• 한국안전학회지
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• 제23권6호
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• pp.38-43
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• 2008

Significant portion of the fire accident is caused by some troubles in electric circuits. To prevent the fire induced by those electric trouble, some indications of electric fire need to be suitably detected at the first stage of the fire development. With this background, the characteristics of soot yielding of electric cables have been investigated using a light extinction method. In this study, a light scattering method was compared with the light extinction method. A slot-type premixed-flame combustor was traversed to bum three types of electric cables by compulsion, then the mass decrease rate and the soot densities were measured. According to the experimental results, the light scattering method is preferred to the light extinction method when the soot yield ratio is relatively small. Thus the former method is more suitable to detect the occurrence of an electric fire in a power distributer box.

• 한국안전학회지
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• 제22권6호
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• pp.13-19
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• 2007

Diesel car's smoke measurement equipment and method were investigated based on the exhaust gas regulations. Reflection photo method and light extinction method for measuring smoke were compared under conditions of both no load mode and Lug-down 3 mode. Free acceleration mode at no load condition was used for regular inspection of diesel car, and Lug-down 3 mode was used for fine inspection of the diesel car. A correlation between no load mode and Lug-down 3 mode was investigated in this research. The smoke measured with reflection photo method was 1.5${\sim}$2 times higher than that of light extinction method The correlation coefficient between reflection photo method and light extinction method for measuring smoke was 0.83, which shows comparatively high correlation between the two methods for measuring smoke in diesel engines.

• Journal of Korean Society for Atmospheric Environment
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• 제21권E2호
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• pp.49-56
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• 2005

A long-path transmissometer is one of the optical instruments widely used to measure atmospheric light extinction coefficient without enclosing a light beam and perturbing aerosols. Over the past two decades, a number of measurements have been carried out using the long-path transmissometer manufactured by OPTEC, Inc. Calibration of the transmissometer should be performed when any component of the transmissometer system is interchanged or installation condition is changed. For a better calibration of the transmissometer, application of a modified calibration method for the existing neutral density (ND)-filter method was recommended for the computation of the atmospheric transmittance using model MODTRAN 4 in this study. It was revealed that the measured light extinction coefficient from the transmissometer which was calibrated using the existing ND-filter method could be overestimated due to the assumption of the atmospheric transmittance suggested by OPTEC, Inc. The uncertainty of the measured light extinction coefficient from the transmissometer calibrated based on the modified ND-filter method was calculated to be approximately $13Mm^{-1}$.

• 한국안전학회지
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• 제25권6호
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• pp.9-13
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• 2010

An experimental study for characteristics of soot were conducted at the post-flame region in jet diffusion flames, where carbon dioxide was used as additives in oxidizer stream. Light-extinction method was performed using He-Ne laser with wave length at 632.8nm for the measurement of relative soot density and soot volume fraction with dimensionless extinction coefficient, $K_e$ and mass specific extinction coefficient, ${\sigma}_s$. To increase of resolution, laser light was modified for sheet-form using concave, convex lenses and slit. C/H ratio was introduced for quantitative analysis of soot growth which is expressed by carbonization and dehydrogen. Also transmission electron microscopy(TEM) was used for observation of morphological shape. The results show that the relative soot density in the post-flame region was lower when carbon dioxide was added in oxidizer stream because of reduction of flame temperature.

• 한국근적외분광분석학회:학술대회논문집
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• 한국근적외분광분석학회 2001년도 NIR-2001
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• pp.1128-1128
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• 2001

We have developed a probe for measuring the light levels inside illuminated fruit. The probe has minimal effect on the light levels being measured and enables the sampling of the light flux at any point within the fruit. We present experimental light extinction rates within apple, nashi, kiwifruit, and mandarin fruit. Moving from the illuminated side to the far side of the fruit, the extinction level follows an initial power law decay as the light diffuses into the fruit then reduces to an exponential decay through the rest of the fruit. Significant variations in the rates of light extinction are found in the core, skin and differing flesh regions. Monte Carlo simulations of the light distribution in fruit, which use scattering and absorption coefficients for the diffusely scattering tissue, and boundary conditions for the skin effects, produce results that follow the experimental results closely.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.708-714
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• 2001

Although LP gas has lots of advantages, there has been limitation in application for automotive engine due to the several disadvantages, such as power decrease, complex fuel supply unit, and back fire etc. However LP gas direct injection engine has possibility to solve the problems above mentioned. LEM(Light Extinction Method) was employed for analysis of spacial and temporal distribution of LP gas which is directly injected into combustion chamber under various pressure and temperature conditions. The results from CVC(Constant Volume Chamber) were compared to those of RICEM(Rapid Induction, Compression and Expansion Machine) which simulate early- and late injection of direct injection engine. LPG fuel spray is affected by temperature and pressure in evaporation characteristics but it is more benefit to direct injection engine in every way such as, fuel distribution, evaporating speed and well wetting reduction.

• Journal of Mechanical Science and Technology
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• 제17권12호
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• pp.1986-1993
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• 2003

The spatially resolved spray volume fractions from both line-of-sight data of direct measuring cells and a laser diffraction particle analyzer (LDPA) are tomographically reconstructed by the Convolution Fourier transformation, respectively. Asymmetric sprays generated from a twin-hole injector are tested with 12 equiangular projections of measurements. For each projection angle, a line-of-sight integrated injection rate was measured using a direct sampling method and also a liquid volume fraction from a set of line-of-sight Fraunhofer diffraction measurements was measured using a light extinction method. Interpolated data between the projection angles effectively increase the number of projections, significantly enhancing the signal-to-noise level in the reconstructed data. The reconstructed volume fractions from the direct sampling cells were used as reference data for evaluating the accuracy of the volume fractions from the LDPA.

• 한국안전학회지
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• 제27권3호
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• pp.1-8
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• 2012

Characteristics of smoke emission in light duty diesel vehicles was investigated according to the year of production, engine displacement volume, and mileage. The smoke emission was measured using light extinction smoke measurement method under free acceleration test mode. Total number of the tested vehicles was 180. The year of production of the tested vehicles distributed from 2002 to 2007. The displacement volumes of the tested vehicles were categorized as 2-liter, 2.5-liter, 2.7-liter, and 3-liter. The mileage of the tested vehicles distributed from 20,000 km to 400,000 km. The more recent in the year of production of the tested vehicles did not show clearly lower in smoke emissions. Smoke emission showed different values according to driver's pedal pushing pattern. Also, smoke emission peak for each free acceleration test initially increased and reach a maximum of the peak values. Afterwards, the smoke peak gradually decreased as number of test increased. A new guide line was proposed to determine the smoke value from the light duty diesel vehicles based on smoke emission peak patterns which were obtained with several repeated free acceleration tests.

• 한국화재소방학회논문지
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• 제27권2호
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• pp.75-79
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• 2013

본 연구는 구획화재의 출입구를 통한 연기밀도를 정량적으로 측정하고 측정기법의 신뢰성을 평가하기 위해 불확실성 해석을 수행한다. 메탄 화재 강도에 따른 축소모형 구획공간의 출입구 상층부를 통해 유출되는 연기 유동에 대해 광소멸 측정을 수행하고 Bouguer's의 법칙을 적용하여 연기밀도를 산정하였다. 광투과율, 경로길이, 질량비광소멸상수에 대하여 연기밀도의 측정 불확실도를 평가하였으며 계산된 연기밀도 측정의 확장불확실도는 20% 정도이며 신뢰수준은 95% 이다. 준정상상태의 화재 발열량에 대하여 출입구에서의 평균 연기밀도를 산정하였으며 구획공간내부의 총괄당량비 증가에 따라 출입구의 연기농도가 선형적으로 증가하는 경향을 보였다.

• ETRI Journal
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• 제27권1호
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• pp.95-101
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• 2005

Waveguide structures of the stand-alone electroabsorption (EA) modulator and the electroabsorption modulated laser (EML) are investigated using the 3D beam propagation method. The EA waveguide structures with InP-based passivation layers show saturation in the extinction ratio (ER) due to the stray light traveling through the passivation layers. This paper demonstrates that narrower passivation layers suppress stray-light excitation in the EA waveguide, increasing the ER. A taper structure in the isolation section of the EML waveguide can reduce the mode mismatch and suppress the excitation of the stray light, increasing the ER further. Low-index-polymer passivation layers can confine the mode more tightly in the active waveguide, yielding an even higher ER.