1. Infrastructure Inspection Research Institute, China Academy of Railway Sciences Corporation Limited, No. 2, Daliushu Road, Haidian District, Beijing 100081, P. R. China
2. INMAI Railway Technology Co., Ltd., No. 2, Daliushu Road, Haidian District, Beijing 100081, P. R. China
3. School of Computer Science and Engineering, Nanjing University of Science and Technology, No. 200, Xiaolingwei Road, Xuanwu District, Nanjing 210094, P. R. China