Vargas J.,CSIC - National Center for Biotechnology |
Restrepo R.,Instituto Nacional Of Tecnica Aerospacial |
Sorzano C.O.S.,CSIC - National Center for Biotechnology |
Du Y.-Z.,University of Sichuan |
Carazo J.M.,CSIC - National Center for Biotechnology
Applied Optics | Year: 2012
We present a Shack-Hartmann (SH) centroid detection algorithm capable to measure in presence of strong noise, background illumination and spot modulating signals, which are typical limiting factors of traditional centroid detection algorithms. The proposed method is based on performing a normalization of the SH pattern using the spiral phase transform method and Fourier filtering. The spot centroids are then obtained using global thresholding and weighted average methods. We have tested the algorithm with simulations and experimental data obtaining satisfactory results. A complete MATLAB package that can reproduce all the results can be downloaded from [http://goo.gl/o2JhD]. © 2012 Optical Society of America.
Duchene G.,CNRS Grenoble Institute for Particle Astrophysics and Cosmology Laboratory |
Bouvier J.,CNRS Grenoble Institute for Particle Astrophysics and Cosmology Laboratory |
Moraux E.,CNRS Grenoble Institute for Particle Astrophysics and Cosmology Laboratory |
Bouy H.,Instituto Nacional Of Tecnica Aerospacial |
And 2 more authors.
Astronomy and Astrophysics | Year: 2013
Aims. We present the first high-angular resolution survey for multiple systems among very low-mass stars and brown dwarfs in the Hyades open cluster. Methods. Using the Keck II adaptive optics system, we observed a complete sample of 16 objects with estimated masses 2;0.1 M·. Results. We have identified three close binaries with projected separation 2;0"I, or 2;5 AU. A number of wide, mostly faint candidate companions are also detected in our images, most of which are revealed as unrelated background sources based on astrometric and/or photometric considerations. The derived multiplicity frequency, 19+13 -6% over the 2-350 AU range, and the rarity of systems wider than 10 AU are both consistent with observations of field very low-mass objects. In the limited 3-50 AU separation range, the companion frequency is essentially constant from brown dwarfs to solar-type stars in the Hyades cluster, which is also in line with our current knowledge for field stars. Combining the binaries discovered in this surveys with those already known in the Pleiades cluster reveals that very low-mass binaries in open clusters, as well as in star-forming regions, are skewed toward lower mass ratios (0.6 2; q 2; 0.8) than are their field counterparts, a result that cannot be accounted for by selection effects. Although the possibility of severe systematic errors in model-based mass estimates for very low-mass stars cannot be completely excluded, it is unlikely to explain this difference. Conclusions. We speculate that this trend indicates that surveys among very low-mass field stars may have missed a substantial population of intermediate mass ratio systems, implying that these systems are more common and more diverse than previously thought. © 2013 ESO.
Barthol P.,Max Planck Institute for Solar System Research |
Gandorfer A.,Max Planck Institute for Solar System Research |
Solanki S.K.,Max Planck Institute for Solar System Research |
Schussler M.,Max Planck Institute for Solar System Research |
And 41 more authors.
Solar Physics | Year: 2010
The first science flight of the balloon-borne Sunrise telescope took place in June 2009 from ESRANGE (near Kiruna/Sweden) to Somerset Island in northern Canada. We describe the scientific aims and mission concept of the project and give an overview and a description of the various hardware components: the 1-m main telescope with its postfocus science instruments (the UV filter imager SuFI and the imaging vector magnetograph IMaX) and support instruments (image stabilizing and light distribution system ISLiD and correlating wavefront sensor CWS), the optomechanical support structure and the instrument mounting concept, the gondola structure and the power, pointing, and telemetry systems, and the general electronics architecture. We also explain the optimization of the structural and thermal design of the complete payload. The preparations for the science flight are described, including AIV and ground calibration of the instruments. The course of events during the science flight is outlined, up to the recovery activities. Finally, the in-flight performance of the instrumentation is discussed. © 2010 The Author(s).
Sawamura P.,University of Maryland Baltimore County |
Vernier J.P.,NASA |
Barnes J.E.,National Oceanic and Atmospheric Administration |
Berkoff T.A.,Joint Center for Earth Systems Technology |
And 16 more authors.
Environmental Research Letters | Year: 2012
Nabro volcano (13.37°N, 41.70°E) in Eritrea erupted on 13 June 2011 generating a layer of sulfate aerosols that persisted in the stratosphere for months. For the first time we report on ground-based lidar observations of the same event from every continent in the Northern Hemisphere, taking advantage of the synergy between global lidar networks such as EARLINET, MPLNET and NDACC with independent lidar groups and satellite CALIPSO to track the evolution of the stratospheric aerosol layer in various parts of the globe. The globally averaged aerosol optical depth (AOD) due to the stratospheric volcanic aerosol layers was of the order of 0.018±0.009 at 532nm, ranging from 0.003 to 0.04. Compared to the total column AOD from the available collocated AERONET stations, the stratospheric contribution varied from 2% to 23% at 532nm. © 2012 IOP Publishing Ltd.
Stelzer S.,University of Leoben |
Brunner A.J.,Empa - Swiss Federal Laboratories for Materials Science and Technology |
Arguelles A.,University of Oviedo |
Murphy N.,University College Dublin |
And 3 more authors.
Engineering Fracture Mechanics | Year: 2014
Two round robins on mode I fatigue delamination propagation organized by Technical Committee 4 of the European Structural Integrity Society compared three unidirectional carbon fiber reinforced composites, one with thermoplastic (poly-ether-ether-ketone) and two with thermoset (epoxy) matrix tested at five laboratories. Different approaches for data evaluation and their effect on the in- and inter-laboratory scatter are discussed and compared. Calculated delamination rates da/dN and applied GImax from displacement controlled tests are sensitive to small scatter in the load signal, and, therefore, a new route to evaluate the crack growth rate from pairs of load and displacement data is presented. © 2013 Elsevier Ltd.
Aguero A.,Instituto Nacional Of Tecnica Aerospacial |
Gutierrez M.,Instituto Nacional Of Tecnica Aerospacial |
Korcakova L.,Haldor Topsøe |
Nguyen T.T.M.,Haldor Topsøe |
And 2 more authors.
Oxidation of Metals | Year: 2011
Metal dusting is a catastrophic form of carburization attack that takes place in carbon-supersaturated gaseous atmospheres, and is most commonly encountered in steam reforming processes such as the production of hydrogen or syngas for ammonia, Fischer-Tropsch and methanol applications. The consequence of metal dusting can be a severe loss of metal from the process units, leading to high-cost maintenance and serious safety issues. The present literature review discusses the latest developments within metal dusting protection of alloys with special emphasis on protective coatings. In the first part of the paper, an overview of the main theories for metal dusting of alloys as well as fundamental studies is provided. In the second part, the paper focuses on the different methods to prevent metal dusting, including surface poisoning, alloying, chemical, mechanical and laser treatments as well as coatings. Particular focus is given to coatings and their composition, and fabrication methods, and a critical analysis of the different materials' behaviours and the suitability perspectives of deposition techniques are provided. © 2011 Springer Science+Business Media, LLC.
Gavioso R.M.,INRIM - Istituto Nazionale di Ricerca Metrologica |
Madonna Ripa D.,INRIM - Istituto Nazionale di Ricerca Metrologica |
Benyon R.,Instituto Nacional Of Tecnica Aerospacial |
Gallegos J.G.,Instituto Nacional Of Tecnica Aerospacial |
And 4 more authors.
International Journal of Thermophysics | Year: 2014
The results of microwave measurements with a quasi-spherical resonator in humid methane samples realized under laboratory conditions at the Istituto Nazionale di Ricerca Metrologica (INRiM) and under industrial conditions in a natural gas sample made available at the facilities of the Technical Manager of the Spanish Gas System and main supplier of natural gas in Spain (ENAGAS) are reported. Measurements at INRiM included vapor phase and condensation tests on methane samples prepared with amount fractions of water between 600 ppm and 5000 ppm at temperatures between 273 K and 295 K and pressures between 150 kPa and 1 MPa. ENAGAS measurements were performed at ambient temperature, 750 kPa on natural gas sampled from the pipeline and successively humidified at amount fractions of water between 140 ppm and 250 ppm for completeness of the comparison with several humidity sensors and instrumentation based on different technologies. To enhance the sensitivity of the microwave method at low humidity, an experimental procedure based on the relative comparison of the dielectric permittivity of the humid gas sample before and after being subject to a chemical drying process was conceived and implemented. The uncertainty budget and the final sensitivity of this procedure are discussed. © 2014 Springer Science+Business Media New York.
Kee N.D.,University of Delaware |
Owocki S.,University of Delaware |
Sundqvist J.O.,Instituto Nacional Of Tecnica Aerospacial |
Sundqvist J.O.,Catholic University of Leuven
Monthly Notices of the Royal Astronomical Society | Year: 2016
The extreme luminosities of massive, hot OB stars drive strong stellar winds through line-scattering of the star's UV continuum radiation. For OB stars with an orbiting circumstellar disc, we explore here the effect of such line-scattering in driving an ablation of material from the disc's surface layers, with initial focus on the marginally optically thin decretion discs of classical Oe and Be stars. For this we apply a multidimensional radiation-hydrodynamics code that assumes simple optically thin ray tracing for the stellar continuum, but uses a multiray Sobolev treatment of the line transfer; this fully accounts for the efficient driving by non-radial rays, due to desaturation of line-absorption by velocity gradients associated with the Keplerian shear in the disc. Results show a dense, intermediate-speed surface ablation, consistent with the strong, blueshifted absorption of UV wind lines seen in Be shell stars that are observed from near the disc plane. A key overall result is that, after an initial adjustment to the introduction of the disc, the asymptotic disc destruction rate is typically just an order-unity factor times the stellar wind mass-loss rate. For optically thin Be discs, this leads to a disc destruction time of order months to years, consistent with observationally inferred disc decay times. The much stronger radiative forces of O stars reduce this time to order days, making it more difficult for decretion processes to sustain a disc in earlier spectral types, and so providing a natural explanation for the relative rarity of Oe stars in the Galaxy. Moreover, the decrease in line-driving at lower metallicity implies both a reduction in the winds that help spin-down stars from near-critical rotation, and a reduction in the ablation of any decretion disc together these provide a natural explanation for the higher fraction of classical Be stars, as well as the presence of Oe stars, in the lower metallicity Magellanic Clouds. We conclude with a discussion of future extensions to study line-driven ablation of denser, optically thick, accretion discs of pre-main-sequence massive stars. © 2016 The Authors.
Sobrino J.A.,University of Valencia |
Oltra-Carrio R.,University of Valencia |
Soria G.,University of Valencia |
Jimenez-Munoz J.C.,University of Valencia |
And 10 more authors.
International Journal of Remote Sensing | Year: 2013
The surface urban heat island (SUHI) effect is defined as the increased surface temperatures in urban areas in contrast to cooler surrounding rural areas. In this article, the evaluation of the SUHI effect in the city of Madrid (Spain) from thermal infrared (TIR) remote-sensing data is presented. The data were obtained from the framework of the Dual-use European Security IR Experiment (DESIREX) campaign that was carried out during June and July 2008 in Madrid. The campaign combined the collection of airborne hyperspectral and in situ measurements. Thirty spectral and spatial high-resolution images were acquired with the Airborne Hyperspectral Scanner (AHS) sensor in a 11, 21, and 4 h UTC scheme. The imagery was used to retrieve the SUHI effect by applying the temperature and emissivity separation (TES) algorithm. The results show a nocturnal SUHI effect with a highest value of 5 K. This maximum value agrees within 1 K with the highest value of the urban heat island (UHI) observed using air temperature data (AT). During the daytime, this situation is reversed and the city becomes a negative heat island. © 2013 Copyright Taylor and Francis Group, LLC.
Ponsin J.,Instituto Nacional Of Tecnica Aerospacial |
ECCOMAS 2012 - European Congress on Computational Methods in Applied Sciences and Engineering, e-Book Full Papers | Year: 2012
Within the EU-funded research program DeSiReH (Design, Simulation and flight Reynolds number testing for advanced High-lift solutions) one activity is being devoted to investigating grid adaptation techniques aimed at improving the accuracy of CFD predictions within optimization processes. This paper describes the application of two grid adaptation approaches suitable to be used within design optimization. The first grid adaptation approach is based on the far-field drag breakdown method. Two adaptation indicators that target regions of spurious drag creation are proposed and applied to a 3D high lift test case (KH3Y tunnel model). The results obtained indicate that an improvement of the drag prediction can be achieved with this method with a moderate increase of nodes relative to the initial grid. The second adaptive approach is based on the application of adjoint methods for a posteriori output functional error estimation and grid adaptation. The results obtained with the A310 section in landing configuration show that similar levels of accuracy with respect to a sequence of uniform adaptations can be achieved with 5-10 times fewer grid points.