• Tunnel and Underground Space
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• v.32 no.2
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• pp.160-172
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• 2022

The design regulations for simple explosive storage in Korea only stipulate standards for the materials and thickness of the wall of the structure because the amount of explosives that can be stored is small. There is concern about secondary damage during an internal explosion in a simple storage facility, and it is necessary to reexamine the current standards. The numerical analysis for the TNT 15 kg explosion inside the simple storage was carried out by setting the factors using the robust experimental design method. The displacement of the structure generated under the same time condition was analyzed, and the contribution was evaluated. The contribution of concrete thickness was the highest, and the contribution of concrete strength and rebar arrangement was lower than that of concrete thickness. The reinforcement diameter contributed extremely little to the displacement. The structural standards of the simple storage that are currently applied are insufficient on blast resistance, and it is necessary to present new design standards. Therefore, the design factor to be applied later analysis and actual experiments were taken into consideration. For the design variables, the thickness of the concrete was 15 cm considering the displacement, the concrete strength was selected as general concrete considering the inlet discharge pressure, the factor with the lowest average displacement was selected for the reinforcement arrangement and the diameter of the reinforcement, the factor with the smallest level was selected in consideration of economic feasibility because the difference in displacement was low.

• Tunnel and Underground Space
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• v.22 no.1
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• pp.69-76
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• 2012

Theoretical backgrounds on the experimental methods of explosive welding, explosive forming and shock consolidation of powders are introduced. Explosive welding experiments of titanium (Ti) and stainless steel (SUS 304) plate were carried out. It was revealed that a series of waves of metal jet are generated in the contact surface between both materials; and that the optimal collision velocity and collision angle is about 2,100~2,800 m/s and $15{\sim}20^{\circ}$, respectively. Also, explosive forming experiments of Al plate were performed and compared to a conventional press forming method. The results confirmed that the shock-loaded Al plate has a larger curvature deformation than those made using conventional press forming. For shock consolidation of powders, the propagation behaviors of a detonation wave and underwater shock wave generated by explosion of an explosive are investigated by means of numerical calculation. The results revealed that the generation and convergence of reflected waves occur at the wall and center position of water column, and also the peak pressure of the converged reflected waves was 20 GPa which exceeds the detonation pressure. As results from the consolidation experiments of metal/ceramic powders ($Fe_{11.2}La_2O_3Co_{0.7}Si_{1.1}$), shock-consolidated $Fe_{11.2}La_2O_3Co_{0.7}Si_{1.1}$ bulk without cracks was successfully obtained by adapting the suggested water container and strong bonding between powder particles was confirmed through microscopic observations.

• Journal of Korea Game Society
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• v.4 no.2
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• pp.13-20
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• 2004

We have been interested in solving escapee-chaser game. In this game, with avoiding chaser, the escapee must escape from given male. The winning strategies of the escapee are driving the chaser to an intended place and closely evading from chaser by using some walls. According to our experience, some stages of the game are too difficult to solve manually. So we take the model checking method to get a solution of the game. Because the model checking with breadth fist search manner exhaustively searches the all state space of the game, the solution using model checking is best solution, shortest path. Fortunately, during the process of finding solution path, the state space explosion problem didn't occur, and the results of the game solving was applied to embedded system, Lego Mindstorm. Two agents, escapee and chaser, were implemented into robots and several experiments conformed the correctness of our solution.

• Fire Science and Engineering
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• v.29 no.5
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• pp.1-6
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• 2015

Flash point is one of the most important variables used to characterize fire and explosion hazard of liquids. The lower flash point data were measured for the binary systems {methanol + 1-butanol}, {ethanol + 1-butanol} and {2-propanol + 1-butanol} at 101.3 kPa. Experiments were performed according to the standard test method (ASTM D 3278) using a SETA closed cup flash point tester. The measured flash points were compared with the predicted values calculated using the following activity coefficient models: Wilson, Non-Random Two Liquid (NRTL), and UNIversal QUAsiChemical (UNIQUAC). The measured FP data agreed well with the predicted values of Raoult's law, Wilson, NRTL and UNIQUAC models. The average absolute deviation between the predicted and measured lower FP was less than 1.14 K.

• Fire Science and Engineering
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• v.13 no.4
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• pp.7-12
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• 1999

Thermal properties of EVA dust and its risks of coexisting with oxidizer were investigated by a pressure vessel. The decomposition of EVA dust with temperature using DSC and the weight loss with temperature using TGA were also investigated to find the thermal hazard of EVA dust. Using the pressure vessel which can estimate ignition and explosion of EVA dust coexisting with oxidizer by bursting of a rupture disc, many experiments have been conducted by varying the orifice diameter, heating rate, the weight ratio of the sample coexisting with oxidizer, and the species of oxidizer. According to the results of the thermal analysis of EVA dust, a little change of the decomposition initiation temperature with the heating rate could be found and the decomposition temperature zone of EVA dust was 250 to 50$0^{\circ}C$. The risk of EVA dust coexisting with oxidizer was increased as the orifice diameter was decreased. On the other hand, it was increased as the heating rate and the weight ratio of the sample coexisting with oxidizer were increased. In addition, the risk of EVA dust coexisting with oxidizer was affected by the decomposition temperature of the sample and oxidizer, respectively, at slow heating rate, but it was affected by the oxygen weight percent of oxidizer at fast heating rate.

• KIISE Transactions on Computing Practices
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• v.23 no.4
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• pp.250-255
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• 2017

Given the explosion of genomic data and expansion of applications such as precision medicine, the importance of efficient genome-database management continues to grow. Traditional compression techniques may be effective in reducing the size of a database, but a new challenge follows in terms of performing operations such as comparison and searches on the compressed database. Based on that many genome databases typically have numerous duplicated or similar sequences, and that the runtime of genome analyses is normally proportional to the number of sequences in a database, we propose a technique that can compress a genome database by eliminating similar entries from the database. Through our experiments, we show that we can remove approximately 84% of sequences with 1% similarity threshold, accelerating the downstream classification tasks by approximately 10 times. We also confirm that our compression method does not significantly affect the accuracy of taxonomy diversity assessments or classification.

• Journal of the Korean Society of Safety
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• v.25 no.4
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• pp.13-18
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• 2010

To investigate electrostatic ignition hazards of commercial gasoline used in the gas station, experiments were conducted dealing with the minimum ignition energy(MIE) of several kinds of gasoline under the various temperature. The conductivity of gasoline that was required for an accurate risk assessment as well as the MIE were also examined. The solvent ignitability apparatus which can heat up the inside of the vessels up to $210^{\circ}C$ was used in this study. Four kinds of premium gasoline and four kinds of regular gasoline, differing with respect to the companies, were used as test specimens. The following results were obtained: (1) all gasoline specimens were so sensitive that even an electrostatic discharge with a very low energy, such as about 0.5mJ, could ignite them. The ignitability of premium gasoline was constant irrespective of the companies. On the other hand, the ignitability of regular gasoline was variable depending on the company. (2) The MIE of all specimens depended markedly on the temperature; in other words, an increase in temperature decreases the ignition energy value. (3) The conductivity values of all specimens were low. Those must be taken into consideration in electrostatic risk assessment.

• Journal of Digital Convergence
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• v.16 no.6
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• pp.197-204
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• 2018

The realistic Visual Effects using fluid simulation in 3D computer graphics are operated as important factors to improve the quality of images. The process of creating realistic motions of water, fire, explosion by controlling each property of fluid is called fluid simulation. In general, the creation of a fluid simulation concentrates on the main simulation work phase, however an effective method for initial set up is important for the main simulation work. The purpose of this study is to analyze the factors involved in the initial emission motion and shape of fluid and propose methods that can efficiently apply this into the initial set up. For the process of the research, first, problems are raised based on related researches, and second, two experiments, 'Dynamic Fluid Emitter Creation' and 'User Design Type Emission Velocity Solution', are conducted for more effective fluid simulation. Through this research, the effective fluid simulation of initial set up phase will be suggested through the user design-type emission control solutions.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.5
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• pp.378-383
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• 2009

Hydrogen is the primary fuel in fuel cell systems. Because of high inflammation and explosion possibility of hydrogen, fuel cell systems require safety measures to prevent hydrogen hazard upon leakage. In this study, a model enclosure was made by referring to a commercial residential fuel cell system and hydrogen leakage experiments and computational simulations were conducted therein. Hydrogen was injected into the cavity through leakage holes located at the bottom while its flow rate was precisely controlled using MFC. The transient sensor signals from hydrogen sensors installed inside the enclosure were recorded and analyzed. The hydrogen sensor signals showed different delay times depending on their position relative to a leakage point, which indicated that hydrogen generally moves upward and accumulates at the upper region of a closed cavity. The inflammable regions with hydrogen concentration over 4% LEL were observed to locate near the leakage hole initially, and broaden towards the upper cavity region afterward. The simulation result showed that detection time at the hydrogen sensor was similar to the pattern of experimental results. However, the maximum concentration of hydrogen had a gap between experiment and simulation at detect point due to measurement errors and reaction rate.

• Computers and Concrete
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• v.22 no.1
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• pp.63-70
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• 2018

The steel fiber reinforced concrete (SFRC) shows better performance under dynamic loading than conventional concrete in virtue of its good ductility. In this paper, a series of quasi-static experiments were carried out on the SFRC with volume fractions from 0 to 6%. The compressive strength increases by 38% while the tension strength increases by 106% when the fraction is 6.0%. The contact explosion tests were also performed on the ${\Phi}40{\times}6cm$ circular SFRC slabs of different volume fractions with 20 g RDX charges placed on their surfaces. The volume of spalling pit decreases rapidly with the increase of steel fiber fraction with a decline of 80% when the fraction is 6%, which is same as the crack density. Based on the experimental results, the fitting formulae are given, which can be used to predict individually the change tendencies of the blast crater volume, the spalling pit volume and the crack density in slabs with the increase of the steel fiber fraction. The new formulae of the thickness of damage region are established, whose predictions agree well with our test results and others. This is of great practical significance for experimental investigations and engineering applications.