1. College of Information Engineering, Shaoguan University, Shaoguan, China
2. School of Information Engineering, Jiangxi University of Science and Technology, Ganzhou, Jiangxi, China
3. College of Information Engineering, Yancheng Teachers University, Yancheng, Jiangsu, China
4. College of Computer Science and Engineering, Central South University, Changsha, China
5. Department of Computer Science, University of California, Davis, CA, USA