包含—受扭迴转轴的半空间的性质*

本文研究包含有一根部份嵌入的迴转轴的半空间的性质.不用知道一给定的嵌入的轴的扭转问题的精确解,这些性质能指出此半空间的位移或应力场的某些特点并且有时可以用来检查数值解.文中给出嵌入半空间的受扭的刚性圆柱的轴的表面上的正确的应力分布的检查的例子.     

方程a~x=loga~x的解

一个方程的解可以看作两个函数的图象的交点的横坐标。反过来,方程的解又可以反映两个函数之间的某种关系,即它们的图象相交的情况。因此,可以利用函数的性质对方程的解,特别是直接求解很困难的某些超越方程的解的情况作出定性的讨论。也可以利用方程的解对函数的图象间的交点个数作出定量的研究,本文主要通过对函数y=x~(1/x)和y=x~x的性质的分析,就方程a~x=x和a~x=loga~x等的解的情况进行讨论。     

三棱锥体积在解题中的应用

三棱锥是一种特殊的棱锥;它的每一个顶点都可为棱锥的顶点,它的每一个面均可为棱锥的底面,而体积总是不变的。利用这一特点,可以把求多面体的体积和多边形的面积分别转化为求三棱锥的体积和三校锥的底面积;把求点到平面的距离、直线和平面的距离以及两条异面直线的距离转化为求三棱锥的高等等。一求多面体的体积多面体的体积,可以转化成若干个三棱锥的体积和,由于三棱锥的底面具有轮换性,可适当选取三棱锥的底面,较容易地求出三棱锥的体积,进而求出多面体的体积。     

模糊有限状态机的积的代数性质

文章利用代数的方法讨论了模糊有限状态机的全直积、级联积、圈积、模糊有限状态机的和的代数性质。证明了模糊有限状态机的和与其因子在子系统(强子系统)、交换性、连通性、可恢复性等方面的相似的结构性质;给出了模糊有限状态机的全直积、级联积、圈积与其因子之间的关系;获得了模糊有限状态机的各种积的容许划分与其因子的容许划分之间的关系、以及模糊有限状态机的积的商与模糊有限状态机的商的积之间的联系。     

关于二次曲线的切线及奇异点的探讨

利用二次曲线的切线的定义,分别讨论过二次曲线上的一点的切线的求法及过二次曲线外的一点的切线的两种求法,并且得到了存在奇异点的二次曲线的具体类型.     

关于直接揭露本貭特征对于学生掌握几何基本概念的作用的問題

一、研究的任务和方法概念乃是一种反映对象和現象的一般的并且是本质的特征的思维形式。概念的形成是在人类历史发展过程中进行的,概念的掌握是掌握現成的、社会上形成的概念。所以概念的掌握就不需要通过概念形成时人类所走过的复杂的、漫长的道路。虽然如此,但是概念的掌握仍然是一种复杂的过程,它取决于过去的經驗、已有的知识、掌握过程中实现的活动(如教学活动、生活活动等)、掌握借以实現的智力过程的系统。概念的教学方法是多种多样的,主要可分为两种:一种是直接揭露本质特征的方法,另一种是間接揭露本质特征的方法(如变式、对比等)。在平面几何的概念的教学中应該采用直接揭露本质特征的方法还是采     

中等學校裹序列的學習

本文的目的是按照中等學校裏應該講授的計畫給中學數學教師以學習序列問題的典型的探討。序列應該看作是以自然數為變元的函數,因此,必需重複一下學生們在八年級就已得到了的關於函數的基本知識。函數的定義大致以下面的形式教給八年級的學生們。如果變元x的每一允許的數值,對應著某個完全確定了的數值y,那末y就是變元x的函數。所給的x值的集合叫做變元的允許的數值的集合或函數的定義域,而相應的y的數值的集合就叫做函數的數值的集合。要規定一個函數,就應該確定變元的允許的數值的集合和一個對應的規律,按照這個規律,可以給變元的每個已給的數值確定一個唯一的函數值。 學生們應該知道,集合和對應的概念是函數的定義的基礎,它們是基層的,那就是說,集合和對應的概念不能藉助更簡單的概念來定義。     

图的点覆盖数与其Laplace谱半径

本文讨论图的点覆盖数与图的 Laplace谱半径的关系 ,利用特征向量的技巧得到由图的 L aplace谱半径所确定的关于图的点覆盖数的紧的界     

微分差分方程积分的近似方法

近二三十年来,由于应用科学,首先是高节理论的需要大大地加强了对于微分差分方程的理论的注意。有特别多的论文是关于描述许多具有后继的过程的、具有時滞的微分方程的。这种类型方程的积分,仅在完全特殊的情况下,才是闭合形式的;因此研究其积分的近似方法就具有头等的意义。然而,据我所知,这些极其迫切的问题还没有得到系统的研究。在本文中,主要是研究具有滞的微分方程积分的近似方法的问题,至于他类型的微分差分方程,只不过是顺便谈到罢了。     

一维活塞问题激波解的整体存在性

本文用改进的Glimm格式的方法,研究一维活塞问题当活塞的运动速度是一个常数的扰动时含有激波的弱解的存在性.对波的相互作用以及扰动波在主激波和活塞上的反射作出了精确的估计,在对主激波的强度不加限制的情况下证明了激波解的整体存在性.     

Investigation of factors mediating the effectiveness of authentic projects in the teaching of elementary statistics

Four instructors used authentic research projects and related curriculum materials when teaching elementary statistics in secondary and undergraduate settings. Projects were authentic in that students selected their own variables, defined their own research questions, and collected and analyzed their own data. Classes using these projects were considered treatment groups in the study. Student outcomes measured were content knowledge, perceived usefulness of statistics, and statistics self-efficacy. These outcomes were compared with those of students taught by the same instructors in prior terms without authentic projects (the control groups). Although all three outcomes increased for the treatment group in both settings, simple t-tests indicated that these gains were not statistically significant. Variables were identified as potential factors mediating the effects of treatment, and multivariate and univariate models were then used to examine treatment, setting, instructor effects, and student achievement level as variables jointly contributing to these three outcomes. Follow-up analyses suggested that some treatment effects were significant in more restricted contexts (e.g., in certain settings for certain types of students). The models also suggest multiple significant interactions among treatment, setting, individual instructor, and student achievement level, particularly on affective outcomes.     

多重尺度法的计算机计算——一类非线性方程组的狄立克雷问题

应用多重尺度的边界层方法和计算机符号运算研究一类非线性方程组的边值问题解的渐近性质,构造出解的渐近展开式和估计了余项.并分析一个实例.为多重尺度方法的应用提供新的前景.     

用可视化方法优化微生物培养基的营养条件

应用可视化方法,对生物发酵培养基的营养条件进行优化.以培养基组成构建多维向量空间,通过降维分析法将多维空间的拓扑结构展现在二维平面上,变成可视化图像,并自动产生目标函数等值线.从中得出同时满足各项指标值的最佳操作区域,并运用逆映射公式将得出最优化区域逆推到原高维空间,进而得到最优培养基组成.以锌酵母为例,介绍可视化方法优化全过程.     

损伤对粘弹性矩形板非线性动力特性的影响

研究了考虑损伤效应的粘弹性矩形板在横向周期载荷作用下的非线性动力学问题．基于Von Karman方程、Boltzmann叠加原理和连续损伤力学理论,建立了以中面位移表示的考虑损伤效应的粘弹性薄板的非线性动力学方程,然后,应用有限差分法和Newmark法进行求解,并与相应的文献作出了比较．具体讨论了外载荷参数和板的几何尺寸对含损伤效应的粘弹性板非线性动力响应的影响．数值结果表明,考虑损伤效应时,结构的非线性动力响应会发生显著的变化．     

A power meaning of multiplication: Three eighth graders’ solutions of Cartesian product problems

This article examines data from five teaching episodes with three eighth grade students who were participants in a 3-year constructivist teaching experiment. The five teaching episodes were a transition point in the teaching experiment: the students were beginning to work in contexts that were deemed to support their development of a meaning for squaring quantities—a power meaning of multiplication. Prior to these teaching episodes, the students had worked in contexts that were deemed to support their development of a linear meaning of multiplication.     

DNA序列的特征数值及相似性分析

利用2维图表示DNA序列,计算与该图对应的距离矩阵,求出距离矩阵的不变量—距离矩阵主对角线以外的次对角线之和的平均值,进而得到了DNA序列的一种特征数值,利用这种新的特征数值,对DNA序列进行相似性比较,得到了与现有的资料符合很好的结果.     

Effects of Cone Angles on Nonlinear Vibration Responses of Functionally Graded Shells北大核心CSCD

The nonlinear vibration responses of functionally graded materials (FGMs) shells with different cone angles under external loads were studied. Firstly, the Voigt model was employed to describe the physical properties along the thickness direction of FGMs conical shells. Then, the motion equations were derived based on the 1st-order shear deformation theory, the von Kármán geometric nonlinearity and Hamilton’s principle. Next, the Galerkin method was applied to discretize the motion equations and the governing equations were simplified into a 1DOF nonlinear vibration differential equation under Volmir’s assumption. Finally, the nonlinear motion equations were solved with the harmonic balance method and the Runge-Kutta method, and the amplitude frequency response characteristic curves of the FGMs conical shells were obtained. The effects of different material distribution functions and different ceramic volume fraction exponents on the amplitude frequency response curves of conical shells were discussed. The bifurcation diagrams of conical shells with different cone angles, as well as time process diagrams and phase diagrams for different excitation amplitudes, were described. The motion characteristics were characterized by Poincaré maps. The results show that, the FGMs conical shells present the nonlinear characteristics of hardening springs. The chaotic motions of the FGMs conical shells are restrained and not prone to motion instability with the increase of the cone angle. The FGMs conical shell present a process from the periodic motion to the multi-periodic motion and then to chaos with the increase of the excitation amplitude. © 2022 Editorial Office of Applied Mathematics and Mechanics. All rights reserved.     

非线性中立双曲型泛函微分方程解的振动判据

讨论一类多滞量非线性中立双曲型泛函微分方程解的振动性质，获得了其一切解振动的充分条件；指出了与普通双曲型偏微分方程质的差异。     

一类弹性储液箱同液体耦合晃动问题的分岔行为分析

建立了弹性圆柱型储液箱同液体耦合系统在外激励下的非线性振动方程组．采用多尺度法、奇异性理论研究此非线性振动系统共振解的分岔行为,通过对其分岔行为的分析和讨论,得到了这一系统的多种转迁集和分岔图,建立了系统参数与其拓扑分岔解的联系,并且分析了不同参数下系统的分岔特性,为实现储液器参数的优化控制提供了理论依据．     

A simulation study for the distribution law of relative moments of evolution

Nine selection‐survival strategies were implemented in a genetic algorithm experiment, and differences in terms of evolution were assessed. The moments of evolution (expressed as generation numbers) were recorded in a contingency of three strategies (i.e., proportional, tournament, and deterministic) for two moments (i.e., selection for crossover and mutation and survival for replacement). The experiment was conducted for the first 20,000 generations in 46 independent runs. The relative moments of evolution (where evolution was defined as a significant increase in the determination coefficient relative to the previous generation) when any selection‐survival strategy was used fit a Log‐Pearson type III distribution. Moreover, when distributions were compared to one another, functional relationships were identified between the population parameters, revealing a degeneration of the Log‐Pearson type III distribution in a one‐parametrical distribution that can be assigned to the chosen variable—evolution strategy. The obtained theoretical population distribution allowed comparison of the selection‐survival strategies that were used. © 2012 Wiley Periodicals, Inc. Complexity, 2012.