bluuebunny/crossref_metadata_2025_split huggingface dataset:
Efficient implementation issues of finite difference time‐domain codes for Maxwell's equations
Authors: Lovetri Joe , Costache George I. 
Published: August 2005

AbstractThe computer implementation of time‐domain finite difference methods for the solution of Maxwell's equations is considered. As the basis of this analysis, Maxwell's equations are expressed as a system of hyperbolic conservation laws. It is shown that, in this form, all the well‐known differencing schemes can be easily expressed, thus increasing the applicability of the implementation issues to be discussed. Practical issues, such as computational efficiency and memory requirements, are discussed for the implementation of the finite difference schemes. Advanced programming techniques in the C language are used to implement the finite difference schemes discussed. The example of the penetration of electromagnetic energy through a shield with a thick gap is used to check the performance of the methods. It is shown that, for cases where the disturbance remains localized in the computational mesh, these techniques result in memory and CPU time savings.
Transmission‐line matrix method for solving the multidimensional continuity equation
Authors: Gui Xiang , Gao Guang‐Bo , Morkoç Hadis 
Published: August 2005

AbstractWe have extended the one‐dimensional transmission‐line modelling (TLM) of diffusion, drift and recombination of charge carriers in semiconductors to multiple dimensions. Detailed TLM formulation of the continuity transport equation in a more general form is presented.
3‐D edge element analysis of dielectric loaded resonant cavities
Authors: Zhu Zhou Le , Davies J. B. , Fernandez F. A. 
Published: August 2005

AbstractThe eigenmodes in electromagnetic cavities, loaded with arbitrarily shaped dielectric materials, are computed by the edge element method. The computation shows that the well known ‘spurious modes’ no longer appear. Formulae are given and verified so that the number of zero eigenvalues, which come from ∇ × H = 0, may be accurately predicted. Formulae for the order and density of the global matrices are given for a rectangular cavity regularly divided into bricks and tetrahedra, allowing an associated comparison between the contrasting edge and nodal element formulations. Comparison of the computed results with available theoretical and previously published data show the edge element approach to be a robust, accurate and effective method.
Function expansion algorithms for the time‐domain alalysis of shielded structures supporting electromagnetic waves
Authors: Mrozowski Michal 
Published: August 2005

AbstractSeries function expansion algorithms of the time‐domain analysis of boundary value problems are discussed. Electromagnetic fields inside a structure under investigation are expanded into series of basis functions and the expansion coefficients are found by means of the Galerkin method. The numerical cost of algorithms is discussed and a cost efficient approach is proposed for formulations using sine and cosine expansion functions. Compared with conventional time‐domain methods the algorithms described show the time evolution of the expansion coefficients rather than the samples of a physical continuum at discrete nodes.
Characteristics of the general rectangular 2D‐TLM network
Authors: Hoefer Wolfgang J. R. , Sautier Pascal 
Published: August 2005

AbstractIn this paper the traditional square mesh 2D‐TLM algorithm is generalized for rectangular meshes of arbitrary aspect ratio. It is shown that the anisotropic rectangular TLM network can be conceived in such a way that the propagation vector remains independent of the direction of propagation in the infinitesimal approximation. A full dispersion analysis of the rectangular mesh in then performed for the general case, and results are compared to that of the traditional square mesh.
Harmonic balance method applied to the numerical electrical physical modelling of two‐terminal, non‐linear microwave circuits in the frequency domain
Authors: Dalle C. 
Published: August 2005

AbstractA numerical frequence‐domain modelling of two‐terminal, non‐linear microwave circuits is presented. It basically relies on a process allowing the solution of the frequency‐domain curcuit harmonic balance equations while accounting for the semiconductor device by means of an accurate numerical macroscopic physical model. In its present state of development, the model allows the study of a single two‐terminal device circuit operating in harmonic mode. Its capabilites are illustrated by means of the results of a study devoted to the optimization of the load curcuit configuration of a millimetre‐wave avalanche diode frequency multiplier. The influence of the output load impedance level on the circuit output RF performance has been investigated for different input power levels in direct frequency multiplication mode and in the presence of additional circuit tunings at low harmonic rank idler frequencies.
A non‐linear and distributed modelling procedure of fets
Authors: Ongareau Eric , Aubourg Michel , Obregon Juan J. , Gayral Michel , Bosisio Renato G. 
Published: August 2005

AbstractThis paper describes a rigorous and systematic procedure to derive a non‐linear distributed FET model that an easily be implemented in CAD routines of simulators based on harmonic balance techniques. The new model is derived from a knowldge of the conventional linear lumped equivalent circuit, from non‐linear current sources extracted with pulsed measurements, and from the physical dimensions of the FET.For fundamental and haromonic requencies, 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 to 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.
Development of an induction motor drive phase model based on the TLM method
Authors: Selhi H. , Christopoulos C. , Howe A. F. , Hui S. Y. R. 
Published: August 2005

AbstractThis paper describes a phase model of an induction motor based on Transmission‐Line Modelling technique. Its main advantage compared to the existing TLM d‐q model is the possibility of using a small part of the stator self‐inductance of each pahase as a link model to connect the motor to external sources and drives. Unlike the d‐q model, the phase model does not therefore require any additional components for connection purposes. The application of the phase model is demonstrated by and example representing a traction drive ciruit. Identical simulation results to those obtained from a different study based on a d‐q model are derived.
Modelling an insulated gate bipolar transistor using bond graph techniques
Authors: Besbes Kamel 
Published: August 2005

AbstractSimulators in power electronics are less developed than in other electronic fields. The main modelling methods are between the numerical simulation of semiconductor device equations that hardly simulate circuits, and equivalent circuit models that show poor accuracy. We propose the application of the bond graph techniques to model modular power semiconductor devices. Furthermore, the IGBT is a new power device which combines a bipolar transistor with a MOSFET transistor. We develop a new IGBT bond graph model. The bond graph techniques give us good primary simulation results. We present in this paper the principle and the results of this modelling method.
A method for algebraic analysis of the TLM algorithm
Authors: Witwit A. R. M. , Wilkinson A. J. , Pulko S. H. 
Published: August 2005

AbstractAn analogy is described between the TLM algorithm and discrete state‐space control theory. The analogy is used to derive the characteristic equations corresponding to parametrized model structures. Characteristic equations corresponding to several widely used node structures are derived by this means and found to be consistent with the observed behaviour of corresponding TLM models. An example is given of the use of the analogy in teh predictive mode.
A parallel implementation of the finite difference time‐domain algorithm
Authors: Chew K. C. , Fusco V. F. 
Published: August 2005

AbstractIn this paper a parallel algorithm is created for solving electromagnetic wave scattering problems. The algorithm based on the finite difference time‐domain (FDTD) representation of the Maxwell's equations written in 3L Parallel Fortran for use on a transputer array.The problem simulated consists of a space (air) where a spherical dielectric scatterer is located. This space is subdivided into fine equisize meshes extending throughout the 3‐D domain; the excitation wave is of sinusoidal form. Geometric decomposition is used as the principal algorithm strategy.Results are presented for the performance of the classical sequential algorithm and compared with the parallel algorithm in terms of computational speed‐up.
On the potential use of cellular automata machines for electromagnetic field solution
Authors: Simons Neil R. S. , Cuhaci Michel , Adnani Nikhil , Bridges Greg E. 
Published: August 2005

AbstractIn this paper, the potential use of cellular automata machines for electromagnetic field solution is investigated. Cellular automata are computational models that operate on a discrete spatial lattice, evolve in discrete time, and employ simple discrete variables. We specifically examine the lattice gas automata which use simple variables to describe particles that interact with nearest neighbours on the lattice through simple rules. They are suitable for modelling the linear wave equation in two dimensions. A benefit of the cellular automata approach is that low‐cost, special‐purpose digital hardware exists for their efficient evaluation. The current state‐of‐the‐art cellular automata machine is CAM‐8. Computational experiments carried out on CAM‐8 are provided for problems involving plane wave interaction with perfectly conducting and dielectric media in two dimensions. The examples indicate the potential use of lattice gas automata for modelling electromagnetics and their efficient evaluation using cellular automata machines.
Improving the analytical figures of merit of SERS for the analysis of model environmental pollutants
Authors: De Jesús M. A. , Giesfeldt K. S. , Sepaniak M. J. 
Published: August 2005

AbstractThe presence of naphthalene, phenol and benzoic acid derivatives in natural waters constitutes a public health issue. The toxicity and chemical activity of these chemicals and their persistence in the environment depend on the types of functional groups attached to their basic aromatic structure. Surface‐enhanced Raman scattering (SERS) spectroscopy has shown promise for the analysis of aromatic compounds owing to a tremendous enhancement of the analytical response and also a large amount of available structural information. Despite these advantages, SERS has not been established as a routine analytical tool owing to limitations in the analytical figures of merit such as reproducibility and linear dynamic range. This paper reports the use of silver–polydimethylsiloxane nanocomposites in combination with a sample translation technique for the improved qualitative and quantitative analysis of model environmental pollutants in water. This novel approach considerably improves the reproducibility and the sensitivity of the technique by minimizing the thermal and photolytic effects inherent in SERS. The results show a linear dynamic range of at least two orders of magnitude with detection limits as low as 2.9 × 10−8 M and a precision of <10% relative standard deviation. The influences of different experimental variables such as irradiation time, translation rate and pH and the potential use of the technique for the analysis of environmental pollutants are presented. Copyright © 2004 John Wiley & Sons, Ltd.
In vitro polarization‐resolved resonance Raman studies of the interaction of hematin with the antimalarial drug chloroquine
Authors: Frosch T. , Küstner B. , Schlücker S. , Szeghalmi A. , Schmitt M. , Kiefer W. , Popp J. 
Published: August 2005

AbstractDespite the public health impact of human malaria, the mechanism of hemozoin inhibition by antimalarial drugs such as chloroquine (CQ) is not yet fully understood. Polarization‐resolved resonance Raman spectra of hematin and its complex with CQ were recorded under Q‐band resonance conditions in order to monitor the binding of the 4‐aminoquinoline drug to the heme macrocycle. Upon drug addition, only wavenumber shifts smaller than 2 cm−1 are detected, indicating a non‐covalent interaction in the electronic ground state of the drug–target complex. The decreased resonance Raman intensity of the anomalously polarized mode ν19(a2g) in the perpendicular polarized spectrum of the complex suggests changes of the excited‐state geometry along the corresponding normal coordinate. Copyright © 2004 John Wiley & Sons, Ltd.
A parametrix construction for the fundamental solution of the evolution equation associated with a pseudo‐differential operator generating a Markov process
Authors: Böttcher Björn 
Published: August 2005

AbstractWe use the method proposed by H. Kumano‐go in the classical case to construct a parametrix of the equation $ \textstyle {{\partial u} \over {\partial t}}$ + q (x, D )u = 0 where q (x, D ) is a pseudo‐differential operator with symbol in the class introduced by W. Hoh. In case where –q (x, D ) extends to a generator of a Feller semigroup our construction yields an approximation for the transition densities of the corresponding Markov process. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New versions of the Colombeau algebras
Authors: Shelkovich V. M. 
Published: August 2005

AbstractWe construct some versions of the Colombeau theory. In particular, we construct the Colombeau algebra generated by harmonic (or polyharmonic) regularizations of distributions connected with a half‐space and by analytic regularizations of distributions connected with an octant. Unlike the standard Colombeau's scheme, our theory has new generalized functions that can be easily represented as weak asymptotics whose coefficients are distributions, i.e., in form of asymptotic distributions . The algebra of asymptotic distributions generated by the linear span of associated homogeneous distributions (in the one‐dimensional case) which we constructed earlier [9] can be embedded as a subalgebra into our version of Colombeau algebra. The representation of distributional products in the form of weak asymptotic series proved very useful in solving problems which arise in the theory of discontinuous solutions of hyperbolic systems of conservation laws [10]–[16], [49] and [50]. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Global existence and nonexistence for a nonlinear wave equation with damping and source terms
Authors: Zhou Yong 
Published: August 2005

AbstractIn this paper we consider a nonlinear wave equation with damping and source term on the whole space. For linear damping case, we show that the solution blows up in finite time even for vanishing initial energy. The criteria to guarantee blowup of solutions with positive initial energy are established both for linear and nonlinear damping cases. Global existence and large time behavior also are discussed in this work. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Representation of the eigenvalues of the p ‐Laplacian by means of a surface integral
Authors: Lamberti Pier Domenico 
Published: August 2005

AbstractWe prove a natural generalization to the p ‐Laplacian of the celebrated Rellich identity. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Boundary value problems on manifolds with fibered boundary
Authors: Savin Anton , Sternin Boris 
Published: August 2005

AbstractWe define a class of boundary value problems on manifolds with fibered boundary. This class is in a certain sense a deformation between the classical boundary value problems and the Atiyah–Patodi–Singer problems in subspaces (it contains both as special cases). The boundary conditions in this theory are taken as elements of theC*‐algebra generated by pseudodifferential operators and families of pseudodifferential operators in the fibers. We prove the Fredholm property for elliptic boundary value problems and compute a topological obstruction (similar to Atiyah–Bott obstruction) to the existence of elliptic boundary conditions for a given elliptic operator. Geometric operators with trivial and nontrivial obstruction are given. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Diagnostic significance of reduced serum caeruloplasmin concentration in neurological disease
Authors: Walshe John M. 
Published: August 2005

AbstractThis study covers patients seen at a Wilson disease clinic between 1960 and 2002. The diagnosis of Wilson disease was confirmed in 316. Of 40 patients with a neurological presentation who were found not to have the disease, caeruloplasmin concentration was found to be reduced in 19. These 19 patients comprised 17 men and 2 women. The various diagnoses included Huntington's disease, multiple sclerosis, subacute sclerosing panencephalitis (SSPE), Hallervorden Spatz syndrome, and acaeruloplasminemia; in 9 no definite diagnosis was made. In view of the marked male preponderance, the lower limit of caeruloplasmin is calculated as for males. In an earlier study this was found to be 33.3 mg/dl (standard deviation, 6.1 mg/dl); therefore, 21.1 mg/dl is taken as the lower limit of normal. Particular attention is paid to 3 patients, 2 of whom had zero concentrations of caeruloplasmin and 1 had a very low level of the protein. Only 1 of these patients conformed to the classical picture of acaeruloplasminemia. The significance of a low caeruloplasmin concentration in patients with a variety of neurological syndromes is not clear but can lead to diagnostic confusion. When the concentration of this protein is very low or absent the diagnosis of acaeruloplasminemia must be considered. © 2005 Movement Disorder Society
On the stationary flows of viscous, incompressible and heat‐conducting fluids
Authors: Łukaszewicz Grzegorz 
Published: August 2005

AbstractWe consider a boundary‐value problem describing the motion of viscous, incompressible and heat‐conducting fluids in a bounded domain in ℝ3. We admit non‐homogeneous boundary conditions, the appearance of exterior forces and heat sources.Our aim is to prove the existence of a solution of the problem in Sobolev spaces.
Singularities of the Laplacian at corners and edges of three‐dimensional domains and their treatment with finite element methods
Authors: Stephan E. , Whiteman J. R. 
Published: August 2005

AbstractThree‐dimensional Poisson problems containing boundary singularities are treated. The forms of the solutions for certain problems of this type are derived, where the domains of the problems can be represented in terms either of spherical‐ or of cylindrical‐polar co‐ordinates. These singular forms are used to augment the basis of a standard piecewise polynomial Galerkin space, thus producing an augmented Galerkin technique which is suited to the context of a problem involving a singularity. Error estimates are derived.
Global existence for the Vlasov‐Poisson/Fokker‐Planck equation in many dimensions, for small data
Authors: Triolo L. 
Published: August 2005

AbstractA global existence result for the Cauchy problem of the Vlasov equation with a diffusive term is given. Smallness of the initial data is needed to show, via a ‘dispersive’ argument, the existence and nearness of the solution to the free one.
Interpolation of coefficients and transformation of the dependent variable in finite element methods for the non‐linear heat equation
Authors: Larsson Stig , Thomée Vidar , Zhang Nai‐Ying , Wendland W. 
Published: August 2005

AbstractError estimates are shown for some spatially discrete Galerkin finite element methods for a non‐linear heat equation. The approximation schemes studied are based on the introduction of the enthalpy as a new dependent variable, and also on the application of the Kirchhoff transformation and on interpolation of the non‐linear coefficients into standard Lagrangian finite element spaces.
Non‐characteristic mixed problems for non‐linear symmetric hyperbolic systems
Authors: Zajaczkowski W. M. , Piskorek A. 
Published: August 2005

AbstractIn this paper the existence and uniqueness of solutions of the following initial boundary value problem for non‐linear symmetric hyperbolic equations of the first order

are shown, where M = I+ −S, has the same from as the Kreiss' condition, but S must be sufficiently small (I+ is the unit matrix in the space generated by eigenvectors of the matrix − A·n̄, corresponding to positive eigenvalues) and n̄ is a unit outward vector normal to the boundary. The main result of the paper is obtaining an a priori estimate for non‐linear equations. This estimate is obtained for sufficiently small time and norms of given data functions. The existence of solutions is proved by the method of successive approximations, which can be used because at each step such properties as symmetry of matrices and the numbers of positive and negative eigenvalues of the matrix − A·n̄ are assured. This can be done because we restrict our attention to such systems of equations for which these properties are satisfied for solutions from some neighbourhood of initial data u0. Therefore, using the fact that solutions in the class of continuous functions are sought, these properties can be satisfied for sufficiently small time. Moreover, some examples of initial boundary value problems for equations of hydrodynamics and magnetohydrodynamics are considered.
On properties of the iterative maximum likelihood reconstruction method
Authors: Mülthei H. N. , Schorr B. , Törnig W. 
Published: August 2005

AbstractIn this paper, we continue our investigations6on the iterative maximum likelihood reconstruction method applied to a special class of integral equations of the first kind, where one of the essential assumptions is the positivity of the kernel and the given right‐hand side. Equations of this type often occur in connection with the determination of density functions from measured data. There are certain relations between the directed Kullback–Leibler divergence and the iterative maximum likelihood reconstruction method some of which were already observed by other authors. Using these relations, further properties of the iterative scheme are shown and, in particular, a new short and elementary proof of convergence of the iterative method is given for the discrete case. Numerical examples have already been given in References 6. Here, an example is considered which can be worked out analytically and which demonstrates fundamental properties of the algorithm.
On stationary flows of asymmetric fluids with heat convection
Authors: Łukaszewicz Grzegorz , Waluś Włodzimierz , Piskorek A. 
Published: August 2005

AbstractExistence, uniqueness and regularity of solutions of equations describing stationary flows of viscous incompressible isotropic fluids with an asymmetric stress tensor have been considered recently.5 In this paper we extend the results of Reference 5 to include heat convection in the hydrodynamic model. We show that the boundary value problem (1.1)–(1.6) below has solutions in appropriate Sobolev spaces, provided the viscosities v and ca + cd are sufficiently large. The proof is based on a fixed point argument. Moreover, we show that the solutions are unique if the heat conductivity κ is large enough.