• Korean Journal of Materials Research
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• v.30 no.10
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• pp.502-508
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• 2020

This paper focuses on the electrical properties and stability against DC accelerated aging stress of ZnO-V₂O₅-MnO₂-Nb₂O₅-Bi₂O₃-Co₃O₄-Dy₂O₃ (ZVMNBCD) varistor ceramics sintered at 850 - 925 ℃. With the increase of sintering temperature, the average grain size increases from 4.4 to 11.8 mm, and the density of the sintered pellets decreases from 5.53 to 5.40 g/㎤ due to the volatility of V₂O₅, which has a low melting point. The breakdown field abruptly decreases from 8016 to 1,715 V/cm with the increase of the sintering temperature. The maximum non-ohmic coefficient (59) is obtained when the sample is sintered at 875 ℃. The samples sintered at below 900 ℃ exhibit a relatively low leakage current, less than 60 mA/㎠. The apparent dielectric constant increases due to the increase of the average grain size with the increase of the sintering temperature. The change tendency of dissipation factor at 1 kHz according to the sintering temperature coincides with the tendency of the leakage current. In terms of stability, the samples sintered at 900 ℃ exhibit both high non-ohmic coefficient (45) and excellent stability, 0.8% in 𝚫E_B/E_B and -0.7 % in 𝚫α/α after application of DC accelerated aging stress (0.85 E_B/85 ℃/24 h).

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.500-504
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• 2004

This research is about the result of leakage current waveform about the situation of surface leakage current and environmental changes(Salt fog, clean fog and rain) by EPDM polymer insulators' amount of salt. The researcher presents the result of changing about fundamental harmonic, 3rd harmonic and 5th harmonic from starting point of supplying power to flashover. In this study, researched environmental affects (clean fog, salt fog and .am) about surface aging of polymer insulators and used frequency spectrum of leakage current waveform to develop the diagnostic technique of surface aging. When amount of salt contents changed, surface aging stage and the degree of aging (distortion factor) about 3rd and 5th harmonir waveform on low frequency harmonic wave. The distortion factor which is harmonic percentage about basic harmonic is important pointer to evaluate the surface condition of polymer insulators.

• Journal of the Korea Society of Computer and Information
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• v.26 no.5
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• pp.127-132
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• 2021

Since the World Health Organization proposed guidelines for creating an age-friendly city in 2007, Efforts have been underway to create an age-friendly city to prepare for an aging society around the world. At this point in time, This study shows the local governments that are currently certified as an age-friendly city and the local governments that prepare for certification, improving the welfare level of single-person households for the elderly. For this purpose, Based on the theoretical discussion of elderly-friendly cities and single-person households, the policy implications are reflecting the eight major areas of the development of an aged-friendly city residential, economic, health, leisure and social participation, and for senior citizens in a single household presented policy reflections on four levels. Finally, The Limitations of the Unsurvey on the Actual Conditions of the Elderly in Single Households and future research directions were presented through the survey.

• Journal of Physiology & Pathology in Korean Medicine
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• v.22 no.4
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• pp.930-942
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• 2008

Following conclusions were derived from researching various consumption caused after surgical operation. The meaning of surgery in HyungSang medical point of view is a big flaw of the original configuration. Therefore meaning, the loss of container to store something. Changes of the body after surgery can be formation of stagnated blood and abnormal cyst of the removed part and entangled undigested food and stagnant blood. After surgery when the symptoms become chronic or the patients develop side effects as they age, consumption and aging process begins. HyungSang medical treatments of consumption caused after surgery are the followings. We should prevent aging of the framework by using appropriate medication to make up for faults in Gall Bladder, Bladder type and six meridian type by considering its form, color, pulse and symptoms. Stability of emotion that can endure various mental stimulation is needed. Prevent stagnation, indigestion, obstruction and numbness by smoothing up the constructive energy and the defensive energy in the operated part. The Heart and Kidney should be under control and Stomach and Spleen should be reinforced so that food intake is accelerated and produce vital substances and Ki and blood. Eum blood and Yang Ki should circulate around the body well. Examine daily life and if small changes in skin complexion, appetite, sleep and excretion occur, also difference in adaptation of external stimulation and mental health occurs immediate treatment and care is necessary. Treatment of side-effects caused from both aging process and post-surgery in HyungSang's view point is considered better than other ways of treatment and will contribute in expanding the field of medical science.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.5
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• pp.532-541
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• 2001

Developments of nondestructive evaluation techniques for reduction of strength or toughness by aging of material have been carried out, and the method using electrical resistivity is one of them. In this study, to examine the application of electrical resistivity to the evaluation of degradation of metallic alloy, ten different non-magnetic materials were selected as test materials. Electrical resistivities measured by DC two-point probe method and those measured by non-contact type eddy current method were compared with each other. In addition, to examine the application possibility of four-point probe technology in field, the electrical resistivities for 1Cr-lMo-0.25V steel measured by DC two-point probe method and four-point probe method were compared with each other Differences between two measured values for the 1Cr-1Mo-0.25V steel were 0.6%. Therefore, the four-point probe method can be applied to the estimation of the degradation of metallic alloy. ect.

• Smart Media Journal
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• v.6 no.2
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• pp.33-41
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• 2017

Railway point machines act as actuators that provide different routes to trains by driving switchblades from the current position to the opposite one. Since point failure caused by the aging effect can significantly affect railway operations with potentially disastrous consequences, replacement detection of point machine at an appropriate time is critical. In this paper, we propose a replacement condition detection method of point machine in railway condition monitoring systems using electrical current signals, after analyzing and relabeling domestic in-field replacement data by means of OLAP(On-Line Analytical Processing) operations in the multidimensional data cube into "does-not-need-to-be replaced" and "needs-to-be-replaced" data. The system enables extracting suitable feature vectors from the incoming electrical current signals by DWT(Discrete Wavelet Transform) with reduced feature dimensions using PCA(Principal Components Analysis), and employs SVM(Support Vector Machine) for the real-time replacement detection of point machine. Experimental results with in-field replacement data including points anomalies show that the system could detect the replacement conditions of railway point machines with accuracy exceeding 98%.

• The Korean Journal of Food And Nutrition
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• v.8 no.2
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• pp.135-144
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• 1995

Lipid oxidation in foods produce the peroxidation products, toxic substance and rancidity odor. In vivo, lipid peroxidation by free radicals or molecular singlet oxygen cause such as a damage of DNA, cancer and aging. Accordingly, the development of new compound Inhibit lipid oxidation in foods and in vivo is very important. Antioxidants are generally used as a protection material of oxidation for a storage and preservation of foods. In terms of stability of foods and health for human, development of high effective antioxidants In a nature is required. In this point of view, this paper presents the research trends of a kind of natural antioxidative substances and its antioxidative activity.

• Proceedings of the Materials Research Society of Korea Conference
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• 2006.05a
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• pp.16.2-16.2
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• 2006

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.10
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• pp.1579-1587
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• 2014

This study aimed to determine the quality characteristics of fermented wine using Nuruk according to the type of aging container (jar or stainless container) and aging time. Alcohol analysis was initiated at 40.4~39.3%, and alcohol contents in the jar and stainless container decreased as aging time increased. Volatile acid content slightly increased in the reduced pressure (RP) jar and stainless container and showed a different result in the atmospheric pressure (AP) container. Amount of acetic acid did not change either in the jar or stainless container as aging time increased. In the case of 2-thiobarbituric acid (TBA), RP was lower than AP after distillation, and TBA value did not change much either in the jar or stainless container. In the case of fusel alcohol by aging time, n-propanol content did not increase either in the jar or stainless container as aging time increased. Iso-butanol content was reduced in the jar but did not change in the stainless container. In the AP container, more aromatic components were measured on the 180th day of aging time than after distillation. High boiling point aromatic components increased in particular. In the stainless container, more aromatic components were generated on the 180th day of aging, but their amount was relatively lower than in the jar. In the jar aging sensory test, the sensory score at RP 50 cmHg was highest on the 180th day of aging. In the case of AP $80^{\circ}C$ liquor, sensory score on the 180th day was the most improved.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.31-34
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• 2005

Hygrothermal aging of the laminates of $Avimid^{R}$ K3B/IM7 in $80^{\circ}C$ water was studied as a function of immersion time prior to forming microcracks. The factors causing the $80^{\circ}C$ water to degradation of the laminates could be the degradation of the matrix toughness, change in residual stresses or interfacial damage between the fiber and matrix. The times to saturation in $80^{\circ}C$ water for the laminates and the neat resin are 100 hours and 500 hours. After 500 hours aging of the neat resin in $80^{\circ}C$ water, the glass transition temperature was changed less than $1\%$ by DSC test and the weight gain was $1.55\%$ increase. After 500 hours aging, the fracture toughness of the neat resin was decreased about $37\%$ by 3-point bending test. After 100 hours aging of the [+45/0/-45/90]s K3B/IM7 laminates in $80^{\circ}C$ water, the weight gain was $0.41\%$ increase. The $80^{\circ}C$ water diffusion rate into the neat resin was faster than into the laminates. In 100 hours, the loss of the microcracking toughness of the laminates was $28\%$ of the original toughness by our own microcracking fracture toughness criterion.