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一、专题的背景与分析
1. 背景
闵行区的沪闵路─春申路口是交通特别拥挤的交叉路口之一.家住莘庄地区的同学有一个共同的感受,在他们到校或回家路上必经的沪闵路─春申路口时常遇到塞车现象.…… 相似文献
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"牛吃草"问题又称为消长问题,是17世纪英国伟大的科学家牛顿提出来的.典型牛吃草问题的条件是假设草的生长速度固定不变,不同头数的牛吃光同一片草地所需的天数各不相同,求若干头牛吃这片草地可以吃多少天.由于吃的天数不同,草又是天天在生长的,所以草的存量随吃的天数不断地变化.…… 相似文献
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导数作为大学的重要内容,进入中学数学教材后,给传统的内容注入了生机与活力,为中学数学命题的研究提供了新视角,新方法.由于导数是研究函数性质的一个很好的工具,它的用途十分广泛,它在解决函数、不等式、解析几何等问题有独到的功能.因此,近几年的高考正逐年加大对导数问题的考查力度,本文通过对07年全国各地高考题的整理和分析寻找命题规律,希望能对今后的教学提供一点复习思路.…… 相似文献
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2010-2011学年度武汉市部分学校新高三起点调研测试的一道试题引起了我的注意.原题如下:
在正四面体P-ABC中,M为△ABC内(含边界)一动点,且点M到三个侧面PAB,PBC,PCA的距离成等差数列,则点M的轨迹是
A.一条线段 B.椭圆的一部分
C.双曲线的一部分 D.抛物线的一部分 相似文献
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利用极值理论来考虑上证综指收益率的尾部.为了选择合理的超越门限,采用平均剩余函数和De-Haan矩估计相结合的方法.在学生t分布和广义误差分布的新患假设下,用GARCH和EGARCH新息的ARMA模型拟合指数收益率,并且使用极值理论的极大似然方法估计模型残差的尾指,估计结果表明收益率的尾指和模型的残差尾指基本一致. 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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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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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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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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The purpose of this short paper is to give a structure theorem for certain Gorenstein ideals. 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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论假设检验中的两类错误 总被引:9,自引:1,他引:8
蔡越江.论假设检验中的两类错误.本文从假设检验的两个例子谈起,指出备择假设也是影响接区域的。接着论述了假设检验中的两类错误之间的关系。最后讨论如何同时控制两类错误。 相似文献