• Journal of Astronomy and Space Sciences
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• 제36권3호
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• pp.187-197
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• 2019

The Optical Wide-field patroL-Network (OWL-Net) is a Korean optical space surveillance system used to track and monitor objects in space. In this study, the characteristics of four Initial Orbit Determination (IOD) methods were analyzed using artificial observational data from Low Earth Orbit satellites, and an appropriate IOD method was selected for use as the initial value of Precise Orbit Determination using OWL-Net data. Various simulations were performed according to the properties of observational data, such as noise level and observational time interval, to confirm the characteristics of the IOD methods. The IOD results produced via the OWL-Net observational data were then compared with Two Line Elements data to verify the accuracy of each IOD method. This paper, thus, suggests the best method for IOD, according to the properties of angles-only data, for use even when the ephemeris of a satellite is unknown.

• Journal of Astronomy and Space Sciences
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• 제36권3호
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• pp.169-180
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• 2019

In this study, a batch least square estimator that utilizes optical observation data is developed and utilized to determine geostationary orbits (GEO). Through numerical simulations, the effects of error sources, such as clock errors, measurement noise, and the a priori state error, are analyzed. The actual optical tracking data of a GEO satellite, the Communication, Ocean and Meteorological Satellite (COMS), provided by the optical wide-field patrol network (OWL-Net) is used with the developed batch filter for orbit determination. The accuracy of the determined orbit is evaluated by comparison with two-line elements (TLE) and confirmed as proper for the continuous monitoring of GEO objects. Also, the measurement residuals are converged to several arcseconds, corresponding to the OWL-Net performance. Based on these analyses, it is verified that the independent operation of electro-optic space surveillance systems is possible, and the ephemerides of space objects can be obtained.

• 천문학회보
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• 제46권1호
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• pp.48.3-48.3
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• 2021

SomangNet is a project that started in 2020 with a network of ten 0.4 to 1.0 m telescopes owned by Korean institutes. By coordinating observations with multiple facilities around the world, we hope to maximize the usefulness of small telescopes which are still competitive for carrying out time-domain astronomy projects. In this talk, we will give an overview of the project, outlining SomangNet facilities, its organization, and current science projects. We hope to open SomangNet for common use in 2021B, and we will present our plan regarding the use of SomangNet.

• 의료ㆍ복지 건축 : 한국의료복지건축학회 논문집
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• 제16권4호
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• pp.33-40
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• 2010

Gross-to-net ratio is the important factor determining size of the building. However it was determined as the empirical method without the exact basis in the existing planning. This paper proposes more accurate methods for determining the gross-to-net ratio of architectural planning in general hospital. This paper analyzes the difference of gross-to-net ratio according to the various conditions and presents the elements of influencing on gross-to-net ratio. These elements is evaluated by applying in the typical hospital case. In conclusion, gross-to-net ratio is influenced by the accuracy of the space program, form type of the space and correspondence potential about the internal variation. In addition, This study has proved that empirical approach is a standard of minimum area.

• 한국콘텐츠학회논문지
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• 제11권1호
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• pp.16-25
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• 2011

컴퓨터 환경에서 한 가지 사건으로 상황이 특징 지워지기도 하지만, 일반적 상황 인식은 공간과 시간을 포함하는 다양한 사건들에 의해서 결정되어 진다. 상황 인식 서비스 관계 설정 방법으로 임베디드 시스템 상황 인식을 시공간적으로 취급하는 것이 요구된다. 물리 공간과 연동되는 시스템의 예외적 동작은 임베디드 시스템의 운영에 심각한 위험과 피해를 초래 할 수 있다. 본 논문은 상황 인식 모델에 시공간적 특성과 예외 관리가 포함 되도록 하는 방법을 제안하고, 이를 확장된 Petri-Net을 이용하여 효과를 확인한다. 실시간 임베디드 시스템 상황 인식을 위해 기본 Petri-Net, 패턴화된 Petri-Net 및 예외 동작을 위한 시공간 Petri-Net 모델 특성을 연구한다. 이 방법을 이용하여 응급의료지원 서비스에 적용 예를 보였다. 본 연구를 통해 시공간 Petri-Net을 사용한 응용 개발 뿐 만아니라 예외 처리를 위한 시공간 상황 인식 모델링에 기여 할 것이다.

• Nuclear Engineering and Technology
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• 제54권12호
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• pp.4776-4797
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• 2022

In the one-dimensional thermal-hydraulic (TH) codes, a subcooled boiling model to predict the void fraction profiles in a vertical channel consists of wall heat flux partitioning, the vapor condensation rate, the bubbly-to-slug flow transition criterion, and drift-flux models. Model performance has been investigated in detail, and necessary refinements have been incorporated into the Safety and Performance Analysis Code (SPACE) developed by the Korean nuclear industry for the safety analysis of pressurized water reactors (PWRs). The necessary refinements to models related to pumping factor, net vapor generation (NVG), vapor condensation, and drift-flux velocity were investigated in this study. In particular, a new NVG empirical correlation was also developed using artificial neural network (ANN) techniques. Simulations of a series of subcooled flow boiling experiments at pressures ranging from 1 to 149.9 bar were performed with the refined SPACE code, and reasonable agreement with the experimental data for the void fraction in the vertical channel was obtained. From the root-mean-square (RMS) error analysis for the predicted void fraction in the subcooled boiling region, the results with the refined SPACE code produce the best predictions for the entire pressure range compared to those using the original SPACE and RELAP5 codes.

• 충청수학회지
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• 제23권1호
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• pp.109-117
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• 2010

In this paper, we define the concept of a c-net and study the convergence of c-nets. Also we show that a c-net in a topological space X has a convergent sub-c-net if and only if X is a $Lindel{\ddot{o}}f$ space, if every $G_{\delta}$ set is open in X.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1132-1134
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• 2005

This paper presents a design strategy of Slotless type BLDC motor using the space harmonic field method. The distribution of Back emf and torque are considered by movement of the Permanent Magnet and armature current. The result of magnetic field distribution, back-emf, and torque are in agreement with FEM.

• Journal of Astronomy and Space Sciences
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• 제33권2호
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• pp.137-146
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• 2016

The correlation between meteorological data collected at the optical wide-field patrol network (OWL-Net) Station No. 1 and the seeing of satellite optical observation data was analyzed. Meteorological data and satellite optical observation data from June 2014 to November 2015 were analyzed. The analyzed meteorological data were the outdoor air temperature, relative humidity, wind speed, and cloud index data, and the analyzed satellite optical observation data were the seeing full-width at half-maximum (FWHM) data. The annual meteorological pattern for Mongolia was analyzed by collecting meteorological data over four seasons, with data collection beginning after the installation and initial set-up of the OWL-Net Station No. 1 in Mongolia. A comparison of the meteorological data and the seeing of the satellite optical observation data showed that the seeing degrades as the wind strength increases and as the cloud cover decreases. This finding is explained by the bias effect, which is caused by the fact that the number of images taken on the less cloudy days was relatively small. The seeing FWHM showed no clear correlation with either temperature or relative humidity.

• The Journal of the Acoustical Society of Korea
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• 제14권2E호
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• pp.43-49
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• 1995

인공지능(AI)의 한기법인 Space Search 기법을 이용하여 회로의 단선 결함의 유무 및 결함위치를 찾아내는 방법을 제시하였다. 보통 회로의 결함은 단선 및 단락의 구조적 결함으로 나뉘어진다. 두가지 결함 모두 회로의 기능에 중대한 이상을 초래한다. 그중 단선에 의한 회로의 결함에 대하여 다루었다. 우선 회로를 net와 net의 연결 path에 따라 tree 구조로 변환하였다. 서로 독립된 net들은 서로 다른 tree의 node를 이루며 각각의 tree는 적기적으로 연결됨이 없다. 각 tree의 최상단부의 root node에 test vector를 입력하고 최하단부의 leaf node에서 vector를 관찰하여 입력된 test vector와 비교한다. 그 비교 결과 동일 유무에 따라 결함의 유무를 판정한다. 결함이 있다고 판정된 leaf node는 depth search 방법에 의하여 root node쪽으로 test vector를 관찰하여, 전기적 신호에 의하여 회로의 서놔 단선된 위치를 찾아내도록 하는 방법을 제시하였다.