• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.423-425
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• 2017

When many space launchers and rockets need to be separated, the pyrotechnic separators have been widely used because of their high reliability and high energy generation. However, intensive pyroshock and debris from the high-explosive type separator may cause fatal damage to the equipment inside of the space launchers or rockets. To solve this problem, a pressure-cartridge type low-impact separator has been developed. In this study, one of the low-impact separators, the split-type pyrolock, was used. We established a mathematical model for the split-type pyrolock that simulates the state of combustion gas and the separation behavior of four independent internal components and verified the mathematical model through comparing with experiment results.

• Fire Science and Engineering
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• v.15 no.3
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• pp.14-20
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• 2001

The flash points are one of the most important fundamental properties used to determine the potential for fire and explosion hazards of flammable substances. A classification of the flash points is important for the safe handling of flammable liquids which constitute the solvent mixtures. Basic to all flash points behavior are vapor pressure and explosive limits(lower explosive limit and upper explosive limit). The flash points of flammable solvent mixtures can be calculated with the appropriate use of the fundamental laws of Raoult, Dalton, Le Chatelier and activity coefficient models. In this study, the reference values of lower flash points were compared with the calculated values by using Raoult's law and MRSM(modified response surface methodology) model. The lower flash points were in agreement with the predicted by Raoult's law and MRSM model. By means of this methodology, it is possible to evaluate reliability of experimental data of the flash points of the flammable mixtures.

• Explosives and Blasting
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• v.31 no.1
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• pp.41-48
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• 2013

Progressive collapse is generally defined as a local failure of structural members occurring due to abnormal load which results in the partial collapse or total collapse of a structure. Unlike progressive collapse, explosive demolition is a method of inducing the total collapse of structure by removing all or portion of structural members. In explosive demolition the partial collapse of the structural members can be controlled at appropriate time intervals by blasting, to induce the progressive collapse of the structure and control the collapse behavior. In this study, a nonlinear dynamic analysis was carried out in order to apply the progressive collapse process to explosive demolition design of the RC structure. The occurrence of progressive collapse of analytical models was examined according to the number of floors, the removed column height and span length. For models that resisted progressive collapse, progressive collapse resisting capacity was evaluated.

• Computers and Concrete
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• v.9 no.4
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• pp.311-325
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• 2012

In this paper, we examine the behavior of the High-Rate Brittle Microplane (HRBM) concrete model based on a series of penetration experiments. These experiments were conducted with three different slab thicknesses (127, 216 and 254 mm) that provided a significant challenge for the numerical simulations. The 127 mm slab provided little resistance, the 216 mm slab provided nominal resistance and the 254 mm slab approached the perforation limit thickness of the projectile. These experiments provide a good baseline for evaluating material models since they have been shown to be extremely challenging; in fact, we have not encountered many material models that can provide quantitatively predictive results in terms of both projectile exit velocity and material damage. In a companion paper, we described the HRBM material model and its fit to various quasi-static material property data for WES-5000 concrete. In this paper, we show that, when adequately fit to these quasi-static data, the HRBM model does not have significant predictive capabilities, even though the quasi-static material fit may be exceptional. This was attributed to the rate-dependent response of the material. After various rate effects were introduced into the HRBM model, the quantitative predictive nature of the calculations dramatically increased. Unfortunately, not much rate-dependent material property data are in the literature; hence, accurate incorporation of rate effects into material models is difficult. Nonetheless, it seems that rate effects may be critical in obtaining an accurate response for concrete during projectile perforation events.

• Journal of the Korea Institute of Building Construction
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• v.12 no.2
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• pp.183-193
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• 2012

Compressive property of high strength concrete with amorphous metal fibers subject to high temperature has been investigated. The measure of this investigation includes explosive spalling, weight loss, residual compressive strength, strain at peak stress, elastic modulus, and residual energy absorption capacity after exposure to $400^{\circ}C$, $600^{\circ}C$and $800^{\circ}C$. In addition to the amorphous metal fiber, two other types of fibers (polypropylene fiber and hooked-end steel fiber) were also included in this investigation for comparison. The experimental program was conducted with high strength concrete using several combinations of the fiber types. The testing result shows that the concrete with amorphous metal fibers plus polypropylene fibers shows a superior behavior than those using other combination or single fiber type ingredient.

• Journal of the Korean Society of Safety
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• v.15 no.3
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• pp.78-82
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• 2000

The flash point is an important property and hazardous index of a flammable liquid. The flash points are used by virtually all the environmental, health, and safety organizations in both government and industry to classify flammable liquids for safety and transportation regulations. The basics of all flash points behavior are concerned with the vapor pressure and explosive limits. The flash points of pure components and the mixture of solvents can be calculated with the use of the laws of Raoult, Dalton and Le Chatelier. In this paper, experimentally determined lower flash points of a p-xylene and epoxy resin system were compared with the calculated values by using Raoults law. Calculated lower flash points were in reasonable agreement with the observed values.

• Journal of Information Technology Applications and Management
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• v.12 no.4
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• pp.71-92
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• 2005

As the Internet establishes and reinforces connections between people, virtual community is becoming one of considerable business model. We believe that benefits of the virtual community go to both customer and vendor organizing virtual community. Despite the explosive growth of virtual communities on the Internet, empirical research has been focused to study the issues related to characteristics of virtual community The objective of this study is to enhance the understanding about virtual communities as an e-business model by Customer Relation Management and by empirically validating their effect on the performance of website. Through path analysis, we find support for relations behavior influence the online commitment. we also find that the online commitment enhance the organization citizenship behavior. Finally, we discuss several theoretical and practical Implications, and suggest limitations for research and future research issue.

• Coupled systems mechanics
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• v.7 no.3
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• pp.333-351
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• 2018

In the present paper, the behavior of the Karaj double curvature arch dam is studied focusing on the effects of structural nonlinearity on the responses of the dam body when an underwater explosion occurred in the reservoir medium. The explosive sources are located at different distances from the dam and the effects of the cavitation and the initial shock wave of the explosion are considered. Different amount of TNT are considered. Two different linear and nonlinear behavior are assumed in the analysis and the dam body is assumed with and without contraction joints. Radial, tangential and vertical displacements of the dam crest are obtained. Moreover, maximum and minimum principal stress distributions are plotted. Based on the results, the dam body responses are sensitive to the insertion of joints and constitutive model considered for the dam body.

• Journal of Information Technology Services
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• v.13 no.2
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• pp.19-34
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• 2014

As the global smartphones market is growing at a brisk pace, their associated mobile applications are becoming increasingly ubiquitous in our daily life. The growth of mobile application business is explosive. Like other digital contents businesses, illegal downloads of copyrighted mobile applications become major obstacle in the future of the industry. In spite of anti-piracy efforts, the phenomenon has been getting worse. It is necessary to change the focus of current deterrence policies and strategies. This study investigates the factors influencing smartphone applications piracy behavior. For better understanding of illegal behavior, a research model of potential determinants for the piracy behavior is developed and empirically tested via path analysis using structural equation modeling. Findings show that social factors, beliefs concerning benefits from piracy, self-efficacy, and habit have significant effects on attitude toward smartphone application piracy. The result also shows perceived risks and facilitating conditions were not significantly related to their attitude. Implications for research and practice are discussed.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.313-318
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• 2008

The blast load is caused by gas or bomb explosions. In this study blast load was simulated using the computer code CONWEP and nonlinear analysis was performed on three-story steel moment frames. It was observed from the analysis results that the response of the structures varied depending on the opening area and the explosive weight.