1. School of Economics and Management, Yan’an University, Yan’an 716000, China
2. Soft Science Research Base for Green and Low Carbon Development of Energy Industry in Shaanxi Province, Yan’an University, Yan’an 716000, China
3. Graduate School, Xi’an University of Science and Technology, Xi’an 710054, China
4. Medical School, Yan’an University, Yan’an 716000, China
5. School of Mines: Minerals, Energy and Chemical Engineering, Faculty of Science and Engineering, Curtin University, Perth 6945, Australia