FINITE GROUPS WHOSE AUTOMORPHISM GROUP HAS ORDER CUBEFREE

ＦＩＮＩＴＥＧＲＯＵＰＳＷＨＯＳＥＡＵＴＯＭＯＲＰＨＩＳＭＧＲＯＵＰＨＡＳＯＲＤＥＲＣＵＢＥＦＲＥＥＬＩＳＨＩＲＯＮＧＡｂｓｔｒａｃｔＬｅｔＧｄｅｎｏｔｅａｆｉｎｉｔｅｇｒｏｕｐ．Ｉｔｉｓｓｈｏｗｎｔｈａｔｉｆ｜Ａｕｔ（Ｇ）｜ｉｓｃｕｂｅｆｒｅ...     

Fouling Mitigation in a Heat Exchanger: High Cycles of Concentration for a Cooling-Tower Application

The purpose of the present study is to investigate the effect of a physical water treatment (PWT) technology on fouling mitigation in a simulated cooling tower operating at high cycles of concentration. Hard water was produced by evaporating pure water in a circulating open cooling tower, where dissolved calcium carbonate ions became concentrated with time. Heat transfer tests were conducted in a rectangular channel by varying the cycle of concentration (COC) from 5 to 10, and fouling resistances were measured over 270 hrs for each case with and without the PWT treatment. Another test was conducted with no blowdown case with and without the PWT treatment. The fouling resistance at 5 cycles with the PWT treatment was about 70% less than that in the case without the PWT treatment at the end of 270-hr tests. Even at 10 cycles, the PWT treatment reduced the fouling resistance by 60% from the value for the no treatment case. Thus, one can conclude that the PWT technology can help circulating cooling-tower water at relatively high COC for significant freshwater conservation, while keeping fouling resistances below industry standards.     

颗粒气体团簇行为实验研究

颗粒体系由于非弹性碰撞和摩擦等内秉的能量耗散特性,由宏观粒子形成的颗粒气体体系经常会有局部凝聚现象,这是颗粒气体体系与分子气体体系的最大区别之一.理解和预测这一现象的发生将有助于人们对远离平衡态体系的复杂现象,如有序结构、斑图和团簇形成的认知.这种局部凝聚现象可以类比于分子气体中亚稳分解形成的液滴,将气液相分离用于解释和寻求局部凝聚现象的此模型得到了分子动力学模拟的校验.但是实验的校验却由于宏观粒子运动受重力作用的影响难以在实验室中实现.作为实践十号卫星的前期实验,本文利用国家微重力实验室落塔装置,以水平激振装有不同尺寸和数目的颗粒样品,在短时微重力条件下,成功观察到颗粒气体团簇的形成;并将实验结果与颗粒气体类范德瓦耳斯气体分子相分离模型对比,由形成团簇样品的颗粒数密度条件,来实验确定了所选颗粒的恢复系数,得到直径为0.5 mm的钛珠颗粒的恢复系数在0.6—0.8之间,直径为1 mm的钛珠颗粒的恢复系数约为0.8,直径为2.5 mm的钛珠颗粒的恢复系数应大于0.8.     

Projective metrics and mixing properties on towers

We study the decay of correlations for towers. Using Birkhoff's projective metrics, we obtain a rate of mixing of the form:

where goes to zero in a way related to the asymptotic mass of upper floors, is some Lipschitz norm and is some norm. The fact that the dependence on is given by an norm is useful to study asymptotic laws of successive entrance times.

     

环保节水型冷却塔的研究

综合湿式冷却塔有热交换效率高且造价低而空气冷却器无水蒸发等特点,提出了环保节水型冷却塔.对该新型塔进行了理论分析,对塔内换热、气动力性能等进行了数值计算,对塔内空气换热器和填料层间的冷却负荷以及与风机性能等进行了耦合匹配,结合北方气候条件的计算分析表明新型塔确有良好的节水和环保效果.     

富氧燃烧烟气喷淋脱水过程数值模拟

富氧燃烧系统中,脱硫后的高湿烟气需要经过脱水处理才能作为循环烟气利用,喷淋塔是一种常用的脱水设备。本文用CFD(Computational Fluid Dynamics)方法对喷淋塔的烟气脱水过程进行了三维建模模拟,得到了喷淋塔内的温湿度分布并用实验结果进行了验证。通过该模型分析了喷嘴的操作参数和运行特性对液滴平均运动时间和脱水效果的具体影响,讨论了数值模拟中出口烟气"过饱和"现象的成因,研究了不凝气组分对脱水过程的影响,为富氧燃烧脱水系统的设计提供了基础数据和理论方法。     

有压腔式吸热器复杂耦合换热机理数值研究

本文建立了有压腔式太阳能吸热器(PVSR)轴对称计算模型,运用蒙特卡罗光线追踪法(MCRT)模拟了二次聚光器(SC)与有压腔式吸热器(PVR)系统内聚光过程与光热转换过程,进而与计算流体与传热的有限容积方法(FVM)结合研究了高温高压吸热器内复杂耦合传热过程.在此基础上,进一步对比考察了考虑不同换热过程的换热机理,分析...     

Atomic Tunneling Effect in Two-Component Bose-Einstein Condensates with a Coupling Drive

In this paper, we have studied the atomic population difference and the atomic tunneling current of twocomponent Bose-Einstein condensates with a coupling drive. It is found that when the two-component Bose-Einstein condensates are initially in the coherent states, the atomic population difference may exhibit the step structure, in which the numbers of the step increase with the decrease of the Rabi frequency and with the increment of the initial phase difference. The atomic population difference may exhibit collapses, and revivals, in which their periods are affected dramatically by the Rabi frequency and the initial phase difference. The atomic tunneling current may exhibit damping oscillation behaviors, and exist the step structure for the time range of 10-10 ～ 10-9 second.     

On Convergence Approach Spaces

The extension of two axioms due to Cook and Fischer to the category CAP of convergence approach spaces leads to the study of non-Archimedean approach spaces as well as two versions of regularity appropriate to CAP and related categories.     

太阳帆塔轨道和姿态耦合动力学建模及辛求解

在建立太阳帆塔太阳能电站简化模型的基础上,将系统的动力学方程从Lagrange体系导入到了Hamilton体系,给出了带约束的Hamilton正则方程;进而采用祖冲之类算法和辛Runge-Kutta方法分析了太阳帆塔轨道和姿态耦合系统的动力学特性,并讨论了算法的保能量、保约束特性;最后,数值模拟了系统的动力学特性,说明了所提方法的有效性.