• 한국측량학회지
• /
• 제17권3호
• /
• pp.265-272
• /
• 1999

현재 우리나라의 수치지도에서는 동경원점계에 의한 Bessel타원체 좌표계를 사용하고 있으므로 새로운 지구중심좌표계(ITRF)에 의한 GRS80타원체 좌표계와는 상당한 차이가 발생하게 된다. 본 연구에서는 새로운 좌표계의 도입에 따른 지도좌표계의 전환에 대비할 수 있도록 하기 위하여 두 체계간의 좌표차와 도엽체계에 대한 특성과 경향을 파악하고, 두 좌표계간의 지도좌표계 전환모듈을 제시하였다.

• 한국항해항만학회지
• /
• 제30권9호
• /
• pp.729-734
• /
• 2006

The authors aim to establish the theory necessary for developing the free gyroscopic compass and focus on mainly two points. One is to suggest north-finding principle by the angular velocity of the earth's rotation, and the other is to suggest orthogonal coordinate transformations of the motion rate of the spin axis, which transforms the components of motion rate in the free gyro frame into those in the platform frame and that this transformed rate is, in turn, transformed into the NED(north-east-down) navigation frame. Subsequently, ship's heading is obtained by using the fore-aft and athwartship components of the motion rate of the spin axis in the NED frame. In addition it was found how to solve the transformation matrix necessary for transforming each frame.

• 한국기계기술학회지
• /
• 제13권4호
• /
• pp.131-136
• /
• 2011

In commercial vehicle, sub-frame which equipped in main frame supporting dump deck and oil tanker. This is the main structure for all equipment which including joint function. Sub-frame is made by welding process, this susceptible to deform and crack by its longitudinal size. Also various kind of sub-frame make it difficult to standardization in manufacturing process and exclusive jig is not adapted yet. Frame size is over 6~8m and weight is more than 300kg this make re-work more difficult. If manufacturing company made precise sub-frame, this is not only convenient for customers but also save the company money by reducing the working time. In this study manufacture the sub-frame be suitable for its main function and develop exclusive welding jig for obtain checking fixture function as well.

• 한국가시화정보학회:학술대회논문집
• /
• 한국가시화정보학회 2002년도 추계학술대회 논문집
• /
• pp.19-22
• /
• 2002

A process of 3-D particle image velocimetry, called here, as '3-D stereo PIV' was developed for the measurement of a section field of 3-D complex flows. The present method includes modeling of camera by a calibrator based on the homogeneous coordinate system, transfromation of oblique-angled image to transformed image, identification of 2-D velocity vectors by 2-D cross-correlation equation, stereo matching of 2-D velocity vectors of two cameras, accurate calculation of 3-D velocity vectors by homogeneous coordinate system and finally 3-D animation as the post processing. In principle, as two frame images only are necessary for the single instantaneous analysis of a section field of 3-D flow, more effective vectors are obtainable contrary to the previous multi-frame vector algorithm. An experimental system was also used for the application of the proposed method. Three analog CCD cameras and an Argon-Ion Laser(300mW) for illumination were adopted to capture the wake flow behind a bluff obstacle.

• 한국측량학회지
• /
• 제14권2호
• /
• pp.141-150
• /
• 1996

최근 우리나라에서는 위성측위시스템의 보급에 따라 측지분야에서 뿐만 아니라 지적 및 GIS/LIS 데이터베이스 관리분야에서도 그 활용성이 커지고 있으며, 지구중심좌표계(geocentric coordinate system)에 대한 관심도 높아지고 있다. 이 논문에서는 현행의 측지기준계를 분석하여 지구중심좌표계에 의한 새로운 측지기준좌표계(geodetic reference frame)의 설정방안을 고찰하였고, 이에 따른 국가기준점망의 구축방법과 기존의 좌표체계에서 새로운 좌표체계로 변경하고자할 경우에 고려되어야 할 기준점관리와 성과관리 등에 대하여 고찰하였다.

• Journal of Astronomy and Space Sciences
• /
• 제16권2호
• /
• pp.159-166
• /
• 1999

As the spatial resolution of remote sensing satellites becomes higher, very accurate determination of the position of a LEO (Low Earth Orbit) satellite is demanding more than ever. Non-symmetric Earth gravity is the major perturbation force to LEO satellites. Since the orbit propagation is performed in the celestial frame while Earth gravity is defined in the terrestrial frame, it is required to convert the coordinates of the satellite from one to the other accurately. Unless the coordinate conversion between the two frames is performed accurately the orbit propagation calculates incorrect Earth gravitational force at a specific time instant, and hence, causes errors in orbit prediction. The coordinate conversion between the two frames involves precession, nutation, Earth rotation and polar motion. Among these factors, unpredictability and uncertainty of Earth rotation, called UTI-UTC, is the largest error source. In this paper, the effect of UTI-UTC on the accuracy of the LEO propagation is introduced, tested and analzed. Considering the maximum unpredictability of UTI-UTC, 0.9 seconds, the meaningful order of non-spherical Earth harmonic functions is derived.

• 한국컴퓨터그래픽스학회논문지
• /
• 제27권5호
• /
• pp.55-61
• /
• 2021

물리 시뮬레이션 기반의 캐릭터 동작 제어 문제를 강화학습을 이용하여 해결해나가는 연구들이 계속해서 진행되고 있다. 강화학습을 사용하여 문제를 풀기 위해서는 네트워크 구조, 하이퍼파라미터 튜닝, 상태(state), 행동(action), 보상(reward)이 문제에 맞게 적절히 설정이 되어야 한다. 많은 연구들에서 다양한 조합으로 상태, 행동, 보상을 정의하였고, 성공적으로 문제에 적용하였다. 상태, 행동, 보상을 정의함에 다양한 조합이 있다보니 학습 성능을 향상시키는 최적의 조합을 찾기 위해서 각각의 요소들이 미치는 영향을 분석하는 연구도 진행되고 있다. 우리는 지금까지 이뤄지지 않았던 상태 표현 방식에 따른 강화학습성능에 미치는 영향을 분석하였다. 첫째로, root attached frame, root aligned frame, projected aligned frame 3가지로 좌표계를 정의하였고, 이에 대해 표현된 상태를 이용하여 강화학습에 미치는 영향을 분석하였다. 둘째로, 상태를 정의 할 때, 관절의 위치, 각도로 다양하게 조합하는 경우에 학습성능에 어떠한 영향을 미치는지 분석하였다.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 1998년도 가을 학술발표회 논문집
• /
• pp.201-207
• /
• 1998

In this study, a geometric nonlinear analysis formulation for spatial frames is developed using the 3D stability functions. For the formulation, the relationships of local and global coordinate systems in force, deformation, and the initial and current configurations of a frame are derived. The force-deformation relationship in global coordinate system is derived as well. The developed formulation is verified in each derivation by reducing the derived equations into 2D equations. The gradual plastification of connections and critical sections can be implemented effectively to this formulation for the complete second order inelastic advanced analysis of spatial frames.

• International Journal of Aeronautical and Space Sciences
• /
• 제16권1호
• /
• pp.77-88
• /
• 2015

The dynamics of relative motion in a perturbed orbital environment are exploited based on Gauss' and Cowell's variational equations. The inertial coordinate frame and relative coordinate frame (Hill frame) are used, and a linear high fidelity model is developed to describe the relative motion. This model takes into account the primary gravitational and atmospheric drag perturbations. Then, this model is used in the design of a navigation, guidance, and control system of a chaser vehicle to approach towards and to depart from a target vehicle in proximity operations. Relative navigation uses an extended Kalman filter based on this relative model to estimate the relative position/velocity of the chaser vehicle with respect to the target vehicle. This filter uses the range and angle measurements of the target relative to the chaser from a simulated LIDAR system. The corresponding measurement models, process noise matrix, and other filter parameters are provided. Numerical simulations are performed to assess the precision of this model with respect to the full nonlinear model. The analyses include the navigation errors and trajectory dispersions.

• Advances in Computational Design
• /
• 제4권4호
• /
• pp.397-413
• /
• 2019

In this paper, static nonlinear analysis of gable frame is performed using OpenSees software. Both geometric and material nonlinearities are considered in analyses. To consider large displacements, co-rotational coordinate transformation is used in software. The effects of symmetric and asymmetric support conditions including clamped and simple supports are studied. On the other hand, the material nonlinearity is reflected on analyses using Giuffre-Menegotto-Pinto steel material. Note that strain hardening characteristics are also considered in this model. Moreover, I-shaped cross-section is assumed for all members. The results are provided for different geometry properties of gable frame including shallow and deep inclined roof. It should be added that buckling and post-buckling behaviors of gable frame are investigated using related equilibrium paths. A comparison study is also implemented on the responses of buckling loads obtained for different support and geometry conditions. To trace snap-through paths completely, a displacement control method entitled arc-length is utilized. Findings show the capability of proposed model in nonlinear analysis of gable frames.