1. Department of Mathematics; Yangzhou University; Jiangsu 225002 China
2. Department of Computer Science; Brunel University London; Uxbridge, Middlesex UB8 3PH UK
3. Faculty of Engineering; King Abdulaziz University; Jeddah 21589 Saudi Arabia
4. Shanghai Key Lab of Modern Optical System, Department of Control Science and Engineering; University of Shanghai for Science and Technology; Shanghai 200093 China