• Journal of Advanced Marine Engineering and Technology
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• v.33 no.3
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• pp.387-394
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• 2009

It has been observed that coated steel structures are rapidly deteriorated than designed lifetime due to acid rain caused by air pollution etc.. Therefore improvement of corrosion resistance of anti-corrosive paint is very important in terms of safety and economic point of view. In this study corrosion resistance for five kinds of anti-corrosive paints including acryl, fluorine and epoxy resin series were investigated with electrochemical methods such as corrosion potential, polarization curves, impedance and cyclic voltammogram measurements etc.. There were somewhat good relationships between values measured by electrochemical methods such as corrosion current density obtained by cathodic and anodic polarization curves, value of impedance estimated with AC impedance, and polarization resistance on the cyclic voltammogram, for example, corrosion current density was decreased with increasing of values of impedance and polarization resistance on the cyclic voltammogram. However their relationships between corrosion current density and corrosion potential were not well coincided each other. Consequently it is considered that although a corrosion potential of F101 of fuoric resin series shifted to negative direction than other anti-corrosive paints, its corrosion resistance, indicating on the cathodic and anodic polarization curves, AC impedance curves and cyclic voltammogram, was the most superior to other paints, whereas A100 containing arcylic resin showed a relatively poor corrosion resistance compared to other paints.

• Journal of Ocean Engineering and Technology
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• v.22 no.5
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• pp.106-111
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• 2008

In this paper, study about property evaluation for the metal matrix composites fabricated by low pressure infiltration process. Aluminum alloy composite which is reinforced by Metal fiber preform was fabricated by low pressure casting process. Infiltration condition was changed the pressure infiltration time of 1 sec, 2 sec and 5 sec under a constant pressure of 0.4 MPa. The molten alloy completely infiltrated the FeCrSi metal perform regardless of the increase in the pressure acceleration time. The the porosity in the FeCrSi/AC8A composite was investigated. The porosity was reduced as the pressure acceleration time as shorter. The FeCrSi/AC8A composite was investigated the wear test for to know the relationship between Porosity and wear resistance. FeCrSi/AC8A composite at pressure acceleration time of 1sec is shown excellent wear resistance.

• Journal of the Korean Ceramic Society
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• v.28 no.2
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• pp.101-108
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• 1991

0.2 mo1% La doped BaTiO3 samples were prepared by a wet chemical process (Pechini process) and electrical conductivity were measured from annealing temperatures(800-110$0^{\circ}C$) to room temperature continuously. 2 probe I-V characteristics showed that Pt electrodes were non-ohmic below about 80$0^{\circ}C$ for Ladoped sample. I-V curves showed varistor behavior and breakdown voltages showed PTC-like behavior. AC complex impedance of 0.2 La and 0.05 Mn mo1% doped BaTiO3 samples with three different electrodes (electroless Ni, Pt, Ag electrodes) were measured with temperature variation. Complex impedance plots showed that the samples with electroless Ni electrodes have negligible electrode resistance. Samples with Ag or Pt paste electrodes showed large electrode resistance. PTC effect, which is defined as the ratio of maximum resistance to minimum resistance, was found to be less than 10 for 0.2 mo1% La doped dense sample however greater than 105 with codoping of 0.05 mo1% Mn and 0.2 mol% La.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.5
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• pp.519-525
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• 2005

An electrochemical evaluation on the corrosion resistance for heavy anticorrosive paint(DFT:25um) was carried out for 5 kinds of heavy anticorrosive paints such as high solid epoxy(HE), solvent free epoxy(SE). tar epoxy(TE), phenol epoxy(PE). and ceramic epoxy(CE). Corrosion current densities obtained by Tafel extrapolation method from anodic and cathodic polarization curves didn't correspond with the values obtained by AC impedance measurement, however, the values of polarization resistance obtained from the cyclic voltammogram showed a good tendency corresponding well with the values of AC impedance measurement. Futhermore there was a good correlation against the corrosion resistance evaluation between passivity current density of the anodic polarization curve and diffusion limiting current density of the cathodic polarization curve. And corrosion resistance increased with corrosion potential shifting to noble direction. From the results discussed above. HE and CE had a relatively good corrosion resistance than other heavy anticorrosive paints.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.138-144
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• 2017

With the increase in power consumption due to the surge in the demand for power, it is necessary to improve the quality or design of the power (supply) for the purpose of reducing the energy consumption and so reduce the power loss. The switchboard is a mechanical device that receives electricity from the electricity generation facilities of KEPCO and divides it into the facilities required for each building. Switchboards generally consist of enclosures, switches, power conductors, and control components. This study deals with energized power conductors, which constitute the main element in the switchboard. Through the measurement of the effective ac resistance, it was confirmed that the vertical array structure of the conventional type plate conductor is inefficient. If the effective AC resistance increases significantly, the sectional area of the conductor becomes relatively large due to the skin effect. In this study, we studied the energy and material savings that could be obtained using the asterisk (*) array structure, which minimizes the effective ac resistance by reducing the skin effect. The core technology principle of this study is the energy saving switchgear based on conductor resistance reduction technology utilizing the asterisk array structure. The present invention involves a plate-shaped conductor arrangement structure capable of canceling out the magnetic field generated on each of the plate conductors (rst or abc) of the AC power supply in the power distribution panel by mutual action. The effect of this structure is to reduce the amount of inductive reactance due to the increase in the cross-sectional area and reduction of the effective AC resistance.

• Current Research on Agriculture and Life Sciences
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• v.20
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• pp.9-18
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• 2002

A total of 31 C. chinense lines selected from 2000 screening were tested again for resistance to P. capsid but resistance was not found in tile lines. A total of 26 selections from Korean land races tested 2001 spring were tested again for resistance to P. capsici, KC180, KC230, KC195 and KC194 showed moderate resistance to P. capsid. However, it was apparent on the basis of horticultural characteristics that KC180 and KC230 had been naturally crossed with AC2258 and CM334, respectively. CM334 and AC2248 seed lots that were increased in different years were taken out and tested for resistance to improve their genetic purity because the resistant genetic resources have been showing some off-types in tile population. Off-types began to be found in 1992 seed lots and tile proportion and degree of tile offs was increasing with time up to 2001. Plants true to the type in 1992 seed lots were selected and their inbred seeds were mass produced in a net cage in the greenhouse. AC2258 included in the experiment together was uniform. In 1995 seed lots of CM334, plants with resistance to P. capsici and low or no number of lateral branching at cotyledonary axil, although they were off from tile original CM334, were found and selection was applied to breed lines fixed in tile characters.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.241-244
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• 2002

We investigated over critical current characteristics of HTS tapes fabricated by KIMM. The critical current (Ic) of the HTS tapes was 68A/cm. In order to acquire over current I-V characteristics of HTS tapes, we applied AC that is 2-7 times of Ic to these tapes. When applied AC whose peak value is twice of Ic, we found out that total resistance of HTS tapes aid not change. In case of 3 times of Ic, resistances of HTS tapes began to increase slowly. However, superconducting regions of them were maintained stably in this condition. In addition, 280 $A_{peak}$was applied, superconducting regions began to be decreased gradually. Finally, 0.62m$\Omega$ of resistance was measured in HTS tapes which was applied AC correspond to 7 times of Ic at first cycle.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.313-316
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• 2008

This paper presents the error factors of Fall-of-potential test method used in measurements of the grounding-system impedance. This test methods inherently can introduce two possible errors in the measurements of grounding-system impedance: (1) ground mutual resistance due to current flow through ground from the ground electrode to the current probe, (2) ac mutual coupling between the current test lead and the potential test lead. The errors of ground mutual resistances and ac mutual coupling are expressed by the equation in calculating grounding impedance. These equations were calculated by Matlab that is commercial tool using mathematical calculation. The results of calculation were applied to correct grounding impedance.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1481-1483
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• 2003

Molecular motions of polyaniline conducting blends were prepared. Surface resistance of its blends was investigated by a Surface Resistance Meter. DC electrical properties were investigated by Thermally Stimulated Currents(TSC) method and AC dielectric properties were investigated by Dielectric Thermal Analyzer (DETA) in the temperature range from $-50^{\circ}C$ to $120^{\circ}C$ at 1E0 Hz $^{\sim}$ 1E7 Hz for a comparative study of molecular relaxation. Using Scanning Electron Microscopy(SEM), relations of both microstructure and conduction behaviors was observed.

• Journal of Hydrogen and New Energy
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• v.21 no.3
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• pp.167-183
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• 2010

This paper analyzes the backgrounds of the standards for protection against electric shock in Global Technical Regulations (GTR) of Fuel Cell Vehicle (FCV). Targets on research were high voltage criteria, safety current, isolation and grounding resistance, time limitation, energy, adequate clearance, and test procedure. Based on human impedance and effect of current in IEC 60479-1, safety of human was examined. Then, isolation and grounding circuit model of FCV were analyzed theoretically. The results give several suggestions: touch voltage less than 25V, AC energy less than 0.0813J, separation considering middle finger length, grounding resistance less than $0.2\Omega$, maximum AC ground voltage of 1V (rms), and isolation resistance between earth and electrical chassis. In MATLAB/Simulink environment, error characteristics of isolation resistance measurement procedure using internal DC sources were analyzed under variations of internal resistance of voltmeter and isolation resistance.