Nur Ozdemirel | Middle East Technical University (original) (raw)
Papers by Nur Ozdemirel
Simulation experts know very well that there are similarities between the models they build for d... more Simulation experts know very well that there are similarities between the models they build for different manufacturing systems. In a previous study, a group technology (GT) classification and coding scheme for discrete manufacturing simulation models was developed by observing those similarities, and generic discrete manutkcturing simulation models were conshucted based on the GT scheme. This article describes a measure of user acceptance for these generic models. The user acceptance measure is based on review of modeling assumptions and computed as the percentage of assumptions that are acceptable to the user. The assumptions, which describe the modeling options that are available in generic models, provide the user a detailed account of the capabilities and limitations of generic models. Hence reviewing the assumptions proves to be a most efficient means of informing the user about the generic models and measuring the user acceptance. 1 BACKGROUND The area of discrete manufacturi...
Evolutionary Learning and Optimization, 2010
Page 1. Chapter 15 An Evolutionary Approach for the TSP and the TSP with Backhauls Haldun Süral, ... more Page 1. Chapter 15 An Evolutionary Approach for the TSP and the TSP with Backhauls Haldun Süral, Nur Evin ¨Ozdemirel, ˙Ilter ¨Onder, and Meltem Sönmez Turan Abstract. This chapter presents an evolutionary approach for ...
1988 Winter Simulation Conference Proceedings, 1988
Abstract Although computer simulation is a well-studied and highly structured research area, its ... more Abstract Although computer simulation is a well-studied and highly structured research area, its use in industry is still limited due to the fact that simulation modeling requires expert knowledge. We believe that this expertise must be embedded in an integrated simulation ...
Total Quality Management & Business Excellence, 2005
Page 1. A Team Performance Measurement Model for Continuous Improvement MURAT CEM ÇI ˙ ÇEK, GULSE... more Page 1. A Team Performance Measurement Model for Continuous Improvement MURAT CEM ÇI ˙ ÇEK, GULSER KOKSAL Ã & NUR EVI ˙ N OZDEMI ˙ REL Industrial Engineering Department, Middle East Technical University, Ankara, Turkey ...
SIMULATION, 1996
Abstract As simulation has become a major tool in studying discrete manufacturing systems, experi... more Abstract As simulation has become a major tool in studying discrete manufacturing systems, experimental design issues have started to receive much attention. Although the importance of proper experimentation is often emphasized in the literature on discrete event ...
Naval Research Logistics (NRL), 2011
... Al-Mutairi and Soland [3] analyze the effectiveness of partially coordinated area defense sys... more ... Al-Mutairi and Soland [3] analyze the effectiveness of partially coordinated area defense systems against a simultaneous attack. Due to the computational complexity of the missile allocation prob-lem, a number of heuristic approaches have been suggested. ... Al-Mutairi et al. ...
Naval Research Logistics (NRL), 2011
ABSTRACT A naval task group (TG) is a collection of naval combatants and auxiliaries that are gro... more ABSTRACT A naval task group (TG) is a collection of naval combatants and auxiliaries that are grouped together for the accomplishment of one or more missions. Ships forming a TG are located in predefined sectors. We define determination of ship sector locations to provide a robust air defense formation as the sector allocation problem (SAP). A robust formation is one that is very effective against a variety of attack scenarios but not necessarily the most effective against any scenario. We propose a 0-1 integer linear programming formulation for SAP. The model takes the size and the direction of threat into account as well as the defensive weapons of the naval TG. We develop tight lower and upper bounds by incorporating some valid inequalities and use a branch and bound algorithm to exactly solve SAP. We report computational results that demonstrate the effectiveness of the proposed solution approach. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011
Journal of the Operational Research Society, 2003
International Journal of Production Research, 2008
We study the profit oriented partial disassembly line balancing problem, which simultaneously det... more We study the profit oriented partial disassembly line balancing problem, which simultaneously determines (i) the parts whose demand is to be fulfilled to generate revenue, (ii) the tasks that will release the selected parts under task and station costs, (iii) the number of stations that will be opened, (iv) the cycle time, and (v) the balance of the disassembly line, i.e. the feasible assignment of selected disassembly tasks to stations such that various types of precedence relations among the tasks are satisfied. We characterize the precedence relation types in disassembly and provide a mixed integer programming formulation of the problem. We propose a linear programming based lower and upper bounding scheme.
IIE Transactions, 1999
In this study, two shared storage assignment policies are compared in an Automated Storage/Retrie... more In this study, two shared storage assignment policies are compared in an Automated Storage/Retrieval System (AS/RS) by using computer simulation. The AS/RS is assumed to operate under a continuous review, order quantity, reorder point inventory policy. The average travel time of the AS/R machine for storing and retrieving products is used as the main performance measure. Sensitivity of the system
European Journal of Operational Research, 2006
We explore use of data mining for lead time estimation in make-to-order manufacturing. The regres... more We explore use of data mining for lead time estimation in make-to-order manufacturing. The regression tree approach is chosen as the specific data mining method. Training and test data are generated from variations of a job shop simulation model. Starting with a large set of job and shop attributes, a reasonably small subset is selected based on their contribution to estimation performance. Data mining with the selected attributes is compared with linear regression and three other lead time estimation methods from the literature. Empirical results indicate that our data mining approach coupled with the attribute selection scheme outperforms these methods.
Computers & Industrial Engineering, 2009
Single model assembly line balancing Station paralleling Branch and bound algorithm a b s t r a c t
Proceedings of XVII …, 2006
The main aim of this study is to identify the most influential variables that cause defects on th... more The main aim of this study is to identify the most influential variables that cause defects on the items produced by a casting company located in Turkey. To this end, one of the items produced by the company with high defective percentage rates is selected. Two approaches-the regression analysis and decision treesare used to model the relationship between process parameters and defect types. Although logistic regression models failed, decision tree model gives meaningful results. Based on these results, it can be claimed that the decision tree approach is a promising technique for determining the most important process variables.
Computers & Operations Research, 2014
ABSTRACT Given a set of n interacting points in a network, the hub location problem determines lo... more ABSTRACT Given a set of n interacting points in a network, the hub location problem determines location of the hubs (transfer points) and assigns spokes (origin and destination points) to hubs so as to minimize the total transportation cost. In this study, we deal with the uncapacitated single allocation planar hub location problem (PHLP). In this problem, all flow between pairs of spokes goes through hubs, capacities of hubs are infinite, they can be located anywhere on the plane and are fully connected, and each spoke must be assigned to only one hub. We propose a mathematical formulation and a genetic algorithm (PHLGA) to solve PHLP in reasonable time. We test PHLGA on simulated and real life data sets. We compare our results with optimal solution and analyze results for special cases of PHLP for which the solution behavior can be predicted. Moreover, PHLGA results for the AP and CAB data set are compared with other heuristics.
Simulation experts know very well that there are similarities between the models they build for d... more Simulation experts know very well that there are similarities between the models they build for different manufacturing systems. In a previous study, a group technology (GT) classification and coding scheme for discrete manufacturing simulation models was developed by observing those similarities, and generic discrete manutkcturing simulation models were conshucted based on the GT scheme. This article describes a measure of user acceptance for these generic models. The user acceptance measure is based on review of modeling assumptions and computed as the percentage of assumptions that are acceptable to the user. The assumptions, which describe the modeling options that are available in generic models, provide the user a detailed account of the capabilities and limitations of generic models. Hence reviewing the assumptions proves to be a most efficient means of informing the user about the generic models and measuring the user acceptance. 1 BACKGROUND The area of discrete manufacturi...
Evolutionary Learning and Optimization, 2010
Page 1. Chapter 15 An Evolutionary Approach for the TSP and the TSP with Backhauls Haldun Süral, ... more Page 1. Chapter 15 An Evolutionary Approach for the TSP and the TSP with Backhauls Haldun Süral, Nur Evin ¨Ozdemirel, ˙Ilter ¨Onder, and Meltem Sönmez Turan Abstract. This chapter presents an evolutionary approach for ...
1988 Winter Simulation Conference Proceedings, 1988
Abstract Although computer simulation is a well-studied and highly structured research area, its ... more Abstract Although computer simulation is a well-studied and highly structured research area, its use in industry is still limited due to the fact that simulation modeling requires expert knowledge. We believe that this expertise must be embedded in an integrated simulation ...
Total Quality Management & Business Excellence, 2005
Page 1. A Team Performance Measurement Model for Continuous Improvement MURAT CEM ÇI ˙ ÇEK, GULSE... more Page 1. A Team Performance Measurement Model for Continuous Improvement MURAT CEM ÇI ˙ ÇEK, GULSER KOKSAL Ã & NUR EVI ˙ N OZDEMI ˙ REL Industrial Engineering Department, Middle East Technical University, Ankara, Turkey ...
SIMULATION, 1996
Abstract As simulation has become a major tool in studying discrete manufacturing systems, experi... more Abstract As simulation has become a major tool in studying discrete manufacturing systems, experimental design issues have started to receive much attention. Although the importance of proper experimentation is often emphasized in the literature on discrete event ...
Naval Research Logistics (NRL), 2011
... Al-Mutairi and Soland [3] analyze the effectiveness of partially coordinated area defense sys... more ... Al-Mutairi and Soland [3] analyze the effectiveness of partially coordinated area defense systems against a simultaneous attack. Due to the computational complexity of the missile allocation prob-lem, a number of heuristic approaches have been suggested. ... Al-Mutairi et al. ...
Naval Research Logistics (NRL), 2011
ABSTRACT A naval task group (TG) is a collection of naval combatants and auxiliaries that are gro... more ABSTRACT A naval task group (TG) is a collection of naval combatants and auxiliaries that are grouped together for the accomplishment of one or more missions. Ships forming a TG are located in predefined sectors. We define determination of ship sector locations to provide a robust air defense formation as the sector allocation problem (SAP). A robust formation is one that is very effective against a variety of attack scenarios but not necessarily the most effective against any scenario. We propose a 0-1 integer linear programming formulation for SAP. The model takes the size and the direction of threat into account as well as the defensive weapons of the naval TG. We develop tight lower and upper bounds by incorporating some valid inequalities and use a branch and bound algorithm to exactly solve SAP. We report computational results that demonstrate the effectiveness of the proposed solution approach. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011
Journal of the Operational Research Society, 2003
International Journal of Production Research, 2008
We study the profit oriented partial disassembly line balancing problem, which simultaneously det... more We study the profit oriented partial disassembly line balancing problem, which simultaneously determines (i) the parts whose demand is to be fulfilled to generate revenue, (ii) the tasks that will release the selected parts under task and station costs, (iii) the number of stations that will be opened, (iv) the cycle time, and (v) the balance of the disassembly line, i.e. the feasible assignment of selected disassembly tasks to stations such that various types of precedence relations among the tasks are satisfied. We characterize the precedence relation types in disassembly and provide a mixed integer programming formulation of the problem. We propose a linear programming based lower and upper bounding scheme.
IIE Transactions, 1999
In this study, two shared storage assignment policies are compared in an Automated Storage/Retrie... more In this study, two shared storage assignment policies are compared in an Automated Storage/Retrieval System (AS/RS) by using computer simulation. The AS/RS is assumed to operate under a continuous review, order quantity, reorder point inventory policy. The average travel time of the AS/R machine for storing and retrieving products is used as the main performance measure. Sensitivity of the system
European Journal of Operational Research, 2006
We explore use of data mining for lead time estimation in make-to-order manufacturing. The regres... more We explore use of data mining for lead time estimation in make-to-order manufacturing. The regression tree approach is chosen as the specific data mining method. Training and test data are generated from variations of a job shop simulation model. Starting with a large set of job and shop attributes, a reasonably small subset is selected based on their contribution to estimation performance. Data mining with the selected attributes is compared with linear regression and three other lead time estimation methods from the literature. Empirical results indicate that our data mining approach coupled with the attribute selection scheme outperforms these methods.
Computers & Industrial Engineering, 2009
Single model assembly line balancing Station paralleling Branch and bound algorithm a b s t r a c t
Proceedings of XVII …, 2006
The main aim of this study is to identify the most influential variables that cause defects on th... more The main aim of this study is to identify the most influential variables that cause defects on the items produced by a casting company located in Turkey. To this end, one of the items produced by the company with high defective percentage rates is selected. Two approaches-the regression analysis and decision treesare used to model the relationship between process parameters and defect types. Although logistic regression models failed, decision tree model gives meaningful results. Based on these results, it can be claimed that the decision tree approach is a promising technique for determining the most important process variables.
Computers & Operations Research, 2014
ABSTRACT Given a set of n interacting points in a network, the hub location problem determines lo... more ABSTRACT Given a set of n interacting points in a network, the hub location problem determines location of the hubs (transfer points) and assigns spokes (origin and destination points) to hubs so as to minimize the total transportation cost. In this study, we deal with the uncapacitated single allocation planar hub location problem (PHLP). In this problem, all flow between pairs of spokes goes through hubs, capacities of hubs are infinite, they can be located anywhere on the plane and are fully connected, and each spoke must be assigned to only one hub. We propose a mathematical formulation and a genetic algorithm (PHLGA) to solve PHLP in reasonable time. We test PHLGA on simulated and real life data sets. We compare our results with optimal solution and analyze results for special cases of PHLP for which the solution behavior can be predicted. Moreover, PHLGA results for the AP and CAB data set are compared with other heuristics.