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See detailInstabilidade de vigas a altas temperaturas - Estudo numérico e experimental
Mesquita, L.; Piloto, P. A. G.; Vaz, M. A. P. et al

in Mecânica Experimental (2004), 10

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See detailInstabilité de Faraday à l'interface entre mousse et solution
Bronfort, Ariane ULg

Conference (2010, April 20)

Detailed reference viewed: 17 (5 ULg)
See detailInstabilité de l'épaule : faillite de la contention musculaire active ? Apport de l'évaluation isocinétique
Gremeaux, V.; Croisier, Jean-Louis ULg; Forthomme, Bénédicte ULg

in Codine, P.; Hérisson, C. (Eds.) Instabilité de l'épaule et médecine de rééducation (2007)

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See detailInstabilité glycémique et anticorps anti-insuline
Renard, E.; Radermecker, Régis ULg; Scheen, André ULg

in Médecine des Maladies Métaboliques (2008), 2(5), 531-535

L’instabilité glycémique est courante chez les malades traités par insuline et invalidante en raison des hypoglycémies répétées, soudaines, parfois sévères. Les formulations d’insuline actuelles sont ... [more ▼]

L’instabilité glycémique est courante chez les malades traités par insuline et invalidante en raison des hypoglycémies répétées, soudaines, parfois sévères. Les formulations d’insuline actuelles sont moins immunogènes, mais ont une réactivité croisée avec les anticorps anti-insuline développés contre des insulines antérieures. Une résistance à l’insuline acquise inexplicable ou l’association d’hyperglycémies postprandiales et d’hypoglycémies nocturnes sans proportion avec l’insuline administrée sont suggestives de l’implication des anticorps anti-insuline, mais exceptionnelles en dehors de l’insulinothérapie intra-péritonéale. Vu la prédominance de la pratique inadéquate de l’insulinothérapie, l’hypothèse du rôle des anticorps anti-insuline dans l’instabilité glycémique doit être dûment documentée en hospitalisation avant de pouvoir être retenue. [less ▲]

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See detailL’instabilité lombaire fonctionnelle : revue de la littérature
Demoulin, Christophe ULg; Distree, Vincent ULg; Tomasella, Marco ULg et al

in Annales de Réadaptation et de Médecine Physique (2007), 50

Les patients lombalgiques présentant une instabilité lombaire semblent constituer un sous-groupe particulier. De nombreuses définitions de l’instabilité lombaire ont été proposées. L’instabilité ... [more ▼]

Les patients lombalgiques présentant une instabilité lombaire semblent constituer un sous-groupe particulier. De nombreuses définitions de l’instabilité lombaire ont été proposées. L’instabilité radiologique se distingue de l’instabilité fonctionnelle. Leur diagnostic demeure délicat : l’intérêt des clichés radiographiques statique et dynamique semble limité tandis que plusieurs signes et tests cliniques de l’instabilité ont été décrits dans la littérature mais demeurent controversés. Trois éléments composent le système de stabilisation fonctionnelle de la colonne : les sous-systèmes passif, actif et neuromusculaire qui sont interdépendants. L’intérêt de programmes de stabilisation lombaire pour les patients lombalgiques a été démontré. Les exercices de stabilisation lombaire visent une reprogrammation sensorimotrice des muscles stabilisateurs de la colonne afin d’améliorer leur potentiel, leur temps de réponse et ainsi compenser des déficits du système passif de stabilisation. Cet article souhaite définir le concept d’instabilité, préciser les moyens de son évaluation, appréhender les anomalies du système de stabilisation présentes chez les sujets lombalgiques, décrire les principaux exercices recommandés dans la littérature et enfin rapporter les bénéfices observés à la suite de programmes de stabilisation lombaire. [less ▲]

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See detailInstabilités de l'écoulement produisant le bruit de fente
Billon, Alexis ULg; Valeau, Vincent; Sakout, Anas

in Comptes Rendus Mécanique (2004), 332(7), 557-563

La nature des instabilités de l’écoulement régissant les sons auto-entretenus produits par l’impact d’un jet plan à faible nombre de Mach sur une plaque fendue, configuration dénommée bruit de fente, est ... [more ▼]

La nature des instabilités de l’écoulement régissant les sons auto-entretenus produits par l’impact d’un jet plan à faible nombre de Mach sur une plaque fendue, configuration dénommée bruit de fente, est identifiées expérimentalement. Pour un même nombre de Reynolds, les fréquences de l’instabilité naturelle de la couche de cisaillement et du mode de battement du jet libre délimitent les valeurs des fréquences d’émission mesurées. Les oscillations aux plus basses fréquences sont le résultat de l’amplification du mode de battement du jet et celles de plus hautes fréquences celui de l’amplification de l’instabilité de la couche de cisaillement. [less ▲]

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See detailInstabilities in Space and Laboratory Plasmas -- D. Melrose
Manfroid, Jean ULg

in Ciel et Terre (1987), 103

Not Available

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See detailInstability analysis of a horizontal evaporating binary liquid layer with transient reference profiles
Machrafi, Hatim ULg; Alexey, Rednikov; Colinet, Pierre et al

(2011)

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See detailInstability and Overshoots of Solutions For A Class of Homogeneous Hybrid Systems By Lyapunov-like Analysis
Forni, Fulvio ULg; Teel, Andrew

in 49th IEEE Conference on Decision and Control (cdc 2010) (2010)

For a class of homogeneous hybrid systems we present a generalization to the hybrid systems framework of Chetaev's theorem and we propose a set of Lyapunov-like conditions for studying instability of the ... [more ▼]

For a class of homogeneous hybrid systems we present a generalization to the hybrid systems framework of Chetaev's theorem and we propose a set of Lyapunov-like conditions for studying instability of the point x e = 0 and overshoots of solutions (namely when the norm of the solution vector x at some time instant exceeds the norm of the initial condition of x). Based on these results, we design a sum of squares algorithm that constructs a suitable Lyapunov-like function to fulfill such conditions. [less ▲]

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See detailInstability regimes and self-excited vibrations in deep drilling systems
Depouhon, Alexandre ULg; Detournay, Emmanuel

in Journal of Sound and Vibration (2013)

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See detailInstability strip for pre-main-sequence stars
Grigahcene, A.; Dupret, Marc-Antoine ULg; Garrido, R. et al

in Communications in Asteroseismology (2006), 147

We apply the Time Dependent Convection (TDC) treatment presented in Grigahcene et al. (2005) to the study of Pre-main sequence pulsating stars. The stabilization of the p-modes at the red edge of the ... [more ▼]

We apply the Time Dependent Convection (TDC) treatment presented in Grigahcene et al. (2005) to the study of Pre-main sequence pulsating stars. The stabilization of the p-modes at the red edge of the Instability Strip (IS) is obtained by our models. The theoretical IS obtained with Mixing Length (ML) parameter alpha=1.8 is compared to observations and a good agreement is obtained. [less ▲]

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See detailThe instability strip of ZZ Ceti white dwarfs and its extension to the extremely low mass pulsators
Van Grootel, Valérie ULg; Fontaine, Gilles; Brassard, Pierre et al

in Astronomical Society of the Pacific Conference Series (2013, December), 479

The determination of the location of the theoretical ZZ Ceti instability strip in the log g − Teff diagram has remained a challenge over the years, due to the lack of a suitable treatment for convection ... [more ▼]

The determination of the location of the theoretical ZZ Ceti instability strip in the log g − Teff diagram has remained a challenge over the years, due to the lack of a suitable treatment for convection in these stars. We report here a detailed stability survey over the whole ZZ Ceti regime, including the very low masses where three pulsators have recently been found. We computed to this aim 29 evolutionary sequences of DA models with various masses and chemical layering. These models are characterized by the so-called ML2/α=1.0 convective efficiency and take into account the important feedback effect of convection on the atmospheric structure. We pulsated these models with the Liege nonadiabatic pulsation code MAD, which is the only one to conveniently incorporate a full time-dependent convection treatment and, thus, provides the best available description of the blue edge of the instability strip. On the other hand, given the failure of all nonadiabatic codes to account properly for the red edge of the strip, including MAD, we tested the idea that the red edge is due to energy leakage through the atmosphere. Using this approach, we found that our theoretical ZZ Ceti instability strip accounts remarkably well for the boundaries of the empirical strip. [less ▲]

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See detailThe instability strip of ZZ Ceti white dwarfs I. Introduction of time-dependent convection
Van Grootel, Valérie ULg; Dupret, Marc-Antoine ULg; Fontaine, Gilles et al

in Astronomy and Astrophysics (2012), 539

Aims. The determination of the location of the theoretical ZZ Ceti instability strip in the log g − Teff diagram has remained a challenge over the years due to the lack of a suitable treatment for ... [more ▼]

Aims. The determination of the location of the theoretical ZZ Ceti instability strip in the log g − Teff diagram has remained a challenge over the years due to the lack of a suitable treatment for convection in these stars. For the first time, a full nonadiabatic approach including time-dependent convection is applied to ZZ Ceti pulsators, and we provide the appropriate details related to the inner work- ings of the driving mechanism at work. Methods. We used the nonadiabatic pulsation code MAD with a representative evolutionary sequence of a 0.6 M⊙ DA white dwarf. This sequence is made of state-of-the-art models that include a detailed modeling of the feedback of convection on the atmospheric structure. The assumed convective efficiency in these models is the so-called ML2/α = 1.0 version. We also carried out, for comparison purposes, nonadiabatic computations within the frozen convection approximation, as well as calculations based on models with standard grey atmospheres. Results. We find that pulsational driving in ZZ Ceti stars is concentrated at the base of the superficial H convection zone, but at depths, near the blue edge of the instability strip, somewhat larger than those obtained with the frozen convection approach. Despite the fact that this approach is formally invalid in such stars, particularly near the blue edge of the instability strip, the predicted boundaries are not dramatically different in both cases. The revised blue edge for a 0.6 M⊙ model is found to be around Teff = 11,970 K, some 240 K hotter than the value predicted within the frozen convection approximation, in rather good agreement with the empirical value. On the other hand, our predicted red edge temperature for the same stellar mass is only about 5600 K (80 K hotter than with the frozen convection approach), much lower than the observed value. Conclusions. We correctly understand the development of pulsational instabilities of a white dwarf as it cools at the blue edge of the ZZ Ceti instability strip. Our current implementation of time-dependent convection however still lacks important ingredients to fully account for the observed red edge of the strip. We will explore a number of possibilities in the future papers of this series. [less ▲]

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See detailThe Instability Strip of ZZ Ceti White Dwarfs
Van Grootel, Valérie ULg; Fontaine, G.; Brassard, P. et al

in Astronomical Society of the Pacific Conference Series (in press)

The determination of the location of the theoretical ZZ Ceti instability strip in the log g − Teff diagram has remained a challenge over the years, due to the lack of a suitable treatment for convection ... [more ▼]

The determination of the location of the theoretical ZZ Ceti instability strip in the log g − Teff diagram has remained a challenge over the years, due to the lack of a suitable treatment for convection in these stars. We report here a detailed stability survey over the whole ZZ Ceti regime, including the low and extremely low masses. We computed to this aim 29 evolutionary sequences of DA models with various masses, chemical layering, and core compositions. These models are characterized by the so- called ML2/α=1.0 convective efficiency and take into account the important feedback effect of convection on the atmospheric structure. We computed pulsation spectra for these models with the Liège nonadiabatic pulsation code MAD, which is the only one to conveniently incorporate a full time-dependent convection treatment and, thus, provides the best available description of the blue edge of the instability strip. On the other hand, given the failure of all nonadiabatic codes to account properly for the red edge of the strip, including MAD, we tested the idea that the red edge is due to energy leakage through the atmosphere. Using this approach, we found that our theoretical ZZ Ceti instability strip accounts remarkably well for the boundaries of the empirical strip. [less ▲]

Detailed reference viewed: 3 (1 ULg)