• 천문학회지
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• 제37권5호
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• pp.381-385
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• 2004

Similarly to other cluster of galaxies previously classified as cooling flow systems, the Chandra observation of MKW 3s reveals that this object has a complex X-ray structure hosting both a X-ray cavity and a X-ray filament. Unlike the other clusters, however, the temperature map of the core of MKW 3s shows the presence of extended regions of gas heated above the radially averaged gas temperature at any radius. As the cluster does not show evidences for ongoing major mergers Mazzotta et al. suggest a connection between the heated gas and the activity of the central AGN. Nevertheless, due to the lack of high quality radio maps, this interpretation was controversial. In this paper we present the results of two new radio observations of MKW 3s at 1.28 GHz and 604 MHz obtained at the GMRT. Together with the Chandra observation and a separate VLA observation at 327 MHz from Young, we show unequivocal evidences for a close connection between the heated gas region and the AGN activity and we briefly summarize possible implications.

• 천문학회보
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• 제44권1호
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• pp.74.2-74.2
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• 2019

Mass measurement of high-redshift galaxy clusters with high accuracy is important in constraining cosmological parameters. Extremely massive clusters at high redshift may impose a serious tension with the current ΛCDM paradigm. SPT-CL J2040-4451 at z=1.48 is considered one such case given its redshift and mass estimate inferred from the SZ data. The system has also been confirmed to be indeed massive from a recent weak-lensing (WL) analysis. Comparison of the WL mass with the spectroscopic result may provide invaluable information on the dynamical stage of the system. However, the existing spectroscopic coverage of the cluster is extremely poor; only 6 blue star-forming galaxies have been found within the virial radius, which results in highly inflated and biased velocity dispersion. In this work, we present a spectroscopic analysis of the member candidates using Gemini Multi-Object Spectrographs (GMOS) observation in Gemini South. The observation was designed to find early-type member galaxies within the virial radius and to obtain reliable velocity dispersion. We explain our selection scheme and preliminary results of the spectra. We also compare the dynamical mass estimate inferred from the velocity dispersion with the WL mass.

• 천문학회보
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• 제45권1호
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• pp.29.5-30
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• 2020

We present an improved weak-lensing (WL) study of the high-z (z=0.87) merging galaxy cluster ACT-CL J0102-4915 ("El Gordo"), the most massive system known to date at z > 0.6. El Gordo has been known to be an exceptionally massive and rare cluster for its redshift in the current ΛCDM cosmology. Previous multi-wavelength studies have also found that the cluster might be undergoing a merging event showing two distinctive mass clumps and radio relics. The previous WL study revealed a clear bimodal mass structure and found that the entire system is indeed massive (M200a = (3.13 ± 0.56) × 1015 Msun). This mass estimate, however, was obtained by extrapolation because the previous HST observation did not extend out to the virial radius of the cluster. In this work, we determine a more accurate mass estimate of the cluster using WL analysis utilizing a new set of WFC3/IR and wide-field ACS observations. While confirming the previous bimodal mass structure, we find that the new data yield a ~20% lower mass for the entire system (M200a = (2.37 ± 0.28) × 1015 Msun). We also discuss the rarity of the cluster in the ΛCDM paradigm and suggest an updated merging scenario based on our new measurement.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 1999년도 한국우주과학회보 제8권2호
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• pp.16-16
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• 1999

No Abstract, See Full Text

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2000년도 추계총회,초청강연,특별강연,연구발표회
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• pp.186.1-186
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• 2000

• 천문학회보
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• 제37권2호
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• pp.72.1-72.1
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• 2012

Sheen et al. 2012 reported a high fraction of galaxies with post-merger features in clusters. The fraction is much higher than what analytic calculation predicts based on the fact that subhalos inside galaxy clusters have high relative velocities. In this study, we aim to address the origin of the post-merger features and to draw an implication for the assembly history of the cluster galaxies. We have performed high-resolution hydrodynamic zoom-in simulations on a cluster of ~1015M using the publicly available Adaptive Mesh Refinements (AMR) code, RAMSES. From the simulations, we have constructed mock images of cluster galaxies taking into account age, metallicity, mass of stellar populations and extinction. The mock images enable us to directly compare the simulation result with deep observation data of cluster galaxies. We discuss possible scenarios for the origin of the post-merger features. We also discuss caveats and future perspectives from the study.

• 한국수자원학회논문집
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• 제43권1호
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• pp.15-24
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• 2010

최근에는 확률강우량을 산정할 경우 지점빈도해석의 단점을 보완한 지역빈도해석법이 자주 실무에 적용되고 있으나, 가뭄에 관련한 연구에서는 대부분 아직까지 지점자료를 이용한 가뭄분석을 실시하고 있다. 본 연구에서는 가뭄의 지역적 특성 분석을 실시하기 위하여 필요한 동질한 가뭄특성을 지닌 지역을 구분하는 연구를 수행하였다. 본 연구에서는 기상청 강우관측 지점자료 중 30년 이상의 강우자료를 보유한 58개의 관측지점을 대상으로 표준강수지수(SPI)를 산정하여 가뭄의 심도, 지속기간, 강도, 발생빈도 등과 같은 가뭄특성인자를 생성하였다. 가뭄특성인자는 수문학적으로 동질한 특성을 지닌 지역을 구분하는데 중요한 정보를 제공한다. 본 연구에서는 다양한 가뭄특성인자를 효율적으로 활용하여 K-means 기법을 적용한 군집분석을 실시하여 동질한 가뭄특성을 지닌 지역을 6개 지역으로 구분하였다. 이러한 지역구분은 가뭄 특성의 공간적 해석을 가능하게 할 수 있고, 지점빈도 해석의 단점을 보완하는 지역빈도 해석도 가능하게 할 수 있다.

• 한국음향학회지
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• 제14권5호
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• pp.5-10
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• 1995

본 논문에서는 단어를 발음하는 방법 이 각각 다른 화자들의 변이성을 잘 흡수하도록 복수개의 통계적인 모델들을 구성하기 위하여 HMM을 기본으로 하는 집단화 방법을 제시한다. 또한 개발된 방법으로부터 얻어진 HMM집단화된 모델들이 불특정화자 고립단어 인식에 응용된다. HMM 집단화 방법은 학습용 데이타로부터 어떤 경계치 보다 낮은 유사도를 갖는 관측열들을 분리하여 새로운 집단을 만들고 이 집단내에 있는 관측열들을 이용하여 새로운 모델들을 학습시키는 방법이다. 집단화 과정은 반복되는데 최고의 유사도를 갖는 모델의 집단에 관측열들을 재분배하고 집단내 관측열들이 변화하면 새로운 모델을 재 추정하여 기존의 모델을 대신한다. 그러므로 이 집단화 방법은 집단화 과정과 파라미터 추정이 일체화되어 기존의 패턴에 의한 집단화 방법보다 더욱 효율적이 된다. 실험결과 HMM에 의한 집단화 방법이 기존의 패턴에 의한 집단화 방법보다. 고립 숫자음 인식에 있어서 $1.43\%$의 인식률을 향상시킬 수 있었으며 단일 모델의 사용보다는 $2.08\%$의 인식률이 향상되었다.

• 천문학회보
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• 제46권1호
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• pp.49.4-49.4
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• 2021

We Present a B and V band time-series CCD photometry of the Delta scuti stars, BV Cnc, BN Cnc, BU Cnc, BS Cnc, in the open cluster M44. The observation was carried out for 36 nights between February, 2020 and February 2021 with a 0.6m telescope equipped 2K CCD camera at Gyeonggi Science High School for the Gifted(GSHS). To detect pulsational frequencies, we wuse Discret Fourier Transformation(DFT) method. We have detected resonable pulsational frequencis compare to previous study.

• 한국초등과학교육학회지:초등과학교육
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• 제34권4호
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• pp.458-475
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• 2015

The purpose of this study was to analyze the responses of pre-service elementary teachers to the plant learning using plant-observation activities and observation journal writings. Thirty pre-service teachers participated in this study. Before and after practicing plant observation and observation journal writing for 11 weeks, pre-service teachers' interest to plants, attitude to plant-observation teaching, and plant-observation teaching efficacy were examined using a questionnaire. Also, the observation journals, reflective journal writings, and interviews were analyzed to investigate their qualitative change. In addition, the pre-service teachers were classified by multi-dimensional scaling and cluster analysis with respect to attitude to plant-observation teaching and observation journal writing, and teaching efficacy. While the pre-service teachers showed significant increase of the interest to plants and plant-observation teaching efficacy, and positive change of the attitude to plant-observation teaching, there was a little difference between gender with more positive effects on females. The positive attitude changes of pre-service teachers included positive recognition about plants and the diversity, increased interest and curiosity about plants, careful observation about nearby plants, and independent learning and positive inquiry with plants. In terms of teaching efficacy, they showed positive change such as enjoyment and satisfaction with plant-observation, confidence as elementary teachers in the future, and recognition about the importance of elementary teachers for plant education. However, the changes were different among the groups classified by attitude to plant-observation teaching and observation journal writings, and plant-observation teaching efficacy.