• 천문학회보
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• 제42권1호
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• pp.48.3-48.3
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• 2017

In our recent investigation of the Oosterhoff dichotomy among globular clusters (GCs), we have shown that the RR Lyrae variables in the Oosterhoff groups I, II, and III are produced mostly by first, second, and third generation stars (G1, G2, and G3), respectively. Unlike GCs, RR Lyrae stars in the Local Group dwarf galaxies show Oosterhoff-intermediate characteristics. The origin of this, however, is yet to be understood. In this poster, we will present our progress in understanding the origin of this phenomenon.

• 천문학회보
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• 제42권1호
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• pp.48.4-49
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• 2017

We aim to trace cosmic mass accretion history of satellites around a dwarf galaxy in Lambda-CDM cosmology frame. Each satellite has a unique mass accretion history due to different environment, potential depth, and different merging events. We perform three different zoom simulations whose target galaxy has a mass of ${\sim}10^{10}Msun$, using ~17 million particles covering a cubic box of $1(Mpc/h)^3$. Here, individual particle masses for dark matter (DM) and gas are $M_{DM}=4.1{\times}10^3Msun$ and $Mgas=7.9{\times}10^2Msun$, respectively, and thus each satellite can be resolved with more than several hundreds of particles.

• 천문학회보
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• 제43권1호
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• pp.42.3-42.3
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• 2018

We investigate surface brightness profiles (SBPs) of dwarf galaxies in field, group, and cluster environments. Using images from the Korea Microlensing Telescope Network (KMTNet) Supernova Program (KSP) for the NGC 2784 group and SDSS for the Virgo cluster, SBP types are classified into profiles with single exponential (Type I), double exponential (Type II and Type III). Type II and Type III have smaller and larger outer sizes than inner sizes, respectively. SBP types of field dwarfs are compiled from a previous study. The distributions of SBP types are different in three environments. After comparing sizes of dwarfs in different environments, we suggest that since sizes of some dwarfs are changed due to the environmental effects, SBP types are able to be transformed. It makes that the distributions of SBP types in three environments are different.

• 한국작물학회지
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• 제24권1호
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• pp.1-10
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• 1979

In order to investigate the causes of epidemic out break of rice blast disease in 1978, investigations were undertaken in respect of climatic conditions, variety, cultural practice and plant pathology. During 1978, especially in August at heading time, it was higher temperature and humidity, higher frequency and amount of rainfall, lower amount of sunshine and solar radiation than less blast infested years. Nitrogen content in rice plant was higher than previous years. Acreage increase of semi-dwarf varieties brought about a result of proportional increase of new blast races which are able to infect the semi-dwarf varieties. It was concluded that those conditions mentioned above might have caused the result of severe neck blast disease in rice varieties in Korea, 1978.

• 천문학회보
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• 제36권2호
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• pp.120.2-120.2
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• 2011

최근 북반구 하늘에 대한 SDSS 관측으로부터 우리은하 주변에서 다수 발견된 Ultra-Faint Dwarf Galaxies (uFDs)는 우주의 차가운 암흑물질 (CDM) 이론에서 예측한 질량이 작은 위성은하의 후보로 알려져 있다. 특히 이 uFDs는 역학적 특성과 관련하여 특이한 특징을 갖는 것으로 알려져 있다. 그러나 아직 그 수가 충분하지 않아 더 많은 수의 uFDs의 발견이 기대되고 있다. 이 연구에서는 남반구에서 가동이 시작된 남반구 전천 탐사 망원경 SkyMapper와 향후 가동하게 될 KMT-Net를 이용하여 남반구 하늘에서 SDSS 보다 더 1~2 등급 깊은 관측을 수행하여 다수의 더 어두운 uFDs를 탐색하고, 그 은하와 CDM의 특성을 연구함으로써 우리은하뿐만 아니라 우주의 구조와 진화에서의 CDM의 역할을 규명하는 프로젝트를 제안하려한다. 이 연구에서는 SkyMapper와 KMT-Net의 상호 역할, 관측전략, 기대효과 등 제반사항을 논의하려 한다.

• Journal of Plant Biology
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• 제14권3호
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• pp.29-35
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• 1971

Various types of short culm rice mutants were obtained by means of gamma-ray irradiation. In the present paper morphological observation and analysis of silicate content of the mutants are reported. 1. Short culm type had more useful characters than bushy and dwarf types. 2. In short culm and bushy types the number of nodes both above and under ground was similar to the mother varieties, while in dwarf type it decreased. 3. In short culm types the variation of length of above-ground culm and internodes tended to vary relattive to the mother varieties. 4. Positive correlation was found between culm length and the first and fourth internode length in short culm type. 5. Silicate content increased in short culm type-the increment being variety specific.

• 천문학논총
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• 제30권2호
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• pp.247-249
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• 2015

We review recent results on superhump period variations in SU UMa-type dwarf novae. Our statistical studies have revealed that the evolution of the superhump period is basically composed of three stages: stage-A, during which the superhump period is long and constant, stage-B, during which the superhump period increases as the superoutburst proceeds, and stage-C, during which the superhump period is short and constant. We also introduce a new method of estimating a mass ratio using the stage-A superhump period. This method can extend to, for example, low mass X-ray binaries or AM CVn stars if the stage-A superhump period is well determined.

• Plant Resources
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• 제3권3호
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• pp.173-178
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• 2000

This test checked jujube witches'-broom disease, sumac witches'-broom disease, paulonia witches'- broom disease, and mulberry dwarf disease whether or not they were infected by phytoplasma, using universal and specific primers. Upon treatment of DNA amplified by PCR of phytoplasma with Alu I , Hpa II and Sat I restricted enzymes, distinction of phytoplasmas was possible. Particularly, phytoplasma of each host was distinguishable by treatment of Hpa II restricted enzyme. Meanwhile, analysis of restricted enzymes of jujube witches'-broom disease showed a higher infectivity of phytoplasmas of two origins. There were a lot of relations between jujube witches'-broom disease and sumac witches'-broom disease, and between paulonia witches'-broom disease and mulberry dwarf disease.

• 천문학회보
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• 제43권2호
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• pp.40.2-40.2
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• 2018

NGC 5024 and NGC 5053 are among the most metal-poor globular clusters in the Milky Way. Both globular clusters are considered to be accreted from dwarf galaxies (like Sagittarius dwarf galaxy or Magellanic clouds), and common stellar envelope and tidal tails between globular clusters are also detected. We present a search for extra-tidal cluster member candidates around these globular clusters from APOGEE survey data. Using 20 chemical elements (e.g., Fe, C, Mg, Al) and radial velocities, t-distributed stochastic neighbour embedding (t-SNE), which identifies an optimal mapping of a high-dimensional space into fewer dimensions, was explored, and we find that globular cluster stars are well separated from the field stars in 2-dimensional map from t-SNE. We also find that some stars selected in t-SNE map are placed outside of the tidal radius of the clusters. The proper motion of stars outside tidal radius is also comparable to that of globular clusters, which suggest that these stars are tidally decoupled from the globular clusters. We manually measure chemical abundances for the clusters and extra-tidal stars, and discuss the association of extra-tidal stars with the clusters.

• 천문학회보
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• 제44권1호
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• pp.61.4-61.4
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• 2019

The key science goal of the KMTNet Supernova Program (KSP) is to detect and study the early explosions of supernovae using one fifth of the KMTNet time. The BVI-band observations of the nearby target fields mostly closer than 30 Mpc distance and the follow-up spectroscopy provide valuable information on the early phase of the supernovae. These data can also be used for the studies of optical transients such as novae, dwarf novae, variable stars, and active galactic nuclei. Stacked images of several hundred images obtained from the time domain observations can be used for the search of low surface brightness galaxies reaching $28mag\;arcsec^{-2}$. Results and status of the KSP including ${\geq}20$ infant supernovae and ${\geq}100$ faint dwarf galaxies will be presented in this talk.