• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.58.3-59
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• 2017

The JCMT is now in its third year of operations under EAO management. During this past year, we continued with calls for regular PI programs as well as the second call for Large Programs. The performance of SCUBA-2 has been improved by replacing internal optical filters. The 230GHz Receiver A is in the process of being replaced by a new closed-cycle system. The SCUBA-2 polarimeter, POL-2, commissioned during the past year, has been working very well in measuring the magnetic field structures in molecular clouds. The JCMT successfully participated in the Event Horizon Telescope experiment during April 2017, which utilized the phased-up ALMA for the first time. The first round of Large Programs are nearing completion, with first publications beginning to be published. The JCMT continues to welcome inputs from the community, and the next users meeting will be held in Seoul in January 2018.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.49.4-49.4
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• 2018

We present measurement results of the fabricated ultra wideband corrugated horn for the planned ASTE band7+8 receiver. Return loss and vector beam pattern measurements were carried out over 275-500 GHz frequency range. Hardware set-ups for these measurements are described as well as beam measurement data are compared with such design criteria as beam width, phase curvature and cross-polarization. We discuss the impact of these beam measurement results to the aperture efficiency of the proposed 2-mirror receiver optics for the ASTE telescope.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.94.2-94.2
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• 2012

NASA는 지난 15년간 주요 과학미션 비용의 약 1%를 교육과 public outreach에 투자했으며 NSF 천문학분야 연구비의 약 6% 이상이 교육과 특별활동에 사용되고 있다는 보고가 있다. 국내 천문학 연구 프로젝트에서도 교육 및 public outreach에 대한 예산 할당과 프로젝트의 교육적 활용 및 대국민 홍보 활동을 위한 구체적인 연구가 필요한 상황이다. 이번 연구에서는 국내 천문학 연구 프로젝트의 교육적 활용을 위하여 1)NASA의 과학미션과 관련된 교육자 가이드들을 사례조사 하였고, 2)사례조사 결과와 2007 개정 과학과 교육과정을 고려하여 KMTNet 프로젝트의 교육자 가이드를 e-book 형태로 개발 하였다. 이번 발표에서는 개발된 교육자 가이드의 배포 및 활용 방안과 국내에서 수행중인 천문학 프로젝트(KVN, GMT, SKA, ALMA 등)들의 교육자 가이드 제작을 위한 사업방안을 소개하고 산업체, 학교, 연구기관에 종사하는 분야별 전문가들로 부터 다양한 의견을 청취하고자 한다.

• Journal of The Korean Astronomical Society
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• v.52 no.3
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• pp.83-88
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• 2019

Using ALMA observations of the $^{13}CN$ and DCN lines in the massive star-forming region G33.92+0.11A, we investigate the CN/HCN abundance ratio, which serves as a tracer of photodissociation chemistry, over the whole observed region. Even considering the uncertainties in calculating the abundance ratio, we find high ratios (${\gg}1$) in large parts of the source, especially in the outer regions of star-forming clumps A1, A2, and A5. Regions with high CN/HCN ratios coincide with the inflows of accreted gas suggested by Liu et al. (2015). We conclude that we found strong evidence for interaction between the dense gas clumps and the accreted ambient gas which may have sequentially triggered the star formation in these clumps.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.33.1-33.1
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• 2019

Protostars grow their mass by the accretion of disk material, which is infalling from the envelope. This accretion process is important to the physical and chemical conditions of the disk and envelope, and thus, the planets yet to be formed from the disk material. Therefore, if we map the physical and chemical properties of disks and envelopes, we can study indirectly the accretion process in star formation. In particular, the chemical distribution in the disk and the inner envelope of a young stellar object is greatly affected by the thermal history, which is mainly determined by the accretion process in the system. In my talk, I will review the episodic accretion model for the low mass star formation and observational efforts to find the evidence of episodic accretion. Finally, I will present our recent ALMA detection of several complex organic molecules associated directly with the planet formation in V883 Ori, which is in the burst accretion phase.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.36.2-36.2
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• 2019

Using VLT/MUSE and ALMA data, we present a spatially-resolved analysis of the central part of NGC 5728. We find enhanced star formation (${\sim}1.8M{\odot}/yr/kpc2$) at a region where AGN gas outflows intersect the star formation ring. In contrast, significantly weaker CO emission (~3.5 times) is found at the same region compared to other regions in ring, suggesting positive AGN feedback on star formation. On the other hand, we detect gas outflows outside of the spiral arms, implying that the inflowing gas in the arms is removed (i.e., negative feedback). Even though the positive and negative feedback are expected at the central part of NGC 5728, the impact of the AGN feedback in galaxy scale may be insignificant.

• International Journal of Computer Science & Network Security
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• v.23 no.6
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• pp.181-192
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• 2023

Blockchain system brought innovation in the area of accounting, credit monitoring and trade secrets. Consensus algorithm that considered the central component of blockchain, significantly influences performance and security of blockchain system. In this paper we presented four consensus protocols specifically as Proof of Work (PoW), Proof of Stake (PoS), Delegated Proof of Stake (DPoS) and Practical Byzantine Fault-Tolerance (PBFT), we also reviewed different security threats that affect the performance of Consensus Protocols and precisely enlist their counter measures. Further we evaluated the performance of these Consensus Protocols in tabular form based on different parameters. At the end we discussed a comprehensive comparison of Consensus protocols in terms of Throughput, Latency and Scalability. We presume that our results can be beneficial to blockchain system and token economists, practitioners and researchers.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.51.4-51.4
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• 2019

We started a systematic observational study of the 22 GHz water and 44 GHz class I methanol masers in 87 high-mass young stellar objects (HM-YSOs) as a KaVA large program (LP). The primary goal is to understand dynamical evolution of HM-YSOs and their circumstellar structures by measuring spatial distributions and 3-dimensional velocity fields of multiple maser species. In the first-year observations (2016-2017), we made snap-shot imaging surveys of 25 water and 19 methanol maser sources. In the second-year observations (2018-2019), we have carried out monitoring observations of 19 water and 3 methanol maser sources that were selected on the basis of the first-year survey results. By combining follow-up observations with VERA (distances), JVN/EAVN (6.7 GHz methanol masers), and ALMA cycles 3 and 6 (thermal lines/continuum), we will provide novel information on physical properties (density, temperature, size, mass), 3D dynamical structures of disk/jet/outflow/infalling envelope, and relationship between evolutionary of HM-YSOs. In this presentation, we will report the current status and future plans of our KaVA large program.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.63.2-63.2
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• 2019

Recent submillimeter observations of ALMA reveal that many protoplanetary disks contain substructures like gaps or rings. The disk-planet interaction is believed to be the most likely gap formation scenario, and most previous numerical work attempted to constrain the planet mass using the density profiles of gas in the gaps. Since the dust and gas distributions likely differ from each other in protoplanetary disks, however, perturbed rotational velocities that directly probe the gas would give a more reliable estimate to the planet mass. In this work, we run two-dimensional hydrodynamic simulations to measure the amplitudes and widths of rotational velocity perturbations induced by planets with different mass. We present the parametric relations of the gap widths and depths as functions of the planet mass and disk properties. We also apply our relations to HD 163296 to infer the masses of embedded planets.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.57.2-57.2
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• 2020

We observed the Class I protostar TMC-1A in polarized dust emission at 1.3 mm at a spatial resolution of ~40 au using ALMA. Previous observations revealed a disk (r~100 au), surrounded by an infalling envelope, and a CO outflow going in the north-south direction in TMC-1A. Our observations detected polarized dust emission in a central region (r~50 au) and ~100 au north and south of the central protostar. The former polarization is likely due to self-scattering because of the polarization direction along the disk minor axis, the polarization fraction independent of Stokes I, and a high optical thickness. The latter polarization is roughly in the outflow region. The position and direction, particularly in the north, imply multiple possible mechanisms: magnetically or mechanically aligned dust grains in the outflow or in an accretion flow.