• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.05a
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• pp.77-78
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• 2011

This study is analysis of effect of binder types and replacement ratio on the properties of blast furnace slag mortar using the recycled fine aggregates. The results of the study were was follows. Compressive strength was increased according to an increase in replacement ratio of fine particle cement and gypsum. Absorption was reduced according to an increase in replacement ratio of fine particle cement and recycled aggregate fine powder.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.1
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• pp.54-64
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• 2007

This study is a fundamental research in order to establish the design code of recycled aggregate concrete structure. The structural properties of recycled aggregate concrete such as flexure, shear, fatigue, compression, and bond development are experimentally investigated and confirmed. In this study, laboratory-scale reinforced concrete beam, column, and pull-out test specimens using recycled coarse aggregate are manufactured. Then, the structural performances of recycled aggregate concrete according to replacement ratios of recycled coarse aggregate are evaluated. Also, finite element analysis using commercial code DIANA is carried out to predict the test results and the analysis results are compared with test results in this study. Structural test results showed that the structural performances of recycled aggregate concrete specimens with 60% replacement ratio are reduced by approximately 15-20%. These results indicated that the replacement ratio of recycled coarse aggregate within 30% is a suitable to use for structural members. The results of finite element analysis showed that the specimens with 30% replacement ratio possessed similar or more excellent structural performance than normal concrete specimens. However, recycled aggregate concrete with 60% replacement ratio of recycled coarse aggregate must be carefully considered for structural applications due to significant decrease of the failure loads.

• Journal of the Korean Data and Information Science Society
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• v.24 no.6
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• pp.1385-1400
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• 2013

This paper discusses income replacement ratios of national pension, retirement pension and individual annuities in Korea. These ratios are useful indicators for the assessment of retirement income security of workers. This paper projects income replacement ratios, using the pension entry rate, decrement rates, and life tables of the National Statistical Office. The result of the actuarial projection is that the income replacement ratio of national pension is approximately 21.0 to 22.7%, that the income replacement ratio of retirement pension is about 5.8 to 9.7%, and that the income replacement ratio of an individual annuity is about 13.5 to 21.0%, respectively. The income replacement ratio by income varies due to the effects of income redistribution in national pension and retirement pension, but the income replacement ratio of an individual annuity is constant, regardless of income.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.2
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• pp.144-151
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• 2017

The mechanical properties such as compressive strength and elastic modulus of recycled aggregate concrete containing fly ash are investigated in this study. The experimental parameters were replacement ratio of recycled coarse aggregate(RCA) and fly ash. Replacement ratio of RCA was 0, 30, 50, and 70% and replacement ratio of fly ash was 0, 15, 30%. The experimental results were extensively discussed about compressive strength and elastic modulus of concrete at ages of 7, 28 and 91 days. Compared with concrete not containing fly ash, the decrease of compressive strength and elastic modulus of concrete containing fly ash with the replacement ratio of 30% was significant. Therefore, the test results represented that the fly ash replacement ratio of less than 30% was favorable in terms of mechanical properties of recycled coarse aggregate concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.947-952
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• 2001

The prediction model is proposed to estimate the variation of compressive strength of fly ash concrete with aging. After analyzing the experimental result with the model, the regression results are presented according to fly ash replacement content and water/cement ratio. Based on the regression results, the influence of fly ash replacement content and water/cement ratio on apparent activation energy was investigated. According to the analysis, the model provides a good estimate of compressive strength development of fly ash concrete with aging. As the fly ash replacement content increases, the limiting relative compressive strength and initial apparent activation energy become greater. The concrete with water/cement ratio smaller than 0.40 shows that the limiting relative compressive strength and apparent activation energy are nearly constant according to water/cement ratio. But, the concrete with water/cement ratio greater than 0.40 has the increasing limiting relative compressive strength and apparent activation energy with increasing water/cement ratio.

• Proceedings of the Korea Concrete Institute Conference
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• 1992.10a
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• pp.5-10
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• 1992

The aim of this study is to decide the optimum replacement method when mineral Admistures as SILCA FUME and FLY ASH are used, as a part of practical use of ultra High-Strength Concrete. For this purpose, Four types of replacement methods are examined and the relationship between replacement methods and concrete properties is studied. As a result, workability and gain of strength are dependent on the replacement method of mineral Admixtures. The methods of using volumn ratio of cement in FIY ASH, weight ratio of cement in SILCA FUME are shown better workability and strength of concrete than any other replacement method.

• Journal of the Korea Institute of Building Construction
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• v.9 no.1
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• pp.43-47
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• 2009

The most of waste foundry sands(WFS) have been discarded. It is very urgent for our country to make a study on recycling of WFS. The one of recycling method of WFS is using them as fine aggregate for concrete. This study provided the optimum amount of WFS and flyash when WFS and flyash were used together in concrete. The concrete made with 60% WFS fine aggregate replacement showed higher compressive strength, splitting tensile strength and modulus of elasticity than normal concrete. In the case that the flyash and WFS are replaced together, the compressive strength and splitting tensile strength were improved at flyash replacement ratio $10%{\sim}20%$ and WFS replacement ratio $40%{\sim}60%$. The increase of WFS and flyash replacement led lower air content. While the increase of WFS replacement led lower slump, the increase of flyash replacement led higher slump.

• Journal of the Korea Institute of Building Construction
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• v.8 no.5
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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.

• Journal of Korea Game Society
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• v.3 no.1
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• pp.67-73
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• 2003

Most web caches save documents temporarily into themselves on the basis of those documents. And when a corresponding document exists within the cache on wei s request, web cache sends the document to corresponding user. On the contrary, when there is not any document within the cache, web cache requests a new document to the related server to copy the document into the cache and then rum it back to user. Here, web cache uses a replacement policy to change existing document into a new one due to exceeded capacity of cache. Typical replacement policy includes document-based LRU or LFU technique and other various replacement policies are used to replace the documents within cache effectively. However, these replacement policies function only with regard to the time and frequency of document request, not considering the popularity of each web site. Based on replacement policies with regard to documents on frequent requests and the popularity of each web site, this paper aims to present the document replacement policies with regard to the popularity of each web site, which are suitable for latest network environments to enhance the hit-ratio of cache and efficiently manage the contents of cache by effectively replacing documents on intermittent requests by new ones.

• Journal of the Korea Society of Computer and Information
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• v.13 no.1
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• pp.227-232
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• 2008

General web caches save documents temporarily into themselves on the basis of those documents. And when a corresponding document exists within the cache on user's request. web cache sends the document to corresponding user. On the contrary. when there is not any document within the cache, web cache requests a new document to the related server to copy the document into the cache and then turn it back to user. Here, web cache uses a replacement policy to change existing document into a new one due to exceeded capacity of cache. Typical replacement policy includes document-based LRU or LFU technique and other various replacement policies are used to replace the documents within cache effectively. However. these replacement policies function only with regard to the time and frequency of document request. not considering the popularity of each web site. Based on replacement policies with regard to documents on frequent requests and the popularity of each web site, this paper aims to present the document replacement policies with regard to the popularity of each web site, which are suitable for latest network environments to enhance the hit-ratio of cache and efficiently manage the contents of cache by effectively replacing documents on intermittent requests by new ones.