23 research outputs found
RĂ©partition des incendies de forĂȘts en fonction des facteurs physiques et biophysiques dans la RĂ©gion du Rif (Maroc)
LâĂ©volution actuelle du rĂ©gime des incendies de forĂȘts pose de nouveaux dĂ©fis quant aux pratiques habituelles des plans dâamĂ©nagement et stratĂ©gies de gestion de ce flĂ©au. La mise en Ćuvre dâactions de prĂ©vention et de lutte nĂ©cessite une comprĂ©hension fine de lâoccurrence et de propagation des feux. Le prĂ©sent travail vise en une analyse spatio-temporelle des feux de forĂȘt en fonction des facteurs physiques et biophysiques dans la rĂ©gion du Rif au Maroc, considĂ©rĂ©e comme une des rĂ©gions les plus touchĂ©es par ce flĂ©au Ă lâĂ©chelle nationale. Les incendies survenus dans cette rĂ©gion, entre 1997 et 2011, ont Ă©tĂ© analysĂ©s et classĂ©s en trois groupes de sĂ©vĂ©ritĂ© selon lâampleur des superficies touchĂ©es. Cette analyse a montrĂ© que presque 80% des superficies incendiĂ©es ont Ă©tĂ© enregistrĂ©es durant les mois dâaoĂ»t et septembre. Par la suite, lâutilisation dâune analyse de variance dĂ©sĂ©quilibrĂ©e Ă deux facteurs a permis de montrer la prĂ©sence dâune diffĂ©rence significative entre la sĂ©vĂ©ritĂ© de lâannĂ©e et les types de bioclimat, notamment pour les bioclimats Ă hiver chaud caractĂ©risĂ©s par une production abondante de biomasse. Aussi, lâĂ©tude rĂ©vĂšle que pendant les annĂ©es sĂ©vĂšres, la vĂ©gĂ©tation des hautes altitudes devient plus vulnĂ©rable aux feux, particuliĂšrement pour les altitudes dĂ©passant 2000 m, en revanche, lâeffet de la pente et de la continentalitĂ© nâest pas significatif et ne prĂ©sente aucune influence sur lâoccurrence des feux
Synthesis and characteristics of Mg doped ZnO thin films: Experimental and ab-initio study
Structural and physical properties of Mg doped zinc oxide (MZO) thin films have been investigated. The samples have been synthesized using a simple spray pyrolysis technique. The hexagonal Wurtzite structured ZnO thin films were confirmed by X-ray diffraction (XRD). The morphology of the thin films was characterized by atomic force microscopy (AFM). The optical properties were studied in details by using ultravioletâvisible (UVâVis) spectrophotometry and Hall Effect measurements for electrical characteristic. The results detected by AFM indicate in a qualitative and quantitative manner how the surface properties (topography, roughness) vary with Mg concentration. The optical characterization showed that the transmittance of MZO thin films increased from 75 to about 90% and optical band gap energy from 3.20 to 3.43 (eV). The electrical properties study showed the lowest resistivity value was 3.45 Ă 10â2 (Ω·cm), which was obtained for the film doped with ZnO:Mg (2 at.%). In order to confirm our results on optical properties, the band structure of Wurtzite Zn1âxMgxO was calculated by ab initio calculations using the KorringaâKohnâRostoker (KKR) method combined with the coherent potential approximation (CPA). Keywords: ZnO, Thin films, Spray pyrolysis, Optical properties, Ab-initio calculation
Evaluation by remote sensing and SIG of potential erosion risk in the Oued Srou Basin (Middle Atlas, Morocco)
peer reviewedThe aim of the present work is to do an evaluation of the potential risk of soils' erosion in the Oued Srou basin situated in the Middle Atlas, Morocco. That objective can be reached by the use of the data processings LEAM (Land Erodibility Assessment Methodology) and SIG (SystĂšme d'Information GĂ©ographique). The first program includes various factors such as soils erosion, slopes steepness and rainfalls effects on erosion; the second one is a database management leading to the drawing up of the cartographic model. As the chosen model don't include the impact of the vegetation, which is important regarding the erosion problem, that disadvantage was compensated by the realization of a vegetation map through interpretation of the satellite imaging LANDSAT ETM+ 2001.Le prĂ©sent travail a pour objectif de contribuer Ă la comprĂ©hension et Ă l'Ă©valuation du risque potentiel d'Ă©rosion des sols du bassin versant du Srou au Moyen Atlas, Maroc, par une modĂ©lisation des principaux facteurs impliquĂ©s dans lâĂ©rosion hydrique, selon le modĂšle : Land Erodibility Assessment Methodology (LEAM). Le modĂšle compte parmi ses facteurs : l'Ă©rodibilitĂ© des sols, l'inclinaison des versants et l'Ă©rosivitĂ© des pluies. Pour le dernier facteurs, nous avons dĂ©cidĂ© de compenser le biais introduit par lâutilisation d'une sĂ©rie des prĂ©cipitations Ă tendance sĂšche (1980/2002), par le calcul de trois indices d'Ă©rosivitĂ© des pluies, correspondant respectivement Ă la moyenne et aux deux annĂ©es extrĂȘmes la plus sĂšche et la plus humide. Ceci nous a permis de cartographier le risque potentiel d'Ă©rosion hydrique dans des conditions sĂšches et humides. L'analyse, la combinaison des donnĂ©es et la modĂ©lisation ont Ă©tĂ© opĂ©rĂ©es dans un SystĂšme d'Information GĂ©ographique (SIG). Le modĂšle choisi dans ce travail ne tient pas compte du couvert vĂ©gĂ©tal. Afin d'y pallier et pour amĂ©liorer le modĂšle, nous avons optĂ© pour l'addition de ce facteur. La rĂ©alisation de la carte d'occupation des sols Ă partir de l'interprĂ©tation visuelle assistĂ© par SIG, de l'imagerie satellitaire Landsat-ETM+ de 2001 qui couvre le bassin du Srou, a facilitĂ© l'extraction de la carte du couvert vĂ©gĂ©tal, ce qui a permis de dĂ©finir avec plus de prĂ©cisions les zones les plus sensibles Ă risque d'Ă©rosion
Revisiting the magnetic and magnetocaloric properties of bulk gadolinium: A combined DFT and Monte Carlo simulations
International audienceIn this paper, a combination of DFT study and Monte Carlo (MC) simulations has been performed on Gd compound which undergoes a second-order phase transition from ferromagnetic state to paramagnetic one. For this single material, the temperature-dependent total magnetization and magnetic susceptibility have been calculated and are revealed that the Curie temperature is acceptable concurrence with the experimental value. Furthermore, it was showed that under an external magnetic field of 2 Tesla (T), MCE of Gd compound around its Curie point in regard to the maximum value of magnetic entropy change ( ), agrees well with the experimental one. Besides, the Relative Cooling Power (RCP) values are found to be 34.37, 69.18, 90.74 and 128 J.kg-1 under different magnetic fields of 0.5, 1.0, 1.5 and 2T, respectively. All findings which are presented here indicate that DFT calculations and Monte Carlo simulations can be efficiently used to predict the magnetic and magnetocaloric features of Gd and related alloys