关键词： Optomechanics   Phase transition   Mode squeezing   Normal mode splitting  

摘要： We study the quantum dynamics of an optomechanical setup comprising two optical modes and one mechanical mode. We show that the same system can undergo a dynamical phase transition analogous to Dicke-Hepp-Lieb superradiant type phase transition. We found that the coupling between the momentum quadratures of the two optical fields gives rise to a new dynamical critical point. We show that selective energy exchange between any two modes is possible by coherent control of the coupling parameters. In addition we also demonstrate the occurrence of normal mode splitting (NMS) in the mechanical displacement spectrum. (C) 2013 Elsevier B.V. All rights reserved.

关键词： 刚-柔耦合机械臂   动力学建模   PID控制   振动抑制  

摘要： 人类对太空领域的探索以及航天事业的发展，极大的推动了机器人技术的发展和应用。其中，柔性机械臂质量轻便、定位精度高的特点尤其适合机器人作业，因此，在刚性基础上加入柔性元素成为机器人研究领域的热点方向。\n 刚-柔耦合性机械臂系统不仅存在大范围刚体运动，也存在柔性小变形弹性振动。柔性臂的弹性振动会增加很多不确定因素，影响系统稳定，且难以保证执行端的精度，因此需要选用合适的控制策略，实现对柔性机械臂振动的控制，使系统运行结果达到预定目标。\n 本学位论文总结了柔性机械臂的研究现状，讨论了机械臂动力学建模方法，以刚-柔耦合机械臂系统为模型，基于假设模态法和Lagrange方程，建立了刚-柔耦合机械臂系统的动力学模型，并截取一阶模态对动力学模型进行数值计算仿真研究。在动力学模型的基础上，通过比较不同控制策略的优缺点，选取滑模变结构控制方法对刚-柔耦合机械臂系统进行控制理论与方法的研究，通过对柔性机械臂采用合适的控制律抑制末端弹性变形并进行仿真分析，所得结果与采用PID控制策略得到的弹性末端变形结果进行对比，得到了两种不同控制策略中更适合柔性机械臂控制的方法。

关键词： 农用动力   机械润滑   故障诊断  

摘要： 搞好设备的润滑能提高生产效率、改善机器产品质量。本文阐述了由润滑引起的问题和润滑的意义以及围绕设备润滑进行的工作和润滑剂的选则原则,对充分发挥机器设备的效能,提高生产率,保证生产质量,降低成本和能源消耗,都有着不可估量的经济意义。

关键词： 机械系统   工艺设计   多体动力学模型   工程约束  

摘要： 产品的开发完整流程是设计、分析与制造的过程。在机械系统领域，三维CAD软件虽然存在接口使得机械系统的设计模型能够导入到动力学分析软件，然而这种导入得到的模型并不是一个装配体，而实质上只是零件的位置摆放，零件之间的约束关系是无法导入的。显然这无法在动力学分析软件中迅速地进行运动学与动力学的分析，还需要进行模型的重新装配。\n 基于上述情况，本课题以国家科技支撑计划制造业信息化重大项目和国家自然科学基金为依托，研究机械系统的三维装配模型到多体动力学模型的转换。这样可以减少用户的重复建模，直接由三维CAD模型生成动力学模型，为解决上述问题找到了很好的解决方案。\n 本文首先研究多体动力学模型的分析与表达，由多体动力学的建模理论得出动力学模型要解决的问题，对多体动力学模型的表达进行研究，包括模型元素的分类，部件、几何元素以及基本几何约束的表达。\n 其次，对于三维CAD系统的结构与表达进行研究，包括三维CAD的装配结构，装配模型元素的分类以及三维装配中的工程约束表达。\n 再次，对装配约束模型向多体动力学模型的转换进行研究，包括转换的流程、模型定位信息的转换，以及刚体物理信息的转换方法，并对工程约束与运动副的区别进行分析，对常见的运动副的识别提供了实现方法。\n 最后，在UG平台上开发装配模型向Simulink动力学模型的转换模块，并在UG上建立挖掘机的装配模型，导入到Simulink环境下进行运动学的分析，验证转换的可行性以及转换模块的正确性。

关键词： 高速板材搬运机械手   动力学   仿真   ADAMS  

摘要： 为了方便、准确地对所设计的高速板材搬运机械手进行动力学仿真分析,利用SolidWorks软件强大的建模功能对机械手进行三维实体建模,然后通过SolidWorks和ADAMS良好的数据接口将模型数据直接导入ADAMS,根据实际设计要求添加相关约束,在此基础上进行动力学仿真,测量重要部件的位移、速度、加速度和力的变化情况,通过观察它们的运动轨迹及相关曲线的变化趋势,对设计阶段的产品进行虚拟性能测试,以便及时发现设计中存在的问题并进行改正。

关键词： banana fiber   ultrasonic treatment   water absorption   mechanical strength   composites.  

摘要： This work focuses on the effect of ultrasonic treatment on the water absorption characteristics and the mechanical properties of woven banana fiber composites. Banana fibers were initially treated with NaOH solution. These were then subjected to ultrasonic treatment while preparing the composites. Similar method was followed earlier to study the effect on water absorption property of the composites which showed encouraging results (Ghosh et al., 2013). A mathematical analysis is done to find the diffusion kinetics. These composites were also tested for their mechanical strengths. The mechanical strengths were found to be better than the composites made in the general procedure. This shows that the composites prepared with ultrasonic treatment have superior properties and can be suitable for wide range of applications.

关键词： 机械动力学   建模   研究型教学  

摘要： 本文在分析了机械动力学课程特点的基础上,基于核心建模理论从教学目标、教学内容、教学方法等方面对机械动力学课程教学模式进行改革与实践。同时在机械动力学课程中开展了研究型教学实践。

关键词： Animal power   micro industry   speed increaser   mechanical device   battery charging   electric generation.  

摘要： In this paper authors designed, fabricated, cost estimated and experimentally studied the animal powered mechanical device to establish micro industry for electric generation to charge the batteries for home lighting, cooking food and minor irrigation at rural areas where grid power is not available and population rely on kerosene, wood and diesel pump-set for light, cooking food and irrigtion. Although animals have been using for domestic works since beginning of mankind, but the electricity generation by animal power is a novel technology. This invention provides animal powered mechanical device to charge the batteries. It has unique features of using animal power as prime mover for electric generator. Animal energy in the form of high-torque low-speed can be converted into low-torque high-speed through speed increaser to energize the electric generator. The electricity generated is stored in the batteries of different capacity and used for lighting, coocking and minor irrigation. This equipment is emission free, low cost and has long life. Also this equipment needs less maintenance and any person can run either skilled or unskilled.

关键词： Bio-polymer network   Mechanical response   Thermal fluctuations   Finite element method   Langevin dynamics  

摘要： A Langevin dynamics based formulation is proposed to describe the shape fluctuations of biopolymer filaments. We derive a set of stochastic partial differential equations (SPDEs) to describe the temporal evolution of the shape of semiflexible filaments and show that the solutions of these equations reduce to predictions from classical modal analysis. A finite element formulation to solve these SPDEs is also developed where, besides entropy, the finite deformation of the filaments has been taken into account. The validity of the proposed finite element-Langevin dynamics (FEM-LD) approach is verified by comparing the simulation results with a variety of theoretical predictions. The method is then applied to study the mechanical behavior of randomly cross-linked F-actin networks. We find that as deformation progresses, the response of such networks undergoes transitions from being entropy dominated to being governed by filament bending and then, eventually, to being dictated by filament stretching. The levels of macroscopic stress at which these transitions take place were found to be around 1% and 10%, respectively, of the initial bulk modulus of the network, in agreement with recent experimental observations. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Graphene   Mechanical properties   Molecular dynamics simulation  

摘要： Molecular dynamics simulations have been performed to study the mechanical properties of hydrogen functionalized graphene under shear deformation. It is found that the mechanical properties of graphene greatly depend on the coverage percent of hydrogen atoms. It is shown that the shear modulus, shear strength and fracture strain of graphene can be reduced as much as 50% with increasing hydrogen coverage percent up to 30%. It is also revealed that the distribution of hydrogen atoms would significantly influence on the strength and fracture strain of hydrogen functionalized graphene under shear deformation. (C) 2013 Elsevier Ltd. All rights reserved.