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.     

反弹还是——宏观与微观的数据透视

目前，中国的宏观经济环境空前复杂。2008年9月15日，美国投资银行雷曼兄弟的破产拉开了这场全球性金融危机的序幕，以2008年第三季度为分水岭，中国经济从2007年的扩张急速转为收缩。     

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...     

“高电压技术”课程教学改革的探讨

随着高电压技术及相关学科的迅猛发展,作为电气工程及其自动化专业重要的基础专业课＂高电压技术＂越来越有必要进行教学改革以适应当前的形势。本文通过分析＂高电压技术＂课程的特点及教学中存在的问题,从教学内容、教学方法及手段、实践教学环节等方面对该课程的教学改革进行了初步探讨。     

科技故事演说家

凯文·布鲁克斯是一位1999年毕业于MIT的博士，他以自己独特的叙事技巧征服了观众——同时也帮助设计师和工程师们发明出更好的产品。     

TS-01C型中波发射机高频激励器中的三级可编程分频器原理分析

文章介绍了TS-01C型中波广播发射机高频激励器的特点，并对其使用的三级可编程分频器的原理进行了分析。     

基于口令识别的无线控制系统的设计

文章将口令识别与无线通信、机器人控制相结合,实现了基于口令识别的智能车无线控制系统。该系统包含接收和识别口令的主机,发送指令和接收指令的通信模块以及带有特定功能的智能车。主机识别口令后,以无线传送方式将指令发送给智能车,智能车按指令实现相应功能。主机和智能车都基于嵌入式系统。主机硬件电路由三星S3C6410处理器和外围电路组成,口令识别部分采用连续隐马尔科夫模型算法。实验表明,该系统有良好的稳定性和实用性。     

柔软的“发电机”

意义：电场活化聚合物又称人工肌肉，是一种在发生形变时可以产生能量的弹性物质。这类被称为“电场活化聚合物发电机”（Dielectric Elastomer Generator，DEG）的可变电容发电机在收集能量方面功能强大。过去的DEG需要又大又硬又昂贵的外置电极。     

用理想气体物态方程求玻耳兹曼常量——宏观理论与微观理论的印证

从热力学与统计物理两个角度建立了理想气体的物态方程，通过比较两个方程求出玻耳兹曼常量，说明宏观理论与微观理论是相互印证的．