• KSBB Journal
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• 제26권3호
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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'.

• 열처리공학회지
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• 제5권4호
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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.

• 한국심리학회지 : 문화 및 사회문제
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• 제12권5호_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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• 제7권5호
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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.

• 한국지진공학회논문집
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• 제23권6호
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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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• 제5권1호
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• pp.55-64
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• 1973

압축변형시킨 순천(0.007% 탄소포함)을 8$0^{\circ}C$이하에서 저온열처리(ageing)한 후, 열처리시간에 따라 증가하는 저항복점(lower yield point)의 변화를 압축시험으로 측정하여 그 strain ageing 효과를 조사했다. 본 실험에서 압축변형된 순철의 strain ageing 속도는 저항복응력의 증가가 그치고 중가의 60% 정도에 이를 때까지 열처리시간의 2/3승에 비례했으나, 이미 알려진 인장변형의 경우에서보다 느렸다. 이 60%의 증가는 순철을 6$0^{\circ}C$에서 약 5시간 열처리함으로써 얻었다. 압축변형된 순철의 strain ageing을 위한 활성화에너지는 열처리의 초기단계(6$0^{\circ}C$에서 약 30분)에서 21,500 cal/mole이었는데, 이것은 인장변형의 경우에서 알려진 것보다 대략 10%가 큰 값이다. 이 증가는 잔유응력에 의해 결정내에 형성되는 strain field로 설명되었다. 열처리공정의 둘깨단계(6$0^{\circ}C$에서 약 5시간까지 계속되는)에서는 그 활성화에너지가 다소 감소되는 경향이 있었다.

• 국제지역연구
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• 제15권1호
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• pp.549-570
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• 2011

이 글은 선진국, 개발도상국 그리고 한국에서의 인구고령화 현 상태와 추세를 고찰하는 것을 목적으로 한다. 2009년 현재 세계인구 중 65세 이상 노인의 비중은 8%이다. 한편 노인인구의 비율은 개발도상국(그리고 한국)보다 선진국이 훨씬 높다. 그래서 우리는 인구고령화 현상을 흔히 유럽, 미국, 일본 등 선진국에서 일어나는 현상으로 간주한다. 이는 잘못이다. 미래에는 인구고령화가 선진국보다 개발도상국 그리고 한국에서 훨씬 더 심각한 사회문제로 나타날 것이다. 인구고령화는 선진국보다 개발도상국(그리고 한국)에서 급격하게 진행되고 있다. 그것은 선진국에 비해 개발도상국에서 인구변천이 최근시점에 그리고 단기간에 이루어졌기 때문이다. 그 결과 현재 노년부양비, 노령화지수, 중위연령은 선진국이 한국과 개발도상국보다 더 높지만, 미래에는 그것들은 선진국보다 한국과 개발도상국에서 크게 그리고 급격하게 변동할 것으로 전망된다. 게다가 젊은세대의 부담을 훨씬 더 가중시키는 초고령인구도 선진국보다 개발도상국에서 급격히 증가할 것으로 전망한다. 그러므로 개발도상국에서 개인의 생존전략 혹은 정부정책을 인구고령화에 관련시켜 수립할 때, 우리는 선진국과 개발도상국에서 이와 같이 인구고령화가 상이하다는 사실을 고려할 필요가 있다.

• 한국세라믹학회지
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• 제27권5호
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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.

• 펄프종이기술
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• 제39권1호
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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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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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.