[1] Georgetown Univ, Dept Phys, Washington, DC 20057 USA
[2] George Mason Univ, Sch Computat Sci, Fairfax, VA 22030 USA
[3] Howard Univ, Sch Engn, Dept Elect Engn, Washington, DC 20059 USA
[4] Howard Univ, Sch Engn, Math Sci Res Ctr, Washington, DC 20059 USA
[5] USN, Res Lab, Ctr Computat Mat Sci, Washington, DC 20375 USA