• Journal of Ocean Engineering and Technology
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• v.33 no.6
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• pp.648-656
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• 2019

The ecological changes in the ocean due to the drastic global warming require that action be taken to sustain the productivity of fisheries. Proper ocean facilities could help prevent the loss of the expenditures made on marine aquaculture and reduce the related compensation for various ocean conditions. The aim of this study was to develop a floating ocean wave-breaker using an eco-friendly concrete and conducting a site survey, a structural analysis, and a test of towing the tank. As a result, the wave at the fish farm would be reduced. The results of the holding power of anchors and the capability of moving the floating structures were considered in the design of the wave-breaker. The analyses of the material properties of concrete and the steel structures, as well as the CAPEX and OPEX analyses of the manufacturing and operation processes confirmed the superiority of the floating concrete wave-breaker. In particular, this study demonstrated that the concrete floating breakwater can protect the fish farm against typhoons and reverse-waves, thereby reducing losses of the fish.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.6
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• pp.876-880
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• 2013

The major causes of electrical fire are classified to short circuit fault, overload fault, electric leakage and electric contact failure. The principal factor of the fire is electric arc or spark accompanied with such electric faults. Earth Leakage Circuit Breaker (ELB) and Molded_case Circuit Breaker (MCCB), that is, Residual Current Protective Devices (RCDs) used on low voltage distribution lines cut off earth leakage and overload, but the RCD can not cut off electric arc or spark to be a major factor of electrical fire. As the RCDs which are applied in low voltage distribution panel are prescribed to rated breaking time about 30[ms] (KS C 4613), the RCDs can't perceive to the periodic electric arc or spark of more short wavelength level. To improve such problems, this paper studies on an arc fault circuit interrupter (AFCI) using the distorted voltage wave in electric arc faults. The proposed voltage sensing type AFCI is an electrical fire prevention apparatus of new conception that operates a circuit breaker with sensing the instantaneous voltage drop of line voltage at electrical faults occurrence. The proposed AFCI is composed of control circuit topology using some semiconductor switching devices. Some experimental tests of the proposed AFCI confirm practicality and the validity of the analytical results.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.523-528
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• 2001

There are many difficult problems in analyzing the flow characteristics in a high voltage circuit breaker such as shock wave and complex geometries, which may be either static or in relative motion. Although a variety of mesh generation techniques are now available, the generation of meshes around complicated, multicomponent geometries like a gas circuit breaker is still a tedious and difficult task for the computational fluid dynamics. This paper presents the computational method for analyzing the compressible flow fields in a high voltage gas circuit breaker using the Cartesian cut-cell method based on the CFD-CAD integration, which can achieve the accurate representation of the geometry designed by a CAD tools. The technique is frequently satisfied, and it will be almost universally so in the future, as the CFD-CAD traffic increases.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.3
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• pp.22-27
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• 2004

Waveheight attenuation efficiencies of floating breakwaters in water of finite depth for a VLFS are studied numerically in accordance with the two body radiation-diffraction problem. Four different forms of the breaker are tested with a solid VLFS. The radiation-diffraction wave elevations between the breakwater and the VLFS are predicted directly instead of the far-field transmission-reflection coefficients of the breakwater.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.1
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• pp.18-23
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• 1991

Recently SLAMECKA suggested the mathematical dynamic arc model of the SF6 gas circuit breaker [1]. The author applied the above dynamic arc model to the E.H.V. transmission line and investigated the interrupting capability of the SF6 gas circuit breaker. In particular the Runge-Kutta-England numerical method suitable for the use in systems that involve nonlinear dynamic arc and traveling wave was used by converting the current source into the voltage source in the DOMMEL's method [2]. The successful computer resultls were obtained and it was found that the arc time constant and the second derivative of the arc conductance are closely related to the interrupting capability of the SF6 gas circuit breaker.

• The KSFM Journal of Fluid Machinery
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• v.12 no.5
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• pp.19-24
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• 2009

This paper is performed to find out the stability of water-hammer in pipe line and pump station that is happened when additional water needs demanded. At first, the water supply construction project is planned to supply $6,000\;m^3/day$ through 17.9 km pipe line. But additional demand ($1,200\;m^3/day$) happened from Cheong-ra water reservoir. In this situation, air-chamber($4\;m^3$) and vacuum breaker valve(${\varphi}100\;mm$) are needed to prevent water-hammer. When the additional water is supplied, the existing facilities (air-chamber, vacuum breaker valve) are sufficient to alleviate shock not changing capacity alteration, judging from the airspace change and rise. Therefore, there is no problem for water-hammer by installing air-chamber($4\;m^3$) and vacuum breaker valve(${\varphi}100\;mm$) at the top of Yeo-ju hill.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.11
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• pp.519-526
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• 2005

This paper presents computer simulation results for developing new type of SF$_{6}$ Circuit Breaker in terms of cold gas flow after small current interruption. This cold gas flows down a nozzle into the chamber of a circuit breaker. There are many difficult problems in analyzing the gas flow due to complex geometry, moving boundary, shock wave and so on. When predicting the dielectric capability of a gas circuit breaker after interruption, the gas pressure and density distributions due to the cold gas must be considered in addition to the electrical field imposed across the gas. A self-coded computational fluid dynamics (CFD) program is used for the simulation of cold gas flow in order to evaluate the electrical field characteristic across open contacts and transient characteristics of insulations after small current interruption.

• Journal of the Korean Society of Visualization
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• v.9 no.3
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• pp.51-58
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• 2011

The purpose of the study is to provide a foundation in predicting a maximum wave force when the ocean structure is laid out under breaking wave. Experiments were conducted with a down-scaled cylindrical model installed in a wave generating water channel. Maximum wave slopes were changed in regular wave condition by the wave breaker in the water channel. Cylinder's diameters were changed to 0.1m and 0.05m, respectively. Using the PIV results qualitative analyses were performed based upon the previous knowledge.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.2
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• pp.65-71
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• 1991

Many investigations of wave deformation without currents have been carried out experimentally and theoretically but, studies treating the effect of longshore current on the wave deformation are few. It is thus necessary to evaluate the effect of longshore current on the wave deformation after breaking. In the paper the wave height attenuation. the wave direction and the variation of mean water level are calculated in which effects of longshore current are involved. To assess the effect of longshore current on the wave deformation, factors above with longshore current are compared with them without longshore current by using calculated results.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.1
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• pp.66-72
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• 2007

In order to control waves in coastal zones effectively, multi-cylinder piles as the economical structures are suggested. A three dimensional hydraulic model experiment was performed to investigate the hydraulic characteristics of the structure. An experimental study was carried out research the effect of wave control and harbor tranquility through the wave height analysis for the existing concrete wave breaker and the structure with acrylic multi-cylinder piles type at the same location. In the results, the effective order of harbor tranquility is shown as the wave breaker > the staggered arrangement of multi-cylinder piles > the regular arrangement of multi-cylinder piles.