关键词： 胶原纤维   分子动力学模拟   点突变   成骨不全症   机械性能  

摘要： 现代人对胶原机械性能和结构的理解程度，对于生物医学材料以及纳米技术的应用至关重要。而且，点突变与许多胶原类疾病有关，其中包括成骨不全症（OI）。我们进行一系列传统研究以及能够操纵原子的分子动力学模拟，以便检测点突变对于胶原纤维结构和机械性能的影响，包括甘氨酸到丙氨酸、天冬氨酸、半胱氨酸和丝氨酸的突变以及羟脯氨酸到精氨酸、天冬酰胺、谷酰胺和赖氨酸的突变。研究发现，所有点突变均能分散胶原纤维的结构，并降低其强度，从而影响纤维的层堆积。相对于羟脯氨酸突变（wT〉Arg〉Glu〉Asn〉Lys），甘氨酸突变（wT〉Ala〉ser〉cys〉Asp）对纤维的机械强度的影响更为有害。甘氨酸突变的临床表现与通过分子模拟预言纤维可拉伸强度降低的趋势相一致。大体上，胶原纤维机械性能的降低能够预言点突变的临床表现。

关键词： 机械加工技术   纳米尺度   分子动力学   机理   表层   晶体   纳米加工技术   金刚石刀具  

摘要： 基于分子动力学的晶体铜纳米机械加工表层形成机理研究 博士：张俊杰 指导教师：孙涛闰永达 毕业学校：哈尔滨工业大学 作为纳米技术分支之一的纳米加工技术是在纳米尺度范围内制造物理、化学和生物等功能结构与器件的基础，已经成为衡量纳米技术发展水平的重要标志。纳米机械加工技术如金刚石刀具车削、金刚石磨粒加工以及金刚石微探针纳米刻划等可以使加工精度达到纳米量级、加工形成的结构与器件的尺寸达到纳米量级，为制造三维纳米结构与器件提供了创新的途径，是一种重要的由上而下的纳米加工技术。

关键词： 稳定土厂拌设备   工程机械   产品发展   中国   江苏   颁奖典礼   北京  

摘要： 3月29日，2013工程机械产品发展（北京）论坛暨中国工程机械年度产品TOP50颁奖典礼在北京隆重举行，江苏华通动力WBS700E稳定土厂拌设备入选中国工程机械年度产品TOP50（2013），江苏华通动力重工有限公司副总裁肖狲宇亲临现场领取奖项，众多企业及媒体共同分享了华通动力这一喜人的成果。

关键词： 输液泵   发条   定时器   涡卷弹簧  

摘要： 目的设计一种动力源,驱动纯机械式无电源输液泵。方法通过气源、磁场、发条三种能量动力源的比较,采用发条作为储能媒介,设计发条定时器;通过无固有周期擒纵调速器,保证发条匀速稳定输出,带动输液泵蠕动泵头的转动。结果发条定时器储能、释放能量驱动匀速机匀速运输,取代传统电机驱动蠕动泵头。结论与气源、磁场相比较,发条作为动力源具有易控制、维护简单、耐热、耐腐蚀等优点。

关键词： zinc   dissolution kinetics   mechanical activation   neutral leach residue  

摘要： Neutral leach residue of zinc calcine （NLRZC） was mechanically activated by a stirring ball mill. Subsequently, the changes in physicochemical properties and dissolution kinetics in sulphuric acid were studied. The crystalline structure, morphology, particle size and specific surface area of the non-activated and mechanically activated NLRZC were characterized by X-ray diffraction, scanning electron microscope, particle size analyzer and volumetric adsorption analyzer, respectively. The characterization results indicate that mechanical activation （MA） induced remarkable changes in the physicochemical properties of NLRZC. The leaching experiments show that MA significantly enhances the leaching reactivity of NLRZC using the zinc extraction as evaluating index. After NLRZC is mechanically activated for 30 min and 60 min, the activation energy decreases from 56.6 kJ/mol of non-activated NLRZC to 36.1 kJ/mol and 29.9 kJ/mol, respectively. The reaction orders of the non-activated, 30 and 60 min activated NLRZC dissolution with respect to H2SO4 concentration were found to be 0.34, 0.30, and 0.29, respectively.

关键词： reciprocating orthosis   powered gait orthosis   spinal cord injury   walking   physiological cost index  

摘要： Objectives: Mechanical orthoses, such as the hip knee ankle foot orthosis (HKAFO) and the isocentric reciprocating gait orthosis (IRGO), are both used for walking in spinal cord injury (SCI) patients. The aim of this study was to analyze the energy expenditure during walking with these orthoses compared with a powered gait orthosis (PGO) in patients with SCI. Methods: Five patients with SCI who were experienced users of HKAFOs participated in this study. Subjects were also fitted with an IRGO and PGO and underwent a specific gait training program. Patients walked along a flat walkway using the three types of orthosis at their self-selected walking speed. A stop watch and a polar heart rate monitor were used to measure the speed of walking and heart rate. Results: Walking speed, the distance walked and the physiological cost index (PCI) all improved with both the new PGO and the IRGO as compared with the HKAFO. Conclusions: A PGO can improve walking speed and the distance walked and reduce the PCI of walking as compared with mechanical orthoses, probably due to the activated movements of the lower limb joints.

关键词： METALS -- Mechanical properties   METAL crystals -- Growth   CHEMICAL kinetics   MAGNESIUM alloys   MATERIALS -- Compression testing   PARTICLE size distribution   TEMPERATURE effect   METAL-metal bonds  

摘要： An ultrafine-grained AZ31 magnesium alloy with a mean grain size less than 1 mu m was fabricated using three-passes of accumulative compression bonding. Three passes were made at temperatures of 693 K, 643 K and 593 K, respectively, with a strain rate of 1.5 s(-1) and a reduction of 75% for each pass. After the first pass, the mean grain size was abruptly refined from 23 mu m to 5.1 mu m and most of the basal planes had been rotated 90 degrees perpendicular to the compression direction. After three passes, the microstructure was homogenous and excellent mechanical properties were obtained: 245 MPa yield stress, 372 MPa ultimate tensile strength and 14.8% fracture elongation. And a study on the kinetics of grain growth was carried out at temperatures range of 623-723 K. The effect of annealing temperature, T, and time, t, on the grain growth kinetics can be well interpreted by the kinetics equation D-n - D-0(n) = kt, where k = k(0)e((-Eg/RT)). According to the experimental data, the activation energy for grain growth E-g was measured to be 105 kJ/mol. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.

关键词： livestock building   design   efficiency   ventilation   cross-mechanical ventilation   poultry farm   broilers  

摘要： Broiler production in modern poultry farms commonly uses mechanical ventilation systems. This mechanical ventilation requires an amount of electric energy and a high level of investment in technology. Nevertheless, broiler production is affected by periodic problems of mortality because of thermal stress, thus being crucial to explore the ventilation efficiency. In this article, we analyze a cross-mechanical ventilation system focusing on air velocity distribution. In this way, two methodologies were used to explore indoor environment in livestock buildings: Computational Fluid Dynamics (CFD) simulations and direct measurements for verification and validation (V&V) of CFD. In this study, a validation model using a Generalized Linear Model (GLM) was conducted to compare these methodologies. The results showed that both methodologies were similar in results: the average of air velocities values were 0.60 +/- 0.56 m s(-1) for CFD and 0.64 +/- 0.54 m s(-1) for direct measurements. In conclusion, the air velocity was not affected by the methodology (CFD or direct measurements), and the CFD simulations were therefore validated to analyze indoor environment of poultry farms and its operations. A better knowledge of the indoor environment may contribute to reduce the demand of electric energy, increasing benefits and improving the thermal comfort of broilers.

关键词： DECAHYDRONAPHTHALENE   METHACRYLATES   CRYSTAL structure   ISOMERS   GLASS transition temperature   CONFORMATIONAL analysis  

摘要： We prepared the geometric isomers of decahydro-2-naphthols as the source materials for the synthesis of poly(decahydro-2-naphthyl methacrylate)s [poly(DNMA)-I, -II, -III, and -IV] including alicyclic ester groups with different geometric structures. The geometry and conformational dynamics of the decahydro-2-naplithyl moieties were investigated by NMR spectroscopy and DFT calculations. We synthesized each isomer of the methacrylic monomers, polymerized them, and investigated the optical, thermal, and mechanical properties of poly(DNMA)s with different isomer compositions. The T-g values of the poly(DNMA)s were in the following order: 139.3 degrees C for poly(DNMA)-II < 142.7 degrees C for poly(DNMA)-I < 146.2 degrees C for poly(DNMA)-III < 152.9 degrees C for poly(DNMA)-III/IV. On the basis of the dynamic motion of the alicyclic substituents determined by dynamic mechanical analysis, the tan 6 peaks due to the beta-relaxation for the a conformation change of the side group were observed for poly(DNMA)-I, while no peak was observed for poly(DNMA)-III. The activation energies for the beta-relaxation were 65 kJ/mol for poly(DNMA)-I and 56-63 kJ/mol for the poly(DNMA)s including the four isomeric ester groups with various compositions. An increase in the DNMA-II content in the repeating units accelerated a dynamic conformation change, resulting in a decrease in the tan 6 peak temperature and the activation energy value, as well as the glass transition temperature of the polymers. The optical property of the resulting polymers as the transparent polymer materials was also investigated. The density, refractive index value, and Abbe number of poly(DNMA)s were 1.04-1.10 cm(3)/g, 1.489, and 42-44, respectively.

关键词： Hydrocarbons   Free energy   Dissociation   Group 15 compounds   Catalysts  

摘要： Density functional theory calculations accounting for dispersion, thermochemical, and continuum solvent effects have been applied to study the metathesis of ethyl vinyl ether (EVE) as mediated by ruthenium catalysts L(PCy3) (X)(2)Ru=CHPh (L = PCy3, IMes (1,3-dimesitylimidazol-2-ylidene), H(2)IMes (1,3-dimesityl-4,5-dihydroimidazol-2-ylidene);X = Cl, Br, I) in toluene. The computational approach has been validated against experimental data for ruthenium-based olefin metathesis catalysts and is found to give acceptable accuracy even for weakly bound transition states of phosphine and olefin dissociation and association. All relevant stationary points of the EVE metathesis reaction have been included in the study, allowing comparison with experimental kinetic data (Sanford, M. S.;Love, J. A;Grubbs, R. H. J. Am. Chem. Soc. 2001, 123, 6543). From the active 14-electron complex, the barriers to both phosphine association (at a rate proportional to k(-1)) and olefin binding (k(2)) involve contributions from entropy and solute-solvent interactions. The overall barrier to EVE cydoaddition (k(2)*) is higher than that to binding only (k(2)). The thus obtained ratios k(-1)/k(2)* compare nicely with those originally measured and interpreted as k(-1)/k(2) by Sanford et al., suggesting that the experimental obtained ratios are better understood as k(-1)/k(2)*. Complementing the theoretical rate constants with concentrations, the thus obtained "computational kinetics" reproduces known trends among the various catalysts and also offers mechanistic insight.