bluuebunny/crossref_metadata_2025_split huggingface dataset:
A non‐linear and distributed modelling procedure of fets
Authors: Ongareau Éaric , Bosisio Renato G. , Aubourg Michel , Obregon Juan J. , Gayral Michel 
Published: August 2005

AbstractThis paper describes a rigorous and systematic procedure to derive a non‐linear distributed FET model that can easily be implemented in CAD routines of simulators based on harmonic balance techniques. The new model is derived from a knowledge of the conventional linear lumped equivalent circuit, from non‐linear current sources extracted from pulsed measurements, and from the physical dimensions of the FET.For fundamental and harmonic frequencies, the FET is modelled byNidentical cells. Each cell is made up of a non‐linear two‐port section inserted between two linear four‐port sections that simulate the coupling and the distributed effects along the electrodes of the FET in the width direction only. This non‐linear distributed scaling approach to FET modelling has been applied to the analysis of a submicrometre‐gate GaAs FET at millimetre‐wave frequencies, and the results were compared with the non‐linear lumped element approach. This approach can be applied to other transistors used in non‐linear regions at microwave and millimetre‐wave frequencies.
Electronic band structure for two‐dimensional periodic lattice quantum configurations by the finite element method
Authors: Ferrari R. L. 
Published: August 2005

AbstractA finite element method formulation is given for solving Schrodinger's wave equation for a single electron in a crystal lattice cell subject to a known periodic potential. The formulation has been implemented for a two‐dimensional lattice, with an arbitrary potential profile, modelled by quadratic isoparametric elements, The FEM solver returns a specified number of electronic energy states, En, and nodal values of the complex wavefunctionψn Input data is generated by a standard FEM mesh generator. The postprocessing, given n, for reproducing a full 2‐D E‐k Brillouin diagram and given k, the electronic distribution, has been implemented. Tests on a 2‐D generalized Kronig‐Penney energy band model showed excellent agreement; between FEM results and analysis. The solver was further satisfactorily checked against published augmented plane wave calculations for a circular potential well within a square lattice. Specimen results are presented for the same circular well but with graded potential distributions and for a rectangular potential barrier set askew in a square lattice. Two‐dimensional energy band solvers have application to superlattice nanostruc‐ tures, whilst a general, full 3‐D FEM quantum solver seems feasible.
Analysis of a thin wire circular loop antenna
Authors: Yung Edward K. N. , Wong Roger S. K. 
Published: August 2005

AbstractA rigorous technique for studying a thin wire circular loop antenna excited by a magnetic frill is developed. The exact kernel is derived and used to improve the accuracy. The scheme is applicable to small as well as large loops. Results obtained are nearly indistinguishable from those determined by the Fourier expansion method for non‐resonant loops. A disagreement of 2 per cent is generally observed when the loop is close to reasonant for βb> 2. Compared with the conventional numerical method where a loop is represented by a polygon of straight wires, the present scheme is much faster and more accurate. Extension of this method to cover an antenna system of arbitrarily oriented loops intermingled with straight wires can be easily achieved.
TLM treatments of changes of phase
Authors: Hurst A. I. , Pulko S. H. 
Published: August 2005

AbstractThe existing treatment of an instantaneous endothermic change of state is extended to deal both with exothermic effects and with first order Arrhenius changes. These extended treatments are used to model complex changes of phase occurring during the firing of ball clay and china clay, both of which are constitutents of the slip used in the production of vitreous china ware. The adequacy of the treatments is investigated for both clays by comparing a TLM simulation of a DSC (differential scanning calorimetry) experiment with measurements made during the experiment.
FDTD analysis of crosstalk in multilayer printed circuits
Authors: Cerri G. , De Leo R. , Primiani V Mariani , Schiavoni A. 
Published: August 2005

AbstractA theoretical analysis has been developed to study the crosstalk in crossed bundles of parallel lines. The model is based on the theory of the coupled transmission lines and the resulting system of differential equations has been solved by means of the finite difference, time‐domain (FDTD) method. The frequency response of the network has been achieved by the discrete fourier transform (DFT) algorithm; measurements, performed with a vectorial network analyser, show a good agreement with numerical simulation.
Numerical drift‐diffusion simulation of Auger hot electron transport in Ingaasp/Inp double heterojunction laser diodes
Authors: Chai Kam‐Wing , Li Zhan‐Ming , McAlister Sean P. , Simmons John G. 
Published: August 2005

AbstractThis paper considers the adaptation of drift‐diffusion device simulation methodology to study Auger‐recombination‐induced hot electron transport characteristics in InGaAsP/InP double heterostructure laser diodes. In order to model the transport behaviour of the Auger hot electrons, we decompose the conventional electron current continuity equation into two components, with one for the Auger hot electrons and the other for the low‐energy electrons. These equations, which use the energy relaxation time parameter to model the dynamics of the Auger hot electrons, are then coupled with the hole current continuity equation and the Poisson equation to obtain self‐consistent solutions. Results from the case studies of one‐dimensional N‐p‐P InGaAsP/InP double heterojunction laser diodes with material composition corresponding to 1·3 μm and 1·55 μm wavelength emissions are presented. We have observed that hot electrons generated through Auger recombination inside the active region can spread into both the N‐ and the P‐InP cladding layers. Within the drift‐diffusion framework, it is demonstrated that the hot electron concentration in the N‐InP cladding layer can be five orders of magnitude higher than that in the P‐InP cladding layer. Because energy transport of the hot electrons in not modelled under the drift‐diffusion approximation, the simulated results are discussed to highlight some of the possible limitations in using drift‐diffusion physics to study Auger hot electron transport behaviour. The importance of taking energy transport into account is emphasized.
Calculation of scattering parameters by orthogonal expansion and finite integration method
Authors: Geib B. , Dohlus M. , Weiland T. 
Published: August 2005

AbstractField computations by mathematical and numerical methods are presented in the time and frequency domain. The techniques used are discretization and modal expansion. The effects of modelling and frequency range on the accuracy and calculation requirements are investigated and discussed. By way of application, several results of RF‐filter designs are presented, where these methods have been implemented in CAD programs.
Parallel implementation of a Monte Carlo particle simulation coupled to Maxwell's equations
Authors: Goodnick Stephen M. , Pennathur Shankar S. , Ranawake Udaya A. , Lenders Patrick M. , Tripathi Vijai K. 
Published: August 2005

AbstractPMC‐3D, a parallel three‐dimensional (3‐D) Monte Carlo device simulator for multicomputers is discussed. The parallel algorithm is and extension of the standard Monte Carlo device simulation model in three dimensions, that combines the stockastic Monte Carlo particle simulation method with a solution of Poisson equation for quasi‐static problems, and full Maxwell's equations for microwave or electro‐optic phenomena. While our implementation of the Poisson solver is based on an iterative method that uses and odd/even ordering with Chebyshev acceleration, a simple leapfrog method based upon the computational unit of Yee cell is used in a finite‐difference, time‐domain (FDTD) formulation to solve Maxwell's equations.The parallel algorithms were implemented on a 1024‐node distributed memory nCUBE multicomputer. In this work, we present the application of PMC‐3D to generate the static current‐Voltage characteristics of GaAs MESFET, and to simulate photogenerated femtosecond electrical transients produced in coplanar stripline on a GaAs substrate.
Modelling of high‐frequency multilayered interconnects using parallel processing techniques
Authors: Jatou F. , Van Deventer T. E. 
Published: August 2005

AbstractThis paper examines the use of parallel processing techniques for the electromagnetic field analysis of multilayered microwave interconnects. These techniques are applied to a full‐wave formulation using an integral equation approach in the frequency domain. In order to demonstrate the feasibility of parallelization and to assess its performance advantages, several variations of the computer code have been developed. Performance tests using domain partitioning and load balancing were conducted on a 32‐processor shared‐memory machine (KSR1).
Re‐working of two standard moment‐method codes for execution on parallel processors
Authors: Excell P. S. , Porter G. J. , Tang Y. K. , Yip K. W. 
Published: August 2005

AbstractTwo separate exercises on a similar theme are reported. In the first, the moment‐method program NEC was extensively modified in order to optimize its performance on a four‐processor Cray X‐MP computer. In the second exercise, the MININEC moment‐method program was completely rewritten into the occam programming language so that it could be executed directly by a transputer system. The NEC exercise exploited judicious use of vectorization and alternative parallelization techniques and achieved a reduction of run times by factors of about five or more. The MININEC exercise has so far achieved only a modest reduction in run‐time but it has the potential for a much greater improvement if an optimum strategy for configuring the transputer network is implemented.
A paraller planar generalized Yee algorithm for the analysis of microwave circuit devices
Authors: Gedney Stephen D. , Lansing Faiza 
Published: August 2005

AbstractThe planar generalized Yee (PGY) algorithm is an extension of the generalized Yee algorithm and the discrete surface integral (DSI) methods, which are based on explicit time‐marching solutions of Maxwell's equations. Specifically, the PGY algorithm exploits the planar symmetries of printed microwave circuit devices, achieving great savings in both CPU time and memory. Since the PGY algorithm is an explicit method, it has a high degree of parallelism. To this end, a highly scalable parallel algorithm based on a spatial decomposition of the general unstructured mesh is presented. Two spatial decompositions are compared, the recursive inertia partitioning (RIP) algorithm and the Greedy algorithm. The Greedy algorithm provides optimal load balance, whereas the RIP algorithm more effectively minimizes shared boundary interface lengths. Through numerical examples, It is demostrated that the Greedy algorithm provides superior speedups. It is also demonstrated that the parallel PGY algorithm is a highly scalable algorithm.
A comparison of the performance of the finite difference time‐domain, finite element time‐domain, and planar generalized Yee algorithms of high‐performance parallel computers
Authors: Gedney Stephen D. , Navsariwala Umesh 
Published: August 2005

AbstractParallel algorithms for the finite difference time‐domain (FDTD), the planar generalized Yee (PGY), and the finite element time‐domain (FETD) methods are presented. The FDTD and the PGY algorithms are both explicit time‐domain solutions of Maxwell's equations, while the PGY algorithm is based on an unstructured grid. The FETD algorithm is a semi‐implicit solution of Maxwell's equations using variational principles, and thus requires a matrix inversion for every time iteration. The three parallel algorithms are based on spatial decompositions of the discrete three‐dimensional problem spaces. A comparative analysis of the parallel algorithms is presented based on their memory and computational efficiency as well as their parallel efficiency.
The complex subspace iteration for the computation of eigenmodes in lossy cavities
Authors: Schmitt D. , Schuhmann R. , Weiland T. 
Published: August 2005

AbstractA typical application of numerical frequency‐domain computations is the calculation of electromagnetic fields in cavities. Not only the field vectors of the desired modes, but also parameters such as the resonance frequency and, in the lossy case, the damping coefficient and the quality factor of the cavity can be obtained. This problem leads to an analytical eigenvalue equation, which can be transformed in an algebraic, complex, linear eigenvalue problem by the finite integration method.The consideration of energy losses in materials is straighforward in the analytical theory, using complex material quantities, but it is still a difficult subject area to solve a complex algebraic eigenvalue problem. Generally problems with very large, complex matrices (dimension >100,000) have to be solved, and no commonly applicable algorithm is known so far.This paper deals with a special variant of subspace iteration with polynomial acceleration, and some problems of the application of the complex Chebyshev polynomials are discussed. Two examples with weakly lossy cavities demonstrate the capability of the new algorithm, which is successfully applied to very large problems of up to 490, 000 real unknowns.
An effective optimization method for the design of broadband microwave absorbers
Authors: Ponnekanti S. , Al‐Khaled F. S. H. , Sali S. 
Published: August 2005

AbstractA novel procedure for synthesizing multilayered radar absorbing materials (RAMs) is presented. The procedure uses a method for global minimization of multimodal functions of continuous variables based on simulated annealing (SA). The technique is very flexible and reliable, allowing the design of absorbing materials for any grazing or normal angles over the specified frequency bandwidth. The technique is particularly suitable for the efficient design of broadband RAMs and hence for EMC applications.
Effect of Macromolecular Crowding on the Conformation of Confined Chain Polymers
Authors: Martínez‐Haya Bruno , Gordillo M. C. 
Published: August 2005

AbstractSummary: The conformational behavior of flexible linear chain polymers confined in cylindrical pores and slab pores has been studied, employing a hard‐bead chain model and a modification of a recently proposed recoil‐growth bias Monte Carlo methodology, which improves the sampling efficiency in confined environments. It is found that the scaling law that correlates the unconstrained component of the radius of gyration of the polymer with the pore diameter in cylindrical pores is close but neatly different than the de Gennes mean‐field value. The results also indicate that the addition of spherical particles with sizes within the protein limit may be employed to tune the folding of the confined polymer, since in this case the depletion constraints work against the effective stretching forces induced by confinement. Remarkably, the presence of the depleting particles at sufficiently high concentration leads to appreciable changes in the exponents of the conformational scaling laws with respect to the uncrowded system.Conformational behavior of flexible hard‐bead chain polymers confined in narrow pores.magnified imageConformational behavior of flexible hard‐bead chain polymers confined in narrow pores.
On Modelling Surface Directed Spinodal Decomposition
Authors: Henderson Ian C. , Clarke Nigel 
Published: August 2005

AbstractSummary: Cahn‐Hilliard theory for symmetric binary polymer mixtures is used to study the influence of a surface which is attractive to one component of the polymer blend. We revisit modelling approaches to the dynamics of a polymer blend at or near a surface to show that quantitative agreement with previous models is only possible if a number of issues are resolved. We address the issue of how the numerical length scales chosen during the simulation affect the accuracy of the magnitude of surface segregation when a blend is undergoing spinodal decomposition. Finally we investigate whether equilibration has any effect on the morphology of the blend at the surface or in the bulk after a quench into the two‐phase region has occurred.magnified image
Medicine‐taking behavior: Implications of suboptimal compliance in Parkinson's disease
Authors: Grosset Katherine A. , Reid John L. , Grosset Donald G. 
Published: August 2005

AbstractManagement of Parkinson's disease (PD) depends primarily on oral medication. There are several drug classes and multiple doses and formulations, which make optimizing therapy complex. Variable drug absorption and the short half‐life of most antiparkinson treatments, especially levodopa, are a main focus in understanding complications and have encouraged alternative delivery systems to limit fluctuation and dyskinesia at later stages. Comparatively little attention is paid to the way patients take their oral medication. Variable medicine‐taking behavior can affect the clinician's understanding of the diagnosis and rate of progression, and further prescription of PD medication. Medicine overuse in later stage PD is well documented and causes psychiatric disturbance and increases motor complications, but evidence of undertreatment and erratic intake is emerging, which is likely to affect motor control and quality of life adversely. Methods of quantifying compliance are compared for accuracy and limitations. Understanding medicine‐taking behavior is a first step in optimizing therapy and requires consideration of a patient's personal beliefs about their medicines. Although the benefits of regularizing oral medicine‐taking in a practical, achievable way in PD remain untested, such an approach might prolong and smooth the benefits of oral medication and is worthy of further research. © 2005 Movement Disorder Society
Existence of solutions for a mathematical model of structural phase transitions in shape memory alloys
Authors: Niezgódka Marek , Sprekels Jürgen 
Published: August 2005

AbstractIn this paper a thermomechanical model for the dynamics of structural phase transitions in the so‐called ‘shape memory alloys’ is developed. These materials exhibit rather spectacular hysteresis phenomena. The resulting mathematical model consists of a coupled and highly non‐linear system of partial differential equations reflecting the balance laws of linear momentum and energy. For an appropriate weak formulation the local‐in‐time existence of weak solutions is shown.
On a thermal stress problem for contacting half‐spaces with inclusions of other material involving a new method for computing potentials and singular integrals
Authors: Jentsch Lothar 
Published: August 2005

AbstractThis paper deals with a thermal stress problem for contacting half‐spaces of different materials having an inclusion of other material. With the aid of the contact tensor of two half spaces the problem is reduced to singular integral equations. Some new theorems on potentials with the contact tensor are used. Finally, a potential of the double layer with the contact tensor in the kernel and a singular integral operator, being the direct value of the potential, are calculated. For this a Kupradze method is applied, interpreting this potential as a solution of a contact problem of elastostatics. Some numerical experiments are communicated.
Explicit formula for scalar non‐linear conservation laws with boundary condition
Authors: Le Floch Philippe 
Published: August 2005

AbstractWe prove an uniqueness and existence theorem for the entropy weak solution of non‐linear hyperbolic conservation laws of the form

, with initial data and boundary condition. The scalar function u = u(x, t), x > 0, t > 0, is the unknown; the function f = f(u) is assumed to be strictly convex. We also study the weighted Burgers' equation: α ϵ ℝ

.We give an explicit formula, which generalizes a result of Lax. In particular, a free boundary problem for the flux f(u(.,.)) at the boundary is solved by introducing a variational inequality. The uniqueness result is obtained by extending a semigroup property due to Keyfitz.
A mathematical study of a continuum‐state cross‐bridge model of muscle contraction
Authors: Comincioli V. , Torelli A. 
Published: August 2005

AbstractIn the framework of the sliding‐filament theory of muscle contraction, we develop a model which describes physioiogical cross‐bridge activity with a continuum of states, from those which are detached and refractory to those which are attached. The latter are kinetically more important.An analytical study of the non‐linear partial differential equations of the mathematical model shows existence and uniqueness of the solution.
On non‐stationary Navier‐Stokes flows with vanishing viscosity associated with a variational inequality
Authors: An Ton Bui 
Published: August 2005

AbstractLet
equation image
g is a positive increasing function with 1⩽g(0). The existence of a unique solution of the Navier‐Stokes flow associated with Kε,γ and the convergence of the solution to that of the Euler equations as the viscosity goes to zero are established.
Inversion of the exponential X‐ray transform. I: Analysis
Authors: Hazou Irene A. , Solmon Donald C. 
Published: August 2005

AbstractThe exponential X‐ray transform arises in single photon emission computed tomography and is defined on functions on ℝn by magnified image, where μ is a constant. Approximate inversion, and inversion formulae of filtered back‐projection type are derived for this operator in all dimensions. In particular, explicit formulae are given for convolution kernels (filters) K corresponding to a general point spread function E that can be used to invert the exponential X‐ray transform via a filtered back‐projection algorithm. The results extend and refine work of Tretiak and Metz17.
Inequalities related to stationary flows of granulated media
Authors: Łukaszewicz Grzegorz , Piskorek A. 
Published: August 2005

AbstractWe investigate some variational inequalities associated with the equations of the stationary motion of granulated media with a constant density. These inequalities replace the usual equations of motion in the case when some additional constraints are imposed on the flow.We prove the existence of solutions of the inequalities, study their regularity, uniqueness, dependence on data and relations to solutions of the equations of motion.
Some remarks on Saint‐Venant's principle
Authors: Levine H. A. , Quintanilla R. , Payne L. E. 
Published: August 2005

AbstractWe consider a three‐dimensional hyperelastic cylinder in Ω = D × [0, ∞]. We study the asymptotic behaviour of the deformations of the cross‐sections in an equilibrium state. In this case we show that the solutions either have exponential decay or exponential growth. We give some initial conditions such that the latter case occurs.
Existence result and discontinuous finite element discretization for a plane stresses Hencky problem
Authors: Dhia H. Ben , Hadhri T. , Nedelec J. C. 
Published: August 2005

AbstractWe hereafter propose and analyse a discontinuous finite element method for a plane stress Hencky problem. For that purpose we begin by proving an existence result for the continuous problem. A kind of Green's formula between

and other intermediate results that may be of independent interest are presented and established separately. Then we formulate the discretized problem, give an existence result for it and prove a result of weak convergence of a subsequence of discrete solutions to a solution of the continuous problem.