Characteristics of flow fields induced by interfacial waves in two-layer fluid

When designing deep ocean structures, it is necessary to estimate the effects of internal waves on the platform and auxiliary parts such as tension leg, riser and mooring lines. Up to now, only a few studies are concerned with the internal wave velocity fields. By using the most representative two-layer model, we have analyzed the behavior of velocity field induced by interfacial wave in the present paper. We find that there may exist velocity shear of fluid particles in the upper and lower layers so that any structures in the ocean are subjected to shear force nearby the interface. In the meantime, the magnitude of velocity for long internal wave appears spatially uniform in the respective layer although they still decay exponentially. Finally, the temporal variation for Stokes and solitary waves are shown to be of periodical and pulse type.

Deformation Of Pdms Membrane And Microcantilever By A Water Droplet: Comparison Between Mooney-Rivlin And Linear Elastic Constitutive Models

In this paper, we studied the role of vertical component Of Surface tension of a water droplet on the deformation of membranes and microcantilevers (MCLs) widely used in lab-on-a-chip and micro-and nano-electromechanical system (MEMS/NEMS). Firstly, a membrane made of a rubber-like material, poly(dimethylsiloxane) (PDMS), was considered. The deformation was investigated using the Mooney-Rivlin (MR) model and the linear elastic constitutive relation, respectively. By comparison between the numerical solutions with two different models, we found that the simple linear elastic model is accurate enough to describe such kind of problem, which would be quite convenient for engineering applications. Furthermore, based on small-deflection beam theory, the effect of a liquid droplet on the deflection of a MCL was also studied. The free-end deflection of the MCL was investigated by considering different cases like a cylindrical droplet, a spherical droplet centered on the MCL and a spherical droplet arbitrarily positioned on the MCL. Numerical simulations demonstrated that the deflection might not be neglected, and showed good agreement with our theoretical analyses. (C) 2008 Elsevier Inc. All rights reserved.

强散射体产生的像面散斑对比度与随机表面及成像系统关系的研究

We study the statistical properties of the image speckles produced by strong-scattering objects in the 4f optical imaging system. Using the generic expression of the complex amplitude of speckles and the approximation of the double-exponential function, we first obtain the ensemble average of the speckle intensity. Then we derive the variance of the speckle intensity based on the rotational transformation of the real and imaginary parts of the complex amplitude of speckles. We finally obtain the expression for the contrast of the. speckles, which is explicitly related to the statistical parameters of random surface and to the parameters of the imaging system. Our results are an obvious improvement compared with those reported in the literature, where the relations including such implicit quantities as the average size of the scattering grains of the random surface and the number of scattering grains are usually used. The results of this paper would be helpful for the characterization of random surface by speckle contrast.

Y2O3 stabilized ZrO2 thin films deposited by electron-beam evaporation: Optical properties, structure and residual stresses

This paper describes the preparation and the characterization Of Y2O3 stabilized ZrO2 thin films produced by electric-beam evaporation method. The optical properties, microstructure, surface morphology and the residual stress of the deposited films were investigated by optical spectroscopy, X-ray diffraction (XRD), scanning probe microscope and optical interferometer. It is shown that the optical transmission spectra of all the YSZ thin films are similar with those of ZrO2 thin film, possessing high transparency in the visible and near-infrared regions. The refractive index of the samples decreases with increasing of Y2O3 content. The crystalline structure of pure ZrO2 films is a mixture of tetragonal phase and monoclinic phase, however, Y2O3 stabilized ZrO2 thin films only exhibit the cubic phase independently of how much the added Y2O3 content is. The surface morphology spectrum indicates that all thin films present a crystalline columnar texture with columnar grains perpendicular to the substrate and with a predominantly open microporosity. The residual stress of films transforms tensile from compressive with the increasing Of Y2O3 molar content, which corresponds to the evolutions of the structure and packing densities. (C) 2008 Elsevier Ltd. All rights reserved.

广东省主要农情动态监测与快速预报研究

该项目在以下四个方面取得了各具特色的成果：1、根据野外农学参数实测数据制定了广东省稻作图谱；建立了区域范围的雷达水稻估产模型； 计算出了广东省早、晚稻产量分布图，估产精度达到90%以上，取得了利用SNB SAR数据进行大面积水稻估产的技术突破，及时为广东省政府提供了农业宏观决策的科学依据。2、利用图像融合的技术及时做出了全国农业产业调整后，广东省农用土地变化的定量分析成果。同时，为研究农田初级生产力提供了基础科学积累。3、通过研究广东植被生产力时空特征，修正了国际上一直沿用的光利用率系数；还证明了在全省重植林后，每年可固定广东全省年CO2排放量的一半，充分证明植树造林对缓解全球变暖的CO2温室效应具有非常重要的意义。被写入了第三世界科学院为南非世界首脑峰会的文件，将对我国合理履行国际协议提供科学依据。4、建立了广东省林业查询系统、树种生产力遥感判读分类模型和面积，并计算得到广东省森林生态系统的总服务价值为371亿元，通过各林型服务价值比较，得出最高的是松林，总值为100.05 亿元。该项目培养了博士、硕士生10多名，完成了专著3部，论文20多篇(其中EI和SCI论文8篇)，经专家鉴定本成果整体上达到国际先进水平，部分成果达到国际领先水平。