• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.102-107
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• 2004

New designed floating breakwater made of Polyethelener with considering the introduction of new material for being harmony with environment and stability of the floater is developed for a marine ranching. Model experiment in order to test its capability is performed for the regular and irregular waves in ocean engineering basin. Good capability to break the incident wave within the 6 second of period and 1 m of height is shown. Breaking efficiency for long period wave is not so good in regular and irregular wave. The results of this study will contribute to the design and construction of the floating breakwater.

• Journal of Power Electronics
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• v.19 no.4
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• pp.934-943
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• 2019

A current balance problem exists in multi-phase LLC converters due to the resonant parameter tolerance. This paper presents a current balancing method for interleaved three-phase half bridge LLC converters. This method regulates the phase shift angle of the driving signals between the three phases based on a converter with a floating Y-connection. The floating midpoint voltage has different influences on each phase current and makes the three-phase current balance performance better than midpoint non-floating systems. Phase shift control between modules can further regulate the midpoint voltage. Then three phase current sharing is realized without adding extra components. The current distributions in a midpoint non-floating system and a midpoint floating system are compared. Then the principle and implementation of the proposed control strategy are analyzed in detail. A 3kW prototype is built to verify the validity and feasibility of the proposed method.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.514-514
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• 2017

Floating breakwaters were treated as solid bodies without any perforation in previous studies. In this study, however, a floating breakwater is perforated to allow the partial absorption of the energy produced by incident waves and an air chamber is placed in the upper part to control the breakwater draft. A series of laboratory experiments for a floating breakwater installed with a mooring system are carried out. In general, a mooring system can be classified by the number of mooring points, the shape of the mooring lines, and the degree of line tension. In this study, a four-point mooring is employed since it is relatively easier to analyze the measured results. Furthermore, both the tension-leg and the catenary mooring systems have been adopted to compare the performance of the system. In laboratory experiments, the hydraulic characteristics of a floating breakwater were obtained and analyzed in detail. Also, a hydraulic model test was carried out on variable changes by changing the mooring angle and thickness of perforated wall. A hydraulic model was designed to produce wave energy by generating a vortex with the existing reflection method. Analysis on wave changes was conducted and the flow field around the floating breakwater and draft area, which have elastic behavior, was collected using the PIV system. From the test results the strong vortex was identified in the draft area of the perforated both-sides-type floating breakwater. Also, the wave control performance of the floating breakwater was improved due to the vortex produced as the tension in the mooring line decreased.

• Journal of the Korean Solar Energy Society
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• v.37 no.1
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• pp.1-14
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• 2017

A series of coupled time domain simulations considering stochastic waves and wind based on five 1-h time-domain analyses are performed in normal operating conditions. Power performance and tower base Fore-Aft bending moment and pitching motion response of the floating spar-buoy wind turbine with 2 MW direct-drive PMSG have been analyzed by using HAWC2 that account for aero-hydro-servo-elastic time domain simulations. When the floating spar-buoy wind turbine is tilted in the wind direction, maximum of platform pitching motion is close to $4^{\circ}$. Statistical characteristics of tower base Fore-Aft bending moment of floating spar-buoy wind turbine are compared to that of land-based wind turbine. Maximum of tower base Fore-Aft bending moment of floating spar-buoy wind turbine and land-based wind is 94,448 kNm, 40,560 kNm respectively. This results is due to changes in blade pitch angle resulting from relative motion between wave and movement of the floating spar-buoy wind turbine.

• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.240-244
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• 2009

In this paper, we present FloatingPad, a touch pad based device with better scrolling feature and more interaction styles than a traditional touch pad. When we interact with a real object like a picture or a book, we manipulate on the object, and we also move, rotate, and flip the object. We applied this idea into a touch pad. In FloatingPad, the touch pad is not fixed to the device. It is floating on the device; it can be slid on the device. Therefore a user can have additional degree of freedom of input by shifting and rotating the touch pad while having the traditional touch pad input. By using this technique, the interactivity of the touch pad can be augmented, and better scrolling feature can be provided by reducing clutching occurs on the position scrolling devices by using the movement of the touch pad as rate control. We implemented the prototype device and conducted a user study with three applications developed for FloatingPad.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.285-293
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• 2019

In the present paper, model tests of suppressing sloshing fitted with two perforated floating plates are carried out. The study involves identification of system performance such as the suppression and the solidity ratio. Three different solidity ratios of perforated plates have been tried out as potential positive slosh damping devices. A series of painstaking experiments have been conducted in a rigid rectangular tank on six degrees of freedom motion platform under roll harmonic excitation. Comparison of the clean tank shows that the three types of perforated plates are all effective on damping the run-up and impact pressure along the bulkhead. The parametric study indicates that the perforated plate with the median solidity ratio is the most optimal one in suppressing sloshing among three configurations.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.50-53
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• 2005

An analysis on the viewing parameters of floating display system based on integral imaging is introduced. A floating display system based on integral imaging is a three-dimensional display system which can display three-dimensional moving pictures with impressive feeling of depth. The analysis given in this paper will optimize the design of the floating display system for the specific application.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.191-197
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• 2002

The motion of a floating OWC chamber in waves is studied taking account of fluctuating.air pressure in the air chamber. An atmospheric pressure drop occurs across the upper opening of the chamber which causes not only hydrodynamic but also pneumatic added mass and damping forces to the floating chamber. A velocity potential in the water due to the free surface oscillating pressure patch is added to the conventional radiation-diffraction potential problem. The potential problem inside the chamber is formulated by making use of the Green integral equation associated with the Rankine Green function while the outer problem with the Kelvin Green function. The two integral equations are solved simultaneously by making use of a matching boundary condition at the lower opening of the chamber to the outer water region. The chamber motion in the frequency domain is calculated for various values of parameters related to the atmospheric pressure drop. The present methods can also be used for the analysis of air-cushion vehicle motion as well as for the design oj a floating owe wave energy absorber.

• Journal of Advanced Research in Ocean Engineering
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• v.1 no.1
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• pp.55-62
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• 2015

Floating structure such as tension leg platform, semi-submersible and spar are widely used in field of oil exploration and renewable energy system. All of these structures have the base cylinder support structure which have effective rule in overall dynamic of response. So the accurate and reliable modeling is needed for optimum design and understanding the physical background of these systems. The aim of this article is an analytical discussion on stochastic modeling of floating cylinder based support structure but an applicable one. Due to this a mathematical mass-damper-spring system of a floating cylinder of HAWAII WTG offshore wind as an applicable and innovative system is adopted to model a coupled degrees using random vibration in analytical way. A fully develop spectrum is adopted to solve the stochastic spectrum analytically by a proper approximation. Some acceptable assumption is adopted. The simplified but analytical and innovative hydrodynamic analysis of this study not only will help researcher to concentrate more physically on hydrodynamic analysis of floating structures but also can be useful for any quick, simplified and closed form analysis of a complicated problem in offshore engineering.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.6
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• pp.175-183
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• 2010

In this study, laboratory experiments are conducted to investigate flow-fields around floating breakwaters by using the LDV(Laser Doppler Velocimetry) system. The LDV system is a well-known equipment to measure fluid particle velocities in laboratory experiments. Although the system requires great efforts and enormous time for measurements, it can provide precise velocity fields comparing to other available equipments. Various types of drafts and shapes for breakwaters are employed in laboratory experiments to analyze a relation between flow-fields and vorticity. A series of numerical experiments are also carried out by using a two-dimensional Navier-Stokes equations model. Numerically predicted results are compared with laboratory measurements.