共查询到20条相似文献,搜索用时 53 毫秒
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本文主要讨论组合地图列举问题.刘的一部专著中提出了一个判定两个地图是否同构的算法.该算法的时间复杂度为O(m2),其中m为下图的规模.在此基础上,本文给出一个用于地图列举以及进而计算任意连通下图的地图亏格分布的通用算法.本文所得结果比之前文献中所给结果更优. 相似文献
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在新课程理论指导下,我们的课堂教学打破了传统教学中老师主宰一切的局面,形成了可变的师生多向互动的关系,形成了开放的课堂教学.在这个过程中,会促使课堂数学中多向、多种类型信息得到交流,学生的个性得到充分的发展,学生的认知、情感等得到有效的发展.…… 相似文献
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三角板、直尺、量角器是学生们熟悉的文具用品,以它们为"道具",以学生常见、熟悉的几何图形为载体,并辅之以平移、旋转、叠放、拼摆等变换手段的问题,能为学生提供动手实践操作设计的空间,较好地考查了学生观察、操作、想象、猜想、类比、联想、类比、归纳、推断、明理的能力以及运动变化、分类讨论思想等的综合运用能力.这类操作性的题目格调清新,立意新颖,充分体现了课标中提出的"培养学生动手动脑、实践探索的能力"的要求,既注重基础知识,同时又具有很强的综合性,因此受到了各地中考命题专家的眷顾.本文以2010年的中考试题中为例,进行分类评析,供大家参考. 相似文献
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本文提出一种估计与调控飞行员宏观数量的方法.文章给出了当航空兵的兵力规模保持稳定、只考虑飞行员年龄分布的情况下,战斗部队飞行员和航校教员总数量与每年的补充量、淘汰率、服役年限之间的函数关系;给出了当航空兵的兵力规模需要变更时,尽快达到变更目标的数学规划模型,模型考虑了每年的补充量、淘汰率、服役年限以及航校学制、规模和效率之间的关系. 相似文献
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一道以群的定义为背景的高考试题赏析 总被引:2,自引:0,他引:2
每一年的高考数学试卷中都有一些以高等数学背景立意的好题目,如2006年四川卷理科第16题,是一道以近世代数中群的定义为背景立意的填空题,这样的试题能够有效考查学生的学习能力、思维能力和数学创新意识,这为高校选拔学习潜质好的学生创造了条件.…… 相似文献
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极限点型 Sturm-Liouville 算子乘积的自伴性 总被引:1,自引:0,他引:1
假设微分算式l(y)=-(py') qy,t∈[a,∞),满足lk(y)(k=1,2,3)均为极限点型,作者研究了由l(y)生成的两个微分算子Li(i=1,2)的乘积L2L1的自伴性问题并获得其自伴的充分必要条件.同时研究了由l(y)=-y" qy,t∈[a,∞),生成的三个微分算子Li(i=1,2,3)的乘积L3L2L1的自伴性问题. 相似文献
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The structure of groups having the same elementary theory as free groups is now known: they and their finitely generated subgroups
form a prescribed subclass
of the hyperbolic limit groups. We prove that if G
1,...,G
n
are in
then a subgroup Γ ⊂ G
1 × … × G
n
is of type FP
n
if and only if Γ is itself, up to finite index, the direct product of at most n groups from
. This provides a partial answer to a question of Sela.
This work was supported in part by Franco–British Alliance project PN 05.004. The first author is also supported by an EPSRC
Senior Fellowship and a Royal Society Wolfson Research Merit Award.
Received: July 2005 Accepted: April 2006 相似文献
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A set S of integers is called a cycle set on {1, 2, . . .,n} if there exists a graph G on n vertices such that the set of lengths of cycles in G is S. Erds conjectured that the number of cycle sets on {1, 2, . . .,n} is o(2
n
). In this paper, we verify this conjecture by proving that there exists an absolute constant c 0.1 such that the number of cycle sets on {1, 2, . . .,n} is
. 相似文献
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The purpose of this short paper is to give a structure theorem for certain Gorenstein ideals. 相似文献
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Eric Jaligot 《Combinatorica》2007,27(1):129-133
Any countably infinite tournament T0 embeds as a moiety of the random tournament T in such a way that its setwise stabilizer in Aut(T) is isomorphic to Aut(T0). 相似文献
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Let Ratk(CPn) denote the space of based holomorphic maps ofdegree k from the Riemannian sphere S2 to the complex projectivespace CPn. The basepoint condition we assume is that f()=[1,..., 1]. Such holomorphic maps are given by rational functions: Ratk(CPn) ={(p0(z), ..., pn(z)):each pi(z) is a monic, degree-kpolynomial and such that there are no roots common to all pi(z)}.(1.1) The study of the topology of Ratk(CPn) originated in [10]. Later,the stable homotopy type of Ratk(CPn) was described in [3] interms of configuration spaces and Artin's braid groups. LetW(S2n) denote the homotopy theoretic fibre of the Freudenthalsuspension E:S2n S2n+1. Then we have the following sequenceof fibrations: 2S2n+1 W(S2n)S2n S2n+1. A theorem in [10] tellsus that the inclusion Ratk(CPn) 2kCPn 2S2n+1 is a homotopy equivalenceup to dimension k(2n1). Thus if we form the direct limitRat(CPn)= limk Ratk(CPn), we have, in particular, that Rat(CPn)is homotopy equivalent to 2S2n+1. If we take the results of [3] and [10] into account, we naturallyencounter the following problem: how to construct spaces Xk(CPn),which are natural generalizations of Ratk(CPn), so that X(CPn)approximates W(S2n). Moreover, we study the stable homotopytype of Xk(CPn). The purpose of this paper is to give an answer to this problem.The results are stated after the following definition. 1991Mathematics Subject Classification 55P35. 相似文献
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