• 대한토목학회논문집
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• 제26권1D호
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• pp.73-79
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• 2006

본 연구의 목적은 포장의 설계수명과 공용년수를 증대시켜 아스팔트 포장의 유지보수비용을 감소시킬 수 있는 장수명 아스팔트 포장용 고강성 혼합물을 개발하는데 있다. 따라서 본 연구에서는 고강성 아스팔트 바인더를 개발하였으며 다양한 실내 물성시험을 수행하였다. 실내 물성시험 결과 새롭게 개발된 고강성 아스팔트 바인더가 프랑스의 고강성 아스팔트 바인더와 유사하다는 것을 알 수 있었고, 바인더 외에 혼합물의 공용성을 평가하기 위해 기존의 일반아스팔트 혼합물과 새롭게 개발된 고강성 아스팔트 혼합물의 비교 시험을 수행하였다. 공용성 시험 결과 동탄성계수 측정시험에서는 고강성 아스팔트 혼합물이 일반 아스팔트 혼합물보다 강성에 있어 $5^{\circ}C$에서는 10~15%, $15^{\circ}C$에서는 20~25%, $30^{\circ}C$에서는 거의 2배가 증가함을 알 수 있었다. 또한 수분손상시험 및 휠트래킹시험, 피로시험을 수행한 결과 일반 아스팔트 혼합물에 비해 고강성 아스팔트 혼합물의 공용성이 우수한 것으로 평가되었다.

• International Journal of Concrete Structures and Materials
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• 제18권1E호
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• pp.43-48
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• 2006

This paper presents an elastic modulus equation more appropriate for predicting the elastic modulus of structural materials designed for and made of high- and ultra high-strength concrete under current domestic situation in Korea. In order to validate and assess the proposed elastic modulus equation, more than 400 laboratory test data available in the domestic literature on compressive strength of concrete in the range between 400 to 1,000 $kgf/cm^2$ were used and analyzed statistically. Comparison analyses of the proposed elastic modulus equation with previously suggested equations of ACI363R, CEB-FIP, NS3473 and New-RC are also presented to demonstrate its applicability in domestic practice.

• Advances in concrete construction
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• 제13권6호
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• pp.411-422
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• 2022

Aggregates mineralogical, and petrographic properties directly affect the mechanical properties of the produced high strength. This study is focused on the effects of magmatic, sedimentary, and metamorphic aggregates on the performance of high strength concrete. In this study, the effect of the mineralogical properties of aggregates on the compressive strength and modulus of elasticity of high-strength concrete was estimated by Artifical Neural Network (ANN). To estimate the compressive strength and elasticity modules, 96 test specimens were produced. After 28 days under suitable conditions, tests were carried out to determine the compressive strength and modulus of elasticity of the test specimens. This study also focused on the application of artificial neural networks (ANN) to predict the 28-day compressive strength and the modulus of elasticity of high-strength concrete. An ANN model is developed, trained, and tested by using the available test data obtained from the experimental studies. The ANN model is found to predict the modulus of elasticity, and 28 days compressive strength of high strength concrete well, within the ranges of the input parameters. These comparisons show that ANNs have a strong potential to predict the compressive strength and modulus of elasticity of high-strength concrete over the range of input parameters considered.

• Carbon letters
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• 제5권1호
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• pp.27-33
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• 2004

Structural changes of high modulus carbon fiber by oxidation in carbon dioxide gas using SEM, TEM, and XRD have been observed. It was shown that the originally high modulus carbon fiber is composed of highly ordered graphitic crystalline area and non-crystalline area. It was observed that the La increases during the whole oxidation process. It was shown that the oxidation of high modulus carbon fiber initiates at the non-crystalline area and at the ends of fiber. The large pores developed in fiber by direction of fiber length at high temperature ($1,100^{\circ}C$), and the small pores developed on the fiber surface at low temperature ($900^{\circ}C$). In conclusion, it is found that the oxidation of the carbon fiber was progressed through the imperfection.

• 한국구조물진단유지관리공학회 논문집
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• 제21권6호
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• pp.206-215
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• 2017

이 연구에서는 고강도 콘크리트의 역학적 특성을 파악하기 위한 실험연구를 수행하였다. 80~120 MPa 범위의 압축강도를 갖는 고강도 콘크리트를 대상으로 실험연구를 수행하였다. 물-결합재비의 압축강도에 대한 영향, 시간에 따른 압축강도의 발현 및 양생조건의 압축강도에 대한 영향을 분석하였다. 또한, 양생조건에 따른 콘크리트의 탄성계수, 쪼갬인장강도 및 파괴계수 특성을 파악하였다. 탄성계수, 쪼갬인장강도 및 파괴계수의 실험결과와 기존설계코드에 의한 예측결과를 비교하였다. 콘크리트구조기준의 탄성계수 제안식은 실험값을 합리적으로 예측한다. 반면에, 콘크리트구조기준은 파괴계수 실험값을 과소평가하고 있다. ACI 363R의 쪼갬인장강도와 파괴계수 예측값과 실험값은 잘 일치하고 있다. 따라서, ACI 363R의 쪼갬인장강도와 파괴계수 예측식은 120 MPa까지의 고강도 콘크리트에 효과적으로 활용될 수 있다.

• Carbon letters
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• 제10권1호
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• pp.38-42
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• 2009

This study aims to find a correlation between XRD and Raman result of the oxidized high modulus carbon fibers as a function of its oxidation degrees, and compare with the isotropic carbon fiber reported early. La of the high modulus carbon fiber prepared by oxidation in carbon dioxide gas have been observed using laser Raman spectroscopy. The basic structural parameters of the fibers were evaluated by XRD as well. The La of the original high modulus carbon fibers were measured to be 144 ${\AA}$ from Raman analysis and 135 ${\AA}$ from XRD analysis. La of the 92% oxidized fiber were 168 ${\AA}$ by using Raman and 182 ${\AA}$ by using XRD. There was some correlation between the La value obtained from Raman and XRD. However the La value changes of the high modulus carbon fiber through whole oxidation process showed opposite tendency compare with the isotropic carbon fiber because of the fiber structure basically.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2003년도 가을 학술발표회 논문집
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• pp.76-79
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• 2003

Recently, many attempts have been made to develop high strength and high modulus fibers from conventional polymers such as poly(vinyl alcohol) (PVA)[1-4] and polyethylene (PE). PVA has potentiality to yield high strength and high modulus fiber, since they have high theoretically attainable moduli because of their planar zig-zag structure. As PVA has a melting temperature as high as 230$^{\circ}C$ in contrast to PE with a low melting temperature such as 130$^{\circ}C$, it seems possible that high strength and high modulus fibers comparable to Aramid can be fabricated from PVA. (omitted)

• 한국염색가공학회지
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• 제6권4호
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• pp.34-39
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• 1994

For the purpose of obtaining high modulus PET tire cord fiber by high spinning speed, the change of initial modulus and taut tie molecules (T.T.M) fraction with the PET tire cord fibers by different spinning speed is investigated. Initial modulus decreased with increasing spinning speed but increased above spinning speed of 1500m/min. Therefore, high modulus PET tire cord fiber may be obtained above spinning speed of 3500m/min. It was found that the initial modulus of fibers depends on fraction of T.T.M.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2006년도 하계학술대회
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• pp.179-182
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• 2006

This paper introduce a different-type voltage-controlled oscillator (VCO) for PLL frequency synthesizer, And also the architecture of a high speed low-power-consumption CMOS dual-modulus frequency divider is presented. It provides a new approach to high speed operation and low power consumption. The proposed circuits simulate in 0.35 um CMOS standard technology.

• 소성∙가공
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• 제13권5호
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• pp.409-414
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• 2004

TRIP steel has got attention in automobile industry because of its high strength and high formability. However, the information on deformation behavior of TRIP steel, including bending and springback, is not enough until now. In this research, the V-die bending experiment and analysis have been done to obtain the information of springback of TRIP steel. And a new numerical method, where elastic modulus is varied with the change of the strain, was suggested. Tensile test for TRIP steel was done to get tensile properties as well as strain dependency of elastic modulus of the material. Strain-dependency of elastic modulus was used the numerical analysis of V-die bending and unbending process to predict springback amount. The results were compared with experiment, showing reasonable agreement. Through the analysis of V-die bending as well as draw bending of TRIP steel, the proposed scheme with variable elastic modulus was proven to well predict the deformation behavior of TRIP steel during bending and springback.