Theory and experiment on the three-dimensional motion of a freely suspended spherical particle at the entrance to a pore at low Reynolds number

This paper examines the three dimensional approach of a neutrally buoyant sphere of any size to a circular hole in a plane wall at very low Reynolds number. The analysis differs from previous studies, largely applied to the multipore filter, in that the authors investigate the three dimensional hydrodynamic interaction of the sphere with the entrance geometry of the pore in the limit of zero inertia. The problem is first exactly formulated as the linear superposition of fundamental Stokes flows for rotation and translation of the sphere and flow past a stationary sphere. Approximate solutions are then obtained for the deviation of sphere trajectories from fluid stream lines and the results compared with laboratory model experiments in a low Reynolds number settling tank. The theory and experiment show that because of the hydrodynamic interaction sphere trajectories and fluid streamlines deviate significantly as the opening is approached, that all spheres eventually enter the pore regardless of their initial position, but that a non-uniform concentration profile develops with large increases in concentration near the walls of the orifice in the vicinity of the opening. The results provide a basic mechanism to explain the onset of Fahraeus phenomenon for red cells entering small blood vessels and glass tubes.     

赫司特赛拉尼斯公司及其聚甲醛产品celcon■

公司发展简史和共聚甲醛的标准品级以及特殊品级。     

浅谈导师制项目在毕业设计的积极作用

高校中的本科生导师制在本科生教育中起到积极作用,针对网络工程专业特点,创新地推行导师制项目制度,由学生在学习阶段直接参加导师的科研项目。在指导教师指导下设计项目方案、进行系统设计和系统编码、撰写科研报告,并探索导师制项目在毕业设计所起到的积极作用．为校内其他专业及校外推广这项制度打下良好的基础。     

聚丙烯工程化研究

采用纳米填充、交联和转晶的复合技术对聚丙烯进行了改性，优选了纳米碳酸钙为填料。当β成核剂用量为0．5％、助交联剂为3％时，复合材料的综合性能达到最好，接近普通工程塑料的各项力学性能。红外光谱分析和熔体质量流动速率的测定表明，复合材料体系产生了微交联；DSC分析发现，PP材料的聚集态结构中含有β球晶。     

嵌入式消毒柜门内衬板拉深模具设计

通过对嵌入式消毒柜门内衬板工艺分析，确定其模具加工方案，同时对试模过程中存在的问题作进一步的剖析。     

坯料外形对镁合金矩形盒拉深成形的影响

用商业有限元软件模拟了在同一套模具和成形条件下不同毛坯外形的镁合金矩形盒拉深成形过程．依据数值模拟结果，分析了不同坯料外形对镁合金矩形盒拉深成形的影响。结果表明：使用矩形圆角坯料比其他坯料的成形性能好。     

基于数值模拟的接水盘冲压成形工艺分析与设计

分析了冰箱接水盘的形状和结构特点 ,设计了零件的冲压成形工艺 ,运用板料成形有限元软件对其中的拉伸和翻边工艺进行数值模拟 ,得到成形过程中工件各部位的厚度分布和成形极限图 ,分析了在不同工艺条件下可能产生的缺陷及其原因 ,并确定其初始毛坯和中间毛坯的合理形状 ,有效地保证了成形工艺的可靠性     

简单断面孔型计算机绘图系统简介

介绍了简单断面孔型计算机绘图系统的编制方法、使用范围 ,计算机绘图的步骤及特点     

Special-shaped tube drawing forming and conformal optimization of die cavity

Aiming at the issues in quick processing and modeling design of drawing special-shaped tube die, by Conformal Mapping Theory and the numerical trigonometry method of interpolation between odd points and even points, the conformal mapping function is obtained. As the result, three-dimension drawing forming were converted into that of two-dimension problems, and the plastic stream function was analyzed, die cavity modeling and its optimized function were set up. Combining with modern processing technology, NC program and CAM of die cavity can be realized. Taking the drawing forming of hexagon tube with arc radii r and ellipse-shaped tube as instances, the drawing die cavity optimization of special-shaped tube was achieved, as well as, the changing principle of wall thickness was analyzed.