Browsing Reprints by Type "Conference Proceedings (CP)"
Now showing items 201-220 of 290
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Relating in situ shear wave velocity to void ratio and grain size for unconsolidated marine sediments
(NATO. SACLANTCEN, 1997)Recent advances in field hardware have meant that it has become possible to measurein situ shear wave velocity in the upper few decimetres of sea floor sediment in a routine manner. It is known that shear wave velocity can ... -
Relative contribution of surface roughness and bottom attenuation to propagation loss in shallow water
(NATO. SACLANTCEN, 1975/10)A simulation study has been performed to investigate the relative importance of the contributions of surface roughness and bottom attenuation to propagation loss under differing environmental conditionso The NRL normal ... -
Results from the use of broad-band, sub-bottom seismic data with statistically based sediment classification techniques
(NATO. SACLANTCEN, 1997)The QTC VIEW sediment classification system has been applied to shallow, high resolution seismic data recorded with the IKB-SEISTEC profiler from the navigable channel of the St. Lawrence estuary in Canada. A number of 10 ... -
Retrodirective array performance case studies and implications for mine countermeasures
(NATO. SACLANTCEN, 1997)The use of focused acoustic fields for the mechanical destruction of fluid-borne targets is applied zn. the medical field for the comminution of kidney stones by lithotripsy. Inhomogeneities in the propagation medzum are ... -
Riverine environmental acoustics at an ocean estuary
(NATO. SACLANTCEN, 1997)The purpose of these studies was to investigate some of the more important geoacoustrc parameters that might govern the use of high frequency sonar in muddy rivers, where they flow into the sea. Both environmental and ... -
Role of propagation in ambient noise
(NATO. SACLANTCEN, 1982/06)To be useful for modern ASW systems design and analyses, descriptions of ambient noise fields must go beyond average omnidirectional spectra and include horizontal and vertical patterns, fluctuations with time, dependencies ... -
SACLANTCEN real-time signal processing system
(NATO. SACLANTCEN, 1979/12)To meet its increasing requirements in real-time signal processing, SACLANTCEN has developed a general purpose. signal processing system called WARP to be uS.ed with a fairly wide range of underwater acoustic research ... -
Scattering from a random interface
(NATO. SACLANTCEN, 1975/10)The problem of scattering from a random interface separating two fluids with different densities and sound speeds is considered. The method is to write coupled integral equations in coordinate space connecting the surface ... -
Scattering from an elastic cylinder buried beneath a rough water/sediment interface
(NATO. SACLANTCEN, 1997)In this paper a plane-wave decomposition method is used to compute the two-dimensional backscattering from a buried elastic cylinder as a function of frequency. The cases of a pat water/sediment interface and deteministically ... -
Seabed characterization by inversion of parametric sonar data: selection of the cost function
(NATO. SACLANTCEN, 1997)A class of possible cost functions to be used in model-based estimation of bottom parameters from highfrequency backscatter signals is introduced. The cost is based on the properttes of the signal in the wavelettransformed ... -
Seabed sediment characteristics assessed geophysically: results of experiments in the Clyde Sea, Scotland
(NATO. SACLANTCEN, 1997)Within a research programme aimed at developing in situ sediment classification methodologies, it has been demonstrated that with only limited ground truth information, sub-bottom profiler data can be inverted to produce ... -
Seabed survey by VHR multichannel seismics: GEOSIS project
(NATO. SACLANTCEN, 1997)Site surveys prior to the installation of offshore facilities are required to obtain shallow soil structural and geotechnical information. The French project GEOSIS was aimed at improving both geophysical and geotechnical ... -
Sedimentological acoustics: an attempt to reduce the gap between acoustical modeling and sedimentoloogical survey
(NATO. SACLANTCEN, 1997)A major task in shallow water acoustics is to provide pertinent geoacoustical data. The purpose of the work is to evaluate the state of the art in this field, connecting in situ sedimentological measurement and acoustical ... -
Seismic and hydroacoustic sensing of infrasonic noise in coastal waters
(NATO. SACLANTCEN, 1982/06)Three-component ocean-bottom seismometers with radio links have been deployed in coastal waters to investigate natural and man-made noise at extremely low frequencies. Seismograms from one or up to three sensor stations ... -
Sensitivity of ray theory to input data
(NATO. SACLANTCEN, 1971/12)Acoustic propagation problems which are solved using ray theory require certain input data. In particular, the source and receiver locations, sound-velocity field and bottom and surface conditions are required. Frequently, ... -
Shallow water propagation incorporating both bubble plumes and sea-surface roughness
(NATO. SACLANTCEN, 1997)The effect of including a range dependent bubble layer and a suitable sea surface spectrum in modeling shallow water propagation is analyzed. Propagation is simulated through a hrghly accurate model based on a modified PE ... -
Shallow water reverberation modeling using an autoregressive range-scattering function approach
(NATO. SACLANTCEN, 1997)The primary limitation on system performance for active sonars is reverberation - the reradiation of acoustic energy back to the receiver from inhomogeneities in the physical properties of the medium and its boundaries. A ... -
Shallow-water ASW sonar design
(NATO. SACLANTCEN, 1993/08) -
Shallow-water coherence of broadband signals
(NATO. SACLANTCEN, 1997)The frequency-dependent spatial and temporal variabilities of sound propagation in coastal regions is investigated by ezperiment and numerical simulations. Experimental observations show that temporal coherence of the ... -
Shallow-water seafloor characterization for high-frequency multibeam echosounder: image segmentation using angular backscatter
(NATO. SACLANTCEN, 1997)Sonar images from multibeam echosounders are submitted to various degradations, partly due to the sensor itself: Signal artefacts and corresponding corrections are presented, both for signal processing and for array ...