关键词： aluminium compounds   amorphous semiconductors   charge exchange   elastic constants   III-V semiconductors   melting   molecular dynamics method   solid-state phase transformations   specific heat   vibrational modes   wide band gap semiconductors  

摘要： An effective interatomic interaction potential for AlN is proposed. The potential consists of two-body and three-body covalent interactions. The two-body potential includes steric repulsions due to atomic sizes, Coulomb interactions resulting from charge transfer between atoms, charge-induced dipole-interactions due to the electronic polarizability of ions, and induced dipole-dipole (van der Waals) interactions. The covalent characters of the Al-N-Al and N-Al-N bonds are described by the three-body potential. The proposed three-body interaction potential is a modification of the Stillinger-Weber form proposed to describe Si. Using the molecular dynamics method, the interaction potential is used to study structural, elastic, and dynamical properties of crystalline and amorphous states of AlN for several densities and temperatures. The structural energy for wurtzite (2H) structure has the lowest energy, followed zinc-blende and rock-salt (RS) structures. The pressure for the structural transformation from wurtzite-to-RS from the common tangent is found to be 24 GPa. For AlN in the wurtzite phase, our computed elastic constants (C-11, C-12, C-13, C-33, C-44, and C-66), melting temperature, vibrational density-of-states, and specific heat agree well with the experiments. Predictions are made for the elastic constant as a function of density for the crystalline and amorphous phase. Structural correlations, such as pair distribution function and neutron and x-ray static structure factors are calculated for the amorphous and liquid state. (C) 2011 American Institute of Physics. [doi:10.1063/1.3525983]

关键词： 柔性机械臂   动力学建模   控制策略  

摘要： 柔性机械臂具有质量轻、惯性小、能耗低等优点,随着机器人技术的发展,针对柔性机械臂的精确建模和有效控制成为国内外学者的重要研究课题。从柔性机械臂动力学建模和动力学控制方法两方面,介绍了近十年国内外学者的研究现状和最新技术的发展,在此基础上对各种方法的优缺点进行分析和比较,并对今后的发展进行了展望。

关键词： 锥型踏面   LM磨耗型踏面   大型养路机械   动力学性能   试验  

摘要： 通过对装配锥型踏面和LM磨耗型踏面轮对的捣固车分别进行正线动力学性能对比试验数据分析表明,锥型踏面轮对的捣固车直线动力学运行平稳性优于LM磨耗型踏面轮对的捣固车,但LM磨耗型踏面轮对的捣固车通过侧线、曲线的脱轨系数和轮轴横向力等稳定性能优于锥型踏面轮对的捣固车。

关键词： 工程机械产品   混合动力   销售收入   徐工集团   工业增长   人民币  

摘要： 混合动力工程机械是本次展会的一大亮点,徐工集团、柳工、山河智能等企业分别推出混合动力工程机械产品,闪耀宝马展。 2009年我国工程机械九大类主机共销售464066台，全行业销售收入超过3100亿元人民币，已成为机械工业增长最快的产业之一。

关键词： 企业创新   高成长   动力因素   裕人模式  

摘要： 宁波裕人公司从诞生到行业"冠军",从本土品牌到国际并购,在短短的五年中其高速发展的"裕人模式"已经成为广大中小企业转型升级的成功模板。本文分析了裕人企业高速发展的动力因素,分析了裕人的"全领域创新":成长时的模仿性创新、成熟时的创造性创新,企业品牌发展的关注,"会议营销"等跨行业营销智慧的借鉴性创新等,为广大制造型中小企业的成长及产业升级提供很好的借鉴意义。

关键词： 虚拟展示系统   Unity3D游戏引擎   机械动力虚拟展件   物理引擎  

摘要： 阐述了利用开发游戏的技术手段来开发机械动力的虚拟展示系统这一构想,并与当前主流的虚拟现实技术和机械动力仿真技术做了对比,最后通过一个基于Unity3D游戏引擎的展示方案实例验证了该思想的可行性。为快速开发虚拟展示系统尤其是动力学的虚拟,提供了科学的依据与先进的手段。

关键词： Malic acid   Photooxidation   Kinetics   Mineralization profile   Mechanism  

摘要： The photocatalytic degradation of malic acid was studied under ambient conditions in an aqueous TiO2 suspension. The results demonstrated the presence of four distinct mineralization rate variations over the course of its degradation. Differences in the mineralization rate were governed by the dominant intermediate present in the solution at that time. Initial mineralization was rapid (similar to 175 mu g C/min) resulting from the swift extraction of a carbon from strongly adsorbed malic acid via the photo-Kolbe mechanism. The mineralization rate then slowed down (similar to 50-70 mu g C/min) with the continued formation of an intermediate product (believed to be malonaldehydic acid), malonic acid and acetic acid in the solution. The findings provide greater insight into the photocatalytic degradation mechanism, illustrating the importance of intermediates and their attributes in relation to the overall rate of organic removal. (C) 2010 Elsevier B.V. All rights reserved.

关键词： 动力传动系统   优化配置   工程机械   燃料经济性   动力性能   技术经济效果   液力变矩器   技术参数  

摘要： 为了改善工程机械的动力性能和燃料经济性,对动力传动系统进行优化配置是一个重要途径。当整机技术参数确定后,如何正确选择发动机的功率、性能及传动系统的参数、型式（如变速器的型式、速比范围、挡位数、速比间隔及驱动桥速比,液力变矩器功率和原始特性等）,都会影响整机的动力性能和燃料经济性。实践证明，对动力传动系统进行优化配置，其技术经济效果显著。

关键词： 蜻蜓   悬停   机电模型   流动显示   测力  

摘要： 为研究蜻蜓等有两对翼的昆虫前后翼相互干扰下的气动力,设计并制作了一个可以模拟蜻蜓悬停的3种拍动模式的机电模型,并以此进行一系列实验,对前后翼相互作用的流场进行了观测。采用染色液流动显示的方法,定性观察了后翼前缘涡在各种不同拍动模式和不同翼间距离时的发展过程,对模型翼在各种拍动模式下的气动力进行了定量测量,并分别从流场结构和力学性能两方面对两翼间的干扰作用进行了分析讨论。

关键词： GENETIC translation   RIBOSOMES   FLUORESCENCE   LIGAND binding (Biochemistry)   ELECTRON microscopy   TRANSFER RNA   MOLECULAR biology  

摘要： The recent growth in single molecule studies of translation has provided an insight into the molecular mechanism of ribosomal function. Single molecule fluorescence approaches allowed direct observation of the structural rearrangements occurring during translation and revealed dynamic motions of the ribosome and its ligands. These studies demonstrated how ligand binding affects dynamics of the ribosome, and the role of the conformational sampling in large-scale rearrangements intrinsic to translation elongation. The application of time-resolved cryo-electron microscopy revealed new conformational intermediates during back-translocation providing an insight into ribosomal dynamics from an alternative perspective. Recent developments permitted examination of conformational and compositional dynamics of the ribosome in real-time through multiple cycles of elongation at the single molecule level. The zero-mode waveguide approach allowed direct observation of the compositional dynamics of tRNA occupancy on the elongating ribosome. The emergence of single molecule in vivo techniques provided insights into the mechanism and regulation of translation at the organismal level.