• Journal of the Korean Physical Society
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• 제73권11호
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• pp.1663-1674
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• 2018

We propose the Poynting vector analysis of the air mode in a top-emitting organic light-emitting diode (OLED) by combining the transfer matrix method and dipole source term. The spatial profiles of the time-averaged optical power flow of the air mode are calculated inside and outside the multilayer structure of the OLED with respect to the thickness of the semi-transparent top cathode and capping layer (CPL). We elucidate how the micro-cavity effect controlled by the thickness variation of the semi-transparent top cathode or CPL affects the internal optical power and absorption loss inside the OLED multilayer and the external optical power coupled into the air. When the calculated absorption loss and external power obtained by the proposed Poynting vector and currently-used point dipole models are compared, two calculation results are identical, which demonstrates the validity of the two models.

• 전기학회논문지
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• 제61권2호
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• pp.270-275
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• 2012

This paper presents a portable and compact optical device which can conveniently be used to perform a functional analysis of human liver function. The proposed system employed red/green LEDs, as a light source, and CMOS image sensor, which is commonly used in cellular phones. With this system, several blood serum samples have been evaluated for liver functional analysis by measuring light absorption level through the blood serum samples depending on aspartate aminotransferase (AST), alanine aminotransferase (ALT), and total bilirubin concentration. The light absorption through the blood serum samples containing AST, ALT, or total bilirubin can provide their concentrations. The green light absorption is more sensitive to the concentration of AST or ALT, and the red light absorption is more sensitive to the total bilirubuin concentration. Additional calibration steps were performed by using a MATLAB program in order to eliminate the light scattering effects from the extraneous particles existing in each blood serum sample. From the blind test, three standard light intensity curves through each enzyme have been obtained and the enzyme concentration values have been compared to those obtained from a commercially available biochemistry analyzer (Toshiba 200 FR). The average percent difference in the obtained concentrations from two systems for AST, ALT, and total bilirubin concentration came out to be 7.79%, 7.98%. and 7.56%, respectively, with the adjusted coefficient of determination (R2) higher than 0.98. This system can possibly lead to a low-cost and simple system that can be used as a point-of-care (POC) system in a condition without advanced equipments.

• 대한화학회지
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• 제61권4호
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• pp.168-178
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• 2017

$La/TiO_2$ - graphene composites were synthesized in this study, and applied to the photocatalytic degradation of Rhodamine B (RhB) under UV-visible light irradiation. X-ray diffraction (XRD), surface analysis, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), and Transmission electron microscopy (TEM) analysis demonstrated that $La/TiO_2$ nanoparticles were well distributed on the surface of graphene, and formed the heterostructure of $La/TiO_2$-graphene. Compared to the pure $TiO_2$, $La/TiO_2$-graphene composites displayed much higher photocatalytic activities in RhB degradation under UV-visible light irradiation. The photocatalytic data of $La/TiO_2$-graphene composites exhibit extended light absorption in the visible light region, and possess better charge separation capability than that of pure $TiO_2$. The high photocatalytic activity was attributed to the composite's high adsorptivity, extended light absorption, and increased charge separation efficiency, due to the excellent electrical properties of graphene, and the large surface contact between graphene and $La/TiO_2$ nanoparticles.

• 한국입자에어로졸학회지
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• 제17권4호
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• pp.91-106
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• 2021

Daily PM_2.5 was collected during summer period in 2020 in Gwangju to investigate its chemical and light absorption properties. In addition, real-time light absorption coefficients were observed using a dual-spot 7-wavelength aethalometer. During the study period, SO₄^2- was the most important contributor to PM_2.5, accounting for on average 33% (10-64%) of PM_2.5. The chemical form of SO₄^2- was appeared to be combination of 70% (NH₄)₂SO₄ and 30% NH₄HSO₄. Concentration-weighted trajectory (CWT) analysis indicated that SO₄^2- particles were dominated by local pollution, rather than regional transport from China. A combination of aethalometer-based and water-extracted brown carbon (BrC) absorption indicated that light absorption of BrC due to aerosol particles was 1.6 times higher than that due to water-soluble BrC, but the opposite result was found in absorption Ångström exponent (AAE) values. Lower AAE value by aerosol BrC particles was due to the light absorption of aerosol BrC by both water-soluble and insoluble organic aerosols. The BrC light absorption was also influenced by both primary sources (e.g., traffic and biomass burning emissions) and secondary organic aerosol formation. Finally the ATR-FTIR analysis confirmed the presence of NH₄⁺, C-H groups, SO₄^2-, and HSO₄^2-. The presence of HSO₄^2- supports the result of the estimated composition ratio of inorganic sulfate ((NH₄)₂SO₄) and bisulfate (NH₄HSO₄).

• 한국농공학회:학술대회논문집
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• 한국농공학회 2000년도 학술발표회 발표논문집
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• pp.340-345
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• 2000

This study was carried out to analyze the light and thermal environment in model greenhouse using infrared absorption film as shading screen and to compare with the case of no shading and using general shading screen such as aluminum foil-backed film, black polyethylene film and thermal blanket. PPFD(photosynthetic photon flux density) of inside the model greenhouse under infrared absorption film was increased by 22% than under general shading screen on the average. And temperature of inside air under infrared absorption film was 2$^{\circ}C$ lower than under general shading screen on the average. So, it is expected that infrared absorption film is useful as shading screen.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.51-55
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• 2007

In this paper Statistical Energy Analysis has been considered to predict high frequency air borne interior noise. Dash panel Insulation is major part to reduce engine excitation noise. Transmission loss and absorption coefficient are considered to predict dash insulation performance. Transmission lose is derived from coupling loss factor and absorption coefficient is derived from internal damping loss factor. Material Biot properties were used to calculate each loss factors. Insulation geometry thickness distribution was hard to measure, so FeGate software was used to calculate thickness map from CAD drawing. Each predicted transmission losses between conventional insulation and light weight insulation were compared with SEA. Transmission loss measurement was performed to validate each prediction result, and it showed good correlation between prediction and measurement. Finally interior noise prediction was performed and result showed light weight insulation system can reduce 40% weight to keep similar performance with conventional insulation system, even though light weigh insulation system has lower sound transmission loss and higher absorption coefficient than conventional system.

• 한국해양환경ㆍ에너지학회지
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• 제15권4호
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• pp.323-329
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• 2012

본 연구에서는 분리된 기름-물 혼합물에 대해 단일 파장대역의 LED 광원으로 부터 흡수된 빛이 전자결합소자(CCD)에 투영된 영상을 분석하는 방법을 통해, 물 위에 기름의 존재 유 무와 상태를 파악할 수 있는 광학적 기름 탐지 방법에 대한 연구 결과를 제시한다. 물위에 기름의 존재 유 무와 기름의 두께 정보를 얻기 위해서, 혼합물을 통과하면서 감소되는 빛의 강도를 전자결합소자로 획득한 영상을 통해 빛의 세기를 분석하는 방법을 이용하였으며, 최고의 선택도를 가진 광원의 파장대역을 찾기 위해서 발광다이오드(LED)의 파장대역별로 선택도를 비교하는 실험을 진행하였다. 본 연구에서 사용된 발광다이오드 중 465 nm의 파장대역을 갖는 발광다이오드가 물과 기름의 존재유무 및 기름의 두께에 따라 감소되는 차이가 가장 크다는 결과를 얻을 수 있었다. 또한 실제 해상조건에서의 탐지 가능성을 확인하기 위해 밝기 조건과 수표면의 기울기 조건을 변화하는 실험을 수행하여 제안된 탐지 방법의 적용가능성을 확인하였다. 해당 연구를 통해서 해상에 유출된 기름을 물과 기름이 갖는 특정파장대역의 빛에 대한 흡수도의 차이로 탐지할 수 있는 새로운 광학적 분석 방법론을 제안한다.

• 한국해양환경ㆍ에너지학회지
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• 제16권4호
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• pp.263-267
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• 2013

본 연구에서는 단일 파장의 빛이 기름과 해수로 구성된 혼합물을 투과하는 과정에서 굴절과 산란으로 인해 감쇠되는 빛의 세기를 평가하는 방법을 통해, 물위에 존재하는 기름의 두께를 측정할 수 있는 새로운 광학적 기름 탐지 방법론을 제시한다. 단일 파장의 광원으로 직진성이 좋고 단색광의 빛을 발산할 수 있는 레이저를 이용하였으며, 기름-물 혼합물을 투과한 빛의 세기를 정량적으로 측정하기 위해서 광 에너지를 전기 에너지로 변환할 수 있는 광전자소자인 포토다이오드를 선택하였다. 기름의 두께가 증가함에 따라서 투과된 빛의 크기가 점차적으로 감쇠되는 성질을 가진 광원의 파장 대역을 실험적으로 도출하기 위해서, 3개의 서로 다른 파장대역을 갖는 레이저를 이용하여 기름의 두께별로 투과된 광량을 측정하여 감쇠되는 경향을 비교하는 실험을 진행하였다. 해당 실험을 통해서 470 nm 파장을 갖는 청색 레이저를 이용하였을 경우, 기름의 두께가 증가함에 따라 투과된 광량의 세기가 점차적으로 감쇠되는 현상을 확인할 수 있었다. 본 연구에서 수행한 실험 결과를 통해서 레이저 광원에 대한 기름의 흡광 광도를 분석하는 방법으로 해수위에 존재하는 기름의 두께를 정량적으로 측정할 수 있는 가능성을 제시하였다.

• Journal of the Optical Society of Korea
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• 제17권1호
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• pp.22-26
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• 2013

The author analyzes the luminous efficiency of the phosphor-conversion white light-emitting diode (LED) that consists of a blue LED chip and a yellow phosphor. A theoretical model is derived to find the relation between luminous efficiency (LE) of a white LED, wall-plug efficiency (WPE) of a blue LED chip, and the phosphor absorption ratio of blue light. The presented model enables to obtain the theoretical limit of LE and the lower bound of WPE. When the efficiency model is applied to the measured results of a phosphor-conversion white LED, the limit theoretical value of LE is obtained to be 261 lm/W. In addition, for LE of 88 lm/W at 350 mA, the lower bound of WPE in the blue LED chip is found to be ~34%. The phosphor absorption ratio of blue light was found to have an important role in optimizing the luminous efficiency and colorimetric properties of phosphor-conversion white LEDs.

• 한국환경과학회지
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• 제14권10호
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• pp.973-978
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• 2005

Biodegradable oil gelling agent was prepared, and their oil absorption capacities using light oil, lubricant oil and corn oil were investigated. The result showed that the oil absorption capacity was depended on the amount of surfactant and starch added, and was increased in the order of light oil, lubricant oil and corn oil. Also, the oil-absorption capacity was saturated within 30 min at $18^{\circ}C$. The biodegradability of the prepared biodegradable oil gelling agent was also studied by determination of reduced sugar produced after enzymatic hydrolysis. Their surface morphologies and thermal properties of the prepared biodegradable oil gelling agent were observed by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA), respectively.