• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.571-572
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• 2012

• Structural Monitoring and Maintenance
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• v.7 no.2
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• pp.85-107
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• 2020

Dynamic responses of porous piezoelectric and metal foam nano-size plates have been examined via a four variables plate formulation. Diverse pore dispersions named uniform, symmetric and asymmetric have been selected. The piezoelectric nano-size plate is subjected to an external electrical voltage. Nonlocal strain gradient theory (NSGT) which includes two scale factors has been utilized to provide size-dependent model of foam nanoplate. The presented plate formulation verifies the shear deformations impacts and it gives fewer number of field components compared to first-order plate model. Hamilton's principle has been utilized for deriving the governing equations. Achieved results by differential quadrature (DQ) method have been verified with those reported in previous studies. The influences of nonlocal factor, strain gradients, electrical voltage, dynamical load frequency and pore type on forced responses of metal and piezoelectric foam nano-size plates have been researched.

• Structural Monitoring and Maintenance
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• v.7 no.2
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• pp.69-84
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• 2020

Based on differential quadrature method (DQM) and nonlocal strain gradient theory (NSGT), forced vibrations of a porous functionally graded (FG) scale-dependent beam in thermal environments have been investigated in this study. The nanobeam is assumed to be in contact with a moving point load. NSGT contains nonlocal stress field impacts together with the microstructure-dependent strains gradient impacts. The nano-size beam is constructed by functionally graded materials (FGMs) containing even and un-even pore dispersions within the material texture. The gradual material characteristics based upon pore effects have been characterized using refined power-law functions. Dynamical deflections of the nano-size beam have been calculated using DQM and Laplace transform technique. The prominence of temperature rise, nonlocal factor, strain gradient factor, travelling load speed, pore factor/distribution and elastic substrate on forced vibrational behaviors of nano-size beams have been explored.

• Transactions of Materials Processing
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• v.14 no.4 s.76
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• pp.319-326
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• 2005

In this study, the nano-deformation behavior of semi-solid Al-Si alloy was investigated using a molecular dynamics simulation as a part of the research on the surface crack behavior in thixoformed automobile parts. The microstructure of the grain-size controlled Al-Si alloy consists of primary and eutectic regions. In eutectic regions the crack initiation begins with initial fracture of the eutectic silicon particles and inside other intermetallic phases. Nano-deformation characteristics in the eutectic and primary phase of the grain-size controlled Al-Si alloy were investigated through the molecular dynamics simulation. The primary phase was assumed to be single crystal aluminum. It was shown that the vacancy occurred at the zone where silicon molecules were.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.117-121
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• 2011

Size-controlled Ag nanoparticles (NPs) were prepared from the decomposition of Ag(I) carboxylates using ethanolamine derivatives as a reducing agent without an additional stabilizing agent. The size of the Ag NPs with a narrow size distribution (sub-10 nm to ca. 40 nm) was controlled precisely by varying the processing parameters, such as the type of reducing agent and the chain length of the carboxylate in the Ag(I) carboxylate. The optical properties, surface composition and crystallinity of the Ag NPs were characterized by ultraviolet-visible spectroscopy, gas chromatography-mass spectrometry, thermal gravimetric analysis, transmission electron microscopy and X-ray diffraction.

• Journal of the Korean institute of surface engineering
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• v.43 no.3
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• pp.121-126
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• 2010

The PS(porous Si) were fabricated with different anodization time and current density. The structural and optical properties of PS were investigated by SEM(scanning electron microscopy), AFM(atomic force microscopy), and PL(photoluminescence). It is found that the pore size and surface roughness of PS are proportional to the current density. The PL spectra show that the PL peak position is red-shifted with increasing anodization time. This behavior corresponds to the change of pore size which is consistent with the quantum confinement model. The FWHM(full width at half maximum) of PL peak is decreased from 97 to 51 nm and the PL peak position is blue-shifted with increasing current density up to 10 mA/$cm^2$. The PL peak intensity of the PS fabricated under 1 mA/$cm^2$ is the highest among samples.

• Journal of the Korean Applied Science and Technology
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• v.28 no.1
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• pp.1-5
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• 2011

In this study, We investigated the properites of nano-emulsions containing hydrogenated lecithin prepared by high pressure homogenizer. The size of droplet of emulsions prepared by homogenizer at various rpm (rotation per minute) was not measured due to the unstability of emulsions, however, the size of droplet of nano-emulsions prepared by high pressure homogenizer was around 300 nm and the appearance of emulsions was bluish. The stability of emulsions with various lecithin concentration was tested against time. POV (Peroxide value) of emulsions were plotted against time. POVs of emulsions prepared with an egg lecithin and a soy lecithin were increased with time, however, POV of emulsion with Lecinol S-$10^{(R)}$ was kept constant within 60 hours and at $60^{\circ}C$. In consumer test, the nano-emulsion showed higher affinity regardless of skin type. Both of irritation scores of emulsions were similar.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.65-65
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• 2003

Chemical mechanical polishing (CMP) is one of the most important processes in recent ULSI (Ultra Large Scale Integrated Circuit) manufacturing technology. Recently, ceria slurries with surfactant have recently been used in STI-CMP,[1] became they have high oxide-to-nitride removal selectivity and widen the processing margin The role of the abrasives, however, on the effect of planarization on STI-CMP is not yet clear. In this study, we investigated how the crystal characteristic affects the planarization efficiency of wafer surface with controlling crystallite size and poly crystalline abrasive size independently.

• Journal of Powder Materials
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• v.11 no.1
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• pp.22-27
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• 2004

The Indium Tin Oxide(ITO) nano powders were prepared by spray drying and heat treatment process. The liquid solution dissolved Indium and Tin salts was first spray dried to prepare chemically homogeneous recursor powders at the optimum spray drying conditions. Subsequently, the precursor powders were subjected to eat treatment process. The nano size ITO powders was synthesized from the previous precursor powders and the npuities also were decreased with increasing heat treatment temperature. Furthermore, the lattice parameter of TO nano powders was increased by doping Tin into Indium with increasing heat treatment temperature. The par icle size of the resultant ITO powders was about 20∼50nm and chemical composition was composed of In:Sn =86:10 wt.％ at 80$0^{\circ}C$.

• Journal of Powder Materials
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• v.18 no.6
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• pp.546-551
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• 2011

Ag spot-coated Cu nanopowders were synthesized by a hydrothermal-attachment method (HA) using oleic acid capped Ag hydrosol. Cu nano powders were synthesized by pulsed wire exploding method using 0.4 mm in diameter of Cu wire (purity 99.9%). Synthesized Cu nano powders are seen with comparatively spherical shape having range in 50 nm to 150 nm in diameter. The oleic acid capped Ag hydrosol was synthesized by the precipitation-redispersion method. Oleic acid capped Ag nano particles showed the narrow size distribution and their particle size were less than 20 nm in diameter. In the case of nano Ag-spot coated Cu powders, nanosized Ag particles were adhered in the copper surface by HAA method. The components of C, O and Ag were distributed on the surface of copper powder.