• 대한전기학회논문지:시스템및제어부문D
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• 제55권5호
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• pp.199-204
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• 2006

To develop a safety-critical network in nuclear power plants that puts more stringent requirements than the competitive commercial ones do, we establish four design criteria - deterministic communication, explicit separation/isolation structure, reliability, verification & validation. According to those design criteria, the fundamental design elements are chosen as follows - a star topology, point-to-point physical link, connection-oriented link control and fixed allocation access control. After analyzing the design elements, we also build a communication architecture with TDM (Time Division Multiplexing) bus switching scheme. Finally, We develop a DDCNet (Deterministic Data Communication Network) based on the established architecture. The DDCNet is composed of 64 nodes and guarantees the transmission bandwidth of 10Mbps and the delay of 10 msec for each node. It turns out that the DDCNet satisfies the aforementioned design criteria and can be adequately utilized for our purpose.

• 천문학회보
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• 제39권2호
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• pp.59.1-59.1
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• 2014

AGN feedback has been believed as playing an important role in the galaxy-super massive black hole (SMBH) co-evolution. AGN gas outflow can lead to AGN feedback. We investigate gas outflow of low-redshift AGNs by using blue shift/asymmetric index (BAI), and velocity offset of CIV line. By comparing these gas outflow indicators (BAI and velocity offset) to AGN properties (i.e., SMBH mass, bolometric luminosity, and Eddington ratio) and BLR gas metallicity, we find positive correlations among outflow, Eddington ratio, and metallicity. These relations are consistent with those observed at high-redshift. We discuss the possibility of the connection between previous star formation with current AGN accretion and outflow.

• KIEAE Journal
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• 제4권3호
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• pp.87-94
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• 2004

The purpose of this study is to improve thermal environment of telecommunication equipment rooms that hold TDX-10, TDX-100, 5ESS-2000, PCM of the latest telecommunication equipment. Analysis program is used the commercial CFD code, Star-CD and DOE-2.1E. The result has been compared by the energy consumption and the temperature contour at the 1 m height of room for each case. Different methods such as the relocation of the existing air-conditioner, the inflow of the ambient air into room, the installation of the forced fan and the cooling system equipment of the duct-connection type have been used to test for improvement of thermal environment. The analysis shows that most efficient method is the inflow of the ambient air into room but auxiliary equipment should be needed to prevent the local thermal spot.

• Journal of Power Electronics
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• 제12권5호
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• pp.739-747
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• 2012

This paper applies carrier phase shifted pulse-width modulation (CPS-PWM) to transformerless modular multilevel converters (MMC) to improve the output spectrum. Because the MMC topology is characterized by the double-star connection of six legs consisting of cascaded modular chopper cells with floating capacitors, the balance control of the DC-link capacitor voltage is essential for safe operation. This paper presents a leg-balancing control strategy to achieve DC-link voltage balance under all operating conditions. This strategy based on circulating current decoupling control focused on DC-link balancing between the upper and lower legs in each phase pair by considering the six legs as three independent phase-pairs. Experiments are implemented on a 100-V 3-kVA downscaled prototype. The experimental results show that the proposed leg-balancing control is both effective and practical.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2002년도 가을 학술발표논문집 Vol.29 No.2 (1)
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• pp.136-138
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• 2002

관계형 OLAP 시스템에서는 다차원 분석에 사용될 데이터를 하나의 사실과 여러 개의 차원 테이블로 구성된 스타 스키마로 표현한다. 사실 테이블은 측정치의 속성을 포함하며, 차원 테이블들은 이러한 사실 테이블에서 중심으로 뻗어져 나온 형태로써, 측정치에 대한 정보를 제공한다. 방대한 크기의 OLTP 소스 데이타베이스로부터 사실과 차원 테이블로 구성된 스타 스키마 설계하기 위해서는 풍부한 경험과 많은 시간을 필요로 한다. 따라서 스타 스키마를 효과적으로 설계하기 위한 체계적인 설계 방법이 필요하다. 본 논문에서는 소스 데이터베이스들에 대한 개념적 모델인 ER 도형을 이용하여 여러 개의 사실 엔터티를 추출하는 알고리즘과 이를 통해 자동적으로 스타 스키마를 설계하는 알고리즘을 제시하였다. 스타 스키마가 하나의 사실 테이블에 여러 개의 차원 테이블이 M:1의 관계로 연결되었다는 성질을 활용하여, 이 방법에서는 EH 도형이 연결된 위상 구조를 이용하여 각 엔터티에 연결된 M:1 관계의 개수에 근거하여 사실과 차원을 추출하는 방법을 제시하였다. 본 논문에는 이러한 방법을 통해 데이터 웨어하우스의 스타 스키마들 자동적으로 쉽게 설계하여 소요되는 시간과 노력을 줄일 수 있도록 하였다.

• 천문학회보
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• 제46권1호
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• pp.30.2-30.2
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• 2021

The extended Lyα nebulae (also known as Lyα blobs or LABs) observed at z=2-6 can provide clues to galaxy formation in the early universe. The connection of LABs with the overdensities of compact Lyα emitters suggests that they are associated with matter density peaks in the universe and thus likely to evolve into the present-day groups and clusters of galaxies. However, the mechanism powering the extended Lyα emission in LABs is remained controversial. The detection of polarization signals that follow the theoretically predicted trend is interpreted as strong evidence supporting that the LABs are caused primarily by the resonance scattering of Lyα originating from star-forming galaxies and AGNs. However, Trebitsch et al. (2016) claimed that the radial profile of polarization could be better explained by the scenario in which Lyα photons are produced in the cooling gas surrounding galaxies and then self-scattered by the gas, rather than by the scattering scenario of photons originating from the central galaxies. In this presentation, using LaRT, a state-of-art Lyα radiative transfer code, it is demonstrated that the observed polarization pattern can be reproduced even with the scattering scenario.

• 천문학논총
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• 제27권4호
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• pp.281-284
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• 2012

We utilize AKARI's slitless spectroscopic capability to detect the $3.3{\mu}m$ polycyclic aromatic hydrocarbons (PAHs) emission and measure star formation (SF) activity for various AKARI programs. First, we obtain $2{\sim}5{\mu}m$ spectra of 20 flux-limited galaxies with mixed SED classes in order to calibrate the $3.3{\mu}m$ PAH luminosity ($L_{PAH3.3}$) as a star formation rate (SFR) indicator. We find that $L_{PAH3.3}$ correlates with $L_{IR}$ as well as with the $6.2{\mu}m$ PAH luminosity ($L_{PAH6.2}$). The correlations does not depend on SED classes. We find that ULIRGs deviate from the correlation between PAH luminosities and $L_{IR}$, while they do not for the correlation between PAH luminosities. We suggest possible effects to cause this deviation. On the other hand, how AGN activity is linked to SB activity is one of the most intriguing questions. While it is suggested that AGN luminosity of quasars correlates with starburst (SB) luminosity, it is still unclear how AGN activity is connected to SF activity based on host galaxy properties. We are measuring SFRs for the LQSONG sample consisting of reverberation mapped AGNs and PG-QSOs. This is an extension of the ASCSG program by which we investigated the connection between SB and AGN activities for Seyferts type 1s at z ~ 0.36. While we found no strong correlation between $L_{PAH3.3}$ and AGN luminosity for these Seyferts 1s, $L_{PAH3.3}$ measured from the central part of galaxies correlates with AGN luminosity, implying that SB and AGN activities are directly connected in the nuclear region.

• 한국철도학회논문집
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• 제12권4호
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• pp.457-464
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• 2009

디젤 엔진 매연 필터의 입구부와 배출 가스 배출을 위한 배기관 연결을 직선 또는 곡선으로 형태로 연결하였을 때의 DPF 입구 유속 분포를 $STAR-CD^{(R)}$ 전산해석 프로그램을 사용하여 시뮬레이션하였다. 곡관의 형상을 나타내는 3 종류의 수치해석 용 격자 모델을 사용하여 DPF 입구에서의 유속 분포를 시뮬레이션 하였다. 피토관을 2차원 이송장치에 탑재하고 위치를 이동시키며 측정한 유속 분포와 동일한 조건에서 시뮬레이션한 결과와 비교하였다. DPF 입구와 $90^{\circ}$의 곡관이 연결된 조건에서 CFD 해석을 수행한 결과 입구 단면에서의 유속 분포가 말발굽 형태를 나타내었으며 최대 유속값이 DPF 중심축에서 약간 벗어난 위치에서 나타나고 있다. 이러한 CFD 해석결과는 실험 결과와 비교적 잘 일치하였다.

• 한국항공우주학회지
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• 제46권7호
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• pp.551-556
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• 2018

인공위성의 자세제어를 수행하기 위해 다양한 하드웨어들이 탑재된다. 그중에서 가장 초기에 위성의 안정된 자세를 확보하며 이상동작시 안전한 자세를 확보하기 위해 사용되는 중요한 하드웨어가 바로 태양센서이다. 따라서, 위성의 개발 초기에 해당 센서의 시야각 확보를 위한 장착과 이를 이용한 자세제어 설계가 매우 중요한 역할을 담당한다. 정지궤도복합위성은 별추적기 탑재로 인해 천리안위성 대비 태양센서의 전체 수량을 축소할 수 있었다. 그리고 천리안위성의 우주이력을 이용한 여분의 하드웨어를 추가로 고려하였다. 본 논문에서는 추가된 태양센서를 통해 시야각을 확장하고 P/R-side 결선도 고려하여 안정도를 높이는 방법에 대해 분석하고 그 결과를 정리하였다.

• 천문학회보
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• 제40권1호
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• pp.79.3-80
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• 2015

Galaxy overdensities such as galaxy clusters and superclusters are the largest gravitationally bound systems in the Universe. Since they contain many different levels of local densities, they are excellent places to test galaxy evolution models in connection to the environments. The environment studies of galaxies at z ~ 1 are important because the environmental quenching seems to be an important mechanism to reduce star formation activities in galaxies at z < 1. However, there have been not many studies about high redshift galaxy clusters at z ~ 1 because of the lack of wide and deep multi-wavelength data. We have used the multi-wavelength data from the UKIDSS DXS (J and K band), the SWIRE (4 IRAC bands), and the PAN-STARRS (g, r, i, z, y bands) in the ELAIS-N1 field. We identified galaxy cluster candidates at 0.2 < z < 1.6 using the multi-wavelength data. We found several superclusters where cluster candidates are concentrated on few tens of Mpc scale. Interestingly, some of the supercluster candidates consist of galaxy clusters which have high blue galaxy. We will present high redshift galaxy cluster and supercluster candidates in ELAIS-N1 field and galaxy properties in different environments including dense clusters and fields.