bluuebunny/crossref_metadata_2025 huggingface dataset:
COMPUTATION OF 3D EDDY CURRENT FIELDS AND LOSSES DUE TO LEADS IN A LARGE POWER TRANSFORMER
Authors: Yongbin Chen , Junyou Yang , Hainian Yu , Renyuan Tang
Published: February 2008

Boundary element method(BEM) is applied to computation of 3D eddy current fields due to heavy current leads in a 360MVA/500kV power transformer. To improve numerical accuracy, triangle polar coodinate mapping and addition‐substraction technique are chosen to evaluate singular integrals. The effects of different shields in cover and arrangements of heavy current leads on eddy current loss and its density are analyzed.
DETERMINATION OF STEP MOTOR PARAMETERS WITH MAGNETIC FIELD SOLUTION
Authors: Juraj Wagner Dipl Ing. , Maga Dušan , Führichová Renata , Ing Roman Guba Dipl , Opaterný Jozef
Published: February 2008

In our contribution we deal with the optimization of the magnetic circuit design of the high torque step motor by numerical solution of the motor magnetic field (the Finite Elements Method — FEM) and with the solution of some electrical parameters of this motor and we introduce the methodology of optimization of the motor size from the parameters dependant.
THE ACCURACY OF CALCULATION OF MAGNETIC FIELDS, INDUCTANCE AND FORCES IN ELECTROMAGNETIC DEVICES USING THE RELUCTANCE NETWORK METHOD (RNM)
Authors: WOROTYŃSKI Jacek , TUROWSKI Marek , MENDRELA Ernest A.
Published: February 2008

Among the many calculation methods that allow the evaluation of magnetic field in different electromagnetic devices is the Reluctance Network Method (RNM). It is based on network theory according to which the analysed space is replaced by the network of magnetic reluctances, with magnetomotive forces as supply sources. This method makes it possible to analyse magnetic fields in two‐dimensional (2‐D) and three‐dimensional (3‐D) domains, and in comparison to other numerical methods (e.g. Finite‐Element Method) the calculation time is much shorter, with relatively good accuracy.
TRANSMEMBRANE VOLTAGE DUE TO ELECTROBIOLOGICAL INTERACTIONS
Authors: Krawczyk Andrzej , Skoczkowski Tadeusz
Published: February 2008

The interactions of electromagnetic fields and biological structures are of great interest both from medical and technological points of view. The medical aspect is well‐known even in archaic medicine while bio‐electrotechnology is being developed just at recent time. Especially it is readily seen when dealing with electric field and its influence on living cells. Biologists and biochemists are mainly interested in the voltage induced in the cell membrane (transmembrane voltage). This gives the information about forces acting on membrane which cause the phenomenon called dielectrophoresis. The other phenomenon which joins electromagnetic field and biological structures is electroporesity when the pores in a membrane are caused by electric field. It seems that the latter case requires carefully carried calculations since the transmembrane voltage decides on the phenomenon. The paper, however, does not aim at very biological effect; our goal is to show how the electric field in the cell and the membrane voltage should be calculated. It should be stressed that the research in bio‐electromagnetism is on very initial step as concerns the calculation methods. This results from two facts: the first is that so far there were no links between people working on computational electromagnetism and biologists and the second comes from the complex nature of biological structures which cannot be modelled as easy as it is with technical products. Thus, the paper is aiming at showing how the cell is modelled and what the main dependencies which govern electromagnetic phenomena are. This may be considered as an introductory step to further activity in this area.
ESTIMATION OF THE ELECTRIC STRENGTH OF INSULATION SYSTEM ELEMENTS USING NUMERICAL METHODS
Authors: Leśniewska E. , Borowska‐Banaś I.
Published: February 2008

In the paper, some cases of using HV insulator in SF6 gas medium are discussed. Computations, permitting to optimize the insulation system geometry and to make use of the HV insulator in atypical constructions, were carried out. The equipotential lines and diagrams of the electric field strength, enabling to draw conclusions concerning shapes of constructions are presented.
AN ENERGY TRANSPORT MODEL FOR HBTS USING ENERGY‐ AND COMPOSITION‐DEPENDENT TRANSPORT PARAMETERS
Authors: Horio Kazushige , Nakatani Akio
Published: February 2008

In this paper, we describe an energy transport simulation method for graded AlGaAs/GaAs HBTs, which uses Al composition‐, doping density‐, and energy‐dependent transport parameters estimated by a Monte Carlo method. For several representative Al composition x and doping densities, parameters such as electron mobility, energy relaxation time and upper valley fraction are evaluated as a function of electron energy. For the other x, these are determined by linear extraporation. The problem of this extraporation method is also described. Calculated cutoff frequency characteristics and electron velocity profiles are compared with those by using more simplified approaches, indicating the importance of using adequate transport parameters.
A NECESSARY CONDITION ON DISCRETIZATION SCHEMES FOR DEVICE SIMULATION
Authors: MONTRONE F. , BULIRSCH R.
Published: February 2008

This paper contributes to the evaluation of discretization schemes for the semiconductor device continuity equation. A simple model problem is described which provides a test any discretization scheme on simplicial grids must pass. Otherwise the scheme will fail to compute the minority charge densities in simulation problems. Many schemes published in literature do not pass this test. In a last section the relevance of the model problem to realistic devices is explained.
A NEW APPROACH OF THE BOX METHOD ADAPTED TO ANY CONVEX POLYGONAL MESH
Authors: Mottet S. , Vermeulen P.F.
Published: February 2008

The main discretisation methods used today for semiconductor device simulations are finite elements, finite differences and the box method. Each of them has disadvantages. We propose a new box method, which avoids the disadvantage of finite elements and allows the flexebillity of geometrical description of this method. This new method can be easily applied to two or three dimensional problems, even if the examples we present are two dimensional test problems.
A GENERALIZED SELF‐SCATTERING TECHNIQUE FOR MONTE CARLO SIMULATION SUITABLE FOR SIMD ARCHITECTURES
Authors: Sheng Henry , Guerrieri Roberto , Sangiovanni‐Vincentelli Alberto
Published: February 2008

We present a generalized self‐scattering method for generating carrier free flight times in Monte Carlo simulation. Compared to traditional approaches, the added flexibility of this approach results in fewer fictitious scatterings, which is especially appealing for load balance and efficiency when a SIMD parallel computer is used. Speedups from 19% to 69% over an optimized variable‐Γ approach are shown for an implementation on the Connection Machine CM‐2. The performance sensitivities to applied fields and grid spacings are also presented. The conversion of existing variable‐Γ software to this new approach requires only a few changes.
THERMO‐ELECTRIC STUDY OF THE TRENCH‐GATE POWER VDMOS TRANSISTOR
Authors: Zeng J. , Mawby P.A. , Towers M.S. , Board K.
Published: February 2008

In this paper, the 2‐D numerical analysis is used to investigate the electro‐thermal performance of a trench power VDMOS transistor having a much reduced quasi‐saturation effect over the conventional VDMOS structure. Taking into account all the appropriate physical mechanisms, the analysis self‐consistently solves Poisson's equation, the electron continuity equation and the heat flow equation. The results show that the trench structure introduced enables the device to operate at higher current levels due to a favorable change in current density distribution within the device. However, these two effects can increase the self‐heating of the device, decrease the forward current and degrade the thermal stability of the new structure. Nevertheless the new device is still found to provide a higher quasi‐saturation current than the conventional VDMOS device even when thermal effects are taken into account.
SIMULATION OF TRANSIENT SELF‐HEATING DURING POWER VDMOS TRANSISTOR TURN‐OFF
Authors: Hu Z.R. , Mawby P.A. , Towers M.S. , Board K.
Published: February 2008

The transient thermal behaviour, based on a rigorous transient thermodynamic treatment, of a power VDMOS transistor during turn‐off is presented. The time variation of the interior lattice temperature within the device is calculated by self‐consistently solving the fully coupled Poisson's equation and transient electron continuity equation together with the transient heat flow equation. The simulation takes account of temperature dependent heat conduction and capacity and includes thermoelectric currents due to temperature gradient. To make the transient thermal simulation more robust, a new analytical expression for heat capacity is used.
POWER 2D: A DEDICATED TOOL FOR TWO‐DIMENSIONAL SIMULATIONS OF OFF‐STATE POWER STRUCTURES
Authors: NOLHIER Nicolas , STEFANOV Evgeny , CHARITAT Georges , ROSSEL Pierre
Published: February 2008

Modelling and designing modern power devices is more and more often performed with two dimensional numerical simulation of basic semiconductor equations. Well‐known simulators, such as PISCES, are powerful and versatile tools, including a lot of physical mechanisms and simulation possibilities. However, this ability to address a very wide range of problems is often paid for by long CPU times and long training periods. These considerations have led us to develop a new two‐dimensional simulator targeted for a very specific goal: the study of the voltage handling capability of high voltage structures. Solving only the Poisson equation allows implementation of very fast numerical algorithms. The calculus of the breakdown voltage is performed by the classical evaluation of ionization integrals, incorporating a new fast iterative technique and an original ionization integral paths determination. Simulation results and comparison with commercial simulator will be presented.
EFFICIENT TRANSIENT SIMULATION OF DISTRIBUTED INTERCONNECTS
Authors: Schutt‐Aine Jose E. , Kuznetsov Dmitri
Published: February 2008

The electrical performance of high‐speed integrated circuits and digital networks strongly depends on the behavior of interconnects between various components of these systems. The prediction of such performance can only be achieved by the used of computer‐aided design and simulation tools. The simulation of high‐speed digital circuits has gained a significant role in the past few years since it is critical in the evaluation of noise levels, signal corruption and signal delay in fast switching circuits. This paper explores the various aspects and techniques for transmission line simulation; in particular, two different methods are described: the scattering parameter method and the optimal method.
A NON QUASI‐STATIC EMPIRICAL MODEL OF THE POWER PIN DIODE FOR CIRCUIT SIMULATION
Authors: Clarke Margaret E , Rahim Suhail
Published: February 2008

Models of power semiconductor devices for use in circuit simulators need to take account of effects which can be neglected in low power device models; they then become very complex and difficult to parameterise. The power PIN diode model described in this paper demonstrates how the use of empirically derived look‐up tables can simplify the characterisation problem and how non quasi‐static effects can be incorporated
ELECTROMAGNETIC ASPECTS OF ELECTRICAL MACHINES
Authors: Kost A.
Published: February 2008

The development of electrical machines is nowadays closely related to the knowledge of the electromagnetic fields throughout the different parts of a machine. Although a machine is often of complicated geometrical structure and of different, mostly nonlinear materials, modern numerical methods and the related software allow calculation of the fields in 2D models and several 3D cases precisely enough in order to derivate from them quantities like energy density distribution, the torque behaviour and characteristics like load and no load. The paper will at first compare numerical methods suited for electromagnetic field calculation in electrical machines. The following topic deals with adaptive mesh generation playing an important role to save computer memory and cpu time. Then examples like a Switched Reluctance Machine, an Asynchronous Machine and a Stepping Motor are shown concerning the results of field calculation. It is shown that anisotropy may have to be taken into account, and finally it is shown that field calculation enables the shape optimization of a machine.
ADAPTIVE REFINEMENT AND OPTIMIZATION OF FIRST ORDER TETRAHEDRAL MESHES FOR ELECTRODYNAMICS
Authors: Gawrylczyk K.M.
Published: February 2008

The geometric properties of finite element mesh are of great importance. The refinement algorithm leads often to very irregular elements. The problem of optimization of 3D‐meshes is unsolved at this time. Only fragmentary methods are known. This paper presents a new concept of optimization algorithm and compares three different strategies for subdivision of tetrahedral elements.
3D EDDY CURRENTS MODELLING BY USING A PARTICULAR TWO COMPONENT TECHNIQUE
Authors: Kladas A.G. , Tegopoulos J.A.
Published: February 2008

Several formulations have been developed solving 3D eddy current problems by the Finite element method based on vector quantities. Scalars, involving only one unknown per node of the mesh seem to be, however, more efficient. A particular scalar potential formulation has already been developed which is able to handle 3D magnetostatics,. This technique has been extended for cases involving eddy currents developed at low frequencies, where the skin effect can be neglected.
COUPLING OF COILS BY AN OPEN MAGNETIC CORE AND ELECTROMAGNETIC SCREEN EFFECTS
Authors: Pawluk K. , Kucharska M.
Published: February 2008

Stationary and quasi‐stationary boundary‐integral models for magnetic and electromagnetic fields in 3D arrangements composed of coils, cores and screens are given. The test results obtained with the use of the authors' test program BIMS are presented.
CALCULATION OF THE TANGENTIAL COMPONENTS OF THE MAGNETIC FIELD STRENGTH FROM VECTOR POTENTIALS FOR 3D
Authors: Demski Wojciech , Szymański Grzegorz
Published: February 2008

Normal components of B and the tangential components of H alike are needed for the force calculation. If the field is calculated numerically, only one of these components is known exactly (in numerical sense), the other one is known only approximately.
THE 3D ANALYSIS OF THE LEAKAGE FIELD IN A TRANSFORMER WITH DISK WINDINGS
Authors: Lukaniszyn M. , Unbehauen R.
Published: February 2008

The calculation of the leakage quasi‐stationary magnetic field of a three‐phase transformer with disk‐windings is presented in the paper. A mathematical model of the transformer based on Maxwell's equations has been applied. Computational results of the short‐circuit reactance have been compared with analytical formulas according to Richter's formulas.
CONTRIBUTION TO THE TRANSIENT ANALYSIS OF INDUCTION MOTORS SOLVING THE ELECTRODYNAMIC EQUATIONS BY USING THE FINITE ELEMENTS METHOD
Authors: Roger‐Folch J. , Lázaro Joares V.J.
Published: February 2008

This paper details how the equations describing the magnetic field inside the motor and the equations of its electric circuit can be integrated in one only system, which can be solved using the Finite Element Method (FEM). When a model of a circuit is used, the solution of the magnetic field equation is the input to calculate the currents of the machine windings. As the magnetic field depends on these currents, it is necessary to follow an iterative process until initial and final currents match. With the technique proposed in this paper, because both magnetic field equations and electric circuit equations are integrated in the system, just in one step, the currents and induced voltages can be obtained with high accuracy and considerable time saving.
TIME‐STEPPING FINITE ELEMENT METHOD IN DESIGNING OF PERMANENT MAGNET SYNCHRONOUS MOTORS
Authors: Szelag Wojciech , Demenko Andrzej , Nowak Lech
Published: February 2008

The time‐stepping finite method of transient analysis in permanent magnet synchronous machines has been presented. This method has been used for determining the steady‐state and dynamic performance of the permanent magnet self‐starting synchronous motor. The movement of the rotor, the saturation of the ferromagnetic core, the properties of permanent magnet and eddy currents in the solid bars of the cage winding have been taken into account.
FEM SHAPING OF THE AIR‐GAP FLUX IN PERMANENT MAGNET DC COMMUTATOR MOTOR
Authors: Cvetkovski Goga , Petkovska Lidija , Čundev Milan
Published: February 2008

This paper deals with an analysis of the effects on the electromagnetic characteristics by changing the dimensions of the permanent magnets such as the overlap angle of the permanent magnets (α) and the radial height of the permanent magnets (hpm) and/or by changing the air‐gap length (δ) and the coil span (y) of the rotor winding.
OPTIMUM GEOMETRY FOR TORQUE RIPPLE MINIMIZATION OF SWITCHED RELUCTANCE MOTORS
Authors: Sahin Funda , Bulent Ertan H. , Leblebicioglu Kemal
Published: February 2008

This paper briefly describes an approach to determine the optimum magnetic circuit parameters to minimize low speed torque ripple for switched reluctance (SR) motors. For prediction of the torque ripple, normalized data obtained from field solution and a neural network approach is used. Comparison of experimental results with computations illustrates the accuracy of the method. The optimization method is briefly described and some results are presented.
DESIGN OF A MULTI‐CHANNEL ROTARY TRANSFORMER FOR APPLICATION TO DIGITAL MAGNETIC RECORDING
Authors: Monson James E.
Published: February 2008

Rotary transformers are important parts of magnetic tape recorders using cylindrical scanners. Typically, heads for recording and playback are mounted on a rotating cylinder which scans the tape at high speed. Writing and reading signals are coupled to the heads through a rotary transformer. This paper describes a design procedure for a multi‐channel, miniaturized transformer for application to high‐density, digital magnetic tape recording. The requirements for the particular example presented were for the transformer to pass six identical recording/playback channels with a minimum insertion loss. The outside diameter of the transformer should be no greater than 16.5mm.
CALCULATION OF FLUX DISTRIBUTION IN TRANSFORMER CORE TAKING HYSTERESIS INTO ACCOUNT
Authors: Rezic A. , Valkovic Z.
Published: February 2008

Calculation of flux distribution in three‐phase three‐limb transformer core has been made using 2D finite element method. The calculation has been performed with and without taking into account lthe hysteresis of magnetic material. Anisotropy of magnetic material has been modelled through the so‐called elliptic permeability model. Comparison of results of calculation and results of measurement has been performed for a scale model of transformer core. An agreement better than 3 per cent has been obtained, for calculated and measured results of third harmonics and of flux distortion factors, when hysteresis has been taken into account. The CPU‐time was 6–10 times longer when hysteresis has been included into calculation.
FIRST STEPS TOWARDS A FULL INTEGRATED CAD SYSTEM FOR ELECTRICAL MACHINES
Authors: Pertusa C. , Astier S. , Lefevre Y. , Lajoie‐Mazenc M.
Published: February 2008

An approach for electrical machines design by using a software which links the sizing procedure to the magnetic field computation is presented in this paper. After reviewing the principles of an electrical machine general design, the process of the development and the use of a special link between the dimensions data and the magnetic field computation is described. The whole solution procedure is conducted automatically. Any change on the machine dimensions can be made and the sequence of the CAD tasks can be prepared and run automatically without any user intervention. The whole procedure is applied to a comparative study of different structures of permanent magnets synchronous motors.
NUMERICAL CALCULATION OF DEMAGNETIZING FACTOR FOR PERMANENT MAGNET
Authors: Muramatsu K. , Nakata T. , Takahashi N. , Fujiwara K. , Ukita H.
Published: February 2008

Recently, rare earth magnets with high coercive force such as Nd‐Fe‐B magnets have been developed. When the magnetic characteristic (M‐H curve) of such a strong magnet is measured, the conventional closed magnetic circuit method using an electromagnet cannot be applicable due to the magnetic saturation of the yoke. Therefore, the open magnetic circuit method has been proposed in which high magnetic fields are generated by using a superconducting or a pulsed magnet. In this method, the correction for demagnetizing field is required. The correction can be done using the demagnetizing factor which is a function of the shape and M‐H curve. The conventional studies take into account only the shape.
COMPUTER AIDED DESIGN OF LOW‐VOLTAGE LINEAR ACTUATOR
Authors: Stoilkov Vlatko , Čundev Milan , Petkovska Lidija , Najdenkoski Krste
Published: February 2008

The paper offers an approach to Computer Aided Design of low‐voltage linear actuators, from the aspect of geometry, as the level preceding their optimal design. Magnetic circuit geometry in addition with the shading pole and exciting coil are taken as the objects of CAD. Complete complex computer program FEM‐3D is developed for this purpose. Finite Element Method — FEM in three dimensional domain is used in order to compute the field distribution, as well as for the evaluation of working characteristics.
DESIGN OPTIMIZATION OF AN ELECTROSTATIC MICROMOTOR WITH AXIAL FIELD
Authors: Di Barba P. , Savini A. , Wiak S.
Published: February 2008

Historically, the idea of using electrostatic phenomena to produce motion has long stimulated the activity of scientists. Although the power generated by electrostatic motors is modest, the absence of windings and ferromagnetic material makes this kind of device competitive for applications characterized by low levels of torque and reduced volumes. During last years a renewed attention appeared towards electrostatic devices in the microscopic scale; their fabrication has been possible thanks to the technology for Si‐integrated‐circuits. In particular, electrostatic micromotors have an increasing role as position actuators when submillimetric movements are required. Methodologies of numerical simulation applied to microdevices are a helpful tool for the designer, who should fulfil criteria often in mutual clash like electromechanical response and fabrication cost. More generally, procedures of automated optimal design are now available, tackling the design problem as the constrained minimization of an objective function suitably set up.
TRANSIENT ANALYSIS OF ELECTROMAGNETIC FIELD PROPAGATION IN THE VICINITY OF MILLIMETRE WAVEGUIDE STRUCTURES WITH AN EFFICIENT FINITE‐DIFFERENCE TIME‐DOMAIN TECHNIQUE
Authors: Kantartzis N.V. , Kriezis E.E. , Tsiboukis T.D.
Published: February 2008

The FDTD approach is rapidly becoming one of the most widely used computational methods in electromagnetics. It is a marching‐in‐time procedure which simulates the continuous actual waves by sampled data numerical analogues propagating in a data space stored in a computer. Thus it leads to a complete understanding of near fields and transient effects. In this paper, the study of the propagating modes and the calculation of the energy forced in the interior of a terminated waveguide is performed with an iterative FDTD technique. Results are obtained and compared with the theoretical ones. Their agreement is almost perfect.
AN IDENTIFICATION AND AN APPROXIMATION OF NONLINEAR CHARACTERISTICS OF THREE‐PHASE WINDING
Authors: Warzecha Adam
Published: February 2008

Electrical machines with nonlinear magnetic circuits are usually modelled by coupling magnetic and electric equations using software for magnetic field investigation. These hybrid methods are practically effective only for steady states, due to their time‐consuming calculations. The separation of both sets of equations will be possible if the unique relationships between linked fluxes and all armature currents become determined. It needs, of course, the neglect of the eddy‐currents in the machine rotor. Generally, they are defined as the partial derivatives of coenergy:
A STUDY ON THE INFLUENCE OF AXIS PARALLEL COOLING DUCTS ON THE FIELD IN HIGHLY SATURATED INDUCTION MACHINES USING NUMERICAL FIELD CALCULATION
Authors: Zwingel R. , Jänicke L. , Stichler M. , Kost A.
Published: February 2008

While optimizing highly utilized induction machines — e.g. for traction applications — the problem of cooling is of importance. The necessary cooling ducts in the rotor lead to saturation problems in the rotor iron. As there exist no analytical means for solving the resulting nonlinear field problem, the effects on the magnetic field have to be investigated by numerical methods. This paper presents the application of the adaptive 2D finite element method for a study of the cooling ducts' effects.
ON THE INDUCTANCE AND FORCE CALCULATION OF A THREE AXES TORQUE MOTOR
Authors: Andresen E. , Anders M.
Published: February 2008

A three axes torque motor for adjusting an airborne telescope to fixed points in the space is shortly presented. Different calculation methods for inductance and force determination and some results are briefly discussed.
MAGNETIC FIELD AND FORCE CHARACTERISTICS OF A SOLENOID ACTUATOR FOR DISPLAY BOARD APPLICATION
Authors: Harris M.R. , Sykulski J.K.
Published: February 2008

The work described concerns a technical assessment of a small linear actuator that was developed for use in large, electronically controlled, electromechanical display boards. Each pixel of the board is driven by an individual actuator and displays alternative colours to the viewer, according to the position occupied by its armature. In operation, the whole screen can be refreshed a few times per second, and an actuator life of about 100M operations is required. No coil excitation must be needed when the armature is stationary, to minimise heating. Detent positions are therefore essential and these are achieved with the aid of a permanent magnet.
A SEMI‐ANALYTICAL METHOD FOR EVALUATION OF THE 3D INHOMOGENEOUS INDUCTION HEATING OF A MOVING HOLLOW CYLINDER
Authors: Gong L. , Hagel R. , Zhang K. , Unbehauen R.
Published: February 2008

A semi‐analytical algorithm for the calculation of 3D induction heating of a uniformly moving conducting and permeable steel shell is presented. The eddy current field problem is solved by the longitudinal component method together with the Fourier transform. The solution of the heat transfer problem under Neumann boundary conditions is obtained by using the separation of variables and considering the movement of the shell.
INFLUENCE OF THE THERMAL DEPENDENCY OF THE CURRENT DENSITY IN THE SOLUTION OF THE HEAT TRANSFER PROBLEM USING THE FINITE ELEMENT APPROACH
Authors: Dias Pinto JoséAmérico , Paulo Breda Coimbra António , Lemos Antunes Carlos F.R.
Published: February 2008

In this paper it is proposed a thermal Finite element formulation that accommodates the current density dependency on the resistivity variation with temperature. As an application example, the steady‐state temperature distribution will be produced for a large 3‐phase induction motor as well as the hot spot temperature for different load conditions. The results produced by the proposed Finite element approach will be compared with the solution obtained considering the current density independent of the temperature as well as with experimental data.
MODELLING AC LOSSES IN HIGH‐TEMPERATURE SUPERCONDUCTORS AS A NONLINEAR DIFFUSION PROCESS
Authors: Stoll R.L. , Mahdi A.E. , Sykulski J.K.
Published: February 2008

Ceramic superconductors experience losses when carrying alternating currents. A first step in an attempt to macroscopically model the loss mechanism is to consider the ac transport current in a ribbon that has a cross‐section of width much greater than thickness. To some extent high‐temperature superconductors behave in a way similar to type II superconductors in which the loss mechanism is described by the critical state model, where the current is assumed to flow with a constant critical density Jc and is independent of the magnetic flux density B and ∂B/∂t. The dominant mechanism is the irreversible motion of fluxoids due to their interaction with the pinning sites, resulting in a form of hysteretic loss that can be represented in macroscopic terms (in a system with only one component of magnetic field) as proportional to ∫HsdBa/T over a complete cycle of period T, where Hs is the surface magnetic field strength and Ba is the space average value of flux density. However, it is found that the high‐temperature materials exhibit strong flux creep effects, and so the critical state model may not provide a sufficient description. To find an alternative formulation it is necessary to consider the flux creep E‐J characteristic of the ceramic material. If a highly nonlinear expression for the resistivity ? can be found, it may be possible to model the flux and current behaviour as a diffusion process.
MAGNETOTHERAPY DUE TO EDDY CURRENTS INDUCED IN NEURAL CELLS BY MAGNETIC STIMULATION
Authors: Krawczyk Andrzej , Skoczkowski Tadeusz , Zyss Tomasz
Published: February 2008

The problem of generating currents of neural cells in human brain has been recently investigated, as it is believed to substitute electroconvulsive therapy (ECT) having the same therapeutic effects but realized in much safer way (painless, non‐invasive and without motor seizure). The magnetic stimulation (transcranial magnetic stimulation — TMS) uses low frequency pulse, from a few cycles per second to a few of tens, magnetic field in order to induce eddy currents in the deeper layer of brain structure.
USING HARMONIC PARAMETERS FOR CHARACTERIZATION OF SOFT MAGNETIC MATERIALS UNDER NON‐SINUSOIDAL CONDITIONS
Authors: Swan Jean‐Paul , Walti Olivier , Brudny Jean‐Fraçois
Published: February 2008

Electrical machines are more and more fed by static converters. These power supplies impose nonsinusoidal statoric waveform to the machines. In these conditions, behaviour of magnetic material can be very different compared with sinusoidal ones. The characterization of magnetic material under non‐sinusoidal excitations is not clearly defined. At the present time, there is not any standard about operating test and specific parameters to be measured in order to get efficient knowledge of soft magnetic materials in distorted excitation mode. The aim of this paper is to present the effect of statoric connections on harmonic characterization parameters. The experimental results correspond to a Fe‐Si non oriented material excited by two different waveforms in a classical Epstein frame. The behaviour of the material is divided into two parts: the fundamental and the harmonic responses. The fundamental parameters are representative of the duty frequency of the machine, harmonic ones give information about additional losses; especially their harmonic distribution. They also allow us to estimate harmonic impact on the fundamental response.
EXPERIMENTAL DESIGN OF PERMANENT MAGNET DEMAGNETIZATION CURVE USING APPROXIMATING EQUATIONS
Authors: Życki Zdzislaw
Published: February 2008

Today the parameters and characteristics of permanent magnets are determined by means of computer as well as analogue‐to‐digital technics. Also digitizing oscilloscopes owing to the advanced digital processing of measured signals may contribute to the processing of measured data (averaging interpolation) and in mathematical operations. The measuring and calculation possibilities together with the possible rapid change of the magnetic state of a magnet due to the pulse magnetization makes the pulse test methods of magnets more and more frequent. The application of either single‐pulse or multiple‐pulse methods is possible. The idea of measurements when using both the latter methods is based on the assumption that the magnet before being subjected to tests is magnetized up to the saturation state. The single‐pulse method described briefly in and more comprehensively in, consists in recording and suitably processing the set of discrete values having a finite number of elements which appear during a single remagnetizing pulse of the magnet. The range of the recorded values covers flux densities from −Br to +Br i.e. covers one half of the hysteresis loop. In consequence, it is necessary to apply in this procedure a magnetic field k‐times exceeding the coercive force HcB of the tested magnet (depending on its type).
INTEGRATING ELECTROMAGNETIC FIELDS INNOVATIONS IN AN UNDERGRADUATE CURRICULUM
Authors: Litynski Daniel M. , Reinhard Karl E. , Tousley Bradford C.
Published: February 2008

Introduction The Department of Electrical Engineering (EE) and Computer Science (CS) educates future national defence leaders in the theory and practice of its two disciplines and supports the overall USMA purpose of “providing the nation with leaders of character who serve the common defense”. Electromagnetic field theory and applications are fundamental to electrical engineering and play an important role in the Department's curriculum. In 1986, the Department began a modernization programme to upgrade its engineering curriculum, facilities, and equipment. This article describes the electromagnetics instructional thread in the curriculum and the laboratory facilities supporting that instruction.
THE ROLE OF THE KNOWLEDGE ON ELECTROMAGNETISM FOR ELECTRIC ENGINEER EDUCATION
Authors: Sikora R. , Zeńezak M.
Published: February 2008

Introduction Depending on the way of teaching process organization the theory of electromagnetic field is considered either as a part of theoretical electrical engineering or as an individual subject. The electromagnetic field theory plays a double role in the education of electric engineers: comprehensive or specialized one. However, the electromagnetic field can be treated from the other point of view. It can be lectured with pointing out the calculation methods or phenomena occurring in “pure” electromagnetic field, and on the other hand, with reference to phenomena occurring in coupled fields, where those fields are affecting non‐living or having objects.
Mechanical processing of copper‐clad laminates
Authors: Shemilt H.R.
Published: February 2008

In this series of articles on printed circuit troubleshooting, the author in this issue of the journal focuses his attention on the mechanical aspects of printed circuit board manufacture by examining the problems commonly encountered in guillotining, roller cutting, piercing and blanking, and milling and routing. This article is the fourth and last in this series by the author.
National and International Committees for Printed Wiring
Authors: Trigg P.A.
Published: February 2008

In this issue of the Journal we continue with our series on National and International Committees for Printed Wiring by examining the work carried out by the Radio and Electronic Components Manufacturers Federation (RECMF). Within the Federation there are two Committees involved with printed circuits, namely, the Printed Circuit Manufacturers Group and Panel Z—Printed Circuit Techniques and Materials. In this article it is the former which is discussed. Note: Readers who are associated with, or are members of committees dealing with printed circuits or applied techniques are invited to contact the Editor with a view to preparing an article on their behalf for publication in this series. This invitation is extended to readers on a world wide basis.
An application of automatic test equipment for detecting and identifying faults on printed circuit boards before functional testing
Authors: Lester R.S.
Published: February 2008

The installation of automatic test equipment can result in substantial savings in fault diagnosis costs if the equipment is able to identify faults down to component level. Types and causes of faults together with techniques to identify them are discussed in the article together with financial justification for the equipment in various typical situations.
Conferences and exhibitions
Authors: Taylor M.
Published: February 2008

IMF/Printed Circuit Group—Annual Conference: Organiser: Institute of Metal Finishing Venue: Queens Hotel, Eastbourne Date: 13–15thMarch, 1979 The Printed Circuit Group of the Institute of Metal Finishing held their Annual Conference at the Queen's Hotel, Eastbourne, on the 13th to 15th March. Twenty technical papers of the usual high standard were presented, and in addition there was one period devoted to a debate and a further period at which a panel of experienced personnel dealt with technical queries. In addition there was a well organised table‐top exhibition.
Manufacture of flexi‐rigid boards
Authors: Scarlett John A.
Published: February 2008

The manufacture of flexi‐rigid multilayer boards poses a number of problems which are not met with in ordinary multilayer production or in the making of plain flexible circuits. Steps have to be taken to overcome the poor dimensional stability of thin polyimide foils during processing and to ensure that those portions of the assembly which need to be rigid are bonded whilst flexible portions are left unbonded other than for a cover coat. Pressure on cover coated flexible areas must be maintained during bonding without allowing resin to now over these areas, and finally the bonded unit must be profiled, often with superimposed flexible areas of different shapes. This article describes some of the techniques used by a leading manufacturer to overcome these problems. Several of the processes described are covered by patents held by Exacta Circuits Ltd. This article is an extract from a forthcoming book ‘Handbook of Multilayer Printed Circuits’ to be published at the end of the year by Electrochemical Publications Ltd., 8 Barns Street, Ayr, Scotland.
Labor Market Deregulation and Industrial Conflict in New Democracies: A Cross-National Analysis
Authors: Alemán José
Published: February 2008

This article studies the effect of recent labor market reforms on industrial relations in new democracies (1994–2003). The literature on labor politics posits two channels through which labor market deregulation may relate to industrial conflict. Wage deregulation may lower wage costs, increasing industrial conflict. Employment deregulation, however, can reduce the ability of workers to act collectively. Using methods uniquely suited for panel data analysis, the study reveals a number of important findings. First, whereas labor quiescence went hand in hand with relatively modest increases in earnings in a number of established democracies, modest wage increases are generally linked with more labor militancy in new democracies. Higher wage and employment regulation minimize wage reductions, lowering the incidence of strikes. Finally, wage regulation has the largest effect on aggregate wages and consequently on the incidence of strikes and lockouts.
Conflict-Triggered Goal Shielding
Authors: Goschke Thomas , Dreisbach Gesine
Published: February 2008

Action control in a changing environment requires that one shield current goals from distracting information (goal shielding) and at the same time monitor the environment for potentially significant stimuli that may afford a goal switch (background monitoring). Response conflicts modulate the balance between goal shielding and background monitoring, as indicated by reduced susceptibility to interference after response conflicts. Such conflict-adaptation effects have been attributed to enhanced recruitment of cognitive control on trials following conflicts. Here we show that conflict triggers increased goal shielding on the conflict trial itself. Subjects performed a spatial compatibility task during which they had to notice rare prospective memory cues. Such cues were overlooked more often on conflict trials than on nonconflict trials, a result indicating that shielding of the current goal and inhibition of distractors were increased on the current trial when it involved a response conflict. Thus, evidence for enhanced recruitment of control following conflict may partly reflect aftereffects of goal shielding on the conflict trial itself.
Age-Related Changes in the Episodic Simulation of Future Events
Authors: Addis Donna Rose , Wong Alana T. , Schacter Daniel L.
Published: February 2008

Episodic memory enables individuals to recollect past events as well as imagine possible future scenarios. Although the episodic specificity of past events declines as people grow older, it is unknown whether the same is true for future events. In an adapted version of the Autobiographical Interview, young and older participants generated past and future events. Transcriptions were segmented into distinct details that were classified as either internal (episodic) or external. Older adults generated fewer internal details than younger adults for past events, a result replicating previous findings; more important, we show that this deficit extends to future events. Furthermore, the number of internal details and the number of external details both showed correlations between past and future events. Finally, the number of internal details generated by older adults correlated with their relational memory abilities, a finding consistent with the constructive-episodic-simulation hypothesis, which holds that simulation of future episodes requires a system that can flexibly recombine details from past events into novel scenarios.
Sensitivity to Object Viewpoint and Action Instructions During Search for Targets in the Lower Visual Field
Authors: Forti Sara , Humphreys Glyn W.
Published: February 2008

We contrasted visual search for targets presented in prototypical views and targets presented in non-prototypical views, when targets were defined by their names and when they were defined by the action that would normally be performed on them. The likelihood of the first fixation falling on the target was increased for prototypical-view targets falling in the lower visual field. When targets were defined by actions, the durations of fixations were reduced for targets in the lower field. The results are consistent with eye movements in search being affected by representations within the dorsal visual stream, where there is strong representation of the lower visual field. These representations are sensitive to the familiarity or the affordance offered by objects in prototypical views, and they are influenced by action-based templates for targets.
Temporal Selection is Suppressed, Delayed, and Diffused During the Attentional Blink
Authors: Vul Edward , Nieuwenstein Mark , Kanwisher Nancy
Published: February 2008

How does temporal selection work, and along what dimensions does it vary from one instance to the next? We explored these questions using a phenomenon in which temporal selection goes awry. In the attentional blink, subjects fail to report the second of a pair of targets (T1 and T2) when they are presented at stimulus onset asyn-chronies (SOAs) of roughly 200 to 500 ms. We directly tested the properties of temporal selection during the blink by analyzing distractor intrusions at a fast rate of item presentation. Our analysis shows that attentional selection is (a) suppressed, (b) delayed, and (c) diffused in time during the attentional blink. These effects are dissociated by their time course: The measure of each effect returns to the baseline value at a different SOA. Our results constrain theories of the attentional blink and indicate that temporal selection varies along at least three dissociable dimensions: efficacy, latency, and precision.
Auditory Change Detection: Simple Sounds Are Not Memorized Better Than Complex Sounds
Authors: Demany Laurent , Trost Wiebke , Serman Maja , Semal Catherine
Published: February 2008

Previous research has shown that the detectability of a local change in a visual image is essentially independent of the complexity of the image when the interstimulus interval (ISI) is very short, but is limited by a low-capacity memory system when the ISI exceeds 100 ms. In the study reported here, listeners made same/different judgments on pairs of successive “chords” (sums of pure tones with random frequencies). The change to be detected was always a frequency shift in one of the tones, and which tone would change was unpredictable. Performance worsened as the number of tones increased, but this effect was not larger for 2-s ISIs than for 0-ms ISIs. Similar results were obtained when a chord was followed by a single tone that had to be judged as higher or lower than the closest component of the chord. Overall, our data suggest that change detection is based on different mechanisms in audition and vision.
Making don't Knows Make Sense: Bourdieu, Phenomenology and Opinion Polls
Authors: Myles John
Published: February 2008

Despite Bourdieu's huge contribution in sociologically operationalizing some of the principles contained in Husserlian phenomenology, this paper argues that by drawing more from this source his criticisms of opinion polls can be extended theoretically and methodologically. In particular, by being aware of the transitions from doxa or ‘dispositional opinion’ to reflective opinion, Husserlian phenomenology gives a theoretical basis which we can draw on to make concrete methodological elaborations, such as in the use of ‘identification bid’ questions, of Bourdieu's account of the drawbacks of opinion polls.
What's in a Name? An Exploration of the Significance of Personal Naming of ‘Mixed’ Children for Parents from Different Racial, Ethnic and Faith Backgrounds
Authors: Edwards Rosalind , Caballero Chamion
Published: February 2008

This article is concerned with how and why parent couples from different racial, ethnic and faith backgrounds choose their children's personal names? The limited literature on the topic of names often focuses on outcomes, using birth name registration data sets, rather than process. In particular, we consider the extent to which the personal names that ‘mixed’ couples give their children represent an individualised taste, or reflect a form of collective affiliation to family, race, ethnicity or faith. We place this discussion in the context of debates about the racial and faith affiliation of ‘mixed’ people, positing various forms of ‘pro’ or ‘post’ collective identity. We draw on in-depth interview data to show that, in the case of ‘mixed’ couple parents, while most wanted names for their children that they liked, they also wanted names that symbolised their children's heritages. This could involve parents in complicated practices concerning who was involved in naming the children and what those names were. We conclude that, for a full understanding of naming practices and the extent to which these are individualised or affiliative it is important to address process, and that the processes we have identified for ‘mixed’ parents reveal the persistence of collective identity associated with race, ethnicity and faith alongside elements of individualised taste and transcendence, as well as some gendered features.