关键词： H-2-storage properties of Mg   Addition of Ni and Fe2O3   Reactive mechanical grinding   Mg2Ni formation   Mg(OH)(2) formation  

摘要： The activated 76.5 wt%Mg-23.5 wt%Ni (Mg-Ni) has a lower hydriding rate, compared with Mg-23.5 wt%Ni heat-treated after melt spinning, due to the nonhomogeneous distribution of Ni particles in the mixture and the larger sizes of the particles. Among 76.5 wt%Mg-23.5 wt%Ni (Mg-Ni), 71.5 wt%Mg-23.5 wt%Ni-5 wt%Fe2O3(Mg-Ni-O), and 71.5 wt%Mg-23.5 wt%Ni-5 wt% Fe2O3(spray conversion) (Mg-Ni-Osc) samples, Mg-Ni-Osc has the highest hydriding and dehydriding rates. The reactive mechanical grinding of Mg with Ni, purchased Fe2O3 or Fe2O3(spray conversion) is considered to facilitate nucleation and shorten diffusion distances of hydrogen atoms. After hydriding-dehydriding cycling, all the samples contain Mg2Ni phase. The samples with Fe2O3 and Fe2O3(spray conversion) as starting materials contain Mg(OH)(2) phase after hydriding-dehydriding cycling as well as after reactive mechanical grinding. (C) 2010 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

关键词： Li2MnO3   Li plus ionic duffusion   NMR  

摘要： XRD, Li-7 MAS NMR, and electrical resistivity measurements were carried out to probe the local structure and the Li+ ionic diffusion in lithium manganese oxide Li2MnO3 prepared by mechanical milling and solid state reaction. XRD profiles and NMR spectra remarkably changed as milling time increased, and it is suggested that a disordered frame structure consisting of Mn-O polyhedral blocks was produced. Such a precursor would enable one to synthesize Li-Mn-O compounds at relatively lower temperatures compared to the synthesis just by solid state reaction. The activation energy for the hopping of the Li+ ions in Li2MnO3 sintered at 900 degrees C was determined to be 0.46 eV from the analysis based on a simple Debye model of electrical resistivity. Changes in the NMR spectra and the electrical resistivities suggest that the Li+ ions begin to occupy available sites in the Mn-O block layer at low temperatures and located in those, forming the lithium layer sandwiched by oxygen layers, at high temperatures in Li2MnO3 prepared via mechanical milling. The establishment of the lithium layers plays an important role in a valid Li+ ionic conduction in layered Li2MnO3. (C) 2010 Elsevier B.V. All rights reserved.

关键词： 农机测试   田间试验   遥测   传感器  

摘要： 针对播种、收获、整地、植保等农业机械的研发需要依靠大量季节性田间试验,而相关试验检测手段却相对薄弱的现状,笔者研制了该系统。系统各传感器全面采用无线传输技术,上悬挂杆传感器和牵引拉力板分别配用角度传感器检测瞬时空间位置,并结合动态应变测试、嵌入式计算机等技术,在牵引车内无线实时接收机具扭矩、水平牵引力与垂直分力、机架载荷、转速等动力学信号,处理、分析并显示旋转功率、全功率等测试结果。同时,简单介绍了遥测系统的组成结构,对传感器电桥、应变片、电源、平衡元件等的参数选择进行了理论分析,介绍了电桥调零、正负极性判断、弹性元件材料确定、标定等采用的技术方法。最后,以动力输出轴一体化扭矩传感器为例详细阐述了农机测试专用传感器的设计与计算依据。

关键词： 肺泡表面活性物质(PS)   ARDS   机械通气   呼吸功能   血流动力学  

摘要： 目的探讨肺泡表面活性物质(PS)对ARDS机械通气危重患者呼吸功能及血流动力学的影响。方法对40例ARDS机械通气的危重患者,比较使用PS治疗前及治疗24h后动脉血气、呼吸力学及血流动力学参数的变化。结果 PS治疗后动脉血氧分压(PaO2)、氧合指数(PaO2/FiO2)、动脉血二氧化碳分压(PaCO2)及肺泡动脉血氧分压差(A-aDO2)较治疗前均有明显改善,P均<0.05;PS治疗后潮气量(Vt)、气道峰压(Ppeak)、平台压(Ppause)、心率(HR)、中心静脉压(CVP)、平均动脉压(MAP)较引流前均有明显改善(P均<0.05)。结论机械通气ARDS危重患者使用PS治疗可以明显改善通气和换气功能,并使患者的血流动力学趋于稳定。

关键词： 机械行业   变频器   C2000   绕线转子异步电动机   起重机行业   工业生产   起重运输设备   综合技术指标  

摘要： 起重运输设备作为国民工业生产特种设备，广泛应用到各种行业，随着工业生产对起重机调速性能要求的不断提高，常用传统的起重机调速方法由于其绕线转子异步电动机的集电环和电刷容易发生故障，再加上大量继电器和接触器的使用，致使现场维护量较大，调速系统的故障率较高，综合技术指标较差，已不能满足工业生产的特殊要求。近年来，随着变频技术的不断发展，变频器陛能日益提高，变频调速机械杼陛硬、凋速范围大、调速精度高、平稳胜好、易于控制和节能等特点，能够很好地满足起重设备安全平稳、可靠、操作性良好可靠、免维护等要求，迅速在起重机行业获得突破并广泛应用。

关键词： Molecular dynamics   bismuth telluride   nanowire   strain rate  

摘要： The mechanical properties of single-crystal bismuth telluride nanowires have been studied by molecular dynamics methods. The mechanical behavior of the Bi(2)Te(3) nanowire for two principal axes was simulated under different strain rates at low temperature and the results compared with those of bulk Bi(2)Te(3). The simulation results show that, due to its marked anisotropy, the nanowire shows quite different failure behaviors in the two directions, with the failure stress for the a-axis (4.7 GPa) being three times that for the c-axis (1.4 GPa). The stress-strain curve of the nanowire is different from that for Bi(2)Te(3) bulk, as surface stress induced by atomic rearrangement significantly reduces the strength of the nanowire. The effect of strain rate on the mechanical properties of the nanowire has also been analyzed, showing that the failure stress and failure strain decrease with decreasing strain rate, a behavior not apparent in the bulk Bi(2)Te(3) simulation.

关键词： Molecular Dynamics   Nanoscratch   Shear   Nanofriction   GaAs  

摘要： Nanomechanical characteristics of gallium arsenide (GaAs) are investigated applying nanoscratch approach combined with molecular dynamics (MD) simulation. Moreover, mechanical responses for the shear deformation and frictional behavior are obtained as well. Based on the MD analysis, the GaAs deforms plastically even for a tiny scratch depth of 0.3 nm. This plastic deformation results from mechanical twinning or dislocation motion during the scratching and therefore this paper also addresses the effects of the scratch depth and speed on the characteristics of interest over the GaAs surface. The shear deformation provided by the atomistic analysis well agrees with that determined by the previous experiment of atomic force microscopy (AFM). It further substantiates the validity of the present results.

关键词： PHASE transformations (Physics)   MATERIALS -- Mechanical properties   MOLECULAR dynamics   SIMULATION methods & models   CRYSTALS   POLYMORPHISM (Crystallography)   TEMPERATURE effect   HIGH pressure chemistry  

摘要： The phase transitions and mechanical properties of the energetic material octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) in three pure polymorphs crystals, alpha-, beta-, and delta-phases, have been studied theoretically. isothermal isobaric molecular dynamics (MD) simulations were performed in the temperature range of (5 to 555) K at 0 GPa and the pressure range of (0 to 40) GPa at 298 K. The lattice parameters and volumes show nonlinear dependence on the temperature and pressure. In the high-temperature regime, there exist two phase transitions, that is, from beta- to alpha-HMX at 360 K and from alpha- to delta-HMX at 440 K. Under high pressure, the beta-HMX transition to delta-HMX is shown at 27 GPa and 298 K. Within the range of temperature and pressure studies, it can be deduced that the beta-HMX at lower temperatures and higher pressures, the alpha-HMX at higher pressures, and the delta-HMX at lower temperatures have better malleability.

关键词： Energy utilization  

摘要： Debate exists regarding the merits and limitations of continuous versus pulsatile flow mechanical circulatory support. To characterize the hemodynamic differences between each mode of support, we investigated the acute effects of continuous versus pulsatile unloading of the failing left ventricle in a bovine model. Heart failure was induced in male calves (n = 14). During an acute study, animals were instrumented through thoracotomy for hemodynamic measurement. A continuous flow (n = 8) and/or pulsatile flow (n = 8) left ventricular assist device (LVAD) was implanted and studied during maximum support (similar to 5 L/min) and moderate support (similar to 2-3 L/min) modes. Pulse pressure (PP), surplus hemodynamic energy (SHE), and (energy equivalent pressure [EEP]/mean aortic pressure (MAP) - 1) x 100% were derived to characterize hemodynamic energy profiles during the different support modes. Standard hemodynamic parameters of cardiac performance were also derived. Data were analyzed by repeated measures one-way analysis of variance within groups and unpaired Student's t-tests across groups. During maximum and moderate continuous unloading, PP, SHE, and (EEP/MAP - 1) x 100% were significantly decreased compared with baseline and compared with pulsatile unloading. As a result, continuous unloading significantly altered left ventricular peak systolic pressure, aortic systolic and diastolic pressure, +/- dP/dt, and rate x pressure product, whereas pulsatile unloading preserved a normal profile of physiologic values. As continuous unloading increased, the pressure-volume relationship collapsed, and the aortic valve remained closed. In contrast, as pulsatile unloading increased, a comparable decrease in left ventricular volumes was noted. However, a normal range of left ventricular pressures was preserved. Continuous unloading deranged the physiologic profile of myocardial and vascular hemodynamic energy utilization, whereas pulsatile unloading preserved more normal phys

关键词： aerodynamic   flight   pectoralis   power  

摘要： There have been few comparisons between the relationship between the mechanical power requirements of flight and flight speed obtained using different approaches. It is unclear whether differences in the power-speed relationships reported in the literature are due to the use of different techniques for determining flight power or due to inter-specific differences. Here we compare the power-speed relationships in cockatiels (Nymphicus hollandicus) determined using both an aerodynamic model and measurements of in vitro performance of bundles of pectoralis muscle fibres under simulated in vivo strain and activity patterns. Aerodynamic power was calculated using different ranges of values for the coefficients in the equations: induced power factor (k 1.0-1.4), the profile (C-D,C-pro 0.01-0.03) and parasite drag (C-D,C-par 0.05-0.195) coefficients. We found that the aerodynamic power-speed relationship was highly sensitive to the values assumed for these coefficients and best fit the power calculated from in vitro muscle performance when k=1.2, C-D,C-pro=0.02 and C-D,C-par=0.13.