• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.103-103
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• 2009

플라스틱 기판위에 스퍼터링과 열 기상증착법을 이용하여 코팅된 주석 박막을 관찰하여 주석 박막의 형상 변화에 영향을 미치는 공정 요인을 알아보았다. 열 기상증착법에 의해 코팅된 주석 박막은 주석 소스의 양에 따라 쉽게 형상을 제어할 수 있었다. 하지만 박막과 기판의 부착력이 낮아 쉽게 박리가 일어났다. 스퍼터링으로 콘팅된 주석 박막은 기판과 부착력은 높았으나 코팅 시 인가된 전원의 세기, 코팅 시간, 코팅 시 진공도등 다양한 공정인자 조절에도 불구하고 형상에 큰 변화는 관찰하지 못하였다. 전원의 세기가 증가하면 주석의 섬 크기가 증가하고 코팅 시간이 늘어나면 전원의 세기가 증가한 것과 유사한 형상 변화가 있어다. 주석 박막 코팅 시 공정 압력은 낮추면 주석 섬의 크기가 감소하였는데 이는 스퍼터된 주석 이온의 평균 자유 행로가 길어져 비교적 작은 핵형성에 의해서 나타난 현상으로 판단된다.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1442-1446
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• 2004

The heat (mass) transfer characteristics on the blade surface of a first-stage turbine rotor cascade has been investigated by employing the naphthalene sublimation technique. A four-axis profile measurement system is employed for the measurements of the local heat (mass) transfer coefficient on the curved blade surface. The experiments are carried out for two free-stream turbulence intensities of 1.2% and 14.7%. The high free-stream turbulence results in more uniform distributions of heat load on the both pressure and suction surfaces and in an early boundary-layer separation on the suction surface. The heat (mass) transfer enhancement on the suction surface due to the endwall vortices is found to be relatively small under the high free-stream turbulence.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.199-199
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• 2012

Display에 사용되는 투명전극의 경우, 가시광 영역에서의 투과도는 중요한 요소 중의 하나이다. 투명 전도막의 광흡수, 반사 및 투과즉성은 박막 내에 존재하는 전공밴드의 전자, 자유전자, polar optical phonon 등의 빛과의 반응에 의해 결정된다고 알려져 있다. 많은 연구결과를 통해 투과 및 반사특성은 알려져 있으나, 가시광 영역내의 흡광특성에 관해서는 밝혀진 연구결과가 많지 않다. 본 연구에서는 ITO 박막의 투과도와 흡광도의 상호관계를 규명하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.10
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• pp.841-847
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• 2021

In this paper, the applicability of the low-density surface film copper mesh for aircraft applications have been analyzed. Recently, low-density surface film copper mesh is developed to reduce weight and cost compared with traditional surface film copper mesh. In order to apply low-density surface film copper mesh to aircraft, it is needed to analyze its electromagnetic effects as well as structural integrity with sandwich panels to prevent pinholes. The structural integrity and electromagnetic characteristics have been analyzed for 2 samples of low-density surface film copper mesh and 1 sample of surface film copper mesh. To review the applicability of the low-density surface film, it is combined with sandwich composite panel to confirm pinhole effects. The low-density surface film has been modeled as a periodic structure and analyzed with 3D electromagnetic simulation tool. The simulation results has been verified through measured electromagnetic transmission results using free space measurements. From the results, it will be possible to use these results for the analysis and the applicability of low-density surface film copper mesh for aircraft.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.1
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• pp.79-83
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• 2015

This paper presents a numerical study on the alignment of ridge-like surface structures evolving on silicon-germanium thin films under localized modulation of surface diffusivity. A situation is considered in which the surface diffusion of film material is selectively promoted such that its morphology is perturbed to periodic patterns. To simulate the growth behavior, a governing equation is formulated taking the surface chemical potential into account, and its solution is numerically sought using a finite-difference method. Results show that an initially planar surface coalesces upon the diffusivity modulation, and the surface structures can be aligned by changing the frequency of modulation condition. This research suggests a bottom-up fabrication technique that can manage the regularity of surface structures for thin film devices.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2001.11a
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• pp.21-21
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• 2001

자원재활용과 원가절감를 위해 고지재활용율이 크게 상승하고 있으며, 이와 아울러 고 지원료로부터 고품질의 제품을 생산할 수 있는 기술에 대한 관심이 증대되고 있는 실 정이다. 저급 고지로부터 고품질의 탈묵펄프를 얻기 위해서는 고지재활용공정의 핵심 공정인 부유부상 공정의 효율화가 가장 중요하다고 믿어진다. 이를 위해서는 부유부상 공정에 가장 큰 영향을 미치는 고형입자의 표면 화학적 특성에 따른 공정의 분리효율 평가와 이에 근거한 공정해석과 개선이 요청된다. 이러한 부유부상 공정을 표면화학적 측면에서 구명하기 위해 마이크로 크리스탈린 셀룰로오스(Microcrystalline cellulose: M MCC)를 모댈 물질로 사용하여 표면화학적 특성은 다르나 입자의 크기와 형태는 동일 한 시료를 준비하였다. 친수성의 표면 특성을 나타내는 MCC의 표면 특성을 바꾸기 위 하여 AKD(alkyl ketene dimer)로 처리비율을 달리하여 솔벤트 사이징 처리를 실시하 였다. 이렇게 준비된 MCC의 표면화학적 특성을 IGC를 이용하여 평가하였다 .. IGC는 G GC를 응용한 표면분석 기술로 고체의 물리화학적 특성과 흡착성을 분석하기 위해서 사용되며 이로부터 흡착제의 표면특성을 평가할 수 있다. 본 실험에서는 AKD로 소수화 정도가 다르도록 소수화시킨 MCC 시료를 이용하여 I IGC 칼럼을 준비하고 n-알칸과 몇가지 극성 용매률 이용하여 이들의 칼럼 내 체류시 간을 측정함으로써 흡착특성을 평가하고 이로부터 흡착현상을 열역학적으로 분석하였다. IGC 분석 시에는 칼럼의 온도를 $30^{\circ}C$, $35^{\circ}C$, $40^{\circ}C$의 3수준으로 변화시켰다. 측정결 과로부터 MCC 표면의 흡착자유에너지와 엔탈피, 엔트로피의 변화량을 평가하였으며, 또한 MCC 표면의 극성에너지와 산염기적 성질을 평가하였다. 실험결과 MCC의 소수화도에 따른 열역학적 흡착현상의 차이가 명백하였다. 이는 소 수화 수준에 따라 소수성 및 친수성 물질의 흡착성이 변화된다는 것을 보여준다. 따라서 탈묵 시 진행되는 기포에의 부착현상을 평가할 수 있는 기초자료로 활용될 수 있다 고 사료되었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.3
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• pp.1-9
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• 2005

The interaction between hypersonic free stream and side jet flow at high altitudes is investigated by using the direct simulation Monte Carlo (DSMC) method. In order to alleviate the difficulty associated with the large density difference between the free stream and the side jet flow and to simulate the two flows simultaneously, a weighting factor technique is applied. For validation, the corner flow over a pair of plates perpendicularly attached is calculated with and without a side jet, and the results are compared with experiment. For a more realistic configuration, the flow past a blunted cone cylinder shape is solved. The leeward or windward jet is injected into the free stream and the effect on the aerodynamic force and moment is observed at various flow angles. The lambda shock effect and the wake structure are studied in terms of the surface pressure differential. A higher interaction between the free stream and the side jet flow is observed when the side jet is injected in the windward direction.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.2
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• pp.167-172
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• 2011

In physical engineering, the turbulent flow on the surface roughness is very important. With the welding, design and paint, the hull surface roughness at each stage in the various aspects are important factors to be considered. In this study, the hull surface roughness geometry that was generalized to the PIV was applied to the tank test. The roughness of the surface changed the distance of the interval. Experimental velocity is Re = $1.1{\times}10^4$, Re = $2.0{\times}10^4$ and Re = $2.9{\times}10^4$. The turbulent intensity at the time-average were examined The roughness coefficient occurred with increasing turbulence intensities was stronger. The turbulence intensity away from the roughness in the shape was zero. The variation of turbulence intensity at the experimental flow conditions change was not affected.

• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.598-603
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• 2023

Electrochemical ammonia production using catalysts offers a promising alternative to the conventional Haber-Bosch process, allowing for ambient temperature and pressure conditions, environmentally friendly operations, and high-purity ammonia production. In this study, we focus on the nitrogen reduction reactions occurring on the surfaces of ruthenium catalysts, employing first-principles calculations. By modeling reaction pathways for nitrogen reduction on the (0001) and (1000) surfaces of ruthenium, we optimized the reaction structures and predicted favorable pathways for each step. We found that the adsorption configuration of N₂ on each surface significantly influenced subsequent reaction activities. On the (0001) surface of ruthenium, the end-on configuration, where nitrogen molecules adsorb perpendicularly to the surface, exhibited the most favorable N₂ adsorption energy. Similarly, on the (1000) surface, the end-on configuration showed the most stable adsorption energy values. Subsequently, through optimized hydrogen adsorption in both distal and alternating configurations, we theoretically elucidated the complete reaction pathways required for the final desorption of NH₃.

• Polymer(Korea)
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• v.27 no.2
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• pp.91-97
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• 2003

The effect of fluorination of nanoscaled silicas on mechanical interfacial properties and thermal stabilities of the silica/polyurethane composites was investigated. The surface properties of the silica were studied in X-ray photoelectron spectroscopy and contact angle measurements. Their mechanical interfacial properties and thermal stabilities of the composites were characterized by tearing energy and decomposition activation energy, respectively. As experimental results, the London dispersive component of surface free energy and fluorine functional groups of silica surfaces were increased as a function of fluorination temperature resulting in improving the trearing energy ($G_{IIIC}$) of the composites. Also, the thermal stabilities of the composites were increased as the treatment temperature increases. These results could be explained that the fluorine functional groups on silica surfaces played an important role in improving the intermolecular interactions at interfaces between silicas and polyurethane matrix in a composite system.