关于折线的一个猜想的证明

文[1]中，王方汉老师有如下猜想：当n为形如4m－1（mEN）的素数时，生成数列凡一l＝（1，2，…，牛／，M，…，2，l）所确定的数列B，，具有遍历性．也就是说，设数列凡1＝（r，12，…，r。－l），h为正整数，B。＝（hi，bZ，…，b。），1＝hi＜bZ＜…＜b。且均为整数，设凡；与B。之间有如下映射关系：。。。。，；；＝（1，2，…，宁，宁，…，2，1）且n为形如4m－1的素数时，数列B。各项被n除的余数恰是0，1，2，…，n－1的一个全排列．显然，数列B。＝（hi，bZ，…，b。）各项被n除的余数恰是0，1，2，…，n一且的一个全排列等价于…     

利用整体思想解含多变元、多个函数的复合最值问题

在数学竞赛试题中经常出现形如max{min{f1（x1，X2，…，xn），f2（x1，x2，…，xn），…，fm（x1，x2，…，xn）}}或min{max{f1（x1，x2，…，xn），f2（x1，x2，…，xn），…，fm（x1，x2，…，xn）}}的多变元、多个函数的复合最值问题，即求函数最大值的最小值或求函数最小值的最大值。这类问题复杂、抽象且综合性强，解题时不能孤立地研究每一个函数，宜采用整体思想。     

空间直线与平面

本单元的知识点主要有：平面的基本性质（三个公理及推论，空间图形的直观画法），线线关系（平行，异面，垂直，异面直线所成的角），线面关系（平行，相交，垂直，斜线在平面内的射影，直线和平面所成的角，三垂线定理），面面关系（平行，垂直，相交，二面角的平面角）．     

以台风为背景的考题的探究

以台风为背景的考题关注现实，贴近生活，涉及的知识点不多，历来被中考、高考、竞赛命题者所青睐，考察这类试题，不难发现命题者构思精巧，设计独特，用心良苦，纵观这类考题，就像一道亮丽的风景线映入眼帘，赏心悦目，心旷神怡，因此，特对以台风为背景的考题进行探究。     

有相依关系的成败型元件串联系统可靠性经典精确最优置信下限

设有由Ｋ个成败型元件Ａ１，Ａ２，…，ＡＫ组成的串联系统，设Ａ１，Ａ２，…，ＡＫ之间有相依关系，要Ａ１成功的条件下Ａ２才可以试验，在Ａ１，Ａ２，都成功的条件下Ａ３才可以试验，…在Ａ１，Ａ２，…ＡＫ－１都成功的条件下Ａｋ才可以试验，设条件概率Ｐ（Ａｉ│Ａ１Ａ２…Ａｉ－１）ｐｉ，ｐｉ未知，ｉ＝１，２，…，Ｋ。设有样本（Ｘ１，Ｘ２，…，ＸＫ）（Ｘ≥Ｘ２≥…≥ＸＫ），本文用样本点排序法求此串联系统可靠性之经     

一道数学竞赛题的探究

一道数学竞赛题的探究刘古胜（华中师范大学中师研究生课程班４３００７９）１９９２年国际数学奥林匹克竞赛中有这样一道题：数列１，１，３，３，３２，３２，…，３１９９２，３１９９２由两个１，两个３，两个３２，…，两个３１９９２按从小到大的顺序排列而成，数列...     

一个数论定理的简证

有一个在解题中应用频繁的命题：设a，b两自然数的最大公约数和最小公倍数分别是（a，b）和［a，b]，则［a，b]·（a，b）=ab.此命题在数论书上或略而不证，或证来太琐碎，思路不清晰，而不能令人满意，许多小学和中学的数学老师感到困惑．今给出两个简单的证法．引理1互素两数的最小公倍数等于它们的积．路证设，n，nEN，；n，n互素，我们来ie明［，n，’。」一n。n．事实上，如人是。n，；l的任一公倍数，则及一l，n一八；．那么din，但On，）一l，删mt．今t＝mP，则k—Pmn，．．m…k．又mn也是m，n的公倍数，故是最小公倍数．命回证法1…     

自然数的分组和勾股数

自然数的分组和勾股数王凯旋（华中师大数学系９３０２４３００７０）自然数１，２，３，…是我们大家很熟悉的了，但通过对自然数按一定的方式分组。却会给我们带来一个意想不到的结果设自然数分组如下：（１），（２，３），（４，５，６）…，（７，８，９，１０），（...     

关于丢番图方程x^2±2^m=y^n

本文证明了：方程ｘ２＋２ｍ＝ｙｎ，ｘ，ｙ，ｍ，ｎ∈Ｎ，ｇｃｄ（ｘ，ｙ）＝１，ｎ＞２仅有有限多组解（ｘ，ｙ，ｍ，ｎ），而且当（ｘ，ｙ，ｍ，ｎ）≠（５，３，１，３），（１１，５，２，３），（７，３，５，４）时，ｎ是适合ｎ≡７（ｍｏｄ８）以及２３≤ｎ＜８．５·１０６的奇素数，ｍａｘ（ｘ，ｙ，ｍ）＜Ｃ１；方程ｘ２－２ｍ＝ｙｎ，ｘ，ｙ，ｍ，ｎ∈Ｎ，ｇｃｄ（ｘ，ｙ）＝１，ｙ＞１；ｎ＞２仅有有限多组解（ｘ，ｙ，ｍ，ｎ），而且这些解都满足ｎ＜２·１０９炉以及ｍａｘ（ｘ，ｙ，ｍ）＜Ｃ２，这里Ｃ１，Ｃ２是可有效计算的绝对常数．     

数学散文——一种新的数学文体

读《中学数学》１９９９．５蔡上鹤先生“２１世纪和中学数学”一文，心中猛然腾起一种感觉——哦，散文！这是以往不能在数学期刊中读到的．看来，散文作为文科的一种专利，恐怕要被打破了！蔡先生的文章分成１２则，每则篇幅不长，两三百字，谈一件事，而件件都是与数学有关，却又没有数学正儿八经的面孔．横贯中西，纵通今古，娓娓道来，清新、隽永，象一注涓涓的清泉，淌入你的心田，让你感到润氵邑，清凉，甜丝丝的．事实上，我们在对学生教学时，往往强调提高学生对数学的兴趣，与此同时，似乎忘了专业数学期刊也应注意对其读者群——…     

培养学生科学思维和创新能力的研究与实践——谈大学数学研究型教学

通过从一个导数值等式的证明谈起,探讨教师在课堂教学中如何根据教学内容创设能激起学生新异感的问题情景,启发和引导学生发散思考,类比、联想、猜想,探索和发现新问题并给出解答.使学生思维不断攀升,丰富教学内容,激发学生兴趣,培养学生科学思维方法和创新能力.     

出租车司机社会贡献评价方法研究

出租车司机的社会贡献对于促进城市经济发展和社会进步具有重要的作用,评价出租车司机的社会贡献是激励出租车司机多做社会贡献的重要手段。为了评价出租车司机的社会贡献,本文提出了一种基于实际出租车运营数据的评价方法。本文设计了运营特性、重点区域、恶劣天气、大事件四个体现司机社会贡献的指标,以此构建了出租车司机社会贡献评价指标体系,进而选用了主观赋权法G1法和客观赋权法拉开档次法相结合的赋权方式对指标赋权,并选择四种评价信息集结方法建立了出租车司机社会贡献评价模型。最后,通过实际的出租车运营数据验证了本方法的可行性。本文为评价出租车司机社会贡献提供了一种研究思路和方法,并对政府政策的制定和企业策略的实施具有一定的启示。     

Learning to Ignore Online Help Requests

Email discussion groups provide a useful way of organizing email communities with a common interest in a certain topic. Emails submitted to the discussion group are sent automatically to each individual member, thereby eliminating the need to send multiple emails. This method may present unexpected difficulties however, when it comes to cooperation between members. An experimental study shows that email requests for help sent through discussion groups received less responses than emails sent individually to members of a group. Furthermore, subscribers to large discussion groups responded less often to help requests, whether they were sent to the group as a whole or to individuals. These results are discussed in terms of the separate roles of social cues and experience on the diffusion of responsibility effect.     

Strategic commitment to price to stimulate downstream innovation in a supply chain

It is generally in a firm’s interest for its supply chain partners to invest in innovations. To the extent that these innovations either reduce the partners’ variable costs or stimulate demand for the end product, they will tend to lead to higher levels of output for all of the firms in the chain. However, in response to the innovations of its partners, a firm may have an incentive to opportunistically increase its own prices. The possibility of such opportunistic behavior creates a hold-up problem that leads supply chain partners to underinvest in innovation. Clearly, this hold-up problem could be eliminated by a pre-commitment to price. However, by making an advance commitment to price, a firm sacrifices an important means of responding to demand uncertainty. In this paper we examine the trade-off that is faced when a firm’s channel partner has opportunities to invest in either cost reduction or quality improvement, i.e. demand enhancement. Should it commit to a price in order to encourage innovation, or should it remain flexible in order to respond to demand uncertainty. We discuss several simple wholesale pricing mechanisms with respect to this trade-off.     

Optimization Models for Forest Road Upgrade Planning

Road blocking due to thawing or heavy rains annually contribute to a considerable loss in Swedish forestry. Companies are forced to build up large stocks of raw material (saw and pulp logs) in order to secure a continuous supply when access to the road network is uncertain. Storage outdoors leads to quality deterioration and monetary losses. Other related costs due to road blocking are road damage and longer haulage distances. One approach to reduce the losses due to road blocks is to upgrade the road network to a standard that guarantees accessibility. We consider the road upgrade problem from the perspective of Swedish forest companies with a planning horizon of about one decade. The objective is to minimize the combined upgrade and transportation costs. We present two mixed integer programming models, which are uncapacitated fixed charge network flow problems including multiple assortments, several time periods and a set of road classes. One model is based on arc flows and one on route flows. For a typical planning instance, the models become large and we propose how to improve solution performance through model strengthening. The models are tested in a case study for a major Swedish forest company.      

Hemivariational inequality approach to constrained problems for star-shaped admissible sets

The hemivariational inequality approach is applied to establish the existence of solutions to a large class of nonconvex constrained problems in a reflexive Banach space. The admissible sets are supposed to be star-shaped with respect to a ball. Due to a discontinuity property of the Clarke directional differential related to the corresponding distance functions, the proposed method permits one to attain the solution without passing to zero with the penalization parameter. Some applications to nonconvex constrained variational problems illustrate the theory.     

Topology Optimization of Trusses—Random Cost Method Versus Evolutionary Algorithms

The recently proposed random cost method is applied to the topology optimization of trusses. Its performance is compared to previous genetic algorithm and evolution strategy simulations. Random cost turns out to be an optimization method with attractive features. In comparison to the genetic algorithm approach of Hajela, Lee and Lin, random cost turns out to be simpler and more efficient. Furthermore it is found that in contrast to evolution strategy, the random cost strategy's ability to find optima, is independent of the initial structure. This characteristic is related to the important capacity of escaping from local optima.     

Factorisation of Littlewood-Richardson coefficients

The hive model is used to show that the saturation of any essential Horn inequality leads to the factorisation of Littlewood-Richardson coefficients. The proof is based on the use of combinatorial objects known as puzzles. These are shown not only to account for the origin of Horn inequalities, but also to determine the constraints on hives that lead to factorisation. Defining a primitive Littlewood-Richardson coefficient to be one for which all essential Horn inequalities are strict, it is shown that every Littlewood-Richardson coefficient can be expressed as a product of primitive coefficients. Precisely the same result is shown to apply to the polynomials defined by stretched Littlewood-Richardson coefficients.     

快递企业航空货运网络的构建

快递业竞争激烈,构建高效合理的航空货运网络是快递企业提高竞争力的重要手段。“枢纽—辐射”式航空货运网络是整合航空快递资源、提高航空快递资源利用效率、提高快递企业竞争力的有效模式。本文以降低航空快递网络成本、加快航空快递处理时间为目标,从航空快递网络枢纽的选取、指派关系的确定、枢纽个数的选择三个方面研究了航空快递网络模型建立问题,选用遗传算法求解不同枢纽个数下航空快递网络的运输成本,并据此进行枢纽的选取,运用重力模型法进行指派关系的确定,在此基础上运用超效率DEA模型确定枢纽个数。接着,以包含17个节点的顺丰航空快递网络的规划为例,对本文所提出的模型和算法进行了验证,验证结果证实了模型的合理性。本文的研究为快递企业构建航空货运网络提供了科学实用的方法,该方法的使用可以降低航空货运成本,提高效率,从而提高快递企业的竞争力。     

System analysis and the world food system

The current world agricultural system generates persistent hunger, economic instability, and ecological degradation. Quantitative analysis has been used primarily to predict or optimize small parts of this system, not to engage with its larger problems, and not to redesign the system to eliminate those problems. New questions are posed here about world agriculture; several systems studies are described that begin to deal with those questions; and a challenge is put forth to combine systems tools with transcendent human qualities, to bring forth a stable, sufficient, sustainable global food system.