• Journal of The Korean Astronomical Society
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• v.36 no.3
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• pp.81-87
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• 2003

It is suggested that a flying-by star in a hot accretion disk may cool the hot accretion disk by the Comptonization of the stellar emission. Such a stellar cooling can be observed in the radio frequency regime since synchrotron luminosity depends strongly on the electron temperature of the accretion flow. If a bright star orbiting around the supermassive black hole cools the hot disk, one should expect a quasi-periodic modulation in radio, or even possible an anti-correlation of luminosities in radio and X-rays. Recently, the unprecedentedly accurate infrared imaging of the Sagittarius A$\ast$ for about ten years enables us to resolve stars around it and thus determine orbital parameters of the currently closest star S2. We explore the possibility of using such kind of observation to distinguish two quite different physical models for the central engine of the Sagittarius A$\ast$, that is, a hot accretion disk model and a jet model. We have attempted to estimate the observables using the observed parameters of the star S2. The relative difference in the electron temperature is a few parts of a thousand at the epoch when the star S2 is near at the pericenter. The relative radio luminosity difference with and without the stellar cooling is also small of order $10^{-4}$, particularly even when the star S2 is near at the pericenter. On the basis of our findings we tentatively conclude that even the currently closest pass of the star S2 is insufficiently close enough to meaningfully constrain the nature of the Sagittarius A$\ast$ and distinguish two competing models. This implies that even though Bower et al. (2002)have found no periodic radio flux variations in their data set from 1981 to 1998, which is naturally expected from the presence of a hot disk, a hot disk model cannot be conclusively ruled out. This is simply because the energy bands they have studied are too high to observe the effect of the star S2 even if it indeed interacts with the hot disk. In other words, even if there is a hot accretion disk the star like S2 has imprints in the frequency range at v $\le$ 100 MHz.

• Korean Journal of Breeding Science
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• v.43 no.6
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• pp.559-563
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• 2011

Cymbidium 'Purple Star' (Miake 'Pieta' ${\times}$ 'Allstar Mariane') was developed from a cross between hybrids at the National Institute of Horticultural & Herbal Science (NIHHS), Rural Development Administration (RDA) in 2008. A cross was made between purple colored flower C. Miake 'Pieta' as maternal line and dark pink colored flower, C. 'Allstar Mariane' as paternal line in 1995. The seed germination, cultivation, selection, and characteristic trials were conducted from 1996 to 2002. The line was named as Wongyo 'F1-21' and phenotype was characterized in 2007 as a new cultivar. The 'Purple Star' has dark purple basal color (RHS, GP186A) on both of sepal and petal with red lip (RHS, RP59A). 'Purple Star' has about 10.7 flowers per flower stalk and flower size of 7.6 cm. General appearance of petals and sepals is slightly incurved shape. The plant size is intermediate having erect peduncle. Blooming is started from the late of January (mid-winter) under optimal culture condition. Leaf attitude and twisting is erect and weak respectively. This hybrid has attractive floral arrangement, long flower stalk (78.4 cm) and vigorous growth. 'Purple Star' has a great potential for exporting to Chinese market.

• Aerospace Engineering and Technology
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• v.4 no.1
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• pp.66-76
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• 2005

In this study, star visibility analysis of a star tracker is performed by using a statistical apprach. The probability of the Sun and the Earth proximity, the solar array masking probability, and the solar array blinding probability by the Sun light are obtained from the arbitrary chosen satellite positions as a function of a line of sight vector of the star tracker in several satellite attitude modes. This analysis demonstrates that the optimized star tracker accomodations can be determined to be an elevation angle -40o and two azimuth angles $-35^{circ}$ and $-150^{circ}$.

• Journal of Arbitration Studies
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• v.27 no.4
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• pp.133-156
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• 2017

The purpose of this paper is to take a countermeasure of the investment treaty arbitration that Lone Star claimed to the Korean government. In particular, this study suggests procedural measures to be prepared by the Korean government after the arbitration award. The actual remedy in ICSID arbitration is the annulment procedure of arbitration award. Therefore, this study analyzed the measures that the Korean government can prepare based on the annulment grounds: the inadequacy of the constitution of the arbitral tribunal, the excessive power of the arbitrator, the corruption of the arbitrator, and the serious violation of the rules. First, the Korean government should decide whether to proceed with the annulment procedure after the arbitration award. Second, if they decide to do it, they should review the grounds of annulment. For example, it is possible to analyze whether the relationship between the arbitrator and Lone Star can be properly in the constitution of the arbitral tribunal, whether Lone Star is eligible to apply for ICSID arbitration, or whether arbitration tribunal ignores the crucial evidence that can affect the arbitration award. Independently, the Korean government needs to discuss the investment arbitration appeal system in a long-term perspective.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.53.3-53.3
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• 2015

We analyzed both HCN J=1-0 and HNC J=1-0 line profiles to study the inflow motions in different evolutionary stages of massive star formation; infrared dark clouds (IRDCs), high-mass protostellar object (HMPOs), and ultra-compact HII regions (UCHIIs). The infall asymmetry in HCN spectra seems to be prevalent throughout all the three evolutionary phases, with IRDCs showing the largest excess in blue profile. In the case of HNC spectra, the prevalence of blue sources does not appear, excepting for IRDCs. We suggest that this line is not appropriate to trace infall motion in evolved stages of massive star formation because of an astrochemical effect. This result spotlights the importance of considering chemistry in dynamical study in star-forming regions. The fact that the IRDCs show the highest blue excess in both infall tracers indicates that the most active infall occurs in the early phase of star formation, i.e., the IRDC phase rather than in the later phases. However, the UCHIIs is likely still accreting matters. We also found that the absorption dips of the HNC spectra in all blue sources are red--shifted relative to their central velocities. These red-shifted absorption dips may indicate the observational signature of overall collapse although observations with better resolutions are needed to examine this feature more in detail.

• International Journal of Contents
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• v.14 no.3
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• pp.46-52
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• 2018

The objective of this study was to determine the status of star chart game applications in the Google play store in Korea. The share of game genres in paid and free star charts of game applications was searched. Also, the average reviewer's rating, average number of reviews, and average age rating based on the genre of paid and free star charts of game applications, and the average price of paid applications based on genre were analyzed. Hypothesis tests for the differences in average reviewer's rating, average number of reviews, average age rating according to the genre of game applications were performed. Also, hypothesis tests for the differences in average reviewer's rating, average number of reviews, average age rating between the paid and free game applications along with the hypothesis test for the differences in price according to the genre of paid game applications were performed. Lastly, hypothesis tests for the correlation between the start chart ranking and number of reviews in association with the correlation between the start chart ranking and reviewer's rating were performed. Statistically significant differences in average reviewer's rating, average number of reviews, average age rating according to the genre of game applications, and between the paid and free game applications were verified. However, the correlation between the start chart ranking and number of reviews in association with the correlation between the start chart ranking and reviewer's rating were not statistically significant.

• Journal of Astronomy and Space Sciences
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• v.11 no.1
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• pp.115-130
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• 1994

In the framework of Thomas-Fermi equation, we have examined the properties of neutron star by assuming the existence of a new intermediate force which is composition dependent. We have found that the structure, size and mass of neutron star are affected by the strength and range of this new force. In the ultrarelativistic limit, we have also confirmed that Chandraseknar mass, $M_{ch}\simeq(1-\alpha)^{-3/2}{m_{pl}}^3/m^2$ is determined by the constants of classical physical laws, which take part in the selfgravitating processes on neutron star as well as the constant of hypothetical fifth force. In the experimental limits of the fifth force, the changes of size and mass of a neutron star are in the order of strength parameter $\alpha$.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.4
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• pp.321-327
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• 2014

A wide scope of numerical simulations was performed to predict model-ship resistances by using STAR-CCM+ and OpenFOAM. The numerical results were compared with experimental measurements in towing tank to analyze statistical reliability of the present simulations. Based on the normal distribution of resistance errors in 113 cases of container carriers, tankers and very large crude-oil carriers, the confidence intervals of numerical error were estimated as [-2.64%,+2.32%] and [-1.82%, +1.87%] with 95% confidence in STAR-CCM+ and OpenFOAM, respectively. The resistance errors of liquefied natural gas carriers with single- and twin-skeg were confident in the ranges of [-2.51%,+2.64%] and [-2.29%, +1.46%], respectively. The grid uncertainty of resistance coefficients for KCS was also quantitatively analyzed by using a grid verification procedure. The grid uncertainty of OpenFOAM (5.1%) was larger than 4.4% uncertainty of STAR-CCM+ although OpenFOAM provided statistically more confident results than those of STAR-CCM+. It means that a grid system verified under a specific condition does not automatically lead to statistical reliability in general cases.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.381-384
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• 2009

The Air-breathing engine like Sea-Star I is a second propulsive force generator to fly to the target after the booster generating initial propulsive force is separated. The performance of Sea-Star I engine should be verified because the cruise missile controls direction and altitude during flight, so ground engine test is executed before flight test. This these presents evaluation method of ground engine test to verify performance of Sea-Star I's engine.

• Aerospace Engineering and Technology
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• v.11 no.2
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• pp.87-95
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• 2012

This technical paper describes the analysis results of telemetry data for the initial activation of star trackers for an agile high accuracy low earth orbit satellite. The satellite was recently launched and is in the Launch and Early Operation Phases. It uses two SED36 star trackers manufactured by SODERN. The star tracker is separated by three parts, an optical head, an electronics box, and a baffle with maintaining optical head base plate temperature 20 degC in order to achieve the better performance in low frequency error. This paper presents the initial activation status, requirements and performance, anomaly occurrence, and noise equivalent angle performance analysis during the mission mode by processing the telemetry data.