1. School of Computer and Information Engineering and Henan Key Laboratory of Big Data Analysis and Processing, Henan University, Kaifeng, China
2. University of Electronic Science and Technology of China, Chengdu, Sichuan, China
3. National Key Laboratory of Fundamental Science on Synthetic Vision, Sichuan University, Chengdu, China
4. Department of Electrical and Computer Engineering, Iowa State University, Ames, IA, USA