Browsing by Author "Ozturkoglu, Omer"

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Citation - WoS: 18
Citation - Scopus: 22
A bi-objective mathematical model for product allocation in block stacking warehouses
(WILEY, 2020) Omer Ozturkoglu; Ozturkoglu, Omer
Put-away and picking operations in warehouses play a critical role in determining operating costs and customer response time. While the place where products are put away has an important effect on picking efficiency due to accessibility it also affects space usage which is critical for space availability and space costs. Hence this study focuses on put-away operations in pallet-in pallet-out block stacking warehouses. We develop a unique bi-objective mathematical model and a constructive heuristic algorithm to allocate products to storage lanes while considering two objectives simultaneously: minimizing total travel distance and maximizing average storage usage. We test our model and heuristic through a real company case study and randomly generated large-sized problem instances. We show that the model and heuristic offer better storage usage with reduced travel distance than the company's approach when the two objectives have equal weight. We also present a set of nondominated solutions for each problem instance. We present that the heuristic seems beneficial for the warehouse industry due to its short run time and effective solutions.
Citation - WoS: 36
Citation - Scopus: 54
A discrete cross aisle design model for order-picking warehouses
(ELSEVIER SCIENCE BV, 2019) Deniz Hoser; Omer Ozturkoglu; Hoser, Deniz; Ozturkoglu, Omer
In this paper we develop new warehouse designs that provide a reduction in travel distance for the order-picking operation which is the most costly operation and the one most closely associated with order delivery time. For this purpose we propose a new layout problem called discrete cross aisle warehouse design. In this problem a linear middle cross aisle is divided into segments called tunnels on each picking aisle. In order to calculate average tour length for the proposed design problem we develop an efficient algorithm that solves the order-picking problem optimally. A harmony search algorithm is used to find optimal tunnel positions that minimize the average tour length under a randomized storage policy by searching the space of all possible designs. A numerical study shows that for small size order lists the best-found solutions have similar layouts to the traditional two-block designs. As the number of locations to be visited increases tunnel positions move away from the center of the warehouse and construct a segregated tunnels on the layout. Compared to the traditional two-block layouts new tunnel based designs provide savings of up to 7% average savings in order-picking tour length. (C) 2018 Elsevier B.V. All rights reserved.
Citation - WoS: 10
Citation - Scopus: 17
A manufacturing-oriented model for evaluating the satisfaction of workers - Evidence from Turkey
(ELSEVIER, 2016) Omer Ozturkoglu; Ebru E. Saygili; Yucel Ozturkoglu; Ozturkoglu, Yucel; Saygili, Ebru E.; Ozturkoglu, Omer
Job satisfaction in terms of worker's satisfaction is one of the intensively studied areas in human resource and management. However there is little information available on how ergonomics and the manufacturing environment affect job satisfaction. This study analyzes the extent of the relationship between job satisfaction and work and workplace related conditions. A conceptual model is proposed to evaluate job satisfaction that considers 34 elements in four categories: manufacturing systems facility design safety and ergonomics and human resources and management. A survey of 169 blue-collar workers working in the automotive industry was conducted to investigate the applicability of the model. A comprehensive exploratory factor analysis was used to determine inter-related elements their underlying factors and their effects on job satisfaction. The analysis revealed 6 factors with 18 related elements. From a multi linear regression analysis we develop a job satisfaction model built on factors of human resource policies safety ergonomics air quality thermal comfort and disturbing equipment. The results reveal that ergonomics plays the most important role in workers' satisfaction for the respondent Turkish automotive workers. In contrast human resource policies seem not play a critical role in job satisfaction because of higher standards in automotive industry compared to other industries in Turkey. (C) 2016 Elsevier B.V. All rights reserved.
A Proposed New Approach for The Single Machine Scheduling Problem: Dynamic Programming
(2024) Yucel Ozturkoglu; OMER OZTURKOGLU; Yeşim Deniz Özkan Özen; Özen, Yeşim Deniz Özkan; Ozturkoglu, Yucel; Ozturkoglu, Omer
A traditional scheduling problem is one of the optimization problems that assign tasks to humans and machines in an optimal order. In real applications many jobs do not have a fixed processing time. During production some machines need to be cooled due to overheating. This activity which takes place outside periodic maintenance is called rate-modifying. During this time the job times increase with each passing second as Jobs wait to be assigned. The rate of deterioration due to this increase is called deteriorating jobs. This paper considers scheduling a set of deteriorating jobs with rate-modifying activity with a single processor. During the speed change activity the production process is halted resulting in increased completion times of jobs. The problem arose from the problem of a machine and an automatic production line. This problem is classified as an NP-Hard problem. The problem addressed by the study has been tried to obtain optimal results with different methods by considering different factors by many authors. When a detailed literature review is made it has been seen that no author has developed a dynamic programming model until today. The most significant advantage of dynamic programming models is that they provide solutions with the closest optimal result faster especially in solving problems classified as Np-Hard. Therefore a dynamic programming algorithm was developed for the first time for large job numbers of the focused problem. Therefore this study presents a dynamic programming algorithm to calculate the optimal solution. The algorithm's efficiency is proven on an extensive randomly generated sample data set. The results prove that the proposed algorithm provides the optimal solution with much less effort than the mathematical model.
An ALNS-Based Decision Support System for Scheduling and Routing in Home Healthcare with Lunch Break Constraints
(Growing Science, 2025) Ozsakalli, Gokberk; Qadri, Syed Shah Sultan Mohiuddin; Ozturkoglu, Omer
This study addresses the daily scheduling and routing problem for home healthcare workers while incorporating lunch break requirements. The Home Healthcare Scheduling and Routing Problem is analysed alongside its common constraints, including patient and caregiver time windows, caregiver qualifications, and mandated breaks. To address this, four different variants of an effective Adaptive Large Neighbourhood Search (ALNS) algorithm were developed to provide high-quality solutions. The algorithms demonstrate significant efficiency, solving 30-patient instances optimally within an average of 12 seconds. For scenarios involving 100 patients, they maintained robust performance with a slight increase in computational time of about 54 seconds. Results indicate operational efficiency improvements of up to 36% through optimized travel routes and patient visitation schedules. To translate these findings into practice, a decision support system, the Home Healthcare Decision Support System (HHDSS), was designed to assist administrators by automating the complex task of scheduling and routing of caregivers. Tested using realistic patient data generated from Turkey, the system effectively allocates healthcare resources and improves responsiveness. Overall, the proposed framework shows strong potential as a valuable practical tool for improving the responsiveness and efficiency of home healthcare logistics. (c) 2026 by the authors; licensee Growing Science, Canada
Citation - WoS: 6
Citation - Scopus: 8
An Evaluation of Order-picking Tour Efficiency in Two-block Warehouses
(OSCM FORUM, 2019) Omer Ozturkoglu; Deniz Hoser; Hoser, Deniz; Ozturkoglu, Omer
This study investigates the effects of critical operational and strategical decisions in order-picking warehouses on order pickers' tour lengths. For this study one of the most-commonly applied layouts in practice called two-block layout with a central cross aisle was considered. A full factorial experimental design and multiple-comparisons (Bonferroni t-tests) were applied to statistically determine the significance of various levels of storage policies pick-list sizes warehouse shape ratios warehouse sizes and their all interactions on average tour length. The analysis showed that deeper storage areas were superior to wider areas in small- and medium-sized warehouses. Warehouse designs with a 1: 1 width-to-depth shape ratio offered the most robust layouts. Within-storage aisle policy significantly reduced order-picking tour length and generally outperformed other storage policies.
Aşı Tedarik Zinciri Süreçleri: Karşılaşılan Sorunlar ve Dijital Çözümler
(2021) OMER OZTURKOGLU; IKBAL ECE DIZBAY; Ozturkoglu, Omer; Dızbay, Ikbal Ece
Salgın hastalıkların yayılımını engelleme yöntemlerinin en önemlilerinden biri aşılama yöntemidir. Aşılama yöntemi kullanılarak salgın hastalıkların tamamen yok edilmesimümkün olabilmektedir.Ancak hastalık veya salgınların önüne geçebilmesi için aşıların tedarik zinciri aşamalarından herhangi birinde soğuk zincirin bozulmaması ve uygun koşullarda işlem yapılmasıgerekmektedir. Aşı tedarik zincirlerinde uygun koşullarsağlanamadığı takdirde bağışıklık oranlarıdüşmekte aşı fireleri çevresel atıklar ve bağışıklama maliyetleri artmaktadır. Bu çalışmada aşı tedarik zinciri aşamalarıanaliz edilmiştir. Literatür taraması iletedarik zinciri aşamalarının etkin yönetilmesi için verilmesi gereken kararlar ve Endüstri 4.0 kapsamında kullanılabilecek teknolojik gelişmeler incelenmiştir.
Citation - WoS: 3
Citation - Scopus: 4
Corporate responsibilities and values in codes of ethics: an exploratory study of the Global Fortune companies
(Inderscience Publishers, 2022) Ebru E. Saygılı; Yucel Yilmaz Ozturkoglu; Ömer Öztürkoǧlu; Saygl, Ebru; Ozturkolu, Yucel; Ozturkoglu, Omer; Ozturkoglu, Yucel; Saygılı, Ebru
This study aims to develop a common language for code of ethics (CofE) statements and explore whether Global Fortune companies have expanded their CofE statements by including all stakeholder responsibilities and universal values. The results of the exploratory factor analysis demonstrated that even though compliance and other first-generation CSR were the dominant concepts second- and third-generation stakeholders were included in the first factor which was named as core values and responsibilities. In the four-factor model with 30 sub-factors the second factor was community issues the third factor was internal conduct and the fourth factor was employee rights. The findings indicated the complete presence of trustworthiness citizenship and respect values whereas responsibility fairness and caring values can be improved in CofE statements. Further due to the dynamic nature of CofE companies should give more importance to new concepts like risks fair dealing fair competition industry issues training and education. © 2022 Elsevier B.V. All rights reserved.
Depolarda Sıralı Sipariş Toplama İşlemi İçin Yenilikçi Koridor Tasarımları
(2017) Ozturkoglu, Omer
Sıralı sipariş toplama işlemi, özellikle işgücü yoğunluklu depolarda en maliyetli işlemdir. Bu işlemin de en maliyetli ve sipariş tepki hızına en çok etki eden parçası lokasyonlar arasında seyahattir. Bu nedenle, bu proje depolarda seyahat mesafesini azaltabilecek yenilikçi fikirler sunan dört problem önermektedir. Bu problemler, Kesikli Ana Koridorlu (KAK), Çok Tünelli (ÇT), Tasarım X ve Tasarım Y olarak adlandırılmıştır. Her bir problemin çözümü için ağ tabanlı depo yerleşim düzeni modeli geliştirilmiştir. Daha sonra, ortalama seyahat mesafesini azaltacak her bir problemdeki tasarım değişkenlerin optimal değerlerini araştırmak için meta-sezgisel algoritmalar kullanılmıştır. KAK probleminde, toplama koridoru üzerinde sadece bir tünele izin verilen bir depo için optimal tur uzunluğunu polinomyal zamanda hesaplayan bir algoritma geliştirilmiştir. Değişkenlerin optimal değerlerinin araştırılması için Harmony Arama optimizasyon algoritması kullanılmıştır. Geliştirilen KAK tasarımları depo ve sipariş büyüklüğüne bağlı olarak %7?ye yakın tur uzunluğunda iyileştirme önermektedir. ÇT problemde, tur uzunluğun hesaplanması için aç gözlü bir algoritma geliştirilmiştir. Değişkenlerin optimizasyonu için genetik algoritma kullanılmıştır. Sonuç olarak, bazı ÇT tasarımların %3?e kadar tur uzunluğunda kısalma sunduğu gösterilmiştir. X ve Y tasarım problemlerinde sipariş toplama rota uzunluğu için Karınca Koloni Algoritması esas alınarak etkin bir algoritma geliştirlmiştir. Ayrıca, tasarım değişkenlerinin optimal değerlerini araştırmak için Diferansiyel Evrim algoritması kullanılmıştır. Elde edilen X tasarımları iyileştirme sunmamasına rağmen, bazı Y tasarımları %3?e kadar tur uzunluğunda tasarruf sunmaktadır. Son olarak, sonuçlar göstermiştir ki iki-bloklu geleneksel tasarım bir çok depo koşulu altında gürbüz bir tasarımdır.
Citation - WoS: 5
Citation - Scopus: 8
Effects of varying input and output points on new aisle designs in warehouses
(Institute of Electrical and Electronics Engineers Inc., 2016) Ömer Öztürkoǧlu; Ozturkoglu, Omer
New aisle designs have been proposed for unit-load warehouses recently in the literature. Most of these designs propose reduction in single-command expected travel distance considering flow from only one input/output (IO) point which is centrally located on the bottom of warehouse. Therefore in this study we investigate the effects of varying number of IO points on both the layout and the distance. We use a warehouse network model to calculate expected single-command distance. We also use a Particle Swarm Optimization algorithm to search for the optimal values of the warehouse design variables. We showed that Leaf designs are robust for less than 7 input and output points on the bottom of the warehouse. © 2017 Elsevier B.V. All rights reserved.
Citation - WoS: 6
Citation - Scopus: 10
Evaluating Chevron aisle design in unit load warehouses with multiple pickup and deposit points
(GAZI UNIV FAC ENGINEERING ARCHITECTURE, 2018) Omer Ozturkoglu; Yeliz Kocaman; Sevkinaz Gumusoglu; Kocaman, Yeliz; Ozturkoglu, Omer; Gümüşoğlu, Şevkinaz
Warehousing is becoming more important in the supply chain management than before because of increasing competitiveness in market. Efficient warehouse management has become a critical factor that affects customer satisfaction. Especially managing the lead-time in a warehouse for preparation of a customer order has become one of the critical issues for warehouse managers. Order delivery time in a warehouse is affected by all warehouse activities such as unloading trucks storing and picking products packaging and shipping. The most critical activities are storing and picking because they are the most time consuming activities. Travel time for storing and picking activities depends on aisle layout of the warehouse. Therefore aisle design in a warehouse becomes a research field for researchers. In this study the effect of multiple P&D point on the performance of Chevron design under various warehouse sizes and under different material flow policies is investigated. A mathematical model is constructed in continuous warehouse space and then the expected travel time in a discrete warehouse is calculated. As a result Chevron design outperforms the equivalent traditional design when there are a few number of P&D points and central P&D points have higher material flows than others in warehouse that have 3/1 width/height shape ratio.
Identical parallel machine scheduling with nonlinear deterioration and multiple rate modifying activities
(2017) OMER OZTURKOGLU; Ozturkoglu, Omer
This study focuses on identical parallel machine scheduling of jobs with deteriorating processing times and rate-modifying activities. We consider nonlinearly increasing processing times of jobs based on their position assignment. Rate modifying activities (RMAs) are also considered to recover the increase in processing times of jobs due to deterioration. We also propose heuristics algorithms that rely on ant colony optimization and simulated annealing algorithms to solve the problem with multiple RMAs in a reasonable amount of time. Finally we show that ant colony optimization algorithm generates close optimal solutions and superior results than simulated annealing algorithm.
Citation - WoS: 5
Citation - Scopus: 10
Investigating the robustness of aisles in a non-traditional unit-load warehouse design: Leverage
(Institute of Electrical and Electronics Engineers Inc., 2015) Ömer Öztürkoǧlu; Ozturkoglu, Omer
Recently [9] proposed a non-traditional aisle design for unit-load warehouse for one centrally located pickup and deposit (PandD) point both on the lower and upper sides of warehouse. We call this design Leverage. However the number of PandD points is limited to one in design Leverage. Hence in this research we investigate the changes in improvement of Leverage as the number of PandD points increases by searching optimal designs by using [9]'s approach. We then compare Leverage with the improved designs to investigate its robustness in terms of changes in aisle structure and cost. © 2016 Elsevier B.V. All rights reserved.
Citation - WoS: 2
Citation - Scopus: 4
Key Performance Measures and Digital-Era Technologies in Warehouses
(OSCM FORUM, 2022) Yeliz Demirkiran; Omer Ozturkoglu; Demirkiran, Yeliz; Ozturkoglu, Omer
The manuscript aims to benchmark warehousing industries in developing and developed countries in terms of performance measures from the perspective of industry professionals and the potential impact of digital-era technologies. Compared with the US-based Warehousing Education Research Council's reports published in 2018 and 2019 this paper presents that on-time shipments is the most critical performance measure in Turkey in both 2018 and 2019 while order picking accuracy is in the US. This study also presented that mobile technologies are considered as the most influential digital-era technology in terms of supporting ongoing improvements in warehousing operations and providing a competitive advantage to the companies in both Turkey and the US. Moreover some digital-era technologies such as driverless vehicles or drones 3D printing and simulation are considered the least supportive or competitive technologies according to the professionals in Turkey.
Citation - Scopus: 1
New business model proposal in the digital age: sustainability-focused servitization
(EMERALD GROUP PUBLISHING LTD, 2025) Yucel Ozturkoglu; Omer Ozturkoglu; Elif Danisman; Ozturkoglu, Yucel; Danisman, Elif; Ozturkoglu, Omer
PurposeWith the pressure of global markets and demanding customers most production companies are moving from pure production to the integration of products and services. This new formation is known as servitization and can give companies a strong competitive advantage. The recent studies in the literature propose that servitization has a positive impact on sustainability by improved energy consumption. However they also underscored the need for better implementation of sustainability and the barriers avoiding sustainable servitization behavior. This research aims to investigate sustainability-oriented servitization barriers which have not taken any attention by previous research and their relationships for successful implementations.Design/methodology/approachWe extracted fifteen servitization barriers from the literature and a focus group study. Then we presented their relationship with sustainable dimensions such as human business economic and market and environment. Using the selected experts' assessments we implemented Fuzzy-TISM to analyze the causal relationship among the barriers. We also implemented Fuzzy-MICMAC analysis to categorize the barriers.FindingsThe findings presented that lack of understanding of customer cultural problems high market risk financial constraints lack of environmental awareness and lack of environmental regulations are independent variables and play a very critical role in the success of sustainable-servitization implementations. Finally we proposed several managerial insights and a structured hierarchical model that can be used as a guide by practitioners to develop a better strategy for their implementations.Originality/valueTo the best of our knowledge a detailed examination of the barriers and challenges in the triple bottom line approach is already missing at the desired level. From this point of view this study is the first research that determines barriers of servitization based on the triple-bottom-line model with a sustainability perspective.
Palet Üzerinde Yer Alan Bir Kolinin Boşaltma ve Yükleme Sürelerine Manüel Malzeme Elleçleme Araçalarının Etkileri
(2016) OMER OZTURKOGLU; Ozturkoglu, Omer
Bu çalışmada malzeme elleçleme ekipmanlarından olan yükseltilebilir döner tabla kullanımının palet üsütnde yer alan bir kolinin boşaltma veya yükleme süresine olan etkisi araştırılmaktadır. Bunun için iki farklı sistemde palet üzerinden alınan kolilerin beklenen toplama (veya çıkartma) süresi karşılaştırılmıştır. Bu iki sistem, döner tablalı ve döner tablasız palet yükün bulunduğu sistemlerdir. Beklenen toplama süresini elde etmek için palet üzerinde bulunan kolilerin posizyonlarını ve ergonomik koşulları dikkate alan toplama zamanı denklemleri geliştirilmiştir. Ayrıca sipariş büyüklüğü ve tam yük bir palette bulunan koli sayısı gibi bazı parametrelerin etkisini araştırmak açısından detaylı bir deneysel tasarım icra edilmiştir. Bunun sonucunda insan faktörlerinin toplanan kolilerin pozisyonlarının ve bir seferde toplanan koli sayısının koli toplama süresi üzerinde önemli bir faktör olduğu gösterilmiştir. Bununla birlikte koli toplama ve yükleme operasyonlarında yükseltilebilir döner tabla kullanımının geleneksel manuel toplamaya göre bir çok durumda koli toplama süresinde iyileştirme sunduğu gösterilmiştir.
Propose a Polynomial Time Algorithm for Total Completion Time Objective
(INT JOURNAL MATHEMATICAL ENGINEERING & MANAGEMENT SCIENCES-IJMEMS, 2021) Yucel Ozturkoglu; Omer Ozturkoglu; Ozturkoglu, Yucel; Ozturkoglu, Omer
In this study we integrate deteriorate jobs with repair&maintenance activity on a single machine scheduling subject to total completion time. This work has more than one motivation. First jobs are assigned to machines in an automated production line. Later to schedule the maintenance activities if needed to prevent machinery from breaking down later. There are some important mathematical models to solve this combination. However due to the complexity of the problem which is Np-hard a polynomial algorithm should be needed for solving large problems. Therefore this article introduces several polnomial algorithms to determine the order of things best. With using these algorithms it will be possible to determine where to assign to the schedule taking into account the number of maintenance activities required and their optimum total completion time.
Citation - WoS: 7
Citation - Scopus: 9
Ranking of Responsible Automotive Manufacturers According to Sustainability Reports Using PROMETHEE and VIKOR Methods
(WILEY-V C H VERLAG GMBH, 2022) Aylin Caliskan; Omer Ozturkoglu; Yucel Ozturkoglu; Caliskan, Aylin; Ozturkoglu, Yucel; Ozturkoglu, Omer
Industrial activities and road transportation are the main contributors to air quality degradation and resource depletion. The automotive sector which is one of the main players of the manufacturing industry and the supplier of road transport demand is considered one of the most prominent symbols of pollution. Therefore the issue of sustainability in the automotive industry is critical as it poses a wide range of challenges and negative externalities on the environment and society. This study aims to present a list of responsible consumption and production dimensions in line with the 12th United Nations Sustainable Development Goal and to rank the auto and auto part manufacturers in the Fortune Global 250. The authors use content analysis and text mining to identify 13 dimensions underlying responsible consumption and production. They then weigh each dimension according to the preferences of the experts using Delphi and the Analytical Hierarchy Process. After examining the dimensions in the sustainability reports of the selected companies they rank them using the PROMETHEE and VIKOR techniques. They also show the robustness of the rankings.
Citation - Scopus: 7
Sustainable Frozen Food Facility Location Selection under Pandemic Era
(CentMa GmbH, 2022) Yeliz Demirkiran; Ömer Öztürkoǧlu; Yucel Yilmaz Ozturkoglu; Demirkiran, Yeliz; Ozturkoglu, Yucel; Ozturkoglu, Omer
Consumption of frozen food has increased significantly in many countries experiencing total closure due to epidemics. In order to meet this increase in demand companies apply different strategies in both production and logistics processes. In particular warehouse locations need to be closer to consumers so as not to disrupt the increasing demand and the cold chain. Considering the sustainable position in the frozen food industry it is essential to focus on both commercial and economic impacts. However especially the environmental and sustainable criteria have always been neglected in terms of planning the country and the city. Therefore this study has three main research questions, (1) identify key criteria for sustainability-focused frozen food facility location (2) understand the relationship between these criteria and (3) develop a hierarchical sustainable location roadmap for pra ctitioners. Initially a literature review was conducted to find the answers to these questions and reveal suitable criteria. Secondly PROMETHEE was used to determine the relative importance of the data-driven performance of the main and sub-criteria. Therefore this study gives the reader a comprehensive insight into how sustainable data-driven performance criteria are applied in frozen food storage facility locations. Finally the proposed model used real-life data to select a developing country's sustainable frozen food storage location. © 2022 Elsevier B.V. All rights reserved.
The integrated network model of pipeline sea and road distribution of petroleum product
(2016) Oyewale LAWAL; OMER OZTURKOGLU; Lawal, Oyewale; Ozturkoglu, Omer
Nigeria ranks high among the community of oil producers both in the world. It is therefore paradoxical that Nigeria with such profile in Organization of Petroleum Exporting Countries (OPEC) statistics finds it difficult to optimize its supply distribution while spending so much money on transportation and distribution. This paper thus reviews the petroleum product supply and distribution systems in the country. Thus we develop a single period single product deterministic mathematical model to effectively distribute the product to the end user through the most effective channel to the interest of the economy of the country. In our model we first consider a perfect condition in the petroleum industry irrespective of the production crises and conflicts like pipeline vandalism communal instability. We then consider different scnearios that presumes several breakdown cases in pipeline connection to anaylze the survivability of the network of petroleum distribution.