胶体中的分形

介绍了胶体与界面化学的基础理论和发展以及溶胶-凝胶方法在各个领域中的应用。对分形理论在胶体科学研究中的应用以及各种求算分形维数的方法进行了综述和总结，指出了现有基本模型和理论的不足和片面性，提出将分形理论引入溶胶-凝胶体系，深入胶体基础理论层面的研究。同时，对实验的局限性和胶体生长的非线性进行了对照，引入了计算机模拟这个有效的手段，并对分形与计算机紧密结合的趋势进行了展望。     

单颗粒化学反应工程的一种新研究方法——分形学方法

分形学思想应用于单颗粒化学反应工程问题研究中 ,是一种研究单颗粒化学反应工程问题的新尝试 ;在计算机辅助下 ,采用正交配点法分别对固体多孔单颗粒内进行的等温反应、等温可逆反应、等温平行反应、等温串连反应进行了研究 ,研究结果证明分形学思想应用于单颗粒化学反应工程中问题的研究是成功的     

分形理论及其在无机材料研究中的应用

分形学是一门处于迅速发展的学科,是研究复杂性科学理论的重要组成部分,其影响范围和应用领域也在日益扩大.在材料科学领域,分形学是一种研究材料的数学工具.笔者介绍了分形学的基本理论,分形维数的测定方法以及其在材料的烧结、氧化,薄膜的生长,材料的磨损、断裂,陶瓷粉体和玻搪材料中的应用,并展望了分形学的发展前景.     

蚓孔的分形模型

蚓孔具有分形性[1]，本文通过分形理论中的L-系统生成法和DLA法对蚓孔进行计算机模拟[2]，其分形图形和蚓孔的形态极其相似，这也暗示了可能反映出蚓孔生长的一些因素。并对蚓孔的分形模型建立了数学模型并求解[3]，从而得出基质酸化中蚓孔的穿刺距离[4]。     

分形理论在化学中的应用

分形理论是现代非线性科学中的一个重要的分支,是科学研究中一种重要的数学工具和手段,做为一门新兴交叉学科,它在自然科学和社会科学都有重要应用。本文分别从电沉积、催化、生物大分子、材料科学和金属腐蚀等方面阐述了分形理论在各学科的应用及最新研究进展。     

分形理论及在高分子科学中的应用和发展

介绍了分形理论的主要内容，包括分形定义、特性和测定分形维数的方法，概括和评述了近年来分形理论在高分子链结构、结晶过程、溶液中、高分子材料断裂、磨损以及其他方面的研究和应用，并展望了分形理论今后的发展趋势。     

MgO－B_2O_3－SiO_2系晶化分形的计算机模拟

采用两段热处理技术，利用Ｘ射线衍射分析、扫描电镜观察等方法研究广２ＭｇＯ－Ｂ＿２Ｏ＿３－ＳｉＯ＿２系的晶化过程，晶化析出相２ＭｇＯ·Ｂ＿２Ｏ＿３的微观形貌具有分形特征，采用密度－密度相关函数法计算其分形维数为１．６３。为揭示２ＭｇＯ·Ｂ＿２Ｏ＿３生长机制，采用Ｍｏｎｔｅ－Ｃａｒｌｏ方法及改进的ＤＬＡ模型对分形生长过程进入计算机模拟。模拟结果与实际分形结构、分形维数相符，表明２ＭｇＯ·Ｂ＿２Ｏ＿３生长是扩散控制凝聚过程。可以预见，分形理论与计算机模拟相结合，将会在探讨未知机理方面发挥重要作用。     

分形图案及其在陶瓷中的应用

叙述了使用LS文法构造分形图案的算法原理，并对这种分形算法进行了适当改进，可以得到相应的分形动画和图案，最后将所得到的分形动画与图案应用于陶瓷图案设计中。     

闭孔泡沫陶瓷气孔微结构的分形表征及其模拟

通过观察发现,闭孔泡沫陶瓷气孔几何结构不是一个整形结构,而是具有分形特征的分形结构。采用分形几何对其气孔结构进行描述,首次获得了闭孔泡沫陶瓷分维表达式D=lnN/lnK。讨论了分维D的大小与闭孔泡沫陶瓷气孔微结构之间关系,并用计算机模拟出闭孔泡沫陶瓷的分形结构。     

分形艺术在陶瓷工艺品上的应用

对分形艺术进行了讨论，展示了几种经典的分形图案，并通过将这些图案应用到碗、花瓶、花壶三种传统的陶瓷工艺品上的实例，揭示了分形几何和分形艺术在陶瓷界应用的巨大潜力。     

分形学在稳态热传导中的应用

本论文给出了一种分形学方法研究稳态热传导问题的一般方法。     

Evolution of Topology during Simulated Sintering of Powder Compacts

Topological features were calculated for three-dimensional microstructures simulated using a computer model. A method in which the material is divided into small volume elements (SVE method) was developed to measure topological features such as numbers of coordinating faces, edges, and corners on the computer-generated microstructures. New relationships between different types of topological features of special interest in ceramics were derived based on the computer simulation statistics. These relationships enabled us to calculate the topological properties of a two-phase system in which one phase has no internal boundaries, such as the pore, liquid, or glass phases in polyerystalline ceramics. Computer simulations allowed averaging those features statistically from large sample sizes, which can be difficult to do in practice. Dependence of topological features, such as the number of coordinating pores around a grain, on particle size distribution and sintered density of the system was studied. Results show that the number of coordinating faces is proportional to the square of particle size, and the number of edges per face is smaller for a wider particle size distribution. Equations are derived to describe the dependence of the number of coordinating faces and number of edges per face on grain size. The simulation shows that closed pores form at a lower sintered density for a wider particle size distribution.     

GAD室温自交联乳液的粒径及其分布

合成得到了含环氧基、羧基和胺基的室温自交联乳液,研究了聚合工艺和乳胶粒结构及组成对乳液粒径及其粒径分布的影响。结果表明：聚合温度对乳液粒径及其分布的影响较小,加大乳化剂用量和乳化单体滴加速率使乳液粒径减小,粒径分布变窄;壳层甲基丙烯酸二甲氨基乙酯用量增加,致仗乳液粒径增大和粒径分布变宽;在合适的中间层分率下获得粒径较小和粒径分布较均匀的乳液;中间层引入（甲基）丙烯酸可减小乳胶粒径,并使粒径分布更均匀。     

Investigating the effect of shape on particle segregation using a Monte Carlo simulation

A Monte Carlo simulation has been used to investigate the segregation potential of a range of particulate systems under conditions in which the particles undergo high amplitude low frequency shaking. These systems involve a wide range of binary powder mixtures in which complex particle shapes have been investigated, including plates and rods which represent the real world materials encountered in pharmaceutical systems such as those which include crystalline components. Previous simulations on the segregation propensity of systems with different shapes were limited to spheres and spherocylinders, with relatively low vibrational amplitude drops. A commercial computer application for particle packing—called MacroPac—has been successfully employed here, as it has been able to model systems that are more complex where the shape variation is much wider. These simulations apply to the case of macroscopic particles, in the absence of air resistance and inter-particle forces. For non-spherical shapes, an ‘effective size’ which relates to the radius of gyration of the particles is determined. Our studies indicate that with high amplitude low frequency shaking, in a mixture of particles with different shapes but with equal volumes, the particles with the larger ‘effective size’, which tend to have a lower packing fraction, segregate to the top.     

A new computer program for correcting particle size distribution data obtained from non-equidistant class intervals

A generalized particle size distribution algorithm has been developed to compensate for two intrinsic shortfalls of electronic sizing instruments. The problem of lower detection limit is handled by first determining if the form of the distribution fits a normal or log-normal model. Then, using the Cohen method for estimating the parameters of a truncated distribution, the missing data are calculated and the usual distribution statistics are computed. To compensate for uneven cell intervals in histogram or frequency polygon representations of size distribution, the cells are treated from an area under the curve consideration rather than height. This gives the true shape, although the lack of resolution in the wider cells is still evident. A FORTRAN computer program is utilized to implement these distribution computations.     

钛液水解工艺对偏钛酸性能的影响

采用外加晶种常压水解法制备偏钛酸,使用激光粒度仪分析偏钛酸的粒度分布,通过沉降高度和洗涤时间判断偏钛酸的过滤性能。考察了晶种加入量、变灰点时间、钛液浓度、二次沸腾保温时间对偏钛酸粒度分布及其过滤性能的影响。结果表明：晶种加入量、钛液浓度和二次沸腾保温时间对偏钛酸性能有显著影响,晶种加入量越大、钛液浓度越低、水解速度就越快,变灰时间越短,得到的偏钛酸的粒度分布也越宽,过滤性能越差。延长二次沸腾保温时间可以使偏钛酸粒度分布更窄,粒子更均匀。     

Particle segregation of binary mixture in a moving bed by penetration model

Segregation patterns of particles of different sizes in a moving bed were theoretically analyzed by a penetration model. Flow experiments with a two-dimensional hopper verified the derived equations in combination with those in the filling of the hopper. The segregating component was revealed to be more unevenly distributed inside the moving bed of wider cone angle at lower feed rate and lower initial mixing ratio as a result of prevalent segregation during heaping on the top of the moving bed. The steeper velocity profile inside the moving bed resulted in a bit more uneven distribution of the segregating component in the angular direction. In general, the segregation profile gradually became smooth during descent of the particle mixture inside the hopper due to particle penetration in the gravitational direction.     

Fluidization of spherical versus elongated particles: Experimental investigation using magnetic particle tracking

In biomass processing fluidized beds are used to process granular materials where particles typically possess elongated shapes. However, for simplicity, in computer simulations particles are often considered spherical, even though elongated particles experience more complex particle– particle interactions as well as different hydrodynamic forces. The exact effect of these more complex interactions in dense fluidized suspensions is still not well understood. In this study we use the magnetic particle tracking technique to compare the fluidization behavior of spherical particles to that of elongated particles. We found a considerable difference between fluidization behavior of spherical versus elongated particles in the time-averaged particle velocity field as well as in the time-averaged particle rotational velocity profile. Moreover, we studied the effect of fluid velocity and the particle's aspect ratio on the particle's preferred orientation in different parts of the bed, which provides new insight in the fluidization behavior of elongated particles.     

Quantitative computer reconstruction of particulate materials from microtomography images

Traditional particle-characterization techniques require particles to be dispersed from their original form, which destroys important morphologic information in materials such as aggregates or porous materials. X-ray computed microtomography provides a powerful tool for non-destructive analysis. However, robust techniques for comprehensive material characterization of these images have not been developed.In this paper we present a new algorithm for the computer analysis of particulate materials from high-resolution tomography images. The key aspect of the algorithm is the assignment of every solid-phase voxel in the image to its associated particle in a physically representative manner, which is in essence a particle-scale computer reconstruction of the material. Once this digital reconstruction is obtained, a vast amount of morphologic information can be extracted, including parameters obtained by traditional particle-analysis techniques (e.g., particle-size distribution and porosity) as well as parameters not usually available (e.g., spatial correlations in particle size, particle aspect ratios, surface areas, and orientations, particle contacts, particle coordination numbers, and more). Additionally, the computer reconstruction allows for complex manipulations such as the comparison of a specific parameter for two different particle-size classes within the material. The paper includes validation of the algorithm using computer-generated packings, as well as an example using microtomography data from a real material.     

Flow of sphero-disc particles in rectangular hoppers—a DEM and experimental comparison in 3D

Flows of “sphero-disc” granular particles in a rectangular hopper are studied both experimentally using high-speed video recording and mathematically using the discrete element method (DEM). The flow behaviour of particles and their arching and discharging in the hopper are analysed and compared with the DEM results for three hopper openings. In general, good agreement is shown on particle static packing, the flow behaviour and hopper discharging rates and the arching effect when flow ceases due to an inadequate hopper outlet opening. Spherical particles with a similar volume to the disc-like particles are also tested and compared and a clear effect of particle shape on flow rates is shown. Although some minor discrepancies are shown, these are likely to be caused by the practical difficulties in matching the exact particle parameters between the simulations and the experiments. The DEM is shown to be a powerful tool to analyse the interactions between irregularly shaped particles and demonstrates a great potential in analysing detailed particle packing structure and flow patterns, which may lead to the elaboration of a novel method for hopper design. Further work will focus on developing DEM to model a wider range of particle shapes and hopper geometries, use of DEM for flow and structure analysis, and the development of more sophisticated measuring tools such as tomography to validate the DEM model.