• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2012.10a
• /
• pp.401-403
• /
• 2012

본 연구는 현재 LED 조명기기에 사용되는 확산판의 두께와 투과율에 따른 광효율 및 색온도, 연색성의 변화를 분석하고자 한다. 이렇게 분석된 확산판에 대한 광특성 변화는 LED 조명기기의 확산판 선정과 설계에 대한 기초 자료로 활용 될 수 있을 것이다.

• Polymer(Korea)
• /
• v.36 no.6
• /
• pp.761-767
• /
• 2012

The polycarbonate (PC)-based optical diffusers for direct-lit LED backlight unit were prepared by using extrusion compounding followed by compression molding process. The application of inorganic porous silica particles as a diffusing agent in addition to conventional poly(methyl methacrylate) (PMMA) beads was attempted, and the optical, thermal, and mechanical properties of the prepared diffusers were investigated. The morphological observations revealed that the diffusing agents could be uniformly dispersed in the PC matrix without agglomeration by high shear stress generated during extrusion process. The incorporation of the porous silica particles mixed with PMMA beads remarkably enhanced the luminance uniformity with respect to both location and view angle for the diffuser, while minimizing the reduction in the absolute luminance, as compared with the diffuser containing only PMMA beads. In addition, thermal and mechanical properties of the diffusers were shown to be improved upon addition of the porous silica particles.

• Journal of Korean Society of Environmental Engineers
• /
• v.33 no.5
• /
• pp.359-367
• /
• 2011

The Process of Pressurized water diffusion is mixing process by pressurized water injection with coagulate and chlorine water in the water treatment system. The objectives of this research were to evaluate the mixing length and diameter of diffusion plate and distance from injection pipe for complete mixing by using computational fluid dynamics. From the results of CFD simulation, when diameter of injection pipe is 50 mm, 100 mm and injection pressure is $5kg/cm^2$ and the diameter of inlet pipe is 2,200 mm, the complete mixing length is 4D (D: Length as diameter of inlet pipe). When diameter of injection pipe is 50 mm, the diameter of the diffusion plate in o.1D and distance from injection pipe is 0.2D, the complete mixing length is 3D that is the most short mixing length. But when diameter of injection pipe is 100 mm and mutually related the diameter, distance of diffusion plate, the complete mixing length is 4D over. Therefore, as the diameter of inlet pipe is 2,200 mm, the injection pipe 50 mm is more efficient than 100 mm.

• Composites Research
• /
• v.34 no.6
• /
• pp.406-411
• /
• 2021

PEM (proton exchange membrane) fuel cells generate only water as a by-product, and thus are in the spotlight as an eco-friendly energy source. Among the various components composing the stack of the fuel cell, research on the bipolar plate that determines the efficiency of the fuel cell is being actively conducted. The composite bipolar plate has high strength, rigidity and corrosion resistance, but has the disadvantage of having a relatively low electrical conductivity. In this study, to overcome these shortcomings, a gas diffusion layer (GDL)-composite bipolar plate assembly was developed and its performance was experimentally verified. The graphite foil coating method developed in the previous study was applied to reduce the contact resistance between the bipolar plate and the GDL. In addition, in order to improve electron path in the stack and minimize the contact resistance between the GDL and the bipolar plate, a GDL-bipolar plate assembly was fabricated using a thin metal foil. As a result of the experiment, it was confirmed that the developed GDL-bipolar plate assembly had 98% lower electrical resistance compared to the conventional composite bipolar plate.

• The Optical Journal
• /
• s.134
• /
• pp.26-31
• /
• 2011

레이저 프로젝터에서 스크린을 조사할 경우 원리적으로 광 손실이 크기 때문에 발생한 스펙클은 시간적으로 독립적인 다수의 스펙클 패턴을 화상에 중첩해서 그 평균 조작에 의해서만 본격적으로 저감할 수 있다. 평균조작에 대한 매우 높은 시간적 다중도를 실현하는 수단으로서 스크린 투영광로 중에 삽입한 확산판을 정현함수적으로 진동시키는 진동확산판 방식이 유망하다. 이 원고는 Kubota Shigeo 교수(도쿄대학 생산기술연구소 1부)가 월간 Optronics(통권 349호)에 기고한 내용으로, 필자는 향후 이러한 전자 액추에이터가 Miniature화 되고, 스펙클 저감 디바이스로서 보급되기를 바란다고 밝혔다.

• Korean Journal of Optics and Photonics
• /
• v.32 no.5
• /
• pp.220-229
• /
• 2021

The optical characteristics of high-power direct-lit white light-emitting diode (LED) lighting were investigated, where a quantum dot (QD) film was adopted to enhance the color-rendering index (CRI). The transmittance of the diffuser plate and the concentration of the QD film were varied in this study. The color coordinates and the correlated color temperature (CCT) did not show any appreciable change, while the CRI values increased slightly as the transmittance of the diffuser plate decreased. The investigated optical properties were nearly independent of the viewing angle, and the luminance distribution was close to Lambertian. The CCT decreased from approximately 6000 K to approximately 4000 K as the concentration of the QD film increased from 0 to 7.5 wt%, which was due to the enhanced red component in the emission spectrum. The CRI increased to approximately 95 for some optical configurations of the lighting. These results demonstrate that glare-free, color-changeable, high-rendering LED lighting can be realized by using a combination of a diffuser plate of appropriate transmittance and a red QD film.

• Proceedings of the Optical Society of Korea Conference
• /
• 2008.02a
• /
• pp.265-266
• /
• 2008

본 논문은 기존 도광판에 복합화된 마이크로 패턴을 이용하여 휴대폰용 LCD Backlight Unit의 설계 및 해석에 대한 연구이다. 현재 상용 시제품의 도광판 패턴에 복합된 마이크로 패턴을 이용하여 광학시트를 줄이는 것을 목표로 진행 하였다. 도광판의 윗면에 프리즘형상을 설계 하였고, 아랫면은 기존의 패턴에 마이크로 패턴을 형성하였다. 마이크로 패턴의 형상은 구면, 프리즘, 실린더로 각 형상에 대해 변수를 바꾸어 가며 최적의 설계 값을 찾아보았다. 설계된 복합패턴으로 기존 Backlight Unit의 구성품인 반사판, 도광판, 확산판, BEF를 반사판과 도광판 만으로도 대체 할 수 있음을 시뮬레이션을 통해 확인하였다.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.4A
• /
• pp.329-335
• /
• 2009

The purpose of this study is to provide the efficient method and guideline of controlling the cracking in bridge deck concrete due to differential drying shrinkage. Drying shrinkage cracking is mainly influenced by the moisture diffusion coefficient that determines moisture diffusion rate inside concrete structures. In addition to the diffusion coefficient, surface coefficient of concrete surface and relative humidity of ambient air simultaneously affect the moisture evaporation from concrete inside to external air outside. Within the framework of cracking shrinkage cracking mechanism, it is necessary to conceive the numerical analysis, which involves these three influencing factors to predict and control the shrinkage cracking of concrete. In this study, moisture diffusion and stress analysis corresponding to drying shrinkage on bridge deck are performed with consideration of diffusion coefficient, surface coefficient, and relative humidity of ambient air. From the numerical results, it is found that cracking behavior due to differential drying shrinkage of bridge deck concrete shows different feature according to three influencing factors and the methodology of controlling of drying shrinkage cracks can be suggested from this study.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.11 no.2
• /
• pp.85-92
• /
• 2007

In 1980s, a number of bridges with bare concrete deck were constructed on the Korea highway. After 20 years service, many bare concrete decks are still in good condition without special maintenance activity. Therefore, the application of the bare concrete deck is being reestimated from the view of construction and maintenance. As a part of the program, the characteristic of penetration(surface chloride and apparent diffusion coefficient) of de-icing salt into bare concrete bridge deck was analyzed in order to predict the service life of bridge on Korea highway.

• Fire Protection Technology
• /
• s.51
• /
• pp.31-38
• /
• 2011