• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.152-154
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• 2001

Recently the extensive use of composite insulators for transmission lines can ultimately be justified only on long-term qualification tests. Especially, it is possible for the Polymer insulator to be aged in according to the environment in which it is used this may bring about the decrease of the duration of voltage application. So, this paper deals with aging property of the polymer insulator installed at real transmission line in the industry area. The contact angle, arc test, tracking test were measured for acquiring the degradation characteristics of silicone rubber and the SEM, XRF, FT-IR tests were measured for analyzing the crack and components. Also the surface leakage current of the polymer insulator was compared with that of the porcelain insulator. Finally, we knew that the aging property was not appeared during seven months at real transmission line in the industry area.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.41 no.1
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• pp.37-43
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• 2009

In this study, the physical properties of base paper for the manufacture of mulching mat for afforestation seedling were investigated. The base paper for mulching mat was prepared by stock conditions of PAE and AKD addition into the screened slurry of KOCC for the strengthening effects of wet tensile and burst strength. The optimum additions of PAE and AKD were considered at 2% and 0.5%, respectively. The accelerated aging by ISO 5630-1 and wet heat aging method under hot water for 2 kinds of commercial mulching and wet strength paper were compared with the base paper prepared for mulching mat manufacture. The accelerated aging test for the base paper prepared for mulching mat manufacture resulted in the same tendency of physical properties as two kinds of commercial products. However, the results of wet heat aging test under hot water indicated that the physical strength for base paper prepared was much higher than others. In addition, the opacity behavior for base paper prepared was enough effects to obstruct weeds growth by isolating transmission of sunlight.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.322-325
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• 2006

The nano/microstructure and mechanical properties of the eutectic regions in thixo and rheo cast A356 alloy parts were investigated using nano/micro-indentation and mechanical scratching, combined with optical microscopy and atomic force microscope (AFM).Most eutectic Si crystals in the A356 alloy showed a modified morphology as fine-fibers, however Si particles of network in eutectic region was formed quickly with aging time increase in thixo-cast. The aging responses of the eutectic regions in both the thixo and rheo cast A356 alloys aged at $150^{\circ}C$ for different times (0, 2, 4, 8, 10, 16, 24, 36, and 72 h) were investigated. Both Vickers hardness ($H_V$) and indentation ($H_{IT}$) test results showed almost the same trend of aging curves, the peak was obtained at the same aging time of 10 h.

• Carbon letters
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• v.28
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• pp.9-15
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• 2018

In the aerospace field, Carbon/Cork composites have been used for rocket propulsion systems as a light weight structural component with a high bending stiffness and high thermal insulation properties. For the fabrication of a carbon composite with a heat insulation cork part, the bonding properties between them are very important to determine the service life of the Carbon/Cork composite structure. In this study, the changes in the interfacial adhesion and mechanical properties of Carbon/Cork composites under accelerated aging conditions were investigated. The accelerated aging experiments were performed with different temperatures and humidity conditions. The properties of the aged Carbon/Cork composites were evaluated mainly with the interfacial strength. Finally, the lifetime prediction of the Carbon/Cork composites was performed with the long-term property data under accelerated conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.2
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• pp.110-116
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• 2002

At elevated temperature, very complex precipitations occur in STS316. To investigate the effect of the precipitation on mechanical properties in SIS316, tensile tests and fatigue crack growth tests were carried out at $650^{\circ}C$ using artificially degraded materials. The material degradation was simulated by aging for up to 20000 hrs. at $750^{\circ}C$, which is equal to 179000hrs (about 20yrs) of service life at $650^{\circ}C$, after conducting solution treatment for 20 min. at $11300^{\circ}C$. The result of the hardness test and the tensile test showed that both properties are closely related to the mean free distance of carbides. Also, from the results of fracture tests at $650^{\circ}C$, ${\triangle}K_{th}$, after values were found to decrease as aging time and microstructure, as the volume fraction of $\sigma$ phase increased.

• Elastomers and Composites
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• v.40 no.2
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• pp.119-127
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• 2005

Material characteristics and lifetime evaluation 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 to predict the useful life of NBR and EPDM rubber mount for a compression motor which is used in a refrigerator. In order to investigate the effects of heat-aging on the material properties, crosslink density, modulus at 100% strain, stress-strain curves were obtained from uniaxial and equi-biaxial tensile tests. The change of compression set were used for assessment of the useful life and the time to threshold value were plotted against the reciprocal of absolute temperature to give the Arrhenius plot. The useful life at variable temperatures are obtained in the Arrhenius relationship.

• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.1-8
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• 2024

In this study, the influence of thermal aging on structural integrity is investigated for Gr. 91 steel. A commercial grade Gr. 91 steel is used for the virgin material, and service-exposed Gr. 91 steel is sampled from a steam pipe of a super critical plant. Time versus creep strain curves are obtained through creep tests with various stress levels at 600 ℃ for the virgin and service-exposed Gr. 91 steels, respectively. Based on the creep test results, the improved Omega model is characterized for describing the total creep strain curve for both Gr. 91 steels. The proposed parameters for creep deformation model are used for predicting the steady-state creep strain rate, creep rupture curve, and stress relaxation. Creep-fatigue damage is evaluated for the intermediate heat exchanger (IHX) in a large-scale sodium test facility of STELLA-2 by using creep deformation model with proposed creep parameters and creep rupture curve for both Gr. 91 steels. Based on the comparison results of creep fatigue damage for the virgin and service-exposed Gr. 91 steels, the thermal aging effect has been shown to be significant.

• Journal of Physiology & Pathology in Korean Medicine
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• v.23 no.5
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• pp.1178-1182
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• 2009

This study was designed to analyze the results of Vaso-Aging Degree in Oriental medical examination. The subjects were workers in the automobile manufacturing industry. The subjects consisted of 24,077 industrial workers who had received Oriental medical examination by Oriental medicine and they submitted questionnaires about drinking history and smoking history, during 9 months from March to November. They were categorized by job class, drinking history and smoking history, exercising history. The percentage of Vaso-Aging Degree were measured by using SA3000P(Medicore, Seoul, Korea). We analyzed the relationship between job class, drinking history, smoking history, exercising history and Vaso-Aging Degree using ${\chi}2$-test of the SPSS Ver. 14.0. In job class, Sales personnel were apt to have a higher level of Vaso-Aging Degree than Office workers. And getting older workers are, the higher Vaso-Aging Degree becomes. Vaso-Aging Degree of the Drinker group showed a higher level than the Non-Drinker group. Vaso-Aging Degree of Smoker group were higher than the Non-smoker group. On the other hand, Vafo-Aging Degree of Non-Exerciser group were higher than the Exerciser group. They have to manage Vaso-Aging Degree closely and educate the workers to quit smoking and drinking for their health promotion. Furthermore, continuous health check up needs to be done connectedly.

• Journal of agricultural medicine and community health
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• v.46 no.2
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• pp.89-97
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• 2021

Objectives: The purpose of this study is to identify the relationship among psychosocial stress, memory, and successful aging of the community-residing elderly. Methods: 152 people over 65 years old living in D area were interviewed, from August 1st, 2020 to October 30th, 2020. The outcomes were measured by Psychosocial Well-being Index (PWI), Mini-Memory Test (MiMeT) and successful aging. Data were analyzed using Pearson correlation coefficients and stepwise multiple regression. Results: There was a positive correlation between successful aging and memory. There was a negative correlation between psychosocial stress and successful aging, and between psychosocial stress and memory. Psychosocial stress was identified as a predictor of successful aging, which explained 26.4% of total variance of successful aging. Conclusions: When we prepare intervention programs which improve successful aging for community-residing older adults, we need to consider psychosocial stress. In addition, stress management programs for successful aging should be developed to improve current successful aging.

• The Journal of Advanced Prosthodontics
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• v.12 no.5
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• pp.265-272
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• 2020

PURPOSE. The aims of this study were to investigate mechanical properties and hydrothermal degradation behaviour of the cubic-containing translucent yttrium oxide stabilized tetragonal zirconia polycrystal (Y-TZP). MATERIALS AND METHODS. Four groups of Y-TZP (T, ST, XT, and P), containing different amount of cubic crystal, were examined. Specimens were aged by autoclaving at 122℃ under 2 bar pressure for 8 h. Phase transformation was analyzed using X-ray diffraction (XRD) to measure phase transformation (t→m). Kruskal-Wallis test was used to determine the difference. Surface hardness, biaxial flexural strength, and fracture toughness in values among the experimental groups and verified with Wilcoxon matched pairs test for hardness values and Mann Whitney U for flexural strength and fracture toughness. RESULTS. XRD analysis showed no monoclinic phase in XT and P after aging. Only Group T showed statistically significant decreases in hardness after aging. Hydrothermal aging showed a significant decrease in flexural strength and fracture toughness in group T and ST, while group XT and P showed no effect of aging on fractural strength and fracture toughness with P<.05. CONCLUSION. Hydrothermal aging caused reduction in mechanical properties such as surface hardness, biaxial flexural strength, and fracture toughness of Y-TZP zirconia. However, cubic-containing zirconia (more than 30% by volume of cubic crystal) was assumed to have high resistance to hydrothermal degradation. Clinical significance: Cubic-containing zirconia could withstand the intraoral aging condition. It could be suggested to use as a material for fabrication of esthetic dental restoration.