• 천문학회보
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• 제44권2호
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• pp.76.1-76.1
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• 2019

After the first identification of electromagnetic counterpart of gravitational wave source (GW170817), era of multi-messenger astronomy has begun. For specifying coordinate, magnitude, and host galaxy information, optical follow-up observation of GW source becomes important. The O3 run of LIGO / VIRGO started after April 2019. We present searching strategy of GW optical counterpart using the KMTNet. By performing tiling observation of high probability area in GW localization map, we expect to observe early light-curve of GW optical counterpart. We will also present observation result for three gravitational wave events of binary black hole mergers. After identification of optical counterpart, we will study collision mechanism, progenitor, and characteristics of host galaxy using observation data of GW source.

• Korean Journal of Mathematics
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• 제23권3호
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• pp.479-489
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• 2015

We study the GMGHS spacetime to analyze anisotropic cosmology model which represents homogeneous but anisotropically expanding(contracting)cosmology. In this paper we investigate the solution of GMGHS spacetime in form of doubly warped products possessing warping functions and find the Ricci curvature associated with three phases in the evolution of the universe.

• 천문학회보
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• 제34권1호
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• pp.190.2-190.2
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• 2009

• 트랜스-
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• 제12권
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• pp.173-222
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• 2022

이 논문은 현재 K-pop분야 콘텐츠 전략으로 활용되고 있는 '세계관' 수용 현상에 대해 K-pop수용자 관점에서 살펴본 후, 그들의 수용 경험과 세계관의 의미 인식을 파악하고자 하였다. 이를 위해 현재 가장 활발하게 세계관을 콘텐츠 전략으로 활용하는 그룹 에스파의 세계관 수용경험과 관련된 트윗을 수집하여, 이 자료를 개인 경험의 의미구조 및 현상의 본질을 탐구하고자 하는 접근방식인 현상학적 접근방식에 따라 분석하였다. 무스타카스의 방식을 활용하여 분석한 결과, 총 21개의 주제를 통해 K-pop 수용자들의 세계관 수용 현상의 의미구조를 도출하였다. 현재 K-pop 수용자들은 세계관 수용을 통해 일방적이거나 수동적이기 보다는 능동적인 문화소비 경험을 하고 있는 것으로 나타났다. 이는 의미를 생산하고 팬덤 내부의 활발한 상호작용을 통해 외부 영향력을 행사하는 대안적 공동체인 능동적 수용자의 특성을 K-pop 수용자들이 지니고 있으며, 동시에 이 특성이 세계관을 수용하는 세부 행위들에 영향을 미치고 있음을 의미한다. 다음으로는 능동적 수용 경험을 통해 K-pop 수용자들이'마케팅 자산', '팬덤 공동체 자산', 'K-pop 산업 확장 자산'이라는 의미를 세계관에 부여하고 있음이 발견되었다. 이 중 '마케팅 자산'인식은 관련 선행연구들의 논의들을 뒷받침하는 근거로 재확인 되었다. 뿐만 아니라, 기존의 생산자적 측면의 선행연구들이 발견하지 못한 '팬덤 고유의 자산'과 'K-pop 산업의 확장 자산'의미를 발견하여 K-pop 분야 세계관의 새로운 가치를 도출하였으며, 향후 세계관의 가치 확장 측면에서 그 의미 및 방향성을 논의하여 제시하였다. 결과적으로, 이 연구는 세계관 수용 현상의 의미구조를 밝혀냈다는 것과, 기존에 논의되지 않았던 K-pop 세계관의 새로운 의미를 발견했다는 데 의의가 있으며, 관련 주제의 후속 연구를 다각도에서 제언하는 것을 통해 연구의 장을 넓히는데 기여하고자 하였다.

• 천문학회보
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• 제39권2호
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• pp.37-37
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• 2014

Magnetic fields appear to be ubiquitous in astrophysical environments. The existence of magnetic fields in the large-scale structure of the universe has been established through observations of Faraday rotation and synchrotron emission, as well as through recent gamma-ray observations. Yet, the nature and origin of the magnetic fields remains controversial and largely unknown. In this talk, I briefly summarize recent developments in our understanding of the nature and origin of magnetic fields. I also describe a plausible scenario for the origin of the magnetic fields; seed fields were created in the early universe and subsequently amplified during the formation of the large-scale structure of the universe. I then discuss the prospect of observation of magnetic fields in the large-scale structure of the universe.

• 천문학회보
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• 제40권1호
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• pp.45.1-45.1
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• 2015

Galaxy clusters have provided important information to understand the evolution of the universe, since the number density and mass of clusters are tightly related to the cosmological parameters. In addition, galaxy clusters are an excellent laboratory to investigate the galaxy evolution in dense environments. However, finding galaxy clusters at high redshift ($z{\geq}1$) still remains as a main subject in astronomy due to their rareness and difficulty in identifying such objects from optical imaging data alone. Here, we report a spectroscopic follow-up observation of distant galaxy cluster candidates identified by a deep optical-NIR dataset of Infrared Medium-deep Survey. Through the galaxy spectra taken with the IMACS instrument on the Magellan telescope, we confirm at least 3 massive clusters at z~0.92. Interestingly, the maximum spatial separation between these clusters is ~8Mpc, which implies that this system is a new supercluster in the distant universe. We also discuss properties of galaxies in these clusters based on multi-wavelength photometric data.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권4호
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• pp.2292-2309
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• 2017

Ciphertext policy attribute-based encryption (CP-ABE) is a useful cryptographic technology for guaranteeing data confidentiality but also fine-grained access control. Typically, CP-ABE can be divided into two classes: small universe with polynomial attribute space and large universe with unbounded attribute space. Since the learning with errors over rings (R-LWE) assumption has characteristics of simple algebraic structure and simple calculations, based on R-LWE, we propose a small universe CP-ABE scheme to improve the efficiency of the scheme proposed by Zhang et al. (AsiaCCS 2012). On this basis, to achieve unbounded attribute space and improve the expression of attribute, we propose a large universe CP-ABE scheme with the help of a full-rank differences function. In this scheme, all polynomials in the R-LWE can be used as values of an attribute, and these values do not need to be enumerated at the setup phase. Different trapdoors are used to generate secret keys in the key generation and the security proof. Both proposed schemes are selectively secure in the standard model under R-LWE. Comparison with other schemes demonstrates that our schemes are simpler and more efficient. R-LWE can obtain greater efficiency, and unbounded attribute space means more flexibility, so our research is suitable in practices.

• 천문학회보
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• 제44권1호
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• pp.75.1-75.1
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• 2019

The universe has been ionized in the post-reionization by several photon contributors. The dominant source to produce the hydrogen ionizing photons is not revealed so far. Faint quasars have been expected to generate UV photon budgets required to maintain ionization state of universe. Observational limits, however, hinder to discover them despite their higher number density than bright one. Consequently, the influence of faint quasars on post-reionization are not considered sufficiently. Therefore, a survey to find faint quasars at z ~ 5 is crucial to determine the main ionizing source in the post-reionization era. Deep images from the Hyper Suprime-Cam Subaru Strategic Program (HSC SSP) allow us to search for quasar swith low luminosities in the ELAIS-N1 field. J band information are obtained by the Infrared Medium-deep Survey (IMS) and the UKIRT Infrared Deep Sky Survey (UKIDSS) - Deep ExtragalacticSurvey (DXS). Faint quasar candidates were selected from several multi-band color cut criteria based on simulated quasars on color-color diagram. To choose the reliable candidates with possible Lyman break, we have performed medium-bands observations. Whether a candidate is a quasar or a dwarf star contamination was decided by results from chi-square minimization of quasar/dwarf model fitting. Spectroscopic follow-up observations confirm three quasars at z ~ 5. 100% spectral confirmation success rate implies that the medium-band observations effectively select faint quasars with strong Lyman alpha emission.

• 천문학회보
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• 제45권1호
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• pp.36.2-36.2
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• 2020

Intensive Monitoring Survey of Nearby Galaxies (IMSNG) has been managed over 6 years. It aimed to constrain the progenitor system and explosion mechanism of SNe by detection of very early signal from shock heated emission. We have conducted monitoring observation of nearby bright galaxies those were carefully selected using global network of 1-m class telescopes. More than 20 SNe have occured in our target fields. As One of result of the survey, we present light curve analysis of type Ia SN 2018kp, which was discovered in NGC 3367. Based on photometric analysis, we calculated explosion parameters and set constraints of physical conditions of this supernova. We compared the results with theoretical model progenitor systems to find out which scenario is the most fitted to SN 2018kp case. Moreover, we estimate the distance to the galaxy and look into the relation between SNe and galactic physical parameters.

• 천문학회보
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• 제5권
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• pp.3-10
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• 1980