• 천문학회보
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• 제46권2호
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• pp.43.2-43.2
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• 2021

Ram-pressure stripping (RPS) is known as the main driver of quenching the star formation (SF) activity in cluster galaxies. However, galaxies undergoing RPS in galaxy clusters often show blue star-forming knots in their disturbed disks and tails. The existence of these "jellyfish galaxies" implies that RPS can temporarily boost the SF activity of cluster galaxies. Thus, jellyfish galaxies are very unique and interesting targets to study the influence of RPS on their SF activity, in particular with integral field spectroscopy (IFS). While there have been many IFS studies of jellyfish galaxies in low-mass clusters (e.g., the GASP survey), IFS studies of those in massive clusters have been lacking. We present an IFS study of five jellyfish galaxies in massive clusters at intermediate redshifts using the Gemini GMOS/IFU. Their star formation rates (SFRs) are estimated to be up to 15 Mo/yr in the tails and 50 Mo/yr in the disks. These SFRs are by a factor of 10 higher than those of star-forming galaxies on the main sequence in the M*-SFR relation at similar redshifts. Our results suggest that the SF activity of jellyfish galaxies tends to be more enhanced in massive clusters than in low-mass clusters. This implies that strong RPS in massive clusters can trigger strong starbursts.

• Tuberculosis and Respiratory Diseases
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• 제61권5호
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• pp.456-462
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• 2006

연구배경: 대량 흉수의 가장 흔한 원인은 악성으로 알려졌으나 이에 대한 보고가 많지 않고, 지역 및 시대에 따라 다른 분포를 보였다. 저자들은 결핵의 유병율이 높은 국내에서 대량 흉수의 원인 질환의 분포를 알아보고, 원인 질환 감별을 위한 흉수의 분석지표에 대해 알아보기 위해 연구를 시행하였다. 방 법: 2002년 7월부터 2005년 7월까지 한양대학교 구리병원에 입원하여 흉수 천자를 시행하였던 298명 환자를 대상으로 후향적 조사를 시행하였다. 대량 흉수는 흉부단순촬영에서 일측 흉곽의 2/3 이상을 차지한 경우로 정의하였고 각 환자에서 혈청 생화학 검사, 흉수 천자 소견을 비교하였다. 결 과: 전체 298명의 흉수 예 중 대량 흉수는 41예, 13.8% 이었다. 대량 흉수의 원인으로는 악성 흉수가 19예(46.3%)로 가장 많았고 결핵 15예(36.6%), 부폐렴성 흉막염 및 농흉 4예(9.8%), 여출성 흉수 3예(7.3%) 순이었다. 대량 흉수 중 악성 흉수(n=19)와 양성 흉수군(n=22)의 비교 시 악성 흉수에서 ADA가 낮고(30.5 vs 86.2;p=0.017), amylase 수치가 높았다(349.0 vs 39.2;p=0.031). 흉수 적혈구는 악성 흉수 군에서 높은 경향을 보였다(95,406 vs 22,105;p=0.052). 결 론: 국내에서 대량 흉수의 원인으로는 악성 외에도 결핵에 의한 경우가 많았으며, ADA가 낮은 혈성 흉수는 악성을, ADA가 높은 림프구성 흉수는 결핵의 가능성을 고려해 볼 수 있겠다.

• 천문학회보
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• 제40권1호
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• pp.76.1-76.1
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• 2015

We study the environmental dependence of the mass-size relation especially for the most massive early type galaxies (M>$10^{11.2}M_{\odot}$) in the redshift range 0.15~0.25. As a measure of the environment, galaxy number densities are measured by the $10^{th}$ nearest galaxies within 7000km/s from galaxies with spectroscopic redshifts. We find that galaxies more massive than $10^{11.6}M_{\odot}$ show the environmental dependence in the mass-size relation. The galaxies with M>$10^{11.6}M_{\odot}$ located in the densest, cluster like environment have larger sizes than their counterparts located in a low dense environment. We also find that this environmental dependence of the mass-size relation originates from the brightest cluster galaxies (BCG) rather than non-BCG galaxies. Our result can be explained with a hierarchical growth of the most massive galaxies through dissipation-less merger in dense environments.

• 천문학회보
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• 제40권1호
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• pp.41.1-41.1
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• 2015

Hierarchical galaxy formation models under LCDM cosmology predict that the most massive structures such as galaxy clusters (M > $10^{14}M_{\odot}$) appear late (z < 1) in the history of the universe through hierarchical clustering of small objects. Galaxy formation is also expected to be accelerated in overdense environments, with the star formation rate-density relation to be established at z ~ 2. In this talk, we present our search of massive structures of galaxies at 0.7 < z < 4, using the data from GOODS survey and our own imaging survey, Infrared Medium-deep Survey (IMS). From these studies, we find that there are excess of massive structures of galaxies at z > 2 in comparison to the Millennium simulation data. At 1 < z < 2, the number density of massive structures is consistent with the simulation data, but the star formation history is more or less identical between field and cluster. The star formation quenching process is dominated by internal process (stellar mass). The environmental effect becomes important only at z < 1, which contributes to create the well known star formation-density relation in the local universe. Our results suggest that galaxy formation models under LCDM cosmology may require further refinements to match the observation.

• 천문학회보
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• 제40권1호
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• pp.46.3-46.3
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• 2015

As theoretical and empirical studies have pointed out, galaxy mergers play a pivotal role in galaxy mass assembly histories. Its contribution is considered to be more significant in more massive galaxies. In order to quantitatively understand the origin of stellar components in galaxies, we investigated stellar mass assembly histories as a function of galaxy and halo mass using semi-analytic approaches. In this study, we found that the most massive galaxies (log $M/M_{\odot}$ ~ 11.75 at z = 0), which are mostly the brightest cluster galaxies, obtain roughly 70% of their stellar components via mergers. The role of mergers monotonically declines with galaxy mass: less than 20% for log $M/M_{\odot}$ = 10.75 at z = 0. The contribution of galaxy mergers to stellar mass growth decays more slowly than that of in-situ star formation. Therefore, merger accretion becomes a dominant channel for stellar mass growth of the most massive group since z~2. However, when it comes to central galaxies in haloes less massive than $10^{13}_{\odot}$, star formation is always dominant.

• 천문학회보
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• 제40권2호
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• pp.29.1-29.1
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• 2015

We study the environmental dependence of the mass-size relation for the most massive early type galaxies (M > $10^{10.7}M_{\odot}$) in the redshift range 0.10~0.15. As a measure of the environment, galaxy number densities are measured by the $10^{th}$ nearest galaxies within 6500km/s from galaxies with spectroscopic redshifts. The sizes of galaxies are measured by non-parametric method. We find that galaxies more massive than $10^{11.1}M_{\odot}$ show the environmental dependence in the mass-size relation. The galaxies with M > $10^{11.1}M_{\odot}$ located in the densest, cluster like environment have larger sizes and extended surface brightness profiles than their counterparts located in a low dense environment. We also find that the environmental dependence of the mass-size relation is more significant for the brightest cluster galaxies (BCGs) than non-BCGs. Our result can be explained with a hierarchical growth of the most massive galaxies through dissipation-less merger in dense environment.

• Tuberculosis and Respiratory Diseases
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• 제38권4호
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• pp.396-400
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• 1991

Massive and untreated hemoptysis is associated with a mortality of greater than 50 percents. Since the bleeding was from a bronchial arterial source in the vast majority of patients, embolization of the bronchial arteries has become an accepted treatment in the management of massive hemoptysis because it achieves immediate control of the patients. We have controlled massive hemoptysis in a case with selective bronchial arteral embolization with Gelfoam.

• 천문학논총
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• 제32권1호
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• pp.123-125
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• 2017

We present our AKARI study of massive star forming regions where a large-scale cloud-cloud collision possibly contributes to massive star formation. Our targets are Spitzer bubbles, which consist of two types of bubbles, closed and broken ones; the latter is a candidate of the objects created by cloud-cloud collisions. We performed mid- and far-infrared surface photometry toward Spitzer bubbles to obtain the relationship between the total infrared luminosity, $L_{IR}$, and the bubble radius, R. As a result, we find that $L_{IR}$ is roughly proportional to $R^{\beta}$ where ${\beta}=2.1{\pm}0.4$. Broken bubbles tend to have larger radii than closed bubbles for the same $L_{IR}$.

• 한국통신학회논문지
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• 제39A권9호
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• pp.566-568
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• 2014

본 논문에서는 대규모 MIMO 시스템을 위한 MMSE 기반 반복 연판정 간섭 제거 기법을 제안한다. 제안 기법은 기존 기법에서의 연산량 감소를 위해 Sherman-Morrison-Woodbury 식을 사용하여 매 Iteration 마다 단 한 번의 역행렬 계산으로 모든 송신 심볼의 MMSE 검출 벡터를 계산한다. 모의실험을 통해 제안 기법이 대규모 MIMO 시스템에서 기존 기법과 거의 동일한 BER을 달성함을 확인하였다.

• 천문학회지
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• 제48권3호
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• pp.191-194
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• 2015

Massive gravity provides a natural solution for the dark energy problem of cosmology and is also a candidate for resolving the dark matter problem. I demonstrate that, assuming reasonable scaling relations, massive gravity can provide for Milgrom’s law of gravity (or “modified Newtonian dynamics”) which is known to remove the need for particle dark matter from galactic dynamics. Milgrom’s law comes with a characteristic acceleration, Milgrom’s constant, which is observationally constrained to a₀ ≈ 1.1 × 10⁻¹⁰ ms⁻² . In the derivation presented here, this constant arises naturally from the cosmologically required mass of gravitons like , with Λ, H₀, and Ω_Λ being the cosmological constant, the Hubble constant, and the third cosmological parameter, respectively. My derivation suggests that massive gravity could be the mechanism behind both, dark matter and dark energy.