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This paper proposed a simulation method for the charge transport in single-layer oil-paper insulation. The method of transient upstream finite-element method (FEM) is derived in order to calculate the time variation of charge densities in medium. The numerical simulation of charge transport in the single-layer oil-paper insulation is realized by applying the transient upstream FEM to the transport equations of bipolar charges. With reasonable microparameter, the charge transport in an experimental object is simulated. The simulation results are consistent with the experimental data. A bent model of oil-paper insulation is analyzed to study the charge distribution under the actual condition. This paper provides an exploratory research to the simulation of charge phenomenon in oil-paper, and has guiding significance to the design of oil-paper insulation. [ABSTRACT FROM AUTHOR]

In this paper, the usage of the Parareal method is proposed for the time-parallel solution of the eddy current problem. The method is adapted to the particular challenges of the problem that are related to the differential algebraic character due to non-conducting regions. It is shown how the necessary modification can be automatically incorporated by using a suitable time-stepping method. This paper closes with the first demonstration of a simulation of a realistic four-pole induction machine model using Parareal. [ABSTRACT FROM AUTHOR]

Applying the Jiles-Atherton (JA) model to simulate the dynamics of power electronics circuit is a challenge but very attractive since it is possible to carry out continuous simulation with only several input parameters. Although other methods such as the Preisach-model can result in approximate waveforms for such applications, it is still a far distance to reach exact ones to suit chaos and other high accuracy-requiring researches. In this paper, the JA model has been successfully applied to model the dynamics of resonant inverter for driving a nonlinear load: a fluorescent lamp. The circuit is driven by a high frequency square wave voltage source. A semi-theoretical fluorescent lamp model developed from HID lamp model is adopted in the modeling. The simulation waveforms of voltage across the lamp and current through it are close to those measured ones reported in the literature papers. [ABSTRACT FROM AUTHOR]

Some soft magnetic materials are strongly dependent on the temperature, because of their low Curie temperature. In order to predict their behavior in electrical devices, engineers need hysteresis models able to consider the temperature. This paper is an attempt to consider the temperature in an existing model of static hysteresis through its parameters. Variations of some parameters with temperature are issued or build thanks to the literature. At the end, all needed parameters have an analytical law versus temperature. The simulation results are compared with measurements and discussed. [ABSTRACT FROM AUTHOR]

AC losses in superconductors are generated every time a time-varying current/field is present. Engineers must be able to predict these losses as accurately as possible during the design phase of power applications. The electrodynamics of superconductors can be formulated as a nonlinear eddy current problem in which the resistivity of the superconducting region is a highly nonlinear function of the current density. In 3-D finite-element simulations, it leads to time-consuming simulations and convergence issues. In this paper, we compare two different $E$ – $J$ constitutive equations, namely: 1) power law model and 2) the percolation model (PM), programmed within both the $H$ – $\phi $ and $T$ – $\phi $ formulations. Based on the 3-D case of a three-filament twisted superconducting wire, the numerical performance of all these formulations/material models is compared in terms of accuracy, computation times, number of time steps, and number of Newton iterations for different relaxation methods. It is shown that the combination of the $T$ – $\phi $ formulation and the $E$ – $J$ PM works fine and should be further developed, as it seems to constitute the best modeling option from both a numerical and physical point of view. [ABSTRACT FROM AUTHOR]

Giant magnetoimpedance (GMI) thin-film magnetic sensors are modeled and evaluated using 3-D physical simulations. In the presented simulation model, the analytical multi-physics equations of MI phenomena are solved with the help of the advanced finite-element method software. In this paper, Co72Si12B6 is considered as the GMI material, forming a tri-layer of Co72Si12B6/Au/Co72Si12B6. The effects of changes in frequency and external magnetic field are discussed in detail. The geometrical dependence of thin-film GMI sensors is also studied. A batch of thin-film sensors is fabricated and tested. The measured data are in good agreement with the simulation results obtained by the proposed model. [ABSTRACT FROM PUBLISHER]

In spite of the wide improvement in computer simulation packages, analyzing, and optimizing the simulation model, particularly under uncertainty can still be computationally expensive and time-consuming. This paper aims to tackle these features by proposing a comprehensive methodology applied to black-box stochastic simulation models under uncertainty. For this purpose, the common surrogate model as Kriging metamodel is served to fit the simulation input–output data produced by Latin hypercube sampling experimental design. Taguchi terminology of robust design enables the optimization methods to control uncertainty and uncontrollable environmental factors. So as to formulate robust counterpart optimization, three different models in the class of dual-response surface are integrated with metamodel and robust design. Leave-one-out cross-validation is applied to validate the Kriging metamodel. Finally, a numerical case study as a direct speed control of dc motor under uncertainty is served to demonstrate the applicability of the proposed method in real engineering problems. This simplified and practical mechatronics case illustrates how the proposed procedure can be expanded for analyzing and optimizing the real complex systems. [ABSTRACT FROM AUTHOR]

The simulation of electrical discharges has been attracting a great deal of attention. In such simulations, the electric field computation dominates the computational time. In this paper, we propose a fast tree algorithm that helps to reduce the time complexity from O(N^2) (from using direct summation) to $O(N\log N)$ . The implementation details are discussed and the time complexity is analyzed. A rigorous error estimation shows the error of the tree algorithm decays exponentially with the number of truncation terms and can be controlled adaptively. Numerical examples are presented to validate the accuracy and efficiency of the algorithm. [ABSTRACT FROM AUTHOR]

The proper generalized decomposition (PGD) is a model order reduction method which allows to reduce the computational time of a numerical problem by seeking for a separated representation of the solution. The PGD has been already applied to study an electrical machine but at standstill without accounting the motion of the rotor. In this paper, we propose a method to account for the rotation in the PGD approach in order to build an efficient metamodel of an electrical machine. Then, the machine metamodel will be coupled to its electrical and mechanical environment in order to obtain accurate results with an acceptable computational time on a full simulation. [ABSTRACT FROM AUTHOR]

Since the flux leakage phenomenon is dominant in the inner and outer radii of axial flux magnetic gears (AFMGs), a prominent overestimation of torque prediction is obtained by the 2-D analytical method (AM) in comparison with the 3-D finite-element method (FEM) simulations. The main motivation of this paper is to present an improved quasi-3-D AM (IQAM), which is an improvement and amendment of the 2-D AM by a simple and effective radial dependence modeling of the axial and tangential magnetic field distribution in AFMGs. This IQAM plays an important role in a reliable and accurate prediction of static and transient behavior of AFMGs. The cogging torque of the AFMG is predicted using the obtained IQAM and Maxwell’s stress tensor. However, the proposed IQAM will become more prominent by focusing on the effects of single- and dual-skews’ designs for ferromagnetic pole-pieces and permanent magnets through suitable step changes in a combined skewed-MG model, as an effective passive method, in order to mitigate the cogging torque and thereby intensively augmenting torque quality in an exemplary AFMG. The accuracy of the developed skewing method is verified using 3-D FEM simulations. [ABSTRACT FROM AUTHOR]

This paper describes that the ferromagnetic resonance (FMR) frequency shift can be calculated by an electromagnetic field simulator based on the Maxwell's equation although the relative permeability and the FMR frequency is defined by the Landau–Lifshitz–Gilbert (LLG) and the Kittel's equation. We evaluate the magnetic circuit model with the leakage magnetic flux path for considering the demagnetizing field generated in the magnetic film. As the result, we clarify that the effect of the demagnetizing field is considered as a reluctance of the leakage magnetic flux path in the magnetic circuit calculation, which is considered as the increase of anisotropy field in the Kittel's equation. Furthermore, we show that the simulated FMR frequency by the electromagnetic simulator agrees with the measured values. These results show that the FMR shift in the magnetic film can be calculated and the integrated ferromagnetic noise suppressor can be designed by an electromagnetic field simulator based on the Maxwell's equation. [ABSTRACT FROM AUTHOR]

This paper presents a new flux-mnemonic dual-magnet brushless machine which incorporates both the neodymium-iron-boron (NdFeB) and aluminum-nickel-cobalt (AlNiCo) permanent magnets (PMs) for hybrid excitation. By applying a temporary current pulse in a small magnetizing winding to online tune the magnetization of AlNiCo PMs, the proposed machine can provide flexible air-gap flux control, thus achieving high efficiency at different speeds and loads. By newly using a parallelogram to model the AlNiCo PM hysteresis loop and then incorporating into the finite element field equation, the performance of the proposed machine is analyzed. Finally, experimental results are given to verify the simulation, confirming the validity of the proposed machine and its analysis. [ABSTRACT FROM AUTHOR]

Heat assisted magnetic recording (HAMR) is a promising hard disk drive technology to reach 4 Tb/in^2 storage densities. However, HAMR introduces significant thermal considerations that must be accounted for in air bearing simulations; the laser spot on the recording bit and heat dissipated into the slider by the laser delivery system result in boundary wall temperatures that are several hundred degrees Celsius above ambient. Since the air bearing film between the slider and disk is non-isothermal, the local air properties should be used in the lubrication equation that governs the pressure generation. A molecular gas lubrication equation for the air bearing that accounts for large temperature variation along the film was previously proposed by Fukui and Kaneko, but it has yet to be applied to a HAMR hard disk drive. This paper explains the generalized lubrication equation and also implements it into a realistic 2D simulation using a production slider with approximate HAMR conditions. The minimum flying height increases substantially, while the pitch and roll are inappreciably affected. Thermal creep flow is negligible compared with Poiseuille and Couette flows, and it can be omitted from consideration. The sensitivity of the read/write transducer would be affected by the large increase in minimum flying height; therefore, the thermal flying height control design process must consider these variations due to thermal variations in the air bearing. [ABSTRACT FROM AUTHOR]

This paper proposes a specific hybrid 2-D simulation model of magnetic field distribution accounting for magnet skew in the case of a linear permanent magnet generator (LPMG). The proposed methodology is based on a hybrid numerical technique implementing standard finite elements for the analysis of stator and rotor parts combined with an analytical solution in the Cartesian coordinate system in the air-gap area specified for magnet skew consideration. The developed technique has been incorporated in a coupled field-circuit model for the overall simulation of the performance of an electrical generating unit for sea-wave energy extraction using LPMG. The derived model has been implemented in the control subsystem aiming to tune the movement of the wave energy absorber to the system resonance frequency enabling to optimize its performance. Simulation results have been validated by measurements on a sea-wave energy extraction demonstration plant. [ABSTRACT FROM PUBLISHER]

Developing a precise system simulation model is a critical step in the design and analysis of optimal control strategies for a switched reluctance motor (SRM). To achieve this objective, the following works have been done in this paper. 1) A 3-D FEA model based on double scalar magnetic potential method (DSMP) is developed for obtaining the distributions of SRM magnetic field, then the flux linkage characteristics are calculated by using enhanced incremental energy method (EIEM). 2) In order to enhance modeling accuracy of the nonlinear flux linkage, a new RBF neural network with boundary value constraints (BVC-RBF) is used for approximating, based on the calculated flux linkage data. 3) The nonlinear BVC-RBF based simulation model of the SRM system is established for dynamic analysis with the power system block (PSB) modules of Matlab/simulink. 4) Simulation and experimental results are presented and compared for model validation. The validation study indicates that the developed model is highly accurate. [ABSTRACT FROM PUBLISHER]

This paper deals with key problems that have been commonly encountered in the implementation of the Preisach model into finite-element (FE) programs. Such problems include the inverse problem imposed by certain FE formulations, the abundance use of experimental data needed for identification, and the complex hysteretic nonlinearity inherited in electromagnetic problems. The aim is to alleviate these problems using new efficient algorithms to facilitate the inclusion of the Preisach model in FE equations. The inversion of the model is evaded by systematically creating an inverted Everett function identified from a few parameters usually provided by the makers of electrical steel. The Everett function and its derivatives are ensured to be smooth and continuous by using cubic spline interpolation, which is important for producing stable iterative solutions in the FE computations. Thorough investigations and FE simulations supported by experiments show that the proposed algorithms are capable of successfully accomplishing good accuracy, fast computation, and numerical convergence. [ABSTRACT FROM AUTHOR]

An equivalent circuit model for planar printed circuit board (PCB) transformers is presented. The model utilizes the 1-D analysis of Maxwell’s equations to develop a frequency-dependent representation of a multilayer, planar PCB transformer that can be implemented in the circuit simulation software. In this transformer model, each conductor layer is implemented as a complex impedance network, while each insulator layer is implemented as an air-cored inductor. Each magnetic core layer is modeled as a non-linear inductance whose magnetic characteristic is based on a temperature-dependent Jiles–Atherton hysteresis model. These impedances and inductances are then arranged side by side as they are arranged in the layer stack of the actual planar PCB transformer. Through this model, the skin and proximity effect in the conductors and current distribution across windings can be simulated. The developed model also enables the modeling of temperature-dependent hysteresis and saturation effects in the magnetic material. The model provides a simpler method to derive the core and winding loss of the transformer than using a finite-element analysis software. It also enables direct integration to circuit simulation tools. A prototype planar PCB transformer was used to obtain experimental data for model validation. Comparisons made show good agreement between the performance of the model and experimental results. [ABSTRACT FROM PUBLISHER]

This paper presents a numerical method to simulate the particle trajectory in the head–disk interface (HDI). The simulator solves the reduced Navier–Stokes equation with the second-slip boundary conditions to get the air velocity distribution, then solves the motion equations of particles and obtains the trajectories of the particles in the HDI using the binary Lagrange interpolation and the fourth-order Runge–Kutta method. The calculated trajectories of particles follow well with the air streamlines in the recessed regions. The particle density, diameter, and initial entering velocity have different effects on particle movement. Furthermore, particle velocity behaviors in the recessed regions are investigated for the first time. The particle is accelerated or decelerated by the action of the drag force and becomes close to the velocity of local air flow. Such effects are more obvious for small particles than large particles. The particle velocity becomes very small when it is close to the leading edge of the trailing pad. The numerical results also show that the particle goes up when it crosses the transition regions, and the particle moves upward more sharply with higher initial entrance height due to the larger vertical velocity of the local air flow. [ABSTRACT FROM AUTHOR]

We investigate the problem of timing recovery for 2-D magnetic recording (TDMR) channels. We develop a timing error model for TDMR channel considering the phase and frequency offsets with noise. We propose a 2-D data-aided phase-locked loop (PLL) architecture for tracking variations in the position and movement of the read head in the down-track and cross-track directions and analyze the convergence of the algorithm under non-separable timing errors. We further develop a 2-D interpolation-based timing recovery scheme that works in conjunction with the 2-D PLL. We quantify the efficiency of our proposed algorithms by simulations over a 2-D magnetic recording channel with timing errors. [ABSTRACT FROM AUTHOR]

A new particle-moving algorithm for particle-in-cell simulation of plasma is developed based on the linear multistep method. The conventional and the new algorithms are investigated by numerical experiments, which are conducted in three typical fashions of the electron motions in electromagnetic fields, namely, cyclotron in homogeneous magnetic field, drift in \boldsymbol E \times \boldsymbol B field, and motions in inhomogeneous magnetic field. The new algorithm not only improves the accuracy, but also relaxes the time step condition for the simulation, thus increasing the computation efficiency. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a standard micromagnetic problem, of a nanostripe of permalloy. We study the magnetization dynamics and describe methods of extracting features from simulations. Spin wave dispersion curves, relating frequency and wave vector, are obtained for wave propagation in different directions relative to the axis of the waveguide and the external applied field. Simulation results using both finite element (Nmag) and finite difference (OOMMF) methods are compared against analytic results, for different ranges of the wave vector. [ABSTRACT FROM AUTHOR]

A thermistor-based proximity sensor enables identification of head-disk contact in a hard disk drive, allowing the setting of head-disk clearance. This sensor also provides thermal information, permitting validation of computational models used to design recording heads. We describe here a set of models, and a related set of experiments to probe thermal and mechanical characteristics at the head-disk interface. Example results are shown, leading to the conclusion that models with diffusive-ballistic equations are capable of simulating heat transfer through the gas bearing. [ABSTRACT FROM AUTHOR]

The calculation of magnetic fields in devices with a nonuniform distribution of magnetomotive force (MMF) and with nonlinear magnetic components has proven problematic within electromagnetic systems. This is caused by insufficiently precise determination of the dependence of magnetic induction B, on magnetic field H. This paper develops a method for analytically calculating the variation of magnetic fields H, in magnetic circuits by introducing a specific expression into to the Ampere's circuital law formula to take into account nonuniform MMF. The new formula uses a conformal mapping procedure which allows calculation of the magnetic field at different displacements from the field generating coil. The analytic approximation proposed is developed for the specific problem of a closed circuit magnetic core. This analytic model gives accurate results faster than can be achieved in FEM software. [ABSTRACT FROM PUBLISHER]

Superconducting accelerator magnets require sophisticated monitoring and means of protection due to the large energy stored in the magnetic field. Numerical simulations play a crucial role in understanding transient phenomena occurring within the magnet, and can, therefore, help to prevent disruptive consequences. We present a 2-D FEM model for the simulation of electrothermal transients occurring in superconducting accelerator magnets. The magnetoquasistatic problem is solved with a modified magnetic vector potential formulation, where the cable eddy currents are resolved in terms of their equivalent magnetization. The heat balance equation is then investigated, and the relevant heat sources are discussed. The model implements a two-port component interface and is resolved, as part of an electrical circuit, in a cooperative simulation scheme with a lumped-parameter network. [ABSTRACT FROM AUTHOR]

A fully coupled simulation framework is developed to predict the dynamic characteristics of the permanent magnet (PM) contactors. Dynamic inductance, magnetic field distribution, and mechanical motion are solved by coupling the electric, magnetic, and mechanical governing equations. The equations are developed in the weak forms and the Weak Form Partial Differential Equation module of Comsol Multiphysics is employed to solve the equations. Influence of PM is taken into account by considering the remanent flux as a static potential. The electromagnetic variables and mechanical variables can be solved in the same discrete time period, which gives much higher calculation efficiency than the existing method. The simulation results show that the framework can predict the changing of the inductance, closing displacement, and excitation current in the time domain. Comparative experiments have been conducted to verify the simulations. Physical measurements show that the dynamic closing process of the contactor can be captured by the model with good precisions. [ABSTRACT FROM PUBLISHER]

The finite-element analysis for the simulation of magnetic fields in electrical machines leads to an index-1 differential-algebraic equation (DAE) (as opposed to a conventional ordinary differential equation), because the electrical conductivity can be zero in certain regions. First, we construct a DAE-compatible time integration scheme which is energy-balanced, meaning that in a linear system, the input stored and lost powers sum exactly to zero. Second, we use a method based on the energy balance to compute torque. We show that the energy balance method approaches the virtual work principle applied at remeshing layer, as the time step is refined. A similar result also holds if the rotation of the rotor is implemented by Nitsche’s method, which is an instance of the so-called mortar methods. [ABSTRACT FROM PUBLISHER]

A discretized magnetic media model is developed to improve our ability to describe the high-frequency recording performance of perpendicular magnetic media. The new model differs from the traditional macrospin model in that the magnetic grains are subdivided into cells, which have varying magnetic properties and independent magnetic moments. This discretized media model has two realizations: one with a discretized magnetic boundary and one without the magnetic boundary. We focus on the resolution and the signal-to-noise ratio obtained from a high-density bit pattern as the bit length approaches the grain pitch. Simulation results demonstrating the impact of a discretized cap in this recording regime will be discussed. The increased computational effort needed to perform a simulation using this discretized media model, and has been addressed by porting this model to a cluster of graphics processing units. [ABSTRACT FROM AUTHOR]

In the numerical integration of the Landau–Lifshitz–Gilbert (LLG) equation, stiffness (stability restrictions on the time step size for explicit methods) is known to be a problem in some cases. We examine the relationship between stiffness and spatial discretization size for the LLG with exchange and magnetostatic effective fields. A maximum stable time step is found for the reversal of a single-domain spherical nanoparticle with a variety of magnetic parameters and numerical methods. From the lack of stiffness when solving a physically equivalent ODE problem, we conclude that any stability restrictions in the partial differential equation case arise from the spatial discretization rather than the underlying physics. We find that the discretization-induced stiffness increases as the mesh is refined and the damping parameter is decreased. In addition, we find that the use of the FEM/BEM method for magnetostatic calculations increases the stiffness. Finally, we observe that the use of explicit magnetostatic calculations within an otherwise implicit time integration scheme (i.e. a semi-implicit scheme) does not cause stability issues. [ABSTRACT FROM AUTHOR]

Conservation of power in time-stepping finite-element (FE) simulation of electrical machines is studied. We propose a method for accurately obtaining the instantaneous time derivative of the FE solution, from which the instantaneous eddy-current losses and the rate-of-change of the magnetic field energy are calculated. The method is shown to be consistent with different time-integration schemes, unlike the typically used backward-difference (BWD) approximation, which is only accurate if the BWD method is also used for the time integration. We first formulate the FE equations for a locked-rotor induction machine as a differential-algebraic equation (DAE) system. An approach called the collocation method is then used to derive the BWD, trapezoidal (TR), and implicit midpoint integration rules in order to show how these methods approximate the solution in time. We then differentiate the constraint equations of the DAE to form a system from which the time derivative of the solution can be solved. The obtained derivative is shown to satisfy the power balance exactly in the collocation points. In case of the TR rule, the losses calculated with the proposed method are shown to be less sensitive to the time-step length than ones obtained with the BWD approximation for the time derivatives. The collocation approach also allows studying the power balance continuously during the time step. [ABSTRACT FROM PUBLISHER]

Recent research results demonstrate that demagnetizing factors for various geometries can be precisely determined by employing 3-D electromagnetic field simulation. Using a technique developed by the authors, the demagnetizing factor resulting from the simulations match very well with experimental results for several series of samples with various geometries. The simulation technique developed by this project was also used for a spherical magnet using various field conditions, which has further proved the accuracy of this technique, whose results agree precisely with the theoretical analyses and mathematical calculation. Such simulation provides advantages over other methods including mathematical calculation and experimental measurement. Since any geometry with any dimensions can be simulated using the electromagnetic field simulation, the simulated results of “N” values can be stored in a data bank for any application using open-circuit measurements in the future. [ABSTRACT FROM AUTHOR]

A novel approach is presented applying capabilities of software agent-based programming to numerical field computations. Distributed and autonomous calculation resources are used in analogy to a machine-to-machine system application for setting up and solving coupled simulations respecting the individual machine capabilities. Within the presented system, the involved machines interact cooperatively and comparatively. No central unit takes any influence to the solution process. Redundant resources do automatically and proactively add variance to the solution process by modifying their partial tasks based on negotiations between the involved resources. In that way, different numerical methods, solution strategies, and solver configurations are automatically evaluated as examples of the variety within coupled simulations. Partial results are dynamically integrated into an overall solver sequence, demonstrated on the coupled electric field computation of a patch antenna array. A quick provision of results is shown contemplating changes at calculation resource and vague user decisions for a nonlinear and bidirectionally coupled simulation of a 3-D multiphysics problem. [ABSTRACT FROM AUTHOR]

For the time domain simulation of coupled systems, co-simulation is a prominent approach. The contraction and the speed of convergence of corresponding schemes depend on the design of the coupling interface and the computational order among others. Here, the field/circuit coupling is investigated, where the standard approach of decoupling is to separate the field and the circuit part. In this context, we introduce a new decoupling approach: $LR$ -coupling. For this coupling type, general stability and contraction are directly influenced by the coupling interface. Thus, these properties are independent of embedded electric networks or embedded electromagnetic devices. Furthermore, first investigations demonstrate that the use of a dedicated coupling interface may enhance the convergence properties, i.e., it may reduce the computational effort for prescribed tolerances. [ABSTRACT FROM AUTHOR]

A general framework is presented for the formulation of steady-state simulation algorithms for magnetically nonlinear eddy-current problems using implicit Runge–Kutta (RK) methods. A close analogy is drawn between equations discretized using the backward-Euler method and fully implicit RK methods. Detailed formulations of the time-periodic finite-element method (TPFEM) and the shooting-Newton method (SNM) are derived using the popular family of diagonally implicit RK (DIRK) methods. Both algorithms employ the generalized minimum residual method to solve the linear equations arising at each Newton iteration. The benefits of higher-order DIRK methods are demonstrated by simulating a surface mount permanent magnet synchronous machine. The effects of using a solid versus a laminated rotor back iron on the simulation time are examined. Simulation results indicate that the performance of TPFEM and SNM is quite similar and much faster than transient analysis. [ABSTRACT FROM AUTHOR]

Nonradiative wireless power transfer is a popular technology that transfers energy over medium range via strongly coupled magnetic resonance. We investigated the effect of transmit diversity on power transfer efficiency under multiple transmitters. We derived closed-form equations for the power transfer efficiency and the optimal load from both coupled mode theory and equivalent circuit model analyses. We also showed that the analytical results obtained from the two types of analysis are basically the same, so they can be expressed as an equivalent equation that consists of a quality factor and coupling coefficient. In addition, we performed simulations using the Ansoft High Frequency Structure Simulator and the Agilent Advanced Design System to demonstrate the accuracy of our analysis. The results show that a multiple-transmitter wireless power-transfer system can improve power transfer efficiency over all regions in both an angular aligned scenario and an angular misaligned scenario, due to the diversity in the transfer of power. [ABSTRACT FROM PUBLISHER]

A new scheme for the simulation of heat-assisted magnetic recording (HAMR) that systematically includes fluctuating material properties above a predefined length scale, while retaining magnetostatic interactions, is introduced. Renormalized media parameters Ms, Ku, Aex, and \alphadamp, suitable for useful length scales, are found numerically. These renormalized parameters are then used to model the Voronoi-cell-composed medium in the HAMR simulation. Transition jitters are obtained under various conditions. The results show that moderate maximum temperature of the heat spot, intergranular exchange coupling, media thickness of at least 10 nm, nonzero canting angle of the head field, relatively low head velocity, and large head-field strength are helpful for a successful recording. [ABSTRACT FROM AUTHOR]

Eddy current testing (ECT) of narrow cracks is an important issue in several industrial areas. Efficient modeling tools are required in order to better interpret measurements, to design adapted probes, and to assess the reliability of testing procedures. A dedicated boundary element model (BEM) suitable for eddy current inspection of several narrow cracks affecting a planar-stratified conductive medium is proposed. The cracks' openings can be arbitrarily small, and their respective orientations be along parallel or orthogonal directions. The approach alleviates most of the computational difficulties of classical methods in such peculiar cases. Comparisons of the results with experimental and simulated data taken from the literature, completed with in-house experiments, illustrate its good accuracy and low computational burden. [ABSTRACT FROM PUBLISHER]

We study noise and recording properties of nonoriented barium-ferrite particulate media using micromagnetic modeling. The packing and orientation distribution of the barium ferrite particles are reproduced very well with our packing algorithm. The distribution of switching fields is determined from experimental hysteresis loops. Using these parameters, we perform recording simulations of periodic waveforms written at various frequencies and extract broad-band signal-to-noise ratio (BB-SNR). Comparison to experimental measurements shows very similar signal and noise characteristics, with however a 6 dB offset in BB-SNR values. Other (e.g., mechanical) noise sources would need to be included in the simulations to account for the difference. Nevertheless, the simulations prove very useful to understand and quantify how particle and media parameters contribute to the signal-to-noise ratio. For the present nonoriented particulate medium, we verify that the particle volume distribution affects the noise power according to the existing analytical expression for particulate noise. The particle anisotropy distribution is found to significantly affect the signal roll-off. The related variation in BB-SNR is found to be in good quantitative agreement with experiments. The effects of other parameters on BB-SNR, such as dipolar coupling, medium thickness, and average head-medium spacing, are also presented. An analytical slope model is proposed for nonoriented media that reproduces the simulations and experimental data very well. [ABSTRACT FROM AUTHOR]