• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.11
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• pp.948-956
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• 2012

This paper presents the computations of the longitudinal and directional stability derivatives for the SDM(Standard Dynamic Model). The static and dynamic derivatives are evaluated at once using forced harmonic oscillations in the pitch and yaw directions. For the numerical simulations, a 3-D Euler solver that uses a dual time stepping method for unsteady time accurate simulations is applied. This work investigates the variation of the derivatives in terms of the Mach number and the several motion parameters. Good agreement of the pitch and yaw stability derivatives with previously published numerical results and experimental results are observed.

• Journal of Aerospace System Engineering
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• v.9 no.3
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• pp.12-16
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• 2015

인간동력 항공기 TORUK MAKTO I에 대하여 양력선이론 및 XFOIL을 사용하여 도출한 공력계수 및 미계수 값과 CATIA를 사용한 관성모멘트 추정 값을 사용하여 지면효과 및 주익과 무게중심 사이의 수직거리 변화가 인간동력 항공기의 세로 정안정성에 미치는 영향과 수평미익(스테빌레이터) 변위각제어에 따른 세로 동안정성 해석 연구를 수행하였다. 연구결과 지면효과가 정적여유에 미치는 영향은 미미했다. 공력중심과 무게중심 사이의 수직거리가 세로 정안정성에 미치는 영향은 매우 컸으며, 수직거리 증가는 세로 정안정성을 증가시켰다. 수평미익 변위각 제어에 따른 세로 동안정성 해석 결과 장주기 진동특성과 감쇄특성이 매우 나쁜 것으로 나타났다. 향후 항공기의 동특성을 고려한 세로 동안정성 해석 및 측풍에 의한 가로 및 방향 안정성 해석연구를 수행할 예정이다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.8
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• pp.711-717
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• 2012

During the conceptual design phase of a light sport aircraft, the wind tunnel tests were conducted to investigate the static stability of newly-designed configuration. The 1/5 scale-down wind tunnel model consisted of fuselage, main wing, vertical tail and horizontal tail. The main wing and tails were able to be attached or detached from the fuselage. The aerodynamic forces and moments acting on the 6 different configurations compounding each component were measured by using the internal balance system and their static stability derivatives were derived. With these experimental data, the baseline lift and drag characteristics as well as the effects of each component to the longitudinal, directional and lateral static stability were quantitatively analyzed.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04b
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• pp.607-610
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• 2002

본 연구에서는 식품 안정성을 검사하기 위해 식품 내 미생물 농도를 계산하는 방법을 제안한다. 기존의 생물학적 방법을 보완하여 영상 분석에 기반한 자동화 방법으로 빠르고 보다 정확한 방법을 제안한다. 현미경으로 확대한 시료의 영상을 자동으로 분석하여 영상 내의 미생물의 수를 측정하면 여러 영상에 대한 결과를 통계적으로 분석하여 식품 내 미생물 농도를 보다 정확히 측정할 수 있다. 영상 처리 과정을 통해 영상으로부터 미생물군을 찾아내고, 해당 미 생물군을 모양에 따라 세 가지 종류-간균, 구균, 효모로 분류하고 계수한다. 제안하는 시스템의 성능을 실험으로 보였다. 영상 내에서 측정된 미생물의 수와 실제 미생물의 수의 비를 검토해 본 바, 본 시스템이 실용적임을 보였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.6
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• pp.45-51
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• 2003

This paper presents a method to improve lateral stability of a four-seat canard aircraft, Velocity-173. Longitudinal stability of Velocity-173 is rather good, but lateral stability is relatively poor. A small panel which increases the area of vertical tail is designed and manufactured. In a design process, AAA(Advanced Aircraft Analysis) is used to predict the change in stability. Flight test is performed to validate the effect of a small panel attached under the vertical panel. Maximum likelihood estimation method is used to extract lateral controllability / stability derivatives from flight test data. This work validates the effect of a small panel attached under the vertical tail.

• The Journal of the Korea Contents Association
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• v.21 no.2
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• pp.195-205
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• 2021

The purpose of this study is to validate the Confusion, Hubbub, and Order Scale (CHAOS), developed by Matheny et al. (1995), in South Korea. Data of 189 parents with children under the age of 5 acquired by online survey were used for the analysis. Descriptive statistics, item-total correlation, internal consistency, confirmatory factor analysis, convergent validity were examined. As a result, 13 items were confirmed and the reliability was .881. By validating K-CHAOS, it became possible to consider the effect of physical environment, that are known to affect psychological and social development of individuals, as one of micro-systems in future studies.

• Journal of Chest Surgery
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• v.35 no.10
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• pp.705-711
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• 2002

The advantages of mitral valve reconstruction have been well established and so mitral valve reconstruction is now considered as the procedure of choice to correct mitral valve disease. This is the report of intermediate-term results of 38 cases that performed mitral valve reconstruction for valve insufficiency(the total number of mitral valve reconstruction were 49 cases, but 11 cases that performed mitral valve replacement due to incomplete reconstruction were excluded). Material and Method : From March 1991 to March 2001, 38 patients underwent mitral valve repair due to mitral valve regurgitation with or without stenosis. Mean age was 47.6$\pm$14.7 years(range 15 to 70 years) : 11 were men and 27 were women. The causes of mitral valve regurgitation were degenerative in 14, rheumatic in 21, infective in 2 and the other was congenital. Result : According to the Carpentier's pathologic classification of mitral valve regurgitation, 3 were type 1 , 16 were type II and 19 were type III. Surgical procedures were annuloplasty 15, commissurotomy 19, leaflet resection and annular plication 9, chordae shortening 11, chordae transfer 5, new chordae formation 2, papillary muscle splitting 2 and vegetectomy 2. These procedures were combined in most patients. There were 2 early death and the causes of death were respiratory failure, renal failure and sepsis. There was no late death. Valve replacement was done in 6 patients after repair due to valve insufficiency or stenosis 3 weeks, 1, 3, 51, 69, 84months later respectively. These patients have been followed up from 1 to 116 months(mean 43.0 months). The mean functional class(NYHA) was 2.36 pre-operatively and improved to 1.70. Conclusion : In most cases of mitral valve regurgitation, mitral valve reconstruction when technically feasible is effective operation that can achieve stable functional results and low surgical and late mortality.

• Korean Journal of Remote Sensing
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• v.36 no.5_4
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• pp.1179-1194
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• 2020

This study investigates the feasibility of three algorithms, K-Nearest Neighbors (K-NN), Random Forest (RF) and Neural Network (NN), for estimating the air temperature of an unobserved area where the weather station is not installed. The satellite image were obtained from Landsat-8 and MODIS Aqua/Terra acquired in 2019, and the meteorological ground weather data were from AWS/ASOS data of Korea Meteorological Administration and Korea Forest Service. In addition, in order to improve the estimation accuracy, a digital surface model, solar radiation, aspect and slope were used. The accuracy assessment of machine learning methods was performed by calculating the statistics of R² (determination coefficient) and Root Mean Square Error (RMSE) through 10-fold cross-validation and the estimated values were compared for each target area. As a result, the neural network algorithm showed the most stable result among the three algorithms with R² = 0.805 and RMSE = 0.508. The neural network algorithm was applied to each data set on Landsat imagery scene. It was possible to generate an mean air temperature map from June to September 2019 and confirmed that detailed air temperature information could be estimated. The result is expected to be utilized for national disaster safety management such as heat wave response policies and heat island mitigation research.

• Journal of Chest Surgery
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• v.39 no.5 s.262
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• pp.359-365
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• 2006

Background: Arterial grafts have been used to achieve better long-term results for coronary revascularization. Bilateral internal thoracic artery (ITA) grafts have a better results, but it may be not used in some situations such as diabetes and chronic obstructive pulmonary disease (COPD). We evaluated the clinical and angiographic results of composite left internal thoracic artery-radial artery (LITA-RA) Y graft. Material and Method: Between April 2002 and September 2004, 119 patients were enrolled in composite Y graft for coronary bypass surgery. The mean age was $62.6{\pm}8.8$ years old and female was 34.5%. Preoperative cardiac risk factors were as follows: hypertension 43.7%, diabetes 33.6%, smoker 41.2%, and hyperlipidemia 22.7%, There were emergency operation (14), cardiogenic shock (6), left ventricle ejection fraction (LVEF) less than 40% (17), and 17 cases of left main disease. Coronary angiography was done in 35 patients before the hospital discharge. Result: The number of distal anastomoses was $3.1{\pm}0.91$ and three patients (2.52%) died during hospital stay. The off-pump coronary artery bypass (OPCAB) was applied to 79 patients (66.4%). The LITA was anastomosed to left anterior descending system except three cases which was to lateral wall. The radial Y grafts were anastomosed to diagonal branches (4), ramus intermedius (21), obtuse marginal branches (109), posterolateral branches (12), and posterior descending coronary artery (8). Postoperative coronary angiography in 35 patients showed excellent patency rates (LITA 100%, and RA 88.5%; 3 RA grafts which anastomosed to coronary arteries <70% stenosed showed string sign with competitive flow). Conclusion: The LITA-RA Y composite graft provided good early clinical and angiographic results in multivessel coronary revascularization. But it should be cautiously used in selected patients.