Optimització d'operacions en aeroports

La ponència tracta les operacions aeroportuàries des de la perspectiva de sistema de transport, desenvolupant models d’optimització per millorar el rendiment del sistema en base a la reducció de les variables temps i costos i la millora de la fiabilitat dels processos

Estimation of flight CO2 emissions and travel time with analytical models

Flights negatively impact the environment and the aviation industry faces significant challenges to decarbonise. This is particularly relevant for short- and medium-haul flights, as operations in these ranges can be less fuel efficient per passenger transported and other transport alternatives could be considered, e.g. rail. The quantification of this environmental impact is usually reliant on estimations of CO2 emissions. Currently available models tend to focus on simple linear relationships between distance and/or time and emissions, which do not differentiate by operation type, or tend to be based on fuel consumption models, which require detailed flight and aircraft parameters on a flight by flight basis, limiting the possibility of network level analysis. We present analytical models calculating gate-to-gate CO2 emissions and travel time based on flight distance and on the number of available seats. These models enable the comparison of the environmental impact of aviation with other means of transport, as operations are translated into passenger transported and time required. Emissions estimated by these models are in line with other CO2 calculators. The models present the advantage of being sensitive to the number of available seats, a parameter generally not explicitly considered. Their applicability is shown in practical examples: analysis of emissions and time of routes, which could potentially be complemented by high-speed rail and night trains.Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraObjectius de Desenvolupament Sostenible::12 - Producció i Consum ResponsablesObjectius de Desenvolupament Sostenible::13 - Acció per al ClimaObjectius de Desenvolupament Sostenible::13 - Acció per al Clima::13.2 - Incorporar mesures relatives al canvi climàtic en les polítiques, les estratègies i els plans nacionalsPostprint (published version

Methodology for optimal design of efficient air transport network in a competitive environment

This thesis aims to dissert about air transport network design taking into consideration the current needs about efficiency in a very competitive industry. The main focus for this work is the airline's point of view and for this reason is going to be common to talk about profitability. A methodology is proposed to analyse current networks and to introduce modifications. First, an analytical approach is proposed with the aim to understand better the interaction of key parameters in network design at strategical level. Analyitical models demonstrate to be very useful because with a few parameters it is possible to decide if point to point or hub and spoke configuration suits better for an airline, given a set of supply conditions. Furthermore, the performance of networks with stopover configuration is tested, basically because for long routes with low demand this newtorks work well, how it was demonstrated by public transport systems. The differenciation of this research, compared against previous studies, is to include the performance of new entrant airlines in the industry. This aspect is carried out evaluating accurately the impact of fixed costs in the evaluation of cost operators. Despite airlines tend to consider aircraft ownership costs and labor costs as variable ones, they are not. They had an important impact in profit and loss account. A bad utilitzation factor of airplane or crew staff is very undesirable for operator and it can consider do not operate new routes if the resources are not well used. Secondly, analytical models are powerful but it is not possible to evaluate accurately the daily operational aspects for real networks with real flight schedules because these models take into consideration average values of some parameters. For this reason, this thesis develops a Tabu search algorithm to carry out airline network planning, based on linear models of each different planning problem. To do this contribution, these models are developed before for linear programming and they are solved with a combination of complete enumeration algorithm and exhaustive search algorithm. Both algorithms provide exact solution or global optimum for any problem statement. Later, Tabu search algorithm improves performance of searching with lower computational cost. The main conclusion is that Tabu developed is a better tool for airline planning than exact techniques because of lower times of computation. This performs better for large networks that, finally, are real networks. However, exact techniques could be interesting for small airlines that can be start-ups. Third, one of main reasons to develop a quantification of costs for managing airlines is due to the problem of complexity in networks. With the growth of air transportation and congestion at airports, primary or reactionary delays become higher day after day. Reactiveness of network depends of configuration and planning. Airlines manages it with extra reources, one way is allocating buffer times in flight schedule and other is having aircrafts at ground at main bases to enter in service and recover flight plans. Airline network design, planning and efficient algorithms are key assets to provide robustness for airlines. Finally, driving airlines in high competitive environments are difficult. Running low costs is the main decision for managers. However, analysing the problem from theory game point of view, allows finding key reasons to support this argument. First, a Stakelberg model is defined for two competing airlines. This model demonstrates that a war on frequencies or fares damages both competitors. Furthermore, a Cournot model it is shown and it proposes a navigation fee attending to correct utilization of capacity. Both models are a theoretical framework but demonstrate consistency and encourage further investigations.El diseño de redes de transporte aéreo es un factor clave de eficiencia en una industria altamente competitiva. A pesar de que la rentabilidad es de suma importancia, el sistema considera la experiencia del usuario y los beneficios sociales para obtener un óptimo global. Un enfoque analítico permite derivar principios de diseño de redes de transporte aéreo: la tesis muestra cómo unas pocas variables y sus interacciones explican los factores clave del diseño de la red a nivel estratégico. Los servicios punto-a-punto muestran supremacía en las redes simples y para demandas altas y compensadas, una configuración con escalas es adecuada para rutas lejanas con poca demanda, y las operaciones hub and spoke mejoran las dos estrategias anteriores para redes grandes, cuando la demanda es baja o cuando las frecuencias son altas, pero son más sensibles a la propagación de demoras. El enfoque analítico permite prever el comportamiento de nuevas compañías aéreas entrando en el sector. El modelo incluye costes fijos de propiedad del avión y laborales (al contrario de las hipótesis habituales de la industria, que trabaja con costes variables), puesto que tienen un impacto importante en la cuenta de resultados. Una vez se han derivado guías de diseño, la tesis formula un planteamiento más realista del diseño de redes de transporte aéreo basado en programación matemática lineal, que se resuelve con una combinación del Algoritmo de Enumeración Completa y el Algoritmo de Búsqueda Exhaustiva (ambos proporcionan la solución exacta o un óptimo global para cualquier planteamiento del problema). El modelo incluye asignación de flotas, rutas de aeronaves y programación de tripulaciones. Mientras que los algoritmos exactos son apropiados para aerolíneas pequeñas, los problemas más grandes necesitan Búsqueda Tabú. El crecimiento del transporte aéreo y la congestión en los aeropuertos (a veces propiciada por las operaciones hub&spoke) pueden afectar las demoras con un efecto de bola de nieve o látigo; sin embargo el análisis de la complejidad de la red aérea puede incrementar la resiliencia de las operaciones. Un buen diseño de la red aérea, una buena planificación y unos algoritmos eficientes, son aspectos clave para proporcionar fiabilidad a las aerolíneas y así reducir los recursos inactivos asociados a “colchones de tiempo” (en los horarios de los vuelos) y/o en aviones “de reserva” en la plataforma para recuperar planes de vuelo. El “acolchado” mejora la percepción de la calidad por parte del pasajero, pero con un control activo del horario de vuelos puede conseguirse la misma percepción con costes menores. El entorno competitivo de las aerolíneas se analiza con teoría de juegos: un modelo de Stakelberg para dos aerolíneas competidoras muestra que una guerra de frecuencias o tarifas es perjudicial para ambas aerolíneas. Un modelo Cournot propone una tasa de navegación y de congestión según la correcta utilización de la capacidad. Vuelos (de la misma alianza) a lo largo del mundo con escalas en los hubs principales se proponen como investigación futur

Conférence de Kevin Jennings, ancien vice-ministre adjoint de l'administration Obama et fondateur du GLSEN (Gay, Lesbian and Straight Education Network), donnée dans le cadre d’une campagne contre l’homophobie dans les écoles.

Conférence de Kevin Jennings, ancien vice-ministre adjoint de l'administration Obama et fondateur du GLSEN (Gay, Lesbian and Straight Education Network), donnée dans le cadre d’une campagne contre l’homophobie dans les écoles

Managing airlines: the cost of complexity

This paper is dedicated to the structure of airline networks as a sink of efficient airline operations. Parameters of complexity were derived and mirrored on level of service as well as efficiency parameters. Airlines usually considerers an operational overhead to predict the total flight operation cost. This parameter includes the expected cost for disruptions and delays. When an airline has to mobilize an aircraft in a base for recovering the service or for breaking an emergent dynamic, then it is running extra costs. The cost of managing complexity in the airline industry has a direct impact on profit and loss account. Therefore, this paper presents an integrated approach to evaluate this cost, based on padding and aircrafts dedicated to recover disruptions. Finally, some additional indicators are derived to evaluate reliability improvement as part of complex performance

The design of interurban bus networks in city centers

This paper proposes a bilevel formulation for solving the Bus Network Design Problem (BNDP) of interurban services entering a major city. It is focused in interurban services because it is a growing problem in most of major cities, yet new in the literature. The layout of interurban bus routes and the locations of transfer stations in the main city are the key factors to provide a competitive public transportation service to commuters in a metropolitan area. The number of commuters in huge urban concentrations is growing due to the difficulties of living near the city center. The objective function of the first level is defined with the aim of reducing user and agency costs. In the second level the performance of users is addressed. Furthermore, a local search method based on the Tabu Search algorithm was carried out to guide the exploration in the solution domain. The results obtained in a set of test problems have demonstrated that the restart parameters of the algorithm play a significant role in the efficiency of the algorithm. Finally, implementation in the large network of Barcelona (Spain) reduces the total cost by 5% with regard to the present situation.Peer ReviewedPostprint (author's final draft

Learnings from urban bus network change

We present a strategy to improve bus service in urban networks that gives equal or better transit service and saves public resources: a win-win strategy. It consists on changing from “direct lines” to mobility centers from each quarter of the city to a bidimensional “network structure”, and from “schedule based” management to “frequency based” management. The implementation in Lleida, a 140,000 inhabitant city of Spain, has proven that it is possible to save 18% of the resources providing equal or better door-to-door service, but a final fine-tuning has found the proper equilibrium between “network structure” and “direct lines” to better fit the users’ perception, still resulting in 10% savings. Several learnings about bottom-up citizen participation, change process and perceived weight for the transfer time are presented as conclusions.Postprint (published version

The application of multi-agent systems to the design of an intelligent geometry compressor

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