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See detailA Non-Local Damage-Enhanced Incremental-Secant Mean-Field-Homogenization For Composite Laminate Failure Predictions
Wu, Ling ULg; Adam, Laurent; Doghri, Issam et al

Conference (2015, July 06)

Recently, the authors have presented an incremental-secant mean-field homogenisation (MFH) process for non-linear composite materials [4]. In this formulation, a virtual elastic unloading is applied to ... [more ▼]

Recently, the authors have presented an incremental-secant mean-field homogenisation (MFH) process for non-linear composite materials [4]. In this formulation, a virtual elastic unloading is applied to evaluate the virtual residual stress and strain states reached in each elasto-plastic phase. These virtual states are then used as a starting point to apply a secant homogenization method. This incremental-secant MFH process can handle non-proportional and nonmonotonic loadings, and naturally possesses an isotropic instantaneous stiffness operator to be used in the Eshelby tensor. This incremental-secant MFH homogenization can account for the first and second statistical moment estimation of the current yield stress in the composite phases during the computation of the plastic flow. When accounting for a second statistical moment estimation, the plastic yield in the composite material phases is captured with a higher accuracy, improving the predictions, mainly in the case of short fiber composite materials [6], see Fig. 1(a). The incremental MFH can handle material softening when extended to include a damage model. Indeed, as the secant formulation is applied from an unloaded state, the inclusion phase can be elastically unloaded during the softening of the matrix phase, contrarily to the case of the incremental-tangent method [3, 5], see Fig. 1(b). Moreover, when formulating the damage model in the composite phases in a non-local way, as with the non-local implicit approach, [1, 2], the MFH scheme can be used to model strain localization in composite structures [5], without suffering from the loss of the solution uniqueness. [less ▲]

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See detailPhytoplankton abundance and diversity in the Congo river at high and low waters
Stoyneva, MP; Descy, JP; Bouillon, S et al

Conference (2015, July 05)

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See detailGaz à effet de serre indirects et qualité de l'air aux latitudes moyennes de l'hémisphère nord : tendances à long terme et variabilité déduites de télémesures effectuées au Jungfraujoch (Alpes suisses, 3580 m)
Franco, Bruno ULg; Bader, Whitney ULg; Lejeune, Bernard ULg et al

Conference (2015, July 01)

Indirect greenhouse gases and air quality at Northern Hemisphere mid-latitudes: long-term trends and variability derived from ground-based remote sensing at Jungfraujoch (Swiss Alps, 3580 m a.s.l.). We ... [more ▼]

Indirect greenhouse gases and air quality at Northern Hemisphere mid-latitudes: long-term trends and variability derived from ground-based remote sensing at Jungfraujoch (Swiss Alps, 3580 m a.s.l.). We present an overview of recent investigations conducted by the Solar and Atmospheric Physics Infrared Group at the University of Liège and dedicated to the long-term monitoring of atmospheric gases with an indirect greenhouse effect and affecting air quality at Northern Hemisphere mid-latitudes. Gas concentrations are derived from high-resolution solar spectra recorded at the Jungfraujoch station (Swiss Alps, 46.5° N, 8.0° E, 3580 m a.s.l.), using Fourier transform infrared spectrometers. Time series obtained from these observations, along with satellite measurements and simulations from numerical models, allow for the study of both variability and recent evolution of these species and are critical for air quality monitoring and understanding climate changes. [less ▲]

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See detailComposite hydraulic modeling to design a complex dam spillway
Erpicum, Sébastien ULg; Dewals, Benjamin ULg; Archambeau, Pierre ULg et al

Conference (2015, July 01)

The paper presents the application of a composite hydraulic modeling approach to the rehabilitation studies of a complex dam spillway. First, a physical scale model of the existing works has been built ... [more ▼]

The paper presents the application of a composite hydraulic modeling approach to the rehabilitation studies of a complex dam spillway. First, a physical scale model of the existing works has been built and operated. It enabled to define very accurately the actual discharge capacity and to validate a numerical model of the system. Second, the numerical model has been used to rapidly test several rehabilitation solutions. Finally, the final design has been validated and optimized using the physical model. The paper shows how composite hydraulic modeling enables to combine the inherent advantages of physical and numerical modeling approaches, which are complementary, while being beneficial to the delay as well as the quality of the analysis. [less ▲]

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See detailQuantitatively mimicking wet colloidal suspensions with dry granular media
Messina, René; Aljawhari, Sarah; Bécu, Lydiane et al

in Scientific Reports (2015)

Athermal two-dimensional granular systems are exposed to external mechanical noise leading to Brownian-like motion. Using tunable repulsive interparticle interaction, it is shown that the same ... [more ▼]

Athermal two-dimensional granular systems are exposed to external mechanical noise leading to Brownian-like motion. Using tunable repulsive interparticle interaction, it is shown that the same microstructure as that observed in colloidal suspensions can be quantitatively recovered at a macroscopic scale. To that end, experiments on granular and colloidal systems made up of magnetized particles as well as computer simulations are performed and compared. Excellent agreement throughout the range of the magnetic coupling parameter Γ is found for the pair distribution as well as the bond-orientational correlation functions. This finding opens new ways to efficiently and very conveniently explore phase transitions, crystallization, nucleation, etc in confined geometries. [less ▲]

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See detailA new test of uniformity for object orientations in astronomy
Pelgrims, Vincent ULg

in Heavens, A. F.; Starck, J.-L.; Krone-Martins, A. (Eds.) Statistical Challenges in 21st Century Cosmology (2015, July 01)

We briefly present a new coordinate-invariant statistical test dedicated to the study of the orientations of transverse quantities of non-uniformly distributed sources on the celestial sphere. These ... [more ▼]

We briefly present a new coordinate-invariant statistical test dedicated to the study of the orientations of transverse quantities of non-uniformly distributed sources on the celestial sphere. These quantities can be projected spin-axes or polarization vectors of astronomical sources. [less ▲]

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See detailBiomechanical Analysis of Abdominal Injury in Tennis Serves. A Case Report
Tubez, François ULg; Forthomme, Bénédicte ULg; Croisier, Jean-Louis ULg et al

in Journal of Sports Science & Medicine (2015), 14

The serve is an important stroke in any high level tennis game. A well-mastered serve is a substantial advantage for players. However, because of its repeatability and its intensity, this stroke is ... [more ▼]

The serve is an important stroke in any high level tennis game. A well-mastered serve is a substantial advantage for players. However, because of its repeatability and its intensity, this stroke is potentially deleterious for upper limbs, lower limbs and trunk. The trunk is a vital link in the production and transfer of energy from the lower limbs to the upper limbs; therefore, kin-ematic disorder could be a potential source of risk for trunk injury in tennis. This research studies the case of a professional tennis player who has suffered from a medical tear on the left rectus abdominis muscle after tennis serve. The goal of the study is to understand whether the injury could be explained by an inappropriate technique. For this purpose, we analyzed in three dimensions the kinematic and kinetic aspects of the serve. We also performed isokinetic tests of the player’s knees. We then compared the player to five other professional players as refer-ence. We observed a possible deficit of energy transfer because of an important anterior pelvis tilt. Some compensation made by the player during the serve could be a possible higher abdominal contraction and a larger shoulder external rotation. These partic-ularities could induce an abdominal overwork that could explain the first injury and may provoke further injuries. [less ▲]

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See detailWASP-80b has a dayside within the T-dwarf range
Triaud, Amaury H. M. J.; Gillon, Michaël ULg; Ehrenreich, David et al

in Monthly Notices of the Royal Astronomical Society (2015), 450

WASP-80b is a missing link in the study of exoatmospheres. It falls between the warm Neptunes and the hot Jupiters and is amenable for characterization, thanks to its host star's properties. We observed ... [more ▼]

WASP-80b is a missing link in the study of exoatmospheres. It falls between the warm Neptunes and the hot Jupiters and is amenable for characterization, thanks to its host star's properties. We observed the planet through transit and during occultation with Warm Spitzer. Combining our mid-infrared transits with optical time series, we find that the planet presents a transmission spectrum indistinguishable from a horizontal line. In emission, WASP-80b is the intrinsically faintest planet whose dayside flux has been detected in both the 3.6 and 4.5 μm Spitzer channels. The depths of the occultations reveal that WASP-80b is as bright and as red as a T4 dwarf, but that its temperature is cooler. If planets go through the equivalent of an L-T transition, our results would imply that this happens at cooler temperatures than for brown dwarfs. Placing WASP-80b's dayside into a colour-magnitude diagram, it falls exactly at the junction between a blackbody model and the T-dwarf sequence; we cannot discern which of those two interpretations is the more likely. WASP-80b's flux density is as low as GJ 436b at 3.6 μm; the planet's dayside is also fainter, but bluer than HD 189733Ab's nightside (in the [3.6] and [4.5]Spitzer bands). Flux measurements on other planets with similar equilibrium temperatures are required to establish whether irradiated gas giants, such as brown dwarfs, transition between two spectral classes. An eventual detection of methane absorption in transmission would also help lift that degeneracy. We obtained a second series of high-resolution spectra during transit, using HARPS. We reanalyse the Rossiter-McLaughlin effect. The data now favour an aligned orbital solution and a stellar rotation nearly three times slower than stellar line broadening implies. A contribution to stellar line broadening, maybe macroturbulence, is likely to have been underestimated for cool stars, whose rotations have therefore been systematically overestimated. [less ▲]

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See detailLa Musique silencieuse de José Muñoz et Carlos Sampayo : déconstruction des normes et lecture émotionnelle
Dejasse, Erwin ULg

Doctoral thesis (2015)

Cette thèse met en lumièredans l'oeuvre de José Muñoz et Carlos Sampayo les mécanismes de déconstruction des normes issues de la bande dessinée de genre fondée sur le principe de l’illusion référentielle ... [more ▼]

Cette thèse met en lumièredans l'oeuvre de José Muñoz et Carlos Sampayo les mécanismes de déconstruction des normes issues de la bande dessinée de genre fondée sur le principe de l’illusion référentielle. Cette entreprise de dislocation des standards graphiques et narratifs vise à substituer à la lecture traditionnelle fondée sur la consommation du récit, une lecture émotionnelle. [less ▲]

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See detailIntégration de la continuité spatiale dans la structure multidimensionnelle d’un entrepôt de données - SOLAP raster
Kasprzyk, Jean-Paul ULg

Doctoral thesis (2015)

Technological advances in recent decades have created a massive acquisition of digital data whose volume grows exponentially. To efficiently extract the information they contain, powerful tools have been ... [more ▼]

Technological advances in recent decades have created a massive acquisition of digital data whose volume grows exponentially. To efficiently extract the information they contain, powerful tools have been developed to collect, store and analyze these data. These tools are gathered in a discipline called “business intelligence”. Among them, data warehouses are responsible for archiving data by structuring them in a multidimensional way (time, space or others). They are called data hypercubes or data cubes when they are limited to three dimensions. Hypercubes can supply OLAP (On Line Analytical Processing) systems that aim at quickly synthesizing information in interactive tables and charts for decision-makers from various fields: marketing, environment, criminology, etc. Thus, users can navigate into hypercubes using OLAP operations such as slicing on dimension members (e.g. data aggregation for the month of January in the time dimension), or drilling into hierarchies (e.g. switching from the “year” level to the “month” level in the time dimension). When OLAP is coupled with spatial analysis techniques supplied by geographic information systems (GIS), a map interface then improves the exploration of data: OLAP operations can be applied to dimensions defined in the geographical space (spatial drilling or spatial slicing). This kind of tool is called SOLAP (Spatial OLAP). SOLAP tools currently available on the market all suffer from the same deficiency: they are unable to represent spatial dimensions (X, Y) in a continuous way. This representation is nevertheless essential for the management of spatially continuous phenomena (temperature, pollution, etc.) but also for visualizing spatially discrete events (product sales, crimes, etc.) while minimizing the Modifiable Areal Unit Problem (MAUP). This kind of visualization is used especially by the police to predict the location of future crimes through hotspot maps which are generated by the Kernel Density Estimation (KDE) method. In the field of GIS, raster data (as opposed to vector data) enable effective representation of spatial continuity through digital georeferenced grids. Whereas current SOLAP tools only consider vector data, our research uses the raster model to integrate spatial continuity into the multidimensional structure of a data warehouse feeding a SOLAP ("raster SOLAP"). Despite its underutilization in the SOLAP literature, the raster model has many similarities with a particular kind of data cube: the MOLAP cube (Multidimensional OLAP). Like a satellite image (raster) representing the two planimetric spatial dimensions and one "spectral band" dimension, a MOLAP cube is a three dimensional array whose cells’ coordinates (similar to raster pixels) enable an efficient indexation of dimensions’ members (describing the analyzed facts). In a first original model that we call "raster cube" we define the bases for a three-dimensional raster SOLAP, starting from the definition of a MOLAP cube. Unlike vector SOLAP - where spatiality is attached to a semantic dimension through pointers to geometries - our model directly integrates spatial dimensions (X, Y) in the multidimensional structure of the data warehouse. With this original feature, any geographical entity (country, building, road, etc.) can be imported on the fly as a member in the analysis of the user, which is hardly possible with conventional vector SOLAP tools. An extension of this SOLAP model, called "raster hypercube", is then developed by entrusting the management of extra non-spatial dimensions to a relational database management system (Relational OLAP or ROLAP). The raster hypercube is then populated by KDE raster fields representing crime densities, which are defined in a continuous space (raster dimensions) through time and crime types (ROLAP dimensions). Our model is able to combine the production of hotspot maps at different scales of analysis with SOLAP navigation operations: slicing on spatial or non-spatial members, and drilling into the hierarchy of spatial or non-spatial dimensions. Our raster hypercube model is validated by an operating prototype which is based on open source tools only. Several datasets are integrated through KDE fields, including crime data from London and Seattle. At the end of our work, the results of a comparative study between raster SOLAP and vector SOLAP demonstrate that hybrid vector/raster SOLAP architectures present the same interest for spatial data as hybrid ROLAP/MOLAP architectures do for purely semantic data (management of detailed hypercubes [less ▲]

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See detailPromoting Competition at the Digital Age with an Application to Belgium
Copée, Pierre ULg; Gautier, Axel ULg; Lefevre, Mélanie ULg

E-print/Working paper (2015)

In this paper, we develop a fully-fledged postal market model to assess the extent of competition in the mail market in a context of declining mail volumes due to e-substitution. Our focus will be on the ... [more ▼]

In this paper, we develop a fully-fledged postal market model to assess the extent of competition in the mail market in a context of declining mail volumes due to e-substitution. Our focus will be on the Belgian market situation that is interesting for at least two reasons. First, the homogenous nature of the country implies that the extent of the entrant's market coverage will be either limited to the few very densely populated areas or large covering the whole country at the exception of the few very sparely populated areas. Second, because strong licensing requirements -including coverage constraints- are imposed on competing postal operators and they may constitute barrier to entry. Our model allows us to estimate the extent of entry, the cost of meeting the licensing requirements for potential entrants and the impact of entry on the cost of the universal service. [less ▲]

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See detailDe nationaliteit van Belgische ‘jihadisten’ op de schopstoel : wanneer worden ‘nieuwe’ Belgen ‘echte’ Belgen?
Wautelet, Patrick ULg

Conference (2015, July)

This presentation first gives an overview of the current legal standards for deprivation of nationality based on terrorism in Belgium and France. In a second part, it focuses on the question whether it ... [more ▼]

This presentation first gives an overview of the current legal standards for deprivation of nationality based on terrorism in Belgium and France. In a second part, it focuses on the question whether it may be justified to treat different categories of nationals differently in nationality law and more specifically when dealing with deprivation of nationality. An attempt is made to analyze the French and Belgian legal framework from the angle of the prohibition of discrimination. [less ▲]

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See detailA ROBUST APPROACH OF TOPOLOGIC OPTIMIZATION OF MECHANICAL AND AERONAUTICAL COMPONENTS FABRICATED BY ADDITIVE MANUFACTURING
Bauduin, Simon ULg

in Bauduin, Simon (Ed.) Poster : A ROBUST APPROACH OF TOPOLOGIC OPTIMIZATION OF MECHANICAL AND AERONAUTICAL COMPONENTS FABRICATED BY ADDITIVE MANUFACTURING (2015)

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See detailCeci n’est pas un conseil !
Choffray, Jean-Marie ULg

E-print/Working paper (2015)

La « Grande Récession de 2008 » a un mérite. Un seul ! Elle a rendu public le fait que personne ne savait exactement ce qui s’était passé, ni ce qui se passait. Pourquoi une telle crise de confiance avait ... [more ▼]

La « Grande Récession de 2008 » a un mérite. Un seul ! Elle a rendu public le fait que personne ne savait exactement ce qui s’était passé, ni ce qui se passait. Pourquoi une telle crise de confiance avait-elle vu le jour ? Quelles en seraient les conséquences ? Toutes et tous se sont trompés, y compris les meilleurs. Même celles et ceux qui étaient convaincus d’avoir raison ! Plus que jamais, l’incertitude, la saine et souveraine incertitude, garantit la liberté de l’investisseur... et du professeur ! [less ▲]

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See detailHPAEC-PAD profiles of maltooligosaccharide produced by hydrolysis of sorghum starches using amylases from various sources
Boudries, Nadia; Sindic, Marianne ULg; Belhaneche-Bensemra, Naima et al

in International Journal of Biotechnology and Food Science (2015), 3 (4)

Starches isolated from white and pigmented sorghum (Sorghum bicolor (L.) Moench) were used to determine enzymatic activity of starch hydrolysis by fungal (Aspergillus Oryzae) and bacterial (Bacillus ... [more ▼]

Starches isolated from white and pigmented sorghum (Sorghum bicolor (L.) Moench) were used to determine enzymatic activity of starch hydrolysis by fungal (Aspergillus Oryzae) and bacterial (Bacillus Subtilis) α-amylase and oligosaccharides profiles of hydrolysate was determinate in same conditions by High Performance Exchange Anion Chromatography with Pulsed Amperometric Detection (HPEAC-PAD). Pure starches from potato, amylose and amylopectin were used for comparison. Oligosaccharide compositions ranging from glucose (DP1) to maloheptaose (DP7) as well as the significantly effect of α-amylase source and starch structure were determined. [less ▲]

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See detailAlignments of quasar axes with large-scale structures
Hutsemekers, Damien ULg; Braibant, Lorraine ULg; Pelgrims, Vincent ULg et al

Conference (2015, July)

Based on measurements of optical linear polarization of quasars belonging to large groups at redshift ~ 1.3, we found that quasar spin axes are likely parallel to their host large-scale structures. The ... [more ▼]

Based on measurements of optical linear polarization of quasars belonging to large groups at redshift ~ 1.3, we found that quasar spin axes are likely parallel to their host large-scale structures. The observations and the statistical analysis will be reviewed, and interpretations discussed. [less ▲]

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See detailWritten Corrective Feedback: A Case Study
Noiroux, Kevin ULg

Conference (2015, July)

The present study looks at the efficacy of 3 types of written corrective feedback on errors made by French-Speaking High School students writing in English. More than 100 students, taught by 5 different ... [more ▼]

The present study looks at the efficacy of 3 types of written corrective feedback on errors made by French-Speaking High School students writing in English. More than 100 students, taught by 5 different teachers in 3 different schools, participated in the study. Each participant was randomly assigned to a different type of written corrective feedback: underlining, direct correct or explanation. Each time the students wrote a text in their EFL class, I (the researcher) corrected it, selected 10 errors and asked the students to state whether they understood the error. If they understood the error, they were asked to correct and/or explain it, depending on their treatment group. I then analyzed the corpus of more than 2000 errors: all the errors were categorized and the uptake moves (students’ corrections and explanations) verified. Finally, I checked whether there was a positive correlation between error types, types of corrective feedback, and students’ uptake. [less ▲]

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