Journal of Next-Generation Research 5.0
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A database for spatial variability assessment of mechanical parameters of Ozigo specie under long-term bending tests in Gabon
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RISQUES PROFESSIONNELS ET RÉGULATION COMPORTEMENTALE CHEZ LES ÉLECTRICIENS TST ET HTA
No full textLa présente recherche a été menée chez les électriciens travaillant en haute tension ampère (HTA) et en sous tension (TST) à la société d'énergie et d'eau du Gabon. Lesdits électriciens courent, quotidiennement, des risques professionnels. Ils font une régulation comportementale pour braver les risques encourus
Subduction dynamics beneath the Eastern Mediterranean: tectonic, metamorphic and thermal consequences from Cretaceous to Present
No full textInternational audienceSlab dynamics (i.e. rollback and tearing) below the Eastern Mediterranean area is well imaged by numerous mantle tomography studies elucidating deep mantle structures. It induces asthenospheric mantle flow that had first order tectonic and metamorphic consequences in the overriding plate. However, there is no consensus about the time-space evolution, the deformation and the thermal consequences of such dynamics. We combine these information (i.e. mantle tomography) to high-resolution laser 40Ar-39Ar dating of micas, U-Pb dating of monazite, RSCM Tmax data and regional-scale kinematic-structural data in the Menderes Massif and in the Eastern Aegean islands, which have been little studied. This study then shed light on a common regional tectono-metamorphic evolution from Cretaceous to Present. In particular, we demonstrate the existence of different nappes which recorded different high-pressure and low-temperature conditions in the studied area: (i) the Upper Cycladic Blueschist Nappe (exclud-ing the Vourliotes Nappe in Samos) characterized by eclogite paragenese and (ii) the Lower Cycladic Blueschist Nappe (e.g. Amorgos, a part of the Dodecanese and Fourni islands) and the colder units of the upper Menderes Complex (i.e. the Kurudere-Nebiler units) witnessing blueschist metamorphism. A part of these units was partly obliterated by the Eocene Barrovian-type metamorphism overprint associated with collision and crustal stacking events in western Turkey. This event was mainly exhumed along the topS syn-orogenic extensional Selimiye shear zone during the Eocene (47 to 33 Ma, 40Ar/39Ar on micas). Then, a second high-temperature low-pressure meta-morphic event (with local anatexis) associated with post-orogenic extension induced by slab dynamics (i.e. tearing and slab retreat) occurred during the Oligo-Miocene. Our geochronological investigations reveal the formation of a large thermal pulse contemporaneous with the exhumation of the Menderes metamorphic core complex (MCC) and other MCCs in Cyclades. This latter is also exploited for geothermal production today, particularly in the Menderes Massif. In details, we suggest that crustal-scale low-angle normal faults convey hot fluids to the surface and represent the first-order control on geothermal systems. In addition, our study of the Eastern Aegean islands, allows us to complete the description of the extensional strain field in the overriding plate around the Miocene slab tear and retreat. Extensional tectonics keeps a constant NNE-SSW direction, without localized crustal-scale strike-slip faults and block rotations above the tear. Such dynamics are also consistent with numerical modelling, suggesting that, when slab tearing occurs, Moho temperatures can temporarily increase by up to 250 • C due to shear heating controlled by the fast-flow of the uppermost mantle. At the scale of MCCs, the bulk fluid flow pattern is controlled by topography-driven flow while buoyancy-driven flow dominates within the permeable detachments, focusing reservoir location of high-energy geothermal systems at shallow depth beneath detachments
Learn2Clean: Optimizing the Sequence of Tasks for Web Data Preparation
No full textInternational audienceIn many applications, data mining and machine learning methods are extensively used to analyze Web data and dis- cover actionable knowledge. But, “dirty data” is a chronic plague that causes incorrect results, misleading conclusions, generally followed by inadequate decisions. To ensure the validity of output results, avoid bias or data snooping, it is necessary to control not only the whole Web data analytics pipeline, but most importantly the quality of Web data with appropriate data preparation and curation choices. For a given dataset and a given machine leaning model, a plethora of data preprocessing techniques and alternative data cleaning strategies may lead to dramatically different outputs with unequal quality performance. It is then crucial to rely on a principled method to select the sequence of data preprocessing steps that can lead to the optimal quality performance. In this paper, we propose Learn2Clean, a method based on Q-Learning, a model-free reinforcement learning technique that selects, for a given dataset, a ML model, and a quality performance metric, the optimal sequence of tasks for preprocessing the data such that the quality of the ML model result is maximized. As a preliminary validation of our approach in the context of Web data analytics, we present some promising results on data preparation for clustering, regression, and classification on real-world data
Tracking groundwater signature in the stream to characterize flow and denitrification in the aquifer
No full textInternational audiencePredicting the evolution of nitrate pollution at the catchment scale implies a global evaluation of residence timesand denitrification rates in the aquifer. Data acquired in wells only result from processes occurring in their capturezone and are rarely representative of the whole aquifer [1]. Stream data, on the opposite, integrate the processesoccurring along all contributing groundwater flowpaths and thus could be more relevant for upscaling. But streamsignal is also controlled by soil, hyporheic zone and in-stream processes. Here we investigate the possibility ofextracting groundwater signature from such a complex stream signal.In-stream spatially-distributed measurements were performed during low flow over a 35 km2 crystallineagricultural catchment in Brittany, Western France. Groundwater inputs into the streams were localized andquantified using radon mass balance. In conjunction with radon, dissolved gases (O2, CO2, N2, N2O, CH4, Ar),wet chemistry and nitrate isotopes were measured at each site. Quantification of in-stream processes was furtherrealized by performing tracer injections in three selected reaches. Injections were coupled with continuous in-situmeasurement of dissolved gases using membrane inlet mass spectrometry (MIMS). Helium injections allowedto calculate gas exchange rates, while nutrient injections (acetate, nitrate) allowed to characterize in-streambiological activity (oxygenic respiration, denitrification).Radon mapping reveals a high localization degree of groundwater inputs into the streams. Groundwatersurfacewater exchanges are strongly concentrated after a major topographic slope that separates two geologicalunits, showing that geomorphology is a major control of hydrogeological circulations. These results are consistentwith a 3D-groundwater flow model of the catchment calibrated with age tracer data acquired in wells [1]. Close togroundwater input zones, stream chemistry is strongly impacted by groundwater signature. Helium and nutrientinjections evidence that gas exchanges between stream and atmosphere constitute the main eraser of groundwatersignature as water is flowing dowstream. Groundwater signature is lost specifically at highly turbulent sites, suchas small cascades, where measured gas exchange rates are one to two orders of magnitude higher than in calmreaches.[1] Kolbe, T., J. Marcais, Z. Thomas, B. W. Abbott, J. R. de Dreuzy, P. Rousseau-Gueutin, L. Aquilina,T. Labasque & G. Pinay, 2016. Coupling 3D groundwater modeling with CFC-based age dating to classifylocal groundwater circulation in an unconfined crystalline aquifer. Journal of Hydrology 543:31-46doi:10.1016/j.jhydrol.2016.05.020
Andresote, le dessein d'un esclave rebelle: Venezuela (1730-1733)
No full textInternational audienceLe présent ouvrage est une étude sur la résistance des afro-vénézuéliens ; elle tâchera de reconstruire la logique de contre-pouvoir du Zambo Andresote, qui, entre 1730 et 1733, lutta non pas contre les esclavagistes, ni, directement du moins, contre les planteurs de cacao ou de tabac, mais contre le monopole colonial et en faveur de la liberté du commerce, position particulièrement en avance pour son temps qui menaçait gravement le contrôle économique exercé par la Compagnie Royale de Guipuzcoa. Dans la longue durée du marronnage, l'action de Juan Andrés Lopez del Rosario prit une orientation qui mérite examen.La documentation envoyée à Madrid au sujet du personnage déposée pour l'essentiel aux Archives Générales des Indes, est entièrement à charge comme il se devait. Même le philosophe éclairé qu'était l'Abbé Raynal, soucieux d’œuvrer contre la politique coloniale, s'y est laissé prendre. Et que dire de certains historiens vénézuéliens jusqu'à une époque assez récente ! Dans ce cas plus que dans d'autres, il conviendra de peser chaque mot pour redonner la parole à un esclave rebelle et à ses gens, bâillonnés par l'histoire officielle
CJUE, (3ème ch.), 23 janvier 2019, aff. C-430/17, Walbusch Walter Busch GmbH:
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Appui au Zonage agricole dans la Région administrative du Centre Cameroun
No full textInternational audienceLa Région administrative du Centre du Cameroun apparaît très urbanisée, du fait de sa position centrale et des institutions qu’elle abrite. Avec une population urbaine qui représente 53% de sa population totale, elle constitue avec la région administrative du Littoral les territoires les plus urbanisés du Cameroun. Cette urbanisation a provoqué une transformation de la forêt originelle en d’autres formes d’utilisation. Dans un tel contexte, l’urgence de procéder à un zonage précis des terres à partir de la ville de Yaoundé et dans les autres villes des départements et communes environnants devient un impératif. L’objectif de cette recherche est de réaliser un zonage agricole expérimental dans cette région. Le zonage est la répartition d’un territoire en zones affectées chacune à un genre déterminé d’occupation des sols. Il prend en compte, outre les contraintes (érosion, dégradation de sols, zones déboisées, urbanisation, etc.) ; la perception des acteurs locaux, les unités biophysiques et agronomiques homogènes suivant les techniques de classification. La démarche méthodologique a consisté en l’acquisition et à la digitalisation des images de très hautes résolutions. Des images SPOT et Landsat ont été classifiées à l’aide du logiciel Erdas imagine®, avec comme algorithme le maximum de vraisemblance. Les données de statistiques agricoles ont été collectées et analysées en dépit des carences y relatives. Une analyse diachronique de la dynamique spatiale de la région entre 1956 et 2017 a été réalisée à partir des images Landsat. Il en est de même d’une carte de la dégradation de sols. Les résultats montrent que l’expansion urbaine autour de Yaoundé est remarquable, la dégradation de la forêt y est effective confortant l’hypothèse selon laquelle, l’urbanisation de Yaoundé et ses environs constitue le moteur essentiel de la déforestation. L’agriculture vivrière et de rente s’est intensifiée avec l’urbanisation, dans certains bassins : Awaé, Lékié et grand Mbam. Il est aujourd’hui impératif de procéder au zonage pour affecter à chaque activité un espace approprié afin d’optimiser la productivité. En outre, le zonage proposé permettra une meilleure gouvernance et gestion des terres. A la question du zonage se double celle de la planification urbaine et de son application
On the Rapid Weakening of Very Intense Tropical Cyclone Hellen (2014)
No full textInternational audienceIn late March 2014, very intense Tropical Cyclone Hellen threatened the Comoros Archipelago and the Madagascan northwest coastline as it became one of the strongest tropical cyclones (TCs) ever observed over the Mozambique Channel. Its steep intensity changes were not well anticipated by operational forecasting models or by La Reunion regional specialized meteorological center forecasters. In particular, the record-setting rapid weakening over the open ocean was not supported by usual large-scale predictors. AROME, a new nonhydrostatic finescale model, is able to closely reproduce these wide intensity changes. When benchmarked against available observations, the model is also consistent in terms of inner-core structure, environmental features, track, and intensity. In the simulation, a northwesterly 400-hPa environmental wind is associated with unsaturated air, while the classic 200-850-hPa wind shear remains weak, and does not suggest a specifically unfavorable environment. The 400-hPa constraint affects the simulated storm through two pathways. Air with low equivalent potential temperature (u e) is flushed downward into the inflow layer in the upshear semicircle, triggering the decay of the storm. Then, direct erosion of the upper half of the warm core efficiently increases the surface pressure and also plays an instrumental role in the rapid weakening. When the storm gets closer to the Madagascan coastline, low-u e air can be directly advected within the inflow layer. Results illustrate on a real TC case the recently proposed paradigm for TC intensity modification under vertical wind shear and highlight the need for innovative tools to assess the impact of wind shear at all vertical levels