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See detailConstraining the efficiency of angular momentum transport with asteroseismology of red giants: the effect of stellar mass
Eggenberger, P.; Lagarde, N.; Miglio, A. et al

in Astronomy and Astrophysics (2017), 599

Context: Constraints on the internal rotation of red giants are now available thanks to asteroseismic observations. Preliminary comparisons with rotating stellar models indicate that an undetermined ... [more ▼]

Context: Constraints on the internal rotation of red giants are now available thanks to asteroseismic observations. Preliminary comparisons with rotating stellar models indicate that an undetermined additional process for the internal transport of angular momentum is required in addition to purely hydrodynamic processes. Aims: We investigate how asteroseismic measurements of red giants can help us characterize the additional transport mechanism. Methods: We first determine the efficiency of the missing transport mechanism for the low-mass red giant KIC 7341231 by computing rotating models that include an additional viscosity corresponding to this process. We then discuss the change in the efficiency of this transport of angular momentum with the mass, metallicity and evolutionary stage. Results: In the case of the low-mass red giant KIC 7341231, we find that the viscosity corresponding to the additional mechanism is constrained to the range 1 x 10^3 - 1.3 x 10^4 cm^2/s. This constraint on the efficiency of the unknown additional transport mechanism during the post-main sequence is obtained independently of any specific assumption about the modelling of rotational effects during the pre-main sequence and the main sequence (in particular, the braking of the surface by magnetized winds and the efficiency of the internal transport of angular momentum before the post-main-sequence phase). When we assume that the additional transport mechanism is at work during the whole evolution of the star together with a solar-calibrated braking of the surface by magnetized winds, the range of nu_add is reduced to 1 - 4 x 10^3 cm^2/s. In addition to being sensitive to the evolutionary stage of the star, we show that the efficiency of the unknown process for internal transport of angular momentum increases with the stellar mass. [less ▲]

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See detailComment les vidéastes gagnent-ils leur vie sur Youtube ?
Krywicki, Boris ULg

in Culture, le Magazine Culturel de l'Université de Liège (2017)

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See detailValidation of SAFIR through DIN EN 1992-1-2 NA: Comparison of the results for the examples presented in Annex CC
Romeiro Ferreira, Joao Daniel ULg; Franssen, Jean-Marc ULg; Gernay, Thomas ULg

Report (2017)

Annex CC of DIN EN 1992-1-2 NA presents a series of cases that allow benchmarking software tools aimed at the design of structures in a fire situation. With the goal of providing a validation document for ... [more ▼]

Annex CC of DIN EN 1992-1-2 NA presents a series of cases that allow benchmarking software tools aimed at the design of structures in a fire situation. With the goal of providing a validation document for the finite element code SAFIR, a comparison of the reference results for the cases presented in the Annex CC with the results obtained with SAFIR has been carried out and is presented in this document. The validation typically consists in a comparison between the value of a result (temperature, displacement or others) obtained by SAFIR and the value given as a reference and supposed to be the « true » result. The value obtained must fall in the interval stipulated by the document. The parametric analysis shows that the solution of SAFIR satisfies the requirement of the standard. The solution converges to the theoretical solution when the density of the mesh is increased and the value of the time step is reduced. When refining the mesh, rectangular elements converge slightly faster than triangular element; regular structured meshes are most efficient, with slight differences being observed in distorted structured meshes; unstructured meshes are somehow less efficient while being still in the acceptable range of the standard. [less ▲]

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See detailChris BEARD - The Prince of the Blues
Sacré, Robert ULg

E-print/Working paper (2017)

Interview de Chris BEARD + record reviews

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See detail« Traitement fiscal des dividendes – Fiscalité européenne et droit comparé »
Richelle, Isabelle ULg; Malherbe, Jacques

in Annunziata, Filippo (Ed.) Le droit comparé des affaires au XXIème siècle – Mélanges à la mémoire de Claude Ducouloux (2017)

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See detailFire resistance testing
Dumont, Fabien ULg

Learning material (2017)

The objective of determining fire resistance is to assess the behaviour of a specimen of a building element when subjected to defined heating, pressure and – if relevant – loading conditions. The ... [more ▼]

The objective of determining fire resistance is to assess the behaviour of a specimen of a building element when subjected to defined heating, pressure and – if relevant – loading conditions. The experimental methods provide a means of quantifying the ability of an element to withstand exposure to such stresses. More precisely, the issue is to quantify the separating and/or loadbearing capacity of a building element in order to ensure the separating function and/or structural stability of a building. A representative sample (called "test specimen") of the building element is exposed to a specified scheme of heating and – where relevant – of loading. The tests are carried out on specimens in full size or on small-scale models for elements exceeding the dimensions of the furnaces. The performances of the test specimen are determined by assessing criteria described in test methods. Fire resistance of the test specimen is expressed as the times for which the appropriate criteria have been satisfied. The times so obtained are a measure of the adequacy of the construction in a fire, but they have no direct relationship with the duration time of a real fire. In Europe, about 50 laboratories currently perform fire resistance tests. [less ▲]

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See detailDioxins! Hunting the Great White Shark
Focant, Jean-François ULg

Scientific conference (2017, March)

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See detailPlaidoyer pour que les innovations en matière de construction « durable » dans le secteur du logement ne soient pas des feux de paille.
Possoz, Jean-Philippe ULg

in Fontaine, Sébastien (Ed.) LES ÉCHOS DU LOGEMENT N°119 (2017)

Nos pratiques constructives évoluent peu à peu sous l’impulsion des défis environnementaux et socio-économiques qui traversent nos sociétés. Où en est-on aujourd’hui ? D’où vient-on et où va-t-on ? Si ces ... [more ▼]

Nos pratiques constructives évoluent peu à peu sous l’impulsion des défis environnementaux et socio-économiques qui traversent nos sociétés. Où en est-on aujourd’hui ? D’où vient-on et où va-t-on ? Si ces techniques ont acquis de la maturité, pourquoi restent-elles aussi marginales ? Cet article formule l’hypothèse que la réponse est moins technique ou économique que culturelle ou systémique. [less ▲]

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See detailL'acte d'imagination: Approches phénoménologiques
Hagelstein, Maud ULg; Hervy, Alievtina ULg; Leclercq, Bruno ULg

in Bulletin d'Analyse Phénoménologique (2017), 13 (2017)(2),

Du 25 au 29 avril 2016, le centre « Phénoménologies » de l’Université de Liège a tenu la dixième édition de son séminaire international de recherche en phénoménologie. Autour du thème général L’Acte ... [more ▼]

Du 25 au 29 avril 2016, le centre « Phénoménologies » de l’Université de Liège a tenu la dixième édition de son séminaire international de recherche en phénoménologie. Autour du thème général L’Acte d’imagination : approches phénoménologiques, vingt-huit chercheurs issus de vingt-deux universités différentes se sont rencontrés pendant une semaine entière pour discuter dans le détail plusieurs aspects de la problématique. Le volume actuel reprend la plupart des communications qui avaient été présentées durant cette semaine, communications ici retravaillées pour intégrer les propositions qu’avaient suscitées leur présentation originale et plus généralement l’ensemble des débats très riches qu’avait permis la constitution ponctuelle d’une vraie communauté philosophique. Kant avait notoirement fait de la faculté d’imagination un intermédiaire (un peu indécis) entre la réceptivité de l’expérience sensible et la spontanéité de l’entendement. En s’installant plus nettement sur le terrain de la psychologie descriptive et en abandonnant le vocabulaire des « facultés » pour lui préférer celui des actes mentaux ou des fonctions psychiques, les brentaniens s’étaient donné les moyens d’analyser plus finement les composantes de l’acte d’imagination (mode de visée, contenu réel, contenu intentionnel...), les rapports de fondation qu’il entretient avec d’autres types d’actes, et par là le rôle qu’il peut jouer dans les fonctions cognitives ou évaluatives de l’esprit. C’est de cet acte d’imagination, envisagé par la phénoménologie en tant que psychologie descriptive, qu’il sera ici question. [less ▲]

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See detailLocal Identification of Voltage Instability from Load Tap Changer Response
Weckesser, Johannes ULg; Papangelis, Lampros ULg; Vournas, Costas et al

in Sustainable Energy, Grids and Networks (2017)

This paper presents a local long-term voltage instability monitoring method, which is suitable for on-line applications. The proposed extended-time Local Identification of Voltage Emergency Situations ... [more ▼]

This paper presents a local long-term voltage instability monitoring method, which is suitable for on-line applications. The proposed extended-time Local Identification of Voltage Emergency Situations (eLIVES) method is a significantly modified version of the previously presented LIVES method. The new method is not bound to assessing system response over a predefined LTC tapping period. This allows handling LTCs with variable delays, as well as events taking place during the tapping sequence impacting the distribution voltages. For that purpose, eLIVES applies recursive least square fitting to acquired distribution voltage measurements and a new set of rules to detect a voltage emergency situation. The effectiveness of the eLIVES method is presented on the IEEE Nordic test system for voltage stability and security assessment. [less ▲]

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See detailRendre compte de la société d’aujourd’hui
Quoilin, Cécile; Postula, Jean-Louis ULg

in Cahiers de muséologie - Dans la marge (2017)

Founded a century ago as a classical museum of regional ethnography, the Museum of Walloon Life is now facing the challenge of an essential update and the redefinition of its museum project. For about ten ... [more ▼]

Founded a century ago as a classical museum of regional ethnography, the Museum of Walloon Life is now facing the challenge of an essential update and the redefinition of its museum project. For about ten years, the choice of the approach known as "society museum" on the occasion of the total renovation of the building, led to an in-depth review of the acquisition and exhibition policies but also of the nature of field research and relationships with its different audiences. This article shows the practical consequences of the implementation of this new model, which now places the man rather than the collections at the center of discourse, on all museum functions. One of its fundamental objectives is to allow the development within the Museum of the sometimes complex issues of contemporary society. [less ▲]

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See detailEntandrophragma cylindricum (Sprague) Sprague (Meliaceae), une espèce ligneuse concurrentielle en Afrique centrale (synthèse bibliographique)
Tabi Eckebil, Paule ULg; Verheggen, François ULg; Doucet, Jean-Louis ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment (2017), 21(1), 80-97

Introduction. De nos jours, la gestion des ressources forestières ne se focalise plus sur l’exploitation exclusive du bois d’oeuvre, mais prend également en considération les produits forestiers non ... [more ▼]

Introduction. De nos jours, la gestion des ressources forestières ne se focalise plus sur l’exploitation exclusive du bois d’oeuvre, mais prend également en considération les produits forestiers non ligneux. Entandrophragma cylindricum (Sprague) Sprague, de son nom commercial « sapelli/sapele », de la famille des Meliaceae, illustre parfaitement cette situation. Le présent article fait un état de l’art des connaissances concernant E. cylindricum et présente quelques informations sur la chenille qui lui est inféodée. Littérature. Le sapelli est une des espèces ligneuses les plus exploitées d’Afrique centrale pour son bois d’oeuvre. Il est répandu dans la forêt dense humide semi-caducifoliée du domaine guinéo-congolais. C’est une espèce semi-héliophile, son mode de dispersion est anémochore et sa phénologie est régulière. Selon la sylviculture appliquée, sa croissance en diamètre peut atteindre jusque 0,82 cm par an. Cette essence est également l’hôte d’une espèce de chenille comestible riche en protéines, I. oyemensis Rougeot. Fortement appréciée par les populations locales, cette chenille fait également l’objet d’un commerce régional et international. Enfin, l’écorce du sapelli est reconnue pour son intérêt ethnobotanique, particulièrement en médecine traditionnelle. Conclusions. Les informations tirées de la littérature ont permis de mettre en évidence certaines lacunes relatives à l’écologie et au mode de reproduction de cette espèce et, ceci, en dépit de son importance pour le commerce du bois. De plus, les inconnues quant à la productivité et la saisonnalité des chenilles d’Imbrasia oyemensis sur cet arbre nécessitent de développer des recherches complémentaires pour garantir la durabilité de l’exploitation simultanée de la ressource ligneuse et non ligneuse et pour proposer des modes de gestion concertés entre exploitants industriels et populations locales. [less ▲]

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See detailFlux penetration in a superconducting film partially capped with a conducting layer
Brisbois, Jérémy ULg; Gladilin, V. N.; Tempere, J. et al

in Physical Review B (2017), 95

The influence of a conducting layer on the magnetic flux penetration in a superconducting Nb film is studied by magneto-optical imaging. The metallic layer partially covering the superconductor provides ... [more ▼]

The influence of a conducting layer on the magnetic flux penetration in a superconducting Nb film is studied by magneto-optical imaging. The metallic layer partially covering the superconductor provides an additional velocity-dependent damping mechanism for the flux motion that helps protecting the superconducting state when thermomagnetic instabilities develop. If the flux advances with a velocity slower than w = 2/µ0σt, where σ is the cap layer conductivity and t is its thickness, the flux penetration remains unaffected, whereas for incoming flux moving faster than w, the metallic layer becomes an active screening shield. When the metallic layer is replaced by a perfect conductor, it is expected that the flux braking effect will occur for all flux velocities. We demonstrate this effect by investigating Nb samples with a thickness step. Some of the observed features, namely the deflection and the branching of the flux trajectories at the border of the thick centre, as well as the favoured flux penetration at the indentation, are reproduced by time-dependent Ginzburg-Landau simulations. [less ▲]

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See detailLiens entre mathématiques et jeux
Bair, Jacques ULg

E-print/Working paper (2017)

Le présent travail se compose de plusieurs parties. En premier lieu, nous définissons le concept général de jeu et présentons quelques mathématiciens célèbres, de toutes époques, qui étaient (ou sont ... [more ▼]

Le présent travail se compose de plusieurs parties. En premier lieu, nous définissons le concept général de jeu et présentons quelques mathématiciens célèbres, de toutes époques, qui étaient (ou sont encore) des adeptes de jeux mathématiques. Ensuite, nous établissons une typologie des jeux mathématiques. Une deuxième partie est consacrée à l’intervention des jeux dans l’enseignement des mathématiques. Nous donnons divers avantages des activités ludiques en classe, mais également des objections relatives à leur usage à des fins pédagogiques. Nous nous demandons aussi comment sélectionner un jeu pour des élèves et exhibons des exemples concrets de jeux exploitables en classe. Ce travail se termine par une bibliographie sur le sujet, ainsi que par une annexe composée de diapositives présentées lors d’un exposé réalisé à l’Université du Luxembourg dans le cadre de la Formation Pédagogique (FOPED) : nous y décrivons brièvement différentes épreuves ludiques proposées ces dernières années à des élèves de l’enseignement secondaire en France, Belgique et au Luxembourg. [less ▲]

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See detailLes éventrations parastomales: prévention et traitement
DETRY, Olivier ULg

Scientific conference (2017, February 24)

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See detailSeven temperate terrestrial planets around the nearby ultracool dwarf star
Gillon, Michaël ULg; Triaud, Amaury; Demory, Brice-Olivier et al

in Nature (2017), 542

One focus of modern astronomy is to detect temperate terrestrial exoplanets well-suited for atmospheric characterisation. A milestone was recently achieved with the detection of three Earth-sized planets ... [more ▼]

One focus of modern astronomy is to detect temperate terrestrial exoplanets well-suited for atmospheric characterisation. A milestone was recently achieved with the detection of three Earth-sized planets transiting (i.e. passing in front of) a star just 8% the mass of the Sun 12 parsecs away. Indeed, the transiting configuration of these planets combined with the Jupiter-like size of their host star - named TRAPPIST-1 - makes possible indepth studies of their atmospheric properties with current and future astronomical facilities. Here we report the results of an intensive photometric monitoring campaign of that star from the ground and with the Spitzer Space Telescope. Our observations reveal that at least seven planets with sizes and masses similar to the Earth revolve around TRAPPIST-1. The six inner planets form a near-resonant chain such that their orbital periods (1.51, 2.42, 4.04, 6.06, 9.21, 12.35 days) are near ratios of small integers. This architecture suggests that the planets formed farther from the star and migrated inward. The seven planets have equilibrium temperatures low enough to make possible liquid water on their surfaces. [less ▲]

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See detailL’imprimerie à Bruxelles sous les archiducs Albert et Isabelle (1598-1633)
Adam, Renaud ULg

Conference (2017, February 23)

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See detailL’impôt des sociétés dans une perspective internationale : entre concurrence et convergence
Richelle, Isabelle ULg

Scientific conference (2017, February 23)

Réformer l’imposition des sociétés implique de tenir compte de sa place dans le système fiscal. L’on songe à l’articulation avec l’impôt des personnes physiques, auquel sont soumis les entreprises ... [more ▼]

Réformer l’imposition des sociétés implique de tenir compte de sa place dans le système fiscal. L’on songe à l’articulation avec l’impôt des personnes physiques, auquel sont soumis les entreprises personnelles et les actionnaires individuels. Par ailleurs, est également abordée la question de l’efficacité des incitants fiscaux à l’Isoc, notamment en matière d’investissement, de recherche ou d’environnement. - Les mutations du cadre fiscal international réduisent fortement la marge de manœuvre du législateur belge. Les initiatives de l’OCDE (BEPS) et de l’Union européenne obligent la Belgique à repenser sa politique dite « de niches fiscales » et pourraient déboucher vers une plus forte convergence des systèmes fiscaux. En parallèle, il faut tenir compte des réformes mises en œuvre dans les autres Etats européens, qui eux aussi cherchent à s’adapter au nouveau contexte tout en restant compétitifs [less ▲]

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See detailComment le changement climatique influence-t-il la croissance du hêtre (Fagus sylvatica L.) le long du gradient bioclimatique de la Belgique ? Une approche dendroécologique.
Latte, Nicolas ULg

Doctoral thesis (2017)

Health anomalies (e.g., worsening crown conditions) on beech (Fagus sylvatica L.) observed throughout Europe since the 1990s have raised growing concerns among foresters, particularly about the future ... [more ▼]

Health anomalies (e.g., worsening crown conditions) on beech (Fagus sylvatica L.) observed throughout Europe since the 1990s have raised growing concerns among foresters, particularly about the future behavior of the species in the face of climate change. This PhD research examined the relationship between beech and its environment in the context of global changes using dendroecology, combination of dendrochronology and forest ecology. The radial growth was used to evaluate the effects of global changes, particularly climate change, on beech development and vitality over time along a bioclimatic gradient in Belgium. Various analyses were carried out using dendrochronological tools (pointer years, mean sensitivity, growth-climate correlation, etc.) and modeling approaches (linear and non-linear mixed models, partial least squares regression, etc.) considering several scales: tree, stand and region. Results show that climate predominantly influenced beech growth since the mid-20th century and did so rather uniformly across Belgium. Beech mean sensitivity increased mainly in response to the higher frequency and intensity of summer heat waves and spring droughts. Isolated but pronounced annual growth reductions induced a gradual diminution of mean growth. The increasing influence of climate progressively concealed the effect of local site growing conditions inducing strong between-sites synchronization along the bioclimatic gradient. Increasing mean sensitivity and decreasing mean growth were more pronounced in lowlands than in uplands, and for a given site, older trees are more affected than younger ones. Although mean sensitivity increases and mean growth decreases naturally with age, the climate change effect was much more important than the age effect. Furthermore, within a tree, along the main stem, climate sensitivity slightly decreased from breast height to crown base and strongly increased from crown base to tree top. These results were interpreted based on ecophysiological knowledge of beech. The influences of silviculture, soil compaction and nitrogen deposition (as part of atmospheric pollution) as well as the consequences of the past and future climate change on beech were discussed. Comparisons with other studies in Europe highlighted that beech is affected on a large part of its natural distribution range (except in high altitude and high latitude). Contrary to what one might think, beech is not only affected in the southern limit (Mediterranean). Although growing conditions are more favorable in Belgium, beech has also more to lose. Beech has coped with global change up to now. Although its climate sensitivity increased and its mean growth decreased, diebacks observed these last years in Belgium were scarce and generally scattered. However, considering the upcoming climate change, the phytosanitary risk will undeniable increased. Forest policy should now integrate that risk and prepare managers to anticipate and prevent it. [less ▲]

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