• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.203-206
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• 2008

Transformation of austenite to martensite during cold rolling has been widely used to strengthen metastable austenitic stainless steel grades. Aging treatment of cold worked metastable austenitic stainless steels, including ${\alpha}'$-martensite phase, results in the further increase of strength, when aging is performed in $200^{\circ}C$ to $450^{\circ}C$ temperature range. The purpose of the present study was to evaluate the effect of time and temperature on the stress-strain behavior of cold worked austenitic stainless steels. The amount of ${\alpha}'$-martensite during cold working and aging was examined by ferrite scope and X-ray diffraction (XRD). During aging at $450^{\circ}C$ for 1hr, tensile strength dramatically increased by 150MPa. Deformed metastable austenitic steels containing the "body-centered" ${\alpha}'$-martensite are strengthened by the diffusion of interstitial solute atoms during aging at low temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.406-409
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• 2002

The primary insulation system used in an oil-filled transformer is Kraft paper, wood, porcelain and, of course, oil. Modern transformers use paper that is chemically treated to improve its tensile strength properties and resistance to aging caused by immersion in oil. These insulation papers are mainly aged to thermal stress. Over the course of the insulation paper and oil's life it is exposed to high temperatures, oxygen and water. Its interaction with the steel of the tank and core plus the copper and aluminium of the windings will eventually cause the chemical properties of the oil to decay. High temperature have an effect on mechanical strength of cellulous paper using the layer insulation. We made two aging cell in which thermal aging tests of insulation papers and mineral oil are conducted. It is measured dielectric strength, number of acid, moisture, etc. of insulation paper and oil aged in the aging cells.

• Journal of the Korea Safety Management & Science
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• v.8 no.2
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• pp.81-90
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• 2006

As aging society makes rapid progress, various social problems arise. The drop of productive labor and the increase of welfare cost can be taken as examples. From this point of view, a use of aged labor is a matter of great Important to national productivity improvement. But, the participation rate of the aged in economical activity amounts to 49.8 percent and their unemployment rate does 2.1 percent. The purpose of this paper is to analyze the deterioration of skill and the lowering of adaption to new working environments due to aging. Since the aging effect is closely related to worker's productivity, it should be properly measured and analyzed. The coordination tester is used to find out activity limitations. Experimental results show that the expert skill of the workers can be improved through the effective of their experience. Therefore we can say that some operation is not influenced by aging.

• Journal of the Korean institute of surface engineering
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• v.50 no.5
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• pp.380-385
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• 2017

Mechanical characteristics of the STS 304 which is heat resistance steel were investigated after artificial aging at $650^{\circ}C$ with 1,000 hours. Tensile test specimens and small test pieces were done artificial aging up to 1,000 hours in the high temperature atmospheric environment. The results present that as the aging time increased, tensile properties were deteriorated. In the case of failure mechanism, the configuration of the fractography presented drastic change from ductile to brittle with aging time. $M_{23}C_6$ carbide leading to the change of the mechanical properties and fracture mode of the aged STS 304 steel continuously precipitated along the grain boundaries of austenite microstructure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.99-100
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• 2005

Reliability of the thyristor has a major effects on the high power systems such as HVDC, SVC and FACTs, etc. Therefore, analyzing method for thyristor aging is important to improve the stability of thyristor and high power systems. In this paper, we explain the analyzing method for examine the thyristor aging effect. And also, the thyristor aging experiments were performed to investigate the characteristic degradation due to the aging.

• Biomolecules & Therapeutics
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• v.19 no.2
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• pp.224-230
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• 2011

In order to develop silk peptide (SP) preparations possessing cognition-enhancing effect, several candidates were screened through in vitro assays, and their effectiveness was investigated in facilitated brain aging model rats. Incubation of brain acetyl-cholinesterase with SP-PN (1-1,000 ${\mu}g/ml$) led to inhibition of the enzyme activity up to 35%, in contrast to a negligible effect of SP-NN. The expression of choline acetyltransferase (ChAT) mRNA of neural stem cells expressing ChAT gene (F3.ChAT) was increased by 24-hour treatment with 10 and 100 ${\mu}g/ml$ SP-NN (1.35 and 2.20 folds) and SP-PN (2.40 and 1.34 folds). Four-week subcutaneous injections with D-galactose (150 mg/kg) increased activated hippocampal astrocytes to 1.7 folds (a marker of brain injury and aging), decreased acetylcholine concentration in cerebrospinal fluid by 45-50%, and thereby impaired learning and memory function in passive avoidance and water-maze performances. Oral treatment with SP preparations (50 or 300 mg/kg) for 5 weeks from 1 week prior to D-galactose injection exerted recovering activities on acetylcholine depletion and brain injury/aging as well as cognitive deficit induced by D-galactose. The results indicate that SP preparations restore cognitive functions of facilitated brain aging model rats by increasing the release of acetylcholine, in addition to neuroprotective activity.

• Journal of Digital Convergence
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• v.16 no.1
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• pp.93-101
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• 2018

This study aims to understand the retirement preparation of Korean baby boom generation. For this purpose, the mediation effect of the parameter of retirement preparation was confirmed to their social participation attitudes that influenced on successful aging. The research tried to present policy alternatives. The frequency analysis, description analysis, correlation analysis, hierarchical multiful-regression analysis for the collected data were conducted with SPSS 23 program. The findings are as follows; First, social participation attitudes affect successful aging. Second, social participation affects retirement preparation. Third, retirement preparation affects successful aging. Fourth, the relationship of social participation attitudes and successful aging are influenced mediation effect of retirement preparation. Finally, discussed the future research topics.

• Journal of the Korean Applied Science and Technology
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• v.38 no.6
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• pp.1616-1626
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• 2021

The purpose of this study was to investigate the relationship among perceived environmental factor, active aging and self-rated health for active senior golf participants. The collected data were analyzed using the SPSS 18.0 and AMOS 18.0 programs for Windows. Frequency analysis, confirmatory factor analysis, reliability analysis. After correlation analysis and structural equation model analysis were used. As a results derived through the research are as follows. First perceived environmental factor had a positive effect on active aging. Second, active aging had a positive effect on self-rated health. Third, perceived environmental factor had a positive effect on self-rated health. Fourth, active aging mediated the relationship between perceived environmental factor and self-rated health.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.5
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• pp.444-450
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• 2008

The conventional studies of the aging effect on cardio-vascular system are mostly obtained from human experiences and can only provide local information. In this study, the effect of fatigue fracture of arterial wall on the blood pressure was investigated by hemodynamic analysis. The aging process was simulated with three stages. The pulse wave velocity increased with age. The systolic blood pressure increases consistently but diastolic blood pressure decreases with age. The simulated results show in good accordance with the clinical ones.

• Journal of Power System Engineering
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• v.18 no.3
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• pp.14-19
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• 2014

The purpose of the study is to investigate the effect of additive catalyst according to the thermal aging of vanadia SCR catalysts. At a fresh condition, the $3V_2O_5-5WO_5-92TiO_2$ SCR showed the highest NOx conversion rate of about 30%, the performance of 5 kinds of SCR to which additive catalysts were added was not improved due to the insignificant effect of acid site control. For catalysts aged for 12h at $700^{\circ}C$, the SCR to which 3wt% Zeolite was added decreased in NOx conversion rate by 2.5% on average compared to the fresh SCR, it showed higher thermal durability than other additive catalyst. For 3Zeolite with high performance of NOx conversion rate during thermal aging, the Zeolite with stronger durability at a high temperature than other 5 kinds of SCR catalysts decreased the sintering of catalysts.