Type the abstract (100 to 150 words) using Italic font with point size 10. The abstract is an essential part of the paper. Use short, direct, and complete sentences. It should be as brief as possible and concise. It should be complete, selfexplanatory, and not require reference to the paper itself. The abstract should be informative giving the scope and emphasize the main conclusions, results, or signi  cance of the work described. Do not use the  rst person; do not include mathematical expressions; do not refer to the references