Using vector-analysis, three kinds of roof blocks at the end face of fully mechanized long wall faces have been studied. The result'indicates that with face
The life cycle of technology is one of the most important indexes to weigh up the risk of the investment to neo-tech, There are so many uncertainties because it
It is necessary to set up a new mathematical model of steam coal blending instead of the old model. Indexes such as moisture content, ash content, volatile matt