http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
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.
다양한 치태조절기구가 타이타늄 임프란트의 표면조도와 형태에 미치는 영향
최승환,임정수,송인택,김형섭,Choi, Seoung-Hwan,Lim, Jeong-Su,Song, In-Taeck,Kim, Hyoug-Seop 대한치주과학회 1998 Journal of Periodontal & Implant Science Vol.28 No.2
The purpose of this' study was to compare surface roughness and morphologic changes after use of various plaque control devices to titanium implant surfaces. The study materials were 6 ITI titanium implants($Bonefit^{(R)}$) and 5 plaque control devices. 6 implants were divided into 6 different groups and instrumented by each plaque control devices as follows. 1) Group I : untreated control 2) Group II : Titanium curette(Titanium $curette^{(R)}$, 3i) 80 vertical/horizontal strokes 3) Group III : Plastic curette($Implacare^{(R)}$, Hu-Friedy) 80 vertical/horizontal strokes 4) Group N : Plastic tip-ultrasonic scaler($Amdent^{(R)}$, Amdent) 160 seconds 5) Group V : Rotating interdental brush($Identobrush^{(R)}$, Identoflex) 160 seconds 6) Group VI : Abrasive rubber cup polisher($Zircate^{(R)}$, Prophy paste, Dentsply) 160 sec-onds. All specimens were prepared for evaluation by surface roughness tester, optical stereomicroscopy(OM) and scanning electron microscopy(SEM). The Ra and Rt mean values of the tested specimens were 1) Group I ($Ra=0.170{\pm}0.007{\mu}m$, $Rt=1.297{\pm}0.016{\mu}m$) 2) Group II ($Ra=0.209{\pm}0.006{\mu}m$, $Rt=1.602{\pm}0.110{\mu}m$) 3) Group III ($Ra=0.179{\pm}0.001{\mu}m$, $Rt=1.429{\pm}0.055{\mu}m$) 4) Group IV ($Ra=0.182{\pm}0.005{\mu}m$, $Rt=1.511{\pm}0.085{\mu}m$) 5) Group V ($Ra=0.301{\pm}0.008{\mu}m$, $Rt=1.882{\pm}0.131{\mu}m$) 6) Group VI ($Ra=0.147{\pm}0.010{\mu}m$, $Rt=1.059{\pm}0.021{\mu}m$) In Ra values, experimental group II, V, VI were statistically significant different when compared with control. OM and SEM observation showed that experimental group III, IV were minimal changes when compared with control and group VI was smoothest among other experimental groups. The results suggested that plastic curette and plastic tip-ultrasonic scaler were predictable devices to titanium implant surface.
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
스마트그리드 운영을 위한 표준 기반 데이터 관리 및 통신 인프라에 관한 연구
최승환(Seung-Hwan Choi),신진호(Jin-Ho Shin),김준성(Jun-Sung Kim) 대한전기학회 2013 전기학회논문지 Vol.62 No.9
Recently, there is a rising interest in smart grid operating system which manages various types of distributed generation, smart meters, and electric vehicles with power grid. Considering the features of smart grid environment, the interoperability should be one of the important factors to build smart grid environment successfully. To secure interoperability, smart grid operating system should conform to some standards in terms of the data representation and communication. CIM and OPC-UA are the international standards widely used in smart grid domain for enabling interoperability. They provide common information model and the unified architecture for communicating between each systems or applications. In this paper, we illustrate a smart grid operating system that we have developed to secure interoperability between not only applications but also numerous legacy systems(applications) by implementing CIM based information model and OPC-UA based communication interface services.
최승환(Seung-hwan Choi),조승완(Seung-wan Cho),김규보(Gyu-bo Kim),전충환(Chung-hwan Jeon),장영준(Young-june Chang) 한국자동차공학회 2003 한국자동차공학회 지부 학술대회 논문집 Vol.2003 No.5
A CVCC was used to investigate the flow characteristics at spark plug and the combustion characteristics of homogeneous charge methane-air mixture under various initial pressure, excess air ratio and ignition times in quiescent mixture. The flow characteristics such as mean velocity and turbulence intensity was analyzed by hot wire anemometer. Combustion pressure development measured by piezoelectric pressure transducer and flame propagation acquired by ICCD camera were used to investigate the effect of initial pressure, excess air ratio and ignition times on pressure, flame speed and burning velocity. Mean velocity and turbulence intensity had the maximum value. at 200 or 300ms and then decreased to near 0 value gradually after 3 seconds. Flame speed and burning velocity were observed to be promoted with excess air ratio of 1.1, lower initial pressure and ignition time of 300ms.<br/> <br/>
HD 음성 서비스를 제공하는 스마트폰 어플리케이션의 구현
최승환(Seung-Han Choi),김도영(Do-Young Kim),서창호(Chang-Ho Seo) 한국정보보호학회 2013 정보보호학회논문지 Vol.23 No.4
본 논문은 ITU-T 표준 코덱인 G.711.1 광대역 코덱을 적용한 HD 보이스 스마트폰 어플리케이션의 개발 내용을 설명한다. 개발 내용에는 G.711.1 광대역 코덱을 적용한 HD 보이스 스마트폰 어플리케이션의 구조와 개발된 HD보이스 어플리케이션의 음성 품질 결과를 포함하고 있으며, ITU-T의 다른 표준 코덱인 G.722 코덱을 적용한 어플리케이션 보다 음성 품질이 MOS값 ? 0.5(패킷 손실 환경 포함)로 향상된 결과가 나왔다. This paper represents the development of the HD-Voice application with G.711.1 coder-the latest wideband codec standard from ITU-T-for smartphone based on android platform. The work also includes the structure of the HD-voice application and the result of speech quality of HD-Voice application with G.711.1 coder. The paper shows that the speech quality of HD-Voice application with G.711.1 coder is excellent.