• Journal of Ocean Engineering and Technology
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• v.15 no.2
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• pp.22-32
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• 2001

The numerical investigation of obliquely incident wave interactions with fully submerged dual buoy/porous-membrane floating breakwaters placed in parallel with spacing is studied based on linear potential theory and Darcy's law. The numerical solutions are obtained by using a discrete-membrane dynamic model and second-kind modified Bessel function distribution over the entire boundaries of fluid regions. First, numerical solutions for an idealized dual submerged system without buoys are obtained. Second, a more practical dual submerged system with membrane tension provided by buoys at its tops is investigated by the multi-domain boundary element method particularly devised for dual buoy/porous-membrane problems with gaps. The velocity potentials of wave motion are coupled with porous-membrane deformation, and solved simultaneously since the boundary condition on porous-membrane is not known in advance. The effects of varying permeability on membranes and wave characteristics are discussed for the optimum design parameters of systems previously studied. The inclusion of permeability on membrane eliminates the resonances that aggravate the breakwater performance. The system is highly efficient when waves generated by the buoys and membranes were mutually canceled and its energy at resonance frequency dissipates through fine pores on membranes.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.10a
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• pp.411-413
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• 2012

다기능 경량 등부표는 바다와 강에 설치되어 선박 항로표시 및 수산, 양식 산업 시설물 경계표시 등 선박충돌사고 및 인명사고를 미연에 방지하기 위한 용도이며, 또한 수심이 낮은 해안과 암초지역은 물론 어떤 장소에서도 설치 및 운용이 용이하여 다양한 용도로 활용할 수 있도록 개발되었다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.26 no.6
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• pp.617-624
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• 2008

In general, RTK-GPS(Real Time Kinematic GPS) based on the single reference station is able to determinate the high accurate position of rover on the spot using error correction information of transmitted carrier phase from the base station via wireless modem. However, single reference station method has some weak points to decrease positioning accuracy because it must be obtained carrier phase from the each satellite continuously, allowed to transmit without obstacle and limited to short base line distance between base and rover station. This paper aims to attempt network based GPS carrier phase differential positioning using three multi reference stations to overcome the method of single reference station and RTK network is realized by real time monitoring program with Visual C++. The optimum error correction value of three multi reference stations by RTK networking is selected automatically to correct the position of rover station. In this paper, this algorithm is applied to determine sea water level using GPS buoy, and the accuracy results of water level change were analyzed and compared with each other using single and multi reference stations.

• Journal of Ocean Engineering and Technology
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• v.27 no.1
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• pp.85-92
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• 2013

This paper deals with the resonant type of a WEC (wave energy converter) and the determination method of its geometric parameters which were obtained to construct the robust and optimal structure, respectively. In detail, the optimization problem is formulated with the constraints composed of the response surfaces which stand for the resonance period(heave, pitch) and the meta center height of the buoy. Use of a signal-to-noise ratio calculated from normalized multi-objective results with the weight factor can help to select the robust design level. In order to get the sample data set, the motion responses of the power buoy were analyzed using the BEM (boundary element method)-based commercial code. Also, the optimization result is compared with a robust design for a feasibility study. Finally, the power efficiency of the WEC with the optimum design variables is estimated as the captured wave ratio resulting from absorbed power which mainly related to PTO (power take off) damping. It could be said that the resultant of the WEC design is the economical optimal design which satisfy the given constraints.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.37.1-37.1
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• 2011

A floating wind turbine dynamic simulation program, 'WindHydro', is newly developed. In order to investigate the characteristics of the program, a series of loading cases are simulated such as (1) wind only case, (2) free decay cases with initial displacement, (3) wave only case (4) wind and wave case. The simulations are carried out for the 5-MW OC3-Hywind model which has a spar buoy and catenary mooring lines. As a result, the reliability of WindHydro is verified in most viewpoints although additional study is still necessary to clear out some uncertainty of the program.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.85-89
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• 2004

The wave interactions with fully submerged and floating dual buoy/vertical porous membrane breakwaters has been investigated in experimentally to validate the developed theory and numerical method in the previous study, in which multi-domain hydro-elastic formulation was carried out in the context of linear wave-body interaction theory and Darcy's law. It is found that the experimental results agrees well with the numerical prediction. Transmission and reflection can be quite reduced simultaneously especially in the region of long waves. The properly tuned system to incoming waves can effectively dissipate wave energy and also offset each other between incident and scattered waves using its hydro-elasticity and geometry.

• Journal of applied mathematics & informatics
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• v.26 no.3_4
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• pp.519-530
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• 2008

This paper studies the multi-domain coupled system of one dimensional Arctic temperature field and establishes identification model about the thermodynamic parameters of sea ice (heat storage capacity, density and conductivity) by the so-called output least-square estimate according to the temperature data acquired by a monitor buoy installed in the Arctic ocean. By the optimal control theory, the existence and dependability of weak solution and the identifiability of identification model have been given. Moreover, necessary optimality condition is proposed. Furthermore, the optimal algorithm for the identification model is constructed. By using the optimal thermodynamic parameters of Arctic sea ice, the numerical simulation is implemented, and the numerical results of temperature distribution of Arctic sea ice are demonstrated.

• Korean Journal of Remote Sensing
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• v.33 no.3
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• pp.275-285
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• 2017

National Meteorological Satellite Center(NMSC) has produced Sea Surface Temperature (SST) using Communication, Ocean, and Meteorological Satellite(COMS) data since April 2011. In this study, we have developed a new regional COMS SST algorithm optimized within the North-West Pacific Ocean area based on the Multi-Channel SST(MCSST) method and made a composite SST using polar orbit satellites as well as the COMS data. In order to retrieve the optimized SST at Northwest Pacific, we carried out a colocation process of COMS and in-situ buoy data to make coefficients of the MCSST algorithm through the new cloud masking including contaminant pixels and quality control processes of buoy data. And then, we have estimated the composite SST through the optimal interpolation method developed by National Institute of Meteorological Science(NIMS). We used four satellites SST data including COMS, NOAA-18/19(National Oceanic and Atmospheric Administration-18/19), and GCOM-W1(Global Change Observation Mission-Water 1). As a result, the root mean square error ofthe composite SST for the period of July 2012 to June 2013 was $0.95^{\circ}C$ in comparison with in-situ buoy data.

• Journal of Ocean Engineering and Technology
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• v.25 no.1
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• pp.67-72
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• 2011

Offshore structures, such as a platform, a buoy, or a floating vessel, are exposed to several dynamic loads, and viscoelastic damping material is used to reduce the vibration of offshore structures. It is important to know the properties of viscoelastic materials because loss factor and Young's modulus of the viscoelastic damping material are dependent on frequency and temperature. In this study, an advanced technique for obtaining accurate loss factor and Young's modulus of the viscoelastic damping material is introduced based on a multi degree of freedom curve-fitting method and the RKU (Ross-Kerwin-Ungar) equations. The technique is based on a modified experimental procedure from ASTM E 756-04. Loss factor and Young's modulus of the viscoelastic damping material are measured for different temperatures by performing the test in a temperature-controlled vibration measurement room where temperature varies from 5 to 45 degrees Celsius.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2011.06a
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• pp.192-192
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• 2011

For the safety of vessels sailing Marine Transport Facility announces sea route, reefs or shallow water. Photovoltaic, independent power system, installation in the general Marine Transport Facilities to be used in the marine lantern. Due to install of communications, controls, power consumption inceases. And the weather of cloudy day or rainy, generation of electricity is decrease. Recently, power system of marine facility using a hybrid generation system, photovoltaic generation system and wave power generation system. But increase of adhered shellfish inside the water column, is the cause of the reduction of efficiency. So study was conducted to Single channel AFS(Anti-Fouling system). In this paper we offer the Multi channel AFS for Marine Transport Facility and have simulated. Improve the accuracy of the research, we using the result of anode, in the experiment were actually in the buoy, is based on simulation. The experimental results is shown every anode's, in the Marine Transport Facility, ionization was conducted identically.