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Perspektiven für die Wasserkraftwerke in der Schweiz. Langfristige Wettbewerbsfähigkeit und mögliche Verbesserungspotenziale
(2001)Forschungsprogramm Energiewirtschaftliche GrundlagenReport -
Routed message driven beans: a new abstraction for using EJBs
(2001)TIK ReportAsynchronous messaging between cooperating software components proves to be useful in many scenarios. One framework supporting this functionality is Suns J2EE platform with its Message-Driven Beans (MDB) model. We present a novel way to use MDBs by providing a way to add routing information to the messages, which is then used to send a message through a given path of processing components. We call this model Routed Message-Driven Beans ...Report -
Sparse Two-Scale FEM for Homogenization Problems
(2001)SAM Research ReportWe analyze two-scale Finite Element Methods for the numerical solution of elliptic homogenization problems with coefficients oscillating at a small length scale \varepsilon << 1. Based on a refined two-scale regularity on the solutions, two-scale tensor product FE spaces are introduced and error estimates which are robust (i.e. independent of \varepsilon) are given. We show that under additional two-scale regularity assumptions on the ...Report -
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Convergence of some two-level overlapping domain decomposition preconditioners with smoothed aggregation coarse space
(2001)SAM Research ReportThe study two-level overlapping preconditioners with smoothed aggregation coarse spaces for the solution of sparse linear systems arising from finite element discretizations of second order elliptic problems. Smoothed aggregation coarse spaces do not require a coarse triangulation. After aggregation of the fine mesh nodes, a suitable smoothing operator is applied to obtain a family of overlapping subdomains and a set of coarse basis ...Report -
Service deployment on high performance active network nodes
(2001)TIK ReportIn order to realize service deployment on high-performance active nodes, the problem of installing and configuring software components in complex, heterogeneous node environments must be addressed. The paper presents our approach to this problem, called Chameleon, which includes two main aspects. First, the service model we propose is based on service components with two interfaces--a data flow interface for programming packet flows and ...Report -
Wavelet-discretizations of parabolic integro-differential equations
(2001)SAM Research ReportWe consider parabolic problems u + Au = f in (0,T)x Ω, T < ∞, where Ω ⊂ Rd is a bounded domain and A is a strongly elliptic, classical pseudo-differential operator of order ρ ∈ [0,2] in H ρ/2 (Ω). We use a θ-scheme for time discretization and a Galerkin method with N degrees of freedom for space discretization. The full Galerkin matrix for A can be replaced with a sparse matrix using a wavelet basis, and the linear systems for each time ...Report -
NP-hardness of broadcast scheduling and inapproximability of single-source unsplittable min-cost flow
(2001)TIK ReportWe consider the version of broadcast scheduling where a server can transmit one message of a given set at each time-step, answering previously made requests for that message. The goal is to minimize the average response time if the amount of requests is known in advance for each time-step and message. We prove that this problem is NP-hard, thus answering an open question stated by Kalyanasundaram, Pruhs and Velauthapillai (Proceedings of ...Report -
Approximation algorithms and complexity results for path problems in trees of rings
(2001)TIK ReportA tree of rings is a network that is obtained by interconnecting rings in a tree structure such that any two rings share at most one node. A connection request (call) in a tree of rings is given by its two endpoints and, in the case of prespecified paths, a path connecting these two endpoints. We study undirected trees of rings as well as bidirected trees of rings. In both cases, we show that the path packing problem (assigning paths to ...Report -