1. School of Management, Huazhong University of Science and Technology, Wuhan, P. R. China
2. Center for Energy & Environmental Policy Research, Beijing Institute of Technology, Beijing, P. R. China
3. School of Management and Economics, Beijing Institute of Technology, Beijing, P. R. China
4. School of Mathematics and Statistics, Huazhong University of Science and Technology, Wuhan, P. R. China