高加速度的柔性3-RRR并联机构尺度综合设计

该文以设计高加速度的平面柔性3-RRR机构为目的,研究一种平面3-RRR并联机构的尺度综合设计方法.建立机构的运动学逆解方程、速度和加速度传递方程以及动力学逆解模型.根据机构的特点,给定末端速度和加速度曲线,分析机构输入和输出加速度与设计参数之间的关系,提出兼顾最大加速度和作业空间要求的并联机床尺度综合设计方法,并通过具体的设计计算,证明该方法可行.最终给出一组满足速度、加速度以及工作空间要求的尺寸参数.     

龙门式混联机床的静刚度分析

静刚度是机床设计的重要指标之一.为了解基于平面三自由度并联机构的龙门式混联机床的静刚度性能,提出了一种分析方法,此方法同时考虑了并联支链和铰链的变形.根据微分误差模型,建立了机床刚度矩阵,得出了机床位置刚度和转动刚度的分布情况,着重讨论了铰链刚度对机床刚度的影响.结果表明 在工作空间内沿Y方向位置刚度具有对称性,转动刚度具有不对称性; 铰链刚度对机床刚度影响很大,在并联机床或者混联机床设计中必须选用刚度好的铰链连接形式.     

3种用于混联机床并联机构的分析

分析了不同参数条件下3种可用于混联机床的并联机构:Stewart并联机构、动平台共用铰链机构以及中心伸缩杆机构,提出了虚拟工作空间和虚拟最大内接圆半径作为指标评价姿态实现能力.     

并联机床主运动模块设计的研究

提出了一种新型模块化并联机床的结构模型，采用并联机构实现了机床的主运动。利用机构尺寸型空间模型理论，研究了机床主运动模块平均二自由度机构的运动特性，给出了机构运动学的正反解。研究表明，末端执行器的奇异位形形式与机构尺寸有关，而机构存在着3种类型的奇异位形，其最大工作空间取决于并联机构两支链中较短杆的长度，研究为快捷地设计开发三轴或多轴并联机床提供了基础理论。     

基于ADAMS的3-TPS混联机床运动学和动力学仿真

针对3-TPS混联机床的电机参数选择和机构设计问题,在SolidWorks软件中建立混联机床的三维实体模型,然后把该装配体模型导入到ADAMS/View里,形成了具有多体动力学的虚拟样机仿真模型.通过对该机床进行运动学和动力学分析,仿真得出各主动杆件的速度和驱动力曲线.以空间搜索的方法,找出各主动杆件的最大速度和最大驱动力,从而获得了3-TPS混联机床的运动和动力特性,为机床的电机选择和机构以及控制系统的设计提供了重要参考依据.     

基于加工空间的并联数控机床参数优化

介绍了机床尺度综合的一般方法和尺度综合中参数设计的优化目标·结合机床的特点和机床设计的实际要求提出了一种新的机床尺度综合流程·给出了一种在机床的加工空间已定的前提下,以各驱动支链的长度最小为优化目标并使各铰链位置和虎克铰摆角在合理范围内以及各驱动支链的最大驱动速度和加速度及机构的灵巧性指标综合最小为条件的机床结构参数优化方法·当机床的加工空间为400mm×400mm×400mm的立方体空间,刀具的最大移动速度和加速度分别设定为0 5m/s和10m/s2时,用该方法对一种三杆并联数控机床的结构参数进行了优化设计,得到了3组较佳的参数·     

球坐标式3自由度并联机器人机构的运动学设计

研究一种球坐标式3自由度并联机器人机构的运动学设计,包括运动学反解、速度、考虑铰链转动范围和干涉等条件下的工作空间,和结构参数对工作空间的影响以及灵巧性能指标及其在保角变换平面上的分布特性,这些分析结果和结论对并联机器人机构的设计、轨迹规划和控制等有重要的指导意义.并联机构在并联机床、坐标测量机构和工业机器人等领域有广阔的应用前景.     

新型混联机床主体—3UPS +1RPU并联机构的自由度分析与仿真

提出了一种新型的以3UPS+1RPU并联机构作为主体机构,再将主体机构串联在y轴方向滑动导轨上,从而达到五坐标联动加工的一种混联机床的设计思路。对于该机床的主体机构——3UPS+1RPU非对称并联机构,基于螺旋理论进行自由度的分析与计算;在此基础上应用多自由度并联机构输入选取理论来确定该机构的驱动输入副。然后运用Solid Works对其进行实体建模;并导入到ADAMS中进行自由度性质和数目的分析验证。虚拟样机验证结果与理论分析的结果具有一致性,这为后续深入研究该新型混联机床其他方面的性能提供了参考依据。     

3自由度并联机构的动力学各向同性评价方法

该文以应用于高速、高加速混联加工装备中的一种3-PRRU空间3自由度并联机构为研究对象,研究其动力学建模及动力学各向同性评价方法。基于虚功原理,建立了3-PRRU并联机构的动力学模型,并从动能角度出发,提出了两个评价机构各向同性性能的指标。针对该指标,提出了一种5维图像描述方法,并对3-PRRU并联机构进行各向同性性能评价。该动力学各向同性评价指标具有量纲统一、物理意义明确的优点,可以更准确地对并联机构的动力学性能分布进行表征。     

2-RRC-SPS并联机器人工作空间的研究

提出了一种并联机器人工作空间分析的解析方法,该方法以曲面分析为基础,结合并联机器人的运动特性,得到了并联机器人工作空间边界曲面的方程.以2-RRC-SPS并联机器人为例,分析计算了其工作空间.在此基础上,描绘出了并联机器人工作空间边界曲面及截面视图.分析结果表明2-RRC-SPS并联机器人的理论工作空间是一个不规则的实心球体,该机构具有几何形状规则的作业空间,是一种较为理想的能实现三维移动操作的并联机构选型,获得的结果可应用于该并联机构的设计之中.     

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.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

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