Load sediments quantification in Algerian North-West basins by ANN (Artificial Neurons Network) method

Due to the complexity of basins morphometric parameters and the hydroclimatic irregularity of the semi-arid regions of North Africa, solid transport has been still far from being clearly assessed. This study attempts to shed light on this problem; in order to conceive a global model for the suspended sediment load quantification, taking into account all stream waters of the North-West area of Algerian. The calculation is based on the use of the ANN artificial neurons network method, which has proven its success and its reliability in several fields of research. The collected data are measured in hydrometric stations of several basins, such as Cheliff, Tafna, Macta, and Oran’s basins. The results obtained using the ANN method are sufficiently reliable, the best correlations were obtained for each studied stream water exceeding 97% (specific model to each station), and 90% in the case of a global model characterizing for all studied stations, which allows the extracted model to give better estimation of the suspended solid flow rates for any measured liquid flow rate of the north-west Algerian basins

Insensitive Bounds for the Stationary Distribution of a Single Server Retrial Queue with Server Subject to Active Breakdowns

The paper addresses monotonicity properties of the single server retrial queue with no waiting room and server subject to active breakdowns. The obtained results allow us to place in a prominent position the insensitive bounds for the stationary distribution of the embedded Markov chain related to the model in the study. Numerical illustrations are provided to support the results

Silting of foum el gherza reservoir

The Foum El Gherza Reservoir fails to satisfy the irrigation of 300,000 palms of Sidi Okba and Seriana due to advanced siltation. Based on data from bathymetric surveys conducted by the National Agency for Dams, the siltation rate was estimated at 0.9 million m3/year. With a total capacity of 47 million of m3, the Foum El Gherza dam is silted up with more than 65 million m3. In this case, the life of the dam will not exceed 11 years of operation. The total silting of the reservoir will occur in 2023. Desilting the dam proves an emergency to save the palms of Seriana and Sidi Okba

ANALYSE MULTI FRACTALE DES ÉCHOS RADAR PAR LA MÉTHODE DES MAXIMUMS DES MODULES DE LA TRANSFORMÉE EN ONDELETTE (MMTO) 2D POUR LES SITES DE BORDEAUX (FRANCE), SÉTIF (ALGÉRIE) : APPLICATION À L'ÉLIMINATION DES ÉCHOS PARASITES

International audienceIn this work, the 2D-WTMM multifractal approach was applied to analysis the radar echoes, and to identify the unwanted echoes coming from terrestrial surface. With this intention, we considered radar images taken from two areas where different climates and relief prevail. We showed that almost Anaprops are characterized by a monofractal spectrum contrary to the echoes of precipitations which present a multifractal character. Moreover, we showed that the Holder coefficient and the combination of the spectrum mode and density of skeleton per pixel present robust factors to discriminate between the two types of echoes. Indeed, the unwanted echoes are practically eliminated at 98 per cent whereas the echoes of precipitation are almost preserved at 98,2 per cent. Also, we showed that the error between the measured intensity on the ground and the estimated intensity after treatment of the unwanted echoes does not exceed 5% for the Sétif site. Because the computation time is three minutes, the radar images can be processed in real-time.Dans le présent travail, l'approche MMTO-2d est appliquée pour l'analyse multi fractale des échos radar et l'identification des échos parasites en provenance de la surface terrestre. Pour ce faire, nous avons considéré des images radar prises dans deux régions où prévalent des climats et des reliefs différents. Il s'agit des sites de Sétif (Algérie) et Bordeaux (France). Nous avons montré que la plupart des Anaprops sont caractérisés par un spectre monofractal contrairement aux échos de précipitations qui présentent un caractère multi fractal. En outre, nous avons montré que le coefficient d'Holder ou la combinaison mode du spectre et densité de squelette par pixel se présentent comme des facteurs robustes de discrimination entre les deux types d'échos. En effet, les échos parasites sont pratiquement éliminés à 98% alors que les échos de précipitation sont quasiment conservés à 98,2%. Aussi, nous avons montré que l'erreur entre l'intensité mesurée au sol et estimée après traitement des échos parasites ne dépasse pas 5% pour le site de Sétif. Etant donné que le temps de traitement est égal à trois minutes, les images radar peuvent être traitées en temps réel

Experimental Analysis of the Physical Degradation of Polymers – The Case of Polymethyl Methacrylate

Polymers are known to be sensitive to aging; their lifetime can be predicted through experimental tests. The present paper presents an experimental study on the long-term performance of polymethyl methacrylate (PMMA) exposed to solar and UV radiations, drinking water and sea water. The performance of this polymer was analyzed in terms of strain variation, strain at break in tension, and Young's modulus. The results obtained showed that the amount of absorbed water is independent of the nature of the solvent, and only the absorption kinetics may be regulated by the species contained in the medium. This seems to indicate that plastification of polymers is a reversible phenomenon. In addition, it was found that the tensile strength and elastic modulus drop with increasing immersion time. Compared with seawater, the absorption of drinking tap water, after 36 months, leads to a non-linear behavior of the polymethyl methacrylate. Exposition of  PMMA to UV radiation and global solar radiation, for the same duration of exposure, resulted in greater performance degradation when the polymer was exposed to UV radiation. In addition, the results obtained after a 19-month exposure period that the UV radiation changes the behavior of this material from viscoelastic to viscoplastic.  &nbsp

A new species for the vascular flora of Algeria: Cyperus eragrostis (Cyperaceae)

This study provides a definition and description of Cyperus eragrostis as a new alien species to Algeria and North African flora. This hemicryptophyte, native to the tropical parts of South America, is recorded for the first time in Jijel eco-complex wetlands in North-East Algeria. Applying the standard phytosociological method we studied the stands in which this alien species grows together with other hygrophilous and ruderal species. The present study improves the knowledge of the Algerian flora and completes the information about the distribution of C. eragrostis reported by the available international literature and public herbaria

Bedload Estimation: Case of Wadi El-Hammam in the North-West of Algeria

In Algeria, only the transport of suspended sediment is measured, the rate of bedload in the global transport of solids is estimated, approximately. Measures of bed load transport in the field are very costly, due to flow disturbances. As a result, evaluations of this type of sediment transport are difficult to carry out in the absence of databases. In this article, we tried to quantify this mode of transport at the wadi El-Hammam using the formula of Meyer-Peter and Müller. Formula that seems best adapted to the physical characteristics and flow conditions of the wadi studied. The results obtained show that the calculated bedload ratio is between 0.6 and 28 % of the suspension. The quantities transported annually are very large and irregular as they vary from 2.3 to 32 Mg.km-2.year-1, characterising the Mediterranean mountains and semi-arid environments. A good correlation was found between the daily bedload flow and the liquid flow, the obtained model Qs = aQb, can be easily used to estimate the bedload transport at the Hacine hydrometric station, located at the output and without data concerning this phenomenon

Static Sorption of Phenol and 4-Nitrophenol onto Composite Geomaterials based on Montmorillonite, Activated Carbon and Cement

International audienceThis paper studies the sorption of phenol and 4-nitrophenol (4NP) onto solid sorbents derived from mixtures of montmorillonite, activated carbon (AC) and cement, denoted herein MACC. These materials are mesoporous and some of their physicochemical properties have been measured and discussed. The weight fraction X1 (%) of montmorillonite in the mixtures strongly influences the sorbate removal rate. The sorption isotherms were experimentally established by batch testing on geomaterials with various X1 values at 20 °C and at different pH values (from 3 to 8). The Langmuir model correctly fits the sorption isotherm data (R2 > 0.95). The results show increased sorption behavior for both phenol and 4NP on the composite geomaterials compared to the pure components, yielding the order: MACC > AC > montmorillonite

Stochastic Approximations and Monotonicity of a Single Server Feedback Retrial Queue

This paper focuses on stochastic comparison of the Markov chains to derive some qualitative approximations for an M/G/1 retrial queue with a Bernoulli feedback. The main objective is to use stochastic ordering techniques to establish various monotonicity results with respect to arrival rates, service time distributions, and retrial parameters

Gestion rationnelle de l’eau de pluie et flux hydriques dans le système sol-plante-atmosphère au bassin du Haut Chéliff, Algérie

L’eau devient un bien rare et coûteux, et ne permet d’irriguer que des surfaces de plus en plus limitées. Les irrigations sont mal maîtrisées, permettent une accumulation de plus en plus importante de sels et participent à la dégradation des sols. L’eau de pluie retenue par le sol est importante et doit être étudiée tout d’abord par son volume et par la suite par ses fluctuations dans le temps. Le volume réel de sol exploité par les racines, les espèces végétales viables et économiques qui seraient capables de valoriser de telles potentialités hydriques doivent également être évalués. La principale contrainte à résoudre pour la mise en valeur de ces sols serait le maintien d’une alimentation équilibrée en eau des cultures. Au cours de ce travail, nous allons traiter simultanément la réserve hydrique du sol sous chaque parcelle considérée (Colza, jachère), durant l’année 2007-2008. L’analyse des profils hydriques montre que les sols maintenus en jachère perdent plus d’eau durant cette période que les sols cultivés. Il est temps de chercher les moyens et les mesures nécessaire pour utiliser rationnellement cette eau. Cela passera nécessairement la compréhension des flux hydriques dans le sol, ses rapports avec la plante et l’atmosphère. Mots clés : Eau de pluie, Propriétés du sol, Espace végétale, Profil hydrique, Réserve hydrique.  Water is becoming a scarce and expensive commodity, allowing to irrigate limited areas. Irrigation is poorly managed and this situation allow salts accumulation and soil degradation. The rainwater retained by soil is important and must be studied, first by its volume and thereafter by its fluctuations over time. The actual soil volume exploited by roots, viable and economic plant species that would be able to value such water potential should also be evaluated. The principal constraint to solve for development of these soils would be maintaining an adequate water supply of crops. The present paper aims to evaluate the means and measures necessary to manage this water rationally. During one year (2007-2008), we investigated soil water reserve in each field (Rapeseed, fallow). The water profile analysis showed that fallow lose more water than cultivated soil over this period. The understanding of water flux through the soil, and its relationship with the plant-atmosphere may be also used for the optimization of rainwater. Keywords: Rainwater, soil properties, Plant species, Water profile, Water reserve &nbsp