Preface   I am happy that fourth issue of International Journal of Computational and Experimental Science and Engineering (IJCESEN) has been published (3-1;2017). There are 9 papers in this issue. All manuscripts were subjected to the peer review procedure. We appreciate all the authors and reviewers for their valuable contribution in order to achieve a publication of high scientific quality.     Prof.Dr. İskender AKKURT                    Founder-Editor-in-Chief