Browsing Technical Reports by Issue Date
Now showing items 241-260 of 322
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Yellow Shark Spring '95: inversion results from sparse broadband acoustic measurements over a highly range dependent soft clay layer
(NATO. SACLANTCEN, 1998/06)In May 1995, SACLANTCEN performed broad-band (200-800 Hz) acoustic measurements in the Giglio basin off the coast of Italy as part of the Yellow Shark inversion experiments. In this paper, inversion of sparse, broad-band ... -
Modelling acousto-elastic waveguide/object scattering with the Rayleigh hypothesis
(NATO. SACLANTCEN, 1998/06)In this memorandum the plane wave scattering matrices for a range-dependent seabed and upper free surface are computed using the -
Oceanographic conditions in the Antalya Basin in water
(NATO. SACLANTCEN, 1998/07)From an oceanographic survey of the Antalya Basin in February 1997 the following horizontal circulation pattern was found: The Asia Minor Current (AMC) was detached from the Turkish coast flowing to the southwest between ... -
Penetration of acoustic waves into sandy seafloors at low grazing angles: the Helmholtz-Kirchhoff approach
(NATO. SACLANTCEN, 1998/08)The Helmholtz-Kirchhoff integral is applied to model the penetration of sound waves into sandy seafloors at grazing angles above and below the critical angle. Although the conditions for the validity -
DUSS97: source localization and environmental inversion using vertical array data
(NATO. SACLANTCEN, 1998/08)Results on source localization and environmental inversion using experimental data acquired on a vertical line array are presented. Global inversion methods based on genetic algorithms are utilized to estimated the range ... -
Probability of false alarm estimation in oversampled active sonar systems
(NATO. SACLANTCEN, 1998/08)The probability of false alarm (Pfa)in active sonar systems is an -
Resonance analysis of the acoustic response of a water-filled cylindrical shell
(NATO. SACLANTCEN, 1998/09)The resonance analysis approach developed for characterizing free-field air-filled cylindrical shells in terms of geometrical and mechanical pararneters is extended to fluid-filled shells either in the freefield or proud ... -
Remote sensing of topographically-induced upwelling in the southern coastal region of Sicily
(NATO. SACLANTCEN, 1998/09)Upwelling signatures caused by variations in bottom topography along the southeastern Sicilian coast are identified, using spaceborne remote sensing Advanced Very High Resolution Radiometer (AVHRR) imagery, ERS-1 and ... -
Detection of buried objects in the seabed: a simple model study
(NATO. SACLANTCEN, 1998/10)The problem of detecting an object buried in the seabed is studied by means of a simple model. In this model, the object is a rigid sphere buried in a bottom modelled as a fluid half space. The scattered field is determined ... -
Generic Oceanographic Array Technologies (GOATS)'98: bi-static seabed scattering measurements using autonomous underwater vehicles
(NATO. SACLANTCEN, 1998/10)The GOATS'98 experiment was performed May 5-29, 1998 in shallow water off Marciana Marina, on the island of Elba, Italy. The experiment addressed some of the fundamental issues associated with using the new Autonomous Ocean ... -
Experimental demonstration of the focused acoustic field in the ocean
(NATO. SACLANTCEN, 1998/10)An experiment conducted in the Mediterranean Sea in April1996 demonstrated that a time reversal mirror (or phase conjugate array) can be implemented to spatially and temporally refocus an incident acoustic field back to ... -
Bottom reverberation in shallow water: coherent properties as a function of bandwidth, waveguide characteristics and scatterer distribution
(NATO. SACLANTCEN, 1998/10)Scattering physics are often modeled using the Helmholtz equation for computational reasons. Likewise, propagation loss to and from scattering regions are often treated in a like manner. The usual approach for generating ... -
Deployable underwater surveillance systems(DUSS): localization and fusion of multistatic contacts: evaluation of feasibility using experimental data
(NATO. SACLANTCEN, 1998/12)Active sonar deployable underwater surveillance systems (DUSS) are based on a distributed network -
High resolution geoacoustic inversion in shallow water: a joint time and frequency domain technique
(NATO. SACLANTCEN, 1998/12)High resolution geoacoustic data are quired for accurate predictions of -
Drifter and float observations in the Adriatic Sea (1994-1996): data report
(NATO. SACLANTCEN, 1998/12)During the period December 1994 to November 1995, 62 Argos tracked surface drifters, one Argos tracked drifter drogued to 300 m and 3 Argos tracked sub-surface floats were released in the Adriatic Sea to describe the ... -
Scintillation instrument for remote environmental analysis (SIREN)
(NATO. SACLANTCEN, 1999/02)A high frequency acoustic propagation instrument which was developed to study ocean variability in the Strait of Istanbul (Bosporus) is described. The scintillation instrument for remote environmental analysis (SIREN) was ... -
Distributions of magnetic field variations, differences and residuals
(NATO. SACLANTCEN, 1999/02)Temporal and spatial variations of the geomagnetic field were recorded in different geographic areas, -
Accuracy of synthetic aperture sonar micronavigation using a displaced phase centre antenna
(NATO. SACLANTCEN, 1999/02)This work evaluates the accuracy of multi-element synthetic aperture sonar (SAS) micronavigation based on the concept of displaced phase centre antenna (DPCA). The Cramér-Rao lower bound (CRLB) for the joint estimation of ... -
Decay of large underwater bubble oscillations
(NATO. SACLANTCEN, 1999/02)Pressure - time series from breathing mode oscillation of large (centimeter scale or larger) underwater bubbles reveal much higher decay rates than can be explained using viscous, thermal, or radiative mechanisms which ... -
The magnetic dipole moment of RV Alliance
(NATO. SACLANTCEN, 1999/02)A SACLANTCEN magnetometry sea trial was performed in September 1998 in the northern Tyrrhenian Sea in the vicinity of the Formiche di Grosseto islands. One of the trial objectives