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      • Nonlocal free vibration analysis of porous FG nanobeams using hyperbolic shear deformation beam theory

        Hadji, Lazreg,Avcar, Mehmet Techno-Press 2021 Advances in nano research Vol.10 No.3

        This paper presents a new nonlocal Hyperbolic Shear Deformation Beam Theory (HSDBT) for the free vibration of porous Functionally Graded (FG) nanobeams. A new displacement field containing integrals is proposed which involves only three variables. The present model incorporates the length scale parameter (nonlocal parameter) which can capture the small scale effect and its account for shear deformation by a hyperbolic variation of all displacements through the thickness without using the shear correction factor. It has been observed that during the manufacture of Functionally Graded Materials (FGMs), micro-voids and porosities can occur inside the material. Thus, in this work, the investigation of the free vibration analysis of FG beams taking into account the influence of these imperfections is established. Four different porosity types are considered for FG nanobeam. Material characteristics of the FG beam are supposed to vary continuously within thickness direction according to a power-law scheme which is modified to approximate material characteristics for considering the influence of porosities. Based on the nonlocal differential constitutive relations of Eringen, the equations of motion of the nanobeam are derived using Hamilton's principle. The effects of nonlocal parameter, aspect ratio, and the porosity types on the dynamic responses of the nanobeam are discussed.

      • KCI등재

        Pedagogically-Driven Courseware Content Generation for Intelligent Tutoring Systems

        Hadji, Hend Ben,Choi, Ho-Jin,Jemni, Mohamed Korean Institute of Intelligent Systems 2012 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.12 No.1

        This paper describes a novel approach to adaptive courseware generation. This approach adopts its structure from existing intelligent tutoring systems and introduces a new component called pedagogical scenario model to support pedagogical flexibility in the adaptation process of courseware generation system. The adaptation is carried out using Dynamic Constraint Satisfaction Problem framework, which is a variant of classical Constraint Satisfaction Problem, to deliver courseware tailored to individual learner. Such a framework provides a high level of expressiveness to deal with the particular characteristics of courseware generation problem. Further, it automatically designs a sound courseware satisfying the design constraints imposed by the domain, the pedagogical scenario and learner models.

      • SCIESCOPUS

        A refined exponential shear deformation theory for free vibration of FGM beam with porosities

        Hadji, Lazreg,Daouadji, T. Hassaine,Bedia, E. Adda Techno-Press 2015 Geomechanics & engineering Vol.9 No.3

        In this paper, a refined exponential shear deformation theory for free vibration analysis of functionally graded beam with considering porosities that may possibly occur inside the functionally graded materials (FGMs) during their fabrication. For this purpose, a new displacement field based on refined shear deformation theory is implemented. The theory accounts for parabolic distribution of the transverse shear strains and satisfies the zero traction boundary conditions on the surfaces of the beam without using shear correction factors. Based on the present refined shear deformation beam theory, the equations of motion are derived from Hamilton's principle. The rule of mixture is modified to describe and approximate material properties of the FG beams with porosity phases. The accuracy of the present solutions is verified by comparing the obtained results with the existing solutions. Illustrative examples are given also to show the effects of varying gradients, porosity volume fraction, aspect ratios, and thickness to length ratios on the free vibration of the FG beams.

      • SCIESCOPUS

        Influence of the porosities on the free vibration of FGM beams

        Hadji, L.,Adda Bedia, E.A. Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.21 No.3

        In this paper, a free vibration analysis of functionally graded beam made of porous material is presented. The material properties are supposed to vary along the thickness direction of the beam according to the rule of mixture, which is modified to approximate the material properties with the porosity phases. For this purpose, a new displacement field based on refined shear deformation theory is implemented. The theory accounts for parabolic distribution of the transverse shear strains and satisfies the zero traction boundary conditions on the surfaces of the beam without using shear correction factors. Based on the present refined shear deformation beam theory, the equations of motion are derived from Hamilton's principle. The rule of mixture is modified to describe and approximate material properties of the FG beams with porosity phases. The accuracy of the present solutions is verified by comparing the obtained results with the existing solutions. Illustrative examples are given also to show the effects of varying gradients, porosity volume fraction, aspect ratios, and thickness to length ratios on the free vibration of the FG beams.

      • Static bending and free vibration of FGM beam using an exponential shear deformation theory

        Hadji, L.,Khelifa, Z.,Daouadji, T.H.,Bedia, E.A. Techno-Press 2015 Coupled systems mechanics Vol.4 No.1

        In this paper, a refined exponential shear deformation beam theory is developed for bending analysis of functionally graded beams. The theory account for parabolic variation of transverse shear strain through the depth of the beam and satisfies the zero traction boundary conditions on the surfaces of the beam without using shear correction factors. Contrary to the others refined theories elaborated, where the stretching effect is neglected, in the current investigation this so-called "stretching effect" is taken into consideration. The material properties of the functionally graded beam are assumed to vary according to power law distribution of the volume fraction of the constituents. Based on the present shear deformation beam theory, the equations of motion are derived from Hamilton's principle. Analytical solutions for static are obtained. Numerical examples are presented to verify the accuracy of the present theory.

      • Challenges to Promoting Population-Based Cancer Registration in Iran: a Workshop Report

        Hadji, Maryam,Nahvijou, Azin,Seddighi, Zahra,Beiki, Omid,Mohagheghi, Mohammad Ali,Mosavi-Jarrahi, Alireza,Marnani, Ahmad Barati,Zendehdel, Kazem Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.10

        In December 2011, the Cancer Research Centre of the Cancer Institute of Iran sponsored a 3-day workshop on "Cancer Registration Principle and Challenges in Iran", which convened cancer registry experts. The objectives of the workshop were: to introduce standard cancer registration, to review the policy and procedure of cancer registration in Iran, and to review the best practices in the cancer registries in Iran. Challenges to cancer registration were discussed and recommendations were developed. The workshop was evaluated by participants for better organization of subsequent workshops. The objective of publication of this report is that based on Cancer in 5 Continents, many low- or middle-income countries do not meet the criteria for a standard population-based cancer registry (PBCR); on the other hand cancer is the most important cause of mortality and the essential part of any cancer control program is the cancer registry. Therefore this report focuses on problems and challenges of PBCR and provides recommendations which might help other developing countries to decrease their PBCR defects.

      • SCIESCOPUS

        A new quasi-3D higher shear deformation theory for vibration of functionally graded carbon nanotube-reinforced composite beams resting on elastic foundation

        Hadji, Lazreg,Meziane, Mohamed Ait Amar,Safa, Abdelkader Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.6

        This study deals with free vibrations analysis with stretching effect of nanocomposite beams reinforced by single-walled carbon nanotubes (SWCNTs) resting on an elastic foundation. Four different carbon nanotubes (CNTs) distributions including uniform and three types of functionally graded distributions of CNTs through the thickness are considered. The rule of mixture is used to describe the effective material properties of the nanocomposite beams. The significant feature of this model is that, in addition to including the shear deformation effect and stretching effect it deals with only 4 unknowns without including a shear correction factor. The governing equations are derived through using Hamilton's principle. Natural frequencies are obtained for nanocomposite beams. The mathematical models provided in this paper are numerically validated by comparison with some available results. New results of free vibration analyses of CNTRC beams based on the present theory with stretching effect is presented and discussed in details. The effects of different parameters of the beam on the vibration responses of CNTRC beam are discussed.

      • Choice Modelling and Simulation of Low Emission Vehicles under Different Policy Scenarios in the Philippines

        Hadji C. Jalotjota,Yoshikuni Yoshida The International Academy of Global Business and T 2015 The International Academy of Global Business and T Vol.11 No.1

        '스콜라' 이용 시 소속기관이 구독 중이 아닌 경우, 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

        Using stated preference data from 300 respondents of a discrete choice experiment, a conditional logit model was estimated to determine preference for low emission vehicles (LEV) and to simulate vehicle share in Metro Manila, Philippines. The model shows that among different vehicle types, there is highest preference for diesel vehicles. Among LEVs, only hybrid electric vehicles (HEV) have a preference level comparable to diesel and gasoline vehicles. Least preferred by the respondents are liquefied petroleum gas and battery electric vehicles (BEV). Initial simulation of vehicle share shows a high share of HEV and BEV, suggesting the large effect of emission levels on choice. However, when acquisition cost and the number of available vehicle models in the Philippines are accounted for, simulation results show a significantly reduced market share for HEV and BEV with AutoLPG vehicles gaining a higher share. The potential co-benefits from reduced emission and fuel savings and the vehicle owners’ preference for lower emission levels are the main factors for adopting LEVs. However, LEVs remain expensive to most Filipino vehicle owners. A significant price reduction and an increase in available LEV models can facilitate faster adoption of LEVs among Filipino vehicle owners.

      • Bending and free vibration analysis of functionally graded beams on elastic foundations with analytical validation

        Hadji, Lazreg,Bernard, Fabrice Techno-Press 2020 Advances in materials research Vol.9 No.1

        The novelty of this paper is the use of a simple higher order shear and normal deformation theory for bending and free vibration analysis of functionally graded material (FGM) beams on two-parameter elastic foundation. To this aim, a new shear strain shape function is considered. Moreover, the proposed theory considers a novel displacement field which includes undetermined integral terms and contains fewer unknowns with taking into account the effects of both transverse shear and thickness stretching. Different patterns of porosity distributions (including even and uneven distribution patterns, and the logarithmic-uneven pattern) are considered. In addition, the effect of different micromechanical models on the bending and free vibration response of these beams is studied. Various micromechanical models are used to evaluate the mechanical characteristics of the FG beams for which properties vary continuously across the thickness according to a simple power law. Hamilton's principle is used to derive the governing equations of motion. Navier type analytical solutions are obtained for the bending and vibration problems. Numerical results are obtained to investigate the effects of power-law index, length-to-thickness ratio, foundation parameter, the volume fraction of porosity and micromechanical models on the displacements, stresses, and frequencies.

      • Bending and free vibration analysis for FGM plates containing various distribution shape of porosity

        Hadji, Lazreg,Bernard, Fabrice,Safa, Abdelkader,Tounsi, Abdelouahed Techno-Press 2021 Advances in materials research Vol.10 No.2

        In this paper hyperbolic shear deformation plate theory is presented for bending and the free vibration of functionally graded plates with considering porosities that may possibly occur inside the functionally graded materials (FGMs) during their fabrication. Four different porosity types are used for functionally graded plates. Equations of motion are derived from Hamilton's principle. In the solution of the governing equations, the Navier procedure is implemented. In the numerical examples, the effects of the porosity parameters, porosity types and geometry parameters on the bending and free vibration of the functionally graded plates are investigated. It was found that the distribution form of porosity significantly influence the mechanical behavior of FG plates, in terms of deflection, normal, shear stress and frequency.

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