摘要： Actin filaments associated with myosin motors constitute the cytoskeletal force-generating machinery for many types of adherent cells. These actomyosin units are structurally ordered in muscle cells and, in particular, may be spatially registered across neighboring actin bundles. Such registry or stacking of myosin filaments have been recently observed in ordered actin bundles of even fibroblasts with super-resolution microscopy techniques. We introduce here a model for the dynamics of stacking arising from long-range mechanical interactions between actomyosin units through mutual contractile deformations of the intervening cytoskeletal network. The dynamics of registry involve two key processes: 1) polymerization and depolymerization of actin filaments and 2) remodeling of cross-linker-rich actin adhesion zones, both of which are, in principle, mechanosensitive. By calculating the elastic forces that drive registry and their effect on actin polymerization rates, we estimate a characteristic timescale of tens of minutes for registry to be established, in agreement with experimentally observed timescales for individual kinetic processes involved in myosin stack formation, which we track and quantify. This model elucidates the role of actin turnover dynamics in myosin stacking and explains the loss of stacks seen when actin assembly or disassembly and cross-linking is experimentally disrupted in fibroblasts.

关键词： 直升机驾驶机器人   机械腿   动力学分析   运动学分析  

摘要： 为了提高直升机驾驶机器人的设计效率,开展了直升机驾驶机器人机械腿的动力学建模和分析。先建立机械腿的运动学模型,分析机械腿脚掌踏板的位置、姿态与驱动关节转角的关系。通过数值计算,分析了机构参数对机械腿运动学特性的影响,并找出机构运动的极限位置,得到机构设计的尺寸限制条件。然后建立了机械腿的动力学模型并对其特性进行了参数化分析,采用ADAMS仿真平台对建立的直升机驾驶机器人机械腿的运动学和动力学模型进行了验证。参数化分析和动力学仿真验证为直升机驾驶机器人脚蹬控制系统设计和研究提供了理论基础。

关键词： 机械手   动力学分析   稳定性  

摘要： 本文分析的水泥插袋机械手臂是一个相对比较复杂的机械结构系统。设备在运行过程中,动态性能分析十分重要,这是评价抗振以及系统噪声的必不可少的指标,若处于高速运行,振动对于机械手的影响更需要关注。在本文中为了保证机械手臂的稳定性,使用ANSYS软件对其进行动态性能分析。

关键词： 机械设计制造   学院   三峡大学   能源与动力工程   机械电子工程   材料成型   机械工程   控制工程  

摘要： 2014年1月原机械与材料学院更名为机械与动力学院,学院现设有机械设计制造及其自动化、机械电子工程、材料成型及控制工程、工业工程、能源与动力工程、核工程与核技术六个本科专业,其中机械设计制造及其自动化为国家特色专业、第二批卓越工程师教育培养计划专业和省本科品牌专业,材料成型及控制工程为第三批卓越工程师教育培养计划专业。拥有机械工程一级硕士点、机械工程专业学位点、机械工程领域工程硕士点、工业工程专业学位点,机械制造及其自动化为湖北省重点学科。

关键词： 船舶   动力系统   机械噪声   辨识   耦合噪声源   骨架线法  

摘要： 针对传统方法对船舶动力系统机械噪声辨识效果差、准确性较低等问题,提出一种新的船舶动力系统机械噪声辨识方法。首先采用传递响应函数矩阵对耦合噪声源进行分离;其次通过主分量缩进法,解除耦合信号的干扰,获取有效噪声源;再次通过导纳曲线计算船舶动力系统的机械物理参数,构建齿轮有限元模型并求出齿轮振动加速度;最后完成船舶动力系统机械噪声辨识。通过仿真实验,验证了该方法的有效性,结果表明该方法辨识特征点压级差值在0~0.09dB,获取二自由度系统物理参数相对误差小于1.7%,说明设计方法对船舶动力系统机械噪声辨识效果好。

关键词： 工业机械臂   动力学   拉格朗日方程   虚拟样机  

摘要： 为了研究六自由度工业机械臂的动力学特性,基于拉格朗日方程建立机械臂的动力学理论和仿真模型。分别建立各个构件的转动动能、平动动能和势能方程,进而得到各个构件的拉格朗日因子,通过虚拟样机模型测量对应构件的拉格朗日因子三个组成部分,与相应的模型计算结果进行对比,验证拉格朗日因子的正确性。基于正确的拉格朗日因子和广义多刚体动力学方程,建立最终的机械臂动力学模型,并通过ADAMS动力学仿真验证所建立的模型的正确性。

关键词： 电控机械式自动变速器   动力学分析   MATLAB   Simulink  

摘要： 电控机械式自动变速器(Automated mechanical transmission,简称AMT)相较于其他形式的自动变速器,传动效率高、燃油经济性好、结构简单、生产继承性好、成本低,在我国具有良好的市场前景。本文提出了动力性能评价指标,对AMT的起步过程和加速过程进行动力学分析,并基于长安逸动整车参数,通过MATLAB/Simulink平台建立AMT的动力性仿真模型。结果表明,试验结果与仿真结果误差较小,AMT动力性仿真模型有效的模拟了AMT的整车性能。

关键词： 环氧树脂   双交联   热机械性能   结构–性能关系   绝缘材料  

摘要： 研究材料宏观性能与微观结构的关系对于设计高性能环氧树脂绝缘材料具有重要意义。为此基于共混改性方法提高聚合物材料性能的基础,提出了双交联网络分子模型构建方法,以期望获得综合性能较好的环氧树脂绝缘材料。采用分子动力学(MD)模拟结合实验验证的方法,验证了双交联模型的准确性,研究了DGEBA/DCPDE双交联环氧树脂摩尔配比对其热机械性能的影响以及其微观结构与宏观性能的关联关系。结果表明:当DGEBA与DCPDE的摩尔配比为7:3时,双交联环氧树脂的整体性能较好;DCPDE/MA体系的引入,使得体系的自由体积占比(FFV)和均方位移(MSD)减小,分子链段运动能力减弱,弹性模量升高;FFV、MSD、非键能和二面角扭转能随温度的变化可用于预测交联体系的玻璃化转化温度(Tg)。

关键词： Nanocomposite films   Active food packaging   Release   Alginate   Zinc oxide   Calcium oxide  

摘要： The aim of this paper was the synthesis of a nano-composed sodium alginate edible film containing ZnO and ZnO/CaO NPs and their mechanical, barrier and optical properties as well as the mechanism and release kinetics of the nanoparticles into food simulants were studied. ZnO NPs have a strong interaction with alginate molecules, reducing water vapour permeability and affecting their mechanical properties. On the other hand, ZnO/CaO NPs form aggregates that disrupt the polymeric structure of the alginate films increasing vapour permeability from 3.5 7.2 +/- 0.3 g/Pa*s*m to 4.1 +/- 0.1 g/Pa*s*m, and reducing the film's opacity from 14.2 +/- 0.1 to 10.6 +/- 0.2 Abs/mm. Also, the Ca and Zn release from the films into several food simulant media was studied, showing a Fickian type behaviour whit Peppas release coefficients (n) around 0.50 and faster release rates in lipophilic media, and that release kinetics are strongly dependent of the NPs concentration in the films. In conclusion, alginate edible films containing ZnO and ZnO/CaO can be used as active agents in the development of active food packaging.

关键词： molecular dynamics simulation   calcium silicate hydrate   degree of saturation   strain rate   uniaxial tension  

摘要： To study the effect of water on the dynamic mechanical properties of calcium silicate hydrate (C-S-H) at the atomic scale, the molecular dynamics simulations were performed in uniaxial tension with different strain rates for C-S-H with a degree of saturation from 0% to 100%. Our calculations demonstrate that the dynamic tensile mechanical properties of C-S-H decrease with increasing water content and increase with increasing strain rates. With an increase in the degree of saturation, the strain rate sensitivity of C-S-H tends to increase. According to Morse potential function, the tensile stress-strain relationship curves of C-S-H are decomposed and fitted, and the dynamic tensile constitutive relationship of C-S-H considering the effect of water content is proposed. This reveals the strain rate effect of the cementitious materials with different water content from molecular insights, and the dynamic constitutive relationship obtained in this paper is necessary to the modelling of cementitious materials at the meso-scale.