Papers by Cynthia Barnhart
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SSRN Electronic Journal, 2017
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International Series in Operations Research & Management Science, 2012
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Handbooks in operations research and management science, 2007
Publisher Summary This chapter discusses problems related to the management of air traffic and ai... more Publisher Summary This chapter discusses problems related to the management of air traffic and airline operations for minimizing the impact and cost of disruptions. Flight and crew schedules and passenger itineraries have become increasingly fragile because of the growing complexity of the air transportation system and the tight coupling of its various elements. The resulting direct and indirect economic costs are very large, certainly amounting to several billion dollars annually. The airline industry has a vital stake in research aimed at mitigating the effects of severe weather and other disruptive events and at expediting recovery from irregular operations. A significant body of recent and ongoing work has led to major progress toward these objectives. Two breakthrough developments have been the primary drivers behind this progress. First, collaborative decision making has made it possible to apply the principles of information sharing and distributed decision making to air traffic flow management (ATFM) by expanding the databases available to airline and Federal Aviation Administration (FAA) traffic flow managers, by creating common situational awareness, and by introducing shared real-time tools and procedures. Second, there is growing recognition in the airline industry of the fact that planning for schedule robustness and reliability may be just as important as planning for minimizing costs in the complex, highly stochastic, and dynamic environment of air transportation.
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Abstract: Many of the existing methods for evaluating an airline's on-time performance are b... more Abstract: Many of the existing methods for evaluating an airline's on-time performance are based on flight-centric measures of flight delay. However, recent research has demonstrated that as much as 50% of passenger delays are caused by passenger travel disruptions, either flight cancelations or missed connections. The propensity for disruptions varies significantly across airports and carriers, based on key factors such as scheduling practices, network structures, and passenger connections. In this paper, we analyze the causes and costs of ...
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Logistics is the cost aware planning, design, and control of material flow and related informatio... more Logistics is the cost aware planning, design, and control of material flow and related information flow (persons, energy, money, information, ...) in production processes. The notion is often used as a synonym for transportation, distribution, or warehouse management. The topic is of a rich variety, has great practical importance , and attracts researchers from the computer science (CS), mathematical programming (MP), and the operations research (OR) communities alike. Today, problems from logistics are widely studied as parts of the disciplines of mathematical programming and operations research; algorithmics and theoretical computer science; and computer systems. The specific models and methods , as well as the objectives to be optimized, differ in the various disciplines; nevertheless, there are remarkable similarities (as well as significant differences) in the general framework adopted by researchers in logistics in these disparate disciplines. The primary objectives of the sem...
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Developed and analyzed discrete choice models with latent variables/classes Clip-Air concept: Int... more Developed and analyzed discrete choice models with latent variables/classes Clip-Air concept: Integrated schedule planning for a new generation of aircraft, 2010-2013 Project manager Bilge (Küçük) Atasoy 2 Developed airline schedule planning and fleet assignment models for the new aircraft, compared its per-formance to standard aircraft. MyTosa: Simulation tool for the dimensioning, commercial promotion and case study set-up for ABB’s rev-
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The Container Relocation Problem (CRP), also called Block Relocation Problem (BRP), is concerned ... more The Container Relocation Problem (CRP), also called Block Relocation Problem (BRP), is concerned with finding a sequence of moves of containers that minimizes the number of relocations needed to retrieve all containers, while respecting a given order of retrieval. The restricted CRP enforces that only containers blocking the target container can be relocated. We improve upon and enhance an existing binary encoding and using it, formulate the restricted CRP as a binary integer programming problem in which we exploit structural properties of the optimal solution. This integer programming formulation reduces significantly the number of variables and constraints compared to existing formulations. Its efficiency is shown through computational results on small and medium sized instances taken from the literature.
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Manuf. Serv. Oper. Manag., 2022
Problem definition: Physical distancing requirements during the COVID-19 pandemic have dramatical... more Problem definition: Physical distancing requirements during the COVID-19 pandemic have dramatically reduced the effective capacity of university campuses. Under these conditions, we examine how to make the most of newly scarce resources in the related problems of curriculum planning and course timetabling. Academic/practical relevance: We propose a unified model for university course scheduling problems under a two-stage framework and draw parallels between component problems while showing how to accommodate individual specifics. During the pandemic, our models were critical to measuring the impact of several innovative proposals, including expanding the academic calendar, teaching across multiple rooms, and rotating student attendance through the week and school year. Methodology: We use integer optimization combined with enrollment data from thousands of past students. Our models scale to thousands of individual students enrolled in hundreds of courses. Results: We projected that ...
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Journal of Scheduling, 2006
The mission of The Journal of General Physiology is to publish articles that elucidate basic biol... more The mission of The Journal of General Physiology is to publish articles that elucidate basic biological, chemical, and physical principles of broad physiological significance. Physiological significance usually means mechanistic insights, which often are obtained only after extensive analysis of the experimental results. The significance of the mechanistic insights therefore can be no better than the validity of the theoretical framework used for the analysis—and it is usually better to be vaguely right than precisely wrong. The uncertainties associated with data analysis are well illustrated in the Perspectives on Ion Permeation through membrane-spanning channels ( J . Gen . Physiol . 113:761– 794) and the related Letters-to-the-Editor in this issue. This exchange moreover identified a particular problem that can be resolved by a change in editorial policy. The problem is the graphic representation of the results of kinetic analyses of ion permeation based on discrete-state rate mo...
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Transportation Science, 2018
The container relocation problem (CRP) is concerned with finding a sequence of moves of container... more The container relocation problem (CRP) is concerned with finding a sequence of moves of containers that minimizes the number of relocations needed to retrieve all containers, while respecting a given order of retrieval. However, the assumption of knowing the full retrieval order of containers is particularly unrealistic in real operations. This paper studies the stochastic CRP, which relaxes this assumption. A new multistage stochastic model, called the batch model, is introduced, motivated, and compared with an existing model (the online model). The two main contributions are an optimal algorithm called Pruning-Best-First-Search (PBFS) and a randomized approximate algorithm called PBFS-Approximate with a bounded average error. Both algorithms, applicable in the batch and online models, are based on a new family of lower bounds for which we show some theoretical properties. Moreover, we introduce two new heuristics outperforming the best existing heuristics. Algorithms, bounds, and ...
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European Journal of Operational Research, 2018
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European Journal of Operational Research, 2018
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Operations Research Letters, 2016
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International Series in Operations Research & Management Science
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Transportation Science, 2017
Airlines and high speed rail are increasingly competing for passengers, especially in Europe and ... more Airlines and high speed rail are increasingly competing for passengers, especially in Europe and Asia. Competition between them affects the number of captured passengers and, therefore, revenues. We consider competition between airlines (legacy and low-cost) and high speed rail. We develop a new approach that generates airline schedules using an integrated mixed integer, nonlinear optimization model that captures the impacts of airlines’ decisions on passenger demand. We estimate the demand associated with a given schedule using a nested logit model. We report our computational results on realistic problem instances of the Spanish airline IBERIA and show that the actual airline schedules are found to be reasonably close to the schedules generated by our approach. Next, we use this optimization modeling approach under multimodal competition to evaluate multiple scenarios involving entry of high speed rail into new markets. We account for the possibility of demand stimulation as a res...
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Transportation Research Part A: Policy and Practice, 2016
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Transportation Science, 1998
Given a schedule of flight legs to be flown by an airline, the fleet assignment problem is to det... more Given a schedule of flight legs to be flown by an airline, the fleet assignment problem is to determine the minimum cost assignment of flights to aircraft types, called fleets, such that each scheduled flight is assigned to exactly one fleet, and the resulting assignment is feasible to fly given a limited number of aircraft in each fleet. Then the airline must determine a sequence of flights, or routes, to be flown by individual aircraft such that assigned flights are included in exactly one route, and all aircraft can be maintained as necessary. This is referred to as the aircraft routing problem. In this paper, we present a single model and solution approach to solve simultaneously the fleet assignment and aircraft routing problems. Our approach is robust in that it can capture costs associated with aircraft connections and complicating constraints such as maintenance requirements. By setting the number of fleets to one, our approach can be used to solve the aircraft routing probl...
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Papers by Cynthia Barnhart