LASER CLADDED TiCN COATINGS ON THE SURFACE OF TTTANIUM

Laser cladded coatings of TiCN were produced on the surface of titanium. To obtain the optimal techniques, several conditions were tested by varying the laser scanning rate. The choice of shielding gas was also studied. The cladded coatings were then evaluated from the surface mechanics point of view based on their microhardness. The microstructure of some interesting samples was investigated by optical micrographs （OM）. The results showed that under the condition of fixed pulse frequency and pulse width, the laser scanning rate and the shielding gas are the main factors influencing the components of coatings. TiCN coatings were decompounded and oxidized during the cladding process in the condition of no shielding gas of N2. X-ray diffraction results indicated that the composite coatings composed of TiCN, TiC, Ti2N, and TiO2 were produced using appropriate techniques. The results indicated that the best condition in terms of the surface microhardness is obtained when the scanning rate is 1.5mm/s, the pulse frequency is 15Hz, the pulse width is 3.0ms, and N2 is chosen as the shielding gas. The microhardness of the composite coatings is about 1331kg · mm^-2, which is about 4 times that of the substrate. The optical micrographs indicated that the cladding zone is made up of TiCN, TiO2 and some interdendritic Ti, but the diffusion zone mainly consists of the dendrites phase, and the cladded depth is about 80μm, which is more than 2 times that of the laser nitrided sample. There were no microcracks or air bubbles in the cladded sample, which was cladded using the above optimal techniques.     

硅压力传感器的应力隔离封装

<正> 当封装压力传感器时,由于传感器芯片和管壳材料之间热膨胀系数的差别,在封接部位引入应力。这一封装应力引起传感器芯片硅膜     

意大利圣·朱斯蒂纳坝实时洪水预报

介绍了用于意大利圣.朱斯蒂纳坝的实时洪水预报方法。根据10 a的小时库水位资料进行流量反演算,并重新构造了洪水系列。采用年最大流量与降雨深资料对简单的水文模型进行调整。考虑相应的洪水事件(11 a一遇洪峰流量),利用蒙特卡罗模拟法为洪峰流量预报制定了统计上可靠的方案。     

钨及其合金的研究与开发现状

<正> 现时的材料开发愈来愈多地受到剧烈竞争市场的冲击,长期的基础研究普遍地转向以应用为基础的短浅研究,与此同时,在过去几年里,工业也发生了很大变化,亦即由材料取向的工业向应用(用户)取向的工业转轨。     

奥斯卡·尼迈耶谈建筑

巴西著名建筑师,1988年普里茨策建筑奖得主奥斯卡·尼迈耶(Oscar Niemeyer)虽已83岁高龄,但他仍在故乡里约热内卢那间能眺望考帕卡巴那湾的办公室工作着。他还是独自设计,而后将其方案的实施工作委托给他的孙女。著名的圣康瑞多郊区别墅,自从他搬到城市公寓后一直空着,现被作为城市的一个景点,并将改建为一个展示其作品的博物馆。尼迈耶对建筑大师     

A comparable study of image approximations to the reaction field

The recently developed high-order accurate multiple image approximation to the reaction field for a charge inside a dielectric sphere [J. Comput. Phys. 223 (2007) 846-864] is compared favorably to other commonly employed reaction field schemes. These methods are of particular interest because they are useful in the study of biological macromolecules by the Monte Carlo and Molecular Dynamics methods.