关键词： ANTIMONY   QUANTUM theory   ELECTRON distribution   SOLVATION   LIGAND binding (Biochemistry)   HYDROGEN bonding  

摘要： An ab initio quantum mechanical charge field molecular dynamics (QMCF MD) simulation was performed to investigate the behavior of the Sb3+ ion in aqueous solution. The simulation reveals a significant influence of the residual valence shell electron density on the solvation structure and dynamics of Sb3+. A strong hemidirectional behavior of the ligand binding pattern is observed for the first hydration shell extending up to the second hydration layer. The apparent domain partitioned structural behavior was probed by solvent reorientational kinetics and three-body distribution functions. The three-dimensional hydration space was conveniently segmented such that domains having different properties were properly resolved. The approach afforded a fair isolation of localized solvent structural and dynamical motifs that Sb3+ seems to induce to a remarkable degree. Most intriguing is the apparent impact of the lone pair electrons on the second hydration shell, which offers insight into the mechanistic aspects of hydrogen bonding networks in water. Such electronic effects observed in the hydration of Sb3+ can only be studied by applying a suitable quantum mechanical treatment including first and second hydration shell as provided by the QMCF ansatz.

关键词： 变速箱   控制分析   大型养路机械  

摘要： 德国ZF公司生产的4WG-65B2型变速箱配以完善的控制系统,应用于大型养路机械,具有操作简便、作业及运行安全系数高等优点,针对其挡位控制复杂、联锁精细、故障处理难度大的特点,从其挡位实现、挡位闭锁、性能联锁等方面进行了分析。

关键词： 单自由度   动力学   动态静力法   连杆机构  

摘要： 单自由度机械在生产实践中经常遇到,对于其动力学分析方法中的动态静力法进行了系统的介绍。给出了使用该方法进行动力学分析的详细步骤。通过用该方法来解决典型的反正弦连杆机械系统动力学问题,进一步阐述了该方法在进行机械动力学分析过程中的运用。

关键词： Anisotropic mechanical property   Graphene   Young's modulus   Fracture   Molecular dynamics  

摘要： Anisotropic mechanical properties are observed for a sheet of graphene along different load directions. The anisotropic mechanical properties are attributed to the hexagonal structure of the unit cells of the graphene. Under the same tensile loads, the edge bonds bear larger load in the longitudinal mode (LM) than in the transverse mode (TM), which causes fracture sooner in LM than in TM. The Young's modulus and the third order elastic modulus for the LM are slightly larger than that for the TM. Simulation also demonstrates that, for both LM and TM, the loading and unloading stress-strain response curves overlap as long as the graphene is unloaded before the fracture point. This confirms that graphene sustains complete elastic and reversible deformation in the elongation process. (C) 2009 Elsevier B.V. All rights reserved.

关键词： 工程船舶   动力机械   状态监测   故障诊断  

摘要： 针对工程船舶动力机械运行特点,详述工程船舶动力机械状态监测和故障诊断研究的意义,介绍国内外常见船舶动力机械状态监测与故障诊断的方法和现状,并指出工程船舶动力机械状态监测和故障诊断技术的发展趋势和研究热点。

关键词： 摆线凸轮   力学模型   动力学  

摘要： 对摆线凸轮—从动杆机构,提出线性及非线性模型,并应用拉氏变换分析了该系统的动力学问题,为进行现代化设计提供了正确的理论科学依据。

关键词： MOLECULAR dynamics   HYDROGEN   GRAPHENE   MATERIALS -- Mechanical properties   SIMULATION methods & models   NANOELECTROMECHANICAL systems   CHEMICAL bonds   MICROFABRICATION  

摘要： Molecular dynamics simulations have been performed to investigate the mechanical properties of hydrogen functionalized graphene for H-coverages spanning the entire range from graphene (H-0%) to graphane (H-100%). We find that the Young's modulus, tensile strength, and fracture strain of the functionalized graphene deteriorate drastically with increasing H-coverage up to about 30%. Beyond this limit the mechanical properties remain insensitive to H-coverage. While the Young's modulus of graphane is smaller than that of graphene by 30%, the tensile strength and fracture strain show a much larger drop of about 65%. We show that this drastic deterioration in mechanical strength arises both from the conversion of sp(2) to sp(3) bonding and due to easy-rotation of unsupported Sp(3) bonds. Our results suggest that the coverage-dependent deterioration of the mechanical properties must be taken into account when analyzing the performance characteristics of nanodevices fabricated from functionalized graphene sheets. (C) 2009 Elsevier Ltd. All rights reserved.

关键词： 动力机械   电子控制  

ISBN: (数字)9787560949765 ISBN: (纸本)9787560949765

摘要： 本书阐述动力机械控制的演变，控制系统的基本组成、工作原理和品质评价，经典控制、现代控制、智能控制的基本概念和特点。主要内容以柴油机、汽油机、燃气轮机的动力性能、经济性能、排放性能为目标，以电子控制技术为重点，叙述各种动力机械控制系统的结构、控制参数的选择、控制模型的建立，综述理论和实验研究成果。整体控制、集中控制、综合优化是电控系统发展的重要趋势，书中与动力机械控制内容相衔接，介绍传统车辆、电动汽车、混合动力电动汽车、高性能船舶动力系统的特点，分析其性能，并以典型产品为实例，进行解析或仿真。

关键词： Poly(butylene succinate-co-terephthalate) (PBST) fibers   Tensile properties   Thermal properties   Isothermal crystallization  

摘要： Biodegradable copolymer poly(butylene succinate-co-terephthalate) (PBST), with 70 mol% butylene terephthalate (BT), was melt-spun into fibers with take-up velocity of 2 km/min. The mechanical and thermal properties of the as-spun fibers were investigated through tensile test, DSC and TGA. Compared to poly(butylene terephthalate) (PBT) fibers, PBST fibers exhibited lower initial tensile modulus and higher tensile elongation at break which indicated their better flexibility. DSC results showed high melting temperature (ca.180.7 A degrees C) of PBST fibers helpful to the textile processing compared to other biodegradable polyesters. Furthermore, isothermal crystallization behaviors of PBST fibers at low and high supercoolings were investigated by DSC and DLI, respectively. The measurement of crystallization kinetics at low supercoolings indicated that Avrami exponent n for PBST fibers was at a range of 2.9 to 3.3, corresponding to the heterogeneous nucleation and a 3-dimensional spherulitic growth. Similar results were given for isothermal crystallization behavior at high supercoolings investigated by DLI technique. Additionally, the equilibrium melting temperature of PBST fibers was obtained for 206.5 A degrees C by Hoffman-Weeks method. Further investigation through DLI measurement provided the temperature at maximum crystallization rate for PBST fibers located at about 90 A degrees C, which was very useful to polymer processing.

关键词： tilting disk valve   major orifice region   minor orifice region   platelet activation   fluid dynamics   FSI   computer simulation  

摘要： The fluid dynamics during valve closure resulting in high shear flows and large residence times of particles has been implicated in platelet activation and thrombus formation in mechanical heart valves. Our previous studies with bileaflet valves have shown that large shear stresses induced in the gap between the leaflet edge and valve housing results in relatively high platelet activation levels, whereas flow between the leaflets results in shed vortices not conducive to platelet damage. In this study we compare the result of closing dynamics of a tilting disk valve with that of a bileaflet valve. The two-dimensional fluid-structure interaction analysis of a tilting disk valve closure mechanics is performed with a fixed grid Cartesian mesh flow solver with local mesh refinement, and a Lagrangian particle dynamic analysis for computation of potential for platelet activation. Throughout the simulation the flow remains in the laminar regime, and the flow through the gap width is marked by the development of a shear (ayes;which separates from the leaflet downstream of the valve. Zones of recirculation are observed in the gap between the leaflet edge and valve housing on the major orifice region of the tilting disk valve and are seen to be migrating toward the minor orifice region. Jet flow is observed at the minor orifice region and a vortex is formed, which sheds in the direction of fluid motion, as observed in experiments using PIV measurements. The activation parameter computed for the tilting disk valve at the time of closure was found to be 2.7 times greater than that of the bileaflet mechanical valve and was found to be in the vicinity of the minor orifice region, mainly due to the migration of vortical structures from the major to the minor orifice region during the leaflet rebound of the closing phase. [DOT: 10.1115/1.4000876]