1. Centre de Recherche, Institut Dupuy de Lôme, Université de Bretagne Sud, EA 4250, Rue de Saint Maudé, BP 92116, F-56100 Lorient, France (corresponding author).
2. Dept. of Mechanical Engineering, Texas A&M Univ., College Station, TX 77843-3123.
3. Dept. of Civil and Environmental Engineering and Engineering Science Programme, National Univ. of Singapore, Kent Ridge, Singapore 119260.