• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.06a
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• pp.291-292
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• 2012

해상에는 막대한 파력 부존량이 존재함에도 불구하고 파력발전은 다른 신재생 에너지 발전에 비하여 효율이 낮고 발전단가가 높아 경제성이 떨어진다. 그러므로 파력발전시스템을 상용화하기 위해서는 파력발전 효율을 증대시키기 위한 연구가 반드시 필요하다. 본 논문에서 제시하는 파력발전시스템은 기존의 파력발전기로는 발전할 수 없었던 작은 파도로도 발전 가능하도록 설계되어 높은 효율의 발전을 기대할 수 있다. 본 실험을 통하여 미세한 파도에서도 충분한 발전을 할 수 있는 시스템인지 여부를 판단하고 나아가서 상사법칙을 이용하여 본 모델 보다 5배 크기로 추정하였을 때 여기서 제시하는 파력발전시스템이 실제 해상에서 상용화 가능성이 있는지를 알아보고자 한다. 본 실험은 2차원 조파수조에서 수행 되었으며 발전시스템의 출력 값은 토크센서와 RPM 측정기를 사용하여 도출하였다.

• 한국전산유체공학회:학술대회논문집
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• 2007.10a
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• pp.39-44
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• 2007

A similarity solution of the Navier-Stokes equation for the axisymmetric stagnation flow near a plane wall coated with a magnetic fluid of uniform thickness is constructed. The shape functions representing the flow in two (magnetic and normal) fluid layer are determined from a third order boundary value problem, which is solved by the Runge-Kutta method with two shooting parameters. Features of the flow including streamline pattern and interface velocity are investigated for the varying values of density ratio, viscosity ratio, and Reynolds number. The results for the interface and wall shear stress, boundary layer and displacement thickness are also presented.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.1
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• pp.52-66
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• 1998

An experimental study on the flow characteristics was performed for a two-dimensional turbulent wall attaching offset jet at different oblique angles to a surface. The flow characteristics were investigated by using a split film probe with the modified Stock's calibration method. The jet mean velocity, turbulent intensity, wall static pressure coefficient profiles, and time-averaged reattachment point were measured at the Reynolds number Re (based on the nozzle width, D) ranging from 17700 to 53200, the offset ratio H/D from 2.5 to 10, and the inclined angle .alpha. from 0.deg. C to 40.deg. C. The Correlations between the maximum pressure position, minimum pressure position, and reattachment point and offset ratios, and inclined angles are presented.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.3
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• pp.53-60
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• 1988

The behavior of plane buoyant jet issuing vertically upwards into cross flow is analysed by experiments and integral scheme. The integral scheme is based on the self similarity and characteristic length scales to governing equations of continuity, momentum and constituent transport equation, in the horizontal and vertical flow region, respectively. Jet trajectories and the temperature distributions of jet centerlines obtained from experiments are analysed for various velocity ratios and densimetric Froude numbers. It was found that the analytical results about the trajectories and temperatures of jet center lines agree with the experiments and can be expressed as power laws.

• The KSFM Journal of Fluid Machinery
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• v.14 no.6
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• pp.26-34
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• 2011

Waterhammer and slamming phenomena can occur when power is cut off due to reversal flow in pipeline and sudden close of check valve. Therefore analysis of reversal flow time, which means the time of reversal flow in pipeline due to pumping station blackout, is needed to protect facilities from waterhammer economically and efficiently. However systematic study on reversal flow time has not been done yet. So theory of reversal flow time analysis is proposed and verified with experiment using several parameters like pump specific speed, motor pole number, and characteristic curve of pipeline in this study.

• 연구논문집
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• s.33
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• pp.67-79
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• 2003

The life of oilless bearing affects the durability of scroll compressor. The main shaft of the scroll compressor is supported by oiiless bearing. Some of the major parameters which influence the life of oilless bearing are rotational speed, normal load, environment of refrigerant and oil film thickness. The reliability evaluation of oiiless bearing is performed through the acceleration life test for reduction of experimental time and costs. In this study, the experimental and computational investigations were performed to verify the effects of various parameters on the life of oilless bearing. The acceleration factor was achieved with the lubrication analysis between the scroll compressor and the developed reliability tester. the expected life of oilless bearing was guaranteed by reliability evaluation accompanied with the acceleration life test.

• Proceedings of the Korean Society of Computer Information Conference
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• 2018.07a
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• pp.242-243
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• 2018

기존 연구들은 과업, 보수, 상사, 부하, 승진 등에 대한 만족도를 조사하고, 만족도가 높아야 직무몰입을 가져온다고 제시하였다. 모든 분야에 대해서 만족도를 높인다면 업무 몰입도와 업무성과는 당연히 높아지겠지만 현실적으로 제약이 있으므로 우선 순위를 정하여 집중적으로 지원을 하는 것이 효율적이다. 직원에 대한 지원 우선순위를 정하기 위하여 '만족도' 연구에 '기대도' 개념을 추가하였다. 즉, 만족도가 낮더라고 기대도가 낮다면 해당 요소는 만족하지 않을 거라는 기대를 하고 입사 및 근무하고 있으므로 지원대상에서 후순위가 된다. 반면에 만족도가 높더라도 기대도가 더 높다면 해당 요소는 기대도에 비해 여전히 부족하므로 지속적인 개선이 필요한 항목이다. 본 연구는 설문조사를 통해 만족도와 기대도의 차이를 분석하고 제한적인 재원으로 직원의 만족도를 높일 수 있는 효율적인 만족도 개선 가이드를 제시하고자 한다.

• Journal of Ocean Engineering and Technology
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• v.18 no.1
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• pp.41-46
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• 2004

This paper describes a study on the tearing damage of a ship's bottom plating, during a grounding. It is widely known that different scaling laws are applied for bodies undergoing simultaneous plastic flow and crack propagation in the deformation of plate tearing. Specifically, the basic scaling law is not followed for the fracture. In this study, in order to verify the problem, plate cutting experiments for geometrically similar models have been performed. From the experimental results, it has been observed that the cutting forces and energy for the larger models are significantly lower than those of the smaller models. A simplified analytical method for the estimation of tearing is proposed, based on the experiments. It has been observed that the results of the present formula are highly correlated with the experiments.

• Journal of computational fluids engineering
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• v.12 no.4
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• pp.20-27
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• 2007

Two-dimensional stagnation flow toward a plane wall coated with magnetic fluid of uniform thickness is investigated. The flow field is represented as a similarity solution of the Navier-Stokes equation for this incompressible laminar flow. The resulting third order ordinary differential equation is solved numerically by using the shooting method and by determining two shooting parameters so as to satisfy the boundary and interface conditions. Features of the flow including streamline patterns are investigated for the varying values of density ratio, viscosity ratio, and Reynolds number. An adverse flow with double eddy pair in magnetic fluid region is found to emerge as the Reynolds number becomes higher than a threshold value. The results for the interface velocity, interface and wall shear stress, and boundary layer and displacement thickness are also presented.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2010.10a
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• pp.257-260
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• 2010

실제 규모 ISO 9705 표준 화재실에서 액체연료를 대상으로 연소효율 개념에 관한 실험적 연구가 수행되었다. 특히 구획 외부에서 측정되는 총괄연소효율과 구획 내부의 고온 상층부에서 측정된 국부연소효율 개념을 비교 검토하였다. 주요 결과로서, 총괄연소효율은 총괄당량비 증가에 따라 비교적 선형적인 감소경향을 보였다. 반면에 국부연소효율은 총괄당량비가 증가함에 따라 2차 곡선의 형태로 크게 감소됨을 확인하였다. 위 결과를 통해 국부연소 효율에 대한 정보는 구획 내부의 화재현상을 이해하는데 유용한 변수임을 알 수 있었다. 또한 국부연소효율은 구획화재의 상사과정에서 중요한 변수로 사용될 수 있음을 논의하였다.