Τα κυκλοφοριακά πλήγματα είναι ένα φαινόμενο που συμβαίνει καθημερινά στα οδικά δίκτυα και προκαλεί από μεγάλες καθυστερήσεις μέχρι σοβαρά ατυχήματα. Η παρούσα μελέτη αφορά στην μικροσκοπική ανάλυση κυκλοφοριακού πλήγματος με την εφαρμογή του μετασχηματισμού wavelet. Με τη βοήθεια του μαθηματικού αυτού εργαλείου για την επεξεργασία των σημάτων της κυκλοφορίας, εξετάζονται 20 διαφορετικές περιπτώσεις συμβάντος, κάθε μία εκ των οποίων περιλαμβάνει ένα πλήγμα. Αποτυπώνονται οι τροχιές των εμπλεκόμενων οχημάτων, υπολογίζονται οι χρονοσειρές των ταχυτήτων τους και από τις κατανομές της ενέργειας wavelet προκύπτουν με ακρίβεια τα σημεία έναρξης και λήξη του πλήγματος. Τα σημεία αυτά χαρακτηρίζουν τον τρόπο που διαδίδονται τα πλήγματα από όχημα σε όχημα και από αυτά προκύπτει το «μονοπάτι» και η ταχύτητα διάδοσης πλήγματος. Τα πλήγματα διαχωρίζονται σε απλά και σύνθετα και αναλύεται η συσχέτιση των ταχυτήτων διάδοσης στα υπό – πλήγματα των σύνθετων πληγμάτων, καθώς και η επίδραση της παρουσίας μεγάλης χρονοαπόστασης στη διάδοση αυτών των πληγμάτων. / One of the most common problems in road networks is the shockwave, which can cause enormous delays and serious problems to traffic. This study presents a microscopic analysis of shockwave, using wavelet transform. Using wavelet transform for traffic signal processing, 20 shockwaves were examinated. By watching videos, trajectories of every single vehicle that was involved in these shockwaves are obtained and speeds are computed. Having the wavelet – based energy distributions, start and end points are marked in the trajectories diagrams. These points characterize the way the shockwave propagates from vehicle to vehicle. Marking these points we can find the shockwave propagation path and we can compute the shockwave propagation speed. A shockwave can be simple or complex. Thus, we can analyze the correlation between the shockwave propagation speeds of the parts of a complex shockwave; and the effect of time headway on shockwave propagation.

Thesis (Ph. D.)--Colorado State University, 2004. / Includes bibliographical references.

Orientador: Osvaldir PecoraTaranto / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-10T20:17:23Z (GMT). No. of bitstreams: 1 Parise_MariaRegina_D.pdf: 3017112 bytes, checksum: f14db15e7314590127e2a9a2ff621c9c (MD5) Previous issue date: 2007 / Resumo: A defluidização parcial ou total de partículas sólidas é um fenômeno indesejável em aplicações industriais envolvendo operações com leito fluidizado. Se as mudanças na fluidodinâmica do leito forem detectadas a tempo, pode-se evitar-la com o aumento da velocidade do gás de fluidização e/ou, em alguns casos, mediante a alteração da vazão de sólidos alimentados no sistema. A utilização de uma técnica que permita rapidamente identificar a região onde o leito está tendendo à defluidização é de suma importância, pois dessa maneira pode-se atuar no processo impedindo que haja perda de eficiência ou até mesmo a necessidade de parar a produção. Este trabalho teve como objetivo o desenvolvimento de uma metodologia capaz de identificar essa região em leito fluidizado gás-sólido, através de medidas de flutuação de pressão analisadas utilizando a transformada de Fourier juntamente com a Distribuição Exponencial Gaussiana. Para a verificação da metodologia proposta foram realizados ensaios experimentais utilizando areia e celulose microcristalina, alterando-se a altura do leito e o diâmetro médio das partículas. Os resultados mostraram que o método identifica claramente a região onde o leito está tendendo à defluidização, e tem grande potencial em aplicações industriais para o controle on line de processos em leito fluidizado gás-sólido. Além disso, a metodologia pode ser importante para detectar mudança de regime para a relação altura do leito e diâmetro da coluna de fluidização (H/D) superiores à unidade. Adicionalmente, foram realizados ensaios de secagem utilizando celulose microcristalina visando à possibilidade da identificação do ponto crítico (teor de umidade existente no final do período de taxa constante) utilizando as seguintes técnicas: metodologia proposta neste trabalho, freqüência dominante e desvio padrão da flutuação de pressão. Observou-se que para o sólido utilizado não foi possível detectar o ponto crítico através desses três tipos de análise. No entanto, a metodologia proposta pode ser utilizada na identificação do momento que a secagem não se encontra na fluidização requerida e está tendendo à defluidização / Abstract: The partial or complete bed defluidization is an undesired phenomenon in industrial application involving fluidized bed operations. If the changes in the hydrodynamic of the fluidized bed are detected early enough, it may be prevented by increasing the gas velocity and/or, in some cases, changing the solid feed in the system. The use of a technique that can quickly identify the region where the bed is tending to the defluidization is very important, because one can act in the process avoiding loss of efficiency or even the necessity of shutting down the process. This work was as objective the development a methodology capable of identifying this region in gas-solid fluidized bed, by pressure fluctuation measurements analyzed using Fourier Transform and exponential Gaussian distribution. In order to verify the methodology proposed, experimental tests were carried out using microcrystalline cellulose and sand, where the fixed bed height and particle mean diameter were varied. Results showed that the method clearly identifies the region where the bed is tending to the defluidization, and it has great potential on industrial applications to on line process control in gas-solid fluidized bed. Also, the methodology can be important to detect regime changes at bed aspect ratios (H/D) higher than unit. Additionally, experimental drying test were carried out using microcrystalline cellulose particles to verify the possibility of identification of the critical drying point (the moisture content related to the end of the constant rate period) by the following techniques: the methodology proposed in the present work, the dominant frequency and standard deviation of pressure fluctuations. It was observed that for the solid material used it was not possible to detect the critical drying point. However, the methodology proposed can be used on identification the moment that the drying is not in the desired fluidization regime and it is tending to defluidization / Doutorado / Engenharia de Processos / Doutor em Engenharia Química