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961.
This paper presents a detailed numerical study of the heat exchange between two parallel plates with prescribed temperature gradients along the plates and a fluid circulating between them. The interplay between the bulk temperature, the heat flow and the Nusselt number has been clarified. 相似文献
962.
We study the semidiscrete Galerkin approximation of a stochastic parabolic partial differential equation forced by an additive space-time noise. The discretization in space is done by a piecewise linear finite element method. The space-time noise is approximated by using the generalized L2 projection operator. Optimal strong convergence error estimates in the L2 and
norms with respect to the spatial variable are obtained. The proof is based on appropriate nonsmooth data error estimates for the corresponding deterministic parabolic problem. The error estimates are applicable in the multi-dimensional case.
AMS subject classification (2000) 65M, 60H15, 65C30, 65M65.Received April 2004. Revised September 2004. Communicated by Anders Szepessy. 相似文献
963.
Energy conservation of numerical integrators is well understood for symplectic one-step methods. This article provides new insight into energy conservation with non-symplectic methods. Sufficient conditions and counter-examples are presented.
AMS subject classification (2000) 65L06, 65P10, 37J99.Submitted June 2004. Accepted October 2004. Communicated by Syvert Nørsett. 相似文献
964.
This paper proposes and analyzes a class of multigrid smoothers called the parallel multiplicative (PM) smoother by subspace decomposition techniques. It shows that the well known additive and multiplicative smoothers and the JSOR smoother are special cases of the PM smoother, and their smoothing properties can be obtained directly from the PM analysis. Moreover, numerical results are presented in this paper to show that the JSOR smoother is more robust and effective than the damped Jacobi smoother on current MIMD parallel computers.
AMS subject classification (2000) 65N55, 65Y05.Received May 2004. Revised September 2004. Communicated by Per Lötstedt.Dexuan Xie: This work was partially supported by the National Science Foundation through grant DMS-0241236. 相似文献
965.
Iterative numerical schemes for solving the electrostatic partial differential equation with variable conductivity, using fast and high-order accurate direct methods for preconditioning, are compared. Two integral method schemes of this type, based on previously suggested splittings of the equation, are proposed, analyzed, and implemented. The schemes are tested for large problems on a square. Particular emphasis is paid to convergence as a function of geometric complexity in the conductivity. Differences in performance of the schemes are predicted and observed in a striking manner.
AMS subject classification (2000) 31A10, 35C15, 65R20.Received May 2004. Accepted September 2004. Communicated by Anders Szepessy.Johan Helsing: This work was supported by the Swedish Science Research Council under contract 621-2001-2799. 相似文献
966.
An asymptotic formula is given for the number of integers x which are discriminants of cyclic fields of odd prime degree.Received: 17 February 2004 相似文献
967.
We introduce the concept of topological finite-determinacy for
germs of analytic functions within a fixed ideal
I, which provides a notion of topological finite-determinacy
of functions with non-isolated singularities. We prove the following statement
which generalizes classical results of Thom and Varchenko: let
A be the complement in the ideal I of the space
of germs whose topological type remains unchanged under a
deformation within the ideal that only modifies sufficiently
large order terms of the Taylor expansion. Then A has infinite
codimension in I in a suitable sense. We also prove the
existence of generic topological types of families of germs of
I parametrized by an irreducible analytic set. 相似文献
968.
We classify the irreducible components of the varieties
\[
\V(n,a,b) = \{ (A,B) \in \M_n(\field) \times \M_n(\field) \mid
AB = BA = A^a = B^b = 0 \}.
\] 相似文献
969.
We reformulate a recent result of Arason and
Elman by giving a very simple presentation of the
powers of the fundamental ideal of the Witt ring of a field
of characteristic 2.
Sur les puissances de lidéal fondamental de lanneau de Witt
Nous reformulons un résultat récent de Arason et Elman en donnant une présentation très simple des puissances de lidéal fondamental de lanneau de Witt dun corps de caractéristique 2.相似文献
970.
We prove that ifX is a Polish space andF a face ofP(X) with the Baire property, thenF is either a meager or a co-meager subset ofP(X). As a consequence we show that for every abelian Polish groupX and every analytic Haar-null set Λ⊆X, the set of test measuresT(Λ) of Λ is either meager or co-meager. We characterize the non-locally-compact groups as the ones for which there exists
a closed Haar-null setF⊆X withT(F) meager, Moreover, we answer negatively a question of J. Mycielski by showing that for every non-locally-compact abelian Polish
group and every σ-compact subgroupG ofX there exists aG-invariantF
σ subset ofX which is neither prevalent nor Haar-null.
Research supported by a grant of EPEAEK program “Pythagoras”. 相似文献