Characterization of the ceramic–metal brazed interface using ultrasonic technique

Sintered Al₂O₃ is brazed with 304 stainless steel (SS) using 97(Ag28Cu)3Ti active filler alloy at 1000 °C. Electron Probe Micro Analysis (EPMA) studies of the interfaces are carried out. The thickness of the interfaces are measured from the concentration penetration profile. Shear strength of the joint is evaluated. The qualities of the joints are characterized using ultrasonic technique. Mechanical properties of the joints are correlated with the obtained ultrasonic signals during the ultrasonic scanning of the sample.     

Exact integration in the boundary element method for two-dimensional elastostatic problems

This paper derives the exact integrations for the integrals in the boundary element analysis of two-dimensional elastostatics. For facilitation, the derivation is based on the simple forms of the fundamental functions by taking constant, discontinuous linear and discontinuous quadratic elements as examples. The efficiency and accuracy of the derived exact integrations are verified against five benchmark problems; the results indicate that the derived exact integrations significantly reduces the CPU time for forming the matrices of the boundary element analysis and solving the internal displacements.     

Electrochemical properties of nanodiamond powder electrodes

Detonation-synthesized nanocrystalline diamond is a novel carbon material. Its increased electrical conductivity, due to the features of giant specific surface area and large numbers of surface defects as well as the cluster structure, makes it possible to be used as an electrode material. Nanodiamond powder electrodes were fabricated and the electrochemistry was investigated by cyclic voltammetry and AC impedance measurement. The results show that nanodiamond powder electrode is electrochemically stable in KCl electrolytes over a wide potential range (− 1.2–2.0 V). The electrode reaction is quasi-reversible in 0.1 M KCl containing the ferricyanide–ferrocyanide redox couple. The electrode reaction rate constant k is estimated to be 2.87 × 10^− 3 cm/s. The peak current increases linearly with the rising of the concentration of [Fe(CN)₆]^3−/4−. The AC impedance spectra have been analyzed and an equivalent circuit proposed.     

因子分析法和熵值法在高校科技创新评价中的应用

在已有研究的基础上总结出了一套科学合理并具有可行性的高校科技创新评价指标体系,并把因子分析法和熵值法应用于高校科技创新评价.首先对高校科技创新评价体系的5个一级指标分别进行因子分析,然后运用熵值法对其确定权重.分析结果表明两种方法的结合使用能够简化分析对象的结构,使评价结果更具科学性、客观性.     

CuO-NiO/Al_20_2催化剂上N-甲基哌嗪合成研究

以共沉淀法制备铜、铝系复合氧化物作为催化剂,二乙醇胺和甲胺为原料,合成了N-甲基哌嗪.利用高压反应釜对其进行活性评价,发现CuO-NiO/Al2O3活性最高.并对铜、铝、镍摩尔比、沉淀剂种类、沉淀方式,焙烧温度等条件进行了优化.结果表明:催化剂中理想的Cu、Al、Ni摩尔比为1:1:3.2,沉淀剂为氢氧化钠,沉淀方式为并流,焙烧温度为500℃.该条件下N-甲基哌嗪的选择性为27.7%,二乙醇胺的转化率达89.8%.另外通过对使用前后催化剂进行表征分析发现催化剂失活原因为表面高聚物的附着和对孔道的堵塞.     

基于ANSYS的车路系统力学分析

车辆荷载对路面的作用是导致路面病害的主要原因.以某道路改建工程为依托,通过大量的室内外实验,把实验的数据借助ANSYS力学分析软件进行路表弯沉、应力等静力学分析,得到最大值出现位置和应力变化趋势.考虑到路面上车辆行驶的运动特点,对车路系统进行了动力学分析,得到位移最大值及应力随时间的变化规律,为道路病害的预防提供了理论依据.     

“双储”模式下的节能控制在小区供水系统中的应用

根据城市居民对供水的可靠性、稳定性、经济节能性的需求,课题组提出了一种基于"双储"模式的供水系统,并按照本市德胜住宅小区的供水要求,设计了一套由储水池、气压罐、变频器、多台水泵机组等主要设备构成的全自动变频恒压供水系统.经过近半年的运行测试,系统有效地解决了传统供水方式中存在的问题,增强了系统的总体性能,有明显的节能效果.     

新型城镇化下欠发达地区传统文化保护研究——以张家口市段家堡村为例

新型城镇化背景下欠发达地区传统文化保护的关键取决于其能否在保护文化资本和环境资本的基础上,实现经济资本的提升、文化价值观念及生活方式的转变.通过对张家口市下花园区段家堡村传统文化的调查研究,提出转变观念,主动保护、挖掘和丰富欠发达地区传统文化特色,提升旅游开发优势,带动地区经济发展,实现新型城镇化的同时更好地保护传统文化.     

文艺复兴透视法的“技巧史”

基于考察透视是如何具体的、实质性的呈现为一种技巧形成的过程.虽然希腊和罗马时出现了简单的有透视特点的壁画,但是真正发生技巧变革的是文艺复兴时期的透视,尤以布鲁内莱斯基和阿尔贝蒂为代表,对透视技巧的变革和形成作了最重要的贡献.