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The effects of frequency and altitude on radar performance with surface ducting
2014 22nd Signal Processing and Communications Applications Conference (SIU), 2014It is possible to see different ducting statistics in the different seas and oceans around the World. The performance of air traffic and sea surface surveillance radars, which is established on the sea shores, are affected especially from ducting over huge water masses.
Cemil Tepecik, Isa Navruz
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The Journal of the Acoustical Society of America, 1978
A simple accurate model has been devised for ocean surface duct propagation. The model assumes the following form for the propagation loss: P.L. = 60 + 10 logrT + 10 logr − “gain,” where the transition range from spherical to cylindrical spreading, rT, is computed from the limiting ray for the duct, and the “gain” term is computed using the normal ...
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A simple accurate model has been devised for ocean surface duct propagation. The model assumes the following form for the propagation loss: P.L. = 60 + 10 logrT + 10 logr − “gain,” where the transition range from spherical to cylindrical spreading, rT, is computed from the limiting ray for the duct, and the “gain” term is computed using the normal ...
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Underwater sound propagation in surface ducts
The Journal of the Acoustical Society of America, 1974Surface duct sound propagation models are compared against data collected on a Naval Undersea Center sea test. Models considered when there are no significant horizontal variations include a ray theory solution, the natural mode wave theory model, and a combination of the above that accounts for surface scattering.
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Interpretation of low-frequency attenuation in a surface duct
The Journal of the Acoustical Society of America, 1974Computed values of the attenuation coefficient, which were derived from long-range measurements of acoustic transmission loss in an ice-free surface duct in the vicinity of the Arctic ice-water boundary are analyzed in the frequency range 0.1 to 1.0 Hz. The resultant attenuation in this oceanic regime, which has also been measured by D. L.
O. I. Diachok, G. K. Long
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Path integrals and propagation in surface ducts
The Journal of the Acoustical Society of America, 1980Acoustic propagation in an ocean surface duct is computed using Feynmann path integral techniques. The surface duct index of refraction, n = c0/c(z), is modeled by a quartic anharmonic-oscillator potential, n2 = aq2 + bq4, with a pressure release boundary condition at the surface. A closed form expression for the acoustic pressure field is obtained for
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Surface-duct propagation: An evaluation of models of the effects of surface roughness
The Journal of the Acoustical Society of America, 1980The results of 25 measurements of acoustic propagation to a range of 6 km in the ocean mixed layer, at frequencies of 4, 8, and 16 kHz, are summarized and compared with a number of propagation models. Within the mixed layer , the acoustic energies have considerable variability and are usually 10 to 20 dB less than the prediction of normal-mode theory ...
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Measurements of propagation loss in isothermal surface ducts
The Journal of the Acoustical Society of America, 1993Over the past several years, the Defence Research Establishment Atlantic has made measurements of propagation loss in surface ducts. The experiments were conducted at deep-water locations, and both the source (SUS charges) and receiver were placed in the duct. At the sites where the surface duct was well defined and constant with range, the data are in
F. D. Cotaras +2 more
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The duct leakage relation for the surface sound channel
The Journal of the Acoustical Society of America, 1991The leakage attenuation from a duct is simply related to the field level outside the duct, and the relation can be applied to the surface sound channel. High-frequency measurements over the Biscay Abyssal Plain support the predicted relation and indicate that the loss is mainly due to scattering at very shallow angles, presumably from the surface waves.
D. E. Weston, C. G. Esmond, A. Ferris
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Role of Virtual Modes in Surface-Duct Leakage
The Journal of the Acoustical Society of America, 1972A three-layer surface-duct model is considered. In the top layer the sound velocity increases linearly (slope g1) from a value C(0) at the surface to C(b) at the bottom of the duct. In the second layer the sound speed decreases linearly from C(b) at depth b to C0 at depth d (slope |g2| > g1).
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Epstein Normal-Mode Model of a Surface Duct
The Journal of the Acoustical Society of America, 1967Equations are given for the normal-mode calculation of the sound field in a surface duct. The velocity-depth profile is represented as 1/v2 (z) = A sech2(z/H) + B tanh (z/H) + D, a form first used by Epstein for calculating the reflection of radio waves from a transition layer.
H. P. Bucker, Halcyon E. Morris
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