Betül YILDIRIM

Bildiri | 2019 | 39. Yöneylem Araştırması ve Endüstri Mühendisliği Kongresi, Başkent Üniversitesi/Ankara ( Optimization ) , pp.81 - 81

Bildiri

Erkan KÖSE

Makale/Derleme | 2019 | Operational Research

Motivated by the increasing civilian use of Unmanned Aerial Vehicles (UAVs), this paper considers the simultaneous location and routing of UAVs for multiple missions and diferent weather conditions. We include modeling and computational experience inspired by requirements for air surveillance by the Turkish government’s public agencies. We model these demands in multiple mission areas and consider the impact of diferent weather conditions on the ability to employ UAVs from diferent geographic locations. We formulate the problem as a two-stage stochastic integer linear program with recourse and get an optimal solution for realistic t . . .est instances in a reasonable amount of time using decomposition by weather and mission combinations. We also introduce an optimization-based heuristic with bounds based on our decomposition for larger test instances Daha fazlası Daha az

Oğuzhan Ahmet ARIK | Erkan KÖSE

Makale/Derleme | 2019 | GROUP DECISION AND NEGOTIATION

Project scheduling has been still one of the hottest topics in the management area. The goal of traditional project management is to complete the project at the earliest possible time in accordance with the available resources without violating priority relations of the activities involved. Unlike traditional project management, this study deals with the possibility of a coalition among the staf available to accomplish tasks of the project. The tasks can be fulflled by more than one staf members. Staf’s coalition shortens the completion time of the tasks. A natural problem that arises in this case is how to share the income generate . . .d. The other side of the problem is concerned with the project owner who wants the project to be completed as early as possible. In this study, a mathematical model proposal is dealt with in order to realize the goals of both the project owner and the stafs as much as possible within the complex structure of the situation Daha fazlası Daha az

Erkan KÖSE

Makale/Derleme | 2015 | KYBERNETES

Purpose – One important assumption in the conventional cooperative game theory is that payoffs are assumed to be deterministic. In terms of the players’ cognitive ability of the realistic world, this is a very strict assumption. The classical game theory can find no way out when a particular game circumstance involves uncertainty, such as limited knowledge, small sample, and inadequate information, the payoff values of the game can only be described with interval grey numbers. The paper aims to discuss these issues. Design/methodology/approach – In this study the concept of N-person grey games is proposed in which payoffs are repres . . .ented with interval grey numbers opposed to the classical game theory. A straight forward solution methodology is submitted compatible to grey numbers. Then, a currency war between anonymous countries is handled and modeled as an N-Person grey game. A generic currency war scenario is developed to follow the proposed solution procedure thoroughly. Findings – Based on the outcomes of this work, the authors can say that N-person grey game is an expansion of the classical N-person game under uncertain grey information and can be applied in more complex and uncertain environments, such as those seen in complicated currency warfare. Originality/value – This study combines the grey system theory with the classic N-person game theory and sets up the N-person grey game with grey payoff functions. Based on the grey number operating methods, the grey linear programming algorithm is established to calculate and distribute benefits to the players. In this respect this study has the feature of being the pioneer in the N-person grey game area. Daha fazlası Daha az

Erkan KÖSE

Bildiri | 2018 | Fırat University Turkish Journal of Science & Technology13 ( 1 ) , pp.65 - 68

Grey theory is one of the methods used to study uncertainty. The uncertain systems characterized by small sample and poor information are the study object of grey system theory. Multivariable grey prediction models are part of grey forecasting system. They are presented if there are mutual relations among the factors in the system. They believe that all the influencing factors are not independent of each other and should be regarded as a whole. In multivariable grey forecasting models, the future value of a variable is tried to be forecasted considering the other influential factors in the system. In this study, deformation consisti . . .ng on the crest of a Dam is aimed to determine by using multivariable grey prediction models. Gri teori, belirsizliği incelemek için kullanılan yöntemlerden biridir. Sınırlı bilgi ve küçük örnekler ile karakterize edilmiş belirsiz sistemler, gri sistem teorisinin inceleme konusudur. Çok değişkenli gri tahmin modelleri gri tahmin sisteminin parçasıdır. Sistemdeki faktörler arasında karşılıklı ilişkiler varsa onlar temsil edilirler. Etkileyen faktörler birbirinden bağımsız değildir ve bir bütün olarak kabul edilmektedir. Çok değişkenli gri tahmin modeli, bir değişkenin gelecek değerini sistemdeki diğer etkilenen faktörleri göz önüne alarak tahmin etmeye çalışmaktadır. Bu çalışmada, çok değişkenli gri tahmin modeli kullanarak bir barajın kreti üzerinde oluşan deformasyonların tahmin edilmesi amaçlanmıştır Daha fazlası Daha az

Erkan KÖSE

Bildiri | 2018 | Pennsylvania Economic Association 2018 Conference Proceedings , pp.43 - 50

Bildiri

Erkan KÖSE

Bildiri | 2017 | X International Logistics & Supply Chain Congress 2012 Proceedings , pp.150 - 157

Bildiri

Oğuzhan Ahmet ARIK

Makale/Derleme | 2019 | An International Journal of Optimization and Control: Theories & Applications

This paper proposes a credibility based chance constrained programming approach for project scheduling problems with fuzzy activity durations where the objective is to minimize the fuzzy project completion time. This paper expresses the fuzzy events such as a project activity’s duration or project completion time with fuzzy chance constraints and the chance of a fuzzy event is illustrated with fuzzy credibility distribution. Due to uncertainty in durations of a project, fuzzy sets and fuzzy numbers can be used in order to illustrate the uncertainty and find a solution space for the problem. Therefore, fuzzy credibility based chance . . .constraint technique is investigated for project scheduling problems with fuzzy activity durations considering the uncertainty or chance of a fuzzy event within a closed interval. In this paper, a fuzzy mathematical model and its crisp equivalent by using credibility measure and chance-constrained programming are given for project scheduling problems with fuzzy activity durations Daha fazlası Daha az

Oğuzhan Ahmet ARIK

Makale/Derleme | 2018 | New Trends and Issues Proceedings on Humanities and Social Sciences

This paper proposes a mixed integer programming approach for seasonal anomalies in stock markets and presents a case study for the XU030 index in the stock market of Istanbul Stock Exchange (BIST). Stock markets are significant for economies of countries all over the world. Investors get economical wealth or lose some of their investment by selling and buying stocks. Therefore, buying and selling times of stocks are so important. This paper investigates a well-known effect called as ‘Sell in May and Go Away’ by proposing a MIP approach that searches best times for buying and selling of stocks in a year. Furthermore, this paper inclu . . .des a numerical example of XU030 stock prices for the past 5 years and shows that most of the XU030 stocks have seasonal anomalies Daha fazlası Daha az

Oğuzhan Ahmet ARIK

Kitap Bölümü | 2018 | Advanced Fuzzy Logic Approaches in Engineering Science , pp.49 - 67

This chapter presents a mixed integer non-linear programming (MINLP) model for a fuzzy parallel machine scheduling problem under fuzzy job deterioration and learning effects with fuzzy processing times in order to minimize fuzzy makespan. The uncertainty of parameters such as learning/deterioration effects and processing times in a scheduling problem makes the solution of the problem uncertain. Fuzzy sets can be used to encode uncertainty in parameters. In this chapter, possibilistic distributions of fuzzy parameters and possibilistic linear programming approaches are used in order to create a solution method for MINLP model of fuzz . . .y parallel machine scheduling problem Daha fazlası Daha az

Oğuzhan Ahmet ARIK

Makale/Derleme | 2018 | Sakarya Üniversitesi Fen Bilimleri Dergisi

Bu çalışmada tamamıyla bulanık ortamdaki tek makine çizelgeleme probleminde, öğrenme ve bozulma etkileri altındaki işlere ait ağırlıklı erken/geç tamamlanma maliyetlerinin en aza indirilmesi için bulanık karma tamsayılı doğrusal olmayan bir matematiksel model sunulmuştur. Çalışma içerisindeki işlem süreleri, öğrenme etkisi ve bozulma etkisi gibi parametreler belirsizlikleri nedeni ile bulanık sayılar olarak modellenmiştir. Öğrenme ve bozulma etkileri çizelgeleme problemlerinde yirmi yıldır oldukça ilgi görmektedirler. Erken/geç tamamlanma problemleri tam zamanında üretim felsefesini benimseyen üretim firmaları için oldukça önemlidir . . .. Tam zamanında üretim yapan bir işletmenin gerçek hayat karmaşıklığını modelleyebilmek için bulanık küme teorisi ve erken/geç tamamlanma problemleri karma tamsayılı matematiksel modeller ile kullanılabilir. Bu çalışma içerisinde önerilen bulanık matematiksel modelin net eşleniğinin belirli güven aralıklarında oluşturularak çözülmesi için bulanık şans kısıtlı programlama tekniği kullanılmıştır. To minimize total weighted earliness/tardiness costs of the jobs under effects of deterioration and learning on a single machine in a fully fuzzy environment, a mixed integer fuzzy non-linear mathematical programming model is presented in this study. Parameters in this study such as processing times, learning effect and deterioration effect are considered as fuzzy numbers because of their uncertainties. Learning and deterioration effects have been considered in scheduling problems for twenty years. Earliness/tardiness scheduling problems are significant for manufactures that adopt themselves in Just-in-Time philosophy. In order to model the real life complexity of Just-in-Time manufactures, earliness/tardiness scheduling problems can be used with mixed integer mathematical programming models. In this study, fuzzy chance constrained mathematical programming technique is used to find crisp equivalent of the proposed mixed integer fuzzy non-linear mathematical programming model and solve it Daha fazlası Daha az

Oğuzhan Ahmet ARIK

Makale/Derleme | 2018 | International Journal of Production Research

This paper investigates a multi-objective parallel machine scheduling problem under fully fuzzy environment with fuzzy job deterioration effect, fuzzy learning effect and fuzzy processing times. Due dates are decision variables for the problem and objective functions are to minimise total tardiness penalty cost, to minimise earliness penalty cost and to minimise cost of setting due dates. Due date assignment problems are significant for Just-in-Time (JIT) thought. A JIT company may want to have optimum schedule by minimising cost combination of earliness, tardiness and setting due dates. In this paper, we compare different approache . . .s for modelling fuzzy mathematical programming models with a local search algorithm based on expected values of fuzzy parameters such as job deterioration effect, learning effect and processing times Daha fazlası Daha az