1. Postdoctoral Research Fellow, Institute of Engineering, Hiroshima Univ., 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527, Japan.
2. Professor, Institute of Engineering, Hiroshima Univ., 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527, Japan (corresponding author).
3. Professor, Dept. of Marine and Civil Engineering, Chonnam National Univ., 96-1 Yeosu, Jeollanamdo 550-740, Republic of Korea.
4. Professor, Dept. of Rural and Biosystems Engineering, Chonnam National Univ., 77 Yongbong-Ro, Buk-gu, Gwangju 500-575, Republic of Korea.