Climate change and water availability in north-west Algeria: investigation by stable water isotopes and dendrochronology

Since the 1970s, rainfall has declined along the North African coast, while the demographic pressure has increased. Supplementing the rainfall data and water level of the Béni Bahdel dam, water isotopic signature and tree ring analyses were used to better understand the effects of climate change (lower rainfall, higher summer temperature) and the water circulation in the Tafna River basin in north-west Algeria. Changes are recommended in water storage and afforestation policies and irrigation techniques

ASMA: towards adaptive secured multipath in MANETs

As they are used to create open communities, Mobile Ad hoc NETworks (MANETs) are not favourable environments to establish trust, which is necessary to provide security. Multipath routing mechanisms within infrastructureless networks environment seems appropriate and useful to enhance security protection. In fact, the level of trust can be increased so as many of potential security attacks are detected, revealed and stopped. Nevertheless an excessive control overhead is always generated. In this paper, we propose a global framework that integrates a set of concepts and mechanisms aiming at enhancing security in highly dynamic decentralized ad hoc networks. Our solution focuses on authentication, routing securing, trust management with reliable estimation of trust. A large panoply of attacks are prevented using our various mechanisms.8th IFIP/IEEE International conference on Mobile and Wireless CommunicationRed de Universidades con Carreras en Informática (RedUNCI

Experimental study of temperature effects on the photovoltaic solar panels performances in Algerian desert

Photovoltaic panels are operated in the Algerian desert areas under high temperatures, especially, in the summer, when the temperature may be reached 70°C on the panel's surface. The high temperature has a significant negative impact on the photovoltaic panels performance. In this paper, an experimental study to track the effects of temperature on the photovoltaic panels performances in different situations has been realized. The obtained results approve the importance of the temperature effects on the electrical power of the photovoltaic panel. The temperature increases lead to decreases in the performance of the panel, where an output power that does not exceed 52% of the nominal power at a high temperature

Ecoulement à surface libre sur fond de rugosité inhomogène

Dans ce travail nous présentons les résultats des travaux expérimentaux et de modélisation relatifs à des écoulements à surface libre en canal rectangulaire dont le fond présente un contraste de rugosité suivant la transversale. Le contraste de rugosité est créé par un système de barrettes parallélépipédiques collées périodiquement au centre du canal, les autres parties adjacentes du fond étant lisses. La configuration de rugosité choisie permet de créer un fort gradient transversal du frottement pariétal, à l’origine des écoulements secondaires dans le plan perpendiculaire à la direction principale de l’écoulement. Au moyen d'un anémomètre Laser Doppler on a déterminé l'évolution transversale des champs de vitesse moyenne et des composantes du tenseur de Reynolds. Ensuite on a déduit la distribution transversale du frottement pariétal, de la position de l'origine de la loi logarithmique et de la fonction de la rugosité. L'interprétation de l'évolution des profils verticaux des fluctuations longitudinales et verticales s'appuie sur deux solutions analytiques d'un modèle algébrique dérivé du modèle de transport du tenseur de Reynolds de Gibson et Rodi (1989). La première solution basée sur l’hypothèse d’équilibre production-dissipation est établie dans la zone de paroi et la seconde, développée prés de la surface libre, est basée sur l’hypothèse de « quasiéquilibre diffusion-dissipation ». Des simulations numériques des écoulements parallèles et non parallèles réalisées à l’aide d’un modèle de transport du tenseur de Reynolds et un modèle k-e anisotrope sont ensuite commentées. Les premiers résultats sont encourageants même si des améliorations doivent être apportées pour mieux rendre compte des interactions près de la surface libre et de la paroi latérale. ABSTRACT : We present new experimental results and, as well analytical as numerical modelling of free surface flows developing on a bottom with transverse gradient of roughness. The contrast of the bottom roughness is created by parallelepipedal barrettes glued in the central zone of the bed wall on a third of the channel width. This configuration of the roughness permits to create a strong transverse variation of the wall shear stress, at the origin of secondary flows in a plan perpendicular to the principal direction of the flow. We determined the transverse evolution of the mean velocity and of the Reynolds tensor components, using a laser Doppler anemometer. Then we obtained the transverse distribution of the wall shear stress, the origin of the logarithmic law and the roughness function. The interpretation of the evolution of the vertical profiles of longitudinal and vertical fluctuations is based on two analytical solutions obtained from an algebraic stress model derived from the Reynolds stress model of Gibson and Rodi (1989). The first solution based on the production-dissipation equilibrium hypothesis is developed in the wall zone and the second, expanded in the vicinity of the free surface, is based on the «diffusion–dissipation quasi-equilibrium» hypothesis. Numerical simulations of parallel and non-parallel flows were realised using a Reynolds stress model and an anisotropic k-e model then commented. The first results are promising although improvements could be introduced in order to better take into account the interactions close to the free surface and the side-wall

CHEMICAL COMPOSITION AND ANTIFUNGAL ACTIVITY OF ESSENTIAL OIL FROM SATUREJA CALAMINTHA NEPETA AGAINST PHYTOPATHOGENS FUNGI

Objective: The increasing incidence of resistance among pathogen towards synthetic fungicides is a cause of serious problem. For this, the fight against fungi is directed to the use of natural products. The main objectives of this study were to investigate the chemical composition and antifungal activity of the essential oil against two post harvest pathogenic fungi: fusarium. sp and Aspergillus. sp and then compare it with the effect of two fungicides (Vapcotop and Propineb) on the same stem.Methods: Essential oil samples of Satureja calamintha nepeta were analyzed using a Gas Chromatography/Mass Spectrometry (GC-MS) technique. The in vitro antifungal activity of the essential oils was done by the poisoned food technique.Results: The GC–MS analysis of the essential oil identified 35 components accounting for 99.40% of the total oil composition. The most abundant components were Menthone (26.46%), piperitone oxide (22.26%), and pulegone (14.04%). Essential oil was found effective against all the tested fungi, and was more potent then the two fungicides with minimum inhibitory concentration (MIC) value of 2 µl/ml.Conclusion: The essential oil exhibited a significant reduction in mycelial growth with the two fungi species, and has a higher biological activity than those of the two fungicides. This study suggests that essential oil represents a good alternative to eliminate fungi that can be pathogens for plants.Â