旋转柔性智能结构振动滑模控制方法研究

基于Hamilton原理和高阶模型理论,建立了旋转刚柔耦合智能结构的动力学模型,并通过滑模变结构控制(SMC)对结构的振动进行控制.通过一阶近似模型理论考虑了结构轴向、横向和转角相互间的耦合作用,即考虑了柔性梁和智能材料的几何非线性.利用有限元方法得到了考虑离心刚化效应的有限维模型.利用滑模控制方法对结构的振动进行抑制.滑模面通过最优化方法得到.数值仿真结果表明滑模控制方法有效地控制了带有参数扰动的旋转柔性智能结构振动.     

作平面运动柔性梁的刚柔耦合动力学建模及分析

从连续介质力学理论出发,考虑变形产生的几何非线性效应对运动柔性梁的影响,在柔性梁的纵向、横向变形中考虑横向弯曲和轴向伸缩的耦合作用,得到了较为精确的变形模式,根据假设模态分析法对柔性梁进行离散,利用Kane方法建立平面柔性梁的刚柔耦合动力学方程.最后通过仿真算例验证了耦合模型的正确性和有效性.     

预压叠层柔性机械臂弯曲试验及有限元数值仿真

为抑制柔性机械臂的振颤，该文提出利用组合构件的滞迟特性来改善机械臂的动力学品质以达到减振的作用；介绍了预压叠层柔性机械臂力-变形本构关系的试验研究及有限元数值仿真。研究了其滞迟特性随预压力、载荷及工作点的变化；分析了叠层结合面的作用机理；表明组合柔性机械臂抑振效果好，结构简单。在用ANSYS进行有限元数值仿真时考虑了几何非线性与叠层之间接触状态非线性的影响，数值仿真结果与试验接近，该方法为组合柔性机械臂的静力学、动力学的研究及设计计算提供了有效手段。     

柔性多体系统弹性碰撞动力学建模

以平面柔性双摆为研究对象,基于Hertz接触理论,考虑几何非线性,用变分原理建立了柔性体的动力学变分方程,根据运动学约束关系,运用缩并法,建立了柔性双摆系统接触碰撞的动力学方程.首先通过柔性单摆和固定刚性物体的撞击实验验证了建模理论的正确性.在此基础上,对柔性双摆系统进行仿真计算,得到了撞击力变化规律,并揭示了横向变形和角速度在冲击波传播过程中的突变现象.     

基于奇异摄动理论的机器人关节控制研究

针对机器人柔性关节存在位置控制精度低的问题,在考虑关节内部非线性摩擦和外界扰动等因素的情况下,建立柔性关节动力学模型,提出基于奇异摄动理论的干扰观测器滑模控制方法,利用该控制方法对关节控制系统进行Lyapunov稳定性分析和MATLAB仿真.结果表明,基于奇异摄动理论的干扰观测器滑模控制方法能够减小关节内部非线性摩擦和...     

柔性体碰撞阻尼模型的适用性分析

用理论和实验相结合的方法研究柔性梁和刚性球正碰撞过程中2种碰撞阻尼模型的适用性.基于Euler Bernoulli假设,考虑几何非线性,用绝对节点坐标法建立了平面柔性梁的动力学模型.用非线性弹簧阻尼模型建立了柔性多体系统的碰撞动力学方程;在考虑局部残余变形的前提下,用弹塑性模型建立了柔性多体系统的碰撞动力学方程,将碰撞过程分3个阶段（弹性碰撞,弹塑性碰撞,弹性恢复）进行分析.设计了柔性梁和刚性球的碰撞实验,将仿真计算与实验数据对比.结果表明,弹塑性模型更适用于碰撞分析.
     

考虑杆件柔性和铰间隙的可展结构动力学数值模拟

为了保证空间可展结构可靠地运行,需精确预测在轨运行中可展结构动力学性能,在动力学模型中应考虑铰间隙和构件柔性的影响。该文采用间隙铰的非线性弹簧阻尼模型,构造可展结构动力学方程。分别对理想连接铰、考虑铰间隙、以及考虑构件柔性等3种情况的典型可展结构进行动力学模拟。仿真结果表明间隙和构件柔性对可展结构动力学性能有较大影响:连接间隙导致销轴与孔体产生一系列内碰撞,且初始碰撞接触力较大;考虑构件柔性后,间隙处产生的碰撞力减小,接触时间增长,销轴与孔体的接触碰撞区域扩大;间隙还引起了中心体姿态角速度的扰动。     

大范围运动的柔性曲线梁动力学建模及仿真

针对航天器等领域中应用柔性曲梁的动力学问题，基于有限元方法，将连续的柔性曲线梁离散化为具有12个自由度的空间梁单元模型．为缩减系统的运动学变量数目，将柔性曲线梁的物理坐标转化为模态坐标．在此基础上，依据Kane方程建立了作大范围运动的柔性空间曲线梁非线性动力学模型．动力学数值仿真的结果表明。对小曲率柔性曲线梁，其横向变形比纵向变形大得多．     

柔性多体系统接触碰撞动力学研究

用有限元方法对柔性系统的接触碰撞问题进行了数值仿真计算．以柔性杆与刚块纵向碰撞为例，建立了接触碰撞动力学模型，利用有限元方法建立了接触碰撞期间的动力学方程．通过对不同的参数进行大量的数值仿真，结果表明，有限元方法能够仿真在接触碰撞期间的柔性杆纵向振动的弹性波，碰撞力时间响应的数值解与解析解吻合较好．     

双柔性机械臂伺服系统PI控制策略

柔性机械臂系统中的负载柔性、关节柔性会导致输出转速波动，故使用PI控制策略对伺服系统进行控制.根据连续体振动理论和拉格朗日方程建立同时考虑负载和关节两种柔性的动力学模型，并分析了两种柔性对系统传动特性的影响.使用Arnoldi方法对传递函数进行降阶，并对降阶误差进行评价.采用极点配置方法设计控制器参数，讨论了极点阻尼系数、自然频率等对系统动态特性的影响.最后进行双柔性机械臂的仿真分析和转动控制实验，结果表明：适当调整控制器参数可以有效减弱柔性机械臂伺服传动系统末端的转速波动，进而抑制机械谐振现象，使系统趋于稳定.     

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