1. School of Information Science and Engineering, Shandong Normal University, Jinan 250358, P. R. China
2. Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University, Jinan 250358, P. R. China
3. School of Electronic and Information Engineering (Department of Physics), Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, P. R. China
4. School of Information Science and Engineering, Key Lab of Intelligent Computing and Information Security in Universities of Shandong, Shandong Normal University, Jinan 250358, P. R. China