1. The Engineering Institute, Los Alamos National Laboratory, Los Alamos, NM 87545.
2. Dept. of Computer Science and Engineering, Univ. of California, San Diego, La Jolla, CA 92093-0114.
3. Dept. of Structural Engineering, Univ. of California, San Diego, La Jolla, CA 92093-0085.
4. Dept. of Electrical and Computer Engineering, Univ. of California, San Diego, La Jolla, CA 92093-0701.