Electro-Osmotic Flow and Mixing in Heterogeneous Microchannels

Analytical and numerical studies of secondary electro-osmotic flow EOF and its mixing in microchannels with heterogeneous zeta potentials are carried out in the present work. The secondary EOFs are analyzed by solving the Stokes equation with heterogeneous slip velocity boundary conditions. The analytical results obtained are compared with the direct numerical simulation of the Navier-Stokes equations. The secondary EOFs could transport scalar in larger areas and increase the scalar gradients, which significantly improve the mixing rate of scalars. It is shown that the heterogeneous zeta potentials could generate complex flow patterns and be used to enhance scalar mixing.

罐体油泥自动清理系统研究

油田罐体内易沉积泥砂，这些合油泥砂的自动清理及无污排放难题长期无法解决。本文通过介绍一个工程应用，给出了一套解决此问题的工艺流程。

乳化油的性质及其制备方法研究

乳化油不仅广泛应用于内燃机和重油锅炉等设备，而且在材料制备工艺等其它领域亦在应用，本文介绍了乳化油微爆机理，物理性质，制备方法等问题。

基体激光淬火对镀铬层界面剪切强度的影响

针对激光淬火基体后再镀铬复合工艺提高镀铬身管寿命的实际工程问题,采用多裂纹拉伸技术证明该复合镀铬工艺可以提高界面剪切强度,并从材料学角度给予解释.离子冲击技术对界面强度的定性分析表明:激光淬火基体在消除铬层和基体之间过渡层的同时也提高了界面附近材料的强度.化学腐蚀去基体法研究表明,铬层界面材料强度的提高是晶粒细化的结果.因此得出激光淬火基体提高镀铬层界面剪切强度的原因是激光淬火消除了铬层和基体之间的过渡层和增强了界面附近材料的硬度和强度.

Size-dependent inelastic behavior of particle-reinforced metal-matrix composites

The strengthening behavior of particle-reinforced metal-matrix composites (MMCp) is primarily attributed to the dislocation strengthening effect and the load-transfer effect. To account for these two effects in a unified way, a new hybrid approach is developed in this paper by incorporating the geometrically necessary dislocation strengthening effect into the incremental micromechanical scheme. By making use of this hybrid approach, the particle-size-dependent inelastic deformation behavior of MMCp is given. Some comparisons with the available experimental results demonstrate that the present approach is satisfactory.

Effects of Microstructural Heterogeneity on the Spallation Behavior of Materials

It is of utmost importance to understand the spallation behaviour of heterogeneous materials. In this paper, a driven nonlinear threshold model with stress fluctuation is presented to study the effects of microstructural heterogeneity on continuum damage evolution. The spallation behavior of heterogeneity material is analyzed with this model. The heterogeniety of mesoscopic units is characterized in terms of Weibull modulus m of strength distibution and stress fluctuation parameter k. At high stress, the maximum damage increases with m; while at low stress, the maximum damage decreases. In addition, for low stress, severe stress fluctuation causes higher damage; while for high stress, causes lower damage.

Fracture mechanics of piezoelectric materials

This paper presents an analysis of crack problems in homogeneous piezoelectrics or on the interfaces between two dissimilar piezoelectric materials based on the continuity of normal electric displacement and electric potential across the crack faces. The explicit analytic solutions are obtained for a single crack in an infinite piezoelectric or on the interface of piezoelectric bimaterials. For homogeneous materials it is found that the normal electric displacement D-2, induced by the crack, is constant along the crack faces which depends only on the remote applied stress fields. Within the crack slit, the perturbed electric fields induced by the crack are also constant and not affected by the applied electric displacement fields. For bimaterials, generally speaking, an interface crack exhibits oscillatory behavior and the normal electric displacement D-2 is a complex function along the crack faces. However, for bimaterials, having certain symmetry, in which an interface crack displays no oscillatory behavior, it is observed that the normal electric displacement D-2 is also constant along the crack faces and the electric field E-2 has the singularity ahead of the crack tip and has a jump across the interface. Energy release rates are established for homogeneous materials and bimaterials having certain symmetry. Both the crack front parallel to the poling axis and perpendicular to the poling axis are discussed. It is revealed that the energy release rates are always positive for stable materials and the applied electric displacements have no contribution to the energy release rates.

定常压力梯度边界层相干结构的直接数值模拟

根据流动稳定性理论，将不稳定波的一个周期作为相干结构的初值，采用直接数值模拟方法对有压力梯度湍流边界层中相干结构的演化进行了研究，得出其各种特性的变化与实验凤测到的结果一致。

两层流体热毛细对流空间实验研究=Space Experiments of Thermo Capillary Convection in Two-liquid Layers

1999年,在我国实践5号卫星上完成了两层流体空间实验,实验研究两层不相混合流体的纯Marangoni对流（温度梯度与界面垂直）与热毛细对流（温度梯度方向与流体界面平行）.前者存在发生Marangoni对流的最小临界温差值△Tc,低于该值流体系统处于静止状态;后者中只要存在沿界面的温度梯度便会产生热毛细对流.空间实验采用石蜡和氟化液两层流体新体系,实现了平整的液-液交界面,并从卫星上传回上万幅数字图像.通过多幅图像叠加处理得到了定量的流速场.数值模拟计算分析了相应工况时对流流动的速度场,两者的流场结构和速度大小基本一致,实验验证了理论模型.

Hierarchy of structure functions for passive scalars advected by turbulent flows

A hierarchical model is proposed for the joint moments of the passive scalar dissipation and the velocity dissipation in fluid turbulence. This model predicts that the joint probability density function (PDF) of the dissipations is a bivariate log-Poisson. An analytical calculation of the scaling exponents of structure functions of the passive scalar is carried out for this hierarchical model, showing a good agreement with the results of direct numerical simulations and experiments.

结构动力模型修正方法研究进展

叙述了结构动力模型修正方法的一般原理及与其密切相关的模型缩聚和模态扩展方法,并且挑选其中具有代表性的文献,介绍和比较了3种主要的修正方法,即传统的动力模型修正方法,包括矩阵型修正方法和参数型修正方法,和最近兴起的基于神经网络的模型修正方法,重点分析了这些方法的优点和不足之处,力图能使读者对于这一研究领域的发展有一个脉络清晰的了解.最后,就目前研究中尚未解决的问题作了一些探讨.

骨动态压电响应的测试研究

测量应力波在骨内传播时骨的压电电位响应是困难的，困难之处在于电位参考点的选定，电位参考点必须是一个电位保持恒定的点，当应力波在骨内部传播时，应力波传及的部位都会产生压电电位变化，不存在电位保持恒定的部位，本文利用屏蔽内电位恒定的特点，将参考点移出骨试件选在屏蔽层上，解决了上述困难。测出了骨的压电电位响应，测试结果表明压电电位决定于应力梯度而不是应力，而且骨受拉伸时其压电电位（绝对值）大于受压缩时的压电电位。

Influence of Local Magnetic Fields on P-Doped Si Floating Zone Melting Crystal Growth in Microgravity

A two-dimensional axisymmetric numerical model is presented to study the influence of local magnetic fields on P-doped Si floating zone melting crystal growth in microgravity. The model is developed based on the finite difference method in a boundary-fitted curvilinear coordinate system. Extensive numerical simulations are carried out, and parameters studied include the curved growth interface shape and the magnetic field configurations. Computed results show that the local magnetic field is more effective in reducing the impurity concentration nonuniformity at the growth interface in comparison with the longitudinal magnetic field. Moreover, the curved growth interface causes more serious impurity concentration nonuniformity at the growth interface than the case with a planar growth interface.