• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 일렉트렛트 및 응용기술
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• pp.132-137
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• 2002

The mold transformers have been widely used in underground substations in large building and have some advantages in comparison to oil-transformer, that is low fire risk, excellent environmental compatibility, compact size and high reliability. In addition, the application of mold transformer for outdoor is possible due to development of epoxy resin. The mold transformer generally has cooling duct between low voltage coil and high voltage coil. A mold transformer made by one body molding method has been developed for small size and low loss. The life of transformer is significantly dependent on the thermal behavior in windings. To analyse winding temperature rise, many transformer designer have calculated temperature distribution and hot spot point by finite element method(FEM). Recently, numerical analyses of transformer are studied for optimum design, that is electric field analysis, magnetic field, potential vibration, thermal distribution and thermal stress. In this paper, the temperature distribution of 50 kVA pole mold transformer for power distribution are investigated by FEM program and the temperature rise test of designed mold transformer carried out and test result is analyzed compare to simulation data. In this result, the designed mold transformer is satisfied to limit value of temperature and the other property is good such as voltage ratio, winding resistance, no-load loss, load loss, impedance voltage and percent regulation.

• 한국건축시공학회지
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• 제16권2호
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• pp.185-192
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• 2016

The semi-adiabatic calorimetry technique is a robust and easy technique that can be used to measure the temperature rise of concrete. This method is often used for investigating the maturity of concrete, as well as to predict maximum temperature rise of mass concrete using various heat loss compensating models. Semi-adiabatic calorimetry can also be used for predicting setting time of concrete. However, it has seldom been used to investigate the hydration characteristics of various cement paste samples. In this research, semi-adiabatic calorimetry and X-ray diffraction methods were used to investigate the hydration characteristics of 3 different ASTM type I Portland cements. First derivative of temperature rise (dT/dt) curve was used to isolate individual peaks. Based on the results of the experiments, a combination of dT/dt curve with XRD could be used to successfully identify hydration at a specific time period, showing its potential to be used as an alternative tool for hydration studies of cement-based materials.

• 한국가스학회지
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• 제14권6호
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• pp.7-14
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• 2010

본 연구에서는 자착화특성이 다른 DME와 n-Butane을 이용하여 다양한 흡기공급방식에 따른 HCCI엔진연소에서 압력상승률의 저감특성에 대하여 조사하였다. 연소실내부의 가스압력측정, 광학측정용 엔진을 이용한 화학발광법의 측정 그리고 화학반응수치계산을 통하여 연소실내부에서 각 국소부분의 연소특성을 파악하였다. 최대압력상승률은 DME와 n-Butane의 혼합 상태에 의해 결정되어진다. DME가 성층화되고 n-Butane이 균일하게 분포되진 조건에서 가장 많이 감소되는데 두 연료가 균일한 경우에 비해서 최대압력상승률은 0.25MPa/ms 로 저감되었고 CA50도 5deg 지각되었다.

• 비파괴검사학회지
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• 제22권6호
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• pp.609-620
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• 2002

It is well known that during tensile testing, a part of the mechanical work done on the specimen is transformed into heat energy. However, the ultimate temperature rise and the rate of temperature rise is related to the nature of the material, conditions of the test and also to the deformation behaviour of the material during loading. The recent advances in infrared sensors and image/data processing techniques enable observation and quantitative analysis of the heat energy dissipated during such tensile tests. In this study, infrared imaging technique has been used to characterise the tensile deformation in AISI type 316 nuclear grade stainless steel. Apart from identifying the different stages during tensile deformation, the technique provided an accurate full-field temperature image by which the point and time of strain localization could be identified. The technique makes it possible to visualise the region of deformation and failure and also predict the exact region of fracture in advance. The effect of thermal gradients on plastic flow in the case of interrupted straining revealed that the interruption of strain and restraining at a lower strain rate not only delays the growth of the temperature gradient, but the temperature rise per unit strain decreases. The technique is a potential NDE tool that can be used for on-line detection of thermal gradients developed during extrusion and metal forming process which can be used for ensuring uniform distribution of plastic strain.

• Earthquakes and Structures
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• 제7권3호
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• pp.365-384
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• 2014

The intensity of a ground motion can be measured by a number of parameters, some of which might exhibit robust correlations with the damage of structures subjected to that motion. In this study, 204 near-fault pulse-type records are selected and their seismic parameters are determined. Time history and damage analyses of a tested 3-storey reinforced concrete frame representing for low-rise reinforced concrete buildings subjected to those earthquake motions are performed after calibration and comparison with the available experimental results. The aim of this paper is to determine amongst several available seismic parameters, the ones that have strong correlations with the structural damage measured by a damage index and the maximum inter-story drift. The results show that Velocity Spectrum Intensity is the leading parameter demonstrating the best correlation, followed by Housner Intensity, Spectral Acceleration and Spectral Displacement. These seismic parameters are recommended as reliable parameters of near-fault pulse-type motions related to damage potential of low-rise reinforced concrete structures. The results also reaffirm that the conventional and widely used parameter of Peak Ground Acceleration does not exhibit a good correlation with the structural damage.

• 한국철도학회논문집
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• 제12권5호
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• pp.687-693
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• 2009

급전시뮬레이션과 함께 수행될 수 있는 '레일 전위 상승 분석을 위한 컴퓨터 알고리즘'이 제안되었다. 본 알고리즘에서 레일전위상승 분석은 2 단계로 진행된다. 첫 단계에서는 급전시스템의 조류해석을 수행하여 차량 및 변전소에서의 인젝션(injection) 전류를 구한다. 두 번째 단계에서는 급전시스템의 등가회로에서 변전소 및 차량을 전류 소스로 대치하고 레일의 대지로의 누설 저항이 삽입된 등가회로를 다시 구성한다. 새로 구성된 등가회로를 해석하여 변전소 및 차량 위치에서의 레일 전위를 구한다. 알고리즘의 타당성을 분석하기 위하여 컴퓨터 프로그램을 작성하여 레일전위상승을 구하였고 동일한 시스템을 대상으로 MatLab 사의 Simulink/SymPowerSystems 소프트웨어를 이용하여 레일전위를 구하였다. 2가지 방법에 의한 결과를 상호 비교 분석한 결과는 그 오차가 허용범위 내에 있음을 보여주었다. 본 알고리즘은 급전시뮬레이션과 연동하여 수행될 수 있는 장점을 가지고 있다.

• 조명전기설비학회논문지
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• 제25권6호
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• pp.68-74
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• 2011

The touch or step voltages which exist in the vicinity of a grounding electrode are closely related to the earth structure and resistivity and the ground current. The grounding design approach is required to determine the grounding electrode location where the hazardous voltages are minimized. In this paper, in order to propose a method of mitigating the electric shock hazards caused by the ground surface potential rise in the vicinity of a counterpoise, the hazards relevant to touch voltage were evaluated as a function of the soil resistivity ratio $\rho_2/\rho_1$ for several practical values of two-layer earth structures. The touch voltage and current on the ground surface just above the test electrode are calculated with CDEGS program. As a consequence, it was found that burying a grounding electrode in the soil with low resistivity is effective to reduce the electric shock hazards. In the case that the bottom layer soil where a counterpoise is buried has lower resistivity than the upper layer soil, when the upper layer soil resistivity is increased, the surface potential is slightly raised, but the current through the human body is reduced with increasing the upper layer soil resistivity because of the greater contact resistance between the earth surface and the feet. The electric shock hazard in the vicinity of grounding electrodes is closely related to soil structure and resistivity and are reduced with increasing the ration of the upper layer resistivity to the bottom layer resistivity in two-layer soil.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1633-1635
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• 1996

This phenomena of streaming-electrification is generated between solid and liquid boundary called electric double-layer which is generated by potential difference. A charge separation at interfaces between a moving fluid and a solid boundary can give rise to the generation of substantial electric field and at last these can give rise ta insulating failure. Therefore injection of the adverse-charge in streaming-electrified insulating oil to eliminate the accumulation charge and its related phenomena was investigated.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 추계학술대회논문집
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• pp.198-201
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• 1997

Aluminum alloy sheets are considered as one of the high potential substitutes for steel sheets considering weight reduction of automobiles. However, aluminum alloy sheets have drawbacks in higher prices and inferior formability compared to steel sheets. In order to achieve good deep drawability, it is imperative to obtain well developed {111} texture which gives rise to higher plastic strain ratio. It is difficult to obtain this texture from conventional rolling and annealing processes. Therefore, an unconventional rolling process which enhances shear deformation has been experimentally studied to obtain the well developed {111} texture, which in turn gives rise to a substantial increase in plastic strain ratio.

• 조명전기설비학회논문지
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• 제19권2호
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• pp.63-68
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• 2005

본 논문은 메쉬 접지전극이나 침부 매설지선이 연결된 심매설 봉상 접지전극의 실효임펄스접지임피던스의 특성을 다루었다. 시험용 접지전극의 전위상승은 인가된 임펄스 전류의 상승시간의 함수로 측정되었고, 실효임펄스접지 임피던스는 산출되었다. 심매설 봉상 접지전극의 임펄스접지임피던스는 임펄스 전류의 상승시간에 강하게 의존하며 메쉬 접지전각과의 병렬연결에 의해 확연히 감소하였다.