• 한국유체기계학회 논문집
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• 제19권1호
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• pp.31-36
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• 2016

Hydraulic actuator is a primary component of the hydraulic valve systems. In this study, the thrust performance of hydraulic actuator was studied with different values of viscosity of hydraulic oil and rod diameter. Numerical analysis was performed using the commercial CFD code, ANSYS with 2-way FSI(Fluid-Structure Interaction) method and $k-{\varepsilon}$ turbulent model. Results show that increase in viscosity of hydraulic oil reduces the thrust of hydraulic actuator. In order to satisfy the output required of the actuator, it is necessary to compensate for the operating pressure. The results of pressure, velocity and thrust efficiency distributions in the hydraulic actuator were graphically depicted.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
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• pp.75-81
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• 2000

Experimental studies on the characteristics of annular jet pump were carried out in this paper. The effects of high pressure chamber on the characteristics of annular jet pump were sought in this paper. Experiments were done for three shapes of high pressure chamber, and for several lengths of the high pressure chamber. Three types of the high pressure chamber's entrances($90^{\circ}$ single inflow, $45^{\circ}$ single inflow, and $45^{\circ}$ double inflow) were tested. Water was used for both the primary fluid and secondary fluid. The results obtained in this study are as follows; $45^{\circ}$ double inflow type is the most effective among the tested three types of the high pressure chamber's entrances. The efficiency of jet pump with 400mm of high pressure chamber length is the highest among the chamber lengths tested in this study, thus indicating appropriate chamber length is required to get an efficient jet pump.

• 한국추진공학회지
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• 제7권4호
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• pp.10-18
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• 2003

본 연구에서는 기존 연구에서 사용된 PSD 성능 시험 장치를 살펴보았다. 성능 시험 장치는 공급관 전체 가진 방식과 작동 유체 가진 방식으로 구분할 수 있다. 작동유체 가진 방식은 다시 피스톤 방식과 면적제한 방식으로 분류할 수 있다. 면적 제한 방식이 기초 연구에 알맞으며, 제작된 실험장치의 구성품을 제시하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제20회 춘계학술대회 논문집
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• pp.19-22
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• 2003

이젝터-디퓨저 시스템은 일종의 유체기계로서, 저압부의 유체를 혼입하여 고압부로 이송한다. 기존의 이젝터-디퓨저 시스템은 유체의 순수한 전단력만을 이용하므로 다른 유체기계에 비하여 효율이 낮은 단점이 있다. 본 연구에서는 이젝터-디퓨저 시스템의 효율을 높이기 위하여, 설계마하수가 M$_{d}$=1.7이고 로브의 개수가 각각 4, 6, 8개인 페탈노즐을 구동노즐로 사용하였고, 원형구동노즐을 사용한 이젝터-디퓨저 시스템의 결과와 비교하였다.

• Structural Engineering and Mechanics
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• 제31권1호
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• pp.25-38
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• 2009

Local failure of a primary structural component induced by direct air-blast loading may be itself a critical damage and lead to the partial or full collapse of the building. As an extensive research to mitigate blast-induced hazards in steel frame structure, a state-of-art analytical approach or high-fidelity computational nonlinear continuum modeling using computational fluid dynamics was described in this paper. The capability of the approach to produce reasonable blast pressures on a steel wide-flange section column was first evaluated. Parametric studies were conducted to observe the effects of section sizes and boundary conditions on behavior and failure of columns in steel frame structures. This study shows that the analytical approach is reasonable and effective to understand the nature of blast wave and complex interaction between blast loading and steel column behavior.

• 한국해양공학회지
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• 제36권4호
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• pp.280-294
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• 2022

This study reviews the recent development and research results of a fixed oscillating water column (OWC) wave energy converter (WEC). The OWC WEC can be divided into fixed and floating types based on the installation location and movement of the structure. In this article, the study on a stationary OWC WEC, which is close to commercialization through the accumulation of long-term research achievements, is divided into five research categories with a focus on primary energy conversion research. These research categories include potential-flow-based numerical analysis, wave tank experiments, computational fluid dynamics analyses toward investigation of fluid viscous effects, U-shaped OWC studies that can amplify water surface displacement in the OWC chamber, and studies on OWC prototypes that have been installed and operated in real sea environments. This review will provide an overview of recent research on the stationary OWC WEC and basic information for further detailed studies on the OWC.

• Structural Engineering and Mechanics
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• 제88권3호
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• pp.251-262
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• 2023

This paper presents a method for assessing the dynamic responses of gravity-based structures (GBS) under various seismic loads, with a focus on fluid-structure-ground interactions. Models of GBSs and their surrounding environments were developed, incorporating interaction effects among the structure, seawater, and seabed. Dynamic responses of the GBS subjected to three seismic loads-Chi-Chi, Northridge01, and Northridge02-were calculated, with consideration of both horizontal and vertical accelerations, as well as displacements. Parametric studies indicated that the primary factors affecting the dynamic responses of GBS were seismic loads characterized by significant input forces and accelerations. The frictional force on the ground had minimal impact on the horizontal and vertical displacements of the GBS. Weight emerged as a critical factor in anchoring the GBS to the ground and minimizing vertical accelerations and displacements.

• Tuberculosis and Respiratory Diseases
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• 제47권1호
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• pp.50-56
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• 1999

연구배경: 양성 질환과 악성 질환의 감별 전단으로 혈청에서의 cyfra 21-1 에 관한 연구는 많이 되고 있으나, 흉수내 cyfra 21-1 의 진단적 의의에 관한 연구는 거의 없는 실정이다. 저자들은 흉수의 원인의 감별 진단으로 흉수의 cyfra 21-1 이 진단적 의의가 있는지를 알아보기 위하여 흉수내 cyfra 21-1 을 측정하였으며 혈청내 cyfra 21-1과도 비교하여 흉수내 cyfra 21-1의 진단적 의의를 알아보았다. 연구방법: 1994년 8월부터 1996년 6월까지 삼출성 흉막염으로 내원하였던 환자 92례를 대상으로 흉수와 혈청의 cyfra 21-1을 측정하였다. 흉수의 원인은 생화학적 검사, 세포학적 검사, 그리고 기관지 내시경 등응로 확진 되었으며, 흉수의 원인 질환에 따라 흉수와 혈청 cyfra 21-1 을 비교하였으며 각각의 민감도와 특이도는 ROC 곡선으로 분석하였다. 결과: 혈청 cyfra 21-1은 폐암군에서 가장 높았으며 양성질환군 및 전이암군과 비교할 때 양성 질환군과는 통계학적 의의가 있었으나, 전이암군과는 통계학적 의의가 없었다. 폐암군의 흉수 cyfra 21-1은 혈청보다 높았고, 각 질병군을 비교하였을 때 혈청에서와 같은 통계학적 결과를 보였다. 혈청과 흉수의 cyfra 21-1의 상관관계는 양성 질환군의 경우 통계학적 의의가 없었으나(r=-0.044, p=0.866), 악성 질환군은 유의한 상관 관계가 있었다(r=0.837, p=0.001). 전체 악성질환군인 경우 혈청 cyfra 21-1의 cut off 치를 2.7ng/mL로 하였을 때 민감도와 특이도는 각각 72.7%, 72.4%였으며, 폐암군은 cut off 치를 2.39ng/mL로 하였을 때 민감도와 특이도는 각각 73.9%, 72.4%로 두 군사이의 cut off 치, 민감도, 특이도는 차이가 없었다. 흉수 cyfra 21-1은 전체 악성 질환군의 경우 cut off 치가 10.74ng/mL 일 때 민감도 및 특이도는 각각 78.7%, 69.6% 이었으며, 폐암군은 cut off 치가 22.25 ng/mL 일 때 민감도 및 특이도는 각각 81.8%, 78.7%였다. 결론: 흉수의 cyfra 21-1 치는 양성 질환보다 악성 질환에 의한 흉막염에서 유의하게 높았으며 특히 원발성 폐암에 의한 악성 흉막염에서 민감도와 특이도가 높아 원발성 폐암에 의한 흉수의 감별진단에 cyfra 21-1을 유용하게 이용할 수 있을 것으로 생각한다.

• Corrosion Science and Technology
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• 제12권2호
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• pp.85-92
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• 2013

This work is concerned with an evaluation of dynamic boric acid corrosion (BAC) of low alloy steel for reactor pressure vessel of a pressurized water reactor (PWR). Mockup test method was newly established to investigate dynamic BAC of the low alloy steel under various conditions simulating a primary water leakage incident. The average corrosion rate was measured from the weight loss of the low alloy steel specimen, and the maximum corrosion rate was obtained by the surface profilometry after the mockup test. The corrosion rates increased with the rise of the leakage rate of the primary water containing boric acid, and the presence of oxygen dissolved in the primary water also accelerated the corrosion. From the specimen surface analysis, it was found that typical flow-accelerated corrosion and jet-impingement occurred under two-phase fluid of water droplet and steam environment. The maximum corrosion rate was determined as 5.97 mm/year at the leakage rate of 20 cc/min of the primary water with a saturated content of oxygen within the range of experimental condition of this work.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2769-2774
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• 2007

In vacuum ejector-diffuser systems where a finite volume secondary chamber is used, the secondary jet exhibits transient characteristics during start-up. A steady state is achieved after some time in which mass entrainment prevails indefinitely inside the ejector, though there is no flow from the secondary chamber. An attempt is made in this work to study the infinite entrainment of secondary jet into the primary jet from a finite secondary chamber, with the help of a computational fluid dynamics method. The present study is also intended to identify the operating range of vacuum ejector-diffuser systems where the steady flow assumption can be applied without uncertainty. The results obtained show that the only condition in which an infinite mass entrainment is possible is the generation of a re-circulation zone near the primary nozzle exit. The flow in the secondary chamber attains a state of dynamic equilibrium at this point. Steady flow assumption is valid only after this point.