基于虚拟仪器的机械转子轴心轨迹分析

转子轴心轨迹是判断机械转子运行状态和故障征兆的重要依据,文中研究了几种机械转子典型故障及其对应的频率和轴心轨迹特征,运用LabVIEW软件平台,开发出智能控件化虚拟式轴心轨迹测试分析系统,调用由VC 编写的动态链接库(DLL)函数实现对机械转子振动信号的采集.试验表明,转子轴心轨迹测试分析系统可实时显示轴心轨迹、轴心位置和两路相互垂直振动信号的波形和频谱,以此可以判断一些常见的旋转机械故障,计算出用来消除转子不平衡的平衡质量块的大小及坐标点位置.     

智能控件化虚拟仪器的模型化开发

介绍了智能虚拟控件及其仪器的有关概念、原理,并讨论了基于计算机的系统建模的五元模型。通过对智能控件化虚拟仪器及其开发系统的深入研究,将基于计算机的系统五元模型引入到智能控件化虚拟仪器系统,提出并详细论述了智能控件化虚拟仪器系统的统一模型。该模型为控件化虚拟仪器的开发和使用提供了统一的规则和方法,规范了控件化虚拟仪器的开发。     

EEMD滤波的转子轴心轨迹提纯方法

针对轴心轨迹提纯问题,研究了集合经验模式分解(Ensemble empirical mode decomposition ,EEMD)抑制模态混叠的特性及其滤波特性,提出了基于EEMD滤波的转子轴心轨迹提纯方法。应用EEMD将信号分解成一系列的固有模式函数(Intrinsic mode function,IMF)分量,再根据先验知识选择相应的IMF分量重构信号,组合成提纯轴心轨迹。对小型转子试验台转子轴心轨迹的成功提纯验证了该方法的有效性,与谐波窗和EMD轴心轨迹提纯方法的对比结果表明了该方法的优势,为转子系统故障诊断提供了一种新的手段。     

静载荷作用下偏心转子电磁振动特性

偏心转子不仅受动载荷作用,还受静载荷作用。该文推导了转子同时考虑动、静偏心的气隙长度统一公式,利用数值方法计算出作用于转子的不平衡磁拉力(UMP),建立了UMP、静载荷(重力)、不平衡质量激励力作用下转子系统的运动微分方程。分析了动偏心和动静复合偏心情形下不计静载荷时和考虑静载荷时转子系统的轴心轨迹和位移频谱,讨论了静偏心方向、初始静偏心量对转子系统振动特性的影响。结果表明:静偏心方向影响转子轴心轨迹的位置分布,使位移频谱中幅值周期性变化,静偏心量的增加使位移频谱中出现4倍旋转频率的振动分量。静载荷对转子系统的作用可视为该静载荷方向上大小恒定的静偏心。     

三维轴心轨迹动态显示的实现方法

轴心轨迹是时域中对转子径向振动进行监测和诊断的基本方法,三维轴心轨迹的动态显示能准确反映转子的振动情况,本文就其显示实现过程作一描述。     

分数阶阻尼裂纹转子的非线性动力学特性分析

为了有效地提高转子系统特性的分析精度,使其能够准确地进行故障诊断,以Jeffcott转子模型为基础,建立了带有分数阶阻尼和横向呼吸裂纹故障的转子系统的动力学模型.采用4阶龙格库塔法和10阶连分式欧拉法对转子系统的动力学方程进行数值仿真计算,利用轴心轨迹图、Poin-care截面映射图和分岔图等,研究了阻尼的分数阶次、转速和裂纹深度对裂纹转子动态特性的影响,并通过实验对理论分析结果进行了验证.分析结果表明:在半临界转速附近,由于裂纹的存在,转子的轴心轨迹呈现明显的双环型(或称内8字形),因此响应中的2倍频分量占主导地位.随着分数次阻尼阶次的增加,转子系统依次经历混沌、准周期和周期运动,同时裂纹深度、不平衡量以及转速对转子系统的动态特性具有明显影响.     

局域波法在转子轴心轨迹特征提取中的应用

为排除转子系统故障诊断中各种噪声干扰,提出基于局域波分解尺度滤波来提纯轴心轨迹的方法,并给出尺度滤波的滤波器表达式.局域波法将任何复杂信号分解成为有限数目的具有一定物理意义的基本模式分量(IMFs),每一个分量描述时变信号中不同频率和尺度范围的固有振动模式.通过对加噪信号的有效去噪,检验了尺度滤波的可行性.诊断实例说明,该方法可合理、有效地提取转子系统的故障特征.     

汽轮发电机转子位置调整

研究了汽轮发电机转子系统位置最佳调整，考虑轴油膜力非线性，用有限元法建立了大型汽轮发电机转子系统非性方程组，用无约束极小化方法求解了转子在工作转速范围内轴心实际位置。     

基于小波包变换的船舶轴系轴心轨迹特征提取

为实现通过轴心轨迹识别船舶轴系的工作状态,在船舶轴系轴心轨迹测试实验台上测试各轴承处水平和垂直的位移信号,应用小波包变换对各轴承处的轴心轨迹进行特征提取及分析.结果表明:实测船舶轴系轴心轨迹混乱,无法用于船舶轴系工作状态的识别;利用小波包变换提取的轴心轨迹呈清晰的香蕉形、椭圆形及外“8”字形,其中香蕉形和外“8”字形轴心轨迹刻画了转子不对中工作状态,椭圆形轴心轨迹刻画了转子不平衡工作状态.因此,小波包变换可用于船舶轴系轴心轨迹的提取,实现船舶轴系工作状态的识别.     

水电机组故障诊断专家系统中图形征兆的提取

将小波包分解及重构技术用于转子轴心轨迹提纯，利用离散余弦变换实现轴心轨迹的自动识别，结合水轮发电机组故障诊断系统，实现了轴心轨迹图形征兆的提取，论证了所述方法的合理性和可行性．利用该方法提高了系统的诊断速度和精度．     

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     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

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