• 한국철도학회:학술대회논문집
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• 한국철도학회 2000년도 춘계학술대회 논문집
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• pp.495-502
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• 2000

For the tunnel design of the first class on new Seoul-Chunchon railway, we investigated for train speeds to run through tunnels without ear-discomfort of passenger in cabin by application of numerical analysis. Also we analyzed the effect of the wind speed induced by train in tunnel that is very harmful to the workers on railroad and the effect of the air-pressure fluctuations which get the fatigue to the tunnel lining and the car body.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 추계학술대회
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• pp.91-92
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• 2017

풍력 발전 시스템에서 정격 풍속 이상의 바람에 대응하기 위해서는 일반적으로 전기적 브레이크와 기계적 브레이크가 요구된다. 기계적 브레이크는 상대적으로 응답성이 느리며 그 시간 동안 발전기 rpm 증가에 따른 DC전압 상승에 대응하는 전기적 브레이크의 역할이 시스템 안정성에 있어 매우 중요한 요소이다. 전기적 브레이크 중에서도 소형풍력 발전시스템에서는 DB(Dynamic Brake)저항을 통해 부하를 걸어주는 방식이 주로 쓰인다. DB 저항 구동에 있어 히스테리시스 루프에 기반한 PWM제어가 일반적으로 통용되는 방식이다. 이러한 방식과 비교하여 제어 안정성, 전압 오버슈트 등의 면에서 우수한 DB저항 제어 방식을 제안하며 히스테리시스 방식과 과도상태 정상상태 특성 비교 및 성능 분석을 시뮬레이션 결과를 통해 제시한다.

• 한국항공운항학회지
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• 제19권4호
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• pp.105-110
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• 2011

The flight test comes at the end of the aircraft development process and is an unique part. The purposes of the flight test are to evaluate the characteristics of the aircraft and validate its design in the real operating environment. Atmospheric considerations are key elements, when the planner of flight test establishes the flight test planning. The primary objective of atmospheric considerations is to ensure safety of the vehicle. The planning through atmospheric considerations can minimize flight cancellations caused by severe weather. In this paper, we present a program for flight suitability distinction, and develop a program for calculation of available sorties.

• Wind and Structures
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• 제6권3호
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• pp.197-208
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• 2003

Galloping instability of dry inclined cables of cable-stayed bridges has been reported by Japanese researchers. A suggested stability criterion based on some experimental studies in Japan implies that many of stay cables would be expected to suffer galloping instability, which, if valid, would cause serious difficulty in the design of cable-stayed bridges. However, this is not the case in reality. Thus, it is practically urgent and necessary to confirm the validity of this criterion and possible restriction of it. In the present study, a 2D sectional cable model was tested in the wind tunnel, and effects of various physical parameters were investigated. It is found that the stability criterion suggested by Japanese researchers is more conservative than the results obtained from the current study.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.757-761
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• 2008

The aerostat dynamic equation of motion has been built including the tether cable dynamic effects. A numerical program to solve the derived equation of motion has been developed. The dynamic motion of the 32m aerostat has been analyzed under discrete gust and continuous turbulence. The aerostat behaviors under discrete gust which represents a deterministic approach for determining design loads for manned aircraft are solved to verify the effect of aerostat mechanical properties on the aerostat dynamic behavior. Continuous turbulences are simulated for each given altitude, translational mean wind velocity and gust intensity. Dynamic behaviors of the 32m aerostat are simulated for each continuous turbulence conditions. Translational and vertical velocity and pitching behavior and tether reaction force are monitored for each simulation.

• International Journal of Aeronautical and Space Sciences
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• 제4권1호
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• pp.19-25
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• 2003

A low speed wind tunnel test for the canard airplane model was conducted in KARI LSWT. To measure the required level of accuracy, the image system was applied for all elevator deflection and different canard incidence conditions. By doing so, the difference in aerodynamic characteristics between the forward swept and straight canards can be precisely evaluated, and the pros and cons of both canards arrangements can be discussed. Compared with both canard configurations at the same incidence angle setting, the straight canard has benefits in lift and drag, and the slope of pitching moment increases more moderately than the forward swept canard. The listed data and discussion would be useful to whom wants to design a canard airplane.

• Wind and Structures
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• 제22권2호
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• pp.161-184
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• 2016

Long-span suspension bridges have evolved through the years and with them, the bridge girder decks improved as well, changing their shapes from standard box-deck girders to twin box and multi-box decks sections. The aerodynamic characteristics of the new generation of twin and multiple-decks are investigated nowadays, to provide the best design wind speeds and the optimum dimensions such bridges could achieve. The multi-box Megane bridge deck is one of the new generation bridge decks, consisting of two side decks for traffic lanes and two middle decks for railways, linked between them with connecting beams. Three-dimensional CFD simulations were performed by employing the Large Eddy Simulation (LES) algorithm with a standard Smagorinsky subgrid-scale model, for $Re=9.3{\times}10^7$ and angles of attack ${\alpha}=-4^{\circ}$, $-2^{\circ}$, $0^{\circ}$, $2^{\circ}$ and $4^{\circ}$. Also, a wind tunnel experiment was performed for a scaled model, 1:80 of the Megane bridge deck section, for $Re=5.1{\times}10^5$ and the aerodynamic static coefficients were found to be in good agreement with the results obtained from the CFD-LES model. However the aerodynamic coefficients determined individually, from the CFD-LES model, for each of the traffic and railway decks of the Megane bridge, varied significantly, especially for the downstream traffic deck. Also the pressure distribution and the effect of the spacing between the connecting beams, on the wind speed profiles showed a slight increase in turbulence above the downstream traffic and railway decks.

• Wind and Structures
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• 제34권2호
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• pp.173-183
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• 2022

The galloping of iced conductors has long been a severe threat to the safety of overhead transmission lines. Compared with normal transmission lines, the ultra-high-voltage (UHV) transmission lines are more prone to galloping, and the damage caused is more severe. To control the galloping of UHV lines, it is necessary to conduct a comprehensive analysis of galloping characteristics. In this paper, a large-span 1000-kV UHV transmission line in China is taken as a practical example where an 8-bundled conductor with D-shaped icing is adopted. Galerkin method is employed for the time history calculation. For the wind attack angle range of 0°~180°, the galloping amplitudes in vertical, horizontal, and torsional directions are calculated. Furthermore, the vibration frequencies and galloping shapes are analyzed for the most severe conditions. The results show that the wind at 0°~10° attack angles can induce large torsional displacement, and this range of attack angles is also most likely to occur in reality. The galloping with largest amplitudes in all three directions occurs at the attack angle of 170° where the incoming flow is at the non-iced side, due to the strong aerodynamic instability. In addition, with wind speed increasing, galloping modes with higher frequencies appear and make the galloping shape more complex, indicating strong nonlinear behavior. Based on the galloping amplitudes of three directions, the full range of wind attack angles are divided into five galloping regions of different severity levels. The results obtained can promote the understanding of galloping and provide a reference for the anti-galloping design of UHV transmission lines.

• 한국전자통신학회논문지
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• 제15권3호
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• pp.503-512
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• 2020

송풍기를 이용한 제품으로는 핸드드라이기, 자동세차기, 건조기, 청소기등이 있다. 이러한 전동기의 특징은 순간에 강한 바람이 나오도록 구조, 제어 알고리즘이 필요하다. 종래의 여자방식에 따른 전동기는 직권식, 분권식, 복권식, 영구자석식이 있다. 이러한 전동기는 고속 회전 시 기동전류가 크고 회전수가 불규칙한 단점이 있다. 이를 개선하고자 고속BLDC 전동기 제어에 관한 연구로 구동회로 설계, 센서리스 제어 알고리즘, 시뮬레이션, 실험 등을 통해 800W급 고속BLDC 모터 제어와 회로 설계하였고, 95% 이상 고효율을 제어기의 운전성능 평가 방법, 시제품 실험 및 검증을 연구하였다.

• 항공우주기술
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• 제9권1호
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• pp.78-83
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• 2010

본 연구에서는 높은 양력을 얻기 위하여 플랩 형상 최적 설계를 시도하였다. 플랩 형태는 플랩 중에서 가장 효율이 좋은 파울러 플랩(fowler flap)이다. 플랩 설계는 최적화 기법을 활용하여 진행하였고 최적화의 초기 형상은 general aviation airfoil과 Wentz 등이 개발한 플랩이다. 최적화 방법으로는 반응면 기법 (Response Surface Method)이 사용되었으며, Hicks-Henne 형상함수가 사용되었고, GA(W)-1 익형과 fowler flap이 조합된 형상의 유동장에 대하여 Navier-Stokes 해석을 수행하였다. 상용 최적화 프로그램인 Visual-Doc, 격자 생성 프로그램인 Gambit/Tgrid, 그리고 유동해석에는 Fluent를 이용하였다. 플랩의 윗면 형상과 gap에 대한 최적화를 수행하여 착륙조건에서의 양력이 증가하였다. 초기 형상과 최적화된 형상의 공력특성 변화를 관찰하기 위하여 항우연의 1m 풍동에서 시험을 수행하였다. 최적화된 형상은 대체로 예측치와 비슷한 경향을 보이나, 이른 실속이 관찰되었다. 또한, 날개와 플랩 간의 간격을 설계치보다 좁혀 줌으로써 양력특성이 향상됨을 알 수 있었는데, 이는 설계시 사용된 난류 모델의 영향이라 판단된다.