Solving a robust airline crew pairing problem with column generation

In this study, we solve a robust version of the airline crew pairing problem. Our concept of robustness was partially shaped during our discussions with small local airlines in Turkey which may have to add a set of extra flights into their schedule at short notice during operation. Thus, robustness in this case is related to the ability of accommodating these extra flights at the time of operation by disrupting the original plans as minimally as possible. We focus on the crew pairing aspect of robustness and prescribe that the planned crew pairings incorporate a number of predefined recovery solutions for each potential extra flight. These solutions are implemented only if necessary for recovery purposes and involve either inserting an extra flight into an existing pairing or partially swapping the flights in two existing pairings in order to cover an extra flight. The resulting mathematical programming model follows the conventional set covering formulation of the airline crew pairing problem typically solved by column generation with an additional complication. The model includes constraints that depend on the columns due to the robustness consideration and grows not only column-wise but also row-wise as new columns are generated. To solve this dicult model, we propose a row and column generation approach. This approach requires a set of modifications to the multi-label shortest path problem for pricing out new columns (pairings) and various mechanisms to handle the simultaneous increase in the number of rows and columns in the restricted master problem during column generation. We conduct computational experiments on a set of real instances compiled from a local airline in Turkey

An efficient heuristic for the multi-vehicle one-to-one pickup and delivery problem with split loads

In this study, we consider the Multi-vehicle One-to-one Pickup and Delivery Problem with Split Loads (MPDPSL). This problem is a generalization of the one-to-one Pickup and Delivery Problem (PDP) where each load can be served by multiple vehicles as well as multiple stops by the same vehicle. In practice, split deliveries is a viable option in many settings where the load can be physically split, such as courier services of third party logistics operators. We propose an efficient heuristic that combines the strengths of Tabu Search and Simulated Annealing for the solution of MPDPSL. Results from experiments on two problems sets in the literature indicate that the heuristic is capable of producing good quality solutions in reasonable time. The experiments also demonstrate that up to 33\% savings can be obtained by allowing split loads; however, the magnitude of savings is dependent largely on the spatial distribution of the pickup and delivery points

A dissident attitude in Turkish press life: Alemdar Newspaper(1919-1921)

Milli Mücadele dönemi basını hakkında son yıllarda önemli çalışmalar yapılmıştır Fakat bu ele alınan çalışmaların geneli Milli Mücadele’ye destek veren basın yayın organları üzerine yapılmıştır. Bu çalışmada Milli Mücadele’ye muhalif bir gazete olan Alemdar Gazetesi’nin Milli Mücadele’ye bakış açısının ortaya konulması amaçlanmıştır. Çalışma sırasında gazete ile ilgili kaynakların azlığı söz konusuydu. 1919 - 1921 tarihleri arasındaki nüshaların taraması yapılmıştır. Çalışma sonucunda, gazetenin Milli Mücadele karşıtı, Hürriyet ve İtilaf yanlısı, teslimiyetçi ve İngiliz taraftarı bir tutum sergilediği anlaşılmıştır.In recent years, important studies have been made about the press of the National Struggle period, but these studies have been carried out on press organs supporting the National Struggle. In this study, it is aimed to put forward the point of view of Alemdar Newspaper, which is opposed to National Struggle, against National Struggle. During the study, there was a lack of resources related to the newspaper. Between 1919 and 1921, copies were screened. As a result of the study, it was understood that the newspaper was anti-National Struggle, pro-Hürriyet and Allied, surrendering and pro-British

Quality of preservice teachers argumentation in socioscientific issues context

This study aimed to explore preservice teachers’ (PTs) argumentation quality during socioscientific issues (SSI) based classroom discussions.  The participants of the study were 20 PTs from the Department of Elementary Education at a large, research oriented public university in Turkey. Qualitative case study  method was used in this study. The study covered four socioscientific issues (food additives, alternative energy sources, climate change, and the industrial revolution).  Each issue was  discussed in the classroom and each discussion was video recorded.  Video recordings were transcribed verbatim and used as data source.  Classroom discussions verbatim transcribes were analyzed by using a  modified version of Toulmin’s argumentation pattern (TAP) model. The modified approach was found to be more conducive to informal argumentation patterns, in order to analyze preservice teachers’ use of claims, grounds, warrants, backings, and rebuttals that support their debate positions, as well as their ability to use evidence-based reasoning, form coherent lines of reasoning, and use of correct (appropriate) evidence. Results of the study revealed that preservice teachers’ use of evidence to support conflicting ideas tended to increase as their use of incorrect or insufficient use of evidence decreased through the present study