• Journal of Radiation Protection and Research
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• v.26 no.3
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• pp.183-190
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• 2001

The activity concentration of primordial radionuclides i.e., $^{238}U$ series, $^{232}Th$ series and $^{40}K$, in soil samples collected from Udagamandalam environment, have been measured by employing NaI (Tl) Gamma ray Spectrometer. The absorbed gamma dose rate has also been simultaneously measured by using both Environmental Radiation Dosimeter at each soil sampling location (ambient gamma dose) as well as from the gamma dose derived from the activity concentration of the primordial radionuclides. The results of activity concentration of each radio nuclides in soil, absorbed dose rate in air due to soil activity and possible cosmic radiation at each location along with human effective dose equivalent for Udagamandalam environment are presented and discussed.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.94.2-94.2
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• 2012

흑점과 오로라의 역사적 기록은 단편적이고 관측 빈도에 의존하는 문제도 있지만 과거 태양활동의 실제 모습을 보여주는 중요한 자료이다. 또한 지구 대기에 유입된 cosmic ray에 의해 만들어지는 14C이나 10Be 그리고 18O와 같은 동위원소들이 나무 테나 polar ice 그리고 바다의 퇴적물 등에 축적되어 나타나는 Proxy data와 함께 과거 태양의 활동뿐만 아니라 지구의 자기장이나 기후 변화 등을 연구하는데 중요한 지표로 사용된다. 최근 태양의 활동과 지구 기후 변화의 관계에 대해 특별히 많은 관심이 집중되고 있으며 많은 연구가 진행되고 있다. 이 연구는 우리 역사서에 실린 흑점과 오로라의 역사적 기록 및 태양의 proxy data를 함께 비교하여 지난 1000년간 태양활동에서 나타난 특징들, 즉 흑점의 출현과 오로라 발생사이의 밀접한 관계 및 태양활동의 장단기 주기변화 그리고 Maunder Minimum과 같은 최대 극소기 때 보이는 기후 변화와 태양활동의 특징 등에 대해 논의해 보고자 한다.

• Journal of The Korean Astronomical Society
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• v.47 no.1
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• pp.15-39
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• 2014

Polarization is a basic property of light and is fundamentally linked to the internal geometry of a source of radiation. Polarimetry complements photometric, spectroscopic, and imaging analyses of sources of radiation and has made possible multiple astrophysical discoveries. In this article I review (i) the physical basics of polarization: electromagnetic waves, photons, and parameterizations; (ii) astrophysical sources of polarization: scattering, synchrotron radiation, active media, and the Zeeman, Goldreich-Kylafis, and Hanle effects, as well as interactions between polarization and matter (like birefringence, Faraday rotation, or the Chandrasekhar-Fermi effect); (iii) observational methodology: on-sky geometry, influence of atmosphere and instrumental polarization, polarization statistics, and observational techniques for radio, optical, and $X/{\gamma}$ wavelengths; and (iv) science cases for astronomical polarimetry: solar and stellar physics, planetary system bodies, interstellar matter, astrobiology, astronomical masers, pulsars, galactic magnetic fields, gamma-ray bursts, active galactic nuclei, and cosmic microwave background radiation.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.35.3-35.3
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• 2017

Neutrinos play an important role in astronomy and therefore they need to be observed as well as other astronomical messengers. The first observation of astronomical neutrinos is from the SN1987a by the Kamiokande neutrino telescope in Japan. Unlike other astronomical messengers neutrinos can cover all energy range of astronomical phenomena due to their weak interactions and neutrality. Multi messenger astronomy including optical, neutrino, and cosmic ray observations, provides more information on astronomical phenomena and thus such collaborational works are ongoing worldwide. A future Korean neutrino telescope consisting of huge (260 kiloton) water Cherenkov detector under a mountain was proposed in 2016 and the sensitivity studies on various topics are in progress with international collaborators. In this talk I will introduce the future Korean neutrino telescope and its science as well as the potential candidate sites in Korea. We invite all of you to work together for the future Korean neutrino telescope that will operate more than 30 years.

• Journal of The Korean Astronomical Society
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• v.37 no.4
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• pp.223-224
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• 2004

The Tycho supernova remnant (SNR), as one of the few historical SNRs, has been widely studied in various wavebands and previous observations have shown evidence that Tycho is interacting with a dense ambient medium toward the northeast direction, In this paper, we report our high-resolution (16') $^{12}CO$ observation of the remnant using the Nobeyama 45m radio telescope. The Nobeyama data shows that a large molecular cloud surrounds the SNR along the northeastern boundary. We suggest that the Tycho SNR and the molecular cloud are both located in the Perseus arm and that the dense medium interacting with the SNR is possibly the molecular cloud. We also discuss the possible connection between the molecular cloud and the Balmer-dominated optical filaments, and suggest that the preshock gas may be accelerated within the cosmic ray and/or fast neutral precursor.

• Bulletin of the Korean Space Science Society
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• 2004.10b
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• pp.64-64
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• 2004

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.26.1-26.1
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• 2009

Many solar, interplanetary and geomagnetic activity parameters have 11-year cycle on the average in sync with solar sunspot number. The galactic cosmic ray (GCR) intensity measured by ground Neutron Monitor (NM) is one of those parameters showing the unprecedented activity levels in the current solar minimum (2008-2009) of solar cycles 23/24. We defined abnormality as the ratio of deviation from long term mean over mean amplitude of solar cycle change. The abnormality distribution map was drawn using all the data of NM stations available online. The implications of those unprecedented levels of GCR intensities of different cutoff rigidities will be discussed.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.206.2-206.2
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• 2012

남극 40km 상공에서 고에너지우주선을 관측하는 CREAM(Cosmic Ray Energetics And Mass)실험은 2004년 CREAM I의 발사 및 운영을 시작으로 2010년 겨울 CREAM VI까지 성공적으로 그 관측 임무를 수행해 왔다. 이미 지난 모든 실험에서 검증된 두 개 층의 실리콘 입자 전하량 검출기(SCD)와 더불어 보다 정확하고 신뢰성 있는 결과를 얻기 위해, CREAM 검출기 최상단에 전 검출 영역을 커버하는 대면적의 Large-SCD를 추가로 장착하고자 한다. 이를 위해 2년간 420개 실리콘 센서, 5040채널로 이루어진 대면적 Large-SCD의 제작을 완료 하였으며, CERN 가속기 연구소에서 Beam 테스트를 마친 후 이미 메릴랜드 대학에서 최종 테스트 중이다. 이번 발표에서는 제작 된 Large-SCD와 이를 통해 기대되는 CREAM 실험에서의 우주선 성분 관측 정확도의 향상에 관하여 이야기 하고자 한다.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.181.2-181.2
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• 2012

우주공간에서는 solar particle과 galactic cosmic ray에 포함된 proton, electron 및 heavy ion등에 의해 radiation 현상이 발생하는데 이는 각종 전자장비의 성능 감쇄 및 디지털 장비의 내부 정보를 교란을 야기할 수 있다. 특히 메모리의 bit 정보가 반전되는 Single Event Upset (SEU)의 경우 인공위성 및 우주정거장 등의 시스템에서도 빈번히 발생할 수 있으며 적절한 조치가 이루어지지 않으면 주어진 임무 수행 실패는 물론 시스템 failure까지 이를 수 있다. 따라서 SEU에 의한 문제 발생 시 신속한 문제 확인 및 대처가 매우 중요하다. 본 논문에서는 SEU의 발생 원인 및 영향과 기존의 오류 검출 및 수정 기법에 대해 소개하도록 한다. 또한 효율적이고 신뢰성 있는 설계를 위해 각 하드웨어 소자 특성에 따른 적합한 SEU 회피 방안을 제시하도록 한다.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.51.3-52
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• 2020

We present the status of the development of a Markov Chain Monte Carlo (MCMC) parameter estimation (PE) pipeline for compact binary coalescences (CBCs) with the Japanese KAGRA gravitational-wave (GW) detector. The pipeline is included in the KAGRA Algorithm Library (KAGALI). Basic functionalities are benchmarked from the LIGO Algorithm Library (LALSuite) but the KAGRA MCMC PE pipeline will provide a simpler, memory-efficient pipeline to estimate physical parameters from gravitational waves emitted from compact binaries consisting of black holes or neutron stars. Applying inspiral-merge-ringdown and inspiral waveforms, we performed simulations of various black hole binaries, we performed the code sanity check and performance test. In this talk, we present the situation of GW observation with the Covid-19 pandemic. In addition to preliminary PE results with the KAGALI MCMC PE pipeline, we discuss how we can optimize a CBC PE pipeline toward the next observation run.