• Journal of Electrical Engineering and Technology
• /
• 제9권3호
• /
• pp.957-963
• /
• 2014

Converter transformers play important roles in high-voltage direct current transmission systems. This paper presents experimental and analysis results of the combined electrical and thermal aging of oil-impregnated paper at pulsating DC voltages. Breakdown voltages and time-to-breakdown of oil-paper specimens were measured by using short-time and constant-stress tests. The breakdown characteristics of combined electrical and thermal aging on insulation system were discussed. According to the relationship between failure time and aging temperature, the two-parameter Weibull model was improved. On the basis of the competing risk algorithm and the improved Weibull model, the two factors failure model was calculated. And the influence of temperature in the insulation system has been analyzed. This model performs better than the two-parameter Weibull model when both time and temperature are considered as variables in estimating the lifetime of oil-paper insulation.

• Advances in nano research
• /
• 제12권6호
• /
• pp.629-638
• /
• 2022

This work shows the impregnation of scents using a graphene sponge (GS). This was functionalized by the modified Hummers method, pursuing to add different functional groups. It is proposed to achieve the release and seek to control it through electrical potential applied to the graphene sponge with essential oils. The graphene sponge was functionalized and steeped with two kinds of oil. The electrochemical study demonstrates the variation in the electrochemical behaviour of the functionalized graphene sponge without and impregnated with oil. The release of the oil and its aromatic scents was carried out by applying an electrical potential of 30 V, with a release rate of 1.86 mg/min. The heating of the sample that causes the release of oil, associated with the electrical resistance of the system, reaches temperatures of about 150℃. The essential oils, graphene sponge, surfactant, graphene sponge with essential oils, graphene sponge recuperated after applying electric potential, graphene sponge recovered by temperature and dipropylene glycol (DPG) were characterized using Fourier transformed infrared spectroscopy (FTIR), digital microscopy, and x-ray photoelectron spectroscopy (XPS).

• Tribology and Lubricants
• /
• 제13권3호
• /
• pp.108-114
• /
• 1997

The electrical and frictional properties of new sintered-metal bearing (S-bearing) with varying loads and speeds were measured. Also those were compared with the same products(J-bearing) made in Japan and the conventionally used ball bearing. The test results show that the frictional values of S-bearing are less than those of J-bearing, and that S-bearing operates in full-hydrodynamic lubrication regime. The values of rating current, starting time and jitter reveal that S-bearing is superior to J-bearing as well as ball bearing.

• 한국표면공학회지
• /
• 제54권2호
• /
• pp.90-95
• /
• 2021

Surface modification technique enabling the control of condensation provides various benefit in various engineering systems, such as heat transfer, desalination, power plants, and so on. In this study, lubricant oil-impregnation into Teflon-coated nanoporous anodic oxide layer of aluminum to enhance a de-wetting and mobility of water droplet on surface. Due to the surface treatment improving water-repellency, the condensation mode is changed to dropwise, thus the frequency of sliding condensed water droplet on surface is increased. For these reasons, the surface of oil-impregnated Teflon-coated nanoporous anodic aluminum oxide shows significantly enhanced condensation heat transfer compared to bare aluminum surface. In addition, the porosity of anodic aluminum oxide affected the mobility of water droplet even with oil-impregnation and Teflon-coating, indicating that the optimization of porous structure of anodic oxide is required for maximizing the condensation heat transfer.

• 전기의세계
• /
• 제27권6호
• /
• pp.76-83
• /
• 1978

This paper reveals the results of fundamental experiments with the breakdown strength- and treeing phenomena, by A.C voltage and impulse voltage, of cross-linked polyethylene insulator, respectively compared in each case of the various specimens; nonvoid, air void, water void, oil void and oil impregnated one, all articially made. In this research, the V-t and V-n characteristics are investigated by means of the Weibull distribution and are analysed the characteristics of fatigue breakdown caused by the A.C and impulse voltage. Based on numerous tests, treeing effect and treeing breakdown mechanism is investigated through microscopic photographs taken to clarify the shapes of each tree and treeing breakdown phenomena.

• 공업화학
• /
• 제23권6호
• /
• pp.604-607
• /
• 2012

본 연구에서는 표면적이 높은 제올라이트나 촤를 지지체로 이용해 알칼리금속을 담지시킴으로써 염기 세기를 증가시켜 전이에스테르화 반응에 있어 보다 좋은 활성을 가지는 고체촉매를 만들고자 하였다. 제올라이트는 KOH 수용액으로 담지하였고, 미역촤는 calcium nitrate를 담지하여 염기의 세기를 증가시켰다. Hammett 지시약과 $CO_2$-TPD를 통하여 촉매의 특성을 분석하였다. 대두유과 메탄올을 사용하여 바이오디젤을 합성한 후 지방산 메틸에스테르 함유량을 측정함으로서 촉매의 활성을 알아보았다. 일정량까지는 담지량과 활성이 비례하였으나, 과량 담지 시 오히려 활성이 감소하는 결과를 보였다.

• 공업화학
• /
• 제23권3호
• /
• pp.344-347
• /
• 2012

본 연구에서는 기존 MgO의 염기세기를 증가시켜 전이에스테르화 반응에 있어 보다 좋은 활성을 가지는 촉매를 만들고자 하였다. MgO를 실험실에서 제조한 후 지지체로 사용하였으며 염기세기를 증가시키기 위하여 KF를 함침법으로 담지하였다. BET, XRD, XRF, $CO_2$ TPO로 촉매의 특성분석을 하였고, 대두유과 메탄올을 사용하여 바이오디젤을 합성한 후 지방산메틸에스테르 함유량을 측정함으로써 촉매의 활성을 알아보았다. 결과적으로, KF를 30% 담지한 촉매가 활성이 가장 좋은 것으로 나타났다. 이는 전이에스테르화 반응에서 중간세기 염기도가 더 많이 관여하기 때문으로 보인다.

• 한국식품과학회지
• /
• 제23권1호
• /
• pp.68-75
• /
• 1991

차과의 일종인 후피향의 종실유에는 틀리글리세리드가 92.4%로 대부분을 차지하고 있었으며, 소량성분으로 극성지절이 5.9%, 스테롤이 1.2%, 색소가 0.5%였다. 지방산 조성을 보면 C18 : 1(36.1%), C18 : 2(30.9%), C16 : 0(15.1%) C16 : (7.6%) 및 C18 : 0(3.4%)가 중요한 성분이었으며, 매우 흥미롭게도 cyclopropane 고리가 탄소 11, 12에 위치한 cis-11, 12-methylene octadecanoic acid가 4.8% 함유되어 있었다.

• Journal of Nutrition and Health
• /
• 제12권2호
• /
• pp.75-85
• /
• 1979

The Korean origin sunflower (Helianthus Annus Linn.) seed of netural lipid were analysed by thinchrography, High performance liquid chromatography, preparative Thinlayer and Gas liquid chromatography. 1) The seed oil triglyceride components were conveniently separated based on their degree of unsaturation by employing the chromatography on silica gel sintered rod impregnated with 12.5% silver nitrate. Sunflower seed oil was composed of triglyceride, especially trilinolein 57. 74% triolein 25.28%, tripalmitin 7 55% ana tristearin 9.43% by a thinctrography. 2) The fatty acid compositions of seed oil have been determined by a high performance liquid chromatographic analysis using a ALC/GPC 244 type from Waters Association (Japan) with ${\mu}$ Bondapak FFAA column. It contained stearic acid 8.59%, oleic acid 27. 19%, palmitic acid 7.50% and linoleic acid 56.72% respectively. 3) The composition of sterols were determined by a preparative Thinlayer and Gas liquid chromatographic analysis. It was noted that sitosterol was the major sterol in the Korean sunflower seed. The results showed that contents of sterols were cholesterol trace, campesterol $13_.^{22\sim}13.9%$, stigmasterol $13.8{\sim}14.1%$, If, sitosterol $58.4{\sim}60.7%$, ${\vartriangle}^7$-stigmastenol $10.2{\sim}10.5%$ and ${\vartriangle}^{7,24(25)}$-stigmastenol $3.6{\sim}3.8%$ by method of planimetry and triangulation.

• 한국연초학회지
• /
• 제18권1호
• /
• pp.76-84
• /
• 1996

Flue-cured tobaccos(cv. NC82, grade AB3O-1) expanded by super steam, volatile organic solvents(tricuorofluoromethane, propane), carbon dioxide, nitrogen, and by freeze-drying were examined for their physico-chemical properties. The expanding rate by using the organic solvents or carbon dioxide at the impregnated pressure was 70% or more, whereas the rate by super steam and freeze-drying was 49.4 and 42.9%, respectively. The contents of total sugar, alkaloid and ether extracts of the expanded tobacco by organic solvents or carbondioxide were decreased to 27.6, 20% or more, and 13%, respectively, when compared to non-expanded one. The contents of citric acid of the tobacco expanded by using trichlorofluoromethane and carbon dioxide were increased to 19.1, 14.0%, respectively. Linoleic acid in the tobacco expanded by super steam or trichlorofluoromethane was also increased to 17.3%, but malonic acid in the tobacco expanded by super steam was 18.5% less than that in the non-expanded one. Nineteen essential oil among 22 assayed in this experiment were decreased in the expanded tobaccos. Key words : expanding method, tobacco, physico-chemical properties.