• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.49.5-50
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• 2021

We report the optical follow-up observations of three long γ-ray burst events, GRB 201020A, GRB 201103B and GRB 210104A by the network of telescopes in the SomangNet project. We show light curves, color evolution and SED evolution, and fit them to a single power law function to derive decay index and compare their properties with other long GRBs samples. Also, we show a good observational example that 0.4-1m class telescopes in SomangNet have potential to catch dim light from high red shift object (R>22 mag) by deep imaging. In conclusion, we found that three GRBs have optical afterglow properties of long GRB and our results are consistent with the reports of high energy analysis.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.73.3-73.3
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• 2019

The AGN unification model suggested the presence of obscuring material, a dusty torus, to explain the various types of AGN. IR SED model fitting is a crucial tool to probe the structure and properties of the dusty torus. We use a sample of 16 local quasi-stellar objects in Martinez-Paredes et al. (2017) with obtained NIR and MIR high-angular resolution (~0.3") imaging data from EMIR, CIRCE and CanariCam on the 10.4-m Gran Telescopio CANARIAS (GTC) while 4 objects have NIR high-angular resolution photometry from NICMOS/HST from the literature. The unresolved NIR emission from the NIR image analysis and low-resolution Spitzer/IRS spectra are used to construct NIR-MIR SEDs covering a larger spectral range. We investigate the sensitivity of the geometrical (e.g. viewing angle) and physical parameters (e.g. optical depth) of the clumpy dusty torus model of Nenkova et al. and the clumpy disk+outflow model of Hoenig et al. We aim to investigate the minimal dataset needed to well constrain the parameters of the models and derive the properties of the dusty torus. These results will allow us to plan future observations for a larger sample of high luminosity AGNs with the James Webb Space Telescope and the Giant Magellan Telescope.

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.311-316
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• 2012

Lyman break Galaxies are galaxies selected in the rest-frame ultraviolet. But, one important and missing information for these Lyman break galaxies is the amount of dust attenuation. This is crucial to estimate the total star formation rate of this class of objects and, ultimately, the cosmic star formation density. AKARI, Spitzer and Herschel are therefore the major facilities that could provide us with this information. As part of the Herschel Multi-tiered Extragalactic Survey, we have began investigating the rest-frame far-infrared properties of a sample of more than 4,800 Lyman Break Galaxies in the GOODS-North fiels. Most LBGs are not detected individually, but we do detect a sub-sample of 12 objects at 0.7 < z <1.6 and one object at z = 2.0. The ones detected by Herschel SPIRE have redder observed NUV-U and U-R colors than the others, while the undetected ones have colors consistent with average LBGs at z > 2.5. We have analysed their UV-to-FIR spectral energy distributions using the code cigale to estimate their physical parameters. We find that LBGs detected by SPIRE are high mass, luminous infrared galaxies. They also appear to be located in a triangle-shaped region in the $A_{FUV}$ vs. $logL_{FUV}$ diagram limited by $A_{FUV}$ = 0 at the bottom and by a diagonal following the temporal evolution of the most massive galaxies from the bottom-right to the top-left of the diagram. In a second step, we move to the larger COSMOS field where we have been able to detect 80 Lyman break galaxies (out of ~ 15,600) in the far infrared. They form the largest sample of Lyman break galaxies at z > 2.5 detected in the far-infrared. We tentatively name them Submillimeter Lyman break galaxies (S-LBGs).

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.347-352
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• 2012

Understanding infrared (IR) luminosity is fundamental to understanding the cosmic star formation history and AGN evolution, since their most intense stages are often obscured by dust. Japanese infrared satellite, AKARI, provided unique data sets to probe this both at low and high redshifts. The AKARI performed an all sky survey in 6 IR bands (9, 18, 65, 90, 140, and $160{\mu}m$) with 3-10 times better sensitivity than IRAS, covering the crucial far-IR wavelengths across the peak of the dust emission. Combined with a better spatial resolution, AKARI can measure the total infrared luminosity ($L_{TIR}$) of individual galaxies much more precisely, and thus, the total infrared luminosity density of the local Universe. In the AKARI NEP deep field, we construct restframe $8{\mu}m$, $12{\mu}m$, and total infrared (TIR) luminosity functions (LFs) at 0.15 < z < 2.2 using 4,128 infrared sources. A continuous filter coverage in the mid-IR wavelength (2.4, 3.2, 4.1, 7, 9, 11, 15, 18, and $24{\mu}m$) by the AKARI satellite allows us to estimate restframe $8{\mu}m$ and $12{\mu}m$ luminosities without using a large extrapolation based on a SED fit, which was the largest uncertainty in previous work. By combining these two results, we reveal dust-hidden cosmic star formation history and AGN evolution from z = 0 to z = 2.2, all probed by the AKARI satellite.

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.213-216
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• 2012

We have collected dozens of mid-infrared spectra showing UIR bands from diffuse Galactic emitting regions with the AKARI's Infrared Camera (IRC) onboard AKARI, as part of the ISMGN Mission Program. The datasets cover various directions in the inner Galactic Plane ($|l|$ < 70 deg), in the outer Galactic Plane ($|l|$ > 70 deg), and in the off-Plane ($|b|$ > 2 deg). The variations in the UIR band ratios are examined in terms of the radiation environments judged from the far-infrared ($50-170{\mu}m$) spectral energy distribution (SED) made with AKARI/FIS All Sky Survey data at each slit position where mid-IR spectra were obtained. We have found that the band ratios of $6.2{\mu}m/11.2{\mu}m$ and $7.7{\mu}m/11.2{\mu}m$ toward the inner Galaxy are systematically higher than those toward the outer Galaxy and off the Galactic plane. Likely causes of the variations in properties of UIR bands in diffuse emission on a Galactic scale are discussed in this paper.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.201-201
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• 2010

The evaporative desalination system with solar energy would be the efficient and attractive method to get fresh water. This study was described the development of Multi Effect Distillation(MED) with solar energy desalination system. The system was designed and manufactured Multi effect distillation on the capacity of $3m^3$/day. The experimental apparatus consists mainly of ejector pump, Hot water pump, flow meter, demister, cooler, evaporator and condenser. Evaporator and condenser were made Shell&Tube Heat Exchanger type with corrugated tube. The experimental variables were chosen $75^{\circ}C$ for hot water inlet temperature, 40, 60 and $80{\ell}$/min for hot water inlet volume flow rate, 6.0 and $8.0{\ell}$/min for evaporator feed seawater flow rate, $18^{\circ}C$ for sea water inlet temperature to cover the average sea water temperature and the salinity of sea water is measured about 33,000 PPM (parts per million). for a year in Korea. This study was analyzed the results of thermal performance of Multi Effect Distillation. The results are as follows, The experimental Multi effect distillation is required about 40 kW heat source for production of $3m^3$/day fresh water. Various operating flow rate was confirm in the experiments to get the optimum design data and the results showed that the optimum total flow was $8.0{\ell}$/min. Comparison of Single Effect Distillation with Multi Effect Distillation showed MED is at least more than double of SED.

• Fashion & Textile Research Journal
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• v.20 no.5
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• pp.600-607
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• 2018

Polypropylene fibers, while having many advantages such as light weight, sweat fast drying, water-repellent, drainage, thermal insulation, anti-static property has a drawback in dyeing. In recent years, the development of dyeable polypropylene fibers has expanded its value in the textile market. The purpose of this study is to fabricate composite spun yarns using polypropylene, acrylic, rayon and wool and to analyze tensile properties, uniformity characteristics, bending properties, hairiness, and surface shape according to the degree of fineness and blended ratio. The specimens consisted of 100% polypropylene spun yarn pp30, pp40 and ppa(pp/acrylic), ppr(pp/rayon), ppw(pp/wool), 5 altogether sed in this study. The results of the study are as follows. The breaking strength of polypropylene spun yarn blended with rayon and acrylic was higher than that of 100% polypropylene spun yarn. The polypropylene spun yarn is higher the fineness been shown to decrease the breaking strength and elongation. The bending properties of polypropylene spun yarns were in the order of ppa>ppr>pp40>pp30>ppw. The unevenness of ppw, ppr, and ppa was higher than pp40 and pp30. With the exception of ppw with crimp properties, pp30 and pp40 were found to have a hairiness index greater than ppr, ppa. In the microscopic photographs of polypropylene spun yarn, pp30, which had the highest hairiness index, was found to have a thick yarn and a large number of hairs, and ppw had hairs of 3 mm or more protruding elongated outwardly.

• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.281-285
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• 2017

We present a summary of our spectroscopic redshift catalogue of 404 sources in the AKARI Deep Field South (ADF-S). We have used the AAOmega spectrograph to target mid-infrared and far-infrared sources selected primarily from AKARI observations in this field for which we were able to obtain optical counterparts. Our sources with identified redshifts include 316 with $H{\alpha}$ detections at $z{\leq}0.345$ and 15 sources at z > 1 with MgII or $Ly{\alpha}$ emission lines. About 13% of our $z{\leq}0.345$ sources are dominated by active galactic nuclei (AGN) emission, although many show emission from both star formation and AGNs. The median Balmer decrement is 5.9. Ultra-luminous infrared galaxies (ULIRGs) were found only in the higher-redshift sources. Optical and near infrared data will be available shortly, enabling calibration of the line luminosities and spectral energy distribution (SED) fitting for these sources.

• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.245-249
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• 2017

We selected 47 DOGs at z ~ 1.5 using optical R (or r'), AKARI $18{\mu}m$, and $24{\mu}m$ color in the AKARI North Ecliptic Pole (NEP) Deep survey field. Using the colors among 3, 4, 7, and 9µm, we classified them into 3 groups; bump DOGs (23 sources), power-law DOGs (16 sources), and unknown DOGs (8 sources). We built spectral energy distributions (SEDs) with optical to far-infrared photometric data and investigated their properties using SED fitting method. We found that AGN activity such as a AGN contribution to the infrared luminosity and a Chandra detection rate for bump and power-law DOGs are significantly different, while stellar component properties like a stellar mass and a star-formation rate are similar to each other. A specific star-formation rate range of power-law DOGs is slightly higher than that of bump DOGs with wide overlap. Herschel/PACS detection rates are almost the same between bump and power-law DOGs. On the other hand SPIRE detection rates show large differences between bump and power-law DOGs. These results might be explained by differences in dust temperatures. Both groups of DOGs host hot and/or warm dust (~ 50 Kelvin), and many bump DOGs contain cooler dust (${\leq}30$ Kelvin).

• Journal of Environmental Health Sciences
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• v.39 no.5
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• pp.465-473
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• 2013

Objectives: This study was undertaken to analyze Staphylococcus aureus from cultivation environments for agricultural products and to confirm antibiotic resistance and enterotoxin genes for the isolated S. aureus. Methods: A total of 648 samples were collected from apple, peach, ginseng and balloon flower farms. S. aureus was isolated from soil, agricultural water, personal hygiene elements (hands, gloves and clothes) and work utensils (boxes). Results: S. aureus was detected in a total of 25 samples and 72 strains were isolated. The resistance rate of the isolated S. aureus strains was confirmed at 33.3%, with 24 resistant strains among the total of 72. Fourteen different patterns types were found, and three pattern types (NV, OX, VA) were confirmed most frequently. As result of the detection of enterotoxin gene type, four gene types (sea: 1, sed: 4, seg: all isolated S. aureus, sei: all isolated S. aureus) were analyzed among a total of nine types. Conclusions: This study demonstrates that personal hygiene techniques should be properly managed, such as washing and sterilization before or after work, because agricultural contamination by S. aureus frequently developed through improper management.