922 research outputs found
Data comparison between three acoustic doppler current profilers deployed in OBSEA platform in North-Western Mediterranean
Three different Acoustic Doppler Current Profilers (ADCP) have been deployed
in OBSEA platform, a 20 meters depth underwater observatory cabled with a
4 km mixt cable to Vilanova i la Geltru’s coast. Two months of continuous data have
been collected in order to confirm their proper operation and long term North current
characteristic from the area.Peer Reviewe
Data comparison between three acoustic doppler current profilers deployed in OBSEA platform in north-western Mediterranean
Three different Acoustic Doppler Current Profilers (ADCP) have been deployed in OBSEA platform, a 20 meters depth underwater observatory cabled with a 4 km mixt cable to Vilanova i la Geltru’s coast. Two months of continuous data have been collected in order to confirm their proper operation and long term North current characteristic from the areaPeer ReviewedPostprint (published version
Actualización de la electrónica de control de la boya oceanográfica del observatorio OBSEA
Peer Reviewe
Automatic panoramic image creation system from OBSEA PTZ underwater camera
This article is a description about how to take advantage of an underwater PTZ camera to obtain an immersive panoramic image of the seabed environment.Peer Reviewe
Underwater light estimation using the OBSEA camera
This is a description of the method used in the OBSEA observatory to obtain a value for the amount of light present in the seafoor using the existing video surveillance camera.Peer Reviewe
Synthesis and study of new piezoelectric (Bi0.5Na0.5)TiO3-BaTiO3 based materials
Treballs Finals de Grau de QuĂmica, Facultat de QuĂmica, Universitat de Barcelona, Any: 2017, Tutor: Elena Cerdeiras MonteroPiezoelectric materials based on lead zirconate titanate (PZT) are widely used in a large number of electronic devices due to their excellent properties. This improvement occurs in a region of the phase diagram related to a morphotropic phase boundary (MPB). However, the major drawback is the environmental and health problems arising from the presence of lead due to its high toxicity. Therefore, nowadays and during last years, the scientific community has focused on the search for lead-free piezoelectric materials.
(Bi0.5Na0.5)TiO3-BaTiO3 based ceramics (BNT-BT) has attracted considerable interest attributable to their similar characteristics to PZT. This system has a morphotropic phase boundary where a great piezoelectric response is obtained and, for this reason, BNT-BT system is considered a promising candidate to replace lead-based piezoelectric materials. However, even with the large number of studies carried out there is no exact composition around MPB where the best properties are obtained. So, it is necessary to continue doing research and try to improve the functional properties.
Hence, the goal of this work has been the study of different aspects associated with (Bi0.5Na0.5)TiO3-BaTiO3 system based ceramic materials.In this work, the preparation of BNT-BT based ceramics has been made by solid state reaction and their characterization has been carried out with the different techniques used on solid state chemistry. The planetary ball mill has been stablished as an important part of the synthesis pathway and optimizing the sintering conditions has been done. High density ceramics have been obtained in all compositions with a relative density around 98%. In all cases, perovskite unique phase ceramics have been obtained with coexistence of rhombohedric and tetragonal phase, confirming that they are on the morphotropic phase boundary. Using Scanning Electron Microscopy, the presence of a BNT matrix with grains of BT on the obtained ceramics has been observed.
In order to improve the functional properties of these materials, the effect of lanthanide donor dopants has been studied, focusing on the influence of different radius and their concentration. Through X-Ray Diffraction the introduction of dopants on the BNT-BT structure has been confirmed since the diffraction maximums have been shifted to higher angles, meaning the incorporation of lower radius cations and the creation of cationic vacancies. The introduction of Lanthanum has provoked a morphologic variation of the barium titanate grains, which leads us to believe that Lanthanum has been introduced on the BaTiO3 structure, as it was expected due to the stoichiometry of the compound.
The dielectric properties of BNT-BT based ceramics have been studied on the morphotropic phase transition, obtaining high values of relative permittivity for the non-doped ceramic and low dielectric losses in all compositions. The Praseodymium doped BNT-BT shows a dielectric behavior dependent on frequency at room temperature, both related to relative permittivity and dielectric losses, better than the non-doped BNT-BT
Cabling, connectors and splices structure for the OBSEA. Expandable subsea observatory
The OBSEA observatory, for its construction, characteristics and location in the seafloor, needs a cabling and connections structure capable to satisfy its finality and to resist the adverse conditions of the sea environment.Peer ReviewedPostprint (published version
Power Supply control of the obsea seafloor
The aim of this paper is to present the design and
construction process of the power supply needed for a remote
data acquisition system. It is based on twelve AC to DC
switching converters in a serial connection and a logic
programmable controller (PLC). The energy is transmitted to
the acquisition system, which is located several kilometers
away, by means of a cable. The supply system has been
designed with a higher capacity than the current requirements
of the subsea station and the controller decides constantly the
best configuration required at each moment.Peer ReviewedPostprint (published version
- …