Endüstri Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/279
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Article Citation - WoS: 7Citation - Scopus: 11A 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; Endüstri MühendisliğiThe 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.Article Citation - WoS: 18Citation - Scopus: 34Comparison of Globoid and Cylindrical Shearer Drums' Loading Performance(South African inst Mining Metallurgy, 2006) Eyyuboğlu, E.Mustafa; Ayhan, M; Eyyuboglu, EM; Endüstri MühendisliğiDrums of a modern longwall shearer are manufactured to include various constructional features conveying extracted material onto the face conveyor as efficiently as possible. Designing a drum with a conical shell or with reduced vane length, consequently with a stepper vane angle, is the most widely employed method in an attempt to increase loading efficiency. This study compares loading performances of two such drums, one having a conical shell with modified loading vanes, the other with a cylindrical shell with reduced vane length, Firstly, the loading performances of drums are predicted and the maximum haulage rate attainable with the drums are calculated. Then the performances of drum are compared by long-term comprehensive underground trials with coal shearers under similar conditions during the production operation of Park Termik Cayirhan coalmine in Turkey. Although higher loading performance is predicted for cylindrical drums, the in situ trials point out that Globoid drums have a slightly higher loading performance than cylindrical drums. Furthermore, the relationship between operational variables, i.e. extraction height, sumping depth, haulage rate and in situ loading performance, were investigated statistically on the basis of data gathered during the underground trials.Conference Object Differential Algebraic Equations in Primal Dual Interior Point Optimization Methods(Amer inst Physics, 2004) Kasap, S; Kasap, Suat; Trafalis, TB; Endüstri MühendisliğiPrimal dual Interior Point Methods (IPMs) generate points that lie in the neighborhood of the central trajectory. The key ingredient of the primal dual IPMs is the parameterization of the central trajectory. A new approach to the parameterization of the central trajectory is presented. Instead of parameterizing the central trajectory by the barrier parameter, it is parameterized by the time by describing a continuous dynamical system. Specifically, a new update rule based on the solution of an ordinary differential equation for the barrier parameter of the primal dual IPMs is presented. The resulting ordinary differential equation combined with the first order Karush-Kuhn-Tucker (KKT) conditions, which are algebraic equations, are called differential algebraic equations (DAEs). By solving DAEs, we find an optimal solution to the given problem.Article Citation - WoS: 2Citation - Scopus: 2Naval Air Defense Planning Problem: a Novel Formulation and Heuristics(Wiley, 2024) Karasakal, Orhan; Kirca, Oemer; Arslan, CanerThis article focuses on air defense in maritime environment, which involves protecting friendly naval assets from aerial threats. Specifically, we define and address the Naval Air Defense Planning (NADP) problem, which consists of maneuvering decisions of the ships and scheduling weapons and sensors to the threats in order to maximize the total expected survival probability of friendly units. The NADP problem is more realistic and applicable than previous studies, as it considers features such as sensor assignment requirements, weapon and sensor blind sectors, sequence-dependent setup times, and ship's infrared/radar signature. In this study, a mixed-integer nonlinear programming model of the NADP problem is presented and heuristic solution approaches are developed. Computational results demonstrate that these heuristic approaches are both fast and efficient in solving the NADP problem.Article Citation - WoS: 5Citation - Scopus: 3Optimum Bidding Strategy for Wind and Solar Power Plants in Day-Ahead Electricity Market(Springer Heidelberg, 2021) Keysan, Ozan; Satir, Benhur; Ozcan, MehmetThere are two possible strategies for wind power plants (WPPs) and solar power plants (SPPs) to maximize their income in day ahead markets (DAM) in the presence of imbalance cost: joint bidding (JB) via collaboration by participating to balancing groups and deployment of storage technologies. There are limited studies in the literature covering the comparative analysis of "JB strategy" with "battery deployment (BD) strategy". In the existence of balancing responsibility, the comparative analysis of these strategies is the main contribution of this study to the literature. Our Second contribution is the analysis of the impact of different regulatory regimes, which are set by the regulatory authority, on total income. JBM (joint bidding model), which is the model for joint bidding via different collaboration groups, is developed for the analysis of JB strategy, BDM (battery deployment model), which is the model covering the deployment of storage technology, is developed for the analysis of BD strategy. The impact of each strategy on total income is analyzed. According to the analysis of the results of the models, while JB strategy, which is sensitive to the regulatory regime, increases the total annual income of the collaboration groups up to 0.65%, BD strategy seems not feasible and financially viable. On the other hand, extra income values per MW of battery for SPP is between $218 and $400 /MW-year, while these values are between $2460 and $6795/MW-year for the group of 15 WPPs. Therefore, deployment of battery for WPPs creates extra income more than tenfold of that of SPP. BD strategy can be viable provided that the levelized cost of deployment of battery drops below the extra income values achieved per MW of battery.Article Citation - WoS: 15Citation - Scopus: 22Intermodal Transportation in Humanitarian Logistics With an Application To a Turkish Network Using Retrospective Analysis(Elsevier, 2022) Akdogan, Muharrem Altan; Kahya, Melike; Ertem, Mustafa AlpIn the event of disruptions in a transportation network following a disaster, humanitarian organizations find it challenging to provide basic requirements for beneficiaries. Demand may be met using intermodal transportation as an alternative when the unimodal transportation infrastructure is damaged. This study proposes a mathematical model for utilizing intermodal transportation using 40 ft standard containers while delivering relief supplies by road, rail, and sea modes. The proposed model is a capacitated multi-period multicommodity intermodal network flow model in which relief supplies are delivered to beneficiaries in three echelons (i.e., supply, intermodal hub, and demand). The Turkish Disaster and Emergency Management Presidency's container warehouses (i.e., supply), logistics centers and container ports (i.e., intermodal hubs) are utilized to test the mathematical model with real-life demand parameters. Retrospective analysis was performed to determine the most frequently used container warehouses, logistics centers, and origin-destination pairs. Hence, an increase in operational capacity and infrastructure reinforcement is recommended to mitigate the effects of future disasters. We found that intermodal transportation is more robust to network disruptions in rapidly delivering relief supplies. We observed that intermodal transportation is utilized in disasters with more than 50,000 beneficiaries or disrupted unimodal infrastructure. For instance, after the future Istanbul earthquake, it would be impossible to deliver the relief materials only by road transportation within the urgent response period. Thus, the benefits of intermodal transportation in humanitarian logistics are more visible in large-scale disasters in which transportation resources are scarce, and transportation infrastructure is more likely to be destroyed.Article A Partial Coverage Hierarchical Location Allocation Model for Health Services(inderscience Enterprises Ltd, 2023) Karasakal, Esra; Toreyen, Ozgun; Karasakal, OrhanWe 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]Conference Object Citation - WoS: 6Citation - Scopus: 7Sustainable Factors for Supply Chain Network Design Under Uncertainty: a Literature Review(Springer-verlag Singapore Pte Ltd, 2022) Yozgat, Simge; Erol, SerpilThe concept of sustainability, which is considered three pillars covering the concept of economic, environmental, and social factors, has become an effectual attempt to increase competitiveness for institutions. Being sustainable in the supply chain enables enterprises to respond to increasing customer needs in the most appropriate way. Today, traditional supply chains are replaced by sustainable logistics network designs due to environmental and social requirements. In this study, considering the uncertainty situation, the studies carried out on closed loop supply chains that are formed as a result of integration of forward and reverse logistics aswell as forward and reverse logistics by itself are examined on the basis of sustainability factors. Sustainability sub-factors are also included in this study. As a result of the research, brief explanations can be seen about sustainable supply chain network under the uncertainty covering all three sustainability factors and gaps in the literature are clarified for future research opportunities.Article Citation - WoS: 11Citation - Scopus: 10Ranking Using Promethee When Weights and Thresholds Are Imprecise: a Data Envelopment Analysis Approach(Taylor & Francis Ltd, 2022) Eryilmaz, Utkan; Karasakal, Orhan; Karasakal, EsraMulticriteria decision making (MCDM) provides tools for the decision makers (DM) to solve complex problems with multiple conflicting criteria. Scalarization of criteria values requires using weights for criteria. Determining weights creates controversy as they are influential on the final ranking and challenges the DM as they are hard to elicit. PROMETHEE method is widely used in MCDM for ranking the alternatives and appropriate in situations when there is limited information on the preference structure of the DM. The DM should provide exact values for parameters such as criteria weights and thresholds of preference functions. Data Envelopment Analysis (DEA) is used for measuring the relative efficiency of alternatives in a non-parametric way without requiring any weight input. In this study, we propose two novel PROMETHEE based ranking approaches that address the determination of weight and threshold values by using an approach inspired by DEA. The first approach can deal with imprecise specification of criteria weights, and the second approach can utilize both imprecise weights and thresholds. The proposed approaches provide the DM substantial flexibility on the required level of information on those parameters. An illustrative example and a real-life case study are presented to show the utility of the proposed approaches.Article Citation - WoS: 17Citation - Scopus: 19Determination of Equivalent Warehouses in Humanitarian Logistics by Reallocation of Multiple Item Type Inventories(Elsevier, 2021) Ertem, Mustafa Alp; Demirbas, SefikaPrepositioning freight containers for storage of relief supplies can be considered an alternative to warehousing with shelves. Recently, 25 container warehouses are located in different cities in Turkey to deliver relief supplies to beneficiaries quickly. We take this existing situation as given and investigate if this investment could be utilised better. The available inventory (i.e., tents, beds, blankets) in these container warehouses is currently not used efficiently. Some warehouses store one type of item and none from other types. Therefore, several warehouses must be activated during a response operation to fully satisfy the beneficiaries' needs for each relief item type. We aim to investigate the benefits of operating equivalent (i.e., a proper inventory level from each relief item type) warehouses while reallocating a total available inventory for better coordination. A locationreallocation type of mathematical model is tested with real-life data from past earthquakes. Three to eight container warehouses are recommended to be converted to an equivalent type. The results indicate potential savings for the proposed model, and this potential is more visible in large-scale demand instances than in small ones.