输电塔动力特性计算与模态试验研究

输电塔是国家电网的重要组成部分,具有结构高、跨度大、柔性强等特点,对风荷载反应灵敏。建立能反映输电塔动态特性的模型对风致振动控制至关重要。为研究输电塔理论模型的准确程度,分别建立3种输电塔实验模型,包括多质点模型、梁单元有限元模型和梁-杆混合单元有限元模型,并对其进行模态分析;同时采用锤击法,以单点激励多点响应(SIMO)的测试方法对输电塔实验模型进行模态测试。将各方案与测试结果进行比较分析,结果表明:梁-杆混合模型的求解精度高于另外两种计算模型的精度,能较好模拟输电塔的动力特性,是最优的输电塔模拟方案。     

基于干涉法的非球面测量技术

随着光学精密加工技术的发展,非球面光学元件在各种光学系统中广泛应用,高精度非球面检测技术对非球面光学元件的发展意义重大。论述了基于干涉法的非球面面形误差检测技术。根据检测原理,分别对零位干涉检验法与非零位干涉检验法进行了详细介绍。概述了近年来主流的非球面检测技术现状,展望了非球面面形检测技术的发展趋势。     

线性调频连续波雷达发射信号的动态测试

本文提出了一种利用点目标差拍信号对线性调频连续波雷达的发射信号进行动态测试的方法，可以实现扫频线性度、扫频斜率、扫频带宽以及瞬时频率偏离的动态测试。文中给出了该方法的原理、误差分析实验结果。     

Interferometric Measurement of Holographic Lenslets

Abstract

A holographic optical element can either be characterized by the wave aberrations or by the point spread function or alternatively by the modulation transfer function. Here we propose the measurement of the wave aberrations with the help of a Twyman-Green interferometer adapted to the requirements for testing holographic optical elements. The evaluation of the interferograms is done with the phase-shifting technique. The resulting wave aberrations are expressed by Zernike coefficients. In addition to this evaluation, the point spread function and the modulation transfer function are calculated from the wave aberrations. The set-up, the evaluation method and also exemplary results of a tested holographic optical element are presented.     

机载合成孔径雷达干涉敏感度分析

采用视向量正交分解方法,在斜视干涉几何关系下,导出了机载干涉SAR目标三维高程重建的解析解,推导了干涉敏感度方程,并进行了详尽的敏感度分析。结果表明,利用导出的敏感度方程可以考察载机姿态测量偏差对干涉三维重建和多普勒频率估计的影响,弥补了目前敏感度分析的不足。     

A Novel Method of Distance Measurement Based on Pulse Position Modulation and Synchronization of Chaotic Signals Using Ultrasonic Radar Systems

This paper deals with a novel method of transmission and receipt of a signal based on both the property of two chaotic systems generating the same chaotic signal when they are synchronized and the property of pulse position modulation (PPM) to be insensitive to the distortions of the transmission channel. The method is discussed in the context of ultrasonic radar systems, in which the transmitter and receiver, which consist of ultrasonic sensors, are near each other, and the received signal consists of the transmitted signal reflected by an obstacle. A reference sinusoidal signal is superimposed to a chaotic signal generated by a master chaotic system, and the whole signal is modulated according to the PPM method and transmitted by the sensor. The received signal is demodulated, and the demodulated signal forces a slave chaotic system to generate the chaotic signal embedded in it, which allows recovery of the sinusoidal signal by subtracting this chaotic signal from the demodulated echo. The difference of the phases of the reference sinusoidal signal and the recovered sinusoidal signal allows computation of the time of flight of the signal and, consequently, the distance of the radar system from the obstacle. The novel method is illustrated and tested by both simulation and experiments. The interference problem between the considered radar system and other radar systems ( crosstalk) is also addressed, and a solution is proposed to avoid it.     

实现微牛级动态推力测试的方法和试验研究

本文介绍了一种微牛级推力的测试方法.该方法的基本思想是将微牛级推力通过悬臂梁转换成微米级位移,然后通过微位移传感器测试该微位移,得到微推力大小.该方法的关键之处在于如何从悬臂梁的自由振动中分离出弯曲量.文章介绍了该方法的理论模型、系统实现以及测试结果.用于微胶体推进器测试时,与理论值相比较,该方法的误差约为10%.     

自消除环境扰动的干涉型波长漂移测量

介绍了一种新颖的干涉波和探测方法,该方法可用于光学传感系统中测量波长的漂移。在本文法中,采用了另一已知波长的参江与被测光波长的光一起注入探测系统中,其中参考波长用于稳定干涉仪的光程差,以保证波长探测系统对环境扰动（如温度波动、机械振动）的不敏感。初步实验表明,使用本可将系统的信噪比提高２５ｄＢ。     

System of Strain and Load Measurement in Dynamic Testing of Materials

A multichannel system of high-speed recording of strains and loads during fracture toughness tests of materials has been developed. A four-channel analog-to-digital converter was used to record signals. Tests were carried out using a rotary and a vertical impact testing machines at various loading rates and temperatures. Some results are presented for impact testing of Charpy specimens with recording of load variation at supports during tests.__________Translated from Problemy Prochnosti, No. 3, pp. 140 – 145, May – June, 2005.     

Engineering Measurement and Testing of Land-based Structures Using Strain Gauges

This paper presents a number of case histories illustrating the benefits and costs of certain types of engineering measurement and testing, with a focus on strain‐gauged land‐based structures. The benefits are described mainly in terms of safety, economy and environment. The costs are related to the amount of data collected and processed. The paper concludes with some technical and financial guidance for clients, owners, consultants and contractors who may be considering these types of activities.     

机动车雷达测速仪检测的现状及测速误差分析

本文就国内外机动车雷达测速仪检测方法的现状进行了介绍,并对检测过程中误差的主要来源进行了探讨,给出提高雷达测速仪模拟检测准确度的理论方案。     

干涉测长中测量湿度的一种新方法

介绍了一种通过测量相对湿度和空气温度来计算湿度值的方法，并推导了计算公式。     

高双折射光纤双折射参数的精密干涉测量法

本文应用干涉技术对高双折射光纤的双折射参数进行了精密测量。这种方法也可以应用于测量高双折射偏振保持光纤中模式耦合点的空间分布。     

多角度动态光散射法的纳米颗粒精确测量

基于动态光散射原理,采用自主研发的多角度动态光散射装置,对纳米及亚微米颗粒粒径准确测量方法进行了探究。自研装置采用带有光阑组的精密入射光路设计,以及匹配液池及Beam-stop设计,极大提高了信噪比;同时避免了测量角度的互补方向上,由于样品池与空气界面折射率不同导致的反射光信号对有效信号的干扰。在此基础上,对不同浓度、粒径的聚苯乙烯(PS)颗粒溶液进行了测定及不确定度分析。结果表明,对同一粒径的PS颗粒,增加颗粒浓度时,多重散射首先发生于大、小测量角度,越接近90°,发生多重散射的浓度越高;随着粒径增大,受不可忽略的颗粒间相互作用的影响,粒径测量结果表现出了强烈的角度依赖性,甚至波动性。     

非球面非零位横向剪切干涉检测与波前重建

本文分析了非球面非零位检测中3种典型的非球面度及其变化率、调整误差、回程误差以及干涉仪系统误差,提出了非球面度变化率是影响检测误差的主要因素,并给出了非球面非零位检测面形加工误差的确定方法.对基于Zernike多项式拟合的最小二乘法和系数转换法进行了对比研究,分析了剪切量和多项式拟合阶数对波前重建精度的影响,并给出了数值模拟结果.为了验证以上方法的可行性及检测精度,针对一单点金刚石车削的抛物面反射镜,利用顶点球作为测试波前进行非零位横向剪切干涉检测,并用最小二乘法进行波前重建.实验结果表明,在非球面度变化率最大的反射镜边缘处面形误差最大,达到0.203μm,研究结果为横向剪切干涉仪用于非球面加工过程中在位检测提供了技术支撑.     

用多齿分度台检测小度盘的刻线位置误差

本文介绍了用多齿分度台检测小度盘的刻线位置误差及其数据处理方法。对检测结果的可靠性进行了分析与估算。     

Center of Mass Measurement Using an Array System

A method is described for measuring the center of mass of uniform object-images using a two-dimensional array system. Measurement error in the center of mass is computed for various images projected in different positions with respect to the array matrix. The effects of two types of two-dimensional image perturbation on measurement accuracy are analyzed.     

磁控摩擦阻尼器对信号塔的地震反应控制

针对常摩擦阻尼器摩擦力恒定的问题,设计一种新型筒式磁控变摩擦阻尼器,并建立磁控变摩擦阻尼器的力学模型。以机场信号塔结构为工程背景,将信号塔的三维空间有限元模型简化为二维串联多自由度模型;采用LQG主动控制算法和界限Hrovat半主动控制策略对磁控变摩擦阻尼器实施控制;讨论常摩擦阻尼器被动控制和磁控摩擦阻尼器半主动控制对地震作用下信号塔结构振动响应的控制效果。计算结果显示,磁控摩擦阻尼器的半主动控制取得明显优于常摩擦阻尼器被动控制的减振效果,在实际工程中有着良好的应用前景。     

典型输电塔气弹模型设计及动力特性研究

输电塔结构受到风荷载激励,极易引起其气动弹性失稳,造成大幅振动,严重威胁着输电线路安全稳定运行。为研究高压输电塔结构风振动力特性,以某典型输电塔为原型,按照结构动力学相似准则,采用一种新型设计方法制作输电塔气弹模型,并利用有限元分析软件以及相关测试系统对其进行动力学分析,验证气弹模型的准确性。最后,进行不同风速和风向角下的气弹模型风洞试验。试验结果表明:输电塔模型的响应随风速增大而增大;输电塔横风向响应显著;通过对试验结果的对比分析,揭示了典型输电塔结构动力特性和风振响应特点,为高压输电线路抗风设计及改造提供依据。