GCRIS Repository Collection:
https://hdl.handle.net/20.500.11851/277
2024-03-29T11:35:19Z
2024-03-29T11:35:19Z
Relief Aid Provision to En Route Refugees: Multi-Period Mobile Facility Location with Mobile Demand
Bayraktar, O. Baturhan
Günneç, Dilek
Salman, F. Sibel
Yücel, Eda
https://hdl.handle.net/20.500.11851/10305
2023-04-16T10:23:28Z
2022-01-01T00:00:00Z
Title: Relief Aid Provision to En Route Refugees: Multi-Period Mobile Facility Location with Mobile Demand
Authors: Bayraktar, O. Baturhan; Günneç, Dilek; Salman, F. Sibel; Yücel, Eda
Abstract: Many humanitarian organizations aid en route refugee groups who are on their journey to cross borders using mobile facilities and need to decide the number and routes of the facilities. We define a multi period facility location problem in which both the facilities and demand are mobile on a network. Refugee groups may enter and exit the network in different periods and follow various paths. In each period, a refugee group moves from one node to an adjacent one in their predetermined path. Each facility should be located at a node in each period and provides service to the refugees at that node. Each refugee should be served at least once in a predetermined number of consecutive periods. The problem is to locate the facilities in each period to minimize the total setup and travel costs of the mobile facilities, while ensuring the service requirement. We call this problem the multi-period mobile facility location problem with mobile demand (MM-FLP-MD) and prove its NP-hardness. We formulate a mixed integer linear programming (MILP) model and develop an adaptive large neighborhood search algorithm (ALNS) to solve large-size instances. We tested the computational performance of the MILP and the metaheuristic algorithm by extracting data from the 2018 Honduras Migration Crisis. For instances solved to optimality by the MILP model, the proposed ALNS determines the optimal solutions faster and provides better solutions for the remaining instances. By analyzing the sensitivity to different parameters, we provide insights to decision-makers.(c) 2021 Elsevier B.V. All rights reserved.
2022-01-01T00:00:00Z
Optimal data backup policies for information systems subject to sudden failure
Tekin, Salih
Bicakci, Kemal
Mersin, Ozgur
Erdem, Gulnur Neval
Canbay, Abdulkerim
Uzunay, Yusuf
https://hdl.handle.net/20.500.11851/9074
2023-11-14T20:22:53Z
2023-01-01T00:00:00Z
Title: Optimal data backup policies for information systems subject to sudden failure
Authors: Tekin, Salih; Bicakci, Kemal; Mersin, Ozgur; Erdem, Gulnur Neval; Canbay, Abdulkerim; Uzunay, Yusuf
Abstract: Purpose With the irresistible growth in digitization, data backup policies become essential more than ever for organizations seeking to improve reliability and availability of organizations' information systems. However, since backup operations do not come free, there is a need for a data-informed policy to decide how often and which type of backups should be taken. In this paper, the authors present a comprehensive mathematical framework to explore the design space for backup policies and to optimize backup type and interval in a given system. In the authors' framework, three separate cost factors related to the backup process are identified: backup cost, recovery cost and data loss cost. The objective function has a multi-criteria structure leading to a backup policy minimizing a weighed function of these factors. To formalize the cost and objective functions, the authors get help from renewal theory in reliability modeling. The authors' optimization framework also formulates mixed policies involving both full and incremental backups. Through numerical examples, the authors show how the authors' optimization framework could facilitate cost-saving backup policies. Design/methodology/approach The methodology starts with designing different backup policies based on system parameters. Each constructed policy is optimized in terms of backup period using renewal theory. After selecting the best back-up policy, the results are demonstrated through numerical studies. Findings Data backup polices that are tailored to system parameters can result in significant gains for IT (Information Technology) systems. Collecting the necessary parameters to design intelligent backup policies can also help managers understand managers' systems better. Designed policies not only provides the frequency of back up operations, but also the type of backups. Originality/value The original contribution of this study is the explicit construction and determination of the best backup policies for IT systems that are prone to failure. By applying renewal theory in reliability, the authors present a mathematical framework for the joint optimization of backup cost factors, i.e. backup cost, recovery time cost and data loss cost.
2023-01-01T00:00:00Z
Nucleolus based cost allocation methods for a class of constrained lane covering games
Öner N.
Kuyzu G.
https://hdl.handle.net/20.500.11851/9031
2023-02-24T19:37:47Z
2022-01-01T00:00:00Z
Title: Nucleolus based cost allocation methods for a class of constrained lane covering games
Authors: Öner N.; Kuyzu G.
Abstract: In truckload transportation procurement networks, shippers purchasing the services of truckload carriers seek to form multi-company tours which consist of regularly scheduled shipments with minimal empty truck movements with the aim of getting better rates from the carriers in return. Identifying the minimum cost collaborative solution and sharing the costs in a fair manner are two interrelated and critical tasks for the success of such networks. The restrictions on the tours which can be formed make both of these tasks very challenging. In this paper, we take a cooperative game theory approach and study the resulting constrained lane covering game. We first show the set of conditions which must be satisfied for the game to have a non-empty core. We propose nucleolus based cost allocation methods. We also develop column and row generation methods for solving these mathematical models. We compare our proposed cost allocation models with alternative cost allocation methods and each other using a set of core stability metrics through computational experiments on randomly generated instances from the literature. © 2022 Elsevier Ltd
2022-01-01T00:00:00Z
Transmission of Cholera Disease with Laplacian and Triangular Parameters
Merdan M.
Bekiryazici Z.
Kesemen T.
Khaniyev T.
https://hdl.handle.net/20.500.11851/9004
2023-02-26T20:10:33Z
2022-01-01T00:00:00Z
Title: Transmission of Cholera Disease with Laplacian and Triangular Parameters
Authors: Merdan M.; Bekiryazici Z.; Kesemen T.; Khaniyev T.
Abstract: A mathematical model has been introduced for the transmission dynamics of cholera disease by GQ Sun et al. recently. In this study, we add Laplacian and Triangular random effects to this model and analyze the variation of results for both cases. The expectations and co-efficients of variation are compared for the random models and the results are used to comment on the differences and similarities between the effects of these probability distributions. The randomness of the model itself is also investigated through comparison of the random and deterministic outcomes. © 2022 Academic Center for Education, Culture and Research TMU.
2022-01-01T00:00:00Z