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Determination of Initial Conditions for Tetrahedral Satellite Formation
유성문,박상영 한국우주과학회 2011 Journal of Astronomy and Space Sciences Vol.28 No.4
This paper presents an algorithm that can provide initial conditions for formation flying at the beginning of a region of interest to maximize scientific mission goals in the case of a tetrahedral satellite formation. The performance measure is to maximize the quality factor that affects scientific measurement performance. Several path constraints and periodicity conditions at the beginning of the region of interest are identified. The optimization problem is solved numerically using a direct transcription method. Our numerical results indicate that there exist an optimal configuration and states of a tetrahedral satellite formation. Furthermore, the initial states and algorithm presented here may be used for reconfiguration maneuvers and fuel balancing problems.
유성문,정태현,Sung-Mo Lee,윤하수,박한얼,정종균,노경민,위석오,조정호,변도영 한국천문학회 2018 Journal of The Korean Astronomical Society Vol.51 No.5
We present the first results of the invariant point (IVP) coordinates of the KVN Ulsan and Tamna radio telescopes. To determine the IVP coordinates in the geocentric frame (ITRF2014), a coordinate transformation method from the local frame, in which it is possible to survey using the optical instrument, to the geocentric frame was adopted. The least-square circles are fitted in three dimensions using the Gauss-Newton method to determine the azimuth and elevation axes in the local frame. The IVP in the local frame is defined as the mean value of the intersection points of the azimuth axis and the orthogonal vector between the azimuth and elevation axes. The geocentric coordinates of the IVP are determined by obtaining the seven transformation parameters between the local frame and the east-north-up (ENU) geodetic frame. The axis-offset between the azimuth and elevation axes is also estimated. To validate the results, the variation of coordinates of the GNSS station installed at KVN Ulsan was compared to the movement of the IVP coordinates over 9 months, showing good agreement in both magnitude and direction. This result will provide an important basis for geodetic and astrometric applications.
ICT센터 사례 연구를 통한 EQS의 건축 구조물 면진에의 적용 연구
유성문,이유인,지용수,최대성,김두기 한국지진공학회 2013 한국지진공학회논문집 Vol.17 No.2
An application of the EQS (Eradi Quake System) bearings to a short period building structure and the structure earthquake responses according to the design parameters of the EQS are studied by the ICT Center case study. The features of the EQS application to seismic isolated building structures are investigated, and the design procedure to determine the yield load and the secondary stiffness of the EQS is also studied. A computational analysis is performed to confirm the applicability of the EQS to the building structure and the earthquake responses according to the design parameters. The ICT Center in Indonesia is adopted as an application case of the EQS. The application of the EQS is found to extend the fundamental period of the ICT Center. Three types of EQS with different yield loads and secondary stiffness are designed and applied in the earthquake response analyses. The analysis results show the response of the structure with respect to the design parameters and which type of EQS is suitable for the ICT Center.
유성문,지광습,차우딘단,이현종,문성호 한국전산구조공학회 2010 한국전산구조공학회논문집 Vol.23 No.5
In this paper, Δ-integral is used to analyze fatigue crack growth of viscoelastic material. Using analytical integral value, the -integral is calculated. So, reduction of calculation time and increase of accuracy are made possible. The stress intensity factor is calculated using the finite element method code. In difference with existed fatigue crack analysis using ΔK, we were successfully able to analyze various load amplitude and the fatigue crack of load cycle only with two fatigue crack growth parameters and creep compliance. The analysis gives curve for simulation of crack growth, and the curve almost corresponds with test results. 본 논문에서는 점탄성 재료의 피로균열 성장을 분석하기 위해 Δ-적분을 이용하였다. -적분의 계산 시 기존의 수치해석 방법이 아닌 해석적인 적분 해를 도출하여 계산시간을 절감하고 정확도를 크게 높였다. 계산 시 응력확대계수는 특정 균열에 대해 참조하는 방법이 아닌 유한요소해석을 통해 구하는 방법을 사용하였다. 기존의 ΔK를 이용한 피로균열 예측과는 달리 크리프 변형계수, 단 두 개의 피로성장 모델 변수만을 가지고 다양한 하중과 하중주기에서의 피로균열 성장을 성공적으로 분석할 수 있었다.