• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.410-410
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• 2012

투명 전도성 TCO (Transparent Conductivity Oxide)박막 중 ITO (Indium Tin Oxide) 박막은 n-type의 전도특성을 갖는 산화물로서 가시광선 영역에서의 높은 투과율, 전기 전도도, 넓은 밴드갭을 나타내기 때문에 디스플레이 및 태양전지 분야에 널리 사용 되어 지고 있다. 이 실험에서는 ITO 증착시 산소 유량의 변화에 따라 특성의 변화를 관찰하고자 실험을 진행 하였다. 실험에서 산소 유량은 0 sccm에서 12 sccm까지 변화를 주었으며, ITO는 RF 마그네트론 스퍼터를 이용하여 유리위에 증착하였다. 실험에서 인가된 RF power는 2 kW, 13.56 MHz, 공정 압력은 $4.5{\times}10^{-6}torr$에서 진행하였다. 유리와 타겟 사이의 거리는 200 mm로 고정하였으며, 온도는 상온에서 공정을 진행하였다. 증착된 ITO의 전기전도도(${\sigma}$)는 3 sccm까지는 증가하는 경향을 보이다가 그 이후부터는 감소하는 것을 확인 할 수 있었다. 투과율과 이차전자방출계수의 결과 또한 전기전도도와 유사한 경향성을 보여 주었다. 이를 통해 3 sccm의 산소 유량으로 증착된 ITO의 전기적 특성이 가장 좋은 것으로 확인이 되었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.187-187
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• 2011

최근 디스플레이 산업과 태양전지 등의 이차 전지 산업이 발달함에 따라 원가절감과 공정단계의 단순화를 위하여 다이렉트 패터닝 인쇄에 대한 연구가 관심을 받고 있으며, 나노전자부품 제작이 요구되는 전기/전자 소자들은 수백 nm에서부터 수십 ${\mu}$m 수준까지 다양한 해상도의 패턴으로 구성되므로 미세패턴이 가능한 정전수력학 잉크젯프린팅 방식은 기존의 인쇄 방식과 달리, 정전기력을 이용하여 인쇄를 하는 방식으로, 수KV의 고전압을 인가하여 잉크를 대전시키고, 대전된 잉크는 대부의 전기적 반발력에 의해 액적이나 액실로 분열하게 된다. 전하를 띤 액적 또는 액실은 정전기력을 받아 기판 쪽으로 이동을 하게 되는데, 이때 액적의 전하량에 의해 액적의 이동속도와 이동경로가 영향을 받게 된다. 본 연구에서는 잉크의 전기전도도에 따른 액적의 전하량을 계산하여 전기전도도와 액적의 전하량과의 관계를 ANASYS 시뮬레이션과 운동경로 분석을 통해 확인하였다. 전기전도도가 0.307s/m~5.6s/m인 잉크에 따른 액적의 전하량을 계산하였으며, 전기전도도가 변화에 따라. 전하량이 $0.5{\times}10^{-13}C{\sim}2.5{\times}10^{-13}C$ 으로 변화하는 것을 확인하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.8
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• pp.611-620
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• 2020

The effect of discharge voltage on electron mean energy, electric potential, ionization rate, neutral and ion density of Hall thruster was analyzed using a two-dimensional axisymmetric hybrid model. The results of the code developed for this study such as discharge current, thrust, and plasma distribution according to discharge voltage of SPT-100ML Hall thruster were compared by experiments and calculations of other researchers for validation. The results show that the electron mean energy, the ionization rate, and the ion density are increased while the neutral density is decreased as the discharge voltage is increased. The thrust and the discharge current are proportional to the discharge voltage.

• Ceramist
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• v.22 no.4
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• pp.357-367
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• 2019

Secondary Ion Mass Spectrometry(SIMS) is an analytical method that measures the distribution and concentration of elements or compounds by analyzing the mass of secondary ions released by irradiating ion beams with energy of hundreds eV to 20 keV on the sample surface. Unlike other similar analytical instruments, SIMS directly detect the elemental ions that constitute a sample, allowing you to accurately identify components and obtain concentration information in the depth direction. It is also a great feature for measuring isotopes and analyzing light elements, especially hydrogen. In particular, with the development of materials science, there is an increasing demand for trace concentration analysis and isotope measurements in the micro-regions of various materials. SIMS has a short history compared to other similar methods; nevertheless, SIMS is still advancing in hardware and is expected to contribute to the development of materials science through research and development of advanced analytical techniques.

• Polymer(Korea)
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• v.26 no.4
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• pp.452-461
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• 2002

In this study, the effect of various concentrations of antioxidants on thermo-oxidative degradation of polyamide 6 was investigated. Unstabilized and stabilized polyamides 6 were subjected to long-term oven aging in ambient atmosphere at 70~$160^{\circ}C$. All of specimens were discolored within 100 hr at temperature range of 70~$160^{\circ}C$. Optimum antioxidant concentration was determined from the data of mechanical properties, yellowness index and relative viscosity. The synergistic effect of each primary and secondary antioxidant concentrations was not observed. Yellowing phenomenon was explained by using NMR, IR and EA. Different carbonyl groups were detected by $^{13}C$/NMR. During thermooxidative degradation, oxygen consumptions were determined by EA. The lifetime after long-term aging was predicted using Arrhenius equation.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.451-451
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• 2011

적외선 소자의 재료로 쓰이는 액상 에피 성장법(Liquid phase epitaxy: LPE)으로 성장된 HgCdTe (MCT)박막의 Hg 분위기 열처리에 따른 구조적 변화를 고 분해능 투과 전자 현미경으로 관찰하였다. 일반적으로 LPE방법으로 성장된 MCT박막은 성장 방법의 특성상 Te 과다 영역의 성장용액이 사용되므로 상온 냉각 과정에서 박막 내 국부적인 Te 석출물을 형성 시킬 가능성이 높다. 또한, 성장 과정시 높은 Hg 증기압으로 인해 Hg-vacancy가 존재하므로 품질을 저하시키는 요인이 된다. 따라서, 본 실험에서는 Hg-vacancy와 국부적인 Te 석출물의 제거를 위해 Hg 분위기 열처리 공정을 실시하여 박막의 결정성 변화 및 국부적인 조성 변화를 관찰하였다. 실험결과, 열처리에 따른 Hg의 박막 내 공급으로 인한 이차상의 형성 등이 관찰 되었으며 부피 팽창으로 인해 격자의 변형이 관찰 되었다. 이는 투과 전자 현미경의 고 분해능 이미지 와 Gaussian mask filtering 기법으로 보여진 격자 줄무늬상 (lattice fringe)으로 확인 하였다. 또한, 열처리에 따른 국부적인 조성 편기의 해소는 high angle annular dark field scanning TEM(HAADF-STEM)을 이용하여 관찰 하였다.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.1
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• pp.101-112
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• 2007

This study has used RMA2 model and RMA4 model, which are depth-averaged two-dimensional flow and water-quality prediction models, to analyze the variation of the water-quality by the gates operation in the Seonakdong River. Sensitivity analysis is performed to get the Manning coefficient and the coefficient of eddy viscosity for RMA2 model, and to get the diffusion coefficient for RMA4 model. Since the numerical simulation using RMA2 and RMA4 models did not consider tributary pollutant load except for that of Joman River, it could make a little difference from the natural phenomenon. Nevertheless, the numerical simulation shows that the discharge of $30m^3/s$, which is the continuous inflow from the Daedong-gate, can make it possible to achieve the target water-quality (BOD 4.3mg/L) of Nakbon-N watershed about 10 days later if the Daejeo-gate could remain opened in connection with the Noksan-gate operation.

• Microbiology and Biotechnology Letters
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• v.42 no.4
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• pp.331-338
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• 2014

Myxococcus stipitatus KYC4013 extract exhibited the most potent antifungal activity among the extracts of 207 Myxococcus strains isolated in Korea. High-resolution LC-MS analysis revealed that M. stipitatus KYC4013 produces five antifungal substances and three other secondary metabolites that were predicted to be melithiazol and phenalamide derivatives, respectively. The putative melithiazol derivatives were best produced in CYS medium and the putative phenalamide derivatives were best produced in VY3 medium.

• Journal of the Korean Chemical Society
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• v.34 no.6
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• pp.534-538
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• 1990

Chromium(Ⅵ) compound, [$C_9H_7$NH]$_2Cr_2O_7$ has been prepared by the reaction of isoquinoline with chromium trioxide under the presence of water. [$C_9H_7$NH]$_2Cr_2O_7$ is nonhydroscopic and dissolved in water very well. Structure of [$C_9H_7$NH]$_2Cr_2O_7$ is identified by FTIR spectra and elemental analysis data. The ability of [$C_9H_7$NH]$_2Cr_2O_7$ for the oxidation of alcohols were examined in methylene chloride. [$C_9H_7$NH]$_2Cr_2O_7$ was found as efficient oxidizing agent for the conversion of allyl, primary and secondary alcohols to the corresponding aldehydes or ketones.

• Journal of Digital Convergence
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• v.9 no.4
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• pp.69-76
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• 2011

With a concentration on online university student behavior in highly-wired countries of Canada, the US, and South Korea, this study is aimed at identifying and comparing students' perception to the Internet use, willingness to use, and performance from its use. The cross-national comparison unveiled that students in each country did not have a compatible pattern of relationship among perception, intention, and performance. This study also examines the impact of levels of Internet use motivations on users' attitude, intentions to use, and performance. The results of the study help understand the factors affecting the Internet use in three countries and identify the differences in willingness to use and performance from cultural heterogeneity. Implications of the study, limitations, and further research directions are also discussed.