• Geomechanics and Engineering
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• v.13 no.1
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• pp.63-77
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• 2017

The failure mechanism of a deep hard rock tunnel under high geostress and high geothermalactivity is extremely complex. Uniaxial compression tests of granite at different temperatures were conducted. The complete stress-strain curves, mechanical parameters and macroscopic failure types of the rock were analyzed in detail. The brittleness index, which represents the possibility of a severe brittleness hazard, is proposed in this paperby comparing the peak stress and the expansion stress. The results show that the temperature range from 20 to $60^{\circ}C$ is able to aggravate the brittle failure of hard rock based on the brittleness index. The closure of internal micro cracks by thermal stress can improve the strength of hard rock and the storage capacity of elastic strain energy. The failure mode ofthe samples changes from shear failure to tensile failure as the temperature increases. In conclusion, the brittle failure mechanism of hard rock under the action of thermal coupling is revealed, and the analysis result offers significant guidance for deep buried tunnels at high temperatures and under high geostress.

• Fire Science and Engineering
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• v.12 no.4
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• pp.13-19
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• 1998

We investigated the weight loss according to temperature using Thermal Gravimetric Analysis(TGA) in order to find the thermal hazard of carbon black(Hi-Black 10, Hi-Black 50L) dusts, and the properties of dust explosion in variation of the surface functional groups and specific surface area of their dust with the same particle size. Using Hartman's dust explosion apparatus which estimate dust explosion by electric ignition after making dust disperse by compressed air, dust explosion experiments have been conducted by varying concentration and size of carbon black dust. The explosion pressure of both carbon black increased as the specific surface area increased. The results indicated that Hi-Block 50L of which specific surface area was larger three to four times than that of Hi-Black 10 was much easier of dust explosion.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.453-458
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• 2011

Air preheater uses the waste heat of the gas which burnt from the boiler from the thermal power plant. Air preheater it is established in the exit of the boiler follows in change of temperature combustion gas and the vibration which it follows in thermal expansion and contraction occurs. Air preheater with ruse the gas the seal the place where it includes a gap in the structure which it does, the vibration which it follows in change of temperature fluctuates the displacement of gap, fluctuation of the leakage quantity which occurs from gap there is a possibility of decreasing an effect to system. Part system it will be able to control the interval of gap in order, control mechanism about under establishing the place where it does the gap control actively, measures a gap the displacement sensor for is necessary. Like this displacement sensor the condition must do continuous running from atmosphere of high temperature was demanded all. This paper investigates the implementation instance of hazard existing which implement the high temperature displacement sensor, it analyzes, produces the result which it examines a model, it was a presentation. These results with the fact that it will contribute in the research for the implementation and a localization of the high temperature displacement sensor and advanced air preheater.

• Nuclear Engineering and Technology
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• v.53 no.2
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• pp.466-473
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• 2021

Fire protection is one of important issues to ensure safety and reduce risks of nuclear power plants (NPPs). While robust programs to shut down commercial reactors in any fires have been successfully maintained, the concept and associated regulatory requirements are constantly changing or strengthening by lessons learned from operating experiences and information all over the world. As part of this context, it is necessary not only to establish specific fire hazard assessment methods reflecting the characteristics of research reactors and educational reactors but also to make decisions based on advancement encompassing numerical analyses and experiments. The objectives of this study are to address fire simulation in the control room of an educational reactor and to discuss integrity of digital console in charge of main operation as well as analysis results through comparison. Three electrical fire scenarios were postulated and twenty-four thermal analyses were carried out taking into account two turbulence models, two cable materials and two ventilation conditions. Twelve supplementary thermal analyses and six subsequent structural analyses were also conducted for further examination on the temperature and heat flux of cable and von Mises stress of digital console, respectively. As consequences, effects of each parameter were quantified in detail and future applicability was briefly discussed. On the whole, higher profiles were obtained when Deardorff turbulence model was employed or polyvinyl chloride material and larger ventilation condition were considered. All the maximum values considered in this study met the allowable criteria so that safety action seems available by sustained integrity of the cable linked to digital console within operators' reaction time of 300 s.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.17 no.2
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• pp.90-100
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• 2021

Molten corium-concrete interaction (MCCI) is one of the most important phenomena that can lead to the potential hazard of late containment failure due to basemat penetration during a severe accident. In this study, MCCI analytical models of the CORQUENCH code were prepared through verification calculations of several experiments, which had been performed using concrete types similar to those of the calandria vault floor in CANDU-6 plants. The behaviors of thermal-hydraulic variables related to MCCI phenomena were analyzed under the conditions of dry floor and water flooding during the severe accident stemming from a hypothetic station blackout. Uncertainty analyses on the ablation depth were also carried out. It was estimated that the concrete ablation was not interrupted due to the continuous MCCI process under the dry condition but was terminated within 24 hours under the water flooding condition. It was confirmed that the water flooding as a mitigating action was effective to achieve the quenching and thermal stabilization of the melt discharged from the calandria vessel, showing that the present models are capable of reasonably simulating MCCI phenomena in CANDU-6 plants. This study is expected to provide the technical bases to the accident management strategy during the late-phase severe accidents.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.432-436
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• 2016

The cooler, which is the main part in a Thermal Observation Device (TOD), makes the TOD function by reducing the temperature. As the cooler is imported, overseas enterprises presented 20,000 hours as the operation time and the military have used the cooler as presented. However, failures have occurred occasionally after mass production stage. Therefore, we need to analyze the MTBF of the TOD cooler. So, military and defense industry companies collected the failure data of the TOD cooler. We analyze the MTBF of the TOD cooler using survival probability function and failure data. We find the optimal distribution by applying parametric method and estimate parameters. We determine that the Log-logistic distribution is the most appropriate for this data. Also, we analyze the reliability per hour of the TOD cooler. The result of MTBF of the TOD cooler was higher than that of presented by oversee enterprises.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.105-108
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• 2007

In resent years, temperature segregation has been identified as one of the most important concepts concerning segregation. An Infrared Camera is one of the tools that have been recognized to be effective in identifying temperature segregation. Several state of USA have recognized the problem and have enacted Specifications, and/or test procedures to eliminate temperature segregation. The major objective of this study is to investigate effective compaction method of hot mix asphalt during road construction using Infrared Camera.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.387-390
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• 2007

The mixing characteristics of heated water discharged from different types of effluents are simulated using a commercial software, Flow-3D model. In order to verify the model, the comparison of numerical results with the experimental data are conducted for each type of effluent, the submerged and surface overfall. It is observed that the numerical results show a reasonable agreement with the experimental data. Based on this study the application to the heated water discharge problem in the field can be expected as a further study and it can be the fundamental data when determining the type of effluent in a powerplant.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.6
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• pp.725-734
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• 1998

When the EED is exposed to the high power radiation, it is possible to verify systems survivability through measuring the induced current of EED. The usual method of performing a system level test is to replace the EED's with modified units from which the explosive charge has been removed and replaced with the fiber optic sensor. The thermal transient test was performed to obtain the temperature vs current characteristic curve for optical sensor installed in EED. The currents measured when the system is exposed to a known EME are compared to the proposed specfication about the EED and a decision is made on whether system is safe or not.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.04a
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• pp.371-375
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• 2011

전지는 고에너지 밀도 제품으로 화학에너지를 전환시켜 전기에너지를 운반하는 것이다. 본 실험에서는 리튬 이온전지의 열적 안정성의 위험을 평가하기 위하여 리튬이온 전해액을 Differential Scanning Calorimeter(DSC)와 modified cloed pressure vessel test(MCPVT)로 분석하였다. 실험 결과 리튬전지는 다른 전지보다 위험하며, 전지를 잘못 사용하면 열적 반응성은 연소성 물질인 전해질을 포함하고 이것이 열을 발생시켜 폭발하거나 화재가 발생할 수 있음을 제시하였다.