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S0140366415002467 | A promising development in the design of datacenters is the hybrid network architecture consisting of both optical and electrical elements, in which end-to-end traffic can be routed through either an electrical path or an optical path. The core optical switch is used to dynamically create optical paths between pairs of electrical edge-switches in such a datacenter network. In this context, the joint problem of bandwidth allocation and VM-placement poses new and different challenges not addressed yet in hybrid datacenter. In particular, we foresee two issues: (i) the number of edge-switches that can be simultaneously reached using optical paths from an edge-switch is limited by the size of the optical switch, (ii) the dynamic creation of optical paths can potentially establish a constrained optical network topology leading to poor performance. In this work, we abstract the requests of tenants as virtual networks, and study the problem of embedding virtual networks on a hybrid datacenter. We formulate the problem as a non-linear optimization problem and analyze its complexity. We develop and analyse three algorithms for embedding dynamically arriving virtual network demands on a hybrid optical–electrical datacenter. Through simulations, we demonstrate the effectiveness of not only exploiting the already established optical paths, but also of using electrical network in embedding requests of virtual networks. | Dynamic resource allocation in hybrid optical–electrical datacenter networks |
S0140366415002479 | Online Social Networks (OSNs) constitute vital communication and information sharing channels. Unfortunately, existing coarse-grained privacy preferences insufficiently protect the shared information. Although cryptographic techniques provide interesting mechanisms to protect privacy, several issues remain problematic, such as, OSN provider acceptance, user adoption, key management and usability. To mitigate these problems, we propose a practical solution that uses Identity-Based Encryption to simplify key management and enforce data confidentiality. Moreover, we devise an Identity-Based outsider anonymous private sharing scheme to disseminate information among multiple users. Furthermore, we demonstrate the viability and tolerable overhead of our solution via an open-source prototype. | Practical identity-based private sharing for online social networks |
S0140366415002480 | The buffer sizing problem is a big challenge for high speed network routers to reduce buffer cost without throughput loss. The past few years have witnessed debate on how to improve link utilization of high speed networks where the router buffer size is idealized into dozens of packets. Theoretically, the buffer size can be shrunk by more than 100 times. Under this scenario, widely argued proposals for TCP traffic to achieve acceptable link capacities mandate three necessary conditions: over-provisioned core link bandwidth, non-bursty flows, and tens of thousands of asynchronous flows. However, in high speed networks where these conditions are insufficient, TCP traffic suffers severely from routers with tiny buffers. To explore better performance, we propose a new congestion control algorithm called Desynchronized Multi-Channel TCP (DMCTCP) that creates a flow with parallel channels. These channels can desynchronize each other to avoid TCP loss synchronization, and they can avoid traffic penalties from burst losses. Over a 10 Gb/s large delay network ruled by tiny buffer routers, our emulation results show that bottleneck link utilization can reach over 80% with much fewer number of flows. Compared with other TCP congestion control variants, DMCTCP can also achieve much better performance in high loss rate networks. Facing the buffer sizing challenge, our study is a new step towards the deployment of optical packet switching networks. | Exploring parallelism and desynchronization of TCP over high speed networks with tiny buffers |
S0140366415002492 | Software-as-a-service (SaaS) is gaining momentum for all business applications, including Unified Communications as a Service (UCaaS). In this context, user identity will play a key role in connecting the future fragmented communication suites in both corporations and cloud SaaS providers. However, SaaS solutions impose strong security challenges to the enterprise's Identity Management (IdM), since cloud services need to be provided with the employees’ identities. UCaaS solutions should therefore enforce security properties such as trust relationship, anonymity, or control on information disclosure. WebRTC is reinforcing the trend towards cloud-based UC by adding real-time voice and video capabilities into browsers. WebRTC does not tackle IdM, and hence it is not evident how WebRTC-based cloud services can meet the corporate requirements on IdM. In this paper, we discuss various IdM models for cloud-based corporate services, and we introduce the major requirements for managing user identities in UCaaS. We assess the impacts of these requirements on WebRTC-based UC services. We finally propose a slight modification of WebRTC to meet the corporate requirements on IdM. | Unified communications as a service and WebRTC: An identity-centric perspective |
S0140366415002510 | While direct social ties have been intensely studied in the context of computer-mediated social networks, indirect ties (e.g., friends of friends) have seen little attention. Yet in real life, we often rely on friends of our friends for recommendations (of good doctors, good schools, or good babysitters), for introduction to a new job opportunity, and for many other occasional needs. In this work we attempt to 1) quantify the strength of indirect social ties, 2) validate the quantification, and 3) empirically demonstrate its usefulness for applications on two examples. We quantify social strength of indirect ties using a measure of the strength of the direct ties that connect two people and the intuition provided by the sociology literature. We evaluate the proposed metric by framing it as a link prediction problem and experimentally demonstrate that our metric accurately (up to 87.2%) predicts link’s formation. We show via data-driven experiments that the proposed metric for social strength can be used successfully for social applications. Specifically, we show that it can be used for predicting the effects of information diffusion with an accuracy of up to 0.753. We also show that it alleviates known problems in friend-to-friend storage systems by addressing two previously documented shortcomings: reduced set of storage candidates and data availability correlations. | The power of indirect ties |
S0140366415002534 | The lack of abstraction in a growing semantic, virtual and abstract world poses new challenges for assessing security and QoS tradeoffs. For example, in Future Internet scenarios, where Unified Communications (UC) will take place, being able to predict the final devices that will form the network is not always possible. Without this information the analysis of the security and QoS tradeoff can only be based on partial information to be completed when more information about the environment is available. In this paper, we extend the description of context-based parametric relationship model, providing a tool for assessing the security and QoS tradeoff (SQT) based on interchangeable contexts. Our approach is able to use the heterogeneous information produced by scenarios where UC is present. | Contextualising heterogeneous information in unified communications with security restrictions |
S0140366415002546 | Online social networks such as Twitter have emerged as an important mechanism for individuals to share information and post user generated content. However, filtering interesting content from the large volume of messages received through Twitter places a significant cognitive burden on users. Motivated by this problem, we develop a new automated mechanism to detect personalised interestingness, and investigate this for Twitter. Instead of undertaking semantic content analysis and matching of tweets, our approach considers the human response to content, in terms of whether the content is sufficiently stimulating to get repeatedly chosen by users for forwarding (retweeting). This approach involves machine learning against features that are relevant to a particular user and their network, to obtain an expected level of retweeting for a user and a tweet. Tweets observed to be above this expected level are classified as interesting. We implement the approach in Twitter and evaluate it using comparative human tweet assessment in two forms: through aggregated assessment using Mechanical Turk, and through a web-based experiment for Twitter users. The results provide confidence that the approach is effective in identifying the more interesting tweets from a user’s timeline. This has important implications for reduction of cognitive burden: the results show that timelines can be considerably shortened while maintaining a high degree of confidence that more interesting tweets will be retained. In conclusion we discuss how the technique could be applied to mitigate possible filter bubble effects. | Retweeting beyond expectation: Inferring interestingness in Twitter |
S0140366415002558 | The wide adoption of smart phones has enabled Online Social Networks (OSNs) to exploit the location awareness capabilities offering users better interaction and context aware content. While these features are very attractive, the publication of users’ location in an OSN exposes them to privacy hazards. Recently, various protocols have been proposed for private proximity testing, where users are able to check if their online friends are near, without disclosing their locations. However, the computation cost of the required cryptographic operations utilized in such protocols is not always efficient for mobile devices. In this paper we introduce a lightweight and secure proximity testing protocol, suitable for online mobile users. We show that our protocol is provably secure under the well-known factoring problem and we analyze its efficiency. Our results show that our approach outperforms other existing protocols, by significantly reducing the computational cost and making it practical for devices with limited resources. Finally, we demonstrate the applicability of our proposal in an actual OSN location-based, mobile application. | Lightweight private proximity testing for geospatial social networks |
S0140366415002571 | Companies and particularly their Chief Security Officers (CSOs) want to ensure that their Security Policies are followed, but this becomes a difficult goal to achieve at the point employees are able to use, or bring, their personal devices at work, in a practice that has been named “Bring Your Own Device” (BYOD). Since this BYOD philosophy is being adopted by many companies everyday, a number of solutions have appeared in the market so that it can be implemented in a secure way and comply with the Security Policies mentioned above. In this paper we propose a taxonomy to classify the features of BYOD systems. This taxonomy is used to present an overview of BYOD security solutions. Also, we describe a novel, adaptive and free software system named MUSES (Multi-platform Usable Endpoint Security), able to securely manage BYOD environments. MUSES has been developed to cope with security issues with regard to enterprise security policies, but as a user-centric tool. It considers users’ behavior in order to adapt, improve, and even increase the defined set of security rules. To do this, the system applies Machine Learning and Computational Intelligence techniques, being also able to predict future security incidences produced by these users. The MUSES framework, which has released its first prototype in early 2015, is compared with the most relevant solutions offered by other companies to deal with the same issues, remarking the advantages that our system offers with respect to them. | Corporate security solutions for BYOD: A novel user-centric and self-adaptive system |
S0140366415002583 | In Vehicular ad-hoc networks (VANETs), one of the challenging tasks is to find an accurate localization information. In this paper, we have addressed this problem by introducing a novel approach based on the idea of cooperative localization. Our proposed scheme incorporates different techniques of localization along with data fusion as well as vehicle-to-vehicle communication, to integrate the available data and cooperatively improve the accuracy of the localization information of the vehicles. The simulation results show that sharing the localization information and deploying that of the neighboring vehicles, not only assures the vehicles in a vicinity to obtain more accurate localization information, but also find the results robust to sensor inaccuracies or even to failures. Moreover, further improvement has been achieved by estimating the vehicle prior (prior mean and covariance) using unscented transform (UT) together with sequential decentralized extended Kalman filtering. | Localization in vehicular ad hoc networks using data fusion and V2V communication |
S0140366415002613 | Graph sampling refers to the process of deriving a small subset of nodes from a possibly huge graph in order to estimate properties of the whole graph from examining the sample. Whereas topological properties can already be obtained accurately by sampling, current approaches do not take possibly hidden dependencies between node topology and attributes into account. Especially in the context of online social networks, node attributes are of importance as they correspond to properties of the social network’s users. Therefore, existing sampling algorithms can be extended to attribute sampling, but still lack the capturing of structural properties. Analyzing topology (e.g., node degree and clustering coefficient) and attribute properties (e.g., age and location) jointly can provide valuable insights into the social network and allows for a better understanding of social processes. As major contribution, this work proposes a novel sampling algorithm which provides unbiased and reliable estimates of joint topological and attribute based graph properties in a resource efficient fashion. Furthermore, the obtained samples allow for the generation of synthetic graphs, which show high similarity to the original graph with respect to topology and attributes. The proposed sampling and generation algorithms are evaluated on real world social network graphs, for which they demonstrate to be effective. | More than topology: Joint topology and attribute sampling and generation of social network graphs |
S0140366415002625 | Online social networking (OSN) websites such as Twitter and Facebook are known to have a wide heterogeneity in the popularity of their users, which is counted typically in terms of the number of followers or friends of the users. We add to the large body of work on information diffusion on online social networking websites, by studying how the behavior of the small minority of very popular users on Twitter differs from that of the bulk of the population of ordinary users, and how these differences may impact information diffusion. Our findings are somewhat counter intuitive. We find that on aggregate metrics such as the tweeting volume and degree of participation on different topics, popular users and ordinary users seem similar to each other. We also find that although popular users do seem to command an influential position in driving the popularity of topics on Twitter, in practice they do not affect growth rates of user participation and the causality of popular users driving event popularity is hard to establish. Our observations corroborate the findings of other researchers who show that user popularity in terms of number of followers does not translate into driving event popularity, but that event popularity may be driven by extraneous factors to do with the importance of the event. | The rich and middle classes on Twitter: Are popular users indeed different from regular users? |
S0140366415002649 | Content Distribution Networks (CDNs) are networks that make intense use of caching and multicast overlay techniques for transmitting video and other stream media, a type of traffic that has been growing tremendously in the last years. To cope with this increasing demand, several telecommunications companies have been associated to create federated CDNs (FCDNs), that involves many different providers and, hence, distinct domains. Although beneficial in terms of increased capillarity and scalability of service delivery, the interaction between FCDN elements from different providers brings many new challenges. Among them, one that has received little attention so far refers to security, an essential service for preventing the misuse of the FCDN resources. Aiming to tackle this issue, this paper presents the Overlay Communication Protocol (OCP), a security mechanism that allows the secure signaling communication in FCDNs. OCP takes into account all elements involved in the content delivery process, addressing Route Forgery attacks and concealing the network structure from potential attackers. Together with the protocol description and security analysis, we also present experimental results on its implementation, showing that it introduces little impact on the overall network performance. | OCP: A protocol for secure communication in federated content networks |
S0140366415002868 | This study examines motives for virtually endorsing others on social media, focusing on the Facebook “like” function. Motives are studied in terms of uses and gratifications, Theory of Reasoned Action, and personality and technology factors. Data from an online survey of 213 respondents were examined using factor- and hierarchical-regression analyses. Findings showed enjoyment and interpersonal relationship as most salient motives. Two types of user profiles emerged. Those with higher self-esteem, more diligence, more emotional stability, and less subjective norm clicked “like” to express enjoyment. Those with lower self-esteem, less diligence, less emotional stability, and higher subjective norm clicked “like” for pleasing others. | What makes us click “like” on Facebook? Examining psychological, technological, and motivational factors on virtual endorsement |
S0140366415003175 | Some social networks, such as LinkedIn and ResearchGate, allow user endorsements for specific skills. In this way, for each skill we get a directed graph where the nodes correspond to users’ profiles and the arcs represent endorsement relations. From the number and quality of the endorsements received, an authority score can be assigned to each profile. In this paper we propose an authority score computation method that takes into account the relations existing among different skills. Our method is based on enriching the information contained in the digraph of endorsements corresponding to a specific skill, and then applying a ranking method admitting weighted digraphs, such as PageRank. We describe the method, and test it on a synthetic network of 1493 nodes, fitted with endorsements. | Endorsement deduction and ranking in social networks |
S0140366415003205 | Online Social Networks (OSNs) are the most popular applications in todays Internet and they have changed the way people interact with each other. Understanding the structural properties of OSNs and, in particular, how users behave when they connect to OSNs is crucial for designing user-centered systems. Results about OSNs demonstrated that the relationships that an individual (ego) maintains with other people (alters) can be organized into a set of circles (named Dunbar’s circles) according to the ego network model. The study of the impact of ego networks structure on the availability patterns of users is seriously limited by the lack of information about users availability patterns. In this work we contribute to fill this gap by analysing availability information of a sample of Facebook users. The data reveal a number of strong temporal dependencies (or temporal homophily) which provide insights into the availability pattern that characterize an ego network. | The impact of user’s availability on On-line Ego Networks: a Facebook analysis |
S0140366415003230 | The capability of accessing multiple channels through multiple interfaces improve network capacity and is desirable for future Mobile Ad-Hoc Networks (MANETs). However, due to the presence of jammers as well as mobility and ad-hoc features, MANETs require distributed and efficient resource management for channel assignment. To address the channel assignment problem, which is a non-deterministic polynomial-time hard (NP-hard) problem, we propose a heuristic algorithm called Channel Assignment and JAmmer Mitigation (CA-JAM). The CA-JAM algorithm assigns a distinct channel for every interface of one station, and then all stations exchange the assignment information through beacon frames on every individual interface. When one station receives a beacon, the station organizes the information into tables. Therefore, each station, distributively, uses the table to reduce the number of neighboring stations using the same channel to avoid interference which in turn improves the throughput. The tables are also used to learn the disconnected neighbors due to jamming so as to mitigate the effect of jamming and maintain connectivity. CA-JAM is fully distributed with no use of control channel or central entity; thus, it improves connectivity and reduces interference by balancing stations over the available channels while mitigating jamming effects from multi channel multi interface MANETs. We confirm that CA-JAM outperforms existing protocols using the OPNET simulator. | Beacon-based channel assignment and jammer mitigation for MANETs with multiple interfaces and multiple channels |
S0140366415003515 | Broadcast scheduling for low-duty-cycle wireless sensor networks (WSNs) has been extensively studied recently. However, existing solutions mainly focused on optimizing delay and (or) total energy consumption without considering load distribution among nodes. Due to limited energy supply for sensor nodes, heavily loaded sensors often run out of energy quickly, reducing the lifetime of the whole network. In this paper, we target at minimizing the maximum transmission load of a broadcast schedule for low-duty-cycle WSNs, subject to the constraint that each node should have the minimum end-to-end delay under the broadcast schedule. We prove that it is NP-hard to find the optimal schedule. Then, we devise a Load-Balanced Parents Assignment Algorithm (LBPA-A) that achieves λ-approximation ratio, where λ denotes the maximum number of neighbors that are scheduled to wake up at the same time and is typically a small number in low-duty-cycle WSNs. Further, we introduce how to solve this problem in a distributed manner. Our simulation results reveal that compared with the traditional solutions, our proposed LBPA-A and distributed solution both exhibit much better average performance in terms of energy-fairness, total energy consumption and delivery ratio. | Towards energy-fairness for broadcast scheduling with minimum delay in low-duty-cycle sensor networks |
S0140366415003588 | Social-aware Opportunistic forwarding algorithms are much needed in environments which lack network infrastructure or in those that are susceptible to frequent disruptions. However, most of these algorithms are oblivious to both the user’s interest in the forwarded content and the limited power resources of the available mobile nodes. This paper proposes PI-SOFA, a framework for integrating the awareness of both interest and power capability of a candidate node within the forwarding decision process. Furthermore, the framework adapts its forwarding decisions to the expected contact duration between message carriers and candidate nodes. The proposed framework is applied to three state-of-the-art social-aware opportunistic forwarding algorithms that target mobile opportunistic message delivery. A simulation-based performance evaluation demonstrates the improved effectiveness, efficiency, reduction of power consumption, and fair utilization of the proposed versions in comparison to those of the original algorithms. The results show more than 500% extra f-measure, mainly by disregarding uninterested nodes while focusing on the potentially interested ones. Moreover, power awareness preserves up to 8% power with 41% less cost to attain higher utilization fairness by focusing on power-capable interested nodes. Finally, this paper analyzes the proposed algorithms’ performance across various environments. These findings can benefit message delivery in opportunistic mobile networks. | On the integration of interest and power awareness in social-aware opportunistic forwarding algorithms |
S0140366415003631 | Twitter is a popular social network which allows millions of users to share their opinions on what happens all over the world. In this work we present a system for real-time Twitter data analysis in order to follow popular events from the user’s perspective. The method we propose extends and improves the Soft Frequent Pattern Mining (SFPM) algorithm by overcoming its limitations in dealing with dynamic, real-time, detection scenarios. In particular, in order to obtain timely results, the stream of tweets is organized in dynamic windows whose size depends both on the volume of tweets and time. Since we aim to highlight the user’s point of view, the set of keywords used to query Twitter is progressively refined to include new relevant terms which reflect the emergence of new subtopics or new trends in the main topic. The real-time detection system has been evaluated during the 2014 FIFA World Cup and experimental results show the effectiveness of our solution. | A framework for real-time Twitter data analysis |
S0140366415003655 | Underlying network provides infrastructures for cloud computing in data centers. The server-centric architectures integrate network and compute, which place routing intelligence on servers. However, the existing multi-port server based architectures suffer from determined scale and large path length. In this paper, we propose FleCube, a flexibly-connected architecture on multi-port servers without using any switches. FleCube is recursively constructed on division of multiple ports in a server by means of complete graph. FleCube benefits data center networks by flexible scale and low diameter, as well as large bisection width and small bottleneck degree. Furthermore, we develop multi-path routing (MPR) to take advantage of parallel paths between any two servers. MPR adopts random forwarding to distribute traffic load and relieve network congestion. Analysis and comparisons with existing architectures show the advantages of FleCube. Evaluations under different degrees of network traffic demonstrate the merits of FleCube and the proposed routings. | FleCube: A flexibly-connected architecture of data center networks on multi-port servers |
S0140366415003667 | Information-Centric Networking (ICN) is regarded as one of the representative network architectures of Future Internet. In this paper, an information-centric architecture called Content-Scent based Architecture (CSAR) will be proposed for mobile ad hoc networks. In CSAR, each content has its special content-scent and can be found by tracing the scent it spreads over the network. The content-scent has the property similar to the natural scent that can spread over air, mix with other scents, decay with distance and time, and strengthen with fresh supplement. Using this property, scent-based routing and reliable content delivery functionalities are provided for the mobile ad hoc environment. Simulation results show that CSAR has an efficient route discovery procedure with less routing overhead and better in-network caching for the mobile ad hoc networks. | CSAR: A Content-Scent based Architecture for Information-Centric mobile ad hoc networks |
S0140366415003813 | To satisfy the demand for higher data rate while maintaining the quality of service, a dense long-term evolution (LTE) cells environment is required. This imposes a big challenge to the network when it comes to performing handover (HO). Cell selection has an important influence on network performance, to achieve seamless handover. Although a successful handover is accomplished, it might be to a wrong cell when the selected cell is not an optimal one in terms of signal quality and bandwidth. This may cause significant interference with other cells, handover failure (HOF), or handover ping-pong (HOPP), consequently degrading the cell throughput. To address this issue, we propose a multiple-criteria decision-making method. In this method, we use an integrated fuzzy technique for order preference by using similarity to ideal solution (TOPSIS) on S-criterion, availability of resource blocks (RBs), and uplink signal-to-interference-plus-noise ratio. The conventional cell selection in LTE is based on S-criterion, which is inadequate since it only relies on downlink signal quality. A novel method called fuzzy multiple-criteria cell selection (FMCCS) is proposed in this paper. FMCCS considers RBs utilization and user equipment uplink condition in addition to S-criterion. System analysis demonstrates that FMCCS managed to reduce handover ping-pong and handover failure significantly. This improvement stems from the highly reliable cell-selection technique that leads to increased throughput of the cell with a successful handover. The simulation results show that FMCCS outperforms the conventional and cell selection scheme (CSS) methods. | A novel cell-selection optimization handover for long-term evolution (LTE) macrocellusing fuzzy TOPSIS |
S0140366415003825 | We present PrivHab+, a secure geographic routing protocol that learns about the mobility habits of the nodes of the network and uses this information in a secure manner. PrivHab+ is designed to operate in areas that lack of network, using the store-carry-and-forward approach. PrivHab+ compares nodes and chooses the best choice to carry messages towards a known geographical location. To achieve a high performance and low overhead, PrivHab+ uses information about the usual whereabouts of the nodes to make optimal routing decisions. PrivHab+ makes use of cryptographic techniques from secure multi-party computation to preserve nodes’ privacy while taking routing decisions. The overhead introduced by PrivHab+ is evaluated using a proof-of-concept implementation, and its performance is studied under the scope of a realistic application of podcast distribution. PrivHab+ is compared, through simulation, with a set of well-known delay-tolerant routing algorithms in two different scenarios of remote rural areas. | PrivHab+: A secure geographic routing protocol for DTN |
S0140366415003928 | This study proposes a capable, scalable, and reliable edge-to-edge model for filtering malicious traffic through real-time monitoring of the impact of user behavior on quality of service (QoS) regulations. The model investigates user traffic, including that injected through distributed gateways and that destined to gateways that are experiencing actual attacks. Misbehaving traffic filtration is triggered only when the network is congested, at which point burst gateways generate an explicit congestion notification (ECN) to misbehaving users. To investigate the behavior of misbehaving user traffic, packet delay variation (PDV) ratios are actively estimated and packet transfer rates are passively measured at a unit time. Users who exceed the PDV bit rates specified in their service level agreements (SLAs) are filtered as suspicious users. In addition, suspicious users who exceed the SLA bandwidth bit rates are filtered as network intruders. Simulation results demonstrate that the proposed model efficiently filters network traffic and precisely detects malicious traffic. | Filtration model for the detection of malicious traffic in large-scale networks |
S0140366415004211 | Publish-subscribe is an increasingly popular messaging pattern for distributed systems, supporting scalable and extensible programming, and optimal spatial, temporal, and control-flow decoupling of distributed components. Publish-subscribe middleware and methods were extended towards supporting security, in particular confidentiality, and increased availability, yet a few prior works addressed anonymity of participants. Anonymity of senders and receivers may however be crucial, e.g., for supporting freedom of expression in regimes where political repression and censorship prevail. In this article, we review basic security and privacy requirements and introduce a new attacker model based on statistical disclosure, used to challenge anonymity. We elaborate on design options for privacy-preserving publish-subscribe systems and present a novel system that leverages peer-to-peer networking concepts; this novel approach protects subscriber anonymity by means of Probabilistic Forwarding (PF) and through a novel so-called Shell Game (SG) algorithm. We verify our solution against the requirements and provide a simulation-based analysis of the effectiveness of our approaches in light of our attacker model. The results show that the SG algorithm efficiently protects subscriber anonymity, and that anonymity sets can be adjusted via PF. | AnonPubSub: Anonymous publish-subscribe overlays |
S0140366415004570 | The normalized Laplacian spectrum (NLS) is a powerful tool for comparing graphs with different sizes. Recently, we showed that two NLS features, namely the weighted spectral distribution (WSD) and the multiplicity of the eigenvalue 1 (ME1), are particularly relevant to the Internet topology at the inter-domain level. In this paper, we examine the physical meaning of the two metrics for the Internet. We show that the WSD reflects the transformation from single-homed nodes to multi-homed nodes for better fault-tolerance and that the ME1 quantifies the initial star-based structure associated with node classification, both of which are critical to the robustness of the Internet structure. We then investigate the relation between the metrics and graph perturbations (i.e., small changes in a graph). We show that these two NLS metrics can be a good choice for study on the Internet optimization. Our work reveals novel insights into the Internet structure and provides useful knowledge for statistical analysis on complex networks. | Graph perturbations and corresponding spectral changes in Internet topologies |
S0140366416300068 | Adoption of SSL/TLS to protect the privacy of web users has become increasingly common. In fact, as of September 2015, more than 68% of top-1M websites deploy SSL/TLS to encrypt their traffic. The transition from HTTP to HTTPS has brought a new challenge for network operators who need to understand the hostnames of encrypted web traffic for various reasons. To meet the challenge, this work develops a novel framework called SFMap, which estimates names of HTTPS servers by analyzing precedent DNS queries/responses in a statistical way. The SFMap framework introduces domain name graph, which can characterize highly dynamic and diverse nature of DNS mechanisms. Such complexity arises from the recent deployment and implementation of DNS ecosystems; i.e., canonical name tricks used by CDNs, the dynamic and diverse nature of DNS TTL settings, and incomplete and unpredictable measurements due to the existence of various DNS caching instances. First, we demonstrate that SFMap establishes good estimation accuracies and outperforms a state-of-the-art approach. We also aim to identify the optimized setting of the SFMap framework. Next, based on the preliminary analysis, we introduce techniques to make the SFMap framework scalable to large-scale traffic data. We validate the effectiveness of the approach using large-scale Internet traffic. | Statistical estimation of the names of HTTPS servers with domain name graphs |
S0140366416300226 | Existing flat peer-to-peer (P2P) systems based on distributed hash tables (DHTs) perform unsatisfactorily under churn due to their non-hierarchical topology. These flat DHTs (FDHTs) experience low lookup success ratio, high lookup latency and high bandwidth usage as a consequence of the presence of churn. With this, we explore the use of hierarchical DHT (HDHT), specifically the superpeer design, in mitigating the effects of churn. To the best of our knowledge, we are the first to intensively examine HDHTs with and without high churn through simulations. Using the OMNeT++ simulator and the OverSim framework, we analyze flat and hierarchical DHTs with and without churn. Results show that the implemented HDHTs perform more satisfactorily than a flat DHT because of better fault isolation and smaller cluster sizes at the cost of higher superpeer traffic. HDHTs are more stable as they have better lookup success ratios. They are more efficient as evidenced by lower lookup latencies and lower average node bandwidth usage. They are more scalable since their performance do not degrade significantly even at high population. With this, the implemented HDHTs can be utilized to alleviate the effects of churn in mobile networks. | Evaluation of hierarchical DHTs to mitigate churn effects in mobile networks |
S0140366416300883 | We observe that the laborious collection of location fingerprints, that could also potentially change with time and space, remains a hurdle towards the widespread deployment of indoor and outdoor positioning systems using the Wi-Fi. Motivated by this, we focus on the error bound analysis of indoor Wi-Fi fingerprint based positioning for intelligent Access Point (AP) placement optimization by using the Fisher Information Matrix (FIM) to characterize the relationship between the positioning errors and signal distributions. We first derive the closed-form error bounds with respect to different system parameters. Second, we use the Simulated Annealing (SA) algorithm to conduct the Wi-Fi AP placement optimization towards the lowest error bounds. Finally, we present the detailed discussion, extensive simulation, and experiment results. | Error bound analysis of indoor Wi-Fi location fingerprint based positioning for intelligent Access Point optimization via Fisher information |
S0140366416300901 | The current age of increased people mobility calls for a better understanding of how people move: how many places does an individual commonly visit, what are the semantics of these places, and how do people get from one place to another. We show that the number of places visited by each person (Points of Interest – PoIs) is regulated by some properties that are statistically similar among individuals. Subsequently, we present a PoIs classification in terms of their relevance on a per-user basis. In addition to the PoIs relevance, we also investigate the variables that describe the travel rules among PoIs in particular, the spatial and temporal distance. As regards the latter, existing works on mobility are mainly based on spatial distance. Here we argue, rather, that for human mobility the temporal distance and the PoIs relevance are the major driving factors. Moreover, we study the semantic of PoIs. This is useful for deriving statistics on people’s habits without breaking their privacy. With the support of different datasets, our paper provides an in-depth analysis of PoIs distribution and semantics; it also shows that our results hold independently of the nature of the dataset in use. We illustrate that our approach is able to effectively extract a rich set of features describing human mobility and we argue that this can be seminal to novel mobility research. | On the properties of human mobility |
S0140366416301141 | A malicious alteration of system-provided timeline can negatively affect the reliability of computer forensics. Indeed, detecting such changes and possibly reconstructing the correct timeline of events is of paramount importance for court admissibility and logical coherence of collected evidence. However, reconstructing the correct timeline for a set of network nodes can be difficult since an adversary has a wealth of opportunities to disrupt the timeline and to generate a fake one. This aspect is exacerbated in cloud computing, where host and guest machine-time can be manipulated in various ways by an adversary. Therefore, it is important to guarantee the integrity of the timeline of events for cloud host and guest nodes, or at least to ensure that timeline alterations do not go undetected. This paper provides several contributions. First, we survey the issues related to cloud machine-time reliability. Then, we introduce a novel architecture (CURE) aimed at providing timeline resilience to cloud nodes. Further, we implement the proposed framework and extensively test it on both a simulated environment and on a real cloud. We evaluate and discuss collected results showing the effectiveness of our proposal. | CURE—Towards enforcing a reliable timeline for cloud forensics: Model, architecture, and experiments |
S0141938213000243 | A two-dimensional tactile display for visually impaired people was fabricated and successfully operated. Character and graphic information is dynamically displayed by an array of pins in up and down positions. The contraction of shape memory alloy (SMA) micro-coil actuators moves the pins up and down when the SMA actuator is heated by an electrical current. A tube fabricated from magnetic material is attached to each pin and a permanent magnet accurately positions the pins in an up or down state without any feedback control. This latch mechanism overcomes problems of heat storage and electrical consumption of the SMA actuator because the current is supplied only when the pins move. The tactile display has a 100 (10×10) pins array. The tactile information is displayed sequentially every 0.3s and the tactile pins are latched at 0.1N by magnetic force. The pins are arranged at a pin interval of 2.5mm and move 2mm up and down. Furthermore, in order to offer tactile graphic information, the interval between pins is narrow. A module for the tactile display with pin intervals of 1.27mm has also been developed. | Tactile display using shape memory alloy micro-coil actuator and magnetic latch mechanism |
S0141938213000255 | This paper presents a new pixel circuit with all-p-type TFTs for AMOLED displays. The proposed pixel circuit can effectively compensate for the threshold-voltage shift of the driving TFT, the degradation of OLED and the parasitic resistance of the power supply line. And thus, the brightness uniformity of AMOLED displays can be enhanced. It is shown that the nonuniformity of the OLED current with an average value of 7.3% can be achieved by the proposed pixel circuit, while that of the conventional 2T1C pixel circuit is 73%. Moreover, a high contrast ratio can be also obtained by the proposed pixel circuit since there is no light emitting except for the emission period. | A new compensation pixel circuit with all-p-type TFTs for AMOLED displays |
S0141938213000267 | To obtain a black matrix (BM) with high optical density (OD) and low dielectric constant, graphene oxide (GO) was prepared from synthetic graphite oxide and then incorporated into the conventional carbon black (CB) pigment to fabricate black matrix films. The introduction of insulating GO effectively lowered the dielectric constant of carbon black-based BM, but maintained the high optical density. The dielectric constant of the BM film significantly decreased from 26 (carbon black-based BM) to 4.5 (GO/CB-based BM). This work demonstrates the successful chemical modification and good dispersion of carbon-based materials (i.e. GO and CB) and their physical effects on the BM films. | High optical density and low dielectric constant black matrix containing graphene oxide and carbon black on color filters |
S0141938213000383 | Iridium(III)bis(4,6-(difluorophenyl)pyridinato-N,C2′)picolinate (Firpic) is one typical bluish-green phosphor widely used in phosphorescent organic light-emitting diodes (PhOLEDs). In order to optimize its electroluminescent performance, 3,6-(di-tert-butyl)carbazolyl was introduced into the pyridine ring of the 2,4-difluorophenyl-pyridine ligand via a non-conjugated CH2 linkage. The generated 3,6-di-tert-butyl-9-((6-(2,4-difluorophenyl)pridine-3-yl)methyl)-9H-carbazole (Cz-CH2-dfppy) was used as cyclometalating ligand to prepare iridium complex 1, (Cz-CH2-dfppy)2Ir(pic). In comparison with the case to attach carbazole directly on pyridine, this non-conjugated CH2 linking strategy avoids the unwanted bathochromic shift of the phosphorescence and improves the solubility of the iridium complex. (Cz-CH2-dfppy)2Ir(pic) (1) was used as doped emitter to fabricate OLEDs by both spin-coating and vacuum evaporation methods. Efficient bluish-green electrophosphorescence was obtained with maximum luminance efficiency of 22cd/A (14lm/W, 8.7%) and 26cd/A (12lm/W, 9.5%) for the solution-processed and vacuum-deposited devices, respectively, which far exceed those of the parent Firpic based device. The improved performance for (Cz-CH2-dfppy)2Ir(pic) was interpreted in terms of improved charge balance brought by the presence of the carbazole groups in the ligands. | Efficient bluish-green phosphorescent iridium complex for both solution-processed and vacuum-deposited organic light-emitting diodes |
S0141938213000395 | Large screen display technology has in recent years become available to industrial control rooms as a supplement to smaller displays. Due to the greater complexity and scale, measured in meters, not inches, it is now a challenge to design for readability and Situation Awareness. Information Rich Design is a design concept for large displays used in many real-life complex processes for almost a decade. The concept simplifies the understanding of large data sets through alignment and Gestalt grouping of process data through a few generic process objects. This paper describes recent design modifications where new functionality is integrated into existing graphical objects, keeping the original simplicity. This paper proposes design principles for large screen displays based on theoretical discussions of Situation Awareness and a user test using crews of certified operators. The user test shows positive results on pattern recognition of process data and a newly developed animation of unacknowledged alarms; however, the concept still suffers from colour and readability issues. | Visualizing complex processes on large screen displays: Design principles based on the Information Rich Design concept |
S0141938213000401 | The materials science and engineering related to the fabrication of conducting polymer thin films and the progress in the development of devices integrated with organic transparent electrodes based on conducting polymers for display applications are reviewed. Transparent electrodes are essential components for many display modules. With the evolution of display technologies, conducting polymers are recently emerging as important alternative materials for the fabrication of transparent electrodes. Conducting polymers offer some advantages, such as light weight, low cost, mechanical flexibility and excellent compatibility with plastic substrates for the development of next-generation display technologies and, in particular, are expected to play an important role in the development of flexible display technologies. | Transparent electrodes based on conducting polymers for display applications |
S0141938213000413 | In a plasma display panel (PDP), ramp pulse is used for the reset operation. In this case, the stability of ramp slope is very important because the variation of ramp slope leads to the reset failure. However, the ramp slope is affected by the image load and operation temperature. In this paper, the variation of ramp slope is analyzed and a new ramp driver circuit is proposed. In the proposed driver circuit, the effect of image load is compensated for by redesigning the current path of the feedback capacitor. The slope variation caused by temperature variation is reduced by compensating for the threshold voltage shift of a MOSFET. The proposed ramp driver circuit provides multiple ramp slopes by adjusting the control signal and guarantees the stability of ramp slope against the changes of image load and temperature. The variation of ramp slope in the proposed method is reduced by 82.7% compared with the previous switched ramp driver circuit. Moreover, the additional hardware cost of the proposed driver circuit is minimal. | Ramp driver circuit for improving the stability of ramp slope in a flat panel display driver |
S0141938213000425 | In this study, the effects of ambient illuminance and light source on participants’ reading performance and visual fatigue during a long reading task were investigated using three electronic paper displays. Reading on electronic paper displays was also compared with reading on paper. In Experiment 1, 100 participants performed a reading task where the display area for the text was equated for the displays. The results indicated that participants’ visual performance and visual fatigue did not differ significantly among different electronic paper displays, ambient illuminance conditions, or light sources. In Experiment 2, another 60 participants performed the same reading task where the full screen of each electronic paper display was used to present the text. The results showed that reading speed differed significantly across different electronic paper displays and ambient illuminance levels. The reading speed was slower for displays with smaller screens and increased as the ambient illuminance increased. Changes in the critical flicker fusion frequency significantly differed across ambient illuminance levels. Implications of the results for the use of electronic paper displays are discussed. | Reading performance and visual fatigue when using electronic paper displays in long-duration reading tasks under various lighting conditions |
S0141938213000437 | Cholesteric liquid crystals (Ch-LCs) have been extensively studied due to their unique self-organized helical molecular structures and selective Bragg reflection properties, which exhibit great potentials for color displays and other practical applications. When functional, nanoscale molecular switches are doped in liquid crystals (LCs), the phases of the LCs or the molecular structures of the Ch-LCs can be changed upon the influence of external stimuli, such as light and temperature. In this paper, the photoresponsive molecular switch-based LCs for display applications are reviewed. The progress and effort in developing molecular switches, the principles of light-tuning, photo-addressed color displays, information processing, bistable displays and flexible displays are presented. | Towards nanoscale molecular switch-based liquid crystal displays |
S0141938213000449 | Seven compounds with pyridine as the backbone modified by carbazole moiety, bromine atom and fluorine atom were synthesized. Compounds 1, 2, 3 with bromo substitution at the 2-position and carbazole modification at the 5-position of pyridine emit not only a sharp blue singlet fluorescence but also a wide banded excimer-based orange emission. The two colors coming from a single molecule can be used to fabricate a simplified white light emitting device. The electroluminescence based on 1 and 2 exhibits white-light emission with CIE coordinates of x =0.25 and y =0.30 for 1 and x =0.33 and y =0.37 for 2 at high current densities, very close to pure white emission. In addition, the role of bromo-substitution at pyridine is concluded to be essential to generate molecular interaction thus an excimer emission. | Small molecules with pyridine backbone modified with carbazole, fluorine and bromine for white light-emitting diode applications |
S0141938213000450 | A series of the Zn3(BO3)2:Eu3+ without or with alkali metal ions doping at a low sintering temperature were synthesized by the solid-state reaction method. The XRD pattern shows that all samples exhibit Zn3(BO3)2 crystalline phase. The samples co-doped with alkali metal ions have better crystallinity compared with the un-compensated ones. The different charge compensation approaches have no influence on the shape and position of the emission and excitation spectra. However, the luminescent intensity of samples has been obviously enhanced with different alkali metal ions co-doping. The introduction of Li+ can increase the red emission of Eu3+ compared with the others. Thus, the volume compensation and the equilibrium of mole number can be taken into consideration by charge compensated (CC) approaches. | Effect of alkali metal ions co-doping on the structure and luminescent properties of phosphor Zn3(BO3)2:Eu3+ |
S0141938213000462 | Menus are commonly employed within user-interfaces, but are not necessarily a suitable solution for emerging new contexts. For instance, for in-vehicle displays, the use of visually oriented menus creates a clear distraction burden. To investigate how the visual demand of menus varied as a function of their breadth, depth and structure, a study was conducted following the ISO occlusion protocol. Participants were asked to find and select target words on a touchscreen by navigating menus of varying breadths and depths (16×3; 8×4; 4×6; 12×2) when options were arranged either in alphabetical order (structured menus) or randomly (unstructured menus). Tasks were achieved either with full vision or whilst wearing occlusion goggles enabling only brief (1.5s) opportunities to visually access the touchscreen. Preliminary equations were derived from the data indicating fundamentally different relationships for the visual demand of an interface dependent on whether anticipation can be used during the task. For structured menus, the visual demand was a logarithmic function of the breadth of the menus, whereas for unstructured menus, the relationship was quadratic. Moreover, results indicated that for structured menus breadth was favoured over depth, as the lowest visual demand was associated with 16×3 menu hierarchies. Conversely, for unstructured menus, compromise hierarchies (e.g. 4×6; 8×4) were associated with the least visual demand. Conclusions are drawn regarding the setting of boundary (acceptable/unacceptable) conditions for alternative menu structures for use within vehicles. | Menu hierarchies for in-vehicle user-interfaces: Modelling the depth vs. breadth trade-off |
S0141938213000474 | Recently, much research has been performed to guarantee viewer’s safety in watching stereoscopic 3D videos. Most of them focused on individual content factors causing viewer discomfort. This paper extends the kinds of content factors, and focuses more on the composite, rather than individual, factors. To analyze them, a subjective test for discomfort is performed for four stereoscopic 3D videos. Also, all the quantitative values of the factors to be considered are extracted from the contents. The quantitative factors we consider are the amount of disparity, the frequency and amount of the disparity changes, object movement, and the color and luminance information. In addition, we also include some situational factors, such as story of the contents, situation or circumstances of a scene, and movement, position, and direction of camera. We analyze qualitatively, by comparing the subject test results and the extracted quantitative factors, as well as the situational factors, to find when and how much those factors, in combination or individually, cause viewer discomfort. We summarize, and substantially show which factors, or their combinations, strongly or weakly affect viewer discomfort. | Qualitative analysis of individual and composite content factors of stereoscopic 3D video causing visual discomfort |
S0141938213000486 | The present work describes indium-zinc oxide (IZO) sputtering depositions onto several types of papers, using radio-frequency (RF) and direct current (DC) sputtering with a ceramic IZO target. The electrical and optical properties of the resulting materials were optimized; by studying the argon and oxygen gas flow rates and the sputtering power effects. At optimal deposition conditions, thin films of IZO were achieved with a low sheet resistance (about 20Ω/sq) and an optical transmittance of ca. 80% in the visible spectrum range. These materials retained these properties for more than 8months. Electrochromic devices (ECDs) with several configurations were built with those conductive papers and life cycling and contrast were measured for the ECDs. These devices exhibited a very good color contrast (as defined using L * a * b * color coordinates, =32) and electrochromic cyclability up to 30,000 redox cycles. | IZO deposition by RF and DC sputtering on paper and application on flexible electrochromic devices |
S0141938213000498 | Ca (or Sr)TiO3:Eu3+, M (Li+ or Na+ or K+) and CaTiO3:Pr3+, M (Li+ or Na+ or Ag+ or K+ or Gd3+ or La3+) powders were prepared by combustion synthesis method and the samples were further heated to ∼1000°C to improve the crystallinity. The structure and morphology of materials were examined by X-ray diffraction (XRD) and a scanning electron microscopy (SEM). The morphologies of SrTiO3:Eu3+, CaTiO3:Eu3+ or CaTiO3:Pr3+ powders co-doped with other metal ions were very similar. Small and coagulated particles of nearly cubical shapes with small size distribution having smooth and regular surface were formed. Photo-luminescence spectra of CaTiO3:Pr3+ and co-doped either with Li+, Na+, K+, Ag+, La3+ or Gd3+ ions showed red emissions at 613nm due to the 1D2 → 3H4 transition of Pr3+. The variation of intensity of emission peak with different co-doping follows the order: K+ >Ag+ >Na+ >Li+ >La3+ >Gd3+. The characteristic emissions of CaTiO3:Eu3+ lattices had strong emission at 614 and 620nm for 5D0 → 7F2 with other weak transitions observed at 580, 592, 654, 705nm for 5D0 → 7Fn transitions where n =0, 1, 3, 4 respectively in all host lattices. Photoluminescence intensity in SrTiO3:Eu3+ is more than CaTiO3:Eu3+ lattices. A remarkable increase of photoluminescence intensity (in 5D0 → 7F2 transition) was observed if co-doped with Li+ ions in CaTiO3:Eu3+ and SrTiO3:Eu3+. | Red emitting MTiO3 (M=Ca or Sr) phosphors doped with Eu3+ or Pr3+ with some cations as co-dopants |
S0141938213000504 | In this paper qualitative colours are named by defining intervals on reference systems built on the Hue Saturation and Lightness (HSL) colour space. The new model for Qualitative Colour Description (QCD) distinguishes rainbow colours, pale, light, dark colours and colours in the grey scale. For comparing the qualitative colours described, a similarity measure based on interval distances (SimQCDInt) is introduced. HSL intervals for each colour label have been defined experimentally using data obtained in a user survey. Preliminary experiments have also been conducted in order to check that the proposed approach is consistent with human appreciations of colour similarity and complementarity. | A model for qualitative colour comparison using interval distances |
S0141938213000607 | Two novel carbazole/anthracene hybrided molecules, namely 2-(anthracen-9-yl)-9-ethyl-9H-carbazole (AnCz) and 2,7-di(anthracen-9-yl)-9-ethyl-9H-carbazole (2AnCz), were designed and synthesized via palladium catalyzed coupling reaction. The anthracene was attached either at the 2-site (AnCz) or at both 2,7-sites (2AnCz) of the central carbazole core to tune the conjugation state and the optoelectronic properties of the resultant molecules. Both of them show good solubility in common organic solvents. They also possess relatively high HOMO levels (−5.39eV, −5.40eV) that would facilitate efficient hole injection and be favorable for high power efficiencies when used in organic light-emitting devices (OLEDs). AnCz and 2AnCz were used as non-doped emitter to fabricate OLEDs by vacuum evaporation. Good performance was achieved with maximum luminance efficiency of 2.61cdA−1 and CIE coordinates of (0.15, 0.12) for AnCz, and 9.52cdA−1 and (0.22, 0.37) for 2AnCz. | Novel carbazole/anthracene hybrids for efficient blue organic light-emitting diodes |
S0141938213000619 | There is a large demand for more fashionable style Chinese characters in advertising, art designing and publishing markets. However, it becomes challenging to create a new font style for so many Chinese characters (over 10,000). To solve this problem, a comprehensive Chinese fonts generating scheme is proposed in this paper. Firstly, a decomposition database for stroke splitting and feature extraction is proposed. Secondly, stroke segmentation rules are defined based on splitting, merging and structural model, location definition and minimum feature extraction. Thirdly, a radical searching algorithm based on stroke splitting is presented. Finally, it is realized that the generated characters can be zoomed, rotated and moved. Experimental result shows that Chinese characters with a new style can be generated rapidly with the proposed scheme. The created characters fit the real ones well with a high fidelity of 96.4%. The usability tests are run and participants’ subjective report show that the performance from the generated characters is similar to the original characters in both recognizability test and style-consistency test. The fonts generating method is also reliable for the other stroke constructed block characters such as Japanese and Korean characters. | Generating Chinese characters based on stroke splitting and feature extraction |
S0141938213000620 | A main requirement for achieving high efficiency in organic light-emitting diodes (OLEDs) is that all charges and electrically generated excitons should be employed for emission. We fabricated blue phosphorescent OLEDs with four types electron transporting layers, which were doped with lithium quinolate (Liq) from 0% to 10%. A series of blue devices consisted of indium tin oxide (ITO, 180nm)/4,4-bis[N-(naphthyl)-N-phenyl-amino]biphenyl (NPB, 50nm)/N,N′-dicarbazolyl-3,5-benzene (mCP, 10nm)/iridium(III)bis[(4,6-di-fluoropheny)-pyridinato-N,C2] picolinate (FIrpic) doped in mCP (8%, 30nm)/1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi, 20nm)/TPBi mixed with Liq (20nm)/Liq (2nm)/aluminum (Al, 100nm). The blue OLED doped with 5% Liq, which demonstrated a maximum luminous efficiency and external quantum efficiency of 17.64cd/A and 8.78%, respectively, were found to be superior to the other blue devices. | Effect of electron transport layer engineering based on blue phosphorescent organic light-emitting diodes |
S0141938213000632 | We have grown the crystals of two thiophene/phenylene co-oligomers (TPCOs) composed of in-line five and seven alternating thiophene and benzene rings. These TPCOs are characterized by thiophenes located at both molecular terminals. The grown crystals had several pairs of parallel crystal faces that function as optical resonators. These produced interference fringes in their emission and reflectance spectra. We measured the emission spectra in both weak broadband excitation and intense laser excitation regimes. From these spectra we determined the phase refractive index dispersion and the anisotropic group refractive indices. We made field-effect transistor devices using the above TPCO crystals and carried out their electrical measurements. These optical and charge transport properties are compared with those of crystals of other alternating TPCOs with phenylenes located at both molecular terminals. | Emission and charge transport properties of thiophene-terminated thiophene/phenylene co-oligomer crystals |
S0141938213000644 | Optical properties of seven regioregular poly(3-alkylthiophene) with different alkyl side chain lengths which are poly(3-butylthiophene-2,5-diyl) (P3BT), poly(3-pentylthiophene-2,5-diyl) (P3PT), poly(3-hexylthiophene-2,5-diyl) (P3HT), poly(3-heptylthiophene-2,5-diyl) (P3hept), poly(3-octylthiophene-2,5-diyl) (P3OT), poly(3-decylthiophene-2,5-diyl) (P3DT), and poly(3-dodecylthiophene-2,5-diyl) (P3DDT) have been studied in the mid-infrared (IR) spectral region by means of Fourier Transformation Infrared (FTIR) spectroscopy and IR spectroscopic ellipsometry (IRSE). Absorbance spectra obtained in this fingerprint region are potential to characterize the structures formed by organic molecules in thin films due to molecular vibrations in detail. In consequence, the vibrational absorption bands of these seven samples demonstrated that P3PT, P3HT, and P3hept exhibited very similar band profiles, in contrast, the stretching vibration of thiophene rings (≈1465cm−1: CC) underwent a blue shift in P3BT, P3OT, P3DT and P3DDT. The highest value of the real part (ɛ 1) of the complex dielectric constant was obtained from P3HT on both indium thin oxide (ITO) and silicon (Si) substrates whereas the imaginary part (ε 2) was directly affected by increasing in the alkyl side chain lengths in a frequency range around 3000cm−1. The optical properties of P3PT in the mid-IR region developed an affinity with those of P3HT. Thus, P3PT is particularly a suitable polymer active material candidate for high-performance devices. | Mid-infrared characterization of thiophene-based thin polymer films |
S0141938213000656 | The characteristics of MoO3/F8BT/ZnO inorganic/organic hybrid light emitting diodes (IO-HyLEDs) fabricated on ZnO/Ag/ZnO dielectric/metal/dielectric (DMD) and conventional ZnO/ITO were investigated. The DMD had a low sheet resistance of 9Ω/sq and a high transmittance of 90.7%. The device fabricated on DMD showed similar current density–voltage (J–V) and luminance–current density (L–J) characteristics to that on ZnO/ITO, indicating the possibility of DMD as a promising transparent conductive layer for IO-HyLEDs. The maximum luminous intensity of 237,000cd/m2 was demonstrated under pulsed condition for the DMD device. We also investigated the effect of the combination interlayer (CIL) at the F8BT/ZnO interface on the IO-HyLEDs. The CIL was composed of a Mg0.52Zn0.48O/Mg0.25Zn0.75O bilayer and a self-assembled dipole molecule (SADM) of BA-CH3. The devices with CIL exhibited an approximately threefold enhancement of the luminous intensity and efficiency in comparison with the devices without CIL. This improvement was considered to be brought about by the enhancement of the electron injection efficiency by CIL. | Effect of MgZnO-bilayer/BA-CH3 combination interlayer on emission characteristics of MoO3/F8BT/ZnO hybrid light emitting diodes fabricated on ZnO/Ag/ZnO transparent cathode |
S0141938213000668 | Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most successful conducting polymer in terms of the practical application. It can be dispersed in water and some polar organic solvents, and high-quality PEDOT:PSS films can be readily prepared through solution processing. In addition, PEDOT:PSS is highly transparent in the visible range and has excellent thermal stability. Nevertheless, PEDOT:PSS has a problem of low conductivity. The as-prepared PEDOT:PSS films from its aqueous solution have a conductivity of lower than 1Scm−1, which severely impedes the application of PEDOT:PSS in various aspects. It has been discovered that the conductivity of as-prepared PEDOT:PSS from its aqueous solution can be significantly enhanced by adding organic compounds like high-boiling point polar organic solvents, ionic liquids and surfactants or through a post-treatment of PEDOT:PSS films with organic compounds, including high-boiling point polar solvents, salts, zwitterions, cosolvents, organic and inorganic acids. Conductivity of more than 3000Scm−1 was recently observed on PEDOT:PSS films after treated with sulfuric acid. This conductivity is comparable to that of indium tin oxide (ITO), the conventional transparent electrode material of optoelectronic devices. In addition, PEDOT:PSS has high mechanical flexibility while ITO is a brittle material. Thus, PEDOT:PSS is very promising to be the next-generation transparent electrode material. This article reviews the methods to enhance the conductivity of PEDOT:PSS, the mechanisms for the conductivity enhancements and the application of the highly conductive PEDOT:PSS films in polymer light-emitting diodes and polymer solar cells. | “Secondary doping” methods to significantly enhance the conductivity of PEDOT:PSS for its application as transparent electrode of optoelectronic devices |
S0141938213000681 | Electroswitching of emission and coloration was achieved by a combination of a luminescent Eu(III) complex and an electrochromic molecule of diheptyl viologen (HV2+), indicating that the complex-molecule combination could be used as a display material with dual emissive and reflective modes. The coloration of the material was associated with the electrochromism of HV2+. Emission control was found to be possible due to the electrochromism of HV2+ via intermolecular energy transfer from the excited state of the Eu(III) ion to the reduced state of HV+. By using this mechanism, dual emissive and reflective representation of numerical characters were demonstrated. | Electrochemically-switchable emission and absorption by using luminescent Lanthanide(III) complex and electrochromic molecule toward novel display device with dual emissive and reflective mode |
S0141938213000693 | We have grown crystals in which two kinds of thiophene/phenylene co-oligomers (TPCOs) are hybridized. Biphenyl-capped thiophene (BP1T) and biphenyl-capped terthiophene (BP3T) were chosen from among the TPCOs. The hybrid crystals were grown in both the vapor phase and the liquid phase. These hybrid crystals showed the emission colors intermediate between the two components. Correspondingly maximum peak positions of the emissions from the hybrid crystals were located halfway between those from single-component crystals of BP1T and BP3T. We made hybrid thin films by co-deposition of the two TPCOs in vacuum. The thin films exhibited both emission colors and emission peak positions similar to those of the hybrid crystals. The X-ray diffraction measurements indicate that the crystallographic structure of the hybrid crystals resembles that of the BP1T crystal. Also we made field-effect transistors using the hybrid crystals and measured their hole mobilities. We briefly discuss the implications of the X-ray diffraction and electrical data. | Hybrid crystals based on thiophene/phenylene co-oligomers |
S0141938213000711 | The study investigates the effect of attention on prospective memory performance in programmer multitasking (N =60) incorporating a taxonomical understanding of prospective memory errors. It also presents an analysis of cognitive workload (CWL). The results demonstrate that people are more vulnerable to prospective memory performance failure when there is a situation that one is required to devote more attention in monitoring to identify a cue for an intended action. Omission error is the most prominent among all types of prospective memory error. Analysis reveals that when there is a stimulus driven situation of attention capture, a performance decrement observed in terms of prospective memory is not necessarily concerned with an increase in CWL. | Attention and intended action in multitasking: An understanding of cognitive workload |
S0141938213000723 | This study investigated the effects of ambient illumination conditions (illumination color and illumination intensity) and background color on visual performance (character identification and reading comprehension) with TFT-LCD screens. Results of Experiment 1 indicated that all the three independent variables had significant effects on mean percentage of character identification. Mean character identification performance was best under white light, 500 lux, and blue background. In general, the backgrounds with primary colors had better mean character identification performance than the middle-point colors and gray. Results of Experiment 2 indicated that the illumination intensity and background color had significant effects on mean text comprehension performance for reading comprehension. Mean text comprehension performance were higher under 500 lux and blue background. The backgrounds with primary colors had better mean correct answers than the gray background. According to the results, white light, normal ambient illumination and a background with primal colors seemed to be the optimal conditions. If the yellow ambient light is necessary, using blue as the TFT-LCD background color of will provide better performance. The Pearson product-moment correlation coefficient indicated that short-term visual task measurement might be suitable to evaluate the visual performance. | Effects of ambient illumination conditions and background color on visual performance with TFT-LCD screens |
S0141938213000735 | The current study investigates the effects of 3D displays (shuttered display vs. polarized display). People experienced superior fidelity and brightness when they watched 2D still images on a shuttered display, rather than on a polarized display. Conversely, people experienced greater brightness when they watched 3D still images on a polarized display, rather than on a shuttered display. Second, people were able to read a smaller font or characters on a shuttered display than on a polarized display. Third, people noticed flickering on a shuttered display when they watched 3D images. Fourth, people experienced greater brightness when they watched 3D moving images on a shuttered display, rather than on a shuttered display. The perceived brightness of the screen positively correlated with enjoyment, content satisfaction, and 3DTV satisfaction when the viewers watched a 3D movie. The flickering, on the other hand, has a negative correlation with enjoyment and 3DTV satisfaction. | Effects of 3D displays: A comparison between shuttered and polarized displays |
S0141938213000759 | Visual secret sharing (VSS) schemes based on visual cryptography (VC) or random grids (RGs) have been proposed in the past decade with the advantages of easy implementation, efficiency secret recovering and perfect security. As the concept of multiple secret images has gained more and more attention in academia, the novel concept of VC-based VSS with cyclic access structure has been discussed recently, which is a special case of multiple VSS, allowing participants to reconstruct the secret with the one next or last to him/her in a cyclic order. To obtain the benefit of RG-based VSS compared with VC-based VSS, this paper proposes the new VSS scheme with cyclic access structure for multiple secret images by random grids. The experimental results and theoretical security analysis demonstrate the feasibility. | A random grid-based cyclic access structure VSS scheme for multiple secret images |
S0141938213000760 | This study examined the effects of display method, text display rate, and observation angle on comprehension performance and subjective preferences for Chinese characters presented on an LED display. The factors and levels studied were as follows: four text display methods (rapid serial visual presentation ‘RSVP’, leading, paged view scrolling, and continuous scrolling), three text display rates (160 characters per min ‘cpm’, 240cpm, and 320cpm), and seven observation angles (−75°, −60°, −30°, 0°, 30°, 60°, and 75°). The results indicated that a display rate of 160cpm was in general superior to 240 and 320cpm for comprehension scores and subjective evaluations. The effects of display method and observation angle were found to be non significant. However, there was a significant interaction between display method and display rate. The results of this study were used to make ergonomics recommendations applicable to LED displays for determining optimum dynamic text display methods for Chinese characters. | Effects of display method, text display rate and observation angle on comprehension performance and subjective preferences for reading Chinese on an LED display |
S0141938213000905 | We have fabricated two kinds of thin film transistors (TFTs) on the glass substrates using polycrystalline silicon (poly-Si) thin films with small and large grain sizes processed by Excimer Laser Annealing (ELA) and carried out a comparative analysis. The grain size was controlled by nickel atom content in amorphous silicon (a-Si) thin films. With increasing grain size of poly-Si thin films, the carrier mobility increased from 40.8 to 54.4cm2/Vs and the absolute value of threshold voltage reduced from 2.1 to 1.5V. The observed improvements in the electrical characteristics of poly-Si TFTs are attributed mainly to the reduction of defect density rendered by large grain size. These observations indicate that the sputtered nickel atom content in a-Si layer is a key parameter in determining the characteristics of ELA processed TFTs fabricated on the glass substrates. | Characteristics of polycrystalline Si TFTs fabricated on glass substrates by excimer laser annealing with nickel-sputtered amorphous Si films |
S0141938213000917 | The color of a displayed image by a projector can be distorted by features of the device, the ambient light, the projection screen, and also the observer. This has raised the need to correct the image during the display to eliminate these effects and to ensure a constancy of the color appearances. In this paper, we propose models for controlling the appearance of the displayed image. We argue that depending on the target application, the computational color constancy can be specified at different steps of the formation scheme of the sensed image by a human. Based on that observation and the image formation models, we reformulate the problem of the color constancy and we show that the resulting transformations cannot be explained by von Kries theory. Two compensation algorithms are deduced. The first allows preserving the appearance of the original image, and it can be used for the constancy of the acquired image whatever the environment conditions. The second algorithm allows to simulate appearances of a sensed image in a specific conditions. It can be used for the compensation of the screen reflectance or to create special effects or the camouflage. In addition, we propose a complementary operation for the contrast compensation which is derived from the Weber’s law. Experimental results show the merits of the proposed models and algorithms. | Color constancy for visual compensation of projector displayed image |
S0141938213000929 | To answer the question: “what is 3D good for?” we reviewed the body of literature concerning the performance implications of stereoscopic 3D (S3D) displays versus non-stereo (2D or monoscopic) displays. We summarized results of over 160 publications describing over 180 experiments spanning 51years of research in various fields including human factors psychology/engineering, human–computer interaction, vision science, visualization, and medicine. Publications were included if they described at least one task with a performance-based experimental evaluation of an S3D display versus a non-stereo display under comparable viewing conditions. We classified each study according to the experimental task(s) of primary interest: (a) judgments of positions and/or distances; (b) finding, identifying, or classifying objects; (c) spatial manipulations of real or virtual objects; (d) navigation; (e) spatial understanding, memory, or recall and (f) learning, training, or planning. We found that S3D display viewing improved performance over traditional non-stereo (2D) displays in 60% of the reported experiments. In 15% of the experiments, S3D either showed a marginal benefit or the results were mixed or unclear. In 25% of experiments, S3D displays offered no benefit over non-stereo 2D viewing (and in some rare cases, harmed performance). From this review, stereoscopic 3D displays were found to be most useful for tasks involving the manipulation of objects and for finding/identifying/classifying objects or imagery. We examine instances where S3D did not support superior task performance. We discuss the implications of our findings with regard to various fields of research concerning stereoscopic displays within the context of the investigated tasks. | Stereoscopic 3D displays and human performance: A comprehensive review |
S0141938213001054 | Dynamic images that possess beauty and are user-friendly can increase the use of digital technology. In addition to information conveyance, dynamic images also act as a communication bridge in the human–machine interface. Dynamic images are widely used in the application of digital media. Therefore, understanding the visual effects of dynamic images on viewers is a very important issue. From a visual communication design perspective, dynamic images influence not only image quality, but also the viewers’ perception and impression of the displayed image. In the contemporary age characterized by universal usage of dynamic images, designers should attain synchronized knowledge and understanding of relevant media technology so as to present preferred design quality in the management of digital design such as animation design, Web page design, multimedia design, and so on. The current study noted that psychological effects such as viewers’ visual attention, preferences, and understanding were more important than image quality. Therefore, this study adopted the viewpoint of “visual design” and conducted a perceptual evaluation of grating frequency and grating velocity. The pair-comparison method and scale method were adopted in the research methodology to simplify perceptual evaluations and enhance their validity. The purpose of this study was: (1) To propose recommendations for displaying dynamic images and improving image performance using perceptual evaluation methods. (2) To examine the influence of psychological factors on viewer’s comfort when they experience dynamic images. (3) To identify the best grating feature combinations that meet viewer’s psychological characteristics and propose recommendations for dynamic images design. The study concludes that it is useful to establish criteria for evaluating users’ perception and to, develop perceptual evaluations of dynamic images. It is recommended that designers find a balance between watching a moving imaging display “clearly” and watching it “comfortably” for successful reception by the viewer. | A perceptual evaluation of grating frequencies and velocities in the analysis of dynamic images |
S0141938213001066 | Interactive displays are becoming an increasingly popular civic engagement mechanism for collecting user feedback in urban settings. However, to date no study has investigated (i) how the situatedness of public displays affects the quantity and quality of collected feedback, and (ii) how public displays compare to traditional paper or web feedback mechanisms. We answer these research questions in a series of lab and field studies. We demonstrate that because people tend to approach this technology with no specific purpose in mind, the feedback collected with public displays is noisier than web and paper forms. However, we also show that public displays attract much more feedback than web and paper forms, and generate much more interest. Furthermore, we found that users appropriated our technology beyond its original purpose. Our analysis provides implications on the tradeoffs of using public displays as a feedback mechanism, and we discuss ways of improving the collected feedback using public displays. | Eliciting situated feedback: A comparison of paper, web forms and public displays |
S0141938214000031 | Visual discomfort is one of the most frequent complaints of the viewers while watching 3D images and videos. Large disparity and large amount of motion are two main causes of visual discomfort. To quantify this influence, three objectives are set in this paper. The first one is the comparative analysis on the influence of different types of motion, i.e., static stereoscopic image, planar motion and in-depth motion, on visual discomfort. The second one is the investigation on the influence factors for each motion type, for example, the disparity offset, the disparity amplitude and velocity. The third one is to propose an objective model for visual discomfort. Thirty-six synthetic stereoscopic video stimuli with different types of motion are used in this study. In the subjective test, an efficient paired comparison method called Adaptive Square Design (ASD) was used to reduce the number of comparisons for each observer and keep the results reliable. The experimental results showed that motion does not always induce more visual discomfort than static conditions. The in-depth motion generally induces more visual discomfort than the planar motion. The relative disparity between the foreground and the background, and the motion velocity are identified as main factors for visual discomfort. According to the subjective results, an objective model for comparing visual discomfort induced by different types of motion is proposed which shows high correlation with the subjective perception. | Visual discomfort of stereoscopic 3D videos: Influence of 3D motion |
S0141938214000043 | It has been common and popular to watch videos in moving vehicles. An important issue in developing comfortable in-vehicle video watching systems is to understand how passengers get motion sickness. With this in mind, the goals of this paper are (1) to introduce an experimental protocol and a statistical analysis procedure for quantitatively evaluating how motion-sickness is developed during car-driving, and (2) to demonstrate their practical usefulness with a working experimental study. In the experimental protocol, motion sickness was induced to subjects by requiring them to watch an in-vehicle video during 15-min driving, and the time-course development of motion sickness was recorded by asking subjects to evaluate their degree of motion sickness every one minute. A main difficulty in analyzing data from these studies is how to incorporate the individual difference in motion-sickness susceptibility. Since susceptibilities are markedly different among subjects, within-subject design experiments are preferred. However, it is practically difficult to conduct complete set of trials because subjects who are not willing to continue experiment (due to heavy motion sickness) should be able to withdraw from the subsequent series of trials in accordance with ethical requirement. To cope with this incomplete data issue, we introduce a statistical data analysis procedure that enables to estimate and impute missing entries in the within-subject design table. Using a working example, we demonstrated that the protocol and the procedure are useful for quantitative assessment of the time-course motion sickness development. We conducted an in-vehicle motion-sickness study with 31 subjects, where the time-course motion sickness developments of video-watching, book-reading, and normal riding conditions were compared. The results indicate that video-watching brings on 2.7 times more severe motion sickness than normal riding, but 25% less severe than book-reading. | Quantitative analysis of time-course development of motion sickness caused by in-vehicle video watching |
S0141938214000055 | The present study investigates the effects of relative positions of stereoscopic objects (PSO) (‘Far’ (from viewers) vs. ‘Near’ (to viewers) vs. ‘Both’) and seat location on viewers’ psychological responses. People who watched a movie with ‘Both’ conditions reported more arousal and satisfaction compared to people who watched a movie with either the ‘Far’ or ‘Near’ condition. More importantly, interaction effects were reported such as more dizziness (a) with the ‘Near’ condition if sitting on the left or right side in the cinema and (b) with the ‘Far’ condition if sitting in the middle of the cinema. Additionally, people who wore glasses felt more eye fatigue than those who did not. Secondly, people felt less presence, sensation of depth, and arousal if they had prior experience viewing stereoscopic movies. The results indicate that viewing experience with different PSOs and/or seat locations can influence psychological response. | Effects of stereoscopic movies: The positions of stereoscopic objects and the viewing conditions |
S0141938214000067 | This paper proposes a power-efficient drive circuit for plasma display panels (PDPs). The proposed circuit reduces reactive power consumption by varying the inductance for energy recovery and by separating the grounds of the sustain and data drivers. Power consumption due to discharge current is reduced by using two soft-switching inductors for the pull-up switches in the bridge circuit. Power consumption for data addressing is reduced by using a dc voltage source to bias the ground for the sustain driver. The proposed circuit was tested on a 50″ full-HD single-scan PDP which had a sustain discharge gap of 80μm; total power consumption to display the dynamic broadcasting content of IEC 62087 was ∼40W (14.5%) less than that required by the conventional drive circuit, and the EMI level for 2< f <9MHz was reduced significantly. The experimental results demonstrate that a high performance power-efficient PDP drive circuit can be built using the proposed method. | Power-efficient drive circuit for plasma display panel |
S0141938214000079 | Phosphorescent white organic light-emitting diodes (WOLEDs) based on single doped platinum(II) [1,3-difluoro-4,6-di(2-pyridinyl)benzene] chloride (Pt-4) emission layers were investigated in this paper. The devices exhibited electroluminescence spectra composed of bluish (λ max =480nm) and reddish (λ max =660nm) emission bands, which corresponding to monomer and excimer emission originated from Pt-4 dopants. With optimized device structures, a maximum current efficiency of 11.5cd/A was obtained and remained above 10cd/A even the brightness was over 6000cd/m2. Furthermore, by integrating the fac-tris(2-phenylpyridine) iridium(III) as a complementary emitter and an additional 2,2′,2″-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole) space layer, the device efficiency was further improved, which exhibited a maximum current efficiency of 20.4cd/A at the luminance of 100cd/m2, and maintained the mild efficiency roll-off that similar to its single Pt-4 doped counterpart. | Doping effect of Ir(ppy)3 on white-light electrophosphorescent devices based on platinum(II) [1,3-difluoro-4,6-di(2-pyridinyl)benzene] chloride |
S0141938214000171 | We investigated green phosphorescent organic light-emitting diodes (PHOLEDs) with charge control layer (CCL) to produce high efficiency and improve operational lifetime. Three types of devices were fabricated following the number of CCL within emitting layer (EML), maintaining the thickness of whole EML. The CCL and host material, which was 4,4′-bis (carbazol-9-yl)biphenyl (CBP) with bipolar property, can control carrier movement in EML. Therefore, the electroluminescent (EL) performance improvement as efficiency and lifetime was realized with a good charge balance, an effective triplet exciton confinement, and the reduced triplet exciton quenching effect in EML. Device 2 with a CCL as exciton distribution structure exhibits the remarkable EL performances for the maximum luminous and external quantum efficiency of 65.34cd/A and 20.42%, respectively. Moreover, operational lifetime is nearly improved 2.5 times than the conventional device. | Improved efficiency and lifetime for green phosphorescent organic light-emitting diodes using charge control layer |
S0141938214000183 | Common projection optics use Köhler illumination to achieve a required lighting. These systems always prevent the realization of a compact optical configuration along with a high lumen output. Based on conventional Köhler illumination, a modified Köhler illumination system for LED-based projection display is presented in this paper, which can significantly reduce the system volume while allowing for adequate and homogeneous illumination. Equipped with the proposed system, a pocket-sized CF-LCoS projector with a physical dimension of 27.4mm×19.4mm×9.6mm is designed, simulated and analyzed. Compared to conventional approaches, this design could offer an average 43% volume reduction with acceptable tolerance. To the best of our knowledge, the screen uniformity of 90.2% and the light efficiency of 56.5% are competitive as compared with those of the currently commercialized pocket-sized CF-LCoS projectors. | Modified Köhler illumination for LED-based projection display |
S0141938214000195 | The aim of the study was to investigate the effect of various character and background colour combinations on cognitive performance during onscreen searching tasks and to identify the best combinations with a multimodal approach of physiological (eye movement recording), subjective and performance data collection. In the absence of proper character and background colour combination the optimum performance for a cognitive task is greatly affected which in turn affects the productivity of the individual worker or communications among the operators working under the same network through information sharing. This study was designed by selecting six colours, i.e., white, black, yellow, red, blue, and green and subsequently combining them to 16 character and background colour combinations for a searching task. Right and left headed arrows were used as the character for the searching maneuver. Forty-four (N =44) volunteers participated in the experiments. Various eye movement variables, legibility rating scale, NASA-TLX questionnaire, searching time and percentage of error were recorded. Subjects performed better wherever a good contrast was there because of a high legibility. A poorly contrasted display affected the physiological variables as well as subjective responses to negative directions. Among the combinations of dark character/light background, blue and red character on white background is highly recommended; and while that for light character/dark background, white is found to be the best character on blue and green backgrounds. | Selection of character/background colour combinations for onscreen searching tasks: An eye movement, subjective and performance approach |
S0141938214000286 | It has been shown that multisensory presentation can improve perception, attention, and object memory compared with unisensory presentation. Consequently, we expect that multisensory presentation of landmarks can improve spatial memory and navigation. In this study we tested the effect of visual, auditory and combined landmark presentations in virtual mazes on spatial memory and spatial navigation. Nineteen participants explored four different virtual mazes consisting of nodes with landmarks and corridors connecting them. Each maze was explored for 90s. After each exploration, participants performed the following tasks in fixed order: (1) draw a map of the maze, (2) recall adjacent landmarks for three given landmarks, (3) place all landmarks on the map of the maze, and (4) find their way through the maze to locate five given landmarks in fixed order. Our study shows significant effects of multisensory versus unisensory landmarks for the maze drawing task, the adjacency task, and the wayfinding task. Our results suggest that audiovisual landmark presentations improve spatial memory and spatial navigation performance in virtual environments. | Navigating virtual mazes: The benefits of audiovisual landmarks |
S0141938214000298 | This paper proposes a novel pixel circuit for high resolution, high frame rate, and low power AMOLED displays that is implemented with one driving n-channel TFT, six switching n-channel poly-Si TFTs, and a storage capacitor. The proposed pixel circuit adopts the voltage programming scheme for threshold voltage compensation. Because the whole line time is in use only for charging the data voltage, this pixel circuit is applicable to high resolution and frame rate displays. In addition, it compensates voltage variation of OLEDs and voltage drop of supply lines at lower power consumption. On the average, the non-uniformity of a proposed circuit is reduced to 2.5%, compared to 7.1% of the previous one at a 240Hz full-HD display. On the other hand, the compensation voltage error, which is caused by feed-through and charge injection noises from falling control signals of switching TFTs, is much less in the proposed scheme than in the previous 5T2C structure. The average error of the proposed circuit is reduced to 0.18V, compared to 0.75V of the previous one. The initialization power consumption of the 7T1C circuit is reduced to 98mW, compared to 530mW of the 5T2C circuit and the average dynamic power saving ratio of data drivers is estimated in the 7T1C pixel as 98.7% over the 5T2C one for 24 test images. | Novel voltage programming n-channel TFT pixel circuit for low power and high performance AMOLED displays |
S0141938214000304 | A series of Bi3+ and Gd3+ doped ZnB2O4 phosphors were synthesized with solid state reaction technique. X-ray diffraction technique was employed to study the structure of prepared samples. Excitation and emission spectra were recorded to investigate the luminescence properties of phosphors. The doping of Bi3+ or Gd3+ with a small amount (no more than 3mol%) does not change the structure of prepared samples remarkably. Bi3+ in ZnB2O4 can emit intense broad-band purplish blue light peaking at 428nm under the excitation of a broad-band peaking at 329nm. The optimal doping concentration of Bi3+ is experimentally ascertained to be 0.5mol%. The decay time of Bi3+ in ZnB2O4 changes from 0.88 to 1.69ms. Gd3+ in ZnB2O4 can be excited with 254nm ultraviolet light and yield intense 312nm emission. The optimal doping concentration of Gd3+ is experimentally ascertained to be 5mol%. The decay time of Gd3+ in ZnB2O4 changes from 0.42 to 1.36ms. | Synthesis of Bi3+ and Gd3+ doped ZnB2O4 for evaluation as potential materials in luminescent display applications |
S0141938214000316 | In order to understand the effect of hole injection on the performance of organic light-emitting diodes (OLEDs) with electron- and hole-type hosts used in the emissive layer, we fabricated OLEDs based on a green fluorescent 10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-(1)benzopyropyrano(6,7-8-I,j)quinolizin-11-one (C545T) with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and MoO3 as the hole injection layer, respectively. Here, N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB) and tris-(8-hydroxyquinoline) aluminum (Alq3) are, respectively, used as the host in the emissive layer for comparison. It is clearly found that different hole injection layers play different roles in the adjustment of the electron/hole injection and the transport balance, thus the different hosts are needed in the emissive layer for high electroluminescence efficiency OLEDs. This means that the selection of appropriate hole injection layers for OLEDs according to the different hosts in the emissive layer is especially important in the fabrication of high efficiency single emissive layer OLEDs. | Effect of PEDOT:PSS vs. MoO3 as the hole injection layer on performance of C545T-based green electroluminescent light-emitting diodes |
S0141938214000328 | The spectral analysis of Heart Rate Variability (HRV) can be used for assessing the autonomic nervous activities and further the physiological conditions of subjects. This study intended to explore whether or not people would have fatigue, faintness and other kinds of uncomfortable conditions after watching a 3D film by using HRV measures as the objective physiological indices, in addition to other subjective physiological indices. Twenty men aged 22±2 experienced watching 3D films and 2D films and were served as the controls of themselves. As the controls, the subjects had to rest at the same place. All subjects were are randomized for taking different experiences, and the electrocardiographic (ECG) signals were recorded during the whole process. The researchers could obtain the indices of the autonomic nervous activities before and after experiencing 3D and 2D movies with the help of spectral HRV analyses, along with the objective physiological information. The subjects were requested to fill out the questionnaire for the subjective feelings after the movie experiences. It was found that the subjects’ high-frequency power (HFP) representing parasympathetic nervous activities decreases after watching a 3D film. The sympathetic and parasympathetic nerve activities before and after watching a 2D film were not significantly different. The subjects complained that they felt dizzy, had headaches, and got visual fatigue while watching a 3D film. This study found that the subjects’ parasympathetic nerve activities were reduced after watching a 3D film, indicating that watching a 3D film would make people uncomfortable and tired. This result was the same as that of the questionnaire. Thus, HRV analyses could be an objective physiological index for discomfort as viewing 3D films. | The influence of polarized 3D display on autonomic nervous activities |
S0141938214000341 | In this study, we explored how stereoscopic depth affects performance and user experience in a mobile device with an autostereoscopic touch display. Participants conducted a visual search task with an image gallery application on three layouts with different depth ranges. The task completion times were recorded, and the participants were asked to rate their experiences. The results revealed that the image search times were facilitated by a mild depth effect and that too great a depth slowed search times and decreased user-experience ratings. | Enhanced user performance in an image gallery application with a mobile autostereoscopic touch display |
S0141938214000353 | We investigate the effect of the metal pattern shape (i.e., square, hexagonal, and random grids) on the starburst phenomenon of touch screen panels (TSPs) based on opaque metallic grids. It is demonstrated that a standalone random metal grid can suppress the starburst phenomenon to a great extent. By way of ray tracing simulation, we have found that specular reflection of light on the gentle slope of the patterned edges of metallic grids contributes to the generation of starburst patterns. It is also addressed that employing a light-absorbing material and increasing metal grid spacing can reduce the intensity of starburst patterns. | Investigation of starburst phenomenon using ray tracing for touch screen panels |
S0141938214000365 | This study investigates impacts of oxygen flow during the deposition of amorphous indium–gallium–zinc oxide (a-IGZO) channel layer with a radio frequency (r.f.) magnetron sputter on the electrical characteristics of the fabricated thin-film transistors (TFTs). Results indicate that as the film was deposited with a higher oxygen flow, the transfer curves are positively shifted while the field-effect mobility (μ FE) is significantly decreased. To get more insight about the effects, channel resistance (R CH) and the parasitic source-to-drain resistance (R SD) of the fabricated devices are extracted using the total resistance method. The extracted a-IGZO channel resistance per unit length (r ch) and RSD are found to increase while the extracted effective mobility (μE ) is decreased with increasing oxygen flow during sputtering. These observations are postulated to be related the decrease in the In/(In+Ga+Zn) ratio and the increase in the Zn/(In+Ga+Zn) ratio of the a-IGZO films with increasing the oxygen flow rate which lead to higher resistivity and lower carrier concentration. The extracted RSD can be comparable with R CH for the devices prepared with high oxygen flow, resulting in the roll-off of μ FE as the channel length is shorter than 20μm. | Electrical characteristics of amorphous In–Ga–Zn–O thin-film transistors prepared by radio frequency magnetron sputtering with varying oxygen flows |
S0141938214000377 | We demonstrated an optimized 8-domain vertical aligned (VA) liquid crystal display (LCD) by minimizing its color washout. The index G is adopted to analyze the degree of color washout through simulation. By using linearly and circularly polarized incident light, the optimized regime of the area and applied voltage ratios of sub-pixels is obtained. In the experiments with the circularly polarized light, the images are sensuously improved in a coupled capacity type LCD by applying the simulated applied voltage ratio of two sub-pixels. | Evaluating and improving color washout of vertical aligned liquid crystal display |
S0141938214000389 | The article investigates how the various colors and color pairs used as grouping factors affect the visual search process and direct manipulation activities in the context of toolbar-like graphical panels. Red, green, and blue colors having the same perceptual distance in the CIELab space are used. The results demonstrate significant influence of the examined color-related factors on the speed and accuracy. The color preattentive property depends strongly on the grouping pattern: layouts with smaller colored areas were operated worse than panels divided into larger parts. Meaningful differences were also observed between panels with single and two colored backgrounds. Preferences were examined by pairwise comparisons before and after performing the ‘search and select’ tasks. Subjective judgments were significantly differentiated by the toolbar background color pattern both prior to the performance tasks and after them. The initial relative weights structure changed decidedly after the performance experience being more consistent with the ‘search and select’ results. The location factor was irrelevant for the speed and accuracy as well as for preferences. Objective and subjective findings are compared and discussed. Linear regression models showing the preference structure change and the relationship between mean acquisition times and mean preference weights are developed and discussed. | The influence of color grouping on users’ visual search behavior and preferences |
S0141938214000390 | This paper presents a new three-dimensional (3-D) display that can display 3-D images at long distances of tens or hundreds of meters in the depth direction and that can control their 3-D positions to meet new requirements for outdoor use. The proposed display uses changing size as a cue to depth perception, i.e., the smoothly expanding motion of virtual images formed with optical systems according to the forward movements of the users to display 3-D images at more distant positions in the depth direction than positions where virtual images are formed with optical systems because conventional 3-D displays that use binocular disparity are only able to display 3-D images at short distances in the depth direction. The feasibility of the proposed display was evaluated by subjective tests using a moving minivan in which observers viewed a test pattern that overlapped the real view ahead of the automobile observed through the windshield. The results obtained from the subjective tests revealed that the test pattern was observed at long distances over tens and hundreds of meters in the depth direction and that the position in the depth direction of the test pattern could be controlled by changing the rate at which the motion of the test pattern smoothly expanded. These results demonstrated that the proposed display was feasible. | New 3-D display that can display 3-D images at long distances and that can control their 3-D positions using changing size as a cue to depth perception |
S0141938214000407 | This research investigated whether carrying red-colored products enhances female sexual attractiveness. In the first experiment, male participants were instructed to observe women carrying laptops in different colors (black, silver, red, or blue). The results indicated that the women who carried red laptops were perceived to possess a significantly higher level of attractiveness and sex appeal than those who carried laptops in other colors; however, the red laptop did not affect men’s perceptions of the assertiveness and health level of the women. In the second experiment, the initial experiment was repeated but female participants observed the women; laptop color did not influence how the participants perceived the women’s attractiveness, sex appeal, assertiveness, and level of health. In other words, women carrying products in red only affected how men, but not women, perceived them; thus, women using red products are more attractive and sexually appealing to men. | Red-colored products enhance the attractiveness of women |
S0141938214000419 | Previous studies on stereoscopic acuity have shown that the percentage of stereo blind subjects is relevant. Moreover, stereoscopic visualization is becoming widely diffused in different fields, like, e.g., entertainment, surgery or VR training, where it is necessary an accurate assessment of stereoscopic abilities of the involved subjects. Therefore, there might be the need of performing a stereo blindness and stereo acuity test before each visualization session involving stereoscopic images. In this paper, we propose a method to assess stereo acuity and stereo blindness directly on the chosen device, under the same visualization condition and setup adopted for the tasks to perform, in order to have the same perceptual response. We present software-based tests suitable for a generic stereoscopic displays, and we compare their effectiveness performing a comparison with a standard physical, card-based, test commonly used in assessment of stereo acuity and stereo blindness. We provide to the reader all the details to perform autonomously the tests, of which images will be downloadable from web. | Assessing stereo blindness and stereo acuity on digital displays |
S0141938214000481 | The TiO2 coated silicate micro-spheres (SMS) core–shell particles (SMS@TiO2) were synthesized using the sol–gel reaction followed by calcination. The SMS@TiO2 particles were used to enhance the light diffusion property of polycarbonate (PC) composites. Our experimental analysis shows that the TiO2 was coated on the SMS particles and the optimum parameters of the reaction were 4:1 of the Si/Ti molar ratio and 500°C of the calcination temperature. The UV–Vis spectra indicate that SMS@TiO2 can absorb or hinder the UV light, which may prolong the service life of PC light diffusion materials. Compared to that of PC composites physically mixed with SMS+TiO2, the haze of the PC/SMS@TiO2 composites was little affected, while the transmittance was obviously enhanced, which can be increased from 55.5% for PC/TiO2/SMS to 70.3% for PC/SMS@TiO2 with only 0.6wt% filler loading. | Preparation of TiO2 coated silicate micro-spheres for enhancing the light diffusion property of polycarbonate composites |
S0141938214000493 | A method for estimating the non-linear gamma transfer function of liquid–crystal displays (LCDs) without the need of a photometric measurement device was described by Xiao et al. (2011) [1]. It relies on observer’s judgments of visual luminance by presenting eight half-tone patterns with luminances from 1/9 to 8/9 of the maximum value of each colour channel. These half-tone patterns were distributed over the screen both over the vertical and horizontal viewing axes. We conducted a series of photometric and psychophysical measurements (consisting in the simultaneous presentation of half-tone patterns in each trial) to evaluate whether the angular dependency of the light generated by three different LCD technologies would bias the results of these gamma transfer function estimations. Our results show that there are significant differences between the gamma transfer functions measured and produced by observers at different viewing angles. We suggest appropriate modifications to the Xiao et al. paradigm to counterbalance these artefacts which also have the advantage of shortening the amount of time spent in collecting the psychophysical measurements. | Limitations of visual gamma corrections in LCD displays |
S0141938214000584 | Large screens have become more popular in recent years. Because of the increasing size of displays, the amount of information presented in the peripheral visual field has gained importance in many tasks on visual display units. Users of displays are often exposed to some change or difference in luminance in or between different areas of a display, which in turn may produce a phenomenon known as discomfort glare. Discomfort glare is likely to affect cognitive performance. The performance in the visual periphery is more susceptible to disturbances as is the case for the performance in the central visual field. This study explored the effects of discomfort glare on detecting and processing peripheral visual information in a complex visual task. The task consisted of comparing the orientation of arrows presented in the central visual field and at 18° in the periphery. The arrows were superimposed on a background video and presented by a projection system in virtual reality. 50% of the presentations were preceded by a mild glare scene with a luminance of 25cd/m2 flashed prior to the stimulus. Experimental results of 56 participants were analyzed using the theory of signal detection. A significant difference (two-tailed t-test p =0.01) in detectability of stimuli (d′glare =1.87; d′no glare =2.11; Δd′=0.24) was obtained when comparing the performance in the two situations of glare. Results show that discomfort glare impairs peripheral visual performance in attending stimuli in a virtual reality environment. We therefore propose to consider discomfort glare as a factor affecting performance in detecting peripheral visual information. Discomfort glare should be included as a quality criterion in rating visual information, as is done in present standards of displays and lighting. | Effects of discomfort glare on performance in attending peripheral visual information in displays |
S0141938214000596 | A novel MEMS display device comprising a light separator and MEMS light shutters is introduced. This device is operable both in transmissive mode using internal light source and in reflective mode using external sun light. In transmissive mode, the light separator directs internal backlight illuminated on its incident surface into a plural of small openings (grooves) on the viewing surface. The MEMS light shutters are used to control the color and intensity of light at individual pixels. Internal light utilization efficiency of this display is the greatest compared to any other transmissive displays. The device is capable of having true black background, hence a very high contrast ratio. In reflective mode, MEMS shutters direct part of the sun light for image display. MEMS shutters have fast response time, making the new device suitable for vivid motion picture display, and operable at very low voltages, suitable for mobile device applications. | Transmission and reflection dual operational mode MEMS display device |
S0141938214000602 | Reliability of MEMS (MicroElectroMechanical-Systems) devices is a crucial aspect as it can discriminate the successful from partially or totally missed reaching of Microsystem technology based market products. However, the topic of MEMS reliability is significantly articulated, as it comprises numerous physics of failure and diverse failure mechanisms. Thereafter, it requires a pronounced sensitivity related to the actual operation conditions (environmental and functional) of the Microsystem device within the final application. In other words, reliability of MEMS is nowadays regarded as a standalone transversal discipline that must be seriously taken into account already from the early design phase. The purpose of this paper is to provide the reader at first with basic knowledge around the concept of reliability. Thereafter, the most relevant physics of failure and failure mechanisms typical of MEMS are grouped and briefly discussed, with specific attention to their employment in the field of displays. A synthetic review of valuable solutions to improve specific reliability aspects of MEMS devices for diverse applications is then proposed to the reader. Eventually, a brief discussion focused on best practices to address properly reliability during the whole development chain of innovative MEMS based products completes the contribution. It is a belief of the author that the particular blend of topics and aspects reported in the following pages, as well as the attitude of considering reliability as a transversal discipline of science, contribute to provide this contribution with an important benefit if compared to the reviews on reliability of MEMS previously published in literature. | Reliability of MEMS: A perspective on failure mechanisms, improvement solutions and best practices at development level |
S0141938214000614 | This paper presents an optimized fabrication method for developing a freestanding bridge for RF MEMS switches. In this method, the sacrificial layer is patterned and hard baked a 220°C for 3min, after filling the gap between the slots of the coplanar waveguide. Measurement results by AFM and SEM demonstrate that this technique significantly improves the planarity of the sacrificial layer, reducing the uneven surface to less than 20nm, and the homogeneity of the Aluminum thickness across the bridge. Moreover, a mixture of O2, Ar and CF4 was used and optimized for dry releasing of the bridge. A large membrane (200×100μm2) was released without any surface bending. Therefore, this method not only simplifies the fabrication process, but also improves the surface flatness and edge smoothness of the bridge. This fabrication method is fully compatible with standard silicon IC technology. | Characterization and optimization to improve uneven surface on MEMS bridge fabrication |
S0141938214000626 | Recombination zone and Förster resonance energy transfer (FRET) in multilayer organic light-emitting diodes (OLEDs) were investigated. Basis device architecture is indium tin oxide (ITO)/N, N′-diphenyl-N, N′-bis(1-naphthyl-phenyl)-1, 1′-biphenyl-4, 4′-diamine (NPB)/4-(dicyanomethylene)-2-tert-butyl-6-(1, 1, 7, 7- tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB)/NPB (spacer)/tris-(8-hydroxyl quinoline) aluminum (Alq3)/2, 9-dimethyl-4, 7-diphenyl-1, 10-phenanthroline (BCP)/Al. Exciton recombination zone is located at DCJTB and Alq3 layers. When the NPB spacer is 10-nm-thick, Alq3 emission governs in electroluminescent (EL) spectra owing to absence of FRET between DCJTB and Alq3. FRET occurs while the NPB spacer is 5-nm-thick and thus DCJTB emission is dominant in EL spectra. As the emissive layout of DCJTB/Alq3/NPB substitutes for DCJTB/NPB/Alq3, both DCJTB and NPB emissions are observed due to electron-blocking effect of NPB. | Effects of emissive layer architecture on recombination zone and Förster resonance energy transfer in organic light-emitting diodes |
S0141938214000638 | Stereoscopic 3D television (S3D TV) is now available in the home. However, little published information is available on viewer use or experience. In this study, 120 people from 29 households were given a new TV (active or passive stereoscopic 3D, or conventional 2D) and reported on their television viewing and other screen use on a near-daily basis over 8weeks. People reported enjoying S3D TV and cinema more than TV and cinema in general, but enjoying S3D video games less than video games in general. S3D TV and video games were both associated with an increased, though still low (∼10%) level of adverse effects, such as headache and eyestrain. I speculate that this may be because video games present a particularly strong conflict between vergence and accommodative demand. | Viewer experience with stereoscopic 3D television in the home |
S0141938214000651 | We report a screen-printing fabrication process for large area electrowetting display (EWD) devices using polyimide-based materials. The poly(imide siloxane) was selected as hydrophobic insulator layer, and relatively hydrophilic polyimide as grids material. EWD devices that use poly(imide siloxane) as hydrophobic insulator fabricated with conventional methods showed good and reversible electrowetting performance on both single droplet level and device level, which showed its potential application in EWDs. The compatibility of polyimide-based materials (hydrophobic poly(imide siloxane) and hydrophilic polyimide) guarantee the good adhesion between two layers and the capability of printable fabrication. To this end, the hydrophilic grids have been successfully built on hydrophobic layer by screen-printing directly. The resulting EWD devices showed good switch performance and relatively high yield. Compared to conventional method, the polyimide-based materials and method offer the advantages of simple, cheap and fast fabrication, and are especially suitable for large area display fabrication. | Screen-printing fabrication of electrowetting displays based on poly(imide siloxane) and polyimide |
S0141938214000663 | Electrowetting display (EWD) is a reflective display technology in which fluidic pixels can response and switch quickly by electronic control, showing the capability for video-speed reflective display applications. In this paper, a new driver system is proposed and realized for video playing function of active matrix electrowetting display (AM-EWD). The hardware system is designed based on Field-Programmable-Gate-Array (FPGA) and the existing electrophoretic display (EPD) driving integrated chips (IC). A driving logic circuit and FPGA software is introduced for providing the EWD system with driving and timing control. And a set of specific driving waveforms, which is loaded to a lookup table of the FPGA in advance, is designed to display grayscale on EWDs. 4-level gray scale videos have been successfully performed by applying the driving waveforms. To our knowledge, such work has not been reported before. | A novel driver for active matrix electrowetting displays |
S0141938214000675 | A series of Sm3+ and Dy3+ doped LaBWO6 phosphors were synthesized by high temperature solid state reaction. Recorded XRD patterns proved that the titled compound in a single phase has been obtained. Sm3+ and Dy3+ doped LaBWO6 could emit orange and white light, respectively. The optimal doping concentration of Sm3+ or Dy3+ was experimentally ascertained to be 6mol%. The critical distance of energy transfer for Sm3+ or Dy3+ doped sample is 1.540nm. In addition, there is no cross energy transfer between the Sm3+ and Dy3+ ions in the co-doped samples. The results indicated that the electric dipole–dipole interaction is predominant energy transfer mechanism for concentration quenching of Sm3+ or Dy3+ doped LaBWO6 phosphor. The charge transfer band was observed in the excitation spectra of Sm3+ or Dy3+ doped LaBWO6 phosphors. Present investigation indicated that Sm3+ and Dy3+ doped LaBWO6 can be applied in solid state lighting and LaBWO6 is a promising host for display applications. | Synthesis of Sm3+ and Dy3+ doped LaBWO6 for evaluation as potential materials in luminescent display applications |
S0141938214000687 | Dysprosium doped di-strontium magnesium di-silicate namely Sr2MgSi2O7:Dy3+ phosphor was prepared by the solid state reaction method. The phase structure, surface morphology, particle size, elemental analysis was analyzed by using XRD, TEM, EDX and FTIR techniques. The EDX and FTIR spectra confirm the present elements in Sr2MgSi2O7:Dy3+ phosphor. The optical properties of Sr2MgSi2O7:Dy3+ phosphor was investigated utilizing thermoluminescence (TL), photoluminescence (PL), long lasting phosphorescence and mechanoluminescence (ML). Under the ultraviolet excitation, the emission spectra of Sr2MgSi2O7:Dy3+ phosphor are composed of a broad band and the characteristic emission of Dy3+ peaking at 470nm (blue), 575nm (yellow) and 678nm (red), originating from the transitions of 4F9/2 → 6H15/2, 4F9/2 → 6H13/2 and 4F9/2 → 6H11/2. CIE color coordinates of Sr2MgSi2O7:Dy3+ are suitable as white light emitting phosphor. Decay graph indicate that this phosphor also contains fast decay and slow decay process. The peak of ML intensity increases linearly with increasing impact velocity of the moving piston. The possible mechanism of this white light emitting long lasting phosphor is also investigated. | Dysprosium doped di-strontium magnesium di-silicate white light emitting phosphor by solid state reaction method |
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