• 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.

• Journal of Powder Materials
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• v.13 no.3 s.56
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• pp.172-177
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• 2006

Aging characteristics and mechanical properties of commercial 7xxx series Al composites were investigated from viewpoint of ceramic contents. After sintering process, sintered densities of blended and composite powder were 95 and 97%, respectively. Each part was solution-treated at $475^{\circ}C$ for 60 min and aged $175^{\circ}C$. And two-step aging was also performed form $120^{\circ}C$ to $175^{\circ}C$. The aging behavior of the sintered composite pow-der was different from that of sintered blended powder. The peak aging time of the composite was rapid as well due to strain. Before aging, mechanical properties of sintered composite powder was significantly higher than that of sintered blended powder. These increments of properties were directly affected by ceramic particles. However, after aging, incremental rate of mechanical properties was slowed in the composite.

• Nuclear Engineering and Technology
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• v.54 no.2
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• pp.709-731
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• 2022

Loss of fracture resistance due to thermal aging degradation is a potential limiting factor affecting the long-term (80+ year) viability of nuclear reactors. To evaluate the effects of decades of aging in a practical time frame, accelerated aging must be employed prior to mechanical characterization. In this study, a variety of chemically and microstructurally diverse austenitic stainless steels were aged between 0 and 30,000 h at 290-400 ℃ to simulate 0-80+ years of operation. Over 600 static fracture tests were carried out between room temperature and 400 ℃. The results presented include selected J-R curves of each material as well as K_0.2mm fracture toughness values mapped against aging condition and ferrite content in order to display any trends related to those variables. Results regarding differences in processing, optimal ferrite content under light aging, and the relationship between test temperature and Mo content were observed. Overall, it was found that both the ferrite volume fraction and molybdenum content had significant effects on thermal degradation susceptibility. It was determined that materials with >25 vol% ferrite are unlikely to be viable for 80 years, particularly if they have high Mo contents (>2 wt%), while materials less than 15 vol% ferrite are viable regardless of Mo content.

• Journal of the Korean Geotechnical Society
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• v.20 no.6
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• pp.137-150
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• 2004

Aging effect of sands showed insignificant result in comparison with that of clay, so that it has not been studied so far. But, as penetration resistance increase has been observed with the lapse of time after deposition and disturbance, aging effect of sands has been actively investigated by field tests, and recently many researchers are performing not oかy field tests but also laboratory tests on sands, so aging effects of sands have been also examined by laboratory tests. In this study, to observe the aging effect of undrained static shear behavior for Nak-Dong River sand, undrained static triaxial tests were performed with changing relative density$(D_r)$, consolidation stress ratio$(K_c)$, and consolidation time. These tests showed that modulus within elastic section increased as consolidation time increased, and in addition, phase transformation point strength$(S_{PT})$ and critical stress ratio point strength $(S_{CSR})$ also increased. But pore water pressure ratio$(u/{p_c}')$ decreased as consolidation time increased, so with this various result, aging effect of static shear for sands can be observed as well.

• 전기의세계
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• v.14 no.3
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• pp.18-27
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• 1965

It is well known that the starting characteristics of the cold cathode type discharge tubes are irregular. We have two kinds of stabilization for starting characteristics of discharge tubes. Which are the aging test immediately after producing the tubes and the using characteristics. This paper was devoted primaliry to the empric study of relation between the aging and the manufacturing process. And then to stabilize the starting characteristics of discharge tubes by the irradiations of radio-isotope.

• The Journal of Korea CHUNA Manual Medicine
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• v.4 no.1
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• pp.55-65
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• 2003

The purpose of this article was to contribute to the knowledge of physiological and pathological changes of aging skeletal muscles, and of therapic method. By aging there were changes of distribution of muscle fibers, the loss of muscle mass, the loss of the number of muscle fibers, the loss of glycolysis capacity, the decrease of the oxidative enzymes and muscle vascularization in the skeletal muscles. And as a pathological change, the exhaustive maximal exercise increased oxidative stress that led to oxidative damage which were shown to be implicated in promoting aging. The property of intensity and duration exercise is important not only in keeping human health and physical fitness from oxidative stress, but also for the maintenance of well-being and quality of life.

• Proceedings of the SCSK Conference
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• 2003.09a
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• pp.313-319
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• 2003

It is well known that ascorbic acid (VC) is an important factor for several physiological reactions. In the skin, VC works as an anti-aging agent due to removing of oxidative stress generated by UV irradiation and stimulation of collagen synthesis. Thus, developing more effective VC derivatives is an important issue in creating anti-aging skin care products. Our study succeeded to develop a novel ascorbic acid derivative, ascorbic acid tetra-2-hexyldecanoate (VC-IP), which is a lipid-soluble pro-VC. The purpose of this study was to indicate the effects of VC-IP as pro-VC and anti-aging agent. First, it was examined whether VC-IP is converted to VC in physiological conditions. Since VC was detected from the cell extracts treated with VC-IP, it was indicated that VC-IP is a pro- VC.(omiited)

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.94-98
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• 2003

The microstructure of Sn1.8Bi0.8Cu0.6In alloys was evaluated at various aging time. The bumps of Sn1.8Bi0.8Cu0.6In alloys after reflowed at $250^{\circ}C$ were well-formed and had 260um height. The craters on the bumps, however, were observed. Intermetallic compounds formed on the interface between so]der and Cu/Ni UBM were consist of $(Cu,Ni)_6Sn_5$. As aging goes on up to 1000hours, the composition of Ni changed from $6.63\%$ at initial stage(as-reflowed) to $13.47\%$ at final stage(1000hours aging ). In addition, after 500hours aging, the floating of IMC to the solder was observed.

• Coupled systems mechanics
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• v.3 no.1
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• pp.53-71
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• 2014

Accurate prognoses of the durability of concrete structures require a detailed description of the continuously running aging processes and a consideration of the complete load history. Therefore, in the framework of continuous porous media mechanics a model is developed, which allows a detailed analysis of the most important aging processes of concrete as well as a flexible coupling of different processes. An overview of the prediction model and the balance equations is given. The material dependent model equations, the consequences of coupling different processes and the solution scheme are discussed. In two case studies the aging of concrete due to hydration and chloride penetration are presented, which illustrate the capabilities and the characteristics of the developed model.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.281-282
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• 2019

In recent years welfare of animals is the biggest challenge because animals, especially dogs are widely recognized as pet as well as they are using as service animals. So, for the wellbeing of the dog it is necessary to perform objective assessment to track their behavior in everyday life. In this paper, we have proposed an automatic behavior assessment system for dogs based on a neck worn and tail worn accelerometer and gyroscope platform, and data analysis techniques that recognize typical dog activities. We evaluate the system based on the analysis of 8 behavior traits in 3 dogs, incorporating 2 breeds of various sizes. Our proposed framework able to reproduce the manual assessment that is based on the video recording which is treated as gold standard that exhibits the real-life use case of automated dog behavior analysis.