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Chandoul I.R.,Water Science Technologies | Chandoul I.R.,Campus UniversitaireCite Erryadh | Bouaziz S.,Campus UniversitaireCite Erryadh | Bouaziz S.,University of Sfax | And 2 more authors.
Arabian Journal of Geosciences | Year: 2015

Aquifer vulnerability has been assessed in the northern part of Jeffarra Basin (Southern Tunisia) using the DRASTIC models, based on a geographic information system. Two vulnerability maps have been developed in this study: the pesticide DRASTIC vulnerability map and the generic DRASTIC vulnerability map. These maps show that the study area is more sensitive to pesticide contamination. About 23 % of this area is under high to very high vulnerability to pesticide contamination, while only 9 % under high vulnerability to generic pollution. In the both cases, the Oued El Maleh Basin and the Oued El Mazra Basin in the coastal plain are the most vulnerable zones. The middle part of the study area is dominated by moderate vulnerability classes, while the southwest part displayed “low” vulnerability classes. The superposition of the DRASTIC maps with land use map shows that most agricultural areas are located in the high to very high vulnerability zones, which imposes a high risk of contamination by pesticides in these areas. Depth to water parameter inflicted the largest impact on the generic vulnerability index followed by the impact of the vadose zone, net recharge, and topography. The pesticide vulnerability index is more sensitive to the removal of the net recharge parameter followed by the depth to water, soil media, and topography. Compared with other studies, the sensitivity analyses show that in the case of porous aquifers, the aquifer media parameter is always the layer which compels less variation of the generic DRASTIC index. © 2014, Saudi Society for Geosciences. Source


Brahimi A.,Mohamed 1st University | Chafi A.,Mohamed 1st University | Nouayti N.,Water Science Technologies | Elmsellem H.,Mohamed 1st University | Hammouti B.,Mohamed 1st University
Der Pharma Chemica | Year: 2015

The region Taourirt endures a big problem of pollution of surface waters. This pollution has diverse origins, domestic, agricultural and industrial. Evaluation of the concentration of the metals studied (Al, As, Se, Mn, Ni, Fe, Zn, Cu, Cr, Pb and Cd) in surface water has revealed the presence of a large metal contamination, mainly in the river downstream of releases. Heavy metals soluble in water after filtration is determined by atomic emission spectroscopy with inductive coupled plasma (ICP-AES) using a JY-type spectrometer. To better assess the impact of wastewater on water quality of the Za River and its tributary oued Tizeghrane, and analyze between the different variables through their structuring and guidance correlations and to identify the main factors responsible for the water quality of the surveyed environment, we treated statistically all data by Principal Component Analysis (PCA). The typological structure of the plan analysis F1 x F2 shows the identification of four areas, depending on the nature of metal pollutants, their degree of contamination and the "season", this factor seems to be a determining factor in the type of flow studied. Source


Laajimi R.H.,Water Science Technologies | Laajimi R.H.,Hail University
Applied Surface Science | Year: 2012

In this work, we search to optimize the surface textures of monocrystalline silicon (c-Si) intended to be used in silicon solar cells. For this purpose, we studied the morphology of formed etch hillocks during anisotropic etching of silicon using alkaline solutions based on sodium hydroxide (NaOH), potassium hydroxide (KOH) and tetramethylammonium hydroxide (TMAH). Such treatments lead to the formation of various pyramids-like textures that can be well optimized to improve the photocurrent of c-Si-based solar cells. The produced textures were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-visible optical reflectivity and minority carrier lifetime measurements. These investigations allow evaluating the size and density of the formed pyramidal textures; the apex angles vary between 75°and 82°, while the heights and bases of the pyramids range from a few hundred nanometers to several micrometers. A minimum reflectivity value of about 6% was obtained at specific conditions using NaOH, whereas it was found that the apparent effective minority carrier lifetime (τ eff) is sensitive to the injection level (Δn), which shows an apparent increase from 1.2 μs to 2.4 μs for a minority carrier density of about Δn = 210 14 cm -3. © 2012 Elsevier B.V. All rights reserved. Source


Stewart B.A.,Tetra Tech Inc. | New C.W.,Environmental Engineer | Hosni A.A.,Water Science Technologies | Dvorak B.I.,University of Nebraska - Lincoln
Journal of Environmental Engineering (United States) | Year: 2013

This study evaluated the system performance in terms of sorbent usage rate (SUR) of single column, two-column parallel, and lead-lag configurations, both with and without bypass blending, based on two normalized parameters describing the breakthrough profile (mass transfer zone length to lag ratio, or MTZ:Lag) and treatment objective (C/Co). The pore surface diffusion model was used to simulate a range of single compound scenarios to develop a framework for comparing configurations. From this analysis, regions on a MTZ:Lag versus C/Co plot could be identified in which particular configurations yielded the lowest system SUR. At low MTZ:Lag ratios, bypass blending (single column or lead-lag operation) offered significant improvements because of the ability to bypass untreated flow and reduce sorbent bed mass. However, at low target C/Co values, bypass offered little improvement. Lead-lag without bypass performed best at high MTZ:Lag ratios by passing the mass transfer zone through two columns in series. At high MTZ:Lag ratios and high target C/Co values, two-column parallel configurations yielded significant benefits by blending high and low concentration effluents and improving sorbent utilization. © 2013 American Society of Civil Engineers. Source


Lau V.K.N.,Water Science Technologies | Cui Y.,Water Science Technologies
IEEE Transactions on Wireless Communications | Year: 2010

In this paper, we consider delay-optimal power and subcarrier allocation design for OFDMA systems with NF subcarriers, K mobiles and one base station. There are K queues at the base station for the downlink traffic to the K mobiles with heterogeneous packet arrivals and delay requirements. We shall model the problem as a K-dimensional infinite horizon average reward Markov Decision Problem (MDP) where the control actions are assumed to be a function of the instantaneous Channel State Information (CSI) as well as the joint Queue State Information (QSI). We propose an online stochastic value iteration solution using stochastic approximation. The proposed power control algorithm, which is a function of both the CSI and the QSI, takes the form of multi-level water-filling. We prove that under two mild conditions in Theorem 1, the proposed solution converges to the optimal solution almost surely (with probability 1) and the proposed framework offers a possible solution to the general stochastic NUM problem. By exploiting the birth-death structure of the queue dynamics, we obtain a reduced complexity decomposed solution with linear O(KNF) complexity and O(K) memory requirement. © 2006 IEEE. Source

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