Journal of Next-Generation Research 5.0
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The Mayotte seismo-volcanic crisis: characterizing a reactivated volcanic ridge from the upper slope to the abyssal plain using multibeam batymetry and backscatter data
No full textInternational audienceSince the 10thof May 2018, theIsland of Mayotte has undergonea seismic crisis characterized by clustered epicentres located offshore between 10 and 50 km east of the Main Island(Grande-Terre). In addition,rapid subsidence and displacement of the island toward the east occurred from July 2018, both with rates over 15 mm.yr-1. These aspects pointed towards a magmato-volcanic origin to the crisis.The MAYOBS offshore geological and geophysical surveys were carried out by IPGP, IFREMER, BRGM and CNRS from May to July 2019 in order torecover and deploy Ocean Bottom Seismometers as well asto acquire bathymetric, backscatter and sub-bottom profiler data over an extensive area of the slope and abyssal plain. These surveys allowed thediscovery of a newly developing800-meter-highvolcano located at the eastern end of an elongated volcanic ridge, at 3500 mof water depth. This N105-N110° ridge is approximately 100 km long and extends to the west until “Petite-Terre” and the northern part of “Grande-Terre”(Feuillet et al., submitted).Bathymetric data highlight thepresence of tenth of volcanic edifices including cones, eruptive fissure ridges, lava flows and plateaus, laccolith domes, and inflated lavaflows. Few of these features have been sampledbut they confirmedthe volcanic origin. Volcanic ridges develop along specific orientation have already described onshore. The sequence of bathymetric and backscatter surveys from May to July allow to describe the evolution of the newbornvolcano and to estimate the volumeof lava and the effusion rate(about 5km3).The eastern Mayotte insular slope has been described using bathymetry and backscatter data. Several large active canyons transport sediments fromthelagoon, the outer-reef drop off, and the upper-slope, down to the abyssal plain. We also detect evidences of past slope instabilities over the area. In the context of the important seismo-volcanic crisis affecting Mayotte for more than a year, these new data offer a reference data set that will provide additional constraints for hazard and risk assessment
Cartographie du couvert forestier et des changements en république du Congo
No full textInternational audienceDans le cadre du processus REDD+, la République du Congo s’est lancée dans une étude relative à la connaissance de la situation antérieure et actuelle de son couvert forestier. Cinq produits cartographiques ont été réalisés à cet effet, présentant chacun des caractéristiques qui lui sont spécifiques. Ces produits, élaborés à des différentes dates, présentent des superficies forestières variables, entre 22 et 24 millions d’hectares. Les pertes par contre, présentant un taux annuel faible, variant entre 0,02% et 0,07%, placent la République du Congo dans la catégorie des pays à forte couverture forestière et un taux faible de déforestation. Ces produits cartographiques, d’auteurs différents ayant utilisé des méthodologies qui leurs sont propres, sont complémentaires et pertinents, et ont permis à la Républiques du Congo de poser des bases solides pour son système de suivi des forêts
Potentiel de l'imagerie multi-capteur dans le suivi des mangroves de l'estuaire du Wouri-Cameroun
No full textInternational audienceReconnues pour leurs services environnementaux et notamment la séquestration du carbone, les mangroves du littoral camerounais restent assez mal documentées, précisément en ce qui concerne leurs superficies actuelles et leur répartition spatio-temporelle. La présente étude se propose d’évaluer le potentiel de la combinaison de l’imagerie optique et radar, de haute et très haute résolution spatiale, dans la délimitation et le suivi des mangroves autour de l’estuaire du Wouri. Les résultats indiquent qu’en l’absence d’une signature spectrale spécifique à la mangrove, permettant de l’isoler des autres peuplements forestiers littoraux, la classification orientée- objet combinant l’interférometry Land Use (ILU) sur image radar (TerraSAR-X Stripmap) et des images SPOT 6 paraît efficace dans le renforcement de leur détectabilité. Aussi, le seuillage sur l’indice d’humidité de la transformation tasseled cap permet d’obtenir des résultats valides. Ces deux méthodes ont permis d’estimer à près de 910 km2 la superficie actuelle des mangroves dans la zone d’étude. Ces mangroves ont connu une régression spatiale dont la vitesse varie localement au cours des trente dernières années: Autour de la métropole urbaine Douala, la régression a été de 7454,55 ha (soit 52% de leur superficie initiale), du fait des aménagements urbains et de la périurbanisation anarchique. Dans le site de Tiko par contre, leurs superficies sont passées de 11310,36 à 11203,41 ha, soit une régression de 106 ha seulement, au profit des faciès de dégradation, des cultures et accessoirement de l’habitat
The AROME-WMED reanalyses of the first special observation period of the Hydrological cycle in the Mediterranean experiment (HyMeX)
No full textInternational audienceTo study key processes of the water cycle, two special observation periods (SOPs) of the Hydrological cycle in the Mediterranean experiment (HyMeX) took place during the autumn 2012 and winter 2013. The first SOP aimed to study high precipitation systems and flash-flooding in the Mediterranean area. The AROME-WMED (West-Mediterranean) model (Fourrié et al., 2015) is a dedicated version of the mesoscale Numerical Weather Prediction (NWP) AROME-France model 5 which covers the western Mediterranean basin providing the HyMeX operational centre with daily real-time analyses and forecasts. These products allowed adequate decision-making for the field campaign observation deployment and the instrument operation. Shortly after the end of the campaign, a first re-analysis with more observations was performed with the first SOP operational software. An ensuing comprehensive second re-analysis of the first SOP which included field research observations (not assimilated in real-time), and some reprocessed observation datasets, was made with AROME-WMED. Moreover, a more recent version of the AROME model was used with updated background error statistics for the assimilation process. This paper depicts the main differences between the real-time version and the benefits brought by HyMeX re-analyses with AROME-WMED. The first re-analysis used 9 % of additional data and the second one 24 % more compared to the real-time version. The second re-analysis is found to be closer to observations than the previous AROME-WMED analyses. The second re-analysis forecast errors of surface parameters are reduced up to the 18-h or 24-h forecast range. In the mid and in the upper troposphere, upper-level fields are also improved up to the 48-h forecast range when compared to radiosondes. Integrated Water Vapour comparisons indicate a positive benefit for at least 24 hours. Precipitation forecasts are found to be improved with the second re-analysis for a thresholds up to 10 mm/24-h. For higher thresholds, the frequency bias is degraded. Finally, improvement brought by the second re-analysis is illustrated with the Intensive Observation Period (IOP 8) associated with heavy precipitation over Eastern Spain and South of France
Advances in plant materials, food by-products, and algae conversion into biofuels: use of environmentally friendly technologies
No full textInternational audienceGreen technologies have emerged as useful tools for the generation of clean fuels with the potential to minimize the effect of human activity on the environment. Currently, these fuels are mainly composed of hydrocarbons obtained from crude oil. Over the past two decades, biomass has gained significant attention as a renewable feedstock for more sustainable biofuel production and has been a great candidate to replace fossil fuels. The principal components of most of the available biomass are cellulose, hemi-cellulose, and lignin. Although the available green technologies for biofuel production are progressing rapidly, productivity and chemical yield from these techniques are still below the required values. Therefore, there is a need for interdisciplinary studies to meet the requirements for more global and efficient production by streamlining processes, integrating technologies and achieving techno-economic improvements. In this context, we aim to give an overview of available biomass such as agricultural wastes suitable for the generation of different classes of biofuels including next-generation biofuels. Unfortunately, expensive, wasteful and energy-consuming pretreatment processes are still used. Therefore, novel technologies that allow a more efficient separation with low resource consumption and the generation of a low number of residues are required. In this regard, novel technologies such as efficient fractionation techniques and genetic and metabolic engineering including the application of CRISPR/Cas tools, as well as microfluidic platforms to improve the overall yield of biofuel production are discussed
Solution asymptotiquement périodique d'une classe d'équation différentielle stochastique
No full textInternational audienceIn this paper, we first introduce the concept and properties of ω-periodic limit process. Then we apply specific criteria obtained to investigate asymptotically ω-periodic mild solutions of a Stochastic Differential Equation driven by a Brownian motion. Finally, we give an example to show usefulness of the theoritical results that we obtain in the paper. MSC : 34C25, 34C27, 60H30, 34 F05
Competition in sonochemical degradation of Naphthol Blue Black: Presence of an organic (nonylphenol) and a mineral (bicarbonate ions) matrix
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Optimal placement of drones for fast sensor energy replenishment using wireless power transfer
No full textBest Paper AwardInternational audienceLifetime is the main issue of wireless sensors net-works. Since the nodes are often placed in inaccessible places, thereplacement of their battery is not an easy task. Moreover, thenode maintenance is a costly and time consuming operation whenthe nodes are high in numbers. Energy harvesting technologieshave recently been developed to replenish part or all of therequired energy that allows a node to function. In this paper, weuse dedicated chargers carried by drones that can fly over thenetwork and transmit energy to the nodes using radio-frequency(RF) signals. We formulate and optimally solve the OptimalDrone Placement and Planning Problem (OD3P) by using a givennumber of flying drones, in order to efficiently recharge wirelesssensor nodes. Unlike other works in the literature, we assumethat the drones can trade altitude with coverage and rechargepower, while each drone can move across different positions inthe network to extend coverage. We present a linear program aswell as a fast heuristic algorithm to meet the minimum energydemands of the nodes in the shortest possible amount of time.Our simulation results show the effectiveness of our approachesfor network scenarios with up to 50 sensors and a50×50mterrain size
Monitoring anthocyanin degradation in Hibiscus sabdariffa extracts with multi-curve resolution on spectral measurement during storage
No full textInternational audienceThis study aims to monitor composition changes in an anthocyanin-rich beverage during storage by the means of UV-VIS measurements associated with a multi-curve resolution procedure. Hibiscus sabdariffa extract was stored at 37 degrees C for 50 days and UV-VIS spectra were measured on the extract and the fractions of the extract every 5 days. MCR was carried out in two steps, first with the fraction and then the extract spectra. The results enabled the main polyphenols initially present to be identified, anthocyanins and chlorogenic acid, but also found the nature of the main degradation products: the polymers from anthocyanin condensation and scission products. In addition, comparison with HPLC analysis results showed that the MCR procedure recovered the correct shapes of the concentration profiles particularly of anthocyanin and polymer kinetics during storage. This work gives perspective for the use of a rapid and efficient technique to monitor pigment-rich beverage processing or storage