#### Electrical and Electronics Engineering publications abstract of: 09-2017 sorted by title, page: 14

» Optical transport solutions for 5G fixed wireless access [Invited]
 Abstract:With the advent of 5G, fixed wireless access (FWA) has emerged as a promising candidate for rolling out fixed broadband services. By means of radio simulations, we define a 5G radio deployment scenario for FWA that can meet the service requirements of future fixed broadband access. Different transport requirements imposed by different radio access network (RAN) split options are considered and a broad range of optical transport technologies/systems to support the FWA scenario is analyzed. For higher-layer RAN split options, we find that conventional 10G passive optical networks (XG-PONs) and coarse wavelength-division multiplexing (CWDM) technologies are the most cost effective. CWDM provides improved support for low-latency services while XG-PON facilitates future migration to fiber to the home. For lower-layer RAN splits, point-to-point (PtP) fiber or PtP-WDM is required. In the considered scenario, CWDM and PtP technologies are found to be the most cost effective. Autors: Björn Skubic;Matteo Fiorani;Sibel Tombaz;Anders Furuskär;Jonas Mårtensson;Paolo Monti; Appeared in: IEEE/OSA Journal of Optical Communications and Networking Publication date: Sep 2017, volume: 9, issue:9, pages: D10 - D18 Publisher: IEEE
» Optimal Bidding of Hybrid Power Stations in Insular Power Systems
 Abstract:This paper presents a method to derive the optimal offering/bidding strategy of a power producer who owns a hybrid power station (HPS), comprising wind farms (WFs) and pumped-hydro storage. The method is in line with the provisions of the Greek grid code for non-interconnected islands regarding the operation of HPSs. The goal of the HPS producer is to construct a single energy offer/bid for the total daily production/absorption, which maximizes his profits in the day-ahead market and minimizes any imbalance penalties during real-time operation. To this purpose, a two-stage stochastic bilevel optimization model is formulated, where the uncertainty lies in the wind power production of both the WFs belonging to the hybrid producer (internal WFs–IWFs) and the WFs belonging to other independent producers (WFs external to the HPS–EWFs). The upper level of the proposed bilevel model represents the hybrid producer's profit maximization, while the lower level represents the system operator's (SO) market clearing problem. This stochastic bilevel model is finally converted to a mixed-integer linear programming model in order to be tractable. Finally, simulation results from two test cases are thoroughly discussed and useful conclusions are drawn. Autors: Andreas V. Ntomaris;Anastasios G. Bakirtzis; Appeared in: IEEE Transactions on Power Systems Publication date: Sep 2017, volume: 32, issue:5, pages: 3782 - 3793 Publisher: IEEE
» Optimal Charging of Li-Ion Batteries With Coupled Electro-Thermal-Aging Dynamics
 Abstract:Fast and safe charging protocols are crucial for enhancing the practicality of batteries, especially for mobile applications, such as smartphones and electric vehicles. This paper proposes an innovative approach to devising optimally health-conscious fast-safe charge protocols. A multiobjective optimal control problem is mathematically formulated via a coupled electro-thermal-aging battery model, where electrical and aging submodels depend upon the core temperature captured by a two-state thermal submodel. The Legendre–Gauss–Radau pseudospectral method with adaptive multi-mesh-interval collocation is employed to solve the resulting highly nonlinear six-state optimal control problem. Charge time and health degradation are, therefore, optimally traded off, subject to both electrical and thermal constraints. Minimum-time, minimum-aging, and balanced charge scenarios are examined in detail. Sensitivities to the upper voltage bound, ambient temperature, and cooling convection resistance are investigated as well. Experimental results are provided to compare the tradeoffs between a balanced and traditional charge protocol. Autors: Hector Eduardo Perez;Xiaosong Hu;Satadru Dey;Scott J. Moura; Appeared in: IEEE Transactions on Vehicular Technology Publication date: Sep 2017, volume: 66, issue:9, pages: 7761 - 7770 Publisher: IEEE
» Optimal Control and Stabilization for Networked Control Systems With Packet Dropout and Input Delay
 Abstract:This brief is concerned with the control problem for discrete-time networked control systems. It is assumed that state and control signals transmit through an unreliable communication channel, where packet dropout and input delay occur simultaneously. The main contributions are twofold. First, we obtain the optimal LQR controller, which is a linear function of the optimal state estimator, with the feedback gain based on a standard difference Riccati equation. It is noted that the state estimator and the controller can be calculated separately. Second, a necessary and sufficient condition for the mean-square stabilization is derived. It should be stressed that the eigenvalues of the system matrix and the packet dropout probability determine the stabilizing condition, which is uncorrelated with input delay. Autors: Xiao Liang;Juanjuan Xu;Huanshui Zhang; Appeared in: IEEE Transactions on Circuits and Systems II: Express Briefs Publication date: Sep 2017, volume: 64, issue:9, pages: 1087 - 1091 Publisher: IEEE
» Optimal Day-Ahead Power Procurement With Renewable Energy and Demand Response
 Abstract:This study proposes the demand-side power procurement problem to optimally reduce consumer's energy cost. The motivation stems from pressing issues on an increase of energy cost in an industrial section. From an energy consumer's perspective, there exists an opportunity to reduce energy cost by adjusting purchase and consumption of energy in response to time-varying electricity price while utilizing renewable energy, which is called demand response. In this case, energy storage can be used to mitigate fluctuation of intermittent renewable supply and volatile electricity price. Although it is anticipated to serve a significant amount of energy consumption from renewable energy and to avoid peak electricity price, variability and uncertainty in power demand, renewable supply, and electricity price make it challenging to determine an optimal power procurement. The main objective of this study is to suggest a decision-making methodology that enables energy consumers to optimally determine power procurement against time varying and stochastic electricity price and renewable supply. Specifically, this study formulates an optimal day-ahead power procurement as a two-stage stochastic mixed-integer program and proposes a solution approach based on Benders decomposition. The proposed methodology can be successfully applied to energy-intensive industries, such as data centers. Autors: Soongeol Kwon;Lewis Ntaimo;Natarajan Gautam; Appeared in: IEEE Transactions on Power Systems Publication date: Sep 2017, volume: 32, issue:5, pages: 3924 - 3933 Publisher: IEEE
» Optimal Demand Response Bidding and Pricing Mechanism With Fuzzy Optimization: Application for a Virtual Power Plant
 Abstract:In this paper, a virtual power plant (VPP) that consists of generation, both renewable and conventional, and controllable demand is enabled to participate in the wholesale markets. The VPP makes renewable energy sources (RES) and distributed generations controllable and observable to the system operator. The main objective is to introduce a framework that optimizes the bidding strategies and maximizes the VPP's profit on day-ahead and real-time bases. To achieve this goal, the VPP trades energy externally with a wholesale market, and trades energy and demand response (DR) internally with the consumers in its territory. That is, when generation exceeds demand, the VPP sells the excess energy to the market, and it buys energy from the market when the generation and reduction in demand due to DR scheme are less than the required demand in its territory. Both load curtailment and load shift are modeled. For the day-ahead internal VPP market, fuzzy optimization is proposed to consider the uncertainty in the RES. Comparison results with deterministic and probabilistic optimizations demonstrate the effectiveness of the fuzzy approach in terms of achieving higher realized profits with reasonable computation effort. It is also shown that considering uncertainties in the optimization can result in reduced dependence on the conventional generator. Autors: Ali T. Al-Awami;Nemer A. Amleh;Ammar M. Muqbel; Appeared in: IEEE Transactions on Industry Applications Publication date: Sep 2017, volume: 53, issue:5, pages: 5051 - 5061 Publisher: IEEE
» Optimal Estimation and Control for Lossy Network: Stability, Convergence, and Performance
 Abstract:In this paper, we study the problems of optimal estimation and control, i.e., the linear quadratic Gaussian (LQG) control, for systems with packet losses but without acknowledgment. Such acknowledgment is a signal sent by the actuator to inform the estimator of the incidence of control packet losses. For such system, which is usually called as a user datagram protocol (UDP)-like system, the optimal estimation is nonlinear and its calculation is time-consuming, making its corresponding optimal LQG problem complicated. We first propose two conditions: 1) the sensor has some computation abilities; and 2) the control command, exerted to the plant, is known to the sensor. For a UDP-like system satisfying these two conditions, we derive the optimal estimation. By constructing the finite and infinite product probability measure spaces for the estimation error covariances (EEC), we give the stability condition for the expected EEC, and show the existence of a measurable function to which the EEC converges in distribution, and propose some practical methods to evaluate the estimation performance. Finally, the LQG controllers are derived, and the conditions for the mean square stability of the closed-loop system are established. Autors: Hong Lin;Hongye Su;Peng Shi;Zhan Shu;Renquan Lu;Zheng-Guang Wu; Appeared in: IEEE Transactions on Automatic Control Publication date: Sep 2017, volume: 62, issue:9, pages: 4564 - 4579 Publisher: IEEE
» Optimal Functional-Unit Assignment for Heterogeneous Systems Under Timing Constraint
 Abstract:In high-level synthesis for real-time systems, it typically employs heterogeneous functional-unit types to achieve high-performance and low-cost designs. In the design phase, it is critical to determine which functional-unit type to be mapped for each operation in a given application such that the total cost is minimized while the deadline can be met. For a path or tree structured application, existing approaches can obtain the minimum-cost assignment, called “optimal assignment”, under which the resultant system satisfies a given timing constraint. However, it is still an open question whether there exist efficient algorithms to obtain the optimal assignment for the directed acyclic graph (DAG), or more generally, the data-flow graph with cycles (cyclic DFG). For DAGs, by analyzing the property of the problem, this paper designs an efficient algorithm to obtain the optimal assignments. For cyclic DFGs, we approach this problem with the combination of retiming technique to thoroughly explore the design space. We formulate a Mixed Integer Linear Programming (MILP) model to give the optimal solution. But because of the high degree of its time complexity, we devise a practical algorithm to obtain near-optimal solutions within a minute. Experimental results show the effectiveness of our algorithms. Specifically, compared with existing techniques, we can achieve 25.70 and 30.23 percent reductions in total cost on DAGs and cyclic DFGs, respectively. Autors: Weiwen Jiang;Edwin Hsing-Mean Sha;Xianzhang Chen;Lei Yang;Lei Zhou;Qingfeng Zhuge; Appeared in: IEEE Transactions on Parallel and Distributed Systems Publication date: Sep 2017, volume: 28, issue:9, pages: 2567 - 2580 Publisher: IEEE
» Optimal Load Scheduling of Plug-In Hybrid Electric Vehicles via Weight-Aggregation Multi-Objective Evolutionary Algorithms
 Abstract:In order to protect the environment and slow down global warming trend, many governments and environmentalists are keen at promoting the use of plug-in hybrid electric vehicles (PHEVs). As a result, more and more PHEVs have been put into use. However, load peak caused by their disordered charging can be detrimental to an entire power grid. Several methods have been proposed to establish ordered PHEV charging. While focusing on single-objective load scheduling, they fail to meet the real requirements that need one to conduct multiple objective optimization. This paper formulates a multi-objective load scheduling problem to minimize two competing objectives: 1) potential serious peak-to-valley difference and 2) economic loss. When we apply existing multi-objective evolutionary algorithms (MOEAs), i.e., multi-objective particle swarm optimization (MOPSO), Nondominated Sorting Genetic Algorithm II, MOEA based on decomposition, and multi-objective differential evolutionary algorithm to solve it, because its high dimension and special conditions we find that they fail to reach the Pareto Front or converge into a relatively small area only. Therefore, we propose a weight aggregation (WA) strategy and implement a novel MOEA algorithm named WA-MOPSO by incorporating WA into MOPSO to solve the problem. Its effectiveness and efficiency to generate a Pareto front of this problem are verified and compared with those of the state-of-the-art approaches. Furthermore, WA is also combined with other MOEAs to solve the defined scheduling problem. Autors: Qi Kang;ShuWei Feng;MengChu Zhou;Ahmed Chiheb Ammari;Khaled Sedraoui; Appeared in: IEEE Transactions on Intelligent Transportation Systems Publication date: Sep 2017, volume: 18, issue:9, pages: 2557 - 2568 Publisher: IEEE
» Optimal Power Splitting in Two-Way Decode-and-Forward Relay Networks
 Abstract:This letter investigates simultaneous wireless information and power transfer in two-way decode-and-forward relay networks, where the relay is an energy-constrained node but is capable of harvesting energy from the radio frequency signal transmitted by the source nodes for forwarding its information. The achievable sum-rate of such network with the power splitting relay protocol is analyzed first. Then, the optimal design of the power allocated for energy harvesting and for information decoding in the sense of maximum achievable sum-rate is determined. Simulation results are presented to assess the influence of various system parameters. The performance of the optimal design is compared with that of amplify-and-forward relay protocols. Autors: Chunling Peng;Fangwei Li;Huaping Liu; Appeared in: IEEE Communications Letters Publication date: Sep 2017, volume: 21, issue:9, pages: 2009 - 2012 Publisher: IEEE
» Optimal Resource Allocation for Power-Efficient MC-NOMA With Imperfect Channel State Information
 Abstract:In this paper, we study power-efficient resource allocation for multicarrier non-orthogonal multiple access systems. The resource allocation algorithm design is formulated as a non-convex optimization problem which jointly designs the power allocation, rate allocation, user scheduling, and successive interference cancellation (SIC) decoding policy for minimizing the total transmit power. The proposed framework takes into account the imperfection of channel state information at transmitter and quality of service requirements of users. To facilitate the design of optimal SIC decoding policy on each subcarrier, we define a channel-to-noise ratio outage threshold. Subsequently, the considered non-convex optimization problem is recast as a generalized linear multiplicative programming problem, for which a globally optimal solution is obtained via employing the branch-and-bound approach. The optimal resource allocation policy serves as a system performance benchmark due to its high computational complexity. To strike a balance between system performance and computational complexity, we propose a suboptimal iterative resource allocation algorithm based on difference of convex programming. Simulation results demonstrate that the suboptimal scheme achieves a close-to-optimal performance. Also, both proposed schemes provide significant transmit power savings than that of conventional orthogonal multiple access schemes. Autors: Zhiqiang Wei;Derrick Wing Kwan Ng;Jinhong Yuan;Hui-Ming Wang; Appeared in: IEEE Transactions on Communications Publication date: Sep 2017, volume: 65, issue:9, pages: 3944 - 3961 Publisher: IEEE
» Optimal Resource Allocation in Multicast Device-to-Device Communications Underlaying LTE Networks
 Abstract:In this paper, we present a framework for resource allocations for multicast device-to-device (D2D) communications underlaying the uplink of a Long-Term Evolution (LTE) network. The objective is to maximize the sum throughput of active cellular users (CUs) and feasible D2D multicast groups in a cell, while meeting a certain signal-to-interference-plus-noise ratio (SINR) constraint for both the CUs and the D2D groups. We formulate the general problem of power and channel allocation as a mixed integer nonlinear programming (MINLP) problem, where one D2D group can reuse the channels of multiple CUs and where the channel of each CU can be reused by multiple D2D groups. Distinct from existing approaches in the literature, our formulation and solution methods provide an effective and flexible means to utilize radio resources in cellular networks and share them with multicast groups without causing harmful interference to each other. The MINLP problem is transformed so that it can be solved optimally by a variant of the generalized Bender decomposition method with provable convergence. A greedy algorithm and a low-complexity heuristic solution are then devised. The performance of all schemes is evaluated through extensive simulations. Numerical results demonstrate that the proposed greedy algorithm can achieve close-to-optimal performance and that the heuristic algorithm provides good performance, even though it is inferior than that of the greedy, with much lower complexity. Autors: Hadi Meshgi;Dongmei Zhao;Rong Zheng; Appeared in: IEEE Transactions on Vehicular Technology Publication date: Sep 2017, volume: 66, issue:9, pages: 8357 - 8371 Publisher: IEEE
» Optimal Sensor Data Scheduling for Remote Estimation Over a Time-Varying Channel
 Abstract:We consider sensor data scheduling with communication energy constraint for remote state estimation over a time-varying fading channel. Given that the fade channel state with temporal correlated variation influences the estimation accuracy, the goal is to obtain a schedule for a sensor to decide whether using high energy to send its local estimate to a remote estimator in order to minimize the expected average estimation error covariance. By exploiting the feedback information, we propose an effective closed-form dynamic stationary scheduling scheme. We prove that such simple schedule is optimal in terms of the estimation performance by comparing with a general stationary schedule under energy constraint. Furthermore, we derive the sufficient and necessary condition for estimation stability when the sensor can only use low energy at each time. Numerical examples are provided to illustrate the effectiveness of the proposed scheme. Autors: Yifei Qi;Peng Cheng;Jiming Chen; Appeared in: IEEE Transactions on Automatic Control Publication date: Sep 2017, volume: 62, issue:9, pages: 4611 - 4617 Publisher: IEEE
» Optimal Training Design for MIMO-OFDM Two-Way Relay Networks
 Abstract:In this paper, we study a training design problem for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) amplify-and-forward (AF) two-way relay networks. Unlike the existing studies, we assume the spatially correlated fading and consider the nonreciprocal channel condition, which is a more practical assumption but makes the training problem more challenging. The equivalent channels of bidirectional relaying links, which consist of self-interfering channels and information-bearing channels, are estimated at each source node based on a linear minimum mean square error (LMMSE) approach. The total mean square error (MSE) of the channel estimation is minimized under the transmit power constraints at the source nodes and at the relay. To solve this problem, we first derive an optimal structure of the training signals, and then, convert the optimization problem into a tractable convex form, from which the optimal training scheme is designed efficiently. Furthermore, for a practical special case, the optimal training design is derived in semi-closed form, which provides useful insights. To reduce the required complexity, a low-complexity training scheme is also derived in closed-form. This scheme is shown to be asymptotically optimal in the high signal-to-noise ratio (SNR) regime and gives further insights into the optimal training. The performance of the proposed schemes is demonstrated through numerical simulations. Autors: Jae-Mo Kang;Il-Min Kim;Hyung-Myung Kim; Appeared in: IEEE Transactions on Communications Publication date: Sep 2017, volume: 65, issue:9, pages: 3675 - 3690 Publisher: IEEE
» Optimal Transport for Domain Adaptation
 Abstract:Domain adaptation is one of the most challenging tasks of modern data analytics. If the adaptation is done correctly, models built on a specific data representation become more robust when confronted to data depicting the same classes, but described by another observation system. Among the many strategies proposed, finding domain-invariant representations has shown excellent properties, in particular since it allows to train a unique classifier effective in all domains. In this paper, we propose a regularized unsupervised optimal transportation model to perform the alignment of the representations in the source and target domains. We learn a transportation plan matching both PDFs, which constrains labeled samples of the same class in the source domain to remain close during transport. This way, we exploit at the same time the labeled samples in the source and the distributions observed in both domains. Experiments on toy and challenging real visual adaptation examples show the interest of the method, that consistently outperforms state of the art approaches. In addition, numerical experiments show that our approach leads to better performances on domain invariant deep learning features and can be easily adapted to the semi-supervised case where few labeled samples are available in the target domain. Autors: Nicolas Courty;Rémi Flamary;Devis Tuia;Alain Rakotomamonjy; Appeared in: IEEE Transactions on Pattern Analysis and Machine Intelligence Publication date: Sep 2017, volume: 39, issue:9, pages: 1853 - 1865 Publisher: IEEE
» Optimal Transport Theory for Cell Association in UAV-Enabled Cellular Networks
 Abstract:In this letter, a novel framework for delay-optimal cell association in unmanned aerial vehicle (UAV)-enabled wireless cellular networks is proposed. In particular, to minimize the average network delay under any arbitrary spatial distribution of the ground users, the optimal cell partitions of the UAVs and terrestrial base stations are determined. To this end, using the powerful mathematical tools of optimal transport theory, the existence of the solution to the optimal cell association problem is proved and the solution space is completely characterized. The analytical and simulation results show that the proposed approach yields substantial improvements in terms of the average network delay. Autors: Mohammad Mozaffari;Walid Saad;Mehdi Bennis;Mérouane Debbah; Appeared in: IEEE Communications Letters Publication date: Sep 2017, volume: 21, issue:9, pages: 2053 - 2056 Publisher: IEEE
» Optimal Zero Delay Coding of Markov Sources: Stationary and Finite Memory Codes
 Abstract:The optimal zero delay coding of a finite-state Markov source is considered. The existence and structure of optimal codes are studied using a stochastic control formulation. Prior results in the literature established the optimality of deterministic Markov (Walrand–Varaiya-type) coding policies for the finite time horizon problem, and the optimality of both deterministic nonstationary and randomized stationary policies for the infinite time horizon problem. Our main result here shows that for any irreducible and aperiodic Markov source with a finite alphabet, deterministic and stationary Markov coding policies are optimal for the infinite horizon problem. In addition, the finite block length (time horizon) performance of an optimal (stationary and Markov) coding policy is shown to approach the infinite time horizon optimum at a rate . The results are extended to systems, where zero delay communication takes place across a noisy channel with noiseless feedback. Autors: Richard G. Wood;Tamás Linder;Serdar Yüksel; Appeared in: IEEE Transactions on Information Theory Publication date: Sep 2017, volume: 63, issue:9, pages: 5968 - 5980 Publisher: IEEE
» Optimality Conditions for Long-Run Average Rewards With Underselectivity and Nonsmooth Features
 Abstract:We study three existing issues associated with optimization of long-run average rewards of time-nonhomogeneous Markov processes in continuous time with continuous state spaces: 1) the underselectivity, i.e., the optimal policies do not depend on their actions in any finite time period; 2) its related issue, the bias optimality, i.e., policies that optimize both long-run average and transient total rewards, and 3) the effects of a nonsmooth point of a value function on performance optimization. These issues require considerations of the performance in the entire period with an infinite horizon, and therefore are not easily solvable by dynamic programming, which works backwards in time and takes a local view at a particular time instant. In this paper, we take a different approach called the relative optimization theory, which is based on a direct comparison of the performance measures of any two policies. We derive tight necessary and sufficient optimality conditions that take the underselectivity into consideration; we derive bias optimality conditions for both long-run average and transient rewards; and we show that the effect of a wide class of nonsmooth points, called semismooth points, of a value function on the long-run average performance is zero and can be ignored. Autors: Xi-Ren Cao; Appeared in: IEEE Transactions on Automatic Control Publication date: Sep 2017, volume: 62, issue:9, pages: 4318 - 4332 Publisher: IEEE
 Abstract:SRAM-based scratchpad memories (SPMs) used in embedded systems impose high leakage power. Designing SPMs based on non-volatile memories (NVMs) were proposed as NVMs have negligible leakage power. The main problem of utilizing NVMs across the SPM is their limited number of write cycles (endurance). This problem threatens the reliability of NVM-based SPMs. To alleviate the problem of limited endurance in NVM-based SPMs, this paper proposes a method, called overwrite purging through in-execution memory address snooping (OPTIMAS). The main idea behind the proposed method is to control the lifetime of NVM-based SPMs, directly by a hardware unit, outside of the SPM mapping algorithm. This idea enables the possibility of using traditional SRAM-based mapping algorithms in NVM-based SPMs. OPTIMAS controls the wear-out of NVM-based SPMs based on the recent write behavior of each block during the runtime of the programs. OPTIMAS is evaluated from the lifetime, energy consumption, and performance point of views. The simulation results show up to two orders of magnitude improvement in lifetime, an average of 50% reduction in dynamic energy consumption, and negligible performance overhead (less than 1%). Furthermore, it is shown that while OPTIMAS is orthogonal to all other approaches, it benefits from significant lifetime improvement in comparison with the state-of-the-art approaches. Autors: Amir Mahdi Hosseini Monazzah;Hamed Farbeh;Seyed Ghassem Miremadi; Appeared in: IEEE Transactions on Device and Materials Reliability Publication date: Sep 2017, volume: 17, issue:3, pages: 481 - 489 Publisher: IEEE
» Optimization of Mixed-ADC Multi-Antenna Systems for Cloud-RAN Deployments
» Optimization of Power Conversion Efficiency in Threshold Self-Compensated UHF Rectifiers With Charge Conservation Principle
 Abstract:This paper presents a compact model for threshold self-compensated rectifiers that can be used to optimize circuit parameters early in the design phase instead of time-consuming transient simulations. A design procedure is presented for finding the optimum aspect ratio of transistors used in the converter and number of rectifying stages to achieve the maximum power conversion efficiency. In the presented analysis, the relation between the power conversion efficiency and the load current over the variation of the output dc voltage is used to find the optimum design parameters. Accurate approximation of the charge entering to and exiting from the rectifier during the steady state helps to get good agreement between the predicted output dc voltage and simulation results under different load current values. Using the Enz-Krummenacher-Vittoz model for the MOS transistor, an accurate formula is derived for optimization. The ability of the model in weak, moderate, and strong inversion region aids to find the optimum design parameters for broad range of RF voltage variation. The presented formula for estimating the optimum size and number of stages shows good agreement with simulations. Further validation is provided by comparing model predictions with measurement results of a four-stage self-compensated rectifier operating at 900 MHz, which is implemented in a commercial 0.18- partially-depleted silicon-on-insulator process. Autors: Kaveh Gharehbaghi;Fatih Koçer;Haluk Külah; Appeared in: IEEE Transactions on Circuits and Systems I: Regular Papers Publication date: Sep 2017, volume: 64, issue:9, pages: 2380 - 2387 Publisher: IEEE
» Optimized Phase Disposition (PD) Modulation of a Modular Multilevel Converter
 Abstract:This paper presents a theoretical harmonic analysis of phase disposition (PD) and phase-shifted carrier pulse-width modulation strategies for modular multilevel converters (MMCs). It is shown that when these strategies are implemented on a per MMC arm basis, their spectral performances converge because of cancellation of odd carrier sideband groups between each phase leg's arms. An improved PD modulation strategy is then presented that uses a single PD modulator for the entire phase leg, followed by a state machine decoder that evenly distributes switching pulses to all submodules across the phase leg upper and lower arms to balance the distribution of submodule commutation events. The resulting strategy achieves optimum phase leg PD spectral performance and also achieves natural voltage balancing of the MMC submodules. All theoretical findings are supported by simulation and experimental results obtained using a five-level MMC prototype. Autors: Brendan Peter McGrath;Carlos Alberto Teixeira;Donald Grahame Holmes; Appeared in: IEEE Transactions on Industry Applications Publication date: Sep 2017, volume: 53, issue:5, pages: 4624 - 4633 Publisher: IEEE
» Optimized Wavelet Denoising for Self-Similar $\alpha$ -Stable Processes
 Abstract:We investigate the performance of wavelet shrinkage methods for the denoising of symmetric--stable () self-similar stochastic processes corrupted by additive white Gaussian noise (AWGN), where is tied to the sparsity of the process. The wavelet transform is assumed to be orthonormal and the shrinkage function minimizes the mean-square approximation error (MMSE estimator). We derive the corresponding formula for the expected value of the averaged estimation error. We show that the predicted MMSE is a monotone function of a simple criterion that depends on the wavelet and the statistical parameters of the process. Using the calculus of variations, we then optimize this criterion to find the best performing wavelet within the extended family of Meyer wavelets, which are bandlimited. These are compared with the Daubechies wavelets, which are compactly supported in time. We find that the wavelets that are shorter in time (in particular, the Haar basis) are better suited to denoise the sparser processes (say, ), while the bandlimited ones (including the Held and Shannon wavelets) offer the best performance for , the limit corresponding to the Gaussian case (fBm) with . Autors: Pedram Pad;Kasra Alishahi;Michael Unser; Appeared in: IEEE Transactions on Information Theory Publication date: Sep 2017, volume: 63, issue:9, pages: 5529 - 5543 Publisher: IEEE
» Optimizing Extended Hodgkin-Huxley Neuron Model Simulations for a Xeon/Xeon Phi Node
 Abstract:Brain modeling has been receiving significant attention over the years, both for its neuroscientific potential and for its challenges in the context of high-performance computing. The development of physiologically plausible neuron models comes at the cost of increased complexity. In this work, we have selected a highly computationally demanding model of the Inferior-Olivary Nucleus (InfOli) based on the Hodgkin-Huxley (HH) neuron model. This brain region, functionally coupled with the cerebellum, is of vital importance for motor skills and time-sensitive cognitive functions. The computing fabric of choice is an Intel Xeon/Xeon Phi system, which is a typical node of modern computing infrastructure. The target application is parallelized with various combinations of MPI and OpenMP and performance is measured on the target platform. The different implementations are compared and the best one is chosen. Further optimization of this implementation is presented in detail. Its behaviour is then examined when scaling up to neuron populations representative of realistic, human Inferior-Olivary neuronal networks. The evaluation’s results highlight the importance of examining a network’s size and density before choosing the best platform for its simulation. All the parallelization and vectorization options presented in the current paper are available on a public repository for further examination. Autors: George Chatzikonstantis;Dimitrios Rodopoulos;Christos Strydis;Chris I. De Zeeuw;Dimitrios Soudris; Appeared in: IEEE Transactions on Parallel and Distributed Systems Publication date: Sep 2017, volume: 28, issue:9, pages: 2581 - 2594 Publisher: IEEE
» Optimizing Parallel Clustering Throughput in Shared Memory
 Abstract:This article studies the optimization of parallel clustering throughput in the context of variant-based parallelism, which exploits commonalities and reuse among variant computations for multithreading scalability. This direction is motivated by challenging scientific applications where scientists have to execute multiple runs of clustering algorithms with different parameters to determine which ones best explain phenomena observed in empirical data. To make this process more efficient, we propose a novel set of optimizations to maximize the throughput of Density-Based Spatial Clustering of Applications with Noise (DBSCAN), a frequently used algorithm for scientific data mining in astronomy, geoscience, and many other fields. Our approach executes multiple algorithm variants in parallel, computes clusters concurrently, and leverages heuristics to maximize the reuse of results from completed variants. As scientific datasets continue to grow, maximizing clustering throughput with our techniques may accelerate the search and identification of natural phenomena of interest with computational support, i.e., Computer-Aided Discovery. We present evaluations on a whole spectrum of datasets, such as geoscience data on space weather phenomena, astronomical data from the Sloan Digital Sky Survey on intermediate-redshift galaxies, as well as synthetic datasets to characterize performance properties. Selected results show a 1,115 percent performance improvement due to indexing tailored for variant-based clustering, and a 2,209 percent performance improvement when applying all of our proposed optimizations. Autors: Michael Gowanlock;David M. Blair;Victor Pankratius; Appeared in: IEEE Transactions on Parallel and Distributed Systems Publication date: Sep 2017, volume: 28, issue:9, pages: 2595 - 2607 Publisher: IEEE
» Origin and Optimization of RF Power Handling Limitations in Inline Phase-Change Switches
 Abstract:The power handling capabilities of inline phase-change switches (IPCS’s) at radio frequencies (RF) have been correlated with the dc threshold voltage () of the devices. The dependence of on microheater pulsing parameters and device layout has been characterized, accompanied by observation of the size of the amorphous chalcogenide region through scanning transmission electron microscopy. All observations are consistent with threshold field () of nominally 50:50 GeTe of 12.6 V/. Use of W-based microheaters in the IPCS processes has improved device performance and reliability, with increases in the product of cutoff-frequency () and over previous IPCS devices using NiCrSi microheaters. The improved devices demonstrated power handling capabilities up to 29 dBm in a 50- system for a switch with submicrometer dimensions, where the improvement is attributed to the larger amorphous zone created at the minimum power to amorphize. These improved devicesdemonstrate the feasibility of these switches in both transmit and receivewireless applications. A correlation between the maximum allowed RF voltage across the OFF-state switch and the dc of the OFF device was observed, indicating the dc is an accurate predictor of RF power handling. Autors: Nabil El-Hinnawy;Pavel Borodulin;Matthew R. King;Carlos R. Padilla;Andris Ezis;Doyle T. Nichols;Jeyanandh Paramesh;James A. Bain;Robert M. Young; Appeared in: IEEE Transactions on Electron Devices Publication date: Sep 2017, volume: 64, issue:9, pages: 3934 - 3942 Publisher: IEEE
» Outstanding Members and Chapters [Chapter News]
 Abstract:Presents information on IAS society Outstanding Chapter and Member awards. Autors: Peter Magyar; Appeared in: IEEE Industry Applications Magazine Publication date: Sep 2017, volume: 23, issue:5, pages: 72 - 74 Publisher: IEEE
» Oxygen Interstitial Creation in a-IGZO Thin-Film Transistors Under Positive Gate-Bias Stress
 Abstract:The electrical recovery behaviors of the amorphous InGaZnO thin-film transistors (a-IGZO TFTs) after positive gate-bias stress (PBS) are investigated. The TFTs show an evident sub-threshold swing (SS) degradation after the PBS removal when the channel layer is deposited at relatively high oxygen flow rates, although they exhibit a parallel positive shift in the transfer characteristics during the PBS. It is inferred that the SS degradation results from the oxygen interstitial defects created in the a-IGZO channel during the PBS, which are in the octahedral configuration and are usually more easily created in the oxygen-rich a-IGZO channel layer. They are electrically inactive during the PBS due to the “negative U” behavior and then become relaxed and electrically active during the recovery process, leading to the SS degradation during the recovery process. Autors: Xiaoliang Zhou;Yang Shao;Letao Zhang;Huiling Lu;Hongyu He;Dedong Han;Yi Wang;Shengdong Zhang; Appeared in: IEEE Electron Device Letters Publication date: Sep 2017, volume: 38, issue:9, pages: 1252 - 1255 Publisher: IEEE
» P$^2$S: A Primary and Passer-By Scheduling Algorithm for On-Demand Charging Architecture in Wireless Rechargeable Sensor Networks
 Abstract:As the interdiscipline of wireless communication and control engineering, the cooperative charging issue in wireless rechargeable sensor networks (WRSNs) is a popular research problem. With the help of wireless power transfer technology, electrical energy can be transferred from wireless charging vehicles to sensors, providing a new paradigm to prolong the network lifetime. However, existing techniques on cooperative charging usually take the periodical and deterministic approach but neglect the influences of the nondeterministic factors such as topological changes and node failures, making them unsuitable for large-scale WRSNs. In this paper, we develop a primary and passer-by scheduling (PS) algorithm for on-demand charging architecture for large-scale WRSNs. In PS, task interdependence is utilized to enhance charging efficiency. We exploit a local searching algorithm, in which nearby nodes on the way to primary nodes, which are the targets of wireless charging vehicle's current movement, will be charged as passer-by nodes. Such a strategy not only makes full use of the available remaining time of a charging deadline but solves the complex scheduling problem with spatial and temporal task interdependence as well. Analysis and simulations are conducted to show the superiority of our scheme, revealing that PS has a higher survival rate and throughput, as well as other performance metrics. Autors: Chi Lin;Ding Han;Jing Deng;Guowei Wu; Appeared in: IEEE Transactions on Vehicular Technology Publication date: Sep 2017, volume: 66, issue:9, pages: 8047 - 8058 Publisher: IEEE
» Package-Level Reconfiguration of RF Matching Networks Using SMD Components
 Abstract:Digital power amplifiers provide an unprecedented level of flexibility in their ability to operate on different signals using simple reprogramming of the digital signal processing, but their output matching networks must be redesigned for different frequency bands. This involves a redesign of part of the back-end-of-line mask set at a great cost. We present a package-level reconfiguration technique that allows a single transmitter to be reconfigured for multiple frequency bands, or different output power levels by soldering different surface mount device (SMD) components directly to the surface of the die, saving design and fabrication cost while delivering similar performance. We demonstrate the technique on a multiphase transmitter IC, showing optimized operation at three different frequencies using soldered SMD components to reconfigure the matching network of the IC at the package level. The transmitter’s linearity and performance are validated using a 5-MHz, 64-QAM LTE signal. Autors: Wen Yuan;Jeffrey S. Walling; Appeared in: IEEE Transactions on Circuits and Systems II: Express Briefs Publication date: Sep 2017, volume: 64, issue:9, pages: 997 - 1001 Publisher: IEEE
» Parallel Continuous Preference Queries over Out-of-Order and Bursty Data Streams
 Abstract:Techniques to handle traffic bursts and out-of-order arrivals are of paramount importance to provide real-time sensor data analytics in domains like traffic surveillance, transportation management, healthcare and security applications. In these systems the amount of raw data coming from sensors must be analyzed by continuous queries that extract value-added information used to make informed decisions in real-time. To perform this task with timing constraints, parallelism must be exploited in the query execution in order to enable the real-time processing on parallel architectures. In this paper we focus on continuous preference queries, a representative class of continuous queries for decision making, and we propose a parallel query model targeting the efficient processing over out-of-order and bursty data streams. We study how to integrate punctuation mechanisms in order to enable out-of-order processing. Then, we present advanced scheduling strategies targeting scenarios with different burstiness levels, parameterized using the index of dispersion quantity. Extensive experiments have been performed using synthetic datasets and real-world data streams obtained from an existing real-time locating system. The experimental evaluation demonstrates the efficiency of our parallel solution and its effectiveness in handling the out-of-orderness degrees and burstiness levels of real-world applications. Autors: Gabriele Mencagli;Massimo Torquati;Marco Danelutto;Tiziano De Matteis; Appeared in: IEEE Transactions on Parallel and Distributed Systems Publication date: Sep 2017, volume: 28, issue:9, pages: 2608 - 2624 Publisher: IEEE
» Parallel Graph Partitioning for Complex Networks
 Abstract:Processing large complex networks like social networks or web graphs has attracted considerable interest. To do this in parallel, we need to partition them into pieces of roughly equal size. Unfortunately, previous parallel graph partitioners originally developed for more regular mesh-like networks do not work well for complex networks. Here we address this problem by parallelizing and adapting the label propagation technique originally developed for graph clustering. By introducing size constraints, label propagation becomes applicable for both the coarsening and the refinement phase of multilevel graph partitioning. This way we exploit the hierarchical cluster structure present in many complex networks. We obtain very high quality by applying a highly parallel evolutionary algorithm to the coarsest graph. The resulting system is both more scalable and achieves higher quality than state-of-the-art systems like ParMetis or PT-Scotch. For large complex networks the performance differences are very big. As an example, our algorithm partitions a web graph with 3.3 G edges in 16 seconds using 512 cores of a high-performance cluster while producing a high quality partition—none of the competing systems can handle this graph on our system. Autors: Henning Meyerhenke;Peter Sanders;Christian Schulz; Appeared in: IEEE Transactions on Parallel and Distributed Systems Publication date: Sep 2017, volume: 28, issue:9, pages: 2625 - 2638 Publisher: IEEE
» Parallel Operation of Inverters With Isolated DC Link for Minimizing Sharing Inductor
 Abstract:In this paper, it is described how the circulating current flows between inverters that have isolated dc link such as cascaded H-bridge (CHB) topology when they are operating in parallel. In this case, zero sequence circulating current, which normally flows through shared dc link, cannot flow between inverters in parallel. However, circulating current is provoked by asynchronous switching instant of devices, difference of dc-link voltages of parallel inverters, and unbalanced impedance. The circulating current should be suppressed by a sharing inductor that is inserted between inverters. Generally, all of the inverters should synthesize the same output voltage reference for load current control to minimize the size of this sharing reactor. However, this conventional method cannot guarantee diminishing circulating current in the transient state and even in the steady state. In this paper, in order to reduce sharing reactance, after deriving circulating current model from general case of n-parallel operation, circulating current control method is devised based on the model. This proposed algorithm is applied to active front end five-level-CHB inverter system for medium voltage drive. Simulation and experimental results are provided to verify the effectiveness of the proposed control scheme. Autors: Hyun-Sam Jung;Jeong-Mock Yoo;Seung-Ki Sul;Hak-Jun Lee;Chanook Hong; Appeared in: IEEE Transactions on Industry Applications Publication date: Sep 2017, volume: 53, issue:5, pages: 4450 - 4459 Publisher: IEEE
» Parameter and Controller Dependent Lyapunov Functions for Robust D-Stability and Robust Performance Controller Design
 Abstract:This paper addresses the design of output controllers of chosen order in a given set for ensuring a number of desired properties, such as robust D-stability and robust performance. It is shown that a sufficient condition for determining such controllers can be obtained by solving convex optimization problems with linear matrix inequality constraints through the introduction of a Lyapunov function depending polynomially on both uncertainty and controller. The proposed condition is also necessary for sufficiently large degrees of the polynomials involved under some assumptions. Autors: Graziano Chesi; Appeared in: IEEE Transactions on Automatic Control Publication date: Sep 2017, volume: 62, issue:9, pages: 4798 - 4803 Publisher: IEEE
» Parameter Identification of Integrated Model of Hydraulic Turbine Regulating System With Uncertainties Using Three Different Approaches
 Abstract:In this paper, three novel parameter identification methods are developed and used to solve the unknown parameters problem of integrated model of hydraulic turbine regulating system with uncertainties. The first and second methods are designed based on different parameter observers using dynamic system stability theorem, which are referred to as unknown parameter observer and synchronization-based parameter observer, respectively, while the third method is designed based on an ant lion optimizer (ALO) algorithm, which is referred to as the ALO-based estimator. Performance of the three methods are compared in various aspects, including the orders, the structure, and the independence of the identification system. Results show that the unknown parameter observer has the lowest identification system orders, while the synchronization-based parameter observer has the simplest system structure, and the ALO-based estimator owns the best system independence. Autors: Zhihuan Chen;Xiaohui Yuan;Yanbin Yuan;Herbert Ho-Ching Iu;Tyrone Fernando; Appeared in: IEEE Transactions on Power Systems Publication date: Sep 2017, volume: 32, issue:5, pages: 3482 - 3491 Publisher: IEEE
» Parameter Uniformity of Submicron-Channel-Length Organic Thin-Film Transistors Fabricated by Stencil Lithography
 Abstract:Using high-resolution stencil lithography, we have fabricated bottom-gate, top-contact (inverted staggered) organic thin-film transistors that have a channel length of 0.5 μm and gate-to-source and gate-to-drain overlaps of 2 μm. Owing to the small channel length, the transistors have a large width-normalized transconductance of (0.50 ± 0.05) S/m, despite the relatively small charge-carrier mobility of (0.36 ± 0.04) cm2/V · s. Across an array of 16 transistors, the uniformity of the transconductance is about 9% (1σ), the uniformity of the carrier mobility is about 7%, the uniformity of the threshold voltage is about 4%, the subthreshold slope varies between 95 and 150 mV/decade, and the on/off current ratio varies between 7 × 104 and 3 × 106. To our knowledge, this is the first time that the parameter distribution of submicron-channel-length organic TFTs is reported. Autors: Ute Zschieschang;Florian Letzkus;Joachim N. Burghartz;Hagen Klauk; Appeared in: IEEE Transactions on Nanotechnology Publication date: Sep 2017, volume: 16, issue:5, pages: 837 - 841 Publisher: IEEE
» Parked Cars are Excellent Roadside Units
 Abstract:A comprehensive implementation of the envisioned traffic safety and efficiency applications of the IEEE 802.11p and Wireless Access for Vehicular Environments (WAVE) standards assume the premise of the use of Dedicated Short-Range Communications (DSRC) technology both as on-board units and as roadside units (RSUs). The high cost associated with RSUs, however, has so far prevented massive deployment of RSUs. Finding alternative solutions to this longstanding problem is therefore very important. In this paper, we propose a self-organizing network approach to using parked cars in urban areas as RSUs. This self-organizing network approach enables parked cars to create coverage maps based on received signal strength and make important decisions, such as if and when a parked car should serve as an RSU. Our results show the feasibility and cost-effectiveness of the proposed approach, which is able to provide excellent coverage using only a small fraction of the cars parked in a city. Autors: Andre B. Reis;Susana Sargento;Ozan K. Tonguz; Appeared in: IEEE Transactions on Intelligent Transportation Systems Publication date: Sep 2017, volume: 18, issue:9, pages: 2490 - 2502 Publisher: IEEE
» PatchMatch Filter: Edge-Aware Filtering Meets Randomized Search for Visual Correspondence
 Abstract:Though many tasks in computer vision can be formulated elegantly as pixel-labeling problems, a typical challenge discouraging such a discrete formulation is often due to computational efficiency. Recent studies on fast cost volume filtering based on efficient edge-aware filters provide a fast alternative to solve discrete labeling problems, with the complexity independent of the support window size. However, these methods still have to step through the entire cost volume exhaustively, which makes the solution speed scale linearly with the label space size. When the label space is huge or even infinite, which is often the case for (subpixel-accurate) stereo and optical flow estimation, their computational complexity becomes quickly unacceptable. Developed to search approximate nearest neighbors rapidly, the PatchMatch method can significantly reduce the complexity dependency on the search space size. But, its pixel-wise randomized search and fragmented data access within the 3D cost volume seriously hinder the application of efficient cost slice filtering. This paper presents a generic and fast computational framework for general multi-labeling problems called PatchMatch Filter (PMF). We explore effective and efficient strategies to weave together these two fundamental techniques developed in isolation, i.e., PatchMatch-based randomized search and efficient edge-aware image filtering. By decompositing an image into compact superpixels, we also propose superpixel-based novel search strategies that generalize and improve the original PatchMatch method. Further motivated to improve the regularization strength, we propose a simple yet effective cross-scale consistency constraint, which handles labeling estimation for large low-textured regions more reliably than a single-scale PMF algorithm. Focusing on dense correspondence field estimation in this paper, we demonstrate PMF’s applications in stereo and optical flow. Our PMF methods achieve top-tier co- respondence accuracy but run much faster than other related competing methods, often giving over 10-100 times speedup. Autors: Jiangbo Lu;Yu Li;Hongsheng Yang;Dongbo Min;Weiyong Eng;Minh N. Do; Appeared in: IEEE Transactions on Pattern Analysis and Machine Intelligence Publication date: Sep 2017, volume: 39, issue:9, pages: 1866 - 1879 Publisher: IEEE
» PCMO-Based RRAM and NPN Bipolar Selector as Synapse for Energy Efficient STDP
 Abstract:Resistance random access memories (RRAMs) are widely explored to show spike time dependent plasticity (STDP) as a learning rule to show biological synaptic behavior, as these devices possess analog conductance change. To implement STDP, pre- and post-neuronal waveforms are superposed. Only the peak voltage changes the conductance of memory. But due to the remaining part of the waveform (which don’t affect the conductance change), there is a significant amount of inadvertent current flow leading to unnecessary energy consumption. In this letter, we experimentally demonstrate that, the PCMO-based RRAM, a memristor (1M) in series with the NPN selector can be used as a synapse to reduce the undesirable energy consumption. First, we propose the pre- and post-neuronal waveform engineering required for PCMO-based memristor + Selector (1S1M) to reduce energy consumption. Second, we demonstrate experimentally that 1S1M synapse gives reduction in energy consumption compared with 1M synapse for a single neuronal waveform. Third, we implement and compare anti-STDP for 1M and 1S1M synapse to show no loss of generality. Thus, we experimentally demonstrate 1S1M-based energy efficient synapse for brain inspired computing. Autors: S. Lashkare;N. Panwar;P. Kumbhare;B. Das;U. Ganguly; Appeared in: IEEE Electron Device Letters Publication date: Sep 2017, volume: 38, issue:9, pages: 1212 - 1215 Publisher: IEEE
» Pea-Sized mmW Transceivers: QFN-?Based Packaging Concepts for Millimeter-Wave Transceivers
 Abstract:Enormous technological progress accomplished over the last several decades has facilitated the use of millimeter-wave (mmW) frequencies for mass-produced products such as automotive radars, industrial sensors, highspeed data communication links, and medical devices. The main enablers are new semiconductor technologies, with constantly improving cut-off frequencies reaching several hundred gigahertz. However, the dominant limiting factor for the mass production of low-cost mmW systems above 100 GHz is that suitable packaging technologies are not yet available. Still, a dramatic increase in research and development is taking place in the area of mmW packaging. The goal of this article is to provide a short overview of the topic and then present one particular approach in detail: the idea of integrating a complete mmW front end, including the antenna, into one small solderable surface mount device (SMD). Autors: Thomas Zwick;Florian Boes;Benjamin Göttel;Akanksha Bhutani;Mario Pauli; Appeared in: IEEE Microwave Magazine Publication date: Sep 2017, volume: 18, issue:6, pages: 79 - 89 Publisher: IEEE
» Perfect Gaussian Integer Sequences of Period $p^{k}$ With Degrees Equal to or Less Than $k+1$
 Abstract:This paper presents the construction of perfect Gaussian integer sequence (PGIS) of period with degrees equal to or less than , where is a prime number and . The study begins with the partitioning of into subsets, from which base sequences are defined to construct degree- PGISs. The constraint equations derived from matching the ideal periodic autocorrelation function criterion in the time domain are nonlinear. We propose a decomposition method that can transform these nonlinear equations into linear equations with variables. The number of nonlinear constraint equations derived from the frequency domain is , where the sequence coefficients can be derived sequentially by an iteration algorithm. These two proposed schemes simplify the construction of the degree- PGIS. PGISs having less th- n degrees can be constructed in two steps. First, some sequence coefficients are assigned a zero value or one or more pairs of two consecutive base sequences are combined into one. The second step involves the adjustment of new sequence coefficients for the associated sequence to be perfect. We show that there exist at least distinct PGIS patterns of period with degrees equal to or less than . Autors: Kuo-Jen Chang;Ho-Hsuan Chang; Appeared in: IEEE Transactions on Communications Publication date: Sep 2017, volume: 65, issue:9, pages: 3723 - 3733 Publisher: IEEE
» Perfect Hashing Based Parallel Algorithms for Multiple String Matching on Graphic Processing Units
 Abstract:Multiple string matching has a wide range of applications such as network intrusion detection systems, spam filters, information retrieval systems, and bioinformatics. To accelerate multiple string matching, many hardware approaches are proposed to accelerate string matching. Among the hardware approaches, memory architectures have been widely adopted because of their flexibility and scalability. A conventional memory architecture compiles multiple string patterns into a state machine and performs string matching by traversing the corresponding state transition table. Due to the ever-increasing number of attack patterns, the memory used for storing the state transition table increased tremendously. Therefore, memory reduction has become a crucial issue in optimizing memory architectures. In this paper, we propose two parallel string matching algorithms which adopt perfect hashing to compact a state transition table. Different from most state-of-the-art approaches implemented on specific hardware such as TCAM, FPGA, or ASIC, our proposed approaches are easily implemented on commodity DRAM and extremely suitable to be implemented on GPUs. The proposed algorithms reduce up to 99.5 percent memory requirements for storing the state transition table compared to the traditional two-dimensional memory architecture. By studying existing approaches, our results obtain significant improvements in memory efficiency. Autors: Cheng-Hung Lin;Jin-Cheng Li;Chen-Hsiung Liu;Shih-Chieh Chang; Appeared in: IEEE Transactions on Parallel and Distributed Systems Publication date: Sep 2017, volume: 28, issue:9, pages: 2639 - 2650 Publisher: IEEE
» Performance Analysis and Scaling Law of MRC/MRT Relaying With CSI Error in Multi-Pair Massive MIMO Systems
 Abstract:This paper provides a comprehensive scaling law and performance analysis for multi-user massive multiple-input-multiple-output (MIMO) relay networks, where the relay is equipped with a massive antenna array and uses maximal-ratio combining/maximal-ratio transmission (MRC/MRT) for low-complexity processing. Imperfect channel state information (CSI) is considered for both source-relay and relay-destination channels. First, a sum-rate lower bound is derived, which manifests the effect of system parameters, including the numbers of relay antennas and users, the CSI quality, and the transmit powers of the sources and the relay. Via a general scaling model on the parameters with respect to the relay antenna number, the asymptotic scaling law of the signal-to-interference-plus-noise-ratio (SINR) is obtained, which shows quantitatively the tradeoff of the network parameters. In addition, a sufficient condition on the parameter scalings for the SINR to be asymptotically deterministic is given, which covers existing results on such analysis as special cases. Then, the scenario where the SINR increases linearly with the relay antenna number is studied. The sufficient and necessary condition on the parameter scaling for this scenario is proved. It is shown that in this case, the interference power is not asymptotically deterministic, and then, the average bit error rate is analyzed. Autors: Qian Wang;Yindi Jing; Appeared in: IEEE Transactions on Wireless Communications Publication date: Sep 2017, volume: 16, issue:9, pages: 5882 - 5896 Publisher: IEEE
» Performance Analysis for Finite Length LT Codes via Classical Probability Evaluation
 Abstract:Luby Transform (LT) codes play an important role in both data transmission and storage, but it is still a challenging problem that how to analyze their performance due to the degree distributions. In this letter, a novel methodology to analyze the performance of LT codes is proposed. This method establishes a probability transfer model between two adjacent steps of the belief propagation decoding algorithm, and provides an intuitive and unifying tool to analyze finite length LT codes. We first present the comprehensive description and theoretical identification of the proposed methodology, and then give some simulation results to validate its effectiveness. Autors: Longlong Suo;Gengxin Zhang;Jing Lv;Xiang Tian; Appeared in: IEEE Communications Letters Publication date: Sep 2017, volume: 21, issue:9, pages: 1957 - 1960 Publisher: IEEE
» Performance Analysis for Two-Way Network-Coded Dual-Relay Networks With Stochastic Energy Harvesting
 Abstract:In this paper, we consider an energy harvesting (EH) two-way (TW) dual-relay network, including one non-EH relay and one EH relay equipped with a finite-sized battery. In the network, a space-time transmission protocol with space-time network coding is designed, and an optimal transmission policy for the EH relay is proposed by using a stochastic solar EH model. In this optimal policy, the long-term paired-wise error probability (PEP) of the system is minimized by adapting the EH relay’s transmission power to the knowledge of its current battery energy, channel fading status, and causal solar EH information. The designed problem is formulated as a Markov decision process framework, and the conditional capability of the contribution to PEP by the EH relay is adopted as the reward function. We uncover a monotonic and limited difference structure for the expected total discounted reward. Furthermore, a non-conservative property and a monotonic structure of the optimal policy are revealed. Based on the optimal policy and its special structures, the expectation, lower and upper bounds, and asymptotic approximation of the PEP are computed and an interesting result on the system diversity performance is revealed, i.e., the full diversity order can be achieved only if the EH capability index, a metric to quantify the EH node’s capability of harvesting and storing energy, approaches to infinity; otherwise, the EH diversity order is only equal to one, and the coding gain of the network is increasing with the EH capability index at this time. Furthermore, a full diversity criterion for the EH TW dual-relay network is proposed. Finally, computer simulations confirm our theoretical analysis and show that our proposed optimal policy outperforms other compared policies. Autors: Wei Li;Meng-Lin Ku;Yan Chen;K. J. Ray Liu;Shihua Zhu; Appeared in: IEEE Transactions on Wireless Communications Publication date: Sep 2017, volume: 16, issue:9, pages: 5747 - 5761 Publisher: IEEE
» Performance Analysis of a Mutually Coupled Linear Switched Reluctance Machine for Direct-Drive Wave Energy Conversions
 Abstract:The requirements of high efficiency and environment-friendly behavior for wave energy conversions (WECs) have promoted improving investigations of linear electric machines. As an alternative to these existing linear machines, a mutually coupled linear switched reluctance machine (MCLSRM) for direct-drive WECs is proposed in this paper. An extensive comparative study is carried out between the proposed machine and other two comparative machines. By analyzing the operation principles of the three machines, the flux linkage and electromagnetic force formulas are theoretically derived based on equivalent magnetic circuit models, and discussed with the aid of finite-element analysis. Due to high utilization of the electrical and magnetic circuits, it is possible to find an MCLSRM design with comparable force capability to a traditional linear permanent-magnet (LPM) machine with the same electrical loading and the similar overall volume. Furthermore, two prototypes of different machines of the proposed machine and its LPM counterpart are manufactured for experimental validation. From the comparison results, the proposed MCLSRM has a good performance to extract more power from the prime mover above the rated velocity and is highly economic. The LPM counterpart has higher efficiency due to its lower fundamental flux density. Autors: Jinhua Du;Deliang Liang;Xinzheng Liu; Appeared in: IEEE Transactions on Magnetics Publication date: Sep 2017, volume: 53, issue:9, pages: 1 - 10 Publisher: IEEE
» Performance Analysis of Multiple Association in Ultra-Dense Networks
 Abstract:In this paper, we propose a general mathematical framework to compute the average downlink rate in a multiple connectivity context considering ultra-dense network (UDN) environment. UDN is a dense small cells network featured by the high density of small cells that may exceed the density of active users. In multiple association, a user connects to base stations (BSs) that provide the maximum average received power forming a multicell. This provides the user with a “data-shower,” where the user’s traffic is split into multiple paths, which helps overcoming the capacity limitations imposed by the backhaul links. The developed framework significantly simplifies the computation of the average downlink rate of the individual connections to the cells of a multicell. Moreover, the accuracy of the mathematical framework is confirmed by extensive simulations. The simulation results show a perfect match with the numerical results computed from the mathematical framework in different combinations of the system parameters including multicell size, small cells density, active users density, pathloss exponent, and fading channel distribution of the signal link. Autors: Mahmoud Kamel;Walaa Hamouda;Amr Youssef; Appeared in: IEEE Transactions on Communications Publication date: Sep 2017, volume: 65, issue:9, pages: 3818 - 3831 Publisher: IEEE
» Performance Assessment of A Novel Vertical Dielectrically Modulated TFET-Based Biosensor
 Abstract:A vertical dielectrically modulated tunnel field-effect transistor (V-DMTFET) as a label-free biosensor has been investigated in this paper for the first time and compared with lateral DMTFET (L-DMTFET) using underlap concept and gate work function engineering. To improve the performance of lateral biosensor (LB), a heavily doped front gate -pocket and gate-to-source overlap is introduced in the vertical biosensor (VB). The integrated effect of lateral tunneling as well as vertical tunneling in VB leads to enhanced ON-state current and decrease the subthreshold swing. To evaluate sensing ability of these devices, charged and charged neutral biomolecules are immobilized in nanogap cavity independently. A deep analysis has been performed to show the effect of variation in dielectric constant (), charge density (), -composition of Ge, % volume filling of , length and thickness of a -pocket and sensitivity of electrical parameters is also incorporated. Dual-pocket (front and back gate pocket) VB is studied and compared with the LB and VB in the tabular form. Noise characteristic of dielectrically modulated field-effect transistor, L-DMTFET, and V-DMTFET is also evaluated. Autors: Madhulika Verma;Sukeshni Tirkey;Shivendra Yadav;Dheeraj Sharma;Dharmendra Singh Yadav; Appeared in: IEEE Transactions on Electron Devices Publication date: Sep 2017, volume: 64, issue:9, pages: 3841 - 3848 Publisher: IEEE
» Performance Assessment of Chirp-Based Time Dissemination and Data Communications in Inductively Coupled Links
 Abstract:Advantages of inductively coupled links for short-range communications are well known. Recently, they gained popularity as a viable solution for wireless power transmission. Interesting to notice that data communication capability is required as well, mainly for coordinating the transfer process. In this paper, the authors address the use of chirp signaling over inductively coupled links for both time dissemination and data communications. Such an approach extends field of applications, including data acquisition and instrumentation that are used in industrial automation. The effectiveness of the proposed approach is verified with extensive simulations and using a proof-of-concept prototype. Despite the prototype simplicity, jitter on the synchronizing reference signal is in the order of few microseconds and the bit error rate, over a short distance, is negligible. Autors: Alessio De Angelis;Paolo Carbone;Emiliano Sisinni;Alessandra Flammini; Appeared in: IEEE Transactions on Instrumentation and Measurement Publication date: Sep 2017, volume: 66, issue:9, pages: 2474 - 2482 Publisher: IEEE
» Performance Bounds Analysis for Semi-Blind Channel Estimation in MIMO-OFDM Communications Systems
 Abstract:Most communications systems require channel estimation for equalization and symbol detection. Currently, this is achieved by using dedicated pilot symbols, which consume a non-negligible part of the throughput and power resources, especially for large dimensional systems. The main objective of this paper is to quantify the rate of reduction of this overhead due to the use of a semi-blind channel estimation. Different data models and different pilot design schemes have been considered in this paper. By using the Cramér Rao Bound (CRB) tool, the estimation error variance bounds of the pilot-based and semi-blind based channel estimators for a multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system are compared. In particular, for large MIMO-OFDM systems, a direct computation of the CRB is prohibitive, and hence, a dedicated numerical technique for its fast computation has been developed. Many key observations have been made from this comparative study. The most important one is that, thanks to the semi-blind approach, one can skip about 95% of the pilot samples without affecting the channel estimation quality. Autors: Abdelhamid Ladaycia;Anissa Mokraoui;Karim Abed-Meraim;Adel Belouchrani; Appeared in: IEEE Transactions on Wireless Communications Publication date: Sep 2017, volume: 16, issue:9, pages: 5925 - 5938 Publisher: IEEE
» Performance Degradation of Typical 1550 nm Optical Intersatellite Communication Systems in Space Ionizing Radiation Environment
» Performance Enhancement in N-Channel Organic Field-Effect Transistors Using Ferroelectric Material as a Gate Dielectric
 Abstract:Organic field-effect transistors (OFETs) were elaborated using N,N’-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C) as transport electron material and two polymeric insulators were used as gate dielectric: polymethyl methacrylate (PMMA), a low-k material widely used in OFETs, and poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)), a ferroelectric material that has a high relative permittivity. Several configurations using both dielectrics were studied. We report a threshold and operating voltage reduction by 3 and 2, respectively, with P(VDF-TrFE)/PMMA gate dielectric compared to PMMA reference OFETs due to a higher capacitance value. It exhibits good performances with a mobility of 0.165 cm/Vs, a threshold voltage of 2.9 V, and an on–off current ratio . Autors: Benjamin Ramos;Manuel Lopes;David Buso;Marc Ternisien; Appeared in: IEEE Transactions on Nanotechnology Publication date: Sep 2017, volume: 16, issue:5, pages: 773 - 777 Publisher: IEEE
» Performance Improvement for RF Energy-Harvesting Relays via Relay Selection
 Abstract:Energy harvesting (EH) is a promising technique to reduce energy consumption for information relaying. With EH capability, an intermediate node, acting as the relay, can replenish energy inherent in the radio-frequency (RF) signal from a source node and use the harvested energy to forward the received signal to the destination. To efficiently utilize the harvested energy, it is important to select proper relays to receive and forward the source signal. In this paper, we investigate the relay selection problem in the context of EH relays. Based on the celebrated time-switching relaying (TSR) protocol, we propose a new relay selection scheme that mitigates the risk of ill relay selection due to the mismatch between the source–relay and relay–destination channel conditions. In addition to the time-division (TD) block structure considered in TSR, we propose a full-duplex (FDX) block structure that improves the effective transmission time of EH relays. The performance of the proposed relay selection scheme in terms of the outage probability and the throughput using both TD and FDX block structures is analyzed. We also provide closed-form expressions of the outage probability under the high signal-to-noise ratio (SNR) assumption. Numerical results are presented to demonstrate the superiority of the proposed relay selection scheme compared with the existing ones. Autors: Kuang-Hao Liu;Te-Lin Kung; Appeared in: IEEE Transactions on Vehicular Technology Publication date: Sep 2017, volume: 66, issue:9, pages: 8482 - 8494 Publisher: IEEE
» Performance Improvement in Wideband Spectrum Sensing Under Fading: Use of Diversity
 Abstract:Diversity is used to combat fading and shadowing in narrowband spectrum sensing. In this paper, we propose two new detection algorithms for wideband spectrum sensing that use square law combining (SLC) diversity to improve the detection performance. We analyze the performance of these algorithms under Nakagami fading. The proposed schemes include channel by channel square law combining (CC-SLC) and ranked square law combining (R-SLC). We first provide the asymptotic analysis for decision statistic of received energy to simplify the analysis. The approximated probability density function (pdf) to decision statistic is used to derive the pdf of received energy for number of diversity branches. The performance of the proposed algorithms is measured in terms of probability of insufficient spectrum opportunity () and probability of excessive interference opportunity (). The analysis provided in this paper is general and can be used with any fading model and diversity scheme. Experiments are carried out using theoretical analysis and also verified by using Monte-Carlo simulation. Our analysis shows that the proposed algorithms using diversity outperform the channel by channel and ranked channel detection algorithms used under no diversity. Our results also indicate that among the proposed detection algorithms R-SLC performs better. Autors: Kamal Captain;Manjunath Joshi; Appeared in: IEEE Transactions on Vehicular Technology Publication date: Sep 2017, volume: 66, issue:9, pages: 8152 - 8162 Publisher: IEEE
» Performance Optimized Expectation Conditional Maximization Algorithms for Nonhomogeneous Poisson Process Software Reliability Models
 Abstract:Nonhomogeneous Poisson process (NHPP) and software reliability growth models (SRGM) are a popular approach to estimate useful metrics such as the number of faults remaining, failure rate, and reliability, which is defined as the probability of failure free operation in a specified environment for a specified period of time. We propose performance-optimized expectation conditional maximization (ECM) algorithms for NHPP SRGM. In contrast to the expectation maximization (EM) algorithm, the ECM algorithm reduces the maximum-likelihood estimation process to multiple simpler conditional maximization (CM)-steps. The advantage of these CM-steps is that they only need to consider one variable at a time, enabling implicit solutions to update rules when a closed form equation is not available for a model parameter. We compare the performance of our ECM algorithms to previous EM and ECM algorithms on many datasets from the research literature. Our results indicate that our ECM algorithms achieve two orders of magnitude speed up over the EM and ECM algorithms of [1] when their experimental methodology is considered and three orders of magnitude when knowledge of the maximum-likelihood estimation is removed, whereas our approach is as much as 60 times faster than the EM algorithms of  [2]. We subsequently propose a two-stage algorithm to further accelerate performance. Autors: Vidhyashree Nagaraju;Lance Fiondella;Panlop Zeephongsekul;Chathuri L. Jayasinghe;Thierry Wandji; Appeared in: IEEE Transactions on Reliability Publication date: Sep 2017, volume: 66, issue:3, pages: 722 - 734 Publisher: IEEE
» Permanent Magnet Temperature Estimation in PM Synchronous Motors Using Low-Cost Hall Effect Sensors
 Abstract:Knowledge of the permanent magnet (PM) temperature in PM synchronous machines (PMSMs) is of great importance both for control and monitoring purposes. Increase in PM temperature during motor operation can degrade the magnetic flux strength and consequently the machine's torque production capability, and can also cause irreversible demagnetization of the PM. Direct measurement of the PM temperature is not viable in practice due to both cost and reliability issues. Indirect PM temperature estimation methods recently studied require knowledge of thermal or electrical model parameters or can have undesired effects on motor operation. In this paper, the feasibility of using low-cost Hall-effect sensors for PM temperature estimation is investigated. Hall sensors are present for detecting the initial position of the rotor in majority of PMSM applications for which incremental encoders are used for control. The proposed method can, therefore, be implemented with low or no additional cost. Experimental results on two interior PMSMs show that the method is capable of providing noninvasive estimation of the PM temperature without a priori motor parameter information for monitoring and protection against excessive increase in temperature. Autors: Daniel Fernandez;Doosoo Hyun;Yonghyun Park;David Díaz Reigosa;Sang Bin Lee;Dong-Myung Lee;Fernando Briz; Appeared in: IEEE Transactions on Industry Applications Publication date: Sep 2017, volume: 53, issue:5, pages: 4515 - 4525 Publisher: IEEE
» Perovskite solar cells on paper and the role of substrates and electrodes on performance
 Abstract:The first perovskite solar cell (PSC) fabricated directly on a paper substrate is here reported delivering a maximum power conversion efficiency of 2.7%. The paper PSCs (PPSC) were developed with a low-temperature paper/Au/SnO2/meso-TiO2/CH3NH3PbI3/Spiro-OMeTAD/MoOx/ Au/MoOx architectureutilizingAu/SnO2 and MoOx/Au/MoOx stacks as electron- and hole- extracting electrodes respectively. The transparent MoOx/Au/MoOx electrode had a favourable combination of transmittance (62.5%) and sheet resistance (). By comparing performance of cells on paper with those fabricated on glass and plastic films with different electrodes, we identify avenues to guide future improvements. All deposition processes are scalable and compatible with large area printing or evaporation technologies. Paper represents a lightweight, flexible, inexpensive, ubiquitous, and environmentally friendly cellulosic material, paving the way for integrating perovskite technology with other electronic components as well as for the development of independent light-harvesting photovoltaic devices on recyclable and low-cost cellulose paper substrates. Autors: Sergio Castro-Hermosa;Janardan Dagar;Andrea Marsella;Thomas M. Brown; Appeared in: IEEE Electron Device Letters Publication date: Sep 2017, volume: 38, issue:9, pages: 1278 - 1281 Publisher: IEEE
» Phase Change and Magnetic Memories for Solid-State Drive Applications
 Abstract:The state-of-the-art solid-state drives (SSDs) now heterogeneously integrate NAND Flash and dynamic random access memories (DRAMs) to partially hide the limitation of the nonvolatile memory technology. However, due to the increased request for storage density coupled with performance that positions the storage tier closer to the latency of the processing elements, NAND Flash are becoming a serious bottleneck. DRAM as well are a limitation in the SSD reliability due to their vulnerability to the power loss events. Several emerging memory technologies are candidate to replace them, namely the storage class memories. Phase change memories and magnetic memories fall into this category. In this work, we review both technologies from the perspective of their possible application in future disk drives, opening up new computation paradigms as well as improving the storage characteristics in terms of latency and reliability. Autors: Cristian Zambelli;Gabriele Navarro;Véronique Sousa;Ioan Lucian Prejbeanu;Luca Perniola; Appeared in: Proceedings of the IEEE Publication date: Sep 2017, volume: 105, issue:9, pages: 1790 - 1811 Publisher: IEEE
» Phase Comparison Method for Wide-Frequency-Range Microwave Photonic Signals
 Abstract:The goal of this study is to establish a phase comparison method using high-frequency microwave photonic signals. The signal is generated as a beat frequency of a dual-wavelength optical signal. We propose a double differential phase comparison method suitable for a phase-locked loop. This is achieved by using an optical frequency shifter and two low-frequency photomixers (optical-to-electrical signal converters). The basic approach of the method is that the phase difference between the high-frequency dual-wavelength signals can be measured as a differential phase of the detected low-frequency microwave signals by two respective low-frequency photomixers without high-frequency photomixers. With this approach, the phase comparison of any range of frequencies of the dual-wavelength signals can be performed by two identical low-frequency photomixers. In an application of this method for separate fiber-coupled stations, a common laser signal transmission is effectively carried out with a dual-wavelength optical signal. We conducted an experiment to verify the effectiveness of the double differential phase comparison method by comparing the direct phase comparison method. Autors: Hitoshi Kiuchi; Appeared in: Journal of Lightwave Technology Publication date: Sep 2017, volume: 35, issue:17, pages: 3643 - 3649 Publisher: IEEE
» Phased Array Ultrasound System for Planar Flow Mapping in Liquid Metals
 Abstract:Controllable magnetic fields can be used to optimize flows in technical and industrial processes involving liquid metals in order to improve quality and yield. However, experimental studies in magnetohydrodynamics often involve complex, turbulent flows and require planar, two-component (2c) velocity measurements through only one acoustical access. We present the phased array ultrasound Doppler velocimeter as a modular research platform for flow mapping in liquid metals. It combines the pulse wave Doppler method with the phased array technique to adaptively focus the ultrasound beam. This makes it possible to resolve smaller flow structures in planar measurements compared with fixed-beam sensors and enables 2c flow mapping with only one acoustical access via the cross beam technique. From simultaneously measured 2-D velocity fields, quantities for turbulence characterization can be derived. The capabilities of this measurement system are demonstrated through measurements in the alloy gallium-indium–tin at room temperature. The 2-D, 2c velocity measurements of a flow in a cubic vessel driven by a rotating magnetic field (RMF) with a spatial resolution of up to 2.2 mm are presented. The measurement results are in good agreement with a semianalytical simulation. As a highlight, two-point correlation functions of the velocity field for different magnitudes of the RMF are presented. Autors: Kevin Mäder;Richard Nauber;Vladimir Galindo;Hannes Beyer;Lars Büttner;Sven Eckert;Jürgen Czarske; Appeared in: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control Publication date: Sep 2017, volume: 64, issue:9, pages: 1327 - 1335 Publisher: IEEE
» Phonon Mean Free Path in Few Layer Graphene, Hexagonal Boron Nitride, and Composite Bilayer h-BN/Graphene
 Abstract:In this study, ab-initio calculations were performed to obtain the phonon dispersions of seven different structures: single layer graphene, bilayer graphene, graphite, single layer h-BN, bilayer h-BN, bulk h-BN, and finally composite bilayer h-BN/graphene. Using these dispersions specific heat, group velocity, and single mode relaxation times of phonons were obtained to calculate their thermal conductivities, and mean free paths at room temperature. Calculated variables were used to understand the effects of additional layers to thermophysical properties, phonon mode contributions to thermal conductivity, and the limits for ballistic-diffusive heat transfer of all seven structures. Finally, based on the obtained data, thermal properties of the composite bilayer h-BN/graphene were investigated and compared to those of few layer graphene and h-BN structures. Autors: Hamed Gholivand;Nazli Donmezer; Appeared in: IEEE Transactions on Nanotechnology Publication date: Sep 2017, volume: 16, issue:5, pages: 752 - 758 Publisher: IEEE
» Photoelectric Response in Indium-Tin Oxide Films
 Abstract:In this paper, the mechanism of photoelectric response of indium tin oxide films is discussed. We observed the photoelectric emission in indium tin oxide films and suggested the physical mechanism describing the photoelectric response based on this phenomenon. We showed that the anisotropy of the electric field could be associated with preferred orientation of the grains in deposited films. We discussed the influence of parasitic capacitance on the shape of the photoelectric response. In this paper, we showed that photoelectric effect in indium-tin oxide films could be applied to measure the temporal characteristics of the laser pulse. Autors: Alexey V. Makhin;Igor K. Meshkovskiy;Semyon A. Plyastsov; Appeared in: IEEE Sensors Journal Publication date: Sep 2017, volume: 17, issue:18, pages: 5880 - 5884 Publisher: IEEE
» Photometric Stereo in a Scattering Medium
 Abstract:Photometric stereo is widely used for 3D reconstruction. However, its use in scattering media such as water, biological tissue and fog has been limited until now, because of forward scattered light from both the source and object, as well as light scattered back from the medium (backscatter). Here we make three contributions to address the key modes of light propagation, under the common single scattering assumption for dilute media. First, we show through extensive simulations that single-scattered light from a source can be approximated by a point light source with a single direction. This alleviates the need to handle light source blur explicitly. Next, we model the blur due to scattering of light from the object. We measure the object point-spread function and introduce a simple deconvolution method. Finally, we show how imaging fluorescence emission where available, eliminates the backscatter component and increases the signal-to-noise ratio. Experimental results in a water tank, with different concentrations of scattering media added, show that deconvolution produces higher-quality 3D reconstructions than previous techniques, and that when combined with fluorescence, can produce results similar to that in clear water even for highly turbid media. Autors: Zak Murez;Tali Treibitz;Ravi Ramamoorthi;David J. Kriegman; Appeared in: IEEE Transactions on Pattern Analysis and Machine Intelligence Publication date: Sep 2017, volume: 39, issue:9, pages: 1880 - 1891 Publisher: IEEE
» Photonic Generation of High Fidelity RF Sources for Mobile Communications
 Abstract:A novel technique for generating RF sources for mobile communications based on dual Mach–Zehnder modulators and high-power charge-compensated modified unitraveling carrier (CC-MUTC) photodiodes is presented. A system model is developed and used to establish and mitigate nonlinearities attributed to its constituent components, i.e., waveform generators, amplifiers, modulators, and photodiodes. In particular, digital predistortion is used to improve source linearity. Extensive experiments are conducted to characterize the proposed system, using a commercial 5 MHz local thermal equilibrium signal. Optimal results are achieved with a CC-MUTC photodiode to attain an RF power greater than 12.5 dBm and an adjacent channel leakage ratio lower than −63.5 dBc. Autors: Fuquan Wang;Shouyuan Shi;Garrett J. Schneider;Peng Yao;Christopher Schuetz;Janusz Murakowski;Xiaofeng Qi;Munawar Kermalli;Xiang Liu;Dennis W. Prather; Appeared in: Journal of Lightwave Technology Publication date: Sep 2017, volume: 35, issue:18, pages: 3901 - 3908 Publisher: IEEE
» Piezoelectric Floating Element Shear Stress Sensor for the Wind Tunnel Flow Measurement
 Abstract:A piezoelectric (PE) sensor with a floating element was developed for direct measurement of flow induced shear stress. The PE sensor was designed to detect the pure shear stress while suppressing the effect of normal stress generated from the vortex lift up by applying opposite poling vectors to the PE elements. During the calibration stage, the prototyped sensor showed a high sensitivity to shear stress (91.3 ± 2.1 pC/Pa) due to the high PE coefficients (1330 pC/N) of the constituent 0.67Pb(MgNb)O3–0.33PbTiO3 (PMN–33%PT) single crystal. By contrast, the sensor showed almost no sensitivity to normal stress (less than 1.2 pC/Pa) because of the electromechanical symmetry of the sensing structure. The usable frequency range of the sensor is up to 800 Hz. In subsonic wind tunnel tests, an analytical model was proposed based on cantilever beam theory with an end-tip-mass for verifying the resonance frequency shift in static stress measurements. For dynamic stress measurements, the signal-to-noise ratio (SNR) and ambient vibration-filtered pure shear stress sensitivity were obtained through signal processing. The developed PE shear stress sensor was found to have an SNR of 15.8 ± 2.2 dB and a sensitivity of 56.5 ± 4.6 pC/Pa in the turbulent flow. Autors: Taeyang Kim;Aditya Saini;Jinwook Kim;Ashok Gopalarathnam;Yong Zhu;Frank L. Palmieri;Christopher J. Wohl;Xiaoning Jiang; Appeared in: IEEE Transactions on Industrial Electronics Publication date: Sep 2017, volume: 64, issue:9, pages: 7304 - 7312 Publisher: IEEE
» PJM Integrates Energy Storage: Their Technologies and Wholesale Products
 Abstract:PJM INTERConnection (PJM) was the first U.S. independent system operator/regional transmission organization (ISO/RTO) to demonstrate how battery energy storage resources provide frequency regulation services in a competitive market. Since its first pilot in 2009, PJM has integrated nearly 300 MW of advanced energy storage resources into its market. During this time period, ISO s/RTOs have developed rules to allow energy storage resources to participate in wholesale electricity markets. The Federal Energy Regulatory Commission (FERC) and state lawmakers have also taken steps to create an environment in which energy storage resources play an increasing role in the reliable operation of the power grid. This article outlines the storage technologies operating in PJM today and the wholesale products they provide to the market as well as discusses services that energy storage resources may provide in the future along with integration opportunities, resulting in a larger amount of storage deployed within the grid. Autors: Hong Chen;Scott Baker;Scott Benner;Aaron Berner;Jianwei Liu; Appeared in: IEEE Power and Energy Magazine Publication date: Sep 2017, volume: 15, issue:5, pages: 59 - 67 Publisher: IEEE
» Planning to Equip the Power Distribution Networks with Automation System
 Abstract:Implementing automation system in distribution networks needs a huge investment that usually cannot be funded entirely in a short period of time. So distribution companies (DISCOs) should develop long-term plans to equip their network with automation technologies as far as economically justifiable. Aiming to provide a methodology for development such plans, this paper presents a novel multistage planning model for implementing distribution automation system considering all main hardware and software infrastructures. The proposed method optimally determines the type, location, and time in which an equipment or infrastructure must be added to network considering the network capacity expansion plan. The objective function of the planning problem is to maximize the net present value of the DISCO's profit in the planning time horizon. In this method, the optimization problem is solved using the genetic algorithm approach as a promising technique in solving the mixed integer nonlinear programming problems. The proposed method is evaluated on an illustrative test network and the obtained results are presented and discussed. Autors: Saeed Heidari;Mahmud Fotuhi-Firuzabad;Matti Lehtonen; Appeared in: IEEE Transactions on Power Systems Publication date: Sep 2017, volume: 32, issue:5, pages: 3451 - 3460 Publisher: IEEE
» Platform Storage Performance With 3D XPoint Technology
 Abstract:Microradian tracking and pointing errors significantly affect the link performance and the bit error probability in free-space optical communication. This paper proposes the measurement method for point-ahead angle and coalignment error, which can significantly mitigate the tracking and pointing error, thus reduces the power of the free-space optical communication system. By using technologies of corner cube reflector, off-axis reflecting telescope, vacuum long-light path and anti-interference support structure design, microangles can be measured accurately, especially the coalignment error angle which is formed by two wide, incoherent beams nearly antiparallel to each other. This paper introduces the measuring equipment's structure, together with the measurement method and theoretical measurement model. The measuring accuracy analysis indicated that the measurement uncertainty of both point-ahead angle and coalignment error was superior to 0.2 μrad and the validation experimental results proved that measuring accuracies of point-ahead angle and coalignment error are all smaller than 1 μrad. Autors: Jianmin Wang;Ye Zhou;Rumeng Bai;Gang Wang; Appeared in: Journal of Lightwave Technology Publication date: Sep 2017, volume: 35, issue:18, pages: 3886 - 3893 Publisher: IEEE
» Polarimetric SAR Image Factorization
 Abstract:This paper reformulates the problem of polarimetric incoherent target decomposition as a general image factorization which aims to simultaneously estimate a dictionary of meaningful atom scatterers and their corresponding spatial distribution maps. Both model-based and eigenanalysis-based decompositions can be seen as special cases of image factorization under specific constraints. The inverse problem of image factorization can be converted to an equivalent nonnegative matrix factorization (NMF) problem via redundant coding. It enables a wide range of NMF algorithms with various regularizations to be directly applicable to polarimetric image analysis. The advantage of the proposed image factorization is demonstrated on both synthesized and real data. It also shows that extended applications such as speckle reduction and classification can benefit from the proposed image factorization. Autors: Feng Xu;Qian Song;Ya-Qiu Jin; Appeared in: IEEE Transactions on Geoscience and Remote Sensing Publication date: Sep 2017, volume: 55, issue:9, pages: 5026 - 5041 Publisher: IEEE
» Polarization-Insensitive Single-/Dual-Band Tunable Absorber With Independent Tuning in Wide Frequency Range
 Abstract:In this communication, polarization-insensitive tunable absorbers are presented for single- and dual-band applications with wide tuning range. The proposed designs consist of periodic patterns of split square loops connected with cross-dipoles through varactor diodes which exhibit tunable performances. Due to four-fold symmetry, the structures have the novel characteristic of polarization insensitivity unlike the earlier reported tunable absorbers. Moreover, the designs are comprised of vias to provide required biasing to the diodes, which also result wide frequency tuning. Two single-band tunable absorbers are initially designed, which are combined to exhibit a dual-band tunable absorber with independent tuning of absorption frequencies. A novel biasing methodology has been developed to provide bias voltages to the semiconductor diodes without disturbing the original frequency response. The fabricated sample, while measured, shows good agreement with the simulated responses under normal incidence. Autors: Saptarshi Ghosh;Kumar Vaibhav Srivastava; Appeared in: IEEE Transactions on Antennas and Propagation Publication date: Sep 2017, volume: 65, issue:9, pages: 4903 - 4908 Publisher: IEEE
» Polarization-Reconfigurable Circularly Polarized Planar Antenna Using Switchable Polarizer
 Abstract:A novel polarization-reconfigurable planar antenna is presented. The antenna consists of an electronically reconfigurable polarizer integrated with a printed slot. By changing the states of the p-i-n diodes on the polarizer, the linearly polarized (LP) waves radiated by the slot can be converted into either right-hand circularly polarized (RHCP) or left-hand CP (LHCP) waves. The polarizer contains 16 unit cells arranged as a array. The antenna radiates RHCP waves if the p-i-n diodes on the top side of the polarizer are switched ON, while LHCP waves are radiated if the p-i-n diodes of the bottom side of the polarizer are switched ON instead. The physical mechanisms of the antenna are discussed and the parametric study is carried out by full-wave simulations. To verify the concept, one prototype at 2.5 GHz is designed, fabricated, and measured. Good agreement between the measured and simulated results is obtained. The antenna achieves a gain ≥8.5 dBic in both RHCP and LHCP with an aperture efficiency of 70%. Advantages of the proposed design include electronically reconfigurable polarizations for RHCP or LHCP, low profile, low cost, high isolation between the dc bias circuit and RF signals, high power handling capability, and easy extension to large-scale arrays without increasing the complexity of the dc bias circuit. To the best of our knowledge, this is the first report of an electronically polarization-reconfigurable CP antenna with a single-substrate polarizer. Autors: Wenting Li;Steven Gao;Yuanming Cai;Qi Luo;Mohammed Sobhy;Gao Wei;Jiadong Xu;Jianzhou Li;Changying Wu;Zhiqun Cheng; Appeared in: IEEE Transactions on Antennas and Propagation Publication date: Sep 2017, volume: 65, issue:9, pages: 4470 - 4477 Publisher: IEEE
» Polycrystalline Diamond MOSFET With MoO3 Gate Dielectric and Passivation Layer
 Abstract:We report the hydrogen terminated polycrystalline diamond MOSFET with a 10-nm MoO3 gate dielectric and a 50-nm MoO3 passivation layer. The device with a gate length of shows the saturation drain current ( of 100mA/mm, the transconductance of 35 mS/mm, and the ON-resistance of mm at V. The stability of the repeated – measurements was demonstrated by a mere decrease of 3.3% between the first and third sweepings. In addition, the devices worked well at 200 °C delivering even larger than that at room temperature. The possible mechanisms for – changes in the successive measurements and induced by the change of the ambient temperature are suggested. Autors: Zeyang Ren;Jinfeng Zhang;Jincheng Zhang;Chunfu Zhang;Dazheng Chen;Pengzhi Yang;Yao Li;Yue Hao; Appeared in: IEEE Electron Device Letters Publication date: Sep 2017, volume: 38, issue:9, pages: 1302 - 1304 Publisher: IEEE
» Position-Based Interference Elimination for High-Mobility OFDM Channel Estimation in Multicell Systems
 Abstract:Orthogonal frequency-division multiplexing (OFDM) and multicell architecture are widely adopted in current high-speed train (HST) systems for providing high-data-rate wireless communications. In this paper, a typical multiantenna OFDM HST communication system with multicell architecture is considered, where the intercarrier interference (ICI) caused by high mobility and the multicell interference (MCI) are both taken into consideration. By exploiting the train position information, a new position-based interference elimination method is proposed to eliminate both the MCI and the ICI for a general basis expansion model. We show that the MCI and the ICI can be completely eliminated by the proposed method to get the ICI-free pilots at each receive antenna. In addition, for the considered multicell HST system, we develop a low-complexity compressed channel estimation method and consider the optimal pilot pattern design. Both the proposed interference elimination method and the optimal pilot pattern are robust to the train speed and position, as well as the multicell multiantenna system. Simulation results demonstrate the benefits and robustness of the proposed method in the multicell HST system. Autors: Xiang Ren;Wen Chen;Bo Gong;Qibo Qin;Lin Gui; Appeared in: IEEE Transactions on Vehicular Technology Publication date: Sep 2017, volume: 66, issue:9, pages: 7986 - 8000 Publisher: IEEE
» Power Management Approach to Minimize Battery Capacity in Wind Energy Conversion Systems
 Abstract:In a wind-battery hybrid power system, minimal battery capacity is a crucial requirement to achieve economic operation. In this paper, an optimal power control strategy based on a first-order low-pass filter is proposed to minimize the battery capacity by adjusting the filter smoothing time constant. We demonstrate the mathematical relationship between the filter smoothing time constant and the fluctuation mitigation requirement during one sampling time, so the optimal filter smoothing time constant can be easily computed to minimize the battery capacity. Moreover, an online short-term power control is also considered to maintain the battery state of charge within a safe range and to regulate the battery power below its rating. The proposed power management approach is simple and easy to implement. In order to verify the effective features of the proposed power management approach, a case study is carried out along with some experimental verification. Autors: Cong-Long Nguyen;Hong-Hee Lee; Appeared in: IEEE Transactions on Industry Applications Publication date: Sep 2017, volume: 53, issue:5, pages: 4843 - 4854 Publisher: IEEE
» Power Spectrum of Refractive-Index Fluctuation in Hypersonic Plasma Turbulence
 Abstract:Anisotropic spatial distribution data of refractive-index fluctuation in hypersonic turbulence are obtained based on the experimental images of hypersonic turbulence. Furthermore, taking re-entry turbulent plasma fluctuation into consideration, the variance of the refractive-index fluctuation in hypersonic plasma is calculated based on the Saha equation and the expression of refractive index in hypersonic plasma. On this basic, the anisotropic power-spectral model of hypersonic plasma turbulence is established by introducing the orientation factor to the modified von Karman spectrum. Finally, the mutual coherence function (MCF) and the angle-of-arrival fluctuations of electromagnetic (EM) waves propagation in hypersonic plasma turbulence are calculated. Results show that the angle-of-arrival fluctuations have obvious differences between the directions of vertical to turbulent plasma flow field and parallel to it. The various gradients of the electron density along the direction of vertical to turbulent plasma flow field are far greater than the parallel to it, which causes the horizontal scale is larger than perpendicular scale of plasma eddies. Therefore, when EM waves propagating through plasma turbulence, the refractive effect of plasma eddies show obvious anisotropy. The results of this paper can be used to analyze the EM waves propagation characteristics in hypersonic plasma turbulence. Autors: Jiangting Li;Shaofei Yang;Lixin Guo;Mingjian Cheng;Teng Gong; Appeared in: IEEE Transactions on Plasma Science Publication date: Sep 2017, volume: 45, issue:9, pages: 2431 - 2437 Publisher: IEEE
» Power System Resilience to Extreme Weather: Fragility Modeling, Probabilistic Impact Assessment, and Adaptation Measures
 Abstract:Historical electrical disturbances highlight the impact of extreme weather on power system resilience. Even though the occurrence of such events is rare, the severity of their potential impact calls for 1) developing suitable resilience assessment techniques to capture their impacts and 2) assessing relevant strategies to mitigate them. This paper aims to provide fundamentals insights on the modeling and quantification of power systems resilience. Specifically, a fragility model of individual components and then of the whole transmission system is built for mapping the real-time impact of severe weather, with focus on wind events, on their failure probabilities. A probabilistic multitemporal and multiregional resilience assessment methodology, based on optimal power flow and sequential Monte Carlo simulation, is then introduced, allowing the assessment of the spatiotemporal impact of a windstorm moving across a transmission network. Different risk-based resilience enhancement (or adaptation) measures are evaluated, which are driven by the resilience achievement worth index of the individual transmission components. The methodology is demonstrated using a test version of the Great Britain's system. As key outputs, the results demonstrate how, by using a mix of infrastructure and operational indices, it is possible to effectively quantify system resilience to extreme weather, identify and prioritize critical network sections, whose criticality depends on the weather intensity, and assess the technical benefits of different adaptation measures to enhance resilience. Autors: Mathaios Panteli;Cassandra Pickering;Sean Wilkinson;Richard Dawson;Pierluigi Mancarella; Appeared in: IEEE Transactions on Power Systems Publication date: Sep 2017, volume: 32, issue:5, pages: 3747 - 3757 Publisher: IEEE
» PowerNetS: Coordinating Data Center Network With Servers and Cooling for Power Optimization
 Abstract:Recently, a lot of research efforts have been made to optimize the large amounts of energy consumed by different devices in data centers, including servers, cooling, and the data center network (DCN). Unfortunately, current research addresses these devices mostly in a separate manner, leading to inferior optimization results. This paper proposes PowerNetS, a power optimization framework that coordinates servers and DCN, as well as cooling, for minimized power consumption of a data center. PowerNetS leverages workload correlation analysis for more energy savings during server and traffic consolidations. More importantly, PowerNetS tries to change the DCN topology during server consolidation, in order to have more intra-server traffic and shorter flows that go through fewer switches. For example, two virtual machines previously located on two different servers can now be migrated to the same server, so that the flow between them no longer needs to use switches, which allows more devices to sleep for energy savings without network performance degradation. PowerNetS has been implemented on a physical testbed with 6 servers and 10 virtual switches that are configured using a production 48-port OpenFlow switch. Our evaluation with Wikipedia, Yahoo!, and IBM traces shows that PowerNetS can save up to 51.6% of energy by coordinating servers and DCN, which is 44.3% and 15.8% more than two state-of-the-art baselines, respectively. By further coordinating with cooling to utilize different cooling efficiencies at different locations within a data center, PowerNetS can achieve 8.8%–14.6% additional energy savings. Autors: Kuangyu Zheng;Wenli Zheng;Li Li;Xiaorui Wang; Appeared in: IEEE Transactions on Network and Service Management Publication date: Sep 2017, volume: 14, issue:3, pages: 661 - 675 Publisher: IEEE
» Precise Sensor Orientation of High-Resolution Satellite Imagery With the Strip Constraint
 Abstract:To achieve precise sensor orientation of high- resolution satellite imagery (HRSI), ground control points (GCPs) or height models are necessary to remove biases in orientation parameters. However, measuring GCPs is costly, laborious, and time consuming. We cannot even acquire well-defined GCPs in some areas. In this paper, a strip constraint model is established according to the geometric invariance that the biases of image points remain the same in dividing a strip image into standard images. Based on the rational function model and the strip constraint model, a feasible sensor orientation approach for HRSI with the strip constraint is presented. Through the use of the strip constraint, the bias compensation parameters of each standard image in the strip can be solved simultaneously with sparse GCPs. This approach remains effective even when the intermediate standard images in the strip are unavailable. Experimental results of the three ZiYuan-3 data sets show that two GCPs in the first image and two GCPs in the last image are sufficient for the sensor orientation of all the standard images in the strip. An orientation accuracy that is better than 1.1 pixels can be achieved in each standard image. Moreover, the inconsistent errors of tie points between adjacent standard images can also be reduced to less than 0.1 pixel. This result can guarantee that the generated complete digital orthophoto map of the whole strip is geometrically seamless. Autors: Jinshan Cao;Xiuxiao Yuan;Jianhong Fu;Jianya Gong; Appeared in: IEEE Transactions on Geoscience and Remote Sensing Publication date: Sep 2017, volume: 55, issue:9, pages: 5313 - 5323 Publisher: IEEE
» Precoder Designs for MIMO Gaussian Multiple Access Wiretap Channels
 Abstract:This paper studies multiple-input multiple-output multiple access wiretap channels (MAC-WT) where an eavesdropper tries to tap the communication between multiple legitimate transmitters and a legitimate receiver. In this system, we propose precoder optimization methods at the transmitters in order to maximize the sum secrecy rate performance. Although this problem can be solved by the well-known difference of convex (DC) programming, we present a more efficient algorithm whose computational complexity is much lower than that of the conventional DC approach. By investigating the Karush-Kuhn-Tucker conditions, it is confirmed that the proposed low-complexity algorithm achieves the same performance as the conventional DC method. Our analysis also reveals that the proposed algorithm ensures global optimality for multiple-input single-output MAC-WT cases, while binary power control is optimal for single-input multiple-output scenarios. Simulation results demonstrate the efficacy of the proposed precoding methods. Autors: Hoon Lee;Changick Song;Jihwan Moon;Inkyu Lee; Appeared in: IEEE Transactions on Vehicular Technology Publication date: Sep 2017, volume: 66, issue:9, pages: 8563 - 8568 Publisher: IEEE
» Predicting Bradycardia in Preterm Infants Using Point Process Analysis of Heart Rate
» Predicting Macular Edema Recurrence from Spatio-Temporal Signatures in Optical Coherence Tomography Images
 Abstract:Prediction of treatment responses from available data is key to optimizing personalized treatment. Retinal diseases are treated over long periods and patients’ response patterns differ substantially, ranging from a complete response to a recurrence of the disease and need for re-treatment at different intervals. Linking observable variables in high-dimensional observations to outcome is challenging. In this paper, we present and evaluate two different data-driven machine learning approaches operating in a high-dimensional feature space: sparse logistic regression and random forests-based extra trees (ET). Both identify spatio-temporal signatures based on retinal thickness features measured in longitudinal spectral-domain optical coherence tomography (OCT) imaging data and predict individual patient outcome using these quantitative characteristics. We demonstrate on a data set of monthly SD-OCT scans of 155 patients with central retinal vein occlusion (CRVO) and 92 patients with branch retinal vein occlusion (BRVO) followed over one year that we can predict from initial three observations if the treated disease will recur within the covered interval. ET predicts the outcome on fivefold cross-validation with an area under the receiver operating characteristic curve (AuC) of 0.83 for BRVO and 0.76 for CRVO. Logistic regression achieved an AuC of 0.78 and 0.79, respectively. At the same time, the methods identified stable predictive signatures in the longitudinal imaging data that are the basis for accurate prediction. Furthermore, our results show that taking spatio-temporal features into account improves accuracy compared with features extracted at a single time-point. Our results demonstrate the feasibility of mining longitudinal data for predictive signatures, and building predictive models based on observed data. Autors: Wolf-Dieter Vogl;Sebastian M. Waldstein;Bianca S. Gerendas;Ursula Schmidt-Erfurth;Georg Langs; Appeared in: IEEE Transactions on Medical Imaging Publication date: Sep 2017, volume: 36, issue:9, pages: 1773 - 1783 Publisher: IEEE
» Predictive Networked Control of Discrete Event Systems
 Abstract:In this technical note, we continue the work of [6] to investigate the networked control problem of discrete event systems. The problem is to find a networked supervisor so that the language generated by the supervised system is equal to a given specification language . While the networked supervisor in [6] is not predictive, we propose a predictive networked supervisor in this technical note, which predicts the impacts of communication delays and losses in the control channel in determining control actions. We derive the existence condition for a predictive networked supervisor. We show that predictive supervisors are better than non-predictive supervisors and no other supervisors are better than predictive supervisors. We further show that the predictive supervisor is least restrictive among all supervisors that generate language . Autors: Shaolong Shu;Feng Lin; Appeared in: IEEE Transactions on Automatic Control Publication date: Sep 2017, volume: 62, issue:9, pages: 4698 - 4705 Publisher: IEEE
» Predictive Resilience Analysis of Complex Systems Using Dynamic Bayesian Networks
 Abstract:Uncertain and potentially harsh operating environments are often known to alter the operational performance of a system. In order to maintain system performance while coping with varying operating environments and potential disruptions, the resilience of engineered systems is desirable. Engineering systems are often interconnected in a dimensional way inherently from basic components to subsystems to the system of systems, which poses a grand challenge for system designers to analyze the resilience of such a complex system. Moreover, further complications in the assessment of resilience in the engineering domain are attributed to time-varying system performances, random perturbation occurrences, and probable failures caused by adverse events. This paper presents a dynamic Bayesian network (DBN) approach for the modeling and predictive resilience analysis for dynamic engineered systems. With the inter-time-slice links and the conditional probability tables in a DBN, the system performance could be molded as changing in a discrete time slice, while capturing the temporal probabilistic dependencies between the variables. An industrial-based case study of an electricity distribution system is further studied to demonstrate the effectiveness of the DBN approach for resilience analysis. The approach presented in this paper hopes to aid in realizing resiliency in system designs and to pave the way toward enhancements in developing resilient engineered systems. Autors: Nita Yodo;Pingfeng Wang;Zhi Zhou; Appeared in: IEEE Transactions on Reliability Publication date: Sep 2017, volume: 66, issue:3, pages: 761 - 770 Publisher: IEEE
» Predictive Stator Flux and Load Angle Control of Synchronous Reluctance Motor Drives Operating in a Wide Speed Range
 Abstract:This paper presents a new simplified finite-control-set model predictive control strategy for synchronous reluctance motors operating in the entire speed range. It is a predictive control scheme that regulates the stator flux and the load angle of the synchronous reluctance motor, incorporating the ability to operate the drive in the field-weakening region and respecting the motor voltage and current limits as well as the load angle limitation needed to operate this type of motor in the maximum torque per voltage region. The proposed control strategy possesses some attractive features, such as no need for controller calibration, no weighting factors in the cost function, good robustness against parameter mismatch, and smaller computational cost compared to more traditional finite-control-set model predictive control algorithms. Simulation and experimental results obtained using a high-efficiency synchronous reluctance motor demonstrate the effectiveness of the proposed control scheme. Autors: Hazem Hadla;Sérgio Cruz; Appeared in: IEEE Transactions on Industrial Electronics Publication date: Sep 2017, volume: 64, issue:9, pages: 6950 - 6959 Publisher: IEEE
» Predistortion for Wideband Nonlinear Satellite Downlinks
 Abstract:In this letter, an efficient predistortion scheme is proposed to compensate imperfections in a satellite channel due to the nonlinear power amplifier and the output channel filter. The predistorter is a Wiener system consisting of the linear and nonlinear components, which are trained independently. The predistorter is well suited to systems where the data bits are generated onboard the satellite. The proposed setup effectively compensates the distortions and has lower complexity compared with other strategies. Autors: Kelvin J. Layton;Azam Mehboob;Assad Akhlaq;Flaviano Bagaglini;William G. Cowley;Gottfried Lechner; Appeared in: IEEE Communications Letters Publication date: Sep 2017, volume: 21, issue:9, pages: 1985 - 1988 Publisher: IEEE
» Predistortion Linearizer for Wideband AM/PM Cancelation With Left-Handed Delay Line
 Abstract:In this letter, a modified predistortion linearizer model is proposed to enable wideband synthesis of phase predistortion function. Additional time delay based on an artificial left-handed transmission line is introduced in the model to characterize the frequency-dependent phase conversion function, which can be utilized for wideband cancelation of the AM/PM distortion in microwave power amplifiers. Based on the proposed model, a microwave monolithic integrated circuit predistorter is designed to generate both positive gain and phase conversion according to the input power, and to realize increasing phase conversion as frequency increases. Large signal measurement of the design is performed at 20, 20.75, and 21.5 GHz. Result shows that +4.8-dB gain conversion is achieved, while phase conversion increases from +12.9° to +30.8° as frequency increases from 20 to 21.5 GHz. Autors: Dawei Zhang;Xin Xu;Hongxi Yu;Jun Li;Thangarasu Bharatha Kumar;Kaixue Ma;Kiat Seng Yeo; Appeared in: IEEE Microwave and Wireless Components Letters Publication date: Sep 2017, volume: 27, issue:9, pages: 794 - 796 Publisher: IEEE
» Preserving Strong Connectivity in Directed Proximity Graphs
 Abstract:This paper proposes a method to maintain the strong connectivity property of a mobile robot ad hoc network in the presence of disturbances or additional control goals. Each robot has a communication range modeled by an -dimensional sphere centered at the robot. The spheres for different robots may have different radii, resulting in a directed communication network. This paper is based on two concepts. The first is the structure of the Perron vector for reducible stochastic matrices. The second is the design of nonlinear controllers that ensure that two robots remain within a certain distance of each other despite disturbances. The results are supported by analysis and simulations. Autors: Hasan A. Poonawala;Mark W. Spong; Appeared in: IEEE Transactions on Automatic Control Publication date: Sep 2017, volume: 62, issue:9, pages: 4392 - 4404 Publisher: IEEE
» Preventive Replacements in Real-Time Standby Systems With Periodic Backups
 Abstract:This paper models a real-time warm standby system that has to accomplish a specified amount of task by a hard deadline. The system is subject to corrective replacements (CRs) upon failure of its operating element. It can also be renewed according to a predetermined schedule through preventive replacements (PRs). To facilitate an effective recovery of system operation after replacements, periodic backups are performed so that warm standby elements, upon being activated, can take over the mission task from the last backup point instead of from scratch. This paper presents a novel integrated model that considers effects of periodic backups, CRs and PRs in analyzing and optimizing real-time warm standby systems. Mission success probability and expected mission completion time are evaluated. Impacts of different mission and element parameters on mission success probability, optimal backup and PR policies, and optimal element activation sequence are investigated. It is shown that in warm standby systems with periodic backups and tight deadlines, PRs can improve the mission success probability even when they take the same time as CRs. When the maximum allowed mission time exceeds a certain level, PRs become ineffective and the optimal policy can involve only periodic backups. Autors: Gregory Levitin;Liudong Xing;Yuanshun Dai; Appeared in: IEEE Transactions on Reliability Publication date: Sep 2017, volume: 66, issue:3, pages: 771 - 782 Publisher: IEEE
» Primary Frequency Regulation With Load-Side Participation—Part I: Stability and Optimality
 Abstract:We present a method to design distributed generation and demand control schemes for primary frequency regulation in power networks that guarantee asymptotic stability and ensure fairness of allocation. We impose a passivity condition on net power supply variables and provide explicit steady-state conditions on a general class of generation and demand control dynamics that ensure convergence of solutions to equilibria that solve an appropriately constructed network optimization problem. We also show that the inclusion of controllable demand results in a drop in steady-state frequency deviations. We discuss how various classes of dynamics used in recent studies fit within our framework and show that this allows for less conservative stability and optimality conditions. We illustrate our results with simulations on the IEEE 68-bus transmission system and the IEEE 37-bus distribution system with static and dynamic demand response schemes. Autors: Andreas Kasis;Eoin Devane;Chrysovalantis Spanias;Ioannis Lestas; Appeared in: IEEE Transactions on Power Systems Publication date: Sep 2017, volume: 32, issue:5, pages: 3505 - 3518 Publisher: IEEE
» Prioritizing Influential Factors for Freeway Incident Clearance Time Prediction Using the Gradient Boosting Decision Trees Method
 Abstract:Identifying and quantifying the influential factors on incident clearance time can benefit incident management for accident causal analysis and prediction, and consequently mitigate the impact of non-recurrent congestion. Traditional incident clearance time studies rely on either statistical models with rigorous assumptions or artificial intelligence (AI) approaches with poor interpretability. This paper proposes a novel method, gradient boosting decision trees (GBDTs), to predict the nonlinear and imbalanced incident clearance time based on different types of explanatory variables. The GBDT inherits both the advantages of statistical models and AI approaches, and can identify the complex and nonlinear relationship while computing the relative importance among variables. One-year crash data from Washington state, USA, incident tracking system are used to demonstrate the effectiveness of GBDT method. Based on the distribution of incident clearance time, two groups are categorized for prediction with a 15-min threshold. A comparative study confirms that the GBDT method is significantly superior to other algorithms for incidents with both short and long clearance times. In addition, incident response time is found to be the greatest contributor to short clearance time with more than 41% relative importance, while traffic volume generates the second greatest impact on incident clearance time with relative importance of 27.34% and 19.56%, respectively. Autors: Xiaolei Ma;Chuan Ding;Sen Luan;Yong Wang;Yunpeng Wang; Appeared in: IEEE Transactions on Intelligent Transportation Systems Publication date: Sep 2017, volume: 18, issue:9, pages: 2303 - 2310 Publisher: IEEE
» Proactive Monitoring Via Jamming for Rate Maximization Over MIMO Rayleigh Fading Channels
 Abstract:Legitimately monitoring suspicious wireless communications is important for national security. In this letter, we investigate average monitoring rate maximization problem for a legitimate monitoring system, which proactively monitors a suspicious wireless link via jamming over multiple-input-multiple-output Rayleigh fading channels. We propose to approximate mutual information rates by Gaussian distributions. Furthermore, we propose low-complexity eigenvalue-based methods to calculate the means and variances of mutual information rates. Simulation results demonstrate that our proposed Gaussian approximation methods perform almost the same with the method to employ true probability density functions of mutual information rates. Autors: Hui Cai;Qi Zhang;Quanzhong Li;Jiayin Qin; Appeared in: IEEE Communications Letters Publication date: Sep 2017, volume: 21, issue:9, pages: 2021 - 2024 Publisher: IEEE
» Probabilistic Models for Ad Viewability Prediction on the Web
» Probabilistic Power Flow for AC/VSC-MTDC Hybrid Grids Considering Rank Correlation Among Diverse Uncertainty Sources
 Abstract:A new, unscented transformation (UT) based probabilistic power flow method for Alternate Current/Voltage Source Control-Multiple Terminal Direct Current hybrid grids is presented herein. The method is able to accurately tackle various random variables, including renewable energy sources with uncertainties such as wind speeds and solar radiations, which are rank correlated and are likely to follow different types of probability distributions. The concept of Gaussian copula is adopted to transform the rank correlated random variables into a group of standard Gaussian distributions with Pearson correlation coefficients, so that the UT method can be later applied to select the critical sample points from Gaussian distributions in a proper and uniform way. The effectiveness of the proposed method is validated using a set of test results on the modified IEEE 39-bus system and IEEE 300-bus system. Autors: Sui Peng;Junjie Tang;Wenyuan Li; Appeared in: IEEE Transactions on Power Systems Publication date: Sep 2017, volume: 32, issue:5, pages: 4035 - 4044 Publisher: IEEE
» Probability of Partially Decoding Network-Coded Messages
 Abstract:In the literature, there exist analytical expressions for the probability of a receiver decoding a transmitted source message that has been encoded using random linear network coding. In this letter, we look into the probability that the receiver will decode at least a fraction of the source message, and present an exact solution to this problem for both non-systematic and systematic network coding. Based on the derived expressions, we investigate the potential of these two implementations of network coding for information-theoretic secure communication and progressive recovery of data. Autors: Jessica Claridge;Ioannis Chatzigeorgiou; Appeared in: IEEE Communications Letters Publication date: Sep 2017, volume: 21, issue:9, pages: 1945 - 1948 Publisher: IEEE

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