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플라즈마분자선에피탁시법을 이용한 사파이어 기판 위 질화알루미늄 박막의 에피탁시 성장
이효성,한석규,임동석,신은정,임세환,홍순구,정명호,이정용,Lee, Hyo-Sung,Han, Seok-Kyu,Lim, Dong-Seok,Shin, Eun-Jung,Lim, Se-Hwan,Hong, Soon-Ku,Jeong, Myoung-Ho,Lee, Jeong-Yong,Yao, Takafumi 한국재료학회 2011 한국재료학회지 Vol.21 No.11
We report growth of epitaxial AlN thin films on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy. To achieve two-dimensional growth the substrates were nitrided by nitrogen plasma prior to the AlN growth, which resulted in the formation of a two-dimensional single crystalline AlN layer. The formation of the two-dimensional AlN layer by the nitridation process was confirmed by the observation of streaky reflection high energy electron diffraction (RHEED) patterns. The growth of AlN thin films was performed on the nitrided AlN layer by changing the Al beam flux with the fixed nitrogen flux at 860$^{\circ}C$. The growth mode of AlN films was also affected by the beam flux. By increasing the Al beam flux, two-dimensional growth of AlN films was favored, and a very flat surface with a root mean square roughness of 0.196 nm (for the 2 ${\mu}m$ ${\times}$ 2 ${\mu}m$ area) was obtained. Interestingly, additional diffraction lines were observed for the two-dimensionally grown AlN films, which were probably caused by the Al adlayer, which was similar to a report of Ga adlayer in the two-dimensional growth of GaN. Al droplets were observed in the sample grown with a higher Al beam flux after cooling to room temperature, which resulted from the excessive Al flux.
이효성,김병호,황종희,임태영,김진호,전대우,정현석,이미재,Lee, Hyo-Sung,Kim, Byung-Ho,Hwang, Jong Hee,Lim, Tae-Young,Kim, Jin-Ho,Jeon, Dae-Woo,Jung, Hyun-Suk,Lee, Mi Jai 한국재료학회 2016 한국재료학회지 Vol.26 No.1
In this study, we fabricated high quality color conversion component with green/red phosphor and low melting glass frit. The color conversion component was prepared by placing the green and red phosphor layer on slide glass via screen printing process. The properties of color conversion component could be controlled by changing coating sequence, layer thickness and heat treatment temperature. We discovered that optical properties of color conversion component were generally determined by the lowest layer. On the other hand, the heat treatment temperature also affected to correlated color temperature (CCT) and color rending index (CRI). The color conversion component with a green (lower) - red (upper) layer which was sintered at $550^{\circ}C$ showed the best optical properties: CCT, CRI and luminance efficacy were 3340 K, 78, and 56.5 lm/w, respectively.
백색 LED용 색변환 렌즈의 열처리 온도 및 코팅 두께에 따른 영향
이효성,황종희,임태영,김진호,정현석,이미재,Lee, Hyo-Sung,Hwang, Jong Hee,Lim, Tae-Young,Kim, Jin-Ho,Jung, Hyun-Suk,Lee, Mi Jai 한국세라믹학회 2014 한국세라믹학회지 Vol.51 No.6
Today, silicon and epoxy resin are used as materials of conversion lenses for white LEDs on the basis of their good bonding and transparency in LED packages. But these materials give rise to long-term performance problems such as reaction with water, yellowing transition, and shrinkage by heat. These problems are major factors underlying performance deterioration of LEDs. In this study, in order to address these problems, we fabricated a conversion lenses using glass, which has good chemical durability and is stable to heat. The fabricated conversion lenses were applied to a remote phosphor type. In this experiment, the conversion lens for white LED was coated on a glass substrate by a screen printing method using paste. The thickness of the coated conversion lens was controlled during 2 or 3 iterations of coating. The conversion lens fabricated under high heat treatment temperature and with a thin coating showed higher luminance efficiency and CCT closer to white light than fabricated lenses under low heat treatment temperature or a thick coating. The conversion lens with $32{\mu}m$ coating thickness showed the best optical properties: the measured values of the CCT, CRI, and luminance efficiency were 4468 K, 68, and 142.22 lm/w in 20 wt% glass frit, 80 wt% phosphor with sintering at $800^{\circ}C$.
이효성 ( Hyo Sung Lee ),송정헌 ( Jung Hun Song ),김용일 ( Yong Il Kim ),안기원 ( Ki Won Ahn ) 大韓遠隔探査學會 2003 大韓遠隔探査學會誌 Vol.19 No.2
본 연구에서는 향후 지속적으로 제공되어질 고해상도 위성영상의 효율적인 대체 센서모델링을 위하여 SPOT-3호의 위성영상으로부터 대상영역에 영상분할을 실시하고 분할된 영상으로부터 분모항이 없는 RFM 즉, 3차 다항식 모델의 적용성을 고찰하였다. 대상영역 전체에 적용한 분모항이 있는 기존 RFM의 적합도와 비교한 결과, 평면오차는 3차 다항식 모델링 방법이 0.8m 정도 낮게 산출된 반면 표고오차는 기존의 RFM이 1.0m 정도 낮게 산출되었다. In this study, for efficient replacement of sensor modelling of high-resolution satellite imagery, image segmentation method is applied to the test area of the SPOT-3 satellite imagery. After that, a third-order polynomial model in the sectioned area is compared with the RFM which is to the entire in the test area. As results, plane error of the third-order polynomial model is lower(approximately 0.8m) than that of RFM. On the other hand, height error of RFM is lower(approximately 1.0m).
이효성 ( Hyo-sung Lee ),김기천 ( Kee-cheon Kim ),김인수 ( In-su Kim ) 한국정보처리학회 2004 한국정보처리학회 학술대회논문집 Vol.11 No.2
본 논문은 Mobile IP 환경의 AAA구조에서 MN의 잦은 이동으로 인한 지역 이동시 발생하는 핸드오프와 MN의 인증 처리과정을 간소화는 방안을 제시한다. MN은 방문망에서 지역이동시 홈망의 AAA 서버로 부터 재인증을 받아야 하며 에이저트간의 인증에 필요한 새로운 세션키를 받아야하는 문제점이 발생한다. 이를 해결하기 위해 지역등록시 AAA 구조에서 발생하는 통신 지연 문제를 해결하고 강화된 AAA구조와의 연동기법을 설계하여 보다 더 부드럽고 안전한 핸드오프 과정을 제안한다.
Determinants for the Employment of the Disabled
Hyo-Sung Lee(이효성),Greene Ko(고그린) 한국콘텐츠학회 2014 한국콘텐츠학회논문지 Vol.14 No.5
본 연구는 장애인 고용의 결정변인에 관한 선행연구가 심리적 특성이 고용에 미치는 영향을 배제했으며, 생의 단계에 따른 고용 결정변인의 차이를 고려하지 못했다는 문제의식으로부터 출발했다. 이와 같은 문제의식에서 본 연구는 첫째, 선행연구에서 고용의 주요 영향요인으로 규명되어 온 인적자본과 함께 심리적 특성을 중심으로 장애인 고용의 결정변인을 규명하고 둘째, 연령집단에 따라 장애인 고용의 결정변인에 어떤 차이가 있는지 밝히고자 했다. 한국복지패널 5차년 자료의 장애인부가조사에 참여한 18세 이상 장애인 1280명의 자료를 이용해 이항로지스틱 분석을 수행했다. 분석결과, 18세에서 40세 이하의 청장년 장애인은 차별을 받은 심리적 경험만이 고용가능성을 유의미하게 낮추었으며, 교육 등 인적자본은 유의미한 영향을 미치지 못하는 것으로 나타났다. 41세 이상 64세 이하의 중년 장애인은 교육수준이 낮고, 건강상태는 높으며, 근로능력이 높을수록 고용 가능성이 유의미하게 증가하는 것으로 나타났다. 65세 이상의 노년 장애인은 근로능력만이 고용가능성을 유의미하게 결정하는 것으로 분석되었다. This study aims to overcome the limitations of prior studies that have failed to take into account the impact of psycho-social factors on the employment of people with disabilities as well as the differences in employment by life stage. This study employs a research model that includes psycho-social factors along with human capital to examine how the determinants of employment differ for the disabled by life stage. The analysis in this study takes the form of logistic regression, using data from the fifth wave of the Korea Welfare Panel Survey. Analysis results how that the employment probability of young people with disabilities is significantly associated with their experience of discrimination, with their chance of employment decreasing when they have more experience of discrimination. Middle-aged people with disabilities are more likely to be employed when they have a lower level of education, a better health condition and a higher level of labor ability. For the disabled elderly, their labor ability is the only factor affecting their possibility of employment; they have a higher chance of getting a job when they have a higher level of labor ability.
이효성 ( Hyo-seong Lee ),정재성 ( Jae-sung Jung ),안기원 ( Ki-won Ahn ) 한국환경기술학회 2008 한국환경기술학회지 Vol.9 No.4
본 연구에서는 IKONOS 2호 고해상도 위성의 Geo레벨 흑백 입체영상과 다중분광영상을 이용하여 정확도가 향상된 정밀 3차원 지형자료 획득을 위해, 첫째, GPS 측량을 통한 지상기준점과 RPC 블럭조정 방법을 적용하여 개선된 DEM을 획득하였다. 둘째, 흑백영상과 동일시기의 다중파장대 영상(공간해상력; 4m)을 이용하여 1m해상도의 융합영상을 작성하였으며, 토지피복도 작성을 위한 참조자료로 활용하였다. 마지막으로, 흑백 입체영상으로부터 획득되어진 DEM자료와 동일시기의 토지피복도 등을 이용하여 복잡하고 다양한 지형요소를 보다 정확하게 분석할 수 있는 3차원 수치지형자료를 작성할 수 있었다. This study is to produce 3D geomorphology data, improved the 3D positioning accuracy, using the IKONOS-2 Geo stereo panchromatic and multispectral data with the high-resolution commercial imagery. For this, we perform the following three steps sequentially: Step 1: digital elevation model(DEM) accuracy is improved by block adjustment method with provided rational polynomial coefficient(RPC) and ground control points(GCPs). GCPs are acquired using the global positioning system(GPS). Where DEM is generated by the area-based matching method and space intersection principal of the adjusted RPC. Step 2: fusion image is made using the high-resolution panchromatic image and multispectral image of the IKONOS-2 satellite. It is utilized for reference data of the land cover classification. Step 3: the 3D digital geomorphology data is produced using the generated DEM and land cover classification map to analysis various topography.