• 천문학회보
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• 제42권1호
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• pp.48.1-48.1
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• 2017

지난 2016년 4월, 젊은 천문학자 모임 (Young Astronomers Meeting, YAM) 정기총회에서 2016-17년도 임원진으로 회장 이주원 (경희대학교), 부회장 김진협(연세대학교), 총무 최두현 (세종대학교) 을 선출하였다. 임원진은 서울대학교 김윤영, 세종대학교 장석준, 연세대학교 백준현, 경북대학교 신지혜를 학교별 운영위원으로 임명하였다. 현 임원진은 YAM 창단 초기에 발간되었다 중단되었던 소식지 <하늘 사랑>의 재창간을 임기 목표로 하고, 2016년 가을에 재창간호 (통권 5호), 2017년 봄에 6호를 발간하였다. 임원진은 <하늘 사랑>을 통해 회원들간의 교류를 증진하고 회원들의 다양한 의견을 수렴하고자 하였다. 이와 더불어 홈페이지를 통한 입회 시스템을 도입하였고, 흩어져있던 과거 자료들을 회원들로부터 제보 받아 통합하는 작업을 마쳤으며 EAMA10에 참여하여 YAM의 활동과 역할에 대해 발표하였다. 이번 포스터에서는 2016-17년도 동안의 활동 내용을 보고하고 이후의 계획에 대해 논의하려고 한다.

• 천문학논총
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• 제30권2호
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• pp.625-628
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• 2015

POLARBEAR is a ground-based experiment located in the Atacama desert of northern Chile. The experiment is designed to measure the Cosmic Microwave Background B-mode polarization at several arcminute resolution. The CMB B-mode polarization on degree angular scales is a unique signature of primordial gravitational waves from cosmic inflation and B-mode signal on sub-degree scales is induced by the gravitational lensing from large-scale structure. Science observations began in early 2012 with an array of 1.274 polarization sensitive antenna-couple Transition Edge Sensor (TES) bolometers at 150 GHz. We published the first CMB-only measurement of the B-mode polarization on sub-degree scales induced by gravitational lensing in December 2013 followed by the first measurement of the B-mode power spectrum on those scales in March 2014. In this proceedings, we review the physics of CMB B-modes and then describe the Polarbear experiment, observations, and recent results.

• 천문학논총
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• 제30권2호
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• pp.447-449
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• 2015

Although the link between activity in the nuclei of galaxy and galactic mergers has been under scrutiny for several years, it is still unclear to what extent and for which populations of active galaxies merger-triggered activity is relevant. The environments of AGN allow an indirect probe of the past merger history and future merger probability of these systems, suffering less from sensitivity issues when extended to higher redshifts than traditional morphological studies of AGN host galaxies. Here we present results from our investigation of the environment of radio selected sources out to a redshift z=2. We employ the first data release J-band catalog of the new near-IR Infrared Medium-Deep Survey (IMS), 1.4 GHz radio data from the Faint Images of the Radio Sky at Twenty-cm (FIRST) survey and a deep dedicated VLA survey of the VIMOS field, covering a combined total of 20 sq. degrees. At a flux limit of the combined radio catalog of 0.1 mJy, we probe over 8 orders of magnitude of radio luminosity. Using the second closest neighbor density parameters, we test whether active galaxies inhabit denser environments. We find evidence for a sub-population of radio-selected AGN that reside in significantly overdense environments at small scales, although we do not find significant overdensities for the bulk of our sample. We show that radio-AGN in the most underdense environments have vigorous ongoing star formation. We interpret these results in terms of the triggering and fuelling mechanism of radio-AGN.

• 천문학회지
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• 제54권5호
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• pp.139-155
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• 2021

We present an updated version of the multilayer spectral inversion (MLSI) recently proposed as a technique to infer the physical parameters of plasmas in the solar chromosphere from a strong absorption line. In the original MLSI, the absorption profile was constant over each layer of the chromosphere, whereas the source function was allowed to vary with optical depth. In our updated MLSI, the absorption profile is allowed to vary with optical depth in each layer and kept continuous at the interface of two adjacent layers. We also propose a new set of physical requirements for the parameters useful in the constrained model fitting. We apply this updated MLSI to two sets of Hα and Ca II line spectral data taken by the Fast Imaging Solar Spectrograph (FISS) from a quiet region and an active region, respectively. We find that the new version of the MLSI satisfactorily fits most of the observed line profiles of various features, including a network feature, an internetwork feature, a mottle feature in a quiet region, and a plage feature, a superpenumbral fibril, an umbral feature, and a fast downflow feature in an active region. The MLSI can also yield physically reasonable estimates of hydrogen temperature and nonthermal speed as well as Doppler velocities at different atmospheric levels. We conclude that the MLSI is a very useful tool to analyze the Hα line and the Ca II 8542 line spectral daya, and will promote the investigation of physical processes occurring in the solar photosphere and chromosphere.

• 한국초전도ㆍ저온공학회논문지
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• 제25권4호
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• pp.5-9
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• 2023

본 연구에서는 PCPO 물질에서 보고된 초전도성을 실험적으로 확인하기 위하여 arXiv 원논문에서 보고된 시료 제조 방법을 이용하여 PCPO 시료를 합성하였다. X선 회절 분석을 통해 PCPO상이 성공적으로 합성됨을 확인하였으나, 많은 불순물상이 함께 형성되는 것 역시 관측하였다. 전기저항 측정을 통해 360~380 K 및 ~160 K 온도 근처에서 저항 변화를 관측하였으며, 이는 합성과정에서 형성된 불순물 상과 밀접한 관련이 있는 것으로 추측된다. 이러한 실험 결과는 고순도의 PCPO 시료 제조의 필요성을 시사하고 있어, 화학 양론적으로 정확한 화학 반응을 통해 불순물 형성을 최소화할 수 있는 전구체를 활용한 합성을 추가적으로 진행하였다. 하지만 활용된 전구체의 높은 안정성과 고온에서의 강한 휘발성으로 인하여 PCPO상 합성이 효과적으로 이뤄지지는 않았다. PCPO상의 물성을 정확히 측정하고 이해하기 위해서는 고순도의 PCPO시료 제작이 필요하며, 이를 위해서는 반응성을 높이면서 불순물 생성을 최소화할 수 있는 적절한 전구체 개발이 필요할 것으로 판단된다.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 1999년도 한국우주과학회보 제8권2호
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• pp.85-85
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• 1999

No Abstract, See Full Text

• 천문학회지
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• 제34권4호
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• pp.305-307
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• 2001

Radiation hydrodynamics in high. velocity or high optical-depth flow should be treated under rigorous relativistic formalism. Relativistic radiation hydrodynamic moment equations are summarized, and its application to the near-critical accretion onto neutron star is discussed. The relativistic effects can dominate the dynamics of the flow even when the gravity is weak and the velocity is small. First order equations fail to describe the intricate relativistic effects correctly.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.582-584
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• 2003

This paper explores two such indexes----the Aerosol Free Vegetation Index (AFRI) and the Atmospherically Resistant Vegetation Index (ARVI). Comparisons were made with the NDVI (normalized vegetation index) to see if they indeed performed better. In general, the results showed that the AFRI and ARVI (with gamma=1) did indeed perform better than their NDVI counterpart study with the related channels were employed.

• 한국환경과학회지
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• 제11권5호
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• pp.419-436
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• 2002

The current paper reports on the enhancement of O$_3$, CO, NO$_2$, and aerosols during the Asian dust event that occurred over Korea on 1 May 1999. To confirm the origin and net flux of the O$_3$, CO, NO$_2$, and aerosols, the meteorological parameters of the weather conditions were investigated using Mesoscale Meteorological Model 5(MM5) and the TOMS total ozone and aerosol index, the back trajectory was identified using the Hybrid Single-Particle Lagrangian Integrated Trajectory Model(HYSPLIT), and the ozone and ozone precursor concentrations were determined using the Urban Ashed Model(UAM). In the presence of sufficiently large concentrations of NO$\sub$x/, the oxidation of CO led to O$_3$ formation with OH, HO$_2$, NO, and NO$_2$ acting as catalysts. The sudden enhancement of O$_3$, CO, NO$_2$ and aerosols was also found to be associated with a deepening cut-off low connected with a surface cyclone and surface anticyclone located to the south of Korea during the Asian dust event. The wave pattern of the upper trough/cut-off low and total ozone level remained stationary when they came into contact with a surface cyclone during the Asian dust event. A typical example of a stratosphere-troposphere exchange(STE) of ozone was demonstrated by tropopause folding due to the jet stream. As such, the secondary maxima of ozone above 80 ppbv that occurred at night in Busan, Korea on 1 May 2001 were considered to result from vertical mixing and advection from a free troposphere-boundary layer exchange in connection with an STE in the upper troposphere. Whereas the sudden enhancement of ozone above 100 ppbv during the day was explained by the catalytic reaction of ozone precursors and transport of ozone from a slow-moving anticyclone area that included a high level of ozone and its precursors coming from China to the south of Korea. The aerosols identified in the free troposphere over Busan, Korea on 1 May 1999 originated from the Taklamakan and Gobi deserts across the Yellow River. In particular, the 1000m profile indicated that the source of the air parcels was from an anticyclone located to the south of Korea. The net flux due to the first invasion of ozone between 0000 LST and 0600 LST on 1 May 1999 agreed with the observed ground-based background concentration of ozone. From 0600 LST to 1200 LST, the net flux of the second invasion of ozone was twice as much as the day before. In this case, a change in the horizontal wind direction may have been responsible for the ozone increase.

• 한국진공학회지
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• 제21권1호
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• pp.12-16
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• 2012

Top-Emitting OLED (Organic Light-Emitting Diode) 디스플레이에서는 반사율이 가장 높은 Ag (silver) 박막이 쓰이고 있지만, 소자에서 요구되는 일함수(work function)가 상대적으로 낮기 때문에 전극과 유기물간에 에너지 장벽이 발생하여 발광효율을 낮추는 요인이 되고 있다. 본 논문에서는 Ag 전극의 일함수를 높이기 위한 연구를 진행하였으며, 박막 형태의 Ag 전극에 대하여 nanotribology 접근법으로 연구를 실행하였다. Ag는 rf magnetron sputter를 이용해 glass 위에 증착한 후 furnace에서 $300^{\circ}C$, 30분간 대기 중에서 열처리하였고, 또 다른 시료는 표면에 산소 상압플라즈마로 처리 시간(30, 60, 90, 120s)을 각기 다르게 하여 시료를 제조하였다. Ag 전극을 nanoindentation을 통해 국부 영역에 대한 물리적 특성의 변화를 측정하였고, Kelvin probe force microscopy을 이용해 시료 표면의 포텐셜을 측정했다. 그 결과 열처리한 시료의 포텐셜값은 가장 크게 증가하였지만 균일도가 낮아졌다. 120s 플라즈마 처리한 시료는 불완전한 산화막의 생성으로 인해 탄성계수 및 경도값과 박막의 Weibull modulus를 극히 낮게 만들었지만, 60s, 90s 플라즈마 처리는 시료의 균일도를 높이고 또한 포텐셜을 증가시켜 T-OLED 성능 개선에 좋은 영향을 미치게 될 것이다.