Journal of Next-Generation Research 5.0
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Modelling, control, and optimization for tropical agriculture
No full textInternational audienceAgriculture plays a major role in the economy of many developing countries, providing export revenues, food and employment. As pests are responsible for severe crop losses every year, their control is a major issue. It often relies on chemical pesticides, which are often costly and detrimental to the environment, so alternative solutions are sought. In this talk, we tackle this issue by designing ecologically friendly controls for two pathosystems: the phytophagous plantain nematode, which attacks plant roots, and the coffee berry borer, which feeds and reproduce in the berries. In both cases, the yield is maximized in order to be economically viable. An efficient method to reduce the nematode population in the soil consists in having fallow periods between cropping seasons. We developed an ODE/hybrid seasonal model for the nematode--root dynamics [1] and we exploit it in the present work to globally optimize the duration of the fallow periods, which potentially vary from one year to the other. For the coffee berry borer, we study how the persistent effect of entomopathogenic fungi can impact the optimal yield, compared to non-persistent controls obtained on a single season ODE model of the berry--borer dynamics [2]. Moreover, we extend our results to a seasonal framework, as for the plantain--nematode pathosystem.[1] I. Tankam Chedjou, S. Touzeau, F. Grognard, L. Mailleret, J.-J. Tewa. An agricultural control of Radopholus similis in banana plantations, 11th ECMTB, Lisbon, Portugal, 2018.[2] Y. Fotso Fotso, S. Touzeau, S. Bowong, F. Grognard, L. Mailleret, B. Tsanou. Modelling and control of coffee berry borer infestation, 11th ECMTB, Lisbon, Portugal, 2018
Mobility of copper and cobalt in metalliferous ecosystems: Results of a lysimeter study in the Lubumbashi Region (Democratic Republic of Congo)
No full textInternational audienceThis paper presents the results of a lysimeter experiment in which a forest soil has been artificially spiked with rock fragments from natural copper (Cu) and cobalt (Co)-hills from Tenke-Fungurume (Democratic Republic of Congo). The Cu and Co contents of the percolating water have been analysed at repeated intervals and the impact of rock on the soil properties was evaluated at the end of the experiment. Five rocks were sampled in one copper hill. In natural conditions, these rock fragments located on the top of the hill are mixed to surface soil horizon along the slope through colluvial processes. The Cu and Co contents in rocks range respectively between 470 mg/kg (siliceous rock) and 140,000 mg/kg (shale) and between 450 mg/kg (dolostone) and 5300 mg/kg (shale). Rock fragments were mixed with two horizons (hemi-organic A with 2.7% total organic carbon (TOC), and mineral B with 0.3% TOC) of an acid (pH water < 4.5) acrisol under forest. The mixture was placed in 1 L lysimeters and left in Lubumbashi ex situ conditions during the rainy season. Percolating water was collected for six periods after and the Cu and Co contents have been analysed. At the end of the experiment, soil from the lysimeter was removed for pH, TOC, available nutrients and trace elements, CaCl2-extractable Cu and Co analysis.The results show great differences between Cu and Co releases in the percolating solutions according to the nature of the rocks. The quantities released were correlated to the concentrations originally present in the unweathered rocks. Differences were also found between the A and B horizons, which indicate that the physicochemical properties of the soil influence reaction with the rocks. The differences between both horizons are mainly organic carbon content, cationic exchange capacity and nutrient content, which were higher in the A horizon. However, the pH of the A horizon was acidic compared with the B horizon.Significant correlations were found between extractable Cu and Co with concentrations of their leaching solution. Because of this, soluble Cu and Co extracted by CaCl2 can be regarded as vertical transfer risk prediction tools of Cu and Co in the soil
Comportement mécanique des massifs rocheux dans les mines profondes : surveillance in situ et modélisation numérique pour l’amélioration de l'évaluation de l'aléa sismique
No full textWith the aim of better understanding interactions between stress modifications induced by mining and the generation of seismic activity, a deep area of Garpenberg mine (Sweden) was instrumented by Ineris with microseismic probes and geotechnical cells. Spatiotemporal analysis of recorded seismicity between 2015 and 2016, as well as seismic source parameters, have highlighted two types of seismic rock mass responses: one local and temporally short directly induced by production blasts, the other long-lasting over time and remote from excavations being mainly controlled by geological heterogeneities. Geotechnical data analysis showed the occurrence of aseismic deformations, as well as creep phenomena induced by mining exploitation. In addition, seismic activity decays proportional to the decaying rate of measured strains. This latter observation implies that creep may be another mechanism driving seismicity, in addition to the immediate stress change induced by blasting. In the last part of this thesis, a 3D elasto-plastic geomechanical model has been realized and its results have been compared with geophysical data. This comparison showed that mine-wide numerical models can be suitable for the analysis of mining induced seismicity at large-scale. However, there are some aspects of the induced seismicity that the model cannot fully explain. This is particularly true for remote seismicity occurring at a distance from excavations, while better correlations are found when considering seismicity close to production areas. Results of this thesis demonstrated that a combined approach which associates seismic and geotechnical data with numerical modelling can significantly improve our understanding of the rock mass response to mining. The combination of these methodologies in an integrated approach can significantly reduce their straightforward limitations, which appears evident when these instruments are considered separately.Afin de mieux comprendre les interactions entre les modifications des contraintes induites par l'exploitation minière et la génération d'activité sismique, une zone profonde de la mine de Garpenberg (Suède) a été instrumentée par l’Ineris avec de sondes microsismiques et de cellules géotechniques. L’analyse spatio-temporelle des événements microsismiques enregistrés entre 2015 et 2016, ainsi que leurs paramètres à la source, ont mis en évidence deux types de réponses sismiques : une locale et courte dans le temps directement induite par les tirs de production, l’autre plus persistante et distante des excavations étant principalement contrôlée par des hétérogénéités géologiques. L’analyse des données géotechniques a montrée l’occurrence de déformations asismiques, ainsi que de phénomènes de fluage induits par l’exploitation. De plus l'activité sismique décroît proportionnellement au taux de diminution des déformations mesurées. Cette dernière observation implique que le fluage peut être un autre mécanisme menant à la sismicité, s’ajoutant au changement de contrainte immédiat induit par les tirs de production. Dans la dernière partie de cette thèse, un modèle géomécanique élasto-plastique 3D a été réalisé et ses résultats ont été comparés aux données géophysiques. Cette comparaison a montré que les modèles numériques à l'échelle de la mine peuvent être des outils puissants pour étudier la sismicité induite à grande échelle. Cependant, il y a certains aspects de la sismicité induite que le modèle ne peut expliquer entièrement. Cela est le cas pour la sismicité déclenchée à distance des excavations, alors que de meilleures corrélations sont trouvées lorsque l'on considère la sismicité à proximité des zones de production. Les résultats de cette thèse ont démontré qu'une approche combinée associent les données sismiques et géotechniques à la modélisation numérique peut améliorer considérablement notre compréhension de la réponse des massifs rocheux à l'exploitation minière. La combinaison de ces méthodologies dans une approche intégrée peut réduire considérablement leurs limites explicites qui sont évidents lorsque ces instruments sont considérés séparément
pizza: an open-source pseudo-spectral code for spherical quasi-geostrophic convection
No full text20 pages, 10 figures, 4 tables, accepted for publication in GJIInternational audienceWe present a new pseudo-spectral open-source code nicknamed pizza. It is dedicated to the study of rapidly-rotating Boussinesq convection under the 2-D spherical quasi-geostrophic approximation, a physical hypothesis that is appropriate to model the turbulent convection that develops in planetary interiors. The code uses a Fourier decomposition in the azimuthal direction and supports both a Chebyshev collocation method and a sparse Chebyshev integration formulation in the cylindrically-radial direction. It supports several temporal discretisation schemes encompassing multi-step time steppers as well as diagonally-implicit Runge-Kutta schemes. The code has been tested and validated by comparing weakly-nonlinear convection with the eigenmodes from a linear solver. The comparison of the two radial discretisation schemes has revealed the superiority of the Chebyshev integration method over the classical collocation approach both in terms of memory requirements and operation counts. The good parallelisation efficiency enables the computation of large problem sizes with grid points using several thousands of ranks. This allows the computation of numerical models in the turbulent regime of quasi-geostrophic convection characterised by large Reynolds and yet small Rossby numbers . A preliminary result obtained for a strongly supercritical numerical model with a small Ekman number of and a Prandtl number of unity yields and . pizza is hence an efficient tool to study spherical quasi-geostrophic convection in a parameter regime inaccessible to current global 3-D spherical shell models
La prise en charge des consommateurs de drogues injectables à Dakar: succès et échecs de la méthadone vus par les patients et les soignants
No full textInternational audienc
Functional classification of artificial alluvial ponds driven by connectivity with the river: Consequences for restoration
No full textInternational audienceChemical and biological functioning of artificial wetlands and lakes in alluvial plains is investigated based on the example of small artificial ponds located within dike fields along the Rhône River (France). The objective is to identify the diversity of metabolism in these artificial aquatic ecosystems and to propose a functional classification linked to the connectivity with the river. A comprehensive characterization of chemical and biological parameters in six shallow ponds was conducted, along with 4-month continuous monitoring of temperature and dissolved oxygen concentration, both in the sub-surface and at depth. Metabolism intensity is quantified using the diel oxygen method. Multivariate analysis of chemical and biological characteristics is performed to identify the functional heterogeneity between the ponds, which is shown to be consistent with the intensity of primary production (GPP) and ecosystem respiration (ER). Some ponds are permanently connected to the river, like backwater, and are very turbid, because of suspended matter and the presence of phytoplankton. The oxyge-nation is limited to the surface layer with anoxia rapidly building up at the bottom due to an intense ER. Ponds that are rarely connected become eutrophic with large concentration of phytoplankton and large GPP and ER values. Anoxia and even denitrification occur close to the bottom sediment. Finally, in the ponds with intermediate degree of connection with the river, macrophytes grow in clear water with limited amount of phyto-plankton, resulting in a gradient of GPP and ER values, controlled by nutrient availability. Rehabilitation of various connection patterns with the river is thus crucial to maintain a functional diversity in large river alluvial plains
Generation of a Reconfigurable Probabilistic Decision-Making Engine based on Decision Networks: UAV Case Study
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Detection of changes in shallow coral reefs status: Towards a spatial approach using hyperspectral and multispectral data
No full textInternational audienceCoral reef degradation due to environmental change, including anthropogenic disturbances, is a major concern worldwide. Detecting and assessing both temporal and spatial changes in benthic cover is a crucial requirement to inform policy makers and guide conservation measures. Here, we introduce a spatial approach based on high resolution multispectral and hyperspectral image analysis, developed in order to detect and quantify changes in benthic cover in a highly heterogeneous shallow coral reef flat in Reunion Island in the South-West Indian Ocean. We propose a new index called HCAI (Hyperspectral Coral to Algae Index), defined as the ratio of living coral cover to the sum of living coral and algal covers. Benthic cover estimates were derived from airborne hyperspectral image processing using water column correction and unmixing models implemented with the four main coral reef benthic components: corals, algae, seagrass and sand. Ground truth and LIDAR data acquired simultaneously were used to validate processing accuracy. A significant positive correlation (adjusted R2 = 0.72, p-value < 0.001) was obtained between coral cover recorded in situ and estimated from image analysis. Moreover, 13 habitat classes based on the four main benthic component covers were mapped at a scale of an entire reef. Diachronic analyses of hyperspectral images between 2009 and 2015 revealed an overall decrease of the HCAI index and a decrease in the area of all the dominant coral classes along the reef (−28.24% for the coral class for example), while the area of habitat classes dominated by algae strongly increased during the same period. Moreover, we detected and documented the spatial and temporal evolutions of coral geomorphological features composed with coral rubble deposits called rubble tongues (RTs) using different available sensors (i.e. hyperspectral, satellite, and orthophotography). Since 2003, four detected (RTs) have spread shoreward at a mean rate of 8.4 m.y−1 including significant loss of reef structural complexity and heterogeneity, a spreading pattern which was confirmed by 2009 and 2015 hyperspectral data. Remote sensing and more specifically airborne hyperspectral approaches open new perspectives for coral reef monitoring, at high temporal and spatial resolutions
