1. Nanyang Research Institute of Big Data, Nanyang Institute of Technology, Nanyang 473004, China
2. School of Computer and Software, Nanyang Institute of Technology, Nanyang 473004, China
3. School of Information Engineering, Nanyang Institute of Technology, Nanyang 473004, China
4. Department of Informatics, University of Leicester, University Rd, Leicester LE1 7RH, UK