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See detailBack to materialism Reflections on Marx’s labour, praxis, cooperative and libertarian socialism in the 19th century
Frère, Bruno ULg

E-print/Working paper (2017)

From Marx to Althusser, the materialist approach has tended to assume that individuals (that is, workers, proletarians and other social actors), unconsciously reproduce the social structures of capitalism ... [more ▼]

From Marx to Althusser, the materialist approach has tended to assume that individuals (that is, workers, proletarians and other social actors), unconsciously reproduce the social structures of capitalism which alienate them. It is assumed that individuals accept the conditions forced upon them and no longer seek to rebel against a world which substantially impoverishes their labour, their spirit and their creativity. In this paper, I will try to show that by dint of favouring almost exclusively Marx's concept of alienation, there is a considerable risk that materialist thought will adopt only a negative path. Whilst I acknowledge Marx’s significance to materialism, I wish to argue that his stance should be combined with that of the anarchist and libertarian French thinker Proudhon. Proudhon has succeeded in presenting a conception of the worker as more than just alienated. Workers can also cooperate and experience a reciprocity seemingly at odds with the character of capitalism. Under Proudhon’s influence materialism takes a positive turn, enabling us to avoid falling into the utopianism that the theory of social economy employs to critique capitalism – a utopianism that renders its critique even less effective than that of Marx. [less ▲]

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See detailHow to account for new forms of resistance to domination: An argument for a materialist renewal in European social theory
Frère, Bruno ULg; Tulle, Emmanuelle

E-print/Working paper (2017)

Many significant intellectual developments have taken place in 20th century European social theories. Notably the first Frankfurt School and Bourdieu’s work have successfully shown how workers, social ... [more ▼]

Many significant intellectual developments have taken place in 20th century European social theories. Notably the first Frankfurt School and Bourdieu’s work have successfully shown how workers, social actors, etc. are alienated or dominated by capitalist social structures. But according to Habermas, neither perspective successfully allows for the possibility that people could contribute to their own emancipation. The emergence of new forms of social resistance to domination such as those embodied by the Indignados, Anonymous, Femen, the practitioners of alternative economy, movements of unemployed people or illegals compels us to envisage the possibility for emancipation, but how? In this paper we explore opportunities for accounting for this by considering the work of a range of other European social theorists, more specifically Boltanski whose critical intent is embodied in his pragmatic sociology, and evident in his coining and use of the concept of the world. In addition we will consider Latour’s own pragmatic stance as we believe that despite his disinterest in new social movements, his work, informed by pure immanence, might offer potential solutions. But we would argue that even in these innovations there is either a persistent tendency to imagine emancipation primarily as a return to some ideal state or a lack of critical engagement with alienation. In response, we propose a materialist renewal, which will lead us to ponder on the political role of sociologists. [less ▲]

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See detailThe np- Control Charts with the Guaranteed In-Control Performance
Faraz, Alireza ULg; Heuchenne, Cédric ULg

E-print/Working paper (2016)

In this paper, we evaluate the in-control performance of np-control charts with estimated parameters. We then apply the bootstrap method to adjust the control charts’ limits to guarantee the desired in ... [more ▼]

In this paper, we evaluate the in-control performance of np-control charts with estimated parameters. We then apply the bootstrap method to adjust the control charts’ limits to guarantee the desired in-control average run length (ARL0) value in monitoring stage. The adjusted limits ensure that ARL0 would take a value greater than the desired value (say, B) with a certain specified probability, that is Pr⁡(ARL_0>B)=1-ρ. We finally provide users with tables which with practitioners do not need to do bootstrapping Phase I data set to obtain the control limit thresholds. [less ▲]

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See detailA Comparison of Departure Time of Day Formulations
Lurkin, Virginie ULg; Garrow, Laurie; Higgins, Matthew et al

E-print/Working paper (2016)

Airline passengers’ itinerary choices are influenced by many factors including carriers, prices, the number of connections, and departure times. This paper compares three different methods that have been ... [more ▼]

Airline passengers’ itinerary choices are influenced by many factors including carriers, prices, the number of connections, and departure times. This paper compares three different methods that have been used to model departure time of day preferences. The first is a discrete formulation that uses indicator variables to represent the hour of departure. The next two methods are based on a continuous formulation that uses a series of sine and cosine functions. One assumes departure time preferences over a 24-hour cycle and the other uses shorter cycle lengths that account for fewer departures during certain hours of the day. We compare models using itineraries in the Continental U.S. that are separated by two time zones. Although the discrete formulation fits the data better, the two continuous time of day formulations are preferred as they provide more intuitive predictions and require fewer parameters. Results between the two continuous time of day formulations are similar but differ in how strongly they weight itineraries that depart very early or very late in the day. Based on empirical results, we recommend testing both 24-hour and less than 24-hour cycle lengths for a particular dataset. [less ▲]

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See detailAccounting for Price Endogeneity in Airline Itinerary Choice Models: An Application to Continental U.S. Markets
Lurkin, Virginie ULg; Garrow, Laurie; Higgins, Matthew et al

E-print/Working paper (2016)

Network planning models, which forecast the profitability of airline schedules, support many critical decisions, including equipment purchase decisions. Network planning models include an itinerary choice ... [more ▼]

Network planning models, which forecast the profitability of airline schedules, support many critical decisions, including equipment purchase decisions. Network planning models include an itinerary choice model which is used to allocate air total demand in a city pair to different itineraries. Multinomial logit (MNL) models are commonly used in practice and capture how individuals make trade-offs among different itinerary attributes; however, none that we are aware of account for price endogeneity. This study formulates an itinerary choice model that is consistent with those used by industry and corrects for price endogeneity using a control function that uses several types of instrumental variables. We estimate our models using database of more than 3 million tickets provided by the Airlines Reporting Corporation. Results based on Continental U.S. markets for May 2013 departures show that models that fail to account for price endogeneity overestimate customers’ value of time and result in biased price estimates and incorrect pricing recommendations. The size and comprehensiveness of our database allows us to estimate highly refined departure time of day preference curves that account for distance, direction of travel, the number of time zones traversed, departure day of week and itinerary type (outbound, inbound or one-way). These time of day preference curves can be used by airlines, researchers, and government organizations in the evaluation of different policies such as congestion pricing. [less ▲]

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See detailContinuous Departure Time of Day Preferences for Continental U.S. Airline Markets Segmented by Distance, Direction of Travel, Number of Time Zones, Day of Week and Itinerary Type
Lurkin, Virginie ULg; Garrow, Laurie; Higgins, Matthew et al

E-print/Working paper (2016)

Airlines use itinerary choice models to allocate the total number of passengers in a city pair to specific itineraries. In a related paper, we estimated a multinomial logit (MNL) itinerary choice model ... [more ▼]

Airlines use itinerary choice models to allocate the total number of passengers in a city pair to specific itineraries. In a related paper, we estimated a multinomial logit (MNL) itinerary choice model using database of more than 3 million tickets for Continental U.S. markets provided by the Airlines Reporting Corporation that accounted for price endogeneity. The size and comprehensiveness of our database allowed us to estimate highly refined continuous departure time of day preference curves that account for distance, direction of travel, the number of time zones traversed, departure day of week and itinerary type (outbound, inbound or one-way). This paper and accompanying Excel spreadsheet located at http://garrowlab.ce.gatech.edu contain the results of all model coefficients (including the 1260 time of day parameters) and summarize results in a series of ten figures. These highly-refined time of day preference curves can be used by airlines, researchers, and government organizations in the evaluation of demand-management and other policies. [less ▲]

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See detailComparison of local outliers detection techniques in spatial multivariate data
Ernst, Marie ULg; Haesbroeck, Gentiane ULg

E-print/Working paper (2016)

Outlier detection techniques in spatial data should allow to identify two types of outliers: global and local ones. Local outliers typically have non-spatial attributes that strongly differ from those ... [more ▼]

Outlier detection techniques in spatial data should allow to identify two types of outliers: global and local ones. Local outliers typically have non-spatial attributes that strongly differ from those observed on their neighbors. Detecting local outliers requires to be able to work locally, on neighborhoods, in order to take into account the spatial dependence between the statistical units under consideration, even though the outlyingness is usually measured on the non-spatial variables. Many procedures have been outlined in the literature, but their number reduces when one wants to deal with multivariate non-spatial attributes. In this paper, focus is on the multivariate context. A review of existing procedures is done. A new approach, based on a two-step improvement of an existing one, is also designed and compared with the benchmarked methods by means of examples and simulations. [less ▲]

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See detailPolitique de la Ville : Dynamisation des coeurs de ville
Bastin, Florine ULg; Lacroix, Gilles; May, Xavier et al

E-print/Working paper (2016)

La régionalisation de la Politique Fédérale des Grandes Villes, suite à la sixième réforme de l’Etat, fut une opportunité de s’interroger sur les objectifs et l’organisation d’une Politique de la Ville en ... [more ▼]

La régionalisation de la Politique Fédérale des Grandes Villes, suite à la sixième réforme de l’Etat, fut une opportunité de s’interroger sur les objectifs et l’organisation d’une Politique de la Ville en Wallonie. Dans ce cadre, la note de recherche CPDT n°63 « Politique de la ville. Dynamisation des cœurs de ville » répond à la volonté du Gouvernement wallon de se doter d’une vision territoriale stratégique sur le long terme et est un premier pas vers la mise en place d’une politique de la ville intégrée en Wallonie. Cette note fait le point sur, d’une part, les différentes politiques et outils relatifs à la restructuration et à la dynamisation des tissus urbains, au sens large, établis au niveau régional, fédéral et européen et, d’autre part, les propositions et recommandations relatives à l’évolution du cadre actuel. Cette réflexion s’adresse évidemment aux acteurs concernés par les enjeux de gouvernance urbaine : les décideurs politiques, les villes et les communes mais concerne aussi le citoyen. [less ▲]

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See detailStructure et négativité dans la Préface de 1961 à L'Histoire de la folie
Oulc'hen, Hervé ULg

E-print/Working paper (2016)

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See detailFertility progression in Germany: An analysis using flexible nonparametric cure survival models
Bremhorst, Vincent; Kreyenfeld, Michaela; Lambert, Philippe ULg

E-print/Working paper (2016)

- Objective - This paper uses data from the German Socio-Economic Panel (GSOEP) to study the transition to second and third births. In particular, we seek to distinguish the factors that determine the ... [more ▼]

- Objective - This paper uses data from the German Socio-Economic Panel (GSOEP) to study the transition to second and third births. In particular, we seek to distinguish the factors that determine the timing of fertility from the factors that influence ultimate parity progression. - Methods - As a method, we employ cure survival models, a technique that is commonly used in epidemiological studies and in the statistical literature, but is only rarely applied to fertility research. - Results - We find that education has a different impact on the timing and the ultimate probability of having a second and a third birth. Furthermore, we show that the shape of the fertility schedule for the total population differs from that of “susceptible women” (i.e., those who have a second or a third child). - Conclusion - Standard event history models conflate timing and quantum effects. Our approach overcomes this shortcoming. It estimates separate parameters for the hazard rate of having a next child for the “susceptible population,” and the ultimate probability of having another child for the entire population at risk. - Contribution - We go beyond standard cure survival models (also known as split population models) used in fertility research by specifying a flexible non-parametric model (using Bayesian P-splines) for the latent distribution (related to the timing of an extra birth), instead of a parametric model. Our approach is (so far) limited to time-constant covariates, but can be extended to include time-varying covariates as well. [less ▲]

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See detailGeneralized Pascal triangle for binomial coefficients of words
Leroy, Julien ULg; Rigo, Michel ULg; Stipulanti, Manon ULg

E-print/Working paper (2016)

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See detailHistoires de rayons verts : phénomène physique, critique de cinéma, spectateurs mélancoliques
Barbion, Sébastien ULg

E-print/Working paper (2016)

En s’appuyant sur la physique, un roman de Jules Verne et un film de Rohmer, ce texte déplie les différents aspects théoriques et pratiques contenus dans le concept de rayon vert : un type de perception ... [more ▼]

En s’appuyant sur la physique, un roman de Jules Verne et un film de Rohmer, ce texte déplie les différents aspects théoriques et pratiques contenus dans le concept de rayon vert : un type de perception, une manière de concevoir la critique de cinéma, une expérience de spectateur. [less ▲]

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See detailOnline Learning for Strong Branching Approximation in Branch-and-Bound
Marcos Alvarez, Alejandro ULg; Wehenkel, Louis ULg; Louveaux, Quentin ULg

E-print/Working paper (2016)

We present an online learning approach to variable branching in branch-and-bound for mixed-integer linear problems. Our approach consists in learning strong branching scores in an online fashion and in ... [more ▼]

We present an online learning approach to variable branching in branch-and-bound for mixed-integer linear problems. Our approach consists in learning strong branching scores in an online fashion and in using them to take branching decisions. More specifically, numerical scores are used to rank the branching candidates. If, for a given variable, the learned approximation is deemed reliable, then the score for that variable is computed thanks to the learned function. If the approximation is not reliable yet, the real strong branching score is used instead. The scores that are computed through the real strong branching procedure are fed to the online learning algorithm in order to improve the approximated function. The experiments show promising results. [less ▲]

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See detailPermutations and negative beta-shifts
Charlier, Emilie ULg; Steiner, Wolfgang

E-print/Working paper (2016)

Elizalde (2011) characterized which permutations can be obtained by ordering consecutive elements in the trajectories of (positive) beta-transformations and beta-shifts. We prove similar results for ... [more ▼]

Elizalde (2011) characterized which permutations can be obtained by ordering consecutive elements in the trajectories of (positive) beta-transformations and beta-shifts. We prove similar results for negative bases beta. [less ▲]

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See detailOn the processing of red pigment by late mousterian Neanderthals in Ormesson, Seine-et-Marne, France, 47000 years ago
Salomon, Hélène ULg; Bodu, Pierre; Geurten, Stéphanie et al

E-print/Working paper (2016)

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See detailIdentification of the concepts at stake during a consultation. Clinical exercises
Jamoulle, Marc ULg

E-print/Working paper (2015)

During a consultation between a patient and a doctor, symptoms, process and health problems are at stake and could be identified and retrieved through the use of ICPC.(refer to www.ph3c.org) Specific ... [more ▼]

During a consultation between a patient and a doctor, symptoms, process and health problems are at stake and could be identified and retrieved through the use of ICPC.(refer to www.ph3c.org) Specific training and managerial competences of the doctor could be identified and explained through the Q-Codes Together ICPC and Q-Codes form 3CGP ; Core Content Classification in General Practice/ Family Medicine The concepts identified in ICPC and Q-Codes could be useful to understand and teach the content of consultation in family medicine. [less ▲]

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See detailFestivals Acadiens et Creoles
Sacré, Robert ULg

E-print/Working paper (2015)

Comptes-rendus avec photos et liens Internet : 1) Houston et Galveston ( TX) 2) Festivals Acadiens et Créoles à Lafayette ( LA) jours 1 , 2 et 3 3) Lafayette by night

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See detailWhy Did the Industrial Revolution Start in Britain?
Van Neuss, Leif ULg

E-print/Working paper (2015)

The main goal of this paper is to provide an integrated overview of the literature devoted to identifying the causes of the British industrial revolution. Why did the industrial revolution, a fascinating ... [more ▼]

The main goal of this paper is to provide an integrated overview of the literature devoted to identifying the causes of the British industrial revolution. Why did the industrial revolution, a fascinating and multifaceted event which brought about modern economic growth, occur in eighteenth-century Britain? This question has animated a lot of discussions among scholars and is still nowadays heatedly debated in the literature. This debate is reflected in the large spectrum of theories which aim at explaining the true origins of the British industrialization. The paper first sheds light on a rising debate concerning the evolution of British incomes per capita before the British industrial revolution and the “Great Divergence”. The paper then investigates the proposed causes of the British industrialization, aggregating them into seven broad categories, i.e. (1) geography and natural resources, (2) demography, (3) agricultural progress, (4) demand-side factors, (5) trade and empire, (6) institutional and political factors, (7) science, technology, and human capital. [less ▲]

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See detailLarge neighborhood search for multi-trip vehicle routing
François, Véronique ULg; Arda, Yasemin ULg; Crama, Yves ULg et al

E-print/Working paper (2015)

We consider two large neighborhood search approaches for the multi-trip vehicle routing problem, where each vehicle can perform several routes during the working shift to serve a set of customers. The ... [more ▼]

We consider two large neighborhood search approaches for the multi-trip vehicle routing problem, where each vehicle can perform several routes during the working shift to serve a set of customers. The problem specifically arises when customers are close to each other and/or when the demands are large. A common approach in the literature consists in solving this problem by mixing vehicle routing heuristics with bin packing routines to assign routes to vehicles. We compare this approach with the use of specific operators designed to tackle the routing and the assignment aspects of the problem simultaneously. We provide several best known solutions for benchmark instances. At the end of the work, we give insights about the proposed algorithm configurations by analyzing the behavior of several method components. [less ▲]

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See detail25 novembre 2015 : cent ans de Relativité
De Rop, Yves ULg

E-print/Working paper (2015)

La théorie proposée par Einstein au début du XXe siècle porte bien mal son nom; car si, historiquement, l'accent fut mis d'abord sur la relativité de certaines notions (en particulier, la mesure de l ... [more ▼]

La théorie proposée par Einstein au début du XXe siècle porte bien mal son nom; car si, historiquement, l'accent fut mis d'abord sur la relativité de certaines notions (en particulier, la mesure de l'intervalle de temps écoulé entre deux événements donnés), on a compris par la suite qu'elle reposait plus fondamentalement sur l'existence de quantités absolues, c'est-à-dire, dont la mesure est identique pour tous les observateurs, quel que soit leur état de repos ou de mouvement. Ces quantités sont inconnues de la mécanique de Newton, laquelle ne reconnaît qu'un seul invariant : le temps. Ce texte cherche à retracer, avec un minimum de formalisme, comment s'est imposé un nouveau cadre géométrique pour la physique, dominé par cette exigence d'invariance des mesures spatio-temporelles et intégrant une description révolutionnaire de la gravitation. [less ▲]

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See detailElmore D. L'intégrale Frémeaux et Ass.
Sacré, Robert ULg

E-print/Working paper (2015)

Compte rendu Coffret 5 CDs + livret . La Wallon et le Blues , un mariage réussi

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See detailMars nighttime aurora
European Space Agency, ESA/ATG medialab; Gérard, Jean-Claude ULg; Soret, Lauriane ULg

E-print/Working paper (2015)

Press release by the European Space Agency (ESA) on the occasion of the publication in two journals of the peer-reviewed literature

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See detailRebates and Article 102 TFEU: The European Commission's Duty to Apply the Guidance Paper
Petit, Nicolas ULg

E-print/Working paper (2015)

This paper shows that the European Union (EU) courts' case-law and general principles of EU law place the European Commission (“Commission”) under a duty to apply the Guidance Communication on Enforcement ... [more ▼]

This paper shows that the European Union (EU) courts' case-law and general principles of EU law place the European Commission (“Commission”) under a duty to apply the Guidance Communication on Enforcement Priorities (“Guidance Paper”) in abuse of dominance cases started after its adoption. This duty includes the obligation to test Article 102 TFEU cases under the As Efficient Competitor (“AEC”) framework, as set out in the 2009 Guidance Paper. The judgments handed down by the Union courts in Intel v Commission and Post Danmark II do not alter in any way the Commission’s “self binding” duty to apply the Guidance Paper. If the Commission wishes to depart from the AEC framework, it must officially withdraw its Guidance Paper. [less ▲]

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See detailLes Nouveaux Réactionnaires : mythe ou réalité ?
Durand, Pascal ULg; Sindaco, Sarah ULg; Devecchio, Alexandre

E-print/Working paper (2015)

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See detailMulti-period vehicle allocation with uncertain transportation requests
Crama, Yves ULg; Pironet, Thierry ULg

E-print/Working paper (2015)

This work investigates optimization techniques for a multi-period vehicle allocation problem with uncertain requests. A company owning a limited fleet of trucks attempts to maximize its operational profit ... [more ▼]

This work investigates optimization techniques for a multi-period vehicle allocation problem with uncertain requests. A company owning a limited fleet of trucks attempts to maximize its operational profit over an infinite horizon by optimally assigning transportation orders to the vehicles. Its profit stems from profits collected when transporting full truckloads, minus costs incurred when waiting or when moving unladen. The stochastic component of the problem arises from the uncertainty on the realization of each transportation order. The methodology is based on optimizing decisions for deterministic scenarios. Several policies are generated in this way, either by simple heuristics, or by more complex approaches, such as consensus and restricted expectation algorithms, or from network flow formulations over subtrees of scenarios. Myopic and a-posteriori deterministic optimization models are used to compute bounds allowing for performance evaluation. Numerical experiments are performed on various instances featuring different numbers of orders, graph sizes, sparsity, and probability distributions, and the performance of the algorithms is assessed by statistical tests. The robustness of various policies with respect to erroneous evaluations of the probability distributions is also analyzed. [less ▲]

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See detailL’accompagnement de projets d’entrepreneuriat social dans leurs phases initiales
Dufays, Frédéric ULg; Lovens, Caroline ULg; Mertens de Wilmars, Sybille ULg

E-print/Working paper (2015)

L’entrepreneuriat social connaît depuis quelques années un intérêt croissant. Mais pour les entrepreneurs sociaux, concilier les dimensions sociales et économiques demande de faire face à des défis bien ... [more ▼]

L’entrepreneuriat social connaît depuis quelques années un intérêt croissant. Mais pour les entrepreneurs sociaux, concilier les dimensions sociales et économiques demande de faire face à des défis bien spécifiques. Ne faut-il donc pas favoriser un accompagnement sur-mesure et modulable ? C’est le défi qu’a choisi de relever en Belgique francophone le programme ImpulCera en proposant aux entrepreneurs sociaux un soutien financier pour la réalisation d’une étude de faisabilité et pour le lancement de leur projet. Le présent article présente quelques résultats de l’évaluation de ce programme ainsi que les enseignements qui peuvent en être dégagés. [less ▲]

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See detailPour analyser la qualité des médicaments
Ziemons, Eric ULg

E-print/Working paper (2015)

Technique permettant de décortiquer les caractéristiques chimiques et physiques des molécules, la spectroscopie vibrationnelle est précieuse dans le domaine pharmaceutique. Les chercheurs du laboratoire ... [more ▼]

Technique permettant de décortiquer les caractéristiques chimiques et physiques des molécules, la spectroscopie vibrationnelle est précieuse dans le domaine pharmaceutique. Les chercheurs du laboratoire de Chimie Analytique de l’Université de Liège, spécialistes dans ce domaine de recherche, collaborent régulièrement avec des entreprises pharmaceutiques pour contrôler leurs matières premières, produits finis et procédés. [less ▲]

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See detailLong-term activity and outburst of comet C/2013 A1 (Siding Spring) from narrow-band photometry and long-slit spectroscopy
Opitom, Cyrielle ULg; Guilbert-Lepoutre, A.; Jehin, Emmanuel ULg et al

E-print/Working paper (2015)

In this paper, we present a unique data set of more than one year's worth of regular observations of comet C/2013 A1(Siding Spring) with TRAPPIST in Chile, along with low-resolution spectra obtained with ... [more ▼]

In this paper, we present a unique data set of more than one year's worth of regular observations of comet C/2013 A1(Siding Spring) with TRAPPIST in Chile, along with low-resolution spectra obtained with the ESO/VLT FORS 2 instrument. The comet made a close approach to Mars on October 19, 2014 and was then observed by many space and ground-based telescopes. We followed the evolution of the OH, NH, CN, $\mathrm{C_3}$, and $\mathrm{C_2}$ production rates as well as the $Af\rho$ parameter as a proxy for the dust production. We detected an outburst two weeks after perihelion, with gas and dust production rates being multiplied by a factor five within a few days. By modelling the shape of the CN and $\mathrm{C_2}$ radial profiles, we determined that the outburst happened around on November 10 around 15:30 UT ($\pm$ 5h) and measured a gas ejection velocity of $1.1\pm0.2$ km/s. We used a thermal evolution model to reproduce the activity pattern and outburst. Our results are consistent with the progressive formation of a dust mantle explaining the shallow dependence of gas production rates, which may be partially blown off during the outburst. We studied the evolution of gas composition, using various ratios such as CN/OH, $\mathrm{C_2}$/OH, or $\mathrm{C_3}$/OH, which showed little or no variation with heliocentric distance including at the time of the outburst. This indicates a relative level of homogeneity of the nucleus composition. [less ▲]

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See detailNew and updated convex shape models of asteroids based on optical data from a large collaboration network
Hanuš, J.; Ďurech, J.; Oszkiewicz, D. A. et al

E-print/Working paper (2015)

Asteroid modeling efforts in the last decade resulted in a comprehensive dataset of almost 400 convex shape models and their rotation states. This amount already provided a deep insight into physical ... [more ▼]

Asteroid modeling efforts in the last decade resulted in a comprehensive dataset of almost 400 convex shape models and their rotation states. This amount already provided a deep insight into physical properties of main-belt asteroids or large collisional families. We aim to increase the number of asteroid shape models and rotation states. Such results are an important input for various further studies such as analysis of asteroid physical properties in different populations, including smaller collisional families, thermophysical modeling, and scaling shape models by disk-resolved images, or stellar occultation data. This provides, in combination with known masses, bulk density estimates, but constrains also theoretical collisional and evolutional models of the Solar System. We use all available disk-integrated optical data (i.e., classical dense-in-time photometry obtained from public databases and through a large collaboration network as well as sparse-in-time individual measurements from a few sky surveys) as an input for the convex inversion method, and derive 3D shape models of asteroids, together with their rotation periods and orientations of rotation axes. The key ingredient is the support of more that one hundred observers who submit their optical data to publicly available databases. We present updated shape models for 36 asteroids, for which mass estimates are currently available in the literature or their masses will be most likely determined from their gravitational influence on smaller bodies, which orbital deflection will be observed by the ESA Gaia astrometric mission. This was achieved by using additional optical data from recent apparitions for the shape optimization. Moreover, we also present new shape model determinations for 250 asteroids, including 13 Hungarias and 3 near-Earth asteroids. [less ▲]

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See detailCharacterization of the K2-19 Multiple-Transiting Planetary System via High-Dispersion Spectroscopy, AO Imaging, and Transit Timing Variations
Narita, Norio; Hirano, Teruyuki; Fukui, Akihiko et al

E-print/Working paper (2015)

K2-19 (EPIC201505350) is an interesting planetary system in which two transiting planets with radii ~ 7 $R_{Earth}$ (inner planet b) and ~ 4 $R_{Earth}$ (outer planet c) have orbits that are nearly in a 3 ... [more ▼]

K2-19 (EPIC201505350) is an interesting planetary system in which two transiting planets with radii ~ 7 $R_{Earth}$ (inner planet b) and ~ 4 $R_{Earth}$ (outer planet c) have orbits that are nearly in a 3:2 mean-motion resonance. Here, we present results of ground-based follow-up observations for the K2-19 planetary system. We have performed high-dispersion spectroscopy and high-contrast adaptive-optics imaging of the host star with the HDS and HiCIAO on the Subaru 8.2m telescope. We find that the host star is relatively old (>8 Gyr) late G-type star ($T_{eff}$ ~ 5350 K, $M_s$ ~ 0.9 $M_{Sun}$, and $R_{s}$ ~ 0.9 $R_{Sun}$). We do not find any contaminating faint objects near the host star which could be responsible for (or dilute) the transit signals. We have also conducted transit follow-up photometry for the inner planet with KeplerCam on the FLWO 1.2m telescope, TRAPPISTCAM on the TRAPPIST 0.6m telescope, and MuSCAT on the OAO 1.88m telescope. We confirm the presence of transit-timing variations, as previously reported by Armstrong and coworkers. We model the observed transit-timing variations of the inner planet using the synodic chopping formulae given by Deck & Agol (2015). We find two statistically indistinguishable solutions for which the period ratios ($P_{c}/P_{b}$) are located slightly above and below the exact 3:2 commensurability. Despite the degeneracy, we derive the orbital period of the inner planet $P_b$ ~ 7.921 days and the mass of the outer planet $M_c$ ~ 20 $M_{Earth}$. Additional transit photometry (especially for the outer planet) as well as precise radial-velocity measurements would be helpful to break the degeneracy and to determine the mass of the inner planet. [less ▲]

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See detailThe HARPS search for southern extra-solar planets. XXXVIII. Bayesian re-analysis of three systems. New super-Earths, unconfirmed signals, and magnetic cycles
Díaz, R. F.; Ségransan, D.; Udry, S. et al

E-print/Working paper (2015)

We present the analysis of the entire HARPS observations of three stars that host planetary systems: HD1461, HD40307, and HD204313. The data set spans eight years and contains more than 200 nightly ... [more ▼]

We present the analysis of the entire HARPS observations of three stars that host planetary systems: HD1461, HD40307, and HD204313. The data set spans eight years and contains more than 200 nightly averaged velocity measurements for each star. This means that it is sensitive to both long-period and low-mass planets and also to the effects induced by stellar activity cycles. We modelled the data using Keplerian functions that correspond to planetary candidates and included the short- and long-term effects of magnetic activity. A Bayesian approach was taken both for the data modelling, which allowed us to include information from activity proxies such as $\log{(R'_{\rm HK})}$ in the velocity modelling, and for the model selection, which permitted determining the number of significant signals in the system. The Bayesian model comparison overcomes the limitations inherent to the traditional periodogram analysis. We report an additional super-Earth planet in the HD1461 system. Four out of the six planets previously reported for HD40307 are confirmed and characterised. We discuss the remaining two proposed signals. In particular, we show that when the systematic uncertainty associated with the techniques for estimating model probabilities are taken into account, the current data are not conclusive concerning the existence of the habitable-zone candidate HD40307 g. We also fully characterise the Neptune-mass planet that orbits HD204313 in 34.9 days. [less ▲]

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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 detailMarkets flash graphs
Choffray, Jean-Marie ULg

E-print/Working paper (2015)

A graph is worth a hundred words... A good graph may suggest some new heuristics. And…, a series of excellent graphs may provide the backbone of a theory! The goal of this paper is to share a set of ... [more ▼]

A graph is worth a hundred words... A good graph may suggest some new heuristics. And…, a series of excellent graphs may provide the backbone of a theory! The goal of this paper is to share a set of graphs from multiple sources that offer as many flashes on current and past market conditions. Inevitably, these graphs reflect my own biases and questionings. They are not meant to induce any action aside, maybe, from their integration in a personal Information System. The Great Recession of 2008, whose consequences are still unfolding, has been for each of us a powerful invitation to modesty. We live in a world where improbable, unthinkable and impossible events happen every day... More than ever, it’s time to sit down, shut up, watch out, build graphs, and think… hard! [less ▲]

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See detailInstitutional repositories: it’s a matter of sticks and carrots
Rentier, Bernard ULg

E-print/Working paper (2015)

Detailed reference viewed: 218 (10 ULg)
See detailWill Big Data Deliver its Promised Productivity Growth?
Artige, Lionel ULg

E-print/Working paper (2015)

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See detailHot Jupiters with relatives: discovery of additional planets in orbit around WASP-41 and WASP-47
Neveu-VanMalle, M.; Queloz, D.; Anderson, D. R. et al

E-print/Working paper (2015)

We report the discovery of two additional planetary companions to WASP-41 and WASP-47. WASP-41 c is a planet of minimum mass 3.18 $\pm$ 0.20 M$_{\rm Jup}$ and eccentricity 0.29 $\pm$ 0.02, and it orbits ... [more ▼]

We report the discovery of two additional planetary companions to WASP-41 and WASP-47. WASP-41 c is a planet of minimum mass 3.18 $\pm$ 0.20 M$_{\rm Jup}$ and eccentricity 0.29 $\pm$ 0.02, and it orbits in 421 $\pm$ 2 days. WASP-47 c is a planet of minimum mass 1.24 $\pm$ 0.22 M$_{\rm Jup}$ and eccentricity 0.13 $\pm$ 0.10, and it orbits in 572 $\pm$ 7 days. Unlike most of the planetary systems that include a hot Jupiter, these two systems with a hot Jupiter have a long-period planet located at only $\sim$1 au from their host star. WASP-41 is a rather young star known to be chromospherically active. To differentiate its magnetic cycle from the radial velocity effect induced by the second planet, we used the emission in the H$\alpha$ line and find this indicator well suited to detecting the stellar activity pattern and the magnetic cycle. The analysis of the Rossiter-McLaughlin effect induced by WASP-41 b suggests that the planet could be misaligned, though an aligned orbit cannot be excluded. WASP-47 has recently been found to host two additional transiting super Earths. With such an unprecedented architecture, the WASP-47 system will be very important for understanding planetary migration. [less ▲]

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See detailWASP-120b, WASP-122b and WASP-123b: Three newly discovered planets from the WASP-South survey
Turner, O. D.; Anderson, D. R.; Collier Cameron, A. et al

E-print/Working paper (2015)

We present the discovery by the WASP-South survey of three planets transiting moderately bright stars (V ~ 11). WASP-120b is a massive (5.0MJup) planet in a 3.6-day orbit that we find likely to be ... [more ▼]

We present the discovery by the WASP-South survey of three planets transiting moderately bright stars (V ~ 11). WASP-120b is a massive (5.0MJup) planet in a 3.6-day orbit that we find likely to be eccentric (e = 0.059+0.025-0.018) around an F5 star. WASP-122b is a hot-Jupiter (1.37MJup, 1.79RJup) in a 1.7-day orbit about a G4 star. Our predicted transit depth variation cause by the atmosphere of WASP-122b suggests it is well suited to characterisation. WASP-123b is a hot-Jupiter (0.92MJup, 1.33RJup) in a 3.0-day orbit around an old (~ 7 Gyr) G5 star. [less ▲]

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See detailDiversité des expressions et numérique: du constat à l'action?
Vlassis, Antonios ULg

E-print/Working paper (2015)

Antonios Vlassis nous livre un compte-rendu des débats de la dernière Conférence des Parties à la Convention sur la protection et la promotion de la diversité des expressions culturelles (CDEC) en ... [more ▼]

Antonios Vlassis nous livre un compte-rendu des débats de la dernière Conférence des Parties à la Convention sur la protection et la promotion de la diversité des expressions culturelles (CDEC) en analysant précisément les enjeux liés au numérique et en décortiquant les prises de position exprimées par différents acteurs. [less ▲]

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See detailBenchmarking for Bayesian Reinforcement Learning
Castronovo, Michaël ULg; Ernst, Damien ULg; Couëtoux, Adrien ULg et al

E-print/Working paper (2015)

In the Bayesian Reinforcement Learning (BRL) setting, agents try to maximise the col- lected rewards while interacting with their environment while using some prior knowledge that is accessed beforehand ... [more ▼]

In the Bayesian Reinforcement Learning (BRL) setting, agents try to maximise the col- lected rewards while interacting with their environment while using some prior knowledge that is accessed beforehand. Many BRL algorithms have already been proposed, but even though a few toy examples exist in the literature, there are still no extensive or rigorous benchmarks to compare them. The paper addresses this problem, and provides a new BRL comparison methodology along with the corresponding open source library. In this methodology, a comparison criterion that measures the performance of algorithms on large sets of Markov Decision Processes (MDPs) drawn from some probability distributions is defined. In order to enable the comparison of non-anytime algorithms, our methodology also includes a detailed analysis of the computation time requirement of each algorithm. Our library is released with all source code and documentation: it includes three test prob- lems, each of which has two different prior distributions, and seven state-of-the-art RL algorithms. Finally, our library is illustrated by comparing all the available algorithms and the results are discussed. [less ▲]

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See detailBlues et Wallon - Elmore D, l'intégrale cåzî complète en cinq CDs
Sacré, Robert ULg

E-print/Working paper (2015)

Analyse d'une anthologie de 5 Cds représentant l'intégrale" cåzî "complète des enregsitrements d'Elmore D ( Prof. Daniel Droixhe) pour la compagnie française FREMEAUX et ASS.

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See detailDans le dédale des Musiques Africaines-Américaines
Sacré, Robert ULg

E-print/Working paper (2015)

Notes du cours " Histoire des Musiques Africaines Américaines, des origines à nos jours" (remise à jour 2015) - cours dispensé depuis 1984

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See detailLe Gevarenwinkel Festival de Herselt
Sacré, Robert ULg

E-print/Working paper (2015)

Compte rendu du Festival Gevarenwinkel à HERSELT les 28 et 29 août 2015 , avec photos

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See detailQuadratic reformulations of nonlinear binary optimization problems
Anthony, Martin; Boros, Endre; Crama, Yves ULg et al

E-print/Working paper (2015)

Very large nonlinear unconstrained binary optimization problems arise in a broad array of applications. Several exact or heuristic techniques have proved quite successful for solving many of these ... [more ▼]

Very large nonlinear unconstrained binary optimization problems arise in a broad array of applications. Several exact or heuristic techniques have proved quite successful for solving many of these problems when the objective function is a quadratic polynomial. However, no similarly efficient methods are available for the higher degree case. Since high degree objectives are becoming increasingly important in certain application areas, such as computer vision, various techniques have been recently developed to reduce the general case to the quadratic one, at the cost of increasing the number of variables. In this paper we initiate a systematic study of these quadratization approaches. We provide tight lower and upper bounds on the number of auxiliary variables needed in the worst-case for general objective functions, for bounded-degree functions, and for a restricted class of quadratizations. Our upper bounds are constructive, thus yielding new quadratization procedures. Finally, we completely characterize all ``minimal'' quadratizations of negative monomials. [less ▲]

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See detailGouvy Jazz & Blues Festival Août 2015
Sacré, Robert ULg

E-print/Working paper (2015)

Compte rendu du festival BLUES avec photos

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See detailColère des agriculteurs, à qui la faute?
Habran, Maxime ULg

E-print/Working paper (2015)

Depuis le début de l’été, la colère gronde du côté des agriculteurs et pour cause, les prix du lait et de la viande ont atteint des seuils dangereusement bas. Que ce soit en France ou en Belgique, le ... [more ▼]

Depuis le début de l’été, la colère gronde du côté des agriculteurs et pour cause, les prix du lait et de la viande ont atteint des seuils dangereusement bas. Que ce soit en France ou en Belgique, le combat est le même. Les agriculteurs veulent des prix plus élevés pour la viande et pour le lait car actuellement ceux-ci sont inférieurs aux coûts de production. Cette note a pour objectif de répondre à trois questions : d’où vient la crise, quelles sont les solutions et les mesures prises sont-elles suffisantes ? [less ▲]

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See detailLa gestation chez les petits camélidés d'Amérique du Sud : physiologie, constat et pathologie
Hanzen, Christian ULg; Cucho Dolmos, Hernan; Ampuero Casquino, Enrique et al

E-print/Working paper (2015)

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

E-print/Working paper (2015)

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 resulted in 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 detailThe French language runs throughout the world
Morato, Nicola ULg; Gaunt, Simon

E-print/Working paper (2015)

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See detailAsymptotic properties of free monoid morphisms
Charlier, Emilie ULg; Leroy, Julien ULg; Rigo, Michel ULg

E-print/Working paper (2015)

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See detailLes biotechnologies de la reproduction des petits camélidés sud-américains
Hanzen, Christian ULg; Cucho Dolmo, Hernan; Ampuero Casquino, Enrique et al

E-print/Working paper (2015)

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See detailWASP-121 b: a hot Jupiter in a polar orbit and close to tidal disruption
Delrez, Laetitia ULg; Santerne, A.; Almenara, J.-M. et al

E-print/Working paper (2015)

We present the discovery by the WASP-South survey, in close collaboration with the Euler and TRAPPIST telescopes, of WASP-121 b, a new remarkable short-period transiting hot Jupiter, whose planetary ... [more ▼]

We present the discovery by the WASP-South survey, in close collaboration with the Euler and TRAPPIST telescopes, of WASP-121 b, a new remarkable short-period transiting hot Jupiter, whose planetary nature has been statistically validated by the PASTIS software. The planet has a mass of 1.183+0.064−0.062 MJup, a radius of 1.865 ± 0.044 RJup, and transits every 1.2749255+0.0000020−0.0000025 days an active F6-type main-sequence star (V=10.4, 1.353+0.080−0.079 M⊙, 1.458 ± 0.030 R⊙, Teff = 6460 ± 140 K). A notable property of WASP-121 b is that its orbital semi-major axis is only ∼1.15 times larger than its Roche limit, which suggests that the planet might be close to tidal disruption. Furthermore, its large size and extreme irradiation (∼7.1 10^9 erg s−1cm−2) make it an excellent target for atmospheric studies via secondary eclipse observations. Using the TRAPPIST telescope, we indeed detect its emission in the z′-band at better than ∼4σ, the measured occultation depth being 603 ± 130 ppm. Finally, from a measurement of the Rossiter-McLaughlin effect with the CORALIE spectrograph, we infer a sky-projected spin-orbit angle of 257.8+5.3−5.5 deg. This result indicates a significant misalignment between the spin axis of the host star and the orbital plane of the planet, the planet being in a nearly polar orbit. Such a high misalignment suggests a migration of the planet involving strong dynamical events with a third body. [less ▲]

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See detailGarantir la légalité et assurer la traçabilité. Deux piliers de la mise en oeuvre de l'APV-FLEGT.
Moumbogou, Carl; Meunier, Quentin; Bracke, Charles et al

E-print/Working paper (2015)

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See detailLes forêts communautaires et l'APV-FLEGT au Gabon
Moumbogou, Carl; Meunier, Quentin; Mvou Biyogo, T. et al

E-print/Working paper (2015)

Promu par l’Union européenne depuis 2003, le plan d’action FLEGT propose une approche novatrice de lutte contre l’exploitation illégale des forêts, en établissant un lien entre l’amélioration de la ... [more ▼]

Promu par l’Union européenne depuis 2003, le plan d’action FLEGT propose une approche novatrice de lutte contre l’exploitation illégale des forêts, en établissant un lien entre l’amélioration de la gouvernance dans les pays producteurs et l’accès au marché de l’UE. Ce plan concerne tous les titres forestiers, dont les forêts communautaires. Ces dernières ont été désignées au Gabon comme source légale de bois à la faveur des négociations d’un APVFLEGT avec l’UE. Dès lors, et afin de stabiliser le système qui sera mis en place, il est nécessaire de préparer des outils adaptés permettant d’articuler le FLEGT et les forêts communautaires. [less ▲]

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See detailBayesian inference in an extended SEIR model with nonparametric disease transmission rate: an application to the Ebola epidemic in Sierra Leone
Frasso, Gianluca ULg; Lambert, Philippe ULg

E-print/Working paper (2015)

The 2014 Ebola outbreak in Sierra Leone is analyzed using an extension of the SEIR compartmental model. The unknown parameters of the system of differential equations are estimated by combining data on ... [more ▼]

The 2014 Ebola outbreak in Sierra Leone is analyzed using an extension of the SEIR compartmental model. The unknown parameters of the system of differential equations are estimated by combining data on the number of new (laboratory confirmed) Ebola cases reported by the Ministry of Health and prior distributions for the transition rates elicited using information collected by the WHO Response Team (2014) during the follow-up of specific Ebola cases. The evolution over time of the disease transmission rate is modeled nonparametrically using penalized B-splines. Our framework represents a valuable and robust stochastic tool for the study of an epidemic dynamic from irregular and possibly aggregated case data. Simulations and the analysis of the 2014 Sierra Leone Ebola data highlight the merits of the proposed methodology. [less ▲]

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See detailLe cycle sexuel de la femelle des petits camélidés sud-américains
Hanzen, Christian ULg; Cucho Dolmos, Hernan; Ampuero Casquino, Enrique et al

E-print/Working paper (2015)

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See detailVariability in the super-Earth 55 Cnc e
Demory, Brice-Olivier; Gillon, Michaël ULg; Madhusudhan, Nikku et al

E-print/Working paper (2015)

Considerable progress has been made in recent years in observations of atmospheric signatures of giant exoplanets, but processes in rocky exoplanets remain largely unknown due to major challenges in ... [more ▼]

Considerable progress has been made in recent years in observations of atmospheric signatures of giant exoplanets, but processes in rocky exoplanets remain largely unknown due to major challenges in observing small planets. Numerous efforts to observe spectra of super-Earths, exoplanets with masses of 1-10 Earth masses, have thus far revealed only featureless spectra. In this paper we report a 4-$\sigma$ detection of variability in the dayside thermal emission from the transiting super-Earth 55 Cancri e. Dedicated space-based monitoring of the planet in the mid-infrared over eight eclipses revealed the thermal emission from its dayside atmosphere varying by a factor 3.7 between 2012 and 2013. The amplitude and trend of the variability are not explained by potential influence of star spots or by local thermal or compositional changes in the atmosphere over the short span of the observations. The possibility of large scale surface activity due to strong tidal interactions possibly similar to Io, or the presence of circumstellar/circumplanetary material appear plausible and motivate future long-term monitoring of the planet. [less ▲]

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See detailAura
Durand, Pascal ULg

E-print/Working paper (2015)

Entrée du Lexique Socius sur le concept d'Aura chez Walter Benjamin

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See detailAnatomie de l'appareil génital femelle des petits camélidés sud-américains
Hanzen, Christian ULg; Cucho Dolmos, Hernan; Amupero Casquino, Enrique et al

E-print/Working paper (2015)

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See detailOptimal Enforcement of Competition Policy: The Commitments Procedure under Uncertainty
Gautier, Axel ULg; Petit, Nicolas ULg

E-print/Working paper (2015)

Since the introduction of a commitments procedure in EU antitrust policy (Article 9 of Council Regulation 1/2003), the European Commission has extensively settled cases of alleged anticompetitive ... [more ▼]

Since the introduction of a commitments procedure in EU antitrust policy (Article 9 of Council Regulation 1/2003), the European Commission has extensively settled cases of alleged anticompetitive practices. In this paper, we use a formal model of law enforcement (Bebchuk, 1984; Shavell, 1988) to identify the optimal procedure to resolve cases in a context of uncertainty related to the law (L-uncertainty) and to the facts (F-uncertainty). We show that commitments are suboptimal when L-uncertainty is high. Furthermore, the generalized use of commitments creates an additional risk of under-enforcement when F-uncertainty is significant. [less ▲]

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See detailParty autonomy in international family relationships : a research agenda
Wautelet, Patrick ULg

E-print/Working paper (2015)

In recent years, party autonomy has conquered new grounds in cross-border private relationships. Building on first attempts in national codifications, party autonomy has become one of the leading ... [more ▼]

In recent years, party autonomy has conquered new grounds in cross-border private relationships. Building on first attempts in national codifications, party autonomy has become one of the leading principles used in various EU regulations dealing with cross-border family relationships. It can now be found in successions, in divorce, in maintenance matters. This new trend has been greeted sometimes with enthusiasm, sometimes with skepticism. While these Regulations constrain the choice that parties can make, it cannot be denied that the principle of freedom of choice has been openly embraced by the European legislator. Hence this principle evolved, at least within the EU, from what was until recently a marginal phenomenon to a well-respected solution for cross-border family relationships This (r-)evolution occurred quite fast and has attracted much attention. However, much of the research in this area has adopted a limited perspective, focusing exclusively on the possibilities and limits of choice in one specific instrument or adopting a comprehensive outlook but with a strong positive flavor. While it is true that a number of contributions provide excellent food for thought, the overall impression is that more time and more research is needed to start apprehending the fundamental questions raised by this evolution. At this stage, it may be too early to offer a comprehensive study of all questions raised by party autonomy in private international law. New developments may in fact modify the picture soon and add to the fields conquered by party autonomy. At the same time, the relative novelty of the changes makes it difficult to take full stock of all issues raised by the development of party autonomy. This is why scholars should first attempt to define a research agenda. This paper offers a first scratch by exploring various questions which should figure prominently in such agenda. It is by no means meant to be exhaustive. Rather, an attempt will be made to shed some light on the main questions raised by recent evolution in the hope of being an invitation for further research. [less ▲]

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See detailTheories of Self-Preferencing Under Article 102 TFEU: A Reply to Bo Vesterdorf
Petit, Nicolas ULg

E-print/Working paper (2015)

Detailed reference viewed: 1 (1 ULg)
See detailPasseport santé pour bananier
Massart, Sébastien ULg

E-print/Working paper (2015)

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See detailApproche agroforestière. Synthèse des travaux menés par le projet DACEFI2 en agroforesterie. Document de capitalisation.
Boldrini, Sylvie; Meunier, Quentin; Boukouendji, Basile et al

E-print/Working paper (2015)

Le projet DACEFI-2 a eu pour mission première la promotion de la foresterie communautaire comme outil de développement des communautés rurales. L’approche au Gabon en matière de gestion des terroirs ... [more ▼]

Le projet DACEFI-2 a eu pour mission première la promotion de la foresterie communautaire comme outil de développement des communautés rurales. L’approche au Gabon en matière de gestion des terroirs villageois s’est voulue plus embrassante, promouvant en sus de l’exploitation forestière des activités comme l’agriculture, le maraîchage, la collecte des produits forestiers non ligneux ou encore l’agroforesterie. L’agroforesterie est une thématique qui converge parfaitement avec la gestion raisonnée de la forêt, et idéalement avec les modes d’interaction préexistants des villageois avec celle-ci. Concilier dans un même espace la culture de plantes vivrières et l’accès à des arbres à fort intérêt socio-économique apporte une plus-value notoire aux parcelles cultivées. L’optimisation des techniques culturales permet une meilleure productivité et une incitation à la sédentarisation des cultures, élément important à considérer compte tenu des difficultés d’entretien des parcelles éloignées du village (notamment liées aux dégâts causés par les animaux). Ce recueil compile les travaux réalisés en agroforesterie par les équipes du projet DACEFI-2. Il rappelle la stratégie d’intervention et les différentes activités menées, de la sensibilisation auprès des plus jeunes à la promotion de certains produits forestiers non ligneux à potentiel économique avéré. La promotion de l’arbre, de la récolte de la graine jusqu’à sa plantation en passant par sa mise en pépinière aura également animé toute l’équipe durant ces années d’exercice, afin de faire un peu plus valoir ses multiples intérêts et susciter les efforts de gestion, de conservation et de reboisement. [less ▲]

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See detailAccess to Electoral Rights Bolivia
Zegada, Maria Teresa; Lafleur, Jean-Michel ULg

E-print/Working paper (2015)

The issue of passive and active electoral rights in Bolivia has gone through various phases that are examined in details in this article. Universal suffrage in Bolivia occurred around the same time as in ... [more ▼]

The issue of passive and active electoral rights in Bolivia has gone through various phases that are examined in details in this article. Universal suffrage in Bolivia occurred around the same time as in most states in that region: in the middle of the 20th century. The next wave of reforms occurred during the 1980s when dictatorships were removed from power. At that time, processes of democratization intensified in Bolivia and other parts of Latin America, eventually leading to the progressive strengthening of democratic institutions. It is really during the 1990s and early 2000s that the most important democratic transformations occurred. Major institutional reforms were passed during this period in particular to increase the participation of women and indigenous peoples in public affairs. The inclusion of the principles of gender equality and interculturality in the new constitution of 2009 is one of the clearest sign of this new approach. Similarly, another sector of the Bolivian population that had been traditionally prevented from exercising political rights. that is, Bolivians residing abroad have been closely attended to by the Evo Morales government since 2006. After the first external voting experience in 2009, the system was once again reformed to enable greater participation from abroad in the 2014 presidential election. These elements confirm that the extension of political rights in Bolivia is a process that has gone trough major changes over the past two decades but remains a work in process. [less ▲]

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See detailEfficient Path Interpolation and Speed Profile Computation for Nonholonomic Mobile Robots
Lens, Stéphane ULg; Boigelot, Bernard ULg

E-print/Working paper (2015)

This paper studies path synthesis for nonholonomic mobile robots moving in two-dimensional space. We first address the problem of interpolating paths expressed as sequences of straight line segments, such ... [more ▼]

This paper studies path synthesis for nonholonomic mobile robots moving in two-dimensional space. We first address the problem of interpolating paths expressed as sequences of straight line segments, such as those produced by some planning algorithms, into smooth curves that can be followed without stopping. Our solution has the advantage of being simpler than other existing approaches, and has a low computational cost that allows a real-time implementation. It produces discretized paths on which curvature and variation of curvature are bounded at all points, and preserves obstacle clearance. Then, we consider the problem of computing a time-optimal speed profile for such paths. We introduce an algorithm that solves this problem in linear time, and that is able to take into account a broader class of physical constraints than other solutions. Our contributions have been implemented and evaluated in the framework of the Eurobot contest. [less ▲]

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See detailPrélèvement, analyse et conservation du sperme du mâle des petits camélidés sud-américains
Hanzen, Christian ULg; Cucho Dolmos, Hernan; Ampuero Casquino, Enrique et al

E-print/Working paper (2015)

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See detailSome misunderstood or unknown tricks (XIII) (LaTeX)
Merciadri, Luca ULg

E-print/Working paper (2015)

We will here again consider many tips and tricks. This time, they will mostly come from Glad Deschrijver, TeX Tricks, 2011. (http://users.ugent.be/~gdschrij/LaTeX/textricks.html.) Tricks: vertically ... [more ▼]

We will here again consider many tips and tricks. This time, they will mostly come from Glad Deschrijver, TeX Tricks, 2011. (http://users.ugent.be/~gdschrij/LaTeX/textricks.html.) Tricks: vertically aligned itemize environments, allowing linebreaks after comma in math mode, writing under and over elements, and using stacks, footnotes with a new number at each section, footnotes in tabular, splitting algorithm environments on multiple pages, let " produce opening/closing quotation marks, indenting some text but not the first line, using diagonal dots positioned according to the opposite diagonal, using a centered verbatim environment, drawing a table with dashed lines, shaded cells and arrows pointing at a row and a column, correct spacing around square brackets (used for sets) in math mode. [less ▲]

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See detailSome misunderstood or unknown LaTeX tricks (XIV) and LaTeX learning curve
Merciadri, Luca ULg

E-print/Working paper (2015)

We will here give three tricks: i. using a personalized \overline, ii. boxing every digit of an integer, iii. using \scalebox. I will then expose my point of view about the LaTeX learning curve, and give ... [more ▼]

We will here give three tricks: i. using a personalized \overline, ii. boxing every digit of an integer, iii. using \scalebox. I will then expose my point of view about the LaTeX learning curve, and give some of the most common beginners’ mistakes. [less ▲]

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See detailSome misunderstood or unknown LaTeX tricks (XV)
Merciadri, Luca ULg

E-print/Working paper (2015)

After having looked at about 150 StackExchange pages of 50 topics (that sums up to about 7500 topics’ names), I give you, in this article and in the next issue, the most interesting topics’ answers to my ... [more ▼]

After having looked at about 150 StackExchange pages of 50 topics (that sums up to about 7500 topics’ names), I give you, in this article and in the next issue, the most interesting topics’ answers to my eyes. We will first begin by two additions in regard to 31(3), 32(1). [less ▲]

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See detailSome misunderstood or unknown LaTeX tricks (XVI)
Merciadri, Luca ULg

E-print/Working paper (2015)

This is the second (and last) part of the tricks I found on StackExchange. First part began in the preceding issue. We will begin by a personal trick, and end by some inquiry about my LaTeX Tips & Tricks.

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See detailImportance et rôle de l’investissement…
Choffray, Jean-Marie ULg

E-print/Working paper (2015)

Quelques observations et réflexions en réponse à une question qui m’est souvent posée sur l’importance et le rôle des investisseurs. Ces « Charognards », particulièrement visés au cours des périodes de ... [more ▼]

Quelques observations et réflexions en réponse à une question qui m’est souvent posée sur l’importance et le rôle des investisseurs. Ces « Charognards », particulièrement visés au cours des périodes de tension géopolitique, de populisme ou de débauche monétaire, semblables à celle que nous vivons aujourd’hui. Ma réponse en peu de mots : les investisseurs sont des défenseurs de la valeur du travail par temps calme et des vigies dans la tempête ! [less ▲]

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See detailDocuments as a source of information; Tabular packages' purposes, conflicts; Same space in matrices; Logic inferences
Merciadri, Luca ULg

E-print/Working paper (2015)

The various aspects of the title are considered.

Detailed reference viewed: 34 (16 ULg)
See detailSome misunderstood or unknown tricks (X) (LaTeX)
Merciadri, Luca ULg

E-print/Working paper (2015)

This is the 10th edition of my `Tips & Tricks.' This time, we shall first see how to write `dancing text,' roman numerals, how to draw under and over braces on same elements, and how to display aligned ... [more ▼]

This is the 10th edition of my `Tips & Tricks.' This time, we shall first see how to write `dancing text,' roman numerals, how to draw under and over braces on same elements, and how to display aligned (in)equations systems. We will then end by discussing on BibLaTeX and Biber, which constitute a promising alternative to BibTeX. [less ▲]

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See detailSome misunderstood or unknown tricks (XI) (LaTeX) and encoding issues (II)
Merciadri, Luca ULg

E-print/Working paper (2015)

Three subjects will be detailed: 1. Using LaTeX syntax as an unambiguous way to communicate, 2. Writing a bold \ell, 3. Fonts' encodings.

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See detailEntretien avec Kathryn Batchelor
Oumarou Mal Mazou, Rachid ULg

E-print/Working paper (2015)

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See detailTransnational Health Insurance Schemes: A New Avenue for Congolese Immigrants in Belgium to Care for Their Relatives’ Health from Abroad?
Lafleur, Jean-Michel ULg; Lizin, Olivier

E-print/Working paper (2015)

What can immigrants do for non-migrant relatives in their home country who need healthcare they cannot afford? To answer this question, we first examine four existing methods that can be found in the ... [more ▼]

What can immigrants do for non-migrant relatives in their home country who need healthcare they cannot afford? To answer this question, we first examine four existing methods that can be found in the existing literature: mobility, remittances, workers’ health insurance and diasporic health insurance. In the second part of the paper, we discuss an innovative strategy called “transnational health insurance” (THI). These insurance schemes are set up by immigrants in cooperation with a multitude of actors including health insurance companies in destination countries and healthcare providers in countries origin. THIs offer health coverage to non-migrant relatives in the home country based on a premium paid directly by immigrants to the insurance company in their country of residence. Analyzing the creation and implementation of Belgian-Congolese THIs, we discuss the strengths and weaknesses of these schemes in responding to the needs of both immigrants and their non-migrant relatives. The article concludes with a discussion on the specificities of THIs as hybrid forms of remittances. [less ▲]

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See detailPropriété coopérative et acceptabilité sociale de l’éolien terrestre
Bauwens, Thomas ULg

E-print/Working paper (2015)

Onshore wind power development in Belgium has provoked considerable opposition at the local level. To cope with this issue, wind power cooperatives seem to present important assets. This article explores ... [more ▼]

Onshore wind power development in Belgium has provoked considerable opposition at the local level. To cope with this issue, wind power cooperatives seem to present important assets. This article explores the reasons why these organizations are likely to enhance social acceptability of this technology. Then it confronts these normative assumptions with empirical data. The results of this analysis confirm the positive effect of cooperative ownership on the social acceptability of onshore wind turbines. [less ▲]

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See detailA semiparametric model for Generalized Pareto regression based on a dimension reduction assumption
Hambuckers, julien ULg; Heuchenne, Cédric ULg; Lopez, Olivier

E-print/Working paper (2015)

In this paper, we consider a regression model in which the tail of the conditional distribution of the response can be approximated by a Generalized Pareto distribution. Our model is based on a ... [more ▼]

In this paper, we consider a regression model in which the tail of the conditional distribution of the response can be approximated by a Generalized Pareto distribution. Our model is based on a semiparametric single-index assumption on the conditional tail index; while no further assumption on the conditional scale parameter is made. The underlying dimension reduction assumption allows the procedure to be of prime interest in the case where the dimension of the covariates is high, in which case the purely nonparametric techniques fail while the purely parametric ones are too rough to correctly fit to the data. We derive asymptotic normality of the estimators that we define, and propose an iterative algorithm in order to perform their practical implementation. Our results are supported by some simulations and a practical application on a public database of operational losses. [less ▲]

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See detailMachine Learning to Balance the Load in Parallel Branch-and-Bound
Marcos Alvarez, Alejandro ULg; Wehenkel, Louis ULg; Louveaux, Quentin ULg

E-print/Working paper (2015)

We describe in this paper a new approach to parallelize branch-and-bound on a certain number of processors. We propose to split the optimization of the original problem into the optimization of several ... [more ▼]

We describe in this paper a new approach to parallelize branch-and-bound on a certain number of processors. We propose to split the optimization of the original problem into the optimization of several subproblems that can be optimized separately with the goal that the amount of work that each processor carries out is balanced between the processors, while achieving interesting speedups. The main innovation of our approach consists in the use of machine learning to create a function able to estimate the difficulty (number of nodes) of a subproblem of the original problem. We also present a set of features that we developed in order to characterize the encountered subproblems. These features are used as input of the function learned with machine learning in order to estimate the difficulty of a subproblem. The estimates of the numbers of nodes are then used to decide how to partition the original optimization tree into a given number of subproblems, and to decide how to distribute them among the available processors. The experiments that we carry out show that our approach succeeds in balancing the amount of work between the processors, and that interesting speedups can be achieved with little effort. [less ▲]

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See detailThe role of market-oriented institutions in the deployment of renewable energies: evidences from Europe
Jacqmin, Julien ULg

E-print/Working paper (2015)

This paper investigates the link between economic freedom and the production of energy using renewable sources, with a specific focus on European countries. Using a dynamic panel approach, we find that ... [more ▼]

This paper investigates the link between economic freedom and the production of energy using renewable sources, with a specific focus on European countries. Using a dynamic panel approach, we find that this relationship is positive and significant. The results of our instrumental variable approach indicate further the causal channel between economic freedom and the deployment of renewable energies. Looking at the subcomponents of the economic freedom index, we find that long term price stability and freedom to trade boost the production of renewable energies. However, the importance given to markets, rather than governments, in the economy has no significant impact. [less ▲]

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See detailQue veut dire FLEGT ? Et pourquoi au Gabon ?
Moumbogou, Carl; Meunier, Quentin; Mvou Biyogo, T. et al

E-print/Working paper (2015)

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See detailA branch-and-price algorithm for 2-period vehicle routing problems
Crama, Yves ULg; Rezaei Sadrabadi, Mahmood ULg; Van Woensel, Tom

E-print/Working paper (2015)

We consider a Vehicle Routing Problem (VRP) with deterministic orders in two periods from a set of stores. Orders in period 1 (2) can be postponed (advanced) to the other period but any diversion from the ... [more ▼]

We consider a Vehicle Routing Problem (VRP) with deterministic orders in two periods from a set of stores. Orders in period 1 (2) can be postponed (advanced) to the other period but any diversion from the initial orders incurs a penalty. From the perspective of a Logistics Service Provider (LSP), such diversions could be beneficial if savings in the routing costs outweigh the penalties. So could they be from a store's view, as the store can set a high enough penalty to compensate the diversion from its own optimal orders. In this paper, we introduce a new model where we seek a better solution for the LSP, compared to solving two independent VRPs with fixed orders, by allowing orders to be fully postponed or advanced. We apply a branch-and-price algorithm to solve this model to optimality. Many cutting-edge techniques are implemented to have an efficient branch-and-price algorithm, and two ideas to possibly improve the upper bound are tested. We draw algorithmic and managerial insights based on our test instances. [less ▲]

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See detailInvesting in the Future
Pahud de Mortanges, Charles ULg

E-print/Working paper (2015)

This paper attempts to address the challenges of how to invest in Synthetic Biology firms, most of which are relatively new start-ups and unprofitable. Valuing an early-stage firm with only a brief ... [more ▼]

This paper attempts to address the challenges of how to invest in Synthetic Biology firms, most of which are relatively new start-ups and unprofitable. Valuing an early-stage firm with only a brief operating history, little or no operating profit (or even revenue), and an immature and untested business model, could be a formidable challenge. We propose a limited number of quantitative, and a larger number of qualitative criteria. An investor may consider these when faced with analyzing a new untried business, but one he/she believes has considerable potential for success in the future. [less ▲]

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See detailOn the nature of cosmological time
Magain, Pierre ULg; Hauret, Clémentine ULg

E-print/Working paper (2015)

Time is a parameter playing a central role in our most fundamental modeling of natural laws. Relativity theory shows that the comparison of times measured by different clocks depends on their relative ... [more ▼]

Time is a parameter playing a central role in our most fundamental modeling of natural laws. Relativity theory shows that the comparison of times measured by different clocks depends on their relative motions and on the strength of the gravitational field in which they are embedded. In standard cosmology, the time parameter is the one measured by fundamental clocks, i.e. clocks at rest with respect to the expanding space. This proper time is assumed to flow at a constant rate throughout the whole history of the Universe. We make the alternative hypothesis that the rate at which cosmological time flows depends on the dynamical state of the Universe. In thermodynamics, the arrow of time is strongly related to the second law, which states that the entropy of an isolated system will always increase with time or, at best, stay constant. Hence, we assume that time measured by fundamental clocks is proportional to the entropy of the region of the Universe that is causally connected to them. Under that simple assumption, we build a cosmological model that explains the Type Ia Supernovae data (the best cosmological standard candles) without the need for exotic dark matter nor dark energy. [less ▲]

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See detailSequential testing of k-out-of-n systems with imperfect tests
Wenchao, Wei; Coolen, Kris ULg; Talla Nobibon, Fabrice et al

E-print/Working paper (2015)

A k-out-of-n system configuration requires that, for the overall system to be functional, at least k out of the total of n components be working. We consider the problem of sequentially testing the ... [more ▼]

A k-out-of-n system configuration requires that, for the overall system to be functional, at least k out of the total of n components be working. We consider the problem of sequentially testing the components of a k-out-of-n system in order to learn the state of the system, when the tests are costly and when the individual component tests are imperfect, which means that a test can identify a component as working when in reality it is down, and vice versa. Each component is tested at most once. Since tests are imperfect, even when all components are tested the state of the system is not necessarily known with certainty, and so reaching a lower bound on the probability of correctness of the system state is used as a stopping criterion for the inspection. We define different classes of inspection policies and we examine global optimality of each of the classes. We find that a globally optimal policy for diagnosing k-out-of-n systems with imperfect tests can be found in polynomial time when the predictive error probabilities are the same for all the components. Of the three policy classes studied, the dominant policies always contain a global optimum, while elementary policies are compact in representation. The newly introduced class of so-called `interrupted block-walking' policies combines these merits of global optimality and of compactness. [less ▲]

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See detailLacunary wavelet series on Cantor sets
Esser, Céline ULg

E-print/Working paper (2015)

We construct functions with prescribed multifractal spectra which satisfy the leaders profile method.

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See detailPolicy dialogue: What it is and how it can contribute to evidence-informed decision-making.
Rajan, D; El Husseiny, D; Porignon, Denis ULg et al

E-print/Working paper (2015)

Detailed reference viewed: 19 (2 ULg)
Peer Reviewed
See detailDoes sector-specific experience matter? The case of European higher education ministers
Lefebvre, Mathieu ULg; Jacqmin, Julien

E-print/Working paper (2015)

This paper looks at the relationship between higher education ministers and the performance of the sector that they govern. Using an original panel dataset with the characteristics of European higher ... [more ▼]

This paper looks at the relationship between higher education ministers and the performance of the sector that they govern. Using an original panel dataset with the characteristics of European higher education ministers, we find that having a past experience in the sector leads to a higher level of performance, as measured by ranking data. Making a parallel with the literature about the impact of education on the educated, we discuss potential explanations behind the impact of this on-the-job learning experience. As we find that this characteristic has no impact on the spendings of the sector, we argue that this academic experience makes them more prone to introduce adequate reforms. Furthermore, we find that this result is driven by ministers with both this sector-specific and an electoral experience, the latter measured by a succesful election at the regional or national level. This tends to show that political credibility should not be overshadowed by the importance of the sector-specific experience of ministers. [less ▲]

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See detailPERFORMANCE ET INVENTION. LE LABORATOIRE DE L’EXPERIENCE ESTHETIQUE
Hagelstein, Maud ULg

E-print/Working paper (2015)

Lorsqu’il cherche à qualifier l’époque de l’art dans laquelle nous baignons actuellement, le philosophe Jacques Rancière parle d’un régime pour lequel l’expérience esthétique serait déterminante ... [more ▼]

Lorsqu’il cherche à qualifier l’époque de l’art dans laquelle nous baignons actuellement, le philosophe Jacques Rancière parle d’un régime pour lequel l’expérience esthétique serait déterminante : sensible (par définition) et prise dans un rapport paradoxal de continuité et d’exception avec l’expérience commune. Le régime esthétique de l’art – celui qui affecte les productions artistiques contemporaines – signerait notamment l’effacement des spécificités des arts (et l’abandon du régime très hiérarchisé des Beaux-Arts) au profit d’une expérience sensible commune à toutes les formes d’expression artistiques . Le propre de l’art serait donc de faire vivre à son spectateur une telle expérience, qui toucherait directement ses sens et son imagination. Une expérience dont la tonalité particulière serait directement reconnaissable. Une expérience en excès par rapport à ses habitudes et qui le ferait basculer progressivement dans le domaine si singulier de l’art. On voudrait ici défendre l’idée suivante : la performance artistique semble l’une des animatrices principales de ce régime contemporain en tant qu’elle vise à dégager – au-delà des particularismes des médias d’expression – un territoire très large (un laboratoire) d’expérimentation pour l’art. À travers leurs propositions, les artistes performeurs ne produisent pas des œuvres d’art (c’est-à-dire des produits finis), ils montrent le travail de la créativité à l’œuvre. [less ▲]

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See detailSocial Enterprise in Belgium: A Diversity of Roots, Models and Fields
Huybrechts, Benjamin ULg

E-print/Working paper (2015)

This working paper is structured as follows. The first introductory section reviews the main historical roots that have led to the emergence of a diversity of models related to social enterprise and the ... [more ▼]

This working paper is structured as follows. The first introductory section reviews the main historical roots that have led to the emergence of a diversity of models related to social enterprise and the social economy in Belgium. Next, the second section sketches the main features of these models in terms of legal forms, types of social missions addressed, governance dynamics and resources. In the third section, these models are then illustrated in different fields of activity both established and emerging. Finally, the fourth section proposes a transversal analysis of the main trends and challenges facing the development and coexistence of the different models. [less ▲]

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See detailCritical analysis and alternative processing of Type Ia supernovae data
Hauret, Clémentine ULg; Magain, Pierre ULg

E-print/Working paper (2015)

Context: Type Ia Supernovae (SNIa) observations in the late 90’s were the first hints for an accelerated expansion of our Universe. Today, hundreds of objects have been observed and seem to confirm the ... [more ▼]

Context: Type Ia Supernovae (SNIa) observations in the late 90’s were the first hints for an accelerated expansion of our Universe. Today, hundreds of objects have been observed and seem to confirm the flat LambdaCDM model as the cosmological model best representing our Universe. Aims: We study the SNIa observations gathered in the Union 2.1 and in the JLA compilations. By analyzing correlations and different ways of comparing cosmological models to the data, we bring to light some statistical biases, due to the current way of computing SNIa luminosity corrections for light-curve shape, color and host galaxy mass. Methods: We suggest an alternative, safer and model-independent methodology to calibrate the luminosity corrections, using only nearby SNIa. Results: With our recalibrated data, biases are strongly reduced. Moreover, open cosmological models are shown to be favoured over flat models (Omega_m,0 = 0.26+-0.08, Omega_Lambda,0 = 0.66+-0.12 for the SCP compilation and Omega_m,0 = 0.20+-0.08, Omega_Lambda,0 = 0.56+- 0.13 for the JLA one). Conclusions: The usual method to process SNIa data, i.e. simultaneously determining the parameters of the cosmological model and of the luminosity corrections on the full sample, is prone to bias the data in favour of the assumed cosmology, currently a flat LambdaCDM model, as well as to bias the cosmological parameters of the assumed model. [less ▲]

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See detailNotice de Barlaam et Josaphat : les versions anonymes françaises (Arlima)
Lambert, Adelaïde ULg

E-print/Working paper (2015)

Contribution au site internet ARLIMA — Archives de littérature du Moyen Âge. Notice des cinq versions françaises anonymes du XIIIe s. de Barlaam et Josaphat : la version champenoise en prose, l'abrégé en ... [more ▼]

Contribution au site internet ARLIMA — Archives de littérature du Moyen Âge. Notice des cinq versions françaises anonymes du XIIIe s. de Barlaam et Josaphat : la version champenoise en prose, l'abrégé en prose de la version champenoise, la traduction française de la version grecque du Mont Athos, la version en vers octosyllabiques et la mise en prose de la version en vers octosyllabiques. Les fiches, composées d'une description des textes (datation, forme, témoins, etc.) assortie d'une bibliographie complète (éditions et études critiques), établissent un bilan de l'état de la recherche sur ces versions. [less ▲]

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See detailNon-renewable and intermittent renewable energy sources: friends and foes?
baranes, edmond; Jacqmin, Julien ULg; poudou, jean-christophe

E-print/Working paper (2015)

This paper studies the links between non-renewable and intermittent renewable energy sources in the production of electricity. We argue that the relationship between the price of natural gas and ... [more ▼]

This paper studies the links between non-renewable and intermittent renewable energy sources in the production of electricity. We argue that the relationship between the price of natural gas and investments in solar and wind capacity is represented by a bell-shaped curve, as opposed to being linear. Hence, for relatively low natural gas prices, the two modes of production are substitutes. After a price threshold is reached, the two are complementary. A theoretical model explains this as the trade-off resulting from two forces: the input price differential of these two modes of production and the risks related to the unpredictable nature of renewable energy. Using U.S. state-level data from 1998 to 2012, we find that this relationship is robust to various empirical specifications. [less ▲]

Detailed reference viewed: 25 (0 ULg)