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Title Υπολογισμός του συντελεστή ανάκλασης επίπεδου ηχητικού κύματος από πολυστρωματοποιημένο μέσο και εφαρμογές στην ακουστική ωκεανογραφία
Alternative Title Calculation of the plane wave reflection coefficient from multilayered elastic media with applications in underwater acoustics
Author Σίσκογλου, Ουρανία
Thesis advisor Ταρουδάκης, Μιχαήλ
Reviewer Παπαδάκης , Παναγιώτης
Κοσσιόρης, Γεώργιος
Abstract For this project we constructed a program for calculating the reflection and transmission coefficients of an acoustic plane wave incident upon multilayered media for each angle of incidence 0 — 90° and each frequency f in a given bandwidth. We used it to calculate the reflection coefficient of a wide¬band signal and then we considered the reflection coefficient a filter to find the reflected signal in time and frequency domain. We first calculated and plotted the reflection coefficient of a plane wave incident from water upon a single layered bottom. We noticed that the reflection coefficient is independent of frequency and that in the case of an elastic bottom it is jl even for angles greater than the critical angle. We compared the reflection coefficients from waves incident upon a lossy two-layered fluid medium for different values of the absorption coefficient and understood how attenuation affects the prop¬agation of acoustic waves in a medium. We compared two contour maps (the reflection coefficient as a function of the angle of incidence θ and the frequency f) of a bottom consisting of two elastic layers with different thicknesses of the intermediate layer. We came to the conclusion that for thin layers the wave behaves as if it is not affected by the existence of the layer, while for thick layers (compared to the wavenumber) the reflections in the boundaries of the layer affect the reflection coefficient from the first layer. Last, we compared pulses incident on a bottom consisting of two layers with different thicknesses of the intermediate layer. We noticed that as the layers become thicker and the frequencies higher the multiple reflections between the interfaces disturb the shape of the signal.
Language Greek
Issue date 2014
Collection   School/Department--School of Sciences and Engineering--Department of Mathematics--Graduate theses
  Type of Work--Graduate theses
Permanent Link https://elocus.lib.uoc.gr//dlib/b/0/5/metadata-dlib-1464335972-981456-8730.tkl Bookmark and Share
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