• Applied Chemistry for Engineering
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• v.22 no.2
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• pp.149-154
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• 2011

In order to explore properties of various rubber compounds after thermal aging under the condition similar to the operating environment of a fuel cell-stack, heat resistance and compression set of those compounds were investigated for a long term operation in $H_2SO_4$, $H_2O$, and LLC (ethylene glycol : $H_2O=50:50$) solution. It was assumed that aging Acrylonitrile butadiene rubber (NBR) and Elthylene Propylene diene rubber (EDPM) compound in the solution resulted in discoloration as time passed. It was also found that hydrolysis was developed on the Silicone rubber (VMQ) compound intentionally aged under acidic condition by means of TGA, SEM, and EDS analysis.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.3
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• pp.367-370
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• 2014

The accelerated thermal aging of a CSPE were carried out for 0, 80.82, 161.63 days at $100^{\circ}C$, which are equal to 0, 40 and 80 years, respectively. The volume electrical resistivities of the non-accelerated thermally aged CSPE and the accelerated thermally aged CSPE for 40y and 80y were $9.620{\times}10^{12}{\sim}1.246{\times}10^{13}{\Omega}{\cdot}cm$, $5.066{\times}10^{12}{\sim}7.576{\times}10^{12}{\Omega}{\cdot}cm$ and $7.195{\times}10^{12}{\sim}9.208{\times}10^{12}{\Omega}{\cdot}cm$ at room temperature, respectively. The dielectric constant of the non-accelerated thermally aged CSPE and the accelerated thermally aged CSPE for 40y and 80y were 3.355~4.030, 2.996~3.963 and 3.020~4.776 at room temperature, respectively. After seawater and freshwater flooding, the volume electrical resistivity of the CSPE trend slightly upward according to drying day at room temperature. After seawater flooding, the dielectric constant of the accelerated thermally aged CSPE were not measured. After seawater flooding, bright open pores of the accelerated thermally aged CSPE were partly transferred to dark close pores due to salinity. After freshwater flooding, dark close pores of the accelerated thermally aged CSPE were partly transferred to bright open pores because salinity of them is decreased. An insulation property of a cable in NPPs was decreased because of the seawater flooding, and an insulation property of them was recovered through the freshwater flooding. As a result, it is considered that an insulation property of a contaminated cable through Tsunami can be recovered if it is cleaned quickly.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1121-1124
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• 2004

Aging test to estimate life property of polymer insulator is executed through several international standard such as IEC 61109 and CEA tracking wheel test, but is not getting clear conclusion yet. There are two methods in the diagnosis method of polymer insulator such as off-line and on-line. The diagnosis methods in off-line are external condition analysis by the eye, contaminant analysis on surface, surface analysis, pollution withstand voltage test, power frequency flashover voltage test, lightning impulse flashover test, tensile fracture load test and flexural load test. The diagnosis methods in off-line most are the method for virgin and last aged sample. However, the diagnosis method in on-line is method that can be evaluate sample state as progressing continuously aging test in beginning, The diagnosis method in on-line is arranged as following: leakage current measurement, electric field, surface state investigation, thermal image, emitting light measurement and then so. In this paper, the tracking performance of polymer insulator with salt solution which is added surface active agent. The diagnosis of insulator sample has been analyzed by leakage current and visual examination.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1909-1911
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• 2005

The electrical and chemical characteristics in transformer insulations are changed due to thermal stress. In the chemical property, as the Kraft paper ages, the cellulose polymer chains breakdown into shorter lengths with a corresponding decrease in both tensile strength and degree of polymerization(DP). Furthermore, cellulous chains breakdown is accompanied by an increase in the content of various furanic compounds within the dielectric liquid. It is known that furanic components in transformer oil come only from the decomposition of insulating paper rather than from the oil itself. Therefore the analysis of furan products provides a complementary technique to dissolved gas analysis for monitoring transformers when we evaluate the aging of insulating paper by the total concentration of carbon monoxide and carbon dioxide dissolved in oil only. In this paper the accelerated aging process of oil--paper samples have been investigated at a temperature up to $140^{\circ}C$ for 500 hours. The oil-paper insulation samples have been measured at intervals of 100 hours. For analysis we used high performance liquid chromatography(HPLC) in accordance with IEC 61198 method.

• Korean Journal of Pharmacognosy
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• v.48 no.1
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• pp.25-30
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• 2017

This study was performed to evaluate the lifespan extending effects of the dried ginger (Zingiber officnale Roscoe, Zingiberaceae). Ethanol extract of the dried ginger was successively partitioned as methylene chloride, ethyl acetate, n-butanol and $H_2O$ soluble fractions, and lifespan-extending effects of the fractions were investigated using Caenorhabditis elegans model system. Ethyl acetate-soluble fraction showed the most potent longevity property. Furthermore, ethyl acetate-soluble fraction elevated thermal stress tolerance, and increased expression of stress resistance protein. Further studies were performed to investigate several aging-related factors such as reproduction, food intake, growth and movement of C. elegans. The results revealed that there were no significant changes in aging-related factors including reproduction, food intake and growth, however, ethyl acetate-soluble fraction treatment led to an up-regulation of locomotory ability of aged worms, suggesting ethyl acetate-soluble fraction affected healthspan as well as lifespan of nematode.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.39 no.2
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• pp.149-158
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• 2013

L-ascorbic acid, the representative antioxidants, has a great effect on skin whitening, collagen synthesis, and anti-aging, but has low oxidative stability during storage. Therefore, in this study, thermal and oxidation properties of L-ascorbic acid under various storage conditions (powder, aqueous phase, changes of temperature, UV-irradiation, and inflow of external air etc.) were investigated. And the storage stability of ingredient was validated in the double-spaced pouch by analysing oxidation properties under each storage conditions (powder phase and blended with essence). In oder to analyze the thermal properties, TGA, DSC, and FT-IR analysis were carried out and UV-visible spectrophotometer & redox titration were used in parallel for oxidation property analyses. From the result of experiment, L-ascorbic acid was oxidized fast when it contained lots of metallic ion, hydroxy ion in aqueous solution under high temperature, UV-irradiation & inflow external air, whereas it was not oxidized for a long time when it was stored as pure powder although it has same condition as heating up, UV-irradiation & inflow external air. Based on this result, retention period of cosmetics which is using L-ascorbic acid, less stable material in oxidation can be innovatively increased when using double-spaced pouch that is designed and produced for separating storage of active ingredients.

• Applied Chemistry for Engineering
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• v.3 no.3
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• pp.422-429
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• 1992

The morphology and adhesion properties of rubber compounds containing resorcinol formaldehyde(RF) resin and hexamethoxymethylmelamine(HMMM) used in adhesion of rubber to brass-plated steel cord was investigated. The resins were spherical particles about $2000{\AA}$ diameter and distributed in rubber compounds homogeneously, and the cured compound with steel cord showed migration of resin to steel cord. Also, modulus was increased with increasing HMMM contents. The loss of adhesion between rubber and steel cord was likely to be at initial stages by thermal aging. Considering the physical properties, suability of adhesion layer and thermal aging property, optimum ratio of RF resin and HMMM was 1 : 0.9.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.250-255
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• 2001

It is inevitable to evaluate the life of turbine rotor because the operating periods of power plants need to be extended. The magnetic methods utilizing Magnetic Barkhausen noise curve were applied to detect the degradation caused by thermal aging. The Magnetic property of material depends on the domain dynamics and it is affected by the microstructure of material. Therefore the magnetic property is very sensitive to the microstructure change of the material. It is, thus, very useful to detect the state of degradation of varying materials. The test specimen made of 1Cr-1Mo-0.25V steel was used widely for turbine rotor material, and seven kinds of specimens with different degradation levels were prepared by the isothermal heat treatment at $630^{\circ}C$. With the increase of degradation, BHN was decreased. The result was compared with coercive force and vickers hardness.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.43-43
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• 2003

Carbon nanotubes(CNTs) have many application points, which are field emission devices, composites, hydrogen storage, nanodevices, supercapacitor and secondary battery. The most promising application point is emitter tip mays of field emission devices. Furthermore, it may be also useful as a vacuum device for high frequency and high power. But, there are some obstacles to fabricate carbon nanotube field emission device. One is that CNTs grown by CVD method has weak adhesion with substrate and the other is non-uniform length of them. These problems are very crucial in aging property and reliability of device in the field emission.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1452-1454
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• 2002

Large turbine generator(rated 22kV) has failed in the stator winding area during normal operation. The capacitance and tan${\delta}$ were measured by Schering bridge in the zone 1, 2 and zone 3-6 stator windings. The capacitance and tan${\delta}$ in the zone 1, 2 of stator winding were higher than those of zone 3-6 in the stator winding. Experiments on microstructure property were conducted in the zone 1, 2 and zone 3-6 insulations, which were drawn out from stator windings of the large turbine generator. Microstructure analysis was characterized using scanning electron microscope(SEM). SEM results indicated that several isolated delaminations occurred at the interface of mica/epoxy insulations. Both thermal and mechanical aging cause the delamination.