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각막내피세포의 증식 및 손상의 회복에 대한 ROCK 억제제 Y-27632의 효과
김경환,정진권,류진숙,고아영,김미금,위원량,Kyeong Hwan Kim,Jin Kwon Chung,Jin Suk Ryu,MS,Ah Young Koh,BS,Mee Kum Kim,Won Ryang Wee 대한안과학회 2013 대한안과학회지 Vol.54 No.3
Purpose: To investigate the effect of ROCK inhibitor Y27632 on the human corneal endothelial cell proliferation in vitro and in vivo. Methods: Using corneal endothelial cells isolated and cultured from human donor cornea, we compared the effect of Y27632 (10 μM ) on the proliferation in vitro by flow cytometry analysis. For the evaluation of the effect of Y27632 (10 mM) in vivo, corneal thickness and wound area were analyzed for the corneal endothelial wound rabbit model induced by transcorneal freezing. Results: Ki67 positive cells were increased in the Y27632 group (9.1 ± 4.1 %) than the control group (8.0 ± 5.9 %), whereas annexin V positive cells in the Y27632 group (2.9 ± 1.0 %) were decreased compared to the control group (4.2 ± 2.2 %). However these were not statistically significant. Wound area after Y27632 application in animal model is concerned, the control group showed significant smaller area (45.6 ± 0.6 mm2) compared to the Y27632 group (49.3 ± 0.8 mm2; p = 0.029, Mann-Whitney U test), however, these were not significantly different from the baseline. Corneal thickness was not different between the two groups. Conclusions: Different from other reports for the effect of Y27632, no significant effect on the proliferation in vitro and wound healing in vivo, regarding human corneal endothelial cell, were found in this study.
김경환,이주은.Kyeong Hwan Kim. MD. Joo Eun Lee. MD. PhD 대한안과학회 2010 대한안과학회지 Vol.51 No.1
Purpose: To describe a transconjunctival sutureless technique for pars plana vitrectomy using conventional 20-gauge instruments. Methods: We performed transconjunctival sutureless pars plana vitrectomy (TSV) using conventional 20-gauge instruments in 36 eyes of 35 patients. We made 20-gauge transconjunctival beveled sclerotomies using microvitreoretinal (MVR) blades and used traditional 20-gauge instruments for the operations. Results: Eighty-three (81.4%) of 102 sclerotomies self-sealed without the need for sutures. The sutureless rate was even higher in the last one-third of the patients: 32 (94.1%) of 34 sclerotomy sites were sutureless. No serious complications were observed in our series, including postoperative hypotony, wound leakage, or endophthalmitis. Conclusions: The 20-gauge TSV technique is safe and can be utilized for almost all vitreoretinal diseases, without incurring additional cost for new instruments. J Korean Ophthalmol Soc 2010;51(1):22-28
건축문화재 유지관리를 위한 BIM 기반 시스템 개발 방안
김경환(Kim, Kyeong-Hwan),지승열(Ji, Seung-Yeul),전한종(Jun, Han-Jong) 대한건축학회 2021 대한건축학회 학술발표대회 논문집 Vol.41 No.2
Architectural cultural heritage is used in various fields, but especially wooden architectural cultural heritage has deteriorated significantly over a long period of time, and the displacement makes it difficult to maintain the original form of architectural elements. This problem occurs because the data of wooden architectural cultural properties are not integrated and not accumulated, making it difficult to determine the original form of architectural elements. This study aims to verify that all the architectural elements repair history data of cultural properties can be easily updated with One-click, using the BIM plug-in for maintenance history management of architectural cultural properties, and suggests that it can contribute to reducing the maintenance cost of architectural heritage.
Cu-1.1wt% AI2O3 합금의 미세 조직과 기계적 성질
김경환(Kyeong Hwan Kim) 한국열처리공학회 2001 熱處理工學會誌 Vol.14 No.2
N/A Al₂O₃-copper alloy has been successfully made by gas atomization, mechanical alloying and hot pressing. In order to investigate microstructure and phase, it has been studied by using scanning electron microscope, transmission electron microscope and X-ray diffractometor. Mechanical properties have been examined using hardness tester and compressive tester according to annealing temperature. Although comparatively large Cu-Al powders are milled, the reaction between Cu-Al and Cu₂O occurs and very fine Al₂O₃particles in the matrix particles (5-10㎚) are obtained. Compressive strength of this alloy is more than that of GlidCop Al60.
김경환(Kyeong-Hwan Kim),이영신(Young-Shin Lee),한재도(Jae-Do Han) 대한기계학회 2014 大韓機械學會論文集A Vol.38 No.3
오늘날 비행기는 없어서는 안 되는 교통수단 중의 하나이다. 비행기는 교통 수단 뿐 만 아니라 여러 분야에서 널리 사용되고 있다. 예를 들어, 사람을 태우고, 짐을 실어 나르고, 군에서는 정찰 등의 임무를 수행하게 된다. 지상에서 이륙ㆍ착륙이 이루어 진다. 이륙할 때 보다는, 착륙할 시 랜딩기어에 많은 하중이 작용하게 된다. 착륙장치는 충격 에너지를 흡수하며, 사고 시에 동체가 파손되지 않도록 방지한다. 본 논문에서는 복합재와, 알루미늄을 적용한 판 스프링형 랜딩기어에 대하여 시뮬레이션을 수행하였다. 두 가지 재료의 랜딩기어에 대한 구조적 안전성이 평가되었다. Aircraft are an indispensable mode of modern transportation. They are also used as in a wide variety of other fields. For example, aircraft are used for accommodating passengers, carrying freight, and for military reconnaissance. Aircraft ground operations include landing and taking off. During landing, a higher load is applied to the landing gear than during takeoff. The landing gear should absorb impact energy and prevent damage to the main body of the aircraft in the case of an accident. In this study, simulations were performed for two types of plate-spring-type landing gear: that made of composite materials and that constructed with aluminum. The structural safety of landing gear made of each material was also evaluated.
김경환(Kyeong Hwan Kim),장직현(Jik Hyun Chang) 한국정보과학회 1994 정보과학회논문지 Vol.21 No.4
본 논문에서는 knapsack 문제에 대한 기존의 two-list 알고리즘에 분할 정복 방법과 정렬행렬을 도입한 병렬 알고리즘을 제안한다. 이 알고리즘은 CREW SM SIMD 모델에서 시간 복잡도 T=O(2 ⁿ/4), 하드웨어 복잡도 H=O(2 ⁿ/4)를 갖는다. 또 이 알고리즘에서는 T≤2 ⁿ/4)인 범위에서 T · H=O(2 ⁿ/2))이고 T≥2 ⁿ/4 인 범위에서 T · H³=O(2ⁿ)인 상반관계가 성립함을 보인다. In this paper, we propose a parallel algorithm based on a previously known two-list algorithm incorporating the divide-and-conquer method and sorted matrix for the knapsack problem. This algorithm achieves time complexity T=O(2 ⁿ /4) and hardware complexity H=O(2 ⁿ /4) on the CREW SM SIMD model. And we prove that there exists a time-hardware tradeoff T · H=O(2 ⁿ /2) when T≤2 ⁿ /4 and T · H³=O(2ⁿ) when T≥(2 ⁿ /4).
김경환(Kyeong-Hwan Kim),최종연(Jong-Yeun Choi) 한국기계가공학회 2012 한국기계가공학회지 Vol.11 No.3
Injection mold is a manufacturing process used to produce parts of complicated shape at a low cost. Many factors affect the quality of injection molded part during injection molding process. A study on the optimization of injection mold is progressed by using a simulation software like Moldflow. Filling, packing and cooling phases of injection molding processes are analyzed according to the mold design considering the shrinkage of molded part, the degree of filling rate and the wearing of a mold. Taguchi method is applied to analyze the significance of processing parameter and the dynamic characteristics according to the variation of processing parameters. From the results, the mold temperature and packing pressure influenced the shrinkage of injection molded part.