Cheng, Shulin, 1. School of Computer Engineering and Science, Shanghai University 99 Shangda Road, BaoShan District, Shanghai, 200444, PR, China chengshulin@shu.edu.cn 2. School of Computer and Information, Anqing Normal University 1318 Jixian North Road, Anqing, Anhui Province, 246133, PR, China chengshL@aqnu.edu.cn, China