• Journal of Astronomy and Space Sciences
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• v.23 no.2
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• pp.127-134
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• 2006

Variation of the Local Time of Ascending Node (LTAN) has been analysed according to initial inclinations when the altitude of Sun-synchronous satellite is continuously decreased due to the atmospheric drag. Orbit predictions of 3 years have been performed with the satellite of 500 km altitude when the initial LTAN were set to 06:00, 09:00, 12:00, 15:00, and 18:00. Different profiles of the inclination and LTAN have been obtained according to the satellite altitude decay and initial LTAN value. Using the profiles of the inclination and LTAN, initial orbital elements can be derived for minimizing the LTAN variations during the mission life time of the sun-synchronous satellite without any on-board thrusters for orbit maneuvers.

• Journal of Advanced Navigation Technology
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• v.26 no.5
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• pp.319-324
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• 2022

If radio interference occurs or there is no navigation device, radio navigation of high-speed moving object becomes impossible. Nevertheless, if there are multiple ground stations and precise range measurement between the high-speed moving object and the ground station can be secured, it is possible to estimate the position of moving object. This paper proposes a position estimation method using high-precision TDOA measurement generated using TLM signal. In the proposed method, a common error of moving object is removed using the TDOA measurements. The measurements is generated based on TLM signal including SOQPSK PN symbol capable of precise timing synchronization. Therefore, since precise timing synchronization of the system has been performed, the timing error between ground stations has a very small value. This improved the position estimation performance by increasing the accuracy of the measured values. The proposed method is verified through software-based simulation, and the performance of estimated position satisfies the target performance.

• Proceedings of the Korea Contents Association Conference
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• 2010.05a
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• pp.618-620
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• 2010

본 논문에서는 위치정보 획득을 위해 GPS로 위치, 자세, 방향 및 시간정보를 추출하고, 6개의 카메라를 이용하여 360도 영상정보를 취득한 후 이들 정보들을 시각 동기화시켜 geoData를 취득하기 위해 개발된 동기화시스템을 기술한다. 이 동기화시스템을 활용하여 360도 파노라믹 영상저작 등 다양한 위치기반서비스를 위한 공간정보시스템을 구축할 수 있다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.6
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• pp.910-915
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• 2018

The precise time, which is an essential element of the Global Navigation Satellite System (GNSS), such as US GPS, GLONASS in Russia, Galileo in Europe, and Beidou in China, is an important foundation for various economic activities around the world. Communication systems, power grids, IoT, Cloud computing and financial networks operate based on the precise time not only for the operating principles, but also for the synchronization and operational efficiency between tasks. In this paper, we introduce the Atomium software for the first time in South Korea. Atomium was developed by ORB in Belgium to calculate the clock error(clock solution) with GNSS signal observation data based on PPP method. The observation data is provided by Korea Research Institute of Standards and Science(KRISS). The results of MJD57106 with Atomium software are presented.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.102-104
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• 2002

시각 동기화된 계통 운전데이터를 이용하여 계통의 안정성을 실시간으로 감시, 분석하는 전력계통 온라인 안정성 감시, 분석시스템을 개발하였다. 개발된 시스템은 대용량 발전소와 주요 345kV 전력소에 설치되어 GPS를 이용한 시각 동기화 된 계통 운전데이터를 측정하고, 지역사고 판단 및 사고데이터를 기록하며, 측정/기록데이터를 Master 시스템으로 온라인 전송해주는 Local 시스템과 각 Local 시스템에서 전송되어진 측정/기록데이터를 수집하고, 광역사고 판단 및 사고데이터를 기록하며. 과도안정도를 온라인으로 평가해주는 Master 시스템으로 구성되어 있다. 전력계통 온라인 안정성 감시, 분석시스템 중 Local 시스템은 울진, 영광, 고리 원자력발전소와 동서울, 신제천, 청양, 아산, 신옥천 전력소 등 8개소에 설치하고, Master 시스템은 한국전력거래소(KPX)에 설치하여 우리 계통의 안정운용을 위해 활용할 예정이다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9A
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• pp.868-877
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• 2006

Sensor network applications need synchronized time to the highest degree such as object tracking, consistent state updates, duplicate detection, and temporal order delivery. In addition, reliability issues and fault tolerance in sophisticated sensor networks have become a critical area of research today. In this paper, we proposed a fault tolerant clock management scheme in sensor networks considering two cases of fault model such as network faults and clock faults. The proposed scheme restricts the propagation of synchronization error when there are clock faults of nodes such as rapid fluctuation, severe changes in drift rate, and so on. In addition, it handles topology changes. Simulation results show that the proposed method has about $1.5{\sim}2.0$ times better performance than TPSN in the presence of faults.

• Journal of Advanced Navigation Technology
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• v.24 no.4
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• pp.267-272
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• 2020

In order to monitor in large area of a ship without any concerns of spacial environments, there can be the use of many sensors that support wireless network technologies. Through the deployment of the wireless sensors and their autonomous network formations, the status of a ship can be easily monitored in real time. Moreover, if all the sensors are timely synchronized with each other, the locations and the moving directions of certain events can be estimated. Thus, the time synchronization amongst wireless sensors are crucial. In this paper, we propose an algorithm which supports reduced message transmissions between the sensors for synchronization.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2000.11a
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• pp.185-188
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• 2000

현재의 3차원 시각 정보 제시기는 Scene Graph 기반의 3차원 그래픽스 API에 기반을 두고 있다. 본 연구에서는 시각 정보 제시에 더불어 다양한 감각을 제시하기 위한 통합 제시 능력을 가지는 시스템으로 시각화 시스템을 확장하였다. 이 확장된 시스템은 다양한 감각 정보를 제시하기 위한 추가적인 정보를 가지는 확장된 Scene Graph을 가지고 운영되며, 통합된 Script System으로 각 감각 제시 시스템들간의 동기화 및 통합 관리와 제시 시스템의 확장에 유리한 장점을 가진다.

• Proceedings of the Korean Society for the Gifted Conference
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• 2003.05a
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• pp.109-126
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• 2003

The Purpose of this study was to develop the instruments which can measure motivation as a component of Visual Artistic Giftedness with in elementary school period. This study prescribed the variable factors of measurement after abstract and classify the characteristics of Visual Artistic Giftedness through literature studies. And it produced instruments those are finally composed of 27 items through the preliminary test. They were evaluated in terms of content validity, construct validity, and reliability by implementing them to 679 elementary school children from the first to sixth grades Statistical analyses were carried out to verify the validities and reliability. Content validity was found to be satisfactory by expert’s evaluation on the test items. Construct validity was also found to be satisfactory through factor analyses which showed the four factors which the identification instruments were intended to measure such as, interest/ attitude/ taste, endurance/ concentration, curiosity/ imagination/ sensitiveness, aesthetic Concurrent validity was also found to be satisfactory with high coeffients of Barron-Welsh which were calculated as .76 in motivation, In conclusion, the instruments about motivation of Visual Artistic Giftedness during elementary school period developed by this study are highly reliable on its reliability and validity.

• Journal of Advanced Navigation Technology
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• v.21 no.3
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• pp.251-257
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• 2017

Recently, hybrid positioning system combining GPS, vision sensor, and inertial sensor has drawn many attentions to estimate accurate vehicle positions. Since accurate multi-sensor fusion requires efficient time synchronization, this paper proposes an efficient method to obtain time synchronized measurements of vision sensor, inertial sensor, and OBD device based on GPS time information. In the proposed method, the time and position information is obtained by the GPS receiver, the attitude information is obtained by the inertial sensor, and the speed information is obtained by the OBD device. The obtained time, position, speed, and attitude information is converted to the color information. The color information is inserted to several corner pixels of the corresponding image frame. An experiment was performed with real measurements to evaluate the feasibility of the proposed method.