• 천문학회지
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• 제37권4호
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• pp.237-241
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• 2004

We perform numerical experiments on supernova-driven turbulent flows in order to see whether or not supernovae playa major role in driving turbulence in the interstellar medium. In a $(200pc)^3$ computational box, we set up, as initial conditions, uniformly magnetized gas distributions with different pairs of hydrogen number densities and magnetic field strengths, which cover the observed values in the Galactic midplane. We then explode supernovae at randomly chosen positions at a Galactic explosion rate and follow up the evolution of the supernova-driven turbulent flows by integrating numerically the ideal MHD equations with cooling and heating terms. From the numerical experiments we find that the density-weighted velocity dispersions of the flows are in the range of 5-10 km $s^{-l}$, which are consistent with the observed velocity dispersions of cold and warm neutral media. Additionally, we find that strong compressible flows driven by supernova explosions quickly change into solenoidal flows.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 E
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• pp.1819-1823
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• 1997

When flammable gases are mixed with air or oxygen in the explosion concentration range and are ignited by sufficiently large electrostatic discharge energy, they may explode causing severe disaster in workplaces. The minimum ignition energy (MIE) of single gas-air mixtures has been already investigated by many researchers, but the MIE of mixtures of more than three substances is not examined yet. The purpose of this study is to investigate the MIE of several three-component gas mixtures experimentally. The result of our experiment shows that the MIE of some gas mixtures is quite different from that we expected based on the characteristics of individual gas-air mixture.

• Journal of Welding and Joining
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• 제14권4호
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• pp.62-70
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• 1996

Al or Al-alloy have been known to be able to be claded on various materials by using explosive welding process, however, the intermetallic layer frequently formed along the interface have made this process very complicated. In this study, it was focussed to select the process variables, which can get rid of interfacial layer in the Al-claded steel plate. As a result, it was demonstrated that there was a certain range of explosive thickness which did not form the intermetallic phase as well as the non-bonded area. On the other hand, ultasonic tests performed for identifying the presence of interfacial layer nondestructively showed that it could be applied for the intended purpose but its result was weakly related with the microstructural quality of interface.

• 천문학회보
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• 제39권1호
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• pp.59.1-59.1
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• 2014

Phosphorus ($^{31}P$), which is essential for life, is thought to be synthesized in massive stars and dispersed into interstellar space when these stars explode as supernovae (SNe). Here we report on near-infrared spectroscopic observations of the young SN remnant Cassiopeia A, which show that the abundance ratio of phosphorus to the major nucleosynthetic product iron ($^{56}Fe$) in SN material is up to 100 times the average ratio of the Milky Way, confirming that phosphorus is produced in SNe. The observed range is compatible with predictions from SN nucleosynthetic models but not with the scenario in which the chemical elements in the inner SN layers are completely mixed by hydrodynamic instabilities during the explosion.

• 한국안전학회지
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• 제28권1호
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• pp.29-34
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• 2013

When flammable gases are mixed with air or oxygen in the explosion concentration range and are ignited by sufficiently large electrostatic discharge energy, they may explode causing severe disaster in workplace. The minimum ignition energy(MIE) of single gas-air mixtures has been already investigated by many research, but the MIE of mixtures of more than ternary gas mixture is not examined yet. The purpose of this study is to investigate the MIE of a ternary gas(methane, ethylene, hydrogen, propane) mixtures experimentally. The results of our experiment show that the ignition of a methane-ethylene-air, methane-hydrogen-air, methane-propane-air, ethylene-hydrogen-air, ethylene-propane-air and hydrogen-propane-air mixture due to electrostatic discharge energy primarily depends on that the mixture: the MIE decreases gradually with the increase of having the lower MIE than other mixture ratio in the normal atmospheric pressure.

• 센서학회지
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• 제24권5호
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• pp.311-318
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• 2015

The excess use and generation of various toxic gases from many industrial complexes and plant facilities have increased the possibility of leakage or explosion accidents, which can cause fatal damage to human beings in the wide range of neighboring area. To prevent the exposure to the fatal toxic gases, it is very important to monitor the leakage of toxic gases using gas sensors in real time. Various types of gas sensors, which can be classified as semiconductor, electrochemical, optical, and catalytic combustion types according to the operating principles, have been developed. In this review, the operation principles of gas sensors are explained and the performance of those sensors is compared. The state-of-the-art gas sensor technologies developed by research institutes or companies are reviewed also.

• 천문학회보
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• 제43권2호
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• pp.40.1-40.1
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• 2018

Among Type I supernovae, which show no evidence for hydrogen lines in spectra, Type Ib/c supernovae lack of strong Si absorption lines and are involved with massive progenitors. While strong helium absorption lines are present in Type Ib supernovae, narrow helium emission lines also can appear in some Type Ib that are often called Type Ibn supernovae (SNe Ibn). We consider helium giant stars as a promising progenitor candidate for SN Ibn and suggest the evolutionary scenario through binary systems using MESA code. In our models the range of primary mass is 11 - 20 solar mass, mass ratio is 0.5 - 0.9, and initial period is 1.5 / 1.7 / 2.0 / 2.5 / 3.0 day. In particular, we find that the evolution of the secondary star can overtake the primary through mass transfer from the secondary to the primary, which is so-called 'reverse case B' mass transfer. In such systems the secondary star may undergo a supernova explosion earlier than the primary star. In this case, the primary star evolves towards a single helium giant to become a SN Ibn progenitor. These cases are more frequent in relatively low initial primary mass.

• Nuclear Engineering and Technology
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• 제54권9호
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• pp.3580-3585
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• 2022

The thermal stability of carbohydrazide, hydrazine nitrate, acetohydroxamic acid in nitric acid solutions has been studied at atmospheric pressure and above atmospheric pressure. The volumes of gaseous products of thermolysis and the maximum rate of gas evolution have been determined at atmospheric pressure. It has been shown that, despite the high rate of gas evolution and large volumes of evolved gases, the conditions for the development of autocatalytic oxidation are not created. Exothermic processes are observed in a closed vessel in the temperature range of 50-250 ℃. With an increase in the concentration of nitric acid, the temperatures of the onset of exothermic effects for all mixtures decrease, and the values of the total thermal effects of reactions increase, to the greatest extent for solutions with carbohydrazide.

• Journal of Yeungnam Medical Science
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• 제39권2호
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• pp.89-97
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• 2022

More than 2 years after the explosion of the coronavirus disease 2019 (COVID-19) pandemic, extensive efforts have been made to develop safe and efficacious vaccines against infections with severe acute respiratory syndrome coronavirus 2. The pandemic has opened a new era of vaccine development based on next-generation platforms, including messenger RNA (mRNA)-based technologies, and paved the way for the future of mRNA-based therapeutics to provide protection against a wide range of infectious diseases. Multiple vaccines have been developed at an unprecedented pace to protect against COVID-19 worldwide. However, important knowledge gaps remain to be addressed, especially in terms of how vaccines induce immunogenicity and efficacy in those who are elderly. Here, we discuss the various vaccine platforms that have been utilized to combat COVID-19 and emphasize how these platforms can be a powerful tool to react quickly to future pandemics.

• 한국추진공학회지
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• 제26권6호
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• pp.1-9
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• 2022

본 연구에서는 현대적 전기식 기폭관의 해석 모델링을 대상으로 실용적 적용이 가능한 금속성 플라즈마 조성비 및 전기전도도 계산모델이 제시되었다. 현 플라즈마 모델은 기폭관 브릿지 전기폭발 현상 시 발생하는 고밀도 플라즈마 영역의 비이상 플라즈마 효과 보정을 포함하였다. 구리 플라즈마를 대상으로 한 계산 결과는 넓은 온도 범위 및 고밀도 영역에서 해당 측정 결과와 전반적으로 잘 일치하여 기폭관 모델링 대상 적용에 적절함을 보여주었다.