Apport des données ASTER et d'un réseau de neurones à rétropropagation à la modélisation de la dégradation du sol d'un bassin marneux du Rif marocain

The study of soil degradation phenomena requires the characterization of surface properties. This characterization is based on the integration of the descriptive variables of the local environment: physical, biological and anthropic. In Morocco, the spectacular expansion of erosive processes shows increasingly alarming aspects. Faced with this situation, the country has an urgent need for evaluating the effects of erosion on soil productivity to measure its amplitude and to foster the implementation of better conservation strategies. The overall objective of our research project is to develop a geomatics approach for the mapping and determination of the surface states in a small Mediterranean watershed that can be used for modeling the soil degradation parameters. In the present research, the class definitions of the different levels of degradation are based on the GLASOD ( Global Assessment of Soil Deterioration ) method. To reach the objectives set for our study, we adopted two approaches. The first is a spectral approach and is based on spectral indices, the SAM (Spectral Angle Mapping ) method, and on spectral unmixing. This procedure gave us a better comprehension of the synergistic relationship between the spectral properties of soils and their state of degradation. Also, we elaborated a new spectral index referred to as the LDI (Land Degradation Index ). This index is interesting and provides quantitative results. We were also able to establish an interesting correlation (R[superscript 2] =0.67) between a spectral index derived from ASTER data and the clayey fraction of the soil surface horizon in our study area. The second approach focuses on the modeling of multisource data through the use of a supervised neural network based on a back-propagation algorithm. The quality of results of this approach depends on the determination of the intrinsic parameters of RN. In the present research, we provide some answers concerning issues relating to these parameters in the hope of better defining them. The comparison of the results obtained using the different approaches outlined the existence of a global correspondence between these parameters, in the sense that they represent ground reality. Moreover, the neural approach stands out with a higher accuracy rate (Kappa =0.91) due to the integration of multisource data and spectral information. The Kappa coefficient permitted the evaluation of the accuracy of the classification and its interpretation was carried out based on the calculation of the Z statistics test. The validation of results is based on photointerpretation, ground truth and the analysis of the spatial variability of the data using the geostatistics approach."--Résumé abrégé par UMI

Towards clinical application of continuum active micro-endoscope robot based on EAP actuation.

International audienceContinuum robots have shown astounding abilities in the medical field as numerous robotized devices have emerged. For instance, colonoscopes, arthroscopes, catheters, endoscopes, and other medical tools have been developed. Their ability to navigate through complex anatomy and narrow spaces represent the attractive features of continuum robots. We foresee to improve their usefulness for Minimally Invasive Surgery (MIS) and Natural Orifice Transluminal Endoscopic Surgery (NOTES). These robots may be downscaled depending on the target application, e.g., from endoscopy to neurosurgery. Shorter hospital stay, less pain and scarring, and quicker recovery might then be provided to the patient. Recently, active cannulas have been used for endonasal skull base surgery for pituitary gland cancer as depicted in Figure 1a, transurethral laser prostate surgery, laser surgery, beating heart surgery, and neurosurgery. Thus, we are interested in developing a micro-endoscope whether for diagnosis or laser surger

Estimation Of Runoff And Erosion Rates Using Agwa - Kineros2 Model: Application To A Mediterranean Watershed

The Mediterranean area is classified as a region highly threatened by water erosion, which depends largely on climatic aggressiveness, erodible soils, sparse vegetation, and irrational human activity. Tleta watershed belongs to a young mountain ridge (Rif), readily erodible and highly vulnerable to water erosion. To assess the extent of this phenomenon, AGWA tool coupled with KINEROS2 (K2) model was used to predict the specific degradation and the hydrological functioning of the studied watershed. The data required consisted of topography, land use, soil type, and precipitation. The model simulations will make it possible to estimate the sediment load deposited at the Ibn Batouta dam, which results from upstream erosion. The evaluation criteria for the predictive skill of K2 model when comparing observed and simulated data are the coefficient of determination (R2) and the Nash–Sutcliffe model efficiency coefficient (NSE). These two coefficients are respectively (R² = 0.99, NSE = 0.71) and (R² = 0.99, NSE = 0.72) for runoff and sediments yield for calibration. For the validation process, these two coefficients are (R² = 0.99 and NSE = 0.98) for runoff and (R² = 0.99 and NSE = 0.97) for sediments yield. This allows us to conclude that the predictive accuracy of the model is promising

Integrated Water Resources Vulnerability Assessment: A Multidimensional Approach and Geographic Information System Based in Fès, Meknès, and Ifrane Perimeters, Morocco

Water resources are disproportionately distributed, and more and more problems related to this precious resource are being reported around the world due to anthropogenic pressures and global environmental changes. This paper focuses on assessing the vulnerability of water resources in an integrated way, by taking into account hydrological, environmental, socio-economic and pollution factors, in order to delineate sensitive areas of water resources under a geographic information system. The framework for assessing the water resources vulnerability in the Fès, Meknès, and Ifrane perimeters was based on a participatory approach through a survey. The data collected on the identified factors are then processed under ArcGIS tool to aggregate the normalized value into a water resources vulnerability index. The result shows that the degree of vulnerability of water resources in most of the study area is considered to be at the "threshold" to "non-vulnerable". However, three (3) main areas were considered to be "moderately vulnerable" to "highly vulnerable" precisely in the South of the city of Meknes (Zone 1), from the West of the city of Fès (Zone 2), and finally the Dayet Ifrah area (Zone 3). The sensitivity analysis showed that five factors have more impact on the overall water resources vulnerability map: topography, poverty, water withdrawal, population density, and access to drinking water. The result of this study could help integrated water resources management planners take action to improve the overall water quantity and quality in the area, and it can be extended to a larger scale like regional, national or cross-country

Gestion de risque de portefeuille : estimation de la VaR et CVaR

International audienceCe mémoire concerne l'estimation de la Value-at-Risk (VaR) et de la Conditional Value-at-Risk (CVaR) pour des portefeuille. Après avoir étudié la VaR et la CVaR dans le modèle normal et en utilisant l'approximation de Cornish-Fisher, nous étudions la modélisation par la loi de Pareto pour le calcul de ces indicateurs de risque et de l'estimation. Dans une dernière partie, nous présentons une partie de développement logiciel concernant la mise en place d'un logiciel de présentation des cours de bourse et de leurs indicateurs

Assessment of Surface Water Quality using Indices and Geographic Information System in the Sebou River Basin, Morocco

The aim of this study is to access the quality of monitored rivers and to map the polluted river sections in the Sebou basin using Geographic Information System (GIS). The potential causes of water quality variation will also be added for suitable measures to be taken. A Water Quality Index (WQI) which developed in Morocco was applied to 17 river water quality monitoring stations with data on 6 parameters (Dissolved oxygen (DO), ammonium ion (NH4 + ), 5-day biochemical oxygen demand (BOD5), chemical oxygen demand (COD), fecal coliforms (FC) and total phosphorus (TP)) collected twice during the wet and dry season over 1990-2017 period. The result shows that river water quality is classified as bad, very bad and medium at 59% of the monitoring stations, while 41% are considered as good to excellent. Interpolation of mean values of overall WQI of the 17 river water quality monitoring stations, revealed evidence of quality degradation along several kilometers of most river sections in the Sebou basin. The correlation matrix between the sub-indices of water quality parameters and the overall WQI showed high positive correlation coefficients and highlights the contribution to water quality degradation as follows: TP ( = +0.96 ) ≥ NH4 + ( = +0.96 ) > BOD5 ( = +0.94) > COD ( = +0.86) > FC ( = +0.83) > DO ( = +0.79). The sections of Fès, Innaounene Rivers, and an extended stretch of Tizguit River must no longer be used for irrigation. River water quality is overall of better quality in the wet season compared to the dry season. Simple linear regressions between the seasonal water quality variation and the overall WQI showed higher coefficients of determination R 2 (0.67 and 0.60) between dry season WQI and the overall WQI and between wet season WQI and the overall WQI respectively. It is clear that discharges of industrial and domestic wastewater during the dry season and agricultural activities are most likely to be the causes of the degradation of river water quality

Modelisation Du Risque D’érosion Hydrique Par L’équation Universelle Des Pertes En Terre Dans Le Rif Occidental: Cas Du Bassin Versant De Moulay Bouchta (Maroc)

Soil erosion causes many environmental and socio-economic problems: loss of biodiversity, decrease in the productivity of agricultural land, siltation of dams and increased risk of flooding. It is therefore essential to establish a detailed evaluation of this process before any spatial planning. To evaluate the effects of soil erosion spatially and quantitatively in order to face this phenomenon, and propose the best conservation and land development strategies, the Universal Soil Loss Equation (USLE) coupled with a geographic information system (GIS) is applied. This model is a multiplication of the five erosion factors: the erosivity of the rain, the erodibility of the soil, the inclination and the slope length, the vegetation cover and the anti-erosion practices. The study area is the Moulay Bouchta watershed (7 889 ha), which is located in the western part of the Rif Mountains, is characterized by a complex and contrasting landscape. The resulting soil loss map shows an average erosion rate of 39.5 (t/ha/yr), 87% of the basin has an erosion rate above the tolerance threshold for soil loss (7 (t/ha/yr)). Soil losses per subbasin range from 16.2 to 81.4 (t/ha/yr). The amount of eroded soil is estimated at 311,591 (t/yr), corresponding to a specific degradation of 12.1 (t/ha/yr). In the absence of any erosion control, 25% of the soil losses would reach the new dam located a little upstream of the basin outlet, reducing its water mobilization capacity to 59,625 (m3/yr). The application of Principal Component Analysis (PCA) to soil erosion factors shows a significant influence of topographic factor (LS) on soil erosion process, followed by the effect of support practices (P), then by soil erodibility (K)

Experimental Characterization of the Hydromechanical Properties of the Gypsum Soil of Sebkha of Oran

This paper deals with hydro-mechanical investigation of salinegypsum soil properties from Sebkha of Oran in respect withtheir impact on the feasibility of the project of the second runwayof the Es-Sénia airport in Oran (Algeria). The geologicaland in-situ geotechnical studies prior to the construction phaseof the airport runway revealed underground cavities supposedto be created from salts and gypsum dissolution in the Sebkhasoil. Standard laboratory experiments are used to determinepermeability coefficient, isotherm curve, shear resistance andelastic parameters of two soils. These ones are affected by thevariation of water table level that varies according to the dryperiod (summer) or the rainy period (winter), creating cyclichydric conditions. The paper presents a comparison of parametersof these two soils in saturated and partially saturatedconditions. The results of tests performed in laboratory arecompared with those performed in situ in order to check theirrepresentativeness before a detailed comparison of the effect ofwater conditions. The two soils have similar behavior highlysensible to water with some particularities

Drought characterization: A systematic literature review

This study examined the worsening severity of global droughts caused by climate change. However, the multiple definitions and varied range of drought indices pose challenges in effectively monitoring and assessing the prevalence and severity of droughts. This study aims to give a comprehensive overview of the various drought definitions found in the literature and how they have evolved based on their applications. Specifically, the focus was to shed light on the dynamic nature of drought characterization and offer insights into the factors that shaped its conceptualization over time. Within this context, this study explored three primary categories of drought indices: climatic, remote sensing, and composite. Each category was discussed in relation to its utility in specific fields, such as meteorological, agricultural, and hydrological drought assessments, along with an analysis of their strengths and limitations. Furthermore, this study presents modified meteorological drought indices that have been adapted to better monitor agricultural droughts. Additionally, the authors used geographic information systems to create a map showing the distribution of drought-related publications globally over the past decade. The findings showed that countries with arid and semi-arid climates are more actively involved in drought research, highlighting their particular interest and concern regarding the subject matter. The implications of this study emphasize the urgent need for immediate and coordinated efforts to address the escalating issue of droughts caused by climate change. By improving monitoring and assessment methods and focusing on tailored strategies in vulnerable regions, it is possible to mitigate the far-reaching consequences of drought and to build more resilient communities and ecosystems