单圆弧盘型凸轮机构特性的比较研究

提出了用高副低代的化归方法研究单圆弧对心直动滚子从动件盘型凸轮机构的特性．论证了化归后的机构瞬时速度、加速度和压力角与原机构等价，在此基础上讨论了原机构的运动特性．并以最大无量纲速度和加速度为标准，将凸轮机构从动件常用运动规律特性与该圆弧凸轮的从动件运动规律特性加以比较，指出其适用场合为中、高速轻载。     

实测开口凸轮廓线的分析与再设计

将拉格朗日三点数值公式应用于实测织机开口凸轮的廓线分析,根据凸轮机构运动简图及凸轮廓线的极坐标实测值可直接计算从动作的位移、速度、加速度,然后由求得的加速度曲线与理论规律的对比,通过计算机CAD重新设计从动件的运动规律.该方法适用于研究缺乏原始设计资料的凸轮机构及其它类型的平面凸轮机构.     

Dynamic modeling and motion analysis of wipe off bamboo surface layer machine

通过建立凸轮机构的数学模型,得到去青机器的运动规律.首先提出去青机器的结构,介绍机器如何实现去除毛竹青色表皮,凸轮机构输出的往复运动是机器的主运动.按质量等效、刚度等效原则简化凸轮机构,建立凸轮机构动力学模型,依据动力学模型与Koster模型建立凸轮机构数学模型,反映出从动件位移、速度和加速度的关联;根据余弦加速度运动与多项式型运动规律,与凸轮机构边界条件推导出从动件输出端运动规律的多项式;结合去青机器的运动参数,简化运动微分方程,推导出从动件输入端运动规律方程组,得到主运动的运动规律,并进行参数扰动分析,作为去青机器设计的理论依据.     

共轭凸轮廓线方程的一种解析设计方法

本文提出一种用解析法分析具有平板从动件或滚子从动件的共轭凸轮所产生的运动,和给定从动件运动规律后设计共轭凸轮廓线方程的方法,就平板和滚子两种情形分别给以简要的推证。这个方法在计算机辅助设计系统里会有一定用处。     

设计直动从动件盘形凸轮的新方法

提出了一种利用凸轮与从动件相对运动设计凸轮的新方法（简称相对运动法）,该方法利用凸与从动件的相对速度确定盘形凸轮的压力角和轮廓,相对加速度确定凸轮曲率半径,基于从动件和支承绕凸轮轴线反转的模型,将从动件滚子轴线对凸轮的相对速度和相对加速度转变为绝对速度和绝对加速度,应用矢量法和从动件坐标系中的分量表达法,导出了滚子摆杆盘形凸轮机构的凸轮压力角,轮廓线方程和曲率半径的解析表达式,并通过CAD方法给出了设计实例。     

蜗式凸轮机构的分度误差计算

以啮合理论为基础,导出了蜗式凸轮机构从动件(即分度转盘)在凸轮实际轮廓和实际机构尺寸诸因素的影响下,分度误差的计算公式。并结合实例,运用变形梯形加速度运动规律,通过微机计算,得出了该凸轮机构从动件的分度误差曲线。     

凸轮最佳运动规律组合曲线的优化设计

本文运用优化方法对凸轮机构从动件的运动规律进行改进,从而可以按要求找出使运动规律的速度、加速度及加速度变化率中最大值均最小,或使其中某一个或某几个最大值为最小的组合曲线方程。给设计高速重载凸轮提供良好的依据。     

平面凸轮廓线分析的一种数值计算方法

本文将拉格朗日五点数值微分公式应用于平面凸轮廓线分析,根据凸轮机构运动简图及凸轮廓线的极坐标值可直接计算从动件的位移、速度、加速度及压力角值.这样就解决了历来沿用的图解微分法存在的误差大的问题.这种方法适用于研究缺乏原始设计资料的凸轮机构(如国外进口机器中的凸轮机构),以及分析凸轮廓线尺寸误差对凸轮机构运动和压力角的影响.文中以滚子摆动从动件平面凸轮为例,其解题方法也适用于其它类型平面凸轮机构.文末附有数值计算实例.     

滚子从动件盘形凸轮的三维快速精确设计

凸轮机构设计主要包括凸轮轮廓曲线和从动件运动规律的设计.在确定从动件的运动规律后,根据从动件的运动规律来确定凸轮的轮廓曲线,利用Matlab编程语言,可以精确作出任意凸轮轮廓曲线和各种从动件的运动规律曲线,同时还可以将设计出来的精密轮廓曲线导入三维软件Pro/engineer中进行三维建模,达到快速精确设计凸轮的目的.     

凸轮机构运动特性系数最优值

本文通过数学方法获得了停—升—停凸轮机构从动件运动规律的特性系数最佳值，速度、加速度、跃动和转矩特性系数最小值分别为１、４、３２和２．２５和它们之间的依赖关系，并提出了对应的最优特性系数搭配的运动规律模式。     

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