关键词： Catalysis   Spline   Mapping   Mechanistic kinetics   Ammonia   Oxidation  

摘要： This paper demonstrates how pre-computed rate data can be used to enable the numerically efficient implementation of mechanistic kinetics in a reactor model for an automotive ammonia slip catalyst. In a pre-processing step the source terms for the gas species are mapped as a function of gas composition and temperature. From this map (80,000 data points), a spline interpolation function is constructed. The spline function approximates the numerical steady state solution of the kinetic model with an average error of less than 1%. Application of the rate mapping procedure results in a speedup of about two orders of magnitude. The spline approximation is implemented in a 2-dimensional model of a monolith reactor channel that includes diffusion in the washcoat layer. Depending on the channel diameter and the washcoat thickness, diffusion limitations in the open channel and in the washcoat can have a significant influence on the NH3 conversion. Surprisingly, the selectivity for the products N-2, N2O and NO is not sensitive to diffusion effects in the gas phase or in the washcoat. (C) 2010 Elsevier B.V. All rights reserved.

关键词： MOLECULAR dynamics   RESEARCH   IONS   IRON ions   HARTREE-Fock approximation   ANGULAR distribution (Nuclear physics)   QUANTUM theory  

摘要： Ab initio quantum mechanical charge field molecular dynamics (QMCF-MD) simulations have been performed for aqueous solutions of Fe2+ and Fe3+ ions at the Hartree-Fock level of theory to describe and compare their structural and dynamical behavior. The structural features of both hydrated ions are characterized by radial distribution functions that give the maximum probability of the ion-O distance for Fe2+ and Fe3+ ions at 2.15 and 2.03 angstrom, respectively. The angular distribution functions of both ions prove the octahedral arrangement of six water ligands, whereas the second shells of these ions differ. Both ions show influence on the water molecules beyond the second shells. The structure-forming abilities of both ions are visible from the ligand mean residence times and ion-O stretching frequencies evaluated for both ions. The substantially improved data obtained from these QMCF-MD simulations show better correlation with available experimental results than the conventional quantum mechanics/molecular mechanics molecular dynamics (QM/MM MD) approaches with one hydration shell treated by quantum mechanics.

关键词： collagen structure   stem cell   mechanical properties   in vitro test   tendon  

摘要： A cell-collagen construct is commonly used to investigate the phenomenon of wound healing and to estimate the variables for tissue engineering. The purpose of this study was to assess the effects of cell concentration and collagen concentration on the contraction kinetics and mechanical properties of bone marrow stromal cell (BMSC) seeded collagen lattices. To investigate the effects of both variables on the contraction kinetics, the construct contraction was monitored up to 13 days. Incremental stress relaxation tests were carried out after a 2-week incubation to obtain the stress strain profiles, which were subsequently assessed in a quasilinear viscoelastic (QLV) model. During contraction, aligned BMSCs were observed first in the interior portion of the ring, followed by the middle portion and finally in the exterior portion. Constructs seeded with a higher initial cell concentration (higher than 1 x 10(5) cells/mL) or lower initial collagen concentration (lower than 2 mg/mL) exhibited faster contraction, higher ultimate stress, and superior elasticity and reduced relaxation behavior (p < 0.05). The cell-collagen model was successfully used to yield information regarding the initial cell concentration and the initial collagen concentration on contraction kinetics and mechanical behavior, which may have possible application in tissue engineering. (C) 2009 Wiley Periodicals, Inc. J Biomed Mater Res 93A: 1132-1139, 2010

关键词： 水下电动机械手   牛顿-欧拉法   水动力学模型   仿真  

摘要： 运用牛顿-欧拉递推算法对机械手进行动力学分析,在此基础上运用单摆动杆水动力方程建立了机械手的水动力学模型,最后对其进行动力学仿真验证。

关键词： 液压动力头   地质探矿   岩心钻机   机械厂   山东省   现场会   施工   装配车间  

摘要： 2010年6月2日，山东省地质探矿机械厂彩旗飘舞、人头攒动，来自国内地矿、煤田、有色、冶金等行业的百余名钻探专家欢聚一堂，兴致勃勃地参观了山东省地质探矿机械厂的生产厂区。在整洁的装配车间，XD-2、XD-3、XD-4A、XD-5A、XD-6、XDL-5A系列全液压动力头式岩心钻机一字排开，整齐壮观，

标准号: NF E88-051/IN1-2010

关键词： 机械手   牛顿-欧拉法   动力学   MATLAB软件  

摘要： 机械手是排爆机器人的关键部分,机器人作业主要依赖于机械手的运动。在机械手运动规划基础上重点描述基于牛顿-欧拉法的机械手动力学建模,并利用MATLAB软件编程对机械手进行动力学分析,为机械手的设计和运动控制实现提供支持。

关键词： 机械动力学   振动   实验教学  

摘要： 结合机械动力学的主要研究内容、特点以及近年来机械动力学领域的最新研究成果,研制既能满足本科生机械动力学的实验教学,又能够满足研究生机械动力学的实验教学和科研工作的综合振动实验台。该综合振动实验台不仅能对离散质量、连续梁和轴的振动问题进行实验研究,而且还能对组合结构的线性振动问题和非线性振动问题进行实验研究,从而为进一步加强和提高学生的动手和创新能力提供一定的实验基础。

关键词： 鼓形齿式联轴器   动力传动   十字轴式万向联轴器   机械行业   企业   发展空间   剪刃   自主知识产权   钢铁行业   市场需求  

摘要： 世界上所有企业的经营者无不朝思暮想把自己的企业做大、做强,然而,影响企业"做大,做强"的因素又有很多,在笔者看来,如果一个企业要想傲视群雄位居行业龙头地位,则必须同时拥有两个条件作为支撑。第一。

关键词： 柔性机械臂   动力学   逆动力学   振动   大范围运动  

摘要： 柔性臂系统的逆动力学问题,是指在已知期望末端操作器运动轨迹的情况下,结合逆运动学与动力学方程对关节力矩进行求解。本文采用割线坐标系对机械臂的运动进行了描述,并分快变(振动)和慢变两方面进行逆动力学问题的分析与求解。在对快变部分逆动力学性质的分析中发现,快变部分精确的逆动力学解是发散的。在进行柔性机械臂逆动力学求解时,应在慢变的意义上进行。文中给出了一种去掉系统快变部分的简单方法,并进行了逆动力学求解。数值仿真结果表明,该处理方法是合理的。