623 results on '"Samadi, R"'
Search Results
152. Test of a new method for seismic indices and granulation parameters extraction
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Peralta R. A., Samadi R., and Michel E.
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Physics ,QC1-999 - Abstract
In the framework of the data base project SSI (Stellar Seismic Indicesb), we have developed and tested a new method aiming at optimizing the simultaneous measurement of both the seismic indices characterizing the oscillations (Δν, νmax) and the indices characterizing the granulation signature. Here, we describe this method which is intended to take advantage of the MLE (maximum likelihood estimate) algorithm combined with the parametrized representation of the red giants pulsation spectrum following the Universal Pattern [6]. We report its performances tested on Monte Carlo simulations.
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- 2015
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153. The red-giant CoRoT target HR 7349
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Carrier, F., primary, Morel, T., additional, Miglio, A., additional, Montalbán, J., additional, Auvergne, M., additional, Baglin, A., additional, Baudin, F., additional, Barban, C., additional, Catala, C., additional, D’Antona, F., additional, De Ridder, J., additional, Eggenberger, P., additional, Hatzes, A. P., additional, Hekker, S., additional, Kallinger, T., additional, Michel, E., additional, Noels, A., additional, Poretti, E., additional, Rainer, M., additional, Samadi, R., additional, Ventura, P., additional, and Weiss, W. W., additional
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- 2009
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154. Stochastic excitation of gravity modes in massive main-sequence stars
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Samadi, R., primary, Belkacem, K., additional, Goupil, M. J., additional, Dupret, M.-A., additional, Brun, A. S., additional, and Noels, A., additional
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- 2009
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155. Modelling the asymmetries of the Sun’s radial p-mode line profiles
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Philidet, J., primary, Belkacem, K., additional, Samadi, R., additional, Barban, C., additional, and Ludwig, H.-G., additional
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- 2020
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156. Solar-like oscillations in _ Scuti stars
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Samadi, R., primary
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- 2007
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157. A numerical study of catalytic reforming reactors
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Al-Samadi, R. A.
- Subjects
660.2832 - Abstract
A fully distributed mathematical model, describing the performance of a single porous compounded bifunctional catalyst pellet, promoting complex endothermic reforming reactions, demonstrates that isothermal conditions obtain within the catalyst pellet. The heat transfer resistance, therefore, resides entirely within the fluid film surrounding the catalyst particle. Application of such a lumped thermal resistance model is then extended to the examination of systems involving a physical mixture of discrete catalyst pellets. Steady state stability analyses of both bifunctional catalyst systems show that, in the case of discrete pellet mixtures contained in a reactor operated in a high temperature region, alternative stationary states may exist because one of the two types of particle supports overall exothermic reactions. A one-dimensional steady state reactor model is employed to predict the behaviour of reactors packed with the two different bifunctional catalyst preparations and which promote chemical reaction in the presence of mass and heat transfer effects. It is concluded that a compounded bifunctional catalyst is, in practice, superior to a physical mixture of discrete pellets due to the favourable mass and heat transfer characteristics of such a catalyst. It is also demonstrated that the complex reactions occurring over compounded pellets may be reasonably described by a relatively simple reaction scheme which emphasizes the role of a cooperative reaction step effecting direct conversion of methyl cyclo-pentene to benzene. Consequently, the overall complexity of the mathematical model and the high computational effort are reduced considerably. Optimisation of benzene yield with respect to the bifunctional catalyst composition indicates that it is more economic, in practice, to employ an optimum uniform catalyst composition than a spatially distributed optimum (e.g. a falling profile along the reactor) since the former policy gives a product yield which is only very slightly lower than for the latter case. A simplified unsteady state mathematical model of a reforming reactor packed with compounded pellets shows that the reactor is stable, for a wide range of operating conditions, when subjected to step perturbations in inlet fluid conditions. However, the approach to the new steady state is found to be particularly slow in the case of adiabatic operation. This is most likely due to the low overall chemical reaction rate. A well known initial value (i.e. stepwise) numerical technique is shown to be suitable for integration of the state equations, both spatially along the reactor and in the time domain, provided that an appropriate arithmetic precision is employed. Furthermore, the computational effort is reduced considerably by using a suitable integration step size distribution in the time domain.
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- 1975
158. Calibration Of The Mixing Length Of The Mlt And Fst Models Using 3D Hydrodynamical Models
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Sonoi, T., Ludwig, H. -G., Dupret, M. -A., Montalban, J., Samadi, R., Belkacem, K., Caffau, E., and Goupil, M. -J.
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Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics - Abstract
The high-quality data of solar-like oscillations by CoRoT and Kepler would enable us to precisely determine stellar characteristics. To make the best of such data, we need stellar models with precise near-surface structure, which significantly impacts on solar-like oscillation frequencies. The mixing length of convection models is a key factor for the near-surface structure. We calibrated values of the mixing length parameters of the classical mixing length theory (MLT) and the full spectrum turbulence (FST) model based on 3D CO5BOLD models. The parameter values are found to vary substantially with effective temperature and surface gravity. It implies that the calibrated parameter values should be implemented into evolution codes instead of fixing the parameter values during the evolution.
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- 2018
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159. Non-radial, non-adiabatic solar-like oscillations in RGB and HB stars
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Noels A., Montalbán J., Belkacem K., Dupret M.A., Grosjean M., and Samadi R.
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Physics ,QC1-999 - Abstract
CoRoT and Kepler observations of red giants reveal rich spectra of non-radial solar-like oscillations allowing to probe their internal structure. We compare the theoretical spectrum of two red giants in the same region of the HR diagram but in different evolutionary phases. We present here our first results on the inertia, lifetimes and amplitudes of the oscillations and discuss the differences between the two stars.
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- 2013
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160. Amplitudes of solar-like oscillations in red giants: Departures from the quasi-adiabatic approximation
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Barban C., Ludwig H.-G., Goupil M.J., Dupret M.-A., Belkacem K., Samadi R., Baudin F., and Caffau E.
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Physics ,QC1-999 - Abstract
CoRoT and Kepler measurements reveal us that the amplitudes of solar-like oscillations detected in red giant stars scale from stars to stars in a characteristic way. This observed scaling relation is not yet fully understood but constitutes potentially a powerful diagnostic about mode physics. Quasi-adiabatic theoretical scaling relations in terms of mode amplitudes result in systematic and large differences with the measurements performed for red giant stars. The use of a non-adiabatic intensity-velocity relation derived from a non-adiabatic pulsation code significantly reduces the discrepancy with the CoRoT measurements. The origin of the remaining difference is still unknown. Departure from adiabatic eigenfunction is a very likely explanation that is investigated in the present work using a 3D hydrodynamical model of the surface layers of a representative red giant star.
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- 2013
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161. Mode lifetime and associated scaling relations
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Marques J.P., Goupil M.J., Dupret M.A., Baudin F., Appourchaux T., Belkacem K., Noels A., and Samadi R.
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Physics ,QC1-999 - Abstract
Thanks to the CoRoT and Kepler spacecrafts, scaling relations (linking seismic indices and global stellar parameters) are becoming the cornerstone of ensemble asteroseismology. Among them, the relation between the cut-off frequency and the frequency of the maximum in the power spectrum of solar-like pulsators as well as the relation between mode lifetime and the effective temperature remain poorly understood. However, a solid theoretical background is essential to assess the accuracy of those relations and subsequently of the derived stellar parameters. We will thus present recent advances on the understanding of the underlying mechanisms governing those relations and show that the physics of mode lifetime (thus of mode damping) plays a major role.
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- 2013
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162. In-flight photometry extraction of PLATO targets
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Marchiori, V., primary, Samadi, R., additional, Fialho, F., additional, Paproth, C., additional, Santerne, A., additional, Pertenais, M., additional, Börner, A., additional, Cabrera, J., additional, Monsky, A., additional, and Kutrowski, N., additional
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- 2019
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163. Solarp-mode damping rates: Insight from a 3D hydrodynamical simulation
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Belkacem, K., primary, Kupka, F., additional, Samadi, R., additional, and Grimm-Strele, H., additional
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- 2019
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164. The PLATO Solar-like Light-curve Simulator
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Samadi, R., primary, Deru, A., additional, Reese, D., additional, Marchiori, V., additional, Grolleau, E., additional, Green, J. J., additional, Pertenais, M., additional, Lebreton, Y., additional, Deheuvels, S., additional, Mosser, B., additional, Belkacem, K., additional, Börner, A., additional, and Smith, A. M. S., additional
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- 2019
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165. Seismic performance
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Mosser, B., primary, Michel, E., additional, Samadi, R., additional, Miglio, A., additional, Davies, G. R., additional, Girardi, L., additional, and Goupil, M. J., additional
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- 2019
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166. Analysis of surface effect on solar-like oscillation frequencies using 3D hydrodynamical models
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Sonoi, T., primary, Samadi, R., additional, Belkacem, K., additional, Ludwig, H.-G., additional, Caffau, E., additional, and Mosser, B., additional
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- 2019
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167. Calibration of mixing-length parameterαfor MLT and FST models by matching with CO5BOLD models
- Author
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Sonoi, T., primary, Ludwig, H.-G., additional, Dupret, M.-A., additional, Montalbán, J., additional, Samadi, R., additional, Belkacem, K., additional, Caffau, E., additional, and Goupil, M.-J., additional
- Published
- 2019
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168. Influence of metallicity on the near-surface effect on oscillation frequencies
- Author
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Manchon, L., primary, Belkacem, K., additional, Samadi, R., additional, Sonoi, T., additional, Marques, J. P. C., additional, Ludwig, H.-G., additional, and Caffau, E., additional
- Published
- 2018
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169. Period spacings in red giants
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Mosser, B., primary, Gehan, C., additional, Belkacem, K., additional, Samadi, R., additional, Michel, E., additional, and Goupil, M.-J., additional
- Published
- 2018
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170. SIGNIFICANCE OF ANTINUCLEAR ANTIBODY TESTING IN UNEXPLAINED SECOND AND THIRD TRIMESTER FETAL DEATHS
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Incerpi, MH, Banks, EH, Goodwein, Samadi, R, and Goodwin, TM
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- 1998
171. Fungal Planet description sheets: 469?557
- Author
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Crous, Pedro Willem, Wingfield, M.J., Burgess, T.I., Hardy, G.E.St.J., Crane, C., Barrett, S., Cano-Lira, J.F., Roux, J.J., Thangavel, R., Guarro, J., Siqueira, C.M., J.P.Z., Souza-Motta, C.M., Stephenson, S.L., Sutton, D.A., Tamakeaw, N., Telleria, M.T., Valenzuela-Lopez, N., Viljoen, A., Visagie, C.M., Vizzini, A., Stchigel, A.M., Wartchow, B.D., F., Wingfield, B.D., Yurchenko, E., Zamora, J.C., Groenewald, J.Z., Martín, M.P., Alfredo, D.S., Barber, P.A., Barreto, R.W., Baseia, I.G., Cano-Canals, J., Cheewangkoon, R., Ferreira, R.J., Gené, J., Lechat, C., Moreno, G., Roets, F., Shivas, R.G., Sousa, J.O., Tan, Y.P., Wiederhold, N.P., Abell, S.E., Accioly, T., Albizu, J.L., Alves, J.L., Antoniolli, Z.I., Aplin, N., Araújo, João, Arzanlou, M., Bezerra, J.D.P., Bouchara, J.-P., Carlavilla, J.R., Castillo, A., Castroagudín, V.L., Ceresini, P.C., Claridge, G.F., Coelho, G., Coimbra, V.R.M., Costa, L.A., Cunha, K.C., Silva, S.S., Daniel, R., Beer, Z.W., Dueñas, M., Edwards, J., Enwistle, P., Fiuza, P.O., Fournier, J., Garcia, D., Gibertoni, T.B., Giraud, S., Guevara-Suarez, M., Gusmão, L.F.P., Haituk, S., Heykoop, M., Hirooka, Y., Hofmann, T.A., Houbraken, J., Hughes, D.P., Kautmanova, I., Koppel, O., Koukol, O., Larsson, E., Latha, K.P.D., Lee, D.H., Lisboa, Á. López-Villalba, D.O., Lisboa, W.S., López-Villalba, Á., Maciel, J.L.N., Manimohan, P., Manjón, J.L., Marincowitz, S., Marney, T.S., Meijer, M., Miller, A.N., Olariaga, I., Paiva, L.M., Piepenbring, M., Poveda-Molero, J.C., Raj, K.N.A., Raja, H.A., Rougeron, A., Salcedo, I., Samadi, R., Santos, T.A.B., Scarlett, K., Seifert, K.A., Shuttleworth, L.A., Silva, G.A., Silva, M., CBS-KNAW Fungal Biodiversity Centre, Department of Microbiology and Plant Pathology, Forestry Agricultural Biotechnology Institute (FABI), University of Pretoria (UPSpace), Universitat Rovira i Virgili, ASCOfrance, Groupe d'Étude des Interactions Hôte-Pathogène (GEIHP), Université d'Angers (UA), Montanuniversität Leoben (MUL), Biologie des organismes marins et écosystèmes (BOME), Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Biodiversity (Mycology and Microbiology), Agriculture and Agri-Food [Ottawa] (AAFC), CBS-KNAW FUNGAL BIODIVERSITY CENTRE, THE NETHERLANDS, JOÃO LEODATO NUNES MACIEL, CNPT., Ministerio de Economía, Industria y Competitividad (España), University of Pretoria [South Africa], Muséum national d'Histoire naturelle (MNHN)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Agriculture and Agri-Food (AAFC), and Naturalis journals & series
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0301 basic medicine ,ITS nrDNA barcodes ,Eucalyptus creta ,Saccharata ,novel fungal species ,Novel fungal species systematics ,Eucalyptus kingsmillii ,Fungal diseases of plants ,03 medical and health sciences ,Botany ,DNA barcoding ,Eucalyptus marginata ,systematics ,Ecology, Evolution, Behavior and Systematics ,ComputingMilieux_MISCELLANEOUS ,[SDV.MP.MYC]Life Sciences [q-bio]/Microbiology and Parasitology/Mycology ,LSU ,biology ,Eucalyptus preissiana ,Doença fúngica ,Eucalyptus lehmannii ,030108 mycology & parasitology ,15. Life on land ,biology.organism_classification ,Eucalyptus pellita ,ITS nrDNA ,[SDV.MP]Life Sciences [q-bio]/Microbiology and Parasitology ,Eucalyptus diversicolor - Abstract
Novel species of fungi described in this study include those from various countries as follows: Australia: Apiognomonia lasiopetali on Lasiopetalum sp., Blastacervulus eucalyptorum on Eucalyptus adesmophloia, Bul- lanockia australis (incl. Bullanockia gen. nov.) on Kingia australis, Caliciopsis eucalypti on Eucalyptus marginata, Celerioriella petrophiles on Petrophile teretifolia, Coleophoma xanthosiae on Xanthosia rotundifolia, Coniothyrium hakeae on Hakea sp., Diatrypella banksiae on Banksia formosa, Disculoides corymbiae on Corymbia calophylla, Elsinoe¿ eelemani on Melaleuca alternifolia, Elsinoe¿ eucalyptigena on Eucalyptus kingsmillii, Elsinoe¿ preissianae on Eucalyptus preissiana, Eucasphaeria rustici on Eucalyptus creta, Hyweljonesia queenslandica (incl. Hyweljonesia gen. nov.) on the cocoon of an unidentified microlepidoptera, Mycodiella eucalypti (incl. Mycodiella gen. nov.) on Eucalyptus diversicolor, Myrtapenidiella sporadicae on Eucalyptus sporadica, Neocrinula xanthorrhoeae (incl. Neocrinula gen. nov.) on Xanthorrhoea sp., Ophiocordyceps nooreniae on dead ant, Phaeosphaeriopsis agava- cearum on Agave sp., Phlogicylindrium mokarei on Eucalyptus sp., Phyllosticta acaciigena on Acacia suaveolens, Pleurophoma acaciae on Acacia glaucoptera, Pyrenochaeta hakeae on Hakea sp., Readeriella lehmannii on Eucalyptus lehmannii, Saccharata banksiae on Banksia grandis, Saccharata daviesiae on Daviesia pachyphylla, Saccharata eucalyptorum on Eucalyptus bigalerita, Saccharata hakeae on Hakea baxteri, Saccharata hakeicola on Hakea victoria, Saccharata lambertiae on Lambertia ericifolia, Saccharata petrophiles on Petrophile sp., Sac- charata petrophilicola on Petrophile fastigiata, Sphaerellopsis hakeae on Hakea sp., and Teichospora kingiae on Kingia australis. Brazil: Adautomilanezia caesalpiniae (incl. Adautomilanezia gen. nov.) on Caesalpina echinata, Arthrophiala arthrospora (incl. Arthrophiala gen. nov.) on Sagittaria montevidensis, Diaporthe caatingaensis (en- dophyte from Tacinga inamoena), Geastrum ishikawae on sandy soil, Geastrum pusillipilosum on soil, Gymnopus pygmaeus on dead leaves and sticks, Inonotus hymenonitens on decayed angiosperm trunk, Pyricularia urashimae on Urochloa brizantha, and Synnemellisia aurantia on Passiflora edulis. Chile: Tubulicrinis australis on Lophosoria quadripinnata. France: Cercophora squamulosa from submerged wood, and Scedosporium cereisporum from fluids of a wastewater treatment plant. Hawaii: Beltraniella acaciae, Dactylaria acaciae, Rhexodenticula acaciae, Rubikia evansii and Torula acaciae (all on Acacia koa). India: Lepidoderma echinosporum on dead semi-woody stems, and Rhodocybe rubrobrunnea from soil. Iran: Talaromyces kabodanensis from hypersaline soil. La Re¿union: Neocordana musarum from leaves of Musa sp. Malaysia: Anungitea eucalyptigena on Eucalyptus grandis × pellita, Camptomeriphila leucaenae (incl. Camptomeriphila gen. nov.) on Leucaena leucocephala, Castanediella communis on Eucalyptus pellita, Eucalyptostroma eucalypti (incl. Eucalyptostroma gen. nov.) on Eucalyptus pellita, Melanco- niella syzygii on Syzygium sp., Mycophilomyces periconiae (incl. Mycophilomyces gen. nov.) as hyperparasite on Periconia on leaves of Albizia falcataria, Synnemadiella eucalypti (incl. Synnemadiella gen. nov.) on Eucalyptus pellita, and Teichospora nephelii on Nephelium lappaceum....
- Published
- 2016
172. Reprocessing spent sulphuric acid
- Author
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Samadi, R. Al, Evans, C.M., and Smith, I.M.
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Recycling (Waste, etc.) -- Analysis ,Chemical industry -- Waste management ,Sulfuric acid -- Waste management ,Business ,Business, international ,Chemicals, plastics and rubber industries ,Environmental services industry - Abstract
Developments in recovery and reconcentration technology Reprocessing spent sulphuric acid It is a peculiarity of sulphuric acid that, in spite of its pre-eminence as a heavy industrial chemical, very little [...]
- Published
- 1990
173. Microstructural change and impact toughness property of Inconel 738LC after 12years of service
- Author
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Golezani, A.S., Bageri, M., and Samadi, R.
- Published
- 2016
- Full Text
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174. Core rotation braking on the red giant branch for various mass ranges
- Author
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Gehan, C, primary, Mosser, B., additional, Michel, E., additional, Samadi, R., additional, and Kallinger, T., additional
- Published
- 2018
- Full Text
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175. A new method for extracting seismic indices and granulation parameters: Results for more than 20,000 CoRoT andKeplerred giants
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de Assis Peralta, R., primary, Samadi, R., additional, and Michel, E., additional
- Published
- 2018
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176. Period spacings in red giants
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Vrard, M., Mosser, B., Samadi, R., Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), and PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
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[PHYS]Physics [physics] ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,ComputingMilieux_MISCELLANEOUS - Abstract
International audience
- Published
- 2016
177. Infill Development: an Approach to the Optimal and Intelligent Development of Cities - Case Study: Zone 8 of Tabriz
- Author
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Samadi R and Mohammad Taghi Razavian
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Sustainable development ,Geography ,Development (topology) ,Horizontal integration ,Analytic network process ,Corporate governance ,media_common.quotation_subject ,Infill ,Smart growth ,Quality (business) ,Environmental planning ,media_common - Abstract
One of the most important issues in the development of modern cities is the dispersed and horizontal expansion of cities. Due to a substantial effect of the form of a city on its stability, it is necessary to know study and understand its different dimensions and guide it to achieve sustainable development. Thus, infill development that is the simplest interpretation of urban endogenous development is considered as one of the urban smart growth strategies. Focusing on the vacant and abandoned lands in cities, infill development tries to load development on these lands. This study aimed to use infill development approach to achieve future development of Zone 8 of Tabriz and identify its potentials, in which several indicators have been used including quality of buildings, access and permeability, compressibility and granularity. In order to determine the final capacity of development and the effect of each indicator, the indicators were weighted by analytic network process (ANP) approach. The results of the study indicated that 38 hectares of the area under study had very high potential of development that accounted for 12.14%. Therefore, Zone 8 of Tabriz has much potential in the infill development. It could be said that half of the total area within the study area is prone to the internal development that requires formulating a suitable planning based on the principles of smart growth.
- Published
- 2016
178. Computation of eigenfrequencies for equilibrium models including turbulent pressure
- Author
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Sonoi, T., primary, Belkacem, K., additional, Dupret, M.-A., additional, Samadi, R., additional, Ludwig, H.-G., additional, Caffau, E., additional, and Mosser, B., additional
- Published
- 2017
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179. Dipole modes with depressed amplitudes in red giants are mixed modes
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Mosser, B., primary, Belkacem, K., additional, Pinçon, C., additional, Takata, M., additional, Vrard, M., additional, Barban, C., additional, Goupil, M.-J., additional, Kallinger, T., additional, and Samadi, R., additional
- Published
- 2017
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180. Calibration of mixing-length parameter α for MLT and FST models by matching with CO5BOLD models.
- Author
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Sonoi, T., Ludwig, H.-G., Dupret, M.-A., Montalbán, J., Samadi, R., Belkacem, K., Caffau, E., and Goupil, M.-J.
- Subjects
OSCILLATIONS ,PARAMETERS (Statistics) ,ENTROPY ,CALIBRATION ,STELLAR evolution - Abstract
Context. Space observations by the CoRoT and Kepler missions have provided a wealth of high-quality seismic data for a large number of stars from the main sequence to the red giant phases. One main goal of these missions is to take advantage of the rich spectra of solar-like oscillations to perform precise determinations of stellar characteristic parameters. To make the best of such data, we need theoretical stellar models with a precise near-surface structure since a near-surface structure of a solar-like star has significant influence on solar-like oscillation frequencies. The mixing-length parameter is a key factor to determine the near-surface structure of stellar models. In current versions of the convection formulations used in stellar evolution codes, the mixing-length parameter is a free parameter that needs to be properly specified. Aims. We aim at determining appropriate values of the mixing-length parameter, α, to be used consistently with the adopted convection formulation when computing stellar evolution models across the Hertzsprung–Russell diagram. This determination is based on 3D hydrodynamical simulation models. Methods. We calibrated α values by matching entropy profiles of 1D envelope models with those of hydrodynamical 3D models of solar-like stars produced by the CO
5 BOLD code. For such calibration, previous works concentrated on the classical mixing-length theory (MLT). We also analyzed full spectrum turbulence (FST) models. To construct the atmosphere in the 1D models, we used the Eddington gray T(τ) relation and that with the solar-calibrated Hopf-like function. Results. For both MLT and FST models with a mixing length l = αHp , calibrated α values increase with increasing surface gravity or decreasing effective temperature. For the FST models, we carried out an additional calibration using an α* value defined as l = rtop − r + α* Hp, top , where α* is found to increase with surface gravity and effective temperature. We provide tables of the calibrated α values across the Teff –log g plane for solar metallicity. By computing stellar evolution with varying α based on our 3D α calibration, we find that the change from solar α to varying α shifts evolutionary tracks particularly for the FST model. As for the correspondence to the 3D models, the solar Hopf-like function generally gives a photospheric-minimum entropy closer to a 3D model than the Eddington T(τ). The structure below the photosphere depends on the adopted convection model. However, we cannot obtain a definitive conclusion about which convection model gives the best correspondence to the 3D models. This is because each 1D physical quantity is related via an equation of state (EoS), but it is not the case for the averaged 3D quantities. Although the FST models with l = rtop − r + α* Hp, top are found to give the oscillation frequencies closest to the solar observed frequencies, their acoustic cavities are formed with compensatory effects between deviating density and temperature profiles near the top of the convective envelope. In future work, an appropriate treatment of the top part of the 1D convective envelope is necessary, for example, by considering turbulent pressure and overshooting. [ABSTRACT FROM AUTHOR]- Published
- 2019
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181. Stellar granulation as seen in disk-integrated intensity
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Samadi, R., Belkacem, K., Ludwig, H.-G., Caffau, E., Campante, T. L., Davies, G. R., Kallinger, T., Lund, M. N., Mosser, B., Baglin, A., Mathur, S., Garcia, R. A., Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), and PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS)
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stars: atmospheres ,turbulence ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,stars: oscillations ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,convection ,Sun: granulation - Abstract
International audience; Context. A large set of stars observed by CoRoT and Kepler shows clear evidence for the presence of a stellar background, which is interpreted to arise from surface convection, i.e., granulation. These observations show that the characteristic time-scale (τeff) and the root-mean-square (rms) brightness fluctuations (σ) associated with the granulation scale as a function of the peak frequency (νmax) of the solar-like oscillations. Aims. We aim at providing a theoretical background to the observed scaling relations based on a model developed in Paper I. Methods. We computed for each 3D model the theoretical power density spectrum (PDS) associated with the granulation as seen in disk-integrated intensity on the basis of the theoretical model published in Paper I. For each PDS we derived the associated characteristic time (τeff) and the rms brightness fluctuations (σ) and compared these theoretical values with the theoretical scaling relations derived from the theoretical model and the measurements made on a large set of Kepler targets. Results. We derive theoretical scaling relations for τeff and σ, which show the same dependence on νmax as the observed scaling relations. In addition, we show that these quantities also scale as a function of the turbulent Mach number (ℳa) estimated at the photosphere. The theoretical scaling relations for τeff and σ match the observations well on a global scale. Quantitatively, the remaining discrepancies with the observations are found to be much smaller than previous theoretical calculations made for red giants. Conclusions. Our modelling provides additional theoretical support for the observed variations of σ and τeff with νmax. It also highlights the important role of ℳa in controlling the properties of the stellar granulation. However, the observations made with Kepler on a wide variety of stars cannot confirm the dependence of our scaling relations on ℳa. Measurements of the granulation background and detections of solar-like oscillations in a statistically sufficient number of cool dwarf stars will be required for confirming the dependence of the theoretical scaling relations with ℳa.
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- 2013
182. Differential asteroseismic study of seismic twins observed by CoRoT
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Ozel, N., Mosser, B., Dupret, M. A., Bruntt, H., Barban, C., Deheuvels, S., García, R. A., Michel, E., Samadi, R., Baudin, F., Mathur, S., Régulo, C., Auvergne, M., Catala, C., Morel, Pierre, Pichon, B., Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)
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techniques: photometric ,Astrophysics::Solar and Stellar Astrophysics ,stars: individual: HD 181420 ,Astrophysics::Earth and Planetary Astrophysics ,stars: evolution ,asteroseismology ,stars: interiors ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,stars: individual: HD 175272 - Abstract
International audience; Context. The CoRoT short asteroseismic runs give us the opportunity to observe a large variety of late-type stars through their solar-like oscillations. We report the observation and modeling of the F5V star HD 175272.Aims. Our aim is to define a method for extracting as much information as possible from a noisy oscillation spectrum. Methods. We followed a differential approach that consists of using a well-known star as a reference to characterize another star. We used classical tools such as the envelope autocorrelation function to derive the global seismic parameters of the star. We compared HD 175272 with HD 181420 through a linear approach, because they appear to be asteroseismic twins.Results. The comparison with the reference star enables us to substantially enhance the scientific output for HD 175272. First, we determined its global characteristics through a detailed seismic analysis of HD 181420. Second, with our differential approach, we measured the difference of mass, radius and age between HD 175272 and HD 181420.Conclusions. We have developed a general method able to derive asteroseismic constraints on a star even in case of low-quality data. This method can be applied to stars with interesting properties but low signal-to-noise ratio oscillation spectrum, such as stars hosting an exoplanet or members of a binary system.
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- 2013
183. Obsessive-Compulsive Disorder in Hospitalized Patients with Schizophrenia
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Samiei, M., primary, Hedayati, K., additional, Mirabzadeh Ardekani, A., additional, Dolatshahi, B., additional, Daneshmand, R., additional, and Samadi, R., additional
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- 2016
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184. Surface-effect corrections for solar-like oscillations using 3D hydrodynamical simulations
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Sonoi, T., primary, Samadi, R., additional, Belkacem, K., additional, Ludwig, H.-G., additional, Caffau, E., additional, and Mosser, B., additional
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- 2015
- Full Text
- View/download PDF
185. CoRoT Observations of O Stars: Diverse Origins of Variability
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Blomme, R., Briquet, M., Degroote, P., Mahy, L., Aerts, Conny, Cuypers, J., Godart, M., Gosset, E., Hareter, M., Montalban, J., Morel, T., Nieva, M.F., Noels, A., Oreiro, R., Poretti, E., Przybilla, N., Rainer, M., Rauw, G., Schiller, F., Simon-Diaz, S., Smolders, K., Ventura, P., Vučković, M., Auvergne, M., Baglin, A., Baudin, F., Catala, C., Michel, E., Samadi, R., Rubert, C., St-Louis, N., Moffat, A.F.J., Drissen, L., and Drissen, L.
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Astronomy ,ComputingMethodologies_DOCUMENTANDTEXTPROCESSING ,Astronomical Society of the Pacific Conference Series - Abstract
Contains fulltext : 111302.pdf (Author’s version preprint ) (Open Access) Contains fulltext : 111302.pdf (Publisher’s version ) (Closed access)
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- 2013
186. An in-depth study of HD 174966 with CoRoT photometry and HARPS spectroscopy. Large separation as a new observable for ��Sct stars
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Hern��ndez, A. Garc��a, Moya, A., Michel, E., Su��rez, J. C., Poretti, E., Mart��n-Ru��z, S., Amado, P. J., Garrido, R., Rodr��guez, E., Rainer, M., Uytterhoeven, K., Rodrigo, C., Solano, E., Rod��n, J. R., Mathias, P., Rolland, A., Auvergne, M., Baglin, A., Baudin, F., Catala, C., and Samadi, R.
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Astrophysics::Solar and Stellar Astrophysics ,FOS: Physical sciences ,Astrophysics::Earth and Planetary Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
The aim of this work was to use a multi-approach technique to derive the most accurate values possible of the physical parameters of the ��Sct star HD174966. In addition, we searched for a periodic pattern in the frequency spectra with the goal of using it to determine the mean density of the star. First, we extracted the frequency content from the CoRoT light curve. Then, we derived the physical parameters of HD174966 and carried a mode identification out from the spectroscopic and photometric observations. We used this information to look for the models fulfilling all the conditions and discussed the inaccuracies of the method because of the rotation effects. In a final step, we searched for patterns in the frequency set using a Fourier transform, discussed its origin and studied the possibility of using the periodicity to obtain information about the physical parameters of the star. A total of 185 peaks were obtained from the Fourier analysis of the CoRoT light curve, being almost all reliable pulsating frequencies. From the spectroscopic observations, 18 oscillation modes were detected and identified, and the inclination angle ($62.5^{\circ}$$^{+7.5}_{-17.5}$) and the rotational velocity of the star (142 km/s) were estimated. From the multi-colour photometric observations, 3 frequencies were detected, which correspond to the main ones in the CoRoT light curve. We looked for periodicities within the 185 frequencies and found a periodic pattern ~64 ��Hz. Using the inclination angle, the rotational velocity and an Echelle diagram, showing a double comb outside the asymptotic regime, we concluded that the periodicity corresponds to a large separation structure. The periodic pattern allowed us to discriminate models from a grid, finding that the value of the mean density is achieved with a 6% uncertainty. So, the pattern could be used as a new observable for A-F type stars., 15 pages, 10 figures, 6 tables
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- 2013
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187. On the seismic scaling relations $����- \bar��$ and $��_{\rm max}-��_{\rm c}$
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Belkacem, K., Samadi, R., Mosser, B., Goupil, M. J., and Ludwig, H. -G.
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Astrophysics::Solar and Stellar Astrophysics ,FOS: Physical sciences ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
Scaling relations between asteroseismic quantities and stellar parameters are essential tools for studying stellar structure and evolution. We will address two of them, namely, the relation between the large frequency separation ($����$) and the mean density ($\bar��$) as well as the relation between the frequency of the maximum in the power spectrum of solar-like oscillations ($��_{\rm max}$) and the cut-off frequency ($��_{\rm c}$). For the first relation, we will consider the possible sources of uncertainties and explore them with the help of a grid of stellar models. For the second one, we will show that the basic physical picture is understood and that departure from the observed relation arises from the complexity of non-adiabatic processes involving time-dependent treatment of convection. This will be further discussed on the basis of a set of 3D hydrodynamical simulation of surface convection., To appear in Proceedings of Fujihara Seminar 2012: "Progress in physics of the sun and stars: a new era in helio- and asteroseismology" H. Shibahashi, ed., ASP Conf. Ser
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- 2013
- Full Text
- View/download PDF
188. Seismic diagnostics for transport of angular momentum in stars
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Goupil, M. J., Mosser, B., Marques, J. P., Ouazzani, R. M., Belkacem, K., Lebreton, Y., and Samadi, R.
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Astrophysics::Solar and Stellar Astrophysics ,evolution ,oscillations ,rotation ,stars ,interiors ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
Asteroseismology based on observations from the space-borne missions CoRoT and Kepler provides a powerful means of testing the modeling of transport processes in stars. Rotational splittings are currently measured for a large number of red giant stars and can provide stringent constraints on the rotation profiles. The aim of this paper is to obtain a theoretical framework for understanding the properties of the observed rotational splittings of red giant stars with slowly rotating cores. This allows us to establish appropriate seismic diagnostics for the rotation of these evolved stars. Rotational splittings were computed for stochastically excited dipolar modes by adopting a first-order perturbative approach for two 1.3 M⊙ benchmark models that assume slowly rotating cores. For red giant stars with slowly rotating cores, we show that the variation in the rotational splittings of ℓ = 1 modes with frequency depends only on the large frequency separation, the g-mode period spacing, and the ratio of the average envelope to core rotation rates (ℛ). This led us to propose a way to infer directly ℛ from the observations. This method is validated using the Kepler red giant star KIC 5356201. Finally, we provide theoretical support for using a Lorentzian profile to measure the observed splittings for red giant stars. peerReviewed
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- 2012
189. CoRoT Observations of O Stars: Diverse Origins of Variability
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Blomme, R., Briquet, M., Degroote, P., Mahy, L., Aerts, C., Cuypers, J., Godart, M., Gosset, E., Hareter, M., Montalban, J., Morel, T., Nieva, M. F., Noels, A., Oreiro, R., Poretti, E., Przybilla, N., Rainer, M., Rauw, G., Schiller, F., Simon-Diaz, S., Smolders, K., Ventura, P., Vučković, M., Auvergne, M., Baglin, A., Baudin, F., Catala, C., Michel, E., Samadi, R., Blomme, Briquet, Degroote, Mahy, Aerts, Cuypers, Godart, Gosset, Hareter, Montalban, Morel, Nieva, M. F., Noels, Oreiro, Poretti, Przybilla, Rainer, Rauw, Schiller, Simon-Diaz, Smolders, Ventura, Vučković, Auvergne, Baglin, Baudin, Catala, Michel, and Samadi
- Published
- 2012
190. First LOFAR results on galaxy clusters
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Ferrari, C., van Bemmel, I., Bonafede, A., Bîrzan, L., Brüggen, M., Brunetti, G., Cassano, R., Conway, J., De Gasperin, F., Heald, G., Jackson, N., Macario, G., McKean, J., Offringa, A. R., Orrù, E., Pizzo, R., Rafferty, D. A., Röttgering, H. J. A., Shulevski, A., Tasse, C., van der Tol, S., van Weeren, R. J., Wise, M., van Zwieten, J. E., Boissier, S., de Laverny, P., Nardetto, N., Samadi, R., Valls-Gabaud, D., Wozniak, H., and Kapteyn Astronomical Institute
- Subjects
galaxies: clusters: general ,Astrophysics::High Energy Astrophysical Phenomena ,radio continuum: general ,telescopes ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
Deep radio observations of galaxy clusters have revealed the existence of diffuse radio sources related to the presence of relativistic electrons and weak magnetic fields in the intracluster volume. The role played by this non-thermal intracluster component on the thermodynamical evolution of galaxy clusters is debated, with important implications for cosmological and astrophysical studies of the largest gravitationally bound structures of the Universe. The low surface brightness and steep spectra of diffuse cluster radio sources make them more easily detectable at low-frequencies. LOFAR is the first instrument able to detect diffuse radio emission in hundreds of massive galaxy clusters up to their formation epoch (z ˜ 1). We present the first observations of clusters imaged by LOFAR and the huge perspectives opened by this instrument for non-thermal cluster studies.
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- 2012
191. Amplitudes of solar-like oscillations in red giant stars
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Samadi, R., Belkacem, K., Dupret, M.-A., Ludwig, H.-G., Baudin, F., Caffau, E., Goupil, M.-J., Barban, C., Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), and Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris
- Subjects
[PHYS]Physics [physics] ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,ComputingMilieux_MISCELLANEOUS - Abstract
International audience
- Published
- 2012
192. Damping rates of solar-like oscillations across the HR diagram
- Author
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Belkacem, K., Dupret, M., Baudin, F., Appourchaux, T., Marques, J., Samadi, R., Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Space Sciences, Technologies and Astrophysics Research Institute (STAR), Université de Liège, Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information (CEA-LETI), Direction de Recherche Technologique (CEA) (DRT (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire d'automatique et de génie des procédés (LAGEP), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École Supérieure de Chimie Physique Électronique de Lyon (CPE)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Université de Lyon-Université de Lyon-École Supérieure Chimie Physique Électronique de Lyon-Centre National de la Recherche Scientifique (CNRS)
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[PHYS]Physics [physics] ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,ComputingMilieux_MISCELLANEOUS - Abstract
International audience
- Published
- 2012
193. Stochastic gravito-inertial modes discovered by CoRoT in the hot Be star HD 51452
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Neiner, C., Floquet, M., Samadi, R., Espinosa-Lara, F., Frémat, Y., Mathis, S., Leroy, B., De Batz, B., Rainer, M., Poretti, E., Mathias, P., Guarro Fló, J., Buil, C., Ribeiro, J., Alecian, E., Andrade, L., Briquet, M., Diago Nebot, Pascual David, Emilio, M., Fabregat Llueca, Juan, Gutiérrez Soto, Juan, Hubert, A.M., Janot-Pacheco, E., Martayan, C., Semaan, T., Suso, J., and Zorec, J.
- Subjects
Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics::Galaxy Astrophysics ,Partícules (Física nuclear) ,Ciència Ensenyament - Abstract
Context.Be stars are rapidly rotating stars with a circumstellar decretion disk. They usually undergo pressure and/or gravity pulsation modes excited by the κ-mechanism, i.e. an effect of the opacity of iron-peak elements in the envelope of the star. In the Milky Way,p-modes are observed in stars that are hotter than or equal to the B3 spectral type, while g-modes are observed at the B2 spectral type and cooler.Aims.We observed a B0IVe star, HD 51452,with the high-precision, high-cadence photometric CoRoT satellite and high-resolution, ground-based HARPS and SOPHIE spectrographs to study its pulsations in great detail. We also used the lower resolution spectra available in the BeSS atabase. Methods.We analyzed the CoRoT and spectroscopic data with several methods: Clean -NG, Freq Find, and a sliding window method.We also analyzed spectral quantities, such as the violet over red (V/R) emission variations, to obtain information about the variation in the circumstellar environment. We calculated a stellar structure model with the ESTER code to test the various interpretation of the results.Results.We detect 189 frequencies of variations in the CoRoT light curve in the range between 0 and 4.5 c d−1. The main frequencies are also recovered in the spectroscopic data. In particular we find that HD 51452 undergoes gravito-inertial modes that are not in the domain of those excited by the κ-mechanism. We propose that these are stochastic modes excited in the convective zones and that at least some of them are a multiplet of r-modes (i.e. subinertial modes mainly driven by the Coriolis acceleration). Stochastically excited gravito-inertial modes had never been observed in any star, and theory predicted that their very low amplitudes would be undetectable even with CoRoT. We suggest that the amplitudes are enhanced in HD 51452 because of the very rapid stellar rotation.In addition, we find that the amplitude variations of these modes are related to the occurrence of minor outbursts.Conclusions.Thanks to CoRoT data, we have detected a new kind of pulsations in HD 51452, which are stochastically excited gravito-inertial modes, probably due to its very rapid rotation. These modes are probably also present in other rapidly rotating hot Be stars.
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- 2012
194. Probing the thick disc formation scenarios outside the solar neighbourhood
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Kordopatis, G., Recio-Blanco, A., de Laverny, P., Gilmore, G., Hill, V., Wyse, R. F. G., Helmi, A., Bijaoui, A., Ordenovic, C., Zoccali, M., Bienaymé, O., Alecian, G., Belkacem, K., Samadi, R., Valls-Gabaud, D., and Astronomy
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Astrophysics::Earth and Planetary Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Galaxy: evolution -- Galaxy: kinematics and dynamics -- stars: abundances -- methods: observational ,Astrophysics::Galaxy Astrophysics - Abstract
The origin and evolution of the Milky Way remains one of the key unanswered questions in astrophysics. From a sample of roughly 700 stars selected in order to probe the galactic thick disc outside the solar neighborhood, we investigate the radial scale length and scale height of this structure, based on the spectroscopic measurement of its star members. Estimations of the scale height and scale lengths for different metallicity bins result in consistent values, with HrValue and HzValue, showing no evidence of relics of destroyed massive satellites and challenging the radial migration mechanisms as being the most important processes of creation of the thick disc.
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- 2011
195. Kinematic imprints from the bar and spiral structures in the galatic disk
- Author
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Figueras, F., Antoja Castelltort, Teresa, Valenzuela, O., Romero-Gómez, M., Pichardo, B., Moreno, E., Alecian, G., Belkacem, K., Samadi, R., Valls-Gabaud, D., and Astronomy
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solar neighbourhood ,Galactic bar ,Galaxy: kinematics and dynamics ,Astrophysics::Galaxy Astrophysics ,spiral structure - Abstract
At 140 years of the discovery of the moving groups, these stellar streams are emerging as powerful tools to constrain the models for the spiral arms and the Galactic bar in the Gaia era. From the kinematic-age-metallicity analysis in the solar neighbourhood it is now well established that some of these kinematic structures have a dynamical origin, different from the classical cluster disruption hypothesis. Test particle simulations allow us to definitively establish that these local structures can be created by the dynamical resonances
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- 2011
196. Characterization of the thick disc properties up to 8~kpc through a spectroscopic survey
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Kordopatis, G., Recio-Blanco, A., de Laverny, P., Gilmore, G., Hill, V., Wyse, R. F. G., Helmi, A., Bijaoui, A., Ordenovic, C., Zoccali, M., Bienaymé, O., Boissier, S., Heydari-Malayeri, M., Samadi, R., Valls-Gabaud, D., and Astronomy
- Subjects
stars: abundances ,galaxy: evolution ,galaxy: kinematics and dynamics ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,methods: observational ,Astrophysics::Galaxy Astrophysics - Abstract
A spectroscopic survey of nearly 600 stars probing the Galactic Thick Disc far from the Solar neighbourhood is performed. The MATISSE (MATrix Inversion for Spectral SynthEsis) algorithm is developed and trained in order to automatically obtain the atmospheric parameters of the stars. The derived effective temperatures, surface gravities and overall metallicities are then combined to stellar evolution isochrones, radial velocities and proper motions to get the distances, kinematics and orbital parameters of the sample stars, up to 8 kpc. The Galactic components Thin and Thick discs and Halo are then characterized. The velocity ellipsoid for the old Thin Disc is found at (σ_u, σ_v, σ_w)= (39,27,20) km s-1 with a mean [M/H] ˜ -0.12~dex, whereas the Thick Disc has a mean [M/H] ˜ -0.4~dex and a rotational lag of V ˜-76 km s-1
- Published
- 2010
197. Herschel/HIFI reveals the first stages of stellar formation
- Author
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Herpin, F., Bontemps, S., Chavarria, L., van der Tak, F., Wyrowski, F., van Dishoeck, E., Boissier, S., Heydari-Malayeri, M., Samadi, R., Valls-Gabaud, D., and Astronomy
- Subjects
stars: formation ,protostars ,abundances ,early-type ,line: profiles ,ISM: molecules - Abstract
The understanding of the star formation is still on progress. Especially, the formation of high-mass stars is much less understood than the low-mass case: even the time order of observational phenomena is uncertain. Water, one of the most important molecules in the Universe, might elucidate key episodes in the process of stellar birth, and especially could be a major role in the formation of high-mass stars. For both types of stars, the source chemical composition is not well known and even less known is the chemical evolution of the interstellar matter throughout the various phases of star formation. This talk presents the first results of the various Herschel Space Observatory star formation key-programs. One of the instruments on-board HSO, HIFI, is the most powerful spectrometer never built, covering a huge frequency range, most of them unaccessible from ground. In particular, one of the KP, WISH, aims at following the process of star formation during the various stages and at using the water as a physical diagnostic throughout the evolution.
- Published
- 2010
198. Helium signature in red giant oscillation patterns observed byKepler
- Author
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Vrard, M., primary, Mosser, B., additional, Barban, C., additional, Belkacem, K., additional, Elsworth, Y., additional, Kallinger, T., additional, Hekker, S., additional, Samadi, R., additional, and Beck, P. G., additional
- Published
- 2015
- Full Text
- View/download PDF
199. Non-adiabatic study of theKeplersubgiant KIC 6442183
- Author
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Grosjean, M., primary, Dupret, M.A., additional, Belkacem, K., additional, Benomar, O., additional, Deheuvels, S., additional, Samadi, R., additional, and Grigahcene, A., additional
- Published
- 2015
- Full Text
- View/download PDF
200. Stellar oscillations - II - The non-adiabatic case
- Author
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Samadi, R., primary, Belkacem, K., additional, and Sonoi, T., additional
- Published
- 2015
- Full Text
- View/download PDF
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