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김종만,손창환,조성대,하영호 대한전자공학회 2007 電子工學會論文誌-SP (Signal processing) Vol.44 No.2
This paper proposes an illuminant-adaptive reproduction method using light adaptation and flare conditions for a mobile display. Displayed images in daylight are perceived as quite dark due to the light adaptation of the human visual system, as the luminance of a mobile display is considerably lower than that of an outdoor environment. In addition, flare phenomena decrease the color gamut of a mobile display and de-saturating the chroma. Therefore, this paper presents an enhancement method composed of lightness enhancement and chroma compensation. First, the ambient light intensity is measured using a lux-sensor, then the flare is calculated based on the reflection ratio of the display device and the ambient light intensity. To improve the perceived image, the image’s luminance is transformed by linearization of the response to the input luminance according to the ambient light intensity. Next, the displayed image is compensated according to the physically reduced chroma, resulting from flare phenomena. This study presents a color reproduction method based on an inverse cone response curve and flare condition. Consequently, the proposed algorithm improves the quality of the perceived image adaptive to an outdoor environment. 본 논문에서는 실외 환경에서 모바일 디스플레이에 발생하는 명순응 현상과 섬광(flare)을 고려하여 주변광원에 적응적인 모바일 디스플레이에서의 색 재현을 제안하였다. 실외 환경에서 디스플레이된 영상은 인간 시각의 명순응 현상에 의해서 어둡게 인지되고 섬광으로 인하여 장치의 밝기는 다소 높아지지만 채도가 감소하는 현상이 발생한다. 이러한 현상을 해결하기 위하여 입력 영상의 밝기를 향상하고 채도를 보상하여 실외에서 영상을 보더라도 실내에서와 유사한 영상으로 인지되도록 하였다. 첫째, 주변광원의 밝기는 조도센서를 사용하여 측정하고, 디스플레이의 반사율을 측정하여 해당 조도 하에서의 섬광을 계산하게 된다. 영상의 밝기는 주변광원의 밝기에 따라 변화하는 추상체(cone) 응답이 선형적으로 되도록 역변환 하여 향상 하였다. 다음은 섬광으로 인하여 발생하는 물리적인 채도 저하 현상은 이것이 발생하기 전과 후의 차를 이용하여 그 크기만큼을 보상해 주었다. 결과적으로 제안한 방법을 적용한 영상을 실외 환경에서 보았을 때 기존의 어둡게 보이고 채도가 낮아지던 현상이 향상됨을 실험을 통하여 알 수 있었다.
Pediatric Liver Transplantation Outcomes in Korea
김종만,이석구,김경모,이남준,최연호,김명수,서경석,김순일,이성규 대한의학회 2013 Journal of Korean medical science Vol.28 No.1
Pediatric liver transplantation is the standard of care for treatment of liver failure in children. The aim of this study was to identify the characteristics of pediatric liver transplantation in centers located in Korea and determine factors that influence outcomes. This retrospective study was performed using data from between 1988 and 2010 and included all recipients 18 yr old and younger who underwent pediatric liver transplantation in Korea during that period. Our data sources were hospital medical records and the outcome measure was overall patient survival. Univariate and multivariate statistical analyses were undertaken using the Cox proportional hazards model. Five hundred and thirty-four pediatric liver transplantations were performed in 502 children. Median age and average pediatric end-stage liver disease (PELD) score were 20 months and 18 point,respectively. Biliary atresia (57.7%, 308/534) was the most common cause of liver disease. Eighty-two (15.3%) were deceased donor liver transplantations and 454 (84.7%) were living donor liver transplantations. Retransplantation was performed in 32 cases (6%). Overall, 1-, 5-, and 10-yr patient survival rates were 87.8%, 82.2%, and 78.1%,respectively. In multivariate analysis, independent significant predictors of poor patient survival were chronic rejection and retransplantation. This study presents the epidemiologic data for nearly all pediatric liver transplantation in Korea and shows that the independent prognostic factors in patient survival are chronic rejection and retransplantation.