Journal of Next-Generation Research 5.0
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Unsustainable Mining Development and the Collapse of Some Ancient Societies: Economic Reasons
No full textInternational audienceThe literature explaining social collapse mainly focuses on factors such as wars, climate change or disease, as exemplified by numerous examples of collapses which have occurred during the Late Bronze Age in the Near East and in the South-eastern Mediterranean region. This paper aims at demonstrating that collapse can also have economic reasons. Indeed, collapse may be the outcome of an economic growth process which is inherently unsustainable. More precisely, we claim that several ancient societies collapsed because their form of economic development eventually proved to be unable to sustain their standard of living. It is believed that the Únĕtice societies (which existed in the central European Early Bronze Age) were among those that collapsed for that reason. Two different simple models are presented to demonstrate how agricultural economies of this type which introduced bronze mining and metallurgy were unable to sustain their economic development
Regards croisés sur le processus menant vers une société inclusive. Place et rôle du chercheur ?
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Clear-sky ultraviolet radiation modelling using output from the Chemistry Climate Model Initiative
No full textInternational audienceWe have derived values of the ultraviolet index (UVI) at solar noon using the Tropospheric Ultraviolet Model (TUV) driven by ozone, temperature and aerosol fields from climate simulations of the first phase of the Chemistry-Climate Model Initiative (CCMI-1). Since clouds remain one of the largest uncertainties in climate projections, we simulated only the clear-sky UVI. We compared the modelled UVI climatologies against present-day climatological values of UVI derived from both satellite data (the OMI-Aura OMUVBd product) and ground-based measurements (from the NDACC network). Depending on the region, relative differences between the UVI obtained from CCMI/TUV calculations and the ground-based measurements ranged between − 5.9 % and 10.6 %. We then calculated the UVI evolution throughout the 21st century for the four Representative Concentration Pathways (RCPs 2.6, 4.5, 6.0 and 8.5). Compared to 1960s values, we found an average increase in the UVI in 2100 (of 2 %-4 %) in the tropical belt (30 • N-30 • S). For the mid-latitudes, we observed a 1.8 % to 3.4 % increase in the Southern Hemisphere for RCPs 2.6, 4.5 and 6.0 and found a 2.3 % decrease in RCP 8.5. Higher increases in UVI are projected in the Northern Hemisphere except for RCP 8.5. At high latitudes, ozone recovery is well identified and induces a complete return of mean UVI levels to 1960 values for RCP 8.5 in the Southern Hemisphere. In the Northern Hemisphere, UVI levels in 2100 are higher by 0.5 % to 5.5 % for RCPs 2.6, 4.5 and 6.0 and they are lower by 7.9 % for RCP 8.5. We analysed the impacts of greenhouse gases (GHGs) and ozone-depleting substances (ODSs) on UVI from 1960 by comparing CCMI sensitivity simulations (1960-2100) with fixed GHGs or ODSs at their respective 1960 levels. As expected with ODS fixed at their 1960 levels, there is no large decrease in ozone levels and consequently no sudden increase in UVI levels. With fixed GHG, we observed a delayed return of ozone to 1960 values, with a corresponding pattern of change observed on UVI, and looking at the UVI difference between 2090s values and 1960s values, we found an 8 % increase in the tropical belt during the summer of each hemisphere. Finally we show that, while in the Southern Hemisphere the UVI is mainly driven by total ozone column, in the Northern Hemisphere both total ozone column and aerosol optical depth drive UVI levels, with aerosol optical depth having twice as much influence on the UVI as total ozone column does
Évaluation et spatialisation du carbone stocké dans le massif forestier de Ngog-Mapubi (Cameroun)
No full textInternational audienceL’étude explore le potentiel du massif forestier de Ngog-Mapubi/Dibang en contexte de la préparation du Cameroun à la REDD+. Elle a pour objectif global d’étudier les variations spatiales du carbone stocké dans la végétation de ce massif forestier et d’esquisser quelques perspectives au regard des changements d’utilisation des terres. Elle se fonde sur l’hypothèse que l’interprétation des images Landsat disponibles et exploitables complétée par une collecte de données de biomasse sur le terrain permettront d’évaluer et de spatialiser les stocks de carbone. La méthodologie s’est appuyée ainsi d’abord sur la télédétection, à travers le traitement et l’interprétation des images Landsat de 2007 et de 2018. Après la stratification, la biomasse a été collectée dans des parcelles de 50 x 50 m délimitées dans différents types d’utilisation des terres du massif. Les échantillons récoltés, séchés à poids constant au laboratoire, ont permis de calculer les stocks de carbone des différents types d’utilisation des terres. Les résultats indiquent que les stocks de carbone totaux varient d’une strate à l’autre soit respectivement de 177,42 à 12,84 tC/ha pour les forêts matures et les cultures. Ces stocks varient aussi suivant les pools de carbone considérés quelle que soit la strate considérée. Les stocks de carbone totaux du massif et de sa zone périphérique sont estimés à 24 086 528,6 tC et à 2 136 016,55 tC pour le massif forestier lui-même. Les forêts matures sont celles qui stockent le plus avec 17 989 374 tC (massif et zone périphérique) et 1 798 795,47 tC pour le massif forestier; Les grandes infrastructures projetées que sont le barrage du Grand Eweng et l’autoroute Yaoundé-Douala conduiront à la perte de plus de 20 000 ha de forêt dont moins de 1500 ha dans la forêt communale proprement dite à l’horizon 2025
Multi-trace-element sea surface temperature coral reconstruction for the southern Mozambique Channel reveals teleconnections with the tropical Atlantic
No full textInternational audienceHere we report seasonally resolved sea surface temperatures for the southern Mozambique Channel in the SW Indian Ocean based on multi-trace-element temperature proxy records preserved in two Porites sp. coral cores. Particularly, we assess the suitability of both separate and combined Sr/Ca and Li/Mg proxies for improved multi-element SST reconstructions. Overall, geochemical records from Europa Island Porites sp. highlight the potential of Sr/Ca and Li/Mg ratios as high-resolution climate proxies but also show significant differences in their response at this Indian Ocean subtropical reef site. Our reconstruction from 1970 to 2013 using the Sr/Ca SST proxy reveals a warming trend of 0.58 ± 0.1 • C in close agreement with instrumental data (0.47 ± 0.07 • C) over the last 42 years (1970-2013). In contrast, the Li/Mg showed unrealistically large warming trends, most probably caused by uncertainties around different uptake mechanisms of the trace elements Li and Mg and uncertainties in their temperature calibration. In our study, Sr/Ca is superior to Li/Mg to quantify absolute SST and relative changes in SST. However, spatial correlations between the combined detrended Sr/Ca and Li/Mg proxies compared to instrumental SST at Europa revealed robust correlations with local climate variability in the Mozambique Channel and teleconnections to regions in the Indian Ocean and southeastern Pacific where surface wind variability appeared to dominate the underlying pattern of SST variability. The strongest correlation was found between our Europa SST reconstruction and instrumental SST records from the northern tropical Atlantic. Only a weak correlation was found with ENSO, with recent warm anomalies in the geochemical proxies coinciding with strong El Niño or La Niña. We identified the Pacific-North American (PNA) atmospheric pattern , which develops in the Pacific in response to ENSO, and the tropical North Atlantic SST as the most likely causes of the observed teleconnections with the Mozambique Channel SST at Europa
A Semantic-Based Approach for Landscape Identification
No full textInternational audienceHere we present an original method for the automation of landscape identification in a satellite image. There are two major challenges in this process. The first lies in the ability to take all expert knowledge into account for the full time it takes to analyze the image. The second is successfully structuring and persisting this knowledge so that it becomes interoperable and usable in the Semantic Web context. In this paper, we explain how the combination of several strategies associating image processing, the calculation of specific characteristics and inductive logic programming (ILP) can feed into the automation process, and how the integration of knowledge via the construction of dedicated ontologies can meet these challenges
Laboratory-scale experimental and modelling investigations of 222Rn profiles in chemically heterogeneous LNAPL contaminated vadose zones
No full textInternational audienceThe potential of LNAPL delineation by 222Rn soil-gas monitoring in a chemically heterogeneous vadose zone was investigated in this study based on laboratory (batch and columns) experiments and numerical modelling. An enhanced version of the MIN3P reactive transport code was used to simulate Rn transport in both uncontaminated and NAPL-contaminated vadose zones and results were validated against analytical solutions and laboratory experiments. Results show that 222Rn activity profiles are mainly controlled by porous media 222Rn production, vadose zone fluid saturations and especially the type and distribution of NAPL in contaminated areas. The results also show that decreases in 222Rn activity and variations in activity gradients provide evidence for the presence and saturation of NAPL. This study demonstrates that LNAPL delineation via 222Rn gas surveys at contaminated sites works best, if gas measurements extend as deep as possible and include regions where 222Rn activity decreases due to elevated NAPL content. In addition, collection and analysis of depth-discrete gas samples allows the characterization of vertical NAPL distribution based on the 222Rn activity gradient. The determination of 222Rn production in the unsaturated zone, as well as water capillary pressure curves are of key importance in enabling the discrimination of an uncontaminated from a NAPL-contaminated area
CasuHAL au service de la science ouverte
No full textInternational audienceLe club des utilisateurs de l’archive ouverte HAL, CasuHAL, favorise les interactions entre ses membres, et avec HAL
Iodine solubility and speciation in glasses
No full textInternational audienceThe study of iodine in glasses and melts is critical in many areas, from geosciences to materials science to waste management. Glasses in the ternary system Na2O-B2O3-SiO2 were studied with the goal of identifying a glass matrix able to dissolve large quantities of this element, and to identify the main parameters affecting the solubility of iodine. Two sets of experiments were carried out: the first one with the aim of determining the solubility limit of iodine, and the second one to identify the structural variations occurring within the glass network upon iodine incorporation, and to identify the parameters influencing the most both iodine solubility and speciation. We demonstrated that there is a strong dependence of iodine incorporation on bulk chemistry and glass physical properties. A solubility limit of ~5 mol% I has been assessed for B2O3-rich glasses and of ~1 mol% for SiO2-rich ones, and this composition dependence has been explained by considering the fragility parameter of the glass network. Structural variations in the iodine local environment and in the glass network were characterized by Raman, X-ray Absorption Spectroscopy, and 11B NMR. Spectroscopy data point out the coexistence of different I species within the glasses, with iodide being the predominant one, surrounded by Na+ ions
A general graph-based framework for top-N recommendation using content, temporal and trust information
No full textInternational audienceRecommending appropriate items to users is crucial in many e-commerce platforms. One common approach consists in selecting the N most relevant items for each user. To achieve this, recom-mender systems rely on various kinds of information, like item and user features, past interest of users for items and trust between users. Current systems generally use only one or two such pieces of information, which limits their performance. In this paper, we design and implement GraFC2T2, a general graph-based framework to easily combine various kinds of information for top-N recommendation. It encodes content-based features, temporal and trust information into a graph model, and uses personalized PageRank on this graph to perform recommendation. Experiments are conducted on Epinions and Ciao datasets, and comparisons are done with systems based on matrix factorization and deep learning using F1-score, Hit ratio and MAP evaluation metrics. The results show that combining different kinds of information generally improves recommendation. This shows the relevance of the proposed framework