• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.10a
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• pp.113-113
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• 2009

휴대형 정보기기의 표시창으로 사용되는 투명한 고분자 소재의 표면을 보호하고 광특성을 유지하기 위해 산화물 다층 박막과 비정질 탄소 박막을 코팅하였다. 산화물 다층 박막은 소재 표면에서 빛의 반사율을 낮춰 투과율을 향상시키는 특성을 가지고 있다. 산화물 다층 박막으로 실리콘 산화물과 티타늄 산화막이 사용되었으며 전자빔 증착법을 이용하여 코팅되었다. 비정질 탄소 박막을 산화물 다층 박막의 최상층에 코팅하여 보호막으로 이용하였다. 고분자 윈도우에 산화물 다층 박막을 코팅하면 투과율이 향상되었으며 보호막으로 코팅된 비정질 탄소 박막에 의해서 일어나는 투과율 저하를 낮추는 효과를 보였다.

• 한국방재학회:학술대회논문집
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• 2009.02b
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• pp.88-88
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• 2009

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.484-485
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• 2011

반사방지(Anti-Reflection, AR) 특성은 태양전지, LED, 광검출기 등의 광전소자와 디스플레이의 효율과 투과도를 향상시키기 위해 적용되고 있다. 또한 최근에 네비게이션, 스마트폰의 보급 증가로 인해 소형 디스플레이에 지문방지와 동시에 반사방지 기능을 갖는 필름이 사용되고 있다. 현재 적용되고 있는 반사방지 필름은 다층박막 코팅으로 형성된 필름[1]으로 생산단가와 박막의 내구성 및 신뢰성에 문제점을 가지고 있다. 이런 문제점을 해결하기 위해 나노구조로 제작 되는 반사방지 필름에 관한 연구가 활발히 진행되고 있다[2]. 나노구조로 형성된 반사방지 구조는 moth-eye 구조라고 하며, 기본 원리는 원뿔 형태를 형성된 나노 구조를 통해 공기와 나노구조 사이의 유효 굴절률을 서서히 변화시켜 반사를 줄이는 것이다. 그러므로 moth-eye 나노구조는 파장 이하의 pitch와 파장 크기의 높이를 갖도록 구조가 제작되어야 한다[3]. Photo-lithography[4], e-beam lithography[5], interference lithography[6], dip-pen nanolithography[7], hybrid nano-patterning lithography[8] 등 여러 가지 방법으로 나노 구조를 제작하고 있으나, 네비게이션이나 스마트폰 등에 적용될 수 있는 대면적으로 제작하기 위해서는 roll-to-roll printing과 같은 대면적 공정을 이용하여 제작하는 것이 필요하다. 본 논문에서는 원통형 알루미늄 rod에 양극산화를 통해 다공성 AAO(anode aluminium oxide) template를 제작하고, roll-to-roll printing 기술을 사용하여 moth-eye 나노구조를 갖는 반사방지 필름을 제작하는 것에 대해 기술하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2010.04a
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• pp.231-233
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• 2010

최근 어항에도 친환경항만을 건설하기 위한 노력이 국제적으로 확산되고 있으며, 우리나라에서도 어항의 정비 및 재개발부분에서 적극적으로 수질개선을 위한 기술 적용이 본격화 되고 있다. 본 연구는 우리나라 남해의 소규모 어항 및 해수욕장에 슬릿형 해안 구조물이 시공된 실해역의 실측자료와 수치해석을 통해 현장적용성의 분석을 수행하였다. 수치실험으로는 파랑작용 평형방정식을 이용하는 SWAN 모델을 구성하고 수리모형실험에서 분석된 실린더 슬릿형 방파제의 반사와 투과계수를 모텔에 도입하였다. 수치실험은 한국해양연구원의 전해역 심해설계파 추정 보고서 II (2005)중의 심해설계파 제원을 사용하였으며, 대상해역의 1970년~2006년 (37년간) 관측된 연최대 풍속자료를 이용하여 모델에 반영하였다. 설리항에서 S, SSE, SE계열의 파랑의 내습에 대한 분석을 수행하였으며, 그 결과 구조물이 항내에서 정온도가 유지되며 해수순환에도 이점이 있음을 현장관측 자료분석과 수치실험결과를 통하여 확인할 수 있었다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.1
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• pp.38-44
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• 2007

Using the mathematical model suggested by Bennet et al.(1992), the reflection and transmission coefficients by a circular pile breakwater has been investigated in the framework of potential theory. Flow separation due to sudden contraction and expansion is generated and is the main cause of significant energy loss. Therefore, evaluation of exact energy loss coefficient is critical to enhance the reliability of mathematical model. To obtain the energy loss coefficient, 2-dimensional turbulent flow is analyzed using the FLUENT commercial code. The energy loss coefficient can be obtained from the pressure difference between upstream and downstream. Energy loss coefficient is the function of porosity and the relation equation between them is suggested throughout the curve fitting processing. To validated the suggested relation, comparison between the analytical results and the experimental results is made for four different porosities with good agreement.

• Journal of IKEEE
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• v.27 no.4
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• pp.512-517
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• 2023

In this study, we propose a liquid crystal-based polarization control technology that can control polarization by adjusting the voltage applied to the liquid crystal, and apply it to a Closed-circuit Television (CCTV) to transmit only the desired angle of polarized light. CCTV with conventional polarizing films cannot control polarization because they focus on backlight compensation, so light reflected from the water surface or highlights reflected from vehicles interfere with subject identification. However, the Vertical Alignment mode allows the polarization to be adjusted electrically, so that only the polarized light at the user's desired angle is transmitted, eliminating reflected highlights. The images obtained using this technique are optimized by computer software. Liquid crystal polarization panels, which can electrically control the polarization angle, transmittance, and polarization rate, have been applied to polarized image monitoring device to improve subject identification in conventional CCTV.

• Journal of Ocean Engineering and Technology
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• v.16 no.3
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• pp.1-7
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• 2002

In this paper, a numerical model to analyze the performance of a vertical slit-type wave absorber is developed under the assumption of inviscid water waves. The formulation combines the linear potential theory with a semi-empirical description of the eddy-shedding at a slit-type wave absorber. We investigated the reflection coefficients over a wide frequency range for a vertical slit-type wave absorber both with and without a solid rear wall. Model test was conducted at KRISO' s two dimensional wave tank to validate the theoretical results. It is found that the agreement between theoretical results and experimental data is surprisingly good. We found that the wave absorbing system using a vertical slit plate has sufficient potentials for breakwaters for ocean development.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.1
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• pp.1-9
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• 2018

In present study, we suggested the quasi-linear model that linearizes the quadratic drag representing the energy loss across the porous plate. The quasi-linear model was solved by Boundary Element Method (BEM) for development of the porous wave absorber suitable for 2-D wave tank. The drag coefficient at the porous plate was newly obtained through comparison of experimental results. It is found that the porous wave absorber with porosity 0.1, submergence depth d/h = 0.1, and inclined angle $10^{\circ}{\leq}{\theta}{\leq}20^{\circ}$ shows the effective wave absorption. Using the developed quasi-linear numerical model, the optimal design of various types of a porous wave absorber will be applied.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.5
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• pp.327-334
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• 2013

The interaction of oblique incident waves with a surface-mounted horizontal porous plate is investigated using matched eigenfunction expansion method under the assumption of linear potential theory. The new boundary condition on the porous plate suggested by Zhao et al.(2010) when it is situated at the still water surface is used. The imaginary part of the first propagating-mode eigenvalue in the fluid region under a horizontal porous plate, is closely related to the energy dissipation across the porous plate. By changing the porosity, plate width, wave frequencies, and incidence angles, the reflection and transmission coefficients as well as the wave loads on the porous plate are obtained. It is found that the transmission coefficients can be significantly reduced by selecting optimal porous parameter b = 5.0, also increasing the plate width and incidence angle.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.6
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• pp.52-60
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• 1999

Fabricability of phase shifted grating filters has been theoretically studied by an effective index transfer matrix method. In the optical band-pass filter with multiple ${\lambda}/4$ phase-shifts, the phase-shift error and random variation of the grating period should be suppressed such that corresponding resonance frequency lies within, the filter pass-band. The tolerance for the relative error is less than $10^3$, and is quite stringent in typical filters for WDM application. End facet reflection produces ripple in the transmission spectra and the reflectivity should be less than 1% in order to keep the ripple less than 0.25dB. Also, the effect of waveguide absorption loss is enhanced by the resonance in the filter, and the absorption should be limited to 1dB/cm for the signal loss of less than 0.2dB.