Risque d'érosion hydrique entre fragilité des équilibres environnementaux et perspectives de durabilité: Cas du bassin d’Oued El Abed (Maroc nord-est)

The objective of this work is to study water erosion phenomenon in El Abed watershed in North Eastern Morocco. With this in mind, we have analyzed the quantitative and qualitative information available on the one hand, and on the other hand, we have carried out field measurements by rain simulation (60 mm/h during 10 mn). Soil loss was estimated using the universal soil loss equation (USLE). The qualitative analysis based on the inventory of the various forms of water erosion showed a strong morphodynamic activity, characterized by diffuse and concentrated streaming, gullying and side extensions of valleys. The quantitative analysis of soil losses using USLE model made it possible to estimate that 4,7% of the watershed surface area are strongly eroded and that average specific degradation is estimated to be 6,4 t/ha/an. Measurements of rain simulation tests showed clear differences between the various land uses. Indeed, runoff coefficient is low on the vegetation covered plots of and the plots cultivated parallel to contour lines. On the other hand, runoff coefficient is high on steeply bare soils. The amount of detached soil varied from 0.014 t/ha for the covered plots to 2.9 t/ha for the steeply bare soils. It should be underlined that the extent of water erosion in El Abed watershed is due to its natural settings, but also to anthropic activities (cultivation and overgrazing).  Keywords: Water erosion, USLE, El Abed watershed, MoroccoL'érosion hydrique est l’un des risques inquiétants qui menacent le milieu physique et la stabilité humaine. Le bassin d’oued El Abed, est sujet à ce phénomène depuis longtemps, ce qui a induit des mutations importantes et a touché divers domaines économiques, sociaux et environnementaux. Ainsi, la problématique de cette étude est axée sur l’étude de l’érosion et son évaluation dans ce bassin. Le bassin d’oued El Abed est situé au sud-ouest de Taourirt, dans la partie ouest du couloir de Guercif-Oujda et comprend une partie de la plaine de Tafrata. Sa surface est de 317 km² à sa confluence avec oued Moulouya. Pour étudier l'érosion dans ce bassin, nous avons, d’une part analysé les données quantitatives et qualitatives disponibles et, d’autre part, réalisé des mesures sur le terrain par simulation de pluie (intensité de 60 mm/h durant 10 mn). L'estimation de la perte en sol a été faite en se basant sur l'équation universelle de perte en sol (USLE). L'inventaire des diverses manifestations et formes d'érosion hydrique dans le bassin de l'oued El-Abed montre clairement qu'il s'agit d'une forte activité morphodynamique caractérisée par un ruissellement diffus et concentré, des ravinements, des extensions latérales des vallées. Après avoir calculé les différents facteurs de l’USLE, on a constaté que 4,7% de la surface du bassin serait fortement érodée. La dégradation spécifique moyenne a été estimée à 6,4 tonnes/ha/an. Les mesures de simulation de pluie ont montré des différences nettes entre les utilisations des terres. En effet, les coefficients de ruissellement sont faibles dans les parcelles couvertes de végétation et celles cultivées parallèlement aux courbes de niveau. Par contre, sur les sols nus et les pentes fortes, ce coefficient est élevé. Les quantités de sols détachées varient de 0,014 pour les parcelles couvertes à 2,9 t/ha pour celles nues et à forte pente. L’érosion dans le bassin d’El Abed est due à sa fragilité naturelle mais surtout aux actions anthropiques (mise en culture, surpâturage). Mots clés: Érosion hydrique, USLE, Bassin d’oued El-Abed, Maroc nord-es

Acoustic Tamm states in slender tubes

International audienceWe present an analytical and numerical study of the possibility of existence of surface localized modes, the so-called Tamm states, in a one-dimensional (1D) comb-like phononic crystal (PnC). The structure is made out of periodic array of stubs of lengths d2grafted along a waveguide and separated from each other by a tube of length d1. We show the existence of surface modes for the semi-infinite structure. In particular, when one considers two complementary semi-infinite systems obtained by cutting the infinite one into two parts, we obtain one surface mode per gap induced by the surface of the two complementary systems. Furthermore, we demonstrate that these surface modes can be detected from the maxima and minima of the transmission spectrum, when the finite structure is grafted vertically along a homogeneous acoustic waveguide. That means that one can observe experimentally this type of modes for acoustic waves in slender tubes. These results may find many practical applications in noise control and highly sensitive PnC sensors. © 2021 Elsevier Ltd. All rights reserved

Photonic demultiplexer based on electromagnetically induced transparency resonances

International audienceWe give an analytical and experimental demonstration of the possibility to realize a simple photonic demultiplexer based on electromagnetically induced transparency resonances. The demultiplexer consists of a Y-shaped waveguide with an input line and two output lines. Each output line contains two grafted stubs at a given position far from the input line. We derive in closed form the expressions for a selective transfer of a single propagating mode through one line keeping the other line unaffected. We illustrate the analytical and numerical results by a simple experiment carried out using coaxial cables in the radio frequency domain

Y-shaped magnonic demultiplexer using induced transparency resonances

We give an analytical demonstration of the possibility to realize a simple magnonic demultiplexer based on induced transparency resonances. The demultiplexer consists on an Y-shaped waveguide with an input line and two output lines. Each line contains two grafted stubs at a given position far from the input line. We derive in closed form the analytical expressions for selective transfer of a single propagating mode through one line keeping the other line unaffected. This is performed through magnonic induced transparency resonances (MIT) characterized by a resonance squeezed between two transmission zeros. The existence of a complete transmission beside a zero transmission, enables to select a given frequency on one output line, by canceling the transmission on the second line as well as the reflection in the input line. Also, we show that despite the existence of a bifurcation of the input line on two output lines, the transmission through each line can be written following a Fano line shape. In addition, in order to understand better the scattering properties of the filtered resonances, we give the analytical expressions of Fano parameter q and quality factor Q of the MIT resonance in each line. The spatial distribution of the spin waves associated to different MIT resonances is performed through an analysis of the magnetization of these modes. Also, the effect of attenuation on the transmission spectra and the quality of demultiplexing is also discussed. The theoretical results are performed using the Green’s function approach which enables to deduce in closed form, the transmission and reflection coefficients as well as the densities of states

Bound in continuum states and induced transparency in mesoscopic demultiplexer with two outputs

International audienceWe investigate the electronic transport in a simple mesoscopic cross structure made of two wires (stubs) grafted at the same point along a quantum waveguide. We show that the structure may exhibit important phenomena such as bound in continuum (BIC) states. These states are transformed into electromagnetically induced transparency (EIT) resonance by detuning slightly the lengths of the stubs. The last phenomenon is used to propose and study a mesoscopic demultiplexer device with an input waveguide and two output waveguides. We give closed-form expressions of the geometrical parameters that allow a selective transfer of a given state in the first waveguide without perturbing the second waveguide. The effect of temperature on the transmission resonances is also examined by using Landauer-Buttiker formula. The analytical results of the dispersion relation and transmission and reflection coefficient are obtained using the Green's function method

The oriented processes for extraction and recovery of paracetamol compound across different affinity polymer membranes. Parameters and mechanisms

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Anti-Corrosive Properties and Quantum Chemical Studies of (Benzoxazol) Derivatives on Mild Steel in HCl (1 M)

International audienceThis work is a contribution to the study about the inhibition of mild steel corrosion in a molar hydrochloric acid medium by some benzoxazol derivatives compounds. The study was carried out using gravimetric and electrochemical methods (stationary and transient). We have considered the influence of the inhibitor concentration, the temperature of the medium and the duration of the immersion of the metal sample in the aggressive medium. These studies are complemented with theoretical calculations aimed to correlate the results obtained from experimental measurements using the DFT method. The results obtained in this work through gravimetric and both transient and stationary electrochemical methods showed a satisfied coherence. Theoretical calculations also revealed a good correlation with the experimental results for our compounds