1. School of Mathematics, Dongbei University of Finance and Economics, Dalian, Liaoning 116025, China
2. Department of General Studies, Dalian University of Finance and Economics, Dalian, Liaoning 116000, China
3. Department of Mathematics, Liaoning Normal University, Dalian, Liaoning 116029, China
4. Department of General Studies, Dalian Neusoft University of Information, Dalian, Liaoning 116023, China
5. Center for Studies of Marine Economy and Sustainable Development, Liaoning Normal University, Dalian, Liaoning 116029, China