wool or plaster through their brightness curves in some scattering angle ranges . These new laboratory measurements indicate that the optical scattered properties could be used in the future to tentatively detect asbestos particles in a medium generated from building materials .
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First scattering functions of asbestos. Low polarization with positive color effect from green to near infrared. Strong variability of brightness scattering function for different asbestos. Chrysotile is the darkest sample at scattering angle of 90.
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S002240731930977X
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Measuring the angular distribution of upwelling artificial light is important for modeling light pollution because the direction of emission affects how light propagates in the atmosphere . We characterize the angular distributions of upwelling artificial light for Europe and northern Africa in 2018 based on night time radiance data for clear nights without twilight and moonlight from the VIIRSDNB sensor on board the Suomi NPP satellite . We find that in general suburban areas of major cities emit more light at larger zenith angles whereas the opposite can be seen at the city centers where the highest radiance is directed upward . The mean numbers of overflights for the year is 83 meaning that there are on average approximately seven suitable overflights per month . Future analysis may consider using moonlight models to compensate for the retrieval of moonlit scenes and analyzing data from different years in order to expand the amount of available data . As the VIIRSDNB sensor on board the NOAA20 satellite has almost the same design this method can also be extended to the data taken by NOAA20 .
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We examined the relationship between incidence angle and radiance values for VIIRSDNB night light observations. We find that the radiance from rural and suburban increase towards the horizon whereas inner cities tend to have highest radiance toward the zenith. Asymmetry of emission of artificial light can be observed in suburban areas where more light is observed in the direction of the inner cities suggesting that scattering of light from cities may play a role in the angular distribution.
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S0022407319309823
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This work introduces the method of circular dichroism spectroscopy in the framework of the electromagnetic optical radiation force theory . This technique is defined here as the difference in radiation force of left handed and right handed circularly polarized electromagnetic waves illuminating an object exhibiting rotary polarization . The example of a lossless material such as the perfect electromagnetic conductor cylinder having a circular geometric cross section is considered . The modal expansion method in cylindrical coordinates is used to obtain exact mathematical series expansions for the longitudinal radiation force per length considering left handed and right handed circularly polarized cylindrically diverging waves emanating from a line source . The case of plane progressive waves is recovered when the source is located far from the cylinder . Numerical illustrative results for the dimensionless radiation force functions as well as the scattering extinction and absorption energy efficiencies and their co polarized and cross polarized components are performed with particular emphasis on the size parameter of the cylinder the dimensionless distance parameter from the line source and the admittance of the cylinder . The results reveal that the individual radiation force functions for left handed and right handed circularly polarized waves can be negative zero or positive depending on the cylinder distance from the source . Moreover the optical radiation force circular dichroism and the extinction energy efficiency circular dichroism are positive for a negative admittance of the cylinder while they reverse sign for a positive admittance . While the EEECD shows some form of symmetry versus admittance sign change the ORFCD does not . The possibility of achieving invisibility cloaking for a small PEMC cylinder is also predicted . The present ORFCD spectroscopy method is applicable to any cylinder material exhibiting rotary polarization such as chiral topological insulator plasma liquid crystal etc .
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This work introduces the optical radiation force circular dichroism spectroscopy method. This method is defined as the force difference of left handed and right handed circularly polarized waves. The example of a perfect electromagnetic circular cylinder is considered. A line source of cylindrically diverging waves with circular polarization is assumed. Radiation force and energy efficiency results are computed and discussed.
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S0022407319309860
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Atmospheric conditions can significantly affect the sky brightness originating from artificial lights . Previous works studied the cloudiness cloud base height optical depth of cloud aerosol optical depth and aerosol scale height as atmospheric parameters affecting night sky brightness . Instead of using these parameters as a simplification of the real cloud and aerosol profile we processed the raw backscatter data of a laser ceilometer instrument . Sky brightness was obtained from camera images available at the same meteorological observation site . Case studies are shown in selected cases where we analyzed the correspondences with the backscatter data and the camera images . We performed Monte Carlo simulations with the dominant light sources to verify the numerical predictions of sky radiances . Although the limitations of the ceilometer device to obtain optical properties of the atmosphere ceilometers provide valuable source of data for evaluation of the light pollution measurements .
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Monte Carlo simulations were performed for skyglow modeling. Ceilometer backscatter data were used as atmospheric input for skyglow modeling. Reproduction of the sky radiance proved more successful with backscatter input data.
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S0022407319309896
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Cloudy sky spectral radiance at the top of the atmosphere has always been an important while difficult variable to simulate for fast radiative transfer models . In this paper we focus on examining the impacts of cloud scattering properties on the spectral radiance signature of the High spectral Resolution Infrared Atmospheric Sounder onboard the Fengyun 3D satellite by using the Advanced Radiative transfer Modeling System and the Community Radiative Transfer Model . Cloud scattering properties used in the radiative transfer models are critical for modeling the spectral radiance under cloudy sky which involves choices of appropriate cloud particle models and particle size distributions etc . Multiple FY 3D HIRAS observations over Southern China and Southeast Asia with ice or liquid water cloud cover on 6 May 2018 are examined respectively . Vertical atmospheric profiles are derived from the Modern Era Retrospective analysis for Research and Applications Version 2 reanalysis product . Cloud property retrievals from the Moderate Resolution Imaging Spectroradiometer are used . Cloud scattering property parameterization schemes based on spherical and nonspherical cloud particle shapes are implemented for liquid water and ice clouds in ARMS and CRTM respectively . Results show that both ARMS and CRTM can well simulate the radiance at the HIRAS spectral ranges under liquid water cloud condition as compared with the HIRAS observation with mean absolute error of brightness temperature of less than 1K . However for ice cloud conditions ARMS model using assumed spherical ice properties exhibits large biases between simulation and observation . CRTM with nonspherical ice properties using 16 stream approximation shows MAE less than 1K and MAE of about 1K using 2 stream approximation .
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Impacts of cloud scattering properties on FY 3D HIRAS simulations are assessed in ARMS and CRTM. ARMS and CRTM simulated brightness temperatures are compared with HIRAS observations to provide quantitative evaluation. Spherical ice cloud approximation has been found to be not appropriate for ARMS model simulations.
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S0022407319309938
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Boltzmann plot of laser produced plasma spectral emission of two Ag I spectral lines at 827.35 and 768.77nm was carried out . Surprisingly two order of magnitude lower inherent transition probabilities of the two Ag I spectral lines could be monitored using optical emission spectroscopy OES technique . Nd YAG laser at 532nm and incident intensities varying from 1.76 to 3.14 GW cm
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The values of the inherent transition probabilities of the Ag I spectral lines at 827.35 and 768.77nm are found two orders of magnitude lower than values calculated by Kurucz et al. The measurements were carried using OES technique to plasma created by laser in laser induced breakdown spectroscopy experiment. Boltzmann plot method was employed utilizing four Ag I lines at 546.54 520.9 328 and 338nm after corrections to spectral lines against effect of self absorption and absolute spectral sensitivity optical setup. The Boltzmann plot was used as calibration line to estimate the amount of deviation of transition probabilities of lines at 827.35 and 768.77nm from the tabulated values. These constant deviations were examined after repeating the experiment at different laser irradiance levels and at different delay times.
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S0022407319309987
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Fengyun satellite program is becoming the important component of global earth observing system . Its instrumental performance i.e . data quality and stability play a critical role to support the quantitative applications such as atmospheric and surface parameter retrievals numerical weather prediction and the production of Climate Data Records . For monitoring the instrumental performance the radiative transfer models together with NWP fields are used to simulate the reference radiance in FY satellite instrument monitoring schemes . Through monitoring the difference of observed and simulated brightness temperature of satellite instruments against instrument parameters the quality and stability can be evaluated from different viewpoint of geographic location viewing geometry time and spectral ranges . Two components of FY SIMS FY satellite data status monitoring system and satellite instrument characterization are introduced . FY SDSMon can provide near real time and long time monitoring using fast RTMs and the China Meteorological Administration operational NWP fields giving a routine and general knowledge of the instrument performance and its potential risk warning . FY SIChar helps on further characterization of instruments by using more kinds of RTMs and comparison with counterpart instruments . Several examples show that FY SIMS gives the insight to understand the instrument performance and characterize the potential bias . With the FY SIMS the performance of IR and MW band is widely monitored and recently the VIS NIR band is also in test to be monitored . Due to the improved quality and stability the FY data is well evaluated and assimilated by worldwide NWP community to improve the forecast skill .
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The principle of Fengyun satellite data monitoring using RTMs and NWP is introduced and analyzed. The design and implementation of Fengyun satellite instrument monitoring schemes are introduced for the first time. The examples of Fengyun satellite instruments monitoring with the tool of RTM based diagnosis given in this article include not only the IR and MW band instrument but also the VIS NIR band instrument.
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S0022407319309999
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Radiative transfer equation is the commonly accepted continuum scale governing equation for radiative heat transfer in particulate system . However its applicability is questionable for non random densely and regularly packed particulate systems due to dependent scattering and strong correlation of particle locations that may largely violate the basic assumptions of the RTE . In this work a new continuum approach is proposed for radiative heat transfer in densely packed particulate system composed of optically large particles which does not rely explicitly on the RTE . The new approach is based on an introduced concept of radiation distribution function which is an extension of the concept of radiation distribution factor at discrete scale to continuum scale . The governing equations are in integral form of spatial coordinates in which the RDF is the key continuum scale physical parameter that characterizes the radiative heat transfer in the system . The continuum approach is verified through heat transfer simulation at particle scale and demonstrated to have excellent performance in predicting the temperature distribution in dense particulate system . This work provides an alternative continuum theory for the analysis and understanding of radiative heat transfer in densely packed particulate and porous materials .
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Proposed new continuum approach for radiative heat transfer in particulate system. The governing equation of the new approach is in integral form of spatial coordinates. Evaluated performance of the new continuum approach by particle scale simulation. The new continuum approach is promising to overcome the limitations of the RTE.
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S0022407319310003
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The Breit interaction is the relativistic correction to the electron electron interaction which mainly affects the level energies and it is minor in general . We present a new manifestation of the Breit interaction effects in the highly charged Li and B like ions based on the multi configuration Dirac Fock calculations where the strongly correlated many body wavefunctions of the doubly excited resonant states 1s2p
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A new mechanism that the Breit interaction effects significantly in the highly charged Li and B like ions are studied the strongly correlated many body wavefunctions of the doubly excited resonant states 1s2p. 2p. or 1s 2s. 2p. 2p. and. are drastically influenced by the Breit interaction. The strong variation of wavefunctions results in a prominent change of the two dominant transitions 2p. 1s and 2p. 1s of the doubly excited states. The variation of the transitions can be observed in experiment by measuring the branching ratio of the doubly excited Li like or B like ions. The variation of the wavefunctions is due to the ion core energy inversion induced by the Breit interaction. Based on the mechanism we propose an alternative experimental determination of the fine structure splitting of 1s2p. or 1s 2s. 2p. in heavy He like or Be like ions from the branching ratio of the doubly excited Li like or B like ions. This work extends the conventional wisdom on the role of the relativistic effects in the electric dipole radiative transitions of highly charged ions which could be useful for future precise high temperature plasma diagnostics.
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S0022407319310015
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The Carbon Dioxide Spectral Databank 4000 is tailored for radiative transfer applications relevant for Mars atmospheric entry studies . This is carried out through the refitting of the original database encompassing individual rovibrational transitions into a more compact form where rotational transitions for specific vibrational bands are obtained through traditional polynomial expressions fitted to the levels and transitions of the original database . This originates a certain loss of precision since the fitted expressions do not always reproduce the original data with full accuracy namely for the perturbed transitions . This is offset by a more compact database suited for wideband radiative transfer simulations . This CDSDv database also provides some minor advantages such as enabling the thermodynamic use of two temperature
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A vibrationally specific database has been produced on the basis of CDSD4000. The database has a compact size 16MB and produces fast spectral simulations when coupled to an adaptive lineshape routine. The resulting numerical routines allow full range spectral simulations for hot nonequilibrium. The code is validated against reference high temperature. infrared spectra evidencing limited loss of accuracy.
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S0022407319310027
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In the wavelength region between 5540 and 6570 systematic laser spectroscopic studies of the hyperfine structure of Niobium I lines were performed detecting laser induced fluorescence signals . Possible transition wavelengths were calculated as combinations between all known energy levels . Altogether about 380 transitions could be successfully excited and their hyperfine structure could be investigated . This large manifold of lines allowed us to evaluate our results via multiple transitions between the system of upper and lower energy levels . In Part I we report on transitions between lower even parity levels between 0 and 13 515 cm
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Systematic investigation of the hyperfine structure constants of Nb I levels. Discovery of a new level 27 994.38cm. odd parity. 1 2. All hf constants for even parity levels up to 13 515cm. are given 11 of them new determined with lower uncertainty. All hf constants for odd parity levels up to 31 025cm. are given most of them new determined with lower uncertainty. Saturation effects are taken into account when hf constants are determined from experimental recordings.
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S0022407319310039
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The present paper is the continuation of the systematic investigation of the hyperfine structure of atomic Niobium presented in Part I of this work . Just like in Part I spectral lines in the wavelength region between 5540 and 6570 were investigated by laser induced fluorescence spectroscopy . From altogether about 380 transitions about 190 are treated in this part . Here we report on transitions between lower even parity levels between 13 515 and 23 048cm
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Systematic investigation of the hyperfine structure constants of Nb I levels. Discovery of two new levels 21 182.31cm. even parity. 5 2 and 39 834.88cm. odd parity. 13 2. All hf constants for even parity levels between 11 044 and 23 048cm 1 are given 23 of them new determined with lower uncertainty. All hf constants for odd parity levels between 31 056 and 42 000cm 1 are given most of them new determined with lower uncertainty. For ca. 50 levels the hf constants are given for the first time. Saturation effects are taken into account when hf constants are determined from experimental recordings.
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S0022407319310040
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The present work is the third part of a systematic investigation of the hyperfine structure of atomic Niobium using laser induced fluorescence spectroscopy . As in the previous two parts spectral lines in the wavelength region between 5540 and 6570 were investigated . In the present part we report on 31 transitions between lower odd parity levels and high lying even parity levels between 37 410 and 43 420 cm
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Systematic investigation of the hyperfine structure constants of nb i levels. Discovery of a new levels 32 361cm. even parity. 5 2. All hf constants for even parity levels between 37 410 and 43 420cm. are given 16 of them new determined with lower uncertainty. A misinterpretation of an hf pattern published earlier was corrected. Saturation effects are taken into account when hf constants are determined from experimental recordings.
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S0022407319310052
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Modelling techniques for the propagation of light pollution in the atmosphere allow the computation of maps of artificial night sky brightness in any direction of the sky involving a large number of details from satellite data . Cinzano etal . introduced a method of mapping naked eye star visibility at the zenith from large areas based on satellite radiance measurements and Garstang models of the propagation of light pollution . It takes into account the altitude of each land area from digital elevation data natural sky brightness in the chosen sky direction based on the Garstang approach eye capability after Garstang and Schaefer and atmospheric extinction in the visual photometric band . Here we discuss how to use these methods to obtain maps of the average number of visible stars when looking at the night sky hemisphere finally answering site by site the question of how many stars are visible in the sky . This is not trivial as the number of stars visible depends on the limiting magnitude in each direction in the sky and this depends on sky brightness in that direction atmospheric extinction at that zenith distance and the observer s visual acuity and experience . We present as an example a map of the number of visible stars in Italy to an average observer on clear nights with a resolution of approximately 1km .
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Method to predict the number of visible stars in the night sky taking into account for all relevant factors. First high resolution map of the number of visible stars in a large territory. Simple formula gives the numbers of stars brighter than a given magnitude.
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S002240731931026X
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The rovibrational levels for truly bound states were calculated for a weakly interacting dimer comprising an atom and a diatomic molecule . The off diagonal Coriolis corrections were evaluated with perturbation theory . For the Ar HCl dimer as a concrete example the obtained results are compared with those from computer code BOUND J.M . Hutson and C. R. Le Sueur . Comput . Phys . Commun .
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A perturbational treatment of Coriolis interaction in the atom diatom dimer is performed taking the Ar HCl complex as an example. The study of rovibrational level structure is performed using coupled channel formulation. The properties of a perturbation series are discussed the results of perturbation analysis are compared with those from close coupling calculations.
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S0022407319310313
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In this study 3179 and 3813 rotational transition frequencies for indole and 1 2 3 4 tetrahydroquinoline respectively were analyzed using the PGOPHER software . In both analyses all the matrix elements of the sextic rotational Hamiltonians were fitted simultaneously to the hyperfine quadrupole terms . The global fits of all the transition frequencies provided the most precise ground state molecular parameters for both molecules so far . The presented experimental results are in concordance with the density functional theory calculations .
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The ground states of heterocyclic organic molecules were investigated. The rotational data were corrected and re analysed. The molecular constants of indole and 1 2 3 4 tetrahydroquinoline are presented. The DFT calculations were performed for both molecules.
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S0022407319310349
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The information in spectroscopic databases is routinely updated therefore it is necessary to evaluate on a regular basis how efficient the improvements in spectroscopic data are with respect to the atmospheric remote sensing problems . One of such problems is the methane total column retrieval from the ground based FTIR measurements of the direct solar radiation . The CH
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The estimation of impact of the differences in CH. absorption line parameters in spectroscopic databases on accuracy of the methane atmospheric total column retrievals is made. The results of atmospheric methane total column retrievals from the solar absorption spectra measured by Fourier transform spectrometers at the Saint Petersburg and Kourovka stations in the mid and near infrared regions are presented. The variability of the methane total column values retrieved using CH. absorption line parameters from different spectroscopic databases reaches 1.7 .
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S0022407319310362
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Topological insulator semiconductors hold unique electronic transport characteristics that allow them behave like graphene at the surface of the nanoscale thin film . Photonic multilayers consisting of alternating layers of topological insulator and layers of its dielectric spacer can be engineered to demonstrate optical and thermal radiative dispersion attributed to electromagnetic metamaterials . This paper presents case studies explain the relationships between material compositions geometrical factors spectral functions and electronic transport mechanisms to the overall visible to far infrared radiative properties . It shows how topological insulator multilayers could be useful in thermal photovoltaic components optoelectronic devices and radiative coatings . Two multilayer cases are investigated Bi
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Multiple methods consistently predict optical properties of topological multilayers. Thickness tuned topological multilayers can be designed as photonic metamaterials. Bi. Se. ZnSe demonstrates hyperbolic negative refractive index in the infrared. Bi. Te. ZnTe is an effective optical absorber in the visible wavelengths. Radiative properties are not affected by Fermi energy in topological quintuple layers.
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S0022407319310374
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The particles deposited on the solar panels can scatter and absorb the solar radiation and then present some negative impact on the output performance of photovoltaic cells . By simulating the field distribution of the external electromagnetic field of particle deposition illuminated by solar radiation it is helpful to accurately predict the impact of particles on the photovoltaic module and then design appropriate devices to reduce its negative effect . In this paper we present a new perspective that the deposition of particles with suitable size can focus the incoming solar radiation in the forward direction . Based on this result we proposed a new method to reduce the negative effects of deposition on the photovoltaic system and to enhance its power output . Our numerical results show that more than 10 times stronger incoming solar radiation in the forward direction can realistically be obtained from the light focusing effect of deposition when the thickness of solar glass in existing solar panels is reduced to 1.5mm . In addition some special cladding structures can be designed to exploit this valuable effect to assemble more efficient photovoltaic panels .
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A new perspective is proposed that particle deposition on photovoltaic panels may have an active impact on it. The focusing light effect of deposition on the PV cells is proposed. A simply method to reduce the negative effect of deposition on the PV cells is suggested.
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S0022407319310465
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Using the high resolution time resolved Fourier transform infrared spectroscopy of a plasma created in a positive column discharge cell we record Kr I spectrum in the 7007600 cm
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105 new Kr I lines in thethe 7002200 cm 1 rangenot observed previously. The6. and 7. 7. levels supported by ionization potential calculation. The updated system of Kr I level energiesconsistentto within 0.0019 cm 1.
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S0022407320300169
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Electron tomography is used to reconstruct the exact 3 dimensional morphologies of fractal like soot aggregates sampled from a household heating stove commonly used in China . Conventional ET techniques suffer from the missing wedge problem caused by unreachable tilt angles leading to noisy reconstructed tomograms . We overcame this problem by implementing a high resolution object edge identification method coupled with a novel voxel filling algorithm to improve the reconstruction quality . Our reconstructed micron length aggregates highlight the local non idealities present throughout a particle s surface these characteristics are almost impossible to account for in existing computational simulation exercises . Q space analysis predicts the fractal dimension of our ET reconstructed aggregates to be in the range between 2.2 and 2.6 which deviates significantly from the universal value of 1.8 obtained using the widely adopted diffusion limited cluster cluster aggregation model . The optical properties of our ET reconstructed aggregates are compared with those built with a DLCA model and equivalent spheres . The most striking optical characteristics of the ET reconstructed aggregates are their wavelength invariant mass absorption cross sections of 3.5 m
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3D structure reconstruction of freshly emitted soot aggregates using Electron Tomography. Fractal Dimension of 3D soot aggregates ranges from 2.2 to 2.6. Soot morphology and optical properties deviates from those modeled using DLCA and equivalent sphere models
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S0022407320300248
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In this paper a method is proposed to solve the scattering of electromagnetic waves by a uniformly charged non spherical scatterer . Based on Waterman s extended boundary method a transition matrix between coefficient of the scattering field and incident field of a charged non spherical scatterer is derived called
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matrix method for charged non spherical scatterers is derived based on extended boundary method. The effect of net surface charges on the scattering of charged non spherical particles e.g. charged spheroids are studied using the abovementioned. matrix method. It is found that the extinction absorption of charged spheroids is augmented by the net surface charges and this augmentation is related to the aspect ratio of the particle and the orientation of the particle with respect to the incident electromagnetic waves. The error of theoretical prediction of extinction absorption resulted from the sphere assumption for non spherical particles e.g. prolate oblate spheorids which was used in many existing studies on optical and scattering properties of charged uncharged particles was evaluated using the proposed. matrix method. This error is enlarged as the non spherical particle is charged and dependent on the aspect ratio of the non spherical particle as well as on the orientation of the particle.
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S0022407320300261
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We discuss an operational scheme for measuring the power extinguished by a single particle in terms of physical energy fluxes . Illumination by an infinite plane wave and a collimated Gaussian beam is considered . For the case of a collimated beam consideration of extinguished power presents an apparent paradox which is resolved in this paper . It is then shown that the extinguished power is measurable as a flow of energy for a narrow collimated incident beam and a small scatterer . In this case the extinguished power is simply removed from the transmitted beam . If we relax the above assumptions definition of the extinguished power in terms of measurable energy fluxes is still possible but becomes more nuanced .
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Extinguished energy can be measured directly as a physical energy flux for collimated incident beams and relatively small scatterers. A paradox related to extinction of narrowly collimated beams is formulated and resolved. In the case of narrow collimated beams and small scatterers the extinguished power is removed from the beam in agreement with the conventional interpretation. In the case of an infinite front incident plane wave or a large scatterer with a sharply forward peaked scattering function the operation definition of extinguished power in terms of energy fluxes is possible but problematic.
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S0022407320300273
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We compare the optical properties of various geometric shapes with single atmospheric Asian dust and marine background air particles collected at Mauna Loa Observatory . Three dimensional representations of the particles were acquired with focused ion beam tomography which involves FIB milling of individual particles followed by imaging and elemental mapping with scanning electron microscopy . Particles were heterogeneous with mainly dolomite or calcite and a minor amount of iron marine air particles contained gypsum but no iron . Extinction and backscatter fraction were calculated with the discrete dipole approximation method . Geometric shapes were grouped as ellipsoids cuboids and pyramids . Each group represented a progression of shapes with 1 2 or 3 non identical axes . Most shapes underestimated particle extinction and overestimated the backscatter fraction . Not surprisingly extinction and the backscatter fraction of the sphere and cube were furthest from those of the particles . While the 3 axis ellipsoid and rectangular prism were closer dimensionally to the particles extinction and the backscatter fraction for the 2 axis spheroid and square prism respectively were often closer to the particles . The extinction and backscatter fraction for the tetrahedron and triangular pyramid were closer on average to the actual particles than were the other shapes . Tetrahedra have the advantage that parameterization of an aerosol model for remote sensing would not require an aspect ratio distribution . Particle surface roughness invariably decreased the backscatter fraction . While surface roughness typically contributes a minor part to overall scattering in some cases the larger surface area of the tetrahedron and triangular pyramid sufficiently accounted for enhanced forward scattering of particles from surface roughness .
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Optical properties of single particles compared with ellipsoids cuboids and pyramids. Most shapes underestimate particle extinction and overestimate backscatter fraction. Extinction from 2 axis shapes is often closer to particle than from 3 axis shapes. Tetrahedron and triangular pyramid perform best in estimating particle extinction. Higher surface area of pyramids may account for scattering from surface roughness.
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S0022407320300297
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In a recent publication Zafar etal . have reported on the use of Doppler free spectroscopy of helium 414nm line for the determination of electron density in helium plasmas . This was done by fitting their experimentally obtained Doppler free line profiles with spectral profiles constructed using a Stark broadening model . But in this model authors have assumed a closed two level system for the 2
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Important errors exists in Zafar s paper for the definition of the spectral line width and for determination of saturation parameter. Zafar s use of the electron impact broadening width as a fit parameter is unjustified. We report the exact value of the broadening parameter. Zafar s errors results in an underestimated minimum measurable electron density and the E field.
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S0022407320300327
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Light matter interaction in all dielectric nanoparticles has attracted more attention because of the ability to control and configure light scattering on high index nanoparticles . In the framework of the discrete dipole approximation we theoretically applied cartesian multipole expansion to a periodic array of nanoparticles . This allows to analyze the contribution of multipole moments including toroidal moments in the scattering spectra of an array of infinite 1D 2D periodic structure of arbitrary shaped nanoparticles . The formulation is based on the Taylor expansion in cartesian coordinate system up to the fifth order that includes a magnetic 16 pole and an electric 32 pole . Examples of a wide band reflector and a wide band transmitter made of silicon nanodisks are studied at IR wavelengths . The results show how constructive and destructive interferences of multipole terms affect the scattering field . The proposed method paves the way to design and analyzenovel types of nanoscale subwavelength metasurfaces .
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Cartesian multipole expansion is theoretically applied to a periodic array of nanoparticles. Multipole expansion of scattered field is formulated in the framework of Periodic Discrete Dipole Approximation. Wide band reflector and a wide band transmitter made of silicon nanodisks are studied at IR wavelengths using the proposed method
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S0022407320300388
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Janus spheres are objects of growing interest in different fields of technology . For example they can be applied in medicine for a precise drug positioning . They have moreover an enormous potential for the development of new and active materials . Some Janus spheres are already manufactured industrially . Nevertheless there is a lack of knowledge about the scattering behavior of such objects although it is important not only for diagnostic purposes but also for discovering new applications . In this paper we present the application of the well known T matrix method to solve the scattering problem of a plane electromagnetic wave on a dielectric sphere whose surface is partially covered with a perfect metal . The application of this approach to a specially oriented Janus sphere reveals an interesting effect for size parameters less than 6 .
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Electromagnetic scattering on Janus spheres is described. The corresponding T matrix is derived by using a least square scheme. The numerical effort to generate accurate results is much higher as for dielectric spheres. A halo effect leads to a sideward shift of the maximum scattered intensity from the forward direction in special orientations at size parameters less than 6.
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S0022407320300406
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An absorbing host medium and surface conductivity of a charged sphere are two emerging factors that influence electromagnetic scattering and play a role in tuning optical properties of the sphere . In this paper we study a general case of the light scattering by a charged sphere embedded in an absorbing host medium . Combining the two established Lorentz Mie theories which apply to the absorbing host medium and the charged sphere we calculate the far field extinction efficiency factor and the electric field amplitude . Our results show that amplifying effect of the increasing absorption of host medium on the interference oscillations of the extinction efficiency factor is opposite to the damping effect of the increasing surface conductivity . On the electric field amplitude the increasing absorption of the host medium enhances the backscattering field in contrast to the front scattering field . However the increasing surface conductivity induces a size parameter dependent change on the pattern of the field distribution and the magnitude of the field .
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We study electromagnetic scattering by a charged sphere embedded in an absorbing medium. Lorenz Mie coefficients are derived to include the parameters of the absorption in host medium and the surface conductivity. The increasing absorption amplifies the interference oscillations of extinction efficiency but the increasing surface conductivity damps them. An enhancement of backscattering electric field in contrast to front scattering electric field is induced by the increasing absorption. The increasing surface conductivity induces a size parameter dependent change on the pattern of the field distribution and the magnitude of the field.
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S002240732030042X
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After Arthur Ashkins pioneering work in optical levitation and manipulation the study of optical forces exerted by laser beams on particles has become an active field of research . The present paper is a contribution to this issue . The interest of Bessel beams is that their intensity does not have any longitudinal gradient along the direction of propagation leading to a trivial separation between gradient and scattering forces . Beside the classical gradient and scattering forces we shall however exhibit a new kind of optical forces associated with the existence of non zero axicon angles .
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Longitudinal optical forces exerted by off axis Bessel beams over a Rayleig particle are investigated. The framework used is the one of generalized Lorenz Mie theory. Beside usual gradient and scattering forces axicon forces associated with the occurrence of an axicon angle are exhibited.
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