• 한국지구과학회지
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• 제25권6호
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• pp.391-401
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• 2004

본 연구에서는 고등학생들의 지질구조에 대한 공간 능력을 향상시키기 위한 프로그램을 개발하고, 개발된 프로그램의 현장 적용효과를 분석하였다. 이 프로그램은 지질 공간 방향 인식 및 공간 시각화 인식 요소로 구성되어 있다. 개발된 학습 프로그램의 효과를 분석하기 위해 경기도에 소재하는 4개 고등학교 학생 60명을 연구대상으로 선정하였다. 또한 연구대상 학생들 중 4명을 대상으로 지질 공간개념 수준의 변화를 알아보기 위해 면담을 실시하였다. 본 연구에서 개발된 프로그램의 투입 결과, 학생들의 지질 공간개념 수준에 유의미한 변화를 보였다(p < 0.05). 또한 4명의 학생들의 면담결과 공간 시각화 과정을 거치는 학생들의 지질 공간 능력이 향상되었다.

• 천문학회보
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• 제36권1호
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• pp.33.1-33.1
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• 2011

The plasma sheet of the Earth's magnetosphere is a sheet of hot plasmas in the magnetotail region, dividing the two (northern and southern) lobes of the Earth's magnetic field. It is the key region that is often closely linked to various electromagnetic dynamics in the Earth's magnetosphere-ionosphere system. In particular, it is the region that is most crucial for substorms, which is one of the most dynamic phenomena in the Earth's magnetosphere. The question of substorm triggering remains highly controversial until today, and at the center of the controversy there are several critical physics issues of the plasma sheet. In this talk I will introduce some of the physics issues of the plasma sheet. The specific topics that this talk will cover are (i) the general properties of the plasma sheet, (ii) fast plasma jets and plasma transport problem, (iii) stability/instability problem, and (iv) effects of thin current sheet. I will also present some of our group's recent findings regarding these topics, as obtained by comprehensive analyses of various observational data. The level and content of this talk are designed to be comprehensible to not only space physicists but also the scientists in a related field such as solar and heliospheric physics.

• Journal of Astronomy and Space Sciences
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• 제35권2호
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• pp.75-81
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• 2018

Solar activity has an important impact not only on the intensity of cosmic rays but also on the environment of Earth. In the present paper, a coupled oscillator model is proposed to explain solar activity. This model can be used to naturally reduce the 89-year Gleissberg cycle. Furthermore, as an application of the coupled oscillator model, we herein attempt to apply the proposed model to El $Ni{\tilde{n}}o$-southern oscillation (ENSO). As a result, the 22-year oscillation of the Pacific Ocean is naturally explained. Finally, we search for a possible explanation for coupled oscillators in actual solar activity.

• 항공우주기술
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• 제3권1호
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• pp.86-96
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• 2004

우주 환경은 두꺼운 대기층에 의해 보호되는 지표 환경에서는 경험할 수 없는 여러 가지 위험 요소가 있다. 근 지구 궤도에서는 플라스마 대기 및 원자 산소 등에 의해 부식이 발생할 수 있으며, 강한 자외선과 입자 복사 등에 의해 위성을 구성하고 있는 재료나 전자 부품 등이 손상을 입을 수 있다. 따라서 위성의 설계 시에는 운용궤도에서 예상되는 환경요인을 적절히 예측하여 이에 대응하는 설계가 이루어지도록 해야 한다.

• 정보처리학회논문지D
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• 제18D권5호
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• pp.323-328
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• 2011

정확한 내용 기반 이미지 검색을 위하여 Earth mover's distance와 Optimal color composition distance와 같은 거리함수들이 제안되었다. 이 거리함수들은 정확도가 높은 검색 결과를 가져오지만 검색 시간이 매우 크기 때문에 대용량 데이터베이스에서 사용하기 어렵다는 문제점을 가지고 있다. 본 논문에서는 이러한 문제를 해결하기 위하여 선형 시간에 근사 Earth mover's distance를 구하기 위한 새로운 거리 함수를 제안한다. 제안하는 방법은 선형 시간에 두 이미지의 거리를 계산하기 위하여 공간 채움 곡선을 이용한다. 다양한 실험을 통하여 본 논문에서 제안하는 방법의 우수성을 검증한다. 실험 결과, 제안하는 기법이 Earth mover's distance에 비해 약 160배 정도의 검색 속도 향상 효과를 보이면서도 매우 유사한 결과를 검색하는 것으로 나타났다.

• 한국항공우주학회지
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• 제37권7호
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• pp.709-716
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• 2009

위성 궤도 자세는 위성 열설계에 영향을 주는 중요한 요소로서, 궤도 운용 자세에 대한 열적 조건을 정확히 파악하는 것을 필요로 한다. 본 연구에서는 저궤도 위성의 yaw motion의 운영 자세에 따른 우주 열환경의 변화와 열설계의 열적 영향을 검토하였다. 본 위성은 고정형의 태양 전지판을 가지고 있기 때문에 태양광 구간 동안에 태양지향(sun-pointing)자세를 유지하고, 위성에 장착되는 별센서인 별추적기의 가시 방향이 심층 우주방향을 향하도록 하기 위하여 위성의 길이 방향을 축으로 일정한 각속도로 회전을 하는 yaw motion을 하도록 운용된다. 이것은 위성이 정밀한 자세 제어의 성능을 발휘할 수 있도록 별추적기가 별의 시야각을 확보하기 위한 것이다. 또한 위성 열설계 측면에서는 이러한 운용을 위한 자세 변화에 따른 열적 영향을 파악하는 것을 필요로 한다. 연구에서는 위성의 열모델에 이러한 궤도 운용 자세를 반영한 후의 궤도 열해석을 통하여 이를 알아보고자 한다.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2010년도 한국우주과학회보 제19권1호
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• pp.40.4-41
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• 2010

Using magnetic field and plasma moment data obtained by THEMIS satellites(A, D, and E), we selected 203 fast flow events accompanied by dipolarization in the near-Earth region( X(GSM) = -7 ~ -12 RE) and statistically examined their properties. It was found that most of the fast flows show the maximum velocity between 1 minute before dipolarization onset and 2 minutes after onset and proceed earthward and duskward. We also found that only the flows with low velocity of less than 400 km/s are observed at X > -8 RE, while the high velocity flows(as well as low velocity flows) are observed at the further tailward region(X < -8 RE). And most of the tailward flows are slow regardless of distance at X(GSM) = -7 ~ -12 RE. On the other hand, if we consider the fast flow as a bubble (Pontius and Wolf, 1990), the entropy parameter, PV5/3 is an important factor to describe the plasma sheet dynamics. Thus we investigated the relationship between the flow velocity and the amount of change in PV5/3 before and after dipolarization onset and found out that the dipolarizations with more depleted entropy parameter tend to show higher flow velocity. Also we examined how the magnetic field at geosynchronous orbit responds to the fast flow accompanied by dipolarization in the near-earth plasma sheet, using the measurements from GOES 11 and 12 statellites. We found that most of the fast flows do not reach geosynchronous orbit as suggested by Ohtani et al. (2006).

• Geomechanics and Engineering
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• 제17권5호
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• pp.413-420
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• 2019

The changes in earth pressure and ground settlement due to underground excavation near an existing retaining wall were studied experimentally according to the separation distance between the underground excavation and the retaining wall. In addition, this study attempted to experimentally prove that the arching phenomenon occurred during the construction of the underground space. A model tank having 120 cm in length, 160 cm in height, and 40 cm in width was manufactured to simulate underground excavation through the use of five separated base wall bodies. The variation of earth pressure on the retaining wall was measured according to the underground excavation phase through the use of 10 separated right wall bodies. The results showed that the earth pressure on the retaining wall was changed by the lowering of the first base bottom wall; however, the earth pressure was not changed significantly by the lowering of the third base bottom wall, since the third base wall had sufficient separation distance from the retaining wall. Lowering of the first base wall induced a decrease in the earth pressure in the lower part of the retaining wall; in contrast, lowering of the first base wall induced an increase in the earth pressure in the middle part of the retaining wall, proving the arching effect experimentally. It is necessary to consider the changes in earth pressure on the retaining wall in designing earth retaining structures for sections where the arching effect occurs.

• 천문학회지
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• 제43권6호
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• pp.183-190
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• 2010

According to the historical documents and paintings in many civilizations, rocks that fell from the sky fascinated humans as the message from the God or supernaturals. Scientific progress allows humans to recognize these exciting extraterrestrial objects as meteorites. Meteorites contain a wealth of pivotal information regarding formation of the early Solar System. Meteorites also provide broader scientific insights on, for example, the origin of life, interplanetary transfer of life forms, massive depletion of biosphere on Earth, and evolution of lithosphere on Earth-like planetary bodies.

• Journal of Astronomy and Space Sciences
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• 제32권3호
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• pp.229-235
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• 2015

We estimated the orbit of the Communication, Ocean and Meteorological Satellite (COMS), a Geostationary Earth Orbit (GEO) satellite, through data from actual optical observations using telescopes at the Sobaeksan Optical Astronomy Observatory (SOAO) of the Korea Astronomy and Space Science Institute (KASI), Optical Wide field Patrol (OWL) at KASI, and the Chungbuk National University Observatory (CNUO) from August 1, 2014, to January 13, 2015. The astrometric data of the satellite were extracted from the World Coordinate System (WCS) in the obtained images, and geometrically distorted errors were corrected. To handle the optically observed data, corrections were made for the observation time, light-travel time delay, shutter speed delay, and aberration. For final product, the sequential filter within the Orbit Determination Tool Kit (ODTK) was used for orbit estimation based on the results of optical observation. In addition, a comparative analysis was conducted between the precise orbit from the ephemeris of the COMS maintained by the satellite operator and the results of orbit estimation using optical observation. The orbits estimated in simulation agree with those estimated with actual optical observation data. The error in the results using optical observation data decreased with increasing number of observatories. Our results are useful for optimizing observation data for orbit estimation.