Browsing by Author "Guesalaga, A."

Now showing 1 - 9 of 9
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    3D non-destructive evaluation techniques for wood analysis
    (2014) Paulina Fernández, M.; Tejos Nunez, Cristian Andres; Rojas, G.; Lillo, I.; Guesalaga, A.; Irarrázaval, P.
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    Energy dispersive X-ray diffraction spectroscopy for rapid estimation of calcite in copper ores
    (PERGAMON-ELSEVIER SCIENCE LTD, 2009) Escarate, P.; Bailo, D.; Guesalaga, A.; Albertini, V. Rossi
    This article presents a novel technique for measuring the concentration of calcite in copper ore samples using energy dispersive X-ray diffraction (ED-XRD). The results are compared with ultraviolet fluorescence spectroscopy (UVF) for the same group of samples. This approach substantially shortens the measuring time with respect to the current laboratory procedures from 300 min down to 15 min and 9 min for energy dispersive X-ray diffraction and ultraviolet fluorescence spectroscopy, respectively, while preserving a good accuracy level (RMSE < 0.577).
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    Expected performance of the Pyramid wavefront sensor with a laser guide star for 40 m class telescopes
    (2024) Oyarzun, F.; Chambouleyron, V.; Neichel, B.; Fusco, T.; Guesalaga, A.
    Context. The use of artificial laser guide stars (LGS) is planned for the new generation of giant segmented mirror telescopes in order to extend the sky coverage of their adaptive optics systems. The LGS, being a 3D object at a finite distance, will have a large elongation that will affect its use with the Shack-Hartmann (SH) wavefront sensor. Aims. In this paper, we compute the expected performance for a Pyramid WaveFront Sensor (PWFS) using an LGS for a 40 m telescope affected by photon noise, and also extend the analysis to a flat 2D object as reference. Methods. We developed a new way to discretize the LGS, and a new, faster method of propagating the light for any Fourier filtering wavefront sensors (FFWFS) when using extended objects. We present the use of a sensitivity model to predict the performance of a closed-loop adaptive optic system. We optimized a point-source-calibrated interaction matrix to accommodate the signal of an extended object by computing optical gains using a convolutional model. Results. We find that the sensitivity drop, given the size of the extended laser source, is large enough to make the system operate in a low-performance regime given the expected return flux of the LGS. The width of the laser beam is identified as the limiting factor, rather than the thickness of the sodium layer. Even an ideal, flat LGS will have a drop in performance due to the flux of the LGS, and small variations in the return flux will result in large variations in performance. Conclusions. We conclude that knife-edge-like wavefront sensors, such as the PWFS, are not recommended for use with LGS for a 40 m telescope, as they will operate in a low-performance regime, given the size of the extended object.
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    FASS: a turbulence profiler based on a fast, low-noise camera
    (2021) Guesalaga, A.; Ayancan, B.; Sarazin, M.; Wilson, R. W.; Perera, S.; Le Louarn, M.
    The measurement of the atmospheric optical turbulence with a new scintillation profiler is described and demonstrated. The instrument, FASS (Full Aperture Scintillation Sensor), uses new fast and low-noise detectors to record and process sequences of scintillation images. Statistical processing of these data is based on the calculation of power spectra of intensity in annular pupil zones over the angular coordinate. The angular power spectra are used to measure the optical turbulence intensity of 14 layers located at logarithmically spaced distances from 0.3 to 25 km. The reference functions relating turbulence strength to the angular power spectra are computed by numerical simulation. Measurement of the ground-later turbulence and total seeing with FASS is possible when the detector is conjugated to a negative (below ground) distance. Results of measurement campaigns at Paranal are reported, documenting a good agreement of turbulence profiles measured by FASS with two other instruments, SCIDAR and MASS.
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    Fuzzy modelling of pulp density in a mineral grinding plant
    (IEEE, 1994) Cipriano, Aldo; Ramos, M.; Munoz, C.; Guarini Hermann, Marcelo Walter; Guesalaga, A.
    This paper describes an identification algorithm of fuzzy models and its application to the modeling of the pulp density in a mineral grinding plant. The parameters of the fuzzy model are estimated using information obtained from a process simulator. The performance of the fuzzy model is only slightly superior to that of a conventional linear model
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    Matching radar and satellite images for ship trajectory estimation using the Hausdorff distance
    (INST ENGINEERING TECHNOLOGY-IET, 2007) Bustos, J. P.; Donoso, F.; Guesalaga, A.; Torres, M.
    A novel technique to obtain position, velocity and radar biases estimates of a ship is described by matching ship-bome radar images to geo-referenced satellite images. The matching is perfortned through the minimisation of the averaged partial Hausdorff distances between data points in each image. The minimisation rapidly yields robust geographical latitude and longitude position measurements, as well as ship heading and radar biases. The accuracy of the measurements is improved by feeding them into a Kalman filter that also allows estimates of the ship's velocity to be obtained. The method provides an alternative effective position sensor for GPS denied environments, which may also be employed for automatic radar calibration of bearing and range biases or for indoor autonomous mobile robot navigation.
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    Mobile robot localization using the Hausdorff distance
    (CAMBRIDGE UNIV PRESS, 2008) Donoso Aguirre, F.; Bustos Salas, J. P.; Torres Torriti, M.; Guesalaga, A.
    This paper presents a novel method for localization of mobile robots in structured environments. The estimation of the position and orientation of the robot relies on the minimisation of the partial Hausdorff distance between ladar range measurements and a floor plan image of the building. The approach is employed in combination with an extended Kalman filter to obtain accurate estimates of the robot's position, heading and velocity. Good estimates of these variables were obtained during tests performed using a differential drive robot, thus demonstrating that the approach provides an accurate, reliable and computationally feasible alternative for indoor robot localization and autonomous navigation.
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    Open-loop tomography with artificial neural networks on CANARY: on-sky results
    (2014) Osborn, J.; Guzman, D.; de Cos Juez, F. J.; Basden, A. G.; Morris, T. J.; Gendron, E.; Butterley, T.; Myers, R. M.; Guesalaga, A.; Sanchez Lasheras, F.; Gomez Victoria, M.; Sanchez Rodriguez, M. L.; Gratadour, D.; Rousset, G.
    We present recent results from the initial testing of an artificial neural network (ANN)-based tomographic reconstructor Complex Atmospheric Reconstructor based on Machine lEarNing (CARMEN) on CANARY, an adaptive optics demonstrator operated on the 4.2 m William Herschel Telescope, La Palma. The reconstructor was compared with contemporaneous data using the Learn and Apply (L&A) tomographic reconstructor. We find that the fully optimized L&A tomographic reconstructor outperforms CARMEN by approximately 5 per cent in Strehl ratio or 15 nm rms in wavefront error. We also present results for CANARY in Ground Layer Adaptive Optics mode to show that the reconstructors are tomographic. The results are comparable and this small deficit is attributed to limitations in the training data used to build the ANN. Laboratory bench tests show that the ANN can outperform L&A under certain conditions, e.g. if the higher layer of a model two layer atmosphere was to change in altitude by similar to 300 m (equivalent to a shift of approximately one tenth of a subaperture).
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    Rapid measurement of calcite concentration in copper ore using fluorescence spectroscopy
    (PERGAMON-ELSEVIER SCIENCE LTD, 2006) Escarate, P.; Guesalaga, A.; Otero, A.
    This work presents the development of a rapid technique for measuring the concentration of calcite in oxidized copper ore. The instrument is based on fluorescence spectroscopy in the visible and infrared range and is excited with a UV-LW lamp. The measurement takes substantially shorter times than standard procedures.