1. Dept. of Safety, Health and Environmental Engineering, National Kaohsiung First Univ. of Science and Technology, No. 2 Juoyue Rd., Nantsu, Kaohsiung 811, Taiwan (corresponding author).
2. Dept. of Civil and Environmental Engineering, Utah State Univ., Logan, UT 84322-4110.
3. Dept. of Environmental Studies, Hankuk Univ. of Foreign Studies, 89 Wangsan-Ri Mohyun-Myun Yongin-Kun, Kyungki-do 449-791, South Korea.
4. Dept. of Safety, Health and Environmental Engineering, National Kaohsiung First Univ. of Science and Technology, No. 2 Juoyue Rd., Nantsu, Kaohsiung 811, Taiwan.