关键词： Dielectric spectroscopy   Liquid-glass transition   Relaxation dynamics  

摘要： Dielectric and mechanical spectroscopy methods have been employed to describe the temperature dependencies of the segmental and macromolecular relaxation rates in epoxy/hydroxy functionalized polybutadiene. Dielectric studies on the dynamics of segments of the polymer as well as the mobility of small ions trapped in the system have been carried out both as a function of temperature and pressure under isobaric and isothermal conditions, respectively.

关键词： POLYETHYLENE synthesis   MOLECULAR weights   POLYMERIZATION   PHASE transformations (Physics)   CHEMICAL kinetics   MATERIALS -- Mechanical properties  

摘要： The synthesis of linear ultra high molecular weight polyethylene, with a "pseudoliving" catalyst in various conditions results in samples of different molecular weights (M-w ranging between 2 to 35 million g/mol), all having a reduced number of entanglements to an extent that allows the solid-state uniaxial deformation of such high molar masses without melting. The solid-state processing of these materials shows a dear relationship between mechanical properties and molecular weight. For the adopted polymerization conditions, stretching forces required for the uniaxial deformation increase with the increasing molar mass, ultimately limiting the achievable maximum draw ratio in the polymers having M-w > 10 million g/mol. The increase in the stretching force is attributed to the increasing number of entanglements between the crystals with the molar mass. The estimation of entanglements is established with the help of melting kinetics involved in the "disentangled" crystals, and rheological response of the polymer melt obtained just after melting of the crystals. In spite of the increase in the stretching forces with the increasing molar mass, tensile modulus increases with the increasing draw ratio and the molecular weight. However, above the molar mass of 10 million g/mol, the stretching force required increases to the level that the uniaxial deformation becomes difficult thus limiting the tensile strength.

关键词： Plasticity   Graphite   Shock wave effects   Molecular dynamics   Friction  

摘要： We study the shock-induced hot spot formation mechanism of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine-based explosives by molecular dynamics, compare different kinds of desensitizers and different shock velocities. A set of programs is written to calculate the physical picture of shock loading. Based on the simulations and analyses, the hot spots are found at the interface and are heated by plastic work in three ways: the interface intrinsic dissipation, the pore collapse, and the coating layer deformation. The work/heat transition rate is proved to be increasing with a loading speed. (C) 2014 AIP Publishing LLC.

关键词： 呼气末正压通气(PEEP)   复苏后综合征(PRS)   心率(HR)   血氧饱和度(SaO2)   血管外肺水(EVLW)   胸腔内血容量(ITBV)   每搏输出量变异度(SVV)   全心射血分数(GEF)  

摘要： 目的观察不同水平的呼气末正压通气（PEEP）对复苏后综合征（PRS）患者血流动力学的影响。方法记录15例实施机械通气的PRS患者在不同PEEP水平时的心率（HR）、血氧饱和度（SaO2）、血管外肺水（EVLW）、胸腔内血容量（ITBV）、每搏输出量变异度（SVV）、全心射血分数（GEF），采用单因素方差分析和一元线性回归模型对数据进行分析。结果不同水平PEEP时EVLW、SVV、SaO2比较差异有统计学意义（P均〈0．05）。其中EVLW与PEEP呈显著正相关（r=0．572，P=0．013），SVV与PEEP呈显著正相关（r=0．498，P=0．021），SaO2与PEEP无显著相关性（r=-0．219，拟合度=0．048，P=0．032），而GEF、ITBV、HR与PEEP呈非线性相关。结论PEEP可影响PRS患者的血流动力学，使实际测得的EVLW、SVV值偏高。

关键词： 漂浮基柔性空间机械臂   捕获载荷   碰撞冲击   自适应镇定控制   振动抑制  

摘要： 分析漂浮基柔性空间机械臂受捕获载荷冲击后动力学响应及控制,利用假设模态法近似描述空间机械臂柔性杆弹性变形;利用第二类拉格朗日方程建立漂浮基空间机械臂系统动力学模型。基于动量守恒原理,利用动量冲量法评估受捕获载荷冲击后漂浮基空间机械臂系统动力学响应。设计自适应控制算法对受捕获载荷碰撞冲击后不稳定漂浮基空间机械臂进行镇定控制;设计线性二次最优控制算法抑制柔性杆弹性振动。用数值仿真验证控制算法的有效性。

关键词： 航空航天科学技术基础学科   空间机械臂   柔性关节   柔性杆   自然坐标法   绝对节点坐标法   轨迹跟踪  

摘要： 大多数研究者在空间机械臂动力学建模时,只考虑了关节柔性或者臂杆柔性,并且通常采用假设模态法对臂杆的变形进行描述,但该方法仅适用于小变形情况。基于这种情况,采用自然坐标法对柔性关节进行建模和绝对节点坐标法对柔性臂杆进行建模,得到了既包含关节柔性又包含臂杆柔性的空间机械臂动力学方程,并能精确地描述臂杆的小变形以及大变形。利用5次多项式对关节轨迹进行规划,通过逆动力学得到关节的前馈驱动力矩;采用PID控制策略,作为反馈输入。在二连杆柔性关节柔性杆机械臂上进行数值仿真。仿真结果表明:该控制策略在实现关节轨迹跟踪控制的同时,也能有效减弱机械臂的振动。

关键词： 机械动力部件   实时监控   S7-300PLC   ET200  

摘要： 煤矿井下的特殊环境使得对机械动力部的检测一直处于相对简单和原始的状态,因此,设计了一种基于S7-300PLC煤矿井下机械动力部工况实时监控系统,并详细介绍了其工作原理、组成硬件的选择和软件的应用.经过定点实验证明,通过应用该系统工作人员数与检测时间都大大减少,检测效率提高29%.

关键词： UG   PRRR机械手   ADAMS   动力学仿真  

摘要： 本文利用UG软件对PRRR机械手进行三维实体建模,将模型导入ADAMS软件,对机械手进行动力学仿真研究,得到其扭矩变化曲线,为机械手的驱动控制提供参考,并为机械手研究人员学习动力学仿真提供帮助。

关键词： 机械活化   石煤   钒   浸出   动力学  

摘要： 通过考察浸出温度及硫酸浓度对石煤提钒浸出的影响,研究了机械活化前后矿样的浸出动力学。结果表明,未活化矿样浸出表观活化能为23.49kJ/mol,反应级数为2.34,矿样活化20min后,浸出表观活化能降为16.85kJ/mol,反应级数降至2.21。机械活化能够增强矿样的表面活性,降低浸出过程对温度和硫酸浓度的依赖。