1. Graduate Inst. of Vehicle Engineering, National Changhua Univ. of Education, Number 1, Jin-De Rd., Changhua City, 500, TW (Corresponding author), e-mail: scyang57@cc.ncue.edu.tw
2. Graduate Inst. of Vehicle Engineering, National Changhua Univ. of Education, Number 1, Jin-De Rd., Changhua City, 500, TW