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  1. Book ; Online: A study of the U.S. domestic air transportation network

    Siozos-Rousoulis, Leonidas / Robert, Dimitri / Verbeke, Wouter

    Temporal evolution of network topology and robustness from 2001 to 2016

    2020  

    Abstract: The U.S. air transportation network (ATN) is critical to the mobility and the functioning of the United States. It is thus necessary to ensure that it is well-connected, efficient, and robust. Despite extensive research on its topology, the temporal ... ...

    Abstract The U.S. air transportation network (ATN) is critical to the mobility and the functioning of the United States. It is thus necessary to ensure that it is well-connected, efficient, and robust. Despite extensive research on its topology, the temporal evolution of the network's robustness and tolerance remains largely unexplored. In the present paper, a temporal study of the domestic U.S. ATN was performed based on annual flight data from 1996 to 2016 and network analytics were used to examine the effects of restructuring that followed the 9/11 events along with the current state of the system. Centrality measures were computed to assess the system's topology and its global robustness. A node deletion method was applied to assess the network's tolerance by simulating a targeted attack scenario. The study showed that the 9/11 terrorist attacks triggered vast restructuring of the network, in terms of efficiency and security. Air traffic expanded, as new airports and air routes were introduced. Airlines reconsidered their strategy and optimized their operations, thus allowing the network to recover rapidly and become even more efficient. Security concerns resulted in significant improvement of the network's robustness. Since 2001, the global traffic and topological properties of the U.S. ATN have displayed continuous growth, due to the network's expansion. On the other hand, the robustness of the system has not shown an improving tendency. Findings suggest that although the system's ability to sustain its operational level under extreme circumstances has lately improved, its tolerance to targeted attacks has deteriorated. The presented methodology may be applied on different network levels or different transportation networks, to provide a general perspective of the system's vulnerabilities.
    Keywords Physics - Physics and Society ; Computer Science - Social and Information Networks
    Subject code 303
    Publishing date 2020-05-03
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article: A time-domain method for prediction of noise radiated from supersonic rotating sources in a moving medium.

    Huang, Zhongjie / Siozos-Rousoulis, Leonidas / De Troyer, Tim / Ghorbaniasl, Ghader

    Proceedings. Mathematical, physical, and engineering sciences

    2018  Volume 474, Issue 2210, Page(s) 20170089

    Abstract: This paper presents a time-domain method for noise prediction of supersonic rotating sources in a moving medium. The proposed approach can be interpreted as an extensive time-domain solution for the convected permeable Ffowcs Williams and Hawkings ... ...

    Abstract This paper presents a time-domain method for noise prediction of supersonic rotating sources in a moving medium. The proposed approach can be interpreted as an extensive time-domain solution for the convected permeable Ffowcs Williams and Hawkings equation, which is capable of avoiding the Doppler singularity. The solution requires special treatment for construction of the emission surface. The derived formula can explicitly and efficiently account for subsonic uniform constant flow effects on radiated noise. Implementation of the methodology is realized through the Isom thickness noise case and high-speed impulsive noise prediction from helicopter rotors.
    Language English
    Publishing date 2018-02-14
    Publishing country England
    Document type Journal Article
    ZDB-ID 209241-4
    ISSN 1471-2946 ; 1364-5021 ; 0962-8444 ; 0080-4630 ; 0950-1207
    ISSN (online) 1471-2946
    ISSN 1364-5021 ; 0962-8444 ; 0080-4630 ; 0950-1207
    DOI 10.1098/rspa.2017.0089
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article: A time-domain Kirchhoff formula for the convective acoustic wave equation.

    Ghorbaniasl, Ghader / Siozos-Rousoulis, Leonidas / Lacor, Chris

    Proceedings. Mathematical, physical, and engineering sciences

    2016  Volume 472, Issue 2187, Page(s) 20150689

    Abstract: Kirchhoff's integral method allows propagated sound to be predicted, based on the pressure and its derivatives in time and space obtained on a data surface located in the linear flow region. Kirchhoff's formula for noise prediction from high-speed rotors ...

    Abstract Kirchhoff's integral method allows propagated sound to be predicted, based on the pressure and its derivatives in time and space obtained on a data surface located in the linear flow region. Kirchhoff's formula for noise prediction from high-speed rotors and propellers suffers from the limitation of the observer located in uniform flow, thus requiring an extension to arbitrarily moving media. This paper presents a Kirchhoff formulation for moving surfaces in a uniform moving medium of arbitrary configuration. First, the convective wave equation is derived in a moving frame, based on the generalized functions theory. The Kirchhoff formula is then obtained for moving surfaces in the time domain. The formula has a similar form to the Kirchhoff formulation for moving surfaces of Farassat and Myers, with the presence of additional terms owing to the moving medium effect. The equation explicitly accounts for the influence of mean flow and angle of attack on the radiated noise. The formula is verified by analytical cases of a monopole source located in a moving medium.
    Language English
    Publishing date 2016-04-27
    Publishing country England
    Document type Journal Article
    ZDB-ID 209241-4
    ISSN 1471-2946 ; 1364-5021 ; 0962-8444 ; 0080-4630 ; 0950-1207
    ISSN (online) 1471-2946
    ISSN 1364-5021 ; 0962-8444 ; 0080-4630 ; 0950-1207
    DOI 10.1098/rspa.2015.0689
    Database MEDical Literature Analysis and Retrieval System OnLINE

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