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See detailEvaluation of the Enhanced Assumed Strain and Assumed Natural Strain in the SSH3D and RESS3 Solid Shell Elements for Single Point Incremental Forming Simulation
Guzmán Inostroza, Carlos Felipe ULg; Ben Bettaieb, Amine ULg; Velosa de Sena, José Ilidio et al

in Key Engineering Materials [=KEM] (2012), 504-506

Single Point Incremental Forming (SPIF) is a recent sheet forming process which can give a symmetrical or asymmetrical shape by using a small tool. Without the need of dies, the SPIF is capable to deal ... [more ▼]

Single Point Incremental Forming (SPIF) is a recent sheet forming process which can give a symmetrical or asymmetrical shape by using a small tool. Without the need of dies, the SPIF is capable to deal with rapid prototyping and small batch productions at low cost. Extensive research from both experimental and numerical sides has been carried out in the last years. Recent developments in the finite element simulations for sheet metal forming have allowed new modeling techniques, such as the Solid Shell elements, which combine the main features of shell hypothesis with a solid-brick element. In this article, two recently developed elements -SSH3D element [1, 2] and RESS3 element [3]- implemented in Lagamine (finite element code developed by the ArGEnCo department of the University of Liège) are explained and evaluated using the SPIF line test. To avoid locking problems, the well-known Enhanced Assumed Strain (EAS) and Assumed Natural Strain (ANS) techniques are used. The influence of the different EAS and ANS parameters are analysed comparing the predicted tool forces and the shape of a transversal cut, at the end of the process. The results show a strong influence of the EAS in the forces prediction, proving that a correct choice is fundamental for an accurate simulation of the SPIF using Solid Shell elements. [less ▲]

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See detailOn the human pose recovery based on a single view
Pierard, Sébastien ULg; Van Droogenbroeck, Marc ULg

in International conference on pattern recognition applications and methods (ICPRAM) (2012, February)

Estimating the pose of the observed person is crucial for a large variety of applications including home entertainment, man-machine interaction, video surveillance, etc. Often, only a single side view is ... [more ▼]

Estimating the pose of the observed person is crucial for a large variety of applications including home entertainment, man-machine interaction, video surveillance, etc. Often, only a single side view is available, but authors claim that it is possible to derive the pose despite that humans evolve in a 3D environment. In addition, to decrease the sensitivity to color and texture, it is preferable to rely only on the silhouette to recover the pose. Under these conditions, we show that there is an intrinsic limitation: at least two poses correspond to the observed silhouette. We discuss this intrinsic limitation in details in this short paper. To our knowledge, this issue has been overlooked by authors in the past. We observe that this limitation has an impact on the way previous reported results should be interpreted, and it has clearly to be taken into account for designing new methods. [less ▲]

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See detailStructuration de la diversité génétique du genre Milicia: taxonomie, phylogéographie, dynamique des populations
Daïnou, Kasso ULg

Doctoral thesis (2012)

Characterizing population genetic structure using phylogeographic approach contributes to understanding of evolutionary processes that affect plant populations. The present study investigated how past ... [more ▼]

Characterizing population genetic structure using phylogeographic approach contributes to understanding of evolutionary processes that affect plant populations. The present study investigated how past environmental variations can shape the spatial genetic diversity of an African timber tree species, Milicia excelsa (Welw) C.C. Berg. Given that plant responses to disturbances are closely linked to life history traits, this research also aimed to describe relationships between the reproductive traits of M. excelsa and its population genetic structure. Phylogeographic analyses were performed throughout the range of M. excelsa using nuclear and chloroplastic markers. Ecological characterization was conducted for a single population located in south-East Cameroon. Since M. excelsa is similar to the other species of its genus, M. regia (A. Chev) C.C. Berg, we first performed a morphogenetic comparison of these two taxa. The results confirmed an important morphological similarity between the two species with very rare discriminating criteria. In fact Bayesian assignment methods and reproductive isolation patterns suggest the occurrence of interspecific hybridization, which appeared to be unidirectional: hybrids displayed the M. regia morphotype. Because M. regia is known to be more adapted to humid tropical forests, one may expect it to occur in the Congo basin zone. However, its range is restricted to the western part of West Africa while M. excelsa occurs from Guinea-Conakry to Zimbabwe. Interestingly, in the case of M. excelsa, Central and West African specimens had no shared haplotype. This result was unexpected because long gene dispersal distances were found in Cameroonian populations, as expected from the behaviours of the main dispersal animals we identified, the bat Eidolon helvum and the parrots Psittacus erithacus and Agapornis swindernianus. In general, despite the likelihood for long distance seed dispersal, distinct genetic clusters were identified over West and Central Africa and their location may support the forest refugia hypothesis. In addition a phylogeographical signal was detected in chloroplast DNA indicating a prolonged separation between West and Central Africa populations with an accumulation of new mutations. At a smaller spatial scale, patterns of genetic structure also seemed to be weakly influenced by divergent reproduction times among sympatric individuals. The level of genetic diversity in the study populations falls within the range of values calculated for other tropical tree species. If phylogeography helps to infer population history, it also requires ecological or biological information to confirm some uncertainties. Such detailed data were often lacking to completely interpret numerous of our results. The present study raised new questions and led to new perspectives for further investigation both in phylogeography and botany. [less ▲]

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See detailLower impact of blue light on non-visual brain functions in older subjects
Daneault, V; Vandewalle, Gilles ULg; Hébert, M et al

Poster (2012, February)

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See detailIdentifying and computing nonlinear normal modes
Cammarano, A.; Carrella, A.; Renson, Ludovic ULg et al

in Proceedings of the SEM IMAC XXX Conference (2012, February)

Non linear normal modes offer a rigorous framework, both mathematical and physical, for theoretical and experimental dynamical analysis. Albeit still in its infancy, the concept of non linear normal modes ... [more ▼]

Non linear normal modes offer a rigorous framework, both mathematical and physical, for theoretical and experimental dynamical analysis. Albeit still in its infancy, the concept of non linear normal modes has the potential of providing to both the academic and the industrial establishment a powerful tool for the analysis of non linear dynamical systems. However, in order to exploit the full potential of this theory (and its associated simulation capability), there is need to integrate it with other branches of non linear structural dynamics: namely, in order for the non linear normal modes of a real - physical - structure to be computed, there is need to identify and quantify its non linearity. In this paper, an identification method based on the measured Frequency Response Function (FRF) is employed to identify and quantify the system's non linearity before computing the system's non linear normal modes. [less ▲]

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See detailQuel traitement pour les patients souffrant de lombalgie ?
Demoulin, Christophe ULg; Bruyère, Olivier ULg; Hill, J. C.

in Axxon Journal (2012)

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See detailLa Foire du livre, terrain d'enquête
Barnabé, Fanny ULg; Bertrand, Charlotte ULg; Duchesne, Laurence

Article for general public (2012)

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See detailAmérique latine: progrès et défis d'une région en plein essor
Santander, Sébastian ULg

in Spirit of Management (2012), 14

Depuis 2003, l'Amérique latine connaît une période économique de croissance importante. Elle parvient à traverser la crise mondiale sans trop de difficultés. La demande chinoise des matières premières ... [more ▼]

Depuis 2003, l'Amérique latine connaît une période économique de croissance importante. Elle parvient à traverser la crise mondiale sans trop de difficultés. La demande chinoise des matières premières latino-américaines combinée à une augmentation de la consommation interne et de l'investissement expliquent ces performances. Par ailleurs, des progrès ont été accompli en matière sociale. En outre, la région connaît une stabilité politique grâce à l'enracinement de la démocratie depuis plus de 20 ans. Toutefois, l'Amérique latine a encore pas mal de défis à relever: diversification économique et des débouchés; réduction des inégalités; lutte contre la criminalité organisée, la violence et la corruption. [less ▲]

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See detailCours de géologie
Poty, Edouard ULg

Learning material (2012)

Notes du cours de géologie de 1 bac en géologie et de 2 bac en géographie

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See detailEuropean project, demo “NETFLEX” For large integration of renewables using DLR, PST and PMU.
Lilien, Jean-Louis ULg

Conference (2012, February)

forecasting ampacity as a need for power system operation

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See detailElectromagnetic absorption properties of carbon nanotube nanocomposite foam filling honeycomb waveguide structures
Quiévy, Nicolas; Bollen, Pierre; Thomassin, Jean-Michel ULg et al

in IEEE Transactions on Electromagnetic Compatibility (2012), 24(1), 43-51

Carbon nanotube reinforced polymer foams filling a metallic honeycomb were processed and characterized for the production of hybrid materials with high electromagnetic absorption potential ... [more ▼]

Carbon nanotube reinforced polymer foams filling a metallic honeycomb were processed and characterized for the production of hybrid materials with high electromagnetic absorption potential. Electromagnetic modeling and experimental characterization of the hybrids proved that the honeycomb, acting as a hexagonal waveguide, improves the absorption properties in the gigahertz range above the cutoff frequency. The electromagnetic absorption can be tuned by changing the hybrid material properties. The required levels of electrical conductivity are attained owing to the dispersion of low amounts (1–2 wt%) of carbon nanotubes inside the polymermatrix. The combination of the foam and honeycomb architecture contributes to decrease the real part of the relative effective permittivity Re{εr,eff }. Varying the cell shape of the honeycomb changes the frequency range for high absorption. An analytical model for the absorption has been developed, showing good agreement with the experimental results. [less ▲]

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See detailRhino vs paquebot: 1-0
Hamers, Jérémy ULg

Article for general public (2012)

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See detail« Spaßmacher » et « Ernstmacher » en poésie allemande. Les poèmes profanes de Robert Gernhardt.
Viehöver, Vera ULg

in Culture, le Magazine Culturel de l'Université de Liège (2012)

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See detailA Finite Element Subproblem Method for Position Change Conductor Systems
Dular, Patrick ULg; Krähenbühl, Laurent; Vazquez Sabariego, Ruth ULg et al

in IEEE Transactions on Magnetics (2012), 48(2), 403-406

Analyses of magnetic systems with position changes of both massive and stranded conductors are performed via a finite element sub- problem method. A complete problem is split into subproblems associated ... [more ▼]

Analyses of magnetic systems with position changes of both massive and stranded conductors are performed via a finite element sub- problem method. A complete problem is split into subproblems associated with each conductor and the magnetic regions. Each complete solution is then expressed as the sum of subproblem solutions supported by different meshes. The subproblem procedure simplifies both meshing and solving processes, with no need of remeshing, and accurately quantifies the effect of the position changes of conductors on both local fields, e.g., skin and proximity effects, and global quantities, e.g., inductances and forces. Applications covering parameterized analyses on conductor positions to moving conductor systems can benefit from the developed approach. [less ▲]

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See detailQuantifications en supergéométrie
Leuther, Thomas ULg

Poster (2012, February)

Le poster présente de façon vulgarisée certaines idées sous-jacentes à la recherche de quantifications invariantes en supergéométrie.

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See detailLa monnaie de sa pièce. Poétique et morale du macairisme dans les Physiologies
Stienon, Valérie ULg

in Fix, Florence; Fougère, Marie-Ange (Eds.) L’argent et le rire, de Balzac à Mirbeau (2012)

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