1. Ph.D. Candidate, College of Management and Economics, Tianjin Univ., Tianjin 300072, P.R. China.
2. Professor, College of Management and Economics, Tianjin Univ., Tianjin 300072, P.R. China.
3. Ph.D. Candidate of Civil Engineering, School of Natural and Built Environment, Queen‘s Univ. Belfast, Belfast BT7 1NN, UK (corresponding author).