• The Korean Journal of Ceramics
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• v.1 no.3
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• pp.147-151
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• 1995

Porous composite of $Al_2O_3$ and AIN based mullite and SiC can be prepared by alumium reaction synthesis and atmosphere controllied sintering in order to improve the durability of a gas filter body. The porous $Al_2O_3$-AIN-mullite, which has a strength of 168 kg/$\textrm{cm}^2$ and porosity of 51.59%, could be obtained by stmospheric firing at $1600^{\circ}C$ and the porous $Al_2O_3$-AIN-SiC with a porosity of 33% and strength of 977 kg/$\textrm{cm}^2$, could also be prepared. The average pore size has been changed from 0.2$\mu\textrm{m}$ in a reduction atmosphere and to 2$\mu\textrm{m}$ in an air atmosphere, respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.321-326
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• 2003

The nonlinear humidity distribution occurs due to the moisture diffusion when a concrete is exposed to an ambient air. These nonlinear humidity distribution induces shrinkage cracks on surfaces of the concrete. Because shrinkage cracks largely affect the durability and serviceability of concrete structures, the moisture diffusion in concrete must be investigated. The purpose of this paper is to propose a model of the moisture diffusion coefficient that governs moisture diffusion within concrete structures. To propose the model, numerical analysis were performed based on several experiments. Because the moisture diffusion coefficient is changed with aging, especially at early ages, the proposed model includes aging effect by terms of the porosity as well as the humidity of concrete.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.553-554
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• 2006

This paper presents the effects of different operating parameters on the performance of a proton exchange membrane (PEM) fuel cell by a three-dimensional computational fluid dynamics (CFD) model. The effects of different operating parameters on the performance of PEM fuel cell studied using pure hydrogen on the anode side and air on the cathode side. The various parameters are temperatures, pressures, humidification of the gas steams and various combinations of these parameters. In addition, geometrical and material parameters such as the gas diffusion layer (GDL) thickness and porosity as well as the ratio between the channel width and the land area were investigated.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.97.1-97.1
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• 2012

Porous ceramics are widely used for applications such as catalysis supports, gas distributors and filters such as DPF. For these purpose, it is important to have proper porosity controlling pore structure while maintaining mechanical and thermal properties. In this work, we have prepared the porous ceramic structures made of reaction bonded silicon nitride with hierarchical pore structures. Uni-directionally aligned pore channels, which are mostly filled with ${\beta}$-Si3N4 whiskers, were achieved by an ice-templating method. The structures of the pore channels and the walls are controllable by the processing conditions, such as solid concentration, freezing rate of the slurry, and additives. We have investigated and characterized the influences of the conditions on the microstructures and the properties, such as porosity, pore size distribution, lamellar thickness, wavelength, and orientations. The compressive strength test and flow test was performed to determine the structural integrity and air permeability.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.614-615
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• 2006

Investigation of influence the morphology of initial powder particles, application pore-formers for sintering of nickel powders and application of flux for sintering of aluminum was made. Using different methods was prepared material with size of porous in wide range size of pores ($1-500{\mu}m$). Using the flux for gravity sintering of aluminum in air atmosphere was manufactured porous material with porosity about 45%..

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.305-308
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• 2008

This paper describes a research study on the durability and strength properties of thin quiet-permeable asphalt concrete. Such asphalt mixes have high porosity, which offers significantly better drainages than normal mix designs. However, these materials also exhibit poor durability and strength limiting their use in pavement application. To remedy this, fiber and polymer modifiers have been proposed. All samples were added to modified binder which were prepared with or without the modifiers and fiber using Marshall mix procedures and were experimentally tested using various standardized testing procedures including percent air void for porosity, cantabro test and marshall stability. In general, the results of marshall stability showed that modified mixtures were equivalent to unmodified mixtures. Especially, the result of cantabro tested modified mixtures was superior to unmodified mixtures.

• Computers and Concrete
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• v.27 no.3
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• pp.269-282
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• 2021

A dynamic analytical solution for a simply supported, rectangular functionally graded plate with a porous middle layer under time-dependent load based on a refined third-order shear deformation theory with a cubic variation of in-plane displacements according to the thickness and linear/quadratic transverse displacement is presented. The solution achieved in the trigonometric series form and rests on the Green's function method. Two porosity types and their influence on material properties, and mechanical behavior are considered. The network of pores is assumed to be empty or filled with low-pressure air, and the material properties are calculated using the power-law distribution idealization. Numerical calculations have been carried out to demonstrate the accuracy of the kinematic model for the dynamic problem, the effect of porosity, thickness of porous layers, power-law index, and type of loading on the dynamic response of an imperfect functionally graded material plate.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.190-193
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• 2005

The air filter in engine intake system filters the dirt in the breathing air but also it attenuates the noise although the phenomenon has been regarded negligible. For the analysis of the acoustical performance of air filter, an acoustical model is suggested in this paper. The air filter consists of a porous filter element, which catches the particulate dirt, and a plastic filter box, which supports the filter element. Fibrous structure of the filter element is modeled as a micro-perforated panel using the flow resistivity and porosity. The pleated geometry of the filter element is modeled as two coupled ducts and a mathematical model is developed for the analysis of sound propagation. The filter box Is modeled as a rigid rectangular box. By combining two models, a 4-pole transfer matrix for the air filter is derived. The transmission loss calculated using the transfer matrix of the suggested model is compared with the measured data. Reasonably good agreement is observed. The result can be improved by considering the visco-thermal effect in modeling, in particular at a frequency range near the troughs of TL curve.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.6
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• pp.767-775
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• 1999

The purpose of this study was to evaluate the effect of wattage and curing time on surface hard-ness, three-point bending strength and internal porosity of microwave curing denture base resin. Two sizes of resin specimens were made of Acron $MC^{(R)}\;;\;3.5{\times}10{\times}60mm$ for surface hardness and three-point bending strength measurement and $5{\times}12{\times}60mm$ for internal porosity measurement. They were cured by microwave energy at varing wattages(500W, 700W) and curing times(2min., 3min., 4min.) to determine if a certain wattage/curing time combination would improve physical properties. Surface hardness was measured with Vikers hardness tester, three-point bend-ing strength with universal testing machine and internal porosity was calculated by measuring the weight in air and in water. The results obtained were as follows: 1. There was no significant difference in percent porosity among experimental groups(p>0.05). 2. 500W/3min. group showed the higher surface hardness than 700W/2, 3, 4min. groups(p<0.05), and 700W/4 min. group showed the lower surface hardness than 500W/2, 3, 4min. groups(p<0.05), but there was no significant difference among others(p>0.05). 3. 500W/3min. group yielded the higher value of bending strength than 500W/2min., 700W/3, 4min. groups(p<0.05), but there was no significant difference among others(p>0.05).

• Korean Journal of Materials Research
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• v.10 no.10
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• pp.659-664
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• 2000

To develop anode-supported tubular cell with proper porosity, we have investigated the anode substrate and t the electrolyte-coated anode tube. The anode substrate was manufactured as a function of carbon content in the range of 20 to 50 vol.%. As the carbon COntent increased, the porosity of the anode substrate increased slightly and the carbon c content with proper porosity is found to be 30 vol.%. The anode-supported tube was fabricated by extrusion process a and the electrolyte layer was coated on the anode tube by slurry coating process. The anode-supported tube was cofired successfully at $^1400{\circ}C$ in air. The porosity of the anode tube was 35%. From the gas permeation test, the anode t tube was found to be porous enough for gas supply. On the other hand, the anode-supported tube with electrolyte layer indicated a very low gas permeation rate. This means that the coated electrolyte was dense.