• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.4
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• pp.265-273
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• 2002

In this paper, wave absorbing characteristics of a horizontal submerged punching plate are investigated throughout the calculation and the experiment. The punching plate with the array of circular holes can force the flow to separate and to form eddies of high vorticity and cause significant energy loss. As an analytic tool, the linear water wave theory and the eigenfunction expansion method is applied. Darcy's law that the normal velocity of the fluid passing through the punching plate is linearly proportional to the pressure difference between two sides of the punching plate is assumed. The proportional constant called the porous coefficient is deeply dependent to the porosity. To obtain the relationship between the porosity and the porous coefficient the systematic model test for the punching plates with 6 different porosities is conducted at 2-dimensional wave tank. It is found that the porous coefficient is linearly proportional to the porosity(b=57.63P-0.9717). It is also noted that the optimal porosity value is near P=0.1 and the optimal range of submergence depth is $d/h\\leq0.2$ within entire frequency range.

• KOREAN POULTRY JOURNAL
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• v.19 no.2 s.208
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• pp.40-45
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• 1987

닭고기는 타육류에 비해 전통적 기호도가 낮고 가공제품화율이 낮아 소비가 부진하다. 닭고기의 소비 주종은 신선육으로 이루어져 있어 유통기간 연장이 무엇보다 중요하다.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.5
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• pp.479-487
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• 2009

This paper describes the design of a full-spade twisted rudder section by using the genetic algorithm based on VLM(Vortex Lattice Method) and panel method. The developed propeller- rudder analysis program has been validated by comparing with experimental data. The developed code has been used for the design of a twisted full-spade rudder especially for finding out optimum section. The optimization has been firstly carried out by the genetic algorithm. The more detail variation of a rudder section has been also conducted by changing section profile in more detail to confirm the most optimum section profile. The developed new twisted rudder has been compared with existing twisted rudder by cavitation testing in the cavitation tunnel at MOERI. It is concluded that the developed twisted rudder has a lower cavity in comparison with existing twisted rudder. The verification of efficiency gain is expected to be carried out through self-propulsion tests in the near future.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.6
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• pp.421-428
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• 2013

This study aims at numerically investigating the angle of attack characteristics of the rudder behind a rotating propeller. The rotating propeller of 5 blades and the full spade rudder are placed in the numerical water tunnel with a uniform flow condition to consider propeller-rudder interaction. The turbulence closure model is employed to simulate the three-dimensional unsteady incompressible viscous turbulent flow around the propeller and the rudder. The present numerical method are well verified by comparing with the experimental results. In order to identify the dependence of the angle of attack of the rudder on the rudder angle, a wide range of rudder angles is considered. The present study carried out the quantitative and qualitative analysis of the angle of attack in terms of the pressure distribution, streamlines and the evaluation of the flow incidence, resulting in that the angle of attack increases as we move from the root and the tip to the center of the rudder, regardless of the rudder angle. The distribution of the angle-of-attack along the span is strongly affected by rotating propeller flow and rudder angle. Consequently, the distribution of the angle-of-attack of the oncoming flow against the rudder leading edge plays a role in determination of rudder performance.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.679-681
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• 2005

본 논문은 정사각형 모양의 사진 타일을 이용하여 장식적인 요소를 표현한 새로운 종류의 모자이크를 소개한다. 이 방법은 입력 영상에서 정사각형의 타일 영역을 정하여 그 영역과 시각적으로 가장 유사한 사진을 데이터베이스에서 찾아내어 매칭시켜 준다. 타일 영역들의 위치는 무게중심의 보로노이 다이어그램을 사용하여 서로의 간격을 균일하게 결정해주고, 그것의 방향은 입력 영상의 에지들을 따라 평행하게 나열되도록 조절해준다. 그리고 타일 영역 사이의 공간은 빈 공간으로 하여 고전적인 모자이크 작품의 장식적인 요소를 표현해 주었다. 다양한 타일 영역에 적합한 사진들을 얻기 위해서는 사진 데이터베이스의 규모가 클수록 좋으므로 많은 양의 사진을 가지고 있어야만 입력 영상과 최대한 유사하게 표현할 수 있다.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.4
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• pp.358-367
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• 2013

In the present paper, we apply a porous modelling technique to accurately predict the pressure drop through the strainer by replacing all or some of the filter composed of perforated plates with porous media and there imposing the streamwise and transverse loss coefficients required according to the Forchheimer law and then confirm its effectiveness. At first, the streamwise coefficient is obtained by performing a simple simulation on the pipe flow mimicking the hole flow. Subsequently, the transverse coefficient is obtained by setting a unit pattern to have common flow loss characteristics with the repeated shape patterns in the filter, then performing numerical simulations on the prototype and porous model of the unit shape pattern, and finally comparing their results of pressure drop. To validate the applied modeling technique, we perform the numerical simulation with the two specified loss coefficients on a whole shape of strainer and compare the modeling results with those of the corresponding prototype numerical simulation. Comparison indicates that the modeling technique can predict the pressure drop and flow characteristics comparatively accurately and save the number of nodes closely related to the computational cost (CPU and memory) by about 3~4 times compared with the prototype simulation.

• Bulletin of the Korean Space Science Society
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• 2004.04a
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• pp.44-44
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• 2004

GPS를 이용하여 대기 수증기의 3차원 분포도를 구하기 위하여, 관측소와 GPS 위성 간 시선방향으로의 수증기에 의한 GPS 신호지연 정도를 결정할 필요가 있다. 이 때 정확성 향상을 위하여 반드시 고려해야하는 위상중심변화(phase center variations)와 조석하중에 의한 지각변위(ocean loading displacements) 등 수직방향 좌표 결정 오차를 유발하는 요인들을 소개한다. 타 연구를 통해 위상중심변화는 크게는 l0cm 이상의 오차를, 그리고 조석하중에 의한 지각변위는 한반도의 경우 최대 3-4cm 정도의 오차를 보임을 알았지만, 이들 오차가 시선방향 습윤지연 결정에 미치는 영향은 규명되지 않았다. (중략)

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.207-212
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• 1996

DUPIC 핵연료 제조를 위해서 PWR 사용후핵연료의 피복관과 소결체를 분리하는 방법이 검토되었다. 약 50 cm의 PWR 사용후핵연료의 길이방향에 일정한 간격으로 구멍을 뚫어 산화하는 방법, 10∼20 m의 길이로 핵연료봉을 절단하여 산화하는 방법, 그리고, 핵연료봉의 길이 방향에서 피복관을 slitting하여 산화하는 방법에 대해 실험을 수행하였다. 실험 결과들로 보아 DUPTC 핵연료 제조 공정에 가장 적합한 방법으로는 핵연료봉 길이방향으로 slitting하여 산화하는 것이 가장 타당한 것으로 판명되었다.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1996.04b
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• pp.75-79
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• 1996

유량 보존 경계 조건을 적용하여 커넥팅 로드 베어링의 성능 해석을 수행하였다. 레이놀즈 경계 조건을 적용하는 경우에 비하여 최소 유막 두께, 동력 손실율과 축방향 유량은 더 작게, 최대 유막 압력은 더 크게 예측되었다. 유량 보존 경계 조건을 적용한 경우 축 방향으로의 공급 유량과 방출 유량이 거의 균형을 이루었다. 물리적으로 타당한 유량 보존 경계 조건을 적용한 커넥팅 로드 베어링의 성능 해석으로 얻어진 동력 손실율과 축 방향 유량을 이용하면, 윤활제의 온도 상승과 그에 따른 점도 변화를 좀 더 정확하게 예측 할 수 있을 것으로 기대된다.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.1
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• pp.23-27
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• 2011

This study analyzes about the variation of pressure and stream velocity according to the movement of tail wing. The pressure at the front part of airplane becomes lower than at the rear part and the stream velocity has decreased by being bumped against the wing of airplane. The pressure at the front part of rudder becomes higher than at its rear part according to the movement of rudder among the tail wings of airplane. The more stream velocity becomes decreased, the more rudder spreads out. As the tail wing of airplane folds, the pressure at its front part becomes higher. And the pressure at its rear part becomes lower than at its front part. The more tail wing of airplane folds, the more stream velocity becomes decreased.