1. Research Student, School of Economics and Management, Chang’An Univ., Xi’an, Shaanxi Province 710064, China.
2. Associate Professor, School of Economics and Management, Chang’An Univ., Xi’an, Shaanxi Province 710064, China (corresponding author).
3. Chief Engineer, China Railway First Group Corp., Ltd, #1 Yantabei Rd., Xi’an, Shaanxi Province 710000, China.
4. Professor, School of Civil and Hydraulic Engineering, Huazhong Univ. of Science and Technology, Wuhan, Hubei Province 430074, China.