• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3A
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• pp.251-260
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• 2011

In this study, the effect of natural jute fiber volume fraction on the bond characteristics of polyolefin based macro fiber in natural jute fiber reinforced cement composites, including bond strength, interface toughness, and microstructure analysis are presented. The experimental results on polyolefin based macro fiber pullout test of different conditions are reported. Natural jute fiber volume fractions ranging from 0.1% to 0.2% are used in the mix proportions. Pullout tests are conducted to measure the bond characteristics of polyolefin based macro fiber from natural jute fiber reinforced cement composites. Test results are found that the incorporation of natural jute fiber can effectively enhance the polyolefin based macro fiber-cement matrix interfacial properties. The bond strength and interface toughness between polyolefin based macro fiber and natural jute fiber reinforced cement composites increases with the volume fraction of natural jute fiber. The microstructural observation confirms the findings on the interface bond mechanism drawn from the fiber pullout test results.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.454-462
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• 2016

Geopolymer concrete is a new class of construction materials that has emerged as an alternative to ordinary Portland cement concrete to reduce the emission of $CO_2$ in the production of concrete. Many researches have been carried out on material developments of geopolymer concrete, however a few studies have been reported on the structural use of them. This paper presents an experiment on the bond behaviors of reinforcements embedded in fly ash based geopolymer concrete. The development lengths of reinforcement for various compressive strength levels of geopolymer concrete, 20, 30 and 40 MPa, and reinforcement diameters, 10, 16 and 25 mm, are investigated. Total 27 specimens were manufactured and pull-out test according to EN 10080 was applied to measure the bond strength and slips between concrete and reinforcements. As the compressive strength levels of geopolymer concrete increase, the bond strength between geopolymer concrete and reinforcement increase. The bond strengths decrease as the diameters of reinforcements increase, which is similar in normal concrete. Also, an estimation equation for the basic development length of reinforcement embedded in geopolymer concrete is proposed based on the experimental results in this study.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.289-295
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• 2008

The purpose of this study was to examine the flexural behavior of reinforced concrete beams strengthened with CFRP strips. A total of 12 rectangular beams were tested. Test variables in this study were the shapes, bonded length and the number of longitudinal layers of CFRP strips. From the experimental study, flexural capacity of the beams strengthened with CFRP strips significantly increased compared to the reinforced concrete beam without a CFRP strip. Maximum increase of ultimate strength was found about 120% more than the control beam. In this test, most of the strengthened beams failed suddenly due to the debonding of CFRP strips. It is also observed that the debonding of the strip was initiated in the flexural zone of the beam and propagated rapidly to the end of the beam. The ultimate tensile strains of CFRP strips in this test were occurred at the level of 36% of rupture tensile strength of the CFRP strip, and an analytical approach to compute the flexural strength of reinforced beams strengthened with CFRP strips based on the effective stresses was conducted.

• Korean Journal of Materials Research
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• v.3 no.5
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• pp.466-475
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• 1993

Adhesion of W to TiN which is used as a glue layer in the blanket tungsten process has been investigated using the pulling and scratch methods and analysed using surface roughness measurements by SEM and the reflectivity measurement, the stress measurement and the SIMS depth profiling Significant differences between the adhesion of the CVD tungsten film to the s-TiN and that to the a-TiN were found. It appeared that the fomer were better than the latter, which is due to the facts that the s-TiN film has a rougher surface and a lower stress level and a higher oxygen content than the a-TiN film. Also the ashesion strength was degreaded with increasing the TIN film thickness because of the increase of the TiN film stress.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2003.02a
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• pp.429-433
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• 2003

온실 내 병충해 방제에 사용하는 상용 연무기에 비해 보다 미세하고 균일한 분무입자를 생성하여 작물에의 부착을 용이하게 할 목적으로 초음파를 적용한 상용 연무기용 2-유체 노즐을 설계, 제작하고 이를 적용한 온실에서의 분무실험을 통하여 부착량과 부착입경을 측정하고 상용분무의 경우의 결과와 비교하여 초음파의 분무특성에 미치는 영향을 분석하였다. (중략)

• Journal of the Korean Society of Marine Environment & Safety
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• v.15 no.3
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• pp.173-177
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• 2009

A total of 3 epiphytic macroalgae were collected from eelgrass bed in Jindong Bay, and Scytosiphon lomentaria and Colpomenia sp. in Phaephyta, Gracilaria sp. in Rhodophyta occurred during study periods. For epiphytic microalgae (diatoms), Cocconeis scutellum and Cocconeis placentula were common species. Seasonal variations of epiphytic algal biomass were marked: the higher epiphytic macroalgae was 3.3 g $DW/m^2$ in November 2003; whereas epiphytic diatoms were 43,153 $cells/m^2$ in June 2003. Diversity and number of epiphytic macroalgae species were the lowest in the study area, compared with those of in other areas such as Koongyang Bay, Dongdae Bay, and Aenggang Bay. These results were therefore likely due to the severe physical characteristics of the intertidal mudflat eelgrass biological characteristics, and the deterioration of water quality.

• Magazine of the Korea Concrete Institute
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• v.10 no.1
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• pp.153-159
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• 1998

최근 교통량의 증가에 의해 직접 하중을 부담하는 교량바닥판의 손상이 심각한문제로 부각되고 있다. 더욱이 차량하중의 증가는 바닥판손상을 더욱 가속화시키고 있는 실정이다. 바닥판의 손상이 심한 경우에는 교체 또는 성능개선공사를 시행하게 되는데, 이때 기존의 현장타설바닥판이 갖는 단점을 보완할 수 있는 프리캐스트 콘크리트 바닥판은 공기단축, 품질확보 등의 측면에서 매우 효과적인 대체공법이 될 수 있다. 프리캐스트 콘크리트 바닥판은 기존의 현장타설바닥판과달리 바닥판간에 이음부를 갖는 구조적 특징이 있으며, 다양한응력상태에 있는 바닥판중에 존재하는 비연속부인 이음부와 콘크리트 부재사이의 원활한 하중전달을 위해 부착강도는 매우 중요하다. 따라서 본 연구에서는 이음부의 부착강도를 함리적으로 평가할 수 있는 새로운 실험방법을 제안하고 이를 이용하여 휨, 직접인장 및 전단실험을 수행하였다. 또한 구성재료에 대한 압축, 휨인장 및 할렬인장강도 특성도 평가하였 다. 부착 및 강도특성에 관한 실험결과, 제안된 실험방법을 이용하면 실제에 근접한 부착강도를 평가할 수 있으며 국내에서 사용되는 충전재료중 무수축모르터가 프리캐스트 콘크리트 바닥판간 이음부의 채움재로서의 기본요건을 만족하고 있는 것을 알 수 있었다.

• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.549-554
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• 2008

Nickel Chloride coated protein chip plates were developed by using a spin coating method after $H_2$ plasma treatment. The adsorption ability of histidine tagged protein was investigated at various times of plasma treatment. The properties of the nickel chloride and protein on the surface of the slides were assayed using particle size analysis and the extent of the protein adsorption was determined by using a bio imaging analyzer system. The results show that the ability of protein adsorption decreased as increasing the time of $H_2$ plasma treatment. The mechanism on the ability of protein adsorption at the plate surface is discussed on results and discussions. The results also suggest that the surface stabilization of protein chip plates treated by plasma technology may be applicable in biosensor markets.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2A
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• pp.103-111
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• 2010

A feasibility study for nondestructively estimating prestress force of a grouted tendon using axial vibrations has been investigated. Total eight prestressed concrete beams with different stress levels have been specially designed and constructed for this investigation. The various axial vibration tests have been conducted in order to extract the dynamic characteristics of the prestressed concrete beams. It turns out that the axial frequency, elastic wave velocity and elastic modulus are nonlinearly increased as the prestress force level increases. It seems that the axial vibration characteristics of the existing grouted tendons are a feasible indicator for the identification of their tensile force.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.2019-2020
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• 2008

옥외에서 폴리머 애자의 사용량이 급격하게 증가하는 이유는 자기제 애자에 비해 경량이면서 오손특성이 우수하다는 장점 때문이다. 약 10년 전 국내 배전선로에 설치된 EPDM(Ethylene propylene diene monomer) 재질의 폴리머 현수애자의 섬락고장이 있었다. 폴리머 애자는 재질 특성상 사용시간에 따라 표면 열화가 진행되고, 표면의 절연저항이 감소하여 누설전류가 증가하게 된다. 표면 섬락고장을 유발하는 누설전류는 절연물 표면 상태에 많은 영향을 받는다. 본 연구에서는 폴리머애자 표면에 부착된 오손물이 전기적 특성에 미치는 영향을 분석하였다. 표면에 부착된 미세한 오손물은 발수성을 급격히 저하시켰으며, 장시간 수분에 노출될 경우 상용전압에서 표면 방전의 원인이 되었다. 결과적으로 부착된 오손물은 누설전류와 절연내력에 영향을 주어 절연 특성을 저하시키게 된다.