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See detailOn the analysis of steel structures made of thin-walled members
Degée, Hervé ULg

in Proceedings of the EUROSTEEL '99 Conference (1999)

A first part of this paper consists in a review of the different existing methods, allowing to study the behaviour of members for which it is necessary to account for the deformability of the cross ... [more ▼]

A first part of this paper consists in a review of the different existing methods, allowing to study the behaviour of members for which it is necessary to account for the deformability of the cross section. A particular attention is paid to the capacity of each method to be used for the global analysis of a complete structure. A second part of the paper presents bases for the adaptation of a beam finite element so as to be able to account for the deformability of the profile cross section. [less ▲]

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See detailOn the analysis of steel structures made of thin-walled members
Degée, Hervé ULg

in Acta Polytechnica (1999), 39(5), 7-14

A first part of this paper consists in a review of the different existing methods, allowing to study the behaviour of members for which it is necessary to account for the deformability of the cross ... [more ▼]

A first part of this paper consists in a review of the different existing methods, allowing to study the behaviour of members for which it is necessary to account for the deformability of the cross section. A particular attention is paid to the capacity of each method to be used for the global analysis of a complete structure. A second part of the paper presents bases for the adaptation of a beam finite element so as to be able to account for the deformability of the profile crosse section. [less ▲]

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See detailOn the application and interpretation of Keeling plots in paleo climate research - Deciphering δ 13C of atmospheric CO 2 measured in ice cores
Köhler, Peter; Fischer, Hubertus; Schmitt, Jochen et al

in Biogeosciences (2006), 3(4), 539-556

The Keeling plot analysis is an interpretation method widely used in terrestrial carbon cycle research to quantify exchange processes of carbon between terrestrial reservoirs and the atmosphere. Here, we ... [more ▼]

The Keeling plot analysis is an interpretation method widely used in terrestrial carbon cycle research to quantify exchange processes of carbon between terrestrial reservoirs and the atmosphere. Here, we analyse measured data sets and artificial time series of the partial pressure of atmospheric carbon dioxide (pCO(2)) and of delta C-13 of CO2 over industrial and glacial/interglacial time scales and investigate to what extent the Keeling plot methodology can be applied to longer time scales. The artificial time series are simulation results of the global carbon cycle box model BICYCLE. The signals recorded in ice cores caused by abrupt terrestrial carbon uptake or release loose information due to air mixing in the firn before bubble enclosure and limited sampling frequency. Carbon uptake by the ocean cannot longer be neglected for less abrupt changes as occurring during glacial cycles. We introduce an equation for the calculation of long-term changes in the isotopic signature of atmospheric CO2 caused by an injection of terrestrial carbon to the atmosphere, in which the ocean is introduced as third reservoir. This is a paleo extension of the two reservoir mass balance equations of the Keeling plot approach. It gives an explanation for the bias between the isotopic signature of the terrestrial release and the signature deduced with the Keeling plot approach for long-term processes, in which the oceanic reservoir cannot be neglected. These deduced isotopic signatures are similar (-8.6 parts per thousand) for steady state analyses of long-term changes in the terrestrial and marine biosphere which both perturb the atmospheric carbon reservoir. They are more positive than the delta C-13 signals of the sources, e.g. the terrestrial carbon pools themselves (similar to -25 parts per thousand). A distinction of specific processes acting on the global carbon cycle from the Keeling plot approach is not straightforward. In general, processes related to biogenic fixation or release of carbon have lower y-intercepts in the Keeling plot than changes in physical processes, however in many case they are indistinguishable (e.g. ocean circulation from biogenic carbon fixation). [less ▲]

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See detailOn the appropriateness of marginal models for repeated measurements in clinical trials
Lindsey, James ULg; Lambert, Philippe ULg

in Statistics in Medicine (1998), 17

Although models developed directly to describe marginal distributions have become widespread in the analysis of repeated measurements, some of their disadvantages are not well enough known. These include ... [more ▼]

Although models developed directly to describe marginal distributions have become widespread in the analysis of repeated measurements, some of their disadvantages are not well enough known. These include producing profile curves that correspond to no possible individual, possibly showing that a treatment is superior on average when it is poorer for each individual subject, implicitly generating complex and implausible physiological explanations, including underdispersion in subgroups, and sometimes corresponding to no possible probabilistic data generating mechanism. We conclude that such marginal models may sometimes be appropriate for descriptive observational studies, such as sample surveys in epidemiology, but should only be used with great care in causal experimental settings, such as clinical trials. [less ▲]

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See detailOn the approximation of incompressible materials in the displacement method
Debongnie, Jean-François ULg

in International Journal for Numerical Methods in Engineering (1979), 14(7), 1095-1099

A mathematical description of the numerical approximation to incompressibility with nearly incompressible displacement finite elements is presented. By the way of functional analysis, it leads to a ... [more ▼]

A mathematical description of the numerical approximation to incompressibility with nearly incompressible displacement finite elements is presented. By the way of functional analysis, it leads to a condition of convergence to the incompressible problem when v is increased up to 0.5, which can be identified with Fried's K1 criterion. [less ▲]

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See detailOn the approximation of incompressible solids in the displacement method
Debongnie, Jean-François ULg

Report (1976)

A mathematical analysis of the numerical approximation to incompressibility with nearly incompressible displacement finite elements is presented. It explains why, as observed by many authors, convergence ... [more ▼]

A mathematical analysis of the numerical approximation to incompressibility with nearly incompressible displacement finite elements is presented. It explains why, as observed by many authors, convergence to the incompressible solution is not necessarily obtained when Poisson's ration is increased up to 0.5. It also allows predicting under which conditions convergence of the nearly incompressible approach is guaranteed. [less ▲]

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See detailOn the Assessment of a Modified Diffusion-Wave Approximation Model in the Framework of Overland Flow
Paulus, Raphaël ULg; Archambeau, Pierre ULg; Erpicum, Sébastien ULg et al

in Chanson, Hubert (Ed.) Balance and Uncertainty: Water in a Changing World (2011)

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See detailOn the asymptotic standard error of a class of robust estimators of ability in dichotomous item response models
Magis, David ULg

in British Journal of Mathematical & Statistical Psychology (in press)

In item response theory, the classical estimators of ability are highly sensitive to response disturbances and can return strongly biased estimates of the true underlying ability level. Robust methods ... [more ▼]

In item response theory, the classical estimators of ability are highly sensitive to response disturbances and can return strongly biased estimates of the true underlying ability level. Robust methods were introduced to lessen the impact of such aberrant responses onto the estimation process. The computation of asymptotic (i.e., large sample) standard errors (ASE) for these robust estimators, however, has not been fully considered yet. This paper focuses on a broad class of robust ability estimators, defined by an appropriate selection of the weight function and the residual measure, for which the ASE is derived from the theory of estimating equations. The maximum likelihood (ML) and the robust estimators, together with their estimated ASE, are then compared through a simulation study. It is concluded that both the estimators and their ASE perform similarly in absence of response disturbances, while the robust estimator and its estimated ASE are less biased and outperform their ML counterparts in presence of response disturbances with large impact on the item response process. [less ▲]

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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),

Detailed reference viewed: 19 (2 ULg)
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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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