• Proceedings of the Korea Concrete Institute Conference
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• 1991.10a
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• pp.26-29
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• 1991

This study is designed for analyzing the properties of water-proofing on concrete according to the using EVA(ethylene vinyle acetate) emulsion, and the fine aggregate grading such as uniform, gap and continuously grading. And is aimed for presenting the reference data on the practical use.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.46-47
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• 2013

This study investigates the effect of a grading of aggregate on the properties of concrete. It is a common sense in Korea that the production of coarse aggregate in ready mixed concrete industry excludes particular aggregate size ranged from 5 mm to 13 mm for saving the production cost. This causes a gap grading of the aggregate for concrete, which can lead to the increase of unit water, the development of drying shrinkage-induced crack and the reduction of compressive strength. In this study, conventional aggregate obtained from a ready mixed concrete factory and the aggregate with a modified grading produced in lab. condition were prepared. Results showed that a good grading of aggregate (i.e., the ratio of 5~13 mm and 13~25 mm is 6 to 4) produced in the lab. condition significantly improved the slump and the compressive strength of the concrete.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.3
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• pp.287-293
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• 1988

This paper calculates the band structure of the GaAs/(Al,Ga) As semiconductor superlttice with the interface3 grading, in consideration of different effective masses in each region. Including the effective masses, superlattice period, well and barrier widths, and the interface, the dispersion relation is derived, and the effects that the above parameters affect the subband (or miniband) structure of the superlattice and effective energy gap are investigated. It is particularly found that this case(ma<>mb<>mc) is significantly different from the same effective mass case(ma<>mb<>mc).

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.137-138
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• 2014

The aim of this research is suggesting the method of obtaining well-graded aggregates for concrete replacing the recycled aggregate which size range is from 5 to 13 mm to currently used gap-graded natural aggregates which size range is only 13 to 25 mm. according to the tests results, the workability of concrete was improved with replacing the aggregates of 5 to 13 mm of size range because of compensating gap-grading. Furthermore, there was an improvement in compressive strength when the aggregates of 5 to 13 mm of size range was replaced because obtained well-graded aggregates contributed on increasing adhesiveness and filling internal pore system. Comparing replacing recycled aggregate to natural aggregate, there was no significant difference on the performances.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.19-20
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• 2013

Consider about aggregate's price, coarse aggregates from 13 to 25mm were widely used in ready mixed concrete company. But if only use 13 to 25mm aggregates in the concrete, gap grading problem would be occurred. When recycled aggregates from 13 to 25mm was used, continuous grading would increase the durability and strength for the concrete, meanwhile the construction waste materials would also be reused. In this paper, 5-13mm recycled aggregates was utilized, to analyse the fundamental properties for concrete, strength has been tested to evaluate the quality and reusing effect of the recycled materials.

• Journal of the Korea Institute of Building Construction
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• v.17 no.1
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• pp.55-61
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• 2017

This paper is to investigate experimentally the effect of substitution of recycled coarse aggregate(RCA) under 13mm on the engineering properties of the concrete using gap graded coarse aggregates. Concretes with 0.4 of water to cement ratio(W/C) were fabricated to achieve 30MPa of design strength with coarse aggregate over 13mm in size with the maximum size of 25mm. RCA was substituted for coarse aggregate over 13mm from 10% to 50% and crushed coarse aggregate under 13mm was also substituted for coarse aggregate over 13mm from 20% to 40%, respectively. Test results indicated that the replacement of RCA up to 20% resulted in an increase of fluidity and strength. It also caused a decrease in the drying shrinkage due to dense packing effect by achieving continuous grading of mixed aggregates. For practical application of RCA, when properly substituted, the use of RCA enabled the concrete to reduce water contents and sand to aggregate ratio in mixing design stage of the concrete. And, it can also enhance the compressive strength of the concrete.

• Journal of the Korean Wood Science and Technology
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• v.41 no.4
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• pp.337-345
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• 2013

Log grading rules are essential tools to ensure the quality of logs in distribution structure. The rules should reflect the long experience and accepted usage practice in the market. A gap between the rules and market should be improved based on analysis of log qualities that produced and market demand. In this study more than ten millions logs which were produced by 5 Regional Forest Services in 2010~2011 period, were analyzed in their qualities including diameters and lengths by species. A proposal was driven to improve the current log grading rules in terms of log diameter classes and length. The followings are the summary of this study. Most of domestic softwood logs are belong to small diameter class of 100~160 mm, which imply the diameter classes of current log grading rules are immoderate. Distributions of log diameter shows distinctive patterns by species, which indicate a necessity of differentiated diameter classes by species in an improved rules. Lengths of logs in productions do not corresponding to the demands and preferences in sawmills. Therefore it is highly recommended to include log length term in an improved log grading system. Based on these findings, 6 log grading systems for 3 species groups of softwood are newly proposed to improve current log grading rules. Limits of log diameter and log length are also proposed for each log grading system.

• Journal of the Korean Institute of Intelligent Systems
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• v.12 no.2
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• pp.151-156
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• 2002

There are two methods in evaluation student s achievement. The two evaluation methods are absolute evaluation and relative evaluation. They have much advantages respectively, but also have some limitations such as being too stereotyped or causing overcompetition among learners. This paper suggests a new evaluation method which evaluates student s achievements by considering the score distribution and the frequency The proposed method classifies the scores into several clusters considering the goodness. This approach calculates the goodness by applying the RE(relaxation error), and grades the achievement scores based on the goodness. The suggested method can avoid the problem of grading caused by the narrow gap of scores because it sets a standard for grading by the calculated goodness considering the score distribution and frequency of occurrence. The method can differentiate achievements of a school from those of others, and that it is useful for selecting advanced students and dull ones, and for evaluation of classes based on student s achievement.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.124-125
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• 2020

In this study, the characteristics of fine aggregates produced according to the jaw crush crushing gap variation were studied and analyzed in terms of recycled aggregates, and the experiments were conducted in terms of grading, density, water absorption, unit volume weight, grain shape. It was shown that the quality of the fine aggregate was affected by the shape of the morphological crushing.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.60-61
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• 2020

In this study, the recycled fine aggregates produced from the waste concrete by using Jaw crusher depending on crushing gap of Jaw crusher were studied to offer a solution for recycled fine aggregate for concrete. The results of the experiment showed that the factors that influence grading and water absorption ratio, density and grain shape were significantly characterized by the generation of the particulate matter and the crushing shape of the aggregate.