1. Professor, Dept. of Ocean Engineering, Univ. of Rhode Island, Narragansett, RI 02882-1197 (corresponding author).
2. Professor, Shandong Provincial Key Lab of Ocean Engineering, Ocean Univ. of China, Qingdao 266100, P.R. China.
3. Ph.D Student, Dept. of Ocean Engineering, Univ. of Rhode Island, Narragansett, RI 02882-1197.