基于小波分析的汽轮机振动故障信号的检测

本文利用小波分析技术在故障信号检测中的应用进行了研究，针对消噪阀值的选取，采用了一种基于非线形浮动阀值的汽轮机振动故障信号的消噪与检测方法，检测结果表明，在故障检测前先对故障信号进行消噪。有利于提高汽轮机振动检测的准确性．     

基于小波分析和神经网络的电机故障诊断方法研究

在电机故障诊断技术中,电机振动信号最能全面反映电机的运行状态.本文提出一种基于小波分析和神经网络的电机故障诊断方法,该方法采用小波时频分析技术对电机故障振动信号进行消噪滤波,通过小波包分解系数求取频带能量,根据各个频带能量的变化提取故障特征,应用BP神经网络进行故障识别,并采用Matlab仿真软件予以实现.结果表明,该方法不需要建立电机的故障诊断模型,能有效提高电机故障诊断的准确性.     

LMD和改进小波阈值去噪的轴承声发射信号故障诊断

针对机械故障声发射信号特征提取的问题,提出了一种局部均值分解(local mean decomposition,LMD)和改进的小波阈值去噪相结合的方法;并应用于滚动轴承的故障诊断。首先,把改进小波阈值与三种小波阈值去噪方法进行比较分析。通过仿真信号表明,改进小波阈值方法能更为有效地去除噪声。其次,采用LMD方法将原始轴承故障的声发射信号分解,分解为若干个乘积函数(production function,PF)的线性组合,通过相关系数原则选取能够反映故障特征的PF分量,利用改进小波阈值去噪法对选出的PF分量进行进一步去噪。最后,对去噪后的声发射信号进行包络谱分析,诊断轴承故障的位置。通过滚动轴承单一故障和耦合故障的声发射实验验证了该方法的有效性。     

基于小波变换的水轮机组故障诊断的研究

对传统傅立叶分析技术在水轮机组振动故障诊断的故障特征提取的应用进行深入研究的基础上,针对使用该方法提取的频率信息精度不够的问题,提出了一种运用小波分析技术对水轮机组振动信号进行故障诊断的方法.采用Mallat算法并运用设定阈值的方法对采集到的裂纹转子的振动信号进行去噪,然后运用Trous算法对滤波后的振动信号的突变信号特征进行提取.结果表明本方法对水轮机组的振动信号故障诊断具有很好的准确性,为水轮机组故障识别提供了一种方法.     

基于HHT和SVM的纤维拉伸断裂声发射信号的特征提取及分类研究

为了研究纤维拉伸断裂声发射信号的特征提取及分类方法,采用声发射技术采集了芳纶1313和阻燃黏胶2种纤维的拉伸断裂的声发射信号。通过小波变换,对采集的2种纤维的声发射信号进行消噪预处理以去除部分噪声,应用希尔伯特-黄变换对2种纤维去噪后的信号进行特征频率的提取,运用最小二乘支持向量机(LSSVM)对2种纤维的特征频率进行分类识别。结果表明:小波去噪方法可以去除信号的部分噪声;希尔伯特时频谱可以一定程度上反映2种纤维材料在时间维度上的断裂情况,边际谱上可以提取2种纤维材料声发射信号的特征频率;LSSVM能够对2种纤维材料拉伸断裂的特征频率分类识别,芳纶1313的识别率为40%,阻燃黏胶的识别率为80%,总的识别率为60%。     

小波分析在电控发动机故障诊断中的应用

为了探讨小波分析技术在电控发动机故障诊断中的应用，以电控汽油机转速传感器为例，采集了转速传感器的正常和异常信号，利用小波变换对信号波形进行了滤波和除噪，利用一维连续变换工具计算出正常和异常信号小波变换系数，并提取了故障信息特征参数。结果表明：转速信号的小波变换系数能够判断发动机的断缸故障；转速信号的小波分析结果能对比发动机各缸的工作性能。实践证明，利用小波分析对电控发动机进行故障诊断是切实可行的。     

采用小波处理的空间光电编码器智能故障诊断

为了检测光电编码器在空间应用时由环境变化引起的故障,提出了一种故障诊断策略.该方法对遥测获得的监测信号进行分析,通过小波消噪和细节提取的方法获得信号的特征数据,作为故障样本.然后利用局部化递推最小二乘法(LRLS)训练神经网络作为离线故障分类器.在空间激光链路的地面研制阶段已进行了应用,实验结果表明该诊断方法切实可行,且能正确诊断未经训练的故障,有较好的泛化能力.     

矿山微震信号小波分析与研究

 针对目前人工信号识别技术和傅里叶变换在分析识别矿山微震信号时的局限性,提出Matlab小波工具箱分析方法。首先对矿山实际监测到的干扰矿震信号进行小波变换,对小波分解之后的矿震信号进行频谱分析,结果表明能够准确地观察到信号的突变点,确定矿震信号P波初到时,从而更加精确得出矿震震源的位置和能量大小;其次对受干扰矿震信号进行小波消噪,同时对小波分析的4种阈值降噪方法进行分析对比,发现无偏似然估计阈值效果最好,显示了小波分析的强大消噪功能。研究结果表明,小波分析具有良好的矿震信号识别效果和消噪能力,是矿震信号处理和分析的一种有效方法。     

基于Park变换的感应电机故障诊断

提取定子电流信号的Park矢量图作为电机故障特征，应用人工神经网络技术对故障特征进行分类与识别，从而避开复杂的谱分析技术，实验测试结果表明，该方法用于电机故障诊断可靠，有交，是一种实际可行的电机故障诊断方法。     

基于声信号的汽车发动机故障诊断方法综述

基于声信号的汽车发动机故障诊断方法近些年发展较快。本文介绍了当前应用于发动机故障诊断领域的声信号测试方法、小波分析故障信号特征提取方法以及神经网络模态识别等智能故障诊断方法,并与传统发动机故障诊断方法进行了比较,阐明了声信号智能诊断方法在发动机故障诊断方面的优越性,可为今后的发动机故障诊断研究工作提供理论依据。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

正~~     

Brief Introduction to “Journal of Jilin University( Science Edition) ”

<正>"Journal of Jilin University(Science Edition)"is a comprehensive academic journal in the fields of science sponsored by Jilin University and administrated by the Ministry of Education of the Peoples Republic of China.The journal started publication in 1955.The original name at starting publication was"Journal of Natural Science of Northeast People University",which was changed into"Acta Scientiarum Naturalium Universitatis Jilinensis"in 1958 owing to the name change of the university.The present journal name has