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OWL-Net: A global network of robotic telescopes for satellite observation
Park, Jang-Hyun,Yim, Hong-Suh,Choi, Young-Jun,Jo, Jung Hyun,Moon, Hong-Kyu,Park, Young-Sik,Bae, Young-Ho,Park, Sun-Youp,Roh, Dong-Goo,Cho, Sungki,Choi, Eun-Jung,Kim, Myung-Jin,Choi, Jin Elsevier 2018 ADVANCES IN SPACE RESEARCH Vol.62 No.1
<P><B>Abstract</B></P> <P>The OWL-Net (Optical Wide-field patroL Network) is composed of 0.5-m wide-field optical telescopes spread over the globe (Mongolia, Morocco, Israel, South Korea, and USA). All the observing stations are identical, operated in a fully robotic manner, and controlled by the headquarters located in Daejeon, Korea. The main objective of the OWL-Net is to obtain the orbital information of Korean LEO and GEO satellites using purely optical means and to maintain their orbital elements.</P> <P>The aperture size of the mirror is 0.5 m in the Ritchey-Chretien configuration, and its field of view is 1.1 deg on the CCD sensor. The telescope is equipped with an electrically cooled 4 K CCD camera with a 9-µm pixel size, and its pixel scale is 1 arcsec/pixel. A chopper wheel with variable speed is adopted to obtain multiple points in a single shot. Each observatory is equipped with a heavy-duty environment monitoring system for robust robotic observation. The headquarters has components for status monitoring, scheduling, network operation, orbit calculation, and database management.</P> <P>The test-phase operation of the whole system began in early 2017, although test runs for individual sites began in 2015. Although the OWL-Net has 7 observation modes for artificial satellites and astronomical objects, we are concentrating on a few modes for LEO satellites and calibration during the early phase. Some early results and analysis for system performance will be presented, and their implications will be discussed.</P>
장기범(KiBeom Jang),김갑수(Kapsu Kim),조성기(SungKi Cho) 한국음악교육공학회 2003 음악교육공학 Vol.- No.3
The ultimate goal of this study is to develop a standardized music aptitude test, for measuring musical potential and ability of korean children. As a part of procedure, this thesis developed test items, field tested the developed items in Seoul area, and has secured relevant statistical results for the developed test items. More specifically, this study conducted the followings: 1) review of literature and related studies have conducted, 2) based on the findings, five elements of music-rhythm, pitch, timbre, tempo, and dynamics are chosen as components of the music aptitude test, 3) one hundred and five test items (21 test items for each element) have developed by the researchers. The developed 105 test items were field tested twice and a reliability, validity, and causal effects factors are examined by using relevant statistical techniques. As the result, 12 test items of rhythm element, 15 test items of pitch element, 13 test items of timbre element, 10 test items of tempo element, and 13 test items of dynamics element are selected as valid test items. Although, the unselected test items could be used to measure the related musical ability, in order to ensure the effectiveness of the test, they are eliminated from the test items. Thus, it could be concluded that finally selected test items are highly reliable and valid (Cronbach s α= .8851) to measure the ability of the related musical elements. It is highly recommended to develope web-based music aptitude test for continuing research and test item analysis. Based on the constructed web-based data base, a continuing test item development for securing a higher reliability and validity should be conducted. The researchers also believe that through the continuing study of predictive and authentic validity test, the standardization of this test could be obtained more accurate calibration.
Ti-계 코팅이 SCM415강의 마찰ㆍ마모 특성에 미치는 영향
장정환(Jeong-Hwan Jang),탁성훈(Sunghoon Tak),장기(Qi Zhang),허철수(Zhezhu Xu),류성기(Sungki Lyu) 한국트라이볼로지학회 2010 한국윤활학회지(윤활학회지) Vol.26 No.3
The purpose of this study is to show the friction and wear characteristics on the vapor deposited Ti-series coating layers on the SCM415 steel. In this research, frictional wear characteristic of coating materials such as TiN, TiCN, TiAlN was investigated under room temperature, normal air pressure and dry lubricating condition. Therefore this study carried out research on the friction coefficient, micro hardness(Hv), roughness, SEM on the vapor deposited coating layers on the SCM415 steel.
TiAIN+WC/C 다층코팅 SCM415강의 마찰·마모 특성에 관한 연구
장정환(Jeong-Hwan Jang),김남경(Nam-Kyung Kim),김해지(Hae-Ji Kim),장기(Qi Zang),허철수(Zhezhu Xu),류성기(SungKi Lyu) 한국기계가공학회 2010 한국기계가공학회지 Vol.9 No.2
The purpose of this study is to show the friction and wear characteristics on the vapor deposited coating layers on the SCM4l5 steel. In this research, frictional wear characteristic of coating materials such as TiAlN+WC/C Multilayer Coating was investigated under room temperature, normal air pressure and nothing lubricating condition. Therefore this study carried out research on the friction coefficient, micro hardness(Hv), roughness, EPMA on the vapor deposited coating layers on the SCM4l5 steel. As the wear experimental result, the coefficient of friction decreased according to experimental load increases.
TiN과 TiCN 코팅층의 마찰ㆍ마모 특성에 관한 연구
장정환(Jeong-Hwan Jang),탁성훈(Sung-Hoon Tag),장기(Qi Zhang),구재준(Jai-Jun Koo),류성기(SungKi Lyu) 한국기계가공학회 2009 한국기계가공학회 춘추계학술대회 논문집 Vol.2009 No.6월
The purpose of this study is to show the friction and wear characteristics on the vapor deposited coation layers on the SCM415 steel. In this research, frictional wear characteristic of coating materials such as TiN, TiCN was investigated under room temperature, normal air pressure and nothing lubrication condition. Therefore this study carried out research on the friction coefficient, micro hardness(Hv), roughness, SEM on the vapor deposited coating layers on the SCM415 steel.
장정환(Jeong-Hwan Jang),김해지(Hae-Ji Kim),김남경(Nam-Kyeong Kim),김준성(Jun-Seong Kim),류성기(SungKi Lyu) 한국기계가공학회 2008 한국기계가공학회 춘추계학술대회 논문집 Vol.2008 No.-
This study makes clear that tool loading force and number of finish roll forming are very important factors to decide involute tooth profile error. Tooth profile is decided in the beginning of roll forming and δ max mainly increases if the number of roll forming process is increased. Gear class is improved by one or two class after roll forming if the gear has convex type error and pressure angle error in KS 1~4 class. If the gear have concave type error and pressure angle error, gear class is not improved in theory, but improved a little in practice. In the finishing roll forming, it inevitably yields both the concaving of tooth profile and plastic deflection of addendum of teeth. Experiments show that the concaving and the plastic deflection are successfully reduced. The accuracy of tooth profile reaches to KS 0 class.