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杨庆贵是幸运的,2006年4月,他加入了北京三元食品股份有限公司.任财务总监,当年就在三元全体职工共同努力下,实现扭亏为盈,上交所批准三元股份摘掉“*”,股价从2005年7月的最低价1.80元上升到2007年5月的11.39元;2008年,公司经上交所批准, 相似文献
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2009年年初,已经在海尔工作了10年的刘明(化名)决定离开,这本应是个艰难的选择.但他却很痛快,“这10年基本是不计投人的工作,最后发现生活里只剩下工作了,而且发现自己只能待在海尔这个平台上,很难适应其他的环境。”大学毕业就去了海尔的刘明,那时候有的更多是激情,对海尔的很多东西从心里面很认可,在海尔工作的这10年,几乎是没有节假日的,每年也就春节可以回家待上三五天,10年之后的刘明已经是海尔的一个中层骨干, 相似文献
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我是1952年到太原市财政局工作.一直到1995年退休,后又在会计师事务所工作六年多,有50多年的财会工龄,始终与算盘打交道,对算盘是情有独钟。特别是1981年8月,我直接参与了市财政学会、会计学会、 相似文献
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为了对全国平均每百户居民私家车拥有量进行预测,建立了可分离变量微分方程的数学模型,采用最小二乘法,借助Excel作为计算工具,得到了微分方程近似解的参数值,并用微分方程的近似解估计了最大拥有量以及2010年以后某些年的拥有量. 相似文献
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Jolanta Słomińska 《Central European Journal of Mathematics》2003,1(3):327-331
In this note we show that the main results of the paper [PR] can be obtained as consequences of more general results concerning
categories whose morphisms can be uniquely presented as compositions of morphisms of their two subcategories with the same
objects. First we will prove these general results and then we will apply it to the case of finite noncommutative sets. 相似文献
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Given a bounded set A, a Chebyshev center (when it exists) is–in some sense–a candidate to give a global information on the
set. Finding the centers of A is of great importance for applications. In many cases, it is very important to understand how
they change when the set A is perturbed. Our main result is a new characterization of Hilbert spaces: in fact, we will show
that the best estimate we can give in these spaces, concerning perturbations of sets, cannot be expected outside this class
of spaces. Moreover, we collect, we partly sharpen and we reprove in a simple way most known results. 相似文献
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广义反射函数的性态与应用 总被引:1,自引:0,他引:1
孙长军 《数学的实践与认识》2010,40(10)
推广了Mironenko的反射函数的概念,给出了广义反射函数的概念并讨论了广义反射函数的性质,应用它研究了微分系统周期解的存在性和稳定性态.作为应用举例,研究了Riccati方程的反射函数. 相似文献
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首先分析了粗糙集理论中现在常用的属性依赖性度量中的不合理性,然后结合概率统计中的卡方分布的思想,给出一种新的属性依赖性度量,根据这种依赖性度量,给出属性重要性的定义,最后详细讨论了它们的性质. 相似文献
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讨论由软件和硬件构成的串联可修计算机系统的时间依赖解,运用C_0-半群理论及算子理论,证明系统的适定性和时间依赖非负解的存在唯一性.通过研究系统相应算子的谱特征,得到系统时间依赖解的渐近稳定性. 相似文献
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钢管订购与运输问题三的数学模型与灵敏度分析 总被引:1,自引:1,他引:0
本文针对 2 0 0 0年全国大学生数学建模竞赛 B题——钢管订购与运输问题的问题 ( 3) ,建立了数学模型 ,给出了该数学模型的精确求解 .然后对问题 ( 1 )与问题 ( 3)给出了灵敏度分析 . 相似文献
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钢管订购与运输问题一的数学模型与求解 总被引:1,自引:0,他引:1
本文针对 2 0 0 0年全国大学生数学建模竞赛 B题—钢管订购与运输问题的问题 ,建立了数学模型 ,并给出了该数学模型的精确求解 相似文献
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In this paper we look at the security of two block ciphers which were both claimed in the published literature to be secure against differential crypt-analysis (DC). However, a more careful examination shows that none of these ciphers is very secure against... differential cryptanalysis, in particular if we consider attacks with sets of differentials. For both these ciphers we report new perfectly periodic (iterative) aggregated differential attacks which propagate with quite high probabilities. The first cipher we look at is GOST, a well-known Russian government encryption standard. The second cipher we look at is PP-1, a very recent Polish block cipher. Both ciphers were designed to withstand linear and differential cryptanalysis. Unhappily, both ciphers are shown to be much weaker than expected against advanced differential attacks. For GOST, we report better and stronger sets of differentials than the best currently known attacks presented at SAC 2000 [32] and propose the first attack ever able to distinguish 16 rounds of GOST from random permutation. For PP-1 we show that in spite of the fact, that its S-box has an optimal theoretical security level against differential cryptanalysis [17], [29], our differentials are strong enough to allow to break all the known versions of the PP-1 cipher. 相似文献
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We consider envelopes of one-parameter families of frontals in hyperbolic and de Sitter 2-space from the viewpoint of duality, respectively. Since the classical notions of envelopes for singular curves do not work, we have to find a new method to define the envelope for singular curves in hyperbolic space or de Sitter space. To do that, we first introduce notions of one-parameter families of Legendrian curves by using the Legendrian dualities. Afterwards, we give definitions of envelopes for the one-parameter families of frontals in hyperbolic and de Sitter 2-space, respectively. We investigate properties of the envelopes. At last, we give relationships among those envelopes. 相似文献