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CONTENTS
Volume 5, Number 4, December 2017
 

Abstract
In this disquisition, an exact solution method is developed for analyzing the vibration characteristics of magneto-electro-elastic functionally graded (MEE-FG) beams by considering porosity distribution and various boundary conditions via a four-variable shear deformation refined beam theory for the first time. Magneto-electro-elastic properties of porous FG beam are supposed to vary through the thickness direction and are modeled via modified power-law rule which is formulated using the concept of even and uneven porosity distributions. Porosities possibly occurring inside functionally graded materials (FGMs) during fabrication because of technical problem that lead to creation micro-voids in FG materials. So, it is necessary to consider the effect of porosities on the vibration behavior of MEE-FG beam in the present study. The governing differential equations and related boundary conditions of porous MEE-FG beam subjected to physical field are derived by Hamilton's principle based on a four-variable tangential-exponential refined theory which avoids the use of shear correction factor. An analytical solution procedure is used to achieve the natural frequencies of porous-FG beam supposed to magneto-electrical field which satisfies various boundary conditions. A parametric study is led to carry out the effects of material graduation exponent, porosity parameter, external magnetic potential, external electric voltage, slenderness ratio and various boundary conditions on dimensionless frequencies of porous MEE-FG beam. It is concluded that these parameters play noticeable roles on the vibration behavior of MEE-FG beam with porosities. Presented numerical results can be applied as benchmarks for future design of MEE-FG structures with porosity phases.

Key Words
magneto-electro-elastic FG material; porous materials; analytical solution; free vibration; refined beam theory

Address
Department of Mechanical Engineering, Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran.


Abstract
The continuum elasticity model is applied to investigate quantitatively the growth features and nucleation mechanism of quantum dots, nanopits, and joint QDs–nanopits structures in GaInAlN quasyternary systems. We have shown that for GaInAlN material system at the critical strain of ε* = 0.039 the sign of critical energy and volume is changed. We assume that at ε = ε* the mechanism of the nucleation is changed from the growth of quantum dots to the nucleation of nanopits. Obviously, at small misfit (ε < ε*), the bulk nucleation mechanism dominates. However, at ε > ε*, when the energy barrier becomes negative as well as a larger misfit provides a lowbarrier path for the formation of dislocations, the nucleation of pits becomes energetically preferable. The free energy of mixing for Ga1-x-yInxAlyN quasiternary system was calculated and studied and its 3D sketch was plotted.

Key Words
quantum dot; nanopit; strain energy; Gibbs free energy; immiscibility gap

Address
Department of Physics of Semiconductors and Microelectronics, Yerevan State University, 1 Alex Manoukian, Yerevan 0025, Armenia.


Abstract
This article investigates vibration behavior of magneto-electro-elastic functionally graded (MEE-FG) nanobeams embedded in two-parameter elastic foundation using a third-order parabolic shear deformation beam theory. Material properties of MEE-FG nanobeam are supposed to be variable throughout the thickness based on power-law model. Based on Eringen's nonlocal elasticity theory which captures the small size effects and using the Hamilton

Key Words
magneto-electro-elastic FG nanobeam; free vibration; nonlocal elasticity theory; higher order beam theory

Address
(1) Farzad Ebrahimi:
Mechanical Engineering Department, Faculty of Engineering, Imam Khomeini International University, Qazvin, P.O.B. 16818-34149, Iran;
(2) Mohammad Reza Barati:
Aerospace Engineering Department & Center of Excellence in Computational Aerospace, Amirkabir University of Technology, Tehran, Iran.

Abstract
Knowledge of thin films mechanical properties is strongly associated to the reliability and the performances of Nano Electro Mechanical Systems (NEMS). In the literature, there are several methods for micro materials characterization. Bulge test is an established nondestructive technique for studying the mechanical properties of thin films. This study improve the performances of NEMS by investigating the mechanical behavior of Nano rectangular thin film (NRTF) made of new material embedded in Nano Electro Mechanical Systems (NEMS) by developing the bulge test technique. The NRTF built from adhesively-bonded layers of basalt fiber reinforced polymer (BFRP) laminate composite materials in Nano size at room temperature and were used for plane-strain bulging. The NRTF is first pre-stressed to ensure that is no initial deflection before applied the loads on NRTF and then clamped between two plates. A differential pressure is applying to a deformation of the laminated composite NRTF. This makes the plane-strain bulge test idea for studying the mechanical behavior of laminated composite NRTF in both the elastic and plastic regimes. An exact solution of governing equations for symmetric cross-ply BFRP laminated composite NRTF was established with taking in-to account the effect of the residual strength from pre-stressed loading. The stress-strain relationship of the BFRP laminated composite NRTF was determined by hydraulic bulging test. The NRTF thickness gradation in different points of hemisphere formed in bulge test was analysed.

Key Words
bulge test technique; mechanical behavior; Micro/Nano Electro-Mechanical Sensors (MEMS/NEMS); basalt fiber reinforced polymer (BFRP)

Address
(1) (Current) International Institute for Urban Systems Engineering, Southeast University, Nanjing 210096, China;
(2) (Previous) Department of Mechanical Engineering, Faculty of Engineering, Alexandria University, Alexandria (21544), Egypt.

Abstract
Metallic copper nanoparticles were synthesised by reduction of copper ions in aqueous solution, and metal-metal bonding by using the nanoparticles was studied. A colloid solution of metallic copper nanoparticles was prepared by mixing an aqueous solution of CuCl2 (0.01 M) and an aqueous solution of hydrazine (reductant) (0.2-1.0 M) in the presence of 0.0005 M of citric acid and 0.005 M of n-hexadecyltrimethylammonium bromide (stabilizers) at reduction temperature of 30-80°C. Copper-particle size varied (in the range of ca. 80-165 nm) with varying hydrazine concentration and reduction temperature. These dependences of particle size are explained by changes in number of metallic-copper-particle nuclei (determined by reduction rate) and changes in collision frequency of particles (based on movement of particles in accordance with temperature). The main component in the nanoparticles is metallic copper, and the metallic-copper particles are polycrystalline. Metallic-copper discs were successfully bonded by annealing at 400°C and pressure of 1.2 MPa for 5 min in hydrogen gas with the help of the metallic-copper particles. Shear strength of the bonded copper discs was then measured. Dependences of shear strength on hydrazine concentration and reduction temperature were explained in terms of progress state of reduction, amount of impurity and particle size. Highest shear strength of 40.0 MPa was recorded for a colloid solution prepared at hydrazine concentration of 0.8 M and reduction temperature of 50°C.

Key Words
metal nanoparticle; nano-particles; nanosized metals; chemical synthesis; nano-materials

Address
(1) Yoshio Kobayashi, Hiroaki Nakazawa, Takafumi Maeda:
Department of Biomolecular Functional Engineering, College of Engineering, Ibaraki University, 4-12-1 Naka-narusawa-cho, Hitachi, Ibaraki 316-8511, Japan;
(2) Yusuke Yasuda, Toshiaki Morita:
Hitachi Research Laboratory, Hitachi Ltd., 7-1-1 Omika-cho, Hitachi, Ibaraki 319-1292, Japan.

Abstract
Silver nanoparticles (AgNPs) were successfully synthesized through a simple green route using the Nelumbo nucifera leaf, stem and flower extracts. These nanoparticles showed characteristic UV-Vis absorption peaks between 410-450 nm which arises due to the plasmon resonance of silver nanoparticles. The Fourier transform infrared spectroscopy (FT-IR) confirmed the presence of amides and which acted as the stabilizing agent. X-ray diffraction spectrum of the nanoparticles confirmed the Face centered cubic (FCC) structure of the formed AgNPs. Dynamic light scattering technique was used to measure hydrodynamic diameter (68.6 nm to 88.1 nm) and zeta potential (-55.4 mV, -57.9 mV and 98.9 mV) of prepared AgNPs. The scanning electron micrographs of dislodged nanoparticles in aqueous solution showed the production of reasonably monodispersed silver nanoparticles (1-100 nm). The antimicrobial activity of prepared AgNPs was evaluated against fungi, Gram-positive and Gram-negative bacteria using disc diffusion method. Anti-corrosion studies were carried out using coupon method (mild steel and iron) and dye degradation studies were carried out by assessing photo-catalytic activity of Nelumbo nucifera extracts mediated AgNPs.

Key Words
Nelumbo nucifera; silver nanoparticles; antimicrobial activity; corrosion; photo-catalytic activity

Address
(1) N. Supraja, T.N.V.K.V. Prasad:
Nanotechnology laboratory, Institute of Frontier Technology, Regional Agricultural Research Station, Acharya N.G. Ranga Agricultural University, Tirupathi – 517502, A.P., India;
(2) B. Avinash:
Department of Veterinary Parasitology, College of Veterinary Sciences, Sri Venkateswara Veterinary University, Tirupati – 517502, A.P., India.

Abstract
Forced vibration behavior of porous metal foam nanoplates on elastic medium is studied via a 4-variable plate theory. Different porosity distributions called uniform, symmetric and asymmetric are considered. Nonlocal strain gradient theory (NSGT) containing two scale parameters is employed for size-dependent modeling of porous nanoplates. The present plate theory satisfies the shear deformation effect and it has lower field variables compared with first order plate theory. Hamilton's principle is employed to derive the governing equations. Obtained results from Galerkin's method are verified with those provided in the literature. The effects of nonlocal parameter, strain gradient, foundation parameters, dynamic loading, porosity distributions and porosity coefficient on dynamic deflection and resonance frequencies of metal foam nanoscale plates are examined.

Key Words
forced vibration; 4-unkonwn plate theory; porous nanoplate; nonlocal elasticity; porosities

Address
Aerospace Engineering Department & Center of Excellence in Computational Aerospace, Amirkabir University of Technology, Tehran, Iran.



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