1. Faculty of Information Science and Engineering, Ningbo University, Ningbo, China
2. College of Science and Technology, Ningbo University, Ningbo, China
3. School of Computer Science and Technology, Hangzhou Dianzi University, Hangzhou, China
4. School of Information Science and Engineering, Hunan University, Changsha, China
5. Department of Information Engineering and Computer Science, Feng Chia University, Taichung, Taiwan