1. Chongqing Key Laboratory of Nonlinear Circuits and Intelligent Information Processing, College of Electronics and Information Engineering, Southwest University, Chongqing 400715, P. R. China
2. Key Laboratory of Machine Perception and Children’s Intelligence Development, Chongqing University of Education, P. R. China
3. College of Mathematics Science, Chongqing Normal University, Chongqing 401331, P. R. China
4. Texas A&M University at Qatar, Doha, P. O. Box 23874, Qatar