1. School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China
2. College of Mining Engineering, Taiyuan University of Technology, Taiyuan 0330024, China
3. Shanxi Key Laboratory of Coal and Coal Measure Gas Geology, Taiyuan 0330024, China
4. School of Instrument Science and Optoelectronics Engineering, Hefei University of Technology, Hefei 230009, China