1. Assoc. Prof., Dept. of Civ. Engrg. and Mech., Univ. of Wisconsin-Milwaukee, P.O. Box 784, Milwaukee, WI 53201. E-mail: helwany@ uwm.edu
2. Prof., Dept. of Civ. Engrg. and Engrg. Mech., Univ. of Arizona, Tucson, AZ 85721. E-mail: budhu@u.arizona.edu
3. Dir., Center of Complex Distributed Systems, Lawrence Livermore Nat. Lab., L-126, Livermore, CA 94550. E-mail: mccallen2@llnl.gov