1. School of Instrumentation and Opto-Electronic Engineering, Beihang University, Beijing, People's Republic of China
2. Department of Mechanical Engineering, National University of Singapore, Singapore
3. School of Civil Engineering, Southeast University, Nanjing, Jiangsu, People's Republic of China
4. School of Mechanical Engineering, Shandong University, Jinan, Shandong, People's Republic of China
5. Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea
6. Center for 3D Printing Nondestructive Testing, Korea Advanced Institute of Science and Technology, Daejeon, Korea