PUMA publications for /group/simtech/elementFri Jul 20 10:54:15 CEST 2018Acta Mathematica Universitatis Comenianae, New Ser.1105-122\textsf{ALBERT} --- {S}oftware for Scientific Computations and Applications702001design software scientific Adaptive finite element software, methods, vorlaeufig Adaptive finite element methods are a modern, widely used tool which make realistic computations feasible, even in three space dimensions. We describe the basic ideas and ingredients of adaptive FEM and the implementation of our toolbox \ALBERT. The design of \ALBERT is based on the natural hierarchy of locally refined meshes and an abstract concept of general finite element spaces. As a result, dimension independent programming of applications is possible. Numerical results from applications in two and three space dimensions demonstrate the flexibility of \ALBERT.Fri Jul 20 10:54:15 CEST 2018Numerical Mathematics: Theory, Methods and Applications3245-274Design of Finite Element Tools for Coupled Surface and Volume Meshes12008design software scientific Adaptive finite element software, methods, vorlaeufig Many problems with underlying variational structure involve a coupling of volume with surface effects. A straight-forward approach in a finite element discretization is to make use of the surface triangulation that is naturally induced by the volume triangulation. In an adaptive method one wants to facilitate "matching" local mesh modifications, i.e., local refinement and/or coarsening, of volume and surface mesh with standard tools such that the surface grid is always induced by the volume grid. We describe the concepts behind this approach for bisectional refinement and describe new tools incorporated in the finite element toolbox ALBERTA. We also present several important applications of the mesh coupling.Fri Jul 20 10:54:15 CEST 2018Computer Methods in Applied Mechanics and Engineering147 - 175Time domain boundary elements for dynamic contact problems3332018method element Boundary vorlaeufig Abstract This article considers a unilateral contact problem for the wave equation. The problem is reduced to a variational inequality for the Dirichlet-to-Neumann operator for the wave equation on the boundary, which is solved in a saddle point formulation using boundary elements in the time domain. As a model problem, also a variational inequality for the single layer operator is considered. A priori estimates are obtained for Galerkin approximations both to the variational inequality and the mixed formulation in the case of a flat contact area, where the existence of solutions to the continuous problem is known. Numerical experiments demonstrate the performance of the proposed mixed method. They indicate the stability and convergence beyond flat geometries.Fri Jul 20 10:54:15 CEST 2018SubmittedA convergent time-space adaptive $dG(s)$ finite element method for parabolic problems motivated by equal error distribution2017a equation estimators, convergence, error finite methods, posteriori adaptivity, element vorlaeufig heat Fri Jul 20 10:54:15 CEST 2018Numerical Methods for Partial Differential Equations41018--1042A posteriori error estimates with point sources in fractional sobolev spaces332017a Dirac estimators, error finite fractional methods, posteriori adaptivity, element spaces mass, Sobolev vorlaeufig Thu May 18 11:32:12 CEST 2017{THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND}{CONSTRUCTION AND BUILDING MATERIALS}{OCT 15}{1007-1018}{Hybrid cross-laminated timber plates with beech wood cross-layers}{Article}{124}{2016}Finite (CLT); Compression Shear Spruce shear (Picea analysis; (Fagus abies); Rolling gamma-Method; method} {Cross-laminated analogy sylvatica); Beech element Bending test; timber wood strength; modulus; {A hybrid, three-layered, softwood-hardwood cross-laminated timber build-up with outer layers of European spruce (Picea abies) and a center cross-layer of European beech (Fagus sylvatica) has been investigated with regard to out-of-plane bending. The determination of the rolling shear properties of the beech cross-layer performed by different test and measurement methods comprising bending and compression shear tests was of primary interest. The shear capacity of the composite is significantly influenced by the spruce longitudinal shear strength at the beech-spruce interface. The characteristic values of rolling shear modulus and strength of the beech cross-layer from the bending tests were G(r), mean = 350 N/mm(2) and f(v,r,05) = 2.6 N/mm(2), respectively. Direct strain gauge measurements and compression shear tests resulted in 10-20\% higher values. The high rolling shear properties render the shear lag implications of the softwood CLTs to a negligible quantity. The hybrid build-up can be designed as a rigid composite with small error versus a more exact analysis. The novel investigations reveal the great potential of mixed softwood-hardwood CLT build-ups for structural elements in the building sector, (C) 2016 Elsevier Ltd. All rights reserved.}Thu May 18 11:32:12 CEST 2017{VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS}{COMPUTATIONAL ECONOMICS}{MAR}{3}{447-472}{A Non-stationary Model of Dividend Distribution in a Stochastic Interest-Rate Setting}{Article}{47}{2016}Finite methods control; for Numerical differential method} Singular equations; distribution; stochastic element {Dividend partial {In this paper the solutions to several variants of the so-called dividend-distribution problem in a multi-dimensional, diffusion setting are studied. In a nutshell, the manager of a firm must balance the retention of earnings (so as to ward off bankruptcy and earn interest) and the distribution of dividends (so as to please the shareholders). A dynamic-programming approach is used, where the state variables are the current levels of cash reserves and of the stochastic short-rate, as well as time. This results in a family of Hamilton-Jacobi-Bellman variational inequalities whose solutions must be approximated numerically. To do so, a finite element approximation and a time-marching scheme are employed.}