一道以群的定义为背景的高考试题赏析

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.……     

负数的自述

我是负数,你以前虽然见过我,但我们还不很熟悉.下面就听听我的自述,我们会成为好朋友的.一、我的出现是实际生活的需要.数的扩充都是由于实际的需要而产生的,负数的引入也不例外,它是由于表示具有相反意义的量的需要而产生的.小学学过的自然数和分数只能表示相反意义的量中的一个量,不能满足实际需要,为了更好的记数而引入一种     

“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.     

分配格上上标准特征向量的求法

本文研究了分配格(L,∧,∨,0,1)上方阵A的上特征向量的性质.利用矩阵的伴随有向图,得到格上方阵A的上标准特征向量的一种实用的新方法.     

抓机会用“嫁接”

把要繁殖的植物的枝或芽接到另一种植物体上使它们结合在一起,成为一个独立生长的植株……叫做嫁接,嫁接能够保持植物原有的某些特性,是常用的改良品种的方法.把“嫁接”的思想应用于数学,常常可以收到意想不到的效果.     

食饵具脉冲扰动与捕食者具连续收获的时滞捕食-食饵模型

本文讨论了与生物资源管理相关的食饵具脉冲扰动与捕食者具连续收获的时滞捕食-食饵模型,得到了捕食者灭绝周期解的全局吸引和系统持久的充分条件.也证明了系统的所有解的一致完全有界.我们的结论为现实的生物资源管理提供了可靠的策略依据,也丰富了脉冲时滞微分方程的理论.     

例谈备课中新课程的导入与设问环节

备课是教师的一项基本功,是教师对教材进行再创造的过程,是集教学内容,教学方式,教学艺术于一体的一项关键设计.备课质量的高低,不仅影响着教学计划的实施和教育方针的落实,更潜在地制约着课堂教学的效率.     

手机套餐问题的一个数学模型

随着信息时代的到来,手机在人们日常工作、社交、经营等社会活动中的作用越来越重要.近年来我国通信业务量飞速增长,手机的功劳更是功不可没.手机资费问题也越来越受到人们的关注,并且对原有的各种资费方案越来越质疑.2007年1月以来上海、北京、广东等地相继推出的手机"套餐"琳琅满目,让人眼花缭乱,人们不能理性分辨手机"套餐"究竟优惠在何处.……     

赏析2011年湖北高考理科立几题

2011年高考已经落幕,笔者有意关注了湖北数学试卷,解读理科数学试卷,两道立体几何试题给我留下了很深的印象.小题的背景和问题设置让人耳目一新;大题的解法入口宽,方法多,涉及的知识面广,打破了单纯考查立体几何的常规,建立了立体几何与函数、三角、向量、解几的密切联系.这两道试题充分体现了源于教材,略高于教     

如何分遗产

古罗马一位寡妇，遵照丈夫的遗嘱，把丈夫遗留下来的3500元遗产同她即将出生的孩子一起分配。如果生的是儿子，那么，按照罗马的法律，做母亲的应分得儿子份额的一半；如果生的是女儿，做母亲的就应分得女儿份额的两倍。可发生的事情是：生了一对双胞胎——一男一女。     

ASYMPTOTIC BEHAVIOR OF ECKHOFF＇S METHOD FOR FOURIER SERIES CONVERGENCE ACCELERATION

The current paper considers the problem of recovering a function using a limited number of its Fourier coefficients. Specifically, a method based on Bernoulli-like polynomials suggested and developed by Krylov, Lanczos, Gottlieb and Eckhoff is examined. Asymptotic behavior of approximate calculation of the so-called ＂jumps＂ is studied and asymptotic L2 constants of the rate of convergence of the method are computed.     

When a compact (countably compact) set is closed. II

We obtain (a) necessary and sufficient conditions and (b) sufficient conditions for a compact (countably compact) set to be closed in products (sequential products) and subspaces (sequential subspaces) of normal spaces. As a consequence of these, sufficient conditions are obtained for (i) the closedness of arbitrary (countable) union of closed sets and (ii) the equality of the union of the closures and the closure of the union of arbitrary (countable) families of sets in these spaces. It is also shown that these results do not hold for quotients of even T ₄,-spaces.     

On a family of vector space categories

In continuation of our earlier work [2] we describe the indecomposable representations and the Auslander-Reiten quivers of a family of vector space categories playing an important role in the study of domestic finite dimensional algebras over an algebraically closed field. The main results of the paper are applied in our paper [3] where we exhibit a wide class of almost sincere domestic simply connected algebras of arbitrary large finite global dimensions and describe their Auslander-Reiten quivers.     

Cartan matrices of selfinjective algebras of tubular type

The Cartan matrix of a finite dimensional algebra A is an important combinatorial invariant reflecting frequently structural properties of the algebra and its module category. For example, one of the important features of the modular representation theory of finite groups is the nonsingularity of Cartan matrices of the associated group algebras (Brauer’s theorem). Recently, the class of all tame selfinjective algebras having simply connected Galois coverings and the stable Auslander-Reiten quiver consisting only of stable tubes has been shown to be the class of selfinjective algebras of tubular type, that is, the orbit algebras /G of the repetitive algebras of tubular algebras B with respect to the actions of admissible groups G of automorphisms of . The aim of the paper is to describe the determinants of the Cartan matrices of selfinjective algebras of tubular type and derive some consequences.     

关于药物对小鼠肝脏细胞色素P-450含量的影响实验结果的分析

肝药酶诱导剂苯巴比妥能诱导细胞色素P-450的合成,而肝药酶抑制剂放线菌素D能抑制细胞色素P-450的合成,本实验应用示差光谱法对P-450含量加以测定.本文改进了传统的计算药后诱导组和抑制组P-450含量增加或减少的百分比来评价药物的方法,在M athem atica数学软件环境下,对数据进行方差分析和t检验,提高了数据处理精度和可信度.并对原方法表示怀疑.     

Bounds of the Hausdorff Measure of Sierpinski carpet

By means of the idea of [2]（Jia Baoguo,J.Math.Anal.Appl.In press） and the self.similarity of Sierpinski carpet, we obtain the lower and upper bounds of the Hausdorff Measure of Sierpinski carpet, which can approach the Hausdorff Measure of Sierpinski carpet infinitely.     

Existence and nonexistence results for reaction-diffusion equations in product of cones

Problems of existence and nonexistence of global nontrivial solutions to quasilinear evolution differential inequalities in a product of cones are investigated. The proofs of the nonexistence results are based on the test-function method developed, for the case of the whole space, by Mitidieri, Pohozaev, Tesei and Véron. The existence result is established using the method of supersolutions.     

Reflexivity of prodiscrete topological groups

We study the duality properties of two rather different classes of subgroups of direct products of discrete groups (protodiscrete groups): P-groups, i.e., topological groups such that countable intersections of its open subsets are open, and protodiscrete groups of countable pseudocharacter (topological groups in which the identity is the intersection of countably many open sets). It was recently shown by the same authors that the direct product Π of an arbitrary family of discrete Abelian groups becomes reflexive when endowed with the ω-box topology. This was the first example of a non-discrete reflexive P-group. Here we present a considerable generalization of this theorem and show that every product of feathered (equivalently, almost metrizable) Abelian groups equipped with the P-modified topology is reflexive. In particular, every locally compact Abelian group with the P-modified topology is reflexive. We also examine the reflexivity of dense subgroups of products Π with the P-modified topology and obtain the first examples of non-complete reflexive P-groups. We find as well that the better behaved class of prodiscrete groups (complete protodiscrete groups) of countable pseudocharacter contains non-reflexive members—any uncountable bounded torsion Abelian group G of cardinality ω² supports a topology τ such that (G,τ) is a non-reflexive prodiscrete group of countable pseudocharacter.     

Academics’ perceptions of the use and relevance of software in quantitative and financial disciplines

Software may be used in university teaching both to enhance student learning of discipline-content knowledge and skills, and to equip students with capabilities that will be useful in their future careers. Although research has indicated that software may be used as an effective way of engaging students and enhancing learning in certain scenarios, relatively little is known about academic practices with regard to the use of software more generally or about the extent to which this software is subsequently used by graduates in the workplace. This article reports on the results of a survey of academics in quantitative and financial disciplines, which is part of a broader study also encompassing recent graduates and employers. Results indicate that a variety of software packages are in widespread use in university programmes in quantitative and financial disciplines. Most surveyed academics believe that the use of software enhances learning and enables students to solve otherwise intractable problems. A majority also rate spreadsheet skills in particular as very important for the employability of graduates. A better understanding of the use of software in university teaching points the way to how curricula can be revised to enhance learning and prepare graduates for professional work.