Department of Material Engineering, Chosun University 375, Seosul-Dong, Dong-Gu,Gwangju 501-759, Korea;
Department of Mechanical Engineering, Mokpo National University 61, Dorim-ri,Chungkye-Myun, Muan-Gun, Jconnam 534-729, Korea;
Department of Mechanical Engineering, Chosun University 375, Seosul-Dong, Dong-Gu,Gwangju 501-759, Korea;