1. Professor, Changsha Univ. of Science & Technology, Changsha 410076, China; and, Texas Dept. of Transportation, 4203 Bull Creek #39, Austin, TX 78731 (corresponding author).
2. Program Manager, The Transtec Group, Inc. 6111 Balcones Dr., Austin TX 78731.
3. Professor, Changsha Univ. of Science & Technology, Changsha 410076, China.