Browsing by Subject "Air transportation"

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Anadolu Üniversitesi Sivil Havacılık Yüksekokulunun tarihçesi
(Bilkent University, 2021) Yeni, Cem; Aybar, Mert; Aldırmaz, Aybüke; Bahriş, Batuhan; Güre, Gamze
1980’lerin ortalarına kadar sivil havacılık konusunda diğer gelişmiş ülkelerle karşılaştırıldığında geride kalan Türk Sivil Havacılığı 1986’dan itibaren köklü değişimler yaşamıştır. Özel sektöre hava taşımacılığı ve havaalanı işletmeciliği yapabilme hakkı verilmesi sonucu oluşan nitelikli personel açığını kapatma amacıyla kurulan Anadolu Üniversitesi Sivil Havacılık Yüksekokulu beraberinde ülkenin sivil havacılık sektörünü derinden etkileyecek değişimlerin başlangıcına yol açmıştır. Bu yazıda, okulun kurucu üyelerinden olan Prof. Dr. Mustafa Cavcar’ın ve grubun elinde bulunan arşivlerin yardımlarıyla Anadolu Üniversitesi Sivil Havacılık Yüksekokulu’nun kuruluş amacı, kuruluş süreci ve sonrasında yaşadıkları ele alınmıştır.
Open Access
Comparison of the formulations for a hub-and-spoke network design problem under congestion
(Elsevier, 2016) Kian, Ramer; Kargar, Kamyar
In this paper, we study the hub location problem with a power-law congestion cost and propose an exact solution approach. We formulate this problem in a conic quadratic form and use a strengthening method which rests on valid inequalities of perspective cuts in mixed integer nonlinear programming. In a numerical study, we compare two well known types of mathematical modeling in the hub-location problems which are solved with different branch and cut strategies. The strength and weakness of the formulations are summarized based on an extensive numerical study over the CAB data set. © 2016 Elsevier Ltd
Open Access
Flight network-based approach for integrated airline recovery with cruise speed control
(Institute for Operations Research and the Management Sciences (I N F O R M S), 2017) Arıkan, U.; Gürel, S.; Aktürk, M. S.
Airline schedules are generally tight and fragile to disruptions. Disruptions can have severe effects on existing aircraft routings, crew pairings, and passenger itineraries that lead to high delay and recovery costs. A recovery approach should integrate the recovery decisions for all entities (aircraft, crew, passengers) in the system as recovery decisions about an entity directly affect the others' schedules. Because of the size of airline flight networks and the requirement for quick recovery decisions, the integrated airline recovery problem is highly complex. In the past decade, an increasing effort has been made to integrate passenger and crew related recovery decisions with aircraft recovery decisions both in practice and in the literature. In this paper, we develop a new flight network based representation for the integrated airline recovery problem. Our approach is based on the flowof each aircraft, crewmember, and passenger through the flight network of the airline. The proposed network structure allows common recovery decisions such as departure delays, aircraft/crew rerouting, passenger reaccommodation, ticket cancellations, and flight cancellations. Furthermore, we can implement aircraft cruise speed (flight time) decisions on the flight network. For the integrated airline recovery problem defined over this network, we propose a conic quadratic mixed integer programming formulation that can be solved in reasonable CPU times for practical size instances. Moreover, we place a special emphasis on passenger recovery. In addition to aggregation and approximation methods, our model allows explicit modeling of passengers and evaluating a more realistic measure of passenger delay costs. Finally, we propose methods based on the proposed network representation to control the problem size and to deal with large airline networks. © 2017 INFORMS.
Open Access
An integrated approach for airline scheduling, aircraft fleeting and routing with cruise speed control
(Elsevier, 2016) Gürkan, H.; Gürel, S.; Aktürk, M. S.
To place an emphasis on profound relations among airline schedule planning problems and to mitigate the effect of unexpected delays, we integrate schedule design, fleet assignment and aircraft routing problems within a daily planning horizon while passengers' connection service levels are ensured via chance constraints. We propose a nonlinear mixed integer programming model due to the nonlinear fuel consumption and CO2 emission cost terms in the objective function, which is handled by second order conic reformulation. The key contribution of this study is to take into account the cruise time control for the first time in an integrated model of these three stages of airline operations. Changing cruise times of flights in an integrated model enables to construct a schedule to increase utilization of fuel efficient aircraft and even to decrease total number of aircraft needed while satisfying the same service level and maintenance requirements for aircraft fleeting and routing. There is a critical tradeoff between the number of aircraft needed to fulfill the required flights and overall operational expenses. We also propose two heuristic methods to solve larger size problems. Finally, computational results using real data obtained from a major U.S. carrier are presented to demonstrate potential profitability in applying the proposed solution methods.
Open Access
The latest arrival hub location problem
(Institute for Operations Research and the Management Sciences (INFORM), 2001) Kara, B. Y.; Tansel, B. Ç.
The traditionally studied hub location problems in the literature pay attention to flight times but not to transient times spent at hubs for unloading, loading, and sorting operations. The transient times may constitute a significant portion of the total delivery time for cargo delivery systems. We focus on the minimization of the arrival time of the last arrived item in cargo delivery systems and develop a model that correctly computes the arrival times by taking into account both the flight times and the transient times. Nonlinear and linear integer formulations are given and computational results are provided. The effects of delays on the system performance are analyzed.