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2.
  • Cirasuolo, M., et al. (author)
  • MOONS: the Multi-Object Optical and Near-infrared Spectrograph for the VLT
  • 2014
  • In: Ground-based and Airborne Instrumentation for Astronomy V. - : SPIE. - 1996-756X .- 0277-786X. ; 9147, s. 91470-91470
  • Conference paper (peer-reviewed)abstract
    • MOONS (the Multi-Object Optical and Near-infrared Spectrograph) has been selected by ESO as a third-generation instrument for the Very Large Telescope (VLT). The light grasp of the large collecting area offered by the VLT (8.2m diameter), combined with the large multiplex and wavelength coverage (optical to near-IR: 0.8 -1.8 mu m) of MOONS will provide the European astronomical community with a powerful, unique instrument able to pioneer a wide range of Galactic, extragalactic and cosmological studies, and it will provide crucial follow-up for major facilities such as Gaia, VISTA, Euclid and LSST. MOONS has the observational power needed to unveil galaxy formation and evolution over the entire history of the Universe, from stars in our Milky Way, through the redshift desert, and up to the epoch of very first galaxies and reionization of the Universe at redshifts of z > 8-9, just a few million years after the Big Bang. From five years of observations MOONS will provide high-quality spectra for > 3M stars in our Galaxy and the Local Group, and for 1-2M galaxies at z > 1 (for an SDSS-like survey), promising to revolutionize our understanding of the Universe. The baseline design consists of similar to 1000 fibres, deployable over a field-of-view of similar to 500 arcmin(2), the largest patrol field offered by the Nasmyth focus at the VLT. The total wavelength coverage is 0.8 -1.8 mu m with two spectral resolving powers: in the medium-resolution mode (R similar to 4,000-6,000) the entire wavelength range is observed simultaneously, while the high-resolution mode will cover three selected sub-regions simultaneously: one region with R similar to 8,000 near the Ca II triplet to measure stellar radial velocities, and two regions at R similar to 20,000 (one in each of the J- and H-bands), for precision measurements of chemical abundances.
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3.
  • Vergani, S. D., et al. (author)
  • GRB 091127/SN 2009nz and the VLT/X-shooter spectroscopy of its host galaxy : probing the faint end of the mass-metallicity relation
  • 2011
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 535, s. A127-
  • Journal article (peer-reviewed)abstract
    • We perform a detailed study of the gamma-ray burst GRB 091127/SN 2009nz host galaxy at z = 0.490 using the VLT/X-shooter spectrograph in slit and integral-field unit (IFU) mode. From the analysis of the optical and X-ray afterglow data obtained from ground-based telescopes and Swift-XRT, we confirm the presence of a bump associated with SN 2009nz and find evidence of a possible jet break in the afterglow lightcurve. The X-shooter afterglow spectra reveal several emission lines from the underlying host, from which we derive its integrated properties. These properties agree with those of previously studied GRB-SN hosts and, more generally, with those of the long GRB host population. We use the Hubble Space Telescope and ground-based images of the host to determine its stellar mass (M⋆). Our results extend to lower M⋆ values the M-Z plot derived for the sample of long GRB hosts at 0.3 < z < 1.0 adding new information to probe the faint end of the M-Z relation and the shift of the LGRB host M-Z relation from that found from emission-line galaxy surveys. Thanks to the IFU spectroscopy, we can build the two-dimensional (2D) velocity, velocity dispersion, and star formation rate (SFR) maps. They show that the host galaxy has perturbed rotation kinematics with evidence of a SFR enhancement consistent with the afterglow position. Based on observations made with ESO Telescopes at Paranal Observatory under programmes ID 084.A-0260 and 086.A-0874.
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  • Prudkovskiy, V. S., et al. (author)
  • Efficient cleaning of graphene from residual lithographic polymers by ozone treatment
  • 2016
  • In: Carbon. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0008-6223 .- 1873-3891. ; 109, s. 221-226
  • Journal article (peer-reviewed)abstract
    • We present an experimental study of time dependent ozone treatment on post-process epitaxial graphene using both electron transport measurements and resonant micro-Raman spectroscopy. We focus on a systematic analysis of residual polymer decomposition on the epitaxial graphene on SiC substrate. It was found that graphene could be effectively cleaned by ultraviolet (UV)/ozone treatment after nano fabrication from residual lithographic polymers. This procedure improves the charge carrier mobility, almost by a factor of two for strongly contaminated samples, decreases the doping level and does not introduce defect inside the graphene lattice. It was found that epitaxial SiC graphene is extremely stable when exposed to radical oxygen atoms. We ascribe this effect to the substrate topography, which significantly affects the graphene stability under UV/ozone treatment. Our calculations reveal that surface roughness of the SiC substrate can change the energy gain from epoxy group adsorption by a few tenths of electron volts. (C) 2016 Elsevier Ltd. All rights reserved.
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  • Anderson, Dan, 1943, et al. (author)
  • Microwave breakdown in RF devices
  • 2006
  • In: 33rd European Physical Society Conference on Plasma Physics, Rome, June 19-23, 2006. ; , s. 429-
  • Conference paper (peer-reviewed)
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8.
  • Buyanova, M., et al. (author)
  • Different saturation regimes of multipactor between parallel metal plates
  • 2008
  • In: Proceedings of the 7th International Workshop “Strong microwaves: Sources and Applications, Nizhny Novgorod, Russia, July 27 – Aug. 2, 2008, Institute of Applied Physics, Russian Academy of Sciences. ; :paper T41, s. 143-
  • Conference paper (peer-reviewed)
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  • Buyanova, M., et al. (author)
  • Influence of secondary emission yield on the saturation properties of multipactor discharges between two parallel metal plates
  • 2010
  • In: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 17:4, s. 043504 -
  • Journal article (peer-reviewed)abstract
    • A detailed numerical simulation analysis is made of the saturation stage of multipactor discharges between two infinite parallel metal plates in vacuum exposed to a rf voltage. The main physical effect causing saturation of the multipactor discharge is increased space charge, as the electron density becomes large. It is found that the properties of the saturation stage depend crucially on the value of the secondary emission yield of the metal surfaces. Below a certain threshold value, the discharge has a two-sided character, but at this threshold the discharge makes an abrupt transition into two decoupled single-sided multipactor discharges containing significantly increased electron densities. The result of the numerical simulations gives a good picture of the saturation properties of the multipactor discharge and is also supplemented by an approximate analytical investigation that highlights and explains the characteristic properties of the observed saturation behavior.
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12.
  • Buyanova, M., et al. (author)
  • Multi-Phase Regimes of Multipactor Breakdown
  • 2005
  • In: Proc. 5th International Workshop on Multipactor, Corona and Passive Intermodulation, September 12 – 14, 2005, ESTEC, Noordwijk, The Netherlands, In: Space RF Hardware (MULCOPIM' 2005). ; , s. 135-142
  • Conference paper (peer-reviewed)
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15.
  • Mader, P., et al. (author)
  • Experimental validation of fringing field effects for the multipactor phenomenon
  • 2012
  • In: 15th International Symposium on Antenna Technology and Applied Electromagnetics, ANTEM 2012, Toulouse, 25-28 June 2012. - 9781467302913
  • Conference paper (peer-reviewed)abstract
    • The multipactor effect is a constraining phenomenon in the design of RF components. Due to an increasing number of channels and power levels for multicarrier signals, specific requirements of design must be taken into account in order to prevent the multipactor effect. The current methods of analysis are based on the Hatch and Williams diagrams, which provide the multipaction threshold voltage for a parallel plate geometry as a function of the frequency gap product. However, whereas experimental results have shown good correlation with the theoretical charts for the parallel plate geometry, discrepancies have been found for complex geometries such as irises.
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  • Pirzkal, Norbert, et al. (author)
  • A Two-dimensional Spectroscopic Study of Emission-line Galaxies in the Faint Infrared Grism Survey (FIGS). I. Detection Method and Catalog
  • 2018
  • In: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 868:1
  • Journal article (peer-reviewed)abstract
    • We present the results from the application of a two-dimensional emission line detection method, EMission-line two-Dimensional (EM2D), to the near-infrared G102 grism observations obtained with the Wide-Field Camera 3 (WFC3) as part of the Cycle 22 Hubble Space Telescope Treasury Program: the Faint Infrared Grism Survey (FIGS). Using the EM2D method, we have assembled a catalog of emission line galaxies (ELGs) with resolved star formation from each of the four FIGS fields. Not only can one better assess the global properties of ELGs, but the EM2D method allows for the analysis and improved study of the individual emission-line region within each galaxy. This paper includes a description of the methodology, advantages, and the first results of the EM2D method applied to ELGs in FIGS. The advantage of 2D emission line measurements includes significant improvement of galaxy redshift measurements, approaching the level of accuracy seen in high-spectral-resolution data, but with greater efficiency; and the ability to identify and measure the properties of multiple sites of star formation and over scales of similar to 1 kpc within individual galaxies out to z similar to 4. The EM2D method also significantly improves the reliability of high-redshift (z similar to 7) Ly alpha detections. Coupled with the wide field of view and high efficiency of space-based grism observations, EM2D provides a noteworthy improvement on the physical parameters that can be extracted from grism observations.
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18.
  • Puech, J., et al. (author)
  • CNES-Chalmers-IAP-ONERA-XLIM activities in the domain of high RF power breakdown phenomena
  • 2017
  • In: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 157
  • Conference paper (peer-reviewed)abstract
    • Multipactor breakdown is an important potential failure mechanism in many different microwave devices working under close to vacuum conditions. Applications range from space borne RF equipment to high-power microwave generators. The basic physics involved in the multipactor phenomenon is well known for the case of two infinite pallel plates made of metal. However, most realistic RF device geometries involve inhomogeneous RF electric fields and curved field lines and sometimes also dielectric material. The purpose of this paper is to set up methodologies to determine the Multipactor threshold in such situations.
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  • Puech, M., et al. (author)
  • IMAGES. III. The evolution of the near-infrared Tully-Fisher relation over the last 6 Gyr
  • 2008
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 484:173
  • Journal article (pop. science, debate, etc.)abstract
    • Using the multi-integral field spectrograph GIRAFFE at VLT, we have derived the K-band Tully-Fisher relation (TFR) at z ˜ 0.6 for a representative sample of 65 galaxies with emission lines (W_0(OII)≥15 Å). We confirm that the scatter in the z ˜ 0.6 TFR is caused by galaxies with anomalous kinematics, and find a positive and strong correlation between the complexity of the kinematics and the scatter that they contribute to the TFR. Considering only relaxed-rotating disks, the scatter, and possibly also the slope, of the TFR, do not appear to evolve with redshift. We detect an evolution of the K-band TFR zero point between z ˜ 0.6 and z=0, which, if interpreted as an evolution of the K-band luminosity of rotating disks, would imply that a brightening of 0.66 ± 0.14 mag occurs between z ˜ 0.6 and z=0. Any disagreement with the results of Flores et al. (2006, A&A, 455, 107) are attributed to both an improvement of the local TFR and the more detailed accurate measurement of the rotation velocities in the distant sample. Most of the uncertainty can be explained by the relatively coarse spatial-resolution of the kinematical data. Because most rotating disks at z˜0.6 are unlikely to experience further merging events, one may assume that their rotational velocity, which is taken as a proxy of the total mass, does not evolve dramatically. If true, our result implies that rotating disks observed at z˜0.6 are rapidly transforming their gas into stars, to be able to double their stellar masses and be observed on the TFR at z=0. The rotating disks observed are indeed emission-line galaxies that are either starbursts or LIRGs, which implies that they are forming stars at a high rate. Thus, a significant fraction of the rotating disks are forming the bulk of their stars within 6 to 8 Gyr, in good agreement with former studies of the evolution of the mass-metallicity relationship.
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  • Semenov, V. E., et al. (author)
  • Multipactor breakdown in waveguide irises
  • 2009
  • In: 2009 IEEE International Vacuum Electronics Conference, IVEC 2009; Rome; Italy; 28 April 2009 through 30 April 2009. - 9781424434992 ; , s. 321-322
  • Conference paper (peer-reviewed)abstract
    • A detailed analysis is made in order to establish the multipactor breakdown threshold in wave guide irises. The analysis involves an analytical investigation based on the conformal mapping technique and also extensive numerical simulations. Comparison with recent experimental results shows good agreement. The main goal of the work is to obtain multipactor charts for the iris, i.e. the breakdown voltage as a function of the frequency - gap product, for different height to width ratios of the iris.
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  • Semenov, V. E., et al. (author)
  • Preliminary results on the Multipactor effect prediction in RF components with ferrites
  • 2013
  • In: 14th IEEE International Vacuum Electronics Conference, IVEC 2013 - Proceedings. - 9781467359757 ; , s. Art. no. 6571019-
  • Conference paper (peer-reviewed)abstract
    • This paper deals with the analysis of the Multipactor effect in RF components with ferrites performed through the preliminary measurements of ferrites secondary emission coefficient and the simulations of the effect of a continuous magnetic field on the electron bunch spread. The impact of this effect on the Multipactor threshold was quantified. © 2013 IEEE.
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