1. School of Mathematics, Dongbei University of Finance and Economics, Dalian, Liaoning 116025, China
2. School of Management, Dalian University of Finance and Economics, Dalian, Liaoning 116600, China
3. Department of Mathematics, Liaoning Normal University, Dalian, Liaoning 116029, China
4. Center for Studies of Marine Economy and Sustainable Development, Liaoning Normal University, Dalian, Liaoning 116029, China