• Journal of Ocean Engineering and Technology
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• v.20 no.1 s.68
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• pp.63-68
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• 2006

Recently, it has been widely recognized that coastal vegetations may have great value in supporting fisheries, protecting from wave attack, stabilizing the sea bed and maintaining good scenery. Hydrodynamic factors play a major role in the functions of water quality and ecosystems. However, the studies on physical and numerical process of wave propagation are few and far behind compared to those on the hydrodynamic roles of coastal vegetations. In general, Vegetation flourishing along the coastal areas attenuates the incident waves, through momentum exchange between stagnated water mass in the vegetated area and rapid mass in the un-vegetated area. This study develops a numerical model for describing the wave attenuation rate in the complex topography with the vegetation area. Based on the numerical results, the physical properties of the wave attenuation are examined under various wave, geometric and vegetation conditions. Through the comparisons of these results, the effects of the vegetation properties, wave properties and model parameters such ac the momentum exchange coefficient have been clarified.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.5
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• pp.366-371
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• 2012

High swell has been known for the one of the main causes of beach erosion in the east coast of Korea. In this study, coastal topography changes due to high swells are simulated to find its effect on the backshore by using movable bed experiments and numerical experiments. Sea bottom topographical changes due to various incident waves were investigated using CSHORE model in the numerical experiments. Furthermore, the mechanism and the phenomena of beach erosion due to waves and high swells on the foreshore and backshore were analyzed and compared with movable bed hydraulic experiments.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.2
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• pp.188-195
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• 2010

Green water load is an important parameter to be considered in designing a modern ship or offshore structures like FPSO and FSRU. In this research, a numerical simulation method for green water phenomenon is introduced. The Navier-Stokes equations and the continuity equation are used as governing equations. The equations are calculated using Finite Difference Method(FDM) in rectangular staggered grid system. To increase the numerical accuracy near the body, the Cartesian cut cell method is employed. The nonlinear free-surface during green water incident is defined by Marker-density method. The green waters on a box in regular waves are simulated. The simulation results are compared with other experimental and computational results for verification. To check the applicability to moving ship, the green water of the ship which is towed by uniform force in regular wave, is simulated. The ship is set free to heave and to surge.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.2
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• pp.149-154
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• 2011

It is very important for ability to be treated to protect and secure the loss of life and property in emergency situation at sea. 80% of maritime casualty are incurred by human factors rather than a mechanical reason, which means that most maritime incident does not come from only one factor by mistake, but multiple potential factors causing a fault and error. Therefore, after research of the leadership effect to the ship, decision making process and behavior characteristics occurred in emergency situation, this paper presents settlement scheme and strategy in order to reduce human error in the ship.

• Journal of Advanced Navigation Technology
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• v.12 no.6
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• pp.611-618
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• 2008

The development of information society together with information telecommunication's influence on the human society is a ripple effect and getting wider. Among those ripple effects the disaster prevention is in the public eye in the present day. On the way to the ubiquitous society the main techniques to be concerned in ubiquitous sensor networks are the field of damage of storm and flood, safety facilities, traffic safety, industrial safety, energy safety, fire fighting, specific safety of radioactivity escape incident, environmental pollution, sea pollution, mountain and forrest disaster so on. In this paper the USN technique based on the disaster prevention communication technology service and its requirement technology and application are studied.

• The Journal of the Acoustical Society of Korea
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• v.29 no.1
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• pp.10-17
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• 2010

In a passive sonar, the improvement of detection performance by using noise cancellation is usually a important problem. In this paper, we have analyzed the own-ship noise cancellation in the two operation modes which are used in the HMS system. In the operator mode, an adaptive line enhancer(ALE) is applied to improve the tonal detection by using broadband noise cancellation and the normalized least mean square(NLMS) algorithm is applied to the design of an adaptive filter. The reference input that is correlated with a primary input can be used to remove the noise incident on the observation directionin the automatic mode. Computer simulations with real sea that data show that the proposed adaptive noise canceller has good performance in passive detection under HMS operation.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.4
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• pp.412-418
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• 2014

In this paper, for better boarding performance and pleasant boarding sensitivity of the ship, comparison and analysis was performed of motion sickness questionnaire with MSI(Motion Sickness Incidence) calculation based on ship motion theory(Strip Method) due to sea condition, incident angle in main sail way, economic speed, and calculation position of the training ship Kaya of Pukyong National University. On theses works, the rougher sea conditions became, the higher total motion sickness rate was occurred. The weights of vertical acceleration and the rates of MSI were higher at the bridge and the accommodation, which were located farther from the center of gravity of the ship. And effects of the vertical acceleration of the ship were increased in rolling then in head sea. In comparison between motion sickness questionnaire with MSI calculation, when the vertical acceleration increased, the motion sickness rate increased. The location to increase vertical acceleration and the location to cause motion sickness were agreed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.4B
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• pp.243-251
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• 2012

To investigate the characteristics of rip current occurring at Haeundae beach, observations obtained from a buoy and a CCTV were analyzed and numerical experiments were conducted. During observed rip-current events, the CCTV images showed that a couple of wave-trains, which are close to regular waves with slightly different directions, propagated to the beach, and wavelet analyses of data from the buoy showed very narrow-banded spectra with a peak frequency. From the evidences, it was inferred that a known mechanism of generating rip current due to the nodal line area of honeycomb-patterned wave crest was one of the significant factors of rip current occurrences of Haeundae beach. The mechanism has been explained by the following: When two wave-trains with slightly different directions propagate to a beach, wave crests of the incident wave-trains form honeycomb pattern due to nonlinear interaction. The nodal lines of honeycomb pattern are developed in the cross-shore direction. And longshore currents flow toward the nodal line area which has very low wave energy. Consequently their mass flux is expelled through the area toward the sea direction. To confirm the generation, numerical experiments were performed using a nonlinear Boussinesq equation model. In the cases with two incident wave-trains with slightly different directions and with a monochromatic wave propagating over a submerged shoal, it was seen that the honeycomb pattern of wave crests was well developed, and thus rip currents were evolved along the nodal lines.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.1
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• pp.61-65
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• 2012

Once oil has spilled, oil spill responders use a variety of countermeasures to reduce the adverse effects of spilled oil on the environment. Mechanical methods of containment and recovery are preferred as the first response when the use of other methods fail or are ineffective. In these cases, the application of oil dispersants shall be use only as a last resort. While effectiveness of dispersants in removing oil form the sea surface is proven, the use of dispersants is controlled in almost all countries due to the toxicity of their active agents and the dispersed oil on the marine environment. However, according to reports, after dispersant application, no significant toxicity to fish or shrimp was observed in the field-collected samples. Moreover, the results also indicate that dispersant-oil mixtures are generally no more toxic to the aquatic test species than oil alone. During the Deepwater Horizon Incident, dispersants were applied to floating oil and injected into the oil plume at depth. These decisions were carefully considered by state and federal agencies, as well as BP, to prevent as much oil as possible from reaching sensitive shoreline habitats. Net Environmental Benefit Analysis for dispersant use assumed that dispersants appear to prevent long-term contamination resulting absence of oil in the substrate and will benefit marine wildlife by decreasing the risk of significant contamination to feathers or fur. Further study to use dispersants with scientific baseline is needed for our maritime environment which consistently threaten huge oil spill incidents occurrence.

• Journal of the Korean Magnetics Society
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• v.21 no.3
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• pp.116-119
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• 2011

A Chinese shipping boat collided with two Japanese coast guard boats in waters near the disputed Senkaku islands (known as Diaoyudao in China) in the East China Sea on September 7th last year. The boat was held and captain was arrested by Japanese Government. The incident soon turned into a big political and economic conflict between the two countries. Japan's intention was to show her tight control over Senkaku, whereas China's intention was to make it a disputed territory in the eyes of international politics. While the conflict was going on, a top-rank bilateral talk between the two countries was suspended, boycott of Japanese goods was suggested, numerous rallies were held in both countries. This situation lasted for several months until China used an extreme card of "Cutting Supply of Rare Earth to Japan". Under this pressure, Japan instantly released the captain and closed the case. Over this incident, public noticed the importance of rare earth and its impact on the global economy. Since then, the policy of Chinese Government for the rare earth has created more confusion and turmoil in the global market. The purpose of this article is to overview the price rally and future of the rare earth.