大气参数变化对VLBI对流层时延计算值的影响

本采用我国上海、昆明和乌鲁木齐三个VLBI站的对流层大气高度参数ht和对流层内温度垂直梯度βt参数月均值资料，估计了对干大气时延的影响，结果表明在地平高度ε＝10°－20°时两参数的变化可引起干大气时延周年变化的幅值分别为1-5mm和2-15mm；ht的周日变化也可引起大气时延周日变化约1mm，因此，对于1ps级精度的VLBI物理模型，ht和βt不应当采用测站的固定常数值。     

未来的国际天球参考架

本文简述了国际天球参考架的发展历史和现在射电参考架的现状—基准源选择的标准和参考架的稳定性。描述了地面上光学观测在依巴谷参考架的维持和加密的一系列工作。介绍由天体测量卫星GAIA和SIM给出的天球参考架可能逵到的精度。详述了在今后十年中地面天体测量的作用以及正在开展有关天球参考架的研究课题 ,同时也列出了我国正在和即将开展天体测量的几个研究课题     

活动星系核VLBI观测的新进展

介绍了活动星系核（AGN）的VLBI观测的新近展，特别关注其中心结构和低光度的活动星系核。主要目的是强调VLBI观测在该领域的重要性。     

The Statistical Analysis of Migration of Strong Earthquakes-Taking the North China Region asan Example

The migration of strong earthquakes is an important research topic because the migration phenomena reflect partly the seismic mechanism and involve the prediction of tendency of seismic activity. Research on migration of strong earthquakes has mostly focused on finding the phenomena. Some attempts on getting regularity were comparatively subjective. This paper suggests that there should be indices of migration in earthquake dataset and the indexes should have statistical meaning if there is regularity in the migration of strong earthquakes. In this study, three derivative attributes of migration, i.e., migration orientation, migration distance and migration time interval, were statistically analyzed. Results in the North China region show that the migration of strong earthquakes has statistical meaning. There is a dominant migration orientation (W by S to E by N), a dominant distance ( ≤ 100kin and on the confines of 300 ～ 700km), and a dominant time interval ( ≤ la and on the confines of 3 - 4a). The results also show that the migration will differ slightly with different magnitude range or earthquake activity phase.     

木星土星边缘的椭圆拟合

将CCD观测的木星或土星光环图像二值化，再用“四邻点模板”检测获得二值图像的边缘，最后用椭圆方程迭代拟合边缘，可以获得行星几何中心的位置。这被证明是一种高精度的位置测量方法。本文给出了用椭圆拟合检测边缘的全部公式及有关说明。