• 열처리공학회지
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• 제27권2호
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• pp.65-71
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• 2014

SMF9060 material is a Fe-based powder sintered alloy that is used for several automobile components such as Synchronize Hub, oil pump and transmission. These components are required excellent wear resistance and durability. In this study, we have performed a dry wear test at the ambient air and Ar gas conditions in the room temperature, and a lubricant wear test at the room temperature and engine oil temperature of $100^{\circ}C$. The amount of wear volume and coefficient friction are measured by a Profilometer and a Ball on disk type wear tester. The wear volume in Ar gas condition was a little higher than that in the ambient air condition. However the wear volume in the lubricant wear condition was much lower than in the dry wear condition. XRD analysis of the debris in Ar gas condition showed that the oxide film was not formed.

• Current Optics and Photonics
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• 제2권1호
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• pp.1-6
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• 2018

Our previous study showed that switching the inhaled gas from hypoxic gas to hyperoxic gas for 10 minutes increased tumor oxygenation and that the magnitude of oxyhemoglobin increase responded earlier than tumor volume change after chemotherapy. During 10 minutes of inhaled-oxygen modulation, oxyhemoglobin concentration first shows a rapid increase and then a slow but gradual increase, which has been fitted with a double-exponential equation in this study. Two amplitude values, amplitudes 1 and 2, respectively represent the magnitudes of rapid and slow increase of oxyhemoglobin. The trends of changes in amplitudes 1 and 2 were different, depending on tumor volume when chemotherapy started. However, both amplitudes 1 and 2 changed earlier than tumor volume, regardless of when chemotherapy was initiated. These results imply that by observing amplitude 1 changes post chemotherapy, we can reduce the time of a respiratory challenge from 10 minutes to less than 2 minutes, to see the chemotherapy response. We believe that by reducing the time of the respiratory challenge, we have taken a step forward to translating our previous study into clinical application.

• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1650-1660
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• 2020

Comparing with the large containment, the gas can not flow freely within the local compartment due to the small volume of the compartment in case of serious accident, which affects the hydrogen flow distribution, and it will determines the location where high concentration occurs in compartment. In this paper, hydrogen distribution and possible hydrogen risk in the vessel under the different conditions are investigated. The results show that when the initial gas momentum is increased, the ability of gas enters into the upper region of the vessel will be strengthened, and the hydrogen volume fraction in the upper region of the vessel is higher. Comparing with horizontal source direction, when source direction is vertically towards upper space, hydrogen is more likely to accumulate in the upper region of the vessel. With the increasing of steam mass flow, the dilution effect of steam on the hydrogen volume fraction will be strengthened, while the pressure in the vessel is also increased. When steam flow is decreased, the hydrogen explosion risk is higher in the vessel. The experiment data can provide technical support for the validation of the CFD software and the mitigation of hydrogen risk in the containment compartment.

• 대한기계학회논문집B
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• 제22권4호
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• pp.520-529
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• 1998

Heat and mass transfer behaviors of metal hydride beds were predicted by solving a set of volume-averaged equations numerically both for the gas (hydrogen) and the solid(metal hydride) phases. Time variations of temperature and hydrogen concentration ratio distributions were obtained for internally cooled, cylindrical-shaped beds with metal(aluminum) fins imbedded in them. Also, time variations of the space-averaged hydrogen concentration ratio were obtained. Temperature and velocity of the coolant, hydrogen pressure at the gas inlet, and the fin spacing were taken as the parameters. The hydrogen absorption rate increases with the higher velocity and the lower temperature of the coolant, and with the decrease of the fin spacing. Increasing of the hydrogen pressure at the gas inlet also promotes the rate of absorption though the increasing rate gradually slows down. The amount of the hydrogen storage per unit volume of the bed decreases with the tighter fin spacing despite of the higher absorption rate ; therefore, there should be an optimum fin spacing for a given volume of the system and the amount of the hydrogen storage, in which the absorption rate is the highest.

• 한국전기전자재료학회논문지
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• 제20권3호
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• pp.273-280
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• 2007

In this paper, the ZnO surge arrester performance of power distribution class has been studied under different manufacturing conditions such as housing materials(polymeric, porcelain), interface sealants and one-body molding type. In the recent years, the polymeric ZnO surge arresters have been developed and put into operations based on their excellent characteristics. For polymeric surge arresters, the inner gas volume is extremely small, especially in solid insulation polymeric arresters there are not any gas volume inside arresters in the structure due to polymeric materials are filled into the internal gas volume. The sealing integrity is related to safe operation of surge arrester, the prime failure reason of porcelain housed arresters is moisture ingress. In this paper, the sealing integrity of polymeric surge arresters is investigated with moisture multi-aging test and ingress test. The evaluation techniques are used to inspect the sealing integrity of polymeric arresters, including leakage current, surface temperature, reference voltage and dissipation factor.

• 한국항공우주학회지
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• 제44권7호
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• pp.593-602
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• 2016

본 연구에서는 근접연계방식의 초음속기체 금속분말 미립화장치에 대한 수치해석을 수행하였다. 액체금속의 미립화 과정에서 발생하는 1, 2차 액적분열을 모사하기 위해서 난류 모델을 선정하고 VOF(Volume of Fluid), DPM(Discrete Phase Model) 해석을 차례대로 수행하였다. 해석결과, Level-Set function 분포도를 통해 1차 분열액적의 직경을 계산할 수 있었으며 이 데이터를 DPM 해석에 반영해 도메인 출구에서 수집된 입자들의 최종직경분포를 확인할 수 있었다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1047-1052
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• 2008

The aim of this paper is that studies on the characteristics of the liquid-gas ejector. Could get data about various model using numerical analysis. Compare and analyze result that get by an experiment and numerical analysis. And studied Characteristics of the ejector. In this paper, Numerical analysis model is gotten divided according to each Throat ratio as three types. Each throat ratio is 0, 4 and 7.5. According to the result that analyze basic model, pressure became lower causing the volume flow rate increase. In CFD studies, Fixed volume flow rate by these result and analyzed ejector performance. As a result, there was no change of pressure to Throat's Enterance, and pressure became low while pass the throat. Since, pressure recovered while passing diffuser. The outer flow velocity did not change greatly to change of volume flow rate. This research expects that is utilized to data for performance elevation hereafter.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.591-595
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• 2017

이상유동 모델과 동적격자계를 활용하여 탄의 사출관 내부의 열유동과 탄의 운동성능을 해석하는 수치모사를 진행하였다. 고온의 공기와 냉각제간의 상호작용 및 유동장을 해석하기 위해, Realizable $k-{\varepsilon}$ 난류 모델과 VOF (Volume Of Fluid) 모델을 선정하고 냉각제 유량변이에 따른 수치 해석을 진행하였다. 해석결과, 사출관의 압력은 냉각제의 유뮤에 따라 큰 차이를 보였고, 냉각제량에 따라서도 각각의 차이를 보였다. 탄의 속도와 가속도의 변이는 압력에 종속하여 나타났다.

• 대한안전경영과학회지
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• 제19권2호
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• pp.31-39
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• 2017

Classify of explosion hazardous areas must be made at the site where flammable materials are used. This reason is that it is necessary to manage ignition sources in of explosion hazardous areas in order to reduce the risk of explosion. If such an explosion hazard area is widened, it becomes difficult to increase the number of ignition sources to be managed. The method using the virtual volume currently used is much wider than the result using CFD(Computational Fluid Dynamics). Therefore, we tried to improve the current method to compare with the new method using leakage characteristics. The result is a realistic explosion hazard if the light gas is calibrated to the mass and the heavy gas is calibrated to the lower explosion limit. However, it is considered that the safety factors should be taken into account in the calculated correction formula because such a problem should be considered as a buffer for safety.

• 무역학회지
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• 제47권1호
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• pp.1-12
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• 2022

This study analyzes FCEV among measures to respond to climate change policies. In particular, it proposes alternatives to solve this problem in the trade industry, which relies on transportation sectors with high greenhouse gas emissions such as exports and imports of goods. Therefore, when FCEV is introduced in the transportation sector, changes in CO2 emissions, a greenhouse gas, and changes in logistics costs for changes in CO2 emissions are set through scenarios to evaluate the impact on product trade, such as imports and exports. As a result, the increase in logistics costs due to carbon dioxide emissions affected the import and export volume of goods, and when FCEV was introduced, the export volume would increase by up to 5.6%, and the import volume by up to 30%. In addition, CO2 emissions decreased to about 60% in 2050. Therefore, the introduction of FCEV in the transportation sector will greatly contribute to increasing sales in the trading industry and will be able to solve environmental problems such as greenhouse gas reduction.