• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.957-963
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• 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
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• v.12 no.6
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• pp.629-638
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• 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
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• v.13 no.3
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• pp.108-114
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• 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.

• Journal of the Korean institute of surface engineering
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• v.54 no.2
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• pp.90-95
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• 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
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• v.27 no.6
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• pp.76-83
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• 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.

• Applied Chemistry for Engineering
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• v.23 no.6
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• pp.604-607
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• 2012

Solid base catalysts for biodiesel production were synthesized by impregnating basic metal species on two support materials with large specific surface area : zeolite and pyrolysis char. KL zeolite and Undaria pinnatifida char were impregnated with KOH aqueous solution and calcium nitrate solution, respectively, to enhance the basic strength. The catalysts synthesized were characterized using Hammett indicators and $CO_2$-TPD analysis. Biodiesel was produced using soybean oil and methanol over the catalysts synthesized. The content of fatty acid methyl esters was measured to evaluate the catalytic activity. Generally, the catalytic activity increased with increasing quantity of basic metal impregnated but impregnation of excessive amount of metal could cause reduction in the activity.

• Applied Chemistry for Engineering
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• v.23 no.3
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• pp.344-347
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• 2012

The basic strength of the MgO catalyst was enhanced by impregnating it with KF to synthesize a highly active catalyst for the bio-diesel production. To increase basicity, KF impregnated on synthesized MgO in laboratory. The synthesized catalyst was characterized using $N_2$ adsorption-desorption, X-Ray diffraction, X-Ray fluorescence, and $CO_2$ temperature programmed desorption analyses. Bio-diesel was produced from soybean and methanol and its fatty acid methyl ester content was measured to evaluate the activity of the catalyst. The catalyst impregnated with 30 wt% KF exhibited the highest activity, which was attributed to its abundant intermediate base site.

• Korean Journal of Food Science and Technology
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• v.23 no.1
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• pp.68-75
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• 1991

The seed oil of Ternstroemia gymnanthera. a species of the Ternstroemiaceae, is mainly composed of triglyceride(92.4%), followed by polar lipids(5.9%), sterol(1.2%) and pigments(0.5%). This oil contains 4.8% of cis-11, 12-methylene octadecanoic acid(lactobacillic acid) in the fatty acid composition of the total oil. This identification is based on information from non-urea inclusion formation, silver nitrate impregnated silica gel column and gas liquid chromatography, $^1H-&\;^{13}C-nuclear$ magnetic resonance and mass spectroscopy. Smaller amounts(0.1%) of presumptive 9, 10-methylene hexadecanoic acid(dihydro malvalic acid) is also detected. The major fatty acids in this oil are C18 : 1(36.1%), C18: 2(30.9%), C16: 0(15.1%), C16: 1(7.6%) and C18: 0(3.4%).

• Journal of Nutrition and Health
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• v.12 no.2
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• pp.75-85
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• 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.

• Journal of the Korean Society of Tobacco Science
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• v.18 no.1
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• pp.76-84
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• 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.