1. School of Information Sciences and Technology, Northwest University, Xi'an, Shaanxi 710127, China
2. School of Computer Science and Information Engineering, Hefei University of Technology, Hefei, Anhui 230601, China
3. Engineering Research Center of Virtual Reality and Applications, Ministry of Education, Beijing Key Laboratory of Digital Preservation and Virtual Reality for Cultural Heritage, Beijing Normal University, Beijing, China
4. Engineering Research Center of Molecular and Neuro Imaging of Ministry of Education & School of Life Science and Technology, Xidian University, Xi'an, Shaanxi 710071, China