• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1591-1593
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• 2001

In this paper, the electrical characteristics of Insulating paper, for pole transformers, subjected to accelerated ageing were observed and the results were compared with those of virgin insulating paper. For the experiment, insulating materials for pole transformers were enclosed together in an oil bath and thermally aged under the real pole transformer operating conditions. After the accelerated ageing of the insulating materials, the dielectrics were measured and compared with the results of the virgin ones.

• Journal of Aquaculture
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• v.14 no.1
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• pp.17-27
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• 2001

Effects of temperature (10, 12, 14, 16, 18 and 2$0^{\circ}C$) and salinity (22.0, 24.5, 27.0, 29.5, 32.0 and 34.5 ppt) were studied on incubation period, hatching success, survival and growth of alevin and juvenile seabass, L. japonicus. Embryonic development was accelerated with increasing temperature but it was not influenced by salinity. Hatching success was the highest at 14$^{\circ}C$ and 34.5 ppt. Higher temperature also accelerated the development of mouth opening, absorption of yolk and oil globules, and alevin growth. Survival of the 5-day old Juvenile was accelerated in the following order : 14<16<18<20<12$^{\circ}C$. Rearing experiment of the juvenile for 30-day indicated the faster growth at 13, 20 and 27 ppt than at 34 ppt.

• Journal of the Korean Society of Tobacco Science
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• v.3 no.2
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• pp.109-114
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• 1981

This experiment was conducted with three varieties (Hicks, Burley 21, Sohyang) and cropping systems (Improved mulching, Mulching, Non mulching) of NC 2326 to analyze growth kinetics by means of growth function involving its velocity and accelerated velocity. The basic growth data were obtained by harvest method at interval of ten days from transplanting to hundred days and analyzed by , regression equation, determinant of matrix, and differentiation. The plot of total dry weight of leaves, stalk and roots per a plant vs. time forms a sigmoid curve and its function fitted logistic satisfactorily. Tobacco plant grows at an accelerated velocity. And growth velocity, symmetric about an inflection point, is proportional to biomass attained and to the difference between biomass attained and the maximum, and to the decrease according to the biomass. Of varieties and cropping systems, the most maximum velocity was 9.58g per day per plant in mulching cultivation of NC 2326 and maximum accelerated velocity was 264mg per $day^2$ per plant in Burley 21.

• Korean journal of food and cookery science
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• v.21 no.2 s.86
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• pp.149-154
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• 2005

The objective of this research was to estimate the shelf-life of 4 kinds of Korean soup (Yukkaejang, Sagol-woogeojitang, Kalbitang, and Seolleongtang), under an accelerated experiment, based on the changes in the selected physico-chemical, microbiological and sensory characteristics. The 4 kinds of Korean soup (Yukkaejang, Sagol-woogeojitang, Kalbitang and Seolleongtang) were 1.sated at $121^{\circ}C$ for 30 min. and the shelf life was evaluatedthrough accelerated experiment, based on tile changes in the physico-chemical, microbiological and sensory characteristics. No viable cells were detected in any of the treatments and no significant differences were shown in pH, TBA and Hunter's color values for 3 weeks at $37^{\circ}C$. The periods found to be acceptable by sensory evaluation were 1 days for Yukkaejang and Kalbitang, 14 days for Sagol-woogeojitang, and 21 days for Seolleongtang. For an assumed $Q_10$ value of 2.5, shelf-life was predicted as 109 days for Yukkaejang and Kalbitang, 219 days for Sagol-woogeojitang, an d 328 days for Seolleongtang at $5^{\circ}C$, suggesting that these 4 kinds of Korean soup are suitable for commercial distribution.

• Elastomers and Composites
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• v.56 no.3
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• pp.124-135
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• 2021

Evaluating service lives of rubber materials at certain temperatures requires a destructive method (typically using elongation at break). In this study, a non-destructive method based on hardness change rate was proposed for evaluating the service life of chloroprene rubber (CR). Compared to the destructive method, this non-destructive method ensures homogeneity of CR specimens and requires a small number of samples. Thermal accelerated degradation test was conducted on the CR specimens at 55, 70, 85, 100, and 125℃, and the tensile strength, elongation at break, and hardness were measured. The results of the experiment were compared to those of the accelerated life evaluation method proposed in this study. Comparing the analyzed lives in the high temperature region (70, 85, 100, and 125℃), the difference between the service lives for the destructive method (using the elongation at break) and non-destructive method (using the hardness) was approximately 0.1 year. Therefore, it was confirmed that the proposed non-destructive evaluation method based on hardness changes can evaluate the actual life of CR under thermally accelerated degradation conditions.

• Fire Science and Engineering
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• v.31 no.1
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• pp.42-49
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• 2017

The present article reports the tracking characteristics of phenolic resin insulation material due to accelerated degradation. For assessing insulation degradation of the phenolic resin insulation material, experiment samples with equivalent years of 0, 10, 20, 30, and 40 years were produced by conducting accelerated degradation experiments using Arrhenius equation. Subsequently, tracking experiments according to KS C IEC 60112 standard were conducted for the experiment samples that were previously subjected to accelerated degradation. According to the measured results for tracking characteristics of phenolic resin subjected to accelerated degradation, upon dropping of 0.1% ammonium chloride, the risks were shown to increase by 1.38 times for the equivalent life of 10 years; 1.45 times for 20 years; 1.62 times for 30 years; and 1.94 times for 40 years based on the equivalent life of 0 year. Upon dropping of 0.01% ammonium chloride, the risks were shown to increase by 1.39 times for the equivalent life of 10 years; 1.52 times for 20 years; 1.99 times for 30 years; and 5.30 times for 40 years. According to the experimental results, the tracking risk was shown to be higher for longer-duration insulation degradation due to aging. In particular, the risk was observed to be greatly increased in the case of the equivalent life of 40 years. Therefore, it is proposed that the occurrence possibility and the risk of electric fires could be minimized through institutional preparation of recommended replacement period by considering risks such as insulation degradation, etc. due to aging.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.12
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• pp.817-821
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• 2017

As a ZnO varistor is subjected to electrical and environmental stresses, it degrades gradually, which may result in power interruption by short circuit. This study investigates changes in the electrical characteristics of ZnO varistors due to deterioration owing to energy absorption, and determines the optimal parameters for on-line diagnosis of the varistor. Two types of varistors were used for an accelerated aging experiment involving the application of the $8/20{\mu}s$ standard lightning impulse current. The electrical characteristics in terms of the reference voltage, total leakage current, resistive leakage current, and third-harmonic component of the total leakage current were measured, and their change rates were analyzed. The results revealed that the total leakage current increased slightly with an increase in the varistor absorbed energy, while the resistive leakage current and the third-harmonic component increased apparently. Therefore, the third-harmonic component of the total leakage current was proposed as the optimal parameter for on-line monitoring of ZnO varistor conditions.

• Journal of ILASS-Korea
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• v.16 no.2
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• pp.82-89
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• 2011

When pipe components made of carbon steel in nuclear, fossil, and industry plants are exposed to flowing fluid, wall thinning caused by FAC(flow accelerated corrosion) can be generated and eventually ruptured at the position of pressure boundary. The aim of this study is to identify the locations at which local wall thinning occurs and to determine the turbulence coefficient related to local wall thinning. Experiment and numerical analyses for the tee sections of down scaled piping components were performed and the results were compared. In particular, flow visualization experiment which was used alkali metallic salt was performed to find actual location of local wall thinning inside tee components. In order to determine the relationship between turbulence coefficients and local wall thinning, numerical analyses were performed for tee components in the main feedwater systems. The turbulence coefficients based on the numerical analyses were compared with the local wall thinning based on the measured data. From the comparison of the results, the vertical flow velocity component(Vr) flowing to the wall after separating in the wall due to the geometrical configuration and colliding with the wall directly at an angle of some degree was analogous to the configuration of local wall thinning.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.3
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• pp.323-334
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• 2008

According to the delivery condition, the breakage of a product occurs when it is delivered to the customers. Therefore product's makers evaluate the durability under the delivery process by accelerated life testing. In order to conduct this accelerated life testing accurately, it is very important to identify the acceleration-factor exactly between on-road and accelerated life test condition. In this paper, the acceleration-factor is identified by applying linear damage summation law, rain-flow cycle counting and Dirlik theory under the conditions of the random vibration. And approximated FEM model of the connecting-pipe to the compressor is developed for fatigue analysis. This model is finally verified by comparing the experiment results to the numerical analysis results.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.407-410
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• 2007

In the RRH (Radio Remote Head) of a WCDMA Node B System, an HPA (High Power Amplifier) is used in order to amplify the transmission RF signal. Upon designing an HPA, the design requirements demand that the intermodulation characteristics are optimized during design and that the stability of the characteristics is maintained in the field. In this DOE (Design of Experiments) research, a few vital factors that affect intermodulation characteristics were first selected; then, an optimal solution was produced for high reliability in a noisy environment in the field by employing the Taguchi Method, a statistical method used for a robust design. Furthermore, by employing HALT(High Accelerated Life Test) during the verification test, this experiment has verified that an HPA that was designed using the Taguchi Method proved to be a far more robust design than an HPA that was designed without using the method.