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See detailImprinting superconducting vortex footsteps in a magnetic layer
Brisbois, Jérémy ULg; Motta, Maycon; Avila Osses, Jonathan ULg et al

in Scientific Reports (2016), 6

Local polarization of a magnetic layer, a well-known method for storing information, has found its place in numerous applications such as the popular magnetic drawing board toy or the widespread credit ... [more ▼]

Local polarization of a magnetic layer, a well-known method for storing information, has found its place in numerous applications such as the popular magnetic drawing board toy or the widespread credit cards and computer hard drives. Here we experimentally show that a similar principle can be applied for imprinting the trajectory of quantum units of flux (vortices), travelling in a superconducting film (Nb), into a soft magnetic layer of permalloy (Py). In full analogy with the magnetic drawing board, vortices act as tiny magnetic scribers leaving a wake of polarized magnetic media in the Py board. The mutual interaction between superconducting vortices and ferromagnetic domains has been investigated by the magneto-optical imaging technique. For thick Py layers, the stripe magnetic domain pattern guides both the smooth magnetic flux penetration as well as the abrupt vortex avalanches in the Nb film. It is however in thin Py layers without stripe domains where superconducting vortices leave the clearest imprints of locally polarized magnetic moment along their paths. In all cases, we observe that the flux is delayed at the border of the magnetic layer. Our findings open the quest for optimizing magnetic recording of superconducting vortex trajectories. [less ▲]

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See detailOn the α-polarization of bacterial suspensions: SIP measurements on four bacterial strains
Pilawski, Tamara ULg; Tappe, Wolfgang; Zimmermann, Egon et al

Poster (2016, June 06)

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See detailA Stochastic Multi-scale Model For Predicting MEMS Stiction Failure
Hoang Truong, Vinh ULg; Paquay, Stéphane; Golinval, Jean-Claude ULg et al

in Proceedings of the SEM XIII International Congress and Exposition on Experimental and Applied Mechanics. (SEMXIII 2016) (2016, June 06)

Adhesion is an important phenomenon in the context of MEMS for which the surface forces become dominant in comparison with the body forces. Because the magnitudes of the adhesive forces strongly depend on ... [more ▼]

Adhesion is an important phenomenon in the context of MEMS for which the surface forces become dominant in comparison with the body forces. Because the magnitudes of the adhesive forces strongly depend on the surface interaction distances, which in turn evolve with the roughness of the contacting surfaces, the adhesive forces cannot be determined in a deterministic way. To quantify the uncertainties on the structural stiction behavior of a MEMS, this work proposes a “stochastic multi-scale methodology”. The key ingredient of the method is the evaluation of the random meso-scale apparent contact forces, which homogenize the effect of the nano-scale roughness and are integrated into a numerical model of the studied structure as a random contact law. To obtain the probabilistic behavior at the structural MEMS scale, a direct method needs to evaluate explicitly the meso-scale apparent contact forces in a concurrent way with the stochastic multi-scale approach. To reduce the computational cost, a stochastic model is constructed to generate the random meso-scale apparent contact forces. To this end, the apparent contact forces are parameterized by a vector of parameters before applying a polynomial chaos expansion in order to construct a mathematical model representing the probability of the random parameters vector. The problem of miro-beam stiction is then studied in a probabilistic way. [less ▲]

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See detailMéthodes historiques de recherche en architecture
Frankignoulle, Pierre ULg

Scientific conference (2016, June 06)

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See detailL’hypothèse d’une Pax Persiana. L’Iran et ses rapports avec l’Occident des années 1850 à 2016
Genin, Vincent ULg

Conference given outside the academic context (2016)

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See detailLe IIe style en reliefs : les ensembles de stucs de la Domus aux Bucranes à Ostia Antica
Morard, Thomas ULg; Girard, Thibault

Scientific conference (2016, June 06)

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See detailScreening study of SFC critical method parameters for the determination of pharmaceutical compounds
Dispas, Amandine ULg; Lebrun, Pierre ULg; Sacre, Pierre-Yves ULg et al

in Journal of Pharmaceutical & Biomedical Analysis (2016), 125

Nowadays, supercritical fluid chromatography is commonly presented as a promising alternative technique in the field of separation sciences. Nevertheless the selection of chromatographic conditions and ... [more ▼]

Nowadays, supercritical fluid chromatography is commonly presented as a promising alternative technique in the field of separation sciences. Nevertheless the selection of chromatographic conditions and sample preparation of pharmaceutical compounds remain a challenge and peak distortion was previously highlighted. The main objective of the present work was to evaluate the impact of different critical method parameters (CMPs), i.e. stationary phase, mobile phase composition and injection solvent nature. The experiments were performed considering two groups of antimalarial molecules: one group with neutral/apolar compounds and the other one with salt form of polar compounds. In this context, another objective was to propose a suitable sample solvent for quantitative analysis. The interest of new generation stationary phase to obtain good peak shape and the interest to tune the mobile phase composition were demonstrated. During this study, design of experiments and desirability function approach enabled to highlight optimal chromatographic conditions in order to maximise peak capacity and to get acceptable value of symmetry factor. Regarding sample injection solvent composition, some counterintuitive results were observed: solvents closer to the mobile phase polarity (i.e heptane or 2-propanol/heptane mixture) did not provide best results in terms of peak symmetry. In addition, acetonitrile and short aliphatic alcohols offered an interesting alternative as injection solvent: toxicity of solvents used is clearly reduced and better quantitative performances could be expected while keeping high peak capacity and symmetric sharp peaks. Finally, the quantitative performances were evaluated by the method validation for the quantitative determination of quinine sulfate in a pharmaceutical formulation. These better understandings on critical method parameters led SFC to be an even more promising technique in the field of the analysis of pharmaceutical compounds. [less ▲]

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See detailRewriting History in the Time of Late Capitalism: Uses and Abuses of Built Heritage : introduction to the session
Houbart, Claudine ULg; Dawans, Stéphane ULg

Conference (2016, June 05)

With his expression ceci tuera cela, Hugo established almost two centuries ago a strong link between words and stones as transmission vehicles of human memory. We heritage experts would be inclined to ... [more ▼]

With his expression ceci tuera cela, Hugo established almost two centuries ago a strong link between words and stones as transmission vehicles of human memory. We heritage experts would be inclined to consider stones as more reliable than words, what semiology seems to confirm : stones are clues, and clues are, according to Roland Barthes, tangible proves of “what has been”. But the inspector Columbo has often shown how we can play with these clues, and Umberto Eco would easily forgive us this incursion into mass culture to agree on the idea that we can rewrite history using false justified clues, that is also, tangible heritage. Since the emergence of the restoration discipline, experts have been aware of the danger of falsification : Ruskin’s texts, Boito’s philological restoration, Brandi’s historical instance or the Venice charter are so many illustrations of this concern. But since the 1990’s in Europe, a growing number of restoration and reconstruction projects very clearly depart from this fundamental idea. Of course, the collapse of the Soviet bloc has created a particular political context in which (re-)emerging nations attempted to (re-)build their identity through architectural symbols (leading to the writing of the Riga charter). But more generally, this phenomenon is closely linked to the cultural context : on the one hand, the postmodern movement has deeply questioned the idea of “sincerity”, with a tendency to blur the limits between true and false and, as a consequence, between original and copy. And on the other hand, in the heritage sphere, the globalisation of the debate progressively rattled european certitudes about concepts as essential as authenticity, leading to the replacement of the self-confidence expressed by the Venice charter by a careful relativism, illustrated by the Nara document thirty years later. These contemporary phenomenons have important side effects. In the context of late capitalism, heritage has become a major economic issue, especially as many cities have well understood its potentialities in terms of city branding. This could of course be seen as a positive opportunity for heritage conservation ; nevertheless, a rich scientific literature has shown that tourism can deeply transform our representation of the past. The tourist is a client rather than an amateur, and his quest of authenticity is often satisfied by what the French philosopher Yves Michaud has called “adulterated authenticity”, the one from over-restored monuments, reconstructed city centres, eco-museums, and, why not, theme parks. More than authentic built remains, the “tourist gaze” shapes more and more our representation of “what has been”, and the arguments developed by heritage experts in response to globalisation and identity issues are seized upon by city marketing specialists willing to meet a mostly commercial demand, sometimes tinged with dubious political motivations. What we intend to question in this session is the limit between uses and abuses of heritage and heritage discourse and more particularly whether, as suggested by Theodore Scaltsas’ inspiring paper “Identity, origin and spatiotemporal continuity” (1981), the intentions underpinning restoration and reconstruction projects affect the very essence of restored or reconstructed objects. Besides architectural history and conservation theory, we welcome contributions in the fields of sociology, anthropology, philosophy, history, political sciences, geography, tourism economy and even psychology. [less ▲]

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See detailNumerical Properties of a Discontinuous Galerkin formulation for electro-thermal coupled problems
Homsi, Lina; Geuzaine, Christophe ULg; Noels, Ludovic ULg

in Papadrakakis, M.; Papadopoulos, V.; Stefanou, G. (Eds.) et al Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering, Crete Island, Greece, 5–10 June 2016 (2016, June 05)

Discontinuous Galerkin (DG) methods are attractive tools to integrate several PDEs in engineering sciences, due to their high order accuracy and their high scalability in parallel simulations. The main ... [more ▼]

Discontinuous Galerkin (DG) methods are attractive tools to integrate several PDEs in engineering sciences, due to their high order accuracy and their high scalability in parallel simulations. The main interest of this work is to derive a constant and stable Discontinuous Galerkin method for two-way electro-thermal coupling analyses. A fully coupled nonlinear weak formulation for electro-thermal problems is developed based on continuum mechanics equations which are discretized using the Discontinuous Galerkin method. Toward this end, the weak form is written in terms of energetically conjugated fields gradients and fluxes. In order to validate the effectiveness of the formulation and illustrate the algorithmic properties, a numerical test for composite materials is performed. [less ▲]

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See detailLe cadre et l'oubli : Mallarmé après Mallarmé
Durand, Pascal ULg

Conference (2016, June 04)

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See detailAnalyser sans compter ni classer. Atelier d'étiquetage réflexif
Lejeune, Christophe ULg

Scientific conference (2016, June 03)

L'atelier est introduit par une brève présentation des principes généraux de la recherche qualitative ainsi que par quelques-unes des ficelles d'étiquetage réflexif exposées dans le «Manuel d'analyse ... [more ▼]

L'atelier est introduit par une brève présentation des principes généraux de la recherche qualitative ainsi que par quelques-unes des ficelles d'étiquetage réflexif exposées dans le «Manuel d'analyse qualitative. Analyser sans compter ni classer» (De Boeck, 2014). Les participants mettront ensuite ces ficelles en pratique en analysant individuellement un court extrait de matériau qualitatif (le témoignage d'un enseignant en difficulté). Christophe Lejeune coordonnera ensuite la mise en commun en identifiant les pièges à éviter. L'atelier débouchera alors sur une discussion collective des pratiques productives en recherche qualitative. La discussion abordera les problèmes qui préoccupent les participants, y compris les questions épistémologiques que soulève la pratique de la recherche qualitative. [less ▲]

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See detailHydrogeological assessment of non-linear underground enclosures
Pujades, Estanislao ULg; Jurado Elices, Anna ULg; Carrera, Jesus et al

in Engineering Geology (2016), 207

Excavations below the water table are usually undertaken by combining the protection of retaining walls with dewatering by pumping wells. Severe difficulties may arise if the retaining walls have defects ... [more ▼]

Excavations below the water table are usually undertaken by combining the protection of retaining walls with dewatering by pumping wells. Severe difficulties may arise if the retaining walls have defects. Therefore, their state must be determined and, if needed, the defects repaired or the dewatering system redesigned. The state of underground retaining walls can be evaluated using hydrogeological methods, but these methods are well-established only for linear excavations. The objective of this work is to propose a procedure to evaluate the state of non-linear underground enclosures by analyzing the groundwater response to pumping inside the enclosure. The proposed method, which is based on diagnostic plots (derivative of drawdown with respect to the logarithm of time), allows (1) determining if an underground non-linear enclosure has isolated openings or numerous defects and (2) computing its effective conductance or effective hydraulic conductivity. The methodology is tested with data collected during the excavation of a shaft required for the construction of the high speed train (HST) tunnel in Barcelona, Spain. The procedure can be applied using the wells drilled for dewatering. Although a test before the excavation is recommended to evaluate the underground retaining walls (Watertightness Assessment Test), the method can be applied using data collected at the beginning of the dewatering stage. [less ▲]

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See detailStructure Characterization and Properties of K‑Containing Copper Hexacyanoferrate
Ojwang, Dickson O.; Grins, Jekabs; Wardecki, Dariusz et al

in Inorganic Chemistry (2016), 55

Copper hexacyanoferrate, CuII[FeIII(CN)6]2/3·nH2O, was synthesized, and varied amounts of K+ ions were inserted via reduction by K2S2O3 (aq). Ideally, the reaction can be written as CuII[FeIII(CN)6]2 ... [more ▼]

Copper hexacyanoferrate, CuII[FeIII(CN)6]2/3·nH2O, was synthesized, and varied amounts of K+ ions were inserted via reduction by K2S2O3 (aq). Ideally, the reaction can be written as CuII[FeIII(CN)6]2/3·nH2O + 2x/3K+ + 2x/3e− ↔ K2x/3CuII[FeIIxFeIII1−x(CN)6]2/3·nH2O. Infrared, Raman, and Mössbauer spectroscopy studies show that FeIII is continuously reduced to FeII with increasing x, accompanied by a decrease of the a-axis of the cubic Fm3̅m unit cell. Elemental analysis of K by inductively coupled plasma shows that the insertion only begins when a significant fraction, ∼20% of the FeIII, has already been reduced. Thermogravimetric analysis shows a fast exchange of water with ambient atmosphere and a total weight loss of ∼26wt % upon heating to 180 °C, above which the structure starts to decompose. The crystal structures of CuII[FeIII(CN)6]2/3·nH2O and K2/3Cu[Fe(CN)6]2/3·nH2O were refined using synchrotron X-ray powder diffraction data. In both, one-third of the Fe(CN)6 groups are vacant, and the octahedron around CuII is completed by water molecules. In the two structures, difference Fourier maps reveal three additional zeolitic water sites (8c, 32f, and 48g) in the center of the cavities formed by the −Cu−N−C−Fe− framework. The K-containing compound shows an increased electron density at two of these sites (32f and 48g), indicating them to be the preferred positions for the K+ ions. [less ▲]

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See detailUnveiling the Room-Temperature Magnetoelectricity of Troilite FeS
Ricci, Fabio ULg; Bousquet, Eric ULg

in Physical Review Letters (2016), 116

We report on a first-principles study of the troilite phase of iron sulfide (FeS). We show that even if, a few decades ago, this material was thought to be ferroelectric, the structural transition from ... [more ▼]

We report on a first-principles study of the troilite phase of iron sulfide (FeS). We show that even if, a few decades ago, this material was thought to be ferroelectric, the structural transition from the high P63/mmc to the low P6¯2c symmetry phase does not involve polar instabilities, though the space inversion center symmetry is broken. Our calculations and symmetry analysis nevertheless reveal that FeS is magnetoelectric at room temperature with a response larger than the prototypical room-temperature magnetoelectric crystal Cr2O3. We also show that the spin channel decomposition of the polarization exhibits nonzero values in the opposite direction in FeS, which is actually a general hint of the presence of a magnetoelectric monopole in diagonal magnetoelectrics. [less ▲]

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See detailAlternative Investments
Platania, Federico ULg; Lambert, Marie ULg

Scientific conference (2016, June 03)

This paper examines the dynamic trading strategies implemented by hedge fund managers using a Kalman filter of hedge fund betas across styles. We further investigate the risk drivers of dynamic trades ... [more ▼]

This paper examines the dynamic trading strategies implemented by hedge fund managers using a Kalman filter of hedge fund betas across styles. We further investigate the risk drivers of dynamic trades, examining which conditioning/macroeconomic variables strongly lead the time variation in fund trades. We report the significance of macroeconomic factors such as interest rates, dividend yield, GDP growth and US unemployment. We show that hedge fund managers do control the intensity of their exposures according to economic uncertainty and that differences between up- and down-market regimes can be observed. Commonly, Hedge funds tend to dislike high-dividend paying stocks. Besides, all hedge fund styles are shown to display pro-cyclical exposures towards directional equity factors as well as credit and liquidity risks. Small growth stocks, however, are revealed to be crisis investments whose allocation increases with unemployment, inflation or volatility. As volatility increases, the value of growth options embedded into growth stocks indeed increases. Growth stocks are shown to hedge market reversals and volatility. The outperformance of growth companies in recessions might also relate to their cost flexibility. Allocation to small stocks embed strong micro risks and might also constitute a hedge in economic slowdowns. This might explain why some funds with such a particular investment focus appear to be countercyclical. [less ▲]

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See detailSur le théorème de Vaschy-Buckingham
Debongnie, Jean-François ULg

Report (2016)

This is a critical review of various proofs of the Vaschy-Buckingham theorem. The analysis tends to be as rigorous as possible, with clear definitions of physical quantities, unities and measures.

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See detailDoes formal 0-3 years old child care availability boost employment rate of mothers ? Panel data based evidence from Belgium
Dujardin, Claire; Fonder, Muriel; Lejeune, Bernard ULg

Conference (2016, June 03)

In 2003, a new multi-annual program aimed at increasing the availability of formal child care for 0-3 year old children was launched in Wallonia, the French-speaking part of Belgium. This paper is ... [more ▼]

In 2003, a new multi-annual program aimed at increasing the availability of formal child care for 0-3 year old children was launched in Wallonia, the French-speaking part of Belgium. This paper is interested in evaluating if this increased availability of formal child care resultedin a higher employment rate for women with at least one child under 3. To this end, we use a difference-in-differences approach based on municipality-level panel data, taking advantage of the fact that the increase in availability of formal child care differed greatly across municipalities. We find that the raise in child care availability significantly increased the maternal employment rate, but to a lesser extent than expected, most likely because of a substantial crowding-out effect. [less ▲]

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See detailDes médecins enquêtent sur le travail ouvrier: terrains et pratiques, Belgique, France, États-Unis, c. 1840-1940
Geerkens, Eric ULg; Rainhorn, Judith

Scientific conference (2016, June 03)

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