• 한국지구과학회지
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• 제40권4호
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• pp.353-381
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• 2019

The general world model for homogeneous and isotropic universe has been proposed. For this purpose, we introduce a global and fiducial system of reference (world reference frame) constructed on a (4+1)-dimensional space-time, and assume that the universe is spatially a 3-dimensional hypersurface embedded in the 4-dimensional space. The simultaneity for the entire universe has been specified by the global time coordinate. We define the line element as the separation between two neighboring events on the expanding universe that are distinct in space and time, as viewed in the world reference frame. The information that determines the kinematics of the geometry of the universe such as size and expansion rate has been included in the new metric. The Einstein's field equations with the new metric imply that closed, flat, and open universes are filled with positive, zero, and negative energy, respectively. The curvature of the universe is determined by the sign of mean energy density. We have demonstrated that the flat universe is empty and stationary, equivalent to the Minkowski space-time, and that the universe with positive energy density is always spatially closed and finite. In the closed universe, the proper time of a comoving observer does not elapse uniformly as judged in the world reference frame, in which both cosmic expansion and time-varying light speeds cannot exceed the limiting speed of the special relativity. We have also reconstructed cosmic evolution histories of the closed world models that are consistent with recent astronomical observations, and derived useful formulas such as energy-momentum relation of particles, redshift, total energy in the universe, cosmic distance and time scales, and so forth. The notable feature of the spatially closed universe is that the universe started from a non-singular point in the sense that physical quantities have finite values at the initial time as judged in the world reference frame. It has also been shown that the inflation with positive acceleration at the earliest epoch is improbable.

• 인지과학
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• 제22권1호
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• pp.19-38
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• 2011

사람이 공간에 대한 표현이나 추론을 기술할 때, 정량적 정보 표현과 관련 추론이 어렵거나 불가능 할 때 정성적 표현과 추론을 사용할 수 있다. 2차원 공간에 대한 많이 알려진 정성적 방법 중에 RCC(Region Connection Calculus)-8이 있다. 지역(region)을 공간에 대한 온톨로지 기본 개체로 하는 RCC-8은 위상학적 의미에서 두 개의 지역에 관해 connection 기반의 논리식 및 개념적 이웃과 변환을 나타낸 것으로 각 지역의 이동이나 크기 변화를 전제로 하고 있다. 그러나 현실 세계의 공간 표현과 추론에는 몇 가지 측면들이 더 고려되어야 한다. 본 논문에서는 중력장내에서 일어나는 물리적 화학적 작용에 의해 변화하는 동적인 물질세계의 정성적 공간 표현을 위해 RCC-8의 수정 확장된 방법을 제안한다. 2D의 정성적 공간 표현 및 추론에서 전역적 참조 프레임(global reference frame)의 필요성을 기술하고, 전역적 참조 프레임을 사용하여 동적 물질세계의 물리적 화학적 변화를 표현하고 추론하기 위한 QSR-14을 기술한다. QSR-14는 RCC-8에서 불가능한 상황을 표현할 수 있어 실제 세계의 정성적 공간 표현 및 변화에 더 적합하다고 판단된다. 몇 개의 예제를 통해 정성적 표현과 추론에 대한 QSR-14의 유용성을 보인다.

• Journal of Astronomy and Space Sciences
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• 제38권3호
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• pp.185-192
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• 2021

This technical paper deals the practical transformation algorithms between several lunar reference frames which will be used for Korea pathfinder lunar orbiter (KPLO) flight operation. Despite of various lunar reference frame definitions already exist, use of a common transformation algorithm while establishing lunar reference frame is very important for all members related to KPLO mission. This is because use of slight different parameters during frame transformation may result significant misleading while reprocessing data based on KPLO flight dynamics. Therefore, details of practical transformation algorithms for the KPLO mission specific lunar reference frames is presented with step by step implementation procedures. Examples of transformation results are also presented to support KPLO flight dynamics data user community which is expected to give practical guidelines while post processing the data as their needs. With this technical paper, common understandings of reference frames that will be used throughout not only the KPLO flight operation but also science data reprocessing can be established. It is expected to eliminate, or at least minimize, unnecessary confusion among all of the KPLO mission members including: Korea Aerospace Research Institute (KARI), National Aeronautics and Space Administration (NASA) as well as other organizations participating in KPLO payload development and operation, or further lunar science community world-wide who are interested in KPLO science data post processing.

• 한국측량학회지
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• 제30권3호
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• pp.241-247
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• 2012

우리나라에서는 2003년부터 세계측지계로 전환하였으며, 이에 따른 우리나라의 행정구역도상의 면적 변화를 살펴보기 위해 통계청에서 제공하는 센서스용 행정구역경계 자료를 이용하여 전국토를 대상으로 면적의 변화량을 계산하였다. 면적 계산 과정에서는 국토지리정보원에서 제시하는 표준절차를 이용하였으며, 전국 단일 원점TM좌표를 세계측지계로 변환한 후 타원체면 및 투영평면상에서 면적을 대상으로 하였다. 광역시도행정경계가 우리나라 직각좌표의 두 개 이상의 원점에 해당하는 경우에는 각 좌표계의 경계선을 기준으로 행정경계를 개별 폴리곤으로 분할한 후 별도의 원점을 기준으로 투영하였다. 세계측지계 변환 후 모든 행정경계가 북서방향으로 이동함으로써 결과적으로 우리나라 전체 면적이 투영평면 기준으로 $1.36km^2$(약 0.0013%) 감소하는 것으로 나타났다. 이는 타원체의 장반경이 확대됨으로 인한 면적증가보다 행정경계의 경위도 좌표가 고위도로 변경됨으로 인한 면적감소가 크기 때문으로 판단된다. 각 행정구역별 면적변화율은 고위도에 위치한 광역시도가 더 민감하게 반영되었다. 이와는 별도로 통계청에서 제공하는 행정구역경계 자료로부터 계산된 면적은 국토해양부의 국토해양통계 자료와 상당한 차이를 보이고 있으며 이에 대한 일원화가 진행되어야 할 것으로 판단된다.

• Asia pacific journal of information systems
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• 제25권2호
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• pp.356-369
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• 2015

Public sectors around the world utilize social media tools and technologies in their daily activities for a variety of purposes, including disseminating useful information, fostering mass collaboration, and enforcing laws and regulations. A number of social media-based government stage models have emerged to document this use. In this chapter, we conducted a qualitative meta-synthesis of four social media-based government models. These models include 1) the open government maturity model, 2) the social media utilization model, 3) the adoption process for social media, and 4) the social media-based engagement model. The concepts, metaphors, and themes contained in these developmental models are extracted through a series of in-depth semantic analyses of descriptions, resulting in a common frame of reference.

• 방송공학회논문지
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• 제1권2호
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• pp.176-187
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• 1996

본고는 로보트 팔의 선단에 부착된 카메라에 의하여 촬영된 일련의 스테레오 영상을 이용하여 운동물체의 3차원 자세 (위치와 방향)를 정확히 추정하는 방법을 다룬다. 본고는 이미 발표된 바 있는 연구결과를 확장한 것으로서[1], 2차원 영상의 측정잡음 뿐만아니라[1], 또한 로보트 팔의 죠인트 각도의 랜덤잡음이 함께 존재할 경우 world 좌표계 (또는 로보트 기지좌표계)를 기준으로 한 운동물체의 3차원 자세의 추정에 중점을 둔다. 이를 위하여, 다음 사항에 근거하여 선형 Kalman 필터를 유도한다. (1) 2차원 영상의 측정잡음이 3차원 공간으로 전파되는 것을 분석함으로써, 이에 기인한 물체좌표계의 방향오차를 카메라 좌표계를 기준으로 하여 모델링한다; (2) 죠인트 각도 오차에 의한 로보트 선단좌표계의 방향오차를 (1)의 결과와 결합하여 extended Jacobian matrix를 유도한다; 그리고 (3) 본질적으로 비선형인 물체의 회전운동을 quaternion을 도입함으로써 선형화 한다. 운동 파라메터는 추정된 quaternion으로부터 반복 최소자승 방법을 이용하여 계산된다. 모의실험 결과, 추정오차가 상당히 감소되고, 실제의 운동 파라메터가 참 값으로 정확히 수렴함을 알 수 있다.

• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.508-518
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• 2016

In this paper, we propose a method combining an accelerometer with a cross structured light system to estimate the golf green slope. The cross-line laser provides two laser planes whose functions are computed with respect to the camera coordinate frame using a least square optimization. By capturing the projections of the cross-line laser on the golf slope in a static pose using a camera, two 3D curves’ functions are approximated as high order polynomials corresponding to the camera coordinate frame. Curves’ functions are then expressed in the world coordinate frame utilizing a rotation matrix that is estimated based on the accelerometer’s output. The curves provide some important information of the green such as the height and the slope’s angle. The curves estimation accuracy is verified via some experiments which use OptiTrack camera system as a ground-truth reference.

• 해양환경안전학회지
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• 제1권2호
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• pp.39-52
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• 1995

There are numerous mapping, charting, geodetic systems and electronic digital products defined in various local geodetic datum. It becomes a straight forward requirement to simplify the complexity by referencing all the products to a common reference globally. WGS-84 is well known as a state-of-the-art global reference system based on the use of data, techniques and technology available within American Defence Mapping Agency(DMA). Its parameters can be translated into more accurate maps, charts and geodetic positioning compared to others previously. Since Global Positioning System(GPS/NAVSTAR), which is asssociated with World Geodetic System(WGS-84)in reference frame, has been widely used, the unified geodetic system has been required for GPS users in many fields.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.30-32
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• 2004

With 3-D vision measuring, camera calibration is necessary to calculate parameters accurately. Camera calibration was developed widely in two categories. The first establishes reference points in space, and the second uses a grid type frame and statistical method. But, the former has difficulty to setup reference points and the latter has low accuracy. In this paper we present an algorithm for camera calibration using perspective ratio of the grid type frame with different line widths. It can easily estimate camera calibration parameters such as lens distortion, focal length, scale factor, pose, orientations, and distance. The advantage of this algorithm is that it can estimate the distance of the object. Also, the proposed camera calibration method is possible estimate distance in dynamic environment such as autonomous navigation. To validate proposed method, we set up the experiments with a frame on rotator at a distance of 1, 2, 3, 4[m] from camera and rotate the frame from -60 to 60 degrees. Both computer simulation and real data have been used to test the proposed method and very good results have been obtained. We have investigated the distance error affected by scale factor or different line widths and experimentally found an average scale factor that includes the least distance error with each image. The average scale factor tends to fluctuate with small variation and makes distance error decrease. Compared with classical methods that use stereo camera or two or three orthogonal planes, the proposed method is easy to use and flexible. It advances camera calibration one more step from static environments to real world such as autonomous land vehicle use.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 D
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• pp.2372-2374
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• 2003

With 3-D vision measuring, camera calibration is necessary to calculate parameters accurately. Camera calibration was developed widely in two categories. The first establishes reference points in space, and the second uses a grid type frame and statistical method. But, the former has difficulty to setup reference points and the latter has low accuracy. In this paper we present an algorithm for camera calibration using perspective ratio of the grid type frame with different line widths. It can easily estimate camera calibration parameters such as focal length, scale factor, pose, orientations, and distance. But, radial lens distortion is not modeled. The advantage of this algorithm is that it can estimate the distance of the object. Also, the proposed camera calibration method is possible estimate distance in dynamic environment such as autonomous navigation. To validate proposed method, we set up the experiments with a frame on rotator at a distance of 1,2,3,4[m] from camera and rotate the frame from -60 to 60 degrees. Both computer simulation and real data have been used to test the proposed method and very good results have been obtained. We have investigated the distance error affected by scale factor or different line widths and experimentally found an average scale factor that includes the least distance error with each image. It advances camera calibration one more step from static environments to real world such as autonomous land vehicle use.