• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.176-179
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• 2001

When the preform is composed of more than two layers with different in-plane permeability in resin transfer molding, effective average permeability should be determined for the flow analysis in the mold. The most frequently used averaging scheme is the weighted average scheme, but it does not account for the transverse flow between adjacent layers. A new averaging scheme is proposed predicting the effective permeability of the multi-layered preform, which accounts for the transverse flow effect. The new scheme is verified by measuring the effective permeability of the multi-layered preforms and the difference in each flow front position.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.134-136
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• 2005

Homogenization method is adopted to predict the permeability tenor for glass fiber plain woven fabrics. Calculating the permeability tensor numerically is an encouraging task because the permeability tensor is a key parameter in resin transfer molding (RTM). Based on multi-scale approach of the homogenization method, the permeability for the micro-unit cell within fiber tow is computed and compared with that obtained from flow analysis for the same micro-unit cell. It is found that they are in good agreement. In order to calculate the permeability tensor of macro-unit cell for the plain woven fabrics, the Stokes and Brinkman equations which describe inter-tow and intra-tow flow respectively are employed as governing equations. The effective permeabilities homogenized by considering intra-tow flow are compared with those obtained experimentally. Control volume finite element method (CVFEM) is used as a numerical method. It is shown that the asymptotic expansion homogenization method is an attractive method to predict the effective permeability for heterogeneous media.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2001년도 학술발표회 발표논문집
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• pp.375-378
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• 2001

This study was peformed to understand permeability characteristic of clays with various pH values. A serious of physical properties and permeability tests, consolidation tests was performed on a clay and a marine clay. Results of the study are as follows. As pH values were decreased, coefficient of permeability was increased because of increase in effective void caused by decrease in thickness of diffuse double layer besides change in soil structures and effective grain size. As pH values were increased, coefficient of permeability of marine clay was increased. Variation of coefficient of permeability of marine clay was increased. Variation of coefficient of permeability of marine clay was largely related because of higher clay contents.

• 한국농공학회지
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• 제44권6호
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• pp.99-105
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• 2002

A series of physical properties and rigid wall permeability tests were performed on two clays to investigate changes in permeability characteristics of clays with various pH values. Results of the study are as follows. As pH values were increased, coefficients of permeability of S-clay(clay fraction 18%) and J-clay(clay fraction 30%) were decreased in 3 and 4 times, respectively. Variation of coefficient of permeability of J-clay was considerably related to clay fraction. It can be said that coefficient of permeability of clays tested was increased, as pH values were decreased. This was because of increase in effective voids caused by decrease in thickness of diffused double layer, that is, change in soil structures and effective grain sizes.

• 터널과지하공간
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• 제8권4호
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• pp.275-286
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• 1998

균열연결망 모델에서의 투수계수 텐서, 주 투수계수 그리고 주 투수계수 방향들에 대한 인자에 근거해서 유효투수계수와 대표요소체적을 구하였다. 전체브록에 대한 소블록의 투수계수의 계산을 통해서 유효투수계수는 조화평균과 산술평균 사이의 범위임을 알 수 있었다. 정육면체 모델에서 체적의 증가에 따른 유량의 변화계산에 대한 수치실험으로부터 유량의 변화는 모델의 체적이 대표요소체적에 접근함에 따라 감소함을 보여 주어ST다. 터널로의 지하수 유입량은 대표요소체적 개념보다는 터널길이대 모델크기의 비에 더 큰 영향을 받는다고 볼 수 있다. 그리고 균열연결망 모델과 등가다공성 모델에서의 지하수 유입량은 정확히 일치하지 않았으며 특히 모델크기에 대한 터널길이가 작을수록 그 차이가 크게 발생하였다.

• Journal of electromagnetic engineering and science
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• 제16권2호
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• pp.67-73
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• 2016

This paper presents simple expressions for the effective permeability of bulk metamaterial consisting of ring resonators (RRs) or split ring resonators (SRRs) based on the convenient geometrical factors of the structure compared with wavelength. The resonant frequency dependence of the medium permeability, including loss effects, is analyzed in detail. Inverting the analysis equations, useful design (or synthesis) equations are derived for a systematic design process with some examples. This paper may particularly be useful for the design of a bulk metamaterial with a specific negative relative permeability at a desired frequency. The loss of metamaterials consisting of RRs (or SRRs) is also analyzed over a wide frequency band from 10 MHz to 10 THz.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.1043-1052
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• 2009

To derive easily the coefficient of permeability from several other soil properties, the estimation model of coefficient of permeability was proposed using linear regression analysis. The coefficient of permeability is one of the major factors to evaluate the soil characteristics. The study area is located in Kangwon-do Pyeongchang-gun Jinbu-Myeon. Soil samples of 45 spots were taken from the study area and various soil tests were carried out in laboratory. After selecting the soil factor influenced by the coefficient of permeability through the correlation analysis, the estimation model of coefficient of permeability was developed using the linear regression analysis between the selected soil factor and the coefficient of permeability from permeability test. Also, the estimation model of coefficient of permeability was compared with the results from permeability test and empirical equation, and the suitability of proposed model was proved. As the result of correlation analysis between various soil factors and the coefficient of permeability using SPSS(statistical package for the social sciences), the largest influence factor of coefficient of permeability were the effective grain size, porosity and dry unit weight. The coefficient of permeability calculated from the proposed model was similar to that resulted from permeability test. Therefore, the proposed model can be used in case of estimating the coefficient of permeability at the same soil condition like study area.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.985-990
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• 2001

Chloride permeability of high strength concrete(HSC) was investigated using saltwater pending test and rapid chloride permeability test by electrical potential(ASTM C 1202). The lower water-cement ratio concrete showed the lower diffusion coefficient of chloride. The relationship between the diffusion coefficient of chloride and charge passed by the rapid chloride permeability test could be obtained. This relationship appears to be an effective method for evaluating chloride permeability of low water-cement HSC.

• Geomechanics and Engineering
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• 제13권2호
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• pp.285-300
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• 2017

Shallow coal resources are increasingly depleted, the mining has entered the deep stage. Due to "High stress, high gas, strong adsorption and low permeability" of coal seam, the gas drainage has become more difficult and the probability of coal and gas outburst accident increases. Based on the flow solid coupling theory of coal seam gas, the coupling model about stress and gas seepage of coal seam was set up by solid module and Darcy module in Comsol Multiphysics. The gas extraction effects were researched after applying hydraulic technology to increase permeability. The results showed that the effective influence radius increases with the expanded borehole radius and drainage time, decreases with initial gas pressure. The relationship between the effective influence radius and various factors presents in the form: $y=a+{\frac{b}{\left(1+{(\frac{x}{x_0})^p}\right)}}$. The effective influence radius with multiple boreholes is obviously larger than that of the single hole. According to the actual coal seam and gas geological conditions, appropriate layout way was selected to achieve the best effect. The field application results are consistent with the simulation results. It is found that the horizontal stress plays a very important role in coal seam drainage effect. The stress distribution change around the drilling hole will lead to the changes in porosity of coal seam, further resulting in permeability evolution and finally gas pressure distribution varies.

• 한국표면공학회지
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• 제36권6호
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• pp.455-460
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• 2003

Microstructural and magnetic properties of nanocrystalline Fe-46 wt%Ni and Fe-36 wt%Ni alloys were investigated. Alloys were prepared by the electrodeposition process. The electrolytes were iron sulfate/nickel chloride-based and iron chloride/nickel sulfamate-based solutions. Fe-46 wt%Ni alloy was FCC structure with grain size of 10 nm, but FCC and BCC phases were found in Fe-36 wt%Ni alloy and its grain size was smaller. Effective permeability of Fe-36 wt%Ni alloy was higher than that of Fe-46 wt%Ni alloy in the high frequency range because of large electrical resistivity and small eddy current loss resulted from grain size decrease. Up to $300^{\circ}C$ of annealing temperature, grain growth of Fe-Ni alloys slowly occured. Conversely, annealing above $450^{\circ}C$ led to a drastic grain growth. In that case, effective permeability was decreased at the temperature lower than $300^{\circ}C$ but at $300^{\circ}C$ or higher effective permeability was increased. At the high frequency of 1 MHz, electrodeposited Fe-Ni alloys had higher effective permeability with an decrease in the grain size.