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231.
In this paper we derive a priori and a posteriori error estimates for cell centered finite volume approximations of nonlinear conservation laws on polygonal bounded domains. Numerical experiments show the applicability of the a posteriori result for the derivation of local adaptive solution strategies.
232.
Onofrio Mario Di Vincenzo Plamen Koshlukov Roberto La Scala 《Advances in Applied Mathematics》2006,37(4):541
In this paper we describe completely the involutions of the first kind of the algebra UTn(F) of n×n upper triangular matrices. Every such involution can be extended uniquely to an involution on the full matrix algebra. We describe the equivalence classes of involutions on the upper triangular matrices. There are two distinct classes for UTn(F) when n is even and a single class in the odd case.Furthermore we consider the algebra UT2(F) of the 2×2 upper triangular matrices over an infinite field F of characteristic different from 2. For every involution *, we describe the *-polynomial identities for this algebra. We exhibit bases of the corresponding ideals of identities with involution, and compute the Hilbert (or Poincaré) series and the codimension sequences of the respective relatively free algebras.Then we consider the *-polynomial identities for the algebra UT3(F) over a field of characteristic zero. We describe a finite generating set of the ideal of *-identities for this algebra. These generators are quite a few, and their degrees are relatively large. It seems to us that the problem of describing the *-identities for the algebra UTn(F) of the n×n upper triangular matrices may be much more complicated than in the case of ordinary polynomial identities. 相似文献
233.
Mario Lamberger Florian Mendel Vincent Rijmen Koen Simoens 《Designs, Codes and Cryptography》2012,62(1):1-18
We investigate generic methods to find near-collisions in cryptographic hash functions. We introduce a new generic approach based on methods to find cycles in the space of codewords of a code with low covering radius. We give an analysis of our approach and demonstrate it on the SHA-3 candidate TIB3. 相似文献
234.
235.
Mario Petrich 《Semigroup Forum》2005,71(3):366-388
On any regular semigroup S, the greatest idempotent pure congruence
τ the greatest idempotent separating congruence μ and the least
band congruence β are used to give the S-classification of regular semigroups as follows. These congruences generate a sublattice
Λ of the congruence lattice C(S) of S. We consider the triples (Λ,K,T), where K and T are the restrictions of the K- and T-relations
on C(S) to Λ. Such triples are characterized abstractly and form the objects of a category S whose morphisms are surjective K- and T-preserving homomorphisms subject to a mild condition. The class of regular semigroups
is made into a category S whose morphisms are fairly restricted homomorphisms. The main result of the paper is the existence of a representative functor
from S to S. The effect of the S-classification on Reilly semigroups and cryptogroups is discussed briefly. 相似文献
236.
Mario Petrich 《Semigroup Forum》2005,71(3):337-365
On any regular semigroup S, the least group congruence σ, the greatest idempotent separating congruence μ and the least band
congruence β are used to give the T-classification of regular semigroups as follows. These congruences generate a sublattice
Λ of the congruence lattice C(S) of S. We consider the triples (Λ,K,T), where K and T are the restrictions of the K- and T-relations
on C(S) to Λ. Such triples are characterized abstractly and form the objects of a category T whose morphisms are surjective K-preserving homomorphisms subject to a mild condition. The class of regular semigroups is
made into a category T whose morphisms are fairly restricted homomorphisms. The main result of the paper is the existence of a representative functor
from T to T. The effect of the T-classification to P-semigroups is considered in some detail. 相似文献
237.
Let M be a complete, connected, two-dimensional Riemannian manifold. Consider the following question: Given any (p1,v1) and (p2, v2) in T M, is it possible to connect p1 to P2 by a curve y in M with arbitrary small geodesic curvature such that, for i = 1, 2, y is equal to vi at pi? In this article, we bring a positive answer to the question if M verifies one of the following three conditions: (a) M is compact, (b) M is asymptotically flat, and (c) M has bounded nonnegative curvature outside a compact subset. 相似文献
238.
Suppose A,B and C are the bounded linear operators on a Hilbert space H, when A has a generalized inverse A- such that (AA-)*=AA- and B has a generalized inverse B- such that (B-B)*=B-B,the general characteristic forms for the critical points of the map Fp:X→‖AXB-C‖pp(1
p=2. Similarly, the same question has been discussed for several operators. 相似文献
239.
IntroductionTheproblemswithlargegradientarecommoninpracticalengineeringfields,e.g.inmateriallocalization,withinthelocalizatio... 相似文献
240.
张福保 《应用数学和力学(英文版)》2000,21(3):363-370
IntroductionConsiderthefollowingperiodicboundaryvalueproblem(PBVP,forshort)forfirst_orderintegro_differentialequationofmixedtypeu′=f(t,u,T1u,T2u) (a.e.t∈I),(1)u(0)=u(2π),(2)whereI=[0,2π],fsatisfiesCaratheodory’sconditions,T1isaVolterraintegraloperator,T2isaFredholminte… 相似文献