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See detailCompositional gap at La Picada (CSVZ, Chile) results from critical cristallinity and compaction
Vander Auwera, Jacqueline ULg; Namur, Olivier ULg; Coumont, Valentin et al

Poster (2017, August 16)

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See detailExergy analysis applied to performance of buildings in Europe
Sartor, Kevin ULg; Dewallef, Pierre ULg

in Energy and Buildings (2017), 148

Energy performance of buildings generally assesses the energy consumption of buildings such as heating, domestic heat water, ventilation systems, etc. However, this approach is based on the first law of ... [more ▼]

Energy performance of buildings generally assesses the energy consumption of buildings such as heating, domestic heat water, ventilation systems, etc. However, this approach is based on the first law of thermodynamics and considers only the quantity of energy used without considering its ‘quality’ and leads to a lack of information about the energy conversion processes. This is particularly true in the new low-energy buildings where sometimes high temperatures sources are used to meet low-temperature needs. The exergy analysis of a system, based on first and second thermodynamic laws, can be used to overcome this. In this work, it is proposed to compare the energy and the exergy consumption and the related CO2 emissions of several kinds of buildings to determine the best systems in terms of energy and exergy needs. The energy demand calculations are performed using the official software available in Belgium and some assumptions are implemented to consider the exergy approach. As exergy calculations require a reference state, some different climatic conditions are also investigated. Finally, some conclusions are discussed to rank the sources of energy and their related exergy losses. [less ▲]

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See detailAssessing quality of life using structural equation modeling
Dardenne, Nadia ULg; Pétré, Benoît ULg; Husson, Eddy ULg et al

Poster (2017, August)

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See detailEarly eukaryotes: insights from microanalyses of proterozoic microfossils
Cornet, Yohan ULg; Beghin, Jérémie ULg; Kabamba Baludikay, Blaise ULg et al

in Goldschmidt Abstracts, 2017 (2017, August)

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See detailAn efficient algorithm to decide periodicity of b-recognisable sets using MSDF convention
Boigelot, Bernard ULg; Mainz, Isabelle ULg; Marsault, Victor ULg et al

in Leibniz International Proceedings in Informatics (2017, August), 80

Given an integer base b>1, a set of integers is represented in base b by a language over {0,1,...,b-1}. The set is said to be b-recognisable if its representation is a regular language. It is known that ... [more ▼]

Given an integer base b>1, a set of integers is represented in base b by a language over {0,1,...,b-1}. The set is said to be b-recognisable if its representation is a regular language. It is known that eventually periodic sets are b-recognisable in every base b, and Cobham's theorem implies the converse: no other set is b-recognisable in every base b. We are interested in deciding whether a $b$-recognisable set of integers (given as a finite automaton) is eventually periodic. Honkala showed that this problem is decidable in 1986 and recent developments give efficient decision algorithms. However, they only work when the integers are written with the least significant digit first. In this work, we consider the natural order of digits (Most Significant Digit First) and give a quasi-linear algorithm to solve the problem in this case. [less ▲]

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See detailNETPerfTrace – Predicting Internet Path Dynamics and Performance with Machine Learning
Wassermann, Sarah ULg; Casas, Pedro; Cuvelier, Thibaut ULg et al

in Proceedings of Big-DAMA ’17 (2017, August)

We study the problem of predicting Internet path changes and path performance using traceroute measurements and machine learning models. Path changes are frequently linked to path inflation and ... [more ▼]

We study the problem of predicting Internet path changes and path performance using traceroute measurements and machine learning models. Path changes are frequently linked to path inflation and performance degradation, therefore the relevance of the problem. We introduce NETPerfTrace, an Internet Path Tracking system to forecast path changes and path latency variations. By relying on decision trees and using empirical distribution-based input features, we show that NETPerfTrace can predict (i) the remaining life time of a path before it actually changes and (ii) the number of path changes in a certain time period with relatively high accuracy. Through extensive evaluation, we demonstrate that NETPerfTrace highly outperforms DTRACK, a previous system with the same prediction targets. NETPerfTrace also offers path performance forecasting capabilities. In particular, our tool can predict path latency metrics, providing a system which can not only predict path changes, but also forecast their impact in terms of performance variations. We release NETPerfTrace as open software to the networking community, as well as all evaluation datasets. [less ▲]

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See detailForeseeing New Control Challenges in Electricity Prosumer Communities
Olivier, Frédéric ULg; Marulli, Daniele; Ernst, Damien ULg et al

in Proc. of the 10th Bulk Power Systems Dynamics and Control Symposium – IREP’2017 (2017, August)

This paper is dedicated to electricity prosumer communities, which are groups of people producing, sharing and consuming electricity locally. This paper focuses on building a rigorous mathematical ... [more ▼]

This paper is dedicated to electricity prosumer communities, which are groups of people producing, sharing and consuming electricity locally. This paper focuses on building a rigorous mathematical framework in order to formalise sequen- tial decision making problems that may soon be encountered within electricity prosumer communities. After introducing our formalism, we propose a set of optimisation problems reflecting several types of theoretically optimal behaviours for energy exchanges between prosumers. We then discuss the advantages and disadvantages of centralised and decentralised schemes and provide illustrations of decision making strategies, allowing a prosumer community to generate more distributed electricity (compared to commonly applied strategies) by mitigating over- voltages over a low-voltage feeder. We finally investigate how to design distributed control schemes that may contribute reaching (at least partially) the objectives of the community, by resort in to machine learning techniques to extract, from centralised solution(s), decision making patterns to be applied locally. First empirical results show that, even after a post-processing phase so that it satisfies physical constraints, the learning approach still performs better than predetermined strategies targeting safety first, then cost minimisation. [less ▲]

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See detailRhétorique du détournement vidéoludique. Le cas de Pokémon
Barnabé, Fanny ULg

Doctoral thesis (2017)

La présente recherche se situe au croisement de plusieurs traditions disciplinaires – les sciences du jeu, les études littéraires, la rhétorique, les cultural studies – et de plusieurs objets – le jeu, le ... [more ▼]

La présente recherche se situe au croisement de plusieurs traditions disciplinaires – les sciences du jeu, les études littéraires, la rhétorique, les cultural studies – et de plusieurs objets – le jeu, le détournement, les fanfictions, machinimas, speedruns, let’s plays et mods. Sans prétendre opérer ici leur synthèse ou leur conciliation, nous tenterons de dégager, entre ces différents domaines, de nouvelles ouvertures : nous montrerons, en circulant parmi eux, qu’ils sont pris dans des tensions, des dynamiques, des questionnements similaires et, surtout, centraux pour la compréhension de la culture populaire contemporaine. Plusieurs objectifs nous animent : définir le détournement et, à travers lui, éclairer sous un autre jour le fonctionnement du jeu ; développer un métadiscours à même de soutenir l’analyse des œuvres produites par les joueurs ; enfin, par la même occasion, défendre l’intérêt d’étudier de près ces œuvres amateurs, trop souvent délaissées par la recherche au profit des pratiques, et qui sont pourtant des épicentres essentiels autour desquels se développent les cultures ludiques. La poursuite de ces objectifs, toutefois, ne va pas sans soulever des questions complexes, qui traversent toute la thèse : quels parallèles et quelle frontière établir entre le détournement et le jeu ? Comment une œuvre est-elle reconnue, étiquetée, classée comme un détournement ? Qu’est-ce au juste qu’une œuvre dans un domaine où l’intertextualité, la reprise, la réinterprétation sont des normes ? Avec quels outils décrire les formes du détournement, et qu’ont en commun les genres disparates regroupés sous cette dénomination ? Nous traiterons ces diverses interrogations en deux temps. La première partie de la thèse, qui comporte deux sous-sections, en constituera le socle théorique : un premier chapitre y aborde les relations intimes entre jeu et détournement, tout en resituant notre recherche dans les différents champs qu’elle fait se croiser ; le second chapitre s’attache à la constitution d’un cadre métadiscursif inspiré de la rhétorique, visant à définir ce que pourraient être des « figures » du détournement vidéoludique. La deuxième partie, plus analytique, servira d’application au cadre précédemment construit, en montrant son utilité sur des études d’œuvres concrètes. Celles-ci sont réparties en trois grandes catégories : les détournements par le play (let’s plays, speedruns, tool-assisted speedruns et machinimas), les détournements du game (fanfictions et mods) et les recontextualisations (« Twitch plays… »). Par ailleurs, en guise de fil conducteur, toutes ces œuvres – de formes et de genres variés – auront pour point commun essentiel d’être dérivées d’un même univers fictionnel : celui de la licence Pokémon. [less ▲]

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See detailProbing the atmosphere of a sub-Jovian planet orbiting a cool dwarf
Sedaghati, Elyar; Boffin, Henri M. J.; Delrez, Laetitia et al

in Monthly Notices of the Royal Astronomical Society (2017), 468

We derive the 0.01 $\mu$m binned transmission spectrum, between 0.74 and 1.0 $\mu$m, of WASP-80b from low resolution spectra obtained with the FORS2 instrument attached to ESO's Very Large Telescope. The ... [more ▼]

We derive the 0.01 $\mu$m binned transmission spectrum, between 0.74 and 1.0 $\mu$m, of WASP-80b from low resolution spectra obtained with the FORS2 instrument attached to ESO's Very Large Telescope. The combination of the fact that WASP-80 is an active star, together with instrumental and telluric factors, introduces correlated noise in the observed transit light curves, which we treat quantitatively using Gaussian Processes. Comparison of our results together with those from previous studies, to theoretically calculated models reveals an equilibrium temperature in agreement with the previously measured value of 825K, and a sub-solar metallicity, as well as an atmosphere depleted of molecular species with absorption bands in the IR ($\gg 5\sigma$). Our transmission spectrum alone shows evidence for additional absorption from the potassium core and wing, whereby its presence is detected from analysis of narrow 0.003 $\mu$m bin light curves ($\gg 5\sigma$). Further observations with visible and near-UV filters will be required to expand this spectrum and provide more in-depth knowledge of the atmosphere. These detections are only made possible through an instrument-dependent baseline model and a careful analysis of systematics in the data. [less ▲]

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See detailA Receding Horizon Approach to Incorporate Frequency Support into the AC/DC Converters of a Multi-Terminal DC Grid
Papangelis, Lampros ULg; Panciatici, Patrick; Debry, Marie-Sophie et al

in Electric Power Systems Research (2017)

This paper proposes a novel control scheme for provision of frequency support among asynchronous AC areas through HVDC grids. It is based on local controllers, each acting on a voltage source converter ... [more ▼]

This paper proposes a novel control scheme for provision of frequency support among asynchronous AC areas through HVDC grids. It is based on local controllers, each acting on a voltage source converter, using local measurements only, and supporting frequency of the adjacent AC area after a significant disturbance. The new discrete control is combined with the existing DC voltage droop technique. The formulation, inspired of Receding Horizon Control, enables providing to the AC area the desired frequency support, while at the same time taking into account various constraints, such as maintaining the DC voltage between secure operating limits. Examples obtained from a test system with a five-terminal DC network connecting two asynchronous areas demonstrate the effectiveness and robustness of the proposed control scheme in various scenarios, with emphasis on component failures. [less ▲]

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See detailReinforcement Learning for Electric Power System Decision and Control: Past Considerations and Perspectives
Glavic, Mevludin ULg; Fonteneau, Raphaël ULg; Ernst, Damien ULg

in The 20th World Congress of the International Federation of Automatic Control, Toulouse 9-14 July 2017 (2017, July)

In this paper, we review past (including very recent) research considerations in using reinforcement learning (RL) to solve electric power system decision and control problems. The RL considerations are ... [more ▼]

In this paper, we review past (including very recent) research considerations in using reinforcement learning (RL) to solve electric power system decision and control problems. The RL considerations are reviewed in terms of speci c electric power system problems, type of control and RL method used. We also provide observations about past considerations based on a comprehensive review of available publications. The review reveals the RL is considered as viable solutions to many decision and control problems across di erent time scales and electric power system states. Furthermore, we analyse the perspectives of RL approaches in light of the emergence of new-generation, communications, and instrumentation technologies currently in use, or available for future use, in power systems. The perspectives are also analysed in terms of recent breakthroughs in RL algorithms (Safe RL, Deep RL and path integral control for RL) and other, not previously considered, problems for RL considerations (most notably restorative, emergency controls together with so-called system integrity protection schemes, fusion with existing robust controls, and combining preventive and emergency control). [less ▲]

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See detailFreeplay-induced limit cycle oscillation mitigation using linear and nonlinear tuned vibration absorbers
Verstraelen, Edouard ULg; Kerschen, Gaëtan ULg; Dimitriadis, Grigorios ULg

in Proceeding of the IFASD 2017 Conference (2017, July)

Structural nonlinearities such as freeplay in control surface bearings and actuators or in connections between wings and external payloads sometimes lead to aeroelastic limit cycle oscillations at ... [more ▼]

Structural nonlinearities such as freeplay in control surface bearings and actuators or in connections between wings and external payloads sometimes lead to aeroelastic limit cycle oscillations at airspeeds lower than the linear flutter speed of the aircraft. In parallel, numerous studies demonstrated the potential of linear and nonlinear tuned vibration absorbers to increase the flutter speed of linear and continuously hardening aeroelastic systems such as two-degree- of-freedom wings or long span bridges. In this work, the effect of linear and nonlinear tuned vibration absorbers is studied on a wing with pitch plunge and control surface deflection degrees of freedom and with freeplay in pitch. Depending on the tuning of the linear absorber, the linear flutter speed of the system can be increased by 10% or the onset of limit cycle oscillations due to the freeplay can be delayed by 7.7% and their amplitude can be significantly decreased. The addition of cubic hardening forces on the absorber can further decrease the limit cycle amplitude in a limited airspeed range at the cost of an increase in limit cycle amplitude in another airspeed range. Conversely, the addition of a freeplay hardening force on the absorber can decrease the limit cycle amplitude without any detrimental effect. [less ▲]

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See detailcopycat: Testing Differential Treatment of New Transport Protocols in the Wild
Edeline, Korian ULg; Kühlewind, Mirja; Trammell, Brian et al

in Applied Networking Research Workshop (2017, July)

Recent years have seen the development of multiple transport solutions to address the ossification of TCP in the Internet, and to ease transport-layer extensibility and deployability. Recent approaches ... [more ▼]

Recent years have seen the development of multiple transport solutions to address the ossification of TCP in the Internet, and to ease transport-layer extensibility and deployability. Recent approaches, such as PLUS and Google's QUIC, introduce an upper transport layer atop UDP; their deployment therefore relies on UDP not being disadvantaged with respect to TCP by the Internet. This paper introduces copycat, a generic transport protocol testing tool that highlights differential treatment by the path in terms of connectivity and QoS between TCP and a non-TCP transport protocol. copycat generates TCP-shaped traffic with custom headers, and compares its performance in terms of loss and delay with TCP. We present a proof-of-concept case study (UDP vs. TCP) in order to answer questions about the deployability of current transport evolution approaches, and demonstrate the extent of copycat's capabilities and possible applications. While the vast majority of UDP impairments are found to be access-network linked, and subtle impairment is rare, middleboxes might adapt to new protocols that would then perform differently in the wild compared to early deployments or controlled environment testing. [less ▲]

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See detailWEATHERING ON THE DEVONIAN SLATES AND CHARACTERIZATION OF A BENTONITE LAYER IN THE WESTERWALD (GERMANY)
Fontaine, François ULg; Hamaekers, Helen; Hoffmann, Andreas et al

Conference (2017, July)

The Westerwald region is one of the largest and oldest clay mining areas of Germany. Those deposits were formed during the Eocene and Oligocene as a result of the weathering, erosion and redeposition of ... [more ▼]

The Westerwald region is one of the largest and oldest clay mining areas of Germany. Those deposits were formed during the Eocene and Oligocene as a result of the weathering, erosion and redeposition of Devonian rocks. During the Miocene, intense volcanic activities led to a large basalt cover, protecting the clays from the erosion. The two main goals of this study are first to improve the knowledge on the weathering processes of the Devonian slates that led to the current setting of those clay deposits by studying the mineralogical and chemical composition of the clays with depth. The second goal is to characterize a bentonite layer underneath the Miocene basalt cover using quantitative X-ray diffraction, chemical analysis, BET, cation exchange capacity and scanning electron microscope. A 20 meter deep quarry mining the Devonian bedrock in southern Westerwald has been sampled on its entire depth. The XRD results show no significant variations of the mineralogy with depth, except for the phyllosilicates. The minerals of the < 2 μm fraction are illite, kaolinite, smectite and mixed-layers minerals (vermiculite-chlorite and illite-chlorite). The proportions of the minerals in the mixed-layers chlorite-vermiculite vary with depth. At the bottom of the quarry, the proportion of vermiculite is very low while in the top, the proportion of vermiculite is higher. This is explained by the degree of the weathering, logically more intense at the top of the quarry. Trace elements compositions are currently being investigated. A 3 meter thick greenish to brownish bentonite layer has been found in the eastern part of the Westerwald region. The XRD performed on different samples of this bentonite shows a relatively heterogeneous composition: montmorillonite (60-80%), kaolinite (5-12%), illite (0-7%), goethite (2-15%), talc (0-10%), K-feldspars (0-7%), plagioclase (0-4%) and traces of amphibole and pyroxene. This bentonite is probably the result of the weathering of volcanic ashes. Since there are not many outcrops of this bentonite layer, its spatial distribution is studied by drilling. [less ▲]

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See detailStable isotopes reveal effects of environmental changes on ecological niches of Iphimediidae amphipods
Michel, Loïc ULg; d'Udekem d'Acoz, Cédric; Frederich, Bruno ULg et al

Poster (2017, July)

When faced with environmental changes, organisms are expected to have some intrinsic ability to adapt through ecological plasticity. However, this process is still poorly understood in many Antarctic ... [more ▼]

When faced with environmental changes, organisms are expected to have some intrinsic ability to adapt through ecological plasticity. However, this process is still poorly understood in many Antarctic invertebrates. Here, we focused on Iphimediidae amphipods, as this widely distributed family shows important ecological diversity. In total, 248 amphipods (19 species) from two widely different zones (the West Antarctic Peninsula, or WAP, and Adélie Land, AL) were studied to elucidate how environment can influence ecological niche parameters. Ecological niches were explored using stable isotope ratios of carbon and nitrogen and the SIBER approach (Jackson et al., 2011). The isotopic niche of the whole amphipod assemblage was wider in WAP than in AL. This was true for both total (proxy of the whole range of resources exploited by animals) and the core (proxy of the most commonly used resources) isotopic niches. The ratio between total and core isotopic niches was smaller in WAP than in AL (4.13 vs. 5.74), suggesting that in WAP, animals commonly use a greater relative percentage of the resources to which they have access. Niche modelling at the specific level revealed that this trend was not found in all taxa. For example, niches of Gnathiphimedia sexdentata and Iphimediella microdentata were bigger in WAP than in AL, following the general pattern. On the other hand, niches of Echiniphimedia echinata and E. hodgsoni had the same width in both areas. Moreover, relative niche overlap between these two species was much higher in WAP (42%) than in AL (20%). Our results indicate that the widely different environmental conditions encountered by the animals in these two zones clearly influence their ecology. Overall, Iphimediidae amphipods tend to exploit more resources in WAP, i.e. in the zone where impacts of global change (temperature increase, sea ice cover decrease) are the strongest. Niche overlap between some closely related (i.e. congeneric) species was also more important in WAP. Ultimately, environmental changes in this region might reinforce these trends, which might lead to competition and perturb amphipod community structure. This research was funded by the Belgian Federal Science Policy Office (BELSPO) in the framework of the vERSO and RECTO projects. [less ▲]

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See detailPlant traits variability within and among populations in the context of calcareous grassland restoration
Harzé, Mélanie ULg

Doctoral thesis (2017)

In Western Europe, abandonment of traditional forms of agriculture has caused the fragmentation of semi-natural grasslands, affecting ecosystems functioning as well as population survival. Habitat ... [more ▼]

In Western Europe, abandonment of traditional forms of agriculture has caused the fragmentation of semi-natural grasslands, affecting ecosystems functioning as well as population survival. Habitat restoration has become a crucial aspect of grasslands conservation, and one of the main issues is evaluating restoration success and setting appropriate criteria to do so. Indicators used to judge whether a restoration has been successful may concern a wide range of organisms. They may be defined at different geographical scales and may concern various levels of biodiversity organization. Among them, population parameters are less represented despite their usefulness. To consider restoration as a success, restored populations of targeted species should demonstrably possess characteristics allowing their dispersal, reproduction, growth and adaptation to the environment. In this thesis, the use of plant population parameters for evaluating grassland restoration was assessed based on a literature review. Then, the success of calcareous grassland restoration was determined regarding colonization of restored grasslands by five calcareous grasslands species; Helianthemum nummularium, Hippocrepis comosa, Potentilla tabernaemontani, Sanguisorba minor and Scabiosa columbaria. Population establishment and intra-specific functional trait variability in response to the environment were observed and compared among restored and reference populations of those species, through field inventories and in-situ traits measurements in calcareous grasslands of south Belgium. Moreover, a glasshouse experiment was set-up with the aim to evaluate the intra-specific variability in response to drought stress in reference populations of P. tabernaemontani. The results indicated that population parameters were less well studied for evaluating grassland restoration success compared to indicators related to ecosystems and communities. The population parameters used to assess the success of calcareous grassland restoration showed that the study species colonized restored sites and established new populations. The fitness of the restored populations was very high. High intra-specific trait variability was highlighted at a very local scale in the reference habitat. Individuals exhibited high leaf dry matter content (LDMC), low specific leaf area (SLA) and low vegetative height in relation to low soil depth and high potential incident radiation (PDIR). These environmental variables are possibly linked to the availability of soil moisture. Further, the relationship between traits and environmental variables was not always consistent in restored sites. However, the intra-specific variability of plant traits was similar in the reference and restored grasslands. Finally, the findings from the glasshouse experiment suggested that individuals originating from drier parts of calcareous grasslands better survive drought stress.   The overall conclusion of this thesis is rather optimistic concerning restored populations of the five specialist plant species studied, specifically regarding their colonization, persistence and response to the environment or to potential climate change. The conclusions must, however, be modified depending on the reference ecosystem used as a model. This approach has to be integrated into a multi-scales and a multi-species approach to fully evaluate restoration outputs. Yet, this thesis has contributed to the understanding of population responsiveness to habitat restoration, as well as to the evaluation of restoration success of calcareous grasslands in Belgium. [less ▲]

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