1. Associate Professor, Dept. of Safety, Health and Environmental Engineering, National Kaohsiung First Univ. of Science and Technology, #2 Juoyue Rd., Nantsu, Kaohsiung 811, Taiwan (corresponding author).
2. Professor, Dept. of Civil and Environmental Engineering, Utah State Univ., Logan, UT 84322-4110.
3. Professor, Dept. of Environmental Studies, Hankuk Univ. of Foreign Studies, 89 Wangsan-Ri Mohyun-Myun Yongin-Kun, Kyungki-do 449-791, South Korea.
4. Ph.D. Student, Dept. of Safety, Health and Environmental Engineering, National Kaohsiung First Univ. of Science and Technology, #2 Juoyue Rd., Nantsu, Kaohsiung 811, Taiwan.
5. Professor, Dept. of Statistics, Tamkang Univ., Tamsui, Taipei 251, Taiwan.