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Samples of a dried composite oil-paper system were thermally aged in the laboratory under N2 in a sealed container and analysed using their dielectric response. The contributing loss processes were separated using an equivalent circuit model containing constant high frequency capacitances, dc-conductances, a dispersive capacitance, and a low frequency quasi-dc (q-dc) dispersion process as circuit elements. This low frequency dispersion in oil-paper samples is a bulk property of the system that is often mistaken for a dc conduction process when only the imaginary capacitance or ac-conductance is measured. The Dissado-Hill response function is proposed for the frequency dependence of the dispersive capacitance in the mid-frequency range rather than the Debye function because its cluster concepts correlate with the sample morphology of a matrix of oil-filled cavities. The quasi-dc dispersion is assigned to the transport of mobile charges between charge-clusters associated with locally connected oil filled cavities, which is a process that can be represented on a global scale by the form of hierarchical circuit system that leads to constant phase angle responses, and is here modelled by the Dissado-Hill q-dc function. It was found that the two dispersions moved together to higher frequency with thermal ageing of the composite material. The characteristic frequency common to the dispersions had an activation energy that decreased with thermal ageing, whereas their amplitude increased. This behavior is discussed in terms of possible changes to the oil-paper composite caused by the ageing process. [ABSTRACT FROM AUTHOR]

A substantial quantity of testing has been performed on the degradation of paper insulation over the decades. The aim being to better educate the electrical industry on how to best operate expensive assets, such as transformers. The longevity of paper insulation is frequently tested using accelerated ageing experiments, where the effects of temperature and the chemical environment on paper lifespan can be studied. Such research has resulted in paper life expectancy curves being published by the IEEE and the IEC. The investigations tend to use sealed vessels. However, the disadvantage of using this method is that the water content of the paper changes during the ageing process which then changes the ageing rate. In these ageing experiments the water and oxygen content was controlled using a special test rig to compare the ageing rate to previous work and to determine the ageing effect of paper by combining temperature, water content of paper and oxygen content of the oil. We found that the rate of paper ageing can be more accurately determined by controlling the water and oxygen during the experiment which then produced noticeable changes in predicting life expectancy. [ABSTRACT FROM PUBLISHER]

Solving nonlinear algebraic equations is a core task in many fields of engineering and the sciences. Iterative methods such as Newton's method have been popular in solving power flow equations. Recently, the non-iterative holomorphic embedding (HE) methods that employ polynomial embedded systems have been proposed to solve power flow equations. It is advantageous for the solution functions obtained by the HE method to possess an algebraic property. The present paper points out that algebraic solution functions can have several desired properties for the HE method to work. This paper also exemplifies that the algebraic property cannot be ensured by the elimination process, which corrects an assertion in the literature. It is hence essential to study required conditions for ensuring the existence of algebraic solution functions. The present paper is devoted to the theoretical foundation of HE methods using a polynomial embedded system and develops a novel general theorem and sufficient conditions to ensure the required algebraic property. Examples and numerical results are presented to better explain the derived theoretical results. [ABSTRACT FROM AUTHOR]

Analytical expressions that have been derived to calculate ac resistance and losses of magnetic devices at high frequencies have primarily used a one-dimensional approximation, and have used Cartesian coordinates or approximations that are equivalent to Cartesian coordinates. The result is Dowell's equation. This paper examines the effect of winding curvature on the losses relative to Dowell's equation by solving the problem completely in cylindrical coordinates. The error in Dowell's equation relative to a full cylindrical solution is found to be as great as 33% for some designs. A mathematical model is derived for the relative error between the two solutions, which can be used to assess the accuracy of Dowell's equation for a particular design, as well as a correction factor for Dowell's equation. The corrected Dowell's equation using the model is validated using finite-element analysis simulations as well as previously published experimental data. This paper is accompanied by Python codes to generate all data and figures used in the paper, a Python object that implements the derived mathematical model, and Lua scripts to run the finite-element simulations using FEMM. [ABSTRACT FROM AUTHOR]

In this paper, the design method of dc capacitor bushing core has been studied. According to the derived epoxy/paper composite life model, the bushing core design methods are proposed based on the life of materials, which can make a more reasonable electric field distribution within bushing core. By adjusting the size of plates, the insulation life of innermost and outermost of the bushing core is made to be equivalent, resulting in more efficiency in usage of insulation material. Taking 800 kV dry bushing for example, the optimization size is designed. An iterative algorithm is used to optimize the design of the bushing core to minimize the volume of bushing core, while meeting the maximum designed withstand field strength under the ac and dc voltage. [ABSTRACT FROM AUTHOR]

This paper proposes a new multilevel converter based on the cascade connection of double flying capacitor multicell (DFCM) converters, as multilevel modules, to decrease the voltage diversity of the flying capacitors. Furthermore, a new switching pattern based on the phase-shifted pulse-width modulation technique is proposed to reduce the voltage ripple across the flying capacitors. Moreover, the proposed modulation technique reduces the rms value of the current flowing through flying capacitors. This results in an increase in the life time of flying capacitors and a decrease in the capacitance of the flying capacitors, to keep the same amount of the ripple, meaning a reduction in the physical size of the converter. In addition, this paper presents an analytical approach to calculate the average and rms currents of the insulated gate bipolar transistors (IGBTs)/diodes in the DFCM converter in a closed-form expression. The derived closed-form equations to calculate the average and rms currents of the IGBTs/diodes are utilized to investigate the conduction power losses in a DFCM converter and the proposed multilevel converter. Numerical results of the derived closed-form equations match the simulation results well, which validates the derived equations. Furthermore, simulation results and experimental measurements of the proposed multilevel power converter, configured by cascading two two-cell five-level DFCM converters, are presented to validate the performance of the proposed converter as well as the suggested modulation technique. [ABSTRACT FROM AUTHOR]

This paper proposes a systematic method for developing a model of a dc distribution system, based on the configuration of the system. The dc distribution system is assumed to host electric vehicles and photovoltaic modules, using dc–dc converters, and to integrate them with an ac power grid. The developed model is of the matrix form and, therefore, can be readily expanded to represent a dc distribution system of any desired number of dc–dc converters. The model captures both the steady-state and dynamic characteristics of the system and includes port capacitors of the converters, as well as the interconnection cables. Thus, it can be used for identifying the condition for existence of a steady state, as well as for stability analysis. This paper further proposes an alternative set of characteristic equations that are less computationally intensive than the original matrix representation, for example, for online stability assessment tasks. The adequacy of the proposed model has been demonstrated through a number of case studies conducted and compared in the PSCAD/EMTDC and MATLAB software environments. [ABSTRACT FROM PUBLISHER]

Since Birnbaum importance was introduced in 1969, there have been more than twenty kinds of importance measures so far. Among the various measures, Birnbaum importance plays an extremely important role because many importance measures have been defined under its illumination and have relationships with it. A lot of work has been done for Birnbaum importance in consecutive-k systems since the systems were introduced. Because the problems in practice are increasingly complicated, in 2007, Zhao proposed consecutive-k systems with sparse d, which is an extension of the current consecutive-k systems. In this paper, we study Birnbaum importance for linear consecutive-k-out-of-n systems with sparse d. Some equations on Birnbaum importance are proposed. With these equations, the ranking of components in the system on the basis of Birnbaum importance is given; and then some patterns of ranking are presented. Finally, two numerical examples are given to illustrate the results obtained in this paper. [ABSTRACT FROM PUBLISHER]

This paper describes a procedure for calculating generator circuit breaker duty. Currently, commercially available software products help in determining the duty for a general-purpose circuit breaker. However, further calculations are needed to determine the duty for a special-purpose generator circuit breaker. IEEE Std C37.010-1999 provides the calculation procedure for general-purpose circuit breakers. In order to evaluate a special-purpose generator circuit breaker, this paper will expand the steps and methodology used in IEEE C37.010-1999 by presenting a procedure and detailed calculations for finding a duty multiplication factor based on the test $X/R$ ratio of generator circuit breakers given in IEEE C37.013-1997 (Standard for AC High-Voltage Generator Circuit Breakers Rated on a Symmetrical Current Basis). This way, engineers can still make a generator circuit breaker assessment although generator circuit breaker evaluation module is not included in many commercial short-circuit programs. [ABSTRACT FROM AUTHOR]

Silicon-on-insulator (SoI) technology has been reported as a technique to improve electrical characteristics over those of bulk MOSFETs. However, this approach results in the disadvantage of increased drain-induced barrier lowering (DIBL) due to drain electric flux (or field) passing through the buried oxide (BOX) layer. Against such a background, the development of a method to easily estimate the amount of this electric flux is expected to support the prediction of BOX-related DIBL. This paper involved the investigation of a model-derived analytically using conformal mapping techniques to represent the amount of flux in subthreshold regions of ground-plane SoI MOSFETs. To create the model, this paper was divided into two parts. In Part I, as preparation for model development, the relationships between coordinates in MOSFETs and potential/stream function were derived using conformal mapping, and related validity was verified. In Part II, the model’s development was considered based on these relationships, and its validity was also verified. [ABSTRACT FROM PUBLISHER]

In earlier papers, analytical formulas were derived to estimate the maximum crosstalk in the frequency domain for systems with electrically long signal lines. These formulas were developed to give designers intuitive feedback as to the causes for crosstalk problems and methods for maximum crosstalk reduction. In one of these papers, the maximum crosstalk estimates are based on intuitive relationships for infinitely long transmission lines. While the resulting model is quite simple and easy to understand, its limitations are poorly understood. In another paper, the maximum crosstalk estimates are based on a mathematically rigorous integral formulation, but the resulting model is relatively complex. This rigorous model is derived assuming the signal lines are weakly coupled and the transmission line characteristic impedances are approximately the same over the entire lengths of the aggressor and victim circuits. The following paper illustrates how the less rigorously developed estimates, based on infinitely long transmission lines, may be derived from the mathematically rigorous maximum crosstalk estimates for lossless and homogeneous transmission lines in the frequency domain. The resulting derivation provides insight into the limitations and mathematical validity of the less rigorous estimates that are not available in the original paper. The mathematically rigorous maximum crosstalk estimates are shown to have fewer and less restrictive assumptions than the estimates based on infinitely long transmission lines. Measurements and simulations are presented that validate results and illustrate maximum crosstalk estimate limitations. [ABSTRACT FROM AUTHOR]

In this paper, an original observation model for multiresolution optical flow estimation is introduced. Multiresolution frameworks, often based on coarse-to-fine warping strategies, are widely used by state-of-the-art optical flow methods. They allow the recovery of large motions by successive estimations of the flow field at several resolution levels. Although such approaches perform very efficiently and usually lead to faster minimizations, they generally consider independent problems at each resolution levels and do not exploit the existing interactions between scales (especially the influences of fine scales on larger ones). In this paper, we tackle this issue by proposing a flexible framework, inspired from fluid mechanics, able to partly counter these limitations. For each resolution level, our process filters the equations of interest and decomposes the key variables into resolved (i.e., at a given resolution) and unresolved (i.e., at finer resolutions) components. This enables to derive a new data term that takes into account, at coarse resolutions, the influence of their unresolved parts. From this new term, we propose two different estimation strategies, depending on whether we explicitly know the type of relations between the different scales (as for physical processes) or not. In order to test the efficiency of this new observation model, we have embedded it in a simple multiresolution Lucas-Kanade estimator. Comparing the usual optical flow constraint equation with this new term in the same motion estimation procedure, it clearly appears that the proposed term leads to more consistent estimates and prevents from errors propagation apparition during the estimation. In all situations (synthetic, real, physical images or not), our new term is able to greatly improve the results compared with usual conservation constraints. [ABSTRACT FROM PUBLISHER]

In this paper, the procedure for designing a sliding-mode controller for maximum power point tracking photovoltaic (PV) applications is proposed. It is applied to a single-ended primary inductor converter, thus to a fourth-order topology, but it can be extended to a wide class of converters suitable for PV applications. The reachability and existence conditions give rise to a number of design inequalities that add to the classical steady-state conditions in order to have the desired closed-loop converter's performances. The superiority of the control technique over the classical tracking methods is analytically demonstrated through the procedure proposed in this paper. The analytical results have been validated by means of both simulations and experiments. [ABSTRACT FROM PUBLISHER]

This paper presents the interaction between the overhead transmission lines (OHTLs) and their towers. In this paper, the electric field around the tower of the overhead transmission lines is calculated. The charge simulation method, combined with the image method, is used to develop a model that consists of subconductors of the OHTLs and the tower. The charges on the surface of each subconductor of the overhead transmission lines are simulated by a set of infinite line charges, of various charge densities, along the length of the subconductor, and the induced charges on the surface of the tower are simulated by a set of finite line charges. [ABSTRACT FROM PUBLISHER]

Black-box models are a valuable tool to simulate dynamic arc-network interactions, such as those that occur during fault current interruption in ac or HVDC circuit breakers. However, accurate determination of characteristic arc parameters from voltage and current measurements is very challenging. This paper aims to improve the accuracy in arc characterization. A new arbitrary current source is used to simplify arc parameter determination through a more complex current waveform, for example, a series of staircase-like increasing steps. With this, the stationary and transient arc characteristics can be measured independently from each other. Therefore, current steps are well suited to: 1) validate the choice of a specific black-box model and 2) determine the arc parameters of the chosen model with higher accuracy. In principle, the source is also well suited to fill a table of the arc voltage response U,\, \mathdot U at various current levels and slopes I,\, \mathdot I. Thus, it would be possible to characterize arcs independent of any black-box model, but it would not be well suited to compare different arcs. Therefore, this paper focuses on an improved black-box parameter determination and the experimental validation of the Schwarz model, with P and \tau being free functions of g. [ABSTRACT FROM PUBLISHER]

In Part I of this two-part paper, fundamental concepts of interlaminar fault and its consequences on magnetic cores were presented. An equivalent configuration, which was proved by FEM modelling, was proposed for magnetic cores with interlaminar fault. In this Part II paper, based on the equivalent configuration of the core and equivalent circuit of eddy current path, an analytical model is developed to estimate eddy current power loss of magnetic cores with interlaminar faults in a wide range of magnetizing frequency. Important factors, such as skin effect, nonuniform flux density distribution, complex relative permeability and nonlinear relation of B (H), which are often neglected in the literature, are highlighted. Packs of two, three, and four Epstein-size laminations of conventional grain oriented were shorted together artificially to measure the extra power loss caused by the interlaminar fault and support the analytical modeling. It was found that in the magnetic cores affected by interlaminar fault, the skin effect is a determinant factor in the magnetic properties determinations, even at low frequencies. [ABSTRACT FROM AUTHOR]

This paper develops a generalized admittance matrix approach in Fortescue coordinate system to solve unbalanced/unsymmetrical distribution networks including different number of phases. This generalized Fortescue \pi equivalent is defined in this paper for solving the heterogeneous phase, and thus Fortescue, network model. The performance of the approach is demonstrated in different model networks with number of nodes ranging between 168 and 14200. It is found that the current iteration method exploiting the decoupling in admittance matrix in Fortescue coordinate is substantially faster than the typical unbalanced three-phase solution in phase domain. The method has a significant potential for application in real time active power network management. [ABSTRACT FROM PUBLISHER]

This paper discusses the bias problem when estimating the population size of big data such as online social networks (OSN) using uniform random sampling and simple random walk. Unlike the traditional estimation problem where the sample size is not very small relative to the data size, in big data, a small sample relative to the data size is already very large and costly to obtain. We point out that when small samples are used, there is a bias that is no longer negligible. This paper shows analytically that the relative bias can be approximated by the reciprocal of the number of collisions; thereby, a bias correction estimator is introduced. The result is further supported by both simulation studies and the real Twitter network that contains 41.7 million nodes. [ABSTRACT FROM AUTHOR]

Rule learning algorithms, for example, Ripper, induces univariate rules, that is, a propositional condition in a rule uses only one feature. In this paper, we propose an omnivariate induction of rules where under each condition, both a univariate and a multivariate condition are trained, and the best is chosen according to a novel statistical test. This paper has three main contributions: First, we propose a novel statistical test, the combined $(5\times 2)$ cv $(t)$ test, to compare two classifiers, which is a variant of the $(5\times 2)$ cv $(t)$ test and give the connections to other tests as $(5\times 2)$ cv $(F)$ test and $(k)$-fold paired $(t)$ test. Second, we propose a multivariate version of Ripper, where support vector machine with linear kernel is used to find multivariate linear conditions. Third, we propose an omnivariate version of Ripper, where the model selection is done via the combined $(5\times 2)$ cv $(t)$ test. Our results indicate that 1) the combined $(5\times 2)$ cv $(t)$ test has higher power (lower type II error), lower type I error, and higher replicability compared to the $(5\times 2)$ cv $(t)$ test, 2) omnivariate rules are better in that they choose whichever condition is more accurate, selecting the right model automatically and separately for each condition in a rule. [ABSTRACT FROM PUBLISHER]

Optimal design problems of electromagnetic devices are generally multimodal, nondifferentiable, and constrained. This makes metaheuristic algorithm a good choice for solving such problems. In this paper, a newly developed metaheuristic algorithm is presented to address the aforementioned issues. The proposed algorithm is based on the paradigm of artificial bee colony (ABC). A drawback of the original ABC algorithm is because its solution variation is only 1-D, as this decreases its convergence speed. In this paper, a one-position inheritance scheme is proposed to alleviate this drawback. An opposite directional (OD) search is also proposed to accelerate the convergence of the ABC algorithm. The novel algorithm is applied to both TEAM Workshop problem 22 and a loudspeaker design problem. Both discrete and continuous cases of problem 22 are tested. The effectiveness and efficiency of the proposed algorithm are demonstrated by comparing its performance with those of the original ABC, an improved ABC known as Gaussian ABC, and differential evolution algorithms. [ABSTRACT FROM PUBLISHER]

This paper presents a method for design and control of dc-bus capacitance and transients in a renewable single-phase grid-connected converter. Conventionally, a proportional (P) or proportional-integrating (PI) controller is commonly used and the design stage is performed using trial-error or using a simplified analysis that does not take the dynamics of the current control loop into consideration. This paper proposes 1) a systematic and efficient method for design of dc-bus PI controller gains; and 2) an accurate method for the design of the dc-bus controller gains without neglecting the dynamics of the current control loop. Two main objectives are to have control over the amount of output current harmonics and over the level of bus fluctuations caused by random input power swings. The proposed method is transparent and it provides a convenient and rigorous insight for the designer to properly select the size of dc-bus component and to determine the controller gains. [ABSTRACT FROM PUBLISHER]

Permeance variation in the air gap of the permanent-magnet synchronous machine induces eddy-current losses in its permanent magnets even in the absence of stator currents. This paper proposes a new analytical approach to analyze these losses using the permeance-variation vector function introduced for the air-gap magnetic-flux density distribution to take into account the stator teeth. The Laplace equation is employed to derive the radial dependency of the stator slotting effect on the magnetic-flux density distribution. The induced eddy currents are further calculated by using Faraday's law. The analytical results are compared with the numerical ones based on the finite-element analysis. The paper offers a faster alternative to the numerically intensive calculations of eddy-current losses, and the method is especially useful in initial design optimization of the electric machine. [ABSTRACT FROM AUTHOR]

In this paper, we consider the problem of determining the weight spectrum of q-ary codes C(3,m) associated with Grassmann varieties G(3,m). For m=6, this was done in a paper by Nogin in 1997. We derive a formula for the weight of a codeword of C(3,m), in terms of certain varieties associated with alternating trilinear forms on \BBFq^{m}. The classification of such forms under the action of the general linear group GL(m, \BBFq) is the other component that is required to calculate the spectrum of C(3,m). For m=7, we explicitly determine the varieties mentioned above. The classification problem for alternating three-forms on \BBFq^{7} was solved in a study by Cohen and Helminck in 1988, which we then use to determine the spectrum of C(3,7). [ABSTRACT FROM AUTHOR]

This paper proposes a new reconfiguration heuristic in order to reduce the total power loss and the maximum current of electrical radial networks. It is based on the branch-and-bound strategy, which is an implicit enumeration method that uses a tree structure and bounds to organize the searching process. The search tree in this paper is constructed by subdividing the feasible set using the branch-exchange technique in the networks. The constraints and the Pareto dominance are responsible for pruning the search tree. The heuristic also returns a feasible switching plan for each solution. The algorithm was successfully applied to medium- and large-scale problems. [ABSTRACT FROM AUTHOR]

This paper demonstrates that for certain choices of mass distribution and addition of springs, an underactuated \two-degree-of-freedom (2-DOF) \bm PRRRP system is static feedback linearizable, i.e., differentially flat as well. This paper is original and provides a ground breaking study in underactuated dynamical systems. [ABSTRACT FROM AUTHOR]

Operational statistics and studies have revealed that, the reduction of insulation strength of transmission line insulators caused by icing is one of the critical reasons of the power grid faults. This paper compares of various test methods for evaluating the flashover characteristic of ice-covered composite insulators. Two types of composite insulators, i.e. FXBW-±800/530 short sample and FXBW-110/100 are investigated. The influences of various test methods on flashover performance of ice-covered insulators are studied in an artificial climate chamber. The test results revealed the influences are significant. The average flashover voltage (Uav) using even raising method is highest, followed by the 50% withstand voltage (U50%) which is corresponding to up and down method, the lowest flashover voltage (Uf.min) using Ucurve method is the third, and the maximum withstand voltage (Uws) using the maximum withstand voltage method is the lowest. Through the statistical analysis, the U50% can be estimated by Uav and σav though the estimated value Ue (Ue=(Uav-k1σav)/( 1+k2δe)). The estimated errors (Ee) are less than 1.80% in this paper. Therefore, there is an intrinsic relationship among the test results obtained by using various test methods. This simplifies selection of the appropriate test method according to the testing specific circumstances. [ABSTRACT FROM PUBLISHER]

Transient simulation programs, either nodal analysis-based electromagnetic transient program (EMTP-like) or state-variable-based, are used very extensively for modeling and simulation of various power and energy systems with electrical machines. It has been shown in the literature that the method of interfacing machine models with the external electrical network plays an important role in numerical accuracy and computational performance of the overall simulation. This paper considers the state-variable-based simulation packages, and provides a constant-parameter decoupled RL-branch equivalent circuit for interfacing the ac induction and synchronous machine models with the external electrical network. The proposed interfacing circuit is based on the voltage-behind-reactance formulation which has been shown to have advantageous properties. For the synchronous machines, this paper describes both implicit and explicit (approximate) interfacing methods. The presented case studies demonstrate the advantages of using the proposed interfacing method over the traditional qd-models that are conventionally used in many simulation packages. [ABSTRACT FROM AUTHOR]

In this paper, an algorithm is proposed to extract two illuminant invariant chromaticity features from three image sensor responses. The algorithm extracts these chromaticity features at pixel level and therefore can perform well in scenes illuminated with nonuniform illuminant. An approach is proposed to use the algorithm with cameras of unknown sensitivity. The algorithm was tested for separability of perceptually similar colors under the International Commission on Illumination standard illuminants and obtained a good performance. It was also tested for color-based object recognition by illuminating objects with typical indoor illuminants and obtained a better performance compared to other existing algorithms investigated in this paper. Finally, the algorithm was tested for skin detection invariant to illuminant, ethnic background and imaging device. In this investigation, daylight scenes under different weather conditions and scenes illuminated by typical indoor illuminants were used. The proposed algorithm gives a better skin detection performance compared to widely used standard color spaces. Based on the results presented, the proposed illuminant invariant chromaticity space can be used for machine vision applications including illuminant invariant color-based object recognition and skin detection. [ABSTRACT FROM AUTHOR]

Arc flash calculations in IEEE 1584 “IEEE Guide for Performing Arc Flash Calculations” calculate the arcing current and the incident energy using logarithmic curve fit equations. These equations are the result of a regression analysis of multiple arc flash tests and describe the arcing current and incident energy over the full range of bolted fault currents. These equations are a multiple-variable fit to the test data rather than a physics-based model. Several papers have been presented with many circuit models to represent the arc in the electrical circuit. This paper will present a circuit model of the arc and subsequently derive the arcing current and incident energy as a function of the circuit arc voltage and arc resistance. The model presented also fits the nonlinear behavior of the arcing current over the entire range of bolted fault currents. The arc voltage model is then related to a single parameter: the length of the arc gap. Having an accurate arcing model has a second advantage. It allows the electrical energy during an event to be calculated specifically for the energy of the arc. This solution then allows calculation of the energy based on the event let-through characteristics. The implication of this result is very powerful. This model implies that the IEEE arcing currents are, in fact, based on a physical circuit model similar to the model presented here. The arcing voltage and arcing resistance are then shown to be independent of the current. [ABSTRACT FROM AUTHOR]

This paper studies the problem of recovering a signal with a sparse representation in a given orthonormal basis using as few noisy observations as possible. Herein, observations are subject to the type of background clutter noise encountered in radar applications. Given this model, this paper proves for the first time that highly sparse signals contaminated with Gaussian background noise can be recovered by adaptive methods using fewer noisy linear measurements than required by any possible recovery method based on nonadaptive Gaussian measurement ensembles. [ABSTRACT FROM AUTHOR]

This paper presents a class of Petri nets, process nets with channels (PNCs) that can model some types of concurrent systems in two aspects: process and interaction. Its significance lies in offering efficient analysis and verification methods for these systems. PNCs belong to the class of extended free choice nets. This paper establishes the conditions to examine their liveness, reversibility, and reachability based on their structural characteristics. Siphons, traps, and a state equation are used to describe these conditions such that analysis techniques based on reachability graphs and siphon enumeration are avoided. A polynomial-time algorithm is presented for the liveness analysis, and an effective method is also given to decide the reachability. A real-world example is used to illustrate the application of PNCs. [ABSTRACT FROM PUBLISHER]

The main objective of this paper is to provide an efficient computational model for fast and accurate calculation of electromagnetically induced vibrations in electrical machines. Although a three-phase permanent-magnet synchronous machine has been used in this paper, the same methodology can be extended to other types of electric machinery. A brief comparison between the different methods for structural analysis in electrical machines is introduced. The method proposed in this paper uses finite-element analysis in order to extract the impulse responses that are used in calculating the vibration. A field reconstruction method is used for the electromagnetic field analysis. [ABSTRACT FROM PUBLISHER]

Core communication networks have seen significant traffic increases in recent years, and availability requirements also continue to increase. This fact has led to a wide array of network design improvements, particularly in the area of network survivability. The various survivability mechanisms and accompanying design models that have been developed use diverse strategies to provision spare capacity throughout a network to restore traffic in case of a failure. The break of a fiber line continues to be the most common type of network failure, and this paper addresses at a common protection mechanism called shared backup path protection (SBPP), which is quite efficient at dealing with this type of failure. SBPP is a popular survivability mechanism, and there has been a significant amount of work done with it in recent years. However, the SBPP integer linear program (ILP) design model has proven difficult to solve using reasonable computing and time resources. While many algorithms and heuristics have been developed to design SBPP-based networks, it has been difficult to know how well these designs perform compared to ILP optimized networks. This paper presents a new SBPP-type protection mechanism and accompanying ILP model that solves in a couple orders of magnitude less time than the benchmark approach by allowing multiple working and backup routes (we compare to one representative version of the traditional approach as our benchmark). This new mechanism and accompanying model will allow better benchmarking of SBPP-like network designs, and enhance further study into the performance of SBPP relative to other network survivability approaches. [ABSTRACT FROM PUBLISHER]

Multiphase (more than three phases) power electronic converters are required mainly for feeding variable-speed multiphase drive systems. This paper presents one such solution by using a direct ac–ac converter that can be used to supply a nine-phase drive system. The input is a fixed-voltage and fixedfrequency three-phase input, and the output is a variable-voltage and variable-frequency nine-phase output. A simple pulsewidthmodulation technique is developed for the proposed ac–ac converter named as a nonsquare three-to-nine-phase matrixconverter configuration. The developed modulation technique is based on the comparison of a high-frequency carrier signal with the duty ratios. Although the carrier-based scheme is widely employed for the control of back-to-back converters, it has recently been used for controlling a three-to-three-phase matrix converter. This concept is extended in this paper for controlling a threeto-nine-phase matrix converter. With the two techniques that are proposed, one outputs 0.75 of the input magnitude and the other outputs reach 0.762 of the input. This is the maximum value of the output voltage in the linear modulation range that can be achieved in this configuration of the matrix converter. The viability of the proposed control techniques is proved analytically through simulation and an experimental approach. [ABSTRACT FROM PUBLISHER]

The video surveillance market is increasingly moving toward cheaper, efficient, portable, and high resolution systems. A typical video surveillance system consists of several cameras, which issue warnings or initiate smart reactions according to the analysis results of the captured video data. Many algorithms in video surveillance systems assume fixed lighting conditions for the monitored area. The performance of these algorithms is severely affected by the illumination changes of the monitored area. This paper presents an efficient intensity correction algorithm for high definition video surveillance applications. The new algorithm corrects both the global and the local intensity changes. It uses an apparent gain factor to correct the global intensity changes. In addition it corrects the local intensity changes using the local intensity mean and standard deviation. The proposed algorithm shows a promising performance when compared with other intensity correction algorithms. It has a low computational cost that makes it a suitable choice for real-time hardware implementation. This paper also presents a hardware implementation of the proposed algorithm using Xilinx Spartan3A digital signal processor (DSP) XC3SD3400A device. The targeted resolution is 1920\,\times\,1080 at 30 f/s. The hardware prototype utilizes 17% of the slices, 21% of the block random access memories, and 24% of the DSP48As available in Spartan3A DSP XC3SD3400A device. [ABSTRACT FROM AUTHOR]

This paper presents an adaptive method for tracking the amplitude, phase, and frequency of a time-varying sinusoid in white noise. Although the conventional techniques like adaptive linear elements and discrete or fast Fourier transforms are still widely used in many applications, their accuracy and convergence speed pose serious limitations under sudden supply frequency drift, fundamental amplitude, or phase variations. This paper, therefore, proposes a fast and low-complexity multiobjective Gauss–Newton algorithm for estimating the fundamental phasor and frequency of the power signal instantly and accurately. Further, the learning parameters in the proposed algorithm are tuned iteratively to provide faster convergence and better accuracy. The proposed method can also be extended to include time-varying harmonics and interharmonics mixed with noise of low signal-to-noise ratio with a great degree of accuracy. Numerical and experimental results are presented in support of the effectiveness of the new approach. [ABSTRACT FROM AUTHOR]

In this paper, the diagnosis of soft faults in lossy electric transmission lines is studied through the inverse scattering approach, extending a recently reported study on lossless transmission lines. The considered soft faults are modeled as continuous spatial variations of distributed characteristic parameters of transmission lines. The diagnosis of such faults from reflection and transmission coefficients measured at the ends of a line can be formulated as an inverse problem. The relationship between this inverse problem and the inverse scattering theory has been studied by Jaulent in 1982 through transformations from the telegrapher's equations of transmission lines to Zakharov-Shabat equations. The present paper clarifies and completes the computation of the theoretic scattering data required by the inverse scattering transform from the practically measured engineering scattering data. The inverse scattering method is then applied to numerically simulated lossy transmission lines to confirm the feasibility of the studied approach to soft fault diagnosis. [ABSTRACT FROM AUTHOR]

A digital sensorless adaptive voltage positioning (SLAVP) control method is presented in this paper in order to realize AVP control without the need for load or inductor current sensing and high-resolution high-speed analog-to-digital converter sampling. The SLAVP control law utilizes the readily available error signal of the conventional voltage-mode closed-loop compensated controller or, in other words, the duty cycle of a dc–dc buck converter in order to realize AVP control. The elimination of the need for high-speed and accurate sensing and sampling of currents using the proposed SLAVP control reduces the size and cost of the digital controller, reduces the power losses associated with current sensing and sampling, and simplifies hardware design. Moreover, the SLAVP control can easily be added to controllers with conventional voltage-mode closed-loop control with minimum size and cost increase, and therefore, SLAVP control can be used for a wide range of applications and not only for high-end applications like powering microprocessors. The theoretical SLAVP control law derivation and analysis and SLAVP controller architecture are presented in this paper and verified by experimental results obtained from a proof-of-concept experimental prototype. [ABSTRACT FROM AUTHOR]

Recent advances in lithium-ion battery modeling suggest unequal but controlled and carefully timed charging of individual cells by reduce degradation. This paper compares anode-side film formation for a standard equalization scheme versus unequal charging through switches that are controlled by deterministic dynamic programming (DDP) and DDP-inspired heuristic algorithms. A static map for film growth rate is derived from a first-principles battery model adopted from the electrochemical engineering literature. Using this map, we consider two cells that are connected in parallel via relay switches. The key results are the following: 1) optimal unequal and delayed charging indeed reduces film buildup, and 2) a near-optimal state feedback controller can be designed from the DDP solution and film growth rate convexity properties. The simulation results indicate that the heuristic state feedback controller achieves near optimal performance relative to the DDP solution, with significant reduction in film growth compared to charging both cells equally, for several film growth models. Moreover, the algorithms achieve similar film reduction values on the full electrochemical model. These results correlate with the convexity properties of the film growth map. Hence, this paper demonstrates that unequal charging may indeed reduce film growth, given certain convexity properties exist, lending promise to the concept for improving battery pack life. [ABSTRACT FROM PUBLISHER]

Aggressive transistor scaling affects the threshold voltage Vth in two ways: space and time. Transistors on the same die can have different Vth due to random dopant fluctuations (RDFs). On the other hand, Vth of a specific transistor can randomly shift in time due to random position of dangling bonds and random motion of atomic H or \H2 molecules in the oxide [negative bias temperature instability (NBTI)]. These two random effects are not totally independent because the dissociation rate of Si–H bonds at the silicon–oxide interface depends on the nonuniform electric field. In this paper, we describe the combined effect of RDF and NBTI on Vth using stochastic differential equation. In this paper, we are able to examine the effect of RDF on critical NBTI parameters such as kf, kr, and temperature and the correlation among these parameters. The efficacy of the proposed model is evaluated by performing Monte Carlo simulations on various transistors under different direct-current stress and obtained distributions for NIT and Vth. [ABSTRACT FROM PUBLISHER]

This paper proposes a spectral-graph-based algorithm for face image repairing, which can improve the recognition performance on occluded faces. The face completion algorithm proposed in this paper includes three main procedures: 1) sparse representation for partially occluded face classification; 2) image-based data mining; and 3) graph Laplace (GL) for face image completion. The novel part of the proposed framework is GL, as named from graphical models and the Laplace equation, and can achieve a high-quality repairing of damaged or occluded faces. The relationship between the GL and the traditional Poisson equation is proven. We apply our face repairing algorithm to produce completed faces, and use face recognition to evaluate the performance of the algorithm. Experimental results verify the effectiveness of the GL method for occluded face completion. [ABSTRACT FROM PUBLISHER]

Permanent-magnet generators (PMGs) have rapidly become important in renewable energy systems, portable and standby generating systems, and in many new applications in industrial, utility, aerospace, and automotive sectors. While there has been some discussion of “fault tolerance” and fault testing of an 8-MW machine has recently been reported [1], understanding the behavior of faulted PMGs remains far from complete. This paper addresses the important case of the sudden short circuit applied to large PMG machines. It explains key differences in short-circuit behavior between the PMG and wound-field generator. The subtransient reactances and time constants of the PMG are calculated by both analytical and finite-element methods and applied to the classical circuit-theory simulation of the short-circuit fault. The finite-element method is also used to assess in detail the risk of loss of magnetization in the magnets. The complexity of the transient magnetic field requires transient nonlinear circuit-coupled finite-element analysis in three dimensions with voltage-source excitation. This paper concludes with a review of the methods of calculation and a discussion of implications for future design and application of the PMG, including factors relevant to the application of standard tests and specifications. [ABSTRACT FROM AUTHOR]

In a previous paper, a method was introduced that used a system of linear equations to determine the frequency and the complex amplitude of a complex single tone signal. The system of linear equations was derived from the model of a complex single tone in the DFT domain and was used as parameters estimator in noisy conditions. In this paper, this approach is extended to a complex multitone signal. As for the complex single tone case, the parameters value is determine from the solution of systems of linear equations and the method is directly applied for parameters estimation in noisy conditions. An analysis of the estimators is provided, including the case of closely spaced frequencies, and criteria and procedures for the appropriate selection of the DFT samples are presented. [ABSTRACT FROM AUTHOR]

Performances in network-based synchronization depend on several related factors, including the instability of local clocks, the rate at which timing information is exchanged, and the accuracy of the resulting correction estimates. This paper analyzes these effects and their relationships, showing how these may affect the design of an IEEE 1588 Precision Time Protocol synchronization scheme. This paper introduces a state-variable clock model for which realistic parameters can be obtained for different kinds of clocks from experimental measurements of Allan variance plots. A Kalman-filter-based clock servo employing this model is developed, and a simulation analysis of the behavior of clock regulation and the effect of parameter variations on its performances is presented. [ABSTRACT FROM PUBLISHER]

This paper introduces a general theory of extended Hamiltonian (second-order) learning on Riemannian manifolds, as an instance of learning by constrained criterion optimization. The dynamical learning equations are derived within the general framework of extended-Hamiltonian stationary-action principle and are expressed in a coordinate-free fashion. A theoretical analysis is carried out in order to compare the features of the dynamical learning theory with the features exhibited by the gradient-based ones. In particular, gradient-based learning is shown to be an instance of dynamical learning, and the classical gradient-based learning modified by a “momentum” term is shown to resemble discrete-time dynamical learning. Moreover, the convergence features of gradient-based and dynamical learning are compared on a theoretical basis. This paper discusses cases of learning by dynamical systems on manifolds of interest in the scientific literature, namely, the Stiefel manifold, the special orthogonal group, the Grassmann manifold, the group of symmetric positive definite matrices, the generalized flag manifold, and the real symplectic group of matrices. [ABSTRACT FROM AUTHOR]

Automatic differentiation (AD) is introduced as a powerful technique to compute derivatives of functions given in the form of computer programs in high-level programming languages such as FORTRAN, C, or C++. This paper applies AD to compute error-free gradients of electromagnetic device sizing models. Then, the obtained gradients are exploited in optimization to size electromagnetic devices by means of minimizing a cost function with constrained parameters and performances. Often, the electromagnetic devices models have to be described not only by analytical formulas, but also by algorithms. This paper proposes an electromagnetic model of a linear actuator dealing with implicit equations solved by numerical algorithms. The ADOL-C package is considered for automatic differentiation. [ABSTRACT FROM PUBLISHER]

A microdosimetric study of nanosecond pulsed electric fields, including dielectric dispersivity of cell compartments, is proposed in our paper. A quasi-static solution based on the Laplace equation was adapted to wideband signals and used to address the problem of electric field estimation at cellular level. The electric solution was coupled with an asymptotic electroporation model able to predict membrane pore density. An initial result of our paper is the relevance of the dielectric dispersivity, providing evidence that both the transmembrane potential and the pore density are strongly influenced by the choice of modeling used. We note the crucial role played by the dielectric properties of the membrane that can greatly impact on the poration of the cell. This can partly explain the selective action reported on cancerous cells in mixed populations, if one considers that tumor cells may present different dielectric responses. Moreover, these kinds of studies can be useful to determine the appropriate setting of nsPEF generators as well as for the design and optimization of new-generation devices. [ABSTRACT FROM PUBLISHER]

This paper presents the evaluation of the performance, in terms of uncertainty, of a tool designed to estimate the main parameters of a model of a photovoltaic panel (PVP) under real and/or simulated working conditions. The presented tool permits the characterization of the panel, and it is useful to predict its behavior in whatever working condition; in this way, it is possible to compare the actual and expected performance to prevent any decrease in the output power, so permitting the replacement of the monitored module before it goes out of order or its efficiency falls under a given threshold. The well-known two-diode model is used to estimate the parameters of the electrical equivalent circuit of the PVP and to simulate the I–V and P–V characteristic curves in any given environmental condition of irradiance and/or temperature. The model and the estimation algorithm are implemented with MATLAB functions, whereas data acquisition and result presentation are managed by a LabVIEW graphics user interface. The presented tool has been validated against an experimentally characterized PVP. The environmental parameters of the model such as irradiance and temperature have been set (with their respective uncertainties) during simulations or directly measured during the outdoor tests, whereas the others parameters have been evaluated using a best-fit algorithm on the measured data. The estimation is based on the minimization of a new objective function and on a modified expression of the model resistances, which differ from those mentioned in the available literature. After a review of the state of the art, this paper provides the description of the estimation technique and its validation by means of simulations and experiments. Some results are also provided to illustrate the performance of the proposed test method. [ABSTRACT FROM AUTHOR]