Electrical and Electronics Engineering publications abstract of: 01-2018 sorted by title, page: 11

» Optimal Operation Control for Multiple BESSs of a Large-Scale Customer Under Time-Based Pricing
Abstract:
This paper presents an online optimal operation framework for multiple battery energy storage systems (BESSs) of a large-scale customer under time-based pricing. Many publications have been reported on optimal battery operation techniques but most of them were analyzed in a simulation environment or a specifically designed test bed. However, this paper focuses on implementing the proposed scheme into actual multiple battery storage units and investigating the performance during long-term field operation. The operation framework consists of two levels: optimal scheduling and real-time dispatch. The optimal scheduling is calculated every hour, using a model predictive control based nonlinear optimization model, to minimize the daily electricity usage cost while regulating the peak. The real-time dispatch determines final commands to multiple battery systems by monitoring the system state and checking for any violations of the operation constraints. The two-level control scheme was designed to handle uncertainty in forecast load and estimated state-of-charge levels of batteries. The operation method was applied into the energy management system supervising one lithium-polymer BESS and two lead-acid BESSs of an industrial site. Comprehensive field operation results prove the reliability and effectiveness of the optimal operation framework.
Autors: Seul-Ki Kim;Jong-Yul Kim;Kyeong-Hee Cho;Gilsung Byeon;
Appeared in: IEEE Transactions on Power Systems
Publication date: Jan 2018, volume: 33, issue:1, pages: 803 - 816
Publisher: IEEE
 
» Optimal Power Control for Transmitting Correlated Sources With Energy Harvesting Constraints
Abstract:
We investigate the weighted-sum distortion minimization problem in transmitting two correlated Gaussian sources over Gaussian channels using two energy harvesting nodes. To this end, we develop off-line and online power control policies to optimize the transmit power of the two nodes. In the off-line case, we cast the problem as a convex optimization and investigate the structure of the optimal solution. We also develop a generalized waterfilling-based power allocation algorithm to obtain the optimal solution efficiently. For the online case, we quantify the distortion of the system using a cost function and show that the expected cost equals the expected weighted-sum distortion. Based on Banach’s fixed point theorem, we further propose a geometrically converging algorithm to find the minimum cost via simple iterations. Simulation results show that our online power control outperforms the greedy power control where each node uses all the available energy in each slot and also performs close to that of the proposed off-line power control. Moreover, the performance of our off-line power control almost coincides with the performance limit of the system.
Autors: Yunquan Dong;Zhi Chen;Jian Wang;Byonghyo Shim;
Appeared in: IEEE Transactions on Wireless Communications
Publication date: Jan 2018, volume: 17, issue:1, pages: 461 - 476
Publisher: IEEE
 
» Optimal Reactive Power Flow of Interconnected Power System Based on Static Equivalent Method Using Border PMU Measurements
Abstract:
A new static equivalent method using border PMU measurements is proposed to effectively retain various voltage and reactive power support characteristics of external network without real-time synchronous information of the entire external system. Based on the proposed method, a set of equivalent criteria is developed to determine whether the simplest and the most widely used PV/PQ equivalence is still appropriate. Based on the proposed equivalent method and criteria, we establish a new equivalent optimal reactive power flow model, which can achieve high calculation accuracy for interconnected power systems. The simulation results of the IEEE 39-bus system and an actual 661-bus system demonstrate the accuracy and effectiveness of the proposed method, criteria, and model.
Autors: Juan Yu;Wei Dai;Wenyuan Li;Xuan Liu;Juelin Liu;
Appeared in: IEEE Transactions on Power Systems
Publication date: Jan 2018, volume: 33, issue:1, pages: 421 - 429
Publisher: IEEE
 
» Optimal Reception Delay in Diffusion-Based Molecular Communication
Abstract:
This letter proposes a simple and novel method for mitigating inter-symbol interference (ISI) in molecular communication via diffusion (MCvD). In MCvD applications, the messenger molecules released from the transmitter need some time to reach the receiver. Therefore, the molecules absorbed at the beginning of a transmission interval can only belong to the previous transmissions. Therefore, if a receiver shifts its absorption interval, ISI can be potentially reduced. We find the optimal delay time that the receiver shifts its absorption interval both numerically and analytically to minimize the ISI in the channel. We demonstrate the improved performance of the proposed shift- method in molecular communication over conventional concentration shift keying modulation. The major benefits of the proposed method are its simplicity and applicability to many other schemes in the literature.
Autors: Bayram Cevdet Akdeniz;Ali Emre Pusane;Tuna Tugcu;
Appeared in: IEEE Communications Letters
Publication date: Jan 2018, volume: 22, issue:1, pages: 57 - 60
Publisher: IEEE
 
» Optimal Segmentation of High-Resolution Remote Sensing Image by Combining Superpixels With the Minimum Spanning Tree
Abstract:
Image segmentation is the foundation of object-based image analysis, and many researchers have sought optimal segmentation results. The initial image oversegmentation and the optimal segmentation scale are two vital factors in high spatial resolution remote sensing image segmentation. With respect to these two issues, a novel image segmentation method combining superpixels with a minimum spanning tree is proposed in this paper. First, the image is oversegmented using a simple linear iterative clustering algorithm to obtain superpixels. Then, the superpixels are clustered by regionalization with a dynamically constrained agglomerative clustering and partitioning (REDCAP) algorithm using the initial number of segments, and the local variance (LV) and the rate of LV change (ROC-LV) indicator diagrams corresponding to the number of segments are obtained. The suitable number of image segments is determined according to the LV and ROC-LV indicator diagrams corresponding to the number of segments. Finally, the superpixels are reclustered using the REDCAP algorithm based on the suitable number of image segments to obtain the image segmentation result. Through two sets of experiments, the proposed method is compared with two other segmentation algorithms. The experimental results show that the proposed method outperforms the others and obtains good image segmentation results.
Autors: Mi Wang;Zhipeng Dong;Yufeng Cheng;Deren Li;
Appeared in: IEEE Transactions on Geoscience and Remote Sensing
Publication date: Jan 2018, volume: 56, issue:1, pages: 228 - 238
Publisher: IEEE
 
» Optimal Sensor Placement for Monitoring of Spatial Networks
Abstract:
The problem of optimal placement of sensors for monitoring a spatial network (e.g., a road network with moving ground targets or intruders) is considered in this paper. In particular, the optimization of locations of a set of sensors (that can each obtain measurements in a local region around the sensor location) is considered so as to maximize an overall sensor coverage metric defined over the spatial network. The sensor coverage optimality metric for spatial network coverage is based on a novel formulation of a sensor influence wave based on a spatiotemporal model of the measurement reach of a set of sensors given a spatial network topology, a probabilistic model of target movements on the network, and spatial weight maps that model the relative importance/utility of different locations in the spatial region. The sensor placement optimization is based on an iterative genetic algorithm for the optimization of a scalar metric computed from the spatial integration of the sensor influence wave. The efficacy of the proposed approach is demonstrated through simulation studies for several road network geometries.

Note to Practitioners—This paper considers the problem of finding optimal locations for sensors for monitoring a spatial network for moving targets (e.g., a road network with moving ground targets or intruders). Sensor-based monitoring of a spatial region is relevant in a variety of applications (including, in general, such diverse application areas as traffic monitoring in transportation applications, intruder monitoring, surveillance, power systems monitoring, structural health monitoring, etc). This paper offers two primary novel aspects: an optimality metric formulation for target monitoring effectiveness on spatial networks and an iterative genetic algorithm-based method for optimization of the sensor placement configuration. The proposed approach enables addressing of multiple spatial criteria within a unified fra- ework, including the probabilistic characterizations of spatial target movements over the network and the models of relative importance/utility of different locations/areas in the spatial region.

Autors: Prashanth Krishnamurthy;Farshad Khorrami;
Appeared in: IEEE Transactions on Automation Science and Engineering
Publication date: Jan 2018, volume: 15, issue:1, pages: 33 - 44
Publisher: IEEE
 
» Optimal Synchronization of Heterogeneous Nonlinear Systems With Unknown Dynamics
Abstract:
Optimal output synchronization of multi-agent leader–follower systems with unknown nonlinear dynamics is considered. The agents are assumed heterogeneous so that the dynamics may be nonidentical. A distributed observer is designed to estimate the leader state for each agent. A discounted performance function is defined for each agent, and an augmented Hamilton–Jacobi–Bellman (HJB) equation is derived to find its minimal value. The HJB solution depends on the trajectories of the local state and the distributed observer state. A control protocol based on the HJB solution assures that the synchronization error goes to zero locally asymptotically fast for all agents. The proposed approach has two main advantages compared to standard output synchronization methods. First, it is optimal in the sense that it not only makes the steady-state synchronization error zero, but also minimizes the transient error. Second, it does not require the explicit solution to the output regulator equations, though the HJB solutions implicitly provide optimal solutions to them. Finally, a reinforcement learning technique is used to learn the optimal control protocol for each agent without requiring any knowledge of the agents or the leader dynamics. Simulation studies on a notional multi-agent system validate the proposed approach.
Autors: Hamidreza Modares;Frank L. Lewis;Wei Kang;Ali Davoudi;
Appeared in: IEEE Transactions on Automatic Control
Publication date: Jan 2018, volume: 63, issue:1, pages: 117 - 131
Publisher: IEEE
 
» Optimal Wind Farm Allocation in Multi-Area Power Systems Using Distributionally Robust Optimization Approach
Abstract:
This paper presents a distributionally robust planning model to determine the optimal allocation of wind farms in a multi-area power system, so that the expected energy not served (EENS) is minimized under uncertain wind power and generator forced outages. Unlike conventional stochastic programming approaches that rely on detailed information of the exact probability distribution, the proposed method attempts to minimize the expectation term over a collection of distributions characterized by accessible statistical measures, so it is more practical in cases where the detailed distribution data is unavailable. This planning model is formulated as a two-stage problem, where the wind power capacity allocation decisions are determined in the first stage, before the observation of uncertainty outcomes, and operation decisions are made in the second stage under specific uncertainty realizations. In this paper, the second-stage decisions are approximated by linear decision rule functions, so that the distributionally robust model can be reformulated into a tractable second-order cone programming problem. Case studies based on a five-area system are conducted to demonstrate the effectiveness of the proposed method
Autors: Fahad Alismail;Peng Xiong;Chanan Singh;
Appeared in: IEEE Transactions on Power Systems
Publication date: Jan 2018, volume: 33, issue:1, pages: 536 - 544
Publisher: IEEE
 
» Optimization of Coil Element Configurations for a Matrix Gradient Coil
Abstract:
Recently, matrix gradient coils (also termed multi-coils or multi-coil arrays) were introduced for imaging and B0 shimming with 24, 48, and even 84 coil elements. However, in imaging applications, providing one amplifier per coil element is not always feasible due to high cost and technical complexity. In this simulation study, we show that an 84-channel matrix gradient coil (head insert for brain imaging) is able to create a wide variety of field shapes even if the number of amplifiers is reduced. An optimization algorithm was implemented that obtains groups of coil elements, such that a desired target field can be created by driving each group with an amplifier. This limits the number of amplifiers to the number of coil element groups. Simulated annealing is used due to the NP-hard combinatorial nature of the given problem. A spherical harmonic basis set up to the full third order within a sphere of 20-cm diameter in the center of the coil was investigated as target fields. We show that the median normalized least squares error for all target fields is below approximately 5% for 12 or more amplifiers. At the same time, the dissipated power stays within reasonable limits. With a relatively small set of amplifiers, switches can be used to sequentially generate spherical harmonics up to third order. The costs associated with a matrix gradient coil can be lowered, which increases the practical utility of matrix gradient coils.
Autors: Stefan Kroboth;Kelvin J. Layton;Feng Jia;Sebastian Littin;Huijun Yu;Jürgen Hennig;Maxim Zaitsev;
Appeared in: IEEE Transactions on Medical Imaging
Publication date: Jan 2018, volume: 37, issue:1, pages: 284 - 292
Publisher: IEEE
 
» Optimization of Error-Bounded Lossy Compression for Hard-to-Compress HPC Data
Abstract:
Since today's scientific applications are producing vast amounts of data, compressing them before storage/transmission is critical. Results of existing compressors show two types of HPC data sets: highly compressible and hard to compress. In this work, we carefully design and optimize the error-bounded lossy compression for hard-to-compress scientific data. We propose an optimized algorithm that can adaptively partition the HPC data into best-fit consecutive segments each having mutually close data values, such that the compression condition can be optimized. Another significant contribution is the optimization of shifting offset such that the XOR-leading-zero length between two consecutive unpredictable data points can be maximized. We finally devise an adaptive method to select the best-fit compressor at runtime for maximizing the compression factor. We evaluate our solution using 13 benchmarks based on real-world scientific problems, and we compare it with 9 other state-of-the-art compressors. Experiments show that our compressor can always guarantee the compression errors within the user-specified error bounds. Most importantly, our optimization can improve the compression factor effectively, by up to 49 percent for hard-to-compress data sets with similar compression/decompression time cost.
Autors: Sheng Di;Franck Cappello;
Appeared in: IEEE Transactions on Parallel and Distributed Systems
Publication date: Jan 2018, volume: 29, issue:1, pages: 129 - 143
Publisher: IEEE
 
» Optimization-Based Contact Fault Alleviation in Deep Brain Stimulation Leads
Abstract:
Deep brain stimulation (DBS) is a neurosurgical treatment in, e.g., Parkinson’s Disease. Electrical stimulation in DBS is delivered to a certain target through electrodes implanted into the brain. Recent developments aiming at better stimulation target coverage and lesser side effects have led to an increase in the number of contacts in a DBS lead as well as higher hardware complexity. This paper proposes an optimization-based approach to alleviation of the fault impact on the resulting therapeutical effect in field steering DBS. Faulty contacts could be an issue given recent trends of increasing number of contacts in DBS leads. Hence, a fault detection/alleviation scheme, such as the one proposed in this paper, is necessary ensure resilience in the chronic stimulation. Two alternatives are considered and compared with the stimulation prior to the fault: one using higher amplitudes on the remaining contacts and another with alleviating contacts in the neighborhood of the faulty one. Satisfactory compensation for a faulty contact can be achieved in both ways. However, to designate alleviating contacts, a model-based optimization procedure is necessary. Results suggest that stimulating with more contacts yields configurations that are more robust to contact faults, though with reduced selectivity.
Autors: Ruben Cubo;Mattias Åström;Alexander Medvedev;
Appeared in: IEEE Transactions on Neural Systems and Rehabilitation Engineering
Publication date: Jan 2018, volume: 26, issue:1, pages: 69 - 76
Publisher: IEEE
 
» Optimized FPGA Implementation of Model Predictive Control for Embedded Systems Using High-Level Synthesis Tool
Abstract:
Model predictive control (MPC) is an optimization-based strategy for high-performance control that is attracting increasing interest. While MPC requires the online solution of an optimization problem, its ability to handle multivariable systems and constraints makes it a very powerful control strategy specially for MPC of embedded systems, which have an ever increasing amount of sensing and computation capabilities. We argue that the implementation of MPC on field programmable gate arrays (FPGAs) using automatic tools is nowadays possible, achieving cost-effective successful applications on fast or resource-constrained systems. The main burden for the implementation of MPC on FPGAs is the challenging design of the necessary algorithms. We outline an approach to achieve a software-supported optimized implementation of MPC on FPGAs using high-level synthesis tools and automatic code generation. The proposed strategy exploits the arithmetic operations necessaries to solve optimization problems to tailor an FPGA design, which allows a tradeoff between energy, memory requirements, cost, and achievable speed. We show the capabilities and the simplicity of use of the proposed methodology on two different examples and illustrate its advantages over a microcontroller implementation.
Autors: Sergio Lucia;Denis Navarro;Óscar Lucía;Pablo Zometa;Rolf Findeisen;
Appeared in: IEEE Transactions on Industrial Informatics
Publication date: Jan 2018, volume: 14, issue:1, pages: 137 - 145
Publisher: IEEE
 
» Optimized Reconfigurable Fast Convolution-Based Transmultiplexers for Flexible Radio Access
Abstract:
Multirate fast-convolution (FC) processing can be used for realizing low-complexity filter banks (FBs) and transmultiplexers (TMUXs). The main advantage of the FC-based realizations when compared with the polyphase FBs is the increased configurability, that is, the number of subchannels, their bandwidths, and the center frequencies can be adjusted independently. In general, FC-based FBs are linear periodically shift-variant systems. In this brief, novel matrix representations for the FC synthesis and analysis FBs are first derived. These representations give all the shift-variant impulse responses of the FC-based FBs. Then the TMUX optimization criteria are expressed using these representations. Two examples are included to demonstrate the performance of the optimized designs as well as to illustrate the flexibility of the resulting FC-based TMUXs.
Autors: Juha Yli-Kaakinen;Markku Renfors;
Appeared in: IEEE Transactions on Circuits and Systems II: Express Briefs
Publication date: Jan 2018, volume: 65, issue:1, pages: 130 - 134
Publisher: IEEE
 
» Optimizing FIPP- ${p}$ -Cycle Protection Design to Realize Availability-Aware Elastic Optical Networks
Abstract:
This letter tries to optimize the availability-aware service provisioning (AaSP) with failure-independent path-protecting pre-configured cycles (FIPP--cycles) in elastic optical networks (EONs). We propose a novel AaSP-FIPP scheme by leveraging bandwidth-squeezed restoration, develop a mathematical model to analyze the service availability of the scheme, and design a topology partitioning method to improve its scalability.
Autors: Xiaoliang Chen;Muqing Zhou;Shilin Zhu;Sheng Kang;Lu Sun;Zuqing Zhu;
Appeared in: IEEE Communications Letters
Publication date: Jan 2018, volume: 22, issue:1, pages: 65 - 68
Publisher: IEEE
 
» Optimizing the Bit Transmission Power for Link Layer Energy Efficiency Under Imperfect CSI
Abstract:
In this paper, we study the issue of selecting the transmission power (energy per symbol) to minimize the expected energy required to successfully deliver a link-layer packet to the destination node in a wireless link performing the automatic repeat request. We consider the system that has a slow-fading channel and employs a minimum mean square error-based channel estimation scheme for a pilot symbol-assisted modulation. We derive a closed-form expression for the packet error probability (PkEP) in the presence of channel estimation error, and we use this expression for minimizing the PkEP in allocating the transmission energy among the pilot and data symbols. We also derive the expected energy required to successfully deliver a link-layer packet as a function of the transmission power and present an optimization method based on the properties of this function.
Autors: Ali Zarei Ghanavati;Daniel C. Lee;
Appeared in: IEEE Transactions on Wireless Communications
Publication date: Jan 2018, volume: 17, issue:1, pages: 29 - 40
Publisher: IEEE
 
» Optimum Transmitter Current Distribution for Dynamic Wireless Power Transfer With Segmented Array
Abstract:
The misalignment problem is a major challenge in dynamic wireless power transfer systems with a segmented transmitter (Tx) array. Tx coils farther away from receiver (Rx) experience higher currents as compared to Tx coils nearer to Rx coil leading to higher losses and lower performances. This paper reports theoretical optimum current distribution among Tx coils for any Rx position. A current amplitude modulation scheme is analyzed with the analogy of N-Cartesian coordinate equivalent of spherical coordinates. Efficiency and transferred power are evaluated for the proposed current distribution, and further optimization is performed with respect to load resistance, operating frequency, and the number of simultaneously powered Tx coils. The maximum performances that can be obtained with the optimized design conditions have been derived as well. The analysis is validated using numerical and experimental results.
Autors: Prasad Kumara Sampath Jayathurathnage;A. Alphones;D. Mahinda Vilathgamuwa;Andrew Ong;
Appeared in: IEEE Transactions on Microwave Theory and Techniques
Publication date: Jan 2018, volume: 66, issue:1, pages: 346 - 356
Publisher: IEEE
 
» Orko: Facilitating Multimodal Interaction for Visual Exploration and Analysis of Networks
Abstract:
Data visualization systems have predominantly been developed for WIMP-based direct manipulation interfaces. Only recently have other forms of interaction begun to appear, such as natural language or touch-based interaction, though usually operating only independently. Prior evaluations of natural language interfaces for visualization have indicated potential value in combining direct manipulation and natural language as complementary interaction techniques. We hypothesize that truly multimodal interfaces for visualization, those providing users with freedom of expression via both natural language and touch-based direct manipulation input, may provide an effective and engaging user experience. Unfortunately, however, little work has been done in exploring such multimodal visualization interfaces. To address this gap, we have created an architecture and a prototype visualization system called Orko that facilitates both natural language and direct manipulation input. Specifically, Orko focuses on the domain of network visualization, one that has largely relied on WIMP-based interfaces and direct manipulation interaction, and has little or no prior research exploring natural language interaction. We report results from an initial evaluation study of Orko, and use our observations to discuss opportunities and challenges for future work in multimodal network visualization interfaces.
Autors: Arjun Srinivasan;John Stasko;
Appeared in: IEEE Transactions on Visualization and Computer Graphics
Publication date: Jan 2018, volume: 24, issue:1, pages: 511 - 521
Publisher: IEEE
 
» Orthogonal Fluxgate Gradiometer With Multiple Coil Pairs
Abstract:
In this paper, we study the possibility to exploit the noise correlation in a fundamental mode orthogonal fluxgate used as a gradiometer in order to maximize the noise suppression. We study the correlation of the noise along a single core fluxgate using two short coils at a variable distance, and we derive how it drops as the distance increases. Furthermore, we observed this phenomenon with the central point of the coils located at different parts of the wire, obtaining a similar behavior. This implies that the noise propagates in the core in a similar fashion, and—most important—that any mechanism taking advantage of the noise correlation to suppress noise can be replicated along the whole length of the core. We have also investigated the dependence of the noise correlation on the ac component of the excitation current, finding out that in the range where the 1/f noise of the magnetometer does not significantly change larger excitation current increases the correlation thus must be preferred as it allows better noise suppression when used as a gradiometer. Next, we verified that the noise suppression mechanism based on correlation does in fact return lower noise at higher correlation verifying that it matches with the expected values. Finally, we proposed a new configuration of the gradiometer where instead of two long coils we use multiple short coils at close distance calculating that the maximum length of such coils in order to take advantage of this configuration. We also explain that the response of such configuration of the gradiometer to the homogeneous field is zero even if the single coils are not symmetric with the respect of the center of the core if the pairs of coils are all symmetric.
Autors: M. Butta;M. Janosek;
Appeared in: IEEE Transactions on Magnetics
Publication date: Jan 2018, volume: 54, issue:1, pages: 1 - 5
Publisher: IEEE
 
» Outage Analysis of a SIMO FSO System Over an Arbitrarily Correlated $mathcal {M}$ -Distributed Channel
Abstract:
In this letter, we present the outage performance analysis of a single-input multiple-output free-space optical system with selection combining over an arbitrarily correlated Málaga -distributed channel. A novel and generalized analytical expression for the joint probability density function of the received signal-to-noise ratio, using Green’s matrix approximation, is derived in the form of power series. The proposed expression is valid for an arbitrary correlation model and can be mapped to most of the other existing distributions characterizing different atmospheric turbulence conditions. Moreover, mapping of correlated -distribution to correlated Gamma–Gamma and distributions is illustrated with the help of derived analytical results; correctness of the mapped distributions is verified by simulation.
Autors: Richa Priyadarshani;Manav R. Bhatnagar;Zabih Ghassemlooy;Stanislav Zvanovec;
Appeared in: IEEE Photonics Technology Letters
Publication date: Jan 2018, volume: 30, issue:2, pages: 141 - 144
Publisher: IEEE
 
» Outage Probability Analysis of Non-Orthogonal Multiple Access in Cloud Radio Access Networks
Abstract:
To improve system capacity and spectral efficiency, as well as support more connections in cloud radio access networks (C-RANs), the application of non-orthogonal multiple access (NOMA), a promising technique in the physical layer, is considered in this letter. The stochastic geometry is used to obtain the outage probability of NOMA-based downlink C-RAN, in which the remote radio heads are uniformly distributed and serve two paired users simultaneously. A closed-form approximation for the outage probability is derived, and Monte Carlo simulations are provided to validate the accuracy of the theoretical analysis. Compared with conventional multiple access techniques, both the obtained analytical and simulation results demonstrate that the proposed NOMA scheme can offer better spectral efficiency and user fairness in C-RANs.
Autors: Xiang Gu;Xiaodong Ji;Zhiguo Ding;Wenbin Wu;Mugen Peng;
Appeared in: IEEE Communications Letters
Publication date: Jan 2018, volume: 22, issue:1, pages: 149 - 152
Publisher: IEEE
 
» p-i-p-i-n Separate Absorption and Multiplication Ultraviolet Avalanche Photodiodes
Abstract:
Front-illuminated GaN-based separate absorption and multiplication (SAM) ultraviolet (UV) avalanche photodiodes (APDs) with various photon detection areas are demonstrated grown by metalorganic chemical vapor deposition on bulk GaN native substrates with low dislocation density. By adopting a front-illuminated UV-APD structure with a thin AlGaN window layer, no additional etching of the substrate for the reduction of strong UV absorption is required. The epitaxial layer structure of the p-i-p-i-n SAM UV-APDs consists of a Mg-doped -Al0.05Ga0.95N window layer to minimize UV absorption at the top surface region and a Mg-graded -GaN charge layer to serve as a field-termination layer. The onset point of the breakdown voltage () is around 73 V for all SAM-APDs with different mesa areas ranging from 1963 to 10, which is a lower than the typical p-i-n UV-APDs with the similar thickness of undoped layer, where the photon absorption and multiplication processes take place simultaneously. Under UV-light illumination at nm, the SAM-APDs exhibit high avalanche gains greater than at a reverse bias of V
Autors: Mi-Hee Ji;Jeomoh Kim;Theeradetch Detchprohm;Yuanzheng Zhu;Shyh-Chiang Shen;Russell D. Dupuis;
Appeared in: IEEE Photonics Technology Letters
Publication date: Jan 2018, volume: 30, issue:2, pages: 181 - 184
Publisher: IEEE
 
» PageSense: Toward Stylewise Contextual Advertising via Visual Analysis of Web Pages
Abstract:
The Internet has emerged as the most effective and a highly popular medium for advertising. Current contextual advertising platforms need publishers to manually change the original structure of their Web pages and predefine the position and style of embedded ads. Although publishers spend significant effort optimizing their Web page layout, a large number of Web pages contain noticeable blank regions. We present an innovative stylewise advertising platform for contextual advertising, called PageSense. The “style” of Web pages refers to the visual appearance of a Web page, such as color and layout. PageSense aims to associate style-consistent ads with Web pages. It provides two advertising options: 1) If publishers predefine ad positions within Web pages, PageSense will analyze the page style and select ads, which are consistent with the Web page layout, and 2) if publishers impose no constraints for ad placement, PageSense will automatically detect blank regions, select the most nonintrusive region for ad insertion, associate color-consistent ads with the Web pages, and deliver them to blank regions without breaking the original Web page style. Our experiments have verified the effectiveness of PageSense as a complement to existing contextual advertising.
Autors: Tao Mei;Lusong Li;Xinmei Tian;Dacheng Tao;Chong-Wah Ngo;
Appeared in: IEEE Transactions on Circuits and Systems for Video Technology
Publication date: Jan 2018, volume: 28, issue:1, pages: 254 - 266
Publisher: IEEE
 
» Parallel Balanced-Bit-Serial Design Technique for Ultra-Low-Voltage Circuits With Energy Saving and Area Efficiency Enhancement
Abstract:
Ultra-low-voltage (ULV) satisfies the energy-constraint on-die acceleration of parallel processing in battery-powered Internet-of-Things applications. However, ULV brings serious leakage energy, throughput reduction, and delay variation issues. Parallel bit-serialization remarkably reduces leakage energy and enhances area efficiency; however, extremely reduced critical path aggravates delay variation makes bit-serial operation not feasible to ULV design. In this paper, we propose a balanced-bit-serial adder (BBSA) as a basic unit of parallel-balanced-bit-serialization (PBBS) operation, which leverages timing borrowing to mitigate delay variation. In addition, we propose two latches to improve the effectiveness of timing borrowing and ease the area and power overhead of BBSA. The proposed BBSA is verified in TSMC 40-nm CMOS technology. Compared with the flip-flop-based bit-serial adder, energy consumption of BBSA is saved by 40% and area efficiency is improved by 15% as well. As a practical demonstration, we present a reconfigurable PBBS single instruction multiple data (SIMD) vector processing tile. The post-layout simulation shows that the proposed design has advantage of overall area efficiency and has significant energy saving as compared with the state-of-art ULV SIMD tile.
Autors: Bing-Chen Wu;I-Chyn Wey;
Appeared in: IEEE Transactions on Circuits and Systems I: Regular Papers
Publication date: Jan 2018, volume: 65, issue:1, pages: 141 - 153
Publisher: IEEE
 
» Parameter-Invariant Monitor Design for Cyber–Physical Systems
Abstract:
The tight interaction between information technology and the physical world inherent in cyber–physical systems (CPS) can challenge traditional approaches for monitoring safety and security. Data collected for robust CPS monitoring is often sparse and may lack rich training data describing critical events/attacks. Moreover, CPS often operate in diverse environments that can have significant inter/intra-system variability. Furthermore, CPS monitors that are not robust to data sparsity and inter/intra-system variability may result in inconsistent performance and may not be trusted for monitoring safety and security. Towards overcoming these challenges, this paper presents recent work on the design of parameter-invariant (PAIN) monitors for CPS. PAIN monitors are designed such that unknown events and system variability minimally affect the monitor performance. This work describes how PAIN designs can achieve a constant false alarm rate (CFAR) in the presence of data sparsity and intra/inter system variance in real-world CPS. To demonstrate the design of PAIN monitors for safety monitoring in CPS with different types of dynamics, we consider systems with networked dynamics, linear-time invariant dynamics, and hybrid dynamics that are discussed through case studies for building actuator fault detection, meal detection in type I diabetes, and detecting hypoxia caused by pulmonary shunts in infants. In all applications, the PAIN monitor is shown to have (significantly) less variance in monitoring performance and (often) outperforms other competing approaches in the literature. Finally, an initial application of PAIN monitoring for CPS security is presented along with challenges and research directions for future security monitoring deployments.
Autors: James Weimer;Radoslav Ivanov;Sanjian Chen;Alexander Roederer;Oleg Sokolsky;Insup Lee;
Appeared in: Proceedings of the IEEE
Publication date: Jan 2018, volume: 106, issue:1, pages: 71 - 92
Publisher: IEEE
 
» Parasitic Effect Analysis in Memristor-Array-Based Neuromorphic Systems
Abstract:
Neuromorphic systems using memristors as artificial synapses have attracted broad interest for energy-efficient computing applications. However, networks based on these purely passive devices can be affected by parasitic effects such as series resistance and sneak path problems. Here, we analyze the effects of parasitic factors on the performance of memristor-based neuromorphic systems. During vector-array multiplication, the line resistance can cause significant distortion of the output current and the activity of the corresponding neurons. An approach to compensate the line resistance effects based on an approximate model consisting of only few known parameters is proposed and shows excellent ability to capture the complex network behavior. During training and feature detection, the series resistance can cause significant degradation of the learned dictionary, with only a few dominant neurons being trained. Using a scaling factor based on the proposed simple model, these effects can be successfully mitigated, and the correct network operations can be restored. These results provide insight and practical measures on the parasitic effects for implementation of the neuromorphic system using memristor arrays.
Autors: YeonJoo Jeong;Mohammed A. Zidan;Wei D. Lu;
Appeared in: IEEE Transactions on Nanotechnology
Publication date: Jan 2018, volume: 17, issue:1, pages: 184 - 193
Publisher: IEEE
 
» Parasitic Resistance-Based High Precision Capacitive MEMS Accelerometer Phase Shift and Its Usage for Temperature Compensation
Abstract:
A novel parasitic resistance-based high precision capacitive MEMS accelerometer temperature compensation method is proposed. The performance of MEMS accelerometer is severely affected by temperature drift. After a careful modeling analysis of the MEMS sensor, it is found that phase shift of the system is majorly affected by the parasitic resistor of the sensor cap. Thus, it can be used for sensor temperature compensation. Detailed analytic models and simulations are provided. Experimental results show that the bias stability is reduced from 0.26 to 0.18 mg after real-time temperature compensation. The temperature drift is reduced.
Autors: Yidong Liu;Tieying Ma;
Appeared in: IEEE Sensors Journal
Publication date: Jan 2018, volume: 18, issue:2, pages: 629 - 634
Publisher: IEEE
 
» PARHELIA: Particle Filter-Based Heart Rate Estimation From Photoplethysmographic Signals During Physical Exercise
Abstract:
The photoplethysmographic (PPG) signal is an important source of information for estimating heart rate (HR). However, the PPG signal could be strongly contaminated by the motion artifact of the subjects, making HR estimation a particularly difficult problem. In this paper, we propose PARHELIA, a PARticle filter-based algorithm for HEart rate estimation using photopLethysmographIc signAls. The proposed method employs a particle filter, and utilizes the simultaneously recorded acceleration signals from a wrist-type sensor, to keep track of multiple HR candidates. This achieves quick recovery from incorrect HR estimations under the strong influence of the MA. Experimental results for a dataset of 12 subjects recorded during fast running showed that the average absolute estimation error was 1.17 beats per minute (BPM) whereas that of the best-known conventional method, JOSS, is 1.28 BPM. Furthermore, the estimation time of PARHELIA is 20 times shorter than JOSS.
Autors: Yuya Fujita;Masayuki Hiromoto;Takashi Sato;
Appeared in: IEEE Transactions on Biomedical Engineering
Publication date: Jan 2018, volume: 65, issue:1, pages: 189 - 198
Publisher: IEEE
 
» Part I: On the Unification of Physics of Quasi-Saturation in LDMOS Devices
Abstract:
There have been a lot of ambiguities related to physics of quasi-saturation (QS) in laterally diffused MOS (LDMOS) devices in the published literature. For example, models that explain QS in input characteristics do not explain the same in output characteristics and vice versa. In addition to this, none of the earlier models explain early onset of QS at higher temperatures nor the models were validated using counter arguments. Attributed to this, a need for unified theory explaining physics of QS is justified in this paper. Furthermore, this paper for the first time, while addressing missing links between the observations reported in the past, develops a unified theory to explain physics of QS behavior. The theory presented here is independent of device architecture and covers all voltage-current–temperature trends. While considering velocity saturation and space charge modulation, we have discovered key role of high field mobility degradation of majority carriers and electric field screening, which is found to be the root cause of QS in LDMOS devices. The theory presented is further validated with numerous counter arguments. Finally, based on the new physical insight developed, we have proposed different approaches to mitigate QS effect. A detailed device design guideline to mitigate QS and its correlation with analog/RF performance, electo static discharge, hot-carrier reliability, self-heating, and safe operating area concern is presented in Part II of this paper.
Autors: B. Sampath Kumar;Mayank Shrivastava;
Appeared in: IEEE Transactions on Electron Devices
Publication date: Jan 2018, volume: 65, issue:1, pages: 191 - 198
Publisher: IEEE
 
» Part II: RF, ESD, HCI, SOA, and Self Heating Concerns in LDMOS Devices Versus Quasi-Saturation
Abstract:
Various LDMOS device design parameters to mitigate quasi-saturation (QS) have been identified. Based on this, a set of independent and mixed device designs to mitigate QS, while maximizing the device performance, are presented. The impact of QS on the analog/RF/switching performance of these independent and mixed designs is investigated thoroughly, while analogizing performance with QS for the first time. Furthermore, hot carrier induced (HCI) degradation in various independent and mixed LDMOS designs is studied using spherical harmonic expansion of Boltzmann transport equation. In addition to this self-heating behavior, safe operating area (SOA) boundaries and electrostatic discharge (ESD) behavior of independent and mixed LDMOS designs with and without QS are studied. For the first time, HCI degradation, self-heating behavior, SOA boundary, and ESD failure in LDMOS devices are correlated with the extent of QS in LDMOS devices, based on which device design guidelines to tackle all performance versus reliability challenges are derived.
Autors: B. Sampath Kumar;Mayank Shrivastava;
Appeared in: IEEE Transactions on Electron Devices
Publication date: Jan 2018, volume: 65, issue:1, pages: 199 - 206
Publisher: IEEE
 
» Partial-Discharge Measuring Produces Uncertain Results: Important Quality Assesment Updates for Stator Windings
Abstract:
The petrochemical industry considers the offline partial-discharge (PD) measurement an important quality assessment for new medium-voltage motor and generator stator windings. A recent edition of American Petroleum Institute (API) Standard 541 [1] requires an instrument to be compliant with International Electrotechnical Commission (IEC) Standard 60270 [3] for PD measurements on sacrificial stator coils and proposes 100 pC for guidance on acceptance criteria until more data becomes available. Given the industry's faith in PD as an acceptance test based on a representative sample, it warrants closer scrutiny. The characteristic PD distribution pattern produced by each test instrument provides information on the origin of the discharges and, therefore, can be used to determine what type of defect has produced them. This article shows how external factors such as instrument selection, testing environment, and time interval between tests can influence PD test results.
Autors: Saeed Ul Haq;Meredith K.W. Stranges;Barry Wood;
Appeared in: IEEE Industry Applications Magazine
Publication date: Jan 2018, volume: 24, issue:1, pages: 52 - 59
Publisher: IEEE
 
» PBTI in GaN-HEMTs With p-Type Gate: Role of the Aluminum Content on $Delta V_{mathrm {TH}}$ and Underlying Degradation Mechanisms
Abstract:
In this paper, we present an experimental analysis of the degradation induced by positive bias temperature instability stress in GaN-based power high electron mobility transistors with p-type gate, controlled by a Schottky metal/p-GaN junction. In particular, the role of the aluminum content (Al%) in the AlGaN barrier layer on the threshold voltage degradation is investigated by means of constant voltage stress measurements. This has been performed for different process conditions with varying Al content. Main results in this paper demonstrate that when a relatively large positive bias is applied on the gate, two competing trapping mechanisms take place in the AlGaN barrier layer or at the p-GaN/AlGaN interface causing instability. First, an aluminum independent hole trapping mechanism, caused by elastic tunneling from p-GaN valence band (2-D hole gas), leads to a relatively short-time and recoverable negative shift. In the second step, defect creation occurs. These additional defects are filled with electrons and cause a permanent or slowly recoverable positive degradation. The amount of defect creation was dependent on the Al% in the barrier.
Autors: Andrea Natale Tallarico;Steve Stoffels;Niels Posthuma;Paolo Magnone;Denis Marcon;Stefaan Decoutere;Enrico Sangiorgi;Claudio Fiegna;
Appeared in: IEEE Transactions on Electron Devices
Publication date: Jan 2018, volume: 65, issue:1, pages: 38 - 44
Publisher: IEEE
 
» Pedestrian-Aware Engine Management Strategies for Plug-In Hybrid Electric Vehicles
Abstract:
Electric vehicles (EVs) and plug-in hybrid EVs (PHEVs) are increasingly being seen as a means of mitigating the pressing concerns of traffic-related pollution. While hybrid vehicles are usually designed with the objective of minimizing fuel consumption, in this paper we propose a engine management strategies that also consider environmental effects of the vehicles to pedestrians outside of the vehicles. Specifically, we present the optimisation-based engine energy management strategies for PHEVs that attempt to minimize the environmental impact of pedestrians along the route of the vehicle, while taking account of route-dependent uncertainties. We implement the proposed approach in a real PHEV and evaluate the performance in a hardware-in-the-loop platform. A variety of simulation results are given to illustrate the efficacy of our proposed approach.
Autors: Yingqi Gu;Mingming Liu;Joe Naoum-Sawaya;Emanuele Crisostomi;Giovanni Russo;Robert Shorten;
Appeared in: IEEE Transactions on Intelligent Transportation Systems
Publication date: Jan 2018, volume: 19, issue:1, pages: 92 - 101
Publisher: IEEE
 
» Peer-Assisted Video Streaming With RTMFP Flash Player: A Measurement Study on PPTV
Abstract:
Real-time media flow protocol (RTMFP) is a protocol developed by Adobe for multimedia delivery under both client–server and peer-to-peer (P2P) paradigms. Currently, major Internet video service providers, such as PPTV and iQIYI, have already built their Web-based video streaming systems with RTMFP. In such a system, a user only needs to install a Flash Player plug-in on his Web browser, and can stream videos in a peer-assisted way. Despite its wide usage, RTMFP has received little attention from the measurement community. In this paper, we select PPTV as an example and study the RTMFP video streaming technology with a measurement approach. We reveal the architecture of PPTV’s RTMFP streaming system and show that, compared with proprietary P2P networks, the RTMFP network has a different content distribution policy, and exhibits different features on peers’ streaming behaviors, potential system bottleneck, and network dynamics. We also study RTMFP’s video transmission and find that the protocol’s selective retransmission scheme can effectively overcome packet losses and improve the video playback quality; however, the TCP-like congestion control mechanism of RTMFP does not lead to fairness between RTMFP and Transmission Control Protocol (TCP) traffics, due to the mismatch between the inherited pull-based video segment distribution model of the P2P streaming application and the protocol’s built-in congestion control mechanism. This paper provides insights into the RTMFP-based video streaming technology and is helpful for people to construct better peer-assisted video systems with RTMFP.
Autors: Shan Zou;Qiang Wang;Junqiang Ge;Ye Tian;
Appeared in: IEEE Transactions on Circuits and Systems for Video Technology
Publication date: Jan 2018, volume: 28, issue:1, pages: 158 - 170
Publisher: IEEE
 
» Performance Analysis of Multiuser Massive MIMO With Spatially Correlated Channels Using Low-Precision ADC
Abstract:
In this letter, we analyze the uplink performance of a multiuser massive MIMO system with spatially correlated channels using low-precision analog-to-digital convertors (ADCs) at the base station. A tight closed-form approximated sum rate for receivers with imperfect channel state information is derived. We further investigate the impact of the spatial correlation on the rate loss caused by low-precision ADC and find that this rate loss is currently overestimated for massive MIMO under spatially correlated channels. This observation promotes the use of low-precision ADC in practical massive MIMO with inherent spatial correlation.
Autors: Peihao Dong;Hua Zhang;Wei Xu;Geoffrey Ye Li;Xiaohu You;
Appeared in: IEEE Communications Letters
Publication date: Jan 2018, volume: 22, issue:1, pages: 205 - 208
Publisher: IEEE
 
» Performance Analysis of NOMA in Training-Based Multiuser MIMO Systems
Abstract:
This paper considers the use of non-orthogonal-multiple-access (NOMA) in multiuser MIMO systems in practical scenarios where channel state information (CSI) is acquired through pilot signaling. A new NOMA scheme that uses shared pilots is proposed. Achievable rate analysis is carried out for different pilot signaling schemes, including both uplink and downlink pilots. The achievable rate performance of the proposed NOMA scheme with shared pilot within each group is compared with the traditional orthogonal access scheme with orthogonal pilots. Our proposed scheme is a generalization of the orthogonal scheme, and can be reduced to the orthogonal scheme when appropriate power allocation parameters are chosen. Numerical results show that when downlink CSI is available at the users, our proposed NOMA scheme outperforms orthogonal schemes. However with more groups of users present in the cell, it is preferable to use multi-user beamforming instead of NOMA.
Autors: Hei Victor Cheng;Emil Björnson;Erik G. Larsson;
Appeared in: IEEE Transactions on Wireless Communications
Publication date: Jan 2018, volume: 17, issue:1, pages: 372 - 385
Publisher: IEEE
 
» Performance Enhancement of a Dielectric Barrier Discharge Vacuum-Ultraviolet Photon Source Using Short-Pulsed Electrical Excitation
Abstract:
We have studied the electrical and optical characteristics of an air-cooled argon excimer vacuum-ultraviolet lamp ( nm) excited by a dielectric barrier discharge powered by: 1) pulsed or 2) sinusoidal high-voltage drivers from 32 to 100 kHz. Compared to sinusoidal excitation, pulsed excitation gives nearly higher vacuum-ultraviolet (VUV) output and electrical-to-VUV conversion efficiency at high pressure (800–900 mbar). Visually, the pulse-driven plasma is spatially homogeneous, whereas for sinusoidal excitation the plasma becomes filamentary at higher pressure and/or frequency. Spectral emission is highly monochromatic with most of the output in the desired VUV band (–140 nm). With the lamp running at pressure >700 mbar and power loadings >1.6 W/cm3, a sharp spike in VUV output was consistently seen at turn-on. We believe that transient phenomena or favorable initial conditions may be partly responsible for this VUV spike, although the equilibrium VUV output appears to be limited due to thermal dissipation, gas heating, and associated loss of gas from the active region. We propose that we may be observing the same intrinsic VUV spiking phenomena as reported in liquid nitrogen-cooled Xe, Kr, and Ar excimer lamps by Gerasimov et al. More importantly, we believe ours is the first such observation reported for an excimer VUV lamp operating near room temperature. This VUV spiking behavior raises the prospect that designs with improved thermal management may achieve even higher VUV power and efficiency.
Autors: Robert J. Carman;Noah T. Goldberg;Stuart C. Hansen;Nigel Gore;Deborah M. Kane;
Appeared in: IEEE Transactions on Plasma Science
Publication date: Jan 2018, volume: 46, issue:1, pages: 90 - 102
Publisher: IEEE
 
» Performance Evaluation of Passivated Silicon Carrier-Selective Contact Solar Cell
Abstract:
In this paper, a solar cell with amorphous silicon (a-Si) passivation that uses transition metal oxides (TMOs) for charge carrier collection has been modeled and analyzed for its performance. Charge carrier selection has been incorporated through selective band alignment provided by NiO and TiO2 TMOs for electrons and holes, respectively. The presence of a-Si interfacial layers for defect passivation prevents carrier loss due to high interface state densities at the Si/TMO interfaces. This structure is a potential candidate for high-efficiency solar cells (>25%) with a realistic approach towards the solution of high defect density. Optical analysis of the proposed structure has been done to analyze the amount of light entering the silicon and capable of generating electron–hole pairs. The amount of light lost has also been quantified into reflection loss, parasitic absorption, and back metal absorption. Impact of surface passivation quality and doping of NiO and TiO2 on its performance has been analyzed through the detailed device simulations. This provides a realistic pathway for engineering of passivation quality and doping of metal oxides for improved performance.
Autors: Astha Tyagi;Kunal Ghosh;Anil Kottantharayil;Saurabh Lodha;
Appeared in: IEEE Transactions on Electron Devices
Publication date: Jan 2018, volume: 65, issue:1, pages: 176 - 183
Publisher: IEEE
 
» Performance of Brain–Computer Interfacing Based on Tactile Selective Sensation and Motor Imagery
Abstract:
A large proportion of users do not achieve adequate control using current non-invasive brain–computer interfaces (BCIs). This issue has being coined “BCI-Illiteracy” and is observed among different BCI modalities. Here, we compare the performance and the BCI-illiteracy rate of a tactile selective sensation (SS) and motor imagery (MI) BCI, for a large subject samples. We analyzed 80 experimental sessions from 57 subjects with two-class SS protocols. For SS, the group average performance was 79.8 ± 10.6%, with 43 out of the 57 subjects (75.4%) exceeding the 70% BCI-illiteracy threshold for left- and right-hand SS discrimination. When compared with previous results, this tactile BCI outperformed all other tactile BCIs currently available. We also analyzed 63 experimental sessions from 43 subjects with two-class MI BCI protocols, where the group average performance was 77.2 ± 13.3%, with 69.7% of the subjects exceeding the 70% performance threshold for left- and right-hand MI. For within-subject comparison, the 24 subjects who participated to both the SS and MI experiments, the BCI performance was superior with SS than MI especially in beta frequency band (p < 0.05), with enhanced R2 discriminative information in the somatosensory cortex for the SS modality. Both SS and MI showed a functional dissociation between lower alpha ([8 10] Hz) and upper alpha ([10 13] Hz) bands, with BCI performance significantly better in the upper alpha than the lower alpha (p < 0.05) band. In summary, we demonstrated that SS is a promising BCI modality with low BCI illiteracy issue and has great potential in practical applications reaching large population.
Autors: Lin Yao;Xinjun Sheng;Natalie Mrachacz-Kersting;Xiangyang Zhu;Dario Farina;Ning Jiang;
Appeared in: IEEE Transactions on Neural Systems and Rehabilitation Engineering
Publication date: Jan 2018, volume: 26, issue:1, pages: 60 - 68
Publisher: IEEE
 
» Performance of Mode Space Detector in Uncertain Shallow Water and Its Robust Realization
Abstract:
The statistics of the mode space detector (MSD) whose modes are characterized by some degree of mismatch to truth [that is, the mismatched mode space detector (MMSD)] are derived. As a measure of the “containing relation” between the mode spaces derived from different environmental realizations we propose the relative projection error metric, through which the performance of the MMSD can be further investigated and compared to the MSD using accurate environmental knowledge. From this performance analysis, we suggest that by simply using the greatest dimensional physically supported mode space, we can obtain a robust MSD. It can achieve the same performance robustness as the energy detector—the performance is only determined by the array signal energy and is insensitive to the specific source position and environmental conditions. It can also avoid the potentially-significant performance degradation of the Bayesian detector when applied to certain deterministic scenarios at a cost of small average performance degradation. Numerical simulations in a typical uncertain shallow-water environment support our assertions.
Autors: Mingyang Li;Chao Sun;Peter Willett;
Appeared in: IEEE Journal of Oceanic Engineering
Publication date: Jan 2018, volume: 43, issue:1, pages: 131 - 144
Publisher: IEEE
 
» Persistent Scatter Identification and Look-Angle Error Estimation Using Similar Time-Series Interferometric Pixels
Abstract:
Persistent scatterer (PS) pixels contain highly coherent information, which is used in the estimation of geophysical parameters of interest. Conventionally, PS pixels are selected on the basis of the estimated noise present in the spatially uncorrelated phase component along with look-angle error. The phase history of selected PS pixels is corrected for the look-angle error followed by phase unwrapping and extraction of spatially correlated nuisance phase component leading to displacement estimation. In this letter, a novel PS selection method, which is based on a new index called the similar time-series interferometric pixels (STIPs) representing the number of neighborhood pixels with similar phase history, is proposed. In this approach, apart from PS selection, corresponding set of STIP is also used in refining look-angle error estimation. The efficiency of the proposed InSAR processing chain is demonstrated for the Sentinel-1A single look complex images of Rajmahal, Jharkhand, India, predominantly a coal mines area. Results, when compared with the conventional PS processing technique, reveal substantial improvement in terms of extracting more number of reliable PS with enhanced density.
Autors: Avadh Bihari Narayan;Ashutosh Tiwari;Ramji Dwivedi;Onkar Dikshit;
Appeared in: IEEE Geoscience and Remote Sensing Letters
Publication date: Jan 2018, volume: 15, issue:1, pages: 147 - 150
Publisher: IEEE
 
» Personalized and Diverse Task Composition in Crowdsourcing
Abstract:
We study task composition in crowdsourcing and the effect of personalization and diversity on performance. A central process in crowdsourcing is task assignment, the mechanism through which workers find tasks. On popular platforms such as Amazon Mechanical Turk, task assignment is facilitated by the ability to sort tasks by dimensions such as creation date or reward amount. Task composition improves task assignment by producing for each worker, a personalized summary of tasks, referred to as a Composite Task (CT). We propose different ways of producing CTs and formulate an optimization problem that finds for a worker, the most relevant and diverse CTs. We show empirically that workers’ experience is greatly improved due to personalization that enforces an adequation of CTs with workers’ skills and preferences. We also study and formalize various ways of diversifying tasks in each CT. Task diversity is grounded in organization studies that have shown its impact on worker motivation  [33] . Our experiments show that diverse CTs contribute to improving outcome quality. More specifically, we show that while task throughput and worker retention are best with ranked lists, crowdwork quality reaches its best with CTs diversified by requesters, thereby confirming that workers look to expose their “good” work to many requesters.
Autors: Maha Alsayasneh;Sihem Amer-Yahia;Eric Gaussier;Vincent Leroy;Julien Pilourdault;Ria Mae Borromeo;Motomichi Toyama;Jean-Michel Renders;
Appeared in: IEEE Transactions on Knowledge and Data Engineering
Publication date: Jan 2018, volume: 30, issue:1, pages: 128 - 141
Publisher: IEEE
 
» Personalized Risk Scoring for Critical Care Prognosis Using Mixtures of Gaussian Processes
Abstract:
Objective: In this paper, we develop a personalized real-time risk scoring algorithm that provides timely and granular assessments for the clinical acuity of ward patients based on their (temporal) lab tests and vital signs; the proposed risk scoring system ensures timely intensive care unit admissions for clinically deteriorating patients. Methods: The risk scoring system is based on the idea of sequential hypothesis testing under an uncertain time horizon. The system learns a set of latent patient subtypes from the offline electronic health record data, and trains a mixture of Gaussian Process experts, where each expert models the physiological data streams associated with a specific patient subtype. Transfer learning techniques are used to learn the relationship between a patient's latent subtype and her static admission information (e.g., age, gender, transfer status, ICD-9 codes, etc). Results: Experiments conducted on data from a heterogeneous cohort of 6321 patients admitted to Ronald Reagan UCLA medical center show that our score significantly outperforms the currently deployed risk scores, such as the Rothman index, MEWS, APACHE, and SOFA scores, in terms of timeliness, true positive rate, and positive predictive value. Conclusion: Our results reflect the importance of adopting the concepts of personalized medicine in critical care settings; significant accuracy and timeliness gains can be achieved by accounting for the patients’ heterogeneity. Significance: The proposed risk scoring methodology can confer huge clinical and social benefits on a massive number of critically ill inpatients who exhibit adverse outcomes including, but not limited to, cardiac arrests, respiratory arrests, and septic shocks.
Autors: Ahmed M. Alaa;Jinsung Yoon;Scott Hu;Mihaela van der Schaar;
Appeared in: IEEE Transactions on Biomedical Engineering
Publication date: Jan 2018, volume: 65, issue:1, pages: 207 - 218
Publisher: IEEE
 
» PES Connections: Being Relevant to the Global Working Professional [Leader's Corner]
Abstract:
Autors: Saifur Rahman;
Appeared in: IEEE Power and Energy Magazine
Publication date: Jan 2018, volume: 16, issue:1, pages: 10 - 12
Publisher: IEEE
 
» Phantomless Auto-Calibration and Online Calibration Assessment for a Tracked Freehand 2-D Ultrasound Probe
Abstract:
This paper presents a method for automatically calibrating and assessing the calibration quality of an externally tracked 2-D ultrasound (US) probe by scanning arbitrary, natural tissues, as opposed a specialized calibration phantom as is the typical practice. A generative topic model quantifies the posterior probability of calibration parameters conditioned on local 2-D image features arising from a generic underlying substrate. Auto-calibration is achieved by identifying the maximum a-posteriori image-to-probe transform, and calibration quality is assessed online in terms of the posterior probability of the current image-to-probe transform. Both are closely linked to the 3-D point reconstruction error (PRE) in aligning feature observations arising from the same underlying physical structure in different US images. The method is of practical importance in that it operates simply by scanning arbitrary textured echogenic structures, e.g., in-vivo tissues in the context of the US-guided procedures, without requiring specialized calibration procedures or equipment. Observed data take the form of local scale-invariant features that can be extracted and fit to the model in near real-time. Experiments demonstrate the method on a public data set of in vivo human brain scans of 14 unique subjects acquired in the context of neurosurgery. Online calibration assessment can be performed at approximately 3 Hz for the US images of pixels. Auto-calibration achieves an internal mean PRE of 1.2 mm and a discrepancy of [2 mm, 6 mm] in comparison to the calibration via a standard phantom-based method.
Autors: Matthew Toews;William M. Wells;
Appeared in: IEEE Transactions on Medical Imaging
Publication date: Jan 2018, volume: 37, issue:1, pages: 262 - 272
Publisher: IEEE
 
» Phase Retrieval Without Small-Ball Probability Assumptions
Abstract:
In the context of the phase retrieval problem, it is known that certain natural classes of measurements, such as Fourier measurements and random Bernoulli measurements, do not lead to the unique reconstruction of all possible signals, even in combination with certain practically feasible random masks. To avoid this difficulty, the analysis is often restricted to measurement ensembles (or masks) that satisfy a small-ball probability condition, in order to ensure that the reconstruction is unique. This paper shows a complementary result: for random Bernoulli measurements, there is still a large class of signals that can be reconstructed uniquely, namely, those signals that are non-peaky. In fact, this result is much more general: it holds for random measurements sampled from any subgaussian distribution , without any small-ball conditions. This is demonstrated in two ways: 1) a proof of stability and uniqueness and 2) a uniform recovery guarantee for the PhaseLift algorithm. In all of these cases, the number of measurements approaches the information-theoretic lower bound. Finally, for random Bernoulli measurements with erasures, it is shown that PhaseLift achieves uniform recovery of all signals (including peaky ones).
Autors: Felix Krahmer;Yi-Kai Liu;
Appeared in: IEEE Transactions on Information Theory
Publication date: Jan 2018, volume: 64, issue:1, pages: 485 - 500
Publisher: IEEE
 
» Phase Transformation of Micrometer-Sized Mn–Al–C
Abstract:
Mn54Al46C2.44 alloy as new permanent magnetic materials was produced by induction melting, and its powders were produced by low energy ball milling. The milled powders were annealed to study the effect on their phase transformation and magnetic properties. The powder undergoes massive phase transformation at an annealing temperature of 450 °C, and reaches the maximum saturation magnetization ( when annealed at 480 °C for 5 min, while its intrinsic coercivity ( continually increases with the temperature. The initial increment of the is due to the phase transformation from paramagnetic -phase to ferromagnetic -phase and remaining -phase and formation of secondary phases, such as nonmagnetic - and -phases, that acts as pinning points for the domain walls. The next one is caused by the increasing percentage of the secondary phases that decreases . Based on the delta analysis, it can be verified that the increased with increasing secondary phases when annealed at temperat- res above 480 °C is due to the decreasing magnetization.
Autors: Jihoon Park;Hui-Dong Qian;Ping-Zhan Si;Chul-Jin Choi;
Appeared in: IEEE Transactions on Magnetics
Publication date: Jan 2018, volume: 54, issue:1, pages: 1 - 3
Publisher: IEEE
 
» Phased Array Focusing for Acoustic Wireless Power Transfer
Abstract:
Wireless power transfer (WPT) through acoustic waves can achieve higher efficiencies than inductive coupling when the distance is above several times the transducer size. This paper demonstrates the use of ultrasonic phased arrays to focus power to receivers at arbitrary locations to increase the power transfer efficiency. Using a phased array consisting of 37 elements at a distance nearly 5 times the receiver transducer diameter, a factor of 2.6 increase in efficiency was achieved when compared to a case equivalent to a single large transducer with the same peak efficiency distance. The array has a total diameter of 7 cm, and transmits through air at 40 kHz to a 1.1-cm diameter receiver, achieving a peak overall efficiency of 4% at a distance of 5 cm. By adjusting the focal distance, the efficiency can also be maintained relatively constant at distances up to 9 cm. Numerical models were developed and shown to closely match the experimental energy transfer behavior; modeling results indicate that the efficiency can be further doubled by increasing the number of elements. For comparison, an inductive WPT system was also built with the diameters of the transmitting and receiving coils equivalent to the dimensions of the transmitting ultrasonic phased array and receiver transducer, and the acoustic WPT system achieved higher efficiencies than the inductive WPT system when the transmit-to-receive distance is above 5 cm. In addition, beam angle steering was demonstrated by using a simplified seven-element 1-D array, achieving power transfer less dependent on receiver placement.
Autors: Victor Farm-Guoo Tseng;Sarah S. Bedair;Nathan Lazarus;
Appeared in: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Publication date: Jan 2018, volume: 65, issue:1, pages: 39 - 49
Publisher: IEEE
 
» Phasor Measurement Sensor-Based Angular Stability Retention System for Smart Power Grids With High Penetration of Microgrids
Abstract:
Emerging phasor measurement sensor (PMS) technology is revolutionizing conventional power grids to smart power grids (SPGs). This also paves the way for deregulations in energy market and wide area infusion of distributed energy-based systems like microgrids (MGs). Advanced energy management of MGs for better consumer gratification may pose severe threat to angular stability of SPGs. This paper outlines the angular stability issues that may emerge in SPGs due to high penetration of MGs. PMS-powered stability monitoring and MG operational-based stability retention technique are proposed for retaining the angular stability. Real-time frequency domain analysis of phase angle oscillations measured from PMS across the grid is the backbone of the proposed stability monitoring technique. Wide area optimized control of MGs with the aid of topological genetic algorithm is proposed for restraining the stability. Case studies conducted on standard bus systems portray the impact of high penetration of MGs on angular stability and the effectiveness of proposed techniques in monitoring and retaining the stability.
Autors: Pathirikkat Gopakumar;Maddikara Jaya Bharata Reddy;Dusmanta Kumar Mohanta;
Appeared in: IEEE Sensors Journal
Publication date: Jan 2018, volume: 18, issue:2, pages: 764 - 772
Publisher: IEEE
 
» PhenoLines: Phenotype Comparison Visualizations for Disease Subtyping via Topic Models
Abstract:
PhenoLines is a visual analysis tool for the interpretation of disease subtypes, derived from the application of topic models to clinical data. Topic models enable one to mine cross-sectional patient comorbidity data (e.g., electronic health records) and construct disease subtypes—each with its own temporally evolving prevalence and co-occurrence of phenotypes—without requiring aligned longitudinal phenotype data for all patients. However, the dimensionality of topic models makes interpretation challenging, and de facto analyses provide little intuition regarding phenotype relevance or phenotype interrelationships. PhenoLines enables one to compare phenotype prevalence within and across disease subtype topics, thus supporting subtype characterization, a task that involves identifying a proposed subtype's dominant phenotypes, ages of effect, and clinical validity. We contribute a data transformation workflow that employs the Human Phenotype Ontology to hierarchically organize phenotypes and aggregate the evolving probabilities produced by topic models. We introduce a novel measure of phenotype relevance that can be used to simplify the resulting topology. The design of PhenoLines was motivated by formative interviews with machine learning and clinical experts. We describe the collaborative design process, distill high-level tasks, and report on initial evaluations with machine learning experts and a medical domain expert. These results suggest that PhenoLines demonstrates promising approaches to support the characterization and optimization of topic models.
Autors: Michael Glueck;Mahdi Pakdaman Naeini;Finale Doshi-Velez;Fanny Chevalier;Azam Khan;Daniel Wigdor;Michael Brudno;
Appeared in: IEEE Transactions on Visualization and Computer Graphics
Publication date: Jan 2018, volume: 24, issue:1, pages: 371 - 381
Publisher: IEEE
 
» Photo-Electrical Properties of MgZnO Thin-Film Transistors With High- ${k}$ Dielectrics
Abstract:
In this letter, magnesium zinc oxide (MgZnO) was deposited to fabricate a thin-film transistor (TFT) by radio-frequency magnetron sputtering. We used alumina as MgZnO TFT gate insulator layer via an atomic layer deposition method. The MgZnO TFT with Al2O3 insulator could exhibit a mobility of 7.73 cm2/Vs, threshold voltage of 4.2 V, and subthreshold swing of 0.29 V/decade. Compared with our previous published study, the current switching ratio was improved by nearly two orders of magnitude. Furthermore, the hysteresis phenomenon had been investigated and the results showed that the high- gate insulator could improve the interface state caused by the traps.
Autors: Jyun-Yi Li;Sheng-Po Chang;Ming-Hung Hsu;Shoou-Jinn Chang;
Appeared in: IEEE Photonics Technology Letters
Publication date: Jan 2018, volume: 30, issue:1, pages: 59 - 62
Publisher: IEEE
 
» Photodarkening-Free Yb-Doped Saddle-Shaped Fiber for High Power Single-Mode 976-nm Laser
Abstract:
We propose a novel saddle-shaped Yb-doped fiber design for high power generation in the spectral range near 0.976 . The fiber has a central single-mode part with a core diameter of approximately and an ultra-thin silica clad of approximately . At both ends of the fiber, the core/clad diameters were adiabatically increased up to 20/80 to be compatible with ordinary passive fibers. A monolithic 976-nm single-mode continuous wave laser based on the proposed fiber was created. The laser’s power was a record high compared with all-fiber laser schemes, with an output power of 10.6 W. Utilization of a photodarkening-free core glass matrix has allowed us to demonstrate perfect long-term stability (without any power degradation) of the developed laser over 45 h.
Autors: Svetlana S. Aleshkina;Andrei E. Levchenko;Oleg I. Medvedkov;Konstantin K. Bobkov;Mikhail M. Bubnov;Denis S. Lipatov;Alexei N. Guryanov;Mikhail E. Likhachev;
Appeared in: IEEE Photonics Technology Letters
Publication date: Jan 2018, volume: 30, issue:1, pages: 127 - 130
Publisher: IEEE
 
» Photonic Crystal-Based High-Power Backward Wave Oscillator
Abstract:
An electron beam traversing a slow wave structure can be used to either generate or amplify electromagnetic radiation through the interaction of the slow space charge wave on the beam with the slow wave structure modes. Here, a cylindrical waveguide with a periodic array of conducting loops is used for the slow wave structure. This paper considers operation as a backward wave oscillator. The dispersion properties of the structure are determined using a frequency-domain eigenmode solver. The interaction of the electron beam with the structure modes is investigated using a 2-D particle-in-cell (PIC) code. The operating frequency and growth rate dependence on beam energy and beam current are investigated using the PIC code and compared with analytic and scaling estimates where possible.
Autors: Brian R. Poole;John R. Harris;
Appeared in: IEEE Transactions on Plasma Science
Publication date: Jan 2018, volume: 46, issue:1, pages: 25 - 32
Publisher: IEEE
 
» Physical-Layer Security in Multiuser Visible Light Communication Networks
Abstract:
In this paper, we study the physical-layer security in a 3-D multiuser visible light communication (VLC) network. The locations of access points (APs) and mobile users are modeled as two 2-D, independent and homogeneous Poisson point processes at distinct heights. Using mathematical tools from stochastic geometry, we provide a new analytical framework to characterize the secrecy performance in multiuser VLC networks. Closed-form results for the outage probability and the ergodic secrecy rate are derived for networks without AP cooperation. Considering the cooperation among APs, we give tight lower and upper bounds on the secrecy outage probability and the ergodic secrecy rate. To further enhance the secrecy performance at the legitimate user, a disk-shaped secrecy protected zone is implemented in the vicinity of the transmit AP. Based on the obtained results, it is shown that cooperating neighboring APs in a multiuser VLC network can bring performance gains on the secrecy rate, but only to a limited extent. We also show that building an eavesdropper-free protected zone around the AP significantly improves the secrecy performance of legitimate users, which appears to be a promising solution for the design of multiuser VLC networks with high security requirements.
Autors: Liang Yin;Harald Haas;
Appeared in: IEEE Journal on Selected Areas in Communications
Publication date: Jan 2018, volume: 36, issue:1, pages: 162 - 174
Publisher: IEEE
 
» Placement of Fault Current Limiters in a Power System Through a Two-Stage Optimization Approach
Abstract:
With the sustainable growth in the number of new power plants and scale of transmission systems, the probability of the current exceeding the short-circuit rating of circuit breakers increases. A fault current limiter (FCL), which can be used to reduce current surges, has attracted considerable attention from utilities. However, the appropriate placement of FCLs in a power system for obtaining the most effective cost-to-benefit solution is crucial. This paper proposes a two-stage placement approach, where Stage I combines the hierarchical fuzzy logic decision (HFLD) method and Hashing-integrated generic algorithm (HIGA). The HFLD method is used for sorting feasible solutions, and the HIGA determines an optimal FCL placement in the reduced search space. Particle swarm optimization is then employed in Stage II for optimizing the FCL parameters. To verify the effectiveness of the proposed approach in solving the optimal FCL placement problem, the method is verified using the IEEE 30-bus system and system of a manufacturing factory in Taiwan. The numerical results show that the proposed method achieves a favorable solution in a short time with fewer placements of FCLs.
Autors: Hong-Tzer Yang;Wen-Jun Tang;Piotr Roman Lubicki;
Appeared in: IEEE Transactions on Power Systems
Publication date: Jan 2018, volume: 33, issue:1, pages: 131 - 140
Publisher: IEEE
 
» Planar UWB MIMO Antenna With Pattern Diversity and Isolation Improvement for Mobile Platform Based on the Theory of Characteristic Modes
Abstract:
This communication presents a planar ultra-wideband multi-input multi-output antenna with pattern diversity and isolation improvement based on the theory of characteristic modes. The proposed antenna (for new-generation wireless mobile terminals) consists of two ultra-wideband antenna elements—a compact quarter loop and a circular planar monopole located on the opposite edges of a rectangular ground plane. These two antenna elements are able to excite different modes in the ground plane and thus realize the desired diverse radiation patterns and high isolation without any additional decoupling structures. The experimental results show that both antenna elements are ultra-wideband with impedance bandwidths (return losses more than 6 dB for the quarter-loop antenna and more than 10 dB for the circular planar monopole antenna) of 130% (2–9.5 GHz). The isolation is over 20 dB with a peak value of 50 dB. The realized gains are above 1.5 dBi. The total efficiencies are above 70%. The envelope correlation coefficient is less than 0.03 assuming that the antenna operates in an isotropic channel.
Autors: Xing Zhao;Swee Ping Yeo;Ling Chuen Ong;
Appeared in: IEEE Transactions on Antennas and Propagation
Publication date: Jan 2018, volume: 66, issue:1, pages: 420 - 425
Publisher: IEEE
 
» Planarization, Fabrication, and Characterization of Three-Dimensional Magnetic Field Sensors
Abstract:
Nanomagnetism deals with magnetic phenomena in nanoscale structures, involving processes at the atomic level. Magnetic sensors, which exhibit the surprising giant magnetoresistance (GMR) effect, are some of the first real applications of nanotechnology, and have become very important in the last two decades. In addition, high-performance magnetoresistance (MR) measurement is a critical technique in modern electrical applications, including electronic compasses, aviation navigation, motion tracking, noncontact current sensing, rotation sensing, and vehicle detection. Both GMR and tunneling magnetoresistance (TMR) sensors have been used in the state-of-art electronic compasses. A new planar design layout of a vector magnetometer is proposed in this report. It can sense variations in three-dimensional (3-D) magnetic fields. The planarization of a vector magnetometer is carried out with consideration of materials, magnetic schematics, as well as transducer circuit designs. The optimization of an advanced magnetic material for use in GMR and TMR sensors and its planarization in a 3-D design are crucial practical issues. This paper presents an overview of the planarization of vector magnetometers and the development of its applications. It focuses on recent works, covers an analytic model of magnetoresistive sensors, and methods of thin film fabrication. It also addresses the planar vector magnetometer with a flux-guide, the chopping technique, and techniques for microfabrication of substrates. Planarization in magnetic sensors will become increasingly exploited as nanomagnetism grows in importance.
Autors: Van Su Luong;Yu-Hsin Su;Chih-Cheng Lu;Jen-Tzong Jeng;Jen-Hwa Hsu;Ming-Han Liao;Jong-Ching Wu;Meng-Huang Lai;Ching-Ray Chang;
Appeared in: IEEE Transactions on Nanotechnology
Publication date: Jan 2018, volume: 17, issue:1, pages: 11 - 25
Publisher: IEEE
 
» Planning and Control for Collision-Free Cooperative Aerial Transportation
Abstract:
This paper presents planning and control synthesis for multiple aerial manipulators to transport a common object. Each aerial manipulator that consists of a hexacopter and a two-degree-of-freedom robotic arm is controlled by an augmented adaptive sliding mode controller based on a closed-chain robot dynamics. We propose a motion planning algorithm by exploiting rapidly exploring random tree star (RRT*) and dynamic movement primitives (DMPs). The desired path for each aerial manipulator is obtained by using RRT* with Bezier curve, which is designed to handle environmental obstacles, such as buildings or equipments. During aerial transportation, to avoid unknown obstacle, DMPs modify the trajectory based on the virtual leader-follower structure. By the combination of RRT* and DMPs, the cooperative aerial manipulators can carry a common object to keep reducing the interaction force between multiple robots while avoiding an obstacle in the unstructured environment. To validate the proposed planning and control synthesis, two experiments with multiple custom-made aerial manipulators are presented, which involve user-guided trajectory and RRT*-planned trajectory tracking in unstructured environments.
Autors: Hyeonbeom Lee;Hyoin Kim;H. Jin Kim;
Appeared in: IEEE Transactions on Automation Science and Engineering
Publication date: Jan 2018, volume: 15, issue:1, pages: 189 - 201
Publisher: IEEE
 
» Plastic Strain Determination With Nonlinear Ultrasonic Waves Using In Situ Integrated Piezoelectric Ultrasonic Transducers
Abstract:
The detection of plastic deformation of metallic alloy materials with second-harmonic Rayleigh ultrasonic wave is first investigated using direct-write piezoelectric ultrasonic transducers, in which piezoelectric poly(vinylidenefluoride/ trifluoroethylene) [P(VDF/TrFE)] polymer coatings and electrodes are directly deposited, processed, and patterned on the alloy to be evaluated. Rayleigh ultrasonic signals, generated by the direct-write transducers on titanium alloy specimens, are characterized by a laser scanning vibrometer. The results show that acoustic nonlinearity increases with plastic strain, and an increase of ~40% in the acoustic nonlinearity corresponding to a plastic strain of 5.1%. The measurement data and technical features with the use of the direct-write transducers are compared with the conventional discrete angle beam piezoelectric transducer. The results and analyses show that compared with the conventional discrete angle beam piezoelectric transducers, implementation of the direct-write piezoelectric transducers has significant technical advantages and is promising for applications in determining nonlinear ultrasonic waves and plastic strain of structural materials.
Autors: Shifeng Guo;Shuting Chen;Lei Zhang;Yi Fan Chen;Kui Yao;
Appeared in: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Publication date: Jan 2018, volume: 65, issue:1, pages: 95 - 101
Publisher: IEEE
 
» PLRC-FDTD Modeling of General GSTC-Based Dispersive Bianisotropic Metasurfaces
Abstract:
A general bianaisotropic metasurface represented by a generalized sheet transition condition is modeled by the finite-difference time-domain (FDTD) method. The dispersive susceptibilities of the metasurface are approximated by FDTD-compatible rational functions which are incorporated in the update equations by the piecewise linear recursive convolution technique. Compared to the existing methods, the proposed technique requires less arithmetic operations. The method is verified by comparing the results with those of the finite-difference frequency-domain method through simulation of wave propagation in five test cases: generalized refraction metasurface, polarization rotator, Bessel beam generator, orbital angular momentum multiplexer, and reflectionless omega-type metasurface.
Autors: Keyhan Hosseini;Zahra Atlasbaf;
Appeared in: IEEE Transactions on Antennas and Propagation
Publication date: Jan 2018, volume: 66, issue:1, pages: 262 - 270
Publisher: IEEE
 
» PMU-Based Estimation of Dynamic State Jacobian Matrix and Dynamic System State Matrix in Ambient Conditions
Abstract:
In this paper, a hybrid measurement- and model-based method is proposed which can estimate the dynamic state Jacobian matrix and the dynamic system state matrix in near real time utilizing statistical properties extracted from PMU measurements. The proposed method can be used to detect and identify network topology changes that have not been reflected in an assumed network model. Additionally, an application of the estimated system state matrix in online dynamic stability monitoring is presented.
Autors: Xiaozhe Wang;Janusz W. Bialek;Konstantin Turitsyn;
Appeared in: IEEE Transactions on Power Systems
Publication date: Jan 2018, volume: 33, issue:1, pages: 681 - 690
Publisher: IEEE
 
» Podium: Ranking Data Using Mixed-Initiative Visual Analytics
Abstract:
People often rank and order data points as a vital part of making decisions. Multi-attribute ranking systems are a common tool used to make these data-driven decisions. Such systems often take the form of a table-based visualization in which users assign weights to the attributes representing the quantifiable importance of each attribute to a decision, which the system then uses to compute a ranking of the data. However, these systems assume that users are able to quantify their conceptual understanding of how important particular attributes are to a decision. This is not always easy or even possible for users to do. Rather, people often have a more holistic understanding of the data. They form opinions that data point A is better than data point B but do not necessarily know which attributes are important. To address these challenges, we present a visual analytic application to help people rank multi-variate data points. We developed a prototype system, Podium, that allows users to drag rows in the table to rank order data points based on their perception of the relative value of the data. Podium then infers a weighting model using Ranking SVM that satisfies the user's data preferences as closely as possible. Whereas past systems help users understand the relationships between data points based on changes to attribute weights, our approach helps users to understand the attributes that might inform their understanding of the data. We present two usage scenarios to describe some of the potential uses of our proposed technique: (1) understanding which attributes contribute to a user's subjective preferences for data, and (2) deconstructing attributes of importance for existing rankings. Our proposed approach makes powerful machine learning techniques more usable to those who may not have expertise in these areas.
Autors: Emily Wall;Subhajit Das;Ravish Chawla;Bharath Kalidindi;Eli T. Brown;Alex Endert;
Appeared in: IEEE Transactions on Visualization and Computer Graphics
Publication date: Jan 2018, volume: 24, issue:1, pages: 288 - 297
Publisher: IEEE
 
» Point-to-Set Distance Metric Learning on Deep Representations for Visual Tracking
Abstract:
For autonomous driving application, a car shall be able to track objects in the scene in order to estimate where and how they will move such that the tracker embedded in the car can efficiently alert the car for effective collision-avoidance. Traditional discriminative object tracking methods usually train a binary classifier via a support vector machine (SVM) scheme to distinguish the target from its background. Despite demonstrated success, the performance of the SVM-based trackers is limited because the classification is carried out only depending on support vectors (SVs) but the target’s dynamic appearance may look similar to the training samples that have not been selected as SVs, especially when the training samples are not linearly classifiable. In such cases, the tracker may drift to the background and fail to track the target eventually. To address this problem, in this paper, we propose to integrate the point-to-set/ image-to-imageSet distance metric learning (DML) into visual tracking tasks and take full advantage of all the training samples when determining the best target candidate. The point-to-set DML is conducted on convolutional neural network features of the training data extracted from the starting frames. When a new frame comes, target candidates are first projected to the common subspace using the learned mapping functions, and then the candidate having the minimal distance to the target template sets is selected as the tracking result. Extensive experimental results show that even without model update the proposed method is able to achieve favorable performance on challenging image sequences compared with several state-of-the-art trackers.
Autors: Shengping Zhang;Yuankai Qi;Feng Jiang;Xiangyuan Lan;Pong C. Yuen;Huiyu Zhou;
Appeared in: IEEE Transactions on Intelligent Transportation Systems
Publication date: Jan 2018, volume: 19, issue:1, pages: 187 - 198
Publisher: IEEE
 
» Pokemon GO: Where VR and AR Have Gone Since Its Inception
Abstract:
Augmented reality (AR), virtual reality (VR), and mixed reality (MR) are the technologies of the future. At the same time, they remain a bit of a mystery to many people.
Autors: Melina Druga;
Appeared in: IEEE Potentials
Publication date: Jan 2018, volume: 37, issue:1, pages: 23 - 26
Publisher: IEEE
 
» Polarimetric Coherence Pattern: A Visualization and Characterization Tool for PolSAR Data Investigation
Abstract:
Polarimetric coherence, which has the potential to reveal physical properties of scatterers, is an important source for polarimetric synthetic aperture radar (PolSAR) data investigation. Target structure and orientation relative to the PolSAR illumination direction are key factors affecting the polarimetric coherence degree. The relative orientation between a sensor and a target can be adjusted using the rotating processing along the radar’s line of sight. The main idea of this paper is to extend the traditional polarimetric coherence at a given rotation state ( to the rotation domain ( along the radar’s line of sight for hidden information exploration. A visualization and characterization tool named as a polarimetric coherence pattern for two arbitrary polarization channels is proposed and developed. This interpretation tool is able to view the variation of polarimetric coherence in the rotation domain containing rich orientation diversity information which is seldom considered. A set of characterization features are derived to completely describe a polarimetric coherence pattern thereafter. Experimental studies with unmanned aerial vehicle SAR (UAVSAR) PolSAR data over crop areas have validated that polarimetric coherence patterns vary in terms of polarization combinations and crop types. The proposed characterization features show good potential to differentiate polarimetric responses from different land covers. Furthermore, a classification scheme combining the selected proposed features and the commonly used roll-invariant features is developed for quantitative and application investigation. Comparison studies with both UAVSAR and Airborne SAR (AIRSAR) data clearly demonstrate the superiority of the proposed classification to the conventi- nal classification with only roll-invariant features. The overall classification accuracies for the seven and eleven land covers of UAVSAR and AIRSAR data are, respectively, increased from 90.21% and 93.87% to 95.12% and 94.63% by the proposed classification scheme. This paper also demonstrates the importance of and potential for utilizing the complementary advantages of roll-invariant features and the proposed roll-variant features.
Autors: Si-Wei Chen;
Appeared in: IEEE Transactions on Geoscience and Remote Sensing
Publication date: Jan 2018, volume: 56, issue:1, pages: 286 - 297
Publisher: IEEE
 
» Polarization-Maintaining Hollow-Core Photonic Bandgap Few-Mode Fiber in Terahertz Regime
Abstract:
We propose a terahertz (THz) hollow-core photonic bandgap fiber (HC-PBGF) supporting few-mode operation with large birefringence. The periodic arrangement of square lattice with round corners in fiber cladding offers bandgap guidance. Numerical simulation indicates that a 21-cell HC-PBGF could support six vector modes in the bandgap. Characteristics of guided modes are comprehensively investigated, suggesting modal confinement loss of the order of 10−3 cm−1, group velocity dispersion under 1 psTHz−1cm−1, and modal birefringence higher than 10−4 for all modes at around 0.92 THz. Moreover, 24-cell and 32-cell HC-PBGFs are discussed to explore the influence of HC geometry on guided mode number and modal birefringence.
Autors: Han Xiao;Haisu Li;Guobin Ren;Yue Dong;Shiying Xiao;Shuisheng Jian;
Appeared in: IEEE Photonics Technology Letters
Publication date: Jan 2018, volume: 30, issue:2, pages: 185 - 188
Publisher: IEEE
 
» Power Delivery Network Benchmarking for Interposer and Bridge-Chip-Based 2.5-D Integration
Abstract:
In this letter, a power delivery network (PDN) modeling framework for emerging heterogeneous 2.5-D integration platforms is presented. The framework is validated using IBM power grid benchmarks, and maximum relative errors of less than 7.29% and 0.67% for IR-drop and transient noise are shown, respectively. Next, the framework is used to evaluate interposer and bridge-chip-based 2.5-D integration platforms. The simulation results show that an interposer with dense power/ground grids and microbumps can suppress power supply noise (PSN) by a small margin. In bridge-chip-based 2.5-D integration, under the assumption that the bridge-chips underneath the active dice block direct access to package power/ground planes, some PDN considerations are highlighted and evaluated. Using multiple bridge-chips and smaller overlap areas between the bridge-chips and the active dice, the worst case PSN in bridge-chip-based 2.5-D integration is minimally impacted.
Autors: Yang Zhang;Md Obaidul Hossen;Muhannad S. Bakir;
Appeared in: IEEE Electron Device Letters
Publication date: Jan 2018, volume: 39, issue:1, pages: 99 - 102
Publisher: IEEE
 
» Power Takeoff Optimization to Maximize Wave Energy Conversions for Oscillating Water Column Devices
Abstract:
This paper presents an investigation on how to optimize the power takeoffs (PTOs) to maximize the mean wave energy conversion from seas for floating oscillating water column (OWC) devices. For this purpose, the linear air turbine PTOs are first analytically optimized to maximize the mean energy conversion for regular waves, based on which a simple and fast-turnaround assessment method is proposed to optimize the linear PTO damping coefficient for maximizing the mean energy conversion for the given sea states. Further on, the focus is on how we can reliably assess the maximized mean wave energy conversions if the OWCs are equipped with nonlinear air-turbine PTOs, as frequently seen in practical OWC plants. Conventionally, the time-consuming time-domain analysis is employed for searching the optimized nonlinear damping coefficients which may be both wave-height- and wave-period-dependent for the given sea state. This may not be suitable in the early design stages of the device when many different options may be compared and checked for optimizing the device itself. As such, a reliable fast-turnaround assessment is very desirable for the device performance and for the assessment of energy conversion for the sea states in the deployment site. From the examples in the study, it is shown that the OWC wave energy converters with the optimized linear PTOs have the same energy capture capacities as those with optimized nonlinear PTOs. As such, it can be suggested that the OWC wave energy capture capacity can be analyzed using the fast-turnaround frequency-domain analysis, regardless of whether the linear or nonlinear PTO is used in the wave energy converter.
Autors: Wanan Sheng;Anthony Lewis;
Appeared in: IEEE Journal of Oceanic Engineering
Publication date: Jan 2018, volume: 43, issue:1, pages: 36 - 47
Publisher: IEEE
 
» Power to the People?: What It Means to the Changing Energy Landscape [In My View]
Abstract:
Autors: Gerd Schonwalder;
Appeared in: IEEE Power and Energy Magazine
Publication date: Jan 2018, volume: 16, issue:1, pages: 76 - 72
Publisher: IEEE
 
» PPC: Popularity Prediction Caching in ICN
Abstract:
Thriving future network conceives embedding the ubiquitous in-network caching. The fine-grained cache behavior reveals an intimate relationship among contents in the same stream—sequenced contents have similar cache behavior. This letter presents a novel cache replacement method named popularity prediction caching (PPC) for chunk-level cache by discovering the relevance among video chunks in information centric network from the perspective of user watching behavior. PPC predicts and caches the future most popular chunks and evicts those with least future popularity in a linear complexity. Simulations in a GEANT model show that PPC outperforms cache policy based on content popularity, least recently used, least frequently used, and first in first out.
Autors: Yuanzun Zhang;Xiaobin Tan;Weiping Li;
Appeared in: IEEE Communications Letters
Publication date: Jan 2018, volume: 22, issue:1, pages: 5 - 8
Publisher: IEEE
 
» Practical Superdirectivity With Resonant Screened Apertures Motivated by a Poynting Streamlines Analysis
Abstract:
Fundamental limits on the degree of practical achievable superdirectivity for antennas include narrow bandwidth, large antenna loss, and sensitivity to excitation and fabrication errors. Superdirective antennas are commonly considered as transmitters, but thinking of the antenna as a receiver may help to understand and overcome some of these limits on practical superdirectivity. We directly model a superdirective antenna in receive mode by calculating streamlines of Poynting vector field near the receiving antennas. Superdirectivity is achieved by expanding the shape of the effective area beyond the antenna physical aperture area. The degree of superdirectivity is parameterized by an effective area expansion distance. The theory predicts that superdirectivity is practical for electrically small and middle size antennas and electrically large antennas with a large aspect ratio. With this motivation, a superdirective horn antenna with resonant screen structure in front of the antenna aperture is designed and fabricated. The superdirective horn achieves a measured antenna efficiency of 115% over a reasonable bandwidth and with moderate sensitivity to fabrication errors.
Autors: Junming Diao;Karl F. Warnick;
Appeared in: IEEE Transactions on Antennas and Propagation
Publication date: Jan 2018, volume: 66, issue:1, pages: 432 - 437
Publisher: IEEE
 
» Precoded Index Modulation for Multi-Input Multi-Output OFDM
Abstract:
Index modulated orthogonal frequency division multiplexing (IM-OFDM) is a novel multicarrier transmission scheme, which provides considerable performance improvement compared with classical OFDM by conveying information via the active subcarrier indices in conjugation with the constellation symbols. In this paper, we extend the idea of IM-OFDM to multi-input multi-output (MIMO) systems and propose precoded MIMO-OFDM (PIM-MIMO-OFDM). Based on the channel state information at the transmitter, PIM-MIMO-OFDM selects the active elements of the receiver-side space-frequency subblocks via linear precoding. The spectral efficiency enhancement method of in-phase/quadrature index modulation is also employed to construct PIM-MIMO-OFDM with in-phase quadrature modulation by selecting the active space-frequency elements in the in-phase and quadrature components of the constellation symbol. Thanks to the carefully designed precoding, the co-channel interference among received antennas can be completely eliminated. Consequently, low-complexity maximum likelihood and suboptimal detectors are devised with linear detection complexity. Both analytical and numerical results show that, with the help of precoding, PIM-MIMO-OFDM can achieve better bit error rateperformance than traditional precoded MIMO-OFDM (P-MIMO-OFDM) in various system configurations. In addition, the spectral efficiency can be also enhanced compared with the P-MIMO-OFDM under certain configurations.
Autors: Shijian Gao;Meng Zhang;Xiang Cheng;
Appeared in: IEEE Transactions on Wireless Communications
Publication date: Jan 2018, volume: 17, issue:1, pages: 17 - 28
Publisher: IEEE
 
» Predicting Locations of High-Risk Plaques in Coronary Arteries in Patients Receiving Statin Therapy
Abstract:
Features of high-risk coronary artery plaques prone to major adverse cardiac events (MACE) were identified by intravascular ultrasound (IVUS) virtual histology (VH). These plaque features are: thin-cap fibroatheroma (TCFA), plaque burden PB ≥ 70%, or minimal luminal area MLA ≤ 4 mm2. Identification of arterial locations likely to later develop such high-risk plaques may help prevent MACE. We report a machine learning method for prediction of future high-risk coronary plaque locations and types in patients under statin therapy. Sixty-one patients with stable angina on statin therapy underwent baseline and one-year follow-up VH-IVUS non-culprit vessel examinations followed by quantitative image analysis. For each segmented and registered VH-IVUS frame pair (), location-specific ( mm) vascular features and demographic information at baseline were identified. Seven independent support vector machine classifiers with seven different feature subsets were trained to predict high-risk plaque types one year later. A leave-one-patient-out cross-validation was used to evaluate the prediction power of different feature subsets. The experimental results showed that our machine learning method predicted future TCFA with correctness of 85.9%, 81.7%, and 77.0% (G-mean) for baseline plaque phenotypes of TCFA, thick-cap fibroatheroma, and non-fibroatheroma, respectively. For predicting PB ≥ 70%, correctness was 80.8% for baseline PB ≥ 70% and 85.6% for 50% ≤ PB < 70%. Accuracy of predicted MLA ≤- 4 mm2 was 81.6% for baseline MLA ≤ 4 mm2 and 80.2% for 4 mm2 < MLA ≤ 6 mm2. Location-specific prediction of future high-risk coronary artery plaques is feasible through machine learning using focal vascular features and demographic variables. Our approach outperforms previously reported results and shows the importance of local factors on high-risk coronary artery plaque development.
Autors: Ling Zhang;Andreas Wahle;Zhi Chen;John J. Lopez;Tomas Kovarnik;Milan Sonka;
Appeared in: IEEE Transactions on Medical Imaging
Publication date: Jan 2018, volume: 37, issue:1, pages: 151 - 161
Publisher: IEEE
 
» Prediction of Moisture Loss in Withering Process of Tea Manufacturing Using Artificial Neural Network
Abstract:
The first and foremost process in tea manufacturing, withering, is the foundation for producing good quality. Moisture plays an important role in the manufacturing process of tea to get the desired quality. In this paper, a novel in situ instrumentation technique is proposed and validated experimentally for prediction of moisture loss (ML) in the withering process. In the proposed technique, ML is predicted based on the inlet and the outlet relative humidity (RH) and temperature during the process of withering. Network capable smart sensor nodes are developed for the measurement of RH and temperature at the inlet and outlet of the withering trough. Architecture of the nodes and network is described. A scaled-down prototype of an enclosed trough is developed to perform withering of tea leaves. Based on the data measured by the system, ML is predicted by using artificial neural network. Nonlinear autoregressive model with exogenous inputs is used for predicting the ML. The predicted ML is compared with the actual amount of ML measured by weight loss. A total of nine experiments are conducted for nine batches of tea leaves. The data collection, their analysis and results are reported in this paper. The observed result shows a good agreement between the predicted and actual ML. The maximum mean error in prediction is −3.6%.
Autors: Nipan Das;Kunjalata Kalita;P K Boruah;Utpal Sarma;
Appeared in: IEEE Transactions on Instrumentation and Measurement
Publication date: Jan 2018, volume: 67, issue:1, pages: 175 - 184
Publisher: IEEE
 
» Preface: Message from the VIS Paper Chairs and Guest Editors
Abstract:
EditorsThis January 2018 issue of the IEEE Transactions on Visualization and Computer Graphics contains the proceedings of IEEE VIS 2017, held during 1-6 October 2017. In 2017, IEEE VIS returns to the city of Phoenix, AZ, USA, for the conference's 28th year. The conference will be held at the Hyatt Regency Phoenix hotel. VIS consists of three conferences, held concurrently: the IEEE Visual Analytics Science and Technology Conference (VAST 2017), the IEEE Information Visualization Conference (InfoVis 2017), and the IEEE Scientific Visualization Conference (SciVis 2017). Information on the paper review process is provided along with an overview of each conference.
Autors: Tim Dwyer;Niklas Elmqvist;Brian Fisher;Steve Franconeri;Ingrid Hotz;Robert M. Mike Kirby;Shixia Liu;Tobias Schreck;Xiaoru Yuan;
Appeared in: IEEE Transactions on Visualization and Computer Graphics
Publication date: Jan 2018, volume: 24, issue:1, pages: xi - xv
Publisher: IEEE
 
» Prefetch-Based Energy Optimization on Smartphones
Abstract:
Cellular network enables pervasive data access, but it also increases the power consumption of smartphones due to the long tail problem, where the cellular interface has to stay in the high-power state for some time after each data transmission. To reduce the tail energy, data that will be used in the future can be prefetched. However, prefetching unnecessary data may waste energy, and this problem becomes worse when the network quality is poor. In this paper, we generalize and formulate the prefetch-based energy optimization problem, where the goal is to find a prefetching schedule that minimizes the energy consumption of the data transmissions under the current network condition. To solve this nonlinear optimization problem, we first propose a greedy algorithm, and then propose a discrete algorithm with better performance. We have implemented and evaluated the proposed algorithms in two apps: in-app advertising and mobile video streaming. Evaluation results show that the proposed algorithms can significantly reduce the energy consumption.
Autors: Yi Yang;Guohong Cao;
Appeared in: IEEE Transactions on Wireless Communications
Publication date: Jan 2018, volume: 17, issue:1, pages: 693 - 706
Publisher: IEEE
 
» Priming and Anchoring Effects in Visualization
Abstract:
We investigate priming and anchoring effects on perceptual tasks in visualization. Priming or anchoring effects depict the phenomena that a stimulus might influence subsequent human judgments on a perceptual level, or on a cognitive level by providing a frame of reference. Using visual class separability in scatterplots as an example task, we performed a set of five studies to investigate the potential existence of priming and anchoring effects. Our findings show that—under certain circumstances—such effects indeed exist. In other words, humans judge class separability of the same scatterplot differently depending on the scatterplot(s) they have seen before. These findings inform future work on better understanding and more accurately modeling human perception of visual patterns.
Autors: André Calero Valdez;Martina Ziefle;Michael Sedlmair;
Appeared in: IEEE Transactions on Visualization and Computer Graphics
Publication date: Jan 2018, volume: 24, issue:1, pages: 584 - 594
Publisher: IEEE
 
» Privacy and Integrity Considerations in Hyperconnected Autonomous Vehicles
Abstract:
The rapid advances in technology can be witnessed in the emergence of cyber–physical systems that pertain to several domains of our society. In transportation, we see the emergence of self-driving vehicles that utilize a multitude of sensors and intelligent learning techniques to navigate autonomously. Such vehicles are complex cyber–physical systems that are mobile and due to their sensor and intrinsic intelligence are able to collect, analyze, and capitalize upon an unprecedented amount of fine-grained data, as well as collaborate in real time with multiple stakeholders. Although such rich data can play a key role in data-driven economies of scale, this raises questions with respect to privacy- and integrity-dependent scenarios. In this work, the feasibility of ensuring integrity, and hence safety, while preserving privacy in the emerging hyperconnected vehicle scenarios is discussed. An exemplary case study on real-time vehicle interactions pertaining to map updates exemplifies the combination of privacy-enhancing technologies with integrity-protecting mechanisms.
Autors: Stamatis Karnouskos;Florian Kerschbaum;
Appeared in: Proceedings of the IEEE
Publication date: Jan 2018, volume: 106, issue:1, pages: 160 - 170
Publisher: IEEE
 
» Probabilistic Forecast for Multiple Wind Farms Based on Regular Vine Copulas
Abstract:
The uncertain nature of wind power causes difficulties in power system operation scheduling. Probabilistic descriptions of the uncertainty have been studied for decades. However, probabilistic forecasts designed for the regional multiple wind farms are few. Although the traditional methods for the single wind farm can still be used, they have the limitations in capturing the spatial correlations among wind farms, and they are less robust when multivariate observations are not so complete. To improve the forecast quality in this case, we combine the multivariate distribution modeling and probabilistic forecasts in this paper. An advanced model—the regular vine copula, which can describe the wind farms’ dependence structure precisely and flexibly with various bivariate copulas as blocks, is used in this paper. Enough simulation data can be generated from the model, which can be easily used to form the conditional forecast distributions under multiple forecast conditions. A case of 10 wind farms in East China has been used to compare the proposed method with its competitors. The results showed the method's advantages of providing reliable and sharp forecast intervals, especially in the case with limited observations available.
Autors: Zhao Wang;Weisheng Wang;Chun Liu;Zheng Wang;Yunhe Hou;
Appeared in: IEEE Transactions on Power Systems
Publication date: Jan 2018, volume: 33, issue:1, pages: 578 - 589
Publisher: IEEE
 
» Probabilistic Framework for Online Identification of Dynamic Behavior of Power Systems With Renewable Generation
Abstract:
The paper introduces a probabilistic framework for online identification of post fault dynamic behavior of power systems with renewable generation. The framework is based on decision trees and hierarchical clustering and incorporates uncertainties associated with network operating conditions, topology changes, faults, and renewable generation. In addition to identifying unstable generator groups, the developed clustering methodology also facilitates identification of the sequence in which the groups lose synchronism. The framework is illustrated on a modified version of the IEEE 68 bus test network incorporating significant portion of renewable generation.
Autors: Panagiotis N. Papadopoulos;Tingyan Guo;Jovica V. Milanović;
Appeared in: IEEE Transactions on Power Systems
Publication date: Jan 2018, volume: 33, issue:1, pages: 45 - 54
Publisher: IEEE
 
» Probabilistic Threat Detection for Risk Management in Cyber-physical Medical Systems
Abstract:
Medical devices are complex cyber-physical systems incorporating emergent hardware and software components. However, this complexity leads to a wide attack surface posing security risks and vulnerabilities. Mitigation and management of such risks during premarket design and postmarket deployment are required. Dynamically mitigating threat potential in the presence of unknown vulnerabilities requires an adaptive risk-based scheme to assess the system’s state, a secure system architecture that can isolate hardware and software components, and design methods that can adaptively adjust the system’s topology based on risk changes. The essential complementary aspects during deployment are detecting, characterizing, and quantifying security threats. This article presents a dynamic risk management and mitigation approach based on probabilistic threat estimation. A smart-connected-pacemaker case study illustrates the approach. This article is part of a special issue on Software Safety and Security Risk Mitigation in Cyber-physical Systems.
Autors: Aakarsh Rao;Nadir Carreón;Roman Lysecky;Jerzy Rozenblit;
Appeared in: IEEE Software
Publication date: Jan 2018, volume: 35, issue:1, pages: 38 - 43
Publisher: IEEE
 
» Progressive Learning of Topic Modeling Parameters: A Visual Analytics Framework
Abstract:
Topic modeling algorithms are widely used to analyze the thematic composition of text corpora but remain difficult to interpret and adjust. Addressing these limitations, we present a modular visual analytics framework, tackling the understandability and adaptability of topic models through a user-driven reinforcement learning process which does not require a deep understanding of the underlying topic modeling algorithms. Given a document corpus, our approach initializes two algorithm configurations based on a parameter space analysis that enhances document separability. We abstract the model complexity in an interactive visual workspace for exploring the automatic matching results of two models, investigating topic summaries, analyzing parameter distributions, and reviewing documents. The main contribution of our work is an iterative decision-making technique in which users provide a document-based relevance feedback that allows the framework to converge to a user-endorsed topic distribution. We also report feedback from a two-stage study which shows that our technique results in topic model quality improvements on two independent measures.
Autors: Mennatallah El-Assady;Rita Sevastjanova;Fabian Sperrle;Daniel Keim;Christopher Collins;
Appeared in: IEEE Transactions on Visualization and Computer Graphics
Publication date: Jan 2018, volume: 24, issue:1, pages: 382 - 391
Publisher: IEEE
 
» PtSe2 Field-Effect Transistors: New Opportunities for Electronic Devices
Abstract:
PtSe2, a new family of transition metal dichalcogenides, has been explored for electronic device applications using density functional theory and non-equilibrium Green’s function within the third nearest neighbor tight-binding approximation. Interestingly, despite its small effective mass ( as low as ; being electron rest mass), PtSe2 has large density of states due to its unique six-valley conduction band within the first Brillouin zone, unlike MoX2 family. This has direct impacts on the device characteristics of PtSe2 field-effect transistors, resulting in superior on-state performance (30% higher on current and transconductance) as compared with the MoSe2 counterpart. Our simulation shows that the PtSe2 device with a channel longer than 15 nm exhibits near-ideal subthreshold swing, and sub-100 mV/V of drain-induced barrier lowering can be achieved with an aggressively scaled gate oxide, demonstrating new opportunities for electronic devices with novel PtSe2.
Autors: AbdulAziz AlMutairi;Demin Yin;Youngki Yoon;
Appeared in: IEEE Electron Device Letters
Publication date: Jan 2018, volume: 39, issue:1, pages: 151 - 154
Publisher: IEEE
 
» Pulsed Vertical Dipole Response of a Thin Sheet With High-Contrast Dielectric and Conductive Properties
Abstract:
The 3-D time-domain Green’s function (GF) for the vector potential excited by a transient vertical electric dipole in the presence of a thin sheet with high-contrast dielectric and conductive properties is derived using a modified Cagniard–de Hoop approach. The resulting expression involves the numerical evaluation of a 2-D integral over a finite integration domain, computationally much less expensive than the direct numerical evaluation of the inverse Laplace/Hankel transform of the relevant spectral-domain GF. Expressions for the transient electromagnetic fields can thus be obtained, and numerical results are provided, which illustrate their salient features and validate the proposed formulation.
Autors: Paolo Burghignoli;Giampiero Lovat;Rodolfo Araneo;Salvatore Celozzi;
Appeared in: IEEE Transactions on Antennas and Propagation
Publication date: Jan 2018, volume: 66, issue:1, pages: 217 - 225
Publisher: IEEE
 
» qSwitch: Dynamical Off-Chip Bandwidth Allocation Between Local and Remote Accesses
Abstract:
Multisocket computer systems are popular in workstations and servers. However, they suffer from the relatively low bandwidth of intersocket communication especially for massive parallel workloads that generate many intersocket requests for synchronizations and remote memory accesses. Intersocket traffic puts pressure on the underlying network connecting all processors with a limited bandwidth confined by pin resources. Given this constraint, we propose to dynamically increase the intersocket bandwidth by sacrificing off-chip memory bandwidth when systems have heavy intersocket communication but few off-chip memory accesses. Our design increases the physical bandwidth for intersocket communication via switching the function of pins from off-chip memory accesses to intersocket communication and can achieve an average performance speedup of 1.28 in geocentric mean for selected parallel multithreaded benchmarks.
Autors: Shaoming Chen;Lu Peng;Samuel Irving;Zhou Zhao;Weihua Zhang;Ashok Srivastava;
Appeared in: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems
Publication date: Jan 2018, volume: 37, issue:1, pages: 75 - 87
Publisher: IEEE
 
» Quality of Experience in a Stereoscopic Multiview Environment
Abstract:
In this paper, we investigate how visualization factors, such as disparity, mobility, angular resolution, and viewpoint interpolation, influence the quality of experience (QoE) in a stereoscopic multiview environment. In order to do so, we set up a dedicated testing room and conducted subjective experiments. We also developed a framework that emulates a supermultiview environment. This framework can be used to investigate and assess the effects of angular resolution and viewpoint interpolation on the QoE produced by multiview systems, and provide relevant cues as to how the baselines of cameras and interpolation strategies in such systems affect user experience. Aspects such as visual comfort, model fluidity, sense of immersion, and the three-dimensional (3D) experience as a whole have been assessed for several test cases. Obtained results suggest that user experience in an motion parallax environment is not as critically influenced by configuration parameters such as disparity as initially thought. In addition, extensive subjective tests have indicated that while users are very sensitive to angular resolution in multiview 3D systems, this sensitivity tends not to be as critical when a user is performing a task that involves a great amount of interaction with the multiview content. These tests have also indicated that interpolating intermediate viewpoints can be effective in reducing the required view density without degrading the perceived QoE.
Autors: Felipe M. L. Ribeiro;José F. L. de Oliveira;Alexandre G. Ciancio;Eduardo A. B. da Silva;Cássius R. D. Estrada;Luiz G. C. Tavares;Jonathan N. Gois;Amir Said;Marcela C. Martelotte;
Appeared in: IEEE Transactions on Multimedia
Publication date: Jan 2018, volume: 20, issue:1, pages: 1 - 14
Publisher: IEEE
 
» Quality-Balanced User Clustering Schemes for Non-Orthogonal Multiple Access Systems
Abstract:
Non-orthogonal multiple access (NOMA) is a promising technology aimed at improving the bandwidth efficiency of wireless transmissions. In this letter, we focus on the optimization of user clustering and power allocation for an NOMA system under a service rate constraint, where the goal is to maximize the total sum rate. Based on the optimal power allocation in a cluster, we propose a suboptimal solution—the quality-balanced clustering approach to optimize the total sum rate in a system. According to the simulations, the proposed user clustering and power allocation schemes can achieve the maximum total sum rate obtained via exhaustive search optimization. The proposed schemes have very low computational complexity, and thus are suitable for real-time NOMA transmissions.
Autors: Yuh-Ren Tsai;Hsuan-An Wei;
Appeared in: IEEE Communications Letters
Publication date: Jan 2018, volume: 22, issue:1, pages: 113 - 116
Publisher: IEEE
 
» Queueing Stability and CSI Probing of a TDD Wireless Network With Interference Alignment
Abstract:
This paper characterizes the performance in terms of queueing stability of a network composed of multiple MIMO transmitter-receiver pairs taking into account the dynamic traffic pattern and the probing/feedback cost. We adopt a centralized scheduling scheme that selects a number of active pairs in each time-slot. We consider that the transmitters apply interference alignment (IA) technique if two or more pairs are active, whereas in the special case where one pair is active point-to-point MIMO singular value decomposition (SVD) is used. We consider a time-division duplex (TDD) system where transmitters acquire their channel state information (CSI) by decoding the pilot sequences sent by the receivers. Since global CSI knowledge is required for IA, the transmitters have also to exchange their estimated CSIs over a backhaul of limited capacity (i.e. imperfect case). Under this setting, we characterize in this paper the stability region of the system under both the imperfect and perfect (i.e. unlimited backhaul) cases, then we examine the gap between these two resulting regions. Further, under each case we provide a centralized probing policy that achieves the max stability region. These stability regions and scheduling policies are given for the symmetric system, where all the path loss coefficients are equal to each other, as well as for the general system. For the symmetric system, we provide the conditions under which IA yields a queueing stability gain compared to SVD. Under the general system, the adopted scheduling policy is of a high computational complexity for moderate numbers of pairs, consequently we propose an approximate policy that has a reduced complexity but that achieves only a fraction of the system stability region. A characterization of this fraction is provided.
Autors: Matha Deghel;Mohamad Assaad;Mérouane Debbah;Anthony Ephremides;
Appeared in: IEEE Transactions on Information Theory
Publication date: Jan 2018, volume: 64, issue:1, pages: 547 - 576
Publisher: IEEE
 
» R-FFAST: A Robust Sub-Linear Time Algorithm for Computing a Sparse DFT
Abstract:
The fast Fourier transform is the most efficiently known way to compute the discrete Fourier transform (DFT) of an arbitrary -length signal, and has a computational complexity of . If the DFT of the signal has only non-zero coefficients (where ), can we do better? We addressed this question and presented a novel fast Fourier aliasing-based sparse transform (FFAST) algorithm that cleverly induces sparse-graph alias codes in the DFT domain, via a Chinese-remainder-theorem-guided sub-sampling operation in the time-domain. The induced sparse-graph alias codes are then exploited to devise a fast and iterative onion-peeling style decoder that computes -sparse DFT of an -length signal using only time-domain samples and computations. In this paper, we generalize the FFAST framework by Pawar and Ramchandran to the noisy setting where the time-domain samples are corrupted by white Gaussian noise. We show that the noise-robust R-FFAST algorithm computes a -sparse DFT of an -length signal using noise-corrupted time-domain samples in complexity, i.e., sub-linear sample and time complexity. In Section IX, we provide extensive simulation results validating the empirical performance of the R-FFAST algorithm, e.g., we show that the R-FFAST algorithm computes a 50-sparse DFT of an ≈ 10 million length signal using only 4800 noisy samples with an effective signal-to-noise ratio of 5 dB. We also provide comparison of the run-time performance of several existing sparse Fourier transform implementations with that of the R-FFAST and show that it is almost 20 times faster, for comparable settings, than the state-of-the-art algorithm, while simultaneously providing better support recovery guarantees. While our theoretical results are for signals with a uniformly random support of the non-zero DFT coefficients and additive white Gaussian noise, we provide simulation results, which demonstrate that the R-FFAST algorithm performs well even for signals like magnetic resonance images, that have an approximately sparse Fourier spectrum with a non-uniform support for the dominant DFT coefficients.
Autors: Sameer Pawar;Kannan Ramchandran;
Appeared in: IEEE Transactions on Information Theory
Publication date: Jan 2018, volume: 64, issue:1, pages: 451 - 466
Publisher: IEEE
 
» Radar Image-Based Positioning for USV Under GPS Denial Environment
Abstract:
Unmanned surface vehicle (USV) is an important application of unmanned systems, and these USVs provide safe and secure operation in hostile environments. But these USVs are highly reliant on their positioning system, such as global position system (GPS), and loss of positioning information from GPS can cause catastrophe. To overcome this positioning challenge for a USV under a GPS denial environment, we propose a real-time positioning algorithm based on radar and satellite images to determine the USV position. The algorithm takes coastline as a registration feature to implement an image registration between a horizontal viewing angle image from a radar and a vertical viewing angle image from a satellite. The contributions of this paper consist of two parts. First, a coastline feature extraction method based on edge gray features for both radar and satellite images is provided. Second, a high-efficiency image registration method, which takes the dimensionality reduction distance as an indicator, was proposed for the USV embedded system. The results from six typical application scenarios show that the maximum positioning error of the proposed algorithm is 28.02 m under the worst case. A continuous positioning experiment shows that the average error of the algorithm is 9.77 m, which indicates that the algorithm can meet the positioning requirements of a USV under GPS denial environment.
Autors: Hongjie Ma;Edward Smart;Adeel Ahmed;David Brown;
Appeared in: IEEE Transactions on Intelligent Transportation Systems
Publication date: Jan 2018, volume: 19, issue:1, pages: 72 - 80
Publisher: IEEE
 
» Radial Velocity Retrieval for Multichannel SAR Moving Targets With Time–Space Doppler Deambiguity
Abstract:
In this paper, with respect to multichannel synthetic aperture radar (SAR), we first formulate the problems of Doppler ambiguities on the radial velocity (RV) estimation of a ground moving target in the range-compressed domain, the range-Doppler domain, and the image domain, respectively. It is revealed that in these problems, the cascaded time–space Doppler ambiguity (CTSDA) may arise; that is, the time domain Doppler ambiguity in each channel arises first and then the spatial domain Doppler ambiguity among multichannels arises second. Accordingly, the multichannel SAR systems with different parameters are investigated in three cases with different Doppler ambiguity properties. Then, a multifrequency SAR is proposed for the RV estimation by solving the ambiguity problem based on the Chinese remainder theorem (CRT). In the first two cases, the ambiguity problem can be solved by the existing closed-form robust CRT. In the third case, it is found that the problem is different from the conventional CRT problem and we call it a double remaindering problem in this paper. We then propose a sufficient condition under which the double remaindering problem, i.e., the CTSDA, can also be solved by the closed-form robust CRT. When the sufficient condition is not satisfied, a searching-based method is proposed. Finally, some results of numerical experiments are provided to demonstrate the effectiveness of the proposed methods.
Autors: Jia Xu;Zu-Zhen Huang;Zhi-Rui Wang;Li Xiao;Xiang-Gen Xia;Teng Long;
Appeared in: IEEE Transactions on Geoscience and Remote Sensing
Publication date: Jan 2018, volume: 56, issue:1, pages: 35 - 48
Publisher: IEEE
 
» Radiation of a Charge Intersecting a Boundary Between a Bilayer Area and a Homogeneous One in a Circular Waveguide
Abstract:
This paper is devoted to the analysis of electromagnetic field excited by a charge moving in a circular waveguide, which consists of two semi-infinite parts. The charge moves with a constant velocity along the waveguide axis from the partially dielectric section into the homogeneous one. It is assumed that Cherenkov radiation is generated in the bilayer section. The total field is represented as a sum of a known forced field that is the field of the charge in the infinite regular waveguide and a free field resulting from the presence of the transverse boundary. The infinite system of algebraic equations for amplitudes of the free-field modes is derived. The further analysis is conducted using numerical calculations. Special attention is given to the study of the so-called Cherenkov-transition radiation (CTR) within the homogeneous part of the waveguide volume. Typical distributions of CTR over frequencies and modes are presented for the case when the channel and the homogeneous area are free of medium. Analytical results obtained for the point charge are generalized for the charged bunch with an arbitrary profile and verified using direct simulations for the case of Gaussian bunch.
Autors: Aleksandra A. Grigoreva;Andrey V. Tyukhtin;Viktor V. Vorobev;Sergey Antipov;
Appeared in: IEEE Transactions on Microwave Theory and Techniques
Publication date: Jan 2018, volume: 66, issue:1, pages: 49 - 55
Publisher: IEEE
 
» Radio Frequency Interference Suppression Algorithm in Spatial Domain for Compact High-Frequency Radar
Abstract:
High-frequency (HF) ground wave radar is an important tool for sea state measurement and low-altitude target detection. Dense radio frequency interference (RFI) in the HF band inhibits the extraction of sea state parameters and degrades the performance of radar. Though many interference suppression methods based on large arrays have been proposed, most of them are weak to deal with the interference in small-aperture radar. In this letter, a spatial subspace method is proposed to suppress RFI, which uses two crossed-loop/monopole antennas to construct interference subspace at the reserved range bins and projects the echoes onto its orthogonal subspace at the interested range bins. The processed results of measured data from OSMAR-SD verify the high performance of this algorithm for dense RFI suppression. Apart from that, the data utilization ratio and the accuracy of estimating wave height are both improved significantly after the RFI suppression.
Autors: Zhen Tian;Biyang Wen;Lijie Jin;Yingwei Tian;
Appeared in: IEEE Geoscience and Remote Sensing Letters
Publication date: Jan 2018, volume: 15, issue:1, pages: 102 - 106
Publisher: IEEE
 
» Radio Map Interpolation Using Graph Signal Processing
Abstract:
Interpolating a radio map is a problem of great relevance in many scenarios such as network planning, network optimization, and localization. In this letter, such a problem is tackled by leveraging recent results from the emerging field of signal processing on graphs. A technique for interpolating graph structured data is adapted to the problem at hand by using different graph creation strategies, including ones that explicitly consider NLOS propagation conditions. Extensive experiments in a realistic large-scale urban scenario demonstrate that the proposed technique outperforms other traditional methods, such as IDW, RBF, and model-based interpolation.
Autors: Alessandro Enrico Cesare Redondi;
Appeared in: IEEE Communications Letters
Publication date: Jan 2018, volume: 22, issue:1, pages: 153 - 156
Publisher: IEEE
 
» Random Forest Ensembles and Extended Multiextinction Profiles for Hyperspectral Image Classification
Abstract:
Classification techniques for hyperspectral images based on random forest (RF) ensembles and extended multiextinction profiles (EMEPs) are proposed as a means of improving performance. To this end, five strategies—bagging, boosting, random subspace, rotation-based, and boosted rotation-based—are used to construct the RF ensembles. EPs, which are based on an extrema-oriented connected filtering technique, are applied to the images associated with the first informative components extracted by independent component analysis, leading to a set of EMEPs. The effectiveness of the proposed method is investigated on two benchmark hyperspectral images: the University of Pavia and Indian Pines. Comparative experimental evaluations reveal the superior performance of the proposed methods, especially those employing rotation-based and boosted rotation-based approaches. An additional advantage is that the CPU processing time is acceptable.
Autors: Junshi Xia;Pedram Ghamisi;Naoto Yokoya;Akira Iwasaki;
Appeared in: IEEE Transactions on Geoscience and Remote Sensing
Publication date: Jan 2018, volume: 56, issue:1, pages: 202 - 216
Publisher: IEEE
 
» Random Number Generation Based on Ferroelectric Switching
Abstract:
Hafnium oxide-based ferroelectric field-effect transistors (FeFETs) have a great potential for fast nonvolatile memory due to their high performance, fully CMOS compatible integration, and low-power operation. The aggressive scaling of these devices has revealed novel features, such as the multilevel storage capability and abrupt switching, which, however, appears to be a stochastic process. In this letter, we propose a path for true random number generation based on the statistical switching in a single FeFET device. It relies on an inherent randomness of the polarization reversal of ferroelectric domains in the gate stack. The bit sequence is generated by repeatedly programming an FeFET at a calibrated voltage and pulse width, and features random and equiprobable “ones” and “zeros,” which are separated by orders of magnitude in drain current. This simple yet reliable operation provides a compact one-transistor solution for the unbiased random number generation.
Autors: Halid Mulaosmanovic;Thomas Mikolajick;Stefan Slesazeck;
Appeared in: IEEE Electron Device Letters
Publication date: Jan 2018, volume: 39, issue:1, pages: 135 - 138
Publisher: IEEE
 
» Random Regular Graph and Generalized De Bruijn Graph with $k$ -Shortest Path Routing
Abstract:
The Random regular graph (RRG) has recently been proposed as an interconnect topology for future large scale data centers and HPC clusters. An RRG is a special case of directed regular graph (DRG) where each link is unidirectional and all nodes have the same number of incoming and outgoing links. In this work, we establish bounds for DRGs on diameter, average -shortest path length, and a load balancing property with -shortest path routing, and use these bounds to evaluate RRGs. The results indicate that an RRG with -shortest path routing is not ideal in terms of diameter and load balancing. We further consider the Generalized De Bruijn Graph (GDBG), a deterministic DRG, and prove that for most network configurations, a GDBG is near optimal in terms of diameter, average -shortest path length, and load balancing with a -shortest path routing scheme. Finally, we use modeling and simulation to exploit the strengths and weaknesses of RRGs for different traffic conditions by comparing RRGs with GDBGs.
Autors: Peyman Faizian;Md Atiqul Mollah;Xin Yuan;Zaid Alzaid;Scott Pakin;Michael Lang;
Appeared in: IEEE Transactions on Parallel and Distributed Systems
Publication date: Jan 2018, volume: 29, issue:1, pages: 144 - 155
Publisher: IEEE
 
» Range Mapping—A Fresh Approach to High Accuracy Mitchell-Based Logarithmic Conversion Circuit Design
Abstract:
A high accuracy Mitchell-based logarithmic conversion method for integrated circuit design is presented in this paper. A novel technique named range mapping is proposed to perform the conversion with a fresh approach that compresses the range of approximation to smaller than one-third of the range of the Mitchell fraction . After mapping, the compressed range possesses three favorable properties. Specifically, the compressed range is smaller, and has smaller gradient variation and fewer Mitchell fractions. All the three properties facilitate accuracy improvement when a four-region piecewise linear approximation is subsequently developed and applied on the compressed range. With the proposed method, the maximum absolute error and maximum absolute error percentage are improved by 15% and 25%, respectively, when compared with the best existing results by Kim et al. and De Caro et al., respectively. The proposed design is implemented in STM 90-nm CMOS technology, and its performance evaluated and compared with the well-known Mitchell-based methods.
Autors: Joshua Yung Lih Low;Ching Chuen Jong;
Appeared in: IEEE Transactions on Circuits and Systems I: Regular Papers
Publication date: Jan 2018, volume: 65, issue:1, pages: 175 - 184
Publisher: IEEE
 
» Rapid Calculation of Max-Min Fair Rates for Multi-Commodity Flows in Fat-Tree Networks
Abstract:
Max-min fairness is often used in the performance modeling of interconnection networks. Existing methods to compute max-min fair rates for multi-commodity flows have high complexity and are computationally infeasible for large networks. In this work, we show that by considering topological features, this problem can be solved efficiently for the fat-tree topology that is widely used in data centers and high performance compute clusters. Several efficient new algorithms are developed for this problem, including a parallel algorithm that can take advantage of multi-core and shared-memory architectures. Using these algorithms, we demonstrate that it is possible to find the max-min fair rate allocation for multi-commodity flows in fat-tree networks that support tens of thousands of nodes. We evaluate the run-time performance of the proposed algorithms and show improvement in orders of magnitude over the previously best known method. We further demonstrate a new application of max-min fair rate allocation that is only computationally feasible using our new algorithms.
Autors: Md Atiqul Mollah;Xin Yuan;Scott Pakin;Michael Lang;
Appeared in: IEEE Transactions on Parallel and Distributed Systems
Publication date: Jan 2018, volume: 29, issue:1, pages: 156 - 168
Publisher: IEEE
 
» Raypath Separation With a High-Resolution Algorithm in a Shallow-Water Waveguide
Abstract:
One intriguing property that is exploited by ocean acoustic tomography (OAT) is that acoustic signals travel in a multipath. As the first step of OAT, each raypath should be identified with a particular travel time. However, the set of multipath rays generated by an emitted signal is correlated or coherent, as they are produced by reflection and or by refraction in propagation. In this paper, a high-resolution method called smoothing multiple signal classification active large band (MUSICAL) is presented in the context of shallow-water OAT for separating coherent or fully correlated raypaths in the direction-of-arrival temporal domain. The method is a combination of the MUSICAL and spatial-frequency smoothing processing. Furthermore, the performance of smoothing-MUSICAL is illustrated by experiments based on both synthetic data and real data. This algorithm largely improves separation performances and presents fewer artifacts compared with conventional beamforming. In particular, experimental results show that smoothing-MUSICAL is more robust than beamforming facing a noisy environment with moderate signal-to-noise ratio.
Autors: Longyu Jiang;Philippe Roux;Jérôme I. Mars;
Appeared in: IEEE Journal of Oceanic Engineering
Publication date: Jan 2018, volume: 43, issue:1, pages: 119 - 130
Publisher: IEEE
 
» Real-Time Dispersion Code Multiple Access for High-Speed Wireless Communications
Abstract:
We model, demonstrate, and characterize dispersion code multiple access (DCMA), and hence, show the applicability of this purely analog and real-time multiple access scheme to high-speed wireless communications. We first mathematically describe DCMA and show the appropriateness of Chebyshev dispersion coding in this technology. We next provide an experimental proof-of-concept in a DCMA system. Finally, we statistically characterize DCMA in terms of bandwidth, dispersive group delay swing, system dimension, and signal-to-noise ratio.
Autors: Lianfeng Zou;Shulabh Gupta;Christophe Caloz;
Appeared in: IEEE Transactions on Wireless Communications
Publication date: Jan 2018, volume: 17, issue:1, pages: 266 - 281
Publisher: IEEE
 

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