• 대한치과보철학회지
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• 제34권2호
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• pp.290-298
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• 1996

The effects of impression tray disinfection procedures on the bond strength of impression-material adhesive to two of types resin trays were evaluated with a tensile test. Autopolyme-rizing acrylic resin was formed into 1x1x1 cm cubes. A hook was attached to each cube with autopolymerizing acrylic resin. Perforated trays were fabricated with stops to maintain an even 3 cm of impression material over the resin block. Hook on the opposite side of the perforated tray permitted attachment of the metal plate to a mechanical testing machine. Before adhesive was applied, one third of the resin specimens were immersed in a 5% sodium hypochlorite solution : one third in a 2% glutaradehyde solution, and one third were kept in the "as fabricated" condition. Three products(Perfect ups, Exafine, and Exp-ress) of polyvynil siloxane impression material-adhesive system were evaluated. The resin-impression material-metal plate couples were attached to a mechanical testing machine and tensile forces were applied at a separation rate of 10 centimeters per second. The results were as follows; 1. Both disinfectant and adhesive had effects on bond strength values, but adhesive had more effect than disinfectant(p<0.01). However, there was no interaction between dinin-fectant and adhesive(p>0.01). 2. Mean bond strength values for the Perfect materials were about 85% less than that of the Exafine or the Express materials. However, there was no stastically significant difference between the mean bond strength values of the Exafine materials and the Express materials(p>0.05). 3. The use of disinfectants produced significant reduction in bond strength values(p<0.05). But there was no stastically significant difference between the mean bond strength values of the groups treated with disinfectants(p>0.05).

• 한국기계가공학회지
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• 제17권1호
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• pp.82-88
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• 2018

An experimental study was performed on the orifice nozzle system that generates micro-bubbles by air self-suction using a venturi nozzle. This study experimentally investigates the amount of air sucked into the venturi nozzle and the number of micro-bubbles generated by the orifice nozzle system in Cases 1 and 2. The experimental conditions were varied by changing the diameter of the orifice nozzle (d=2~7 mm) and the number of holes of the perforated plate nozzle (n = 2-12). In Case 1, the air self-suction was more than 2 LPM at $d{\leq}4mm$. When d = 4 mm, the total number of bubbles was 29,777, and it was confirmed that micro-bubbles occupied approximately 65% of the total number of bubbles. In Case 2, the air self-suction was maintained constant at approximately 2.5 LPM regardless of the number (n) of holes. The total amount of bubbles increased when n increased but remained constant at approximately 44,000 when $n{\geq}7EA$. It was also confirmed that more than 80% of all bubbles were micro-bubbles when $n{\geq}10EA$. Thus, the number of micro-bubbles increased by approximately 15% compared to the experimental result of Case 1, which was optimized with d = 4 mm.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3049-3052
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• 2008

MCFC(molten carbonate fuel cell) power generation system is prime candidate for the utilization of fossil based fuels to generate ultra clean power with a high efficiency. In the MCFC power plant system, a combustor performs a role to supply high temperature mixture gases for cathode and heat for reformer by using the stack off-gas of the anode which includes a high concentration of $H_2O$ and $CO_2$. Since a combustor needs to be operated in a very lean condition and to avoid excessive local heating, catalytic combustor is usually used. The catalytic combustion is accomplished by the catalytic chemical reaction between fuel and oxidizer at catalyst surface, different from conventional combustion. In this study, a mathematical model for the prediction of internal flow and catalytic combustion characteristics in the catalytic combustor adopted in the MCFC power plant system is suggested by using the numerical methods. The numerical simulation models are then implemented into the commercial CFD code. After verifying result by comparing with the experimental data and calibrated kinetic parameters of catalytic combustion reaction, a numerical simulation is performed to investigate the variation of flow and combustion characteristics by changing such various parameters as inlet configuration and inlet temperature. The result show that the catalytic combustion can be effectively improved for most of the case by using the perforated plate and subsequent stable catalytic combustion is expected.

• Steel and Composite Structures
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• 제33권4호
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• pp.569-581
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• 2019

Corrugated steel plate shear wall (CSPSW) as an innovative lateral load resisting system provides various advantages in comparison with the flat steel plate shear wall, including remarkable in-plane and out-of-plane stiffnesses and stability, greater elastic shear buckling stress, increasing the amount of cumulative dissipated energy and maintaining efficiency even in large story drifts. Employment of low yield point (LYP) steel web plate in steel shear walls can dramatically improve their structural performance and prevent early stage instability of the panels. This paper presents a comprehensive structural performance assessment of corrugated low yield point steel plate shear walls having circular openings located in different positions. Accordingly, following experimental verification of CSPSW finite element models, several trapezoidally horizontal CSPSW (H-CSPSW) models having LYP steel web plates as well as circular openings (for ducts) perforated in various locations have been developed to explore their hysteresis behavior, cumulative dissipated energy, lateral stiffness, and ultimate strength under cyclic loading. Obtained results reveal that the rehabilitation of damaged steel shear walls using corrugated LYP steel web plate can enhance their structural performance. Furthermore, choosing a suitable location for the circular opening regarding the design purpose paves the way for the achievement of the shear wall's optimal performance.

• 대한기계학회논문집B
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• 제21권1호
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• pp.165-173
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• 1997

The present study investigates heat/mass transfer for flow through perforated plates for application to combustor wall and turbine blade film cooling. The experiments are conducted for hole length to diameter ratios of 0.68 to 1.5, for hole pitch-to-diameter ratios of 1.5 and 3.0, for gap distance between two parallel perforated plates of 1 to 3 hole diameters, and for Reynolds numbers of 60 to 13, 700. Local heat/mass transfer coefficients near and inside the cooling holes are obtained using a naphthalene sublimation technique. Detailed knowledge of the local transfer coefficients is essential to analyze thermal stress in turbine components. The results indicate that the heat/mass transfer coefficients inside the hole surface vary significantly due to flow separation and reattachment. The transfer coefficient near the reattachment point is about four and half times that for a fully developed circular tube flow. The heat/mass transfer coefficient on the leeward surface has the same order as that on the windward surface because of a strong recirculation flow between neighboring jets from the array of holes. For flow through two perforated plate layers, the transfer coefficients on the target surface (windward surface of the second wall) affected by the gap spacing are approximately three to four times higher than that with a single layer.

• 대한토목학회논문집
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• 제28권6A호
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• pp.853-859
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• 2008

본 연구에서는 유공강판 전단연결재를 강관말뚝머리 연결부의 결합용 구조 요소로 활용하기 위한 연구의 일환으로 유공강판 전단연결재의 홀 형상, 홀 직경, 홀 관통철근, 매입깊이 등에 따른 구조적 성능 및 거동 특성을 실험적으로 규명하였으며, 그 결과 유공강판 전단연결재가 충분한 인발저항성능을 확보하기 위해서는 콘크리트 다웰 효과가 충분히 발현될 수 있도록 확보가능한 만큼의 다수의 홀을 가공 배치하되, 각 홀의 직경은 전단연결재 높이의 절반 정도임과 동시에 관통철근 배근 후에도 콘크리트의 완전한 충전이 가능할 만큼의 홀 내 여유 공간을 충분히 확보하는 것이 바람직하며, 아울러 유공강판 전단연결재가 강관말뚝머리 연결부의 결합용 구조 요소로서의 제기능을 발휘할 수 있도록 충분한 정착성능을 확보할 필요가 있다.

• 한국해안·해양공학회논문집
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• 제36권3호
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• pp.116-127
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• 2024

부잔교는 연안에 설치되는 대표적인 부유식 구조물로 선박의 접안 및 계류시설로 주로 활용되고 있으나, 파랑제어 및 파력발전 구조체와 같은 다양한 목적으로 활용하려는 시도가 계속되고 있다. 본 연구에서는 상하동요와 제한된 횡동요만을 허용하는 말뚝계류 부잔교를 대상으로 부유체의 유공구조 및 몰수판 부착에 따른 반사특성 및 동요특성을 실험적으로 검토하였다. 수리실험결과, 말뚝계류된 부잔교의 반사특성과 동요특성은 뷰유체의 유공구조 유무에 비해 몰수판의 설치 유무와 설치수심에 크게 의존함을 확인하였다. 특히, 몰수판의 설치는 단주기 파랑에서 반사계수를 증가시키고, 부유체의 상하동요 및 횡동요를 감소시키는 효과가 있었다.

• 설비공학논문집
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• 제9권2호
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• pp.221-228
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• 1997

A strong combustion-driven sound from a surface burner made of a perforated metal fiber plate for premixed gas was investigated to clarify the physical mechanism of its generation. A simple model was developed for the acoustic power generation in terms of the heat transfer response function and the acoustic impedance of the burner. The acoustic impedance of the perforated metal fiber placed on the open exit was measured and the heat release response of the burner to the oscillating flow associated with the acoustic disturbance was expressed in terms of a response function. It was found that the power is generated by the heat release in response to the downstream particle velocity, in contrast to the upstream velocity in the case of the Rijke oscillation driven by a heater placed in the lower half of a columm with upstream flow. The measured frequencies of the oscillation were in agreement with the estimated resonance frequencies and their excitation was varied with the combustion conditions. For the same fuel rate, the excited frequency increases with the air ratio if it is low but decreases with the ratio if not so low. Such frequency characteristics were explained by assuming a heat release response function with a time constant and it was shown that the excited frequency decreases as the time constant increases.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권6호
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• pp.554-562
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• 2016

Recently, regulations pertaining to the noise and vibration environment of offshore plants have been strengthened. For example, the NORSOK standards have been applied, which are very strict regulations that are comparable to those applied to passenger ships. Furthermore, the use of porous materials, such as those used in most of the current insulating panels, has been forbidden. Therefore, honeycomb-backed Micro-Perforated Plates (MPPs) are now regarded as next-generation absorber materials. This paper reports the results of parametric studies that were performed using numerical methods to determine the effect of the thickness on the performance of a honeycomb panel and the effect of the perforation ratio on the MPP performance. The numerical results were verified through experiments. Finally, we propose a combined honeycomb/MPP panel where the MPP is placed between upper and lower honeycomb panels and one end surface is also replaced with an MPP.

• 한국수소및신에너지학회논문집
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• 제18권4호
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• pp.406-412
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• 2007

An experimental study on the design of a catalytic combustor for 1.6 kW MCFC system has been performed. The roles of the catalytic combustor are to completely burn anode off-gas and to supply sufficient $CO_2$ to cathode channels. In order to avoid hot spot or fuel slippage, flow uniformity at the catalyst inlet was achieved by installing two crossing perforated plates between the catalyst and the mixing chamber with minimal pressure drop. A Pd/Ce/Ni-$Al_2O_3$ catalyst was used for complete combustion of the off-gas at GHSV=36,000.