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See detailElectrochemical Mechanism of TiMnSn4 as Anode Material for Li-ion Batteries
Lippens, Pierre-Emmanuel; Jumas, Jean-claude; Olivier-Fourcade, Josette et al

Conference (2017, September 04)

Li-ion batteries are widely used in portable electronic devices, electric vehicles or energy storage systems for intermittent energy sources, due to their high energy density, light weight and long cycle ... [more ▼]

Li-ion batteries are widely used in portable electronic devices, electric vehicles or energy storage systems for intermittent energy sources, due to their high energy density, light weight and long cycle life. However, the performances must be continuously improved, which requires the development of new electrode materials. Carbon is commercially used for the anode but its specific capacity is limited to 372 mAh g-1 due to the electrochemical insertion mechanism involving only 1 Li per 6 C. In order to increase the specific capacity, Sn was considered as electrochemically active element although it is about ten times heavier than C. This is due to the alloying/dealloying mechanism with up to 4.4 Li per Sn, providing a theoretical capacity of 992 mAh g-1. However, the Sn ↔ Li4.4Sn reversible transformations are associated with large volume variations responsible for capacity fading.Tin intermetallic compounds of the form MSnx, where M is a transition metal, were proposed to overcome this problem. The first lithiation transforms the pristine material into Li7Sn2/M nanocomposites where the M nanoparticles are expected to buffer the volume variations [1]. However, the delithiation process is more complex involving a possible back reaction of M with Sn, which could play a crucial role in the cycling stability. Such reaction was observed for Ni3Sn4 [2] and MnSn2 [3] but not for FeSn2 [4]. In addition, TiSnx intermetallics show very poor electrochemical activity [5]. The present work concerns the tin based ternary phase TiMnSn4 as new anode material for Li-ion batteries. This compound is of particular interest because it contains two different transition metals that are expected to react differently with Sn during delithiation, if we consider the previous results obtained for MnSnx and TiSnx. TiMnSn4 was obtained by mechanosynthesis to optimize the microstructure and characterized by different experimental tools and DFT (density functional theory) calculations. We propose an analysis of the reaction mechanism based on operando X-ray diffraction and 119Sn Mössbauer spectroscopy combined with a DFT interpretation of the electrochemical potential curve. References 1) M. Chamas, M.T. Sougrati, C. Reibel, P.E. Lippens, Chem. Mater. 25, 2410 (2013). 2) K.K.D. Ehinon, S. Naille, R. Dedryvère, P.E. Lippens, J.C. Jumas, D. Gonbeau, Chem. Mater. 20, 5388 (2008). 3) A. Mahmoud, M. Chamas, J.C. Jumas, B. Philippe, R. Dedryvère, D. Gonbeau, I. Saadoune, P.E. Lippens, J. Power Sources 244, 246 (2013). 4) M. Chamas, P.E. Lippens, J.C. Jumas, K. Boukerma, R. Dedryvère, D. Gonbeau, J. Hassoun, S. Panero, B. Scrosati, J. Power Sources 196, 7011 (2011). 5) A. Ladam, L. Aldon, P.E. Lippens, J. Olivier-Fourcade, J.C. Jumas, C. Cenac-Morthe, Hyperfine Interact. 237, 51 (2016). [less ▲]

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See detailSurface solar radiation modelling over 1900-2014: comparison between the regional climate model MAR and reanalyses
Wyard, Coraline ULiege; Doutreloup, Sébastien ULiege; Belleflamme, Alexandre ULiege et al

Poster (2017, September 04)

Many studies show that the surface solar radiation has underwent large variations over the second half of the 20th century as a result of variations in cloud cover and aerosol loading in the atmosphere ... [more ▼]

Many studies show that the surface solar radiation has underwent large variations over the second half of the 20th century as a result of variations in cloud cover and aerosol loading in the atmosphere. However, it is difficult to build strong conclusions before the 1950s because of the observations scarcity. The evolution of the surface solar radiation has been reconstructed over 1900-2014 using the regional model MAR (« Modèle Atmosphérique Régional ») which has recently been chosen to be part of the EURO-CORDEX project, thanks to the CORDEX.be project. Simulations were performed at a horizontal resolution of 5 km over a domain of 600 x 550 km² covering Belgium. Boundary conditions were provided by four reanalysis products: ERA-interim (1979-2014) completed by the ERA40 (1958-1978), NCEP/NCAR-v1 (1948-2014), ERA-20C (1900-2010) and 20CRV2C (1900-2010). Surface solar radiation measurements from the Global Energy Balance Archive and cloud cover observations from Belgocontrol covering 1966-2007 were used for the evaluation of the MAR model and the forcing reanalyses. Results show that MAR produces much better results than the reanalyses. The driving reanalyses can generate divergent trends while they assimilate observations and are supposed to represent the same climate. [less ▲]

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See detailRadiological monitoring and statistical approach of primordial and anthropogenic radionuclides in surface soil of Mami-water site in the Western Cameroon
Nguelem, Eric J.; Ndontchueng, Maurice; Motapon, Ousmanou et al

in Environmental Earth Sciences (2017), 76

The study referred to measure activity concentrations of some primordial radionuclides and anthropogenic of 137Cs in soil samples of Mami-water in the Menoua subdivision, Dschang employing gamma-ray ... [more ▼]

The study referred to measure activity concentrations of some primordial radionuclides and anthropogenic of 137Cs in soil samples of Mami-water in the Menoua subdivision, Dschang employing gamma-ray spectrometry-based characterized Broad Energy Germanium (BE6350) detector and a comparison of radiological and safety impact parameters on human due to primordial radioactivity in soil with some internationally approved values. In addition, statistical analysis of primordial radionuclides of 226Ra, 232Th and 40K was performed to evaluate the distribution and the interrelation of radionuclides. Samples were randomly collected from a depth of about 0 to 5 cm from the top surface layer. Each of the sampling points was considered as being overlaid with a grid and subdivided into cells. The observed radioactivity level of 226Ra, 232Th and 40K in the investigated soil samples was compared with some published data available in some countries including Cameroon and observed varying within some reported data of radioactivity in soil from bauxite ore deposit. 235U and 137Cs were found in very few samples with a very low average of activity concentrations. In the majority of the samples, the observed radiological safety parameters seem to be greater than the internationally approved values. Consequently, using bricks made of soil as building materials might lead to an increase in radiation risk for the population. Multivariate statistical analysis of activity concentrations of primordial radionuclides performed showed an asymmetrical distribution with more peaked than Gaussian distribution and relatively flatter distribution of radionuclides in soil. In addition, a good positive interrelation between 226Ra and 232Th was observed and a weak negative one observed between 40K and 226Ra–232Th. [less ▲]

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See detailIntrasite spatial analysis based in a Geographic Information System and apply to extensive Middle Palaeolithic open-air sites in northern France. The example of Caours (Somme, France).
Moreau, Gwénaëlle ULiege; Locht, Jean-Luc; Auguste, Patrick

Conference (2017, September 02)

During middle Palaeolithic, northern France was occupied only by Neanderthals groups. However, the succession of glacial and interglacial periods explain a complex and discontinuous settlement, which ... [more ▼]

During middle Palaeolithic, northern France was occupied only by Neanderthals groups. However, the succession of glacial and interglacial periods explain a complex and discontinuous settlement, which involved complication in the study of the population dynamics at regional scale. Thereby, some aspects of Neanderthals behaviour are still obscure: in many cases, the sites function have to be precise. The intrasite spatial analysis will help us to answer those questions through the description of human activity areas and their interactions. However, for Middle Palaeolithic sites, we can’t see systematically on the field the spatial organisation directly, we sometimes need modelization. Therefore, we started to build a spatial analysis protocol based on a Geographic Information System and rely on sites of Caours and Beauvais (France). They are two open air sites that are exceptionally well preserved and displaying a large amount of faunal and lithic rests. Our protocol’s aim is showing the existence of a spatial organisation in form of artefacts concentration area. We first hypothesize with mesh analysis – or density, widely used in archaeology. Nevertheless, this method is limited by subjective choices like that of the mesh analysis. For that reason, we decided to use another methodology based on artefacts density but also on the distance between each other: The Kernel Density Estimation. Then, we will specified the function of this areas in a life space and their interactions through the spatial distribution of different lithic artefacts and faunal remains. [less ▲]

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See detailAnalyse de l’effet de la température et du préférendum thermique sur les mécanismes du déterminisme sexuel et de la différenciation gonadique chez le poisson-chat Africain, Clarias gariepinus
Santi, Saïdou ULiege

Doctoral thesis (2017)

Les poissons constituent le groupe de vertébré le plus diversifié présentant des systèmes de déterminisme et de différenciation sexuels aussi divers que variés. Ces systèmes sont caractérisés par une ... [more ▼]

Les poissons constituent le groupe de vertébré le plus diversifié présentant des systèmes de déterminisme et de différenciation sexuels aussi divers que variés. Ces systèmes sont caractérisés par une grande labilité et sont influencés par des facteurs génétiques, physiologiques et environnementaux, ces derniers pouvant influencer à la fois, le déterminisme du sexe et la différenciation des gonades. Le poisson chat africain Clarias gariepinus, une espèce présentant un déterminisme sexuel à homogamétie femelle (XX/XY), n’a fait l’objet que de peu d’études sur le rôle des facteurs environnementaux sur la détermination et différenciation sexuelle. Nous avons choisi d’étudier le rôle de la température dans ces mécanismes par trois approches complémentaires. Une approche histologique nous a permis de mettre en évidence qu’une haute température (36°C) influence la différenciation gonadique très précocement, de 6 à 8 jours post-l’éclosion (jpe), en entrainant fréquemment une déviation significative du sexe-ratio vers les mâles. La précocité de la thermosensibilité, avant le premier signe de différenciation histologique des gonades, suggère que la haute température pourrait agir sur d’autres cibles que les gonades elles-mêmes, telles que les cellules germinales primordiales, ou le cerveau, pour induire une masculinisation de la progéniture. Nous avons de plus mis en évidence que la distribution du sexe-ratio dans les différentes populations était très variable, suggérant le rôle de déterminants génétiques mineurs dans le processus de déterminisme du sexe chez le poisson-chat africain. Globalement, nous ces résultats sont caractéristiques de la présence d’une inversion du sexe température-induite (TISR) ainsi que des traits d’un déterminisme génétique polyfactoriel du sexe chez le poisson-chat africain. Une approche physiologique et génétique nous a permis de mettre en évidence que globalement, la haute température n’influence ni les profils des concentrations des trois principaux stéroïdes sexuels (17β-œstradiol, 11-cétotestostérone et testostérone), ni les expressions des gènes cyp19a1b et dmrt1 généralement impliqués dans ces mécanismes. Toutefois, les progénitures très thermosensibles présentent des expressions plus faibles du gène cyp19a1b six jours après l’exposition à la haute température. De même, les plus fortes expressions du gène de dmrt1 ont été observées chez les individus contrôles. Ces résultats renforcent notre hypothèse de sexualisation précoce du cerveau dans le processus de masculinisation température-induite. Des études supplémentaires sur l’action de la haute température sur la prolifération de cellules germinales primordiales, ainsi que d’autres processus comme l’activité ou la méthylation des gènes de la différenciation sexuelle doivent être envisagées. Une approche comportementale nous a finalement permis de mettre en évidence que les juvéniles indifférenciés présentent un comportement migratoire vers les hautes températures lorsqu’ils sont placés dans un continuum thermique (28,0 – 32,0 – 36,0°C), associés à une masculinisation de 50,0 à 82,5%, soulevant la question suivante : le déplacement à hautes températures confère-t-il des avantages particuliers aux individus ou à la population en milieu naturel ? Cette thermosensibilité contribuerait à augmenter la proportion de femelles dans la population, lorsque les pseudomales (XX) vont se reproduire avec des femelles XX. L’augmentation de la capacité reproductive de la population, résultante, pourrait permettre un accroissement de l’effectifs des larves et juvéniles, pour rétablir l’équilibre du sexe-ratio lors du retour à des conditions environnementales normales. Globalement nous pouvons conclure que Clarias gariepinus présente un TISR avec une implication des déterminants génétiques mineurs dans la différenciation du sexe. La thermolabilité pourrait conférer un avantage adaptatif à l’espèce, mais l’adaptabilité d’un tel processus d’établissement du sexe reste une question très ouverte. [less ▲]

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See detailApplication of a two-step approach for mapping ice thickness to various glacier types on Svalbard
Fürst, J.; Gillet-Chaulet, F.; Benham, T. et al

in Cryosphere (The) (2017)

The basal topography is largely unknown beneath most glaciers and ice caps, and many attempts have been made to estimate a thickness field from other more accessible information at the surface. Here, we ... [more ▼]

The basal topography is largely unknown beneath most glaciers and ice caps, and many attempts have been made to estimate a thickness field from other more accessible information at the surface. Here, we present a two-step reconstruction approach for ice thickness that solves mass conservation over single or several connected drainage basins. The approach is applied to a variety of test geometries with abundant thickness measurements including marine- and land-terminating glaciers as well as a 2400 km2 ice cap on Svalbard. The input requirements are kept to a minimum for the first step. In this step, a geometrically controlled, non-local flux solution is converted into thickness values relying on the shallow ice approximation (SIA). In a second step, the thickness field is updated along fast-flowing glacier trunks on the basis of velocity observations. Both steps account for available thickness measurements. Each thickness field is presented together with an error-estimate map based on a formal propagation of input uncertainties. These error estimates point out that the thickness field is least constrained near ice divides or in other stagnant areas. Withholding a share of the thickness measurements, error estimates tend to overestimate mismatch values in a median sense. We also have to accept an aggregate uncertainty of at least 25 % in the reconstructed thickness field for glaciers with very sparse or no observations. For Vestfonna ice cap (VIC), a previous ice volume estimate based on the same measurement record as used here has to be corrected upward by 22 %. We also find that a 13 % area fraction of the ice cap is in fact grounded below sea level. The former 5 % estimate from a direct measurement interpolation exceeds an aggregate maximum range of 6–23 % as inferred from the error estimates here. [less ▲]

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See detailL'abandon de sanctuaires et le transfert de cultes en Grèce antique
Palamidis, Alaya ULiege

Doctoral thesis (2017)

Dans la Grèce antique, les sanctuaires anciens comme les sanctuaires nouvellement fondés étaient censés continuer à être fréquentés indéfiniment. Cependant, ce n’était pas le cas de tous les lieux de ... [more ▼]

Dans la Grèce antique, les sanctuaires anciens comme les sanctuaires nouvellement fondés étaient censés continuer à être fréquentés indéfiniment. Cependant, ce n’était pas le cas de tous les lieux de culte: certains pouvaient être abandonnés, de même que les divinités qui y étaient honorées, tandis que d’autres divinités continuaient à être honorées à un emplacement différent. Ce travail vise en premier lieu à analyser les sources littéraires, épigraphiques et surtout archéologiques qui nous renseignent sur des tels abandons de sanctuaires et transferts de cultes. L’étude de deux types de déplacements de population, les synécismes et les métécismes, au cours desquels de tels abandons et transferts sont documentés, permet par la suite de réfléchir notamment aux raisons qui expliquent l’abandon de certains sanctuaires plutôt que d’autres. L’analyse des sources disponibles suggère que ni les abandons de sanctuaires, ni les transferts de culte n’étaient considérés comme la transgression d’une norme tacite ou orale et que ces phénomènes sont beaucoup plus courants que ce qui est généralement supposé. [less ▲]

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See detailA bottom-up approach to the analysis of deliberate metaphors in Belgian political discourse
Heyvaert, Pauline ULiege

Conference (2017, September 01)

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See detailPouvoir et action publique
Grandjean, Geoffrey ULiege

Learning material (2017)

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See detailImproving pedestrian detection using motion-guided filtering
Wang, Yi; Pierard, Sébastien ULiege; Su, Song-Zhi et al

in Pattern Recognition Letters (2017), 96

In this letter, we show how a simple motion-guided nonlinear filter can drastically improve the accuracy of several pedestrian detectors. More specifically, we address the problem of how to pre-filter an ... [more ▼]

In this letter, we show how a simple motion-guided nonlinear filter can drastically improve the accuracy of several pedestrian detectors. More specifically, we address the problem of how to pre-filter an image so almost any pedestrian detector will see its false detection rate decrease. First, we roughly identify moving pixels by cumulating their temporal gradient into a motion history image (MHI). The MHI is then used in conjunction with a nonlinear filter to filter out background details while leaving untouched foreground moving objects. We also show how a feedback loop as well as a merging procedure between the filtered and the unfiltered frames can further improve results. We tested our method on 26 videos from 6 categories. The results show that for a given miss rate, filtering out background details reduces the false detection rate by a factor of up to 69.6 times. Our method is simple, computationally light, and can be implemented with any pedestrian detector. Code is made publicly available at: https://bitbucket.org/wany1601/pedestriandetection. [less ▲]

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See detailPolitique de la fonction publique
Grandjean, Geoffrey ULiege

Learning material (2017)

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See detailMunicipalities’ understanding and importance of the concept of Smart Cities: an exploratory analysis in Belgium
Desdemoustier, Jonathan ULiege; Crutzen, Nathalie ULiege; Giffinger, Rudolf

Conference (2017, September 01)

Even if an increasing number of scientific publications are dealing with it, the concept of “smart city” is not yet well defined and it is not fully understood (Anthopoulos and Vakali 2012; Caragliu,Bo ... [more ▼]

Even if an increasing number of scientific publications are dealing with it, the concept of “smart city” is not yet well defined and it is not fully understood (Anthopoulos and Vakali 2012; Caragliu,Bo, and Nijkamp 2009; Lazaroiu and Roscia 2012). Due to the lack of a proper conceptualization, defined method or credentials for smart cities (Angelidou 2015; Nam and Pardo 2011), cities across the geographical spectrum claim themselves 'smart' with self-congratulatory note (Hollands 2008). Despite this increasing popularity of smart cities, there are few critical discourse and rigorous analytical or statistical analyses of the concept and its application on urban territories (Caragliu, Bo, and Nijkamp 2009; R G Hollands 2015; Kitchin 2015; Vanolo 2014). This paper aims at understanding where Belgian municipalities stand in the field of smart city in 2016. How Belgian municipalities approach the phenomenon smart city? Which focus in smart city -sustainable, technologic, creative and human-do attract Belgian municipalities? The paper answers to these questions thanks to a comprehensive territorial analysis of the country, a presentation of current trends on smart cities in the three Belgian regions, and the construction of a typology of municipalities’ understandings of the phenomenon. It also analyses how these understandings impact priorities and smart city developments of Belgian municipalities. It investigates how they affect municipal priorities in the six dimensions of the smart city and their state of development in some key smart city fields. Finally, it examines how do this typology is related to the municipal perception of difficulty to set up smart city projects and the relevance of the concept for their territories. The data used comes from the results of a quantitative research amongst Belgian municipalities carried out in 2016 by the Smart City Institute. The research points out key statistical observations around the smart city phenomenon in Belgium. A typology with four different understandings (technological, holistic, specialized and inexistent) emerged from the analyses. [less ▲]

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See detailNew constraints on quasar broad absorption and emission line regions from gravitational microlensing
Hutsemekers, Damien ULiege; Braibant, Lorraine ULiege; Sluse, Dominique ULiege et al

in Frontiers in Astronomy and Space Sciences (2017), 4

Gravitational microlensing is a powerful tool allowing one to probe the structure of quasars on sub-parsec scale. We report recent results, focusing on the broad absorption and emission line regions. In ... [more ▼]

Gravitational microlensing is a powerful tool allowing one to probe the structure of quasars on sub-parsec scale. We report recent results, focusing on the broad absorption and emission line regions. In particular microlensing reveals the intrinsic absorption hidden in the P Cygni-type line profiles observed in the broad absorption line quasar H1413+117, as well as the existence of an extended continuum source. In addition, polarization microlensing provides constraints on the scattering region. In the quasar Q2237+030, microlensing differently distorts the Hα and CIV broad emission line profiles, indicating that the low- and high-ionization broad emission lines must originate from regions with distinct kinematical properties. We also present simulations of the effect of microlensing on line profiles considering simple but representative models of the broad emission line region. Comparison of observations to simulations allows us to conclude that the Hα emitting region in Q2237+030 is best represented by a Keplerian disk. [less ▲]

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See detailSex and gender in family business succession research: A review and forward agenda from a social construction perspective
Nelson, Teresa; Constantinidis, Christina ULiege

in Family Business Review (2017), 30(3), 219-241

This article focuses on how family business succession research has engaged and may be further enriched by application of a gender lens as socially constructed. We analyze the succession literature ... [more ▼]

This article focuses on how family business succession research has engaged and may be further enriched by application of a gender lens as socially constructed. We analyze the succession literature developing a gender terms vocabulary and five themes of historical engagement. Finding a lack of theoretical grounding, we apply the construct of gender, through expectation states theory, revising the Sharma and Irving model of successor commitment to examine how a socially constructed view of gender shifts and opens up points of view. We then present a forward looking agenda to motivate future scholarship. [less ▲]

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See detailLe service minimum à l'aune de la Convention européenne des droits de l'homme : interdiction, possibilité ou obligation pour le législateur belge?
Bouhon, Frédéric ULiege; Vandenbosch, Sofia ULiege

in Revue de Droit Social = Tijdschrift voor Sociaal Recht (2017), 3(2017), 585-612

The implementation of minimum service, which aims at guaranteeing continuity of some activities despite a strike, constitutes an interference with the right to strike. Considered under article 11 of the ... [more ▼]

The implementation of minimum service, which aims at guaranteeing continuity of some activities despite a strike, constitutes an interference with the right to strike. Considered under article 11 of the European Convention on Human Rights, this implementation appears to be, depending on the situation, either a legally forbidden measure, or an option open to the authorities or an adequate mean to fulfil a positive obligation. This legal context circumscribes the margin of appreciation of the Belgian legislator in this field. [less ▲]

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