1. School of Environment and Chemical Engineering
2. North China Electric Power University
3. Beijing 102206
4. P.R. China
5. NAAM Research Group
6. Faculty of Science
7. King Abdulaziz University
8. Jeddah 21589
9. Saudi Arabia
10. Department of Mathematics
11. Quaid-I-Azam University
12. Islamabad 44000
13. Pakistan
14. Laboratory SUBATECH
15. UMR Ecole des Mines/CNRS/Universite
16. Nantes cedex 03
17. France