Frequency domain identification of Wiener models

This paper proposes a frequency domain algorithm for Wiener model identifications based on exploring the fundamental frequency and harmonics generated by the unknown nonlinearity. The convergence of the algorithm is established in the presence of white noise. No a priori knowledge of the structure of the nonlinearity is required and the linear part can be nonparametric.     

Markov analysis of qualitative dynamics1

Common sense sometimes predicts events to be likely or unlikely rather than merely possible. We extend methods of qualitative reasoning to predict the relative likelihoods of possible qualitative behaviors by viewing the dynamics of a system as a Markov chain over its transition graph. This involves adding qualitative or quantitative estimates of transition probabilities to each of the transitions and applying the standard theory of Markov chains to distinguish persistent states from transient states and to calculate recurrence times, settling times, and probabilities for ending up in each state. Much of the analysis depends solely on qualitative estimates of transition probabilities, which follow directly from theoretical considerations and which lead to qualitative predictions about entire classes of systems. Quantitative estimates for specific systems are derived empirically and lead to qualitative and quantitative conclusions, most of which are insensitive to small perturbations in the estimated transition probabilities. The algorithms are straightforward and efficient.     

A direct estimate of JIc from the load versus load-line displacement record

The purpose of this study is to examine the current standard fracture toughness test procedure to determine if there could be an easier method to get a J_Ic value from the test record. The current method for determining J_Ic involves a detailed computational and construction procedure. The objective in this study is to simplify the analysis for the determination of J_Ic. The results of this study show that the load and displacement record for a fracture toughness test can be used to directly estimate a J_Q value, a provisional value for fracture toughness, J_Ic. The J value taken at the maximum load point can be used along with an adjustment factor to estimate a J_Q value. This J_Q estimate is close to the one obtained from the construction procedure of ASTM Standard E 1820. When a unit‐sized specimen is tested, that is, a specimen with a width of 50 mm and a thickness of 25 mm the maximum load point provides a direct estimate of J_Q. Other sizes require a size adjustment factor, which is simply a square root relationship between the width of the test specimen and a unit width. The proposed new method of estimating J_Q is simple in concept and requires a minimum number of calculations. It appears to produce values of J_Q which are comparable to those obtained from the ASTM E1820 construction procedure and may produce less scatter.     

Schwingfestigkeit von Schraube‐Mutter‐Verbindungen

High cycle fatigue of bolted connections Extensive tests regarding the influences on the fatigue of bolt‐nut‐connections of preloading with torsion, of preloading with yielding, of loading with superimposed bending and of the tested lot are processed. These influences are not yet known according to VDI 2230. New testing devices were designed for these tests, which allow a far less expensive operation and may easily be used for bolts of diameters up to M100 and testing frequencies up to 1000 Hz. The validity of fatigue resistance according to VDI 2230 is specified with respect to the test results. The determined influence of the tested lots is unexpectedly high. The manufacturing process of bolts should be improved to minimize this influence.     

GM300电台的调试原理及方法

GM300电台是一种性能优良的电台，目前在我国的地震勘探领域广泛应用。与其它类型的电台相比，GM300电台的调试方法完全不同。掌握其调试原理及方法是对该类电台进行正确维护的基础。本文从分析GM300电台调试原理入手，总结了该电台的调试方法。     

利用多普勒信息的波达方向最大似然估计方法

为了充分利用信号的时域特性来改善信号波达方向（ＤＯＡ）的估计性能，本文从最大似然估计出发，推导出了有限快拍，低信噪比情况下多普勒信号波达方向的迭代估计计算法，为进一步减小运算量，本文还推导了一种简化算法，本文提出的两种算法对低信噪比，少快拍数下多普勒信号的ＤＯＡ估计性能比不利用时域特性的ＭＬ方法有明显改善，Ｍｏｎｔｅ－Ｃａｒｌｏ实验验证了本文方法的有效性。     

自动线性跟踪Butterworth有源滤波器研究

滤波是通信、测试、数据采集和实时控制等领域至关重要的环节。通常的模拟滤波器，由于截止频率固定，在某些宽频率动态范围且有实时性要求的应用场合，往往达不到预期的滤波效果，有时甚至影响整个系统的正常运行。本文从有源滤波器的机理分析入手，提出了一种由单片机参与的滤波系统，它能自动跟踪输入信号频率，线性地选择合适的滤波器截止频率，弥补了原有滤波器的不足。     

带限信号高频重建的一种新的正则外推算法

本文提出生种新的带限信号的外推方法，该方法能够很好地抑制噪声干扰，且计算复杂性较低，本文给出算法，证明了收敛性，最后给出了误差计算机实验结果。     

正交双频光栅CCD系统剪切干涉测量二维温度场

以半导体激光器为光源，利用正交双频光栅（ＯＤＦＧ）ＣＣＤ系统剪切干涉对带平板边界的半圆柱体热源的二维温度场进行实时诊断，分析剪切干涉图时，用柱函数系作为拟合基底，给出二维自然对流温度场的定量分布。     

噪声测量作为筛选光电耦合器件的一种方法

本文针对目前用于光电耦合器件筛选方法的不足，提出了用测量耦合器件噪声功率谱的方法来筛选掉噪声值大的器件，给出一批光电耦合器件的测量统计结果及在不同工作点时的噪声功率谱，并给出相应的筛选标准，实验结果表明，这种方法是有效、可行的。