关键词： 农用设备   农业机械   控制装置   液压联轴器   液压传动   液压系统   液压装置   识别   处理   惰性气体铠装电弧焊   作标记   数字代码   操作元件   遥控   拖拉机   牵引车  

标准号: BS ISO 11471-1995

关键词： HYDROGEN fluoride   QUANTUM theory   BORN-Oppenheimer approximation   MOLECULAR dynamics   ELECTRONIC excitation   DIPOLE moments  

摘要： The electronic properties of liquid hydrogen fluoride (HF) were investigated by carrying out sequential quantum mechanics/Born-Oppenheimer molecular dynamics. The structure of the liquid is in good agreement with recent experimental information. Emphasis was placed on the analysis of polarisation effects, dynamic polarisability and electronic excitations in liquid HF. Our results indicate an increase in liquid phase of the dipole moment (similar to 0.5 D) and isotropic polarisability (5%) relative to their gas-phase values. Our best estimate for the first vertical excitation energy in liquid HF indicates a blue-shift of 0.4 +/- 0.2 eV relative to that of the gas-phase monomer (10.4 eV). (C) 2010 Elsevier B.V. All rights reserved.

摘要： Microtubules (MTs) are the largest type of cellular filament, essential in processes ranging from mitosis and meiosis to flagellar motility. Many of the processes depend critically on the mechanical properties of the MT, but the elastic moduli, notably the Young's modulus, are not directly revealed in experiment, which instead measures either flexural rigidity or response to radial deformation. Molecular dynamics (MD) is a method that allows the mechanical properties of single biomolecules to be investigated through computation. Typically, MD requires an atomic resolution structure of the molecule, which is unavailable for many systems, including MTs. By combining structural information from cryo-electron microscopy and electron crystallography, we have constructed an all-atom model of a complete MT and used MD to determine its mechanical properties. The simulations revealed nonlinear axial stress-strain behavior featuring a pronounced softening under extension, a possible plastic deformation transition under radial compression, and a distinct asymmetry in response to the two senses of twist. This work demonstrates the possibility of combining different levels of structural information to produce all-atom models suitable for quantitative MD simulations, which extends the range of systems amenable to the MD method and should enable exciting advances in our microscopic knowledge of biology.

关键词： PHBV   P3/4HB   miscibility   crystallization kinetics   morphology  

摘要： Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV)/poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB) blend films were prepared by solvent-cast method. The nonisothermal crystallization results showed that PHBV and P3/4HB are miscible due to a single glass transition temperature (T-g), which is dependent on blend composition. The isothermal crystallization results demonstrate that the crystallization rate of PHBV becomes slower after adding amorphous P3/4HB with 19.2 mol%, 4HB, which could be proved through depression of equilibrium melt point (T-m(o)) from 183.7 degrees C to 177.6 degrees C. For pure PHBV and PHBV/P3/4HB (80/20) blend, the maximum crystalli-zation rate appeared at 88 degrees C and 84 degrees C, respectively. FTIR analysis showed that PHBV/P3/4HB blend films would maintain the helical structure, similar to pure PHBV. Meanwhile, with increasing P3/4HB content, the inter- and intra-interactions of PHBV and P3/4HB decrease gradually. Besides, a lower elastic modulus and a higher elongation at break were obtained, which show that the addition of P3/4HB would make the brittle PHBV to ductile materials. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 838-848, 2010

关键词： Animals   Biosensing Techniques   Calibration   Cattle   Cell Line   Cell Movement/physiology   Fluorescent Dyes   Focal Adhesions/metabolism   Humans   Mice   Microscopy, Confocal   Movement   Optical Tweezers   Spectrometry, Fluorescence   Stress, Mechanical   Vinculin/chemistry   Vinculin/deficiency   Vinculin/genetics   Vinculin/metabolism  

摘要： Mechanical forces are central to developmental, physiological and pathological processes(1). However, limited understanding of force transmission within sub-cellular structures is a major obstacle to unravelling molecular mechanisms. Here we describe the development of a calibrated biosensor that measures forces across specific proteins in cells with piconewton (pN) sensitivity, as demonstrated by single molecule fluorescence force spectroscopy(2). The method is applied to vinculin, a protein that connects integrins to actin filaments and whose recruitment to focal adhesions (FAs) is force-dependent(3). We show that tension across vinculin in stable FAs is similar to 2.5 pN and that vinculin recruitment to FAs and force transmission across vinculin are regulated separately. Highest tension across vinculin is associated with adhesion assembly and enlargement. Conversely, vinculin is under low force in disassembling or sliding FAs at the trailing edge of migrating cells. Furthermore, vinculin is required for stabilizing adhesions under force. Together, these data reveal that FA stabilization under force requires both vinculin recruitment and force transmission, and that, surprisingly, these processes can be controlled independently.

关键词： curing of polymers   crosslinking   mechanical properties   resins  

摘要： Dynamics of mechanical, acoustical, and electric properties is studied in the cure of three samples of polymeric compositions produced on the basis of epoxy oligomer with different content of the curing agent. The measurements were made in a parallel mode with an automated measuring complex. Variations in elastic modules, sound speed, attenuation coefficient, relaxation of the shear stress, electric resistance of the samples during the complete cure in the transition from a liquid into a glass state are considered. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 143-147, 2010

关键词： 河北太行机械工业有限公司   中国兵器工业集团   党委委员   总会计师   财务创新   科学发展   董事   文峰  

摘要： “七一”前夕．笔者从北京驱车前往石家庄，采访了优秀共产党员、中国兵器工业集团河北太行机械工业有限公司（简称“河北太行机械工业有限公司”）党委委员、董事、总会计师李文峰。

关键词： 农业机械   配备   小麦生产机械化   能量消耗   实践经验   单位面积   运城市   山西省  

摘要： 本文根据山西省运城市小麦生产机械化多年实践经验和数据．参考有关资料。对小麦生产单位面积能量消耗和以能量消耗配备动力进行了粗浅的研究。

关键词： 伺服驱动技术   直线电机   可编程计算机控制器   运动控制  

摘要： 本文主要分析和综述了全闭环交流伺服驱动技术、直线电机驱动技术、可编程计算机控制器、运动控制卡的基本原理、特点以及应用现状等。

关键词： 机械测试   航天   内蒙   高空模拟试验台   并行数据采集系统   地面试车   固体火箭发动机   调度通讯系统  

摘要： 内蒙航天动力机械测试所创建于1965年，是我国第一座大型固体火箭发动机地面试验基地。经过四十多年的发展，该所现建有三座不同等级推力地面试验台和一座高空模拟试验台，配备了高速多通道并行数据采集系统、环境温度试验系统、推力向量控制系统、试验指挥调度通讯系统，能够进行常规地面试车、高空模拟试车、旋转试车、六分力试车、喷管双摆试车、喷管冷态摆动、销毁试车、冲击、振动、温度循环、转动惯量、模态、弹射等多种型号固体发动机各种状态的地面试验。