基于S变换与核Fisher的模拟电路故障诊断

故障特征的有效提取和分类器的设计是模拟电路故障诊断的两个至关重要的环节,为此,提出了一种基于S变换与核fisher相结合的模拟电路故障诊断新方法,首先利用S变换对原始数据进行时频分析,其次利用奇异值分解对提其降维去冗处理,选取最佳表示故障的特征量,最后对特征量进行核fisher判别分析,把非线性数据映射到一个高维空间,在高维空间对其进行线性分类处理,完成故障的识别和定位;实例仿真结果表明,该方法能够准确有效地实现故障定位,具有更高的诊断准确率和良好的应用前景。

关于F(s)和F(z)对应性的研究

在计算机测控系统上应用控制理论,首先要建立被控对象的时间离散的数学模型。把s传递函数近似转换成z传递函数的方法很多,用“L变换和Z变换表”得到的z传递函数对于脉冲输入的响应性能相当满意,然而对于阶跃输入的响应虽然形状相似而幅度相差太大以至于不能用。反之,用MATLAB的control-tools得到的z传递函数对于阶跃输入的响应性能相当满意,然而对于脉冲输入的响应虽然形状相似而幅度相差太大以至于不能用。这是每个应用计算机控制理论的工程师必须知道的知识。

OWL-S到Z规格说明的转换

OWL-S是重要的Semantic Web Service描述框架,但缺乏有效的形式化验证工具.Z语言是基于集合论和一阶谓词逻辑的形式化规格说明语言,比OWL-S具有更强的表达力.该文研究基于Z的OWL-S形式化方法,提出从OWL-S到Z规格说明的模型转换规则.基于这些规则,用Z定义OWL-S中概念的形式化语义,并开发了从OWL-S描述到Z规格说明的自动转换工具OWLS2Z.

On Sample Size Determination When Comparing Two Independent Spearman or Kendall Coefficients

One of the most commonly used statistical methods is bivariate correlation analysis. However, it is usually the case that little or no attention is given to power and sample size considerations when planning a study in which correlation will be the primary analysis. In fact, when we reviewed studies published in clinical research journals in 2014, we found that none of the 111 articles that presented results of correlation analyses included a sample size justification. It is sometimes of interest to compare two correlation coefficients between independent groups. For example, one may wish to compare diabetics and non-diabetics in terms of the correlation of systolic blood pressure with age. Tools for performing power and sample size calculations for the comparison of two independent Pearson correlation coefficients are widely available;however, we were unable to identify any easily accessible tools for power and sample size calculations when comparing two independent Spearman rank correlation coefficients or two independent Kendall coefficients of concordance. In this article, we provide formulas and charts that can be used to calculate the sample size that is needed when testing the hypothesis that two independent Spearman or Kendall coefficients are equal.

Direct Fisher Inference of the Quartic Oscillator’s Eigenvalues

It is well known that a suggestive connection links Schr?dinger’s equation (SE) and the information-optimizing principle based on Fisher’s information measure (FIM). It has been shown that this entails the existence of a Legendre transform structure underlying the SE. Such a structure leads to a first order partial differential equation (PDE) for the SE’s eigenvalues from which a complete solution for them can be obtained. We test this theory with regards to anharmonic oscillators (AHO). AHO pose a long-standing problem and received intense attention motivated by problems in quantum field theory and molecular physics. By appeal to the Cramer Rao bound we are able to Fisher-infer the energy eigenvalues without explicitly solving Schr?dinger’s equation. Remarkably enough, and in contrast with standard variational approaches, our present procedure does not involve free fitting parameters.

SVD滤波的串联故障电弧特征分析

为进一步研究故障电弧特征,针对三相电动机及变频器负载开展了串联故障电弧实验。首先将电流信号经过一阶差分预处理,再通过奇异值分解SVD(singular value decomposition)对信号进行两级滤波,剔除信号中的工频和噪声成分。采用柯尔莫可洛夫-斯米洛夫K-S(Kolmogorov-Smirnov)检验法分析SVD滤波信号的正态分布情况。采用线性调频Z变换CZT(chirp-Z transform)对SVD滤波信号0~500 Hz频段进行频谱细化分析。提取时域峭度和特征频段幅值平均值组成特征向量,并构建故障电弧区矩形。通过大量数据测试表明:该方法可有效识别三相电动机及变频器负载回路中发生的故障电弧。

Brain functional network connectivity based on a visual task: visual information processing-related brain regions are significantly activated in the task state

It is not clear whether the method used in functional brain-network related research can be applied to explore the feature binding mechanism of visual perception. In this study, we inves-tigated feature binding of color and shape in visual perception. Functional magnetic resonance imaging data were collected from 38 healthy volunteers at rest and while performing a visual perception task to construct brain networks active during resting and task states. Results showed that brain regions involved in visual information processing were obviously activated during the task. The components were partitioned using a greedy algorithm, indicating the visual network existed during the resting state.Z-values in the vision-related brain regions were calculated, conifrming the dynamic balance of the brain network. Connectivity between brain regions was determined, and the result showed that occipital and lingual gyri were stable brain regions in the visual system network, the parietal lobe played a very important role in the binding process of color features and shape features, and the fusiform and inferior temporal gyri were crucial for processing color and shape information. Experimental ifndings indicate that understanding visual feature binding and cognitive processes will help establish computational models of vision, improve image recognition technology, and provide a new theoretical mechanism for feature binding in visual perception.

基于LS-AGA伺服系统连续模型参数辨识

为了解决伺服系统连续模型参数辨识不足的问题,提出一种间接的连续模型辨识算法,建立了伺服系统的动力学模型。首先使用最小二乘法(LS算法)来辨识出系统的离散模型参数,其次通过自适应遗传算法(AGA算法)对离散参数进行Z-S变换,获得连续系统模型参数。根据LS-AGA辨识算法设计了辨识实验,采用扫频正弦模拟量电压作为输入信号对系统中的连续参数模型进行辨识,并对所获得的连续模型进行了分析和验证。研究结果表明,辨识模型的预测输出与实际实验输出匹配度较高,该连续模型能够反映伺服系统的特性。

2013年岷县—漳县6.6级地震前地磁日变化异常及机理分析

利用空间相关法对2013年岷县—漳县6.6级地震前后151个台站地磁垂直分量日变化进行分析,结果显示:(1)2013年7月3日、4日在震中附近分别出现16和17个台站的地磁Z分量日变化明显反相位异常,具有明显的分界线。(2)利用S变换方法对分界线两侧的天水和兰州台的Z分量日变化进行分频率相关系数计算,发现7月3日、4日的地磁Z分量的日变化均在6 h左右的周期出现负相关变化。其他时段未出现类似变化,认为岷县—漳县6.6级地震前地磁Z分量日变化异常产生的反相位异常主要在6 h左右。此外,还对异常产生的机理进行了解释。

基于快速小波变换和FLD的人脸识别算法

针对快速性和识别率要求较高的人脸识别应用场合,提出了一种基于快速小波变换(FWT)和Fisher线性鉴别(FLD)的人脸识别算法.首先用Haar小波对标准人脸图像分别进行1尺度和2尺度分解,然后用Fisher线性鉴别法对原始图像、1尺度和2尺度分解图像提取特征,最后利用最近邻法对提取到的特征进行识别.利用ORL标准人脸图像库对算法进行了仿真,结果表明,此算法取得了较快的识别速度和较高的识别率.

中国股市行业板块的动态相关性建模——基于DCC-MVGARCH模型

相关性的讨论是现代金融分析的重要内容,行业板块的相关分析是组合投资的关键步骤。基于能刻画动态相关的DCC-MVGARCH模型对我国波动剧烈的六个股市行业板块进行了相关性研究,结果表明:十个板块相关性序列可看成常量,Pearson相关系数仍能刻画其相对大小,这为机构投资者按Pearson相关系数进行组合构建提供了实证依据;五个动态相关性序列是宽平稳而非严平稳的,适合采用随机过程建模以实现预测,另外动态相关性与时变波动率存在一定的关系,当波动率增强时,相关性有随之增大的趋势。

累积正态分布函数的逼近函数综述

Fisher z变换是一个显式的初等函数,用来逼近累积正态分布函数(标准正态分布的累积分布函数)。介绍了累积正态分布函数逼近函数的评价标准,对有代表性的逼近函数表达式及相应的最大距离误差值进行归纳总结。

扬声器频响自适应数字滤波优化补偿方法

从模拟滤波器到数字滤波器的转换以及寻找滤波器参数的最优解是IIR参数滤波器用于扬声器频响实时补偿的两个关键问题。提出一种根据模拟滤波器的中心频率、增益和品质因数来自适应选择S域到Z域转换方法,通过扬声器频响曲线的实时包络来划分峰谷,给出了一种滤波器参数的优化方法,提升了数字滤波器与模拟原型的匹配度,从而减少滤波器个数、加速了滤波器的优化计算。实验结果表明,所提出的方法使补偿滤波器的个数和总时间开销比现有的补偿方法分别减少了大约43%和55%。

Noninvasive Surface Detection of Papillary Thyroid Carcinoma by Fourier Transform Infrared Spectroscopy

Previously Fourier transform infrared（FTIR） spectroscopy has been applied to detecting thyroid cancer during operations and to discriminating cervical metastatic ones from non-metastatic lymph nodes. This study explored the possibility of establishing a sensitive, accurate and noninvasive screen or diagnosis by preoperative FTIR spectroscopy. 111 patients undergone a thyroid operation and 50 healthy volunteers were enrolled in the study. The FTIR spectra were obtained by two mid-infrared optical fibers with an attenuated total reflectance（ATR） probe closely contacting the subjects＇ skin on the thyroid nodules. The FTIR spectra obtained from normal thyroid, nodular goiter（NG） and papillary thyroid carcinoma（PTC） patients were compared. A Fisher＇s discriminant analysis was created based on these data. There were 41 PTC patients and 70 NG patients according to their histopathological examinations. A total of 23（of 39） parameters were statistically different among the three groups（P〈0.05）. The Fi300 and F1080 parameters were significantly different between the three groups. In total, 9 out of 39 FTIR parameters were selected as independent factors by the Wilks＇ lambda stepwise discriminant analysis. The discrimination accuracy of papillary thyroid carcinoma in the three groups was 88.8%. Surface detection of PTC by FTIR spectroscopy is feasible. FTIR spectroscopy can be used for rapid and noninvasive PTC screen and auxiliary diagnosis.