A New Equation for Temperature Dependent Solute Impurity Diffusivity in Liquid Metals

An equation to predict the temperature dependence of solute impurity diffusivity in liquid metals has been derived by combining the Sutherland-Einstein formula with Kaptay’s unified equation on the dynamic viscosity of liquid metals. It has been demonstrated that consideration of the temperature dependence of the atomic radius of the diffusing species results in better agreement of the predicted diffusivities with the experimental data compared to when the temperature independent Goldschmidt atomic radius is used. Due to the simple-parameter nature of the equation, it could be very useful in predicting the solute impurity diffusivity in liquid metal when experimental data are scarce.     

一体双驱对称式压电悬臂梁微驱动器

设计了一种一体化加工的双驱对称式压电悬臂梁微驱动器。对压电驱动器工作原理、压电驱动器在准静态工况与共振工况下的输出特性进行了理论分析,确定压电驱动器几何尺寸。介绍了压电驱动器的多层复合结构与一体双驱的实现方式。制作了压电驱动器样机,并通过有限元仿真分析与测试实验相结合的方式得到压电驱动器的阻抗特性与输出特性曲线。将压电驱动器运用在轮式机器人,验证了设计的可行性。     

Influence of fiber surface treatment on mechanical performance of Xanthoceras sorbifolia bunge husk fibers/PP composites

The PP Composites containing Xanthoceras sorbifolia Bunge husks fibers with different surface treatments were prepared. The mechanical properties such as tensile properties and impact properties of the composites were investigated. It is revealed that the composites with fibers treated by alkali and the following treatments of silane coupling agents KH570, titanate coupling agent JN‐9A, acetic anhydride, MAPP, or bleach, all performed higher in tensile properties than that with untreated fibers, while lower in impact properties. Meanwhile, all treated fibers performed better thermal stability than untreated fibers. The fibers treated by alkali followed by KH570 treatment were added into PP with different contents. It is found that as the fiber content increases, the elastic modulus and impact strength of the composites increase sharply at first followed by a decrease, while the tensile strength decrease initially and increase with a peak at 10%, then decrease continuously. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41217.     

基于前推回代法和牛顿拉夫逊法的配电网潮流计算

针对牛顿拉夫逊法计算潮流时对节点电压初值的要求高的缺点,结合配电网为放射状网络的特征,提出基于前推回代法和牛顿拉夫逊法的配电网潮流计算,利用前推回代法第一次迭代的结果作为牛顿拉夫逊法的初值,能够满足牛顿拉夫逊法对初值的要求,且具有良好的收敛速度。最后,应用实例证明基于前推回代法和牛顿拉夫逊法的配电网潮流计算迭代次数少,收敛性好。     

透水性混凝土强度-渗透性模型试验研究

高透水性是透水性混凝土的重要特征,现有的透水性混凝土渗透系数测试装置存在试件侧壁渗漏问题,为此提出了一种试件侧面防水涂抹+柔性夹层+套筒刚性壁的防侧漏复合结构,提高了渗透系数测试精度。透水性混凝土的透水性和强度是一对矛盾体,此消彼长,但目前对它们之间关系缺乏系统的研究。通过室内渗透性和强度试验研究了多种因素（如：水灰比、集灰比、孔隙率）对透水性混凝土的强度和透水性的影响,建立了强度孔隙率模型、渗透性孔隙率模型和强度渗透性模型。研究结果表明：透水性混凝土与普通混凝土不同,存在一个最佳水灰比,最佳水灰比对应的强度最大;强度和水灰比成开口向下的二次抛物线关系,而孔隙率和集灰比均与渗透系数成正相关关系;透水性混凝土强度和渗透性关系服从Lorentzian函数,强度随渗透性的增大而逐渐降低,降低速度先快后慢。在工程设计中应根据具体要求,确定最佳的强度和渗透性组合。     

Analysing ownership,locational and internalization advantages of Chinese construction MNCs using rough sets analysis

The rough sets analysis focusing on the ownership, locational and internalization (OLI) advantages of Chinese construction multinational corporations (MNCs) in the international market under Dunning's Eclectic Paradigm was adopted to overcome the sample size constraint in MNC research that seeks to examine the causality patterns of the factors identified. The rough sets methodology provides a solution that conventional statistical methods do not offer to ascertain how these factors are determined and their influence in the OLI analysis of the performance of Chinese construction MNCs. The rough sets approach to handling imperfect data with uncertainty and vagueness was adopted to describe dependencies between attributes, evaluate the significance of attributes and deal with inconsistencies. Based on a questionnaire survey of 31 Chinese construction MNCs, findings from the rough sets analysis suggest, among other things, that: (1) a firm is likely to perform well in terms of its ownership advantages when it has a significant advantage on its reputation and its accessibility to resources when compared with local contractors; (2) a firm may be expected to achieve better results in terms of its locational advantages if the large number of competitors from China in the host countries becomes its most important consideration; and (3) a firm that conscientiously avoids or reduces information search and business negotiation costs would tend to perform well in terms of its internalization advantages.     

Compressive mechanical properties of HTPB propellant at low,intermediate, and high strain rates

Low, intermediate, and high strain rate compression testing (1.7 × 10^?4 to 2500 s^?1) of the hydroxyl‐terminated polybutadiene (HTPB) propellant at room temperature, were performed using a universal testing machine, a hydraulic testing machine, and a split Hopkinson pressure bar (SHPB), respectively. Results show that the stress linearly increases with strain at each condition; the increasing trend of stress at a given strain with the logarithm of strain rate changes from a linear to an exponential form at 1 s^?1. By combining these characteristics, we propose a rate‐dependent constitutive model which is a linearly elastic component as a base model, then multiplied by a rate‐dependent component. Comparison of model with experimental data shows that it can characterize the compressive mechanical properties of HTPB propellant at strain rates from 1.7 × 10^?4 to 2500 s^?1. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43512.     

The Effects of KCl,NaCl and K<Subscript>2</Subscript>CO<Subscript>3</Subscript> on the High-Temperature Oxidation Onset of Sanicro 28 Steel

The present study investigates the early stages in the oxidation process of Sanicro 28 (Fe31Cr27Ni) stainless steel when exposed to an alkali salt (KCl, NaCl or K₂CO₃) for 2 h at 450 and 535 °C. After the exposure, the oxidized samples were analyzed with a combinatory method (CA, XPS and SEM–EDX). It was found that all three salts were corrosive, and the overall oxidation reaction rate was much higher at 535 °C than at 450 °C. There were clear differences in terms of the impact of cations (Na⁺, K⁺) and anions (Cl^?, CO₃ ^2?) on the initial corrosion process at both temperatures. When focusing on the cations, the presence of potassium ions resulted in a higher rate of chromate formation than in the presence of sodium ions. When studying the effect of anions, the oxidation of iron and chromium occurred at higher rates in the presence of both chloride salts than in the presence of the carbonate salt, and chloride salts seemed to possess higher diffusion rate in the gas phase and along the surface than carbonate salts. Moreover, at the higher temperature of 535 °C, the formed chromate reacted further to chromium oxide, and an ongoing oxidation process of iron and chromium was identified with a significantly higher reaction rate than at 450 °C.