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    Wyświetlanie 1-2 z 2
    Tytuł:
    An Experimental Approach to Vibro-Acoustic Study of Beam-Type Structures
    Autorzy:
    Torres-Romero, J.
    Cardenas, W.
    Carbajo, J.
    Segovia Eulogio, E. G.
    Ramis-Soriano, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/178014.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    beam
    modal shape
    modal analysis
    MLS
    Maximum Length Sequence
    bending wave propagation velocity
    Opis:
    In this paper an alternative procedure to vibro-acoustics study of beam-type structures is presented. With this procedure, it is possible to determine the resonant modes, the bending wave propagation velocity through the study of the radiated acoustic field and their temporal evolution in the frequency range selected. As regards the purely experimental aspect, it is worth noting that the exciter device is an actuator similar to is the one employed in distributed modes loudspeakers; the test signal used is a pseudo random sequence, in particular, an MLS (Maximum Length Sequence), facilitates post processing. The study case was applied to two beam-type structures made of a sandstone material called Bateig. The experimental results of the modal response and the bending propagation velocity are compared with well-established analytical solution: Euler-Bernoulli and Timoshenko models, and numerical models: Finite Element Method – FEM, showing a good agreement.
    Źródło:
    Archives of Acoustics; 2018, 43, 2; 283-295
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analysis of the influence of expressway emergencies on transmission speeds and travel delays
    Autorzy:
    Shi, Xianfu
    Liu, Xingliang
    Li, Menghui
    Liu, Tangzhi
    Powiązania:
    https://bibliotekanauki.pl/articles/2173933.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    expressway
    congestion
    propagation
    travel time delay
    logistic velocity
    droga ekspresowa
    kongestia transportowa
    transport drogowy
    prędkość logistyczna
    Opis:
    Expressway emergencies tend to cause traffic congestion, and understanding the travel time delays of on-road vehicles under different combinations of event scenarios and road traffic conditions is valuable for guiding the accurate emergency dispatch services. Most existing studies used methods that combine the Lighthill-Whitham-Richards (LWR) theory and basic traffic diagrams to solve this problem, but the discrete traffic flow characteristics caused by the presence of heavy vehicles have not been considered, thus affecting the applicability of those results to road traffic characteristics in China. Moreover, there is a lack of systematic research on multiple combinations of unexpected event scenarios and traffic conditions, and the guidance value of the previously obtained results is limited. In order to improve the applicability of the prediction model and accurately predict the severity of emergencies, based on a logistic model that is applicable to emergencies, a velocity–density model is constructed to describe discrete traffic flow characteristics. Based on LWR theory, the internal driving force of expressway traffic state evolution under emergency conditions is explored. Combined with real-time traffic flow data, the parameters of the logistic model are calibrated, and a logistic velocity-density model is constructed using a goodness-of-fit test and a marching method, including the free-flow velocity, turning density and heavy vehicle mixing ratio. Thus, the problem that existing models lack applicability to road traffic characteristics in China is solved. Travel time delay is associated with the impact range of an emergency, and it is an effective index for evaluating the severity of emergency incidents. Thus, the travel time delays under different scenarios, different numbers of blocked lanes and different orthogonal combinations of approximate saturation conditions are explored, and the impacts of lane blockage on emergency incidents and travel time delays are obtained. The conclusions show that the presented logistic velocity-density model constructed based on discrete traffic flow characteristics can properly quantify the impact of the presence of heavy vehicles. Additionally, the results can provide theoretical support for handling emergencies and emergency rescues.
    Źródło:
    Archives of Transport; 2022, 63, 3; 7--21
    0866-9546
    2300-8830
    Pojawia się w:
    Archives of Transport
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-2 z 2

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