Effect of a Porous Layer on the Flow Structure and Heat Transfer in a Square Cavity

Abstract: A two-dimensional rectangular enclosure containing a binary-fluid saturated porous layer of finite thickness placed in the centre of the cavity is considered. Phase change is neglected. Vertical and horizontal solid boundaries are assumed to be isothermal and adiabatic, respectively. A horizontal temperature gradient is imposed, driving convection of buoyancy nature. The Darcy equation, including Brinkman and Forchheimer terms is used to account for viscous and inertia effects in the momentum equation, respectively. The problem is then solved numerically in the framework of a Velocity-Pressure formulation resorting to a finite volume method based on the standard SIMPLER algorithm. The effects of the governing parameters (geometric, hydrodynamic and thermal) on fluid flow and heat transfer are investigated. Nomenclatur

Właściwości hydrochemiczne i pochodzenie głównych pierwiastków w wodach gruntowych basenu Béchar–Kénadsa w strefie suchego klimatu południowozachodniej Algierii

Béchar region is located in the southwest of Algeria, characterized by an arid climate with a Saharan tendency. It is subject to an increasing demand for water like all the great agglomerations due to the economic and demographic development. The groundwater of region is deteriorating because of the economic development, and the rapid growth of population. This article is devoted to the study of hydrochemistry and processes of mineralization of groundwater in this region. The results of physicochemicals analyses shows the same chemical facies of the chloride and sulphate-calcium and magnesium type, with high mineralization from North-East to South- -West to the outlet of Béchar–Kénadsa basin. The determination of the mineralization origin and the main major elements were approached by multivariate statistical treatment and geochemical. This method has identified the main chemical phenomena involved in the acquisition of mineralization of water in this aquifer. These phenomena are mainly related to the dissolution of evaporite formations, the infiltration of runoff water and direct ion exchange and mixing. However, the high mineralization anomaly is observed at the centre of Béchar–Kénadsa basin progressively by going to the outlet of this basin.Region Béchar w południowozachodniej Algierii charakteryzuje klimat suchy z wpływami saharyjskimi. Jak wszystkie duże aglomeracje, region ten wykazuje rosnące zapotrzebowanie na wodę w związku z rozwojem ekonomicznym i demograficznym. Rozwój gospodarczy i szybki przyrost populacji jest powodem pogarszania się jakości wód gruntowych. Niniejszy artykuł jest poświęcony badaniom właściwości hydrochemicznych i procesów mineralizacji wód gruntowych w regionie. Wyniki analiz wykazują występowanie podobnych facji chemicznych typu chlorkowego i siarczanowo-wapniowych lub magnezowych o wysokim stopniu mineralizacji od północnego wschodu do południowego zachodu basenu Béchar–Kénadsa. Źródła mineralizacji i główne pierwiastki zostały oznaczone metodami geochemicznymi z zastosowaniem wieloczynnikowej analizy statystycznej. Metody te dały podstawy do identyfikacji głównych zjawisk chemicznych wpływających na mineralizację wody, takie jak rozpuszczanie formacji ewaporytowych, infiltracja spływów powierzchniowych, bezpośrednia wymiana jonowa i mieszanie. Anomalię wysokiej mineralizacji malejącą w kierunku odpływu zaobserwowano w środkowej części basenu Béchar–Kénadsa

Effect of Pre-Post TIG Welding Heat Treatment on Cast NI Superalloy

The effect of a pre (before) and post (after) heating welding treatment on the microstructure and mechanical properties of the scrap blades made of cast INC738LC superalloy is the main goal of the present investigation. The filler used in TIG welding was a INC 625 solution hardened superalloy as the proposed solution for hot cracking of the INC738LC cast superalloy in literature. The TIG welding was processed with respect to the constantly optimized parameters (current, voltage, speed, gas flux rate and number of passes) to make a mechanical properties comparison between the as received superalloy and the welded superalloy with heat treated specimens. The characterization techniques employed in this study are hardness measurements, tensile tests, optical microscopy and scanning electron microscopy. We found that the proposed preheating improves the TIG welding of the INC 738 LC superalloy specimens and the post welding heat treatment enhances its mechanical properties

High-temperature carboreduction of kaolins of different crystallinity

The high-temperature 1600x2013;17008C carboreduction of x2018;kaolinrcarbon blackx2019; raw mixture has been processed under argon atmosphere with two kaolins of quite different crystallinity. Although no transition metal catalyst was added, the growth of SiC whiskers SiCw proceeded via the vaporx2013;liquidx2013;solid VLS -like mechanism, due to the well-known particular role played by iron and titanium impurities contained in the raw kaolin samples. This work shows that the whisker yield essentially depends on the crystallinity of high-temperature phases mullite and silica , which is obtained with kaolin having the highest degree of crystallinity. This later observation and complementary experiments made by varying the carbonrkaolin ratio indicate that the carboreduction reaction must be processed with well-crystallized kaolin sample and carbon excess to produce hot-pressed high-strength x2018;aluminarSiC whiskerx2019; ceramic composites

A Statistical Analysis of Size, Shape and Tensile Properties of Fibres Extracted from Date Palm (Phoenix Dactylifera L.) Rachis

Algeria is the largest country in Africa by in terms of land area, which makes it contain large quantities of agricultural residues. The aim of this study is the valorisation of the huge amount of agricultural residue of date palm rachis available in Algeria to be used as reinforcement in bio-composite materials for various industrial applications. The analysis of the morphology of the of the date palm rachis cross-section allowed us to identify two main types of fibres according to their microstructure: vascular bundles and fibre strands. The chemical and molecular structure analysis of the date palm rachis fibres was examined by Fourier transform infrared spectroscopy (FTIR). The tensile properties of the fibre extracted were investigated under tensile loading test. The experimental results obtained for the tensile strength, Young’s modulus and strain at break of the fibres have been analysed, because of their dispersion, using three-parameter and two-parameter Weibull statistical laws. The tensile strength and Young’s modulus of the fibre strand were found to be about than four times higher than for the vascular bundle and their predicted model was determined. The tensile properties obtained for the investigated fibre were compared with other lignocelluloses fibres, existing in the literature, and it shows its great potential for use as reinforcement in bio-composite materials

Gènes de susceptibilité HLA et rétinopathie diabétique chez la population algérienne

Introduction : La rétinopathie diabétique (RD) est la complication microvasculaire la plus fréquente du diabète de type 1 (DT1). Certains sujets DT1 avec un bon équilibre glycémique peuvent développer la RD alors que d’autres sujets mal équilibrés ne développent pas de RD. Cela peut être expliqué par la présence de certains gènes de susceptibilité ou de protection. L’objectif de notre étude est de rechercher une association entre les marqueurs HLA de classe I et classe II et la RD dans la population algérienne. Patients et méthode : L’étude a été réalisée chez 52 sujets DT1 avec et sans RD et 140 témoins sains. Le typage HLA a été réalisé par la technique de « microlymphocytotoxicité ».Résultats : La fréquence des antigènes HLA-A29 et HLA-DR9 est plus élevée chez les DT1 avec RD par rapport aux DT1 sans RD et aux témoins avec comme valeurs respectives : HLA-A29 (59,26 % vs 0 %, OR=∞, pc=4,6×10−7), (59,26 % vs 5,66 %, OR=24,24, pc=7,6×10–10) et HLA-DR9 (29,63 % vs 0 %, OR=∞, pc=1,310−3), (29,63 % vs 4,29 %, OR=9,40, pc=7,010−5). Cependant, la fréquence de l’antigène HLA-B49 est plus faible chez les DT1 avec RD par rapport aux DT1 sans RD (3,7 % vs 28 %, OR=0,10, pc=8,8×10−3) et par rapport aux témoins (3,7 % vs 22,64 %, OR=0,13, pc=0,011) avec une différence statistiquement significative. Conclusion : Les antigènes HLA-A29 et DR9 sont probablement des marqueurs de susceptibilité à la RD alors que l’antigène HLA-B49 a probablement un effet protecteur dans la population algérienne.Susceptibility genes, HLA and diabetic retinopathy in the Algerian population Background: Diabetic retinopathy (DR) is the most frequent microvascular complication of type I diabetes (T1D). Some well-controlled type I diabetics may develop DR, while other poorly-controlled diabetics do not develop DR. This might be explained by certain susceptibility genes or protective genes. The purpose of our study is to search for any association between the HLA class I and II markers and DR in the Algerian population. Patients and methods: This study was carried out in 52 T1D subjects with and without DR compared to 140 healthy controls. HLA typing was performed using the " microlymphocytotoxicity" technique. Results: The frequency of HLA-A29 and HLA-DR9 antigens is higher in T1D with DR compared to T1D without DR and to controls with frequencies of HLA-A29 (59.26% vs. 0%, OR = ∞, pc = 4.6 × 10-7), (59.26% vs. 5.66%, OR = 24.24, pc = 7.6 × 10-10) and HLA-DR9 (29.63% vs. 0%, OR = ∞, pc = 1.310-3), (29.63% vs. 4.29%, OR = 9.40, pc = 7.010-5) respectively. However, the frequency of HLA-B49 antigen is significantly lower in T1D with DR than in T1D without DR (3.7% vs. 28%, OR = 0.10, pc = 8.8 × 10-3) and compared to controls (3.7% vs. 22.64%, OR = 0.13, pc = 0.011). Conclusion: HLA-A29 and HLA-DR9 antigens are probably markers of susceptibility for DR while HLA-B49 antigen is probably associated with a protective effect in the Algerian population