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See detailExtension of Lyman-alpha Complexes from HST Observations of Four Pairs of Quasars
Aracil, B.; Petitjean, P.; Smette, A. et al

in Combes, F.; Barret, D. (Eds.) SF2A-2002: Semaine de l'Astrophysique Francaise (2002, June 01)

We present HST observations of four pairs of quasars with 2,3 arcmin angular separation and redshift z 0.9. We apply the Nearest-Neighbor method to the sample of observed Lyman-alpha lines with rest ... [more ▼]

We present HST observations of four pairs of quasars with 2,3 arcmin angular separation and redshift z 0.9. We apply the Nearest-Neighbor method to the sample of observed Lyman-alpha lines with rest equivalent width greater than 0.3 Angstrum. According to Monte-Carlo simulations, we detect an excess of coincidences with velocity difference smaller than 500 km/s. [less ▲]

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See detailExtension of the component method to joints in tubular construction
Jaspart, Jean-Pierre ULg; Weynand, K.

in Puthli, R.; Herion, S. (Eds.) Proceedings of the Ninth International Symposium and Euroconference on Tubular Structures (2001)

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See detailExtension of the Direct Strength Method to hot-rolled and welded H profile cross-sections
Li, Yongzhen ULg

Doctoral thesis (2014)

The cross-sectional capacity is limited by material yielding on one hand and local buckling on the other hand. Most current metallic structural design codes use the concept of section classification for ... [more ▼]

The cross-sectional capacity is limited by material yielding on one hand and local buckling on the other hand. Most current metallic structural design codes use the concept of section classification for determining the section capacity of hot-rolled profiles. In this system, there exists a discontinuity between the classes 2 and 3 under pure bending load condition, while for the class 4, the effective width method (EWM) must be used to account for local buckling phenomenon. With the appearance of the more complex cross-sections, especially for thin-walled steel structures, the calculation using EWM becomes more and more intolerable and complicated. In order to overcome these difficulties when evaluating the cross-section strength, the alternative Direct Strength Method (DSM) approach, developed only for cold-formed thin-walled members, has gained importance over the last few years, and has been adopted by the North American and Australian standards for the design of cold-formed steel structural members recently. This thesis investigates the possibility to extend the DSM method to hot-rolled and welded structural steel members, and the objective is to derive a new formulation that would cover the whole field of section slenderness without section classification system used in Eurocode 3, using the same procedure for the DSM developed for cold-formed thin-walled steel structural members. Hot-rolled and welded H sections are mainly considered in this thesis. The DSM is premised on the assumption that the strength can be predicted from the yield strength to the elastic critical load ratio used in conjunction with a strength curve; i.e. the same concept than the one used in Eurocode 3, in terms of member buckling phenomenon. In the DSM approach applied for cold-formed thin-walled sections, local buckling and distortional buckling modes should be considered. For common hot-rolled or welded sections, only local buckling needs to be considered since distortional buckling does not occur for these sections. All available test results in literature are collected and evaluated with the current methods for calculating the cross-section resistance such as EWM, DSM, and the recent Continuous Strength Method (CSM). A short comparison is made and their domains of applicability are commented. A consistent approach has been adopted to develop numerical models for hot-rolled and welded sections subjected to compression and bending respectively. The FE model was built in FineLg and verified against test results of the “Semi-comp: Plastic member capacity of semi-compact steel sections - a more economic design” project, which was carried out earlier with the objective of improving the utilization of plasticity in rolled and welded sections with medium cross-section slenderness. Measured material and geometric properties, initial geometrical imperfections and residual stresses distributions have been highlighted. Once verified against the test results, the FE models have been used to carry out a parametrical study aimed at providing more FE results and highlighting the local buckling interaction between the webs and the flanges. All the experimental and FE numerical results constitute data base for the derivation of the new DSM curves. On the basis of Winter Formula for plate buckling and the generic DSM strength curve, different formulas are proposed for hot-rolled and welded H cross-sections under axial and bending load respectively. Also the statistical evaluation and safety study is conducted to obtain the safety factor γ_M, which is required for practical design. [less ▲]

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See detailExtension of the Direct strength method to hot-rolled profiles cross-sections
Li, Yongzhen ULg; Rossi, Barbara ULg; Jaspart, Jean-Pierre ULg

in 6th European Conference on Steel and Composite Structures : Eurosteel 2011, Budapest 30 October - 2 September 2011 (2011, September)

Current metallic structural design codes use the concept of section classification for determining the section capacity of hot-rolled profiles. In this system, there exists a discontinuity between the ... [more ▼]

Current metallic structural design codes use the concept of section classification for determining the section capacity of hot-rolled profiles. In this system, there exists a discontinuity between the classes 2 and 3, while for the class 4, the effective width method (EWM) must be used to account for local buckling phenomenon. In order to overcome the complicate and time consuming EWM for evaluating the strength, the alternative Direct Strength Method (DSM) approach, developed only for cold-formed thin-walled members, has gained importance over the last few years. The DSM is premised on the assumption that the strength can be predicted from the yield strength to the elastic critical load ratio in conjunction with a strength curve. The DSM has been advanced for calculating the strength of compression members over the past decades and in this paper, the extension of DSM to hot-rolled profiles cross-sections is investigated. Firstly, the methods for calculating the cross-section resistance such as EWM, DSM, and the recent Continuous Strength Method (CSM) are reviewed; a short comparison is made and their domains of applicability are commented. Secondly, a numerical model carried out in the frame of this research is described. The model was built in ABAQUS and verified against test results of the “Semi-comp: Plastic member capacity of semi-compact steel sections - a more economic design” project, which was carried out earlier with the objective of improving the utilization of plasticity in rolled and welded sections with medium cross-section slenderness. On the basis of these premises, the final goal of the project is detailed: to derive a new formulation that would cover the whole field of section slenderness (present class 1 to class 4), which can be seen as an extension of the so-called DSM approach. [less ▲]

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See detailExtension of the Direct strength method to hot-rolled profiles cross-sections
Rossi, Barbara ULg

Conference (2011, September)

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See detailExtension of the DSM to welded H profile cross-sections
Rossi, Barbara ULg; Li, Yongzhen ULg

in Research and Applications in Structural Engineering, Mechanics and Computation (2013)

The objective of the paper is to assess the accuracy of current Direct Strength Method (DSM) equations applied to steel structural welded H shapes in axial compression. Commercialised hot-rolled H ... [more ▼]

The objective of the paper is to assess the accuracy of current Direct Strength Method (DSM) equations applied to steel structural welded H shapes in axial compression. Commercialised hot-rolled H sections covering IPE, HE, HD, HL, HP, W and UB profiles and made of three grades (235MPa, 355MPa and 460MPa) were treated in (Li & Rossi 2012). This analysis focuses on welded sections made of the same three grades, including sections characterized by local buckling with a significant post-buckling reserve. The finite element model is described. Then, the results of a parametric analysis using the finite element model are re-ported. The codified resistances are also compared to the numerical results. For each cross-section, the recently developed analytical expressions provided in (Seif & Schafer 2010) for hot-rolled profiles are used to cal-culate the elastic cross-section local buckling stress. A comparison with CUFSM results is also reported. Then, the possibility to use the concept of DSM for the design of structural welded steel shapes is discussed. [less ▲]

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See detailExtension of the experiment of J.H.C. Smith on the onset of oxygen evolution in etiolated leaves
Franck, Fabrice ULg; Sironval, Cyrille; Schmid, G.H.

in Brouers, Michel; Sironval, Cyrille (Eds.) Protochlorophyllide Reduction and Greening (1984)

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See detailExtension of the Gurson model for the LAGAMINE code
Guzmán Inostroza, Carlos Felipe ULg

Report (2014)

Damage and fracture modeling deals with material softening and strain localization, which usu- ally leads to unwanted numerical features like loss of ellipticity of equilibrium equations, bifurcation into ... [more ▼]

Damage and fracture modeling deals with material softening and strain localization, which usu- ally leads to unwanted numerical features like loss of ellipticity of equilibrium equations, bifurcation into a shear band, etc. A first step before dealing with these problems is to have already a stable, accurate integration scheme for the damage model. Here, the numerical integration of an extended version of the Gurson model (comprising plastic anisotropy and mixed isotropic-kinematic hardening) proposed by Ben Bettaieb et al. (2011b), is revisited and further extended to include nucleation, coalescence and shear. The main feature of this scheme is that all the variables are integrated in an implicit way based on the projection algorithm, while the consistent tangent matrix is obtained analytically. A detailed derivation of the equations used to extend the model is presented and a link with the developed subroutine is made. The efficiency of the implementation is assessed by comparing the numerical results from homogeneous cases from those taken from the literature. The results are in good agreement, hence implying that the model can be used in more complex simulations involving heterogeneous strain paths. [less ▲]

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See detailThe extension of the INCL model for simulation of shielding in space
Pedoux, Sophie ULg; Cugnon, Joseph ULg; Mancusi, Davide ULg et al

in Advances in Space Research (2011), 48(2), 383-389

Radiation hazard for space missions is mainly due to cosmic ray protons, helium nuclei and light ions, whose energy spectrum is maximum around 1 GeV per nucleon but remains non-negligible for energies up ... [more ▼]

Radiation hazard for space missions is mainly due to cosmic ray protons, helium nuclei and light ions, whose energy spectrum is maximum around 1 GeV per nucleon but remains non-negligible for energies up to 15 GeV per nucleon. Nuclear reactions induced by high energy protons are often described by intranuclear cascade plus evaporation models. The attention is focused here on the Liège Intranuclear Cascade model (INCL), which has been shown to reproduce fairly well a great deal of experimental data for nucleon-induced reactions in the 200 MeV to 2 GeV range, when coupled with the ABLA evaporation-fission code. In order to extend the model to other conditions relevant for space radiation, three improvements of INCL are under development. They are reported on here. First, the reaction model has been extended to nucleon-nucleus reactions at incident energies up to 15 GeV, mainly by the inclusion of additional pion production channels in nucleon-nucleon collisions during the cascade. Second, a coalescence mechanism for the emission of light charged particles has been implemented recently. Finally, the model has been modified in order to accommodate light ions as projectiles. First results are shown and compared with illustrative experimental data. Implications for issues concerning radiation protection in space are discussed. [less ▲]

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See detailExtension of the Liège Intra Nuclear Cascade model to light ion-induced collisions for medical and space applications
Leray, S.; Mancusi, D.; Kaitaniemi, P. et al

in Journal of Physics: Conference Series (2013), 420

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See detailExtension of the Liège Intranuclear Cascade Model to the 2-15 GeV Incident Energy Range
Pedoux, Sophie ULg

Doctoral thesis (2011)

The Liège Intra-Nuclear Cascade model (INCL4) has been shown to be quite successful for the description of spallation reactions. However its validity domain is limited to an upper incident energy of ~2 ... [more ▼]

The Liège Intra-Nuclear Cascade model (INCL4) has been shown to be quite successful for the description of spallation reactions. However its validity domain is limited to an upper incident energy of ~2 GeV, because inelastic elementary processes are restricted to the excitation and de-excitation of the Delta resonance. In this thesis, the INCL4 model is extended to higher incident energy. This is realised by including other inelastic elementary collisions, direct multipion production in elementary nucleon-nucleon and pion-nucleon collisions. This is somehow opposite to the usual extension to high energy of such models, as it is usually realised by including excitation of heavier baryonic resonances. Experimental data and isospin symmetry have been exploited in the implementation of multipion channels, but we could not avoid to introduce specific models for the energy-momentum and charge repartition on the final pions. The predictions of the modified model for production of protons, neutrons and charged pions by proton and pion beams off nuclei are compared with experimental data. A short study on nuclear fragmentation is also presented. [less ▲]

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See detailExtension of the long-term total column time series of atmospheric methane above the Jungfraujoch station: analysis of grating infrared spectra between 1976 and 1989
Bader, Whitney ULg; Lejeune, Bernard ULg; Demoulin, Philippe ULg et al

in Geophysical Research Abstracts (2011), 13

Methane (CH4) is one of the most abundant greenhouse gases in the Earth’s atmosphere, with current mean volume mixing ratio close to 1800 ppb. Since methane has a global warming potential of 25 (100-yr ... [more ▼]

Methane (CH4) is one of the most abundant greenhouse gases in the Earth’s atmosphere, with current mean volume mixing ratio close to 1800 ppb. Since methane has a global warming potential of 25 (100-yr horizon) and an atmospheric lifetime of 12 years, the Kyoto Protocol has included it among the species to be regulated to limit global warming. Anthropogenic sources of methane are mainly energy production (coal and leaks) and agriculture while main natural sources are swamps and biomass waste. The main sink of methane is oxidation in the troposphere, primarily by reaction with the hydroxyl radical. Methane trends have exhibited significant changes during the last twenty-five years. For instance, long-term monitoring of its vertical total column above the high-altitude station of the Jungfraujoch (46.5°N, 8°E, 3580 m asl) has indeed allowed to derive column changes ranging from +0.72% in 1987-1988 to +0.14% in 1999-2000 (Zander et al., 2002), relative to 1988 and 2000, respectively. More recently and for the same site, Duchatelet et al. (2010) have even reported a significant slowdown of -0.02%/yr between years 2000 and 2005. This study also showed that since then, CH4 is on the rise again, at a rate close to +0.30%/yr. While the numbers reported here above have been derived from the Fourier Transform Infrared (FTIR) data set starting in 1984, earlier pioneering observations have been collected at the Jungfraujoch since 1950, using grating spectrometers. During the 1958-1975 period, the main objectives has been the study of the solar photosphere in the visible and the near infrared and the publication of high-resolution solar atlases. From 1976 to 1989, narrow-band IR solar absorption observations achieving a spectral resolution of about 0.02 cm-1 have been recorded with the high-performance double-pass grating spectrometer. Analysis of these historical spectra provides a unique opportunity to extend the Jungfraujoch’s total column time series of important atmospheric gases, including methane, by nearly 10 years. The aim of this contribution is to present the inversion strategy adopted to derive CH4 from the grating spectra, using the SFIT-2 algorithm (v3.91) We will evaluate the impact of resolution, spectroscopic parameters (from the EU HYMN project -see www.knmi.nl/samen/hymn-, and from HITRAN 2004), atmospheric pressure and temperature profiles on the error budget. The 1976-1989 total column time series produced will be presented and critically discussed. In particular, we will identify and correct for possible biases between double-pass grating spectrometer measurements and more recent FTIR total columns. The harmonized and consolidated time series will be investigated to characterize the long-term trend of methane for the 1976-2010 time period. Comparisons with synthetic data produced by the CHASER 3-dimensional chemical transport model will also be presented and analyzed. [less ▲]

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See detailExtension of the Marchenko equation to non-Hermitian differential systems
Coz, Marcel; Rochus, Pierre ULg

in Annals of Physics (1980), 126(2), 460-499

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See detailAn extension of the radial return algorithm to account for rate-dependent effects in frictional contact and visco-plasticity
Ponthot, Jean-Philippe ULg

in Journal of Materials Processing Technology (1998), 80-1

This paper deals with unified elasto-plastic and elastic-visco-plastic constitutive equations for metals submitted to large deformations. We present here a newly developed time integration algorithm which ... [more ▼]

This paper deals with unified elasto-plastic and elastic-visco-plastic constitutive equations for metals submitted to large deformations. We present here a newly developed time integration algorithm which is an extension to the visco-plastic range of the classical radial return algorithm for plasticity. The resulting implicit algorithm is both efficient and very inexpensive. This algorithm is also subsequently extended to frictional problems where it allows a generalisation of the classical Coulomb dry friction criterion to a criterion depending on the relative slip velocity such as those encountered in the hydrodynamic regime. (C) 1998 Elsevier Science S.A. All rights reserved. [less ▲]

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See detailAn Extension of the Radial Return Algorithm to Account for Visco- Plasticity and Rate-Dependent Effects in Frictional Contac
Ponthot, Jean-Philippe ULg

in Proceedings of "World Congress on Computational Mechanics IV" (1998)

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See detailAn extension of the Radial Return Scheme for Springback Similation in Sheet Metal Forming
GOHY, S.; Papeleux, Luc ULg; COLLARD, X. et al

in 6th ICTP-International Conference on Technology of Plasticity, Nuremberg (1999)

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See detailExtension of the Super-Elements Method to the Analysis of Oblique Collision Between Two Ships
Buldgen, Loïc ULg; Le Sourne, Hervé; Rigo, Philippe ULg

in Marine Structures (2012)

Extension of the Super-Elements Method to the Analysis of Oblique Collision Between Two Ships

Detailed reference viewed: 50 (8 ULg)