全铰链Ⅲ级六杆机构的有曲柄条件

以Ⅲ级六杆机构为例，采用降级法加以研究。改变Ⅲ级机构的原动件，将其变为Ⅲ级机构，并用由此确定的机构极限位置为机构模型以建立Ⅲ级六杆机构的有曲柄条件。     

铰链四杆机构中RRR杆组装配模式

铰链四杆机构中的RRR二级杆组可能存在2种装配模式.运用几何学中三角形三边长的关系对铰链四杆机构中RRR杆组的装配模式进行探讨,得到铰链四杆机构中的RRR杆组两杆件共线的条件,进而结合Grashof条件得到了各种铰链四杆机构死点存在情况及在整个运动过程中RRR杆组装配模式发生变化的可能性.     

Ⅲ—Ⅳ级六杆机构的传力特性分析及曲柄存在准则

本文讨论了Ⅲ级六杆机构的曲柄存在准则及其使用方法；研究了几种六杆机构的传力特性；得出几条重要结论，提出用“合力臂”评价六杆机构传力特性的方法；并对常用六杆机构的实用性作出了定性的评价。     

基于阿苏尔杆组的混合驱动机构动力学建模分析

通过对定轴转动的刚体构件、II级杆组和RR-RR-RR型III级杆组进行动力学分析,建立了一种新的机构动力学分析计算模型,根据模型对混合驱动机构进行拆分,并对得到的相应杆组模块进行计算.最后,运用该计算模型对一种混合驱动九杆机构进行实例分析,得到常速电机和伺服电机的平衡力矩,证实此建模计算分析方法可用于简化混合驱动机构动力学参数的计算.     

复杂平面机构运动分析的角变量逼近法

将机构中的高级杆组的一个或几个多副构件离散化后将其划分为几个Ⅱ级杆组,根据机构运动的几何等同条件,通过逼近不同Ⅱ级杆组中的同一构件的角变量(角位移、角速度、角加速度),实现对复杂平面机构的运动分析,建立了一种模块化求解复杂平面机构的数学模型·该方法在逼近过程中实现了搜索方向及步长的自调整,使问题大大简化·程序运行结果验证了该方法的正确性和高效性     

空间杆组结构分析及全部零阶杆组的分类

应用螺旋理论从杆组的角度进行空间机构的结构分析,推导出各阶机构的结构公式.根据空间杆组的公共约束数确定空间杆组的阶数,空间杆组所包含的构件数确定空间杆组的级数.利用空间杆组的结构公式,按照阶数与级数对其分类,综合出零阶Ⅲ级以下的所有空间杆组.通过杆组结构分析,为空间机构的创新设计提供了理论依据.     

关于机构定义及平面多杆多环连杆机构一种分类法的商榷

给出了机构的一个新定义,提出将平面多杆多环连杆机构分为Ⅱ级组、准Ⅱ级组和非Ⅱ级组机构,并阐述了这种分类法的优越性。     

用约束构件快速搜索法求解高级杆组的位置问题

提出了一种简单、有效的解决高级杆组位置问题的方法——约束构件快速搜索法．它将复杂的高级杆组转化为一个约束构件、几个Ⅱ级杆组和包含虚拟变量的虚拟原动件,建立被转化的Ⅱ级杆组的位置参数与虚拟变量之间的函数关系,根据约束构件的装配条件形成优化目标,使用一维搜索方法获得原高级杆组的位置解、该方法具有很好的收敛速度,适用于任意复杂的高级杆组,对所提方法的原理和分析步骤进行了介绍,编制了通用的高级平面机构的可视化分析程序．通过对含RR—PR—RPⅢ级杆组的多功能家用缝纫机送料机构的分析实例,演示了该方法的具体应用．     

齿轮-五杆组合机构运动学特征仿真分析

机械手常采用齿轮-五杆组合机构完成物料抓取动作,它由定轴轮系匀速旋转,向两自由度五杆机构传递运动.由于Ⅱ级杆组轨迹通过第Ⅰ级两个齿轮转角合成为位移输出,致使外伸点位移计算过程相对复杂,基于零件坐标变换求解的通用办法给出齿轮-杆组合机构的运动学推导结果,但编写程序完成仿真及后处理过程仍相对困难.为直观表达机构运动学规律,由AD-AMS软件建立参数化模型,通过改变杆件长度、传动比和连架杆起始角相位差,寻求连架杆输出轨迹的改变规律.仿真结果表明齿轮对两曲柄的运动关联输出导致增大连架杆初始相位角时,外伸杆端点轨迹在横、纵两方向上均增大.     

用一维优化对III级以上平面机构进行运动分析

提要利用间接法的原理,将Ⅲ级或Ⅲ级以上的平面机构转化为Ⅱ级机构,然后调用Ⅱ级杆组运动分析的通用子程序求解.对求解过程中的关键问题——位置分析,提出了用一维优化的方法求解.此方法无需建立位置分析解析式,只需要调用Ⅱ级杆组位移分析子程序和一维优化子程序.其求解方便,初值范围宽,精度高,计算速度快,具有通用性.文中有两个计算实例,便于在微机上应用.     

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     

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