On the Spectral Index－Flux Density Relation for Large Samples of Radio Sources

We present new statistical results on the spectral index-flux density relation for large samples of radio sources using archival data of the most sensitive surveys, such as 6C, Miyun, WENSS, B3, NVSS, GB87. Instrumental selection effects and the completeness of the catalogs are discussed. Based on the spectral indices calculated for about 200 000 sources from the WENSS (327 MHz) and NVSS (1.4 GHz) catalogs, we obtained (1) The median spectral index increases from amed --0.9 toαmed --0.8 (Svαvα), while S327 flux densities decrease from 0.1 Jy down to 25mJy. The median spectral indices nearly show no variation within the error bars when the flux density is larger than 0.1 Jy. (2) A dependence of the fraction of ultra-steep spectrum sources (USS, -1.5 <α<-1.0), steep spectrum sources (SSS, -1.0 <α< -0.5) and flat spectrum sources (FSS, -0.5≤α≤0.0) is partly responsible for the spectral flattening. Another contribution to the spectral flattening comes from the variation of αmed of steep spectrum so     

建立在PC机上的区域化探数据库系统

建立在ＰＣ机上的区域化探数据库系统李松（辽宁有色地球物理勘查大队）一、系统设计的基本思想１．数据库系统的硬件运行环境为ＩＢＭＰＣ／ＸＴ机或兼容机和针式打印机。２．在中文状态下进行人机对话，给出必要的提示，便于用户使用。３．可以用多种方式录入数据，能够...     

通过微机管理软件的设计

本将数据库与应用程序分开，应用程序只从数据字典中取出数据库信息，解决了微机管理软件的通用性问题，对数据字典的三个件库结构进行了较详细的叙述。     

新型波浪采集系统平台设计

主要介绍了新型波浪采集系统的设计思想与主要参数，采集、存储、运算和电源控制部分的结构与组成，以及各部分的特点和关键技术。     

全数字十二相稳压稳流微机控制系统

提出用于十二相可控整流器的８０９８单片机控制系统的电路原理和软件策略。包括自适应控制算法和触发相序计算在内的多种操作全部用软件实现．与通常的方法相比，此系统的成本更低，动态性能和静态性能更好。