• 제목/요약/키워드: Gravitation

검색결과 84건 처리시간 0.029초

지구동주기위성의 위치보전해석과 궤도결정 (Station Keeping Analysis and Orbit Determination of Feosynchronous Satellite)

  • 박수홍;조겸래
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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    • pp.783-787
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    • 1993
  • The dynamics for a two-body problem including perturbations due to nonspherical gravitation of the earth, gravitation of the sun and moon, radiation of the sun is studied. Orbit determination was performed by SVD filter. The simulation result shows that the characteristics of the satellite orbit have east-west and south-north drift. Therefore, the periodic magnitude of the control time and value in the view of the periodicity of error can be provided, and this result can be basic data to a station keeping problem with an orbit determination result.

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A SIMPLIFIED TREATMENT OF GRAVITATIONAL INTERACTION ON GALACTIC SCALES

  • Trippe, Sascha
    • 천문학회지
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    • 제46권1호
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    • pp.41-47
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    • 2013
  • I present a simple scheme for the treatment of gravitational interactions on galactic scales. In anal- ogy with known mechanisms of quantum field theory, I assume ad hoc that gravitation is mediated by virtual exchange particles-gravitons-with very small but non-zero masses. The resulting den- sity and mass profiles are proportional to the mass of the gravitating body. The mass profile scales with the centripetal acceleration experienced by a test particle orbiting the central mass, but this comes at the cost of postulating a universal characteristic acceleration $a_0{\approx}4.3{\times}10^{-12}msec^{-2}$ (or $8{\pi}a_0{\approx}1.1{\times}10^{-10}msec^{-2}$). The scheme predicts the asymptotic flattening of galactic rotation curves, the Tully-Fisher/Faber-Jackson relations, the mass discrepancy-acceleration relation of galaxies, the surface brightness-acceleration relation of galaxies, the kinematics of galaxy clusters, and "Renzo's rule" correctly; additional (dark) mass components are not required. Given that it is based on various ad-hoc assumptions and given further limitations, the scheme I present is not yet a consistent theory of gravitation; rather, it is a "toy model" providing a convenient scaling law that simplifies the description of gravity on galactic scales.

부산항의 입출항국가에 대한 유인분석 소고 - 중력모형적용 - (A Small Study on Gravitation Analysis of the Port of Busan to the Import and Export Countries : Application of Gravity Model)

  • 박노경
    • 한국항만경제학회지
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    • 제19권1호
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    • pp.23-41
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    • 2003
  • The purpose of this paper is to analyze the gravitation of ship's cargo tons of arriving and leaving port of Busan based on the gravity model empirically and experimentally and to suggest possible ways to expand the trade quantities(cargo tons) by identifying important factors determining the port of Busan's bilateral trade flows with foreign countries by using the 1995, and 2001 data. In this paper, new independent variables, such as land, populations, and the APEC and ASEAN memberships, and new dependent variable, such as the ship's cargo tons of arrival and leaving port of Busan were used for expanding the previous studies. Empirical analysis found that the port of Busan tends to trade more with countries in close proximity and the large size of economies. The fact that the port of Busan's trades more with APEC countries than with non-APEC countries is a clear empirical evidence of the growing importance of the regional trade agreement and strategic alliance with the ports of these member countries. The main policy implication based on the findings of this study is that GDP, distance, adjacency, and APEC membership which were the affecting variables to the bilateral trade with the port of Busan should be closely investigated for enhancing the trade quantities with those foreign countries.

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Learning from an Expert Teacher: Feynman's Teaching of Gravitation as an Examplar

  • Park, Jiyun;Lee, Gyoungho;Kim, Jiwon;Treagust, David F.
    • 과학교육연구지
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    • 제43권1호
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    • pp.173-193
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    • 2019
  • An expert teachers' instruction can be helpful to other teachers because good teaching effectively guides students to develop meaningful learning. Feynman is an excellent physics lecturer as well as one of the greatest physicists of the 20th century who presented and explained physics with his unique teaching style based on his great store of knowledge. However, it is not easy to capture and visualize teaching because it is not only the complex phenomena interrelated to various factors with the content to be taught but also the tacit representation. In this study, the framework of knowledge & belief based on the integrated mental model theory was used as a tool to capture and visualize complex and tacit representation of Feynman's teaching of 'The theory of gravitation,' a chapter in The Feynman Lectures on Physics. Feynman's teaching was found to go beyond the transmission of physics concepts by showing that components of the framework of knowledge & belief were effectively intertwined and integrated in his teaching and the storyline was well-organized. On the basis of these discussions, the implications of Feynman's teaching analyzed within the framework of knowledge & belief for physics teacher education are derived. Finally, the characteristics of the framework of knowledge & belief as tools for the analysis of teaching are presented.

퍼지로직과 포텐셜 필드를 이용한 자율이동로봇의 최적경로계획법 (Optimal Path Planning of Autonomous Mobile Robot Utilizing Potential Field and Fuzzy Logic)

  • 박종훈;이재광;허욱열
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 A
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    • pp.11-14
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    • 2003
  • In this paper, we use Fuzzy Logic and Potential field method for optimal path planning of an autonomous mobile robot and apply to navigation for real-time mobile robot in 2D dynamic environment. For safe navigation of the robot, we use both Global and Local path planning. Global path planning is computed off-line using sell-decomposition and Dijkstra algorithm and Local path planning is computed on-line with sensor information using potential field method and Fuzzy Logic. We can get gravitation between two feature points and repulsive force between obstacle and robot through potential field. It is described as a summation of the result of repulsive force between obstacle and robot which is considered as an input through Fuzzy Logic and gravitation to a feature point. With this force, the robot fan get to desired target point safely and fast avoiding obstacles. We Implemented the proposed algorithm with Pioneer-DXE robot in this paper.

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통신위성에 작용하는 섭동력의 영향평가와 궤도결정 (A Study on Perturbation Effect and Orbit Determination of Communication Satellite)

  • 박수홍
    • 한국정밀공학회지
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    • 제9권3호
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    • pp.157-164
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    • 1992
  • This study concerns about the orbit prediction and orbit determination of Korean future communication satellite, called 'Moogunghwa", which will be motioned in the geo-stationary orbit. Perturbation effect on the satellite orbit due to nonspherical gravitation of the earth, gravitation of the sun and moon, radiation of sun, drag of the atmosphere was investigated. Cowell's method is used for orbit prediction. Orbit determination was performed by using Extended Kalman Filter which is suitable for real-time orbit determination. The result shows that the chacteristics of the satellite orbit has east-west and south-north drift. So the periodic control time and control value in the view of the periodic of error can be provided. The orbit determination demonstrated the effectiveness since the convergence performance on the positon and velocity error, and state error standard deviation is reasonable.able.

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Dealing with gravity on galactic scales

  • Trippe, Sascha
    • 천문학회보
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    • 제38권1호
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    • pp.36.1-36.1
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    • 2013
  • I present a simple scheme for the treatment of gravitational interactions on galactic scales. In analogy with known mechanisms of quantum field theory, I assume ad hoc that gravitation is mediated by virtual exchange particles - gravitons - with very small but non-zero masses. The scheme predicts the asymptotic flattening of galactic rotation curves, the Tully-Fisher/Faber-Jackson relations, the mass discrepancy-acceleration relation of galaxies, and the surface brightness-acceleration relation of galaxies correctly; additional (dark) mass components are not required. The well-established empirical scaling laws of Modified Newtonian Dynamics follow naturally from the model. The scheme I present is not a consistent theory of gravitation; rather, it is a toy model providing a convenient scaling law that simplifies the description of gravity on galactic scales.

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메타볼을 이용한 중력장내의 물방울 모델 (A Model for Water Droplet using Metaball in the Gravitation Force)

  • 유영중;정호열;조환규
    • 한국컴퓨터그래픽스학회논문지
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    • 제4권1호
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    • pp.79-88
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    • 1998
  • 현재까지 불과 같은 유체를 렌더링하기 위한 많은 모델들이 개발되었다. 특히 메타볼은 단순성과 유동성의 특정으로 인해 눈이나 물과 같은 유체의 곡면을 모델링하기 위한 기법으로 많이 사용되어졌다. 본 논문은 중력장내에서 변형되는 물방울을 모델링하기 위한 새로운 방법을 제안한다. 이전의 연구에서 물방울은 단순한 메타볼에 의해 표현되었다. 물방울에 중력이 고려되지 않았기 때문에 렌더링 결과는 실제적인 물방울의 형태를 표현할 수 없었다. 우리는 기존의 메타볼에 실세계의 중력과 마찰력을 고려함으로서 평탄한 지면위에 놓여진 물방울의 형태를 생성하는 새로운 방법을 보여준다. 본 연구의 새로운 메타볼 모델은 이전의 메타볼이 가지는 스칼라 공간의 isosurface값을 중력을 고려한 벡터 공간으로 이동하여 얻어진다. 결과로서 광선 추적 기법과 물방울의 그림자 형성을 통해 실제적인 물방울의 형태를 렌더링한다.

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상대인력 모델에 기반한 자연적 개체 군집화 알고리즘 (A Natural Clustering Algorithm based on the Relative Gravitation Model)

  • 김은주;고재필;변혜란;이일병
    • 한국정보과학회논문지:소프트웨어및응용
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    • 제28권10호
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    • pp.757-763
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    • 2001
  • 본 논문에서는 상대인력 모델에 기반한 새로운 군집화 알고리즘, G-CLUS를 제안한다. 제한한 방법에서 모든 개체들은 초기에 동일한 질량을 가지고, 개체간의 인력에 의해 인력이 작용하는 방향으로 점진적으로 이동하게 되어, 초기 시작점 선택이나 군집의 개수를 미리 지정하지 않은 상태에서 자연스럽게 군집을 형성한다. 제안한 방법을 인력작용과정에서 군집의 수가 자연스럽게 결정되며, 한 개체가 받는 힘은 개체간의 인력을 합한 합력을 사용하기 때문에 이상치에 대한 민감성을 완화하였다. 본 알고리즘은 계산복잡도를 낮추기 위하여 큐브개념을 적용하여 O(nk)의 계산 복잡도를 유지하도록 하였다. 실험에서는 개체들의 움직임 특성, 군집화 모델에 따른 군집화 과정, 임의의 데이타 집합에 대한 군집화 결과를 보이고, 또한 타 군집화 알고리즘과 제안한 알고리즘 군집화 결화를 비교한다.

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