• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.453-457
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• 2011

In this study, transonic aeroelastic response analyses haw been conducted for the business jet aircraft configuration considering shockwave and flow separation effects. The developed fluid-structure coupled analysis system is applied for aeroelastic computations combining computational structural dynamics(CSD), finite element method(FEM) and computational fluid dynamics(CFD) in the time domain. It can give very accurate and useful engineering data on the structural dynamic design of advanced flight vehicles. For the nonlinear unsteady aerodynamics in high transonic flow region, Navier-Stokes equations using the structured grid system have been applied to wing-body configurations. In transonic flight region, the characteristics of static and dynamic aeroelastic responses have been investigated for a typical wing-body configuration model. Also, it is typically shown that the current computation approach can yield realistic and practical results for aircraft design and test engineers.

• 한국생산제조학회지
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• 제19권6호
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• pp.731-738
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• 2010

Cavitation is described by formation and collapse of the bubbles in a liquid when the ambient pressure decreases. Formed bubbles grow and collapse by change of pressure, and when they collapse, shockwave by high pressure is generated. In general, bubble behavior can be described by Rayleigh-Plesset equation under adiabatic or isothermal condition and hence, phase shift by the pressure change in a bubble cannot be considered in the equation. In our study, a numerical model is developed from the mathematical model considering the phase shift from the previous study. In the developed numerical model, size of single spherical bubble is calculated by the change of mass calculated from the change of the ambient pressure in a liquid. The developed numerical model is verified by a case of liquid flow in a narrow channel.

• 정보교육학회논문지
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• 제8권1호
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• pp.91-99
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• 2004

유비쿼터스 환경이 도래함에 따라 언제 어디서나 어떤 단말기를 통해서도 정보를 얻을 수 있는 환경이 제시되었고, 모바일 장비의 성능이 개선되어가면서 무선인터넷 환경을 기반으로 운영될 수 있는 솔루션의 수요가 점차 증가되고 있는 추세이다. 이에 본 논문에서는 무선인터넷 환경에 적응력 있게 대응하기 위한 원격 교육 솔루션을 개발하고자 하며 이를 위하여 다른 그래픽 포맷들과는 달리 해상도의 크기가 변경되더라도 고품질의 가독성을 유지할 수 있는 SWF를 이용하여 포켓 PC의 대역폭 및 해상도 문제를 해결한 원격교육시스템을 설계 및 구현하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.556-561
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• 2003

Flight bodies are subject to highly unstable and severe flow conditions during taking-off and landing periods. In this situation, the flight bodies essentially experience accelerating or decelerating flows, and the aerodynamic characteristics can be completely different from those of steady flows. In the present study, unsteady aerodynamic characteristics of an aerofoil accelerating at subsonic speeds are investigated using a computational method. Two-dimensional, unsteady, compressible Navier-Stokes simulations are conducted with a one-equation turbulence model, Spalart-Allmaras, and a fully implicit finite volume scheme. An acceleration factor is defined to specify the unsteady aerodynamics of the aerofoil. The results show that the acceleration of the subsonic aerofoil generally leads to a variation in aerodynamic characteristics and it is more significant at angles of attack.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.441-447
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• 2005

The present study is aimed at understanding the flow physics associated with a safety valve applied to LNG ship engines. One-dimensional gasdynamic analyses and axisymmetric, compressible Navier-Stokes computations have been carried out to provide a qualitative and quantitative knowledge base for an effective design of the safety valve. Gasdynamic forces and thrust coefficients are obtained regarding a change in chamber pressure and distance between the nozzle exit and valve sheet which are major parameters to offer a variation in the flow feature. The present results show that the control of the passage area between the nozzle exit and valve sheet can attenuate the strength of shockwave generated in front of the valve sheet, which causes harm to stable system operation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 춘계학술대회 논문집
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• pp.299-299
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• 2011

In this study, transonic aeroelastic response analyses have been conducted for the business jet aircraft configuration considering shockwave and flow separation effects. The developed fluid-structure coupled analysis system is applied for aeroelastic computations combining computational structural dynamics(CSD), finite element method(FEM) and computational fluid dynamics(CFD) in the time domain. It can give very accurate and useful engineering data on the structural dynamic design of advanced flight vehicles. For the nonlinear unsteady aerodynamics in high transonic flow region, Navier-Stokes equations using the structured grid system have been applied to wing-body configurations. In transonic flight region, the characteristics of static and dynamic aeroelastic responses have been investigated for a typical wing-body configuration model. Also, it is typically shown that the current computation approach can yield realistic and practical results for aircraft design and test engineers.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.347-352
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• 2004

The unsteady aerodynamic characteristics of an aerofoil gradually accelerating or decelerating at subsonic speeds are investigated through two-dimensional, unsteady, compressible Navier-Stokes simulations. An acceleration factor is defined to provide various acceleration or deceleration characters of the time-dependent flow over the aerofoil. The results show that an increase in the absolute value of the non-dimensional acceleration factor leads to a lesser change in the location and range of flow featues such as shockwave and boundary layer separation in a specific time range. Generally, the gradual speed-up and speed-down of the subsonic aerofoil results in different aerodynamic characteristics whose changes are more significant at angles of attack.

• 한국연소학회지
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• 제19권1호
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• pp.1-10
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• 2014

An analytical study on performance evaluation of superdetonative mode ram accelerator was conducted for understanding the experimental result. The quasi-one dimensional continuum, momentum, energy equations were solved under the assumption of inviscid flow. It would be noticeable that experimental result could be analytically simulated with the assumptions of inlet shockwave, temperature dependent specific heat, and additional aluminum combustion due to ablation of aluminum projectile in superdetonative operation mode. The acceleration of ram accelerator was comparable to experimental result with the consideration of the additional aluminum combustion energy by ablation of projectile. As result, the experimental result with the aluminum projectile could be affected by heat of aluminum.

• 한국지하수토양환경학회지:지하수토양환경
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• 제21권1호
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• pp.80-85
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• 2016

Acoustic cavitation can induce various sonochemical effects including pyrolysis and radical reactions and sonophysical effects including microjets and shockwave. In environmental engineering field, ultrasound technology using sonochemical effects can be useful for the removal and mineralization of recalcitrant trace pollutants in aqueous phase as one of emerging advanced oxidation processes (AOPs). In this study, the effect of liquid height, the distance from the transducer to the water surface, on sonochemical oxidation reactions was investigated using KI dosimetry. As the liquid height/volume increased (40~400 mm), the cavitation yield steadily increased even though the power density drastically decreased. It was found that the enhancement at higher liquid height conditions was due to the formation of standing wave field, where cavitation events could stably occur and a large amount of oxidizing radicals such as OH radicals could be continuously provided.

• 대한정형외과 초음파학회지
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• 제2권2호
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• pp.79-84
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• 2009

목적: 주관절 내상과염 및 외상과염은 주관절 통증의 가장 흔한 원인 중의 하나로 이에 대한 치료방법으로 최근 체외충격파 치료가 임상에서 점점 많이 시도되고 있다. 이에 본 연구에서는 내, 외상과염에 대한 체외충격파 치료를 시행한 후 그 임상적 결과를 알아보고자 하였다. 대상 및 방법: 2005년 11월부터 2009년 1월까지 본원에서 주관절 내, 외상과염으로 진단받은 환자 중 72명 74예(남자 11명, 여자 61명)를 대상으로 하였으며 평균 연령은 52.4세였다. 모든 환자는 타 병원에서 국소 주사, 물리 치료, 약물치료, 주관절 석고 고정 등의 보존적 치료방법을 시행받았으나 증상이 호전되지 않아 본원을 방문한 경우로 치료 효과의 판정은 통증의 개선 정도를 통해 평가하였는데 휴식 시와 작업 시의 통증의 정도를 각각 치료 전과 치료 후 6주, 12주, 24주에 visual analogue scale (VAS)를 이용하여 측정하고 이와 함께 통증으로 수면 중 깨어나는 횟수를 조사하여 이를 같은 방식으로 치료 전, 후를 비교하여 평가하였다. 결과: 치료 24주 째 최종 추시에서 휴식시 통증의 경우 우수 70예, 양호 4예였으며 불량은 없었고 작업시 통증의 경우 우수 42예, 양호 14예, 보통 8예였으며 불량은 없었다. 이에 따라 작업시 VAS를 바탕으로 한 치료 성공률은 약 89.2%로 확인되었다. 휴식시 통증의 VAS 평균값은 치료 전 4.60에서 치료 6주째 2.01, 12주째 0.43, 24주째 0.16으로 개선되었고 작업시 통증의 경우 평균값이 치료 전 7.20에서 치료 6주째 4.05, 12주째 2.01, 24주째 0.36으로 유의하게 개선되었다. 수면 중 깨어나는 빈도 역시 치료 전 1주일에 평균 9.64회에서 치료 6주, 12주, 24주가 되면서 각각 1.21회, 0.08회, 0.09회로 유의한 치료 효과를 보여주었다. 결론: 체외충격파를 이용한 주관절 내, 외상과염의 치료는 보존적 치료에 반응하지 않는 환자들에서 통증의 감소와 근력 증진을 위한 효과적인 치료법으로 사료된다.