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See detailFrustrated symmetries in NHDM
Keus, Venus ULg

Speech (2010)

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See detailFrustrated symmetries in NHDM
Keus, Venus ULg

Speech (2010)

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See detailFT-IR measurement of tagitinin C after solvent extraction from Tithonia diversifolia
Ziemons, Eric ULg; Goffin, Eric ULg; Lejeune, Robert ULg et al

in Talanta (2004), 62(2), 383-387

Tagitinin C, an antiplasmodial compound, identified as one major compound of the subtropical medicinal plant, Tithonia diversifolia, was, determined by FT-IR spectroscopy method. The crude ether extracts ... [more ▼]

Tagitinin C, an antiplasmodial compound, identified as one major compound of the subtropical medicinal plant, Tithonia diversifolia, was, determined by FT-IR spectroscopy method. The crude ether extracts from aerial parts of the plant were evaporated to dryness and re-dissolved in tetrachloroethylene (C2Cl4) before analysis. The magnitude of the absorbance of the very specific C=O stretching vibration (v(c=o)) at 1664.8 cm(-1) was exploited in order to quantify tagitinin C. The determination coefficient (r(2)) of the calibration scale was 0.9994, the detection limit was lower than 3 mug ml(-1) and the quantification limit was lower than 10 mug ml(-1). Recovery values from 100.5 to 101.7% were found for spiked concentration levels from 19.91 to 89.95 mug ml(-1). The main characteristics of the curves obtained from the calibration standards and from the standard addition technique were not statistically different (Student t-test) suggesting that matrix effects were negligible. The results obtained for the determination of tagitinin C in the crude ether extract from aerial parts of T diversifolia by LC and FT-IR spectroscopic method agreed well: 0.76 +/- 0.02 and 0.773 +/- 0.009, of tagifinin C in dried plant respectively. (C) 2003 Elsevier B.V. All rights reserved. [less ▲]

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See detailFT-Raman Spectroscopy of Extant and Fossil Micro-Algae
Marshall, craig; Javaux, Emmanuelle ULg

Conference (2005)

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See detailFTIR characterisation of the chemical composition of Silurian miospores (cryptospores and trilete spores) from Gotland, Sweden
Steemans, Philippe ULg; Lepot, Kevin ULg; Marshall, Craig et al

in Review of Palaeobotany and Palynology (2010), 162

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See detailFTIR Observations at the Jungfraujoch Station for long-term monitoring of the Troposphere and Validation of the Space-based Sensors.
Mahieu, Emmanuel ULg; Zander, Rodolphe ULg; Demoulin, Philippe ULg et al

in Burrows, J.; Borrell, P. (Eds.) Measuring Tropospheric Trace Constituents from Space. (2007)

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See detailFTIR signal acquisition based on simultaneous analog sampling of the laser reference and IR detectors.
Servais, Christian ULg; Blavier, J. F.; Toon, G. C. et al

Scientific conference (2007)

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See detailLa fugue en institution
Born, Michel ULg

in Bulletin de l'Union Mondiale Pour la Sauvegarde de l'Enfance et de l'Adolescence (1978), 56

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See detailFuguer: ... pour fuir quoi ? Étude sur le profil et le vécu des fugueurs en Belgique
Van de Water, G.; Vettenburg, N.; Glowacz, Fabienne ULg

Book published by Ed. Fondation Roi Baudouin (2003)

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See detailFukuyama et Huntington. Du "clash of civilizations" à la "fin de l'histoire"
Brüll, Christoph ULg

Scientific conference (2011, May 04)

La conférence vise à interroger l'utilité de certaines théories politiques et historiques récentes pour le travail pratique de recherche de l'historien du temps présent.

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See detailA Full Discontinuous Galerkin Formulation Of Euler Bernoulli Beams In Linear Elasticity With Fractured Mechanic Applications
Becker, Gauthier ULg; Noels, Ludovic ULg

Conference (2010, July 21)

A full discontinuous Galerkin method is used to predict the fracture of beams thanks to insertion of an extrinsic cohesive element. In fact, The formulation developed originally by G. Wells etal. to ... [more ▼]

A full discontinuous Galerkin method is used to predict the fracture of beams thanks to insertion of an extrinsic cohesive element. In fact, The formulation developed originally by G. Wells etal. to guarantee weakly the high order derivatives of plates with only displacement field unknown and extended by L. Noels etal. for shells is derived for beam with full discontinuous elements. This new formulation can be advantageously combined, as shown first by J. Mergheim etal. , with an extrinsic cohesive approach as there is no need to modify dynamically the mesh, which is the major drawback of this approach. The pre-fractured stage is modeled by full discontinuous elements in a manner which is proved stable and consistent and the fracture is modeled by a cohesive law applied on stress resultant an stress couple defined by J.C. Simo etal. The suggested study produces two type of results. On one hand, it is shown analytically and verified by numerical examples that the presented framework has got the properties of consistency and convergence expected for a numerical scheme. On the other hand, it is proved by some test cases that the energy released during fracture process is equal to the fracture energy except in the case where the difference of internal energy between not fractured and fractured configurations is bigger than the fracture energy. In this case, the fracture occurs in one time step. The presented work proposed a novel interesting manner to take into account fracture in thin bodies. The verification made on the particularized case of beams suggested great perspectives for plates and shells which allow to simulate more complex problems. [less ▲]

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See detailFull discontinuous Galerkin formulation of shell in large deformations with fracture mechanic applications
Becker, Gauthier ULg; Noels, Ludovic ULg

in Hogge, Michel; Van Keer, Roger; Dick, Erik (Eds.) et al Proceedings of the 5th International Conference on Advanded COmputational Methods in Engineering (ACOMEN2011) (2011, November)

Different methods have been developed to model tearing prediction, as e.g., the combination between the cohesive principle and the finite element method. Unfortunately, this method has some well known ... [more ▼]

Different methods have been developed to model tearing prediction, as e.g., the combination between the cohesive principle and the finite element method. Unfortunately, this method has some well known issues that can be fixed by recourse to discontinuous Galerkin formulation. Such a formulation allows to insert very easily an extrinsic cohesive element at onset of fracture without any mesh modification. This promising technique has been recently developed by the authors for linear shell. Although promising numerical results were obtained, it is difficult to compare the method with experiments due to the large plastic deformation present in material before the fracture apparition. Thus, the method is extent herein to elasto-plastic finite deformations. The simulations of some benchmarks prove the ability of this new framework to model accurately the continuum part of the deformation and the crack propagation. [less ▲]

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See detailFull discontinuous Galerkin formulation of shells in large deformations with parallel and fracture mechanics applications
Becker, Gauthier ULg; Noels, Ludovic ULg

Conference (2012, July 11)

Fracture mechanical problems can be solved by coupling the finite elements with a cohesive approach. Unfortunately, the classical cohesive methods suffer from severe limitations. Indeed, on one hand, the ... [more ▼]

Fracture mechanical problems can be solved by coupling the finite elements with a cohesive approach. Unfortunately, the classical cohesive methods suffer from severe limitations. Indeed, on one hand, the intrinsic approach, which inserts the cohesive elements at the beginning, has to model the prefracture stage. This requires an initial slope in the traction separation law that should tend toward infinity to avoid lack of consistency leading to obvious numerical problems. On the other hand, the extrinsic cohesive method inserts the cohesive elements during the simulation when a fracture criterion is reached. This insertion requires topological mesh modifications and therefore a very complicated implementation, especially in a parallel code. To overcome these limitations, new methods were developed and in particular, an approach based on discontinuous Galerkin formulation (DG) has been pioneered by R. Radovitzky (Radovitzky cmame2011). The use of the DG principle allows to formulate the problem with discontinuous elements and the continuity between them is ensured weakly by terms integrated on the elements interface . These interface elements can be easily replaced by a cohesive element during the simulation. We have recently developed this approach for shells (Becker cmame2011) to obtain a full DG method. Moreover, a new cohesive law based on the reduced stresses of the thin bodies formulation is developed to propagate a fracture through the thickness. This cohesive model dissipates the right amount of energy during crack phenomena. These developments are implemented in parallel and validated by the study the blast of a notched cylinder, for which experimental and numerical (by XFEM method) data are reported in the literature by R. Larsson (Larsson ijnme2011). Finally, as thin structures are often made of ductile materials, which show large deformations before fracture, the formulation is extended to the non linear case with hyperelastic material law. This one can take into account the damage and a criterion based on the work of Huespe (Huespe plasticity2009) is developed to localize the damage leading to the apparition and propagation of cracks. [less ▲]

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See detailFull electrochemical synthesis of conducting polymer films chemically grafted to conducting surfaces
Labaye, David E; Jérôme, Christine ULg; Gueskin, V. M. et al

in Langmuir (2002), 18(13), 5222-5230

This paper reports on the full electrochemical synthesis of electrically conducting polymers chemically grafted to conducting surfaces (e.g., glassy carbon, stainless steel, nickel, gold). It is based on ... [more ▼]

This paper reports on the full electrochemical synthesis of electrically conducting polymers chemically grafted to conducting surfaces (e.g., glassy carbon, stainless steel, nickel, gold). It is based on new functional acrylate monomers, i.e., 3-(2-acryloyloxyethyl)thiophene and N-(2-acryloyloxyethyl)pyrrole, whose the synthesis is reported in this work. The polymerization process consists of two electrochemical steps. The first one is the cathodic electrografting of polyacrylate chains bearing a precursor of the conducting polymer in the ester group, either thiophene or pyrrole. In the second step, this precursor is polymerized under anodic polarization, in the presence or not of additional unsubstituted monomer in the electrochemical bath. Cyclic voltammetry was used to confirm that the two-component film is conducting and electrochemically active (reversible doping and dedoping). The chemical composition and the microscopic morphology of these composites were characterized by X-ray photoelectron spectroscopy and atomic force microscopy, respectively. [less ▲]

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See detailA full heteroscedastic one-way error components model: Pseudo-maximum likelihood estimation and specification testing
Lejeune, Bernard ULg

in Baltagi, Badi H. (Ed.) Panel Data Econometrics: Theoretical Contributions and Empirical Applications (2006)

This paper proposes an extension of the standard one-way error components model allowing for heteroscedasticity in both the individual-specific and the general error terms, as well as for unbalanced panel ... [more ▼]

This paper proposes an extension of the standard one-way error components model allowing for heteroscedasticity in both the individual-specific and the general error terms, as well as for unbalanced panel. On the grounds of its computational convenience, its potential efficiency, its robustness to non-normality and its robustness to possible misspecification of the assumed scedastic structure of the data, we argue for estimating this model by Gaussian pseudo-maximum likelihood of order two. Further, we review how, taking advantage of the powerful m-testing framework, the correct specification of the prominent aspects of the model may be tested. We survey potentially useful nested, non-nested, Hausman and information matrix type diagnostic tests of both the mean and the variance specification of the model. Finally, we illustrate the usefulness of our proposed model and estimation and diagnostic testing procedures through an empirical example. [less ▲]

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