1. School of Automation and Information Engineering
2. Xi'an University of Technology
3. Xi'an 710048
4. Republic of China
5. College of Optoelectronics Technology
6. Chengdu University of Information Technology
7. Chengdu 610225
8. People's Republic of China
9. School of Physics & Astronomy
10. Queen Mary University of London
11. London E1 4NS
12. UK