1. School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China;
2. School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China
3. School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China e-mail:
4. School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China
5. School of Mathematical Sciences, Queensland University of Technology, GPO Box 2434, Brisbane, QLD 4001, Australia