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161.
利用中心投影变换的思想证明一类平面三次拟齐次向量场的几何性质依赖于它的切向量场和诱导向量场.讨论了该系统的拓扑结构,并进行了分类;证明了该系统具有25类不同类的拓扑结构相图. 相似文献
162.
A. A. Novotny J. Sokołowski E. A. de Souza Neto 《Mathematical Methods in the Applied Sciences》2010,33(5):676-686
This paper deals with the sensitivity analysis of the macroscopic elasticity tensor to topological microstructural changes of the underlying material. In particular, the microstucture is topologicaly perturbed by the nucleation of a small circular inclusion. The derivation of the proposed sensitivity relies on the concept of topological derivative, applied within a variational multi‐scale constitutive framework where the macroscopic strain and stress at each point of the macroscopic continuum are defined as volume averages of their microscopic counterparts over a representative volume element (RVE) of material associated with that point. We consider that the RVE can contain a number of voids, inclusions and/or cracks. It is assumed that non‐penetration conditions are imposed at the crack faces, which do not allow the opposite crack faces to penetrate each other. The derived sensitivity leads to a symmetric fourth‐order tensor field over the unperturbed RVE domain, which measures how the macroscopic elasticity parameters estimated within the multi‐scale framework changes when a small circular inclusion is introduced at the micro‐scale level. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
163.
L—Fuzzy拓扑空间中的可数F紧性与几乎可数F紧性 总被引:1,自引:0,他引:1
本文在L-uzzy拓扑空间中引入可数F紧性与几乎可数F紧性的概念,并讨论了它们的性质及其相互关系。 相似文献
164.
Consider a sequenceF
1,F
2,... of i.i.d. random transformations from a countable setV toV. Such a sequence describes a discrete-time stochastic flow onV, in which the position at timen of a particle that started at sitex isM
n(x), whereM
n
=F
n
F
n–1
F
1. We give conditions on the law ofF
1 for the sequence (M
n) to be tight, and describe the possible limiting law. an example called the block charge model is introduced. The results can be formulated as a statement about the convergence in distribution of products of infinite-dimensional random stochastic matrices. In practical terms, they describe the possible equilibria for random motions of systems of particles on a countable set, without births or deaths, where each site may be occupied by any number of particles, and all particles at a particular site move together. 相似文献
165.
我们得到了H-空间闭(开)覆盖性质的几个定理,改进和推广了Sperner,Klee,Alexandroff-Pasynkoff,Berge,Ghouila-Houri,Danzer-Grunbaum-Klee,Ky Fan,shih-Tan,Horvath和Lassonde等人的相应结果。作为应用,我们对l.c.-空间内的下半连续集值映象证明了一个几站不动点定理并且推广吉洪诺夫不动点定理到l.c. 相似文献
166.
Correlation Functions and Boundary Conditions in Rational Conformal Field Theory and Three-Dimensional Topology 总被引:3,自引:0,他引:3
Giovanni Felder Jürg Fröhlich Jürgen Fuchs Christoph Schweigert 《Compositio Mathematica》2002,131(2):189-238
We give a general construction of correlation functions in rational conformal field theory on a possibly nonorientable surface with boundary in terms of three-dimensional topological field theory. The construction applies to any modular category in the sense of Turaev. It is proved that these correlation functions obey modular invariance and factorization rules. Structure constants are calculated and expressed in terms of the data of the modular category. 相似文献
167.
168.
Jiří Adámek Horst Herrlich Jiří Rosický Walter Tholen 《Applied Categorical Structures》2002,10(3):237-249
Weak factorization systems, important in homotopy theory, are related to injective objects in comma-categories. Our main result is that full functors and topological functors form a weak factorization system in the category of small categories, and that this is not cofibrantly generated. We also present a weak factorization system on the category of posets which is not cofibrantly generated. No such weak factorization systems were known until recently. This answers an open problem posed by M. Hovey. 相似文献
169.
Canfield and Williamson gave the first loopless algorithm for generating all linear extensions of a poset. It elegantly generates all signed extensions, resulting in each extension appearing somewhere with each sign, but retains only every other one independent of its sign. It uses an array for the extension. In this paper we give another loopless algorithm for generating all the linear extensions. It generates each extension only once and uses a list for the extensions. 相似文献
170.
M. Petrich 《Acta Mathematica Hungarica》2002,97(4):303-322
The relation in the title is S defined by
on an arbitrary semigroup. We investigate antisymmetry of S by means of a (minimal) family whose members can not appear as subsemigroups. Transitivity of S is characterized similarly by means of the family and homomorphic images of a certain semigroup. We study the transfer of certain properties of a monoid T and the Bruck semigroup B(T,) over T. The paper concludes with a consideration of certain properties of the relation S on inverse semigroups. 相似文献