IDENTIFICATION OF DAMPING: PART 3, SYMMETRY-PRESERVING METHODS

In two recent papers (Adhikari and Woodhouse 2001 Journal of Sound and Vibration243, 43-61; 63-88), methods were proposed to identify viscous and non-viscous damping models for vibrating systems using measured complex frequencies and mode shapes. In many cases, the identified damping matrix becomes asymmetric, a non-physical result. Methods are presented here to identify damping models which preserve symmetry of the system. Both viscous and non-viscous models are considered. The procedure is based on a constrained error minimization approach and uses only experimentally identified complex modes and complex natural frequencies together with, for the non-viscous model, the mass matrix of the system. The methods are illustrated by numerical examples.     

双反射镜式光电经纬仪测角误差的分析(轴系部分)

双反射镜式光电经纬仪由于采用了反射镜跟踪头,轴系误差对测角精度的影响不同于典型光电经纬仪。本文从建立经纬仪三维直角坐标系入手,建立了该类型经纬仪轴系误差引起测角误差的数学模型,为精度分析和误差修正提供了依据。     

IN-SERVICE IDENTIFICATION OF NON-LINEAR DAMPING FROM MEASURED RANDOM VIBRATION

A non-linearly damped single-degree-of-freedom (s.d.o.f.) system under broadband random excitation is considered. A procedure for in-service identification of the damping characteristic from measured stationary response is described. The procedure is based on the stochastic averaging method. The explicit analytical solution is obtained for the integral equation, which relates the desired damping characteristics to the apparent force in the shortened equation for the slowly varying response amplitude, and thus to the measured probability density of the amplitude. The approach is of a non-parametric nature, which makes it convenient for testing hypotheses of damping mechanisms from measured random vibration data. Extensive results of numerical tests for the procedure are presented.     

欧姆表测量误差的分析

本从欧姆表原理出发，导出了电阻测量的相对误差公式。     

SENSITIVE ERROR ANALYSIS OF CHAOS SYNCHRONIZATION

We study the synchronizing sensitive errors of chaotic systems for adding other signals to the synchronizing signal. Based on the model of the Henon map masking, we examine the cause of the sensitive errors of chaos synchronization. The modulation ratio and the mean square error are defined to measure the synchronizing sensitive errors by quality. Numerical simulation results of the synchronizing sensitive errors are given for masking direct current, sinusoidal and speech signals, separately. Finally, we give the mean square error curves of chaos synchronizing sensitivity and three-dimensional phase plots of the drive system and the response system for masking the three kinds of signals.     

QZ算法误差分析

在这编文章中,我们给出求解λB-A型矩阵偶特征值的QZ算法的误差分析。全文分两部分。在第一部分中,我们估计QZ算法的变换次数。在第二部分中,我们给出误差估计式。     

简易弧高计的误差分析

本文介绍了使用简易弧高计测量球面弧高时的误差公式，并用实例说明了此类弧高计在一般光学元件件加工测量中的可靠性。     

Michelson干涉仪的调节和误差分析

本文提出一种用Michelson干涉仪观察干涉的简捷的调节方法 ,并对实验测量过程中误差的来源进行了细致的分析     

反射镜稳定系统的仿真与误差分析

提出一种光电稳定系统的误差分析方法。该方法建立在对稳定控制系统仿真设计的基础上,利用稳定系统刚度传递函数曲线,对各种扰动源引起的误差进行分析与计算。利用该误差分析方法,将使设计者在设计中明确应该对哪些误差进行控制,从而实验总体精度要求。最后用一具体设计实例验证本方法。     

混沌系统的时间延迟同步误差分析

对Pecora和Carroll的混沌自同步方案的延迟同步误差进行了研究.在计算机上对Lorenz混沌系统伪装的延迟同步误差进行了模拟:给定系统参数,对应不同延迟时间,得出了均方误差与采样步长的关系曲线;给定系统参数和延迟时间,对应不同采样步长,得到了混沌时间序列的误差曲线;给定采样步长,对应不同的系统参数,获得了混沌时间序列的尺度效应和均方误差与采样步长的关系曲线.提出了减小延迟同步误差的一些方法,得到一些对混沌同步和混沌控制应用有意义的结果. 关键词： 混沌同步 时间同步 误差分析     

误差控制分析的简单数值方法

本文以密立根油滴实验为例，介绍了用相对百分比对误差进行控制分析的方法。     

牛顿第二定律实验中的误差分析

本文是通过对加速度的实验值和理论值进行比较和分析，给出误差的合理范围。     

惠斯登电桥测电阻的误差分析

本文较系统地分析了用惠斯登电桥测电阻实验中的系统误差，并提出了代换法消除系统误差的方法．     

等离子体涨落信号的相关分析——波和不稳定性识别

一、引言 等离子体诊断中的低频涨落,包含了反映带电粒子随机运动和集体运动(如等离子体波、不稳定性过程)的信息。前者的信号呈“噪声”状态,后者则有一定规律。对涨落信号作相关分析,可从涨落信号的“噪声”背景中提取有规信号,并识别出不同来源的涨落信号     

分光计的调节要求及系统误差分析

本对分光计调节过程中允许产生的系统误差进行分析,并以分光计测量玻璃三棱镜顶角的实验为例给出定量讨论。     

非球面干涉测量方法的原理误差分析

在非球面干涉测量中,常用标准球面波作为测量光束,由于入射光线不垂直于被测表面,因此反射波面的波差并不能真实反映被测非球面与顶点球面的偏差,还会引起严重的测量误差。本文从理论上对这一误差进行分析和讨论。     

阻尼Bloch振荡和负微分电导现象的简单理论分析

用能带理论分析一维超晶格电子在直流外场作用下的阻尼运动，对Ｂｌｏｃｈ振荡和负微分电导现象给出清楚的物理图象，并通过数值解得到有阻尼时振荡频率随外场增加而趋近于Ｂｌｏｃｈ频率的一般规律。     

EXAFS方法在金属玻璃结构研究中的误差分析

本文对EXAFS方法在金属玻璃结构研究中所得径向距离的误差进行了分析。所做的模拟计算表明当前流行的关于这个问题的误差理论不能圆满地解释这一现象。本文分析了玻璃态和晶态的相移函数,指出在相似的体系中玻璃态和晶态相移函数与k的关系采用线性函数近似时,其斜率可能是不同的,而且无序度相差越大,两者的偏差可能也越大。在EXAFS数据处理过程中,没有考虑这种偏差的影响是造成EXAFS方法结果中径向距离误差的一个原因。本文还提出了一个修正参考样品(晶态)相移函数斜率偏差的方法,并将它应用于Cu₅₅Zr₄₅金属玻璃的EXAFS数据处理中,所得结果与用X射线异常散射方法测定的结果符合得很好。 关键词：     

牛顿环实验中的误差分析

本文对牛顿环测透镜曲率半径实验中引起误差的各种原因进行分析讨论，指出了误差的主要来源及比较完善可行的处理方法。     

INDUCED DAMPING BY A NEARLY CONTINUOUS DISTRIBUTION OF NEARLY UNDAMPED OSCILLATORS: LINEAR ANALYSIS

The induced damping in a master oscillator contributed by a set of satellite oscillators is obtained in terms of a summation over a discrete distribution of the set. (The distribution is with respect to the resonance frequencies of the satellite oscillators in the set. The distribution is cast in an ascending order and is assumed to be centered about the resonance frequency of the master oscillator in isolation). If the modal overlap parameters are less than unity, significant undulations are present in the induced damping; the less the modal overlap parameters are compared with unity, the more prominent are the undulations. The undulations are largely suppressed when the local modal overlap parameters exceed unity. Moreover, appropriately averaging the undulations yields values for the induced damping that coincide with those obtained when the modal overlap parameters exceed unity. Further, it transpires that these common values are independent of the individual modal overlap parameters. When the summation is replaced by an integration, the first order results are undulations-free and the values, so obtained, again, coincide with those pertaining to modal overlap parameters that exceed unity. Without defining the excursions in the undulations, the transition from a discrete-to-a continuous distribution, that is implied by a summation-to-an integration, must assume that the modal overlap parameters exceed unity. In particular, without careful and meaningful qualifications, it may be misleading to assume, a priori, that the modal overlap parameters are equal to zero.