1. College of Automation, Nanjing University of Aeronautics and Astronautics, Nanjing 211100, China
2. Nondestructive Detection and Monitoring Technology for High Speed Transportation Facilities, Key Laboratory of Ministry of Industry and Information Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China
3. College of Electrical and Information Engineering, Lanzhou University of Technology, Lanzhou 730050, China