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Search Results: 1 - 10 of 191 matches for " Abdelkrim Kahoul "
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Corrosion Behavior of Commercial Aluminum Alloy Processed by Equal Channel Angular Pressing
Atef Korchef,Abdelkrim Kahoul
International Journal of Corrosion , 2013, DOI: 10.1155/2013/983261
Abstract: A commercial aluminum alloy was subjected to severe plastic deformation through equal channel angular pressing (ECAP). The alloy contains a low volume fraction of α-AlFeSi located essentially at the grain boundaries. The corrosion behavior of the ECAP’ed alloy was investigated in NaCl solution using potentiodynamic polarization and immersion tests. The effects of scan rate and NaCl concentration on the alloy susceptibility to corrosion were also studied. The results obtained were compared with those of the nonpressed alloy. ECAP leads to an intensive grain refinement accompanied by an increased dislocation density. All electrochemical tests confirm that corrosion resistance of the alloy remarkably diminished with increasing the ECAP number of passes. This is presumably due to the breakdown of the α-AlFeSi after ECAP leading to higher number of galvanic cells and enhanced dissolution of the aluminum matrix. 1. Introduction It is now well known that severe plastic deformation (SPD) leads to enhanced grain refinement to the submicrometer (100–1000?nm) or nanometer (<100?nm) levels. The intensive grain refinement is responsible for the enhancement of physical and mechanical properties of the processed materials, such as high strength and ductility. SPD techniques include, among others, torsion under high pressure [1], accumulative roll bonding (ARB) [2], and equal channel angular pressing (ECAP) [3, 4]. The latter procedure, introduced almost 30 years ago to achieve enhanced plastic strains, is especially attractive for several near superplastic applications. Since the cross-section of the sample remains unchanged during ECAP, repetitive pressings on the same sample are possible to achieve the required strains and to invoke different slip systems by rotating differently the sample between consecutive passes [4]. Thus, the microstructure obtained after ECAP depends on the introduced strains and whether and how the sample is rotated between two successive passes. In the early stages of pressing, reported results in the literature showed that the microstructure was reasonably homogeneous and consisted of parallel bands of subgrains. For further pressings, these subgrains evolved into an array of refined grains separated by high angle boundaries [5]. As a result of the grain refinement, a significant improvement of the mechanical properties was observed after ECAP [6]. In addition, ECAP process alters the bulk of the material leading to changes in material flow, residual stress, texture, size and distribution of a second phase if any exists in the material, and
Additive Fault Tolerant Control Applied to Delayed Singularly Perturbed System  [PDF]
Nouceyba Abdelkrim, Adel Tellili, Mohamed Naceur Abdelkrim
Journal of Software Engineering and Applications (JSEA) , 2012, DOI: 10.4236/jsea.2012.54027
Abstract: The additive fault tolerant control (FTC) for delayed system is studied in this work. To design the additive control, two steps are necessary; the first one is the estimation of the sensor fault amplitude using a Luenberger observer with delay, and the second one consists to generate the additive fault tolerant control law and to add it to the nominal control of delayed system. The additive control law must be in function of fault term, then, in the absence of fault the expression of additive control equal to zero. The generation of nominal control law consist to determinate the state feedback gain by using the Lambert W method. Around all these control tools, we propose an extension of the additive FTC to delayed singularly perturbed systems (SPS). So, this extension consists to decompose the delayed SPS in two parts: delayed slow subsystem (delayed SS) and fast subsystem (FS) without time delay. Next, we consider that the delayed SPS is affected at its steady-state, and we apply the principal of FTC to the delayed SS and finally we combine them with the feedback gain control of FS by using the principal of composite control.
Study of Dielectric and Piezoelectric Properties in the Ternary System Pb0.98Ca0.02[{(Zr0.52Ti0.48)0.98(Cr3+0.5 , Ta5+0.5)0.02}1–zPz]O3 Doping Effects  [PDF]
Hamzioui Louanes, Kahoul Fares, Abdessalem Nora, Boutarfaia Ahmed
Materials Sciences and Applications (MSA) , 2012, DOI: 10.4236/msa.2012.31007
Abstract: The effects of P2O5 oxide on microstructure, dielectric and piezoelectric properties of Pb0.98Ca0.02[{(Zr0.52Ti0.48)0.98( Cr3+1/2,Ta5+1/2)0.02}1–zPz]O3 ternary ceramics were investigated. Specimens with various contents of P2O5 from 0 to 12 wt. % were prepared by a conventional oxide mixing technique. The effect of P2O5 doping with regard to the development of the crystalline phase, density, microstructure, dielectric, ferroelectric and piezoelectric characteristics has been investigated. It has been found that the sintering temperature of piezoelectric Pb0.98Ca0.02[{(Zr0.52Ti0.48)0.98(Cr3+1/2,Ta5+1/2)0.02}1–zPz]O3 can be reduced by phosphorus addition without compromising the dielectric properties. A sintered density of 94 % of the theoretical density was obtained for 4 wt. % P2O5 addition after sintering at 1050°C for 4 h. Ceramics sintered at 1050°C with 4 wt. % P2O5 achieve excellent properties, which are as follows: kp = 0.73, ρ = 0.09 × 10+4 (Ω. cm), εr = 18800, tanδ = 0.0094 and Tc = 390°C.
Synthesis and Piezoelectric Properties of Pb0.98Sm0.02[(Zry,Ti1–y)0.98(Fe1/23+,Nb1/25+)0.02]O3 Ceramics  [PDF]
Fares Kahoul, Louanes Hamzioui, Nora Abdessalem, Ahmed Boutarfaia
Materials Sciences and Applications (MSA) , 2012, DOI: 10.4236/msa.2012.31008
Abstract: The structural and electrical properties of Pb0.98Sm0.02[(Zry,Ti1–y)0.98( Fe1/23+,Nb1/25+)0.02]O3 ceramics system with the composition near the morphotropic phase boundary were investigated as a function of the Zr/Ti ratio by X-ray diffraction (XRD). Studies were performed on the samples prepared by solid state reaction for y = 0.47, 0.49, 051, 0.53, 0.55 and 0.57. Combined with piezoelectric properties results, it was consistently shown that an MPB exists between y = 0.51 and y = 0.55 in this system. When y < 0.51, the tetragonal phase dominates at ambient temperatures. In the range of y > 0.55, the rhombohedral phase dominates. Lattice parameters of the tetragonal phase and rhombohedral phase were found to vary with chemical composition. The average particle size ranged from 17.18 to 26.05 nm. The dielectric (ε = 1076), tan δ = 0.013 and piezoelectric properties (d31 = 122 pC/N, kp = 0.631 and Qm = 462) obtained were maximum at y = 0.55 which could be suitable for possible electromechanical and energy harvesting applications.
Interdisciplinarity in Primary and Secondary School: Issues and Perspectives  [PDF]
Yves Lenoir, Abdelkrim Hasni
Creative Education (CE) , 2016, DOI: 10.4236/ce.2016.716233
Abstract: The article deals with three questions which feed the debates on the school interdisciplinarity. Firstly, why promote interdisciplinarity in basic education? To answer this question requires to make a fast historical reminder of the emergence and the evolution of the interdisciplinarity in the field of education, so as to highlight three distinct readings of interdisciplinarity before presenting four arguments which show the relevance of its use in teaching. Secondly, how can interdisciplinary practices be fostered in education? The results of various works lead us to draw four strong trends, ideal-typical, to which the teachers use in their practices. Thirdly, what are the educational questions and issues raised by such practices, and what challenges must we address to make sure they are properly applied? We then suggest six principles by which to found and describe what we understand by school interdisciplinarity. A definition of the school interdisciplinarity is then moved forward. To conclude, we call back to mind a few aspects which appear essential when contemplating the use of interdisciplinarity in school, what leads us to place this one with regard to the transdisciplinarity.
Simple and Multi Linear Regression Model of Verbs in Quran  [PDF]
Abdelkrim El Mouatasim
American Journal of Computational Mathematics (AJCM) , 2018, DOI: 10.4236/ajcm.2018.81006
Abstract: This paper mainly presented a good simple and multi-linear regression model of verbs in the Quran book. This model, gives an analysis for the influence to frequency of words with the form (—un, \"\"---) made by the frequency of plural present verbs (t—un, \"\"---\"\") or (y—un, \"\"---\"\"), and models, and the relationship between independent variables and dependent variable by fitting a linear equation to the observed data with simple linear regression model. The matlab function is used for finding the parameters of the linear regression model and plotting the fits. The results show that the parameters of the model are one vector (1, 1) and mean of dataset is (6, 7). Its corresponding to the verb with input is frequency of the verb they enter and the frequency of enter (yadkolun \"\"?dakilun), also other 17 points exist in the line and in the dataset of 387
Inappropriateness of prostate cancer screening by PSA in young Algerian farmers  [PDF]
Abdelkrim Berroukche, Malika Bendahmane-Salmi, Badreddine Abdelkrim Kandouci
Open Journal of Immunology (OJI) , 2013, DOI: 10.4236/oji.2013.33016
Abstract:

Introduction: It is not yet established, in Algeria, a consensus on the use of prostate specific antigen (PSA) for the screening of prostate cancer (PCA) while some doctors speculate and recommend a serum-PSA assay to the young men. The objective is to assess the prevalence of PSA by age in young farmers. Methods: This study was undergone on 403 farmers, exposed to the risk of pesticides, aged between 30 - 70 years and living in rural areas of Saida (Western Algeria), during the period 2006 to 2012. The values of the PSA were collected during PCA screening and compared by statistical tests that revealed significant difference. Results: It was found that 15.6% of patients were under the age of 40 years. The total PSA (TPSA) increases with age and varies from 1 to 2 ng/ml for the respective age groups of 30 - 39 and 60 - 69 years. Approximately, 16.6% of men (or 1/6), who underwent PSA assay were under the age of 40 years. Conclusion: According to the recommendations of Algerian associations of cancer, men younger than 50 years may not be candidates for screening by PSA.

Economic and social life in Morocco Middle Between centuries 13 - 15 A.M
Abdelkrim Hassaine
Historical Kan Periodical , 2012,
Abstract: / / . .
Common Fixed Point Theorems In Fuzzy Metric Spaces via properties
Aliouche Abdelkrim
Albanian Journal of Mathematics , 2010,
Abstract: We prove common xed point theorems for weakly compatiblemappings via an implicit relation in fuzzy metric spaces using property (E.A)and a common property (E.A). Our theorems extend theorems of [1, 3, 4, 6,15, 16] and a corollary of [2].
Towards a Requirements Model for Crosscutting Concerns
Abdelkrim Amirat
Information Technology Journal , 2007,
Abstract: Techniques such as use cases, viewpoints and goals help achieve separation of stakeholders concerns but ensuring their consistency with global requirements and constraints is largely unsupported. The work on early aspects, therefore, complements these approaches by providing systematic means for handling such concerns. In this study we focus on a methodology to elicit the crosscutting concerns aspects in the early life phases of software development generally and especially during requirements analysis. Early aspects cannot be localized and tend to be scattered over multiple early life cycle modules. This reduces the modularity of the artifacts and might consequently lead to serious maintenance problems and low degree of reusability. Unfortunately, conventional aspect oriented software development approaches have mainly focused on identifying the aspects at the programming level and less attention has been taken on the impact of crosscutting concerns at the early phases of the software development.
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