1. Dept. of Industrial Engineering, Univ. of Houston, E206 Engineering Bldg. 2, 4722 Calhoun Rd., Houston, TX 77204-4008 (corresponding author).
2. Boeing Research and Technology, Seattle, WA 98124.
3. Dept. of Industrial Engineering, Univ. of Houston, E206 Engineering Bldg. 2, 4722 Calhoun Rd., Houston, TX 77204-4008.