• 농업과학연구
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• 제47권4호
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• pp.1159-1168
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• 2020

The conduits of agricultural reservoirs undergo deterioration over a considerable period of time and this is highly likely to cause structural problems such as cracks. It is therefore important to consider the effects of structural defects on the body from the viewpoint of stability and maintenance of the embankment. In this study, basic data on the effects of the crack location on the stability of the embankment is obtained by identifying, comparing, and analyzing the erosion characteristics and pore water pressure behavior through a large-scale model experiment that involves classifying the location of the conduit cracks. From the results of the experiment, it was confirmed that when a crack occurred, the amount of leakage increased as the location of the crack portion was closer to the water level, and the internal erosion phenomenon accelerated, thereby increasing the possibility of piping. It was also found that an upstream conduit crack affects the erosion and water pressure change of the central and downstream conduit of the embankment, and the conduit crack has a very large effect on the pore water pressure despite the low upstream water level. Therefore, the seepage behavior of the embankment for each conduit crack identified in this study is considered to be useful basic data for preparing a repair and reinforcement plan according to the crack location in the future.

• 한국구조물진단유지관리공학회 논문집
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• 제16권6호
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• pp.73-81
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• 2012

콘크리트 구조물은 일반적으로 동결융해 작용을 받는 조건에 노출되고, 이러한 동결융해작용은 콘크리트의 공극구조를 변화시키고, 콘크리트의 내구성을 저하시킬 우려가 있다. 따라서 본 연구에서는 동결융해작용에 의한 콘크리트 내부공극구조 변화와 동결융해작용을 받은 콘크리트의 내구특성을 평가하고자 하였다. 실험결과, 기존의 동결융해 평가기법에 따르면 모든 배합에서 우수한 내구성능을 나타내었으나, 동결융해 작용에 노출됨에 따라 50~100nm 크기의 공극이 크게 증가하며, 콘크리트 염화물침투저항성이 저하하였다. 수중양생 콘크리트의 공극구조와 염화물 침투저항성은 선형관계를 보이지만, 동결융해작용을 받으면 내부공극구조의 변화로 선형관계가 저하하였다. 동결융해작용과 염화물침투를 동시에 받는 구조물의 내구성 평가기준에 대한 재검토가 필요할 것으로 판단된다.

• 한국건축시공학회지
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• 제18권3호
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• pp.305-312
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• 2018

This study is about the development of a non-sintered binder (NSB) which does not require a sintering process by using the industrial by-products Phosphogypsum (PG), Waste Lime (WL) and Granulated Blast Furnace Slag (GBFS). In this report, through SEM analysis of the NSB paste hardening body, micropore analysis of paste using the mercury press-in method and microstructure observation were executed to consider the influence of the formation of the pore structure and the distribution of pore volume on strength, and the following conclusions were reached. 1) Pore structure of NSB paste of early age is influenced by hydrate generation amount by GBFS and activator. 2) Through observing the internal microstructure of NSB binder paste, it was found that the strength expression at early age due to hydration reaction was achieved with a large amount of ettringite serving as the frame with C-S-H gel generated at the same time. It was confirmed that C-S-H gel wrapped around ettringite, and as time passed, the amount generated continually increased, and C-S-H gel tightly filled the pores of hardened paste, forming a dense network-type web structure. 3) For NSB-type cement, the degree of formation of gel pores below $10{\mu}m$ had a greater influence on strength improvement than simple pore reduction by charging capillary pores, and the pore size that had the greatest effect on strength was micropores with diameter below $10{\mu}m$.

• 공업화학
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• 제9권5호
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• pp.615-618
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• 1998

수성 교질법에 의한 제올라이트 합성 과정에서 활성탄을 부가함으로써 제올라이트 결정화 과정에 미치는 영향과 활성탄 기공 내에서의 제올라이트 결정의 담지현상을 조사하였다. A형 제올라이트를 합성하기 위한 몰 조성비로 조절된 알루미노 실리케이트 겔상에 5 wt % 정도의 활성탄을 첨가할 경우에는 그대로 A형 제올라이트가 생성되었으나 15 wt % 정도 첨가할 경우에는 대부분이 X형이고 일부 A형과 P형 제올라이트가 혼재된 상태로 결정화가 일어났으며, 20 wt %이상 첨가할 경우에는 순수한 X형 제올라이트가 생성되었다. 활성탄의 기공 입구와 내부에는 $1{\mu}m$ 이하의 미세한 제올라이트 결정들이 서로 엉겨붙어 있는 형태로 관찰되었으며, 기공분포 및 입도분포 결과로부터 단순히 제올라이트와 활성탄의 혼합물 형태가 아니라 활성탄 기공 내에 미세한 제올라이트 결정들이 담지되어 있는 복합 소재임을 확인하였다.

• 한국방재학회 논문집
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• 제7권3호
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• pp.19-31
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• 2007

플라이 애쉬와 고로슬래그를 함유하고 물-결합재비가 낮은 고성능 콘크리트의 자기건조에 의한 습도감소와 수축과의 연관성을 파악하기 위하여 내부 습도와 변형률을 측정하였다. 그 결과 일반 콘크리트 내부 습도 감소는 약 10% 수축변형률은 약 $320{\times}10^{-6}$까지 진행하였으며 플라이 애쉬 10%, 20% 혼입한 콘크리트의 경우 각각 10%, 7%의 습도 감소와 $274{\times}10^{-6}$, $231{\times}10^{-6}$의 변형률을 나타내었다. 고로슬래그 40%, 50%를 혼입한 콘크리트는 11%, $371{\times}10^{-6}$, O30G50은 11%, $350{\times}10^{-6}$의 습도감소와 수축 변형률을 나타내었으며 플라이 애쉬 혼입 콘크리트는 일반 콘크리트에 비해 습도 감소량과 변형률이 감소하며 고로슬래그 혼입 콘크리트는 증가하는 경향을 보였다. 자기수축의 경우 내부 습도와 변형률의 관계만을 고려할 때 플라이 애쉬, 고로슬래그 혼입 유무에 상관없이 모두 습도와 변형률은 강한 선형성을 보였다. 콘크리트 내부 습도 변화와 수축변형률의 관계를 보다 구체화하기 위하여 콘크리트 내부 공극을 단일 네트워크로 가정하고 확장 메니스커스 생성 가정 하에 공극수에서 발생하는 모세관 압력과 수화조직체에서 발생하는 표면에너지 변화를 습도의 함수로 모델링하여 수축의 구동력으로 작용시킨 결과 실험값과 비교적 일치하는 값을 나타내었다. 이를 근거로 물-결합재비가 낮은 고성능 콘크리트에서 자기건조에 의한 습도감소는 20nm이하의 소형공극에서 발생함을 파악할 수 있었으며 따라서 자기수축에 대한 제어 방안은 이러한 소형공극에서의 공극수 표면장력과 포화도에 초점을 맞추어야 함을 확인할 수 있었다.

• 한국분말재료학회지
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• 제21권1호
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• pp.34-38
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• 2014

Cu-Ni alloys with unidirectionally aligned pores were prepared by freeze-drying process of CuO-NiO/camphene slurry. Camphene slurries with dispersion stability by the addition of oligomeric polyester were frozen at $-25^{\circ}C$, and pores in the frozen specimens were generated by sublimation of the camphene during drying in air. The green bodies were hydrogen-reduced at $300^{\circ}C$ and sintered at $850^{\circ}C$ for 1 h. X-ray diffraction analysis revealed that CuO-NiO composite powders were completely converted to Cu-Ni alloy without any reaction phases by hydrogen reduction. The sintered samples showed large and aligned parallel pores to the camphene growth direction, and small pores in the internal wall of large pores. The pore size and porosity decreased with increase in CuO-NiO content from 5 to 10 vol%. The change of pore characteristics was explained by the degree of powder rearrangement in slurry and the accumulation behavior of powders in the interdendritic spaces of solidified camphene.

• 대한치과기공학회지
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• 제36권3호
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• pp.179-184
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• 2014

Purpose: This study was performed to investigate the release behavior of bioactive materials as a BMP-2 embedding on the porous titanium implant. Methods: Porous Ti implant samples were fabricated by sintering of spherical Ti powders in a high vacuum furnace. Specimens diameter and height were 4mm and 10mm. Embedding materials were used to stamp ink. Sectional images, porosity and release behavior of porous Ti implants were evaluated by scanning electron microscope(SEM), mercury porosimeter and UV-Vis-NIR spectrophotometer. Results: Internal pore structure was formed fully open pore. Average pore size and porosity were $8.993{\mu}m$ and 8.918%. Embedding materials were released continually and slowly. Conclusion: Porous Ti implant was fabricated successfully by sintering method. Particles are necking strongly each other and others portions were vacancy. Therefore bioactive materials will be able to embedding to porous Ti implants. If the development of the fusion implant of the bioactive material will be able to have the chance to several patients.

• 한국항공우주학회지
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• 제39권8호
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• pp.711-718
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• 2011

본 논문에서는 열화학적 분해 및 열기계학적 변형이 고려된 구성 방정식을 사용하여 다공성 탄소/페놀릭 복합재료의 열탄성 거동을 예측하였다. 다공성 복합재료의 온도 의존성 및 열화학적 분해 과정에서의 기공도, 분해 가스에 의한 기공 압력, 재료의 수축을 고려하였다. 기공도와 기공 압력이 고려된 대표 체적 요소 모델의 유한요소 해석을 통해 산출된 거시적 기공 탄성 계수를 구성 방정식에 적용하였다. 간단한 수치 실험을 통해 기공탄성 계수가 다공성 재료의 열탄성 거동에 미치는 영향을 분석하였으며, 재료 내부에 형성된 기공과 기공 압력에 의한 응력 구배 및 변형을 확인하였다.

• 한국막학회:학술대회논문집
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• 한국막학회 2003년도 The 4th Korea-Italy Workshop
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• pp.133-135
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• 2003

The removal of dissolved oxygen(DO) from water was studied using a poly(vinyliene fluoride)(PVDF) hollow fiber membrane contactor(HFMC) with the vacuum degassing process(VDP), Asymmetric porous PVDF hollow fiber membranes (HFM) for membrane contactor were prepared by a wet phase inversion method. In spinning of these PVDF hollow fibers, dimethy lacetamide (DMAc), LiCl and pure water were used as a solvent, a pore-forming additive and internal/external coagulant, respectively. The characteristics of the structure(pore size, porosity etc.) of the prepared PVDF HFMs as a function of concentration of pore-forming additive in polymer dope solution were studied. Also, the removal efficiency of DO from water according to flow rates of water, using PVDF HFMC with VDP, was studied. The performance of the asymmetric porous PVDF HFMC and a symmetric porous PP HFMC commercialized were compared. As a result, the asymmetric porous PVDF HFMC showed higher removal efficiency of DO than that of a symmetric porous PP HFMC.

• 한국세라믹학회지
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• 제37권1호
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• pp.26-32
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• 2000

Preparation and characteristics of a matrix retaining electrolyte using SiC whisker, PES binder, and NMP(n-methyl-2-pyrrolidone) as a non-volatile solvent for a phosphoric acid fuel cell were investigated. The conditions of binder and plasticizer, and the effects of substituting a volatile solvent by a non-volatile solvent were also studied. The minimum amount of the binder was about 17 wt% for the proper bubble pressure and surrounding SiC whiskers. And the maximum amount of the plasticizer was about 10wt% to be fitted into the polymer chain of the binder. The matrix prepared by using a non-volatile solvent needed longer time to dry, and its pore size was smaller compared with that of the matrix prepared by using volatile solvent. The small pore size resulted in decrease of the overall pore volume. The ionic conductivity in the condition of the same thickness was decreased due to decrease of phosphoric acid absorbancy. As the internal resistance of the electrolyte increased, the fuel cell performance slightly decreased.