Department of Computer Science, University of Missouri, Columbia, MO 65211, USA. chengji@missouri.edu.|Department of Computer Science, University of Missouri, Columbia, MO 65211, USA. chengji@missouri.edu.|Department of Computer Science, University of Missouri, Columbia, MO 65211, USA. chengji@missouri.edu.|Department of Computer Science, University of Missouri, Columbia, MO 65211, USA. chengji@missouri.edu.