例析解平面向量问题的常用方法与技巧

向量是近代数学最基本的概念之,它具有代数形式和几何形式的“双重身份”．是沟逋几何、代数、三角等内容的桥梁．“平面向量”足高中数学知识体系的重要组成部分,     

代数问题几何化的几条途径

数”和“形”是不可分割的统一体。数形沟通,相互印证。不仅是数学研究的重要手段,也是数学解题的重要技巧。解析几何开创了用“数”研究“形”的先例,使灵活多变的几何问题转化为有程序的代数问题,解题有路可循,易于解决;反之,以“形”研究“数”,代数问题转化为几何问题,会使得问题直观形象,解法灵活、简洁,本文从几方面谈谈如何实现这一转化。 (一)利用概念的几何意义: 数学中许多代数概念都有较强的几何意义,充分应用它的几何意义剖析代数问题,可使许多繁杂的代     

数形结合思想在初中数学解题中的应用

数形结合思想方法作为初中阶段十分重要的数学方法,将代数思想与图形分析思想完美结合,通过对代数关系以及图形性质的把控来完成数学题目的巧妙解答,是学生在数学解题应用中应该着重培养的数学思想.培养数形结合思想,需要学生掌握以“数”辅“形”、以“形”助“数”以及“数”“形”互助的解题技巧,在遇到代数问题时多考虑图形辅助,在遇到几何问题时多思考其中的代数关系,将数形结合思想熟练运用到日常的数学学习,提高学习质量.     

初中代数中对学生抽象能力培养的几个阶段——初中代数教材分析之一

抽象,是数学的一大特点,所以,从某种角度说,抽象能力的强弱可以是数学学得好坏的一个标志,因此对学生抽象能力的培养应算提高数学教学的关键性的一环.于是,下面一个问题就成为值得重视的问题被提出来了,这就是:初中代数教材中,对学生抽象能力的培养是如何展开的?笔者想就这个问题谈点粗浅意见. 初中代数中对学生抽象能力的培养大抵可分为三个阶段,不妨称之为“初始阶段”、“中间阶段”、“提高阶段”.     

关于九年一貫制数学教学改革方案中的两个问题

我們制訂的九年一貫制数学教学改革方案初稿,在中国数学会第二次代表大会上提出以后,引起了广泛的討論。关于数学教学体系问题,不少同志对“以函数为綱”,“数形結合”这两个原則展开了討論。我們愿意进一步阐明对这两个原則的看法,提出商榷,参加讨论。一、关于“以函数为網”新体系以函数为綱,把旧的算术、代数、几何、三角、解析几何的材料結合在一个系統之中。从小学算术开始就培养学生的函数及运动变化的观点。过去初中代数部分,現在也用函数的观点加以研究。原高中代数中的初等函数、三角和解析几何的一些知識按数形結合的原則合为一門初等函数課。在初等函数中系     

加强初中代数推理教学的实践与思考--以“完全平方公式”为例北大核心

推理是用数学思维思考现实世界的基本方式,渗透在数学的产生与发展过程中.回顾我国数学课程改革的发展历程,推理能力始终作为数学课程目标的重要成分,1《义务教育数学课程标准(2022年版)》中“推理”出现的频次高达102次,并新增“了解代数推理”,同时指出:“要关注基于代数的逻辑推理,如代数运算规律的论证(例66)、韦达定理的论证(例67)、基于图象的函数想象(例68)”[2]这充分表明,初中数学要加强基于代数的推理教学。     

《代数与几何基础》(张肇炽教授主编)一书评析

数学是研究现实事物的数量关系与空间形式的一门科学 .分析学、代数学与几何学是数学的三大基础 ,分析与代数侧重于数学中的“数”,而几何则侧重于数学中的“形”.坐标、向量、矩阵等概念的建立 ,将代数和几何紧密地结合在一起 ,代数为几何提供了研究方法 ,而几何也为代数提供了直观的几何背景 .事实上 ,线性代数中所讨论的“线性”概念来源欧氏几何、线性方程组理论和解析几何 ,线性空间的概念是几何空间的一种代数抽象 .变换的理论 ,如正交变换、仿射变换、射影变换等都是从几何中产生的 .线性代数中的很多重要概念 ,如矩阵的等价、相合、…     

P.Griffith的“代数曲线”的评介

P.Griffith所著的由北京大学出版社出版的“代数曲线”一书,是根据P.Griffith教授于1982年春,在北京大学讲授“代数曲线”课程的讲稿经整理而成的.此书是一本很有特色的书.对于从事基础数学,应用数学乃至计算数学工作的人都可以从本书中得到益处,而对于有志于从事代数几何、多复变函数与黎曼曲面等方面研究的人,更是一本不可多得的好书.     

中学生空间概念发展特点的研究

l问题的提出 数学教育研究主要包括以下几方面，这就是“为何教?”、“教什么?”、“如何教?”、“教谁?”．但是，事实上，目前大多数的研究是关于“为何教?”、“教什么?”、“如何教?”的．这些研究通过考察社会需要、数学、培养等若干方面的发展，来论证数学教育的重要性，研究“为什么教数学”；通过考察各级各类数学教育的内容，研究教学大纲、课程计划、教材编排体系等来研究“教什么”；至于“如何教”呢?     

数学思想方法在高等代数教学中的渗透

介绍高等代数中的降阶法、同构、类比、变换、化归、分类等思想方法,并逐条说明如何在高等代数的教学过程中逐步渗透这些数学思想方法．从而使得高等代数的教学过程成为一个发展与培养学生良好数学思维品质的过程．     

Algebraic <Emphasis Type="Italic">K</Emphasis>-theory of Gorenstein projective modules

We introduce the Gorenstein algebraic K-theory space and the Gorenstein algebraic K-group of a ring, and show the relation with the classical algebraic K-theory space, and also show the ‘resolution theorem’ in this context due to Quillen. We characterize the Gorenstein algebraic K-groups by two different algebraic K-groups and by the idempotent completeness of the Gorenstein singularity category of the ring. We compute the Gorenstein algebraic K-groups along a recollement of the bounded Gorenstein derived categories of CM-nite Gorenstein algebras.     

A Lower Bound for the Algebraic Connectivity of a Graph in Terms of the Domination Number

We investigate how the algebraic connectivity of a graph changes by relocating a connected branch from one vertex to another vertex, and then minimize the algebraic connectivity among all connected graphs of order n with fixed domination number \(\gamma\leq\frac{n+2}{3}\), and finally present a lower bound for the algebraic connectivity in terms of the domination number. We also characterize the minimum algebraic connectivity of graphs with domination number half their order.     

关于“多项式样条磨光公式”的若干注记

0.李岳生在“微分算子样条函数磨光法”的一般框架下,推导了“多项式样条磨光公式”:以及处理f由离散数据给出的相应公式?_hf(x),这里m是任意正整数,q是任意非负整数,h为任意正数,     

Properness Defects of Projections and Computation of at Least One Point in Each Connected Component of a Real Algebraic Set

Computing at least one point in each connected component of a real algebraic set is a basic subroutine to decide emptiness of semi-algebraic sets, which is a fundamental algorithmic problem in effective real algebraic geometry. In this article we propose a new algorithm for the former task, which avoids a hypothesis of properness required in many of the previous methods. We show how studying the set of non-properness of a linear projection enables us to detect the connected components of a real algebraic set without critical points for . Our algorithm is based on this observation and its practical counterpoint, using the triangular representation of algebraic varieties. Our experiments show its efficiency on a family of examples.     

Rigid actions of amenable groups

Given a countable discrete amenable group G, does there exist a free action of G on a Lebesgue probability space which is both rigid and weakly mixing? The answer to this question is positive if G is abelian. An affirmative answer is given in this paper, in the case that G is solvable or residually finite. For a locally finite group, the question is reduced to an algebraic one. It is exemplified how the algebraic question can be positively resolved for some groups, whereas for others the algebraic viewpoint suggests the answer may be negative.     

Higher Algebraic <Emphasis Type="Italic">K</Emphasis>-theory of Ring Epimorphisms

Given a homological ring epimorphism from a ring R to another ring S, we show that if the left R-module S has a finite-type resolution, then the algebraic K-group K _n (R) of R splits as the direct sum of the algebraic K-group K _n (S) of S and the algebraic K-group K _n (R) of a Waldhausen category R determined by the ring epimorphism. This result is then applied to endomorphism rings, matrix subrings, rings with idempotent ideals, and universal localizations which appear often in representation theory and algebraic topology.     

Algebraic -actions of entropy rank one

We investigate algebraic -actions of entropy rank one, namely those for which each element has finite entropy. Such actions can be completely described in terms of diagonal actions on products of local fields using standard adelic machinery. This leads to numerous alternative characterizations of entropy rank one, both geometric and algebraic. We then compute the measure entropy of a class of skew products, where the fiber maps are elements from an algebraic -action of entropy rank one. This leads, via the relative variational principle, to a formula for the topological entropy of continuous skew products as the maximum of a finite number of topological pressures. We use this to settle a conjecture concerning the relational entropy of commuting toral automorphisms.

     

Generating equations approach for quadratic matrix equations

We show how Van Loan's method for annulling the (2,1) block of skew‐Hamiltonian matrices by symplectic‐orthogonal similarity transformation generalizes to general matrices and provides a numerical algorithm for solving the general quadratic matrix equation: For skew‐Hamiltonian matrices we find their canonical form under a similarity transformation and find the class of all symplectic‐orthogonal similarity transformations for annulling the (2,1) block and simultaneously bringing the (1,1) block to Hessenberg form. We present a structure‐preserving algorithm for the solution of continuous‐time algebraic Riccati equation. Unlike other methods in the literature, the final transformed Hamiltonian matrix is not in Hamiltonian–Schur form. Three applications are presented: (a) for a special system of partial differential equations of second order for a single unknown function, we obtain the matrix of partial derivatives of second order of the unknown function by only algebraic operations and differentiation of functions; (b) for a similar transformation of a complex matrix into a symmetric (and three‐diagonal) one by applying only finite algebraic transformations; and (c) for finite‐step reduction of the eigenvalues–eigenvectors problem of a Hermitian matrix to the eigenvalues– eigenvectors problem of a real symmetric matrix of the same dimension. Copyright © 1999 John Wiley & Sons, Ltd.     

Arbitrary Pole Assignability by Static Output Feedback under Structural Contraints

Using a few elementary concepts from algebraic geometry such as multidimensional projective space, quadric hypersurface and its tangential variety, the known problem of arbitrary pole placement is transformed into a system of well‐structured (partly non‐linear) algebraic equations. Necessary and sufficient solvability conditions are derived. Finally, it is outlined how to calculate admissible output feedback matrices which ensure the desired pole assignment.     

Arithmetic Properties of Generalized Hypergeometric <Emphasis Type="Italic">F</Emphasis>-Series

A generalization of the Siegel–Shidlovskii method in the theory of transcendental numbers is used to prove the infinite algebraic independence of elements (generated by generalized hypergeometric series) of direct products of fields \(\mathbb{K}_v\), which are completions of an algebraic number field \(\mathbb{K}\) of finite degree over the field of rational numbers with respect to valuations v of \(\mathbb{K}\) extending p-adic valuations of the field ? over all primes p, except for a finite number of them.