• 대한기계학회논문집A
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• 제34권10호
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• pp.1513-1519
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• 2010

최근 고품질 제품 생산을 위한 방법으로 센서를 이용한 사출공정모니터링 시스템이 적용되고 있다. 그러나 마이크로 금형, 광학용 금형 및 구조가 복잡한 금형에는 센서 설치가 어렵기 때문에, 공정 모니터링 시스템이 적용되기 어려운 단점이 있다. 본 연구에서는 금형과 사출성형기 노즐의 압력 을 측정하여 공정 모니터링 데이터의 정량적 지수를 정의하고, 성형품 중량에 대한 상관분석을 수행하여 노즐에 설치된 압력센서의 공정모니터링 적용성을 알아보았다. 또한 공정모니터링 데이터를 분석하여 다단사출속도, 보압 및 제한 사출 압력의 영향에 따른 사출성형기의 공정 제어 특성도 알아보았다.

• Neurospine
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• 제15권4호
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• pp.394-399
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• 2018

Subarachnoid pleural fistula (SPF) is an aberrant communication between the pleural cavity and subarachnoid space, resulting in uncontrolled cerebrospinal fluid drainage. The negative pressure of the pleural cavity creates a continuous suctioning effect, thereby impeding the spontaneous closure of these fistulas. Dural tears or punctures in cardiothoracic procedures, spinal operations, and trauma are known to cause such abnormal communications. Failure to recognize this entity may result in sudden neurological or respiratory complications. Hence, a high index of suspicion is required for early diagnosis and prompt management. Noninvasive positive pressure ventilation has been described to be effective in managing such fistulas, thus mitigating the high morbidity associated with exploratory surgery for primary repair. Herein, we describe the typical presentation of SPF and the clinical course, treatment, and follow-up of a patient who sustained SPF following anterior thoracic spinal surgery.

• 터널과지하공간
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• 제26권6호
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• pp.493-507
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• 2016

본 연구에서는 축소모형실험을 통해 석회암 공동 상부에 존재하는 구조물 기초의 안정성을 검토하였다. 공동의 형상은 단축장축비율 1/3인 타원형으로 가정하고, 공동의 심도, 위치, 경사, 크기, 개수를 변화시킨 5가지 그룹, 12개 모형들을 실험하였다. 실험결과로서 모형별 균열개시압력, 최대압력, 변형거동, 파괴양상, 침하곡선을 구하였으며, 공동의 제반 조건들이 기초의 안정성에 어떠한 영향을 미치는지를 알아보았다. 무공동 모형은 전단파괴를 보였으나, 공동 포함 모형들은 관입파괴만 발생한 경우, 전단파괴와 관입파괴가 함께 발생한 경우, 전단파괴가 이중으로 발생한 경우 등의 다소 복잡한 파괴형식을 보였다. 공동의 심도가 작을수록, 크기가 클수록, 개수가 많을수록 기초의 안정성은 감소하였다. 공동의 일부가 기초저면의 직하부에 놓일 때는 부등침하가 관찰되었고, 공동들의 분포상태에 따라 침하곡선은 다른 형태를 보였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.312-317
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• 2001

Modifying effects of the rectangular forward step for suppressing the unsteady pressure fluctuation during interaction between the upstream vortical flow with the edge are studied numerically. The vortical flow is modeled by a point vortex, and the unsteady pressure coefficient is obtained from the velocity and the potential field. To investigate the effects of the edge shape the rectangular forward step is chamfered with various angles. Calculation show that the pressure peaks become decreased by increasing the vortex height as well as the chamfering angle. The pressure amplitudes are very sensitive to the change of the initial vortex height. From this study we can find out that the chamfered edge has two effects; the one is that it suppresses the pressure amplitude generated from the edge, and the other is that it decreases the time variation of unsteady pressure fluctuation. These modifying concepts can be applied to attenuate the self-sustained oscillation mechanism at the open cavity flow.

• 한국소음진동공학회논문집
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• 제12권3호
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• pp.213-220
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• 2002

Modifying effects of the rectangular forward step for suppressing the unsteady pressure fluctuation during interaction between the upstream vortical flow and the edge are studied numerically. The vertical flow is modeled by a point vortex, and the unsteady pressure coefficient is obtained from the velocity and the potential fields. To investigate the effects of the edge shape the rectangular forward step is chamfered wish various angles. Calculation shows that the pressure peaks become decreased by increasing the vortex height as well as the chamfering angle. The pressure amplitudes are very sensitive to the change of the initial vertex height and its strength. From this study we can find out that the chamfered edge has two effects; the one is that it suppresses the pressure amplitude generated from the edge, and the other is that it decreases the time variation of unsteady pressure fluctuation. These modifying concepts can be applied to attenuate the self-sustained oscillation mechanism at the open cavity flow.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2005년도 제31회 KOSCO SYMPOSIUM 논문집
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• pp.261-267
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• 2005

A comprehensive DES quality numerical analysis has been carried out for reacting flows in constant-area and divergent scramjet combustor configuration with and without a cavity. Transverse injection of hydrogen is considered over a broad range of injection pressure. The corresponding equivalence ratio of the overall fuel-air mixture ranges from 0.167 to 0.50. The work features detailed resolution of the flow and flame dynamics in the combustor, which was not typically available in most of the pervious studies. Much of the flow unsteadiness is related not only the cavity, but also to the intrinsic unsteadiness in the flowfield. The interactions between the unsteady flow and flame evolution may cause a large excursion of flow oscillation. The roles of the cavity, injection pressure, and heat release in determining the flow dynamics are examined systematically.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제21회 추계학술대회 논문집
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• pp.191-194
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• 2003

A series of computational simulations have been carried out for non-reacting and reacting flows in a supersonic combustor configuration with and without a cavity. Transverse injection of hydrogen, a simplest form of fuel supply, is considered in the present study with the injection pressure of 0.5 and 1.0 ㎫. The corresponding equivalence ratios are 0.17 and 0.33. The work features detailed resolution of the flow and flame dynamics in the combustor, which was not typically available in most of the previous studies. In particular, oscillatory flow characteristics are captured at a scale sufficient to identify the underlying physical mechanisms. Much of the flow unsteadiness is related not only to the cavity, but also to the intrinsic unsteadiness in the flowfield. The interactions between the unsteady flow and flame evolution may cause a large excursion of flow oscillation. The role of the cavity, injection pressure, and amount of heat addition are examined systematically.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.785-790
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• 2000

The resonant frequency of a gas-filled cylindrical Helmholtz resonator in a liquid is obtained analytically. The equation of motion of the resonator is derived by using the condition of equilibrium of forces acting on the mass in the neck of the resonator. The reaction force on the upper side of the cylinder due to the acceleration of external fluid and sound radiation is obtained by using the analytical results for the baffled circular-piston problem. From the frequency response function of the resonator, a formula to predict the resonant frequency of the resonator is derived. It is shown that the resonant frequency of the Helmholtz resonator significantly decreases due to the cushioning effect of gas inside the cavity. Therefore, when a pressure transducer is to be installed in a pin-hole type mounting method, much care should be paid to remove the gas from the cavity.

• 한국유체기계학회 논문집
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• 제15권1호
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• pp.36-40
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• 2012

The magnitude of the axial thrust acting on pump bearings has a great influence on the operational reliability and service life of a pump for turbopumps. In the present study, radial vanes are introduced to the pump casing to control the axial thrust by changing the cavity pressure between the impeller and the casing. To investigate the effect of the vanes on the axial thrust of the pump, experimental and computational studies were performed with and without the vanes. It is shown that the vanes reduce the cavity pressure by preventing the flow from rotating with the impeller. Experimental and computational results show similar trend for the axial thrust difference between two cases with and without the vanes. The results show that the cavity vanes are very effective in controlling the magnitude of the axial thrust.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 추계 학술대회논문집
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• pp.126-131
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• 2003

A series of computational simulations have been carried out for supersonic flows in a scram jet engine with and without a cavity. Transverse injection of hydrogen, a simplest form of fuel supply, is considered in the present study with the injection pressure varying from 0.5 to 1.5 MPa. The corresponding equivalence ratios are 0.167 - 0.50. The work features detailed resolution of the flow dynamics in the combustor, which was not typically available in most of the Previous studies. In particular, oscillatory flow characteristics are captured at a scale sufficient to identify the underlying physical mechanisms. Much of the flow unsteadiness is related not only to the cavity, but also to the intrinsic unsteadiness in the flowfield. The interactions between shock waves and shear layer may cause a large excursion of flow oscillation. The role of the cavity and injection pressure are examined systematically.