1. School of Electronic and Information Engineering, Hebei University of Technology, Tianjin 300130, P. R. China
2. School of Mathematics and Information Technology, Hebei Normal University of Science and Technology, Qinhuangdao 066004, Hebei, P. R. China
3. Department of Information Engineering, Qinhuangdao Institute of Technology, Qinhuangdao 066100, Hebei, P. R. China
4. Science and Technology on Electro-Optical Information, Security Control Laboratory, Tianjin 300308, P. R. China