• Journal of Advanced Marine Engineering and Technology
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• v.27 no.3
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• pp.447-452
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• 2003

Crevice corrosion is localized form of corrosion usually associated with a stagnant solution on the micro-environmental level. Such stagnant micro environments tend to occur in crevices (shielded areas) such as those formed under gaskets washers insulation material. fastener heads. surface deposits. disbonded coatings. threads. lap joints and clamps. Crevice corrosion is initiated by changes in located electrochemical reaction within the crevice such as a) depletion of inhibitor in the crevice b) depletion of oxygen in the crevice c) a shift to acid conditions in the crevice and d) build-up of aggressive ion species (e.g chloride) in the crevice. In this study. the mechanism of crevice corrosion for Type 430 stainless steel is investigated undercondition that the size of specimen is $15{\times}20\{times}3mm$, in 1N $H_2SO_4$ + 0.05N NaCl solution. and the artificial crevice gap size of 3 x 0.2 x 15 mm. Crevice corrosion is measured under applied potential -300mV(SCE) to the external surface. The obtained result of this study showed that 1) the induced time for initiation of crevice is 750 seconds. 2) potential of the crevice was about from -320mV to -399mV. which is lower than that of external surface potential of -300mV It is considered that potential drop in the crevice is one of mechanisms for the crevice corrosion

• Journal of the Korean Institute of Educational Facilities
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• v.18 no.2
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• pp.3-14
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• 2011

This study aims to identify differences and lessons in eco-school planning techniques and sustainable design methods by analyzing comparatively green building certification system and the cases of sustainable schools in US, Korea and Japan. As a result of the comparative analysis, green building certification system for school facilities, both domestic and international, is categorized into external environment, energy, materials and resources, and indoor environment. From the case study, it is common that roof garden and biotopes are installed for external environment, while energy saving, passive energy utilization methods for natural lighting and ventilation such as arrangement planning, courtyard, top-light, shading devices, solar panel and insulation by roof garden are most frequently used. Also, storm water uses, water saving equipment and sustainable materials are often introduced for resource savings. Concerns for indoor environment is frequently addressed by introducing natural light and ventilation in the buildings, which makes ultimately a comfortable space.

• 전기의세계
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• v.25 no.1
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• pp.95-100
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• 1976

The main purpose of this paper is to study on the transient current due to the change of environmental temperature under no external field in the arrangement of M$_{1}$(metal)-P(polyver)-M$_{2}$(metal). The specimer of polymeric insulator sandwiched by two metal electrodes composes a parallel-plate condenser represented by Maxwell-model. The behaviors of short circuit current flowing in M-P-M arrangement are very complex and the analysis of its conduction mechanism appears to be much complicated. In this paper we can suggest that a contact potential difference as an energetic state exists in the thin film specimen both sides of which are contacted by two different metals having different cook functions. Futhermore the contact potential difference appears to be constant through the course of temperature change, however, the dielectric constant and caparitance of the specimen must be temperature dependent. Accordingly the charge difference induced on both sides of electrodes may be a cause for the shory circuited transient current flowing through the external circuit. It is also suggestive that the results of the observation must be considered in cases of insulation design of electrical machines and D.C. cable for high voltage use.

• Progress in Superconductivity and Cryogenics
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• v.21 no.4
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• pp.48-52
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• 2019

Recently, many studies have been reported on the magnetoresistance and Hall effect of REBCO thin films and bulk. The voltage interferes quench detection of high-temperature superconducting magnet and generates leakage current in no insulation high-temperature superconducting coil. Therefore, in this paper, experiments on magnetoresistance and Hall effect of commercial YBCO and GdBCO tapes have been carried out. As a result, anomalous voltages expected for the magnetoresistance and Hall effect of REBCO tapes were observed and analyzed. In addition, the voltage characteristics of REBCO have been identified, and the Hall coefficient are calculated for use in high magnetic field magnet applications.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.3
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• pp.208-214
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• 2011

In this thesis, the partial discharge according to applied voltage and variations of cross-sectional area and length of the conductor related to general condition for using cable was measured in order to study degradation diagnosis for 2-Core cable of the PVC insulator used in industrial fields for other safety installations. Also the thermal degradation conditions under various installation circumstances of cables were studied by assuming degradation conditions with each different degradation rate (50%, 67%, 100%) such as variation in degradated temperature, thermal exposure time, normal state, partially degradated state and overall degradated state for thermal degradation diagnosis. The quantity of electric discharge (V-Q) according to applied voltage was measured for measurement of inception voltage and extinction voltage. The quantity of electric discharge and the number of electric discharge (Q-N) were measured with applied voltage kept constantly. In addition, pictures were taken using SEM (scanning electron microscope) to compare the surface of external insulator to degradated state of internal insulator according to thermal degradation temperature and also compare the surface of external insulator to degradated surface state of internal insulator according exposure time of cables to thermal stress.

• Journal of Industrial Technology
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• v.43 no.1
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• pp.15-23
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• 2023

Lithium-ion batteries are predominantly employed in electric vehicles and energy storage devices, offering the advantage of high energy density. However, they are susceptible to efficiency degradation when operated at high temperatures due to their sensitivity to the external environment. In this study, we conducted experiments using an indirect cooling method to prevent thermal runaway and explosions in lithium-ion batteries. The results were validated by comparing them with heat transfer simulations conducted through a commercial finite element analysis program. The experiments included single-cell exothermic tests and cooling experiments on a battery pack with 10 cells connected in series, utilizing 21700 lithium-ion batteries. To block external temperature influences, the experimental environment featured an extrusion method insulation in the environmental chamber. The cooling system, suitable for indirect cooling, was constructed with copper tubes and pins. The heat transfer analysis began by presenting a single-cell heating model using commercial software, which was then employed to analyze the heating and cooling of the battery pack.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.2130-2131
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• 2011

Electric fire breaks out by various causes such as electric short, overload(over current), leakage current, poor contact, static electricity, insulation deterioration, partial disconnection and etc. In this paper, we studied analysis technique for scientific and systematic judgment for distinction of electricity fire existence and nonexistence, and described about electricity fire cause analysis process for collecting physical evidences. We handled external form analysis, Substance extension analysis, X-ray transmission analysis, cross-section analysis, thermal analysis, chemical structure analysis, surface structure analysis, component analysis, electrical properties analysis, and circuit analysis by analysis technique for electricity fire cause judgment. We expect that analysis technic elevation and correct cause of fire analysis of scene of a fire investigators and analysts through this paper which see help.

• Proceedings of the KIEE Conference
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• 2008.10a
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• pp.103-104
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• 2008

this paper describes the electric field distribution analysis along a shield gap inner vacuum interrupter(VI). The equipotential line and electric field and field vector in a VI are analysed by a finite element method and experiment at shield gap. in result, The equipotential line and electric field distribution was affected to VI shield gap. The reason is as it gets distortion of equipotential line done. finally, this paper recognized whether or not affected, and proposed gap with the most suitable shield length and an external insulation.

• Proceedings of the KIEE Conference
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• 2008.05a
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• pp.143-144
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• 2008

this paper describes the electric field distribution interpretation along a shield form inner vacuum interrupter(VI). The equipotential line and electric field in a VI are analysed by a finite element method at various shield form. in result, The electric potentials of end shield form was increased or decreased because it was various the length of shield and between external insulation and source area or fix._end shield. finally shield is how to electric field affect, and advance, and will achieve the optimum design of VI inside shield.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1135-1138
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• 2003

ERFs(Electrorheological Fluids) arc a complex system consisting of polarizable particles and insulation liquid. When an external electric field is applied to ERFs, its apparent viscosity increases dramatically. This phenomenon is called the ER effect. Generally, the behavior of ERFs has been modeled on those of Bingham fluids. But the behavior of ERFs differs from those of Bingham fluids in many respects. In the paper, ER effect concerning flow mode of ERFs is analyzed experimentally. According to several flow conditions, the change of ER effect is presented and visualized. A new modeling methodology of ER effect to reduce the modeling error is presented.