• The Journal of Bigdata
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• v.7 no.1
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• pp.89-97
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• 2022

Various efforts are needed to prevent accidents because ship collisions can cause various negative situations such as economic losses and casualties. Therefore, research to prevent accidents is being actively conducted, and in this study, new leading indicators for preventing ship collision accidents is proposed. In previous studies, the risk of collision was expressed in consideration of the distance between ships in a specific sea area, but there is a disadvantage that a new model needs to be developed to apply this to other sea areas. In this study, the density-based ship domain DESD (Density-based Empirical Ship Domain) including the environment and operating characteristics of the sea area was defined using AIS (Automatic Identification System) data, which is ship operation information. Deep clustering is applied to two-dimensional DESDs created for each sea area to cluster the seas with similar operating environments. Through the analysis of the relationship between clustered sea areas and ship collision accidents, it was statistically tested that the occurrence of accidents varies by characteristic of each sea area, and it was proved that DESD can be used as a leading indicator of accidents.

• International Journal of Naval Architecture and Ocean Engineering
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• v.2 no.3
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• pp.119-126
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• 2010

The response of ship roll oscillation under random ice impulsive loads modeled by Poisson arrival process is very important in studying the safety of ships navigation in cold regions. Under both external and parametric random excitations the evolution of the probability density function of roll motion is evaluated using the path integral (PI) approach. The PI method relies on the Chapman-Kolmogorov equation, which governs the response transition probability density functions at two close intervals of time. Once the response probability density function at an early close time is specified, its value at later close time can be evaluated. The PI method is first demonstrated via simple dynamical models and then applied for ship roll dynamics under random impulsive white noise excitation.

• Journal of Ship and Ocean Technology
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• v.12 no.1
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• pp.16-27
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• 2008

The interaction between advancing ships and the waves generated by them plays important roles in wave resistances and ship motions. Wave breaking phenomena near the ship bow at different speeds are investigated both numerically and experimentally. Numerical simulations of free surface profiles near the fore bodies of ships are performed and visualized to grasp the general trend or the mechanism of wave breaking phenomena from moderate waves rather than concentrating on local chaotic irregularities as ship speeds increase. Navier-Stokes equations are differentiated based on the finite difference method. The Marker and Cell (MAC) Method and Marker-Density Method are employed, and they are compared for the description of free surface conditions associated with the governing equations. Extra effort has been directed toward the realization of extremely complex free surface conditions at wave breaking. For this purpose, the air-water interface is treated with marker density, which is used for two layer flows of fluids with different properties. Adaptation schemes and refinement of the numerical grid system are also used at local complex flows to improve the accuracy of the solutions. In addition to numerical simulations, various model tests are performed in a ship model towing tank. The results are compared with numerical calculations for verification and for realizing better, more efficient research performance. It is expected that the present research results regarding wave breaking and the geometry of the fore body of ship will facilitate better hull form design productivity at the preliminary ship design stage, especially in the case of small and fast ship design. Also, the obtained knowledge on the impact due to the interaction of breaking waves and an advancing hull surface is expected to be applicable to investigation of the ship bow slamming problem as a specific application.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_3
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• pp.1289-1295
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• 2023

Polyurethane foam insulation required for storing and transporting cryogenic liquefied gas is already widely used as a thermal insulation material for commercial LNG carriers and onshore due to its stable price and high insulation performance. These polyurethane foams are reported to have different mechanical performance depending on the density, and the density parameter is determined depending on the amount of the blowing agent. In this study, density-dependent polyurethane foam was fabricated by adjusting the amount of blowing agent. The mechanical properties of polyurethane foam were analyzed in the room temperature and cryogenic temperature range of -163℃ at 1.5 mm/min, which is a quasi-static load range, and the cells were observed through microstructure analysis. The characteristics of linear elasticity, plateau, and densification, which are quasi-static mechanical behaviors of polyurethane foam, were shown, and the correlation between density and mechanical properties in a cryogenic environment was confirmed. The correlation between mechanical behavior and cell size was also analyzed through SEM morphology analysis. Polyurethane foam with a density of 180 kg/m³ had a density about twice as high as that of a polyurethane foam with a density of 96 kg/m³, but yield strength was about 51% higher and cell size was about 9.5% smaller.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2009.10a
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• pp.50-51
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• 2009

This paper aims to improve survival ratio at ship fires by soot density reduction This study examines soot density and visibility using FDS. And also examines evacuation time by Pathfinder. The FDS(Fire Dynamic Simulator) is a 3 zone model(Field Model) analysis tool and the patherfinder is a useful analysis tool for evacuation. This research examined about evacuation time using the current regulations of the ship's corridor width and exit width first And then studied evacuation time again when ship's structure was changed according to the method that is proposed in this paper. And finally compared the results each other.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.195-199
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• 2005

Wave breaking phenomenon near the fore body of a ship is numerically simulated. The ship advance with uniform velocity in calm water. For the simulation, incompressible Navier-Stokes equations and continuity equation are adopted as governing equations. The simulation is carried out in staggered variable mesh system with finite difference method. Marker and Cell(MAC) method and Marker-Density method are employed to track the free surface. Body boundary conditions are satisfied with the adoption of porosity method and no-slip condition on the hull surface. The ship model has a wedge type fore-body, and the computational domain is an appropriate region around the fore-body. The computation results are compared with some experimental results. Also the difference of the free surface tracking methods are discussed.

• Ocean Systems Engineering
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• v.1 no.3
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• pp.249-261
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• 2011

The stochastic nonlinear dynamic behavior and probability density function of ship rolling are studied using the nonlinear dynamical systems approach and probability theory. The probability density function of the rolling response is evaluated through solving the Fokker Planck Equation using the path integral method based on a Gauss-Legendre interpolation scheme. The time-dependent probability of ship rolling restricted to within the safe domain is provided and capsizing is investigated from the probability point of view. The random differential equation of ships' rolling motion is established considering the nonlinear damping, nonlinear restoring moment, white noise and colored noise wave excitation.

• Journal of Computational Design and Engineering
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• v.1 no.4
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• pp.266-271
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• 2014

The survivability of the naval ship is the capability of a warship to avoid or withstand a hostile environment. The survivability of the naval ship assessed by three categories (susceptibility, vulnerability and recoverability). The magnitude of susceptibility of a warship encountering with threat is dependent upon the attributes of detection equipment and weapon system. In this paper, as a part of a naval ship's survivability analysis, an assessment process model for the ship's susceptibility analysis technique is developed. Naval ship's survivability emphasizing the susceptibility is assessed by the probability of detection, and the probability of hit. Considering the radar cross section (RCS), the assessment procedure for the susceptibility is described. It's emphasizing the simplified calculation model based on the probability density function for probability of hit. Assuming the probability of hit given a both single-hit and multiple-hit, the susceptibility is accessed for a RCS and the hit probability for a rectangular target is applied for a given threat.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.2
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• pp.336-343
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• 2009

Because ships are very isolated and independent objects when sailing on the ocean, if a fire and smoke occurs, nobody can be sure to escape safely from ship at the moment. On the focus of the relationship between the sight transmissivity by fire smoke density and the life safety, this study performs simulations and experiments, respectively. To evaluate the theoretical evacuation time, CFAST software which is known as a 2 zone model analysis tool is used, and the result is 54 seconds from ECR(Engine Control Room) exit to upper deck exit and 34 seconds from bosun store to upper deck exit. And totally 12 types of experiments are performed with other 10 persons per experiment. As the result, it is cleared that the low sight transmissivity leads to the low life safety and the obstruction which can be happen unexpectedly on the evacuation way on fire makes it worse. At the condition of the smoke density 0%, over 90% people arrive at upper deck exit safely. But with the transmissivity of 8%, 70%(from ECR) and 30%(from bosun store) among experiment persons of each can survive, and with same density and unexpected obstruction, the survival ratio goes down to only 20% and 10%.

• Journal of Navigation and Port Research
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• v.32 no.2
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• pp.127-132
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• 2008

The safety degree of navigation for collision avoidance is closely related with the combination between mariner's behavior and navigational environment. The condition of navigational environment is mainly decided by navigable waters, ship traffic, rule of road, sea state, weather and so on. Especially, the condition of navigable waters and ship traffic in navigational environment are ones of the important factors to attain safe navigation when mariners are underway and crossing, head on or overtaking situation. Thus this paper is to analyze the characteristics of mariner's behavior for collision avoidance caused by ship traffic and navigable waters by analyzing the contents of questionnaire and the results of international collaborative research. As a result, it can be concluded that the density of ship traffic and the area of navigable waters affect mariner's ship handling for collision avoidance.