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See detailTowards an Improved Single-Frequency Ionospheric Correction: Focus on Mid-Latitudes
Bidaine, Benoît ULg; Warnant, René ULg

in 4th ESA Workshop on Satellite Navigation User Equipment Technologies NAVITEC (2008, December)

The modelling of the Total Electron Content (TEC) plays an important role in global satellite navigation systems (GNSS) accuracy, especially for single frequency receivers, the most common ones ... [more ▼]

The modelling of the Total Electron Content (TEC) plays an important role in global satellite navigation systems (GNSS) accuracy, especially for single frequency receivers, the most common ones constituting the mass market. For the latter and in the framework of Galileo, the NeQuick model has been chosen for correcting the ionospheric error contribution. It has been designed to calculate the electron density at a given point of the ionosphere according to the time conditions and the solar activity. This electron density can be integrated along the path from the receiver to the considered satellite to provide the TEC. For Galileo, a parameter Az (“effective ionisation level”) will be provided to the model as solar activity information and will be daily updated by the ground stations. In order to reach the ionosphere error correction level objective (70% or 20 TECu whichever is larger), the model itself as well as its use for Galileo are investigated. Different situations have to be considered: different latitude regions (space conditions), different hours, seasons and years (time conditions) and specific phenomena appearance (magnetic storms, Travelling Ionospheric Disturbances – TIDs). In addition the results can be compared to different data sets among which GPS slant or vertical TEC (sTEC or vTEC) measurements, Global Ionospheric Maps, ionosonde profiles, topside soundings but also other ionosphere models results such as IRI. In our comparison process, we take benefit of various ionosphere data from several European stations (Chilton in UK, Dourbes in Belgium, El Arenosillo and Roquetes in Spain, Pruhonice in Czech Republic) where ionosonde and GPS TEC data are available for different solar activity levels. These data allow us to study NeQuick representation of the ionosphere at mid-latitudes. We investigate the difference between GPS-derived vTEC and corresponding values from NeQuick for the latest years (between solar maximum in 2000 and minimum in 2007) in order to observe the temporal dependencies towards Universal Time, season and solar activity. On the one hand, we use ionosonde data to constrain the model so that we can concentrate on its formulation of the profile only. We especially highlight the improvements from the latest (second) version of NeQuick and show the critical importance of the topside formulation. On the other hand, we analyse the model residual errors for the same situations computing vTEC through the Galileo algorithm. [less ▲]

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See detailInternal dynamics from asteroseismology for two sdB pulsators in close binary systems
Van Grootel, Valérie ULg; Charpinet, Stéphane; Fontaine, Gilles et al

in Communications in Asteroseismology (2008, December), 157

Since their discovery eleven years ago, short-period pulsating sdB stars have proved their potential for quantitative asteroseismological studies. We have recently updated our astero- seismic diagnostic ... [more ▼]

Since their discovery eleven years ago, short-period pulsating sdB stars have proved their potential for quantitative asteroseismological studies. We have recently updated our astero- seismic diagnostic tools in order to incorporate the effects of stellar rotation on pulsations, assuming various internal rotation laws. It is possible, with these new tools, to determine the internal rotation profile of two short-period pulsating sdB stars residing in close binary systems, namely Feige 48 and PG 1336 -018. They exhibit orbital periods of 9.024 h and 2.424 h respectively, as measured from spectroscopy. For the two stars, we show that spin-orbit synchronism is reached from the surface down to ˜ 0.22 R∗ and 0.55 RxE2x88x97 , respectively. The rotation of deeper layers cannot be inferred with the type of modes p-modes observed in short-period pulsating sdB stars. These results can potentially provide new elements to test tidal friction theories, particularly the angular momentum transport, in close binary systems. [less ▲]

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See detailAn-Naïm, pour une réforme du droit musulman
Carlier, Jean-Yves ULg

in Revue Nouvelle (2008)

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See detailDevelopment of products for GNSS users at the Belgian Solar-Terrestrial Centre of Excellence
Warnant, René ULg; Lejeune, Sandrine; Stankov, Stanimir et al

Conference (2008, December)

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See detailSéparation de fait - Commentaire pratique. La sécurité sociale
Michiels, Olivier ULg

in Michiels, Olivier (Ed.) Séparation de fait - Commentaire pratique (2008)

L'auteur analyse les conséquences de la séparation de fait des époux sur les prestations de sécurité sociale

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See detailA decision problem for ultimately periodic sets in non-standard numeration systems
Charlier, Emilie ULg

Scientific conference (2008, December)

Given a linear numeration system U and a set X (include in N) such that repU(X) is recognized by a (deterministic) finite automaton. Is it decidable whether or not X is ultimately periodic, i.e., whether ... [more ▼]

Given a linear numeration system U and a set X (include in N) such that repU(X) is recognized by a (deterministic) finite automaton. Is it decidable whether or not X is ultimately periodic, i.e., whether or not X is a finite union of arithmetic progressions? Honkala showed that this problem turns out to be decidable for the usual b-ary numeration system (b greater than 2) defined by U_n = bU_{n-1} for n greater than 1 and U_0 = 1. In this work, we give a decision procedure for this problem for a large class of linear numeration systems. [less ▲]

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See detailNorme(s) linguistique(s) et représentations des enseignants. Aperçu du traitement des 'écarts' linguistiques au cours de français
El Karouni, Salima; Collès, Luc; Lucchini, Silvia ULg

in Enjeux : Revue de Formation Continuée et de Didactique du Français (2008), 73

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See detailControlled flow of smart powders
Lumay, Geoffroy ULg; Vandewalle, Nicolas ULg

in Physical Review E (2008), 78(6),

The flow properties of powders are mainly due to the interplay of cohesive forces and intergrain frictional forces. We have experimentally investigated a "smart granular system" for which the ... [more ▼]

The flow properties of powders are mainly due to the interplay of cohesive forces and intergrain frictional forces. We have experimentally investigated a "smart granular system" for which the interparticle cohesion can be tuned by a magnetic field B. We show that the rheological features of such a system can be controlled. Indeed, the granular flow can be controlled or even stopped by the magnetic field. Depending on the orientation of B, different dynamical regimes can be obtained like a "dry liquid state" forming conical droplets as well as a "layered soft state". Scaling lows are given for the flow rate outside a funnel as a function of B and for the stopping threshold of the flow as a function of the funnel output diameter D. From this analysis, it appears that the flowing properties are related to the dimensionality of the magnetic aggregates. [less ▲]

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See detailFrancophones et plurilingues : le rapport au français des Belges issus de l’immigration
Lucchini, Silvia ULg; Hambye, Philippe; Forlot, Gilles et al

in Français et Société (2008), 19

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See detailLe documentaire belge contemporain saisi par la pédagogie de la Shoah: Modus Operandi
Van Cauwenberge, Geneviève ULg

in Témoigner entre Histoire et Mémoire : Revue Pluridisciplinaire de la Fondation Auschwitz (2008), 101

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See detailUnderstanding Non-equilibrium Thermodynamics
Lebon, Georgy ULg; Jou, david; Casas-Vazquez, jose

Book (2008)

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See detailResearch and Education Activities in Electric Power Systems at the University of Liège
Wehenkel, Louis ULg; Ernst, Damien ULg; Rousseaux, Patricia ULg et al

in Revue E Tijdschrift (2008), (4), 54-59

This paper presents research and education activities of the power systems group of the Department of Electrical Engineering and Computer Science of the University of Liège. These activities cover power ... [more ▼]

This paper presents research and education activities of the power systems group of the Department of Electrical Engineering and Computer Science of the University of Liège. These activities cover power systems stability, security, reliability, and markets, within the contexts of expansion planning, operation planning and real-time operation and automatic control. The paper also reviews the international collaborations of the team. [less ▲]

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See detailNeonatal Osteopenia and Bone Mineralization
Rigo, Jacques ULg

in eNeonatal review (2008), 6(4),

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See detailArthrose et obésité : Modèles expérimentaux
Gabay, Odile; Hall, David; Berenbaum, Francis et al

in Revue du Rhumatisme (2008), 75(12), 1215-1219

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See detailA comparative study of cannibalism and predation in seven species of flour beetle
Alabi, Taofic ULg; MICHAUD, J. P.; ARNAUD, Ludovic et al

in Ecological Entomology (2008), 33(6), 716-726

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