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Abdelhak El Ghandouri,Salaheddine Sayouri,TajEddine Lamcharfi,Lahoucine Hajji 한양대학교 세라믹연구소 2018 Journal of Ceramic Processing Research Vol.19 No.2
Structural, dielectric and piezoelectric properties of nanopowders of pure and strontium-doped BaTiO3 (Ba1-xSrx)TiO3 (x =0.00; 0.10; 0.20; 0.30 and 0.40), synthesized by the sol gel process, have been investigated. The samples crystallize in the pureperovskite structure and transform from tetragonal to pseudocubic under doping with Sr. The calculated average crystallitesize was about 30 nm. Dielectric parameters (dielectric permittivity and losses) were determined. Sr doping gives rise to adecrease of the ferro-to-paraelctric transition temperature and to an enhancement of the Positive Temperature Coefficient ofResistivity (PTCR). Piezoelectric parameters were also determined and their thermal behavior investigated.
Abdelhak Berkia,Soumia Benguediab,Abderrahmane Menasria,Abdelhakim Bouhadra,Fouad Bourada,Belgacem Mamen,Abdelouahed Tounsi,Kouider Halim Benrahou,Mohamed Benguediab,Muzamal Hussain 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.44 No.4
This paper presents the mechanical buckling of bi-directional functionally graded sandwich beams (BFGSW) with various boundary conditions employing a quasi-3D beam theory, including an integral term in the displacement field, which reduces the number of unknowns and governing equations. The beams are composed of three layers. The core is made from two constituents and varies across the thickness; however, the covering layers of the beams are made of bidirectional functionally graded material (BFGSW) and vary smoothly along the beam length and thickness directions. The power gradation model is considered to estimate the variation of material properties. The used formulation reflects the transverse shear effect and uses only three variables without including the correction factor used in the first shear deformation theory (FSDT) proposed by Timoshenko. The principle of virtual forces is used to obtain stability equations. Moreover, the impacts of the control of the power-law index, layer thickness ratio, length-to-depth ratio, and boundary conditions on buckling response are demonstrated. Our contribution in the present work is applying an analytical solution to investigate the stability behavior of bidirectional FG sandwich beams under various boundary conditions.
ABDELHAK DJEBABLA,DALLEL OUCIF,AHMED BERKANE 장전수학회 2016 Advanced Studies in Contemporary Mathematics Vol.26 No.3
In this paper we consider a one-dimensional von Karman system in the presence of a thermo-viscoelastic dissipation acting on the longitudinal component and the frictional damping acting on the transversal component of the beam. by using a suitable Lyapunov function, we establish a general decay result which is not necessarily of exponential or polynomial type.
Critical thermal buckling analysis of porous FGP sandwich plates under various boundary conditions
Abdelhak Zohra,Benferhat Rabia,Hassaine Daouadji Tahar 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.87 No.1
Critical thermal buckling of functionally graded porous (FGP) sandwich plates under various types of thermal loading is considered. It is assumed that the mechanical and thermal nonhomogeneous properties of FGP sandwich plate vary smoothly by distribution of power law across the thickness of sandwich plate. In this paper, porosity defects are modeled as stiffness reduction criteria and included in the rule of mixture. The thermal environments are considered as uniform, linear and nonlinear temperature rises. The critical buckling temperature response of FGM sandwich plates has been analyzed under various boundary conditions. By comparing several numerical examples with the reference solutions, the results indicate that the present analysis has good accuracy and rapid convergence. Further, the effects of various parameters like distribution shape of porosity, sandwich combinations, aspect ratio, thickness ratio, boundary conditions on critical buckling temperature of FGP sandwich plate have been studied in this paper.
Abdelhak, Z.,Hadji, L.,Khelifa, Z.,Hassaine Daouadji, T.,Adda Bedia, E.A. Techno-Press 2016 Wind and Structures, An International Journal (WAS Vol.22 No.3
In this paper, a refined shear deformation plate theory which eliminates the use of a shear correction factor was presented for FG sandwich plates composed of FG face sheets and an isotropic homogeneous core. The theory accounts for parabolic distribution of the transverse shear strains and satisfies the zero traction boundary conditions on the surfaces of the plate. The mechanical properties of the plate are assumed to vary continuously in the thickness direction by a simple power-law distribution in terms of the volume fractions of the constituents. Based on the present refined shear deformation plate theory, the governing equations of equilibrium are derived from the principle of virtual displacements. Numerical illustrations concern buckling behavior of FG sandwiches plates with Metal-Ceramic composition. Parametric studies are performed for varying ceramic volume fraction, volume fraction profiles, Boundary condition, and length to thickness ratios. The accuracy of the present solutions is verified by comparing the obtained results with the existing solutions.
Assets, Risks and Vulnerability to Poverty Traps: A Study of Northern Region of Malaysia
Abdelhak Senadjki,Saidatulakmal Mohd,Zakaria Bahari,Abdul Fatah Che Hamat 한국유통과학회 2017 The Journal of Asian Finance, Economics and Busine Vol.4 No.4
The Northern States of Malaysia comprises of four states (Penang, Kedah, Perlis and Perak) still record high poverty incidence eventhough Malaysia has experienced a remarkable reduction of poverty over the past century. Economic activities in Perlis and Kedah that are predominantly agriculture in the rural area contribute to this disparity. To add, rural households are also subject to risks and uncertainties that make them more vulnerable to poverty. This study examines the impact of risks and assets on households’ vulnerability to poverty. A survey of 400 respondents was conducted in December 2015 in the northern region of Malaysia. From these 400 questionnaires, only 298 were considered valid and used in the analysis. Using a logistic probability function, the results indicated that risks are not a significant threat to households. Gender and strata are crucial elements that significantly determine households’ vulnerability. While human capital and financial capital significantly reduce households’ vulnerability to poverty, physical and natural capitals were not statistically significant. The study suggests that the government and practitioners design strategies and policies with an assets-based approach. The asset-based approach is more appropriate for linking the causes of poverty to vulnerability.
Combining Multi-Criteria Analysis with CBR for Medical Decision Support
Abdelhak, Mansoul,Baghdad, Atmani Korea Information Processing Society 2017 Journal of information processing systems Vol.13 No.6
One of the most visible developments in Decision Support Systems (DSS) was the emergence of rule-based expert systems. Hence, despite their success in many sectors, developers of Medical Rule-Based Systems have met several critical problems. Firstly, the rules are related to a clearly stated subject. Secondly, a rule-based system can only learn by updating of its rule-base, since it requires explicit knowledge of the used domain. Solutions to these problems have been sought through improved techniques and tools, improved development paradigms, knowledge modeling languages and ontology, as well as advanced reasoning techniques such as case-based reasoning (CBR) which is well suited to provide decision support in the healthcare setting. However, using CBR reveals some drawbacks, mainly in its interrelated tasks: the retrieval and the adaptation. For the retrieval task, a major drawback raises when several similar cases are found and consequently several solutions. Hence, a choice for the best solution must be done. To overcome these limitations, numerous useful works related to the retrieval task were conducted with simple and convenient procedures or by combining CBR with other techniques. Through this paper, we provide a combining approach using the multi-criteria analysis (MCA) to help, the traditional retrieval task of CBR, in choosing the best solution. Afterwards, we integrate this approach in a decision model to support medical decision. We present, also, some preliminary results and suggestions to extend our approach.
Abdelhak Benaoum,Hadj Youzera,Moussa Abualnour,Mohammed Sid Ahmed Houari,Sid Ahmed Meftah,Abdelouahed Tounsi 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.80 No.6
In this work, mathematical modeling of the passive vibration controls of a three-layered sandwich beam under hard excitation is developed. Kelvin-Voigt Viscoelastic model is considered in the core. The formulation is based on the higher-order zig-zag theories where the normal and shear deformations are taken into account only in the viscoelastic core. The dynamic behaviour of the beam is represented by a complex highly nonlinear ordinary differential equation. The method of multiple scales is adopted to solve the analytical frequency-amplitude relationships in the super-harmonic resonance case. Parametric studies are carried out by using HSDT and first-order deformation theory by considering different geometric and material parameters.
Abdelhak Zohra,Rabia Benferhat,Hassaine Daouadji Tahar,Abdelouahed Tounsi 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.77 No.6
A new simple solution for critical buckling of FG sandwich plates under axial and biaxial loads is presented using new modified power-law formulations. Both even and uneven distributions of porosity are taken into account in this study. Material properties of the sandwich plate faces are assumed to be graded in the thickness direction according to a modified power-law distribution in terms of the volume fractions of the constituents. Equilibrium and stability equations of FG sandwich plate with various boundary conditions are derived using the higher-order shear deformation plate theory. The results reveal that the distribution shape of the porosity, the gradient index, loading type and functionally graded layers thickness have significant influence on the buckling response of functionally graded sandwich plates.