Yıldırım, Gonca
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Dr. Öğr. Üyesi
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Endüstri Mühendisliği
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Scholarly Output
8
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10
Citation Count
13
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0
8 results
Scholarly Output Search Results
Now showing 1 - 8 of 8
Article Citation - WoS: 1Citation - Scopus: 1Cycle Cost Considerations in A Continuous Review Inventory Control Model(Taylor & Francis Ltd, 2021) Konur, Dincer; Yıldırım, Gonca; Yildirim, Gonca; 45908; Endüstri MühendisliğiIn 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.Article Broiler House Performance Analysis and Chick Entrance Planning for a Broiler Chicken Integration(2012) Satır, Benhür; Yıldırım, Gonca; Kırca, Ömer; 54700; 45908; Endüstri MühendisliğiIncreasing 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.Conference Object Improving Evaluation System of Program Educational Objectives and Outcomes based on MÜDEK Criteria Using Fuzzy Approach(2015) Yıldırım, Gonca; Yıldırım, Fetih; Yıldırım, Fetih; 45908; Endüstri Mühendisliği; Ortak Dersler BölümüArticle Citation - WoS: 1Citation - Scopus: 1DESIGNING 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 MühendisliğiProviding 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.Book Part Citation - Scopus: 7Toward Sustainability: A Review of Analytical Models for Circular Supply Chains(Emerald Group Publishing Ltd., 2022) Ülkü, M.A.; Yıldırım, Gonca; Skinner, D.M.; Yildirim, G.; 45908; Endüstri MühendisliğiThe earth's carrying capacity cannot withstand the pace of consumption resulting from current economic models, mainly the linear economy (LE) built on a throwaway culture. In the last few decades, the concept of a circular economy (CE), aiming to design waste out of the economy and mimic ecosystems, emerged as a strong alternative to LE. Being at the heart of the economic landscape, supply chains (SCs) need to respond to the necessary shift to CE. In so doing, the planning and execution of circular supply chains (CSCs) require a broader comprehension of CE and more sophisticated and large-scale analytical decision models. This chapter surveys extant literature on available best practices and quantitative models for sustainable supply chains (SSCs) and offers a new definition of CSC. Mapping on the knowledge extracted from this classification, potential gaps and strengths in the literature are identified. Key research papers on the "closed-loop" and "open-loop" ends of CSCs are highlighted. Challenges in developing CSC performance indicators and prescriptive models are emphasized. © 2022 by Emerald Publishing Limited. All rights reserved.Article Design of a Rectangular Parking Lot Using a Cutting-Stock Formulation(2019) Yıldırım, Gonca; Satır, Benhür; Satır, Benhür; 54700; Endüstri MühendisliğiEver-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 lotArticle Citation - WoS: 3Citation - Scopus: 5A General Production and Financial Planning Model: Case of A Poultry Integration(Springer Heidelberg, 2020) Satır, Benhür; Satir, Benhur; Yildirim, Gonca; Yıldırım, Gonca; 45908; 54700; Endüstri MühendisliğiWe propose a general linear programming formulation for a poultry integration to facilitate decision making in production and financial planning. The formulation is motivated by a medium-size application and by involving practitioners from the industry. It is a realistic and strategic model since we incorporate all divisions in a complex poultry integration, (including, but not limited to, feed mill, breeder coops, incubation house, broiler coops, slaughterhouse and distribution centers) as well as the interrelations among these divisions. The horizon we consider is in years, which makes the plan a strategic level plan in this fast-paced industry. Through extensive experimentation with various end-customer demand scenarios, we found out that the quantity of breeder chicks to buy at certain times during the planning horizon is the robust key decision variable in the overall system.Conference Object Sansürlü veriler temelinde yeniden örnekleme tekniklerine dayalı tahmin edicilerin istatistiksel değerlendirilmesi(2003) Yıldırım, Fetih; Yıldırım, Gonca; 4590; Ortak Dersler Bölümü; Endüstri Mühendisliği
