• 한국유체기계학회 논문집
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• 제19권6호
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• pp.19-25
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• 2016

Anti-icing is important in gas turbines because ice formation on compressor inlet components, especially inlet guide vane, can cause performance degradation and mechanical damages. In general, the compressor bleeding anti-icing system that supplies hot air extracted from the compressor discharge to the engine intake has been used. However, this scheme causes considerable performance drop of gas turbines. A new method is proposed in this study for the anti-icing in combined cycle power plants(CCPP). It is a heat exchange heating method, which utilizes heat sources from the heat recovery steam generator(HRSG). We selected several options for the heat sources such as steam, hot water and exhaust gas. Performance reductions of the CCPP by the various options as well as the usual compressor bleeding method were comparatively analyzed. The results show that the heat exchange heating system would cause a lower performance decrease than the compressor bleeding anti-icing system. Especially, the option of using low pressure hot water is expected to provide the lowest performance reduction.

• KCI Concrete Journal
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• 제11권3호
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• pp.29-43
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• 1999

The effects of superplasticizers on fresh and hardened concrete were investigated. The experimental program included tests on the workability and slump loss, bleeding, setting time, air content, compressive, tensile and flexural strength, permeability, shrinkage, freeze-thaw durability and creep deformation. Properties of superplasticized concrete were compared with those of conventional and base concretes. Superplasticizers were observed to have an appreciable fluidifying action in fresh concrete. They permitted a significant water reduction while maintaining the same workability. Bleeding of superplasticized concrete was much lower than that of conventional concrete of the same consistency. This indicates that the use of superplasticizers did not affect the tendency of segregation of fresh concrete. The compressive, tensile, and flexural strengths of superplasticized concrete were significantly higher than those of conventional concrete. The permeability and drying shrinkage and creep of superplasticized concrete were less than those of conventional concrete, but there were no significant differences between base and superplasticized concrete. Compared with base concrete, non-air-entrained superplasticized concrete had slightly higher freeze-thaw durability. and superplasticized concrete with an appropriate amount of entrained air Eave even better resistance to freezing and thawing.

• 생약학회지
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• 제19권1호
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• pp.39-46
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• 1988

Experimental studies were conducted to investigate the hemostatic effect of the water extracts of Kwibitang. For this purpose, the effects of the extracts on the bleeding time in mouse tail and prothrombin time in vitro were estimated. Furthermore, its activity on the isolated uterine muscle in rats were investigated. The results obtained were as following; The bleeding time was not shortened, but the plasma prothrombin time in vitro test was significantly shortened. The uterotonic action produced by the extract was not inhibited by pretreatment of diltiazem at the doses of $10^{-5}g/ml$.

• Natural Product Sciences
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• 제8권4호
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• pp.152-154
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• 2002

The methanol extract of Viscum album var. coloratum, Korean mistletoe, showed potent prolongation effects on the bleeding time in rats in vivo, and whole blood clotting time and plasma recalcification time in rats ex vivo. The prolongation effect on the bleeding time of Korean mistletoe is comparable to that of Viscum album L., European mistletoe, 185.6% and 176.5%, respectively. However, the water extracts of the both plants did not show any prolongation effects. Platelet activating factor (PAF) receptor binding assay was carried out to elucidate the action mechanisms of the extracts, and both of the methanol extracts did not show any inhibitory activity. The $LD_{50}$ of the methanol extracts of both mistletoes are more than 2 g/kg. These results suggest that the mehtanol extract of Korean mistletoe might be a potential candidate to develop new drug to improve microcirculation.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2002년도 학술논문발표회
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• pp.57-60
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• 2002

Recently, the coal ash production has been increased by increase of consumption of electric power. So it is important to find a reclaimed place and treatment utility for treating coal ash. Accordingly, in this study we performed an experimental study to compare and analyze the Properties of concrete according to W/C and bottom ash replacement ratio. As a result of this study, it was found that the bleeding content was decreased according to decrease of W/C and increase of bottom ash replacement ratio, and the compressive strength of concrete using bottom ash was similar to plain concrete(replacement ratio 0%).

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2002년도 학술논문발표회
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• pp.7-12
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• 2002

The purpose of this study is to design and to apply the self-compaction concrete mixture to field, having not only high strength but also compensation for shrinkage without thermal crack under 4 sides outer restraint of the member. In the experimental mix, replacement ratio of limestone Powder, CSA expansive additives, and unit water were selected as parameters, using portland blast-furnace slag cement. And, bleeding test, expansibility test, hydration heat analysis were performed. As a results, when Cement is replaced with 35% limestone Powder, 6% CSA expansive additives at unit water 175kg/$m^3$, demanded performances of fresh and hardened self-compaction concrete are accomplished in the field application.

• 한국건축시공학회지
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• 제3권4호
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• pp.135-138
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• 2003

The purpose of this study was to design the self-compaction concrete mixture, having not only high strength but also compensation of shrinkage without thermal crack under 4 sides outer restraint of the member. In the experimental mix, replacement ratio of limestone Powder, CSA expansive additives, and unit water were selected as parameters, using portland blast-furnace slag cement. And, bleeding test, expansibility test, hydration heat analysis were performed. As a results, when 35% of limestone Powder, 6% CSA expansive additives are replaced at unit water 175kg/$\textrm{m}^3$, demanded performances of fresh and hardened self-compaction concrete are accomplished.

• 한국건축시공학회지
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• 제4권1호
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• pp.85-88
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• 2004

The purpose of this study was to design the self-compaction concrete mixture, having not only high strength but also compensation of shrinkage without thermal crack under 4 sides outer restraint of the member. In the experimental mix, replacement ratio of limestone Powder, CSA expansive additives, and unit water were selected as parameters, using portland blast-furnace slag cement. And, bleeding test, expansibility test. hydration heat analysis were performed. As a results, when 35% of limestone Powder, 6% CSA expansive additives are replaced at unit water 175kg/$\textrm{m}^3$, demanded performances of fresh and hardened self-compaction concrete are accomplished.

• 한국건축시공학회지
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• 제8권5호
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• pp.85-91
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• 2008

Prepacked concrete has recently been used in the special constructions fields such as underwater concrete work, heavy-weight concrete work, underground structure work, partial repair works for damaged reinforced concrete structures. and polymer-modified mortars have been employed as grouting mortars for the prepacked concrete. The purpose of this study is to recommend the optimum mix design of polymer-modified grouting mortars for prepacked concrete. Polymer-modified mortars using SBR and EVA emulsions as admixture of grouting mortars for prepacked concrete are prepared with various mix proportions such as sand-binder ratio, fly ash replacement ratio, polymer-binder ratio. and tested for flowability, viscosity of grouting mortars, bleeding ratio, expansion ratio, flexural and compressive strengths of grouting mortars and compressive and tensile strengths of prepacked concretes. From the test results, it is apparent that polymer-modified mortars can be produced as grouting mortars when proper mix design is chosen. We can design the mix proportions of high strength mortars for prepacked concrete according to the control of mix design factors such as type of polymer, polymer-binder ratio, sand-binder ratio and fly ash replacement ratio. Water-binder ratio of plain mortars for a constant flowability value are in the ranges of 43% to 50%. SBR-modified mortar has a little water-binder ratios compared to those of plain mortar, however, EVA-modified mortar needs a high water-binder ratio due to a high viscosity of polymer dispersion. The expansion and bleeding ratios of grouting mortars are also controlled in the proper value ranges. Polymer-modified grouting mortars have good flexural. compressive and tensile strengths, are not affected with various properties with increasing fly ash replacement to cement and binder-sand ratio. In this study, SBR-modified grouting mortar with a polymer-binder ratio of 10% or less, a fly ash replacement of 10% to cement and a sand-binder ratio of 1.5 is recommended as a grouting mortar for prepacked concrete.

• 한국지반공학회논문집
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• 제22권7호
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• pp.65-72
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• 2006

본 연구는 배합수를 일반수 대신 자화수로 사용한 시멘트 그라우트재의 역학적 특성을 파악하는 것에 그 목적이 있다. Magnetic field를 통과한 물을 MFTW라 하는데, 이는 시멘트의 Bleeding 감소와 Freezing에 대한 저항을 향상시킴으로써 시멘트 사용량을 5% 절감시킬 수 있다고 알려져 있다. MFTW는 자기력에 의해 물 분자를 좀 더 작게 만들어서 물 분자의 활성도를 증가시켜 좀 더 쉽게 시멘트 분자의 Core Region으로 침투할 수 있게 함으로써 수화를 원활하게 한다. 결과적으로, MFTW는 좀 더 효율적인 수화를 일으키게 함으로써 콘크리트의 일축압축강도를 크게 향상시켰으며, 규산나트륨-시멘트그라우트재에 MFTW를 사용한 결과 일축압축강도가 약 $20{\sim}50%$ 증가되었음을 알 수 있었다.