bluuebunny/crossref_metadata_2025_split huggingface dataset:
Equivalent governing equilibrium equations for nonlinear magnetoelastic solids
Authors: Bustamante Roger , Dorfmann Luis , Ogden Ray W. 
Published: October 2008

AbstractMagneto‐sensitive elastomers are materials that rapidly and reversibly change their mechanical and magnetic properties in response to the application of a magnetic field. Typically, the magneto‐mechanical coupling is achieved and optimized by mixing, during the vulcanization process, nano or micron‐sized magnetizable particles with high magnetic saturation within a soft and highly elastic elastomeric matrix. Preferred materials are gels, resin, natural rubber, silicone rubber and nitrile rubber. The particles of choice are spherical or irregularly shaped carbonyl iron particles because of their high permeability, low remanent magnetization and high saturation magnetization. In this paper we provide an overview of different ways in which the equations of mechanical equilibrium of magneto‐sensitive materials can be written in the presence of magneto‐mechanical interactions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Supersonic turbulence as an agent of structure formation in space
Authors: Folini Doris , Walder Rolf , LeVeque R.J. , Favre J. M. 
Published: October 2008

AbstractSupersonic turbulence is a main agent for structure formation in space, from stellar winds to wind‐blown bubbles, supernovae remnants, ‐ray bursts, and star‐formation in molecular clouds. Dissipation is mostly due to shocks. Under isothermal conditions, the density follows a log‐normal distribution whose variance grows with Mach number. The exact scaling is under debate. We focus on problems with not strictly periodic boundary conditions and present 2D and 3D numerical simulation of supersonic turbulence in plan‐parallel slabs. From dimensional analysis we derive scaling laws for the mean quantities under isothermal conditions. Simulations including spatially extended radiative cooling layers reveal a complex interplay between turbulence and RM‐ and RT‐unstable interfaces. Turbulent Mach numbers here are significantly reduced compared to the isothermal case and are of order 1. However, unstable interfaces between the different thermal component of the gas are equally able to produce structure. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A fast multiphase level set algorithm for solving the Chan‐Vese model
Authors: He Lin , Osher Stanley 
Published: October 2008

AbstractIn this work, we specifically solve the C‐V active contour model by multiphase level set methods. We first develop a fast algorithm based on calculating the variational energy of the C‐V model without the length term. We check whether the energy decreases or not when we move a point to another segmented region. Then we draw a connection between this algorithm and the topological derivative, a concept emerged from the shape optimization field. Furthermore, to include the length term of the C‐V model, a preprocessing step is taken by using nonlinear diffusion. Numerical experiments have demonstrated the efficiency and the robustness of our algorithm. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computation of risk contribution in the Vasicek portfolio credit loss model
Authors: Huang Xinzheng , Oosterlee Cornelis W. 
Published: October 2008

AbstractFor the calculation of the VaR contribution in the Vasicek one‐factor portfolio credit loss model, two methods, namely the saddlepoint approximation and importance sampling, are very attractive in terms of accuracy, speed and robustness. We explore their connection with the Esscher transform. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Time integration of inelastic material models exhibits an order reduction for higher‐order methods – can this be avoided?
Authors: Kuhn C. , Eidel B. 
Published: October 2008

AbstractFor the numerical treatment of inelastic material behavior within the finite element method a partitioned ansatz is standard in most of the software frameworks; the weak form of equilibrium is discretized in space and solved on a global level, whereas the initial value problem for the evolution equations of internal state variables is separately solved on a local, i.e. Gauss‐point level, where strains, derived from global displacements, serve as input, [1]. Applying higher order methods (p > 2) to the time integration of plasticity models an order reduction is reported where Runge‐Kutta schemes have shown hardly more than order two at best [2, 3]. In the present contribution, we analyze the reason for order reduction and in doing so, introduce an improved strain approximation and switching point detection which play a crucial role for the convergence order of multi‐stage methods used in this context. We apply Runge‐Kutta methods of Radau IIa class to the evolution equations of viscoelastic and elastoplastic material models and show ther improved performence in numerical examples. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Scalable algorithm for solving 3D contact problems with friction
Authors: Kučera Radek , Haslinger Jaroslav , Dostál Zdeněk 
Published: October 2008

AbstractA scalable algorithm for solving contact problems with Coulomb friction is presented. It combines fixed point iterations with an augmented Lagrangian loop and an active set strategy. Numerical experiments indicate scalability. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Regularized total least squares based on the nonlinear Arnoldi method
Authors: Lampe Jörg , Voss Heinrich 
Published: October 2008

AbstractA computational approach for solving regularized total least squares problems via a sequence of quadratic eigenvalue problems has recently been introduced by Sima, Van Huffel, and Golub. Combining this approach with the nonlinear Arnoldi method and reusing information from all previous quadratic eigenvalue problems, together with an early update of search spaces we arrive at a very efficient method for large regularized total least squares problems. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
FronTier and applications to scientific and engineering problems
Authors: Bo Wurigen , Fix Brian , Glimm James , Li Xiaolin , Liu Xingtao , Samulyak R. , Wu Lingling 
Published: October 2008

AbstractWe report significant developments of the FronTier code and applications in science and engineering. The progress includes the extraction of an independent software library from the front tracking code, robust and accurate locally grid based method, applications to fluid mixing problem, fuel injection jet and fusion pellet injection in a magnetically confined plasma, among other problems. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Discontinuous Galerkin relaxation algorithm for solute transport in porous media
Authors: Mahmood Mohammed Shuker 
Published: October 2008

AbstractWe consider a degenerate parabolic convection dominated equation which models the transport of contaminant in porous media. The numerical scheme is fulfilled by combining the DG – Discontinuous Galerkin Method with and an efficient relaxation algorithm that recently developed. Numerical results show the efficiency of our scheme. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A mixing model providing statistics of the conditional scalar dissipation rate
Authors: Meyer D. W. , Jenny P. 
Published: October 2008

AbstractJoint composition probability density function (PDF) methods are used for the numerical simulation of turbulent reactive flows. Here, other than in classical Reynolds averaged Navier–Stokes (RANS) or large eddy simulation (LES) approaches, the highly non‐linear chemical source term appears in closed form. On the other hand, mixing models are required for the closure of the molecular diffusion term. In the present work, the joint statistics of the scalar and the scalar dissipation rate provided by the parameterized scalar profile (PSP) mixing model are validated. The goal is to combine the PDF method with a flamelet approach, where the scalar dissipation rate plays a crucial role in determining the contribution of the chemical source term. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A novel method of control using chaotic dynamics in systems having many degrees‐of‐freedom
Authors: Li Yongtao , Tanaka Tai , Suemitsu Yoshikazu , Nara Shigetoshi 
Published: October 2008

AbstractChaotic dynamics in systems having many degrees of freedom are investigated from the viewpoint of harnessing chaos and is applied to complex control problems to indicate that chaotic dynamics has potential capabilities for complex control functions by simple rule(s). An important idea is that chaotic dynamics generated in these systems give us autonomous complex pattern dynamics itinerating through intermediate state points between embedded designed attractors in high‐dimensional state space. A key point is that, with the use of simple adaptive switching between a weakly chaotic regime and a strongly chaotic regime, complex problems can be solved. As an actual example, a two‐dimensional maze, where it should be noted that the set context is one of typical ill‐posed problems, is solved with the use of chaos in a recurrent neural network model. Our computer experiments show that the success rate over several hundreds trials is much better, at least, than that of a random number generator. Our functional simulations indicate that harnessing of chaos is one of essential ideas to approach mechanisms of brain functions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adaptive numerical components for PDE‐based simulations
Authors: Norris Boyana , McInnes Lois Curfman , Bhowmick Sanjukta , Li Li 
Published: October 2008

AbstractNumerical simulations based on nonlinear partial differential equations (PDEs) using Newton‐based methods require the solution of large, sparse linear systems of equations at each nonlinear iteration. Typically in large‐scale parallel simulations such linear systems are solved by using preconditioned Krylov methods. In many cases, especially in time‐dependent problems, the attributes of the linear systems can change throughout the stimulation, potentially leading to varying times for solving the linear systems during different nonlinear iterations. We present an approach to characterizing the nonlinear and linear system solution and using the resulting application performance information to dynamically select linear solver methods, with the goal of reducing the total time to solution. We discuss the effect of these adaptive heuristics on fluid dynamics and radiation transport codes. We also introduce general component infrastructure to support dynamic algorithm selection and adaptation in applications involving the solution of nonlinear PDEs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling, analysis and simulation of case hardening of steel
Authors: Panizzi Lucia , Hömberg Dietmar , Fasano Antonio 
Published: October 2008

AbstractA mathematical model for the gas carburizing in steel is presented. Carbon is dissolved in the surface layer of a low‐carbon steel part at a temperature sufficient to render the steel austenitic, followed by quenching to form a martensitic microstructure. We have a nonlinear evolution equation for the temperature, coupled with a nonlinear evolution equation for the carbon concentration, both coupled with two ordinary differential equations to describe the phase fractions. We present mathematical results concerning the well‐posedness of the model and finally present a simulation of the process using a finite element approximation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The composite mini element: a new mixed FEM for the Stokes equations on complicated domains
Authors: Peterseim Daniel , Sauter Stefan A. 
Published: October 2008

AbstractWe introduce a new finite element method, the composite mini element, for the mixed discretization of the Stokes equations on two and three‐dimensional domains that may contain a huge number of geometric details. Instead of a geometric resolution of the domain and the boundary condition by the finite element mesh the shape of the finite element functions is adapted to the geometric details. This approach allows low‐dimensional approximations even for problems with complicated geometric details such as holes or rough boundaries. It turns out that the method can be viewed as a coarse scale generalization of the classical mini element approach, i.e. it reduces the computational effort while the approximation quality depends linearly on the (coarse) mesh size in the usual way. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sparsity of the average curvature information matrix
Authors: Frimannslund Lennart , Steihaug Trond 
Published: October 2008

AbstractWe present a theorem regarding the average curvature properties of partially separable functions which need not be differentiable or continuous. This has implications for derivative‐free optimization methods which make use of average curvature information to select the set of search directions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A quasi‐static approach for constrained systems in real‐time simulation
Authors: Burgermeister Bernhard , Arnold Martin , Eichberger Alex 
Published: October 2008

AbstractDetailed multi‐body system models in applications like vehicle dynamics, robotics and bio‐mechanics are designed for accurate off‐line simulation. For real‐time applications simplified models are used. The presented quasi‐static solution method focuses on accelerated computation of the low frequency parts of the solution of the nonlinear equations of motion. The high frequency parts are eliminated by neglecting some of the inertia forces and torques. This reduces numerical stiffness and allows larger step‐sizes for the time‐integration.The efficient and real‐time capable combination with existing highly efficient algorithms for multi‐body dynamics (𝒪(N) multi‐body formalisms) requires appropriate integration methods that are adapted to the special structure of the multi‐body formalism and solve the non‐linear constraints with a small, limited number of calculation steps. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantum dynamics of ultrafast photoinduced processes in organic semiconductors: exciton dissociation at polymer heterojunctions
Authors: Burghardt Irene , Bittner Eric R. , Tamura Hiroyuki 
Published: October 2008

AbstractA molecular‐level, quantum‐dynamical analysis of phonon‐driven exciton dissociation in semiconducting polymers is presented, using a linear vibronic coupling model in conjunction with a recently developed hierarchical chain representation. Quantum‐dynamical simulations in 20‐30 dimensions are carried out using efficient multiconfigurational techniques. The decay of the exciton towards a charge‐separated state is shown to be an ultrafast, coherent process of pronounced non‐equilibrium character, which cannot be modeled by conventional kinetic equations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Betti numbers of random manifolds
Authors: Farber Michael , Kappeler Thomas 
Published: October 2008

AbstractBetti numbers of configuration spaces of mechanical linkages (known also as polygon spaces) depend on a large number of parameters – the lengths of the bars of the linkage. Motivated by applications in topological robotics, statistical shape theory and molecular biology, we view these lengths as random variables and study asymptotic values of the average Betti numbers as the number of links n tends to infinity. We establish a surprising fact that for a reasonably ample class of sequences of probability measures the asymptotic values of the average Betti numbers are independent of the choice of the measure. The main results of the paper apply to planar linkages as well as for linkages in R3. We also prove results about higher moments of Betti numbers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the L2–discrepancies of van der Corput sequences
Authors: Faure Henri 
Published: October 2008

AbstractWe present a selection of results concerning the L2–discrepancies of the two classical generalizations of van der Corput sequences. Especially, we give very simple linear digit scramblings producing very small L2–discrepancies and we show that digitally shifted sequences are not a good choice to improve the star L2–discrepancy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Seismic sources and waves using iterative operator splitting methods
Authors: Geiser Jürgen 
Published: October 2008

AbstractIn this paper, we discuss iterative operator‐splitting methods for wave equations motivated from a realistic problem in seismic sources and waves. The operator splitting methods are well‐known to solve such complicated multi‐dimensional and multi‐physical problems, while decomposing into simpler and computable equations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Energy estimates for reaction‐diffusion processes of charged species
Authors: Glitzky Annegret 
Published: October 2008

AbstractWe consider electro‐reaction‐diffusion systems consisting of continuity equations for a finite number of species coupled with a Poisson equation. We take into account heterostructures, anisotropic materials and rather general statistical relations.We investigate thermodynamic equilibria and prove for solutions to the evolution system the monotone and exponential decay of the free energy to its equilibrium value. Here the essential idea is an estimate of the free energy by the dissipation rate. The same properties are obtained for a fully implicit time discretized version of the problem. Moreover, we provide a space discretized scheme for the electro‐reaction‐diffusion system which is dissipative (the free energy decays monotonously). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of Rosenbrock‐type methods to a constitutive model of polymeric material
Authors: Hamkar Ahmad‐Wahadj , Hartmann Stefan 
Published: October 2008

AbstractThe consistent application of the time‐space discretization in the case of quasi‐static structural problems based on constitutive equations of evolutionary type yields after the finite element discretization to a system of differential‐algebraic‐equations (DAE). In order to carry out the time discretization, time‐adaptive Rosenbrock‐type methods are applied to the DAE‐system, which offer the possibility of a completely iteration‐less procedure. This presentation shows the behavior of a new global finite element approach and compares it to the classical implicit (iterative) procedure. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Extended flamelet model and improved interaction of chemistry and turbulence for modeling partially premixed combustion with a joint PDF method
Authors: Hegetschweiler Michael , Jenny Patrick 
Published: October 2008

AbstractTurbulent combustion is commonly categorized into premixed, non‐premixed and partially premixed combustion. For nonpremixed combustion simulations the laminar flamelet concept proved to be very valuable while for the more complex case of partially premixed combustion this model shows considerable deficiencies. Here, the classical laminar flamelet approach is extended to the partially premixed combustion regime. For that, the joint statistics of mixture fraction, scalar dissipation rate and a progress variable, calculated with a joint probability density function (PDF) method, is used to get the statistics of the compositions and of the chemical energy source term from pre‐processed flame tables. This approach can be compared with the unsteady flamelet concept; the main differences consists of the way the progress variable evolution is computed and in the pre‐computed flame tables. The progress variable describes the point of time a fluid parcel is consumed by a flame front. The fluid parcels are represented by computational particles, which are used for PDF methods. The pre‐computed flame tables are computed from steady solutions 2D stabilized flames propagating into an unburnt mixture with varying mixture fraction. The corresponding position of a fluid particle in such a 2D laminar flame is determined by its mixture fraction and a burning time; both to be modeled for each computational particle in the PDF simulation. Numerical experiments of turbulent diffusion jet flames demonstrate that this approach can be employed for challenging test cases. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On a decoupling approach in inverse option pricing
Authors: Hein Torsten 
Published: October 2008

AbstractWe present a decoupling approach for the inverse problem of option pricing which separates the identification of term and smile structure into two subproblems. The determination of the smile structure is reduced to the case of purely price‐dependent options. For the identification of the term structure we suppose a Tikhonov regularization approach and present a convergence rates result including the special situation of at‐the‐money options. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A BE based finite element for crack propagation processes
Authors: Helldörfer Bastian , Kuhn Günther 
Published: October 2008

AbstractA boundary element based finite macro element for the simulation of 3D crack propagation in the framework of linear elastic fracture mechanics is presented. While the major part of the numerical model is discretized with finite elements, a small domain containing the crack is meshed with boundary elements. By means of the Symmetric Galerkin BEM a stiffness formulation for the cracked BE domain is obtained which enables a direct FEM/BEM coupling. All necessary operations for the crack propagation are carried out within this boundary element based finite macro element and exploit the potential of the boundary integral formulation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study groups in Denmark: A tale of three cities
Authors: Hjorth Poul G. 
Published: October 2008

AbstractSince 1998 European Study Groups have been held in Denmark, and Danish companies from LEGO and NOVO to very small high‐tech firms have participated. Here, I briefly describe the history, the organization and the format of the Danish Study Groups, and highlight a few problem solutions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The vibrational behaviour of bladed disks with multiple coupling devices
Authors: Hohl A. , Panning L. , Siewert C. , Buerge A. 
Published: October 2008

AbstractIn turbomachinery applications turbine blades are subjected to high static and dynamic loads. Static loads are due to centrifugal stresses and thermal strains. Especially the dynamic excitation caused by fluctuating gas forces results in high vibration amplitudes which can lead to high cycle fatigue failures (HCF). Therefore, in practical applications, coupling devices like underplatform dampers, lacing wires and tip shrouds are installed to the structure. In case of blade vibrations the relative displacements between these coupling devices and the blades generate friction forces. The resulting energy dissipation provides additional damping to the structure. Furthermore, coupling devices, in particular tip shrouds, snubbers and lacing wires, increase the stiffness of the structure. Hence, they lead to a shift of the resonance frequencies.So far, only effects of single coupling devices and the influencing properties have been examined. Within this paper the effect of multiple couplings is determined and compared with single couplings. The forced response of turbine bladings with multiple couplings is calculated under consideration of geometrical and mechanical parameters of the blading and contacts, respectively. The results are compared with the single coupled blading. Furthermore, a multiple coupled device with under‐platform damper and connecting pin is compared with respect to his effectiveness. Especially the influence on the resonance frequency and the achievable damping is analysed. The results of the simulation are verified by measurements at a two‐blade non‐rotating test rig with an underplatform damper and connecting pin. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)