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1.
危机应对术     
陈缨 《珠算》2009,(4):45-45
回忆去年的情况,用一段比较流行的话来说,基本上眼睛一闭一睁,发现世界变了,箭头的方向变了,指标的颜色变了,公司的形势变了,经营业绩变了。  相似文献   

2.
老歪的礼物     
《数学大王》2009,(7):25-25
放暑假了,庄库欢天喜地地和爸爸妈妈旅游去了,贝卡在Q岛上乐不思蜀,卡卡西被她朋友拉去逛街,正好遂了她的意,柯西探长视休息为无聊。只有老歪,学生不用上课了,看着空荡荡的教室和空荡荡的校园,他突然不知道该干啥了。  相似文献   

3.
阿摹米德(Archimcdes)古希腊数学家、物理学家,生于叙拉古(公元前287~212),他用了毕生精力专研数学,发展了穷竭法,解决了许多复杂的曲线求长问题,及曲面或曲面体的求积问题,他的极微穷竭思想,埘后来微积分的产生奠定了基础,同时他撰写了《抛物线的求积》、《论螺线》、……等五部巨著,故许多人认为,阿基米德是世界...  相似文献   

4.
这个地方原是部队演习基地,去年部队开发了更好的基地以后,将这里交给了地方政府,后来有家公司买得了此地的使用权,将它开发成了一个集度假,拓展训练,探险于一体的野外活动基地。  相似文献   

5.
我校建筑经济设置的计算课程,按照教学大刚要求,珠算技术达标水平由原来的普通六级提高到五普通级,这就为教学工作提出了新的要求,增加了教学难度,为此,经过教学实践摸索,进行了因材施教.分类指导.普遍提高的教学方法的尝试,收到了较好的效果。  相似文献   

6.
猜想是数学发展的不竭动力,就如那哥德巴赫猜想,跨越了千年,而今仍旧无法完全证明,但正是有了“猜想”这个神奇的动力,才让它一点点的被完善,一点点韵进步.数学亦是如此,正因为有了数学猜想才让它更具魅力.数学猜想不但促进了数学的理论的发展,也促进了数学方法的应用和研究以及数学发展的历史,  相似文献   

7.
有幸听到了一节几何概型的公开课,学生配合默契投入,课堂气氛和谐愉快,师生互动风落水上。自然成纹,听课教师如沐春风,耳目一新,更坚定了我们开展探究性学习的信心.这节课通过学生自主学习、主动思考、合作交流、归纳总结,使学生对知识的发生、发展有了切身的感受和清晰的理解,同时也提高了课堂效率,培养了学生的创新能力和实践能力,学生的才智和各种潜能也得到了充分的展示和发挥.  相似文献   

8.
每文 《数学大王》2013,(12):15-17,39
晚上的一场大雨,让酷热的小镇稍微清凉了一些。不过,后半夜雨就停了,太阳照常升起,才8点钟,地面就已被烤干,完全看不出下过雨的痕迹了。福尔摩西刚到办公室,就接到了一起钻石失窃案的报警电话。  相似文献   

9.
2008年湖北高考数学试卷贯彻了《考试大纲》和《补充说明》的考试要求,融入了新课程理念,较好的体现了“平稳中重基础、朴实中显特色”的命题思想.全卷题型布局稳中求变,选择题、填空题坡度适当,解答题难易适中,应用题新旧兼顾,探究能力动态考查,合情推测之中隐含着深刻的数学背景.与2007年相比,笔者认为命题更加成熟、规范,正视了文理科考生的差异,合理的设计了文理科试卷的难度系数,  相似文献   

10.
《珠算》2011,(1):68-69
各位同仁:你们好! 过去十几年,是中国的高速发展时代。中国经济迅速崛起,创造了举世注目的经济奇迹。而大量的中国民营企业,历经多年艰难创业,也铸就了辉煌的事业,制造了无数的财富神话。百度,腾讯,携程,新东方,阿里巴巴这些耳熟能详的创业故事,又鼓舞了无数后来者继续在这个激动人心的时代续写更多辉煌创业篇章。  相似文献   

11.
Brett McElwee 《Order》2001,18(2):137-149
The map which takes an element of an ordered set to its principal ideal is a natural embedding of that ordered set into its powerset, a semilattice. If attention is restricted to all finite intersections of the principal ideals of the original ordered set, then an embedding into a much smaller semilattice is obtained. In this paper the question is answered of when this construction is, in a certain arrow-theoretic sense, minimal. Specifically, a characterisation is given, in terms of ideals and filters, of those ordered sets which admit a so-called minimal embedding into a semilattice. Similarly, a candidate maximal semilattice on an ordered set can be constructed from the principal filters of its elements. A characterisation of those ordered sets that extend to a maximal semilattice is given. Finally, the notion of a free semilattice on an ordered set is given, and it is shown that the candidate maximal semilattice in the embedding-theoretic sense is the free object.  相似文献   

12.
讨论了线性度量空间中凸子集在什么情况下为该空间的收缩核,以及在什么情况下为绝对收缩核。  相似文献   

13.
起源于稀疏矩阵计算和其它应用领域的图G的最小填充问题是在图G中寻求一个内含边数最小的边集F使得G F是弦图.这里最小值|F|称为图G的填充数,表示为f(G).作为NP-困难问题,该问题的降维性质已被研究,其中包括它的可分解性.基本的可分解定理是:如果图G的一个点割集S是一个团,则G经由S是可分解的.作为推广,如果S是一个"近似"团(即只有极少数边丢失的团),则G经由S是可分解的.本文首先给出基本分解定理的另外一个推广:如果S是G的一个极小点割集且G-S含有至少|S|个分支,则G经由S是可分解的;其次,给出了这个新推广定理的一些应用.  相似文献   

14.
孙万贵 《数学学报》2006,49(2):465-468
类似与标型谱算子,U-标算子是否拟仿射相似于自伴算子是一“公开问题”.尽管对具纯离散谱的U-标算子答案是肯定的,但一般情况下并不成立.本文继续探讨这一问题,证明了U-标算子在一强范数拓扑意义下是Hermite算子,或者说U-标算子拟仿射相似于Hermite算子,并给出U-标算子是标型谱算子的充要条件.  相似文献   

15.
This paper concerns continuous subsonic-sonic potential flows in a two-dimensional convergent nozzle. It is shown that for a given nozzle which is a perturbation of a straight one, a given point on its wall where the curvature is zero, and a given inlet which is a perturbation of an arc centered at the vertex, there exists uniquely a continuous subsonic-sonic flow whose velocity vector is along the normal direction at the inlet and the sonic curve, which satisfies the slip conditions on the nozzle walls and whose sonic curve intersects the upper wall at the given point. Furthermore, the sonic curve of this flow is a free boundary, where the flow is singular in the sense that the speed is only C1/2 Hölder continuous and the acceleration blows up. The perturbation problem is solved in the potential plane, where the flow is governed by a free boundary problem of a degenerate elliptic equation with two free boundaries and two nonlocal boundary conditions, and the equation is degenerate at one free boundary.  相似文献   

16.
Mathematical models with stage structures are proposed to describe the process of awareness, evaluation and decision-making. First, a system of ordinary differential equations is presented that incorporates the awareness stage and the decision-making stage. If the adoption rate is bilinear and imitations are dominant, we find a threshold above which innovation diffusion is successful. Further, if the adoption rate has a higher nonlinearity, it is shown that there exist bistable equilibria and a region such that an innovation diffusion is successful inside and is unsuccessful outside. Secondly, a model with a time delay is proposed that includes an evaluation stage of a product. It is proved that the system exhibits stability switches. The bifurcation direction of equilibria is also discussed.  相似文献   

17.
In this paper a methodology for profit maximized bidding under price uncertainty in a day-ahead, multi-unit and pay-as-bid procurement auction for power systems reserve is proposed. Within this novel methodology a bidder is considered to follow a Bayes-strategy. Thereby, one bidder is assumed to behave strategically and the behavior of the remaining is summarized in a probability distribution of the market price and a reaction function to price dumping by the strategic bidder. With this approach two problems arise: First, as a pay-as-bid auction is considered, no uniform price and therefore no single probability distribution of the market price is readily available. Second, if historic bidding data of all participants are used to estimate such a distribution and market power is a relevant factor, the bid of the strategically behaving bidder is likely to influence the distribution. Within this paper for both of the problems solutions are presented. It is shown that by estimating a probability of acceptance the optimal bidding price with respect to a given capacity can be calculated by maximizing a stochastic non-linear objective function of expected profit. Taking the characteristics of recently established markets in Germany into account, the methodology is applied using exemplary data. It is shown that the methodology helps to manage existing price uncertainties and hence supports the trading decisions of a bidder. It is inferred that the developed methodology may also be used for bidding on other auction markets with a similar market design.  相似文献   

18.
This work deals with catastrophe of a spherical cavity and cavitation of a spherical cavity for Hooke material with 1/2 Poisson's ratio. A nonlinear problem, which is the Cauchy traction problem, is solved analytically. The governing equations are written on the deformed region or on the present configuration. And the conditions are described on moving boundary. A closed form solution is found. Furthermore, a bifurcation solution in closed form is given from the trivial homogeneous solution of a solid sphere. The results indicate that there is a tangent bifurcation on the displacement-load curve for a sphere with a cavity. On the tangent bifurcation point, the cavity grows up suddenly, which is a kind of catastrophe. And there is a pitchfork bifurcation on the displacement-load curve for a solid sphere. On the pitchfork bifurcation point, there is a cavitation in the solid sphere.  相似文献   

19.
孔祥智  刘开振 《数学杂志》2011,31(6):1087-1090
本文研究了正则带的结构问题.利用拟强半格分解方法,获得了带为正则带当且仅当它为矩形带的拟强半格,推广了Yamada和Kimura关于正规带是矩形带的强半格的结果.  相似文献   

20.
N-环Von-Neumann正则性   总被引:10,自引:0,他引:10  
环R称为N-环,如果R的素根N(R)={r∈R|存在自然数n使rn=0}.本文不仅对N-环进行了刻划,而且还研究了N-环的VonNeumann正则性.特别证明了:对于N-环R,如下条件是等价的:(1)R是强正则环;(2)R是正则环;(3)R是左SP-环;(4)R是右SF-环;(5)R是MELT,左p-V-环;(6)R是MERT,右p-V-环.因此推广了文献[4]中几乎所有的重要结果,同时也改进或推广了其它某些有关正则环的有用结果.  相似文献   

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