• 대한기계학회논문집
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• 제9권5호
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• pp.621-626
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• 1985

본 논문에서는 정해를 구하기 어려운 이질의 세개의 층으로 된 비피압대수층 내에서의 물의 비정상유동에 대한 이론 및 실험에 대하여 연구하고자 한다.

• Coupled systems mechanics
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• 제8권3호
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• pp.259-271
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• 2019

This paper presents forced vibration analysis of sandwich deep beams made of functionally graded material (FGM) in face layers and a porous material in core layer. The FGM sandwich deep beam is subjected to a harmonic dynamic load. The FGM in the face layer is graded though the layer thickness. In order to get more realistic result for the deep beam problem, the plane solid continua is used in the modeling of The FGM sandwich deep beam. The equations of the problem are derived based the Hamilton procedure and solved by using the finite element method. The novelty in this paper is to investigate the dynamic responses of sandwich deep beams made of FGM and porous material by using the plane solid continua. In the numerical results, the effects of different material distributions, porosity coefficient, geometric and dynamic parameters on the dynamic responses of the FGM sandwich deep beam are investigated and discussed.

• 한국수소및신에너지학회논문집
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• 제30권5호
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• pp.455-464
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• 2019

Experiments were conducted to investigate the sensitivity of steel plate oxidation with temperature in a simulated furnace. Used steel plates were a general steel and a high tensile steel. Porous media burner (PM burner) used in model furnace was made for uniform temperature profile. The surrounding temperature was controlled by adjusting the flow rate of the mixture in the combustor. Oxide layer analysis was performed using SEM image analysis and EDS line scanning. Both steel sheets showed a tendency to increase the thickness of the steel sheet surface oxide layer as the temperature increases, and it was confirmed that the flaking phenomenon in surface oxidation layer appeared when the temperature was above a certain temperature.

• 전기화학회지
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• 제10권4호
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• pp.270-278
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• 2007

다양한 종류의 기체확산층 (gas diffusion layer, GDL)을 이용하여 고분자전해질 연료전지의 성능을 시험하였으며 이를 통해 GDL의 물리적 특성과 연료전지의 성능과의 상관관계를 규명하고자 하였다. 전기전도도, 기공도, air permeability, water flux, PTFE 함량, micro-porous layer (MPL)의 유무에 따른 연료전지 성능의 변화가 고찰되었다. GDL의 물리적 특성들은 서로 밀접한 관계를 가지고 있어 연료전지의 성능변화에 영향을 주었다. Carbon paper나 carbon cloth상에 MPL의 형성이 GDL의 물리적 특성을 변화시켜 연료전지의 성능을 변화시킬 수 있음을 관찰하였다. 물리적 특성과 연료전지 성능과의 관계는 전류밀도의 크기에 따라 다른 경향을 나타내거나 혹은 무관한 경향을 보였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.734-741
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• 2004

Boundary layer ingestion in airframe-integrated scramjet engines causes engine stall (“engine un start” hereafter) and restricts engine performance. To improve the unstart characteristics in engines, boundary layer bleed and a two-staged injection of fuel were examined in Mach 4 and Mach 6 engine tests. A boundary layer bleed system consisting of a porous plate, an air coolers, a metering orifice and an ON/OFF valve, was designed for each of the engines. First, a method to determine bleed rate requirements was developed. Porous plates were designed to suck air out of the Mach 4 engine at a rate of 200 g/s and out of the Mach 6 engine at a rate of 30 g/s. Air coolers were then optimized based on the bleed airflow rates. The exhaust air temperature could be cooled below 600 K in the porous plates and the compact air coolers. The Mach 4 engine tests showed that a small bleed rate of 3% doubled the engine operating range and thrust. With the assistance of two-staged fuel injection of H2, the engine operating range was extended to Ф0.95 and the maximum thrust was tripled to 2560 N. The Mach 6 tests showed that a bleed of 30 g/s (0.6% of captured air in the engine) extended the start limit from Ф0.48 to Ф1 to deliver a maximum thrust of 2460 N.

• 자원환경지질
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• 제50권2호
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• pp.159-170
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• 2017

다공성 구조의 장석과 주택 시방기준으로 제작된 바닥 축열층 모르타르의 열적 특성과 소비전력을 비교하였다. 실험을 위해 온수관이 설치된 2개의 실대형 모형을 제작하였다. 자외선 열화상 온도와 온도센서를 이용하여 가열과 냉각과정에서 축열층의 온도변화를 모니터링하였다. 시험동의 축열층은 $20-30^{\circ}C$ 구간의 온도 범위의 가열조건에서 $2-3.5^{\circ}C$ 높은 온도를 보였고 목표 온도에 도달하는 시간이 단축되었다. 온수관에서 멀어질수록 $4-4.8^{\circ}C$ 이상의 차이를 보였고 이는 장석 기반의 모르타르 축열층이 열적 평형에 빨리 도달하는 것을 지시한다. 가열 온도 $30^{\circ}C$를 기준으로 산정한 소비전력은 2.2배 차이를 보였고 단계별 온도 상승에서 소비전력은 66% 절감되었다. 냉각에서 시험동의 표면온도는 지속해서 $2^{\circ}C$ 이상 높았고 축열로 인해 보일러의 재가동 시간이 연장되는 것을 고려하면 에너지 효율은 더 증가할 것이다.

• Bulletin of the Korean Chemical Society
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• 제30권11호
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• pp.2577-2583
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• 2009

Presented are the formation of iron oxide layers on evaporator tubes in an actual fossil power plant operated under all volatile treatment (AVT) condition and an experimental simulation of iron oxide formation in the presence of ferrous and ferric ions. After actual operations for 12781 and 36326 hr in the power plant, two iron oxide layers of magnetite on the evaporator tubes were found: a continuous inner layer and a porous outer layer. The experimental simulation (i.e., artificial corrosion in the presence of ferrous and ferric ions at 100 ppm level for 100 hr) reveals that ferrous ions turn the continuous inner oxide layer on tube metal to cracks and pores, while ferric ions facilitate the production of porous outer oxide layer consisting of large crystallites. Based on a comparison of the oxide layers produced in the experimental simulation with those observed on the actually used tubes, we propose possible routes for oxid layer formation schematically. In addition, the limits of the proposed corrosion routes are discussed in detail.

• 전기학회논문지
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• 제61권1호
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• pp.85-88
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• 2012

DSCs are based on a dye-adsorbed porous $TiO_2$ layer as a photo electrode [1]. Under the illumination, dye molecules are excited and electrons are produced. The injected electrons in the conduction band of $TiO_2$ may recombine with the electrolyte. To obtain high performance DSCs, it is essential to retard the recombination. The charge recombination can be reduced by forming core-shell structure. In this work, we investigated the core-shell structure with $Al_2O_3$ and MgO coating layer on the porous $TiO_2$ layer. We confirmed the photovoltaic properties by I-V characteristics. The current and the efficiency was improved. In addition to, Through decrease in the width of EIS arc, which is the sum of the interfacial charge transfer resistances of both electrodes, we can be indicated that the block effect.

• 설비공학논문집
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• 제11권5호
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• pp.588-597
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• 1999

Sokkuram grotto, a UNESCO cultural heritage in Kyongju Korea, was originally covered with crushed rocks over its dome with ventilating holes. The grotto was perfectly preserved for more than 12 centuries until the upper structure was replaced with a concrete dome in the early 20th century to protect from total collapse. Since then, heavy dew formed on the granite surface to seriously damage the sculptures until it was further remodeled with air-conditioning facilities in the 60s. It is considered that the original upper porous structure had a dehumidifying capability. This research is made to unveil the dehumidifying mechanism of the rock layer during the rainy season in that area. A rock layer and a concrete layer are tested in a temperature/humidity-controlled room. No dew formation is observed for the two specimen for continued sunny days or continued rainy days. However, heavy dew formed on the concrete surface for a sunny day after long rainy days. It is thought that the sun evaporates water on the ground and dew is formed at the surface as the highly humid air touches the yet cold concrete. On the contrary, no dew formation is observed for the rock layer at any time. Even in the above worst situation, air flows downward through the cool rock layer and moisture is removed before reaching inside. Temperature measurement, flow visualization, observation of dew formation and measurement of air velocity are made to verify the mechanisms.

• 대한전자공학회논문지
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• 제23권5호
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• pp.699-705
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• 1986

Sb2S3 thin films were fabricated by vacuum evaporation of compound Sb2S3 at a pressure of 10**-5 torr. and in argon ambient. Then, their electrical and photoconductive properties were investigated. The Sb2S3 glass-layer showed maximum photosensitivity at the deposition rate of 250\ulcornersec, and Sb2S3 porous layer had mininum dielectric constant of 1.5 at the deposition rate of 0.3 um/sec and argon partial pressure of 0.2torr. Sb2S3 multi-layers were prepared at the different thickness ratio (B/A) to find the proper structural property suited for camera pick-up tube. Here, A is the sum of the thickness of Sb2S3 porous layer and Sb2S3 fine grain layer, and B is the thickness of Sb2S3 fine grain layer. As a result, photosensitivity had a peak value at the thickness ratio (B/A) of 60%.