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Observation of long-term disappearance and reappearance of the outer radiation belt
이대영,신대규,김경찬,김진희,조정희,박미영,황정아,이용희,김경호,Lee, Dae-Young,Shin, Dae-Kyu,Kim, Kyung-Chan,Kim, Jin-Hee,Cho, Jung-Hee,Park, Mi Young,Angelopoulos, Vassilis,Hwang, Junga,Lee, Yonghee,Kim, Thomas 한국천문학회 2012 天文學會報 Vol.37 No.2
In this study we have used the data of various instruments onboard the THEMIS spacecraft to study the characteristics of the outer radiation belt during the ascending phase of solar cycle 24. The most astonishing result is that we discovered four long-term (a month or so) periods during which the belt has nearly disappeared. The first disappearance started late 2008, followed by reappearance in ~a month, and three more similar events repeated until early 2010 when the belt has reappeared. This is well revealed at 719 keV electrons, which is the currently available uppermost energy channel from the THEMIS SST observation, but also seen at even lower energies. Overall consistent features were confirmed using the NOAA-POES observations. The vanished belt periods are associated with extremely weak solar wind conditions, low geomagnetic disturbances (in terms of Kp and AE/AL), greatly suppressed wave (ULF and chorus) activities, greatly reduced storm and substorm activities (little source particle supply), and expanded plasmapause locations. The direct observations of such events shed light on the fundamental question of the origin of the radiation belt, which is the main focus of our presentation.
중심성장액맥락망막병증에서 레이저검안경검사상 과형광부위에 대한 광간섭단층촬영 검사결과 분석
이대영,김동희,남우호,유승영,곽형우,Dae-Young Lee,Dong-Hee Kim,Woo-Ho Nam,Seung-Young Yu,Hyung-Woo Kwak 대한안과학회 2005 대한안과학회지 Vol.46 No.6
Purpose: To analyze the optical coherence tomography (OCT) result at the area of hyperfluorescence by scanning laser ophthalmoscopy (SLO) in central serous chorioretinopathy. Methods: We investigated sensory detachment, pigment epithelial detachment (PED), choroidal neovascularization (CNV), and retinal pigment epithelial atrophy using OCT in the area of hyperfluorescein by scanning laser ophthalmoscopy (SLO) in 29 eyes of 29 patients with CSC. Results: Of 29 eyes, no specific finding was noted in 19 eyes. Small PED corresponding to the leaking point was noted in 3 eyes, large serous PED with leaking point in 2 eyes, hemorrhagic PED in 1 eye, subretinal precipitate and PED in 1 eye, and retinal pigment epithelial atrophy in 2 eyes. Conclusions: OCT provided intuitive and objective information on the pathophysiologic state of the retinal pigment epithelial layer at the area of hyperfluorescence by SLO in CSC.
분산 네트워크 환경하에서 암호화 된 사용자 인증 모듈을 적용한 데이터베이스 보안 시스템
이대영,김옥환,Lee Dae-Young,Kim Ok-Hwan 한국정보통신학회 2006 한국정보통신학회논문지 Vol.10 No.2
분산 컴퓨터 네트워크는 단일 시스템의 동작 정지로 인한 전체 시스템에 미치는 영향을 적 게 함으로써 신뢰도를 높일 수 있고, 한 개의 대형 시스템을 활용하는 것 보다 저렴한 비용으로 보다 나은 성능을 얻을 수 있는 장점이 있다. 또한 시스템이 확장 및 재구성이 용이하다[1]. 그러나, 분산 컴퓨팅 환경에서 네트워크를 통한 데이터의 공유는 실생활이 되고 있는 반면 네트워크 환경에서 데이터의 무결성과 보안에 대한 위험성은 증가하고 있다[2],[3]. 따라서 본 논문에서는 운영적 요소와 기술적 요소에 대한 분석을 통해 이러한 요소들을 결합시키기 위한 네트워크 암호화 데이터베이스 보안시스템 모델을 제시한다. 제시한 모델에 운영적 요소와 기술적 요소를 체계적으로 결합시킨다면 분산 컴퓨팅 환경에서 허가받지 않은 사용자로부터 데이터를 안전하게 보호할 암호화 데이터베이스 보안 시스템을 구축할 수 있을 것이다. This paper describes access control, user authentication, and User Security and Encryption technology for the construction of database security system from network users. We propose model of network encrypted database security system for combining these elements through the analysis of operational and technological elements. Systematic combination of operational and technological elements with proposed model can construct encrypted database security system secured from unauthorized users in distributed computing environment.
이대영,조관식,노승탁,강병하,Lee, Dae-Yeong,Jo, Gwan-Sik,No, Seung-Tak,Kim, Byeong-Ha 대한기계학회 1996 大韓機械學會論文集B Vol.20 No.4
A theoretical analysis was performed on the heat transfer by laminar oscillating flow in a simplified heat exchanger of a Stirling cycle machine and the results were compared with the experiment of Hwang. In the analysis the general solution to the temperature field obtained by Lee et. al was applied and extended to a more realistic situation. The results show that the heat transfer is influenced by the ratio of the swept distance of the fluid to the length of the heat exchanger as well as the oscillation frequency. This is well consistent with the result of Hwang's experiment. It is also revealed that there exist three distinct regimes having different heat transfer mechanisms. Through the scale analysis the main parameters governing the heat transfer in each regime are reduced and the dependency of the heat transfer on the parameters are examined.
설계기준초과지진 하의 원전 배관 구조건전성 평가를 위한 변형률 기반 방법
이대영,박흥배,김진원,류호완,김윤재,Lee, Dae Young,Park, Heung Bae,Kim, Jin Weon,Ryu, Ho Wan,Kim, Yun-Jae 한국압력기기공학회 2016 한국압력기기공학회 논문집 Vol.12 No.2
Following the 2011 Fukushima Nuclear Power Plant accident, the IAEA has issued a revised version of the Nuclear Safety Standard for beyond design basis earthquake to consider the core meltdown accident. In Korea, relevant laws and regulations were also revised to consider beyond design basis earthquake to nuclear components. In this paper, CAV, an seismic damage factor that determines the restart of nuclear power plant after operating breakdown earthquake, is proposed for extension to the beyond design basis earthquake. For pipings not satisfying the beyond design basis earthquake condition, several evaluation methods are suggested, such as strain-based evaluation methods, simple nonlinear analysis method and cumulative damage evaluation method.
이대영,박흥배,김진원,김윤재,Lee, Dae Young,Park, Heung Bae,Kim, Jin Weon,Kim, Yun-Jae 한국압력기기공학회 2016 한국압력기기공학회 논문집 Vol.12 No.1
After Japanese Fukushima nuclear power plant accident caused by the beyond design basis earthquake and tsunami, it has turned to be a major challenge for nuclear safety. IAEA, US NRC and EU have provided new safety design standards for beyond design basis event, Domestic regulatory bodies have also enacted guidances for licensees and applicants on additional methods related to beyond design basis events. This paper describes several evaluation methods for applying to nuclear power plants piping for beyond design basis earthquake. As a results, energy method based on the absorbed energy on nuclear power plant, deterministic method following design code and theory, experience method considering past earthquake data and information and probabilistic methods similar to probabilistic risk assessment were reviewed.
이대영,신대규,Lee, Dae-Young,Shin, Dae-Kyu 한국천문학회 2012 天文學會報 Vol.37 No.2
The radiation belt structure can be approximately reproduced by a form of diffusion equation, which takes into account the radial diffusion process as well as those in pitch angle and energy. The solution of the equation depends on several factors including initial and boundary conditions, diffusion coefficients, and plasmapause location. In this paper, we have attempted to determine a set of approximate functions for the energetic electron fluxes near the outer edge of the outer belt in terms of solar wind variable. We used the electron flux data from SST onboard the THEMIS spacecraft and determined its correlation with solar wind conditions in a systematic way. The functions were determined separately for different energy channels from ~30 keV up to 719 keV. Our determination of these functions allows us to predict the radial boundary condition for the electron flux, which can be implemented in a forecast model.
하드 디스크 드라이브 회전수 변화가 내부 필터 입자 포집 성능에 미치는 영향
이대영,박희성,유용철,황정호,Lee, Dae-Yeong,Park, Hui-Seong,Yu, Yong-Cheol,Hwang, Jeong-Ho 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.8
Contamination particles in a hard disk drive can cause serious problems including slider crash and thermal asperities. A recirculation filter is typically installed in the hard disk drive to remove the particles. Measurements and theoretical predictions of particle concentration decay with the filter are carried out for a commercially available HDD. Especially, the effect of disk rotational speed on the particle capture efficiency is investigated. Results show that filter efficiency is higher for higher disk rotational speed.
좌 고유구조지정법 기반 결실 고장 분리 필터 설계 및 비행체 시스템에의 응용
이대영,최재원,Lee, Dae-Yung,Park, Jae-Weon 제어로봇시스템학회 2001 제어·로봇·시스템학회 논문지 Vol.7 No.5
In this paper, we propose a novel robust fault isolation filter design method using the left eigenstructure assignment scheme proposed by the authors. The proposed method guarantees that the ${\gamma}$ simultaneous faults can be isolated when the number of available outpur measurements is ${\gamma}$. Moreover, if there exist redundant output measurements, the eigenvaluses of te filter system can be assigned to the desired position or the filter can be designed robustly to, the system parameter variation. Liu & Si developed a filter design method which has the same purpose, fault isolation. However their method cannot use the redundant freedom of the output matrix C. The proposed filter can use the redundant freedom of the matrix C effectively. Beside this in this paper, an eigenstructure assignment methodology that satisfies the required fault isolation conditions is also proposed. The proposed fault isolation filter was applied for isolating the simultaneous faults to a VTOL aircraft in order to verify the fault isolation performance.