Potentially Environmentally Detrimental

PED-graphs are a class of new defined graphs by Qiongxiang Huang in 2006, the nullity of PED-graphs has been studied in depth.

PED-图是黄琼湘教授在2006年定义的一类新图,并对其零化度进行了深入的研究。

This paper describes the present situation of our country's undermine communication, and introduces the principle of PED system and current development and utilization of PED system.

简单叙述了我国井下通信的现状,介绍了PED系统的原理及矿井PED系统目前的发展和应用情况。