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See detailFirst results for the solar neighborhood of the Asiago Red Clump Survey
Valentini, Marica ULg; Munari, U.; Saguner, T. et al

in European Physical Journal Web of Conferences (2012, February 01)

The Asiago Red Clump Spectroscopic Survey (ARCS) is an ongoing survey that provides atmospheric parameters, distances and space velocities of a well selected sample of Red Clump stars distributed along ... [more ▼]

The Asiago Red Clump Spectroscopic Survey (ARCS) is an ongoing survey that provides atmospheric parameters, distances and space velocities of a well selected sample of Red Clump stars distributed along the celestial equator. We used the ARCS catalog for a preliminary investigation of the Galactic disk in the Solar Neighborhood, in particular we focused on detection and characterization of moving groups. [less ▲]

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See detailModelling a high-mass red giant observed by CoRoT
Baudin, F.; Barban, C.; Goupil, M. J. et al

in Astronomy and Astrophysics (2012), 538

Context. The advent of space-borne photometers such as CoRoT and Kepler has opened up new fields in asteroseismology. This is especially true for red giants as only a few of these stars were known to ... [more ▼]

Context. The advent of space-borne photometers such as CoRoT and Kepler has opened up new fields in asteroseismology. This is especially true for red giants as only a few of these stars were known to oscillate with small amplitude, solar-like oscillations before the launch of CoRoT. <BR /> Aims: The G6 giant HR 2582 (HD 50890) was observed by CoRoT for approximately 55 days. We present here the analysis of its light curve and the characterisation of the star using different observables, such as its location in the Hertzsprung-Russell diagram and seismic observables. <BR /> Methods: Mode frequencies are extracted from the observed Fourier spectrum of the light curve. Numerical stellar models are then computed to determine the characteristics of the star (mass, age, etc.) from the comparison with observational constraints. <BR /> Results: We provide evidence for the presence of solar-like oscillations at low frequency, between 10 and 20 μHz, with a regular spacing of (1.7 ± 0.1) μHz between consecutive radial orders. Only radial modes are clearly visible. From the models compatible with the observational constraints used here, We find that HR 2582 (HD 50890) is a massive star with a mass in the range (3-5 M[SUB]&sun;[/SUB]), clearly above the red clump. It oscillates with rather low radial order (n = 5-12) modes. Its evolutionary stage cannot be determined with precision: the star could be on the ascending red giant branch (hydrogen shell burning) with an age of approximately 155 Myr or in a later phase (helium burning). In order to obtain a reasonable helium amount, the metallicity of the star must be quite subsolar. Our best models are obtained with a mixing length significantly smaller than that obtained for the Sun with the same physical description (except overshoot). The amount of core overshoot during the main-sequence phase is found to be mild, of the order of 0.1 H[SUB]p[/SUB]. <BR /> Conclusions: HR 2582 (HD 50890) is an interesting case as only a few massive stars can be observed due to their rapid evolution compared to less massive red giants. HR 2582 (HD 50890) is also one of the few cases that can be used to validate the scaling relations for massive red giants stars and its sensitivity to the physics of the star. The CoRoT space mission, launched on 2006 December 27, was developed and is operated by the CNES with participation of the Science Programs of ESA; ESA's RSSD, Austria, Belgium, Brazil, Germany and Spain. [less ▲]

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See detailSolar-like pulsating stars as distance indicators: G-K giants in the CoRoT and Kepler fields
Miglio, A.; Morel, Thierry ULg; Barbieri, M. et al

in European Physical Journal Web of Conferences (2012, February 01)

The detection of radial and non-radial solar-like oscillations in thousands of G-K giants with CoRoT and Kepler is paving the road for detailed studies of stellar populations in the Galaxy. The available ... [more ▼]

The detection of radial and non-radial solar-like oscillations in thousands of G-K giants with CoRoT and Kepler is paving the road for detailed studies of stellar populations in the Galaxy. The available average seismic constraints allow a precise and largely model-independent determination of stellar radii (hence distances) and masses. We here briefly report on the distance determination of thousands of giants in the CoRoT and Kepler fields of view. [less ▲]

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See detailA quantitative study of O stars in NGC 2244 and the Monoceros OB2 association
Martins, F.; Mahy, Laurent ULg; Hillier, D. J. et al

in Astronomy and Astrophysics (2012), 538

<BR /> Aims: Our goal is to determine the stellar and wind properties of seven O stars in the cluster NGC 2244 and three O stars in the OB association Mon OB2. These properties give us insight into the ... [more ▼]

<BR /> Aims: Our goal is to determine the stellar and wind properties of seven O stars in the cluster NGC 2244 and three O stars in the OB association Mon OB2. These properties give us insight into the mass loss rates of O stars. They allow us to both check the validity of rotational mixing in massive stars and to better understand the effects of the ionizing flux and wind mechanical energy release on the surrounding interstellar medium and its influence on triggered star formation. <BR /> Methods: We collected optical and UV spectra of the target stars that we analyzed by means of atmosphere models computed with the code CMFGEN. The spectra of binary stars were disentangled and the components studied separately. <BR /> Results: All stars have an evolutionary age less than 5 million years, with the most massive stars being among the youngest. Nitrogen surface abundances show no clear relation with projected rotational velocities. Binaries and single stars show the same range of enrichment. This is attributed to the youth and/or wide separation of the binary systems in which the components have not (yet) experienced strong interaction. A clear trend toward greater enrichment in higher luminosity objects is observed, consistent with what evolutionary models with rotation predict for a population of O stars at any given age. We confirm the weakness of winds in late O dwarfs. In general, mass loss rates derived from UV lines are lower than mass loss rates obtained from Hα. The UV mass loss rates are even lower than the single-line driving limit in the latest type dwarfs. These issues are discussed in the context of the structure of massive stars winds. The evolutionary and spectroscopic masses are in agreement above 25 M[SUB]&sun;[/SUB], but the uncertainties are large. Below this threshold, the few late-type O stars studied here indicate that the mass discrepancy still seems to hold. Appendix A is available in electronic form at <A href="http://www.aanda.org">http://www.aanda.org</A> [less ▲]

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See detailMicrolensing Binaries Discovered through High-magnification Channel
Shin, I.-G.; Choi, J.-Y.; Park, S.-Y. et al

in Astrophysical Journal (2012), 746

Microlensing can provide a useful tool to probe binary distributions down to low-mass limits of binary companions. In this paper, we analyze the light curves of eight binary-lensing events detected ... [more ▼]

Microlensing can provide a useful tool to probe binary distributions down to low-mass limits of binary companions. In this paper, we analyze the light curves of eight binary-lensing events detected through the channel of high-magnification events during the seasons from 2007 to 2010. The perturbations, which are confined near the peak of the light curves, can be easily distinguished from the central perturbations caused by planets. However, the degeneracy between close and wide binary solutions cannot be resolved with a 3σ confidence level for three events, implying that the degeneracy would be an important obstacle in studying binary distributions. The dependence of the degeneracy on the lensing parameters is consistent with a theoretical prediction that the degeneracy becomes severe as the binary separation and the mass ratio deviate from the values of resonant caustics. The measured mass ratio of the event OGLE-2008-BLG-510/MOA-2008-BLG-369 is q ~ 0.1, making the companion of the lens a strong brown dwarf candidate. [less ▲]

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See detailProceedings of the 7th International Conference on Si Epitaxy and Heterostructures (ICSI-7)
Hartmann, Jean-Michel; Loo, Roger; Nguyen, Ngoc Duy ULg et al

Book published by Elsevier (2012)

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See detailTransiting exoplanets from the CoRoT space mission Resolving the nature of transit candidates for the LRa03 and SRa03 fields
Cavarroc, C.; Moutou, C.; Gandolfi, D. et al

in Astrophysics & Space Science (2012), 337

CoRoT is a space telescope which aims at studying internal structure of stars and detecting extrasolar planets. We present here a list of transits detected in the light curves of stars observed by CoRoT ... [more ▼]

CoRoT is a space telescope which aims at studying internal structure of stars and detecting extrasolar planets. We present here a list of transits detected in the light curves of stars observed by CoRoT in two fields in the anti-center direction: the LRa03 one observed during 148 days from 3 October 2009 to 1 March 2010 followed by the SRa03 one from the 5 March 2010 to the 29 March 2010 during 25 days. 5329 light curves for the LRa03 field and 4169 for the SRa03 field were analyzed by the detection team of CoRoT. Then some of the selected exoplanetary candidates have been followed up from the ground. In the LRa03 field, 19 exoplanet candidates have been found, 8 remain unsolved. No secured planet has been found yet. In the SRa03 field, there were 11 exoplanetary candidates among which 6 cases remain unsolved and 3 planets have been found: CoRoT-18b, CoRoT-19b, CoRoT-20b. [less ▲]

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See detailLa production de viande par les bovins
Beckers, Yves ULg

Conference given outside the academic context (2012)

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See detailTraitement à la source d'eaux usées hospitalières par boues activées: faisabilité et impact sur la biomasse
Alrhmoun, Moussab; Louvet, Jean-Noël ULg; Stalder, Thibault et al

Conference (2012, February 01)

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See detailLe droit des marchés publics et les écoquatiers
Durviaux, Ann-Lawrence ULg

Conference given outside the academic context (2012)

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See detailEducational orientation and social heritage. The choice of working-class students
Andre, Géraldine ULg

Conference (2012, February 01)

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See detailInvisible computer for collaborative design : evaluation of a multimodal sketch-based environment
Defays, Aurore ULg; Safin, Stéphane ULg; Darses, Françoise et al

in Work: A Journal of Prevention, Assessment and Rehabilitation (2012), Supplement 1

In the areas of design, especially in architectural design, collaboration has become an important challenge. The specialization of skills increase, work teams are more and more extensive and the ... [more ▼]

In the areas of design, especially in architectural design, collaboration has become an important challenge. The specialization of skills increase, work teams are more and more extensive and the geographic distance between them increases too. The economic and ecological stakes related to remote collaboration are an evidence. This context involves the need to support most efficiently possible remote working meetings. We present the Distributed Collaborative Digital Studio (DSDC), a tool designed to recreate, in distant situations, the context of copresence meetings. This shared environment is created in the “invisible computer” approach. The idea is that the tool should disappear from user’s consciousness. Indeed, creative design activities require some fluidity in their process. Therefore, any involuntary interruption created by the system can potentially brake creativity. In this perspective, we investigate specifically the “invisibility” of our environment. To do this, we propose a framework for the operationalization of the concept and a methodology to test the system invisibility. This methodology was applied through a case study consisting of a corpus of 12 hours of remote collaborative design sessions with the DSDC. We highlight the learning effects while using our system, conclude on its effectiveness and discuss our methodology. [less ▲]

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See detailA dynamic analysis of higher-comoment risk premiums in Hedge Fund returns
Lambert, Marie ULg

in Journal of Derivatives and Hedge Funds (2012), 18(1), 73-84

Hedge funds display a strong non-linear payoff structure because of the use of highly dynamic trading strategies. This article examines the relevance of using higherorder comoment equity risk premiums ... [more ▼]

Hedge funds display a strong non-linear payoff structure because of the use of highly dynamic trading strategies. This article examines the relevance of using higherorder comoment equity risk premiums implied in the United States and the emerging markets for capturing these return non-linearities. We provide evidence that the higherorder comoment equity risk premiums help in explaining the returns of the different hedge fund strategies from the Hedge Fund Research classification. We perform a dynamic analysis where moment risk exposures are examined separately in up and down markets. We show that hedge fund styles tend to vary their exposures to moment risks according to the market regimes. [less ▲]

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See detailInfluence of Particle Packing on Elastic Properties of Concrete
He, Huan ULg; Stroeven, Piet; Stroeven, Martijn et al

in Magzine of Concrete Research (2012), 64(2), 163-175

Concrete is a complex composite material. Hence, the main components of concrete on meso-scale should be considered when studying its global elastic properties. As a main ingredient of concrete, aggregate ... [more ▼]

Concrete is a complex composite material. Hence, the main components of concrete on meso-scale should be considered when studying its global elastic properties. As a main ingredient of concrete, aggregate will exert influences on the elastic properties of concrete. In the present study, particularly particle shape and particle packing are considered of relevance. The densely packed structure of arbitrary shaped aggregate is simulated by a concurrent algorithm-based discrete element modelling (DEM) system. A comparison is pursued of data, produced by numerical models, either based on arbitrary angular-shaped particles or on spherical ones. This will be accomplished by means of the finite element method (FEM). The results can be used to evaluate the adequacy for this purpose of conventional numerical or analytical models based on spherical aggregates. The influences exerted on the elastic properties of concrete by other factors, such as the mechanical and physical properties of the aggregate, the ITZ and the matrix will also be addressed in this study. [less ▲]

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See detailCoordinated primary frequency control among non-synchronous systems connected by a multi-terminal high-voltage direct current grid
Dai, Jing; Phulpin, Yannick; Sarlette, Alain et al

in IET Generation, Transmission & Distribution (2012), 6(2), 99-108

The authors consider a power system composed of several non-synchronous AC areas connected by a multiterminal high-voltage direct current (HVDC) grid. In this context, the authors propose a distributed ... [more ▼]

The authors consider a power system composed of several non-synchronous AC areas connected by a multiterminal high-voltage direct current (HVDC) grid. In this context, the authors propose a distributed control scheme that modifies the power injections from the different AC areas into the DC grid so as to make the system collectively react to load imbalances. This collective reaction allows each individual AC area to downscale its primary reserves. The scheme is inspired by algorithms for the consensus problem extensively studied by the control theory community. It modifies the power injections based on frequency deviations of the AC areas so as to make them stay close to each other. A stability analysis of the closed-loop system is reported as well as simulation results on a benchmark power system with five AC areas. These results show that with proper tuning, the control scheme makes the frequency deviations converge rapidly to a common value following a load imbalance in an area. [less ▲]

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See detailRapport 2 FIRST Spin Off IMONIC
Goffin, Dorothée ULg

Report (2012)

Rapport du projet FIRST spin-off IMONIC financé par le SPW (Production de mélanges à valeur santé contenant des isomaltooligosaccharides et de l’acide gluconique prébiotiques et répondant au cahier des ... [more ▼]

Rapport du projet FIRST spin-off IMONIC financé par le SPW (Production de mélanges à valeur santé contenant des isomaltooligosaccharides et de l’acide gluconique prébiotiques et répondant au cahier des charges de l’agriculture biologique). [less ▲]

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See detailEloge académique du professeur Charles-Léon Lapière
Angenot, Luc ULg

in Bulletin et Mémoires de l'Académie Royale de Médecine de Belgique (2012), 167(1), 21-27

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See detailRutherford backscattering analysis of porous thin TiO2 films
Mayer, Matej; von Toussaint, Udo; Dewalque, Jennifer ULg et al

in Nuclear Instruments & Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms (2012), 273

The additional energy spread due to sample porosity was implemented in the SIMNRA simulation code, version 6.60 and higher. Deviations of the path length and energy loss distributions from the ones ... [more ▼]

The additional energy spread due to sample porosity was implemented in the SIMNRA simulation code, version 6.60 and higher. Deviations of the path length and energy loss distributions from the ones expected from a Poisson distribution of the number of traversed pores are taken into account. These deviations are due to the interaction of pores at higher pore concentrations by overlap or blocking. The skewnesses of the energy distributions are approximated by two-piece normal distributions with identical first three moments. Propagation of porosity-induced energy spread in thick layers is taken into account. Calculated results are compared to experimental data obtained with thin TiO2 mesoporous films measured by Rutherford backscattering (RBS),transmission electron microscopy (TEM), and atmospheric poroellipsometry. [less ▲]

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