• Nuclear Engineering and Technology
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• 제43권4호
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• pp.391-398
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• 2011

The U metal chips generated in developing nuclear fuel and a gamma radioisotope shield have been stored under immersion of water in KAERI. When the water of the storing vessels vaporizes or drains due to unexpected leaking, the U metal chips are able to open to air. A new oxidation treatment process was raised for a long time safe storage with concepts of drying under vacuum, evaporating the containing water and organic material with elevating temperature, and oxidizing the uranium metal chips at an appropriate high temperature under conditions of controlling the feeding rate of oxygen gas. In order to optimize the oxidation process the uranium metal chips were completely dried at higher temperature than $300^{\circ}C$ and tested for oxidation at various temperatures, which are $300^{\circ}C$, $400^{\circ}C$, and $500^{\circ}C$. When the oxidation temperature was $400^{\circ}C$, the oxidized sample for 7 hours showed a temperature rise of $60^{\circ}C$ in the self-ignition test. But the oxidized sample for 14 hours revealed a slight temperature rise of $7^{\circ}C$ representing a stable behavior in the self-ignition test. When the temperature was $500^{\circ}C$, the shorter oxidation for 7 hours appeared to be enough because the self-ignition test represented no temperature rise. By using several chemical analyses such as carbon content determination, X-ray deflection (XRD), Infrared spectra (IR) and Thermal gravimetric analysis (TGA) on the oxidation treated samples, the results of self-ignition test of new oxidation treatment process for U metal chip were interpreted and supported.

• 조명전기설비학회논문지
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• 제29권4호
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• pp.1-10
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• 2015

The light emitting diodes(LED) package of new structure is proposed to promote the reliability and lifespan by maximize heat dissipation occurred on the chip. We designed and fabricated the LED packages mixing the advantages of chip on board(COB) based on conventional metal printed circuit board(PCB) and the merits of Si sub-mount using base as a substrate. The proposed LED package samples were selected for the superior efficiency of the material through the sealant properties, chip characteristics, and phosphor properties evaluations. Reliability test was conducted the thermal shock test and flux rate according to the usage time at room temperature, high-temperature operation, high-temperature operation, high-temperature storage, low-temperature storage, high-temperature and high-humidity storage. Reliability test result, the average flux rate was maintained at 97.04% for each items. Thus, the Si sub-mount based LED package is expected to be applicable to high power down-light type LED light sources.

• Elastomers and Composites
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• 제36권4호
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• pp.255-261
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• 2001

Precut을 가지고 있는 고무 시편에서 서로 다른 온도에서 인장 강도의 영향을 조사하였다. 온도 조건에 따라 precut이 있는 시편과 precut이 없는 시편의 인장 강도는 서로 다른 거동을 보였다. $80^{\circ}C$에서는 임계 Precut 크기보다 더 큰 precut를 가지는 시편은 상온에서 시편보다 높은 인장 강도를 보였다. 상온에서 측정한 시편에 비하며 $80^{\circ}C$에서 측정한 시편은 잘 발달된 2차 균열들을 가지고 있는 반면, $110^{\circ}C$에서 측정한 시편의 경우 2차 균열들이 명확하게 발달하지 못하였다. 서로 다른 온도에서 인장강도의 차이는 인장시 발달된 결정화도와 균열 끝 부분에서 형성된 미세 균열 형상과 관계가 있는 것으로 보인다.

• International Journal of Aeronautical and Space Sciences
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• 제3권1호
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• pp.9-18
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• 2002

Thermal humidity characteristics were considered theoretically and experimentally. A Simply well-fitted correlation of a saturated vapor pressure-temperature curve of water was introduced based on Antoine equation to make theoretical prediction of relative humidity according to temperature variation. Characteristics of dew point were also examined theoretically and its relation with temperature and humidity was evaluated. The exact mass of water vapor in a specified humidity and temperature condition was estimated to provide useful insight into the idea about how much amount of water corresponds to a specified humidity and temperature condition in a confined system. A simple but well-fitting model of dehumidification process was introduced to anticipate the trend of relative humidity level during GN2(gaseous nitrogen) purge process in a humidity chamber. Well-suitedness of this model was also verified by comparison with experimental data. The overall appearance and specification of two thermal humidity chambers were introduced which were used to perform various thermal humidity tests in order to yield useful data necessary to support validity of theoretical models.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1994년도 추계학술대회 논문집
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• pp.74-79
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• 1994

The log-log presentation of stress versus Larson-Miller parameter is obtained by uniaxial tensile test instead of the long time creep test. The used material for example calculations is SUS304 stainless steel. The temperature of the uniaxial tensile test can be determined by the Larson-Miller parameter of the design stress and the 0.1hr's rupture time of the uniaxial tensile test. The rupture time at the design temperature and stress can be determined by the Larson-Miller parameter of the stress. The average creep rate is the total deformation of the tensile test divided by the rupture time at the design stress and temperature. The liner trend and the order of the data of the average creep rate by this method is almost same as that of experimental results.

• 대한기계학회논문집A
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• 제29권4호
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• pp.600-605
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• 2005

In this study, the ring tensile test at high temperature was suggested to evaluate the hoop tensile properties of small tube such as the cladding in the nuclear reactor Using the Arsene's ring model, the ring tensile test was performed and the test data were calibrated. From the result of the ring test with strain gauge and the numerical analysis with 1/8 model, LCRR(load-displacement conversion relationship of ring specimen) was determined. We could obtain the hoop tensile properties by means of applying the LCRR to the calibrated data of the ring tensile test. A few difference was observed in view of the shape of fractured surface and the fracture mechanism between at the high temperature and at the room temperature.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.231-236
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• 2001

A newly developed Advanced Indentation System (AIS), which is a portable and nondestructive system for evaluating tensile properties, was used to measure mechanical behavior of materials used under high temperature and pressure conditions. This test measures indentation load-depth curve during indentation and analyzes the mechanical properties related to deformation and fracture. Aging effects of Cr-Mo and Cr-Mo-V steel at high temperature were simulated. Tensile properties including yield strength and tensile strength at various temperature are obtained from the test. For all test materials and conditions, the AIS-derived results were in good agreement with those from conventional standard test method. Examples of the test results ate given and potential applications of the AIS to assess the integrity of aging structures are briefly discussed.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2004년도 한국우주과학회보 제13권2호
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• pp.281-284
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• 2004

According to the National Space Program of Korea, KARI (Korea Aerospace Research Institute) has been developing a large space simulator (working dimension; $\Phi8m\;\times\;L10m$) to verify the performance of future large satellites under the space environment conditions. Especially, a very low temperature condition of space will be simulated by shrouds covering the inside surface of the vessel. The surface of shrouds will be cooled down to 17K by liquid nitrogen (LN2) from ambient temperature and hence, an optimal LN2 circulation system design is necessary to remove gaseous nitrogen (GN2) sufficiently and maintain the shrouds at the LN2 temperature.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 전력전자학술대회
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• pp.290-291
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• 2017

This study deals with an evaluation method for testing the robustness of the 4 kW commercial power electronic cooling system to the thermal environment. The power electronic cooling system consists of a cascaded push-pull DC / DC converter, a three-phase DC / AC inverter, and an electric compressor. The system manufactured by the thermal environment evaluation test (heat distribution test, thermal impact test, high temperature operation test, temperature cycle test, low temperature operation test) for the commercial electric power cooling system for commercial vehicle proves that it is robust against thermal environment.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.423-428
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• 2006

Twenty nine HRV models have been tested for last two years since the attestation system has been started by KARSE. It is the objective of the present study to analyze the performance test results. Uncertainty analysis has been conducted to find the effects of measured variables on the uncertainties of test results. The uncertainty of enthalpy is found to be affected by the uncertainty of wet bulb temperature significantly, but not by that of dry bulb temperature for the present range of parameters. The uncertainty of effective enthalpy efficiency is calculated to be 6%P for the cooling condition, and 3%P for the heating condition approximately. In order to reduce the uncertainty of the test results, the uncertainty of wet bulb temperature should be minimized and the indoor/outdoor test conditions should be modified so as to increase the enthalpy difference.