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.

关键词： 六自由度机械手   动力学模型   Pro   E   ADAMS  

摘要： 采用拉格朗日方法建立了一种六自由度机械手的动力学模型。利用Pro/E软件建立机械手的三维模型,将其导入到ADAMS软件中进行动力学仿真,得出各个关节的力矩、速度、加速度和各关节转角的关系曲线,为机械手控制的研究奠定基础。

关键词： H-abstraction   fluoroesters   potential energy surface   G2(MP2)   canonical transition state theory  

摘要： Theoretical investigations are carried out on the title reactions by means of ab initio and DFT methods. The optimized geometries, frequencies and minimum energy path are obtained at MPWB1K/6-31+G(d,p) level. Single point energy calculations are performed at MP2 and QCISD(T) levels of theory. Energetics were further refined by calculating the energy of the species with a high level G2(MP2) method. The rate constant of the two reactions are calculated at 298K and 1atm using Canonical Transition State Theory (CTST) utilizing the ab initio data obtained during the present study. The rate constant values are found to be 5.5x10(-14) and 5.9x10(-14)cm(3) molecule(-1) s(-1), respectively which are in good agreement with the experimental data.

关键词： 动力学方程   机械臂   质心   符号表达式  

摘要： 由于机械臂大部分为不规则、不均匀的连杆构成,所以在计算过程中使用质心法推导,简化了运算过程,降低了运算复杂度,仿真结果表明,使用质心法能正确推导出多自由度机械臂动力学方程,为以后在不规则连杆构成的机械臂上使用质心法推导动力学方程提供了依据。