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This paper proposes a new method to improve re performance of intra-field interpolation which is the mos~ important element of deinterlacing method. Traditional edge- based methods were poor at determining accurate edge iirection which decides interpolation performance. The 7roposed method decides the direction and slope of edge based on locally adaptive-thresholded binary image to mprove efficiency and accuracy, and it also increased the ~orizontal size of search window to 15 for better direction ietermination at gentle slope. Compared to traditional edge- based methods, interpolation based on binary image, which is ,`enerated using the proposed method, leads to great erformance improvement. With computer simulations for a ~`ariety of images, this paper shows the new approach is much ~etter than traditional methods.. [ABSTRACT FROM AUTHOR]

This paper presents an implementation of an ~daptive beamformer in a hands-free unit. The proposec~ ~daptive beamformer suppresses stationary noise an~ nterference sound. The adaptive beamformer and acoustic `cho canceller were implemented in a compact hands-free mit with a low-cost DSP. Experimental results demonstrate he noise reduction performance of the hands-free unit'. [ABSTRACT FROM AUTHOR]

In this paper, we propose a tunable terahertz (THz) radiation source that utilizes a free electron beam to generate THz diffraction radiation coupled with the guided modes in a cylindrical corrugated waveguide. Detailed theoretical analyses and computer simulations are conducted, and the results demonstrate the characteristics of the tunable radiation frequency. In particular, the coherent diffraction radiation excited by a prebunched electron beam is discussed both theoretically and numerically with regard to the enhancement of the radiation power and efficiency. This paper may offer attractive prospects for the development of compact and tunable radiation sources in the THz frequency regime. [ABSTRACT FROM AUTHOR]

Electromagnetic shielding of metallic enclosures with an aperture are simulated and measured in the frequency and time domain in this paper. Recently, several new figures of shielding effectiveness (SE) in the time domain have been proposed. Much work has been done regarding numerical simulations; however, little work related to measurements has been carried out. In this paper, we obtain the simulated and measured results for these SE definitions when an incident plane wave, with a determined bandwidth, excites the enclosure. The plane wave can be treated as a reference interference to compare with other cases. Measurements and simulations are in good agreement. This study evaluates the new definitions and compares them with the classical definition in the frequency domain. The effect of the probes, a dipole or a loop, has also been analyzed. Finally, the SE values are obtained for a sweep of the size of the aperture providing a unique value of equivalent SE for the most critical parameter and for a determined bandwidth, and allowing direct comparison with other enclosures. [ABSTRACT FROM PUBLISHER]

Time-frequency (TF) analysis (TFA) method is an important tool in industrial engineering fields. However, restricted to Heisenberg uncertainty principle or unexpected cross terms, the classical TFA methods often generate blurry TF representation, which heavily hinder its engineering applications. How to generate the concentrated TF representation for a strongly time-varying signal is a challenging task. In this paper, we propose a new TFA method to study the nonstationary features of strongly time-varying signals. The proposed method is based on synchrosqueezing transform and employs an iterative reassignment procedure to concentrate the blurry TF energy in a stepwise manner, meanwhile retaining the signal reconstruction ability. Two implementations of the discrete algorithm are provided, which show that the proposed method has limited computational burden and has potential in real-time application. Moreover, we introduce an effective algorithm to detect the instantaneous frequency trajectory, which can be used to decompose monocomponent modes. Numerical and real-world signals are employed to validate the effectiveness of the proposed method by comparing with some advanced methods. By comparisons, it is shown that the proposed method has the better performance in addressing strongly time-varying signals and noisy signals. [ABSTRACT FROM AUTHOR]

To improve the interception performance in missile guidance applications, this paper proposes a novel control strategy for the integrated guidance and control design subject to input constraints. The system constraints are translated into a restriction in an invariant set, which is then enforced by manipulating the derivative of the applied reference. For the integrated system in the presence of disturbances and parametric uncertainties, disturbance observers are applied to estimate the lumped disturbances existing in each loop. The quadratic stability via dynamic surface control is guaranteed, and an ellipsoidal approximation of the invariant set is obtained, which can be enlarged to allow some degree of the input saturation. The effectiveness of the proposed scheme is illustrated using numerical simulations against a maneuvering target. [ABSTRACT FROM AUTHOR]

An inter-turn fault (ITF) is conventionally analyzed by a method that uses negative-sequence components obtained by symmetrical coordinate transformations. However, this method is inefficient because it involves solving complex equations that include many parameters. This paper proposes a simplified d–q equivalent circuit model of a permanent magnet synchronous motor with an ITF. The model is developed by reflecting representative phenomena related to the negative sequence components of the fault in advance of a final model construction, such that the final model does not require the separation of positive and negative sequence components. As a result, the model can rapidly examine the influence of the fault due to the simplicity of the equations, and can help build the detection and tolerance control techniques of the fault. The model is verified by numerical analysis, simulation and experiment. [ABSTRACT FROM AUTHOR]

In an era of ubiquitous large-scale streaming data, the availability of data far exceeds the capacity of expert human analysts. In many settings, such data is either discarded or stored unprocessed in data centers. This paper proposes a method of online data thinning, in which large-scale streaming datasets are winnowed to preserve unique, anomalous, or salient elements for timely expert analysis. At the heart of this proposed approach is an online anomaly detection method based on dynamic, low-rank Gaussian mixture models. Specifically, the high-dimensional covariance matrices associated with the Gaussian components are associated with low-rank models. According to this model, most observations lie near a union of subspaces. The low-rank modeling mitigates the curse of dimensionality associated with anomaly detection for high-dimensional data, and recent advances in subspace clustering and subspace tracking allow the proposed method to adapt to dynamic environments. Furthermore, the proposed method allows subsampling, is robust to missing data, and uses a mini-batch online optimization approach. The resulting algorithms are scalable, efficient, and are capable of operating in real time. Experiments on wide-area motion imagery and e-mail databases illustrate the efficacy of the proposed approach. [ABSTRACT FROM AUTHOR]

In the real world, the two challenges of stereo vision system include a robust system under various radiometric changes and real-time process. To extract depth information from stereoscopic images, this paper proposes Patchmatch-based robust and fast stereo matching under radiometric changes. For this, a cost function was designed and minimized for estimating an accurate disparity map. Specifically, we used a prior probability to minimize the occlusion region and a smoothness term that considers convexity of objects to extract a fine disparity map. For evaluating the performance of the proposed scheme, we used Middlebury stereo data sets with radiometric changes. The experimental result showed that the proposed method outperforms state-of-the-art methods by up to 3.35 percent better and a range of 4.71 - 27.24 times faster result in terms of bad pixel error and processing time, respectively. Therefore, we believe that the proposed scheme can be a useful tool for computer vision-based applications. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of clock skew and offset estimation (CSOE) for the IEEE 1588 precision time protocol. Built on the classical two-way message exchange scheme, IEEE 1588 is a prominent synchronization protocol for packet switched networks. Due to the presence of random queuing delays in a packet switched network, the joint recovery of clock skew and offset from the received packet timestamps can be viewed as a statistical estimation problem. Recently, assuming perfect clock skew information, minimax optimum clock offset estimators were developed for IEEE 1588. Building on this work, we first develop joint optimum invariant clock skew and offset estimators for IEEE 1588 for known queuing delay statistics and unlimited computational complexity. We then show that the developed estimators are minimax optimum, i.e., these estimators minimize the maximum skew normalized mean square estimation error over all possible values of the unknown parameters. Minimax optimum estimators that utilize information from past timestamps to improve accuracy are also introduced. The developed optimum estimators provide useful fundamental limits for evaluating the performance of CSOE schemes. These performance limits can aid system designers to develop algorithms with the desired computational complexity that achieve performance close to the performance of the optimum estimators. If a designer finds an approach with a complexity they find acceptable and which provides performance close to the optimum performance, they can use it and know they have near optimum performance. This is precisely the approach used in communications when comparing to capacity. [ABSTRACT FROM AUTHOR]

In this paper, we consider a general cooperative wireless sensor network (WSN) with multiple hops and the problem of channel estimation. A matrix-based conjugate gradient (CG) algorithm is first developed, which is then incorporated with the set-membership filtering framework to improve the performance of complex channel estimation for WSNs. Due to selective update, the proposed set-membership matrix-based CG (SM-MCG) algorithm can reduce the computational complexity significantly and extend the lifetime of WSN. In addition, by introducing an exponentially decaying bound and combining with SM-MCG algorithm, we design an updating criterion to accurately track the optimal maximum iteration number of each data window while reducing complexity further. Simulation results show good performance of our proposed algorithms in terms of convergence speed, steady state mean-square error, and indicate reduced complexity. [ABSTRACT FROM AUTHOR]

Currently, surgical continuum robots (CRs) are predominantly used as telemanipulators where modeling errors are overcome by the user. Such errors preclude their use for autonomous tasks. In this paper, we investigate the calibration of CRs with specific focus on capturing joint space errors due to homing offsets, assembly errors causing twist about the robot's backbone, and uncertainty in the equilibrium bending shapes of segments of these robots. A kinematic framework focusing on multibackbone CR is presented with emphasis on deriving calibration identification Jacobians. This framework captures the coupling between twist and the equilibrium shapes of a continuum segment as a function of its bending angle. To capture equilibrium shape variations as a function of bending, a homotopy of curves is defined and represented by respective modal coefficients. The estimation of the calibration parameters is cast as a nonlinear least-squares problem. The framework is validated by simulations and experimentally using a single-port access surgery robot. We believe this calibration framework will facilitate semiautomation of surgical tasks carried out by CRs. [ABSTRACT FROM AUTHOR]

This paper presents the numerical simulation results of characteristics and efficiency of separation of uranium ion fluxes and its fission products in the process of the plasma separation. The movement of beams of heavy (238 u) and light (160 u) single-charged ions in vacuum and in helium buffer plasma has been investigated at a pressure of 10 mtorr, magnetic fields 0.8–1.2 kG and electrical potentials up to 1 kV. The interaction between the ion beams and their interaction with the buffer plasma has been taken into account. The numerical simulation of plasma has been conducted in a drift–diffusion approximation. It has been shown that the presence of buffer plasma in the area of ion fluxes and occurring compensation of their space charge can greatly improve the separation efficiency compared to the separation of ion fluxes in vacuum. [ABSTRACT FROM AUTHOR]

Most man-made environments, such as urban and indoor scenes, consist of a set of parallel and orthogonal planar structures. These structures are approximated by the Manhattan world assumption, in which notion can be represented as a Manhattan frame (MF). Given a set of inputs such as surface normals or vanishing points, we pose an MF estimation problem as a consensus set maximization that maximizes the number of inliers over the rotation search space. Conventionally, this problem can be solved by a branch-and-bound framework, which mathematically guarantees global optimality. However, the computational time of the conventional branch-and-bound algorithms is rather far from real-time. In this paper, we propose a novel bound computation method on an efficient measurement domain for MF estimation, i.e., the extended Gaussian image (EGI). By relaxing the original problem, we can compute the bound with a constant complexity, while preserving global optimality. Furthermore, we quantitatively and qualitatively demonstrate the performance of the proposed method for various synthetic and real-world data. We also show the versatility of our approach through three different applications: extension to multiple MF estimation, 3D rotation based video stabilization, and vanishing point estimation (line clustering). [ABSTRACT FROM AUTHOR]

Existing depth sensing techniques have many shortcomings in terms of resolution, completeness, and accuracy. The performance of 3-D broadcasting systems is therefore limited by the challenges of capturing high-resolution depth data. In this paper, we present a novel framework for obtaining high-quality depth images and multi-view depth videos from simple acquisition systems. We first propose a single depth image recovery algorithm based on auto-regressive (AR) correlations. A fixed-point iteration algorithm under the global AR modeling is derived to efficiently solve the large-scale quadratic programming. Each iteration is equivalent to a nonlocal filtering process with a residue feedback. Then, we extend our framework to an AR-based multi-view depth video recovery framework, where each depth map is recovered from low-quality measurements with the help of the corresponding color image, depth maps from neighboring views, and depth maps of temporally adjacent frames. AR coefficients on nonlocal spatiotemporal neighborhoods in the algorithm are designed to improve the recovery performance. We further discuss the connections between our model and other methods like graph-based tools, and demonstrate that our algorithms enjoy the advantages of both global and local methods. Experimental results on both the Middleburry datasets and other captured datasets finally show that our method is able to improve the performances of depth images and multi-view depth videos recovery compared with state-of-the-art approaches. [ABSTRACT FROM AUTHOR]

This paper is devoted to the terrain aided navigation (TAN) systems based on the state estimation algorithms. In particular, the emphasis is laid on the design of the Bayesian Rao–Blackwellized point-mass filter for nonlinear state-space models of a specific structure typically used in the terrain aided navigation. The proposed filter preserves advantages of the point-mass filter, including the high estimation accuracy, robust initialization, deterministic nature of the algorithm, and predictable computational complexity, while the computational complexity is significantly reduced. The performance of the Rao–Blackwellized point-mass filter is illustrated using a simulated numerical example and a TAN system based on the real data. [ABSTRACT FROM AUTHOR]

The magnetic fluid seal is one of the best known and widely used technical applications of magnetic fluid. However, the boundary and the flow regime with the rotation shaft cannot be observed by the experiment method. This paper presents a novel numerical simulation method to obtain the boundary and the velocity of the fluid in seals. The magnetic field of the seal is solved by the finite-element method, and the Navier–Stokes equations of the magnetic fluid based on the influence of magnetic force are solved by the finite-volume method. The two-phase flow is solved by the volume of fluid method. The seal capacities of the rectangle tooth and the trapezoid tooth with different rotation velocities are obtained. The result shows that the seal capacity decreases with the increase in the rotation velocity. [ABSTRACT FROM AUTHOR]

This paper presents a probabilistic environment representation that allows efficient high-fidelity modeling and inference toward enabling informed planning (active perception) on a computationally constrained mobile autonomous system. The proposed approach exploits the fact that real-world environments inherently possess structure that introduces dependencies between spatially distinct locations. Gaussian mixture models are employed to capture these structural dependencies and learn a semiparametric, arbitrary resolution spatial representation. A hierarchy of spatial models is proposed to enable a multifidelity representation with the variation in fidelity quantified via information-theoretic measures. Crucially for active perception, the proposed modeling approach enables a distribution over occupancy with an associated measure of uncertainty via incorporation of free space information. Evaluation of the proposed technique via a real-time graphics processing unit based implementation is presented on real-world data sets in diverse environments. The proposed approach is shown to perform favorably as compared to state-of-the-art occupancy mapping techniques in terms of memory footprint, prediction accuracy, and generalizability to structurally diverse environments. [ABSTRACT FROM AUTHOR]

Dynamic control of soft robotic manipulators is an open problem yet to be well explored and analyzed. Most of the current applications of soft robotic manipulators utilize static or quasi-dynamic controllers based on kinematic models or linearity in the joint space. However, such approaches are not truly exploiting the rich dynamics of a soft-bodied system. In this paper, we present a model-based policy learning algorithm for closed-loop predictive control of a soft robotic manipulator. The forward dynamic model is represented using a recurrent neural network. The closed-loop policy is derived using trajectory optimization and supervised learning. The approach is verified first on a simulated piecewise constant strain model of a cable driven under-actuated soft manipulator. Furthermore, we experimentally demonstrate on a soft pneumatically actuated manipulator how closed-loop control policies can be derived that can accommodate variable frequency control and unmodeled external loads. [ABSTRACT FROM AUTHOR]

In Internet of Things, wireless access networks are required to support a large number of user equipments (UEs) in real time. With UEs’ frequently arrival and departure, plenty of packet collisions can occur. Successive decoding thus becomes a promising technique to support the massive connectivity as it is capable of recovering packets from mixed received signals. In this paper, we propose an adaptive framing with successive decoding (AFSD) frame structure to deal with the fluidity of UEs. In the AFSD structure, the frame length is adaptively adjusted based on the present UE number, and successive decoding is adopted to alleviate the packet loss caused by packet collision. To quantify its performance, we provide exact as well as asymptotic results for the average delay. The analytical results are validated by simulations, and further extended to practical systems with estimated UE number, which shows that knowledge of active UE number is useful for delay reduction. Optimizations on UE transmission probability and frame length are also presented. In particular, the numerical studies reveal that by using optimized parameters, the average delay is reduced significantly for a wide range of arrival rates, which validates the effectiveness of the AFSD structure. [ABSTRACT FROM AUTHOR]

Electromagnetic (EM) coupling between radio frequency (RF) coils is a common cause of coil performance degradation and must be sufficiently reduced in the design of RF coils. The EM field simulation is a primary tool in analyzing the coupling condition and optimizing the decoupling method. A theoretical analysis of co-simulation under the conditions of strongly coupled RF coils is proposed in this paper. The proposed co-simulation method is evaluated through the comparison with the conventional simulation methods in terms of the efficiency and of the EM fields and specific absorption rate (SAR) of a two-channel strongly coupled coil array. The results demonstrate that the proposed co-simulation method saves approximately 94.5% of the total simulation time for strongly coupled coil arrays while the EM field and SAR variation is less than 4%. As a method demonstration, the proposed co-simulation method was used to analyze the capacitance decoupling of adjacent coils with the scattering matrix and saves about 95.78% of the total simulation time for the optimization of decoupling capacitors. [ABSTRACT FROM AUTHOR]

In this paper, a new systematic technique to design manifold-coupled multiplexers in waveguide technology is proposed. The new technique uses generalized low-order electromagnetic (EM) distributed models, which constitute a half-way point between the fast, but imprecise, analytical models, and the more accurate, but costly, full-wave EM models. The method can be applied to contiguous and noncontiguous channel multiplexers, in both E-plane or H-plane configurations. This paper covers the complete design procedure for manifold multiplexers, starting from the required specifications and finishing with the physical dimensions. After explaining the general design technique for multiplexers with channel filters based on transmission-line resonators, the method is specialized for the design of classic multiplexers with circular-waveguide dual-mode filters. As a further application example, the same methodology is also used for the design of a nonconventional tuningless wideband multiplexer with a new type of rectangular waveguide filters. This paper is concluded with a comparison between simulation and measurements for the wideband multiplexer. Excellent agreement between measurements and simulations are demonstrated, thereby validating the complete design procedure. [ABSTRACT FROM AUTHOR]

Traditional lightning protection measures of transmission lines have been restricted by a variety of uncontrollable factors, and it has been difficult to achieve the ideal effect. In this paper, a novel Jet Stream Arc-quenching Lightning Protection Gap (JSALPG), based on the "channeling type" lightning protection method, was studied. JSALPG may be triggered to generate high-speed jet streams while its parallel gap is broken down by lightning strokes; the resulting jet stream will intensely act on the initial development stage of subsequent power frequency arc and completely extinguish the arc in a much shorter time than the operation of relay protection; thus, suppressing the ?arc establishing rate? and reducing the lightning tripout rate significantly. In this paper, the operating principle of JSALPG is introduced, and the MHD model and modified Mayr arc model of jet stream arc-quenching field are developed. Relevant numerical calculations, simulations and experiments are carried out to verify the arc-quenching effect of JSALPG. Finally, the actual operation of JSALPG on a 35 kV line is analyzed, verifying the validity and reliability of JSALPG. [ABSTRACT FROM AUTHOR]

Device-level power electronic circuit simulation is so cumbersome that engineers are forced to make model simplification or reduce circuit size to obtain a reasonable execution time for repeated simulation runs. This paper proposes a massive-thread parallel simulation of large-scale power electronic circuits employing device-level modeling on the graphics processors (GPUs) to obtain higher data throughput and lower execution times. Parallel massive-thread modules are proposed for the nonlinear physics-based insulated gate bipolar transistor and power diode components. The nonlinear solution algorithm comprised of Newton–Raphson iterations and partial LU decomposition is fully parallelized on the GPU. Furthermore, the commonly used behavioral model with reduced computational complexity is also employed to represent the switches. The developed simulation codes are used to run large-scale test cases of the modular multilevel converter (MMC) system. The accuracy and efficiency of the GPU-based parallel simulation are compared with sequential CPU-based codes and the SaberRD program to show the advantages of the parallelized simulation; execution time speedups of 15 times and 70 times are reported for the MMC system using the nonlinear physics-based modeling and behavior-based modeling, respectively. [ABSTRACT FROM AUTHOR]

The mixed separation thickening process (MSTP) of hematite beneficiation is a strong nonlinear cascade process with frequency of slurry pump as input, underflow slurry flow-rate (USF) as inner-loop output, and underflow slurry density (USD) as outer-loop output. The model parameters such as settling velocity of slurry particles and slurry height are unknown and nonlinear. Moreover, these model parameters vary from flotation middling, sewage, and magnetic separation slurry. In this paper, the unknown change of the above dynamic characteristics are described by the previous sample unmodeled dynamics and its change rate. A novel adaptive controller using compensation signal based approach is developed. Inner-loop closed-loop control system equation and lifting technology are adopted to develop dual rate adaptive control method. Two compensation signals are constructed and added onto the linear proportional-integral (PI) controller. Such two compensation signals aim at eliminating the effects of the previous sample unmodeled dynamics and tracking error, respectively. The stability and convergence analysis is given and a simulation experiment on hardware-in-the-loop simulation system of MSTP based on industrial data is carried out, where it shows that the USD, USF, and its changing rate can be controlled well inside their targeted ranges when the system is subjected to unknown variations of its parameters. [ABSTRACT FROM AUTHOR]

Simulation is a valuable tool to evaluate energy consumptions and design of railway systems. The system limitations have an important influence on the system behavior and must be taken into account in the simulation. Especially, the electromechanical limitations have a major impact on the kinematical behavior. However, such limitations are often neglected in classical studies. This paper deals with the development of an adaptive electrokinematical simulation to adapt the kinematical behavior of the system according to its limitations. A flexible simulation tool is thus obtained by taking into account electrical, mechanical, as well as kinematical limitations. This tool is validated by experimental results on a real railway track. It is then used to study different solutions to increase the transport capacity of a subway system, even when limitations occur. [ABSTRACT FROM AUTHOR]

In string photovoltaic (PV) systems, the power–voltage (P–V) characteristic under partial shading conditions (PSC) displays multiple peaks requiring global maximum power point (GMPP) tracking (GMPPT) algorithms to identify the PV array GMPP. Several GMPPT algorithms scan wide voltage tracks to detect the GMPP, even larger than a P–V curve full scan. Moreover, many algorithms have been tested only for simple PSC that lead to three well distinct peaks at most. This paper initially presents a trapezoidal area, called the maximum power trapezium (MPT), in the P–V plane that contains all possible GMPPs for any PSC. Using the MPT and information about the minimum voltage difference between adjacent local peaks, a GMPPT algorithm is proposed, which tracks the GMPP of a string PV array under any severe PSC reducing its voltage track and so its tracking time. Simulation and experimental results show the superior performance of the proposed algorithm, in comparison to the state-of-art algorithms, in terms of tracking time, energy loss, and total voltage track during the search for the GMPP. [ABSTRACT FROM AUTHOR]

In this paper, a fast explicit and unconditionally stable finite-difference time-domain (FDTD) method is developed, which does not require a partial solution of a global eigenvalue problem. In this method, a patch-based single-grid representation of the FDTD algorithm is developed to facilitate both theoretical analysis and efficient computation. This representation results in a natural decomposition of the curl–curl operator into a series of rank-1 matrices, each of which corresponds to one patch in a single grid. The relationship is then theoretically analyzed between the fine patches and unstable modes, based on which an accurate and fast algorithm is developed to find unstable modes from fine patches with a bounded error. These unstable modes are then upfront eradicated from the numerical system before performing an explicit time marching. The resultant simulation is absolutely stable for the given time step irrespective of how large it is, the accuracy of which is also ensured. In addition, both lossless and general lossy problems are addressed in the proposed method. The advantages of the proposed method are demonstrated over the conventional FDTD and the state-of-the-art explicit and unconditionally stable FDTD methods by numerical experiments. [ABSTRACT FROM PUBLISHER]

The increased use of carbon-fiber composites in unmanned aerial vehicles is a challenge for their EMC assessment by numerical solvers. For accurate and reliable simulations, numerical procedures should be tested not only for individual components, but also within the framework of complete systems. With this aim, this paper presents a benchmark test case based on experimental measurements coming from direct-current injection tests in the SIVA unmanned air vehicle, reproduced by a numerical finite-difference-time-domain solver that employs a new subgridding scheme to treat lossy composite thin panels. Validation was undertaken by applying the feature selective validation method, which quantifies the agreement between experimental and numerical data. [ABSTRACT FROM PUBLISHER]

This paper addresses the question of the most efficient couple (f, θ3dB) for airborne radar precipitating system observations, where f is the microwave frequency and θ3dB is the beamwidth aperture at 3 dB. This problem is of importance. The meteorological hazard in civil aviation is mainly due to convective precipitating systems, particularly hail and strong turbulence areas. A realistic and flexible model of precipitating systems is presented, and simulations of airborne radar observations are performed at the six meteorological frequency bands (S, C, X, Ku, Ka, and W). In this paper, the effect of f and θ3dB modification is shown through radar simulations of two precipitating systems. One is a numerical simulation composed of two successive rows of convective towers; the other is inspired from a real mesoscale system, presenting hail-bearing convective towers. It is shown that some (f, θ3dB) couples are better than the one currently used by civil aviation. Notably, C band allows a better description than X band of a meteorological radar scene if the radar antenna size is increased. The model and methodology presented herein are adaptable to ground-based and satellite radars. [ABSTRACT FROM PUBLISHER]

The saturated-core-type superconducting fault current limiter (SCSFCL) is an important device to limit increasing fault currents in electrical power grids. However, there have been few numerical simulations carried out to simulate the properties of the superconducting DC coil in the SCSFCL, but such modeling is indispensable to the design and analysis of such devices. In this paper, a simulation method to simulate the SCSFCL with COMSOL Multiphysics is presented, and the AC losses of the DC coil in the normal, nonlimiting state, which is its usual operating state, are simulated and analyzed for the first time. A strategy to simulate the AC loss of the superconducting coil with a three-dimensional (3-D) model is given first. The nonlinear electric and magnetic problems are decoupled first. Next, the model is divided into smaller models for separate calculations. The 3-D model is further simplified into a 2-D model based on the worst case scenario for a conservative design. The AC loss distribution within the coil is given and the relationship between the AC loss and an AC component of the current is analyzed, and it is found that the outermost coil regions have much larger AC loss than the coils near the centre. [ABSTRACT FROM PUBLISHER]

Nowadays, as more systems are regarded to be complex, the processes to develop them are becoming more complex too. This increasing trend makes more effective analysis methods inevitable necessities. Meanwhile, matriarchal tools are becoming the most prominent, this paper has tried to study a work transformation matrix (WTM) at the level of coupled blocks of activities (CBAs). The neighboring matrices of such a WTM act as its information flow interfaces with other activities. It is shown how these are equivalent to some state-space representation matrices. The equivalency helps us to improve the analysis method for a set of CBAs constituting the whole WTM. Additionally, the concepts of powers of adjacency matrices and elementary dynamic properties of process as a system in modern control theory are brought together to analyze the behavior of activities in coupled blocks. By analyzing these properties in a case study, five heuristic are derived and proposed for improving the process through better preference and ordering of activities. Effectiveness of these heuristics is tested by a simple discrete-time simulation for which results show 17% of time reduction for the case study. [ABSTRACT FROM PUBLISHER]

A 3-D flow model, combined with the volume of fluid method, was developed to track capillary driven epoxy flow front, during the underfill process. Die edge effects and fillet spread based on the effect of process parameters were included in this model. Numerical results were validated against flow visualization data. Full field imaging experiments with quartz die were performed to observe flow front as a function of flow time. Development of this new modeling methodology focuses on predicting the capillary underfill flow behavior both in the first level interconnect area between a die and a substrate, and the area surrounding the die. This paper revealed that the edge flow effect contributes to pulling the overall flow front in the bump field area and formation of the fillet spread, which affects the risk associated with underfill delamination in flip chips. A comparative study, which included modeling results and experimental data, clearly indicated that the die edge effect cannot be neglected in order to capture the right trends of flow front shape evolution and an accurate fill time prediction. These comparisons also showed that the model developed in this paper is adequate to approximately simulate the fillet configuration all around the die after encapsulation of flip chips. The modeling methodology developed in this paper provides a fundamental understanding of underfill flow as a function of dispense process parameters, material properties, and package design parameters. [ABSTRACT FROM PUBLISHER]

A multiagent system is a distributed system where the agents or nodes perform complex functions that cannot be written down in analytic form. Multiagent systems are highly connected, and the information they contain is mostly stored in the connections. When agents update their state, they take into account the state of the other agents, and they have access to those states via the connections. There is also external user-generated input into the multiagent system. As so much information is stored in the connections, agents are often memory less. This memory-less property, together with the randomness of the external input, has allowed us to model multiagent systems using Markov chains. In this paper, we look at multiagent systems that evolve, i.e., the number of agents varies according to the fitness of the individual agents. We extend our Markov chain model and define stability. This is the start of a methodology to control multiagent systems. We then build upon this to construct an entropy-based definition for the degree of instability (entropy of the limit probabilities), which we used to perform a stability analysis. We then investigated the stability of evolving agent populations through simulation and show that the results are consistent with the original definition of stability in nonevolving multiagent systems, proposed by Chli and De Wilde. This paper forms the theoretical basis for the construction of digital business ecosystems, and applications have been reported elsewhere. [ABSTRACT FROM PUBLISHER]

Equal allocation of bandwidth and/or power may not be efficient for wireless multi-user networks with limited bandwidth and power resources. Optimal joint bandwidth and power allocation strategies for wireless multi-user networks with and without relaying are proposed in this paper for 1) the maximization of the sum capacity of all users; 2) the maximization of the worst user capacity; and 3) the minimization of the total power consumption of all users. It is shown that the proposed allocation problems are convex and, therefore, can be solved efficiently. Moreover, joint bandwidth and power allocation for admission control is considered. A suboptimal greedy search algorithm is developed to solve the admission control problem efficiently. Instructive analysis of the greedy search shows that it can achieve good performance, and the condition under which the greedy search is optimal is derived. The formal and in-depth analysis of the greedy search algorithm presented in this paper can serve as a benchmark for analyzing similar algorithms in other applications. The performance improvements offered by the proposed optimal joint bandwidth and power allocation are demonstrated by simulations. The advantages of the suboptimal greedy search algorithm for admission control are also shown in numerical results. [ABSTRACT FROM PUBLISHER]

This paper presents a generalized, parallel implementation methodology for real-time simulation of ac machine transients in an FPGA-based real-time simulator. The proposed method adopts nanosecond range simulation time-step and exploits the large response time of a rotating machine to: 1) eliminate the need for predictive-corrective action for the machine electrical and mechanical variables, 2) decouple the solution of the dq0 stator currents, and 3) enable the use of one-time-step delayed interface between the machine and the rest of the system which decouples the machine solution from that of the rest of the system. The proposed method simplifies the solution of the machine model without compromising accuracy or numerical stability of the simulation. This paper also presents a massively parallel, customized hardware architecture tailored to the solution of the mathematical model of ac machines. The proposed method and the developed hardware architecture are tested and verified based on the implementation of a permanent-magnet synchronous machine model and an induction machine-based ac-drive system in a field-programmable gate-array-based simulator. Real-time simulation is achieved with a computation time of 44 ns within the simulation timestep. [ABSTRACT FROM AUTHOR]

A three-phase, two-winding transformer model is presented in this paper. Nonlinear magnetizing curves are piece-wise linearized, while the input winding capacitances are lumped onto the transformer terminals. A stiff system of differential equations in a state space, describing the transformer transient behavior, is solved using the L-stable backward differentiation formulas (BDFs) numerical rule. It has been shown that using the BDF numerical rule has resulted in better stability properties than using the trapezoidal rule. A computer program has been developed for generation of variable-state waveforms. The developed program is suitable for simulations of low-frequency three-phase transformer transients such as inrush currents and ferroresonance. This computer program has proved to be nu- merically stable for the problems investigated in this paper. The results acquired in this way are compared to results obtained using MATLAB/Power System Blockset, as well as to results of laboratory measurements. [ABSTRACT FROM AUTHOR]

In this paper, we consider performance analysis of the decentralized power method for the eigendecomposition of the sample covariance matrix based on the averaging consensus protocol. An analytical expression of the second order statistics of the eigenvectors obtained from the decentralized power method, which is required for computing the mean square error (MSE) of subspace-based estimators, is presented. We show that the decentralized power method is not an asymptotically consistent estimator of the eigenvectors of the true measurement covariance matrix unless the averaging consensus protocol is carried out over an infinitely large number of iterations. Moreover, we introduce the decentralized ESPRIT algorithm which yields fully decentralized direction-of-arrival (DOA) estimates. Based on the performance analysis of the decentralized power method, we derive an analytical expression of the MSE of DOA estimators using the decentralized ESPRIT algorithm. The validity of our asymptotic results is demonstrated by simulations. [ABSTRACT FROM PUBLISHER]

The construction of highly incoherent frames, sequences of vectors placed on the unit hyper sphere of a finite dimensional Hilbert space with low correlation between them, has proven very difficult. Algorithms proposed in the past have focused on minimizing the absolute value off-diagonal entries of the Gram matrix of these structures. Recently, a method based on convex optimization that operates directly on the vectors of the frame has been shown to produce promising results. This paper gives a detailed analysis of the optimization problem at the heart of this approach and, based on these insights, proposes a new method that substantially outperforms the initial approach and all current methods in the literature for all types of frames, with low and high redundancy. We give extensive experimental results that show the effectiveness of the proposed method and its application to optimized compressed sensing. [ABSTRACT FROM PUBLISHER]

In this paper, an optimal unbiased finite impulse response (OUFIR) filter is proposed as a linking solution between the unbiased FIR (UFIR) filter and the Kalman filter (KF). We first derive the batch OUFIR estimator to minimize the mean square error (MSE) subject to the unbiasedness constraint and then find its fast iterative form. It is shown that the OUFIR filter is full horizon (FH) and that its estimate converges to the KF estimate by increasing the horizon length N. As a special feature, we note that the FH OUFIR filter operates almost as fast as the KF. Several other critical properties of the OUFIR filter are illustrated based on simulations and practical applications. Similar to the UFIR filter, and contrary to the KF, the OUFIR filter is highly insensitive to the initial conditions. It has much better robustness than KF against temporary model uncertainties. Finally, the OUFIR filter allows for ignoring system noise, which is typically not well known to the engineer. [ABSTRACT FROM PUBLISHER]

This paper presents a Scott-transformer-based power factor correction (PFC) rectifier for a three-level neutral-point-clamped (NPC) inverter-fed induction motor drive (IMD) for enhanced power quality at ac mains. Here, the Scott-transformer-based PFC rectifier is digitally controlled by a current feedforward control. The torque component of the stator current is added to the output of the dc-bus voltage proportional plus integral (PI) controller as a feedforward term, which enhances the dynamic performance of the dc-bus voltage regulation. The three-level NPC inverter is controlled by a space vector-modulated (SVM) indirect vector control scheme. The performance of the proposed dc-bus voltage loop with feedforward control is compared with the conventional one and found to offer faster response with less overshoot and undershoot. The proposed IMD system is simulated using MATLAB/Simulink and the same is validated experimentally. The proposed drive system is analyzed for a wide variation in reference speed and load torques demonstrating significant improvement in the performance indices. [ABSTRACT FROM AUTHOR]

In order to improve the shielding effect of the transmission line, the accurate line system design is significant. The electrogeometric model and leader progression model are two typical and most widely used numerical analysis models to analyze the shielding failure performance. However, both models call for more experimental evidence for accurate application. This paper investigates the characteristics of an upward leader emerging from 110-, 220-, 500-, and 1000-kV single-phase conductors through simulated experiments, and the conductor parameters and heights adopted are similar to the actual transmission lines in operation. The ac voltage generator is connected to the conductor to apply an operating voltage to the conductor. The influence of bundle number and conductor height on the upward leader is also discussed in detail. The obtained characteristics of an upward leader will be helpful to build appropriate numerical analysis models for the shielding failure of the transmission line. [ABSTRACT FROM AUTHOR]

This paper presents a procedure to implement the concept of surface impedance boundary condition (SIBC) for lossy dielectrics in time domain. The SIBC formulation, validation, and results are obtained with a time domain numerical method, namely the transmission-line matrix (TLM). The formulation of surface impedance in frequency domain is converted to the time domain using a rational approximation followed by a bilinear transform with a canonical representation in the state-space. This surface impedance formulation has been implemented in TLM. Simulations show that the proposed model is valid for interfaces between air and a lossy dielectric, and arbitrary conductivity $\sigma$. An application that concerns mode propagation in a rectangular tunnel with lossy dielectric walls is shown. A comparison with an approximate method proposed by Marcatilli is presented. It confirms that the propagation in electrically large guided structures, such as tunnels with lossy dielectric walls, can be efficiently modeled by this approach. [ABSTRACT FROM PUBLISHER]

The fourteen papers in this special section provides an overview of some of the leading current research themes in validation of computational electromagnetics. Over the last two decades, the power of affordable computing has dramatically increased. In addition to computational horsepower, the capabilities of available electromagnetic simulation packages have improved. Hence, there has been a significant increase in the reliance on numerical modeling in electromagnetic compatibility and signal integrity design and analysis. Such increased reliance makes it vital to be able to demonstrate that the models provide a reasonable simulation of the system being modeled. In 2008, the IEEE Standard 1597.1 was published that provided the first ever approach to formalized validation of computer modeling. Since that time, there has been an increase in interest in validation and more research on the methods and applications of formalized validation. [ABSTRACT FROM PUBLISHER]