• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.7
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• pp.635-640
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• 2015

In this paper, we report a non-explosive separation device for a small satellite which utilize a shape memory alloy actuator. Based on previous research, we try to increase the reliability of the proposed device by changing some components. It enables the proposed device to activate under high preload. Also, we confirm it generates low shock which is main advantage of non-explosive separation device. Finally, vibration test which mimics launching environment and thermal vacuum test which mimics space environment are carried out respectively. After each environment test, we confirm the proposed device is successfully activated. Conclusively, we develop a non-explosive separation device which can activate with low shock under high preload after shock and environment tests(vibration and thermal vacuum tests).

• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.248-256
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• 2020

In this study, predictive models based on machine learning for evaluating the extent of hazardous zone of explosive gases are developed. They are able to provide important guidelines for installing the explosion proof apparatus. 1,200 research data sets including 12 combustible gases and their extents of hazardous zone are generated to train predictive models. The extent of hazardous zone is set to an output variable and 12 variables affecting an output are set as input variables. Multiple linear regression, principal component regression, and artificial neural network are employed to train predictive models. Mean absolute percentage errors of multiple linear regression, principal component regression, and artificial neural network are 44.2%, 49.3%, and 5.7% and root mean square errors are 1.389m, 1.602m, and 0.203 m respectively. Therefore, it can be concluded that the artificial neural network shows the best performance. This model can be easily used to evaluate the extent of hazardous zone for explosive gases.

• Journal of the Korean Institute of Gas
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• v.26 no.5
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• pp.35-40
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• 2022

PCVD (Plasma Chemical Vapor Deposition), a solar cell manufacturing facility, is a facility that deposits plasma generated in a chamber (NH₃, SIH₄, O₂ on a wafer. In the PCVD facility, gas movement and injection is performed in the gas cabinet, and there are many leak points inside because MFC, regulator, valve, pipe, etc. are intricately connected. In order to prevent explosion in case of leakage of NH₃ with an upper explosive limit (UEL) of 33.6% and a lower explosive limit (LEL) of 15%, the dilution capacity must be capable of allowing the concentration of NH₃ to be out of the explosive range. This study was analyzed using the CFD analysis technique, which can confirm the dilution ability in 3D and numerical values when NH₃ gas leaks from the existing PCVD gas cabinet. As a result, it was concluded that it corresponds to medium dilution and that testicular ventilation is possible through facility improvement.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.935-940
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• 2008

When reinforced concrete is subjected to high temperature as in fire, there is deterioration in its properties of particular importance are loss in compressive strength, cracking and spalling of concrete, destruction of the bond between the cement paste and the aggregates and the gradual deterioration of the hardend cement paste. Assessment of fire-damaged concrete usually starts with visual observation of color change, cracking and spalling of the surface. In this paper, it was reported the trends of research and practical use on the Explosive Spalling Properties and Performance Based of Structural Design of the High-Strength Concrete.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.2
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• pp.150-155
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• 2013

We present a kevlar rope based Non-Explosive Actuator(NEA) device which has simple structure and is activated by burning Ni-Cr wire. Through performance test, we find it can be operated under various pre-load by simply changing turn number of Ni-Cr wire. It shows release time of 680ms and shock level of 110G under pre-load of 6.0kN. Launching environment and space environment tests are planned to verify performance of the NEA based on European Satellite Agency test manual. Conclusively, we expect the proposed NEA can be applicable to release solar panel and fairing separation.

• Journal of Korean Society for Quality Management
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• v.48 no.3
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• pp.395-408
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• 2020

Purpose: This study was performed for advancement of aviation security equipments certification system. Methods: We investigated aviation security equipments certification-related registrations and the latest research trends of explosive detection technologies. Based on the literature studies, we draw the critical issues of the aviation security equipment certification system and suggested improvement direction. Results: We found some inaccuracies of the definition of explosive trace detection equipments, accreditation review committee, and performance evaluation test method. These problems should be modified to suit being practical. Conclusion: The present results would be useful for basic data for modifying aviation security equipments certification systems.

• Journal of the Korea Institute of Building Construction
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• v.20 no.4
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• pp.305-311
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• 2020

Polymer modified cement mortar (PCM) can improve the performance of adhesion strength, flexural strength, chemical resistance, etc., compared with cement mortar, and is widely used when repairing RC structures. However, PCM causes a burst in an environment with high temperature and fire rate, which causes problems in the stability of the structure. In this study, for the purpose of developing explosive reduction PCM, the polymer mixing ratio is 2%, 4%, 6%, the fiber length is 6mm, 12mm, 6+12mm, and the PP fiber mixing rate is 0.05 Vol% and 0.1 Vol%. Furnace heating experiment (600℃, 800℃) was carried out. As a result of comparative analysis of the explosive properties, it was confirmed that the explosive reduction effect due to the fiber incorporation was insufficient when the polymer mixing amount was 6% or more.

• Magazine of the Korea Concrete Institute
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• v.17 no.3 s.86
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• pp.20-25
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• 2005

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2008.11a
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• pp.195-201
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• 2008

When reinforced concrete is subjected to high temperature as in fire, there is deterioration in its properties of particular importance are loss in compressive strength, cracking and spalling of concrete, destruction of the bond between the cement paste and the aggregates and the gradual deterioration of the hardend cement paste. Assessment of fire-damaged concrete usually starts with visual observation of color change, cracking and spalling of the surface. In this paper, it was reported the trends of research and practical use on the Explosive Spalling Properties of the High-Strength Concrete.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.4
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• pp.66-74
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• 2003

In non-contact underwater explosion shock test of a real naval ship, measurement of shock loadings and responses should require onboard system to be able to safely trigger an explosive and to simultaneously and successfully measure scores of shock signals in the deteriorated environment. For this purpose, we have developed a shock-hardened measurement system resistible to 170g peak acceleration having 4 msec duration by resiliently mounting general purpose measurement instruments in racks. The system can simultaneously measure and record 200 signals to evaluate shock leadings and responses of the test ship by triggering an explosive and measurement instruments at the same time. We prove the performance of the developed system by introducing the signal acquisition results from of a real ship underwater shock test, firstly performed in Korea.