bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some results on coupled linear wave equations
Authors: Eden Alp , Erbay Saadet , Hacinliyan Irma 
Published: August 2008

AbstractIn the present study, we consider a generalized Davey‐Stewartson (GDS) system consisting of a nonlinear Schrödinger (NLS) type equation and two asymmetrically coupled linear wave equations. We obtain integral representation of solutions to the coupled linear wave equations. As applications, we present some localized solutions to the GDS system for a special choice of parameters and find some estimates of the solutions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the moving boundary formulation for parabolic problems on unbounded domains
Authors: Fazio Riccardo , Iacono Salvatore 
Published: August 2008

AbstractA parabolic problem defined on unbounded domains and admitting invariance property to Lie group of scalings can be transformed into an equivalent boundary value problem governed by an ODE defined on an infinite interval. A free boundary formulation and a convergence theorem for this kind of transformed problems are available in [Fazio, SIAM J. Numer. Anal., 33 (1996), pp. 1473‐1484]. Depending on its scaling invariance properties, the free boundary problem is then solved numerically using either an iterative or a non‐iterative method. Finally, the solution of the parabolic problem is retrieved applying the inverse map of similarity. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Design of cold‐formed thin‐walled beams with application of an expert system
Authors: Kasperska R. , Ostwald M. , Mikolajewski D. 
Published: August 2008

AbstractThe aim of this paper is to present the problem of optimal design of selected cross section shapes of the thin‐walled coldformed beams under combined loads. The optimization problem is given as the bicriteria one, where the cross‐sectional area of the thin‐walled beam and the deflection of the beam centre are the objective functions. The work provided optimal parameters of cross‐sections of the beams, satisfying the conditions of general and local stability, strength, limiting loading capacity of the beam, structural, technological and exploitation constraints. This paper outlines the application of a knowledge‐based expert system built to assist engineers in the designing process and multicriteria optimization of cold‐formed thin‐walled beams. The paper includes some exemplary numerical results in the form of figures. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sort‐Jacobi and generalizations of the symmetric eigenvalue problem
Authors: Kleinsteuber M. 
Published: August 2008

AbstractIn this paper, it is sketched how the Sort‐Jacobi method for the symmetric eigenvalue problem extends to the (–1)‐eigenspace of the Cartan involution on an arbitrary semisimple Lie algebra. The proposed method is independent of the representation of the underlying Lie algebra and generalizes well‐known normal form problems such as the symmetric, Hermitian, skewsymmetric, symmetric and skew‐symmetric ℝ‐Hamiltonian eigenvalue problem and the singular value decomposition. It allows a unified treatment of the above eigenvalue methods, including local convergence analysis. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A predictor‐corrector method for a class of equilibrium problems
Authors: Preda Vasile , Beldiman Miruna , Bătătorescu Anton 
Published: August 2008

AbstractWe consider two classes of generalized monotone functions and generalized skew symmetric functions. By applying the method of auxiliary‐principle, we propose and study a predictor‐corrector algorithm for solving mixed quasiequilibrium problems involving σ ‐pseudomonotone functions with respect to a ξ ‐skew symmetric bifunction, which are concepts introduced in this paper. We prove the convergence of the iterative sequence under generalized pseudomonotonicity and skew symmetry assumptions, improving some known results in the recent literature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sufficient conditions for exact penalty in constrained optimization
Authors: Zaslavski Alexander J. 
Published: August 2008

AbstractIn this paper we use the penalty approach in order to study constrained minimization problems. A penalty function is said to have the exact penalty property if there is a penalty coefficient for which a solution of an unconstrained penalized problem is a solution of the corresponding constrained problem. We discuss very simple sufficient conditions for the exact penalty property. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical benchmarks for creep‐damage modeling
Authors: Altenbach Holm , Naumenko Konstantin , Gorash Yevgen 
Published: August 2008

AbstractThe aim of creep modeling is to reflect basis features of creep in structures including the evolution of inelastic deformations, relaxation and redistribution of stresses as well as the local reduction of material strength. A model should be able to account material deterioration processes in order to predict long term structural behavior and to analyze critical zones of creep failure. In recent years general purpose finite element codes have become the widely accepted tool for the structural analysis. To consider both the creep and the damage processes, a specific constitutive model with selected internal state variables, special types of stress and temperature functions as well as material constants identified from available experimental data should be incorporated into the commercial finite element code by writing a user defined material subroutine. To assess the reliability of the developed subroutine as well as the accuracy of the results with respect to the mesh density, type of finite element, the time step, and the iteration methods, numerical benchmark problems are required. Here we present two benchmark problems of creep‐damage mechanics which can be solved by approximate numerical methods. The reference solutions are compared with the finite element solutions by ANSYS and ABAQUS finite element codes with user creep model subroutines. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mechanisms for oscillations in a biological competition model
Authors: Curtu Rodica 
Published: August 2008

AbstractA four‐dimensional dynamical system that models perceptual bistability in the brain is analyzed. Two variables represent the activity of two competing neural populations and they evolve in fast time; other two variables are slow and they are associated with an intrinsic negative feedback to each population. The external stimulus strength I is the bifurcation parameter. We construct the normal form and prove that oscillations occur in the system through supercritical Hopf bifurcations: as I decreases from large to moderate values a limit cycle is born; then it disappears for lower values of I. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The magic of SPSA
Authors: Gerencsér L. , Vágó Zs. , Hill Stacy D. 
Published: August 2008

AbstractThe basics of SPSA (simultaneous perturbation stochastic approximation) initiated and developed in [1] will be desctribed. We point out the advantages of SPSA over the finite difference stochastic approximation (FDSA) or Kiefer‐Wolfowitz (KW) method. Its applicability in noise free optimization and in discrete optimization will be also briefly described. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Statistical modeling of compressible turbulent channel flow
Authors: Heinz Stefan 
Published: August 2008

AbstractSeveral questions that are relevant to turbulence modeling are addressed on the basis of recently obtained direct numerical simulation results of turbulent supersonic channel flow. In particular, this concerns the turbulence frequency production mechanism, wall damping effects on turbulence model parameters, and the relevance of compressibility effects. Limited support is found for usually applied models for the turbulence frequency production and wall damping effects. In contrast to that it is shown that turbulence frequency production mechanisms and wall damping effects may be explained very well on the basis of a frequency scaling that characterizes mean flow changes. The influence of compressibility is found to be relevant. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal control of a thermomechanical model of phase transitions in steel
Authors: Hömberg Dietmar , Kern Daniela 
Published: August 2008

AbstractWe consider an optimal control problem concerning heat treatment of steel. The mathematical model consists of the equations of thermoelasticity coupled to a system of rate laws accounting for the phase transition kinetics. For the coupling a mixture ansatz for the different thermal expansion coefficients is used. In contrast to classical thermoelasticity this leads to residual deformations whenever the resulting phase distribution at end‐time is inhomogenous. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wavelets and splines for modelling the earth's magnetic field
Authors: Mayer Carsten 
Published: August 2008

AbstractAt the present time there is an unprecedented opportunity to use satellite magnetometer data, as for example Oersted and CHAMP records, to improve our knowledge of the Earth's magnetic field and its sources. These measurements contain contributions from the main magnetic field of the Earth, the crustal field as well as contributions coming from different exterior (ionospheric and magnetospheric) sources. For the mathematical analysis of the data it is critical to have in hand appropriate tools which separate these sources and which are able to analyze the different contributions independently. We present in this talk an approach in terms of (spherical) scalar and vectorial scaling functions and wavelets to handle these problems. Examples include crustal field modelling and reconstruction of ionospheric currents. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An hp finite element method for singularly perturbed systems of reactiondiffusion equations
Authors: Oberbroeckling Lisa , Xenophontos Christos 
Published: August 2008

AbstractWe consider the approximation of a coupled system of two singularly perturbed reaction‐diffusion equations by the finite element method. The solution to such problems contains boundary layers which overlap and interact, and the numerical approximation must take this into account in order for the resulting scheme to converge uniformly with respect to the singular perturbation parameters. We present results on a high order hp finite element scheme which includes elements of size O (εp) and O (μp) near the boundary, where ε, μ are the singular perturbation parameters and p is the degree of the approximating polynomials. Under the assumption of analytic input data, the method yields exponential rates of convergence as p → ∞, independently of ε and μ. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A holistic finite element and multi‐body systems approach for the virtual product development
Authors: Barthel Corinna 
Published: August 2008

AbstractThis article describes the creation of a holistic modeling of a machine tool using a multi‐body‐systems approach with an integrated flexible body. This lower order model is validated by a detailed finite element model and its eigenvalues are improved by a model‐updating algorithm. The improved model is used for investigation of the machine vibration during the cutting process and the prediction of chatter. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coarse‐to‐fine partitioning of signals
Authors: Florack Luc 
Published: August 2008

AbstractAn empirically acquired signal can be analyzed in a multi‐scale framework. Its multi‐scale structure induces a hierarchical partitioning of the signal domain into topologically meaningful segments. A method is proposed to operationalize this using elementary results from singularity theory for certain generic solutions of the one‐dimensional heat equation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hölder continuity of minimizers for the state constrained Boza problem
Authors: Bettiol Piernicola , Frankowska Hélène 
Published: August 2008

AbstractRegularity of minimizers for the Bolza optimal control problem has been extensively studied by several authors (cf. For instance [2–5] and the references contained therein). Here we give a generalization of some results of [5] by using an approach introduced in [3]. We consider a Bolza problem under state constraints and show that, if the Hamiltonian function is smooth enough and enjoys some monotonicity properties, then both the adjoint state and optimal trajectory enjoy Hölder type regularity. We also provide sufficient conditions for Hölder regularity of optimal controls. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transonic viscous inviscid interactions in narrow channels
Authors: Meyer G. , Kluwick A. 
Published: August 2008

AbstractUnsteady as well as steady transonic flows through channels which are so narrow that the classical boundary layer approach fails are considered. As a consequence the properties of the inviscid core and the viscosity dominated boundary layer region can no longer be determined in subsequent steps but have to be calculated simultaneously. The resulting interaction problem for laminar flows is formulated for both perfect and dense gases under the requirement that the channel is sufficiently narrow so that the flow outside the viscous wall layers becomes one‐dimensional in the leading order approximation. The latter allows an interpretation of the flow in the core region by means of the theory of one‐dimensional transonic inviscid flow through a Laval nozzle while preserving the essential features of the interaction problem associated with the internal structure of pseudoshocks. The sensitivity of a separation bubble caused by a pseudoshock of sufficient strength to perturbations under the condition of choked flow will be demonstrated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical propagator method solutions for the linear parabolic initial boundary‐value problems
Authors: Rimshans Janis , Guseynov Sharif 
Published: August 2008

AbstractOn the base of our numerical propagator method a new finite volume difference scheme is proposed for solution of linear initial‐boundary value problems. Stability of the scheme is investigated taking into account the obtained analytical solution of the initial‐boundary value problems. It is shown that stability restrictions for the propagator scheme become weaker in comparison to traditional semi‐implicit difference schemes. There are some regions of coefficients, for which the elaborated propagator difference scheme becomes absolutely stable. It is proven that the scheme is unconditionally monotonic. Analytical solutions, which are consistent with solubility conditions of the problem are formulated for the case of constant coefficients of parabolic equation by using Green function approach. Solubility of the linear initial‐boundary value problem with Newton boundary conditions containing lower order derivatives is discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Schwarz‐type smoothers for elliptic optimal control problems
Authors: Simon René , Zulehner Walter 
Published: August 2008

AbstractWe present a multigrid method for elliptic optimal control problems using a patch smoother. The method allows a rigorous multigrid convergence analysis and shows good convergence properties, which are comparable with known results from literature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental and numerical investigation of shock wave‐loaded plates
Authors: Stoffel Marcus , Schmidt Rüdiger , Weichert Dieter 
Published: August 2008

AbstractIn the present paper measured and simulated vibrations of viscoplastic plates under impulsive loadings are compared to each other. The aim is to determine how accurately the measured deformations can be calculated by the chosen constitutive and structural theories. The damage growth in the plate specimens until failure is predicted by finite element simulations and compared to shock tube experiments. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ergodicity, mixing and the Bernoulli property in a DNA hybridization microarray
Authors: Sturman Rob , Wiggins Stephen 
Published: August 2008

AbstractPulsed source–sink devices are an effective way of achieving dynamic hybridization in DNA microarrays. These can be modelled as linked twist maps, and in particular, basing the design on the dynamics of a hyperbolic toral automorphism allows the application of a set of techniques from ergodic theory. This gives a rigorous framework in which to discuss mixing. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiscale damage simulation
Authors: Timmel Mario , Kaliske Michael , Kolling Stefan , Mueller Ralf 
Published: August 2008

AbstractNumerous materials show a softening behaviour at dynamic loading. The decrease of stress is caused by the evolution in the microscale in terms of areas where the local stiffness is reduced, e.g. due to micro‐void growth. For a numerical treatment of this material behaviour, phenomenological damage approaches are used in daily engineering practice. For a better understanding of the micromechanical process of such phenomenological models, multiscale methods are becoming increasingly important. The physical quantities that are responsible for the microstructural evolution associated with the damage process are transferred into the numerical model. In this context, the method of configurational forces will be used to describe the geometrical changes of damaged areas. With the help of homogenization, macro‐ and microscale will be coupled. In consequence, each Gaussian point of the macroscale is modelled by an own microstructure (RVE), where the microscale evolves during the loading process according to observable damage phenomena. Hereby, we present the general case of hyperelastic materials at finite strains. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On projected gradient methods for regularizing reconstruction of synchrotron radiation spectra distribution function
Authors: Wang Yanfei , Du Yonghua , Hu Tiandou 
Published: August 2008

AbstractWe study the numerical methods for the reconstruction of the spectral distribution function of SR by measurement of the attenuation of the SR energy spectrum. The reconstruction of the spectral distribution function of SR is an ill‐posed integral operator equation of the first kind. Therefore, robust method to overcome the ill‐posedness and to improve the computational efficiency is a major task in numerical computation. Because of the physical meaning of the problem, we study projected gradient methods in this paper. Numerical simulations are given. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical methods for inferring phylogenies
Authors: Albrecht Felipe , Borges Nelson 
Published: August 2008

AbstractMolecular phylogenies describe the study of evolution relationships between living beings, protein and genetic sequences and other molecular taxons. In recent years there has been increased interest in producing large and accurate phylogenies trees using some numerical computational methods approach. One class of molecular phylogenies is the distance matrices method, with the matrix whose entries represent the distinctions between the taxons under study. To construct large and accurate trees for a large number of taxons, the computational processing increases and parallel computing can be helpful. So far we have tested some methods to solve the linear systems, being driven to important conclusions, like which is the best tested method, and having also reached some questions about communication. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Elastic properties of microcomponents under uniaxial stress
Authors: Jöchen K. , Böhlke T. 
Published: August 2008

AbstractIn order to develop highly stressable microcomponents for various applications, the structural behavior of such parts has to be examined with respect to an accurate prediction of the elastic and plastic characteristics. When simulating microparts, the major challenge is to capture the significant material heterogeneities, which are the result of the small geometrical dimensions of the components being of the same order of magnitude as the grain size. For this reason, the concept of effective properties fails and apparent properties have to be considered. In this paper we examine the elastic properties of microspecimens made of gold. Therefore, various finite element simulations have been evaluated statistically in order to identify the characteristic parameters of the distribution. Polycrystals are modeled as a periodic Voronoi tesselation with a uniform distribution of crystal orientations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On‐line state estimation for nonlinear dynamical systems
Authors: Dmitruk Natalia M. 
Published: August 2008

AbstractA problem of estimation of states of a dynamical object on the base of incomplete and inexact measurements is studied. The focus is on a set‐based estimation of states required for construction of optimal guaranteeing feedbacks. In particular, the aim is to construct at every current time instant polyhedral approximations of sets of all states consistent with the obtained measurements. A problem of constructing estimates, associated with these approximations, is called an optimal observation problem. This note presents a numerical method for solving optimal observation problems for nonlinear dynamical systems. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bifurcations on a spring‐pendulum oscillator
Authors: Gonzalez‐Buelga A. , Kyrychko Y. , Wagg D.J. 
Published: August 2008

AbstractIn this paper we study experimentally the dynamics of a non linear system: a spring pendulum coupled to an oscillator. The system was tested using a hybrid technique called Real Time Dynamic Substructuring (RTDS)[1, 2]. RTDS is a testing technique that involves splitting the system under study into two subsystems: one will be physically tested (physical substructure) and the other will be simulated in the computer (numerical model). These substructures interact in real time through a set of transfer systems. RTDS is a very powerful experimental methodology that not only allows full scale and real time testing but also real‐time bifurcation tracking in complex engineering systems [3, 4]. In our hybrid experiment the spring pendulum is taken to be the physical substructure while oscillator is the simulated numerical model. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐order accurate iterative solution of the Navier–Stokes equations for incompressible flows
Authors: Henniger Rolf , Obrist Dominik , Kleiser Leonhard 
Published: August 2008

AbstractAn iterative solution scheme for the incompressible Navier–Stokes equations is presented. It is split into inner and outer iteration cycles, such that the momentum and continuity equations are satisfied within prescribed accuracy. The spatial discretization is based on high‐order finite differences which makes it well suited for massively parallel computers. This is demonstrated in a scaling test. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical analysis of uncertainties in the effective material behaviour of disordered structural foams
Authors: Hohe Jörg , Hardenacke Volker 
Published: August 2008

AbstractThe present contribution is concerned with a numerical analysis of the uncertainties in the structural response of threedimensional structural foams with partially open cells. The effective thermo mechanical material response is determined by means of an energy based homogenization procedure. Stochastic effects in the geometry and topology of the microstructure are treated by means of a repeated analysis of small‐scale representative volume elements with prescribed relative density and prescribed cell size distribution. The results are evaluated by stochastic methods. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)