1. Ph.D. Candidate, Train & Track Research Institute, State Key Laboratory of Traction Power, Southwest Jiaotong Univ., Chengdu 610031, P.R. China.
2. Professor, Train & Track Research Institute, State Key Laboratory of Traction Power, Southwest Jiaotong Univ., Chengdu 610031, P.R. China (corresponding author).
3. Professor, Train & Track Research Institute, State Key Laboratory of Traction Power, Southwest Jiaotong Univ., Chengdu 610031, P.R. China.