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누리호 탑재 위성들의 충돌위험의 예측 및 향후 상황의 대응을 위한 분석
최승환,유중현,김종원,김성애,신경우,김용일,이재진,최성환,송재욱,김해동,마미순,김덕수,Shawn Seunghwan Choi,Peter Joonghyung Ryu,John Kim,Lowell Kim,Chris Sheen,Yongil Kim,Jaejin Lee,Sunghwan Choi,Jae Wook Song,Hae-Dong Kim,Misoon Mah,Doug 한국우주과학회 2023 우주기술과 응용 Vol.3 No.2
Space is becoming more commercialized. Despite of its delayed start-up, space activities in Korea are attracting more nation-wide supports from both investors and government. May 25, 2023, KSLV II, also called Nuri, successfully transported, and inserted seven satellites to a sun-synchronous orbit of 550 km altitude. However, Starlink has over 4,000 satellites around this altitude for its commercial activities. Hence, it is necessary for us to constantly monitor the collision risks of these satellites against resident space objects including Starlink. Here we report a quantitative research output regarding the conjunctions, particularly between the Nuri satellites and Starlink. Our calculation shows that, on average, three times everyday, the Nuri satellites encounter Starlink within 1 km distance with the probability of collision higher than 1.0E-5. A comparative study with KOMPSAT-5, also called Arirang-5, shows that its distance of closest approach distribution significantly differs from those of Nuri satellites. We also report a quantitative analysis of collision-avoiding maneuver cost of Starlink satellites and a strategy for Korea, being a delayed starter, to speed up to position itself in the space leading countries. We used the AstroOne program for analyses and compared its output with that of Socrates Plus of Celestrak. The two line element data was used for computation.
최승환(Seunghwan Choi),곽진호(Jinho Kwak),김명일(Myungil Kim),노명현(Myunghyun Roh),권해붕(Haeboung Kwon),최선모(Sunmo Choi) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In case of conventional speed humps, there are problems of grounding because of the induced heavy pitching motion for the buses especially. Therefore it is strongly needed to new vehicle speed reduction schemes. It will be thought that speed cushions do not generally cause excessive discomfort to passengers of large buses, or excessive discomfort to emergency vehicles such as fire service vehicles or ambulances. To optimize the shape of speed cushion which is replaced with the conventional speed humps, the specifications of the domestic vehicles are surveyed. Based on these survey results, several types of speed cushions are designed and the vertical acceleration data are acquired through the 3D-accelerometers. Two-types of design with heights of 75 or 100 ㎜, plateau width of 1400 ㎜, plateau length of 2400 ㎜, ramp slope of 1-in-8 and side slope of 1-in-4 would give the least effect on buses while still causing discomfort for car occupants.
최승환(Seunghwan Choi),권해붕(Haeboung Kwon),이정기(Jungki Lee),정혁(Hyuk Jung),최동석(Dongseok Choi),김남용(Namyong Kim),박용성(Yongsung Park) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
DPF cleaning is considered as one of good solutions of DPF regenerations. And the DPF cleaning is expected to be subsidized by the government in near future in Korea. But nobody knows the quantitative effect of DPF cleaning on the improvement of DPF regenerative performance, especially damaged DPF filter. This study shows the characteristics of damaged DPF regeneration by DPF cleaning through the field data of DPF cleaning shop and the engine dynamometer test.
최승환(Seunghwan Choi),최선모(Sunmo Choi),정동수(Dongsoo Jeong),장영준(Youngjune Chang),Yasuo Moriyoshi 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
A new gasoline internal combustion engine was designed and built by improving the cranking mechanism. Numerical simulations were also performed to optimize the cranking mechanism to achieve both a high compression ratio operation without knocking and a high thermal efficiency operation. As a result, a special cranking mechanism was considered to make a rapid piston motion near TDC, leading to less heat loss and also a tolerance for knocking limit. To evaluate this new concept, a leaf-shaped gear system was employed in a test engine. As a result, indicated thermal efficiency with the gear system in compression ratio of 12 was improved by 12% compared to a conventional engine with compression ratio of 10. Moreover, the exhaust gas emissions of HC and NOx were much reduced
최승환(Seunghwan Choi),정애라(Aera jeong),김배수(Baesoo Kim),이정기(Jungki Lee),박용성(Yongsung Park) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
Eco driving is considered as one of good solutions for high fuel consumption rate and low concentration of green house gases. Generally, fuel economy is defined as km/L, but vehicle velocity does not considered. The comparison of fuel economy for several vehicles is only possible to the same vehicle speed conditions. To solve the problems, the authors define the eco-index and this study shows the characteristics of eco-driving by using the eco-index.
승용자동차의 운전조건이 연료소모량에 미치는 영향에 관한 연구
최승환(Seunghwan Choi),정혁(Hyuk Jung),신영복(Youngbok Shin),임종순(Jongsoon Lim),신용일(Yongil Shin),박용성(Yongsung Park) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
Eco driving is considered as one of good solutions for high fuel consumption rate and low concentration of green house gases. It is very important to estimate the effects of driving conditions on the fuel consumption. But there is few research results for the quantitative effect of driving conditions on the fuel saving. This study shows the quantitative fuel- economy of passenger car for 6-kinds of driving mode.
최승환(Seunghwan Choi),김남용(Namyong Kim),정혁(Hyuk Jung),이정기(Jungki Lee),권해붕(Haeboung Kwon),박용성(Yongsung Park) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5
It is needed to install the DPF for construction Machine. But there is few study on the characteristics of construction machine engine temperature and exhaust pressure. This study shows the validity of using DPF for construction machine through the field test. And the result is expected to be subsidized by the government in near future in Korea.