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Fault-tolerant real-time scheduling under execution time constraints
(1999)TIK ReportThe primary/backup with deallocation approach of [Ghosh 97] is a strategy for the fault-tolerant online scheduling of hard real-time tasks. In this scheme, tasks are either rejected within a short time after the request or guaranteed to be executed even in case of a processor failure. In this paper several heuristics for the guarantee algorithm are investigated. For the first time different processor selection strategies for guarantee ...Report -
Exponential Convergence in a Galerkin Least Squares hp-FEM for Stokes Flow
(1999)SAM Research ReportA stabilized hp-Finite Element Method (FEM) of Galerkin Least Squares (GLS) type is analyzed for the Stokes equations in polygonal domains. Contrary to the standard Galerkin FEM, this method admits equal-order interpolation in the velocity and the pressure, which is very attractive from an implementational point of view. In conjunction with geometrically refined meshes and linearly increasing approximation orders it is shown that thehp-GLSFEM ...Report -
Advanced boundary element algorithms
(1999)SAM Research ReportWe review recent algorithmic developments in the boundary element method (BEM) for large scale engineering calculations. Two classes of algorithms, the clustering and the wavelet-based schemes are compared. Both have $O(N(\log N)^a)$ complexity with some small $a \ge 0$ and allow in-core simulations with up to $N = O(10^6)$ DOF on the boundary on serial workstations. Clustering appears more robust for complex surfaces.Report -
Mobility as a function of social and spatial factors
(1999)Arbeitsberichte Verkehrs- und RaumplanungThe research presented here explores the interactions between land use, household structure and travel patterns. The data are from an extensive travel diary of over 100,000 households in the Land of Upper Austria, combined with extensive data on land uses and local economic activities. Structural equation models are developed at both the person and household levels to explain mobility simultaneously in terms of socio-economic and spatial ...Working Paper -
Labeling downtown
(1999)ETH, Eidgenössische Technische Hochschule Zürich, Departement Informatik, Institut für ComputersystemeAmerican cities, especially their central regions usually have a very regular street pattern: We are given a rectangular grid of streets, each street has to be labeled with a name running along its street, such that no two labels overlap. For this restricted but yet realistic case an efficient algorithmic solution for the generally hard labeling problem gets in reach. The main contribution of this paper is an algorithm that guarantees to ...Report -
A Scale-Residual Model for Large-Eddy Simulation
(1999)SAM Research ReportA subgrid-scale model for large-eddy simulation is developed and a conservative formulation of the filtered compressible Navier-Stokes equations is derived. We introduce a different way of looking at LES modelling: In contrast to other approaches, which estimate the subgrid-scale quantities explicitly out of the instantaneous filtered solution, the residual between the time evolution of two solutions of the Navier-Stokes equations (without ...Report -
Approximation on Simplices with respect to Weighted Sobolev Norms
(1999)SAM Research ReportInequalities of Jackson and Bernstein type are derived for polynomial approximation on simplices with respect to Sobolev norms. Although we cannot use orthogonal polynomials, sharp estimates are obtained from a decomposition into orthogonal subspaces. The formulas reflect the symmetries of simplices, but comparable estimates on rectangles show that we cannot expect rotational invariance of the terms with derivatives.Report -
A survey of synchronous RAM architectures
(1999)TIK ReportThe functionality of volatile random access memories (RAMs) in personal computers, embedded systems, networking devices, and many other products is based on an access scheme which was designed over thirty years ago. Since then a variety of different realizations has evolved. Due to the fact that VLSI designs for memory chips have always been optimized for area and not for access speed, RAM chips have become more and more the performance ...Report -
3D exploration of Uniprocessor Schedules for DSP algorithms
(1999)TIK ReportWhen implementing software for programmable digital signal processors (PDSPs), the design space is defined by a complex range of constraints and optimization objectives. Three implementation metrics that are crucial in many PDSP applications are the program memory requirement (code size), data memory requirement, and execution time. This paper addresses the problem of exploring the 3-dimensional space of trade-offs that is defined by these ...Report -
Homogenization via p-FEM for Problems with Microstructure
(1999)SAM Research ReportA new class of $p$ version FEM for elliptic problems with microstructure is developed. Based on arguments from the theory of $n$-widths, the existence of subspaces with favourable approximation properties for solution sets of PDEs is deduced. The construction of such subspaces is addressed for problems with (patch-wise) periodic microstructure. Families of adapted spectral shape functions are exhibited which give exponential convergence ...Report