几种逻辑方法在理论力学课程教学中的应用

针对学生在学习理论力学课程过程中,各章知识点、解题方法、力学建模、分析和解决综合问题不容易掌握的特点,将力学竞赛辅导采用的科学方法论中3 种逻辑方法:比较-分类法、归纳-演绎法、分析-综合法,引入到理论力学的课程教学中. 实践证明,在理论力学课程教学中,采用了这几种逻辑方法,不仅提高了理论力学课程的教学质量,激发了学生的学习兴趣;而且学生也很容易掌握各章的知识点、解题方法、力学建模,并将它们熟练地应用于分析和解决综合问题.     

对学生进行科学方法教学的几点体会——在理论力学教学中

在理论力学教学中,除讲授基本课程内容外,还对学生进行一些科学、方法的教学,让学生学习和掌握一定的科学方法,不仅可以加深对课程内容的理解和掌握,对培养分析问题和解决问题的能力和走向工作岗位后继续提高都具有重要意义.本文介绍了作者在理论力学教学中进行科学方法教学的体会.     

强化学生力学建模能力的几点思考

本文提出了以培养力学建模能力为载体, 强化力学思维方式的教学思想. 重点以固体力学主干课程为基础分析和讨论了力学模型的概念和要点, 强调了力学基本量和基本原理学习的重要性, 并对力学模型的建模方法、分类、基本原则进行了讨论. 通过理论力学和材料力学的典型例题分析, 举例说明了建模步骤. 最后, 对如何在教学中培养学生力学建模能力、学习要点、学习方法进行了探讨.     

理论力学课程英译名称引发的思考

现有理论力学课程英文名称普遍译成"Theoretical Mechanics".作者从课程发展的历史主线以及欧美惯用表述出发,提出对此译文的质疑,并进一步探讨分析力学在整个经典力学体系中的地位.针对我国现有理论力学教学现状,比较中美高校理论力学教学内容上的差异,呼吁在高校理论力学教学内容中增加分析力学的比重.在课程教学中,注重力学发展史主线的描绘,帮助学生树立力学学科的历史发展观,以进一步适应人才培养与时代发展需求.     

基于3S学习模式的理论力学课程教学研究与实践

3S学习模式包括自学(study independently)、研讨(seminar)、科学研究(science research)三部分.本文以突出培养大学生的自主学习能力、自我驱动能力和创新意识为出发点,以理论力学课程为教学研究平台,开展3S学习模式在理论力学课程中的应用研究与实践.介绍了结合理论力学课程的3S学习模式的实施方法和实施内容以及存在的问题,对实施的效果进行了评估,给出了教学设计的总体思路,为推动理论力学课程教学新体系和教学新模式的建立提供了重要依据和参照.     

工科理论力学教学体系改革的探索与实践

本文针对目前工科理论力学教学体系的现状,从当前工程的需要、计算技术的冲击与面向２１世纪等角度提出理论力学教学体系必须进行改革的原因．重点介绍了所编写的理论力学教材新体系．     

在理论力学教学中采用协作学习的改革实践研究

 在理论力学教学中采用了协作学习方式来全面提高学生的能力. 在简单介绍协作学习方法以后,阐述了理论力学协作学习的准备工作以及具体实施办法:分散讨论课,集中讨论课,课堂测验的运作方式以及讨论课评分的方法. 改革实践表明,对于大班上课而言,协作式学习方法具有传统方法无可比拟的优越性,值得在理论力学课堂中进行推广.     

心血管内流场的高质量模拟实验研究（Ⅰ）：动态流体双折射测试原理与分析…

本文系统地讨论了以动态流体双折射方法实现心血管内流场的高质量模拟测试的基本理论和实用分析方法。首先，分析了稳态流动和振荡剪切流中光－力学关系的差异，提出了脉动流中简化的光－力学关系假设，然后给出了其适用于低频脉动流动的实验验证。     

谈工科理论力学教学中数学工具的应用

分析了当前理论力学教学由于缺乏对数学工具的充分应用而带来问题,提出在理论力学教学 中应充分利用矢量、矩阵等数学工具,重视对学生计算机数值求解方法的训练. 在具体的求 解过程中选用MATLAB或Maple软件作为数值计算的工具.     

理论力学创新思维实验教学的探索与实践

结合力学实验教学示范中心建设,全面实施实验教学改革.在力学理论教学中,向学生灌输创新意识.开设理论力学创新思维实验课程,注重创新教育的普及.开展创新实践活动,定期开展创新大赛,培养创新精英.几年的理论力学创新思维实验教学实践表明,学生创新意识和科学思维方法得到全面提升,并完成了一批具有实用价值的创新成果.     

Photoelastic analysis of frozen stressed specimens using spectral-contents analysis

The complete birefringence, or isochromatic fringe order, in stress-frozen photoelastic models has been found by measuring the spectral contents of idividual points. A calibration procedure is porposed. The effects of nonuniform birefringence and dispersion of birefringence are considered. The results are presented from the analysis of models of a plate with a central hole and a disk subject to three radial loads.     

Sorting-free Hill-based stability analysis of periodic solutions through Koopman analysis

In this paper, we aim to study nonlinear time-periodic systems using the Koopman operator, which provides a way to approximate the dynamics of a nonlinear system by a linear time-invariant system of higher order. We propose for the considered system class a specific choice of Koopman basis functions combining the Taylor and Fourier bases. This basis allows to recover all equations necessary to perform the harmonic balance method as well as the Hill analysis directly from the linear lifted dynamics. The key idea of this paper is using this lifted dynamics to formulate a new method to obtain stability information from the Hill matrix. The error-prone and computationally intense task known by sorting, which means identifying the best subset of approximate Floquet exponents from all available candidates, is circumvented in the proposed method. The Mathieu equation and an n-DOF generalization are used to exemplify these findings.

     

Dynamical analysis of compositions

This paper analyzes musical opus from the point of view of two mathematical tools, namely the entropy and the multidimensional scaling (MDS). The Fourier analysis reveals a fractional dynamics, but the time rhythm variations are diluted along the spectrum. The combination of time-window entropy and MDS copes with the time characteristics and is well suited to treat a large volume of data. The experiments focus on a large number of compositions classified along three sets of musical styles, namely ??Classical??, ??Jazz??, and ??Pop & Rock?? compositions. Without lack of generality, the present study describes the application of the tools and the sets of musical compositions in a methodology leading to clear conclusions, but extensions to other possibilities are straightforward. The results reveal significant differences in the musical styles, demonstrating the feasibility of the proposed strategy and motivating further developments toward a dynamical analysis of musical compositions.     

Stress-optical analysis of fluids

Summary Recent advances in Rheology have emphasized the necessity of measuring the stress distribution in flowing viscoelastic fluids which is qualitatively different from the one in Newtonian liquids. The use of flow-birefringence for this purpose has advantages. The concept of the stress-optical coefficient, well known in the stress optical analysis of solids, can be also applied to fluid flow. The extinction angle determines the recoverable shear strain,s a parameter in the flow of viscoelastic fluids. This would mean that mechanical and optical flow phenomena are caused primarily by stresses, not by the rate of shear. Experimental results presented confirm this postulate.     

弦支穹顶结构动力分析

基于局部分析法并且在以预应力作为自平衡的初始内力情况下对弦支穹顶结构的动力特性进行了初步分析。局部分析法采用将索杆体系和上部单层网壳分开的思想,使弦支穹顶结构的初始预应力分布的确定得到简化。随着上部网壳结构的整体刚度的降低,预应力对体系的自振特性的影响逐渐增大。该体系的低阶振型大多为竖向振动振型。由时程分析的结果可见竖向常遇地震作用下索杆内力上下变化的幅度并不大（不超过7％）。竖向常遇地震作用下结构响应由内环、中环到外环逐渐减弱。常遇水平地震作用下体系索杆内力上下变化的幅度更小。相比竖向常遇地震作用下的索杆内力的变化要小的多。同时,常遇水平或竖向地震作用下线性和非线性时程分析差别不大。     

Three-dimensional stress analysis of textile composites: Part I. Numerical analysis

Three-dimensional stress analysis in a unit-cell of a plain-woven composite was performed by using B-spline displacement approximation. The spline approximation provides continuity of displacement and stress components within each yarn and matrix subregion. Two types of unit-cell problems with and without inter-yarn delamination were considered. A penalty function approach along with a contact surface characteristic function was used to obtain a full-field numerical solution for the frictionless contact problem between delaminated yarn surfaces.Yarn interfaces at yarn-crossover locations represent three-material wedge-type regions resulting in singular stress behavior. In the case of unit-cells with perfect bonding between the yarn interfaces, the numerical values of the inter-yarn normal stress did not exhibit trends typical for unbounded stress behavior, whereas the inter-yarn shear stress components displayed discontinuous behavior typical for numerical results in the vicinity of the stress singularity. In the presence of the delamination, both the inter-yarn normal and shear stress components exhibited unbounded behavior near the singularity. Notably, the inter-yarn normal stress showed signs of singular behavior in both cases of open and closed delaminations. Due to the stress singularity that exists at yarn-crossover locations containing three materials (yarn–yarn–matrix) interface intersections, the full-field numerical solution, even with high-order approximation functions, was not able to capture the directional nonuniqueness of the stress values in the vicinity of the singularity, and therefore calls for incorporation of the asymptotic singular stress analysis, which will be given in a follow-on paper [Sihn and Roy, International Journal of Solids and Structures (accepted for publication)].     

极限分析和安定分析的并行算法

本文基于结构极限分析和安定分析的温度参数法，研究了线性规划的并行算法，温度参数法求解的关键是线性规划的求解效率，在分布式布储的多处理机系统上，采用了线性规划的分块单纯形法。对相当于大量工况的结构，子结构是一个很好的并行结构分析方法。