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코드북 영상을 이용한 고속 프랙탈 영상 복호기에 관한 연구
이기욱,곽노윤 한국산학기술학회 2003 한국산학기술학회논문지 Vol.4 No.4
Since Jacquine introduced the image coding algorithm using fractal theory, many fractal image compression algorithms providing good quality at low bit rate have been proposed by Fisher and Beaumount et al.. But a problem of the previous implementations is that the decoding rests on an iterative procedure whose complexity is image-dependent. This paper proposes an iterative-free fractal image decoding algorithm to reduce the decoding time. In the proposed method, under the encoder previously with the same codebook image as an initial image to be used at the decoder, the fractal coefficients are obtained through calculating the similarity between the codebook image and an input image to be encoded. As the decoding process can be completed with received fractal coefficients and predefined initial image without repeated iterations, the decoding time could be remarkably reduced. Jacquin에 의해 프랙탈 이론을 이용한 영상 부호화 기법이 소개된 이래로, Fisher와 Beaumont 등에 의하여 낮은 비트율에서도 우수한 화질을 제공하는 프랙탈 영상 압축 기법들이 다수 제안되었다. 그러나 기존에 고안된 기법들이 갖고 있는 하나의 문제점은 복호화가 반복 처리를 통해 구현되며 그 복잡도가 각각의 영상에 따라 상이하다는 것이다. 본 논문에서는 복호 시간을 단축시키기 위해 반복 변환이 필요 없는 프랙탈 영상 복호 알고리즘을 제안하고자 한다. 제안된 방법은 복호기에서 사용할 초기 영상과 동일한 코드북 영상을 부호기에 보유하고 있는 상태에서 부호화 과정에서는 이 코드북 영상과 부호화하려는 영상의 유사성을 찾아 프랙탈 계수를 구한다. 이후, 복호화 과정에서는 수신된 프랙탈 계수와 기설정된 초기 영상을 이용하여 반복 변환 없이 한 번에 영상을 복호함으로써 복호 시간을 현저하게 단축시킬 수 있었다.
이기욱,배경남,손진화,신기혁,김훈수,고현창,김병수,김문범 대한피부과학회 2022 대한피부과학회지 Vol.60 No.7
Background: Green nail syndrome (GNS) is characterized by a greenish discoloration of the nail with accompanying nail apparatus disorders, such as onycholysis or paronychia. To date, data on the clinical characteristics of GNS are limited, especially in Korea. Objective: This study aimed to investigate the clinical characteristics of GNS. Methods: We retrospectively reviewed the medical records and clinical photographs of 78 patients with 91 GNS lesions diagnosed at the Pusan National University Hospitals (Busan and Yangsan) from 2009 to 2021. Results: Among 78 patients, 47 (60.3%) were female and 31 male (39.7%), with a mean age of 53.1 years (23∼82 years). This study included 56 fingernail (61.5%) and 35 toenail lesions (38.5%). Thumbnails and great toenails were the most common site, with 62 lesions (68.1%). Most patients presented predisposing conditions, such as frequent exposure to wet conditions (55.1%), immunosuppressive conditions (26.9%), and trauma history (29.5%). The most common colors, shapes, and eccentricities of GNS were blackish-green (31.9%), reverse triangle (53.8%), and distal eccentricity (42.9%), respectively. The GNS was accompanied by various nail diseases that mostly (80.2%) preceded the syndrome, and onycholysis was the most common (83.5%). Based on the involvement of the nail surface or subsurface, GNS can be divided into the superficial (15.4%), subungual (73.6%), and mixed (11.0%) subtypes, each of which shows different clinical features, such as multiplicity, color, shape, and eccentricity. Conclusion: This is the largest-scale study showing the clinical characteristics of GNS and can be helpful for dermatologists who usually and primarily treat GNS.