• Fire Science and Engineering
• /
• v.31 no.1
• /
• pp.89-97
• /
• 2017

This study analyzed the case of diesel car fires that occurred while driving in a tunnel 5 days after maintenance at a car service center. The results of the investigation and analysis found that a large amount of white foreign matter adhered to the inside of the exhaust port and the insulating plate above the DPF (diesel particulate filter) installed in the middle of the exhaust pipe was melted and lost. In particular, the metal floor of the car above the DPF was molten and pierced, and the rubber mat placed on the metal floor was burnt. Moreover, while the exhaust pipe in front of the DPF showed no overheating mark, such a mark was observed in the exhaust pipe from the DPF to the exhaust port. Because these findings may appear only when the DPF is overheated and ignited, this car fire is believed to have been caused by internal overheating of the DPF. The car fire investigation of this study suggests that if white foreign matter is found in the inside of the exhaust port during a fire cause investigation of a diesel car, the cause of the fire should be determined by removing the DPF and examining the internal damage of the DPF.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.16 no.2
• /
• pp.59-64
• /
• 2002

This paper analyzed the effect of ribs on the breakdown characteristics when a metallic particle attaches on the various spot of GIS spacer, using electric field analysis. Also, it was compared with the experimental result of breakdown voltage characteristics for the spacer with a metallic particle on its various spot and with the shape, the length, and the thickness of the ribs varying. The results of electric field analysis show that the electric field concentration of the rib is more weakened than other parts and therefore it restrains the proceeding of streamer, which occurs at the breakdown. And it is verified through experiments that the breakdown voltage of the spacer with rib is higher than that of the spacer without rib. The breakdown characteristics depend on the shape, the length, and the thickness of the rib as well. Also, it is confirmed by the electric field analysis and the experimental results that the electric breakdown characteristics could be improved by rounding the rib edge.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.11a
• /
• pp.37-38
• /
• 2006

본 연구에서는 압전체의 횡 진동모드를 이용한 압전 초음파 진동자를 설계 분석하였다. 이전의 란쥬반 진동자는 진동을 얻기 위하여, 복수의 원판 또는 사각판 형태의 압전 세라믹을 서로 반대 방향으로 분극하여 마주 보도록 설치한 후 전기적으로 병렬로 연결하고 상단 및 하단에 금속부을 부착하여 전체를 볼트로 조인 복잡한 구조와 큰 출력 파워를 갚는 반면, 본 연구에서는 판상형의 압전소자와 일체형 금속진동체를 이용하여 기계적 출력 파워 조절이 용이한 구조의 압전 진동자를 고안하여, 압전진동자의 횡 진동 모드를 이용함으로써 신뢰성과 정확도가 높고 진동효율이 최대가 되도록 설계하였다. 설계 개발된 압전 진동자는 진동의 크기 조절이 용이하여 일반 진동자 뿐 만 아니라, 외과 및 안과 수술에 있어서 인체조직이나 각막상피의 활성화를 유지한 상태에서 안전하게 절개 및 분리 시술용 진동자로 사용 할 수 있는 이점이있다. 압전 진동자는 유한요소법 시뮬레이션 프로그램 (ATILA 5.2.4)을 이용하여 설계를 하였으며 압전소자의 두께는 각각 0.2 mm, 0.5 mm로 제작하여 시뮬레이션 결과와 제작된 샘플의 특성을 비교하였고, 변위측정은 칼날을 결합 한 상태에서 공진 주파수대역 부근 주파수별로 측정 비교하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.2
• /
• pp.143-151
• /
• 2010

In this paper, a novel rectangular patch antenna is proposed to have Zeroth Order Resonance(ZOR) generated based on the Metamaterial Complosite Right- and Left-Handed(CRLH) structure. Making the in-phase electric field over the entire antenna other than a half-wavelength as the fundamental resonance mode of a standard microstrip patch or its positive multiple, the metallic patch is suggested to be capacitively coupled with only one surrounding rectangular ring, different from the previous 1D ZOR antennas commonly having several metal cells in line. The performance of the proposed antenna is simulated by a 3D field solver that inputs the sizes of the physical structure corresponding to the equivalent circuit designed to have ZOR at 2.4 GHz. Consequently, the resonance frequency, the gain and the antenna efficiency are observed 2.4 GHz, 5 dB and 98%, respectively. Besides, the important property of the proposed antenna is addressed as the combination of the low profile as an advantage of microstrip patch antennas, and the omni-directional field pattern typical of monopole antennas.

• Fire Science and Engineering
• /
• v.22 no.2
• /
• pp.91-96
• /
• 2008

This research studied about the cause analysis of fire that was occurred in far infrared rays heater to base on the fire examples. Fire of electric heater was apt to commit error that handled an over-heating accident by judged molten mark in heat ray. Molten mark which was attached in heat ray was appeared to the form of layer short circuit by other metal material, but other metal material was not found beside the ingredient of heat wire which was mixed to an alloy of Fe-Cr-Al according to result of ingredient distribution by SEM/EDX. Also, the result of overheating experiment by layer short circuit and overvoltage showed higher febrility than normal, but there was no possibility of fire occurrence. This paper will be contributed to science for cause analysis of electric fire through analyzing physical, chemical and flame features of burnout heater on the basis of diagnosis of fire that was happened in infrared rays heater.

• Journal of the Korean Vacuum Society
• /
• v.6 no.2
• /
• pp.159-164
• /
• 1997

We have studied initial oxidation of the alkali metal(AM)/Si(111) surface using X-ray photoelectron spectroscopy(XPS) and reflection high energy electron diffraction(RHEED) at room temperature(RT) and high temperature(HT)(300~50$0^{\circ}C$). The oxidation of the Si(111)7$\times$7 surface was promoted by the adsorption of 1 momolayer(ML) AM, whereas no promotion occurred for submonolayer(<0.5 ML) adsorbed Si(111)7$\times$7 surface at RT. O Is core level spectra were measured with increasing oxygen exposure. It was found that the oxygen adsorbed on the Si(111)7$\times$7-AM surface have two different bond configuration, Si-O and Am-O, respectively. From these results, we discussed the role of AM-O bonding in the promoted oxidation. At HT(300~50$0^{\circ}C$), the AM-adsorbed surface became very inactive with the structural transformation to the 3$\times$1-AM. We present the results of the oxidation of the Si(111)3$\times$1-AM(Na, K, Cs) surface.

• The Korean Journal of Mycology
• /
• v.11 no.1
• /
• pp.15-21
• /
• 1983

Exodextranase from Aspergillus ustus was purified by chromatography and characterized by various conditions. The optimal pH of the purified dextranase was 6.5 and this enzyme was maximally activated at $40^{\circ}C$. The enzyme was stable at the temperature below $50^{\circ}C$. The enzyme was markedly inactivated by $Hg^{2+},\;Cu^{2+},\;KCN\;and\;Co^{2+},\;but\;Ba^{2+},\;Fe^{2+},$ cysteine, EDTA, and ascorbic acid enhanced the activity of the enzyme. The main products from the hydrolysis of dextran incubated with the dextranase were glucose, isomaltotriose and oligosaccharide. When dextran was incubated with the mixture of pullulanase and ${\alpha}-amylase$, it was hydrolyzed into glucose, isomaltose and oligosaccharide. Polysaccharides in the decade teeth powder were hydrolyzed by the dextranase into glucose, isomaltotriose and oligosaccharides. In the hydrolysis of the teeth powder with the mixture of dextranase, pullulanase and ${\alpha}-amylase$, were proved to be similar to the dextran hydrolysates.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1999.07a
• /
• pp.212-212
• /
• 1999

Ar-O2 분위기의 Plasma 표면 처리된 OPP 의 polymer 위에 약 400$\AA$ 정도로 sputter 코팅된 Al의 부착력에 관하여 연구를 하였다. 금속과 polymer와 같이 성질이 서로 다른 물질이 서로 결합할 때 접착력은 제품의 성능과 신뢰도를 결정하는데 매우 중요한 인자이다. 최근 고분자재료의 표면을 플라즈마 처리 (plasma surface treatment)에 의해 고분자와 금속도포(coating) 층간의 접착력향상에 따라, 증착필름 및 인쇄용 필름 등의 기능도 향상시킬 수 있다. 저온 plasma를 이용한 표면처리는 plastic 재료가 가지고 있는 기본적인 특성을 저해하지 않고, 그 표면 층만을 개량하는 plasma 또는 sputter etching 갚은 electrical discharge 방법은 진공 증착 방식에서 많이 사용되고 있다. 7$\mu\textrm{m}$의 두께 OPP polymer를 10m/min의 속도로 OPP의 표면을 연속 plasma pretreatment를 하였다. 5$\times$10-2torr에서, PEM(Plasma Emission Monitor)를 이용하여 plasma intensity에 따른 Ar/O2비를 변화시키면서 test를 하였다. AFM과 XPS를 이용하여 OPP의 표면분석을 하였다. 이 plasma처리는 기존의 D.C plasma 처리 방식과는 달리 Midium frequency AC voltage hollow cathod 방식으로 plasma를 발생된 high energy plasma 분위기를 만들 수 있다. 이러한 방식은 -cycle일 때 plasma로부터 발생된 전자가 polymer 표면을 bombard 하게 되고, +cycle 일 때 polymer 표면이 cathod 가 되어 active ion에 의해 sputtering 이 된다. 이때 plasma 처리기의 polymer 기판 후면에 magnet를 설치하여 높은 ionization을 발생시켜 처리 효과를 한층 높여 주었다. 이 plasma 처리는 표면 청정화, 표면 etching 이 동시에 행하는 것과 함께 장시간 처리에 의해 표면에서는 미세한 과, C=C기, -C-O-의 극성기의 도입에 의한 표면 개량이 된다는 것을 관찰할 수 있다. OPP polymer 표면을 Ar 100%로 plasma 처리한 경우 C-O, C=O 등의 carbonyl가 발생됨을 알 수 있었다. C-O, C=O 등의 carbynyl polor group이 도입됨에 따라 sputter된 Al의 접착력이 향상됨을 알 수 있으며, TEM 관찰 결과 grain size도 상당히 작아짐을 알 수 있었다.

• Journal of the Mineralogical Society of Korea
• /
• v.23 no.4
• /
• pp.331-346
• /
• 2010

This study was carried out to leach valuable metals from galena using indigenous bacteria with no optimum pH conditions at room temperature. Even in these conditions, the rod-shaped indigenous bacteria, ranging from $0.4{\times}0.2{\mu}m$ to $0.5{\times}1.7{\mu}m$, were attached to the surface of the galena. For the 19 days of the bioleaching experiment, the content of Ph, Fe, Zn ions was found to be 347, 222 and 1.7 times higher than that of the control leaching agent, respectively. Numerous hexagonal column crystals were observed on the surface of galena. Those crystals may be formed from the biooxidation of galena by the indigenous bacteria. XRD analysis showed the peaks of anglesite observed in the bioleached galena. It is expected that more valuable elements can be leached out of the galena, if the bacteria is used under optimum pH and temperature conditions in future bioleaching experiments.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.25 no.3
• /
• pp.56-61
• /
• 2021

In this study, Al₂O₃ and H-ZSM-5 were coated on the inner wall of the stainless steel tube for the stable use of liquid hydrocarbon fuel and an endothermic catalyst used as coolant for hypersonic flying vehicles. Coke production is inevitable by the endothermic decomposition reaction of the liquid hydrocarbon fuel, and Fe, Ni metals induce the production of the filamentous coke by using a stainless steel tube reactor as a cooling channel. By coating the stainless steel with H-ZSM-5, Fe and Ni metals are prevented from being directly exposed to the liquid hydrocarbon fuel, and the formation of the filamentous coke is inhibited. In addition, Al₂O₃ is coated between the stainless steel and H-ZSM-5 to enhance adhesion bond strength.