• Proceedings of the KIEE Conference
• /
• 2000.07c
• /
• pp.1593-1595
• /
• 2000

We present a new procedure to evaluate the degradation in a lCr-lMo-0.25V steel. The method is based on the existence of the peak of reversible permeability in the differential magnetization around the coercive field strength. The apparatus is based on the detection of the voltage induced in a surface type coil using a lock-in amplifier tuned to a frequency to the exciting one. Results obtained the reversible permeability and Vickers hardness on the annealed samples show the peak interval of reversible permeability and Vickers hardness decreased as ageing time increased. The correlation between Vickers hardness and the peak interval of reversible permeability could well be evaluated non destructively.

• Journal of the Korean Society for Railway
• /
• v.7 no.4
• /
• pp.307-311
• /
• 2004

Arresters are the best protective device on electrical power systems against transient overvoltages generated by lightning and/or switching operation. Nonetheless, arresters are deteriorated by absorption of moisture in the environments of its use, repetition in the protective operation to overvoltages, and some defects at manufacturing. It is therefore important to estimate the electrical characteristic changes of ZnO blocks. In this paper, an accelerated ageing test by a standard lightning impulse current was carried out to extract parameters needed for arrester diagnosis, and leakage current components were measured. Total energy applied to the ZnO blocks at each time is about 1,050[J] in 8/20[${\mu}\textrm{s}$] impulse current. From the experimental results, we proposed electrical parameters and leakage current level to diagnose arrester soundness.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.11a
• /
• pp.501-504
• /
• 1999

The polymer insulators which are installed on outdoor have a great advantage than porcelain and 71ass, due to suppression of leakage current, light weight, low cost, etc. It needs variable evaluation methods for application of these insulators on service. The analysis of measuring leakage current is useful for ageing diagnosis because of monitoring in real-time. In this paper, we look over the recovery of hydrophobicity of silicone rubber in mini salt-fog chamber with leakage current monitoring. also, we understand the relation of between hydrophobicity and leakage current and discuss on method of leakage current monitoring.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.29 no.3_4 s.141
• /
• pp.561-568
• /
• 2005

The irradiation of Ultra-Violet (UV) is an efficient treatment for polymer to improve hydrophilic properties. 4-Channel PET knit fabrics were treated with UVA and UVC to develop functional and environment-friendly fabric. The fabric was treated with various treatment times and distances from UV lamps having different wavelength. FT-IR and XPS investigated the chemical changes. To confirm the change of surface properties, contact angle, surface energy and SEM were examined. The study of UV as a treatment for PET knit fabric shows significant changes in chemical and surface properties, which is proved by analyses. FT-IR and XPS analyses prove the augmentation of carboxylic, Hydrophilic groups on the surfaces treated by UV. The increase of water contact angle and surface energy means more water wettable and surface energy of PET film was substantially increased by UV irradiation time. The ageing after surface treatment had little influence on the surface energy of the irradiated PET film. SEM proves the surface modification of PET such as etching, bubble and crack. The negative effects are increased in accordance with increasing treatment time.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2009.05c
• /
• pp.99-102
• /
• 2009

This paper is to present the performance data for pressure setting method using some tile bonds for application on the Ondol-Heating floor system. For this purpose, powder and liquid tile bonds(Organic.Inorganic mixed tile bonds) were compared with the conventional tile cement for pressure setting method in the sight of the adhesive stability of porcelain tile. It tested for tiles after 14, 28days under standard condition and severe conditions. The severe conditions were water immersion and heat ageing($70^{\circ}C$). Another experimental factors concerned tile bond properties such as mixing ratio(in case of using liquid admixture), open time, which are supposed to affect the tensile strength of tile, were studied and discussed through the experiments.

• Journal of the Korean Society for Precision Engineering
• /
• v.18 no.4
• /
• pp.151-159
• /
• 2001

As huge energy transfer systems like a nuclear power plant, steam power plant and petrochemical plant are operated for a long time, mechanical properties are changed by degradation. The life time of the systems can be affected by the mechanical properties. BI(Ball Indentation) test has a potential to replace conventional fracture tests like a uniaxial tensile test, fracture toughness test, hardness test and so on. In this paper, we would like to present the ageing evaluation technique by the BI method. The four classes of the thermally aged 1Cr-!mo-0.25V specimens were prepared using an artificially accelerated aging method. Tensile tests, fracture toughness tests, hardness tests and BI tests were performed. The results of the BI tests were in good agreement with fracture characteristics by a standard fracture test method within 5%. The IDE(Indentation Deformation Energy) of a BI technique as a new parameter for evaluating a degradation was suggested and the new IDE parameter clearly depicts the degradation degree.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.07a
• /
• pp.886-889
• /
• 2001

Silicone rubber is being used for the housing material of outdoor high voltage insulators such as composite insulator, bushing, surge arrestor and cable terminator because of good tracking and erosion resistance, good hydrophobicity and recovery of hydrophobicity and chemical stability. But, the leakge current occurs on surface of the composite polymeric insulation materials when the insulator is used for a long time with severe contaminative condition and it can lead the contamination flashover. So the leakage current is important to estimate the condition of the silicone rubber surface. In this paper, aging characteristics of silicone rubber used for outdoor insulation have been hydrophobicity of silicone rubber in salt fog chamber with average leakage current monitoring for observing the transformation of surface degradation properties of silicone rubber with different ATH(alumina trihydrate, A1$_2$O$_3$$.$3H$_2$O) filler contents. The experimental results show that a higher peak leakage current and to raise a long time for tracking with increasing amount of ATH by the salt fog and heat recycle ageing.

• Journal of the Architectural Institute of Korea Planning & Design
• /
• v.34 no.11
• /
• pp.67-74
• /
• 2018

With the rapid increase in the elderly population, numerous problems arise related to the decreased cognitive function such as the declines of reaction time and concentration which are both resulting from ageing. Recently, ICT-based smart home and other residential services are being developed as a means of complementing human cognitive functions, but the elderly, who are in most cases digital-illiterate, find it hard to utilize these tools actively and if so it usually takes longer time and endeavor for the elderly to be familiarized with ICT devices. In this context, this study suggests a configuration of the holographic system in houses that complement the cognitive function of the elderly with the consideration of the interaction with the vision which is a critical function in the cognitive process. The method of this study consists of a literature review on topics including the characteristics of the cognitive function among the elderly, holographic technology and residential services; a configuration of residential services for different space types, depending on the aspects of the cognitive function among the elderly; and finally a suggestion of a holographic system configuration and application depending on various scenarios.

• Health Policy and Management
• /
• v.32 no.1
• /
• pp.21-28
• /
• 2022

Background: To investigate the association between regular physical exercise and falling experience for 2 years and fear of falling (FOF) in Korean middle-aged and elderly population. Methods: Data from the Korean Longitudinal Study on Aging was used and 3,871 participants who exercised regularly were included at 2006 and follow-up until 2018. An analysis was performed to investigate the association between exercise (exercise time per week and duration) and falls (experience over past 2 years and FOF) using the generalized estimating equation model. Results: Compared to those who exercised more than 5 hours a week (reference group), those who exercised less than 3 hours were more likely to experience falls and FOF (odds ratio [OR], 1.334; 95% confidence interval [CI], 1.059-1.682; OR, 1.218; 95% CI, 1.119-1.326, respectively). Compared to the group who exercised for more than 5 years, those who exercised for less than 1 year were more likely to experience FOF (OR, 1.310; 95% CI, 1.162-1.478). Conclusion: This study showed that there was a negative relationship between physical exercise time and falling experience and FOF in Korean 45 years or more community-dwelling adults. Based on these results, physical activity can be expected to have a positive effect on fall prevention, which implies the need for policy and research on long-term physical activity programs.

• Journal of Animal Science and Technology
• /
• v.65 no.4
• /
• pp.865-877
• /
• 2023

Thirty Hanwoo cattle including bulls, cows, and steers (n = 10 each) were slaughtered and investigated for carcass traits (weight, meat color, fat color, yield index, maturity, marbling score, back-fat thickness, and firmness) and meat quality. The meat quality such as: pH, color, cooking loss, fatty acid, thiobarbituric acid reactive substance, warner-bratzler shear force, tensile tests, and texture profiles were analyzed on longissimus lumborum (LL) muscles of the carcasses at different aging times (3 d and 21 d). The results showed that steers and cows had higher back-fat thickness and marbling score, and a lower firmness (p < 0.001) than bulls. Bulls exhibited a lower meat quality indicating by higher cooking loss, thiobarbituric acid reactive substance content, warner-bratzler shear force and tensile test values (p < 0.01). Regarding the sensory property, the bull meat also had higher hardness, and lower tenderness, juiciness and flavor scores than the cow or steer meat (p < 0.01). Additionally, the bull meat had a higher polyunsaturated fatty acid and a lower monounsaturated fatty acid contents (p < 0.01). With increased aging time, the meat tenderness was improved in all the genders. Taken together, the present study demonstrated that the gender and aging time affected the carcass traits, fatty acid and sensory quality of beef. Postmortem aging could improve the meat tenderness of all genders especially bulls.