• 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 Advanced Marine Engineering and Technology
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• v.26 no.1
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• pp.68-75
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• 2002

Stellite 12 alloy-powders were overlaid on 410 stainless steel valve seat by plasma transferred arc(PTA)process. Variation of microstructure and hardness of overlaid deposit with aging time at $750^{\circ}C$ was investigated. The deposit showed hypoeutectic microstructure, which was consisting of primary cobalt dendrite and networked $M_{7}C_{3}$type eutectic carbides. After aging new M_{23}C_{6}$ carbide was formed by the partial decomposition of $M_7C_3$ type eutectic carbides and finely dispersed $M_{23}C_6$ type carbides were also precipitated in the matrix. Hardness of the deposit was increased with increase of aging time at $750^{\circ}C$ and showed maximum value at 35hours. After showing maximum value, it was fallen down again at 70hours because of overaging. The increase of hardness in aging is ascribed to the formation of new stable $M_{23}C_6$ type carbide by the partial decomposition of $M_7C_3$ type eutectic carbides and also precipitation of finely dispersed $M_{23}C_6$ carbides in matrix.

• Journal of Bone Metabolism
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• v.25 no.4
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• pp.219-226
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• 2018

Background: Although studies and interest in sarcopenia have increased, it is still a matter of debate which muscle mass index better represents the aging process. We compared 3 indices for muscle mass (appendicular skeletal muscle mass [ASM]/weight, $ASM/height^2$, and the body mass index [BMI]-adjusted muscle mass index [ASM/BMI]) to determine which better reflected the aging process in terms of the decline in bone mineral density (BMD), visual acuity (VA), hearing power, renal function, pulmonary function, and handgrip strength. Methods: We performed a retrospective cross-sectional study using the Korea National Health and Nutrition Examination Survey in the Korean population. Between 2008 and 2011, a total of 14,415 men and 17,971 women aged 10 years or older participated in the study. We plotted the changes in the 3 indices of muscle mass and compared these with changes in BMD, VA, hearing power, renal function, pulmonary function, and handgrip strength according to each age group. Results: The ASM/BMI showed similar changes in terms of surrogate markers of the aging process, while the ASM/weight and $ASM/height^2$ showed no correlation. Conclusions: Among muscle indices for sarcopenia, only the ASM/BMI represented the aging process.

• Journal of the Korean Vacuum Society
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• v.16 no.3
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• pp.227-230
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• 2007

In the Li ion battery fabrication process, an aging step has treated as a miner step because there is not so much data to define the relationship between the phenomena generated in aging process and the battery performances. However, the OCV(open circuit voltage) change in the aging process is shown by the electrochemical absorption of the electrolyte component to the both electrodes(anode or cathode) and the absorbed layer to the electrode affects to form the solid electrolyte interface(SEI) layer during the first charge process. In this report, the adsorbed materials are designed deliberately and are cleared to affect to the SEI layer formation.

• Journal of Korean Academy of Nursing
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• v.18 no.3
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• pp.269-280
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• 1988

Although everyone grows old, perception about the aging process and aging as measured physiologically vary widely. Perecptions of aging have psychologically influence on physical aging. This study was to examine the relationships between, self-concept, perception of aging, and physical aging in the elderly and to contribute to the theory development which may direct nursing intervention to promote well-being of the aged. Subjects were 70 women residents of a nursing home for the elderly in Seoul. Data collection was done from May 15 to June 15, 1988 using interview schedules and mechanical instruments. The instruments were selected items from the Health Self Concept Scale developed by Jacox and Stewart for self concept, and Secord and Jourad's Body Cathexis Scale and Osgood's Semantic Differential Scale for perception of aging. Physical aging was measured by mechanical instruments, inspection, questions, and palpation. The data were analysed for mean, 1-test, ANOVA, and Pearson Correlation Coefficient using an S.P.S.S computerized program. The results of the analysis were as follows. 1. The mean level of self concept for the subject group was 16.97(SD＝$\pm$6.17)in a range from 6-30. The mean level of perception of aging was 39.6. (SD＝$\pm$6.51) in a range from 13-65. The mean level of physical aging was 14.09(SD＝$\pm$2.05)in a range from 8-40. 2. Relationships among self - concept, perception of aging, and physical aging. 1) There was a positive relationship between self-concept and perception of aging(r＝0.4461, p＝0.000). 2) There was a negative relationship between physical aging and perception of aging(r＝-0.2975, p＝0.006). 3) There was a tendancy toward a negative relationship between physical aging and self -concept, but not a significant relationship (r＝-0.1033, p＝0.197). 3. 1) No general charcteristic variables were related to self concept. 2) The general characteristic variable related to the level of perception of aging was religion (t＝4. 17, p＝0.001). 3) The general characteristic variable related to the level of physical aging was age (F＝12.008, p＝0.000). There was a significant relationship between self - cencept and perception of aging, and between physical aging and perception of aging. Therefore nursing intervention should focus on promoting a positive perception of aging and strengthening self- concept during the physical aging process.

• Journal of the Korean Society for Heat Treatment
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• v.31 no.3
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• pp.91-96
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• 2018

Microstructural development of ferritic 11Cr-3.45W heat-resistance steel for ultra-supercritical power plant during creep and thermal aging was investigated using electron microscopy. The test samples were isothermally aged at $700^{\circ}C$ for up to 4000 hours and subjected to creep loading at $700^{\circ}C$ for predetermined periods of lifetime to prepare the damaged materials. In this structural material, a various secondary phases are the primary influence on mechanical properties of ferritic heat-resistance steel. The typical precipitates of $M_{23}C_6$, MX and $M_2X$ secondary phases had been analyzed through qualitative and quantitative manner. Coarsening of precipitates and increase of lath width were observed during creep and thermal aging. This phenomenon was remarkable for creep process compared with isothermal aging process.

• Journal of Powder Materials
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• v.12 no.3
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• pp.220-224
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• 2005

Boehmite (AlOOH) powder with uniform pore size and high specific surface area were synthesized via sol-gel method using metal salts, $Al_2(SO_4)_3$ and $NaAlO_2$. During these synthetic process, the effects of the aging time were investigated to determine the optimal synthetic conditions of boehmite. X-ray diffraction, BET, Raman/IR, and scanning electron microscopy techniques were used for the characterization of the powder. Boehmite gel synthesized at the first stage of the experimental procedure transformed to crystalline boehmite phase after aging for 6 hours. The specific surface area of the crystalline boehmite showed a maximum value, $350m^2/g$, at aging time of 72 hours. The pore size of the boehmite increased with increasing aging time and the boehmite with average pore diameter of 3.6 nm was obtained at aging time of 96 hours.

• Journal of the FoodService Safety
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• v.3 no.1
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• pp.8-18
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• 2022

Dry-aging is one of the traditional aging processes, especially for beef. This aging process is being popular, because it produces unique brown/roasted flavor and texture that consumers prefer. However, as it is exposed to outside without packaging food safety concerns have been raised. The objective of this study was to investigate the presence of total aerobic bacteria (TAB) and pathogenic bacteria in manufacturing environment and suggest the safety management plan for the production of dry-aged meat. Surface samples from 66 environmental and 6 beef carcass samples were collected. According to the monitoring results, the contamination levels of TAB were in the order of shelves (5.4±1.1 Log CFU/cm²), cotton gloves (2.9±0.2 Log CFU/cm²), and door knobs (2.8±0.4 Log CFU/cm²) in the dry-aging room. In the door knobs, the level of mold was higher than that of yeast. These results indicate that the mold spores may be cross-contaminated with environmental factors inside the aging room. The risk factors that may occur during the manufacturing process were presented and possibility of risk was determined. From the aspect of microbiology, aging and trimming steps were determined as the critical control points. The temperature of the aging room should be maintained below 10℃ and the humidity below 75-85%. Based on the monitoring and the risk assessment of the dry-aging process, we prepared the safety management plan for the production of dry-aged meat, and it should be useful in improving the food safety of dry-aged meat.

• Journal of Marine Bioscience and Biotechnology
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• v.12 no.1
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• pp.66-74
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• 2020

Marine algae contain a variety of substances, such as mycosporine-like amino acids, which can defend against UV irradiation. Among them, Porphyra-334 derived from Porphyra yezoensis is attracting attention as a novel active ingredient for anti-aging cosmetics because of its excellent anti-oxidative, anti-inflammatory, and wound-healing properties through promoting skin cell migration. In this study, a process using direct current (DC) for increasing the yield of large-scale purification of Porphyra-334 was developed. When DC was applied to obtain Porphyra-334 efficiently, the purification time was shortened by approximately 1/4 compared with the process wherein DC was not applied; moreover, the yield of purification was improved.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.224-227
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• 2002

The relationship between the discharge aging time and the superficial layer thickness of MgO thin film was investigated in an AC PDP. The discharge characteristics of an AC PDP with the various aging time were evaluated by discharge aging experiments. We find the presence of a superficial lay which is related to the discharge characteristics during aging process. The superficial layer of MgO thin film was observed by Transmission Electron Microscope (TEM). It was found that the superficial layer thickness of MgO was dependent on discharge aging time.