bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coupling of deterministic and stochastic simulation methods for gas‐solid‐flows
Authors: Kanther Wolfgang , Grüner Christof , Götz Sören , Strauß Karl 
Published: June 2004

AbstractA new simulation method is proposed coupling deterministic and stochastic methods by an adaptive domain decomposition based on local granular equilibrium rating. This method reduces the computational effort compared to the fully stochastic method by roughly an order of magnitude, without significant loss of accuracy. Furthermore with this method appropriate boundary conditions for the solid phase can easily be derived.
Shear Flow of Suspensions under Wall Influence: Phenomenological Theory and Effects
Authors: Muckenfuss Silke , Buggisch Hans 
Published: June 2004

AbstractThe influence of solid boundary walls in shear flow of suspensions leads to structure formation and particle transport. We have developed a phenomenological model to describe the wall effects such as the formation of a wall boundary layer, the occurence of pseudo wall slip as well as discontinuities of the particle concentration. Using the model particle concentration profiles, thickness of boundary layer and suitably defined wall slip velocities depending on the total particle concentration of the suspension can be determined.
Peculiarities of fully Lagrangian approach for modeling dilute two‐phase mixtures with close phase densities
Authors: Osiptsov Alexander 
Published: June 2004

AbstractThe methods of calculating dilute two‐phase flows with a collisionless dispersed phase (particles, drops, or bubbles) fall essentially in two categories: Eulerian and Lagrangian. A limitation of the Eulerian approach is the exclusion of flows with crossing particle trajectories. An effective Lagrangian method for calculating flows with the formation of caustics in particle‐trajectory patterns was proposed earlier (see, for example [1]) for the case when the interphase force contains only “local” interaction terms (aerodynamic drag, Saffman force, etc.). In this paper, the fully Lagrangian approach is generalized to the case of similar phase densities, when in the interphase momentum exchange, in addition to the Stokes drag, the differential terms (virtual‐mass and Archemedes forces) and the integral term (Basset force) should be taken into account. The use of the method is illustrated by the calculation of redistributing particles or bubbles in a rotating spherical volume of a self‐gravitating viscous fluid (a model of development of density nonuniformities in the Earth core). A substantial anisotropy in radial particle concentration distributions and the possibility of forming local particle accumulation zones in the equatorial plane is indicated in the calculations.
Transport in a capillary thermo‐elastic porous material
Authors: Ricken T. , de Boer R. 
Published: June 2004

AbstractIn this contribution, the coupled flow of liquids and gases in capillary thermo‐elastic porous materials is investigated using a continuum mechanical model based on the Theory of Porous Media (TPM). In order to describe the behaviour of the three constituents involved, the balance equations of mass, of momentum and of energy concerning to all phases must be taken into account. The aim of this investigation is to simulate the behavior of liquid and gas phases in a thermo‐elastic porous body.
On the Improvement of Efficiency and Storage Requirements of the Discontinuous Galerkin Method for Aeroacoustics
Authors: Dumbser M. 
Published: June 2004

AbstractFor Computational Aeroacoustics (CAA), good wave propagation properties are a crucial point for numerical schemes which solve the linearized Euler equations (LEE) in the time domain. A recently developed high order scheme with excellent wave propagation properties is the Discontinuous Galerkin (DG) method. The DG schemes are based on the Finite Element Method (FEM), using discontinuous piecewise polynomial basis functions to represent the solution. The efficiency can be highly improved for CAA applications if a quadrature‐free formulation of the DG method is used, but nevertheless the DG schemes consume much computer storage due to the Runge‐Kutta time integration procedure and the high number of degrees of freedom to be stored for each element. We managed to develop a high order single‐step quadrature‐free DG method which does not use a Runge‐Kutta time integration procedure but which applies the ADER approach of Toro, Schwartzkopff et al. and where the accuracy of the scheme can further be improved using additionally a reconstruction technique working on the degrees of freedom of the element and its neighbors.
Sound wave channeling near–critical sulfurhexafluoride (SF6)
Authors: Schlamp Stefan , Rösgen Thomas 
Published: June 2004

AbstractStrong density and sound speed gradients exist in near–critical isothermal fluid columns under gravity. The sound speed profile has a minimum, allowing table–top sound channeling experiments. The three characteristic length scales (ray curvature, correlation length of critical fluctuations, wavelength) can be changed independently by adjusting the temperature, frequency, and the strength of the gravitational field.
Computational Aeroacoustics using the new FASTAder approach
Authors: Schwartzkopff T. , Munz C.‐D. 
Published: June 2004

AbstractTo overcome the problems of a aeroacoustical simulation in the time domain, we use a heterogenous domain decomposition where the domains can be adapted to geometrical or physical constraints. We were able to show, that the commonly used conditions of constant fluxes at the interface yields to a solution which produces reflections. The correct condition is to prescribe constant values and to allow a discontinuous flux at the interfaces. In the domain where no obstacles and nonlinear effects are present, a structured mesh is used to solve the linearized Euler equations. For these problems the FASTAder approach has been developed.
Well‐posed and ill‐posed situations in option pricing problems when the volatility is purely time‐dependent
Authors: Hofmann Bernd , Hein Torsten 
Published: June 2004

AbstractWe consider an inverse problem in option pricing with time‐dependent option price and volatility functions over a finite interval. Such problems may serve as benchmark problems for studying the character of ill‐posedness in option pricing and the impact of data smoothness and no arbitrage on solution properties.
Rhombic Periodicity Lattice in Bifurcational Symmetry Breaking Problems
Authors: Konopleva Irina , Loginov Boris 
Published: June 2004

AbstractGeneral theory of symmetry breaking problems in branching theory is presented in the works [1–3]. Such problems are invariant relative to Euclidean space motions group and their solution which is invariant relatively this group is the rest state or uniform linear motion. At the stability loss cell structure solutions arise, which are invariant relative to the group of the definite period shifts along the definite directions, passing mutually under discrete subgroup transformations that is defined by the symmetry of elementary cell of the periodicity. Thus the Euclidean space motions group is changed by the symmetry of a certain crystallographic group.In this article for the case of 4–dimensional degeneracy of the linearized Fredholm operator abstract bifurcational symmetry breaking problems both for stationary and Andronov‐Hopf bifurcation with planar rhombic periodicity lattice are considered. Applications to hydrodynamical problems are given.
Mixed Boundary Value Problem of Plate Bending
Authors: Kutnjak Milan 
Published: June 2004

AbstractThe bending problem of thin plates is presented through biharmonic equations expressed in terms of plate deflections. The theory of analytical functions is used to transform the problem to the Hilbert boundary value problem. The stress and deformation state of the plate is descibed by analitical functions which satisfy mixed boundary conditions. A circular plate with corresponded boundary conditions is treated.
On Regularization of Pseudoperturbation Method for Sharpening of Approximately Given Generalized Jordan Chains
Authors: Loginov Boris , Konopleva Irina 
Published: June 2004

AbstractCombination of pseudoperturbation and Newton‐Kantorovich (N.‐K.) methods are applied for the sharpening of approximately given eigenvalue and generalized Jordan chains (GJChs) of linear by spectral parameter operator function.
Numerical Simulation of Pollution Dispersion over Real Terrain
Authors: Beneš Luděk , Bodnár Tomáš , Fraunié Philippe , Kozel Karel , Sládek Ivo 
Published: June 2004

AbstractThe paper presents a mathematical and numerical investigation of the atmospheric boundary layer (ABL) flow over coal depot. Two mathematical models have been mentioned based upon: 1) the RANS equations in the conservative form and 2) the Boussinesq approximation of RANS equations in the non–conservative form, both formulated for an incompressible flow with a simple algebraic turbulence closure and given stationary boundary conditions. Also pollution dispersion of passive pollutants has been considered.
A note to the linearity proof of Lorentz transformation
Authors: Günther Helmut 
Published: June 2004

AbstractThe traditional proof of the linearity of Lorentz transformation makes use of a definition of simultaneity and a physical law for the propagation of light. For unravelling these two elements we use a reverse axiomatic approach to special relativity. In this case we are free, in principle, to introduce an arbitrary simultaneity. Linear coordinate transformations require a linear synchronisation. Lorentz transformation results from a special kind of linear synchronisation.
Numero‐Fuzzy Hybrid for Modelling and Simulation of the Fouling of Milk Heat Exchangers
Authors: Petermeier Hannes , Benning Rainer , Becker Thomas , Delgado Antonio 
Published: June 2004

AbstractTo overcome the lack of a selfcontained description of the fouling process in dairy industry, a fuzzy system is integrated in a process model using wellknown numerics thus resulting in a numero‐fuzzy hybrid model. Results concerning the simulation of a dairy plant and a new approach for the study of the applied fuzzy systems are presented.
A Coincidence Degree for Bifurcation Problems with Applications to Steady State Flow
Authors: Sburlan S. , Sburlan C. 
Published: June 2004

AbstractIn this paper we study the steady state flow of incompressible fluids treated as an eigenvalue problem. We can define a coincidence degree under some conditions weaker than the ones when the classical coincidence degree was defined, and use the properties of this degree to our problem.
Discrete and continuum models of heat conduction problems in periodic lattice structures
Authors: Szymczyk Jolanta , Wozniak Czeslaw 
Published: June 2004

AbstractA new modelling approach to the hyperbolic heat conduction problems in periodic lattice structures of an arbitrary form is proposed. To this end we introduce a special description of the periodic lattice geometry which leads to the discrete lattice model governed by the system of finite difference equations. The continuum models are derived from the discrete model, by using the principle of stationary action.
Energy Conservative Methods for Numerical Solution of ODE‐s Based on Taylor series Algorithm
Authors: Miletics E. 
Published: June 2004

AbstractThe numerical solution of the ODE initial value problems is an intensively researched field. We have a lot of methods, eg. R‐K, Adams, symplectic but it isn't known well, how the approximate solutions behave from point of wiev of conservative quantities, for example energy [3], impulse etc. In this work we present an energy conservative algorithm based on the Taylor series method which was realized by MapleV system [2].
Overdetermined Elliptic Systems
Authors: Seiler Werner M. , Tuomela Jukka 
Published: June 2004

AbstractWe show that the weights classically used for the definition of ellipticity are not necessary, as any differential system that is elliptic with weights becomes elliptic without weights during its completion. Furthermore, there are systems which are not elliptic for any choice of weights but whose completed form is nevertheless elliptic.
Robustness of shortfall risk minimising strategies in the binomial model
Authors: Favero Gino , Vargiolu Tiziano 
Published: June 2004

AbstractIn this paper we study the dependence on the loss function of the strategy which minimises the expected shortfall risk when dealing with a financial contingent claim in the particular situation of a binomial model. After having characterised the optimal strategies in the particular cases when the loss function is concave, linear or strictly convex, we analyse how optimal strategies change when we approximate a loss function with a sequence of suitable loss functions.
ℐ–invariant random strict total orderings on ℤ
Authors: Hirth Ulrich 
Published: June 2004

AbstractIn a recent preprint ([4]) Saul Jacka and Jon Warren develop further the ideas of Paul Ressel and myself [3], though they work without positive definite functions on semigroups. I approach the results of [4] on ℐ–invariant random strictly total orderings by semigroup methods as in [3]. These orderings are most directly related to card shuffling, cf. the rich work of Persi Diaconis. Although more concrete applications are not yet known to me, the related papers [3], [2] and [1] definitively do have a background in population genetics, so the present work on ℐ–invariant random orderings is certainly not far from real–life applications.
Ship Capsize Risk Assessment and Designing Against Capsize
Authors: Sichermann Wolfgang , Kreuzer Edwin 
Published: June 2004

AbstractA promissing approach for assessing ship safety against capsize is presented by Melnikov's method. The mean zero up‐crossing rate of the dynamical system's associated Melnikov process provides an upper bound for the mean capsizing rate in a stationary sea state. Due to its moderate computational effort if low dimensional systems are considered, this approach is particularly suited for applications in ship design.
Generalizations of Optimal Control Problems by Comparison
Authors: Irrgang H. , Bittner L. 
Published: June 2004

AbstractGeneralizations of optimal control problems can be used for deciding the existence of solutions as well as for constructions of approximate solutions. In such cases one has to ask for gaps between the original problem and its generalizations. An overview will be given on several generalizations of a special kind of optimal control problems and the connections between them will be pointed out.These connections allow to answer the question about gaps for special cases.
Real‐Time Trajectory Planning of the Industrial Robot IRB6400
Authors: Knauer Matthias , Büskens Christof 
Published: June 2004

AbstractPath planning of industrial robots requires the calculation of trajectories with respect to different optimization criteria, e.g. time optimal, energy optimal or wear and tear optimal solutions. These optimal control problems can be solved numerically, e.g., by direct solvers. In practice, inaccuracies or perturbations in the underlying model can cause the robot to fail in following the calculated path. When deviations of the precalculated trajectory or system parameters are detected an update of the robot trajectory is required in real‐time. Therefore, a method based on the parametric sensitivity analysis of the optimal control problem is proposed to calculate admissible approximations for the solution of the perturbed robot trajectory problem in real‐time. A model of ABB's common robot IRB 6400 is used to reveal the capabilities of the proposed method.
Stability Optimization of Periodic Mechanical Systems without Feedback
Authors: Mombaur Katja , Bock Hans Georg , Schlöder Johannes , Longman Richard 
Published: June 2004

AbstractThe open‐loop stability of periodic mechanical systems with multiple motion phases and state discontinuities is investigated. We make the assumption that the systems do not have any active feedback, but must rely entirely on their kinematic and dynamic properties to stabilize their motion. By means of a newly developed stability optimization method we are able to determine model parameters as well as actuator inputs and cycle times for which such selfstabilizing motions are possible.
Numerical Simulation of a 1D Model of a Molten Carbonate Fuel Cell
Authors: Pesch Hans Josef , Chudej Kurt , Petzet Verena , Scherdel Sabine , Schittkowski Klaus , Heidebrecht Peter , Sundmacher Kai 
Published: June 2004

AbstractWithout combustion, molten carbonate fuel cells (MCFC) convert chemical energy contained in fuel and oxidizer to electric energy via electro‐chemical reaction. Performance and service life of MCFCs depends on its operating temperature. So control of the operation temperature within a specified range and reducing temperature fluctuations is highly desirable. In a first step towards this goal numerical simulations are computed.
On a Smoothing Quasi‐Newton Method for Nonlinear Complementarity Problems
Authors: Rapajić Sanja , Krejić Nataša , Lužanin Zorana 
Published: June 2004

AbstractNonlinear complementarity problems (NCP) arise from optimization theory, engineering and economic applications. These problems are usually solved applying iterative methods to equivalent systems of nonlinear equations. We consider Jacobian smoothing quasi‐Newton method for a semismooth equation reformulation of NCP based on Fisher‐Burmeister function. Some numerical experiments of Jacobian smoothing method with modification of the right‐handside vector are presented.
Optimal Control and Parametric Sensitivity Analysis in Cancer Chemotherapy
Authors: Sternberg Kati , Büskens Christof 
Published: June 2004

AbstractThe chemotherapeutic treatment of a tumor is based on the growth‐retarding effect of the given medicinal drug dose to a cancer cell population. Preserving the health of the patient this can be formulated as an optimal control problem. We use a modified model of Ledzewicz and Schättler and present the optimal solution calculated numerically. Especially we attend a parametric sensitivity analysis, which indicates the dependency of the optimal solution with respect to disturbances in model parameters. In detail we examine the parametric sensitivity in case of disturbances in the cell‐cycle parameters.
Optimal kinematic design of a link‐drive mechanism with prescribed velocity characteristics
Authors: Vohar Bojan , Gotlih Karl , Flašker Jože 
Published: June 2004

AbstractThe paper presents an example of a link‐drive mechanism for a deep drawing mechanical press. Because of its characteristics such a drive is much more appropriate than conventional crankshaft or eccentric drive. The existing design of the drive has proved unsatisfactory and does not meet all the demands and constraints, which are ideal for deep drawing process. Optimization of the drive is therefore necessary. The intention is to achieve the required velocity characteristics in a defined area of movement. Firstly, the drive is analyzed and a mathematical model is made and prepared for optimization procedure. The process is time‐dependent, so it cannot be used directly in the optimization algorithm. Mathematical model is transformed into a form suitable for the standard non‐linear optimization procedure and then optimization is carried out. The method used is sequential quadratic programming. The final objective of the optimization process is to find such dimensions of link‐drive members that the given requirements are satisfied in the best possible manner.
Computation of 3D exterior stationary incompressible Navier‐Stokes flowswith non‐zero velocity at infinity
Authors: Calgaro Caterina , Deuring Paul , Jennequin Delphine 
Published: June 2004

AbstractWe aim to find numerical approximations of stationary incompressible Navier‐Stokes flows in 3D exterior domains. To this end, we consider the Navier‐Stokes system with local artificial boundary conditions on a truncated exterior domain. This boundary value problem is solved approximately by a finite element method. The corresponding error is estimated with respect to the discretisation depth and the size of the truncated exterior domain.
Modified ℋ︁‐matrices for convection dominated problems
Authors: Le Borne Sabine 
Published: June 2004

AbstractHierarchical matrices (ℋ︁‐matrices) provide a technique for the sparse approximation of large, fully populated matrices. These matrices are constructed by using an algorithm that iteratively partitions the (block) index set until a certain admissibility condition is satisfied for an index block. For elliptic operators with L∞‐coefficients, the standard partitioning algorithm in connection with the standard admissibility condition lead to hierachical matrices that approximate the (inverse) of the stiffness matrix with an error of the same order as the discretization order while having nearly optimal storage complexity [1]. The standard partitioning and admissibility condition fail to provide satisfactory results when applied to the singularly perturbed convection‐diffusion equation. We will introduce a modified (hierarchical) partitioning of the index and block index sets together with a modified admissibility condition, both depending on the (constant) convection direction. Numerical results will illustrate the positive effect of the changes.
Artificial Multilevel Boundary Element Preconditioners
Authors: Steinbach Olaf 
Published: June 2004

AbstractA hierarchical multilevel preconditioner is constructed for an efficient solution of a first kind boundary integral equation with the single layer potential operator discretized by a boundary element method. This technique is based on a hierarchical clustering of all boundary elements as used in fast boundary element methods. This hierarchy is applied to define a sequence of nested boundary element spaces of piecewise constant basis functions as used in the definition of the preconditioning multilevel operator.
MGM Optimal convergence for certain (multilevel) structured linear systems
Authors: Aricó Antonio , Donatelli Marco , Serra‐Capizzano Stefano 
Published: June 2004

AbstractWe present a multigrid algorithm to solve linear systems whose coefficient metrices belongs to circulant, Hartley or τ multilevel algebras and are generated by a nonnegative multivariate polynomial f.It is known that these matrices are banded (with respect to their multilevel structure) and their eigenvalues are obtained by sampling f on uniform meshes, so they are ill‐conditioned (or singular, and need some corrections) whenever f takes the zero value. We prove the proposed metod to be optimal even in presence of ill‐conditioning: if the multilevel coefficient matrix has dimension ni at level i, i = 1, … , d, then only $ N(n) = \prod ^{d} _{i=1} n_{i} $ ni operations are required on each iteration, but the convergence rate keeps constant with respect to N(n) as it depends only on f.The algorithm can be extended to multilevel Toeplitz matrices too.
Slow Initial Convergence of GMRES for SUPG Discretized Convection‐Diffusion Problems
Authors: Liesen Jörg , Strakoš Zdeněk 
Published: June 2004

AbstractWhen GMRES [6] is applied to streamline upwind Petrov Galerkin (SUPG) discretized convection‐diffusion problems, its residual norms typically exhibit an initial period of slow convergence. For a model problem we offer a quantitative explanation of this behavior and relate it to the boundary conditions.
On Estimation of the A‐norm of the Error in CG and PCG
Authors: Strakoš Zdeněk , Tichý Petr 
Published: June 2004

AbstractWe concentrate on the preconditioned conjugate gradient method and describe a simple and numerically well‐justified way of estimation of the A‐norm of the error. In this way this note represents an extension of [5] and its aim is to mediate the analytic results from [5] to practical users of the preconditioned conjugate gradient method.