共查询到19条相似文献,搜索用时 78 毫秒
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Topos理论简介 总被引:1,自引:0,他引:1
Topos概念的提出(即elementary topos的公理化)是在研究了如下几类范畴之后:Grothendieck topos,集合的范畴S,以及集合论的布尔值模型。 Grothendieck提出用拓扑空间X上的set valued sheaf的全体做成的范畴Sh(X)作为推广了的拓补空间X,用以研究空间X上的上同调.他把拓扑的概念推广到小范畴(smallcategory)C上,称为一个site(或称为Grothendieck拓扑,参看第2节)。这样就可以考虑给出的site(C,J)上的set valued sheaf的全体做成的范畴Sh(C,J),用它来研究site(C,J) 相似文献
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本文研究了卡氏积码的r-广义Hamming重量计算公式和广义Singleton界,利用r-卡氏积码的子码仍为卡氏积码,证明了r-MDR码或Pr-MDR码的卡氏积码仍为r-MDR码或Pr-MDR码.同时也给出了这一个结果的部分逆命题. 相似文献
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介绍了涉及集合笛卡儿积(Cartesian product)的运算性质讨论的一种类似于文氏图(Venn diagram)的方法. 相似文献
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沈荣鑫 《高校应用数学学报(A辑)》2010,25(2)
讨论了拟第一可数空间和弱拟第一可数空间的遗传性和可积性,给出了一些反例来说明这两类空间在某些拓扑运算下的不封闭性,同时研究了它们具有遗传性和可积性的充要条件. 相似文献
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G是顶点集为{v_1,v_2,…,v_n}的连通简单图,G_1,G_2,…,G_n是有限图。联并图G[G_1,G_2,…,G_n】是按如下方式在G_1UG_2U…UG_n上加边而成的图:在G_i和G_j之间的任何两个顶点间加边,若v_i和v_j在G中相邻.[7]给出了两个距离正则图的卡氏积的距离谱.本文计算了联并图和距离正则图的卡氏积及两个联并图的卡氏积的距离谱.在此基础之上,我们得到了两个利用联并图与非同谱距离正则等能量图作卡氏积及联并图作卡氏积构造非同谱等距离能量图族的方法. 相似文献
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三对角逆M矩阵的判定 总被引:5,自引:0,他引:5
1、引言 三对角逆M矩阵是指同时为三对角矩阵和逆M矩阵的一类特殊矩阵.文用图论方法探讨三对角逆M矩阵结构,给出了三对角矩阵为逆M矩阵的充分必要条件.此条件提供了判定三对角矩阵是逆M矩阵的方法,但较复杂.文讨论了这类矩阵在Hadamard积下的封闭性.由于三对角逆M矩阵在理论和应用上都有一定价值,所以,寻求一种简单而实用的判定方法是必要的.本文通过对这类矩阵结构特点的研究找到了这样一种方法.同时,由此证明了这类矩阵在Hadamard积下的封闭性. 相似文献
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本我们引进了无穷维Banach空间中的一种新的集合序列收敛性概念,讨论了它与其它收敛性概念的关系。另外,我们还研究了集合序列根限的Minkowski和。 相似文献
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J. Richter-Gebert 《Discrete and Computational Geometry》2000,24(2-3):503-518
We prove that it is NP-hard to decide whether a polyhedral 3-ball can be triangulated with k simplices. The construction also implies that it is difficult to find the minimal triangulation of such a 3-ball. A lifting
argument is used to transfer the result also to triangulations of boundaries of 4-polytopes.
The proof is constructive and translates a variant of the 3-SAT problem into an instance of a concrete polyhedral 3-ball
for which it is difficult to find a minimal triangulation.
Received February 17, 1999, and in revised form October 20, 1999. Online publication May 16, 2000. 相似文献
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A sphere of dimension 4n+3 admits three Sasakian structures and it is natural to ask if a submanifold can be an integral submanifold for more than one of the contact structures. In the 7-sphere it is possible to have curves which are Legendre curves for all three contact structures and there are 2 and 3-dimensional submanifolds which are integral submanifolds of two of the contact structures. One of the results here is that if a 3-dimensional submanifold is an integral submanifold of one of the Sasakian structures and invariant with respect to another, it is an integral submanifold of the remaining structure and is a principal circle bundle over a holmophic Legendre curve in complex projective 3-space. 相似文献
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Aart Blokhuis Andries E. Brouwer Willem H. Haemers 《Designs, Codes and Cryptography》2007,44(1-3):293-305
We give some necessary conditions for a graph to be 3-chromatic in terms of the spectrum of the adjacency matrix. For all known distance-regular graphs it is determined whether they are 3-chromatic. A start is made with the classification of 3-chromatic distance-regular graphs, and it is shown that such graphs, if not complete 3-partite, must have λ ≤ 1. 相似文献
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将血浆中[HCO3-]作为自变量、△PaCO2/△[HCO3-]作为因变量,对酸碱平衡紊乱中肺的缓冲作用进行了量化处理并初步建立了数学模型.利用两者间的函数关系,看到:代谢性酸中毒时,随着血浆中[HCO3-]值越来越小,△PaCO2/△[HCO3-]的变化率也越来越小;代谢性碱中毒时,随着血浆中[HCO3-]值越来越大,△PaCO2/△[HCO3-]的变化率越来越小.这一结果完全符合生物学规律.提示这一数学模型对研究酸碱平衡紊乱时,肺代偿调节机制、代偿强度等情况有一定的意义. 相似文献
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O. M. Davydov 《Acta Appl Math》2003,75(1-3):51-54
Complexity is a function which maps a set of 3-manifolds to a set of nonnegative integers. This function has some natural properties (finiteness, additivity, etc.) and it shows, in some sense how complex the manifold is. This function seems important for the classification of 3-manifolds. We evaluate of the complexity of 2-fold branched coverings of a 3-sphere. We present a theoretical estimate and compare it with experimental data. 相似文献
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We show that a 3-edge-connected graph embedded in a surface of Euler characteristic χ has at most 3 – 3χ singular edges, except in the projective plane, where it has at most one singular edge, and the sphere, where it has none. This bound is best possible for all surfaces. 相似文献
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A GENERAL PROPERTY OF THE QUADRATIC DIFFERENTIAL SYSTEMS 总被引:1,自引:0,他引:1
Zhu Deming 《数学年刊B辑(英文版)》1989,10(1):26-32
In this paper, it is proved that the quadratic differential systems with a weak saddle of order 2 or 3 have no closed or singular closed orbit. Then by the results of [3], it follows that the greatest order of the homoclinic loop bifurcation of a quadratic differential system is between 2 and 3 It means a homoclinic loop can be split into at most three limit cycles. 相似文献
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本文证明了3-连通非偶图的色多项式根2的阶为1;满足一定条件的非3-连通非偶图的色多项式根2的阶是图的非偶块和非偶可分块数.从而,把色多项式P(G)中1的阶是图G的非平凡块数这一结果进一步加以推广. 相似文献