• Advances in nano research
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• v.13 no.4
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• pp.351-368
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• 2022

Recently, promising structural technologies like multi-function, ultra-load bearing capacity and tailored structures have been put up for discussions. Finite Element (FE) modelling is probably the best-known option capable of treating these superior properties and multi-domain behavior structures. However, advanced materials such as Functionally Graded Material (FGM) and nanocomposites suffer from problems resulting from variable material properties, reinforcement aggregation and mesh generation. Motivated by these factors, this research proposes a unified shape function for FGM, nanocomposites, graded nanocomposites, in addition to traditional isotropic and orthotropic structural materials. It depends not only on element length but also on the beam's material properties and geometric characteristics. The systematic mathematical theory and FE formulations are based on the Timoshenko beam theory for beam structure. Furthermore, the introduced element achieves C1 degree of continuity. The model is proved to be convergent and free-off shear locking. Moreover, numerical results for static and free vibration analysis support the model accuracy and capabilities by validation with different references. The proposed technique overcomes the issue of continuous properties modelling of these promising materials without discarding older ones. Therefore, introduced benchmark improvements on the FE old concept could be extended to help the development of new software features to confront the rapid progress of structural materials.

• Advances in nano research
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• v.6 no.2
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• pp.113-133
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• 2018

In this work, free vibration characteristics of functionally graded piezoelectric (FGP) nanobeams based on third order parabolic shear deformation beam theory are studied by presenting a Navier type solution as the first attempt. Electro-mechanical properties of FGP nanobeam are supposed to change continuously throughout the thickness based on power-law model. To capture the small size effects, Eringen's nonlocal elasticity theory is adopted. Using Hamilton's principle, the nonlocal governing equations for third order shear deformable piezoelectric FG nanobeams are obtained and they are solved applying analytical solution. By presenting some numerical results, it is demonstrated that the suggested model presents accurate frequency results of the FGP nanobeams. The influences of several parameters including, external electric voltage, power-law exponent, nonlocal parameter and mode number on the natural frequencies of the size-dependent FGP nanobeams is discussed in detail.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.192.1-192.1
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• 2015

We demonstrated the nonvolatile memory functionality of nano-crystalline silicon (nc-Si) and InGaZnOxide (IGZO) thin film transistors (TFTs) using mobile protons that are generated by very short time hydrogen neutral beam (H-NB) treatment in gate insulator (SiO2). The whole memory fabrication process kept under $50^{\circ}C$ (except SiO2 deposition process; $300^{\circ}C$). These devices exhibited reproducible hysteresis, reversible switching, and nonvolatile memory behaviors in comparison with those of the conventional FET devices. We also executed hydrogen treatment in order to figure out the difference of mobile proton generation between PECVD and H-NB CVD that we modified. Our study will further provide a vision of creating memory functionality and incorporating proton-based storage elements onto a probability of next generation flexible memorable electronics such as low power consumption flexible display panel.

• Transactions on Electrical and Electronic Materials
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• v.11 no.6
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• pp.266-270
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• 2010

The effect of an Ar plasma treatment on polycarbonate substrates was investigated using $TiO_2$ coatings produced by reactive ion-beam assisted sputtering. The typical pressure used during sputtering was about $10^{-4}$ Torr. After the Ar plasma treatment, the contact angle of a water droplet was reduced from $88^{\circ}$ to $52^{\circ}$ and then further decreased to $12^{\circ}$ with the addition of oxygen into the chamber. The surface of the polycarbonate substrate hanged from hydrophobic to hydrophilic with these treatments and revealed its changing nano-scale roughness. The $TiO_2$ films on the treated surface showed various colors and periodic ordering dependant on the film thickness due to optical interference.

• JSTS:Journal of Semiconductor Technology and Science
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• v.6 no.3
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• pp.131-135
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• 2006

High electron mobility transistors with InAs channels and antimonide barriers were grown on Si and GaAs substrates by means of molecular beam epitaxy. While direct growth of Sb materials on Si substrate generates disordered and coalescences 3-D growth, smooth and mirror-like 2D growth can be repeatedly obtained by inserting AlSb QD layers between them. Room-temperature electron mobilities of over 10,000 $cm^2/V-s$ and 20,000 $cm^2/v-s$ can be routinely obtained on Si and GaAs substrates, respectively, after optimizing the buffer structure as well as maintaining InSb-like interface.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.6
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• pp.558-564
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• 2009

To aim at obtaining a correct and fine small pattern by an electron beam lithography several conditions and methods affecting a real pattern shape needs to be investigated. A micro/nano sized pattern shape is sometimes dependent on the scanning method. In this work, four types of scanning methods are implemented and their characteristics are investigated. For a $11\times11um$ pattern, a Zigzag scanning method proves a precise pattern generation. The other ways such as SEM scanning and swirl in-out scanning method result in some distorted pattern shape. It is proved that abrupt change in the pattern generation limits to obtaining a fine and small pattern.

• Advances in nano research
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• v.5 no.4
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• pp.313-336
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• 2017

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's principle, the nonlocal governing equations of motions are derived and then solved analytically. Then the influences of elastic foundation, magnetic potential, external electric voltage, nonlocal parameter, power-law index and slenderness ratio on the frequencies of the embedded MEE-FG nanobeams are studied.

• Advances in nano research
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• v.13 no.1
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• pp.47-61
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• 2022

The present research investigates the dynamic behavior of a rotating functionally graded (FG) nonlocal cylindrical beam. The cylindrical beam is mathematically modeled via third-order beam theory linked with nonlocal strain gradient theory. The tube structure is made of functionally graded materials composed of Aluminum oxide coated on the Nickel, which the mechanical properties vary in the tube radius direction according to the power law. The bending harmonic force is applied in the tube length middle. The nonlocal spinning equations of the tube are derived via the energy method of the Hamilton principle, and they are solved via a robust numerical procedure for different boundary conditions. The main application of the rotating nanostructures is for the production of small-scale motors and devices and the drug-delivery application, the presented results can help the researcher have a better view regarding the different conditions.

• Structural Engineering and Mechanics
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• v.82 no.5
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• pp.629-641
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• 2022

This study deals with the spinning impact on flap-wise vibration characteristics of nonlocal functionally graded (FG) cylindrical beam based on the Hyperbolic shear deformation beam theory. The nonlocal strain gradient theory is used to investigate the small-scale impact on the nonlocal motion equation as well as corresponding nonlocal boundary conditions. Based on the mathematical simulation and according to the Hamilton principle, the computerized modeling of a rotating functionally graded nanotube is generated, and then, via a numerical approach, the obtained mathematical equations are solved. The calculated outcomes are helpful to the production of Nano-electro-mechanical-systems (NEMS) by investigating some designed parameters such as rotating speed, hub radius, length-scale parameters, volume fraction parameters, etc.

• Advances in nano research
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• v.12 no.4
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• pp.353-363
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• 2022

This paper presents an investigation about superharmonic and subharmonic resonances of a carbon nanotube reinforced composite beam subjected to lateral harmonic load with damping effect based on the modified couple stress theory. As reinforcing phase, three different types of single walled carbon nanotubes (CNTs) distribution are considered through the thickness in polymeric matrix. The governing nonlinear dynamic equation is derived based on the von Kármán nonlinearity with using of Hamilton's principle. The Galerkin's decomposition technique is utilized to discretize the governing nonlinear partial differential equation to nonlinear ordinary differential equation and then is solved by using of multiple time scale method. Effects of different patterns of reinforcement, volume fraction, excitation force and the length scale parameter on the frequency-response curves of the carbon nanotube reinforced composite beam are investigated. The results show that volume fraction and the distribution of CNTs play an important role on superharmonic and subharmonic resonances of the carbon nanotube reinforced composite beams.