Dept.of Naval Architecture and Ocean Eng.,Chosun University,Kwangju 501-759,Korea;
Dept.of Automotive Eng.,Woosuk University,Samrae-up,Wanju-kun,Chonbuk,565-701,Korea;
Center for Nondestructive Evaluation,Iowa State University,Ames,Iowa 50011,USA;
Division of Precision Mec.Eng.,Chonbuk National University,Jeonju 561-756,Korea;
School of Mechanical Engineering,Chosun University,Kwangju 501-759,Korea;