• 한국연소학회:학술대회논문집
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• 1999.10a
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• pp.55-61
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• 1999

A convolution algorithm combined with Fourier transformation is applied to the tomographic reconstruction of the asymmetric soot structure to identify the local soot volume fraction distribution. The line of sight integrated data from light extinction measurement with multi-angular scanning form basic information for the deconvolution. Multi-peak following interpolation technique is applied to obtain the effect of increasing number of scanning angles. Measurement of LII signal for the same flame shows the validity of this reconstruction technigue.

• Journal of the Korean Society of Combustion
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• v.8 no.3
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• pp.24-30
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• 2003

A convolution algorithm combined with Fourier transformation has been applied to the tomographic reconstruction of asymmetric soot structure to identify the local soot volume fraction distribution. Line-of-sight integrated data from light extinction measurement with multi-angular scanning formed basic information for the deconvolution. Multi-peak following interpolation technique was applied to obtain the effect of increasing number of scanning angles. Height-by-height reconstructed soot volume fraction distribution was compared with laser-induced incandescence signals.

• Journal of the Optical Society of Korea
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• v.1 no.1
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• pp.44-47
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• 1997

The integration of a GaAs/AlGaAs multi-quantum well electroabsorption modulator and a tapered waveguide vertical direction optical interconnect has been performed without the complicated regrowth process. Zn impurity-induced layer disordering of MQW layer is used to achieve the energy transfer between SQW and MQW regions. Light coupled into a SQW region was transferred to an MQW region and an intensity modulation of 10 dB extinction ratio was demonstrated.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.6
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• pp.647-661
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• 2003

For continuous monitoring of atmospheric visibility in the city of Kwanaju, Korea, a transmissometer system consisting of a transmitter and a receiver was installed at a distance of 1.91 km across the downtown Kwanaju. At the transmitter site an integrating nephelometer and an aethalometer were also installed to measure the scattering and absorption coefficients of the atmosphere, respectively. At the receiver site. an URG PM$_{2.5}$ cyclone sampler and an URG-VAPS (Versatile Air Pollutant Sampler) with three filter packs and two denuders were used to collect both PM$_{2.5}$ and PM$_{10}$ samples at a 2-hour or 12-hour sampling interval for aerosol chemical analysis. Sulfate, organic mass by carbon (OMC), nitrate, elemental carbon (EC) components of fine aerosol were the major contributors to visibility impairment. Diurnal variation of visibility during best-case days showed rapid improvement in the morning hours, while it was delayed until afternoon during the worst-case days. Aerosol mass concentration of each aerosol component for the worst-case was calculated to be 11.2 times larger than the best-case for (NH$_4$)$_2$SO$_4$(NHSO), 19.0 times for NH$_4$NO$_3$ (NHNO), 2.2 times for OMC, respectively. Also result shows that elemental carbon and fine soil (FS) were 3.7 and 2.2 times more than those of best-case. respectively- Sum of total contributions of wet NHSO and NHNO to light extinction was calculated to be 301 Mm$^{-1}$ for the worst-case. However, sum of contributions by dry NHSO and NHNO was calculated to be 123 Mm$^{-1}$ for the best case. Mass extinction efficiencies of fine and coarse particles were calculated to be 5.8$\pm$0.3 $m^2$/g and 1.8$\pm$0.1 $m^2$/g, respectively.ely.

• Fire Science and Engineering
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• v.29 no.4
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• pp.81-88
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• 2015

A low-cost device using the light-extinction method was developed to measure the optical smoke density in various fire experiments in the present study. The relative measurement accuracy of low-cost device was evaluated through the comparison of optical density measured by a high-cost standard device consisting of He-Ne laser, photo detector and various optical components. The low-cost device was composed of laser module, photocell and acrylic board. From the experiments using a smoke generator can be easily adjusted the smoke concentration, it was found that the low-cost device could measure the smoke density within the range of ${\pm}10%$, compared to the standard device. In addition, the reliability of low-cost device was also confirmed in the experiment using a polyethylene flame. Finally, it is expected that the low-cost device developed with real-time measurement and simple installation for measuring the smoke density will be used instead of the high-cost standard device.

• Fire Science and Engineering
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• v.33 no.5
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• pp.13-18
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• 2019

In this study, the soot formation characteristics of Jet-A1 liquid fuel droplet flames were investigated by measuring the soot concentration under atmospheric conditions similar to the working environment of the Korea Space Launch Vehicle (KSLV) To obtain the desired atmospheric conditions, the oxygen concentration in the combustion chamber was maintained at 30% and the pressure was varied between 0.1 and 0.06 MPa. The full-field light extinction technique was used to measure the concentration of soot particles generated by applying the identical to 2-mm-diameter Jet-A1 fuel droplets. The soot concentration of the Jet-A1 droplet flames was the highest in the nitrogen-substituted atmosphere and the lowest in the carbon dioxide-substituted atmosphere, despite the pressure. the pressure was decreased the measured soot concentrations reduced as a function of Pⁿ.

• 한국연소학회:학술대회논문집
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• 1997.06a
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• pp.1-11
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• 1997

The soot and OH radical distributions have been experimentally studied in ethylene and propane laminar diffusion flames. The integrated soot volume fraction was measured along the centerline of a flame using a laser light extinction method. Planar laser light scattering and PLIF techniques are employed for the soot and OH radical distribution measurements utilizing Nd:YAG laser and OPO, FDO system. The concentration of OH radical is rapidly decreased at the edge of sooting region, which implies the importance of OH radical species on the soot oxidation process. For ethylene flames, the addition of air in fuel moves the OH radical distribution towards the center line of a flame at the soot oxidation region, while the concentration of OH radical remains relatively high at the soot formation region. The interaction between soot particles and OH radicals becomes more active with fuel-air at the soot oxidation region. For propane flames, however, any indication of the increased interaction between soot particles and OH radicals with fuel-air was not noticed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.10
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• pp.1823-1825
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• 2007

Based on Faraday effect, the variation of current flowing through the conductor can be encoded as that of azimuth angle of light polarization propagating through the fiber coil wound onto the conductor. The amount of current can be obtained by measuring the variation of the light intensity transformed from that of the azimuth angle through a polarization analyzer. In this paper we propose a fiber-optic current sensor system that employs a fiber polarization analyzer as a sensor interrogation device. The fiber polarization analyzer was prepared by inscribing a long-period fiber grating on a high birefringent fiber. At the fixed wavelength of 1522.5 nm, the fabricated fiber device has the polarization extinction ratio of more than 25 dB. The measurement of large current up to 600 Arms was accomplished based on a simple fiber interrogation device and the measurement output of the sensor system showed a good linearity.

• Journal of Astronomy and Space Sciences
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• v.27 no.4
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• pp.279-288
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• 2010

To study properties of the pulsation in the infrared emission for long period variables, we have collected and analyzed the infrared observational data at M band for 12 OH/IR stars. We present the light curves using the data that cover about 30 years including recent observations of ISO and Spitzer. We use Marquardt-Levenberg algorithm to determine the pulsation periods and amplitudes and compare them with previous results of infrared and radio investigations. Generally, the newly determined pulsation parameters show much less errors because of the larger database. We find that the relationship between the pulsation period and amplitudes at M band is fairly well fitted with a simple linear equation in a wide period range. For OH 42.3-0.1, we find some evidences that the object could be a post-asymptotic giant branch star.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.62.3-63
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• 2018

Trends of Type Ia supernova (SN Ia) luminosities with the properties of host galaxies are important to study the underlying physics for an SN progenitor system and explosion mechanism. In the YONSEI SN catalog, we have a sample of ~600 SN and host data in the wider redshift range, and two independent light-curve models, SALT2 and MLCS2k2. From this catalog, here we present that SNe Ia in low-mass, globally and locally star-forming environments are fainter than those in high-mass, globally and locally passive environments, after light-curve shape and color or extinction corrections. Our results are then compared to previous studies, and show consistent results.