• 천문학회보
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• 제45권1호
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• pp.63.2-63.2
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• 2020

FLASH is a blind neutral hydrogen (HI) absorption line survey, eventually targeting about 100,000 background radio continuum sources in the entire southern sky using the full 36-antenna of the Australian Square Kilometre Array Pathfinder (ASKAP). Our primary goal is to search for associated and intervening HI absorption lines in the intermediate redshift range 0.4 < z < 1.0. The survey aims to understand the evolution of HI gas in galaxies as well as various physical mechanisms in active galactic nuclei, such as accretion and feedback processes. In this poster, we give an overview of the FLASH survey and present the preliminary results from our first 100-hrs of pilot observations. The latest survey data covers 1,000 square degrees and is ideal for validating observation and data processing in the continuous 300MHz-width low frequency ASKAP band (700-1000MHz). One of the crucial objectives of the pilot survey is to establish the analysis methodology that will be applied to upcoming large absorption surveys in the future. We discuss our data quality validation and present some detections of associated/intervening HI absorption lines. These absorption lines allow us to trace the cold gas properties of active and normal galaxies at higher redshifts where the HI emission line is too weak to be detectable.

• Journal of Electrical Engineering and information Science
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• 제1권2호
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• pp.134-144
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• 1996

In this paper, we propose a new access method, called the HG-tree, to support indexing and retrieval by image content in large image databases. Image content is represented by a point in a multidimensional feature space. The types of queries considered are the range query and the nearest-neighbor query, both in a multidimensional space. Our goals are twofold: increasing the storage utilization and decreasing the area covered by the directory regions of the index tree. The high storage utilization and the small directory area reduce the number of nodes that have to be touched during the query processing. The first goal is achieved by absorbing splitting if possible, and when splitting is necessary, converting two nodes to three. The second goal is achieved by maintaining the area occupied by the directory region minimally on the directory nodes. We note that there is a trade-off between the two design goals, but the HG-tree is so flexible that it can control the trade-off. We present the design of our access method and associated algorithms. In addition, we report the results of a series of tests, comparing the proposed access method with the buddy-tree, which is one of the most successful point access methods for a multidimensional space. The results show the superiority of our method.

• 전자공학회논문지S
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• 제35S권4호
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• pp.10-19
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• 1998

With the advent of high-speed networks, the increasingly stringent performance requeirements are being placed on the underlying switching systems. Under these circumstances, simulation methods for evaluating the performace of such a switch requires vast computational cost and accordingly the importance of anlytical methods increases. In general, the performance analysis of a switch architecture is also a very difficult task in that the conventional queueing system such as switching systems, which consists of a large numbe of queues which interact with each other in a fiarly complicated manner. To overcome these difficulties, most of the past research results assumed that multiple queues become decoupled as the switch size grows unboundely large, which enables the conventional queueing theory to be applied. In this apepr, w analyze a non-blocking space-division ATM swtich with input queueing, and prove analytically the pheonomenon that virtual queues formed by the head-of-line cells become decoupled as the switch size grows unboundedly large. We also establish various properties of the limiting queue size processes so obtained and compute the maximum throughput associated with ATM switches with input queueing.

• 한국공간구조학회논문집
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• 제7권2호
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• pp.97-104
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• 2007

최근 산업 발전과 더불어 대공간 건축물의 수요가 급증하고 있다. 이 분야 선진 기술은 지간 300m 이상의 대공간 건축물 실현도 가능하게 하고 있다. 대공간 구조에는 쉘구조, 스페이스 프레임 구조, 막구조, 케이블구조 등이 있다. 대공간 건축물은 기둥 없이 넓은 공간을 확보해야 하는 구조적 특성 때문에 설계초기 단계에서부터 시공문제를 병행하여 검토할 필요가 있다. 대공간 건축물 시공에 있어서 erection 공법은 공사비용, 공사기간 그리고 안전성 등에 큰 영향을 주는 것으로 알려져 있다. 대공간 건축물 erection 공법은 현장 여건 및 제반 조건에 따라서 그 수를 헤아릴 수 없을 정도로 많고 다양하지만, 대표적인 공법으로는 Element 방식, Block 방식, Sliding 방식, Lift-up 방식 그리고 복합방식 등이 있다. 본 연구에서는 기존 대공간 건축물을 대상으로 시공당시 적용한 erection공법을 조사하여 이것을 규모별, span별, 층고별, 구조형식별로 분석 및 검토하여 향후 대공간 건축물의 효율적 erection 공법 개발을 위한 기초 자료를 제공하는데 그 목적이 있다.

• Journal of Astronomy and Space Sciences
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• 제34권3호
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• pp.199-205
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• 2017

A high resolution spectroscopic observation of the red supergiant star RM_1-390 in the Large Magellanic Cloud was made from a 3.6 m telescope at the European Southern Observatory. Spectral resolving power was R=20,000, with a signal-to-noise ratio S/N > 100. We found the atmospheric parameters of RM_1-390 to be as follows: the effective temperature $T_{eff}=4,250{\pm}50K$, the surface gravity ${\log}\;g=0.16{\pm}0.1$, the microturbulent velocity $v_{micro}=2.5km/s$, the macroturbulence velocity $v_{macro}=9km/s$ and the iron abundance $[Fe/H]=-0.73{\pm}0.11$. The abundances of 18 chemical elements from silicon to thorium in the atmosphere of RM_1-390 were found using the spectrum synthesis method. The relative deficiencies of all elements are close to that of iron. The fit of abundance pattern by the solar system distribution of r- and s-element isotopes shows the importance of the s-process. The plot of relative abundances as a function of second ionization potentials of corresponding chemical elements allows us to find a possibility of convective energy transport in the photosphere of RM_1-390.

• 한국항공우주학회지
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• 제36권8호
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• pp.734-739
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• 2008

본 논문에서는 미시 및 중시 역학의 2-단계 해석 전략을 채택하여 유연직물 복합재료의 기계적 거동을 예측하였다. 미시역학에서는 섬유다발의 유효물성치를 계산하였고 그 결과를 이용해 중시역학에서 유연직물복합재료의 인장탄성계수를 예측하였다. 중시역학 해석 과정에서는 섬유다발의 회전 및 전단 대변형에 의한 기하학적 비선형성을 고려하기 위하여 사용자 정의 부프로그램을 개발하여 ABAQUS 내에 삽입하였다. 해석결과, 인장하중을 받는 유연직물복합재료의 응력-변형률은 비선형 거동을 보였고, 계산된 유효탄성계수는 시험값과 잘 일치하는 것으로 나타났다.

• 로봇학회논문지
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• 제7권1호
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• pp.29-34
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• 2012

This paper suggests a new observation model for Extended Kalman Filter based Simultaneous Localization and Mapping (EKF-SLAM). Since the EKF framework linearizes non-linear functions around the current estimate, the conventional line model has large linearization errors when a mobile robot locates faraway from its initial position. On the other hand, the model that we propose yields less linearization error with respect to the landmark position and thus suitable in a large-scale environment. To achieve it, we build up a three-dimensional space by adding a virtual axis to the robot's two-dimensional coordinate system and extract a plane by using a detected line on the two-dimensional space and the virtual axis. Since Jacobian matrix with respect to the landmark position has small value, we can estimate the position of landmarks better than the conventional line model. The simulation results verify that the new model yields less linearization errors than the conventional line model.

• 한국주거학회논문집
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• 제17권5호
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• pp.137-146
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• 2006

This study was aimed to analyze the influences of urban expansion by developing a new large scale residential district on changes of whole urban spatial structure. For the analysis, time serial analysis was conducted on the Daejeon Metropolitan City by using the space syntax method. The results of the study are as follows ; First, an expansion of urban area led to lower both of the local and global integration levels, second, the spatial occupation ratio of upper 10% in the whole integration showed that old city center was separated, and moved to the Dunsan District, third, the results also showed that an integration of the old city center region maintained a high level in spite of a movement of city center and its local integration still had highest level so that the old city center will take one of the two city center roles together with Dunsan District.

• 한국화재소방학회논문지
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• 제18권3호
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• pp.108-113
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• 2004

백화점, 할인매장과 같이 불특정 다수가 이용하는 대규모 판매시설은 화재시 방화관리 담당자의 비상대응능력 및 방화관리의 적절성이 내부 공간에 익숙하지 않은 고객의 피난행동에 결정적인 영향을 미치게 된다. 특히 대규모 판매시설의 경우 대부분의 피난계단 등 안전한 피난출구가 평상시 고객이 접근할 수 없는 백스페이스(Back space)에 위치하기 때문에 고객의 안전한 피난을 위해서는 방화관리자에 의한 신속한 피난개시 및 적절한 피난유도가 이루어져야 한다. 본 연구에서는 백화점과 할인매장 방화관리 담당자를 대상으로 한 설문조사를 통하여 방화관리측면에서 피난행동에 영향을 미치는 요인 및 화재 시 방화관리자의 대응행동 특성에 대하여 분석하였다.

• 한국항공우주학회지
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• 제37권9호
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• pp.863-878
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• 2009

초음속 주 유동내 연료의 수직분사에 따른 비정상 3차원 유동장을 DES 난류 모델을 이용해 모사하였다. 해석 결과는 시간에 따른 에디 거동 및 생성 빈도에 대해 실험과 비교되었으며, 에디 생성 메커니즘을 이해하기 위해 분사기 주변 와도에 대한 분석을 수행하였다. DES 난류 모델은 에디의 대류 특성을 비교적 정확하게 모사하고 있으나, 에디 생성빈도는 다소 과대 예측하고 있다. 분사기 상류 재순환 영역에서 엇회전하는 와류가 번갈아 떨어져 나가면서 에디 구조가 생성된다.