1. School of Economics, Ocean University of China, Qingdao 266100, China
2. Marine Development Studies Institute of OUC, Key Research Institute of Humanities and Social Sciences at Universities, Ministry of Education, Qingdao 266100, China
3. College of Transportation, Shandong University of Science and Technology, Qingdao 266590, China
4. School of Transportation Engineering, Shandong Jianzhu University, Ji’nan 250101, China