• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1
  • Tagged with
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

A NETWORK LEVEL FEASIBILITY FRAMEWORK FOR BEAM-POWERED AIRCRAFT

Ethan Charles Wright (15342052) 24 April 2023 (has links)
<p>Beam-powered aircraft are a promising solution to reducing the air transportation system's operating costs and emissions due to their reliance on typically more efficient ground-based electricity sources.</p> <p>However, modeling these aircraft is a non-trivial task due to their multi-disciplinary nature and the required interconnectedness between the aircraft, air transportation network, and power-beaming models.</p> <p><br></p> <p>This thesis establishes a methodology for holistically modeling beam-powered aircraft as a freight transportation asset in the context of their operating environment.</p> <p>This methodology accounts for elements of aircraft conceptual design, the limits of power-beaming technology, and non-idealities associated with the air transportation network.</p> <p>As a product of this methodology, this thesis also approximates beam-powered aircraft's economic and environmental feasibility based on current and future technological capabilities.</p> <p><br></p> <p>This work concludes that with an optimistic enough "engine absent" mass fraction and with sufficiently advanced technologies -- particularly with higher power density rectennas -- beam-powered aircraft are both economically and environmentally feasible, having a lower operating cost and emitting less carbon dioxide per ton-mile compared to current-day and near-future freight transportation aircraft.</p> <p><br></p> <p>More specifically, this work concludes that when using a simplified and more optimistic engine absent mass fraction model, power train specific power only needs to improve by a factor of 1.2-3.7 and rectenna power density only needs to improve by a factor of 20-30 compared to the baseline technologies considered in this work in order for beam-powered aircraft to be a feasible alternative to jet fuel powered aircraft in a freight transportation role.</p> <p>However, with a more pessimistic albeit more realistic engine absent mass fraction model, this work concludes that beam-powered aircraft are not feasible in a freight transportation role with the technology levels considered in this work.</p>
2

Terrorisme international et mesures de sûreté : analyse économique du comportement du voyageur sur le réseau de transport aérien mondial / International terrorism and security measures : economic analysis of the traveler’s behavior on the global air transportation network

Depigny, Marine 27 September 2011 (has links)
Dans cette thèse, nous questionnons l’impact du terrorisme international et des mesures de sûreté sur le comportement des usagers du réseau de transport aérien mondial. A l’aide d’un modèle économétrique, nous analysons une base de données inédite, AirNetTerror, composée de l’ensemble des vols internationaux à destination des Etats-Unis de 1990 à 2006, et des données du terrorisme international par pays sur cette période. La pertinence de notre travail est double. D’une part, nos interrogations sur les comportements des voyageurs et leurs éventuelles substitutions d’itinéraires en lien avec le terrorisme international n’ont, à notre connaissance, jamais été traitées. D’autre part, en abordant le transport aérien sous l’angle du réseau, nous proposons une vision dynamique des répercussions des comportements des usagers en lien avec la menace terroriste et les mesures de sûreté. En particulier, la prise en compte de la situation de sûreté interdépendante régissant le réseau aérien mondial nous permet de questionner l’existence de failles dans les mesures de sûreté. Nos résultats soulignent l’impact avéré et significatif des événements du terrorisme international, mais aussi des mesures de sûreté sur le réseau de transport aérien mondial. De plus, nous observons localement des substitutions d’itinéraires des voyageurs aériens en lien avec ces phénomènes. Ainsi, l’effet combiné de la menace terroriste internationale et des mesures de sûreté semble être à l’origine de ruptures d’équilibre, certes limitées mais réelles, des flux de passagers du réseau de transport aérien mondial. Notre thèse, parce qu’elle place le comportement du voyageur au centre des interactions stratégiques entre les acteurs de la sûreté et les terroristes, permet d’apporter une vision inédite de l’impact du terrorisme international sur le transport aérien. / In our dissertation, we question the impact of both international terrorism and security measures on the behavior of the users of the global air transportation network. Using an econometric model, we analyze a new database, AirNetTerror, which contains data on all international passenger flows toward the U.S. from 1990 to 2006 as well as the events of international terrorism by country for the same period. The relevance of our research is twofold. On the one hand, our investigation regarding air travelers’ behavior and their possibilities of modifying their itinerary in light of international terrorism has – so far as we know – never been studied. On the other hand, as we analyze passenger flows from the perspective of the network, we propose a dynamic representation of the impact of travelers’ behavior changes related to terrorist threats and security measures. In particular, taking into account the interdependent security that rules the global air transport network, allows us to question the existence of failures in security measures. Our results underline a significant impact of both international terrorist events and security measures. Furthermore, we locally observe itinerary modifications of travelers that are linked to the previous phenomena. Thus, the combined effect of terrorist threats and security measures seems to lead to equilibrium breaks – that are limited but real – in passenger flows of the global air network. Our thesis offers a different representation of the impact of international terrorism on air transport by placing the traveler’s behavior at the center of the strategic interactions between security actors and terrorists.

Page generated in 0.1648 seconds