1-3型水泥基压电复合材料在冲击载荷下的电学响应

采用切割-浇注法制备1-3型水泥基压电复合材料,并利用分离式霍普金森压杆测量装置(SHPB),对PZT5压电陶瓷和1-3型水泥基压电复合材料在冲击载荷作用下的力电响应进行实验研究与分析。研究表明:在冲击载荷作用下,PZT5压电陶瓷和1-3型水泥基压电复合材料的电位移与应力具有较好的动态响应;在相同荷载作用下,两者的电位移随应变率的增加而增加,且产生相同应变所对应的应力值也随着应变率的增加而增加,表现出"率相关"的材料特征。     

压电陶瓷材料电学性能参数测量研究

从双层压电梁在电场作用下的位移响应与电场的关系式出发，借助于试验数据逆推导出压电陶瓷材料的电学性能参数。位移响应的试验数据采用非接触激光测振仪得到。该文方法相对压电参数测量的静态法、动态线路传输法和动态电容法减少了许多中间测量环节和等效处理手段，且易于具体实施，相对于动态位移法又有更好的精度，为压电陶瓷类材料电学性能参数测量提供了一种全新的测量方法。     

基于Nd:YAG激光回馈干涉效应的PZT精密测量技术与系统

压电陶瓷在精密控制中具有重要作用,而其在快速控制中的实际高频响应却缺少有效且精密的方法。总结了目前测量压电陶瓷特性的方法,分析了测量中存在的困难和不足,使用基于激光回馈干涉原理的Nd:YAG微片激光回馈干涉测量系统对压电陶瓷的动态特性进行了研究。使用两种压电陶瓷在100 Hz~7 kHz驱动电压下对位移响应进行了测量,相应测量位移范围7~34 nm。测量精度达到纳米量级,对较高的振动频率实现了准确测量。该方法具有很高的测量精度,对被测对象要求较低。     

压电加速度传感器测量电路的设计

在动态测量中,压电加速度传感器是振动与冲击测量的核心部件。但压电加速度传感器作为一个能产生电荷的高内阻发电元件,产生的电荷量很小。通过一般的测量电路测量压电片上的电荷时,电荷会被输入阻抗迅速泄漏而引入测量误差。因此,提出一种采用集成芯片TL084代替大量分离元件的电荷放大器的测量电路设想。通过与标准电荷放大器的性能对比,实验表明本设计可行,且对研究类似测量系统的设计开发具有一定的借鉴意义,有望应用于各种动态力、机械冲击与振动的测量及声学、医学、力学等领域。     

压电双晶片型惯性冲击式直线精密驱动器研究

研制了一种以自由端带有集中质量的悬臂式压电双晶片为驱动单元的新型惯性冲击式直线精密驱动器。对自由端带有集中质量的悬臂式压电双晶片的动态特性进行了有限元法(FEM)分析和实验研究,提出了压电双晶片型惯性冲击式精密驱动器特定的定频调压驱动方法。对压电双晶片型惯性冲击式直线精密驱动器进行了性能测试,测试表明该驱动器具有结构简单,行程大,驱动力强和分辨率高等特点,特别是其成本不足传统惯性冲击式驱动器的百分之一。     

压电智能复合材料层板冲击压电响应仿真分析

基于1阶剪切变形理论,采用有限单元方法,建立了压电智能复合材料层板有限元模型,采用低速冲击对其压电传感器的瞬态响应进行了仿真分析.结果表明,各压电传感器响应信号特征与各传感器的布置位置、冲击荷载位置及层板的边界条件等因素有关.综合分析各传感器响应信号并进行特征提取,可建立传感器响应与冲击位置间的非线性关系,从而实现结构加载损伤位置的自诊断.     

超声键合过程中键合压力特性的实验研究

建立了超声键合压力的测量工作台,对工作台进行静态线性度标定和动态重复性测量,利用动态压电测力传感器对超声键合系统键合压力大小进行测量,得出不同压力作用下传感器力响应曲线图,分析其频谱图,发现保持某一固定功率(4.5格2.25W),可以找到合适的键合压力(5格0.719N)与其匹配.这些实验现象和结果可作为超声键合过程参数匹配及优化的依据.     

PVDF压电薄膜传感特性研究

聚偏氟乙烯(PVDF)压电薄膜是一种压电高分子材料,它具有独特的压电效应,被广泛应用于振动测量等各个领域。但对于压电薄膜在受到外加应力时其输出特性的研究较少。该文理论分析了PVDF压电薄膜的传感机理和电路等效模型;然后利用COMSOL软件进行仿真;最后实验研究了PVDF压电薄膜在不同激励振幅、激励频率及外加应力下的动态响应。研究结果表明,压电薄膜输出信号的幅值与薄膜振幅成线性关系,与所受外加静态应力无关。     

PVDF薄膜机电特性试验装置设计

与采用悬臂梁或Hopkinson压杆等来研究聚偏二氟乙烯(PVDF)薄膜性能不同,该文针对PVDF压电薄膜在不同载荷和频率范围内机电响应特性问题,设计了一种可全面研究PVDF压电薄膜机电响应特性的试验装置。该装置由激振器加载部分与应变、加速度、动态力测量部分及试验台架组成,利用此装置可实现动态力的快速加载及加载力、应变及PVDF薄膜响应的同步测量。利用该试验装置对PVDF压电薄膜实施了动态加载试验,获得了较稳定的PVDF响应、应变及加载力的试验曲线,证实了该试验装置的可靠性,为PVDF压电薄膜粘弹性和压电特性的研究提供了一种试验手段。     

热释电系数的测量方法

描述热释电系数的两种测量方法。其一为电荷积分法，测试系统简单，测量数据准确，且能满足零电场条件下的测量。其二为动态电流法，采用调制热源技术，研究在特定温度条件下热释电材料的动态热释电响应。     

光电探测系统激光辐照效应的远场仿真分析

建立了激光辐照软损伤的远场仿真模型,仿真了不同作用距离下激光辐照的远场功率分布,三维关系曲线是一个斜率很大的上翘鞍形结构。分析和讨论了单元探测型和CCD型两种光电探测系统的远场激光辐照软损伤情况。     

The effect of a dielectric cover on the current distribution and input impedance of printed dipoles

The effect of the thickness and relative permittivily of a dielectric cover on a printed microstrip dipole has been analyzed. It is shown that the current distribution and the input impedance are, in general, very sensitive to variations of the cover parameters. For a dielectric plate with a constant thickness the dipole resonant length decreases substantially with an increase of the relative permittivity. Because of the limited bandwidth presented by single-element microstrip antennas the effects of the dielectric cover on the design of these antennas have to be carefully considered. For the calculation of the current distribution, the Hertz vector potential associated with the problem was determined for an element of current located in a stratified medium with four layers. Pocklington's integral equation was solved for the currents, using Galerkin's method with piecewise-sinusoidal expansion and weighting functions.     

A double-element broad-band liquid crystal tunable filter-factorsaffecting contrast ratio

A double-element broad-band liquid crystal tunable filter consisting of a high-order quartz wave plate in series with a very-low-order electrooptically tunable liquid crystal phase plate and placed between crossed polarizers is described. A possible application for such a device is protection against intrusive laser radiation. The advantage of this double-element filter over a single-element low-order LC filter is that it increases the wavelength resolution of the device, which, when operated in the protect mode, allows continued sensing of the scene. Experimental and theoretical studies were made of the contrast ratios obtainable with such a filter     

利用成像型任意反射面速度干涉仪测量石英中的冲击波速度

在神光Ⅲ原型激光装置上,利用自行研制的成像型任意反射面速度干涉仪（I-VISAR）对石英中冲击波速度进行了测量,获得了清晰的实验信号。实验结果表明,在8路能量为400 J、波长为351 nm的激光注入腔靶时,经过60μm的Al后,石英中的冲击波速度为36.47 km/s。     

在冲击作用下捷联惯性系统结构的设计方法

针对捷联惯性系统对冲击环境敏感,在冲击条件下动态精度差的特点,分别分析了微机电系统(MEMS)陀螺仪、石英加速度计及安装框架的冲击适应性。提出了在冲击载荷作用下捷联惯性系统结构设计的方法:首先,从结构设计上保证传感器的正交布局;其次,设计了一种简单实用的隔冲结构方式,通过有限元仿真和实物试验,结果表明,此方法可靠有效。     

Electron-beam controlled switching using quartz and polycrystallineZnS

Results of electron-beam controlled switching experiments with switch samples of quartz crystal and polycrystalline zinc selenide (ZnSe) are presented. For switch samples of both materials, drastic reductions of the switch resistance were induced by the electron beam. The quartz sample showed very fast temporal response (less than 1 ns) with potential applicability for current control. The ZnSe samples, on the other hand, showed longer current transients (on the order of 10 ns) with exponential development of the switch resistance after the electron beam pulse     

Fibrillating Parameters of Direct and Alternating (20 Hz) Currents Separately and in Combination--An Experimental Study

In an experimental Study on anesthetized mongrel dogs, the current levels of dc and 20-Hz ac, both singly and in combination, necessary to evoke ventricular fibrillation were investigated. The following shock durations were investigated: for dc; 50, 100, 200, 500, 1000, and 2000 ms, for 20-Hz ac; 100, 200, 500, 1000, and 2000 ms, and for combination dc and ac shocks; 200, 500, 1000, and 2000 ms. It is shown that threshold fibrillating currents of a given shock duration and type are apparently more nearly log normally than normally distributed. The tests of linear combinations of ac and dc resulted in the following working principles. The hazard of any shock of whatever combination of ac and dc is essentially the same as that of a pure ac shock of 1) the same duration and peak-to-peak current if the shock duration is 0.5 s or longer, or 2) the same peak current if the duration is 0.2 s (and possibly shorter).     

Lethal electric currents

Commercial-frequency currents of a few milliamperes flowing through the body will cause muscular contractions, resulting in the inability of the victim to release his grasp on a live conductor. Values of ``let-go' current are very important criteria in the establishment of safe-current requirements. Since ventricular fibrillation, a condition in which circulation is arrested, is probably the most common cause of death from electric shock, studies of minimum fibrillating currents under various conditions are also significant. This article discusses investigations of both let-go and fibrillating current and presents some of the experimental data that have been obtained to date.     

Multibit microwave memory readout from a ferrite-loaded stripline

Experimental multibit-microwave-memory-readout results obtained using direct-loaded and secondary-coupled toroidal ferrite memory elements in a strip transmission line are presented. Typical single-element readout response to a 4ns 650mA interrogation pulse was a bipolar 15ns ±21 mV signal using secondary coupling. The output-response magnitude decreases significantly as the number of memory elements loading the same stripline is increased.     

JS—2红外涂料与95号玻璃复合体高热辐射强度的研究

将作者研制的JS-2红外涂料涂复在95号硬质玻璃载体上构成复合体.与乳白石英玻璃相比较,在相同的条件下,其热辐射强度可提高10%以上.