Conceptual design studies of the 5 m terahertz antenna for Dome A,Antarctica

As the highest, coldest and driest place in Antarctica, Dome A provides exceptionally good observing conditions for ground-based observations over terahertz wavebands. The 5 m Dome A Terahertz Explorer （DATES） has been proposed to explore new terahertz windows, primarily over wavelengths between 350 and 200 pm. DATE5 will be an open-air, fully-steerable telescope that can function by unmanned operation with remote control. The telescope will be able to endure the harsh polar environment, including high altitude, very low temperature and very low air pressure. The unique specifications, including high accuracies for surface shape and pointing and fully automatic year-around remote operation, along with a stringent limit on the periods of on-site assembly, testing and maintenance, bring a number of challenges to the design, construction, assembly and operation of this telescope. This paper intro- duces general concepts related to the design of the DATE5 antenna. Beginning from an overview of the environmental and operational limitations, the design specifications and requirements of the DATE5 antenna are listed. From these, major aspects on the conceptual design studies, including the antenna optics, the backup structure, the pan- els, the subreflector, the mounting and the antenna base structure, are explained. Some critical issues of performance are justified through analyses that use computational fluid dynamics, thermal analysis and de-icing studies, and the proposed approaches for test operation and on-site assembly. Based on these studies, we conclude that the specifications of the DATE5 antenna can generally be met by using enhanced technological approaches.     

The impact of physical processes on pollutant transport in Hangzhou Bay

A Lagrangian tracer model is set up for Hangzhou Bay based on Coupled Hydrodynamical Ecological model for Regional Shelf Sea (COHERENS). The study area is divided into eight subdomains to identify the dominant physical processes, and the studied periods are March (the dry season) and July (the wet season). The model performance has been first verified by sea-surface elevation and tidal current observations at several stations. Eight tracer experiments are designed and Lagrangian particle tracking is simulated to examine the impact of physical processes (tide, wind and river runoff) on the transport of passive tracer released within the surface layer. Numerical simulations and analysis indicate that: (1) wind does not change the tracer distribution after 30 days except for those released from the south area of the bay during the wet season; (2) the tide and the Qiantang River runoff are important for particle transport in the head area of the bay; (3) the Changjiang River runoff affects the tracer transport at the mouth of the bay, and its impact is smaller in the dry season than in the wet season. Supported by the Natural Science Foundation of China (No.40576080); National High Technology Research and Development Program of China (863 Program, No. 2007AA12Z182)     

投稿预告

欢迎向主题专辑投稿也欢迎非主题投稿《地学前缘》为双月主题性期刊,欢迎按主题投稿,也欢迎非主题投稿,因本刊设有“非主题来稿选登”。近期投稿预告如下:(1)2011年第2期为“地球物质科学”主题:具体专辑名为“变质作用与造山带演化”。(2)2011年第3期为“地球结构、构造与动力学”主题:具体专辑名为“大陆地质与大陆构造”。第4期为特约专辑“沉积地质与资源”。(3)2011年第5期为特约专辑“成矿流体动力学”第6期为“地球表层科学”主题:具体专辑名为“中国土壤碳库与全球变化”。(4)2012年第1、2期“地球物质科学”主题:具体专辑名为第1期“油气沉积地质”第2期“油气藏开发地质”(5)2012年     

波浪条件下小型回转体高速入水动力学特性研究

采用光滑粒子流体动力学（SPH）方法,建立了刚体入水六自由度响应模型,实现了波浪环境下小型回转体高速入水过程的数值模拟。对波浪环境下小型回转体高速入水过程中的运动姿态、冲击载荷进行讨论分析,结果表明：波浪条件下入水点相位不同,导致回转体实际入水角不同,实际入水角越大,入水冲击载荷越大,弹道越稳定;实际入水角越小,入水冲击载荷越小,弹道越易发生失稳。本研究表明,入水点相位对小型回转体弹道特性和冲击载荷产生影响,进而为波浪条件下跨介质武器低载稳定入水提供基础性技术支撑。     

渗流的PFC-CFD耦合细观数值模拟

本文针对饱和多孔介质中渗流特点,在分析渗流连续介质力学模型的基础上,采用描述多孔介质中固相颗粒和液相流体耦合的细观力学模型,其中固相颗粒采用离散元的颗粒流理论(PFC)模拟,液相流体通过求解平均Navier-Stokes方程的计算流体动力学(CFD)技术计算,并利用建议的模型对二维渗流问题进行了模拟验证。数值模拟结果表明,采用PFC-CFD耦合细观力学模型能够描述从低雷诺流到高雷诺流范围很大的流体运动,可以用于多孔介质中的渗流问题分析。     

水氡异常的水动力学机制

在水氡异常机制研究中，人们以往都强调岩石力学机制，即孕震过程中岩石微破裂产生氡射气。然而，大量的震例表明，水氡异常可出现在孕震早期，可见于距震中较远的井中，那里的与那时的含水层岩石很难处在微破裂状态。因此，笔者提出水氡异常的水动力学机制，即在较低的应力水平下含水岩体的变形与其水动力状态的变化引起水氡异常的机制     

沉积盆地动力学的研究现状、问题与展望

沉积盆地动力学研究沉积盆地在地质历史时期的地质结构特征、成因机制及其对成矿、成藏的控制作用, 是地球动力学研究的重要组成部分.30多年来, 沉积盆地动力学经历了沉积盆地的板块构造分类与构造环境解释、盆地动力学的兴起, 盆地综合建模与盆地系统动力学3个发展阶段; 在沉积盆地的深部构造背景、盆-山关系、沉降机制、充填模式及其对能源、矿产的控制方面取得重要进展.目前, 在对不同层次、不同尺度、不同机制的盆地动力学综合分析, 全3-D和4-D盆地动力学模型的构建与检验, 及学术界与工业界的充分结合等方面面临重要挑战.需解决一系列关键科学问题: 沉积盆地的深部结构、过程与盆地形成; 沉积盆地的构造-气候古地理; 多旋回沉积盆地叠合动力学过程与原型盆地演化; 叠合盆地复合成矿(藏)系统流体运聚及其资源、能源效应等.基于大数据综合集成、多学科交叉渗透、观测技术与分析方法的不断进步与完善, 盆地动力学将在其结构构造、形成演化及其控矿(藏)的4-D综合模型方面取得突破, 并为人类社会、经济发展做出贡献.     

浅海流体动力学一种含变湍粘性系数的流速分解模型（Ⅱ）——模型在超浅海风暴潮零阶问题中的应用

本文将流速分解模型应用于作为超浅海风暴潮的渤海风潮，并讨论了变湍帖系数的确定。作为一个初步的，但较为成功的数值试验例子，描述了实际风场作用下的渤海风潮，比较了变湍粘性系数模型与常湍粘性系统模型的计算结果间的差异。     

热液成矿分带的溶解－沉淀波结构

热液成矿分带是一种输运－反应问题。热液成矿分带基本属于渗滤交代分带性质，它是溶解－沉淀波在可渗透介质中形成和传播的结果。本文应用物理化学流体动力学中的渗滤与溶解－沉淀反应耦合过程理论研究溶解－沉淀波的结构特征，并进一步应用多组分耦合系统动力学中的用于原理揭示其形成的动力学机制，最后提出了一种热流成矿分带理论，对热液成矿分带问题的性质、热液成矿分带的本质和热液成矿分带的结构特征与形成机制提出了新认识。