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We have studied the sensitivity of soft error rate (SER) to an external magnetic field in longitudinal hard disk drives. We found that during writing SER is generally quadratic with field amplitude and symmetric with field direction. The application of an external field during writing also shifts the center of the track. In contrast, during reading SER is predominantly linear with field amplitude and antisymmetric with field direction. There is no shift in the track center when the field is applied during reading up to 100 Oe. We explain the difference in the track center shift between writing and reading in terms of the effect of the stray field on the servo positioning system. Index Terms--Longitudinal recording, perpendicular recording, servo system, stray field.

Electromagnetic theory presents difficult task for the student. The essence of the problem is not the pretentious mathematical treating of the field, but in the field presentation and understanding of field interaction with the material. The paper presents our program tools (FIELD_EDU) for teaching of electromagnetic field, based on the finite element method (FEM). The program concept enables the student to build in the very simple way an arbitrary problem, without being burdened with specific demands of FEM at field analysis. When doing this, the students can help themselves with the library of simple geometrical objects, which have already predefined material properties and boundary conditions. The program tools enable a complete graphical and numerical analysis of one or more examples at the same time. Index Terms--Computer science education, electric fields, finite element method (FEM), magnetic fields.

This paper addresses the problem of mobile robot navigation using artificial potential fields. Many potential field based methodologies are found in the robotics literature, but most of them have problems with spurious local minima, which cause the robot to stop before reaching its target position. Although some free of local minima methodologies are found in the literature, none of them are easy to implement and generalize for complex shaped environments and robots. We propose a perfect analogy between electrostatic field computation and robot path planning. Thus, an easy solution to the problem, which is based on standard finite-element methods, can be applied with generic geometries and can even take into account the robot's orientation. To demonstrate the elegance of the proposed methodology, several experimental results with actual mobile robots are included. Index Terms--Finite element methods, mobile robots, motion-planning.

This paper deals with the modeling of cells for electrolytic conductivity measurements. The characteristics of these equipments have to be accurately determined in order to perform reliable measurements, traceable to the units of the International System (SI). A numerical three-dimensional model, based on the boundary element method, is developed and applied here to different cell geometries for evaluating the electric/current field inside the solution and, consequently, the cell impedance. Index Terms--Boundary element method (BEM), electric fields, electrochemical devices.

This paper proposes to use a new and realistic finite element model of a single turn human cochlea and cochlear implant electrode array with electrode-tissue interface to model the electric field imaging technique, which creates an impedance matrix. Due to discrepancy in the Warburg capacitor in the active and nonactive electrode contacts and electric power lost along the cochlea, the diagonal terms of the impedance matrix is larger than the off diagonal terms, which represent the impedance values of the nonactive electrode contacts. The impedance matrix from electric field imaging measurements is compared with the simulation results. Index Terms--Cochlear implant, electric field imaging, finite element method, tissue-interface model, volume conduction model.

Combined electric field and flow field are numerically simulated based on the computation of the N-S equation and turbulent model, taking the influence of temperature, pressure, and the effect of gas flow on the dynamic are into consideration. In computing, self-adaptive adjustment of the current has been considered for reflecting the variation of the dynamic are during the whole interrupting course. Moreover, the gas flow field of high voltage S[F.sub.6] circuit breakers (HVCBs) with complex flow path, supersonic nozzle, source, viscous, compressible and variable boundaries has been solved. Consequently, the interaction of dynamic arc and gas flow has been simulated. The feature of dynamic arc-gas flow interaction has been numerically analyzed, and the arc choke varying with the pressure of gas flow, velocity, and the flow flux has been simulated. The theoretical foundation for further studying the utilization of arc energy and improving interrupting performance has been established. Index Terms--Arc, electric field, gas flow field, S[F.sub.6] interrupter.

This paper presents a hybrid method for the calculation of the electric far field outside the enclosure. The method computes electric near fields on the opening by finite-difference time-domain (FDTD) to determine the equivalent magnetic current. Then the far fields are calculated using this equivalent current. Simulation results show that the proposed method significantly reduces the computational effort and still maintains satisfactory results in comparison to a full FDTD simulation and the traditional hybrid method. Index Terms--Electric far field, finite-difference time-domain (FDTD) method, hybrid method.

A finite-element formulation based on a discrete electromagnetism is developed to simulate electro-quasistatic fields on unstructured meshes. The presented formulation takes dielectric effects into account as well as nonlinear conductive effects. The implementation is based on discrete differential forms on an unstructured 3-D mesh. Numerical results of the simulation of a three dimensional high-voltage surge arrester consisting of linear and nonlinear materials are shown. An algebraic multigrid method is introduced as a preconditioner to nonstandard projected preconditioned conjugate-gradient linear system solver. Index Terms--Finite-element-method, electro-quasistatic-fields, time integration, discrete electromagnetism.

When dc current is injected into the earth through the grounding electrodes of a high-voltage direct current (HVDC) system, transformers in ac system may be under dc bias if the dc currents flowing through the transformers are large enough. In this paper, a numerical method coupling the method of moments (MOM) to circuit equations is presented to calculate the dc current distribution in ac power system caused by an HVDC system. The MoM is used to calculate the electric fields in complex earth structure caused by all the grounding systems including the dc grounding electrodes, the ac substation grounding systems and the long metal pipe lines. The circuit equations are coupled to the moment method to take account of the effects of the transmission lines. By using the method, the dc current distribution in an ac power system caused by an HVDC system is analyzed. Some useful conclusions are drawn from the analyzed results. Index Terms--Current distribution, grounding electrodes, high-voltage direct current (HVDC) transmission, method of moments (MOM).

Suspension insulators are widely used in power systems to provide electrical insulation and mechanical support for high-voltage (HV) transmission lines. To detect and replace the faulty insulators on power transmission lines is of great importance for the safe operation of the power system. A nontouch electric-field measurement method to detect faulty ceramic insulators is presented, which involves measuring the electric-field of measuring points in the vicinity of insulator strings and calculating the potential distribution along HV outdoor insulator strings. It also suggests a way to process the influence from the tower. The salient feature of this method is the significantly smaller number of measuring points and the greater distance between measuring points and insulator strings. Ceramic suspension insulators of 110-kV voltage ratings have been modeled under clean and dry surface conditions. Good agreement is obtained between the present calculations and the actual value, which demonstrates the practical viability of the technique. Index Terms--Ceramic insulator, charge simulation method, detection, electric-field measurement method.

This paper presents the numerical resolution of the problem defined by corona discharge in a gas at the edge of a blade facing a plate. We use the finite element method to solve the Poisson equation and the method of characteristics to determine the distribution of charge density (charge conservation equation). The main point is the use of a structured mesh which is redefined at each iteration step to avoid artificial numerical diffusion when solving the charge conservation equation. This algorithm is applied using an injection law giving the charge density at the injector as a function of the local electric field. Index Terms--Finite elements, injection through corona discharge, method of characteristics (MOC), space charge effect.

In this paper, the accuracy of the integral equation of the hybrid finite-element-method-Dirichlet boundary condition iteration method is improved for the computation of open boundary electrostatic fields. This is achieved by selecting the integration curve (or surface) as lying in the middle of the triangular (or tetrahedral) elements. A notable improvement in accuracy is obtained compared with selecting the integration curve (or surface) as constituted by element sides. Index Terms--Finite-element method (FEM), integral equations, open boundary problems.

A transient electric field takes place in gas-insulated switch-gears (GIS) while lightning impulse voltage is imposed on it. Taking permittivity, conductivity, and polarization loss into consideration, the differential equations of transient field are deduced, where the response caused by lightning impulse voltage is expressed by Duhamel integration. The equivalent conductivity contributed by polarization loss of epoxy spacer is obtained from the experiment. The potential distribution curves of epoxy spacer in GIS are given at representative time, and the electric intensity distribution curves on the spacer surface with respect to time are illustrated. The maximum of intensity on the spacer surface is also calculated, which is compared with the one in the static field. Some distinguishing features of the transient field in GIS are also discussed. Index Terms--Gas-insulated switch-gear (GIS), lightning impulse voltage, spacer, transient electric field.

In this paper, the Finite Analytic concept is introduced for calculating the electric field distribution. To express the relationship between central potential and vertex potentials on a grid, the exponential function is adopted instead of the series function in conventional Finite Analytic Method (FAM). On this consideration, the finite analytic equation for electric field calculation is deduced. And aiming at accelerating the computational convergence, the improved FAM is combined with Multi-grid Method and the body fitting grids are generated at each divided subregion for generating the regular grids and for distinguishing the fine grids and coarse grids. Index Terms--Electric field, FAM, interrupter, MGM.

Solving the thin-wire electric field integral equation (EFIE) by the multiresolution wavelet expansion method involves a time-consuming double numerical integration for each nonzero element of the moment matrix which in turn can outweigh the advantages of achieving a sparse matrix. To speed up the matrix fill process in wavelet-based moment method codes, first, the triangular scaling functions of a nonorthogonal piecewise liner wavelet at the finest spatial resolution are appropriately replaced by sinusoidal dipoles for which mutual impedances are available in closed-form analytical expressions. The fast wavelet bases transform is then exploited to effectively transfer the resultant matrix equation to multiresolution wavelet domain. Numerical results obtained by the compactly supported semi-orthogonal linear B-spline wavelet demonstrate dramatic reduction of the overall solution time without any degradation in the accuracy of the final solution. Index Terms--Fast wavelet transform, moment matrix sparsification, sinusoidal dipoles, thin-wire EFIE, wavelet expansion method.

An approach coupling indirect boundary element method with charge simulation method to calculate the electric fields around the head of transmission tower and its composite insulators is presented. On the composite insulators, the indirect boundary element method is used, while on the transmission tower and the transmission lines, the charge simulation method is used. Therefore, both the heterogeneous medium such as the composite insulators and the filament metal structure such as the transmission tower and the transmission lines are considered all together. The electric field distribution around a 330-kV transmission tower and its composite insulators was analyzed. The method gives the possibility to model very complex geometries. Index Terms--Boundary element method (BEM), charge simulation method (CSM), electric fields, insulators.

This paper applies the method of images, an analytical method, to calculate electric field on conductor particles with a surface film. The method utilizes the multipole re-expansion and appropriate fundamental solutions. Electric field is repetitively calculated so as to satisfy all the boundary conditions. The main advantage over numerical field-calculation methods is that high accuracy can be realized as neither approximation nor discretization of the particle surface or the film thickness is involved. The calculation results for arrangements of a particle chain under a uniform field show the field intensification due to the film thickness and electrical properties. We have also carried out field calculation by the boundary element method (BEM), and compared the results with the analytical ones. The results by the BEM exhibit higher error with decreasing film thickness. Force and yield stress have been calculated from the electric field and compared with experimental results. The comparison shows a good agreement for the ac field, but significant difference for the dc one. Index Terms--Dielectrophoretic force, electric field, electrorheological (ER) fluid, method of images, particle, surface film.

In this paper, the algorithm of design for an insulation system of a high-voltage combined instrument transformer using the field method is considered. The commercial software OPERA 3D was used to compute field distribution and the author's software SHIELDS was used to optimize the number, dimensions, and position of each electrostatic control shield in the insulation of the voltage and current parts. The programs interact with each other. This work presents the results of the use of numerical methods in the designing process. Index Terms--Electric field, electrical insulation, high-voltage techniques, instrument transformers.

In this paper, a domain decomposition approach for finite-element method calculation of electric field of insulators applied on high-voltage transmission lines is presented. Using this method, the electric stresses acting around and inside on insulators are determined considering the interactions of the three-dimensional environment. First, a large-scale model is used to determine the potential distribution near the insulator. Next, a local domain including the exact model of the insulator is investigated. Finally, a series of iterative solutions is applied on these overlapping domains to reach the correct field distribution along the insulator. This method gives the possibility to examine the effects of various hardware structures such as line and tower configurations and grading devices and ensures to model very complex geometry without extra high computational effort. Index Terms--Composite insulators, domain decomposition, electric field calculation, finite-element method, power transmission lines.

The characteristics of corona discharge in needle-to-plane electrodes have been simulated by two-dimensional fluid method. It was assumed that the transport coefficients of nitrogen gas were only the function of reduced electric field. In this discharge mechanism, Townsend first ionization and a secondary electron emission were considered. The spatio-temporal distributions of electron and ion densities at three discharge steps were obtained by solving continuity equations using the flux-corrected transport algorithm. This paper also describes the effect of space charges on the electric field distribution. Index Terms--Corona discharge, FCT method, fluid method, reduced electric field.

An adaptive triangular mesh generation method for BEM is proposed. In this method, an estimated error is used as the criterion for refinement of triangular mesh. The error estimation is performed by using a smoothness of unknown variable distribution, which is an approximate equation of the Laplacian of the discrete unknown variables at the node on triangular element. In this paper, the procedure of the adaptive triangular mesh generation and some examples are described. Index terms - Adaptive mesh generation, electrostatic field, boundary element method.

A finite element mesh generator based on an artificial neural network is described. The generator grows an initial mesh of triangles up to a user-selected number of nodes. The mesh growth is driven by a node probability density function, which is obtained from an error estimation for the solution of the problem with the initial mesh. Good-accuracy solutions are obtained with a lower computational effort. Index terms - Finite element methods, neural networks, electric fields, adaptive mesh refinement.

Krylov-subspace methods for complex-valued systems are still a present research topic in numerical mathematics. Due to the lack of theoretical results systematic numerical experiments are very important in order to find a sufficiently robust solution method. An important problem in high-voltage power plants are arc-overs on moist or contaminated insulators. A quantitative knowledge of the electric behaviour of layers of water droplets is necessary in order to understand the resulting ageing processes. Discretization of the electro-quasistatic problem leads to large sparse complex systems of linear equations. Comparisons between different Krylovsubspace methods, also in combination with residual smoothing techniques, and parameter studies are presented in this paper. Index terms - Electric fields, electro-quasistatics, linear algebra, algorithms, epoxy resin insulation

The present paper describes a finite-element formulation for static and stationary electric and magnetic fields in terms of the electric and of the magnetic field strength. The formulation is based on a simultaneous minimisation in the least-squares sense of the error in modelling the curl and the divergence equations. For consistently modelling the field equations and the interface and boundary conditions, use is made of generalised Cartesian expansion functions. Index terms - finite-element formulation, static and stationary fields, least-squares minimisation.

A mathematical model that couples the electrical potential in the arc with the resulting thermal and flow fields has been developed to describe the behaviour of the arc plasma in DC electric arc furnace. The set of conservation equations, along with a potential equation for the electric field, were solved using the PHOENICS software package. Key aspects of the modelling problem, necessary to achieve a stable and meaningful numerical solution for the long DC electric arc, are evaluated. These aspects involve convergence issues as well as the treatment of the nonlinearities. Particular attention was given to the selection and adjustment of several under-relaxation factors.

When the frequency of power converters increases, the wound components like inductors or transformers can no longer be supposed ideal. In this paper a formulation using 2D finite elements is presented for studying the high frequency coupled magnetic and electric field problem (eddy currents, proximity effects and stray capacitance). This formulation is based on a particular division of the 3D spatial domain which enables a 2D calculation.

The method of moments applied to the electric field integral equation or the combined field integral equation has been in recent years, the main computational technique for determining far-field scattering from resonant size objects comprising dielectric material and pec surfaces. However very little has been published on their performance in modelling the near-field scattering. This paper discusses the computation of the near-field scattering from such a method of moments code and compares the results to those from a recently reported conjugate gradient FFT method.

This paper deals with the numerical solution of the linear complex Poisson equation. The practical background of posing this problem are arc-overs on moist or contaminated insulators in high-voltage power plants. The electrostatic field of the charge-free space prevails essentially below a critical voltage [U.sub.k]. However, the dielectric material looses its insulating characteristics above [U.sub.k]. It becomes the carrier of a discharge which builds up a conducting connection along the insulator. It is a matter of slowly varying fields (50 Hz), for which the displacement current is a significant quantity. These slowly varying fields can be determined by solving a complex potential problem. Discretization leads to a complex system of linear equations with symmetric matrix. This system is solved by various modern conjugate gradient-type methods. Numerical simulations for test and real life problems are presented.

An application of region-oriented charge simulation to the computation of quasi-static electric fields for systems with perfectly conducting and lossy components is presented. In contrast to other integral methods this formulation does not require any special treatment of thin conducting layers. This method shows good agreement between numerical and analytical calculations for both 2D and 3D formulations, and has been effectively applied to practical problems.

A finite-element method is described for computing static and stationary electric and magnetic fields directly in terms of the electric or magnetic field strength. In this way the use of (vector) potentials is avoided and a much higher accuracy is achieved with the same computational effort. The curl equation is supplemented with the electromagnetic compatibility relations and a problem is defined which is known to have a unique solution. For satisfying the conditions at the interfaces between different media use is made of both edge and nodal elements. The validity of our approach is illustrated by solving a simple sample problem.

The charge iteration procedure, recently presented by the authors for the FEM solution of unbounded electrical fields, makes use of a fictitious boundary whose position strongly affects convergence properties and performance in terms of computational effort. In this paper the problem of the optimal placement of this boundary is first addressed analytically in the case of simple systems and then it is illustrated how the obtained conditions can be used for more complex systems so as to offer simple criteria for the application of the procedure to practical cases.

Studies of the current-voltage characteristics of typical superconducting wires under static and dynamic conditions up to 50 Hz frequency have revealed much higher instantaneous local loss power densities in an external DC magnetic field than those which occur by magnetization in a transverse AC magnetic field. In this paper, the measured loss characteristics are compared with theoretical ones derived from the critical state model, and the self field AC losses are also estimated. Possible errors that can result by applying the critical state model are discussed.

A human body in the vicinity of an overhead cable is subject to two kinds of electrical effects, inductive and capacitive, that together are responsible for tiny currents. Recent concerns about possible biological effects of such currents have made their accurate computation necessary. We address the mathematical modelling that has to precede such computations: what are the equations to solve? By an asymptotic analysis of the full set of Maxwell equations, (displacement currents not neglected), which takes into account the smallness of the electrical permittivity and the large penetration depth, we arrive at a standard conduction problem, to which both kinds of effect contribute source-terms: inductive effects give a right-hand side, and capacitive effects give a non-homogeneous boundary condition. Some numerical results are displayed.

Effects on magnetic and optical properties of perpendicular electric fields up to 1 MV/m were studied on thin ferromagnetic films of MnAs grown epitaxially on GaAs(001) substrates. Film thicknesses were 20, 50, 100 and 200 nm. With positive electric field corresponding to positive polarity of the MnAs film with respect to the GaAs substrate, it was found that at a field magnitude of 1 MV/m: (a) the magnetizations of the 20 and 50 nm films decreased by 3.5 and 1 percent, respectively, under both positive and negative fields as measured by vibrating sample magnetometry; (b) the magnetooptical Kerr effect (MOKE) of the 20 nm samples decreased by 3.5 percent in negative field but was unchanged by positive field; (c) the index of refraction of the 20 nm films determined by ellipsometry increased by 1 percent in positive field but was unchanged by negative field. No effects were found in thicker films, indicating the observed effects arise from the region of MnAs near the substrate. The MOKE signal of the 20 nm films has a power law dependence on electric field with an exponent of 0.36 with a standard deviation of 0.04. The intensity of the (10-10) x-ray diffraction peak from the ferromagnetic, hexagonal MnAs phase of a 20 nm film decreased by 5 percent in both positive and negative fields of 1 MV/m; however, there was no corresponding increase in the nonmagnetic, orthorhombic phase. Index Terms - Electric fields, ferromagnetic films, magnetoelectric, magnetooptic

Barkhausen transition fields for anisotropic Permalloy films, measured by the resonance enhancement technique, were found to be a function of the maximum field to which a sample was subjected before the occurrence of these transitions. In these experiments, the Barkhausen transitions were monitored after repeated cycling of the field applied along the easy axis between given maximum positive and negative values to obtain a nearly repeatable initial state. For a film with an H(sub c) of 1.4 oe, the Barkhausen transition fields for repeated passes through Hc differed from each other by no more than 4.2% if the field was cycled between + or - 48 oe. For a cycling field between + or - 22.5 oe, the corresponding deviation increased to 9.9%.

This paper describes various aspects and results of 2D finite element (FE) modelling of electrostatic fields in 12-electrode capacitive systems for two-phase flow imaging. The capacitive technique relies on changes in capacitances between electrodes (mounted on the outer surface of the flow pipe) due to the change in permittivities of flow components. The measured capacitances between various electrode pairs and the field computation data are used to reconstruct the cross sectional image of the flow components. FE modelling of the electric field is necessary to optimize design variables and evaluate the system response to various flow regimes, likely to be encountered in practice. Results are presented in terms of normalized capacitances for various flow regimes. The effects of key geometric parameters of the electrode system are also presented and analyzed.

The application potential of dc electric fields to promote and optimize the ferrite bonding between single- and polycrystalline manganese-zinc ferrite was investigated. The ferrite bonding process was accelerated under the application of a dc electric field. The degree of bonding increased as the bonding time and bonding temperature were increased. It was also found that the direction of an applied current from the poly- to single-crystalline ferrite regions enhances bonding. Index Terms--Chemical potential, electrical bonding, Mn-Zn ferrite, polycrystal, single crystal.

To develop the most efficient electrophotographic system, numerical analysis method, which estimates the output image on the paper, is developed. This method is based on the numerical analysis method, which calculate the field distribution in each process using fundamental measurement data. This method is applied to a electrophotographic system for digital copier, and numerical results of gamma characteristics and line width are conformed with measured ones. This developed method enables us to optimize design parameters taking into account of each process. Index Terms--Electric field, electrophotography, finite element method, process simulation.