Browsing Reprints by Title
Now showing items 342-361 of 548
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Obtaining the ocean index of refraction spectrum from the acoustic amplitude fluctuations
(NATO. SACLANTCEN, 1997)The feasibility of using acoustic measurements to determine the properties of a shallow water internal wave field is investigated through numerical simulations. The random intemal wave field is modeled by a generalized ... -
The ocean noise coherence matrix and its rank
(CMRE, 2019/05)An expression for the cross-spectral density matrix of ocean noise naturally separates into a Toeplitz part and a Hankel part [Harrison (2017). J. Acoust. Soc. Am. 141, 2812?2820]. The Toeplitz part is shown to be substantially ... -
Ocean-basin reverberation from large underwater explosions: part 1: source-level and propagation-loss modelling
(NATO. SACLANTCEN, 1975/10)Predicting the reverberant returns from ocean basin reflectors requires describing acoustic source levels for large, conventional underwater explosions, defining the two way propagation loss and signal spreading from the ... -
Ocean-basin reverberation from large underwater explosions: part 2: computer model for reverberation
(NATO. SACLANTCEN, 1975/10)Following detonation of an underwater explosion, sound reverberates from the ocean surface and bottom and from scatterers within the medium. In addition, the boundaries of the ocean basin and obstructions within it, such ... -
Ocean-bottom reflectivity (a point of view)
(NATO. SACLANTCEN, 1975/10)The analysis procedures for extracting bottom loss values from pulsed acoustic signals that have interacted with the ocean bottom do not inherently consider sub-bottom refraction and reflection of sound, which are important ... -
Oceanic layered microstructure and fronts
(NATO. SACLANTCEN, 1971/12)This talk is divided into two parts: one deals with oceanic microstructure, with particular attention to the so-called "layered microstructure"; the other part is concerned with oceanic fronts. As an example of the latter ... -
Oceanic-acoustic experiments at SACLANTCEN
(NATO. SACLANTCEN, 1971/12)Last year, at the Director's suggestion, a project in oceanicacoustics was set up at the Centre with scientists from at least 3 groups playing some part in the planning and execution of experiments. The p roject represents ... -
Oceanographic field estimates from remote sensing and glider fleets
(CMRE, 2014/01)This work investigates the merging of temperature observations from a glider fleet and remote sensing, based on a field experiment conducted in an extended coastal region offshore La Spezia, Italy, in August 2010. Functional ... -
On adaptive modulation for low SNR underwater acoustic communications
(CMRE, 2019/05)This paper deals with adaptive underwater acoustic (UWA) communications where the receiver must operate at low signal-to-noise ratios (SNRs). The proposed modem is equipped with a set of direct sequence spread spectrum ... -
On adaptive underwater object detection
(NURC, 2012/04)A new algorithm for the detection of underwater objects in sonar imagery is proposed. One particularly novel component of the algorithm also detects the presence of, and estimates the orientation of, sand ripples. The ... -
On the effects of synthetic-aperture length on SAS seabed segmentation
(NURC, 2009/12)In this work, we quantify the relationship between synthetic-aperture length (or equivalently, along-track resolution) and seabed segmentation performance experimentally for real synthetic aperture sonar (SAS) imagery. The ... -
On the integration of through-the-sensor geoacoustic inversion techniques for environmental adaptation schemes in low frequency active sonars
(NURC, 2007/12)The environmental conditions in shallow water areas are known to strongly affect the performances of low frequency active sonars (LFAS). In particular, interactions of the acoustical field with the seabed interface have ... -
On the physics and design of electrical discharge sources for active undersea surveillance
(NATO. SACLANTCEN, 1993/08)Underwater electrical arcs have long been used as an impulsive sound source, although efforts to improve efficiency and control acoustic output have been limited by inadequate understanding of the arc initiation process. ... -
On the relationship between SAS image resolution and target-detection performance
(CMRE, 2019/06)The relationship between synthetic aperture sonar (SAS) image resolution and target-detection performance is quantified. It is first demonstrated how a lower-resolution SAS system can be simulated in a principled manner ... -
On-board real-time assessment of acoustic environmental parameters relevant to the estimation of sonar performance for autonomous underwater vehicles
(CMRE, 2019/05)CMRE is evaluating the use of autonomous robots for the detection and tracking of underwater targets. Robotic detection and localization comes with many challenges, not the least of which is the requirement to maximize the ... -
Online estimation of unknown parameters in multisensor-multitarget tracking: a belief propagation approach
(CMRE, 2019/05)We propose a Bayesian multisensor-multitarget tracking framework, which adapts to randomly changing conditions by continually estimating unknown model parameters along with the target states. The time-evolution of the model ... -
Optimal detection and tracking of acoustical noise sources in a time-varying environment
(NATO. SACLANTCEN, 1982/06)A dynamical detector estimator is derived for nonlinear nongaussian signal processes based on Bucy's representation theorem which is the fundamental result in stochastic filtering. A quantized version of two-dimensional ... -
Optimum sampling designs for a glider-mooring observing network
(CMRE, 2014/01)Ocean observing systems (OOSs) constituted by moorings and gliders are becoming relevant in oceanographic and climate studies. In these observing networks, the temporal variability is captured by mooring observations, while ... -
An ordered family of consistency measures of belief functions
(CMRE, 2019/05)We propose a family of measures of consistency (and induced conflict) derived from a definition of consistent belief functions introduced previously. Besides satisfying the desired properties of monotonicity, boundedness, ... -
Overview of the ADPS signal processor
(NATO. SACLANTCEN, 1979/12)