• Journal of the Korean Vacuum Society
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• v.22 no.2
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• pp.66-78
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• 2013

In order to develop of 80 kW RF plasma torch system, we achieved three-dimensional simulations for the extraction of more information as temperature in torch and fluid behavior analysis, etc. The position of powder injection tube, the plasma discharge characteristics with various input current and various length of ceramic tube, and the plasma temperature characteristics with process gas flow rate such those was simulated. RF thermal plasma torch designed by simulation was manufactured that was measured to the maximum of 89.3 kW power. The mass production using developed 80 kW RF thermal plasma torch system were investigated by characteristics manufactured of Si nano powder. The mass-production level of Si nano-powder was average of 539 g/hr and high yield rate of 71.6%, respectively. The particle size distribution $D_{99}/D_{50}$ of manufacturing nano-powder was investigated to 1.98 as a good uniform.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.42 no.3
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• pp.211-216
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• 2016

Micronucleus test is genotoxicity assay for detection of micronuclei in the cytoplasm of interphase cells. The reduction and replacement of in vivo toxicity testing on animals require the development of in vitro models to predict the genotoxicity or other tests for cosmetic products. In this study, we evaluated a genotoxicity assay for topically applied chemicals using a three-dimensional human reconstructed skin model, KeraSkin$^{TM}$. Two genotoxins, mitomycin C (MMC) and methyl methanesulfonate (MMS), induced significant dose-related increases in cytotoxicity and micronuclei induction in the skin model. In contrast, two non-genotoxins, 4-nitrophenol (4-NP) and trichloroethylene (TCE), induced cytotoxicity but not micronucleus formation. In conclusion, micronucleus test using human skin model may be useful for predicting in vitro genotoxic potentials of cosmetic products.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.284-284
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• 2016

Topological insulator (TI) is a bulk-insulating material with topologically protected Dirac surface states in the band gap. In particular, $Bi_2Se_3$ attracted great attention as a model three-dimensional TI due to its simple electronic structure of the surface states in a relatively large band gap (~0.3 eV). However, experimental efforts using $Bi_2Se_3$ have been difficult due to the abundance of structural defects, which frequently results in the bulk conduction being dominant over the surface conduction in transport due to the bulk doping effects of the defect sites. One promising approach in avoiding this problem is to reduce the structural defects by heteroepitaxially grow $Bi_2Se_3$ on a substrate with a compatible lattice structure, while also preventing surface degradation by encapsulating the pristine interface between $Bi_2Se_3$ and the substrate in a clean growth environment. A particularly promising choice of substrate for the heteroepitaxial growth is hexagonal boron nitride (h-BN), which has the same two-dimensional (2D) van der Waals (vdW) layered structure and hexagonal lattice symmetry as $Bi_2Se_3$. Moreover, since h-BN is a dielectric insulator with a large bandgap energy of 5.97 eV and chemically inert surfaces, it is well suited as a substrate for high mobility electronic transport studies of vdW material systems. Here we report the heteroepitaxial growth and characterization of high quality topological insulator $Bi_2Se_3$ thin films prepared on h-BN layers. Especially, we used molecular beam epitaxy to achieve high quality TI thin films with extremely low defect concentrations and an ideal interface between the films and substrates. To optimize the morphology and microstructural quality of the films, a two-step growth was performed on h-BN layers transferred on transmission electron microscopy (TEM) compatible substrates. The resulting $Bi_2Se_3$ thin films were highly crystalline with atomically smooth terraces over a large area, and the $Bi_2Se_3$ and h-BN exhibited a clear heteroepitaxial relationship with an atomically abrupt and clean interface, as examined by high-resolution TEM. Magnetotransport characterizations revealed that this interface supports a high quality topological surface state devoid of bulk contribution, as evidenced by Hall, Shubnikov-de Haas, and weak anti-localization measurements. We believe that the experimental scheme demonstrated in this talk can serve as a promising method for the preparation of high quality TI thin films as well as many other heterostructures based on 2D vdW layered materials.

• Journal of the Korean Society for Railway
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• v.12 no.1
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• pp.31-38
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• 2009

The selection of the support system is an important design parameter in design and construction of the tunnel using the new Australian tunnel method. It is a common practice to select the support based on the rock mass grade, in which the rock mass is classified into five rock groups. The method is applicable if the characteristics of the rock mass are uniform in the direction of tunnel excavation. However, such case is seldom encountered in practice and not applicable when the properties vary along the longitudinal direction. This study performs comprehensive three dimensional finite difference analyses to investigate the ground deformation pattern for cases in which the rock mass properties change in the direction of the tunnel axis. The numerically calculated displacements at the tunnel crown show that the displacement is highly dependent on the stiffness contrast of the rock masses. The results strongly indicate the need to select the support type $0.5{\sim}1.0D$ before the rock mass boundary. The paper proposes a new guideline for selecting the support type based the results of the analyses.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.11
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• pp.837-842
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• 2017

In this paper, as a basic study for combination of turbo equalizer and 4D-8PSK-TCM(4 Dimensional 8 Phase Shift Keying Trellis Coded Modulation) system, which is recommended for X-band band satellite communication in CCSDS, a system combining 8PSK-TCM system and turbo equalizer has designed and performance evaluation of the system has performed. BER performance of 8PSK and 8PSK-TCM systems has evaluated and analyzed in AWGN, Proakis B and Proakis C channels in detail. As results of simulation, BER performance of 8PSK-TCM system is better than 8PSK system in AWGN environment. Furthermore, it can be confirmed that the system combining the 8PSK-TCM system with the turbo equalizer can further improve the BER performance through iterative equalization in the ISI channel environment. The 8PSK-TCM system combined with the turbo equalizer requires SNR of 5.9 dB for BER performance of $10^{-3}$ with 5 iterative equalization in Proakis B and SNR of 9.1 dB for BER of $10^{-2}$ with 5 iterative equalization in Proakis C.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.7
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• pp.4659-4664
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• 2014

The noise produced in a factory is a cause of the noise complaint of the surrounding residential areas. In addition, it affects the work efficiency and health of workers. This paper presents the results of a basic study to reduce the noise generated from the blower, which is often used in the factory of a small and medium scale, using an active noise controller (ANC) in three-dimensional space. For this purpose, the simulator program, which can compare various parameters of the original noise and controlled noise, such as sound pressure levels, power spectra, and equivalent noise levels, was developed. The noise data was recorded at 17 points around a turbo fan blower currently being operated in a small-medium size factory. The simulation results showed that the power spectrum was reduced by a maximum of 40dB in the low frequency band and the average equivalent noise level attenuation was 12.6dB.

• Journal of Advanced Navigation Technology
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• v.21 no.4
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• pp.371-376
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• 2017

In this paper, we propose a magnetic resonant WPT(wireless power transfer) scenario using a large coil resonating at 6.78 MHz, and compare the characteristics through a three-dimensional electromagnetic field simulation and a magnetic resonant WPT equivalent circuit. The magnetic resonant WPT equivalent circuit proposed in this paper considers the parasitic capacitance generated between the coils in addition to the conventional equivalent circuit. Based on this analysis, we fabricated the magnetic resonant WPT coil and compared it with simulation prediction. As a result of comparison, the transfer characteristics and the resonance frequency shift can be predicted. Error proposed characteristics of equivalent circuit for the magnetic resonant WPT and the measured values are estimated to be ${\Delta}{\mid}S11{\mid}=1.31dB$ and ${\Delta}{\mid}S21{\mid}=1.21dB$, respectively.

• Journal of computational fluids engineering
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• v.21 no.2
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• pp.54-61
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• 2016

When spent fuel assemblies from the reactor of nuclear power plants(NPPs) are transported, the assemblies are exposed to short-term operations that can affect the peak cladding temperature of spent fuel assemblies. Therefore, it needs to perform the analysis of heat transfer on spent fuel dry cask during the operation. For 3 dimensional computational fluid dynamnics(CFD) simulation, it is proposed that the short-term operation is divided into three processes: Wet, dry, and vacuum drying condition. The three processes have different heat transfer mode and medium. Metal transportation cask, which is Korea Radioactive Waste Agency(KORAD)'s developing cask, is evaluated by the methods proposed in this work. During working hours, the boiling at wet process does not occur in the cask and the peak cladding temperatures of all processes remain below $400^{\circ}C$. The maximum peak cladding temperature is $173.8^{\circ}C$ at vacuum drying process and the temperature rise of dry, and vacuum drying process occurs steeply.

• Wind and Structures
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• v.23 no.6
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• pp.505-521
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• 2016

The objective of this study is to investigate numerically the effect of building roof shaps on wind flow and pollutant dispersion in a street canyon with one row of trees of pore volume, $P_{vol}=96%$. A three-dimensional computational fluid dynamics (CFD) model is used to evaluate air flow and pollutant dispersion within an urban street canyon using Reynolds-averaged Navier-Stokes (RANS) equations and the Explicit Algebraic Reynolds Stress Models (EARSM) based on k-${\varepsilon}$ turbulence model to close the equation system. The numerical model is performed with ANSYS-CFX code. Vehicle emissions were simulated as double line sources along the street. The numerical model was validated by the wind tunnel experiment results. Having established this, the wind flow and pollutant dispersion in urban street canyons (with six roof shapes buildings) are simulated. The numerical simulation results agree reasonably with the wind tunnel data. The results obtained in this work, indicate that the flow in 3D domain is more complicated; this complexity is increased with the presence of trees and variability of the roof shapes. The results also indicated that the largest pollutant concentration level for two walls (leeward and windward wall) is observed with the upwind wedge-shaped roof. But the smallest pollutant concentration level is observed with the dome roof-shaped.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.286-286
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• 2011

최근 폴리머를 기판으로 하는 Flexible TFT (thin film transistor)나 3D-ULSI (three dimensional ultra large-scale integrated circuit)에서 높은 에너지 소비효율과, 빠른 반응 속도를 실현 시키기 위해 낮은 비저항(resistivity)을 가지며, 높은 홀 속도(carrier hall mobility)를 가지는 다결정 반도체 박막(poly-crystalline thin film)을 만들고자 하고 있다. 이를 실현 시키기 위해서는 높은 온도에서 장시간의 열처리가 필요하며, 이는 폴리머 기판의 문제점을 야기시킬 뿐 아니라 공정시간이 길다는 단점이 있었다. 이에 반도체 박막의 재결정화 온도를 낮춰주는 metal (Al, Ni, Co, Cu, Ag, Pd etc.,)을 이용하여 결정화 시키는 방법이 많이 연구 되어지고 있지만, 이 또한 재결정화가 이루어진 반도체 박막 안에 잔여 금속(residual metal)이 존재하게 되어 비저항을 높이고, 홀 속도를 감소시키는 단점이 있다. 이에 본 실험은 HiPIMS (High power impulse magnetron sputtering)와 PIII and D (plasma immersion ion implantation and deposition) 공정을 복합시킨 프로세스로 적은양의 금속이온주입을 통하여 재결정화 온도를 낮췄을 뿐 아니라, 잔여 하는 금속의 양도 매우 적은 다결정 반도체 박막을 만들 수 있었다. 분석 장비로는 박막의 결정화도를 측정하기 위해 GAXRD (glancing angle X-ray diffractometer)를 사용하였고, 잔여 하는 금속의 양과 화학적 결합 상태를 알아보기 위해 XPS를 통해 분석을 하였다. 마지막으로 홀 속도와 비저항을 측정하기 위해 Hall measurement와 Four-point prove를 사용하였다.