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1.
在魔术中有一类扑克牌的魔术,当我们看到魔术师经过眼花缭乱的洗牌、抽牌、翻牌的动作之后,在他的手上出现了所想要的牌,不少人叹为观止.在惊奇之余,人们会想魔术师是怎么做到的?是魔术师的超常记忆力,还是魔术师作弊,蒙骗了众人的眼睛?特别是有些魔术需要观众上台配合以显示魔术  相似文献   

2.
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   

3.
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   

4.
拜读了王先进老师的文章《例谈选择题的命制》,不禁有感而发:命制一份合格的试卷,除了知识点的覆盖,题目的坡度、难度以及题目的处置等之外,题目的来源和新颖也是命题者必须考虑的因素.直接搬用现有的题目,在一定的情况下会有损试卷的信用度,公平公正就打折扣.如何组织题目,这就涉及到对题目的技术处理.本文试以案例的形式,浅谈解答题命制的几种方法.  相似文献   

5.
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   

6.
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   

7.
数学与文学     
龟兔赛跑的故事,是大家很熟悉的.兔子本来跑在前面,但由于骄傲,路上睡了一觉,结果输给了乌龟.作为文学作品来说,当然要大力渲染兔子的骄傲自满,乌龟的坚持不懈.而从数学角度来看,则可抽象为下面的行程图.  相似文献   

8.
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   

9.
“1”的自述     
我是数字1,大家对我似乎很熟悉,其实却不然,为了以后我们能够成为好朋友,也为了同学们能学好数学,下面请听我的自我介绍:一、我是最小的正整数,我的绝对值还是我;我的相反数是-1,-1的绝对值也是我;我的任何次幂都是我1n=1;我的算术根还是我n1=1;一个数与它倒数的积也等于我,怎么样,牛吧?其实这也不算什么,下面还有更牛的呢.  相似文献   

10.
小琪是个聪明好学、事事都想探个究竟的同学,今年刚上九年级.星期天,小琪陪奶奶去社区商店购物.奶奶想买一千克软糖,不巧的是商店的电子秤坏了.于是,商店的售货员阿姨找来了一架旧天平和一只保存完好的250g的砝码,可惜的是这架天平的两臂长并不相  相似文献   

11.
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   

12.
彭忠益  王艳 《运筹与管理》2020,29(7):144-155
定量的评判城市老旧居住小区整体交通环境质量并进而科学有效的提出老旧小区交通环境更新与改善措施,对城市老旧居住小区交通环境进行了调查,明确了老旧居住小区存在的突出交通问题,并提出了城市老旧居住小区交通环境评价的指标体系,包括行人跨路出行指数、无人行道路段长度占比、停车泊位供需比、路内非法停车占比、平均停车步行距离、泊位数量户数比、人均步行空间、无障碍通道、盲道设置比例、非机动车泊位供需比、地面停放车辆数小区面积比、外部穿行交通周转量小区面积比等。并给出了具体指标的计算方法与获得办法。以长沙市四个典型老旧居住小区为例,对评价方法进行了论证,并得到城市老旧居住小区存在的一般问题,包括人车混杂、人车交织现象严重,停车泊位短缺、车辆乱停乱放,交通设施、特别是弱势群体交通设施缺乏。给出的评价指标、评价方法与结论可为城市老旧小区改造更新,特别是其中很重要的交通环境更新提供决策依据。  相似文献   

13.
We consider a productive asset, called equipment or capital good, and we examine the properties of, as well as the interactions between, the operating policies, which are determined by its optimal utilization and maintenance, and the capital policy of scrapping, which defines the optimal time when the productive asset is retired from its current use. Starting with an abstract model and using the approach of optimal control, initially we characterize the various types of equipment by assigning to them a single total profit index, which indicates how the above policies affect the flow of operating revenues plus capital gains or losses. This index is a function of market-determined prices. So using it we then investigate how the operating and capital policies are influenced by the rate of discount, the price of new equipment, and the rise or fall of the price of new equipment relative to the value of its output. Among other interesting results, we find that the effects of these prices on the nature and interactions of optimal policies depend crucially on whether the equipment is of the usual profit making type, where output is the main source of revenue, or of the antique type, where the main source of revenue is capital gains.  相似文献   

14.
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   

15.
为研究卷烟纸、成型纸、接装纸及嘴棒组合搭配对"中式卷烟"焦油量、烟气烟碱量、烟气水分、烟气一氧化碳量及过滤效率的影响,尝试采用L_(27)(3~(13))裂区正交设计方法对RR卷烟进行在线试验和取样.检测结果经过直观分析、方差分析及贡献率分析,结果表明:嘴棒长度、吸阻及接装纸透气度是影响试验指标的高度显著因素及重要因素.所以重点对嘴棒长度、吸阻及接装纸透气度进行调整和控制,可以很好地实现卷烟产品的质量控制,减少产品质量波动,降低产品成本.使用该方法可快捷、高效、经济、准确地寻找并确定卷烟材料多因素对卷烟主流烟气量及过滤效率的影响规律及卷烟产品的材料搭配优化方案.从而实现卷烟产品材料搭配精益化,满足烟草企业的实际需求.  相似文献   

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18.
将环境的波动性和度量噪音看作是影响绩效度量的两类不同的随机误差,在Linear-exponential-normal框架下,建立了以价值绩效度量和补偿绩效度量的线性组合为基础的收益激励模型,并分析了激励强度与绩效度量的一致性、敏感性和准确性之间的关系,以及环境波动性对上述关系的影响.研究发现,在确定性环境条件下,激励强度与绩效度量的"信号噪音比"成正比关系,但绩效度量的一致性的提高并不必然增加该度量指标在激励契约中的权重,而要视敏感性或噪音相对于一致性的变化幅度来定.特别地,在绩效度量的敏感性与一致性之间并不存在权衡取舍关系.研究还发现,波动性与激励强度之间存在负向关系,且波动性的存在降低了绩效度量的一致性和敏感性,但波动性对绩效度量的准确性的影响则呈非单调性变化.  相似文献   

19.
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   

20.
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   

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