• 한국식품영양과학회지
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• 제16권2호
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• pp.69-74
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• 1987

일반계인 천마벼와 다수계인 가야벼를 이용하여 팥알의 수분흡수속도와 부피증가속도, 침지조건별 가열시 호화도 및 취반속도를 구하여 일반계와 다수계 쌀의 조리특성을 비교 검토하였다. 수분흡수량과 부피증가량은 모두 침지시간의 평방근과 직선적인 관계를 보였고, 동일한 침지온도와 침지시간에서는 부피증가량이 수분증가량 보다 많았다. 쌀의 조리중 호화도는 무침지한 것보다 침지한 것이 더 빨랐으며, $120^{\circ}C$에서의 취반속도는 100%에 비하여 천마벼가 1.79배, 가야벼가 1.83배 높았다. 수분흡수량, 부피증가량, 쌀의 조리중 호화도 및 취반속도는 모두 다수계인 가야벼가 일반계인 천마벼 보다 높았다.

• International Journal of Concrete Structures and Materials
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• 제9권2호
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• pp.207-217
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• 2015

The influence of powdered and colloidal nano-silica (NS) on the mechanical properties of cement mortar has been investigated. Powdered-NS (~40 nm) was synthesized by employing the sol-gel method and compared with commercially available colloidal NS (~20 nm). SEM and XRD studies revealed that the powdered-NS is non-agglomerated and amorphous, while colloidal-NS is agglomerated in nature. Further, these nanoparticles were incorporated into cement mortar for evaluating compressive strength, gel/space ratio, portlandite quantification, C-S-H quantification and chloride diffusion. Approximately, 27 and 37 % enhancement in compressive strength was observed using colloidal and powdered-NS, respectively, whereas the same was up to 19 % only when silica fume was used. Gel/space ratio was also determined on the basis of degree of hydration of cement mortar and it increases linearly with the compressive strength. Furthermore, DTG results revealed that lime consumption capacity of powdered-NS is significantly higher than colloidal-NS, which results in the formation of additional calcium-silicate-hydrate (C-S-H). Chloride penetration studies revealed that the powdered-NS significantly reduces the ingress of chloride ion as the microstructure is considerably improved by incorporating into cement mortar.

• Journal of Microbiology and Biotechnology
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• 제12권1호
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• pp.149-152
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• 2002

The effect of pressure on the catalytic properties of glutamate racemase from Aquifex pyrophilus, an extremophilic bacterium, was investigated. The activation volume for the overall reaction $({\Delta}V^{\neq})$ and catalysis $({{Delta}V_{cat}}^{\neq})$ was -96.97 ml/mol and 4.97 ml/mol, respectively, while the reaction volume for the substrate binding (${\Delta}V_{K_m^-1}$) was -101.94 ml/mol. The large negative ${\Delta}V^{\neq}$ for the overall reaction indicated that the pressurization of glutamate racemase resulted in enhanced catalytic efficiencies. In addition, this value was also due to the large negative ${Delta}V_{K_m^-1}$ for the substrate binding. The negative value of ${Delta}V_{K_m^-1}$ implied that the conformational changes in the enzyme molecule occurred during the substrate binding process, thereby increasing the degree of hydration. The small value of ${{Delta}V_{cat}}^{\neq}$suggested that the pressure did not affect the glutamate racemase catalysis after the substrate binding.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.363-364
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• 2009

매스 콘크리트의 균열저항성능의 개선효과를 기대함 수 있는 850 $\sim$ 1,000 ${^\circ}C$의 온도로 저온 조성한 MgO 의 반응성 확인을 위하여 활성지표 실험과 안정성 실험을 실시하였으며, 이를 혼입한 콘크리트의 수화생성물을 재령에 따라 고찰하기 위하여 10%의 MgO 를 혼합한 시멘트 페이스트를 대상으로 재령 1일, 3일, 7일, 28일, 56일, 90일, 180일에 SEM을 사용하여 3000배와 10000배로 확대하였을 때의 수화생성물을 촬영하였으며, XRD 를 사용하여 MgO 의 변화량을 정성적으로 측정하였고, DSC를 사용하여 Ca(OH)$_2$와 Mg(OH)$_2$ 의 열분석 곡선을 구하여 재령에 따라 수화생성물의 증감을 확인하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.405-410
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• 2000

Multi-level (macro-level, meso-level, and micro-level) mechanism of prefinitely strained concrete materials os studied The multi-level analysis explains the additional quasibrittle concrete material ductility that comes from lateral confinement and their multi-level interaction mechanisms. The so-called "upgraded tube-squash test" is used to achieve 50% axial strain and over 70 degree of deviatoric strain of quasibrittle concrete materials under extremely high pressure without producing visible cracks. In the micro-level analysis, the variations of hydration rte, micropores, and hydrate phased are analyzed. In the meso-level analysis, mesocracks (the initial invisible cracks) at the interfaces between aggregates and cement paste matrices are studied. The high confining effect in the specimen on the meso-level cracks is also studied. In the macro-level analysis, the physical behavior of prefinitely strained concrete materials is studied. The co-relationships of the results from the three distinct levels of analyses based in various prestraining (0%, 15%, 35%, and 50%) are studied. For the extremely deformed or strained concrete problems, multi-level analysis will be used to explain the unclear and unstudied mechanism of concrete materials, The multi-level analysis can provide us with valuable insights that can explain the additional ductility and confining effect in concrete. concrete.

• 한국건축시공학회지
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• 제11권4호
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• pp.379-386
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• 2011

Durability of concrete is an important issue, and one of the most critical aspects affecting durability is chloride diffusivity. Factors such as water.cement ratio, degree of hydration, volume of the aggregates and their particle size distribution have a significant effect on chloride diffusivity in concrete. The use of polypropylene fibers(particularly very fine and well dispersed micro fibers) or mineral additives has been shown to cause a reduction in concrete's permeability. The main objective of this study is to evaluate the manner in which the inclusion of fiber(in terms of volume and size) and blast furnace slag(BFS) (in terms of volume replacement of cement) influence the chloride diffusivity in concrete by applying 3D computer modeling for the composite structure and performing a simulation of the chloride penetration. The modeled parameters, i.e. chloride diffusivity in concrete, are compared to the experimental data obtained in a parallel chloride migration test experiment with the same concrete mixtures. A good agreement of the same order is found between multi.scale microstructure model, and through this chloride diffusivity in concrete was predicted with results similar to those experimentally measured.

• 한국재료학회지
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• 제23권10호
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• pp.599-605
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• 2013

CSA, a cement mineral compound that is mainly composed of $3CaO{\cdot}3Al_2O_3{\cdot}CaSO_4$, generates ettringite as a hydration product after a reaction with glass (lime), gypsum and water to speed up the hardening process and enhance the strength and degree of expansion. When used as a cement admixture, there is increased production of ettringite, which can improve the initial strength in the first three days and ameliorate the reduction in the initial strength caused by the use of fly ash in particular. In this study, a hydrate analysis was performed using XRD and SEM after substitution with fly ash (30%) and CSA (8%) with the goal of observing the effect of CSA on the initial strength of a cement mixture containing fly ash. The results of the analysis showed that an addition of CSA promoted the production of ettringite and improved the initial strength, resulting in the generation of hydrates, which can effectively enhance the long-term strength of these materials.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.825-828
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• 2008

최근 현대인들의 생활수준과 의식수준의 향상과 더불어 건강에 대한 새로운 요구증가로 생활환경과 밀접한 콘크리트에 대한 관심이 높아졌으며, 환경에 대한 정성 정량적인 평가가 요구되고 있다. 그러나 콘크리트의 대기환경에 관련한 평가는 기존의 규정된 평가방법이 없어 대기환경공정시험법 및 실내공기질 분석방법 등에 의존 할 수밖에 없는 실정이며, 이 또한 분석방법 및 항목이 다양하고 분석방법이 명확하게 규정되지 않는 점 등으로 인해 연구자마다 다양한 방법을 통해 분석하고 있어, 분석결과에 대한 신뢰도도 한계를 지니고 있는 것이 현실이다. 이에 본 연구는 콘크리트의 대기환경에 관한 기초 평가방법으로 건강한 사람의 후각을 이용하여 악취의 취기강도를 측정하는 관능시험방법을 건축 재료에 적용하여 시멘트모르타르의 악취평가 프로세서를 제시하고, 시멘트가 수경성 경화체를 형성하는 초기수화과정단계에서 발생 가능한 악취의 정도를 측정하였다.

• 방사선산업학회지
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• 제5권2호
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• pp.151-157
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• 2011

Crosslinked SPEEK/PVDF membrane were prepared by EB radiation method with various contents of PVDF. The prepared membranes were subjected to a comparative study of proton exchange membranes for fuel cell appreciations. The crosslinked SPEEK/PVDF membranes were characterized by using DMA, DSC and SAXS. The DMA data indicate that the ionic modulus values and cluster $T_g$ decrease with increasing PVDF content. Thus, it was suggested that the number of clustering in the crosslinked membranes can be reduced with increasing PVDF content. The DSC results were shown that the degree of crystalline of the membrane increased with increasing PVDF content. The morphology of the crosslinkied membranes was shown that with increasing PVDF content, the number of crystalline domain of the SPEEK/PVDF membranes increased but ionic aggregation of the membranes decreased. The water uptake behavior, ionic exchange capacity (IEC) and proton conductivity were decreased with increasing PVDF content. The overall findings suggest that the crosslinked membranes offer the possibility for improving the performance of PEMFC, provided that the membranes have thermal and hydration stability.

• Computers and Concrete
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• 제23권5호
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• pp.351-359
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• 2019

In this study, the calcium hydroxide, an inherent product of cement hydration, was treated using biomimetic carbonation method of incorporating stearic acid to generate the hydrophobic calcium carbonate on concrete surface. Carbonation reaction was carried out at various $CO_2$ pressure and temperatures and utilizing the Scanning Electron Microscope (SEM), chloride-ion penetration test apparatus, and compression test machine to investigate the hydrophobicity, durability, and mechanical properties of the synthesized products. Experimental results indicate that the calcium stearate may change the surface property of concrete from hydrophilicity to hydrophobicity. Increasing reaction temperature can change the particles from irregular shapes to needle-rod structures with increased shear stress and thus favorable to hydrophobicity and microhardness. The contact angle against water for the concrete surface was found to increase with increasing $CO_2$ pressure and temperature, and reached to an optimum value at around $90^{\circ}C$. The maximum static water contact angle of 128.7 degree was obtained at the $CO_2$ pressure of 2 atm and temperature of $90^{\circ}C$. It was also found that biomimetic carbonation increased the permeability, acid resistance and chloride-ion permeability of the concrete material. These unique results demonstrate that the needle-rod structures of $CaCO_3$ synthetized on concrete surface could enhance hydrophobicity, durability, and mechanical properties of concrete.