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
A partial coverage hierarchical location allocation model for health services
(inderscience Enterprises Ltd, 2023) Karasakal, Orhan; Karasakal, Orhan; Karasakal, Esra; Toreyen, Ozgun; 216553; Endüstri Mühendisliği
We consider a hierarchical maximal covering location problem (HMCLP) to locate health centres and hospitals so that the maximum demand is covered by two levels of services in a successively inclusive hierarchy. We extend the HMCLP by introducing the partial coverage and a new definition of the referral. The proposed model may enable an informed decision on the healthcare system when dynamic adaptation is required, such as a COVID-19 pandemic. We define the referral as coverage of health centres by hospitals. A hospital may also cover demand through referral. The proposed model is solved optimally for small problems. For large problems, we propose a customised genetic algorithm. Computational study shows that the GA performs well, and the partial coverage substantially affects the optimal solutions. [Submitted: 20 January 2021; Accepted: 15 January 2022]
Citation - WoS: 17
Citation - Scopus: 17
A study on nutrient removal from municipal wastewater by struvite formation using Taguchi's design of experiments
(Mary Ann Liebert, inc, 2008) Uludag-Demirer, Sibel; 45685
The aim of this study is to investigate the removal of NH4+-N and PO43--P from the municipal wastewater by struvite (MgNH4PO4.6H(2)O) formation. The optimization of the NH4+-N and PO43--P removals is made by changing the total concentrations of struvite forming ions (Mg2+, NH4+, PO43-) and pH of the wastewater. The experimental design was made using Taguchi's L-9(3(4)) orthogonal array technique in the first stage of the study. The conditions yielding maximum removals of NH4+-N and PO43--P are found as molar concentration ratio of Mg:N:P of 2:2:2 and 3:3:2, respectively, using the signal-to-noise (S/N) ratio of experimental results. The removal of NH4+-N followed the stoichiometry of struvite formation, while PO43--P removal required the excess amount of Mg2+. The pH of wastewater in which the maximum NH4+-N and PO43--P removals are observed was 9.0. All of the factors tested influenced the removal of NH4+-N opposite to the removal Of PO43--P, in which the concentration of NH4+-N was found insignificant statistically. Therefore, the addition of NH4+ ion is eliminated and Taguchi's L-4(2(3)) orthogonal array was used in the second stage of experimental study. The molar concentration ratios of struvite forming ions (Mg:N:P) were found to be as 1:1:1 and 2:1:1 for maximum NH4+-N and PO43--P removals at the levels of 52.4 and 67.7%, respectively, at pH 9.0 using the S/N ratios of experimental results. The performance of proposed method in removing NH4+-N and PO43--P and foreseen problems related with effluent quality is discussed.
Citation - WoS: 6
Citation - Scopus: 10
A Warehouse Design With Containers For Humanitarian Logistics: A Real-Life Implementation From Turkey
(Univ Cincinnati industrial Engineering, 2019) Sahin-Arslan, Aysenur; Ertem, Mustafa Alp; Ertem, Mustafa Alp; 52460; Endüstri Mühendisliği
The purpose of this study is to investigate how and at what cost freight containers could be used as an inventory holding mechanism for humanitarian logistics. The layout and cost comparison of two alternatives are performed-stocking in a warehouse and material storage in containers. An optimum layout for storage in containers is proposed. It was found that container stockpiling uses the available area and space better than the warehouse option to stock the same number of material pallets. Leasing and purchasing costs of these alternatives are compared using present worth analysis. The results revealed that the container leasing option is not cost effective when land cost is included. Warehouse leasing results in the least setup cost, however, it incurs more operating costs, including lighting, ventilation, and maintenance as well as handling of the pallets. A real-life implementation of the proposed container stockpiling idea is presented for Turkey.
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: 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.
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: 5
Citation - Scopus: 7
LP relaxation-based solution algorithms for the multi-mode project scheduling with a non-renewable resource
(inderscience Enterprises Ltd, 2015) Azizoglu, Meral; Çetinkaya, Ferda Can; Cetinkaya, Ferda Can; Pamir, Selin Kirbiyik; 5546; 50129; Endüstri Mühendisliği
In this study, we consider a multi-mode resource allocation problem with a single non-renewable resource. We assume the resource is released at defined time points and at defined quantities. We also assume that the activity costs are charged once they are completed. Our aim is to minimise the project completion time. We formulate the problem as a pure integer programming model and show that it is strongly NP-hard. We find lower bounds by pure and mixed integer linear programming relaxations of the model and develop three heuristic procedures based on those relaxations. The results of our computational study have revealed the satisfactory performances of our lower bounds and heuristic procedures.
Citation - Scopus: 6
A Partial Coverage Hierarchical Location Allocation Model for Health Services
(Inderscience Publishers, 2023) Karasakal, O.; Karasakal, E.; Töreyen, Ö.
We consider a hierarchical maximal covering location problem (HMCLP) to locate health centres and hospitals so that the maximum demand is covered by two levels of services in a successively inclusive hierarchy. We extend the HMCLP by introducing the partial coverage and a new definition of the referral. The proposed model may enable an informed decision on the healthcare system when dynamic adaptation is required, such as a COVID-19 pandemic. We define the referral as coverage of health centres by hospitals. A hospital may also cover demand through referral. The proposed model is solved optimally for small problems. For large problems, we propose a customised genetic algorithm. Computational study shows that the GA performs well, and the partial coverage substantially affects the optimal solutions. © 2023 Inderscience Enterprises Ltd.
Citation - WoS: 6
Citation - Scopus: 6
Solution approaches to the blood distribution problem of the Turkish Red Crescent
(inderscience Enterprises Ltd, 2018) Kurt, Atıl; Kurt, Atil; Azizoglu, Meral; Çetinkaya, Ferda Can; Cetinkaya, Ferda Can; 21650; 5546; 50129; Endüstri Mühendisliği
This paper considers the blood distribution problem that includes irradiation centres, urgent demands, and product availability in Turkey, Central Anatolian Regional Blood Center of the Turkish Red Crescent. To address the problem, we develop a mixed integer linear program with two objectives: maximising the demand satisfaction and minimising total time travelled by the vehicles. We propose two decomposition-based heuristic solution approaches. The results of our experiments have revealed that the model cannot solve even small sized instances in reasonable times; however, the heuristic solution approaches are appropriate for solving complex real life problems.

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