1. Tao Bu, PhD Candidate, School of Economics and Management, Beijing Jiaotong University, Beijing, China
2. Daisheng Tang, Professor, School of Economics and Management, Beijing Jiaotong University, Beijing, China;, Email: Daisheng_Tang@163.com
3. Yahong Liu, PhD Candidate, School of Economics and Management, Beijing Jiaotong University, Beijing, China
4. Dangui Chen, Postgraduate Candidate, School of Economics and Management, Beijing Jiaotong University, Beijing, China