• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.260-265
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• 2004

The materials of ship screw propeller are commonly the manganese bronze. The seawater corrosion and cavitation of the screw propeller reduce tire propulsive performance of ship. In screw manufactory, tire corrosion rust of tire screw propeller is removed by a hand grinding. The grinding work makes the dust of the heavy metals from the manganese bronze. The dust makes indoor working environment poor. A friendly-environmental and automatic corrosion removing apparatus was developed for the improvement of screw processing and working environment. The corrosion rust of a screw propeller was remarkably removed by using apparatus. And the screw surface roughness was improved by a blasting effect of the apparatus performance test. Anode polarization curves on jour processing conditions, that is to say, grinding, blasting, wire-brushing, fine sand papering, were confirmed by a potentiostat. Especially, two kinds of medias, alumina and emery, were used in the blasting processing. Then, investigated tire cavitation erosion of specimen. This result proved that tire blasting work has considerably improved the corrosion resistance of a screw propeller.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.1115-1118
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• 2015

Two wheel type electric vehicles driving with the electric motors for guard are used increasingly at the airport and harbor place to move between narrow indoors. This type two wheel electric vehicles are powerd by batteries and using the steering control apparatus including multi sensors and handle operating device for forward and backward, rotating moving. At this research, we design sensor interfacing electronic control system use only the center of foot balance without the handle type steering apparatus. This design is for safety of drivers at one's cornering.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.12
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• pp.1953-1958
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• 2012

The major causes of electrical fire are classified to short circuit fault, overload fault, electric leakage and electric contact failure. The occurrence factor of the fire is electric arc or spark accompanied with such electric faults, specially short circuit 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 30ms(KS C 4613), the RCDs can't perceive to the periodic electric arc or spark of more short wavelength level. To improve such problem, this paper proposes a prevention apparatus using the line voltage drop of neutral wire and some semiconductor switching devices. Some experimental tests of the proposed apparatus confirm the validity of the analytical results.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.1
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• pp.43-48
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• 2001

In conventional wind generation systems, since the blade rotates at low speed when the velocity of wind decreases their operations are possible only under limited conditions. Therefore they are in trouble of self-generation without the help of auxiliary generation devices outside. In addition, most of them have very low usage efficiency because of the characteristic changes of wind. For the solution of these problems and for enough generation regardless of districts and geographical features the rotation energy stored in a spring drives a compact generator and then electric power is stored at battery and supplied to the load continuously according to the lack of wind force. In this paper, the fabricated system consisting of a wind generator and power storage apparatus was introduced and its operation characteristics were analyzed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.1
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• pp.56-61
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• 1996

A hot wall epitaxy (HWE) apparatus with double source tubes was manufactured. This apparatus can be used to grow two kinds of epilayers at the same time or to grow heterostructures and multilayers. Undoped ZnSe single crystal films were grown on GaAs(100) substrates byusing this apparatus. SEM, XRD and PL analyses indicated that epilayers had good crystalline and optical quality. The epilayers grown at the source temperature 660 .deg. C and the substrates temperature $350^{\circ}C$. in $2 {\times} 10^{-6}$ toor were mirror like and good quality. PL measurements show that the crystalline qualityis comparable with that of the ZnSe/GaAs epilayer grown by molecular beam epitaxy.

• Korean Journal of Materials Research
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• v.24 no.7
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• pp.344-350
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• 2014

Metal films (i.e., Ti, Al and SUH310S) were prepared in a magnetron sputtering apparatus, and their cross-sectional structures were investigated using scanning electron microscopy. The apparatus used consisted of a cylindrical metal target which was electrically grounded, and two anode rings attached to the top and to the bottom of the target. A wire was placed along the center-line of the cylindrical target to provide a substrate. When the electrical potential of the substrate was varied, the metal-film formation rate depended on both the discharge voltage and the electrical potential of the substrate. As we made the magnetic field stronger, the plasma which appeared near the target collected on the plasma wall surface and thereby decreased the bias current. The bias current on the conducting wire was different from that for cation collection. The bias current decreased because the collection of cations decreased when we increased the magnetic-coil current. When the substrate was electrically isolated, the films deposited showed a slightly coarse columnar structure with thin voids between adjacent columns. In contrast, in the case of the grounded substrate, the deposited film did not show any clear columns but instead, showed a densely-packed granular structure. No peeling region was observed between the film and substrate, indicating good adhesion.

• Journal of the Korean Geotechnical Society
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• v.19 no.2
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• pp.147-157
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• 2003

The characteristics of a rock joint which influence the stability of rock mass structures such as cut slopes and tunnels are largely controlled by the conditions of the rock joint as well as its boundary conditions. The conditions of rock joints comprise asperity strength, roughness, and filling materials. Boundary conditions can be represented by assuming that the deformability(or stiffness) of the rock mass surrounding the joints is modelled by a spring with stiffness. A new direct shear apparatus was developed in this study, which adapts a servo control system using PID algorithm. This apparatus can be used to investigate the various aspects of shear characteristics of the rock joints at conditions of constant normal stress and constant normal stiffness and so on. The test results for saw-cut teeth joints show that shear strength should be evaluated by considering its specific boundary conditions far the design of tunnels and cut slopes.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1620-1622
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• 2003

Recently, as the technology for the development of high voltage power apparatus using SF6 gas has made remarkable progress, it became possible to develop more compact power apparatus adopting single body substation system. In these gas insulated power apparatus, it is impossible to achieve perfect and safe insulation using only SF6 gas, because some solid insulation parts should be installed to support current-carrying conductor parts for electrical and mechanical safety. When spacers were installed in SF6 gas insulation system, they were exposed to severe electrical intensification which could reduce system insulation performance and restrict the rated operating voltage So, it is necessary to clarify the dielectric characteristics of spacers by analytically and experimentally, in order to design and develop more compact and optimum gas insulated systems. In this paper, the field distribution of three-phase spacers were investigated using three dimensional electrostatic field analysis tool adopting BEM method. And the obtained results were compared to the conventional two dimensional computations. According to these three dimensional calculations, it was possible to find out weak points in the spacer more clearly and these results could be applied to design more compact and optimum three phase spacer developments.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.6
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• pp.527-536
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• 2009

A cascade apparatus was designed with only one blade. Its passage is a 160% width of the cascade pitch. This kind of apparatus can give more accurate experimental result than those applying multi-blades even though the apparatus is small. However, this causes difficulties to make the periodic condition along the pitchwise direction. In this study, sidewalls were designed to satisfy the periodic condition based on the flow structure using a gradient based optimization and a genetic algorism. The objective function was adopted the surface Mach number obtained on the cascade and fourteen design variables were selected for controlling sidewall shapes. The designed sidewalls using the genetic algorism shows better result.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.05a
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• pp.458-461
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• 2009

In 3-phase 4 wire system, appearance of the $3^{rd}$ harmonic current by increasing non-liner load is the one of causes overheating neutral wire of power line, and apparatus. So it is necessary to protect power-factor decreasing by the $3^{rd}$ harmonic, and electric power apparatus, and line safely, in this study, power system accidents caused by the $3^{rd}$ harmonic were investigated, then harmonic components analysis and unbalanced load analysis got accomplished. As result, we proposed the method to protect the power line and apparatus from over-current of neutral line by using the most economic 4-pole low voltage circuit breaker.