1. Associate Professor, Computer Science Department, Old Dominion University, Norfolk, VA 23529-0162, USA
2. Associate Research Fellow, ICASE, NASA Langley Research Center, Hampton, VA 23681-0001, USA
3. Graduate Research Assistant, Computer Science Department, Old Dominion University, and an ICASE intern, USA
4. Computer Scientist in the Mathematics and Computer Science Division at Argonne National Laboratory, Argonne, IL 60439-4844, USA