Accueil » Publications dans le domaines des technologies » 10-2017
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 Publications dans les journaux scientifiques dans le domaine de l'ingénierie : 10-2017 trié par par titre, page: 5
» 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
» 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 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
» Event-Triggered Control of Multiagent Systems for Fixed and Time-Varying Network Topologies
 Résumé:A decentralized controller that uses event-triggered communication scheduling is developed for the leader-follower consensus problem under fixed and switching communication topologies. To eliminate continuous interagent communication, state estimates of neighboring agents are designed for control feedback and are updated via communication to reset growing estimate errors. The communication times are based on an event-triggered approach and are adapted based on the trade-off between the control system performance and the desire to minimize the amount of communication. An important aspect of the developed event trigger strategy is that communication is not required to determine when a state update is needed. Since the control strategy produces switched dynamics, analysis is provided to show that Zeno behavior is avoided by developing a positive constant lower bound on the minimum inter-event interval. A Lyapunov-based convergence analysis is also provided to indicate bounded convergence of the developed control methodology. Auteurs: Teng-Hu Cheng;Zhen Kan;Justin R. Klotz;John M. Shea;Warren E. Dixon; Apparue dans: IEEE Transactions on Automatic Control Date publication: 10.-2017, volume: 62, issue:10, pages: 5365 - 5371 Editeur: IEEE Document complet vers site de l'éditeur
» Event-Triggered Suboptimal Tracking Controller Design for a Class of Nonlinear Discrete-Time Systems
 Résumé:In this paper, using the state-dependent Riccati equation approach, an event-triggered technique is proposed to solve the tracking problem for a broad class of nonlinear discrete-time networked control systems. It is shown that the proposed tracking controller leads to an asymptotically stable system, while the information exchange between the controller and the actuator can be directly affected with predictable results by changing a parameter of the controller called the triggering factor. The proposed method is experimentally validated on a laboratory three-tank system. The obtained results demonstrate the effectiveness of the proposed event-triggered technique for solving the tracking problem of a nonlinear system in a networked control framework. Auteurs: Yazdan Batmani;Mohammadreza Davoodi;Nader Meskin; Apparue dans: IEEE Transactions on Industrial Electronics Date publication: 10.-2017, volume: 64, issue:10, pages: 8079 - 8087 Editeur: IEEE Document complet vers site de l'éditeur
» Ex-Post Max-Min Fairness of Generalized AGV Mechanisms
 Résumé:We generalize the standard Arrow-d'Aspremont-Gerard-Varet (AGV) mechanism to balance the net payoffs received by all agents, while maintaining Bayesian incentive compatibility, ex-post efficiency, and ex-post budget balance of the standard AGV mechanism. In a private-value setting with independent agents' types and the principal's cost, we formulate a convex optimization problem to find the mechanism (that achieves ex-post max-min fairness) over a set of parameterized generalized AGV mechanisms, through maximizing the expected value of the minimum ex-post net payoff. We reformulate the convex program as a linear program that can be effectively solved when the number of agents is small. When the number of agents is large, we propose to solve the formulated convex program through the incremental subgradient method. Numerical results on two action models show that the proposed mechanism significantly outperforms the standard AGV mechanism in terms of the expected minimum ex-post payoff. Auteurs: Tao Wang;Yunjian Xu;Selin Damla Ahipasaoglu;Costas Courcoubetis; Apparue dans: IEEE Transactions on Automatic Control Date publication: 10.-2017, volume: 62, issue:10, pages: 5275 - 5281 Editeur: IEEE Document complet vers site de l'éditeur
» Example-Based Subspace Stress Analysis for Interactive Shape Design
 Résumé:Stress analysis is a crucial tool for designing structurally sound shapes. However, the expensive computational cost has hampered its use in interactive shape editing tasks. We augment the existing example-based shape editing tools, and propose a fast subspace stress analysis method to enable stress-aware shape editing. In particular, we construct a reduced stress basis from a small set of shape exemplars and possible external forces. This stress basis is automatically adapted to the current user edited shape on the fly, and thereby offers reliable stress estimation. We then introduce a new finite element discretization scheme to use the reduced basis for fast stress analysis. Our method runs up to two orders of magnitude faster than the full-space finite element analysis, with average $L_2$ estimation errors less than 2 percent and maximum $L_2$ errors less than 6 percent. Furthermore, we build an interactive stress-aware shape editing tool to demonstrate its performance in practice. Auteurs: Xiang Chen;Changxi Zheng;Kun Zhou; Apparue dans: IEEE Transactions on Visualization and Computer Graphics Date publication: 10.-2017, volume: 23, issue:10, pages: 2314 - 2327 Editeur: IEEE Document complet vers site de l'éditeur
» Exchangeability Characterizes Optimality of Sequential Normalized Maximum Likelihood and Bayesian Prediction
 Résumé:We study online learning under logarithmic loss with regular parametric models. In this setting, each strategy corresponds to a joint distribution on sequences. The minimax optimal strategy is the normalized maximum likelihood (NML) strategy. We show that the sequential NML (SNML) strategy predicts minimax optimally (i.e., as NML) if and only if the joint distribution on sequences defined by SNML is exchangeable. This property also characterizes the optimality of a Bayesian prediction strategy. In that case, the optimal prior distribution is Jeffreys prior for a broad class of parametric models for which the maximum likelihood estimator is asymptotically normal. The optimal prediction strategy, NML, depends on the number $n$ of rounds of the game, in general. However, when a Bayesian strategy is optimal, NML becomes independent of $n$ . Our proof uses this to exploit the asymptotics of NML. The asymptotic normality of the maximum likelihood estimator is responsible for the necessity of Jeffreys prior. Auteurs: Fares Hedayati;Peter L. Bartlett; Apparue dans: IEEE Transactions on Information Theory Date publication: 10.-2017, volume: 63, issue:10, pages: 6767 - 6773 Editeur: IEEE Document complet vers site de l'éditeur
» Expanding Acquisition and Clutter Filter Dimensions for Improved Perfusion Sensitivity
 Résumé:A method is explored for increasing the sensitivity of power-Doppler imaging without contrast enhancement. We acquire 1–10 s of echo signals and arrange it into a 3-D spatiotemporal data array. An eigenfilter developed to preserve all three dimensions of the array yields power estimates for blood flow and perfusion that are well separated from tissue clutter. This method is applied at high frequency (24-MHz pulses) to a murine model of an ischemic hindlimb. We demonstrate enhancements to tissue perfusion maps in normal and ischemic tissues. The method can be applied to data from any ultrasonic instrument that provides beamformed RF echo data. Auteurs: MinWoo Kim;Craig K. Abbey;Jamila Hedhli;Lawrence W. Dobrucki;Michael F. Insana; Apparue dans: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control Date publication: 10.-2017, volume: 64, issue:10, pages: 1429 - 1438 Editeur: IEEE Document complet vers site de l'éditeur
» Experimental Analysis of Small Drone Polarimetry Based on Micro-Doppler Signature
 Résumé:We present a polarimetric analysis of small drones from different aspect angles. Polarimetric analysis can provide more information of a target, since the returned radar signal is affected by different wave polarization. The analysis is performed with micro-Doppler signature (MDS) to investigate micromotions of the drone detected by the radar. We measured operating small drones in an anechoic chamber from two aspect angles, 0° and 90°. An outdoor experiment was carried out with metal clutters for verification in real environment. The indoor analysis result shows that copolarized antenna receives signals better than cross polarized when the aspect angle is 0°, and vice versa. We also verified that cross-polarized antenna receives MDS from the drone better than copolarized antenna, from outdoors when an aspect angle is almost 90°. By utilizing the polarimetric characteristic of the drone at this frequency band, it is preferable to use a polarimetric radar for drone detection. Auteurs: Byung Kwan Kim;Hyun-Seong Kang;Seong-Ook Park; Apparue dans: IEEE Geoscience and Remote Sensing Letters Date publication: 10.-2017, volume: 14, issue:10, pages: 1670 - 1674 Editeur: IEEE Document complet vers site de l'éditeur
» Experimental Demonstration of the Distributed Feedback Semiconductor Laser With S-Bent Waveguide and Sampled Grating
 Résumé:A distributed feedback (DFB) semiconductor laser based on s-bent waveguide and sampled grating is theoretically studied and experimentally demonstrated. The proposed laser operates with a high side mode suppression ratio (SMSR) when the bias current is changed from 50 to 130 mA. When the bias current is fixed at 130 mA, the SMSR is larger than 55 dB, which is benefit from the suppressed spatial hole burning, while the SMSR of the equivalent phase shifted DFB laser decreases to 39 dB. The wavelength spacing error between two proposed DFB lasers is measured to be 0.089 nm compared with the designed value. When temperature is increased from 20 °C to 42 °C, the presented DFB laser achieves stable single longitudinal mode (SLM) operation with SMSR >51 dB and the wavelength varies from 1562.24 to 1564.6 nm with a slope of 0.11 nm/°C. The s-bent waveguide and sampled grating can be fabricated simply by the common holography exposure and photolithograph technique resulting in a low cost. Besides, the wavelength accuracy and SLM yield can be improved significantly, which is very beneficial for the multiwavelength DFB laser array. Auteurs: Yunshan Zhang;Yuechun Shi;Lianyan Li;Zhengpeng Zou;Jun Lu;Yinchao Du;Wenxuan Wang;Yating Zhou;Xin Chen;Jilin Zheng;Xiangfei Chen; Apparue dans: IEEE Photonics Journal Date publication: 10.-2017, volume: 9, issue:5, pages: 1 - 11 Editeur: IEEE Document complet vers site de l'éditeur
» Experimental Investigation of a New Tribo-Aeroelectrostatic Separation Process for Micronized Plastics From WEEE
 Résumé:Tribo-electrostatic separation of mm-size granular insulating materials is a process widely used in the plastics recycling industry. However, the separation of micronized plastics is still inefficient because of their tendency to aggregate. The paper is aimed at validating the feasibility of a new tribo-aero-electrostatic separation process for micronized mixed plastics originating from waste electric and electronic equipment. The separation process is based on a fluidized bed tribocharging system equipped with rotating roll electrode connected to a dc high-voltage supply. The micronized insulating materials to be separated (white and grey polyvinyl chloride particles of average size 20 µm) were tribocharged using the fluidization air provided by a variable-speed blower. The charged particles were pinned to the rotating electrode of opposite polarity. This process enabled the sorting of one product while the other materials were left in the fluidized bed. The new electrode configuration has the merit to significantly reduce the particle aggregation problem that affects the operation of other fluidized-bed-type tribocharging devices. The separation outcome, in terms of recovery and purity, depended on several factors, and was found to be optimal for a voltage of 35 kV and a rotation speed of roll electrode of 60 r/min. This new process was also tested for ternary mixtures of granular plastics and the obtained results demonstrate its effectiveness for recovering a targeted product, according to the voltage polarity, leaving the other products in the fluidized bed. Auteurs: Mohamed El-Mouloud Zelmat;Amar Tilmatine;Seddik Touhami;Abdelber Bendaoud;Karim Medles;Rabah Ouiddir;Lucian Dascalescu; Apparue dans: IEEE Transactions on Industry Applications Date publication: 10.-2017, volume: 53, issue:5, pages: 4950 - 4956 Editeur: IEEE Document complet vers site de l'éditeur
» Experimental Investigation on Improved Predistortion Circuit for Directly Modulated Radio Over Fiber System
 Résumé:An extension of the conventional dual Schottky diode-based predistortion circuit (PDC) is proposed to linearize directly modulated radio over fiber (RoF) system. The main advantages of the proposed PDC are simple configuration, excellent distortion suppression, and broad bandwidth from dc to 6 GHz. By using the proposed cascaded Schottky diodes-based PDC, the condition of third-order intermodulation nonlinearities suppression can be more easily satisfied and the optimal linearization effect can be achieved due to the fact that it has more circuit adjustment parameters. The experimental results show that by using the proposed PDC, the spurious-free dynamic range (SFDR) @2 GHz of the optical transceiver which is designed by ourselves can be improved from 93.8 dB·Hz2/3 to 112.1 dB·Hz4/5 in a 1-Hz bandwidth, corresponding to 7.21% error vector magnitude performance improvement for 20 MHz 64QAM-OFDM @2 GHz signal transmission over 10 km standard single mode fiber. The linearity improvement by using the proposed PDC has also been verified in a commercial optical transceiver based RoF system, and the achieved SFDR @ 2 GHz can be increased from 102.8 dB·Hz2/3 to 121.6 dB·Hz4/5 in a 1-Hz bandwidth. Auteurs: Shichao Chen;Lei Deng;Yao Ye;Xiaoman Chen;Mengfan Cheng;Ming Tang;Songnian Fu;Fengguang Luo;Deming Liu; 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
» Experimental Study on Microsecond Pulse Breakdown Characteristics of Propylene Carbonate Modified by Al Nanoparticles
 Résumé:Liquid dielectrics are very important and useful in pulsed power systems, due to their unique characteristics of large energy storage densities, ease of circulation, and low cost. They are applicable to power systems which have complex geometries. Propylene carbonate (PC), as a kind of polar liquids, shows bright prospects in compact pulsed power sources because of its great permittivity, high electrical breakdown stress, and broad environmental operating ability. In this paper, a dielectric breakdown experiments were conducted with a microsecond pulsed power source and a test cell with spherical electrodes. The breakdown properties of PC and PC-based nanofluids (NFs) were investigated by changing the increasing rate of the charging voltage. Besides, the influence of nanoparticles on the dielectric breakdown characteristics of PC was analyzed. Results show that with a slow increasing rate of the charging voltage, the introduction of nanoparticles greatly improved the breakdown stability of PC; while with a fast increasing rate of the charging voltage, NFs exhibited much larger mean breakdown voltage. We also demonstrated that the improvement effect of NFs’ dielectric performance could be explained by the energy band theory very well. Auteurs: Binbin Xu;Zicheng Zhang;Yanpan Hou;Hongwei Liu; Apparue dans: IEEE Transactions on Plasma Science Date publication: 10.-2017, volume: 45, issue:10, pages: 2691 - 2695 Editeur: IEEE Document complet vers site de l'éditeur
» Experimental Validation of 3-D Magnet Eddy Current Loss Prediction in Surface-Mounted Permanent Magnet Machines
 Résumé:This paper presents the experimental validation of three-dimensional (3-D) Fourier method employed for predicting magnet eddy current loss in surface-mounted permanent magnet (SPM) machines. The magnet loss is measured for a 12-slot 14-pole SPM machine from experimental tests when the machine is operated with inverter under locked rotor conditions by repeating tests with two rotors, one with magnets and one without. The eddy current loss associated with each significant harmonic in the captured armature currents is predicted separately employing the developed method and the total magnet loss is evaluated by applying the principle of superposition. The magnet loss at real operating conditions of the machine is predicted from the method using the phase current captured when the SPM is operating at its maximum speed conditions. The result is used as an example to devise an effective means of further reduction in the total magnet loss. Auteurs: Sreeju Sreedharan Nair;Jiabin Wang;Tianfu Sun;Liang Chen;Robert Chin;Minos Beniakar;Dmitry Svechkarenko;Iakovos Manolas; Apparue dans: IEEE Transactions on Industry Applications Date publication: 10.-2017, volume: 53, issue:5, pages: 4380 - 4388 Editeur: IEEE Document complet vers site de l'éditeur
» Experimental Validation of a Wideband Metasurface for Wide-Angle Scanning Leaky-Wave Antennas
 Résumé:Beam scanning arrays typically suffer from scan loss; an increasing degradation in gain as the beam is scanned from broadside toward the horizon in any given scan plane. Here, a metasurface is presented that reduces the effects of scan loss for a leaky-wave antenna (LWA). The metasurface is simple, being composed of an ultrathin sheet of subwavelength split-ring resonators. The leaky-wave structure is balanced, scanning from the forward region, through broadside, and into the backward region, and designed to scan in the magnetic plane. The metasurface is effectively invisible at broadside, where balanced LWAs are most sensitive to external loading. It is shown that the introduction of the metasurface results in increased directivity, and hence, gain, as the beam is scanned off broadside, having an increasing effect as the beam is scanned to the horizon. Simulations show that the metasurface improves the effective aperture distribution at higher scan angles, resulting in a more directive main beam, while having a negligible impact on cross-polarization gain. Experimental validation results show that the scan range of the antenna is increased from $-39 {^{\circ }} \leq \theta \leq +32 {^{\circ }}$ to $-64 {^{\circ }} \leq \theta \leq +70 {^{\circ }}$ , when loaded with the metasurface, demonstrating a flattened gain profile over a 135° range centered about broadside. Moreover, this scan range occurs over a frequency band spanning from 9 to 15.5 GHz, demonstrating a relative bandwidth of 53% for the metasurface. Auteurs: Trevor R. Cameron;George V. Eleftheriades; Apparue dans: IEEE Transactions on Antennas and Propagation Date publication: 10.-2017, volume: 65, issue:10, pages: 5245 - 5256 Editeur: IEEE Document complet vers site de l'éditeur
» Experimental Validation of Leak and Water-Ingression Detection in Low-Pressure Gas Pipeline Using Pressure and Flow Measurements
 Résumé:In underground low-pressure gas distribution pipelines, ground water enters the pipeline through cracks. This is known as the water ingress problem, and it occurs predominantly in the monsoon season, when the water table is high. This issue is currently detected based on complaints from the users. In order to arrive at an efficient and reliable processing technique, experimental results of pressure and flow on an existing low-pressure gas pipeline are reported in this paper. Several experiments for leak location, severity of the leak, water ingression with various volumes of water followed by removal of water are conducted. Healthy network loading data collected over a 24 h period is used to verify the robustness of the derived parameters for water ingression detection. The present technique can detect leaks easily with a leak valve opening of 30o. Robust detection of water ingression with more than 10% of pipe volume is possible. Auteurs: Sugunakar Reddy Ravula;Srivathsan Chakaravarthi Narasimman;Libo Wang;Abhisek Ukil; Apparue dans: IEEE Sensors Journal Date publication: 10.-2017, volume: 17, issue:20, pages: 6734 - 6742 Editeur: IEEE Document complet vers site de l'éditeur
» Explicit Constructions of Optimal-Access MDS Codes With Nearly Optimal Sub-Packetization
 Résumé:An $(n,k,l)$ maximum distance separable (MDS) array code of length $n$ , dimension $k=n-r$ , and sub-packetization $l$ is formed of $l\times n$ matrices over a finite field $F$ , with every column of the matrix stored on a separate node in the distributed storage system and viewed as a coordinate of the codeword. Repair of a failed node (recovery of one erased column) can be performed by accessing a set of $d\le n-1$ surviving (helper) nodes. The code is said to have the optimal access property if the amount of data accessed at each of the helper nodes meets a lower bound on this quantity. For optimal-access MDS codes with $d=n-1$ , the sub-packetization $l$ satisfies the bound $l\ge r^{(k-1)/r}$ . In our previous work (IEEE Trans. Inf. Theory, vol. 63, no. 4, 2017), for any $n$ and $r$ , we presented an explicit construction of optimal-access MDS codes with sub-packetization $l=r^{n-1}$ . In this paper, we take up the question of reducing the sub-packetization value $l$ to make it to approach the lower bound. We construct an explicit family of optimal-access codes with $l=r^{\lceil n/r\rceil }$ , which differs from the optimal value by at most a factor of $r^{2}$ . These codes can be constructed over any finite field $F$ as long as $|F|\ge r\lceil n/r\rceil$ , and afford low-complexity encoding and decoding procedures. We also define a version of the repair problem that bridges the context of regenerating codes and codes with locality constraints (LRC codes), which we call group repair with optimal access. In this variation, we assume that the set of $n=sm$ nodes is partitioned into $m$ repair groups of size $s$ , and require that the amount of accessed data for repair is the smallest possible whenever the $d=s+k-1$ helper nodes include all the other $s-1$ nodes from the same group as the failed node. For this problem, we construct a family of codes with the group optimal access property. These codes can be constructed over any field $F$ of size $|F|\ge n$ , and also afford low-complexity encoding and decoding procedures. Auteurs: Min Ye;Alexander Barg; Apparue dans: IEEE Transactions on Information Theory Date publication: 10.-2017, volume: 63, issue:10, pages: 6307 - 6317 Editeur: IEEE Document complet vers site de l'éditeur
» Exploiting Data Reliability and Fuzzy Clustering for Journal Ranking
 Résumé:Journal impact indicators are widely accepted as possible measurements of academic journal quality. However, much debate has recently surrounded their use, and alternative journal impact evaluation techniques are desirable. Aggregation of multiple indicators offers a promising method to produce a more robust ranking result, avoiding the possible bias caused by the use of a single impact indicator. In this paper, fuzzy aggregation and fuzzy clustering, especially the ordered weighted averaging (OWA) operators are exploited to aggregate the quality scores of academic journals that are obtained from different impact indicators. Also, a novel method for linguistic term-based fuzzy cluster grouping is proposed to rank academic journals. The paper allows for the construction of distinctive fuzzy clusters of academic journals on the basis of their performance with respect to different journal impact indicators, which may be subsequently combined via the use of the OWA operators. Journals are ranked in relation to their memberships in the resulting combined fuzzy clusters. In particular, the nearest-neighbor guided aggregation operators are adopted to characterize the reliability of the indicators, and the fuzzy clustering mechanism is utilized to enhance the interpretability of the underlying ranking procedure. The ranking results of academic journals from six subjects are systematically compared with the outlet ranking used by the Excellence in Research for Australia, demonstrating the significant potential of the proposed approach. Auteurs: Pan Su;Changjing Shang;Tianhua Chen;Qiang Shen; Apparue dans: IEEE Transactions on Fuzzy Systems Date publication: 10.-2017, volume: 25, issue:5, pages: 1306 - 1319 Editeur: IEEE Document complet vers site de l'éditeur
» Exploiting Multiple-Antenna Techniques for Non-Orthogonal Multiple Access
 Résumé:This paper aims to provide a comprehensive solution for the design, analysis, and optimization of a multiple-antenna non-orthogonal multiple access (NOMA) system for multiuser downlink communication with both time duplex division and frequency duplex division modes. First, we design a new framework for multiple-antenna NOMA, including user clustering, channel state information (CSI) acquisition, superposition coding, transmit beamforming, and successive interference cancellation. Then, we analyze the performance of the considered system, and derive exact closed-form expressions for average transmission rates in terms of transmit power, CSI accuracy, transmission mode, and channel conditions. For further enhancing the system performance, we optimize three key parameters, i.e., transmit power, feedback bits, and transmission mode. Especially, we propose a low-complexity joint optimization scheme, so as to fully exploit the potential of multiple-antenna techniques in NOMA. Moreover, through asymptotic analysis, we reveal the impact of system parameters on average transmission rates, and hence present some guidelines on the design of multiple-antenna NOMA. Finally, simulation results validate our theoretical analysis, and show that a substantial performance gain can be obtained over traditional orthogonal multiple access technology under practical conditions. Auteurs: Xiaoming Chen;Zhaoyang Zhang;Caijun Zhong;Derrick Wing Kwan Ng; Apparue dans: IEEE Journal on Selected Areas in Communications Date publication: 10.-2017, volume: 35, issue:10, pages: 2207 - 2220 Editeur: IEEE Document complet vers site de l'éditeur
» Exploring Consensus RNA Substructural Patterns Using Subgraph Mining
 Résumé:Frequently recurring RNAquery id="Q1"> structural motifs play important roles in RNA folding process and interaction with other molecules. Traditional index-based and shape-based schemas are useful in modeling RNA secondary structures but ignore the structural discrepancy of individual RNA family member. Further, the in-depth analysis of underlying substructure pattern is insufficient due to varied and unnormalized substructure data. This prevents us from understanding RNAs functions and their inherent synergistic regulation networks. This article thus proposes a novel labeled graph-based algorithm RnaGraph to uncover frequently RNA substructure patterns. Attribute data and graph data are combined to characterize diverse substructures and their correlations, respectively. Further, a top-k graph pattern mining algorithm is developed to extract interesting substructure motifs by integrating frequency and similarity. The experimental results show that our methods assist in not only modelling complex RNA secondary structures but also identifying hidden but interesting RNA substructure patterns. Auteurs: Qingfeng Chen;Chaowang Lan;Baoshan Chen;Lusheng Wang;Jinyan Li;Chengqi Zhang; Apparue dans: IEEE/ACM Transactions on Computational Biology and Bioinformatics Date publication: 10.-2017, volume: 14, issue:5, pages: 1134 - 1146 Editeur: IEEE Document complet vers site de l'éditeur
» Exploring High Quality Chaotic Signal Generation in a Mutually Delay Coupled Semiconductor Lasers System
 Résumé:High quality chaotic signal generation in a mutually delay coupled semiconductor lasers (MDC-SLs) system is numerically explored by evaluating the time-delay signature (TDS) and complexity of chaotic signals. Autocorrelation function is utilized for quantitatively identifying the TDS of chaotic signal, and Kolmogorov–Sinai entropy and Kaplan–York dimensions are applied to estimate the complexity of chaotic signal. The results show that, under suitable parameters, two sets of chaotic signals with weak TDS and high complexity can be obtained simultaneously. By analyzing the influences of the mutual coupling strength and frequency detuning between the two MDC-SLs on the TDS and complexity of chaotic signals, the optimized parameter regions are specified for simultaneously generating two sets of high quality chaotic signals based on the MDC-SLs system. Auteurs: Yu-Shuang Hou;Li-Lin Yi;Guang-Qiong Xia;Zheng-Mao Wu; 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
» Exploring the LCL Characteristics in GaN-Based Single-L Quasi-Z-Source Grid-Tied Inverters
 Résumé:As more widebandgap (WBG) devices are becoming commercially available, it is beneficial to use WBG device to increase the switching frequency in order to reduce the passive components. For quasi-Z-Source (qZS) grid-tied inverters, the reduction of passive components raises stability concerns as the coupling effect between the dc side and ac side of qZS inverter will increase. In this paper, the coupling effect between qZS impedance network and the output filter is analyzed by modeling both dc and ac sides. Analysis reveals the resonant characteristic of the qZS inverter. Controller parameter boundaries are derived, and a design method to improve stability is then proposed. Case studies for a 2.5-kW 10-kHz Si-based qZS inverter and a 1-kW 100-kHz GaN-based qZS inverter are presented. Circuit simulations and experimental verifications results are provided to assess analysis and the control design. Auteurs: Yanjun Shi;Thierry Kayiranga;Yuan Li;Hui Li; Apparue dans: IEEE Transactions on Industrial Electronics Date publication: 10.-2017, volume: 64, issue:10, pages: 7758 - 7768 Editeur: IEEE Document complet vers site de l'éditeur
» Exploring Viewer Gazing Patterns for Touch-Based Mobile Gamecasting
 Résumé:Recent years have witnessed an explosion of gamecasting applications, in which game players (or gamers in short) broadcast game playthroughs by their personal devices in real time. Such pioneer platforms, such as YouTube Gaming, Twitch, and Mobcrush, have attracted a massive number of online broadcasters, and each of them can have hundreds or thousands of fellow viewers. The growing number, however, has created significant challenges to the network and end-devices, particularly considering that bandwidth- and battery-limited smartphones or tablets are becoming dominating for both gamers and viewers. Yet the unique touch operations of the mobile interface offer opportunities, too. In this paper, our measurements based on the real traces from gamers and viewers reveal that strong associations exist between the gamers’ touch interactions and the viewers’ gazing patterns. Motivated by this, we present a novel interaction-aware optimization framework to improve the energy utilization and stream quality for mobile gamecasting. Our framework incorporates a touch-assisted prediction module to extract association rules for gazing pattern prediction and a tile-based optimization module to utilize energy on mobile devices efficiently. Trace-driven simulations illustrate the effectiveness of our framework in terms of energy consumption and stream quality. Our user study experiments also demonstrate much improved (3%–13%) quality satisfaction over the state-of-the-art solution with similar network resources. Auteurs: Cong Zhang;Qiyun He;Jiangchuan Liu;Zhi Wang; Apparue dans: IEEE Transactions on Multimedia Date publication: 10.-2017, volume: 19, issue:10, pages: 2333 - 2344 Editeur: IEEE Document complet vers site de l'éditeur
» Extended Kalman Filter for Multichannel InSAR Height Reconstruction
 Résumé:One of the main challenges in Interferometric Synthetic Aperture Radar (SAR) is the accurate height reconstruction of the observed scene. Recently, approaches based on Extended Kalman Filter (EKF) have been proposed. Most of them are based on the hypothesis of height profile continuity. Such condition greatly reduces their applicability, being only valid for particular scenarios. Within this paper, we present a novel Kalman-based height reconstruction approach, specifically designed to work with multichannel data related to any type of scenario, both smooth or sharp. The novelty of the technique consists in its ability in detecting and correctly handling sharp height discontinuities while regularizing smooth areas. The approach is able to maintain the high computational efficiency typical of EKF and to work in an almost unsupervised way. The methodology has been tested and validated on both simulated and real X-band (TerraSAR-X and COSMO-SkyMed) high-resolution data sets. Reported results are encouraging and interesting, showing the correctness and the validity of the proposed approach. Auteurs: Roberto Ambrosino;Fabio Baselice;Giampaolo Ferraioli;Gilda Schirinzi; Apparue dans: IEEE Transactions on Geoscience and Remote Sensing Date publication: 10.-2017, volume: 55, issue:10, pages: 5854 - 5863 Editeur: IEEE Document complet vers site de l'éditeur
» Fabrication and Electromechanical Modeling of a Flexural-Mode MEMS Piezoelectric Transformer in AlN
 Résumé:This paper presents the fabrication and electromechanical characterization of a novel AlN-based microelectromechanical systems (MEMS) flexural-mode piezoelectric transformer (PT) realized in a silicon-on-insulator bulk-micromachining process with segmented electrodes at the secondary side, which are series-connected in order to increase the output voltage. The goal of this work is to propose a MEMS-based alternative to inductors and magnetic transformers for power management in micro-power mm-scale electronic systems. The fabricated device is fully modeled by means of the Butterworth-Van Dyke (BVD) two-port network. The device is modeled analytically with the classic equations of a fully clamped-edge membrane and through finite-element method simulations. Characterization is performed through impedance measurements and an alternative empirical method suitable for MEMS devices is proposed for directly extracting its lumped parameters electromechanical circuit. Finally, the effect of the feed-through capacitance is fully analytically modeled, and this paper presents a variant of the BVD network of the PT with an inner BVD circuit, allowing an easier estimation of the effects of the complex zeros introduced by the feed-forward capacitance. The presented device achieves a measured maximum voltage gain of 58mV/V at ~36.3 kHz and maximum efficiency of ~75%. Auteurs: Antonio Camarda;Guido Sordo;Jacopo Iannacci;Michael Schneider;Ulrich Schmid;Marco Tartagni;Aldo Romani; Apparue dans: Journal of Microelectromechanical Systems Date publication: 10.-2017, volume: 26, issue:5, pages: 1110 - 1121 Editeur: IEEE Document complet vers site de l'éditeur
» Fabrication, Characterization, and Analysis of Ge/GeSn Heterojunction p-Type Tunnel Transistors
 Résumé:We present a detailed study on fabrication and characterization of Ge/GeSn heterojunction p-type tunnel-field-effect-transistors (TFETs). Critical process modules as high-k stack and p-i-n diodes are addressed individually. As a result an ultrathin equivalent oxide thickness of 0.84 nm with an accumulation capacitance of $3~\mu \text{F}$ /cm2 was achieved on an extremely scaled tri-layer stack of GeSnOx/Al2O3/HfO2 deposited by atomic-layer deposition monitored in situ by spectroscopic ellipsometry. Combining these process modules, Ge/GeSn heterojunction pTFETs are fabricated and characterized to demonstrate the best in-class pTFET performance in the GeSn material system. The transfer characteristics of the TFETs show signatures of the trap-assisted thermal generation in the subthreshold regime which is explained by a modified Shockley–Read–Hall model. For the ON-state current, we used band-to-band tunneling models calculated using parameters from the density functional theory. We then use the calibrated model to project performance of GeSn pTFETs with increased Sn content (lower bandgap), reduced trap density and ultrathin body geometry. Both experimental and projected results are benchmarked against state-of-the art III–V (e.g., In0.65Ga0.35/GaAs0.4Sb0.6) pTFETs. We demonstrate the ability of GeSn to achieve superior performance with both high ON-current and sub-60mV/decade switching benefiting from the small and direct bandgap for higher Sn contents. Auteurs: Christian Schulte-Braucks;Rahul Pandey;Redwan Noor Sajjad;Mike Barth;Ram Krishna Ghosh;Ben Grisafe;Pankaj Sharma;Nils von den Driesch;Anurag Vohra;Gilbert Bruce Rayner;Roger Loo;Siegfried Mantl;Dan Buca;Chih-Chieh Yeh;Cheng-Hsien Wu;Wilman Tsai;Dimit Apparue dans: IEEE Transactions on Electron Devices Date publication: 10.-2017, volume: 64, issue:10, pages: 4354 - 4362 Editeur: IEEE Document complet vers site de l'éditeur
» Facilitating the Integration of Renewables in Latin America: The Role of Hydropower Generation and Other Energy Storage Technologies
 Résumé:It is well known that storage facilities can provide value to various electricity sectors through several services, which we group into five main classes. Auteurs: Rodrigo Moreno;Rafael Ferreira;Luiz Barroso;Hugh Rudnick;Eduardo Pereira; Apparue dans: IEEE Power and Energy Magazine Date publication: 10.-2017, volume: 15, issue:5, pages: 68 - 80 Editeur: IEEE Document complet vers site de l'éditeur
» Facilitating Time Critical Information Seeking in Social Media
 Résumé:Social media plays a major role in helping people affected by natural calamities. These people use social media to request information and help in situations where time is a critical commodity. However, generic social media platforms like Twitter and Facebook are not conducive for obtaining answers promptly. Algorithms to ensure prompt responders for questions in social media have to understand and model the factors affecting their response time. In this paper, we draw from sociological studies on information seeking and organizational behavior to identify users who can provide timely and relevant responses to questions posted on social media. We first draw from these theories to model the future availability and past response behavior of the candidate responders and integrate these criteria with user relevance. We propose a learning algorithm from these criteria to derive optimal rankings of responders for a given question. We present questions posted on Twitter as a form of information seeking activity in social media and use them to evaluate our framework. Our experiments demonstrate that the proposed framework is useful in identifying timely and relevant responders for questions in social media. Auteurs: Suhas Ranganath;Suhang Wang;Xia Hu;Jiliang Tang;Huan Liu; Apparue dans: IEEE Transactions on Knowledge and Data Engineering Date publication: 10.-2017, volume: 29, issue:10, pages: 2197 - 2209 Editeur: IEEE Document complet vers site de l'éditeur
» Falling Water, Rising Power
 Résumé:Hydropower is the production of electricity utilizing the force of falling water. Hydroelectric generators typically found in the United States range greatly in capacity from microhydro units rated between 5 kW-100 kW up to the large units at Grand Coulee Dam in Washington state, which are rated at 805 MW. The newly constructed Three Gorges Dam in China houses 32 units rated at 700 MW as well as two units rated at 50 MW to power the plant itself. Three Gorges is the world's largest hydroelectric power plant in terms of installed electrical generating capacity. Hydropower production can vary throughout the year as water supplies fluctuate. Peak hydropower generation typically occurs during the spring and summer months during snow melt and rain run-off season. Auteurs: Mark Skoric; Apparue dans: IEEE Potentials Date publication: 10.-2017, volume: 36, issue:5, pages: 30 - 31 Editeur: IEEE Document complet vers site de l'éditeur
» Fano Resonance in a Metasurface Composed of Graphene Ribbon Superlattice
 Résumé:We present a metasurface composed of graphene ribbon superlattice that supports plasmonic Fano resonance in a simple symmetric configuration. Without the necessity of changing the geometry size of graphene ribbons, we tune the Fano resonance of the metasurface containing identical graphene ribbons by simply changing the global or local periods of the superlattice. The increase of the global period of the superlattice leads to a blue-shift of the broad resonance of the bright mode, while the increase of the local period leads to simultaneous shifts of the broad resonance of the bright mode and the sharp resonance of the dark mode toward opposite direction with respect to each other. The resonance shift mechanism can be well explained by the restoring force model for longitudinal dipole arrays. In addition, the overall spectral position of the Fano resonance can be actively tuned by the fermi level of graphene ribbons. Our methods provide a simple and flexible pathway to tune the plasmonic Fano resonance, which holds great potentials for tunable biosensing and slow light applications with improved performance. Auteurs: Zi-Lan Deng;Xiangping Li;Tao Fu;Guo Ping Wang; 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
» Fast and Accurate Frequency-Dependent Behavioral Model of Bonding Wires
 Résumé:A proposed model of bonding wires is presented in this paper. For a regular double-π bonding-wire model considering the skin effect, nine parameters should be determined, including inductance $(L_{S})$, series parasitic resistances $(R_{{1}},\,R_{{2}})$, shunt parasitic capacitances $(C_{{\rm{PAR1}}},\,C_{{\rm{PAR2}}})$, and parameters for skin effects $(R_{S{1}},\,L_{S{1}},\,R_{S{2}},\,L_{S{2}})$ , so procedures to extract the design parameters for a bonding-wire model are complicated. To reduce the complexity, a proposed model is presented. Introducing a frequency-dependent resistor $R_{{\rm{skin}}}{f^m}$ can significantly reduce the number of design parameters for a bonding-wire model considering the skin effect from nine to five. This can resolve the design complexity of the bonding wires and cables. Moreover, it is suitable for industrial applications. In addition, the proposed design methodology is presented and the mechanisms are validated by experiments. According to experimental results, the model accuracy with 10% difference in magnitude between measured and modeled $S_{{21}}$ of the 2, 4, 6, and 8 mm aluminum bonding wires is at the frequencies of 5.9, 5.0, 3.5, and 2.9 GHz, respectively. Auteurs: To-Po Wang;You-Fu Lu; Apparue dans: IEEE Transactions on Industrial Informatics Date publication: 10.-2017, volume: 13, issue:5, pages: 2389 - 2396 Editeur: IEEE Document complet vers site de l'éditeur
» Fast Antenna Far-Field Characterization via Sparse Spherical Harmonic Expansion
 Résumé:A procedure is proposed to significantly reduce the amount of time to characterize 3-D antenna far-field patterns. The measured far field is expanded into spherical harmonics, and a sparse recovery algorithm is used to recover the spherical wave coefficients giving access to the field radiated by the antenna everywhere. A small number of measurement points are required, since the relevant information of the most antenna patterns is concentrated in only a few spherical wave coefficients. Sampling strategies enabling fast spherical scans are discussed, which makes the approach both efficient and easy to implement in existing far-field measurement facilities. Simulations are first provided to show the potentialities of this compressive sensing-based approach. The proposed strategy is then applied to characterize 3-D far-field patterns radiated by several antennas operating in different frequency bands measured in far field in direct line of sight configuration and in a compact antenna test range. Experimental results show that a saving in the number of measurement points up to 70% can be achieved compared with standard approaches. These results pave the way to a more efficient use of far-field measurement facilities. Auteurs: Benjamin Fuchs;Laurent Le Coq;Sébastien Rondineau;Marco Donald Migliore; Apparue dans: IEEE Transactions on Antennas and Propagation Date publication: 10.-2017, volume: 65, issue:10, pages: 5503 - 5510 Editeur: IEEE Document complet vers site de l'éditeur
» Fast Background Calibration of Sampling Timing Skew in SHA-Less Pipeline ADCs
 Résumé:This brief presents a digital calibration technique for compensating timing-skew errors between the sub-ADC and the MDAC in the first stage of sample-and-hold amplifier (SHA)-less pipeline ADCs. In the presence of clock-skew errors, sub-ADC comparators produce time-variant offsets depending on the input-signal slope at the sampling instants. These increase residue excursions at the MDAC output, potentially causing overranging and an increment in nonlinear errors. This paper derives close analytical expressions for these effects. The proposed method uses the overranging information to perform a low-cost estimation and correction of the skew error with the following features: 1) very fast convergence (in the order of 1-k input samples); 2) indirect evaluation of the skew error signal, without any previous knowledge of the input signal’s frequency distribution; and 3) relatively simple digital logic—basically, two digital comparators and one small accumulator. The method was verified in behavioral and transistor-level simulations. As a demonstrator, its implementation in a 1.8-V 80-dB SNDR 100-Msps SHA-less pipeline ADC in a 0.18- $\mu \text{m}$ CMOS process is shown. Auteurs: A. J. Ginés;E. J. Peralías;A. Rueda; Apparue dans: IEEE Transactions on Very Large Scale Integration Systems Date publication: 10.-2017, volume: 25, issue:10, pages: 2966 - 2970 Editeur: IEEE Document complet vers site de l'éditeur
» Fast Binary Counters Based on Symmetric Stacking
 Résumé:In this brief, a new binary counter design is proposed. It uses 3-bit stacking circuits, which group all of the “1” bits together, followed by a novel symmetric method to combine pairs of 3-bit stacks into 6-bit stacks. The bit stacks are then converted to binary counts, producing 6:3 counter circuits with no xor gates on the critical path. This avoidance of xor gates results in faster designs with efficient power and area utilization. In VLSI simulations, the proposed counters are 30% faster than existing parallel counters and also consume less power than other higher order counters. Additionally, using the proposed counters in existing counter-based Wallace tree multiplier architectures reduces latency and power consumption for 64 and 128-bit multipliers. Auteurs: Christopher Fritz;Adly T. Fam; Apparue dans: IEEE Transactions on Very Large Scale Integration Systems Date publication: 10.-2017, volume: 25, issue:10, pages: 2971 - 2975 Editeur: IEEE Document complet vers site de l'éditeur
» Fast Depth Imaging Denoising With the Temporal Correlation of Photons
 Résumé:This paper proposes a novel method to filter out the false alarm of LiDAR system by using the temporal correlation of target reflected photons. Because of the inevitable noise, which is due to background light and dark counts of the detector, the depth imaging of LiDAR system exists a large estimation error. Our method combines the Poisson statistical model with the different distribution feature of signal and noise in the time axis. Due to selecting a proper threshold, our method can effectively filter out the false alarm of system and use the ToFs of detected signal photons to rebuild the depth image of the scene. The experimental results reveal that by our method it can fast distinguish the distance between two close objects, which is confused due to the high background noise, and acquire the accurate depth image of the scene. Our method need not increase the complexity of the system and is useful in power-limited depth imaging. Auteurs: Zhenchao Feng;Weiji He;Jian Fang;Guohua Gu;Qian Chen;Ping Zhang;Yuanjin Chen;Beibei Zhou;Minhua Zhou; 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
» Fast Detection of Compressively Sensed IR Targets Using Stochastically Trained Least Squares and Compressed Quadratic Correlation Filters
 Résumé:Target detection of potential threats at night can be deployed on a costly infrared focal plane array with high resolution. Due to the compressibility of infrared image patches, the high resolution requirement could be reduced with target detection capability preserved. For this reason, a compressive midwave infrared imager (MWIR) with a low-resolution focal plane array has been developed. As the most probable coefficient indices of the support set of the infrared image patches could be learned from the training data, we develop stochastically trained least squares (STLS) for MWIR image reconstruction. Quadratic correlation filters (QCF) have been shown to be effective for target detection and there are several methods for designing a filter. Using the same measurement matrix as in STLS, we construct a compressed quadratic correlation filter (CQCF) employing filter designs for compressed infrared target detection. We apply CQCF to the U.S. Army Night Vision and Electronic Sensors Directorate dataset. Numerical simulations show that the recognition performance of our algorithm matches that of the standard full reconstruction methods, but at a fraction of the execution time. Auteurs: Brian Millikan;Aritra Dutta;Qiyu Sun;Hassan Foroosh; Apparue dans: IEEE Transactions on Aerospace and Electronic Systems Date publication: 10.-2017, volume: 53, issue:5, pages: 2449 - 2461 Editeur: IEEE Document complet vers site de l'éditeur
» Fast ISAR Imaging Based on Enhanced Sparse Representation Model
 Résumé:Traditional sparse representation-(SR) based inverse synthetic aperture radar (ISAR) imaging schemes can achieve significant performance, but they suffer from high costs of memory and computational complexity, because the SR of a 2-D image is converted into that of a 1-D vector. Instead of memory consuming vector operations, we propose a fast ISAR imaging algorithm, where the decomposition and reconstruction of a 2-D scene is implemented using matrix operations directly. Besides the spatial sparsity of a scene, its structural sparsity is presented using the range profile of the scene, where both can be used to enhance sparsity exploitation during image reconstruction. Also, benefitting from the structural sparsity of the range profile, the target energy can be accumulated during the process, which further improves performance. Compared to available SR-based ISAR imaging algorithms, the proposed algorithm reduces both memory costs and computational complexity significantly, which is proven using simulated and real data. Auteurs: Guanghui Zhao;Fangfang Shen;Jie Lin;Guangming Shi;Yi Niu; Apparue dans: IEEE Transactions on Antennas and Propagation Date publication: 10.-2017, volume: 65, issue:10, pages: 5453 - 5461 Editeur: IEEE Document complet vers site de l'éditeur
» Fast Parallel Path Concatenation for Graph Extraction
 Résumé:Heterogeneous graph is a popular data model to represent the real-world relations with abundant semantics. To analyze heterogeneous graphs, an important step is extracting homogeneous graphs from the heterogeneous graphs, called homogeneous graph extraction. In an extracted homogeneous graph, the relation is defined by a line pattern on the heterogeneous graph and the new attribute values of the relation are calculated by user-defined aggregate functions. The key challenges of the extraction problem are how to efficiently enumerate paths matched by the line pattern and aggregate values for each pair of vertices from the matched paths. To address above two challenges, we propose a parallel graph extraction framework, where we use vertex-centric model to enumerate paths and compute aggregate functions in parallel. The framework compiles the line pattern into a path concatenation plan, which determines the order of concatenating paths and generates the final paths in a divide-and-conquer manner. We introduce a cost model to estimate the cost of a plan and discuss three plan selection strategies, among which the best plan can enumerate paths in $\mathcal {O}(log(l))$ iterations, where $l$ is the length of a pattern. Furthermore, to improve the performance of evaluating aggregate functions, we classify the aggregate functions into three categories, i.e., distributive aggregation, algebraic aggregation, and holistic aggregation. Since the distributive and algebraic aggregations can be computed from the partial paths, we speed up the aggregation by computing partial aggregate values during the path enumeration. Auteurs: Yingxia Shao;Kai Lei;Lei Chen;Zi Huang;Bin Cui;Zhongyi Liu;Yunhai Tong;Jin Xu; Apparue dans: IEEE Transactions on Knowledge and Data Engineering Date publication: 10.-2017, volume: 29, issue:10, pages: 2210 - 2222 Editeur: IEEE Document complet vers site de l'éditeur
» Fast Real-Time Causal Linewise Progressive Hyperspectral Anomaly Detection via Cholesky Decomposition
 Résumé:Real-time processing of anomaly detection has become one of the most important issues in hyperspectral remote sensing. Due to the fact that most widely used hyperspectral imaging spectrometers work in a pushbroom fashion, it is necessary to process the incoming data line in a causal linewise progressive manner with no future data involved. In this study, we proposed several processes to well improve the computational performance of real-time causal linewise progressive anomaly detection (RCLP-AD). At first, Cholesky decomposition along with linear system solving (CDLSS) was used since the background statistical matrix are symmetric positive definite. The computational performance as well as the numerical stabilities is well improved. In order to show the computational advantage of the proposed method, we did a comprehensive comparative analysis regarding the computational complexity of different linewise processing techniques, in terms of the theoretical floating point operations (flops) and the real computer processing time. Moreover, the symmetric property of some intermediate resulting matrices in the process is considered for further computational optimization. Finally, from an onboard detection point of view, we defined the line-varying global background (i.e., an area covered by recently acquired data lines) to improve the detection power. To substantiate the performance of the CDLSS-based RCLP-AD regarding the accuracy and efficiency, two hyperspectral datasets were used in our experiments. Auteurs: Lifu Zhang;Bo Peng;Feizhou Zhang;Lizhe Wang;Hongming Zhang;Peng Zhang;Qingxi Tong; Apparue dans: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing Date publication: 10.-2017, volume: 10, issue:10, pages: 4614 - 4629 Editeur: IEEE Document complet vers site de l'éditeur
» Fast Rise Time High Current Electron Beam: Emission, Acceleration, and Drift Motion
 Résumé:Fast processes associated with emission, acceleration, and drift motion of a high current, moderately magnetized electron beam (particles energy ~300 keV; current ~3 kA) were studied experimentally when tubular explosive-emission cathode was supplied by subnanosecond rise time voltage pulse. Kinematic effect causes the sharpening of the observed beam front which was proven by particle-in-cell numerical modeling. The angular structure of tubular beam was studied through the current waveform records from collector probe after beam propagation through a radial-slit collimator. Current waveforms had time resolution no worse than 10 ps and provided the analysis of the beam temporal structure after its acceleration as well as in the process of further electrons drift motion in a finite guiding magnetic field. Auteurs: Sergei A. Shunailov;Gennady A. Mesyats;Ilya V. Romanchenko;Vladislav V. Rostov;Konstantin A. Sharypov;Valery G. Shpak;Marat R. Ul’maskulov;Michael I. Yalandin; Apparue dans: IEEE Transactions on Plasma Science Date publication: 10.-2017, volume: 45, issue:10, pages: 2755 - 2761 Editeur: IEEE Document complet vers site de l'éditeur
» Fast Semiconductor Switching Modules for Transformer-Coupled LC Inversion Generators
 Résumé:The recent availability of fast high-power semiconductor switches makes the transformer coupled LC inversion generator (TCLCG) topology a very promising candidate for the realization of reliable, multi-kHz repetition rate pulse generators with an output voltage in the range of 200 kV and more. Usage of 1:1 transformers instead of closing switches in each generator stage reduces the total number of switches inside the TCLCG to only one, independent of the numbers of stages. Thus, problem of synchronization as in Marx-generators or classical LC inversion generators can be omitted. In principle, capacitors are initially charged to the charging voltage, whereas the odd-numbered of each stage are charged with the opposite polarity to the even-numbered capacitors. Fast voltage inversion of the even-numbered capacitors leads to efficient voltage multiplication provided the semiconductor switching module will be sufficiently fast to minimize switching losses. For initial investigations, a special asymmetrically compensated three-stage test TCLCG was designed and set up. Three high-voltage semiconductor switching modules were experimentally tested in detail; two 20-kV high-voltage switching modules consisting of a series arrangement of 15 Si-based insulated gate bipolar transistors or 15 SiC-based MOSFETs, with in each case 1700-V breakdown voltage, and a fast experimental 10-kV thyristor switching module with kilo ampere current carrying capability. The achievable output signal rise time and generator efficiency for different electrical loads (resistive, capacitive, or inductive) are discussed. Auteurs: Rainer Bischoff;Volker Brommer;Meik Stoll;Sigo Scharnholz; Apparue dans: IEEE Transactions on Plasma Science Date publication: 10.-2017, volume: 45, issue:10, pages: 2618 - 2622 Editeur: IEEE Document complet vers site de l'éditeur
» Fast Simulation of Dynamic Ultrasound Images Using the GPU
 Résumé:Simulated ultrasound data is a valuable tool for development and validation of quantitative image analysis methods in echocardiography. Unfortunately, simulation time can become prohibitive for phantoms consisting of a large number of point scatterers. The COLE algorithm by Gao et al. is a fast convolution-based simulator that trades simulation accuracy for improved speed. We present highly efficient parallelized CPU and GPU implementations of the COLE algorithm with an emphasis on dynamic simulations involving moving point scatterers. We argue that it is crucial to minimize the amount of data transfers from the CPU to achieve good performance on the GPU. We achieve this by storing the complete trajectories of the dynamic point scatterers as spline curves in the GPU memory. This leads to good efficiency when simulating sequences consisting of a large number of frames, such as B-mode and tissue Doppler data for a full cardiac cycle. In addition, we propose a phase-based subsample delay technique that efficiently eliminates flickering artifacts seen in B-mode sequences when COLE is used without enough temporal oversampling. To assess the performance, we used a laptop computer and a desktop computer, each equipped with a multicore Intel CPU and an NVIDIA GPU. Running the simulator on a high-end TITAN X GPU, we observed two orders of magnitude speedup compared to the parallel CPU version, three orders of magnitude speedup compared to simulation times reported by Gao et al. in their paper on COLE, and a speedup of 27000 times compared to the multithreaded version of Field II, using numbers reported in a paper by Jensen. We hope that by releasing the simulator as an open-source project we will encourage its use and further development. Auteurs: Sigurd Storve;Hans Torp; Apparue dans: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control Date publication: 10.-2017, volume: 64, issue:10, pages: 1465 - 1477 Editeur: IEEE Document complet vers site de l'éditeur
» Fast Startup of LC VCOs Using Circuit Asymmetries
 Résumé:An LC VCO whose design includes deliberate circuit mismatches is presented. It is shown that such mismatches can reduce the oscillation start-up time due to a common-mode disturbance simultaneous with the turn-on of the tail current. The use of this technique is applied to a low-power transmitter for an ultra-wideband wireless communication system using the on–off keying modulation scheme. Measurements using a 0.18- ${\mu }\text{m}$ CMOS technology with a 4.2-GHz carrier frequency demonstrate the technique. Auteurs: Joshua H. Kim;Ali Tazarv;Michael M. Green; Apparue dans: IEEE Transactions on Circuits and Systems II: Express Briefs Date publication: 10.-2017, volume: 64, issue:10, pages: 1172 - 1176 Editeur: IEEE Document complet vers site de l'éditeur
» Fast-Lipschitz Power Control and User-Frequency Assignment in Full-Duplex Cellular Networks
 Résumé:In cellular networks, the three-node full-duplex transmission mode has the potential to increase spectral efficiency without requiring full-duplex capability of users. Consequently, three-node full-duplex in cellular networks must deal with self-interference and user-to-user interference, which can be managed by power control and user-frequency assignment techniques. This paper investigates the problem of maximizing the sum spectral efficiency by jointly determining the transmit powers in a distributed fashion, and assigning users to frequency channels. The problem is formulated as a mixed-integer nonlinear problem, which is shown to be non-deterministic polynomial-time hard. We investigate a close-to-optimal solution approach by dividing the joint problem into a power control problem and an assignment problem. The power control problem is solved by Fast-Lipschitz optimization, while a greedy solution with guaranteed performance is developed for the assignment problem. Numerical results indicate that compared with the half-duplex mode, both spectral and energy efficiencies of the system are increased by the proposed algorithm. Moreover, results show that the power control and assignment solutions have important, but opposite roles in scenarios with low or high self-interference cancellation. When the self-interference cancellation is high, user-frequency assignment is more important than power control, while power control is essential at low self-interference cancellation. Auteurs: José Mairton B. da Silva;Gábor Fodor;Carlo Fischione; Apparue dans: IEEE Transactions on Wireless Communications Date publication: 10.-2017, volume: 16, issue:10, pages: 6672 - 6687 Editeur: IEEE Document complet vers site de l'éditeur
» Fault Detection Over Frequency Region: Generalized Spectral Factorization Approach
 Résumé:We present results on fault detection in presence of disturbances of descriptor systems over a frequency region. Instead of the methodology of the generalized KYP lemma, used in the literature, we use the methodology of generalized spectral factorization. Illustrative examples are given. Auteurs: Jovan D. Stefanovski; Apparue dans: IEEE Transactions on Automatic Control Date publication: 10.-2017, volume: 62, issue:10, pages: 5296 - 5301 Editeur: IEEE Document complet vers site de l'éditeur
» Fault Diagnosis of Space-Borne Fiber-Optic Gyros Based on Random Walk Coefficient Prediction and In-Orbit Calculation
 Résumé:A novel fault diagnosis method for the space-borne interferometric fiber-optic gyroscope (IFOG) is presented in this paper. The noise source of the fiber-optic gyroscope is analyzed first. Then, the prediction model of the random walk coefficient (RWC) is established based on the radiation-induced attenuation effect on optical fiber, and the estimation model of RWC is developed by using the detected signal acquired by the photo-detector. In addition, an improved iterative method to calculate the RWC with the output data of the IFOG in orbit is proposed. The three RWC values mentioned above are compared to determine the operational state of the gyroscope. And an in-situ fault diagnosis strategy for the IFOG is proposed finally. Based on the ground simulation and fault injection, the feasibility of the strategy is proved. Auteurs: Jing Jin;Ting Zhang;Kun Ma;Haoshi Zhang;Fei Teng;Shaobo Zhang; Apparue dans: IEEE Sensors Journal Date publication: 10.-2017, volume: 17, issue:20, pages: 6637 - 6645 Editeur: IEEE Document complet vers site de l'éditeur
» Fault Tolerance Capability and Semiconductor’s Hold-Off Voltage of Solid-State Bipolar Marx Modulators
 Résumé:Two solid-state bipolar Marx modulators are analyzed and compared regarding hold-off semiconductor voltages and open-fault tolerance capability. Normal and abnormal operating conditions are considered, such as switch synchronization mismatches, failures, and open faults. Ten-stage laboratory prototypes of two bipolar Marx modulators have been assembled using 1200-V insulated gate bipolar transistors and matching diodes, to operate at 500-V dc input voltage. Outputs are 4-kV bipolar pulses, 1% duty ratio, into resistive loads, and 1-kHz frequency. Lack of synchronization and open-fault tests confirm that only topologies with redundant switches can operate without semiconductors being subjected to double hold-off voltages while presenting current paths to clear faults. Auteurs: Hiren Canacsinh;J. Fernando Silva;L. M. Redondo; Apparue dans: IEEE Transactions on Plasma Science Date publication: 10.-2017, volume: 45, issue:10, pages: 2661 - 2666 Editeur: IEEE Document complet vers site de l'éditeur
» Feast or Famine [From the Editor's Desk]
 Résumé:Presents the introductory editorial for this issue of the publication. Auteurs: Alfy Riddle; Apparue dans: IEEE Microwave Magazine Date publication: 10.-2017, volume: 18, issue:6, pages: 6 - 22 Editeur: IEEE Document complet vers site de l'éditeur
» Feature-Fused SAR Target Discrimination Using Multiple Convolutional Neural Networks
 Résumé:Target discrimination has been one of the hottest issues in the interpretation of synthetic aperture radar (SAR) images. However, the presence of speckle noise and the absence of robust features make SAR discrimination difficult to deal with. Recently, convolutional neural network has obtained state-of-the-art results in pattern recognition. In this letter, we propose a target discrimination framework that jointly uses intensity and edge information of SAR images. This framework contains three parts, namely, feature extraction block, feature fusion block, and final classification block. In addition, a novel feature fusion method that can preserve the spatial relationship of different features is introduced. Experimental results on the miniSAR data demonstrate the effectiveness of our method. Auteurs: Ning Wang;Yinghua Wang;Hongwei Liu;Qunsheng Zuo;Jinglu He; Apparue dans: IEEE Geoscience and Remote Sensing Letters Date publication: 10.-2017, volume: 14, issue:10, pages: 1695 - 1699 Editeur: IEEE Document complet vers site de l'éditeur
» Feedback Stabilized Optical Fabry–Pérot Interferometer Based on Twin-Core Fiber for Multidimension Microdisplacement Sensing
 Résumé:A novel optical Fabry–Pérot interferometer (FPI) is proposed and experimentally demonstrated for multidimension microdisplacement sensing (MMS). The sensor structure consists of a section of twin-core fiber with a length of 2.4 cm and a section of feedback fiber (FBF) fabricated by normal single-mode fiber. The end faces of two fibers can be formed as the reflection cavity (RC) of the FPI. Mounting the sensor on translation stages, and moving the FBF in different directions to change the RC, the changing mode interference of the reflected beam can be measured. A maximum microdisplacement sensitivity of 0.954 nm/μm with a higher resolution 0.052 μm was achieved. Due to the advantages of the MMS and simple configuration, the sensor is significantly beneficial to practical application. Auteurs: Chuanbiao Zhang;Tigang Ning;Jingjing Zheng;Jing Li;Heng Lin;Xuekai Gao;Li Pei; 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
» Feedback-Based Online Network Coding
 Résumé:Current approaches to the practical implementation of network coding are batch-based, and often do not use feedback, except possibly to signal completion of a file download. In this paper, the various benefits of using feedback in a network coded system are studied. It is shown that network coding can be performed in a completely online manner, without the need for batches or generations, and that such online operation does not affect the throughput. Although these ideas are presented in a single-hop packet erasure broadcast setting, they naturally extend to more general lossy networks, which employ network coding in the presence of feedback. The impact of feedback on sender-side queue size and receiver-side decoding delay is studied in an asymptotic sense as the traffic load approaches capacity. Different notions of decoding delay are considered, including an order-sensitive notion, which assumes that packets are useful only when delivered in order. Strategies for adaptive coding based on feedback are presented. Our scheme achieves throughput optimality and asymptotically optimal sender queue size and is conjectured to achieve asymptotically optimal in-order delivery delay for any number of receivers. This paper may be viewed as a natural extension of Automatic Repeat reQuest to coded networks. Auteurs: Jay Kumar Sundararajan;Devavrat Shah;Muriel Médard;Parastoo Sadeghi; Apparue dans: IEEE Transactions on Information Theory Date publication: 10.-2017, volume: 63, issue:10, pages: 6628 - 6649 Editeur: IEEE Document complet vers site de l'éditeur
» Fekete Points, Formation Control, and the Balancing Problem
 Résumé:We study formation control problems. Our approach is to let a group of systems maximize their pairwise distances while bringing them all to a given submanifold, determining the shape of the formation. The algorithm we propose allows us to initialize the positions of the individual systems in the ambient space of the given submanifold but brings them to the desired formation asymptotically in a stable fashion. Our control inherently consists of a distributed component, maximizing the pairwise distances, and a decentralized component, asymptotically stabilizing the submanifold. We establish a graph-theoretical interpretation of the equilibria that our control enforces and extends our approach to systems living on the special Euclidean group. Throughout this paper, we illustrate our approach on different examples. Auteurs: Jan Maximilian Montenbruck;Daniel Zelazo;Frank Allgöwer; Apparue dans: IEEE Transactions on Automatic Control Date publication: 10.-2017, volume: 62, issue:10, pages: 5069 - 5081 Editeur: IEEE Document complet vers site de l'éditeur
» Fermi Level Depinning in Ti/GeO2/n-Ge via the Interfacial Reaction Between Ti and GeO2
 Résumé:A new method of forming an ohmic contact without an increase in parasitic resistance is proposed in the Ti/GeO2/Ge substrate. Fermi-level depinning in Ti/GeO2/n–Ge contacts is possible with the formation of an interfacial TiOx layer in the contacts via an interfacial reaction. Unlike the intentional deposition of a metal oxide on a Ge substrate, this method provides easy process integration to lessen Fermi-level pinning in n-type Ge substrates. Auteurs: Yujin Seo;Tae In Lee;Hyun Jun Ahn;Jungmin Moon;Wan Sik Hwang;Hyun-Yong Yu;Byung Jin Cho; Apparue dans: IEEE Transactions on Electron Devices Date publication: 10.-2017, volume: 64, issue:10, pages: 4242 - 4245 Editeur: IEEE Document complet vers site de l'éditeur
» Fiber Optic Magnetic Field Sensor Based on Magnetic Nanoparticle Assembly in Microcapillary Ring Resonator
 Résumé:A magnetic field sensor based on the magnetic-field-induced nanoparticle assembly effect in microcapillary whispering gallery mode (WGM) ring resonator is proposed and experimentally demonstrated. The chemical characteristics of nanoparticles and the silica microcapillary are used to link up the surface density of the resonator and the magnetic field intensity. The magnetic field variation changes the surface density of nanoparticles adsorbed on the sensor surface and respond to the WGM transmission spectra shift. Because of the powerful surface sensing capability of WGM, the maximum sensing sensitivity reaches 57.59 nm/mT and the detection limit reaches 1.39 × 10 –4, respectively. The magnetic field response characteristic of the sensor is studied as well. This provides the potential to fiber-based magnetic field sensing applications. Auteurs: Zhe Yu;Junfeng Jiang;Xuezhi Zhang;Kun Liu;Shuang Wang;Wenjie Chen;Tiegen Liu; 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
» File Updates Under Random/Arbitrary Insertions and Deletions
 Résumé:The problem of one-way file synchronization, henceforth called “file updates”, is studied in this paper. Specifically, a client edits a file, where the edits are modeled by insertions and deletions (InDels). An old copy of the file is stored remotely at a data-centre, and is also available to the client. We consider the problem of throughput- and computationally-efficient communication from the client to the data-centre, to enable the data-centre to update its old copy to the newly edited file. Two models for the source files and edit patterns are studied: the random pre-edit sequence left-to-right random InDel (RPES-LtRRID) process, and the arbitrary pre-edit sequence arbitrary InDel (APES-AID) process. In both models, we consider the regime, in which the number of insertions and deletions is a small (but constant) fraction of the length of the original file. For both models, information-theoretic lower bounds on the best possible compression rates that enable file updates are derived (up to first order terms). Conversely, a simple compression algorithm using dynamic programming (DP) and entropy coding (EC), henceforth called DP-EC algorithm, achieves rates that are within constant additive gap (which diminishes as the alphabet size increases) to information-theoretic lower bounds for both models. For the RPES-LtRRID model, a dynamic-programming-run-length-compression (DP-RLC) algorithm is proposed, which achieves a compression rate matching the information-theoretic lower bound up to first order terms. Therefore, when the insertion and deletion probabilities are small (such that first order terms dominate), the achievable rate by DP-RLC is nearly optimal for the RPES-LtRRID model. Auteurs: Qiwen Wang;Sidharth Jaggi;Muriel Médard;Viveck R. Cadambe;Moshe Schwartz; Apparue dans: IEEE Transactions on Information Theory Date publication: 10.-2017, volume: 63, issue:10, pages: 6487 - 6513 Editeur: IEEE Document complet vers site de l'éditeur
» Finding Measurement Configurations for Accurate Robot Calibration: Validation With a Cable-Driven Robot
 Résumé:It is well known that, by properly selecting the measurement configurations in robot calibrations, the observability index of unknown parameters can be maximized, leading to high calibration accuracy. For this purpose, many configuration-search methods were proposed. However, the established methods were mainly based on derivative-free or metaheuristic techniques, whose computational costs were high. Moreover, the robustness of observability index and convergences of configuration searches were not investigated. In this paper, by extending a recent result in matrix perturbation theory to robot kinematics, we establish the closed-form mapping from configuration perturbations to singular-value variations. Based on this mapping, an efficient configuration-search method is proposed, the robustness of the observability index under bounded configuration perturbations is analyzed, and the convergence of configuration searches is studied. The proposed methods were validated by simulations on serial and parallel robots. With roughly estimated initial parameters, self-calibration experiments on a redundant cable-driven parallel robot were performed. The effectiveness of the proposed methods is demonstrated by the experiment results. Auteurs: Hongbo Wang;Tianqi Gao;Jun Kinugawa;Kazuhiro Kosuge; Apparue dans: IEEE Transactions on Robotics Date publication: 10.-2017, volume: 33, issue:5, pages: 1156 - 1169 Editeur: IEEE Document complet vers site de l'éditeur
» Fixed-Time Connectivity-Preserving Distributed Average Tracking for Multiagent Systems
 Résumé:This brief studies the fixed-time average tracking problem for multiagent systems under communication constraints, in which each agent has a limited sensing range. A distributed nonlinear control protocol is proposed to make a team of agents track the average of multiple time-varying reference signals with bounded derivatives. Furthermore, the initial interaction patterns can be preserved under the designed protocol and the average tracking can be achieved within fixed time, where the bound of settling time is independent of the initial conditions. Thus, the fixed convergence time can be flexibly adjusted. Finally, some numerical examples are provided to illustrate the performance and effectiveness of the theoretical results. Auteurs: Huifen Hong;Wenwu Yu;Xinghuo Yu;Guanghui Wen;Ahmed Alsaedi; Apparue dans: IEEE Transactions on Circuits and Systems II: Express Briefs Date publication: 10.-2017, volume: 64, issue:10, pages: 1192 - 1196 Editeur: IEEE Document complet vers site de l'éditeur
» Flexibility Needed: Challenges for Future Energy Storage Systems [Guest Editorial]
 Résumé:The articles in this special section focus on the technologies that will support future energy storage systems. In modern power systems, we are transitioning to an increasing penetration of massive low-cost wind and solar generation, which will require indispensable system flexibility for balancing requirements to maintain system performance. The existing actors have limited technical capabilities to provide the needed flexibility, and new alternatives are required. The flexibility providers are diverse and being assessed extensively, with a clear sense of urgency. Auteurs: Hugh Rudnick;Luiz Barroso; Apparue dans: IEEE Power and Energy Magazine Date publication: 10.-2017, volume: 15, issue:5, pages: 12 - 19 Editeur: IEEE Document complet vers site de l'éditeur
» Flexible and Fine-Grained Attribute-Based Data Storage in Cloud Computing
 Résumé:With the development of cloud computing, outsourcing data to cloud server attracts lots of attentions. To guarantee the security and achieve flexibly fine-grained file access control, attribute based encryption (ABE) was proposed and used in cloud storage system. However, user revocation is the primary issue in ABE schemes. In this article, we provide a ciphertext-policy attribute based encryption (CP-ABE) scheme with efficient user revocation for cloud storage system. The issue of user revocation can be solved efficiently by introducing the concept of user group. When any user leaves, the group manager will update users’ private keys except for those who have been revoked. Additionally, CP-ABE scheme has heavy computation cost, as it grows linearly with the complexity for the access structure. To reduce the computation cost, we outsource high computation load to cloud service providers without leaking file content and secret keys. Notably, our scheme can withstand collusion attack performed by revoked users cooperating with existing users. We prove the security of our scheme under the divisible computation Diffie-Hellman assumption. The result of our experiment shows computation cost for local devices is relatively low and can be constant. Our scheme is suitable for resource constrained devices. Auteurs: Jiguo Li;Wei Yao;Yichen Zhang;Huiling Qian;Jinguang Han; Apparue dans: IEEE Transactions on Services Computing Date publication: 10.-2017, volume: 10, issue:5, pages: 785 - 796 Editeur: IEEE Document complet vers site de l'éditeur
» Flexible Efficient Top-Emitting Organic Light-Emitting Devices on a Silk Substrate
 Résumé:A flexible efficient top-emitting organic light-emitting device (TOLED) on an off-the-shelf silk substrate has been demonstrated by planarizing the silk substrate with photopolymer NOA63. The flexibility of the bare silk substrates was retained in the planarized silk substrates due to ductile characteristics of cured NOA63. The planarized silk substrate has shown superiority on surface morphology, which is beneficial to the performances of OLEDs. Their maximum luminance and current efficiency are 45545 ${\rm{cd/ m}}^{2}$ and 37.7 cd/A, respectively. Moreover, our devices show not only high luminance and efficiency but also high flexibility and mechanical robustness. Emission of operating devices is uniform and free of defects under a very small bending radius and the luminance and efficiency do not deteriorate obviously after repeated bending. TOLEDs on silk substrate are a potential alternative to wearable displays. Auteurs: Yue-Feng Liu;Ming-Hui An;Yan-Gang Bi;Da Yin;Jing Feng;Hong-Bo Sun; Apparue dans: IEEE Photonics Journal Date publication: 10.-2017, volume: 9, issue:5, pages: 1 - 6 Editeur: IEEE Document complet vers site de l'éditeur
» Flexible Low-Power Organic Complementary Inverter Based on Low- ${k}$ Polymer Dielectric
 Résumé:Organic complementary inverters that have high performance, low-power operation, and flexible compatibility are achieved using a simple and low-cost method to prepare a thin low- ${k}$ polymer dielectric on sputtered C nanoparticles. The operation voltage of the flexible inverter can be as low as 3 V, and the gain is close to 200, which is superior to most reported organic-based inverters. The flexible inverter also exhibits outstanding switching stability in multiple signal processing. The present organic inverters may be of value in portable and wearable electronics. Auteurs: Jie Liu;Xu Gao;Jian-Long Xu;Antonio Ruotolo;Sui-Dong Wang; Apparue dans: IEEE Electron Device Letters Date publication: 10.-2017, volume: 38, issue:10, pages: 1461 - 1464 Editeur: IEEE Document complet vers site de l'éditeur
» Flexible PCC Voltage Unbalance Compensation Strategy for Autonomous Operation of Parallel DFIGs
 Résumé:This paper proposes a flexible compensation strategy for parallel-connected doubly fed induction generators (DFIGs) when connected to an unbalanced weak grid. The proposed strategy has two main advantages, the voltage unbalance factor at the point of common coupling (PCC) can be continuously controlled, thus, the flexible tradeoff between the balanced DFIG output current and the balanced PCC voltage can be achieved, and the negative sequence current required by the compensation can be properly shared among the parallel DFIGs and their grid side converters according to their respective operation conditions without the need of real-time communication. The operation performance and stability of the proposed strategy are analyzed. Simulation and experimental results are carried out to verify the proposed compensation strategy. Auteurs: Tao Wang;Heng Nian;Z. Q. Zhu;Hongyang Huang;Xiaoming Huang; Apparue dans: IEEE Transactions on Industry Applications Date publication: 10.-2017, volume: 53, issue:5, pages: 4807 - 4820 Editeur: IEEE Document complet vers site de l'éditeur
» Flexible Tactile Sensor Array Mounted on the Curved Surface: Analytical Modeling and Experimental Validation
 Résumé:This paper presents an analytical model to study the sensing performance of the flexible capacitive tactile sensor array when mounted on a curved surface. To predict the deformation of the sensor unit, a cylindrical coordinate is constructed for the upper Polyethylene Terephthalate (PET) and truncated pyramids dielectric layer. The displacement functions model is developed and solved by using the Ritz method. Then, this model is utilized to investigate the capacitance change of the sensor unit and the model-calculated results are compared with the experiment data. Both model calculated and experiment measured results indicate that the capacitances of the sensor array are increased by about 30% when the sensor is mounted on the curved surface with a radius of curvature of 10 mm. Due to the bending effects of the curved surface, the sensitivities of the sensor array are decreased based on the model calculation and are confirmed by experimental validation. Thus, results demonstrate that the developed analytical model can accurately predict the sensing performance of the tactile sensor array on the curved surface and could be utilized for the real applications. [2016-0235] Auteurs: Yancheng Wang;Guanhao Liang;Deqing Mei;Zichen Chen; Apparue dans: Journal of Microelectromechanical Systems Date publication: 10.-2017, volume: 26, issue:5, pages: 1002 - 1011 Editeur: IEEE Document complet vers site de l'éditeur
» Floating Monopole Antenna on a Tethered Subsurface Sensor at 433 MHz for Ocean Monitoring Applications
 Résumé:Low-cost tethered buoys are important for seawater observation, coastal area monitoring, and pollution sensing. Underwater sensor networks operating at 433 MHz (ISM band) suffer high attenuation due to seawater conductivity. Significant propagation distance cannot be achieved through seawater or along the seabed. This paper reports a novel technique for communication between sensors operating in shallow water. A sensor tethered to the bottom was connected to a floating monopole antenna via an insulated wire transmission line. Experiments and calculations show that the attenuation along the transmission line was 38 dB/m. Surface propagation for buoy-to-base station was approximately 1 dB/m with a communication range of 30 m using a 10-dBm transmitter circuit with receiver sensitivity of ${-}$110 dBm. For buoy to buoy the surface propagation was measured as 3.5 dB/m with a communication range of 4 m. Experiments were carried out in calm water conditions. The results demonstrate that significant sensor network coverage of coastal regions is possible. Auteurs: Zia M. Loni;Hugo G. Espinosa;David V. Thiel; Apparue dans: IEEE Journal of Oceanic Engineering Date publication: 10.-2017, volume: 42, issue:4, pages: 818 - 825 Editeur: IEEE Document complet vers site de l'éditeur
» Flocking of the Cucker-Smale Model on General Digraphs
 Résumé:In the literature, the study of the Cucker-Smale (C-S) flocking model is all restricted to connected undirected graphs or digraphs of some special types, containing only a single root. In this technical note, we establish the flocking behavior of the C-S model on general digraphs, which contain all existing interaction topologies in relation to the C-S model as special cases. In particular, the topology with multiple leaders is included. The flocking results are guaranteed under some conditions on the initial state of the flock only. The critical exponent below which unconditional convergence holds is given, depending only on the interaction topology. It is consistent with the ones obtained under some known special topologies in the literature. Auteurs: Jiu-Gang Dong;Li Qiu; Apparue dans: IEEE Transactions on Automatic Control Date publication: 10.-2017, volume: 62, issue:10, pages: 5234 - 5239 Editeur: IEEE Document complet vers site de l'éditeur
» Fog-Aided Wireless Networks for Content Delivery: Fundamental Latency Tradeoffs
 Résumé:A fog-aided wireless network architecture is studied in which edge nodes (ENs), such as base stations, are connected to a cloud processor via dedicated fronthaul links while also being endowed with caches. Cloud processing enables the centralized implementation of cooperative transmission strategies at the ENs, albeit at the cost of an increased latency due to fronthaul transfer. In contrast, the proactive caching of popular content at the ENs allows for the low-latency delivery of the cached files, but with generally limited opportunities for cooperative transmission among the ENs. The interplay between cloud processing and edge caching is addressed from an information-theoretic viewpoint by investigating the fundamental limits of a high signal-to-noise-ratio metric, termed normalized delivery time (NDT), which captures the worst case coding latency for delivering any requested content to the users. The NDT is defined under the assumptions of either serial or pipelined fronthaul-edge transmission, and is studied as a function of fronthaul and cache capacity constraints. Placement and delivery strategies across both fronthaul and wireless, or edge, segments are proposed with the aim of minimizing the NDT. Information-theoretic lower bounds on the NDT are also derived. Achievability arguments and lower bounds are leveraged to characterize the minimal NDT in a number of important special cases, including systems with no caching capabilities, as well as to prove that the proposed schemes achieve optimality within a constant multiplicative factor of 2 for all values of the problem parameters. Auteurs: Avik Sengupta;Ravi Tandon;Osvaldo Simeone; Apparue dans: IEEE Transactions on Information Theory Date publication: 10.-2017, volume: 63, issue:10, pages: 6650 - 6678 Editeur: IEEE Document complet vers site de l'éditeur
» Foreground Removal Approach for Hole Filling in 3D Video and FVV Synthesis
 Résumé:The depth-image-based rendering is a key technique for 3D video and free viewpoint video synthesis. One of the critical problems in current synthesis methods is that the background (BG) occluded by the foreground objects might be exposed in the new view, and some holes are produced in the synthesized video. However, most of the traditional hole-filling approaches may bring some blurry effect or artifacts in the virtual view. In this paper, a foreground removal approach for hole filling is proposed, in which the foreground objects are removed from both the 2D video and its corresponding depth map, and then a BG video and its depth map are generated before the 3D warping and used to eliminate the holes in the synthesized video. Moreover, a BG extension method is applied in the reference view to prevent the large holes occurring along the border areas in the virtual view. Our analysis and experimental results have indicated that the proposed approach has better performance compared with the other methods in terms of the quality of synthesized video, computational complexity, and running time in multiview synthesis or multiframe synthesis. Auteurs: Guibo Luo;Yuesheng Zhu; Apparue dans: IEEE Transactions on Circuits and Systems for Video Technology Date publication: 10.-2017, volume: 27, issue:10, pages: 2118 - 2131 Editeur: IEEE Document complet vers site de l'éditeur
» Foreword to the Special Issue on Advances in Ground-Penetrating Radar Research and Applications
 Résumé: Auteurs: Wallace W. L. Lai;Sébastien Lambot;Jan van der Kruk; Apparue dans: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing Date publication: 10.-2017, volume: 10, issue:10, pages: 4271 - 4272 Editeur: IEEE Document complet vers site de l'éditeur
» Fountain-Coded File Spreading Over Mobile Networks
 Résumé:Spreading a large file consisting of many packets over a mobile network is challenging due to the short meeting duration for each transmission. Moreover, two typical causes of inefficient file spreading are duplicate packet reception at the destination nodes and excessive overhead exchanges. We propose to employ fountain codes at the source node to jointly addresses the three issues: 1) each coded packet can be small enough to fit into the meeting duration; 2) duplicate packet reception is significantly reduced since each coded packet is innovative; and 3) overhead is greatly saved by using file-level ACK instead of packet-level ACK. We conduct performance analysis in terms of the source-to-destination file delay and source-to-destination file spreading time in both non-relaying and relaying scenarios. While packet duplication can be eliminated in the former scenario, there is still a non-trivial duplication probability if relaying is allowed. Therefore, we propose a fountain-coded two-hop relaying (FTTR) protocol to further reduce the packet duplication ratio so that the spreading performance does not degrade with network size. The file spreading time and packet duplication ratio of FTTR are derived in closed form and verified through simulations. Auteurs: Zhaoyang Zhang;Huazi Zhang;Huaiyu Dai;Xiaoming Chen;Dapeng Oliver Wu; Apparue dans: IEEE Transactions on Wireless Communications Date publication: 10.-2017, volume: 16, issue:10, pages: 6766 - 6778 Editeur: IEEE Document complet vers site de l'éditeur
» FPGA Implementation of a Tone-Based Flight Termination System in a Software-Defined Radio Platform
 Résumé:This paper outlines the design and implementation of a tone-based flight termination system (FTS) in a software-defined radio (SDR) platform. It is completely a novel implementation of an analog FTS in an SDR platform of NI Flex-RIO system. This single platform based design appears as a substitute for the previously used multiple platforms based complex system. Ruggedization and relevance design methods are required for the FTS design. Hence, the blueprint of the FTS is carried out in a field-programmable gate array. It ensures reconfigurable, interoperable operations with precise, reliable, and future upgradable implementation. Efficient optimization methods have been adopted to minimize the use of hardware resources. LabVIEW, a graphical programming language, is used for rapid prototyping. The validation of the system was done both in subsystem level as well as the integrated level at real-time mission scenario. Auteurs: Amiya Ranjan Panda;Debahuti Mishra;Hare Krishna Ratha; Apparue dans: IEEE Transactions on Industrial Informatics Date publication: 10.-2017, volume: 13, issue:5, pages: 2360 - 2368 Editeur: IEEE Document complet vers site de l'éditeur
» FPGA-Based Scalable and Power-Efficient Fluid Simulation using Floating-Point DSP Blocks
 Résumé:High-performance and low-power computation is required for large-scale fluid dynamics simulation. Due to the inefficient architecture and structure of CPUs and GPUs, they now have a difficulty in improving power efficiency for the target application. Although FPGAs become promising alternatives for power-efficient and high-performance computation due to their new architecture having floating-point (FP) DSP blocks, their relatively narrow memory bandwidth requires an appropriate way to fully exploit the advantage. This paper presents an architecture and design for scalable fluid simulation based on data-flow computing with a state-of-the-art FPGA. To exploit available hardware resources including FP DSPs, we introduce spatial and temporal parallelism to further scale the performance by adding more stream processing elements (SPEs) in an array. Performance modeling and prototype implementation allow us to explore the design space for both the existing Altera Arria10 and the upcoming Intel Stratix10 FPGAs. We demonstrate that Arria10 10AX115 FPGA achieves 519 GFlops at 9.67 GFlops/W only with a stream bandwidth of 9.0 GB/s, which is 97.9 percent of the peak performance of 18 implemented SPEs. We also estimate that Stratix10 FPGA can scale up to 6844 GFlops by combining spatial and temporal parallelism adequately. Auteurs: Kentaro Sano;Satoru Yamamoto; Apparue dans: IEEE Transactions on Parallel and Distributed Systems Date publication: 10.-2017, volume: 28, issue:10, pages: 2823 - 2837 Editeur: IEEE Document complet vers site de l'éditeur
» Fractional-N DPLL-Based Low-Power Clocking Architecture for 1–14 Gb/s Multi-Standard Transmitter
 Résumé:A low-power clocking solution is presented based on fractional-N highly digital LC-phase-locked loop (PLL) and sub-sampled ring PLL targeting multi-standard SerDes applications. The shared fractional-N digital LC-PLL covers 7–10 GHz frequency range consuming only 8-mW power and occupying 0.15 mm2 of silicon area with integrated jitter of 264 fs. Frequency resolution of the LC-PLL is 2 MHz. Per lane clock is generated using wide bandwidth ring PLL covering 800 MHz to 4 GHz to support the data rates between 1 and 14 Gb/s. The ring PLL supports dither-less fractional resolution of 250 MHz, corrects I/Q error with split tuning, and achieves less than 400-fs integrated jitter. Transmitter works at 14 Gb/s with power efficiency of 0.80 pJ/bit. Auteurs: Masum Hossain;Waleed El-Halwagy;AKM Delwar Hossain; Aurangozeb; Apparue dans: IEEE Journal of Solid-State Circuits Date publication: 10.-2017, volume: 52, issue:10, pages: 2647 - 2662 Editeur: IEEE Document complet vers site de l'éditeur
» Fragmentation-Avoiding Spectrum Assignment Strategy Based on Spectrum Partition for Elastic Optical Networks
 Résumé:A fragmentation-avoiding spectrum assignment strategy based on spectrum partition is proposed, which is used to resolve the spectrum fragmentation problem in elastic optical networks. For alleviating spectrum fragmentation, a spectrum partition policy, splitting the whole optical spectrum into several dedicated partitions, is presented. Based on this, a joint first-last-fit spectrum assignment policy is presented to enhance the probability of successful transmission of request and spectrum efficiency, where each partition is first used to transmit requests with the same rate in the first-fit policy; and other partitions are used to search available spectrum resources in the last-fit policy when there are no available spectrum resources in the dedicated partition. Meanwhile, a partition selection formula is designed to minimize the interference of spectrum resources during the last-fit spectrum assignment. Moreover, a reconfiguration mechanism, moving requests that are not transmitted in their dedicated partition to their dedicated partition, is also studied. The simulation results indicate that the proposed algorithm can reduce the bandwidth blocking probability and improve spectrum efficiency. Auteurs: Huan-Lin Liu;Lei Lv;Yong Chen;Chengying Wei; Apparue dans: IEEE Photonics Journal Date publication: 10.-2017, volume: 9, issue:5, pages: 1 - 13 Editeur: IEEE Document complet vers site de l'éditeur
 Résumé:Presents the introductory editorial for this issue of the publication. Auteurs: Mahta Moghaddam; Apparue dans: IEEE Antennas and Propagation Magazine Date publication: 10.-2017, volume: 59, issue:5, pages: 4 - 4 Editeur: IEEE Document complet vers site de l'éditeur
» Freestanding Micro-Supercapacitor With Interdigital Electrodes for Low-Power Electronic Systems
 Résumé:With the rapid development of miniaturized multi-functional systems, micro-energy-storage devices have drawn increasing attention due to the importance of power supply. In this paper, a novel fabrication for freestanding solid-state micro-supercapacitors (MSCs) has been proposed and developed by combining electrolyte transferring with laser patterning process. Typical freestanding MSC is composed of interdigital carbon nanotube/nanofibers as active material employed by laser patterning process, PVA/H3PO4 as both the solid-state electrolyte and the flexible substrate, and gold layer as the current collector. With the in-planar electrode and electrolyte-substrate layout, the dimension of the MSC could be greatly decreased without excess substrate. Taking advantage of electrospinning nanofibers with large surface area and carbon nanotubes with high conductivity, we optimize the line-width (200 $\mu \text{m}$ ) of the interdigital finger of the MSC, which exhibits high areal capacitance (15.6 mF/cm2) and excellent cycling stability. With the serial design, the working range of MSC units could be greatly enhanced in wearable devices and low-power electronic systems. Therefore, such flexible MSC is a promising candidate to satisfy the requirements of miniaturized energy systems. [2017-0059] Auteurs: Yu Song;Xue-Xian Chen;Jin-Xin Zhang;Xiao-Liang Cheng;Hai-Xia Zhang; Apparue dans: Journal of Microelectromechanical Systems Date publication: 10.-2017, volume: 26, issue:5, pages: 1055 - 1062 Editeur: IEEE Document complet vers site de l'éditeur
» Frequency Doubling of a Pulsed Wavelength-Agile Erbium-Doped Fiber MOPA for Oxygen A-Band Spectroscopy
 Résumé:We report a pulsed wavelength-agile laser near 765 nm, which was frequency doubled from an erbium-doped fiber amplifier for oxygen A-band spectroscopy. A single frequency distributed feedback laser around 1529.6 nm was employed as the seed. After three stages of amplification, its average power was boosted to 610 mW and was then frequency doubled via a 15-mm-long MgO:PPLN crystal with the highest conversion efficiency of 34%. Thanks to the short crystal length expanding the acceptance bandwidth, a power difference of only 36% for the second harmonic output was achieved within the whole wavelength tuning range benefitting low-noise remote sensing. The measured oxygen transmission spectra using a 0.5-meter-long gas cell with multiple passes were mostly in good agreement with the calculations from HITRAN 2012 database indicating the capability of our laser for oxygen A-band related remote sensing. Auteurs: Feng You;Tao Chen;Wei Kong;Hao Liu;Yihua Hu;Rong Shu; 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
» Frequency Shifts of Spectral Lines Generated by Young's Pinhole Wave Scattering Upon a Quasi-Homogeneous Medium
 Résumé:Frequency shifts of light scattered from either a deterministic or random medium have shown great importance in remote sensing imaging applications, however, such scattering system which combines random scatterer with obstacles has not been specifically discussed so far. To solve this problem, we derive analytical expressions for showing the phenomenon that the Young's pinhole wave scattered from a quasi-homogeneous (QH) medium exhibits the red shift of spectral lines, while the first-order Born approximation is applied to treat the weak scattering between the diffractive wave and the medium. The shifted amount of spectrum is strongly dependent of the scattering angle, correlation length of the medium, and Young's pinhole parameter. Furthermore, we also observe that the red shift of the scattered spectrum converts to the blue shift when the correlation length reaches a certain magnitude. Through numerical simulations, analyses are performed on revealing the effects of Young's pinhole parameter and medium's correlation on the spectral shift and spectral switch of the scattered spectrum. Auteurs: Jia Li;Yuechun Shi; Apparue dans: IEEE Photonics Journal Date publication: 10.-2017, volume: 9, issue:5, pages: 1 - 12 Editeur: IEEE Document complet vers site de l'éditeur
» From Cool Chips to Hot Interconnects
 Résumé:This column briefly introduces the articles and departments in the issue. Auteurs: Lieven Eeckhout; Apparue dans: IEEE Micro Date publication: 10.-2017, volume: 37, issue:5, pages: 4 - 5 Editeur: IEEE Document complet vers site de l'éditeur
» From Pthreads to Multicore Hardware Systems in LegUp High-Level Synthesis for FPGAs
 Résumé:In the last decade, processor speeds have remained fairly stagnant, and to improve performance further, the industry started to increase the number of processor cores. The use of specialized hardware, such as field-programmable gate arrays (FPGAs), has also been on the rise. The traditional design methodology for FPGAs, however, requires hardware knowledge, which makes the platform inaccessible to software engineers. High-level synthesis (HLS) tools aim to resolve this issue by allowing software design methodologies to be used for FPGAs. However, HLS remains difficult to use for many software engineers, as there are tasks, such as system integration, which is still mostly a manual process. Consequently, creating a multicore hardware system on an FPGA is not feasible for most software engineers. To this end, we provide an HLS framework, which can automatically generate a multicore hardware system from software. We provide support for POSIX threads, which can be compiled to concurrently executing hardware cores that can be used in a processor–accelerator hybrid system, or in a hardware-only system without a processor. With this, we show that we can create multicore FPGA systems that can provide significant benefits in performance and energy-efficiency compared with hardware executing sequentially, and software executing on MIPS/ARM/x86 processors. Auteurs: Jongsok Choi;Stephen D. Brown;Jason H. Anderson; Apparue dans: IEEE Transactions on Very Large Scale Integration Systems Date publication: 10.-2017, volume: 25, issue:10, pages: 2867 - 2880 Editeur: IEEE Document complet vers site de l'éditeur
» From the editors' desk
 Résumé:Presents the introductory editorial for this issue of the publication. Auteurs: Ed Cherney;Robert Fleming; Apparue dans: IEEE Electrical Insulation Magazine Date publication: 10.-2017, volume: 33, issue:5, pages: 7 - 8 Editeur: IEEE Document complet vers site de l'éditeur
» FTC and Apple Sue Qualcomm for Cell Phone Standardization Skullduggery, Part 3: Determining SEP Reasonable Royalty
 Résumé:This article, the third in a multipart series, describes and comments on the relief that the courts award in cases involving standard-essential patents (SEPs)—the law that courts have established on how to determine a reasonable royalty—in particular, a royalty on reasonable and nondiscriminatory terms (RAND royalty) for a SEP. Auteurs: Richard H. Stern; Apparue dans: IEEE Micro Date publication: 10.-2017, volume: 37, issue:5, pages: 61 - 69 Editeur: IEEE Document complet vers site de l'éditeur
» Fully Convolutional Network With Task Partitioning for Inshore Ship Detection in Optical Remote Sensing Images
 Résumé:Ship detection in optical remote sensing imagery has drawn much attention in recent years, especially with regards to the more challenging inshore ship detection. However, recent work on this subject relies heavily on hand-crafted features that require carefully tuned parameters and on complicated procedures. In this letter, we utilize a fully convolutional network (FCN) to tackle the problem of inshore ship detection and design a ship detection framework that possesses a more simplified procedure and a more robust performance. When tackling the ship detection problem with FCN, there are two major difficulties: 1) the long and thin shape of the ships and their arbitrary direction makes the objects extremely anisotropic and hard to be captured by network features and 2) ships can be closely docked side by side, which makes separating them difficult. Therefore, we implement a task partitioning model in the network, where layers at different depths are assigned different tasks. The deep layer in the network provides detection functionality and the shallow layer supplements with accurate localization. This approach mitigates the tradeoff of FCN between localization accuracy and feature representative ability, which is of importance in the detection of closely docked ships. The experiments demonstrate that this framework, with the advantages of FCN and the task partitioning model, provides robust and reliable inshore ship detection in complex contexts. Auteurs: Haoning Lin;Zhenwei Shi;Zhengxia Zou; Apparue dans: IEEE Geoscience and Remote Sensing Letters Date publication: 10.-2017, volume: 14, issue:10, pages: 1665 - 1669 Editeur: IEEE Document complet vers site de l'éditeur
» Fully Distributed Demand Response Using the Adaptive Diffusion–Stackelberg Algorithm
 Résumé:In this paper, we consider the demand response problem in smart grid consisting of a retailer and multiple residential consumers, where the retailer determines consumers’ payments based on their power consumption profile. Our aim is to propose a fully distributed algorithm that is able to optimize the aggregate cost, utility, and retailer's profit simultaneously. To this end, we first formulate the consumer-side trend as a constrained convex optimization problem and propose a fully distributed adaptive diffusion algorithm to solve it. In addition, we design a one-leader $N$-follower Stackelberg game to model interactions among the retailer and consumers. The proposed framework is able to continuously track the drifts resulting from the changes in the real-time pricing or the consumer preferences. Moreover, it is scalable and does not require network-wide information or rely on central controller. We provide comprehensive simulation results to show the effectiveness of the proposed framework. Auteurs: Milad Latifi;Azam Khalili;Amir Rastegarnia;Saeid Sanei; Apparue dans: IEEE Transactions on Industrial Informatics Date publication: 10.-2017, volume: 13, issue:5, pages: 2291 - 2301 Editeur: IEEE Document complet vers site de l'éditeur
» Fully Programmable Redundancy Circuits for STT-MRAM
 Résumé:We propose fully programmable redundancy schemes for spin-transfer-torque magnetic random access memories (STT-MRAMs). To store redundancy information, these schemes use magnetic tunnel junctions (MTJs), which are core memory elements of STT-MRAMs. This can greatly simplify the fabrication process of STT-MRAMs. Furthermore, it also allows reprogramming of the redundancy information after packaging or even during normal use by end-users without requiring any special high-voltage setup. We propose two redundancy schemes. First, we propose an address comparator, which uses MTJs and is a direct replacement of a conventional address comparator. Second, we propose a scheme in which the redundancy circuits share the storage cells and read–write peripheral circuits with the normal data array structure. Auteurs: Dong-Gi Lee;Sang-Gyu Park; Apparue dans: IEEE Transactions on Magnetics Date publication: 10.-2017, volume: 53, issue:10, pages: 1 - 6 Editeur: IEEE Document complet vers site de l'éditeur
» Fully Reconfigurable Manifold Multiplexer
 Résumé:In this paper, a fully reconfigurable three channel manifold-coupled output multiplexer is presented. The multiplexer is based on frequency and bandwidth reconfigurable four-pole filters with two transmission zeros. The filters employ nonresonating cavities to achieve tunability of couplings. A novel manifold reconfiguration concept has been developed, allowing frequency and bandwidth tuning for filters connected to the manifold. This is achieved by adding tunable reactive elements along the manifold. These reactive elements allow the phase relationships between the channels to be adapted. This concept has been demonstrated on a three-channel multiplexer operating at ka-band frequencies (in satellite communication ka-band denotes the 17.7–21.2-GHz band for downlink). It allows contiguous as well as noncontiguous frequency plans. The multiplexer band could be tuned to a frequency range of 500 MHz (19.9–20.4 GHz), and the bandwidth for the individual filters could be tuned from 36 to 72 MHz. Even swapping the center frequencies of two filters on the manifold is possible. Auteurs: Christian Arnold;Jean Parlebas;Richard Meiser;Thomas Zwick; Apparue dans: IEEE Transactions on Microwave Theory and Techniques Date publication: 10.-2017, volume: 65, issue:10, pages: 3885 - 3891 Editeur: IEEE Document complet vers site de l'éditeur
» Fully Solution Processed Bottom-Gate Organic Field-Effect Transistor With Steep Subthreshold Swing Approaching the Theoretical Limit
 Résumé:This letter realizes both large gate dielectric capacitance and reduced sub-gap density of states at the channel in the same organic field effect transistor (OFET) structure by adopting optimized low-k/high-k bilayer gate dielectric. Subthreshold swing (SS) as small as 64 mV dec $^{-1}$ can be achieved with a thick (>360 nm) gate dielectric layer. This is the smallest SS value reported so far for all reported low voltage OFETs, and is even comparable with that of 22 nm technology node Si-FETs. The device can thus be switched within a very small voltage swing of 0.8 V, while having an ON/OFF ratio larger than 105. The device also shows excellent operational and storage stabilities. Auteurs: Jiaqing Zhao;Wei Tang;Qiaofeng Li;Wenjiang Liu;Xiaojun Guo; Apparue dans: IEEE Electron Device Letters Date publication: 10.-2017, volume: 38, issue:10, pages: 1465 - 1468 Editeur: IEEE Document complet vers site de l'éditeur
» Functional Graphical Models for Manufacturing Process Modeling
 Résumé:Graphical models are widely used to model the statistical relationships among variables in a system. Existing graphical models can be used to model the relationships among scalar variables, but cannot be directly applied to model a system with functional variables. In this paper, a novel functional graphical model is proposed to model complex systems where functional variables are measured. To cope with the small sample size problem, we further develop a special sparsity penalization approach to robustly learn the graphical model from limited sample size, and develop a difference from the mean penalization for functional variables. Simulation studies and a case study in a plasma spray manufacturing process are used to demonstrate the effectiveness of the proposed method.Note to Practitioners—Emerging sensing and information technologies have provided unprecedented functional data collection capacity from systems over time. It is important and challenging to model the relationships among these variables. Among many different modeling alternatives, graphical models are powerful tools to characterize the underlying relationships among variables in systems. However, traditional graphical models cannot directly model a system with a mixture of functional and scalar variables. The proposed model aims to address this challenge by proposing a functional graphical model. Based on simulation studies and a case study for a plasma spray manufacturing process, it is shown that the proposed method performs well under various conditions. Auteurs: Hongyue Sun;Shuai Huang;Ran Jin; Apparue dans: IEEE Transactions on Automation Science and Engineering Date publication: 10.-2017, volume: 14, issue:4, pages: 1612 - 1621 Editeur: IEEE Document complet vers site de l'éditeur
» Fundamental Limits of Non-Coherent Interference Alignment via Matroid Theory
 Résumé:We consider the problem of non-coherent interference alignment, in which the goal is to align the signals of multiple interfering transmitters at a single receiver where the transmitters are not aware of the channel state information. We cast this problem as a problem of determining rank loss conditions for a column concatenation of full-rank matrices, such that each row of the composing matrices is scaled by a random coefficient. We determine necessary and sufficient conditions for the design of each matrix, such that the random ensemble will almost surely lose rank by a certain amount. The result is proved by converting the problem to determining rank loss conditions for the union of some specific matroids, and then using tools from matroid and graph theories to derive the necessary and sufficient conditions. As an application, we discuss how this result can be applied to the problem of topological interference management, and characterize the linear symmetric degrees of freedom for a class of network topologies. Auteurs: Navid Naderializadeh;Aly El Gamal;A. Salman Avestimehr; Apparue dans: IEEE Transactions on Information Theory Date publication: 10.-2017, volume: 63, issue:10, pages: 6573 - 6586 Editeur: IEEE Document complet vers site de l'éditeur
» Further Results on Extended Delivery Time for Secondary Packet Transmission
 Résumé:Cognitive radio transceiver can opportunistically access the underutilized spectrum resource of primary systems for new wireless services. With interweave cognitive implementation, secondary transmission may be interrupted by primary transmission. To facilitate the packet delay analysis of such secondary transmission, we study the extended delivery time of secondary packet transmission. In particular, we derive the exact distribution function of extended delivery time of a fixed-size secondary packet with non-work-preserving strategy, where interrupted packets must be repeated. We also analyze the effect of imperfect periodic sensing, i.e., the secondary user periodically senses the spectrum for availability, with a chance of missing an available channel on a certain sensing attempt. These results complement previous work on work-preserving strategy with perfect sensing. Selected numerical and simulation results are presented for verifying the mathematical formulation. Auteurs: Muneer Usman;Hong-Chuan Yang;Mohamed-Slim Alouini; Apparue dans: IEEE Transactions on Wireless Communications Date publication: 10.-2017, volume: 16, issue:10, pages: 6451 - 6459 Editeur: IEEE Document complet vers site de l'éditeur
» Fusing Complete Monotonic Decision Trees
 Résumé:Monotonic classification is a kind of classification task in which a monotonicity constraint exist between features and class, i.e., if sample $x_i$ has a higher value in each feature than sample $x_j$ , it should be assigned to a class with a higher level than the level of $x_j$ 's class. Several methods have been proposed, but they have some limits such as with limited kind of data or limited classification accuracy. In our former work, the classification accuracy on monotonic classification has been improved by fusing monotonic decision trees, but it always has a complex classification model. This work aims to find a monotonic classifier to process both nominal and numeric data by fusing complete monotonic decision trees. Through finding the completed feature subsets based on discernibility matrix on ordinal dataset, a set of monotonic decision trees can be obtained directly and automatically, on which the rank is still preserved. Fewer decision trees are needed, which will serve as base classifiers to construct a decision forest fused complete monotonic decision trees. The experiment results on 10 datasets demonstrate that the proposed method can reduce the number of base classifiers effectively and then simplify classification model, and obtain good classification performance simultaneously. Auteurs: Hang Xu;Wenjian Wang;Yuhua Qian; Apparue dans: IEEE Transactions on Knowledge and Data Engineering Date publication: 10.-2017, volume: 29, issue:10, pages: 2223 - 2235 Editeur: IEEE Document complet vers site de l'éditeur
» Fusion of Visible Light Indoor Positioning and Inertial Navigation Based on Particle Filter
 Résumé:With the increasing demand for indoor positioning-based services, indoor positioning methods based on Bluetooth, Wi-Fi, ultra wide band (UWB), inertial navigation, and visual light communications (VLC) have been proposed. Considering the limitations of accuracy, cost and complexity, we propose a fusion positioning scheme integrating VLC positioning and inertial navigation base on particle filter. The experimental results demonstrated that the performance degradation caused by the multipath effect and light obstruction in VLC-based positioning and the cumulative error associated with inertial navigation are solved in the proposed fusion system. The accuracy of the fusion positioning system is in centimeters, which is two to four times better as compared to the VLC-based positioning or inertial navigation alone. Furthermore, the fusion positioning system has the advantages of high accuracy, energy saving, low cost, and easy to install, making it a promising candidate for future indoor positioning applications. Auteurs: Zhitian Li;Aiying Yang;Huichao Lv;Lihui Feng;Wenzhan Song; Apparue dans: IEEE Photonics Journal Date publication: 10.-2017, volume: 9, issue:5, pages: 1 - 13 Editeur: IEEE Document complet vers site de l'éditeur
» Future trends in security for Instrumentation and Measurement [Trends in Future I&M]
 Résumé:In the past several issues of I&M Magazine, I have introduced to you people who explained how their lives are influenced by instrumentation and measurement. I am still preparing some articles that are meant to show you how various fields of activity are influenced by this topic. Auteurs: Irina Florea; Apparue dans: IEEE Instrumentation & Measurement Magazine Date publication: 10.-2017, volume: 20, issue:5, pages: 21 - 22 Editeur: IEEE Document complet vers site de l'éditeur
» Fuzzy Color Spaces: A Conceptual Approach to Color Vision
 Résumé:In this paper, we introduce formal definitions of the concepts of fuzzy color and fuzzy color space. First, we formalize the notion of fuzzy color for representing the correspondence between computational representation of colors and perceptual color categories identified by a color name. Second, we propose a methodology for learning fuzzy colors based on the paradigm of conceptual spaces, where prototypes are used for each category to be learnt. Since the conceptual space approach yields crisp categorizations, we introduce a novel methodology for defining fuzzy boundaries of color categories on the basis of a Voronoi tessellation of a color space. Finally, we also formalize the notion of fuzzy color space as the collection of fuzzy colors corresponding to the color categories employed in a certain context/application and/or for a specific user. Different typologies of fuzzy color spaces are proposed in order to be consistent with the nature of the categories we want to model. Our approach is illustrated by defining fuzzy color spaces using RGB with the Euclidean distance. Examples based on the well-known ISCC-NBS color naming system are presented, as well as others based on collections of color names and prototypes provided by users. The proposal is evaluated and compared with the most used approaches for color modeling. Additionally, a website located at http://www.jfcssoftware.com including all experimentation data, software implementing our models, and additional materials is available to researchers in color modeling. Auteurs: Jesus Chamorro-Martínez;Jose Manuel Soto-Hidalgo;Pedro Manuel Martínez-Jiménez;Daniel Sánchez; Apparue dans: IEEE Transactions on Fuzzy Systems Date publication: 10.-2017, volume: 25, issue:5, pages: 1264 - 1280 Editeur: IEEE Document complet vers site de l'éditeur
» Fuzzy Fault Detection Filter Design for T–S Fuzzy Systems in the Finite-Frequency Domain
 Résumé:This paper deals with the fault detection filter design for a nonlinear discrete-time system in the Takagi–Sugeno fuzzy form with faults and unknown inputs. Both unknown input and fault frequencies are assumed to be known and to reside in low-/middle-/high-frequency ranges. A filter is proposed in the finite-frequency domain to reduce the conservatism generated by those designed in the entire-frequency domain. In order to guarantee the best robustness to disturbances and sensitivity to faults, the developed filter combines the $H_{-}$/$H_{\infty }$ performances. The asymptotic stability of the filtering error dynamics is ensured by using a fuzzy Lyapunov function and a linear matrix inequality approach. Finally, two examples are presented to validate the proposed new design techniques. Auteurs: Ali Chibani;Mohammed Chadli;Peng Shi;Naceur Benhadj Braiek; Apparue dans: IEEE Transactions on Fuzzy Systems Date publication: 10.-2017, volume: 25, issue:5, pages: 1051 - 1061 Editeur: IEEE Document complet vers site de l'éditeur
» Fuzzy Wavelet Polynomial Neural Networks: Analysis and Design
 Résumé:In this study, we propose a concept of fuzzy wavelet polynomial neural networks (FWPNNs) based on concepts and constructs of polynomial neural networks and fuzzy wavelet neurons (FWNs). These networks exhibit a rule-based architecture while each rule in the FWN consists of the premise part and consequence part. The premise part is realized by using C-means clustering method, while the consequence part is realized by means of wavelet functions whose parameters are estimated with the aid of the least square method. In some sense, the FWPNN can be regarded as a generalized fuzzy wavelet neural network (FWNN). Unlike Gaussian membership functions that are commonly utilized to implement the premise part of the rules in typical FWNNs, C-means method is employed here to overcome a possible curse of dimensionality. Polynomial neural networks (PNNs) are used to express the nonlinearity of a complex system. Furthermore, the particle swarm optimization is used to optimize the design parameters of the proposed network. Based on the PNNs and FWNNs, the proposed FWPNNs take advantages of these two neural networks: it exhibits the abilities to describe high-order nonlinear relations between input and output variables and it is beneficial to describe models impacted by uncertainty. The proposed FWPNNs are applied for time-series prediction and regression problems (e.g., control of dynamic plants). Several well-known modeling benchmarks including regression and time series are considered to evaluate the performance of the proposed FWPNNs. A comparative analysis shows that the proposed FWPNNs result in better performance when comparing with some previous models reported in the literature. Auteurs: Wei Huang;Sung-Kwun Oh;Witold Pedrycz; Apparue dans: IEEE Transactions on Fuzzy Systems Date publication: 10.-2017, volume: 25, issue:5, pages: 1329 - 1341 Editeur: IEEE Document complet vers site de l'éditeur
» Gait Phase Estimation Based on Noncontact Capacitive Sensing and Adaptive Oscillators
 Résumé:This paper presents a novel strategy aiming to acquire an accurate and walking-speed-adaptive estimation of the gait phase through noncontact capacitive sensing and adaptive oscillators (AOs). The capacitive sensing system is designed with two sensing cuffs that can measure the leg muscle shape changes during walking. The system can be dressed above the clothes and free human skin from contacting to electrodes. In order to track the capacitance signals, the gait phase estimator is designed based on the AO dynamic system due to its ability of synchronizing with quasi-periodic signals. After the implementation of the whole system, we first evaluated the offline estimation performance by experiments with 12 healthy subjects walking on a treadmill with changing speeds. The strategy achieved an accurate and consistent gait phase estimation with only one channel of capacitance signal. The average root-mean-square errors in one stride were 0.19 rad (3.0% of one gait cycle) for constant walking speeds and 0.31 rad (4.9% of one gait cycle) for speed transitions even after the subjects rewore the sensing cuffs. We then validated our strategy in a real-time gait phase estimation task with three subjects walking with changing speeds. Our study indicates that the strategy based on capacitive sensing and AOs is a promising alternative for the control of exoskeleton/orthosis. Auteurs: Enhao Zheng;Silvia Manca;Tingfang Yan;Andrea Parri;Nicola Vitiello;Qining Wang; Apparue dans: IEEE Transactions on Biomedical Engineering Date publication: 10.-2017, volume: 64, issue:10, pages: 2419 - 2430 Editeur: IEEE Document complet vers site de l'éditeur
» Gamesman Problems [Gamesman Problems]
 Résumé:Various puzzles, games, humorous definitions, or mathematical that should engage the interest of readers. Auteurs: Athanasios Kakarountas; Apparue dans: IEEE Potentials Date publication: 10.-2017, volume: 36, issue:5, pages: 48 - 48 Editeur: IEEE Document complet vers site de l'éditeur
» Gamesman Solutions [Gamesman Solutions]
 Résumé:Various puzzles, games, humorous definitions, or mathematical that should engage the interest of readers. Auteurs: Athanasios Kakarountas; Apparue dans: IEEE Potentials Date publication: 10.-2017, volume: 36, issue:5, pages: 5 - 5 Editeur: IEEE Document complet vers site de l'éditeur
» Gamifying Video Object Segmentation
 Résumé:Video object segmentation can be considered as one of the most challenging computer vision problems. Indeed, so far, no existing solution is able to effectively deal with the peculiarities of real-world videos, especially in cases of articulated motion and object occlusions; limitations that appear more evident when we compare the performance of automated methods with the human one. However, manually segmenting objects in videos is largely impractical as it requires a lot of time and concentration. To address this problem, in this paper we propose an interactive video object segmentation method, which exploits, on one hand, the capability of humans to identify correctly objects in visual scenes, and on the other hand, the collective human brainpower to solve challenging and large-scale tasks. In particular, our method relies on a game with a purpose to collect human inputs on object locations, followed by an accurate segmentation phase achieved by optimizing an energy function encoding spatial and temporal constraints between object regions as well as human-provided location priors. Performance analysis carried out on complex video benchmarks, and exploiting data provided by over 60 users, demonstrated that our method shows a better trade-off between annotation times and segmentation accuracy than interactive video annotation and automated video object segmentation approaches. Auteurs: Concetto Spampinato;Simone Palazzo;Daniela Giordano; Apparue dans: IEEE Transactions on Pattern Analysis and Machine Intelligence Date publication: 10.-2017, volume: 39, issue:10, pages: 1942 - 1958 Editeur: IEEE Document complet vers site de l'éditeur
» GaN HEMT DC $I$ – $V$ Device Model for Accurate RF Rectifier Simulation
 Résumé:Recently, various high-efficiency RF rectifiers have been proposed. In this letter, to improve the simulation accuracy of RF active rectifier circuits, a new device model for GaN HEMTs is proposed that improves the reproducibility of $I_{D}$ – $V_{\mathrm{ DS}}$ characteristics in the third-quadrant region (both drain voltage and drain current are negative). Based on measured characteristic data of an actual GaN HEMT, the device parameters for this model have been decided, and the advantage of the new device model has been confirmed. Auteurs: Tsukasa Yasui;Ryo Ishikawa;Kazuhiko Honjo; Apparue dans: IEEE Microwave and Wireless Components Letters Date publication: 10.-2017, volume: 27, issue:10, pages: 930 - 932 Editeur: IEEE Document complet vers site de l'éditeur
» GaN-Based Generic Bifunction LED for Potential Duplex Free-Space VLCs
 Résumé:A generic bifunction GaN light-emitting diode (LED) structure, which has a 300 nm n+ -ZnO epitaxial layer grown on a standard GaN LED epistack and a mesa size of $200\, \mathrm{\mu} {\rm{m\, \times \, 600\, }}\mathrm{\mu} {\rm{m}}$ , exhibits a peak responsivity of 450 mA/W to purple lights (380–400 nm) under zero bias and a narrow bandpass of around 60 nm. The corresponding product of quantum efficiency and gain is estimated as 140%. The purple light (380–400 nm) to blue light (>460 nm) rejection ratio can reach two orders of magnitude. The generic bifunction LED does not sacrifice its optical and modulation performances as a light transmitter. The optical power reaches 100 mW with a peak wavelength around 447 nm. A new proposition for duplex free-space visible light communications is depicted. Auteurs: Lilin Liu;Xiangying Zhang;Zhenkun Sun;Bing Yan;Dongdong Teng;Gang Wang; Apparue dans: IEEE Photonics Journal Date publication: 10.-2017, volume: 9, issue:5, pages: 1 - 11 Editeur: IEEE Document complet vers site de l'éditeur
» Gaussian Fitness Functions for Optimizing Analog CMOS Integrated Circuits
 Résumé:Analog CMOS integrated circuits (ICs) designs depend typically on designer knowledge and experience, as such problems are multivariate and multiobjective, presenting many combinations of input variables to be investigated in order to meet the required specifications. Nowadays, the a posteriori approach is widely used to perform the optimization processes of analog CMOS ICs using evolutionary algorithms. However, these techniques are not totally able to explore potential solutions in specific regions of the Pareto front. Designers then have difficulty in choosing the best solution capable of achieving all desired specifications simultaneously among all the ones found. In this context, the a priori approach using fitness functions has become an important alternative method to overcome these issues of the a posteriori methodology. This paper aims to compare different fitness function profiles used in the a priori optimization processes to boost the effectiveness of the search processes in relation to robustness, accuracy, and yield in analog CMOS ICs designs. We show that the Gaussian profile, proposed here, applied to the lower limit, center value, and upper limit fitness functions is able to improve all the a priori optimization evolutionary techniques investigated, including the genetic, imperialist competitive, and shuffled frog leaping algorithms. Auteurs: Rodrigo Alves de Lima Moreto;Carlos Eduardo Thomaz;Salvador Pinillos Gimenez; Apparue dans: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems Date publication: 10.-2017, volume: 36, issue:10, pages: 1620 - 1632 Editeur: IEEE Document complet vers site de l'éditeur
» General Lyapunov Functions for Consensus of Nonlinear Multiagent Systems
 Résumé:In this brief, we investigate the consensus problem of nonlinear multiagent systems by means of general Lyapunov functions. That is, by constructing general Lyapunov functions, such as polynomial Lyapunov functions beyond quadratic forms, a sufficient condition is established for achieving global consensus. Compared with the existing consensus criteria deduced by quadratic Lyapunov functions, our consensus criterion is less conservative and can be applicable for more systems. In particular, for polynomial systems and even certain classes of nonpolynomial systems, our consensus criterion can be formulated based on polynomial Lyapunov functions, which can be calculated by using the sum-of-squares (SOS) programming tools such as SOSTOOLS. Finally, two simulation examples are given to illustrate the effectiveness of our proposed theoretical results. Auteurs: Quanyi Liang;Zhikun She;Lei Wang;Housheng Su; Apparue dans: IEEE Transactions on Circuits and Systems II: Express Briefs Date publication: 10.-2017, volume: 64, issue:10, pages: 1232 - 1236 Editeur: IEEE Document complet vers site de l'éditeur
» General Power Equation of Switched Reluctance Machines and Power Density Comparison
 Résumé:Switched reluctance machines (SRMs) are becoming increasingly attractive due to their inherent advantages, such as robust and rare-earth-permanent magnet-free topology, as well as excellent fault-tolerance and temperature management. However, the accurate and efficient analyses of SRMs are always challenging since they operate with variable reluctance and pulsating excitation, suffering severe nonlinear characteristics. This paper first introduces a general power equation of SRMs, which can be a powerful tool in the investigation of SRMs. Then, the proposed power equation is validated by finite element (FE) results and experimental results with different excitations. Afterwards, the calculated results with various conditions including different stator inner diameters and different stator outer diameters are compared with the FE-predicted results. Finally, the comparison between SRMs and several conventional machines is carried out to evaluate the power density of SRMs. Auteurs: Wei Hua;Guishu Zhao;Hao Hua;Ming Cheng; Apparue dans: IEEE Transactions on Industry Applications Date publication: 10.-2017, volume: 53, issue:5, pages: 4298 - 4307 Editeur: IEEE Document complet vers site de l'éditeur
» Generalized Analytical Expression for Natural Frequencies of a Single Isolated Air-Core Inhomogeneous Transformer Winding
 Résumé:Given a completely inhomogeneous, fully-coupled, N-section ladder network in which elements of each section are distinct from the others, there exists no closed-form solution which connects the ladder network elements to its natural frequencies. Instead of the present practice of comparing individual natural frequencies, finding such a generalized solution would not only permit quantification of deviations between two frequency responses (FRA) but also provides a generic platform for its interpretation. Presently, interpretation of FRA is mostly empirical and difficult to generalize. Although pioneering contributions by Bewley et al., Abetti and Maginniss, Heller and Veverka, and many others, were made towards developing analytical solutions, they were essentially suitable for a homogeneous winding. For any formulation to become suitable for FRA interpretation (corresponding to a pre and postdamage condition), it must obviously be applicable to an inhomogeneous winding structure. Pursuing this motivation, this paper presents complete details of derivation of analytical expressions that aims to correlate natural frequencies (and their deviations as well) of the ladder network to its basic inductances and capacitances. For this, both short-circuit and open-circuit natural frequencies are examined. Finally, the analytical solution is extended from the discrete-domain to the continuous-domain (transformer winding). Recently, authors have shown practical usefulness of this derived formula for localization and severity assessment of radial/axial displacements in an actual single-isolated continuousdisk transformer winding. Auteurs: Pritam Mukherjee;L. Satish; Apparue dans: IEEE Transactions on Power Delivery Date publication: 10.-2017, volume: 32, issue:5, pages: 2313 - 2319 Editeur: IEEE Document complet vers site de l'éditeur
 Résumé:For optimal detection of ON–OFF keying symbols in free-space optical (FSO) communication, the receiver requires the instantaneous channel fading coefficient. In this letter, to increase the bandwidth efficiency of the FSO channel, we propose a blind data detection method, i.e., without requiring transmission of any training symbols. The proposed blind detection is a two-step method that performs block-by-block detection. Simulation results show that the proposed receiver can achieve a significantly lower bit-error-rate performance compared with the existing blind methods in the context of FSO communications. In addition, the proposed blind method has a simple structure, which makes it particularly suitable for fast FSO communications. Auteurs: Mohammad Taghi Dabiri;Seyed Mohammad Sajad Sadough; Apparue dans: IEEE Communications Letters Date publication: 10.-2017, volume: 21, issue:10, pages: 2170 - 2173 Editeur: IEEE Document complet vers site de l'éditeur
» Generalized Debye Sources-Based EFIE Solver on Subdivision Surfaces
 Résumé:The electric field integral equation is a well-known workhorse for obtaining fields scattered by a perfect electric conducting object. As a result, the nuances and challenges of solving this equation have been examined for a while. Two recent papers motivate the effort presented in this paper. Unlike traditional work that uses equivalent currents defined on surfaces, recent research proposes a technique that results in well-conditioned systems by employing generalized Debye sources (GDS) as unknowns. In a complementary effort, some of us developed a method that exploits the same representation for both the geometry (subdivision surface representations) and functions defined on the geometry, also known as isogeometric analysis (IGA). The challenge in generalizing GDS method to a discretized geometry is the complexity of the intermediate operators. However, thanks to our earlier work on subdivision surfaces, the additional smoothness of geometric representation permits discretizing these intermediate operations. In this paper, we employ both ideas to present a well-conditioned GDS-electric field integral equation. Here, the intermediate surface Laplacian is well discretized by using subdivision basis. Likewise, using subdivision basis to represent the sources results in an efficient and accurate IGA framework. Numerous results are presented to demonstrate the efficacy of the approach. Auteurs: Xin Fu;Jie Li;Li Jun Jiang;Balasubramaniam Shanker; Apparue dans: IEEE Transactions on Antennas and Propagation Date publication: 10.-2017, volume: 65, issue:10, pages: 5376 - 5386 Editeur: IEEE Document complet vers site de l'éditeur
» Generalized Degrees of Freedom of the Symmetric $K$ User Interference Channel Under Finite Precision CSIT
 Résumé:The generalized degrees of freedom (GDoF) characterization of the symmetric $K$ user interference channel is obtained under finite precision channel state information at the transmitters (CSIT). The symmetric setting is where each cross channel is capable of carrying $\alpha$ DoF, while each direct channel is capable of carrying 1 DoF. Remarkably, under finite precision CSIT the symmetric $K$ user interference channel loses all the GDoF benefits of interference alignment. The GDoF per user diminish with the number of users everywhere except in the very strong (optimal for every receiver to decode all messages) and very weak (optimal to treat all interference as noise) interference regimes. The result stands in sharp contrast to prior work on the symmetric setting under perfect CSIT, where the GDoF per user remain undiminished due to interference alignment. The result also stands in contrast to prior work on a subclass of asymmetric settings under finite precision CSIT, i.e., the topological interference management problem, where interference alignment plays a crucial role and provides substantial GDoF benefits. Auteurs: Arash Gholami Davoodi;Syed Ali Jafar; Apparue dans: IEEE Transactions on Information Theory Date publication: 10.-2017, volume: 63, issue:10, pages: 6561 - 6572 Editeur: IEEE Document complet vers site de l'éditeur
» Generalized Determination of Device Noise Parameters
 Résumé:This paper presents a rigorous analysis to determine the noise parameters of linear noisy microwave networks with any number of ports. The analysis expands a well-established approach for the determination of the noise parameters of a linear two-port network to any linear $N$ -port networks and enhances the understanding of its measurement procedure as a particular case of this analysis. A thorough discussion of the results of this analysis identifies constraints and highlights practical requirements for a successful noise characterization setup of any $N$ -port networks. The analysis is then applied to the measurement of four-port networks. The determination of passive network’s noise parameters allows the experimental validation of the theory, while the determination of an active four-port network’s noise parameters is of particular interest, because its differential noise figure can be determined directly from its noise parameters without the use of external baluns. Auteurs: Luciano Boglione; Apparue dans: IEEE Transactions on Microwave Theory and Techniques Date publication: 10.-2017, volume: 65, issue:10, pages: 4014 - 4025 Editeur: IEEE Document complet vers site de l'éditeur
» Generalized Dual-Band Unequal Filtering Power Divider With Independently Controllable Bandwidth
 Résumé:In this paper, a novel design method of generalized dual-band unequal filtering power divider (DUFPD) is proposed. Using this method, the power divider (PD) could be designed to realize the dual-band filtering response with arbitrary power division, arbitrary frequency ratio, arbitrary real terminated impedances, independently controllable bandwidth, and excellent isolation. To satisfy these characteristics, a proper dual-band filtering structure is selected to replace the conventional quarter-wave length transmission line in the PD. In addition, a single resistor structure is utilized to obtain effective isolation between the output ports. Furthermore, the complete design procedures and analytical equations of the proposed generalized DUFPD are presented based on the circuit and transmission line theories. To demonstrate the validity of the proposed design method, a DUFPD with different real terminated impedances is designed, fabricated, and measured. We show that there is a good agreement between the simulated and measured results. Auteurs: Yongle Wu;Zheng Zhuang;Guangyou Yan;Yuanan Liu;Zabih Ghassemlooy; Apparue dans: IEEE Transactions on Microwave Theory and Techniques Date publication: 10.-2017, volume: 65, issue:10, pages: 3838 - 3848 Editeur: IEEE Document complet vers site de l'éditeur
» Generalized Orthopair Fuzzy Sets
 Résumé:We note that orthopair fuzzy subsets are such that that their membership grades are pairs of values, from the unit interval, one indicating the degree of support for membership in the fuzzy set and the other support against membership. We discuss two examples, Atanassov's classic intuitionistic sets and a second kind of intuitionistic set called Pythagorean. We note that for classic intuitionistic sets the sum of the support for and against is bounded by one, while for the second kind, Pythagorean, the sum of the squares of the support for and against is bounded by one. Here we introduce a general class of these sets called q-rung orthopair fuzzy sets in which the sum of the ${\rm{q}}$th power of the support for and the ${\rm{q}}$th power of the support against is bonded by one. We note that as q increases the space of acceptable orthopairs increases and thus gives the user more freedom in expressing their belief about membership grade. We investigate various set operations as well as aggregation operations involving these types of sets. Auteurs: Ronald R. Yager; Apparue dans: IEEE Transactions on Fuzzy Systems Date publication: 10.-2017, volume: 25, issue:5, pages: 1222 - 1230 Editeur: IEEE Document complet vers site de l'éditeur
» Generalized Plateaued Functions and Admissible (Plateaued) Functions
 Résumé:Plateaued functions are very important crypto- graphic functions due to their various desirable cryptographic characteristics. We point out that plateaued functions are more general than bent functions (that is, functions with maximum nonlinearity). Some Boolean plateaued functions have large nonlinearity, which provides protection against fast correlation attacks when they are used as combiners or filters in stream ciphers, and contributes, when they are the component functions of the substitution boxes in block ciphers, to protection against linear cryptanalysis. P-ary plateaued functions have attracted recently some attention in the literature, and many activities on generalized $p$ -ary functions have been carried out. This paper increases our knowledge on plateaued functions in the general context of generalized $p$ -ary functions. We first introduce two new versions of plateaued functions, which we shall call generalized plateaued functions and admissible plateaued functions. The generalized plateaued functions extend the standard notion of plateaued $p$ -ary functions to those whose outputs are in the ring $\mathbb {Z}_{p^{k}}$ . Next, we study the generalized plateaued functions and use admissible plateaued functions to characterize the generalized plateaued functions by means of their components. Finally, we provide for the first time two constructions of generalized plateaued functions. In particular, we generalize a known secondary construction of binary generalized bent functions and derive constructions of binary generalized plateaued functions with different amplitudes. Auteurs: Sihem Mesnager;Chunming Tang;Yanfeng Qi; Apparue dans: IEEE Transactions on Information Theory Date publication: 10.-2017, volume: 63, issue:10, pages: 6139 - 6148 Editeur: IEEE Document complet vers site de l'éditeur
» Generation of Colored Noise Patterns With Gaussian Jitter Distribution
 Résumé:Bit rates of high-speed serial links (USB, SATA, PCI-express, etc.) have reached the multigigabits per second, and continue to increase. The transmitted jitter at a given bit error rate is one of the key parameters used to describe the performances of a serializer/deserializer. Generating white- and colored-noise synthetic jitter patterns would allow to better analyze the effect of jitter in a system for design verification and to achieve the desired figure of merit. To our knowledge, there is no other method proposed in the literature to generate colored-noise patterns with the Gaussian distribution. This paper then presents for the first time a novel method for generating the Gaussian distribution synthetic jitter patterns from colored-noise profiles. Auteurs: Klodjan Bidaj;Jean-Baptiste Begueret;Jerome Deroo; Apparue dans: IEEE Transactions on Instrumentation and Measurement Date publication: 10.-2017, volume: 66, issue:10, pages: 2576 - 2584 Editeur: IEEE Document complet vers site de l'éditeur
» Generation of Orthogonally Polarized Mode-Locked Lasers at Wavelength of 1342 nm
 Résumé:A mode-locked laser with orthogonal polarization at the wavelength of 1342 nm is experimentally achieved by using the natural birefringence of the Nd:YVO4 crystal. A total output power of 2.64 W could be obtained at an incident power of 14.4 W and the pulse durations are measured to be 15.1 and 16.9 ps with pulse repetition rates of 6.0 and 6.45 GHz for the laser output along the π- and σ-polarization, respectively. The mode-locked output is further found to exhibit a complex temporal trace with beat frequencies originated from the different central frequencies and pulse repetition rates. Auteurs: Hsing-Chih Liang;Feng-Lan Chang;Tai-Wei Wu;Cheng-Lin Sung;Yung-Fu Chen; 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
» Generic Construction of Bent Functions and Bent Idempotents With Any Possible Algebraic Degrees
 Résumé:As a class of optimal combinatorial objects, bent functions have important applications in cryptography, sequence design, and coding theory. Bent idempotents are a subclass of bent functions and of great interest, since they can be stored in less space and allow faster computation of the Walsh-Hadamard transform. The objective of this paper is to present a generic construction of bent functions from known ones. It includes the previous constructions of bent functions by Mesnager and Xu et al. as special cases, and produces new bent functions, which cannot be produced by earlier ones. In particular, it also generates infinite families of bent idempotents over ${F}_{2^{2m}}$ of any algebraic degree between 2 and $m$ . This together with a recent construction by Su and Tang gives a positive answer to an open problem on bent idempotents proposed by Carlet. In addition, an infinite family of anti-self-dual bent functions is obtained in which the sum of any three distinct functions is again an anti-self-dual bent function in this family. This solves an open problem recently proposed by Mesnager. Auteurs: Chunming Tang;Zhengchun Zhou;Yanfeng Qi;Xiaosong Zhang;Cuiling Fan;Tor Helleseth; Apparue dans: IEEE Transactions on Information Theory Date publication: 10.-2017, volume: 63, issue:10, pages: 6149 - 6157 Editeur: IEEE Document complet vers site de l'éditeur
» Genetic Algorithm-Based Current Optimization for Torque Ripple Reduction of Interior PMSMs
 Résumé:This paper investigates the torque ripple modeling and minimization for interior permanent magnet synchronous machines (PMSMs). At first, a novel torque ripple model is proposed in which the torque ripples resulted from the spatial harmonics of permanent magnet flux linkage, time harmonics of stator currents and the cogging torque are included. Based on the torque ripple model, a genetic algorithm (GA)-based harmonic current optimization approach is proposed for torque ripple minimization. In this approach, GA is applied to optimize both the magnitude and phase angle of the stator harmonic currents to minimize the peak-to-peak torque ripple, minimize the sum of squares of the harmonic currents, and maximize the average torque component produced by the injected harmonic currents. The results demonstrate that the magnitude of the harmonic current can be significantly reduced by optimizing the phase angles of these harmonic currents. This leads to further suppression of the torque ripple when compared with that of a case where phase angles are not considered in the optimization. Also, an increase of the average torque is achieved when the optimum harmonic currents are injected. The proposed model and approach are evaluated through both numerical and experimental investigations on a laboratory interior PMSM. Auteurs: Chunyan Lai;Guodong Feng;K. Lakshmi Varaha Iyer;Kaushik Mukherjee;Narayan C. Kar; Apparue dans: IEEE Transactions on Industry Applications Date publication: 10.-2017, volume: 53, issue:5, pages: 4493 - 4503 Editeur: IEEE Document complet vers site de l'éditeur
» Geodetic Imaging of Time-Dependent Three-Component Surface Deformation: Application to Tidal-Timescale Ice Flow of Rutford Ice Stream, West Antarctica
 Résumé:We present a method for inferring time-dependent three-component surface deformation fields given a set of geodetic images of displacements collected from multiple viewing geometries. Displacements are parameterized in time with a dictionary of displacement functions. The algorithm extends an earlier single-component (i.e., single line of sight) framework for time-series analysis to three spatial dimensions using combinations of multitemporal, multigeometry interferometic synthetic aperture radar (InSAR) and/or pixel offset (PO) maps. We demonstrate this method with a set of 101 pairs of azimuth and range PO maps generated for a portion of the Rutford Ice Stream, West Antarctica, derived from data collected by the COSMO-SkyMed satellite constellation. We compare our results with previously published InSAR mean velocity fields and selected GPS time series and show that our resulting three-component surface displacements resolve both secular motion and tidal variability. Auteurs: Pietro Milillo;Brent Minchew;Mark Simons;Piyush Agram;Bryan Riel; Apparue dans: IEEE Transactions on Geoscience and Remote Sensing Date publication: 10.-2017, volume: 55, issue:10, pages: 5515 - 5524 Editeur: IEEE Document complet vers site de l'éditeur
» Geometry Analysis and Optimization of PM-Assisted Reluctance Motors
 Résumé:This paper deals with a detailed geometry analysis of the rotor structure for both synchronous reluctance and permanent magnet (PM)-assisted reluctance motor in order to suggest an automatic procedure to design the rotor structure. The shape of flux barriers is selected to achieve both high $d$ -axis inductance and low $q$ -axis inductance to obtain high output torque and high power factor. Methods to properly design the geometry of the ends of each barrier and PMs are adopted. In order to draw a rotor with proper shape, different modifications are discussed. All details are described to allow any reader to adopt the same procedures. After that, such a procedure is used to rapidly analyze the impact of some geometry changes on the machine performance to give a design guideline. The analyzing process starts from a reluctance motor considering the number of barriers, insulation ratio, split ratio, and slots per pole per phase. Then, the PMs are inset into flux barriers and the effect of PM width on torque, power factor, and flux weakening capability is investigated. At last, the demagnetization limit under overload operations is analyzed. Auteurs: Yawei Wang;Giacomo Bacco;Nicola Bianchi; Apparue dans: IEEE Transactions on Industry Applications Date publication: 10.-2017, volume: 53, issue:5, pages: 4338 - 4347 Editeur: IEEE Document complet vers site de l'éditeur
» Geometry of Line Start Synchronous Motors Suitable for Various Pole Combinations
 Résumé:Line start synchronous motors (LSSM) have been recently introduced in the motor market to meet new efficiency class requirements. They exhibit high efficiency and power factor compared with induction motors. On the other hand, the difficult design, manufacture, and high cost due to the presence of permanent magnets limit their widespread use in the market. Another key factor that limits the LSSM diffusion is the need of having a wide variety of different laminations of different sizes, increasing the number of pieces to be stored, the number of mold geometries, etc. This paper investigates the opportunity to use a proper geometry of LSSM that allows the same stator and rotor laminations to be used for a different number of poles. From the manufacturing point of view, the adoption of a unique rotor lamination is extremely advantageous. It is shown that satisfactory performance can be achieved rearranging the stator winding according to the number of poles. Experimental measurements are carried out on an LSSM prototype in which the same lamination is used for 2-pole and 4-pole machines. Auteurs: Damiano Mingardi;Nicola Bianchi;Michele Dai Prè; Apparue dans: IEEE Transactions on Industry Applications Date publication: 10.-2017, volume: 53, issue:5, pages: 4360 - 4367 Editeur: IEEE Document complet vers site de l'éditeur
» Geotagging Text Content With Language Models and Feature Mining
 Résumé:The large-scale availability of user-generated content in social media platforms has recently opened up new possibilities for studying and understanding the geospatial aspects of real-world phenomena and events. Yet, the large majority of user-generated content lacks proper geographic information (in the form of latitude and longitude coordinates). As a result, the problem of multimedia geotagging, i.e., extracting location information from user-generated text items when this is not explicitly available, has attracted increasing research interest. Here, we present a highly accurate geotagging approach for estimating the locations alluded by text annotations based on refined language models that are learned from massive corpora of social media annotations. We further explore the impact of different feature selection and weighting techniques on the performance of the approach. In terms of evaluation, we employ a large benchmark collection from the MediaEval Placing Task over several years. We demonstrate the consistently superior geotagging accuracy and low median distance error of the proposed approach using various data sets and comparing it against a number of state-of-the-art systems. Auteurs: Giorgos Kordopatis-Zilos;Symeon Papadopoulos;Ioannis Kompatsiaris; Apparue dans: Proceedings of the IEEE Date publication: 10.-2017, volume: 105, issue:10, pages: 1971 - 1986 Editeur: IEEE Document complet vers site de l'éditeur
» GeSn Nanobeam Light-Emitting Diode as a GHz-Modulated Light Source
 Résumé:Designs and theoretical analysis are presented for a room temperature resonant-cavity-enhanced GeSn LED whose emission peaks at the 2 $\mu$m wavelength. The Ge/GeSn/Ge PIN hetero-diode of length 1 $\mu$m is embedded in a rib-type Ge-on-Si nanobeam having either 24 or 36 air holes. The maximum LED modulation bandwidth $f_{3\text{dB}}$ is proportional to the Purcell factor and is inversely proportional to $\tau _{s\,p0}$ the GeSn bulk spontaneous emission lifetime. For an emission linewidth of 200 nm and $\tau _{s\,p0}$ of 10 ns, an $f_{3\text{dB}}$ of 1.6 GHz is predicted. Auteurs: Ricky Gibson;Joshua Hendrickson;Richard A. Soref; Apparue dans: IEEE Photonics Journal Date publication: 10.-2017, volume: 9, issue:5, pages: 1 - 11 Editeur: IEEE Document complet vers site de l'éditeur
» Global Time-Delay Estimation in Ultrasound Elastography
 Résumé:A critical step in quasi-static ultrasound elastography is the estimation of time delay between two frames of radio-frequency (RF) data that are obtained while the tissue is undergoing deformation. This paper presents a novel technique for time-delay estimation (TDE) of all samples of RF data simultaneously, thereby exploiting all the information in RF data for TDE. A nonlinear cost function that incorporates similarity of RF data intensity and prior information of displacement continuity is formulated. Optimization of this function involves searching for TDE of all samples of the RF data, rendering the optimization intractable with conventional techniques given that the number of variables can be approximately one million. Therefore, the optimization problem is converted to a sparse linear system of equations, and is solved in real time using a computationally efficient optimization technique. We call our method GLobal Ultrasound Elastography (GLUE), and compare it to dynamic programming analytic minimization (DPAM) and normalized cross correlation (NCC) techniques. Our simulation results show that the contrast-to-noise ratio (CNR) values of the axial strain maps are 4.94 for NCC, 14.62 for DPAM, and 26.31 for GLUE. Our results on experimental data from tissue mimicking phantoms show that the CNR values of the axial strain maps are 1.07 for NCC, 16.01 for DPAM, and 18.21 for GLUE. Finally, our results on in vivo data show that the CNR values of the axial strain maps are 3.56 for DPAM and 13.20 for GLUE. Auteurs: Hoda Sadat Hashemi;Hassan Rivaz; Apparue dans: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control Date publication: 10.-2017, volume: 64, issue:10, pages: 1625 - 1636 Editeur: IEEE Document complet vers site de l'éditeur
» Govern by blockchain dubai wants one platform to rule them all, while Illinois will try anything
 Résumé:Governments everywhere would like to cut red tape, reduce bureaucracy, and speed the delivery of services. But constituents are still often frustrated by mounds of paperwork and the snail-like pace of official business. Could a blockchain help? Just as blockchains have shaken up the financial industry and changed our perception of money, some government agencies now believe the technology could rejuvenate the public sector. Proponents argue that its immutability will protect records from fraudsters, its transparency will keep employees accountable, and its ability to automatically process new entries can make agencies more efficient. Such promises have persuaded city, state, and federal governments to launch the first batch of public-sector blockchain experiments. Two of the most enthusiastic early adopters have been the U.S. state of Illinois and the city of Dubai in the United Arab Emirates. And intriguingly enough, the two have adopted very different strategies for mixing blockchains into government. Auteurs: Amy Nordrum; Apparue dans: IEEE Spectrum Date publication: 10.-2017, volume: 54, issue:10, pages: 54 - 55 Editeur: IEEE Document complet vers site de l'éditeur
» Granular Encoders and Decoders: A Study in Processing Information Granules
 Résumé:Information granules are generic building blocks supporting the processing realized in granular computing and facilitating communication with the environment. In this paper, we are concerned with a fundamental problem of encoding–decoding of information granules. The essence of the problem is outlined as follows: given a finite collection of granular data X1, X2,…,XN (sets, fuzzy sets, etc.), construct an optimal codebook composed of information granules A 1, A2, …, Ac, where typically c << N, so that any Xk represented in terms of A i's and then decoded (reconstructed) with the help of this codebook leads to the lowest decoding error. A fundamental result is established, which states that in the proposed encoders and decoders, when encoding–decoding error is present, the information granule coming as a result of decoding is of a higher type than the original information granules (say, if Xk is information granule of type-1, then its decoded version becomes information granule of type-2). It would be beneficial to note that as the encoding–decoding process is not lossless (in general, with an exception of a few special cases), the lossy nature of the method is emphasized by the emergence of information granules of higher type (in comparison with the original data being processed). For instance, when realizing encoding–decoding of numeric data (viz., information granules of type-0), the losses occur and they are quantified in terms of intervals, fuzzy sets, probabilities, rough sets, etc., where, in fact, the result becomes- an information granule of type-1. In light of the nature of the constructed result when Xk is an interval or a fuzzy set, an optimized performance index engages a distance between the bounds of the interval-valued membership function. We develop decoding and encoding mechanisms by engaging the theory of possibility and fuzzy relational calculus and show that the decoded information granule is either a granular interval or interval-valued fuzzy set. The optimization mechanism is realized with the aid of the particle swarm optimization (PSO). A series of experiments are reported with intent to illustrate the details of the encoding–decoding mechanisms and show that the PSO algorithm can efficiently optimize the granular codebook. Auteurs: Xiubin Zhu;Witold Pedrycz;Zhiwu Li; Apparue dans: IEEE Transactions on Fuzzy Systems Date publication: 10.-2017, volume: 25, issue:5, pages: 1115 - 1126 Editeur: IEEE Document complet vers site de l'éditeur
» Granular Fuzzy Rule-Based Models: A Study in a Comprehensive Evaluation and Construction of Fuzzy Models
 Résumé:Fuzzy models are regarded as numeric constructs and as such are optimized and evaluated at the numeric level. In this study, we depart from this commonly accepted position and propose a granular evaluation of fuzzy models and present an augmentation of fuzzy models by forming information granules around numeric values of the parameters and constructions of the models. The concepts and algorithms of granular fuzzy models are discussed in the setting of Takagi–Sugeno rule-based architectures. We show how different protocols of forming and allocating information granules lead to the improvement of the granular performance of the models. Different from the standard numeric performance measure of fuzzy models coming in the form of the root mean squared error index, two performance measures are introduced that are pertinent to granular constructs, namely coverage and specificity. Furthermore, we propose a global indicator implied by these two measures, called an area under the curve, being computed for the characteristics of the granular model expressed in the coverage-specificity coordinates. A series of experimental studies is reported, which offers a comprehensive overview of the introduced performance measure criteria as well as the underlying realization of the granular fuzzy models. Auteurs: Xingchen Hu;Witold Pedrycz;Xianmin Wang; Apparue dans: IEEE Transactions on Fuzzy Systems Date publication: 10.-2017, volume: 25, issue:5, pages: 1342 - 1355 Editeur: IEEE Document complet vers site de l'éditeur
» Graph Regularized and Locality-Constrained Coding for Robust Visual Tracking
 Résumé:Visual tracking is complicated due to factors, such as occlusion, background clutter, abrupt target motion, and illumination variations, among others. In recent years, subspace representation and sparse coding techniques have demonstrated significant improvements in tracking. However, performance gain in tracking has been at the expense of losing locality and similarity attributes among the instances to be encoded. In this paper, a graph regularized and locality-constrained coding (GRLC) technique that encapsulates local manifold structure of the data in order to preserve locality and similarity information among instances is proposed. The GRLC methodology incorporates a similarity-preserving term within the objective function of the locality-constrained linear coding model, thereby overcoming some of the inherent instability issues common to such coding methods. In the proposed GRLC scheme, a graph Laplacian regularizer is chosen as a smoothing operator to learn both the representation dictionary and the coefficients by preserving the local structure of the data. This graph Laplacian smoothing operator ensures that the representations vary smoothly along the geodesics of the data manifold. Thus, by deriving the objective function of the GRLC method, a discriminative dictionary of instances can be iteratively obtained and the corresponding coefficients for each candidate can be computed using this learned dictionary. Finally, an effective observation likelihood function based on reconstruction error and a simple dictionary update scheme for visual target tracking are also proposed. Experimental results on the CVPR2013 visual tracker benchmark have demonstrated a favorable performance of the proposed technique both in terms of accuracy and robustness. Auteurs: Tao Zhou;Harish Bhaskar;Fanghui Liu;Jie Yang; Apparue dans: IEEE Transactions on Circuits and Systems for Video Technology Date publication: 10.-2017, volume: 27, issue:10, pages: 2153 - 2164 Editeur: IEEE Document complet vers site de l'éditeur
» Graphene Electrodes as Barrier-Free Contacts for Carbon Nanotube Field-Effect Transistors
 Résumé:This work evaluates the performance of carbon nanotube field-effect transistors (CNTFETs) using few layer graphene as the contact electrode material. We present the experimental results of the barrier height at carbon nanotube–graphene junction using temperature dependent ${I}$ – ${V}$ measurements. The estimated barrier height in our devices for both holes and electrons is close to zero indicating the ohmic contact of graphene for both p-type and n-type CNTFETs thus demonstrating the suitability of graphene as electrode material for CMOS-type circuits based on CNTFETs. Furthermore, we observe that there is no correlation between the barrier height and thickness of graphene. Auteurs: P. R. Yasasvi Gangavarapu;Punith C. Lokesh;K. N. Bhat;A. K. Naik; Apparue dans: IEEE Transactions on Electron Devices Date publication: 10.-2017, volume: 64, issue:10, pages: 4335 - 4339 Editeur: IEEE Document complet vers site de l'éditeur
» Graphene Oxide Doped SU-8 Waveguide and Its Application as Saturable Absorber
 Résumé:Graphene oxide (GO)-doped SU-8 waveguides have been fabricated and characterized. The GO-doped SU-8 can be processed using standard photolithography parameters. The optical characteristics of the developed waveguides are determined using fibre-butt coupling and cut-back method. Propagation loss of 1.9 dB/cm and a coupling loss of 4 dB per point measured at 1550 nm wavelength are obtained. Q-switched laser operation is achieved by inserting a 3 mm GO-doped SU-8 waveguide into a ring fibre laser configuration, making it a potential candidate as integrated saturable absorber for on-chip polymer waveguide applications. Auteurs: Khairul Zafri Mustafa;Wu Yi Chong;Mohd Haniff Ibrahim;Yuen Kiat Yap;Fauzan Ahmad;Choon Kong Lai;Nur Afiqah Mohd Ariffin;Harith Ahmad; 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
» Graphene Surface Plasmons With Dielectric Metasurfaces
 Résumé:An approach to capture light efficiently into graphene surface plasmons by patterning the sinusoidal dielectric metasurfaces above and below the graphene sheet is proposed. The presence of plasmonic resonance is demonstrated by means of an analytical model based on the transformation optics through the extraction of effective graphene conductivity, which is further revealed via a numerical study of the optical spectra as a function of grating parameters at the subwavelength scale. Besides, the resonant position is found to be sensitive to the dielectric contacted with graphene. These findings can deepen our understanding of plasmon resonances and pave the way to the design of graphene plasmonic devices like refractive index sensors. Auteurs: Sheng-Xuan Xia;Xiang Zhai;Yu Huang;Jian-Qiang Liu;Ling-Ling Wang;Shuang-Chun Wen; Apparue dans: Journal of Lightwave Technology Date publication: 10.-2017, volume: 35, issue:20, pages: 4553 - 4558 Editeur: IEEE Document complet vers site de l'éditeur
» Gray Box Modeling of Power Transformer Windings for Transient Studies
 Résumé:For the fast transient study of power transformers, several types of models are available that can be categorized into three groups: white box models, black box models, and gray box models. The identification of their parameters and their usages make the models different. Since white and black box models cannot cover certain cases, such as the failure analysis of a transformer with unknown geometrical data, a new type of model has recently become important for industry and academic researchers. This model, called the gray box model, is intensely analyzed in the current paper, both theoretically and experimentally. The gray box model conceptually lies between the black and white box models. The outcomes of this work have been verified using a suitable test object. The parameter identification of the model is performed by artificial methods. Some useful new ideas, including applying the Weibull Distribution function in inductance estimation and employing an exponential function for the series resistance of windings, are developed in this paper. The number of unknown parameters to be identified in the gray box model is reduced by applying these ideas, which makes the model more simple and feasible. Auteurs: Reza Aghmasheh;Vahid Rashtchi;Ebrahim Rahimpour; Apparue dans: IEEE Transactions on Power Delivery Date publication: 10.-2017, volume: 32, issue:5, pages: 2350 - 2359 Editeur: IEEE Document complet vers site de l'éditeur
» Grid Interfaced Distributed Generation System With Modified Current Control Loop Using Adaptive Synchronization Technique
 Résumé:This paper presents real-time implementation of a grid interfaced distributed generation (DG) system with modified current control loop using three phase amplitude adaptive notch filter (AANF) based synchronization tool. A grid current feedback based modified $dq$-current control technique for interfacing inverter is developed in order to achieve constant loading on the grid, transient-free operation, and power factor improvement close to unity power factor (UPF) of the utility grid during sudden load variations. This technique does not require separate calculation of reference reactive component and harmonics component of currents hence reduces control circuit complexity. In addition, it requires only three voltage and three current sensors. Three phase AANF is developed and is used for online extraction of utility voltage phase angle to generate synchronized reference current signals for interfacing inverter. AANF is used because of its adjustable accuracy and amplitude adaptability even under unbalanced voltage sag and swell, frequency variation, and distorted grid conditions. Fast and accurate behavior of three phase AANF improves the dynamic response of entire DG system control performance for sudden load variations. The dynamic behavior of the proposed grid interfaced DG system is experimentally evaluated in maintaining constant loading on grid, transient-free operation, and power factor improvement close to UPF operation of the utility grid, by compensating total reactive power and harmonic current demanded by variable linear as well as nonlinear load. Auteurs: Amardeep B. Shitole;Hiralal M. Suryawanshi;Girish G. Talapur;Shelas Sathyan;Makarand S. Ballal;Vijay B. Borghate;Manoj R. Ramteke;Madhuri A. Chaudhari; Apparue dans: IEEE Transactions on Industrial Informatics Date publication: 10.-2017, volume: 13, issue:5, pages: 2634 - 2644 Editeur: IEEE Document complet vers site de l'éditeur

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