• Nuclear Engineering and Technology
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• v.41 no.4
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• pp.545-548
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• 2009

Korean utility has utilized a Periodic Safety Review (PSR) that assesses the cumulative effects of plant aging, modifications, operating experience, technical developments, and site characteristics since 2000. In particular, the assessment and management of plant aging is one of the major areas in PSR. It includes identification of critical Systems, Structures, and Components (SSCs) for aging, assessment of aging effects, and implementation of aging management programs. Since the PSR system was introduced based on the atomic energy acts and related laws, PSRs of eight sets for 12 Nuclear Power Plants (NPPs) that have been operating more than 10 years have been completed. PSRs of two sets for 4 NPPs are currently being carried out. The utility has confirmed that domestic NPPs have been operated safely through these PSRs and have implemented the follow-up corrective activities to increase the nuclear safety. In this paper, the status of PSR implementation is discussed and improvement programs to conduct PSR follow-up corrective activities efficiently for NPPs are suggested based on experiences with aging assessments.

• International Journal of Automotive Technology
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• v.7 no.3
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• pp.245-249
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• 2006

Accelerated aging of engine exhaust system components such as catalytic converters are traditionally performed using an engine/dynamometer test stand. $SwRI^{(R)}'s\;FOCAS^{(R)}$ system reduces or eliminates many of the engine based aging limitations. This paper will describe several studies. These include: 1) replication of engine based catalyst aging cycles with added precision and dependability; 2) catalyst aging with and without lubricating oil effects; 3) effects of lubricant phosphorus on catalyst performance; and 4) the potential to thermally age components beyond the capabilities of engine based systems. The first study includes the development of the SwRI FOCAS system to run programmed aging conditions with or without lubricating oil. A description of the subsystems is given. The second two studies used the SwRI FOCAS system to age catalysts. One study compared thermal-only aging using of the SwRI FOCAS system with equivalent aging on a traditional engine/dynamometer test stand. The other study examined the effect on catalyst performance of two lubricating oils containing different levels of phosphorus, and compared the results to field data generated using the same oils in a fleet of vehicles.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.1
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• pp.31-37
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• 2019

This study investigates the effects of long-term artificial-aging on hardness variation in the dissimilar metal weldments for nuclear power plant facilities. These dissimilar welds are inevitably required to join the components in nozzle parts of pressurized vessels, such as austenitic stainless steels and ferritic steels. A artificial thermal aging was conducted in an electrical furnace to simulate material degradation at high temperatures. The test materials were held at the temperature of $600^{\circ}C$ for 10000 hours and interrupted at various levels of degraded specimens. The degradation of hardness is a well-known phenomenon resulting from long-term aging or high-temperature degradation of structural materials. In this study, the variation of hardness at each position was different, and complicated in relation to microstructures such as twins, grains, precipitates, phase transformations, and residual stresses in dissimilar weldments. We discussed the variation of hardness in terms of microstructural changes during long-term aging.

• Journal of Microbiology and Biotechnology
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• v.33 no.5
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• pp.680-686
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• 2023

Aging is a complex series of multi-organ processes that occur in various organisms. As such, an in vivo study using an animal model of aging is necessary to define its exact mechanisms and identify anti-aging substances. Using Drosophila as an in vivo model system, we identified Crataegus pinnatifida extract (CPE) as a novel anti-aging substance. Regardless of sex, Drosophila treated with CPE showed a significantly increased lifespan compared to those without CPE. In this study, we also evaluated the involvement of CPE in aging-related biochemical pathways, including TOR, stem cell generation, and antioxidative effects, and found that the representative genes of each pathway were induced by CPE administration. CPE administration did not result in significant differences in fecundity, locomotion, feeding amount, or TAG level. These conclusions suggest that CPE is a good candidate as an anti-aging food substance capable of promoting a healthy lifespan.

• Journal of the Korean Ceramic Society
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• v.27 no.8
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• pp.971-978
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• 1990

The ifluence of transformability and stabilized effects in tetragonal phase on the isothermal phase transformation of Y-TZP at low temperature were investigated. The transformability of Y-TZP powders were gradually increased with calcination temeprature and reached maximum at critical temperature, but when the Y-TZP powders were calcined above critical temperature, transformability of Y-TZP were gradually decreased with increasing calcination temperature. It was concluded that maximum transformability was appeared because particle size effects decreased and constrain effects increased with calcined temperature. The isothermal phase transformation during aging at 25$0^{\circ}C$ only observed in Y-TZP stabilized by constrain effects and the amounts of transformation during aging at 25$0^{\circ}C$ only observed in Y-TZP stabilized by constrain effects and the amount of transformed monoclinic phase during aging decreased with increasing constrain effects. From these results, the mechanism of isothermal phase transformation and degradation behaviors at low temperature in Y-TZP was concluded that occurred by decreasing of constrain effects due to stress relaxation at grian boundary.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.3
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• pp.45-54
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• 2000

Ignition transient is a. very rapid process lasting only in the order of 100 milliseconds and therefore it is difficult to measure all relevant ballistic properties. Numerical simulation is thus useful to quantify some of these hard to measure flow and ballistic properties. One-dimensional model was employed to study the effects of aging using simplified aging scenarios for both N-H sustainer and booster motors. Also the effects of newly designed igniter on the ignition of N-H sustainer was simulated. Radiation effects could be significant in terms of energy flux increase to the propellant surface and the energy exchange between the combustion gas itself. One dimension implementation of radiation showed significant effects for rear-mounted igniter. Implementation of radiation effects into 2-D axi-symmetric numerical model was completed and its effects on the N-H sustainer were examined. To have a reliable prediction of computer model on ignition transient, accurate chemical property data on the propellant and igniter gas are required. It was found that such property data on aged N-H motors are not available. Chemical aging model can be used to predict to some degree of accuracy effects of aging on chemical and mechanical properties. Such a model was developed, albeit 2-dimensional, to study migration of moisture through a representative solid rocket motor configuration.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.39-44
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• 2005

The effects of aging of PSF/AS4 laminates on fatigue was studied using the new energy release rate analysis. The analysis by the variational mechanics has been useful in providing fracture mechanics interpretation of matrix microcracking in cross-ply laminates. This paper describes the changes of the critical energy release rate (microcracking toughness) according to the aging period under fatigue loading. The master plot by modified Paris-law gives a characterization of a material system's resistance to microcrack formation. PSF $[0/90_{s}]_{s}$ laminates were aged at four different temperature based on the glass transition temperature for 0 to 60 days. At all temperatures, the toughness decreased with aging time. The decrease of the toughness at higher temperature was faster than at lower temperature. To assess the effects of aging on fatigue, the unaged laminates were compared with the laminates which had been aged for 60 days at 170$^{\circ}C$ near 180 $^{\circ}C$ t$_g$. The slope of dD/dN versus ${\Delta}G_m$. of the aged laminates was lower than that of the unaged laminates. There was a significant shift of the aged data to formation of microcracks at the lower values of ${\Delta}G_m$.

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.148-155
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• 2002

This research investigates the moisture and aging effects of wastepaper fiber-cement composites. Wastepaper fibers is obtained by a dry process. Wastepaper fiber-cement composites was manufactured by the hatscheck process. The effects of moisture and aging on the performance of wastepaper fiber-cement composites were investigated through accelerated laboratory tests simulating the effects of moisture sensitivity and wet-dry cycles as well as freeze-thaw cycles and long-term drying. They were shown to possess acceptable moisture and aging performance compared with virgin fiber cement composites.

• Journal of Korea Society of Industrial Information Systems
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• v.18 no.6
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• pp.25-30
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• 2013

In nanoscale MOSFET technology, aging effects such as Negative Bias Temperature Instability(NBTI), Hot carrier Injection(HCI), Time Dependent Dielectric Breakdown (TDDB) and so on which affect circuit reliability can lead to severe degradation of digital circuit performance. Therefore, this paper has proposed the adaptive compensation circuit to overcome the aging effects of digital circuits. The proposed circuit deploys a power gating structure with variable power switch width and variable forward body-biasing voltage in order to adaptively compensate for aging induced performance degradation, and has been designed in 45nm technology.

• Korean Journal of Health Education and Promotion
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• v.32 no.5
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• pp.33-42
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• 2015

Objectives: It has been found that health promotion interventions are effective to decrease morbidity among older people. The acceptability of interventions are, however, still troublesome for achievement of efficacy of health promotion interventions. The current study examines the effects of age identity and attitude toward aging on the use of health promotion programs among older people. Methods: Data from the Survey of Living Conditions of Korean Older Persons were used. Logistic regression models were tested using a nationally representative sample of 9,461 community-dwelling older individuals who are 65 years old and over. Results: Older individuals who have younger age identity and more negative attitude toward aging were less likely to use health promotion programs, after adjusting the effects of other predisposing, enabling, and need factors such as demographic characteristics and personal health characteristics. Conclusions: Strategies for mitigating the possible effects of age identity and attitude toward aging on the acceptability of health promotion programs are also discussed.