1. College of Environmental Science and Engineering, Taiyuan University of Technology, Jinzhong 030600, Shanxi, P. R. China
2. State Key Laboratory of Clean and Efficient Coal Utilization, Taiyuan University of Technology, Taiyuan 030024, Shanxi, China
3. Shanxi Key Laboratory of Gas Energy Efficient and Clean Utilization, Taiyuan University of Technology, Taiyuan 030024, Shanxi, P. R. China
4. Department of Microsystems, University of South-Eastern Norway, Borre 3184, Norway