• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.5 s.57
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• pp.169-179
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• 2009

The purpose of this paper is to find an efficient heat source to amplify the surface temperature of damaged concrete structures for infrared thermography. we compare two different heat sources of far-infrared lamp and halogen lamp each other for their efficiency. The two heat sources were applied to the concrete specimens. Two different concrete specimens were used: one was the concrete containing internal void and the other was wrapped with partially unbonded fiber reinforced polymer sheet. it was found that the far-infrared lamp was more efficient than the halogen lamp. In addition, we propose a new algorithm to make the damage zone displayed clear in the image obtained from the thermographic operation. The algorithm is a combination of Gauss filtering process and the Prewitt mask operation.

• International Journal of Highway Engineering
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• v.15 no.3
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• pp.65-74
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• 2013

PURPOSES: This study is to evaluate the dynamic modulus changes of permeable asphalt mixtures by using non-destructive impact testing method and to compare the dynamic moduli of permeable asphalt mixtures through repeated freezing and thawing conditions. METHODS: For the study, non-destructive impact testing method is used in order to obtain dynamic modulus of asphalt specimen and to confirm the change of dynamic modulus before and after freezing and thawing conditions. RESULTS : This study has shown that the dynamic moduli of asphalt concrete specimens consisting of 10%, 15% and 20% porosity are reduced by 11.851%, 1.9564%, 24.593% after freezing and thawing cycles. CONCLUSIONS : Non-destructive impact testing method is very useful and has repeatability. Specimen with 15% porosity has high durability than others.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.4
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• pp.43-52
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• 2005

It is known in some literatures that the B value is not equal to unity in saturated soil when effective stress is given, in which the B Value is the ratio of measured excess pore water pressure and isometric loading pressure. In this study the B value was measured on various effective stresses and on various incremental loading stresses in various grain size of specimens with saturated sand. The test results showed that the B value was affected largely by grain size of sand in specimen and the amount of effective stress. There was the semi-logarithmic relationship between B value and effective stress, and also there was the linear relationship between the gradient of the former semi-logarithmic relationship and grain size of specimen.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.377-378
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• 2010

This study was performed an evaluation of engineering properties of cement composite according to type and content of Nano-silica as admixture for marine concrete. As the results of study, when considering the porosity and compressive strength, the proper type and content are thought to be type of sodium silicate and under 5%.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.339-340
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• 2010

This study was performed an evaluation of physical & mechanical properties of porous concrete according to contents of pumice. As the results of study, when considering the void ratio, permeability coefficient, compressive strength of porous concrete, the proper content are thought to be 10~20%.

• Journal of the Korean Society for Railway
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• v.9 no.4 s.35
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• pp.455-460
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• 2006

본 논문에서는 자속 궤환을 포함하는 자기부상 시스템의 open-loop 특성에 대해서 다룬다. 훌륭한 외란 억제 특성을 포함하고 파라메타 변동에 대해서 둔감한 제어기를 설계하기 위해서 자속 궤환을 이용하는 것이 효과적일 수 있다. 적절한 센서에 의해서 측정 가능한 자속은 전류와 공극의 시간 변화에 대해서 선형적인 관계를 가지고 있으며, 자속의 궤한은 자기 부상시스템이 본질적으로 갖고 있는 전기적 엑츄에이터와 기계적 플랜트 사이의 간섭에 의해서 발생하는 비선형성을 감소시키는 역할을 한다. 모의시험 결과를 통해서 자속의 궤환이 자기부상 시스템의 부하변동에 대해서 Open-loop 성능 향상에 효과적임을 보인다.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.4
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• pp.126-136
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• 2003

The B value on the saturated soil is commonly known as the amount of 1. Usually this concept is consistent with the condition that effective stress is equal to zero, but it was reported in some literatures that the B value was less than 1 in spite of saturated condition in the test of very stiff material such as rock and quasi-stiff material on which the stiffness can be mobilized because of effective stress not equal to zero. In this study the B value was measured on various effective stress conditions on normally consolidated clay. The test results in the B value less than 1 in spite of perfect saturation. The measured excessive pore water pressure was not only smaller than the change of the total stress, but also the function of time on clay.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.121-122
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• 2012

합금도금강판의 일시 방청과 기능성 부여 후처리는 크로메이트, 인산염처리 등과 같은 방법을 시행하는 것이 일반적이다. 최근에는 아연합금도금 강판의 사용 및 보관 환경이 가혹해짐에 따라 보다 우수한 일시 방청성과 내식성이 요구되고 있다. 본 연구는 솔젤법을 이용하여 zirconium n-propoxide와 3-glycidoxypropyltrimethoxysilane(GPTS)으로부터 중합된 코팅막과 이에 zirconia nanoparticle입자를 첨가한 코팅막의 공극율(prosity)과 방식효율(protective efficiency)을 분극데이터를 이용하여 비교 평가하였으며, 염수분무시험을 통해 내식성 평가를 진행하였다.

• Magazine of the Korea Concrete Institute
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• v.4 no.2
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• pp.111-118
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• 1992

본 연구는 실리카흄을 혼화재료로 사용하여 1200kg/$ extrm{cm}^2$정도의 초고강도 콘크리트를 제조하였으며 이에 대한 재료특성을 실험 및 보부재의 휨거동을 실험을 실시 비교 분석하였다. 재료특성 실험으로는 기본적인 강도 시험, 파괴음 측정에 의한 AE실험 그리고 수은압입법에 의한 세공실험을 실시하였다. 초고강도 콘크리트의 재료특성치는 ACI 363의 고강도 콘크리트 재료특성 결가보다 크게 나타났으며 압축강도와 미세공극량은 선형적으로 비례하였다. 보부재의 휨특성을 파악하기 위해 인장철근비 변화, 전단보강근의 유무 및 철근 표면형상의 변화 등을 실험인자로 하였으며 각각의 현상을 비교분석함으로써 균열성상에 따른 하중-변위 관계, 중립축 이동에 따른 부재거동 및 응력블록의 변화에 관하여 비교 고찰하였다. 초고강도 콘크리트 사용한 보부재의 경우 중립축 상승으로 단면의 압축영역은 매우 작아져 급격히 압축파괴되는 경향을 보였으며 응력블록 형태는 삼각형의 분포를 보였다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.158-159
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• 2013

In this study, effects of supplementary cementitious materials(fly ash, blast furnace slag and waste glass) on drying shrinkage of cement mortar were compared and evaluated. The results showed drying shrinkage of cement mortar using blast furnace slag and waste glass is larger than shrinkage due to capillary pressure, while using fly ash is smaller.