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.     

用无粘结预应力技术加固吊车梁

论述了用无粘结预应力技术改造加固吊车梁的升级设计与施工。     

镍基单晶气膜孔模拟试样的低周疲劳断裂机理

采用镍基单晶合金DD6带不同数量激光加工气膜孔的薄壁平板模拟试样,对其在900℃下的低周疲劳性能进行了研究,并对试验数据和断口的SEM形貌进行了分析。结果表明:在相同的试验条件下,气膜孔的数量对低周疲劳的寿命影响很大,单孔试样的寿命约为密排多孔试样的10倍;气膜孔周围存在大量微裂纹,带气膜孔试样的破坏属于典型的多源断裂;对于单孔试样及密排多孔试样的中间孔,裂纹沿{001}面扩展;密排多孔试样的上下2排气膜孔周围的裂纹沿多个滑移面扩展。     

Phase Equilibria in the Zn-Rich Corner of the Zn-Cu-Ti-RE (Ce,La) Systems at 450 °C

The Zn-rich corner of the Zn-Cu-Ti-RE(Ce, La) quaternary systems at 450 °C have been experimentally investigated by scanning electron microscopy coupled with energy dispersive x-ray spectrometer and x-ray diffraction. The liquid containing phase regions have been well identified in these two systems. The ternary compound τ (Cu₂TiZn₂₀) can equilibrate with all phases in the Zn-rich corner of these two systems. Neither Ce nor La can dissolve into TiZn₁₆, ε(CuZn₄) and τ(Cu₂TiZn₂₀). While the solubility of Cu in CeZn₁₁ and LaZn₁₃ can reach 2.9 at.% and 5.0 at.%, respectively. The results can help to design and analyze the Zn-Cu-Ti-RE alloys.     

基于广义S变换的滚动轴承故障诊断方法研究

鉴于广义S变换继承了短时Fourier变换、小波变换和标准S变换的所有优点,同时也弥补了它们存在的不足,具有良好的自适应的独特特性,提出了一种基于广义S变换的滚动轴承故障诊断方法,并与传统的短时Fourier变换、Wgner-Ville分布、小波变换、标准S变换等时频分析方法进行了对比分析。仿真研究表明,广义S变换具有明显的优势,能灵活地通过调节参数来自适应地调节窗函数的宽度,以便达到最佳的时频分辨率。最后,滚动轴承故障实验研究进一步验证了提出的方法的有效性。提出的方法能有效地反映不同轴承故障的特征频率,为滚动轴承故障诊断提供了一种有效的方法。     

ATP合酶β亚基功能与疾病

ATP合酶,又称F1F0-ATP合成酶,是位于线粒体内膜、叶绿体类囊体膜和光合菌质膜上的参与呼吸链氧化磷酸化的最后环节。其结构包含F1和F0两个亚单位,共同作用于ATP的分解和合成。ATP合酶β亚基是F1F0-ATP合成酶F1亚单位的重要组件,该亚基包含ATP合成和水解所需的催化位点,其功能好坏与疾病发生直接相关。本文就ATP合酶β亚基功能与糖尿病、肿瘤、肥胖症等疾病的关系作一综述。     

基于光流的无人机自主着陆控制策略

为解决无人机自主导航过程中自主着陆时难以满足特征识别条件的问题,提出一种基于光流的高度估计及自主着陆控制策略.依据无人机高度和垂直速度的关系,建立状态空间模型,通过模拟着陆,采用小扰动线性化系统模型,分析在恒定光流散度着陆过程中自激振荡的发生.仿真结果表明:控制增益给定的情况下,控制回路的稳定性仅取决于对地高度,当接近地面时,控制回路出现自激振荡,此时机载设备可以检测到震荡,并计算出高度.     

无轴式摩天轮安装施工技术模拟分析

无轴式摩天轮安装过程中,杆件间的位移关系到整个工程的质量,它贯穿于施工期直至运行期。对无轴式摩天轮的安装施工技术过程进行模拟,采用MIDAS数值分析软件,对潍坊白浪河大桥及摩天轮安装工程进行模拟分析,数值计算结果表明,将高度138m的无轴式摩天轮分成四部分安装,下部安装采用地面支撑,通过重型塔吊车进行构件单元安装;中部采用下部结构及格构柱提供支撑,配合塔吊及脚手架完成;上部安装通过格构柱支撑,配合塔支撑体系及操作脚手架完成;摩天轮上部节点最大位移258mm,下部最小位移54mm,节点最大位移小于1/500H,满足施工规范要求,为同类工程提供理论数值参考。     

厚硬基本顶综放沿空巷道应力分布特征及煤柱宽度确定

厚硬基本顶综放工作面开采强度高、基本顶厚度大,区段煤柱的稳定性直接影响着巷道的安全稳定,针对这一影响因素,采用理论分析、数值模拟的方法计算分析沿空巷道的覆岩结构特征及应力位移变化情况,确定合理煤柱宽度。结果表明:厚硬基本顶主要破断方式为两端拉断作用下破坏,计算得到巷道煤柱的留设宽度为7.5 m以上,分析了不同宽度煤柱下的垂直应力及形变量,最终确定煤柱合理留设宽度应为8 m。     

Microstructure and Mechanical Properties of ε-Phase-Reinforced ZnAl4Y Matrix Composite Prepared by Mixed Solid-Liquid Casting

ε-Phase-reinforced ZnAl4Y matrix composite has been fabricated by mixed solid-liquid casting method. The results show that the size of primary η-Zn phase in the composite decreases remarkably with the increase of adding amount of Cu-10wt.%Al powders till it reaches 6.0 wt.% in ZnAl4Y alloy. Besides, a large amount of small ε-phase particles form in ZnAl4Y matrix when the adding amount of Cu-10wt.%Al powders is in the range of 4.0-6.0 wt.% in ZnAl4Y alloy. Coarse ε-phase particles forms when the adding amount of Cu-10wt.%Al powders exceeds 8.0 wt.% in ZnAl4Y alloy. Compared with ZnAl4Y alloy, the composite could obtain optimal mechanical properties when the added amount of Cu-10wt.%Al powders is 6.0 wt.%.