1. College of Safety Science and Engineering, Xi’an University of Science and Technology, Xi’an, 710054 Shaanxi, P. R. China
2. Key Laboratory of Western Mine and Hazard Prevention, Ministry of Education of China, Xi’an, 710054 Shaanxi, P. R. China
3. College of Energy Engineering, Xi’an University of Science and Technology, Xi’an, 710054 Shaanxi, P. R. China