Encontrados 162 documentos, a visualizar página 1 de 17
Using active and passive acoustics to assess O2 production of a Posidonia ocean...
Felisberto, P.; Zabel, F.; Rodriguez, O. C.; Santos, P.; Jesus, S. M.; Champenois, W.; Borges, A. V.; Santos, RuiThis work discusses the data acquired during two experiments conducted in October 2011 and May 2013 in the Bay of la Revellata, Calvi, Corsica for the purpose of developing an acoustic system for monitoring the oxygen production of a seagrass meadow.
Experimental testing of Asymmetric Underwater Acoustic Networks
Vilaipornsawai, U.; Silva, António J.; Jesus, S. M.The coordinated operation of multiple vehicles within the framework of multipoint non-cabled observatories and offshore activities sprung the necessity for complex underwater acoustic networks (UANs). An example of such UAN consisting of fixed and mobile underwater nodes, was recently developed and tested at sea. A star-shaped network topology was adopted, where wide area network (WAN) integration was ensured t...
Correlation between the acoustic noise field measured in a Posidonia oceanica b...
Felisberto, P.; Zabel, F.; Rodriguez, O. C.; Santos, P.; Jesus, S. M.; Champenois, W.; Borges, A. V.; Santos, R.During the period of one week, from May 8 to 15, 2013, acoustic data was gathered at three locations over a Posidonia oceanica bed in the Bay of Revellata, Corsica. Preliminary analysis of the acoustic data shows that the environmental noise field in the band 2-7kHz was dominant during the period. The noise in this band is generally associated with wind and surface agitation. However, the noise power was not si...
Passive acoustics as a tool for global ocean monitoring and exploration
Jesus, S. M.; Rodriguez, O. C.; Felisberto, P.; Soares, C.The ocean is vast, rich, fragile and unexplored. Despite a massive investment in the last years, ocean exploration remains localized at the ocean surface and in shallow coastal areas, covering merely 5% of the total volume. It is well known that marine life has perfectionned acoustics as its primarily sense for every day tasks such as locating preys, sensing danger, breeding, etc. So, in the ocean, sound has th...
Accounting for source depth variations in time-reversal communications
Jesus, S.M.; Ijaz, S.; Silva, A.Passive Time Reversal (pTR) is a low complexity receiver scheme that uses multichannel probing for time signal refocusing, thus reducing time spreading and improving inter-symbol interference. Recognizing that signals travelling through different paths are subject to arrival-angle-related Doppler displacements, this letter proposes a further improvement to pTR that applies correcting frequency shifts optimized ...
Comparing the resolution of Bartlett and MVDR estimators for bottom parameter e...
Felisberto, P.; Schneiderwind, J.; Santos, P.; Rodriguez, O. C.; Jesus, S. M.This work compares the resolution of a pressure and vector sensor based conventional Bartlett estimator, with their MVDR estimator counterparts, in the context of bottom characterization with a short vertical array. Santos et al. [1]demonstrated the gain of a vector sensor array (VSA) based linear estimator (Bartlett) for generic parameter estimation. Moreover, it was shown that for bottom characterization the ...
Is the underwater gliding test a valid procedure to estimate the swimmers’ drag?
Morais, J.E.; Costa, M.J.; Jesus, S.; Mejias, J.E.; Moreira, M.; Garrido, N.; Silva, A.J.; Marinho, D.A.; Barbosa, Tiago M.The aim of this study was to develop a structural equation model for underwater gliding distance based on its determinant variables, in order to confirm whether it is an informative test of young swimmers’ hydrodynamic profile. Methods: Twenty-three subjects (twelve boys and eleven girls with a mean age of 13.61 ± 0.83 years old) were evaluated. The following were determined: (i) the underwater gliding distance...
Experimental results of underwater cooperative source localization using a sing...
Felisberto, P.; Rodriguez, O. C.; Santos, P.; Ey, Emanuel; Jesus, S. M.This paper aims at estimating the azimuth, range and depth of a cooperative broadband acoustic source with a single vector sensor in a multipath underwater environment, where the received signal is assumed to be a linear combination of echoes of the source emitted waveform. A vector sensor is a device that measures the scalar acoustic pressure field and the vectorial acoustic particle velocity field at a single...
Linking acoustic communications and network performance: integration and experi...
Caiti, N.; Grythe, Knut; Hovem, Jens M.; Jesus, S. M.; Lie, Arne; Munafò, Andrea; Reinen, Tor Arne; Silva, António J.; Zabel, FriedrichAbstract—Underwater acoustic networks (UANs) are an emerging technology for a number of oceanic applications, ranging from oceanographic data collection to surveillance applications. However, their reliable usage in the field is still an open research problem, due to the challenges posed by the oceanic environment. The UAN project, a European-Union-funded initiative, moved along these lines, and it was one of t...
Comparing the resolution of Bartlett and MVDR processors for bottom parameter e...
Felisberto, P.; Schneiderwind, J.; Santos, P.; Rodriguez, O. C; Jesus, S. M.This work compares the resolution of a pressure and vector sensor based conventional Bartlett estimator, with their MVDR estimator counterparts, in the context of bottom characterization with a short vertical array. Santos et al. [1] demonstrated the gain of a vector sensor array (VSA) based linear estimator (Bartlett) for generic parameter estimation. Moreover, it was shown that for bottom characterization the...
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