Zr-2/Cr反应扩散研究

研究了Zr-2/Cr扩散偶在1023－1123K范围内的反应扩散，用扫描电镜观察反应宽度，用能谱仪（EDS）测定了反应层Zr,Fe和Cr沿扩散方向的浓度分布，研究了反应层的生长动力学，结果表明，反应层生长基本符合抛物经规律，生长过程受扩散控制，用Boltzman-Matano-Heumann模型计算了Cr在反应层Zr（Fe,Cr）2中的互扩散系数D，得到了互扩散系数D与温度的Arrhenius方程，由计算的扩散数据与Cr在Zr中形成稀固溶体时Cr的扩散数据比较可知，Cr在金属间化合物Zr（Fe,Cr）2中的扩散比在稀因溶体中的扩散快5个数量级。     

节理岩体参数对围岩破损区影响的敏感性分析

本文针对黄河拉西瓦地下水电站工程，对节理岩体诸参数对围岩破损区范围的影响进行了敏感性分析。指出了主要敏感参数，对这些参数影响围岩破损区的趋势和可能程度进行了讨论，并对勘察和施工提出了一些意见。     

搅拌工艺对半固态Y112铝合金组织及性能的影响

采用自行研制的机械搅拌装置,研究了不同工艺参数对半固态Y112铝合金组织及性能的影响.研究表明,搅拌温度越高,搅拌速度越大,固相颗粒越细小、均匀和圆整,其抗拉强度与伸长率越高;但温度太高,固相颗粒会熔化,抗拉强度及伸长率也降低;随搅拌时间的延长,固相颗粒先变得细小、均匀和圆整,然后长大,抗拉强度、伸长率先升高后降低.     

Numerical study on PEMFC’s geometrical parameters under different humidifying conditions

Steady-state and three-dimensional simulations were carried out to study the influences of geometrical parameters on the performance of PEMFC under different hydrating conditions. Flow fields, species transport, transport of water in polymer membrane and movement of liquid water in cathode and anode porous layers were determined, in order to accomplish a complete estimation of ohmic and concentration losses of PEMFC power. The geometrical parameters were thickness of the polymer membrane, cathode catalyst layer as well as gas channel to rib width ratio. Every simulation was made under different relative humidities of inlet flows (50 and 100%) for every change of characteristic length. Results show that the influence of the geometrical parameters on ohmic and concentration losses is of considerable importance. The performance of PEMFC is seriously affected under dehydrating conditions. However, such performance may be considerably improved by using suitable geometrical parameters. Cathode and anode liquid saturation may not only affect the transport of species, but also the polymer electrolyte water content. These results show the importance of simultaneously calculating both the water absorption and desorption through the polymer electrolyte and the liquid saturation in the cathode and anode porous mediums to obtain an actual view of ohmic and concentration losses of the PEMFC performance.     

X射线三轴晶衍射法测量半绝缘GaAs单晶的化学配比

采用X射线三轴晶衍射法,根据As间隙原子对作为过量As在GaAs单晶材料中存在的主要形式的模型,可以无损、高精度测量半绝缘GaAs单晶的化学配比.并探讨了引起晶格变化的原因及其与熔体组分的关系,对于制备高质量GaAs单晶及其光电器件具有重要的意义.     

New Engineered Particles from Spray Dryers: Research Needs in Spray Drying

This article reviews developments in the simulations of spray dryer behavior, including the challenges in modeling the complex flow patterns inside the equipment, which are often highly transient and three-dimensional in nature. There appears to be considerable scope for using CFD simulations for investigating methods to reduce the rates of wall deposition and of thermal degradation for particles by modifying the air flow patterns in the chamber through small changes in the air inlet geometry. Challenges include building particle drying kinetics and reaction processes, as well as agglomeration behavior, into these simulations. The numerical simulations should be valuable supplements to pilot-scale testing, enabling more extensive and accurate optimization to be carried out than hitherto possible. New understanding of reaction processes and materials science, in combination with recent knowledge of the application of CFD to these problems, may enable new engineered powder products to be developed from the one-step spray-drying process.     

Development of Low-Oxide MCrAlY Coatings for Gas Turbine Applications

Advanced high-energy plasma systems are being used to achieve the benefits of the high-velocity oxy-fuel (HVOF) system without losing the inherent advantages of plasma for coating of gas turbine parts. MCrAlY coatings play a very important role in the performance and reliability of gas turbine components. One of the important considerations for next generation of gas turbines, which have more demanding conditions and need to withstand ever increasing operating temperatures, is that they should possess very low oxygen content levels in the coating. Low oxygen content coatings are applied by the expensive low-pressure plasma spray (LPPS)/vacuum plasma spray (VPS) technique for critical components in aero- and land-based gas turbines. This work deals with the development of low-cost LPPS equivalent coatings (having low oxygen content) using the high-energy high-velocity plasma spray (HEHVPS) gun and inert gas shroud. A comparison has also been made with CoNiCrAlY coatings by HVOF.     

Time and Temperature Factors in Construction of Rock Strength Criteria

Using the synthesis of the kinetic concept on solid strength and the Coulomb - Mohr strength theory as the base, the failure conditions taking into account the time and temperature factors are obtained.     

Ultrasonic properties of hexagonal ZnS at nanoscale

Higher order elastic constants have been calculated in ZnS at 300 K and 500 K following the interaction potential model. Ultrasonic attenuation, velocity and other related parameters have been calculated using the higher order elastic constants for the different size of the material at 500 K. The size dependency of the ultrasonic properties is discussed in correlation with elastic, thermal and electrical properties. It has been found that the thermal conductivity is the main contributor to the behaviour of the ultrasonic attenuation as a function of the size and the responsible cause of attenuation is phonon-phonon interaction. The semiconducting nature of ZnS film has been achieved with the study of size variation of thermal relaxation time and ultrasonic attenuation.     

高坝洲电站碾压混凝土纵向围堰拆除爆破设计与实践

介绍了高坝洲电站碾压混凝土下游纵向围堰现场爆破试验成果,在分析爆破试验效果的基础上进行碾压混凝土围堰拆除爆破设计,详细分析了拆除爆破实施效果及主要影响因素.