1. a Ningxia Hydrology and Water Resources Monitoring and Early Warning Center, Yinchuan 750000, China
2. b School of Business, Hohai University, Nanjing 211100, China
3. c School of Economics and Finance, Hohai University, Changzhou 213200, China
4. d School of Marxism, Hohai University, Nanjing 211100, China