Merah A.,University of Laghouat |
Krobba B.,University of Laghouat
Construction and Building Materials | Year: 2017
Ductility is an important factor used in the design of para seismic structures. In this paper, the effect of the carbonation and the type of cement (limestone cement (CEM II) and ordinary Portland cement (CEM I)) on ductility and compressive strength of concrete is investigated. From two concrete formulations, cubic samples of size 10 cm,10 cm and 10 cm) and beam samples of size (10 cm,10 cm and 40 cm) were made and subjected to the accelerated carbonation test over several periods for this purpose. The cubic samples were used for measurements of carbonation depths and compressive strength, beam samples were made for measurements of carbonation depths and displacement ductility. Based on these experiments, the results show that displacement ductility is reduced by carbonation. On the other hand, the compressive strength increases with the duration of exposure to carbonation. Moreover, for concrete formulated with Portland cement (CEM I), it is noted that the rate of reduction of the displacement ductility coefficient is 30% for the 7th day of exposure to accelerated carbonation for the carbonated samples compared to the control samples. However, the concrete samples formulated with calcareous additions cement (CEM II), the reduction rate of the displacement ductility coefficient is only 14% for the carbonated samples compared to the control samples. The results obtained show that the compressive strength, increases with the duration of exposure to carbonation for the two concretes and it is more important for the concrete with ordinary Portland cement, the rate of increase is about 12%. Hence, the carbonation decreases the service life of reinforced concrete structures mainly their ductility capacity and consequently their resistance against seismic actions. © 2017 Elsevier Ltd
Benmouiza K.,Abou Bekr Belkaid University Tlemcen |
Cheknane A.,University of Laghouat
Energy Conversion and Management | Year: 2013
In this paper, we review our work for forecasting hourly global horizontal solar radiation based on the combination of unsupervised k-means clustering algorithm and artificial neural networks (ANN). k-Means algorithm focused on extracting useful information from the data with the aim of modeling the time series behavior and find patterns of the input space by clustering the data. On the other hand, nonlinear autoregressive (NAR) neural networks are powerful computational models for modeling and forecasting nonlinear time series. Taking the advantage of both methods, a new method was proposed combining k-means algorithm and NAR network to provide better forecasting results. © 2013 Elsevier Ltd. All rights reserved.
Bessedik S.A.,University of Laghouat |
Hadi H.,University of Science and Technology of Oran
Electric Power Systems Research | Year: 2013
This paper describes the application of least squares support vector machine combined with particle swarm optimisation (LS-SVM-PSO) model to estimate the critical Flashover Voltage (FOV) on polluted insulators. The characteristics of the insulator: the diameter, the height, the creepage distance, the form factor and the equivalent salt deposit density were used as input variables for the LS-SVM-PSO model, and critical flashover voltage was estimated. In order to train the LS-SVM and to test its performance, the data sets are derived from experimental results obtained from the literature and a mathematical model. First, the LS-SVM regression model, with Radial Basis Function (RBF) kernel, is established. Then a global optimiser, PSO is employed to optimise the hyper-parameters needed in LS-SVM regression. Afterward, a LS-SVM-PSO model is designed to establish a nonlinear model between the above mentioned characteristics and the critical flashover voltage. Satisfactory and more accurate results are obtained by using LS-SVM-PSO to estimate the critical flashover voltage for the considered conditions compared with the previous works. © 2013 Elsevier B.V. All rights reserved.
Boutoubat M.,University of Laghouat |
Mokrani L.,University of Laghouat |
Machmoum M.,37 Boulevard Of Luniversite
Renewable Energy | Year: 2013
The aim of this paper is to improve the reactive power compensation and active filtering capability of a Wind Energy Conversion System (WECS). The proposed algorithm is applied to a Doubly Fed Induction Generator (DFIG) with a stator directly connected to the grid and a rotor connected to the grid through a back-to-back AC-DC-AC PWM converter. The control strategy of the Rotor Side Converter (RSC) aims, at first, to extract a maximum of power under fluctuating wind speed. Then, depending on the rate power of the RSC, the power quality can be improved by compensating the reactive power and the grid harmonics current due to nonlinear loads. Hence, the RSC is controlled in order to manage the WECS function's priorities, between production of the maximum active power captured from the wind, and power quality improvement. The main goal of the proposed control strategy is to operate the RSC at its full capacity, without any over-rating, in terms of reactive power compensation and active filtering capability. Elsewhere, the Grid Side Converter (GSC) is controlled in such a way to guarantee a smooth DC voltage and ensure sinusoidal current in the grid side. Simulation results show that the wind turbine can operate at its optimum power point for a wide range of wind speed and power quality can be improved. It has been shown also that the proposed strategy allows an operating full capacity of the RSC in terms of reactive power compensation and active filtering. © 2012 Elsevier Ltd.
Cheknane A.,University of Laghouat
Progress in Photovoltaics: Research and Applications | Year: 2011
The aim of this work is to present an optimized model of metallic micro-grid used as anode electrode in organic photovoltaic devices excluding the use of expensive ITO (Indium Tin Oxide). A design of circular grid, adapted for silcon-based solar cells, is proposed here. A clear advantage of using the grid as opposed to ITO is the elimination of the absorptive losses the ITO adds to the structure. In order to optimize the collecting grid dimensions one must choose a compromise between the resistive losses, represented by the series resistance Rs, and the shadowing loss. Therefore, in order to find the best geometry of the grid, a comparative study has been done between the linear geometry and the circular one. Our results show clearly that the efficiency is enhanced when using the circular geometry. © 2010 John Wiley & Sons, Ltd.
Ghernaout D.,Blida University |
Ghernaout B.,University of Laghouat
Desalination and Water Treatment | Year: 2012
The coagulation/flocculation (C/F) processes are mainly due to charge neutralisation (CN) and sweep flocculation (SF) mechanisms. However, the SF mechanism has also its CN property moreover than its well-known weighting characteristic. On this weighting characteristic, the literature has usually focused without taking in consideration the SF's CN property. This review discusses the implicated mechanisms in destabilisation of colloids and aggregation of flocs. Colloids are very small particles that have extremely large surface area. The consequence of this smallness in size and mass and largeness in surface area is that in colloidal suspensions: gravitational effects are negligible and surface phenomena predominate. Hence, during C/F process, colloids are removed by CN and SF mechanisms which act on the anionic charge of the colloid by its neutralisation prior to its removal by sedimentation/filtration. The sweep flocs can be described as large aggregates of Al(OH)3/Fe(OH)3 that are formed when Al/Fe salt is added to water. Further, sweep flocs are positively charged and the colloids of clay minerals abundantly found in the water are negatively charged. As a result, the colloidal particles are electrostatically attached to the sweep flocs in the neutral pH water as to the hydrolysed metallic cations. Even if researches have greatly elucidated the growth, breaking and the re-growth of flocs, further research is required to understand CN and SF mechanisms and optimise the C/F process at the nano level. © 2012 Desalination Publications. All rights reserved.
Bouziani T.,University of Laghouat
Construction and Building Materials | Year: 2013
The present paper provides a statistical approach to evaluate the effect of different sand types on the properties of self-compacting concrete (SCC). A mixture design modelling approach was used to highlight the effects of river sand (RS), crushed sand (CS) and dune sand (DS) as proportions in binary and ternary systems, on flowability, passing ability, segregation and mechanical strength of SCC. The responses of the derived statistical models are slump flow, v-funnel time, L-box, stability and compressive strength at 2, 7 and 28 days. The derived mathematical models make it possible to illustrate the variation of different responses in ternary contour plots with respect to the proportions of RS, CS and DS. This provides flexibility to optimize RS, CS and DS blends with tailor-made of a given property that suit particular recommendations. Results indicate that when flowability requirements are combined, proportions of DS and CS in binary or ternary systems with RS must be below 0.24 and 0.6 respectively. Moreover, it is shown that passing ability can be satisfied by using a CS proportion above 0.3 in RS-CS binary system and above 0.65 in CS-DS binary system. On other hand, proportions above 0.5 of CS in RS-CS binary system and above 0.2 of DS in RS-DS binary system are recommended to meet stability limits. Results also indicate that compressive strength at 2, 7 and 28 days increased with the increase of CS proportion and decreased with the increase of DS proportion in binary and ternary systems. © 2013 Elsevier Ltd. All rights reserved.
Rogti F.,University of Laghouat
Journal of Electrostatics | Year: 2013
In this paper, space charge behavior in dielectric material and the capacitive charge at an electrode-dielectric interface, at room temperature under an applied electric field, has been investigated. This was done for a single sample and for a combination of the sample and a non-stressed sample using the pulsed electro-acoustic (PEA) method. A negative charge injected at the dielectric interface under an electric field (polarization) and high temperatures was focused on. It was found that negative charge injection takes place under all the test conditions, and this charge can be affected by the electric field and the temperature. © 2013 Elsevier B.V.
Rogti F.,University of Laghouat
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2011
In this paper the behavior of positive charge formed in the vicinity of the Semi-conducting sheet anode at room temperature and under applied dc has been investigated just after the reversal of the sample, and when the sample was combined with another sample without pre-stressing using the pulsed electro acoustic (PEA) method. The results suggest that the PEA system can only show the net charge density, and the space charge distribution is drastically changed when the sample is reversed just after the removal of the applied voltage (depolarization), or when this sample was combined with another without prestressing. A positive charge injected at the dielectric interface XLPE/XLPE under electric field (polarization) and high temperature has been paid much attention. It is found that the positive charge injection takes place under all the test conditions and this charge can be affected by the electric field and/or the temperature. Physical interfaces constituted by the association of two identical dielectrics store the positive carriers for long time. © 2006 IEEE.
Rogti F.,University of Laghouat |
Ferhat M.,University of Laghouat
Applied Physics Letters | Year: 2014
This paper reports on an investigation into space charge formation and decay at dielectric interfaces. In particular, the influence of temperature on the formation of the trap deep has been studied. A multi-dielectrics structure composed of two dielectric films, Low Density Polyethylene (LDPE) and Fluorinated Ethylene Propylene (FEP), was subjected to an electric stress level of +14.3 kV/mm at two temperatures, 40 °C and 60 °C, and space charge measurements were taken using the pulsed electro-acoustic technique. Space charge distributions were investigated for combinations of LDPE/FEP flat specimens. The time dependence of the space charge distribution was subsequently recorded at different temperatures under short circuit (depolarization) conditions. It was found that temperature plays a significant role in space charge dynamics at the dielectric interface, charge mobility, electrical conductivity, filling of the trap, and the formation of the shallow trap. © 2014 AIP Publishing LLC.