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    Column generation based solution for bi-objective gate assignment problems
    (Springer Heidelberg, 2024) Das, Gulesin Sena; Gzara, Fatma
    In this paper, we present a column generation-based algorithm for the bi-objective gate assignment problem (GAP) to generate gate schedules that minimize squared slack time at the gates while satisfying passenger expectations by minimizing their walking distance. While most of the literature focuses on heuristic or metaheuristic solutions for the bi-objective GAP, we propose flow-based and column-based models that lead to exact or near optimal solution approaches. The developed algorithm calculates a set of solutions to approximate the Pareto front. The algorithm is applied to the over-constrained GAP where gates are a limited resource and it is not possible to serve every flight using a gate. Our test cases are based on real data from an international airport and include various instances with flight-to-gate ratios between 23.9 and 34.7. Numerical results reveal that a set of solutions representing a compromise between the passenger-oriented and robustness-oriented objectives may be obtained with a tight optimality gap and within reasonable computational time even for these difficult problems.
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    Designing Public Policies to Support SME Innovation Capacity: Proposal of an Approach based on Innovativeness Profiles
    (Ege Univ, Fac Economics & Admin Sciences, 2016) Yülek, Murat; Das, Gulesin Sena
    It is crucial for enterprises to follow sustainable and competitive growth strategies to survive in the global market. Companies which cannot produce adequate levels of innovation outputs are likely to lose their competitiveness. Small and medium size enterprises (SMEs) which constitute a large part of enterprises face more diverse set of obstacles than larger enterprises. Thus, in many countries public policies that encourage innovation are encountered. In this study, an approach is proposed to design public policies based on innovation profiles of SMEs. The approach would lead to different strategic roadmaps and public support tools designed for SMEs with different innovative profiles. That would increase the contribution of SMEs to the country's overall technological development process and international competitiveness.
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    Forecasting the energy demand of Turkey with a NN based on an improved Particle Swarm Optimization
    (Springer London Ltd, 2017) Das, Gulesin Sena
    Forecasting the future energy demand accurately is a critical issue, especially for countries like Turkey where the energy dependency ratio is high. This paper presents a neural network based on the particle swarm optimization algorithm with mutation (PSOM-NN) to enhance the prediction accuracy of the energy demand of Turkey. Unlike some studies in the field which are using all the observed data for training purpose, the proposed network used only a part of these data for training. Approximately 63 % and 37 % of the mentioned data are used for the training and test, respectively. Detrending is applied to the data to avoid nonlinear transfer functions that constrain the model to the input range values. The analysis of the results revealed that PSOM-NN produced better forecasts of energy demand compared to the earlier studies in terms of root-meansquare error, mean absolute percentage error and mean absolute deviation. Finally, future projections under different scenarios are also employed and discussed. It is believed that the proposed model could be applied to any country that needs accurate forecasts of the energy demand for sustainable energy policies.
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    An Intrusion Detection System Based on a Hybrid Tabu-Genetic Algorithm
    (Ieee, 2017) Bakour, Khaled; Das, Gulesin Sena; Unver, H. Murat
    In this paper, we proposed a framework for detecting network's intrusions using Genetic Algorithm (GA) with multiple criteria. First of all, we build an intrusion detection system (IDS) using a pure GA with multiple selection methods. Then, we proposed one of the few hybrid algorithms in the literature, which is hybridized using a GA and a Tabu search (TS) algorithm. The proposed hybrid algorithm and the pure GA were tested to detect malicious traffic using DARPA dataset. The test results revealed that the proposed hybrid algorithm gives a higher Detection Rate (DR) and Detection Accuracy (AC) compared to the pure GA.
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    A new approach based on OEE to improve equipment effectiveness in SMEs: an application in a wood processing facility
    (Gazi Univ, Fac Engineering Architecture, 2017) Yasin, Mehmet Fatih; Das, Gulesin Sena
    In this study, a new method based on Overall Equipment Effectiveness (OEE) is presented to improve equipment effectiveness of a Small and Medium Sized Enterprise (SME). As known, the aim of OEE is to enable an increase in the productivity of equipment by revealing the equipment losses in the system. However, there are various difficulties that SMEs face when utilizing this tool. One of these difficulties faced by SMEs is to allocate time and money to these improvement studies. Another difficulty that arises during these studies is that application of OEE differs by the industry and production environment. In this study, a new method based on OEE is proposed by considering the above-mentioned difficulties. The proposed method is trying to find an answer to the question of "Which equipment should be improved to what extend?" during the improvement studies of SMEs (having limited resources). By applying of the method to a wood processing facility, an increase of the OEE value of the selected machine from %64.7 to %72.4 is observed and this in turn positively affected the effectiveness of the selected production line.
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    A review on airport gate assignment problems: Single versus multi objective approaches
    (PERGAMON-ELSEVIER SCIENCE LTD, 2020) Das, Gulesin Sena; Gzara, Fatma; Stutzle, Thomas
    Assigning aircraft to gates is an important decision problem that airport professionals face every day. The solution of this problem has raised a significant research effort and many variants of this problem have been studied. In this paper, we review past work with a focus on identifying types of formulations, classifying objectives, and categorising solution methods. The review indicates that there is no standard formulation, that passenger oriented objectives are most common, and that more recent work are multi-objective. In terms of solution methods, heuristic and metaheuristic approaches are dominant which provides an opportunity to develop exact and approximate approaches both for the single and multi-objective problems. (C) 2019 Elsevier Ltd. All rights reserved.