A numerical investigation into the solids phase chromatography using a combined continuous and discrete approach

Solids phase chromatography for particle classification is based on different retention times of particles with different properties when they are elutriated through a confined geometry. This work aims at a fundamental understanding of such a technology by using the combined continuous and discrete method. A packed bed is employed as the model confined geometry. The numerical method is compared first with experimental observations, followed by a parametric analysis of the effects on the flow hydrodynamics and solids behaviour of various parameters including the number of injected particles, the superficial gas velocity, the contact stiffness and the diameter ratio of the packed column to the packed particles. The results show that the modelling captures some important features of the flow of an injected pulse of fine particles in a packed bed. An increase in the number of injected particles or the superficial gas velocity reduces the retention time, whereas the contact stiffness does not show much effect over the range of 5 × 10^2 to 5× 10^4 N/m. It is also found that the effect on the retention time of the diameter ratio of the packed column to the packed particles seems complex showing a non-monotonous dependence.     

多相高分子体系中的粘弹相分离行为

相分离广泛存在于各种凝聚态物质中.根据局部浓度的变化形式,可将相分离分为固体模型(model B)和流体模型(model H),这两种模型适用于动力学对称的体系.近年来,Tanaka发现在一些动力学不对称的多组分高分子体系里存在一种新的相分离模式,其相分离过程分为动力学过程可用一个普适的粘弹模型来进行描述.动力学不对称可由体系中两组分间大的尺寸差异或玻璃化温度差异引起.本文介绍了多相高分子体系中产生粘弹相分离的原理及其基本特征,并讨论了模量、粘度、填料等因素对粘弹相分离动力学过程及多相体系微观结构的影响.     

^1H自旋扩散方法研究离子化聚氨酯的相态结构

本文用改进的Goldman-Shen脉冲序列研究了聚丁二烯加MDI离子化聚氨酯体系中磁化矢量的自旋扩散过程,通过一些合理的简化,求解了扩散方程,得到了一种可定量的求出多相高聚物微区尺寸的简便方法.     

纤维悬浮流场动力学研究综述

阐述了纤维悬浮流研究的学术价值及其在实际中的应用，回顾了近10年来该领域的主要研究结果，提出了尚未解决而又非常重要的几个问题，指出了该领域的发展前景。     

Chaos,transport and mesh convergence for fluid mixing

Chaotic mixing of distinct fluids produces a convoluted structure to the interface separating these fluids. For miscible fluids （as considered here）, this interface is defined as a 50% mass concentration isosurface. For shock wave induced （Richtmyer-Meshkov） instabilities, we find the interface to be increasingly complex as the computational mesh is refined. This interfacial chaos is cut off by viscosity, or by the computational mesh if the Kolmogorov scale is small relative to the mesh. In a regime of converged interface statistics, we then examine mixing, i.e. concentration statistics, regularized by mass diffusion. For Schmidt numbers significantly larger than unity, typical of a liquid or dense plasma, additional mesh refinement is normally needed to overcome numerical mass diffusion and to achieve a converged solution of the mixing problem. However, with the benefit of front tracking and with an algorithm that allows limited interface diffusion, we can assure convergence uniformly in the Schmidt number. We show that different solutions result from variation of the Schmidt number. We propose subgrid viscosity and mass diffusion parameterizations which might allow converged solutions at realistic grid levels.     

一类对称正交多带小波的构造

收稿考滤了一类多带正交对称小波滤波器对应多相矩阵分解结构,系统地构造了一类具有自由参数多带小波滤波器簇,以4带小波为例得到了用参数角表示的一类正交对称滤波器序列.     

3D Multiphase Piecewise Constant Level Set Method Based on Graph Cut Minimization

Segmentation of three-dimensional (3D) complicated structures is of great importance for many real applications. In this work we combine graph cut minimization method with a variant of the level set idea for 3D segmentation based on the Mumford-Shah model. Compared with the traditional approach for solving the Euler-Lagrange equation we do not need to solve any partial differential equations. Instead, the minimum cut on a special designed graph need to be computed. The method is tested on data with complicated structures. It is rather stable with respect to initial value and the algorithm is nearly parameter free. Experiments show that it can solve large problems much faster than traditional approaches.     

铑(Ⅱ)和锆(Ⅳ)共同催化的重氮乙酸酯,苄醇和醛的多组分反应

重氮乙酸酯和苄醇在铑(Ⅱ)催化下形成的氧叶立德中间体被锆(Ⅳ)活化的醛捕捉,以中等收率生成α,β-双羟基酸衍生物.     

铁催化芳烃与苄位碳氢键的脱氢交叉偶联反应

碳氢键的官能团化是当今有机化学最重要的研究领域之一, 发展环境友好的催化体系来实现碳氢键选择性地官能团化是合成化学家长期追求的目标(Chem. Rev. 1997, 97, 2879和Nature 2008, 451, 417). 以贵金属钯、钌、铱等作为催化剂的碳氢键的官能团化已有很多报道, 但高昂的价格和相对较高的毒性限制了这些反应的工业化. 相对而言, 使用廉价、无毒的过渡金属铁作为催化剂的碳氢键的官能团反应报道较少. 北京大学化学与分子工程学院施章杰发展了利用便宜、无毒的铁盐作为催化剂, 在温和条件下同时实现不同分子中sp2和sp3两种C—H活化, 首次实现了苄位sp3 C—H的直接“交叉脱氢芳基化”的催化过程. 此工作不仅提供了一条简单、高效的途径构建三芳基甲烷类化合物的方法, 成为绿色化学的一个重要的例子, 同时为实现不同种类的C—H活化提供了新思路.     

熔融X射线荧光光谱法测定高炉返粉组份

建立了X射线荧光光谱法测定高炉返粉中化学成分的方法,采用高温熔融法将试样制成玻璃状体,消除了基体干扰;通过对熔样条件、干扰元素、仪器参数、工作曲线拟合方式等方面进行实验研究,确定了最佳分析条件,实现了高炉返粉中主要成分SiO2等8种成分的同时测定,方法具有准确度高、同时测定多元素、分析速度快等特点。