• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.380-381
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• 2012

Bioinspired sea urchin-like structures were fabricated on silicon by inductively coupled plasma (ICP) etching using lens-like shape hexagonally patterned photoresist (PR) patterns and subsequent metal-assisted chemical etching (MaCE) [1]. The lens-like shape PR patterns with a diameter of 2 ${\mu}m$ were formed by conventional lithography method followed by thermal reflow process of PR patterns on a hotplate at $170^{\circ}C$ for 40 s. ICP etching process was carried out in an SF6 plasma ambient using an optimum etching conditions such as radio-frequency power of 50 W, ICP power of 25 W, SF6 flow rate of 30 sccm, process pressure of 10 mTorr, and etching time of 150 s in order to produce micron structure with tapered etch profile. 15 nm thick Ag film was evaporated on the samples using e-beam evaporator with a deposition rate of 0.05 nm/s. To form Ag nanoparticles (NPs), the samples were thermally treated (thermally dewetted) in a rapid thermal annealing system at $500^{\circ}C$ for 1 min in a nitrogen environment. The Ag thickness and thermal dewetting conditions were carefully chosen to obtain isolated Ag NPs. To fabricate needle-like nanostructures on both the micron structure (i.e., sea urchin-like structures) and flat surface of silicon, MaCE process, which is based on the strong catalytic activity of metal, was performed in a chemical etchant (HNO3: HF: H2O = 4: 1: 20) using Ag NPs at room temperature for 1 min. Finally, the residual Ag NPs were removed by immersion in a HNO3 solution. The fabricated structures after each process steps are shown in figure 1. It is well-known that the hierarchical micro- and nanostructures have efficient light harvesting properties [2-3]. Therefore, this fabrication technique for production of sea urchin-like structures is applicable to improve the performance of light harvesting devices.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.3
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• pp.230-237
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• 2007

Titania nanotube(TiNT) and CdS sol were synthesized by hydrothermal reaction under strongly basic condition and by precipitation reaction of $Cd(N0_3)_2$ and $Na_2S$ aqueous solutions, respectively. After preparing a series of CdS-TiNT composite films on $F:SnO_2$ conducting glass with variation of the mole ratio (r) of TiNT/(CdS+TiNT), their visible light absorption, photocatalytic activities for hydrogen production, and the photocurrent generation were examined. In general, this CdS-TiNT series showed lower photocatalytic activities and photocurrent generation under Xe light irradiation compared to their counterparts, i.e., CdS-$TiO_2$ particulate series. It appeared that TiNTs are not so effective photocatalyic material in spite of their larger specific surface areas compared to $TiO_2$ nanoparticles, because they indicate a poor crystallinity and less intimate interaction or contact with CdS particles owing to the tubular morphology and an easy agglomeration among themselves.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2425-2433
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• 2018

This study investigates a new organic based material and its dielectric and mechanical properties. It is a comprehensive nanocomposite comprising a combination of various types of nanofillers with hydrophobic silica nanoparticles (AEROSIL R 974) as a matrix modifier and a polyamide nano nonwoven textile, Ultramid-Polyamide 6, pulped in the electrostatic field as a dielectric barrier. The polymer matrix is an epoxy network based on diglycidyl ether of bisphenol A (DGEBA) and cycloaliphatic diamine (Laromine C260). The designed nanocomposite material is an alternative to the conventional three-component composites containing fiberglass and mica with properties that exceed current electroinsulating systems (volume resistivity on the order of $10^{16}{\Omega}{\cdot}m$, dissipation factor tan ${\delta}=4.7{\cdot}10^{-3}$, dielectric strength 39 kV/mm).

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.18
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• pp.8259-8263
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• 2016

Background: Nano-therapy has the potential to revolutionize cancer therapy. Chrysin, a natural flavonoid, was recently recognized as having important biological roles in chemical defenses and nitrogen fixation, with anti-inflammatory and anti-oxidant effects but the poor water solubility of flavonoids limitstheir bioavailability and biomedical applications. Objective: Chrysin loaded PLGA-PEG-PLGA was assessed for improvement of solubility, drug tolerance and adverse effects and accumulation in a gastric cancer cell line (AGS). Materials and Methods: Chrysin loaded PLGA-PEG copolymers were prepared using the double emulsion method (W/O/W). The morphology and size distributions of the prepared PLGA-PEG nanospheres were investigated by 1H NMR, FT-IR and SEM. The in vitro cytotoxicity of pure and nano-chrysin was tested by MTT assay and miR-34a was measured by real-time PCR. Results: 1H NMR, FT-IR and SEM confirmed the PLGA-PEG structure and chrysin loaded on nanoparticles. The MTT results for different concentrations of chrysin at different times for the treatment of AGS cell line showed IC50 values of 68.2, 56.2 and $42.3{\mu}M$ and 58.2, 44.2, $36.8{\mu}M$ after 24, 48, and 72 hours of treatment, respectively for chrysin itslef and chrysin-loaded nanoparticles. The results of real time PCR showed that expression of miR-34a was upregulated to a greater extent via nano chrysin rather than free chrysin. Conclusions: Our study demonstrates chrysin loaded PLGA-PEG promises a natural and efficient system for anticancer drug delivery to fight gastric cancer.

• Applied Chemistry for Engineering
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• v.28 no.3
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• pp.351-354
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• 2017

An experimental design method was used to optimize the synthesis of gamma-alumina with a superior thermal stability using the reverse micelle method. First, twelve experimental conditions were derived by using the mixture design method to optimize conditions for the ratio of surfactant, water and oil, which are main factors in the synthesis process. When the particles synthesized by reverse micelle method were calcined at $900^{\circ}C$ under the designed condition, they all had gamma-alumina crystal structure although there were differences in particle sizes. The coefficient of determination of the second-order regression model using the derived experimental results was 93.68% and the P-value was 0.002. The synthesis conditions forgamma-alumina with various particle sizes were presented using surface and contour lines. As a result, it was calculated that the smallest particle size of about 2.8 nm was synthesized when the ratio of surfactant/water/oil was 0.3450/0.0729/0.5821.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.10
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• pp.887-894
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• 2013

Effective thermal conductivity of nanofluids has been predicted by using generalized self-consistent model and modified Eshelby model, which have been used for analysis of material properties of composites. A nanolayer between base fluid and nanoparticle, one of key factors for abrupt enhancement of thermal conductivity of nanofluids, is included in the analysis. The effective thermal conductivities of the nanofluid predicted by the present study show good agreement with those by models in the literature for the nanolayer with a constant or linear thermal conductivity. The predicted results by the present approach have been confirmed to be consistent with experiments for representative nanofluids such as base fluids of water or ethyleneglycol and nanoparticles of $Al_2O_3$ or CuO to be validated.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.100-105
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• 2005

$Ni_{0.9}Zn_{0.1}Fe_2O_4$ nanoparticles have been prepared by a sol-gel method. The structural and magnetic properties have been investigated by DTA/TGA, XRD, SEM, and $M\ddot{o}ssbauer$ spectroscopy, VSM. $Ni_{0.9}Zn_{0.1}Fe_2O_4$ powder that was annealed at $300^{\circ}C$ has spinel structure and behaved superparamagnetically. The estimated size of superparammagnetic Ni-Zn ferrite nanoparticle is around 10 nm. The hyperfine fields at 13 K for the A and B patterns were found to be 533 and 507 kOe, respectively. The blocking temperature ($T_B$) of superparammagnetic $Ni_{0.9}Zn_{0.1}Fe_2O_4$ nanoparticle is about 250 K. The magnetic anisotropy constant and relaxation time constant of $Ni_{0.9}Zn_{0.1}Fe_2O_4$ nanoparticle were calculated to be $1.6\times10^6\;ergs/cm^3$ and ${\tau}_0=5.0{\times}10^{-13}$ s, respectively. Also, Temperature increased up to $43^{\circ}C$ within 10 minutes under AC magnetic field of 7 MHz. It is considered that $Ni_{0.9}Zn_{0.1}Fe_2O_4$ powder that was annealed at $300^{\circ}C$ is available for biomedicine application such as hyperthermia, drug delivery system and contrast agents in MRI.

• Journal of the Korean Magnetics Society
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• v.18 no.3
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• pp.120-125
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• 2008

In this study, NiCoZn ferrites with the variation of sintering temperature and chemical composition were prepared by the coprecipitation. Microstructures Crystal structure of NiCoZn ferrites were analyzed by XRD and their electric magnetic characteristics were analyzed by LCR meter and their morphology observed by SEM. We identified that these powders have a typical NiCoZn spinel structure and nanoparticles average size of 40 nm. The impurity, the initial permeability and the Q factor value are the lowest of sintered NiCoZn ferrite at $1250^{\circ}C$. Also, we measured S-parameter for $(Ni_{0.4}Co_{0.1}Zn_{0.5})Fe_2O_4$ which showed a maximum reflection loss of -3.1 dB at 6 GHz for the 2 mm thick sample. From this result, we found that the NiCoZn ferrite can be used in ferrite microwave-absorbing application at a higher frequency region (> 6 GHz).

• Textile Coloration and Finishing
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• v.35 no.2
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• pp.128-136
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• 2023

Recently, the automobile industry is developing as the demand for automo- biles increases due to industrial development and population growth. In addition, many studies are being conducted to reduce heat loss inside the automobiles in order to save energy inside the automobiles due to environmental regulations. In this study, alumina, nanosilicon, and aerogel, which are adiabatic materials, were filled in PET to manufacture yarn, identify physical and mechanical properties, and weave into fabric to confirm adiabatic performance. As the content of the adiabatic material increased, the tensile strength of the fibers filled with alumina and nanosilicon decreased greatly, and the adiabatic property slightly increased. The tensile strength of fibers filled with the aerogel decreased slightly, but the adiabatic properties were greatly increased. Therefore, it is considered to be due to the large volume fraction in the PET yarn due to the low density of the aerogel.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.220-221
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• 2003

Equiatomic FePt and CoPt alloy thin films have received considerable attention as possible magnetic and magneto-optic recording because of their high magnetic anisotropy energy and high coercivity. The high coercivity in these thin films is due to the presence of finely dispersed ordered FePt phase mixed with disordered FePt phase. However, a high temperature treatment, either substrate heating during deposition or post annealing, is needed to obtain the ordered L1$\_$0/ phase with high value of magneto crystalline anisotropy. Recent microstructural studies on these films suggest that the average grain size ranges from 10-50 nm and the grains are magnetically coupled between each other. On the other hand, the ultrahigh-density magnetic recording media with low media noise imposes the need of a material, which consists of magnetically isolated grains with size below 10 nm. The magnetic grain isolation can be controlled by the amount of additional non-magnetic element in the system which determines the interparticle separation and therefore the interparticle interactions. Recently, much research work has been done on various non-magnetic matrices. Preliminary studies showed that the samples prepared in B$_2$O$_3$ and Carbon matrices have shown strong perpendicular anisotropy and fine grain size down to 4nm, which suggest these nanocomposite films are very promising and may lead to the realization of a magnetic medium capable of recording densities beyond 1 Tb/in$^2$. So, in this work, the effect of Carbon doping on the magnetic properties of FePt nanoparticles were investigated.