1. Postdoctoral Research Fellow, State Key Laboratory of Traction Power, Southwest Jiaotong Univ., Chengdu 610031, China.
2. Professor, Dept. of Mechanical Engineering, Univ. of Maryland, Baltimore County, Baltimore, MD 21250 (corresponding author).
3. Professor, State Key Laboratory of Traction Power, Southwest Jiaotong Univ., Chengdu 610031, China.
4. Professor, State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum Univ., Chengdu 610500, China.
5. Professor, Dept. of Engineering Mechanics, Tsinghua Univ., Beijing 100084, China.