A Numerical Study for Turbulent Flow and Thermal Influence Over Inhomogenous Canopy of Roughness Elements

A large-eddy simulation with transitional structure function(TSF) subgrid model we previously proposed was performed to investigate the turbulent flow with thermal influence over an inhomogeneous canopy, which was represented as alternative large and small roughness elements. The aerodynamic and thermodynamic effects of the presence of a layer of large roughness elements were modelled by adding a drag term to the three-dimensional Navier-Stokes equations and a heat source/sink term to the scalar equation, respectively. The layer of small roughness elements was simply treated using the method as described in paper (Moeng 1984, J. Atmos Sci. 41, 2052-2062) for homogeneous rough surface. The horizontally averaged statistics such as mean vertical profiles of wind velocity, air temperature, et al., are in reasonable agreement with Gao et al.(1989, Boundary layer meteorol. 47, 349-377) field observation (homogeneous canopy). Not surprisingly, the calculated instantaneous velocity and temperature fields show that the roughness elements considerably changed the turbulent structure within the canopy. The adjustment of the mean vertical profiles of velocity and temperature was studied, which was found qualitatively comparable with Belcher et al. (2003, J Fluid Mech. 488, 369-398)'s theoretical results. The urban heat island(UHI) was investigated imposing heat source in the region of large roughness elements. An elevated inversion layer, a phenomenon often observed in the urban area (Sang et al., J Wind Eng. Ind. Aesodyn. 87, 243-258)'s was successfully simulated above the canopy. The cool island(CI) was also investigated imposing heat sink to simply model the evaporation of plant canopy. An inversion layer was found very stable and robust within the canopy.

Measuring Binding Kinetics Of Surface-Bound Molecules Using The Surface Plasmon Resonance Technique

Surface plasmon resonance (SPR) technology and the Biacore biosensor have been widely used to measure the kinetics of biomolecular interactions in the fluid phase. In the past decade, the assay was further extended to measure reaction kinetics when two counterpart molecules are anchored on apposed surfaces. However, the cell binding kinetics has not been well quantified. Here we report development of a cellular kinetic model, combined with experimental procedures for cell binding kinetic measurements, to predict kinetic rates per cell. Human red blood cells coated with bovine serum albumin and anti-BSA monoclonal antibodies (mAbs) immobilized on the chip were used to conduct the measurements. Sensor-grams for BSA-coated RBC binding onto and debinding from the anti-BSA mAb-immobilized chip were obtained using a commercial Biacore 3000 biosensor, and analyzed with the cellular kinetic model developed. Not only did the model fit the data well, but it also predicted cellular on and off-rates as well as binding affinities from curve fitting. The dependence of flow duration, flow rate, and site density of BSA on binding kinetics was tested systematically, which further validated the feasibility and reliability of the new approach. Crown copyright (c) 2008 Published by Elsevier Inc. All rights reserved.

Molecular dynamics simulations of DFZ

Dislocation emission from the crack tip in copper under mode II loading is simulated with molecular dynamics method. After 26 partial dislocations are emitted and then relaxed to reach the equilibrium under the constant displacement, the double pile-ups (including an inverse pile-up and a pile-up) are formed. i.e., the first dislocation is piled up before the obstruction, and the last dislocation is piled up ahead of the crack tip. These results conform to the TEM observations.

关于热-塑剪切带的演变

本文简要地概述了对热塑剪切带的演变所进行的解析研究,其中包括不稳定性的发生,不稳定性发生后剪切带的发展,以及剪切带的晚期行为。所讨论的情况是,在温度和应变速率有关的材料中所发生的简单剪切变形,而且热传导在其中是不可忽略的。倘若没有热流流出试件,那么在某临界状态前,可以存在一个均匀的剪切变形场。而达到该临界状态时,扰动便会导致不稳定性的发生。这便可以是狭窄剪切带的形成。剪切带在其早期的非定常变形流动中,可能变狭,并伴随升温和应变速率提高。热传导对剪切带的作用是使其变宽。对剪切带的晚期行为的分析,表明其宽度是塑性功率和热扩散二者相互平衡的某种表现。包含热-塑剪切带的试件的观察支持了上述结果。分析还指出,剪切带中是可能出现熔化现象的,这也已在电镜观察中看到。

岩石介质变模量帽盖模型的弹塑性本构关系

本文用连续介质力学的理论分析了岩石屈服前的性状,导出了岩石介质的非线性弹性的本构方程,并与实验资料进行了比较,二者十分接近.进而用非线性弹性取代一般帽盖模型中关于弹性区的线弹性假设,导出了非线性弹性—塑性硬化的帽盖模型.

频闪He-Ne激光高速干涉摄影装置

用光振子调制连续输出的He-Ne激光,配合转鼓相机,形成了频闪He-Ne激光高速干涉摄影装置。摄影频率达每秒20000幅。配合超高速转镜相机,可作为超高速干涉摄影的可控同步单脉冲光源。

在强激光下Ge平行板的动态F-P干涉效应

实验表明,在连续CO_2激光辐照下,Ge平行板透射光强度随时间呈准周期性的变化。基于平行平面板的多光束干涉理论,并考虑激光引起的温升对Ge片折射率和厚度的影响,得到的计算结果与实验相符合。这说明平行平面Ge在高功率连续CO_2激光作用下因折射率和厚度随温度的变化而具有一种动态的法布里-珀罗干涉效应。

Dynamic-response of a laminated plate with friction damping

薄板激光弯曲温度场的数值模拟与校验

采用MSC.Marc非线性有限元软件，对薄板激光变曲过程中的温度场进行了数值模拟，得到了引起薄板激光弯曲形的温度场的变化规律。通过温度传感器测量与激光扫描线相对应的薄板下表面温度变化的规律来验证数值模拟的结果。模拟值与实测值基本吻合，表明数值模拟结果可作为激光加工工艺参数选择的依据。

微槽道气体流动的统计模拟

利用基于分子模型的统计模拟方法-信息保存方法（IP）统计模拟了实验条件下微槽道气体流动，仔细讨论了用IP方法模拟长槽道稀薄气流时遇到的问题，并给出了解决的方法，即采取守恒形式的控制方法避免质量流量计算误差积累，并利用超松弛方法使收敛过程加速。将IP计算结果与压力分布和质量流量实验数据进行了比较。

结构破坏的尺度律

文中综述了结构破坏的尺度律和尺寸效应的研究进展，尤其将重点放在准脆性材料的分析上，因为它们的尺寸效应是重要和复杂的．在回顾了尺寸效应研究的悠远发展史以后。着重讨论了三种主要类型的尺寸效应，即由于强度随机性引起的统计尺寸效应、能量释放的尺寸效应和由于微裂纹或断裂的分形特性可能引起的尺寸效应．得出了这些理论应用的明确结论．之后讨论了如何运用已知的尺寸效应律来测量材料的断裂特性，并采用内聚裂纹模型（cohesivecrackmodel）、非局域化有限元模型和离散元模型等对尺寸效应进行模化．文中还进而分析了尺寸效应在压缩失效和车相关材料行为下的有关问题，并讨论了在断裂扩展区描述含微裂纹材料所需的损伤本构关系．最后也讨论了尺寸效应对准脆性材料的多种应用，这些材料包括，如混凝土、海冰、纤维复合材料、岩石和陶瓷等．本文包含了参考文献377篇．

浮区热毛细对流

概述了浮区中平行于自由面的表面张力梯度驱动热毛细对流领域的研究.研究兴趣集中于振荡热毛细对流的起振,或者说从定常流动到振荡流动的转捩.起振依赖于一系列的临界参数,临界关系可以表示为这些临界参数的复杂函数.实验结果表明,振荡流中速度的变化和平均流动的速度有相同的量级,而其它量的变化,比如温度和自由面半径的波动,相比于它们的平均量而言则要小得多.因此,起振应是流体中动力学过程的结果,该问题是强非线性的.在过去几十年中,一些理论模型被引入米研究这个问题,使用的方法包括理论分析方法、线性不稳定性分析方法、能量稳定性分析方法以及非定常的三维直接数值模拟.其中直接数值模拟被认为是对强非线性过程进行深入分析的最适合方法,通常能得到和实验较符合的结果.从振荡热毛细对流向湍流的转捩提供了一个研究混沌行为的新系统,开创了一个非线性科学的新前沿,是一个集中了大量近期工作的研究热点.该文对浮区热毛细对流作了一个回顾,包括理论模型和分析,以及实验研究.

基于掺镧锆钛酸铅电光材料的光学相控阵光束扫描器

基于掺镧锆钛酸铅(PLZT)电光陶瓷材料的光学特性,提出了一种具有上下电极结构的光学相控阵高速光束扫描器。在理论上,分析了具有这种结构的光学相控阵的光束电光偏转特性和机制;在实验上,分析了掺镧锆钛酸铅材料的相位调制特性和损耗特性,制作了相关的光学相控阵器件,并构建了相应的测试系统,获得了光束在空间的角度偏转,与理论分析结果相符。