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See detailModes d'Organisation et Distribution de l'eau: Une Evaluation empirique de la Performance par les Méthodes des frontières de production
Mande Buafua, Patrick ULg

Doctoral thesis (2014)

Cette thèse est une contribution à l’analyse empirique de la performance (efficacité technique et effectivité) dans le secteur de la distribution de l’eau en Afrique Subsaharienne. Nous cherchons à ... [more ▼]

Cette thèse est une contribution à l’analyse empirique de la performance (efficacité technique et effectivité) dans le secteur de la distribution de l’eau en Afrique Subsaharienne. Nous cherchons à répondre à la question de l’impact des modes d’organisation (participation du secteur privé, régulation et une combinaison de deux) sur l’amélioration de la performance dans ce secteur. Notre analyse s’appuie sur les données issues de la base des données de l’AICD pour la période 2000 à 2005. Premièrement, grâce au modèle de Battese & Coelli (1995), nous calculons les scores d’efficacité technique et nous identifions les sources de l’inefficacité technique. L’approche PLP nous sert de technique complémentaire pour approfondir l’examen des élasticités d’échelle et du coût implicite des pertes d’eau sur le réseau pour chaque opérateur. En moyenne, les entreprises de l’échantillon sont techniquement inefficaces sur la période. Réguler par contrat de performance conduit à des scores d’efficacité technique plus élevés que réguler par agence. La participation du secteur privé dans la gestion ou l’exploitation du service présente un effet positif sur l’efficacité technique. Il n’y a pas de preuve d’une différence significative entre l’efficacité technique des entreprises sous gestion publique régulées par contrat de performance ou par agence de régulation et celles avec participation du secteur privé dans la gestion ou l’exploitation régulées par contrat de performance ou par agence de régulation. Les élasticités d’échelle sont, en moyenne, décroissantes. Le coût des pertes d’eau sur le réseau est évalué, en moyenne, à 4 travailleurs pour 100.000 m³ d’eau perdue. De plus, ce coût marginal a tendance à augmenter avec les niveaux de la qualité du réseau. Deuxièmement, nous analysons notre question de recherche en prenant en compte la performance en termes d’effectivité. Nous nous appuyons sur la méthode DEA basée sur la procédure en double bootstrap (Simar & Wilson, 2007) en appliquant l’approche analytique, en 4 étapes, inspirée de Mbuvi et al., (2012). Les résultats laissent entrevoir l’existence d’un problème d’ineffectivité plus élevé que celui d’inefficacité technique. Ainsi, les opérateurs ont besoin des ressources additionnelles pour atteindre 100% de leur effectivité. Réguler par contrat de performance conduit à une plus grande effectivité que réguler par agence de régulation. La variable relative à la participation du secteur privé dans la gestion ou l’exploitation du service a un effet négatif et significatif sur l’effectivité. Enfin, il n’y a pas de différence significative, en termes d’effectivité, entre les entreprises avec participation du secteur privé dans la gestion ou l’exploitation régulées par agence ou par contrat de performance et celles publiques régulées par agence ou par contrat de performance. Enfin, nous évaluons l’impact des variables institutionnelles sur les taux de couverture du service en utilisant les modèles à effets fixes. Nous nous attaquons à la question de l’endogénéité en utilisant le cadre proposé par Heckman (1978). Réguler par contrat de performance a un effet positif et significatif sur les taux de couverture. La participation du secteur privé dans la gestion ou l’exploitation du service possède un effet négatif et significatif sur les taux de couverture du service. Combiner la gestion publique avec la régulation par agence ou par contrat de performance conduit à des taux de couverture du service plus élevés que combiner la participation du secteur privé dans la gestion ou l’exploitation du service avec la régulation par agence ou par contrat de performance. [less ▲]

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See detailLes déterminants de la désinsertion professionnelle
Mairiaux, Philippe ULg

Conference (2014, June 02)

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See detailComparison of Indicators to Evaluate the Resilience of Lab Scale Continuously Stirred Anaerobic Reactors Submitted to Biological Dysfunctions
Lemaigre, Sébastien; Adam, Gilles ULg; Goux, Xavier et al

Poster (2014, June 02)

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See detailRay tracing enhancement for space thermal analysis: isocell method
Jacques, Lionel ULg; Masset, Luc ULg; Kerschen, Gaëtan ULg

in Sarler, Bozidar; Massaroti, Nicola; Nithiarasu, Perumal (Eds.) Third International Conference on Computational Methods for Thermal Problems (2014, June 02)

The finite element method (FEM) is widely used in mechanical engineering, especially for space structure design. However, FEM is not yet often used for thermal engineering of space structures where the ... [more ▼]

The finite element method (FEM) is widely used in mechanical engineering, especially for space structure design. However, FEM is not yet often used for thermal engineering of space structures where the lumped parameter method is still dominant. Radiative exchange factors (REFs) are usually computed through Monte Carlo ray-tracing. Due to the large number of elements composing a FE model, the computation of the REFs is prohibitively expensive. The developments of the new Isocell quasi-Monte Carlo ray tracing method are presented. The Isocell method enhances the uniformity of the generated quasi-random sequence of ray directions and leads to faster convergence. It is associated with different surface sampling to derive the REFs. The method is benchmarked against ESARAD, the standard ray-tracing engine for thermal analysis used in the European aerospace industry. Various geometries are used. In particular, one entrance baffle of the Extreme Ultraviolet Imager (EUI) instrument developed at the Centre Spatial de Liège in Belgium is used. The EUI instrument of the Solar Orbiter European Space Agency mission and will be launched in a Sun-centered 0.28 perihelion orbit in 2018. [less ▲]

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See detailPrincipaux outils de prévention précoce de la désinsertion professionnelle - Approche comparée des dispositifs réglementaires
Kéfer, Fabienne ULg

Scientific conference (2014, June 02)

Quels sont les dispositifs que le droit met à la disposition des travailleurs, des employeurs et des institutions de sécurité sociale qui incitent au retour au travail le plus tôt possible ou au contraire ... [more ▼]

Quels sont les dispositifs que le droit met à la disposition des travailleurs, des employeurs et des institutions de sécurité sociale qui incitent au retour au travail le plus tôt possible ou au contraire freinent les tentatives de reprise du travail de la part d'un salarié victime d'une incapacité de travail? [less ▲]

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See detailHOLOCENE DUST RECORD IN A BELGIAN PEAT BOG: MULTIPROXY GEOCHEMICAL APPROACH
Allan, Mouhamd ULg; gael, le roux; Fagel, Nathalie ULg et al

in dust 2014, Book of ABSTRACTS, International Conference on ATMOSPHERIC DUST (2014, June 01)

Ombrotrophic peatlands are unique environmental archives of natural and anthropogenic atmospheric dust deposition. Their surface layers are exclusively fed by atmospheric inputs. A peat bog core from ... [more ▼]

Ombrotrophic peatlands are unique environmental archives of natural and anthropogenic atmospheric dust deposition. Their surface layers are exclusively fed by atmospheric inputs. A peat bog core from Misten in Eastern Belgium southern covering the last 7500 years (dated by 210Pb and 14C methods) was investigated to reconstruct dust depostion based on a combination of the Rare Earth Elements (REE) and lithogenic elements concentrations, as well as Nd and Pb isotopes data. Nd isotope signature was used to decipher between local and distal dust supplies, the Pb isotopes to trace the antropogenic influences. Peat humification was used to evaluate hydroclimatic conditions. Dust fluxes show pronounced increase at 3200-2800BC, 600BC, AD600, 1000AD, 1200AD and from 1700 AD. Lead isotope signatures are consistent with local and regional contamination by coal combustion and smelting activities. The Nd values show large variability, between -5 and –13, identifying three major sources of dust: local soils, distal volcanic and desert particles. Our results are in agreement with atmospheric reconstructions from other continental archives, confirming that the Misten peat is a valid archive for dust deposition. The approach combining geochemical elementary content and isotope data in ombrotrophic peat allows to decipher between dust flux changes related to human and climate forcing. [less ▲]

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See detailDe la matière à l'espace: une voie d'intégration numérique et matérielle
Delvaux, Frederic ULg; Bianchi, Romuald ULg; Jancart, Sylvie ULg

in Kubicki, Sylvain; Halin, Gilles; Bignon, Jean-CLaude (Eds.) Scan 14 séminaire de conception architecturale numérique : Interaction(s) des maquettes numériques (2014, June 01)

From a collaboration of formal and architectural research between architect and artist, we present the summary of an experimental approach that illustrates the creation and construction of a functional ... [more ▼]

From a collaboration of formal and architectural research between architect and artist, we present the summary of an experimental approach that illustrates the creation and construction of a functional space, located at the borders of the sculpture and the architecture. We present a look at the method, according to a revised approach to digital modeling / re-design. This has been an exploratory approach through the study of three generic models of the form. We present the experimental method, the selection of relevant parameters in form finding coupled with the integration of material and physical data specific to the object. We also expose the benefits of this approach, its limitations and the possibilities it offers as a generic point of view. [less ▲]

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See detailDiscovery of X-ray pulsations from a massive star
Oskinova, Lidia M.; Nazé, Yaël ULg; Todt, Helge et al

in Nature Communications (2014), 5

X-ray emission from stars much more massive than the Sun was discovered only 35 years ago. Such stars drive fast stellar winds where shocks can develop, and it is commonly assumed that the X-rays emerge ... [more ▼]

X-ray emission from stars much more massive than the Sun was discovered only 35 years ago. Such stars drive fast stellar winds where shocks can develop, and it is commonly assumed that the X-rays emerge from the shock-heated plasma. Many massive stars additionally pulsate. However, hitherto it was neither theoretically predicted nor observed that these pulsations would affect their X-ray emission. All X-ray pulsars known so far are associated with degenerate objects, either neutron stars or white dwarfs. Here we report the discovery of pulsating X-rays from a non-degenerate object, the massive B-type star ξ[SUP]1[/SUP] CMa. This star is a variable of β Cep-type and has a strong magnetic field. Our observations with the X-ray Multi-Mirror (XMM-Newton) telescope reveal X-ray pulsations with the same period as the fundamental stellar oscillations. This discovery challenges our understanding of stellar winds from massive stars, their X-ray emission and their magnetism. [less ▲]

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See detailPhase resolved X-ray spectroscopy of HDE 288766: Probing the wind of an extreme Of+/WNLha star
Rauw, Grégor ULg; Mahy, Laurent; Nazé, Yaël ULg et al

in Astronomy and Astrophysics (2014), 566

Context. HDE 228766 is a very massive binary system hosting a secondary component, which is probably in an intermediate evolutionary stage between an Of supergiant and an WN star. The wind of this star ... [more ▼]

Context. HDE 228766 is a very massive binary system hosting a secondary component, which is probably in an intermediate evolutionary stage between an Of supergiant and an WN star. The wind of this star collides with the wind of its O8 II companion, leading to relatively strong X-ray emission. <BR /> Aims: Measuring the orbital variations of the line-of-sight absorption toward the X-ray emission from the wind-wind interaction zone yields information on the wind densities of both stars. <BR /> Methods: X-ray spectra have been collected at three key orbital phases to probe the winds of both stars. Optical photometry has been gathered to set constraints on the orbital inclination of the system. <BR /> Results: The X-ray spectra reveal prominent variations of the intervening column density toward the X-ray emission zone, which are in line with the expectations for a wind-wind collision. We use a toy model to set constraints on the stellar wind parameters by attempting to reproduce the observed variations of the relative fluxes and wind optical depths at 1 keV. <BR /> Conclusions: The lack of strong optical eclipses sets an upper limit of ~ 68° on the orbital inclination. The analysis of the variations of the X-ray spectra suggests an inclination in the range 54-61° and indicates that the secondary wind momentum ratio exceeds that of the primary by at least a factor 5. Our models further suggest that the bulk of the X-ray emission arises from the innermost region of the wind interaction zone, which is from a region whose outer radius, as measured from the secondary star, lies between 0.5 and 1.5 times the orbital separation. Based on observations collected with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and the USA (NASA), and on data collected at the San Pedro Mártir observatory (Mexico). [less ▲]

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See detailThe four duties of family doctors. Quaternary prevention: First, do no harm
Jamoulle, Marc ULg

in Hong Kong Practitioner (2014), 36

Cl inical prevent ion has been organised in a chronological manner since the middle of the 20th century. A paradigm shift from a chronological to a relationship-based preventive pattern of care offers new ... [more ▼]

Cl inical prevent ion has been organised in a chronological manner since the middle of the 20th century. A paradigm shift from a chronological to a relationship-based preventive pattern of care offers new insight into the practice of doctors, and brings to light the concept of quaternary prevention, a critical look at medical activities with an emphasis on the need not to harm. Quaternary prevention addresses the fundamental question of what constitutes too much or too little medicine. It is the fourth form of disease prevention, but also the fourth frame of action for family doctors. New definitions of prevention published in the Wonca Dictionary of Family Medicine offer a structured way to discuss the activities of family doctors, including ethical considerations on the patient-doctor encounter. 摘要 [less ▲]

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See detailEvaluation of the Economic Statistical Design of the Multivariate T2 Control Chart with Multiple Variable Sampling Intervals Scheme: NSGA-II Approach
Faraz, Alireza ULg; Seif, Asghar; Sadeghifar

in Journal of Statistical Computation & Simulation (2014)

The economic and statistical merits of a multiple variable sampling intervals (MVSI) scheme are studied. The problem is formulated as a double-objective optimization problem with the adjusted average time ... [more ▼]

The economic and statistical merits of a multiple variable sampling intervals (MVSI) scheme are studied. The problem is formulated as a double-objective optimization problem with the adjusted average time to signal as the statistical objective and the expected cost per hour as the economic objective. Bai and Lee’s ‎[2] economic model is considered. Then we find the Pareto-optimal designs in which the two objectives are minimized simultaneously by using the non-dominated sorting genetic algorithm. Through an illustrative example, the advantages of the proposed approach is shown by providing a list of viable optimal solutions and graphical representations, which indicate the advantage of flexibility and adaptability of our approach. [less ▲]

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See detailSpondylolysis with or without spondylolisthesis
Gillet, Philippe ULg

in Bentley, George (Ed.) European surgical orthopaedics and traumatology, The EFORT Textbook (2014)

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See detailComputational homogenization of cellular materials
Nguyen, Van Dung ULg; Noels, Ludovic ULg

in International Journal of Solids and Structures (2014), 51(11-12), 2183-2203

In this work we propose to study the behavior of cellular materials using a second–order multi–scale computational homogenization approach. During the macroscopic loading, micro-buckling of thin ... [more ▼]

In this work we propose to study the behavior of cellular materials using a second–order multi–scale computational homogenization approach. During the macroscopic loading, micro-buckling of thin components, such as cell walls or cell struts, can occur. Even if the behavior of the materials of which the micro–structure is made remains elliptic, the homogenized behavior can lose its ellipticity. In that case, a localization band is formed and propagates at the macro–scale. When the localization occurs, the assumption of local action in the standard approach, for which the stress state on a material point depends only on the strain state at that point, is no–longer suitable, which motivates the use of the second-order multi–scale computational homogenization scheme. At the macro–scale of this scheme, the discontinuous Galerkin method is chosen to solve the Mindlin strain gradient continuum. At the microscopic scale, the classical finite element resolutions of representative volume elements are considered. Since the meshes generated from cellular materials exhibit voids on the boundaries and are not conforming in general, the periodic boundary conditions are reformulated and are enforced by a polynomial interpolation method. With the presence of instability phenomena at both scales, the arc–length path following technique is adopted to solve both macroscopic and microscopic problems. [less ▲]

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See detailAquifères de l'Ardenne
Debbaut, Vincent ULg; Cajot, Odette; Ruthy, Ingrid ULg et al

in Dassargues, Alain; Walraevens, Kristine (Eds.) Watervoerende lagen & grondwater in België - Aquifères & eaux souterraines en Belgique (2014)

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See detailArrival of european eel in Belgian Part of the Meuse: who and how are they?
Nzau Matondo, Billy ULg; Benitez, Jean-Philippe ULg; Dierckx, Arnaud ULg et al

in Proceedings of the 10th International Conference on Ecohydraulics (2014, June)

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See detailPhilosophy of economic security of organization: The constructivist approach
Shutyak, Yuliya ULg

Conference (2014, June)

The purpose of this paper is to present the concept of economic security of the organization. Guiding by the constructivism approach, the author conducts a narrative literature review on economic security ... [more ▼]

The purpose of this paper is to present the concept of economic security of the organization. Guiding by the constructivism approach, the author conducts a narrative literature review on economic security of organization in parallel with well-known theories of business management.The presented in the paper ideas are an impulse for a new wave in organizational research basing on a new globalizing theoretical framework. The proposed approach to organizational management through the prism of security allows connecting disjoined concepts used in organizational studies and highlights aspects important for organizational survival and growth but mostly overlooked by scientists. The paper’s value consists in evolving of a relatively unexploited concept of economic security of the organization. [less ▲]

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