1. Faculty of Software, Fujian Normal University, Fuzhou 350108, P. R. China
2. Department of Statistics, West Virginia University, Morgantown, WV 26506, USA
3. Pathology, Anatomy & Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
4. Computer Science & Elect. Engineering, West Virginia University, Morgantown, WV 26506, USA