MATHEMATICAL MODELING OF THROUGH-HOLE-PLATING IN ELECTROCHEMICAL MICROFABRICATION II. AXISYMMETRIC TWO-DIMENSIONAL CONVECTIVE MASS TRANSFER

Axisymmetrical, two dimensional mass transfer in a tube and a through-hole was studied. The elliptic convective-diffusion equation was solved numerically by taking into account both the axial and radial diffusion in the entrance region of an infinite tube. The whole mass-transfer region in a tube of finite length was also studied by dividing the domain into several regions according to different mass-transfer mechanisms. A similar analysis is then conducted for a through-hole geometry by assuming a modified Hagen-Poiseuille fluid pattern. Results show that mass-transfer rate in a through-hole is larger than that in a tube by approximately 10%. This is due primarily to faster fluid flow within the concentration boundary layer in a through-hole.     

拟稳态法测定气相扩散系数

根据拟稳态一维扩散原理,建立了气相扩散系数的测定装置。在该装置上,测定了8个体系的气相扩散系数,其中CH_2Cl_2-空气,CH_2Cl_2-H_2,CH_3CH_2Br-空气,CH_3Cl_2Br-H_2,CHCl_3-H_2等5个体系的气相扩散系数实验值,迄今尚未见文献报道。实验结果表明,本测试装置稳定性好,实验误差小,实验装置体积小,测试过程较为简便。     

纳米SiO2粉体的制备与研究

纳米SiO2粉体的制备是以硅酸钠和盐酸为原料，添加适宜的稳定剂(非离子表面活性剂)和分散剂，在适宜的pH值和温度下，采用化学沉淀法合成。研究表明，要得到性能优良纳米的SiO2粉体，最佳工艺条件为：温度20～40℃，pH=6，反应液质量浓度P1=20g／L，P2=1．20g／L，反应时间15min。结果表明：制备的纳米SiO2粒径30～50nm，比表面积大，分散性好，质量优良，可达到产业化的生产。     

Some novel polymer-supported optically active phase transfer catalysts: 2. Use in displacement,reduction, epoxidation and addition reactions

The performance of 27 novel polymer-supported chiral phase transfer catalysts in a range of phase separated reactions has been studied. The later include a number of displacement reactions, sodium borohydride reductions of prochiral ketones, the epoxidation of chalcone, the addition of nitromethane to chalcone and the addition of thiophenol to cyclohexenone. Some of the reactions were performed under liquid/liquid conditions and others using solid/liquid. No systematic difference emerged between these. In general many of the catalysts provided fast reactions and good chemical yields of products. However, in no case was any significant enantiomeric excess achieved. The latter observation is discussed in the light of the reported behaviour of analogous non-supported catalytic systems, and suggestions proposed to explain these differences.     

关于中压电缆网双环接线方式供电能力的分析

结合北京地区现阶段对相关技术的规定,以实际供用电方案为例,对中压电缆网双环接线方式的供电能力进行深入讨论。通过设计环网单元划分,发现某些条件下双环网供电能力可以得到进一步提升。     

光学镜头调制传递函数的测试

为了定量、客观、全面地评价光学镜头的像质,介绍了光学镜头调制传递函数的测试。先简要叙述了测试的原理,并给出计算公式;然后介绍了测试步骤,其中包括固定、穿轴、测试中心视场和测试轴外视场;最后介绍了测试时的注意事项,包括对测试工装的要求、对测试平面的要求和正、负轴外视场测试值相差较大时的处理办法。     

电厂电气运行中常见故障分析及其应对措施探讨

为了保证电厂的生产效率,必须要分析电气的运行特征,确定电气故障发生的原因,综合考虑多方面因素,选择切实可行的措施解决问题。简要分析了电厂电气运行常见故障发生原因,并提出了相应的解决措施。     

A three-dimensional model for suspension-to-membrane-wall heat transfer in circulating fluidized beds

A three-dimensional model is proposed for both furnace-side and wall-side heat transfer in circulating fluidized beds with membrane walls. Following previous publications (Int. J. Heat Mass Transfer (2003a, b)), a core-annulus flow structure is employed in the model, with consideration of the membrane wall influence on bed hydrodynamics. The model couples radiation, conduction and convection on the furnace side to conduction and convection on the wall side. Radiation in the wall layer is simulated by the moment method. A finite-element method is employed to solve the set of non-linear, partial differential equations. The solution is demonstrated for a typical example. The model gives predictions of suspension-to-wall heat transfer which show satisfactory agreement with published experimental data.     

Prediction of liquid film mass transfer coefficients in packed columns using liquid holdup

A unique characteristic linear dimension (d), defined as the cube root of the specific liquid holdup (h_sp) in the packed column, was used to correlate successfully the liquid film mass transfer coefficient k_La for gas absorption-desorption for sparingly soluble gases in liquids below loading. To produce this simple, dimensionless correlation, k_La data reported in literature were used, covering a wide range of physical properties of liquids, packings and operating conditions. This new approach showed operating holdup as an important factor in gas liquid mass transfer.     

氯化聚乙烯接枝氯乙烯聚合速率及传热

本文用气相色谱技术研究氯化聚乙烯(CPE)-接枝(g)-氯乙烯(VC)聚合动力学,对不同引发剂体系分析热负荷分布,并对7 m~3聚合釜传热面进行校核。