基于关联维数的高压电机定子绕组局部放电信号模式识别

提出了利用分形理论对高压电机定子绕组局部放电信号进行处理的方法,得到局部放电信号的关联维数,并将其作为特征参量对几种典型的局部放电信号进行模式识别。局部放电信号是非线性、非平稳随机信号。因此采用非线性理论中的分形理论对其进行分析,即计算关联维数。考虑到相空间重构中嵌入维数和时间延迟对关联维数精度的影响,采用联合算法确定2个参数。仿真结果表明,关联维数用于局部放电信号模式识别是行之有效的。     

基于关联维数的超声Lamb波损伤成像

研究了混沌分形理论的一种特征参数——关联维数的定义计算及参数选择。提出了一种基于关联维数的板状复合材料超声兰姆(Lamb)波损伤检测方法。通过计算采集健康与无损信号的关联维数,对比其数据差异,作为一种损伤指标,用于概率成像算法的损伤位置定位成像。利用有限元分析进行模拟实验研究,结果表明,提出的算法能准确对复合材料脱层缺陷进行定位成像。     

基于广义维数距离的语音端点检测方法

为能够准确有效地对含噪声语音信号进行起止位置的端点检测,该文提出了一种基于广义维数距离的端点检测方法。首先利用覆盖法求取广义维数得到该语音信号的三维特征向量,包括容量维数、信息维数、关联维数;然后计算信号的维数特征距离;最后根据特征距离对语音信号类别进行决策分类。实验结果表明,与仅使用单一维数特征检测语音起止端点相比,该文所提出的方法具有较好的鲁棒性,对混杂有不同噪声、不同信噪比的语音信号都能有较好的检测结果,尤其适用于低信噪比的语音端点检测。     

基于EMD分形维数的轧机主传动系统故障诊断方法研究

提出了一种基于EMD分解和分形维数的轧机主传动系统故障诊断方法.利用EMD方法对轧机主传动系统的振动信号进行分解,得到若干个基本模式分量,进一步求出包含主要故障信息的几个IMF分量的关联维数并计算它们的均方根值,作为判断轧机的故障状态和类别的特征量.实验分析表明,此方法达到了去除噪声的效果,同时增大了故障类别标准的判别距离,从而可以有效地判断轧机主传动系统系统的故障状态和故障类型.     

机械加工、工具与机床

0608955新型真空热水机组及其应用〔刊,中〕/翟家佩//真空.—2005,42(6).—55-57(D2)阐述了VH真空热水机组的工作原理、结构组成和性能特点,介绍了该机组在供热、采暖系统中的应用。参50608956关联维数在齿轮箱振动信号特征提取中的应用〔刊,中〕/谢向荣//海军工程大学学报.—2005,17(6).—102-107(G)论述了关键维数的基本概念和性质,给出了定量描述分形特征的重要参数——关联维数的计算方法,分析了齿轮箱故障振动的特点。通过对试验获取的齿轮故障振动信号进行分析计算,确定了关联维数与齿轮箱故障程度之间的关系。结果表明,齿轮箱的不…     

音频信号高维矢量编码算法研究

在音频信号编码中,提出在线性预测编码、SOM神经网络矢量编码以及Huffman编码相结合的声音信号联合编码算法的基础上,通过将声音量化编码算法中原有的2维量化矢量的维数增加,以进一步减小声音信号码率的方法。利用Matlab软件编程进行不同量化矢量维数条件下的声音信号编解码实验。实验结果表明,在保证声音质量的前提下,通过提高量化矢量维数,可使联合编码的最低码率在音频编码格式Opus码率的范围内,且接近Opus码率的下限。文中提出的编码算法可为音频压缩编码的进一步研究提供参考。     

基于分形理论的拍波与调幅波信号识别方法研究

现有的拍波与调幅波的识别方法存在不足,本文提出了基于分形几何原理的辅助判别方法。仿真及工程实例表明:通过计算时间序列信号的关联维数并根据其值的大小能辅助判断信号的类别。     

激光、大脑和经络——它们的混沌的分数维数

混沌和分数维数(Chaos and Fractal)是研究复杂系统的有力工具,近来被用于研究激光、大脑和经络的动力学行为。 激光器和大脑都有混沌和分数维数特性。由激光和脑电波的混沌信号可分别再造它们的奇异吸引子并计算关联维数D_2。最近我们对经络动力学提出了三个预言:(1)人体的气具有混沌特性;(2)气的关联维数D_2应在n=5时饱和(n是描述气的矢量空     

基于混沌、分形理论的多径衰落分析

本文首次将混沌、分形等非线性理论引入多径衰落的研究,针对现场实测数据分析了它的非线性动力特征.首先通过重构状态空间和关联维数验证了其动力机制的有限维自由度,然后通过计算其Lyapunov指数考察了系统的时空演化特性,最后利用分形机制对多径信号进行了重构.研究结果表明,与传统的随机模型相比,非线性动力模型能更恰当地描述多径衰落的内在物理机制.     

电话机无响铃声的几种常见原因

1)响铃控制开关处于关闭(OFF)状态。有些电话机上有响铃控制开关,即可控制响铃声音的大小,又可关闭响铃信号。有时因用户或小孩误动些控制开关,使其处于OFF状态,使所有外线电话无法打入,即会出现无响铃声音故障。另外,控制开关发生故障时,也会出现类似故障。     

Efficient estimation of a time-varying dimension parameter and its application to EEG analysis

This paper considers the problem of estimating the dimension of nonstationary electroencephalogram (EEG) signals and describes the implementation of an efficient algorithm to calculate a time-varying dimension estimate. The algorithm allows the practical calculation of a dimension estimate and its statistical significance over large data sets with a high temporal resolution. The method is applied to EEG recordings from patients with temporal lobe epilepsy and in one case the results of the analysis are compared with those obtained from an existing method of computing the correlation density.     

Study of features based on nonlinear dynamical modeling in ECG arrhythmia detection and classification

We present a study of the nonlinear dynamics of electrocardiogram (ECG) signals for arrhythmia characterization. The correlation dimension and largest Lyapunov exponent are used to model the chaotic nature of five different classes of ECG signals. The model parameters are evaluated for a large number of real ECG signals within each class and the results are reported. The presented algorithms allow automatic calculation of the features. The statistical analysis of the calculated features indicates that they differ significantly between normal heart rhythm and the different arrhythmia types and, hence, can be rather useful in ECG arrhythmia detection. On the other hand, the results indicate that the discrimination between different arrhythmia types is difficult using such features. The results of this work are supported by statistical analysis that provides a clear outline for the potential uses and limitations of these features.     

Fractal dimension estimation via spectral distribution function and its application to physiological signals

Rhythmic signals from physiological systems usually have memory and long-term correlation. They can be modeled as fractional Brownian motion or fractional Gaussian noise depending on if the signals are derived from cumulative effects of nerves and muscles. That is, they can be treated as signals with fractional dimension, and the value of its fractal dimension can be used to characterize the intensity of physiological signals. In this communication, a novel method of dimension estimation based on the calculation of spectral distribution function of discrete-time fractional Gaussian noise using Legendre polynomials as basis set is proposed. The effectiveness of this proposed method is demonstrated in the dynamic behavior of detrusor of the bladder and external urethral sphincter during micturition.     

Fiber-optic switch arrays for optical subscriber transmissionsystems

Optical array devices play an important role in subscriber transmission systems because they can efficiently accommodate the large number of optical channels required. The use of two single-mode fiber-optic switch arrays in subscriber transmission systems is discussed. The first is a 16-element micromechanical switch array which is electrostatically driven and is used to separate abnormal subscriber units that transmit disturbing light signals. The second is a 16-element switch array which interconnects a pair of probe fibers and any one of 16-channel subscriber-line fibers to execute fault testing     

基于线性相关的不同点循环相关 计算方法

在“数字信号处理”课程中，相关是一项重要的信号处理运算，在时延估计、随机信号的统计特性分析以及随机信号的功率谱估计等方面有着重要的应用。结合相关和卷积的关系，本文推导了线性相关与循环相关的转化关系，提出了一种基于线性相关的循环相关计算方法，能基于线性相关结果来快速计算不同点数的循环相关，仿真结果表明，相比于直接根据定义计算循环相关的方法，本文提出的方法能显著提高计算效率。     

基于STM32的空调散热片粉尘自动监测仪的设计

为了对空调散热片上的粉尘进行准确检测,设计并实现了一种超低功耗高精度粉尘自动监测仪。该系统由ARM处理器、阵列式光电传感器模块、微弱信号调理电路、模/数转换电路、触摸屏液晶显示及输入模块、声光报警系统、继电器开关控制电路、时钟模块以及串口通信模块构成。以STM32微处理器为主控,通过脉冲驱动阵列式光电传感器对空调散热片粉尘进行差分检测,并利用交流激励低噪声AD7195模数转换器将经过放大滤波处理后的电压信号转换成数字量。微处理器接受数字量后进行分析与处理,可实现分级别通过液晶显示和声光报警及时提醒用户清洗空调散热片,并且带有强制断电功能。经实际应用,该智能化空调散热片粉尘自动监测仪能有效精确实现实时显示、光电报警、上位机通信等功能,对各类空调内部散热片都能很好的监测,具有很强的实用价值。     

Strictly nonblocking directional-coupler-based switching networksunder crosstalk constraint

Directional-coupler (DC)-based switching systems can switch signals at the rate of several terabits per second. Such switches can also transmit signals with multiple wavelengths simultaneously. Despite these advantages, DCs suffer from an intrinsic crosstalk problem that must be overcome in building a robust switching system. In this paper, the principles of constructing strictly nonblocking DC-based photonic switching systems under various crosstalk constraints are explored. We demonstrate how crosstalk adds a new dimension to the theory of switching systems. We find the sufficient nonblocking condition for photonic networks under crosstalk constraints and demonstrate that some well-known nonblocking networks can tolerate a stricter crosstalk constraint while retaining their hardware complexity. The theory developed in the paper can guide us in making the design tradeoff between the level of crosstalk and the amount of hardware     

Étude des séquences sphéroïdales discrètes dans le cas d’un échantillonnage à la fréquence de Shannon

Representation of band-limited, time sampled signals, on a finite-time support, leads to privilege sets, of finite dimension, called discrete spheroidal sequences. The obtention of such sets is, on numerical point of vue, generally quite fine. Here the authors show that sampling at Shannon rate can supply a very simple algorithm for calculation of these spheroidal sequences in the discrete case.