关键词： beta-HMX (beta-cyclotetramethylene tetranitramine)   PBXs (polymer-bonded explosives)   Sensitivity   Molecular structure   Mechanical property   Molecular dynamics simulation  

摘要： Molecular dynamics simulation was applied to investigate structures, sensitivity and mechanical properties of beta-HMX (beta-cyclotetramethylene tetranitramine) crystal and beta-HMX based PBXs (polymer-bonded explosives) with F-2311 polymer binder. The N-NO2 trigger bond lengths of the HMX and its PBXs were obtained under different temperatures, and discussed in terms of their relations with sensitivity. Mechanical properties were also calculated at different temperatures, based on which, their relations with the sensitivity were discussed. It finds that the maximum bond length L-max of N-NO2 trigger bond is an important structural parameter to effectively judge the sensitivity, the mechanical properties correlate well with the sensitivity, and especially. Cauchy pressure is an important mechanical parameter that can be used to effectively evaluate the sensitivity. (C) 2012 Elsevier B.V. All rights reserved.

关键词： 无轨胶轮车   机械装备   天然气   气动力   国家专利   矿用   煤机   专利证书  

摘要： 日前，由机械装备集团石煤机公司设计的天然气动力矿用无轨胶轮车取得国家实用新型专利证书，该车摈弃了柴油机动力污染环境、噪音大等缺点，利用了天然气辛烷值高、抗爆性好、低污染的优点，使整车具有经济实用、基本无环境污染的特点，为改善矿井环境、打造绿色矿山提供了绿色装备保障。

关键词： DELTA并联机械手   虚拟样机   动力学仿真   伺服选型   运动平台  

摘要： 通过编程逆解DELTA机械手最大运动空间轨迹;采用虚拟样机技术,利用ProE/Mechanism和ADAMS软件对DELTA并联机械手进行动力学仿真,对比验证机构仿真结果,得出驱动轴运动参数;在此基础上,提出一种伺服电机精确选型的新方法。所建立的虚拟样机模型也为DELTA机械手的研究提供了一个运动学分析和控制的平台。

关键词： 学科服务   服务创新   双语教学   高校图书馆   嵌入服务  

摘要： 国际化办学已成为国家本科教育模式中的重要组成部分,如何有效地开展面向国际化院系的嵌入式学科服务需要学科服务团队深入思考。以上海交通大学图书馆机械动力学科服务团队的实践为例,从信息素养教育、基地值班、院系专刊策划、电子教参系统搭建、LibGuides建设、学科博客维护和信息专员培养7个方面,全面解读该团队主动创新嵌入式学科服务工作、融入密西根联合学院国际化办学环境的系列举措,并分析其嵌入式学科服务创新实践的特色。

关键词： 上海柴油机股份有限公司   工程机械行业   供应商   流动   宝马   产品   发动机   装载机  

摘要： 作为国内工程机械行业最具影响力的发动机供应商,上海柴油机股份有限公司以＂工程机械全领域主流动力供应商＂为主题参加了＂Bauma China 2012＂（即上海宝马展）,上柴产品已经广泛应用于装载机、起重机、压路机、推土机、平地机、摊铺机等领域。

关键词： 农业机械化水平   农村劳动力   中国工程院院士   农业生产效率   农机化管理   进程   农机购置补贴   华南农业大学  

摘要： 近年来，农机逐渐取代人畜力成为中国农业生产的重要工具，大幅提升了农业生产效率。农业部农机化管理司司长宗锦耀日前透露，2011年全国农作物耕种收综合机械化水平已达到54．8％，比2002年增加22．5个百分点，10年间的增幅相当于前35年的总和。对于中国农业机械化水平近年来大幅提升的原因，中国工程院院士、华南农业大学教授罗锡文将其归结为农村劳动力的不断外流和农机购置补贴力度的逐年加大。

关键词： Planetary Fluid Dynamics   Angular Momentum Dynamics   Variational Principle   Symmetry  

摘要： In this paper we shall derive integral angular momentum equations for shallow water dynamics on a rotating planet and in doing so we shall show that these equations are a consequence of the partial spherical symmetry of an appropriate Lagrangian density for this dynamics. (C) 2012 Elsevier B.V. All rights reserved.

关键词： Carvacrol   Cinnamaldehyde   Polymeric film   Mechanical properties   Release kinetic   Biofilm  

摘要： Polyethylene-co-vinylacetate (EVA) films with different concentrations (3.5 wt% and 7 wt%) of essential oil constituents, carvacrol or cinnamaldehyde, were prepared and characterized by mechanical, antibacterial and antibiofilm properties. The incorporation of the compounds into copolymer films affected their elastic modulus, tensile stress and elongation at break. Carvacrol and cinnamaldehyde act as plasticizers which reduce the intermolecular forces of polymer chains, thus improving the flexibility and extensibility of the film. The analysis of the surface characteristics demonstrated that essential oil constituents lowered the contact angle values without causing any remarkable variation of the surface roughness. The films allowed progressive diffusion of the bioactive molecules and the kinetic of release was correlated with the damaging effect on bacterial growth. The kill curves proved that the film with essential oil constituents (7 wt%) had a significant bactericidal effect (reduction of 4 and 2 log CFU) against Staphylococcus aureus and Escherichia coli and a bacteriostatic effect against Staphylococcus epidermidis and Listeria monocytogenes (reduction of about 1 log CFU). With regard to biofilm formation the biomass formed on polymeric films surface was significantly reduced if compared with the pure copolymer control. The results were confirmed by fluorescence microscopy images by Live/dead staining. The reduction in the surface tension coupled to an inherent bactericidal property of carvacrol and cinnamaldehyde could in turn affect the initial attachment phase of bacteria and compromise the normal biofilm development.

关键词： 13~C{ 1H} CP-MAS NMR   Degradation kinetics   PMMA   Silica   thermal degradation   silica nanoparticle   degradation kinetics   Polymethyl Methacrylate   Thermogravimetry  

摘要： Silica–PMMA nanocomposites with different silica quantities were prepared by a melt compounding method. The effect of silica amount, in the range 1–5 wt.%, on the morphology, mechanical properties and thermal degradation kinetics of PMMA was investigated by means of transmission electron microscopy (TEM), X-ray diffractometry (XRD), dynamic mechanical analysis (DMA), thermogravimetric analyses (TGA), Fourier-transform infrared spectroscopy (FTIR), 13C cross-polarization magic-angle spinning nuclear magnetic resonance spectroscopy (13C{1H} CP-MAS NMR) and measures of proton spin-lattice relaxation time in the rotating frame (T1ρ(H)), in the laboratory frame (T1(H)) and cross-polarization times (TCH). Results showed that silica nanoparticles are well dispersed in the polymeric matrix whose structure remains amorphous. The degradation of the polymer occurs at higher temperature in the presence of silica because of the interaction between the two components.

关键词： nanocomposites   PMMA   zirconia   morphology   dynamic mechanical analysis   thermal degradation  

摘要： Zirconia nanoparticles were synthesized by means of a sol-gel method and embedded in poly(methyl methacrylate) (PMMA) by melt compounding. The zirconia was well dispersed in the PMMA matrix, with only a few clusters, especially for the highest investigated zirconia content. NMR results showed heteronuclear dipolar interactions involving the carbons and the surrounding hydrogen nuclei. The effect of the amount of zirconia, in the range of 1-5 wt%, on the thermo-mechanical properties and thermal degradation kinetics of PMMA was also investigated by means of dynamic mechanical analysis (DMA), thermogravimetric analyses (TGA), and Fourier-transform infrared spectroscopy (FTIR). The presence of zirconia showed a decrease in the storage and loss moduli at lower temperatures, probably due to a plasticization effect. The presence of zirconia in PMMA slightly increased its thermal stability, but the activation energies of thermal degradation for the nanocomposites were significantly lower, at degrees of conversion higher than 0.3, than those of pure PMMA.