supervising law enforcement, and protecting resource environment. 

This paper, based on the natural gas CIF of three gas importers, Japan, America and Germany and Brent crude oil price, uses vector auto regressive mode to study their longterm balance and dynamics. The results show a long term balance between the natural gas prices and Brent crude oil prices. Changes of Brent crude oil price by 1% will lead to positive change to the imported natural gas prices by 0.358% in Japan, by 0.061% in America, and by 0.802% in Germany. Variance decomposition indicates the natural gas prices of the three countries and Brent crude oil prices react largely with their own new information, but big difference in duration. In a long term, the natural gas prices will be influenced by Brent crude oil prices, Japan largely, followed by Germany, and then America.

 The Ordovician limestone water is a main threat in mining No.5 coal bed in Fenyuan coal field. This paper applies water inrush coefficient approach to study the water inrush risk of coal floor from water pressure, floor destruction, water resisting capability, confined water level height, and aquiclude thickness in limestone top. Combined with drilling logs, this paper measures water inrush coefficient and draws a contour map, marks safe zones, relative safe zones, relative dangerous zones and dangerous zones, which can provide a reference for mining planning and water disaster prevention.
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