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See detailEulerian Formulation of Spatially Constrained Elastic Rods
Huynen, Alexandre ULg

Doctoral thesis (2015)

Slender elastic rods are ubiquitous in nature and technology. For a vast majority of applications, the rod deflection is restricted by an external constraint and a significant part of the elastic body is ... [more ▼]

Slender elastic rods are ubiquitous in nature and technology. For a vast majority of applications, the rod deflection is restricted by an external constraint and a significant part of the elastic body is in contact with a stiff constraining surface. The research work presented in this doctoral dissertation formulates a computational model for the solution of elastic rods constrained inside or around frictionless tube-like surfaces. The segmentation strategy adopted to cope with this complex class of problems consists in sequencing the global problem into, comparatively simpler, elementary problems either in continuous contact with the constraint or contact-free between their extremities. Within the conventional Lagrangian formulation of elastic rods, this approach is however associated with two major drawbacks. First, the boundary conditions specifying the locations of the rod centerline at both extremities of each elementary problem lead to the establishment of isoperimetric constraints, i.e., integral constraints on the unknown length of the rod. Second, the assessment of the unilateral contact condition requires, in principle, the comparison of two curves parametrized by distinct curvilinear coordinates, viz. the rod centerline and the constraint axis. Both conspire to burden the computations associated with the method. To streamline the solution along the elementary problems and rationalize the assessment of the unilateral contact condition, the rod governing equations are reformulated within the Eulerian framework of the constraint. The methodical exploration of both types of elementary problems leads to specific formulations of the rod governing equations that stress the profound connection between the mechanics of the rod and the geometry of the constraint surface. The proposed Eulerian reformulation, which restates the rod local equilibrium in terms of the curvilinear coordinate associated with the constraint axis, describes the rod deformed configuration by means of either its relative position with respect to the constraint axis (contact-free segments) or its angular position on the constraint surface (continuous contacts.) This formulation circumvents both drawbacks that afflict the conventional Lagrangian approach associated with the segmentation strategy. As the a priori unknown domain, viz. the rod length, is substituted for the known constraint axis, the free boundary problem and the associated isoperimetric constraints are converted into a classical two-point boundary value problem. Additionally, the description of the rod deflection by means of its eccentricity with respect to the constraint axis trivializes the assessment of the unilateral contact condition. Along continuous contacts, this formulation expresses the strain variables, measuring the rod change of shape, in terms of the geometric invariants of the constraint surface, and emphasizes the influence of the constraint local geometry on the reaction pressure. Formalizing the segmentation strategy, a computational model that exploits the Eulerian formulation of the rod governing equations is devised. To solve the quasi-static deflection of elastic rods constrained inside or around a tube-like surface, this computational model identifies the number of contacts, their nature (either discrete or continuous), and the rod configuration at the connections that satisfies the unilateral contact condition and preserves the rod integrity along the sequence of elementary problems. [less ▲]

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See detailAn overview of potamodromous fish upstream movements in medium-sized rivers, by means of fish passes monitoring
Benitez, Jean-Philippe ULg; Nzau Matondo, Billy ULg; Dierckx, Arnaud ULg et al

in Aquatic Ecology (2015), 49(4), 481-497

This study aims to investigate the upstream movement patterns of potamodromous fish species using multi-annual monitoring of modern multi-species fish passes in two medium-sized Belgian rivers: the ... [more ▼]

This study aims to investigate the upstream movement patterns of potamodromous fish species using multi-annual monitoring of modern multi-species fish passes in two medium-sized Belgian rivers: the Berwinne and the Amble`ve. During a 6-year monitoring period including a frequency of 1–5 times per week, the captured individuals were identified, measured and weighed to determine species abundance, and the periodicity of their seasonal movement patterns was investigated in relation to environmental factors. In the Amble`ve, 22 different fish species were monitored (n = 1513 individuals; biomass of 154 kg) and 14 species in the Berwinne (n = 3720; 408 kg). In both fish passes, inter-annual differences were observed, but the first year of monitoring was the best in terms of biomass, indicating the existence of an opening effect just after the fish passes opening, which allowed new migration routes. Salmonids and rheophilic cyprinids were predominant in terms of biomass, while minnow and spirlin were predominant in terms of number of fishes. The diversity in sizeranged from 46 to 760 mm demonstrating the importance of movements in various life stages. The capture periodicity showed different mobility patterns between the adult and juvenile stages in most species. Movements occurred frequently during the circus reproduction period for some species, but many species moved also apart from spawning period. This study highlights the omnipresence of patrimonial holobiotic potamodromous fish at different life stages that reflect their biological needs to move throughout the annual cycle. They must be considered as target species in river continuity restoration programmes and fish-pass design. [less ▲]

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See detailA probabilistic model for predicting the uncertainties of the humid stiction phenomenon on hard materials
Hoang Truong, Vinh ULg; Wu, Ling ULg; Paquay, Stéphane et al

in Journal of Computational & Applied Mathematics (2015), 289

Stiction is a major failure in microelectromechanical system (MEMS) devices in which two contacting surfaces can remain stuck together because of the adhesive forces. Due to the difference between the ... [more ▼]

Stiction is a major failure in microelectromechanical system (MEMS) devices in which two contacting surfaces can remain stuck together because of the adhesive forces. Due to the difference between the surfaces roughness and the adhesive force range, the real contact areas are usually smaller than the apparent one, resulting in a scatter in the adhesive forces. Consequently, the stiction is an uncertain phenomenon. In this work, we develop a probabilistic model to predict the uncertainties of stiction due to the capillary forces acting on stiff materials. This model contains two levels: at the deterministic level, the model can predict the pull-out adhesive contact forces for a given surface topology; at the probabilistic level, the model generates independent identically distributed surfaces on which the deterministic solution can be applied to evaluate the uncertainties related to the stiction phenomenon. [less ▲]

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See detailMAVEN/IUVS Apoapse Observations of the Martian FUV Dayglow
Correira; IUVS team; Stiepen, Arnaud ULg

Poster (2015, December)

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See detailThe Two Types of Aurora on Mars as Observed by MAVEN's Imaging UltraViolet Spectrograph
Schneider; IUVS team; Stiepen, Arnaud ULg

Poster (2015, December)

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See detailH Escape in 3D: MAVEN IUVS observations of the Mars corona
Chaffin; IUVS team; Stiepen, Arnaud ULg

Conference (2015, December)

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See detailMars Ozone Mapping with MAVEN IUVS
Lefèvre; IUVS team; Stiepen, Arnaud ULg

Poster (2015, December)

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See detailTides in the Martian Atmosphere as Observed by MAVEN IUVS
Lo; IUVS team; Stiepen, Arnaud ULg

Poster (2015, December)

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See detailThe Hot Oxygen Corona of Mars: Observations by MAVEN IUVS
Deighan; IUVS team; Stiepen, Arnaud ULg

Poster (2015, December)

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See detailStudy of the Martian cold oxygen corona from the O I 130.4 nm by IUVS/MAVEN
Chaufray; IUVS team; Stiepen, Arnaud ULg

Poster (2015, December)

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See detailRetrieval of Mars' Upper Atmospheric Composition using Dayglow Observations by IUVS on MAVEN
Evans; IUVS team; Stiepen, Arnaud ULg

Poster (2015, December)

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See detailProbing the Martian Atmosphere with MAVEN/IUVS Stellar Occultations
Gröller; IUVS team; Stiepen, Arnaud ULg

Poster (2015, December)

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See detailComparison of serum fractionation methods by data independent label-free proteomics
Baiwir, Dominique ULg; Mazzucchelli, Gabriel ULg; Smargiasso, Nicolas ULg et al

in EuPA Open Proteomics (2015), 9

Off-line sample prefractionations applied prior to biomarker discovery proteomics are options to enable more protein identifications and detect low-abundance proteins. This work compared five commercial ... [more ▼]

Off-line sample prefractionations applied prior to biomarker discovery proteomics are options to enable more protein identifications and detect low-abundance proteins. This work compared five commercial methods efficiency to raw serum analysis using label-free proteomics. The variability of the protein quantities determined for each process was similar to the unprefractionated serum. A 49% increase in protein identifications and 12.2% of reliable quantification were obtained. A 61 times lower limit of protein quantitation was reached compared to protein concentrations observed in raw serum. The concentrations of detected proteins were confronted to estimated reference values. [less ▲]

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See detailSemantic Web and the Future of Health Care Data in Family Practice
Jamoulle, Marc ULg; Vander Stichele, Robert H; Cardillo, Elena et al

in Merit Research Journal of Medicine and Medical Sciences (2015), 3(12), 586-594

Abstract New tools in data management have emerged in the last decade, which are going to revolutionize electronic health records and health information systems. Family practitioners are the first, main ... [more ▼]

Abstract New tools in data management have emerged in the last decade, which are going to revolutionize electronic health records and health information systems. Family practitioners are the first, main and continuous contact with the patient. They are the source and endpoint of the circle of information, generated by judicious medical documentation and smart secondary use of medical data. This article is an introduction to health terminologies, ontologies, semantic data, and linked open data, all expressions used by computer scientists, preparing themselves for the next step: semantic web for health care data [less ▲]

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See detailModeling the dependence between extreme operational losses and economic factors: a conditional semi-parametric Generalized Pareto approach
Hambuckers, julien ULg; Heuchenne, Cédric ULg; Lopez, Olivier

Conference (2015, December)

In this paper, we model the severity distribution of operational losses data, condi- tional on some covariates. Indeed, previous studies [Chernobai et al., 2011, Cope et al., 2012, Chavez-Demoulin et al ... [more ▼]

In this paper, we model the severity distribution of operational losses data, condi- tional on some covariates. Indeed, previous studies [Chernobai et al., 2011, Cope et al., 2012, Chavez-Demoulin et al., 2014a] suggest that this distribution might be in uenced by macroeconomic and rm-speci c factors. We introduce a conditional Generalized Pareto model, where the shape parameter is an unknown function of a linear combina- tion of the covariates. More precisely, we rely on a single-index assumption to perform a dimension reduction that enables to use univariate nonparametric techniques. Hence, we su er neither from too strong parametric assumption nor from the curse of dimen- sionality. Then, we develop an iterative approach to estimate this model, based on the maximisation of a semiparametric likelihood function. Finally, we apply this method- ology on a novel database provided by the bank UniCredit. We use rm-speci c factors to estimate the conditional shape parameter of the severity distribution. Our analysis suggests that the leverage ratio of the company, the proportion of the revenue coming from fees as well as the risk category have an important impact on the tail thickness of this distribution and thus on the probability of su ering from large operational losses. [less ▲]

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See detailThe cultivable surface microbiota of the brown alga Ascophyllum nodosum is enriched in macroalgal-polysaccharide-degrading bacteria
Martin, Marjolaine ULg; Barbeyron, Tristan; Martin, Renée ULg et al

in Frontiers in Microbiology (2015), 6(december),

Bacteriadegradingalgalpolysaccharidesarekeyplayersintheglobalcarboncycleandinalgalbiomassrecycling.Yetthewatercolumn,whichhasbeenstudiedlargelybymetagenomicapproaches,ispoorinsuchbacteriaandtheiralgal ... [more ▼]

Bacteriadegradingalgalpolysaccharidesarekeyplayersintheglobalcarboncycleandinalgalbiomassrecycling.Yetthewatercolumn,whichhasbeenstudiedlargelybymetagenomicapproaches,ispoorinsuchbacteriaandtheiralgal-polysaccharide-degradingenzymes.Evenmoresurprisingly,thefewpublishedstudiesonseaweed-associatedmicrobiomeshaverevealedlowabundancesofsuchbacteriaandtheirspecificenzymes.However,asmacroalgalcell-wallpolysaccharidesdonotaccumulateinnature,thesebacteriaandtheiruniquepolysaccharidasesmustnotbethatuncommon.We,therefore,lookedatthepolysaccharide-degradingactivityofthecultivablebacterialsubpopulationassociatedwithAscophyllumnodosum.FromA.nodosumtriplicates,324bacteriawereisolatedandtaxonomicallyidentified.Outoftheseisolates,78(∼25%)werefoundtoactonatleastonetestedalgalpolysaccharide(agar,i-ork-carrageenan,oralginate).Theisolates“active”onalgal-polysaccharidesbelongto11genera:Cellulophaga,Maribacter,Algibacter,andZobelliaintheclassFlavobacteriia(41)andPseudoalteromonas,Vibrio,Cobetia,Shewanella,Colwellia,Marinomonas,andParaglaceciolaintheclassGammaproteobacteria(37).Amajorpartrepresentslikelynovelspecies.Differentproportionsofbacterialphylaandclasseswereobservedbetweentheisolatedcultivablesubpopulationandthetotalmicrobialcommunitypreviouslyidentifiedonotherbrownalgae.Here,BacteroidetesandGammaproteobacteriawerefoundtobethemostabundantandsomephyla(asPlanctomycetesandCyanobacteria)frequentlyencounteredonbrownalgaeweren’tidentified.Atalowertaxonomiclevel,twelvegenera,well-knowntobeassociatedwithalgae(withtheexceptionforColwellia),wereconsistentlyfoundonallthreeA.nosodumsamples.Evenmoreinteresting,9ofthe11abovementionedgeneracontainingpolysaccharolyticisolateswerepredominantinthiscommoncore.ThecultivablefractionofthebacterialcommunityassociatedwithA.nodosumis,thus,significantlyenrichedinmacroalgal-polysaccharide-degradingbacteriaandthesebacteriaseemimportantfortheseaweedholobionteventhoughtheyareunder-representedinalga-associatedmicrobiomestudies. [less ▲]

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See detailLa vie littéraire au kaléidoscope des Physiologies
Stienon, Valérie ULg

in Site de la Société des Études romantiques et dix-neuviémistes (SERD) (2015)

En mots et en vignettes, la Physiologie littéraire de la monarchie de Juillet élabore ses propres modalités de mise en fiction de la société. Selon un point de vue à la fois avisé et distancié, induit par ... [more ▼]

En mots et en vignettes, la Physiologie littéraire de la monarchie de Juillet élabore ses propres modalités de mise en fiction de la société. Selon un point de vue à la fois avisé et distancié, induit par l’association d’une centralité culturelle parisienne et d’une faible légitimité à l’ombre de la grande littérature, ces petites monographies réorganisent le système des valeurs à travers lesquelles est perçu le fait littéraire à leur époque. C’est l’occasion d’investiguer sur les à-côtés de la littérature, en interrogeant les manières de circonscrire le territoire des lettres et de le faire interagir avec d’autres domaines d’activités. Deux questions font plus particulièrement l’objet de cet article. D'une part, ces textes livrent-ils un traitement englobant et univoque du profil de l’homme de lettres ou s’attachent-ils au contraire à en souligner les nuances et les singularités en multipliant ses variétés, autour de la dichotomie bien connue des figures archétypales du poète et du journaliste ? D'autre part, dans quelle mesure ces textes reconduisent-ils le mythe du génie créateur et les valeurs romantiques du talent et de l’inspiration, compte tenu du fait que celles-ci sont difficilement compatibles avec les stratégies du parvenu et les expédients du jeune auteur pressé d’arriver, ruses que les Physiologies s’appliquent à débusquer, dans la foulée d’une abondante thématisation du macairisme et des fourberies du floueur ? [less ▲]

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See detailExperimental and computational micro–mechanical investigations of compressive properties of polypropylene/multi–walled carbon nanotubes nanocomposite foams
Wan, Fangyi; Tran, Minh Phuong; Leblanc, Christophe ULg et al

in Mechanics of Materials (2015), 91(Part 1), 95-118

The compressive behavior of nanocomposite foams is studied by both experimental and computational micro-mechanics approaches with the aim of providing an efficient computational model for this kind of ... [more ▼]

The compressive behavior of nanocomposite foams is studied by both experimental and computational micro-mechanics approaches with the aim of providing an efficient computational model for this kind of material. The nanocomposites based on polypropylene (PP) and different contents of multi-walled carbon nanotubes (CNTs) are prepared by melt mixing method. The nanocomposite samples are foamed using super-critical carbon dioxide (ScCO2) as blowing agent at different soaking temperatures. The influence of this foaming parameter on the morphological characteristics of the foam micro-structure is discussed. Differential Scanning Calorimetry (DSC) measurements are used to quantify the crystallinity degree of both nanocomposites and foams showing that the crystallinity degree is reduced after the foaming process. This modification leads to mechanical properties of the foam cell walls that are different from the raw nanocomposite PP/CNTs material. Three--point bending tests are performed on the latter to measure the flexural modulus in terms of the crystallinity degree. Uniaxial compression tests are then performed on the foamed samples under quasi-static conditions in order to extract the macro-scale compressive response. Next, a two-level multi-scale approach is developed to model the behavior of the foamed nanocomposite material. On the one hand, the micro-mechanical properties of nanocomposite PP/CNTs cell walls are evaluated from a theoretical homogenization model accounting for the micro-structure of the semi-crystalline PP, for the degree of crystallinity, and for the CNT volume fraction. The applicability of this theoretical model is demonstrated via the comparison with experimental data from the described experimental measurements and from literature. On the other hand, the macroscopic behavior of the foamed material is evaluated using a computational micro-mechanics model using tetrakaidecahedron unit cells and periodic boundary conditions to estimate the homogenized properties. The unit cell is combined with several geometrical imperfections in order to capture the elastic collapse of the foamed material. The numerical results are compared to the experimental measurements and it is shown that the proposed unit cell computational micro-mechanics model can be used to estimate the homogenized behavior, including the linear and plateau regimes, of nanocomposite foams. [less ▲]

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See detailTribulations d’une vieille dame : De la « loi relative aux anormaux et délinquants d’habitude » à la « loi relative à l’internement des personnes atteintes d'un trouble mental »
Garcet, Serge ULg

in Revue Médicale de Liège (2015), 70e année

Le système belge de prise en charge des délinquants atteints de troubles mentaux est organisé selon un principe de défense sociale. Il se caractérise par une double attention pour, d’une part, la ... [more ▼]

Le système belge de prise en charge des délinquants atteints de troubles mentaux est organisé selon un principe de défense sociale. Il se caractérise par une double attention pour, d’une part, la protection de la société par une neutralisation du risque et, d’autre part, la nécessité de soins à prodiguer à la personne internée. L’évolution du cadre juridique de la loi de 1930 relative aux anormaux et délinquants d’habitude à la loi relative à l’internement des personnes atteintes d'un trouble mental de 2014 rend compte des vicissitudes nées du tiraillement entre ces deux piliers sécuritaire et thérapeutique. Dans ce difficile rapport de forces, bien que publiée mais pas encore d’application, la version de 2014 de la loi constitue à bien des égards une évolution positive dans la prise en compte des personnes internées et de leurs besoins. [less ▲]

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