Kadir Ertogral | TOBB University of Economics and Technology (original) (raw)
Papers by Kadir Ertogral
2019 International Conference on Power Generation Systems and Renewable Energy Technologies (PGSRET), 2019
With the growing impact of global warming and depletion of fossil fuels, the necessity of renewab... more With the growing impact of global warming and depletion of fossil fuels, the necessity of renewable energy resources is becoming more and more obvious. However, investing in intermittent renewable resources, such as wind power, by only considering the regional power potentials jeopardizes system reliability and increases the necessity of spinning reserves which balance the instability in power systems. In this paper, we suggest a stochastic mixed integer nonlinear programming model that decide the regional allocation of wind power capacity with the objective of minimizing the needed spinning reserves to compensate for the negative effects of intermittent nature of wind power. We also suggest a heuristic approach for solving the suggested model. Both the stochastic mixed integer nonlinear programming model and the heuristic approach are new in the literature. Parameters used for numerical analysis are gathered from real-life data sets which are provided by Turkish State Meteorologica...
Journal of the Faculty of Engineering and Architecture of Gazi University
Havacılık sektöründe bakım onarım (BO) uçakların güvenli ve devamlı uçuşlarının sağlanması için r... more Havacılık sektöründe bakım onarım (BO) uçakların güvenli ve devamlı uçuşlarının sağlanması için regülâsyona tabi tutulan zorunlu bir faaliyettir. Gerek ticari gerekse askeri uçaklar için belirli aralıklarla bakıma girme zorunluluğu vardır. BO faaliyetleri uçuş firmaları için yakıttan sonra en çok maliyet yaratan alandır. BO sistemlerini klasik üretim sistemlerinden ayıran önemli bir faktör bazı parça ya da modüllerin devinimli (rotable) envanter şeklinde kullanılmasıdır. Devinimli envanter durumunda, BO işletmesine servis için gelen uçağın ilgili modülü BO'nun takas envanterinde bulunan uçuşa hazır modülle değiştirilir. Bu durumda müşteri olan havacılık şirketi nerdeyse anlık değişimle uçuşa ara vermeden faaliyetlerini sürdürür. BO şirketi takas yaptığı devinimli envanter türü modülü bakım onarım sürecinden geçirir ve sonra tekrar takasta kullanmak üzere gelecek talepler için envanterinde saklar. BO şirketi uçakların devinimli modül takas zamanlarını ve bakım onarım çizelgesini yaparken, uçakların en son bakım geçirdikleri zaman dikkate alındığında regülasyonlara göre bir sonraki bakım için gelebilecekleri en son tarihe veya bu tarihten önce ancak yakın bir zamanda gelip servis almalarını sağlamaya çalışmalıdır. Çünkü vaktinden erken gelişleri havacılık şirketleri ekonomik açıdan tercih etmeyecektir. BO şirketi için sabit bir tamir bakım kapasitesi ve limitli envanter üretim çizelgeleme üzerindeki önemli kısıtlardır. Bu çalışmada yukarıda açıklanan problem toplam erken servis alışların en azlanması amacıyla, belirli bir başlangıç stoğu, kısıtlı üretim kapasitesi, çok tipli devinimli envanter, ve sonlu planlama ufku varsayımları altında modellenmiş, sayısal çözümler yardımıyla problemin analizi yapılmıştır. Devinimli envanter başlangıç seviyesini veya proses kapasitesini bir birim artırmanın azalan marjinal faydası ortaya konulmuş ve bu faydanın proses süresiyle ve proses kapasitesiyle ilişkisi gösterilmiştir.
IMSE Technical Reprot 98T, 1998
Page 1. Integrating Production and Transportation Logistics in a Supply Chain Environment: A Lagr... more Page 1. Integrating Production and Transportation Logistics in a Supply Chain Environment: A Lagrangean Decomposition Approach Kadir Ertograî S. David Wu Laura I. Burke Lehigh University Report No. 98T-010 Page 2. INTEGRATING ...
European Journal of Operational Research, 2008
ABSTRACT
European J. of Industrial Engineering, 2011
In this study, we consider the joint economic lot sizing problem (JELP) under stochastic demand. ... more In this study, we consider the joint economic lot sizing problem (JELP) under stochastic demand. Almost all of the literature on JELP assumes that the demand is deterministic and constant with very limited exceptions. We indicate the shortcomings of the work in the literature in this regard, and suggest a service-level based model for JELP under stochastic demand with an exact solution procedure. We also include numerical examples to illustrate the procedure and the value of the stochastic solution.
Journal of the Faculty of Engineering and Architecture of Gazi University
International Journal of Production Economics, 2005
The multi period inventory problems have been studied under two main assumptions. Continuous revi... more The multi period inventory problems have been studied under two main assumptions. Continuous review assumption where an order can be made at any time depending on inventory position and periodic review assumption where an order can be initiated only at discrete time epochs. In this study, we analyze a multi period inventory problem that falls under neither of these two
IIE Transactions, 2000
Most planning and optimization methods in manufacturing logistics assume centralized or hierarchi... more Most planning and optimization methods in manufacturing logistics assume centralized or hierarchical decision making using monolithic models. Motivated by the increasing needs to coordinate diverse decision processes and systems, we investigate an auction-theoretic mechanism for production coordination in a supply chain. Our efforts focuses on structural mappings between mathematical decomposition and iterative auction mechanisms wherein agents compete based on their local utilities, announced conflict pricing, and production targets. Building upon the rich literature in optimization and auction-theoretic analysis, we investigate the advantages and limitations of this distributed decision scheme on a large set problems in supply chain production planning. Experimental results show that the proposed auction mechanism provides impressive improvement over traditional monolithic method without significant degradation to the solution quality.
European Journal of Operational Research, 2007
... The reader is referred to Goyal and Gupta, 1989 and Ben-Daya et al., 2005 for comprehensive r... more ... The reader is referred to Goyal and Gupta, 1989 and Ben-Daya et al., 2005 for comprehensive reviews. In all models above, it has been implicitly assumed that the transportation cost is part of the ordering cost. ... The vendor and the buyer incur holding costs as well. ...
European Journal of Operational Research, 2008
With the growing focus on supply chain management, firms realize that inventories across the enti... more With the growing focus on supply chain management, firms realize that inventories across the entire supply chain can be more efficiently managed through greater cooperation and better coordination. This paper presents a comprehensive and up-todate review of the joint economic lot sizing problem (JELP) and also provides some extensions of this important problem. In particular, a detailed mathematical description of, and a unified framework for, the main JELP models are given. Additionally, a comparative empirical study of the main policies proposed for JELP is conducted. The focus of this study is on assessing the deviation of these policies from the optimal solution. Studying the performance of different models provides additional insights that will help in justifying their use in more complex supply chain models that involve more stages or other practical considerations of interest. (C) 2007 Elsevier B.V. All rights reserved.
Computers & Industrial Engineering, 2010
Facility layout problem has been extensively studied in the literature because the total material... more Facility layout problem has been extensively studied in the literature because the total material handling cost can be a significant portion in the operational costs for a company and in the manufacturing cost of a product. Today's severe global competition, rapid changes in technology and shortening life cycle of products force companies to evaluate and modify their facility layout in a periodic fashion. This type of layout problems is categorized as the dynamic facility layout problem (DFLP). As a realistic dimension of the problem, one has to consider also the limited budget to cover the cost of changing the layout. In this study, we propose a simulated annealing heuristic for the DFLP with budget constraint, and show the effectiveness of this heuristic on a set of numerical experiments.
Computers & Industrial Engineering, 2008
ABSTRACT
Dept. IMSE, Lehigh Univ., Bethlehem, PA, …, 1998
Coordinating operational and logistic functions across facilities and companies is key to supply ... more Coordinating operational and logistic functions across facilities and companies is key to supply chain integration. In this paper, we consider the coordination of production and transportation scheduling, a crucial link of this integration. In manufacturing-centric industries such as automotive and electronics, costs constitute the second transportation largest cost component following the costs. While the potential of integrating production production and transportation planning could be significant, there has been a lack of research and practice in integrating these functions. Functional silos or ad hoc interfaces are commonly seen in the industry. In this research, we propose an analytic study that investigates the effects of integrating production and transportation planning. We study integrated optimization models that reconcile the viewpoints from transportation and production planning and analyze the costs introduced by coordination. Using a Lagrangean decomposition scheme, we demonstrate computationally the nature of the comprise between production and transportation decisions, and the value of integration.
2019 International Conference on Power Generation Systems and Renewable Energy Technologies (PGSRET), 2019
With the growing impact of global warming and depletion of fossil fuels, the necessity of renewab... more With the growing impact of global warming and depletion of fossil fuels, the necessity of renewable energy resources is becoming more and more obvious. However, investing in intermittent renewable resources, such as wind power, by only considering the regional power potentials jeopardizes system reliability and increases the necessity of spinning reserves which balance the instability in power systems. In this paper, we suggest a stochastic mixed integer nonlinear programming model that decide the regional allocation of wind power capacity with the objective of minimizing the needed spinning reserves to compensate for the negative effects of intermittent nature of wind power. We also suggest a heuristic approach for solving the suggested model. Both the stochastic mixed integer nonlinear programming model and the heuristic approach are new in the literature. Parameters used for numerical analysis are gathered from real-life data sets which are provided by Turkish State Meteorologica...
Journal of the Faculty of Engineering and Architecture of Gazi University
Havacılık sektöründe bakım onarım (BO) uçakların güvenli ve devamlı uçuşlarının sağlanması için r... more Havacılık sektöründe bakım onarım (BO) uçakların güvenli ve devamlı uçuşlarının sağlanması için regülâsyona tabi tutulan zorunlu bir faaliyettir. Gerek ticari gerekse askeri uçaklar için belirli aralıklarla bakıma girme zorunluluğu vardır. BO faaliyetleri uçuş firmaları için yakıttan sonra en çok maliyet yaratan alandır. BO sistemlerini klasik üretim sistemlerinden ayıran önemli bir faktör bazı parça ya da modüllerin devinimli (rotable) envanter şeklinde kullanılmasıdır. Devinimli envanter durumunda, BO işletmesine servis için gelen uçağın ilgili modülü BO'nun takas envanterinde bulunan uçuşa hazır modülle değiştirilir. Bu durumda müşteri olan havacılık şirketi nerdeyse anlık değişimle uçuşa ara vermeden faaliyetlerini sürdürür. BO şirketi takas yaptığı devinimli envanter türü modülü bakım onarım sürecinden geçirir ve sonra tekrar takasta kullanmak üzere gelecek talepler için envanterinde saklar. BO şirketi uçakların devinimli modül takas zamanlarını ve bakım onarım çizelgesini yaparken, uçakların en son bakım geçirdikleri zaman dikkate alındığında regülasyonlara göre bir sonraki bakım için gelebilecekleri en son tarihe veya bu tarihten önce ancak yakın bir zamanda gelip servis almalarını sağlamaya çalışmalıdır. Çünkü vaktinden erken gelişleri havacılık şirketleri ekonomik açıdan tercih etmeyecektir. BO şirketi için sabit bir tamir bakım kapasitesi ve limitli envanter üretim çizelgeleme üzerindeki önemli kısıtlardır. Bu çalışmada yukarıda açıklanan problem toplam erken servis alışların en azlanması amacıyla, belirli bir başlangıç stoğu, kısıtlı üretim kapasitesi, çok tipli devinimli envanter, ve sonlu planlama ufku varsayımları altında modellenmiş, sayısal çözümler yardımıyla problemin analizi yapılmıştır. Devinimli envanter başlangıç seviyesini veya proses kapasitesini bir birim artırmanın azalan marjinal faydası ortaya konulmuş ve bu faydanın proses süresiyle ve proses kapasitesiyle ilişkisi gösterilmiştir.
IMSE Technical Reprot 98T, 1998
Page 1. Integrating Production and Transportation Logistics in a Supply Chain Environment: A Lagr... more Page 1. Integrating Production and Transportation Logistics in a Supply Chain Environment: A Lagrangean Decomposition Approach Kadir Ertograî S. David Wu Laura I. Burke Lehigh University Report No. 98T-010 Page 2. INTEGRATING ...
European Journal of Operational Research, 2008
ABSTRACT
European J. of Industrial Engineering, 2011
In this study, we consider the joint economic lot sizing problem (JELP) under stochastic demand. ... more In this study, we consider the joint economic lot sizing problem (JELP) under stochastic demand. Almost all of the literature on JELP assumes that the demand is deterministic and constant with very limited exceptions. We indicate the shortcomings of the work in the literature in this regard, and suggest a service-level based model for JELP under stochastic demand with an exact solution procedure. We also include numerical examples to illustrate the procedure and the value of the stochastic solution.
Journal of the Faculty of Engineering and Architecture of Gazi University
International Journal of Production Economics, 2005
The multi period inventory problems have been studied under two main assumptions. Continuous revi... more The multi period inventory problems have been studied under two main assumptions. Continuous review assumption where an order can be made at any time depending on inventory position and periodic review assumption where an order can be initiated only at discrete time epochs. In this study, we analyze a multi period inventory problem that falls under neither of these two
IIE Transactions, 2000
Most planning and optimization methods in manufacturing logistics assume centralized or hierarchi... more Most planning and optimization methods in manufacturing logistics assume centralized or hierarchical decision making using monolithic models. Motivated by the increasing needs to coordinate diverse decision processes and systems, we investigate an auction-theoretic mechanism for production coordination in a supply chain. Our efforts focuses on structural mappings between mathematical decomposition and iterative auction mechanisms wherein agents compete based on their local utilities, announced conflict pricing, and production targets. Building upon the rich literature in optimization and auction-theoretic analysis, we investigate the advantages and limitations of this distributed decision scheme on a large set problems in supply chain production planning. Experimental results show that the proposed auction mechanism provides impressive improvement over traditional monolithic method without significant degradation to the solution quality.
European Journal of Operational Research, 2007
... The reader is referred to Goyal and Gupta, 1989 and Ben-Daya et al., 2005 for comprehensive r... more ... The reader is referred to Goyal and Gupta, 1989 and Ben-Daya et al., 2005 for comprehensive reviews. In all models above, it has been implicitly assumed that the transportation cost is part of the ordering cost. ... The vendor and the buyer incur holding costs as well. ...
European Journal of Operational Research, 2008
With the growing focus on supply chain management, firms realize that inventories across the enti... more With the growing focus on supply chain management, firms realize that inventories across the entire supply chain can be more efficiently managed through greater cooperation and better coordination. This paper presents a comprehensive and up-todate review of the joint economic lot sizing problem (JELP) and also provides some extensions of this important problem. In particular, a detailed mathematical description of, and a unified framework for, the main JELP models are given. Additionally, a comparative empirical study of the main policies proposed for JELP is conducted. The focus of this study is on assessing the deviation of these policies from the optimal solution. Studying the performance of different models provides additional insights that will help in justifying their use in more complex supply chain models that involve more stages or other practical considerations of interest. (C) 2007 Elsevier B.V. All rights reserved.
Computers & Industrial Engineering, 2010
Facility layout problem has been extensively studied in the literature because the total material... more Facility layout problem has been extensively studied in the literature because the total material handling cost can be a significant portion in the operational costs for a company and in the manufacturing cost of a product. Today's severe global competition, rapid changes in technology and shortening life cycle of products force companies to evaluate and modify their facility layout in a periodic fashion. This type of layout problems is categorized as the dynamic facility layout problem (DFLP). As a realistic dimension of the problem, one has to consider also the limited budget to cover the cost of changing the layout. In this study, we propose a simulated annealing heuristic for the DFLP with budget constraint, and show the effectiveness of this heuristic on a set of numerical experiments.
Computers & Industrial Engineering, 2008
ABSTRACT
Dept. IMSE, Lehigh Univ., Bethlehem, PA, …, 1998
Coordinating operational and logistic functions across facilities and companies is key to supply ... more Coordinating operational and logistic functions across facilities and companies is key to supply chain integration. In this paper, we consider the coordination of production and transportation scheduling, a crucial link of this integration. In manufacturing-centric industries such as automotive and electronics, costs constitute the second transportation largest cost component following the costs. While the potential of integrating production production and transportation planning could be significant, there has been a lack of research and practice in integrating these functions. Functional silos or ad hoc interfaces are commonly seen in the industry. In this research, we propose an analytic study that investigates the effects of integrating production and transportation planning. We study integrated optimization models that reconcile the viewpoints from transportation and production planning and analyze the costs introduced by coordination. Using a Lagrangean decomposition scheme, we demonstrate computationally the nature of the comprise between production and transportation decisions, and the value of integration.