Preface

The Conference Optimization is a process to achieve the ideal or optimal value of an objective function. In the discipline of mathematics, optimization also refers to the study of problems trying to find the minimum and maximum values of a real function. To achieve these minimum and maximum values, some processes were systematically carried out by selecting integers or real numbers that will provide optimal solutions. The true discriminant between “easy” and “hard” optimization problems in mathematical programming is the convex/non-convex issue. A problem is convex if it is a minimization of a convex function (or a maximization of a concave function) where the admissible points are in a convex set. The fundamental result in convex analysis says that a locally optimal solution of a convex problem is also globally optimal. This is practically very important since algorithmic termination tests occur at each iteration in the algorithm, they must be computationally very efficient; thus, virtually all termination conditions of optimization algorithms are local conditions, i.e. they test whether the current solution is locally optimal with respect to a pre-defined neighborhood. If the problem is convex this is enough to guarantee that the solution is globally optimal. Non-convex problems, on the other hand, may have many different local optimal, and choosing the best one is an extremely hard task. The field of applied mathematics that studies extremal locations of non-convex functions subject to (possibly) non-convex constraints is called Global Optimization. Research on global optimization has been continuing rapidly and many of the findings are of new techniques that are more sophisticated and efficient. The 7th International Conference on Global Optimization and Its Application (ICoGOIA) 2018 is hosted and organized by Faculty of Mathematics and Natural Sciences Universitas Pakuan, Indonesia. List of Conference Publication, Conference Theme, Organization, Participants, Committee, Secretariat, Welcoming Speech, Table of Contents and all the titles are available in this pdf.

The Conference Optimization is a process to achieve the ideal or optimal value of an objective function. In the discipline of mathematics, optimization also refers to the study of problems trying to find the minimum and maximum values of a real function. To achieve these minimum and maximum values, some processes were systematically carried out by selecting integers or real numbers that will provide optimal solutions.
The true discriminant between "easy" and "hard" optimization problems in mathematical programming is the convex/non-convex issue. A problem is convex if it is a minimization of a convex function (or a maximization of a concave function) where the admissible points are in a convex set. The fundamental result in convex analysis says that a locally optimal solution of a convex problem is also globally optimal. This is practically very important since algorithmic termination tests occur at each iteration in the algorithm, they must be computationally very efficient; thus, virtually all termination conditions of optimization algorithms are local conditions, i.e. they test whether the current solution is locally optimal with respect to a pre-defined neighborhood. If the problem is convex this is enough to guarantee that the solution is globally optimal. Non-convex problems, on the other hand, may have many different local optimal, and choosing the best one is an extremely hard task.
The field of applied mathematics that studies extremal locations of non-convex functions subject to (possibly) non-convex constraints is called Global Optimization. Research on global optimization has been continuing rapidly and many of the findings are of new techniques that are more sophisticated and efficient.
The 7th International Conference on Global Optimization and Its Application (ICoGOIA) 2018 is hosted and organized by Faculty of Mathematics and Natural Sciences Universitas Pakuan, Indonesia.

Conference Publication
All papers received are reviewed by two peer reviewers and selected papers will be published in IOP Conference Series: Materials Science and Engineering, indexed by SCOPUS. On behalf of the Conference Committee, I would like to welcome all attendees and thank you for your presence in this conference. In particular we would like to thank the Rector of Universitas Pakuan for their willingness to give a speech and at the same time officially open this conference. Thank you also to the Keynote Speakers and the speakers and conference participants who have attended this conference.
The holding of this conference aims to gather researchers, lecturers, and observers of science and technology to gather together to share knowledge and experience in optimizing activities in various fields. Therefore, this conference took the theme "Optimization of Green Science and Technology for Collaboration Sustainability." This international conference is a series of conference activities that have been carried out previously and the conference that we held in 2018 is a conference for the seventh time. Therefore, we call it "The 7th ICoGOIA 2018".
Distinguished ladies and gentlemen.
We report that this conference will be attended by 113 participants from 10 countries and 20 institutions/universities. There are the same number of papers which will be presented and discussed in this conference. Some of the papers discussed in this conference will be published in Scopus indexed IOP Publications and parts of the others will be published in proceedings from this international conference.
In this good opportunity, once again we would like to thank the Rector of Universitas Pakuan for their support, the speakers for the contribution of the paper, and thank you also to the steering committee and the organizing committee so that the 7th Icogoia conference 2018 was held at Discovery Kartika Hotel Denpasar Bali Indonesia can be carried out properly. Do not forget we remind you that in addition to following the ICoGOIA conference we also recommend you to explore the island of Bali to enjoy the foods and its natural beauty. Have a nice conference and pleasant stay at Bali. We know that to organize an international conference is needed a hard works and many preparations. But I do believe that in the near future ICoGOIA will be able to promote the increase of the publication from many researchers and university lectures. This event can be considered as good platforms for researchers, academicians and professionals in Indonesia and also researchers, academicians and professionals from other countries to meet each other, exchange ideas and strengthen their collaboration in the field of science and technology. I would also like to thank Dr. Prasetyorini the Dean of Mathematic and Natural Sciences (FMIPA) of Universitas Pakuan and all members of Organizing Committee who have worked very hard so that this conference can be held properly.

Welcoming Speech
Finally, I wish all participants enjoy a most fruitful day with interesting and stimulating discussions and exchange of knowledge in this conference.
Thank you very much.