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해역별 기름유출사고 위험도 매핑 프로그램 개발에 관한 연구
문정환,윤종휘,Moon, Jung-Hwan,Yun, Jong-Hwui 해양환경안전학회 2016 해양환경안전학회지 Vol.22 No.5
본 연구에서는 시스템 다이내믹스 기법을 적용하여 기름유출사고의 동태적 현상을 분석하고, 기름유출 사고초기 사고해역의 위험성을 판단할 수 있도록 기름유출사고의 사고이력에 기초하여 해역별 위험도를 산출하고 위험도 프로그램을 개발하였다. 이를 통해 다음의 결과를 얻었다. 첫째, 기름유출사고 고유데이터를 기초하여 전혀 다른 변수를 단일점수로 산출했으며, 해역별 기름유출 위험도를 정량적인 수치로 산출했다. 둘째, 산출된 사고별 위험도로 해역별 위험도를 도출했으며 이용의 극대화를 위해 스마트기기에서 실행기 가능한 프로그램을 구현했다. 셋째, 우리나라 해역별 기름오염 위험도를 직접적으로 비교평가가 가능해졌으며, 긴급시 신속한 의사결정을 유도할 수 있다. 기름유출사고 위험도를 특별한 제약없이 편리하고 신속하게 판단할 수 있게 됨에 따라 기름유출사고의 선제적인 대비(전략)에 도움을 줄 수 있을 것이라 판단된다. A study was conducted to analyze the oil spill dynamic state using system dynamics method, and to developed regional risk program based on oil spill history for better judgement of the situation at the early stage of oil spill. Results were obtained as follows: Firstly, various variables were calculated by a score based on raw data of oil spill history in Korea. Regional oil spill risk was also calculated in a quantitative way. Secondly, calculated regional oil spill risk was analyzed and programmed with a help of smart-device for better use. Thirdly, comparison of oil spill risk between regions became possible and regional oil spill risk program proved to be useful in prompt decision under urgent situation in response to oil spill at sea. Convenient and quick oil spill risk without special restrictions have been able to determine. and it can help in anticipative preparation (strategy) for oil spills.
Gate-Bias Control Technique for Envelope Tracking Doherty Power Amplifier
문정환,김장헌,김일두,김정준,김범만,Moon, Jung-Hwan,Kim, Jang-Heon,Kim, Il-Du,Kim, Jung-Joon,Kim, Bum-Man The Korean Institute of Electromagnetic Engineerin 2008 한국전자파학회논문지 Vol.19 No.8
본 논문에서는 선형성 증가를 위해 도허티 증폭기의 게이트 바이어스를 조정하는 방식을 제시하였다. 도허티 증폭기의 선형성 향상은 출력 결합 지점에서의 고조파 상쇄를 통해 이루어진다. 하지만 고조파의 상쇄는 그 크기와 위상이 출력 지점에서 같은 크기와 서로 다른 위상을 가지고 있어야 이루어질 수 있는데, 넓은 출력 전력 범위에서 위와 같은 조건을 만족시키는 것은 쉽지 않다. 선형성 증가를 위해 도허티 증폭기의 캐리어 증폭기와 피킹 증폭기의 선형성 특성을 입력 전력과 각 증폭기의 게이트 바이어스를 조정함으로써 살펴보았다. 살펴본 특성을 기본으로 하여 고조파 상쇄 전력 범위를 증가시키기 위해, 각 전력 레벨에 맞는 게이트 바이어스를 증폭기에 인가하였다. 게이트 바이어스 제어를 통한 선형성 향상을 알아보기 위해, 2.345 GHz에서 Eudyna사의 10-W PEP GaN HEMT EGN010MK 소자를 이용하여 도허티 전력 증폭기를 설계하였고, $P_{1dB}$로부터 10 dB back-off 지점인 33 dBm에서 고효율과 고선형성을 위해 최적화 되었다. WCDMA 1-FA 신호에 대해 제안된 게이트 바이어스 컨트롤 된 도허티 증폭기는 2.8 dB의 선형성 개선을 확인할 수 있었으며, 26 %의 PAE를 확인할 수 있었다. 또한, 802.16-2004 신호에 대해 RCE가 2 dB 증가됨을 확인할 수 있었다. The gate-biases of the Doherty power amplifier are controlled to improve the linearity performance. The linearity improvement mechanism of the Doherty amplifier is the harmonic cancellation of the carrier and peaking amplifier at the output power combining point. However, it is difficult to cancel the harmonic power for the broader power range because the condition for cancelling is varied by power. For the linearity improvement, we have explored the linearity characteristic of the Doherty amplifier according to the input power and gate biases of the carrier and peaking amplifier. To extend the region of harmonic power cancellation, we have injected the proper gate bias to the carrier and peaking amplifier according to the input power levels. To validate the linearity improvement, the Doherty amplifier is designed using Eudyna 10-W PEP GaN HEMT EGN010MKs at 2.345 GHz and optimized to achieve a high linearity and efficiency at an average output power of 33 dBm, backed off about 10 dB from the $P_{1dB}$. In the experiments, the envelope tracking Doherty amplifier delivers a significantly improved adjacent channel leakage ratio performance of -37.4 dBc, which is an enhancement of about 2.8 dB, maintaining the high PAE of about 26 % for the WCDMA 1-FA signal at an average output power of 33 dBm. For the 802.16-2004 signal, the amplifier is also improved by about 2 dB, -35 dB.
해상방제능력 향상을 위한 대형 방제선 도입의 필요성과 운용에 관한 연구
문정환(Jung-Hwan, Moon),윤종휘(Jong-Hwui Yun) 한국항해항만학회 2009 한국항해항만학회 학술대회논문집 Vol.2009 No.추계
2007년 우리나라 서해에서 발생한 Hebei Spirit호 사고와 1997년 일본의 Nakhodka호 유출사고, 2002년 스페인의 Prestige호 유출사고 등 재난적 유류유출사고를 통해서 대형 방제선박의 필요성을 확인하고, 대형 방제선의 도입과 도입이후, 방제 외 활용방안을 제시함으로 빈번하지는 않지만 천문학적 피해를 발생하는 재난적 유류유출사고에 효율적이고 효과적으로 대응하고자 한다. Needs of Large Oil Recovery Vessels will be checked by Hebei Spirit Oil Spill in Korea in 2007, Nakhodka Oil Spill in Japan in 1997, Prestige Oil Spill in Spain in 2002. and offer a efficient proposals for practical use besides Catastrophic Oil Spill Response
나노디스크에서의 자기 소용돌이 핵의 3차원 동역학 연구
문정환(Jung-Hwan Moon),이경진(Kyung-Jin Lee),김동현(Dong-Hyun Kim),박홍광(Hong-Guang Piao) 한국자기학회 2012 韓國磁氣學會誌 Vol.22 No.6
Using micromagnetic simulation, we investigated the effect of thickness of a nanodisk on a resonance frequency of vortex gyration. We observed that the resonance frequency increases with increasing thickness in both cases of 2-dimensional (2D) and 3-dimensional (3D) calculation. However, there is a difference in the increasing rate of resonance frequency between 2D and 3D modeling owing to dynamically developed inhomogeneous magnetic texture along the thickness direction of disk in 3D modeling.
문정환(Jung Hwan Moon),김진호(Jin Ho Kim),이승철(Seung Chul Lee) 대한설비공학회 2018 대한설비공학회 학술발표대회논문집 Vol.2018 No.6
In this study, the surge analysis was performed to find out the risk for overflow in a pump station of power plant with different design cases. In case of original design which intake bay length is 36 m, the water level of pump station increases to a maximum of 4.1 m. This result means there is no overflow at the pump station, launching shaft and end shaft, respectively by surging. In case of alternative design, there was no possibility of overflow occurrence since the water level of pump station increased up to 4.4 m. When 4 pumps are tripped, the water level of pump station increases under the height of structure in both original and alternative cases. It was found that the stability of sea water intake system could be secured in spite of the reduction of inlet bay length.
문정환(Jung-Hwan Moon),문승재(Seung-Jae Moon),이재헌(Jae-Heon Lee) 대한설비공학회 2007 설비공학 논문집 Vol.19 No.4
In this paper, the experimental study has been carried out to investigate the reliability lifetime of two bearing units based on the oil temperature. Measurements for the oil temperature as well as the bearing temperature during normal operation were performed to study the effects of oil viscosity and oil submergence percentages in the two bearing units. The optimal lubrication condition to increase the lifetime of the bearing unit A was found that its viscosity and submergence percentage were VG32 and 25%, respectively. For the bearing unit B, when the oil viscosity and submergence percent were VG32 and 75%, the lubrication condition was the most efficient. Finally, the adjusted rating times of both the bearing units were calculated to be over 28,000 h, which is greater than the minimum adjusted rating times of 25,000 h. Therefore, they satisfied the regulated lifetime of API 610.
문정환(Jung Hwan Moon),이재오(Jae Ou Lee),이승철(Seung Chul Lee),손봉세(Bong Sei Son),김용성(Yong Sung Kim) 대한설비공학회 2020 대한설비공학회 학술발표대회논문집 Vol.2020 No.6
In this study, the field application and improvement method of firestop system were investigated. There are currently no standard specification related to through-penetration firestop system in Korea. Basically, the quality of firestop system can be different with construction site because the supplier has its own test certification. It is necessary to prepare standard certificated test methods with insulation material, pipe diameter as well as standard specifications When the fire stop system for vertical and horizontal penetrations of ducts are used in fire partitions, it is not legally required the additional firestop system. This means that the fire damper only can be installed instead of firestop system. However, if it is difficult to secure fire safety with only a fire damper, an automatic fire detector can be installed to prevent from fire and smoke. In addition, the fire partition areas can be installed in the sprinkler system with a quick response type head in order to secure the earlier fire safety.