• 천문학회보
• /
• 제40권1호
• /
• pp.79.3-80
• /
• 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.

• 천문학회보
• /
• 제37권1호
• /
• pp.48.2-48.2
• /
• 2012

We present preliminary results of a statistical study on the nuclear activity of compact group galaxies. What triggers Active Galactic Nuclei (AGN) is still a puzzling problem. One of the suggested AGN triggering mechanisms is galaxy-galaxy interaction. Many simulations have shown that gas can be supplied to the center of galaxies during galaxy encounters. In this regard, compact groups of galaxies are an ideal laboratory for studying the connection between galaxy interaction and nuclear activity because of their high densities and low velocity dispersions. We study the environmental dependence of the activity in galactic nuclei using 59 compact groups in the SDSS DR6. Using the emission line data, we classify galaxies in the compact groups. We find that 19% of the compact group galaxies are pure star-forming nuclei, 10% as transition objects, and only 7% of the galaxies in compact groups show the nuclear activity. The AGN fraction of compact group is higher than galaxy clusters, but lower than field environment. Implications of this result will be discussed.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2007년도 추계학술대회 논문집
• /
• pp.468-475
• /
• 2007

The Steel deck a structural analysis in head plate form change the objective bridge which it sells it accomplished a detailed structural analysis from the research which it sees and Bulk-head plate it accomplished. The length rib where the fatigue crack which is considerable generally occurs, width rib connection department and the length rib side, the width rib side it compares principal stress in the object and it does to sleep. It applied the grudge element model which it describes consequently after words and a load and a boundary condition and it executed it compared a static test and principal stress. It grasped the stress conduct of the The Steel deck petal which it follows in hand weaving rib affix location and the affix location to sleep in order to analyze a same location Bulk-head the head and comparison considered. From the detailed section which is reinforced with the stress investigation result hand weaving rib of the location which is weak in structural analysis result fatigue crack of form star reinforcement details basic form and Bulk-head the form which is reinforced with the head plate compared to principal stress investigation hour it is judged at the section which separates most.

• 천문학회보
• /
• 제35권1호
• /
• pp.74.2-74.2
• /
• 2010

We present a multi-wavelength study of a supercluster in the NEP region at z=0.087, using AKARI (Infrared space telescope) NEP-Wide (5.8 deg2) survey which has obtained an unique IR imaging dataset with contiguous wavelength coverage from 2 to $24{\mu}m$, overcoming the Spitzer limitation of imaging capability at $10-20{\mu}m$. The NEP-Wide survey is also covered in other wavelength such as X-ray, Radio, GALEX UV in the archive, optical (BRI from Maidanak 1.5m and CFHT's MegaPrime), and NIR imaging data (JH from KPNO 2.1m), with nearly 1900 optical spectra, mostly obtained by our group using MMT/Hectospec and WIYN/Hydra. Armed with the multiwavelength datasets, we investigate the connection between IR properties of galaxies and their environments as a tool to understand the evolution of galaxies in a supercluster environment. Specific attention will be given to MIR emission which can trace star formation activities and passive phases right after post-starbursts, and its relation to other wavelength data.

• 대한교통학회:학술대회논문집
• /
• 대한교통학회 1998년도 제34회 추계 학술발표회
• /
• pp.452-452
• /
• 1998

1. 세계 항공시장의 동향 ○ 항공운송산업의 규제완화 및 항공자유화 추세의 확산 -78년 미국의 규제완화 이후 유럽, 대양주, 아시아 등으로 파급 ○ 미국의 항공자유의 정책(Open skies Policy)은 EU의 역대 완전자유화와 함께 세계항공시장의 자유화 촉진 ○ 항공사간 전략적 제휴의 확산 -British Connection, Star Alliance, Southern Comfort, Dutch Treat 등 4대 범세계적 제휴가 결성 또는 추진 중. 2. 우리나라 항공운송산업의 현황 ○ 세계 10위권 항공운송국가로 성장 -화물 세계5위, 여객 11위(97 ICAO통계) -김포공항은 97년 중 36.5백만명 처리로 세계9위 차지 ○ IMF체계의 영향과 경영수지 변화 추이 -98년 내국인 출국자는 감소하였으나, 외국인 관광객은 증가(10.8%) * 98. 1∼8전년대비 수송수요 국제선 17%, 국내선 26% 감소 -97년 양 항공사 적자규모 약 4,000억원으로 대폭 증가, 98상반기 회복추세. 3. 21세기 국제항공정책 방향 ○ 적극적인 항공시장 개방정책 추진과 역내 주요도시간 셔틀화 ○ 세계 주요 항공사와의 전략적 제휴를 지원하여 세계항공시장에서의 경쟁력 제고 * KAL-이, AAR-AA -인천국제공항의 HUB화 추진(민간 경영기법 도입, 항공개방정책 등) ○ 항공사가 최적의 노선망과 경제성을 갖도록 하는 적정 성장방안 강구 ○ 선진국 수준의 획기적 항공안정 체계 확립

• 천문학회보
• /
• 제37권2호
• /
• pp.74.2-74.2
• /
• 2012

Metallicity is an important tracer of star formation in galaxy evolution. Based on the flux ratios of broad emission lines, AGN metallicity has shown a correlation with AGN luminosity. However, it is not clear what physical parameter drives the observed correlation. Using a sample 69 Palomar-Green QSOs at low-z (z<0.5), we determine BLR gas metallicity from emission line flux ratios, i.e., N V1240/C IV1549, (Si IV1398+O IV1402)/C IV1549 and N V1240/He II1640 based on the UV spectra from the HST and IUE archives. We compare BLR gas metallicity with various AGN properties, i.e., black hole mass, AGN luminosity and Eddington ratio, in order to investigate physical connection between metal enrichment and AGN activity. In contrast to high-z QSOs, which show the correlation between metallicity and black hole mass, we find that the metallicity of low-z QSOs correlates with Eddington ratio, but not with black hole mass, suggesting that metallicity enrichment mechanism is different between low-z and high-z.

• Journal of Astronomy and Space Sciences
• /
• 제36권3호
• /
• pp.181-186
• /
• 2019

The attitude information of spacecraft can be obtained by the sensors attached to it using a star tracker, three-axis magnetometer, three-axis gyroscope, and a global positioning signal receiver. By using these sensors, the spacecraft can be maneuvered by actuators that generate torques. In particular, electromagnetic-torque bars can be used for attitude control and as a momentum-canceling instrument. The spacecraft momentum can be created by the current through the electrical circuits and coils. Thus, the current around the electromagnetic-torque bars is a critical factor for precisely controlling the spacecraft. In connection with these concerns, a solar-cell array can be considered to prevent generation of a magnetic dipole moment because the solar-cell array can introduce a large amount of current through the electrical wires. The maximum value of a magnetic dipole moment that cannot affect precise control is $0.25A{\cdot}m^2$, which takes into account the current that flows through the reaction-wheel assembly and the magnetic-torque current. In this study, we designed a 300-W solar cell array and presented an optimal wire-routing method to minimize the magnetic dipole moment for space applications. We verified our proposed method by simulation.

• 대한지구과학교육학회지
• /
• 제13권3호
• /
• pp.297-304
• /
• 2020

이 연구의 목적은 지구의 공전 실험에 대해 알아보고, 학교 급별로 효과적인 지구의 공전 실험이 무엇인지 알아보는데 있다. 연구자는 지구의 공전을 학습할 수 있는 8가지의 실험 방법을 조사 또는 개발하였다. 초등 예비교사 26명에게 이 실험을 실시하고 토의하도록 한 후, 학교 급별로 효과적인 지구의 공전 실험을 선택하고 이유를 쓰도록 하였다. 그 결과 초등학교에서는 계절별 별자리가 달라지는 실험, 중·고등학교에서는 계절별 별의 스펙트럼을 비교하는 실험, 대학교에서 외행성의 역행운동이 효과적이라고 선택하였다. 예비교사는 직접 체험의 가능 여부, 교과 내용과 연계되는 정도, 배경지식과 고차원적인 사고의 정도를 실험 선택의 이유로 제시하였다.

• 한국통신학회논문지
• /
• 제37권1C호
• /
• pp.89-96
• /
• 2012

최근에 전술 무기의 첨단화, 무인화 및 네트워크화에 따라서 무선 전술 데이터 네트워크의 생존성은 매우 중요하다. 본 논문에서는 무선 전술 데이터 네트워크에서 저고도 소형 무인항공기를 이용한 네트워크의 연결성 약화지역을 탐색하는 기법을 제안하였다. 본 논문에서는 간단한 polling 접속 기능을 갖는 소형 무인항공기를 사용하여 무선 전술 데이터 네트워크의 노드들과 접속을 통하여 네트워크의 형태를 파악하고, 파악된 네트워크 그래프를 라플라스 매트릭스로 변환한다. 변환된 라플라스 매트릭스의 eigenvalue를 찾아내는 방법에 기초하여 서브 네트워크를 정의하고 약화된 eigenvalue의 집합을 통하여 네트워크의 연결성 약화지역을 탐색하는 알고리즘을 제안하였다. 하나의 UAV를 사용한 경우 좁은 네트워크 및 광범위 네트워크의 연결성 약화지역을 제안 알고리즘을 사용하여 탐색 가능하였다. 제안된 알고리즘으로 탐색된 약화지역의 노드에 UAV 링크로 중계 기능을 한 경우, 성형 네트워크 및 MST(Minimum Spanning Tree) 알고리즘에 의한 네트워크와 비교하여 스루풋 성능이 우수함을 검증하였다. 본 기법은 무선 전술 네트워크의 연결성을 보장하는 기법에 적용 될 수 있을 것으로 기대된다.

• 천문학논총
• /
• 제27권4호
• /
• pp.285-286
• /
• 2012

We combine data from two all-sky surveys, the Swift/Burst Alert Telescope 22 Month Source Catalog and the AKARI Point Source Catalogue, in order to study the connection between the hard X-ray (> 10 keV) and infrared (IR) properties of local active galactic nuclei (AGN). We find two photometric diagnostics are useful for source classification: one is the X-ray luminosity vs. IR color diagram, in which type 1 radio-loud AGN are well isolated from other AGN. The second one uses the X-ray vs. IR color-color diagram as a redshift-independent indicator for identifying Compton-thick (CT) AGN. Importantly, CT AGN and starburst galaxies in composite systems can also be separated in this plane based upon their hard X-ray fluxes and dust temperatures. This diagram may be useful as a new indicator to classify objects in new surveys such as with WISE and NuSTAR.