Simulation of natural convection under high magnetic field by means of the thermal lattice Boltzmann method

The thermal lattice Boltzmann method (TLBM), which was proposed by J. G. M. Eggels and J. A. Somers previously, has been improved in this paper. The improved method has introduced a new equilibrium solution for the temperature distribution function on the assumption that flow is incompressible, and it can correct the effect of compressibility on the macroscopic temperature computed. Compared to the previous method, where the half-way bounce back boundary condition was used for non-slip velocity and temperature, a non-equilibrium extrapolation scheme has been adopted for both velocity and temperature boundary conditions in this paper. Its second-order accuracy coincides with the ensemble accuracy of lattice Boltzmann method. In order to validate the improved thermal scheme, the natural convection of air in a square cavity is simulated by using this method. The results obtained in the simulation agree very well with the data of other numerical methods and benchmark data. It is indicated that the improved TLBM is also successful for the simulations of non-isothermal flows. Moreover, this thermal scheme can be applied to simulate the natural convection in a non-uniform high magnetic field. The simulation has been completed in a square cavity filled with the aqueous solutions of KCl (11wt%), which is considered as a diamagnetic fluid with electrically low-conducting, with Grashof number Gr=4.64× 10^4 and Prandtl number Pr=7.0. And three cases, with different cavity locations in the magnetic field, have been studied. In the presence of a high magnetic field, the natural convection is quenched by the body forces exerted on the electrically low-conducting fluids, such as the magnetization force and the Lorentz force. From the results obtained, it can be seen that the quenching efficiencies decrease with the variation of location from left, symmetrical line, to the right. These phenomena originate from the different distributions of the magnetic field strengths in the zones of the symmetrical central line of the magnetic fields. The results are also compared with those without a magnetic field. Finally, we can conclude that the improved TLBM will enable effective simulation of the natural convection under a high magnetic field.     

随机容错设施选址问题的原始-对偶近似算法

研究两阶段随机容错设施选址问题,其中需要服务的顾客在第二阶段出现（在第一阶段不知道）．两个阶段中每个设施的开设费用可以不同,设施的开设依赖于阶段和需要服务的顾客集合（称为场景）．并且在出现的场景里的每个顾客都有相同的连接需求,即每个顾客需要由r个不同的设施服务．给定所有可能的场景及相应的概率,目标是在两个阶段分别选取开设的设施集合,将出现场景的顾客连接到r个不同的开设设施上,使得包括设施费用和连接费用的总平均费用最小．根据问题的特定结构,给出了原始。对偶（组合）3-近似算法．     

多层砌体1/4比例模型墙体顶部裂缝试验研究

为了研究多层砌体结构房屋顶端裂缝问题,根据简单相似性原理构建了一1:4比例、每层均布有构造柱和圈梁的H型六层混凝土小型空心砌块砌体结构墙体模型.通过对墙体模型进行竖向加载的拟静力试验,模拟了纵横墙荷载差,深入研究了在竖向荷载差作用下砌体房屋顶端裂缝的产生行为和发展规律.研究结果表明:随着承重墙上竖向荷载的增加,承重墙与...     

区域行政法治机制建立之必要性与基本思路——以成都经济区为例

区域经济一体化的核心是区域行政法治一体化。建立行政法治机制,是经济区的整体性、协作性、系统性和互补性的客观要求。以成都经济区为例,只有建立起成都经济区的行政协调组织机制、行政立法机制、行政执法机制、行政规划机制等,才能保障成都经济区经济一体化的健康发展。     

带一类非精确搜索的Broyden非凸族的全局收敛性

对于一致凸函数，采用一种比较广泛的线搜索技术，证明了Ｂｒｏｙｄｅｎ非凸族的全局收敛性。     

周予同先生传略

周予同(1898-1981)，原名周毓懋，学名周蓬，浙江温州瑞安我。父亲是清末禀生，家境并不宽裕。少年时期曾就读于晚清朴学大师孙贻让所办的蒙学堂．小学毕业后考入瑞安中学，在史学家陈介石韵一位门人教育下，养成对文史的爱好。1916年以第一名成绩考入北京     

大分子引发剂的合成及其在嵌段共聚中的应用

一、前言大分子引发剂(macroinitiator)是指在分子链上带有可分解成自由基的偶氮、过氧基的高分子化合物。早在五十年代,Shah就报道过这种高分子化合物的合成,他用邻苯二甲酰氯与过氧化钠反应制成聚邻苯二甲酸过氧化     

异构化聚合

评述了阳离子型聚合中电子重排、基团迁移异构化聚合反应和机理。同时,对羰甲基内酰胺、羰基内酰胺和它们衍生特的聚合,各种烯烃在齐格勒-纳塔催化剂作用下发生的单体异构化聚合及共聚合,以及烯烃的歧化聚合进行了介绍。     

无约束优化DFP算法的全局收敛性

讨论了无约束优化问题的ＤＦＰ算法的全局收敛性。在适当的条件下，证明了对一致凸目标函数，在非精确线搜索下ＤＦＰ算法具有全局收敛性。