• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.241-245
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• 1988

This paper reports the experiments regarding to diagnosis techniques for power transformers by measuring dissipation factor and moisture contents of mineral oils. Thermal aging environments of mineral oils were varied by the specially designed systems. Thermal aging of elevated temperature of $90^{\circ}C$ was performed for about 240 and 460 hours, respectively. Dissipation factor, permittivity, and water content were measured. Our test samples were not exposed to air. Dissipation factor increased while permittivity did not change. The level of dissipation factor determining the insulating quality of mineral oil was compared with the previous results of resistivity and several correction factor.

• Membrane Journal
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• v.4 no.3
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• pp.122-141
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• 1994

식품가공공장은 제품의 특성에 따라 필요로 되는 여러 가지의 단위공정이 조합되어 가동되고 있다. 식품제조 공정중 분리, 분획 및 농축은 매우 중요한 처리로 이를 위해서 증류, 증발, 원심분리, 여과 등의 조작이 절대적으로 필요하고, 최종 제품이 액상일 경우 유통중 변질 발생을 방지하기 위해 살균 공정을 반드시 거치도록 되어 있다. 또한 제품의 생산과정 중 사용되는 폐수에 의한 환경오염을 막기 위해서 폐수정화시설이 필수적으로 되어 있다. 이러한 대부분의 조작과정 중에는 열처리가 반드시 수반됨에 다라 가공원료 중에 함유된 각종 영양 성분이 부분적으로 열에 의해 파괴되고 냄새나 색 등이 변함에 따라 제품의 품질이 열화됨은 물론, 에너지 비용, 관련시설의 설치에 소요되는 부지, 시설비 및 운영비 등이 많이 필요로 된다.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.265-266
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• 2009

To know the thermal-moisture condition of the concrete is very important to expect the concrete durability such as chloride attack, carbonation, alkali-aggregate reaction, freezing damage. The purpose of this study is to establish the temperature-moisture coupled model which is based on the finite element method and measure temperature and relative humidity under the exposured condition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.406-409
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• 2002

The primary insulation system used in an oil-filled transformer is Kraft paper, wood, porcelain and, of course, oil. Modern transformers use paper that is chemically treated to improve its tensile strength properties and resistance to aging caused by immersion in oil. These insulation papers are mainly aged to thermal stress. Over the course of the insulation paper and oil's life it is exposed to high temperatures, oxygen and water. Its interaction with the steel of the tank and core plus the copper and aluminium of the windings will eventually cause the chemical properties of the oil to decay. High temperature have an effect on mechanical strength of cellulous paper using the layer insulation. We made two aging cell in which thermal aging tests of insulation papers and mineral oil are conducted. It is measured dielectric strength, number of acid, moisture, etc. of insulation paper and oil aged in the aging cells.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.81-81
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• 2010

This paper presents results of experimental investigations on natural ester regarding the breakdown strength. Aging of insulating material in a pole transformer has been studied by performing accelerated thermal aging test. Sealed aging test vessels containing copper, laminated core, Krapt paper and insulating oil(Natural oil and Mineral oil) were aged at $140^{\circ}C$ for 30days. Compared to the conventional transformer oil, electric property of the natural ester fluid is excellent.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.9
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• pp.1897-1904
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• 2002

Monotonic torsional and pure torsional low cycle fatigue(LCF) test with artificial degradation were performed on duplex stainless steel(CF8M). CF8M is used in pipes and valves in nuclear reactor coolant system. It was aged at 430$^{\circ}C$ for 3600hrs. Through the monotonic and LCF test, it is found that mechanical properties(i.e., yield strength, strain hardening exponent, strength coefficient etc.) increase and fatigue life(N$\sub$f/) decreases with degradation of material. The relationship between shear strain amplitude(${\gamma}$$\sub$a/)and N$\sub$f/ was proposed.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.125-130
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• 2001

Diagnosis or measurements using Infrared thermo-image hasn t been available. A quick diagnosis and thermal analysis can be possible when that kind of system is introduced to the investigation of each part. In this study, Infrared Camera, Thermo-vision 900 was used in order to investigate. Infrared Camera usually detects only Infrared wave from the light in order to illustrate the temperature distribution. Infrared diagnosis system can be applied to various field. Also, it is more effective to analyze temperature distribution on the machining center main-axis process.

• Solar Energy
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• v.9 no.2
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• pp.22-30
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• 1989

Since the energy storage method by means of the thermochemical reaction has no heat loss by separating the reactants under the storage period, it is remarked as one of promising means particularly for long-term heat storage. In this study, the heat-storage/-release characteristics of the reversible chemical reaction cycle, $Ca(OH)_2/CaO$, is numerically analysed by a mathematical modelling. As a result, the effectiveness of the heat exchanger by the chemical heat storage method is considerably higher than that by the sensible heat storage method. It is found that the major parameters, which determines the effectiveness of the heat exchanger, are the mass flow rate and inlet temperature of fluid, the residence time, etc.. The heat-storage/-release period can be controlled by changing the operation conditions. It is expected that the results obtained here will supply useful informations in designing a regenerative heat exchanger utilizing the thermochemical reaction.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.10
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• pp.1832-1838
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• 2010

Aging of transformer insulating material in natural ester insulating oil is compared to that in conventional transformer oil. Aging of insulating paper and insulating oil have been studied by performing accelerated thermal aging test. Sealed aging test vessels containing cooper, laminated core, Kraft paper and insulating oil(natural oil or mineral oil) were aged at $140^{\circ}C$ for 500, 1000, 1500 and 2000 hours. Insulating oils after aging are investigated with total acid number, breakdown voltage and viscosity. Also, degradation of insulating paper after aging is determined using breakdown voltage and mechanical strength. Accelerated aging studies demonstrate a slower aging rate for natural ester insulating oil compared to the rate for conventional mineral oil.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.404-405
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• 2008

This paper is analyzed that the development of intelligent terminal unit for the switchgear partial discharge diagnosis. It is the core technology for supplying with stable and trust electric as a technology that be economic of the high efficient, the maintain, the confidence and the repair. So the condition diagnosis of the switchgear is necessary by developing inteligent terminal unit.