• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.5
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• pp.420-427
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• 2008

For simulation of a fin unfolding motion for the various aerodynamic conditions, equations and moments applying to the unfolding fin were modelled. Aerodynamic roll moment consists of the static roll moment and the damping moment, which were obtained through wind tunnel tests and numerical analyses respectively. Panel method was used to compute the roll damping coefficient with deflected fin, whose angle was equivalent to angle of attack due to the deployment motion. Roll damping coefficient is a function of angle of attack, sideslip angle, and deployment angle but not of angular velocity of deployment. Simulation with aerodynamic damping model gave more similar deployment time compared to fin deployment test results.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.1
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• pp.43-51
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• 2001

The unsteady problems of ships in waves are analyzed by a low order panel method with Rankine source. Considering the basic flow as the uniform incoming flow(so called Kelvin flow) and also the double body flow. the solutions to satisfy the governing equation with the boundary conditions are obtained, and these two results are compared. The hydrodynamic coefficients for the modified Wigley hull and Series 60($C_B=0.7$) are computed and compared with the experimental data available and also other computational results published. It is shown that the computational results by the double body approximation agree well with the experimental results compared with those by the uniform Kelvin flow approximation.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.4
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• pp.248-254
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• 2013

In this paper, we establish an analysis algorithm and a design procedure for a Vane-Wheel which is a freely rotating device behind a propeller, by using a panel method. Vane-Wheel's function is to extract energy from the propeller slipstream in turbine part which is inner part of the Vane-Wheel, and convert this energy into an additional propulsive thrust in propeller part which is outer part of the Vane-Wheel. Two parts must satisfy torque balance and thrust has to act to the ship's forward direction. A Vane-Wheel has large interaction effect with propeller since it is placed behind of the propeller. Therefore, in order to consider interaction effect correctly, incoming velocity to the Vane-Wheel in a circumferential mean wake was calculated considering induced velocity from propeller to the Vane-Wheel. Likewise, incoming velocity to the propeller was calculated considering induced velocity from the Vane-Wheel to the propeller. This process is repeated until a converged result is obtained.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.672-680
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• 2017

A solar photovoltaic system is composed of a module mounting structure, supporting trunk, and a control unit that supplies generated electrical power to an external power grid or a load. The efficiency of the system depends on the incident solar light, so the mounting structure is installed to face the sun. However, because the sun always moves, systems that track the sun have better efficiency than fixed systems. The structure experiences wind pressure, snow load, seismic load, and structure weight. The wind pressure has the most serious effect on the structure. The pressure was obtained using finite element method for various gaps between modules and angles between the panel and the ground. The wind pressure is lowest when the gap is zero, and it increases with the inclination angle. Based on the results, a mounting structure module was designed.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.3
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• pp.69-77
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• 2003

This paper presents test results on eight reduced beam section(RBS) steel moment connections. The testing program addressed bolted versus welded web connection and panel zone(PZ) strength as key variables, Specimens with medium PZ strength were designed to promote energy dissipation from both PZ and RBS regions such that the requirement for expensive doublet plates could be reduced. Both strong and medium PZ specimens with a welded web connection were able to provide satisfactory connection rotation capacity for special moment-resisting frames. On the other hand, specimens with a bolted web connection performed poorly due to premature brittle fracture of the beam flange of the weld access hole. If fracture within the beam flange groove weld was avoided using quality welding, the fracture tended to move into the beam flange base metal of the weld access hole. Plausible explanation of a higher incidence of base metal fracture in bolted web specimens was presented. The measured strain data confirmed that the classical beam theory dose not provide reliable shear transfer prediction in the connection. The practice of providing web bolts uniformly along the beam depth was brought into question. Criteria for a balanced PZ strength improves the plastic rotation capacity while reduces the amount of beam distortion ore also proposed.

• Journal of Korean Society of Steel Construction
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• v.17 no.1 s.74
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• pp.45-52
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• 2005

The object of this study was a cold-formed steel wall stud panel sheathed by gypsum boards. In the beam-analysis, the panel was treated as a simple beam with a uniform lateral loading. The deflections were calculated by considering the primary factors that reduced the stiffness of the panel. In the column-analysis, the panel was treated as a bearing wall with an axial load. By using an energy method, nominal axial strength could be evaluated by considering both flexural buckling and torsional-flexural buckling. All calculations were programmed and compared with the results of the experiment. In the beam-analysis, experimental deflections were close to theoretical deflections. In the column-analysis, the experimental values were also close to theoretical values in axial strength.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.183-184
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• 2016

태양광 패널 등가모델을 결합한 태양광 발전 패널 모의 장치(SAS)는 정확도 면에서 많은 장점이 있다. 특히 SAS에서 사용되는 등가회로 모델은 주변 환경에 맞게 빠르게 변하는 I-V 출력특성을 추출할 수 있어야 하며, 추출시간이 짧을수록 좋다. 본 논문은 태양광 등가회로 모델의 파라미터를 빠르게 추출하여 I-V 특성곡선을 모사할 수 있는 방법을 제안한다. 제안한 모델은 실시간으로 변화하는 태양광 패널의 출력 특성을 빠르게 모사하기 위해 미분을 사용해서 등가회로의 파라미터를 추출한다. 제안 모델의 타당성 검증은 기존의 사용하는 방법들과의 비교를 통해 진행하였고, 그 결과 정확도는 기존의 사용하는 방법과 비슷하게 유지하면서 속도는 향상됨을 확인할 수 있었다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.3
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• pp.159-163
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• 2003

This study is object to minimum weight design of stiffened laminated composite flat panel. Various buckling load factors are obtained for stiffened laminated composite flat panels with rectangular type longitudinal stiffeners and various aspect ratios, which are made from Carbon/Epoxy USN150 prepreg and are simply-supported on four edges under uniaxial compression.

• Proceedings of the KAIS Fall Conference
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• 2010.11b
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• pp.551-554
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• 2010

유도탄고속함은 우리 해군의 최신예 함정으로서 디젤엔진 2기와 개스터빈 엔진 2기로 구성되어 최대 속력 40노트를 낼 수 있도록 구성되어 있다. 이를 위해 각각의 엔진에는 발전기가 배치되도록 구성되어 있는데, 이러한 발전기는 엔진 및 감속기어가 설치되어 있는 엔진룸에 배치되어 있어 커다란 진동에 그대로 노출이 되어 있는 상황이다. 따라서 이러한 진동의 저감을 위해 이중탄성마운트 등으로 발전기에 전달되는 진동을 저감하고자 하였으나 발전기의 패널에 전달되는 진동의 저감이 불충분하여 패널의 접지 불량이 수차례 발생하였다. 본 연구에서는 이러한 불량을 없애고자 유한요소법을 이용하여 발전기 패널의 위치를 변경하고 구조를 변경하였으며, 이를 통해 그 효과를 검증하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.11a
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• pp.37-38
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• 2009

터치스크린 기능이 있는 LCD 패널이 부착된 임베디드 시스템의 경우, 사용자 입력 명령의 전달을 위해 사각형, 오각형, 원, 화살표 같은 다양한 도형들이 자주 사용된다. 이 경우, 특정 명령 입력 여부의 판단을 위해 터치된 지점이 그 명령을 의미하는 도형 내에 있는지의 여부를 판단하는 알고리즘이 필요하다. 그러나 이런 알고리즘들은 제한된 컴퓨팅 자원을 갖는 임베디드 시스템의 경우 상당한 오버헤드를 유발 할 수 있다. 본 논문은 도형 영역의 터치 여부의 판단을 위해 사용 되고 있는 사각형의 범위 검사법, 다각형의 교차 수(crossing number) 검사법, 원의 거리 측정법, 그리고 이런 모든 도형들에 적용 가능한 색상 비교법을 구현하고, 성능 평가를 위해 각 방법에 따라 사각형, 오각형, 원, 그림 같은 도형들의 영역 터치 여부를 판단하는데 걸리는 시간을 측정한다. 이 측정 결과, 사각형은 범위 검사법이, 원은 거리 측정법이, 다각형 및 그림을 이용한 도형일 경우에는 색상 비교법이 가장 적합한 것으로 나타났다.