Endüstri Mühendisliği Bölümü

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Citation - WoS: 4
Citation - Scopus: 4
A Bi-Objective Integrated Mathematical Model For Blood Supply Chain: Case Of Turkish Red Crescent
(Amer inst Mathematical Sciences-aims, 2023) Satir, Benhur; Satır, Benhür; Yolcu, Vahdi; 54700; Endüstri Mühendisliği
Various 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.
Citation - WoS: 5
Citation - Scopus: 5
A blood distribution problem with new transportation options - an application for the Turkish Red Crescent
(inderscience Enterprises Ltd, 2019) Kurt, Atıl; Kurt, Atil; Cetinkaya, Ferda Can; Çetinkaya, Ferda Can; Azizoglu, Meral; 50129; Endüstri Mühendisliği
This paper considers the blood distribution problem in the Central Anatolian Regional Blood Centre of the Turkish Red Crescent (TRC) and proposes several demand satisfaction options considering the irradiation centres, urgent demands, and product availability. Our aim is to maximise the total weighted blood demand satisfaction. To address the problem, we develop a mixed integer linear programming model and propose a hybrid genetic algorithm (HGA). The results of our experiments have revealed that the mathematical model cannot handle even small sized problem instances in reasonable times; however, the hybrid genetic algorithm is capable of handling complex daily operations of the Turkish Red Crescent.
Citation - WoS: 0
Citation - Scopus: 2
A Paradox of the Average Waiting Time for the Case of a Single Bottleneck on the Commuters' Route
(Hindawi Ltd, 2021) Ozaktas, Hakan; Kırkavak, Nureddin; Kirkavak, Nureddin; Alpay, Ayse Nilay; 58272; Endüstri Mühendisliği
Average waiting time is considered as one of the basic performance indicators for a bottleneck zone on a route for commuter traffic. It turns out that the average waiting time in a queue remains paradoxically unchanged regardless of how fast the queue dissolves for a single bottleneck problem. In this study, the paradox is verified theoretically for the deterministic case with constant arrival and departure rates. Consistent results with the deterministic case have also been obtained by simulation runs for which vehicle interarrival time is a random variable. Results are tabulated for interarrival times which have uniform, triangular, normal, and exponential distributions along with a statistical verification of the average waiting time paradox.
An approach for extending PROMETHEE to reflect choice behaviour of the decision maker
(2019) Karasakal, Orhan; Karasakal, Orhan; Bozkurt, Ahmet; 216553; Endüstri Mühendisliği
In this study, an approach based on PROMETHEE is developed to correctly reflect the choice behavior of the decision maker that is not explained by the utility theory. The prospect theory argues that losses have higher impact than gains. We integrate the prospect theory into PROMETHEE through defining new preference functions. The proposed approach is behaviorally realistic and tolerates some degree of intransitivities in the preferences of the decision maker. For determining the criteria weights, we utilize pairwise comparison method of Analytic Hierarchy Process. Performance of the approach is demonstrated on a university ranking problem.
Citation - WoS: 23
Citation - Scopus: 35
An exact solution procedure for multi-item two-echelon spare parts inventory control problem with batch ordering in the central warehouse
(Elsevier Science Bv, 2010) Topan, Engin; Topan, Engin; Bayindir, Z. Pelin; Tan, Tarkan; Endüstri Mühendisliği
We consider a multi-item two-echelon inventory system in which the central warehouse operates under a (Q, R) policy, and the local warehouses implement basestock policy. An exact solution procedure is proposed to find the inventory control policy parameters that minimize the system-wide inventory holding and fixed ordering cost subject to an aggregate mean response time constraint at each facility. (C) 2010 Elsevier B.V. All rights reserved.
Citation - WoS: 11
Analysis of Dengue Transmission Dynamic Model by Stability and Hopf Bifurcation with Two-Time Delays
(Imr Press, 2023) Murugadoss, Prakash Raj; Baleanu, Dumitru; Ambalarajan, Venkatesh; Sivakumar, Vinoth; Dhandapani, Prasantha Bharathi; Baleanu, Dumitru; 56389; Matematik
Background: 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.
Basit Doğrusal Otoregresif Modeller Sisteminde Parametre Tahmini ve Hipotez Testi: Simetrik İnovasyonlar
(2005) Türker, Özlem; Akkaya, Ayşen D.; 56416
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.
Citation - WoS: 18
Citation - Scopus: 21
Bi-Objective Adaptive Large Neighborhood Search Algorithm for the Healthcare Waste Periodic Location Inventory Routing Problem
(Springer Heidelberg, 2022) Aydemir-Karadag, Ayyuce; 116059
There has been an unexpected increase in the amount of healthcare waste during the COVID-19 pandemic. Managing healthcare waste is vital, as improper practices in the waste system can lead to the further spread of the virus. To develop effective and sustainable waste management systems, decisions in all processes from the source of the waste to its disposal should be evaluated together. Strategic decisions involve locating waste processing centers, while operational decisions deal with waste collection. Although the periodic collection of waste is used in practice, it has not been studied in the relevant literature. This paper integrates the periodic inventory routing problem with location decisions for designing healthcare waste management systems and presents a bi-objective mixed-integer nonlinear programming model that minimizes operating costs and risk simultaneously. Due to the complexity of the problem, a two-step approach is proposed. The first stage provides a mixed-integer linear model that generates visiting schedules to source nodes. The second stage offers a Bi-Objective Adaptive Large Neighborhood Search Algorithm (BOALNS) that processes the remaining decisions considered in the problem. The performance of the algorithm is tested on several hypothetical problem instances. Computational analyses are conducted by comparing BOALNS with its other two versions, Adaptive Large Neighborhood Search Algorithm and Bi-Objective Large Neighborhood Search Algorithm (BOLNS). The computational experiments demonstrate that our proposed algorithm is superior to these algorithms in several performance evaluation metrics. Also, it is observed that the adaptive search engine increases the capability of BOALNS to achieve high-quality Pareto-optimal solutions.
Broiler House Performance Analysis and Chick Entrance Planning for a Broiler Chicken Integration
(2012) Satır, Benhür; Yıldırım, Gonca; Kırca, Ömer; 54700; 45908; Endüstri Mühendisliği
Increasing 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.
Citation - WoS: 3
Citation - Scopus: 9
Customer order scheduling with job-based processing on a single-machine to minimize the total completion time
(Growing Science, 2021) Cetinkaya, Ferda Can; Çetinkaya, Ferda Can; Yeloglu, Pinar; Catmakas, Hale Akkocaoglu; 50129; Endüstri Mühendisliği
This study considers a customer order scheduling (COS) problem in which each customer requests a variety of products (jobs) processed on a single flexible machine, such as the computer numerical control (CNC) machine. A sequence-independent setup for the machine is needed before processing each product. All products in a customer order are delivered to the customer when they are processed. The product ordered by a customer and completed as the last product in the order defines the customer order's completion time. We aim to find the optimal schedule of the customer orders and the products to minimize the customer orders' total completion time. We have studied this customer order scheduling problem with a job-based processing approach in which the same products from different customer orders form a product lot and are processed successively without being intermingled with other products. We have developed two mixed-integer linear programming models capable of solving the small and medium-sized problem instances optimally and a heuristic algorithm for large-sized problem instances. Our empirical study results show that our proposed tabu search algorithm provides optimal or near-optimal solutions in a very short time. We have also compared the job-based and order-based processing approaches for both setup and no-setup cases and observed that the job-based processing approach yields better results when jobs have setup times. (C) 2021 by the authors; licensee Growing Science, Canada
Citation - WoS: 1
Citation - Scopus: 1
Cycle Cost Considerations in A Continuous Review Inventory Control Model
(Taylor & Francis Ltd, 2021) Konur, Dincer; Yıldırım, Gonca; Yildirim, Gonca; 45908; Endüstri Mühendisliği
In this study, the continuous review order-quantity-re-order point (Q, R) model is analysed with cycle cost considerations. First, we formulate the maximum cycle cost of a given (Q, R) policy using a distribution-free approach. Then, two approaches are introduced to minimize the maximum cycle cost: (i) adjusting R of a given (Q, R) policy and (ii) designing a new (Q, R) policy. Optimum inventory control decisions are characterized for each approach. A set of numerical studies is presented to compare the outcomes of both approaches to three long-term cost minimization approaches, namely the cost minimizing (Q, R) policy, the distribution-free minmax (Q, R) policy, and the distribution-free (Q, R) policy based on the maximum entropy principle. Our numerical results demonstrate the viability of the two approaches introduced and discuss implications of penalty costs and lead time demand's coefficient of variation. Later, we formulate a bi-objective model with the objectives of expected cost and maximum cycle cost minimizations and propose a bi-directional method to approximate the set of Pareto efficient solutions. Numerical examples are presented to illustrate the algorithm and demonstrate the Pareto front.
Citation - WoS: 3
Cyclical Behavior of Stock ExchangeIndex By Sectors: A Case From Turkey
(Elsevier Science Bv, 2012) Yuksel, Ebru; Bayrak, Ozlem Turker; 18500
In this study, the relation between the cyclical behaviors of stock market indices of industry, service, finance and technology sectors at Istanbul Stock Exchange and gross domestic product of Turkey between the 1998 January and 2011 September, is analyzed. The results suggest that stock exchange indices move in the same direction with economic activity and stock market leads the economy by about one quarter. However, when the sectoral differences are considered, movements in technology sector index are transmitted to economy in two months whereas it is three months for the industrial and service sector. The slowest sector is the financial sector for which pass-through speed is four months. (C) 2012 Published by Elsevier Ltd. Selection and/or peer review under responsibility of Prof. Dr. Huseyin Arasli
Citation - WoS: 0
Citation - Scopus: 0
Design of a distribution network for the school lunch program
(Academic Publication Council, 2023) Aydemir-Karadag, Ayyuce; Akdere, Erol; 116059
The 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.
Design of a Rectangular Parking Lot Using a Cutting-Stock Formulation
(2019) Yıldırım, Gonca; Satır, Benhür; Satır, Benhür; 54700; Endüstri Mühendisliği
Ever-increasing number of vehicles on the roads and in need of parking facilities at a site creates a constant burden for drivers trying to find a parking space and obstructs maneuvering both in parking areas and also along the roadways on which cars are, sometimes arbitrarily, parked. These problems are aggravated for sites built long time ago when demand for parking used to be much less than it is now. The available space may be limited because of the buildings, green areas, etc., surrounding the parking spaces and the site, and construction of a multi-story garage may not be an option in some cases due to regulations and/or financial reasons. We use a cutting-stock formulation to redesign parking lots that are rectangular in shape but with various dimensions in order to maximize the number of parking stalls. Spreadsheets are used to facilitate pattern generation and Excel Solver add-in is used to solve the optimization model for a set of selected parking lots at a university campus and we obtained improvements up to 22% more parking stalls per lot
Citation - WoS: 1
Citation - Scopus: 1
DESIGNING AN ANNUAL LEAVE SCHEDULING POLICY: CASE OF A FINANCIAL CENTER
(Amer inst Mathematical Sciences-aims, 2022) Yildirim, Gonca; Yıldırım, Gonca; Aydemir-Karadag, Ayyuce; 45908; 116059; Endüstri Mühendisliği
Providing 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.
Citation - WoS: 8
Citation - Scopus: 12
Estimating parameters of a multiple aoutoregressive model by the modified maximum likelihood method
(Elsevier, 2010) Bayrak, Oezlem Tuerker; Akkaya, Aysen D.; 56416; 2337
We consider a multiple autoregressive model with non-normal error distributions, the latter being more prevalent in practice than the usually assumed normal distribution. Since the maximum likelihood equations have convergence problems (Puthenpura and Sinha, 1986) [11], we work Out modified maximum likelihood equations by expressing the maximum likelihood equations in terms of ordered residuals and linearizing intractable nonlinear functions (Tiku and Suresh, 1992) [8]. The solutions, called modified maximum estimators, are explicit functions of sample observations and therefore easy to compute. They are under some very general regularity conditions asymptotically unbiased and efficient (Vaughan and Tiku, 2000) [4]. We show that for small sample sizes, they have negligible bias and are considerably more efficient than the traditional least Squares estimators. We show that Our estimators are robust to plausible deviations from an assumed distribution and are therefore enormously advantageous as compared to the least squares estimation. We give a real life example. (C) 2009 Elsevier B.V. All rights reserved.
İnsani Yardım Lojistiği için Konteyner Deposu Tasarımı
(2019) Ertem, Mustafa Alp; Şahin Arslan, Ayşenur; 52460; Endüstri Mühendisliği
Citation - WoS: 6
Citation - Scopus: 6
Intermodal Humanitarian Logistics Using Unit Load Devices
(Springer Heidelberg, 2022) Kavlak, Hasan; Kavlak, Hasan; Ertem, Mustafa Alp; Ertem, Mustafa Alp; Satir, Benhur; Satır, Benhür; 57708; 52460; 54700; Endüstri Mühendisliği
Intermodal 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.
Kamu Kurumlarında Risk Değerlendirmesi İçin Karar Destek Sistemi Önerisi
(2018) Tok, Elif Gülce; Satır, Benhür; Satır, Benhür; 54700; Endüstri Mühendisliği
6331 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.
Katı Atık Depolama Tesisi Yer Seçimi için Birleştirilmiş Hedef Programlama ve AHP Yaklaşımı
(2019) Aydemir-karadag, Ayyuce; 116059
Tüm dünyada, nüfus ve kentleşmenin artması ve gelişen teknoloji ile beraber üretilen atık miktarı da artmaktadır. Katı atıkların bertarafı, büyük oranda düzenli depolama yöntemiyle sağlanmaktadır. Bir düzenli depolama sahasının uygun şekilde projelendirilmesi ve işletilmesi için en önemli ön şart uygun kuruluş yeri seçiminin yapılmasıdır. Sağlıklı, verimli, uzun ömürlü, sürdürülebilir ve yasal düzenlere uygun düzenli depolama yer seçimi çok kriterli bir karar problemidir. Bu çalışmada; Ankara ili ve çevresinde kurulabilecek katı atık düzenli depolama tesisi kuruluş yeri alternatifleri, çevresel, ekonomik, sosyal ve zeminsel kriterler açısından Analitik Hiyerarşi Prosesi (AHP) ile değerlendirilmiştir. Ankara'nın yıllık depolanan atık talebini karşılayacak alternatiflerin arasından seçim yapılması, AHP ile hesaplanan kriter ağırlıklarını ve alternatif önceliklerini kullanan ve sistem gerçeklerini yansıtan hedef programlama (HP) modeli ile sağlanır.

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