• Journal of Ocean Engineering and Technology
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• v.5 no.2
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• pp.51-57
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• 1991

불규칙 해상에서 선박의 큰 횡요각의 예측이 중요한 과제로 대두 되고 있다. 본 논문에서는 통계적 해석에 의한 이의 예측 방법을 제시한다. 즉 주어진 비 선형 횡요운동 방정식으로 부터 배의 횡요각과 각속도의 결합 확률 밀도 함수를 구하는 방법을 도입하고 각종 계수들의 값의 변화에 따른 예측 결과를 다른 논문에서 제시한 시뮬레이션 결과와 비교하였다.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.1
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• pp.61-70
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• 1992

The method presented in this paper predicts the rolling motion of ships due to wave action. The Forker-Planck-Kolmogrov(FPK) method is adopted to evaluate the probability density function of the rolling motion which is of vital importance for design purposes. The apprximate solution of the FPK equation is obtained through averaging procedure. The accuracy of the proposed method is demonstrated by comparing with Dalzell's simulation and those from Roberts method as well.

• Journal of Ocean Engineering and Technology
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• v.6 no.2
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• pp.41-45
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• 1992

In this paper an application technique of moment equation method to solution of nonlinear rolling equation of motion of ships is investigated. The exciting moment in the equation of rolling motion of ships is described as non-white noise. This non-white exciting moment is generated through use of a shaping filter. These coupled equations are used to generate moment equations. The nonstationary responses of the nonlinear system are obtained. The results are compared with those of a linear system.

• Journal of Ocean Engineering and Technology
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• v.7 no.1
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• pp.92-98
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• 1993

불규칙 해상에서 선박의 큰 횡요각의 예측이 중요한 과제로 대두 되고 있다. 본 논문에서는 추계적 해석에 의한 이의 예측 방법을 제시한다. 즉, 주어진 비선형 횡요 운동 방정식으로 부터 배의 횡요각과 각속도의 확률 밀도 함수를 구하는 방법으로 평균화 법과 등가 비선형화 법을 적용하였고 각종 계수들의 값의 변화에 따른 예측 결과를 다른 논문에서 제시한 simulation 결과와 비교하였다.

• Journal of Navigation and Port Research
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• v.29 no.10 s.106
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• pp.839-845
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• 2005

A rudder roll control system is developed and analyzed to control the yawing and rolling motion of ship in irregular waves. The 4-DOF maneuvering equations of motion are derived to carry out the simulation of the motion of a ship and the wave forces are considered as the external forces of a ship in the simulation. The wave forces in the time domain analysis are generated from the frequency transfer function calculated by 3-D source distribution method. The rudder roll control system is developed by linear combination of PD rudder controllers of yawing and rolling motion. Rudder rate speed and Schilling rudder are considered to increase the roll reduction efficiency.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.55-61
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• 2005

A rudder roll control system is developed and analyzed to control yawing and rolling motion of ship in irregular waves. The 4-DOF maneuvering equations of motion are derived to carry out the simulation of the motion of a ship and the wave forces are considered as the external forces of a ship in the simulation. The wave forces in the time domain analysis are generated from the frequency transfer function calculated by 3-D source distribution method. The rudder roll control system is developed by linear combination of PD rudder controllers of yawing and rolling motion Rudder rate speed and Schilling rudder are considered to increase roll reduction efficiency.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.2
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• pp.60-65
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• 1992

The roll response of a ship to random beam seas is investigated in terms of the threshold crossing process. The non-white excitation process is modeled as an equivalent white-noise one based on the assumption that the upcrossing properties of the response can be approximately replaced by the excitation with a white noise process with a suitable intensity. Then the non-linear damping is reinstated. The reinstated equation of motion with the equivalent white-noise intensity is solved using the equivalent non-linear method to get the desired probability density function. The proposed scheme is tested extensively with varing coefficients.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.2
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• pp.57-64
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• 1994

The subject of this paper is the simulation of a nonlinear stochastic differential equation. The Monte-Carlo solution of stochastic problems is applied to solve it. The method has been applied to problems involving nonlinear rolling motion of ships in irregular waves. These results are compared with those obtained by the stochastic linearization method and the equivalent nonlinear equation method to demonstrate its usefulness.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.3
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• pp.235-239
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• 2016

The capsizing speed of an unstable vessel with a lost restoring moment can be understood as a unique response to an accident situation, and is naturally affected by such parameters as moment of inertia, metacentric height, and transverse damping coefficient of the hull in the case of free roll motion. Additionally, it is supposed that the analysis of capsize accidents can be further simplified when a vessel's leaning velocity is shown to be quite low. Therefore, capsize accidents with low leaning speeds are desirably categorized in view of rescuing strategies, as opposed to fast capsize accidents, since the attitude of the declining hull can be properly estimated, which allows rescuers to have more time for helping accident cases. This study focuses on deriving some analytical equations based on the roll decay ratio parameter, which describes how a hull under a low-speed capsize is related to the situational hull characteristics. The suggested equations are applied to a particular ship to disclose the analytical responses from the model ship. It was confirmed that the results show the general characteristics of slow capsizing ships.