1. Department of Electrical Engineering, Chulalongkorn University, Bangkok 10330, Thailand
2. Department of Mechanical Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia
3. Department of Chemical Engineering, Chulalongkorn University, Bangkok 10330, Thailand
4. Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, Kanagawa 226-8501, Japan