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Peer Reviewed
See detailMulti-Scale Modelisation of the Optical Second Harmonic Generation of Tyrosine-Containing Iturinic Antimicrobial Lipopeptides
Loison, Claire; Nasir, Mehmet Nail ULg; Benichou, Emmanuel et al

Poster (2013)

The optical Second Harmonic Generation (SHG) of Mycosubtilin Langmuir Layers at the air/water interface are modeled. In this tyrosine-containing lipopepeptide, the environment of the tyrosine residue is ... [more ▼]

The optical Second Harmonic Generation (SHG) of Mycosubtilin Langmuir Layers at the air/water interface are modeled. In this tyrosine-containing lipopepeptide, the environment of the tyrosine residue is critical in defining the SHG response. To propose reasonable the structure of Mycosubtilin aggregates at the air-water interface, molecular dynamics simulations (all-atom and coarse-grained) are performed. Molecular hyperpolarizability of the lipopeptide are obtained by Quantum Chemistry calculations. Finally, the SHG susceptibilities of the interface are calculated using a simple additive model. The molecular dynamics simulations suggest that lipopeptides aggregate at the interface into half-micelles, and that this phenomena is the origin of a constraint on Tyrosine orientation. In particular the C-OH bond of the Tyrosine residue has a preferential orientation along the interface normal, pointing towards the air. This inhomogneneous orientation distribution, associated with a dominant hyperpolarizability component along the C-OH bond of the Tyrosine, yields a characteristic SHG response. Comparison with experimental data gathered in our lab are proposed. [less ▲]

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See detailMulti-scale modelling
Noels, Ludovic ULg; Becker, Gauthier; Mulay, Shantanu Shashikant ULg et al

Scientific conference (2013, March 11)

Detailed reference viewed: 22 (9 ULg)
Peer Reviewed
See detailMulti-scale modelling of failure in heterogeneous periodic thin shells
Mercatoris, Benoît ULg; Massart, Thierry J.

Conference (2010)

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See detailMulti-scale modelling of heterogeneous shell structures
Massart, T. J.; Mercatoris, Benoît ULg; Piezel, B. et al

in Computer Assisted Mechanics and Engineering Sciences [=CAMES] (2011), 18(1-2), 53-71

This paper reviews multi-scale computational homogenisation frameworks for the non-linear behaviour of heterogeneous thin planar shells. Based on a review of some of the currently available methods, a ... [more ▼]

This paper reviews multi-scale computational homogenisation frameworks for the non-linear behaviour of heterogeneous thin planar shells. Based on a review of some of the currently available methods, a computational homogenisation scheme for shells is applied on to representative volume elements for plain weave composites. The effect of flexural loading on the potential failure modes of such materials is analysed, focusing on the reinforcement-matrix delamination mechanism. The attention is next shifted toward failure localisation in masonry unit cells. Subsequently, a recently developed computational FE 2 solution scheme accounting for damage localisation at structural scales based on RVE computations is applied. Copyright © 2011 by Institute of Fundamental Technological Research, Polish Academy of Sciences. [less ▲]

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Peer Reviewed
See detailMulti-scale modelling of permeability evolution in the excavation damaged zone around tunnels
Levasseur, Séverine ULg; Collin, Frédéric ULg; Charlier, Robert ULg et al

in PROCEEDINGS OF THE 2nd INTERNATIONAL SYMPOSIUM ON COMPUTATIONAL GEOMECHANICS (COMGEO I ) (2011)

A zone with significant irreversible deformations and significant changes in flow and transport properties is expected to be formed in indurated clay around underground excavations. The stress perturbation ... [more ▼]

A zone with significant irreversible deformations and significant changes in flow and transport properties is expected to be formed in indurated clay around underground excavations. The stress perturbation around the excavation could lead to a significant increase of the permeability, related to diffuse and/or localized crack propagation in the material. The main objective of the study is to model these processes at large scale with a micromechanical damage approach, based on the Ponte-Castaneda and Willis approximation (PCW) in the presence of initial stress, in order to assess the crack impacts on the performance of radioactive waste geological repositories. Combined with this model, permeability tensor is described as a function of micromechanical damage that is generated during the excavation. Advantages and drawbacks of this approach are described thanks to the results on Opalinus Clay and of the Selfrac long term dilatometer experiment. [less ▲]

Detailed reference viewed: 47 (20 ULg)
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Peer Reviewed
See detailMulti-scale modelling of sediment transport
Dewals, Benjamin ULg

Conference (2010, January 07)

Detailed reference viewed: 22 (2 ULg)
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See detailMulti-scale modelling of shell failure for periodic quasi-brittle materials
Mercatoris, Benoît ULg

Doctoral thesis (2010)

In a context of restoration of historical masonry structures, it is crucial to properly estimate the residual strength and the potential structural failure modes in order to assess the safety of buildings ... [more ▼]

In a context of restoration of historical masonry structures, it is crucial to properly estimate the residual strength and the potential structural failure modes in order to assess the safety of buildings. Due to its mesostructure and the quasi-brittle nature of its constituents, masonry presents preferential damage orientations, strongly localised failure modes and damage-induced anisotropy, which are complex to incorporate in structural computations. Furthermore, masonry structures are generally subjected to complex loading processes including both in-plane and out- of-plane loads which considerably influence the potential failure mechanisms. As a consequence, both the membrane and the flexural behaviours of masonry walls have to be taken into account for a proper estimation of the structural stability. Macrosopic models used in structural computations are based on phenomenological laws including a set of parameters which characterises the average behaviour of the material. These parameters need to be identified through experimental tests, which can become costly due to the complexity of the behaviour particularly when cracks appear. The existing macroscopic models are consequently restricted to particular assumptions. Other models based on a detailed mesoscopic description are used to estimate the strength of masonry and its behaviour with failure. This is motivated by the fact that the behaviour of each constituent is a priori easier to identify than the global structural response. These mesoscopic models can however rapidly become unaffordable in terms of computational cost for the case of large-scale three-dimensional structures. In order to keep the accuracy of the mesoscopic modelling with a more affordable computa- tional effort for large-scale structures, a multi-scale framework using computational homogeni- sation is developed to extract the macroscopic constitutive material response from computa- tions performed on a sample of the mesostructure, thereby allowing to bridge the gap between macroscopic and mesoscopic representations. Coarse graining methodologies for the failure of quasi-brittle heterogeneous materials have started to emerge for in-plane problems but remain largely unexplored for shell descriptions. The purpose of this study is to propose a new periodic homogenisation-based multi-scale approach for quasi-brittle thin shell failure. For the numerical treatment of damage localisation at the structural scale, an embedded strong discontinuity approach is used to represent the collective behaviour of fine-scale cracks using average cohesive zones including mixed cracking modes and presenting evolving orientation related to fine-scale damage evolutions. A first originality of this research work is the definition and analysis of a criterion based on the homogenisation of a fine-scale modelling to detect localisation in a shell description and determine its evolving orientation. Secondly, an enhanced continuous-discontinuous scale tran- sition incorporating strong embedded discontinuities driven by the damaging mesostructure is proposed for the case of in-plane loaded structures. Finally, this continuous-discontinuous ho- mogenisation scheme is extended to a shell description in order to model the localised behaviour of out-of-plane loaded structures. These multi-scale approaches for failure are applied on typical masonry wall tests and verified against three-dimensional full fine-scale computations in which all the bricks and the joints are discretised. [less ▲]

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See detailMulti-scale modelling of shell failure for periodic quasi-brittle materials
Mercatoris, Benoît ULg; Massart, Thierry J.

in Fifth International Conference on Multiscale Material Modeling (MMM2010) (2010)

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Peer Reviewed
See detailMulti-scale optimal interpolation: application to DINEOF analysis spiced with a local optimal interpolation
Beckers, Jean-Marie ULg; Barth, Alexander ULg; Tomazic, Igor ULg et al

in Ocean Science Discussions (2014), 11

We present a method in which the optimal interpolation of multi-scale processes can be untangled into a succession of simpler interpolations. First, we prove how the optimal analysis of a superposition of ... [more ▼]

We present a method in which the optimal interpolation of multi-scale processes can be untangled into a succession of simpler interpolations. First, we prove how the optimal analysis of a superposition of two processes can be obtained by different mathematical formulations involving iterations and analysis focusing on a single process. From the 5 different mathematical equivalent formulations we then select the most efficient ones by analyzing the behavior of the different possibilities in a simple and well controlled test case. The clear guidelines deduced from this experiment are then applied in a real situation in which we combine large-scale analysis of hourly SEVIRI satellite images using DINEOF with a local optimal interpolation using a Gaussian covariance. It is 10 shown that the optimal combination indeed provides the best reconstruction and can therefore be exploited to extract the maximum amount of useful information from the original data [less ▲]

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Peer Reviewed
See detailMulti-Scale Simulation of the Simian Immunodeficiency Virus Fusion Peptide.
Crowet, Jean-Marc ULg; Parton, Daniel L.; Hall, Benjamin A. et al

in Journal of Physical Chemistry B (2012)

Fusion peptides of type I fusion glycoproteins are structural elements of several enveloped viruses which enable the fusion between host and virus membranes. It is generally suggested that these peptides ... [more ▼]

Fusion peptides of type I fusion glycoproteins are structural elements of several enveloped viruses which enable the fusion between host and virus membranes. It is generally suggested that these peptides can promote the early fusion steps by inducing membrane curvature and that they adopt a tilted helical conformation in membranes. Although this property has been the subject of several experimental and in silico studies, an extensive sampling of the membrane peptide interaction has not yet been done. In this study, we performed coarse-grained molecular dynamic simulations in which the lipid bilayer self-assembles around the peptide. The simulations indicate that the SIV fusion peptide can adopt two different orientations in a DPPC bilayer, a major population which adopts a tilted interfacial orientation and a minor population which is perpendicular to the bilayer. The simulations also indicate that for the SIV mutant that does not induce fusion in vitro the tilt is abolished. [less ▲]

Detailed reference viewed: 38 (16 ULg)
See detailMulti-scale simulations of membrane active peptides: The fusion peptides
Crowet, Jean-Marc ULg

Scientific conference (2010, May 19)

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See detailMulti-scale spatial variability of amphipod assemblages from the foliar stratum of the Posidonia oceanica (L.) Delile meadow
Sturaro, Nicolas ULg; Lepoint, Gilles ULg; Michel, Loïc ULg et al

Conference (2008, October 31)

Studying spatial patterns is of ecological importance in order to understand the causes of the distribution and abundance of organisms, and it also provides valuable basis for management and conservation ... [more ▼]

Studying spatial patterns is of ecological importance in order to understand the causes of the distribution and abundance of organisms, and it also provides valuable basis for management and conservation. In the Mediterranean coastal zone, the Posidonia oceanica seagrass meadows constitute one of the dominant ecosystems and are an important habitat for vagile invertebrates. Among these, amphipods comprise a large number of species, with considerable abundance and biomass, as well as being an important trophic resource for fish populations. Until now, little attention has been given to the horizontal variability at different spatial scales of amphipod assemblages associated with P. oceanica meadows. A hierarchical sampling design, spanning three orders of magnitude (from 1 to 100s of metres) was elaborated. Sampling was undertaken in March 2007 in the meadows of Calvi Bay (NW Corsica), at depths ranging from 10 to 13 m, using a suction sampler. Our results indicated an important horizontal variability of the studied assemblage, and this at different spatial scales. In addition, these results tend to show that the small scale (~ 1 m and ~ 10 m) influenced abundance, while the medium-scale (~ 100 m) influenced diversity. Some potential causes of the observed patterns are discussed. These results emphasize the importance of considering different spatial scales in the study of the vagile invertebrates associated with P. oceanica meadows. [less ▲]

Detailed reference viewed: 57 (18 ULg)
Peer Reviewed
See detailA multi-scale strategy for the modelling of failure in masonry plates and shells
Massart, Thierry J.; Mercatoris, Benoît ULg; Diaby, Adama

Conference (2007)

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See detailMulti-scale studies of foamed materials
Nguyen, Van Dung ULg; Noels, Ludovic ULg

Conference (2013, September)

We propose a multi-scale study to predict micro-buckling that could happen in foamed materials. At the macroscopic scale, when localization occurs, the characteristic size of macroscopic deformation is ... [more ▼]

We propose a multi-scale study to predict micro-buckling that could happen in foamed materials. At the macroscopic scale, when localization occurs, the characteristic size of macroscopic deformation is the same order of the microscopic size. The assumption of material action in standard multi-scale computational homogenization approach where the stress only depends on the strain at this point is no-longer suitable, which motivates the uses of the second-order scheme. In this work, an implementation of the second-order continuum based on a discontinuous Galerkin approximation is shown to be particularly efficient to constrain weakly the continuities of the displacement field and of its gradient. At the microscopic scale, classical finite element resolutions of RVEs are considered. To enforce the periodic boundary condition of this micro problem, we propose an efficient method, which is based on the polynomial interpolation, and allows applying the periodic boundary condition without requiring conformal meshes. The micro-macro transition follows the second-order computational homogenization scheme. With the proposed framework it is shown that, during the macroscopic loading, the micro- buckling of the thin components of the foamed structure (cell walls and edges) can occur even if the tangent modulus of micro-material is still elliptic since the homogenized tangent modulus at macro-scale can lose its ellipticity. In that case, the localization occurs at macro- scale and can be captured by the model. [less ▲]

Detailed reference viewed: 44 (16 ULg)
Peer Reviewed
See detailMulti-Sensor 3D Image Fusion: Technologies for an Urban Common Operating Picture
Waxman, Allen M.; Verly, Jacques ULg; Fay, David A.

Conference (2001, June)

Detailed reference viewed: 6 (0 ULg)
Peer Reviewed
See detailMulti-Sensor Image Fusion: 3-D Visualization and Search Agents
Waxman, Allen M.; Ross, William; Streilein, William et al

Conference (1999, October)

Detailed reference viewed: 3 (0 ULg)
Peer Reviewed
See detailMulti-Sensor Image Fusion: 3D Visualization and Search Agents
Waxman, Allen M.; Ross, William; Streilein, William et al

Conference (2000, June)

Detailed reference viewed: 5 (0 ULg)
See detailMulti-site quantitative ultrasound measurements of the third metacarpal bone in young thoroughbred horses
Carstanjen, B; Lepage, OM; Langlois, P et al

in Proceedings of the CESMAS congress 2002 (2002)

Detailed reference viewed: 8 (0 ULg)
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See detailA multi-step process for an alternative wheat bran biorefinery
Aguedo, Mario ULg; Fougnies, Christian; Richel, Aurore ULg

Poster (2014, May 21)

Detailed reference viewed: 6 (1 ULg)