• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.399-407
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• 1986

본 연구에서는 공기역학 탄성베어링의 설계에 필요한 기본이론에 대하여 고찰 하고 그의 신빙성을 그러한 베어링에 지지된 고속회전축의 진등측정을 통하여 검토하 고저 한다. 탄성베어링의 한 예로써 여러 개의 탄성박판이 겹쳐 저어널을 지지하는 겹판베어링(

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.10
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• pp.112-117
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• 2004

This work is on numerical and experimental studies on the new type igniter using aerodynamic energy. The aerodynamic igniter consists of a nozzle and a resonance tube. The supersonic jet from a nozzle coming into the resonance tube generates pressure oscillation between the nozzle and the resonator. This oscillation changes the kinetic energy to thermal energy in the resonator under a certain condition. In this study, sonic and supersonic nozzles were tested in two different resonators, results has been compared. And geometrical optimum values of a supersonic nozzle has been suggested to reduce aerodynamic loss and friction in the expanded surface of the nozzle.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.1
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• pp.91-98
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• 2011

In this study, we measure the aerodynamic forces acting on an AREX train in a crosswind by wind tunnel testing. A detailed test model scaled to 5% of the original and including the inter-car, under-body, and the bogie systems was developed. The aerodynamic forces on the train vehicles have been measured in a 4 m $\times$ 3 m test section of the subsonic wind tunnel located in Korea Aerospace Research Institute (KARI). The aerodynamic forces and moments of the train model on two different track models have been plotted for various yaw angles, and the characteristics of the aerodynamic coefficients have been analyzed at the experimental conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.1
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• pp.10-17
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• 2007

Numerical results from the "figure-of-eight" motion of Phormia-Regina in Part 1 indicate that vortical structure and vortex dynamics do play a critical role in lift and thrust generation. The aerodynamic force generation of insects' wing could be governed by aerodynamic parameters such as Reynolds number; kinematic parameters such as frequency, amplitude, and component of the figure of eight motion; and morphological parameters such as wing shape and the number of wing. In the present work, the effects of Reynolds number, reduced frequency and motion component are investigated in detail to clarify aerodynamic characteristics of insect wing. Through numerical results and their physical interpretation, the mechanism of aerodynamic force generation is presented more clearly. Rotation turns out to be the most important component in thrust generation and subsequent counterclockwise rotational circulation is closely related with thrust generation.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.3
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• pp.51-61
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• 1993

The hydrodynamic problem when the pressurized bag submerges partially into water and oscillates was formulated by Lee(1992), and the solution method was given. In his formulation, however, the compressibility of air was neglected and the pressure inside the bag was assumed to be constant. In this paper, the formulation was done including the air compressibility and the wall to block fling around phenomenon. The compression process was assumed to be a isothermal process for a static problem, isentropic process for a dynamic problem. And the stability was analyzed for the static problem. Through the various numerical calculations, the forces and the shape of the bag were compared with those of a rigid body case, constant pressure case, and variable pressure case.

• Tunnel and Underground Space
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• v.21 no.5
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• pp.394-405
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• 2011

In this paper, we applied coupled non-isothermal, multiphase fluid flow and geomechanical numerical modeling using TOUGH-FLAC coupled analysis to study the complex thermodynamic and geomechanical performance of underground lined rock caverns (LRC) for compressed air energy storage (CAES). Mechanical stress in concrete linings as well as pressure and temperature within a storage cavern were examined during initial and long-term operation of the storage cavern for CAES. Our geomechanical analysis showed that effective stresses could decrease due to air penetration pressure, and tangential tensile stress could develop in the linings as a result of the air pressure exerted on the inner surface of the lining, which would result in tensile fracturing. According to the simulation in which the tensile tangential stresses resulted in radial cracks, increment of linings' permeability and air leakage though the linings, tensile fracturing occurred at the top and at the side wall of the cavern, and the permeability could increase to $5.0{\times}10^{-13}m^2$ from initially prescribed $10{\times}10^{-20}m^2$. However, this air leakage was minor (about 0.02% of the daily air injection rate) and did not significantly impact the overall storage pressure that was kept constant thanks to sufficiently air tight surrounding rocks, which supports the validity of the concrete-lined underground caverns for CAES.

• 한국기계연구소 소보
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• s.12
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• pp.83-92
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• 1984

• Proceedings of the KSLP Conference
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• 1994.06b
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• pp.83-83
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• 1994

발성기구의 생리학적 연구나 발성장애의 병태를 검사함에 있어서 폐로부터 송출되는 호기의 에너지가 성문에 있어서 어느 정도로 목소리의 음원으로 변환되는 지를 아는 것은 대단히 중요하다. 이것을 알기 위해서는 발성시의 호기류율과 함께 성문하에 있어서의 호기압을 측정하여 발성된 목소리의 강도와의 관계를 조사할 필요가 있다. 기류 저지법을 이용한 발성시의 공기역학적 검사법은 발성장애에 대한 공기역학적 검사의 한 방법으로, 기류 저지법을 사용한 발성시의 호기압(폐내압)측정을 호기류율, 목소리 강도, 높이의 측정과 조합시키는 방법으로 장치는 기류저지용의 회전 셧터를 발성기능 검사장치의 mouth piece에 접촉시킨 것이다. (중략)

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.636-641
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• 2015

초소형 비행체는 길이 150mm, 무게 100g 이하의 비행체이다. 초소형 비행체는 그 특성상 저 레이놀즈수에서 비행하며 저 레이놀즈수에서의 공기역학적 특성은 고 레이놀즈수에서의 공기역학적 특성과 큰 차이가 있다. 이는 초소형 비행체 개발 위해 저 레이놀즈수에서의 공력특성 연구가 필요함을 의미한다. 이에 따라 본 연구에서 NACA 4digit Airfoil의 캠버크기와 캠버위치의 변화에 따른 공기역학적 특성의 변화를 확인하였다. 캠버의 위치가 앞전 또는 뒷전으로 이동함에 따라 양력계수가 상승하는 것을 확인하였으며 캠버가 뒷전으로 이동함에 따라 실속이 지연되는 것을 확인하였다. 약 4도 이하의 받음각에서 익형의 아랫변에 발생하는 박리는 고 레이놀즈수에서의 실험에서 확인되어지는 공력특성과 큰 차이를 발생시켰다. 양항비 특성이 가장 우수한 익형은 NACA5808 인 것으로 확인되었다.

• Korean Journal of Food Science and Technology
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• v.26 no.2
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• pp.184-187
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• 1994

Size distributions of rice flour measured by microscope, sieve, Coulter counter (electrozone) and aerodynamic (Aerosizer) methods were compared. Among the particle sizes measured by four methods, those by microscope and sieve were the smallest and the largest, respectively. Difference was found between the particle sizes measured by Coulter counter and aerodynamic methods.