• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1604-1615
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• 2023

In an open-pool type research reactor with a downward forced flow in the core, pipes can be under sub-atmospheric pressure because of the large pressure drop at the reactor core in the atmospheric pool. Sub-atmospheric pressure can result in air inflow into the pipe from the pressure difference between the atmosphere and the inside of the pipe, which in a postulated pipe break scenario can lead to the breakdown of the cooling pump. In this study, a plant-scale experiment was conducted to study air inflow in large piping systems by considering the actual operational conditions of an advanced research reactor. The air inflow rate was measured, and the entrained air was visualized to investigate the behavior of air inflow and flow regime depending on the pipe break size. In addition, the developed drift-flux model for a large vertical pipe with a diameter of 600 mm was compared with other correlations. The flow regime transition in a large vertical pipe under downward flow was also studied using the newly developed drift-flux model. Consequently, the characteristics of two-phase flow in a large vertical pipe were found to differ from those in small vertical pipes where liquid recirculation was not dominant.

• 한국과학교육학회지
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• 제22권2호
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• pp.240-251
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• 2002

이 연구에서는 초등학교 자연 교과서, 중학교 과학교과서, 고등학교 화학 교과서와 지구과학 교과서, 그리고 대학교 일반화학 및 일반지구과학 교과서 중심으로 기압과 대기압에 대한 설명 방식의 차이점을 3가지 유형으로 분석하였다. 유형 1은 무게로 설명하는 경우이며, 유형 2는 단위 면적에 작용하는 공기의 압력으로 설명하는 경우이고, 유형 3은 기체 분자 운동으로 설명하는 경우이다. 과학 교과서 분석 결과, 초등학교 자연 교과서는 유형 1로, 중 고등학교 화학 영역 교과서에서는 모두 유형 3으로 설명하였으며, 지구과학 영역 교과서에서는 주로 유형 1로 설명하였다. 한편, 대학교 일반화학 교과서는 주로 유형 1과 유형 2로 설명하였으며, 일반지구과학 교과서는 중 고등학교 지구과학 영역 교과서와 마찬가지로 주로 유형 1로 설명하였다. 이러한 과학 교과서에서 기압과 대기압에 대한 설명 방식의 차이는 학생들이 기압과 대기압을 이해하는데 혼란을 가져올 수 있을 것이라고 생각된다.

• 한국대기환경학회지
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• 제13권6호
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• pp.475-486
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• 1997

The characteristics of atmospheric aerosols were investigated as a function of particle size and water solubility. The atmospheric aerosols were sampled with classifying into 12 size ranges by the use of Andersen low-pressure impactor. Collected aerosol particles were extracted by ultrapure water and filtered to be separated into water-soluble and insoluble components. The concentrations 12 elements in both components were determined by PIXE analysis. And the concentrations of 8 ions in the soluble component were analyzed by ion chromatography. In general, the mass size distribution of particulate matter was represented as a bimodal distribution. The mass size distributions of S$(SO_4^{2-}), K(K^+), Zn and NH_4^+$ skewed to the smaller size range and those of Si, Ca$(Ca^{2+}), Fe, Na^+ and Mg^{2+}$ skewed to the larger size range. They had roughly one peak in the fine and coarse particle region,respectively. On the other hand, the mass size distribution of Ti, Mn, Ni, Cu, $Cl^- and NO_3^-$ were represented as the bimodal distribution. Fe and Si in the aerosol particles extracted into pure water are existing in high insoluble state. Conversely, almost the whole of S is dissolved in water.

• 한국대기환경학회지
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• 제18권3호
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• pp.193-204
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• 2002

To investigate the relationships between the atmospheric concentrations of PCBs and temperature, quantity of both parameters was performed at an urban site in Korea from July 1999 to January 2000. The strength of correlations between total PCB and temperature was found to be significant (r = 0.752, p < 0.001). It hence indicates that total PCB contents were affected sensitively by temperature change during the sampling period. The ratio of PCB homologs and Deca-CB(PCB 209) also behaved quite similarly to the change of temperature (r>0.60, p<0.05). This may be inferable with the progress of the gas/particle partitioning to the gas phase, especially for fri-and tetra-CBs. Because they have high vapor pressure, they generally exist in the gas phase. The Clausius-Clapeyron equation was applied to the atmospheric PCB data, relating PCB partial vapor pressure to inverse temperature. This may essentially represent the temperature-controlled transition between condensed phase and atmospheric gas phase. The slopes of the resulting plot with International Council for the Explanation of the Seas (ICES) congener ranged from -2810 to -5887, with significantly steep slope and $R^2$(p< 0.005) It was inferred that the PCB atmospheric concentration was also affected by change in the surrounding conditions such as soil, lakes and trees.

• 전기학회논문지
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• 제56권10호
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• pp.1802-1806
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• 2007

Nowadays, many configurations and applications of small atmospheric plasma source have been investigated with growing interest, as it provides the bacteria inactivation, the surface modification and removal of unwanted small regions, and so on. In this paper, the non-thermal micro plasma source under atmospheric pressure by means of submicrosecond pulse voltage waveforms is suggested. Plasma operates in helium is appears as a small (sub-mm) glow at the tip of a plasma gun. Electrical measurements show that the plasma source operates at low voltage (about 500V) and the power consumption is about 1W at 25kHz. Moreover, the emission spectrum shows the relatively higher emission intensity of oxygen particles than those of helium and nitrogen.

• 한국식품저장유통학회지
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• 제16권6호
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• pp.869-874
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• 2009

새로운 돔배기 절임공정을 개발하고자 상압과 감압하에 직간법과 물간법으로 염절임한 돔배기의 품질특성을 비교하였다. 무게 감소율은 물간법으로 상압하에서 절임 하였을 때 12.23%로 높았으며, 수분함량은 감압상태에서 물간법으로 절임한 돔배기가 65.46%로 높았다. 염함량은 직간법으로 감압상태에서 절임 하였을 때 3.02%로 높았으며, 보수력은 직간법으로 감압상태에서 절임한 돔배기가 60.2%로 높았다. 수분활성도는 상압상태에서 직간법으로 절임 하였을 때 0.926으로 낮았으며, 색차는 감압상태에서 물간법으로 절임한 돔배기가 9.75로 가장 낮았으며, 탄력성은 직간법으로 감압상태에서 절임한 돔배기가 91.7%로 높았다. 상압과 감압상태에서 절임한 돔배기을 비교하였을 때, 감압상태에서 절임한 돔배기의 품질특성이 더 좋은 것으로 나타났다. 따라서 감압상태에서의 절임법은 새로운 절임 가공 기술로 활용할 수 있는 가능성을 보였다.

• Current Photovoltaic Research
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• 제4권3호
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• pp.87-92
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• 2016

The effects of selenization pressure on the structural, optical and electrical properties of the CIGS thin films prepared by RF magnetron sputtering using a single quaternary target were investigated. At selenization pressures lower than atmospheric pressure, CIGS thin films formed non-stoichiometric compounds due to deficiencies of Se vapor. In contrast, when selenization process was conducted at above atmospheric pressure, the residence time of Se vapor inside the tube increased so that the Se element could be incorporated within vacant sites of the CIGS structure, resulting in the formation of stoichiometric CIGS thin films. High quality CIGS thin films could be obtained when the selenization process was performed at pressures greater than atmospheric and $550^{\circ}C$.

• 설비공학논문집
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• 제16권11호
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• pp.1021-1027
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• 2004

Design performances of various configurations of hybrid systems combining an atmospheric pressure molten carbonate fuel cell and a gas turbine have been analyzed. Two different fuel reforming methods (internal and external reforming) were considered. Influences of turbine inflow heating method, location of fuel combustor and associated component arrangements were investigated. In general, internal reforming leads to higher system efficiencies. The optimum design pressure ratio varies among different system configurations. In particular, the design point selection is closely related to the allowable turbine inlet temperature. Configurations with direct heating of turbine inlet flow may realize both higher efficiency and higher specific power than those with indirect heating.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.441-444
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• 2006

Extrusion molding concrete panel is cured two times, that is the steam curing at atmospheric pressure and a high-pressure steam curing(autoclaving). Steam curing at atmospheric pressure is done before autoclaving and to acquire the proper strength for treat in process. Though this curing is the important factor on the quality of product and the speed in manufacturing process, it was not evaluated properly so far. Because of ignorance about curing, some engineers even think that the dry curing is better than the steam curing. This study is to investigate the properties of specimen according to variation of curing conditions in the coring chamber such as laboratory scale, pilot plant, and commercial plant. As estimating, in case of steam curing at atmospheric pressure to make extrusion molding concrete panel, moisture curing is better than dry curing and the desirable maximum temperature in curing chamber is about $50^{\circ}C$.

• 한국정밀공학회지
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• 제19권8호
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• pp.34-37
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• 2002