关键词： 机械设计制造   工程学院   重庆市   工程技术研究中心   科技   机械电子工程   教学示范中心   石油装备  

关键词： 农村富余劳动力   农业机械化   中国   第三产业   工业化   城镇化  

摘要： 农业机械化使中国平均每年产生1000万农村富余劳动力，为中国工业化、城镇化和第二、第三产业的发展提供有力支撑。

关键词： 空间机械臂   关节   动力学建模   间隙   啮合误差  

摘要： 关节是空间机械臂的核心部件,是保证空间机械臂安全、平稳运行的关键。为全面反映大型空间机械臂关节的动力学特性并从细节之处优化关节设计,利用集中参数法建立了综合考虑轮齿柔性、啮合阻尼、齿侧间隙、啮合误差等非线性因素的细化关节动力学模型。模型中采用一种基于tanh的连续函数对传统分段线性间隙函数进行近似,从而降低了模型的求解难度。研究了各级齿轮精度、关节转速和负载对关节动力学特性的影响。仿真结果表明,三级齿轮的精度变化会影响关节转速波动的振幅并分别影响高、中、低频特性;转速的增加将提高振动频率和幅值;力矩负载的增大会使关节转速波动幅值显著增大,且在满载时,所有的高阶频率都得到明显激励;惯性负载的增大会减小转速波动,并将能量集中在中频上。

关键词： Emergent quantum mechanics   Diffusion   Superposition principle   Born's rule  

摘要： Based on the modelling of quantum systems with the aid of (classical) non-equilibrium thermodynamics, both the emergence and the collapse of the superposition principle are understood within one and the same framework. Both are shown to depend in crucial ways on whether or not an average orthogonality is maintained between reversible Schrodinger dynamics and irreversible processes of diffusion. Moreover, the said orthogonality is already in full operation when dealing with a single free Gaussian wave packet. In an application, the quantum mechanical "decay of the wave packet" is shown to simply result from sub-quantum diffusion with a specific diffusivity varying in time due to a particle's changing thermal environment. The exact quantum mechanical trajectory distributions and the velocity field of the Gaussian wave packet, as well as Born's rule, are thus all derived solely from classical physics. (C) 2010 Elsevier B.V. All rights reserved.

关键词： Molecular dynamics simulations   Ni-Al bimetallic nanowires   Mechanical properties   Stress-strain curve   Young Modulus  

摘要： We employed molecular dynamics simulations to study mechanical properties of Ni-Al nanowires by calculating the stress-strain response of the wires under various loading conditions. For this purpose, nanowires were subjected to uniaxial strain at different strain rates and temperatures using embedded atom model potential. The behaviour of the wires at lower and higher strain rates was investigated, and the yield and rupture strain values and also Young's Modulus were obtained which are essential factors for the ductility of the wires. This work indicates that how the stress-strain response of the nanowires are affected by varying strain rates and temperatures. (C) 2010 Published by Elsevier B.V.

关键词： Fluorinated ketones   Esterase   Quantum mechanical computations   Molecular dynamics   Structure-based drug design  

摘要： Carboxylesterases (CEs) are a family of ubiquitous enzymes with broad substrate specificity, and their inhibition may have important implications in pharmaceutical and agrochemical fields. One of the most potent inhibitors both for mammalian and insect CEs are trifluoromethyl ketones (TFMKs), but the mechanism of action of these chemicals is not completely understood. This study examines the balance between reactivity versus steric effects in modulating the activity against human carboxylesterase 1. The intrinsic reactivity of the ketone moiety is determined from quantum mechanical computations, which combine gas phase B3LYP calculations with hydration free energies estimated with the IEF/MST model. In addition, docking and molecular dynamics simulations are used to explore the binding mode of the inhibitors along the deep gorge that delineates the binding site. The results point out that the activity largely depends on the nature of the fluorinated ketone, since the activity is modulated by the balance between the intrinsic electrophilicity of the carbonyl carbon atom and the ratio between keto and hydrate forms. However, the results also suggest that the correct alignment of the alkyl chain in the binding site can exert a large influence on the inhibitory activity, as this effect seems to override the intrinsic reactivity features of the fluorinated ketone. Overall, the results sustain a subtle balance between reactivity and steric effects in modulating the inhibitory activity of TFMK inhibitors.

关键词： Bond formation   Insight   Kinetics   Dislocated Workers  

摘要： A novel series of 1,2,4-triazol-3-yl-azabicyclo[3.1.0]hexanes was recently identified as new highly potent and selective dopamine (DA) D-3 receptor antagonists. This dais of molecules deserved the Chemical Development special attention to quantify the reliability and robustness of the pivotal S(N)2 displacement step between the 1,2,4-triazol-3-yl-halide derivative (4) and variously substituted azabicyclo[3.1.0]hexanes (5). To reach this goal we applied the classical Design of Experiment (DoE) approach, simultaneously trying to build up a descriptive kinetic model of the chemistry. The synergistic use of these two techniques allowed us to select new, higher-yielding and more robust reaction conditions and, at the same time, to identify their Design Space.

关键词： Kinetic elucidation   ctc-Ru(II) complex   pi-Acidity   Thiosulfate   Substituent effect   Ru-OH2 cleavage  

摘要： The nucleophilic substitution reaction of S2O32- with [Ru(HaaiR')(2)(OH2)(2)](ClO4)(2) (1) [HaaiR' = 1-alkyl-2-(phenylazo)imidazole] and [Ru(ClaaiR')(2)(OH2)(2)](ClO4)(2) (2) [ClaaiR' = 1-alkyl-2-(chlorophenylazo)imidazole] [where R' = Me(a), Et(b) or Bz(c)] in acetonitrile-water (50% v/v) medium to yield Na-2[Ru(HaaiR')(2)(S2O3)(2)] (3a, 3b or 3c) and Na-2[Ru(ClaaiR')(2)(S2O3)(2)] (4a, 4b or 4c) has been studied. The products were characterized by microanalytical data and spectroscopic techniques (UV-Vis, NMR and mass spectroscopy). The reaction proceeds in two consecutive steps (A -> B -> C);each step follows first order kinetics with respect to each complex and S2O32-, and the first step second order rate constant (k'(2)) is greater than the second step one (k ''(2)). An increase in the it-acidity of the ligand increases the rate. Thermodynamic parameters, the standard enthalpy of activation (Delta double dagger H-0) and the standard entropy of activation (Delta double dagger S-0), have been calculated for both steps using the Eyring equation from variable temperature kinetic studies. The low Delta double dagger H-0 and large negative Delta double dagger S-0 values indicate an associative mode of activation for both aqua ligand substitution processes. (C) 2010 Elsevier Ltd. All rights reserved.

关键词： 工程研究中心   华东理工大学   橡塑机械   工程学院   国家自然科学基金项目   博士生导师   高分子材料   863项目  

关键词： fistula/shunts   percutaneous coronary intervention   complications adult cath/intervention   angiography   coronary  

摘要： Noninvasive assessment of mechanical heart valve function with echocardiography is challenging. There are important safety issues when considering placing a standard catheter across a mechanical valve with for invasive hemodynamic measurements. The feasibility of using a high-fidelity micromanometer coronary pressure guide wire to assess hemodynamics across mechanical valves has been reported. Although this method appears feasible, safe, and free of major complication, its application and utility remains obscure and underappreciated. We report a series of two patients with mitral and aortic (St. Jude and Bjork-Shiley) mechanical valves in which we successfully used this pressure wire technique to assess valvular function in patients evaluated for repeat surgical valve replacement. We include the first report of this guide wire technique to assess hemodynamics across a Bjork-Shiley single-tilting disk valve. (C) 2010 Wiley-Liss, Inc.