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See detailModeling in Air Transportation: Cargo Loading and Itinerary Choice
Lurkin, Virginie ULg

Doctoral thesis (2016)

We examine two problems as part of this dissertation. The first is a cargo loading problem. The aim is to load a set of containers and pallets into a cargo aircraft that serves multiple airports. Our work ... [more ▼]

We examine two problems as part of this dissertation. The first is a cargo loading problem. The aim is to load a set of containers and pallets into a cargo aircraft that serves multiple airports. Our work is the first to model cargo transport as a series of trips consisting of several legs at the end of which pickup and delivery operations might occur. This problem is crucial for airlines because in an attempt to reduce their costs, most airlines prefer to load as many containers as possible, even if all the loaded containers do not have the same final destination. Our results demonstrate that it is possible to quickly find near optimal or excellent feasible loading plans, and that our approach leads to substantial savings with respect to typical manual approaches currently used in practice. The second problem we examine involves the estimation of itinerary choice models that include price variables and correct for price endogeneity using a control function that uses several types of instrumental variables. The motivation for developing these models is to demonstrate the importance of accounting for price endogeneity and to estimate different price sensitivities as a function of advance purchase periods. This is important as the airline industry can use our results to incorporate different customer segments as revealed through high-yield and low-yield booking curves when evaluating the profitability of airline schedules. Results based on Continental U.S. markets for May 2013 departures showed 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 advanced models estimated (nested logit and ordered generalized extreme value (OGEV) models) are shown to outperform the baseline multinomial logit model with regard to statistical tests and behavioral interpretations. Additionally, results show that price sensitivities vary as a function of advance purchase periods, with those purchasing high-yield products being less price sensitive than those purchasing low-yield products (across any advance purchase periods) and those purchasing closer to departure being less price sensitive. Results also indicate that inter-alternative competition is strong for itineraries that share similar departure times. Finally, as part of the itinerary choice model developed in this dissertation, we estimate highly refined departure time of day preferences. Results are intuitive and show that departure time of day preferences vary across many dimensions including the length of haul, direction of travel, number of time zones crossed, departure day of week, and itinerary type (i.e., outbound, inbound, and one-way itineraries). To the best of our knowledge, these curves represent the most refined publicly-available estimates of airline passengers' time of day preferences. [less ▲]

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See detailYearbook 2015 Ateliers d'Architecture III: Logement collectif durable et conception régénérative
Attia, Shady ULg

Book published by SBD Lab, Liege University - 1 (2016)

C’est en Wallonie que la naissance de la seconde révolution industrielle a débuté. La Wallonie est une terre d’innovation. Dans ce contexte, c’est le lieu de création comme le béton de chanvre, les ... [more ▼]

C’est en Wallonie que la naissance de la seconde révolution industrielle a débuté. La Wallonie est une terre d’innovation. Dans ce contexte, c’est le lieu de création comme le béton de chanvre, les briques d’argiles, les panneaux photovoltaïques en acier, les panneaux de paille préfabriqués etc.,… Dans le contexte de lutte contre le changement climatique, du développement durable et d’économie circulaire, les ingénieurs architectes s’allient afin de réinventer une architecture responsable économiquement et écologiquement. Les activités de l’atelier 2014 se concevaient comme une synergie entre les apports théoriques inter disciplinaires, l’expérimentation complète de durabilité régénérative, la construction circulaire et leur intégration dans un projet architecturale. Grâce à un engagement remarquable des étudiants de l’atelier de SBD Lab (Sustainable Buildings Design Lab) et à l’apport enrichissants d’intervenants de multiples disciplines, les résultats obtenus durant cette année 2014 ont complété les prévisions faites pour un site à Liège. D’un point de vue architectural, la multiplicité et l’originalité de solutions proposées par les étudiants nourrissent les réflexions en cours à l’échelle de la ville de Liège et les questions relatives aux conditions de densification et renouveau urbain. D’un point de vue didactique, cette démarche exigeante a favorisé l’émergence chez chaque étudiant d’un savoir structuré tant au niveau conceptuel que pratique. [less ▲]

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See detailSensitivity of turbulent Schmidt number and turbulence model to simulations of jets in crossflow
Valero Huerta, Daniel ULg; Bung, Daniel B

in Environmental Modelling & Software (2016), 82

Environmental discharges have been traditionally designed by means of cost-intensive and timeconsuming experimental studies. Some extensively validated models based on an integral approach have been often ... [more ▼]

Environmental discharges have been traditionally designed by means of cost-intensive and timeconsuming experimental studies. Some extensively validated models based on an integral approach have been often employed for water quality problems, as recommended by USEPA (i.e.: CORMIX). In this study, FLOW-3D is employed for a full 3D RANS modelling of two turbulent jet-to-crossflow cases, including free surface jet impingement. Results are compared to both physical modelling and CORMIX to better assess model performance. Turbulence measurements have been collected for a better understanding of turbulent diffusion's parameter sensitivity. Although both studied models are generally able to reproduce jet trajectory, jet separation downstream of the impingement has been reproduced only by RANS modelling. Additionally, concentrations are better reproduced by FLOW-3D when the proper turbulent Schmidt number is used. This study provides a recommendation on the selection of the turbulence model and the turbulent Schmidt number for future outfall structures design studies. [less ▲]

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See detailOptical flow estimation in aerated flows
Bung, Daniel B.; Valero Huerta, Daniel ULg

in Journal of Hydraulic Research (2016)

Optical flow estimation is known from Computer Vision where it is used to determine obstacle movements through a sequence of images following an assumption of brightness conservation. This paper presents ... [more ▼]

Optical flow estimation is known from Computer Vision where it is used to determine obstacle movements through a sequence of images following an assumption of brightness conservation. This paper presents the first study on application of the optical flow method to aerated stepped spillway flows. For this purpose, the flow is captured with a high-speed camera and illuminated with a synchronized LED light source. The flow velocities, obtained using a basic Horn–Schunck method for estimation of the optical flow coupled with an image pyramid multi-resolution approach for image filtering, compare well with data from intrusive conductivity probe measurements. Application of the Horn–Schunck method yields densely populated flow field data sets with velocity information for every pixel. It is found that the image pyramid approach has the most significant effect on the accuracy compared to other image processing techniques. However, the final results show some dependency on the pixel intensity distribution, with better accuracy found for grey values between 100 and 150. [less ▲]

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See detailLa critique génétique dans la collection "Poétique"
Lorent, Fanny ULg

Conference (2016, April 29)

La critique génétique est, comme le dit bien Jean-Louis Jeannelle, une « théorie en quête d’elle-même » , tiraillée entre la tradition philologique et les avancées structuralistes. Elle doit sans cesse, à ... [more ▼]

La critique génétique est, comme le dit bien Jean-Louis Jeannelle, une « théorie en quête d’elle-même » , tiraillée entre la tradition philologique et les avancées structuralistes. Elle doit sans cesse, à la fois, se défaire des suspicions positivistes qui pèsent sur elle et justifier son appartenance possible à la (une ?) poétique . Nous voudrions étudier, dans cette communication, les mécanismes de légitimation de cette discipline aux contours épistémologiques complexes au sein même de la collection « Poétique », qui accueillit, en 1998, Les brouillons de soi de Philippe Lejeune et, en 2011, Logiques du brouillon de Daniel Ferrer. Comment les auteurs vont-ils, dans leur ouvrage, justifier leur parution au sein d’une collection dont les présupposés théoriques semblent, a priori, contraires à ceux présidant à leur travail ? Quelles en sont alors les implications méthodologiques, pour chacune des deux disciplines ? [less ▲]

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See detailLe droit du travail (re)visité par la Cour constitutionnelle
Kéfer, Fabienne ULg

in Boufflette, Sophie (Ed.) La cour constitutionnelle. De l'art de modeler de droit pour préserver l'égalité (2016, April 29)

L'étude porte sur le rôle de la Cour constitutionnelle dans l’édification du droit du travail. Arrêt après arrêt, elle consolide la norme attaquée ou au contraire redessine – ou presse le législateur de ... [more ▼]

L'étude porte sur le rôle de la Cour constitutionnelle dans l’édification du droit du travail. Arrêt après arrêt, elle consolide la norme attaquée ou au contraire redessine – ou presse le législateur de redessiner – les contours de cette branche du droit fortement marquée par son histoire. Elle se penche sur un peu plus de trente arrêts prononcés par la Cour constitutionnelle, principalement depuis 2008, dans les domaines suivants : le travail à temps partiel (chapitre 1), le droit de la non-discrimination (chapitre 2), certaines questions intéressant le licenciement, à savoir la durée du préavis, les mesures destinées à stimuler l’employabilité, la motivation, la notion de rémunération en cours en cas de réduction temporaire des prestations de travail, et l’indemnité d’éviction du représentant de commerce (chapitres 3 à 7), les distinctions entre employés et ouvriers autres que les conditions de licenciement (chapitre 8), la procédure de réorganisation judiciaire (chapitre 9) et la prescription (chapitre 10). [less ▲]

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See detailCrop residue management in arable cropping systems under temperate climate. Part 1: Soil biological and chemical (phosphorus and nitrogen) properties. A review
Lemtiri, Aboulkacem ULg; Degrune, Florine ULg; Barbieux, Sophie ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment (2016)

Interacting soil organisms support biological processes that participate in soil functions, organic matter decomposition, and nutrient cycling. Earthworms and microorganisms play a range of beneficial ... [more ▼]

Interacting soil organisms support biological processes that participate in soil functions, organic matter decomposition, and nutrient cycling. Earthworms and microorganisms play a range of beneficial roles in agricultural systems, including increased organic matter mineralization, nutrient cycling, and soil structure stabilization. The following aspects of crop residue management effects are examined in this paper: (i) earthworm composition and structure; (ii) soil microbial communities; and (iii) phosphorus (P) and nitrogen (N) element availability and distribution in the soil profile. Conventional tillage (ploughing) is often reported to generate decreased soil organism abundance and diversity, primarily earthworms and microorganisms, as well as a uniform distribution of the nutrients P and N within the ploughed soil horizon. Soil residue incorporation of mineral particles can maintain P and N levels, however returning soil also increases aeration and the activation of microbial activity. Hence, comparisons of tillage effects on soil biological functioning and nutrient cycling remain unclear. This review highlights the challenges in establishing definitive evidence regarding the effects of crop residue management on soil organisms and nutrient dynamics. The studies examined reported variability in soil and climate, and the complexity of soil processes contributed to the absence of clear findings. Further research is required under temperate climate conditions. [less ▲]

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See detailPrêt "coup de pouce": un nouvel incitant fiscal wallon pour le financement des entreprises débutantes
Bourgeois, Marc ULg; Pace, Xavier ULg

in Bourgeois, Marc (Ed.) Les incitants fiscaux pour les PME - actualités et aspects comptables (2016, April 28)

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See detailCOP21 and Electrical Systems
Ernst, Damien ULg

Speech/Talk (2016)

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See detailSexual attraction in lady beetles: fundamentals and applications
Fassotte, Bérénice ULg

Doctoral thesis (2016)

Sustainable agriculture relies on the development of environmentally friendly methods of crop production. Therefore, alternative solutions are required to decrease insecticide use and to promote the ... [more ▼]

Sustainable agriculture relies on the development of environmentally friendly methods of crop production. Therefore, alternative solutions are required to decrease insecticide use and to promote the efficacy of natural enemies against insect pests. Investigating the sexual behavior of lady beetles is of practical relevance, because these insects could be used to reduce plant-feeding insect populations in crop fields by taking advantage of their predatory behavior. In this context, the objective of this PhD thesis was twofold: (1) a fundamental research that focuses on the identification of the sex pheromone of Harmonia axyridis (Pallas) and (2) an applied approach aimed at elaborating semiochemicals slow-release dispensers with these compounds, in order to attract individuals in cultivated fields. We have demonstrated that virgin females of H. axyridis display a typical male-calling behavior in presence of prey, which is associated with the release of a pheromonal blend that is highly attractive for conspecific males. Dynamic headspace sampling and subsequent chemical analyses allowed the characterization of this sex pheromone. Finally, we focused on the development of a formulation releasing a combination of semiochemicals that attract aphid predators. The formulation, composed of alginate beads, was optimized under laboratory conditions. The release rate of the formulation was assessed by dynamic headspace sampling coupled with adsorbent trapping. The formulation was efficient at attracting two natural enemies of aphids. All these results are discussed in the context of sustainable agriculture, with the use of semiochemicals, and especially pheromones, as potential tools to enhance current cropping systems. In near future, the application of such molecules, based on strong knowledge of insect olfaction, is expected to increase considerably with the development of new methods aimed at attracting predators and/or parasitoids. In addition, improvements of experimental devices, such as the elaboration of slow release dispensers, are suggested in the last chapter of this PhD thesis. [less ▲]

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See detailTerrorisme, flux médiatique et petits chatons. De quelques narrations de l'invisible.
Hamers, Jérémy ULg

Scientific conference (2016, April 28)

Partant de quelques événements terroristes récents (Paris 2015, Verviers 2015, Bruxelles 2016), cette conférence une analyse critique des multiples réactions médiatiques que ces événements ont suscité en ... [more ▼]

Partant de quelques événements terroristes récents (Paris 2015, Verviers 2015, Bruxelles 2016), cette conférence une analyse critique des multiples réactions médiatiques que ces événements ont suscité en télévision comme sur internet. Editions spéciales de journaux télévisés, enquêtes d'amateurs sur des sites dédiés aux théories du complot, détournements d'images sur les réseaux sociaux seront abordés ici comme autant de narrations qui, malgré leur hétérogénéité, répondent toutes à l'invisibilité partielle et momentanée de l'acte terroriste au moment où il surgit dans le paysage médiatique. [less ▲]

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See detailLa Paix de Fexhe. Qui ? Quoi ? Comment ? Pourquoi ?
Masson, Christophe ULg

Conference given outside the academic context (2016)

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See detailPercevoir et reconnaître des symboles. La théorie de la représentation iconique de Dominic Lopes.
Hagelstein, Maud ULg

Conference (2016, April 28)

Perceiving and recognizing symbols. Dominic Lopes’ theory of iconic representation. In his works on the epistemological value of images (Understanding Pictures - 1996), Dominic Lopes (Department of ... [more ▼]

Perceiving and recognizing symbols. Dominic Lopes’ theory of iconic representation. In his works on the epistemological value of images (Understanding Pictures - 1996), Dominic Lopes (Department of Philosophy - University of British Columbia) develops an analytical aesthetics primarily concerned with iconic representation. His analysis distinguishes two models of iconic representation comprehension. In the first model, inspired by perceptual approaches like that of Richard Wollheim, the process of image recognition is rooted in perception (to sum it up: perceptualism embraces the idea of « likeness » between the image and what it represents). One of this model’s shortcomings, however, is that it too readily assumes that perception can be a natural, straightforward process. Indeed, iconic representation can not be understood through perception alone, as vision is of course influenced by cultural and, most of all, cognitive processes. A representative model thus needs to account for the ways in which iconic recognition differs from ordinary visual recognition. In the second model, which build off of symbolic approaches like that of Nelson Goodman, iconic representation works the same way as other types of symbols, particularly linguistic ones. Thus, this approach considers the similarities between images and language (representations which are both affected by processes of denotation and predication). However, we all know how strongly image theoreticians have been resisting the linguistic paradigm (iconic turn topic): some worry about overlooking the image’s semantic density in favor of its « simple » descriptive quality. Lopes finds a path between these two models by developing a « theory of aspect recognition », which incorporates perceptive elements into a symbolic structure. According to Lopes, if we agree that images belong to symbolic systems of denotation, then « they might be symbols for which the reference is dependent on the carrying out of perceptive aptitudes », a claim which my talk will explore. I will also discuss how Lopes’ theory accounts for skills acquisition (the capacity to recognize) through images, and shows how images help these skills progressively develop. [less ▲]

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See detailAdministration of Third-Party Mesenchymal Stromal Cells at the Time of Kidney Transplantation: Interim Safety Analysis at One-Year Follow-Up
Erpicum, Pauline ULg; WEEKERS, Laurent ULg; DETRY, Olivier ULg et al

Conference (2016, April 28)

Objective. Mesenchymal stromal cells (MSC) therapy has been suggested in kidney transplantation (KTx). We report on the 1-year follow-up of an open-label phase I trial using MSC at the time of KTx ... [more ▼]

Objective. Mesenchymal stromal cells (MSC) therapy has been suggested in kidney transplantation (KTx). We report on the 1-year follow-up of an open-label phase I trial using MSC at the time of KTx. Methods. On postoperative day 3 (D3), third-party MSC (~2.0x106/kg) were administered to 7 non-immunized first-transplant recipients from deceased donors, under standard immunosuppression (Basiliximab, Tacrolimus, MMF and steroids). No HLA matching was required for MSC donors. In parallel, 7 comparable KTx recipients were included as controls. Written informed consent was obtained from all participants. Results. No hemodynamic or immune-allergic side-effect was noted at the time of MSC injection. Still, 1 patient with a history of ischemic heart disease had a NSTEMI ~3h after MSC infusion. Four MSC patients presented with CMV reactivation within 165 ± 96 days post KTx, whereas 3 controls had positive polyoma-BK viremia within 92 ± 4d post KTx. Three MSC patients were affected by pneumonia within 269 ± 98d post KTx, whereas 3 controls had urinary infection within 48 ± 43d post KTx. No MSC engraftment syndrome was observed. At D14, eGFR in MSC and control groups was 47.1 ± 6.8 and 39.7 ± 5.9 ml/min, respectively (p, 0.05). At 1 year, eGFR in MSC and control groups was 43.1 ± 17.8 and 53.9 ± 13.4 ml/min, respectively (p, 0.25). At 3-month protocol biopsy, no rejection was evidenced in MSC or control patients. Later on, 1 acute rejection was diagnosed at D330 in 1 MSC patient. No biopsy-proven AR was noted in controls. Three patients developed anti-HLA antibodies against MSC (n=1) or shared kidney/MSC (n=2) mismatches. Conclusions. MSC infusion was safe in all patients except one. Incidence of opportunist and non-opportunist infections was similar in both MSC and control groups. No MSC engraftment syndrome was documented. No difference in eGFR was found at 1 year post KTx. Putative immunization against MSC was observed in 3 patients. [less ▲]

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See detailLa ligne et la boucle. Michel Strogoff ou l'involution
Durand, Pascal ULg

Conference (2016, April 28)

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See detailImpact de l'incertitude sur la gouvernance des institutions de microfinance: cas de coopératives burundaises
Niyungeko, Thadée ULg

Doctoral thesis (2016)

The microfinance sector has attracted increasing attention particularly in literature and in political circles in recent years. Microfinance is seen as a key means for the poors to access to financial ... [more ▼]

The microfinance sector has attracted increasing attention particularly in literature and in political circles in recent years. Microfinance is seen as a key means for the poors to access to financial services. Nevertheless, one of the challenges of microfinance institutions lies in their governance. To study the governance of microfinance institutions, many authors recommend to consider not only their diversity related to their natures and their missions, but also the context of the country in which they operate. However, existing works have not fully taken into account the contextual factors in the study of the governance of MFIs. This thesis contributes to bridge these gaps. It is in this sense of a specific and suitable approach to microfinance institutions. It analyzes the impact of the uncertainty related to an internal armed conflict in Burundi cooperatives. This research shows that face of uncertainty, policymakers are faced with the decision-making problems in compliance with the rules. Conflicts of interest arise, the paradoxes in the roles of directors or in inter-organizational relationships are observed. The results of this research also show the limits of volunteer principle in cooperative organizations in times of uncertainty. To cope with uncertainty, cooperatives undertaking various coping strategies despite their organizational similarities. They further develop inter-organizational relationships in search of legitimacy and scope of expression. Belonging to the network and the pressures of supervisor push these organizations to adopt isomorphic structures and practices. This thesis is a first milestone in the studies on the governance of cooperatives under uncertainty. It goes beyond the Burundian context by formulating hypotheses to be tested in future studies and in other places. [less ▲]

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See detailGestion des pyodermites superficielles récidivantes chez le chien
Mignon, Bernard ULg

Conference given outside the academic context (2016)

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See detailUnderground pumped storage hydroelectricity using abandoned works (deep mines or open pits) and the impact on groundwater flow
Pujades, Estanislao ULg; Willems, Thibault ULg; Bodeux, Sarah ULg et al

in Hydrogeology Journal (2016)

Underground pumped storage hydroelectricity (UPSH) plants using open-pit or deep mines can be used in flat regions to store the excess of electricity produced during low-demand energy periods. It is ... [more ▼]

Underground pumped storage hydroelectricity (UPSH) plants using open-pit or deep mines can be used in flat regions to store the excess of electricity produced during low-demand energy periods. It is essential to consider the interaction between UPSH plants and the surrounding geological media. There has been little work on the assessment of associated groundwater flow impacts. The impacts on groundwater flow are determined numerically using a simplified numerical model which is assumed to be representative of open-pit and deep mines. The main impact consists of oscillation of the piezometric head, and its magnitude depends on the characteristics of the aquifer/geological medium, the mine and the pumping and injection intervals. If an average piezometric head is considered, it drops at early times after the start of the UPSH plant activity and then recovers progressively. The most favorable hydrogeological conditions to minimize impacts are evaluated by comparing several scenarios. The impact magnitude will be lower in geological media with low hydraulic diffusivity; however, the parameter that plays the more important role is the volume of water stored in the mine. Its variation modifies considerably the groundwater flow impacts. Finally, the problem is studied analytically and some solutions are proposed to approximate the impacts, allowing a quick screening of favorable locations for future UPSH plants. [less ▲]

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