关键词： 两挡变速器   电动汽车   机械式自动变速器   试验台   实时仿真  

摘要： 该文以实现动力不中断的高效动力传动系统为基本目标,对一种适用于电动汽车的动力保持型机械式自动两挡变速器进行了仿真与试验研究。该变速器主要由单排行星齿轮系统、膜片弹簧式离合器以及鼓式制动器构成,旨在解决换挡过程中的动力中断问题。该文建立了一个采用新型变速器的纯电动汽车前置前驱传动系统动力学模型。在MATLAB/Simulink环境下,搭建了一个纯电动车整车仿真模型。该模型用来进行分析、选定变速器的基本参数,研制出一台变速器功能样机。该仿真模型适合于实时仿真与试验,在试验过程中可以灵活地改变调整各种参数。根据新型变速器试验的需求,该文建立了一个变速器硬件在环仿真平台,搭建了一个变速器样机的试验台,进行实时仿真和台架试验。仿真和试验结果表明:该变速器解决了在换挡过程中存在的动力中断问题,使驱动电机工作在高效区间,提高了纯电动汽车的动力性和经济性。

关键词： 机械动力   自动绕障   教具小车   协调运动  

摘要： 为帮助工科大学生理解所学理论知识,提高大学生的工程实践能力及创新能力,设计了一种可依靠纯机械控制,自动完成多个"8"字轨迹的绕桩小车。此小车可以调节转向机构的转向角来适应桩距的改变,小车的总体结构设计主要包含五大方面:小车行走轨迹设计、能量转换机构的设计、传动机构设计、差速机构设计和转向机构设计。其效果是:结构简洁,启动性能好,行走平稳;精度很高;无碳、节能、环保;对提高实践教学效果发挥了重要作用。

关键词： 柔性机械臂   斜碰撞   动力学分析   柔性多体系统  

摘要： 对作大范围运动柔性机械臂系统,进行斜碰撞动力学分析.基于柔性多体系统刚柔耦合动力学理论,计入耦合变形项,全面考虑大范围刚体运动与弹性小变形运动的耦合,建立系统连续动力学方程.引入斜碰撞力学模型,将法向和切向碰撞力以广义力的形式加入动力学方程中,对系统进行斜碰撞动力学建模分析.法向碰撞模型选取基于连续接触力法的非线性弹簧阻尼模型,切向碰撞模型选取一种修正Coulomb摩擦模型,对切向摩擦力进行统一描述.给出接触、分离判据,实现不同状态的动力学模型转换与求解.对斜碰撞全局动力学进行了仿真验证,分析了柔性机械臂全局过程的动力学特性变化以及碰撞对大范围运动和小变形运动的作用,并对比了不同碰撞方向对大范围运动、变形、机械能、碰撞力等动力学参数的影响.

关键词： 工程机械臂   系统结构   动力学   特性  

摘要： 随着科学技术的不断进步,机械产品在先进技术的引导下逐渐向环保、优质方向发展。工程机械臂作为重要元件应用于机械工程中,在实际应用中充分发挥动力学性能,这不仅会促进工作稳定进行,还会提高机械工程的经济效益。首先介绍了研究现状,然后分析了动力学特点。

关键词： 六连杆机构   运动学分析   静力学   动力学  

摘要： 提出了一种新型的单自由度六连杆机械压力机机构,为了实现机构的动态静力学以及动力学分析,采用复数矢量法建立了机构的运动学模型,基于达朗贝尔原理建立了机构的动态静力学方程,利用拉格朗日法建立了机构的动力学方程;分别利用MATLAB理论计算与ADAMS虚拟样机仿真得到压力机机构中滑块的位置曲线、速度曲线、加速度曲线,以及曲柄的平衡力矩和驱动力矩变化曲线。研究不仅为六连杆压力机运动学分析、平衡力矩和驱动力矩的求解和结构设计提供了理论依据,也为其他压力机机构的静力学和动力学分析提供了有效方法。

关键词： Atrial   KCNA5 mutations   Electromechanical coupling   Atrial contraction   Computer simulation  

摘要： A recent study has identified six novel genetic variations (D322H, E48G, A305T, D469E, Y155C, P488S) in KCNA5 (encoding Kv1.5 which carries the atrial-specific ultra-rapid delayed rectifier current, I-Kur) in patients with early onset of lone atrial fibrillation. These mutations are distinctive, resulting in either gain-of-function (D322H, E48G, A305T) or loss-of-function (D469E, Y155C, P488S) of Ikur channels. Though affecting potassium channels, they may modulate the cellular active force and therefore atrial mechanical functions, which remains to be elucidated. The present study aimed to assess the inotropic effects of the identified six KCNA5 mutations on the human atria. Multiscale electromechanical models of the human atria were used to investigate the impact of the six KCNA5 mutations on atrial contractile functions. It was shown that the gain-of-function mutations reduced active contractile force primarily through decreasing the calcium transient (CaT) via a reduction in the L-type calcium current (I-CaL) as a secondary effect of modulated action potential, whereas the loss-of-function mutations mediated positive inotropic effects by increased CaT via enhancing the reverse mode of the Na+/Ca2+ exchanger. The 3D atrial electromechanical coupled model predicted different functional impacts of the KCN5A mutation variants on atrial mechanical contraction by either reducing or increasing atrial output, which is associated with the gain-of-function mutations or loss-of-function mutations in KCNA5, respectively. This study adds insights to the functional impact of KCNA5 mutations in modulating atrial contractile functions. (C) 2017 The Authors. Published by Elsevier Ltd.

关键词： Ni   Boriding   Powder pack   Boride layer   Hardness  

摘要： Kinetics of boride layer growth and tensile behaviour in bonded commercial-purity nickel was investigated. Bonding was carried out in a solid medium consisting of Ekabor-II powders at 1173, 1223 and 1273 K for periods of 3, 5 and 8 h. Scanning electron microscopy (SEM) and optical microscopy showed column morphology in the boride layer. X-ray diffraction (XRD) analyses indicated that the boride layer formed on the surface consisted mainly of Ni2B, with precipitates of Ni6Si2B. A parabolic relationship between layer thickness and processing temperature was observed. The obtained results showed that although the boride layer thickness increased with increasing boriding temperature and time, boriding parameters had no significant effect on the hardness of the boride layer or the matrix. Tensile properties were negatively influenced by the bonding treatment;both yield and tensile strength values decreased due to the presence of the hard yet brittle surface coating. In addition, the growth kinetics of boride layers was also analysed. The results showed a nearly parabolic relationship between the layer thickness and the process temperature, with activation energy of 47.3 kJ mol(-1).

关键词： Yield stress  

摘要： Using molecular dynamics simulation, tension and bending tests of a Fe nanopillar are carried out to obtain its Young's modulus and yield strength. Then the comparative study of Young's modulus and yield strength of a Fe nanopillar under bending and tension are carried out varying its diameter in the range of diameter 1-15nm. We find out the reasons why bending Young's modulus and yield strength of a Fe nanopillar are higher than those of tension Young's modulus and yield strength of a Fe nanopillar. Using the mobility parameters of bulk Fe from the experimental study [N. Urabe and J. Weertman, Materials Science and Engineering 18, 41 (1975)], its temperature dependent stress-strain relationship, yield strength and strain hardening modulus are obtained from the dislocation dynamics simulations. Strain rate dependent yield strength and strain hardening modulus of bulk Fe pillars under tension are studied. Temperature dependent creep behaviors of bulk Fe pillars under tension are also studied. To verify the soundness of the present dislocation dynamics studies of the mechanical properties of bulk Fe pillars under tension, the stress vs. strain relationship and dislocation density vs. strain of bulk Fe pillars obtained by us are compared with the published results obtained by S. Queyreau, G. Monnet, and B. Devincre, International Journal of Plasticity 25, 361 (2009). (C) 2017Author(s).

关键词： CL-20/TNTcocrystal explosive   Molecular dynamics   Mechanical properties Sensitivity   Binding energy   Detonation performance  

摘要： To investigate and compare the differences of structures and properties of CL-20/TNT cocrystal and composite explosives, the CL-20/TNT cocrystal and composite models were established. Molecular dynamics simulations were performed to investigate the structures, mechanical properties, sensitivity, stabilities and detonation performance of cocrystal and composite models with COMPASS force field in NPT ensemble. The lattice parameters, mechanical properties, binding energies, interaction energy of trigger bond, cohesive energy density and detonation parameters were determined and compared. The results show that, compared with pure CL-20, the rigidity and stiffness of cocrystal and composite models decreased, while plastic properties and ductility increased, so mechanical properties can be effectively improved by adding TNT into CL-20 and the cocrystal model has better mechanical properties. The interaction energy of the trigger bond and the cohesive energy density is in the order of CL-20/ TNT cocrystal > CL-20/TNT composite > pure CL-20, i.e., cocrystal model is less sensitive than CL-20 and the composite model, and has the best safety parameters. Binding energies show that the cocrystal model has higher intermolecular interaction energy values than the composite model, thus illustrating the better stability of the cocrystal model. Detonation parameters vary as CL-20 > cocrystal > composite, namely, the energy density and power of cocrystal and composite model are weakened;however, the CL-20/TNT cocrystal explosive still has desirable energy density and detonation performance. This results presented in this paper help offer some helpful guidance to better understand the mechanism of CL-20/TNT cocrystal explosives and provide some theoretical assistance for cocrystal explosive design.

关键词： Advanced oxidation processes   Congo red   Langmuir-Hinshelwood   N-TiO2   Photocatalysis  

摘要： In this study, the photocatalytic degradation of Congo red has been investigated in N-doped TiO2 (N-TiO2) aqueous suspensions under visible light irradiation. Visible light-active N-TiO2 was successfully prepared at three different weight contents (2.5, 5, and 7%) employing sol-gel method. It was able to harvest the visible irradiation with wavelength suitable for activation. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometer, diffused reflectance UV-Vis spectroscopy, nitrogen adsorption Brunauer-Emmert-Teller, Raman spectroscopy, photoluminescence and X-ray photoelectron spectrometer were used to characterize the doped catalyst. The samples had a relatively large specific Brunauer-Emmert-Teller surface areas of about 42 m(2) g(-1) with average X-ray diffraction crystalline size of 52 nm and showed visible light photocatalytic activity at about 408 nm. The impacts of several operating parameters on the Congo red photodegradation process were examined. Langmuir-Hinshelwood model exhibited pseudo-first-order degradation kinetics. N-TiO2-assisted plausible photodegradation mechanism has been suggested based on the qualitatively detected intermediate compounds.