• Structural Engineering and Mechanics
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• 제2권4호
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• pp.403-412
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• 1994

The durability of concrete is related to the permeation characteristics of its near surface. An attempt was made to use the permeation characteristics namely, absorptivity, permeability and diffusivity, to predict the freeze/thaw resistance of concrete. Test results indicate that in general, there was a trend that freeze/thaw resistance of concrete was enhanced with improved absorptivity and diffusivity whilst the freeze/thaw resistance of normal concrete was found to have the best relationship with its intrinsic permeability. The latter method is therefore proposed to be adopted to predict freeze/thaw resistance of normal concrete. Since Figg air test is an inexpensive and simple test method that measures indirectly the intrinsic permeability of concrete, it is further proposed that it could be used as a quality control tool to assess, non-destructively, the freeze/thaw durability potential of in-situ concrete.

• 멤브레인
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• 제29권4호
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• pp.191-201
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• 2019

산업 응용에 적용할 수 있는 중합체 막의 상용화 전에, 고성능 중합체가 실질적인 도전, 즉 연장된 서비스 시간에 대한 장기 안정성을 극복해야하는 과제가 남아있다. 매우 높은 분수 자유 부피(fractional free volume) 및 높은 투과성을 나타내는 고유한 미세 다공성 중합체(polymers of intrinsic microporosity)는 비효율적 무작위 패킹에 의해 생성된 여분의 부피가 물질의 부피적 평형에서 멀어짐과 동시에, 다시 부피적 평형 상태로 복귀하려는 특성, 즉 자유 부피를 줄여가는 특정으로 인해 투과성을 감소시키는 물리적 노화에 영향을 받기 쉽다. 본 논문에서 우리는 미세 다공성 고분자의 물리적 노화를 재검토하고 PIM에서 물리적 노화를 완화하려는 가장 두드러진 시도 중 일부를 논의할 것이다.

• 한국수자원학회논문집
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• 제50권5호
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• pp.325-334
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• 2017

본 연구에서는 다공성 매질의 공극율과 투수능 그리고 유체의 동점성 계수와 같은 물리적 특성에 따른 유체흐름의 비선형 거동에 대한 수치적 분석을 수행하였다. 적용된 수치모형은 ANSYS CFX 3차원 유동해석 모형이며, 모형의 검증은 기존의 물리적 실험 결과 및 수치모의 결과의 적용을 통해 수행되었으며, 적용된 압력경사와 유속과의 관계 그리고 마찰계수와 레이놀즈 수와의 관계에 대해 비교적 잘 일치하였다. 다공성 매질의 공극율과 투수능 그리고 유체의 동점성 계수의 값을 변화시키면서 모의한 결과 유체의 동점성 계수가 다공성 매질의 유체흐름의 비선형 거동에 가장 큰 영향을 미치는 것으로 나타났다.

• 멤브레인
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• 제30권6호
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• pp.420-432
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• 2020

(PIM-1)과 ellagic acid로 만든 랜덤형 공중합체가 간단한 방법으로 합성되었으며, 이산화탄소 분리막에 대한 적용 가능성에 대해서 연구하였다. 이 공중합체의 경우 PIM (polymers with intrinsic microporosity) 고분자의 미세 기공 구조에 기인한 높은 기체 투과도와 평면 구조와 친수성을 갖는 ellagic acid에 기인한 높은 이산화탄소에 대한 선택성에 의해 우수한 이산화탄소 기체 분리 성능을 나타내었다. 즉, 이산화탄소에 대한 투과도 4516 Barrer와 CO2/N2 (> 23~26) 및 CO2/CH4 (>18~19)의 높은 선택성으로 두 쌍의 가스 혼합물에 대해 Robeson 상한(2008)을 초과한 결과를 나타내었다. 이와 같이 PIM-1에 평면구조를 갖는 ellagic acid을 혼입하면 PIM-1의 꼬인 구조를 방해하여 기체 투과성을 향상 시킬 뿐만 아니라 공중합체의 강성과 극성이 증가하여 N2 및 CH4에 대한 CO2의 선택성을 증가시키는 결과를 확인하였다.

• Computers and Concrete
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• 제2권3호
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• pp.189-202
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• 2005

This paper presents an analysis of some experimental results concerning micro-structural tests, permeability measurements and strain-stress tests of four types of High-Performance Concrete, exposed to elevated temperatures (up to $700^{\circ}C$). These experimental results, obtained within the "HITECO" research programme are discussed and interpreted in the context of a recently developed mathematical model of hygro-thermal behaviour and degradation of concrete at high temperature, which is briefly presented in the Part 2 paper (Gawin, et al. 2005). Correlations between concrete permeability and porosity micro-structure, as well as between damage and cracks' volume, are found. An approximate decomposition of the thermally induced material damage into two parts, a chemical one related to cement dehydration process, and a thermal one due to micro-cracks' development caused by thermal strains at micro- and meso-scale, is performed. Constitutive relationships describing influence of temperature and material damage upon its intrinsic permeability at high temperature for 4 types of HPC are deduced. In the Part II of this paper (Gawin, et al. 2005) effect of two different damage-permeability coupling formulations on the results of computer simulations concerning hygro-thermo-mechanical performance of concrete wall during standard fire, is numerically analysed.

• 터널과지하공간
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• 제20권6호
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• pp.434-445
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• 2010

대용량 전력에너지저장시설로서의 복공식 압축공기 지하저장시설의 기밀시스템을 구성하는 콘크리트 라이닝 및 현장 타설 과정에서 발생하는 시공이음부의 투기특성을 파악하고자 콘크리트 블록시료를 이용한 모형실험을 수행하였다. 시공이음부의 투과계수는 콘크리트 블록보다 약 $10^1{\sim}10^4$ 배 정도의 투과성이 큰 것으로 파악되어, 현장 타설과정에서 시공이음부의 품질관리가 저장시설의 기밀성능 확보 관점에서 매우 중요함을 확인하였다. 또한, 접합면에 아크릴계 접착제를 타설함으로써 시공이음부의 투과계수를 콘크리트 블록 수준까지 감소시킬 수 있었으며 콘크리트 블록의 초기 수분함량이 높을수록 투과계수가 감소하여 기밀성능을 향상시킬 수 있음을 확인하였다.

• Computers and Concrete
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• 제2권3호
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• pp.203-214
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• 2005

In the Part 1 paper (Gawin, et al. 2005) some experimental results concerning micro-structural tests, permeability measurements and stress-strain tests of four types of High Performance Concrete, exposed to elevated temperatures (up to $700^{\circ}C$) are presented and discussed. On the basis of these experimental results parameters of the constitutive relationships describing influence of damage and temperature upon material intrinsic permeability at high temperature were determined. In this paper the effects of various formulations of damage-permeability coupling on results of computer simulations are analysed and compared with the results obtained by means of the previously proposed approach, that does not take into account the thermo-chemical concrete damage directly. Numerical solutions are obtained using the recently developed fully coupled model of hygro-thermal and damage phenomena in concrete at elevated temperatures. High temperature effects are considered by means of temperature and pressure dependence of several material parameters. Based on the mathematical model, the computer code HITECOSP was developed. Material parameters of the model were measured by several European laboratories, which participated in the "HITECO" research project. A model problem, concerning hygro-thermal behaviour and degradation of a HPC structure during fire, is solved. The influence of two different constitutive descriptions of the concrete permeability changes at high temperature, including thermo-chemical and mechanical damage effects, upon the results of computer simulations is analysed and discussed.

• Archives of Pharmacal Research
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• 제24권6호
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• pp.584-589
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• 2001

Isopropryl 2-(1-3-dithiethane-2-ylidene)-2 [N-(4-methyl-thiazole-2-yl) carbamoyl] acetate (YH439) is currently under phase ll clinical trials by the Yuhan Research Center for use as a hepatoprotective agent. Unfortunately, the oral bioavailbility of YH439, which is sparingly soluble in water (i.e., $0.3{\;}\mu\textrm{g}/ml{\;}or{\;}0.91{$\mu}M$ at room temperature), reportedly, is negligibleregardless of the dose administered to rats in the 10-300 mg/kg range. The bioavailability of the compound increased up to 24%, when administered in the form of a micellar solution ($700{\;}\mu\textrm{g}/ml$or 2.1 mM for YH439) at a dose of 10 mg/kg, suggesting that its limited solubility is associated with its negligible bioavailability. In order to obtain additional informmation concerning the bioavailability of YH439, the mechanism(s) involved in gastrointestinal (Gl) absorption were investigated in the present study. For this purpose, the transport of YH430 across a Caco-2 cell monolayer was measured in a $Transwell^{\circledR}$. A permeability of $4.07{\times}10^{-5}{\;}cm/s$ was obtained for the absorptive (i.e., apical to basolateral direction) transport of $0.42{\mu}M$ YH439, implicating that the in vivo Cl absorption is nearly complete. The absorptive transport exhibited a slight concentration-dependency with an intrinsic clearance ($CL_{i}$) of $0.38{\mu}L/{\textrm{cm}^2}/sec$, which accounted for 28.1% of the total intrinsic clearance (i.e., $CL_i$ plus the intrinsic clearance for the linear component) of the transport. Thus, saturation of the absorption process appears to be a minor factor in limiting the bioavailability of the compound. The apparent permeability of YH439 from the basolateral to the apical direction (i.e., efflux, $6.67{\times}10^{-5}{\;}cm/s$) was comparable to that for absorptive transport, but, interestingly, a more distinct concentration-dependency was observed for this transport. However, the efflux does not appear to influence the bioavailability of the compound, as evidenced by the sufficiently high permeability in the absorption direction. Rather, a reportedly extensive first-pass hepatic metabolism appears to be a principal factor in limiting the bioavailability. In this respect, reducing the first-pass metabolism by some means would lead to a higher bioavailability of the compound. Thus, elevation of the absorption rate of YH439 becomes a necessity. From a practical point of view, increasing the concentration of YH439 in the Cl fluid appears to be a feasible way to increase the absorption rate, because the compound is primarily absorbed via a linear mechanism. In summary, the solubilization of YH439, as previously demonstrated for a micellar solution of the compound, appears to be a practical way to increase the oral bioavailability of YH439.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -1
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• pp.627-630
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• 2002

A methodology based on factorial design and Motto Carlo methods is developed and implemented for incorporating uncertainties within a multiphase subsurface flow and transport simulation system. Due to uncertainties in intrinsic permeability and longitudinal dispersivity, the predicted output is also uncertain based on the well-developed multiphase compositional simulator. The simulation results reveal that the uncertainties in input parameters pose considerable influences on the predicted output, and the mean and variance of permeability will have significant impacts on the modeling output. The proposed method offers an effective tool for evaluating uncertainty in multiphase flow simulation system.

• 연구논문집
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• 통권34호
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• pp.121-129
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• 2004

The influence of powder size and ball-milling time on the magnetic properties of $Fe_{73}Si_{16}B_7Nb_3Cu_1$ nanocrystalline alloy powder was investigated. Flake-shaped powders were produced by pulverizing the ribbons annealed at $550^\circC$ for 1 hour. The powders were classified and consolidated into core shapes at a pressure of 18ton/$cm^2$. The initial permeability at 100kHz of the inductor core produced using $53-75\mum$ powders showed the highest value although its consolidated density showed the lowest one. The reason for the result is due to the cracking of the particles larger than $75\mum$ during the consolidation process. The ball-milling of powders for 2-4 hours improved the consolidation density and the initial permeability of the cores. The intrinsic coercivity of the powder decreased as well, resulting from the stress relief of the powder by a short-time milling.