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An advanced eddy current (EC) sensor incorporating with direct current (dc) magnetizing unit is presented, and its sensor signals are evaluated numerically considering hysteresis behavior. In this article, we propose an efficient method to calculate sensor signals while considering both a moving magnetizer and a high-frequency alternating current (ac) excitation. The calculation process is divided into two sequential analyses. The first step is a time-domain simulation to calculate a gradual change of dc magnetic field from the moving magnetizer. Then, its solution of the magnetic flux density is stored and used to make a subsequent magnetization curve based on the fitting equation-based hysteresis model. The obtained sub-magnetization curve is used for a time-harmonic simulation, and the sensor signal can be finally obtained. We applied the calculation method to a prototype sensor, and it enables to evaluate sensor signals quantitatively at the different magnetizing field and defect size. [ABSTRACT FROM AUTHOR]

The present work addresses the ongoing development of a mesh-based magnetic equivalent circuit (MEC) to estimate the magnetic flux distribution in a superconducting hybrid rotating synchronous machine, superconducting (SC) rotor, and conventional stator. The MEC is to be integrated in an existing thermoelectric lumped-parameter machine model for the transient simulation of High Temperature Superconductor (HTS) field coil synchronous generator (SG) in the dq0 frame of reference. It will allow the inclusion of the magnetic flux density inside the definition of the non-linear resistance of the superconductor in addition to the already-present temperature and current. The objective is to gain further accuracy on the coupled thermal and electromagnetic behavior of superconducting hybrid machines during partial or total loss of the superconducting state. In the present work, the MEC is benchmarked against a Finite Element Model (FEM). It is shown that the MEC can provide proper magnitude of the magnetic flux density over the HTS winding achieving a good estimation of the magnetic response of the field winding by taking into account the penetration of current within the superconductor. The case study is a 100-MVA hydroelectric HTS field coil SG considering a field current ramp. [ABSTRACT FROM AUTHOR]

A method for estimating the stability criterion in the space-time finite integration (FI) method using the subgrid technique was developed. Numerical- and analytical-dependent domains were compared to estimate the stability limit. Space-time subgrids locally refined with two, three, and four divisions were examined. The stability limit based on the proposed method almost agrees with that of the numerical experiment. [ABSTRACT FROM AUTHOR]

The quasi-static approximation that considers inductive–capacitive–resistive effects is referred to as the Darwin model of Maxwell’s equation. However, numerical analysis of the Darwin model is computationally expensive on account of large ill-conditioned equations. In this article, we proposed a new model order reduction technique for the Darwin model of Maxwell’s equations to drastically reduce the computational cost. In this method, four symmetric non-gauged equations were solved to obtain the basis vectors and avoid solving the non-symmetric equations. The reduced-order model (ROM) was obtained through congruent transformation, and time-domain analysis was performed using the time-difference method. We observed that the symmetric ROM was superior to the asymmetric ROM, in terms of accuracy and stability of the time-domain analysis. [ABSTRACT FROM AUTHOR]

Deep learning has achieved remarkable success in diverse applications; however, its use in solving partial differential equations (PDEs) has emerged only recently. Here, we present a feasibility study of applying physics-informed deep learning methods for solving PDEs related to the physical laws of electromagnetics. The methodology uses automatic differentiation, and the loss function is formulated based on the underlying PDE and boundary conditions. The feasibility of the method is shown using three electromagnetic problems of varying complexity and the results show close agreement with the ground truth from a finite-element analysis solver. The application of transfer learning is also explored and results in faster training. Furthermore, a hybrid approach involving physics-based governing equations and labeled data is also introduced to improve the accuracy of the results. [ABSTRACT FROM AUTHOR]

Magnetic fluid seals are widely used. However, during the filling process of the magnetic fluid, a large part of the magnetic fluid is attracted to the magnet, causing the loss of the magnetic fluid, and the magnetic fluid sealing device can easily cause damage to the pole teeth due to the problem of disassembly and installation. To solve the above problems, this article designs a pole piece integrated magnetic-fluid sealing structure and a new type of disassembly and installation method. The finite element method is used to calculate the magnetic field distribution of the pole piece integrated magnetic fluid seal structure, and the theoretical withstand pressure value is obtained according to the withstand pressure calculation formula. Three kinds of magnetic fluids were used to conduct comparative experiments on the magnetic fluid sealing device at different temperatures and different filling amounts. The results showed that the pressure resistance of the magnetic fluid sealing increased with the increase of the filling amount, and the increase of the saturation magnetization, consistent with theory. It is also found that the thickness of the pole piece is very thin. During the processing, Compared with the ordinary pole piece, the integrated pole piece has the advantage of large length, the coaxial is easily ensured, and the processing difficulty is reduced; second, during the filling process, all the magnetic fluid is sucked to the pole teeth, there is no loss of the magnetic fluid, and the pole teeth are intact after more than a hundred times of disassembly and installation, which further improves the life of the magnetic fluid sealing device. [ABSTRACT FROM AUTHOR]

A soliton is a unique wave that maintains its shape and constant velocity. It has been observed widely in natural nonlinear systems. In particular, a magnetic soliton has been observed experimentally on a nonlinear LC ladder circuit array. The aim of this article is to excite a magnetic soliton on the LC ladder circuit array using a permanent-magnet-flux-biased (PMFB) inductor. Electromagnetic analysis reveals that the PMFB inductor has exponential inductance characteristics due to the effective use of magnetic saturation in the stator core. Four PMFB inductors with different magnetic circuit topologies are analyzed and compared, to decrease the inductor current. Finally, this article numerically solves the loop equation for the LC ladder circuit array and shows that the magnetic soliton is successfully excited and propagates without changing its shape and velocity. This technique is equivalent to a rotating magnetic field and has a great potential in developing new ac motors or actuators. [ABSTRACT FROM AUTHOR]

To reduce the serious accident caused by coiled tubing (CT) defects, the full axial defect detection of CT outer surface based on alternating current field measurement (ACFM) was studied. Combined with the advantages of traditional magnetic flux leakage (MFL) circumferential detection, the arbitrary direction defects detection problem of CT was realized. Currently, the study of the ACFM theoretical model only involves excitation in a single direction, and it is difficult for the probe to provide sufficient magnetic field information in an arbitrary direction for visual inversion of defects. In this work, the magnetic disturbance on the axial defects of CT is analyzed. The characteristic signals of defects recognition are extracted, and the excitation frequency, liftoff height, defects shape, defect depth, and defects cluster are analyzed. The optimal parameters of magnetic field characteristic signal distribution and defects detection on the CT surface are obtained. Finally, a new ACFM array probe is designed for CT 360° (full circumferential) axial defect detection. The results show that the method overcomes the limitation of the directional detection of the single detection technique. The designed ACFM probe can completely evaluate the 360° axial defects of CT. [ABSTRACT FROM AUTHOR]

Mutation of the K-Ras gene has been widely found in non-small cell lung cancer. Compared with other mutations of lung cancer, the drugs cannot effectively target mutant K-Ras. However, the mitosis of cancer cells is vulnerable to external interference. Our previous study showed that electromagnetic fields (MFs) could suppress cell proliferation. In this article, a cell proliferation model based on the A549 cell line was established while considering the effects of MFs. In addition, the parameters of the A549 cell proliferation model were regressed by the finite difference method and verified by numerical simulation. Based on the calculations, the density of the A549 cells reflects the trend of measured data from optical microscopy. This approach not only helps reveal the mechanism of MFs on cancer cells but also suggests a new way to predict the effects of magnetic stimulation on cancer inhibition. [ABSTRACT FROM AUTHOR]

This article presents the theoretical analysis and numerical modeling of various cogging torque suppression methods of the slotted limited angle torque motor (LATM). The relationship between the cogging torque, the output characteristics, and the structure parameters of new methods is revealed by derived equations and finite-element analysis (FEA), which provides a theoretical basis for the optimization of the slotted LATM. The effectiveness of the best suppression method is verified by the prototype experiment. In addition, a method to predict torque distortion caused by armature reaction is proposed and it is verified by the finite-element simulation and prototype experiment. [ABSTRACT FROM AUTHOR]

Nutation reducers have recently attracted increasing attention, as they are used in important components of industrial robot joints. A novel disk-type nutation magnetic drive (NMD), based on the nutation gearing principle, is proposed in this article. Subsequently, a 3-D method for analyzing the magnetic field and predicting the torque of the disk-type NMD is presented. The 3-D analytical formula of the disk-type NMD is established on the basis of the equivalent current theory of permanent magnet, which is verified by the finite-element approach. Optimization design of the disk-type NMD is also carried out by applying the genetic algorithm. The results provide a reference for the design and optimization of the magnetic gears. [ABSTRACT FROM AUTHOR]

This article provides both a theoretical analysis and a numerical method for the inverse source problem of locating multiple passive 3-D coils based on measurements of their superposed magnetic fields. In our context, a 3-D coil consists of three concentric circular coils being mutually perpendicular, and the term “passive” means that these coils are not connected to an active power source. Instead, their current is induced externally by a low-frequency alternating magnetic field which is generated by a closed exciter wire. The underlying inductively coupled system is modeled with regard to the 3-D coils as magnetic dipoles and their localization is formulated as an inverse problem. Since its ill posedness mainly arises from strong sensitivity to observational noise, an approximate upper bound for the localization error is derived mathematically by linearization. The Levenberg–Marquardt algorithm is applied as a method for localization and modified for better performance as well as the ability to estimate the number of 3-D coils in the localization area. Our method is tested with simulated and real data in order to confirm its capability of locating up to three passive 3-D coils within the front of a wooden shelf surrounded by the exciter wire and eight rectangular loop antennas. [ABSTRACT FROM AUTHOR]

This article proposes an enhanced dynamic vector magnetic hysteresis model for describing the effect of dc-biased field and eddy current on vector magnetic quantities. A governing equation combining the proposed model is derived for finite-element analysis of magnetic characteristics distribution of transformer core under dc-biased excitation. The numerical results of the transformer core by using the enhanced model with consideration of dc-biased excitation and eddy current are compared with the numerical results obtained by using the magnetizing curve. It proves that the proposed model can consider vector magnetic properties and iron loss of electrical steel sheet under both dc-biased and rotating magnetic fields during numerical analysis. [ABSTRACT FROM AUTHOR]

A novel technique of optimizing selected models of electroheat processes (laser or induction-assisted laser welding, cladding, and so on) is presented, based on the calibration of temperature-dependent material properties. These properties often exhibit uncertainties that negatively influence the quality of the results. Their calibration starts from experimental investigation and evaluation of temperature profiles of welds or tracks, and the goal is to obtain the same profiles by solving the numerical models. The technique is illustrated with an example of induction-assisted laser welding. [ABSTRACT FROM AUTHOR]

In this article, an asynchronous machine with ferrofluid in the gap (AM-WFIG) is analyzed. The principle of this machine was derived theoretically. The magnetic-flux density distribution inside the machine is analyzed and calculated by the numerical finite-element analysis methods. The electromagnetic force performances, loss, power factor, and efficiency are also investigated for the asynchronous machine (AM) by using a 2-D finite-element analysis of Ansoft Maxwell. The computational friction model of the AM-WFIG is built to analyze the influence of the viscosity of the ferrofluid. Finally, a prototype of the AM-WFIG is created and tested, and the performance curve of power factor versus speed is acquired to confirm the proposed design. [ABSTRACT FROM AUTHOR]

The stray loss in a transformer structure is difficult to measure. Thus, it is very important to predict the loss accurately by numerical modeling. This article deals with numerical modeling and experiments for the prediction of the stray loss in power transformer tank. Before numerical analysis, the finite-element model should be verified in advance. In this article, results from finite element analysis (FEA) were compared with those from experiments by using a prototype model. Experiments were carried out by changing the wall shunt thickness by turns. The magnetic flux density obtained from the experiment is compared and agreed well with those predicted by 3-D FEA. After verifying the validity of FEA, the actual transformer was modeled and the wall shunt was applied to the tank to reduce the stray loss. [ABSTRACT FROM AUTHOR]

This paper describes the effectiveness of a geometric multi-grid (GMG) method in current density analysis using numerical human body models. The scalar potential finite difference (SPFD) method is used as a current analysis method inside a human body in the low-frequency domain, and studies have been conducted to solve faster large-scale linear equations made by the SPFD method. In the previous research, the block incomplete Cholesky conjugate gradients (ICCG) method is proposed as an effective method to solve linear equations faster. However, even though the block ICCG method is applied, many iterations are still needed. Therefore, in this research, the GMG method is considered as an effective solver for the problem. GMG method is developed and evaluated performances comparing with the block ICCG method with multi-color (MC) ordering in terms of computation time and the number of iterations. The results show that the number of iterations needed for GMG method is much smaller than that for the block ICCG and the ICCG with MC ordering. In addition, computation times are much shorter, depending on the number of threads and the number of coarse grids. Also, by using MC ordering, the scalability of the GMG method can be greatly improved. [ABSTRACT FROM AUTHOR]

In order to mitigate the numerical dispersion errors of the compact precise integration time-domain (CPITD) algorithm, the fourth-order CPITD [CPITD(4)] method is proposed recently which is based on the fourth-order finite-difference scheme and the precise integration technique. Both the stability condition and the numerical dispersion equation have been obtained. In this paper, the numerical dispersion characteristics of the CPITD(4) method, especially the improvement of the numerical dispersion by using the fourth-order finite-difference scheme are discussed in detail. It is found that the numerical dispersion errors of the CPITD(4) method are much less than those of the CPITD, compact finite-difference time-domain (CFDTD), and CFDTD(2,4) methods and can be made nearly independent of the time-step size. Furthermore, the numerical experiments validate the accuracy and the efficiency of the CPITD(4) method, and also verify our analysis of the numerical dispersion characteristics of the CPITD(4) method. [ABSTRACT FROM AUTHOR]

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

The superconducting magnetically levitated (Maglev) transportation system has been developed in Japan. This system is based on the side wall electrodynamic suspension (EDS). Although the EDS system has the advantage of stable levitation without active control, results of the numerical simulation show that the damping factor of the levitation system is small. Thus additional damper system has been proposed to increase damping of the system against oscillation of the bogie. The specifications of the damper coils are decided by the damping effect against the natural vertical oscillation of the bogie. The weight of the conventional damper coils is heavy. So weight reduction of the damper coils is needed. In this paper reduction of the damper coil weight is considered. Optimization of the damper coil with 50% weight reduction is studied. Running simulations with the weight reduction have been undertaken. The weight of the reduction model becomes half as that of the conventional one. This means size of the damper coils becomes small, and effect of the damper coil should decrease. But in this semi-active damper mode, it’s damping factor increases and oscillation of the bogie converges faster than that by the conventional one. [ABSTRACT FROM AUTHOR]

This paper applied the finite-element method (FEM) with topological data structures to the optimization of electrical devices. A generic modifiable graph data structure is built according to the graph-theoretic foundation for these data structures. The employed topological FEM avoids rebuilding of the mesh in traditional FEM method while geometrical variations happen. It is an effective algorithm which can save computer storage and working time when applied to successive optimization. The effectiveness is verified by numerical example and comparison of the topological FEM with traditional FEM on storage load and working time is shown in this paper. [ABSTRACT FROM AUTHOR]

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

The topology and breakpoints of the grounding grid will directly affect its working performance. This paper proposed a resistivity reconstruction method based on magnetic detection electrical impedance tomography (MDEIT) to measure the topology and breakpoints of the grounding grid. First, this paper describes the forward problem of grounding grid detection in MDEIT, and calculates the magnetic-field distribution above the grounding grid. Then, the resistivity reconstruction method based on the least squares method is proposed. Finally, this paper verifies the feasibility of the proposed method by a numerical example, which shows that the proposed method can be applied to measure the topology and breakpoints of the grounding grid. [ABSTRACT FROM AUTHOR]

This paper presents a systematic analysis of the influence of magnetic measurement modeling on the regularized solution of magnetostatic inverse problems. The focus is on the application of the inverse problem technique to current distribution reconstruction of arc plasmas inside low-voltage switching devices. The inverse problems modeled with both the ideal sensor assumption and non-ideal sensor modeling are studied, considering the geometry and active area of sensors. The Tikhonov regularization is adopted to address the ill posedness of the inverse problem. Sensor arrays with random variations in sensor directions and positions are compared with arrays using perfectly aligned setup. The numerical results reveal that for mono-axial planar sensor arrays the ideal sensor assumption could be used to simplify the modeling process with serious environmental noises. Better reconstruction can be obtained using the non-ideal sensor model when the sensor variations are large. [ABSTRACT FROM AUTHOR]

To consider the nonlinear and 2-D characteristics of the carriers in the draft region of a planar-gate insulated-gate bipolar transistor, which are not properly modeled in the existing physics-based IGBT models, a 2-D ambipolar diffusion equation model is proposed and solved using the finite-element method. Moreover, a numerically iterative procedure is introduced to simply and efficiently solve the 2-D nonlinear finite-element equations. The numerical results of the transient performances obtained using the proposed model and solution methodology show a good agreement with those of the experiment ones, showing the high accuracy and feasibility of the proposed model and method. [ABSTRACT FROM AUTHOR]

To eliminate the checkerboard pattern in topology optimizations (TOs), a new TO methodology based on the constrained maximum-weight connected graph (CMWG) theorem and algorithm is proposed. The underlying principle to extend the CMWG to TO is to convert the topology pattern into a network, and to employ a dynamic programming method to search the optimal solution. Also, a kriging model based on the support vector machine for predicting the sensitivity is introduced to reduce the overwhelmingly heavy computational burden as required in a topology optimizer. According to the numerical results as reported, the proposed methodology is able to avoid the checkerboard pattern, and can improve significantly the final solutions with a significantly reduced computation cost. [ABSTRACT FROM AUTHOR]

This paper examines the applicability of hierarchical-matrices (H-matrices) to a computation of the demagnetizing field, which is the most time-consuming part in the micromagnetic simulation of spin torque oscillators (STO). Given that the kernel function of the convolution integral operator for the demagnetizing field has a second-order singularity, efficient approximation cannot be expected using conventional H-matrices employing adaptive cross approximation as the low-rank approximation. We introduce improved H-matrices to overcome this challenge. Furthermore, matrix sizes appearing in STO simulations are relatively small compared with the usual sizes of H-matrices. Through numerical experiments, we confirm the size conditions for memory usage and the computational time of H-matrix-vector products to demonstrate the advantages of using H-matrices. [ABSTRACT FROM AUTHOR]

Numerical analysis in frequency-domain guarantees convincing accuracy by reflecting non-linearity of material without massive computation time, combining advantages of the equivalent circuit method and numerical analysis method. However, at highly magnetic saturated regions where non-linearity of the material is severe, error in torque calculation is evident, as parameters in frequency domain are presumed to be in a sinusoidal condition. Many researchers have been suggested a compensating method by creating fictious material with logically modified $B$ – $H$ curve. Nevertheless, the error between the results of the numerical analysis in frequency-domain and time-domain analysis is not small enough to estimate motor characteristic. Therefore, the compensation method for improving accuracy on the estimation of induction motor characteristics is proposed in this paper. The numerical analysis based on finite-element method in frequency domain has been conducted using the proposed fictious material and the result is compared to those of the conventional methods and time-domain analysis to validate its improvement on accuracy. [ABSTRACT FROM AUTHOR]

A methodology of optimizing the process of combined laser cladding with induction preheating is proposed and verified. The resultant shape of the deposited layer consisting of a series of parallel tracks should be as uniform as possible and resistant with respect to cracks of any origin. The main aim is to develop a technique (based on a simple experiment) of calibrating geometrically more complex 3-D arrangements. The task consists of a solution of a strongly nonlinear coupled electromagnetic-thermal problem (forward part) and multi-parametric optimization (backward part). The solution of the forward part uses a specific $h$ -adaptive technique developed by authors that allows working with continuously varying geometry of the system due to added powder material. [ABSTRACT FROM AUTHOR]

Accurate and simple magnetic material behavior law is necessary to correctly model complete electromagnetic systems. In this paper, a new formulation based on the scalar quasi-static hysteresis Preisach model extended to dynamic behavior using fractional derivation dynamic contribution is proposed. The fractional contribution is solved using convolution which highly reduces the numerical issues. The order of the fractional derivation provides a new degree of freedom and allows to correctly obtain simulation results on a very large frequency bandwidth. By using such formulation, space discretization techniques (finite differences, finite elements) are avoided which are highly space and time consuming while keeping the global simulation results precise. The numerical implementation of the problem and some experimental validations are shown in this paper. [ABSTRACT FROM AUTHOR]

The problem of the computationally efficient analysis of the electromagnetic system with nonlinearity is considered in the proposed work. Unlike the previously proposed proper orthogonal decomposition (POD)-based model order reduction (MOR), the proposed method based on the dynamic mode decomposition works well even under the highly nonlinear system. Using the proposed method, a highly saturated interior permanent-magnet (IPM) motor model is analyzed. Comparisons in terms of the radial air-gap flux density and torque are made with that of the full and POD-based models. The results show that the proposed method is capable of giving a good approximation of the full model of the IPM motor. Also, a reduction in the computational time can be achieved compared with that of the traditional POD-based MOR. [ABSTRACT FROM AUTHOR]

Electromagnetic (EM) field simulation plays a key role in the design of magnetic resonance imaging radio frequency (RF) coils. However, the values of the components in tuning and matching circuits often need to be iterated repeatedly in the conventional simulation method in order to achieve optimal scattering parameters. This leads to a time-consuming optimization to tune and match RF coils, particularly dual-tuned coils that are comprised of multiple lumped elements. A method combining EM field simulation and circuit simulation was employed in this paper, which can dramatically improve simulation efficiency for the optimization of the values of the lumped elements and corresponding EM field distribution. A systematical theoretical analysis of the co-simulation method was presented. To validate the accuracy and efficiency of the co-simulation method, a comparison study was conducted between the conventional simulation and the proposed co-simulation approaches. [ABSTRACT FROM AUTHOR]

A multi-element arbitrary polynomial chaos (ME-aPC) scheme is introduced for uncertainty quantification in sensors. Similar to the classical aPC, the ME-aPC scheme is most usable in data-driven applications, in which the input uncertainty is represented numerically by raw data samples. In sensors, the input samples are usually obtained by real-time measurements. With the two examples considered in this paper, the proposed scheme is shown to have better numerical stability than the classical aPC, without compromising the accuracy of the solutions. [ABSTRACT FROM AUTHOR]

This paper presents the numerical analysis and experiments on the electromechanical behavior of conducting wired-shape particles. We investigate the effects of particle ending profiles and orientation on the initial motion. The boundary element method is used to analyze the electric field, forces, and torques on the particles. The calculated liftoff electric field is smaller than the estimated value based on a model of infinitely long cylinder, and slightly decreases for a particle with a sharp end when the sharp tip is separated from the electrode. The measured liftoff electric field agrees with the tendency obtained from the numerical analysis. Particles mostly began the motion at either end. When the sharp tip was separated from the electrode, the initial motion almost exclusively took place at the sharp end. On the other hand, the probability was slightly higher for the motion at the rounded end when the sharp tip was close to the electrode. The numerical calculation clarifies that the electrostatic and gravitational torques contribute to such liftoff behavior. [ABSTRACT FROM AUTHOR]

A method has been developed for demonstrating a flow nanogenerator by using a mixture of magnetic nanofluid (MNF) and bubbles in a fluid circulating system, and notable phenomena related to the power generation properties of the nanogenerator have been explored. MNF is widely used in various areas because of its interesting magnetic properties under an external magnetic field. The objective of the proposed technique is to obtain the induced electromotive force (EMF) based on Faraday’s law due to the flow of MNF in a closed-circulating system. To maximize the induced EMF, magnetic nanoparticles (MNPs) should pass through the induction coil with a perpendicular magnetization direction in accordance with Faraday’s law. To control the magnetization direction of the MNPs, a permanent magnet was employed to produce an external magnetic field that considers the Brownian and Néel motions. To obtain a continuously induced voltage, a circulation system was implemented ensuring the flow of the MNF in the closed cycle. Further, power generation properties were investigated considering electric, magnetic, and fluidic effects. To analyze this complicated physics, a multiphysics analysis was used to calculate the flow pattern of the MNF according to its magnetic properties, and the acquired results were compared with those obtained from the experiment. From these experiments, we investigated the generation properties of the nanogenerator considering the flowrate of the MNF as well as the presence or absence of bubbles within the MNF. Our experimental tests demonstrated that the continuous power generation mode was successfully achieved with a mixture of MNF and bubbles. [ABSTRACT FROM AUTHOR]

On the wheel-rail supported hybrid railway system, the linear synchronous motor (LSM) for very high-speed transit must be a system that can maintain a large air gap, and the maximum vertical displacement must be taken into consideration in designing the LSM. As such, this paper designs two small-scale LSM models that produce equal output power—one with the normal-conducting magnet and the other with the superconducting magnet. In addition, this paper conducts a comparative analysis of the various characteristics by applying the electromagnetic numerical analysis method. Furthermore, this paper manufactures two small-scale LSM prototypes which have the normal-conducting magnet and the superconducting magnet, while also conducting a no-load and load test. Through such comparisons, this paper attempts to verify the characteristic values of the two models. [ABSTRACT FROM AUTHOR]

A spin-torque nano-oscillator (STNO) driven by a ramped bias current can perform spectrum analysis quickly over a wide frequency bandwidth. The STNO spectrum analyzer operates by injection locking to external microwave signals and produces an output dc voltage V\mathrm{ dc} that temporally encodes the input spectrum. We found, via numerical analysis with a macrospin approximation, that an STNO is able to scan a 10 GHz bandwidth in less than 100 ns (scanning rate R exceeds 100 MHz/ns). In contrast to conventional quadratic microwave detectors, the output voltage of the STNO analyzer is proportional to the amplitude of the input microwave signal I_{\mathrm{ rf}} with sensitivity S = dV_{\mathrm{ dc}}/dI_{\mathrm{ rf}} \approx 750~\rm mV/mA$ . The minimum detectable signal of the analyzer depends on the scanning rate $R$ and, at low $R \approx 1~\rm MHz/ns$ , is about 1 pW. [ABSTRACT FROM AUTHOR]

This paper presents a new method to model healthy and faulty wound-rotor induction machines (WRIMs) with and without inter-turn short circuit fault by a single set of equations. The model is presented for a machine with arbitrary pole, and rotor and stator slot numbers. A single set of equations, including both electric and magnetic parts, is solved to obtain full dynamic behavior of the machine. Therefore, the modified magnetic equivalent circuit with non-linear elements is used for modeling and a numerical technique is employed to solve the non-linear equations. The proposed modified method has a simple calculation procedure in comparison with the conventional magnetic equivalent circuit method. Solving the electric and magnetic equations by a single set of equations is the main advantage of the presented method, which is proposed for a WRIM machine, for the first time. In addition, to increase the accuracy, the saturation phenomenon is also considered in the model. Due to the saturation effect, there are some non-linear algebraic magnetic equations, which should be simultaneously solved with differential equations. A trapezoidal technique is used to convert differential equations to algebraic ones. To solve the non-linear equations, non-linear equations, Newton Newton–Raphson method is employed. Current signature analysis is used for rotor and stator inter-turn short circuit fault detection. Finally, the finite-element method is used to verify the effectiveness of the proposed modeling method. It is worth noting that the proposed method can model a healthy and faulty machine with different faults by a single model. [ABSTRACT FROM AUTHOR]

Finite element analysis-based optimal design of electric machines takes up a considerable amount of time for characteristic analyses and the analysis region has many local optima. Thus, selecting the appropriate global search optimization algorithm, known as the with fast convergence characteristics is necessary in the optimal design of electric machines. In this paper, a novel global search optimization algorithm known as the global-simplex optimization (GSO) algorithm, is proposed. The GSO is an optimization algorithm that adopts the characteristics of the simplex method for searching the optimum point but utilizes its global searching capability by scattering many initial points at the beginning of the algorithm. The global searching capability and convergence speed of GSO is validated through a comparison with particle swarm optimization, which has already been proven for its global searching capability through its application in the well-known Goldstein–Price benchmark function. In addition, the GSO has been applied to the optimal design of an interior permanent magnet synchronous machine to reduce the torque ripple and total harmonic distortion in its back electromotive force. [ABSTRACT FROM AUTHOR]

The Douglas–Gunn method has been applied to the solution of Pennes’ bioheat equation to estimate the heating of bulk metallic prostheses caused by the energy deposition due to the gradient magnetic field of a magnetic resonance imaging (MRI) scanner. The proposed method has been implemented to work on a graphic processing unit and the accuracy and numerical efficiency has been compared with the explicit Euler scheme. As an example of application, the heating of a realistic hip prosthesis during the execution of a 3-D true fast imaging with steady precession MRI sequence has been finally evaluated. [ABSTRACT FROM AUTHOR]

The Cauer-equivalent circuit of electric apparatus is synthesized by applying the model order reduction to the finite-element equations. In this method, the admittance function of a given electric apparatus is expressed by a rational polynomial from which the Cauer-equivalent circuit is directly synthesized. Magnetic saturation in the magnetic core is considered by introducing nonlinearity in the primal inductance of the circuit. The synthesized circuit is shown to express the input–output properties of inductors and induction heating devices in good accuracy. [ABSTRACT FROM AUTHOR]

A full-wave integral equation scheme for modeling resonant coils applied in wireless power transfer systems is presented. An A-\Phi formulation is applied with current and charge densities on the wire surface as unknowns. The method overcomes the limitation of the “thin-wire approximation” as it enables the unknowns to vary on the wire surface. Thus, proximity effects (that typically emerge when modeling dense windings) are taken into account. The numerical implementation of the formulation has smaller computation cost than, for example, finite element methods. The proposed scheme is tested against closed-form solutions and alternative simulations. [ABSTRACT FROM AUTHOR]

Three-dimensional (3-D) finite element analysis is generally required to analyze the performance of an axial flux permanent magnet (AFPM) motor because it has asymmetrical characteristics along the z-axis. Although the computing performance of CPU is enhanced owing to technological developement, a large amount of analysis time is required for 3-D finite element analysis (FEA). This paper presents a method of AFPM motor to an equivariant linear synchronous permanent magnet (ELSPM) motor, both of which have identical output performance. The output performance of the proposed ELSPM motor becomes identical to that of the AFPM under the mandatory condition that the PM magnetic energy of both the models must be identical. The validity of the proposed ELSPM motor in terms of the accuracy and computation time is verified by comparing its results with the results of the AFPM motor based on the FEA. [ABSTRACT FROM AUTHOR]

Optimization metaheuristics is a powerful way to deal with many electromagnetic optimization problems. Their main advantages are that they don’t require gradient computation, they are more likely to give a global optimum solution and have a higher degree of exploration and exploitation ability. Recently, the symbiotic organisms search (SOS) algorithm was proposed to solve single-objective optimization problems. SOS mimics the symbiotic relationship among the living beings. In order to extend the classical mono-objective SOS algorithm approach, this paper proposes a new multiobjective SOS (MOSOS) based on nondominance and crowding distance criterion. Furthermore, an improved MOSOS (IMOSOS) based on normal (Gaussian) probability distribution function also was proposed and evaluated. Results on a multiobjective constrained brushless direct current (dc) motor design show that the MOSOS and IMOSOS present promising performance. [ABSTRACT FROM AUTHOR]

This paper analyzed transient magnetic fields generated by the lightning current in the presence of 3-D conductive plates. An extended partial element equivalent circuit method was introduced to establish a network with frequency-invariant parameters for time-domain simulation. Three techniques were proposed to reduce the computational complexity in the large-plate simulation, including the analytical function of current density, the non-uniform meshing scheme, and the vector fitting technique. Numerical and experimental results were presented to validate the proposed method. Good agreements were observed. [ABSTRACT FROM AUTHOR]

In order to seek new vibration reduction method for magnetically controlled saturable reactors (MCSRs), this paper studies the stress characteristic which is the inherent reason of vibration and noise. Under the practical working condition, dc and ac excitations make iron cores work in a magnetic saturation state. Meanwhile, the stress in reactor cores always exists and influences on magnetic properties of the core material. Because the core material shows different magnetization and magnetostrictive properties under dc bias and stress, a database of magnetization and magnetostrictive curves of silicon steel under different tensile stresses with different dc bias excitations is tested. Based on the measured constitutive relations, an electromagneto-mechanical two-way coupled numerical model for MCSRs is presented. Vibrations considering magnetostrictive effect, electromagnetic force effect, and the combination of them are calculated to compare the influence of the two forces on MCSR vibration. From the computation results, it can be seen that the total vibration stress is not a simple superposition of electromagnetic stress and magnetostrictive stress. Finally, vibration stress of an MCSR prototype under working conditions is tested to prove the validity of the proposed model. [ABSTRACT FROM AUTHOR]

This paper proposes a coupled analysis method to deal with ion generation and ion drift in the air. Electric discharge is utilized in various products, and it is very important to clarify not only how much ion is generated but also where ion drifts in the air. The proposed method, which modeled interactions between electric field and ion behavior, including ion generation, ion drift, and charging of a dielectric body, has succeeded in calculating charge removal of a metallic target, which was tens of millimeters away from a pin electrode as a source of generated ion. The calculated results show that the amount of generated ion is drastically changed because electric field is affected by electric charge of ion in the air and charging of a dielectric body. This paper also reports a comparison of measured and calculated results of charge removal time of a metallic target, which were found to be in good agreement. [ABSTRACT FROM AUTHOR]