Browsing by Author "Taner, M. R."
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Item Open Access Endogenous effects of hubbing on flow intensities(Springer, 2016) Taner, M. R.; Kara, B. Y.Location of hub facilities and the allocation decisions in transport networks endogenously affect both the flow intensities and the transportation costs. Since the introduction of the hub location problem to the operations research literature in mid-1980s, many researchers investigated different ways of modelling the effects of hub facilities on the transportation costs. On the other hand, there has been very limited research on their effect on the flow intensities. This study proposes a new approach, inspired by the Bass diffusion model, to forecast the change in the demand patterns generated at different locations as a result of the placement of new hubs. This new model is used in the context of the uncapacitated single allocation p-hub median problem to investigate the effects of endogenous attraction, caused by the spatial interaction of present hubs, on future hub location decisions. Computational results indicate that the location and allocation decisions may be greatly affected when these forecasts are taken into account in the selection of future hub locations.Item Open Access Hub location problems : the location of interacting facilities(Springer New York LLC, 2011) Kara, B. Y.; Taner, M. R.[No abstract available]Item Open Access Minimizing Lmax for the single machine scheduling problem with family set-ups(Taylor & Francis, 2004) Schultz, S. R.; Hodgson, T. J.; King, R. E.; Taner, M. R.A procedure for the single machine-scheduling problem of minimizing the maximum lateness for jobs with sequence independent set-ups is presented. The procedure provides optimal/near-optimal solutions over a wide range of problems. It performs well compared with other heuristics, and it is effective in finding solutions for large problems.Item Open Access The role of repair strategy in warranty cost minimization: an investigation via quasi-renewal processes(Elsevier, 2009) Samatlı-Paç, G.; Taner, M. R.Most companies seek efficient rectification strategies to keep their warranty related costs under control. This study develops and investigates different repair strategies for one- and two-dimensional warranties with the objective of minimizing manufacturer's expected warranty cost. Static, improved and dynamic repair strategies are proposed and analyzed under different warranty structures. Numerical experimentation with representative cost functions indicates that performance of the policies depend on various factors such as product reliability, structure of the cost function and type of the warranty contract.Item Open Access Satisfying due-dates in a job shop with sequence-dependent family set-ups(Taylor & Francis, 2003) Taner, M. R.; Hodgson, T. J.; King, R. E.; Thoney, K. A.This paper addresses job shop scheduling with sequence dependent family set-ups. Based on a simple, single-machine dynamic scheduling problem, state dependent scheduling rules for the single machine problem are developed and tested using Markov Decision Processes. Then, a generalized scheduling policy for the job shop problem is established based on a characterization of the optimal policy. The policy is combined with a ‘forecasting’ mechanism to utilize global shop floor information for local dispatching decisions. Computational results show that performance is significantly better than that of existing alternative policies.Item Open Access Satisfying due-dates in the presence of sequence dependent family setups with a special comedown structure(Elsevier, 2007-12-22) Taner, M. R.; Hodgson, T. J.; King, R. E.; Schultz, S. R.This paper addresses a static, n-job, single-machine scheduling problem with sequence dependent family setups. The setup matrix follows a special structure where a constant setup is required only if a job from a smaller indexed family is an immediate successor of one from a larger indexed family. The objective is to minimize the maximum lateness (Lmax). A two-step neighborhood search procedure and an implicit enumeration scheme are proposed. Both procedures exploit the problem structure. The enumeration scheme produces optimum solutions to small and medium sized problems in reasonable computational times, yet it fails to perform efficiently in larger instances. Computational results show that the heuristic procedure is highly effective, and is efficient even for extremely large problems.Item Open Access Scheduling beams with different priorities on a military surveillance radar(Institute of Electrical and Electronics Engineers, 2012) Taner, M. R.; Karasan O. E.; Yavuzturk, E.The problem of scheduling the searching, verification, and tracking tasks of a ground based, three-dimensional military surveillance radar is studied. Although the radar is mechanically steered in the sense that a servomechanism rotates the antenna at a constant turn rate, it has limited electronic steering capability in azimuth. The scheduling problem arises within a planning period during which the antenna scans a given physical range. A task/job corresponds to sending a transmission beam to hit a particular target. Targets are allowed to be hit with an angular deviation up to a predetermined magnitude. The steering mechanism of the radar helps alter these deviations by imposing a scan-off angle from broadside on the transmission beam. A list of jobs along with their priority weights, processing times, and ideal beam positions are given during a predetermined planning period. The ideal beam position for a given job allows hitting the corresponding target with zero deviation. Each job also has a set of available scan-off angles. It is possible to map the antennas physical position, beam positions, scan-off angles, and angular deviations to a time scale. The goal is to select the subset of jobs to be processed during the given planning period and determining the starting time and scan-off angle for each selected job. The objectives are to simultaneously minimize the weighted number of unprocessed jobs and the total weighted deviation. An integer programming model and two versions of a heuristic mechanism that relies on the exact solution of a special case are proposed. Results of a computational study are presented.Item Open Access Selective vehicle routing for a mobile blood donation system(Elsevier, 2015) Şahinyazan, F. G.; Kara, B. Y.; Taner, M. R.In this study, a mobile blood collection system is designed with the primary objective of increasing blood collection levels. This design also takes into account operational costs to aim for collection of large amounts of blood at reasonable cost. Bloodmobiles perform direct tours to certain activities to collect blood, but at the end of each day, they bring the collected blood to a designated depot to prevent its spoilage. The proposed system consists of the bloodmobiles and a new vehicle called the shuttle that visits the bloodmobiles in the field on each day and transfers the collected blood to the depot. Consequently, bloodmobiles can continue their tours without having to make daily returns to the depot. We propose a mathematical model and a 2-stage IP based heuristic algorithm to determine the tours of the bloodmobiles and the shuttle, and their lengths of stay at each stop. This new problem is defined as an extension of the Selective Vehicle Routing Problem and is referred to as the SVRP with Integrated Tours. The performances of the solution methodologies are tested first on a real data set obtained from past blood donation activities of Turkish Red Crescent in Ankara, and then on a constructed data set based on GIS data of the European part of Istanbul. The Pareto set of optimum solutions is generated based on blood amounts and logistics costs, and finally a sensitivity analysis on some important design parameters is conducted.