关于解的延拓定理之注解

在数学专业的常微分方程课程里有关解的存在唯一性、解的延拓和解对初值与参数的连续性构成了微分方程最基本的理论,这部分内容既是常微分方程的重点,又是该课程的难点.本文的目的是对解的延拓定理所涉及的概念和论证进行系统的梳理和完善,并希望能够弥补微分方程教材中的有关不足.     

高职常微分方程教学案例及思考

高职常微分方程的教材编排不尽合理、存在较大缺陷,关于二阶常系数非齐次线性微分方程求解的教学案例显示:高职常微分方程教学不仅要重数学知识,更应重教学方法;探究性学习应是常微分方程教学的主旋律;猜想在常微分方程教学中应有一席之地.     

一门"国家精品课程"的建设--南开大学"高等代数与解析几何"课程

陈省身先生在南开大学创建的数学试点班后,对本科数学教学进行很多改革和建设。高等代数与解析几何的改革和建设是其中的一个重要部分。本文简要地介绍这部分工作,涉及课程体系、内容、教材、教学方法、教学手段和师资等。本课程教育部国际理科基地“创建名牌课程”的首批项目,首批优秀项目,2003年被评为天津市“精品课程”,2004年被评为“国家精品课程”。     

常系数线性微分方程的W解法

常系数线性微分方程的Ｗ解法王勇志，路云才（辽河油田职工大学）（鞍山师范专科学校）求解常系数线性方程，在《常微分方程》内容中占有重要的地位。尤其在工科院校使用的数学教材中，二阶常系数线性微分方程更是突出的重点。各种版本的教材所介绍的解法也不尽相同。有的...     

n阶常系数非齐次线性微分方程的降阶解法

给出一阶线性非齐次微分方程的积分因子解法,避免了常数变易法带来的不便和不自然;给出,n阶常系数非齐次线性微分方程的降阶解法,可以看出,高阶常系数线性非齐次微分方程最终都可以归结为求解一阶线性微分方程,从而避免了待定系数法求非齐次方程特解的繁琐,并最终说明了一般微积分教材中只给出两种类型常系数非齐次线性微分方程的待定系数解法的原因．     

从偏导数恒等式变换到偏微分方程求解

从高等数学教材课后习题的偏导数恒等式变换求解,引导学生讨论一类偏微分方程的求解.在拓展课程内容、应用和常微分方程变量分离方法的基础上,巩固多元复合函数求导法则,常系数线性微分方程求解方法和傅里叶级数的相关理论与方法.     

泛函延拓方法在分数阶常微分方程中的应用

应用线性泛函分析课程中泛函延拓的思想方法结合分数阶常微分方程理论以及Schauder不动点定理,获得了分数阶常微分方程初值问题解的局部存在性以及爆破二择一结果.     

对“常系数非齐次线性微分方程”的一种讲授法

就"常系数非齐次线性微分方程"的讲授设计了一种不同于教材的教学安排,并就文章所给的辅助方程法和教材的解法进行了比较.     

“应用数学基础”课程改革的思考

本探讨了“应用数学基础”课程改革的必要性，从教师队伍建设、教学内容改革、教学手段与教学方法改革、课程教材建设和教学实战等五个方面提出了我们的想法。     

某常微分方程教材中的一个错例

针对东北师范大学微分方程教研室所编教材《常微分方程》中的一道例题,经过实际验算发现,原题所给向量函数并非如其所称是其所给微分方程组的基本解组；随后通过两种方法对该道例题给出正确求解．     

Sell’s conjecture for non-autonomous dynamical systems

This paper is dedicated to the study of the G. Sell’s conjecture for general non-autonomous dynamical systems. We give a positive answer for this conjecture and we apply this result to different classes of non-autonomous evolution equations: Ordinary Differential Equations, Functional Differential Equations and Semi-linear Parabolic Equations.     

Convergence results for general linear methods on singular perturbation problems

Many numerical methods used to solve Ordinary Differential Equations, or Differential Algebraic Equations can be written as general linear methods. The B-convergence results for general linear methods are for algebraically stable methods, and therefore useless for nearly A-stable methods. The purpose of this paper is to show convergence for singular perturbation problems for the class of general linear methods without assuming A-stability.     

The ODEs forms of linearly elastic shell model and its numerical computing

In this paper, we successfully use 1D model to approximate the 3D problems. Firstly the PDEs (Partial Differential Equations) forms of Koiter’s Model for 2D linear elastic shell is proposed on special curvature coordinate system, i.e., spherical-coordinate system. Then the ODEs (Ordinary Differential Equations) forms of Koiter’s Model for 2D linear elastic shell is proposed under the assumption that the shell is axis-symmetric. Finally, we do numerical experiments to verify validity and accuracy of 1D models.     

A note on topological methods for a class of differential-algebraic equations

We study a particular class of autonomous Differential-Algebraic Equations that are equivalent to Ordinary Differential Equations on manifolds. Under appropriate assumptions we determine a straightforward formula for the computation of the degree of the associated tangent vector field that does not require any explicit knowledge of the manifold. We use this formula to study the set of harmonic solutions to periodic perturbations of our equations. Two different classes of applications are provided.     

Book Reviews

Book reviewed in this article: It's All Done by Numbers, by Douglas St. Paul Barnard. Introduction to Probability and Statistics, Fourth Edition, by Henry L. Alder and Edward B. Roessler Ordinary Differential Equations and Stability Theory: An Introduction, by David A Sanchez     

Systematic dynamic modelling of mechanical systems containing kinematic loops

In this tutorial paper a systematic procedure is presented to obtain the dynamic models of mechanical systems containing kinematic loops, with a main emphasis on efficiency and with particular regard to robotic systems. The procedure retains a minimal set of generalized coordinates for the corresponding open loop structure, obtained by removing some additional constraints closing loops in the original structure, while adopting an efficient Newton-Euler formulation of the equations of motion. Two methods for including the loop closure equations are then discussed: the Lagrange multipliers method and the method based on an explicit solution of the constraint equations. In the first case the dynamic model is given in the form of an implicit Differential Algebraic Equations (DAE) system, while in the second case an Ordinary Differential Equations (ODE) system could be obtained.     

A modified Runge-Kutta method for the numerical solution of ODE''s with oscillation solutions

A modified Runge-Kutta method with minimal phase-lag is developed for the numerical solution of Ordinary Differential Equations with oscillating solutions. The method is based on the accurate Runge-Kutta method of Sharp and Smart RK4SS(5) (see [1]) of order five. Numerical and theoretical results show that this new approach is more efficient, compared with the fifth order Runge-Kutta Sharp and Smart method.     

Time-stepping algorithms for semidiscretized linear parabolic PDEs based on rational approximants with distinct real poles

Time dependent problems in Partial Differential Equations (PDEs) are often solved by the Method Of Lines (MOL). For linear parabolic PDEs, the exact solution of the resulting system of first order Ordinary Differential Equations (ODEs) satisfies a recurrence relation involving the matrix exponential function. In this paper, we consider the development of a fourth order rational approximant to the matrix exponential function possessing real and distinct poles which, consequently, readily admits a partial fraction expansion, thereby allowing the distribution of the work in solving the corresponding linear algebraic systems in essentially Backward Euler-like solves on concurrent processors. The resulting parallel algorithm possesses appropriate stability properties, and is implemented on various parabolic PDEs from the literature including the forced heat equation and the advection-diffusion equation.Dedicated to Professor J. Crank on the occasion of his 80th birthday     

A differential-equation-based model of the glass ceiling in career progression

ABSTRACT

We introduce a model based on Ordinary Differential Equations to describe how two mutually exclusive groups progress through a career hierarchy, whether in a single organization, or in an entire economic sector. The intended application is to gender imbalance at the top of the academic hierarchy in European Universities; however, the model is entirely generic and may be applied in other contexts also. Previous research on gender imbalance in European universities has focused on large-scale statistical studies. Our model represents a point of departure, as it is deterministic (i.e., based on Ordinary Differential Equations). The model requires a precise definition of the progression rates for the different groups through the hierarchy; these are key parameters governing the dynamics of career progression. The progression rate for each group can be decomposed into a product: the proportion of group members at a low level in the hierarchy who compete for promotion to the next level a given year, multiplied by the in-competition success rate for the group in question. Either of these two parameters can differ across the groups under consideration; this introduces a group asymmetry into the organization’s composition. We introduce a glass-ceiling index to summarize this asymmetry succinctly. Using case studies from the literature, we demonstrate how the mathematical framework can pinpoint the proximate cause of the glass ceiling in European academia.