• Explosives and Blasting
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• v.41 no.3
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• pp.73-92
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• 2023

With the increase of risk of gas explosion, various methods for indirectly estimating the explosion paramaters, which are required for the prediction of gas explosion scale and impact. In this study, the characteristics of the most frequently used methods such as TNT equivalent method, TNO multi-energy method, and BST method and the processes for determining the parameters of the methods were compared. In the case of TNT equivalent method, an adequate selection of the efficiency factor for various conditions such as the type of vapor cloud explosion and explosion material is needed. There is no objective guidelines for the selection of class number in TNO multi-energy method and it is not possible to estimate negative overpressure. It was found that there were some mistakes in the reported parameter values and suggested corrected values. BST method provides more detailed guidelines for the estimation of the explosion parameters including negative overpressure, but the graphs used in this methods are not clear. In order to overcome the problem, the graphs were redrawn. A more convenient estimation of explosion parameters with the numerical expression of the redrawn graphs will be available in the future.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1997.05a
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• pp.45-50
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• 1997

가스사고 중 단순 누설, 누설에 의한 폭발 및 화재사고가 ‘77년부터 ‘95년까지 전체사고의 97,2%를 차지하고 있고, ‘95년 한해동안에는 90%를 초과하여 발생하였으나, 사고의 원인은 명백하게 규명하면서도 폭발 또는 화재발생에 따른 가스의 누출량을 입증하기 위한 자료나 실험자료가 없어 사고조사에 곤란을 격고 있었으며, 이에 따라 가스의 누출량을 추정할 때 조정기의 용량이나 일반적인 누출량 계산식에 근거하여 가스의 누출량을 추산하여 폭발 및 화재발생의 원인을 추정하고 있는 등 사고발생과정을 설명하는데 미진한 부분이 많아 실제로 LPG의 누출량을 측정하여 그 기록을 사고조사시 활용하고 사고 발생과정을 과학적으로 입증하는데 다소 보탬이 되도록 하기 위하여 이번 실험을 실시하게 되었고 본 실험의 통계적인 수치를 전적으로 실제 사고에 적용하기란 아직까지 미흡한 점이 많다고 생각되나 정확한 사고원인조사가 가스안전관리 정책수립의 기본 바탕이 되어야 함으로 이러한 실험이 계속 발전적으로 실시되어 자료로 활용될 수 있기를 바라며, 다소 아쉽고 미흡한 점도 많은 실험이었으나 가스의 누출량에 대한 첫 실험이었다는 점에 의의를 두고, 앞으로 이와 같은 실험이 지속되어 가스안전에 관한 시험 및 자료수집이 활발해 질수 있기를 바란다. (중략)

• Explosives and Blasting
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• v.33 no.3
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• pp.1-13
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• 2015

Accidents related to gas explosion are frequently happened in foreign countries and in Korea. For the evaluation and the analysis of gas explosions, TNT equivalent methods are used. In this study, the influence of the selection of chemical equation in TNT explosion and the selection of enthalpy of the products on the explosion energy, detonation pressure, velocity of detonation, and temperature was calculated. Depending on the chemical equations, the maximum detonation pressure can be 2 times higher than the minimum. As an example for applying TNT equivalent method, an explosion of methane gas in a confined volume was assumed. With the TNT equivalent, it was possible to predict the variation of peak overpressure and impulse with the distance from the explosion location.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.6
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• pp.355-362
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• 2021

Various blast pressure calculation methods have been developed for predicting the explosion pressure of vapor cloud explosions. Empirical methods include the TNT equivalent method, and multi-energy method. The multi-energy method uses a charge strength that considers environmental factors. Although the Kinsella guideline was provided to determine the charge strength, there are limitations such as guidelines related to ignition sources. In this study, we proposed an improved charge strength guideline, by subdividing the ignition source intensity and expanding the type classification through literature analysis. To verify the improved charge strength guideline, and to compare it with the result obtained using the Kinsella guideline, four vapor cloud explosion cases which could be used to estimate the actual blast pressure were investigated. As a result, it was confirmed that the Kinsella guidelines showed an inaccurate, that is, wider pressure than the actual estimated blast pressure. However, the improved charge strength guideline enabled the selection of the intensity of the ignition source, and more subdivided types through the expansion of classification, hence it was possible to calculate the blast pressure relatively close to that of the actual case.

• Journal of the Korean earth science society
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• v.41 no.5
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• pp.478-489
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• 2020

This study presents an analysis of infrasonic signals from two accidental explosions in Gwangyang city, Jeonnam Province, Korea, on December 24, 2019, recorded at 12 infrasound stations located 151-435 km away. Infrasound propagation refracted at an altitude of ~40 km owing to higher stratospheric wind in the NNW direction, resulting in favorable detection at stations in that direction. However, tropospheric phases were observed at stations located in the NE and E directions from the explosion site because of the strong west wind jet formed at ~10 km. The transmission losses on the propagation path were calculated using the effective sound velocity structure and parabolic equation modeling. Based on the losses, the observed signal amplitudes were corrected, and overpressures were estimated at the reference distance. From the overpressures, the source energy was evaluated through the overpressure-explosive charge relationship. The two explosions were found to have energies equivalent to 14 and 65 kg TNT, respectively. At the first explosion, a flying fragment forced by an explosive shock wave was observed in the air. The energy causing the flying fragment was estimated to be equivalent to 49 kg or less of TNT, obtained from the relationship between the fragment motion and overpressure. Our infrasound propagation modeling is available to constrain the source energy for remote explosions. To enhance the confidence in energy estimations, further studies are required to reflect the uncertainty of the atmospheric structure models on the estimations and to verify the relationships by various ground truth explosions.

• Journal of the Economic Geographical Society of Korea
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• v.18 no.1
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• pp.76-86
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• 2015

In this study, we presented a method for estimating the potential population damage of the Seoul Nowon-gu area in the event of a terrorist using a vehicle improvised explosive devices (IED). Using the object-based building extraction method with orthophoto image, the area of the apartment has been determined, and the apartment's height and level were estimated based on the elevation data. Using the population estimation method based on total floor area of building, each apartment resident population was estimated, and then potential population damage at the time of terrorist attacks was estimated around the subway station through a scenario analysis. Terrorism damage using IED depends on the type of vehicle greatly because of the amount loadable explosives. Therefore, potential population damage was calculated based on the type of vehicle. In the results, the maximum potential damage population during terrorist attacks has been estimated to occur around Madeul station, Nowon-gu. The method used in this study can be used various population estimation research and disaster damage estimation.

• Journal of the Korean Data and Information Science Society
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• v.26 no.4
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• pp.791-799
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• 2015

In random walk hypothesis, we assume that current change of financial time series is independent of past values. It is interpreted as an existency of a unit root in ARMA models and many researches have been focused on whether ${\rho}$ < 1 or not. If some financial data are generated from an explosive autoregressive model, the chance of a bubble economy increases. We have to find the symptoms of it in advance. Since some well-known parameter estimators contain the parameter itself and other statistic is constructed under a specific parameter structure assumption, those are difficut to be adopted. In this paper we investigate a test for explosive autoregressive models using slope signs. We found the properties of the slope sign test statistic under both independent error and correlated error conditions, mainly by simulations.

• Explosives and Blasting
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• v.37 no.4
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• pp.10-16
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• 2019

Information on overpressure, positive phase duration, and impulse are required to assess the effects of shock waves or pressure waves on the structure. In this study, the overpressure and positive phase duration were determined by applying the Multi-Energy Method, which is found to be effective in analyzing the explosion of vapor clouds. Based on the total heat of combustion estimated in the cyclohexane vapor cloud explosion in the Nypro Ltd(UK), overpressure and positive phase duration at the distance of 40, 80, 120, 160, 200, 240, 280, 320, 360(m) from the source of explosion were evaluated. Overpressure was shown to decrease exponentially and positive phase duration increased almost linearly with distance. A probit function was used to assess the probability of damages for the structures at each distance using the overpressure and impact obtained at the above mentioned distances. The Analyses of probability of damages have shown that there is a high probability of collapse at distances within 120m, major damage to structures within 240m, and minor damage and breakage of window panes of structures occur over the entire distances.

• Explosives and Blasting
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• v.21 no.1
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• pp.85-94
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• 2003

발파후에 2차연소 또는 폭발(이하, 2차연소라 한다. )이 일어났다는 사실은 폭약이 폭발후에 어떤 가연성가스가 발생하고 그 가연성가스가 잔존하는 폭발열 또는 기타의 점화원에 의해 연소되었음을 의미한다. 폭약이 폭발하였을 때, 발생 가능한 가연성물질은 유리탄소, 일산화탄소, 수소 등으로 추정할 수 있는데 실험결과에서는 가연성물질의 주성분이 수소인 것으로 나타났다. 본 연구에서는 에멀존계 함수폭약이 산소평형, 알루미늄함량, 알루미늄형태와 크기 그리고 포장지의 두께에 따라 수소가 발생되는 양을 가스크로마토그라피를 이용하여 측정하였다. 상기의 열거한 요인들은 모두 수소발생량과 관계가 있는데, 이중에서도 가장 중요한 요인은 산소평형과 알루미늄의 함량인 것으로 나타났다. 한 예로 알루미늄이 15%가 포함되고 산소평형이 -10인 에멀존계 함수폭약은 폭발후에 19.4%의 수소를 함유하고 있는 후가스를 발생시켰으며 이 가스를 포집하여 공기중에 방출시키면서 성냥불을 가까이 하였더니 연소가 되었다. 따라서 에너지를 높이기 위하여 알루미늄의 함량을 높이고 산소평형을 지나치게 마이너스로 설계한다면, 2차연소는 언제든지 발생할 가능성이 있다고 판단된다. 알루미늄의 함량을 가능한 적게, 산소평형을 가능한 0에 가깝게 설계해야 만이 2차연소 현상을 방지할 수 있을 것이며 ㄸ한 최적의 설계뿐만이 아니라 정확한 제조와 품질검사도 2차연소 현상을 방지하는데 중요한 몫을 할 것으로 판단된다.

• The Journal of the Petrological Society of Korea
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• v.25 no.2
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• pp.143-149
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• 2016

Eruptive volumes of three monogenetic volcanoes (Songaksan tuff ring, Biyangdo scoria cone, and Ilchulbong tuff cone) with the youngest eruption age are calculated using the model, applied to Auckland Volcanic Field in New Zealand, to investigate the volcanic eruption scale and to evaluate volcanic hazard of Jeju Island. Calculated eruptive volumes of the volcanoes are $24,987,557m^3$, $9,652,025m^3$, and $11,911,534m^3$, respectively, and the volumes include crater infill, tuff ring (tuff cone), scoria cone, and lava flow. Volcanic explosivity indices of Songaksan tuff ring, Biyangdo scoria cone, and Ilchulbong tuff cone are estimated based on the eruptive volumes to be 3, 2, and 3 respectively, and eruption type is Strombolian to Surtseyan. It is assumed that the amount of emitted sulfur dioxide gas is $2-8{\times}10^3kt/y$ according to the correlation between volcanic explosivity index and volcanic sulfur dioxide index. Recent age dating researches reveal evidences of several volcanic activities during the last 10,000 years indicating the possible volcanic eruption in Jeju Island in the near future. Therefore, it is necessary for appropriate researches regarding volcanic eruption of the island to be accomplished. In addition, establishment of the evaluation and preparation system for volcanic hazard based on the researches is required.