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1.
《数学大王》2014,(11):26-27
1.从前,在大海里生活着一条快乐的美人鱼,她每天悠闲地在海里游弋,从来没有烦心事儿,每天脸上都挂着微笑。她很美丽,大海里的每一个居民都喜欢她,他们叫她人鱼公主。2.有一天,海的北边王国有位王子出海航行,却遇上了大风浪。船被风浪掀翻,王子也落人了大海中。人鱼公主恰好经过,救了溺水的王子。王子非常英俊,美人鱼对他一见钟情。  相似文献   

2.
王海 《珠算》2011,(4):26-27
摄影记者们几乎无法扑捉到震后日本人的悲痛神情,他们脸上更多呈现出平静,地震与海啸过后的人们,在核辐射的阴影下仍能保持秩序与镇定,这是一种什么力量,有人将此归结为他们隐忍的气质,这样的灾后表现,让很多人对日本经济仍未完全丧失信心,尽管此前的20年,它的表现并不尽人意。 在海外资本回流参与灾后重建的背景下,日元升值在所难免;与此同时,也可能拉高美元的利率,毕竟日本仍是美债的重要力量。  相似文献   

3.
疯狂的黄金     
姚国会 《珠算》2011,(9):42-44
原本应当“休养生息”的黄金,在这个夏天异常活跃,以屡创历史新高的态势,挑战着市场的心理极限。根据世纪金行提供的数据,2011年7月以来,金价始终保持着单边飙涨的行情,29个交易日已经上涨近335美元。而在8月第一周的短短4个交易日内,金价就完成了120美元的飞跃,并以势如破竹的速度一举突破1800美元大关。这是自2008年11月以来连续上涨幅度最大的一次。  相似文献   

4.
旋转的车轮     
同学们,你们知道吗?自行车上也有数学问题。如果你仔细观察的话,一定会发现自行车总是由踏脚带动大齿轮通过链条传到小齿轮,然后带动后轮转动的。一般大齿轮转一圈,小齿轮要转好几圈呢。想要骑得快,就得将小齿轮齿数变少,骑得慢,就将小齿轮齿数变多,不过也不能相差太多,那样的话骑车的时候就会感到非常吃力!  相似文献   

5.
罗长生 《中学生数学》2011,(8):35-36,37
长方体是一个很基本的多面体,所含的线线,线面,面面的位置关系的内容十分丰富,数学中的有些问题,如果用常规法去求,将难以求出或十分繁琐,甚感“山穷水复疑无路”,但如果能构造长方体去求,将会把问题化难为易,化繁为简,从而“柳暗花明又一村”了。  相似文献   

6.
失踪的古画     
佚名 《数学大王》2010,(9):11-12
李老收藏着一幅价值连城的古画。他逢人就夸此画,作为炫耀的资本。 一天,有三位古董商来访,李老把三人迎入珍藏室,只见古玩陈列架上端端正正地放着一只檀木珍宝箱,健谈的主人边介绍,边打开箱子,那幅古画使来客们赞不绝口。随后,主人合上珍宝箱,  相似文献   

7.
郭兰峰 《珠算》2009,(4):40-41
2008年以来美国次贷危机不断蔓延,引发了上世纪大萧条以来最严重的金融危机,特别是去年三季度以后,金融危机愈演愈烈,其影响已从局部发展到全球,从发达国家传导到发展中国家,从金融领域覆盖到实体经济。这场金融危机覆盖之广、影响之深,长度之大,超乎人们的预料,世界主要经济体出现多年没有过的重度经济衰退。  相似文献   

8.
沈剑 《珠算》2009,(6):46-51
继2008年6月1日《内控双刃剑》的封面报道之后,一年后的今天,本刊再次将目光聚焦内控,只是与上次不同的是,大环境已然变化。 一是,中国版“萨班斯法案”延期,主因在于金融危机下内控给企业带来的客观成本。二是,内部控制与风险管理事实上正在融合,曾经“厘不清”的内控的价值正在凸显。  相似文献   

9.
魏洋的哲学     
张铭 《珠算》2009,(4):84-85
修道与处世就如庖丁解牛,虽然处于很复杂的世间,但要“批大卻,导大窾”,处理大关键,把握大要点,始终保持着自己的头脑,保持着自己的初心,那么,就可以永远使生命健康,永远使生命青春。——南怀瑾  相似文献   

10.
沈文选 《中学生数学》2010,(6):F0003-F0003,48
设H为锐角△ABC的垂心,以H为圆心的任一圆,分别交与BC,AC,BA平行的中位线依次于P1,Q1,P2,Q2,P3,Q3,则 AP1=BP2=CP3=AQ1=BQ2=CQ3。  相似文献   

11.
12.
Results of single transverse compression testing of PPTA and PIPD fibers, using a novel test device, are presented and discussed. In the tests, short lengths of single fibers are compressed between two parallel, stiff platens. The fiber elastic deformation is analyzed as a Hertzian contact problem. The inelastic deformation is analyzed by elastic-plastic FE simulation and by laser-scanning confocal microscopy of the compressed fibers ex post facto. The results obtained are compared to those in the literature and to the theoretical predictions of PPTA fiber transverse elasticity based on PPTA crystal elasticity.Presented at the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000).3TEX, Inc. 109, MacKenan Drive, Cary, North Carolina 27511, USA. Published in Mekhanika Kompozitnykh Materialov, Vol. 36, No. 4, pp. 533–544, March–April, 2000.  相似文献   

13.
In typical stochastic simulations, randomness is produced by generating a sequence of independent uniform variates (usually real-valued between 0 and 1, or integer-valued in some interval) and transforming them in an appropriate way. In this paper, we examine practical ways of generating (deterministic approximations to) such uniform variates on a computer. We compare them in terms of ease of implementation, efficiency, theoretical support, and statistical robustness. We look in particular at several classes of generators, such as linear congruential, multiple recursive, digital multistep, Tausworthe, lagged-Fibonacci, generalized feedback shift register, matrix, linear congruential over fields of formal series, and combined generators, and show how all of them can be analyzed in terms of their lattice structure. We also mention other classes of generators, like non-linear generators, discuss other kinds of theoretical and empirical statistical tests, and give a bibliographic survey of recent papers on the subject.  相似文献   

14.
How much information does a small number of moments carry about the unknown distribution function? Is it possible to explicitly obtain from these moments some useful information, e.g., about the support, the modality, the general shape, or the tails of a distribution, without going into a detailed numerical solution of the moment problem? In this, previous and subsequent papers, clear and easy to implement answers will be given to some questions of this type. First, the question of how to distinguish between the main-mass interval and the tail regions, in the case we know only a number of moments of the target distribution function, will be addressed. The answer to this question is based on a version of the Chebyshev–Stieltjes–Markov inequality, which provides us with upper and lower, moment-based, bounds for the target distribution. Then, exploiting existing asymptotic results in the main-mass region, an explicit, moment-based approximation of the target probability density function is provided. Although the latter cannot be considered, in general, as a satisfactory solution, it can always serve as an initial approximation in any iterative scheme for the numerical solution of the moment problem. Numerical results illustrating all the theoretical statements are also presented.  相似文献   

15.
The influence of displacements of tensioned fibers on the impregnation of fibrous layers with a polymer melt and on the final composite structure is studied. Using computer simulation, it is shown that, during impregnation, the structure of tensioned fibrous layers changes considerably depending on the initial arrangement and tensioning of fibers. The consolidated regions formed under the melt front move inside the impregnated layer with the advancing melt front. Displacement of the tensioned fibers as well as the formation of “washouts” favors the impregnation of internal layers, but cause significant inhomogeneity of the polymer structure. The surface (on the side of the melt flow) regions are more saturated with the polymer than the internal ones. A difference in the melt percolation mechanisms at various impregnation regimes is revealed. The effective permeability coefficients of a tensioned fiber layer are not constant but depend on the conditions and regimes of impregnation. Submitted to the 11th Conference on the Mechanics of Composite Materials (Riga, June 11–15, 2000). Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 2, pp. 259–270, March–April, 2000.  相似文献   

16.
Varieties of associative algebras over a field of characteristic zero are considered. Belov recently proved that, in any variety of this kind, the Hilbert series of a relatively free algebra of finite rank is rational. At the same time, for three important varieties, namely, those of algebras with zero multiplication, of commutative algebras, and of all associative algebras, a stronger assertion holds: for these varieties, formulas that rationally express the Hilbert series of the free product algebra via the Hilbert series of the factors are well known. In the paper, a system of counterexamples is presented which shows that there is no formula of this kind in any other variety, even in the case of two factors one of which is a free algebra. However, if we restrict ourselves to the class of graded PI-algebras generated by their components of degree one, then there exist infinitely many varieties for each of which a similar formula is valid. Translated fromMatematicheskie Zametki, Vol. 65, No. 5, pp. 693–702, May, 1999.  相似文献   

17.
Biological adaptation assumes the evolution of structures toward better functions. Yet, the roots of adaptive trajectories usually entail subverted—perverted—structures, derived from a different function: what Gould and Vrba called “exaptation.” Generally, this derivation is regarded as contingent or serendipitous, but it also may have regularities, if not rules, in both biological evolution and technological innovation. On the basis of biological examples and examples from the history of technology, the authors demonstrate the centrality of exaptation for a modern understanding of niche, selection, and environment. In some cases, biological understanding illuminates technical exaptation. Thus, the driver of exaptation is not simply chance matching of function and form; it depends on particular, permissive contexts. © 2013 Wiley Periodicals, Inc. Complexity 18: 7–14, 2013  相似文献   

18.
A generalization of both the hierarchical product and the Cartesian product of graphs is introduced and some of its properties are studied. We call it the generalized hierarchical product. In fact, the obtained graphs turn out to be subgraphs of the Cartesian product of the corresponding factors. Thus, some well-known properties of this product, such as a good connectivity, reduced mean distance, radius and diameter, simple routing algorithms and some optimal communication protocols, are inherited by the generalized hierarchical product. Besides some of these properties, in this paper we study the spectrum, the existence of Hamiltonian cycles, the chromatic number and index, and the connectivity of the generalized hierarchical product.  相似文献   

19.
20.
Using the predicate language for ordered fields a class of problems referred to aslinear problems is defined. This class contains, for example, all systems of linear equations and inequalities, all linear programming problems, all integer programming problems with bounded variables, all linear complementarity problems, the testing of whether sets that are defined by linear inequalities are semilattices, all satisfiability problems in sentenial logic, the rank-computation of matrices, the computation of row-reduced echelon forms of matrices, and all quadratic programming problems with bounded variables. A single, one, algorithm, to which we refer as theUniversal Linear Machine, is described. It solves any instance of any linear problem. The Universal Linear Machine runs in two phases. Given a linear problem, in the first phase a Compiler running on a Turing Machine generates alinear algorithm for the problem. Then, given an instance of the linear problem, in the second phase the linear algorithm solves the particular instance of the linear problem. The linear algorithm is finite, deterministic, loopless and executes only the five ordered field operations — additions, multiplications, subtractions, divisions and comparisons. Conversely, we show that for each linear algorithm there is a linear problem which the linear algorithm solves uniquely. Finally, it is shown that with a linear algorithm for a linear problem, one can solve certain parametric instances of the linear problem.Research was supported in part by the National Science Foundation Grant DMS 92-07409, by the Department of Energy Grant DE-FG03-87-ER-25028, by the United States—Israel Binational Science Foundation Grant 90-00434 and by ONR Grant N00014-92-J1142.Corresponding author.  相似文献   

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