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- 주제어 : Poison ratio (검색결과 5 건)
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Duc, Nguyen Dinh,Seung-Eock, Kim,Cong, Pham Hong,Anh, Nguyen Tuan,Khoa, Nguyen Dinh Elsevier 2017 International journal of mechanical sciences Vol.133 No.-
<P><B>Abstract</B></P> <P>The purpose of the present study is to investigate dynamic response and vibration of composite double curved shallow shells with negative Poisson's ratios in auxetic honeycombs core layer on elastic foundations subjected to blast and damping loads using analytical solution. This study considers composite double curved shallow shells with auxetic core which have three layers in which the top and bottom outer skins are isotropic aluminum materials; the central layer has honeycomb structure using the same aluminum material. Based on the first order shear deformation theory (FSDT) with the geometrical nonlinear in von Karman and using Airy stress functions method, Galerkin method and the fourth-order Runge–Kutta method, the resulting equations are solved to obtain expressions for nonlinear motion equations. The effects of geometrical parameters, material properties, elastic foundations Winkler and Pasternak, the nonlinear dynamic analysis and vibration of double curved shallow shells with negative Poisson's ratios in auxetic honeycombs core layer are studied.</P> <P><B>Highlights</B></P> <P> <UL> <LI> To investigate dynamic response and vibration of composite double curved shallow shells by using analytical solution. </LI> <LI> The composite shells have the central auxetic core layer—honeycomb structures with negative Poisson's ratio. </LI> <LI> Based on the first order shear deformation theory (FSDT). </LI> <LI> Used airy stress functions, Galerkin method and fourth-order Runge–Kutta method. </LI> <LI> The effects of geometrical parameters, material properties, elastic Winkler and Pasternak foundations, mechanical and blast loads are studied. </LI> </UL> </P>
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Elucidating the effect of Ce/Zr ratio on high temperature shift activity with sulfur poisoning
김경진,전경원,홍가람,전병훈,배종욱,장원준,이열림,노현석 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.115 No.-
To elucidate the effect of CeO2/ZrO2 ratio on the sulfur-tolerance in high temperature shift using wastederived synthesis gas, the Ce/Zr ratio in Pt/CexZr1-xO2 catalysts was systematically changed. Pt/CexZr1-xO2 catalysts were applied to the high temperature shift reaction with 500 ppm H2S. In the presenceof H2S, the catalysts were deactivated with time on stream due to the poisioning of H2S. Sulfurtolerancein high temperature shift activity depended upon the oxygen storage capacity of the catalysts. The regeneration rate of the catalysts was also related with the oxygen storage capacity. In addition, thePt dispersion matched the oxygen storage capacity trend. The oxygen storage capacity is a main functionto determine the sulfur tolerance in high temperature shift activity compared to the dispersion of Pt.
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하윤석,이명수,Ha, Yunsok,Yi, Myungsu 대한용접접합학회 2015 대한용접·접합학회지 Vol.33 No.3
A very large shell-structure built in shipyards like ship hulls or offshore structures are joined by welding through full process. As the welding contains a high thermal cycle at a local area, the welded structures should be distorted unavoidably. Because a distorted ship block should be revised to the designed value before the next stage, the ability to predict and to control the weld distortion is an accuracy level of the yard itself. Despite the ship block size, several present thermal distortion methodologies can deal those sizes, but it is a different story to deal full ship size model. Even a fully constructed ship hull not remaining any welding can have an accuracy issue like outfitting installation problems. Any present thermal distortion methodology cannot accept this size for its recommended element size and the number. The ordinary welding breadth at erection stage is about 20~40 mm. It can hardly be a good choice to make finite element model of these sizes considering human effort and computational environment. The finite element model for structure analysis of a ship hull is prepared at front-end engineering design stage which is the first process of the project. The element size of the model is as fine as the longitudinal space, and it is not proper to obtain a weld distortion at the erection stage. In this study, a methodology is suggested that a weldment can be shrunk at original place instead of using structural finite element model. We cut the original shell elements at erection weld-line and put truss elements between the edges of cut elements for weld shrinkage. Additional truss elements are used to facsimile transverse weld shrinkage which cannot be from the weld-line truss element shrink. They attach to weld-line truss element like twigs from barks. The capacity of developed elements is verified through an accuracy check of erection process of a container vessel at the apt. hull. It can be a useful tool for verifying a centering accuracy after renew and for block-separating planning considering accuracy.
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Sungmin Kim,Yunseong Ji,Young-Jun Sohn,Seunghee Woo,Seok-Hee Park,Namgee Jung,Yun Sik Kang,Sung-Dae Yim 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.11 No.2
In this study, we suggest an experimental method to accurately understand the unique performance of membrane electrode assembly (MEA) according to the simulation environment (relative humidity and oxygen concentration) by using a small cell of 3 cm2 and supplying excess gas flow for minimizing reaction environmental gradient during cell operation. Through this, we thoroughly examine the characteristics of the catalysts and composition of electrodes which maximizes the performance of the large-area fuel cell, and also find the composition that minimizes deviations from non-uniformity during large-area operation. Furthermore, we also study the performance characteristics of the MEAs according to the physicochemical properties of catalysts, and microstructures from catalyst and ionomer in detail. The unit cell experiment confirms that different performance characteristics of MEAs during results from the structure of carbon support of each catalyst. In addition, the performance characteristics of MEAs at different operating voltages varies depending on the location of Pt nanoparticles on carbon support caused by its structural characteristics. We believe that this analytic methodology can greatly contribute to the development of optimized electrode structure, which are specialized in various fuel cell application fields, and further commercialization of fuel cell systems.
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