Investigation of Structure and Hydriding Properties of La0.6 Nd0.4 Ni4.8 Mn0.2 Cux Alloys

The structure and hydriding performance of La0.6Nd0.4Ni4.8Mn0.2Cux (x = 0 ～ 0.4) alloys were investigated in order to develop suitable materials for metal hydride air conditioner. The effect of Cu addition on the crystal structure,equilibrium pressure, hydrogen capacity and hysteresis as well as hydrogen absorption/desorption kinetics were systematically studied by using the measurement of P-C isotherms, X-ray diffraction and scanning electron microscopy. As the amount of Cu increases, the plateau pressure increases and hydrogen absorption/desorption kinetics is improved, but the effective hydrogen storage capacity decreases. It is shown that variations in the basal plane parameter a can be used as an indication for the plateau pressure changes. With the increase of parameter a, the plateau pressure decreases. For La0.6 Nd0.4Ni4.8Mn0.2Cux(x = 0 ～ 0.4) alloys there is a relationship between the effective hydrogen storage capacities and the ratios of their unit cell parameters c and a. The effective hydrogen storage capacity decreases with increase of a/c.     

基于H∞控制器的柔性机械手优化设计研究

针对柔性机械手设计中手臂变形涉及的柔性和参数分布式系统的复杂性,采用H∞控制技术对柔性机械手进行优化设计。在设计过程中,考虑了参数分布式系统中各子系统之间的相互作用,分析了模型的不确定性并进行了定量描述,导出了广义装置的空间状态方程。设计了具有稳定闭环的H∞控制器,减小了系统的不确定性和扰动所产生的各种影响,从而解决了控制问题和模型精度问题。对阶跃输入和扰动的响应进行了研究,给出了各种情形的数值结果,显示系统具有良好的鲁棒性。     

Integrated Circuit 卡应用系统安全设计研究

针对许多ＩｎｔｅｇｒａｔｅｄＣｉｒｃｕｉｔ（ＩＣ）卡应用系统采用的被动存储型ＩＣ卡一般不能防止非法复制或篡改,对ＩＣ卡应用系统的安全结构进行了分析,基于安全核存在假设和算法安全性假设提出了ＩＣ卡应用系统理论安全模型．并以ＩＣ卡预付费电表系统为例,对攻击者的破译策略进行了分析,讨论了其安全设计策略．     

一个拓扑熵等于∞的非浑沌系统

本文构造了一个离散动力系统(E,σ),其中E是一个可数集。σ:E→E是一个连续映射,满足: 1)σ的拓扑熵是+∞; 2)σ的非游荡集是空集; 3)σ只在E的聚点处有初值敏感性     

中国铜镍工业进展及前景展望

回顾了中国铜镍工业的发展历程 ,展望了 2 1世纪铜镍工业的前景。     

施工管理科学化的论述

施工管理中的施工技术管理、质量管理以及生产要素管理是施工管理的主要方面,处理好三者之间的关系以及解决好三个方面中的任何一方面是在施工中面临的重要问题     

核与辐射事件医学应急管理体系国际比较

介绍了我国核与辐射事件医学应急管理体系的构成,并将之与日本、美国、法国、俄罗斯和加拿大的核与辐射事件医学应急管理体系进行比较,分析其优缺点,同时介绍了WHO和IAEA在核与辐射事件医学应急中的作用,在此基础上提出建立健全我国核与辐射应急医学管理体系、提升医学应急救援能力的建议。     

Orientationability analyses of a special class of the Stewart–Gough parallel manipulators using the unit quaternion representation

This paper addresses the orientation-singularity and orientationability analyses of a special class of the Stewart–Gough parallel manipulators whose moving and base platforms are two similar semi-symmetrical hexagons. Employing a unit quaternion to represent the orientation of the moving platform, an analytical expression representing the singularity locus of this class of parallel manipulators in a six-dimensional Cartesian space is obtained. It shows that for a given orientation, the position-singularity locus is a cubic polynomial expression in the moving platform position parameters, and for a given position, the orientation-singularity locus is an analytical expression but not a polynomial directly with respect to the mobile platform orientation parameters. Further inspection shows that for the special class of parallel manipulators, there must exist a nonsingular orientation void in the orientation space around the orientation origin for each position in the position-workspace. Therefore, a new performance index referred to as orientationability is introduced to describe the orientation capability of the special class of manipulators at a given position. A discretization algorithm is proposed for the computation of the orientationability of the special class of manipulators. Moreover, effects of the design parameters and position parameters on the orientationability are investigated in details. Based on the orientationability performance index, another novel performance index referred to as practical orientationability is presented which represents the practical orientation capability of the manipulator at a given position. The practical orientationability not only can satisfy all the kinematic demands and constraints of such class of manipulators, but also can guarantee that the manipulator is nonsingular.     

Nanoindentation measurement of core–skin interphase viscoelastic properties in a sandwich glass composite

Mechanics of Time-Dependent Materials - Debonding at the core–skin interphase region is one of the primary failure modes in core sandwich composites under shear loads. As a result, the...     

热挤压变形力计算的研究

本文考虑到变形区内切应力非线性分布的特点,采用球坐标系下的平衡微分方程和塑性条件联立求解,得出圆棒热挤压时变形区入口球面上的应力分布方程,然后应用功平衡法导出了圆棒热挤压力的计算公式。