1. State Key Laboratory for Strength and Vibration of Mechanical Structures, Shaanxi Engineering Research Center of NDT and Structural Integrity Evaluation, Xi'an Jiaotong University 1 , Xi'an 710049, China
2. Institute of Applied Mathematics and Mechanics, School of Mathematics and Statistics, Ningxia University 2 , Yinchuan, Ningxia 750021, China
3. Ningxia Basic Science Research Center of Mathematics, Ningxia University 3 , Yinchuan, Ningxia 750021, China
4. School of Mechanical and Electrical Engineering, Guilin University of Electronic Technology 4 , Guangxi, Guilin 541004, China