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See detailOn the numerical modelling of shear banding around an excavation
Collin, Frédéric ULg; Lambarki, A.; Charlier, Robert ULg et al

Conference (2005)

For an underground storage of nuclear waste, it is necessary to minimize the excavation damage zone (EDZ) that could be a higher permeability zone. This paper deals with the FE modelling of the EDZ extent ... [more ▼]

For an underground storage of nuclear waste, it is necessary to minimize the excavation damage zone (EDZ) that could be a higher permeability zone. This paper deals with the FE modelling of the EDZ extent during tunnelling. A Drucker – Prager law with cohesion strain softening is used. Results show a shear banding around the excavation. Its extent and the tunnel convergence are highly dependent on the hydraulic boundary condition within the tunnel (imposed pore pressure – suction or unilateral flow condition). [less ▲]

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See detailOn the numerical simulation of sheet metal blanking process
Canales Cardenas, Cristian ULg; Bussetta, Philippe ULg; Habraken, Anne ULg et al

Conference (2014)

One of the most widely used cutting techniques in sheet metal forming processes for mass production is the blanking process. In this process, a metallic sheet is placed between a die and a blankholder ... [more ▼]

One of the most widely used cutting techniques in sheet metal forming processes for mass production is the blanking process. In this process, a metallic sheet is placed between a die and a blankholder, and is then cut by the action of a punch which moves downward. The quality of the final product is directly linked to the resulting shape of the cut edge. Due to the complexity of the separation step, the set-up of the blanking process in practice is often driven by empirical knowledge. Thus, an accurate numerical tool is extremely desirable to optimize the setting parameters of this technique and will lead to a better understanding of the entire process. The numerical approach must be able to deal with three main issues involved in blanking: large and localized deformation, friction and contact, and ductile fracture. Furthermore, due to requirements of mass production the punch velocity is normally high and the effects of the strain rate must also be considered. Several approaches have been developed in order to model this cutting process but its accuracy still presents some numerical challenges. [less ▲]

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See detailOn the O(1) Solution of Multiple-Scattering Problems
Geuzaine, Christophe ULg; Bruno, O.; Reitich, F.

in Proceedings of the 11th IEEE Conference on Electromagnetic Field Computation (CEFC'2004) (2004)

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See detailOn the O(1) Solution of Multiple-Scattering Problems
Geuzaine, Christophe ULg; Bruno, O.; Reitich, F.

in IEEE Transactions on Magnetics (2005), 41(5), 1488-1491

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See detailOn the observability of resonant structures in planetesimal disks due to planetary migration
Reche, R.; Beust, H.; Augereau, J.-C. et al

in Astronomy and Astrophysics (2008), 480

Context: The observed clumpy structures in debris disks are commonly interpreted as particles trapped in mean-motion resonances with an unseen exo-planet. Populating the resonances requires a migrating ... [more ▼]

Context: The observed clumpy structures in debris disks are commonly interpreted as particles trapped in mean-motion resonances with an unseen exo-planet. Populating the resonances requires a migrating process of either the particles (spiraling inward due to drag forces) or the planet (moving outward). Because the drag time-scale in resolved debris disks is generally long compared to the collisional time-scale, the planet migration scenario might be more likely, but this model has so far only been investigated for planets on circular orbits. Aims: We present a thorough study of the impact of a migrating planet on a planetesimal disk, by exploring a broad range of masses and eccentricities for the planet. We discuss the sensitivity of the structures generated in debris disks to the basic planet parameters. Methods: We perform many N-body numerical simulations, using the symplectic integrator SWIFT, taking into account the gravitational influence of the star and the planet on massless test particles. A constant migration rate is assumed for the planet. Results: The effect of planetary migration on the trapping of particles in mean motion resonances is found to be very sensitive to the initial eccentricity of the planet and of the planetesimals. A planetary eccentricity as low as 0.05 is enough to smear out all the resonant structures, except for the most massive planets. The planetesimals also initially have to be on orbits with a mean eccentricity of less than than 0.1 in order to keep the resonant clumps visible. Conclusions: This numerical work extends previous analytical studies and provides a collection of disk images that may help in interpreting the observations of structures in debris disks. Overall, it shows that stringent conditions must be fulfilled to obtain observable resonant structures in debris disks. Theoretical models of the origin of planetary migration will therefore have to explain how planetary systems remain in a suitable configuration to reproduce the observed structures. [less ▲]

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See detailOn the observability of the quark orbital angular momentum distribution
Courtoy, Aurore ULg; Goldstein, Gary R.; Hernandez, J. Osvaldo Gonzalez et al

in Physics Letters B (2014), 731(0), 141-147

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See detailOn the occurrence of (iso-)dolichantoside in Strychnos mellodora
Quarré, Marie-Noëlle; Tits, Monique ULg; Wauters, Jean-Noël ULg et al

Poster (1994, March)

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See detailOn the optimisation of the mechanical properties of two aluminium-alloyed multiphase TRIP-assisted steels
Mertens, Anne ULg; Jacques, Pascal J.; Harlet, Philippe et al

in De Cooman, Bruno C. (Ed.) Proccedings of the International Conference on TRIP-Aided High Strength Ferrous Alloys (2002, June)

Aluminium-alloyed multiphase TRIP-assisted steels have been recently developed, so as to get rid of the disdavantages related to the high silicon contents classically used so far in TRIP-assisted steels ... [more ▼]

Aluminium-alloyed multiphase TRIP-assisted steels have been recently developed, so as to get rid of the disdavantages related to the high silicon contents classically used so far in TRIP-assisted steels. It has been shown that aluminium has a stronger ferritising effect than silicon and that it is slightly less efficient as far as austenite retention is concerned. A careful selection of the aluminium content and of the processing conditions is thus of primary importance in order to optimise the mechanical properties. The present study aims at determining the optimal heat treatment conditions leading to enhanced mechanical properties for two low aluminium-alloyed grades containing with mass contents of 0.12% C, 1.5% Mn and 0.5% Al or 1.0% Al, respectively. The microstructures generated during the heat treatment were assessed using SEM, X-ray diffraction and Mössbauer spectrometry. The mechanical properties were evaluated by uniaxial tensilte testing and the strain-hardening behaviour was characterised by means of an incremental strain-hardening exponent. The relations between the observed microstructures and the mechanical properties were discussed and, as a consequence, the importance of a careful control of the isothermal bainitic holding was highlighted. [less ▲]

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See detailOn the origin and systematics of the northern African wood mouse (Apodemus sylvaticus) populations: a comparative study of mtDNA restriction patterns
Libois, Roland ULg; Michaux, Johan ULg; Ramalhinho, M. G. et al

in Canadian Journal of Zoology (2001), 79(8), 1503-1511

Conflicting hypotheses have been formulated regarding the origin of wood mouse (Apodemus sylvaticus) populations in northern Africa. In this study, the mtDNA restriction patterns of mice (n = 28 ... [more ▼]

Conflicting hypotheses have been formulated regarding the origin of wood mouse (Apodemus sylvaticus) populations in northern Africa. In this study, the mtDNA restriction patterns of mice (n = 28) collected in Tunisia and Morocco are compared with those of representatives from southern Europe (n = 102). The neighbour-joining tree confirms the existence of the three lineages previously found in the Mediterranean area: western, Tyrrhenian-Balkan, and Sicilian. The western group is isolated from the two others, with bootstrap values of 89 and 95%. Northern African patterns are included in the western group. Their variability is low, the same pattern being shared by five Tunisian and all Moroccan animals (n = 18), caught either in the north of the country (Cap Spartel) or in the south (Marrakech). This implies that northern African wood mouse populations have a southwestern European origin and that their presence in the region is probably recent, which corresponds to both paleontological data and the hypothesis of anthropogenic introduction. [less ▲]

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See detailOn the origin of bacterial resistance to penicillin: comparison of a beta-lactamase and a penicillin target
Kelly, Judith A.; Dideberg, Otto; Charlier, Paulette ULg et al

in Science (1986), 231

Structural data are now available for comparing a penicillin target enzyme, the D-alanyl-D-alanine-peptidase from Streptomyces R61, with a penicillin-hydrolyzing enzyme, the beta-lactamase from Bacillus ... [more ▼]

Structural data are now available for comparing a penicillin target enzyme, the D-alanyl-D-alanine-peptidase from Streptomyces R61, with a penicillin-hydrolyzing enzyme, the beta-lactamase from Bacillus licheniformis 749/C. Although the two enzymes have distinct catalytic properties and lack relatedness in their overall amino acid sequences except near the active-site serine, the significant similarity found by x-ray crystallography in the spatial arrangement of the elements of secondary structure provides strong support for earlier hypotheses that beta-lactamases arose from penicillin-sensitive D-alanyl-D-alanine-peptidases involved in bacterial wall peptidoglycan metabolism. [less ▲]

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See detailOn the origin of macroturbulence in hot stars
Aerts, C.; Puls, J.; Godart, Mélanie ULg et al

in Communications in Asteroseismology (2009), 158

Since the use of high-resolution high signal-to-noise spectroscopy in the study of massive stars, it became clear that an ad-hoc velocity field at the stellar surface, termed macroturbulence, is needed to ... [more ▼]

Since the use of high-resolution high signal-to-noise spectroscopy in the study of massive stars, it became clear that an ad-hoc velocity field at the stellar surface, termed macroturbulence, is needed to bring the observed shape of spectral lines into agreement with observations. We seek a physical explanation of this unknown broadening mechanism. We interprete the missing line broadening in terms of collective pulsational velocity broadening due to non-radial gravity-mode oscillations. We also point out that the rotational velocity can be seriously underestimated whenever the line profiles are fitted assuming a Gaussian macroturbulent velocity rather than an appropriate pulsational velocity expression. [less ▲]

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See detailOn the Origin of Model Relations among Transverse-Momentum Dependent Parton Distributions
Lorce, Cédric ULg; Pasquini, B.

in Physical Review. D, Particles, Fields, Gravitation, and Cosmology (2011), D84

Transverse-momentum dependent parton distributions (TMDs) are studied in the framework of quark models. In particular, quark-model relations among TMDs are reviewed, elucidating their physical origin in ... [more ▼]

Transverse-momentum dependent parton distributions (TMDs) are studied in the framework of quark models. In particular, quark-model relations among TMDs are reviewed, elucidating their physical origin in terms of the quark-spin structure in the nucleon. The formal aspects of the derivation of these relations are complemented with explicit examples, emphasizing how and to which extent the conditions which lead to relations among TMDs are implemented in different classes of quark models. [less ▲]

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See detailOn the origin of Planosols – the process of ferrolysis revisited
Van Ranst, Eric; Cornelis, Jean-Thomas ULg; Dumon, Mathijs et al

Conference (2010)

Abstract : Planosols have been recognized as a Major Soil Group right from the beginning in the legend of the FAO Soil Map of the World. Also in WRB system it maintained that position at Reference Soil ... [more ▼]

Abstract : Planosols have been recognized as a Major Soil Group right from the beginning in the legend of the FAO Soil Map of the World. Also in WRB system it maintained that position at Reference Soil Group level on the account that a major pedogenetic process, ferrolysis, is underlaying the severe stagnic properties that characterize this group. With the recent introduction of Stagnosols in WRB it appears that a serious overlap has been introduced at Reference Soil Group level. This paper aims to throw new light on the genesis of Planosols, drawing from new soil surveys conducted in the south-western Ethiopian highlands. The conclusion is that it is highly unlikely that ‘ferrolysis’ can be called in to explain the genesis of Planosols in the Ethiopian highlands. As Ethiopia is one of the mainstays of Planosols, it is suggested that WRB rethinks its strategy on soils with stagnic properties as there is room for rationalization. [less ▲]

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See detailOn the origin of Saturn's outer auroral emission
Grodent, Denis ULg; Radioti, Aikaterini ULg; Bonfond, Bertrand ULg et al

in Journal of Geophysical Research. Space Physics (2010), 115

Ultraviolet Hubble Space Telescope images reveal a faint but distinct auroral emission equatorward of the main ring of emission of Saturn's southern polar region. This outer auroral emission is only ... [more ▼]

Ultraviolet Hubble Space Telescope images reveal a faint but distinct auroral emission equatorward of the main ring of emission of Saturn's southern polar region. This outer auroral emission is only visible near the nightside limb for the strongly tilted viewing geometry achieved in January 2004. We model the limb-brightening amplification of this emission, and we show that the observations are compatible with an ∼7° wide emission ring approximately centered on the 67°S parallel. The 1.7 kR brightness of this emission requires an injected electron energy flux of ∼0.3 mW m[SUP]‑2[/SUP]. The outer auroral emission maps to a region of the equatorial plane between 4 and 11 R[SUB]S[/SUB]. We suggest that a population of suprathermal electrons observed by Cassini can provide more than the required energy flux without the need for field-aligned acceleration. This auroral UV emission may also be associated with energetic neutral oxygen and hydrogen atoms originating from the energetic protons and O[SUP]+[/SUP] of magnetosphere and/or with a secondary infrared auroral oval. [less ▲]

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See detailOn the origin of Saturn's polar auroral arcs
Radioti, Aikaterini ULg; Grodent, Denis ULg; Gérard, Jean-Claude ULg et al

Conference (2012, September 27)

Saturn’s main auroral emission similarly to Earth’s is suggested to be associated with the open-closed field line boundary. The polar auroral emissions at Saturn, emissions located poleward of the main ... [more ▼]

Saturn’s main auroral emission similarly to Earth’s is suggested to be associated with the open-closed field line boundary. The polar auroral emissions at Saturn, emissions located poleward of the main emission consist of several arc-like and spotty features. In this study we focus on the arc-like structures observed with the UVIS instrument onboard Cassini and we characterize them into three groups: ‘bending arcs’ arcs whose one end is connected to the main emision, ‘oval aligned arcs’ arcs oriented parallel to the main emission and ‘moving arcs’ arcs which move with time inside the main emission. We study their occurrence rate, location, size as well as their associated expansion or contraction of the main emission. Finally, we compare the auroral arcs at Saturn with those in the terrestrial aurora and we examine their relation to a combination of solar wind parameters such as northward IMF, strong IMF magnitude and high solar wind speed. [less ▲]

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See detailOn the origin of the 2-3 minutes quasi-periodicity in the Jovian magnetosphere
Bonfond, Bertrand ULg; Vogt, Marissa F.; Gérard, Jean-Claude ULg et al

Poster (2011, October 05)

Several kinds of periodicities have been observed at Jupiter since the first probes fly-by. However, pre- vious investigations mainly focused on the longer timescales, such as the 40 minutes (QP40) or the ... [more ▼]

Several kinds of periodicities have been observed at Jupiter since the first probes fly-by. However, pre- vious investigations mainly focused on the longer timescales, such as the 40 minutes (QP40) or the 2- 3 days quasi-periodicity. Here we describe the recent finding of the 2-3 minutes quasi-periodic occurrence of UV flares in the active region of the polar aurora. These observations are then compared to other measurements of such quasi-periodic behaviors in electron and magnetic field data and their probably common origin is discussed. [less ▲]

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See detailOn the origins of historical linguistics. Materials and proposals for the Italian case
Droixhe, Daniel ULg

in Gambarara, D.; Formigari, L. (Eds.) Historical roots of linguistics theories (1995)

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See detailOn the parameters of absorbing layers for shallow water models
Modave, Axel ULg; Deleersnijder, Eric; Delhez, Eric ULg

in Ocean Dynamics (2010), 60(1), 65-79

Absorbing/sponge layers used as boundary conditions for ocean/marine models are examined in the context of the shallow water equations with the aim to minimize the reflection of outgoing waves at the ... [more ▼]

Absorbing/sponge layers used as boundary conditions for ocean/marine models are examined in the context of the shallow water equations with the aim to minimize the reflection of outgoing waves at the boundary of the computationaldomain. The ptimization of the absorption coefficient is not an issue in continuous models, for the reflection coefficient of outgoing waves can then be made as small as we please by increasing the absorption coefficient. The optimization of the parameters of absorbing layers is therefore a purely discrete problem. A balance must be found between the efficient damping of outgoing waves and the limited spatial resolution with which the resulting spatial gradients must be described. Using a one-dimensional model as a test case, the performances of various spatial distributions of the absorption coefficient are compared. Two shifted hyperbolic distributions of the absorption coefficient are derived from theoretical considerations for a pure propagative and a pure advective problems. These distribution show good performances. Their free parameter has a well-defined interpretation and can therefore be determined on a physical basis. The properties of the two shifted hyperbolas are illustrated using the classical two-dimensional problems of the collapse of a Gaussianshaped mound of water and of its advection by a mean current. The good behavior of the resulting boundary scheme remains when a full non-linear dynamics is taken into account. [less ▲]

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