用空牛奶盒做有趣的物理实验

有一种纸质牛奶盒,实际上它不是一个简单的纸盒,而是由纸、铝、塑组成的六层复合包装盒,俗称"利乐砖".牛奶喝完了,我们就用利乐砖做几个有趣的实验吧.     

“曲线运动”的速度方向演示实验缺陷及改进

曲线运动的速度方向是高一物理"曲线运动"一节的教学难点,教材试图通过"砂轮"和"转伞"的实例加以说明.可是很多学生没见过用砂轮磨刀具时形成的火星是何形状,课堂上演示此实验,既不现实,也不安全.     

60微弧度激光发射天线模拟设计及测试

为了实现远距离激光能量传输,根据光学相差理论和优化的组合透镜设计,着重研究了影响激光发射天线发射的激光光束随望远光学系统离焦量的变化规律和初步的实验测试.实验中利用三级像差理论消除激光天线系统像差对离焦量控制精度的影响,在不同的距离,实现了远场激光光斑的测量.采用高斯曲线拟合法,消除CCD探测器的饱和影响,提高了远场激...     

品味立体几何中的“即时定义题”

所谓“即时定义题”就是给出一个新定义，要求学生在短时间内利用这个新定义和已学过的知识解决题目给出的问题．旨在考查学生接受新事物、临场发挥等综合能力和创新能力．下面采撷四道立体几何中的即时定义题并予以深刻剖析，供同学们品读．     

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.