立柱直径比对四立柱平台涡激运动性能影响的数值研究

与单立柱平台(Spar)类似,四立柱平台在洋流作用下也容易发生涡激运动,对锚泊和立管系统的疲劳寿命产生不利影响。一种非对称半潜式平台具有两种不同尺寸的立柱,立柱直径比对非对称平台涡激运动性能的影响尚需深入研究。采用计算流体力学(CFD)方法,对直径比分别为1.0、1.5和2.0的立柱组合在两种不同角度水流作用下的运动响应进行了二维数值模拟,分析发现:立柱直径比不为1时四立柱平台也具有明显的涡激运动,其横荡运动具有显著的锁定现象;在广义折合速度定义下,与相同直径的四立柱平台相比,立柱直径比不为1时其横荡运动锁定区间变宽且滞后,横荡响应幅值的峰值具有明显差异;在所研究的直径比范围内,大直径立柱在上游时涡激运动响应比其在下游时更显著,且这种差异随着直径比变大而变大。     

赤道东太平洋SST强增温过程特征分析

本文利用太平洋海温距平场资料,对１９８６年以来发生的厄尔尼诺过程的开始时间、发展过程及强度等方面进行了分析。并与历史上的厄尔尼诺过程进行比较,结果表明,９０年代是厄尔尼诺事件的多发期,在１９９１￣９８年的８年中,间连续发生四次厄经诺事件,其中１９９７￣９８年的厄尔尼诺,成为有历史记录以来最强的一次过程。     

好望角附近海域春季大风的几种主要形势分析

通过普查和分析，概括出了春季好望角附近海域三种主要大风出现时的模型图，并以一个月中逐日4次船舶测风报告为例，分析了好望角大风的某些主要特征。     

Proper motion surveys in the infrared

Current and future wide field surveys in infrared passbands present opportunities for ultra low‐mass stellar sample selection via proper motions, as well as or instead of purely photometric techniques. Furthermore, proper motion measurements yield additional clues as to candidate membership of cluster or field (kinematic) populations. In this paper we review some recent results and speculate as to the possibilities afforded by the next generation of wide‐field infrared surveys. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

CVN硬盘系统和软件相关处理在e-VLBI试验中的应用

介绍了中国VLBI网（CVN）的e-VLBI技术研究进展．CVN包括上海佘山、乌鲁木齐南山2个固定观测站和云南昆明的流动站，以及上海天文台的2台站硬件相关处理机。2003年上海天文台自行研制了基于PC技术的VLBI数据记录、回放系统，命名为CVN硬盘系统，并成功将其安置于CVN观测站和处理机系统。硬件处理机经过改造后，已能处理来自硬盘和原有磁带系统的数据．从2003年至今，中国VLBI网采用该硬盘系统进行了多次VLBI观测和e-VLBI试验。在CVN硬盘系统基础上，软件相关处理技术的研究也得以开展。软件相关处理原型程序已经被用于台站条纹检测、卫星条纹搜索和数据处理中。该软件获得的计算结果被成功用于国内第一个3台站卫星VLBI的延迟和延迟率闭合试验，以及国内首次利用VLBI数据进行的卫星定轨试验。除此之外，该软件还用作硬件处理机的条纹引导器。为适应未来“嫦娥”月球探测工程，CVN将扩展成含有4个观测站和2个相关处理机（硬件、软件）的实时VLBI网。今后，e-VLBI将被应用于月球卫星导航以及测地和天体物理的VLBI观测。     

Simulation of the full two rigid body problem using polyhedral mutual potential and potential derivatives approach

Herein we investigate the coupled orbital and rotational dynamics of two rigid bodies modelled as polyhedra, under the influence of their mutual gravitational potential. The bodies may possess any arbitrary shape and mass distribution. A method of calculating the mutual potential’s derivatives with respect to relative position and attitude is derived. Relative equations of motion for the two body system are presented and an implementation of the equations of motion with the potential gradients approach is described. Results obtained with this dynamic simulation software package are presented for multiple cases to validate the approach and illustrate its utility. This simulation capability is useful both for addressing questions in dynamical astronomy and for enabling spacecraft missions to binary asteroid systems.     

Numerical Stabilization of Orbital Motion

Mainly, the author focuses on Baumgarte's method and its applications in satellite, asteroid, stellar and planetary problems. In the paper arguments are given for the use of energy relations for stabilization in the elliptical two-body problem. Stabilizing properties of Baumgarte's equations and others are discussed. A simple approach is proposed for stabilizing the equations of almost circular motion. By using Baumgarte's technique, the author derives stabilized equations of perturbed restricted three-body problem. It is shown experimentally that stabilization in the problems mentioned above can raise the accuracy of numerical integration by several orders.     

One more explanation of superluminal motion

The occurrence of superluminal motion in extragalactic radio sources is believed to be quite common. Among others, the geometrical scattering of radio radiation can also cause superluminal expansion and or motion and halo formation, In this paper, the effectiveness of the stimulated Raman scattering in producing these features is investigated. The scattering medium is a plasma whose position, density and temperature decide the rate and angle of scattering. When the radiation from a stationary and constant source gets scattered from a stationary plasma, a halo is formed around the source. However, the scattering of a rotating radiation beam does produce superluminal motion of the virtual source. It is found that the plasma should have the characteristics of the emission-line regions and the intercloud medium in order to Raman scatter the radiation. Since the scattering is polarization dependent, it is possible to estimate the rotation of the electric vector along the direction of the apparent motion of a radio source.     

应用GPS观测青藏高原东北缘应力场变化

采用各向同性弹性地球模型推导了地面位移场速率与地壳内任意点应力场变化的边界积分关系,同时利用青藏高原东北缘1999～2001年观测的GPS资料对观测区地壳深度为5 km和25 km的主应力和最大剪应力进行了计算分析.结果表明,青藏高原东北缘的主应力变化主要集中在祁连山断裂、海原断裂等,在1920～1954年间历史上发生过多次震级为7.0～8.5级强震的断裂附近,并具有主应力变化沿断层走向分布、最大剪应力沿断层走向交替变化等特征.     

施密特巡天星表的现状和展望

扼要介绍了施密特巡天底片及基于此编制而成的施密特巡天星表的发展历程,并详细介绍了GSC2.3和USNO-B1.0的情况.分析研究了这类星表存在的问题和原因所在,并提出了一个新的计划:利用现有施密特底片资料并增加新的第3期观测,编制一个具有绝对自行、多色测光、系统均匀的高密度全天星表以满足各方面的需要.