改进的谱相关分析方法及其在故障诊断中的应用

提出一种基于峭度能量的谱相关分析方法.它利用每个循环频率切片的峭度值来衡量该循环频率的调制能力,并以此作为加权因子进行循环频率的能量累积,最终实现故障特征的有效提取.相对于传统的谱相关分析方法,本文方法降低了信号中多倍频谐波对故障特征频率的干扰,能更清晰准确地提取出故障频率特征.利用传统的谱相关分析方法、本文方法和共振解调三种方法对仿真信号、低速重载试验台的滚动轴承外圈故障信号进行分析,证明了本文方法的有效性.     

基于非局部均值去噪和快速谱相关的滚动轴承早期故障诊断方法

针对如何从非线性、多分量、强背景噪声的滚动轴承早期故障振动信号中有效提取出微弱故障特征并准确判断故障类型,提出基于非局部均值去噪和快速谱相关的故障诊断方法。首先利用非局部均值去噪算法对原始振动信号进行降噪预处理,提高信号信噪比。然后,对降噪信号进行快速谱相关分析,增强信号中的周期成分,获得快速谱相关谱及其对应的增强包络谱。最后,将增强包络谱中幅值突出的频率成分与故障特征频率进行对比,判定故障类型并实现故障诊断。使用本文提出方法对仿真故障信号、实验故障信号进行分析。研究结果表明:相较于快速谱相关方法、谱峭度结合非局部均值去噪方法以及非局部均值去噪结合经验模态分解方法,本文提出方法可以抑制轴承早期故障振动信号中的背景噪声,有效提取出微弱故障特征,准确判断故障类型,避免出现误诊。     

基于改进的EEMD数据融合方法在轴承故障诊断中的应用

提出一种基于改进的EEMD谱峭度的多传感器联合轴承故障诊断方法,通过多个加速度传感器联合采集振动信号,利用EEMD自适应地将信号分解成多个分量,通过计算每个IMF分量的互相关系数法进行自适应重构以突出故障特征信号;对合成后的信号画快速峭度图,获得峭度最大时的中心频率和带宽;根据快速峭度图自适应确定电子谐振器的参数,并对此合成信号进行谐振增益;对谐振增益后的信号进行Hilbert解调,并与理论计算的轴承故障特征频率比较,从而确定故障部位.通过仿真的故障轴承信号和滚动轴承实验进行了验证,结果表明:该方法对滚动轴承故障的检测精度更高,提取精度和抗噪声能力方面有了明显的改进,对工程实践具有重要的指导意义.     

改进经验模态分解与谱峭度法的步态信号特征分析

通过对步态信号进行分析,提出基于能量矩占比与方差贡献率的改进经验模态分解和谱峭度法的步态信号特征频率分析方法. 改进的经验模态分解消除了传统分解过程中存在的低频虚假本征模态分量,抑制了高频噪声的干扰. 通过确定谱峭度图上的中心频率和带宽构造带通滤波器对信号进行包络解调分析,并通过实验验证了该方法能有效提取步态信号的特征频率,为步态信号的后期研究提供一条新的思路.     

基于双树复小波分解的风机齿轮箱故障诊断

风机齿轮箱振动信号具有非平稳、非高斯特性,多种模式混叠和复杂的传递路径使得故障信息微弱完全淹没在噪声之中.针对故障特征提取的难题,将双树复小波变换引入振动信号分析,提出了一种新的工业风力发电机齿轮箱故障诊断方法.首先对风机齿轮箱振动信号进行双树复小波分解,然后计算各频带分量的峭度值,利用峭度筛选故障敏感分量.最后对故障敏感分量进行频谱分析提取故障特征频率.实验结果表明:双树复小波变换可将复杂信号分解为不同频带分量,抑制平移敏感性和频率混叠.与传统离散小波变换相比,能有效抑制虚假频率出现并准确提取故障特征.本文提出的方法已成功用于风力发电机工业运行监测并准确诊断多种类型的齿轮箱故障.     

基于粒子群优化的MCKD算法在轴承故障诊断中的应用

针对最大相关峭度解卷积(MCKD)算法在提取轴承故障特征过程中对滤波效果评价的不足,提出以峭度和故障特征频率能量比值组成的复合评价指标来评价故障诊断结果的优劣;MCKD算法中影响故障诊断结果的参数为滤波器结构元素长度L,本文中通过粒子群算法对参数L进行自适应寻优。仿真信号和实测信号表明:采用该方法得到的最优L对信号进行处理,可以提取出故障特征,找到故障频率;对比发现,该方法明显提高了轴承故障诊断的精度和准确度。     

基于FSK-CNN的轴承故障诊断研究

在旋转机械设备的运维保障过程中，采用基于专家经验的传统故障检测方法难以对轴承的健康状态做出实时的状态检测。针对这一问题，本文提出一种基于快速谱峭度与卷积神经网络（FSK-CNN）的故障诊断方法。首先采用快速谱峭度（FSK）法对振动信号进行特征提取，将一维时域信号转化为二维的谱峭度图；之后，采用一种结合卷积注意力模块（CBAM）的卷积神经网络模型完成故障分类。试验结果表明，快速谱峭度法可以有效提取轴承振动信号故障特征，引入卷积注意力模块对传统卷积神经网络模型具有明显的优化作用，FSK-CNN的故障诊断方法对于10种不同的轴承故障类型的诊断准确率可以达到99%。     

参数化S谱幅值调制及轴承故障诊断应用

针对传统谱幅值调制方法易受噪声影响的问题,利用参数化S变换得到信号在时频域中的幅值,提出了一种参数化S谱幅值调制方法。该方法首先使用参数化S变换将信号转换到时频域并得到幅值和相位,然后将不同权重赋予时频域中的幅值以改变不同能量频率成分在信号中的占比,最后将调制后的幅值与原相位结合,使用参数化S逆变换重构一系列修正信号并计算其平方包络谱以提取故障特征。仿真和实验结果表明,该方法获得的幅值信息相比传统谱幅值调制方法更加准确和全面,对强噪声环境更具鲁棒性,能够有效实现滚动轴承的外圈、内圈和复合故障诊断。将所提方法与传统谱幅值调制方法和快速谱峭度方法进行对比,证明了参数化S谱幅值调制既能检测强噪声环境下的轴承故障信息,又能同时提取多种故障分量,在滚动轴承的故障特征提取中更具优越性。     

VMD的时频特性及其在滚动轴承故障诊断中的应用

针对在强噪声干扰下的滚动轴承早期故障振动信号信噪比低导致故障特征提取困难的问题,提出了基于变分模态分解和Teager能量算子包络解调的滚动轴承故障诊断方法.该方法首先利用VMD算法对故障信号进行分解成若干不同频率的本征模态分量(Intrinsic Mode Function,IMF);通过峭度准则筛选出峭度值最大的IMF,将其作为故障特征最敏感分量;利用Teager能量算子解调算法对该分量进行包络解调分析,提取调制故障特征.将该方法应用到仿真信号和滚动轴承故障振动信号分析当中,同时与EMD、小波变换方法进行了比较.结果表明,该方法提高了信号的分解效率,在噪声鲁棒性和抑制模态混叠方面具有良好的性能,能够实现滚动轴承故障的精确诊断,具有一定的理论研究意义和工程实用价值.     

强噪源干扰下的滚动轴承复合故障分离方法研究

针对强背景噪声干扰下的轴承复合故障难以准确分离提取,噪声与复合故障各成分间相互影响容易造成误诊或漏诊的问题,提出基于变分模态分解(VMD)及最大相关峭度解卷积(MCKD)的复合故障分离方法。首先对复合故障信号进行变分模态分解并根据峭度及相关系数准则重构信号作为前置滤噪处理,然后选取合理的滤波器长度及解卷积周期对重构信号进行最大相关峭度解卷积运算以实现故障特征分离,并结合1.5维能量谱强化信号瞬时冲击特征的优点,准确实现复合故障诊断,最后通过噪源干扰下的外圈、内圈复合故障实测信号分析验证该方法的有效性。研究结果表明:VMD方法能够有效滤除噪声干扰,且其滤噪效果比集合经验模态分解(EEMD)方法的滤噪效果好;MCKD方法能够将外圈、内圈故障分离,避免复合故障各成分间的相互干扰;1.5维能量谱能够强化谱图中的瞬时冲击特征。     

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

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