Endüstri Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/279
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Article Design of a Distribution Network for the School Lunch Program(Academic Publication Council, 2023) Aydemir-Karadag, Ayyuce; Akdere, Erol; Karadag, Ayyuce AydemirThe national school lunch program (NSLP) is crucial for providing healthy, inexpensive, or free lunches to children, thus benefiting society. Designing a distribution network for the program requires solving a location and routing problem. In this paper, first, we formulate a multi -objective non-linear integer programming formulation of the problem. Next, we develop a two-step approach since the problem is Np-hard. The first stage presents a K -mean clustering method that deals with routing decisions by determining the locations of food processing centers and allocating schools to these centers. The second stage offers a multi -objective mixed -integer linear mathematical model for finding the locations of distribution centers. Besides economic and environmental factors, we optimize travel time in the network as perishable items are involved. A weighted sum approach is presented for different weights of objectives. We provide a real case study in Turkey to demonstrate the applicability of the two -stage approach proposed in this study. The numerical results provide valuable information for decision -makers and authorities to prioritize and prepare action plans.Article Citation - Scopus: 4Scheduling With Lot Streaming in a Two-Machine Re-Entrant Flow Shop(Regional Association for Security and crisis management, 2021) Duman, M.; Çetinkaya, F.C.Lot streaming is splitting a job-lot of identical items into several sublots (portions of a lot) that can be moved to the next machines upon completion so that operations on successive machines can be overlapped; hence, the overall performance of a multi-stage manufacturing environment can be improved. In this study, we consider a scheduling problem with lot streaming in a two-machine re-entrant flow shop in which each job-lot is processed first on Machine 1, then goes to Machine 2 for its second operation before it returns to the primary machine (either Machine 1 or Machine 2) for the third operation. For the two cases of the primary machine, both single-job and multi-job cases are studied independently. Optimal and near-optimal solution procedures are developed. Our objective is to minimize the makespan, which is the maximum completion time of the sublots and job lots in the single-job and multi-job cases, respectively. We prove that the single-job problem is optimally solved in polynomial-time regardless of whether the third operation is performed on Machine 1 or Machine 2. The multi-job problem is also optimally solvable in polynomial time when the third operation is performed on Machine 2. However, we prove that the multi-job problem is NP-hard when the third operation is performed on Machine 1. A global lower bound on the makespan and a simple heuristic algorithm are developed. Our computational experiment results reveal that our proposed heuristic algorithm provides optimal or near-optimal solutions in a very short time. © 2021 by the authors. Submitted for possible open access publication under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).Article Marjinal Analiz Yoluyla Güvenilirlik Optimizasyonu(2005) Yüceer, ÜmitMarjinal analizin güvenilirlik redandansı optimizasyonuna bir uyarlaması anlatılmaktadır. Amaç fonksiyonu ayrışık hale dönüştürülüp, konkav olduğu gösterilecek ve marjinal analiz metodunun çok seri ve hızlı bir şekilde, optimal olmasa bile, optimala çok yakın çözümler ürettiği bir örnekle gösterilecektir.Article Kamu Kurumlarında Risk Değerlendirmesi İçin Karar Destek Sistemi Önerisi(2018) Tok, Elif Gülce; Satır, Benhür6331 Sayılı İş Sağlığı ve Güvenliği (İSG) Kanunu’nun 31.12.2012’de yürürlüğegirmesinden itibaren risk değerlendirmesi bütün işyerlerinde zorunlu halegelmiştir. Bu çalışmada iş sağlığı ve güvenliğinin önemli bir öğesi olan riskdeğerlendirmesinin kamu kurumlarında yapılmasını daha sağlıklı hale getirecekve kolaylaştıracak bir rehber hazırlanmıştır. Bu rehber bir kontrol listesi ve ilgilirisk tablosundan oluşmaktadır. Gerek ülkemizdeki 6331 Sayılı İSG Kanununda veilgili yönetmeliklerde, gerekse de OHSAS 18001 İSG Yönetim Sisteminde, sürekliiyileştirmenin önemi açıkça görülmektedir. Bu çalışmada hazırlanan rehberinuygulanmasında riskin kabul edilebilir seviyeye inene kadar risk değerlendirmesiniizlemeyi sistemli ve kolay hale getirerek sürekli iyileştirmenin gereklerini sağlamaküzere bir Karar Destek Sistemi önerilmiştir. Birim, kaynak ve tehlike parametreleribir bütün olarak ele alınarak BKT olarak değerlendirilmiş ve sistemin veri tabanıaltyapısı bunun üzerine kurulmuştur. Risk değerlendirmesinin ana öğeleri olan BKT,risk ve önlem ilişkilerinin Varlık-İlişki Çiziti hazırlanarak en büyük ve en küçükkardinallik oranları her ilişki arasında tanımlanmıştır. Fikir vermesi açısından bazı kullanıcı arayüzleri tasarlanmış ve önerilmiştir. Farklı sektörlerde yapılmış benzerçalışmalar mevcuttur ancak gerek kamu kurumları düşünüldüğünde gerekse deuygulama için önerilen karar destek sistemi düşünüldüğünde bu çalışma bilgimizdahilinde literatürdeki ilk çalışmadır.Article Broiler House Performance Analysis and Chick Entrance Planning for a Broiler Chicken Integration(2012) Satır, Benhür; Yıldırım, Gonca; Kırca, ÖmerIncreasing rates of chicken meat production has a substantial impact on the Turkish economy. Per capita production in Turkey is close to the average production of the top 20 countries in the world. The production is done by integrated organizations, incorporating an integrator chicken company affiliated with all aspects of the production in an organization. There are many complicated processes, stages and parties involved in a typical integration, bringing with them many interesting problems. In this paper, we focus on tactical and operational decisions required during the broiler growing stage, motivated by the requirements of a moderate-sized integrator in the Marmara Region of Turkey. We use analysis of variance to compare the performances of available broiler houses, and to find the factors effecting the performance measures. Then, we present a mixed-integer linear program which uses the results of our performance analysis to find the least costly set of broiler houses with which the integrator should work, and the chick entrance times into these houses over a planning period.Article Basit Doğrusal Otoregresif Modeller Sisteminde Parametre Tahmini ve Hipotez Testi: Simetrik İnovasyonlar(2005) Türker, Özlem; Akkaya, Ayşen D.Bu çalışmada, simetrik dağılıma sahip hata terimli basit otoregresif modeller sistemi incelenerek normal dağılım varsayımının geçersiz olduğu durumlardaki metodoloji birden fazla bağımsız bilgi kaynağı olduğu durumlara genellenmiş, uyarlanmış en çok olabilirlik yöntemi ile tahmin ediciler elde edilmiş ve parametre vektörünün tüm kaynaklar için değişip değişmediğini test edecek sağlam ve etkin test istatistikleri geliştirilmiştir. Elde edilen tahmin ediciler ve test istatistikleri bu alandaki uygulamalarda sıkça kullanılan en küçük kareler yöntemi ile elde edilen tahmin edici ve test istatistikleri ile karşılaştırılmış ve daha iyi sonuçlar verdiği görülmüştür.Article Citation - WoS: 12Analysis of Dengue Transmission Dynamic Model by Stability and Hopf Bifurcation With Two-Time Delays(Imr Press, 2023) Ambalarajan, Venkatesh; Sivakumar, Vinoth; Dhandapani, Prasantha Bharathi; Baleanu, Dumitru; Murugadoss, Prakash RajBackground: Mathematical models reflecting the epidemiological dynamics of dengue infection have been discovered dating back to 1970. The four serotypes (DENV-1 to DENV-4) that cause dengue fever are antigenically related but different viruses that are transmitted by mosquitoes. It is a significant global public health issue since 2.5 billion individuals are at risk of contracting the virus. Methods: The purpose of this study is to carefully examine the transmission of dengue with a time delay. A dengue transmission dynamic model with two delays, the standard incidence, loss of immunity, recovery from infectiousness, and partial protection of the human population was developed. Results: Both endemic equilibrium and illness-free equilibrium were examined in terms of the stability theory of delay differential equations. As long as the basic reproduction number (R0) is less than unity, the illness-free equilibrium is locally asymptotically stable; however, when R0 exceeds unity, the equilibrium becomes unstable. The existence of Hopf bifurcation with delay as a bifurcation parameter and the conditions for endemic equilibrium stability were examined. To validate the theoretical results, numerical simulations were done. Conclusions: The length of the time delay in the dengue transmission epidemic model has no effect on the stability of the illness-free equilibrium. Regardless, Hopf bifurcation may occur depending on how much the delay impacts the stability of the underlying equilibrium. This mathematical modelling is effective for providing qualitative evaluations for the recovery of a huge population of afflicted community members with a time delay.Article Citation - WoS: 4Citation - Scopus: 4A Bi-Objective Integrated Mathematical Model for Blood Supply Chain: Case of Turkish Red Crescent(Amer inst Mathematical Sciences-aims, 2023) Yolcu, Vahdi; Satir, Benhur; Satr, BenhurVarious criteria feature in blood supply chain (BSC) designs, where cost-based and time-based are the most commonly found in the literature. In the current study, total annual cost is used together with a new time-based objective. The total time spent in the transportation of blood products is considered as time lost, and weight is given to that time according to the product amount and then normalized with respect to shelf life. In using cost and time objectives, we developed a bi-objective mixed-integer mathematical programming model for the BSC of Turkish Red Crescent (TRC, the singular authority controlling BSC throughout Turkey), including collection, production, and distribution echelons, and also considering bag-type decisions for whole-blood collection. The objective of the study was to propose a BSC design model and solution approach. With all real-life TRC instances resolved optimally, a linear programming relaxation-based heuristic was developed for large-scale problem sizes. Real-life data were obtained from the TRC and the remainder from open-to-public sources. The study's main finding is that cost and time objectives alone produce significantly different designs, whilst using them together to form efficient-frontier solutions for decision-makers adds practical value.Article Citation - WoS: 8Citation - Scopus: 9Intermodal Humanitarian Logistics Using Unit Load Devices(Springer Heidelberg, 2022) Kavlak, Hasan; Ertem, Mustafa Alp; Satir, BenhurIntermodal freight transportation facilitates today's global trade. The benefits of intermodal freight transportation have been studied and are more observable in commercial logistics; however, the potential benefits of humanitarian logistics have not been thoroughly investigated. This research aims to present a resilient transportation framework by modeling intermodal transportation utilizing interoperable loading devices during disaster responses. We developed an integer programming model based on a time-space network by considering route and vehicle availabilities that are allowed to change with time. We consider vehicles with varying capacities in three transportation modes (i.e., ground, maritime, and air). The contribution of this study is threefold: (1) Two compatible unit load devices are proposed for humanitarian logistics; (2) a mathematical model that includes integer variable representation for vehicle fleets in different transportation modes is developed; and (3) intermodal transportation is compared with single-mode transportation using a real-life dataset. Our main results are as follows: In terms of cost, intermodal transportation is effective when demand occurs in consecutive periods and response time is short. Inventory is held more in intermodal transportation when it is cost-effective to use transportation modes with large capacities. Thus, the benefits of the responsiveness of intermodal transportation outweigh the costs of mode interchange and inventory holding for sudden-onset disasters where quick responses are needed within a short time.Article Citation - WoS: 1Citation - Scopus: 1Designing an Annual Leave Scheduling Policy: Case of a Financial Center(Amer inst Mathematical Sciences-aims, 2022) Aydemir-Karadag, Ayyuce; Yildirim, GoncaProviding annual leave entitlements for employees can help allevi-ate burnout since paid-time off work directly affects the health and productivity of workers as well as the quality of the service provided. In this paper, we de-velop realistic vacation scheduling policies and investigate how they compare from both the employer and the employees' perspectives. Among those poli-cies, we consider one that is used in practice, another that we propose as a compromise which performs very well in most cases, and one that is similar to machine scheduling for benchmarking. Integer programming models are for-mulated and solved under various settings for workload distribution over time, substitution and unit of time for vacations. We use three performance mea-sures for comparisons: penalty cost of unused vacation days, percent vacation granted and level of employee satisfaction. We provide a real-life case study at a bank's financial center. Numerical results suggest that an all-or-nothing type of vacation policy performs economically worse than the others. Attrac-tive annual leave scheduling policies can be designed by administering vacation schedules daily rather than weekly, ensuring full cover for off-duty employees, and offering employees some degree of choice over vacation schedules.
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