不完全分布柔度的全柔性机构的研究

针对介于具有集中柔度和具有分布柔度之间的全柔性机构,提出了第三类具有不完全分布柔度的全柔性机构的概念,并定义了其特征尺寸比值,根据这类全柔性机构的特点,提出在用伪刚体模型分析具有集中柔度全柔性机构的基础上,考虑构件弹性变形的分析方法.实例计算结果表明了该方法的有效性.     

平面柔性铰链机构的柔度计算方法

作为一种高精度的微动机构,柔性铰链机构已经在多个工业领域得到应用。该文针对平面柔性铰链机构,对机构设计中柔度计算方法进行了研究。在分析了一般柔性铰链的柔度计算方法的基础上,利用虚功原理,推导出单个铰链的变形/受力相较于整个机构的变形/受力的关系;利用矩阵分析方法,结合串联机构和并联机构的单元与终端的变形/受力的互逆形式的传递规律,分别获得了简洁的串并联柔性铰链机构的柔度计算公式。针对3种典型的串并联柔性铰链机构,进行了柔度计算和不同机构参数与各方向柔度关系的分析,并利用经典的有限元法进行了对比仿真实验。实验结果表明:该方法的计算结果与有限元法最大相差7%,平均相差3%。这表明该方法能够为平面柔性铰链机构的设计和结构优化提供参考。     

基于柔性相似度量和可能性歪度的尾矿坝风险评估方法

针对现有相似性度量方法只能处理线性信息以及信息的非对称性所导致的尾矿坝风险评估效果差的问题,提出了一种基于柔性相似度量和可能性歪度的尾矿坝风险评估方法.将广义模糊数扩展为自适应模糊数,给出了柔性相似度量方法,并对其基本性质进行了证明;剖析各评估指标信息的非对称性,建立了可能性歪度矩阵;利用柔性相似度量和可能性歪度,构建尾矿坝风险评估模型,并通过尾矿坝实例来验证方法的有效性.     

双轴柔性铰链转动柔度的计算与分析

利用力学和微积分基本公式推导了双轴柔性铰链转动柔度的一般设计计算公式.在此基础上得到了常用的直圆双轴柔性铰链转动柔度的设计计算公式.利用该公式定量地分析了柔性铰链参数对转角柔度的影响.同时针对多个不同尺寸的直圆双轴柔性铰链,采用推出的公式、Paros公式和有限元法进行计算,三种计算方法的结果吻合很好.由此说明了推出的计算公式的正确性和简洁性.     

双轴柔性铰链柔度的设计计算

文章利用能量法推导了双轴柔性铰链柔度的系列设计计算公式,在此基础上得到了常用的直圆双轴柔性铰链柔度的设计计算公式.针对多个不同尺寸的双轴柔性铰链,采用推出的计算公式、J.M Paros公式进行计算,2种计算方法的结果吻合很好,由此说明了推出的计算公式的正确性和简洁性.     

椭圆型柔性铰链闭式扭转柔度研究

针对变矩形截面梁扭转柔度难以解析求解问题,基于矩形截面梁扭转柔度公式及利用微分和积分思想,采用非线性曲线拟合方法得到了可用于推导变矩形截面梁闭式扭转柔度的设计公式,解决了变矩形截面梁扭转柔度不可积或可积情况下精度较低的问题,并用于解析推导椭圆型柔性铰链闭式扭转柔度公式.通过数值算例和有限元对闭式解析结果进行验证,并分析了结构参数对柔性铰链扭转柔度的影响,结果表明:闭式解与数值解结果一致,与有限元结果相比相对误差小于7.5%,且当铰链宽度和最小槽口厚度较小时对扭转柔度的影响较大,从而为变矩形截面柔性铰链受扭转力矩时的尺寸优化及结构设计奠定理论基础.     

一类轴孔装配混联柔性机构构型综合

被动装配是实现轴孔高精度配合的重要方法之一,其基本原理为柔性装配机构针对外界装配力与装配反力做出自适应柔顺变形,补偿由于工业机器人定位误差导致的轴孔中心线位移偏差及倾角偏差.作为被动装配方法的核心使能部件,柔性装配机构的性能直接决定装配成功与否,为此,开展了一类基于五自由度混联柔性机构轴孔装配的方案设计和柔性机构构型综合研究.该机构由分别具有2T1R(T表述移动运动,R为转动运动)和3R自由度运动的柔性并联模块串联组成,并采用片弹簧作为实现柔顺变形的基本柔性单元.在整体方案设计的基础上,以旋量作为数学工具,提出一种并联柔性机构构型综合的一般流程,讨论在片弹簧不同变形情况下的支链组成形式,拟定支链装配条件.结合实际工况,本文优选出3-RFS-3-RFS作为轴孔装配的柔性机构,利用有限元软件对得到的机构进行仿真以验证机构自由度及各向柔度,仿真结果表明该机构具备五自由度且各向柔性差异小于0.05%.搭建了轴孔装配实验台,装配实验结果表明对于直径为20 mm与10 mm的轴孔对,装配成功率分别可达90%与70%.     

中职学校实训课程教学改革探究

传统的技术工人已经不能满足现代社会飞速发展的要求,如何培养国家急需的高素质技能人才成为摆在中职学校面前的一个主要问题。本文从市场调研、掌握各种现代化加工技能、抓好办学特色、加强团队协助精神、以及注重基本手工操作技能等及格方面,针对如何培养社会急需的高素质技能人才,进行了探讨,提出了一些举措与建议,以期为中职学校的教学改革提供参考。     

柔性生产中基于人员任务匹配度的人员调度

文章针对单件小批量生产的柔性生产方式,考虑操作人员技能的多样性和对于不同任务技能水平的差异性等特点,根据操作人员对各任务的累计工作时间计算任务人员之间的匹配度,在此基础上建立柔性生产中资源受限下人员调度数学模型;通过启发式算法得到模型的初始解,并运用改进的遗传算法对模型进行求解,得到最优的人员调度方案以实现任务总完成时间最小的优化目标;最后结合具体实例验证了该求解模型的准确性与可行性。     

三自由度精密定位工作台的设计与运动学分析

针对精密柔性工作台多自由度高精度运动的需求,设计了一种采用柔性并联构型和压电陶瓷驱动的三自由度定位平台,通过建立的伪刚体模型进行运动学正解分析,并引入修正系数消除长杆柔性及柔性铰链中心偏移对工作台位移输出的影响,进一步提高了所建数学模型的精确度.利用有限元分析工具仿真了所设计的定位工作台的性能,确定了该工作台的修正系数矩阵,最终仿真试验验证了所建运动学模型的正确性.     

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~~