12 documents found, page 1 of 2
Acoustic pressure and particle velocity for spatial filtering of bottom arrivals
Felisberto, Paulo; Santos, P. J.; Jesus, SergioThis paper discusses the advantages of using a combination of acoustic pressure and particle velocitymotion for filtering bottom arrivals. A possible area of application is reflection seismology where, traditionally, the seismic image is extracted from the bottom-reflected broadband acoustic signals received on hydrophones. Since hydrophones are omnidirectional in nature, the received bottom returns are often c...
Tank and field experiments of short-range acoustic propagation through a seagra...
Felisberto, Paulo; Silva, J. P.; Jesus, Sergio; A.J. Silva; Silva, A.T.; Silva, J.; Santos, R.; Ferreira, H.; Pousao, P.Aiming at monitoring the bubbles released during seagrass photosynthesis in different conditions, three experiments were made: two in an outdoor tank and one in the field. The outdoor tank experiments were conducted in winter and summer conditions with Cymodocea nodosa plants transplanted from a nearby meadow. The field experiment took place in September 2018 on a Posidonia oceanica meadow, where bubbles format...
Using shipping noise for sound speed inversion in coastal areas
Santos, Ana Bela; Felisberto, Paulo; Jesus, SergioPassive sound speed estimation using radiated ship noise is an appealing approach for long-term ocean observation close to ship lanes. In this paper we analyze the noise recorded in two drifting vertical line arrays (VLAs) deployed 1 km apart, in Setubal's underwater canyon area off the west coast of Portugal during the RADAR' 07 sea trial. Automatic Information System (AIS) recordings for this period reveal a ...
Depth-specific fluctuations of gene expression and protein abundance modulate t...
Procaccini, Gabriele; Ruocco, Miriam; Marin-Guirao, Lazaro; Dattolo, Emanuela; Brunet, Christophe; D'Esposito, Daniela; Lauritano, ChiaraHere we present the results of a multiple organizational level analysis conceived to identify acclimative/adaptive strategies exhibited by the seagrass Posidonia oceanica to the daily fluctuations in the light environment, at contrasting depths. We assessed changes in photophysiological parameters, leaf respiration, pigments, and protein and mRNA expression levels. The results show that the diel oscillations of...
Development and testing of a dual accelerometer vector sensor for AUV acoustic ...
Mantouka, Agni; Felisberto, Paulo; Santos, Paulo; Zabel, Friedrich; Saleiro, Mário; Jesus, Sergio M.; Sebastiao, LuisThis paper presents the design, manufacturing and testing of a Dual Accelerometer Vector Sensor (DAVS). The device was built within the activities of theWiMUST project, supported under the Horizon 2020 Framework Programme, which aims to improve the efficiency of the methodologies used to perform geophysical acoustic surveys at sea by the use of Autonomous Underwater Vehicles (AUVs). The DAVS has the potential t...
The application of a dual accelerometer vector sensor for the discrimination of...
Mantouka, A.; Felisberto, Paulo; Jesus, Sergio; J. Santos, P.; Sebastiao, Luís; Pascoal, A.This paper describes the application of a Dual Accelerometer Vector Sensor (DAVS) for the discrimination between the bottom reflections, the source direct arrival and the source ghost or multipath in an unconventional seismic acquisition scenario. The realisation of the DAVS device and the seismic acquisition scenario described in this paper, were carried out in the scope of the WiMUST project, an EU project, s...
Seismoacoustic bottom inversion with AUV towed streamers: a multi-stage approach
Soares, Cristiano; Jesus, Sergio; Mantouka, Agni; Felisberto, PauloThe WiMUST (Widely scalable Mobile Underwater Sonar Technology) Project envisions using a team of autonomous underwater vehicles towing short acoustic arrays for seismic surveying of seabottom geoacoustic properties. One of the objectives in the project is to tackle the inversion of acoustic data collected with short towed horizontal arrays by means of a Matched-Field Inversion (MFI) technique. While there is g...
Monitoring bubble production in a seagrass meadow using a source of opportunity
Felisberto, Paulo; Rodríguez, Orlando; Silva, João P.; Jesus, Sergio; Ferreira, Hugo Q.; Ferreira, Pedro P.; Cunha, Maria E.; de los Santos, Carmen B.Under high irradiance, the photosynthetic activity of dense seagrass meadows saturates the water forming oxygen bubbles. The diel cycle of bubble production peaks at mid-day, following light intensity pattern. It is well known that bubbles strongly affect the acoustic propagation, increasing signal attenuation and decreasing the effective water sound speed, noticeable at low frequencies. Thus, the diurnal varia...
Acoustic detection of bubbles in a pond covered by the seagrass Cymodocea nodosa
Felisberto, Paulo; Silva, J. P.; Silva, A. J.; Jesus, Sergio; Olivé, Irene; Santos, Rui; Quental-Ferreira, H.; Pousao-Ferreira, P.; Cunha, M. E.This paper describes two experiments conducted in a pond covered by the seagrass Cymodocea nodosa at the Aquaculture Research Station of the Portuguese Institute for the Sea and Atmosphere in Olhao, Portugal, aiming at developing acoustic methods to assess oxygen production of seagrasses. The first experiment was carried out in July covering two days, when warm water and high photosynthetic rates give a high pr...
On the performance of geo-acoustic estimation for a distributed sensor array
Jesus, Sergio; Mantouka, A.; Felisberto, Paulo; Soares, CristianoThe vision underlying the Widely scalable Mobile Underwater Sonar Technology (WiMUST) project is that of developing advanced cooperative and networked control / navigation systems to enable a large number (tenths) of marine robots towing small acoustic arrays to act as a coordinated team for seismic sub-bottom imaging. The space-time coherent processing of bottom returns requires the ensemble of short acoustic ...