• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.406-409
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• 2002

The primary insulation system used in an oil-filled transformer is Kraft paper, wood, porcelain and, of course, oil. Modern transformers use paper that is chemically treated to improve its tensile strength properties and resistance to aging caused by immersion in oil. These insulation papers are mainly aged to thermal stress. Over the course of the insulation paper and oil's life it is exposed to high temperatures, oxygen and water. Its interaction with the steel of the tank and core plus the copper and aluminium of the windings will eventually cause the chemical properties of the oil to decay. High temperature have an effect on mechanical strength of cellulous paper using the layer insulation. We made two aging cell in which thermal aging tests of insulation papers and mineral oil are conducted. It is measured dielectric strength, number of acid, moisture, etc. of insulation paper and oil aged in the aging cells.

• Structural Engineering and Mechanics
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• v.16 no.4
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• pp.405-422
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• 2003

Scaled brick masonry panels were tested under cyclic unialxial compression loading to evaluate its deformation characteristics. An envelope stress - strain curves, a common point curves and stability point curves were obtained for various cyclic test conditions. Loops of the stress-strain hysteresis were used to determine the energy dissipation for each cycle. Empirical expressions were proposed for the relations between energy dissipation and envelope and residual strains. These relations indicated that the decay of masonry strength starts at about two-third of peak stress.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.100-103
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• 2003

The primary insulation system used in an oil-filled transformer is kraft paper, wood, porcelain and oil. Modern transformers use paper that is chemically treated to improve its tensile strength properties and resistance to aging caused by immersion in oil. But these insulation papers are mainly aged to thermal stress. Over the course of the insulation paper and oil's life it is exposed to high temperatures, oxygen and water. Its interaction with the steel of the tank and core plus the copper and aluminium of the windings will eventually cause the chemical properties of the oil to decay. High temperature have an effect on mechanical strength of cellulous paper using the layer insulation. We made two aging cell in which thermal aging tests of insulation papers and mineral oil are conducted. It is measured dielectric strength, number of acid, moisture, etc. of insulation paper and oil aged in the aging cells.

• Journal of the Korean Geotechnical Society
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• v.28 no.3
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• pp.45-54
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• 2012

Various geosynthetics are widely applied to civil structures and waste landfill site for reinforcement and water resistance. The use of geosynthetics inevitably involves the coupled behaviors of different materials which include large displacement and strain-softening behaviors, etc. In this study, the effect of chemical element in the leachate on the interface shear strength under the cyclic loading condition was analyzed. The Multi-purpose Interface Apparatus (M-PIA) has been modified and cyclic direct shear tests have been performed. The submerging period of each specimen is 200 days. Additionally, the Field-Emission Scanning Electronic Microscopy (FIB) analysis has been also performed to induce the reason of the variation of disturbance function and verify the hypothesis on the decay-proof ability of geosynthetics. Consequently, the charateristics of chemical degradation of geosynthetic-soil interface are verified and the variation of the disturbance function is mainly caused by the different type of soil mineral decay, based on the FIB results.

• Journal of the Korean Wood Science and Technology
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• v.10 no.3
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• pp.166-166
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• 1982

This study has been made to make an observation regarding present status of the coal mine props which is desperately needed for coal production, despite of great shortage of the timber resources in this country, and investigate the effects of diffusion process on the decay resistances of the mine props as applied preservatives of Malenit and chromated zinc chloride. The results are as follows. 1. Present status of the coal mine props Total demand of coal mine props in the year of 1975 was approximately 456 thousand cubic meters. The main species used for mine props are conifer (mainly Pinus densiflora) and hardwood (mainly Quercus). Portions between them are half and half. With non fixed specification, wide varieties of timber in size and form are used. And volume of wood used per ton of coal production shows also wide range from 0.017 cubic meter to 0.03 cubic meter. 2. Decay resistance test a) The oven dry weight decreased between untreated specimen and treated specimen has not shown any significantly, although it has shown some differences in average values between them. It may be caused by the shorter length of the test. b) The strength of compression test between untreated specimen and treated specimen has also shown the same results as shown in case of weight decrease. Reasons assumed are the same. c) The amounts of the extractives in one percent of sodium hydroxide (NaOH) between untreated and treated specimen have shown the large value in case of untreated specimen than that of treated. 3. The economical benifit between untreated and treated wood when applied in field has seen better in long tenn base in case of treated wood, although the primary cost of treated wood add a little bit more cost than that of the untreated wood.

• Journal of the Korean Society of Safety
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• v.16 no.3
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• pp.61-67
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• 2001

In this study the electrical and mechanical characteristics of PET films ore analyzed after plasma surface treatment. After plasma treatment, the surface potential decay, surface potential and dielectric property were evaluated to analyze the electrical insulating property, and the tensile strength was measured as the mechanical characteristic. When plasma treatment was conducted for less than 10 minutes, it was found that the electrical insulating property was improved through evaporation of low molecular weight materials md cleaning of surface. However, for more than 10 minutes, the insulating property of plasma treated PET films was decreased due to excessive discharge energy. The tensile strength was hardly changed by Plasma treatment.

• Journal of architectural history
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• v.3 no.1
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• pp.45-55
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• 1994

This study deals with the method of constructing and repairing column, important element of traditional wooden building. Column should have long-lasting strength and resistance to decay and vermin because it is more important in role of structure than in that of ornament. And the rotten or the split part of wooden column should be repaired regularly or irregularly. First of all, this study treats of general character related to the life length and strength of wood. Then it describes the technical method of choosing proper wood for column and that of carpentering, painting, and mending wooden column.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.6
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• pp.281-287
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• 2001

In order to obtain guidelines for design and operation of a new plasma source by a magnetic neutral loop discharge(NLD), the electron behavior was studied experimentally and numerically. Experimentally, the magnetic field gradient was changed over a wide range, and it was found that there existed an optimum value for efficient plasma production. Analyses of the electron behavior were performed using a model that included effects of a three dimensional electromagnetic field configuration considering the spatial decay of the electric field, and the limitation to the motion of electron caused by the existence of walls and thus electron loss at wall surfaces. These three dimensional factors were found to explain the existence of the optimum magnetic field gradient. It was shown that the L dependence of the plasma production efficiency was firstly decided by the finite decay length of the electric field strength, which was further modified by electron elastic collisions with neutral atoms which drove the electron to walls. The latter effect tends to reduce the optimum value of L.

• Korean Journal of Food Science and Technology
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• v.31 no.6
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• pp.1577-1582
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• 1999

Carrot juice inoculated with $2\;{\times}\;10^8\;cfu/mL$ of Escherichia coli was treated with pulsed electric fields(PEF) for the purpose of a development of new cold pasteurization processes. Inactivation of E. coli in carrot juice increased with increase in intensity of the electric field strength and treatment time. The cells were suspended at concentration of ca. $2\;{\times}\;10^8$ cells per ml. A reduction of 4D was obtained at 40 kv/cm and 256 exponential decay pulses at room temperature. Critical electric field strength(Ec) and treatment time(tc) needed for inactivation of E. coli were 11.74 kV/cm and $3.6\;{\mu}s$ at room temperature, respectively. The combination of PEF and thermal treatment inactivated E. coli more effectively. The reductions of up to 5.5D were observed when the carrot juice was treated with PEF of 22.5 kV/cm and $205\;{\mu}s$ at $50^{\circ}C$. PFF treatment did not effect in color, pH, $^{\circ}Brix$, titratable acidity and ${\alpha}-,\;{\beta}-carotene$ contents of carrot juice.

• Geomechanics and Engineering
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• v.23 no.3
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• pp.227-244
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• 2020

Earthen structures have an excellent bioclimatic performance, but they are vulnerable against earthquakes. In order to investigate the edification process and costs, a full-scale rammed soil house was constructed in 2004. In 2016-2019, it was studied its seismic damage, durability and degradation process. During 2004-2016, the house presented a relatively good seismic performance (M_w=5.6-6.4). The damaged cover contributed in the fast deterioration of walls. In 2018 it was observed a partial collapse of one wall due to recent seismicity (M_w=5.6-6.1). The 15-year-old samples presented a reduced compressive strength (0.040 MPa) and a minimum moisture (1.38%). It is estimated that the existing house has approximately a remaining 20% of compressive strength with a degradation of about 5.4% (0.0109 MPa) per year (considering a time frame of 15 years) if compared to the new soil samples (0.2028 MPa, 3.52% of moisture). This correlation between moisture and compressive strength degradation was compared with the study of new soil samples at the same construction site and compared against the extracted samples from the 15-year-old house. At 7-14-days, the specimens presented a similar compressive strength as the degraded ones, but different moisture. Conversely, the 60-days specimens shown almost five times more strength as the existing samples for a similar moisture. It was observed in new rammed soil that the lower the water content, the higher the compressive/shear strength.