Development of integrated precision vibration-assisted micro-engraving system

A novel precision vibration-assisted micro-engraving system was developed by the integration of fast tool servo and ultrasonic elliptical vibration system, in which the flexure hinge was designed to avoid backlash and PID control algorithm was established to guarantee specific precision. Apart from experimental validation of the performance of the system, various micro-V-grooves cutting experiments on aluminum alloy, ferrous material and hard cutting material were performed, in which Kistler force sensor was used to measure cutting force. Through experiments, it was clear that the vibration-assisted micro-engraving system can ensure good quality of micro-V-grooves and reduce cutting force by about 60% compared with traditional removal process without ultrasonic vibration.     

Stochastic optimal control of first-passage failure for rectangular thin plate vibration model under gaussian white-noise excitations

A rectangular thin plate vibration model subjected to inplane stochastic excitation is simplified to a quasinonintegrable Hamiltonian system with two degrees of freedom. Subsequently a one-dimensional Ito? stochastic differential equation for the system is obtained by applying the stochastic averaging method for quasi-nonintegrable Hamiltonian systems. The conditional reliability function and conditional probability density are both gained by solving the backward Kolmogorov equation numerically. Finally, a stochastic optimal control model is proposed and solved. The numerical results show the effectiveness of this method.     

走进儿童画的世界

儿童画是指儿童自己动脑动手所创作的画。它没有固定的表现形式,可以是彩色水笔画,油画棒画,也可以是国画等等表达形式,只要是适合儿童学习的画种都可以是儿童画的表现形式。儿童画从内容到形式,无不渗透着成人想不到的美妙和趣味。     

一类奇数阶非线性脉冲微分方程的振动性与渐近性

研究了一类奇数阶非线性脉冲微分方程解的振动和渐近性态.应用脉冲微分不等式和Ricatti变换,得到这类奇数阶非线性脉冲微分方程或者振动,或者渐近的若干充分性判定定理.     

平板叶片的相关激励响应试验

为了研究不同频率的激振力叠加作用下平板叶片的位移响应变化,在平板叶片上选取激励点和多个响应点进行相关性激励试验。试验中,首先运用设计的加法器对频率为112、280和583 Hz的简谐力分别进行叠加,然后以压电陶瓷片作为激振器对平板叶片进行激励,同时以压电陶瓷片作为感应器采集位移响应,最后应用谱分析方法对位移响应进行分析。通过对比不同频率的激振力叠加作用下的位移响应自功率谱幅值,发现自功率谱幅值比单一频率激振力作用时有所降低,并且降低的程度和与其叠加的激振力频率的大小和个数有关,叠加的个数越多,降低的程度越大。     

基于LPC2132的轴承振动监测系统的设计

为了实时监测机械设备运行状态,避免严重机械故障发生,减少损失,设计了一种基于LPC2132微处理器的轴承振动监测系统,并对数据采集模块、主控模块、上位机显示模块进行了设计和分析．通过Matlab对振动信号进行分析,显示该系统具有采集精度高、性能稳定、成本低廉等优点,实现了对轴承振动信号的实时监测．     

同尺寸弯振圆盘辐射声场指向性研究

对薄圆盘的弯曲振动和辐射声场的特性进行了研究,推导出了三种边界条件下圆盘辐射声场指向性的数值表达式,编制程序并研究其声辐射特性。结果表明,相同尺寸不同边界条件下圆盘指向性的尖锐程度不同,固定边界条件下圆盘辐射声场指向性最佳,自由边界条件下较差,并且随着圆盘模式和几何尺寸的增加各边界条件下圆盘的指向性均逐渐变差。     

变一变

下图是由十五根火柴棒组成的大小九个三角形。请你只移动2根火柴棒,使图中只剩下七个三角形。该如何移呢?     

移火柴棒

下图是由9根火柴棒围成的3个三角形,请只移动其中的3根火柴棒,把3个三角形变成5个三角形。     

寄语

闻邦椿,1930年生,东北大学教授,博士生导师,中国科学院院士。国际机器理论与机构学联合会(IFToMM)中国委员会委员,国际转子动力学技术委员会委员,亚太振动会议指导委员会委员,中国振动工程学会名誉理事长