1. School of Computer and Information Technology at the Xinyang Normal University, No.237, Nanhu Road, Xinyang 464000, Henan Province, P.R. China
2. Department of Computer Science at the Virginia Commonwealth University, 401 West Main Street, Room E4225, Richmond, Virginia 23284, USA
3. Department of Computer Science from the Virginia Commonwealth University, 401 West Main Street, Room E4225, Richmond, Virginia 23284, USA