###### Accueil » Publications dans le domaines des technologies » 10-2017
 Pages: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
 Publications dans les journaux scientifiques dans le domaine de l'ingénierie : 10-2017 trié par par titre, page: 5
» Device-Free WiFi Human Sensing: From Pattern-Based to Model-Based Approaches
 Résumé:Recently, device-free WiFi CSI-based human behavior recognition has attracted a great amount of interest as it promises to provide a ubiquitous sensing solution by using the pervasive WiFi infrastructure. While most existing solutions are pattern-based, applying machine learning techniques, there is a recent trend of developing accurate models to reveal the underlining radio propagation properties and exploit models for fine-grained human behavior recognition. In this article, we first classify the existing work into two categories: pattern-based and model-based recognition solutions. Then we review and examine the two approaches together with their enabled applications. Finally, we show the favorable properties of model-based approaches by comparing them using human respiration detection as a case study, and argue that our proposed Fresnel zone model could be a generic one with great potential for device-free human sensing using fine-grained WiFi CSI. Auteurs: Dan Wu;Daqing Zhang;Chenren Xu;Hao Wang;Xiang Li; Apparue dans: IEEE Communications Magazine Date publication: 10.-2017, volume: 55, issue:10, pages: 91 - 97 Editeur: IEEE Document complet vers site de l'éditeur
» DEXTRA: A Fast Algorithm for Optimization Over Directed Graphs
 Résumé:This paper develops a fast distributed algorithm, termed DEXTRA, to solve the optimization problem when $n$ agents reach agreement and collaboratively minimize the sum of their local objective functions over the network, where the communication between the agents is described by a directed graph. Existing algorithms solve the problem restricted to directed graphs with convergence rates of $O(\ln k/\sqrt{k})$ for general convex objective functions and $O(\ln k/k)$ when the objective functions are strongly convex, where  $k$ is the number of iterations. We show that, with the appropriate step-size, DEXTRA converges at a linear rate $O(\tau ^{k})$ for $0<\tau <1$ , given that the objective functions are restricted strongly convex. The implementation of DEXTRA requires each agent to know its local out-degree. Simulation examples further illustrate our findings. Auteurs: Chenguang Xi;Usman A. Khan; Apparue dans: IEEE Transactions on Automatic Control Date publication: 10.-2017, volume: 62, issue:10, pages: 4980 - 4993 Editeur: IEEE Document complet vers site de l'éditeur
» DI2S Multiswath Innovative Technique for SAR Acquisitions Optimization
 Résumé:The DIscrete stepped strip (DI2S) technique (actually patent pending) introduces an innovative method to use a synthetic aperture radar in time-sharing allowing the acquisition of different images either to increase azimuth resolution (DI2S-improved resolution) or to have a multi-image system improving the system capability and flexibility (DI2S multiswath). In this letter, the approach used by the DI2S multiswath technique will be described highlighting the main advantages in terms of performance and application. Auteurs: Diego Calabrese;Vanessa Mastroddi;Stefano Federici; Apparue dans: IEEE Geoscience and Remote Sensing Letters Date publication: 10.-2017, volume: 14, issue:10, pages: 1820 - 1824 Editeur: IEEE Document complet vers site de l'éditeur
» Different Modular Techniques Applied in a Synchronous Boost Converter With SiC MOSFETs to Obtain High Efficiency at Light Load and Low Current Ripple
 Résumé:This paper is focused on a high-voltage (400 to 800 V) bidirectional converter, which is intended to be used for the interconnection of battery-based energy-storage systems with the cells of a modular multilevel converter, providing distributed energy-storage capability to a solid-state transformer. This converter must have a high efficiency at medium and light load and also a low current ripple due to the charging and discharging processes. This work takes advantage of the use of SiC MOSFETs into a synchronous boost converter to accomplish the previous requirements. First, the adoption of a variable-switching frequency control to keep the efficiency high is analyzed, and second, the use of a modular converter with different control techniques to provide a current ripple reduction is also addressed in this study. An input-parallel-output-parallel synchronous boost converter, made up with three modules (3 kW per module), is used to validate experimentally the advantages of the use of SiC MOSFETs and to compare different control techniques. Auteurs: Aitor Vazquez;Alberto Rodriguez;Maria R. Rogina;Diego G. Lamar; Apparue dans: IEEE Transactions on Industrial Electronics Date publication: 10.-2017, volume: 64, issue:10, pages: 8373 - 8382 Editeur: IEEE Document complet vers site de l'éditeur
» Differential Protection in Low-Voltage Buses: An Exploration of Principles and Models
 Résumé:Current-differential principles are well known and commonly used for the protection of medium and large transformers, large motors, medium-voltage (MV) generators, MV and high-voltage buses, and any type of important power equipment with measurable input and output currents. However, is it practical to protect low-voltage (LV) distribution buses using differential protection? This article describes bus differential protection principles as well as interlocking principles for overcurrent protection. We discuss specific issues in applying differential protection in LV systems. Additionally, we present a concept of partial differential (PD) protection, which can be used in conjunction with zone-selective interlocking (ZSI) or as backup to traditional overcurrent protection to achieve high-speed and selective fault clearance. Additional concepts for the implementation of bus differential protection using networked data in LV systems are introduced. Auteurs: Lubomir Sevov;Marcelo Valdes; Apparue dans: IEEE Industry Applications Magazine Date publication: 10.-2017, volume: 23, issue:5, pages: 28 - 39 Editeur: IEEE Document complet vers site de l'éditeur
» Digital Predistortion of an RF Power Amplifier Using a Reduced Volterra Series Model With a Memory Polynomial Estimator
 Résumé:A technique for reducing the number of basis waveforms used in a Volterra series model for digital predistortion (DPD) of radio frequency power amplifiers is proposed. An effective delay is defined for each basis waveform. The DPD model is constrained so that the basis waveforms used have unique delays. When several of the original Volterra terms have a common delay, they are either grouped together to form a single basis waveform or pruned to discard all but the dominant term. It is shown that grouping and pruning produce similar ACLR results when the coefficient estimator notch filters the linear signal bandwidth and applies regularization. Unique delay DPD basis sets are compatible with a fractionally sampled memory polynomial estimator. The basis waveforms within the estimator are specified in the frequency domain as a function of memoryless waveforms and delay operators, thereby reducing the number of fast Fourier transforms needed and allowing for fractional tap spacing that matches the effective delays of Volterra basis waveforms used within the DPD basis set. The approximation associated with using a memory polynomial estimator is sufficiently accurate for a closed-loop estimator to converge to a desired steady state. Auteurs: R. N. Braithwaite; Apparue dans: IEEE Transactions on Microwave Theory and Techniques Date publication: 10.-2017, volume: 65, issue:10, pages: 3613 - 3623 Editeur: IEEE Document complet vers site de l'éditeur
» Digital Predistortion Parameter Identification for RF Power Amplifiers Using Real-Valued Output Data
 Résumé:This brief presents a novel digital predistortion parameter identification technique that requires only the acquisition of either the in-phase (I) or the quadrature (Q) component of the power amplifier output signal. To this end, an approach that allows us to estimate the parameters of a model using only one of the IQ components of the model output is presented. Based on experimental results, it is shown that the proposed real-valued measurements-based technique can offer linearization capabilities similar to its complex-valued counterparts. The experimental results also indicate that the proposed technique can be used in combination with other techniques that focus on reducing the speed of analog-to-digital converters. Auteurs: Jessica Chani-Cahuana;Mustafa Özen;Christian Fager;Thomas Eriksson; Apparue dans: IEEE Transactions on Circuits and Systems II: Express Briefs Date publication: 10.-2017, volume: 64, issue:10, pages: 1227 - 1231 Editeur: IEEE Document complet vers site de l'éditeur
» Digitally Controlled Analog Cancellation for Full Duplex Broadband Power Line Communications
 Résumé:Although in-band full-duplexing (IBFD) has long been implemented in various communication media, it was only recently that an IBFD solution was presented for broadband power line communications (BB-PLCs). The maximum attainable echo suppression using this solution is, however, limited by the dynamic range of the analog-to-digital converter (ADC). To counter this critical constraint, we propose echo cancellation in the analog domain, while persisting with a low-complexity frequency domain digital echo estimation. By formulating an expression for the number of ADC bits lost in IBFD over a conventional half-duplex operation, we show that the ADC dynamic range is no longer a limiting factor for our solution. We further extend our solution to present an analog cancellation method for multiple-input multiple-output IBFD BB-PLC systems. Finally, we present simulation results of echo cancellation and data rate gains obtained under realistic in-home BB-PLC settings, to demonstrate that our solution is capable of doubling bidirectional transfer rates in a large number of the tested network conditions. Auteurs: Gautham Prasad;Lutz Lampe;Sudip Shekhar; Apparue dans: IEEE Transactions on Communications Date publication: 10.-2017, volume: 65, issue:10, pages: 4419 - 4432 Editeur: IEEE Document complet vers site de l'éditeur
» Direct Measurements of Sediment Sound Speed and Attenuation in the Frequency Band of 2–8 kHz at the Target and Reverberation Experiment Site
 Résumé:The sediment acoustic-speed measurement system is designed to measure in situ sediment sound speed and attenuation within the surficial 3 m of sediments in the frequency band of 2–8 kHz. Measurements were carried out during the Target and Reverberation EXperiment 2013 (TREX13) off Panama City, FL, USA. During TREX13, nine deployments at five selected sites were made along the 20-m isobath, termed the main reverberation track. The sediment types at the five selected sites ranged from coarse sand to a mixture of soft mud over sand, and the measured results show a spread of 80 m/s in sediment sound speed among the different types of sediments for all frequencies. Between 2–8 kHz, about 3% dispersion was observed at the sandy sites, whereas little dispersion was observed at the sites with mud. Preliminary attenuation results show 0.5–3.3 dB/m at the sandy sites, and 0.5–1.0 dB/m at the sites with mud in the same frequency band. Auteurs: Jie Yang;Dajun Tang; Apparue dans: IEEE Journal of Oceanic Engineering Date publication: 10.-2017, volume: 42, issue:4, pages: 1102 - 1109 Editeur: IEEE Document complet vers site de l'éditeur
» Direct Multitype Cardiac Indices Estimation via Joint Representation and Regression Learning
 Résumé:Cardiac indices estimation is of great importance during identification and diagnosis of cardiac disease in clinical routine. However, estimation of multitype cardiac indices with consistently reliable and high accuracy is still a great challenge due to the high variability of cardiac structures and the complexity of temporal dynamics in cardiac MR sequences. While efforts have been devoted into cardiac volumes estimation through feature engineering followed by a independent regression model, these methods suffer from the vulnerable feature representation and incompatible regression model. In this paper, we propose a semi-automated method for multitype cardiac indices estimation. After the manual labeling of two landmarks for ROI cropping, an integrated deep neural network Indices-Net is designed to jointly learn the representation and regression models. It comprises two tightly-coupled networks, such as a deep convolution autoencoder for cardiac image representation, and a multiple output convolution neural network for indices regression. Joint learning of the two networks effectively enhances the expressiveness of image representation with respect to cardiac indices, and the compatibility between image representation and indices regression, thus leading to accurate and reliable estimations for all the cardiac indices. When applied with five-fold cross validation on MR images of 145 subjects, Indices-Net achieves consistently low estimation error for LV wall thicknesses (1.44 ± 0.71 mm) and areas of cavity and myocardium (204 ± 133 mm2). It outperforms, with significant error reductions, segmentation method (55.1% and 17.4%), and two-phase direct volume-only methods (12.7% and 14.6%) for wall thicknesses and areas, respectively. These advantages endow the proposed method a great potential in clinical cardiac function assessment. Auteurs: Wufeng Xue;Ali Islam;Mousumi Bhaduri;Shuo Li; Apparue dans: IEEE Transactions on Medical Imaging Date publication: 10.-2017, volume: 36, issue:10, pages: 2057 - 2067 Editeur: IEEE Document complet vers site de l'éditeur
» Direct Synthesis and Design of Wideband Bandpass Filter With Composite Series and Shunt Resonators
 Résumé:In this paper, a wideband bandpass filter with composite series and shunt resonators is proposed together with a direct synthesis and design theory. The filter configuration can provide transmission zeros (TZs) on both sides of the passband. Two types of composite shunt resonators are introduced; one provides extra controllable TZs in the far stopband, whereas the other not only produces close-to-band TZs, but also high-order TZs in the far stopband in planar realization. The composite series resonator is realized by a high-impedance transmission line in shunt with a lumped capacitor. By introducing legitimate wideband circuit model approximations for the basic circuit blocks, a mixed lumped/distributed element version of the proposed filter is realized and experimentally verified. Design flexibility of circuit topology and spurious resonance suppression using TZs is discussed. Two design examples of the fifth-order and ninth-order filter prototypes are synthesized, designed, and measured, demonstrating the effectiveness of the synthesis and design theory as well as the superior performance of the proposed filter configuration. Auteurs: Zhiliang Li;Ke-Li Wu; Apparue dans: IEEE Transactions on Microwave Theory and Techniques Date publication: 10.-2017, volume: 65, issue:10, pages: 3789 - 3800 Editeur: IEEE Document complet vers site de l'éditeur
» Disambiguation-Free Partial Label Learning
 Résumé:In partial label learning, each training example is associated with a set of candidate labels among which only one is the ground-truth label. The common strategy to induce predictive model is trying to disambiguate the candidate label set, i.e., differentiating the modeling outputs of individual candidate labels. Specifically, disambiguation by differentiation can be conducted either by identifying the ground-truth label iteratively or by treating each candidate label equally. Nonetheless, the disambiguation strategy is prone to be misled by the false positive labels co-occurring with ground-truth label. In this paper, a new partial label learning strategy is studied which refrains from conducting disambiguation. Specifically, by adapting error-correcting output codes (ECOC), a simple yet effective approach named Pl-ecoc is proposed by utilizing candidate label set as an entirety. During training phase, to build binary classifier w.r.t. each column coding, any partially labeled example will be regarded as a positive or negative training example only if its candidate label set entirely falls into the coding dichotomy. During testing phase, class label for the unseen instance is determined via loss-based decoding which considers binary classifiers’ empirical performance and predictive margin. Extensive experiments show that Pl-ecoc performs favorably against state-of-the-art partial label learning approaches. Auteurs: Min-Ling Zhang;Fei Yu;Cai-Zhi Tang; Apparue dans: IEEE Transactions on Knowledge and Data Engineering Date publication: 10.-2017, volume: 29, issue:10, pages: 2155 - 2167 Editeur: IEEE Document complet vers site de l'éditeur
» Discrete Data AGC of Hydrothermal Systems Under Varying Turbine Time Constants Along With the Power System Loading Conditions
 Résumé:The paper deals with the discrete data automatic generation control (AGC) of two area hydrothermal power system operating at different loading conditions. The power system load varies considerably throughout the day and accordingly, thermal and hydropower systems are scheduled to operate at different loading conditions. It is found that steam as well as hydro turbine time constants vary as the power system loading varies. In earlier AGC studies, these parameters are considered to be constant, irrespective of power system loadings. This paper studies the dynamic performance of hydrothermal power system considering the variation of these turbine time constants along with the nominal loading of power system. The studies have been conducted for linear as well as nonlinear models of speed governor and hydroturbine models recommended by the IEEE committee. It is also discovered that conventional empirical formula-based hydraulic governor settings recommended by the IEEE working group are completely unacceptable for hydrothermal power system. A maiden attempt is made to optimize the hydraulic governor settings simultaneously along with the controller gains using metaheuristic algorithm. The comparison of system dynamic responses reveal that optimization-based hydrogovernor settings give the better dynamic performance in case of linear as well as nonlinear models of hydro system, and therefore are strongly recommended over the conventional settings. The paper also deals with the optimum selection of sampling periods for discrete data AGC operation of hydrothermal systems. Auteurs: Nikhil Pathak;T. S. Bhatti;Ashu Verma; Apparue dans: IEEE Transactions on Industry Applications Date publication: 10.-2017, volume: 53, issue:5, pages: 4998 - 5013 Editeur: IEEE Document complet vers site de l'éditeur
» Dispersion Differences and Consistency of Artificial Periodic Structures
 Résumé:Dispersion differences and consistency of artificial periodic structures, including phononic crystals, elastic metamaterials, as well as periodic structures composited of phononic crystals and elastic metamaterials, are investigated in this paper. By developing a $K(\omega )$ method, complex dispersion relations and group/phase velocity curves of both the single-mechanism periodic structures and the mixing-mechanism periodic structures are calculated at first, from which dispersion differences of artificial periodic structures are discussed. Then, based on a unified formulation, dispersion consistency of artificial periodic structures is investigated. Through a comprehensive comparison study, the correctness for the unified formulation is verified. Mathematical derivations of the unified formulation for different artificial periodic structures are presented. Furthermore, physical meanings of the unified formulation are discussed in the energy-state space. Auteurs: Zhi-Bao Cheng;Wen-Kai Lin;Zhi-Fei Shi; Apparue dans: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control Date publication: 10.-2017, volume: 64, issue:10, pages: 1591 - 1598 Editeur: IEEE Document complet vers site de l'éditeur
» Dispersion Engineering in Single-Polarization Single-Mode Photonic Crystal Fibers for a Nearly Zero Flattened Profile
 Résumé:We propose a systematic solution to the problem on dispersion engineering in single-polarization single-mode (SPSM) photonic crystal fibers (PCFs) for a nearly zero flattened profile. Based on dispersion-approximating and -normalizing methods as well as a clever engineering strategy, we have succeeded in a design of SPSM PCF with nearly zero flattened dispersion ${\text{0.82}}\pm {\text{0.30}}\,\text{ps}/\text{nm}/\text{km}$ over a broad band of ${\text{1.12}}\sim {\text{1.51}}\,\mu{\text{m}}$. Moreover, such a fiber presents a very low confinement-loss level, which is less than 0.001 dB/km over the operation band. Auteurs: Dunke Lu;Xiaohang Li;Guohui Zeng;Jin Liu; Apparue dans: IEEE Photonics Journal Date publication: 10.-2017, volume: 9, issue:5, pages: 1 - 8 Editeur: IEEE Document complet vers site de l'éditeur
» Distinguishing Cloud and Snow in Satellite Images via Deep Convolutional Network
 Résumé:Cloud and snow detection has significant remote sensing applications, while they share similar low-level features due to their consistent color distributions and similar local texture patterns. Thus, accurately distinguishing cloud from snow in pixel level from satellite images is always a challenging task with traditional approaches. To solve this shortcoming, in this letter, we proposed a deep learning system to classify cloud and snow with fully convolutional neural networks in pixel level. Specifically, a specially designed fully convolutional network was introduced to learn deep patterns for cloud and snow detection from the multispectrum satellite images. Then, a multiscale prediction strategy was introduced to integrate the low-level spatial information and high-level semantic information simultaneously. Finally, a new and challenging cloud and snow data set was labeled manually to train and further evaluate the proposed method. Extensive experiments demonstrate that the proposed deep model outperforms the state-of-the-art methods greatly both in quantitative and qualitative performances. Auteurs: Yongjie Zhan;Jian Wang;Jianping Shi;Guangliang Cheng;Lele Yao;Weidong Sun; Apparue dans: IEEE Geoscience and Remote Sensing Letters Date publication: 10.-2017, volume: 14, issue:10, pages: 1785 - 1789 Editeur: IEEE Document complet vers site de l'éditeur
» Distinguishing the Role of Wind in Snow Distribution by Utilizing Remote Sensing and Modeling Data: Case Study in the Northeastern Tibetan Plateau
 Résumé:Snow distribution has a profound impact on natural processes such as the hydrological cycle, the climate system, and ecological evolution. Many studies suggest that elevation, temperature, and precipitation are the three major factors controlling snow distribution. Our study explores the influence of wind on the snow distribution and finds that wind is another important factor controlling the snow distribution in the northeastern Tibet Plateau. We select the Qilian Mountains in the northeastern Tibetan Plateau as the study area, and the data include the moderate-resolution imaging spectroradiometer snow area product and the atmosphere dataset generated by the Weather Research and Forecasting model. The results indicate that there is a threshold elevation for the correlation between the fractional snow cover (FSC) area and the wind speed in the study area. At elevations above 3900 m, the FSC and wind speed exhibit a significant negative correlation, and at elevations below 3900 m, they exhibit a significant positive correlation. Our analyses indicate that the probability for the occurrence of snowdrifts is higher in regions above 3900 m and that the wind transports snow from regions above 3900 m to lower elevations. Auteurs: Donghang Shao;Hongyi Li;Jian Wang;Xiaoduo Pan;Xiaohua Hao; Apparue dans: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing Date publication: 10.-2017, volume: 10, issue:10, pages: 4445 - 4456 Editeur: IEEE Document complet vers site de l'éditeur
» Distributed Biased Min-Consensus With Applications to Shortest Path Planning
 Résumé:Distributed consensus has been intensively studied in recent years as a means to mitigate state differences among dynamic nodes on a graph. It has been successfully employed in various applications, e.g., formation control of multirobots, load balancing, and clock synchronization. However, almost all the existing applications cast an impression of consensus as a simple process to iteratively reach agreement, without any clue on possibility to generate advanced complexity, say shortest path planning, which has been proved to be NP-hard. Counterintuitively, we show for the first time that the complexity of shortest path planning can emerge from a perturbed version of a min-consensus protocol, which as a case study may shed lights to researchers in the field of distributed control to rethink the nature of complexity and the distance between control and intelligence. Besides, we rigorously prove the convergence of graph dynamics and its equivalence to shortest path solutions. An illustrative simulation on a small-scale graph is provided to show the convergence of the biased min-consensus dynamics to shortest path solution over the graph. To demonstrate the scalability to large-scale problems, a graph with 43 826 nodes, which corresponds to a map of a maze in 2-D, is considered in the simulation study. Apart from possible applications in robot path planning, the result is further extended to robot complete coverage, showing its potential in real practice such as cleaning robots. Auteurs: Yinyan Zhang;Shuai Li; Apparue dans: IEEE Transactions on Automatic Control Date publication: 10.-2017, volume: 62, issue:10, pages: 5429 - 5436 Editeur: IEEE Document complet vers site de l'éditeur
» Distributed Charging Control of Electric Vehicles Using Online Learning
 Résumé:We propose an algorithm for distributed charging control of electric vehicles (EVs) using online learning and online convex optimization. Many distributed charging control algorithms in the literature implicitly assume fast two-way communication between the distribution company and EV customers. This assumption is impractical at present and also raises security and privacy concerns. Our algorithm does not use this assumption; however, at the expense of slower convergence to the optimal solution and by relaxing the sense of optimality. The proposed algorithm requires one-way communication, which is implemented through the distribution company publishing the pricing profiles for the previous days. We provide convergence results for the algorithm and illustrate the results through numerical examples. Auteurs: Wann-Jiun Ma;Vijay Gupta;Ufuk Topcu; Apparue dans: IEEE Transactions on Automatic Control Date publication: 10.-2017, volume: 62, issue:10, pages: 5289 - 5295 Editeur: IEEE Document complet vers site de l'éditeur
» Distributed Continuous-Time Algorithm for Constrained Convex Optimizations via Nonsmooth Analysis Approach
 Résumé:This technical note studies the distributed optimization problem of a sum of nonsmooth convex cost functions with local constraints. At first, we propose a novel distributed continuous-time projected algorithm, in which each agent knows its local cost function and local constraint set, for the constrained optimization problem. Then we prove that all the agents of the algorithm can find the same optimal solution, and meanwhile, keep the states bounded while seeking the optimal solutions. We conduct a complete convergence analysis by employing nonsmooth Lyapunov functions for the stability analysis of differential inclusions. Finally, we provide a numerical example for illustration. Auteurs: Xianlin Zeng;Peng Yi;Yiguang Hong; Apparue dans: IEEE Transactions on Automatic Control Date publication: 10.-2017, volume: 62, issue:10, pages: 5227 - 5233 Editeur: IEEE Document complet vers site de l'éditeur
» Distributed Cooperative Reinforcement Learning-Based Traffic Signal Control That Integrates V2X Networks’ Dynamic Clustering
 Résumé:With the acceleration of urbanization in the world, urban traffic congestion has become an urgent challenge in most cities. Adaptive traffic signal control is the most approved control method to solve the problem, and accurate real-time traffic information is critical to this solution. This paper presents distributed cooperative reinforcement learning-based traffic control that integrates V2X networks’ dynamic clustering algorithm. To obtain traffic flow information accurately and instantaneously, it is important to improve the cluster stability in V2X networks. A dynamic clustering algorithm is proposed based on the enhanced affinity propagation. The proposed clustering algorithm introduces the initial cluster partition to maintain a proper cluster size and adds the lane and destination factors to improve the cluster's stability. The algorithm can provide efficient and accurate traffic state information to traffic signal controls. By integrating the clustering algorithm, a cooperative reinforcement learning control scheme is proposed to balance the traffic load. To address the tough dimensionality curse of reinforcement learning, a distributed mechanism for intersection cooperation is introduced, and a fast gradient-descent function approximation method is proposed to improve the controls’ real-time performance. The proposed intelligent traffic control scheme that integrates the stable clustering algorithm can effectively improve the traffic throughput, reduce the average waiting time, and avoid congestion. Numerical simulations on real scenarios validate the performance of the proposed approach. Auteurs: Weirong Liu;Gaorong Qin;Yun He;Fei Jiang; Apparue dans: IEEE Transactions on Vehicular Technology Date publication: 10.-2017, volume: 66, issue:10, pages: 8667 - 8681 Editeur: IEEE Document complet vers site de l'éditeur
» Distributed Filtering for Switched Linear Systems With Sensor Networks in Presence of Packet Dropouts and Quantization
 Résumé:This paper is concerned with the distributed $H_\infty$ filtering problem of discrete-time switched linear systems in sensor networks in face of packet dropouts and quantization. Specifically, due to the packet dropout phenomenon, the filters may lose access to the real-time switching signal of the plant. It is assumed that the maximal packet dropout number of switching signal is bounded. Then, a distributed filtering system is proposed by further considering the quantization effect. Based on the Lyapunov stability theory, a sufficient condition is obtained for the convergence of filtering error dynamics. The filter gain design is transformed into a convex optimization problem. In this paper, a quantitative relation between the switching rule missing rate and filtering performance is established. Furthermore, the upper bound of the switching rule missing rate is also calculated. Finally, the effectiveness of the proposed filter design is validated by a simulation study on the pulse-width-modulation-driven boost converter circuit. The impact of noise covariance, system dynamics, and network connectivity is studied, and some discussions are presented on how these parameters affect the filtering performance. Auteurs: Dan Zhang;Zhenhua Xu;Hamid Reza Karimi;Qing-Guo Wang; Apparue dans: IEEE Transactions on Circuits and Systems I: Regular Papers Date publication: 10.-2017, volume: 64, issue:10, pages: 2783 - 2796 Editeur: IEEE Document complet vers site de l'éditeur
» Distributed Flight Routing and Scheduling for Air Traffic Flow Management
 Résumé:Air traffic flow management (ATFM) is an important component in an air traffic control system and has significant effects on the safety and efficiency of air transportation. In this paper, we propose a distributed ATFM strategy to minimize the airport departure and arrival schedule deviations. The scheduling problem is formulated based on an en-route air traffic system model consisting of air routes, waypoints, and airports. A cell transmission flow dynamic model is adopted to describe the system dynamics under safety related constraints, such as the capacities of air routes and airports, and the aircraft speed limits. Our ATFM problem is formulated as an integer quadratic programming problem. To overcome the computational complexity associated with this problem, we first solve a relaxed quadratic programming problem by a distributed approach based on Lagrangian relaxation. Then a heuristic forward-backward propagation algorithm is proposed to obtain the final integer solution. Experimental results demonstrate the effectiveness of the proposed scheduling strategy. Auteurs: Yicheng Zhang;Rong Su;Qing Li;Christos G. Cassandras;Lihua Xie; Apparue dans: IEEE Transactions on Intelligent Transportation Systems Date publication: 10.-2017, volume: 18, issue:10, pages: 2681 - 2692 Editeur: IEEE Document complet vers site de l'éditeur
» Distributed Formation Control of Networked Multi-Agent Systems Using a Dynamic Event-Triggered Communication Mechanism
 Résumé:This paper addresses the distributed formation control problem of a networked multi-agent system (MAS) subject to limited communication resources. First, a dynamic event-triggered communication mechanism (DECM) is developed to schedule inter-agent communication such that some unnecessary data exchanges among agents can be reduced so as to achieve better resource efficiency. Different from most of the existing event-triggered communication mechanisms, wherein threshold parameters are fixed all the time, the threshold parameter in the developed event triggering condition is dynamically adjustable in accordance with a dynamic rule. It is numerically shown that the proposed DECM can achieve a better tradeoff between reducing inter-agent communication frequency and preserving an expected formation than some existing ones. Second, an event-triggered formation protocol is delicately proposed by using only locally triggered sampled data in a distributed manner. Based on the formation protocol, it is shown that the state formation control problem is cast into an asymptotic stability problem of a reduced-order closed-loop system. Then, criteria for designing desired formation protocol and communication mechanism are derived. Finally, the effectiveness and advantages of the proposed approach are demonstrated through a comparative study in multirobot formation control. Auteurs: Xiaohua Ge;Qing-Long Han; Apparue dans: IEEE Transactions on Industrial Electronics Date publication: 10.-2017, volume: 64, issue:10, pages: 8118 - 8127 Editeur: IEEE Document complet vers site de l'éditeur
» Distributed Learning for Energy-Efficient Resource Management in Self-Organizing Heterogeneous Networks
 Résumé:In heterogeneous networks, a dense deployment of base stations (BSs) leads to increased total energy consumption, and, consequently, increased cochannel interference (CCI). In this paper, to deal with this problem, self-organizing mechanisms are proposed, for joint channel and power allocation procedures, which are performed in a fully distributed manner. A dynamic channel allocation mechanism is proposed, in which the problem is modeled as a noncooperative game, and a no-regret learning algorithm is applied for solving the game. In order to improve the accuracy and reduce the effect of shadowing, we propose another channel allocation algorithm executed at each user equipment (UE). In this algorithm, each UE reports the channel with minimum CCI to its associated BS. Then, the BS selects its channel based on these received reports. To combat the energy consumption problem, BSs choose their transmission power by employing an on–off switching scheme. Simulation results show that the proposed mechanism, which is based on the second proposed channel allocation algorithm and combined with the on–off switching scheme, balances load among BSs. Furthermore, it yields significant performance gains up to about $40.3\%$, $44.8\%$ , and $70.6\%$ in terms of average energy consumption, UE's rate, and BS's load, respectively, compared to a benchmark based on an interference-aware dynamic channel allocation algorithm. Auteurs: Atefeh Hajijamali Arani;Abolfazl Mehbodniya;Mohammad Javad Omidi;Fumiyuki Adachi;Walid Saad;Ismail Güvenç; Apparue dans: IEEE Transactions on Vehicular Technology Date publication: 10.-2017, volume: 66, issue:10, pages: 9287 - 9303 Editeur: IEEE Document complet vers site de l'éditeur
» Distributed Scheduling and Cooperative Control for Charging of Electric Vehicles at Highway Service Stations
 Résumé:The increasing number of electric vehicles (EVs) on highways calls for the installment of adequate charging infrastructure. Since charging infrastructure has limited capacity, EVs need to wait at a charging station to get charged, and their waiting times may differ significantly from one location to another. This paper aims at developing a strategy to coordinate the queues among the charging stations, with only local information about traffic flows and the status of EV charging stations along a bidirectional highway, so that excessively long waiting times can be avoided. Specifically, a distributed algorithm is presented to schedule EV flows into neighboring charging stations, so that EVs are all appropriately served along the highway and that all the charging resources are uniformly utilized. In addition, a distributed decision making policy is developed to influence the aggregate number of EVs entering any given service station, so that each EV makes an appropriate decision (i.e., whether or not it should enter the next charging station) by contributing positively to meeting the desired queue length at service stations and by considering its own battery constraint. Performance improvement of the proposed strategy is illustrated via one of the highways in the United States, namely the Florida Turnpike. Auteurs: Azwirman Gusrialdi;Zhihua Qu;Marwan A. Simaan; Apparue dans: IEEE Transactions on Intelligent Transportation Systems Date publication: 10.-2017, volume: 18, issue:10, pages: 2713 - 2727 Editeur: IEEE Document complet vers site de l'éditeur
» Distributed Simulation of Continuous Random Variables
 Résumé:We establish the first known upper bound on the exact and Wyner’s common information of $n$ continuous random variables in terms of the dual total correlation between them (which is a generalization of mutual information). In particular, we show that when the pdf of the random variables is log-concave, there is a constant gap of $n^{2}\log e+9n\log n$ between this upper bound and the dual total correlation lower bound that does not depend on the distribution. The upper bound is obtained using a computationally efficient dyadic decomposition scheme for constructing a discrete common randomness variable $W$ from which the $n$ random variables can be simulated in a distributed manner. We then bound the entropy of $W$ using a new measure, which we refer to as the erosion entropy. Auteurs: Cheuk Ting Li;Abbas El Gamal; Apparue dans: IEEE Transactions on Information Theory Date publication: 10.-2017, volume: 63, issue:10, pages: 6329 - 6343 Editeur: IEEE Document complet vers site de l'éditeur
 Résumé:We propose and study the application of distributed non-orthogonal multiple access (NOMA) for the uplink of cloud radio access networks. By considering that the remote radio heads are able to exchange digital information through high capacity links of the cloud, they can cooperate in performing interference cancellation, enhancing the users’ achievable rate region. The achievable rates are presented in simple closed form, while simulations show that distributed NOMA can offer substantial improvement over benchmark schemes, by exploiting the cloud capabilities. Auteurs: Koralia N. Pappi;Panagiotis D. Diamantoulakis;George K. Karagiannidis; Apparue dans: IEEE Communications Letters Date publication: 10.-2017, volume: 21, issue:10, pages: 2274 - 2277 Editeur: IEEE Document complet vers site de l'éditeur
» Disturbance Estimator-Based Predictive Current Controller for Single-Phase Interconnected PV Systems
 Résumé:A digital predictive current controller for a single-phase grid-side power electronics converter employed in photovoltaic (PV) systems is presented in this paper. A disturbance estimator is employed with the controller in order to minimize its sensitivity to any parameter variation, as well as to reject grid-side disturbances. The design of the controller and the estimator are carried out using the pole placement method. The performance of the developed current controller was tested and verified experimentally using a 5.4-kW grid-connected PV system. These experiments are carried out for different levels of power delivered to the grid under different variation in the system parameters. In addition, other controllers used for interconnected PV systems are also tested to highlight the advantages of the developed current controller. The testing results illustrate the capability of the developed current controller to provide accurate, fast, and robust responses with negligible sensitivity to parameters variations and disturbances on the grid side. Auteurs: H. Mohomad;S. A. Saleh;L. Chang; Apparue dans: IEEE Transactions on Industry Applications Date publication: 10.-2017, volume: 53, issue:5, pages: 4201 - 4209 Editeur: IEEE Document complet vers site de l'éditeur
» Disturbance-Observer-Based Robust Backstepping Attitude Stabilization of Spacecraft Under Input Saturation and Measurement Uncertainty
 Résumé:The problem of control input saturation and measurement uncertainties in spacecraft attitude control systems is investigated in this paper. Asymmetric limitation of the control torque and additive attitude measurement errors are considered in the backstepping attitude controller design. Stable antiwindup compensator is employed to handle the adverse effect of input saturation. The additive attitude measurement errors, external disturbances, and parametric uncertainties are compensated by the outputs of stable nonlinear disturbance observers in the robust controller design. The tuning conditions of controller parameters are derived based on the Lyapunov analysis, and it is proved that attitude, angular velocity, saturation compensator states, and disturbance observer states converge to small neighborhoods of zero. Simulation results illustrate the effectiveness of the proposed control approach. Auteurs: Liang Sun;Zewei Zheng; Apparue dans: IEEE Transactions on Industrial Electronics Date publication: 10.-2017, volume: 64, issue:10, pages: 7994 - 8002 Editeur: IEEE Document complet vers site de l'éditeur
» Do We Need Minimal Solutions of Fuzzy Relational Equations in Advance?
 Résumé:Minimal solutions play a crucial role in description of all solutions to a fuzzy relational equation. The reason is that all solutions form a convex set with respect to (fuzzy) set inclusion; therefore, having all extremal solutions, we can represent the entire solution set as a union of intervals bounded from above by the greatest solution and from below by the minimal solutions. However, when computing the intervals, we obtain many duplicate solutions. The obvious question is as follows: Is there another way of representing the solution set, for instance, without the need of having all the minimal solutions in advance? We provide the positive answer to this question. Auteurs: Eduard Bartl;Pavel Prochazka; Apparue dans: IEEE Transactions on Fuzzy Systems Date publication: 10.-2017, volume: 25, issue:5, pages: 1356 - 1363 Editeur: IEEE Document complet vers site de l'éditeur
» DORE: An Experimental Framework to Enable Outband D2D Relay in Cellular Networks
 Résumé:Device-to-Device (D2D) communications represent a paradigm shift in cellular networks. In particular, analytical results on D2D performance for offloading and relay are very promising, but no experimental evidence validates these results to date. This paper is the first to provide an experimental analysis of outband D2D relay schemes. Moreover, we design D2D opportunistic relay with QoS enforcement (DORE), a complete framework for handling channel opportunities offered by outband D2D relay nodes. DORE consists of resource allocation optimization tools and protocols suitable to integrate QoS-aware opportunistic D2D communications within the architecture of 3GPP Proximity-based Services. We implement DORE using an SDR framework to profile cellular network dynamics in the presence of opportunistic outband D2D communication schemes. Our experiments reveal that outband D2D communications are suitable for relaying in a large variety of delay-sensitive cellular applications, and that DORE enables notable gains even with a few active D2D relay nodes. Auteurs: Arash Asadi;Vincenzo Mancuso;Rohit Gupta; Apparue dans: IEEE/ACM Transactions on Networking Date publication: 10.-2017, volume: 25, issue:5, pages: 2930 - 2943 Editeur: IEEE Document complet vers site de l'éditeur
» Dosimetric Characterization and Image Quality Assessment in Breast Tomosynthesis
 Résumé:The aim of this paper was to investigate the diagnostic potential of tomosynthesis imaging compared with the performance of 2-D digital mammography in terms of radiation dose and image quality. In particular, suitable dosimeter and phantom were used for quantifying the average glandular dose and image quality parameters, respectively. First, according to standard protocols and European guidelines, the characterization of the used tomosynthesis system was carried out to verify the reliability of characteristic parameters of the system. Successively, the absorbed dose was calculated by means of experimental measurements and the application of estimation methods. The calculated dose was then compared with the value provided by the system; this approach has confirmed the tendency of mammography equipment manufacturers to underestimate the mean glandular dose. Finally, the detection capability of different details with different contrasts was objectively assessed for both breast tomosynthesis and 2-D mammography. Auteurs: Gregorio Andria;Filippo Attivissimo;Attilio Di Nisio;Anna M. L. Lanzolla;Alberto Maiorana;Marco Mangiatini;Maurizio Spadavecchia; Apparue dans: IEEE Transactions on Instrumentation and Measurement Date publication: 10.-2017, volume: 66, issue:10, pages: 2535 - 2544 Editeur: IEEE Document complet vers site de l'éditeur
» Double-Sided Design of Electrodes Driving Tunable Dielectrophoretic Miniature Lens
 Résumé:We demonstrate the design methodology, geometrical analysis, device fabrication, and testing of a double-sided design of tunable-focus dielectrophoretic liquid miniature lenses. This design is intended to reduce the driving voltage for tuning the lens, utilizing a double-sided electrode design that enhances the electric field magnitude. Fabricated devices were tested and measurements on a goniometer showed changes of up to 14° in the contact angle when the dielectrophoretic force was applied under 25 Vrms. Correspondingly, the back focal length of the liquid lens changed from 67.1 to 14.4 mm when the driving voltage was increased from 0 to 25 Vrms. The driving voltage was significantly lower than those previously reported with similar device dimensions using single-sided electrode designs. This design allows for a range of both positive and negative menisci dependent on the volume of the lens liquid initially dispensed. [2017-0011] Auteurs: Yousuf D. Almoallem;Hongrui Jiang; Apparue dans: Journal of Microelectromechanical Systems Date publication: 10.-2017, volume: 26, issue:5, pages: 1122 - 1131 Editeur: IEEE Document complet vers site de l'éditeur
» Double-Sided Parallel-Strip Line Resonator for Dual-Polarized 3-D Frequency-Selective Structure and Absorber
 Résumé:Double-sided parallel-strip line (DSPSL) resonator is employed in the unit cell (UC) of a 3-D frequency-selective structure (3-D FSS) in order to exhibit the desired response (bandstop, bandpass, and absorption) under an incident wave of arbitrary polarization. It is found that this UC supports the propagation of three quasi-TEM modes. The first and third modes are concentrated in the substrate and air regions of the UC, respectively. While the second mode is concentrated in the interface between air and substrate of the UC, the polarization of the second mode is perpendicular to the polarization of the first and third modes. Detailed analysis of these propagating modes is provided with equivalent circuit models to explain the operating principle. A dual-polarized bandstop 3-D FSS is then proposed. It exhibits a stable frequency response with a constant out-of-band bandwidth under a large range of oblique incidence angle. A dual-polarized absorber is also realized employing a UC with DSPSL resonator. By properly exciting and absorbing the second mode of the modified UC, an ultra-wideband absorber is constructed, which has −10 dB fractional bandwidth of 148% from 1.51 to 10.1 GHz with an absorber thickness of $0.1~\lambda _{0}$ at the lowest absorption frequency. Auteurs: Ahmed Abdelmottaleb Omar;Zhongxiang Shen; Apparue dans: IEEE Transactions on Microwave Theory and Techniques Date publication: 10.-2017, volume: 65, issue:10, pages: 3744 - 3752 Editeur: IEEE Document complet vers site de l'éditeur
» Downlink Coverage Analysis for a Finite 3-D Wireless Network of Unmanned Aerial Vehicles
 Résumé:In this paper, we consider a finite network of unmanned aerial vehicles serving a given region. Modeling this network as a uniform binomial point process, we derive the downlink coverage probability of a reference receiver located at an arbitrary position on the ground assuming Nakagami- $m$ fading for all wireless links. The reference receiver is assumed to connect to its closest transmitting node as is usually the case in cellular systems. After deriving the distribution of distances from the reference receiver to the serving and interfering nodes, we derive an exact expression for downlink coverage probability in terms of the derivative of Laplace transform of interference power distribution. In the downlink of this system, it is not unusual to encounter scenarios in which the line-of-sight component is significantly stronger than the reflected multipath components. To emulate such scenarios, we also derive the coverage probability in the absence of fading from the results of Nakagami- $m$ fading by taking the limit $m \to \infty$ . Using asymptotic expansion of incomplete gamma function, we concretely show that this limit reduces to a redundant condition. Consequently, we derive an accurate coverage probability approximation for this case using dominant interferer-based approach in which the effect of dominant interferer is exactly captured and the residual interference from other interferers is carefully approximated. We then derive the bounds of the approximate coverage probability using Berry-Esseen theorem. Our analyses reveal several useful trends in coverage probability as a function of height of the transmitting nodes and the location of reference receiver on the ground. Auteurs: Vishnu Vardhan Chetlur;Harpreet S. Dhillon; Apparue dans: IEEE Transactions on Communications Date publication: 10.-2017, volume: 65, issue:10, pages: 4543 - 4558 Editeur: IEEE Document complet vers site de l'éditeur
» DRIE Trenches and Full-Bridges for Improving Sensitivity of 2-D Micromachined Silicon Thermal Wind Sensor
 Résumé:This paper presents the design, fabrication, and performance of a micromachined silicon thermal wind sensor with improved sensitivity. Deep reactive ion etching (DRIE) trenches are fabricated between the heater and the thermistors to suppress the lateral heat conduction in the chip. In addition, eight thermistors symmetrically arranged in four directions around the heater form two Wheatstone full-bridges, resulting in about 50% increase of the sensitivity with respect to four thermistors. Based on these two methods, the sensitivity of the micromachined silicon thermal wind sensor is improved remarkably, which is verified by the experiment. The results show that the measurement wind speed range is up to 33 m/s in constant voltage (CV) mode with the initial heating power of 256 mW. The sensitivity is measured to be 29.37 mV/ms−1 at the wind speed 3.3 m/s, achieving improvement of about 226%, compared with that of the traditional wind sensor. Wind direction measurement results show that airflow direction over the full range of 360° is determined with an accuracy of ±5°. [2017-0052] Auteurs: Yizhou Ye;Zhenxiang Yi;Shixuan Gao;Ming Qin;Qing-An Huang; Apparue dans: Journal of Microelectromechanical Systems Date publication: 10.-2017, volume: 26, issue:5, pages: 1073 - 1081 Editeur: IEEE Document complet vers site de l'éditeur
» DRIMUX: Dynamic Rumor Influence Minimization with User Experience in Social Networks
 Résumé:With the soaring development of large scale online social networks, online information sharing is becoming ubiquitous everyday. Various information is propagating through online social networks including both the positive and negative. In this paper, we focus on the negative information problems such as the online rumors. Rumor blocking is a serious problem in large-scale social networks. Malicious rumors could cause chaos in society and hence need to be blocked as soon as possible after being detected. In this paper, we propose a model of dynamic rumor influence minimization with user experience (DRIMUX). Our goal is to minimize the influence of the rumor (i.e., the number of users that have accepted and sent the rumor) by blocking a certain subset of nodes. A dynamic Ising propagation model considering both the global popularity and individual attraction of the rumor is presented based on a realistic scenario. In addition, different from existing problems of influence minimization, we take into account the constraint of user experience utility. Specifically, each node is assigned a tolerance time threshold. If the blocking time of each user exceeds that threshold, the utility of the network will decrease. Under this constraint, we then formulate the problem as a network inference problem with survival theory, and propose solutions based on maximum likelihood principle. Experiments are implemented based on large-scale real world networks and validate the effectiveness of our method. Auteurs: Biao Wang;Ge Chen;Luoyi Fu;Li Song;Xinbing Wang; Apparue dans: IEEE Transactions on Knowledge and Data Engineering Date publication: 10.-2017, volume: 29, issue:10, pages: 2168 - 2181 Editeur: IEEE Document complet vers site de l'éditeur
» Drivers Characterization based on a Signal Analysis of Vehicle Telemetry
 Résumé:This paper presents a computational analysis of drivers behaviors by using signals and data generated from a velicular telemetry system. The proposal diagnoses driver's behaviours looking for potential and dangerous driving manoeuvres. Experimental testing has been performed in real environment around the city of Barranquilla, Colombia. The testing results show how driving diagnosis can be successfully achieved through the analysis of real time telemetry data that are directly related to the driver's actions. Auteurs: Christian G. Quintero M.;Rafael Medina U.;Alejandro Tapia T.; Apparue dans: IEEE Latin America Transactions Date publication: 10.-2017, volume: 15, issue:10, pages: 1840 - 1846 Editeur: IEEE Document complet vers site de l'éditeur
» Dual Phase-Shifted Modulation Strategy for the Three-Level Dual Active Bridge DC–DC Converter
 Résumé:In high-voltage dc-dc applications, the switches in the conventional two-level dual active bridge (DAB) dc-dc converter have to bear the whole port voltage, so high voltage switches should be selected. The voltage stress of the switches in the three-level DAB converter can be reduced to half of the port voltage, so it is suitable for high-voltage applications. However, part of the switches still has to bear the entire port voltage under some operation conditions with the single phase-shifted (SPS) modulation strategy. A dual phase-shifted (DPS) modulation strategy is proposed for the converter, compared with SPS modulation strategy, it expands regulating range of transmission power and enhances control flexibility. Moreover, a control algorithm can be developed to ensure that the voltage stress of each switch is half of the port voltage. The detailed operation principle of the three-level DAB converter with DPS control is analyzed in the paper. The characteristics of each operation region and the critical conditions between different operating regions are derived. Finally, the performance of the three-level DAB converter and DPS modulation strategy are verified by the simulation and experimental results of a 125 kW prototype. Auteurs: Peng Liu;Changsong Chen;Shanxu Duan;Wenjie Zhu; Apparue dans: IEEE Transactions on Industrial Electronics Date publication: 10.-2017, volume: 64, issue:10, pages: 7819 - 7830 Editeur: IEEE Document complet vers site de l'éditeur
» Dual-Band Circularly Polarized Shared-Aperture Array for $C$ -/ $X$ -Band Satellite Communications
 Résumé:A novel method of achieving a single-feed circularly polarized (CP) microstrip antenna with both broad impedance bandwidth and axial ratio (AR) bandwidth is presented. The CP characteristics are generated by employing a resonator to excite the two orthogonal modes of the patch via two coupling paths and the required 90° phase difference is achieved by using the different orders of the two paths. The presented method, instead of conventional methods that power dividers and phase delay lines are usually required, not only significantly enhances the bandwidths of the antenna but also results in a compact feed, reduced loss and high gain. Based on this method, a dual-band shared-aperture CP array antenna is implemented for $C$ -/ $X$ -band satellite communications. The antenna aperture includes a $2 \times 2$ array at $C$ -band and a $4 \times 4$ array at $X$ -band. To accommodate the $C$ - $X$ -band elements into the same aperture while achieving a good isolation between them, the $C$ -band circular patches are etched at the four corners. The measured results agree well with the simulations, showing a wide impedance bandwidth of 21% and 21.2% at $C$ -band and $-$ -band, respectively. The $C$ -band and $X$ -band 3 dB AR bandwidths are 13.2% and 12.8%. The array also exhibits a high aperture efficiency of over 55%, low sidelobe ( $C$ -band: −12.5 dB and $X$ -band: −15 dB), and high gain ( $C$ -band: 14.5 dBic and $X$ -band: 17.5 dBic). Auteurs: Chun-Xu Mao;Steven Gao;Yi Wang;Qing-Xin Chu;Xue-Xia Yang; Apparue dans: IEEE Transactions on Antennas and Propagation Date publication: 10.-2017, volume: 65, issue:10, pages: 5171 - 5178 Editeur: IEEE Document complet vers site de l'éditeur
» Dual-Band Filter Synthesis Based on Two Low-Pass Prototypes
 Résumé:In this letter, we propose a new coupling matrix synthesis method for dual-band filter. Different from traditional frequency transformation method, which transforms a low-pass prototype into a dual-band filter, we transform two low-pass prototypes into a dual-band filter. The dual-band filter synthesized by this method can have different orders, bandwidths, or return losses in different passbands. And the filter-prescribed transmission zeros can also be realized. To verify this method, asymmetric and symmetric dual-band filters are synthesized. Auteurs: Xianhong Chen;Lijun Zhang;Can Xu;Zhanqi Zheng;Xueping Jiang; Apparue dans: IEEE Microwave and Wireless Components Letters Date publication: 10.-2017, volume: 27, issue:10, pages: 903 - 905 Editeur: IEEE Document complet vers site de l'éditeur
» Dual-Phase Transmit Focusing for Multiangle Compound Shear-Wave Elasticity Imaging
 Résumé:Shear-wave elasticity imaging (SWEI) enables the quantitative assessment of the mechanical properties of tissue. In SWEI, the effective generation of acoustic radiation force is of paramount importance. Consequently, several research groups have investigated various transmit beamforming and pulse-sequencing methods. To further improve the efficiency of the shear-wave generation, and therefore, to increase the quality of SWEI, we introduce a technique referred to as “multiangle compound SWEI” (MAC-SWEI), which uses simultaneous multiangular push beams created by dual-phase transmit focusing. By applying a constant phase offset on every other element of an array transducer, dual-phase transmit focusing creates both main and grating lobes (i.e., multiangular push beams for pushing) to simultaneously generate shear waves with several wavefront angles. The shear waves propagating at different angles are separated by multidirectional filtering in the frequency domain, leading to the reconstruction of multiple spatially co-registered shear-wave velocity maps. To form a single-elasticity image, these maps are combined, while regions associated with known artifacts created by the push beams are omitted. Overall, we developed and tested the MAC-SWEI method using Field II quantitative simulations and the experiments performed using a programmable ultrasound imaging system. Our results suggest that MAC-SWEI with dual-phase transmit focusing may improve the quality of elasticity maps. Auteurs: Heechul Yoon;Salavat R. Aglyamov;Stanislav Y. Emelianov; Apparue dans: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control Date publication: 10.-2017, volume: 64, issue:10, pages: 1439 - 1449 Editeur: IEEE Document complet vers site de l'éditeur
» Dual-Regularized Feedback and Precoding for D2D-Assisted MIMO Systems
 Résumé:This paper considers the problem of efficient feedback design for massive multiple-input multiple-output (MIMO) downlink transmissions in frequency division duplexing (FDD) bands, where some partial channel state information (CSI) can be directly exchanged between users via device-to-device (D2D) communications. Drawing inspiration from classical point-to-point MIMO, where efficient mechanisms are obtained by feeding back directly the precoder, this paper proposes a new approach to bridge the channel feedback and the precoder feedback by the joint design of the feedback and precoding strategy following a team decision framework. Specifically, the users and the base station (BS) minimize a common mean squared error (MSE) metric based on their individual observations on the imperfect global CSI. The solutions are found to take similar forms as the regularized zero-forcing (RZF) precoder, with additional regularizations that capture any level of uncertainty in the exchanged CSI, in case the D2D links are absent or unreliable. Numerical results demonstrate superior performance of the proposed scheme for an arbitrary D2D link quality setup. Auteurs: Junting Chen;Haifan Yin;Laura Cottatellucci;David Gesbert; Apparue dans: IEEE Transactions on Wireless Communications Date publication: 10.-2017, volume: 16, issue:10, pages: 6854 - 6867 Editeur: IEEE Document complet vers site de l'éditeur
» Dynamic Adaptive Video Streaming: Towards a Systematic Comparison of ICN and TCP/IP
 Résumé:Streaming of video content over the Internet is experiencing an unprecedented growth. While video permeates every application, it also puts tremendous pressure in the network—to support users having heterogeneous accesses and expecting a high quality of experience, in a furthermore cost-effective manner. In this context, future internet paradigms, such as information centric networking (ICN), are particularly well suited to not only enhance video delivery at the client (as in the dynamic adaptive streaming over HTTP (DASH) approach), but to also naturally and seamlessly extend video support deeper in the network functions. In this paper, we contrast ICN and transmission control protocol/internet protocol (TCP/IP) with an experimental approach, where we employ several state-of-the-art DASH controllers (PANDA, AdapTech, and BOLA) on an ICN versus TCP/IP network stack. Our campaign, based on tools that we developed and made available as open-source software, includes multiple clients (homogeneous vesrus heterogeneous mixture and synchronous vesrus asynchronous arrivals), videos (up to 4k resolution), channels (e.g., DASH profiles, emulated WiFi and LTE, and real 3G/4G traces), and levels of integration with an ICN network (i.e., vanilla named data networking (NDN), wireless loss detection and recovery at the access point, and load balancing). Our results clearly illustrate, as well as quantitatively assess, the benefits of ICN-based streaming, warning about potential pitfalls that are however easy to avoid. Auteurs: Jacques Samain;Giovanna Carofiglio;Luca Muscariello;Michele Papalini;Mauro Sardara;Michele Tortelli;Dario Rossi; Apparue dans: IEEE Transactions on Multimedia Date publication: 10.-2017, volume: 19, issue:10, pages: 2166 - 2181 Editeur: IEEE Document complet vers site de l'éditeur
» Dynamic Analysis of Three Snake Robot Gaits
 Résumé:In the present paper, a dynamic analysis is presented, comparing three snake-like robot gaits: lateral undulation, sidewinding locomotion, and sinus-lifting motion. To simplify calculations, sidewinding locomotion and sinus-lifting motion are considered planar movements. Vertical movements are assumed to be small but play a critical role in change where contacts are made. Thus, the normal forces acting on grounded links and the torques applied to pitch joints can be calculated by solving equilibrium equations. The tradeoff between locomotion speed and energy efficiency is studied for all three gaits, at eight different environmental settings distinguished by friction coefficients. Simulation results reveal that sinus-lifting motion and sidewinding locomotion are generally more energy-efficient gaits than is lateral undulation. More specifically, if the anisotropy in friction is large enough, sinus-lifting motion is the most energy-efficient gait; otherwise, sidewinding locomotion is more efficient. However, there are some critical speeds at which the most efficient gait changes, in some environmental settings. Auteurs: Ryo Ariizumi;Fumitoshi Matsuno; Apparue dans: IEEE Transactions on Robotics Date publication: 10.-2017, volume: 33, issue:5, pages: 1075 - 1087 Editeur: IEEE Document complet vers site de l'éditeur
» Dynamic Cell Association for Non-Orthogonal Multiple-Access V2S Networks
 Résumé:To meet the growing demand of mobile data traffic in vehicular communications, the vehicle-to-small-cell (V2S) network has been emerging as a promising vehicle-to-infrastructure technology. Since the non-orthogonal multiple access (NOMA) with successive interference cancellation (SIC) can achieve superior spectral and energy efficiency, massive connectivity and low transmission latency, we introduce the NOMA with SIC to V2S networks in this paper. Due to the fast vehicle mobility and varying communication environment, it is important to dynamically allocate small-cell base stations and transmit power to vehicular users with considering the vehicle mobility in NOMA-enabled V2S networks. To this end, we present the joint optimization of cell association and power control that maximizes the long-term system-wide utility to enhance the long-term system-wide performance and reduce the handover rate. To solve this optimization problem, we first equivalently transform it into a weighted sum rate maximization problem in each time frame based on the standard gradient-scheduling framework. Then, we propose the hierarchical power control algorithm to maximize the equivalent weighted sum rate in each time frame based on the Karush–Kuhn–Tucker (KKT) optimality conditions and the idea of successive convex approximation. Finally, theoretical analysis and simulation results are provided to demonstrate that the proposed algorithm is guaranteed to converge to the optimal solution satisfying KKT optimality conditions. Auteurs: Li Ping Qian;Yuan Wu;Haibo Zhou;Xuemin Shen; Apparue dans: IEEE Journal on Selected Areas in Communications Date publication: 10.-2017, volume: 35, issue:10, pages: 2342 - 2356 Editeur: IEEE Document complet vers site de l'éditeur
» Dynamic Inter-Operator Spectrum Sharing via Lyapunov Optimization
 Résumé:The problem of spectrum sharing between two operators in a dynamic network is considered. We allow both operators to share (a fraction of) their licensed spectrum band with each other by forming a common spectrum band. The objective is to maximize the gain in profits of both operators by sharing their licensed spectrum bands rather than using them exclusively, while considering the fairness among the operators. This is modeled as a two-person bargaining problem, and cast as a stochastic optimization. To solve this problem, we propose centralized and distributed dynamic control algorithms. At each time slot, the proposed algorithms perform the following tasks: 1) determine spectrum price for the operators; 2) make flow control decisions of users data; and 3) jointly allocate spectrum band to the operators and design transmit beamformers, which is known as resource allocation (RA). Since the RA problem is NP-hard, we have to rely on sequential convex programming to approximate its solution. To derive the distributed algorithm, we use alternating direction method of multipliers for solving the RA problem. Numerically, we show that the proposed distributed algorithm achieves almost the same performance as the centralized one. Furthermore, the results show that there is a trade-off between the achieved profits of the operators and the network congestion. Auteurs: Satya Krishna Joshi;K. B. Shashika Manosha;Marian Codreanu;Matti Latva-aho; Apparue dans: IEEE Transactions on Wireless Communications Date publication: 10.-2017, volume: 16, issue:10, pages: 6365 - 6381 Editeur: IEEE Document complet vers site de l'éditeur
» Dynamic Logic Circuits Using a-IGZO TFTs
 Résumé:Previously reported thin-film transistor (TFT) digital logic gates are mostly static circuits. If the static logic circuits are implemented using either nMOS or pMOS technologies alone, unlike CMOS technologies, the circuits consume high power because of the steady-state current, and take large circuit area. In this paper, the dynamic logic circuits using n-type a-IGZO TFTs are proposed to resolve the power and circuit area issues. The dynamic logic circuits such as inverters and nand gates are fabricated in an amorphous indium–gallium–zinc–oxide TFT technology, and traditional static logic circuits are also implemented with the same technology for comparison purposes. The measurement results show that the proposed dynamic logic circuit consumes no steady-state current, and the circuit area is reduced by 93.1%. Auteurs: Jong-Seok Kim;Jun-Hwan Jang;Yong-Duck Kim;Jung-Woo Byun;Kilim Han;Jin-Seong Park;Byong-Deok Choi; Apparue dans: IEEE Transactions on Electron Devices Date publication: 10.-2017, volume: 64, issue:10, pages: 4123 - 4130 Editeur: IEEE Document complet vers site de l'éditeur
» Dynamic Output Feedback Control for Continuous-Time T–S Fuzzy Systems Using Fuzzy Lyapunov Functions
 Résumé:A novel relaxation approach is proposed for the analysis and dynamic output feedback control of continuous-time Takagi–Sugeno (T–S) fuzzy systems using fuzzy Lyapunov functions. Previous relaxation methods for T–S fuzzy systems have some drawbacks in relaxing quadratic functions depending on normalized fuzzy weighting functions. They often introduce conservatism or lead to computational difficulty in analysis and control synthesis. Different from previous works, the proposed approach employs linear fractional transformation mechanism and full-block $S$-procedure to reduce the conservatism in analysis. Furthermore, the relaxation technique proposed in this paper can be used in solving the controller synthesis problem effectively. As a result, a design procedure of a nonparallel distributed compensation output feedback controller, which ensures asymptotic stability and optimizes ${\mathcal L}_2$ gain performance of the closed-loop systems, is provided. Several examples have been used to illustrate the advantages and efficiency of the proposed method extensively. Auteurs: Yang Liu;Fen Wu;Xiaojun Ban; Apparue dans: IEEE Transactions on Fuzzy Systems Date publication: 10.-2017, volume: 25, issue:5, pages: 1155 - 1167 Editeur: IEEE Document complet vers site de l'éditeur
» Dynamic Output-Feedback Control for Singular Markovian Jump System: LMI Approach
 Résumé:For the dynamic output-feedback stabilization of continuous-time singular Markovian jump systems, this paper introduces the necessary and sufficient condition, whereas the previous research works suggested the sufficient conditions. A special choice of the block entries of Lyapunov matrices leads to derive the necessary and sufficient condition in terms of linear matrix inequalities. A numerical example shows the validity of the derived results. Auteurs: Nam Kyu Kwon;In Seok Park;PooGyeon Park;Chaneun Park; Apparue dans: IEEE Transactions on Automatic Control Date publication: 10.-2017, volume: 62, issue:10, pages: 5396 - 5400 Editeur: IEEE Document complet vers site de l'éditeur
» Dynamic Parameterized $ell _{1}$ -Regulation for Single-Snapshot DOA Estimations
 Résumé:Standard sparse algorithms always assume that all the azimuths lie in prior discretized spatial grids in direction-of-arrival (DOA) estimations. However, this assumption may lead to poor performance in practice owing to the spatial arbitrariness of true azimuths. Several techniques have been proposed to overcome this off-the-grid issue, but the performance of these techniques is not satisfactory (i.e., they are either inaccurate or computationally expensive). In this letter, we propose a post-processing algorithm, called dynamic parameterized ℓ1-regulation, which efficiently provides compressed-sensing-based single-snapshot DOA estimations. The advantages of our proposed algorithm are verified from our numerical results. Auteurs: Wei Zhang;Feng Yu; Apparue dans: IEEE Communications Letters Date publication: 10.-2017, volume: 21, issue:10, pages: 2218 - 2221 Editeur: IEEE Document complet vers site de l'éditeur
» Dynamic Parameterized $\ell _{1}$ -Regulation for Single-Snapshot DOA Estimations
 Résumé:Standard sparse algorithms always assume that all the azimuths lie in prior discretized spatial grids in direction-of-arrival (DOA) estimations. However, this assumption may lead to poor performance in practice owing to the spatial arbitrariness of true azimuths. Several techniques have been proposed to overcome this off-the-grid issue, but the performance of these techniques is not satisfactory (i.e., they are either inaccurate or computationally expensive). In this letter, we propose a post-processing algorithm, called dynamic parameterized $\ell _{1}$ -regulation, which efficiently provides compressed-sensing-based single-snapshot DOA estimations. The advantages of our proposed algorithm are verified from our numerical results. Auteurs: Wei Zhang;Feng Yu; Apparue dans: IEEE Communications Letters Date publication: 10.-2017, volume: 21, issue:10, pages: 2218 - 2221 Editeur: IEEE Document complet vers site de l'éditeur
» Dynamic Parameterized $\ell _{1}$ -Regulation for Single-Snapshot DOA Estimations
 Résumé:Standard sparse algorithms always assume that all the azimuths lie in prior discretized spatial grids in direction-of-arrival (DOA) estimations. However, this assumption may lead to poor performance in practice owing to the spatial arbitrariness of true azimuths. Several techniques have been proposed to overcome this off-the-grid issue, but the performance of these techniques is not satisfactory (i.e., they are either inaccurate or computationally expensive). In this letter, we propose a post-processing algorithm, called dynamic parameterized $\ell _{1}$ -regulation, which efficiently provides compressed-sensing-based single-snapshot DOA estimations. The advantages of our proposed algorithm are verified from our numerical results. Auteurs: Wei Zhang;Feng Yu; Apparue dans: IEEE Communications Letters Date publication: 10.-2017, volume: 21, issue:10, pages: 2218 - 2221 Editeur: IEEE Document complet vers site de l'éditeur
» Dynamic Parameterized $\ell _{1}$ -Regulation for Single-Snapshot DOA Estimations
 Résumé:Standard sparse algorithms always assume that all the azimuths lie in prior discretized spatial grids in direction-of-arrival (DOA) estimations. However, this assumption may lead to poor performance in practice owing to the spatial arbitrariness of true azimuths. Several techniques have been proposed to overcome this off-the-grid issue, but the performance of these techniques is not satisfactory (i.e., they are either inaccurate or computationally expensive). In this letter, we propose a post-processing algorithm, called dynamic parameterized $\ell _{1}$ -regulation, which efficiently provides compressed-sensing-based single-snapshot DOA estimations. The advantages of our proposed algorithm are verified from our numerical results. Auteurs: Wei Zhang;Feng Yu; Apparue dans: IEEE Communications Letters Date publication: 10.-2017, volume: 21, issue:10, pages: 2218 - 2221 Editeur: IEEE Document complet vers site de l'éditeur
» Dynamic Positioning of Vessels Using a UKF-Based Observer and an NMPC-Based Controller
 Résumé:This paper presents a solution to the problem of dynamic positioning (DP) of vessels in ice-infested environments using a nonlinear observer and a finite-horizon optimal control-based approach. An unscented Kalman filter-based nonlinear observer is developed to estimate both the vessel states and the unknown inputs, such as the ice load. To perform better control and disturbance rejection, a nonlinear model predictive controller is employed for DP. The developed modules are integrated with a commercial vessel maneuvering software, and promising real-time results are generated.Note to Practitioners—Accurate dynamic positioning (DP) of vessels in the presence of environmental disturbances is very important for Arctic explorations. This paper proposes a tightly coupled approach to estimate the unknown forces acting on a vessel and the vessel states. Also, an optimum control-based solution is proposed for robust DP. Auteurs: Awantha Jayasiri;Anirudh Nandan;Syed Imtiaz;Don Spencer;Shameem Islam;Salim Ahmed; Apparue dans: IEEE Transactions on Automation Science and Engineering Date publication: 10.-2017, volume: 14, issue:4, pages: 1778 - 1785 Editeur: IEEE Document complet vers site de l'éditeur
» Dynamic Rerouting Behavior and Its Impact on Dynamic Traffic Patterns
 Résumé:Advanced information is increasingly being used as an external intervention tool to positively influence system performance. In many traffic assignment problems, the proportion of travellers that reroute is assumed to be constant (static rerouting behavior), whereas the number of travellers that modify their routes will change dynamically with the cost difference (dynamic rerouting behavior). In this paper, dynamic rerouting behavior is considered in day-to-day traffic assignment models to capture travellers’ reactions to advanced information. The properties of a dynamic rerouting weight function are studied using survey data. Our goal is to better understand the dynamic evolution of network flow. In the model, the rerouting weight varies dynamically with the cost difference between travellers’ estimated and expected costs. The linear stability of the equilibrium is analyzed. Both theoretical analyses and numerical simulations indicated that dynamic rerouting behavior increases the stability domain and decreases the parameter sensitivity. Additionally, the dynamic evolution of the cost and flow near the stability boundary is studied. The results show that the dynamic rerouting behavior helps to improve the convergence speed and dampen the oscillations in the evolution process. This paper explains the influence of dynamic rerouting choice behavior on the evolution patterns of transportation networks and provides guidance for network design and management. Auteurs: Xiaomei Zhao;Chunhua Wan;Huijun Sun;Dongfan Xie;Ziyou Gao; Apparue dans: IEEE Transactions on Intelligent Transportation Systems Date publication: 10.-2017, volume: 18, issue:10, pages: 2763 - 2779 Editeur: IEEE Document complet vers site de l'éditeur
» Dynamic Resource Allocation for Virtualized Wireless Networks in Massive-MIMO-Aided and Fronthaul-Limited C-RAN
 Résumé:This paper considers the uplink dynamic resource allocation in a cloud radio access network (C-RAN) serving users belonging to different service providers (called slices) to form virtualized wireless networks (VWN). In particular, the C-RAN supports a pool of base-station (BS) baseband units (BBUs), which are connected to BS radio remote heads (RRHs) equipped with massive massive multiple input multiple output (MIMO), via fronthaul links with limited capacity. Assuming that each user can be assigned to a single RRH–BBU pair, we formulate a resource allocation problem aiming to maximize the total system rate, constrained on the minimum rates required by the slices and the maximum number of antennas and power allocated to each user. The effects of pilot contamination error on the VWN performance are investigated and pilot duration is considered as a new optimization variable in resource allocation. This problem is inherently nonconvex, NP-hard and, thus, computationally inefficient. By applying the successive convex approximation and complementary geometric programming approach, we propose a two-step iterative algorithm: one to adjust the RRH, BBU, and fronthaul parameters, and the other for power and antenna allocation to users. Simulation results illustrate the performance of the developed algorithm for VWNs in a massive-MIMO-aided and fronthaul-limited C-RAN, and demonstrate the effects of imperfect channel state information estimation due to pilot contamination error, and the optimal pilot duration. Auteurs: Saeedeh Parsaeefard;Rajesh Dawadi;Mahsa Derakhshani;Tho Le-Ngoc;Mina Baghani; Apparue dans: IEEE Transactions on Vehicular Technology Date publication: 10.-2017, volume: 66, issue:10, pages: 9512 - 9520 Editeur: IEEE Document complet vers site de l'éditeur
» Dynamic State Estimation Based Protection on Series Compensated Transmission Lines
 Résumé:Series compensated transmission lines challenge legacy protection schemes. In this paper, a dynamic state estimation based protection (EBP) method is proposed to address these challenges. The method requires GPS synchronized measurements at both ends of the line and a high-fidelity model of the protection zone. The paper presents the dynamic model of the protection zone and its impact on the performance of the protection scheme. Numerical simulations show that the method can correctly identify faults, independently of position and type. The paper also compares the proposed method versus legacy protection functions such as distance protection and line differential protection. The comparison shows faster detection of internal faults, immunity to current inversion caused by series capacitors (SCs) and improved detection sensitivity for high-impedance faults. Auteurs: Yu Liu;A. P. Sakis Meliopoulos;Rui Fan;Liangyi Sun;Zhenyu Tan; Apparue dans: IEEE Transactions on Power Delivery Date publication: 10.-2017, volume: 32, issue:5, pages: 2199 - 2209 Editeur: IEEE Document complet vers site de l'éditeur
» Dynamic Teams and Decentralized Control Problems With Substitutable Actions
 Résumé:This technical note considers two problems—a dynamic team problem and a decentralized control problem. The problems we consider do not belong to the known classes of “simpler” dynamic team/decentralized control problems such as partially nested or quadratically invariant problems. However, we show that our problems admit simple solutions under an assumption referred to as the substitutability assumption. Intuitively, substitutability in a team (resp. decentralized control) problem means that the effects of one team member's (resp. controller's) action on the cost function and the information (resp. state dynamics) can be achieved by an action of another member (resp. controller). For the non-partially-nested LQG dynamic team problem, it is shown that under certain conditions linear strategies are optimal. For the non-partially-nested decentralized LQG control problem, the state structure can be exploited to obtain optimal control strategies with recursively update-able sufficient statistics. These results suggest that substitutability can work as a counterpart of the information structure requirements that enable simplification of dynamic teams and decentralized control problems. Auteurs: Seyed Mohammad Asghari;Ashutosh Nayyar; Apparue dans: IEEE Transactions on Automatic Control Date publication: 10.-2017, volume: 62, issue:10, pages: 5302 - 5309 Editeur: IEEE Document complet vers site de l'éditeur
» Dynamic-Hash-Table Based Public Auditing for Secure Cloud Storage
 Résumé:Cloud storage is an increasingly popular application of cloud computing, which can provide on-demand outsourcing data services for both organizations and individuals. However, users may not fully trust the cloud service providers (CSPs) in that it is difficult to determine whether the CSPs meet their legal expectations for data security. Therefore, it is critical to develop efficient auditing techniques to strengthen data owners’ trust and confidence in cloud storage. In this paper, we present a novel public auditing scheme for secure cloud storage based on dynamic hash table (DHT), which is a new two-dimensional data structure located at a third parity auditor (TPA) to record the data property information for dynamic auditing. Differing from the existing works, the proposed scheme migrates the authorized information from the CSP to the TPA, and thereby significantly reduces the computational cost and communication overhead. Meanwhile, exploiting the structural advantages of the DHT, our scheme can also achieve higher updating efficiency than the state-of-the-art schemes. In addition, we extend our scheme to support privacy preservation by combining the homomorphic authenticator based on the public key with the random masking generated by the TPA, and achieve batch auditing by employing the aggregate BLS signature technique. We formally prove the security of the proposed scheme, and evaluate the auditing performance by detailed experiments and comparisons with the existing ones. The results demonstrate that the proposed scheme can effectively achieve secure auditing for cloud storage, and outperforms the previous schemes in computation complexity, storage costs and communication overhead. Auteurs: Hui Tian;Yuxiang Chen;Chin-Chen Chang;Hong Jiang;Yongfeng Huang;Yonghong Chen;Jin Liu; Apparue dans: IEEE Transactions on Services Computing Date publication: 10.-2017, volume: 10, issue:5, pages: 701 - 714 Editeur: IEEE Document complet vers site de l'éditeur
» ECG-Based Classification of Resuscitation Cardiac Rhythms for Retrospective Data Analysis
 Résumé:Objective: There is a need to monitor the heart rhythm in resuscitation to improve treatment quality. Resuscitation rhythms are categorized into: ventricular tachycardia (VT), ventricular fibrillation (VF), pulseless electrical activity (PEA), asystole (AS), and pulse-generating rhythm (PR). Manual annotation of rhythms is time-consuming and infeasible for large datasets. Our objective was to develop ECG-based algorithms for the retrospective and automatic classification of resuscitation cardiac rhythms. Methods: The dataset consisted of 1631 3-s ECG segments with clinical rhythm annotations, obtained from 298 out-of-hospital cardiac arrest patients. In total, 47 wavelet- and time-domain-based features were computed from the ECG. Features were selected using a wrapper-based feature selection architecture. Classifiers based on Bayesian decision theory, k-nearest neighbor, k-local hyperplane distance nearest neighbor, artificial neural network (ANN), and ensemble of decision trees were studied. Results: The best results were obtained for ANN classifier with Bayesian regularization backpropagation training algorithm with 14 features, which forms the proposed algorithm. The overall accuracy for the proposed algorithm was 78.5%. The sensitivities (and positive-predictive-values) for AS, PEA, PR, VF, and VT were 88.7% (91.0%), 68.9% (70.4%), 65.9% (69.0%), 86.2% (83.8%), and 78.8% (72.9%), respectively. Conclusions: The results demonstrate that it is possible to classify resuscitation cardiac rhythms automatically, but the accuracy for the organized rhythms (PEA and PR) is low. Significance: We have made an important step toward making classification of resuscitation rhythms more ef- icient in the sense of minimal feedback from human experts. Auteurs: Ali Bahrami Rad;Trygve Eftestøl;Kjersti Engan;Unai Irusta;Jan Terje Kvaløy;Jo Kramer-Johansen;Lars Wik;Aggelos K. Katsaggelos; Apparue dans: IEEE Transactions on Biomedical Engineering Date publication: 10.-2017, volume: 64, issue:10, pages: 2411 - 2418 Editeur: IEEE Document complet vers site de l'éditeur
» Edge Caching for Layered Video Contents in Mobile Social Networks
 Résumé:To improve the performance of mobile video delivery, caching layered videos at a site near to mobile end users (e.g., at the edge of mobile service provider's backbone) was advocated because cached videos can be delivered to mobile users with a high quality of experience, e.g., a short latency. How to optimally cache layered videos based on caching price, the available capacity of cache nodes, and the social features of mobile users, however, is still a challenging issue. In this paper, we propose a novel edge caching scheme to cache layered videos. First, a framework to cache layered videos is presented in which a cache node stores layered videos for multiple social groups, formed by mobile users based on their requests. Due to the limited capacity of the cache node, these social groups compete with each other for the number of layers they request to cache, aiming at maximizing their utilities while all mobile users in each group share the cost involved in the cache of video contents. Second, a Stackelberg game model is developed to study the interaction among multiple social groups and the cache node, and a noncooperative game model is introduced to analyze the competition among mobile users in different social groups. Third, leveraging the backward induction method, the optimal strategy of each player in the game model is proposed. Finally, simulation results show that the proposed method outperforms the exiting counterparts with a higher hit ratio and lower delay of delivering video contents. Auteurs: Zhou Su;Qichao Xu;Fen Hou;Qing Yang;Qifan Qi; Apparue dans: IEEE Transactions on Multimedia Date publication: 10.-2017, volume: 19, issue:10, pages: 2210 - 2221 Editeur: IEEE Document complet vers site de l'éditeur
» Editorial
 Résumé:In Australia many university engineering research projects are funded by 3- to 5-year grants where the cost is split evenly between government and industry. Due to the small industrial manufacturing base in Australia, much power engineering research is funded by the utilities. In our project we set out to investigate new strategies for working with industry, in order to strengthen collaboration and enrich the education of our students. We took great care to set research aims in cooperation with our industrial partners so that, where appropriate, the outcomes could be implemented by the partner organizations. The planned research work was outlined in course materials for the students, who then had the opportunity to work on thesis projects co-supervised by industry. Auteurs: Dan Martin; Apparue dans: IEEE Electrical Insulation Magazine Date publication: 10.-2017, volume: 33, issue:5, pages: 4 - 6 Editeur: IEEE Document complet vers site de l'éditeur
» Editorial
 Résumé: Auteurs: N. Ross Chapman; Apparue dans: IEEE Journal of Oceanic Engineering Date publication: 10.-2017, volume: 42, issue:4, pages: 753 - 753 Editeur: IEEE Document complet vers site de l'éditeur
» Editorial to the regular issue
 Résumé:This is the 10st issue of the IEEE Latin America Transactions of the year 2017. Volume 15 Issue 10, October 2017 Auteurs: Mirela Sechi Moretti Annoni Notare; Apparue dans: IEEE Latin America Transactions Date publication: 10.-2017, volume: 15, issue:10, pages: 1811 - 1820 Editeur: IEEE Document complet vers site de l'éditeur
» Editorial: Security and Dependability of Cloud Systems and Services
 Résumé: Auteurs: Stefano Russo;Marco Vieira; Apparue dans: IEEE Transactions on Services Computing Date publication: 10.-2017, volume: 10, issue:5, pages: 673 - 674 Editeur: IEEE Document complet vers site de l'éditeur
» EEG/ERP: Within Episodic Assessment Framework for Cognition
 Résumé:This work explores the potential for electroencephalography (EEG)-based event-related potential (ERP) measurements to be included in the framework for episodic assessment. In current discrete clinical cognitive assessment methods used to diagnose mild cognitive impairment (MCI)/dementia, physicians see patients annually or biannually. They rely on patient’s history and clinical cognitive assessments to identify changes in memory or functional ability as indications of MCI/dementia in conjunction with exclusionary tests. They are limited in these discrete assessments by their accuracy and infrequent occurrence. The episodic assessment framework proposed will allow better ongoing information about the true well-being of the patient through assessment of memory and functional cognitive ability on a weekly or even daily basis between appointments. This paper identifies features of EEG/ERP measurements during Neuropsychological Behavioral Testing that could allow the future inclusion in the framework using now available consumer EEG devices. A pilot group of 32 participants (17 healthy, 15 MCI) was studied using a 1-back test, while their brain activity was measured using EEG. Features of the ERP thus generated were identified and measured. These ERP features and associated behavioral measurements from the 1-back test were analyzed to identify features both alone and in combination that allowed the correct classification of the participants using a repeated leave-one-out train and test method. A feature pair (1-back response time and CPz correlation) was identified that provides the best two-feature performance (1 false positive/1 false negative error) with a third feature (response required – Pz P1 to N1 latency) providing additional improvement. Given these results, it is possible that episodic ERP measurements may help with cognitive impairment diagnosis in the future. Auteurs: Bruce Wallace;Frank Knoefel;Rafik Goubran;Rocío A. López Zunini;Zhaofen Ren;Aaron Maccosham; Apparue dans: IEEE Transactions on Instrumentation and Measurement Date publication: 10.-2017, volume: 66, issue:10, pages: 2525 - 2534 Editeur: IEEE Document complet vers site de l'éditeur
» EEMD Domain AR Spectral Method for Mean Scatterer Spacing Estimation of Breast Tumors From Ultrasound Backscattered RF Data
 Résumé:We present a novel method for estimating the mean scatterer spacing (MSS) of breast tumours using ensemble empirical mode decomposition (EEMD) domain analysis of deconvolved backscattered radio-frequency (RF) data. The autoregressive (AR) spectrum from which the MSS is estimated is obtained from the intrinsic mode functions (IMFs) due to regular scatterers embedded in RF data corrupted by the diffuse scatterers. The IMFs are chosen by giving priority to the presence of an enhanced fundamental harmonic and the presence of a greater number of higher harmonics in the AR spectrum estimated from the IMFs. The AR model order is chosen by minimizing the minimum absolute percentage error (MAPE) criterion. In order to ensure that the backscattered data is indeed from a source of coherent scattering, at first, a non-parametric Kolmogorov-Smirnov (KS) classification test is performed on the backscattered RF data. Deconvolution of the backscattered RF data, which have been classified by the K-S test as sources of significant coherent scattering, is done to reduce the system effect. EEMD domain analysis is then performed on the deconvolved data. The proposed method is able to recover the harmonics associated with the regular scatterers and overcomes many problems encountered while estimating the MSS from the AR spectrum of raw RF data. Using our technique, a mean absolute percentage error (MAPE) of 5:78%is obtained while estimating the MSS from simulated data which is lower than that of the existing techniques. Our proposed method is shown to outperform the state of the art techniques, namely, singular spectrum analysis (SSA), general spectrum (GS), spectral autocorrelation (SAC), and modified SAC for different simulation conditions. The MSS for in vivo normal breast tissue is found to be 0.69 ±0.04mm; for benign and malignant tumors it is found to be 0.73 ±0.03 mm and 0.79 ±0.04 mm, respect- vely. The separation between the MSS values of normal and benign tissues for our proposed method is similar to the separations obtained for the conventional methods but the separation between the MSS values for benign and malignant tissues for our proposed method is slightly higher than that for the conventional methods. When the MSS is used for classifying between benign and malignant tumors, for a threshold based classifier, the increase in specificity, accuracy, and area under curve are 18%, 19%, and 22%, respectively, and that for statistical classifiers are 9%, 13%, and 19%, respectively, from that of the next best existing technique. Auteurs: Navid Ibtehaj Nizam;S. Kaisar Alam;Md. Kamrul Hasan; Apparue dans: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control Date publication: 10.-2017, volume: 64, issue:10, pages: 1487 - 1500 Editeur: IEEE Document complet vers site de l'éditeur
» Effect of Correlation on BER Performance of the FSO-MISO System With Repetition Coding Over Gamma–Gamma Turbulence
 Résumé:In free space optical (FSO) communication systems, atmospheric turbulence is the major cause of bit error rate (BER) performance degradation. The error performance of the system can be significantly improved with the help of spatial diversity by employing multiple transmit or receive apertures. However, correlation of channels under turbulence in the case of small separation between transmit apertures can substantially reduce the benefits of spatial diversity. Still, a thorough analysis of the system performance in terms of diversity order and coding gain for the FSO multiple-input single-output (MISO) system under turbulence influenced correlated channels has not been studied when the repetition coding is used to achieve improved BER performance. In this paper, we provide unique results of the BER performance analysis of the considered correlated FSO-MISO system over Gamma–Gamma distributed turbulence channel. Using the joint moment generating function of received signal-to-noise ratio (SNR), a novel generalized approximate BER expression is derived, followed by convergence test of the power series based BER expression using the Cauchy's ratio test. Then, an asymptotic analysis at high SNR is performed to obtain a novel closed-form expression for BER of FSO-MISO system. We also derive expressions for coding gain, diversity gain, and coding gain loss due to correlation in channels. Although the effect of correlation in channels on the BER performance of the system is analyzed under different scenarios, while it is observed that it does not affect the diversity order; it significantly degrades the coding gain of the considered system. Auteurs: Richa Priyadarshani;Manav R. Bhatnagar;Zabih Ghassemlooy;Stanislav Zvanovec; Apparue dans: IEEE Photonics Journal Date publication: 10.-2017, volume: 9, issue:5, pages: 1 - 15 Editeur: IEEE Document complet vers site de l'éditeur
» Effect of Human Brain Edema on Light Propagation: A Monte Carlo Modeling Based on the Visible Chinese Human Dataset
 Résumé:Brain edema originates from the excessive accumulation of cerebrospinal fluid (CSF) in the brain attributing to brain trauma or nontrauma diseases such as cancer, ischemic stroke, meningitis, and encephalitis. The high intracranial pressure could extrude the vessels in brain and block the blood circulation, yielding the risk of intracranial hemorrhage (ICH). In this study, we investigated the feasibility of utilizing functional near infrared spectroscopy (fNIRS) for brain edema inspection through Monte Carlo simulations over the head model of the Visible Chinese Human dataset. The outstanding influence of the development (4 levels) of edema and the occurrence of ICH on the light migration were observed. With the increase of CSF volume, the results show a strong linear relationship between the volumes of CSF and the intensities of the detected signal and the deeper penetration of photons. An outstanding contrast was also observed before and after the occurrence of ICH. The study revealed that fNIRS holds promise to be an easy and reliable solution for inspecting edema aggression inside brain through the observation on the variation of optical signals, and is very suitable for continuous bedside inspection. Auteurs: Lanhui Wu;Yu Lin;Ting Li; Apparue dans: IEEE Photonics Journal Date publication: 10.-2017, volume: 9, issue:5, pages: 1 - 10 Editeur: IEEE Document complet vers site de l'éditeur
» Effect of Outdated CSI on Handover Decisions in Dense Networks
 Résumé:We consider an ultra-dense network where each mobile is attached to the access point, which provides the best reference signal received power considering both path-loss and small-scale fading. In order to evaluate the effect of outdated channel state information (CSI) brought by feedback delay, we first derive the estimated and accurate handover probability according to outdated and perfect CSI, respectively. Furthermore, two metrics are proposed to measure the handover failure, i.e., false handover probability and miss handover probability. Simulations show that in sparse or ultra-dense networks, the imperfection of CSI is acceptable for handover decisions; however, in between, i.e., dense networks (medium-size networks), handover decisions are very sensitive to the user velocity and CSI imperfection. Auteurs: Yinglei Teng;Mengting Liu;Mei Song; Apparue dans: IEEE Communications Letters Date publication: 10.-2017, volume: 21, issue:10, pages: 2238 - 2241 Editeur: IEEE Document complet vers site de l'éditeur
» Effect of Structural Disorder on Photonic Crystal Logic Gates
 Résumé:In this paper, we study the effect of structural disorder on photonic crystals logic gates applying a new approach based on the evaluation of two metrics: the error rate (ER) and the mean absolute deviation of transmission of the error cases (MATEC). ER is the probability that a fabricated photonic crystal logic gate does not accomplish its logic function correctly, and MATEC measures the imperfection degree of the device through the transmission coefficient. The process consists in introducing disorder in specific regions in the boundary of the waveguides that form the logic gate structure. A significant number of simulations is randomly performed for each input combination of the logic gate. The ER and MATEC are calculated, and the process is replicated 20 times with different seed numbers. Finally, a statistical test T is carried out to establish the most critical regions for the device. We evaluate some photonic crystal logic gates with different lattice configurations using this approach. The results show that, for structures with a triangular lattice, regions in the corners and close to the output are more critical to ER and MATEC, respectively. For structures with a square lattice, we found that the intersection regions are the most sensitive for both metrics. As a final consideration, we remark that this methodology can be easily applied to evaluate other kinds of disorder and to analyze photonic crystals devices based on waveguides with different lattice configurations, and can guide the design of future robust gates. Auteurs: Luis Eduardo Pedraza Caballero;Juan Pablo Vasco Cano;Paulo S. S. Guimarães;Omar Paranaiba Vilela Neto; Apparue dans: IEEE Photonics Journal Date publication: 10.-2017, volume: 9, issue:5, pages: 1 - 15 Editeur: IEEE Document complet vers site de l'éditeur
» Effect of Surface Stresses on Microwave Surface Resistance and Its Impact for Cavity Perturbation Measurements
 Résumé:For microwave characterization of materials over a wide temperature range, it is often desirable to perform cavity perturbation measurements at elevated temperatures. Careful cavity design, involving the minimization of electrical contacts, ensures high measurement stability as the temperature varies. However, examining the Q-factor of a cylindrical cavity resonator during heating has shown that heat treatment can permanently modify the surface resistance of an aluminum surface. X-Ray diffraction measurements of Al-6082 confirm that the source of change can be due to changes in surface stress and the appearance of solution precipitates. Here we discuss the necessity to pretreat microwave cavities to stabilize their Q-factors in order to reliably measure material properties via cavity perturbation across a wide temperature range. Auteurs: Nicholas Clark;Greg Shaw;Adrian Porch; Apparue dans: IEEE Microwave and Wireless Components Letters Date publication: 10.-2017, volume: 27, issue:10, pages: 939 - 941 Editeur: IEEE Document complet vers site de l'éditeur
» Effect of the Vegetation Fire on Backscattering: An Investigation Based on Sentinel-1 Observations
 Résumé:This paper aims at investigating the potential of Sentinel-1 C-band synthetic aperture radar (SAR) observations for detecting fire scars in vegetated areas at regional scale. A comprehensive analysis of the backscattering coefficients is carried out. The experimental analysis is conducted by analyzing the scenario of the Sardinia Island, which is one of the Italian regions most affected by fire events over the summer season. The detection capability of fire scars in such an environment is demonstrated by exploiting information extracted from dual-polarized SAR data. Our results reveal a significant decrease of the VH response over the fire-disturbed forests, thus, highlighting the effectiveness of such cross-polarized observations. In order to prove the validity of the proposed approach for the detection of fire scars in the vegetation layer, the results of the conducted experiments have been suitably compared with burned areas identified by using an existing fuzzy-based algorithm, which has been applied to multispectral Landsat-8 operational land imager data. This investigation opens the way to systematic methods for monitoring fire scars in heterogeneous environments, and in particular in fire-prone Mediterranean ecosystems. Auteurs: Pasquale Imperatore;Ramin Azar;Fabiana Calò;Daniela Stroppiana;Pietro Alessandro Brivio;Riccardo Lanari;Antonio Pepe; Apparue dans: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing Date publication: 10.-2017, volume: 10, issue:10, pages: 4478 - 4492 Editeur: IEEE Document complet vers site de l'éditeur
» Effective Current Model for Inverter-Transmission Gate Structure and Its Application in Circuit Design
 Résumé:In this paper, we present an effective switching current model ( ${I}_{\textsf {eff}}$ ) for inverter followed by a transmission gate structure (Inv-Tx) based on its switching trajectory. Unlike an inverter or NAND/NOR gates, where ${I}_{\textsf {eff}}$ depends only on nMOSFET (pMOSFET) current for a falling (rising) transition, it is a function of both nMOSFET and pMOSFET currents for an Inv-Tx cell. The proposed model is verified against HSPICE simulations for a wide range of supply voltages and fan-outs at different technology nodes (e.g., 180, 130, and 65 nm). The model predicts the transition delay values with an average (maximum) error of 7% (11%) compared with HSPICE simulations. Synopsys TCAD Sentaurus simulations at 32-nm technology node are also used to validate the basic model assumptions. To demonstrate the utility of our model, design of some representative circuits while incorporating layout-dependent effects and inverse-narrow-width effect is presented. Finally, we show that a 256X1 multiplexer and a static D-flip-flop, with their transistor sizes and layout, optimized using the proposed model improves the performance of these circuits significantly over the conventional design methodologies. Auteurs: Arvind Sharma;Naushad Alam;Anand Bulusu; Apparue dans: IEEE Transactions on Electron Devices Date publication: 10.-2017, volume: 64, issue:10, pages: 4002 - 4010 Editeur: IEEE Document complet vers site de l'éditeur
» Effects of Armature Height and Position on the Performance of Induction Coil Launcher
 Résumé:Induction coil launcher (ICL) is an electromagnetic accelerator that uses Lorentz force to accelerate a projectile with a conducting armature. In this paper, the effects of the height and starting position of the armature on the performance of the ICL were analyzed. Launching experiments were conducted to verify the analysis results. The speed of the projectile converged to a saturated value as the armature height increased. We found that there exists an optimal starting position of the armature for the highest speed. The concept of inductance gradient was adopted to explain the analysis results. It was possible to predict the acceleration characteristics and to estimate the optimal starting position using this concept. Results show that the armature height should be longer than the drive coil height ( $\text{H}_{\mathrm {coil}})$ , and the bottom of the armature should be positioned between ${({1}/{4})H}_{\mathrm {coil}}$ and ${({1}/{2})H}_{\mathrm {coil}}$ at the start to obtain the highest speed. The experimental results showed good agreement with the simulation analysis results. Auteurs: Daehwan Kwak;Yun Sik Jin;Young Bae Kim;Jong Soo Kim;Chuhyun Cho; Apparue dans: IEEE Transactions on Plasma Science Date publication: 10.-2017, volume: 45, issue:10, pages: 2696 - 2700 Editeur: IEEE Document complet vers site de l'éditeur
» Effects of Bi(Zn2/3Nb1/3)O3 Modification on the Relaxor Behavior and Piezoelectricity of Pb(Mg1/3Nb2/3)O3–PbTiO3 Ceramics
 Résumé:Relaxor lead magnesium niobate (PMN)-based materials exhibit complex structures and unusual properties that have been puzzling researchers for decades. In this paper, a new ternary solid solution of Pb(Mg1/3Nb2/3)O3–PbTiO3–Bi(Zn2/3Nb1/3)O3 (PMN–PT–BZN) is prepared in the form of ceramics, and the effects of the incorporation of BZN into the PMN-PT binary system are investigated. The crystal structure favors a pseudocubic symmetry and the relaxor properties are enhanced as the concentration of BZN increases. The relaxor behavior and the related phase transformations are studied by dielectric spectroscopy. A phase diagram mapping out the characteristic temperatures and various states is established. Interestingly, the piezoelectricity of the PMN-PT ceramics is significantly enhanced by the BZN substitution, with an optimal value of $d_{33}$ reaching 826 pC/N for 0.96[0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3]-0.04Bi(Zn2/3Nb1/3)O3. This paper provides a better understanding of the relaxor ferroelectric behavior, and unveils a new relaxor-based ternary system as piezoelectric materials potentially useful for electromechanical transducer applications. Auteurs: Zenghui Liu;Hua Wu;Alisa Paterson;Wei Ren;Zuo-Guang Ye; Apparue dans: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control Date publication: 10.-2017, volume: 64, issue:10, pages: 1608 - 1616 Editeur: IEEE Document complet vers site de l'éditeur
» Effects of Image Quality on the Fundamental Limits of Image Registration Accuracy
 Résumé:For image-guided procedures, the imaging task is often tied to the registration of intraoperative and preoperative images to a common coordinate system. While the accuracy of this registration is a vital factor in system performance, there is a relatively little work that relates registration accuracy to image quality factors, such as dose, noise, and spatial resolution. To create a theoretical model for such a relationship, we present a Fisher information approach to analyze registration performance in explicit dependence on the underlying image quality factors of image noise, spatial resolution, and signal power spectrum. The model yields analysis of the Cramer–Rao lower bound (CRLB), in registration accuracy as a function of factors governing image quality. Experiments were performed in simulation of computed tomography low-contrast soft tissue images and high-contrast bone (head and neck) images to compare the measured accuracy [root mean squared error (RMSE) of the estimated transformations] with the theoretical lower bound. Analysis of the CRLB reveals that registration performance is closely related to the signal-to-noise ratio of the cross-correlation space. While the lower bound is optimistic, it exhibits consistent trends with experimental findings and yields a method for comparing the performance of various registration methods and similarity metrics. Further analysis validated a method for determining optimal post-processing (image filtering) for registration. Two figures of merit (CRLB and RMSE) are presented that unify models of image quality with registration performance, providing an important guide to optimizing intraoperative imaging with respect to the task of registration. Auteurs: Michael D. Ketcha;Tharindu De Silva;Runze Han;Ali Uneri;Joseph Goerres;Matthew W. Jacobson;Sebastian Vogt;Gerhard Kleinszig;Jeffrey H. Siewerdsen; Apparue dans: IEEE Transactions on Medical Imaging Date publication: 10.-2017, volume: 36, issue:10, pages: 1997 - 2009 Editeur: IEEE Document complet vers site de l'éditeur
» Effects of Inclined Sidewall Structure With Bottom Metal Air Cavity on the Light Extraction Efficiency for AlGaN-Based Deep Ultraviolet Light-Emitting Diodes
 Résumé:An inclined sidewall scattering structure with air cavity characterized by a metal bottom and flat parallel top (Bottom_metal) is proposed to enhance the light extraction efficiency (LEE) for AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs). Compared to the reported sidewall metal inclined sidewall (Sidewall_metal) structure, the Bottom_metal structure can greatly enhance the LEE of DUV LEDs based on three-dimensional finite difference time domain simulations. Further analysis indicates that the existence of the air cavity promotes the Bottom_metal DUV LEDs to mainly utilize the total internal reflection and the Fresnel scattering to scatter the light into the escape cone, which avoids the light absorption from the sidewall metal mirror in the Sidewall_metal structure. Moreover, the unique air cavity having a bottom metal also enhances the scattering ability of the Bottom_metal DUV LEDs because any light within the cavity directing downward will be reflected back, and the parallel top interface of air cavity/AlGaN functions as additional out-light planes not limited by total internal reflection. Auteurs: Yonghui Zhang;Ruilin Meng;Zi-Hui Zhang;Qiang Shi;Luping Li;Guoxu Liu;Wengang Bi; Apparue dans: IEEE Photonics Journal Date publication: 10.-2017, volume: 9, issue:5, pages: 1 - 9 Editeur: IEEE Document complet vers site de l'éditeur
» Effects of Notch Filters on Imbalance Rejection With Heteropolar and Homopolar Magnetic Bearings in a 30-kW 60 000-r/min Motor
 Résumé:Active magnetic bearings (AMBs) have achieved great advantages in the high-speed and high-power-density rotating machine. Various vibration control strategies based on the notch filter have been reported to reduce the rotor imbalance vibration. But, the study is still insufficient to determine why the vibration gets reduced. This paper addresses a concise and direct explanation of the effects of notch filter on the rotor imbalance vibration with AMBs. An analytic solution for the synchronous response of rotor imbalance is introduced using the simple planar rotor model and general notch filter method. Then, combined with practical matters, the amplifier of a heteropolar radial AMB is further specified to uncover the effect of motion induced voltage to rotor self-centering, as a comparison with the homopolar radial AMB. Since the developed motor is equipped with both types of radial AMBs, a detailed control design is exhibited based on the dynamics of rigid body motion. The traditional simplification of two-plane separate control is improved, and a centralized controller is constructed. The effects of the rotor imbalance vibration rejection are demonstrated by the simulation results and experiments in a 30-kW 60000-r/min permanent magnet motor. Auteurs: Jinxiang Zhou;Shiqiang Zheng;Bangcheng Han;Jiancheng Fang; Apparue dans: IEEE Transactions on Industrial Electronics Date publication: 10.-2017, volume: 64, issue:10, pages: 8033 - 8041 Editeur: IEEE Document complet vers site de l'éditeur
» Effects of Signal Saturation on QUS Parameter Estimates Based on High-Frequency-Ultrasound Signals Acquired From Isolated Cancerous Lymph Nodes
 Résumé:Choosing an appropriate dynamic range (DR) for acquiring radio frequency (RF) data from a high-frequency-ultrasound (HFU) system is challenging because signals can vary greatly in amplitude as a result of focusing and attenuation effects. In addition, quantitative ultrasound (QUS) results are altered by saturated data. In this paper, the effects of saturation on QUS estimates of effective scatterer diameter (ESD) and effective acoustic concentration (EAC) were quantified using simulated and experimental RF data. Experimental data were acquired from 69 dissected human lymph nodes using a single-element transducer with a 26-MHz center frequency. Artificially saturated signals ( $x_{c})$ were produced by thresholding the original unsaturated RF echo signals. Saturation severity was expressed using a quantity called saturate-signal-to-noise ratio (SSNR). Results indicated that saturation has little effect on ESD estimates. However, EAC estimates decreased significantly with decreasing SSNR. An EAC correction algorithm exploiting a linear relationship between EAC values over a range of SSNR values and ${l}^{1}$ -norm of $x_{c}$ (i.e., the sum of absolute values of the true RF echo signal) is developed. The maximal errors in EAC estimates resulting from saturation were −8.05, −3.59, and −0.93 dB/mm3 with the RF echo signals thresholded to keep 5, 6, and 7-bit from the original 8-bit DR, respectively. The EAC correction algorithm reduced maximal errors to −3.71, −0.89, and −0.26 dB/mm3 when signals were thresholded at 5, 6, and 7-bit, respectively. Auteurs: Kazuki Tamura;Jonathan Mamou;Alain Coron;Kenji Yoshida;Ernest J. Feleppa;Tadashi Yamaguchi; Apparue dans: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control Date publication: 10.-2017, volume: 64, issue:10, pages: 1501 - 1513 Editeur: IEEE Document complet vers site de l'éditeur
» Efficiency Enhancement for an Inductive Wireless Power Transfer System by Optimizing the Impedance Matching Networks
 Résumé:Inductive wireless power transfer (IWPT) is a promising power technology for implantable biomedical devices, where the power consumption is low and the efficiency is the most important consideration. In this paper, we propose an optimization method of impedance matching networks (IMN) to maximize the IWPT efficiency. The IMN at the load side is designed to achieve the optimal load, and the IMN at the source side is designed to deliver the required amount of power (no-more-no-less) from the power source to the load. The theoretical analyses and design procedure are given. An IWPT system for an implantable glaucoma therapeutic prototype is designed as an example. Compared with the efficiency of the resonant IWPT system, the efficiency of our optimized system increases with a factor of 1.73. Besides, the efficiency of our optimized IWPT system is 1.97 times higher than that of the IWPT system optimized by the traditional maximum power transfer method. All the discussions indicate that the optimization method proposed in this paper could achieve a high efficiency and long working time when the system is powered by a battery. Auteurs: Zhidong Miao;Dake Liu;Chen Gong; Apparue dans: IEEE Transactions on Biomedical Circuits and Systems Date publication: 10.-2017, volume: 11, issue:5, pages: 1160 - 1170 Editeur: IEEE Document complet vers site de l'éditeur
» Efficient Analysis of Metasurfaces in Terms of Spectral-Domain GSTC Integral Equations
 Résumé:We present a spectral-domain (SD) technique for the efficient analysis of metasurfaces. The metasurface is modeled by generalized sheet transition conditions (GSTCs) as a zero-thickness sheet creating a discontinuity in the electromagnetic field. The SD expression of these GSTCs for a specified incident field leads to a system of four surface integral equations for the reflected and transmitted fields, which are solved using the method of moments in the SD. Compared with the finite-difference and finite-element techniques that require meshing the entire computational domain, the proposed technique reduces the problem to the surface of the metasurface, hence eliminating one dimension and providing substantial benefits in terms of memory and speed. A monochromatic generalized-refractive metasurface and a polychromatic focusing metasurface are presented as illustrative examples. Auteurs: Nima Chamanara;Karim Achouri;Christophe Caloz; Apparue dans: IEEE Transactions on Antennas and Propagation Date publication: 10.-2017, volume: 65, issue:10, pages: 5340 - 5347 Editeur: IEEE Document complet vers site de l'éditeur
» Efficient Coded Cooperative Networks With Energy Harvesting and Transferring
 Résumé:In this paper, a multi-user multi-relay network with integrated energy harvesting and transferring (IEHT) strategy is studied. In our system, a simultaneous two-level cooperation, i.e., information- and energy-level cooperation is conducted for uplink data transmissions (from the users to a destination). Specifically, network coding is employed at the relays to facilitate the information-level cooperation; meanwhile, ET is adopted to share the harvested energy among the users for the energy-level cooperation. For generality purposes, the Nakagami- $m$ fading channels that are independent but not necessarily identically distributed (i.n.i.d.) are considered. The problem of energy efficiency maximization under constraints of the energy causality and a predefined outage probability threshold is formulated and shown to be non-convex. By exploiting fractional and geometric programming, a convex form-based iterative algorithm is developed to solve the problem efficiently. Close-to-optimal power allocation and energy cooperation policies across consecutive transmissions are found. Moreover, the effects of relay locations, wireless energy transmission efficiency, battery capacity as well as the existence of direct links are investigated. The performance comparison with the current state of solutions demonstrates that the proposed policies can manage the harvested energy more efficiently. Auteurs: Nan Qi;Ming Xiao;Theodoros A. Tsiftsis;Lin Zhang;Mikael Skoglund;Huisheng Zhang; Apparue dans: IEEE Transactions on Wireless Communications Date publication: 10.-2017, volume: 16, issue:10, pages: 6335 - 6349 Editeur: IEEE Document complet vers site de l'éditeur
» Efficient Constant Modulus Based Carrier Frequency Offset Estimation for CO-OFDM Systems
 Résumé:This paper proposes a blind carrier frequency offset (CFO) estimation method for coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems, using constant modulus signaling. The proposed scheme is based on a robust cost-function, which deviates from the common assumption that the channel frequency response slowly varies either in time or frequency domain. The proposed method adopts a cost-function similar to the Godard's method for blind channel equalization. Using Monte Carlo simulations, the proposed method is shown to offer a superior performance compared to prominent existing methods, in a practical optical link scenario. Also, we show that the proposed cost-function can be approximated and expressed in a closed-form in such a way that the CFO estimate is obtained using only three trial values. Auteurs: Muyiwa B. Balogun;Olutayo O. Oyerinde;Fambirai Takawira; Apparue dans: IEEE Photonics Journal Date publication: 10.-2017, volume: 9, issue:5, pages: 1 - 15 Editeur: IEEE Document complet vers site de l'éditeur
» Efficient Discrete Rate Assignment and Power Optimization in Optical Communication Systems Following the Gaussian Noise Model
 Résumé:Computationally efficient heuristics for solving the discrete-rate capacity optimization problem for optical fiber communication systems are investigated. In the Gaussian noise nonlinearity model regime, this class of problem is an NP-hard mixed integer convex problem. The proposed heuristic minimizes the number of calls required to solve the computationally intensive problem of determining the feasibility of proposed discrete rate allocations. In a live system, optimization using this algorithm minimizes the number of potential discrete rate allocations tested for feasibility while additional discrete system capacity is extracted. In exemplary point-to-point links at 50 Gbaud with 50 Gb/s rate steps, the mean lost capacity per modem is reduced from 24.5 Gb/s with truncation to 7.95 Gb/s with discrete-rate optimization. With 25 Gb/s rate steps, the mean lost capacity is reduced from 12.3 Gb/s to 2.07 Gb/s. An unbiased metric is proposed to extend the capacity optimization objective from point-to-point links to mesh networks. A gain of 13% in distance-times-capacity metric is obtained from discrete-rate optimization with 50 Gb/s rate steps, and a 7.5% gain is obtained with 25 Gb/s rate steps. Auteurs: Ian Roberts;Joseph M. Kahn; Apparue dans: Journal of Lightwave Technology Date publication: 10.-2017, volume: 35, issue:20, pages: 4425 - 4437 Editeur: IEEE Document complet vers site de l'éditeur
» Efficient Memory Partitioning for Parallel Data Access in FPGA via Data Reuse
 Résumé:Parallelizing the memory accesses in a nested loop is a critical challenge to facilitate loop pipelining. An effective approach for high-level synthesis on field-programmable gate array is to map these accesses to multiple on-chip memory banks using a memory partitioning technique. In this paper, we propose an efficient memory partitioning algorithm with low overhead and low time complexity for parallel data access via data reuse. We find that for most applications in image and video processing, a large amount of data can be reused among different iterations of a loop nest. Motivated by this observation, we propose to cache reusable data using on-chip registers, organized as register chains. The nonreusable data are then separated into several memory banks by a memory partitioning algorithm. We revise the existing padding method to cover cases occurring frequently in our method wherein certain components of partition vector are zeros. Experimental results have demonstrated that compared with the state-of-the-art algorithms, the proposed method is efficient in terms of execution time, resource overhead, and power consumption across a wide range of access patterns extracted from applications in image and video processing. As for the testing patterns, the execution time is typically less than one millisecond. And the number of required memory banks is reduced by 59.7% on average, which leads to an average reduction of 78.2% in look-up tables, 65.5% in flip-flops, 37.1% in DSP48Es, and therefore 74.8% reduction in dynamic power consumption. Moreover, the storage overhead incurred by the proposed method is zero for most widely used access patterns in image filtering. Auteurs: Jincheng Su;Fan Yang;Xuan Zeng;Dian Zhou;Jie Chen; Apparue dans: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems Date publication: 10.-2017, volume: 36, issue:10, pages: 1674 - 1687 Editeur: IEEE Document complet vers site de l'éditeur
» Efficient OCT Volume Reconstruction From Slitlamp Microscopes
 Résumé:Since its introduction 25 years ago, Optical Coherence Tomography (OCT) has contributed tremendously to diagnostic and monitoring capabilities of pathologies in the field of ophthalmology. Despite rapid progress in hardware and software technology however, the price of OCT devices has remained high, limiting their use in private practice, and in screening examinations. In this paper, we present a slitlamp-integrated OCT device, built with off-the-shelf components, which can generate high-quality volumetric images of the posterior eye segment. To do so, we present a novel strategy for 3D image reconstruction in this challenging domain that allows us for state-of-the-art OCT volumes to be generated at fast speeds. The result is an OCT device that can match current systems in clinical practice, at a significantly lower cost. Auteurs: Stefanos Apostolopoulos;Raphael Sznitman; Apparue dans: IEEE Transactions on Biomedical Engineering Date publication: 10.-2017, volume: 64, issue:10, pages: 2403 - 2410 Editeur: IEEE Document complet vers site de l'éditeur
» Efficient Ordinary Differential Equation-Based Discontinuous Galerkin Method for Viscoelastic Wave Modeling
 Résumé:We present an efficient nonconformal-mesh discontinuous Galerkin (DG) method for elastic wave propagation in viscous media. To include the attenuation and dispersion due to the quality factor in time domain, several sets of auxiliary ordinary differential equations (AODEs) are added. Unlike the conventional auxiliary partial differential equation-based algorithm, this new method is highly parallel with its lossless counterpart, thus requiring much less time and storage consumption. Another superior property of the AODE-based DG method is that a novel exact Riemann solver can be derived, which allows heterogeneous viscoelastic coupling, in addition to accurate coupling with purely elastic media and fluid. Furthermore, thanks to the nonconformal-mesh technique, adaptive hp-refinement and flexible memory allocation for the auxiliary variables are achieved. Numerical results demonstrate the efficiency and accuracy of our method. Auteurs: Qiwei Zhan;Mingwei Zhuang;Qingtao Sun;Qiang Ren;Yi Ren;Yiqian Mao;Qing Huo Liu; Apparue dans: IEEE Transactions on Geoscience and Remote Sensing Date publication: 10.-2017, volume: 55, issue:10, pages: 5577 - 5584 Editeur: IEEE Document complet vers site de l'éditeur
» Efficient Privacy-Preserving Dual Authentication and Key Agreement Scheme for Secure V2V Communications in an IoV Paradigm
 Résumé:The Internet of Vehicles (IoV) aims to provide a new convenient, comfortable, and safe driving way, and in turn enables intelligent transportation through wireless communications among road-side units, on-board units (OBUs), phones, and other devices inside a vehicle. However, significantly increasing reliance on wireless communication, control, and computing technology makes IoV more vulnerable to potential attacks, such as remote intrusion, control, and trajectory tracking. Therefore, efficient authentication solutions preventing unauthorized visitors need to be addressed to cope with these issues. Hence, in this paper we focus on the security and privacy-preserving by developing a dual authentication scheme for IoV according to its different scenarios. First, the OBU self-generates an anonymous identity and temporary encryption key to open an authentication session. Second, the legitimacy of the vehicle’s real and anonymous identity can be verified by trust authority (TA). After that, the vehicle’s reputation is evaluated according to its history interactive behavior and the session key for V2V can be finally established. There are three major advantages, including privacy-preserving and security enhancement without a burden of key management in the condition of acceptable time delay range, introducing trust evaluation into authentication protocol, as well as considering the vehicle behavior attributes in the new reputation evaluation method. In addition, we also prove the correctness of this scheme using the Burrows–Abadi–Needham (BAN) logic, and the performance comparison against the existing schemes is given as well. Auteurs: Yanbing Liu;Yuhang Wang;Guanghui Chang; Apparue dans: IEEE Transactions on Intelligent Transportation Systems Date publication: 10.-2017, volume: 18, issue:10, pages: 2740 - 2749 Editeur: IEEE Document complet vers site de l'éditeur
» Efficient Retrieval of Bounded-Cost Informative Routes
 Résumé:The widespread location-aware applications produce a vast amount of spatio-textual data that contains both spatial and textual attributes. To make use of this enriched information for users to describe their preferences for travel routes, we propose a Bounded-Cost Informative Route (BCIR) query to retrieve the routes that are the most textually relevant to the user-specified query keywords subject to a travel cost constraint. BCIR query is particularly helpful for tourists and city explorers to plan their travel routes. We will show that BCIR query is an NP-hard problem. To answer BCIR query efficiently, we propose an exact solution with effective pruning techniques and two approximate solutions with performance guarantees. Extensive experiments over real data sets demonstrate that the proposed solutions achieve the expected performance. Auteurs: Wengen Li;Jiannong Cao;Jihong Guan;Man Lung Yiu;Shuigeng Zhou; Apparue dans: IEEE Transactions on Knowledge and Data Engineering Date publication: 10.-2017, volume: 29, issue:10, pages: 2182 - 2196 Editeur: IEEE Document complet vers site de l'éditeur
» Electric Field Reconstruction and Transport Parameter Evaluation in CZT X-Ray Detectors
 Résumé:The laser-induced current technique has been successful used to reconstruct the spatial profile of the electric field along the thickness of a set of CdZnTe spectroscopic X-ray detectors. Current transient profiles for electrons at different applied voltages have been analyzed by means of a minimization procedure demonstrating its applicability to samples with thickness ranging from 250 $mu text{m}$ to 4 mm. Mobility and lifetime of electrons have also been deduced and compared with the mobility-lifetime products, as evaluated by fitting the charge collection efficiency curves under a suitable electric field profile model. Comparison between results from both techniques gives a good agreement and confirms the validity of the procedure. This method results applicable each time that carrier transit times can be evaluated from the laser-induced current transients. It could be suitable for many other devices provided that they are made of materials with sufficiently high resistivity, i.e., with a sufficiently low density of free carriers in dark conditions. Auteurs: M. Pavesi;A. Santi;M. Bettelli;A. Zappettini;M. Zanichelli; Apparue dans: IEEE Transactions on Nuclear Science Date publication: 10.-2017, volume: 64, issue:10, pages: 2706 - 2712 Editeur: IEEE Document complet vers site de l'éditeur
» Electric Vehicle Route Selection and Charging Navigation Strategy Based on Crowd Sensing
 Résumé:This paper has proposed an electric vehicle (EV) route selection and charging navigation optimization model, aiming to reduce EV users’ travel costs and improve the load level of the distribution system concerned. Moreover, with the aid of crowd sensing, a road velocity matrix acquisition and restoration algorithm is proposed. In addition, the waiting time at charging stations is addressed based on the queue theory. The formulated objective of the presented model is to minimize the EV users’ travel time, charging cost or the overall cost based on the time of use price mechanism, subject to a variety of technical constraints such as path selections, travel time, battery capacities, and charging or discharging constraints, etc. Case studies are carried out within a real-scale zone in a city where there are four charging stations and the IEEE 33-bus distribution system. The effects of real-time traffic information acquisition and different decision targets on EV users’ travel route and effects of charging or discharging of EVs on the load level of the distribution system are also analyzed. The simulation results have demonstrated the feasibility and effectiveness of the proposed approach. Auteurs: Hongming Yang;Youjun Deng;Jing Qiu;Ming Li;Mingyong Lai;Zhao Yang Dong; Apparue dans: IEEE Transactions on Industrial Informatics Date publication: 10.-2017, volume: 13, issue:5, pages: 2214 - 2226 Editeur: IEEE Document complet vers site de l'éditeur
» Electric-Field-Controlled Interface Exchange Coupling in Cobalt–Chromia Thin Films
 Résumé:First-principle calculations are used to determine the interface exchange coupling in cobalt–chromia thin films as a function of the electric field. Both bilayer Co/Cr2O3 and trilayer Co/Pt/Cr2O3 are investigated. The sign and magnitude of the interface exchange depend on the thickness of the cobalt layer, and oscillatory sign changes of the interface exchange are found in the trilayer system. The electric field dependence of the exchange may be exploited in voltage-controlled spin-electronics applications. Auteurs: Renu Choudhary;Ralph Skomski;Arti Kashyap; Apparue dans: IEEE Transactions on Magnetics Date publication: 10.-2017, volume: 53, issue:10, pages: 1 - 4 Editeur: IEEE Document complet vers site de l'éditeur
» Electrical and Acoustic Parameters of Wire-Guided Discharges in Water: Experimental Determination and Phenomenological Scaling
 Résumé:This paper is focused on investigation of the electrical, hydrodynamic, and acoustic parameters of underwater plasma discharges, stabilized with thin copper wires. The experimental current and acoustic waveforms have been obtained using different combinations of the circuit capacitance, charging voltage, and wire length. The resistances of plasma discharges have been calculated for all combinations of electrical and topological parameters, based on the constant resistance approach. Phenomenological scaling relationships that link the plasma resistance and the total energy delivered to the plasma, the period of discharge cavity oscillation and the peak magnitude of the acoustic impulse have been obtained. These relationships can be used in optimization of the acoustic output from the wire-guided discharges for different practical applications. Auteurs: Ying Sun;Igor V. Timoshkin;Scott J. MacGregor;Mark P. Wilson;Martin J. Given;Tao Wang;Nelly Bonifaci; Apparue dans: IEEE Transactions on Plasma Science Date publication: 10.-2017, volume: 45, issue:10, pages: 2648 - 2655 Editeur: IEEE Document complet vers site de l'éditeur
» Electricity Auction Simulation Platform for Learning Competitive Energy Markets
 Résumé:Considering that each energy market presents its own singularities according to its maturity, liquidity, generation matrix characteristics, and generation capacities, energy auctions are widely used to guarantee fair tariffs. These auctions also promote competition and the search for more efficient generation sources. The platform developed is designed to be an auxiliary tool for stimulating students in learning the processes of electricity market mechanisms. It enables students to develop a better sensitivity regarding energy auctions as they can train and see the results of those auctions. The energy auction platform developed in our work is easy to use and to update, and it can support the learning of electricity auctions. This platform also can be used in any computer and in almost all computer networks. It can be adapted to other kind of auctions and designed to address different electricity markets. Auteurs: Edgar B. Xavier;David A.V. Goncalves;Bruno H. Dias;Bruno S.M.C. Borba; Apparue dans: IEEE Potentials Date publication: 10.-2017, volume: 36, issue:5, pages: 32 - 36 Editeur: IEEE Document complet vers site de l'éditeur
» Electromagnetic Inverse Problems [Guest Editorial]
 Résumé: Auteurs: Maokun Li;Aria Abubakar; Apparue dans: IEEE Antennas and Propagation Magazine Date publication: 10.-2017, volume: 59, issue:5, pages: 9 - 115 Editeur: IEEE Document complet vers site de l'éditeur
» Electromagnetic Tomography for Detection, Differentiation, and Monitoring of Brain Stroke: A Virtual Data and Human Head Phantom Study.
 Résumé:Brain stroke is one of the leading causes of death and disability worldwide [1]. It can be classified as ischemic stroke (i-stroke), e.g., blood flow is restricted by a blood clot, or hemorrhagic stroke (h-stroke), e.g., a bleeding in the brain. Approximately 80% of total stroke cases are ischemic. The most common treatment for i-stroke to date is the use of thrombolytics: drugs that dissolve the blood clots. The clinical decision to apply a thrombolytic should be made within 3-4.5 h from the onset of the stroke symptoms (e.g., [2]), and it relies on imaging methods such as computed tomography (CT) and magnetic resonance imaging (MRI). Further evaluation of stroke evolution is done mainly by imaging to assess the extent of the ischemic injury and to correlate with the functional behavior of the patient. However, to date there is no accurate way to provide reliable information about the key components of i-stroke physiology that include the position and size of the acute stroke (arterial occlusion), the core infarct region that contains irreversibly injured tissues, and the ischemic penumbra, i.e., the tissue that could potentially be restored by rapid revascularization [1], [3]. Auteurs: Markus Hopfer;Ramon Planas;Abouzar Hamidipour;Tommy Henriksson;Serguei Semenov; Apparue dans: IEEE Antennas and Propagation Magazine Date publication: 10.-2017, volume: 59, issue:5, pages: 86 - 97 Editeur: IEEE Document complet vers site de l'éditeur
» Electromagnetic Wave Propagation in the Turbulent Atmosphere With an Anisotropic Exponent of the Spectrum
 Résumé:In this communication, we propose a new model for describing the anisotropy of turbulence relative to the vertical and horizontal directions, through the anisotropy of the structure function exponent. Using the obtained anisotropy spectrum, we calculate various parameters such as log-amplitude variance for various atmospheric communication channels with comparison to the classical Kolmogorov model and newer models developed in previous works. Auteurs: Elad Dakar;Ephim Golbraikh;Natan Kopeika;Arkadi Zilberman; Apparue dans: IEEE Transactions on Antennas and Propagation Date publication: 10.-2017, volume: 65, issue:10, pages: 5654 - 5657 Editeur: IEEE Document complet vers site de l'éditeur
» Electromagnetically Induced Transparency in an All-Dielectric Metamaterial-Waveguide With Large Group Index
 Résumé:We investigate numerically an analog of electromagnetically induced transparency (EIT) in an all-dielectric metamaterial-waveguide (ADMW) that consists of a two-dimensional silicon rod array on quartz slab waveguide. The EIT-like response is achieved by the destructive interference between a broad magnetic resonance and a narrow guide mode resonance. By tailoring the guided mode through the thickness of the slab waveguide or the lattice period of the metamaterial, an EIT-like transmission window is achieved with both high Q-factor (>104) and high transmission (>94%). And the group refractive index at the EIT-like resonance of the ADMW can be up to several thousands. These results demonstrate that the proposed ADMW has potential applications in low-loss slow-light based devices, bio-chemical sensing, and optical modulations. Auteurs: Chuanshuai Sui;Bingxin Han;Tingting Lang;Xiangjun Li;Xufeng Jing;Zhi Hong; Apparue dans: IEEE Photonics Journal Date publication: 10.-2017, volume: 9, issue:5, pages: 1 - 8 Editeur: IEEE Document complet vers site de l'éditeur
» Electromechanical and Electronic Integrated Harvester for Shoes Application
 Résumé:Energy harvesting allows making sensors or transmitters electrically autonomous. Several studies have been proposed but most cases lack electrical and mechanical parts integration and practical application purpose. Here, with the aim of supplying a Bluetooth step-counter placed in the sole of a training shoe, a complete system is presented. It consists of a magnetoinductive transducer embedded with an electronic interface for power conditioning and exploits only the energy recovered by the impact on the ground. A $phi$  27 $times$  16 mm cylindrical device containing the transducer, the electronic interface, the step-counter electronics, and the protective shell is developed. Energy recovery derives from the magnet-free oscillation following the shoe impact. The proposed interface exploits pulse-width modulation to perform transducer output rectification and to emulate optimal load impedance while charging a storage capacitor. Numerical and experimental analysis show effective optimal resistive load emulation and energy recovery gain of 2 compared with the standard ac–dc interface. Prototypes have been manufactured and tested. Considering a sample footstep, energy recovery is 360 μJ against 400 μJ dissipated on optimal resistor. Mean energy recovery over a complete run is 644 μJ/footstep. In spite of variable excitation, energy recovery at each footstep is larger than the required and allows the step-counter transmitting the information. Auteurs: Elvio Bonisoli;Maurizio Repetto;Nicolò Manca;Alessandro Gasparini; Apparue dans: IEEE/ASME Transactions on Mechatronics Date publication: 10.-2017, volume: 22, issue:5, pages: 1921 - 1932 Editeur: IEEE Document complet vers site de l'éditeur
» Electromigration-Aware Local-Via Allocation in Power/Ground TSVs of 3-D ICs
 Résumé:With increasing temperature and current density, electromigration (EM) becomes a major interconnect reliability concern for 3-D integrated-circuits (3-D ICs). In 3-D power delivery networks, local vias are used inside power/ground (P/G) through-silicon-vias (TSVs) for vertical power delivery, which are susceptible to EM effects. In order to improve the EM reliability of P/G TSVs, it is desirable to insert multiple local vias in each P/G TSV whereby the current density of each local via can be reduced. However, excessive local vias may consume too much routing area, which leads to exacerbated routing congestion and increased delay overhead. In this paper, we propose a design technique to handle this tradeoff between EM reliability of P/G TSVs and timing performance of 3-D ICs. By utilizing an integer-linear-programming formulation, the optimal local-via number in each P/G TSV can be determined to minimize the local via-induced routing congestion while satisfying the given requirement of EM reliability. Auteurs: Shengcheng Wang;Mehdi B. Tahoori; Apparue dans: IEEE Transactions on Very Large Scale Integration Systems Date publication: 10.-2017, volume: 25, issue:10, pages: 2881 - 2892 Editeur: IEEE Document complet vers site de l'éditeur
» Electrospun Iron-Based Fibers for Use in MEMS Sensors
 Résumé:This letter reports on the characterization of iron containing nanofibers using a polyvinyl alcohol (PVA)-based solution in a batch electrospinning processing method. Variation of iron content within the pre-fiber solution, and characterization of fiber size and porosity are important for the use of these nanomaterials in sensing. Simulated non-porous fibers are compared with nanofibers obtained utilizing this method. Pre-calcination (thermal) fibers had diameters of 243 nm on average with a standard deviation of ±43 nm and a standard error of ±4.53 nm. Fabrication of mesoporous iron-based nanofibers was achieved after the calcination of the iron/PVA fibers. With the calcination process, we produced fibers with 32-nm diameters, and a standard deviation of ±12 nm and a standard error of ±1.41 nm. The error between model and experimental results is 37.5% for producing Fe3O4 fibers. This error percentage and oversized dimensions suggest near total conversion to Fe3O4 occurring due to calcination as well as creating mesoporous fibers. [2017-0014] Auteurs: Nicholas Groden;William Clower;Chester G. Wilson; Apparue dans: Journal of Microelectromechanical Systems Date publication: 10.-2017, volume: 26, issue:5, pages: 987 - 989 Editeur: IEEE Document complet vers site de l'éditeur
» Embedded Deterministic Test Points
 Résumé:There is mounting evidence that automatic test pattern generation tools capable of producing tests with high coverage of defects occurring in the large semiconductor nanometer designs unprecedentedly inflate test sets and test application times. A design-for-test technique presented in this paper aims at reducing deterministic pattern counts and test data volume through the insertion of conflict-aware test points. This methodology identifies and resolves conflicts across internal signals allowing test generation to increase the number of faults targeted by a single pattern. This is complemented by a method to minimize silicon area needed to implement conflict-aware test points. The proposed approach takes advantage of the conflict analysis and reuses functional flip-flops as drivers of control points. Experimental results on industrial designs with on-chip test compression demonstrate that the proposed test points are effective in achieving, on average, an additional factor of $2\times$ – $4\times$ compression for stuck-at and transition patterns over the best up-to-date results provided by the embedded deterministic test (EDT)-based regular compression. Auteurs: Cesar Acero;Derek Feltham;Yingdi Liu;Elham Moghaddam;Nilanjan Mukherjee;Marek Patyra;Janusz Rajski;Sudhakar M. Reddy;Jerzy Tyszer;Justyna Zawada; Apparue dans: IEEE Transactions on Very Large Scale Integration Systems Date publication: 10.-2017, volume: 25, issue:10, pages: 2949 - 2961 Editeur: IEEE Document complet vers site de l'éditeur
» Embedding Learning on Spectral–Spatial Graph for Semisupervised Hyperspectral Image Classification
 Résumé:Scarcity of labeled samples is the main obstacle for hyperspectral image classification tasks when labeling data is considerably costly and time-consuming in real-world scenarios. To alleviate any underfitting problem that may occur due to lack of training data, semisupervised classification frameworks explore the intrinsic information of unlabeled samples and bridge labeled and unlabeled data. In this letter, we propose a novel framework that learns underlying manifold representation and semisupervised classifier simultaneously. It avoids explicit eigenvector decomposition and directly samples via iterating random walk on the similarity graph, which makes it feasible to implement on huge graphs. To verify the efficacy of embedding the learning process, we compare the proposed method with other dimensionality reduction and manifold-learning-based approaches. Experimental results show that compared to the methods using traditional semisupervised strategies, the graph embedding method gives a better result. Auteurs: Jiayan Cao;Bin Wang; Apparue dans: IEEE Geoscience and Remote Sensing Letters Date publication: 10.-2017, volume: 14, issue:10, pages: 1805 - 1809 Editeur: IEEE Document complet vers site de l'éditeur
» Empirical Study of DSRC Performance Based on Safety Pilot Model Deployment Data
 Résumé:Dedicated short range communication (DSRC) was designed to provide reliable wireless communication for intelligent transportation system applications. Sharing information among cars and between cars and the infrastructure, pedestrians, or “the cloud” has great potential to improve safety, mobility, and fuel economy. DSRC is being considered by the U.S. Department of Transportation to be required for ground vehicles. In the past, their performance has been assessed thoroughly in the laboratories and limited field testing, but not on a large fleet. In this paper, we present the analysis of DSRC performance using data from the world’s largest connected vehicle test program—Safety Pilot Model Deployment lead by the University of Michigan. We first investigate their maximum and effective range, and then study the effect of environmental factors, such as trees/foliage, weather, buildings, vehicle travel direction, and road elevation. The results can be used to guide future DSRC equipment placement and installation, and can be used to develop DSRC communication models for numerical simulations. Auteurs: Xianan Huang;Ding Zhao;Huei Peng; Apparue dans: IEEE Transactions on Intelligent Transportation Systems Date publication: 10.-2017, volume: 18, issue:10, pages: 2619 - 2628 Editeur: IEEE Document complet vers site de l'éditeur
» Enabling Anonymous Authorization and Rewarding in the Smart Grid
 Résumé:The smart grid leverages infrastructural support to achieve fine-grained power consumption monitoring in an attempt to offer higher efficiency, reliability, and security. Such functionality, however, requires the collection of fine-grained usage data which may raise serious concerns with respect to consumer privacy. Thus far, existing work has solely focused on the problem of privately aggregating energy measurements. However, these solutions do not allow the provider to acquire detailed energy measurements which are essential for maintaining the network, debugging configuration problems, etc. In this work, we address this problem and we propose an authentication scheme that allows a smart meter to anonymously interact with the utility provider when submitting detailed consumption data. We then move one step further, enabling the incorporation of anonymous rewarding mechanisms in the smart grid in exchange for detailed measurements that users report. We argue that such rewarding mechanisms provide solid incentives for users to accept the release of their detailed energy consumption; we show that our proposal does notleak any information about the identity of users-even when redeeming the rewards. Finally, we implement a prototype based on our proposal and we evaluate its performance in realistic deployment settings. Auteurs: Tassos Dimitriou;Ghassan O. Karame; Apparue dans: IEEE Transactions on Dependable and Secure Computing Date publication: 10.-2017, volume: 14, issue:5, pages: 565 - 572 Editeur: IEEE Document complet vers site de l'éditeur
» End-to-End Backlog and Delay Bound Analysis for Multi-Hop Vehicular Ad Hoc Networks
 Résumé:Vehicular ad hoc network (VANET) is able to facilitate data exchange among vehicles and provides diverse data services. Intuitively, end-to-end backlog and delay bounds are considered significant metrics to evaluate the quality of service in VANETs. In order to analyze how the multi-hop transmission impacts the delay performance, we model the multi-hop service process into a virtualized single service in a min-plus convolution form. To obtain multi-hop end-to-end backlog and delay bound, we consider the stochastic network traffic characteristics and the highly dynamic channel environment under the static priority, first in first out, and earliest deadline first scheduling policies by applying the martingale theory. The IEEE 802.11p enhanced distributed channel access mechanism is also adopted to analyze the access performance in the MAC sub-layer. With three kinds of real wireless data traces, i.e., VoIP, gaming, and UDP, we verify our algorithm by considering the double Nakagami- $m$ fading channel model among vehicles. From the simulation results, we can see that the supermartingale end-to-end backlog and delay bound are remarkably tight to the real simulation results when compared with the existing standard bounds. The effect of the number of vehicles on the highway on the end-to-end backlog and delay performance is also investigated. Auteurs: Yun Hu;Hongyan Li;Zheng Chang;Zhu Han; Apparue dans: IEEE Transactions on Wireless Communications Date publication: 10.-2017, volume: 16, issue:10, pages: 6808 - 6821 Editeur: IEEE Document complet vers site de l'éditeur
» End-to-End Throughput of Ad Hoc Multi-Hop Networks in a Poisson Field of Interferers
 Résumé:This paper proposes a novel approach to assess the performance in terms of end-to-end throughput of an ad hoc multi-hop wireless network, where each link is affected by interference coming from other multi-hop paths nearby. The approach captures the mutual impact of each path on all others. It can be applied to both, contention-based and scheduled, medium access control (MAC) protocols. Sources have data to send to destination nodes through $n$ relays. Nodes are assumed to be uniformly and randomly distributed in the 2-D infinite plane. The model shows the impact on the end-to-end throughput of $n$ ; it also captures the influence of node density, traffic generated, number of retransmissions, and other MAC parameters. Finally, the model provides the throughput-delay tradeoff. Unlike most previous approaches, the mathematical tool proposed appears to be scalable, allowing easy extension to any number of hops. Comparison with simulation results is provided to prove that the impact of the approximations introduced in the analysis is almost negligible. Auteurs: Chiara Buratti;Roberto Verdone; Apparue dans: IEEE/ACM Transactions on Networking Date publication: 10.-2017, volume: 25, issue:5, pages: 3189 - 3202 Editeur: IEEE Document complet vers site de l'éditeur
» Energy Big Data Security Threats in IoT-Based Smart Grid Communications
 Résumé:Increased intelligence and automation in smart grid results in many heterogeneous applications benefiting from the Internet of Things, such as demand response, energy delivery efficiency/reliability, and fault recovery. However, vulnerabilities in smart grid arise due to public communication infrastructure and Internet-based protocols. To deal with security threats, energy big data should be thoughtfully stored and processed to extract critical information, and security and blackout warnings should be given in an early stage. This work gives a comprehensive tutorial and survey to highlight research challenges on the aforementioned issues in the Internet-of-Things-based smart grid. We demonstrate that a stealthy and blind energy big data attack can be launched using a replay scheme. Also, we elucidate an intuitive geometric viewpoint for this type of attack. The proposed attack can bypass bad data detection successfully using either DC or AC state estimation. Auteurs: Wen-Long Chin;Wan Li;Hsiao-Hwa Chen; Apparue dans: IEEE Communications Magazine Date publication: 10.-2017, volume: 55, issue:10, pages: 70 - 75 Editeur: IEEE Document complet vers site de l'éditeur
» Energy Consume Analysis for Ring-Topology TWDM-PON Front-Haul Enabled Cloud RAN
 Résumé:Cloud radio access network (C-RAN) is a new architecture to meet the ever increasing internet data traffic. In particular, the operating expense (OPEX), mainly the energy consumption, of C-RAN is an issue of common concern. Several former works in this area lacked the essential consideration for the optical front-haul part, as a result that it cannot provide overall energy consumption study for the whole system. In this paper, we analyze the energy consume problem in a new C-RAN architecture, i.e., the ring-topology time-wavelength division multiplexing (TWDM) passive optical network (PON) front-haul enabled C-RAN, considering the requirements for large transmission capacity, high energy efficiency, and the appropriate utilization in the large-scale and densely populated cities. After bringing in this optical front-haul and considering the quality of service, a network traffic modeling is provided to analyze the energy problem based on queueing theory. We also conduct the network optimization to ensure that the system works in the most energy-efficient state. Besides, the energy comparisons among the ring-topology TWDM-PON front-haul enabled C-RAN, the time division multiplexing (TDM) PON enabled C-RAN and the ring-topology TWDM-PON-LTE architecture have also been made. According to the numerical results, the new C-RAN, after energy optimization, can save up to 58.1% energy compared with the TWDM-PON-LTE architecture, and also has a slight advantage over the TDM-PON enabled C-RAN (saving more than 2% energy), demonstrating its broad application prospects and large potential in the future. Auteurs: Zhongwei Tan;Chuanchuan Yang;Ziyu Wang; Apparue dans: Journal of Lightwave Technology Date publication: 10.-2017, volume: 35, issue:20, pages: 4526 - 4534 Editeur: IEEE Document complet vers site de l'éditeur
» Energy Efficient Communication for Secure D2D Underlaid Cellular Networks
 Résumé:We study energy-efficient secure communication in large-scale device-to-device (D2D) underlaid cellular networks, where base stations (BSs) and D2D users send their messages occupying the same spectrum while eavesdroppers (Eve nodes) overhear their transmissions. First, we consider the secure cellular network where users operate only in the cellular mode. We propose a link adaptation of the cellular network that strikes a balance between secrecy energy efficiency (SEE) and secrecy spectral efficiency (SSE) by maximizing the weighted product of SEE and SSE. Besides, we show that SSE first increases and then decreases with the BS power when the ratio of the eavesdropper (Eve) node density to the BS density is above a certain threshold while it monotonically increases when the Eve-to-BS density ratio is below the threshold. On the other hand, SEE first increases and then decreases with the BS power regardless of the Eve-to-BS density ratio. Next, we study how to deploy the secure D2D network under the existing secure cellular network while guaranteeing an acceptable secrecy performance of the cellular network. We show that the secrecy performance of the cellular network decreases with the D2D power when the Eve nodes are sparse while it first increases and then decreases when the Eve nodes are dense. Based on the result, we propose a link adaptation for the D2D network that maximizes the weighted product of SEE and SSE under the secrecy performance constraint of the cellular network. Simulation results show that the proposed link-adaptation schemes can achieve all the points on the Pareto boundary in SSE–SEE plane. Auteurs: Younggap Kwon;Hyunjoon Suh;Jintaek Oh;Taewon Hwang; Apparue dans: IEEE Transactions on Vehicular Technology Date publication: 10.-2017, volume: 66, issue:10, pages: 9110 - 9123 Editeur: IEEE Document complet vers site de l'éditeur
» Energy Efficient Ethernet on MapReduce Clusters: Packet Coalescing To Improve 10GbE Links
 Résumé:An important challenge of modern data centers is to reduce energy consumption, of which a substantial proportion is due to the network. Switches and NICs supporting the recent energy efficient Ethernet (EEE) standard are now available, but current practice is to disable EEE in production use, since its effect on real world application performance is poorly understood. This paper contributes to this discussion by analyzing the impact of EEE on MapReduce workloads, in terms of performance overheads and energy savings. MapReduce is the central programming model of Apache Hadoop, one of the most widely used application frameworks in modern data centers. We find that, while 1GbE links (edge links) achieve good energy savings using the standard EEE implementation, optimum energy savings in the 10 GbE links (aggregation and core links) are only possible, if these links employ packet coalescing. Packet coalescing must, however, be carefully configured in order to avoid excessive performance degradation. With our new analysis of how the static parameters of packet coalescing perform under different cluster loads, we were able to cover both idle and heavy load periods that can exist on this type of environment. Finally, we evaluate our recommendation for packet coalescing for 10 GbE links using the energy-delay metric. This paper is an extension of our previous work [1], which was published in the Proceedings of the 40th Annual IEEE Conference on Local Computer Networks (LCN 2015). Auteurs: Renan Fischer e Silva;Paul M. Carpenter; Apparue dans: IEEE/ACM Transactions on Networking Date publication: 10.-2017, volume: 25, issue:5, pages: 2731 - 2742 Editeur: IEEE Document complet vers site de l'éditeur
» Energy Savings of a Hybrid Truck Using a Ravigneaux Gear Train
 Résumé:The series–parallel powertrains for high-power vehicles have complex architectures. They generally require multiple planetary gear trains with several clutches. The maintenance and durability of the clutches are nonetheless not relevant for on-board implementation. In this paper, a new architecture with a Ravigneaux gear train without clutches is proposed. The complexity of the architecture is then reduced. The objective of this paper is to illustrate the benefits of such a powertrain in terms of energy savings in comparison to a conventional truck. Due to the mechanical constraints of the gear train, the control scheme of the vehicle is complex to design. A functional description, the Energetic Macroscopic Representation, is then used to organize the control scheme. Simulation results, with a rules-based energy management strategy, show a reduction of the fuel consumption from 6% to 19% depending on the driving cycles. To prove the use of a Ravigneaux gear train as a power split device, the basic operating modes are validated in the open-loop control on a test bed. Auteurs: Walter Lhomme;Alain Bouscayrol;Sajjad Ali Syed;Sébastien Roy;Frédéric Gailly;Olivier Pape; Apparue dans: IEEE Transactions on Vehicular Technology Date publication: 10.-2017, volume: 66, issue:10, pages: 8682 - 8692 Editeur: IEEE Document complet vers site de l'éditeur
» Energy Storage in Microgrids: Compensating for Generation and Demand Fluctuations While Providing Ancillary Services
 Résumé:Driven by global environmental emission issues, energy access in remote communities, and tighter requirements for system resilience and reliability, electricity production is shifting from a centralized paradigm to a decentralized one. In this context, renewable energy sources (RESs) have proliferated over the past decade, exhibiting a steadily increasing trend. Thus, today, a large number of wind turbines and photovoltaic (PV) panels are connected to medium- (1-69 kV) and low-voltage (=1 kV) grids, with traditional integrated bulk power systems becoming decentralized in the presence of active distribution networks, where the flow of power is bidirectional between generators and "prosumers." In particular, with decreasing RES s costs, these technologies are becoming attractive solutions to bring energy to remote communities and/or replace expensive fossil-fuel-based generators. However, RES s such as wind and solar are intermittent sources of energy, difficult to predict, and prone to large output fluctuations-therefore, significantly affecting system voltage and frequency. Auteurs: Mostafa Farrokhabadi;Bharatkumar V. Solanki;Claudio A. Canizares;Kankar Bhattacharya;Sebastian Koenig;Patrick S. Sauter;Thomas Leibfried;Sören Hohmann; Apparue dans: IEEE Power and Energy Magazine Date publication: 10.-2017, volume: 15, issue:5, pages: 81 - 91 Editeur: IEEE Document complet vers site de l'éditeur
» Energy Storage Systems: Applications, Regulations, & Renewable Resources [From the Editor]
 Résumé:Presents the introductory editorial for this issue of the publication. Auteurs: Michael Henderson; Apparue dans: IEEE Power and Energy Magazine Date publication: 10.-2017, volume: 15, issue:5, pages: 4 - 8 Editeur: IEEE Document complet vers site de l'éditeur
» Energy Storage: From Holywood Stunt Double to Action Hero [In My View]
 Résumé:Discusses the growing market for advanced battery-based energy storage systems and reports on applications for their use. Auteurs: J. Chris Shelton; Apparue dans: IEEE Power and Energy Magazine Date publication: 10.-2017, volume: 15, issue:5, pages: 112 - 108 Editeur: IEEE Document complet vers site de l'éditeur
 Résumé:Would you pay slightly more for your electricity if you knew it was sourced from photovoltaic panels on your neighbor's roof? Or, if you are that neighbor, would you use your solar power to charge a battery and dump that energy back onto the grid at peak hours, when the price was highest? The answers to these questions-which depend on how people would behave in an open energy market-are unknown, because that market does not exist. Net metering and feed-in tariff programs, the two dominant schemes for reimbursing residential energy production, pay out at a fixed rate, effectively decoupling producers from the price signals that might otherwise direct their behavior. But that may be changing. And we may have the blockchain to thank. Multiple projects are now under way to use technology that was originally intended to account for transactions in digital currency to track electricity production and put it up for sale. Auteurs: Morgen E. Peck;David Wagman; Apparue dans: IEEE Spectrum Date publication: 10.-2017, volume: 54, issue:10, pages: 56 - 61 Editeur: IEEE Document complet vers site de l'éditeur
» Energy-Arrival-Aware Detection Threshold in Wireless-Powered Cognitive Radio Networks
 Résumé:Traffic patterns associated with different primary user (PU) channels may provide different spectral access and energy harvesting opportunities in wireless-powered cognitive radio networks (WP-CRNs). Considering this, we propose traffic-specific optimal spectrum sensing policy such that the expected transmission rate of secondary user (SU) is maximized under the energy causality and PU collision constraints in orthogonal frequency-division multiple access (OFDMA)-based WP-CRN. Toward this, we cluster $N$ subcarriers (subchannels) into $K$ clusters (where $K \leq N$) and derive an optimal energy detection threshold for the SU under each traffic pattern. Using traffic features, we propose an unsupervised and nonparametric classification technique to determine the number of unique traffic patterns $K$ over all subchannels. Then, the traffic patterns are used to predict the idle/busy period statistics for subchannels, based upon which SU identifies harvest and transmit PU subchannels for energy harvesting and data transmission, respectively. We derive an optimal detection threshold based on the harvested energy such that it maximizes the expected transmission rate of SU while protecting PU from collision. We demonstrate the effectiveness of the proposed scheme in terms of rate gains under design constraints and show the optimal detection threshold under various energy arrival rates. Auteurs: Muhammad Ejaz Ahmed;Dong In Kim;Jin Young Kim;Yoan Shin; Apparue dans: IEEE Transactions on Vehicular Technology Date publication: 10.-2017, volume: 66, issue:10, pages: 9201 - 9213 Editeur: IEEE Document complet vers site de l'éditeur
» Energy-Efficient Near-Threshold Parallel Computing: The PULPv2 Cluster
 Résumé:This article presents an ultra-low-power parallel computing platform and its system-on-chip (SoC) embodiment, targeting a wide range of emerging near-sensor processing tasks for Internet of Things (IoT) applications. The proposed SoC achieves 193 million operations per second (MOPS) per mW at 162 MOPS (32 bits), improving the first-generation Parallel Ultra-Low-Power (PULP) architecture by 6.4 and 3.2 times in performance and energy efficiency, respectively. Auteurs: Davide Rossi;Antonio Pullini;Igor Loi;Michael Gautschi;Frank Kağan Gürkaynak;Adam Teman;Jeremy Constantin;Andreas Burg;Ivan Miro-Panades;Edith Beignè;Fabien Clermidy;Philippe Flatresse;Luca Benini; Apparue dans: IEEE Micro Date publication: 10.-2017, volume: 37, issue:5, pages: 20 - 31 Editeur: IEEE Document complet vers site de l'éditeur
» Energy-Efficient Reconfigurable SRAM: Reducing Read Power Through Data Statistics
 Résumé:This paper introduces a framework for designing data-dependent SRAMs taking advantage of statistical dependencies present in the binary values processed and stored in the intermediary stages of various algorithms. To demonstrate the framework, a reconfigurable conditional precharge (CP) SRAM is designed in a 28-nm fully-depleted silicon-on-insulator CMOS process. To reduce read power consumption, the SRAM reconfigures its prediction scheme for each column as the data statistics evolve. A 10T bit cell, a prediction-based CP circuit, and a compact column circuit implemented in a 16-kbit SRAM test chip demonstrate the power savings of 63%, 50%, and up to 69% for the applications sparse fast Fourier transform, object detection, and motion estimation, respectively, as compared with similar memories with naive prediction. Analysis tools for optimal prediction selection for the presented class of low-power memories are also provided. Auteurs: Chuhong Duan;Andreas J. Gotterba;Mahmut E. Sinangil;Anantha P. Chandrakasan; Apparue dans: IEEE Journal of Solid-State Circuits Date publication: 10.-2017, volume: 52, issue:10, pages: 2703 - 2711 Editeur: IEEE Document complet vers site de l'éditeur
» Energy-Efficient Resource Allocation in Buffer-Aided Wireless Relay Networks
 Résumé:In this paper, we study energy-efficient resource allocation in the downlink of buffer-aided wireless relay networks. We aim at maximizing the system average energy efficiency while maintaining the queue stability at both the base station (BS) and relays. We formulate the resource allocation design as a novel stochastic network optimization problem and based on the well-known Lyapunov drift-plus-penalty policy and the system constraints, we transform it to an instantaneous non-convex optimization problem to be solved in each time slot. We analyze the instantaneous utility function and propose a novel algorithm to find its optimum point. Based on that, we present an effective distributed strategy to get the globally optimal solution for channel and power allocation. Furthermore, we show that the proposed algorithm can be used as a building block for energy-efficient resource allocation in conventional relay networks, where the relays do not have buffering capability, but the BS queues need to be stabilized. Using extensive simulations, we show that the proposed algorithm is able to provide higher energy efficiency compared with the existing algorithms, while keeping the system queues stable. Auteurs: Javad Hajipour;Javad Musevi Niya;Derrick Wing Kwan Ng; Apparue dans: IEEE Transactions on Wireless Communications Date publication: 10.-2017, volume: 16, issue:10, pages: 6648 - 6659 Editeur: IEEE Document complet vers site de l'éditeur
» Energy-optimal routing on VCSEL-based interconnected networks
 Résumé:Optical interconnection networks are being used in systems on chip, supercomputers, and datacenters, fueling exascale computing, big data, and artificial intelligence applications. The vertical cavity surface emitting laser (VCSEL) is a popular, mature, and cost-effective photonic transmitter technology that enables energy proportionality by allowing the links’ data rate and the associated power consumption to be adjusted. Our work assumes VCSEL-based optical interconnects and presents intelligent centralized and distributed mechanisms to jointly and optimally select the routes, the flow sizes, and the transmission powers needed to serve a given input traffic load, minimize the consumed energy, and optimize performance. For this purpose, we use a detailed VCSEL energy model and formulate the energy minimization problem as a constrained nonlinear multicommodity optimization problem, which is solved optimally with the proposed approaches. The simulation results, carried out under a variety of scenarios, show the efficiency of these methods in terms of throughput and energy consumption. Auteurs: Ilias Gravalos;Apostolos Siokis;Panagiotis Kokkinos;Emmanouel A. Varvarigos; Apparue dans: IEEE/OSA Journal of Optical Communications and Networking Date publication: 10.-2017, volume: 9, issue:10, pages: 833 - 843 Editeur: IEEE Document complet vers site de l'éditeur
» Enhanced Autofocusing in Optical Scanning Holography Based on Hologram Decomposition
 Résumé:Optical scanning holography is a compact and powerful method for capturing hologram of a wide three-dimensional (3-D) view scene. After a hologram has been taken, it is often necessary to determine the locations of the focal plane on which the objects are residing, so that the 3-D scene can be numerically reconstructed for further analysis or processing. Recent research has shown that automatic detection of the depth (focal plane) of objects represented in a hologram can be conducted with entropy minimization method. Despite the success, the method could fail if the entropy information of objects in a hologram are interfering with each other. In this paper, we propose a method based on the hologram decomposition to overcome this problem. Briefly, the hologram is decomposed into subholograms and the focal plane distance is determined separately for each subobject. Simulation results reveal that our proposed method has good accuracy and reliability. Auteurs: Shuming Jiao;Peter Wai Ming Tsang;Ting-Chung Poon;Jung-Ping Liu;Wenbin Zou;Xia Li; Apparue dans: IEEE Transactions on Industrial Informatics Date publication: 10.-2017, volume: 13, issue:5, pages: 2455 - 2463 Editeur: IEEE Document complet vers site de l'éditeur
» Enhanced Negative Bias Stress Degradation in Multigate Polycrystalline Silicon Thin-Film Transistors
 Résumé:In this brief, a negative bias stress (NBS) induced degradation in n-type multigate polycrystalline silicon (poly-Si) thin-film transistor (TFT) is investigated. It is observed that after NBS the transfer characteristic curves shift to the negative gate bias direction and multigate TFTs degrade more than the single-gate TFTs with the same effective channel length. The observed degradation phenomenon is explained with short channel effect that is resulted from the diffusion and distribution of hole carriers in the channel, which are generated in the source/drain depletion region and swept into the channel when the junctions are reversely biased during NBS. Pronounced NBS degradation caused by increased hole carriers in the channel is also verified in NBS experiment with light illumination. Auteurs: Dongli Zhang;Mingxiang Wang;Huaisheng Wang;Yilin Yang; Apparue dans: IEEE Transactions on Electron Devices Date publication: 10.-2017, volume: 64, issue:10, pages: 4363 - 4367 Editeur: IEEE Document complet vers site de l'éditeur
» Enhanced Output Power of Light-Emitting Diodes With Embedded Air-Gap Photonic Crystals by Nanosphere Lithography
 Résumé:Large-scale two-dimensional air-gap photonic crystals (PhCs) were embedded in an n-type GaN layer to enhance the light emission of GaN-based light-emitting diodes (LEDs). The embedded-PhCs were obtained through overgrowth on n-GaN templates, which had air holes array previously fabricated by using nanosphere lithography technology. The effects of the distance D from active region to PhCs on the light extraction efficiency (LEE) of LEDs are investigated by experiments and finite difference-time domain simulation. The PhC LEDs with D = 2370 nm showed an improved light output power by 80.8% on average at forward current of 350 mA without degradation of electrical performance compared to conventional LEDs. It is mainly attributed to the improved LEE by enhancing the interaction of the guided modes and the embedded air-gap PhCs. Auteurs: Chengxiao Du;Wanrong Zhang;Tongbo Wei;Xiaoli Ji;Jinmin Li;Chong Geng;Qingfeng Yan; Apparue dans: IEEE Photonics Journal Date publication: 10.-2017, volume: 9, issue:5, pages: 1 - 7 Editeur: IEEE Document complet vers site de l'éditeur
» Enhanced UV Photodetector Response of ZnO/Si With AlN Buffer Layer
 Résumé:Studies have been carried out on the enhancement of responsivity and detectivity of the ZnO thin-films-based ultraviolet photodetectors by introducing an AlN buffer layer on silicon substrate. The ZnO film grown with AlN buffer layer established an epitaxial relation with the substrate and was found to show improved crystallinity with excellent optical properties. A strong and narrow photoluminescence emission was observed on the ZnO film grown with buffer layer, while a defect related broad emission was dominated on the film without buffer layer. The photodetectors showed a higher responsivity ( $R_{\lambda }$ ) of ${1.03} \times {10}^{{{{4}}}}$ A/W with a specific detectivity ( $D^{\ast }$ ) of ${5.21} \times {10}^{{{{12}}}}~ \text {cm}\cdot \text {Hz}^{{{{1/2}\cdot }}}\text {W}^{{{\text {-1}}}}$ at an applied bias of 3 V due to their excellent crystal quality. Auteurs: Basanta Roul;Rohit Pant;Saraswathi Chirakkara;Greeshma Chandan;K. K. Nanda;S. B. Krupanidhi; Apparue dans: IEEE Transactions on Electron Devices Date publication: 10.-2017, volume: 64, issue:10, pages: 4161 - 4166 Editeur: IEEE Document complet vers site de l'éditeur
» Enhancement-Mode AlGaN/GaN Nanowire Channel High Electron Mobility Transistor With Fluorine Plasma Treatment by ICP
 Résumé:This letter reports on a novel enhancement-mode (E-mode) AlGaN/GaN high electron mobility transistor (HEMT) that combines nanowire channel and fluorine plasma treatment using inductively coupled plasma (ICP). Compared with the conventional HEMTs, the threshold voltage of E-mode HEMT shifts from −2.8 to +0.7 V, and the Schottky reverse leakage current is reduced by one order of magnitude. The device exhibits a superior performance with a drain current of 460 mA/mm at ${V} _{{{\text {GS}}}}$ - ${V} _{{{\text {TH}}}} = 2$ V. High $\text{I}_{{ \mathrm{\scriptscriptstyle ON}}}/\text{I}_{{ \mathrm{OFF}}}$ ratio of approximately $10^{{\mathbf {9}}}$ and high breakdown voltage of 138 V with $\text{L}_{{{\text {DS}}}}=4~\mu \text{m}$ are obtained, i.e., the breakdown voltage of E-mode HEMT is improved by 25% than that in conventional HEMTs. The drain induced barrier lowering (DIBL) is as low as 4 mV/V, and the subthreshold swing (SS) of 70 mV/decade is achieved. The device exhibits an intrinsic current gain cutoff frequency $f_{{\text T}}$ of 22 GHz and a maximum oscillation frequency ${f} _{{\text {max}}}$ of 60 GHz. Auteurs: Yunlong He;Minhan Mi;Chong Wang;Xuefeng Zheng;Meng Zhang;Hengshuang Zhang;Ji Wu;Ling Yang;Peng Zhang;Xiaohua Ma;Yue Hao; Apparue dans: IEEE Electron Device Letters Date publication: 10.-2017, volume: 38, issue:10, pages: 1421 - 1424 Editeur: IEEE Document complet vers site de l'éditeur
» Enhancing QoE-Aware Wireless Edge Caching With Software-Defined Wireless Networks
 Résumé:Software-defined networking and in-network caching are promising technologies in the next generation wireless networks. In this paper, we propose enhancing the quality of experience (QoE)-aware wireless edge caching with bandwidth provisioning in software-defined wireless networks (SDWNs). Specifically, we design a novel mechanism to jointly provide proactive caching, bandwidth provisioning, and adaptive video streaming. The caches are requested to retrieve data in advance dynamically according to the behaviors of users, the current traffic, and the resource status. Then, we formulate a novel optimization problem regarding the QoE-aware bandwidth provisioning in SDWNs with jointly considering in-network caching strategy. The caching problem is decoupled from the bandwidth provisioning problem by deploying the dual-decomposition method. Additionally, we relax the binary variables to real numbers so that those two problems are formulated as a linear problem and a convex problem, respectively, which can be solved efficiently. Simulation results are presented to show that the latency is decreased and the utilization of caches is improved in the proposed scheme. Auteurs: Chengchao Liang;Ying He;F. Richard Yu;Nan Zhao; Apparue dans: IEEE Transactions on Wireless Communications Date publication: 10.-2017, volume: 16, issue:10, pages: 6912 - 6925 Editeur: IEEE Document complet vers site de l'éditeur
» Enhancing the Light-Extraction Efficiency of an AlGaN Nanowire Ultraviolet Light-Emitting Diode by Using Nitride/Air Distributed Bragg Reflector Nanogratings
 Résumé:The performance and efficiency of AlGaN ultraviolet light-emitting diodes have been limited by the extremely low light-extraction efficiency (LEE) due to the intrinsic material properties of AlGaN. Here, to enhance the LEE of the device, we demonstrate an AlGaN nanowire light-emitting diode (NW-LED) integrated with nitride/air distributed Bragg reflector (DBR) nanogratings. Compared to a control device (only mesa), the AlGaN NW-LED with the nitride/air DBR nanogratings exhibits enhancement in the light output power and external quantum efficiency (EQE) by a factor of ∼1.67. The higher light output power and EQE are attributed mainly to the multiple reflectances laterally for the transverse magnetic (TM)-polarized light and scattering introduced by the nanogratings. To further understand the LEE enhancement, the electrical field distribution, extraction ratio, and polar pattern of the AlGaN NW-LED with and without the nitride/air DBR nanogratings were analyzed using the finite-difference time-domain method. It was observed that the TM-field emission was confined and scattered upward, whereas the polar pattern was intensified for the AlGaN NW-LED with the nanogratings. Our approach to enhance the LEE via the nitride/air DBR nanogratings can provide a promising route for increasing the efficiency of AlGaN-based LEDs, also, to functioning as facet mirror for AlGaN-based laser diodes. Auteurs: Mohd Sharizal Alias;Bilal Janjua;Chao Zhao;Davide Priante;Abdullah A. Alhamoud;Malleswararao Tangi;Lafi M. Alanazi;Abdullah A. Alatawi;Abdulrahman M. Albadri;Ahmed Y. Alyamani;Tien Khee Ng;Boon S. Ooi; Apparue dans: IEEE Photonics Journal Date publication: 10.-2017, volume: 9, issue:5, pages: 1 - 8 Editeur: IEEE Document complet vers site de l'éditeur
» Enhancing the Physical Layer of Contention Resolution Diversity Slotted ALOHA
 Résumé:There is an urgent need for substantially enhancing random access schemes to be able to support native massive machine-to-machine communications in the next generation wireless systems. Lately, contention resolution diversity slotted ALOHA (CRDSA) and its variants have contributed to a drastic improvement in throughput compared with the traditional slotted ALOHA protocols. In this paper, we further enhance the CRDSA flexibility and performance along different physical layer dimensions. Based on simulation results, we show that there is still room for improvement in terms of throughput and, using heuristic methods, we find an optimized distribution of the packets power that is entering the demodulator for an additive white Gaussian noise channel. Applying this power distribution, which is easy to implement at the terminal in open loop and in a decentralized manner, is shown to achieve significantly enhanced performance. By introducing multi-frequency CRDSA, a drastic reduction in the terminal’s peak power requirement is attained. Furthermore, we investigate spread spectrum CRDSA, which improves the robustness of the scheme against irresolvable packet collisions allowing for enhanced energy efficiency. To support the work presented herein, we have developed a computationally efficient yet accurate methodology for estimating CRDSA performance, a novel approximate centrally coordinated CRDSA achievable sum rate analysis accounting for modulation and forward error correction constraints, as well as a more accurate loop probability analysis. Auteurs: Alberto Mengali;Riccardo De Gaudenzi;Pantelis-Daniel Arapoglou; Apparue dans: IEEE Transactions on Communications Date publication: 10.-2017, volume: 65, issue:10, pages: 4295 - 4308 Editeur: IEEE Document complet vers site de l'éditeur
» Enriching Triangle Mesh Animations with Physically Based Simulation
 Résumé:We present a system to combine arbitrary triangle mesh animations with physically based Finite Element Method (FEM) simulation, enabling control over the combination both in space and time. The input is a triangle mesh animation obtained using any method, such as keyframed animation, character rigging, 3D scanning, or geometric shape modeling. The input may be non-physical, crude or even incomplete. The user provides weights, specified using a minimal user interface, for how much physically based simulation should be allowed to modify the animation in any region of the model, and in time. Our system then computes a physically-based animation that is constrained to the input animation to the amount prescribed by these weights. This permits smoothly turning physics on and off over space and time, making it possible for the output to strictly follow the input, to evolve purely based on physically based simulation, and anything in between. Achieving such results requires a careful combination of several system components. We propose and analyze these components, including proper automatic creation of simulation meshes (even for non-manifold and self-colliding undeformed triangle meshes), converting triangle mesh animations into animations of the simulation mesh, and resolving collisions and self-collisions while following the input. Auteurs: Yijing Li;Hongyi Xu;Jernej Barbič; Apparue dans: IEEE Transactions on Visualization and Computer Graphics Date publication: 10.-2017, volume: 23, issue:10, pages: 2301 - 2313 Editeur: IEEE Document complet vers site de l'éditeur
» Enumerating Maximal Bicliques from a Large Graph Using MapReduce
 Résumé:We consider the enumeration of maximal bipartite cliques (bicliques) from a large graph, a task central to many data mining problems arising in social network analysis and bioinformatics. We present novel parallel algorithms for the MapReduce framework, and an experimental evaluation using Hadoop MapReduce. Our algorithm is based on clustering the input graph into smaller subgraphs, followed by processing different subgraphs in parallel. Our algorithm uses two ideas that enable it to scale to large graphs: (1) the redundancy in work between different subgraph explorations is minimized through a careful pruning of the search space, and (2) the load on different reducers is balanced through a task assignment that is based on an appropriate total order among the vertices. We show theoretically that our algorithm is work optimal, i.e., it performs the same total work as its sequential counterpart. We present a detailed evaluation which shows that the algorithm scales to large graphs with millions of edges and tens of millions of maximal bicliques. To our knowledge, this is the first work on maximal biclique enumeration for graphs of this scale. Auteurs: Arko Provo Mukherjee;Srikanta Tirthapura; Apparue dans: IEEE Transactions on Services Computing Date publication: 10.-2017, volume: 10, issue:5, pages: 771 - 784 Editeur: IEEE Document complet vers site de l'éditeur
» Environmental Sensors-Based Occupancy Estimation in Buildings via IHMM-MLR
 Résumé:Occupancy estimation in buildings can benefit various applications such as heating, ventilation, and air-conditioning control, space monitoring, and emergency evacuation. Due to the consideration of temporal dependency in occupancy data, hidden Markov model (HMM) has been shown to be effective in occupancy estimation. However, the conventional HMM that assumes invariant temporal dependency of occupancy dynamics for different time instances is unrealistic. Moreover, the performance of the conventional HMM that utilizes mixture of Gaussian for emission probability in terms of continuous observations can be easily affected by the noise in sensory data. To address these problems, in this paper, we propose a new architecture, i.e., inhomogeneous hidden Markov model with multinomial logistic regression (IHMM-MLR), for building occupancy estimation using nonintrusive environmental sensors. Instead of using the time-invariant transition probability matrix, we apply a time-dependent (inhomogeneous) transition probability matrix which can capture the temporal dependency for different time instances. Meanwhile, we employ an efficient probabilistic model, i.e., MLR, for emission probability. Online and offline occupancy estimation schemes are presented for real-time and accurate long-term applications respectively. Real experiments have indicated the effectiveness of our proposed approach. Auteurs: Zhenghua Chen;Qingchang Zhu;Mustafa Khalid Masood;Yeng Chai Soh; Apparue dans: IEEE Transactions on Industrial Informatics Date publication: 10.-2017, volume: 13, issue:5, pages: 2184 - 2193 Editeur: IEEE Document complet vers site de l'éditeur
» Equivalence of Finite Dimensional Input–Output Models of Solute Transport and Diffusion in Geosciences
 Résumé:We show that for a large class of finite dimensional input–output positive systems that represent networks of transport and diffusion of solute in geological media, there exist equivalent multirate mass transfer and multiple interacting continua representations, which are quite popular in geosciences. Moreover, we provide explicit methods to construct these equivalent representations. The proofs show that controllability property is playing a crucial role. These results contribute to our fundamental understanding on the effect of fine-scale geological structures on the transfer and dispersion of solute. Auteurs: Alain Rapaport;Alejandro Rojas-Palma;Jean-Raynald de Dreuzy;Hector C. Ramírez; Apparue dans: IEEE Transactions on Automatic Control Date publication: 10.-2017, volume: 62, issue:10, pages: 5470 - 5477 Editeur: IEEE Document complet vers site de l'éditeur
» Error Characterization of Soil Moisture Satellite Products: Retrieving Error Cross-Correlation Through Extended Quadruple Collocation
 Résumé:The triple collocation (TC) technique is being increasingly used to validate soil moisture retrievals derived from different systems, like satellites, hydrological models, or in situ probes. In recent years, several extensions of this method were proposed in order to evaluate the error standard deviations of more than three systems and to soften the TC hypothesis. In this paper, a novel extended quadruple collocation (E-QC) method is proposed, in order to consider the possibility of a cross correlation between product errors, identifying automatically the couple of error cross-correlated systems. The method is applicable even to a larger number of collocated datasets, although it may be unfeasible to collect them in practice. A synthetic experiment showed promising results, concluding that the E-QC is able to individuate (if any) the pair of systems with cross-correlated errors. It correctly compensates for the latter contribution and accurately retrieves error standard deviations of each system, otherwise biased if cross correlation is not taken into account. The E-QC was applied to soil moisture retrievals provided by satellite (SMOS, ASCAT, and SMAP), model (ERA Interim), and in situ probes (ISMN). The E-QC method identified the presence of error cross-correlation between the satellite products. This was also confirmed by analyzing the five datasets all together. E-QC showed fair performances of satellite products, especially of SMAP, although not as good as in case the presence of error correlation is not correctly taken into account. Auteurs: Nazzareno Pierdicca;Fabio Fascetti;Luca Pulvirenti;Raffaele Crapolicchio; Apparue dans: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing Date publication: 10.-2017, volume: 10, issue:10, pages: 4522 - 4530 Editeur: IEEE Document complet vers site de l'éditeur
» Error-Voltage-Based Open-Switch Fault Diagnosis Strategy for Matrix Converters with Model Predictive Control Method
 Résumé:This paper proposes an error-voltage-based open-switch fault-diagnosis a strategy for a matrix converter (MC). A finite control set model predictive control method is used to operate the MC. The MC system performances under normal operation and under a single open-switch fault operation are analyzed. A fault-diagnosis strategy has also been implemented in two steps. First, the faulty phase is detected and identified based on a comparison of the reference and estimated output line-to-line voltages. Then, the faulty switch is located by considering the switching states of the faulty phase. The proposed fault-diagnosis method is able to locate the faulty switch accurately and quickly without additional voltage sensors. Simulation and experimental results are presented to demonstrate the feasibility and effectiveness of the proposed strategy. Auteurs: Hanbing Dan;Tao Peng;Mei Su;Hui Deng;Qi Zhu;Ziyi Zhao;Patrick Wheeler; Apparue dans: IEEE Transactions on Industry Applications Date publication: 10.-2017, volume: 53, issue:5, pages: 4603 - 4612 Editeur: IEEE Document complet vers site de l'éditeur
» Estimating Circuit Aging Due to BTI and HCI Using Ring-Oscillator-Based Sensors
 Résumé:The performance of nanometer-scale circuits is adversely affected by aging induced by bias temperature instability (BTI) and hot carrier injection (HCI). Both BTI and HCI impact transistor electrical parameters at a level that depends on the operating environment and usage of the circuit. This paper presents a novel method, using on-chip sensors based on ring oscillators (ROSCs), to detect the delay shifts in circuits as a result of aging. Our method uses presilicon analysis of the circuit to compute calibration factors that can translate BTI- and HCI-induced delay shifts in the ROSC to those in the circuit of interest. Our simulations show that the delay estimates are within 1% of the true values from presilicon analysis. Further, for post-silicon analysis, a refinement strategy is proposed where sensor measurements can be amalgamated with infrequent online delay measurements on the monitored circuit to partially capture its true workloads. This leads to about 8% lower delay guardbanding overheads compared to the conventional methods as demonstrated using benchmark circuits. Auteurs: Deepashree Sengupta;Sachin S. Sapatnekar; Apparue dans: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems Date publication: 10.-2017, volume: 36, issue:10, pages: 1688 - 1701 Editeur: IEEE Document complet vers site de l'éditeur
» Estimating Cortical Feature Maps with Dependent Gaussian Processes
 Résumé:A striking example of brain organisation is the stereotyped arrangement of cell preferences in the visual cortex for edges of particular orientations in the visual image. These “orientation preference maps” appear to have remarkably consistent statistical properties across many species. However fine scale analysis of these properties requires the accurate reconstruction of maps from imaging data which is highly noisy. A new approach for solving this reconstruction problem is to use Bayesian Gaussian process methods, which produce more accurate results than classical techniques. However, so far this work has not considered the fact that maps for several other features of visual input coexist with the orientation preference map and that these maps have mutually dependent spatial arrangements. Here we extend the Gaussian process framework to the multiple output case, so that we can consider multiple maps simultaneously. We demonstrate that this improves reconstruction of multiple maps compared to both classical techniques and the single output approach, can encode the empirically observed relationships, and is easily extendible. This provides the first principled approach for studying the spatial relationships between feature maps in visual cortex. Auteurs: Nicholas J. Hughes;Geoffrey J. Goodhill; Apparue dans: IEEE Transactions on Pattern Analysis and Machine Intelligence Date publication: 10.-2017, volume: 39, issue:10, pages: 1918 - 1928 Editeur: IEEE Document complet vers site de l'éditeur
» Estimating Fractional Vegetation Cover From Landsat-7 ETM+ Reflectance Data Based on a Coupled Radiative Transfer and Crop Growth Model
 Résumé:Fractional vegetation cover (FVC) is an important parameter for earth surface process simulations, climate modeling, and global change studies. Currently, several FVC products have been generated from coarse resolution (~1 km) remote sensing data, and have been widely used. However, coarse resolution FVC products are not appropriate for precise land surface monitoring at regional scales, and finer spatial resolution FVC products are needed. Time-series coarse spatial resolution FVC products at high temporal resolutions contain vegetation growth information. Incorporating such information into the finer spatial resolution FVC estimation may improve the accuracy of FVC estimation. Therefore, a method for estimating finer spatial resolution FVC from coarse resolution FVC products and finer spatial resolution satellite reflectance data is proposed in this paper. This method relies on the coupled PROSAIL radiative transfer model and a statistical crop growth model built from the coarse resolution FVC product. The performance of the proposed method is investigated using the time-series Global LAnd Surface Satellite FVC product and Landsat-7 Enhanced Thematic Mapper Plus reflectance data in a cropland area of the Heihe River Basin. The direct validation of the FVC estimated using the proposed method with the ground measured FVC data ( $R^{\mathrm {\mathbf {2}}} = 0.6942$ , RMSE =0.0884), compared with the widely used dimidiate pixel model ( $R^{\mathrm {\mathbf {2}}} = 0.7034$ , RMSE = 0.1575), shows that the proposed method is feasible for estimating finer spatial resolution FVC with satisfactory accuracy, and it has the potential to be applied at a large scale. Auteurs: Xiaoxia Wang;Kun Jia;Shunlin Liang;Qiangzi Li;Xiangqin Wei;Yunjun Yao;Xiaotong Zhang;Yixuan Tu; Apparue dans: IEEE Transactions on Geoscience and Remote Sensing Date publication: 10.-2017, volume: 55, issue:10, pages: 5539 - 5546 Editeur: IEEE Document complet vers site de l'éditeur
» Estimation of Significant Wave Height From X-Band Marine Radar Images Based on Ensemble Empirical Mode Decomposition
 Résumé:In this letter, an ensemble empirical mode decomposition (EEMD)-based method is proposed to estimate significant wave height (SWH) from the X-band marine radar sea surface images. First, the data sequence in each radial direction of a radar subimage is decomposed by the EEMD into several intrinsic mode functions (IMFs). A normalization scheme is then applied to the IMFs to obtain their amplitude modulation components. Finally, by adopting a linear model, the SWH is estimated from the sum of the amplitudes from the second to the fifth modes. The method is tested using radar and buoy data collected in a sea trial off the east coast of Canada. The root-mean-square differences with respect to the buoy reference for the SWH estimations using the traditional signal-to-noise-based method, a recent shadowing-based method, and the proposed technique are 0.78, 0.48, and 0.36 m, respectively. The result indicates that the proposed technique produces improvement in the SWH measurements. Auteurs: Xinlong Liu;Weimin Huang;Eric W. Gill; Apparue dans: IEEE Geoscience and Remote Sensing Letters Date publication: 10.-2017, volume: 14, issue:10, pages: 1740 - 1744 Editeur: IEEE Document complet vers site de l'éditeur
» Evaluating Scattering Contributions to C-Band Radar Backscatter From Snow-Covered First-Year Sea Ice at the Winter–Spring Transition Through Measurement and Modeling
 Résumé:In this paper, we present model and measurement results for time-series angular dependencies of C-band HH and VV normalized radar cross-sections (NRCS) over first-year snow-covered sea ice during a winter–spring transition period. Experimental scatterometer and physical data were collected near Cambridge Bay, Nunavut, Canada, between May 20 and May 28, 2014, covering a severe storm event on May 25. We use the small perturbation scattering theory to model small-scale surface scattering, the Mie scattering theory to estimate the level of volume scattering in snow, and the Kirchhoff physical optics model to compute the large-scale surface scattering component. We observed good agreement between the model and experimental HH and VV NRCS. Before the storm, $R^{2}$ between model and experimental NRCS was 0.88 and 0.82 for VV and HH, respectively. After the storm, $R^{2}$ was 0.81 and 0.78 for VV and HH, respectively. Our model results suggest an overall increase in surface roughness after the storm event, supported by LiDAR measurements of the snow surface topography. Before the storm, the large-scale and small-scale surface scattering from the air-snow interface as well as volume scattering components dominated. After the storm, the large- and small-scale scattering contributions increased, while the volume scattering component considerably dropped. We attribute these effects to the increase in surface roughness and snow moisture content during the poststorm period. Our results could aid in interpretation of time-series synthetic aperture radar images with respect to physical properties of snow and ice during the winter–spring transition period. Auteurs: Alexander S. Komarov;Jack C. Landy;Sergey A. Komarov;David G. Barber; Apparue dans: IEEE Transactions on Geoscience and Remote Sensing Date publication: 10.-2017, volume: 55, issue:10, pages: 5702 - 5718 Editeur: IEEE Document complet vers site de l'éditeur
» Evaluating the Performance of Digital Modular Protection for Grid-Connected Permanent-Magnet-Generator-Based Wind Energy Conversion Systems With Battery Storage Systems
 Résumé:This paper develops and tests a new method for managing the responses of multiple digital relays employed in interconnected permanent-magnet generator (PMG)-based wind energy conversion systems (WECSs) with battery storage. The developed method utilizes digital relays (modules), each of which provides protection for a specific location of the PMG-based WECS and battery storage. The outputs of the developed digital protection scheme are trip signals to operate circuit breakers in PMG-based WECS, battery storage, and point-of-common-coupling. The modular digital protection is implemented for experimental testing on a 5-kW PMG-based WECS that has a 2.3-kW battery storage. Test results show that the developed protection can offer fast, accurate, and reliable responses to faults occurring in different parts of the tested WECS and battery storage. In addition, test results show that the modular digital protection has minor sensitivity to the location of faults, charge/discharge cycles of the battery storage, and/or levels of power delivery to the host grid. Auteurs: S. A. Saleh;Ryan Meng;Ryan McSheffery; Apparue dans: IEEE Transactions on Industry Applications Date publication: 10.-2017, volume: 53, issue:5, pages: 4186 - 4200 Editeur: IEEE Document complet vers site de l'éditeur
» Evaluation of Fast Neutron Fluence for Reactor Pressure Vessel Surveillance of Chashma Nuclear Power Plants Units 1 and 2
 Résumé:The energy-dependent neutron flux incident on surveillance capsule assemblies (SCAs) installed at the outer surface of the core barrel in two pressurized water reactors—Chashma Nuclear Power Plants Units 1 and 2 was evaluated. This safety study was made for the reactor pressure vessel surveillance program to determine the fast-neutron-induced radiation embrittlement of vessel materials in sections facing the core side and the upper weld positions. A total of 68 radiometric sensors were irradiated in each SCA of these two reactors, and dosimetry data were measured from radiometric sensors. Fast neutron flux ( $E> 1$ MeV) was best estimated using the least-squares method by employing LSL-M2 package. Measured results were compared with the fast neutron flux calculated using MCNP5 at the base and weld metal sections of SCA. The results agreed within ±20% of each other in both reactors, which satisfy the regulatory acceptance criteria. Therefore, these results can be used in life assessment of reactors. Auteurs: Asim Saeed;Noureen Akhtar;Tariq Rashid;Saleem A. Ansari; Apparue dans: IEEE Transactions on Nuclear Science Date publication: 10.-2017, volume: 64, issue:10, pages: 2661 - 2668 Editeur: IEEE Document complet vers site de l'éditeur
» Evaluation of Negative Capacitance Ferroelectric MOSFET for Analog Circuit Applications
 Résumé:Negative capacitance ferroelectric (FE) field-effect transistor (FeFET) is promising to address the issue of the increasing power density in digital circuit by realizing sub-60 mV/decade subthreshold swing. This inspires us to evaluate its applications in analog circuit. In this paper, the evaluation is performed based on the equivalent circuit model and through device- and circuit-level benchmarking against MOSFET counterpart. It is found that the selection of FE thickness is important to balance current amplification and saturated output characteristics. As compared with MOSFET, FeFET exhibits a larger current, transconductance, and current-to-transconductance generation efficiency. Its output resistance is smaller in the linear region and larger in the saturation region. It also has less variation in threshold voltage with temperature. When implementing FeFETs into various analog circuit applications, we find that a node capacitor could be discharged within shorter time to increase circuit speed; A better analog switch consisting of complementary FeFETs exhibits a lower and more linear on-resistance; Differential amplifier provides larger voltage amplification to small input signal; Current mirror transfers a more precise output current to the reference one. Auteurs: Yang Li;Yuye Kang;Xiao Gong; Apparue dans: IEEE Transactions on Electron Devices Date publication: 10.-2017, volume: 64, issue:10, pages: 4317 - 4321 Editeur: IEEE Document complet vers site de l'éditeur
» Evaluation of Segmentation Quality via Adaptive Composition of Reference Segmentations
 Résumé:Evaluating image segmentation quality is a critical step for generating desirable segmented output and comparing performance of algorithms, among others. However, automatic evaluation of segmented results is inherently challenging since image segmentation is an ill-posed problem. This paper presents a framework to evaluate segmentation quality using multiple labeled segmentations which are considered as references. For a segmentation to be evaluated, we adaptively compose a reference segmentation using multiple labeled segmentations, which locally matches the input segments while preserving structural consistency. The quality of a given segmentation is then measured by its distance to the composed reference. A new dataset of 200 images, where each one has 6 to 15 labeled segmentations, is developed for performance evaluation of image segmentation. Furthermore, to quantitatively compare the proposed segmentation evaluation algorithm with the state-of-the-art methods, a benchmark segmentation evaluation dataset is proposed. Extensive experiments are carried out to validate the proposed segmentation evaluation framework. Auteurs: Bo Peng;Lei Zhang;Xuanqin Mou;Ming-Hsuan Yang; Apparue dans: IEEE Transactions on Pattern Analysis and Machine Intelligence Date publication: 10.-2017, volume: 39, issue:10, pages: 1929 - 1941 Editeur: IEEE Document complet vers site de l'éditeur
» Evaluation of SiC Schottky Diodes Using Pressure Contacts
 Résumé:The thermomechanical reliability of SiC power devices and modules is increasingly becoming of interest especially for high-power applications, where power cycling performance is critical. Press-pack assemblies are a trusted and reliable packaging solution that has traditionally been used for high-power thyristor-based applications in FACTS/HVDC, although press-pack IGBTs have become commercially available more recently. These press-pack IGBTs require antiparallel PiN diodes for enabling reverse conduction capability. In these high-power applications, paralleling chips for high current conduction capability is a requirement, hence, electrothermal stability during current sharing is critical. SiC Schottky diodes not only exhibit the advantages of wide bandgap technology compared to silicon PiN diodes, but they have significantly lower zero temperature coefficient (ZTC), meaning they are more electrothermally stable. The lower ZTC is due to the unipolar nature of SiC Schottky diodes as opposed to the bipolar nature of PiN diodes. This paper investigates the implementation and reliability of SiC Schottky diodes in press-pack assemblies. The impact of pressure loss on the electrothermal stability of parallel devices is investigated. Auteurs: Jose Ortiz Gonzalez;Olayiwola Alatise;Attahir Murtala Aliyu;Pushparajah Rajaguru;Alberto Castellazzi;Li Ran;Philip A. Mawby;Chris Bailey; Apparue dans: IEEE Transactions on Industrial Electronics Date publication: 10.-2017, volume: 64, issue:10, pages: 8213 - 8223 Editeur: IEEE Document complet vers site de l'éditeur
» Event-Based Energy Disaggregation Algorithm for Activity Monitoring From a Single-Point Sensor
 Résumé:The massive deployment of smart meters and other customized meters has motivated the development of nonintrusive load monitoring (NILM) systems. This is the process of disaggregating the total energy consumption in a building into individual electrical loads using a single-point sensor. Most literature is oriented to energy saving. Nevertheless, activity of daily livings monitoring through NILM is recently receiving much interest. This proposal presents an event-based NILM algorithm of high performance for activity monitoring applications. This is divided into two stages: 1) an event detector and 2) an event classification algorithm. The first one does not need to be trained and shows a detection rate up to 94%. The event classification algorithm uses a novel load signature based on trajectories of active, reactive, and distortion power (PQD) to obtain general models of appliance classes using principal component analysis. The F1 score and the F0.5 score (the last one is more relevant to activity monitoring) draw values of 90.6% and 98.5, respectively. Auteurs: José Alcalá;Jesús Ureña;Álvaro Hernández;David Gualda; Apparue dans: IEEE Transactions on Instrumentation and Measurement Date publication: 10.-2017, volume: 66, issue:10, pages: 2615 - 2626 Editeur: IEEE Document complet vers site de l'éditeur
» Event-Driven Nonlinear Discounted Optimal Regulation Involving a Power System Application
 Résumé:By employing neural network approximation architecture, the nonlinear discounted optimal regulation is handled under event-driven adaptive critic framework. The main idea lies in adopting an improved learning algorithm, so that the event-driven discounted optimal control law can be derived via training a neural network. The stability guarantee and simulation illustration are also included. It is highlighted that the initial stabilizing control policy is not required during the implementation process with the combined learning rule. Moreover, the closed-loop system is formulated as an impulsive model. Then, the related stability issue is addressed by using the Lyapunov approach. The simulation studies, including an application to a power system, are also conducted to verify the effectiveness of the present design method. Auteurs: Ding Wang;Haibo He;Xiangnan Zhong;Derong Liu; Apparue dans: IEEE Transactions on Industrial Electronics Date publication: 10.-2017, volume: 64, issue:10, pages: 8177 - 8186 Editeur: IEEE Document complet vers site de l'éditeur

Publication archives by date
2018:   janvier     février     mars     avril     mai     juin     juillet     août     septembre     octobre     novembre     décembre
2017:   janvier     février     mars     avril     mai     juin     juillet     août     septembre     octobre     novembre     décembre
2016:   janvier     février     mars     avril     mai     juin     juillet     août     septembre     octobre     novembre     décembre
2015:   janvier     février     mars     avril     mai     juin     juillet     août     septembre     octobre     novembre     décembre
2014:   janvier     février     mars     avril     mai     juin     juillet     août     septembre     octobre     novembre     décembre
2013:   janvier     février     mars     avril     mai     juin     juillet     août     septembre     octobre     novembre     décembre
2012:   janvier     février     mars     avril     mai     juin     juillet     août     septembre     octobre     novembre     décembre
2011:   janvier     février     mars     avril     mai     juin     juillet     août     septembre     octobre     novembre     décembre
2010:   janvier     février     mars     avril     mai     juin     juillet     août     septembre     octobre     novembre     décembre
2009:   janvier     février     mars     avril     mai     juin     juillet     août     septembre     octobre     novembre     décembre