1. U.S. Army Research Laboratory, Adelphi, Maryland 20783, USA
2. U.S. Naval Academy, Annapolis, Maryland 21402, USA
3. National Academy of Sciences, National Research Council, Under Research Associateship Program with U.S. Army Research Laboratory, Adelphi, Maryland 20783, USA
4. General Technical Services Under Contract with U.S. Army Research Laboratory, Adelphi, Maryland 20783, USA