Browsing CMRE Publications by Title
Now showing items 753-772 of 882
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Subcritical penetration of narrow Gaussian beams into sediments
(NATO. SACLANTCEN, 1988/03)Complete wave-theory solutions have been obtained numerically for both the reflected and the transmitted fields associated with a narrow Gaussian beam incident on a water-sediment interface near the critical grazing angle. ... -
Summary and recommendations
(NATO. SACLANTCEN, 1971/12)An unfortunate first impression might be that ray tracing is dull, simply because the idea is a very old one. In fact, ray tracing is the single most powerful method available to us for understanding the complexities of ... -
Supporting AUV localisation through next generation underwater acoustic networks: results from the field
(CMRE, 2017/11)This work describes how the localisation of autonomous underwater vehicles can be supported through net-worked acoustic communication. The localisation approach in-cludes timing information within acoustic messages to ... -
SUPREMO: a multistatic sonar performance model
(NATO. SACLANTCEN, 2002/11)Multistatic sonars introduce new problems to the modeller such as mutual interference from multiple sources and variable target aspect in a background of range-dependent bistatic reverberation. A multistatic sonar performance ... -
Surface duct propagation loss measurements and model predictions at low and mid frequencies
(NATO. SACLANTCEN, 1993/08)Side-by-side measurements of low- and mid-frequency propagation loss were obtained during a sea test conducted in the North Atlantic during February of 1992. These measurements are compared to each other and with model ... -
Surface measurements made during the Icelandic Current Experiment (ICE 89) from the R/V Alliance
(NATO. SACLANTCEN, 1991/10)Measurements of surface meteorology and sea temperature taken during the GIN '89A cruise of the research vessel Alliance are presented in the form of time-series plots. The cruise was in the southern Icelandic and Norwegian ... -
Surface measurements made from the R/V ALLIANCE during the Mediterranean aircraft-ship transmission experiment (MASTEX), June 1990
(NATO. SACLANTCEN, 1992/12)Measurements of sea-surface temperature, surface meteorology and atmospheric profiles taken during the June 1990 cruise of the R/V Alliance in the Aegean and Ionian Seas are presented in graphical form. True winds, net ... -
Surface wave spectra
(NATO. SACLANTCEN, 1975/10)A classification is made of the different types of wave elevation spectra namely lD time spectra, lD spatial spectra, 2D spatial spectra and 3D space-time spectra. Relations with simple single parameter measures of surface ... -
Swath bathymetry and SAS autofocus using a Chirp source
(NATO. SACLANTCEN, 1997)Swath bathymetry and SAS autofocus can both be treated as problems in correlating echoes from a scatterer distribution on the seabed. Using a chirp source, the phase derived from quadrature match-filtering can replace the ... -
System functional migration: high-level language to hardware
(NATO. SACLANTCEN, 1979/12)This paper intends to examine system functional allocation among available processing resources in a systematic way. The discussion will focus first on the criteria for assigning functions to processors, that is, horizontal ... -
Tactical data acquisition experiences
(NATO. SACLANTCEN, 1972/05)The requirements of Tactical Data Acquisition systems are discussed and summarized. Experiences with equipment and their utilization are described including : quantities measured, input signal conditioning, analogue ... -
Tank measurements of elastic scattering by a resin-filled fiberglass spherical shell
(NURC, 2007/12)Acoustic elastic scattering measurements were conducted in a tank on a 6cm radius fibreglass spherical shell filled with a low-shear-speed epoxy resin. Preliminary measurements were conducted also on the void shell before ... -
Tank measurements of scattering from a resin-filled fibreglass spherical shell with internal flaws
(NURC, 2008/09)This paper presents results of acoustic inversion and structural health monitoring achieved by means of low to midfrequency elastic scattering analysis of simple, curved objects, insonified in a water tank. Acoustic elastic ... -
Target detection and location with ambient noise
(NURC, 2008/09)By placing a vertical array in an ambient noise field and forming an upward and a downward beam one obtains two time series which can be cross correlated to reveal a subbottom profile of the seabed [Siderius et al., J. ... -
Target detection using a three-layered neural network trained by supervised back-propagation
(NATO. SACLANTCEN, 1990/05)In any sonar system a detection process has to be performed at -
Target localization with multiple sonar receivers
(NATO. SACLANTCEN, 2000/01)Deployable Underwater Surveillance Systems (DUSS) are a network of small multistatic transmitter/receiver sonar nodes. This study analyzes the contact localization capabilities of DUSS in term of range, time and bearing ... -
Target motion effects on passive sonar: an appraisal of basic factors
(NATO. SACLANTCEN, 1986/12)Detection and tracking by passive sonar involve the observation of the target-radiated noise in bearing-cells and time-cells that have their dimensions predetermined by a combination of physical limitations, e.g. the size ... -
Target time smearing with short transmmissions and multipath propagation
(NURC, 2012/04)In active sonar the target echo level is often estimated with a propagation model that adds all multipath arrivals. If the (post-correlator) transmitted pulse is short compared to the multipath time spread then there is ... -
Temporal and spatial variabilities in shallow water acoustics: measurements and predictions
(NATO. SACLANTCEN, 1985/03)An acoustic signal propagating in the sea is generally degraded not only by interactions with the bottom and surface boundaries, but also by volume inhomogeneities caused by non-uniformities in temperature, density, and ... -
Temporal fluctuation of backscattered field due to bioturbatioon in marine sediments
(NATO. SACLANTCEN, 1997)Biological activity in marine sediments creates a time-varying, randomly fluctuating medium. A bio-diffusive model is proposed for predicting the temporal and spatial spectrum of sediment density fluctuations. Perturbation ...