1. Department of Electrical and Computer Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260
2. Institute of Complexity Science College of Automation Engineering, Qingdao University, Qingdao 266071, China
3. Faculty of Mathematics and Mechanics, St. Petersburg State University, Universitetskij pr. 28, Petrodvoretz, St. Petersburg 198504, Russia