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통신망 응용을 위한 주기억장치 데이타베이스 저장 시스템의 개발
윤창기(Chang-Ki Yoon),유한양(Han-Yang Yoo),김진호(Jin-Ho Kim),백영식(Young-Sik Baek) 한국정보과학회 1994 한국정보과학회 학술발표논문집 Vol.21 No.1
고속의 통신망을 관리하기 위해 통신망의 각 장치에 대한 정보를 신속하고 정확하게 처리하는 고속의 데이타베이스 기능이 필요하다. 이 논문에서는 이러한 고속의 자료를 저장하고 관리하기 위해 주기억장치 데이타베이스 저장 시스템을 개발하였다. 이 시스템에서는 모든 데이타베이스를 주기억장치에 저장하여 디스크 입출력 없이 고속으로 자료를 처리할 수 있다. 이 논문에서는 개발한 저장 시스템은 주기억장치를 효율적을 사용하면서 데이타의 저장과 회복을 쉽게 하기 위해 데이타베이스를 파티션과 세그먼트를 이용하여 저장한다. 또한 주기억 장치 특성에 적합한 효율적인 인덱스 즉, T 트리와 수정된 선형 해싱을 제공하고자 하였다. 또 C 응용 프로그램에서 이 저장 시스템을 쉽게 사용할 수 있도록 C 함수 형태의 응용 인터페이스를 제공하였다. 이 인터페이스로 인해 데이타베이스 언어의 번역과 실행에 대한 부담을 줄일 수 있는 장점이 제공된다.
Ce 첨가에 따른 저온수성가스전이반응용 Cu/Zn 촉매의 활성 연구
변창기(Chang Ki Byun),임효빈(Hyo Bin Im),박지혜(Jihye Park),백정훈(Jeonghun Baek),정정민(Jeongmin Jeong),윤왕래(Wang Ria Yoon),이광복(Kwang Bok Yi) 한국청정기술학회 2015 청정기술 Vol.21 No.3
산화세륨의 첨가가 수성가스전이반응 효율에 미치는 영향을 조사하기 위해서, Cu-ZnO-CeO₂촉매를 공침법을 사용하여 제조하였다. 일련의 Cu-ZnO-CeO₂ 촉매는 Cu 함량(50 wt%)을을 고정시키고 산화세륨(CeO₂ 기준으로, 0, 5, 10, 20, 30, 40 wt%)의 함량을 조절하면서 제조되었고 이를 이용하여 GHSV 95,541 h<SUP>-1</SUP>의 기체 유량범위, 200~400 ℃의 온도범위에서 수성가스전이반응 촉매활성이 측정되었다. 또한, BET, SEM, XRD, H₂-TPR, XPS 분석을 통하여 촉매특성이 분석되었다. CeO₂가 첨가된 촉매는 구리 분산도와 결합에너지 같은 촉매특성의 다양한 변화를 나타내었다. 10wt%의 CeO₂가 최적의 첨가량으로 판단되며 이때 촉매는 가장 낮은 온도에서 환원이 일어났으며 반응에서 가장 높은 촉매 활성을 보였다. 또한 CeO₂가 첨가된 촉매는 CeO₂가 첨가되지 않는 촉매와 비교하여 높은 온도영역에서 활성이 향상되었다. 따라서, 최적 조성의 CeO₂첨가는 높은 구리 분산도, 낮은 결합에너지, 구리 금속의 응집 방지를 유도하여 높은 촉매활성을 유도하였다. In order to investigate the effect of cerium oxide addition, Cu-ZnO-CeO₂ catalysts were prepared using co-precipitation method for water gas shift (WGS) reaction. A series of Cu-ZnO-CeO₂ catalyst with fixed Cu Content (50 wt%, calculated as CuO) and a given ceria content (e.g., 0, 5, 10, 20, 30, 40 wt%, calculated as CeO₂) were tested for catalytic activity at a GHSV of 95,541 h<SUP>-1</SUP>, and a temperature range of 200 to 400 ℃. Cu-ZnO-CeO₂ catalysts were characterized by using BET, SEM, XRD, H₂-TPR, and XPS analysis. Varying composition of Cu-ZnO-CeO₂ catlysts led the difference characteristics such as Cu dispersion, and binding energy. The optimum 10 wt% doping of cerium facilitated catalyst reduction at lower temperature and improved the catalyst performance greatly in terms of CO conversion. Cerium oxide added catalyst showed enhanced activities at higher temperature when it compared with the catalyst without cerium oxide. Consequently, ceria addition of optimal composition leads to enhanced catalytic activity which is attributed to enhanced Cu dispersion, lower binding energy, and hindered Cu metal agglomeration.
다국소 망막전위도를 통한 특발성 망막전막제거술 전후의 황반 기능 평가
윤창기(Chang Ki Yoon),김태훈(Tae Hoon Kim),김현웅(Hyun Woong Kim) 대한검안학회 2016 Annals of optometry and contact lens Vol.15 No.1
Purpose: To assess macular function after vitrectomy and membrane removal in eyes with idiopathic epiretinal membrane by means of multifocal electroretinogram (mfERG). Methods: Visual acuity, macular thickness measured by optical coherence tomography, and mfERG recordings were achieved for 14 eyes of 14 patients who having idiopathic epiretinal membrane. All exams were performed before epiretinal membrane surgery and 1, 3, and 6 months after surgery. Results: Amplitude of mfERG were 139.18 ± 73.63 nV/deg2, 114.25 ± 29.16 nV/deg2 and 134.66 ± 69.64 nV/deg2 at before surgery, after 1 month and 3 months, respectively. Implicit time were 75.23 ± 31.34 nV/deg2, 66.20 ± 25.04 nV/deg2 and 74.79 ± 15.47 nV/deg2 at before surgery, after 1 month and 3 months, respectively. There were no significant changes in amplitude and implicit time measured by mfERG before and after the surgery (p>0.05). There were no significant correlations between the changes of amplitude and implicit time and visual acuity and macular thickness change. Conclusions: Changes in mfERG recordings were not concluded to be useful for predicting clinical prognosis after epiretinal membrane surgery in this study.
일즈병의 치료에서 레이저광응고술과 유리체강내 베바시주맙 주입 병합 치료의 효과
윤창기(Chang Ki Yoon),이동은(Dong Eun Lee),김현웅(Hyun Woong Kim) 대한검안학회 2016 Annals of optometry and contact lens Vol.15 No.1
Purpose: To evaluate clinical outcomes of a combined therapy of laser photocoagulation and intravitreal bevacizumab for vitreous hemorrhage in Eales’ disease. Methods: In the present retrospective study, medical records of patients who were treated with laser photocoagulation for vitreous hemorrhage due to Eales’ disease. The eyes were divided into 2 groups, the combined therapy group of laser photocoagulation and intravitreal bevacizumab, and the monotherapy group of laser photocoagulation. Best corrected visual acuity, vitreous hemorrhage grade were investigated at 1, 2, 6, and 9 months. Change of nonperfusion area and neovascularizaition area in fluorescein angiography were compared. Results: Among 14 eyes, 7 eyes underwent intravitreal bevacizumab injection and 7 eyes did not. Visual acuity improved significantly at 1 and 3 months in the combined therapy group, but not in the monotherapy group. Vitreous hemorrhage decreased significantly at 1 and 3 months in the combined group, and 1 month in the monotherapy group. There was significant difference in visual acuity at 3 months and in vitreous hemorrhage at 1 and 3 months between the groups. Neovascularizaiton area was significantly regressed only in combined therapy group (p=0.027). Conclusions: Combined laser photocoagulation with intravitreal bevacizumab injection decreased vitreous hemorrhage and neovascularization in Eales’ disease at 1 and 3 months after treatment. But these effect have not maintained thereafter.
윤창기,김정훈,김성준,유영석,Chang Ki Yoon,M,D,Jeong Hun Kim,M,D,Seong Joon Kim,M,D,Young Suk Yu,M,D 대한안과학회 2008 대한안과학회지 Vol.49 No.6
Purpose: To evaluate the results of simple keratectomy for limbal dermoids. Methods: We reviewed the ocular records of 29 consecutive patients with limbal dermoids who had undergone simple keratectomy in Seoul National University Children’s hospital from 1989 to 2006. The preoperative and postoperative visual acuity and astigmatism levels as well as the cosmetic outcomes were measured. Results: The mean age at surgery was 28 months (range, 6~70 months), and the mean follow-up period was 56 months (range, 18~168 months). The mean visual acuity at the last follow-up was 20/30. The mean preoperative and postoperative cylinder was -2.64D and -2.12D, respectively, in the affected eye (p=0.064); and -0.79D and -0.43D, respectively, in the fellow eye (p=0.149). There was a significant correlation between preoperative astigmatism and the final visual acuity in the involved eye. No opaque lesions were visible at a distance of 1 meter in 16 of the 29 eyes (55.2%), and there were no significant complications related to the surgery. Conclusions: Simple keratectomy of limbal dermoids can be a good surgical technique to get a cosmetically acceptable corneal clarity without complication. J Korean Ophthalmol Soc 49(6):897-903, 2008
정전 분무를 이용한 중공입자/PLA 복합재료 필름 제작
윤창기(Chang Ki Yoon),박병규(Byung Kyu Park),이우일(Woo Il Lee),이준식(Joon Sik Lee) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
For the development of a super insulation material, this study proposed a fabrication procces for the fabrication of glass beads/PLA(Poly lacticacid) composite by use of electrospray. We observed distinctive composite structure under various conditions such as concentration and flow rate of PLA solution, voltage difference and distance between the needle and target surface. Thought it is usually not easy to mix glass beads and PLA soultion due to the difference of there density, we successfully obtained the composite film with uniform thickness. The composite film contains lots of vacancies the size of which is about 40㎛.
유형곤(Hyeong Gon Yu),윤창기(Chang Ki Yoon) 대한검안학회 2021 Annals of optometry and contact lens Vol.20 No.3
망막색소변성 환자는 시야결손, 색각이상, 대비감도 감소, 읽기와 운전장애 등 다양한 시각 이상과 기능적 시각 이상을 나타낸다. 망막색소변성 환자에 대한 시기능 이해는 치료 효과를 판정하는 임상시험에서 필수적으로 고려되어야 한다. 또한 시각장애 판정 등에서 망막변성 환자가 불이익을 당하지 않도록 도와줄 수 있을 것이다. Patients with retinitis pigmentosa have defects in visual function, including the visual field, color vision, contrast sensitivity, and impaired functional vision, such as reading and driving. An assessment of visual function is required when interpreting the outcome of clinical trials of retinitis pigmentosa. Various defects of functional vision should be considered when assessing visual impairment for patients with retinitis pigmentosa.
간섭계 레이더 고도계를 활용한 지형참조항법의 성능 분석
정승환(Seung-Hwan Jeong),윤주홍(Ju-Hong Yoon),박민규(Min-Gyu Park),김대영(Dae-Young Kim),성창기(Chang-Ki Sung),김현석(Hyun-Suk Kim),김윤형(Yoon-Hyung Kim),곽희준(Hee-Jun Kwak),선웅(Woong Sun),윤국진(Kuk-Jin Yoon) 한국항공우주학회 2012 韓國航空宇宙學會誌 Vol.40 No.4
본 논문에서는 간섭계 레이더 고도계를 활용한 지형참조항법의 성능을 분석하고자 한다. 간섭계 레이더 고도계는 항체의 주변 지형의 고도 중 가장 높은 값을 측정값으로 취함으로써 항법의 정확성을 향상시키고 있다. 이에 본 연구에서는 간섭계 레이더 고도계의 적용에 따른 새로운 측정 모델을 제시하고 이에 따른 지형참조항법 시스템을 구축하려 한다. 또한 필터에 따른 지형참조항법의 성능 분석을 위하여 확장형 칼만 필터, 무향 칼만 필터, 파티클 필터를 적용하며 여러 환경의 변화에 따른 지형참조항법의 성능을 도출고자 한다. The paper experimentally verifies the performance of Terrain-Aided Navigation (TAN) using an interferometric radio altimeter, which is recently used due to its accuracy. First, we propose a TAN system that utilizes an interferometric radio altimeter as a measurement system. Second, we implement extended Kalman filter, unscented Kalman filter, and particle filter to evaluate the performance of TAN according to the selection of filters and the difference of environments.