1. School of Electronic and Information Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, P. R. China
2. School of Artificial Intelligence, Nanjing University of Information Science and Technology, Nanjing 210044, P. R. China
3. Collaborative Innovation Center of Memristive Computing Application, Qilu Institute of Technology, Jinan 250200, P. R. China
4. School of Artificial Intelligence and Engineering, Jiangsu Vocational Institute of Commerce, Nanjing 210044, P. R. China