• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.56.1-56.1
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• 2013

We have carried out follow-up observations of transiting extrasolar planets using small- to medium-sized reflectors located in Korea. Using the 0.60m telescope stationed at CbNUO (Chungbuk National University Observatory) we have achieved a photometric precision of 1.48 milli-magnitudes (root-mean-square scatter of data) of a HAT-P-09b (transit duration of 3.43 hrs) transit light curve (transit depth ~ 1.3%) with V=12.3 mag for the host star. We expect a photometric precision of 1.0 - 1.2 milli-magnitude for brighter targets (V ~ 10 - 11 mag). The transit technique and its application will be outlined. The results of test observations will be presented and the defocus technique will be discussed.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.64.4-65
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• 2016

Observations of the early photons from evolution of optical afterglows or internal shock provides the crucial clues on the nature of the bursts and environments. Hundreds of GRBs afterglow observations in multi-wavelength region have been made mainly thanks to the fast (~ 60 seconds after the trigger) localisation GRB by Swift and its fast alert to the ground telescope. It helps to improve our understandings tremendously, however many enigmas still remain, such as burst mechanism, transition prompt emission to the afterglow, early optical flash, rise phase of the early optical light curve and some missing afterglows. They could be addressed by fast slewing and multi colour and IR follow-up by future telescopes. The primary aim of UFFO/Lomonosov is to follow up optical fast ever, within a couple of seconds after trigger by onboard X-ray telescope. Its optical FOV is $30{\times}30degrees$. As a key instrument, the Slewing Mirror to redirect the optical beam from GRBs rapidly to the Ritchey-Chretien telescope. The status and launch schedule of the UFFO/Lomonosov and its test performance will be reported and prospects for the next missions will be discussed.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.429-432
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• 2015

We present a kinematic study of the parsec-scale radio jet in OJ 287, one of the most studied BL Lac objects, during ${\gamma}$-ray flares, to explore the relation between parsec-scale radio jet activity and ${\gamma}$-ray emission. The 22-GHz light curve of OJ 287 show three obvious flare events around 2011 May, 2011 October, and 2012 March. The second radio flare occurred during the ${\gamma}$-ray flaring period, and the third radio flare seemed to precede the ${\gamma}$-ray flare by one month. One jet component moved outward with respect to the core component with an apparent superluminal speed (~ 11c) from 2010 November to 2011 November. Then it changed direction, moving apparently inward in 2011 November, when the ${\gamma}$-ray flare occurred. The observed apparent inward motion of the jet at 22 GHz could be caused by a new jet component, unresolved at 22 GHz, in the innermost region.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.141.2-141.2
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• 2012

We present photometric solutions of the 26,212 eclipsing binaries discovered in the LMC by Graczyk et al. (2011). They published that 70 percent of a total are detached systems. Another 25 and 5 percent are semi-detached and contact binaries, respectively. We discovered that 21 percent of 26,121 eclipsing binary stars are eccentric orbit systems. The binary star distribution in the LMC is different from those of the Galactic center direction (Bade window). It is very interesting that there are only 5 of 357 (2 percent) stars have eccentric orbit in the Galactic Center (Kang 2011). We selected the light curve of 18,274 detached systems. Then we estimated the fundamental parameters on the basis of their photometric solutions and the semi-major-axis (a) assuming the distance modulus to the LMC~18.50. We compared the estimated fundamental parameters with an empirical mass-luminosity relation and consistency between mass-radius relation base on stellar evolution model in the low metallicity (Z=0.008) by Bertelli et al. (2009). This method allows for independent determine of the fundamental parameters of the eclipsing binaries in the LMC without the radial velocity curves.

• Korean Journal of Materials Research
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• v.24 no.1
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• pp.33-36
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• 2014

This study was aimed at synthesizing and characterizing cerium-doped titania. Cerium-doped anatase titania powders were prepared by sol-gel process, with ammonium (IV) nitrate and titanium (IV) butoxide as the raw materials. The characteristics of pure $TiO_2$ and cerium-doped $TiO_2$ were investigated by XRD, TG/DTA, FE-SEM, and UV-vis spectroscopy. The results of this study show that anatase type of $TiO_2$ was obtained in as-prepared and calcined $TiO_2$ and Ce-$TiO_2$ powder. A DTA curve was also observed as the crystallization temperature decreased with increasing cerium contents. We found that the crystallite size of the obtained anatase particles decreased from 55 nm to 25 nm and the particle size decreased with increasing cerium contents. Moreover, UV-vis spectra showed that anatase titania powders with various cerium contents effectively extend the light absorption properties to the visible region.

• The Korean Journal of Ecology
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• v.8 no.4
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• pp.201-204
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• 1985

The author reared the bandwinged grasshoppers, Oedaleus infernalis infernalis in the growth cabinet controlled as temperature of 25。C and 30。C under the conditiion of photoperiod 16L:8D, light intensity 510$\pm$240lux, relative humidity 65$\pm$3%. The results are summarized as follows: The female has six instars and male five instars. The larva reared in the temperature of 25。C died at the second larva stage, and the development to the third instar was impossible. The developmental periods of the egg stage of both sexes in the 30。C are 24.06 days. In the larval development periods, the fourth statge (19.73 days) was longer than that of any stage, and the second stage has the shortest period (9.9 days) in female. In male, the developmental period (9.59 days). The total developmental periods of female and male from the egg to the fifth instar were approximately 95.02 and 95.04 days, respectively. The total developmental period of female was as long as the period (15.75 days) of sixth instar which is not in the male. The survivorship curve in the temperature of 30。C shows concave type.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.9
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• pp.863-867
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• 2008

In this paper, to increase the light current efficiency of photodiode, we fabricated aluminum-doped zinc oxide(AZO) thin films by RF magnetron sputtering. AZO thin films were deposited at low temperature of 100 $^{\circ}C$ and different RF powers of 50, 100, 150 and 200 W due to selective process technology. Then the AZO thin films were annealed at 400 $^{\circ}C$ for 1 hr in vacuum ambient to increase crystalline. The lowest resistivity of 1.35 ${\times}$ $10^{-3}$ ${\Omega}cm$ and a high transmittance over 90 % were obtained under the conditions of 3 mTorr, 100 'c and 150 W. The optimized AZO thin films were deposited as anti-reflection coating on PN junction of silicon photodiode. It was confirmed by the result of $V_r-I_{ph}$ curve that the efficiency of photodiode with AZO thin film was enhanced 17 % more than commercial photodiode.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.7
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• pp.650-657
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• 2007

This paper had mentioned about CCP light source application for increasing the efficiency of Xe lamp the mercury-free lamp. In order to increase the efficiency of Xe EEFL, we designed and manufactured the lamp used by mixture gas of Xe, Ne and He. Also, we have analyzed the electrical and optical properties with the firing voltage, sustain voltage, paschen's curve, wall charge, and capacitance. As a result, the firing voltage decreased by increasing the ration of mixture gas. and, It is owing to include the gas with high ionization energy. The firing voltage decreased in condition happening the penning effect, Because the ion of metastable state created from penning effect, Which can encourage the ionization phenomena. Also, the wavelength of 467.12 is increase. because of the energy transition in the wavelength of 147 nm. therefore, we can know about the affection of phosphor with UV emission properties. Through an experiment, Xe 100 % and Xe 75 % confirmed same spectrum properties by each mixture gas ratio. In the case of Xe 50 %, spectrum properties appeared Xe discharge and Ne-He discharge. That analyzed an electrical and optical properties. Therefore, confirmed that is excellent because properties of firing voltage, wall charge, capacitance in Xe 50 %, Ne : He = 9 : 1. We offered parameter in inverter manufacture and lamp manufacture by electrical and optical properties.

• Journal of Preventive Medicine and Public Health
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• v.45 no.4
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• pp.259-266
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• 2012

Objectives: This study aims to determine the risk factors predicting rehospitalization by comparing three models and selecting the most successful model. Methods: In order to predict the risk of rehospitalization within 28 days after discharge, 11 951 inpatients were recruited into this study between January and December 2009. Predictive models were constructed with three methods, logistic regression analysis, a decision tree, and a neural network, and the models were compared and evaluated in light of their misclassification rate, root asymptotic standard error, lift chart, and receiver operating characteristic curve. Results: The decision tree was selected as the final model. The risk of rehospitalization was higher when the length of stay (LOS) was less than 2 days, route of admission was through the out-patient department (OPD), medical department was in internal medicine, 10th revision of the International Classification of Diseases code was neoplasm, LOS was relatively shorter, and the frequency of OPD visit was greater. Conclusions: When a patient is to be discharged within 2 days, the appropriateness of discharge should be considered, with special concern of undiscovered complications and co-morbidities. In particular, if the patient is admitted through the OPD, any suspected disease should be appropriately examined and prompt outcomes of tests should be secured. Moreover, for patients of internal medicine practitioners, co-morbidity and complications caused by chronic illness should be given greater attention.

• Analytical Science and Technology
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• v.35 no.5
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• pp.218-227
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• 2022

A simple and fast throughput flow injection (FI) system with a merging-zone technique was designed to determine ferrous and ferric in an aqueous solution. The method is based on the direct reaction of ferrous with a Bathophenanthroline reagent (Bphen) in acidic media. The forming red complex absorbs light at 533 nm. All conditions of the flow injection system were investigated. The analytical curve of ferrous was linear in the range of 0.07 to 4 mg/L with an r² value of 0.9968. The detection and quantification limits were 0.02 and 0.04 mg/L, respectively. The molar absorptivity and Sandell's sensitivity were 4.0577 × 10⁶ L/mol cm and 25 × 10^-5 ㎍/cm², respectively. The homemade valve was low-cost with high repeatability (n = 7) at an RSD of 1.26 % and zero dead volume. The values of the dispersion coefficient were 2.318, 2.022, and 1.636 for the concentrations of 0.2, 1, and 3 mg/L, respectively. The analysis throughput of the designed flow injection unit was 57 sample per hour.