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See detailOn the behaviour of the bands of CH and CN in the spectrum of Delta Cephei
Swings, Polydore ULg

in Monthly Notices of the Royal Astronomical Society (1932), 92(2), 140-147

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See detailOn the behaviour of the bands of CH and CN in the spectrum of δ Cephei
Swings, Polydore ULg

in Monthly Notices of the Royal Astronomical Society (1931), 92

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See detailOn the behaviour of the residence time at the bottom of the mixed layer
Deleersnijder, Eric; Beckers, Jean-Marie ULg; Delhez, Eric ULg

in Environmental Fluid Mechanics (2006), 6(6), 541-547

To understand why the findings of Deleersnijder et al. [(2006), Environ Fluid Mech 6: 25-42]-the residence time in the mixed layer in not necessarily zero at the pycnocline-are consistent with those of ... [more ▼]

To understand why the findings of Deleersnijder et al. [(2006), Environ Fluid Mech 6: 25-42]-the residence time in the mixed layer in not necessarily zero at the pycnocline-are consistent with those of Delhez and Deleersnijder [(2006), Ocean Dyn 56:139-150]-the residence time in a control domain vanishes at the open boundaries of this control domain-, it is necessary to consider a control domain that includes part of the pycnocline, in which the eddy diffusivity is assumed to be zero. Then, depending on the behaviour of the eddy diffusivity near the bottom of the mixed layer, the residence time may be seen to exhibit a discontinuity at the interface between the mixed layer and the pycnocline. If such a discontinuity exists, the residence time is non-zero in the former and zero in the latter. This is illustrated by analytical solutions obtained under the assumption that the eddy diffusivity is constant in the mixed layer. [less ▲]

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See detailON THE BLUES
Sacré, Robert ULg

Scientific conference (1993, February)

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See detailOn the breakdown behavior of TCLUST clustering procedure
Ruwet, Christel ULg; Garcia-Escudero, Luis Angel; Gordaliza, Alfonso et al

in Test (2013), 22(3), 466-487

Clustering procedures allowing for general covariance structures of the obtained clusters need some constraints on the solutions. With this in mind, several proposals have been introduced in the ... [more ▼]

Clustering procedures allowing for general covariance structures of the obtained clusters need some constraints on the solutions. With this in mind, several proposals have been introduced in the literature. The TCLUST procedure works with a restriction on the "eigenvalues-ratio" of the clusters scatter matrices. In order to try to achieve robustness with respect to outliers, the procedure allows to trim off a proportion of the most outlying observations. The resistance to infinitesimal contamination of the TCLUST has already been studied. This paper aims to look at its resistance to a higher amount of contamination by means of the study of its breakdown behavior. The rather new concept of restricted breakdown point will demonstrate that the TCLUST procedure resists to a proportion of contamination equal to the trimming rate as soon as the data set is sufficiently "well clustered". [less ▲]

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See detailOn the Characteristics and Source Regions of Dayside Proton Precipitation
Chua, D. H.; Dymond, K. F.; Budzien, S. A. et al

Conference (2004, December 01)

The source regions of precipitating protons on the dayside and their dependence on solar wind conditions are studied using far-ultraviolet (FUV) spectral observations and imaging. The High-resolution ... [more ▼]

The source regions of precipitating protons on the dayside and their dependence on solar wind conditions are studied using far-ultraviolet (FUV) spectral observations and imaging. The High-resolution Ionospheric and Thermospheric Spectrograph (HITS) aboard the Advanced Research and Global Observation Satellite (ARGOS) observes Doppler-shifted H Lyman-α emissions from precipitating protons with a spectral resolution of 1.5 Angstroms. The shapes of these Doppler spectra are indicative of the energy and pitch angle distributions of the proton precipitation. Global images of H Lyman-α emissions obtained by the SI-12 instrument on the IMAGE spacecraft are examined to relate the spectral observations to the dayside morphology of the proton aurora. During periods of sustained southward interplanetary magnetic field (IMF), the dayside proton aurora spectra exhibit broad Doppler shifts and are similar to those observed on the nightside with inferred mean energies typical of plasma sheet protons of magnetospheric origin. Global images of proton aurorae under these conditions show continuous regions of H Lyman-α emissions across the dayside extending from the nightside. In contrast, during periods of northward or variable IMF, proton aurora emissions on the dayside often appear in an isolated spot in the noon to late afternoon MLT sector. The Doppler-spectra of the proton emissions in these regions are narrow, indicating precipitation with low mean energies and from a different origin than that observed in the southward IMF cases. These spectra may be indicative of magnetosheath protons that have direct access to the ionosphere through high-latitude dayside reconnection. This study further quantifies the characteristics of dayside proton precipitation under various states of the magnetosphere and highlights the importance of IMF orientation on the coupling between the high-latitude, dayside ionosphere and its plasma sources at higher altitudes. [less ▲]

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See detailOn the characterization of concrete surface roughness and its relation to adhesion in repair systems
Garbacz, Andrzej; Kostana, Katarzyna; Courard, Luc ULg

in Chaponski, J.; Chraponski; Cwajna, J. (Eds.) et al Stereology and Image Analysis (2005)

The aim of this work is the analysis of an effect of concrete surface geometry on adhesion of repair systems. Several types of surface preparation techniques are selected and analysed via different ... [more ▼]

The aim of this work is the analysis of an effect of concrete surface geometry on adhesion of repair systems. Several types of surface preparation techniques are selected and analysed via different systems: laser profilometry, mechanical profilometry, microscopy and "sand" patch test method. [less ▲]

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See detailOn the characterization of some terpenes from Renealmia alpinia Rott. (Maas) oleoresin.
Lognay, Georges ULg; Marlier, M.; Severin, M. et al

in Flavour and Fragrance Journal (1991), 6(1),

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See detailOn the charge transfer pathway in the Merocyanine 540 triplet state quenching by nitroxyl radical
Hoebeke, Maryse ULg; Van de Vorst, A.

in Photochemistry & Photobiology (1995), 61

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See detailOn the circular polarisation of light from axion-photon mixing
Payez, Alexandre ULg; Cudell, Jean-René ULg; Hutsemekers, Damien ULg

in Alimi, Jean-Michel; Füzfa, André (Eds.) INVISIBLE UNIVERSE: Proceedings of the Conference. AIP Conference Proceedings 1241. (2010)

From the analysis of measurements of the linear polarisation of visible light coming from quasars, the existence of large-scale coherent orientations of quasar polarisation vectors in some regions of the ... [more ▼]

From the analysis of measurements of the linear polarisation of visible light coming from quasars, the existence of large-scale coherent orientations of quasar polarisation vectors in some regions of the sky has been reported. Here, we show that this can be explained by the mixing of the incoming photons with nearly massless pseudoscalar (axion-like) particles in extragalactic magnetic fields. We present a new treatment in terms of wave packets and discuss its implications for the circular polarisation. [less ▲]

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See detailOn the Classification of Leptons
Renson, Pierre ULg

in Physica (1961), 27

The formulae giving the electric charge and the neutrinonic charge in terms of T3 and S are generalized in order to apply them to leptons. There remains an unknown parameter. For a particular value of ... [more ▼]

The formulae giving the electric charge and the neutrinonic charge in terms of T3 and S are generalized in order to apply them to leptons. There remains an unknown parameter. For a particular value of this parameter these formulae assume the particularly symmetric forms (15) and (16). Values for S, T and T3 are assigned to the different leptons. At the time this investigation was carried out the following difficulty arose: in addition to the known leptons (neutrino, electron and muon) there remained a vacancy for an undisovered lepton, which, with regard to the charges, is similar to the neutrino. Yet this has no longer to be considered as a difficulty but well as a prediction of the theory since one was recently led to admit the existence of two neutral leptons instead of one, namely the neutrino. [less ▲]

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See detailOn the co-existence of chemically peculiar Bp stars, slowly pulsating B stars and constant B stars in the same part of the HR diagram
Briquet, Maryline ULg; Hubrig, S.; De Cat, P. et al

in Astronomy and Astrophysics (2007), 466

Aims: In order to better model massive B-type stars, we need to understand the physical processes taking place in slowly pulsating B (SPB) stars, chemically peculiar Bp stars, and non-pulsating normal B ... [more ▼]

Aims: In order to better model massive B-type stars, we need to understand the physical processes taking place in slowly pulsating B (SPB) stars, chemically peculiar Bp stars, and non-pulsating normal B stars co-existing in the same part of the H-R diagram. <BR />Methods: We carry out a comparative study between samples of confirmed and well-studied SPB stars and a sample of well-studied Bp stars with known periods and magnetic field strengths. We determine their evolutionary state using accurate HIPPARCOS parallaxes and Geneva photometry. We discuss the occurrence and strengths of magnetic fields as well as the occurrence of stellar pulsation among both groups. Further, we make a comparison of Geneva photometric variability for both kinds of stars. <BR />Results: The group of Bp stars is significantly younger than the group of SPB stars. Longitudinal magnetic fields in SPB stars are weaker than those of Bp stars, suggesting that the magnetic field strength is an important factor for B type stars to become chemically peculiar. The strongest magnetic fields appear in young Bp stars, indicating a magnetic field decay in stars at advanced ages. Rotation periods of Bp and pulsation periods of SPB stars are of the same order and the behaviour of Geneva photometric variability of some Bp stars cannot be distinguished from the variability of SPB stars, illustrating the difficulty to interpret the observed variability of the order of days for B-type stars. We consider the possibility that pulsation could be responsible for the variability among chemically peculiar stars. In particular, we show that a non-linear pulsation model is not excluded by photometry for the Bp star HD 175362. [less ▲]

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See detailOn the coherent drag-reducing and turbulence-enhancing behaviour of polymers in wall flows
Dubief, Yves; White, Christopher M.; Terrapon, Vincent ULg et al

in Journal of Fluid Mechanics (2004), 514

Numerical simulations of turbulent polymer solutions using the FENE-P model are used to characterize the action of polymers on turbulence in drag-reduced flows. The energetics of turbulence is ... [more ▼]

Numerical simulations of turbulent polymer solutions using the FENE-P model are used to characterize the action of polymers on turbulence in drag-reduced flows. The energetics of turbulence is investigated by correlating the work done by polymers on the flow with turbulent structures. Polymers are found to store and to release energy to the flow in a well-organized manner. The storage of energy occurs around near-wall vortices as has been anticipated for a long time. Quite unexpectedly, coherent release of energy is observed in the very near-wall region. Large fluctuations of polymer work are shown to re-energize decaying streamwise velocity fluctuations in highspeed streaks just above the viscous sublayer. These distinct behaviours are used to propose an autonomous regeneration cycle of polymer wall turbulence, in the spirit of Jimenez & Pinelli (1999). [less ▲]

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See detailOn the collapse behaviour of oil reservoir chalk
De Gennaro, Vincenzo; Delage, Pierre; Priol, Grégoire et al

in Geotechnique (2004), 54(6), 415-420

Oil exploitation in North Sea Ekofisk oilfield started in 1971, the reservoir is located in a 150 m thick layer of porous chalk (n = 40-50%) at a 3000 m depth. Enhanced oil recovery procedure by sea water ... [more ▼]

Oil exploitation in North Sea Ekofisk oilfield started in 1971, the reservoir is located in a 150 m thick layer of porous chalk (n = 40-50%) at a 3000 m depth. Enhanced oil recovery procedure by sea water injection (waterflooding) was initiated in 1987. Starting from this date, seabed subsidence due to chalk compaction evolves at a fairly constant rate (i.e. 40 cm/year). Nowadays, the decrease of the seafloor level is of about 10 m. Reservoir management and production strategies are at the origin of the growing interest of petroleum industry in disposing of a comprehensive description of the chalk mechanical behaviour. In this note the subsidence due to waterflooding is interpreted within a framework taken from the mechanics of unsaturated soils. By considering oil as the non-wetting fluid and water as the wetting fluid, chalk compaction is depicted as a collapse phenomenon due to oil-water suction decrease. A series of suction controlled tests in the osmotic oedometer cell are presented. Water weakening effects and chalk compaction (collapse) seem likely to occur through the lost of strength of the inter-granular links existing in the oil saturated sample. The nature of these links includes both capillary and physico-chemical fluids-chalk interactions, and is well characterised by the oil-water suction. [less ▲]

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See detailOn the combination of corpus-based and experimental methodologies in the study of causal, contrastive and metadiscourse connectives in L1 and L2 text comprehension and production
Perrez, Julien ULg; Degand, Liesbeth

in Archer, Dawn; Rayson, Paul; Wilson, Andrew (Eds.) et al Proceedings of the Corpus Linguistics 2003 Conference (2003)

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See detailOn the complementarity of contrastive linguistics and interlanguage studies
Rasier, Laurent ULg; Hiligsmann, Philippe

Conference (2008)

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See detailOn the concept of exposure time
Delhez, Eric ULg

in Continental Shelf Research (2013), 71

The concept of exposure time offers an interesting alternative to the residence time for the quantitative assessment of the water renewal of estuaries and semi-enclosed basins. It can cope with the ... [more ▼]

The concept of exposure time offers an interesting alternative to the residence time for the quantitative assessment of the water renewal of estuaries and semi-enclosed basins. It can cope with the oscillations or meandering of the flow around the boundary of the control domain and is therefore particularly suited for tidal seas and sub-basins with strong mesoscale activity. We show however that the exposure time in a control domain \omega cannot be properly defined if \omega is part of a larger bounded system unless some removal process is taken into account. It is therefore suggested to revise and extend the definition of the exposure time by including a first order decay : ``the exposure time for the rate constant \lambda is the total time spent in a control domain \omega by particles subject to a first order decay with a rate constant $\lambda$, irrespective of their possible excursions in and out the control domain''. The exposure time revised in this way is well-defined in all circumstances provided that the decay rate differs from zero but depends on the rate constant \lambda. Alternatively, in order to diagnose the movement of water masses, the first order decay can be considered only outside the control domain. [less ▲]

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See detailOn the concrete complexity of the successor function
Berthé, Valérie; Frougny, Christiane; Rigo, Michel ULg et al

Conference (2012, September 11)

We consider two kinds of questions about the successor function. The first one is concerned with the estimation of the length of the carry propagation when applying the successor map on the first n ... [more ▼]

We consider two kinds of questions about the successor function. The first one is concerned with the estimation of the length of the carry propagation when applying the successor map on the first n integers (or more generally on the first n elements in a given language). This leads to the notion of amortized (or average) carry propagation when applying the successor function. The second question is a computational issue: estimating the number of operations (in classical terms of Turing machines complexity) required to compute the representations of the first n integers from the first one by applying n times the successor function. This leads to the notion of (amortized) complexity, i.e., the average amount of computations required to obtain the successor of an element. [less ▲]

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See detailOn the constitutive equations of the chalk
Charlier, Robert ULg; Radu, Jean-Pol ULg

in ICONMIG'88 (1988)

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See detailOn the construction of automata from linear arithmetic constraints
Wolper, Pierre ULg; Boigelot, Bernard ULg

in Lecture Notes in Computer Science (2000, March), 1785

This paper presents an overview of algorithms for constructing automata from linear arithmetic constraints. It identifies one case in which the special structure of the automata that are constructed ... [more ▼]

This paper presents an overview of algorithms for constructing automata from linear arithmetic constraints. It identifies one case in which the special structure of the automata that are constructed allows a linear-time determinization procedure to be used. Furthermore, it shows through theoretical analysis and experiments that the special structure of the constructed automata does, in quite a general way, render the usual upper bounds on automata operations vastly overpessimistic. [less ▲]

Detailed reference viewed: 33 (6 ULg)