• 항공우주의학회지
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• 제31권3호
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• pp.73-76
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• 2021

Changes the gravity has a significant affect on the immune system. Astronauts experience the gravity changing during spaceflight, especially when launching and landing they experience hypergravity, and during spaceflight they feel microgravity. Both hypergravity and microgravity has an impact to the immune system, but not the same effect. These impacts have been investigated extensively during spaceflight in astronauts and in model experiments conducted on Earth as well. Astronauts during spaceflight feel the hypergravity, psychological stress, fear, high doses of radiation and microgravity. All these factors and changes may affect immune system directly or indirectly.

• 한국항공우주학회지
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• 제31권7호
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• pp.100-111
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• 2003

극소형 피코위성 HAUSAT-1(Hankuk Aviation University SATellite-1)의 궤도는 고도 650km~800km, 경사각 65도 또는 98도에서 비행할 예정이다. 저궤도에서 운용되기 때문에 외란으로 작용하는 요소 중 지구중력과 지구 자기장에 의한 영향이 크다. HAUSAT-1은 자세제어를 하기 위해서 자기 토커를 사용하며, 부가적으로 탑재체인 태양전지셀 전개 매커니즘을 중력구배 붐으로 사용한다. 위성의 자세 안정화 성능을 판단하기 위해서 MATLAB을 이용해서 시뮬레이션 하였고, 시뮬레이션은 8차 자기장 모델, 비선형 외란 방정식, 그리고 비선형 위성 자세방정식을 사용해서 수행되었다. 시뮬레이션을 통해서 HAUSAT-1의 중력구배붐 전개 전과 후 그리고 외란에 의한 자세 변화를 확인하고 결과를 비교했다. 자기 토커를 이용한 효율적인 HAUSAT-1의 자세제어 시스템 개발을 위한 자세 안정화 방법에 대해서도 분석하였다.

• 한국중재학회지:중재연구
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• 제26권2호
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• pp.91-114
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• 2016

The purpose of this study is to promote trade between Korea and South American countries. Korea's trade with South America has decreased recently. This study analyzed the effects of arbitration on trade between Korea and South America. To this end, we conducted an analysis of the gravity model of trade between Korea and South America. The gravity model is a research method that is widely used to analyze the pattern of international trade. The dependent variables of the gravity model were trade in Korea and South America. The independent variables were GDP, population, and distance between Korea and South America. In addition, dummy variables were the FTA and whether to join the New York Convention or Washington Convention. Joining either Convention indicated the establishment of an international arbitration system. As a result, an arbitration system appeared to be effective in increasing trade. Depending on the results it shows the importance of utilizing the system of arbitration in South America. So this study analyzed the current status of arbitration in South America. To companies doing business in South America it provided the implications for an arbitration system there. Also it proposed a method for increasing trade for the Korean government and institutions.

• Structural Engineering and Mechanics
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• 제36권4호
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• pp.499-511
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• 2010

This paper examines the ice cover effects on the seismic response of concrete gravity dam-reservoir-foundation interaction systems subjected to a horizontal earthquake ground motion. ANSYS program is used for finite element modeling and analyzing the ice-dam-reservoir-foundation interaction system. The ice-dam-reservoir interaction system is considered by using the Lagrangian (displacementbased) fluid and solid-quadrilateral-isoparametric finite elements. The Sariyar concrete gravity dam in Turkey is selected as a numerical application. The east-west component of Erzincan earthquake, which occurred on 13 March 1992 in Erzincan, Turkey, is selected for the earthquake analysis of the dam. Dynamic analyses of the dam-reservoir-foundation interaction system are performed with and without ice cover separately. Parametric studies are done to show the effects of the variation of the length, thickness, elasticity modulus and density of the ice-cover on the seismic response of the dam. It is observed that the variations of the length, thickness, and elasticity modulus of the ice-cover influence the displacements and stresses of the coupled system considerably. Also, the variation of the density of the ice-cover cannot produce important effects on the seismic response of the dam.

• 한국측량학회지
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• 제27권1호
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• pp.713-722
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• 2009

중력측량은 지구중력장 결정, 지각의 수직운동, 지오이드면의 변화, 해수면변화, 기후변화 등 측지학적, 지구동력학적 연구의 기초이다. 국토지리정보원에서는 최근 들어 FG-5 절대중력계를 도입하여 절대중력 기준망의 구축을 위한 틀을 마련하였고 다차원 다기능 기준점인 통합기준점을 전국에 약 1,200점을 설치하여 상대중력측량을 실시함으로써 한국의 고정밀 지오이드모델의 개발에 큰 기여를 할 것으로 판단된다. 본 연구에서는 상대중력측량의 기본적인 이론 및 방법을 상세하게 설명하였고, 최신 상대중력계 Scintrex CG-5를 이용하여 총 21점에 대한 상대중력측량을 수행하였으며, 자유망조정 및 무게제한 망조정 방법을 이용하여 중력성과를 계산 및 비교 분석하였다. 결과, 두 가지 방법 모두 높은 정밀도의 중력성과 계산이 가능하지만 자유망조정이 무게제한 망조정 방법에 비해 상대적인 우위를 보여주는 것으로 나타났다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.449-452
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• 2008

Originally developed in Scandinavia over 40 years ago, syphonic roof drainage systems have been in use in the UK since the early 1990's. Since then, many large projects have used the syphonic system to overcome installation problems which would have been difficult to solve using a traditional gravity rainwater system.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2006년도 춘계학술논문 발표대회 제6권1호
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• pp.111-114
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• 2006

Recently, it is increased on the concern for the reuse of waste concrete because of the shortage of natural aggregate and the increase of waste concrete. And recycled coarse aggregate is used variously, but the existing wet method producted recycled fine aggregate has problem like the high price facilities, the long time progress of the work and the poor of recycled fine aggregate. The aim of this study is to investigate outline and performance evaluation of the drying specific gravity separation method to product high duality recycled fine aggregate. Finally, this study is shown investigate process flowing of drying separation type with gravity manufacture, producte system and function of detail devices. The performance of the method of drying specific gravity separation is certificated as the qualities of recycled fine aggregate satisfied the KS

• 대한원격탐사학회지
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• 제22권4호
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• pp.255-264
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• 2006

2002년 3월에 발사 된 GRACE (Gravity Recovery and Climate Experiment)는 미국과 독일 합작으로 개발된 최초의 지구중력장 측정 전용 위성으로 동일한 궤도를 비행하는 두 개의 위성 사이 거리 변화를 측정하여 지구 중력장을 추정하는 사업이다. 위성 발사 후 이전 보다 수 십배 정확한 지구중력장 모델을 생성하였으며, 지구중력장 변화도 30일마다 추정하고 있다. GRACE 위성의 핵심 관측기인 위성간 거리 측정기의 원리에 대해 소개하고, 운용 결과 및 성능에 대해 소개 하였다. 발사 전 성능 분석 단계에서 고려되지 못했던 거리측정기 오차 요인에 대해 분석하고, 향후 연구 방향을 제시 하였다.

• 대한기계학회논문집A
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• 제33권12호
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• pp.1427-1432
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• 2009

The pitch motion of a generic gravity gradient satellite is investigated in terms of chaos. The Melnikov method is used for detecting the onset of chaotic behavior of the pitch motion of a gravity gradient satellite. The Melnikov method determines the distance between stable and unstable manifolds of a perturbed system. When stable and unstable manifolds transverse on the Poincare section, the resulting motion can be chaotic. The Melnikov analysis indicates that the pitch dynamics of a generic gravity gradient satellite can be chaotic when the orbit eccentricity is small.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.1019-1022
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• 2002

Pipe-cutting machines have been used in many fields. Recently, an automatic pipe-cutting machine that uses magnet has born developed. In this paper, a magnetic-type automatic pipe-cutting machine that attaches itself and performs unmanned cutting process is proposed. It is designed that there is a room at the bottom of its body to contain a magnet. And it uses magnetic force between the magnet and the pipe surface to prevent slip and to attach the machine to the pipe against gravity. Also the magnetic force is adjustable by changing the gap between the magnet and the pipe. This machine is, however, necessary to control cutting velocity for the elevation of work efficiency and the adjustable faculties. During pipe cutting process, the gravity acting on the pipe-cutting machine widely varies. That is, the cutting machine gets fast when moving from the top to the bottom of the pipe and slow when moving from the bottom to the top. Actually the system is kind of a non-linear system where the gravity is function of climbing angle of the cutting machine along the pipe. Especially jerking motion is critical. Therefore, authors design the non-linear controller that estimates the current position of the machine along the pipe and compensates the effect of gravity in this paper. It receives the feed back signal from the encoder.