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    Removal of Chromium (VI) from Water onto Activated Carbon by Adsorption in Dynamic Mode
    (2020) Naouel Hezil,
    Abstract Hexavalent chromium pollution from industrial waste water is a serious problem as it can cause adverse effects on the environment. Several methods are used to reduce the harmful effects of this pollutant, especially physico-chemical methods, such as adsorption technology. The present study aims to remove Cr (VI) from industrial sources in a fixed-bed column of activated carbon. The experiments were carried out at natural pH and temperature with a flow rate (5, 10, and 20 mL/min) and bed height (3.5 cm). Breakthrough curves for feed concentrations (0.01, 0.03, and 0.05 mol/L) were investigated. The results indicated a marked decrease up to 99%. The value of the flow constant for the Thomas model decreased with the increase in the concentration of the incoming substance, but increased with the increase in the flow rate.
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    Synthesis and structural and mechanical properties of nanobioceramic (α-Al 2 O 3 )
    (2019-02-19) Naouel Hezil
    The structural and mechanical properties of the nanostructured alpha-alumina (α-Al compact powders, formed by calcination of aluminum hydroxide (Al(OH) gibbsite at different temperatures (100–1100 °C), followed by uniaxial pressing and subsequently hot isostatically pressed (HIP), were investigated using X-ray diffraction, scanning electron microscopy (SEM), and type ball-on-disk oscillating tribometer. X-ray diffraction analysis indicates that the transformation sequence involves the formation of κ-Al as an intermediate phase between χ-andα-Al . The crystallite size of calcined alumina (α-Al )was as small as 8 nm after calcination at 1100 °C. The sliding friction and wear rate were lower in the nanocrystalline samples calcined at 1100 °C at same applied load (3, 6, or 10 N). The enhanced friction and wear resistance were endorsed to have fin microstructure similar to the sample calcined at 1100 °C.
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    Structural, and tribological properties of nanostructured a þ b type titanium alloys for total hip
    (2022-06-12) Naouel Hezil
    Titanium alloys are in demand for various biomedical applications and the most popular among them being, Tie6Ale4V. Hence, in this study, Tie6Ale7Nb are fabricated through the route of mechanical milling using different sintering temperatures. X-ray diffraction and hardness tests were conducted to characterize the developed sams to evaluate the effect of sintering temperatures on the structural and mechanical properties. It is observed that the sams sintered at a temperature of 1250 C had the smallest crystallite and pore size, with enhanced relative density and mechanical properties. Tribological tests were conducted at varying normal loads to characterize the wear and frictional behaviour and showed that the sams sintered at 1250 C presented the lowest friction coefficient and wear rate. © 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (
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    Numerical Study of the Behavior of a Zirconia Dental Prosthesis with Prior Defect
    The biomechanics field continues with its progress and will not cease to grow due to ongoing research in this area to find better solutions to problems. It is in this context that this work aims to simulate the mechanical behavior of a dental prosthesis made from zirconia. The proposal of zirconia as a material for dental prosthesis is the main aim of this paper. Indeed, Zirconia as a bioceramic material presents many advantages, and especially good biocompatibility and high resistance of wear. On the other hand the disadvantage of this material is its fragility i.e. it has weak strength against cracking. So, in this paper we considered a dental prosthesis assumed to be implanted to an adult person. In order to study the crack initiation we considered a defect in this prosthesis. Using the conditions of blocking and loading by Abaqus simulating tool, we obtained the results revealing the possibility of using zirconia as a material for dental prosthesis
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    Thickness stretching and nonlinear hygro-thermo-mechanical loading effects on bending behavior of FG beams
    (2022-12-06) FAICEL KHADRAOUI
    In this paper, the nonlinear vibration behavior of the spiral stiffened multilayer functionally graded (SSMFG) cylindrical shells exposed to the thermal environment and a uniformly distributed harmonic loading using a semi-analytical method is investigated. The cylindrical shell is surrounded by a nonlinear viscoelastic foundation consisting of a two-parameter Winkler-Pasternak foundation augmented by a Kelvin-Voigt viscoelastic model with a nonlinear cubic stiffness. The distribution of temperature and material constitutive of the stiffeners are continuously changed through the thickness direction. The cylindrical shell has three layers consisting of metal, FGM, and ceramic. The interior layer of the cylindrical shell is rich in metal, while the exterior layer is rich in ceramic, and the FG material is located between two layers. The nonlinear vibration problem utilizing the smeared stiffeners technique, the von Kármán equations, and the Galerkin method has been solved. The multiple scales method is utilized to examine the nonlinear vibration behavior of SSMFG cylindrical shells. The considered resonant case is 1:3:9 internal resonance and subharmonic resonance of order 1/3. The influences of different material and geometrical parameters on the vibration behavior of SSMFG cylindrical shells are examined. The results show that the angles of stiffeners, temperature, and elastic foundation parameters have a strong effect on the vibration behaviors of the SSMFG cylindrical shells.
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    Effect of Broken Glass Particle on Stress Transfer of Nylon Matrix Composite
    (2023-10-30) , F. Khadraoui
    Some of the material demands in the advanced industries cannot be fulfilled by monolithic materials. Therefore, composite materials have been developed. The combination of desired properties of thermoplastics and glass particles (high strength and high modulus) is the aim of composites production Particles are becoming increasingly popular reinforcing elements in products made by injection molding. Particles reinforcement allows the polymer to be processed employing the same methods as those used for unreinforced polymers. The loads are not directly applied to the reinforcements, but they are applied to the matrix and some of the loads applied are transferred to the particles. The development of micromechanics equations for the particulate composites follows along the same lines as those for the short fiber reinforced composites. Particles are used to increase the strength or other properties of inexpensive materials during reinforcement with other matrix materials. The objective of this study is to analyse the particle breaking effect in composite made of nylon 66 (PA) matrix reinforced with glass particles, in which the particles diameters of 19.61, 26.15, 39.22 and 78.45 m were used. A volume fraction of 20 % was assumed in each model.
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    Investigating the Influence of Material Composition on Bending Analysis of Functionally Graded Beams Using a 2D Refined Theory
    (2024) Faicel Khadraoui
    This study attempts to shed light on the analysis of the static behavior of simply supported FG type property gradient material beams according to an original refined 2D shear deformation theory. Young's modulus is considered to vary gradually and continuously according to a power-law distribution in terms of volume fractions of the constituent materials. The equilibrium equations are obtained by applying the principle of virtual work. The governing equilibrium equations obtained are thus solved by using the analytical model developed here and Navier's solution technique for the case of a simply supported sandwich beam. Moreover, Using the numerical results of the non-dimensional stresses and displacements are calculated and compared with those obtained by other theories. Two studies are presented, comparative and parametric, the objective of which is the first to show the accuracy and efficiency of the theory used and the second to analyze the mechanical behavior of the different types of beams under the effect of different parameters. Namely boundary conditions, the material index , the thickness ratio and the type of beam.
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    Effect of Idealization Models on Deflection of Functionally Graded Material (FGM) Plate
    (2023-02-24) F. Khadraoui
    Functionally graded materials (FGM) are a class of composites, in which the properties of the material gradually change over one or more Cartesian directions, the combination of which results in an assembly with higher performance than components taken separately. This class of composite materials has gained considerable attention in the engineering community, especially in high-temperature applications such as nuclear reactors, aerospace, and power generation industries. The aim of the current work is to study the influence of homogenization (idealization) models and thermal loads on static deflection behavior of sandwich functionally graded plate. Several micromechanical models have been employed to obtain the effective material properties of the two-phase FGM plate. The FGM plate is subjected to linear and no linear thermal loads. The integral theory used contains only four variable functions as against five in the case of other HSDTs. The governing equation are derived and resolved via virtual work principle and Navier’s model. The accuracy of the proposed analytical model is confirmed by comparing the results with those given by others model existing in the literature.
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    Blade Exit Angle Impact on Turbulent Fluid Flow and Performance of Centrifugal Pump Using CFD
    (2015) Abdelmadjid CHEHHAT
    Rotor is a working part that adds energy to the fluid; its geometry plays a fundamental role in the centrifugal pump performance. Any change in the rotor geometry would have an effect on the impeller inlet or exit velocity triangles, which may cause a significant performance change. Hence the blade exit angle have very important role in the performance of the centrifugal pump. In this paper three impeller designs that differ in their outlet blade angles, with the casing and other geometric parameters keep constant, are considered to investigate its effect on the flow parameters and turbulence intensity as well as on the performance of the centrifugal pump. For this purpose, a threedimensional flow is simulated solving Reynolds averaged Navier Stokes (RANS) equations by using FLUENT code. Standard k-ε model is used for the turbulent closure of steady incompressible flow. The CFD analysis shows that the blade exit angle has influence on the head and efficiency. Rise in head and hydraulic efficiency have been observed with increasing blade exit angle. The research results are helpful for energy efficiency and hydraulic design of centrifugal pump.
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    Numerical Study of Natural Convection in Square Tilted Solar Cavity Considering Extended Domain
    (2018) Abdelmadjid Chehhat
    This work presents a numerical investigation on heat transfer and fluiddynamic aspects for a solar open cavities in an extended fluid flow domain. The vertical wall inside the open cavities facing the aperture is assumed to be isothermal while the other walls are kept insulated. Heat transfer steady laminar natural convection is studied by solving the non-dimensional governing equations of mass, momentum and energy in the framework of a finite volume method. The analysis are carried out under Rayleigh number range of 9.41×105 to 3.76×106, inclination 0° to 90° and opening ratio 0.25, 0.5 and 1. The model results for avaergar Nusselt number evaluation was in good agreement with other published work for similar configuration. The results show that convective average Nusselt number decreases by 93% when the inclination angle increased from 0° to 90°due to the trapped vortices that limit the airflow throughout the cavity. The air flowing through the cavit is maximum when the the inclination angle is zero even at higher values of Raylight number. Results show also that decreasing the opening ratio from 1 to 0.25 leads to a drop in heat loss by 22.79%. A simple correlation has been developed for calculating the the average Nusselt number as a function of Rayleigh number, opening ratio and inclination angle.
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    Numerical simulation of convective heat losses in a helical tube of a cylindrical solar receiver Simulation numérique des pertes thermiques par convection dans un tube hélicoïdal d’un récepteur solaire cylindrique
    (2018-06-27) Abdelmadjid Chehhat
    n this paper, natural convection heat losses in a cylindrical solar receiver are investigated numerically. The study is conducted using three helical tube diameters: 12mm, 16mm and 25mm. The diameter of the receiver is 0.3 m with an aspect ratio equal to one and three aperture ratios of 1, 0.75 and 0.5. In each case, the receiver tube inside the cylindrical cavity is modelled by a helical spiral similar to those of real systems. The simulations are performed for three inlet temperatures (of 50, 75 and 100°C) and four receiver tilt angles (of 0, 30, 60 and 900) with a constant mass flow rate of 0.0885 kg/s. The effects of some parameters such as receiver size, boundary conditions, tube diameter, receiver tilt, inlet temperature and opening ratio on convective heat losses and outlet temperature are presented in form of graphs. It has been found that the convective heat losses are reduced by using the adiabatic boundary condition imposed on the half-circumference of the tube. Thus, increasing the helical tube diameter causes an increasing in the convective heat losses. The increasing of the fluid temperature and the opening ratio are found proportional to the increasing of convective heat losses.
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    CFD Simulation of Heat Transfer and Fluid Flow within Metallic Foam in Forced Convection Environment
    (2017-07-21) A. Chehhat
    In the present study, a CFD simulation of forced convection in a rectangular block of aluminum foam is investigated. A two energy equations model with the BrinkmanForchheimer extended Darcy model is considered in the CFD investigation. The governing equations are solved using COMSOL, a commercial multiphysics finite-element PDE solver. Three types of aluminum foam 10-, 20-, 40- pore per inch with different porosity are studied. A parametric study for the range of Reynolds number Re = 250–2000 and the imposed heat flux qw = 0:8−1:6 (W/cm2) is carried out to examine the thermal and the fluid flow behaviors of the aluminum foams. It is found that the plug flow conditions are prevalence for the aluminum foams. The 40-pore per inch aluminum foam has a better heat transfer performance with a larger pressure drop, followed by the 20-, and then by the 10- pore per inch. The validation of the simulation results is made against experimental data from the literature and showed a perfect agreement.
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    Numerical investigation of diffuser solidity effect on turbulent airflow and performance of the turbocharger compressor
    (2016-11-14) ABDELMADJID . Chehhat
    Low solidity diffuser in centrifugal compressors can achieve both high efficiency and wide operating ranges which is of great importance for turbocharger compressor. Low solidity is achieved by using a low chord to pitch ratio. In this work, a CFD simulation is carried out to examine the effect of solidity on airflow field of a turbocharger centrifugal compressor which consists of a simple-splitter impeller and a vaned diffuser. By changing the number of diffuser vanes while keeping the number of impeller blades constant, the solidity value of the diffuser is varied. The characteristics of the compressor are evaluated for 6, 8, 10 and 12 stator vanes which correspond to solidity of: 0.78, 1.04, 1.29 and 1.55, respectively. The spatial distribution of the pressure, velocity and turbulent kinetic energy show that the diffuser solidity has significant effect on flow field and compressor performance map. The compressor with a 6 vanes diffuser has higher efficiency and operates at a wider range of flow rate relative to that obtained with larger vans number. However a non-uniform flow at the compressor exit was observed with relatively high turbulent kinetic energy
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    Simulation numérique de la convection naturelle laminaire dans une conduite verticale
    (2007-08-29) Abdelmadjid Chehhat
    Dans ce travail, nous présentons une étude numérique du phénomène de la convection naturelle laminaire dans une conduite verticale, dont la paroi est maintenue à une température constante. Les équations régissant ce phénomène, ont été résolues par une approche numérique basée sur la méthode des volumes finis. Nous avons représenté les champs de vitesses, de températures, et de pressions, ainsi que la variation du nombre de Nusselt moyen en fonction du nombre de Rayleigh. Les simulations numériques ont été faites en considérant des valeurs du nombre de Rayleigh qui varient entre 1 et 105, et cela pour des rapports d’aspect égalent 3, 5, 8 et 12. Les résultats obtenus sont comparés à ceux de la littérature et un bon accord a été trouvé.
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    Free Convection in a Vertical Duct: Numerical Study
    The subject of this paper is a direct numerical study of laminar and laminar-to-turbulent transient natural convection in a vertical duct, with a constant wall temperature, that exceeds the ambient fluid temperature. The governing equations are solved without modeling of the turbulence effect using a finite volume method. We presented the fields of velocity, temperature, and pressure as well as variation of the mean Nusselt number as a function of the Rayleigh number. The numerical simulation has been made for the Rayleigh number in the range from 1 to 105 for aspect ratios 3, 5, 8, and 12. The obtained results are compared with those given in the literature and a good agreement has been found.
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    CFD Analysis of the Volute Geometry Effect on the Turbulent Air Flow through the Turbocharger Compressor
    (2013) Chehhat Abdelmadjid
    n this work a numerical solution with moving mesh technique is made. Many research works both experimental and numerical on the diffuser volute interactive phenomenon have been undertaken so far. But it is found from the literature that the study on the impeller-diffuser-volute interaction as well on the performance of the turbocharger centrifugal compressor by varying the geometry of volute has not been the focus of attention in these works. Hence a numerical analysis has been carried out in this work to extensively explore impeller-diffuser-volute fluid interaction as well as to predict the flow and turbulence characteristics of the centrifugal compressor by varying the volute geometry without changing the number of impeller blades. It is found from the analysis that volute geometry presents a considerable effect on the pressure and temperature at the compressor outlet.
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    (2014-10-10) ABDELMADJID CHEHHAT
    In this work a numerical study with moving reference frame (MRF) technique is made. Many research works both experimental and numerical on the impeller-diffuser interactive phenomenon have been undertaken so far. But it is found from the literature that the study on the impeller-diffuser-volute interaction as well on the performance of the turbocharger centrifugal compressor by varying the number of diffuser vanes has not been the focus of attention in these works. Hence a numerical analysis was accomplished in order to extensively explore impeller-diffuser fluid interaction in a real turbocharger used in military engines applications, when the number of diffuser vanes was changed at unaltered number of the impeller blades. It was concluded that the number of diffuser vanes gives a considerable effect on the pressure and temperature at the compressor outlet.
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    Modélisation d’une fraise de forme en acier rapide de type HS 18-0-1
    (2019) abdelmadjid Chehhat
    Durant le suivi des outils de coupe dans des ateliers d’usinage de production nous avons remarqué que les fraises de formes travaillent dans des conditions sévères, pour cela nous avons pensé à améliorer leurs caractéristiques mécaniques et d’augmenter leurs rendement. Deux facteurs essentiels influent sur ces outils à savoir la géométrie et le traitement thermique .Dans cette étude nous avons choisi d’étudié la géométrie pour cette raison nous allons déterminer les points dangereux de l’arrête tranchante sur le profil de la dent, dans ce but nous avons appliqué une charge répartie le long de la dent puis par un logiciel CASTEM nous pouvons connaître les zones sensibles,c,est –dire la détermination des contraintes Van Mises et les contraintes tangentielles. L’outil choisi est une fraise de forme fabriqué en acier rapide HS 18-0- 01
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    CFD Modeling of Thermophysical Properties Influence on The Heat Transfer in Metal Foam Heat Sinks
    (2018) Abdelmadjid Chehhat
    This study presents a CFD simulation by COMSOL multiphysics software of a metal foam heat sink used for cooling electronic power component. The simulation is a transient 3D of air laminar flow through a channel equipped with a plate-electronic component system cooled by a metal foam heat sink. The goal is to determine the thermohydraulic behavior of the system. The foam heat sink is considered as a porous medium, the Darcy-Forchheimer-Brinkman model is used. We discussed the effects of air velocity, heat flux dissipated by the electronic device and the type of metal foam on the system phenomenology.