1. Ph.D. Candidate, Center for Green Engineering and Sustainable Development, College of Transportation Engineering, Chang’an Univ., Middle Section of South Second Ring Rd., Xi’an, Shaanxi 710064, China.
2. Professor, Center for Green Engineering and Sustainable Development, School of Economics and Management, Chang’an Univ., Middle Section of South Second Ring Rd., Xi’an, Shaanxi 710064, China (corresponding author).