• Proceedings of the KSME Conference
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• 2008.11a
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• pp.576-580
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• 2008

Rubber material properties and useful life evaluation are very important in design procedure to assure the safety and reliability of the rubber components. In this paper, the evaluation of characteristics and useful life prediction of rubber component for elevator cabin were experimentally investigated. The material test and accelerated heat-aging test were carried. Rubber material constants were obtained by curve fittings of simple tension, pure shear and bi-axial tension test data. Heat aging test results changes as the threshold are used for assessment of the useful life and time to threshold value were plotted against reciprocal of absolute temperature to give the Arrhenius plot. By using the rubber material and component test several useful life prediction equations for rubber component were proposed. Predicted useful life of rubber component for elevator cabin agreed fairly with the experimental lives.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.2
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• pp.149-157
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• 2003

The purpose of this paper is to quantitatively investigate aging state of epoxy coating on containment structure at nuclear power plant. In order to evaluate an physical bonding of the epoxy coating, adhesion test was performed on a degraded epoxy coating on concrete specimens fabricated by accelerated aging experiment. In addition, impedance data by ultrasonic test were measured to compare with adhesion data. From almost 50 % of the specimens, aging phenomena of epoxy coating such as pin hole, blistering was discovered. To improve reliability on quality degradation of epoxy, co-relation between two kinds of different data was analyzed. By tracing co-related these data, it was possible to figure out physical state of as-built epoxy coating. The possibility to develop new methodology of time - dependent aging state on epoxy coating was found and discussed.

• Journal of Life Science
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• v.9 no.5
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• pp.548-555
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• 1999

Long-term effects of Ganoderma lucidum (GL) on memory and oxidative stress of senescence-accelerated mice (SAM) were investigated. Senescence-resistant (R1) and prone (P8) strains of SAM were fed GL diets, premixed with low (20 mg/kg/day, T1) or high (200 mg/kg/day, T2) levels of GL powder for 9 months starting from young (3 months of age) or for 5 months starting from old (7 months of age). After the final feeding at 12 months of age, all animals were subjected to passive avoidance test for the evaluation of memory function. In addition, the changes in hepatic thiobarbituric acid-reactive substance (TBARS) and glutathione were analyzed. SAMP8 fed GL diets from old age (7 months) exhibited the improvement of memory, although GL rather inhibited the memory function of both SAMR1 and SAMP8 mice fed diets from young (3 months of age). Hepatic TBARS contents were decreased in SAMP8 fed high GL diet for 9 months and in SAMR1 fed low GL diet for 5 months. Hepatic glutathione content was also remarkably increased in SAMR1 following both feeding periods, and less extent in SAMP8 fed diet for 5 months of age. Taken together, it is proposed that GL extracts may play an anti-aging role through antioxidant action, and thereby may improve the senescence-related memory dysfunction.

• Elastomers and Composites
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• v.37 no.2
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• pp.107-114
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• 2002

This paper discusses the accelerated heat aging tests were carried out to predict the useful life of EPDM isolating rubber components of ventilation fan motor for clean room. 20% compression set results changes as the threshold are used for assessment of the useful life and the time to threshold value were plotted against reciprocal of absolute temperature to give the Arrhenius plot. The useful life at variable temperatures and activation energy are obtained from the Arrhenius relationship. An accelerated test program to assess useful life can be represented an appreciable investment in time was designed. We also considered the effect of antioxidant agents.

• Fire Science and Engineering
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• v.18 no.3
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• pp.45-50
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• 2004

Thermal degradation of PVC which used for insulator of 600V vinyl insulated wire has been studied by thermo gravimetry analysis and accelerated thermal aging test. The activation energy using thermo gravimetry analysis was determined by the kinetic methods, such as Kissinger and Flynn-Wall-Ozawa. The activation energy was determined to from 89.29 kJ/mol to 111.39 kJ/mol in 600V PVC insulated wire and from 97.80 kJ/mol to 119.25 kJ/mol in 600v heat-resistant PVC insulated wire. And also, the activation energy through a long-term thermal aging test was calculated by using Arrhenius equation In the low temperature of 8$0^{\circ}C$, 9$0^{\circ}C$, 10$0^{\circ}C$. The results showed that 600V PVC insulated wire was 92.16 kJ/mol, and 600v heat-resistant PVC insulated wire was 97.52 kJ/mol. Consequently, the activation energy of 600V heat-resistant PVC insulated wire is larger than 600V PVC insulated wire. Therefore, it can be predicted that 600V heat-resistant PVC insulated wire has a long-term stability relatively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.212-216
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• 2000

ZnO varistors for distribution surge arrester (18kV, 5kA) were developed and tested microstructure and electrical characteristics. Microstructure of ZnO varistor was consisted of ZnO grain, spinel phase and Bi-rich phase. Average grain size of ZnO varistor was $\mu\textrm{m}$ Reference voltage and lightning impulse residual voltage of ZnO varistor exhibited a good haracteristics above 5.5kV and below 11.56kV, respectively. Consequently, discharge capacity which is the most important characteristics of ZnO varistor for surge arrester exhibited excellent properties above 70kA at twice high-current impulse test. Moreover, variation rate of reference voltage and lightning impulse residual voltage showed below 5% and 2% after high-current impulse test, respectively. Leakage current and watt loss of ZnO varistor will not increase during accelerated aging test at stress condition, such as 3.213kV/$115^{\circ}C$/1000h.

• Corrosion Science and Technology
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• v.5 no.3
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• pp.99-105
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• 2006

This paper is to investigate feasibility on quantitative aging state of epoxy coating on concrete wall in containment structure under operation of nuclear power plants. For evaluating the physical characteristics of the epoxy coating, adhesion strengths of two kinds of degraded epoxy coating systems on both steel surfaces and concrete surfaces were measured via accelerated aging. Comparatively impedance data taken by ultrasonic test were also taken to relate with adhesion data. After aging, in case of concrete, from half of specimens, aging of epoxy coating was developed. As for steel, on $4^{th}$ inspection day, adhesion force was failed. To improve reliability on quality degradation of epoxy, relationship between adhesion and impedance was analyzed. By tracing to co-respond to these data, it was possible to Fig. out physical state of as-built epoxy coating. The possibility to develop new methodology of time - dependent aging state on epoxy coating was found and discussed.

• Elastomers and Composites
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• v.42 no.1
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• pp.32-46
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• 2007

Mechanical properties of rubber material are very important in design procedure to assure the safety and reliability of the rubber components. In this paper, the material test and accelerated heat aging test were carried out. In order to investigate the effects of heat-aging on the material properties, hardness, elongation, stress-strain curves and dynamic characteristics were obtained from various test conditions. Also, rubber material coefficients were determined by both the uniaxical and equi-biaxial tensile tests.

• Safety and Health at Work
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• v.11 no.4
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• pp.405-417
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• 2020

Background: Electrical socket outlets are used continuously until a failure occurs because they have no indication of manufacturing date or exchange specifications. For this reason, 659 electrical fires related to electrical socket outlets broke out in the Republic of Korea at 2018 only, an increase year on year. To reduce electrical fires from electrical socket outlets, it is necessary to perform an accelerated test and analyze the thermal, insulation resistance, and material properties of electrical socket outlets by installation years. Methods: Thermal characteristics were investigated by measured the temperature increase of electrical socket outlets classified according to year with variation of the current level. Insulation resistance characteristics was measured according to temperature for an electrical socket outlets by their years of use. Finally, to investigate the thermal and insulation resistance characteristics in relation to outlet aging, this study analyzed electrical socket outlets' conductor surface and content, insulator weight, and thermal deformation temperature. Results: Analysis showed, regarding the thermal characteristics, that electrical socket outlet temperature rose when the current value increased. Moreover, the longer the time that had elapsed since an accelerated test and installation, the higher the electrical socket outlet temperature was. With respect to the insulation resistance properties, the accelerated test (30 years) showed that insulation resistance decreased from 110 ℃. In relation to the installation year (30 years), insulation resistance decreased from 70 ℃, which is as much as 40 ℃ lower than the result found by the accelerated test. Regarding the material properties, the longer the elapsed time since installation, the rougher the surface of conductor contact point was, and cracks increased. Conclusion: The 30-year-old electrical socket outlet exceeded the allowable temperature which is 65 ℃ of the electrical contacts at 10 A, and the insulation resistance began to decrease at 70 ℃. It is necessary to manage electrical socket outlets that have been installed for a long time.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.2
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• pp.70-79
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• 2015

This study was carried out to analyze deterioration characteristics of color-pigments painted Hanji to preserve and restore the cultural properties. On the traditional painting technique, glue was used with pigments in various ways for painting, but it eventually caused the deterioration of paintings. Thus, five colors were selected and analyzed for this study for investigating their characteristics of deteriration. Three kinds of glues (Wugyo, Nokgyo, and Togyo) and two kinds of pigments (Chinese and Gilsang) were painted on the Hanji for the accelerated aging test. And then color fastness of pigments and tensile strength of painted Hanji were measured for the estimation of deterioration degree. The results of SEM-EDS showed that Chinese pigments including blue, yellow, green, and red were composed of inorganic substances but the brown was organic substance. Gilsang pigments were composed mainly of Si and Ti ions. Color fastness of the Gilsang pigment blue, yellow, green, and brown were better than those of Chinese. Chinese pigment brown with organic substance showed the worst color fastness. Generally, Chinese pigments painted Hanji showed higher tensile strength than Gilsang in the accelerated aging test. Hanji treated with Chinese pigment and Nokgyo (antler glue) blends and Gilsang pigment and Togyo (rabbit pelt glue) blends showed higher tensile strength than the others. And Andong Hanji showed the highest tensile strength.