On September 29, 2021, Dr. Liwei Wu completed the pre defense of his doctoral thesis. Prof. Qing Zhang, Prof. Wenxiong Huang, Prof. Dan Huang, Prof. Tiantang Yu, Prof. Lei Wang, Dr. Yepeng Xu, and Prof. Zaixing Huang of Nanjing University of Aeronautics and Astronautics were specially invited to the pre defense and put forward valuable suggestions on the revision of thesis. It is hoped that Dr. Liwei Wu will maintain his enthusiasm for scientific research and complete the revision of his doctoral thesis according to the suggestions of experts. We wish him every success in his graduation.