1. Department of Multimedia and Internet Technology, B322, Hong Kong Institute of Vocational Education (Tsing Yi), Tsing Yi, Hong Kong, China
2. Hong Kong Productivity Council, Tat Chee Road, Kolwoon Tong, Hong Kong, China
3. Department of Electronic and Information Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
4. Warwick Manufacturing Group, International Manufacturing Centre, University of Warwick, Coventry, CV4 7AL, UK