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See detailMultifractal analysis of the divergence of wavelet series
Esser, Céline ULg

Conference (2016, June 07)

In this talk, we study pointwise divergence properties of wavelet expansions of functions in a given Besov space. We obtain deterministic upper bounds for the Hausdorff dimensions of the sets of points ... [more ▼]

In this talk, we study pointwise divergence properties of wavelet expansions of functions in a given Besov space. We obtain deterministic upper bounds for the Hausdorff dimensions of the sets of points where a given rate of divergence is observed, and we show that these bounds are generically (in the sense of Baire's categories) optimal. This gives a complement to the works done by F. Bayart and Y. Heurteaux in the case of Fourier series and by J.M. Aubry. [less ▲]

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See detailUniversal amorphous-amorphous transition in GexSe100−x glasses under pressure
Yildirim, Can ULg; Micoulaut, Matthieu; Boolchand, Punit et al

in Scientific Reports (2016), 6

Pressure induced structural modifications in vitreous GexSe100−x (where 10 ≤ x ≤ 25) are investigated using X-ray absorption spectroscopy (XAS) along with supplementary X-ray diffraction (XRD) experiments ... [more ▼]

Pressure induced structural modifications in vitreous GexSe100−x (where 10 ≤ x ≤ 25) are investigated using X-ray absorption spectroscopy (XAS) along with supplementary X-ray diffraction (XRD) experiments and ab initio molecular dynamics (AIMD) simulations. Universal changes in distances and angle distributions are observed when scaled to reduced densities. All compositions are observed to remain amorphous under pressure values up to 42 GPa. The Ge-Se interatomic distances extracted from XAS data show a two-step response to the applied pressure; a gradual decrease followed by an increase at around 15–20 GPa, depending on the composition. This increase is attributed to the metallization event that can be traced with the red shift in Ge K edge energy which is also identified by the principal peak position of the structure factor. The densification mechanisms are studied in details by means of AIMD simulations and compared to the experimental results. The evolution of bond angle distributions, interatomic distances and coordination numbers are examined and lead to similar pressure-induced structural changes for any composition. [less ▲]

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See detailBoltzmann Transport Calculations in Systems with Electron-phonon Coupling
Pike, Nicholas ULg; Dewandre, Antoine ULg; Di Gennaro, Marco ULg et al

Scientific conference (2016, June 07)

Recent experimental and theoretical calculations point to a complex interplay between the electron and phonon baths in a wide variety of materials [1,2]. We propose a method of coupling the Boltzmann ... [more ▼]

Recent experimental and theoretical calculations point to a complex interplay between the electron and phonon baths in a wide variety of materials [1,2]. We propose a method of coupling the Boltzmann equations for the electron and phonon baths within the relaxation time approximation to describe the changes in the electron and phonon distributions and thus calculate the thermoelectric transport coefficients. Our model for the coupled system will include tight-binding and ${\bf k \cdot p}$ Hamiltonians for both the electron and phonon energies and analytic calculations for the electron and phonon relaxation mechanisms. From these calculations we hope to better understand the role and interplay of electron-phonon and phonon-phonon interactions on the thermoelectric transport coefficients. [1] - Phys. Rev. Lett. ${\bf 114}$, 115901 (2015). [2] - PNAS ${\bf 112}$, 14777-14782 (2015). [less ▲]

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See detailCohesive band model: a triaxiality-dependent cohesive model for damage to crack transition in a non-local implicit discontinuous Galerkin framework
Leclerc, Julien ULg; Wu, Ling ULg; Noels, Ludovic ULg et al

Conference (2016, June 07)

Numerical modelling of the complete ductile failure process is still a challenge. On the one hand, continuous approaches, described by damage models, succeed in the initial diffuse damage stage but are ... [more ▼]

Numerical modelling of the complete ductile failure process is still a challenge. On the one hand, continuous approaches, described by damage models, succeed in the initial diffuse damage stage but are still unable to represent physical discontinuities. On the other hand, discontinuous approaches, such as the cohesive zone models, are able to represent the crack propagation behaviour. They are suited for local damaging processes as crack initiation and propagation, and so, fail in diffuse damage prediction of ductile materials. Moreover, they do not usually capture triaxiality effects, mandatory for accurate ductile failure simulations. To describe the ductile failure process, the numerical scheme proposed here combines both approaches [1] in order to beneficiate from their respective advantages: a non-local damage model combined with an extrinsic cohesive law in a discontinuous Galerkin finite element framework. An application example of this scheme is shown on the attached figure. The initial diffuse damage stage is modelled by an implicit nonlocal damage model as suggested by [2]. Upon damage to crack transition, a cohesive band [3] is used to introduce in-plane stretch effects inside the cohesive law or in other words, a triaxiality-dependent behaviour. Indeed, these in-plane strains play an important role during the ductile failure process and have to be considered. Concretely, when crack appears in the last failure stage, all the damaging process is assumed to occur inside a thin band ahead of the crack surface. Thanks to the small but finite numerical band thickness, the strains inside this band can be obtained from the in-plane strains and from the cohesive jump. Then, the stress-state inside the band and the cohesive traction forces on the crack lips are deduced from the underlying continuum damage model. The band thickness is not a new material parameter but is computed to ensure the energetic consistency during the transition. [1] Wu L, Becker G, Noels L. Elastic damage to crack transition in a coupled non-local implicit discontinuous Galerkin/extrinsic cohesive law framework. Comput. Methods Appl. Mech. Eng. 279 (2014): 379–409 [2] Peerlings R., de Borst R., Brekelmans W., Ayyapureddi S. Gradient-enhanced damage for quasi-brittle materials, Int. J. for Num. Methods in Eng. 39 (1996): 3391-3403 [3] Remmers J. J. C., de Borst R., Verhoosel C. V., Needleman A. The cohesive band model: a cohesive surface formulation with stress triaxiality. Int. J. Fract. 181 (2013): 177–188 [less ▲]

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See detailDe l'avatar au personnage : regards croisés entre game studies et études littéraires
Dozo, Björn-Olav ULg; Delbouille, Julie ULg

Conference (2016, June 07)

Si les game studies se sont développées en prenant appui, dans un premier temps, sur les études littéraires et en particulier sur la narratologie (Ryan 2004, Atkins et Krzywinska 2007) pour interroger la ... [more ▼]

Si les game studies se sont développées en prenant appui, dans un premier temps, sur les études littéraires et en particulier sur la narratologie (Ryan 2004, Atkins et Krzywinska 2007) pour interroger la notion de récit appliquée au jeu vidéo, elles ont ensuite fait appel à d’autres disciplines (psychologie et sociologie en particulier) pour construire leur approche de certaines notions, dont celle d’avatar qui nous paraît utile dans le cadre de recherches sur le personnage en littérature. Confrontées à des objets irréductibles à leur textualité (l’étude de la composante « play » du jeu a pris le pas sur celle du « game », surtout en francophonie – voir à ce sujet Triclot, 2011), les game studies se sont dotées d’outils et de théories propres, réélaborant pragmatiquement certaines notions à partir de théories antérieures (les « univers fictionnels », voir Barnabé, 2014) ou forgeant des concepts spécifiques (l’« impératif d’action », voir Genvo, 2005). Dans cette communication, nous souhaitons mobiliser une série de réflexions récentes sur la notion d’avatar vidéoludique pour les étendre à l’étude des personnages au sein de la littérature contemporaine. [less ▲]

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See detailSmall-scale heritage; the canary in the coalmine.
Gantois, Gisele ULg; Schoonjans, Yves

Conference (2016, June 07)

Flanders, a Belgian region, has a historically grown dense network of routes and paths, linking towns and villages on an average one-day walking distance. Within the fabric we detect numerous small-scale ... [more ▼]

Flanders, a Belgian region, has a historically grown dense network of routes and paths, linking towns and villages on an average one-day walking distance. Within the fabric we detect numerous small-scale historical buildings and industrial relicts with an identity importance way beyond the artefact itself, representing an old mesh, entwined with societal narratives. Through newly developed methodologies we both examine the importance of this daily collectively used mesh and unveil and carefully map new complex realities such as the increasing ‘requisition’ of rural built heritage and the reframing of its boundaries as a tangible warning of a continuous urbanisation process. [less ▲]

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See detailSet theory and foundational mereology as logical tools for descriptive psychology
Leclercq, Bruno ULg

Conference (2016, June 07)

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See detailL’abus de droit et le manque de réelle substance économique : Belgique
Bourgeois, Marc ULg

Conference given outside the academic context (2016)

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See detailEmbedded solids of any dimension in the X-FEM defined on higher-order approximations
Duboeuf, Frédéric ULg; Béchet, Eric ULg

Conference (2016, June 06)

Embedded interface methods bring a significant simplification of the modelling process before analysis. Complex geometries and moving boundaries may be described with great flexibility, reducing the ... [more ▼]

Embedded interface methods bring a significant simplification of the modelling process before analysis. Complex geometries and moving boundaries may be described with great flexibility, reducing the meshing step to that of a simple bounding box. Following this idea – to dissociate the field approximation from the geometric description – manifolds of different dimensions may be embedded in the same bulk mesh. However, special attention should be given to the difference of dimensions between that of problem domain and that of bulk mesh (the codimension). Whereas the direct use of the shape functions of the bulk mesh is possible for a problem domain of codimension zero, this approach is no longer possible in other configurations, for instance a beam in a 3D mesh. Unlike approaches introducing independent overlapping meshes for each subdomain, function spaces may be built from the traces of higher dimensional spaces built upon the bulk mesh. For closed curves in 2D and closed surfaces in 3D, the resulting discrete method based on P1 FE have already been studied in the literature. To avoid badly conditioned linear systems, specific treatments are required, e.g. preconditioning approaches or stabilization techniques. Here, we propose to deplete wisely the trace space. We investigate higher-order function spaces to solve the diffusion equation in embedded solids of any codimension. A new space-reducer algorithm is introduced to design the dedicated spaces that avoids ill-conditionning while treating boundary conditions. We present the results of several numerical experiments with convergence analyses. To conclude, applications of this technique to embedded beams or shells is discussed. [less ▲]

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See detailFunction-structure uncoupling in patients with severe brain injury as measured by MRI-DWI and FDG-PET
Annen, Jitka ULg; Heine, Lizette ULg; Ziegler, Erik et al

in Human Brain Mapping (2016)

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See detailPolitique internationale de la culture: patrimoine culturel et industries culturelles
Vlassis, Antonios ULg

Scientific conference (2016, June 06)

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See detailMOISTURE CONTENT DETERMINATION OF FREEZE-DRIED PRODUCTS BY NEAR-INFRARED SPECTROSCOPY: A CASE STUDY FOR UNIVERSAL REGRESSION MODEL
Clavaud, Matthieu ULg; Roggo, Yves; Degardin, Klara et al

Poster (2016, June 06)

Karl Fischer titration is the reference method for moisture content determination in the pharmaceutical industry. Near-infrared spectroscopy is considered the most suitable alternative technique. Indeed ... [more ▼]

Karl Fischer titration is the reference method for moisture content determination in the pharmaceutical industry. Near-infrared spectroscopy is considered the most suitable alternative technique. Indeed, NIRS is a safe and fast method which does not require sample preparation. Nevertheless, the development and validation phases are time-consuming. In addition, the NIRS methods presented so far were mostly product specific. The main objective of this study is to highlight that an universal calibration model can be validated for several freeze-dried products in order to speed up the validation time. This objective was led in two steps. A universal model was first evaluated. A calibration set and a validation set were built up with three freeze-dried products. An antibody drug conjugate, a large molecule and a small molecule all packed in sealed vials were used to introduce more variability. Regression methods were then compared in order to optimize the prediction values. [less ▲]

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See detailImprinting superconducting vortex footsteps in a magnetic layer
Brisbois, Jérémy ULg; Motta, Maycon; Avila Osses, Jonathan ULg et al

in Scientific Reports (2016), 6

Local polarization of a magnetic layer, a well-known method for storing information, has found its place in numerous applications such as the popular magnetic drawing board toy or the widespread credit ... [more ▼]

Local polarization of a magnetic layer, a well-known method for storing information, has found its place in numerous applications such as the popular magnetic drawing board toy or the widespread credit cards and computer hard drives. Here we experimentally show that a similar principle can be applied for imprinting the trajectory of quantum units of flux (vortices), travelling in a superconducting film (Nb), into a soft magnetic layer of permalloy (Py). In full analogy with the magnetic drawing board, vortices act as tiny magnetic scribers leaving a wake of polarized magnetic media in the Py board. The mutual interaction between superconducting vortices and ferromagnetic domains has been investigated by the magneto-optical imaging technique. For thick Py layers, the stripe magnetic domain pattern guides both the smooth magnetic flux penetration as well as the abrupt vortex avalanches in the Nb film. It is however in thin Py layers without stripe domains where superconducting vortices leave the clearest imprints of locally polarized magnetic moment along their paths. In all cases, we observe that the flux is delayed at the border of the magnetic layer. Our findings open the quest for optimizing magnetic recording of superconducting vortex trajectories. [less ▲]

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See detailOn the α-polarization of bacterial suspensions: SIP measurements on four bacterial strains
Pilawski, Tamara ULg; Tappe, Wolfgang; Zimmermann, Egon et al

Poster (2016, June 06)

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See detailA Stochastic Multi-scale Model For Predicting MEMS Stiction Failure
Hoang Truong, Vinh ULg; Paquay, Stéphane; Golinval, Jean-Claude ULg et al

in Proceedings of the SEM XIII International Congress and Exposition on Experimental and Applied Mechanics. (SEMXIII 2016) (2016, June 06)

Adhesion is an important phenomenon in the context of MEMS for which the surface forces become dominant in comparison with the body forces. Because the magnitudes of the adhesive forces strongly depend on ... [more ▼]

Adhesion is an important phenomenon in the context of MEMS for which the surface forces become dominant in comparison with the body forces. Because the magnitudes of the adhesive forces strongly depend on the surface interaction distances, which in turn evolve with the roughness of the contacting surfaces, the adhesive forces cannot be determined in a deterministic way. To quantify the uncertainties on the structural stiction behavior of a MEMS, this work proposes a “stochastic multi-scale methodology”. The key ingredient of the method is the evaluation of the random meso-scale apparent contact forces, which homogenize the effect of the nano-scale roughness and are integrated into a numerical model of the studied structure as a random contact law. To obtain the probabilistic behavior at the structural MEMS scale, a direct method needs to evaluate explicitly the meso-scale apparent contact forces in a concurrent way with the stochastic multi-scale approach. To reduce the computational cost, a stochastic model is constructed to generate the random meso-scale apparent contact forces. To this end, the apparent contact forces are parameterized by a vector of parameters before applying a polynomial chaos expansion in order to construct a mathematical model representing the probability of the random parameters vector. The problem of miro-beam stiction is then studied in a probabilistic way. [less ▲]

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See detailMéthodes historiques de recherche en architecture
Frankignoulle, Pierre ULg

Scientific conference (2016, June 06)

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See detailL’hypothèse d’une Pax Persiana. L’Iran et ses rapports avec l’Occident des années 1850 à 2016
Genin, Vincent ULg

Conference given outside the academic context (2016)

Detailed reference viewed: 21 (2 ULg)
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See detailLe IIe style en reliefs : les ensembles de stucs de la Domus aux Bucranes à Ostia Antica
Morard, Thomas ULg; Girard, Thibault

Scientific conference (2016, June 06)

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See detailNumerical Properties of a Discontinuous Galerkin formulation for electro-thermal coupled problems
Homsi, Lina; Geuzaine, Christophe ULg; Noels, Ludovic ULg

in Papadrakakis, M.; Papadopoulos, V.; Stefanou, G. (Eds.) et al Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering, Crete Island, Greece, 5–10 June 2016 (2016, June 05)

Discontinuous Galerkin (DG) methods are attractive tools to integrate several PDEs in engineering sciences, due to their high order accuracy and their high scalability in parallel simulations. The main ... [more ▼]

Discontinuous Galerkin (DG) methods are attractive tools to integrate several PDEs in engineering sciences, due to their high order accuracy and their high scalability in parallel simulations. The main interest of this work is to derive a constant and stable Discontinuous Galerkin method for two-way electro-thermal coupling analyses. A fully coupled nonlinear weak formulation for electro-thermal problems is developed based on continuum mechanics equations which are discretized using the Discontinuous Galerkin method. Toward this end, the weak form is written in terms of energetically conjugated fields gradients and fluxes. In order to validate the effectiveness of the formulation and illustrate the algorithmic properties, a numerical test for composite materials is performed. [less ▲]

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