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노안에서 조절미세파동의 고 진동수 영역 및 조절래그와 조절력의 관계
주락현,이동호,이도형,김진형,Lock Hyun Ju,MD,Dong Ho Lee,MD,Do Hyung Lee,MD,PhD,Jin Hyoung Kim,MD,PhD 대한안과학회 2014 대한안과학회지 Vol.55 No.11
Purpose: To determine the relationship between the high-frequency component of accommodative microfluctuation (HFC) and accommodative lag in presbyopic eyes and how they affect the subjective accommodation power with other ophthalmic factors, such as pupil diameter and corneal multifocality. Methods: Forty subjects (80 eyes) were included in this study, and the non-corrected distance and near visual acuity was measured and then converted to log MAR vision. The addition power for 33 cm near visual work was also measured and the accommodative power was measured by the push-up method. The HFC, accommodative lag and pupil size according to accommodative stimuli (-1.0 to -3.0 D) was measured by Speedy-i Autorefractor (Right Mfg Co., Tokyo). The corneal multifocality and corneal astigmatism was measured by corneal topography (TMS-4; Tomey, Erlangen, Germany). Results: The mean age was 60.0 ± 4.66 years (51-68) and there were 23 male and 17 female subjects (1.35:1). The HFC and pupil size showed no significant change according to accommodation demand, however, the accommodative lag showed a statistically significant increase (<EM>p</EM> < 0.001 by one-way ANOVA). Accommodative lag (-2.0 D) showed a statistically significant negative correlation with the subjective accommodative power, and the pupil size (0 D) showed a positive correlation with the subjective accommodative power. Conclusions: In presbyopia patients, the objective accommodative lag and initial pupil size showed a statistically significant relationship with subjective accommodative power. On the other hand, HFC, pupil size and corneal multifocality, alone may not be indicators to predict accommodative power, but these are important components to explain the dynamic aspect of accommodation. J Korean Ophthalmol Soc 2014;55(11):1606-1612
김보경,주영도,이동호,Kim, Bo-Kyeong,Joo, Young-Do,Lee, Dong-Ho 한국정보처리학회 2008 정보처리학회논문지D Vol.15 No.6
최근 NAND 플래시 메모리는 하드 디스크에 비해 작고, 속도가 빠르며, 저 전력 소모 등의 장점을 가지고 있어 차세대 저장 매체로 각광받고 있다. 그러나 쓰기-전-소거 구조, 비대칭 연산 속도 및 단위와 같은 독특한 특징으로 인하여, 디스크 기반의 시스템이나 응용을 NAND 플래시 메모리 상에 직접 구현시 심각한 성능저하를 초래할 수 있다. 특히 NAND 플래시 메모리 상에 B-트리를 구현할 경우, 레코드의 잦은 삽입, 삭제 및 재구성에 의한 많은 양의 중첩 쓰기가 발생할 수 있으며, 이로 인하여 급격한 성능 저하가 발생할 수 있다. 이러한 성능 저하를 피하기 위해 ${\mu}$-트리가 제안되었으나, 잦은 노드 분할 및 트리 높이의 빠른 신장 등의 문제점을 가지고 있다. 본 논문에서는 갱신 연산을 위해 특정 단말 노드에 해당하는 로그 노드를 할당하고, 해당 로그 노드에 있는 변경된 데이터를 한 번의 쓰기 연산으로 저장하는 로그 기반의 B-트리(LSB-트리)를 제안한다. LSB-트리는 부모 노드의 변경을 늦추어 추가적인 쓰기 연산의 횟수를 줄일 수 있다는 장점을 가지고 있다. 또한 키 값에 따라 데이터를 순차적으로 삽입할 때, 로그 노드를 새로운 단말 노드로 교환함으로써 추가적인 쓰기 연산의 횟수를 줄일 수 있다. 마지막으로, 다양한 비교 실험을 통하여 ${\mu}$-트리와 비교함으로써 LSB-트리의 우수성을 보인다. Recently, NAND flash memory is becoming into the spotlight as a next-generation storage device because of its small size, fast speed, low power consumption, and etc. compared to the hard disk. However, due to the distinct characteristics such as erase-before-write architecture, asymmetric operation speed and unit, disk-based systems and applications may result in severe performance degradation when directly implementing them on NAND flash memory. Especially when a B-tree is implemented on NAND flash memory, intensive overwrite operations may be caused by record inserting, deleting, and reorganizing. These may result in severe performance degradation. Although ${\mu}$-tree has been proposed in order to overcome this problem, it suffers from frequent node split and rapid increment of its height. In this paper, we propose Log-Structured B-Tree(LSB-Tree) where the corresponding log node to a leaf node is allocated for update operation and then the modified data in the log node is stored at only one write operation. LSB-tree reduces additional write operations by deferring the change of parent nodes. Also, it reduces the write operation by switching a log node to a new leaf node when inserting the data sequentially by the key order. Finally, we show that LSB-tree yields a better performance on NAND flash memory by comparing it to ${\mu}$-tree through various experiments.
플래시 메모리상에 B+트리를 위한 효율적인 색인 버퍼 관리 정책
이현섭,주영도,이동호,Lee, Hyun-Seob,Joo, Young-Do,Lee, Dong-Ho 한국정보처리학회 2007 정보처리학회논문지D Vol.14 No.7
최근 NAND 플래시 메모리는 충격에 강한 내구력과, 저 전력 소비, 그리고 비휘발성이라는 특징 때문에 MP3 플레이어, 모바일 폰, 노트북과 같은 다양한 이동 컴퓨팅 장비의 저장 장치로 사용되고 있다. 그러나 플래시 메모리의 특수한 하드웨어적 특징 때문에 디스크 기반의 시스템을 플래시 메모리상에 곧바로 적용 하는 것은 여러 단점들을 발생 시킬 수 있다. 특히 B트리가 구축될 때 레코드의 삽입, 삭제연산 및 노드 분할 연산은 많은 중첩쓰기 연산을 발생하기 때문에 플래시 메모리의 성능을 심각하게 저하시킬 것이다. 본 논문에서는 IBSF로 불리는 효율적인 버퍼 관리 기법을 제안한다. 이것은 색인 단위에서 중복된 색인 단위를 제거하여 버퍼가 채워지는 시간을 지연시키기 때문에 B트리를 구축할 때 플래시 메모리에 데이터를 쓰는 횟수를 줄인다. 또한 다양한 실험을 통하여 IBSF 기법이 기존에 제안되었던 BFTL 기법보다 좋은 성능을 보이는 것을 증명한다. Recently, NAND flash memory has been used for a storage device in various mobile computing devices such as MP3 players, mobile phones and laptops because of its shock-resistant, low-power consumption, and none-volatile properties. However, due to the very distinct characteristics of flash memory, disk based systems and applications may result in severe performance degradation when directly adopting them on flash memory storage systems. Especially, when a B-tree is constructed, intensive overwrite operations may be caused by record inserting, deleting, and its reorganizing, This could result in severe performance degradation on NAND flash memory. In this paper, we propose an efficient buffer management scheme, called IBSF, which eliminates redundant index units in the index buffer and then delays the time that the index buffer is filled up. Consequently, IBSF significantly reduces the number of write operations to a flash memory when constructing a B-tree. We also show that IBSF yields a better performance on a flash memory by comparing it to the related technique called BFTL through various experiments.
김혜영(Hye Young Kim),이동호(Dong Ho Lee),윤세진(Sei Jin Youn),엄재호(Jae Ho Earm),조명찬(Myeong Chan Cho),이상도(Sang Do Lee),궁성수(Sung Soo Koong),이복희(Bok Hee Lee),정화숙(Hwa Sook Jeong),성노현(Ro Hyun Sung) 대한소화기학회 1994 대한소화기학회지 Vol.26 No.2
Primary biliary cirrhosis is a chronic, progressive liver disease of unknown etiology that is characterized by inflammatory destruction of intrahepatic bile ducts and by association of multiple autoimmune disease. Ten cases of primary biliary cirrhosis were reported so far in Korea. None of these was associated with pleural effusion. bV experienced a case of a 68-year old female with primary biliary cirrhosis with unexplained pleural effusion who has suffered from pruritus, generalized weakness and dyspnea. She was treated with pleurodesis, cholestyramine and ursodeoxycholic acid. We report a case of primary biliary cirrhosis with pleural effusion. (Korean J Gastroenterol 1994; 26; 378-383)