1. Department of safety engineering, School of Environmental and Chemical Engineering, Shenyang Ligong University, Shenyang, China
2. Department of Mining Engineering and Metallurgical Engineering, Western Australian School of Mines, Curtin University, Kalgoorlie Australia
3. Department of gas research, Shenyang Research Institute, China Coal Technology & Engineering Group Corp, Fushun, China; State Key Laboratory of Coal Mine Safety Technology, Fushun, China