关键词： 并联机械手   柔性构件   滑模变结构控制   假设模态法  

摘要： 对一种新型两自由度柔性并联机械手的动力学模型和运动控制进行研究。首先,考虑刚—柔耦合影响,利用假设模态法和Lagrange乘子法,推导出系统的动力学方程,该方程为微分—代数方程组。为了设计控制器,采用坐标分块法将该微分—代数方程组化为二阶微分方程组。然后,根据机械手的控制要求,采用滑模变结构方法设计控制器,该控制器能跟踪所期望的运动轨迹,同时柔性构件的弹性振动得到抑制。仿真结果表明该控制器的可行性和有效性。

关键词： 工程机械   动力传动   优化  

摘要： 机械动力传动系统的优化配置是改善机械性能和提高燃油经济性的重要手段。对动力传动系统进行优化配置,其技术经济效果显著。本文结合笔者多年工程机械教学经验,重点研究了改善工程机械的动力性能和燃料经济性。

关键词： 公司债券   宗申   动力机械   债券发行  

摘要： 2011年10月21日证监许可[2011]1681号重庆宗申动力机械股份有限公司:你公司报送的《重庆宗申动力机械股份有限公司关于公开发行公司债券的申请报告》(重宗股[2011]168号)及相关文件收悉。根据《公司法》、《证券法》和《公司债券发行试点办法》(证监会令第49号)等有关规定,经审核,现批复如下:

关键词： 柔性机械臂   多领域建模   机电一体化   建模仿真  

摘要： 柔性机械臂是一个复杂的机电一体化系统,涉及到多个物理领域。传统柔性结构建模一直存在建模复杂、模型不易扩展、运行速度慢等缺点,而且难以实现多领域建模,忽略了不同物理领域相互作用给整体系统所造成的影响。为了提高建模效率和仿真准确度,采用MapleSim多领域建模仿真平台,建立了六自由度柔性机械臂模型,包括柔性臂杆、关节、伺服驱动系统、传感器等。基于模型,从多领域的角度研究了柔性机械臂的动力学特性。该方法建模工作量小,所建模型易修改。仿真结果表明了该方法的有效性。

关键词： 实验课程   实验教学改革   实践能力   创新意识  

摘要： 实验教学在机械类专业教育中具有不可替代的功能和作用。为适应机械类专业知识体系发展需求,我们进行了动力机械实验课程建设与实验教学改革,构建了"三层次三结合"的的实验课程教学新体系,提升学生的创新意识和实践能力。

关键词： 接箍作业   3P3R机械臂   Kane方法   动力学分析  

摘要： 目的为分析一种6自由度3P3R接箍自动上下料机械臂的操作性能并实现对其精确运动控制.方法采用Kane方法和旋量理论分析方法建立了机器人的操作臂运动学和动力学模型,利用该模型,针对原理样机的具体结构,应用Mathematica平台研究了机械臂的操作性能.结果得到在一定作业任务规划下,末端执行器的位姿变化规律,以及按照该规划轨迹运动时各关节的驱动力;结论3自由度普通汇交RBR型腕部结构,具有足够灵活性,可以满足诸多地表附近的作业任务.整体上,机械臂具有较高的承载能力和灵活性,能够满接箍自动上下料的作业要求.结合了Kane方法和旋量理论的动力学模型具有准确、简单、有效等特点,能够满足机械臂的运动学动力学分析的要求,为机械臂的设计改进和精确运动控制实施奠定了理论基础.

关键词： Ethylene-octene copolymer   Dicumylperoxide   Cross-linking   RPA   DMA   Creep  

摘要： Ethylene-octene copolymer (EOC) was cross-linked by dicumyl peroxide (DCP) at various temperatures (150-200 degrees C). Six concentrations of DCP in range 0.2-0.7 wt.% were investigated. Cross-linking was studied by rubber process analyzer (RPA). From RPA data analysis real part modulus s', tan(delta) and reaction rate constant K were investigated as a function of peroxide content and temperature. The highest s',, and the lowest tan(delta) were found for 0.7% of DCP at 150 degrees C. The quantitative analysis confirmed that the DCP-EOC cross-linking was occurring as first order reaction. The highest cross-linking kinetics constant K was found for 0.6% of peroxide at 200 degrees C. The activation energy of cross-linking EA obtained by Arrhenius plot had maximum at 0.5-0.6% of peroxide. While at 190-200 degrees C temperature range there was no detectable degradation for 0.2% of peroxide, for 0.4-0.7% of peroxide there was increasing level of degradation with increasing peroxide content. Generally, at low temperatures (150-180 degrees C) the increasing peroxide content caused increase in cross-linking kinetics. However at higher temperatures (190-200 degrees C) increase in kinetics (for 0.2-0.5% of peroxide) was followed by decrease. Especially in 0.6-0.7% peroxide level range the cross-linking is in competition with degradation which lowers the overall cross-linking kinetics. Gel content of the cross-linked EOC samples was found to be increasing with increase in peroxide content, which is caused by the increased cross-link network. Cross-linked samples were subjected to creep studies at elevated temperature (150 degrees C) and the result was found in agreement with the gel content and RPA results. Storage modulus and tan(delta) values obtained by Dynamic Mechanical Analysis (DMA) also support the RPA results. (C) 2011 Elsevier Ltd. All rights reserved.

关键词： Implicit   TIPARP gene   molecules   Halobenzenes   halogens   Binding energy   Experimental data   solvation   positive charge  

摘要： The performance of semiempirical molecular-orbital-methods MNDO, MNDO-d, AM1, RM1, PM3 and PM6-in describing halogen bonding was evaluated, and the results were compared with molecular mechanical (MM) and quantum mechanical (QM) data. Three types of performance were assessed: (1) geometrical optimizations and binding energy calculations for 27 halogen-containing molecules complexed with various Lewis bases (Two of the tested methods, AM1 and RM1, gave results that agree with the QM data.);(2) charge distribution calculations for halobenzene molecules, determined by calculating the solvation free energies of the molecules relative to benzene in explicit and implicit generalized Born (GB) solvents (None of the methods gave results that agree with the experimental data.);and (3) appropriateness of the semiempirical methods in the hybrid quantum-mechanical/molecular-mechanical (QM/MM) scheme, investigated by studying the molecular inhibition of CK2 protein by eight halobenzimidazole and -benzotriazole derivatives using hybrid QM/MM molecular-dynamics (MD) simulations with the inhibitor described at the QM level by the AM1 method and the rest of the system. described at the MM level. The pure MM approach with inclusion of an extra point of positive charge on the halogen atom approach gave better results than the hybrid QM/MM approach involving the AM1 method. Also, in comparison with the pure MM-GBSA (generalized Born surface area) binding energies and experimental data, the calculated QM/MM-GBSA binding energies of the inhibitors were improved by replacing the G(GB,QM/MM) solvation term with the corresponding G(GB,MM) term.

关键词： ZnO-MnO2   Defect   Mechanothermal effect   Solid solution   ZnMnO3  

摘要： Experimental results of electron paramagnetic resonance spectra, X-ray diffraction, scanning electron microscopy and infrared spectroscopy demonstrate that the kinetic of the physical and chemical processes that takes place during prolonged intensive mechanical processing (MP, 0 < t(MP) > 3120 min) of powder mixtures of 50%wt ZnO + 50%wt MnO2 can be described as a three stage process. (1) 0 < t(MP) > 30 min, particles destruction, formation of superficial defects, fast increment of sample average temperature (from 290 to similar to 600 K) and annealing of defects with the lowest energy of activation E-ac. (2) 30 < t(MP) > 390 min, further particle destruction, slow increment of sample average temperature (from similar to 600 to similar to 700 K), formation and growth of a very disordered layer of beta-MnO2 around ZnO particles, dehydration of MnO2, formation of solid solution of Mn2+ ions in ZnO, formation of nano-quasiamorphous states in the ZnO-MnO2 mixture and onset of the formation of the ZnMnO3 phase. (3) 390 < t(MP) > 3120 min, the sample average temperature remains constant (similar to 700 K), the reaction is completed and the spinel ZnMnO3 phase with a unit cell a = 8.431(1) angstrom and space group Fd (3) over barm is the only phase present in the sample. No ferromagnetism at room temperature was detected in this study. (C) 2011 Elsevier B.V. All rights reserved.

关键词： silsesquioxane   epoxy resin   curing kinetics   mechanical properties  

摘要： The curing reaction and kinetics of o-cresol formaldehyde epoxy resin (o-CFER) with polyhedral oligomeric silsesquioxane of N-aminoethyl-gamma-amino propyl group (AEAP-POSS) were investigated by differential scanning calorimetry (DSC). The thermal, mechanical, and dielectric properties of o-CFER/AEAP-POSS nanocomposites were investigated with thermogravimetric analysis (TGA), torsional braid analysis (TBA), tensile tester, impact tester, and electric analyzer, respectively. The results show that the activation energy (E) of curing reaction is 58.08 kJ/mol, and the curing reaction well followed the Sestak-Berggren (S-B) autocatalytic model. The glass transition temperature (T(g)) increases with the increase in AEAP-POSS content, and reaches the maximum, 107 degrees C, when the molar ratio (N(s)) of amino group to epoxy group is 0.5. The nanocomposites containing a higher percentage of AEAP-POSS exhibited a higher thermostability. The AEAP-POSS can effectively increase the mechanical properties of epoxy resin, and the tensile and impact strengths are 2.84MPa and 143.25 kJ m(-2), respectively, when N(s) is 0.5. The dielectric constant (epsilon), dielectric loss factor (tan delta), volume resistivity (rho(v)), and surface resistivity (rho(s)) are 4.98, 3.11x10(-4), 3.17x10(12) Omega cm(3), and 1.41x10(12) Omega cm(2), respectively, similarly at N(s) 0.5. Copyright (C) 2009 John Wiley & Sons, Ltd.