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Browsing by Author "Freese, Herbert"

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    A Markov process model of ocean sediments
    Sockell, Michael; Besieris, Ioannis M.; Kohler, Werner E.; Freese, Herbert (Acoustical Society of America, 1985-01-01)
    Monochromatic plane-wave illumination of a randomly stratified, laterally homogeneous sediment layer is considered. The deposition process creating the stochastic layering is assumed to be a continuous parameter, finite state Markov chain. A Riccati equation for the plane-wave reflection coefficient is formulated and first-order partial differential equations for relevant probability density functions are subsequently obtained. These equations are solved numerically for a two-material turbidite model similar to the one considered by Gilbert [J. Acoust. Soc. Am. 68, 1454-1458 (1980)]. Statistical moments of the reflection coefficient are computed at 25 and 250 Hz as a function of overall sediment thickness. These equations are also used to derive the nonrandom or "smooth" geoacoustic model that is appropriate in the low-frequency limit.
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    A transport-theoretic analysis of pulse propagation through ocean sediments
    Besieris, Ioannis M.; Kohler, Werner E.; Freese, Herbert (Acoustical Society of America, 1982-09-01)
    The reflection of pulsed acoustic plane waves from ocean sedimentary layers is studied using a stochastic transport theory originally introduced by Barabanenkov et. al. [Izv. Vyssh. Uchebn. Zaved., Radiofiz 15, 1852 (1972)]. The sediments are assumed to be a random medium in which the density and sound speed undergo small, highly laminated (pancakelike) fluctuations. Although the problem is formulated in a general context, the predictions of the theory are fully evaluated only in the special case of normal incidence and no refracting profile. However, even with these approximations, some reasonable qualitative agreement of theoretical predictions with measured data is achieved.