Browsing by Type "Conference Proceedings (CP)"
Now showing items 61-80 of 314
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Application of the Riesz potential to the Cauchy problem for wave propagation in an inhomogeneous medium
(NATO. SACLANTCEN, 1971/12)The method of Riesz [Ref. l] for the solution of hyperbolic partial differential equations is applied to the Cauchy problem for the wave equation. It is shown that the first term in the Riesz potential function, which is ... -
Approximate methods for ray tracing
(NATO. SACLANTCEN, 1971/12) -
Arctic ambient noise statistical measurement results and their implications to sonar performance improvements
(NATO. SACLANTCEN, 1982/06)Recent analyses of FRAM II arctic data have shown that under ice ambient noise can be at times highly impulsive and non-Gaussian. The analyses included time domain statistical measurements which were consistent with ... -
Areal seabed classification using backscatter angular response at 95kHz
(NATO. SACLANTCEN, 1997)A sediment classification scheme is developed based on the angular response (AR) of the seabed backscatter strength. The AR is characterised based on its mean level and slope over predefined angular sectors, and the presence ... -
Array and cable tracking data through ship maneuvers
(NATO. SACLANTCEN, 1993/08)This paper presents tracking results from two sea tests in which a towed cable and array were tracked at the Atlantic Undersea Test and Evaluation Center (AUTEC). The tracking tests involved instrumenting the cable with ... -
Array performance and variability at short range near Vestfjorden
(NATO. SACLANTCEN, 1993/08)An experiment was conducted in October 1989 in shallow water near Vestfjorden in support of low frequency active sonar system research at SACLANTCEN. This report addresses some acoustic measurement results from that test ... -
Array shape determination with a real-time model
(NATO. SACLANTCEN, 1993/08)A shape estimation scheme based on precomputed frequency-domain solutions of array motion is presented. The boundary conditions supporting each solution are discrete Fourier transform (OFT) components of sensor measurements, ... -
Arrays and array processors: future real time applications in oceanography and sonar
(NATO. SACLANTCEN, 1979/12)In the last several years oceanographic applications of arrays have increased substantially. The spatial resolution and redundancy provided by arrays have been necessary in the interpretation of signal propagation in complex ... -
Assessment techniques for computer models of sound propagation
(NATO. SACLANTCEN, 1975/10)Computer models of sound propagation have exactly three drawbacks: the model only approximates reality,the computer program only approximates the model, and the cost approximates infinity. The only way to assess these ... -
Attenuation of shear waves in near-surface sediments
(NATO. SACLANTCEN, 1997)In situ measurement of compressional and shear speed and compressional attenuation in near-surface marine sediments is a well-developed technology but techniques required to measure shear attenuation have lagged behind. ... -
Autofocusing a synthetic aperture sonar using the temporal and spatial coherence of seafloor reverberation
(NATO. SACLANTCEN, 1997)An autofocusing algorithm for the compensation of translational motion errors of a sea floor rmaging synthetic aperture side scan sonar is presented. The algorithm does not depend on the presence or absence of dominant ... -
Bathymetry, gravity and magnetism in the Strait of Sicily
(NATO. SACLANTCEN, 1972/09)In cooperation with SACLANTCEN, O.G.S. started in 1961 the geophysical survey of the Mediterranean Sea (Allan, Morelli, 1971 ), which after 1966 was continued in the seas around Italy on the oceanographic ships of C.N.R. ... -
Bayesian inference and sidescan restoration
(NATO. SACLANTCEN, 1997)We consider a Bayesian approach to the problem of inferring parameters of the SONAR environment given only the gathered sidescan image. A simplified model of the process is developed along with suitable distributions on ... -
Beam spreading and loss of spatial coherence in an inhomogeneous and fluctuating ocean
(NATO. SACLANTCEN, 1975/10)A theory has been developed that enables estimates to be made of beam bending, beam spreading and loss of spatial coherence. In this paper we concentrate on the loss of spatial coherence due to scattering. Using a minus ... -
Bottom bistatic scattering: experimental results and model comparison for a carbonate sediment
(NATO. SACLANTCEN, 1997)Bistatic scattering measurements were carried out under the Coastal Benthic Boundary Layer (CBBL) program. The results presented here are for a carbonate sand-silt-clay, and the data were collected in Februar) 1995 near ... -
Bottom time spread and bistatic scattering by rough basalt
(NATO. SACLANTCEN, 1993/08)Scattering from oceanic basalt affects low-frequency active sonar systems in at least two important ways: (1) Significant time, angle and frequency spreading reduces target echo levels when systems over-resolve the spread; ... -
Bottom-interacting ocean acoustics: proceedings of a conference held at SACLANTCEN on 9-13 June 1980
(NATO. SACLANTCEN, 1980/07) -
Bottom/subbottom surveying using a new, parametric, sidescan sonar
(NATO. SACLANTCEN, 1997)The Naval Research Laboratory (NRL) has developed a dual-frequency, towed, interferometric, sidescan sonar system known as the Subbottom Swath System, which is capable of detecting objects and structures buried below the ... -
Calculation of propagation losses in a medium with a velocity profile approximated by a number of Epstein profiles
(NATO. SACLANTCEN, 1971/12)This paper presents a digital ray-theory program, by which the ray trace, travel time and intensity can be calculated for velocity profiles approximated by a number of Epstein functions. -
Channel-adapted source for shallow water
(NATO. SACLANTCEN, 1993/08)In shallow water areas the utilization of active sonar is complicated by the fact that in these environments the performance of active systems is degraded by source signal interaction with channel boundaries. These boundary ...