1. Institute of Information Science and Engineering, Ningbo University, Zhejiang 315211, China
2. Qianjiang College, Hangzhou Normal University, Zhejiang 310012, China
3. Faculty of Engineering, The University of Tokushima, Tokushima 770-8506, Japan
4. Center for Advanced Information Technology, The University of Tokushima, Tokushima 770-8506, Japan