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.

关键词： dissolution   ESPI   benzoic acid   mass transfer   mathematical modeling  

摘要： In many cases, classic in vitro tests are used to investigate dissolution from powders and solids. A problem with these kinds of tests is the frequent use of agitation, leading to a lumped description of the properties at the solid-liquid intetface. The hydrodynamic forces arising from agitation might have a nontrivial impact on the dissolution properties, thus calling for a comparison of results with those stemming from stagnant dissolution with the aim to increase the understanding of the dissolution process. Stagnant dissolution of compressed solid benzoic acid was examined using the noninvasive electronic speckle pattern interferometry technique in this study. The diffusion coefficient for benzoic acid in 37 degrees C water was measured using the same technique, and, by combining the results, the surface kinetics at the solid-liquid intetface were calculated. A comparison with previous dissolution data from a rotating disk suggests that the presence of convection can increase the observed surface kinetics. (C) 2010 American Institute of Chemical Engineers AlChE J, 57: 2610-2617, 2011

关键词： finite element   stress   flow regime   shell morphology   trade-off  

摘要： Aquatic species can experience different selective pressures on morphology in different flow regimes. Species inhabiting lotic regimes often adapt to these conditions by evolving low-drag (i.e., streamlined) morphologies that reduce the likelihood of dislodgment or displacement. However, hydrodynamic factors are not the only selective pressures influencing organismal morphology and shapes well suited to flow conditions may compromise performance in other roles. We investigated the possibility of morphological trade-offs in the turtle Pseudemys concinna. Individuals living in lotic environments have flatter, more streamlined shells than those living in lentic environments;however, this flatter shape may also make the shells less capable of resisting predator-induced loads. We tested the idea that "lotic" shell shapes are weaker than "lentic" shell shapes, concomitantly examining effects of sex. Geometric morphometric data were used to transform an existing finite element shell model into a series of models corresponding to the shapes of individual turtles. Models were assigned identical material properties and loaded under identical conditions, and the stresses produced by a series of eight loads were extracted to describe the strength of the shells. "Lotic" shell shapes produced significantly higher stresses than "lentic" shell shapes, indicating that the former is weaker than the latter. Females had significantly stronger shell shapes than males, although these differences were less consistent than differences between flow regimes. We conclude that, despite the potential for many-to-one mapping of shell shape onto strength, P. concinna experiences a trade-off in shell shape between hydrodynamic and mechanical performance. This trade-off may be evident in many other turtle species or any other aquatic species that also depend on a shell for defense. However, evolution of body size may provide an avenue of escape from this trade-off in some cases, as changes in size

关键词： Receptor of advanced glycation end products   Surfactant-protein-type-B   Vascular surgery   Mechanical ventilation  

摘要： Receptor-of-Advanced-Glycation-End-products (RAGE) and Surfactant-Protein-type-B (SPB) are reported as lung injury markers. Unlike SPB, RAGE is secreted by several tissues, so that RAGE specificity as lung injury marker is questionable. We measured SPB and RAGE in 19 patients undergoing major vascular abdominal surgery. SPB and RAGE were measured before mechanical ventilation (T(0)), at 1st (T(1)), 2nd (T(2)) and, when present, 3rd (T(3)) hour of mechanical ventilation, and 1 h after extubation (T(POST)). Last data during mechanical ventilation, either T(2) or T(3), are reported as T(END). SPB and RAGE values were normalized for total protein (SPB(N) and RAGE(N)). SPB(N) and RAGE(N) increments from To to T(END) Were 56.2 [39.1] ng/mg (mean [75-25 percentile]) and 10.6[7.1] pg/mg, respectively. SPB values increased progressively during mechanical ventilation, whereas RAGE values increased at T(1) but not thereafter. SPB(N) increase (T(END) - T(0)), but not RAGE(N), was related to Delta PaO(2)/FiO(2) changes during mechanical ventilation (r=0.575, p = 0.01). Plasma RAGE(N) and SPB(N) kinetics in patients undergoing major vascular surgery are different. (C) 2011 Elsevier B.V. All rights reserved.

关键词： 工程机械行业   东方红柴油机   动力元件   上海新国际博览中心   宝马   展放   品牌   亚太地区  

摘要： 1展会情况 ＂上海宝马工程机械展＂是世界最大的工程机械展bauma在中国的延伸,同时也是2010年亚太地区最具影响力的国际性行业博览会。bauma China2010暨第5届中国国际工程机械、建材机械、工程车辆及设备博览会于2010年11月23—26日在上海新国际博览中心召开。