磁电弹复合材料和刚性导电导磁圆柱压头的二维微动接触分析

本文求解平面应变状态下磁电弹复合材料半平面和刚性导电导磁圆柱压头的二维微动接触问题。假设压头具有良好的导电导磁性，且表面电势和磁势是常数。微动接触依赖载荷的加载历史，所以首先求解单独的法向加载问题，然后在法向加载问题的基础上求解循环变化的切向加载问题。整个接触区可以分为内部的中心粘着区和两个外部的滑移区，其中滑移区满足Coulomb摩擦法则。利用Fourier积分变换，磁电弹半平面的微动接触问题将简化为耦合的Cauchy奇异积分方程组，然后数值离散为线性代数方程组，利用迭代法求解未知的粘着/滑移区尺寸、电荷分布、磁感应强度、法向接触压力和切向接触力。数值算例给出了摩擦系数、总电荷和总磁感应强度对各加载阶段的表面接触应力、电位移和磁感应强度的影响。     

关于落实学生实验操作能力的思考及尝试

1配分函数及其物理意义 由麦克斯韦——玻尔兹曼分布中各能级上的粒子数ni=Wie^-α-βsi或处在能量为εi；的量子态s上的平均粒子数fs=e-^-α-βsi得     

Detectivity of Fe Kα Lines in Gamma-Ray Bursts by Cerenkov Line Mechanism

The Fe Kα lines in gamma-ray bursts （GRBs） produced with the Cerenkov line mechanism are studied. We theoretically predict the Fe Kα line luminosities in both the early （before i hour） and late （～1 day） afterglows. Assuming about 200 GRBs could be detected by Swift per year, we sampled the redshift of these GRBs using the Monte Carlo method according to the GRB formation rate derived from the statistical correlation between the spectral peak energy and the peak luminosity of GRBs. Then we obtain the Fe Kα line flux distributions of the simulated GRB sample in the early and late phases. The simulated results show that the iron line flux is relatively low, so the line detection would be still a rare event at present. In addition, our results suggest that the iron lines from GRBs could be detected in the high redshift： z ～ 3 for the early phase and z ～ 6 for the late phase. Therefore, it is possible that the identification of Fe Ka lines in GRBs provides a tool to directly measure redshift and to study the high-redshift GRBs in the Swift era.     

Time Periodic Electroosmotic Flow of The Generalized Maxwell Fluids in a Semicircular Microchannel

Analytical solutions are presented using method of separation of variables for the time periodic electroosmotic flow (EOF) of linear viscoelastic fluids in semicircular microchannel. The linear viscoelastic fluids used here are described by the general Maxwell model. The solution involves analytically solving the linearized Poisson-Boltzmann (P -B) equation, together with the Cauchy momentum equation and the general Maxwell constitutive equation. By numerical computations, the influences of electric oscillating Reynolds number Re and Deborah number De on velocity amplitude are presented. For small Re, results show that the larger velocity amplitude is confined to the region near the charged wall when De is small. With the increase of the Deborah number De, the velocity far away the charged wall becomes larger for large Deborah number De. However, for larger Re, the oscillating characteristic of the velocity amplitude occurs and becomes significant with the increase of De, especially for larger Deborah number.     

微平行管道内Jeffrey流体的非定常电渗流动

研究了微平行管道内线性黏弹性流体的非定常电渗流动, 其中线性黏弹性流体的本构关系是由Jeffrey流体模型来描述的. 利用Laplace变换法, 求解了线性化的Poisson-Boltzmann方程、 非定常的柯西动量方程和Jeffrey流体本构方程, 给出了黏弹性Jeffrey流体电渗速度的解析表达式, 分析了无量纲弛豫时间λ₁和滞后时间λ₂对速度剖面的影响. 发现滞后时间为零时, 弛豫时间越小, 速度剖面图越接近牛顿流体的速度剖面图; 随着弛豫时间和滞后时间的增加, 速度振幅也变得越来越大, 随着时间的增加, 速度逐渐趋于恒定. 关键词： 双电层 微平行管道 Jeffrey流体 非定常电渗流动     

高密度封装倒装焊的新简化模型及疲劳寿命分析

高密度封装结构中存在大量焊球，在进行有限元建模时，考虑到焊球数量多且尺寸小的特点，需简化焊球层模型．本文针对高密度封装结构中倒装焊及底填胶，提出了一种新的简化模型，采用非重点部位简化和材料均匀化相结合的方法，将内部焊球层和底填胶简化为均匀层，只保留外圈几层焊球．通过建立代表性体积单元，计算得到均匀化层的材料参数．讨论了外层焊球圈数对焊球层危险点应力的影响，发现保留外圈两层焊球就能得到非常精确的结果．利用新简化模型计算了高密度封装结构的疲劳寿命，所获得的结果与未均匀化模型结果误差在0.3%以内．