• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.251-254
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• 2004

The aging diagnosis technique using partial discharge detection method detects partial discharge signals cause of power equipment failuer and able to forecast the aging state of insulation system through analysis algorithm, in this paper accumulates HFPD signal during constant scheduled cycles to build HFPD pattern and then analyzes HFPD pattern using statistical parameters and ${\Delta}F$ pattern. The 3D pattern is composed of detected signal frequency, amplitude and repeated number and the FRPDA(frequency resolved partial discharge analysis) technique is used in 3D pattern construction. The ${\Delta}F$ pattern shows variation characteristics of amplitude gradient of consecutive HFPD signal Pulses and able to classify discharge types-internal discharge, surface discharge and coronal discharge etc. Fractal mathematics applied to ${\Delta}F$ pattern quantification and neural networks is used in aging diagnostic algorithm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.6
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• pp.495-499
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• 2020

Power factor improvement at high temperatures has been a major research topic for the development of skutterudite thermoelectric materials. Here, we attempted to optimize the process parameters for manufacturing skutterudite materials, especially for p-type systems. We focused on the effect of aging time variation to maximize the high-temperature performance of the Ce-filled Fe³CoSb¹² skutterudite system. The optimized aging time was concluded to be a key parameter for the formation of single-phase nanostructures in this p-type skutterudite system. The optimized condition was effective in reducing the bipolar effect at high temperature ranges by increasing the carrier concentration in the p-type system. To confirm the conclusions, the electrical conductivity, Seebeck coefficient, and power factor were measured. The results matched well with the microstructure and with those of an XRD analysis performed for the system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.383-386
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• 2004

DC accelerated aging characteristics of Zn-Pr-Co-Cr-La oxides-based varistors were investigated with various sintering temperatures. The varistors sintered at $1240^{\circ}C$ exhibited the highest nonlinearity, with a nonlinear exponent of 79.3 and a leakage current of $0.3\;{\mu}A$, whereas completely degraded because of thermal runaway owing to low sintered density. The varistors sintered at $1250^{\circ}C$ exhibited not only a high nonlinearity with the nonlinear exponent 61.4 and the leakage current 0.7 ${\mu}A$, but also a high stability with the variation rates of varistor voltage and nonlinear exponent are -1.01% and -10.67%, respectively, under DC stress condition such as $(0.85\;V_{1mA}/115^{\circ}C/24\;h)+(0.90\;V_{1mA}/120^{\circ}C/24\;h)+(0.95\;V_{1mA}/125^{\circ}C/24\;h)+(0.95\;V_{1mA}/150^{\circ}C/24\;h)$.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.947-952
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• 2001

The prediction model is proposed to estimate the variation of compressive strength of fly ash concrete with aging. After analyzing the experimental result with the model, the regression results are presented according to fly ash replacement content and water/cement ratio. Based on the regression results, the influence of fly ash replacement content and water/cement ratio on apparent activation energy was investigated. According to the analysis, the model provides a good estimate of compressive strength development of fly ash concrete with aging. As the fly ash replacement content increases, the limiting relative compressive strength and initial apparent activation energy become greater. The concrete with water/cement ratio smaller than 0.40 shows that the limiting relative compressive strength and apparent activation energy are nearly constant according to water/cement ratio. But, the concrete with water/cement ratio greater than 0.40 has the increasing limiting relative compressive strength and apparent activation energy with increasing water/cement ratio.

• Biomedical Science Letters
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• v.16 no.1
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• pp.65-67
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• 2010

The endoplasmic reticulum (ER) is a multifunctional intercellular organelle in which several posttranslational modification steps occurred such as protein folding, lipid biosynthesis, calcium storage and release. Perturbations that disrupt ER homeostasis lead to the misfolding of proteins in the ER lumen and up-regulation of ER signaling pathway called the unfolded protein response (UPR). Here, we have demonstrated that ageing changes the expression of ER chaperone and associated ER membrane kinases of IRE1, ATF6 and PERK.

• Journal of Ocean Engineering and Technology
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• v.8 no.1
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• pp.154-164
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• 1994

In this paper, fatigue testing was carried out under the change of aging time(0.5,1.5.10hrs) by electric heating method which is one of the useful method in the application of Robot's actuator. Fatigue degradation behaviors such as cyclic deformation property, amount of deformation, decrease in recovery and variation of transformation temperature for each specimen were examined closely, and the effect of aging time condition was studied on their fatigue degradation behaviors.

• Journal of the Korean Society of Safety
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• v.9 no.4
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• pp.69-76
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• 1994

Low density polyethylene is widely used as an insulating material In electric power cables. It is most important to know the beginning of its aging by partial discharge and UV-ray. That Is reason which we investigate chemiluminescence of the LDPE treated by partial discharge, UV-ray and corona discharge. We find that it takes one hour on spectra of IR but 0.17 minutes on chemiluminescence in the variation of chemical by partial discharge. Also we knew that Lithium carbonate-added(1phr) LDPE offered obvious suppressing effect on aging by partial discharge through the chemiluminescence. Therefore, the chemiluminescence is a highly sensitive and effective measurement method to appreciate characteristics of the treated surface and the oxidation reaction.

• Journal of the Korean Society of Safety
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• v.21 no.4 s.76
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• pp.13-18
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• 2006

In spite of frequent defect in industrial boilers, life assessment or diagnostic method for them has not been actively studied. In this research, SS400 carbon steel used in industrial boilers is simulated with artificial aging heat treatment. To do qualitative life assessment, differences in micro-structures and hardness of SS400 by the degradation time are studied. In addition, variation in material properties by aging was observed with the tensile test at room temperature and $179^{\circ}C$ and changes in ductile to brittle transition temperature was observed with the charpy impact test performed at several test temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.744-746
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• 2003

A ZnO varistor with reference voltage 250V/mm was fabricated through the control of particle size in slurry and the variation of sintering conditions. It was found that to measure the flatness of the V-I characteristic curve in the small-current region and the flatness of the V-I characteristic curve in a large-current region was improved nonlinearity of the fabricated ZnO varistor. According to the IEC 60099-4 was measured the accelerated aging test and high current test of the distribution class surge varistor which is excellent in respect to the property of ZnO varistor.

• Journal of IKEEE
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• v.4 no.2 s.7
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• pp.266-273
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• 2000

A frequency model of an OCXO (Oven Controlled X-tal Oscillator) is suggested to implement a holdover algorithm in a DP-PLL (Digital Processing-Phase Locked Loop) system. This model is presented simply with second order polynomials with respect to temperature and aging of the OCXO. The model parameters are obtained from experimental data by applying the LSM (Least Squared Method). A holdover algorithm is also suggest using the frequency model. The obtained model is verified to simulate the holdover algorithm with experimental phase data due to variation of temperature.