bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fourier approach to semiconductor device modelling
Authors: Axelrad V. 
Published: August 2005

AbstractA novel procedure for the numerical modelling of current transport in semiconductor devices is presented. The method is based on high‐order trigonometric expansions (Fourier series) of the solution. The expansion coefficients are calculated in a Galerkin‐type algorithm. The method offers infinite‐order accuracy regardless of the number of spatial dimensions of the model. Well‐conditioning and diagonal dominance of the discrete equations render the numerical procedure stable and effective. Significant advantages are expected, particularly for the solution of strongly non‐linear multidimensional device models. Properties of the algorithm are demonstrated on standard semiconductor devices.
A multicompartment TLM model for solving first‐order rate equations
Authors: Saleh A. H. M. 
Published: August 2005

AbstractThis paper introduces a simple model for solving a system of first‐order rate equations using the TLM numerical method. A general algorithm is developed by setting up a matrix of discrete compartments. The rate constants provide the linkage between each compartment and the neighbouring ones. The method is demonstrated by some examples in which saturation conditions are considered. The TLM solution is compared with analytical solutions and the Rung‐Kutta method of solving differential equations.
Mathematical modelling of a 3 ‐phase to single ‐phase cycloinverter
Authors: Smith I. R. , Vadher V. V. , Kettleborough J. G. , Ahishalilar Y. 
Published: August 2005

AbstractThe paper outlines the operating principles of a 3 ‐phase to single ‐phase cycloinverter, as used in heating and melting applications, and presents a digital computer model on which performance predictions may be based. Ideal power switches, an input filter and a compensated heating load are assumed in formulating an initial set of state ‐variable equations which are valid when all the switching devices are conducting. Connection matrix techniques are then used to generate the mesh equations relevant to the continually changing pattern of the switching devices, leading to a very versatile simulation program. Experimental results from a laboratory ‐scale unit are presented for different output power levels, and these are compared with corresponding computed results to illustrate the close similarity that exists.
Characterization of microstrip antennas using the TLM simulation associated with a Prony‐Pisarenko method
Authors: Dubard J. L. , Pompei D. , Le Roux J. , Papiernik A. 
Published: August 2005

AbstractThe transmission‐line matrix (TLM) method enables simulation of interior electromagnetic field propagation problems. With the use of absorbent walls, we can simulate exterior problems such as the radiaition of a microstrip antenna. The input impedance is deduced from the standing wave observed in the feedline. The radiation pattern is determined from the field over a plane located in the immediate vicinity of the antenna, using the theory of radiating apertures. However, the CPU time and memory space involved are excessive. Since the radiating structure has several resonant frequencies, it is convenient to apply classical digital signal processing techniques such as finite impulse response filtering associated with a linear prediction method. The present paper focuses on a Prony–Pisarenko method to improve on the TLM method in terms of both computation time and precision of the frequency‐domain analysis of the results. In this case, overall CPU time is reduced by a factor of 2 to 3. The paper discusses the results obtained for radiation patterns. This represents a new field of application for the TLM method whose drawbacks are reduced by using appropriate signal processing methods.
Adaptive refinement in 2‐D finite element applications
Authors: Golias N. A. , Tsiboukis T. D. 
Published: August 2005

AbstractAn adaptive mesh refinement scheme in the finite element method is presented in this paper. The new criterion Bdiff for adaptive refinement is tested for its validity. A technique for approximating curved boundaries employing the concept of triangle subdivision in conjunction with Delauney triangulation is also considered, so that the mesh produced is optimal. The implementation of the adaptive mesh refinement criterion in conjunction with the proposed technique of including the curved boundaries in the finite element model is described in detail and several examples of its application are given by way of illustration.
The modified semiconductor equations and associated algorithms for physical simulation
Authors: Xue Hongxi , Howes Michael J. , Snowden Christopher M. 
Published: August 2005

AbstractA set of modified semiconductor equations is described together with novel algorithms for solving them. These ensure a well‐behaved, guaranteed convergent solution for a steady‐state semiconductor model. Examples results on the simulation of a GaAs Dual Gate MESFET are given to demonstrate the efficiency of the new scheme.
Analysis of cross‐talk on high‐speed digital circuits using the finite difference time‐domain method
Authors: Pothecary N. M. , Railton C. J. 
Published: August 2005

AbstractCross‐talk and pulse distortion in high‐speed digital circuits have long been major design considerations. With the present trend towards increased speed and packing density the commonly used TEM approximation is no longer capable of producing sufficiently accurate results. In this contribution, the finite‐difference time‐ domain technique incorporating a novel means of launching the pulses is used to provide a rigorous three‐ dimensional simulation of cross‐talk on high‐speed digital circuits. This includes the often‐neglected effects of higher‐order modes and surface waves. Results are presented for pulses propagating along a single track and for coupling between two and three tracks using square, gaussian and raised cosine pulse excitation functions. The results are shown to be in good agreement with other rigorous analyses.
TLM modelling of diffusion, drift and recombination of charge carriers in semiconductors
Authors: Al‐Zeben M. Y. , Saleh A. H. M. , Al‐Omar M. A. 
Published: August 2005

AbstractThe paper provides an extension to the one‐dimensional TLM diffusion model. The extended diffusion node presented here models the exact transport equation with diffusion drift and recombination of charge carriers in semiconductors. A general algorithm for providing a numerical solution to the transport phenomena is also presented here. The analytical solution for infinitely long semiconductors is compared with the TLM numerical results.
A note on the computational storage in the subsectional basis function approach to the method of moments
Authors: Sattler Sebastian , Russer Peter 
Published: August 2005

AbstractIn order to efficiently store the information of a special class of matrices, a very useful algorithm has been derived and applied to the subsectional basis function approach to the method of moments. The algorithm represents a simple law of mapping and allows a reduction in the required computational storage by several orders of magnitude.
The use of transmission‐line modelling (TLM) for the solution of heat diffusion in electric fuses
Authors: Cheim Luiz , Howe Alan F. 
Published: August 2005

AbstractThis paper describes an application of transmission‐line modelling (TLM) for the solution of heat diffusion in a three‐dimensional metallic structure, surrounded by a dielectric material. The example of heat propagation along an electric fuse embedded in granular silica is presented. Heat is generated by the flow of an electric current through the metallic element and results are shown for the variation of temperature with time and temperature distribution along the fuse element.
Calculating frequency‐domain data by time‐domain methods
Authors: Dehler M. , Dohlus M. , Weiland T. 
Published: August 2005

AbstractWe show the derivation of parameters in the frequency domain from time‐domain data. Far‐field characteristics are obtained by a convolution formula with the harmonic field amplitudes, which are obtained via a Fourier transform or by sampling. The electric field of filter ports is expanded into the discrete eigenmodes. By this method, a monochromatic exact open boundary can be formulated and the fields divided into the incident and the reflected part. For wide band operation an a posteriori error correction scheme is presented.
The hilbert space formulation of the TLM method
Authors: Russer Peter , Krumpholz Michael 
Published: August 2005

AbstractThe Hilbert space representation of the TLM method for time‐domain computation of electromagnetic fields and the algebraic computation of the discrete Green's function are investigated. The complete field state is represented by a Hilbert space vector. The space and time evolution of the field state vector is governed by operator equations in Hilbert space. The discrete Green's functions may be represented by a Neumann series in space‐ and time‐shift operators. The Hilbert space representation allows the description of the geometric structures by projection operators, too. The system of difference equations governing the time evolution of the electromagnetic field in configuration space is derived from the operator equation for the field state vector in the Hilbert space.
Consistent finite difference modelling of Maxwell's equations with lossy symmetrical condensed TLM node
Authors: Hein Steffen 
Published: August 2005

AbstractA propagator integral interpretation for general TLM processes is presented and applied to discretized Maxwell's equations. The approach provides exact algebraic solutions of finite difference equations along a quite universal scheme.Specifically, Johns's process based on the symmetrical condensed node is reconstructed and generalized as a clear‐cut FD algorithm. The fields computed are exact time‐domain solutions of the FD equations, provided that total voltages and currents are evaluated and stub quantities are not externally excited. Losses are very naturally incorporated into the TLM algorithm.The structural similarity of the TLM process (properly operated) with the propagator integral appears just as fundamental as general and should have further applications.
New technique for finite difference analysis of optical waveguide problems
Authors: Matin M. A. , Benson T. M. , Kendall P. C. , Stern M. S. 
Published: August 2005

AbstractThe method of effective penetration depth is used to produce a novel scalar or polarized finite difference approach for the solution of optical rib waveguide field problems. The new method is quicker than previous finite difference approaches and requires less computer memory. Propagation constant values are presented for a range of semiconductor rib waveguides and are found to be indistinguishable from benchmark results produced using earlier methods of analysis. A simple polarization correction formula recently derived is confirmed by utilizing the good accuracy of these results. This enables discussion of the relationship between quasi‐TE, quasi‐TM and scalar modes, and a further substantial reduction of the cpu time.
Two‐dimensional FDTD and TLM
Authors: Krumpholz M. , Russer P. 
Published: August 2005

AbstractApplying the method of moments to Maxwell's equations, Yee's two‐dimensional FDTD scheme with central difference approximations and the two‐dimensional TLM method are dervied from first principles of field theory. By comparing the eigenvalues of the two methods, the differences between two‐dimensional FDTD and TLM are illustrated.
Parallel computation of 3‐D electromagnetic scattering using finite elements
Authors: Chatterjee A. , Volakis J. L. , Windheisser D. 
Published: August 2005

AbstractThe finite element method (FEM) with local absorbing boundary conditions has been recently applied to compute electromagnetic scattering from large 3‐D geometries. In this paper, we present details pertaining to code implementation and optimization. Various types of sparse matrix storage schemes are discussed and their performance is examined in terms of vectorization and net storage requirements. The system of linear equations is solved using a preconditioned biconjugate gradient (BCG) algorithm and a fairly detailed study of existing point and block preconditioners (diagonal and incomplete LU) is carried out. A modified ILU preconditioning scheme is also introducted which works better than the traditional version for our matrix systems. The parallelization of the iterative sparse solver and the matrix generation/assembly as implemented on the KSR1 multiprocessor is described and the interprocessor communication patterns are analysed in detail. Near‐linear speed‐up is obtained for both the iterative solver and the matrix generation/assembly phases. Results are presented for a problem having 224,476 unknowns and validated by comparison with measured data.
Finite element method solutions of field distributions in large cavities
Authors: Tharf Mohammed S. , Costache George I. 
Published: August 2005

AbstractTo make possible the application of the three‐dimensional finite element method to electrically large problems, it is combined with the analytical solutions of arbitrary large cavity with aperture. In this paper, detailed analysis for this hybrid method is presented. The element matrices necessary for coupling the finite element method to analytical solutions are given. The proposed hybrid method significantly reduces the number of unknown since only the inhomogeneity needs to be discretized. Thus computer memory and storage demands are reduced. In addition. This hybrid method employs the edge element which is not expected to produce spurious solutions. Also, the formulation presented in this paper preserves the sparsity of the finite element matrix, and does not require any matrix inversion. This new hybrid method is used to compute the field distributions in various partially filled rectangular enclosure. The results match well with the pure edgebased finite element method and analytical solutions.
Iterative solution of boundary element approximations for electric and magnetic fields
Authors: Weiss Rüdiger , Meroth Ansgar , Levin Peter 
Published: August 2005

AbstractThe calculation of potentials in homogeneous and isotropic media by the boundary element method has the advantage that a harmonic solution of Laplace's equation is obtained for given approximated boundary conditions. The technique leads to the solution of linear systems with full matrices of dimension 1000–10,000 for medium‐ and large‐sized three‐dimensional problems, An efficient solution procedure of the linear systems is required.While the iterative solution of the large and sparse linear systems arising from the finite difference or the finite element method is well documented, the systems resulting from the boundary element method are typically solved by direct methods. However, in many cases an iterative solver needs far fewer operations to achieve a sufficient accuracy. Importantly, there are many alternative methods, each of them well suited for different types of problem.Here, we provide an overview of state‐of‐the‐art iterative solvers. We will discuss the particular methods that have been successfully applied to systems arising from field calculations in the high‐voltage engineering by the boundary element method. The selection of appropriate methods is discussed. We demonstrate that iterative solutions can be much faster than direct solvers with regards to the number of operations. Furthermore, these solvers are optimally suited for today's supercomputers because they can be efficiently vectorized and parallelized.
Numerical algorithms for modelling microwave semiconductor devices
Authors: Cole Eric A. B. , Snowden Christopher M. 
Published: August 2005

AbstractThis paper presents an analysis of the numerical algorithms used to model microwave semiconductor devices. A comparison is made of the relative merits and features of the more popular finite difference schemes. A new generalized Scharfetter–Gummel formulation is presented which is compatible with drift diffusion and energy‐transport formulations, and is suitable for implementing in two‐dimensional simulations on personal computers. The treatment allows for fully degenerate semiconductors, but implementation for the nondegenerate situation is easily obtained as a special case. The convergence and stability properties of the generalized scheme are discussed. The simulation of a planar submicrometre gate length GaAs MESFET is used to illustrate the application of these algorithms.
Efficient material‐gain models for the transmission‐line laser model
Authors: Nguyen Linh V. T. , Lowery Arthur J. , Gurney Phil C. R. , Novak Dalma , Murtonen Casper N. 
Published: August 2005

AbstractTransmission‐line laser models (TLLMs) are time‐domain models suitable for the simulation of complex phenomena in semiconductor lasers. TLLMs include time‐domain filters based on transmission‐line stubs to model the spectral dependence of the material gain. In this paper, numerical simulations are presented which show that the accuracy of these gain models is dependent on the model's iteration timestep. Analytical formulae are derived that relate the accuracy of the filters to the timestep, filter centre frequency, and filter bandwindth. A new wideband stub filter which allows the material gain to be modelled using a larger timestep is presented. This is equivalent to a digital infinite‐impulse‐response filter, which is more computationally efficient than finite‐impulse‐response filters, and is unconditionally stable. The new gain model can improve the computational speed for simulating for multimode Fabry‐Perot lasers by a factor of 10–100.
An efficient algorithm for computing the transmission through highly conducting thin sheild in TLM
Authors: Fuchs Ch. , Kopp G. , Schwab A. J. 
Published: August 2005

AbstractThis paper presents a new method in TLM for very efficient computation of highly conducting thin shielding walls. Firstly, the impulse response of a finite conducting sheet is computed analytically via inverse Laplace transform. Subsequently, a recursive convolution integral is formulated with the analytical impulse response. This allows a very efficient and accurate calculation of the diffusion process through imperfectly conducting walls.
Transport equations with boundary conditions of reverse reflection type
Authors: Frosali G. , van der Mee C. V. M. , Protopopescu V. 
Published: August 2005

AbstractA study is performed of transport equations on arbitrary three‐dimensional domains with boundary conditions of reverse reflection type. The existence of the dominant eigenvalue of the criticality problem is proved and its independence of the functional setting and its continuous dependence on a variety of data are established. The corresponding time‐dependent problem is shown to be well‐posed, also for a conservative boundary. The relationship between the criticality and the time‐dependent problem is given explicitly.
Reduction of quasilinear elliptic equations in cylindrical domains with applications
Authors: Mielke Alexander 
Published: August 2005

AbstractFor certain types of semilinear partial differential equations in a cylindrical domain small bounded solutions are known to lie on a so‐called centre manifold of finite dimension. In this paper we prove the result for quasilinear partial differential equations of elliptic and parabolic type.Possible applications include free surface waves and problems in non‐linear elasticity. Here we investigate, pars pro toto, the stationary inviscid potential flow in a channel with a free surface and an obstacle at the bottom.
Application of the Schwarz function to boundary problems for Laplace's equation
Authors: Millar R. F. 
Published: August 2005

AbstractA method is described for studying analytic boundary problems for the Laplace equation in a simplyconnected domain D of the plane. The aim is ultimately to obtain solutions in closed form when D is bounded by a simple analytic curve C with Schwarz function G. The basis for the procedure is that a functional F of the incompletely known boundary Cauchy data determines the solution and is analytic in D, and that there exists a further integral relation between these data and the analytic function G. Elimination of the unknown data from the latter relation by using the former leads to an integral on C that relates F to prescribed data and which, in some cases, may be solved for F in D. Some necessary properties of G are derived; in particular, it is shown that C must be a circle if G is analytic in D except for a single, simple pole (Theorem 1), or if a certain integral that appears prominently in this work is analytic throughout D (Theorem 2). The Dirichlet problem is treated in some detail. If C is a circle, a representation for the solution is obtained that is equivalent to one given by P. J Davis, and to the Poisson integral. When G is meromorphic in D and C is not a circle, Theorem 2 implies that the Davis result is not applicable, and the problem is reduced to that of solving Schröder's functional equation. Integral equations for F are obtained when C is an ellipse and G is multivalued in D. Other linear boundary value problems that can be handled are noted. A class of non‐linear Riemann‐Hilbert problems is described and studied briefly. For all these problems, closed solutions have been obtained when C is a circle; it is not clear whether closed solutions for other forms of C can be found without the explicit use of conformal mapping techniques. Finally, some possible generalizations to different equations and more complicated geometries are mentioned.
On the instability of resonances in parallel‐plane waveguides
Authors: Morgenröther K. , Werner P. 
Published: August 2005

AbstractIt has been observed13 that the propagation of acoustic waves in the region Ω0= ℝ2 × (0, 1), which are generated by a time‐harmonic force density with compact support, leads to logarithmic resonances at the frequencies ω = 1, 2,… As we have shown9 in the case of Dirichlet's boundary condition U = 0 on ∂Ω, the resonance at the smallest frequency ω = 1 is unstable and can be removed by a suitable small perturbation of the region. This paper contains similar instability results for all resonance frequencies ω = 1, 2,… under more restrictive assumptions on the perturbations Ω of Ω0. By using integral equation methods, we prove that absence of admissible standing waves in the sense of Reference 7 implies the validity of the principle of limit amplitude for every frequency ω ≥ 0 in the region Ω =Ω0 −B, where B is a smooth bounded domain with B̄⊂Ω0. In particular, it follows from Reference 7 in the case of Dirichlet's boundary condition that the principle of limit amplitude holds for every frequency ω ≥ 0 if n·x′ ⩽ 0 on ∂ B, where x′ = (x1, x2, 0) and n is the normal unit vector pointing into the interior B of ∂ B. In the case of Neumann's boundary condition, the logarithmic resonance at ω = 0 is stable under the perturbations considered in this paper. The asymptotic behaviour of the solution for arbitary local perturbations of Ω0 will be discussed in a subsequent paper.
Continuous dependence on the time and spatial geometry for the equations of thermoelasticity
Authors: Song J. C. , Payne L. E. 
Published: August 2005

AbstractIn this paper we establish the stability of the solution of the standard initial‐boundary value problem of linear anisotropic thermoelasticity under perturbations of the initial time geometry and of the spatial geometry. This is done by deriving appropriate explicit a priori inequalities which permit us to bound in particular the L2 integral of the perturbation in terms of some well defined measure of the perturbation in the geometry.