基于核主元分析的滚动轴承故障混合域特征提取方法

为有效利用时域、频域、时-频域中各类具有显著类别差异信息的非平稳统计特征,提高滚动轴承状态监测和故障诊断的性能和效率,提出一种基于核主元分析的混合域特征提取方法.通过对原始信号分别生成时域、频域状态特征,并利用多分辨率小波分解生成时-频域状态特征,构建出144个表征原始振动信号特征的混合域特征集.采用核主元分析方法对其中能敏感地反映故障特性的特征进行二次非线性特征提取,按累计贡献率大于90％的标准,选取前11个核主元作为主要特征量,将其输入支持向量机分类器进行状态识别.仿真结果表明:混合域特征集比单个特征、单域特征能更全面准确地反映故障特性,核主元分析方法能有效降低输入特征维数,并确保输出特征具有较高的反映轴承运行状态的敏感性和适于模式识别的可分性;与通常使用的基于小波分解的特征提取方法相比,本文方法能更加准确有效地提取不同运行条件下滚动轴承不同类型不同程度的故障特征.     

基于核函数主元分析的机械设备状态识别

研究了核函数主元分析在机械故障模式分类中的应用，通过计算原始空间的内积核函数实现原始数据空间到高维数据空间的非线性映射，再对高维数据作主元分析，求取更易于分类的核函数主元，实验表明，核函数主元分析更适于提取故障信号的非线性特征，能有效区分不同的故障模式，可以应用于机械设备的状态识别。     

基于听觉显著性特征的发电机组主轴承性能评估

人类的听觉系统在处理声音信号这类非平稳、非线性信号上具备优异的识别能力及抗噪能力。本文依据振动与声音信号同源性的特点,提出了一种基于听觉显著性信号的数据降噪、典型特征提取和自组织映射（self-organizing feature map,SOM）网络相结合进行发电机组主轴承性能评估的方法。首先,利用Gammatone滤波器组构建人的耳蜗模型对原始振动信号进行识别,并剔除噪声信号。其次,通过模拟人耳的听觉注意机制获得显著帧和显著通道的典型特征,然后构建特征空间。最后,将构建的特征空间分为训练样本和测试样本两部分,利用SOM网络,实现发电机组主轴承的性能评估。试验结果表明,本文提出的性能评估方法能够精准的识别噪声信号并构建特征空间,可有效评估发电机组主轴承的性能,为其视情维修提供依据。     

基于双核独立元分析的化工过程故障诊断算法研究

由于化工生产过程数据具有强非线性和非高斯性特征,提出了核主元分析与核独立元分析相结合的可用于化工过程故障诊断的双核独立元分析算法,该算法利用核主元分析的非线性核函数把数据从原空间映射到高维特征空间进行白化预处理,再用核独立元分析算法进行独立元分析,在特征空间中获得故障监控统计量,计算控制置信限,达到有效的故障诊断.提出的算法应用在连续搅拌反应釜过程中,结果表明,该算法对化工过程故障诊断能有效提高准确度、降低漏报率和误报率.     

基于差分进化和核主元分析的燃气轮机故障检测

燃气轮机气路部件的状态检测参数具有极强的非线性,其故障特征难以提取,而利用传统核主成分分析(KPCA)进行故障检测难以对核参数进行科学取值,从而降低故障检测的准确性.针对该问题,论文提出了基于优化混合核的核主元分析故障检测算法(DE-KPCA).首先建立动态权值混合核函数,通过调节核函数的权重比实现全局映射和局部映射优化组合.以样本检测精度作为优化目标,对混合核参数进行逐次优化.最后构造了基于优化混合核函数的主元异常状态检测方法,实现对燃气轮机气路故障的在线检测.本文通过对双轴涡喷发动机气路故障仿真的验证,证明了该方法相较传统KPCA检测,能够实现核参数的科学取值且对燃气轮机气路故障检测具有更高的准确性和实用性.     

基于噪声小波包络谱的主轴承磨损故障诊断

传统的基于振动信号的内燃机主轴承磨损故障诊断中安装传感器以及提取故障特征频率很繁琐,为此,提出了基于噪声和正交小波监测往复式活塞发动机滑动主轴承磨损故障的一种新方法.利用Symlets小波分析将测得的机体噪声信号变换到时频域,得到含有内燃机主轴承间隙磨损状态的时频信息.主轴承磨损故障会使机体噪声信号的高频成分增加,而且高频滤波成分特征与内燃机的冲击过程相对应,所以,需选择合适的高频带加以提取并进行包络谱分析.通过声级计测取了代表主轴承4类间隙磨损程度的噪声信号,发现2个特征频率处的能量对间隙磨损状态比较敏感,均随着磨损量的增加而增加.通过该方法,可利用机体噪声信号监测主轴承的磨损状态.     

采用EEMD-KPCA处理的IHHO-LSSVM滚动轴承寿命预测模型

为提高滚动轴承剩余寿命预测精度,提出一种基于集合经验模态分解-核主成分分析(EEMD-KPCA)和改进的哈里斯鹰优化-最小二乘支持向量机(IHHO-LSSVM)的滚动轴承剩余寿命预测模型.首先,使用集合经验模态分解方法对原信号进行分解,根据相关系数和峭度值选取合适的本征模态函数进行重构;然后,提取时域、频域、小波包能量谱等指标,并用核主成分分析,选取累计贡献率大于85%的主成分作为轴承退化性能指标;建立最小二乘支持向量机寿命预测模型,针对模型参数,提出一种改进的哈里斯鹰优化算法,并在新算法基础上设计新的能量周期性递减调控机制.采用轴承全寿命实验数据进行验证,结果表明:该方法提取的轴承性能评估指标能够更全面地表征轴承性能退化情况,建立的模型具有良好的预测效果.     

主分量分析和隐马尔科夫模型结合的轴承监测诊断方法

为了快速识别轴承的故障模式以及性能退化状态,提出了一种基于主分量分析和隐马尔科夫模型的轴承监测诊断方法。该方法首先提取了轴承振动信号的混合域故障特征集,使用主分量分析对混合域故障特征集降维,然后使用降维后的特征训练隐马尔科夫模型,最后用降维后的测试样本测试模型的性能,根据隐马尔科夫模型输出的对数似然概率,确定轴承故障模式以及轴承的性能退化状态。开展了不同状态滚动轴承振动测试实验,数据分析结果表明,提出的方法诊断准确率均能达到100%,相比基于补偿距离选择特征降维及隐马尔科夫模型诊断方法,最高将分类离散度提高123.74%,并且在轴承的性能退化实验中,提出的方法能在故障早期给出故障预警,证明了该方法的有效性和准确性。     

基于VMD和马氏距离SVM的滚动轴承故障诊断

针对滚动轴承早期故障识别较困难的问题,提出一种基于变分模态分解(VMD)和马氏距离支持向量机(SVM)的诊断方法。首先,采用小波阀值法对原始振动信号进行去噪处理,获得有效的振动信号。其次,根据VMD分解后每个模态的中心频率大小不同,确定最终分解层数。同时,从分解后的变分模态分量中提取能量特征。最后,为了对样本间进行距离度量,将马氏距离引入SVM的高斯核函数计算中,建立了一个基于马氏距离的高斯函数核,用于支持向量机分类器。利用改进的SVM对轴承的运行状态进行识别,实验结果表明所提方法在识别轴承正常状态、内圈、外圈以及滚珠体故障时,具有较高的准确率。     

采用改进回归型支持向量机的滚动轴承剩余寿命预测方法

为准确评估滚动轴承运行状态、预测其性能退化趋势以及剩余寿命,提出一种改进回归型支持向量机(SVR)的滚动轴承寿命预测方法。提取轴承信号的时域和时频域特征,通过主成分分析(PCA)方法将特征指标融合成一个归一化综合指标来表征轴承运行状态;利用特征指标和综合指标构建训练和预测向量数据集,结合差分进化灰狼群算法(DEGWO)确定最优惩罚参数和径向基函数(RBF)核参数并构建回归型支持向量机模型;将预测数据集输入到DEGWO算法优化的SVR模型中得到轴承状态评估指标的预测值,实现轴承剩余寿命的预测。利用IEEE PHM 2012数据集验证所提方法的有效性,并将其结果与灰狼群算法(GWO)优化的SVR、网格搜索算法(GSA)优化的SVR和长短期记忆神经网络(LSTM)模型所得结果进行对比分析。仿真结果表明：与其他方法相比,采用所提方法得到的轴承剩余寿命预测均方误差分别降低了44.74%、66.67%、77.27%,决定系数则分别提高了7.25%、20.72%、11.94%,该结果说明了所提方法在轴承剩余寿命预测应用方面的优越性。     

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     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

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~~