• 대한조선학회논문집
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• 제50권4호
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• pp.206-216
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• 2013

The present study considers the prediction of wind-induced heel of cruise ship and its stabilization. Wind load in ocean exerts on the surface of superstructure of cruise ship, which causes the heel moment on the ship. The calculation of wind load starts from choosing wind speed profile, so that the logarithmic wind profile model is applied in this study. Heel moment by wind load is calculated by adopting approximate formulation and applied to the ship motion analysis in time domain. Motion stabilizers, such as stabilizing fin and U-tube tank, are considered to reduce the heel effect as well as excessive roll motion. From this study, it is expected that the present method can be applied to the prediction and stabilization of the heel motion of cruise ships.

• 대한조선학회논문집
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• 제35권1호
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• pp.40-45
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• 1998

불규칙파중의 선박의 운동을 해석하는 방법으로 주파수 영역해석법과 시영역해석법이 있다. 주파수영역해석법은 스펙트럴해석기법에 의해 불규칙파중 선박의 운동특성을 구하는 방법이고, 시영역해석법은 불규칙파를 생성하여 이 파를 실제의 입력으로 하여 선박의 운동을 직접 계산하는 방법이다. 보통 취급이 간편한 주파수 영역해석법이 선박의 자동조타 시스템 평가에 자주 사용되고 있으나, 본 연구에서는 주파수 영역해석법과 시영역해석법에 의한 불규칙파중의 선박의 보침운동 및 자동조타 시스템 평가를 수행하고 두 방법을 비교 검토하였다.

• International Journal of Internet, Broadcasting and Communication
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• 제16권3호
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• pp.221-227
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• 2024

In autonomous navigation systems, the need for fast and accurate image processing using deep learning and advanced sensor technologies is paramount. These systems rely heavily on the ability to process and interpret visual data swiftly and precisely to ensure safe and efficient navigation. Despite the critical importance of such capabilities, there has been a noticeable lack of research specifically focused on ship image classification for maritime applications. This gap highlights the necessity for more in-depth studies in this domain. In this paper, we aim to address this gap by presenting a comprehensive comparative study of ship image classification using two distinct neural network models: the Feedforward Neural Network (FNN) and the Convolutional Neural Network (CNN). Our study involves the application of both models to the task of classifying ship images, utilizing a dataset specifically prepared for this purpose. Through our analysis, we found that the Convolutional Neural Network demonstrates significantly more effective performance in accurately classifying ship images compared to the Feedforward Neural Network. The findings from this research are significant as they can contribute to the advancement of core source technologies for maritime autonomous navigation systems. By leveraging the superior image classification capabilities of convolutional neural networks, we can enhance the accuracy and reliability of these systems. This improvement is crucial for the development of more efficient and safer autonomous maritime operations, ultimately contributing to the broader field of autonomous transportation technology.

• 대한조선학회논문집
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• 제61권4호
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• pp.278-288
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• 2024

According to International Association of Classification Societies (IACS) Unified Requirement (UR) E26, ships contracted for construction after July 1, 2024 should be designed, constructed, commissioned and operated taking into account of cyber security. In particular, ship network monitoring tools should be installed in accordance with requirement 4.3.1 in IACS UR E26. In this paper, we propose a Security Information and Event Management (SIEM) security policy model for ships as an effective threat detection method by analyzing the cyber security regulations and ship network status in the maritime domain. For this purpose, we derived the items managed in the SIEM from the maritime cyber security regulations such as those of International Maritime Organization (IMO) and IACS, and defined 14 detection policies considering the status of the ship network. We also presents the detection policy for non-expert crews to understand it, and occurrence conditions depending on the ship's network environment to minimize indiscriminate alarms. We expect that the results of this study will help improve the efficiency of ship SIEM to be installed in the future.

• International Journal of Naval Architecture and Ocean Engineering
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• 제3권1호
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• pp.9-19
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• 2011

The paper describes the validation of two time domain methods to simulate the behaviour of a destroyer operating in steep, stern-quartering seas. The significance of deck-edge immersion and water on deck on the capsize risk is shown as well as the necessity to account for the wave disturbances caused by the ship. A method is described to reconstruct experimental wave trains and finally two deterministic validation cases are shown.

• International Journal of Naval Architecture and Ocean Engineering
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• 제3권1호
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• pp.20-26
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• 2011

A weakly nonlinear seakeeping methodology for predicting motions and loads is presented in this paper. This methodology assumes linear radiation and diffraction forces, calculated in the frequency domain, and fully nonlinear Froude-Krylov and hydrostatic forces, evaluated in the time domain. The particular approach employed here allows to overcome numerical problems connected to the determination of the impulse response functions. The procedure is divided into three consecutive steps: evaluation of dynamic sinkage and trim in calm water that can significantly influence the final results, a linear seakeeping analysis in the frequency domain and a weakly nonlinear simulation. The first two steps are performed employing a three-dimensional Rankine panel method. Nonlinear Froude-Krylov and hydrostatic forces are computed in the time domain by pressure integration on the actual wetted surface at each time step. Although nonlinear forces are evaluated into the time domain, the equations of motion are solved in the frequency domain iteratively passing from the frequency to the time domain until convergence. The containership S175 is employed as a test case for evaluating the capability of this methodology to correctly predict the nonlinear behavior related to wave induced motions and loads in head seas; numerical results are compared with experimental data provided in literature.

• 한국해양공학회지
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• 제11권2호
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• pp.100-106
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• 1997

Viscous flow around an actual ship is calculated by an use of RANS(Reynolds-averaged Navier-Stokes) solver. Reynolds stress is modelled by using k-$\varepsilon$ turbulence model and the law of wall is applied near the body. Body fitted coordinates are introduced for the treatment of the complex boundary of the ship hull form. The transformed equations in the computational domain are numerically solved by an employment of FVM(Finite Volume Method). SIMPLE(Semi-Implcit Pressure Linked Equation) method is adopted in the calculation of pressure and the solution of the disssssssscretized equation is obtained by the line-by-line method with the use of TDMA(Tri-Diagonal Matrix Algorithme). The subject ship model of actual calculation is 4,410 TEU class container carrier. For 4 geosim models the calculated viscous resistancce values are compared with the model test results and analyzed on their componentss. The resistance performance of an actual ship is predicted very resonably, so this mothod may be utilized as a design tool of hull form.

• 한국해양공학회지
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• 제23권6호
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• pp.77-81
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• 2009

The radar cross section (RCS) of a warship is one of the most important design features in terms of her survivability in hostile environments. Ocean waves continuously changes the attitude of an objective warship to hostile radar and distorts the RCS as a result. This paper presents a dynamic RCS analysis technique and procedure that considers temporal ship motion. First, data sets are prepared for ship motions in 6 degrees of freedom, which are numerically simulated for an objective warship via frequency to time domain conversion with response amplitude operators and specified ocean wave spectra. Second, a series of RCS analysis models are transformed geometrically by referring to ship motion data sets. Finally, temporal RCS analyses are carried out with the RCS simulation code, SYSCOS. As an example, RCS analysis results are given for a virtual warship, which show that ship motions temporally change RCS values and cause RCS reduction compared with static value in terms of mean values.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권1호
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• pp.37-47
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• 2018

Dynamic simulation is critical for electrical ship studies as it obtains the necessary information to capture and characterize system performance over the range of system operations and dynamic events such as disturbances or contingencies. However, modeling and simulation of the interactive electrical and mechanical dynamics involves setting up and solving system equations in time-domain that is typically time consuming and computationally expensive. Accurate assessment of system dynamic behaviors of interest without excessive computational overhead has become a serious concern and challenge for practical application of electrical ship design, analysis, optimization and control. This paper aims to develop a systematic approach to classify the sophisticated dynamic phenomenon encountered in electrical ship modeling and simulation practices based on the design intention and the time scale of interest. Then a novel, comprehensive, coherent, and end-to-end mathematical modeling and simulation approach has been developed for the latest Medium Voltage Direct Current (MVDC) Shipboard Power System (SPS) with the objective to effectively and efficiently capture the system behavior for ship-wide system-level studies. The accuracy and computation efficiency of the proposed approach has been evaluated and validated within the time frame of interest in the cast studies. The significance and the potential application of the proposed modeling and simulation approach are also discussed.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2003년도 춘계공동학술대회논문집
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• pp.132-138
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• 2003

대형 유조선 접이안시 발생하는 비정상 운동을 이해하기 위해서는 천수역에서 작용하는 유체력의 크기와 성질을 명학히 파악해야 한다. 본 논문에서는 수식선형인 wigley 선형을 대상으로 수심과 가속도에 따른 유체력 변화에 대해 CFD를 이용하여 직접 시간영역에서 수치 계산을 행하였다. 또한 계산 결과를 수조 실험결과와 비교하여 CFD의 타당성 및 유효성을 검증하였다. CFD의 계산 결과는 선박 접이안시 선체에 작용하는 유체력의 산출은 물론이고 선체 주위 물리적 현상이나 유장 등의 특징을 상세히 파악할 수 있었다. 또한 수심과 가속도를 변수로 행한 계산 결과를 바탕으로 최초 정지상태에서 등속운동까지의 과도 횡력을 선체 이동속도에 이동거리를 곱한 순환함수의 개념을 이용하여 모델화하였다.