bluuebunny/crossref_metadata_2025 huggingface dataset:
On phenomenological and micro‐mechanical models in finite elasticity and viscoelasticity for rubber‐like materials
Authors: Hossain Mokarram , Denzer Ralf , Possart Gunnar , Steinmann Paul
Published: December 2008

The structure of rubber‐like materials is characterised through chain‐like macromolecules which are linked together at certain points. This special structure leads to a completely random three‐dimensional network [5]. There are several phenomenological based models and micro‐mechanically motivated network models for elastic and viscoelastic polymeric materials which have been proposed in the literature [4]. The aim of the research work is to give an overview of various phenomenological and micro‐mechanical models for elastic and viscoelastic processes at large deformations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Solution of industrial CFD problems with structured Boltzmann approach
Authors: Ibraghimova Elena
Published: December 2008

A new algorithm and acorresponding software package are developed that contain a fast tensor algorithm for the deterministic solution of the Boltzmann equation. The domain space discretisation performed with the Delaunay grid and the velocity space discretisation is performed with the tensor grid, and benefits with multilinear decomposition. This algorithm is also implemented for GPGPU processors, which allows to reach very high computational performance. The memory and complexity requirements are comparable with most Navier‐Stockes solvers, however we solve the Boltzmann equation with chemical reactions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinear vibrations of a ropeway system with moving passenger cabins
Authors: Knawa Marta , Bryja Danuta
Published: December 2008

The dynamic continuous model of a carrying rope for circulating bicable aerial ropeway is formulated. To describe nonlinear in‐plane vibrations excited by moving masses of passenger cabins a closed form model with Green‐Lagrange deformation is developed. The equations of motion of the system are derived on the basis of Lagrange equations with Ritz approximation of cable displacements applied. Numerical example of linear and nonlinear cable vibrations is presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exact first and second derivatives by automatic differentiation
Authors: Naumann Uwe
Published: December 2008

Automatic differentiation (AD) is a method for computing derivatives of outputs of numerical programs with respect to its inputs both accurately (with machine precision) and efficiently. The two basic modes of AD – forward and reverse – and combinations thereof yield products of a vector with the Jacobian, its transposed, or the Hessian, respectively. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modellierung der Schwingungen beim Werkzeugschleifen
Authors: Panning L. , Kröger M.
Published: December 2008

Die Fertigung von Bohrern und Schaftfräsern aus Hartmetall oder Schnellarbeitsstahl (HSS) erfolgt aufgrund der großen Härte der Werkstücke häufig durch Profilschleifprozesse mit Diamant‐ oder CBN‐Schleifscheiben. Aufgrund der Wechselwirkung zwischen Werkstück, Schleifscheibe und Prozess kommt es während der Erzeugung der Spannuten zu Werkstückschwingungen, die zu unerwünschten Fertigungsungenauigkeiten und Formfehlern führen. Ziel ist es, mit Hilfe von Simulationen kritische Prozessparameter zu ermitteln, bei denen z.B. durch regeneratives Rattern instabile Zustände auftreten. Diese können die Werkstückqualität erheblich reduzieren. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Asymptotics for some vibro‐impact problems with a linear dissipation term
Authors: Cabot Alexandre , Paoli Laetitia
Published: December 2008

We consider a mechanical system with a finite number of degrees of freedom submitted to a non smooth potential Φ and a viscous dissipation force. We study the asymptotic behavior of dissipative solutions when the time variable tends to +∞. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bridged interface cracks under transient thermal loading
Authors: Perelmuter Mikhail
Published: December 2008

The direct boundary element method is used to analyze of the stress‐strain state and fracture parameters of fiber‐reinforced layered composites structures with interface bridged cracks under transient thermal and mechanical loadings. It is supposed that unbroken fibers make up bridged zone along of whole or part of a delamination region between layers of composite materials. For modeling purposes the bridged zone is considered as a part of the interface crack between of joined materials and supposed that distributed nonlinear spring‐like bonds link and constrain the crack surfaces. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adaptive time series filters to smooth and forecast economic variables
Authors: Pervukhina Elena , Emmenegger Jean‐François
Published: December 2008

Four monthly Ukrainian trucking industry time series are investigated within period of January 2003 to February 2007. The AR(1) models are used to filter and predict real values of the series. The problems are solved on the basis of a differentiable matrix functional, defined on the coefficient matrix of the filter. The functional presents an information measure of the distribution parameters of the vector state and its tentative estimations and is well known as Kullback information divergence. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On kinematics of a parallel robot used for the minimally invasive surgery
Authors: Plitea N. , Pisla D. , Vaida C.
Published: December 2008

One of the pioneer fields for robots is their assimilation in surgery, especially in minimally invasive procedures. The paper presents the kinematics of an innovative parallel structure for the manipulation of surgical instruments in minimally invasive surgery. The parallel architecture has been chosen for its superiority in precision, repeatability, stiffness, higher speeds and occupied volume. The equations, which model the kinematics are pointed out for this robot based on its mathematically determined functional parameters. The results of the kinematical modeling are systematically presented and lead to the facile solving of the parallel structure. Some simulation results have been presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Deconvolving blood‐alcohol concentration and alcohol beverage consumption from sensor measurements of transdermal alcohol
Authors: Dumett M.A. , Piterbarg Y. , Rosen I.G. , Schumitzky A.
Published: December 2008

We utilize mathematical, statistical and deconvolution techniques to estimate blood alcohol concentration and alcohol ingestion rate from vapor alcohol measurements coming from a new electro‐chemical transdermal alcohol bio‐sensor. A protocol suggesting how this can be done and a theoretical framework for the convergence of the method are also shown. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Anwendung eines Schmerzsensors
Authors: Schiefer F. , Ostermeyer G.‐P.
Published: December 2008

Die Erforschung von Schmerz aus technischer Sicht ist ein bisher wenig behandeltes Forschungsgebiet. Ein erster Ansatz zur Problembeschreibung ist in [1] gegeben. Die Grundlage zur Anwendung eines Technischen Schmerzsensors ist ein Sensorkonzept zur technischen Schmerzdetektierung [2,3], mit dessen Hilfe ein Energieeintrag gemessen wird, der als ein Schmerzmaß für technische Systeme infolge periodischer und stoßartiger mechanischer Beanspruchungen interpretiert werden kann. Dieses Technische Schmerzmaß enthält implizit u. a. frequenzselektive Informationen über das Zeitverhalten des Energieeintrages sowie über die Ruckbeanspruchung dynamischer Systeme. Erste Anwendungen sind ein Stoßexperiment und die Trajektorienoptimierung eines Demonstrators, der bspw. ein Laufmaschinenbein repräsentieren kann. Zeit‐ und energieoptimale Trajektorien werden mit schmerzoptimierten Trajektorien verglichen. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evaluation of automotive disk brake noise behavior using piezoceramic actuators and sensors
Authors: Schlagner S. , Wagner U. von
Published: December 2008

One problem of disk brakes is the occurence of noise. This work in particular addresses the occurrence of disk brake squeal with frequencies from 1 up to 12 kHz which does generally not affect the basic functionality of the brake. Nevertheless it is a serious comfort problem and it causes a high amount of costs to design noiseless brake systems. This work examines methods to evaluate the noise behaviour of disk brakes using piezoceramic actuators and sensors. In comparison to conventional methods they provide the advantage to quantify the effect of new design features without the necessity to make the brake squeal. In this paper the investigation of phase shifts between characteristic dynamic state variables is examined more in detail. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the piezoelectric shear effect in ultrasonic motors
Authors: Schönecker Martin , Conrado Ana
Published: December 2008

A new actuator for piezoelectric ultrasonic motors (USM) using the d15 effect was conceived. Whereas the piezoelectric d33 and d31 effects are normally used in commercial motors, there exist hardly any USM based on shear actuation. The actuator is a piezoelectric block polarized in axial direction and electroded circumferentially with four electrodes. The suitable superposition of two standing waves generates ultrasonic traveling waves in the actuator, which drives the rotor. The dimensions of the actuator are optimized with respect to the dynamic piezoelectric coupling factor. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Explicit solutions for a general class of Markov processes
Authors: van Leeuwaarden Johan S.H. , Squillante Mark S. , Winands Erik M.M.
Published: December 2008

We derive explicit solutions for the matrix‐geometric stationary distribution (and related measures) of a general class of infinite multidimensional Markov processes based on the probabilistic interpretations of the fundamental solution matrices and Bernoulli excursions, leading to explicit expressions for these matrix elements in terms of hypergeometric functions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimization over the Stiefel manifold
Authors: Fraikin C. , Hüper K. , Dooren P. Van
Published: December 2008

In this note we parameterize the Stiefel manifold Stk,n in a manner that allows to perform a constrained Newton step in a relatively simple way. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Critical exponents for large time asymptotics for fractal Hamilton‐Jacobi‐KPZ equations
Authors: Karch G. , Woyczynski W.A.
Published: December 2008

Nonlinear and nonlocal evolution equations of the form ut = ℒ︁u ± |∇u |q, where ℒ︁ is a pseudodifferential operator representing the infinitesimal generator of a Lévy stochastic process, have been derived (see, [6]) as models for growing interfaces in the case when the continuous Brownian diffusion surface transport is augmented by a random hopping mechanism. The goal of this note is to report properties of solutions to this equation resulting from the interplay between the strengths of the “diffusive” linear and “hyperbolic” nonlinear terms, posed in the whole space RN , and supplemented with nonnegative, bounded, and sufficiently regular initial conditions. The full text of the paper, including complete proofs and other results, will appear in the Transactions of the American Mathematical Society. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimization in constrained crack problems
Authors: Kovtunenko Victor A. , Khludnev Alexander M.
Published: December 2008

Following the optimization approach to brittle fracture, we consider the evolution of a crack in a domain as solution of the global problem of constrained minimization of the total potential energy with respect to both state variables (the displacement vector) and shape variables (parameters of the crack shape). This formulation describes the initiation of a crack in a homogeneous body and its stable as well as unstable propagation, which allows also a kink (topology change) of the crack during the evolution process. By this we assume that contact can occurs between the opposite crack faces. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
MPEG‐4 video transmission over UMTS mobile networks
Authors: Ali M. , Pathak B. , Childs G.
Published: December 2008

This paper presents an overview [1] of the MPEG‐4 (Motion Picture Experts Group) coded video file structure and the VOP (Video Object Plane) types followed by classification of errors and introduction of the NEWPRED mechanism in MPEG‐4 for error concealment. An UEP (Unequal Error Protection) scheme is described with a discussion on how the proposed scheme affects the UMTS (Universal Mobile Telecommunications System) network efficiency. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On orthogonal collocation by the zeros of orthogonal 0‐interpolants
Authors: Bokhari M. A. , Al‐Attas H.
Published: December 2008

The orthogonal collocation method is quite prominent among the collocation methods that determine approximate solutions of boundary value problems. This method involves Gaussian knots as collocation points and, in general, has fourth order convergence. Here, we discuss a similar method in which the knots are based on pre‐assigned and free zeros of polynomials that arise in orthogonal 0‐interpolants. Some numerical results demonstrate an advantage of the proposed collocation points over the Gaussian knots. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wave propagation and diffraction in discrete structures: Effect of anisotropy and internal resonance
Authors: Chesnais Céline , Hans Stéphane , Boutin Claude
Published: December 2008

This paper is devoted to the study of wave propagation within anisotropic structures made of the periodic repetition of un‐braced frames. Thanks to the homogenization method of periodic discrete media, a macroscopic description of the system is obtained. Then the effects on the wave propagation of anisotropy and resonance in bending of the elements are presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analytical modeling of chatter stability using multi‐dimensional approach
Authors: Budak E.
Published: December 2008

Machining is one of the most common manufacturing processes in industry due to its high flexibility and ability to produce parts which excellent quality. Chatter, a type of self excited vibrations arising in metal cutting operations, is a major limitation in machining resulting in poor quality and reduced productivity. Under certain conditions, the cutting process may become unstable yielding oscillations with high amplitudes and cutting forces. Stability analysis of the dynamic cutting process can be used to determine chatter‐free machining conditions with high material removal rate. Usually, one dimensional models are used for stability analysis of machining. However, based on the geometry of the actual machining process, multi‐directions would have to be used for accurate modeling of the process dynamics and the stability. In this presentation, multi directional models for turning and milling processes are presented. The effects of multi directional process mechanics on the stability are demonstrated by applications. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the motion of magnetic domain walls
Authors: Kort Antonio Capella , Otto Felix
Published: December 2008

In certain regimes and for relative small applied fields, magnetic domain walls behave as mechanical particles in a viscous fluid. By analogy their dynamic can be described with an evolution equation of the form
Mq̈ + β–1 q̇ = H
where M and are the effective wall mass and wall mobility, and H is an applied forcing. These effective parameters depend on the particular geometrical configuration and dynamical model considered. We present a method that can be used to systematically estimate the wall mass and wall mobility in terms of the static wall geometry and various physical constants. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Anatomically realistic finite element simulations of Pelvic floor mechanics
Authors: Cheng Leo K. , Noakes Kimberley F. , Bissett Ian P. , Pullan Andrew J.
Published: December 2008

An anatomically realistic computational model of the pelvic floor and anal canal regions was used to examine the mechanics of normal defecatory function within the female pelvic floor. The subject specific model was constructed from MR images acquired from a healthy nulliparous 32 year old female. Deformation of the levator ani was simulated during a ‘bear down’ manoeuvre. A pressure of 4 kPa was imposed on the mesh and the computed mesh displacements were compared to those obtained from dynamic MR images of the same subject. The average RMS difference between the simulated mesh position and that determined by the dynamic MRI was 14 mm. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study of wave dispersion in periodic composites by higher‐order asymptotic homogenization method
Authors: Andrianov Igor V. , Bolshakov Vladimir I. , Danishevs'kyy Vladyslav V. , Weichert Dieter
Published: December 2008

We present [1] an application of the higher‐order asymptotic homogenization method (AHM) to the study of wave dispersion in periodic composite materials. When the wavelength of a travelling signal becomes comparable to the size of heterogeneities, successive reflections and refractions of the waves at the components interfaces lead to the formation of a complicated sequence of pass and stop frequency bands. The AHM provides a long‐wave approximation valid in the low frequency range. Solution for the high frequencies is obtained on the basis of the Floquet–Bloch theorem by the plane‐wave (PW) expansions method. Anti‐plane shear waves in a fibre‐reinforced composite with a square lattice of cylindrical fibres are considered. The dispersion curves are obtained, the pass and stop bands are identified. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermomagnetic convection induced by a time‐modulated driving force in magnetic fluids
Authors: Engler H. , Odenbach S.
Published: December 2008

It is well‐known that the flow properties of magnetic fluids – so called ferrofluids – can be modified by applying an external magnetic field. Under certain conditions, the magnetic force induced by this external field causes a convective flow. What has yet to be investigated is what happens when this driving force is modulated in time. For this purpose, a horizontal ferrofluid layer has been exposed to an intermittent magnetic field, which causes a time‐modulated force. This force depends on the strength of the external magnetic field and the fluid temperature, and therefore the flow phenomenon generated is called thermomagnetic convection. In addition, if the fluid layer is heated from below, the classical thermal convection contributes to the flow system. In our studies, both effects – thermomagnetic and thermal – contribute together to the convection. The experimental results presented here confirm previous theoretical investigations about the influence of the frequency of the driving force on the strength of the convective flow, which reach minimum values at certain frequencies. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A phase field model in electrowetting and related phenomena
Authors: Eck C. , Fontelos M. , Grün G. , Klingbeil F. , Vantzos O.
Published: December 2008

The term electrowetting is commonly used for some techniques to change the shape and wetting behaviour of liquid droplets by the application of electric fields and charges. We developand analyze a model for electrowetting that combines the Navier‐Stokes system for fluid flow, a phase‐field model of Cahn‐Hilliard type for the movement of the interface, a charge transport equation, and the potential equation of electrostatics. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Taylor‐model‐based enclosure of invariant manifolds for planar diffeomorphisms and applications
Authors: Grote Johannes , Berz Martin , Makino Kyoko , Newhouse Sheldon
Published: December 2008

Fundamental questions in the study of interesting dynamics of planar diffeomorphisms like the Hénon map involve homoclinic phenomena, topological entropy and strange attractors. Inherently, answering these questions requires knowledge about the stable and unstable manifolds, which in the typical case in the plane are smooth curves. We present a method to find highly accurate Taylor Model enclosures of the invariant curves near hyperbolic fixed points. Successive iteration of these local enclosures yields similarly accurate enclosures of pieces of the global manifold tangle. Applications presented include the automatic computation of rigorous enclosures of all homoclinic points up to finite iterates. This allows to find symbolic dynamics in the original system and consequently compute rigorous lower bounds for its topological entropy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some aspects about quantitative reconstruction for differential interference contrast (DIC) microscopy
Authors: Heise Bettina , Arminger Bernd
Published: December 2008

We demonstrate different appraches to reconstruct the optical path length map from DIC images: Line Integration, Deconvolution and solving the Laplace problem depending whether one or two orthogonally scanned images are available. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Data uncertainty analysis in environmental management
Authors: Hejč M. , Hřebíček J.
Published: December 2008

Imprecision of input data is an important characteristic feature of environmental monitoring. When making evaluations, conclusions and the decisions from collected data, one has to be very careful not to make fatal mistake. The important task of computing and current information and communication technology is to deal with the primary data uncertainty and thus to reduce the risk of mistake. At present new approaches and methodologies to handle environmental data uncertainty are explored as opposite to standard. The paper presents comparison of such new approach against European Environment Agency and U.S. Environmental Protection Agency standards in the several cases of the assessment environmental management indicators in the Czech Republic. The new approach brings more modular way of dealing with uncertainty and is supposed to bring better results and less workload then standard approach. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Design strategies for libration point missions: theory to application
Authors: Howell Kathleen C.
Published: December 2008

Spacecraft missions to the libration points in Sun‐planet and planet‐moon systems are of increasing interest. A number of such missions have already been launched. As the theoretical understanding of the dynamical structure in these regions of space expands, however, trajectory design to support actual mission requirements is more complex. Baseline trajectories for some recent mission scenarios are presented. Example approaches for transition of the designs to higher fidelity models is discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vergleichende Messungen und Simulationen annähernd homogener Belastungsverteilungen
Authors: Alshuth Thomas , Hohl Carsten , Ihlemann Jörn
Published: December 2008

Experimentell ermittelte Daten bezüglich homogener Belastungsverteilungen werden häufig zur Materialcharakterisierung und zur Identifizierung von Stoffgesetzparametern verwendet. Dementsprechend wichtig sind der Grad der im Experiment erreichbaren Homogenität und die Genauigkeit, mit der die nahezu homogen verteilten Spannungen und Verzerrungen aus den gemessenen Größen berechnet werden können. Zur Erfassung und Beurteilung dieser beiden Qualitätsmerkmale bei verschiedenen, in der Praxisüblichen Prüfmethoden wurden parallel zu einem umfassenden Programm vergleichender Messungen an einem Gummiwerkstoff FEM‐Simulationen der jeweiligen Spannungs‐ und Verzerrungsverteilungen durchgeführt. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiscale deflation solvers for flow in porous media
Authors: Klie Hector , Rodriguez Adolfo , Wheeler Mary F.
Published: December 2008

This work describes a novel physics‐based deflation preconditioner approach for solving porous media flow problems characterized by highly heterogeneous media. The approach relies on high‐conductivity block solutions after rearranging the linear system coefficients into high‐conductive and low condutive blocks from a given physically driven threshold value. This rearranging relies on the Hoshen‐Kopelman (H‐K) algorithm that is commonly used to determine percolation clusters. The resulting preconditioner may alternatively be combined with a deflation preconditioning stage. The proposed approach is coined as a physics‐based 2‐stage deflation preconditioner (P2SDP). Numerical experiments on different permeability distributions reveal that P2SDP is a powerful means to solve pressure systems when compared to more conventional algebraic approaches such as the incomplete Cholesky factorization. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient parallel simulation of biphasic materials in biomechanics
Authors: Berrenberg Stefanie , Krause Rolf
Published: December 2008

Biphasic materials are widely used for the modelling and the numerical simulation of articular cartilage within joints. In combination with contact, the numerical solution of the arising discrete systems is a demanding task, in particular for realistic geometries. We consider the stability and efficiency of different multilevel approaches for the numerical solution of the resulting non–smooth systems. Moreover, multilevel methods are derived which allow for the efficient numerical simulation of biphasic materials in contact. Numerical examples on problem specific geometries in three space dimensions are given. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Performance & packet traffic dynamics of Packet Switching Network model
Authors: Lawniczak Anna. T.
Published: December 2008

Dynamics of packet traffic in data communication networks can be complex and often not well understood. Understanding of these complex dynamics is important for their control, prediction purposes and for the data networks design. The engineering community has described wired data networks architectures and studied them by means of a layered, hierarchical abstraction called ISO OSI (International Standard Organization Open System Interconnect) Reference Model. The Network Layer of the ISO OSI Reference Model is responsible for routing packets across the network from their sources to their destinations and for control of congestion in data networks. Using an abstraction of the Network Layer that we developed, we investigate packet traffic dynamics in our data network models of data communication networks of packet switching type, in particular near the phase transition point from free flow to congestion. We explore how these dynamics and network performance indicators are affected by network connection topology and routing algorithms. We consider static and adaptive routing algorithms. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the simulation of textile reinforced concrete using a multi scale approach
Authors: Lepenies Ingolf , Zastrau Bernd W. , Richter Mike
Published: December 2008

Textile reinforced concrete (TRC) is a composite of textile structures made of multi‐filament yarns (rovings) within a cementitious matrix. Experimental investigations of textile reinforced concrete specimen show very complex failure mechanisms on different length scales. Therefore mechanical models on the micro, meso and macro scale are introduced. The paper presents a hierarchical material model of TRC on three scales. While on the micro scale the individual filaments of the fiber bundles are distinguished to determine an effective roving behavior, models on the meso scale are used to predict the macroscopic response of the composite material. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
FIO‐product representation of solutions to symmetrizable hyperbolic systems
Authors: Rousseau Jérôme Le
Published: December 2008

The solution operator of a symmetrizable hyperbolic system is approximated by a multi‐product of Fourier integral operators. Exact convergence is obtained as we let the number of operators in the product grow to infinity, which yields an alternative representation of the solution. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Matched asymptotic expansions for the determination of the electromagnetic field near the edge of a patch antenna
Authors: Bendali Abderrahmane , Makhlouf Abdelkader , Tordeux Sébastien
Published: December 2008

We consider a simple but representative model incorporating the main behavior of the electromagnetic field near the edge of a patch antenna. Recall that this kind of antenna is obtained by a metal patch laying on a dielectric substrate covering a ground metallic plane. The functioning principle of such an electric device is based on the matching of an N‐dimensional behavior of the field outside the antenna with an (N‐1)‐dimensional one inside the zone limited by the patch and the ground plane, N = 3 or 2 according to the considered model. In this study, we make use of the technique of matched asymptotic expansions and computation of singularities to describe this behavior for the two‐dimensional case. Proved error estimates enable us to give a rigorous background to the underlying asymptotic analysis. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
ILU++: A new software package for solving sparse linear systems with iterative methods
Authors: Mayer Jan
Published: December 2008

ILU++ is a software package for solving sparse linear systems with iterative methods using state‐of‐the‐art incomplete multilevel LU‐factorisations as preconditioners. It implements several types of preprocessing (permuting and scaling both rows and columns prior to factorisation to make the matrix more suitable for LU‐factorisation), different pivoting strategies and a number of dropping rules to ensure sparsity. ILU++ is available under the GNU public licence. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Occurrence of a delta‐shock in non‐linear chromatography
Authors: Mazzotti Marco
Published: December 2008

We consider a hyperbolic system of two first order partial differential equations that can be used to describe nonlinear chromatography, and the corresponding Riemann initial value problems. It can be shown that these equations admit classical solutions made of constant states separated by continuous (simple wave) or discontinuous (shock) transitions, but also – for exactly specified initial states – singular solutions. Such solutions are due to the occurrence of an overcompression condition that leads to the formation of a spike travelling at constant speed and increasing strength in space. Such singular solution can be observed by solving numerically a regularized form of the original equations, but eludes the application of techniques proposed in the literature to study singular shocks and delta‐shocks, which share with the system studied here its overcompressive character. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Global existence in rate‐independent infinitesimal strain gradient plasticity
Authors: Neff Patrizio
Published: December 2008

We propose a model of infinitesimal strain gradient plasticity including phenomenological Prager type linear kinematical hardening and nonlocal kinematical hardening due to dislocation interaction. The model is a thermodynamically admissible model of infinitesimal plasticity involving only the Curl of the non‐symmetric plastic distortion p. Linearized spatial and material covariance under constant infinitesimal rotations is satisfied. Uniqueness of strong solutions of the infinitesimal model is obtained if two non‐classical boundary conditions on the plastic distortion p are introduced: ṗ.τ = 0 on the microscopically hard boundary ΓD ⊂ ∂Ω and [Curl p ].τ = 0 on the microscopically free boundary ∂Ω\ΓD, where τ are the tangential vectors at the boundary ∂Ω. Moreover, a weak reformulation of the infinitesimal model allows for a global in‐time solution of the corresponding rate‐independent initial boundary value problem. The method of choice are a formulation as a quasi‐variational inequality with symmetric and coercive bilinear form. Use is made of new Hilbert‐space suitable for dislocation density dependent plasticity. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of vehicular traffic system
Authors: Nugrahani E. H.
Published: December 2008

The behavior of traffic systems controlled by traffic lights on a single lane is presented using the optimal velocity model. The effect of different traffic light control strategies on the traffic flow is discussed using three different strategies, i.e. the synchronized, green wave, and random offset. Some simulation results on the model using cellular automata are presented. The flow‐density diagrams are analyzed using these strategies. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An overview of fast component‐by‐component constructions of lattice rules and lattice sequences
Authors: Nuyens Dirk , Cools Ronald
Published: December 2008

Since the initial work by I. H. Sloan and his collaborators on the component‐by‐component construction of good lattice rules for the approximation of multivariate integrals, a lot of variations on this theme have been published. These include various function spaces, prime and composite number of points, intermediate‐rank rules, polynomial lattice rules and extensible rules. We sketch the different variations and discuss the properties needed to have a fast component‐by‐component construction. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Existence and uniqueness of level sets for spiral crystal growth
Authors: Ohtsuka Takeshi
Published: December 2008

We outline a new level set approach for spirals whose evolution follows the generalized curvature flow with a constant driving force. Our basic idea is that a spiral can be expressed as the intersection of an auxiliary surface and a Riemannian surface. Also we state and discuss the basic ideas for the uniqueness and existence of spiral motion using the level set approach. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of magnetic fields on crystal growth
Authors: Kao A. , Djambazov G. , Pericleous K. , Voller V.
Published: December 2008

The effects of a constant uniform magnetic field on thermoelectric currents during dendritic solifification were investigated using an enthalpy based numerical model. It was found that the resulting Lorentz force generates a complex flow influencing the solidification pattern. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Large‐scale high‐fidelity atomistic simulations for emerging materials and electronics devices
Authors: Polizzi E.
Published: December 2008

The quest for ever higher levels of detail and realism in nanoelectronics simulations presents formidable modeling and computational challenges. These simulations are expected, however, to benefit from the development of specific advanced mathematical techniques and high‐performance parallel algorithms to achieve high‐fidelity simulations of materials and transport problems. Here, we propose to investigate novel simulation strategies which aim to go beyond qualitative predictions by proposing quantitative simulations from the atomistic scale to the transistor macroscale. Results obtained on carbon nanotubes to compute the electron density using these advanced techniques and first‐principle calculations, are presented here. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The differentiation‐enabled NAGWare Fortran compiler
Authors: Riehme Jan , Naumann Uwe , Christianson Bruce
Published: December 2008

We present a research prototype of the differentiation‐enabled NAGWare Fortran compiler. The compiler provides built‐in automatic differentiation capabilities for the generation of code for computing first and second derivatives of numerical simulation codes written in Fortran. Tangent‐linear, adjoint, and second‐order adjoint code is obtained by a semantic transformation of the compiler's intermediate representation. Three successful reference applications are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiscale methods for the wave equation
Authors: Engquist Bjorn , Holst Henrik , Runborg Olof
Published: December 2008

We consider the wave equation in a medium with a rapidly varying speed of propagation. We construct a multiscale scheme based on the heterogeneous multiscale method, which can compute the correct coarse behavior of wave pulses traveling in the medium, at a computational cost essentially independent of the size of the small scale variations. This is verified by theoretical results and numerical examples. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Elastic‐plastic sandwich beams with optimized properties for the impact case
Authors: Schmidt Jürgen , Winter Werner , Kuhn Günther
Published: December 2008

An approach for the design of lightweight sandwich beams with optimal performance under low velocity impact loading is presented. Exemplary for beams with stainless steel faces and aluminium foam cores a procedure is proposed that bases on simulation results using an explicit finite element code. Experimental tests assure the accuracy of numerical analyses and provide data to fit the applied plastic compressible material model. By means of a multicriteria optimization method failure mechanisms are identified which dissipate a maximum of energy and lead to minimal deflections as well as to minimal beam thickness and weight at the same time. Face and core thicknesses are used as design variables. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the influence of the kink's asymptotic field on crack propagation
Authors: Schütte H. , Molla‐Abbasi K.
Published: December 2008

The aim of the presentation is to highlight the influence of the kink, developing at the beginning of mixed‐mode crack growth, on the propagation behavior of the crack. Le et al. (1999) have shown that the variational principle of a body containing a crack results in the principle of maximum energy release rate incorporating the stress intensity factors of the kinked crack. In the present paper, the influence of the kink and the kinking angle, resulting in a singular field around the corner, on the crack growth is analyzed. The generalized stress intensity factors at the kink's corner are computed with the help of a FEM strategy. The influence of these on the T‐stresses and the combined plastic zone is presented (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Undergraduate computational science and engineering education: Undergraduate internships section of a SIAM working group report
Authors: Shiflet Angela B.
Published: December 2008

The SIAM Working Group on Undergraduate Computational Science and Engineering (CSE) Education, chaired by Peter Turner (Clarkson University), wrote a report on the topic, which states that a “common feature among CSE programs is the requirement for an internship in the form of an undergraduate research experience” [1][2]. The report and this article elaborate on the value of such experiences and how students, often with the help of faculty members, can obtain internships. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Generalized solutions of integral‐functional equations: construction and applications in power industry
Authors: Sidorov Nikolay A. , Sidorov Denis N. , Trufanov Andrey V.
Published: December 2008

Deterministic approaches to the Volterra models learning is considered. First approach is based on kernels identification procedure and the second one employs product indegration method. Generalized solutions of linear and nonlinear integral Volterra equations are also addressed covering the discontinuous solutions cases. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multipoint nonlocal boundary value problem for Schrödinger equations
Authors: Ashyralyev Allaberen , Sirma Ali
Published: December 2008

The multipoint nonlocal boundary value problem for Schrödinger equations in a Hilbert space are investigated. Stability estimates for the solution of this problem are established. The first and second order accuracy difference schemes for the approximate solution of this multipoint nonlocal boundary value problem are presented. The stability of these difference schemes is established. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Starting with the right matrices
Authors: Strang Gilbert
Published: December 2008

Over the past 20 years we have developed a course that combines applied mathematics with scientific computing. Each lecture discusses a model problem and a code to solve it. The course is popular with engineering students and their departments, who want exposure to ideas and also to software (including MATLAB). The need to move beyond the old formula‐ based approach is widely recognized.

The starting point is to understand the second difference matrices that appear everywhere in scientific computing and simulation. Four special matrices with fixed and free and periodic boundary conditions (and ‐1,2,‐1 on all interior diagonals) have names. They become familiar. We discuss the “A'CA framework” for so many numerical methods and engineering applications. The Computational Science and Engineering course 18.085 will be videotaped for MIT's OpenCourseWare ocw.mit.edu. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A directed binding model of motor protein motion on protein filaments
Authors: Bolterauer H. , Tuszynski J.A.
Published: December 2008

We propose a new mechanism of motor protein motion on protein filaments, treating the heads as extended objects connected by an elastic neck linker region. In our model, ATP hydrolysis provides chemical energy while directed binding is key in force generation coupled with an elastic neck linker region storing elastic energy. Simulations of the differential equation of motion, based on this model, agree with experiment for both kinesin and its analog, Ncd, and can also be applied to myosin. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Acoustic simulations with higher order finite and infinite elements
Authors: Estorff Otto von , Petersen Steffen , Biermann Jan
Published: December 2008

The efficiency of finite element based simulations of Helmholtz problems is primarily affected by two facts. First, the numerical solution suffers from the so‐called pollution effect, which leads to very high element resolutions at higher frequencies. Furthermore, the spectral properties of the resulting system matrices, and hence the convergence of iterative solvers, deteriorate with increasing wave numbers. In this contribution the influence of different types of polynomial basis functions on the efficiency and stability of interior as well as exterior acoustic simulations is analyzed. The current investigations show that a proper choice for the polynomial shape approximation may significantly increase the performance of Krylov subspace methods. In particular, the efficiency of higher order finite and infinite elements based on Bernstein polynomial shape approximation and the corresponding iterative solution strategies is assessed for practically relevant numerical examples including the sound radiation from rolling vehicle tires. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Functional differential equations arising in cell‐growth
Authors: Wake G. C. , Begg R. E.
Published: December 2008

Non‐local differential equations are notoriously difficult to solve. Cell‐growth models for population growth of a cohort structured by size, simultaneously growing and dividing, give rise to a class of non‐local eigenvalue problems, whose “principal” eigenvalue is the time‐constant for growth/decay. These and other novel non‐local problems are described and solved in special cases in this paper. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A singular function boundary integral method for elliptic problems with singularities
Authors: Xenophontos Christos , Georgiou Georgios , Elliotis Miltiades
Published: December 2008

In this work we present a singular function boundary integral method for elliptic problems with boundary singularities. In this method, the approximation is constructed from the truncated asymptotic expansion for the solution near the singular point and the Dirichlet boundary conditions are weakly enforced by means of Lagrange multiplier functions. The resulting discrete problem is posed and solved on the boundary of the domain, away from the point of singularity. We are able to show that the method approximates the generalized stress intensity factors, i.e. the coe cients in the asymptotic expansion, at an exponential rate. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An evaluation of test statistics for detecting temporary change in Bl(1,1,1,1) models
Authors: Zaharim Azami , Ismail Amiruddin , Abdullah Shahrum , Mohamed Ibrahim , Ahmad Ibrahim
Published: December 2008

A study is carried out to investigate the sampling properties of the outlier test statistics of a procedure developed for detecting temporary change in BL(1,1,1,1) processes. It is done with respect to the sample size, the type of outlier and the size of the coefficients of the BL(1,1,1,1) process. The results show that, in general, the outlier detection procedure is capable of detecting TC, although the performance is affected if ω is large. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical solution of a minimax ergodic optimal control problem
Authors: S. Aragone Laura , Soledad Aronna María , Lotito Pablo A.
Published: December 2008

In this work we consider an L∞ minimax ergodic optimal control problem with cumulative cost. We approximate the cost function as a limit of evolutions problems. We present the associated Hamilton‐Jacobi‐Bellman equation and we prove that it has a unique solution in the viscosity sense. As this HJB equation is consistent with a numerical procedure, we use this discretization to obtain a procedure for the primitive problem. For the numerical solution of the ergodic version we need a perturbation of the instantaneous cost function. We give an appropriate selection of the discretization and penalization parameters to obtain discrete solutions that converge to the optimal cost. We present numerical results. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sedimentation of volcanic particles
Authors: Bonadonna C. , Phillips J.C.
Published: December 2008

Volcanic eruptions present many hazards including pyroclastic flows and volcanic mud flows (lahars) that together have caused the death of more than 65000 people in the last two centuries (e.g. eruptions of Tambora 1815, Mount Pelee 1902 and Nevado del Ruiz 1985). However tephra (volcanic rock and glass fragments) can be transported in the atmosphere for long times and distances after the eruptive event, representing one of the most widespread hazards with significant human health consequences and the potential to significantly affect crucial economical sectors such as agriculture, social services, tourism and industry. In addition, the associated deposits retain a considerable amount of information of the generating processes, such as total erupted mass, initial grainsize distribution and also important constraints on plume dynamics and eruption intensity. As a result, the study of tephra fallout is crucial to the understanding of volcanic processes and to the hazard assessment of volcanoes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stability analysis of thermodynamic lubrication problems in journal bearings
Authors: Durany J. , Pereira–Pérez J. , Varas F.
Published: December 2008

A new numerical scheme (which combines FEM, FVM and BEM methods) for solving thermohydrodynamic lubrication transient problems with cavitation is described. The algorithm is then applied to study the stability of a journal‐bearing system. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)