540 research outputs found
Coastal bathymetry estimation using an ensemble of synthetic aperture radar images from Sentinel-1
In this study, coastal bathymetry is estimated with a wave ray-tracing algorithm using wave parameters retrieved from Synthetic Aperture Radar (SAR) images acquired by the Sentinel-1 satellites. The method relies on the long swell wave’s detection by SAR imagery and the wave’s properties adjustment to the underwater topography, which can be mathematically related using the linear dispersion relation. The ray-tracing algorithm tracks the shoaling waves until the wave breaking zone, using the wavelength and wave direction retrieved from the 2D directional spectra applied at consecutive sub-images. Then, by inverting the linear wave dispersion relationship, the depth is calculated based on the mean wavelength obtained for each sub-image and maintaining the wave period retrieved at the first offshore position, which is computed using a mean depth from an independent bathymetric source. The output of the algorithm is a bathymetric model that results from the interpolation of the depth computed at each tracking position to a uniform grid and the results are compared with bathymetric information from the General Bathymetric Chart of the Ocean. The use of a monthly ensemble of SAR images, instead of individual ones, to reproduce the bathymetry near Aveiro, Portugal, resulted in a smoother topography with lower relative errors, suggesting that the final bathymetric model retrieved from SAR should result from a combination of SAR images. The methodology presented here to infer the bathymetry using space-borne SAR imagery can be useful to retrieve the mean bottom topography (especially in remote areas where the traditional hydrographic surveying methods are not performed regularly) and to reproduce new underwater structures, such as banks, reefs or bars, which are important to detect for the safety of navigation.Peer Reviewe
Real-time control of a laboratory heat exchanger using the particle swarm optimisation algorithm
In the past decade, evolutionary based algorithms have been a popular research theme in many
disciplinary areas like control systems. Although, due to the computational load required, this type of
algorithms usually are applied off-line. In this paper, a stochastic search algorithm known as particle
swarm is used as an optimisation tool for on-line control of a custom made laboratory thermodynamic
system
Hardware-in-the-loop control using the particle swarm optimisation
In the last two decades, evolutionary based algorithms have proved to be an
important tool in solving optimisation problems in many disciplinary areas namely in
control system design. However one of its limitations, for some type of applications, is
the usually high computational load required, which restricts its use for on-line control.
This paper proposes the use of a stochastic search algorithm, known as particle swarm, as
an optimisation tool for an on-line predictive control of a custom made thermodynamic
system. Preliminary results are presented
Greenhouse air temperature control using the particle swarm optimisation algorithm
The particle swarm optimisation algorithm is proposed as a new method to
design a model based predictive controller subject to restrictions. Its performance is
compared with the one obtained by using a genetic algorithm for the environmental
temperature control of a greenhouse. Controller outputs are computed in order to optimise
future behaviour of the greenhouse environment, regarding set-point tracking and
minimisation of the control effort over a prediction horizon of one hour with a one-minute
sampling period
Greenhouse air temperature modelling
This paper describes two implementation approaches for modelling the air temperature of an automated greenhouse located in the campus of the University of Trás-os- Montes e Alto Douro. Linear models, based in the discretization of the heat transfer physical laws, and non-linear neural networks models are used. These models are describes as functions of the outside climate and control actions performed for heating and cooling. Results are presented to illustrate the performance of each model in the simulation and prediction of the greenhouse air temperature. The data used to compute the simulation models was collected with a PC-based acquisition and control system using a sampling time interval of 1 minute.The authors appreciate the support of the Portuguese Foundation for Science and Technology (FCT) through the project MGS/ 33906/2000
On-line control using the particle swarm optimisation algorithm
In the last two decades, evolutionary based algorithms have proved to be an important tool in solving
optimisation problems in many disciplinary areas, namely in control system design. However one of
its limitations for some type of applications is the usually high computational load required, which
restricts its use for on-line control. This paper proposes the use of a stochastic search algorithm,
known as particle swarm, as an optimisation tool for an on-line model predictive control of a custom
made laboratory thermodynamic system. Preliminary results are presented
Automation and control of the SORTEGEL wastewater plant
Food Processing Industries produce large amounts of wastewater with high
environmental impact. Due to the high content of suspended matter and inadequate pH
value of the wastewater, national laws prohibit direct discharges of the influent to the
environment. This work describes the design and operation of a wastewater treatment
plant installed in the Sortegel food-processing company located in Sortes, Portugal. This
industry uses the water collected from groundwater wells to process raw materials and to
wash the equipments, being the volume of wastewater produced season dependent (80 to
300m3/day). Results show that the implemented wastewater treatment plant and the
automation solutions generate treated effluents that comply with the Portuguese
legislation
Scanning Fourier Spectroscopy: A microwave analog study to image transmission paths in quantum dots
We use a microwave cavity to investigate the influence of a movable absorbing
center on the wave function of an open quantum dot. Our study shows that the
absorber acts as a position-selective probe, which may be used to suppress
those wave function states that exhibit an enhancement of their probability
density near the region where the impurity is located. For an experimental
probe of this wave function selection, we develop a technique that we refer to
as scanning Fourier spectroscopy, which allows us to identify, and map out, the
structure of the classical trajectories that are important for transmission
through the cavity.Comment: 4 pages, 5 figure
Transport spectroscopy in a time-modulated open quantum dot
We have investigated the time-modulated coherent quantum transport phenomena
in a ballistic open quantum dot. The conductance and the electron dwell
time in the dots are calculated by a time-dependent mode-matching method. Under
high-frequency modulation, the traversing electrons are found to exhibit three
types of resonant scatterings. They are intersideband scatterings: into
quasibound states in the dots, into true bound states in the dots, and into
quasibound states just beneath the subband threshold in the leads. Dip
structures or fano structures in are their signatures. Our results show
structures due to 2 intersideband processes. At the above
scattering resonances, we have estimated, according to our dwell time
calculation, the number of round-trip scatterings that the traversing electrons
undertake between the two dot openings.Comment: 8 pages, 5 figure
Waterborne Toxoplasmosis, Brazil, from Field to Gene
Water was the suspected vehicle of Toxoplasma gondii dissemination in a toxoplasmosis outbreak in Brazil. A case-control study and geographic mapping of cases were performed. T. gondii was isolated directly from the implicated water and genotyped as SAG 2 type I
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