• KSBB Journal
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• v.26 no.3
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• pp.183-188
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• 2011

Adult stem cells, which have characteristic of self-renewal and multipotency, are specialized cell types, responsible for the tissue regeneration of the damaged tissue. Recent studies suggest that stem cells senescence (or stem cells' ageing) is closely associated with the variety of ageing-related phenotypes such as tissue atrophy, degenerative diseases and onset of cancers. During ageing, declining of stem cells function and subsequently occurring mal-differentiation of stem cells would be important to understand the biological process of development of ageing-related phenotypes such as tissue degenerations and cancers. This review focuses on the DNA damage stress as a cause of senescence of stem cells and their mal differentiation, which is closely link to defect of regeneration potentials and neoplastic transformation. Understanding of molecular mechanisms governingsuch events is likely to have important implications for developing novel avenues for balancing tissue homeostasis longer period of time, further leading to 'Healthy ageing'.

• Journal of the Korean Society for Heat Treatment
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• v.5 no.4
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• pp.233-239
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• 1992

A study of the precipitation process of Al-Li binary alloy at low ageing temperature has been carried by electrical resistivity measurement. Two types of G.P.zones were formed during ageing at low temperature. G.P. (1) zone and G.P. (2) zone have been formed primarily at ageing temperature below $60^{\circ}C$ and at ageing temperature range of $80^{\circ}C$ to $100^{\circ}C$, respectively. Therefore the precipitation process of Al-Li binary alloy was as follows; G.P.(1) zone ${\rightarrow}$ G.P.(2) zone ${\rightarrow}{\delta}^{\prime}{\rightarrow}{\delta}$ G.P. (1) zone might be affected by excess vacancies, but G.P. (2) zone might be affected by secondary defects. clusters and Li-vacancy pairs. The activation energy for formation of G.P. (2) zone is 0.87eV. It is lower than that of Al-Cu alloy.

• Korean Journal of Culture and Social Issue
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• v.12 no.5_spc
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• pp.29-43
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• 2006

With longevity (75 years plus and still increasing) now commonly achievable, the new challenge for individuals and society is less concerned with adding more years to life, though that remains important, and more with adding life to years. To explore the quality of long life more fully, a concept broader than healthy ageing or active ageing is needed. For this purpose, the present article describes a framework of Positive Ageing, also known as Successful Ageing, which views the quality of long life as comprising good health, physical and cognitive functional independence, and meaningful engagement with life. Narrowly defined, it refers to old people ageing well in all these aspects. More broadly defined, it refers to ageing well from midlife on. The framework also identifiesvariables that may affect the process of ageing positively. These variables include the social-cognitive styles of control, humour and future-time perspective on the one hand, and on the other hand, resources based on finance, social network and lifestyle.

• Transactions on Electrical and Electronic Materials
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• v.7 no.5
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• pp.230-234
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• 2006

One of the methods currently being investigated as a possible non-intrusive diagnostic tool for condition monitoring of power transformer and cable is the recovery voltage measurement, which will be improving the ability to detect the content of water concentration and the ageing process in the insulation system and may thus be an indicator of insulation quality and its ageing status. The polarization phenomenon was studied using RVM with oil-paper samples. In order to interpret its mechanism, the Extended Debye model was introduced. With different circuit parameters, various simulation results were gotten. Furthermore, with the test samples of different ageing condition, measurements are accomplished in the lab. On the basis of this experiment as well as theoretical analysis, correlations between polarizations and ageing were analyzed.

• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.6
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• pp.311-319
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• 2019

The number of aged bridges is increasing so that bridges over 30 years old account for about 11% of all bridges. Consequently, the development of a seismic performance evaluation method that considers the effects of ageing is essential for a seismic retrofitting process for improvement of the seismic safety of existing old bridges. Assessment of the damage situation of bridges after the recent earthquakes in Korea has been limited to the bearings, anchor, and concrete mortar on piers. The purpose of this study is to evaluate the seismic responses of PSC box girder bridges by considering the ageing effect of rubber bearings (RBs) and lead-rubber bearings (LRBs). The modification factor proposed by AASHTO is used to take into account the ageing effect in the bearings. PSC box girder bridges with RBs and LRBs were 3D modeled and analyzed with the OpenSEES program. In order to evaluate the ageing effect of RBs and LRBs, 40 near fault and 40 far field records were used as the input earthquakes. When considering the effect of ageing, the displacement responses and shear forces of bridge bearings (RBs and LRBs) were found to increase mostly under the analytical conditions. It was shown that the effect of ageing is greater in the case of RBs than in the case of LRBs.

• Nuclear Engineering and Technology
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• v.5 no.1
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• pp.55-64
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• 1973

The effect of compression in the strain ageing of Ferrovac E iron has been examined with compressive testing following the prestrain in compression. Both prestraining and testing were preformed at room temperature with the strain rate of 1.9$\times$10$^{-4}$ se $c^{-1}$ and that of 0.95$\times$10$^{-4}$ se $c^{-1}$ , respectively. Ageing was carried out at several temperatures below 8$0^{\circ}C$ using thermostatically controlled oil baths with a temperature control within$\pm$1$^{\circ}C$. It was found that the rate of strain ageing obeyed the $t^{2}$3/ law up to about five hours ageing at 6$0^{\circ}C$. The rate was slower than theses reported in case of the tensile prestrained iron. Activation energy for strain ageing has been estimated as 21.5 Kcal/mole at tile first stage of the aging process. At the second stage of ageing where the $t^{2}$3/ law is still valid, however, the activation energy was somewhat decreased. The activation energy at the first stage of ageing was about 10% larger than published results on the tensile-prestraining. This difference between the activation energies is explained in terms of the residual stress field in lattice.

• International Area Studies Review
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• v.15 no.1
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• pp.549-570
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• 2011

The purpose of this article is to review the current states and future trends in the more developed countries(MDC), the less developed countries(LDC), and Korea. In 2009, the percentage of persons ages 65 and older in the world's population is 8%. However, the ratio of elderly to the total population is higher in MDC than LDC (and Korea). In future, population ageing will be a serious social problem in the LDC (and Korea). Population ageing process will occur at a much faster rate in LDC (and Korea). The reason is that the demographic transition in LDC (and Korea) has occurred in much shorter and recent periods. Though the ageing indices such as the old-age dependency ratio, aging index, and the median ages are higher in MDC, they will change rapidly in LDC. In addition, the oldest old population will increase in LDC than MDC. Therefore, when establishing the government policy related to population ageing, we need to consider the different population ageing process between in MDC and in Korea(or LDC).

• Journal of the Korean Ceramic Society
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• v.27 no.5
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• pp.577-582
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• 1990

The synthesis conditions of fibrous calcium sulfate hemihydrate were investigated by using phosphogypsum and calcium sulfate hemihydrate. The unstable organogel was deposited by adding methanol to the saturated solution with gypsum at ageing temperature, and it was crystallized to fibrous gypsum hemihydrate while methanol was removed by rapid filtrating. In case of using calcium sulfate hemihydrate, fibrous $\beta$-calcium sulfate hemihydrate was formed by adding methanol of 67% to saturated solution at 6$0^{\circ}C$ and ageing for 5 minutes and filtering with suction. Minor components in phosphogypsum did not affect the reaction.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.39 no.1 s.119
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• pp.16-24
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• 2007

This study was performed to investigate the reaction between alkylketene dimer(AKD) and cellulose molecules in AKD-sized paper sheet. AKD was added to highly beaten($80{\pm}3^{\circ}SR$) SwBKP(ca. 0.8% on pulp) in order to have much AKD retention in the paper sheet. This AKD-sized paper sheet was aged at different temperatures, $60^{\circ}C,\;80^{\circ}C,\;105^{\circ}C\;and\;125^{\circ}C$. Changes in FT-IR spectra of AKD in paper sheet during the ageing were measured. In addition, sizing degrees of the AKD-sized paper sheet pretreated for 30 sec. at $105^{\circ}C$ were measured by HST size tester during the storage at different temperature. IR spectra of AKD-sized paper sheet preheated at $105^{\circ}C$ for 30 sec. showed unchanged spectra two absorption bands at $1849cm^{-1}\;and\;1722cm^{-1}$ which refer to the typical AKD IR bands. However, these typical AKD bands were gradually reduced with increasing ageing, completely disappeared after 6 hrs. and formed new absorption band at $1706cm^{-1}$, which refers to carbonyl stretching vibration of dialkylktone. Eventually the AKD molecule was hydrolyzed to diakylketone without formation of ${\beta}$-ketoester with cellulose in paper sheet. After 6 days ageing, a little amount of ${\beta}$-ketoester bands was identified in 6 or 7 days ageing, because of the absence of water due to long-term heating. The same tendency was observed at different ageing conditions. At the practical papermaking process, AKD reacts prevailing with water, and mostly seems to be hydrolyzed to dialkylketene. Concerned to the sizing development, AKD-sized paper sheet was shown no sizing development at the initial stage of ageing at $60^{\circ}C$ after heating treatment at $105^{\circ}C$ for 30 sec., and gradually increased the sizing degree with increasing ageing, such as Hercules Sizing Tester (HST) 130 see for 12 hr, HST 300 sec. for 3 days and HST 400 sec. for 5 days. It was concluded that hydrolyzed AKD could contributed to the sizing development of the paper sheet.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2408-2410
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• 1999

The ageing process was checked by leakage current monitoring in Inclined-Plane Method. In order to monitor leakage current, DAS with 12-bit, 8-channel A/D converter was prepared. The monitored components of leakage current were averages of the rms and peak, max peak, cumulative charge, and the number of peaks in the ranges of 1-10, 10-20, 20-30, 30-40, 40-50, >50 mA. And, erosion depth was measured to be used as the index of the ageing. So, the results of leakage current components and erosion depth measurement were compared to find one or more components of which trends of changes were similar to that of erosion.