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See detailOne day walk
Gantois, Gisele ULg

Scientific conference (2016, January 29)

One day walk Within my research I’m trying to find methods and tools to trace, unveil and map social & ecological values of built heritage in rural areas. In this contribution I’d like to discuss one of ... [more ▼]

One day walk Within my research I’m trying to find methods and tools to trace, unveil and map social & ecological values of built heritage in rural areas. In this contribution I’d like to discuss one of the methods I developed namely ‘A protocol for walking.’ The approach focuses on thinking through walking and drawing rather than an attempt to directly resolve or structure a problem. It aims at triggering curiosity not necessarily resulting in a solution or a conclusion while following a non-linear path. Walking acts like a starting trigger to investigate the cultural landscape and aims at generating and facilitating a thought process. It is therefore a way of reflecting. While walking, the act of watching closely can lead to real closeness and might help to gain insight into people’s and other living creatures attitudes, value system, concerns, motivations, aspirations, culture and behaviours and their interaction with space. As one needs the sharp eye to discover even the most trusted things, the act of drawing while walking becomes a way of observing. The drawing turns into a tool for the eye and makes one seeing things differently. The essential concept in this methodology is to approach the problem in an indirect way by postponing the problem. This is a way of tackling the uncertainty of the ‘ill-defined’ nature of the problem statement as values and significances cannot easily or clearly be defined. [less ▲]

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See detailCaught in the middle: the Maisierian, a lithic tradition between two worlds
Touzé, Olivier ULg

Conference (2016, January 29)

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See detailExperimental comparison of organic fluids for low temperature ORC (organic Rankine cycle) systems for waste heat recovery applications
Desideri, Adriano ULg; Gusev, Sergei; Van den Broek, Martijn et al

in Energy (2016), 97

This contribution experimentally evaluates and compares the performance of an ORC (organic Rankine cycle) system for stationary bottoming WHR (waste heat recovery) application operating with two different ... [more ▼]

This contribution experimentally evaluates and compares the performance of an ORC (organic Rankine cycle) system for stationary bottoming WHR (waste heat recovery) application operating with two different working fluids, SES36 and R245fa. The test rig is a regenerative cycle equipped with a single screw expander modified from a standard compressor characterized by a nominal shaft power of 11 kW. A total of 36 and 43 steady-state points are collected for SES36 and R245fa respectively, over a wide range of operating conditions by changing the expander rotational speed, the pump frequency and the cooling condenser flow rate. The performances of the ORC components are individually evaluated. A maximum expander isentropic efficiency of 60% is reached using SES36 at 3000 rpm, and a value of 52% is reached with R245fa at 3000 rpm. However, for a given pressure ratio the expander output power is higher with R245fa than with SES36. The overall performance of the ORC unit are investigated in terms of first and second law efficiencies and net output power for the two fluids. The results experimentally demonstrate the correlation between the working fluid critical temperature and the ORC unit working characteristics for low temperature waste heat recovery applications. Open experimental data are provided for both fluids. [less ▲]

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See detailData-driven selection of the minimum-gradient support parameter in time-lapse focused electrical imaging
Nguyen, Frédéric ULg; Kemna, Andreas; Robert, Tanguy et al

in Geophysics (2016), 81(1), 1-5

We have considered the problem of the choice of the minimum-gradient support (MGS) parameter in focused inversion for time-lapse (TL) electric resistivity tomography. Most existing approaches have relied ... [more ▼]

We have considered the problem of the choice of the minimum-gradient support (MGS) parameter in focused inversion for time-lapse (TL) electric resistivity tomography. Most existing approaches have relied either on an arbitrary choice of this parameter or one based on the prior information, such as the expected contrast in the TL image. We have decided to select the MGS parameter using a line search based on the value of the TL data root-mean-square misfit at the first iteration of the nonlinear inversion procedure. The latter was based on a Gauss-Newton scheme minimizing a regularized objective function in which the regularization functional was defined by the MGS functional. The regularization parameter was optimized to achieve a certain target level, following the Occam principles. We have validated our approach on a synthetic benchmark using a complex and heterogeneous model and determined its effectiveness on electric tomography TL data collected during a salt tracer experiment in fractured limestone. Our results have determined that the approach was successful in retrieving the focused anomaly and did not rely on prior information. [less ▲]

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See detailWalphy, un projet expérimental de réhabilitation de cours d’eau : suivis hydromorphologiques et écologiques
Castelain, Liévin; Peeters, Alexandre ULg; Halleux, Marie et al

in Hydroécologie Appliquée (2016)

Le projet Life Environnement WALPHY, co-financé par l’Union Européenne, a eu pour objectif de réaliser des travaux de restauration de la qualité hydromorphologique du Bocq, affluent de la Meuse. La ... [more ▼]

Le projet Life Environnement WALPHY, co-financé par l’Union Européenne, a eu pour objectif de réaliser des travaux de restauration de la qualité hydromorphologique du Bocq, affluent de la Meuse. La continuité longitudinale, qui concerne la libre circulation des poissons et le transport naturel des sédiments, a été fortement perturbée par un grand nombre d’obstacles (vannages, déversoirs, …). Afin de rétablir cette continuité, des travaux d’arasement ou d’aménagement (passes à bassins, bras de contournement, rampes rugueuses...) d’obstacles ont été réalisés. De plus, des travaux de reméandration, de diversification des écoulements ou de création d’habitats piscicoles ont été menés afin d’améliorer la continuité transversale. Ces travaux ont fait l’objet de suivis scientifiques sur base d’analyses géomorphologiques, hydromorphologiques et écologiques. Des méthodes standardisées et reproductibles ont été mises au point pour comparer la situation avant et après travaux. L’application de ces méthodes a montré que le suivi des microhabitats couplé à l’analyse des populations de macroinvertébrés et de poissons est à même de mettre en évidence les évolutions post-travaux. Deux exemples d’études avant et après travaux sont présentés : l’arasement d’un déversoir et la reméandration d’un secteur rectifié. Les résultats montrent une bonne évolution des indicateurs biologiques. [less ▲]

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See detailTwo cases of atypical CALR mutations in MPN patients
SAGOT, Clémence ULg; CHARLIER, Hélène ULg; KOOPMANSCH, Benjamin ULg et al

Poster (2016, January 29)

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See detailThe BRICS New Development Bank: a China-led challenge to the Western Hegemony
WCusson, Gabrielle ULg; Culpi, Ludmila ULg

Scientific conference (2016, January 28)

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See detailActualités en matière de fiscalité régionale et locale
Bourgeois, Marc ULg

Scientific conference (2016, January 28)

Detailed reference viewed: 9 (0 ULg)
Peer Reviewed
See detailHéroïsme en clôture : de la contemplative silencieuse à l’amazone chrétienne. Discours et représentations de l’héroïsme féminin sous la plume d’annonciades célestes au XVIIe siècle
Henneau, Marie-Elisabeth ULg

Conference (2016, January 28)

Les annonciades célestes – ordre féminin d’origine génoise fondé en 1604 et implanté en pleine Guerre de Trente Ans sur la Dorsale catholique, face aux territoires protestants – ont produit une nombre ... [more ▼]

Les annonciades célestes – ordre féminin d’origine génoise fondé en 1604 et implanté en pleine Guerre de Trente Ans sur la Dorsale catholique, face aux territoires protestants – ont produit une nombre considérable de chroniques, annales, journaux, mémoires, biographies spirituelles, abrégés de vertus, lettres, autobiographies et autres billets d’humeur, autant de témoignages d’expériences, vécues en espace clos, mais toujours en prise sur le monde, en quête d’éternité, mais sans cesse plongées dans le temps en cours. Des expériences riches et singulières, qui ont eu souvent raison des timidités ou des retenues des intéressées pour aboutir à des relations particulièrement savoureuses où alternent écriture de soi et écriture de l’histoire. Cette documentation inédite et pour une bonne part inexploitée – au contraire des fonds relatifs aux Visitandines – permet, notamment, d’approcher leur conception de la moniale tridentine idéale, mise en scène et en mots par des autrices dont le génie littéraire n’égale sans doute pas les grandes plumes de Port-Royal, mais dont la production révèle tant le large éventail de représentations de soi élaborées par les annonciades que la réception intra muros des discours tenus à leur propos dans le siècle. Contemplatives vouées à une très stricte clôture, ces femmes se voient néanmoins en missionnaires conquérantes d’un espace à (ré)évangéliser. Il s’agira d’étudier d’une part comment elles intègrent les recommandations de leur entourage masculin qui les incitent à la discrétion, à l’effacement, au silence, bref, à un héroïsme comparable à celui de la Vierge, qui dans le secret de sa chambre n’en conçoit pas moins le Sauveur de l’humanité et, d’autre part, et sans que cela soit contradictoire, comment ces cloîtrées vivent les péripéties de leur expansion en aventurières de Dieu et souhaitent, en les narrant, manifester au monde leur héroïsme au service de la Réforme catholique. [less ▲]

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See detailHolocene paleoenvironmental reconstructions from speleothem and peat bog archives
Allan, Mohammed ULg; VERHEYDEN; CRUCIFIX, Michel et al

Poster (2016, January 28)

The geological materials (speleothems and peatbogs) presented in Belgium (Hautes-Fagnes Plateau, Ardennes caves) are interesting archives for atmospheric pollution record and climate variability. Both ... [more ▼]

The geological materials (speleothems and peatbogs) presented in Belgium (Hautes-Fagnes Plateau, Ardennes caves) are interesting archives for atmospheric pollution record and climate variability. Both archives are easily dated (U/Th and counting for laminated speleothems, 210Pb and 14C for peatbogs), have a high temporal resolution (decadal to seasonal), contain multiple measurable parameters (elemental geochemistry, stable isotopes, radiogenic Nd and Pb isotopes, pollens, rates of peat humification, luminescence and thickness of laminated speleothems) and depending on environmental conditions of temperature and / or humidity. The aim of this study is to determine the sensitivity of both archives (speleothems and peatbogs) to human perturbations and climate changes. Our ultimate goal is to contribute to a better understanding of natural interglacial climate variability by generating and confronting high resolution paleoclimate reconstructions from 2 continental archives. [less ▲]

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See detailTightening linearizations of non-linear binary optimization problems
Rodriguez Heck, Elisabeth ULg; Crama, Yves ULg

Conference (2016, January 28)

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See detailOptimisation and uncertainty: comparing stochastic and robust programming
Cuvelier, Thibaut ULg

Speech/Talk (2016)

Traditional optimisation tools focus on deterministic problems: scheduling airline flight crews (with as few employees as possible while still meeting legal constraints, such as maximum working time ... [more ▼]

Traditional optimisation tools focus on deterministic problems: scheduling airline flight crews (with as few employees as possible while still meeting legal constraints, such as maximum working time), finding the shortest path in a graph (used by navigation systems to give directions), etc. However, this deterministic hypothesis sometimes provides useless solutions: actual parameters cannot always be known to full precision, one reason being their randomness. For example, when scheduling trucks for freight transportation, if there is unexpected congestion on the roads, the deadlines might not be met, the company might be required to financially compensate for this delay, but also for the following deliveries that could not be made on schedule. Two main approaches are developed in the literature to take into account this uncertainty: make decision based on probability distributions of the uncertain parameters (stochastic programming) or considering they lie in a so-called ¿uncertainty set¿ (robust programming). In general, the first one leads to a large increase in the size of the problems to solve (and thus requires algorithms to work around this dimensionality curse), while the second is more conservative but tends to change the nature of the programs (which can impose a new solver technology). This talk compares the two approaches on three different cases: facility location, unit-commitment, and reservoir management. On the implementation side, multiple specific algorithms have been implemented to solve stochastic programs in order to compare their relative performance: Benders¿ decomposition, progressive hedging, and the deterministic equivalent. When comparing stochastic and robust programming, many differences appear in many aspects, even though the literature about those is very scarce. (Furthermore, those two approaches are not incompatible: both can be used in the same optimisation model to take into account different parts of the uncertainty.) Concerning solving time, stochastic programming quickly gives rise to intractable problems, which requires the development of more specific algorithm just to be able to solve them to an acceptable accuracy in decent time. What is more, the stochastic description of the uncertain values (with a discretisation of the probability distribution through scenarios) must cover all the possible uncertainty, otherwise the solution risks overfitting those scenarios, and is likely to have poor performance on close but different scenarios that may happen in practice ¿ which imposes to use a large number of scenarios, which yields very large (and hardly tractable) optimisation programs. On the other hand, by using specific uncertainty sets, robust programming yields programs that are only very slightly harder to solve, with an objective function that is very close to that of stochastic programming, but with totally different robustness properties: by using an uncertainty set computed from the scenarios, and not the scenarios themselves, it is able to withstand a much higher uncertainty than stochastic programming. However, when facing other types of uncertainty, this conclusion might turn untrue, with robust programming unable to cope with them and to bring interesting solutions to the table. [less ▲]

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See detailCombining acceleration techniques for pricing in a VRP with time windows
Michelini, Stefano ULg; Arda, Yasemin ULg; Küçükaydin, Hande

Conference (2016, January 28)

In this study, we investigate a solution methodology for a variant of the VRP with time windows. The cost of each route depends on its overall duration (including waiting times), while the departure time ... [more ▼]

In this study, we investigate a solution methodology for a variant of the VRP with time windows. The cost of each route depends on its overall duration (including waiting times), while the departure time of a vehicle is a decision variable. Furthermore, each route has a maximum permitted duration. In order to solve this problem with a branch-and-price methodology, we study also the associated pricing problem, an elementary shortest path problem with resource constraints (ESPPRC). Compared to the classical ESPPRC, this variant admits an infinite number of Pareto-optimal states. In order to tackle this, it was shown in [1] that it is possible to represent the total travelling time as a piecewise linear function of the service start time at the depot. Together with this representation, an appropriate label structure and domi- nance rules are proposed and integrated into an exact bidirectional dynamic programming algorithm [2]. It is possible to implement certain acceleration techniques in the dynamic program- ming algorithm used to solve the pricing problem. We focus on two of these techniques: decremental state space relaxation (DSSR), introduced in [3], and ng-route relaxation, in- troduced in [4] and [5]. DSSR aims to enforce gradually the constraints on the elementarity of the path, which adversely affect the number of generated and dominated labels. A set of critical nodes is iteratively populated, and elementarity is enforced only on these critical nodes. When using ng-route relaxation, a neighbourhood is defined for each vertex. Then, the labels are extended such that, thanks to this neighbourhood structure, it is possible to allow only cycles that are relatively expensive and therefore less likely to appear in the optimal solution. In this study, we explore several different strategies used to apply these techniques, for example initialization strategies for the critical vertex set in DSSR, or the size of the neighbourhoods for ng-route relaxation. We also analyze two ways of combining DSSR and ng-route relaxation. The different algorithmic choices are represented as categorical parameters. The categorical parameters, together with the numerical ones, can be tuned with tools for automatic algorithm configuration such as the irace package [6]. We discuss how this column generation procedure can be included as a component in the development of a matheuristic based on the idea in [7], which consists in a collaboration scheme between a branch-and-price algorithm, an exact MIP solver, and a metaheuristic. [less ▲]

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See detailGeoarchaeology of the Ancient Harbour of Utica in a Deltaic Context (2014 and 2015)
Pleuger, Elisa ULg; Gadhoum, Ahmed; Abichou, Hakim et al

Conference (2016, January 28)

Ancient authors mention Utica as a maritime and port city and estimate its origin around the 11th c. BC. However, in the present state of research, no archaeological evidence is earlier than the 9th c. BC ... [more ▼]

Ancient authors mention Utica as a maritime and port city and estimate its origin around the 11th c. BC. However, in the present state of research, no archaeological evidence is earlier than the 9th c. BC, and the location of the Phoenician and Roman port infrastructures remains unknown. Today, the ancient city is located on a promontory in the heart of the Medjerda delta, 10 km inland. Based on this observation, our geoarchaeological research focuses on two main issues: - Was there a marine environment around the promontory of Utica, which could shelter harbour structures? - Why the city, formerly a seaport city, is today located 10 km from the coast? Can the wadi be solely responsible of such an important sediment accumulation in a few millennia? Have any natural or anthropogenic factors influenced this deltaic progradation over the centuries? First results permitted drawing an hypothesis of the coastline during Antiquity to the effect that the Utica promontory was surrounded by the sea in an earlier era. (1) Effectively, the «North compartment» of the delta was covered by the sea at a given time, which will be determined by the next radiocarbon dating. But the sea still brushed the north side of the promontory during the Roman period, as evidenced by the potsherds found in one of the cores. This deep marine bay could be a potential location for harbour infrastructure prior to clogging of the bay by the sediments carried by the wadi. (2) The «corridor» area, materialised by the promontories of Utica and Kalâat el-Andalous, was also invaded by the sea at one time. The many artifacts found in this core attest the occupation of this area, outside of the maximal extension of the ancient city according to A. Lézine. Dating of the marine units in the two cores will bring essential data: * to establish the chronological framework of the retreat of the coastline and of the clogging of the bay; * to understand the passage of the Medjerda into the «North compartment» by the corridor Utica-Kalâat. The geoarchaeological results corroborate ancient sources. Utica was able to welcome important harbour structures, since the presence of a deep marine environment is attested around the promontory, but these remains are probably 5 m deep under the alluvium of the Wadi Medjerda. [less ▲]

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See detailLa violence de l’image. Débats autour de l’irreprésentable (G. Didi-Huberman/ J. Rancière)
Hagelstein, Maud ULg

Scientific conference (2016, January 28)

L’image peut être vectrice de débats politiquement complexes (tendus), notamment quand elle est porteuse de violence – quand elle montre/représente la violence. Or, on sait bien qu’au XXème siècle, il y a ... [more ▼]

L’image peut être vectrice de débats politiquement complexes (tendus), notamment quand elle est porteuse de violence – quand elle montre/représente la violence. Or, on sait bien qu’au XXème siècle, il y a un événement qui fait rupture de ce point de vue, en tant qu’il pousse la violence exercée par des hommes sur d’autres hommes à son paroxysme : la Shoah. Comme on peut l’observer dans toutes sortes de polémiques qui entourent la possibilité même de sa représentation (la littérature sur le sujet est vraiment très dense), la Shoah implique un rapport extrêmement difficile au document visuel, dont on a d’ailleurs longtemps pensé qu’il était pratiquement inexistant. « Il n’y a pas d’images de la Shoah » peut s’entendre de deux manières : soit qu’il n’y ait pas d’images effectives du processus d’extermination, soit que la possibilité même de représenter ce processus soit refusée par l’intensité de sa violence. La représentation visuelle de la Shoah pose problème. Non seulement la représentation imagée fictionnelle (cf. le cas récent du film Le fils de Saul de László Nemes – grand prix du jury au festival de Cannes), mais aussi, de manière plus étonnante encore peut-être, la représentation imagée documentaire. Autrement dit : même la diffusion de l’iconologie concentrationnaire, qui se réduit à presque rien puisque bon nombre de photographies ont été détruites par les nazis, soulève des réactions extrêmement vives. [less ▲]

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See detailEffets anthropiques sur les écosystèmes marins
Richir, Jonathan ULg; Grosjean, Philippe

Scientific conference (2016, January 28)

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