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See detailWASP-South transiting exoplanets: WASP-130b, WASP-131b, WASP-132b, WASP-139b, WASP-140b, WASP-141b & WASP-142b
Hellier, Coel; Anderson, D. R.; Collier Cameron, A. et al

in Monthly Notices of the Royal Astronomical Society (2017), 465

We describe seven new exoplanets transiting stars of V = 10.1 to 12.4. WASP-130b is a "warm Jupiter" having an orbital period of 11.6 d, the longest yet found by WASP. It transits a V = 11.1, G6 star with ... [more ▼]

We describe seven new exoplanets transiting stars of V = 10.1 to 12.4. WASP-130b is a "warm Jupiter" having an orbital period of 11.6 d, the longest yet found by WASP. It transits a V = 11.1, G6 star with [Fe/H] = +0.26. Warm Jupiters tend to have smaller radii than hot Jupiters, and WASP-130b is in line with this trend (1.23 Mjup; 0.89 Rjup). WASP-131b is a bloated Saturn-mass planet (0.27 Mjup; 1.22 Rjup). Its large scale height coupled with the V = 10.1 brightness of its host star make the planet a good target for atmospheric characterisation. WASP-132b is among the least irradiated and coolest of WASP planets, being in a 7.1-d orbit around a K4 star. It has a low mass and a modest radius (0.41 Mjup; 0.87 Rjup). The V = 12.4, [Fe/H] = +0.22 star shows a possible rotational modulation at 33 d. WASP-139b is the lowest-mass planet yet found by WASP, at 0.12 Mjup and 0.80 Rjup. It is a "super-Neptune" akin to HATS-7b and HATS-8b. It orbits a V = 12.4, [Fe/H] = +0.20, K0 star. The star appears to be anomalously dense, akin to HAT-P-11. WASP-140b is a 2.4-Mjup planet in a 2.2-d orbit that is both eccentric (e = 0.047) and with a grazing transit (b = 0.93) The timescale for tidal circularisation is likely to be the lowest of all known eccentric hot Jupiters. The planet's radius is large (1.4 Rjup), but uncertain owing to the grazing transit. The host star is a V = 11.1, [Fe/H] = +0.12, K0 dwarf showing a prominent 10.4-d rotational modulation. The dynamics of this system are worthy of further investigation. WASP-141b is a typical hot Jupiter, being a 2.7 Mjup, 1.2 Rjup planet in a 3.3-d orbit around a V = 12.4, [Fe/H] = +0.29, F9 star. WASP-142b is a typical bloated hot Jupiter (0.84 Mjup, 1.53 Rjup) in a 2.1-d orbit around a V = 12.3, [Fe/H] = +0.26, F8 star. [less ▲]

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See detailL'ocytocine et la biologie du coup de foudre
Geenen, Vincent ULg

Conference given outside the academic context (2017)

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See detailA new asteroseismic diagnostic for internal rotation in γ Doradus stars
Ouazzani, Rhita-Maria; Salmon, Sébastien ULg; Antoci, V. et al

in Monthly Notices of the Royal Astronomical Society (2017), 465

With four years of nearly-continuous photometry from Kepler, we are finally in a good position to apply asteroseismology to $\gamma$ Doradus stars. In particular several analyses have demonstrated the ... [more ▼]

With four years of nearly-continuous photometry from Kepler, we are finally in a good position to apply asteroseismology to $\gamma$ Doradus stars. In particular several analyses have demonstrated the possibility to detect non-uniform period spacings, which have been predicted to be directly related to rotation. In the present work, we define a new seismic diagnostic for rotation in $\gamma$ Doradus stars that are too rapidly rotating to present rotational splittings. Based on the non uniformity of their period spacings, we define the observable $\Sigma$ as the slope of the period spacing when plotted as a function of period. We provide a one-to-one relation between this observable $\Sigma$ and the internal rotation, which applies widely in the instability strip of $\gamma$ Doradus stars. We apply the diagnostic to a handful of stars observed by Kepler. Thanks to g-modes in $\gamma$ Doradus stars, we are now able to determine the internal rotation of stars on the lower main sequence, which is still not possible for Sun-like stars. [less ▲]

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See detailStrong XUV irradiation of the Earth-sized exoplanets orbiting the ultracool dwarf TRAPPIST-1
Wheatley, Peter J.; Louden, Tom; Bourrier, Vincent et al

in Monthly Notices of the Royal Astronomical Society (2017), 465

We present an XMM-Newton X-ray observation of TRAPPIST-1, which is an ultracool dwarf star recently discovered to host three transiting and temperate Earth-sized planets. We find the star is a relatively ... [more ▼]

We present an XMM-Newton X-ray observation of TRAPPIST-1, which is an ultracool dwarf star recently discovered to host three transiting and temperate Earth-sized planets. We find the star is a relatively strong and variable coronal X-ray source with an X-ray luminosity similar to that of the quiet Sun, despite its much lower bolometric luminosity. We find L_x/L_bol=2-4x10^-4, with the total XUV emission in the range L_xuv/L_bol=6-9x10^-4. Using a simple energy-limited model we show that the relatively close-in Earth-sized planets, which span the classical habitable zone of the star, are subject to sufficient X-ray and EUV irradiation to significantly alter their primary and perhaps secondary atmospheres. Understanding whether this high-energy irradiation makes the planets more or less habitable is a complex question, but our measured fluxes will be an important input to the necessary models of atmospheric evolution. [less ▲]

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See detailThe importance of open data and software: Is energy research lagging behind?
Pfenninger, Stefan; DeCariolis, Joseph; Hirth, Lion et al

in Energy Policy (2017)

Energy policy often builds on insights gained from quantitative energy models and their underlying data. As climate change mitigation and economic concerns drive a sustained transformation of the energy ... [more ▼]

Energy policy often builds on insights gained from quantitative energy models and their underlying data. As climate change mitigation and economic concerns drive a sustained transformation of the energy sector, transparent and well-founded analyses are more important than ever. We assert that models and their associated data must be openly available to facilitate higher quality science, greater productivity through less duplicated effort, and a more effective science-policy boundary. There are also valid reasons why data and code are not open: ethical and security concerns, unwanted exposure, additional workload, and institutional or personal inertia. Overall, energy policy research ostensibly lags behind other fields in promoting more open and reproducible science. We take stock of the status quo and propose actionable steps forward for the energy research community to ensure that it can better engage with decision-makers and continues to deliver robust policy advice in a transparent and reproducible way. [less ▲]

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See detailApproximate Bayes Optimal Policy Search using Neural Networks
Castronovo, Michaël ULg; François-Lavet, Vincent ULg; Fonteneau, Raphaël ULg et al

in Proceedings of the 9th International Conference on Agents and Artificial Intelligence (ICAART 2017) (2017, February)

Bayesian Reinforcement Learning (BRL) agents aim to maximise the expected collected rewards obtained when interacting with an unknown Markov Decision Process (MDP) while using some prior knowledge. State ... [more ▼]

Bayesian Reinforcement Learning (BRL) agents aim to maximise the expected collected rewards obtained when interacting with an unknown Markov Decision Process (MDP) while using some prior knowledge. State-of-the-art BRL agents rely on frequent updates of the belief on the MDP, as new observations of the environment are made. This offers theoretical guarantees to converge to an optimum, but is computationally intractable, even on small-scale problems. In this paper, we present a method that circumvents this issue by training a parametric policy able to recommend an action directly from raw observations. Artificial Neural Networks (ANNs) are used to represent this policy, and are trained on the trajectories sampled from the prior. The trained model is then used online, and is able to act on the real MDP at a very low computational cost. Our new algorithm shows strong empirical performance, on a wide range of test problems, and is robust to inaccuracies of the prior distribution. [less ▲]

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See detailVoyage[s] à travers le thymus
Geenen, Vincent ULg

in Science et Culture (2017), (465), 14-15

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See detailAn App-based Algorithmic Approach for Harvesting Local and Renewable Energy Using Electric Vehicles
Dubois, Antoine; Wehenkel, Antoine; Fonteneau, Raphaël ULg et al

in Proceedings of the 9th International Conference on Agents and Artificial Intelligence (ICAART 2017) (2017, February)

The emergence of electric vehicles (EVs), combined with the rise of renewable energy production capacities, will strongly impact the way electricity is produced, distributed and consumed in the very near ... [more ▼]

The emergence of electric vehicles (EVs), combined with the rise of renewable energy production capacities, will strongly impact the way electricity is produced, distributed and consumed in the very near future. This position paper focuses on the problem of optimizing charging strategies for a fleet of EVs in the context where a significant amount of electricity is generated by (distributed) renewable energy. It exposes how a mobile application may offer an efficient solution for addressing this problem. This app can play two main roles. Firstly, it would incite and help people to play a more active role in the energy sector by allowing photovoltaic (PV) panel owners to sell their electrical production directly to consumers, here the EVs’ agents. Secondly, it would help distribution system operators (DSOs) or transmission system operators (TSOs) to modulate more efficiently the load by allowing them to influence EV charging behaviour in real time. Finally, the present paper advocates for the introduction of a two-sided market-type model between EV drivers and electricity producers. [less ▲]

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See detailResidential heat pump as flexible load for direct control service with parametrized duration and rebound effect
Georges, Emeline ULg; Cornélusse, Bertrand ULg; Ernst, Damien ULg et al

in Applied Energy (2017), 187

This paper addresses the problem of an aggregator controlling residential heat pumps to offer a direct control flexibility service. The service consists of a power modulation, upward or downward, that is ... [more ▼]

This paper addresses the problem of an aggregator controlling residential heat pumps to offer a direct control flexibility service. The service consists of a power modulation, upward or downward, that is activated at a given time period over a fixed number of periods. The service modulation is relative to an optimized baseline that minimizes the energy costs. The load modulation is directly followed by a constrained rebound effect, consisting of a delay time with no deviations from the baseline consumption and a payback time to return to the baseline state. The potential amount of modulation and the constrained rebound effect are computed by solving mixed integer linear problems. Within these problems, the thermal behavior of the building is modeled by an equivalent thermal network made of resistances and lumped capacitances. Simulations are performed for different sets of buildings typical of the Belgian residential building stock and are presented in terms of achievable modulation amplitude, deviations from the baseline and associated costs. A cluster of one hundred ideal buildings, corresponding to retrofitted freestanding houses, is then chosen to investigate the influence of each parameter defined within the service. Results show that with a set of one hundred heat pumps, a load aggregator could expect to harvest mean modulation amplitudes of up to 138 kW for an upward modulation and up to 51 kW for a downward modulation. The obtained values strongly depend on the proposed flexibility service. For example, they can decrease down to 2.6 kW and 0.4 kW, respectively, if no rebound effect is allowed. [less ▲]

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See detailDépolution des sédiments d’une mangrove de l’estuaire du Wouri : évaluation du potentiel de microflores.
Semboung Lang, Firmin ULg

Doctoral thesis (2017)

L’importance des écosystèmes de mangroves n’est plus à démontrer dans l’équilibre naturel des côtes des régions tropicales. Elles constituent un écosystème particulier et jouent un rôle important dans la ... [more ▼]

L’importance des écosystèmes de mangroves n’est plus à démontrer dans l’équilibre naturel des côtes des régions tropicales. Elles constituent un écosystème particulier et jouent un rôle important dans la production de la biomasse. Mais l’exploitation excessive du bois des palétuviers, les pollutions diverses suite à l’exploitation pétrolière et gazière, sont autant de facteurs qui contribuent à la dégradation des forêts de mangroves. Ainsi, entre 1980 et 2000, environ 35% de la superficie mondiale des mangroves a disparu. La pollution a entraîné une dégradation considérable des mangroves. Une quantité grandissante de déchets résultant des activités urbaines, industrielles et agricoles et de l’exploitation en mer du pétrole et du gaz est rejetée sans aucun traitement dans la mer et se retrouve au niveau des mangroves. Les déversements accidentels d’hydrocarbures en mer entraînent une grave pollution des mangroves et la pollution marine provenant des navires est une menace qui va sans doute s’accroître avec le développement de l’exploitation pétrolière. L’objectif de cette thèse était de mettre au point une méthode de dépollution par voie biologique des sédiments de mangroves pollués par les hydrocarbures. Il s’agissait plus précisément d’évaluer les capacités intrinsèques de dégradation de la microflore spécifique endogène, de comparer le potentiel de dégradation de cette microflore avec d’autres souches pures connues pour leur capacité à dégrader les hydrocarbures et enfin d’évaluer les différentes techniques de biodégradation adaptées pour l’élimination des hydrocarbures dans les sédiments de mangroves. Des procédés biologiques adaptés ont été mis en œuvre au cours de ce travail pour restaurer les écosystèmes de mangroves. Différentes techniques de traitements biologiques impliquant la microflore spécifique endogène ont été mises en œuvre. L’évaluation du potentiel de dégradation de cette microflore a été réalisée par rapport à trois souches pures exogènes. Les résultats obtenus ont montré que le potentiel de dégradation de la microflore spécifique est comparable à celui de Rhodococcus erythropolis lorsqu’on augmente sa concentration dans les sédiments (107 CFU.g-1 de matière sèche). La croissance de cette microflore est accélérée avec la présence des nutriments tels l’azote et le phosphore. Ce qui relève davantage le taux de dégradation des hydrocarbures. Le taux de dégradation obtenu en combinant les traitements par bioaugmentation de la microflore spécifique endogène et biostimulation (86%) nous ont amené à proposer cette méthode pour dépolluer les sédiments de mangroves. L’utilisation de la microflore spécifique endogène évite de travailler avec des souches exogènes qui nous exposent aux problèmes écologiques et éthiques liés à leur utilisation. [less ▲]

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See detailUber-like Models for the Electrical Industry
Ernst, Damien ULg

Speech/Talk (2017)

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See detailPresent-day central African forest is a legacy of the 19th century human history
Morin, Julie ULg; Fayolle, Adeline ULg; Favier, Charly et al

in eLife (2017)

The populations of light-demanding trees that dominate the canopy of central African forests are now aging. Here, we show that the lack of regeneration of these populations began ca. 165 ya (around 1850 ... [more ▼]

The populations of light-demanding trees that dominate the canopy of central African forests are now aging. Here, we show that the lack of regeneration of these populations began ca. 165 ya (around 1850) after major anthropogenic disturbances ceased. Since 1885, less itinerancy and disturbance in the forest has occurred because the colonial administrations concentrated people and villages along the primary communication axes. Local populations formerly gardened the forest by creating scattered openings, which were sufficiently large for the establishment of light-demanding trees. Currently, common logging operations do not create suitable openings for the regeneration of these species, whereas deforestation degrades landscapes. Using an interdisciplinary approach, which included paleoecological, archaeological, historical, and dendrological data, we highlight the long-term history of human activities across central African forests and assess the contribution of these activities to present-day forest structure and composition. The conclusions of this sobering analysis present challenges to current silvicultural practices and to those of the future. [less ▲]

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See detailLeidenfrost effect at its limits
Maquet, Laurent ULg

Doctoral thesis (2017)

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See detailIs Büchi's theorem useful for you? (for an audience of logicians)
Rigo, Michel ULg

Conference (2017, January 17)

Almost a century ago, Presburger showed that the first order theory of the natural numbers with addition is decidable. Following the work of B\"uchi in 1960, this result still holds when adding a function ... [more ▼]

Almost a century ago, Presburger showed that the first order theory of the natural numbers with addition is decidable. Following the work of B\"uchi in 1960, this result still holds when adding a function $V_k$ to the structure, where $V_k(n)$ is the largest power of $k\ge 2$ diving $n$. In particular, this leads to a logical characterization of the $k$-automatic sequences. During the last few years, many applications of this result have been considered in combinatorics on words, mostly by J. Shallit and his coauthors. In this talk, we will present this theorem of B\"uchi where decidability relies on finite automata. Then we will review some results about automatic sequences or morphic words that can be proved automatically (i.e., the proof is carried on by an algorithm). Finally, we will sketch the limitation of this technique. With a single line formula, one can prove automatically that the Thue-Morse word has no overlap but, hopefully, not all the combinatorial properties of morphic words can be derived in this way. We will not assume any background in combinatorics on words from the audience. [less ▲]

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See detailLes institutions politiques belges
Grandjean, Geoffrey ULg

Learning material (2017)

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See detailPrésentation de cas cliniques
WANG, François-Charles ULg

Scientific conference (2017, January 16)

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See detailLandscape ecological consequences of the (sub)urbanization process in an African city: Lubumbashi (Democratic Republic of Congo)
Andre, Marie ULg

Doctoral thesis (2017)

If anthropogenic effect is a general term accounting for the influence of human activities on environment, it may also designate specific influences that may be inter- and intralinked. Thus, urbanization ... [more ▼]

If anthropogenic effect is a general term accounting for the influence of human activities on environment, it may also designate specific influences that may be inter- and intralinked. Thus, urbanization and suburbanization are anthropogenic processes contributing to the broad anthropogenic effect. They hide in turn other subprocesses of land transformation that will be called here the secondary spatial impacts. However, although the growing influence of the latter processes, they are still not defined consensually nor exist a comprehensive and applied-oriented methodology to delimit them. The general objective of this thesis is to develop a spatially explicit methodology to evaluate the landscape ecological consequences of the urbanization and suburbanization processes, taking a representative city of Sub-Saharan Africa as a case study: Lubumbashi (Democratic Republic of Congo), and the last decade as the period of study. That general objective is addressed through two themes, to which correspond specific objectives. The first theme concerns the evaluation of the anthropogenic land use and land cover dynamics and the second one proposes a methodology to evaluate the expansion of urban and suburban areas, in relation with consistent definitions of the areas in the urban-rural gradient. For both themes, the propositions are based on remote sensing techniques and landscape ecology metrics. Results show that the region of Lubumbashi underwent a global anthropisation increase mostly constituted of minor rises of anthropisation levels but impacting mainly the most natural landscape classes. Urban and suburban areas were located through the use of the proportion of built-up metric, the secondary spatial impact area through the use of adjacencies of the less natural landscape patches. The growth shape of the urban and suburban areas is concentric, except in the south-western part of the city where an affluent of the river Kafubu and its adjacent wetlands slow the urban expansion. The secondary spatial impact area dynamics seems determined, in the north-west, by the relief and, in the north-east, by a transportation axis. It is the latter dynamics that is dominant for the period. It corresponds to the so-called savanisation process, probably due to wood fuel and charcoal production. The methodologies developed here could be improved by taking connectedness into account, by using an additional configuration metric for the definition of urban areas or by taking advantage of spatially explicit socio-economic data. They could also be tested on mining sites, other cities and/or using images of different spatial resolution. [less ▲]

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