Tamer Eren

Minimizing the total weighted completion time on a single machine scheduling with release dates and a learning effect

In this study, single machine scheduling problem with unequal release dates and a learning effect is considered. The objective function of the problem is minimization of the total weighted completion time. A non-linear mathematical programming model is developed for the problem which belongs to NP-hard class. Also the model is tested on an example. Results of computational tests show that the proposed model is effective in solving problems with up to 30 jobs.

A bicriteria scheduling with sequence-dependent setup times

In this paper a bicriteria scheduling problem with sequence-dependent setup times on a single machine is considered. The objective function of the problem is minimization of the weighted sum of total completion time and total tardiness. An integer programming model is developed for the problem which belongs to NP-hard class. Results of computational tests show that the proposed model is effective in solving problems with up to 12 jobs. For solving problems containing large number of jobs a special heuristic algorithm is proposed. Besides the proposed heuristic algorithm tabu search based heuristic is also used for large jobs problems. To improve the performance of tabu search method the result of the proposed heuristic algorithm is taken as an initial solution of tabu search method. According to computational results both heuristic algorithms are effective in finding problem solutions with up to 1000 jobs. According to the best of our knowledge, no works exists on the minimization of the weighted sum of total completion time and total tardiness with sequence-dependent setup times.

A note on minimizing maximum lateness in an m-machine scheduling problem with a learning effect

Abstract Conventionally, job processing times are assumed to be constant from the first job to be processed until the last job to be completed. However, recent empirical studies in several industries have verified that unit costs decline as firms produce more of a product and gain knowledge or experience. This phenomenon is known as the “learning effect”. In this paper a m -identical parallel machine scheduling problem with a learning effect is considered. The objective function of the problem is to find a sequence that minimizes maximum lateness. A mathematical programming model is developed for the problem which belongs to NP-hard classes. Also the model is tested on an example. Results of computational tests show that the proposed model is effective in solving problems with 18 jobs and four machines. We also proposed heuristic approach for solving large jobs problems.

A Bicriteria Scheduling Problem with a Learning Effect: Total Completion Time and Total Tardiness

Abstract This paper considers a bicriteria scheduling problem with a learning effect on a single machine to minimize a weighted sum of total completion time and total tardiness. A mathematical programming model is developed for the problem, and optimal solutions are only obtained up to 25 jobs. Since the problem is NP-hard, heuristic methods based on tabu search and random search are proposed to solve large size problems, and their effectiveness is comparatively investigated considering 3600 problems.

A bicriteria flowshop scheduling problem with setup times

Most of research in production scheduling is concerned with the minimization of a single criterion. However, scheduling problems often involve more than one aspect and therefore require bicriteria analysis. In this study, bicriteria two-machine flowshop scheduling problem with setup times is considered. The objective function of the problem is minimization of the weighted sum of total completion time and total tardiness. An integer programming model is developed for the problem which belongs to NP-hard class. Only small size problems with up to 20 jobs can be solved by the proposed integer programming model. Heuristic methods are also used to solve large size problems. These heuristics are four tabu search based heuristics and random search method. According to computational results the tabu search based methods are effective in finding problem solutions with up to 1000 jobs.

Spor Toto Basketbol Süper Ligi ve Turkish Airline Euroleague Basketbol Takımlarının AHS-TOPSIS Yöntemleriyle DeğerlendirilmesiSpor Toto Basketbol Süper Ligi ve Turkish Airline Euroleague Basketbol Takımlarının AHS-TOPSIS Yöntemleriyle Değerlendirilmesi

Basketbol, dunyada en cok izlenen spor alanlarinin basinda gelmektedir. Ulkemizde de basketbolda en cok Spor Toto Basketbol Super ligi ve Turkish Airline Euroleage izlenmektedir. Ulkemizin en iyi basketbol ligi ayni zamanda Avrupa’nin da en iyi ligi olarak kabul edilmektedir. Bu calismada basketbol ligindeki takimlarin degerlendirilmesi, cok olcutlu karar verme yontemleri ile yapilmistir. Kullanilan cok olcutlu karar verme yontemleri analitik hiyerarsi sureci (AHS) ve TOPSIS yontemleridir. Calismada ilk olarak istatistikleri tutulan 10 kriter ele alinmistir. Bu kriterler sirasiyla; sut sayisi, ucluk atma yuzdesi, serbest atis yuzdesi, hucum rebound, savunma rebound, asist, blok, top calma, faul ve skordur. Kriter agirliklari AHS yontemi ile belirlenmis ve TOPSIS yontemi ile de takimlarin siralamasi yapilmistir. Uygulama olarak 2016-2017 sezonu Turkiye Spor Toto Basketbol Ligi ve Turkish Airline Euroleage secilmistir. Cok olcutlu karar verme yontemleri ile bulunan siralama ile normal sezon siralamasinin birbirine yakin sonuclar verdigi gosterilmistir.

Application of Operational Research Techniques in Operating Room Scheduling Problems: Literature Overview

Increased healthcare costs are pushing hospitals to reduce costs and increase the quality of care. Operating rooms are the most important source of income and expense for hospitals. Therefore, the hospital management focuses on the effectiveness of schedules and plans. This study includes analyses of recent research on operating room scheduling and planning. Most studies in the literature, from 2000 to the present day, were evaluated according to patient characteristics, performance measures, solution techniques used in the research, the uncertainty of the problem, applicability of the research, and the planning strategy to be dealt within the solution. One hundred seventy studies were examined in detail, after scanning the Emerald, Science Direct, JSTOR, Springer, Taylor and Francis, and Google Scholar databases. To facilitate the identification of these studies, they are grouped according to the different criteria of concern and then, a detailed overview is presented.

The single machine scheduling problem with sequence-dependent setup times and a learning effect on processing times

Abstract For the past few years, learning effect has been receiving wide attention in the scheduling problems. There are many studies that take into account the learning effect with several structural constraints and some specific conditions of machine scheduling problems. However, very few studies have explored the scheduling problem including learning effect and sequence-dependent setup times simultaneously, although both are found in the scheduling literature. Therefore, this study addresses an NP-Hard problem of minimizing the total tardiness on a single machine with sequence-dependent setup times and a position-based learning effect on processing times. Several dominance properties are verified and a lower bound is provided to develop a branch and bound algorithm for solving the problem. In addition, four heuristic algorithms (two genetic algorithms and two variable neighborhood search algorithms) are developed in order to obtain near optimal solutions in reasonable time limits. Furthermore, some computational experiments are performed on randomly generated test problems to evaluate the performance of the algorithms.

Çok Kriterli Karar Verme Yöntemleriyle Taşeron Firma Seçimi: Kırıkkale İlinde Bir Uygulama

Gunumuz piyasalarinda firmalarin hayatta kalabilmeleri icin rekabet etmeleri gerekmektedir. Arz talep dengesinin yon degistirdigi gunumuzde, firmalar, asil islerini kendileri yapip diger islerini o alanda calisan yetkin firmalara birakmaktadirlar. Bu sayede is gucu ve malzeme envanterlerini minimum seviyede tutarak fazla isgucu ve stok maliyetlerinden kurtulmaktadirlar. Taseron isciler gunumuzde bircok sirket tarafindan yardimci islerde kullanilmaktadir. Bunun baslica sebebi buyuk isletmeler icin dis kaynak kullanimi yoluyla esas yaptiklari uretime odaklanmak iken kucuk isletmeler icin kendi bunyesinde calistirdiklari iscilerin sigorta, sosyal imkân, vb. masraflarindan kurtularak uzerlerindeki bu yuku atarak daha fazla kâr etmektir. Gayrimenkul ve proje sirketleri de ev satmanin yaninda tadilat isleri de yapmaktadir. Bunun icin taseron firma kullanmaktadirlar. Taseron firma kullanimina en fazla ihtiyac duyulan sektorlerden birisi de insaat sektorudur. Bu amacla Kirikkale ilinde faaliyet gosteren bir gayrimenkul ve proje sirketinin anahtar teslim tadilat isi icin taseron firma secimi problemi ele alinmistir. Problemin cozumunde cok kriterli karar verme (CKKV) yontemlerinden Analitik Ag Sureci ve PROMETHEE yontemlerinden yararlanilmistir. Taseron firma secimine etkiyen kriterlerin agirliklarinin belirlenmesinde Analitik Ag Sureci yontemi kullanilmistir. Analitik Ag Sureci yontemi ile bulunan kriter agirliklari kullanilarak PROMETHEE yontemi ile alternatif firmalarin siralamasi yapilmistir. PROMETHEE I kismi siralama sonucuna gore MAK firmasi diger alternatiflere tam ustunluk saglarken, diger alternatiflerin net siralamasi cikarilamamaktadir. Bu sebeple PROMETHEE II ile net ustunlukler siralandiginda yine MAK sirketi net ustunluk saglayarak yapilacak isi almistir.

A Disassembly Line Balancing with Multicriteria Decision Making

Waste is increasing rapidly because of developments in the world. It would be economic return when the waste assesses truly, but when it is not assess, it is a financial loss as well as a serious problem for countries. Useful parts can be separated at the recycling facility in disassembly process. In this study, a disassembly line balancing problem is considered. The disassembly line is a part of recycling process on which parts are separated to subparts in stations. Ideal disassembly orders of pieces are determined by various criteria and also a time factor is taken into account. AHP and PROMETHEE methods that are multi-criteria decision-making methods are used to solve problem for determining disassembly orders. Weights of criteria are determined with AHP and subparts’ disassembly orders are obtained with PROMETHEE.