机械结构中的接触热阻

论述了接触热阻在机械工程和机床研究中的应用；接接触突峰宰化为圆锥接触模型，经出了计算单点接触热阻的新公式；在分析机械加工表面微形状和接触变形的基础上，推出了计算多点接触热阻的理论算法；对所提出的算法进行了实验验证。     

直线滚动导轨结合面参数对数控机床动态特性的影响

对某机床厂CKS6116卧式数控机床导轨结合面的静、动刚度与阻尼等参数特性进行了研究.首先利用静、动态特性实验得出机床的各项动态参数,然后用ANSYS有限元分析软件模拟和显示机床在考虑导轨结合面参数条件下的各阶模态下的振型和固有频率.最后对整个机床进行激振试验,验证了仿真参数的准确性.说明直线滚动导轨结合面的静、动刚度与阻尼对机床的动态特性具有很大的影响.     

高速电主轴力-热耦合特性建模

针对高速电主轴工作在力热耦合状态下,结合部刚度、阻尼、热阻等物理参数确定及结合部的精确计算困难等问题,采用分形接触理论和赫兹接触理论,研究了高速电主轴固定结合部和可动结合部的力-热耦合特性,建立了高速电主轴结构界面的物理表征方法.在此基础上,提出了一种考虑结合部特性的高速电主轴力-热耦合建模及其数值方法,并结合机床高速电主轴实验测试,验证了该方法的有效性.     

基于结合面的机床摄动分析及优化设计

从简单结构的动力学本构出发,采用撮动理论对基于结合面的机床整机动力学特性进行了分析,指出了结合面的参数变化对整体质量、刚度和阻尼矩阵的影响.通过对比摄动前后刚度和阻尼矩阵的变化,阐述了在整体刚度矩阵摄动下机床动态性能的变化规律,并对动梁式龙门机床进行了特征值的灵敏度分析和定量化动态优化设计,指出了4个结合面刚度对机床固有频率的影响程度,获得了将机床第1阶固有频率从29 Hz提高到35 Hz所需的导轨结合面的确定刚度值.有限元仿真结果表明,特征值一阶摄动法的误差在5%以内,从而为机床结合面的定量化设计提供了理论依据.     

不同载荷下的球轴承内部接触热阻计算

针对球轴承滚动球体与内、外滚道之间的不完全接触而引起的接触热阻,结合半空间椭球坐标系拉普拉斯温度分布方程,提出了滚动球体与内、外滚道之间接触热阻的理论计算方法.以赫兹接触理论为依据,研究了轴承内部载荷分布和椭圆接触区域参数的确定方法.分析了不同载荷对轴承内部接触热阻的影响.高速进给系统平台的实验结果表明理论值和实验测试值的最大误差仅为4.62％,该方法为不同载荷条件下球轴承内部接触热阻的解析计算提供了一种有效方法.     

真空低温下卫星常用材料接触热阻的试验研究

真空、低温环境下接触热阻的准确测量对于卫星内部热控制具有重要的实际意义。自行搭建了一套优化的基于稳态法测量接触热阻的试验平台,用于在真空、低温环境下测量由螺栓压紧的材料间的接触热阻。测量了卫星中常用接触对（铝合金-铝合金、铝合金-玻璃钢、铝合金-聚酰亚胺）在不同温度、不同预紧力矩下的接触热阻,研究了预紧力矩、温度、材料对接触热阻的影响,结果表明：玻璃钢与聚酰亚胺的隔热性能优于铝合金;3种接触对的接触热阻均随温度升高而减小,随螺栓预紧力矩的增大而减小。     

机床结合面结构动态参数识别

该文充分考虑机械结合面的接触特性,提出了利用三维接触单元和弹簧-阻尼单元相结合的方法建立结合面的有限元模型,再应用优化参数法对结合面的接触刚度和阻尼等参数进行识别。在此基础上,建立了螺栓连接固定结合面模型,并与一内圆磨床组件的模态测试结果相比较。研究表明:该方法有很好的精度,可以用于实际计算。     

进给系统成对安装的角接触球轴承热分析

考虑轴承的离心力、陀螺力矩等因素建立滚珠的动载荷平衡模型,利用牛顿-拉弗逊法求解.然后对轴承、丝杠轴、轴承座取温度节点,考虑轴承热节点之间的接触热阻并利用轴承内部温度变化结合润滑剂的黏温效应实时修正轴系热源发热量、热边界条件等特性参数,建立机床进给轴承系统成对安装角接触球轴承的瞬态热网络模型.利用差分矩阵结合Matlab软件数值求解预测出不同进给速度下轴承座表面等重要节点的瞬态温升曲线,分析不同转速下轴系温度场的变化.并对不同进给速度下的轴系安排实际工况下的试验验证,证明了预测模型的有效性.     

机床固定结合面接触热导三维分形模型

结合面的热变形是影响机床精度的一个主要原因,而对接触热导的研究可以从理论上探究影响热变形的深层原因,基于对固定结合面单点接触模型的研究,并在考虑了弹塑性变形机制的情况下,建立了固定结合面接触热导分形模型并通过仿真计算得出了分形维数、分形粗糙度尺度参数等材料性能参数对固定结合面接触热导的影响关系。     

不同材料翅片管换热器特性的试验研究

针对目前对翅片管换热器的试验研究大多不涉及到接触热阻,或者实际上将接触热阻归纳到气体侧热阻中的问题,对翅片管换热器的接触热阻进行了研究,逐步积累有关的数据。利用风洞试验台研究了在相同的加工工艺条件下,基管和翅片材料对接触热阻的影响。通过对4种工程常用材料的翅片管换热器的试验研究,在工业常用的雷诺数Re范围内给出了换热和阻力特性的试验关联式。试验结果表明,在1 300Re4 500的范围内,铁白铜管-铝翅片管外空气努赛尔数比304不锈钢管-铝翅片高28%~40%,在相同的加工工艺以及相同的翅片材料(铝)的情况下,304不锈钢管比铁白铜管增加的附加接触热阻为4.53×10-3 m2·K·W-1。本试验的不确定度为7.28%,接触热阻数据可靠,可供工程实际选用。     

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

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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