105 research outputs found
A time-frequency approach to blind deconvolution in multipath underwater channels
Blind deconvolution is presented in the underwater acoustic channel context, by time-frequency processing. The acoustic propagation environment was modelled as a multipath propagation channel. For noiseless simulated data, source signature estimation was performed by a model-based method. The channel estimate was obtained via a time-frequency formulation of the conventional matched-filter. Simulations used a ray-tracing physical model, initiated with at-sea recorded environmental data, in order to produce realistic underwater channel conditions. The quality of the estimates was 0.793 for the source signal, and close to I for the resolved amplitudes and time-delays of the impulse response. Time-frequency processing has proved to overcome the typical ill-conditioning of single sensor deterministic deconvolution techniques
Optimal design of a whale of anti-collision system
This paper summerizes tools coming from estimationâs theory to evaluate and design experimental device. Theses tools
are applied to the "Whale Anti Collision System" dedicated to localise Sperm Whales and to avoid collision with ships.
Relying on theoretical tools, our approach tries to be as close as possible of reality by using true sperm clicks, realistic
measurement noise by allowing sensors and acoustic environmental missknowledges. Without any acoustic
environmental assesment, WACS system shows to be a good tool for biology study but may not be enougth accurate to
be included in a anti-collision network. With an acoustic environmental assesment, WACS system is accurate enough to
be included in an anti-collision network. WACS settings and step of the anti-collision network are identified.Dans cet article, des outils issus de la thĂ©orie de lâestimation sont proposĂ©s pour permettre lâĂ©valuation des
performances et le dimensionnement de systÚmes expérimentaux. Ceux-ci ont été appliqués au systÚme
WACS (Whales Anti Collision System), systĂšme de localisation passive des cachalots vocalisants ou non afin de
contribuer Ă rĂ©duire les collisions avec les navires. BasĂ©e sur des outils thĂ©oriques, lâapproche proposĂ©e
sâattache Ă se rapprocher au mieux de la rĂ©alitĂ© par les hypothĂšses effectuĂ©es. Sans monitorage de
lâenvironnement acoustique, il est dĂ©montrĂ© que WACS est un bon outil pour le biologiste mais pourraĂźt ne pas
ĂȘtre assez prĂ©cis pour ĂȘtre insĂ©rĂ© au sein dâun rĂ©seau anti-collision. AssociĂ© Ă un monitorage de
lâenvironnement acoustique, il est dĂ©montrĂ© que WACS est assez prĂ©cis pour ĂȘtre inclus dans un rĂ©seau
anti-collision, les degrés de liberté de WACS sont optimisés et la maille du réseau est identifiée
Modelling of ambient noise created by a shipping lane to prepare passive inversion: application to Ushant
The Ushant thermal front is a seasonal phenomenon which occurs from May to October in a shallow water environment (100m) of the Iroise Sea (off the coast of the north-western France). It corresponds to the boundary separating a well mixed inner shelf water from an open sea stratified water. To determine the dynamic of the front -or more basically the presence of a stratified or homogeneous water column- the possibility to use a shipping lane as a continuous acoustic source is studied. The originality of this work is to use a single receiver. Simulation results of sounds radiated by a shipping lane in a shallow water environment are presented, both for stratified and homogeneous water column. The corresponding pressure fields show a mean level difference in the frequency band 50-300 Hz. This feature will be used in the future as an observable to differentiate both environments, and thus passively detect the Ushant thermal front. One of the issue to get the mean level offset is to record the shipping lane noise without isolated ship interferences. As a consequence, an optimum mooring position to track the thermal front is suggested by the analysis of the vessel traffic from AIS data (Automatic Identification System)
Passive geoacoustic inversion of very shallow water environment with ship's noise: incoherent processing
In the context of the passive geoacoustic inversion, this manuscript proposes a new Inversion Method suitable for very
shallow water environments (10 to 30 m) from the broadband noise produced by ships of opportunity. The solution is
dedicated to a small number of hydrophones and is easy to implement. The interference patterns generated by the ship
movement and the propagation properties are exploited to extract the relative dispersion curves on a chosen bandwidth
then the geoaoustic inversion is performed. Here, we describe our algorithms and validate them on realistic synthetic data as well as on real data from a very shallow water trial performed off the Southern coast of Barcelona, Spain.
Valuable results are obtained and allow to draw some way of improvement.Dans le contexte de l'inversion géoacoustique passive, nous proposons une méthode d'estimation
des propriétés acoustiques d'un canal océanique trÚs petits fonds (profondeur de 10 à 30 m) à partir du bruit
large bande rayonné par des navires en transit. La solution est développée afin de conduire à un systÚme de
mesure minimisant le nombre d'hydrophones requis, pour cela elle utilise le mouvement des sources. Ă partir
de l'observation acoustique de radiales centrées sur un hydrophone, les phénomÚnes d'interférences entre
modes de propagation sont utilisés pour extraire les courbes de dispersion relatives du canal sur une bande
fréquentielle choisie entre 50 et 500Hz. La contribution d'un navire est alors inversée pour fournir les
propriétés du canal. Une description des algorithmes et de leurs implémentations est effectuée et leurs
validations sont envisagées sur des données synthétiques réalistes ainsi que sur des données réelles issues
d'une campagne expérimentale trÚs petits fonds (profondeur~20 m) réalisée au sud de Barcelone à partir de
petits navires d'opportunité constitués principalement de chalutiers. Les résultats produits sont encourageants
et permettent de dresser des perspectives d'amélioration pour la méthode
proposée
Measuring hearing in wild beluga whales
Author Posting. © The Author(s), 2016. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in "The Effects of Noise on Aquatic Life II," edited by Arthur N. Popper, Anthony Hawkins, 729-735. New York, NY: Springer, 2016. doi: 10.1007/978-1-4939-2981-8_88.We measured the hearing abilities of seven wild beluga whales (Delphinapterus leucas)
during a collection-and-release experiment in Bristol Bay, AK, USA. Here we summarize the
methods and initial data from one animal, discussing the implications of this experiment.
Audiograms were collected from 4-150 kHz. The animal with the lowest threshold heard best
at 80 kHz and demonstrated overall good hearing from 22-110 kHz. The robustness of the
methodology and data suggest AEP audiograms can be incorporated into future collection-and-release health assessments. Such methods may provide high-quality results for multiple
animals facilitating population-level audiograms and hearing measures in new species.Project funding and field support provided by Georgia Aquarium and the National Marine
Mammal Laboratory of the Alaska Fisheries Science Center (NMML/AFSC). Field work also
supported by National Marine Fisheries Service Alaska Regional Office (NMFS AKR),
WHOI Arctic Research Initiative, WHOI Ocean Life Institute, U.S. Fish and Wildlife
Service, Bristol Bay Native Association, Alaska SeaLife Center, Shedd Aquarium and Mystic
Aquarium. Audiogram analyses were funded by the Office of Naval Research award number
N000141210203 (from Michael Weise)
David Hume on Banking and Hoarding
David Hume opposes banks and favors hoarding. The only bank he reluctantly approves of is a public, 100% reserve bank. Other banks increase money supply and prices, hindering exports and economic growth. For Hume, a 100% reserve public bank would lead to ââthe destruction of paper-creditââ ([1752] 1985, p. 285), fostering economic growth instead by preventing inflation. Additionally, a 100% reserve bank hoards a large quantity of gold and silver, which is available in case of national emergency
In vitro studies and preliminary in vivo evaluation of silicified concentrated collagen hydrogels
Hybrid and nanocomposite silicacollagen materials derived from concentrated collagen hydrogels were evaluated in vitro and in vivo to establish their potentialities for biological dressings. Silicification significantly improved the mechanical and thermal stability of the collagen network within the hybrid systems. Nanocomposites were found to favor the metabolic activity of immobilized human dermal fibroblastswhile decreasing the hydrogel contraction. Cell adhesion experiments suggested that in vitro cell behavior was dictated by mechanical properties and surface structure of the scaffold. First-to-date in vivo implantation of bulk hydrogels in subcutaneous sites of rats was performed over the vascular inflammatory period. These materials were colonized and vascularized without inducing strong inflammatory response. These data raise reasonable hope for the future application of silicacollagen biomaterials as biological dressings.Fil: Desimone, MartĂn Federico. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Houssay. Instituto de QuĂmica y Metabolismo del FĂĄrmaco. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica. Instituto de QuĂmica y Metabolismo del FĂĄrmaco; ArgentinaFil: HĂ©lary, Christophe. UniversitĂ© Pierre et Marie Curie; FranciaFil: Quignard, Sandrine. UniversitĂ© Pierre et Marie Curie; FranciaFil: Rietveld, Ivo B. Universite de Paris; FranciaFil: Bataille, Clement. UniversitĂ© de Versailles Saint-quentin-en-yvelines.; FranciaFil: Copello, Guillermo Javier. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Houssay. Instituto de QuĂmica y Metabolismo del FĂĄrmaco. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica. Instituto de QuĂmica y Metabolismo del FĂĄrmaco; ArgentinaFil: Mosser, Gervaise. UniversitĂ© Pierre et Marie Curie; FranciaFil: Giraud Guille, Marie-Madeleine. UniversitĂ© Pierre et Marie Curie; FranciaFil: Livage, Jacques. UniversitĂ© Pierre et Marie Curie; FranciaFil: Meddahi PellĂ©, Anne. UniversitĂ© de Versailles Saint-quentin-en-yvelines.; FranciaFil: Coradin, Thibaud. UniversitĂ© Pierre et Marie Curie; Franci
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