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전산 유체역학을 통한 베개 높이가 폐쇄성 수면 무호흡증에 미치는 영향 분석
최장원(Jang-Won Choi),박세현(Se-Hyun Park),김원태(Won-Tae Kim),유민규(Min-Gyu Yu),이호석(Ho-Seok Lee),허재식(Jae-Sig Huh),김경욱(Kyung-wuk Kim),최영호(Young-Ho Choi),김형호(Hyoung-Ho Kim) 대한기계학회 2020 大韓機械學會論文集B Vol.44 No.8
본 연구의 목적은 전산 유체역학을 사용하여 베개 높이에 따라 상기도에서 폐쇄성 수면 무호흡증의 발생에 대하여 분석하는 것이다. 머리 지지대의 초기 높이가 0cm인 모델 1, +2㎝인 모델 2, 그리고 +4㎝인 모델 3에 대한 CB-CT(cone beam CT) 이미지를 통해 만들어진 3차원 상기도 모델이 전산 유체역학을 위해 이용되었다. 인두에서 6개의 단면은 각 모델에 대하여 최대 흡기, 휴식기, 호기에 따라 속도, 압력, 면적의 변화를 측정하기 위해 사용하였다. 머리 지지대의 높이는 상기도의 유동 특성과 관계가 있었다. 모든 모델에서 단면적이 좁을수록 큰 유량과 음압이 발생하였지만, 모델 2에서 상기도 저항과 연인두에서의 평균 압력이 가장 낮았다. 그러므로 적절한 베개 높이를 선택하는 것은 폐쇄성 수면무호흡증을 줄일 수 있을 것으로 보인다. The objective of this study was to investigate the development of obstructive sleep apnea (OSA) in the upper airway according to pillow height using computational fluid dynamics (CFD). Three-dimensional upper airway models made from cone-beam computed tomography images (using the initial height of the head support for model 1 and 2- and 4-㎝ heights of the head support for models 2 and 3, respectively) were used for the CFD. Six cross-sectional planes in the pharynx were used to measure the variations of the area, pressure, and velocity at maximum inspiration, rest, and maximum expiration at each plane according to the models. The height of the head support was related to the fluid characteristic information in the upper airway. In all the cases, the narrower the cross-sectional area, the greater the flow rate and negative pressure. However, model 2 showed the lowest upper airway resistance and average pressure in the velopharynx. Therefore, selection of the appropriate pillow height might reduce the incidence of OSA.
김기우(Ki Woo Kim),최지영(Ji Young Choi),목차수(Cha Soo Mok),신동진(Dong Jin Shin),최호천(Ho Cheon Choi),김경욱(Gyeong Wook Kim),최대섭(Dae Seop Choi) 대한내과학회 1989 대한내과학회지 Vol.36 No.4
N/A Multiple myeloma is a malignant disease charcterized by an abnormal proliferation of plasma cells. In 1847, Bence Jones first found paraprotein in urine, and Mclntyre described it in 1950. The frequencies of M-protein isotypes were followed by IgG, IgA, IgD, and IgE. Type D-myeloma occurs in less than 1 per cent of patients with multiple myeloma. It is male predominate and 90% of IgD multiple myelomas are type 1mbda and 10% are kappa, with most patients having Bence Jones proteinuria. The authors recently experienced a case of IgD multiple myeloma with lambda light chain which developed in a woman.
나무칩, 톱밥 바이오매스와 갈탄의 수증기 가스화반응 특성 연구
김경욱 ( Kyung Wook Kim ),( Vergel C Bungay ),송병호 ( Byung Ho Song ),최영태 ( Young Tai Choi ),이정우 ( Jeung Woo Lee ) 한국화학공학회 2013 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.51 No.4
바이오매스 및 저등급 석탄인 갈탄은 잠재력이 큰 에너지원으로 이들을 가스화하여 합성가스를 얻으면 발전을 하거나 수송용 연료를 생산할 수 있다. 본 연구에서는 상압의 열천칭 반응기(thermobalance)에서 woodchip, 톱밥, 갈탄의 수증기 가스화반응의 kinetics를 조사하였다. 가스화 온도 600∼900℃, 수증기 분압 20∼90 kPa 범위에서 수증기 가스화 반응을 수행하였다. 세 가지의 기체-고체 화학반응모델들이 가스화반응의 거동을 묘사하는 능력을 비교하였다. 이들 중에서 탄소전환율의 변화를 가장 잘 나타내는 modified volumetric model을 사용하여 가스화반응의 kinetic 정보를 도출하였다. Arrehenius plot으로부터 얻어진 시료들의 활성화에너지는 문헌상의 범위 내에서 얻어졌으며 톱밥 > woodchip > 갈탄의 순으로 나타났다. 각 시료에 대하여 수증기 분압에 대한 반응차수를 결정하였으며, 가스화공정 설계의 기초 데이터로서 겉보기 반응속도식을 제시하였다. Biomass and low-grade coals are known to be better potential sources of energy compared to crude oil and natural gas since these materials are readily available and found to have large reserves, respectively. Gasification of these carbonaceous materials produced syngas for chemical synthesis and power generation. Woodchip, sawdust and lignite were gasified with steam in a thermobalance reactor under atmospheric pressure in order to evaluate their kinetic rate information. The effects of gasification temperature (600∼900℃) and partial pressure of steam (20∼90 kPa) on the gasification rate were investigated. The three different types of gas-solid reaction models were applied to the experimental data to predict the behavior of the gasification reactions. The modified volumetric model predicted the conversion data well, thus the model was used to evaluate kinetic parameters in this study. The observed activation energy of biomass, sawdust and lignite gasification reactions were found to be in reasonable range and their rank was found to be sawdust > woodchip > lignite. The expression of apparent reaction rates for steam gasification of the three solids was proposed to provide basic information on the design of coal gasification processes.
Haar 웨이블릿 변환을 활용한 객체 경계면 추출 기반 실시간 얼굴 검출 방법
김경욱(Kyeonguk Kim),최철호(Cheol-Ho Choi),김정환(Junghwan Kim),문병인(Byungin Moon) 한국정보기술학회 2021 Proceedings of KIIT Conference Vol.2021 No.11
얼굴 검출을 위한 영상 처리 알고리즘 중 하나인 Haar classification은 얼굴 검출에 효과적이지만 영상의 크기 혹은 오검출 횟수가 증가할수록 연산 시간이 증가한다는 문제가 있다. 이러한 문제를 개선하기 위해 본 논문에서는 Haar 웨이블릿 변환을 활용하여 추출한 경계면을 기반으로, 특정 영역에서만 연산을 수행하는 방법을 제안한다. 제안하는 방법의 평균 처리 시간, 검출률과 오검출률 성능을 종래 방법과 비교함으로써, 실시간 동작 성능을 확인하였다. Haar classification, one of the image processing algorithms for face detection, is effective in face detection, but there is a problem that the processing time increases as the size of the image or the number of false detection increases. To solve this problem, this paper proposes a method for performing the face detection only in the specific regions based on the extracted edge using Haar wavelet transform. The performance of the proposed method, which consists of mean processing speed, detection rate and false detection rate, is compared with the conventional method to verify real-time performance.
논문 : 노외기계시스템공학 ; 차축의 중량 분포와 타이어의 공기압이 트랙터 작업의 연료 효율에 미치는 영향
이진웅 ( Jin Woong Lee ),김경욱 ( Kyeong Uk Kim ),김동현 ( Dong Hyeon Gim ),최규정 ( Kyu Jeong Choi ) 한국농업기계학회 2011 바이오시스템공학 Vol.36 No.5
This study was conducted to investigate the effects of axle weight distribution and inflation pressure of tire on the fuel economy of tractors as well as operational range of tractor engine in terms of engine speed and power when a 4WD tractor of 38.2 kW rated power at 2500 rpm is used for plowing and flooded-field rotavating in paddy fields. (1) Plowing operation required an average engine power of 9.6~13.5 kW which equals 25~35% of rated PTO power. Engine speed ranged from 1,320.4 to 1,737.4 rpm, work velocity from 3.4 to 4.8 km/h, and fuel consumption from 3.2 to 4.2 L/h, respectively. (2) Flooded-field rotavating required an average engine power of 11.5~18.5 kW which equals 30~48.4% of rated PTO power. Out of this 6.2~12.2 kW was used for PTO power. Engine speed ranged from 1,557 to 2,067 rpm, work velocity from 2.5~5.4 km/h and fuel consumption from 3.2~5.5 L/h, respectively. (3) Axle weight distribution, inflation pressure of tire and moisture content of soil did not affect significantly the specific volumetric fuel consumption but affected significantly the fuel consumption per unit area of operation. Fuel savings amounted to 65% in plowing operation and 20% in flooded-field rotavating when the axle weight distribution and inflation pressure of tire were optimally adjusted. (4) Optimal adjustment of axle weight distribution and inflation pressure of tire are expected to save fuel consumption by 10~65% per unit area of operation in plowing and 10~20% in flooded-field rotavating.
5-Fluorouracil이 백서 체모에 미치는 영향에 관한 실험적 연구
최용철,김경욱,이재훈,Choi, Yong-Chul,Kim, Kyung-Wook,Lee, Jae-Hoon 대한악안면성형재건외과학회 1998 Maxillofacial Plastic Reconstructive Surgery Vol.20 No.2
This study was undertaken to observe the effects of the antineoplastic agent, 5-Fluorouracil(5 FU) on the hair in Sprague-Dawley white rats. Twenty four sprague-Dawley strain white rats, each weighing about 150-200 grams were used and divided into control and experimental groups. In the experimental group, eighteen rats were injected intraperitonially with 60 mg of 5-FU per killogram body weight with one time per two days, Six rats were injected with 0.5 cc of normal saline solution intraperitoneally as a placebo on this control group. Rats were serially sacrificed on the first, third, fifth, seventh, tenth and fourteenth day after 2 times of injection of 5-FU and saline. The hair were obtained and observed SEM. After examination and comparision of all specimens, the results of this study were as follows: 1. In the control group, the scale and cuticle of hair was observed smooth surface and equal interval 2. In the experimental group, the first day, scale change was seen from body of hair and crack was seen. from fifth day, and irregular scale and cuticle of hair was seen from 10, 14 days 3. The apperance of root of hair was not almost change From above results, 5-Fluorouracil was more effective on the hair body. The change was begun from first day and crack of scale was seen from fifth day and irregular scale and cuticle of hair was seen from 10,14 days. The.
플라즈마 밀도와 기판의 기울임 정도에 따른 탄소나노튜브의 성장
최은창,김경욱,홍병유,Choi, Eun-Chang,Kim, Kyung-Uk,Hong, Byung-You 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.7
We need to control the growth orientation of CNTs on a substrate for applications to various electric devices. Generally, the flow direction of feed gases and electric field between two electrode affect to growth orientations of CNTs. In this paper, we varied tilt degrees $(0^{\circ},\;20^{\circ},\;35^{\circ},\;50^{\circ},\;65^{\circ},\;90^{\circ})$ of substrates on a cathode and DC bias voltages (0, 500, 700 V) applied between two electrodes in order to change growth orientations of CNTs. We confirmed that tilt degrees of the substrate and variation of DC bias voltages affected to the shape and orientation of the grown CNTs on the substrate.