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See detailComputational homogenization of cellular materials capturing micro-buckling, macro-localization and size effects
Nguyen, Van Dung ULg

Doctoral thesis (2014)

The objective of this thesis is to develop an efficient multi-scale finite element framework to capture the macroscopic localization due to the micro-buckling of cell walls and the size effect phenomena ... [more ▼]

The objective of this thesis is to develop an efficient multi-scale finite element framework to capture the macroscopic localization due to the micro-buckling of cell walls and the size effect phenomena arising in structures made of cellular materials. Under the compression loading, the buckling phenomenon (so--called micro--buckling) of the slender components (cell walls, cell faces) of cellular solids can occur. Even if the tangent operator of the material of which the micro--structure is made, is still elliptic, the presence of the micro--buckling can lead to the loss of ellipticity of the resulting homogenized tangent operator. In that case, localization bands are formed and propagate in the macroscopic structure. Moreover, when considering a cellular structure whose dimensions are close to the cell size, the size effect phenomenon cannot be neglected since deformations are characterized by a strain gradient. On the one hand, a classical multi-scale computational homogenization scheme (so-called first-order scheme) looses accuracy with the apparition of the macroscopic localization or the high strain gradient arising in cellular materials because the underlying assumption of the local action principle, in which the stress state on a macroscopic material point depends only on the strain state at that point, is no--longer suitable. On the other hand, the second-order multi-scale computational homogenization scheme proposed by Kouznetsova exhibits a good ability to capture such phenomena. Thus this second--order scheme is improved in this thesis with the following novelties so that it can be used for cellular materials. First, at the microscopic scale, the periodic boundary condition is used because of its efficiency. As the meshes generated from cellular materials exhibit a large void part on the boundaries and are not conforming in general, the classical enforcement based on the matching nodes cannot be applied. A new method based on the polynomial interpolation without the requirement of the matching mesh condition on opposite boundaries of the representative volume element (RVE) is developed. Next, in order to solve the underlying macroscopic Mindlin strain gradient continuum of this second-order scheme by the displacement-based finite element framework, the presence of high order terms (related to the higher stress and strain) leads to many complications in the numerical treatment. Indeed, the resolution requires the continuities not only of the displacement field but also of its first derivatives. This work uses the discontinuous Galerkin (DG) method to weakly impose these continuities. This proposed second--order DG--based FE2 scheme appears to be easily integrated into conventional parallel finite element codes. Finally, the proposed second-order DG-based FE2 scheme is used to model cellular materials. As the instability phenomena are considered at both scales, the path following technique is adopted to solve both the macroscopic and microscopic problems. The micro--buckling leading to the macroscopic localization and the size effect phenomena can be captured within the proposed framework. [less ▲]

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See detailLangue, culture, littérature
Defays, Jean-Marc ULg

Scientific conference (2014, March 10)

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See detailL'Homme de Spy, 125 ans plus tard
Flas, Damien ULg

Conference given outside the academic context (2014)

Detailed reference viewed: 8 (3 ULg)
See detailPerforming Emotions at the Canonization of St. Ignatius and St. Xavier
Delfosse, Annick ULg; Vermeir, Koen; Delbeke, Maarten et al

Conference (2014, March 08)

This paper will approach the celebrations of the canonization of St. Ignatius and St. Xavier in different localities of the Southern Netherlands over the course of 1622 as performances of emotion. We will ... [more ▼]

This paper will approach the celebrations of the canonization of St. Ignatius and St. Xavier in different localities of the Southern Netherlands over the course of 1622 as performances of emotion. We will analyze little known visual and textual testimonials of festivals and theatrical representations in Antwerp, Douai, Brussels, Dunkerque and Leuven to examine which means were used to represent, convey and enhance emotions, which actors were involved, how emotions were meant to address and affect the audience, and to what end emotions were activated. The double canonization of 1622 consecrated the Jesuits as stalwarts of the Roman papacy. In the Southern Netherlands, the celebrations of 1622 were a key moment in confirming the legitimacy of the order by displaying both how it was embedded in the local political and religious arena, and how it mastered the most advanced artistic means to support its mission. After a sketch of the celebrations and their political and religious context, we will analyze how and why emotion was performed in three steps. The sources attach enormous attention to the material, architectural and urban setting of the celebrations, by emphasizing the splendor and artistic sophistication of the events, and by pointing out the prestigious patronage that had accrued around them. We will examine whether and how the sources charged the material context of the celebration with emotion. What was the intended effect of this context on the audience? How did this context enable the performance of emotion in different forms of public display (pageantry, performances, …)? In order to answer this last question, in a second step we will have a closer look at the Triumphus dedicated to St Ignatius and St. Xavier performed in Brussels. We will examine how, in this ensemble, the material context is activated by the movement of the viewer. The description of the Triumphus singles out moments of transition as instances of heightened emotivity, suggesting that emotions are not mobilized by singular details but by overall views that impress themselves when the beholder crosses a treshold. In a third step we will describe the intended effect of the performance of emotions as a sacer horror, the bodily manifestation of religious awe, the organic sensation of respect mixed with fear and wonder felt in the presence of gods or cosmic forces. The performance of emotions, engendered by multiple layers of transformation (of the material context by means of ephemeral architecture, of the views and the experiences of the viewer, and ultimately, of their affective state) was directed at effectuating a lasting change of heart. [less ▲]

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See detailCorsican seagrass detritus: An opportune shelter or a copepod Eldorado?
Mascart, Thibaud ULg; Lepoint, Gilles ULg; Remy, François ULg et al

Poster (2014, March 07)

Seagrass ecosystems are extensive beds of marine flowering plants bordering tropical and temperate coastal regions. They play an important role in maintaining biological productivity and bio-geochemical ... [more ▼]

Seagrass ecosystems are extensive beds of marine flowering plants bordering tropical and temperate coastal regions. They play an important role in maintaining biological productivity and bio-geochemical cycles in the sea and support higher diversity and abundance of fauna in comparison to adjacent non-vegetated areas. The seagrass meadow primary production can be directly consumed through herbivory but the majority of the plant material falls on the sea floor during the autumnal leaf senescence. The leaf litter then degrades within the meadow or accumulates with other micro- and macrophytodetritus to form detritus accumulations on the adjacent non-vegetated sand patches. These exported accumulations are quite dynamic in relation to seafloor geomorphology and local hydrodynamics. Thus, the detritus accumulations are an easily disturbed ephemeral environment with one large influx a year. Consequently the physico-chemical characteristics can change very fast and impact the sheltering capacity and food supply present. Nonetheless, fishes, macrofauna and meiofauna are omnipresent throughout the year. In our study site along the shore of N-W Corsica, Posidonia oceanica seagrass meadows are characterised by substantial detritus accumulations. The present study aimed to analyse the biodiversity of the copepod species communities (Crustacea, Copepoda) in those detritus accumulations. The results showed that the copepod detritus community consisted of a mixture of species that are also found in adjacent habitats (seagrass meadow, sediment, epilithic habitats, water column). Each adjacent habitat is characterised by organisms that are morphologically adapted to the specific features of that habitat. The majority of copepods are epiphytic (order Harpacticoida), that occur typically on seagrass leaves and macroalgae. Other species are planktonic (orders Cyclopoida and Calanoida) and some were benthic (order Harpacticoida), known from the nearby sediment. A minority of the copepod community were parasitic on fish or invertebrate (order Siphonostomatoida). In order to clarify their origin, we assume that passive transport by currents plays a significant role next to the active migration from the anoxic sediments under the detritus. For sure they also reproduce within the detritus packages as we found many nauplii, copepodites and gravid females. The above mentioned suggestions cannot explain such high density of copepods by themselves. Other attraction mechanisms are needed to explain the important amount of planktonic and epiphytic species with good swimming ability, such as higher food accessibility. In the detritus no plant-defence mechanisms are present anymore and a lot of micro-organisms and thus potential food sources are present. Furthermore, the dense detritus package provides shelter and protection from potential predators. Subsequently we may consider the detritus accumulations as a copepod species-specific opportune Eldorado for sheltering, nursing and feeding. [less ▲]

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See detailA framework for using decision-support tools at various spatial scales for the management of irrigated agriculture in semi-arid West-Africa
Wellens, Joost ULg

Doctoral thesis (2014)

The Kou watershed, situated in the Southwestern part of Burkina Faso, has succumbed since a couple of decades to a typical theater play of anarchistic water management. With its 1.800 km², this small ... [more ▼]

The Kou watershed, situated in the Southwestern part of Burkina Faso, has succumbed since a couple of decades to a typical theater play of anarchistic water management. With its 1.800 km², this small watershed includes the second largest city of Burkina Faso (Bobo-Dioulasso), a former state run irrigated rice scheme and several informal agricultural zones. Despite the abundance of water resources, most water users find themselves regularly faced with shortages due to an increase in population and low irrigation efficiencies. Local stakeholders are hence in need of easy to use and low-cost decision support tools for the monitoring and exploitation of the water resources at different spatial and user levels. A top-to-bottom string of adapted water management tools has successfully been installed to tackle the problems: from watershed (top) to field level (bottom), not to mention the 1200 ha irrigation scheme. Land use maps have been derived from satellite and aerial images. Combined with data from a network of hydrologic gauging stations, regional water use maps were established. Hot spots in inefficient water use could be geographically identified and more detailed actions undertaken. Scheme Information Management Information System (SIMIS) was put in place for the management of the regions irrigated rice scheme. A more equitable distribution for the ever diminishing available water resources could be elaborated. A public-private partnership was installed to guarantee its sustainability. Day to day water use on irrigated plots was monitored by soil humidity and crop canopy measurements. A simple field-crop-water balance model AquaCrop was calibrated and validated, and is used by extension workers to draft optimal irrigation charts. Each tool is applied independently, requiring only limited data; but their combined results contribute to an improved integrated water management. [less ▲]

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See detailModes intentionnels
Dewalque, Arnaud ULg

Conference (2014, March 07)

Je dresse le bilan de la situation des recherches actuelles en théorie de la perception (entre représentationalisme et relationalisme), et je suggère que la voie d'investigations la plus prometteuse est l ... [more ▼]

Je dresse le bilan de la situation des recherches actuelles en théorie de la perception (entre représentationalisme et relationalisme), et je suggère que la voie d'investigations la plus prometteuse est l'intentionalisme modal. D'après l'intentionalisme modal, un état mental est individualisé par son contenu intentionnel et par son mode intentionnel. En m'appuyant sur la méthode descriptive de Franz Brentano, je propose alors un argument en faveur de cette conception: l'argument de la complétude. [less ▲]

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See detailDiversification artistique et politiques culturelles dans les villes multiculturelles
Martiniello, Marco ULg

in SociologieS [Online], Files, Diversification artistique et politiques culturelles (2014)

Cet article introductif part du constat que la mondialisation se traduit par une diversification culturelle des villes européennes. Cette diversité donne lieu à deux tendances contradictoires. D'une part ... [more ▼]

Cet article introductif part du constat que la mondialisation se traduit par une diversification culturelle des villes européennes. Cette diversité donne lieu à deux tendances contradictoires. D'une part, on observe une tendance à la polarisation et à la fragmentation ethniques dans de nombreuses villes. D'autre part, on observe des mouvements vers plus d'intégration résidentielle et la formation de quartiers multi-ethniques dans lesquels se développent la co-inclusion et les interactions entre les citoyens de différentes origines ethniques et sociales. Ces tendances contradictoires se marquent aussi dans le domaine artistique qui est assez peu étudié dans les débats sociologiques et politiques sur l’immigration, l’intégration et le multiculturalisme. Après avoir proposé un cadre pour cette étude ainsi que les enjeux principaux de la question artistique dans les villes post-migratoires, l’article présente brièvement les autres contributions qui composent ce dossier. [less ▲]

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See detailUsing features of mercury and methylmercury to discriminate contamination profiles between sea bass, Dicentrarchus labrax, populations
Cransveld, Alice ULg; Amouroux, David; Koutrakis, Emmanuil et al

Poster (2014, March 07)

Despite many efforts consented in the last decades, Mercury (Hg) emissions have kept rising worldwide. Currently, anthropogenic inputs dominate Hg emissions to the atmosphere by far, natural releases ... [more ▼]

Despite many efforts consented in the last decades, Mercury (Hg) emissions have kept rising worldwide. Currently, anthropogenic inputs dominate Hg emissions to the atmosphere by far, natural releases accounting only for a 4th of the total. Because Hg has a stable gaseous form (Hg0) with a long residence time in the atmosphere (~1year), both natural and industrially produced Hg can be transported far from point sources. Therefore, many uncertainties remain in our knowledge about Hg biogeochemistry. Our study aims at identifying the different Hg forms found in marine predators in order to discriminate different polluted areas and potential pollution sources. More specifically, we seek to discriminate contaminations of local origins versus contamination of global origins. To achieve this, we are currently studying different sea bass, Dicentrarchus labrax, populations from the Atlantic Ocean and Mediterranean. In muscle, liver, kidney and brain tissues, we analyze total Mercury (THg) and methylmercury (MeHg). We are also testing the discrimination power of Hg's stable isotopes (199Hg, 201Hg and 202Hg). Indeed, recent findings show that Hg isotopes can exhibit both mass-dependent (MDF) and mass-independent fractionation (MIF). This means that Hg isotopes provide two different types of information at once, both on biological cycling of Hg, including bioaccumulation (MDF), and on chemical pathways such as photochemical transformations (MIF). Eventually, we are planning to extend our results with compound specific isotope analysis (CSIA) on the carbon of methylmercury. Preliminary analysis performed on 14 juvenile specimens from the North Sea and the Aegean Sea indicate that THg concentrations are higher in individuals from the North Sea than from Greece. The lack of correlation with size and weight indicate that it is likely linked to a difference in contamination levels between the two areas. MeHg is the predominant form of Hg in muscle, while the same cannot be asserted for liver. Mass dependent isotopic values (δ202Hg), were always higher in muscle than in liver and, for each tissue, values were similar between the two areas. This is probably related to the species distribution and to some internal Hg metabolism. For mass independent isotopic signature (MIF), sea bass from the Aegean Sea had a systematically higher Δ201Hg value than individuals from the North Sea. Thus, mass independent values seem definitely site dependent and might be in agreement with differences in both mercury sources and cycling in the North and Aegean Seas. These preliminary results consequently indicate that Hg isotopes may help to discriminate fish from different areas. This promising outcome must be further confirmed by extending our sampling and will be coupled to other results obtained through CSIA. [less ▲]

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Peer Reviewed
See detailMicroplastics caught in herring gill rakers: illustration by scanning electron microscopy
Collard, France ULg; Das, Krishna ULg; Parmentier, Eric ULg

Conference (2014, March 07)

Plastics are produced in huge quantity (280 million of tons in 2012) and more than 10% end up in the oceans. It is estimated that between 60 and 80% of all marine debris are plastics. Plastics are ... [more ▼]

Plastics are produced in huge quantity (280 million of tons in 2012) and more than 10% end up in the oceans. It is estimated that between 60 and 80% of all marine debris are plastics. Plastics are persistent and have accumulated in the oceans for several decades. Plastics may adverse wildlife in many ways: they can be ingested by marine vertebrates and cause internal wounds in the digestive tract. Plastics are also vectors of organic pollutants including. Once ingested, plastics may release these pollutants in the organism. Plastics present in the marine environment fragment in small pieces by mechanical stress and UV radiation leading to the so-called microplastics smaller than 5 mm. Little is known about microplastics ingestion and toxicity in planktivorous fish such as the herring, Clupea harengus. Planktivorous fish have gill rakers, which may function as a trap for microplastics. This study aims to describe and characterise microplastics present on gill rakers of the herring, Clupea harengus. Ten gill cavities were sampled in January 2013 in the Channel and the North Sea during a fishery campaign organized by the IFREMER. Gills cavities were placed in a fixating solution until preparation for scanning electron microscopy (SEM). SEM was used in order to detect microplastics which are too small to be observed by a dissection microscope, to compare them with the distance between gill rakers and to characterise the surface and the shape of microplastics. Scanning electron microscopy revealed large variety of microplastics, which lengths ranged from 0.05 to 5mm. Relationship between microplastics length and distance between gill rakers was analysed on the same branchial arch. The present study revealed the presence of microplastics in an edible species of high economic value and raise question about potential impact on the herring and its consumers, including human beings. [less ▲]

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See detailEquations fantaisistes : l'argent comme ressort burlesque dans l'œuvre de Pierre La Police
Belloi, Livio ULg

Conference (2014, March 06)

Conçue comme une vaste parodie du discours médiatique en général et de la presse quotidienne en particulier, la série "Véridique !" (Cornélius, 1999-2002) du dessinateur français Pierre La Police met ... [more ▼]

Conçue comme une vaste parodie du discours médiatique en général et de la presse quotidienne en particulier, la série "Véridique !" (Cornélius, 1999-2002) du dessinateur français Pierre La Police met volontiers en scène des questions ou des rapports d’argent. Le plus souvent lié à la sphère politique, le thème de l’argent autorise l’auteur à jeter un regard narquois et particulièrement acéré sur des événements qui firent grand bruit dans la France des années 1990 (l’affaire Roland Dumas, le scandale de l’ARC, l’affaire des emplois fictifs à la ville de Paris, etc.). Ma communication étudie au plus près les mises en scène de l’argent dans l’œuvre de Pierre La Police et s'efforce de porter au jour les véritables équations mises au point à cet égard par l’auteur. Toutes à leur manière, ces équations concourent à faire du thème de l’argent un ressort burlesque à part entière ; elles participent également d’une esthétique générale de la distorsion et de l’approximation, qui est comme la marque de fabrique de Pierre La Police. [less ▲]

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See detailEarly neuropsychological detection of Alzheimer's disease
Bastin, Christine ULg

Conference (2014, March 06)

Considering that brain pathology due to Alzheimer’s disease starts many years before the clinical symptoms become evident, subtle cognitive changes may exist already in the predementia phase. Different ... [more ▼]

Considering that brain pathology due to Alzheimer’s disease starts many years before the clinical symptoms become evident, subtle cognitive changes may exist already in the predementia phase. Different approaches have been used to detect initial cognitive impairments indicative of Alzheimer’s disease. One approach is the assessment of the predictive power of neuropsychological tools in characterizing patients with stable mild cognitive impairment (MCI) versus MCI patients who subsequently develop Alzheimer’s disease. Another approach is the longitudinal evaluation of large cohorts of older adults in population-based studies. Findings from several studies suggest that a memory test that ensures deep encoding of information and assesses retrieval with free as well as cued recall is a useful tool to distinguish patients at an early stage of Alzheimer disease from MCI non-converters. Impaired semantic memory has also been proposed as a neuropsychological marker of predementia Alzheimer’s disease. Beyond the memory domain, category verbal fluency has been shown to predict progression to Alzheimer’s disease. Moreover, combining neuropsychological scores of memory and executive functions and neuroimaging data allows a better discrimination between stable MCI and converters than neuroimaging data alone. Altogether, it is possible to detect cognitive changes that are predictive of the typical form of probable Alzheimer’s disease already in the predementia stage. Such at risk people are thought to be the best target for therapeutic interventions. [less ▲]

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See detailFrance-Brésil : une relation stratégique ?
Santander, Sébastian ULg

Scientific conference (2014, March 06)

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See detailIntentionalisme et représentationalisme de Brentano à Crane
Boccaccini, Federico ULg

Conference (2014, March 06)

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See detailLes quartiers 'ghettos' : des étiquettes collées sur des phénomènes complexes?
Ruelle, Christine ULg

Conference given outside the academic context (2014)

Detailed reference viewed: 11 (1 ULg)