CMRE Open Library: Recent submissions
Now showing items 401-420 of 882
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The Strait of Sicily in relation to the general circulation of the Mediterranean
(NATO. SACLANTCEN, 1972/09) -
Very low frequency ambient noise measurements in the Ionian Sea: data report
(NATO. SACLANTCEN, 1997/09)This memorandum describes an experiment and provides a data -
Observations of Mediterranean flow into the Black Sea
(NATO. SACLANTCEN, 1997/10)Mediterranean Sea water inflow into the Black Sea is investigated using acoustic and oceanographic data obtained in the Black Sea exit region. The path of Mediterranean water and the resulting spreading on the continental ... -
Modelling of scattering by objects on the seabed
(NATO. SACLANTCEN, 1997/12)This paper describes some of the theory and implementation issues of modeling the backscattered -
Automatic target classification using multiple sidescan sonar images of different orientations
(NATO. SACLANTCEN, 1997/09)In this report, the target classification performance of a multiple view sidescan sonar is investigated. The classification statistics are estimated using model based automatic classifiers. The guidelines to the design of ... -
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 ... -
Determination of velocity profile and sea bed characteristics from high frequency pulse propagation in a shallow water Mediterranean environment
(NATO. SACLANTCEN, 1997)Time-domain features of shallow water Mediterranean and Yellow Sea data are simulated for frequency band widths of 0.8 kHz with a centralfrequency of 3.2 kHz. Contour plots of pulse arrivals in time and depth are analyzed ... -
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 ... -
Uniqueness problems in extracting environmental parameters from high-frequency shallow-water reverberation measurements
(NATO. SACLANTCEN, 1997)Inversion techniques that extract environmental parameters from measured reverberation often lead to mathematical problems that are not well-posed. Two examples illustrate this possibility. The first hows how a model can ... -
Analysis and problems of HF acoustic coherent and incoherent simulations in shallow water
(NATO. SACLANTCEN, 1997)Shallow water environments create complex scattering condit~ons due to the sea surface and bottom scattering mechanisms. An analysis of the effects of the scattering mechan~smso n sonar images of simple targets in shallow ... -
A PC/Linux software toolkit for coastal swath mapping
(NATO. SACLANTCEN, 1997)Assembly of a PC/Linux based data acquisirion and processing software toolkit for coastal (shallow water) multibeam and sidescan swath mapping sonar systems has been undertaken by the URI Ocean Mapping Development center ... -
A novel method to enlarge the scanning region of a focused beamformer
(NATO. SACLANTCEN, 1997)Often focused beamforming systems use the Fresnel approximation to compute the required delays. Unfortunately, such an approximation has a validity region that is very narrow around the broadside direction. To investrgate ... -
Modeling of subcritical penetration into sediments due to interface roughness
(NATO. SACLANTCEN, 1997)Recent experimental results reveal acoustic penetration into sandy sediments at grazing angles below the critical angle. We have been investigating a mechanism for subcritical penetration based on scattering at a rough ... -
Oceanography of the Strait of Sicily: proceedings of a conference held at SACLANTCEN on 11-12 April 1972
(NATO. SACLANTCEN, 1972/09) -
Effects of sea bed structure on high frequency acoustic reverberation in shallow water
(NATO. SACLANTCEN, 1997)Although undoubtedly sea bed structures, patterns, and composition affect the reverberation of high-frequency acoustic energy, the extent of their influence is not well known. The effects of varying selected bedform ... -
Small scale volumetric inhomogeneities of shallow water sediments: measurements and discussion
(NATO. SACLANTCEN, 1997)There is a consensus that high-frequency acoustic scattering by the ocean bottom is partly due to sediment volumetric inhomogeneities, r e., random fluctuations in sediment sound speed and density. Understanding the spatial ... -
Intensity moments of underwater sound scattered by a Gaussian spectrum corrugated surface: measurements and comparison with a catastrophe theory approximation
(NATO. SACLANTCEN, 1997)An underwater forward-scattering investigation was undertaken with random rough corrugated pressure release surface manufactured out of Styrofoam. Measured wavefields associated with the reflection caustics agree with ... -
Geoacoustic modeling of the seabed at higher frequencies
(NATO. SACLANTCEN, 1997)In propagation at higher frequencies, local fluid motion in "hidden coordinate" systems and local discontinuities due to gas bubbles and bioturbation have a perturbing effect on the wave field. To model these effects, a ... -
Temporal modeling of high frequency (30-100 kHz) acoustic seafloor backscatter: shallow water results
(NATO. SACLANTCEN, 1997)A temporal model of high frequency seafloor acoustic backscatter is presented and compared to recorded echoes from terrigenous sediments. Using acoustic properties correlated with mean grain size, the echo shapes and ... -
Wavefront curvature ranging as a passive synthetic aperture problem
(NATO. SACLANTCEN, 1997)A new method of wavefront curvature passive ranging is introduced that is based on a model-based approach. The signal and measurement systems are placed into state-space form, thereby allowing the unknown parameters of the ...