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CONTENTS
Volume 4, Number 4, December 2016
 

Abstract
In this paper, a simple and refined nonlocal hyperbolic higher-order beam theory is proposed for bending and vibration response of nanoscale beams. The present formulation incorporates the nonlocal scale parameter which can capture the small scale effect, and it considers both shear deformation and thickness stretching effects by a hyperbolic variation of all displacements across the thickness without employing shear correction factor. The highlight of this formulation is that, in addition to modeling the displacement field with only two unknowns, the thickness stretching effect (ez=/0) is also included in the present model. By utilizing the Hamilton\'s principle and the nonlocal differential constitutive relations of Eringen, the equations of motion of the nanoscale beam are reformulated. Verification studies demonstrate that the developed theory is not only more accurate than the refined nonlocal beam theory, but also comparable with the higher-order shear deformation theories which contain more number of unknowns. The theoretical formulation proposed herein may serve as a reference for nonlocal theories as applied to the static and dynamic responses of complex-nanobeam-system such as complex carbon nanotube system.

Key Words
nonlocal theory; stretching effect; nanobeam

Address
Boumediene Kheroubi: Laboratoire de Modelisation et Simulation Multi-echelle, Universite de Sidi Bel Abbes, Departement de Physique, BP 89 Cite Ben M\'hidi, 22000 Sidi Bel Abbes, Algeria
Abdelnour Benzair: Laboratoire de Modelisation et Simulation Multi-echelle, Universite de Sidi Bel Abbes, Departement de Physique, BP 89 Cite Ben M\'hidi, 22000 Sidi Bel Abbes, Algeria; Algerian National Thematic Agency of Research in Science and Technology (ATRST), Algeria
Abdelouahed Tounsi: Laboratoire de Modelisation et Simulation Multi-echelle, Universite de Sidi Bel Abbes, Departement de Physique, BP 89 Cite Ben M\'hidi, 22000 Sidi Bel Abbes, Algeria; Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria; Algerian National Thematic Agency of Research in Science and Technology (ATRST), Algeria
Abdelwahed Semmah: Laboratoire de Modelisation et Simulation Multi-echelle, Universite de Sidi Bel Abbes, Departement de Physique, BP 89 Cite Ben M\'hidi, 22000 Sidi Bel Abbes, Algeria; Algerian National Thematic Agency of Research in Science and Technology (ATRST), Algeria

Abstract
Present study interests with the longitudinal forced vibration of nanorods. The nonlocal elasticity theory of Eringen is used in modeling of nanorods. Uniform, linear and sinusoidal axial loads are considered. Dynamic displacements are obtained for nanorods with different geometrical properties, boundary conditions and nonlocal parameters. The nonlocal effect increases dynamic displacement and frequency when compared with local elasticity theory. Present results can be useful for modeling of the axial nanomotors and nanoelectromechanical systems.

Key Words
nonlocal theory; nanorod model; forced vibration; dynamic displacement; mode shape

Address
Metin Aydogdu and Mustafa Arda: Department of Mechanical Engineering, Trakya University, 22030 Edirne, Turkey

Abstract
The advantages of nano-scale materials (size 1-99 nm in at least in one dimension) could be realized with their potential applications in diversified avenues. Herein, we report for the first time on the successful synthesis of homogeneous epoxy coatings containing phytogenic silver nanoparticles (Ag) on PVC and glass substrates by room-temperature curing of fully mixed epoxy slurry diluted by acetone. Alstonia scholaris bark extract was used to reduce and stabilize the silver ions. The surface morphology and mechanical properties of these coatings were characterized using the techniques like, UV-Vis (UV-Visible) spectrophotometry, X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FT-IR), Epifluorescence microscopy and scanning electron microscopy (SEM). The effect of incorporating Ag nanoparticles on the biofilm (scale) resistant epoxy-coated PVC was investigated by total viable counts (CFU/cm2) from epoxy coating from (Initial) 1st day to 25th days. The phytogenic Ag nanoparticles were found to be significantly improving the microstructure of the coating matrix and thus enhanced the antibiofilm performance of the epoxy coating. In addition, the antimicrobial mechanism of Ag nanoparticles played an important role in improving the anti-biofilm performance of these epoxy coatings.

Key Words
Alstonia scholaris; Ag nanoparticles; epoxy coating; biofilm resistance; PVC coupons

Address
Nookala Supraja, Naga Venkata Krishna Vara Prasad Tollamadugu and S. Adam: Nanotechnology Laboratory, Institute of Frontier Technology, Regional Agricultural Research Station, Acharya N G Ranga Agricultural University, Tirupathi 517 502, AP, India

Abstract
The present research work reports a low temperature (40oC) chemical precipitation technique for synthesizing hydroxyapatite (HAp) nanoparticles of spherical morphology through a simple reaction of calcium nitrate tetrahydrate and di-ammonium hydrogen phosphate at pH 11. The crystallinity of the singlephase nanoparticles could be improved by calcinating at 600oC in air. Thermogravimetric and differential thermal analysis (TG-DTA) revealed the synthesized HAp is stable up to 1200oC. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) studies confirmed the formation of spherical nanoparticles with average size of 23.15+-2.56 nm and Ca/P ratio of 1.70. Brunauer-Emmett-Teller (BET) isotherm of the nanoparticles revealed their porous structure with average pore size of about 24.47 nm and average surface area of 78.4 m2g-1. Fourier transform infrared spectroscopy (FTIR) was used to confirm the formation of P-O, OH, C-O chemical bonds. Cytotoxicity and MTT assay on MG63 osteogenic cell lines revealed nontoxic bioactive nature of the synthesized HAp nanoparticles.

Key Words
hydroxyapatite; nanomaterials; wet chemical precipitation; biomaterials

Address
Sudip Mondal and Umapada Pal: Instituto de Física, Universidad Autónoma de Puebla, Apdo. Postal J-48, Puebla, Pue. 72570, Mexico
Apurba Dey: Department of Biotechnology, National Institute of Technology Durgapur, M.G. Avenue, Durgapur-713209, Burdwan, WB, India

Abstract
The buckling response of a single-layered graphene sheet (SLGS) embedded in visco-Pasternak\'s medium is presented. The nonlocal first-order shear deformation elasticity theory is used for this purpose. The visco-Pasternak\'s medium is considered by adding the damping effect to the usual foundation model which characterized by the linear Winkler\'s modulus and Pasternak\'s (shear) foundation modulus. The SLGS be subjected to distributive compressive in-plane edge forces per unit length. The governing equilibrium equations are obtained and solved for getting the critical buckling loads of simply-supported SLGSs. The effects of many parameters like nonlocal parameter, aspect ratio, Winkler-Pasternak\'s foundation, damping coefficient, and mode numbers on the buckling analysis of the SLGSs are investigated in detail. The present results are compared with the corresponding available in the literature. Additional results are tabulated and plotted for sensing the effect of all used parameters and to investigate the visco-Pasternak\'s parameters for future comparisons.

Key Words
nonuniform buckling; nonlocal shear deformation model; visco-Pasternak\'s medium

Address
Ashraf M. Zenkour: Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabial Department of Mathematics, Faculty of Science, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt



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