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Guettala S.,Ziane Achour University of Djelfa | Mezghiche B.,University Mohamed Khider of Biskra
Construction and Building Materials | Year: 2011

This experimental work has focused on studying the possibility of using dune sand powder (DSP) as a part mass addition to Portland cement. Studying the effect of addition dune sand powder on development of compressive strength and hydration with age of cement pastes as a function of water/binder ratio, was varied, on the one hand, the percentage of the dune sand powder (physico-chemical and chemical effect) and on the other, the fineness of dune sand powder (physical effect). In order to understand better the chemical effect (pozzolanic effect) of dune sand powder in cement pastes, we followed the mixtures hydration (50% pure lime + 50% DSP) by X-ray diffraction. These mixtures pastes present a hydraulic setting which is due to the formation of a C-S-H phase (calcium silicate hydrate). The latter is semi-crystallized. This study is a simplified approach to that of the mixtures (80% ordinary Portland cement + 20% DSP), in which the main reaction is the fixing of the lime coming from the cement hydration in the presence of the dune sand powder (pozzolanic reaction), to form calcium silicate hydrate C-S-H semi-crystallized of second generation. The results proved that up to 20% of dune sand powder as Portland cement replacement could be used with a fineness of 4000 cm2/g without affecting adversely the compressive strength. The dune sand powder, despite its crystalline nature, presents a partial pozzolanic reactivity. © 2010 Elsevier Ltd. All rights reserved. Source


Achour B.,University Mohamed Khider of Biskra
Advanced Materials Research | Year: 2013

A new theory is presented to design pressurized conduits, particularly vaulted rectangular conduit. This theory is based on a referential rough conduit model characterized by an arbitrarily assigned relative roughness taken in the fully turbulence flow regime. Thus, the geometric elements of the chosen model are well defined. These allow a direct determination of the required geometric elements of the conduit by the use of a non-dimensional correction factor. A practical example is presented to explain the procedure of calculation. © (2013) Trans Tech Publications, Switzerland. Source


Chala A.,University Mohamed Khider of Biskra
Automatica | Year: 2014

The present study deals with a new approach of optimal control problems where the state equation is a Mean-Field stochastic differential equation, and the set of strict (classical) controls need not be convex and the diffusion coefficient depends on the term control. Our consideration is based on only one adjoint process, and the necessary conditions as well as a sufficient condition for optimality in the form of a relaxed maximum principle are obtained, with application to Linear quadratic stochastic control problem with mean-field type. © 2014 Elsevier Ltd. All rights reserved. Source


Achour B.,University Mohamed Khider of Biskra
Advanced Materials Research | Year: 2014

The recurring problem of calculating the normal depth in a trapezoidal open channel is easily solved by the rough model method. The Darcy-Weisbach relationship is applied to a referential rough model whose friction factor is arbitrarily chosen. This leads to establish the nondimensional normal depth relationship in the rough model. Through a non-dimensional correction factor of linear dimension, the aspect ratio and therefore normal depth in the studied channel is deduced. © (2014) Trans Tech Publications, Switzerland. Source


Benramache S.,University Mohamed Khider of Biskra | Benhaoua B.,El - Oued University Center
Superlattices and Microstructures | Year: 2012

Transparent conducting indium doped zinc oxide was deposited on glass substrate by ultrasonic spray method. The In doped ZnO samples with indium concentration of 3 wt.% were deposited at 300, 350 and 400 °C with 2 min of deposition time. The effects of substrate temperature and annealing temperature on the structural, electrical and optical properties were examined. The DRX analyses indicated that In doped ZnO films have polycrystalline nature and hexagonal wurtzite structure with (0 0 2) preferential orientation and the maximum average crystallite size of ZnO: In before and annealed at 500 °C were 45.78 and 55.47 nm at a substrate temperature of 350 °C. The crystallinity of the thin films increased by increasing the substrate temperature up 350 °C, the crystallinity improved after annealing temperature at 500 °C. The film annealed at 500 °C and deposited at 350 °C show lower absorption within the visible wavelength region. The band gap energy increased from E g = 3.25 to 3.36 eV for without annealing and annealed films at 500 °C, respectively, indicating that the increase in the transition tail width. This is due to the increase in the electrical conductivity of the films after annealing temperature. © 2012 Elsevier Ltd. All rights reserved. Source

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