• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.5
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• pp.675-682
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• 2021

Fire accidents on land and at sea can cause serious casualties; specifically, owing to the nature of marine plants and ships, the mortality rate at sea from suffocation in confined spaces is significantly higher than that on land. To prevent such cases of asphyxiation, it is essential to install ventilation fans that can outwardly direct these toxic gases from fires; however, considering the scale of marine fires, the installation of large ventilation fans is not easy owing to the nature of marine structures. Therefore, in this study, we developed a new concept for fire safety technology to control toxic gases generated by fires from applied direct current (DC) electric fields. In the event of a fire, most flames contain large numbers of positive and negative charges from chemi-ionization, which generates an "ionic wind" by Lorentz forces through the applied electric fields. Using these ionic winds, an experimental study was performed to artificially control the fire smoke caused by burning paper and styrofoam, which are commonly used as insulation materials in general buildings and ships. The experiments showed that a fire smoke could be artificially controlled by applying a DC voltage in excess of ±5 kV and that relatively effective control was possible by applying a negative voltage rather than a positive voltage.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.464-469
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• 2019

A remote monitoring panel and control system was developed to control various valves and access control chambers, including gas shutoff valves used in CBR(Chemical, Biological and Radiological) facilities. The remote monitoring panel consisted of a main panel installed in the NBC (Nuclear, Biological and Chemical) control room and auxiliary panel installed in the clean room, and the size was divided into pure control and control including CCTV. This system can be monitored and controlled remotely according to the situation where an explosion door and gas barrier door can occur during war and during normal times. This system is divided into normal mode and war mode. In particular, it periodically senses the operation status of various valves, sensors, and filters in the CBR facilities to determine if each apparatus and equipment is in normal operation, and remotely alerts situation workers when repair or replacement is necessary. Damage due to the abnormal operation of each device in the situation can be prevented. This enables control of the blower, supply and exhaust damper, emergency generator, and coolant pump according to the state of shutoff valve and positive pressure valve in the occurrence of NBC, and prevents damage caused by abrupt inflow of conventional weapons and nuclear explosions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.7
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• pp.921-927
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• 2013

The performance estimation of a landing gear with uncertain parameters is presented. In actual use, many parameters can have certain degrees of variations that affect the energy absorbing performance. For example, the shock strut gas pressure, oil volume, tire pressure, and temperature can deviate from their nominal values. The objective function in this study is the ground reaction during touchdown, which is a function of the abovementioned parameters and time. To consider the uncertain properties, convex modeling and interval analysis are used to calculatethe objective function. The numerical results show that the ground reaction characteristics are quite different from those of the deterministic method. The peak load, which affects the efficiency and structural integrity, is increases considerably when the uncertainties are considered. Therefore, it is important to consider the uncertainties, and the proposed methodology can serve as an efficient method to estimate the effect of such uncertainties.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.97-97
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• 2015

전 세계적으로 화석연료의 고갈 및 환경오염 문제를 해결하기 위해 신재생에너지에 대한 관심이 급증하고 있다. 이러한 신재생에너지에는 수소 에너지, 자연 에너지(태양열, 지열 등), 바이오 매스 에너지 등이 포함된다. 이 중 수소 에너지는 지구상에 풍부하게 존재하고 있는 물과 탄화수소로부터 얻어지며, 연소 시에도 다시 물을 형성하여 오염 물질을 배출하지 않는 차세대 무공해 에너지원으로써 주목을 받고 있다. 수소 제조를 위한 공정에는 수증기 개질 공정(steam reforming), 부분 산화(partial oxidation) 및 자열개질(autothermal reforming) 등이 있으며 실제로 생산되는 대부분의 수소는 탄소/수소비(1:4)가 높은 메탄($CH_4$) 가스를 이용한 메탄 수증기 개질 공정(steam methane reforming)을 통하여 제조된다. 이 때 수소 제조의 고효율화 및 저비용화를 위해서는 반응물에 대한 높은 선택도, 고활성도 및 높은 안정성을 갖는 촉매가 반드시 필요하며, 대표적으로 Ni, Pt, Ru 등이 보고되고 있다. 이러한 촉매들은 대부분 세라믹 pellet 형태로 제작되어 왔으나 열전도도가 낮고 물리적 충격에 취약하다는 단점이 존재한다. 따라서 우리는 이러한 단점을 극복하고, 촉매의 활성을 높이기 위하여 다공성 금속 합금 폼을 촉매 지지체로 도입하였다. 또한, 다공성 금속 합금 폼 표면에 촉매의 분산 및 안정성을 향상시키기 위해 지지체와 촉매 사이에 원자층 증착법을 이용하여 inter-layer를 도입하였다. 이들의 구조, 형태, 및 표면의 화학적 상태는 주사전자현미경, EDS (energy dispersive spectroscopy)가 탑재된 주사전자현미경, X-선 회절, 및 X-선 광전자 분광법을 이용하여 규명하였다. 더하여 정전압-전류 측정법 및 유도 결합 플라즈마 분광 분석기을 이용하여 전기 화학 반응을 유도하고, 반응 후 전해질의 성분분석을 통해 촉매와 지지체 간의 안정성을 평가하였다. 따라서 본 결과들은 한국진공학회 하계정기학술대회를 통해 좀 더 자세히 논의될 것이다.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.5
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• pp.242-248
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• 2002

It is important to develop new effective technologies to increase the interruption capacity and to reduce the size of a UB(Gas Circuit Breakers). Major design parameters such as nozzle geometries and interrupting chamber dimensions affect the cooling of the arc and the breaking performance. But it is not easy to test real GCB model in practice as in theory. Therefore, a simulation tool based on a computational fluid dynamics(CFD) algorithm has been developed to facilitate an optimization of the interrupter. Special attention has been paid to the supersonic flow phenomena between contacts and the observation of hat-gas flow for estimating the breaking performance. However, there are many difficult problems in calculating the flow characteristics in a GCB such as shock wave and complex geometries, which may be either static or in relative motion. Although a number of mesh generation techniques are now available, the generation of meshes around complicated, multi-component geometries like a GCB is still a tedious and difficult task for the computational fluid dynamics. This paper presents the CFD program using CFB-CAD integration technique based on Cartesian cut-cell method, which could reduce researcher's efforts to generate the mesh and achieve the accurate representation of the geometry designed by a CAD tools.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.3
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• pp.59-65
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• 1999

In this paper, we had studied the possibility of application as Cu thin films from (hfac)Cu(VTMOS) which is very stable. Cu thin films had been studied as a function of deposition temperature. Substrates used in the experiment were PVD TiN on Si wafer. Deposition conditions were as follow : deposition temperature $50^{\circ}C$. Cu thin films were analyzed by AES, four point probe, XRD and SEM. All of deposited films were very pure and some favoring of <111> planes perpendicular to the substrate surface were observed. Cu thin films had two distinct growth rates at various deposition temperature. One is the surface reaction limited region below $200^{\circ}C$, and the other is the mass transport limited region above $200^{\circ}C$. The resistivity of deposited Cu thin films under the optimum deposition condition is $2.5mu\Omega.cm$ Thus, properties of deposited Cu thin films using (hfac)Cu(VTMOS) didn't show difference with Cu thin films from other precursors.

• Journal of fish pathology
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• v.6 no.1
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• pp.65-70
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• 1993

The delicate histological structure of gill in teleosts can be easily affected by a variety of biological, chemical or physical detrimental agents because it is directly exposed to the surrounding water. The epithelium of secondary lamella is thin to allow efficient gaseous exchange and this also renders it particularly vulnerable to various pathogens. As well as the main respiratory role, the gill has other various important functions such as acid-base balance, osmoregulation or the excretion of nitrogenous waste products. Thus destruction of epithelial integrity such as epithelial necrosis or thickening can render a fish very vulnerable to respiratory, secretory and excretory difficulties. This article was tried to describe in detail the common processes of pathological responses correlated to the normal histological structures of the gill in teleosts.

• Journal of the Korean earth science society
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• v.28 no.7
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• pp.847-856
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• 2007

The Planetary nebula NGC 6881 displays quadrupole morphology and it also has a jet feature in its image. We investigated the line profiles of the optical region spectral emission lines, using the Hamilton Echelle Spectrograph (HES) at the Lick observatory. The HES data obtained in this study was the radiation coming from the inner region within the diameter of 4 second of arc. Expansion velocity was obtained, based on the strong emission line profiles of e.g. H, Hel, Hell, [OIII], [NII], [ArIII], [SII], and [SIII}, using the IRAF and StarLink/Dipso reduction packages. The HI recombination lines showed one single peak profile, while the He and forbidden strong lines displayed double peaks. The results of this study show that the outflow velocity of gas increases radially outwards due to the central stellar radiation pressure. It was concluded that three central rings appeared in the HST image are the result of a combined structure of bipolar cones (seen in e.g. HI lines) and a ring (seen in He, [SIII] lines) in projection.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.4
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• pp.238-243
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• 2014

This paper dealt with the measurement and analysis of partial discharge (PD) under high voltage direct current (HVDC) in SF6 gas. Electrode systems such as a protrusion on conductor (POC), a protrusion on enclosure (POE), a crack on epoxy plate and a free particle (FP) were fabricated to simulate the insulation defects. The analysis system was designed with a Time-Frequency (T-F) map algorithm programed based on LabVIEW. This can arrange the acquired PD pulses into frequency and time domain. A HVDC power source is composed of a transformer (220 V/50 kV), a diode (100 kV) and a capacitor (50 kV, 0.5 ${\mu}F$). The gap between the electrodes is 3 mm, and the $SF_6$ gas was set at 5 bar. PD pulses were detected by a 50 ${\Omega}$ non-inductive resistor. In the analysis, PD pulses were distributed below 0.5 MHz and 20 ns ~ 35 ns for the POC, 0.7 MHz ~ 1.7 MHz, below 0.6 MHz and 10 ns ~ 40 ns and 60 ns ~125 ns for the POE, below 0.1 MHz and 135 ns ~ 215 ns for the crack, and below 1.6 MHz and 250 ns for the FP.

• Resources Recycling
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• v.21 no.5
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• pp.58-64
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• 2012

Ti button type ingots were prepared by recycling of Ti turning scraps using vacuum arc melting process for production of consumable arc electrode. The behavior of impurities such as Fe, W, O, and N in the Ti button ingots was investigated and the properties of the Ti button ingots were also evaluated. In the case of oxygen gaseous impurity, the oxygen layers on the surface of the Ti turning scraps were easily removed by the first vacuum arc melting. On the other hand, the solute oxygen in the Ti turning scraps was not removed by the next melting. In the case of Fe, major impurity in the Ti turning scraps, the removal degree in the final Ti button ingot refined by vacuum arc melting for 20 minutes was approximately 43 %, which is due to the vapor pressure difference between Ti and Fe. As a result, the Ti button ingots with ASTM grade 3 could be obtained by multiple vacuum arc melting from the Ti turning scraps. Therefore, it was confirmed that the preparation of consumable electrode for vacuum arc remelting could be possible by recycling of Ti turning scraps.