• Fire Science and Engineering
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• v.30 no.2
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• pp.133-140
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• 2016

Currently, the maintenance of fire products at the site of fire-fighting property are presumably carried out by a fireand/or self. On the other hand, of the special fire-fighting property, only 3.4% of them are the target for a comprehensive precision inspection, which is performed by fire protection management firms. Aging fire products for the rest of special fire-fighting property are absolutely beyond any inspection and reliability verification. This is also true with respect to general households. In this report, the current practice of fire products' useful life management at the site of fire-fighting property were studied. For this study, 32 items of fire products were identified. For the sample data, public institutions and 17 cities and provinces were classified into 18 groups, from which 30 sample targets for each group were determined. Of these targets 422 samples were recovered, based on which this study for establishing a useful 'Management Control System of the Fire Products and its Useful Life' was conducted.

• Korean Journal of Materials Research
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• v.15 no.1
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• pp.19-24
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• 2005

For the good combination of high-temperature strength, toughness and creep property, $9-12\%$ chromium steels are often used for gas turbine compressors, steam turbine rotors, blade and casing. In this study, the correlation of microstructural evolution and mechanical properties was investigated fur the specimens heat-treated at 600, 650 and $700^{\circ}C$ for 1000, 3000 and 5000 hrs. The microstructure of as-received specimen was tempered martensite with a high dislocation density, small sub-grains and fine secondary phase such as $M_23C_6$. Aging for long-time at high temperature caused the growth of martensite lath and the decrease of dislocation density resulting in the decrease in strength. However, the evolution of secondary phases had influence on hardness, yield strength and impact property. In the group A specimen aged at $600^{\circ}C\;and\;650^{\circ}C$, Laves phase was observed. The Laves phase caused the increase of the hardness and the decrease of the impact property. In addition, the abrupt growth of secondary phases caused decrease of the impact property in both A and B group specimens.

• Journal of the Korean Vacuum Society
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• v.21 no.3
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• pp.164-170
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• 2012

The dependance of degradation on the blue-peak wavelength is investigated with the blue light-emitting diode (LED) of InGaN/GaN with respect to the optical and the electrical characteristics of the devices. The LED devices emitting the blue-peak wavelength ranging from 437 nm to 452 nm is prepared to be stressed for a long aging time with three different currents of 60 mA, 75 mA and 90 mA, respectively. The degradation of optical intensity is observed with and without phosphor in the devices. The device without phosphor has been degraded significantly as the wavelength of blue-peak is decreased while the optical intensity of LED device with phosphor become less sensitive than that of device without phosphor. The electrical property does not depend on the emission peak wavelength. However, the series-resistance of LED device is slowly increased as the aging time is increased. The deformation of device is observed severely the short wavelength of blue-peak even with the same current since the short wavelength is absorbed substantially at the materials of device during the aging time. Consequently, in order to enhance the lifetime of LED devices, it is important to understand the optical degradation property of the materials against the specific wavelengths emitted from the blue chip.

• Journal of the Korean Institute of Gas
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• v.16 no.6
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• pp.115-122
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• 2012

Polyurethane foams were synthesized with different contents and kinds of catalysts to know change of properties under various NCO index. UTM(universal testing machine), DSC(differential scanning calorimetry), SEM(scanning electron microscope) and FT-IR(Fourier transform spectroscopy) were used for studying the PUF's physical properties change. Compressive strength of PUF increased with increasing contents of catalyst. Glass transition temperature(Tg) and compressive strength of PUF using PC-8 and 33LV catalyst, increased with increasing NCO index at the aging. According to the results of Infrared spectral analysis, reduction of NCO peak was found in gelling catalyst, because unreacted NCO reacted with polyurethane. Although Tg and compressive strength of PUF using TMR-2, unchanged with increasing NCO index at the aging, because trimerization of isocyanate.

• Journal of the Korean housing association
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• v.24 no.6
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• pp.163-176
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• 2013

This paper investigates housing defects and housing satisfaction of the aged according to the personal characteristics and their housing environment. Personal interview was made on the 280 senior persons living in Jeonbuk area. Research results are following. Low levels were found in education, self privately-owned property, monthly income. Most of them live in a detached house that is outdated and obsolete. The facility defects of housing were the most serious level in case of the female senior citizen who lives alone. Their house aging was old but had the high deviation among households. Main influencing factors on facility defects of housing were perceived economic status and ownership of house, the next was age of the aged. Main influencing factors on the housing satisfaction were perceived economic status. Housing satisfaction was higher, the better economic level of the aged was, male than female, the less the age was, in case of hot-water usage in bathroom, owner of houses, no difference in floor level, larger storage space of kitchen was. According to the empirical results, we propose the supporting policy of hosing safety for the aged in order to reduce the risk and social cost. Especially the rate of population aging, the aged household, and the detached houses are higher in Jeonbuk rural areas than the other area. Housing facility defects of the elder who lives alone and house aging of theirs are serious level. Local government should have supporting system that considers local difference and characteristics of the aged housing.

• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.475-482
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• 2007

The property and applicability of the organic-inorganic synthesized penetrating and reinforcing agent, which is developed in order to improve durability of concrete structures and prevent deterioration that may occur as service years increased, are researched with experimental works. TEOS (tetra-ethoxyorthosilicate) and acrylate monomer are synthesized by the solution polycondensation method in order to formulate silicate with sol-gel process and improve durability of concrete. Additional substances such as isobutyl-orthosilicate is supplemented in order to improve the performance of the agent. After the developed organic-inorganic penetrating reinforcing agent penetrates, a flexible impact alleviating layer is formed with organic monomers as well as the agent strengthens concrete by filling up the internal pore of concrete with stable compounds after penetration. Penetrating and reinforcing agent can be applied as an effective life management method because it makes concrete more durable against the aging factors, such as chloride ion, carbonation, freezing-thawing, and compound aging.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1162-1168
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• 2015

Accelerated thermal aging of chlorosulfonated polyethylene (CSPE) was performed for 0 days, 80.82 days, and 161.63 days at 100℃, which is equivalent to 0 y, 40 y, and 80 y of aging, respectively, at 50℃. After freshwater flooding, the volume electrical resistivity of CSPE was highest after 180 days of drying, and its insulating property recovered when dried for more than 300 days. The dielectric constant of the CSPE was not measured after seawater flooding. The dielectric constant of the accelerated thermally aged CSPE was higher after freshwater flooding than that before seawater flooding. The bright, open pores of CSPE were converted into dark, closed pores after seawater flooding, and the dark, closed pores of the accelerated thermally aged CSPE samples were partly converted into bright, open pores after freshwater flooding. The apparent density of CSPE increased slightly whereas its elongation at break (EAB) decreased until 80 y of accelerated thermal aging before seawater flooding. The peak binding energies of oxygen in the non-accelerated and accelerated thermally aged CSPE for 40 y and 80 y were shifted by more than 1.0 eV after seawater and freshwater flooding. The CH2 content in the non-accelerated and accelerated thermally aged CSPE for 40 y and 80 y after seawater flooding for 5 days was lower than that before seawater flooding whereas atoms such as Cl, O, Pb, Al, Si, Sb, and S that are related to conducting ions such as Na⁺, Cl^-, Mg²⁺, SO4 ^2-, and K⁺ were relatively increased.

• Journal of the Korean Society for Heat Treatment
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• v.2 no.4
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• pp.47-55
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• 1989

The effects of thermal cycle, aging heat treatment and Boron addition on the phase transformation characteristics and mechanical properties of the shape memory alloys of Cu-Zn-Al system, which was designed to operate about $80^{\circ}C$ by this research group, were studied. From the view point of the effects of thermal cycle on the phase transformation temperature change, it was found that up to 100 cycles Ms and Af points increased by $3-7^{\circ}C$ and Mf decreased a little bit and after that all of them were remain constant, and As point was not affected. All of the phase transformation temperatures were decreased $5-7^{\circ}C$ by aging heat treatment, at $140^{\circ}C$ for 24h however the effects of thermal cycle on aged alloys were same as on unaged alloys. As the thermal cycle increased the shape memory ability decreased a little up to 20 cycles, but above that it kept almost same ability. By Boron addition, grain size was refined from $1500{\mu}m$ to about $330{\mu}m$ and the hardness, fatigue property were improved but shape memory ability was lowered.

• Korean Journal of Materials Research
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• v.10 no.8
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• pp.558-563
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• 2000

$Y_2SiO_5:Ce$ phosphor was coated with $In_2O_3$, $Al_2O_3$ and $SiO_2$ and then their cathodoluminance(CL)proper-ties required in field emission display were investigated. It was found that luminance efficiency and aging p개perty of $Y_2SiO_5:Ce$ phosphor was decreased with $In_2O_3$coating. For the case of coating, the luminance intensity was in blue phosphor was dramatically increased with $SiO_2$ coating. And also the aging property of $Y_2SiO_5:Ce$ Phosphor coated with $SiO_2$ was significantly improved compared to non-coated sample.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.6
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• pp.247-257
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• 2021

This study was started to investigate why autoclave curing (AC) specimen showed an improvement in compressive strength after immersion in water for a long time, although AC specimen did not showed a high initial compressive strength unlike our expectations. Distilled water and alkaline solutions were used for immersion and three different curing methods were engaged. It was expected that the compressive strength would be improved after immersion in alkaline solutions; however, there was little difference in compressive strength after 21 day immersion because both new crystallites produced by additional geopolymerization and expansion caused by the alkaline aggregate reaction may prevent the additional improvement in compressive strength. It was concluded that in order to secure the long-term commonality and underwater stability of the geopolymers, it is desirable aging geopolymers while immersing it underwater for more than 21 days after curing using an autoclave.