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Volume 7, Number 3, May 2019

In this article, the influence of small scale effects on the free vibration response of curved magneto-electro-elastic functionally graded (MEE-FG) nanobeams has been investigated considering nonlocal elasticity theory. Power-law is used to judge the through thickness material property distribution of MEE nanobeams. The Euler-Bernoulli beam model has been adopted and through Hamilton's principle the Nonlocal governing equations of curved MEE-FG nanobeam are obtained. The analytical solutions are obtained and validated with the results reported in the literature. Several parametric studies are performed to assess the influence of nonlocal parameter, magnetic potential, electric voltage, opening angle, material composition and slenderness ratio on the dynamic behaviour of MEE curved nanobeams. It is believed that the results presented in this article may serve as benchmark results in accurate analysis and design of smart nanostructures.

Key Words
curved nanobeam; free vibration; magneto-electro-elastic materials; functionally graded material; nonlocal elasticity

(1) Farzad Ebrahimi, Mohammad Reza Barati:
Mechanical Engineering Department, Faculty of Engineering, Imam Khomeini International University, Qazvin, P.O.B. 16818-34149, Iran;
(2) Vinyas Mahesh:
Department of Mechanical Engineering, Nitte Meenakshi Institute of Technology, Karnataka 5600064, India.

In this paper, a classical plate model is utilized to formulate the wave propagation problem of magnetostrictive sandwich nanoplates (MSNPs) while subjected to hygrothermal loading with respect to the scale effects. Herein, magnetostriction effect is considered and controlled on the basis of a feedback control system. The nanoplate is supposed to be embedded on a visco-Pasternak substrate. The kinematic relations are derived based on the Kirchhoff plate theory; also, combining these obtained equations with Hamilton\'s principle, the local equations of motion are achieved. According to a nonlocal strain gradient theory (NSGT), the small scale influences are covered precisely by introducing two scale coefficients. Afterwards, the nonlocal governing equations can be derived coupling the local equations with those of the NSGT. Applying an analytical solution, the wave frequency and phase velocity of propagated waves can be gathered solving an eigenvalue problem. On the other hand, accuracy and efficiency of presented model is verified by setting a comparison between the obtained results with those of previous published researches. Effects of different variants are plotted in some figures and the highlights are discussed in detail.

Key Words
wave propagation; magnetostrictive materials; nonlocal strain gradient theory (NSGT); sandwich nanoplates; hygro-thermal environments

(1) Farzad Ebrahimi, Ali Dabbagh:
Department of Mechanical Engineering, Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran;
(2) Francesco Tornabene:
Department of Civil, Chemical, Environmental, and Materials Engineering, University of Bologna, Bologna, Italy;
(3) Omer Civalek:
Akdeniz University, Engineering Faculty, Civil Engineering Department, Division of Mechanics, 07058 Antalya, Turkey.

Plasmonic effects of gold and platinum alloy nanoparticles (Au-Pt NPs) and their comparison to size was studied. Various factors including ratios of gold and platinum salt, temperature, pH and time of addition of reducing agent were studied for their effect on particle size. The size of gold and platinum alloy nanoparticles increases with increasing concentration of Pt NPs. Temperature dependent synthesis of gold and platinum alloy nanoparticles shows decrease in size at higher temperature while at lower temperature agglomeration occurs. For pH dependent synthesis of Au-Pt nanoparticles, size was found to be increased by increase in pH from 4 to 10. Increasing the time of addition of reducing agent for synthesis of pure and gold-platinum alloy nanoparticles shows gradual increase in size as well as increase in heterogeneity of nanoparticles. The size and elemental analysis of Au-Pt nanoparticles were characterized by UV-Vis spectroscopy, XRD, SEM and EDX techniques.

Key Words
nanoparticles; platinum nanoparticles; bimetallic nanoparticles, alloy nanoparticles; plasmonic effects; Au-Pt

(1) Muhammad Jawad, Shazia Ali, Ahson J. Shaikh:
Department of Chemistry, COMSATS University Islamabad – Abbottabad Campus, Abbottabad-22060, KPK, Pakistan;
(2) Amir Waseem:
Department of Chemistry, Quaid-i-Azam University, Islamabad-45320, Pakistan;
(3) Faiz Rabbani:
Department of Environmental Sciences, COMSATS University Islamabad – Vehari Campus, Vehari, Pakistan;
(4) Bilal Ahmad Zafar Amin, Muhammad Bilal:
Department of Environmental Sciences, COMSATS University Islamabad – Abbottabad Campus, Abbottabad-22060, KPK, Pakistan.

The thermal buckling temperature values of the graded carbon nanotube reinforced composite shell structure is explored using higher-order mid-plane kinematics and multiscale constituent modeling under two different thermal fields. The critical values of buckling temperature including the effect of in-plane thermal loading are computed numerically by minimizing the final energy expression through a linear isoparametric finite element technique. The governing equation of the multiscale nanocomposite is derived via the variational principle including the geometrical distortion through Green-Lagrange strain. Additionally, the model includes different grading patterns of nanotube through the panel thickness to improve the structural strength. The reliability and accuracy of the developed finite element model are varified by comparison and convergence studies. Finally, the applicability of present developed model was highlight by enlighten several numerical examples for various type shell geometries and design parameters.

Key Words
thermal buckling; FG-CNT; HSDT; thermal load; FEM; micromechanical model

(1) Kulmani Mehar:
Department of Mechanical Engineering, Madanapalle Institute of Technology & Science, Madanapalle, India;
(2) Subrata Kumar Panda:
Department of Mechanical Engineering, National Institute of Technology Rourkela, Odisha, 769008, India.

In the present work the dynamic analysis of the functionally graded rectangular nanoplates is studied. The theory of nonlocal elasticity based on the quasi 3D high shear deformation theory (quasi 3D HSDT) has been employed to determine the natural frequencies of the nanosize FG plate. In HSDT a cubic function is employed in terms of thickness coordinate to introduce the influence of transverse shear deformation and stretching thickness. The theory of nonlocal elasticity is utilized to examine the impact of the small scale on the natural frequency of the FG rectangular nanoplate. The equations of motion are deduced by implementing Hamilton\'s principle. To demonstrate the accuracy of the proposed method, the calculated results in specific cases are compared and examined with available results in the literature and a good agreement is observed. Finally, the influence of the various parameters such as the nonlocal coefficient, the material indexes, the aspect ratio, and the thickness to length ratio on the dynamic properties of the FG nanoplates is illustrated and discussed in detail.

Key Words
nonlocal elasticity theory; FG nanoplate; free vibration; refined theory; elastic foundation

(1) Sabrina Boutaleb, Kouider Halim Benrahou, Ahmed Bakora, Abdelouahed Tounsi, Abdeldjebbar Tounsi:
Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
(2) Ahmed Bakora:
Département de Génie Civil, Faculté d\'Architecture et de Génie Civil, Université des Sciences et de la Technologie d\'Oran, BP 1505 El M\'naouer, USTO, Oran, Algeria;
(3) Ali Algarni:
Statistics Department, Faculty of Science, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia;
(4) Abdelmoumen Anis Bousahla:
Laboratoire de Modélisation et Simulation Multi-échelle, Département de Physique, Faculté des Sciences Exactes, Département de Physique, Université de Sidi Bel Abbés, Algeria;
(5) Abdelmoumen Anis Bousahla:
Centre Universitaire Ahmed Zabana de Relizane, Algeria;
(6) Abdelouahed Tounsi:
Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia;
(7) S.R. Mahmoud:
Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia.

Graphene, with impressive electronic properties, have high potential in the microelectronic field. However, graphene itself is a zero bandgap material which is not suitable for digital logic gates and its application. Thus, much focus is on graphene nanoribbons (GNRs) that are narrow strips of graphene. During GNRs fabrication process, the occurrence of defects that ultimately change electronic properties of graphene is difficult to avoid. The modelling of GNRs with defects is crucial to study the non-idealities effects. In this work, nearest-neighbor tight-binding (TB) model for GNRs is presented with three main simplifying assumptions. They are utilization of basis function, Hamiltonian operator discretization and plane wave approximation. Two major edges of GNRs, armchair-edged GNRs (AGNRs) and zigzag-edged GNRs (ZGNRs) are explored. With single vacancy (SV) defects, the components within the Hamiltonian operator are transformed due to the disappearance of tight-binding energies around the missing carbon atoms in GNRs. The size of the lattices namely width and length are varied and studied. Non-equilibrium Green.s function (NEGF) formalism is employed to obtain the electronics structure namely band structure and density of states (DOS) and all simulation is implemented in MATLAB. The band structure and DOS plot are then compared between pristine and defected GNRs under varying length and width of GNRs. It is revealed that there are clear distinctions between band structure, numerical DOS and Green\'s function DOS of pristine and defective GNRs.

Key Words
graphene nanoribbons (GNRs); non-equilibrium Green.s function (NEGF); single vacancy (SV); tight binding; electronic structure

School of Electrical Engineering, Faculty of Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia.

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