• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.589-592
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• 2001

Generally, hanger insulator for polymer arrestor have to be good insulation properties and mechanical strength and weatherability, But many remark and repairs have been to think about low cost and light weight. The Paper is used Polymer arrestor for post and performance analysis and mechanical strength insulator hanger according to development of simplest product. To enhance the efficiency of experimental modal analysis, we proposed the process which is the selection of the locations and the number of measurement points for pre-test.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.6
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• pp.379-383
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• 2015

Some insulating materials are organized and analyzed with variables to obtain the optimized profile of encapsulated three phase of epoxy barrier which is applied to gas compartment and supporting conductors for high voltage GIS (gas insulated switchgear). The high voltage GIS is used in electrical power system and operating reliability. In this paper, optimization possibility of barrier shape including both electrical insulation performance and mechanical strength, premised on that condition minimizing volume and light weight should be kept for high voltage GIS, could be achieved by analysis simulation. As a result, filling material which is lower permittivity such as $SiO_2$ instead of $Al_2O_3$ properly to the epoxy material, can be improved to increase the electrical insulation performance and mechanical strength for an optimized profile barrier of a high voltage GIS.

• Journal of the Korea Institute of Building Construction
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• v.17 no.6
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• pp.493-498
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• 2017

This study is a pioneer investigation to enhance the insulation capacity of the conventional aerated concrete using hydrophobic aerogels. As the main test parameters, aerogel content varied from 0% to 40% of the foam volume. Test results showed that the compressive strength of aerated concrete containing aerogels was lower by 17%~34% than that of the conventional aerated concrete. In addition, the effect of the aerogels on reducing thermal conductivity of aerated concrete is insignificant because of the partial condensation and abnormal distribution of the hydrophobic aerogels. Hence, further hydrophilic treatment for the surface of aerogels is recommended to minimize the decrease in compressive strength and enhance the insulation capacity of aerated concrete.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05e
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• pp.65-68
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• 2003

In this paper, we researched breakdown characteristics of paper/liquid nitrogen composite insulation system for application of a high temperature superconducting cable. And, we have studied the AC breakdown performance of paper/ice composite insulating system immersed in liquid nitrogen. The electric strength in this paper/ice composite system is higher than that of paper/liquid nitrogen system. Furthermore this system shows a self-healing type breakdown behavior. Among the many kinds of liquid to be immersed and frozen to the ice, deionized water gives the highest electric breakdown strength. The paper/ice composite insulation system is thought to be one of good candidate for the electrical insulating system at cryogenic temperature.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.9
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• pp.1518-1523
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• 2016

In this study, in order to understand the degradation characteristics of oil-paper insulation for power transformers and OF cables, tan delta was measured using cable model specimens with long-term accelerated thermal and electrical aging. In addition, to find out the degradation level due to the accelerated aging, tensile strengths of aged papers were measured. As a result, tan ${\delta}$ showed the characteristics of slight decrease at the first stage and then increase with the aging time, which could be analyzed due to the evaporation of remaining moisture and the change of aging rate with time. Also, the trend of tensile strengths with aging temperature and time was appeared to be exponentially decreased and by use of these data equivalent calculated lifetimes and accelerated aging factors were derived for each aging temperatures. After then, tan ${\delta}$ was analyzed with the equivalent operating years. For all different aging temperatures, the aged data were very well fit to the equivalent operating years and it is shown that tan ${\delta}$ was increased with the decrease of tensile strength.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.628-631
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• 2004

A tetrafluoromethane$(CF_4)$ is most useful gas in plasma dry etching, because it has a electron attachment cross-section. therefor it is important to calculate transport coefficients like electron drift velocity, ionization coefficient, attachment coefficient, effective ionization coefficient. and critical E/N. The aim of this study is to get these transport coefficients for information of the insulation strength and efficiency of etching process. Electron transport coefficients in $CF_4+Ar$ gas mixture are simulated in range of E/N values from 1 to 250 [Td] at 300[K} and 1 [Torr] by using Boltzmann equation method. The results of this method can be important data to present characteristic of gas for plasma etching and insulation, specially critical E/N is a data to evaluate insulation strength of a gas. and is presented in this paper for various mixture ratios of $CF_4+Ar$ gas mixture.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1608-1610
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• 2000

In this work, the effect of annealing on physical and electrical properties of XLPE cable insulation was investigated. One sample was non-annealed and the other two samples were treated under air circulated oven at 80$^{\circ}C$ for five and ten days. In the DSC patterns of annealed specimen, new peaks appeared at near 80$^{\circ}C$ as a proof of thermal history. The degree of crystallinity increased by annealing effect. In the FT-IR spectrums, the change of absorbances to acetophenone and cumyl alcohol were observated according to the radial direction of cable insulation. They slowly diffused into both semi-conductive layer of the cable in proportion to annealing time and lastly led to near equilibrium state through cable insulation. The AC breakdown strength did not increased but the values were stabilized by effects of crystallinity and diffusion of by-products.

• Journal of Ceramic Processing Research
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• v.19 no.5
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• pp.428-433
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• 2018

In this study, using the pilot plant activation system, the activated cement has been manufactured and then applied to the manufacturing process of mineral hydrate insulating material. The fineness of the activated cement is controlled at $5,000cm^2/g$ and $7,500cm^2/g$ and the features of mineral hydrate insulating material, using OPC and the activated cement for each degree of fineness, has been analyzed. As the result of analyzing the crystal habit of the manufactured mineral hydrate insulting material, it is analyzed that the main crystal phase of specimen is tobermorite and some quartz peak has been detected. As the degree of fineness of the activated cement increases, the height of bubble of slurry increases as well, whereas the tendency for the density character to decrease has been detected. Along with it, as the density character decreases, the compression strength has decreases, whereas the tendency for the thermal characteristic to increases has been detected. The main features of mineral hydrate insulating material, using the activated cement with the fineness of $7,500cm^2/g$, the compression strength of 0.36 MPa, and the thermal conductivity of $0.044W/m{\cdot}K$, presents the excellent features as insulation.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.4
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• pp.33-40
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• 2020

A sturdy on the adhesion properties of solid propellants, liners, and insulation was carried out according to the types of barrier coats. A barrier coats were used to prevent migration of the plasticizer or curative between the propellant/liner/insulation, and the barrier coat was selected out of Isocyanates with different molecular weight and number of -NCO in one molecule. As a result, it was found that the more the -NCO group and the larger molecular weight, the stronger adhesion. In addition, as a result of experiments about effects of the pot life after applying the barrier coat on bond strength, the adhesion strength was shown to increase as the pot life was short.

• Computers and Concrete
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• v.26 no.3
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• pp.257-273
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• 2020

Concrete bond strength with steel re-bars depends on multiple factors including concrete-steel interface and mechanical properties of concrete. However, the hydration development of cementitious paste, and in turn the mechanical properties of concrete, are negatively affected by cold weather. This study aimed at exploring the concrete-steel bonding behavior in concrete cast and cured under freezing temperatures. Three concrete mixtures were cast and cured at -10 and -20℃. The mixtures were protected using conventional insulation blankets and a hybrid system consisting of insulation blankets and phase change materials. The mixtures comprised General Use cement, fly ash (20%), nano-silica (6%) and calcium nitrate-nitrite as a cold weather admixture system. The mixtures were tested in terms of internal temperature, compressive, tensile strengths, and modulus of elasticity. In addition, the bond strength between concrete and steel re-bars were evaluated by a pull-out test, while the quality of the interface between concrete and steel was assessed by thermal and microscopy studies. In addition, the internal heat evolution and force-slip relationship were modeled based on energy conservation and stress-strain relationships, respectively using three-dimensional (3D) finite-element software. The results showed the reliability of the proposed models to accurately predict concrete heat evolution as well as bond strength relative to experimental data. The hybrid protection system and nano-modified concrete mixtures produced good quality concrete-steel interface with adequate bond strength, without need for heating operations before casting and during curing under freezing temperatures down to -20℃.