bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new solution for the acoustic pressure‐field in a perfect wedge
Authors: Borejko Piotr 
Published: June 2004

AbstractA time domain analytical solution is presented for the acoustic pressure‐field due to an impulsive point source in a liquid wedge with a rigid sloping bottom. The horizontal boundary of the wedge is a pressure‐release surface. The wedge is isovelocity, and it is three‐dimensional (3‐D) in that the source and the receiver are not restricted to the plane perpendicular to the wedge apex. This 3‐D wedge with perfectly reflecting (i.e., impenetrable) boundaries, the 3‐D perfect wedge, is the simplest theoretical model of a shallow water environment in which the ocean bottom has a constant slope, but it is inadequate in that it cannot account for acoustic penetration of the bottom typical for a real ocean floor.In a perfect wedge, the acoustic field produced by a point source consists of two components: the diffraction field due to scattering at the apex, which under certain conditions vanishes [1], and the image field including the wave emitted by the source and a number of waves reflected off the wedge boundaries. These waves with spherical wave fronts propagate along the stationary time paths (the ray paths). The repeated reflections from the sloping bottom introduce the curvature into the projection of the ray path onto the horizontal boundary, provided that the first segment of this path originating at the source has a cross‐slope component. This path curvature in the horizontal is known as “horizontal, or bathymetric refraction” [2]. The ray path that leaves the source propagating up‐slope may be turned around to reach the receiver propagating back down‐slope. This change in propagation direction, known as “backscattering” [2], is due to multiple bottom reflections. The receiver can thus be reached along one of the two ray paths: the direct path or the indirect path which is turned around on approaching the apex. The image field in the wedge is thus three‐dimensional, i.e., it depends on three spatial coordinates: the range (normal to the apex), the cross‐range (parallel to the apex), and the depth coordinate.
Sound Insulation by Laminated Viscoelastic Plates
Authors: Langer S. , Schanz M. , Antes H. 
Published: June 2004

AbstractPlates are basic components in industrial structural design whose acoustical properties are often very important to reduce noise, e.g., in a car or a building. The sound insulation by plates is influenced by various effects, e.g., by the plate's mass but also by their damping capability. Hence, for a realistic analysis, damping should be taken into account which can approximatively be modelled by the use of a viscoelastic material law.Moreover, in automotive industry and structural engineering, laminated plates are very common to improve stiffness and stability, where plates with a viscoelastic core and rigid faces show additionally an excellent acoustical behaviour. Those laminated panes with a viscoelastic core are used in the design of windscreens, and, to improve sound insulation, in the design of building windows.Here, the mechanical behaviour of such a laminated plate is described by using a homogenisation procedure. The damping property of the plate is influenced by the stiffness of the viscoelastic core, it's dissipation factor, and by the thickness of the dissipating layer. These properties of a three‐layer‐plate are mapped on homogenised material parameters of a simple plate via the Ansatz of Ross, Kerwin and Ungar (RKU‐Ansatz).Finally, the sound insulation effectiveness of plates is analysed numerically.
Influence of Incompressibility on Different Wave Types in Porous Media
Authors: Pryl Dobromil , Schanz Martin 
Published: June 2004

AbstractThere are three wave types in poroelastic continua, the fast compressional wave, with solid and fluid moving inphase, the shear wave, and the second (slow) compressional wave, which has no equivalent in elastic materials, with solid and fluid moving in opposite directions. The fast compressional wave propagates with infinite speed if both constituents are modelled incompressible.Numerical results of BEM calculations showing the influence of incompressible constituents will be presented as well as elements employing different shape functions for the solid displacements and the pore pressure.
Capillary and Gravity Waves on Bounded Region of Flow Free Surface
Authors: Sherykhalina Nataliya , Zhitnikov Vladimir 
Published: June 2004

AbstractThe problems of two‐dimensional flow of inviscid incompressible fluid are considered. The flow is bounded on one side with rectilinear wall possessing a gap. The fluid is assumed to be weightless in the first problem and surface tension is taken into account. The fluid is to be gravity in the second problem. The problems are solved at linear and nonlinear statement.
Stieltjes Truncated Moment Problem with Point Constraints
Authors: Adamyan Vadim M. , Tkachenko Igor M. 
Published: June 2004

AbstractThe truncated Hamburger and Stieltjes moment problems [1] were solved elsewhere (see [3] and references therein) using the methods of the extension theory of Hermitian operators and, in particular, the results on extensions of nonnegative operators and matrices. Moreover, applying methods of the extension theory we found a purely algebraic algorithm for the solution of both problems. Here we solve the corresponding moment problems with point constraints.
On the representation of generalized axially symmetric potentials in the neighbourhood of an isolated singularity
Authors: Berglez Peter 
Published: June 2004

AbstractWe give explicit representations of generalized axially symmetric potentials using certain differential operators acting on holomorphic functions. This is done for potentials defined in simply connected domains as well as defined in the neighbourhood of an isolated singularity. Further the kernel of an integral operator ‐ the so called Riemann matrix function ‐ is given in an explicit form for an integral representation of the potentials.
Anisotropic Wavelet Bases and Restricted Nonlinear Approximation
Authors: Hochmuth Reinhard 
Published: June 2004

AbstractRestricted nonlinear approximation is a generalization of n‐term approximation in which a weight function is used to control the terms of the approximant. Here, restricted nonlinear approximation is considered with respect to anisotropic wavelet bases. In particular, characterizations for those functions, which provide a specific convergence rate by restricted nonlinear approximation, are presented.
Thermal control of Huygens mock up probe in Earth atmosphere: Thermo‐fluid dynamic simulation and mission data
Authors: Bettanini Carlo , Antonello Marco , Bianchini Giannandrea 
Published: June 2004

AbstractA mock up of Huygens probe with 76 channels acquisition has been developed at University of Padova and successfully flown with a stratospheric space balloon from Italian Space Agency Base in Trapani on May 30th 2002. Temperature sensors have monitored temperature profiles in critical points of electronics, batteries and structure during raise at 40 km altitude, floating and parachuted descent. A thermal model of the probe has been implemented taking into consideration incoming external fluxes (solar direct, albedo and radiative heat fluxes), internal heat fluxes generation and convective heat transfer with atmosphere as a function of probe altitude. For the evaluation of convective fluxes and probe spinning rates an algebraic turbulent model, developed by the present authors, has been employed. This model is suitable to predict effects such as flow curvature and separation and solid boundary rotations. Simulation results have been utilized during project phase to optimize thermal paths in order to keep critical components in the allowable temperature range and for post flight analysis of mission data. These data show that passive thermal control of the probe has performed as expected contributing to a extremely successful scientific flight.
On the mathematical modelling of dynamic problems in a micro‐periodic composite material
Authors: Rychlewska Jowita , Wozniak Czeslaw 
Published: June 2004

AbstractThe aim of this paper is to propose a certain new approach to the formulation of both discrete and continuum models for the analysis of dynamic problems in elastic composite solids with a periodic microstructure. The proposed approach is based on a periodic simplicial division of the unit cell and on the assumption of a uniform strain in every simplex. The main feature of the obtained discrete model is the finite‐difference form of governing equations. By applying smoothing operation the continuum models are derived directly from the discrete ones.
Traveling waves for chemotaxis–systems
Authors: Schwetlick Hartmut 
Published: June 2004

AbstractIn this paper we study the existence of traveling wave solutions to the Keller‐Segel model, a general model of chemotaxis, where the species do not reproduce. In the case of logarithmic sensitivity we show that various functionals modeling the reactive feedback on the chemo‐attractant do allow for traveling waves and a wide range of qualitatively different behavior is possible. We can find monotone fronts as well as pulse solutions in the densities of the population and the chemical. In particular, a new kind of solution exists, where both densities travel as pulses.
A constructive approach to modelling the tight shapes of some linked structures
Authors: Starostin E.L. 
Published: June 2004

AbstractA variational approach is used to find the shortest curves confined to lie in two orthogonal planes and separated by a constant distance. The method is applicable to constructing tight shapes of linked structures each component of which is known to be planar. The shapes of the Borromean rings and two clasped pieces of rope are two examples. A concept of tight periodic structures is introduced and discussed.
Vibration of the soil caused by a vehicle moving over the randomly uneven surface of a slab track
Authors: Grundmann H. , Lenz S. 
Published: June 2004

AbstractA vehicle which passes an uneven surface of a slab track causes vibrations of the whole system: the vehicle, the slab track and the subsoil. For a given random unevenness Δw of the slab track surface, covariances of the soil surface motion are calculated.
Sparse Quadrature as an Alternative to Monte Carlo for Stochastic Finite Element Techniques
Authors: Keese A. , Matthies H. G. 
Published: June 2004

AbstractWe consider the solution of nonlinear stochastic partial differential equations by a Galerkin‐method and by projection in the stochastic dimension and compute the occurring high‐dimensional integrals by sparse (Smolyak)‐ and Monte Carlo‐integration.
Reliability of a Rail with Respect to the Shakedown
Authors: Sieniawska R. , Wysocka A. , Żukowski S. 
Published: June 2004

AbstractAn approach for calculating the reliability of a rail with respect to elastic‐plastic work of the material is presented. The algorithm integrates the random nature of static and dynamic load with elastic‐plastic strains of the structure. The rail is modelled as a beam of infinite length founded on a rigid sleepers and visco‐elastic soil. The rail is loaded by a moving train in which the locomotive and railway cars are modelled by random point forces. The approach presented can be useful in reliability analysis of railway rails. Numerical examples have been provided.
Application of the Stochastic Renewal Processes in the Dynamics of Beams under Moving Load
Authors: Śniady P. , Sieniawska R. , Żukowski S. 
Published: June 2004

AbstractThe problem of stochastic dynamics of elastic beams of deterministic parameters loaded by the trafic flow is considered. Each vehicle is modelled by one or more random point forces travelling with the same constant speed. As a model of vehicle arrivals the renewal stochastic processes are adopted. An analytical technique is developed to determine the two first probabilistic characteristics of the beams response. Numerical examples are provided.
Crack Identification as an Optimization Task
Authors: Engelhardt M. , Stavroulakis G.E. , Antes H. 
Published: June 2004

AbstractIn this paper, crack and hole identification problems are studied. From the knowledge about the reflected wave forms of an embedded crack, an identification may be performed by an evolutionary strategy or by a neural network. This approach corresponds to a generalization of the impact‐echo nondestructive evaluation technique. The numerical solution of the two‐dimensional elastodynamical problem, i.e., to determine the reflected waveforms, is performed by means of boundary element techniques.
Optimal design of an ellipsoidal head of a pressure cylindrical vessel
Authors: Magnucki Krzysztof , Lewinski Jerzy 
Published: June 2004

AbstractThe subject of analysis is a stress concentration problem in a circular cylindrical vessel with ellipsoidal heads. The region of the junction of ellipsoidal and cylindrical shells is subject to stress concentration. Intensity of the concentration depends, first of all, on relative convexity of the ellipsoidal head, and the ratio of thicknesses of the shells. Based on the boundary disturbance theory the stress state in this cylindrical vessel was analytically described. Optimal ellipsoidal heads were determined on the grounds of three optimisation criteria.
Multi‐grid solver for the p‐version of the fem.
Authors: Beuchler Sven 
Published: June 2004

AbstractIn this paper we propose a pre‐conditioner for an element stiffness matrix of the p‐version of the fem in two dimensions. We prove that the condition number of the preconditioned system matrix is bounded by a constant independent of the polynomial degree. The origin of this pre‐conditioner is the multi‐grid method.
Bounds for the Effective Interest Rate for Constant, Periodic Annuities
Authors: Boese F. G. 
Published: June 2004

AbstractFor the title's financial credit class, arbitrary tight bounds for the effective interest rate, evaluable on (+, −, ∗︁, /,√)‐pocket calculators, are propounded. Starting with an initial bound with at most 0.85% relative error, in each refinement step about 61% more valid decimal places are won.
A multi‐level solution of scalar and vectorial interpolation problems based on iterated elliptic operators
Authors: Gáspár Csaba 
Published: June 2004

AbstractOne of the most popular methods to solve scattered data interpolation problems is the method of radial basis functions. However, it leads to a linear system with large, dense and ill‐conditioned matrix, which causes severe numerical difficulties. Here a relatively new approach is presented which completely avoids the large and dense matrices and significantly reduces the computational cost. The interpolation problem is converted to a higher order (typically to an iterated elliptic) partial differential equation supplied with the interpolation condition as special boundary conditions. This new problem is well‐posed in a suitable Sobolev space and can be solved by using robust, multi‐level methods. The approach is generalized also to vectorial interpolation problems, where the interpolation vector field is assumed to satisfy some additional conditions e.g. it is irrotational or divergence‐free.
Relationship Between Geršgorin‐type Theorems for Certain Subclasses of H‐Matrices
Authors: Cvetković Ljiljana , Kovačević Maja , Kostić Vladimir 
Published: June 2004

AbstractIt is well known that the eigenvalue inclusion domain can be obtained by Geršgorin theorem. It is also known that the Geršgorin theorem is equivalent to the statement that each strictly diagonally dominant (SDD) matrix is nonsingular. Similarly, statements about nonsingularity of some classes of matrices, which are generalizations of SDD class, produce new Geršgorin‐type theorems for eigenvalue inclusion domain. In this paper we will consider some subclasses of H‐matrices and corresponding (Geršgorin‐type) eigenvalue inclusion theorems. Finally, we will establish relationship between given inclusion domains.
Iterative Method with the Preconditioner (I + Smax) for H‐Matrices
Authors: Kostić Vladimir , Cvetković Ljiljana 
Published: June 2004

AbstractIn 2002 Kotakemori et al. have reported the Modified Gauss‐Seidel method with a preconditioner (I + Smax). The convergence of the new method they investigated only for Z‐matrices, for which the new method can be superior to other iterative methods. But, in the case of H‐matrices this method can be superior to the others, too. In this paper we will give some sufficient conditions for the convergence in the case of H‐matrices.
Special preconditioners for solution of transport‐dominated convectiondiffusion problem
Authors: Krukier L.A. , Lapshina O.A. , Krukier B.L. 
Published: June 2004

AbstractSpecial class of preconditioners based on skew‐symmetric part of the matrix have been created for CG and BiCG type's methods. Theoretical and numerical investigation was carried out by the model of the linear algebraic equation system generated by finite‐difference approximation of the convection‐diffusion equation.
Energy conservation in modified Nyström methods for separable Hamiltoniansystems
Authors: Arnold Martin , Pfeiffer Andreas 
Published: June 2004

AbstractNumerical integration methods that preserve structural properties of time dependent di.erential equations have often improved stability and smaller errors in long‐term simulations than classical standard methods like Runge–Kutta or BDF. In the present paper an energy conserving Galerkin type approach of Betsch and Steinmann is generalized to modified Nyström methods for separable Hamiltonian systems. The bene.ts of this new class of methods are illustrated by numerical tests for a benchmark problem from celestial mechanics.
Implicit Extension of Taylor Series Method with Numerical Derivatives
Authors: Molnárka Gy. , Miletics E. 
Published: June 2004

AbstractThe Taylor series method is one of the earliest analytic‐numeric algorithms for approximate solution of initial value problems for ordinary differential equations. The main idea of the rehabilitation of these algorithms is based on the approximate calculation of higher order derivatives using well‐known technique for the partial differential equations. The implicit extension based on a collocation term added to the explicit truncated Taylor series. This idea is different from the general collocation method construction, which led to the implicit R‐K algorithms [1].
H−1 LSFEM for Fluid‐Structure Problems
Authors: Kayser‐Herold Oliver , Matthies Hermann G. 
Published: June 2004

AbstractThe instationary incompressible Navier‐Stokes equations, which appear in the context of a instationary fluid‐structure problem are solved with a Space‐Time LSFEM formulation. Convergence rates of the proposed scheme are examined using the Taylor vortex.
Algebraic Multigrid Preconditioners for Sparse Approximations of Boundary Element Matrices
Authors: Langer U. , Pusch D. , Reitzinger S. 
Published: June 2004

AbstractThis paper presents new algebraic multigrid preconditioners for sparse representations of boundary element matrices which arise from the so‐called adaptive‐cross‐approximation to dense boundary element matrices resulting from the standard collocation, or Galerkin boundary element discretization of the single layer potential operator.
The approximate solution of integro‐ differential equations
Authors: Takaci Djurdjica 
Published: June 2004

AbstractWe consider a class of partial integro‐differential equations with appropriate conditions and its corresponding equation in the field of Mikusiński operators. As is usual in numerical analysis, we construct the corresponding difference equation, determine its solution, analyze its character and treat it as the approximate solution of the considered problem. We also estimate the error of approximation.
Genetic lineage of poorly differentiated gastric carcinoma with a tubular component analysed by comparative genomic hybridization
Authors: Peng Dun‐Fa , Sugihara Hiroyuki , Mukaisho Ken‐ichi , Ling Zhi‐Qiang , Hattori Takanori 
Published: June 2004

AbstractAnalysis of cell lineage is based on the use of genetic markers inherent to the lineage to be analysed. The breakpoints of unbalanced translocations, and the pattern of chromosomal loss/gain determined by comparative genomic hybridization (CGH), have been previously used to demonstrate lineages in diffuse‐type gastric carcinoma. Signet ring cell carcinoma was shown to progress to poorly differentiated adenocarcinoma, and early diffuse‐type gastric carcinoma to advanced diffuse‐type gastric carcinoma. The present study focuses on poorly differentiated adenocarcinoma with a tubular component to clarify its derivation. CGH and array CGH were applied to DNA extracted from multiple portions of individual tumours and amplified by degenerate oligonucleotide‐primed (DOP) PCR and the changes common to the samples in each tumour (stemline changes) were compared between the tumours with and those without a tubular component. Within individual tumours, the samples from the tubular component and those from the other components had common stemline changes and a very similar frequency pattern of chromosomal changes, indicating their common derivation. Frequent stemline changes were 8q+, 7p+, 3q+, 20q+, and 10p+, and these were different from those in the tumours without a tubular component. It was noticed that there were two subgroups in the tumours with a tubular component: one with 5p+, 6p+, 7p+, and 10p+, and the other without these changes. The latter had cytogenetic and clinicopathological features similar to those of the tumours without a tubular component. Analysis of the clonal evolution process by constructing dendrograms for each tumour gave results consistent with the notion that the latter subgroup may derive from signet ring cell carcinoma and the former from tubular adenocarcinoma. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Gastric B‐cell mucosa‐associated lymphoid tissue (MALT) lymphoma in an animal model of ‘Helicobacter heilmannii’ infection
Authors: O'Rourke JL , Dixon MF , Jack A , Enno A , Lee A 
Published: June 2004

AbstractWhile Helicobacter pylori is accepted as the dominant human gastric bacterial pathogen, a small percentage of human infections have been associated with another organism, commonly referred to as ‘Helicobacter heilmannii’, which is more prevalent in a range of animal species. This latter bacterium has been seen in association with the full spectrum of human gastric diseases including gastritis, peptic ulceration, and gastric carcinomas, including gastric B‐cell mucosa‐associated lymphoid tissue (MALT) lymphoma. This study describes an analysis of the pathogenic potential of a number of ‘H heilmannii’ isolates in an animal model of gastric MALT lymphoma. BALB/c mice were infected with ten different ‘H heilmannii’ isolates originating from both human and animal hosts. The animals were examined at various time points for up to 28 months after infection. The infected animals initially developed a chronic inflammatory response within 6 months. This histological response increased in severity with the length of infection, with the development of overt lymphoma in some animals 18 months after infection. MALT lymphomas were detected in up to 25% of the infected animals. The prevalence of lymphoma was dependent on the length of infection and the origin of the infecting isolates. A range of other histological features accompanied the lymphocytic infiltration, including invaginations of the gastric epithelium and associated hyperplastic tissue, mucus metaplasia, and a small number of diffuse large B‐cell lymphomas. The ability to manipulate experientially the presence of the bacterium in the animal model will allow further studies examining the role of antigen drive in the development of Helicobacter‐associated MALT lymphoma. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.