• Proceedings of the Korea Air Pollution Research Association Conference
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• 2001.11a
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• pp.303-304
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• 2001

주 구성요소가 산소와 질소 기체인 대기는 백색광을 지닌 광원, 즉 태양광에 대하여 선택적으로 빛을 산란시킴으로써 파란색을 나타낸다. 이것은 Rayleigh scattering 효과가 파장의 4승에 반비례하기 때문에 450nm 부근의 파란색은 700nm 부근의 빨간색에 비하여 약 6배이상 강한 빛을 산란시키기 때문이다. 그러나 실제로 하늘은 고정된 색을 지니고 있지는 않다. 태양과 관측자 및 관측지점의 유기적 관계에 의하여 하늘의 색은 주기적이며 임의적으로 다르게 보인다. (중략)

• Journal of Ocean Engineering and Technology
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• v.10 no.4
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• pp.128-140
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• 1996

To analyze a formation process of the soots in spray flame in the combustion chamber, an optically accessible DI Diesel engine was used for visualization. The images of the flames and soots were visualiaed with high speed camera by Schlieren method and Light extinction method. The spray flame and soot images on the films were analyzed at the various engine operating conditions. Soot distributed widely in spray flame and its concentration was about $100g/m^3$ at the position close by nozzle tip of spray flame region, however it decreased below $20g/m^3$ at the corner of combustion chamber due to soot oxidation.

• Fire Science and Engineering
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• v.24 no.6
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• pp.170-175
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• 2010

The effect of carbon dioxide addition on soot formation was investigated in jet diffusion flames in coflow. Flame temperature were measured with R-type thermocouple and the boundary temperature between blue and yellow flame was confirmed. Light-extinction method was introduced for the relative soot density (1-I/$I_0$) in the in-flame region. He-Ne laser with wave length at 632.8 nm was used for the light source, and the signal attenuated by absorption and scattering was detected directly. Oxidizer velocity effect on soot formation was studied to know that the thermal influence for soot formation. The results showed that the temperature of both blue and yellow flame were decreased according to the dilution of carbon dioxide but boundary temperature was nearly constant. The relative soot density was lower when carbon dioxide was added in oxidizer stream and oxidizer velocity increased. These were caused by the reduction of flame temperature and shorter residence time for soot growth. Also carbon dioxide addition enhanced the instability of jet flames like flickering, so the flame length was a little longer than pure ethylene/air flame.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.6
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• pp.1-5
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• 2000

Recently alternating-current Plasma Display Panel(AC-PDP) is in the spotlight as a digital television and high definition television. The panel structure widely adapted in commercial AC-PDP is three electrodes surface discharge type. At present time, the luminous efficiency is around 1lm/W, it should be a key factor for the commercialization. For the high luminous efficiency, the development of panel structure is necessary. At a given panel structure, a driving method should be optimized to get a sufficient luminous efficiency. The display image of AC-PDP could be realized by the repeated light emission from the discharge. Because most of discharge power is consumed in the sustaining period, the optimization of sustaining waveform is very important for the high luminous efficiency. ADS (Address and Display period Separated) driving method is commonly used. The average driving frequency of ADS driving method is ranged by several tens kilo of [kHz], however the actual frequency of sustaining period is in range of 100[kHz] to 200[kHz]. Based on this study, when the phosphor emits the visible light, it has a decay time of few milliseconds due to the material transfer to the phosphor to emit the visible light. Consequently the luminous efficiency decreases in proportion to the driving frequency. It is found that the luminous efficiency could be significantly improved by the low frequency sustaining driving method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.4
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• pp.468-480
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• 1998

The temporal and spatial distributions of soot volume fractions were measured for single toluene droplet flames as a function of pressure under the normal-gravity condition. In order to characterize the transient nature of the flame and sooting regions, a full-field light extinction and subsequent tomographic inversion technique was used. The reduction in sooting as a function of pressure was assessed by comparison of the maximum soot volume fractions at several vertical positions along the axis above the droplet. The maximum soot volume fraction was reduced by 70% when the pressure was reduced by 60% from 1 atm to 0.4 atm. The reduction in sooting is attributed to variation of the geometric configuration of flame which reduces the system Grashof number as well as only the change in the adiabatic flame temperature as the pressure decreases. The gravimetrically-measured total soot yield was also compared to the optically-measured soot volume fraction to obtain a correlation between the two measurements. As a result, the total soot yield was linearly proportional to the optically-measured maximum soot volume fraction and linearly reduced as the pressure decreased. Accordingly, the non-intrusive full-field light extinction-measurements were able to be calibrated not only to measure soot volume fraction, but to simultaneously evaluate the total soot yield emitted from the toluene droplet flame (which is useful in the practical application).

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.6
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• pp.630-639
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• 2001

This study proposes a new calculation method for generating real nighttime lamp-lit images. In order to improve the color appearance in the prediction of a nighttime lamp-lighted scene, the lamp-lit image is synthesized based on spectral distribution using the estimated local spectral distribution of the headlamps and the surface reflectance of every object. The Principal component analysis method is introduced to estimate the surface color of an object, and the local spectral distribution of the headlamps is calculated based on the illuminance data and spectral distribution of the illuminating headlamps. HID and halogen lamps are utilized to create beam patterns and captured road scenes are used as background images to simulate actual headlamp-lit images on a monitor. As a result, the reproduced images presented a color appearance that was very close to a real nighttime road image illuminated by single and multiple headlamps compared to the conventional graphic-based algorithm.

• Journal of Biomedical Engineering Research
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• v.16 no.4
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• pp.387-394
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• 1995

A simple method for determining the absorption coefficient of oxyhemoglobin and deoxyhemoglobin in human blood is proposed as an application of the complex propagation constant of a guided wave in a thin-film optical waveguide. A serial multichannel sample chamber is constructed on the waveguide to vary the interaction length between the evanescent field and the sample, and the dependence of the sensor response on the interaction length is investigated for the various concentration of two hemoglobins. The sensor response is linearly proportional to the interaction length and the concentration of two hemoglobins. The attenuation constant due to the evanescent field absorption between the samples is experimentally obtained with the designed sensor, and then the absorption coefficient is determined by the proposed method. The absorption coefficients determined by the proposed method fairly well coincided with those obtained by the conventional transmission measurement.