1. Dept. of Safety, Health, and Environmental Engineering, National Kaohsiung First Univ. of Science and Technology, Juoyue Rd., Nantsu District, Kaohsiung 811, Taiwan.
2. Dept. of Safety, Health, and Environmental Engineering, National Kaohsiung First Univ. of Science and Technology, Juoyue Rd., Nantsu District, Kaohsiung 811, Taiwan (corresponding author).