• 한국자동차공학회논문집
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• 제15권1호
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• pp.49-55
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• 2007

The characteristics of auto-ignition and combustion process of a single droplet of emulsified fuel suspended in a high-temperature air chamber have been investigated experimentally with various droplet sizes, surrounding temperatures, and water contents. The used fuels was n-Decane and it was emulsified with varied water contents whose maximum is 30%. The high-speed camera has been adopted to measure the ignition delay and flame life time. It was also applied to observe micro-explosion behaviors. The increase of droplet size and chamber temperature cause the decrease of the ignition delay time and flame life-time. As the water contents increases, the ignition delay time increases and the micro-explosion behaviors are strengthened. The starting timings of micro-explosion and fuel puffing are compared for different droplet sizes and the amount of water contents.

• 한국전산유체공학회지
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• 제21권3호
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• pp.8-14
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• 2016

A numerical analysis is conducted to estimate the core expansion and the energy behaviors induced by a core disruptive accident in a sodium-cooled fast reactor. The numerical formulation based on underwater explosion theory is carried out to simulate the core explosion inside the reactor vessel. The transient pressure, temperature and expansion of the core are examined by solving the equation of state and nonlinear governing equation of momentum conservation in one-dimensional spherical coordinates. The energy balance inside the computation domain is examined during the core expansion process. Heat transfer between the core and the sodium coolant, and the bubble rise during the expansion process are briefly investigated.

• 한국안전학회지
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• 제21권3호
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• pp.38-44
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• 2006

The majority of both small and large-scale experiments on gas explosion have been carried out in the explosion instruments with cylindrical tubes of a high length/diameter ratio and vessels of a high height/length ratio, focusing on investigating the interaction between propagating flame and obstacles inside the tubes or vessels. The results revealed that there is a strong interaction between the propagating flame and turbulence formed after the flame passes the obstacle. However this paper focuses on analyzing the pressure impact or profile outside the vent in vented gas explosion in a partially confined chamber by performing gas explosion experiments in a reduced-scale experimental assembly properly constructed. This study has considered eight different cases in gas explosion based on variation of three kinds of parameters such as height of vessel, shape of the vent and vent size, and reveals that the large vessel with big size circle vent is more danger to the target than others because the overpressure is spread out faraway horizontally and vertically.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.877-888
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• 2021

The water entry behaviors of projectiles with different cone-headed angles were studied numerically, experimentally and theoretically, mainly focusing on the hydrodynamic impact in the initial stage. Based on MMALE algorithm, it was proposed a formula of impact deceleration, which relied on the initial entry velocity and cone-headed angle. Meanwhile, in order to verify the validity of the simulation model, experiments using accelerometer and high-speed camera were carried out, and their results were in a good agreement with simulation results. Also, theoretical calculation results of cavity diameter were compared with experiments and simulation results. It was observed that the simulation method had a good reliability, which would make forecast on impact deceleration in an engineering project.

• Structural Engineering and Mechanics
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• 제89권5호
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• pp.525-538
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• 2024

An explosion from a specific source can generate high pressure, causing damage to structures and people in and around them. For the design of protective structures, although explosion overpressure is considered the main loading parameter, parts are only considered using standard design procedures, excluding special installations. Properties of the explosive, such as molecular structure, shape, dimensional properties, and the physical state of the charge, determine the results in a high-grade or low-grade explosion. In this context, it is very important to determine the explosion behaviors of the structures and to take precautions against these behaviors. Especially structures in areas with high explosion risk should be prepared for blast loads. In this study, the behavior of non-anchored blast resistant modular buildings was investigated. In the study, analyzes were carried out for cases where modular buildings were first positioned on a reinforced concrete surface and then directly on the ground. For these two cases, the behavior of the modular structure placed on the reinforced concrete floor against burst loads was evaluated with Stribeck curves. The behavior of the modular building placed directly on the ground is examined with the Pais and Kausel equations, which consider the structure-ground interaction. In the study, head and neck injuries were examined by placing test dummies to examine human injury behavior in modular buildings exposed to blast loads. Obtained results were compared with field tests. In both cases, results close to field tests were obtained. Thus, it was concluded that Stribeck curves and Pais Kausel equations can reflect the behavior of modular buildings subjected to blast loads. It was also seen at the end of the study that the human injury criteria were met. The results of the study are explained with their justifications.

• 한국전기전자재료학회논문지
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• 제29권12호
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• pp.786-790
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• 2016

Hole explosion behaviors were observed during drilling fine holes with laser beam on the LTCC green bar of $320{\mu}m$ thick after lamination of green sheets prepared by tape casting of thick film process. The incidence of these hole explosions was inversely proportional to hole sizes. The incidence of hole explosion was 20 % number of hole with the size of $60{\mu}m$ exploded for the UV radiation, while the explosion did not appear for hole sizes over $100{\mu}m$. To prevent hole explosion behavior during laser-drilling of fine holes, carbon black powder was added as an additive in the LTCC composition, which has superior thermal durability. As a consequence, hole explosion rate was suppressed to 0.8 % for the hole size of $50{\mu}m$ green sheet with the carbon black amount of 10 weight % and the laser power of 3 watt. Added carbon is thought to reduce the heat-affected region during laser drilling.

• 대한토목학회논문집
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• 제37권1호
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• pp.1-7
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• 2017

일반적으로 구조물에 폭발, 충돌, 지진과 바람 등과 같이 짧은 시간에 큰 하중이 작용하게 되면 구조물은 국부적으로 재료의 대변형(large deformation), 대회전(large rotation), 대변형률(large strain)등이 발생하게 된다. 이와 같은 현상을 해석하려면 전산연속체 역학에 기초하여 유체-구조물 상호작용 등을 고려할 수 있는 하이드로코드(Hydrocode)의 도움이 필요하다. 또한, 폭발로 인해 발생되는 순간 동역학적인 폭발 메커니즘은 매우 복잡하기 때문에 폭발실험을 병행하여 거동을 예측하는 것이 합리적인 방법이지만 막대한 비용과 시설이 요구되므로 한계가 있는 것도 사실이다. 따라서 본 논문에서는 하이드로코드인 AUTODYN을 사용하여 폭발해석한 결과를 기수행된 철근콘크리트 슬래브의 폭발실험 결과와 비교하여 폭발해석 방법의 타당성을 검토하였고, 동일한 폭발해석 모형에 대하여 철근 배근간격, 피복두께의 변화 및 수직철근 유무에 따른 폭발 손상도를 비교검토하였다. 검토한 결과, 철근의 배근간격에 대한 철근콘크리트 슬래브 두께의 비가 커질수록, 지름이 큰 철근보다 지름이 작은 철근을 많이 사용할수록, 마지막으로 수직철근을 배근할수록 콘크리트 구조물의 내폭성능이 향상됨을 알 수 있었다.

• 에너지공학
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• 제16권3호
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• pp.113-119
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• 2007

데칸에 물을 혼합하여 일정한 크기와 간격으로 유화액적배열을 형성하여 물과의 혼합비율, 액적의 수 그리고 액적 간격 등이 연소특성에 어떠한 영향을 주는가를 고온의 연소실에서 파악하였다. 각각 10%, 20%, 30%의 물을 혼합하여 유화액적을 만든 후 일정한 크기의 액적을 각각의 서스펜더에 매달아서 일정한 간격의 액적배열을 만들어 고온에서 자발화를 시켰을 때, 점화지연, 수명시간, 전연소기간 그리고 미소폭발 등의 연소특성을 비교하였다. 대기압에서 연소실의 온도를 920 K로 하고 서스펜더의 수를 3개와 5개로 하였으며 액적배열의 간격은 $3{\sim}7\;mm$ 범위에서 1 mm 간격으로 각각 실험을 수행하였다. 본 실험을 통하여 물의 혼합비율이 높을수록, 그리고 액적배열의 간격이 넓을수록 점화지연현상이 길게 나타났으며, 수명시간은 액적의 간격이 넓을수록 짧게 나타났으며 점화지연시간과 수명시간의 합인 전연소기간은 액적의 수량이 3개인 경우가 점화지연시간이 긴 관계로 5개에 비해 길게 나타남을 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제31권10호
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• pp.2867-2872
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• 2010

Two new energetic organic alkali metal salts, 1,1-diamino-2,2-dinitroethylene rubidium salt [Rb(FOX-7)${\cdot}H_2O$] and 1,1-diamino-2,2-dinitroethylene cesium salt [Cs(FOX-7)${\cdot}H_2O$], were synthesized by reacting of 1,1-diamino-2,2-dinitroethylene (FOX-7) and rubidium chloride or cesium chloride in alkali methanol aqueous solution, respectively. The thermal behaviors of Rb(FOX-7)${\cdot}H_2O$ and Cs(FOX-7)${\cdot}H_2O$ were studied with DSC and TG methods. The critical temperatures of thermal explosion of the two compounds are 216.22 and $223.73^{\circ}C$, respectively. Specific heat capacities of the two compounds were determined with a micro-DSC method, and the molar heat capacities are 217.46 and $199.47\;J\;mol^{-1}\;K^{-1}$ at 298.15 K, respectively. The adiabatic times-to-explosion were also calculated to be a certain value of 5.81 - 6.36 s for Rb(FOX-7)${\cdot}H_2O$, and 9.92 - 10.54 s for Cs(FOX-7)${\cdot}H_2O$. After FOX-7 becoming alkali metal salts, thermal decomposition temperatures of the compounds heighten with the rise of element period, but thermal decomposition processes become intense.

• 동서간호학연구지
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• 제13권2호
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• pp.130-137
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• 2007

Purpose: This study aimed to identify the safety perception and behaviors of mothers with school age children. Method: The subjects were 265 mothers of third graders in one elementary school located in metropolitan Seoul area. Framingham safety survey were used to guide the development of a self administered questionnaire for mothers. The questionnaire were sent home at school and the children returned them to their class teachers. Results: Among 265 mothers, 62 mothers (23.4%) had experience of visiting hospitals because of accidents and 201 mothers (75.8%) had no opportunities on safety education. Mothers with education higher than high school graduation showed more safety behaviors. Also, mothers having the experience of safety education showed higher scores on safety behaviors and mothers with the experience of hospital visits related to accidents showed low scores on safety behaviors. In the practice of safety behaviors, it showed high score to the traffic safety, followed by the home safety, child supervision, the safety from fire and explosion, the safety from electric devices, the safety from burn, and the safety from medicines. Conclusion: Mothers' overall practice on safety were poor. Based on these results, it is necessary to provide more safety education for mothers with school age children.