• Steel and Composite Structures
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• 제45권3호
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• pp.349-367
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• 2022

In this research, an approach combining a semi-analytical method and an analytical method is presented to investigate the static and dynamic post-buckling behavior of the sandwich functionally graded (FG) porous cylindrical shells exposed to external pressure. The sandwich cylindrical shell considered is composed of a viscoelastic core and two FG porous (FGP) face layers. The viscoelastic core is made of Kelvin-Voigt-type material. The material properties of the FG porous face layer are considered continuous through each face thickness according to a porosity coefficient and a volume fraction index. Two types of sandwich FG porous viscoelastic cylindrical shells named Type A and Type B are considered in the research. Type A shell has the porosity evenly distributed across the thickness direction, and Type B has the porosity unevenly distributes across the thickness direction. The FG face layers are considered in two cases: outside metal surface, inside ceramic surface (OMS-ICS), and inside metal surface, outside ceramic surface (IMS-OCS). According to Donnell shell theory, von-Karman equation, and Galerkin's method, a discretized nonlinear governing equation is derived for analyzing the behavior of the shells. The explicit expressions for static and dynamic critical buckling loading are thus developed. To study the dynamic buckling of the shells, the governing equation is examined via a numerical approach implementing the fourth-order Runge-Kutta method. With a procedure presented by Budiansky-Roth, the critical load for dynamic post-buckling is obtained. The effects of various parameters, such as material and geometrical parameters, on the post-buckling behaviors are investigated.

• 한국응용과학기술학회지
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• 제37권5호
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• pp.1200-1207
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• 2020

본 연구에서는 다공성 활성탄소와 금속유기골격체 복합재료 기반의 전극 재료와 "이온젤" 이라고 불리는 고분자 고체 전해질을 이용하여 슈퍼커패시터를 제작 하였으며, 금속유기골격체의 함량에 따른 전기화학적 거동을 관찰하여 보았다. 슈퍼커패시터의 전기화학적 특성은 순환전압전류법(CV), 전기화학적 임피던스 분광법(EIS) 및 전정류 충·방전법(GCD)으로 분석하였으며, 그 결과로, 다공성 활성탄소 대비 금속유기골격체를 0.5 wt% 첨가 하였을 때 가장 높은 전기용량값을 확인 할 수 있었으며, 0.5 wt% 이상의 금속유기골격체의 함유량은 전기화학적 특성 감소에 영향을 주는 것으로 사료되며, 이러한 결과를 바탕으로 제조된 다공성 활성탄소/금속유기골격체 복합재료 기반의 슈퍼커패시터는 다양한 분야에 활용이 가능할 것으로 판단된다.

• Korean Chemical Engineering Research
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• 제45권6호
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• pp.591-595
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• 2007

기존 마이크론 금속섬유 필터를 지지체로 그 표면 위에 나노입자 증착 후, 열처리를 하여 나노구조 기공층이 표면에 부착 형성된 멤브레인 필터를 제작하였다. 가지상 구조의 나노입자 응집체를 마이크론 금속섬유 필터상에 부착함으로써 기존 금속 멤브레인 필터에 비하여 여과성능이 향상된 나노구조 기공층 멤브레인 필터를 개발하였다. 증착한 나노구조 기공층을 지지체 필터 표면상에 부착시키기 위한 열처리 온도가 증가함에 따라 나노입자 응집체의 수축 현상으로 인하여 나노구조 기공층 멤브레인 필터의 차압은 감소하였지만, 여과효율의 감소는 미미하였다.

• 공업화학
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• 제33권6호
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• pp.646-652
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• 2022

Dead ended anode (DEA) 시스템은 수소극(anode) 출구를 막고 압력으로 연료를 공급하는 방식이다. DEA 방식은 시스템 단순화를 통해 연료이용효율과 전력 효율을 향상시킬 수 있다. 하지만 DEA 운전 중 공기극(cathode)에서 수소극으로 질소와 물의 역확산으로 인한 범람(flooding)이 발생한다. 이러한 범람 현상은 연료전지 성능 저하와 전극 열화의 주요 요인이 된다. 따라서 DEA 운전 시 범람을 방지하기 위하여 연료전지 구조와 구성요소가 최적화되어야 한다. 본 연구에서는 DEA 시스템에서 연료전지의 성능과 연료이용효율 향상을 위해 발포 금속을 적용한 다공성 유로에 대한 영향을 조사하였다. 그 결과, 공기극에 다공성 유로를 사용한 경우 효과적인 물 관리로 연료전지 성능과 배출 간격(purge interval)이 개선되었고, 이를 통하여 공기극 유로 구조가 물 역확산에 영향을 미치는 것을 확인하였다. 이에 반해 수소극의 다공성 유로가 연료전지 성능에 미치는 영향은 미미하였다. DEA 시스템에서는 발포 금속 물성이 배출 간격에 영향을 미치며 cell 크기가 큰 발포 금속에서 안정적인 성능을 나타내었다.

• 한국분말재료학회지
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• 제8권4호
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• pp.215-222
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• 2001

• 한국연소학회지
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• 제14권4호
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• pp.7-16
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• 2009

Porous metal plates (Metal fiber, muti-hole metal plate) using mainly in surface burner are known to have a corrosion and durability problem under high temperature condition. In this study, premixed flat flame with perforated ceramic tile of more durable cordierite material was examined with respect to combustion stability and emission. The flat premixed ceramic burner consists of perforated ceramic tile and various type of baffle plates to form stable surface flame. The results show that most stable flat flame is generated using baffle plate with open ratio of 0.193. In downward flat flame mode which is widely used in condensing boiler, CO is measured below 50ppm from equivalence ratio 0.755 to 0.765 and $NO_X$ is measured below 12ppm from equivalence ratio 0.75 to 0.79. It is also found that the range of blue flame in flame stability curve becomes wider with increasing heat capacity.

• 한국표면공학회지
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• 제48권1호
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• pp.11-22
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• 2015

Pd alloy hydrogen membranes for hydrogen purification and separation need thermal stability at high temperature for commercial applications. Intermetallic diffusion between the Pd alloy film and the porous metal support gives rise to serious problems in long-term stability of Pd alloy membranes. Ceramic barriers are widely used to prevent the intermetallic diffusion from the porous metal support. However, these layers result in poor adhesion at the interface between film and barrier because of the fundamentally poor chemical affinity and a large thermal stress. In this study, we developed Pd alloy membranes having a dense microstructure and saturated composition on modified metal supports by advanced DC magnetron sputtering and heat treatment for enhanced thermal stability. Experimental results showed that Pd-Cu and Pd-Ag alloy membranes had considerably enhanced long-term stability owing to stable, dense alloy film microstructure and saturated composition, effective diffusion barrier, and good adhesive interface layer.

• 연구논문집
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• 통권23호
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• pp.5-13
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• 1993

The present work deals with the theoretical prediction of static & dynamic characteristic of annular type externally pressurized thrust air bearings with metal-sintered porous media. For the evaluation of surface loading effect by machining, it is assumed that the flow at the porous surface is dominant and which is equivalent to the flow through orifice. Finite different method with over-relaxation method is used to solve the numerical problems. The influences of radius ratio, supply pressure and squeeze number on performances are investigated, as the results. The results of this study can be used to predict the optimal running condition and stable realm of porous bearings.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 II
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• pp.1085-1088
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• 2003

In this work, we fabricated a gas-sensing device based on porous silicon(PS), and its I-V and C-V properties were investigated for sensing alcohol vapor. The structure of the sensor consists of thin Au/Oxidized porous silicon/porous silicon/Silicon/Al, where the silicon substrate is etched anisotropically to be prepared into a membrane shape. As the result, I-V curves showed typical tunneling property, and C-V curves were shaped like those of a MIS (metal-insulator- semiconductor) capacitor, where the capacitance in accumulation was increased with alcohol vapor concentration.

• Bulletin of the Korean Chemical Society
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• 제31권6호
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• pp.1459-1460
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• 2010