bluuebunny/crossref_metadata_2025 huggingface dataset:
INTRINSIC HIGH‐FREQUENCY OSCILLATIONS AND EQUIVALENT CIRCUIT MODEL IN THE NEGATIVE DIFFERENTIAL RESISTANCE REGION OF RESONANT TUNNELING DEVICES
Authors: Buot F.A. , Jensen K.L.
Published: February 2008

Intrinsic high‐frequency oscillations (≈2.5 THz) in current and corresponding quantum well density, which have been simulated for a fixed bias voltage in the Negative Differential Resistance (NDR) region of the Current‐Voltage (I‐V) characteristics of a Resonant Tunneling Diode (RTD), suggest an equivalent nonlinear autonomous circuit model. The intrinsic circuit parameters are calculated directly from the results of the quantum transport numerical simulations. These consist of a resistor in series with a two‐branch parallel circuit, one branch consists of a capacitor and the other branch consists of an inductor in series with a nonlinear resistor. It is however suggested that much more complex external circuit‐induced behavior can occur in real RTD experiments.
TWO‐DIMENSIONAL MODELING OF QUANTUM‐WELL SEMICONDUCTOR LASERS
Authors: Li Z.‐M. , Dzurko K.M. , McAlister S.P.
Published: February 2008

We have developed a two‐dimensional model for quantum‐well lasers which solves, self‐consistently, the semiconductor equations together with the complex scalar wave equation and the photon rate equation. To predict the threshold current accurately we have included the wavelength‐ and position‐dependence of the gain and the spontaneous emission. For the complex wave equation successive over relaxation (SOR) is used with two adaptive acceleration parameters for the complex wave amplitude and for the eigenvalue. Since the rate equation near threshold can be driven into divergence during iteration for a steady state solution, we have introduced a special damping technique to overcome this problem. Our model enables us to predict the characteristics of a quantum‐well laser with a minimal number of empirical constants. The output of the model includes light‐current characteristics, and the current and optical field intensity distributions. We show the results of a calculation for a graded‐index separate‐confinement heterostructure single quantum‐well (GRIN‐SCH SQW) laser.
AN EMPIRICAL MODEL FOR THE ELECTRONIC STOPPING OF BORON IN SILICON
Authors: Hobler G. , Pötzl H. , Palmetshofer L. , Schork R. , Lorenz J. , Tian C. , Gara S. , Stingeder G.
Published: February 2008

A three‐parameter model for the electronic stopping power of boron in silicon is presented. The model parameters are determined from implantations into amor‐phous silicon and from channeling implantations into <100> and <100> silicon. Simulated boron profiles obtained with the new model, with the Lindhard model, and with the Oen‐Robinson model, respectively, are compared with experimental data on channeling and tilted implantations at 17 and 150 keV.
WAVEFORM RELAXATION BASED CIRCUIT OPTIMIZATION
Authors: Olde Bo , Mattisson Sven
Published: February 2008

A multicomputer implementation of a circuit optimization program is presented. The program, called COCO, is tailored for the design problems encountered when the large signal dynamic response of VLSI circuits is to be optimized. The optimization part of the program runs on a host computer and controls the action of a concurrent circuit simulation program running on a multicomputer. Thus, when run on a parallel computer, COCO is able to exploit concurrency during the simulation phase.
MONTE CARLO TECHNIQUE FOR SIMULATION OF HIGH ENERGY ELECTRONS
Authors: Nedjalkov M. , Vitanov P.
Published: February 2008

A Monte Carlo (MC) technique useful for calculation of the high energy tail of the distribution function (d.f) is proposed. The well known MC technique for simulation in rarely visited region splits the real history of the particle, that has entered in this region, in N subhystories with weights 1/N. But the lucky event for entering must be waited to happen during the simulation. A presentation of the d.f is found here, which allows, knowing the d.f in the low (common) energy region, to simulate only high energy events. This technique can be used for example when gate current in submicrometer MOS devices is calculated.
MONTE CARLO SIMULATION OF SiGe/Si MESFETs
Authors: Gokhale M. , Anwar A.F.M. , Carrol R.D. , Jain F.C.
Published: February 2008

The current‐voltage (Id—Vd) characteristics and microwave performance of Si1−xGex MESFETs are discussed. The 2D Poisson's equation along with the drift and diffusion equation are solved using a finite difference technique to calculate device parameters such as gm and fT. The low field carrier mobility is computed by using a single partice Monte Carlo program. In the simulation all relevant scattering mechanisms are accounted for.
DISCRETIZATION METHODS AND PHYSICAL MODELS FOR SIMULATING LEAKAGE CURRENTS IN SEMICONDUCTOR DEVICES WITH APPLICATION TO MODELING TRENCH‐DRAM CELLS
Authors: Johnson J.B. , Voldman S.H. , Linton T.D.
Published: February 2008

Challenges to a robust and accurate implementation of electric‐field‐enhanccd thermal‐generation mechanisms in a drift‐diffusion‐based semiconductor‐device simulation code are discussed and solutions proposed. The implementation of the physical models and associated numerical methods is applied to the simulation of leakage currents in trench‐DRAM cells.
MUSIC — A MULTIGRID SIMULATOR FOR IC FABRICATION PROCESSES
Authors: Mijalković S. , Pantić D. , Prijić Z. , Mitrović S. , Stojadinović N.
Published: February 2008

This paper describes a new two‐dimensional process simulation program MUSIC (MUltigrid Simulator for IC fabrication processes) which is prospective for the efficient IC process simulations due to its capability to eliminate strong bottlenecks present in the existing two‐dimensional process simulation programs. Multistep processes, including ion implantation, diffusion and oxidation, can be simulated, giving the doping profile. Robust and efficient adaptive multigrid numerical techniques for the simulation of coupled multiparticle diffusion processes are used. The capabilities of program MUSIC are illustrated by the results of the process flow simulation of a typical NMOS and bipolar transistors fabricated in BiCMOS technology.
STATUS OF THE DEVICE SIMULATOR PRISM
Authors: Schoenmaker Wim , Vankemmel Rudi , Cartuyvels Rudi , Magnus Wim , Tijskens Bert
Published: February 2008

PRISM assumes that the physics of semiconductor devices, at least the electrical behaviour, can be explained with the following equations. Poisson equation:
ACCURATE INTEGRATIONS IN THE BOUNDARY ELEMENT METHOD FOR 2D‐ EDDY CURRENTS
Authors: Shen Jinxing , Kost Amulf
Published: February 2008

An accurate integration is one of the key steps in the application of the Boundary Element Method (BEM) to the computation of electromagnetic fields. The integrations are generally calculated by means of Gaussian Quadrature Formulas, which work efficiently when d ≥ 1, where d = δ/Lj and δ is the minimum distance from a source point to an element of length Lj. But difficulties will occur when the source point is situated at or very near to the field point (i.e. r=0 or r<ε with r≠0), leading to a singular or nearly singular integration.
AN EFFICIENT OPEN BOUNDARY FINITE ELEMENT METHOD FOR ELECTROMAGNETIC PROBLEMS
Authors: Stochniol A.
Published: February 2008

An efficient approach for the solution of open boundary field problems with the finite element method is presented. The principle of the solution method consists in the spatial mapping of the infinite unbounded region, exterior to the main region of interest, onto a finite region and then in solving the closed boundary problem for two connected regions.
COMPUTATIONAL MODELS FOR STAGGERED BUTTED JOINTS IN LAMINATED FERROMAGNETICS
Authors: Silvester Peter P. , Omeragić Dževat
Published: February 2008

The conventional representation of a laminated packet of electrical sheet steel as a homogeneous but anisotropic material is extended by treating any butted joints in the packet as a distinct homogeneous, two‐dimensionally nonlinear, material. Its magnetic characteristics are derived from the energy increment that results from closing the gap, obtained by solving the two‐dimensional field problem in the gap region. This technique is rigorously valid for any anhysteretic, nonlinear, anisotropic material.
FINITE ELEMENT MODELLING OF INDUCTIVE SENSORS
Authors: Sykulski J.K. , Stoll R.L.
Published: February 2008

Practical aspects of finite‐element modelling of magnetic fields and calculating integral parameters such as a reflected impedance in inductive sensing devices are discussed. The electromagnetics of such sensors is briefly explained and some practical modelling techniques are put forward. Excellent agreement with experiment is reported.
MODELLING VERY SMALL AIR GAPS BETWEEN MAGNETIC SURFACES IN FINITE‐DIFFERENCE FIELD SOLUTIONS
Authors: Stoll R.L.
Published: February 2008

The finite‐difference discretization required to model accurately very small air gaps between ferromagnetic surfaces can be enormous. Provided the surrounding permeability is high, a simple representation of the air gap can be formulated within a finite‐difference equation, thus substantially reducing the number of nodes required. The method is applied to the determination of the force on a rectangular magnetic filler bar in the centre slot of the pole face of a turbogenerator rotor.
SOME ASPECTS OF ADDITIONAL LOSSES IN STEP‐LAP JOINTS OF TRANSFORMER CORE
Authors: Valković Z.
Published: February 2008

Magnetic properties of step‐lap joints have been investigated experimentally on scale‐models of a three‐phase three‐leg transformer core. The influence of core induction, number of steps and overlapping length has been investigated.
NEW ELECTROMAGNETIC PUMP BASED ON THE EFFECT OF MAGNETIC FLUX CONCENTRATION
Authors: Bessho K. , Krawczyk A. , Nakamoto K.
Published: February 2008

Eddy currents, being of either positive or negative nature, have recently gained more and more importance in their positive aspects. New devices that may be called “eddy current based” have been worked out in recent years. This paper intends to present a quite new application of eddy currents which is an electromagnetic pump of novel design. The pump can be employed to transport liquid sodium for the Fast Breeder Reactor or other conducting materials, like melted metals. Eddy currents are used here for two pur‐poses: the first one is the typical usage to create electromagnetic force (as in tube‐type linear motors or conventional electromagnetic pumps) while the second one is just newly invented. Normally, in linear motors or conventional electromagnetic pump the air gap is relatively big which makes the leakage flux increase. Then the electromagnetic force is strongly reduced. To overcome this negative influence of the air‐gap, i.e. to minimize the leakage flux a conducting plate of special structure is inserted into the exciting coil. The first idea of it was given by K. Bessho for high magnetic field generation. Although the purpose of the application presented here is different from the initial one the idea is common and it is likely to be used for other purposes too. The basic features of the pump resulting from both numerical and experimental investigations are presented in the paper.
FIELD AND FORCE CALCULATION OF ELECTROMAGNET WITH HIGH FREQUENCY OPERATION
Authors: Komeza K. , Tarocinski J. , Wiak S.
Published: February 2008

This paper deals with the field and force calculation in a model electromagnet which is the power drive of the shuttle loom. Hermitian hierarchical finite elements have been successfully applied to the field and force computation of the electromagnet. The computational results have been reported.
A 3‐D SPACE ANALYSIS OF AN ELECTROMAGNETIC FIELD IN A THREE PHASE INDUCTION PUMP WITH A COMPENSATING WINDING
Authors: Gierczak E. , Mendrela E.A.
Published: February 2008

Three‐phase inductors with a magnetic travelling field are often used to pump a liquid metal or to stir it in induction stirrers. Due to a finite length of inductor an alternating magnetic field is generated as an additional component to the magnetic travelling field. When an induction pump is used with a rectangular shaped transport channel and a flat inductor shown in Fig.1,this component deforms a force distribution in liquid metal and causes some local whirls. This may play a positive role in stirring of molten metal but it cannot be tolerated in the channel of an induction pump,where a smooth flow is required. In that case the alternating magnetic field should be eliminated. It can be done by using an additional compensating winding or by applying a special type of three‐phase winding that eliminates or reduces the alternating field component. The objective of this paper is to examine the magnetic field and force distribution in molten metal of an induction pump when the alternating magnetic field component is compensated.
APPLICATION OF COUPLING FIELD‐CIRCUIT FORMULATION FOR FAST ACTING ELECTROMAGNETIC ACTUATORS SUPPLY SYSTEMS DESIGN
Authors: Nowak Lech
Published: February 2008

An electromechanical converter supplied with the special feed systems which accelerate its operation in transient states is investigated. To solve the problem the field‐circuit procedure is applied. The transients in an axisymmetric plunger‐type actuator with conducting core, after the application of supply voltage, taking the movement of some core parts into account are considered. The converter winding is composed of two coils connected with a system of external elements: resistors, capacitors and transistors.
STRAY LOSSES IN A SINGLE‐SIDED LINEAR INDUCTION MOTOR
Authors: Gieras Jacek F.
Published: February 2008

The paper deals with the method of the stray losses calculation in single‐sided linear induction motors. The stray losses produced by the higher space harmonics of the primary winding MMF and by the primary slots have been discussed.
SIMPLE METHOD FOR CALCULATING THE PEAK TORQUE OF A SWITCHED RELUCTANCE MOTOR: A COMPUTATIONAL INVESTIGATION
Authors: Harris M.R. , Sykulski J.K.
Published: February 2008

The tractive force between two slightly overlapped steel teeth exhibits a remarkably linear relationship with m.m.f. over a considerable range of variables. This occurs despite complex and varying patterns of field at the tooth surfaces, with local flux densities approaching 3 Tesla. A theoretical explanation is not readily available. Results of a computational investigation are reported and analytical approaches considered.
3‐D CALCULATION OF MAGNETIC FIELD AND INDUCTANCE OF A REACTOR, WITH OPEN MAGNETIC CORE, BY INTEGRAL EQUATIONS METHOD
Authors: Zakrzewski K. , Tomczuk B.
Published: February 2008

The reactor with rectangular shape of the winding turns and open magnetic core has been considered in the work. The integral equation has been solved numerically and components of magnetic flux density as well as leakage inductance of the winding have been computed for the object. A computer program for the analysis of magnetically open problems and a procedure, for numerical calculation of inductance, have been worked out. The computer codes were implemented for IBM PC/AT. The calculations were verified by measurements for physical model of the reactor.
MODELLING OF FLAW RESPONSES IN EDDY CURRENT TESTING
Authors: Gawrylczyk K. , Gramz M. , Gratkowski S. , Sikora R. , Zidlkowski M.
Published: February 2008

This paper presents the practical configuration for detecting cracks in material, by applying an electromagnetic field along the largest dimension of the crack. An electromagnetic field formulation is proposed using Helmholtz's equation and Biot‐ Savart's law. The system equation is solved by using the finite element method (FEM). The exemplary results of calculation ‐ eddy currents lines in material and relative resistance versus probe position are presented.
INVESTIGATIONS OF A NEW IMPACT IONIZATION MODEL FOR SUBMICRON DEVICES
Authors: Souissi Kamel , Tang Henry H.K.
Published: February 2008

We discuss the device applications of a new impact ionization model. This model is based on a new formulation of the impact ionization rate for bulk semiconductors, derived from solvable high‐field Boltzmann transport equations. The model inputs are relaxation times which simulate the dominant electron‐phonon scatterings and are calibrated by realistic Monte Carlo simulations. Our impact ionization model is shown to be physically motivated and is easily implemented in the standard hydrodynamic device simulators HFIELDS and FIELDAY. An efficient numerical scheme is used to simulate three thin‐base silicon bipolar transistors. Results based on this impact ionization model are found to agree well with the experimental multiplication factors over a large range of applied voltages. These results are contrasted with the more phenomenological treatment of Scholl and Quade which is shown to be a low‐field limit of our model.
TWO‐DIMENSIONAL SIMULATIONS OF CUTOFF FREQUENCY CHARACTERISTICS FOR AlGaAs/GaAs HBTs WITH PLANAR STRUCTURES
Authors: Horio K. , Nakatani A.
Published: February 2008

Cutoff frequency ƒT characteristics for AlGaAs/GaAs HBTs with planar structures are studied, by two‐dimensional simulation, with an emphasis placed on their dependences on the collector parameters. It is shown that the sub‐collector resistance becomes an important factor to achieve a higher ƒT in the high current region, and so it should be made as low as possible. Effects of introducing semi‐insulating external collectors are also studied. It is shown that the introduction of semi‐insulating layer is effective to improve the ƒT characteristics provided that it is slightly away from the intrinsic collector region.
LATERAL GATE BIAS EFFECTS IN RESISTIVE GATE NMOS TRANSISTORS
Authors: Schieke P , du Plessis M
Published: February 2008

In order to simulate resistive gate transistors, a one‐dimensional simulator, which permits the use of multiple gate contacts on the transistor structure, has been developed. In the case of the multiple gate contact resistive gate transistor, there is a voltage gradient in the gate. The gate voltage thus varies at each point in the channel of the transistor. A gate structure was designed with a geometric profile that gave either a decreasing or an increasing electric field in the gate, depending on the differential voltage applied to the gate contacts. In the saturation region, this parabolically shaped gate structure resulted in a linear relationship between the drain current and the differential gate voltage or gate current. A significant result obtained was the reversal of the drift current direction at certain bias levels. It was also found that the diffusion current may dominate in the strong inversion region of the channel of an NMOS transistor with a resistive gate.
SIMULATION OF THE ELECTRICAL BEHAVIOUR OF GaAs MESFETS WITH DOPING AND LOW‐FIELD MOBILITY PROFILES IN THE ACTIVE LAYER
Authors: Schwierz Frank
Published: February 2008

A quasi‐two‐dimensional analytical model for GaAs MESFETs is proposed. It enables the calculation of the dc, the small‐signal, and the noise behaviour of GaAs MESFETs and takes into account both doping and low‐field mobility profiles in the active layer of the transistor. It is shown that the profile of the low‐field mobility near the bottom of the active layer has a considerable influence on the minimum noise figure.
MODULE LEVEL PERFORMANCE SIMULATOR FOR ELECTRICAL AND OPTICAL INTERCONNECTS
Authors: Guan L. , Pusarla C. , Halkias G. , Christou A.
Published: February 2008

As speed and complexity of electronic systems increase, the interconnect density has become the critical limitation to the performance of electrical systems. The performance of computing and switching systems can be increased by optimizing the interconnect density and throughput. At the board to board level, electrical interconnects at high speeds require a bulky and expensive backplane. At the chip to chip area, the allocation of interconnects limits the performance of the chips. Electrical lossy lines limit the maximum interconnect distance due to reflections, risetime degradation, increased delay, attenuation and cross talk . Optical interconnects present the possibility of solving the interconnect problems by potentially achieving a high bandwidth and high volume density of channels. At high data rates (greater than 1 Gb/s) several channels may operate with negligible mutual interference.
THE USE OF REALISTIC BANDSTRUCTURE IN IMPACT IONISATION CALCULATIONS FOR WIDE BANDGAP SEMICONDUCTORS: APPLICATION TO INP AND GaAS
Authors: Wilson S.P. , Brand S. , Beattie A.R. , Abram R.A.
Published: February 2008

A non‐local pseudopotential model is used to generate realistic bandstructure for InP and GaAs. This is used to calculate the thresholds for impact ionisation and ionisation rates in these materials as a function of direction in wavevector space. Results are presented for a range of transitions.
SIMULATION OF DEFECT ASSISTED TUNNELING AND ITS EFFECT ON I‐V CHARACTERISTICS IN RESONANT TUNNELING DIODES
Authors: Lee Sangyong , Weichold Mark H. , Parker Donald L. , Spencer Gregory F.
Published: February 2008

This paper presents a self‐consistent I‐V simulation technique for an RTD with defect wells placed inside the barriers. The motivation of this paper was to model the excess valley current by a defect‐assisted tunneling mechanism. We have calculated the transmission coefficients and I‐V characteristics self consistently with Poisson's equation coupled to quantum mechanical tunneling through the barrier. The shape of transmission coefficient was broadened and greatly enhanced in the off‐resonance region when the defect well was introduced in the barriers. Our results gave a good qualitative estimation of the valley current and the peak to valley current ratio (PVCR).
SOME APPLICATIONS OF INTEGRAL EQUATIONS FOR 2‐D ELECTROMAGNETIC FIELD ANALYSIS
Authors: Apanasewicz Stanislaw
Published: February 2008

In presented paper the algorithm for 2‐d electromagnetic field calculation using the simple layer potential is describing. Owing to the simple operation — the location of lines of integration in the metall medium (line Γ1) and in the nonconducting medium (line Γ2) — it succeeded to eliminate of integral singularities. The boundary conditions are taking on the Γ0 — line which separates above — mentioned two media.
SPECIAL FINITE ELEMENTS FOR EFFICIENT COMPUTATION OF MAGNETIC HELD IN r‐z AND r‐φ GEOMETRY
Authors: Gratkowski Stanislaw
Published: February 2008

This paper presents ‘infinite’ finite elements for magnetic field problems with open boundaries in r‐z and r‐φ geometries. The formulations of the elements are so simple that closed‐form expressions for the element matrix are obtained. In order to test the new elements, simple examples, for which analytical solutions exist, are analysed.
3D SCALAR OR VECTOR MAGNETIC FIELD — HOW ONE CAN SEE IT
Authors: Ziólkowski Marek
Published: February 2008

The paper presents the features of an interactive “cube lens” approach to overcome some problems of visualization of 3D scalar or vector magnetic field. The “cube lens” is defined as a cubic part of the space where the 3D field is calculated using any method. The field data are given over a regular cubic grid. Several methods of scalar and vector fields visualization are presented.
NUMERICAL INTEGRATIONS IN THE BEM FORMULATION WITH E AND H FOR 3‐D EDDY CURRENTS
Authors: Shen Jinxing , Yuan Jiansheng , Kost Arnulf
Published: February 2008

The computation of 3‐D eddy current problems is an important topic both in theoretical and engineering areas. Based on Green's theorem, Kost theoretically developed a BEM formulation for general 3‐D nonlinear eddy current problems. The parallel implementation of this formulation in the linear case has been made on a massively parallel supercomputer, where a constant triangular element was used.
COIL INDUCTANCE DEPENDENT ON SCREEN AND CORE PLATES
Authors: Pawluk K. , Krauze U. , Kucharska M.
Published: February 2008

Metallic elements placed in the vicinity of coils and conducting rings exert an influence on the inductance of them. Authors' BIMS package based on the boundary‐integral approach leads up to determine the monopole and/or dipole surface densities of the ‘magnetic charge’ on the walls of simple metallic boxes. The special considerations have been performed in order to study the influence of these boundary magnetic charge densities on the magnetic flux of the coils. The general algorithms for computing the magnetic flux is presented.
THREE‐DIMENSIONAL ADAPTIVE MESH REFINEMENT IN FINITE ELEMENT COMPUTATIONS OF ELECTROMAGNETIC FIELDS
Authors: Li C , Ren Z. , Razek A.
Published: February 2008

In the applications of FEM. a compromise between the accuracy and the computation cost is often required, especially when 3D cases are concerned Adaptive mesh refinement is a good answer to this demand.
3‐D CALCULATION OF ZERO‐COMPONENT FLUX IN THREE‐PHASE THREE‐COLUMN TRANSFORMER
Authors: Zakrzewski K. , Tomczuk B.
Published: February 2008

The paper discusses the problem of space distribution of zero‐component magnetic flux generated in three‐column transformer. For 3‐D magnetic field calculation the method of integral equations was used. The numerical calculations were made for physical model of the transformer and compared with experimental results. The accuracy of the calculations of the magnetic field, achieved in the work, proves that the modelling may be used as a computer aided designing tool.
ELECTROMAGNETIC FIELD THEORY AS A BASIS TO THE ANALYSIS OF SWITCHED RELUCTANCE MOTOR DYNAMIC
Authors: PhD MSc A.Pelikant
Published: February 2008

In this work author proposed complex alghorithm where field and circuit parts are strictly linked so that circuit and mechanical parameters are calculated strictly. In this case field analysis was based on two dimmensional integrated boxes finite difference, distributions of the flux density for some excitations values and rotor positions allow to calculate some very important integral parameters, flux inkeage and the coenergy — static torque. In presented paper author show full description of the motor dynamic with the speed feed back.
TRANSIENT SIMULATION OF PERMANENT MAGNET DC COMMUTATOR MOTORS USING THE FINITE ELEMENT APPROACH
Authors: Wing M. , Gieras J.F.
Published: February 2008

The transient performance of permanent magnet dc commutator motors has been simulated using a two dimensional finite element model. The simulations of start‐up characteristics and braking conditions are concentrated on. The finite element approach in simulating transients of dc motors is discussed with a proposed solution to the problem A finite element solution that ignores the induced eddy current losses in the small volume rotor is shown as a quick solution that gives fair accuracy. The results are compared against experimental data obtained for a 370 W permanent magnet dc motor using a data acquisition system.
END COMPONENT OF STATOR LEAKAGE REACTANCE OF SQUIRREL CAGE INDUCTION MOTORS
Authors: Yannopoulos‐Lascaratos P.P. , Tegopoulos J.A.
Published: February 2008

The leakage reactance end component is calculated by considering the net flux linking the stator end winding when both stator and rotor are excited with currents so that the net flux density in the airgap is zero. The stator and rotor end windings are assumed to consist of coils that close through the airgap by means of fictitious filaments and thus their respective current distributions are represented by systems of closed currents. Iron boundaries other than the end plate are neglected and the end plate is considered to be unsaturated and also a magnetic mirror, i.e. μ=∞, ό=0.
OPTIMAL SHAPE DESIGN OF A DC TORQUE MOTOR
Authors: Di Barba P. , Savini A. , Arpino F. , Navarra P.
Published: February 2008

The optimal design of a small dc torque motor, acting as a position actuator, is considered. The magnetic field is simulated by means of a 2‐D finite element model, taking into account the magnetization curve of iron and permanent magnets. The optimum shape of the motor, exhibiting the minimum cost, subject to a set of behavioural constraints, is found by a stochastic optimizer of lowest order.
MOVING FERROMAGNETIC ELEMENT INFLUENCE ON SUPERCONDUCTOR SEPARATOR MAGNET
Authors: Cieśla Antoni , Matras Andrzej
Published: February 2008

In the paper a field model of superconductor matrix separator is shortly presented. It allows to determine the electromagnetic induction voltage value in magnet winding during matrix removing out of the field. The case of matrix removing taking place with various as well as constant velocity will is regarded. The last concept allowed to determine optimum velocity function regarding minimal removing matrix time satisfying the condition of superconductor winding stable work.
GENERIC FIELD PROBLEMS IN DESIGN STUDIES OF HIGH TEMPERATURE SUPERCONDUCTING TRANSFORMERS
Authors: Harris MR , Stoll RL , Sykulski JK
Published: February 2008

A feasibility study for a large power transformer reveals several key design issues, each of which is expressible in terms of simple, fundamental field effects. Six generic effects are briefly reviewed and their importance explained. In all cases but one their influence can be estimated, to an accuracy adequate for feasibility purposes, without computation or detailed analysis. They are: mechanical stress due to magnetic fields; electrical breakdown caused by winding capacitance distribution; dielectric breakdown caused by the mixing of different materials, including liquid nitrogen; reduction of critical current density due to internal magnetic fields; the need, or otherwise, for conductor transposition; modelling of field penetration and ac losses in HTc superconductors.
VERIFICATION OF THREE‐DIMENSIONAL MAGNETIC FIELD DISTRIBUTION
Authors: Sikora Ryszard , Chady Tomasz , Komorowski Mieczyslaw , Ziółkowski Marek
Published: February 2008

Development in microcomputer systems has led to their use for a three‐dimensional magnetic field calculation. It caused a great progress in numerical methods used for a magnetic field analysis in electric machines and devices. Determination of the calculations quality may be achieved by comparing with the measurements. For this purpose real objects or simplified models can be used.
DETERMINATION OF PERMANENT MAGNET CHARACTERISTICS BY SINGLE‐SHOT TEST
Authors: Źycki Zdzisław , Sokolnicki Eugeniusz
Published: February 2008

The authors presents mathematical models of hysteretical relations of main magnetic parameters in pulse measuring procedures. Fragments of hysteresis loop specific for assessment of magnets as well as particular hysteresis parameters are discerned.
TRAVELLING WAVE INDUCTION HEATERS WITH COMPENSATING WINDINGS
Authors: Vadher VV , Smith IR
Published: February 2008

A major cause of the relatively low power transfer to the load on an induction heater, of either the pulsating or travelling field type, is the low magnetising reactance due to the large effective airgap when compared with a conventional transformer or induction motor. Although the power factor of an induction heater can be improved by capacitors connected in parallel with the induction coil, this does not lead to any improvement in the performance of the heater. This paper discusses how the power transfer to the load can be improved by using a compensating winding connected to capacitors, to improve the performance of the heater. The technique leads to an increased airgap voltage, resulting in both a greater power transfer to the load and an improved input power factor.
MODELING OF VLSI INTERCONNECT
Authors: Poltz J.
Published: February 2008

Digital systems utilize frequencies into the GHz range Attempts to reduce the propagation delay by lowering the interconnect capacitance (decreasing cross‐sectional dimensions) cause an increase in wire resistance which, in turn, increases the rise time and indirectly slows down the response Therefore, it is impossible to optimize VLSI and packaging interconnections to maximize the clock rate without analyzing losses (solving Helmholtz equation) and implementing lossy transmission line models This paper presents modeling and simulation of a gate array interconnect.
MIXED FINITE ELEMENT APPROACH AND NONLINEAR IMPLICIT SCHEMES FOR DRIFT‐DIFFUSION EQUATION SOLUTION OF 2D HETEROJUNCTION SEMICONDUCTOR DEVICES
Authors: EL Doukili A. , Marrocco A.
Published: February 2008

We present an abstract mathematical and numerical analysis for Drift‐Diffusion equation of heterojunction semiconductor devices with Fermi‐Dirac statistic. For the approximation, a mixed finite element method is considered. This can be profitably used in the investigation of the current through the device structure. A peculiar feature of this mixed formulation is that the electric displacement D and the current densities jn and jp for electrons and holes, are taken as unknowns, together with the potential φ and quas‐Fermi levels φn and φp. This enably D, jn and jp to be determined directly and accurately. For decoupled system, existence, uniqueness, regularity and stability results of the approximate solution are given. A priori and a posteriori error estimates are also presented. A nonlinear implicit scheme with local time steps is used. This algorithm appears to be efficient and gives satisfactory results. Numerical results for an heterojunction bipolar transistor, In two dimension, are presented.
MONTE CARLO MODELLING OF 0.1µm DELTA‐DOPED MOSFETs
Authors: Kelsall R.W. , O'Neill A.G.
Published: February 2008

A 2‐dimensional multilayer MOSFET simulator has been developed, based on self‐consistently coupled ensemble Monte Carlo and Finite Element Poisson Solver algorithms. The simulator is used to investigate electron transport in 0.1µm delta‐doped n‐channel MOSFETs. The simulations demonstrate a buried channel mode of operation in these devices, whereby conduction occurs primarily along the delta‐doped layer. In this mode, the electron density at the Si/SiO2 interface is significantly reduced, implying corresponding reductions in interface scattering and hot electron degradation.
AN EFFICIENT RESPONSE SURFACE TECHNIQUE FOR INVESTIGATING CMOS PROCESS RELATED EFFECTS ON CIRCUIT ELECTRICAL PERFORMANCE
Authors: Theron A.E. , Du Plessis M.
Published: February 2008

The ability to simulate the effects of process technology on final product circuits has become virtually indispensable in modern VLSI production. It is especially significant as a toot for controlling parametric yield by appropriate design centering and in determining the sensitivity of the electrical parameters to process control tolerances. The system demands the combined use of process simulation device simulation and circuit simulation all three of which rely heavily on computationally intensive numerical solution of partial differential equations. The severe computational overhead involved in ‘technology simulation TCAD)’ means it is generally expensive and limits the scope of statistical design centering and optimisation, which depend on a large number of simulations. A compromise solution is often resorted to by limiting simulation to one or two spatial dimensions, replacing numerical simulation by analytical approximations as implemented in the statistical process simulator: FABRICS 11, or combining numerical and analytical models as in the process/device simulator PRIDE.) This paper addresses the problem of simpler, higher efficiency TCAD evaluation by restricting the domain of the simulation and approximating the process/device characteristic relationship by a set of simple, computationally efficient empirical equations. These equations offer a high speed solution at the expense of decreasing accuracy away from the nominal process centre. Referred to as a ‘response surface model’, it is generated using the results of a small number of statistically designed TCAD simulations. As the process sample is centred around the nominal design parameters, the model can be used to statistically analyze the effects of process perturbations.
TWO‐CARRIER QUANTUM WELL TRANSPORT MODEL WITH APPLICATION TO SEMICONDUCTOR OPTICAL AMPLIFIERS
Authors: Pleumeekers J.L. , Mercier T. , Clérot F. , Mottet S.
Published: February 2008

For the design and optimisation of modern quantum well based opto‐electronic devices, a numerical simulator is required. This paper describes such a simulator. It includes the carrier transport through the quantum wells as well as the optical gain and the propagation of a light flux. This simulator is then used for the simulation of multi quantum well semiconductor optical amplifiers.
COMPARISON OF COUPLED AND DECOUPLED METHODS FOR SEMICONDUCTOR DEVICE MODELING
Authors: Obrecht M.S. , Heasell E.L. , Elmasry M.I.
Published: February 2008

Computational speed and robustness of the coupled (MEDICI) and decoupled (TRASIM) method based simulators are compared. Transient and steady‐state avalanche simulations are presented. The decoupled method shows significantly lower memory requirements, higher robustness and up to 30 times higher speed.
TEMPERATURE DEPENDENT NOISY MODELS OF PSEUDOMORPHIC HEMTs
Authors: Caddemi A. , Sannino M. , Mogavero G.
Published: February 2008

From a complete characterization in terms of noise and scattering parameters carried out at room temperature in the 8–16 GHz frequency range, the noisy small‐signal model of a pseudomotphic HEMT series has been extracted. The transistor scattering parameters have been subsequently measured at lower temperatures (down to −50 °C) by placing the device text fixture in a thermo‐controlled chamber. The model effectiveness has then been tested by determining the circuit element values at the different temperatures and by observing the model noise performance.
EFFICIENT SIMULATION OF 3‐D STRESS DISTRIBUTIONS AT TRENCH STRUCTURES CAUSED BY THERMAL MISMATCH OF TRENCH FILLING AND SILICON SUBSTRATE
Authors: Slehobr R. , Hobler G.
Published: February 2008

An efficient method for the calculation of 3‐D stress distributions at embedded structures in silicon caused by different thermal expansion coefficients between silicon and inclusion is presented. The method is based on the analytical solution for the stress field outside a rectangular parallelepipedic trench. This solution is adapted for the calculation of arbitrarily shaped inclusions and for the stress calculation inside the inclusion, too.
NUMERICAL MODELLING OF A NOVEL TWIN‐RIDGE WAVEGUIDE OPTICAL AMPLIFIER
Authors: Sabesan L , Ray AK , Mawby P , Towers M
Published: February 2008

Modelling of a Twin ridge waveguide optical Amplifier is reported here. In this paper appropriate physical mechanism such as current spreading, carrier diffusion, waveguiding and switching etc. have been take into consideration and the effects on characteristics and performance as a switch were investigated. With this model, physical phenomenon appropriate to the device can be analysed with respect to electrical, optical and geometrical parameters. Mixture of analytical and numerical techniques were employed.
ON THE HOMOGENIZATION OF MAXWELL EQUATIONS
Authors: Bossavit A.
Published: February 2008

We discuss the following general problem: given a composite, made from at least two different materials with each its own (scalar, and possibly complex‐valued) ε and μ, distributed in space in a regular, crystal‐like, pattern, find the equivalent permittivity and permeability (they will, in general, be tensors). This is homogenization. A computation in which such repetitive composites are present can then be done by simply replacing these with their equivalent, homogenized, materials.
CALCULATION OF ELECTROMAGNETIC DEVICE PARAMETERS ON THE BASIS OF 3D MAGNETIC FIELD TAKING ANISOTROPY INTO ACCOUNT
Authors: Nowak L. , Demenko A. , Kowalski K. , Szelag W.
Published: February 2008

Paper presents an effective iterative method for 3D magnetic field calculation taking the nonlinearity and anisotropy of the material into account. Algorithm for simulation of coupled 3D field‐circuit transient problems has been also elaborated. Some steady‐state and transient characteristics of the E‐core electromagnet and shell‐type transformer have been calculated.
ANALYTICAL SOLUTION FOR THE EDDY CURRENT PROBLEM INSIDE A CONDUCTING CYLINDER USING THE SECOND ORDER MAGNETIC VECTOR POTENTIAL
Authors: Theodoulidis T.P. , Antonopoulos C.S. , Kriezis E.E.
Published: February 2008

The evaluation of eddy currents in cylindrical geometries is examined analytically by using a method, which utilises the second order magnetic vector potential. As an example the three‐dimensional problem of the calculation of eddy currents inside a long conducting cylinder excited by a saddle shaped coil is studied.
A SYSTEMATIC APPROACH TO THE CONSTRUCTION OF HIGHER ORDER VECTOR FINITE ELEMENTS FOR THREE‐DIMENSIONAL ELECTROMAGNETIC FIELD COMPUTATION
Authors: Yioultsis T.V. , Tsiboukis T.D.
Published: February 2008

The importance of vector finite elements for electromagnetic field computation has been extensively demonstrated in the recent literature. In this study we present a systematic approach to the construction of higher order vector shape functions based on dual vector expansions. The methodology presented results in explicit forms for second order elements. Moreover, it reveals the presence of a whole family of vector finite elements depending on the choice of the degrees of freedom and a set of arbitrary parameters.
INFINITE ELEMENTS FOR 2D UNBOUNDED WAVE PROBLEMS
Authors: Gratkowski S. , Pichon L. , Razek A.
Published: February 2008

A basic difficulty encountered in applying the finite element method to unbounded wave problems is that the domain in which the field is to be computed is unbounded, while finite element models are of finite size. There are several ways to overcome this difficulty. The widely used method is to truncate the finite element model at a finite position and apply suitable boundary conditions there. The relevant boundary conditions must absorb the outgoing wave and have been called absorbing boundary conditions (ABC's).
NUMERICAL SIMULATION OF HIGH SPEED INDUCTION MACHINE WITH SOLID ROTOR
Authors: Andresen E. , Racinowski B. , Szymański G.
Published: February 2008

In this paper the calculation method of High Speed Induction Machine with solid rotor is presented. 2D model is assumed. FD method is used. Nonlinear effect of permeability is take into account.
THE OPTIMAL SCALING OF A LINEAR RELUCTANCE MOTOR BY FIELD COMPUTATION
Authors: Rizzo M. , Savini A.
Published: February 2008

The work aims at investigating the law of miniaturization of a linear reluctance motor by expressing the ratio of force to mass as a function of bar position in per unit, for different scale factors. Corresponding to the same factors, inductance is also computed. Finally the ratio of the bar length to external diameter is changed and the analysis is accordingly repeated.
MAGNETIC FIELD OF HIGHTORQUE STEPPING MOTOR WITH MULTIPHASE SUPPLY
Authors: Wagner J. , Maga D. , Ort‐Šnep R.
Published: February 2008

In spite of our previous results, where we have investigated the simplified 2D model, we would like to present our results coming out from real motor geometry. We use the Finite Element Method to solve the magnetic field of real cross‐section of hightorque stepping motor. This point of view allows us to investigate the multiphase (2 phase) supply. We are able to supply the motor with different current amplitude in each phase and with different polarity as well. The simplified model was used for slot and tooth shapes and sizes design optimisation, air‐gap width optimisation with reaching the maximal possible torque. Now we are going to verify these results and compare them to our latest ones. The comparison will be made by showing the magnetic field layout in the motor (with different current supply) in different stator‐rotor position. We will present tables and figures of some important variables, necessary for torque computation. We will compare these variables in the simplified and in the real motor. Then, on the base of the magnetic field solution, we will show the possible ways of rotor torque computation.
3D MAGNETIC FIELD DISTRIBUTION OF YOKE FLUX IN THREE‐PHASE TRANSFORMERS WITHOUT FERROMAGNETIC TANKS
Authors: Zakrzewski K. , Tomczuk B.
Published: February 2008

The 3D calculation of the monophase flux, due to n‐triple harmonics of the windings currents is considered. For small, three‐phase transformers without ferromagnetic tanks the calculation consists in unbounded problem solution. The 3D magnetic field of the yoke flux outside the magnetic core was analysed numerically by means of integral equations method. Our computer program subroutines, written in Fortran 77, have been implemented to a personal computer. The calculated components of the magnetic flux density were compared with the measured ones. The distribution of the different flux parts was calculated and tested by measurements for a three‐phase transformer.
CALCULATION OF 3D EDDY‐CURRENTS PROBLEMS IN NONLINEAR MAGNETIC FIELDS WITH VOLTAGE EXCITATION
Authors: Patecki Andrzej
Published: February 2008

Electromagnetic field problems arising in electrical machinery and devices are in general truly three dimensional in nature. In many devices natural excitation is the voltage excitation, for example: relays and electrical motor. Several research papers have been published on the subject of three dimensional field solutions. Many different formulations of the 3D electromagnetic problems are possible. They involve differential or integral formulations in terms of scalar or vector unknowns. The aim of this paper is to present a method capable of solving general 3D eddy currents with voltage excitation in nonlinear magnetic field using the A, A‐V formulation. The method of the finite difference equations formulation based on minimising of the energy functional has been given.
SURFACE POWER LOSSES IN THE CORE OF INDUCTION MOTORS SUPPLIED BY A PWM VOLTAGE INVERTER
Authors: Anuszczyk Jan , Gmyrek Zbigniew
Published: February 2008

The calculation of additional power loss components in an induction motor supplied from a PWM inverter has been carried out with the assumption of constant load torque, the frequency of fundamental harmonic being adjusted in the range of 20 to 70Hz. The tests presented refer to a squirrel‐cage induction motor Sf 132 M4: PN = 7.5kW, UN = 380V (&Dgr),ƒN = 50Hz, 2p = 4.
ELECTROMAGNETIC FIELDS IN TRACTION SYSTEMS: MODELLING AND APPLICATIONS
Authors: Brillante S. , Hill R.J. , Leonard P.J. , Pozzobon P.
Published: February 2008

A two‐dimensional electromagnetic field model of a railway track and traction line is used to determine the equivalent track distributed transmission line parameters in the frequency range DC to 30kHz. The model is solved using the finite‐element method to find the minimum energy condition for two conditions: current excitation to obtain the resistance and inductance, and voltage excitation for the conductance and capacitance. The results have been confirmed using practical test data, and their application is illustrated in a time‐domain circuit simulation to model interference between power and signalling currents in a 750V DC electric railway.
THE MAGNETOSTRICTION FORCES IN THE INDUCTION MOTOR
Authors: Witczak Pawel
Published: February 2008

The paper describes how the classical formula of the Maxwell magnetic stress tensor may be extended to cover the magnetostriction phenomena. It is assumed that the ferromagnetic continuum is isotropic and conservative. The method takes into account the magnetic nonlinearity and it assumes that mechanical deflections are sufficiently small to neglect the nonlinearity of the Hooke's law. The paper presents also the experimental method, which has been used to measure the magnetostriction intensity for electrotechnical laminations. As the final result, the distribution of the volume magnetostriction forces acting on the stator core of the induction motor has been calculated.
SOFT MAGNETIC MATERIAL POWER LOSSES IN HARMONIC REGIME
Authors: D&acaronnut Olteanu Ioan , Helerea Elena , Cernat Mihai
Published: February 2008

Magnetic power losses in harmonic magnetizing regime: The soft magnetic materials used as magnetic cores in wide frequency band transformers for DC/DC converters must be characterized by high saturation flux density Bs and and low magnetic power losses for all working frequencies. An adequate design of these devices is possible if the magnetic characteristics of cores are known.