1. Chongqing University, State Key Laboratory of Coal Mine Disaster Dynamics and Control Shazheng Street 174 400044 CHONGQING, P. R. CHINA
2. Henan University of Technology, College of Environmental Engineering Lianghua Street 100 450001 ZHENGZHOU, P. R. CHINA
3. Yibin University, College of Resources and Environmental Engineering Jiusheng Street 8 644000 YIBIN, P. R. CHINA