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This article presents the $\epsilon$ -stealthy attack against cyber-physical systems under the stochastic communication protocol (SCP), which is used to avoid data collisions. The aim is to develop an optimal attack strategy to degrade the estimation performance maximally, while remaining a certain level of stealthiness characterized by the Kullback–Leibler divergence. Taking the SCP-introduced effects into account, a novel attack model is proposed, where only a part of the transmitted data is utilized to construct the attack signal at each time instant. Subsequently, the optimization problem is formulated. Different from the existing results, where only the numerical solution is given, the analytical expression of the optimal attack parameters is presented, where the analytical solution has more advantage in analyzing how the parameters affect the attack performance. Finally, the numerical simulations on a three-tank system and the experiments performed on a networked permanent magnet synchronous machine prototype system are provided to validate our results. [ABSTRACT FROM AUTHOR]

This article’s primary motivation is to propose a nonsingular and continuous terminal sliding-mode (TSM) control with reduced chattering, which is able to rapidly stabilize the second-order plant with high precision. To this end, a novel sliding-mode manifold, coined as practical TSM (PTSM) one, is first constructed. Once the proposed sliding surface is reached, a Lipschitz-continuous but slope-steep generalized velocity will be established at the origin such that the global nonsingularity of the equivalent control is ensured. The fast dynamic response with local high gain characterizes the sliding behavior inside the unit neighborhood of the origin. Importantly, the analytical solution of the proposed sliding-mode reduced-order system is deduced, which indicates that the finite time taken to slide into a preset small neighborhood of the origin can be calculated. The above designability of convergence time is necessary for control practices with accurate time sequence planning. Further, the corresponding globally singular-free PTSM reaching law with reduced chattering is designed based on the super-twisting algorithm. Finally, several groups of linear-motor-based control experiments verify the superiorities of proposed controllers. [ABSTRACT FROM AUTHOR]

The three-phase dual active bridge (3ph-DAB) converter is a promising topology attracting increasing attention. However, because it is limited to symmetrical three-phase bridge control, the conventional single-phase-shift control method (SPS) remains the most common method for 3ph-DAB converter. The obvious shortcomings of SPS control include the soft-switching failure, massive circulating energy, and high root-mean-square (rms) current value at the light load, particularly with large voltage variation-ratio conditions. To overcome these drawbacks, this article proposes a novel asymmetrical phase shift (APS) control strategy. Unlike other optimized modulation schemes, this optimized strategy breaks the symmetrical control rules of three-phase bridges by introducing variable phase-shift angles among three-phase legs. The novel APS control strategy can substantially reduce the current's rms value and extend the soft-switching operation range due to these additional phase-shift angles. Further, the analytical solutions for the optimal phase-shift angles are derived by solving the global optimal condition equations. Analytical solutions, compared with complex numerical solutions derived by other optimized schemes, can be easily adopted in digital implementation and perform well under changing parameter conditions. Finally, experimental results verify the outstanding performance of the proposed modulation strategy. [ABSTRACT FROM AUTHOR]

In recent years, very high frequency (VHF) converter has attracted much attention. However, with rich parasitic parameters and complex resonance links, there are some great difficulties to the modeling of such systems. Taking the on-off controlled VHF resonant boost converter as an example, this paper presents an accurate modeling and analysis method that considers multiple parasitic parameters. First, the closed-loop VHF converter system is divided into a main network and a parasitic oscillation network. Then, based on the operation analysis, an equivalent circuit model characterized by a time-varying input voltage source and two variable duty-cycle controlled switches is proposed. It worth noting that both the time-varying input and the controlled switches take into account the influences of the parameters. Furthermore, the periodic approximate analytical solution of the output voltage in the on stage is obtained by using the equivalent small parameter method to the proposed circuit model. And then combining the solution of the parasitic oscillation network and on-off state switching conditions, the steady-state waveform of output voltage can be obtained quickly. Finally, a prototype with operating frequency of 21.44 MHz is built to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

A surface field analytical solution of the impedance boundary condition circular cylinder canonical problem is contributed in the work at hand. The accurate representation of the primary ray contribution of the tangential surface magnetic field, of a tangential magnetic current excited relative electromagnetic structure, is given via series expansion in powers of the normalized surface impedance. Furthermore, each term in the series is represented as series of the inverse of the cylinder radius. This is achieved by approximating the Hankel functions by a uniform asymptotic expansion within the spectral integral representation of the relevant Green’s function. All the resulted integrals are evaluated analytically in an exact fashion, and thus, the final process entails only summations and differentiations. The attained formulas are valid both within and outside the paraxial region. Validity of the contributed analytical solution is provided by successful comparison with published results. [ABSTRACT FROM AUTHOR]

Since the Gaussian-inverse Wishart hierarchical form has similar properties to Student’s $t$ distribution, we name it generalized $t$ distribution in this article. Based on this, a robust generalized $t$ distribution-based Kalman filter (GTKF) is proposed for state-space models that are eroded by state and measurement outliers. Different from the existing algorithms, the state transition and measurement likelihood densities are directly modeled as generalized $t$ distributions by employing the one-step smoothing strategy.An analytical closed-form solution can be obtained through the variational inference approach. Moreover, two variants of the proposed GTKF are also presented to apply to different engineering scenarios. Simulation and experimental examples demonstrate that the proposed GTKFs yield improved robustness over the existing algorithms. [ABSTRACT FROM AUTHOR]

An increasing trend for reducing cost, space, and weight leads to modern embedded systems that execute multiple tasks with different criticality levels on a common hardware platform while guaranteeing a safe operation. In such mixed-criticality (MC) systems, multiple worst case execution times (WCETs) are defined for each task, corresponding to the system operation mode to improve the MC system’s timing behavior at runtime. Determining the appropriate WCETs for lower criticality (LC) modes is nontrivial. On the one hand, considering a very low WCET for tasks can improve the processor utilization by scheduling more tasks in that mode, on the other hand, using a larger WCET ensures that the mode switches (which causes by task overrunning) are minimized, thereby improving the quality of service for all tasks, albeit at the cost of processor utilization. Hitherto, no analytical solutions are proposed to determine WCETs in LC modes. In this regard, we propose a scheme to determine WCETs by the Chebyshev theorem, to make a tradeoff between the number of scheduled tasks at design-time and the number of dropped low-criticality tasks at runtime as a result of frequent mode switches. To have a tight bound of execution times and mode switching probability, we also propose a distribution analytics-based scheme, in which the mode switching probability is obtained based on the cumulative distribution function. Our experimental results show that our scheme improves the utilization of state-of-the-art MC systems by up to 72.27%, while maintaining 24.28% mode switching probability in the worst case scenario. Besides, the results of running embedded real-time benchmarks on a real platform show that the distribution-based scheme can improve the utilization by 7.30% while bounding the mode switching probability by 4.85% more, compared to the Chebyshev-based scheme. [ABSTRACT FROM AUTHOR]

We present a surface integral equation (SIE) solution for a special class of anisotropic media, whose permittivity and permeability are both symmetric full tensors with the same or multiple values. This kind of media is generated from the invisible cloaking or absorbing material of a perfectly matched layer (PML) design. A new derivation based on the potential functions is presented to obtain the closed-form Green’s function. Detailed and rigorous proofs of some vector identities are given for the first time. Special treatments are detailed to address the singularity of the anisotropic Green’s function for discretizing the SIE. Numerical experiments validate the accuracy, stability, and high efficiency of the proposed solution compared with the analytical solution or the finite element-boundary integral (FE-BI) method. [ABSTRACT FROM AUTHOR]

This article investigates the longitudinal end effect of the line-start permanent magnet linear synchronous motor (line-start PMLSM), where conductive ladder rungs embedded into the mover enhances line-start capability but induces the longitudinal end effect due to the eddy current. The longitudinal end effect is first analyzed by virtue of analytical solutions of the electromagnetic field. Then, the coefficient of longitudinal end effect is presented in a piecewise format for convenient application. An algorithm is proposed based on the simplified piecewise theory to evaluate transient responses of the line-start PMLSM. To validate the feasibility of the proposed simplified piecewise theory, cases of the line-start PMLSM are investigated, with which a prototype is manufactured and the theoretical method is proven effective and accurate by experiments. Feasible principles involving the transient characteristics are also investigated via the design cases and experiments. The major contribution of this research is a feasible and convenient method to analyze the transient responses during the line-start process. [ABSTRACT FROM AUTHOR]

Relevance vector regression (RVR) is a useful tool for degradation modeling and remaining useful life (RUL) prediction. However, most RVR models are for 1-D degradation processes and can only handle univariate observations. This article proposes a degradation path-based RUL prediction framework using a dynamic multivariate relevance vector regression model. Specifically, a multistep regression model is established for describing the degradation dynamics and extending the classical RVR into a multivariate one with consideration of the multivariate environment. The article introduces a matrix Gaussian distribution-based RVR approach and then estimates the hyperparameters with Nesterov’s accelerated gradient method to avoid the exhausting re-estimation phenomenon in seeking analytical solutions. It further forecasts the degradation path for monitoring the degradation status. Based on the forecasted path, the RUL is predicted by the first hitting time method. Finally, the proposed methods are illustrated by two case studies, one is presented in this article and the other in the supplement, which investigate the capacitors’ and bearings’ performance degradations. [ABSTRACT FROM AUTHOR]

Harmonic injection is commonly used in permanent magnet synchronous motor torque ripple minimization (TRM) of electric vehicle. Traditional inverter switching frequency limits TRM application at high speed due to harmonic modulation accuracy and inverter loss. To achieve TRM in the whole speed range and reduce inverter loss, a novel online calculated low carrier ratio pulsewidth modulation (LCRPWM) is proposed in this article. The carrier ratio determining regular according to the injected harmonics is established first. The relationship between injected harmonics and LCRPWM switching angle is revealed and a set of nonlinear equations is established. Thus, the problem is transformed from solving nonlinear equations into optimization by establishing a cost function. The analytical solutions of nonlinear equations are obtained, which avoids iterative operation and plunging into local minimum. Therefore, the switch angle solution method is suitable for online calculation. The LCRPWM is verified in simulation compared with the traditional regularly sampled space vector PWM, which achieves better results in voltage harmonic injection and flux tracking at a much lower switching frequency. At last, the LCRPWM is used in a test bench experiment that shows good TRM effects. The influence of sideband harmonics on torque ripple is analyzed. [ABSTRACT FROM AUTHOR]

The traditional system frequency response (SFR) model is not applicable to the study of the frequency response of contemporary power grid due to the response of the large capacity (single unit up to 500 MW) type-II doubly-fed variable speed pumped storage (VSPS) unit is not considered. This article proposes an improved reduced-order SFR model for the power grid integrated with the large-scale type-II VSPS. proposed models Compared with the traditional SFR model, this model takes into account the active power coupling effect of this type of VSPS, and the computational burden increase of the model is small due to the model of VSPS has been reduced to the greatest extent. Therefore, the SFR model can be used by the system operators to rapidly calculate and evaluate the frequency response of contemporary power grid. Firstly, a reduced-order frequency response transfer function model of the Type-II VSPS is established by using the state-space model and small-signal incremental method. Compared with the higher-order nonlinear model of the Type-II VSPS, the state variables and computation burden of the established model is dramatically decreased. Secondly, an improved SFR model for the power grid integrated with the type-II VSPS is presented, and then the reduced-order analytical solution for the frequency response of the grid is put forward based on the parameter weighted aggregation method. The improved SFR model is more realistic and can better express the frequency response characteristics of the contemporary power grid. The proposed SFR model have demonstrated advantages in solving speed and efficiency when contrast it with the higher-order nonlinear model of the grid. Finally, the simulation and experimental results are respectively compared with the analytical solution of the reduced-order models, and the results have demonstrated the effectiveness of the. [ABSTRACT FROM AUTHOR]

Strongly coupled electromagnetic–mechanical (ME) problems are presently very relevant for academic research and industrial technology and product development. Although the algorithm basis for such coupled simulations is rather extensive and available in numerous publications, verification of the obtained results is very difficult and relies mainly on expensive, tedious, and time-consuming measurements. The main reason for this is an evident deficiency of reference examples with analytical solutions (ASs) in the available literature. To mitigate the problem, this article defines two strongly coupled electromagnetic–ME problems and presents their AS in detail. The obtained ASs were cross-validated by comparing them against an in-house developed multiphysics finite element method (FEM) solver and an excellent agreement between the two was found. [ABSTRACT FROM AUTHOR]

Closed-form formulations are difficult to find when the material behavior law is nonlinear. A linear approximation, on the other hand, has a very narrow range of validity. In this communication, the normal form (NF) method is used to solve a 1-D nonlinear magnetodynamic problem. The discrete model is formulated in a state-space form suitable for NF applications. The resulting system is then expanded on a linear mode basis to cubic order. Analytical solutions are obtained using the NF technique and compared with traditional solutions. The results show that the cubic polynomial adequately approximates the problem, and the NF solution is valid for some range of magnetic field intensity. [ABSTRACT FROM AUTHOR]

Current omnidirectional circularly polarized (CP) antennas meet the difficulty of limited bandwidth and bulky configuration. An exact analytical far-field solution for a conventional tilted dipole array (TDA) has been proposed, where the origin of axial ratio (AR) bandwidth limitation has been investigated. Then, it has been shown that the AR bandwidth can be efficiently improved when a conventional straight dipole is folded into a multi-segment one, where the deviation of two perpendicular far-field components, $E_{\theta }$ and $E_{\phi }$ , can be reduced at both the lower and higher frequencies. The dipole was further modified to be of a parabolic shape, a continuous and optimized variation for the multisegment one, which brings about an even wider AR bandwidth. For a compatible wide impedance bandwidth, several impedance matching techniques like radiator tapering, parasitic loading, and feeding network design have been applied. Measured results show the proposed TDA has a 3 dB AR bandwidth (also the antenna usable bandwidth) of 65%, within which the desired omnidirectional radiation is well maintained. Compared with the performances of some recent omnidirectional CP antennas, our design has a much wider usable bandwidth, and is also superior in the compact size, simple structure, and ease of fabrication. [ABSTRACT FROM AUTHOR]

This article presents a 6-DOF attitude-orbit synchronous control problem for the space circumnavigation (SCN) mission with parameter uncertainties, time-varying uncertainties, and input constraints. In particular, from the perspective of engineering application, time-varying measurement uncertainties are taken into account of the 6-DOF attitude–orbit coupling kinematics and dynamics, and the analytical solution of the desired attitude is derived based on the measured relative orbit information with measurement uncertainties. To drive the active spacecraft approach to the faulty target safely, a time-varying exponential prescribed convergence boundary is introduced into the sliding surface. A finite-time disturbance observer is involved in equivalent tracking errors for compensating the mismatched uncertainties. In addition, an auxiliary system is designed to overcome the instability danger caused by input constraints. The stability of the controlled system is discussed in the nonautonomous finite-time stable framework, which is proved via Lyapunov analysis that the attitude-orbit tracking errors converge to the equilibrium within finite time. The simulation experiment with mismatched uncertainties and prescribed constraints shows the superiority of the designed control scheme. [ABSTRACT FROM AUTHOR]

Prediction of elastic parameters (e.g., P-, S-wave velocity, and density) from observed seismic data is one of the most common means of reservoir characterization. Recently, deep learning (DL), as a data-driven approach, has been attracting increasing interest in seismic inversion. DL is proven to have the potential to learn complex systems and solve inverse problems efficiently. One of the most key components of DL is the training dataset, and an effective training dataset is a prerequisite for the success of DL-based methods. In seismic inversion, the training dataset needs to be artificially expanded due to the limited number of actual training data pairs. Traditional approaches of using the exact Zoeppritz equation (EZE) or its approximations for training dataset construction have limitations, principally, the single interface assumption and the neglect of wave propagation effects. Alternatively, the analytical solution of the 1-D wave equation (i.e., reflectivity method [RM]) can simulate the full wave, including transmission losses and internal multiples, and can be executed in a target-oriented manner. Inspired by this, we develop a data-driven elastic parameter prediction method based on waveform formulation. The method uses RM to construct training dataset, which both compensates for the inadequate training dataset in data-driven seismic inversion and improves the accuracy of the inversion results. We implement the method in a synthetic model as well as field data. The results are compared with model-driven methods (EZE and RM) and data-driven method based on EZE, and it is shown that the proposed method outperforms these three methods. [ABSTRACT FROM AUTHOR]

Electromagnetic nondestructive testing methods to inspect metal rods and pipes are widely used in industrial production. When the scanning speed of the electromagnetic coil is close to the magnitude of eddy current diffusion speed in conductive specimens, the coil motion will significantly affect the distribution of the eddy current field and detection signal. In this article, based on the basic equations and boundary conditions of electromagnetic field problems for moving conductors, the eddy-current analytical model of coaxial relative motion between the coil and the cylindrical conductor rod is solved by using Fourier transform method, and the impedance change expression of the pick-up coil is obtained. The theoretical results are in excellent agreement with the experimental results, which verify the analytical expression of impedance change. Furthermore, the effects of a conductor moving velocity and excitation frequency on impedance-change modulus values for differential and absolute pick-up coils are analyzed, respectively. The theoretical methods proposed in this article quantitatively analyze the velocity effect on the eddy current field, which can be applied to fast real-time eddy current testing for conductive specimens. [ABSTRACT FROM AUTHOR]

In this paper, we investigate non-orthogonal multiple access (NOMA) assisted secure computation offloading under the eavesdropping-attack, in which a malicious node overhears the edge-computing user's (EU’s) offloading transmission to the edge-computing server (ES), and NOMA is used for the EU's offloading and meanwhile for providing artificial jamming to the eavesdropper. Since multi-user simultaneous transmission over a same frequency channel can be enabled by NOMA, a wireless user (WU) can form a NOMA pair with the EU to provide cooperative jamming to the eavesdropper while also gaining an opportunity of sending its data. Focusing on the EU-WU pair with the fixed WU's energy-provisioning, we exploit the physical layer security to quantify the EU's offloading throughput with the help of WU's jamming. We then study the joint optimization of the EU's computation offloading and the EU-WU's NOMA transmission for minimizing the EU's total energy consumption subject to its latency-requirement in completing the computation-task. By utilizing the feature of analytical solution of the WU's transmission, we then investigate the WU's optimal energy-provisioning for the EU-WU pair, such that both the EU and WU can benefit from the cooperative jamming in a fairness manner. Specifically, we formulate the EU-WU's cooperation as a Nash bargaining game. By identifying the monotonic feature of Nash bargaining problem, we propose a polyblock approximation based algorithm for determining the WU's optimal energy-provisioning to achieve the win-win solution for the paired EU and WU. Finally, we investigate the scenario of multiple EUs and WUs, and aim at finding the stable pairing between the EUs and WUs, such that no individual EU (or WU) would like to change its partner. An efficient algorithm, which is based on the Gale-Shapley theory while exploiting the quantitative feature of EUs’ and WUs’ net-rewards, is proposed to achieve the stable EU-WU pairings. Numerical results are provided to validate our proposed algorithms and demonstrate the advantage of our proposed NOMA assisted computation offloading via cooperative jamming. [ABSTRACT FROM AUTHOR]

Analytical entry guidance is designed to control the atmospheric gliding of a hypersonic glider. The guidance uses only approximate analytical solutions for a 3-D hypersonic gliding trajectory to fast plan reference trajectory onboard and thus has an extremely high computational efficiency. To reduce the amount of calculation, the adopted analytical solutions are improved first such that their coefficients depend only on generalized flight states. As the coupling of longitudinal and lateral dynamical equations is fully considered, the analytical solutions are of high accuracy but complicated, which consist of zeroth-and first-order solutions. To resolve the resulting difficulty of trajectory planning, an efficient scheme is proposed. In the first guidance cycle of steady glide, the scheme uses only the zeroth-order solutions to plan a trajectory rapidly. In the subsequent guidance cycles, the scheme first uses some profiles obtained from the previously planned trajectory to specify part of the coefficients of the zeroth-and first-order solutions in order to offset the impact of the equations coupling and then utilizes the complete solutions to update the trajectory by proposing a method based on a virtual endpoint of glide and virtual terminal crossrange, which can achieve a very small terminal heading error. The superiority of the guidance is demonstrated by conducting Monte-Carlo simulations. [ABSTRACT FROM AUTHOR]

This letter proposes an approximate analytical formulation for the shielding problem of a perfectly electric conducting disk against the low-frequency magnetic field produced by a circular current loop placed coaxially with the disk. First, this problem is related to a complementarity problem: The leakage of the magnetic field through a circular hole on a perfectly magnetic conducting plane of infinite extension. Then, for the complementarity problem, we develop the accurate analytical solution if only the distribution of the normal component of the unshielded magnetic field along the surface of the hole can be expressed as a polynomial function of radial distance. The analytical formulation is verified with finite element simulations and measured results. [ABSTRACT FROM AUTHOR]

Railway power conditioner (RPC) can provide comprehensive reactive power, unbalanced current, and harmonics compensation in the traction power supply system. Under full compensation (FC), RPC can increase the three-phase power factor (PF) to unity but leads to high current rating and operation loss. In previous studies, partial compensation (PC) for the reduction of RPC current rating was proposed. An analytical solution of PC coefficients was used, which limits design freedom since identical PF is required at three-phase. This uniform power factor partial compensation (UPFPC) limits RPC in achieving a further reduction in its current rating. This article proposes a nonuniform power factor partial compensation (NPFPC), which can further reduce RPC current rating within the acceptable PF region and under the voltage unbalance threshold. However, determining an analytical solution under NPFPC is complicated, considering three degrees of freedom. This is achieved in this article by defining the lower boundary of grid side PFs and optimizing by particle swarm optimization. It is found through investigations that NPFPC can effectively reduce the compensating current rating by 56% compared to FC mode and 53% compared to UPFPC. Simulation and experimental results verify the validity of the proposed NPFPC. [ABSTRACT FROM AUTHOR]

This article introduces a semi-analytical method of predicting ac loss in commercial Litz wires. Simple finite-element simulations are used to compute the resultant proximity fields in a coil system of arbitrary geometry. The approach addresses non-ideal Litz wire construction by applying a surrogate skin effect model to inform and distribute the current over the cross Section into segmented layers. This simplifies the finite-element problem into a 2-D, dc simulation with a low number of mesh elements. Analytical solutions are then used to compute frequency-dependent loss due to skin and proximity effect. The method is demonstrated using two 14 American Wire Gauge (AWG) equivalent Litz wires with very different constructions and is validated with experimental results from several coil configurations. Finally, an appeal is made to commercial Litz wire manufacturers to provide an empirical “fabrication factor” specification that would allow consumers to predict the performance of a conductor in their application. [ABSTRACT FROM AUTHOR]

Community detection is a key data analysis problem across different fields. During the past decades, numerous algorithms have been proposed to address this issue. However, most work on community detection does not address the issue of statistical significance. Although some research efforts have been made towards mining statistically significant communities, deriving an analytical solution of $p$ p -value for one community under the configuration model is still a challenging mission that remains unsolved. The configuration model is a widely used random graph model in community detection, in which the degree of each node is preserved in the generated random networks. To partially fulfill this void, we present a tight upper bound on the $p$ p -value of a single community under the configuration model, which can be used for quantifying the statistical significance of each community analytically. Meanwhile, we present a local search method to detect statistically significant communities in an iterative manner. Experimental results demonstrate that our method is comparable with the competing methods on detecting statistically significant communities. [ABSTRACT FROM AUTHOR]

An efficient method is proposed to predict eddy current loss of Litz wire coils, or completely transposed multi-strand coils, in transient finite element analysis (FEA). The method is based on analytical solutions of eddy current loss in a solid wire due to skin effects and proximity effects. The bundle of Litz or solid wires is homogenized by introducing a fill factor to describe the conducting area ratio. The analytical solutions in the frequency domain for round, square, and rectangular wires are further expanded to those in the time domain. The wire length direction in each 3-D mesh is automatically detected so that the flux density vector in each mesh can be correctly decomposed to the orthogonal and tangential components for anisotropic proximity effect loss computation. The method is applied to calculating eddy current loss of a gapped inductor in both 2-D and 3-D, and the results are compared with that using real solid wires. [ABSTRACT FROM AUTHOR]

The problem of vehicle-target assignment (VTA) to capture a team of evading targets using a swarm of pursuing vehicles is investigated in this article. The VTA problem is formulated as an integer linear programming (ILP), such that the time to intercept all the targets is minimized subject to a number of constraints. To obtain closed-form formulas for the time-to-go matrix in the framework of ILP optimization, a one-on-one pursuit-evasion problem based on the ideal proportional navigation (IPN) guidance law is investigated. By considering two different scenarios of non-maneuvering and maneuvering evaders, analytical closed-form solutions for the pursuit-evasion time-to-go as explicit functions of the position and velocity vectors of the pursuers and evaders are developed, and efficient evasion strategies based on IPN guidance scheme are presented. The efficacy of the theoretical results in estimating the elements of time-to-go matrix is demonstrated by solving the VTA problem in simulations. [ABSTRACT FROM AUTHOR]

This paper focuses on optimal time-of-arrival (TOA) sensor placement for multiple target localization simultaneously. In previous work, different solutions only using non-shared sensors to localize multiple targets have been developed. Those methods localize different targets one-by-one or use a large number of mobile sensors with many limitations, such as low effectiveness and high network complexity. In this paper, firstly, a novel optimization model for multi-target localization incorporating shared sensors is formulated. Secondly, the systematic theoretical results of the optimal sensor placement are derived and concluded using the A-optimality criterion, i.e., minimizing the trace of the inverse Fisher information matrix (FIM), based on rigorous geometrical derivations. The reachable optimal trace of Cramér-Rao lower bound (CRLB) is also derived. It can provide optimal conditions for many cases and even closed form solutions for some special cases. Thirdly, a novel numerical optimization algorithm to quickly find and calculate the (sub-)optimal placement and achievable lower bound is explored, when the model becomes complicated with more practical constraints. Then, a hybrid method for solving the most general situation, integrating both the analytical and numerical solutions, is proposed. Finally, the correctness and effectiveness of the proposed theoretical and mathematical methods are demonstrated by several simulation examples. [ABSTRACT FROM AUTHOR]

This article develops a new closed-form analytical solution to the harmonic spectrum of the full-bridge (FB) modular multilevel converter (MMC) with phase shifted carrier pulse width modulation. It considers FB-MMC operation in boost mode where the negative-voltage states of the FB submodules (SMs) are utilized to extend the ac operating voltage range and/or reduce the dc link voltage which is known to reduce the energy storage requirement. The solution is based on double Fourier series expansion in two variables. The harmonic distribution of the output voltage is analyzed and the effects of the modulation index and the number of SMs on the output voltage harmonics are revealed. The influence of the upper/lower arm carrier phase shift angle is also investigated. Using the analysis, selection of the number of SMs, the modulation index and the upper/lower arm carrier phase shift angle are specified for output voltage harmonic minimization. The findings are verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

A process-oriented wafer-scale finite element model is developed and validated. The model is used to study the relationship between the in-plane residual stress and the deformation of state-of-the-art 0.13- $\mu \text{m}$ SiGe BiCMOS fully processed 8-inch wafers. Based on the in-situ wafer bow measurement results, the residual stress values are extracted regarding each deposited material per process step. The extracted material residual stress values are integrated into the in-plane stresses of each back-end redistribution layer by knowing the material densities, greatly reducing the computational effort. An advanced finite element model composed of these integrated redistribution layers is therefore developed by exploiting the first order shear deformation theory. The model is validated using analytical solutions and is used to characterize the wafer thickness-deflection non-linear relationship. As a comparison, 8 fully processed BiCMOS wafers from the same lot are thinned to different thicknesses ranging from 50 $\mu \text{m}$ to 600 $\mu \text{m}$ for bow measurement. After taking the gravity-induced deflection and grinding effect into consideration, the wafer bow predicted by the finite element model deviates less than 20% from the measurement results for all the thickness values. [ABSTRACT FROM AUTHOR]

This paper presents a dual active bridge (DAB) converter with reactive power control capability (Q-capability) for a battery energy storage system (BESS) or an electric vehicle (EV) to deliver vehicle-to-home (V2H) and vehicle-to-grid (V2G) services. The DAB topology is preferable for EV charging systems due to its galvanic isolation and bidirectional power flow capabilities. However, this topology increases reactive current peak and loses zero voltage switching (ZVS) operation at light loads if it is not controlled with improved modulation strategies and proper Q control. This paper proposes a mixed modulation method and a reactive power optimization (RPO) algorithm based on power system load flow concepts. Due to the complexities associated with the analytical solution using time domain analysis, this paper develops detailed universal expressions of a DAB converter using the harmonic analysis method. Analytical identification of ZVS boundaries and DSP implementation of the RPO algorithm become easier with these universal expressions. Multiple modes analysis for different operational states is no longer required. Simulation results have been shown for different modulation strategies of the DAB converters. The theoretical analysis of modulation strategies, RPO algorithm and ZVS operation are validated by experimental results on a DAB prototype. Results show that the proposed control strategy reduces the reactive power and provide ZVS operation over a wide ranges of voltages. [ABSTRACT FROM AUTHOR]

Resonant converter is a good solution as the isolated high step-up converter due to its soft-switching features and less component count. However, since the resonant tank is placed on the primary side (low-voltage side) in most traditional resonant converters, large input current still leads to a big proportion of power loss. Besides, synchronous rectification (SR) is also a big issue. The diode conducting time in a resonant converter is hard to be predicted so a current transformer or an analog SR chip is usually employed to detect the current zero-crossing point when the higher efficiency is required. In this article, an isolated high step-up converter with active secondary-side quasi-resonant tank is proposed. Since the whole resonant tank is placed on the high-voltage side, the current stress of the resonant capacitors and their power loss can be greatly alleviated. Besides, the analytical solution of the diode conducting time is derived and two SR control schemes are proposed, without the need to detect the current zero-crossing point. All the switches and diodes achieve the soft-switching so this leads to a good efficiency performance. The validity is confirmed by the experimental results of a 500 W prototype with 36–48 V input and 380 V output. [ABSTRACT FROM AUTHOR]

A two-way time-of-arrival (TOA) system is composed of anchor nodes (ANs) and user devices (UDs). Two-way TOA measurements between AN-UD pairs are obtained via round-trip communications to achieve localization and synchronization (LAS) for a UD. Existing LAS method for a moving UD with clock drift adopts an iterative algorithm, which requires accurate initialization and has high computational complexity. In this letter, we propose a new closed-form two-way TOA LAS approach, namely CFTWLAS, which does not require initialization, has low complexity and empirically achieves optimal LAS accuracy. We first linearize the LAS problem by squaring and differencing the two-way TOA equations. We employ two auxiliary variables to simplify the problem to finding the analytical solution of quadratic equations. Due to the measurement noise, we can only obtain a raw LAS estimation from the solution of the auxiliary variables. Then, a weighted least squares step is applied to further refine the raw estimation. We analyze the theoretical error of the new CFTWLAS and show that it empirically reaches the Cramér-Rao lower bound (CRLB) with sufficient ANs under the condition of proper geometry and small noise. Numerical results in a 3D scenario verify the theoretical analysis that the estimation accuracy of the new CFTWLAS method reaches CRLB in the presented experiments when the number of ANs is large, the geometry is appropriate, and the noise is small. Unlike the iterative method whose complexity increases with the iteration count, the new CFTWLAS has constant low complexity. [ABSTRACT FROM AUTHOR]

The conversion efficiency of annular thermoelectric generator (ATEG) is studied in consideration of temperature-dependent material parameters based on a 1-D steady model. A power series iteration approximation (PSIA) method is proposed for solving the weak nonlinear thermoelectric coupling equation in the cylindrical coordinate system. The convergence of the solution obtained by PSIA is discussed, and the numerical simulation for the 2-D finite-element model is compared with the PSIA solution. Results show that the obtained approximate solution using the PSIA method in the cylindrical coordinate system has high precision and converges rapidly, and the analytical solution and the numerical solution are in good agreement. For regular Bi2Te3 material, when the material is independent of temperature and is homogeneous, the location of the heat source of the thermoelectric device has no effect on efficiency; when the material is dependent on temperature, the inner cooling and outer heating thermoelectric configuration has a good thermoelectric performance. The energy conversion efficiency of the temperature-dependent TEG is lower than that of the temperature-independent device at an average temperature. [ABSTRACT FROM AUTHOR]

This article presents a systematic design procedure for a dual-active-bridge (DAB) dc–dc converter. Design of a DAB converter involves determination of two key parameters, i.e., transformer turns ratio and the series inductance value. Existing literature addresses this problem through numerical optimization, which is computation intensive and does not provide much insight. In general, loss is minimized by applying equal weightage to all operating conditions, which may not be practical. Given an operating power range, terminal voltage range, and switching frequency, this article presents a way to optimally select the design variables through analytical solution of a constrained optimization problem. Analysis is carried out in the time domain, and an optimal triple-phase-shift modulation strategy is considered that ensures minimum inductor rms current and soft switching. The choice of the design parameters results in minimization of the worst-case inductor rms current over the entire operating range of the converter, which leads to both efficiency and size optimization. A procedure for selection of devices and filter capacitors and design of magnetics is given. A 2.6-kW experimental prototype is designed to validate the theoretical analysis. [ABSTRACT FROM AUTHOR]

This article presents a high-fidelity analytical solution and a fast integrated optimization method for vernier machines. First, a harmonic modeling method (HMM) is adopted to obtain the magnetic field distribution of vernier machines. Particularly, the stator teeth of vernier machines are divided into several blocks to take account of the local magnetic saturation of soft-magnetic material. Then, the electromagnetic parameters, such as the average torque, torque ripple, and efficiency, can be calculated via the analytical model. Next, the proposed harmonic model is combined with the nondominated sorting genetic algorithm II (NSGA-II) to determine a multiobjective optimal design for the studied vernier machine. This integrated optimization method can save computation time, because the data interaction process between the finite-element analysis (FEA) software and the optimization software is eliminated. Finally, the performances of the optimal case are verified by both FEA and experiments with the prototype. [ABSTRACT FROM AUTHOR]

This paper addresses time-dependent rating calculations for groups of power cables with temperature-dependent losses. It is a continuation of a recent publication [1] – the presentation of a new transient calculation method for one cable – and offers an extension of the algorithm presented there to the problem of multiple cables subjected to variable loading. Whereas the standards offer simplified solutions for one load step and for equally loaded cables only, the new approximate algorithm is providing a complete analytical solution to this problem. In the following, this will be explained in detail and demonstrated by practical numerical examples. [ABSTRACT FROM AUTHOR]

This article presents an explainable fuzzy theoretic nonparametric deep model for an analysis of heart rate variability in application to stress assessment. We are concerned with the development of a model that evaluates and explains a short-time (3–5 min long) heartbeat interval sequence of an individual to estimate the level of acute perceived stress on a numerical scale from 0 to 100 via monitoring the functioning of the autonomic nervous system. The salient features of the approach are the following. 1) A deep model, consisting of a nested composition of mappings, discovers layers of increasingly abstract heartbeat interval data representation. 2) An analytical solution of the deep model's learning problem facilitates inducing a mapping from the noninterpretable heartbeat-interval-data-space onto another interpretable domain spanned by a stress index. A given noninterpretable R– R interval feature vector is explained by: 1) estimating the corresponding stress value; 2) providing the weights which must be assigned to the subjective ratings of stress; and 3) providing various information about the sympathetic and parasympathetic activities of autonomic nervous system by analyzing R-R interval sequence in frequency domain at different abstraction levels. The proof-of-concept is provided by experimentation on a previously studied dataset of 50 subjects and a new dataset of 100 subjects. [ABSTRACT FROM AUTHOR]

An accurate and efficient method is proposed to characterize waveguides with arbitrary cross sections exhibiting discrete rotational symmetries, known in the literature as $C_{N}$ symmetries. This new method is based on a novel tailored 2-D finite element method (FEM) formulation exploiting rotationally periodic boundary conditions involved in the minimum sector that defines the waveguide cross section. While retaining the proven accuracy and convergence rate of FEM, it allows for a reduction in dimensionality of the problem and classifies the modes with respect to their rotational symmetry. Most importantly, it discriminates reliably and unambiguously degenerate modes (no matter how high their order is) with the exact same computed cutoff frequency value. This is especially interesting in modal analysis of devices involving circular polarization, since the formulation inherently provides different mode sets for clockwise and counterclockwise circularly polarized modes. The method has been tested on a wide variety of waveguides and computed higher order modes have been compared against analytical solutions and general-purpose FEM. [ABSTRACT FROM AUTHOR]

Phase-only nulling with low sidelobe level is a problem of interest in array synthesis which is a tedious problem without an analytical solution. In this communication, a novel framework for the phase-only nulling based on radial basis function neural network (RBFNN) is proposed to predict the phase adjustment for the array pattern nulling with sidelobe control. In the process of network training, the parameters of the RBFNN are optimized simultaneously based on the self-adaptive differential evolution (SADE) algorithm, which aims to improve the approximation ability and reduce the complexity of the network. Simulation results of the optimized RBFNN models show compact network structure and form the array pattern under desired performance with good generalization capability. [ABSTRACT FROM AUTHOR]

Pulsed power has been generated by using either capacitive energy storage (CES) or inductive energy storage (IES). In this article, the combination of CES and IES, which is called hybrid energy storage (HES), is studied. Both the capacitor and the inductor can be charged with initial energy and they can release their stored energy together either in series or in parallel with each other. Circuit equations have been solved and, based on the analytical solutions, the circuit behavior has been investigated. It is found that, compared with CES or IES, HES can largely improve the circuit operation flexibility and the output waveform variation. This conclusion has been confirmed by circuit simulation and experiment. [ABSTRACT FROM AUTHOR]

This article introduces a general technique for intermapping the complex spatial frequency (or propagation constant) $\gamma =\alpha +j\beta $ and the temporal frequency $\omega = \omega _{\text {r}}+j\omega _{\text {i}}$ of arbitrary electromagnetic media and structures. This technique is based on the analytic property of complex functions that describe physical phenomena; it invokes the analytic continuity theorem to assert the unicity of the mapping function and builds this function from known data within a restricted domain of its analyticity by curve fitting to a generic polynomial expansion. It is not only applicable to canonical problems admitting an analytical solution but also to general medium or structure problems, from eigen- or driven-mode full-wave simulation results. The proposed technique is demonstrated for several systems, namely, an unbounded lossy medium, a dielectric-filled rectangular waveguide, a periodically loaded transmission line, a 1-D photonic crystal, and a series-fed patch (SFP) leaky-wave antenna (LWA), and it is validated either by analytical results or by full-wave simulated results. [ABSTRACT FROM AUTHOR]

This paper addresses procedures for power cable time-dependent rating calculations. Such calculations are required to obtain cable emergency ratings and also to observe the conductor temperature variations with time when subjected to variable loading. The calculation procedure is described in the IEC Standards 60853-1 and 2. A real difficulty in applying those procedures lies in an ability to take into account variation of the electrical resistances of the cable metallic components with temperature. The standard gives an approximate equation, developed by Goldenberg. However, this equation is applicable to a single current step applied to the cable. The paper shows that it cannot be easily applied to multiple current steps and proposes a new approximate algorithm providing an analytical solution to this problem. A comparison with a complex iterative procedure is also offered. [ABSTRACT FROM AUTHOR]

The current a conductor can carry for short durations can be significantly greater than under steady state conditions. In power system applications short duration events are usually associated with faults, typically lasting for 100 ms up to a few seconds. Power systems use these differences in current levels to discriminate between normal and abnormal operational conditions. High magnitude short duration currents, such as those which occur during power system faults, can significantly heat conductors, potentially resulting in damage or destruction. Specifying minimum conductor sizes potentially subject to these conditions requires an understanding of the physical effects resulting from the consequential stresses, particularly the heating. This paper investigates the established approach to rating these conductors, which uses an equation based on an adiabatic system. This equation, Onderdonk's equation, is demonstrated to have four identifiable limitations. Novel analytical solutions are proposed for two of the four limitations, being skin effect and cooling resulting in an improved equation for rating conductors for high magnitude short duration currents. [ABSTRACT FROM AUTHOR]

This paper presents novel numerical approaches to finding the secrecy capacity of the multiple-input multiple-output (MIMO) wiretap channel subject to multiple linear transmit covariance constraints, including sum power constraint, per antenna power constraints and interference power constraint. An analytical solution to this problem is not known and existing numerical solutions suffer from slow convergence rate and/or high per-iteration complexity. Deriving computationally efficient solutions to the secrecy capacity problem is challenging since the secrecy rate is expressed as a difference of convex functions (DC) of the transmit covariance matrix, for which its convexity is only known for some special cases. In this paper we propose two low-complexity methods to compute the secrecy capacity along with a convex reformulation for degraded channels. In the first method we capitalize on the accelerated DC algorithm which requires solving a sequence of convex subproblems, for which we propose an efficient iterative algorithm where each iteration admits a closed-form solution. In the second method, we rely on the concave-convex equivalent reformulation of the secrecy capacity problem which allows us to derive the so-called partial best response algorithm to obtain an optimal solution. Notably, each iteration of the second method can also be done in closed form. The simulation results demonstrate a faster convergence rate of our methods compared to other known solutions. We carry out extensive numerical experiments to evaluate the impact of various parameters on the achieved secrecy capacity. [ABSTRACT FROM AUTHOR]

The first comprehensive three-phase state-space dynamic phasor model (DPM) for the emerging class of dc/dc/ac modular multilevel converters (MMCs) is presented that accounts for both dc/dc and dc/ac power transfer mechanisms. The phasor model is derived in the $\alpha \beta ~0$ -frame and includes frequency components from dc to third harmonic, which is shown to yield a high degree of matching for both steady-state and transients when compared against switched and time-averaged models, the latter of which is also derived in this work. An analytical solution procedure is then proposed that takes advantage of the phasor model time-invariance to find the full state solution at any operating point including the requisite open-loop modulating signals. Several analyses are carried out for two different dc/dc/ac MMC case study designs to explore the utility and versatility of the proposed DPM and solution procedure. Results show the patterns of internal current stresses and capacitor voltage ripples for the arms can vary significantly and in a nonsymmetrical manner, which is in stark contrast to the traditional dc/ac MMC. [ABSTRACT FROM AUTHOR]

In this paper, the bifurcation trees of analytical solutions of a 3-D brushless DC motor with the voltage disturbance are obtained through the generalized harmonic balance method. The electrical and mechanical model of the 3-D brushless motor is transformed to the dynamic system of coefficients of finite Fourier series. Stable and unstable analytical solutions of the 3-D brushless motor are solved based on such a Fourier series coefficient system. Bifurcation trees of analytical solutions of period-1 to period-2 and period-1 to period-4 motions are achieved. Stability and bifurcations of the analytical solutions of the 3-D brushless motor are determined by the eigenvalues of Jacobian matrix of the coefficient dynamic system. Frequency-amplitude characteristics of periodic motions are presented for a better understanding of the motion complexity in frequency domain. Numerical illustrations are completed for comparison of the analytical solutions with numerical results. The complex dynamics of the 3-D brushless motor are exhibited through the bifurcation trees of analytical solutions.

The adaptive array theory has been successfully employed to the weighted least-squares (WLS)-based beampattern synthesis of arbitrary arrays for adjusting the weighting coefficients of WLS cost function, which enables flexible control of both mainlobe and sidelobe responses. However, the problem with the existing WLS beampattern synthesis approach is that the weighting coefficients, interpreted as “artificial interferers,” are adjusted in an ad hoc way since some key user parameters used therein need to be chosen via a tedious trial-and-error process. Moreover, it may not guarantee that the desired beampattern control objective can be met. To deal with the problem, this communication establishes theoretically the relationship between the weighting coefficients of WLS cost function and the desired array response and proposes an analytical solution for the WLS beampattern synthesis, which can guarantee the objective of desired beampattern control without fine-tuning of any user parameters. The effectiveness of the proposed solution is further verified by several numerical examples of beampattern synthesis for linear and planar arrays. [ABSTRACT FROM AUTHOR]