Cross-shelf circulation and phytoplankton distribution at the summertime New England shelfbreak front

We investigate aspects of the secondary (cross-shelf) circulation at the Middle Atlantic Bight shelfbreak front using high-resolution data collected on the New England Shelf in August 2002. The alongshore shelfbreak jet coincides with the front at the seaward edge of the cold pool (remnant winter shelf water) and there is a suggestion of a cross-stream convergence centered at the jet core. Despite indications of convergence we found no evidence of a surface subduction on the seaward side of the front. At depth 70 m near the shelfbreak there was a patch of chlorophyll, located within a local temperature–salinity maximum which, though significantly below the euphotic zone, appeared to be photo-acclimated and viable. The chlorophyll feature could be the result of a local subduction by a larger scale eddy circulation seaward of the front.Dye tracer experiments directly observed the convergence at the foot of the shelfbreak front and subsequent upwelling of bottom boundary layer water along the shoreward side of the shelfbreak front. But, we found no evidence that this upwelling influenced productivity at the front. Further, since there was no cross-shelf maximum in subsurface chlorophyll at the front, we conclude that this productivity is in general, sustained by a broadly distributed local vertical nutrient flux from an underlying nutrient reservoir.     

Large eddy simulations for quasi-2D turbulence in shallow flows: A comparison between different subgrid scale models

In this study, the performance of the horizontal large eddy simulation module, developed at the University of Leuven (HLES-KULeuven module) is assessed. A comparison between different subgrid scale models has been carried out. The study is concerned with the non-rotating and unstratified flows. The results of the simulation for an oscillatory backward facing (BFS) flow are presented in case of an expanding flume based on a one-length scale approach and a two-length scale approach. Three subgrid scale (SGS) models have been tested: Smagorinsky SGS model (Smagorinsky, J., (1963). General circulation experiments with the primitive equations, I. the basic experiments. Monthly Weather Review, 91(3), 99–164), Uittenbogaard SGS model (Uittenbogaard, R.E., and van Vossen, B., (2004). Subgrid-scale model for quasi-2D turbulence in shallow water. Shallow Flows. Jirka and Uijttewaal (Eds.), Taylor & Francis Group, London, ISBN 90 5809 700 5) and a proposed two-length scale approach. The first two models are considered to be a one-length scale models. A simulation without a subgrid scale model for the horizontal mixing has also been conducted. In all simulations, a quadratic friction model parameterizes the dissipation produced by the 3D-subdepth scale turbulence. The two-length scale concept uses a newly mixing length formulation for the quasi-2D turbulence and doesn't depend on the filter width in contrast to the one-length scale approach, in which the mixing length is function of the filter width. The outputs of the HLES-KULeuven module have been compared with the experimental data taken from Stelling, G.S., and Wang, L.X., (1984). Experiments and computations on separating flow in an expanding flume. Dept. Civil Engineering, Delft University of Technology, Report 2–84.). The two-length scale approach has been validated with experimental data from SERC Flood Channel Facility at HR Wallingford. In general, there is a qualitative agreement with the experimental data. It has also been found that the two-length scale approach produces more elongated and less isotropic vortex than the one-length scale models.     

二维凹槽内加机翼减阻效果的数值分析

对平板、二维凹槽和二维凹槽内加机翼三种模型进行对比分析,数值探讨二维凹槽内加机翼的减阻效果。数值摸拟采用商业软件fluent,结果表明在二维凹槽内加入机翼后的阻力比平板的阻力有14．8％的减阻效果。     

基于DS18820的多路温度采集系统

提出了基于采用DS18820和AT89C51单片机组成的单总线多路温度检测系统,详细给出了硬件和软件系统的设计过程。该系统设计可靠性高、性价比高,在智能化自动检测和控制系统中具有广阔的前景。     

沥青混合料细观结构离散元分析

为了在细观层次上分析沥青混合料的力学特性,本文用多边形单元模拟粗集料,球形单元粘结在一起模拟沥青玛蹄脂,在细观尺度上建立比较直观、清晰的离散元数值模型,采用3种接触模型描述沥青混合料内部的相互作用,并进行单轴压缩虚拟试验,分析沥青混合料的变形与应力情况。论文对虚拟试验结果进行分析,得出一些重要结论,并对本文的后继研究提出有意义的建议。     

高速复合水翼双体船的运动预报(英文)

基于2.5D理论,考虑粘性影响,预报了高速复合水翼双体船在规则波中的运动响应,并与试验结果进行了比较.在计算过程中,对复合水翼模型进行了简化,且计算了不同升力浮力比对运动的影响.结果反应出在计算高速双体船和水翼双体复合船型纵向运动性能时,水的粘性影响不可忽略,且计算表明计算值与试验值符合较好,文中提供的方法可提高这类高速水翼双体复合船型的运动预报精度.     

VHF雷达数字中频接收机研究与实现

雷达传统接收机常采用模拟正交检波,其I／Q信号幅度一致性误差和相位正交性误差较大,数字接收机可以较好的解决这一问题。文章研究了数字接收机的相关理论和技术,介绍了数字下变频,数控振荡器、级联积分梳状滤波器。给出了一种基于FPGA的数字中频接收机实现方案,进行了分析和仿真,给出了测试结果。     

主机控制台三维视景建模及起动控制仿真研究

基于Web3D虚拟轮机模拟器的研究与开发是仿真器研制的热点。主机控制台的三维视景建模及起动控制的交互仿真是这种新型轮机模拟器的重要组成部分。文章从建模工具的采用、三维控制台数学模型的建立、控制台动画效果的实现等方面分析主机控制台的构建过程;详细阐述了主机起动控制仿真过程的设计思路及人机交互的方式,全面分析建模与仿真过程的整体结构及实现方式,以达到远程、网络式的教学与培训之目的。     

机械系统三维设计的关联要素研究

通过对企业设计软件的应用现状调查,分析了企业机械系统应用现代设计技术中存在的问题.结合车载起重机专用取力器的三维设计过程,论述了机械系统三维设计的建模技术、模拟仿真、工程分析以及工程图导出等关联要素.     

人乳腺癌组织中Wnt/β-catenin信号传导通路的异常表达与Her2阳性表达间的关系

目的 观察人乳腺癌组织中Wnt/β-catenin信号传导通路主要组分E-cadherin、β-catenin、Cyclin D1的异常表达及其关键组分β-catenin的异常表达与Her2阳性表达之间的关系.方法 采用免疫组织化学Elivision两步法检测了90例人乳腺癌组织中Her2、E-cadherin、β-catenin以及Cyclin D1的表达情况.结果 E-cadherin表达正常组中β-catenin的异常表达率(27.3%)显著低于E-cadherin表达缺失组(75.0%);β-catenin异常表达组中Cyclin D1过表达率(83.3%)显著高于β-catenin正常组(40.7%).Her2阳性组中β-catenin的异常表达率(73.5%)明显高于Her2阴性组(19.6%).当Her2的阳性表达与β-catenin的异常表达同时存在时腋窝淋巴结转移的阳性率较高.结论 在一些人乳腺癌组织中存在Wnt/β-catenin信号传导通路的异常表达,并且其异常表达与Her2的阳性表达有关,二者的异常表达能够协同促进乳腺癌细胞的淋巴结转移.