可否走停

你有没有注意到,我们周围的许多事物,只出现两种情形？ 电灯不是开的,就是关的; 婴儿不是睡着的,就是醒着的; 门不是开的,就是关的; 吊桥不是升起的,就是放下的。     

两类图的符号控制数

图G的符号控制数γs(G)有着许多重要的应用背景,因而确定其精确值有重要意义.Cm表示m个顶点的圈,n-Cm和n·Cm分别表示恰有一条公共边或一个公共顶点的n个Cm的拷贝.给出了n-Cm和n·Cm的符号控制数.     

Gauss白噪声激励下分数阶导数系统的非平稳响应

研究了Gauss(高斯)白噪声激励下具有分数阶导数阻尼的非线性随机动力系统的非平稳响应.应用等价线性化方法将非线性系统转化为等价的线性系统,之后采用随机平均法获得系统响应满足的FPK(Fokker-Planck-Kolmogorov)方程,其中分数阶导数近似为一个周期函数.使用Galerkin方法求解FPK方程进而得到系统的近似非平稳响应.数值结果验证了方法的正确性和有效性.     

基于C~2R模型的广义链式网络DEA模型

传统网络DEA方法是将传统DEA方法评价过程中的"黑箱"打开,考虑输入到输出的中间环节,对生产过程中的各个环节分别评价。传统网络DEA方法获得的是相对于有效决策单元评价的结果,但有时可能要相对于非有效决策单元或者非决策单元进行评价,传统网络DEA方法无法解决该类问题。为此给出相对于非有效决策单元或者非决策单元进行评价的基于C~2R模型的广义链式网络DEA模型,并探讨相关性质.     

基于ST7单片机的液体电导率传感器

基于ST7LITEF15B单片机研制了用于实验教学的低成本液体电导率传感器. 介绍了测试方案、系统的硬件结构和软件的设计思路,进行了典型标样的测量实验,结果表明该液体电导率传感器的研制是成功的.     

Analytical and experimental studies on nonlinear characteristics of an L-shape beam structure

This paper focuses on theoretical and experimental investigations of planar nonlinear vibrations and chaotic dynamics of an L-shape beam structure subjected to fundamental harmonic excitation,which is composed of two beams with right-angled L-shape.The ordinary differential governing equation of motion for the L-shape beam structure with two-degree-of-freedom is firstly derived by applying the substructure synthesis method and the Lagrangian equation.Then,the method of multiple scales is utilized to obtain a four-dimensional averaged equation of the L-shape beam structure.Numerical simulations,based on the mathematical model,are presented to analyze the nonlinear responses and chaotic dynamics of the L-shape beam structure.The bifurcation diagram,phase portrait,amplitude spectrum and Poincare map are plotted to illustrate the periodic and chaotic motions of the L-shape beam structure.The existence of the Shilnikov type multi-pulse chaotic motion is also observed from the numerical results.Furthermore, experimental investigations of the L-shape beam structure are performed,and there is a qualitative agreement between the numerical and experimental results.It is also shown that out-of-plane motion may appear intuitively.     

Achievement of chaotic synchronization trajectories of master-slave manipulators with feedback control strategy

This paper addresses a master-slave synchronization strategy for complex dynamic systems based on feedback control.This strategy is applied to 3-DOF planar manipulators in order to obtain synchronization in such complicated as chaotic motions of end-effectors.A chaotic curve is selected from Duffing equation as the trajectory of master end-effector and a piecewise approximation method is proposed to accurately represent this chaotic trajectory of end-effectors.The dynamical equations of master-slave mani...     

浅谈物理规律教学的有效性

美国的著名学者波斯纳（Posner）提出的教师成长公式：成长=经验＋反思，新课标的实行，要求我们教师必须要从单纯的知识传递者走向研究者、反思者。在新时期，我们教师不仅仅需要有较为丰富的专业学识，还必须要善于对教学问题进行研究和反思。面对新形式，我们教师必须要积极地对自己的学科教学进行反思。本文主要就在新课标下高中物理教学进行反思。     

碱硅酸盐玻璃的电导率

在Na_2O-SiO_2、K_2O-SiO_2和Cs_2O-SiO_2系统中,已在一定的温度和组成范围内测定过玻璃的电导率。均质的Cs_2O-SiO_2和K_2O-SiO_2玻璃的激活能随着玻璃的成份不同而变化,并且,由于Na_2O-SiO_2玻璃分相作用的影响使其发生不连续的变化。在简单的碱硅酸盐玻璃中,早已发现等温的电导率总是随着碱浓度的增大而增高。电导激活能与成分的关系曲线形式还不太清楚。在某些情况下,根据在各个成分下记录下来的折断点,可用不同斜率的直线描述上述关系;在另外一些情况     

担载液相催化剂的研究——Ⅴ. 担载液相催化剂的EXAFS表征

本文利用EXAFS(Extended X-ray Absorption Fine Structure)对铑基担载液相催化剂(Supported Liquid Phase Catalyst SLPC)进行了结构表征。采用球面波理论对SLPC的EXAFS结果进行了多参数拟合。结果表明,在新鲜催化剂上,铑络合物以二聚物形式存在,推测其结构为(PPh_3)_2(CO)Rh-Rah(CO)(PPh_3)_2,Rh-C-O偏离共线分布。在经过羰化反应活化的活性SLPC上,铑络合物为单核的HRh(CO)_2(PPh_3)或Rh(CO)_2(PPh_32)_3。文中还讨论了SLPC的XRD谱。