References of "First made available on ORBi"      in Complete repository Arts & humanities   Archaeology   Art & art history   Classical & oriental studies   History   Languages & linguistics   Literature   Performing arts   Philosophy & ethics   Religion & theology   Multidisciplinary, general & others Business & economic sciences   Accounting & auditing   Production, distribution & supply chain management   Finance   General management & organizational theory   Human resources management   Management information systems   Marketing   Strategy & innovation   Quantitative methods in economics & management   General economics & history of economic thought   International economics   Macroeconomics & monetary economics   Microeconomics   Economic systems & public economics   Social economics   Special economic topics (health, labor, transportation…)   Multidisciplinary, general & others Engineering, computing & technology   Aerospace & aeronautics engineering   Architecture   Chemical engineering   Civil engineering   Computer science   Electrical & electronics engineering   Energy   Geological, petroleum & mining engineering   Materials science & engineering   Mechanical engineering   Multidisciplinary, general & others Human health sciences   Alternative medicine   Anesthesia & intensive care   Cardiovascular & respiratory systems   Dentistry & oral medicine   Dermatology   Endocrinology, metabolism & nutrition   Forensic medicine   Gastroenterology & hepatology   General & internal medicine   Geriatrics   Hematology   Immunology & infectious disease   Laboratory medicine & medical technology   Neurology   Oncology   Ophthalmology   Orthopedics, rehabilitation & sports medicine   Otolaryngology   Pediatrics   Pharmacy, pharmacology & toxicology   Psychiatry   Public health, health care sciences & services   Radiology, nuclear medicine & imaging   Reproductive medicine (gynecology, andrology, obstetrics)   Rheumatology   Surgery   Urology & nephrology   Multidisciplinary, general & others Law, criminology & political science   Civil law   Criminal law & procedure   Criminology   Economic & commercial law   European & international law   Judicial law   Metalaw, Roman law, history of law & comparative law   Political science, public administration & international relations   Public law   Social law   Tax law   Multidisciplinary, general & others Life sciences   Agriculture & agronomy   Anatomy (cytology, histology, embryology...) & physiology   Animal production & animal husbandry   Aquatic sciences & oceanology   Biochemistry, biophysics & molecular biology   Biotechnology   Entomology & pest control   Environmental sciences & ecology   Food science   Genetics & genetic processes   Microbiology   Phytobiology (plant sciences, forestry, mycology...)   Veterinary medicine & animal health   Zoology   Multidisciplinary, general & others Physical, chemical, mathematical & earth Sciences   Chemistry   Earth sciences & physical geography   Mathematics   Physics   Space science, astronomy & astrophysics   Multidisciplinary, general & others Social & behavioral sciences, psychology   Animal psychology, ethology & psychobiology   Anthropology   Communication & mass media   Education & instruction   Human geography & demography   Library & information sciences   Neurosciences & behavior   Regional & inter-regional studies   Social work & social policy   Sociology & social sciences   Social, industrial & organizational psychology   Theoretical & cognitive psychology   Treatment & clinical psychology   Multidisciplinary, general & others     Showing results 1 to 100 of 290 1 2 3     Maqriziana XIV: Al-Maqrīzī’s Last Opus (Al-Ḫabar ʿan al-Bašar) and Its Significance for the History of IslamBauden, Frédéric E-print/Working paper (in press)Detailed reference viewed: 108 (18 ULg) Hedge fund styles and macroeconomic uncertaintyPlatania, Federico ; Lambert, Marie E-print/Working paper (in press)This paper examines the dynamic trading strategies implemented by hedge fund managers using a Kalman filter of hedge fund betas across styles. We further investigate the risk drivers of dynamic trades ... [more ▼]This paper examines the dynamic trading strategies implemented by hedge fund managers using a Kalman filter of hedge fund betas across styles. We further investigate the risk drivers of dynamic trades, examining which conditioning/macroeconomic variables strongly lead the time variation in fund trades. We report the significance of macroeconomic factors such as interest rates, dividend yield, GDP growth and US unemployment. We show that hedge fund managers do control the intensity of their exposures according to economic uncertainty and that differences between up- and down-market regimes can be observed. Commonly, Hedge funds tend to dislike high-dividend paying stocks. Besides, all hedge fund styles are shown to display pro-cyclical exposures towards directional equity factors as well as credit and liquidity risks. Small growth stocks, however, are revealed to be crisis investments whose allocation increases with unemployment, inflation or volatility. As volatility increases, the value of growth options embedded into growth stocks indeed increases. Growth stocks are shown to hedge market reversals and volatility. The outperformance of growth companies in recessions might also relate to their cost flexibility. Allocation to small stocks embed strong micro risks and might also constitute a hedge in economic slowdowns. This might explain why some funds with such a particular investment focus appear to be countercyclical. [less ▲]Detailed reference viewed: 14 (1 ULg) Zum Thema Präpositionen – oder über die mühselige Rekonstruktion präpositionaler Ergänzungen aus KorpusbelegenMünzberg, Franziska E-print/Working paper (in press)Detailed reference viewed: 17 (0 ULg) Sostanza e forma nella tradizione del romanzo arturiano in prosaLeonardi, Lino; Morato, Nicola E-print/Working paper (in press)Detailed reference viewed: 18 (1 ULg) Market efficiency and hedge fund trading strategiesPlatania, Federico ; Lambert, Marie ; Papageorgiou, NicolasE-print/Working paper (in press)Stock and option markets can at times reflect differing information. We identify three reasons for the presence of these periods of "disagreement" between the cash and derivatives markets: 1) high ... [more ▼]Stock and option markets can at times reflect differing information. We identify three reasons for the presence of these periods of "disagreement" between the cash and derivatives markets: 1) high volatility and noise trading; 2) high level of risk aversion; 3) speculation versus hedging trades. This paper investigates the role that hedge funds, a proxy for sophisticated investors, play in the price discovery process between stock and option markets and the disagreement/agreement periods. We observe that a disparity in information between the two markets is often associated with deleveraging in directional exposures and reversal strategies. Posterior to the event, active tactical asset allocation in small and value factor investing takes place. We investigate four specific macro events which resulted in significant rebalancing by hedge fund manegers: the Thai Baht depreciation, the Dot-com bubble, the credit crunch and the Nasdaq correction. [less ▲]Detailed reference viewed: 14 (1 ULg) Back to materialism Reflections on Marx’s labour, praxis, cooperative and libertarian socialism in the 19th centuryFrère, Bruno 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 ▲]Detailed reference viewed: 52 (1 ULg) How to account for new forms of resistance to domination: An argument for a materialist renewal in European social theoryFrère, Bruno ; Tulle, EmmanuelleE-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 ▲]Detailed reference viewed: 35 (1 ULg) The np- Control Charts with the Guaranteed In-Control PerformanceFaraz, Alireza ; Heuchenne, Cédric 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 ▲]Detailed reference viewed: 87 (1 ULg) Nouvelles normes sylvicoles pour les peuplements purs équiennes d'épicéa et de douglasPerin, Jérôme ; Hebert, Jacques ; Lejeune, Philippe et alE-print/Working paper (2016)Ces documents rassemblent les tables de production (version 2016) représentant les nouvelles normes sylvicoles recommandées pour les peuplements purs équiennes d'épicéa commun et de douglas. Un ensemble ... [more ▼]Ces documents rassemblent les tables de production (version 2016) représentant les nouvelles normes sylvicoles recommandées pour les peuplements purs équiennes d'épicéa commun et de douglas. Un ensemble de 10 tables de production est présentée pour chaque essence, associant deux densités de plantation (2.5 x 2 m et 2 x 2 m) et 5 classes de productivité (0 à IV). [less ▲]Detailed reference viewed: 235 (17 ULg) A class of valid inequalities for multilinear 0-1 optimization problemsCrama, Yves ; Rodriguez Heck, Elisabeth E-print/Working paper (2016)This paper investigates the polytope associated with the classical standard linearization technique for the unconstrained optimization of multilinear polynomials in 0-1 variables. A new class of valid ... [more ▼]This paper investigates the polytope associated with the classical standard linearization technique for the unconstrained optimization of multilinear polynomials in 0-1 variables. A new class of valid inequalities, called 2-links, is introduced to strengthen the LP relaxation of the standard linearization. The addition of the 2-links to the standard linearization inequalities provides a complete description of the convex hull of integer solutions for the case of functions consisting of at most two nonlinear monomials. For the general case, various computational experiments show that the 2- links improve both the standard linearization bound and the computational performance of exact branch & cut methods. The improvements are especially significant for a class of instances inspired from the image restoration problem in computer vision. The magnitude of this effect is rather surprising in that the 2-links are in relatively small number (quadratic in the number of terms of the objective function). [less ▲]Detailed reference viewed: 81 (14 ULg) Early Detection of University Students in Potential DifficultyHoffait, Anne-Sophie ; Schyns, Michael E-print/Working paper (2016)Using data mining methods, this paper presents a new means of identifying freshmen's profiles likely to face major difficulties to complete their first academic year. Academic failure is a relevant issue ... [more ▼]Using data mining methods, this paper presents a new means of identifying freshmen's profiles likely to face major difficulties to complete their first academic year. Academic failure is a relevant issue at a time when post-secondary education is ever more critical to economic success. We aim at early detection of potential failure using student data available at registration, i.e. school records and environmental factors, with a view to timely and efficient remediation and/or study reorientation. For the sake of accuracy, we adapt three data mining methods, namely random forest, logistic regression and artificial neural network algorithms. Real data pertaining to undergraduates at the University of Liège (Belgium), illustrates our methodology. [less ▲]Detailed reference viewed: 15 (6 ULg) Appropriability and the European Commission’s Android InvestigationAuer, Dirk E-print/Working paper (2016)This paper seeks to ascertain whether Google’s Android licensing terms, which are currently under scrutiny from the European Commission, could be excused under an innovation defense framework. The paper ... [more ▼]This paper seeks to ascertain whether Google’s Android licensing terms, which are currently under scrutiny from the European Commission, could be excused under an innovation defense framework. The paper starts by analyzing Google’s business model with regard to its Android OS. It then identifies the Commission’s main concerns. It argues that Google is simply pursuing a sensible appropriation strategy. Finally, it puts forward a framework which hinges on the concept of “appropriability”, and tentatively applies it to Google’s behavior. [less ▲]Detailed reference viewed: 37 (4 ULg) Revealing the role of network rigidity on the fragility evolution of glass-forming liquidsYildirim, Can ; Raty, Jean-Yves ; Micoulaut, MathieuE-print/Working paper (2016)If quenched fast enough, a liquid is able to avoid crystallization and will remain in a metastable supercooled state down to the glass transition, with an important increase in viscosity and relaxation ... [more ▼]If quenched fast enough, a liquid is able to avoid crystallization and will remain in a metastable supercooled state down to the glass transition, with an important increase in viscosity and relaxation time towards equilibrium upon further cooling [1,2]. There are important differences in the way liquids relax as they approach the glass transition, rapid or slow variation in dynamic quantities under moderate temperature changes, and a simple means to quantify such variations is provided by the concept of "fragility". Here, we report molecular dynamics simulations of a typical network-forming glass, and find that the relaxation behaviour of the supercooled liquid is strongly correlated to the variation of rigidity with temperature and the spatial distribution of the corresponding topological constraints which, ultimately connect to fragility minima . This permits extending the fragility concept to aspects of topology/rigidity, and to the degree of homogeneity of the atomic-sale interactions for a variety of structural glasses. [less ▲]Detailed reference viewed: 31 (3 ULg) Challenges in Managing State Land in Cambodia: Addressing Competing Interests for Lands inside Protected Areas (PAs)Ngin, Chanrith; Diepart, Jean-Christophe E-print/Working paper (2016)Detailed reference viewed: 22 (3 ULg) Some characterizations about Generalized Hölder-Zygmund Spaces Λ_{σ,N}^{α}(R^d)Kreit, Damien ; Nicolay, Samuel E-print/Working paper (2016)Generalized Hölder-Zygmund spaces $\Lambda_{\sigma, N}^{\alpha}(\R^{d})$ were recently introduced and are based on a generalization of Besov spaces. Under some conditions, generalized Hölder-Zygmund and ... [more ▼]Generalized Hölder-Zygmund spaces $\Lambda_{\sigma, N}^{\alpha}(\R^{d})$ were recently introduced and are based on a generalization of Besov spaces. Under some conditions, generalized Hölder-Zygmund and Besov spaces are equal. It has been proved that most properties of classical Hölder-Zygmund spaces are held for spaces $\Lambda^{\sigma,\alpha}(\R^{d})$, which constitute a particular case of spaces $\Lambda_{\sigma, N}^{\alpha}(\R^{d})$ with $N_{j}=2^{j}$. The goal of the present document is to prove that most of these properties are kept for $\Lambda_{\sigma, N}^{\alpha}(\R^{d})$ spaces. [less ▲]Detailed reference viewed: 11 (1 ULg) A Comparison of Departure Time of Day FormulationsLurkin, Virginie ; Garrow, Laurie; Higgins, Matthew et alE-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 ▲]Detailed reference viewed: 15 (6 ULg) Accounting for Price Endogeneity in Airline Itinerary Choice Models: An Application to Continental U.S. MarketsLurkin, Virginie ; Garrow, Laurie; Higgins, Matthew et alE-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 ▲]Detailed reference viewed: 22 (3 ULg) Structure et négativité dans la Préface de 1961 à L'Histoire de la folieOulc'hen, Hervé E-print/Working paper (2016)Detailed reference viewed: 19 (2 ULg) Résumé de la thèse: Rôle du climat et de la compétition interspécifique dans la limitation de l'aire d'invasion d'Ambrosia artemisiifolia L. en Europe de l'OuestOrtmans, William E-print/Working paper (2016)The invasion continuum is classically described from a temporal point of view, where a species overcomes a defined number of barriers linked to the environment. First, an exotic species has to get through ... [more ▼]The invasion continuum is classically described from a temporal point of view, where a species overcomes a defined number of barriers linked to the environment. First, an exotic species has to get through the geographical barrier, in order to be introduced in the new area. When introduced, the species has to face the new environmental conditions and survive to start the naturalization phase. When the environmental barrier is overcome, i.e. when the species is able to reproduce and its populations are self-sufficient, it has to overcome the dispersal barrier to spread in the ecosystem and finally become invasive. Within a given continent, a species could have overcome a variable number of barriers depending on the considered area. One can observe depending on the geographical zone some non-naturalized populations that cannot survive without a human introduction of new propagules, some naturalized populations that are not invasive yet, and some invasive populations. This geographical variation may be the result of a variation of the environmental conditions at the continental scale. The common ragweed (Ambrosia artemisiifolia L.) invasion in Western Europe is a good opportunity to study this aspect of the invasion biology. The invasion history and the species distribution are well documented, and highlight a geographical variation of the invasion dynamic. This is particularly clear in Western Europe, where lies a contrast between the highly invaded zone of the South of France, and the areas that are farther north (e.g. the North of France, Belgium, and the Netherlands). In this work, the general objective was to determine if this situation will remain stable or not, by assessing if the local climate and the interspecific competition were liming the species expansion northward. In order to answer this general objective, four different questions were asked: 1) Is the climate and/or the interspecific competition causing a plant performance variation within the different areas of the introduced range in Western Europe?; 2) Is the local climate allowing the establishment and the reproduction of newly introduced populations north to the current invaded range, in an agricultural habitat?; 3) What is the role of the morphological variability of the seeds in the invasion of areas experiencing rigorous climatic conditions?; and 4) What is the role of the priority effect in the species establishment? The results showed that once introduced in an agricultural habitat outside the current invaded range, the species was able to establish self-sustaining populations. On average, each plant produced a number of offspring equal to 273 ± 18.4 (mean ± standard error). In ruderal habitats, populations already exist in Belgium and in the South of The Netherlands, and are able to produce a high quantity of seeds: on average, measured plants carried 222± 32.0 seeds. The measured plant performances were similar to those measured within the invaded area. No limit to the colonization of the area beyond the current invaded range was found in this study. The local climate and the interspecific competition did not appear to limit the naturalization of the species in the studied area, which is located north to the current invaded range, in agricultural or ruderal situations. This work highlighted the obsolescence of the species status in Belgium, and illustrated the dynamic aspect of the invasion. The results showed the importance of the temporality in the colonization of disturbed habitats. When the species started its development a few weeks before the rest of the community, its performance was decupled, and this increase was higher than the one other Asteraceae ruderals species showed in the same position: its above ground biomass was 30.5 ± 1.94 times higher, and the number of flower heads 570 ± 160 times more important.. The high variability of the species observed all along this work is probably playing an important role in the invasion success. The high variability of the seeds morphology can widen the range of environmental conditions of the habitats the species is able to colonize. In addition, the plasticity of the morphological traits of the plant in response to climate and competition appeared to allow the species to maintain a good performance, even in stressful conditions. The results of this work suggest an invasion potential north to the current invaded area in Western Europe. In this uncertain situation, it appears critical to implement structure allowing the early detection of the species. This early detection may allow the eradication of the species before that the invasion was as problematic as in France. Sensitization campaigns of the agricultural sector should be encouraged in Belgium in order to avoid new occurrence of the species in field to be overlooked. These measures could allow the dispersion to remain a limiting factor for the invasion process in Belgium. [less ▲]Detailed reference viewed: 19 (1 ULg) A useful result related with zeros of continuous compactly supported mother waveletsAyache, Antoine; Esser, Céline E-print/Working paper (2016)In the last two decades, wavelet bases and associated methodologies have become quite important in many domains, such as signal and image processing, harmonic analysis, statistics, and so on. More ... [more ▼]In the last two decades, wavelet bases and associated methodologies have become quite important in many domains, such as signal and image processing, harmonic analysis, statistics, and so on. More recently, they also turn out to be quite useful in the probabilistic framework of stochastic processes, in which, among other things, they allow to obtain fine results concerning erratic sample paths behavior. The goal of our article is to derive a result, related with zeros of continuous compactly supported mother wavelets, which is useful in this probabilistic framework. More precisely, let $\psi$ be any arbitrary such wavelet; we show that being given an arbitrary point $x_0\in\R$ there always exists at least one integer $k_{x_0}\in\Z$ such that $\psi(x_0-k_{x_0}) \neq 0$. [less ▲]Detailed reference viewed: 14 (2 ULg) Fiscalité en faveur du mécénat d'entreprise: présentation synthétique des éléments juridiquesBourgeois, Marc ; Garroy, Sabine ; Vandenbulke, Antoine et alE-print/Working paper (2016)Detailed reference viewed: 32 (5 ULg) Nonparametric control charts: economic statistical designMarcos Alvarez, Alejandro ; Heuchenne, Cédric ; Faraz, Alireza E-print/Working paper (2016)This paper studies economic statistical designs (ESD) for nonparametric control charts based on the sign and Wilcoxon tests. The main advantage of the procedures is that, except for the tested location ... [more ▼]This paper studies economic statistical designs (ESD) for nonparametric control charts based on the sign and Wilcoxon tests. The main advantage of the procedures is that, except for the tested location parameter, they do not use either any parametric distribution for the quality characteristic or any information about the possible involved parameters, neither in the in-control nor in the out-of-control state. This is made possible by minimizing a cost function specified independently of these quantities. Unlike the ESD for the $\overline{x}$ chart, the resulting charts designs are robust to changes of the distributions of the observations (in control or out of control), provide reliable statistical guarantees when the $\overline{x}$ chart ESD does not and stay competitive even when the strong assumptions of the $\overline{x}$ chart ESD are fully satisfied. These new techniques can therefore be applied to a definitely wider class of problems and their designs may stay constant over time without losing performance. [less ▲]Detailed reference viewed: 44 (1 ULg) Online Learning for Strong Branching Approximation in Branch-and-BoundMarcos Alvarez, Alejandro ; Wehenkel, Louis ; Louveaux, Quentin 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 ▲]Detailed reference viewed: 53 (4 ULg) On the processing of red pigment by late mousterian Neanderthals in Ormesson, Seine-et-Marne, France, 47000 years agoSalomon, Hélène ; Bodu, Pierre; Geurten, Stéphanie et alE-print/Working paper (2016)Detailed reference viewed: 17 (7 ULg) Bispecial factors in the Brun S-adic systemLabbé, Sébastien ; Leroy, Julien E-print/Working paper (2016)Detailed reference viewed: 21 (2 ULg) El idealismo europeo frente a la realidad global: ¿del enfoque regional a la preferencia por las potencias emergentes?Santander, Sébastian E-print/Working paper (2016)Detailed reference viewed: 65 (5 ULg) Robust asymptotic tests for the equality of multivariate coefficients of variationAerts, Stéphanie ; Haesbroeck, Gentiane E-print/Working paper (2016)In order to easily compare several populations on the basis of more than one feature, multivariate coefficients of variation (MCV) may be used as they allow to summarize relative dispersion in a single ... [more ▼]In order to easily compare several populations on the basis of more than one feature, multivariate coefficients of variation (MCV) may be used as they allow to summarize relative dispersion in a single index. However, up to date, no test of equality of one or more MCV's has been developed in the literature. In this paper, several classical and robust Wald type tests are proposed and studied. The asymptotic distributions of the test statistics are derived under elliptical symmetry, and the asymptotic efficiency of the robust versions is compared to the classical tests. Robustness of the proposed procedures is examined through partial influence functions of the test statistic, as well as by means of power and level influence functions. A simulation study compares the performance of the classical and robust tests under uncontaminated and contaminated schemes, and the difference with the usual covariance homogeneity test is highlighted. As a by-product, these tests may also be considered in the univariate context where they yield procedures that are both robust and easy-to-use. They provide an interesting alternative to the numerous parametric tests of comparison of univariate coefficients of variation existing in the literature, which are, in most cases, unreliable in presence of outliers. The methods are illustrated on a real data set. [less ▲]Detailed reference viewed: 6 (0 ULg) HST-Juno synergistic approach of Jupiter's magnetosphere and ultraviolet aurorasGrodent, Denis ; Bonfond, Bertrand ; Gérard, Jean-Claude et alE-print/Working paper (2016)Jupiter's system is not only fundamental to our understanding of the solar system but also of planetary systems around other stars as well as more distant astrophysical bodies, not accessible to a ... [more ▼]Jupiter's system is not only fundamental to our understanding of the solar system but also of planetary systems around other stars as well as more distant astrophysical bodies, not accessible to a detailed investigation. Fully exploiting any rare opportunity to explore the Jovian system through synergistic observations is thus critical, as it will impact significantly across wider astronomical studies. Such an exceptional opportunity will occur in Cycle 24, when the NASA Juno spacecraft will achieve its prime mission around Jupiter. Since Juno will literally fly through the auroral acceleration regions, the combination of HST auroral observations with Juno in situ measurements will allow us to finally unravel the origins and consequences of Jupiter's powerful and highly variable ultraviolet auroras. This occasion has never occurred before and is unlikely to ever repeat. Juno will address key scientific issues related to unexplored regions of the Jovian magnetosphere. The auroral signatures associated with these magnetospheric processes will be precisely observed with STIS and COS. This program responds to the UV initiative and is only possible during Cycle 24. Indeed, HST is the only observatory capable of making these high spatial and temporal resolution FUV observations during the Juno mission. This ambitious campaign will yield high-impact results and significantly augment the science return of the NASA Juno mission. [less ▲]Detailed reference viewed: 25 (1 ULg) Fisheries reforms and right-based fisheries: insights from community fisheries across CambodiaChap, Sreyphea; Touch, Panha; Diepart, Jean-Christophe E-print/Working paper (2016)The working paper uses a right-based approach to examine recent wave of reforms in the Cambodian fisheries sector and what these reforms mean for community fisheries management.Detailed reference viewed: 20 (2 ULg) ALPI project - Green Incentives : Belgian and European AspectsBourgeois, Marc ; Vanrykel, Fanny ; Defoy, Xavier E-print/Working paper (2016)Finance is one of the main critical issues for the development of a low-carbon society especially during times of economic recession. Closing this green investment gap will require policy intervention ... [more ▼]Finance is one of the main critical issues for the development of a low-carbon society especially during times of economic recession. Closing this green investment gap will require policy intervention. The ALPI project will concentrate on promoting relevant ins truments to accelerate the transition towards a low-carbon society by demonstrating the performance and impact of policy instruments on economic, government budget and environmental aspects. [less ▲]Detailed reference viewed: 8 (0 ULg) Feasibility-oriented Branching Strategies for Global OptimizationGerard, Damien ; Köppe, Matthias; Louveaux, Quentin E-print/Working paper (2016)We study the spatial Brand-and-Bound algorithm for the global optimization of nonlinear problems. In particular we are interested in a method to find quickly good feasible solutions. Most spatial Branch ... [more ▼]We study the spatial Brand-and-Bound algorithm for the global optimization of nonlinear problems. In particular we are interested in a method to find quickly good feasible solutions. Most spatial Branch-and-Bound-based solvers use a non global solver at a few nodes to try to find better incumbents. We show that it is possible to improve the branching rules and the node priority by exploiting the solutions from the non global solver. We also propose several smart adaptive strategies to choose when to run the non global solver. We show that despite the time spent in solving many more NLP problems in the nodes, the new strategies enable the algorithm to find the first good incumbents faster and to prove the global optimality faster. Numerous easy, medium size as well as hard NLP instances from the Coconut library are benchmarked. All experiments are run using the open source solver Couenne. [less ▲]Detailed reference viewed: 10 (1 ULg) Why Did the Industrial Revolution Start in Britain?Van Neuss, Leif 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 ▲]Detailed reference viewed: 285 (23 ULg) Large neighborhood search for multi-trip vehicle routingFrançois, Véronique ; Arda, Yasemin ; Crama, Yves et alE-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 ▲]Detailed reference viewed: 137 (18 ULg) 25 novembre 2015 : cent ans de RelativitéDe Rop, Yves 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 ▲]Detailed reference viewed: 67 (12 ULg) Multi-period vehicle allocation with uncertain transportation requestsCrama, Yves ; Pironet, Thierry 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 ▲]Detailed reference viewed: 157 (15 ULg) L’accompagnement de projets d’entrepreneuriat social dans leurs phases initialesDufays, Frédéric ; Lovens, Caroline ; Mertens de Wilmars, Sybille 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 ▲]Detailed reference viewed: 71 (5 ULg) Ceci n’est pas un conseil !Choffray, Jean-Marie 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 ▲]Detailed reference viewed: 1994 (125 ULg) Markets flash graphsChoffray, Jean-Marie 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 ▲]Detailed reference viewed: 219 (30 ULg) Blues et Wallon - Elmore D, l'intégrale cåzî complète en cinq CDsSacré, Robert 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.Detailed reference viewed: 32 (0 ULg) Dans le dédale des Musiques Africaines-AméricainesSacré, Robert 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 1984Detailed reference viewed: 26 (4 ULg) Does formal child care availability for 0-3 year olds boost mothers' employment rate? Panel data based evidence from BelgiumDujardin, Claire; Fonder, Muriel; Lejeune, Bernard 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 ▲]Detailed reference viewed: 130 (7 ULg) Garantir la légalité et assurer la traçabilité. Deux piliers de la mise en oeuvre de l'APV-FLEGT.Moumbogou, Carl; Meunier, Quentin; Bracke, Charles et alE-print/Working paper (2015)Detailed reference viewed: 116 (5 ULg) Les forêts communautaires et l'APV-FLEGT au GabonMoumbogou, Carl; Meunier, Quentin; Mvou Biyogo, T. et alE-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 ▲]Detailed reference viewed: 47 (4 ULg) Bayesian inference in an extended SEIR model with nonparametric disease transmission rate: an application to the Ebola epidemic in Sierra LeoneFrasso, Gianluca ; Lambert, Philippe 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 ▲]Detailed reference viewed: 110 (34 ULg) Criminal and Administrative Investigations in the field of VAT and Customs DutiesBourgeois, Marc ; Verscheure, Céline E-print/Working paper (2015)Detailed reference viewed: 6 (1 ULg) Optimal Enforcement of Competition Policy: The Commitments Procedure under UncertaintyGautier, Axel ; Petit, Nicolas 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 ▲]Detailed reference viewed: 37 (4 ULg) Approche agroforestière. Synthèse des travaux menés par le projet DACEFI2 en agroforesterie. Document de capitalisation.Boldrini, Sylvie; Meunier, Quentin; Boukouendji, Basile et alE-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 ▲]Detailed reference viewed: 84 (8 ULg) Importance et rôle de l’investissement…Choffray, Jean-Marie 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 ▲]Detailed reference viewed: 476 (18 ULg) Entretien avec Kathryn BatchelorOumarou Mal Mazou, Rachid E-print/Working paper (2015)Detailed reference viewed: 22 (8 ULg) Propriété coopérative et acceptabilité sociale de l’éolien terrestreBauwens, Thomas 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 ▲]Detailed reference viewed: 132 (17 ULg) A semiparametric model for Generalized Pareto regression based on a dimension reduction assumptionHambuckers, julien ; Heuchenne, Cédric ; Lopez, OlivierE-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 ▲]Detailed reference viewed: 56 (8 ULg) Machine Learning to Balance the Load in Parallel Branch-and-BoundMarcos Alvarez, Alejandro ; Wehenkel, Louis ; Louveaux, Quentin 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 ▲]Detailed reference viewed: 81 (9 ULg) The role of market-oriented institutions in the deployment of renewable energies: evidences from EuropeJacqmin, Julien 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 ▲]Detailed reference viewed: 35 (2 ULg) Que veut dire FLEGT ? Et pourquoi au Gabon ?Moumbogou, Carl; Meunier, Quentin; Mvou Biyogo, T. et alE-print/Working paper (2015)Detailed reference viewed: 104 (3 ULg) A branch-and-price algorithm for 2-period vehicle routing problemsCrama, Yves ; Rezaei Sadrabadi, Mahmood ; Van Woensel, TomE-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 ▲]Detailed reference viewed: 123 (7 ULg) Investing in the FuturePahud de Mortanges, Charles 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 ▲]Detailed reference viewed: 100 (3 ULg) On the nature of cosmological timeMagain, Pierre ; Hauret, Clémentine 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 ▲]Detailed reference viewed: 37 (9 ULg) Sequential testing of k-out-of-n systems with imperfect testsWenchao, Wei; Coolen, Kris ; Talla Nobibon, Fabrice et alE-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 ▲]Detailed reference viewed: 35 (4 ULg) Lacunary wavelet series on Cantor setsEsser, Céline E-print/Working paper (2015)We construct functions with prescribed multifractal spectra which satisfy the leaders profile method.Detailed reference viewed: 10 (0 ULg) Social Enterprise in Belgium: A Diversity of Roots, Models and FieldsHuybrechts, Benjamin 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 ▲]Detailed reference viewed: 114 (8 ULg) Critical analysis and alternative processing of Type Ia supernovae dataHauret, Clémentine ; Magain, Pierre 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 ▲]Detailed reference viewed: 49 (11 ULg) The Cambodian peasantry and the formalisation of land rights: historical overview and current issuesDiepart, Jean-Christophe ; Sem, TholE-print/Working paper (2015)Detailed reference viewed: 45 (1 ULg) Real options valuation under uncertaintyPlatania, Federico ; Lambert, Marie ; Moreno, ManuelE-print/Working paper (2015)In this paper we develop a novel valuation model and methodology to value a pharmaceutical R&D project based on real options approach. The real options approach enables the possibility of optimally ... [more ▼]In this paper we develop a novel valuation model and methodology to value a pharmaceutical R&D project based on real options approach. The real options approach enables the possibility of optimally abandon the project before completion whenever the investment cost turns out to be larger than the expected net cash flow stream. On the other hand, the proposed model accounts for two different sources of uncertainty, those are technical and economic risk. This model incorporates a novel economic state vector where each economic state captures the interaction among different market and economic forces using Fourier series as the particular basis for the economic function space. In this sense, Fourier series are considered as an aggregate of forces playing a relevant role in the process evolution determining the cash flow structure and also allowing us to properly define an economic scenario where the project will be developed. [less ▲]Detailed reference viewed: 68 (11 ULg) Patterns of administrative integration in the European Union: a cross-country empirical analysis of political intentions to reform national public administrations (1997-2011)Esposito, Giovanni ; Gaeta, Giuseppe Lucio; Trasciani, GiorgiaE-print/Working paper (2015)In the aftermath of the worst financial and economic crisis in generations, the modernization of public administrations of the EU’s Member States (MSs) is among the structural reforms recommended by the ... [more ▼]In the aftermath of the worst financial and economic crisis in generations, the modernization of public administrations of the EU’s Member States (MSs) is among the structural reforms recommended by the European Commission to relaunch growth in the European economy. This type of reforms has a longstanding tradition in the MSs as they sharply intensified during the 1990s following the paradigm of New Public Management (NPM). Indeed, by backing NPM-style reforms, the European Commission has fostered convergence between the administrative systems of the MSs based on a soft strategy of integration where, instead of establishing binding pan-European rules enforced directly in all the MSs, it has set a number of regulatory standards implemented in the MSs with the support of national legislators and political parties. This paper empirically addresses the above-mentioned process of soft integration by unveiling the domestic determinants that have led MSs’ political parties to call for NPM-style reforms in their national contexts between 1997 and 2011. The hypothesis tested in this study is that MSs’ political parties have called for NPM-style reforms in order to respond to specific challenges issuing from the macro-economic, institutional and political configuration of their domestic contexts. The contribution of this paper is twofold. On the one hand, it contributes to a better understanding of the process of European administrative integration by providing robust empirical evidence about the patterns of diffusion NPM-style reforms across the MSs of the EU. On the other hand, the empirical evidence provided by this paper for the comprehension of NPM-style reforms in the context of the EU also contributes to a better understanding of some traditional theories addressing the reasons of the worldwide striking international trend of the NPM paradigm. [less ▲]Detailed reference viewed: 29 (2 ULg) The European Public Sectors in The Age of Managerialism: a cross-country empirical study reconstructing the political history of public administrations in Europe during the XX centuryEsposito, Giovanni ; Gaeta, Giuseppe LucioE-print/Working paper (2015)During the XX century European administrative systems have undergone a profound process of managerial revolution during which private sector managerial tools and principles have spread across both central ... [more ▼]During the XX century European administrative systems have undergone a profound process of managerial revolution during which private sector managerial tools and principles have spread across both central and local governments in many countries. As many scholars have associated this process of change with the raise and diffusion of a managerialist ideology, this paper empirically investigates the electoral propaganda that since 1950s has supported the diffusion of managerialist values across the national administrative systems of the European countries. On the basis of a longitudinal study of the electoral programs released by the European parties since 1950s, this research provides evidence-based knowledge about: i) the different patterns of diffusion of the public-sector managerialist propaganda in Eastern and Western Europe; ii) the controversial relationship that exists between the spread of the managerialist ideology and the actual adoption of managerialist reforms in the national structures of the public sector. [less ▲]Detailed reference viewed: 18 (1 ULg) La guerre des chous. Monographie Kaol KozhHecquet, Corentin E-print/Working paper (2015)Detailed reference viewed: 27 (2 ULg) A NLP-MILP iterating algorithm for operational planning in electrical distribution systemsGerard, Damien ; Louveaux, Quentin ; Cornélusse, Bertrand E-print/Working paper (2015)We consider a class of optimal power flow (OPF) applications where some loads offer a modulation service in exchange for an activation fee. These applications can be modeled as multi-period formulations ... [more ▼]We consider a class of optimal power flow (OPF) applications where some loads offer a modulation service in exchange for an activation fee. These applications can be modeled as multi-period formulations of the OPF with discrete variables that define mixed-integer non-convex mathematical programs. We focus on the optimization of this Mixed-Integer Non-Linear Programming (MINLP) problem through a separation into a non-linear programming (NLP) and a mixed-integer programming (MIP) component. The NLP is a feasibility problem involving the power flow equations and the flexible loads needs. The MIP is used to choose which flexible loads to activate and in which order. In several papers, the MIP is based on a linearization of the non-linear power flow equations. We compare several variants of the linearization. We propose new formulations based on prior knowledge of the network to improve the decision-making process when the relaxation is inappropriate. We show computationally with many real-world instances that they help find feasible solutions faster than standard MINLP techniques. [less ▲]Detailed reference viewed: 11 (3 ULg) Towards generic image classification: an extensive empirical studyMarée, Raphaël ; Geurts, Pierre ; Wehenkel, Louis E-print/Working paper (2014)This paper considers the general problem of image classification without using any prior knowledge about image classes. We study variants of a method based on supervised learning whose common steps are ... [more ▼]This paper considers the general problem of image classification without using any prior knowledge about image classes. We study variants of a method based on supervised learning whose common steps are the extraction of random subwindows described by raw pixel intensity values and the use of ensemble of extremely randomized trees to directly classify images or to learn image features. The influence of method parameters and variants is thoroughly evaluated so as to provide baselines and guidelines for future studies. Detailed results are provided on 80 publicly available datasets that depict very diverse types of images (more than 3800 image classes and over 1.5 million images). [less ▲]Detailed reference viewed: 147 (13 ULg) Lettre d'information du projet Dacefi-Synthèse & réalisations majeuresMeunier, Quentin; Morin, Amélie; Moumbougou, Carl et alE-print/Working paper (2014)Cette dernière lettre d'information du projet présente le bilan de ses réalisations et les avancées importantes du Gabon en termes de foresterie communautaireDetailed reference viewed: 159 (67 ULg) Projet DACEFI 2. Principes fondateurs d'une forêt communautaire au Gabon. Outils de vulgarisation et de sensibilisation.Meunier, Quentin; Boldrini, Sylvie; Larzillière, Adélaïde et alE-print/Working paper (2014)Faisant suite à une première phase (2006-2008), le projet pilote Développement d’Alternatives Communautaires à l’Exploitation Forestière Illégale (DACEFI-2, de 2010 à 2014) s’emploie à tester au Gabon la ... [more ▼]Faisant suite à une première phase (2006-2008), le projet pilote Développement d’Alternatives Communautaires à l’Exploitation Forestière Illégale (DACEFI-2, de 2010 à 2014) s’emploie à tester au Gabon la mise en oeuvre des premières forêts communautaires. Un de ses objectifs majeurs consiste à tester le concept de foresterie communautaire au sein de plusieurs sites partenaires et de témoigner de l’expérience acquise afin que le Ministère en charge des Forêts adapte le cadre réglementaire. Quatre textes majeurs régissent la foresterie communautaire au Gabon, une loi (n°16/01), un décret d’application (n°1028/PR/MEFEPEPEN) et deux arrêtés (n°018/MEF/SG/DGF/DFC et n°106/MEFEPRN). Ils encadrent le processus de création d’une forêt communautaire. Afin de les rendre accessibles à un plus grand nombre, le projet DACEFI-2 s’est proposé de développer plusieurs supports de vulgarisation à destination des agents des Eaux et Forêts et des villageois. En éditant et en diffusant une série de posters, de films ou encore de bandes dessinées, le projet a contribué à faire connaître dans les provinces de l’Ogooué-Ivindo et du Moyen-Ogooué, l’esprit de ces textes légaux qui visent à favoriser le développement des communautés locales. Ce document de capitalisation présente une compilation des outils développés par les équipes du projet pour mener à bien cette campagne de sensibilisation. Nous abordons la gestion forestière durable par le prisme de la foresterie communautaire en évoquant l’esprit de la loi et les enjeux de la foresterie sociale. Nous proposons également une série de recommandations, basées sur notre expérience au Gabon, afin d’optimiser l’efficacité des communautés engagées dans ce processus. [less ▲]Detailed reference viewed: 55 (8 ULg) La mora débitoris chez Charles de Méan (esquisse)Lagasse, Benoît E-print/Working paper (2014)Detailed reference viewed: 31 (1 ULg) Corporate board attributes and conditional accounting conservatism: Evidence from French firmsBoussaid, Nabila ; Sougné, Danielle ; Hamza, TaherE-print/Working paper (2014)In this paper we investigate the relationship between boards of directors’ attributes and conditional accounting conservatism in the French context. Using a pooled regression model to evaluate this ... [more ▼]In this paper we investigate the relationship between boards of directors’ attributes and conditional accounting conservatism in the French context. Using a pooled regression model to evaluate this relationship for the period 2009-2012, our empirical results can be summarized as follows. Firstly, greater board activity encourages more conservative reporting in financial statements. Secondly, greater board size diminishes conditional accounting conservatism. Lastly, there is a positive relationship between gender diversity and conservatism. To ensure robustness we have calculated our results using alternative measures of accounting conservatism, namely time series and accrual-based measures in addition to asymmetric timeliness of earnings. These findings suggest that boards of directors’ attributes are an important factor in determining the financial reporting quality of French firms. [less ▲]Detailed reference viewed: 52 (4 ULg) MOLIERE PROJECT - Belgian National ReportNaedenoen, Frédéric E-print/Working paper (2014)This document aims at introducing the restructuring phenomena in Belgium. It makes part of a larger project (called the MOLIERE project) undertaken by eleven European countries gathered to analyse ... [more ▼]This document aims at introducing the restructuring phenomena in Belgium. It makes part of a larger project (called the MOLIERE project) undertaken by eleven European countries gathered to analyse restructurings. This national document follows a common reporting format: an introduction of the complex Belgian restructuring frameworks (1), a presentation of the main actors involved in the process (2), a synthesis of the measures created to anticipate change (3) and a synthesis of the measures established to manage change (4). [less ▲]Detailed reference viewed: 17 (1 ULg) Le nouveau cadre d’action en matière de climat et d’énergie à l’horizon 2030Habran, Maxime E-print/Working paper (2014)Cette note a pour but de fournir un éclairage sur le nouveau cadre d'action européen en matière de climat et d'énergieDetailed reference viewed: 34 (9 ULg) L-surface and V-valley for optimal anisotropic 2D smoothingFrasso, Gianluca ; Paul, EilersE-print/Working paper (2014)We present the L-surface as an attractive generalization of the L-curve framework for the selection of the optimal smoothing parameters in two dimensional applications. It preserves the desirable features ... [more ▼]We present the L-surface as an attractive generalization of the L-curve framework for the selection of the optimal smoothing parameters in two dimensional applications. It preserves the desirable features of its unidimensional analogous. The optimal amount of smoothing is indicated by the pair of parameters located in the point of maximum (Gaussian) curvature. Locate this point on a discrete parametric surface can be not straightforward. We introduce the V-valley as a simplified selection criterion based on distance minimization. [less ▲]Detailed reference viewed: 36 (9 ULg) Réveillez-vous, le monde vous attend…Gerkens, Jean-François ; Faymonville, Marie-Elisabeth ; Destiné, Jacques et alE-print/Working paper (2014)Par-delà le brouillard des temps présents, un message d’optimisme, de volontarisme, de foi en l’avenir et en la vie, conduisant à sept principes, ou suggestions d’action, faciles à mettre en œuvre.Detailed reference viewed: 741 (89 ULg) Estimating the out-of-sample predictive ability of trading rules: a robust bootstrap approachHambuckers, julien ; Heuchenne, Cédric E-print/Working paper (2014)In this paper, we estimate the out-of-sample predictive ability of a set of trading rules. Usually, this ability is estimated using a rolling-window sample-splitting scheme, true out-of-sample data being ... [more ▼]In this paper, we estimate the out-of-sample predictive ability of a set of trading rules. Usually, this ability is estimated using a rolling-window sample-splitting scheme, true out-of-sample data being rarely available. We argue that this method makes a poor use of the available information and creates data mining possibilities. Instead, we introduce an alternative bootstrap approach, based on the .632 bootstrap principle. This method enables to build in-sample and out-of-sample bootstrap data sets that do not overlap and exhibit the same time dependencies. We illustrate our methodology on IBM and Microsoft daily stock prices, where we compare 11 trading rules specifications. For the data sets considered, two different filter rule specifications have the highest out-of-sample mean excess returns. However, all tested rules cannot beat a simple buy-and-hold strategy when trading at a daily frequency. [less ▲]Detailed reference viewed: 103 (18 ULg) Embargo russe sur les aliments européens : l'Europe doit montrer l'exempleHabran, Maxime E-print/Working paper (2014)Cette note a pour but d’apporter des éclaircissements sur les mesures en matière de politique agricole commune prises par l’Union européenneDetailed reference viewed: 156 (10 ULg) Lettre d'information trimestrielle n° 15 du projet DACEFI 2Boldrini, Sylvie; Meunier, Quentin; Moumbogou, Carl et alE-print/Working paper (2014)Detailed reference viewed: 20 (1 ULg) Towards a system of concept in GP/FM. Part I towards a specific indexation system. working draftJamoulle, Marc E-print/Working paper (2014)EXECUTIVE SUMMARY Towards a system of concept on general practice / family medicine Part 1 Towards a specific indexation system in GP/FM Status of this document ; preliminary draft, not for diffusion ... [more ▼]EXECUTIVE SUMMARY Towards a system of concept on general practice / family medicine Part 1 Towards a specific indexation system in GP/FM Status of this document ; preliminary draft, not for diffusion Intended audience : Members of the board of the PhD thesis of Marc Jamoulle, department of general practice, Liege University and experts in the field contacted by the author Background :Thousands of general practitioners/ family doctors are gathering each year in local, national or international congresses. They are exchanging thoughts, researches and methods through thousands of communications in various formats; posters, oral communications, workshops and so on. Although this huge collection of bottom-up knowledge is sometimes available through Internet sites, there is no specific indexation system allowing a real knowledge management of the exposed works. Consequently the information could not be reached, which don’t favor the exchange between researchers. The absence of a common indexation system is also a problem to organize the congresses and the participants have always difficulties to find communications relevant of their interest. The technology of semantic web and Linked data have emerged as a future solution to exchange data distributed in many languages between so many providers, the family physicians, spread around the globe. The considerable development of medical ontologies demonstrates the vitality of this field of discovery. Aim of the thesis; To find the best way to identify the main concepts effectively used by practicing GPs by the development of a system of classification embedded in the International classification of Primary Care aiming at retrieval of clinical and non-clinical issues addressed by the authors in their communications To propose a mapped terminology to this classification systems, in other words an ontology of GP/FM, to participle to a linked data based automatic or semi-automatic indexation of knowledge in GP/FM and its implementation in the realm of the semantic web. Content of the part 1 : the first steps towards a global classification system in GP/FM are related as well as previous experiences and difficulties with usual coding systems. The new information technology tools for information management are concisely described which permit the understanding of their importance in future research networks of knowledge in G/FM A comparison of the coding process and results of 6 congress of GP/FM in several countries and 4 languages has been performed to examine the internal reproducibility of the classifying system proposed. Next steps of the thesis are discussed of which first of them would be the constitution of an International research group. [less ▲]Detailed reference viewed: 35 (3 ULg) Presidential election in Turkey: a wide range of intricate challenges ahead of the next presidentSisu, Madalina E-print/Working paper (2014)Detailed reference viewed: 22 (7 ULg) Recueil de réglementation interne des principaux partis allemands, belges et britanniquesBouhon, Frédéric E-print/Working paper (2014)Le présent recueil compile des extraits de la réglementation interne des principaux partis allemands, belges et britanniques. Cette documentation vient principalement appuyer le chapitre 1er de la ... [more ▼]Le présent recueil compile des extraits de la réglementation interne des principaux partis allemands, belges et britanniques. Cette documentation vient principalement appuyer le chapitre 1er de la deuxième partie de notre étude sur le droit électoral et le principe d’égalité (à paraître en septembre 2014 aux éditions Bruylant) dans laquelle nous avons notamment étudié une partie du droit interne de certaines formations politiques. [less ▲]Detailed reference viewed: 46 (8 ULg) Les métiers du développement durableCornet, Annie ; dubois, valérieE-print/Working paper (2014)Detailed reference viewed: 29 (1 ULg) Procedural rights in antitrust proceedingsMuheme, Daniel ; Neyrinck, Norman ; Petit, Nicolas E-print/Working paper (2014)Detailed reference viewed: 59 (5 ULg) Short Prime Quadratizations of Cubic Negative MonomialsCrama, Yves ; Rodriguez Heck, Elisabeth E-print/Working paper (2014)Pseudo-Boolean functions naturally model problems in a number of different areas such as computer science, statistics, economics, operations research or computer vision, among others. Pseudo-Boolean ... [more ▼]Pseudo-Boolean functions naturally model problems in a number of different areas such as computer science, statistics, economics, operations research or computer vision, among others. Pseudo-Boolean optimization (PBO) is NP-hard, even for quadratic polynomial objective functions. However, much progress has been done in finding exact and heuristic algorithms for the quadratic case. Quadratizations are techniques aimed at reducing a general PBO problem to a quadratic polynomial one. Quadratizing single monomials is particularly interesting because it allows quadratizing any pseudo-Boolean function by termwise quadratization. A characterization of short quadratizations for negative monomials has been provided. In this report we present a proof of this characterization for the case of cubic monomials, which requires a different analysis than the case of higher degree. [less ▲]Detailed reference viewed: 61 (28 ULg) Optimization of the service start time for an elementary shortest path problem with time windowsArda, Yasemin ; Crama, Yves ; Kucukaydin, Hande E-print/Working paper (2014)We investigate an elementary shortest path problem with resource constraints where a single capacitated vehicle, initially located at a depot, must serve a set of customers while respecting their ... [more ▼]We investigate an elementary shortest path problem with resource constraints where a single capacitated vehicle, initially located at a depot, must serve a set of customers while respecting their individual time windows. When the vehicle visits a customer, it delivers the customer's demand and collects a revenue in return for the delivery. The vehicle can start its trip at any desired time. The transportation cost is a function of both the total distance traveled and the duration of the assigned trip. The objective is to determine the service start time from the depot, the subset of customers to be served, and the trip to be performed so as to minimize the total loss, which is calculated as the di erence between the transportation cost and the revenue collected from the customers. We develop two exact dynamic programming algorithms which can deal with an in nite number of Pareto-optimal states arising from the fact that the starting time and the duration of the trip act like continuous decision variables. We report computational results obtained with these algorithms and with a faster heuristic for the elementary shortest path problem. We also examine the performance of these algorithms when they are used to solve the pricing subproblem arising in the framework of a column generation algorithm for a related vehicle routing problem with time windows. [less ▲]Detailed reference viewed: 243 (13 ULg) Half a century of French organizational sociology: methodological roots, compositionist branchesDubois, Christophe E-print/Working paper (2014)Now that 50 years have gone by since the publication of The Bureaucratic Phenomenon (French title: Le phénomène bureaucratique, 1963) by Michel Crozier, what is the legacy bequeathed by the sociology of ... [more ▼]Now that 50 years have gone by since the publication of The Bureaucratic Phenomenon (French title: Le phénomène bureaucratique, 1963) by Michel Crozier, what is the legacy bequeathed by the sociology of organizations, in France and elsewhere, to today’s researchers? This contribution considers the premises of this methodology in order to establish two important achievements: the “decomposition” of the notions of organization, State and market; and the distinction of three dimensions of organizations, i.e. their managerial discourse, formal and informal structures. This article ends by considering one contemporary challenge this tradition of research has to face: how to account for the mechanisms of collective action, in order to take part in its composition? [less ▲]Detailed reference viewed: 50 (14 ULg) Lettre d'information trimestrielle n° 14 du projet DACEFI 2Meunier, Quentin; Moumbogou, Carl; Boldrini, Sylvie et alE-print/Working paper (2014)Detailed reference viewed: 19 (3 ULg) The Macroeconomics of PAYG Pension Schemes in an Aging SocietyArtige, Lionel ; Cavenaile, Laurent; Pestieau, Pierre E-print/Working paper (2014)Detailed reference viewed: 40 (1 ULg) A new methodological approach for error distributions selection in FinanceHambuckers, julien ; Heuchenne, Cédric E-print/Working paper (2014)In this article, we propose a robust methodology to select the most appropriate error distribution candidate, in a classical multiplicative heteroscedastic model. In a first step, unlike to the ... [more ▼]In this article, we propose a robust methodology to select the most appropriate error distribution candidate, in a classical multiplicative heteroscedastic model. In a first step, unlike to the traditional approach, we don't use any GARCH-type estimation of the conditional variance. Instead, we propose to use a recently developed nonparametric procedure (Mercurio and Spokoiny, 2004): the Local Adaptive Volatility Estimation (LAVE). The motivation for using this method is to avoid a possible model misspecification for the conditional variance. In a second step, we suggest a set of estimation and model selection procedures (Berk-Jones tests, kernel density-based selection, censored likelihood score, coverage probability) based on the so-obtained residuals. These methods enable to assess the global fit of a given distribution as well as to focus on its behavior in the tails. Finally, we illustrate our methodology on three time series (UBS stock returns, BOVESPA returns and EUR/USD exchange rates). [less ▲]Detailed reference viewed: 72 (28 ULg) Les determinants des Price-Earnings ratios en EuropeLambert, Marie ; Lenglois, Julien ; Streel, Alexandre et alE-print/Working paper (2014)Méthode largement employée en matière d’évaluation d’entreprise, l’analyse dite comparative s’appuie sur une estimation de la valeur des entreprises selon un multiple de leur agrégat financier. Aussi ... [more ▼]Méthode largement employée en matière d’évaluation d’entreprise, l’analyse dite comparative s’appuie sur une estimation de la valeur des entreprises selon un multiple de leur agrégat financier. Aussi appelée ‘méthode des pairs’, les multiples sont définis sur base d’un échantillon d’entreprises considérées comme comparable en termes de croissance et de risque. Le secteur est généralement retenu en pratique comme critère sous-tendant la croissance et le profil de risque opérationnel de l’entreprise. L’analyse menée dans cet article démontre l’importance des fondamentaux tels que la croissance, le risque et le taux de distribution des bénéfices dans la définition des pairs et donc de la valeur des entreprises. Sur base d’un échantillon des 100 entreprises cotées sur l’EURONEXT, entreprises les plus capitalisées et liquides, l’étude met en évidence un impact différencié de ces déterminants selon les conditions économiques. Les conséquences de notre analyse sont multiples. Premièrement, notre étude témoigne de l’importance des variables telles que le profil de risque et les perspectives croissance pour la sélection des pairs. Notre approche permet par ailleurs d’appréhender la valeur des entreprises sur base de leurs propres fondamentaux, corrigeant ainsi la méthode des multiples ‘sectoriels’ pour les différences qui subsistent au sein des sous-jacents de la valeur. Finalement, cet article nourrit une discussion quant à l’impact de la finance comportementale sur la valorisation de l’entreprise de par l’impact différencié des fondamentaux sur la valeur des entreprises au cours du temps. [less ▲]Detailed reference viewed: 112 (14 ULg) Tentatives de réflexion sémiotique et psychanalytique au sujet du voile islamiqueDemoulin, Laurent E-print/Working paper (2014)La sémiotique et la psychanalyse sont peut-être de nature à enrichir le débat sur l'interdiction du voile islamique dans les lieux publics.Detailed reference viewed: 51 (5 ULg) Examining the Effect of Earnings Management on Bid-Ask Spread and Market LiquiditySougné, Danielle ; Ajina, Aymen E-print/Working paper (2014)The main purpose of this paper is to argue the extent that earnings management lowers liquidity. It should increase information asymmetry and impair trading liquidity. Using a sample of French firms from ... [more ▼]The main purpose of this paper is to argue the extent that earnings management lowers liquidity. It should increase information asymmetry and impair trading liquidity. Using a sample of French firms from 2008 to 2011, we find that firms that manage earnings have wider bid-ask spreads. Our results are robust for both of two well established measures of market liquidity. Therefore the empirical results indicate that firms that exhibit greater earnings management are associated with lower market liquidity. These findings are in line with adverse selection and shed light on the role corporate governance devices can play in the consideration of shareholder interest’s protection, which leads to improved stock market liquidity levels. [less ▲]Detailed reference viewed: 156 (8 ULg) Proposition de révisions de l'arrêté n° 018/MEF/SG/DGF/DFCOM du 31 janvier 2013 fixant les procédures d'attribution et de gestion des forêts communautairesMoumbogou, Carl; Boldrini, Sylvie; Morin, Amélie et alE-print/Working paper (2014)Detailed reference viewed: 31 (4 ULg) Lettre d'information trimestrielle n° 13 du projet DACEFI 2Meunier, Quentin; Moumbogou, Carl; Boldrini, Sylvie et alE-print/Working paper (2014)Detailed reference viewed: 34 (8 ULg) Lettre d'Information N° 12 projet DacefiMeunier, Quentin; Mezui Mba, C.; Boldrini, Sylvie et alE-print/Working paper (2014)Detailed reference viewed: 28 (2 ULg) Experimental Study and Statistical Modeling of an Injection Scroll Compressor Operating with R407c.Quoilin, Sylvain E-print/Working paper (2014)This working paper describes an experimental study carried out on a refrigeration scroll compressor with and without vapour injection. The test rig designed for that purposed allows evaluating the ... [more ▼]This working paper describes an experimental study carried out on a refrigeration scroll compressor with and without vapour injection. The test rig designed for that purposed allows evaluating the performance over a wide range of operating conditions, by varying the supply pressure, the injection pressure, the exhaust pressure, the supply superheating and the injection superheating. 97 Steady-state points are measured, with a maximum isentropic efficiency of 64.1% and a maximum consumed electrical power of 13.1 kW. A critical analysis of the experimental results is then carried out to evaluate the quality of the data using a machine learning method. This method based on Gaussian Processes regression, is used to build a statistical operating map of the compressor as a function of the different inputs. This statistical operating map can then be compared to the experimental data points to evaluate their accuracy. [less ▲]Detailed reference viewed: 142 (15 ULg) Visibilité des femmes d'affaires dans la presse d'affaires francophone belgeCornet, Annie ; dubois, valérieE-print/Working paper (2014)Detailed reference viewed: 28 (0 ULg) Nonparametric regression with cross-sectional data: an alternative to conditional product-limit estimatorsHeuchenne, Cédric ; Laurent, Géraldine E-print/Working paper (2014)Suppose the random vector (X,Y) satisfies the nonparametric regression model Y=m(X)+varepsilon, where m(x)=E[Y|X=x] and sigma²(x)=Var[varepsilon|X=x] are unknown smooth functions and the error varepsilon ... [more ▼]Suppose the random vector (X,Y) satisfies the nonparametric regression model Y=m(X)+varepsilon, where m(x)=E[Y|X=x] and sigma²(x)=Var[varepsilon|X=x] are unknown smooth functions and the error varepsilon has zero mean and finite variance conditionally on X=x. The pair (X,Y) is obtained by cross-sectional sampling involving left-truncated and right-censored responses. The considered model is completely nonparametric but the conditional truncation distribution is assumed to be known. The novelty of this work is twofold: first, it extends the results on cross-sectional data to the conditional case and second, it generalizes the length bias results in the conditional case to right censoring and to any truncation distribution. New estimators for m(.) and sigma²(.) are constructed and relevant tools are used to quickly provide the main asymptotic properties for this kind of estimators. Extensive simulations are carried out and show that the new estimators outperform classical nonparametric estimators for left-truncated and right-censored data (when the truncation model is known). Finally, a data set on the mortality of diabetics is analyzed. [less ▲]Detailed reference viewed: 45 (3 ULg) Intentionality as DispositionBoccaccini, Federico E-print/Working paper (2014)Detailed reference viewed: 17 (2 ULg) 1 2 3