An analytic solution to the transient diffusion-reaction problem in particles dispersed in a slurry reactor

In this work, we present the solution of the equations that govern the reactant transport in a well mixed system that contains particles where diffusion and first-order reaction occur. The transport equations are coupled by an interfacial boundary condition that includes mass transfer resistance. The statement of the problem allows arbitrary time depending feed functions. The evaluation of the solution obtained by the Laplace method requires the solution of an eigenvalue problem. We discuss the evaluation of the solution, and typical results for three different feed functions: step, pulse and oscillatory functions are presented. The resulting equations are able to show the effect of internal and external mass transfer limitations on the particle and fluid concentrations and on kinetic experimental results.     

Effect of H2O adsorption on the electrical transport properties of double-walled carbon nanotubes

Water molecules adsorbed on a double-walled carbon nanotube (DWCNT) serve as charge trapping centers when present in low density and as electron donors when present in high density. There is a discontinuous change between the low- and high-density regions. H₂O molecules are apt to be adsorbed on the outer surface of DWCNTs, and in this case the electrical transport properties are extremely sensitive to environment, which suggests that DWCNTs are hole doped and act as an electric dipole with the inner tube.     

Miscibility and carbon dioxide transport properties of poly(3-hydroxybutyrate) (iPHB) and its blends with different copolymers of styrene and vinyl phenol

This work summarizes the miscibility and transport properties of different polymer blends obtained by mixing a bacterial, isotactic poly(3-hydroxybutyrate) (iPHB) with copolymers of styrene and vinyl phenol (Sty-co-VPh copolymers). Given that iPHB and pure commodity poly(styrene) (PS) form immiscible blends, PS has been modified by copolymerizing it with vinyl phenol (VPh) units, in an attempt to promote blend miscibility. VPh units have appropriate functional groups that interact with iPHB ester moieties. The potential miscibility was investigated by differential scanning calorimetry (DSC) measuring the glass transition temperatures of blends of different compositions. As an additional test, the interaction parameter between the two components, using the iPHB melting point depression caused by the second component, was also measured. Copolymers containing less than 90% styrene showed miscibility with iPHB.Given the remarkable barrier properties of iPHB to gases and vapours, the study has been completed by measuring transport properties of carbon dioxide through different iPHB/Sty-co-VPh copolymer blends, using gravimetric sorptions in a Cahn electrobalance. A clear difference was observed between the behaviour of rubbery blends and those that exhibit a glassy behaviour at the selected experimental temperature (303 K).     

Modelling of membrane nanofiltration—pore size distribution effects

The effects of log-normal pore size distributions on the rejection of uncharged solutes and NaCl at hypothetical nanofiltration membranes have been assessed theoretically. The importance of pore radius-dependent properties such as solvent viscosity and dielectric constant is increased by the introduction of a pore size distribution in calculations. However, the effect of porewise variation in viscosity is less apparent when considered at a defined applied pressure rather than at a defined flux, showing a further advantage of basing theoretical analysis of nanofiltration in terms of applied pressure.Truncated pore size distributions gave better agreement than full distributions with experimental rejection data for a Desal-DK nanofiltration membrane. Such truncation is in agreement with the findings of atomic force microscopy (AFM). Analysis of uncharged solute rejection data alone could not give useful information about membrane pore size distribution. Neither could such a distribution be obtained quantitatively directly from AFM images. However, use of the shape of the distribution obtained by AFM in conjunction with experimental rejection data for an uncharged solute allows calculation of corrected distributions. Importantly, incorporation of such a corrected pore size distribution in calculations of NaCl rejection gave better agreement with experimental data, compared to calculations assuming uniform pores, at high pressure, the region of industrial interest.     

“工作室”制的图形图像制作专业人才培养模式的思考

近些年来,伴随着素质教育在各个高校以及职业学校普及的大趋势。以及社会上的各个集团公司和部门对公司工作人员综合素质的需求的目益增加,如何培养除具备高素质的人才已经成为了摆在各个职业学校面前的大难题。截至目前为止。为了响应国家职业教育高速发展的大趋势也是为了提升自己学生的综合职业素养能力,各个高等职业学校纷纷推行了一种新型的人才培养模式——工作室培养人才的新型人才培养机制。“工作宣”教育制度的培育模式是在教育教学的过程之中大力提倡实践教育,不是以前的传统的只注重考试成绩的教育,通过这样的注重过程与培养学生们的动手能力的教学,让学生们可以极大地加强自己的专业技术能力。通过这种方式,各个职业学校也可以圆满的完成自己为国家培育优秀职业技能人才的重要任务。     

联合制碱母液精制研究(下)

Brief review of the evolutive course of preparation and refining of mother liquor in Hou's soda-manufacturing Process and the historical root of inferior quality of the product from Hou's Process to that of Ammonium Soda Process. By determination in production, the technical causes of carrying of "escaping crystal" in flooding liquid from the salting out crystallizer and necessity of replacing the existing mother liquor Ⅱ vat by mother liquor Ⅱ settling tank. Theoretical and engineering basis of refining of mother liquor in Hou's Process is emphasized. Main results from field test of purification and filtration at low temperature of mother liquor Ⅱ prepared from three kinds of salt as raw material are introduced. Principle opinions of application on production are put forward.     

Modeling and control of Wiener-type processes

We develop a simple relay feedback method to identify Wiener-type nonlinear processes. It separates the identification problem of the nonlinear static function from that of the linear dynamic subsystem to simplify the identification procedure significantly. Owing to the separation, the unmeasurable output of the linear dynamic subsystem can be obtained in a straightforward manner. Then, determining the model structure of the nonlinear static function becomes very simple and the estimates are robust to additive output noises. We can identify the whole activated region of the nonlinear static function as well as the ultimate information of the linear dynamic subsystem from only one relay feedback test. More information on the linear dynamic subsystem can be estimated by well-established linear system identification methods from additional tests. We use a nonlinear control strategy to compensate the nonlinear dynamics of the Wiener process so that the design parameters can be determined by usual tuning rules developed for linear processes and a high control performance can be achievable as in linear processes.     

Interbay物料自动搬运系统性能分析

Interbay物料自动搬运系统的运行效率对于晶圆制造系统影响较大,研究Interbay物料自动搬运系统的绩效具有较大的意义[1]。该文以带有捷径的单闭环背脊式布局的物料自动搬运系统为研究对象,通过问题描述,简化、假设将实际问题抽象为导引运输模型。然后,建立数学模型,采用Dijkstra算法确定工件搬运的最短路径。最后,利用Arena仿真软件建立含有导引运输设备的模型,采用控制变量法探究小车数量小车占用轨道的方式、调度规则等因素对于产出的影响,发现对于本文中的模型,其它条件相同时,搬运系统采用Release-at-end的控制方式,系统最大搬运量越大。     

The Chemistry of Water Treatment Processes Involving Ozone,Hydrogen Peroxide and Ultraviolet Radiation

Advanced oxidation processes are defined as those which involve the generation of hydroxyl radicals in sufficient quantity to affect water purification. The theoretical and (practical yield of OH from O₃ at high pH, 0₃/H₂0₂, O₃/UV and H₂O₂/UV systems is reviewed. New data is presented which illustrates the importance of direct photolysis in the O₃/UV process, the effect of the H₂0₂:0₃ ratio in the O₃/H₂O₂ process, and the impact of the low extinction coefficient of H₂O₂ in the H₂0₂/UV process.     

Transport processes during electrowashing of filter cakes

Applications of electric fields during washing of filter cakes increases the removal rate of ions from the cake mother liquor, and under appropriate conditions the field also increases the wash flow rate by electroosmosis. Experimental data that show the key effects of the fields on the rates of ion mass transfer are presented: with the downstream electrode acting as a cathode, cation removal rates are increased whilst the removal rate of the anions is decreased. The concentration profile of the cations with washing time shows an increase in concentration to a value above that of the mother liquor, before it decreases due to displacement by the fresh wash liquor. A model is formulated that describes the advection, dispersion, ion migration and electroosmosis transport processes in the cake. Numerical solution of the model gives cation concentration profiles at the exit of the cake that are in qualitative agreement with the experimental observations. Experimentally measured wash liquor flow rates tend to be lower than what traditional colloid science principles predict by a factor of 5-10: reasons for this difference, supported by experimental work from other researchers, are discussed.