• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.877-880
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• 2008

Recently the press and institute recognized fly ash as it had excellent performance. Its research and applications are on the rise largely as a substitute for cement. On the contrary, it is in a situation that the regulation of high quality fly ash remains at a low level. Accordingly, this study was to establish 8000 class of fineness of fly ash and three levels of substitute like 15%, 3 0%, and 45% in order to analyze the replacement ratio and effect of water-binder ratio for fly ash that affected the properties of ternary system concrete. As a result of experiment by planning water-binder ratio for two levels like 40% and 50%, it increased the fluidity in a fresh state, and it decreased the air content. This study has found out the setting acceleration and reduction of heat of hydration. As for the strength property in a set state, this study has shown the tendency of being equal or higher in age 28 days.

• Journal of the Korean Chemical Society
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• v.34 no.3
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• pp.227-231
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• 1990

Kinetic studies on the nucleophilic reactions of p-substituted benzylnitrates with substituted anilines have been conductometically carried out in 50-100% $CH_3CN-CH_3OH$ mixtures. From the kinetic data, Hammett ${\rho}_C$ and ${\rho}_N$ values, Bronsted $\beta$ values, and solvatochromic coefficients were determined in order to examine the transition state variations caused by changes in substituents and solvent properties. It is concluded that the reaction proceeds via a synchronous $S_N2$ mechanism in which bond formation is more advanced than bond cleavage.

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.315-320
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• 2002

The effects of slag content and polymer-binder ratio on the strength properties of the polymer-modified concretes using ground granulated blast-furnace slag and a styrene-butadiene rubber (SBR) latex are examined. As a result, the compressive, tensile and flexural strengths of the SBR-modified concretes using slag increase with increasing polymer-binder ratio and slag content, and maximized at a slag content of 40 ％. In particular, the SBR-modified concretes with a slag content of 40 ％ provide approximately two times higher tensile and flexural strengths than unmodified concretes. Such high strength development is attributed to the high tensile strength of SBR polymer and the improved bond between cement hydrates and aggregates because of the addition of SBR latex.

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.164-170
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• 2002

Effect of the polymer-binder ratio and slag content on the properties of combined wet/dry-cured polymer-modified mortars using granulated blast-furnace slag are examined. Results shows that the flexural and compressive strengths of polymer-modified mortar using the slag tend to increase with increasing slag content, and reaches a maximum at a slag content of 40 ％, and is inclined to increase with increasing polymer-binder ratio. Water absorption, carbonation depth and chloride ion penetration depth tend to decrease with increasing polymer-binder ratio and slag content. Accordingly, the incorporation of slag into polymer-modified mortars at a slag content of 40％ is recommended for a combined wet/dry curing regardless of the types of polymer.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.5
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• pp.87-92
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• 2010

This study set up 25, 35% for silica fume, SFFB's 2 level and water-combination material ratio, silica fume 10% for substitution ratio, and 4 level of SFFB 5, 10, 15(%) in order to compare and analyze the quality characteristic of ultra high strength concrete according to the substitution ratio of silica fume free binder (SFFB) that can be utilized as a substitute material for silica fume. As a result of an experimentation, the lower water-combination material ratio was, the higher addition ratio of high performance water-reducing agent for securing target liquidity increased, and it indicated the tendency that addition ratio of high performance water-reducing agent decreases because of material characteristic that SFFB has a lower absorptiveness than silica fume. The best strength was shown when SFFB substitution ratio is 10% at compressive strength and when substitution ratio is 15% at tensile strength, and it was indicated that at autogenous shrinkage contraction decreases compared to Plain(SF) regardless of substitution ratio of W/B and SFFB.

• Journal of the Korean Chemical Society
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• v.33 no.4
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• pp.413-418
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• 1989

The rates for the reaction of substituted 2-phenylethyl tosylates with substituted pyridines were measured in acetonitrile and that of 2-PNS with substituted pyridines were investigated in both acetonitrile and methanol. The substitutent effect was accelerated by an electron-donating substituent on both substrate and nucleophile. Results showed that More O'Ferrall and quantum mechanical model of predicting transition state structure suggest the reaction proceeds via an $S_N2$ mechanism, in which bond-breaking is more advanced than bond-formation. Transition state variation predicted with the quantum mechanical model is consistent with the experimental results, whereas the predictions provided by the More O'Ferrall plots is found to be inconsistent in leaving group. In the reaction of 2-PNS, the rate constants in acetonitrile were larger than that in methanol.

• Korean Journal of Materials Research
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• v.6 no.11
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• pp.1121-1126
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• 1996

(Pb0.63Ca0.37)ZrO3 세라믹에 MgO와 SrO를 첨가하여 Ca를 Mg와 Sr 이온으로 치환하였을 때의 고주파 유전특성에 대해 연구하였다. Ca 이온의 일부를 Mg 이온으로 치환시킨 경우에는 A-O결합에 의한 분극의 증가로 인하여 유전상수는 직선적으로 증가하지만 품질계수는 감소한다. 또한 Ca 이온을 Sr 이온으로 치환시킨 경우에는 결합길이의 증가로 인해 분극이 감소되어 유전상수와 품질계수가 감소한다. 고주파용 유전재료의 설계에 있어서 관용인자와 이온결합성의 평가가 중요하다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.18-24
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• 2013

Recently, the interest is increasing about the eco-friendly concrete. Accordingly, the blast furnace slag(BFS), a by-product of industry is known for improving the durability through compaction in concrete and is expanding the use. The research about BFS in concrete be accomplished frequently. In this study, we should know the hydration characteristic of BFS concrete the through the adiabatic temperature rise test due to the replacement of a variety of BFS. In addition, we produced the regression analysis factors through the test result and analyzied the effect for the replacement of BFS. According to test results, the compressive strength showed a slight degradation or equal and the the adiabatic temperature rise figure and rising factors are went down for rising replacment of BFS. In the future, the study about the adiabatic temperature rise equation for the various replacement of BFS and binder is considered necessary.

• Journal of the Korea Institute of Building Construction
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• v.14 no.6
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• pp.523-529
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• 2014

Large amounts of waste shells have been produced each year from shellfish raising industries located in Korean costal areas. Due to the limited space for the waste shell disposal, the related environmental problem has been a serious issue. It is believed that using the waste shells as a source of aggregate for mortar, concrete or bricks can be a good solution. In this research, possibility of utilizing waste shells as an aggregate of mortar is investigated. Waste shells of manila clam, cockle, clam, sea mussel, and oyster were properly crushed, sieved, and sorted to meet the requirements of the grading of standard fine aggregate. After that, the waste shells were used as partial and total replacement of the fine aggregate, and their absorption and 28-day compressive strengths of mortar were measured. In general, replacement of waste shells increased the absorption and decreased the strength. However, one specimen with cockle increased compressive strength as replacement ratio increased. Mortar with cockle of 50% and 100% replacement showed higher compressive strength than that of control mortar. This increase of compressive strength was found to be affected by the strong interfacial bonding properties of the cockle and a cement matrix.

• Review of KIISC
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• v.3 no.1
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• pp.26-30
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• 1993

본 논문에서는Akl-Meijer가 설계한 랜덤 치환 발생기를 일반화한 알고리즘을 제안한다. Akl과 Meijer는 사이즈가 m인 치환(Permutation)과 0과 m!-1사이의 정수를 일대일 대응시키는 Knuth의 알고리즘을 이용하여, 선형 합동법 Y=X+C mod m! (C는 상수)에서 발생되는 난수와 일대일 대응되는 치환을 발생하는 치환 발생 알고리즘을 설계하였으며, 이를 응용하여, 이진 난수 발생기를 제시하였다. 본 논문에서는 선형 합동법 Y=AX+C mod m!(A, C는 상수)에서 발생되는 난수와 일대일 대응되는 치환 계산과정을 상삼각 행렬(Upper triangular matrix) 의 곱으로 변환하여 고속으로 계산하는 알고리즘을 제시한후, 이 알고리즘의 출력 치환을 n 개 결합하여 치환을 발생하는 랜덤치환 발생기를 설계한다. 또한 이의 암호적인 응용으로, 치환 발생기를 이용한 이진 난수 발생기를 제시한다.