IMPROVEMENT OF FLUIDIZABILITY OF FINE POWDERS ——A COMPUTER STUDY

Simulations of the gas fluidization of a cohesive powder were performed using the Stokesian Dynamics method and an agglomeration-deagglomeration model to investigate methods of improving the fluidizability of fine powders. Three techniques (a) high gas velocity (b) vibration-assisted fluidization and (c) tapered fluidizer were used in the simulations which provided detailed information on the bed microscopy such as the motion of 1 O0 particles in a fluidizing vessel along with the formation and destruction of cohesive bonds dudng collisions. While all three techniques were found to effectively improve the fluidizability of a strongly cohesive powder, we suggest a combination of high velocity fluidization assisted by extemal vibration of the fluidized bed to minimize entrainment of particles.     

岩土介质非稳态热固结耦合问题的热源函数法

考虑耦合效应的饱和土体热固结问题控制方程,利用Fourier变换、Laplace变换给出其在变换域上的解,将初始温度场分布视为虚拟的热源或者将热源等价为特定的初始温度分布,利用热源函数法给出瞬时线热源非稳态温度场、应力场和位移场的解析求解方法,通过在时间域和空间域上进行积分,给出有初始温度场分布以及有分布内热源存在且热源强度随时间变化条件下的热固结问题计算方法。对一无限大物体内存在有平面矩形域热源情况下周围介质的温度、孔隙水压力以及位移等的变化特征进行分析。研究表明,热源函数法可有效地求解一系列复杂情况下的热固结问题。     

内共振条件下直线运动梁的动力稳定性

基于Kane方程,建立起了包含有耦合的三次几何及惯性非线性项大范围直线运动梁动力学控制方程．利用多尺度法并结合笛卡尔坐标变换,对所得方程进行一次近似展开,着重对满足一、二阶模态间3:1内共振现象的两端铰支梁参激振动平凡解稳定性进行了详尽的分析,得出了稳定性边界的解析表达式．采用中心流形定理对调制微分方程组进行降维处理,分析了相应Hopf分岔类型并通过数值计算发现了稳定的极限环存在．     

STRESS CONCENTRATIONS IN CYLINDRICAL SHELLS WITH LARGE OPENINGS

Based on Donnell's shallow shell equation, a new method is given in this paper to ana-lyze theoretical solutions of stress concentrations about cylindrical shells with large openings. With themethod of complex variable function, a series of conformal mapping functions are obtained from dif-ferent cutouts' boundary curves in the developed plane of a cylindrical shell to the unit circle. And,the general expressions for the equations of a cylindrical shell, including the solutions of stress concen-trations meeting the boundary conditions of the large openings' edges, are given in the mapping plane.Furthermore, by applying the orthogonal function expansion technique, the problem can be summa-rized into the solution of infinite algebraic equation series. Finally, numerical results are obtained forstress concentration factors at the cutout's edge with various opening's ratios and different loadingconditions. This new method, at the same time, gives a possibility to the research of cylindrical shellswith large non-circular openings or with nozzles.     

应力函数及其对偶理论在有限元中的应用

借助于Cosserat连续介质模型，探讨了应力函数和位移对避免有限元C$^{1}$ 连续性困难的互补性作用. 通过对应力函数对偶理论的深入分析，为将应力函数列式得到的 余能单元转化为具有一般位移自由度的势能单元提供了严格的理论基础，在此基础上， 给出应用应力函数构造有限元的一般方法.     

MAIN FACTORS IN PREPARATION OF ANTIBACTERIAL PARTICLES／PVC COMPOSITE

Zirconium phosphate containing silver was chosen as antibacterial particles in preparing antibacterial particles/PVC composite. The effect of surface property of the antibacterial particles and of their filler content on the properties of antibacterial particles/PVC composite was studied. The effect of the interracial compatibility on mechanical properties of the composite was also discussed. Experimental results showed that the antibacterial PVC composite had good antibacterial property, reaching almost 100% bacteriostatic level at an antibacterial powder filler content of 1.5phr.     

Pore size effects of nanoporous carbons with ultra-high surface area on high-pressure hydrogen storage

In this work, the morphologies and pore structures of a series of corncob-derived activated carbons and zeolite templated carbon with ultrahigh surface area were carefully investigated by SEM, HRTEM and N2-sorption characterization technologies. The high-pressure hydrogen uptake performance was analyzed using standard Pressure-Composition-Temperature apparatus in order to study the pore size effects on hydrogen uptake. These as-obtained porous carbons showed different characteristics of pore size distribution as well as specific surface area. The results indicate that the most effective pores for adsorbing hydrogen depended on the storage pressure. These ultramicropores(0.65-0.85 nm) could be the most effective pores on excess H2 uptake at 1 bar, however, micropores(0.85-2 nm) would play a more important role in excess H2 uptake at higher pressure at 77 K. At room temperature, pore size effects on H2 uptake capacity were very weak. Both specific surface area and total pore volume play more important roles than pore size for H2 uptake at room temperature, which was clearly different from that at 77 K.For applications in future, the corncob-derived activated carbons can be more available than zeolite templated carbons at 77 K. Element doping enhanced hydrogen uptake could be main research direction for improving H2 uptake capacity at room temperature.     

液晶的转动粘质系数的测试原理与方法(英文)

液晶的转动粘质度是液晶用于显示和通讯的重要物理参量.本文设计开发了基于微机的液晶参数测试光学系统,在该系统上研究了液晶的转动粘质系数的测试原理与方法:通过测试液晶盒在偏置电压下相位驰预时间,推导出转动粘质系数的值.测试Merck公司的E7液晶的转动粘质系数随温度变化的曲线,进行了理论拟合,测试结果与理论符合得很好.通过分析另一系统对液晶介质常数随温度变化的曲线的测试结果,验证了该测试原理与方法的正确性.该测试方法具有简单、自动化的特点.     

高稳定LD泵浦腔内倍频Nd∶YVO4/KTP连续绿光激光器

设计出一种能够较好地补偿激光晶体热效应的激光谐振腔,实现了高稳定LD单端泵浦KTP腔内倍频Nd∶YVO4连续绿光激光器·当晶体吸收的泵浦功率为24.56W时,532nm激光功率达到5.3W,光-光转换效率达到21.6%,激光模式为TEM00模·在输出功率5W左右时,激光器1h功率不稳定度优于0.6%·     

LD泵浦Nd∶LuVO_4/Cr~(4 )∶YAG被动调Q激光器

采用大功率半导体激光器端面泵浦Nd∶LuVO4晶体,利用Cr4 ∶YAG晶体作为可饱和吸收元件,实现了1.06μm激光的被动调Q运转.在泵浦功率为19.1W时,获得最高平均输出功率为4.58W,脉冲宽度为84ns,单脉冲能量为36.6μJ以及峰值功率为436.2W的激光脉冲.