• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.1
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• pp.118-125
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• 2011

Conventional erosion function apparatus (EFA) which has been used to measure the hydraulic resistance of soil was improved to consider direction change of the current flow. Using improved apparatus, hydraulic resistance capacities of the artificially composed clayey soil and sandy soil were compared. Test result shows that scour rates which were measured under the bi-directional flow were much higher than those measured under unidirectional flow for both type soils. Scour rate of sandy soil was higher than that of clayey soil. Velocity averaged scour rate of specimen which was consolidated under the relatively large consolidation pressure is higher than that of specimen which is consolidated under small consolidation pressure, which means scour problem under bidirectional flow may be more serious for the deep seabed ground.

• Resources Recycling
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• v.15 no.4 s.72
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• pp.52-59
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• 2006

The purpose of this study was to evaluate the effects of ground granulated blast-furnace slag on strength development and durability of ordinary portland cement concrete (OPC) with steam curing types. Main experimental variables were slag contents(0%, 10%, 30%, 50%, 70%) and curing types (standard, accelerated curing). It were performed to check the basic properties of concretes that compressive strength, rapid chloride ion permeability and chemical resistance. From the result, we have found that increasing the amount of blast-furnace slag produced concrete with increased compressive strength and permeability resistance. Rapid freezing-thawing test showed that they were good enough to protect the concrete structures and to carry out cyclic freezing and thawing. The freeze-thaw resistance of blast-furnace slag produced concretes maintained above 90% of relative dynamic modulus after 300 freezing-thawing cycles. Increasing the amount of blast-furnace slag produced concretes with increased chemical resistance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.233-234
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• 2009

박막 재료의 면저항 측정은 일반적으로 FPP(Four-Point Probe)원리를 적용한 측정기률 사용하고 있다. 개발된 면저항 측정기의 특징은 dual configuration 기술을 적용하여 탐침 간격에 대한 시료의 크기 및 두께에 대한 보정계수를 고려하지 않아도 되므로 누구나 업고 정확하게 사용 할 수 있다. 측정범위는 $1\;m{\Omega}{/\square}\;{\sim}\;1\;G{\Omega}{/\square}$이며, 반복성과 재현성 및 직선성은 0.1 %이하로서 우수한 특성을 나타냈다. 또한 기존의 면저항 측정기에 적용된 single configuration 기술에서 나타나는 가장자리 효과의 단점을 dual configuration 기술을 적용하여 해결하였고 정밀 정확도를 향상시켰다. 개발된 면저항 측정기의 특성평가는 국가측정표준으로부터 소급성이 유지된 표준저항, 분할저항기, 면저항 인증표준물질 등을 사용하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.342.2-342.2
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• 2014

IZO, ITO, ITO 등의 투명전극들 중 Indium Tin Oxide (ITO) 다른 전극에 비해 높은 광투과도와 낮은 저항으로 인하여 다양한 부분에서 널리 이용되고 있다. 본 연구에서는 우수한 투과도의 멀티 layer 단열 창호를 위한 film 개발을 위해 RF magnetron system을 이용하여 Sodalime Glass와 polyethylene terephthalate (PET) substrate에 ITO를 증착함으로써 전기적 광학적 특성을 조사하였다. 실험은 power 변화와 Ar, O2의 가스 분압비, Working Pressure의 변화를 변수로 두어 진행하였다. 측정은 Ellipsometry를 이용하여 광학적인 두께와 굴절률을 조사하였고 UV visible spectrometer를 통해 광학적인 투과도를 확인하였다. Power는 100 Watt 늘려가며 진행하였고 O2 유량의 변화에 따라 투과도와 면저항, 굴절률 특성이 달라짐을 확인할 수 있었다. O2의 유량에 따라 면저항이 줄어들다가 어느 정도 이상이 되면 급격히 증가함을 확인할 수 있었다. Working Pressure 변화에 따른 전기적 광학적 특성 또한 확인 하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.8
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• pp.601-606
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• 1998

ZnO thin film had been deposited on the glass by sputtering method, and the electrical and structural properties were investigated. When the rf power was 180W and sputtering was 10 m Torr at room temperature, Al-doped ZnO thin film had the lowest resistivity(1$\times10^{-4}\Omega\cdot{cm}$) and then carrier concentration and Hall mobility were $6.27\times10^{20} cm^{-3} and 22.04 cm^2/V\cdot$s, respectively. The undoped ZnO thin film had about 10$\times10^{14}\Omega\cdot cm$ resistivity when oxygen content was 10% or more at room temperature. When the oxygen content was 50% and below and sputtering pressure was 1.0$\times$1.0 \ulcorner Torr, the surface morphology of thin film observed by SEM was overall uniform.

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.3
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• pp.173-180
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• 2013

This paper is to investigate an effect of waste cooking oil(WCO) on the engineering properties and durability of high volume admixture concrete. Fly ash with 30% and blast furnace slag with 60% were incorporated in OPC to fabricate high volume admixture concrete with 0.5 of W/B. Emulsified refining cooking oil(ERCO) was made by mixing WCO and emulsifying agent to improve fluidity. ERCO was replaced by cement from 0.25 to 1.0%. As results, the increase of ERCO resulted in decrease of slump and air contents. For compressive strength, the use of ERCO led to decrease the compressive strength at 28 days, while it had similar strength or much higher strength than plain concrete at 180 days. Resistance to carbonation and chloride penetration was improved with the increase of ERCO contents due to decreased pore distribution by saponification between ERCO and concrete, while freeze-thaw resistance was degraded due to air loss.

• Proceedings of the KIEE Conference
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• 2009.04a
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• pp.80-83
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• 2009

현장 대지구조의 측정과 분석은 정확하고 신뢰성 있는 접지시스템의 설계와 시공에 매우 중요하며, 특히 대지 구조의 분석은 접지방식의 선정과 시공에 있어 절대적인 요소이다. 현장 측정 대지저항률의 실제적 분석을 통해 더 정확한 접지설계와 접지의 효율성을 높일 수 있으며, 시공 후 접지성능의 설계 오차를 최소화할 수 있게 된다. 대지는 다양한 형태의 지층과 구조로 이루어져 있으며, 접지설계의 신뢰성과 정확성은 대지 조건을 얼마나 현장 지질 조건에 가깝게 모델링 하는가에 달려있다. 현장 대지구조 및 지질 특성에 가깝게 분석하여 적용된 접지 설계는 시공 오류의 최소화, 성능의 안정화 그리고 비용의 절감은 물론 운용 설비의 운용 품질을 높여 주게 된다. 본 연구에서는 현장에서 측정된 대지저항률을 수직 지층와 수평지층 구조로 분석하여 그 결과를 비교하였고, 분석된 각각의 구조 대지저항률을 적용하여 접지시스템을 설계 비교하였다. 또한 설계된 접지시스템을 현장에 시공하여 측정된 결과값을 수직구조의 접지 설계치와 수평구조의 접지 설계치를 비교하므로써, 이를 통해 대지구조의 유형분석에 따른 접지설계의 신뢰성과 오류를 최소화하기 분석방안을 제시하였다.

• Economic and Environmental Geology
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• v.46 no.3
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• pp.215-220
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• 2013

We estimated the hydraulic conductivity of the sediments using constant-head permeability tests and electrical resistivity measurements with Jumoonjin standard sand of a uniform size and glass beads of different grain sizes. In this study, we determined the variations of the porosity, the hydraulic conductivity, and the resistivity in case 1 (changing the packing of the Jumoonjin standard sand) and in case 2 (varying the size of the glass beads). The results of case 1 showed that the hydraulic conductivity decreased with an increase in the electrical resistivity. This occurred because the sand grain while packing became rhombohedral with the a decrease of both the pore size and porosity. The results of the case 2 showed that the hydraulic conductivity increased due to the increase in the pore size as caused by the increased glass bead size. In addition, the porosity decreased and the electrical resistivity increased. Therefore, the relationship between the hydraulic conductivity and the electrical resistivity is negatively proportional as regards the grain packing with a change from cubic to rhombohedral whereas this relationship is positively proportional to the increase in the grain size.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.8
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• pp.536-543
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• 2016

The installation of grounding systems is important for the safe operation of power systems, and the soil resistivity is an important design consideration for such systems. It varies markedly with the soil type, moisture content and temperature. The Jeju geological structure is formed in a multi-layered structure characteristic of volcanic areas and, and the geological ground resistance values can appear even constructed the same areas ground system different from the soil structure. In this study, a mock-up system using representative soil from Jeju was constructed to analyze the variation of the grounding resistance. The mock-up system was configured using the Gauss-Newton algorithm inversion method to analyze the model numerically using the Wenner method through the soil resistivity measurements used to create the ground model. Also, we analyzed the change in the general ground resistance characteristics of the copper rod, copper pipe, and carbon rod that are used for grounding. The variation of the grounding resistance with the hydration status was found to be $2.9[{\Omega}]$, $16.5[{\Omega}]$ and $20.1[{\Omega}]$ for the copper rod, copper pipes, and carbon rod, respectively, and the influence of the ground moisture resistance of the carbon rod was found to be the lowest with a value of $141[{\Omega}]$.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.4
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• pp.363-370
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• 2020

This paper reports the results of an experimental study using the BOTDR sensor to detect the unbonded location of attached CFRP sheet for structural rehabilitation. A specimens with the unattached CFRP sheet were fabricated for this study, on which BOTDR sensor was attached with a nylon net. During the flexural test of the specimens, the strain of the CFRP sheet was measured using the BOTDR sensor and electric resistance gauges. From the results, it was confirmed that the strain distribution obtained through the BOTDR sensor can be effectively used to visualize and detect the unbonded position of the CFRP sheet. In addition, In addition, the strain measured by the BOTDR sensor was found to be more effective in analyzing the overall structure behavior than the electric resistance strain gauge. The development of a BOTDR sensor with a measuring longth of less than 100 mm will enable accurate detection of the local unbonded position of the CFRP sheet.