Browsing by Author "Azizoglu, Meral"

Now showing 1 - 5 of 5

Citation - WoS: 4
Citation - Scopus: 4
Beam Search Algorithm for Capacity Allocation Problem in Flexible Manufacturing Systems
(Pergamon-Elsevier Science Ltd, 2009) Özpeynirci, Selin; Azizoglu, Meral
This study considers the operation assignment and tool allocation problem in flexible manufacturing systems. A set of operations together with their required tools are selected so as to maximize the total weight. The machines have limited time and tool magazine capacities and the tools are available in limited quantities. We develop a beam search algorithm and obtain near optimal solutions for large size problems very quickly. (C) 2008 Elsevier Ltd. All rights reserved.
Citation - WoS: 8
Citation - Scopus: 10
Bounding Approaches for Operation Assignment and Capacity Allocation Problem in Flexible Manufacturing Systems
(Pergamon-Elsevier Science Ltd, 2009) Özpeynirci, Selin; Azizoglu, Meral
This study considers an operation assignment and capacity allocation problem that arises in flexible manufacturing systems. Automated machines are assumed to have scarce time and tool magazine capacities and the tools are available in limited quantities. The aim is to select a subset of operations with maximum total weight. The weight of an operation may represent its profit, processing load, relative priority. Several upper bounding procedures have been taken into account. The results of computational tests have revealed that the proposed upper bounding procedures produce satisfactory solutions in reasonable CPU times. We suggest using some of the bounds when the quality of the solutions is more important than the speed of achieving them and some others when the speed is more important than the quality. (C) 2008 Elsevier Ltd. All rights reserved.
Citation - WoS: 4
Citation - Scopus: 6
Capacity Allocation Problem in Flexible Manufacturing Systems: Branch and Bound Based Approaches
(Taylor & Francis Ltd, 2009) Özpeynirci, Selin; Azizoglu, Meral
This study considers an operation assignment and capacity allocation problem that arises in flexible manufacturing systems. The machines have limited time and tool magazine capacities and the available tools are limited. Our objective is to maximise total weight of assigned operations. We develop a branch and bound algorithm that finds the optimal solutions and a beam search algorithm that finds high quality solutions in polynomial time.
Citation - WoS: 11
Citation - Scopus: 11
Heuristics for Operational Fixed Job Scheduling Problems With Working and Spread Time Constraints
(Elsevier, 2011) Eliiyi Türsel, Deniz; Azizoglu, Meral
Operational fixed job scheduling problems select a set of jobs having fixed ready and processing times and schedule the selected jobs on parallel machines so as to maximize the total weight. In this study, we consider working time and spread time constrained versions of the operational fixed job scheduling problems. The working time constraints limit the total processing load on each machine. The spread time constraints limit the time between the start of the first job and the finish of the last job on each machine. For the working time constrained problem, we present a filtered beam search algorithm that evaluates the promising nodes of the branch and bound tree. For the spread time constrained problem we propose a two phase algorithm that defines the promising sets for the first jobs and finds a solution for each promising set. The results of our computational tests reveal that our heuristic algorithms perform very well in terms of both solution quality and time. (C) 2011 Elsevier B.V. All rights reserved.
Citation - WoS: 6
Citation - Scopus: 6
Working Time Constraints in Operational Fixed Job Scheduling
(Taylor & Francis Ltd, 2010) Eliiyi Türsel, Deniz; Azizoglu, Meral
In this study we consider the operational fixed job scheduling problem under working time limitations. The problem has several practical implications in both production and service operations; however the relevant research is scarce. We analyse pre-emptive and non pre-emptive versions of the problem and its special cases. We provide polynomial-time algorithms for some special cases. We show that the non pre-emptive jobs problem is strongly NP-hard, and propose a branch-and-bound algorithm that employs efficient bounding procedures and dominance properties. We conduct a numerical experiment to observe the effects of parameters on the quality of the solution. The results of our computational tests for the branch-and-bound algorithm reveal that our algorithm can solve the instances with up to 100 jobs in reasonable times. To the best of our knowledge our branch-and-bound algorithm is the first optimisation attempt to solve the problem.