• Geomechanics and Engineering
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• 제11권6호
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• pp.771-785
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• 2016

The thermal conductivity of soils is an important property in energy-related geotechnical structures, such as underground heat pumps and underground electric power cable tunnels. This study explores the effects of geotechnical engineering properties on the thermal conductivity of soils. The thermal conductivities of quartz sands and Korean weathered silty sands were documented via a series of laboratory experiments, and its variations with effective stress, porosity, and water saturation were examined. While thermal conductivity was found to increase with an increase in the effective stress and water saturation and with a decrease in porosity, replacing air by water in pores the most predominantly enhanced the thermal conductivity by almost one order of magnitude. In addition, we have suggested an improved model for thermal conductivity prediction, based on water saturation, dry thermal conductivity, saturated thermal conductivity, and a fitting parameter that represents the curvature of the thermal conductivity-water saturation relation.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.63-63
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• 1999

The stability of hydrogenated amorphous silicon (a-Si:H) films under the light soaking are very important since the applications of a-Si:H films are solar cells, color sensors, photosensors, and thin film transistors(TFTs). We found the changes of the electric conductivity and the conductivity activation energy (Ea) of a-Si:H films by argon radical annealing. The deposition rate of a-Si:H films depends on the argon radical annealing time. The optical band gap and the hydrogen contents in the a-Si:H films are changes along the argon radical annealing time. We will discuss the microscopic processes of argon radical annealing in a-si:H films.

• 전기학회논문지
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• 제60권10호
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• pp.1881-1887
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• 2011

In this work the recyclable new polyethylene(PE) and polypropylene(PP), which are thermoplastic, have been investigated as the eco-friendly insulating candidates to replace the cross-linked polyethylene (XLPE). The temperature dependence of conductivities of these materials has been measured and its effects on electric field and space charge distribution in polymeric insulated power cable under temperature gradient have been calculated. It is shown that the sensitivity of conductivity to temperature change has more critical influence to determine the electric field distribution in the power cable than the absolute value of conductivity does and it can be said that the temperature dependence is one of most important factors for the power cable design.

• 전기학회논문지
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• 제57권2호
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• pp.314-319
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• 2008

In this paper, the electric field distribution induced inside the brain during Transcranial Magnetic Stimulation(TMS) has been thoroughly investigated in terms of tissue heterogeneity and anisotropy as well as different head models. To achieve this, first, an elaborate head model consisting of seven major parts of the head has been built based on the Magnetic Resonance(MR) image data. Then the Finite Element Method(FEM) has been used to evaluate the electric field distribution under different head models or three different conductivity conditions when the head model has been exposed to a time varying magnetic field achieved by utilizing the Figure-Of-Eight(FOE) stimulation coil. The results show that the magnitude as well as the distribution of the induced field is significantly affected by the degree of geometrical asymmetry of head models and conductivity conditions with respect to the center of the FOE coil.

• 펄프종이기술
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• 제39권2호
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• pp.45-53
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• 2007

When micro flute corrugated paperboards are used for food packaging, they necessarily need to meet the requirements for the distribution, transportation, and storage of food. The requirements could vary ac-cording to the contents in the packaging boxes. Microflute corrugated packaging paperboard for hot foods such as just-made coffee and hamburger requires to have a decent resistance property against high temperature. Along with a recent trend for small-quantity-multi-item upgraded packaging, semiconductor products and consumer-electronic appliances become to be packed using the environmental friendly micro flute corrugated paperboard. In this case, the electric resistance property of the microflute corrugated paperboard becomes important. This study was carried out to investigate on the thermal conductivity and electric resistance properties of micro flute corrugated paperboard.

• KEPCO Journal on Electric Power and Energy
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• 제2권1호
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• pp.127-131
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• 2016

Polymer electrolyte membrane for unitized regenerative fuel cells requires high proton conductivity, high dimensional stability, low permeability, and low cost. However, DuPont's Nafion which is a commercial polymer electrolyte membrane has high permeability, high cost, and decreasing proton conductivity and dimensional stability over $80^{\circ}C$. To address these problems, sulfonated poly ether ether ketone (sPEEK) which is a low cost hydrocarbon polymer is selected as matrix polymer for the preparation of polymer electrolyte membrane. In addition, composite membrane with improved proton conductivity and dimensional stability is prepared by introducing sulfonated graphene oxide (sGO). The fundamental properties of polymer electrolyte membranes are analyzed by investigating membrane's water content, dimensional stability, proton conductivity, and morphology. The cell test is conducted to consider the possibility of application of sPEEK/sGO composite membrane for an unitized regenerative fuel cell.

• 한국분말재료학회지
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• 제19권4호
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• pp.285-290
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• 2012

The present study was focused on the analysis of the electric and thermal properties of spark plasma sintered $Bi_{0.5}Sb_{1.5}Te_3$ thermoelectric material. The crystal structure, microstructure, electric and thermal properties of the sintered body were evaluated by measuring XRD, SEM, electric resistivity, Hall effect and thermal conductivity. The $Bi_{0.5}Sb_{1.5}Te_3$ sintered body showed anisotropic crystal structure. The c-axis of the $Bi_{0.5}Sb_{1.5}Te_3$ crystal aligned in a parallel direction with applied pressure during spark plasma sintering. The degree of the crystal alignment increased with increasing sintering temperature and sintering time. The electric resistivity and thermal conductivity of the $Bi_{0.5}Sb_{1.5}Te_3$ sintered body showed anisotropic characteristics result from crystal alignment.

• 대한지리학회지
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• 제38권1호
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• pp.1-15
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• 2003

본고는 강원도 양구군 대암산 정상부(1,280m)에 위치한 우리나라 대표적 고층습원인 용늪의 늪 환경을 유지시키기 위해 실시된 지하수 수질 기초조사 결과이다. 용늪의 지하수 수질 특성을 파악하기 위하여 지하수온과 pH, 전기전도도의 변화값이 2000년 7월부터 12월까지 6개월에 걸쳐 29개소의 관측정에서 조사되었다. 용늪의 건조화가 진행되고 있는 지점의 수질 값은 다른 지점과 비교할 때 수질항목별 각월의 일정한 분포 범위를 벗어나고 있는 특성을 보인다. 용늪내 월별 지하수온은 매일 평균수온과 비교할 때 대개 2$^{\circ}C$ 정도의 편차를 보이고 있으며, 용늪의 지하수위가 높아질수록 지하수온도 증가하는 패턴을 보인다. 용늪 지하수의 pH는 대개 5.0 에서 6.0 사이의 값을 갖고 있으나 국지적으로는 4.0 미만의 강산성을 띠고 있는 경우도 있다. 나지에서 측정된 지하수 pH 값은 다른 지점의 pH 값보다 높게 나타나고 있다. 용늪의 전기전도도값은 지하수위가 높을수록 증가하는 경향을 보인다. 그러나. 지하수의 전기전도도값은 지표수의 전기전도도값과 계절별로 서로 다른 변화를 갖는다. 용늪내 지하수의 pH와 전기전도도간에는 정비례 관계를 갖고 있으며. 수온과 pH. 수온과 전기전도도는 각각 계절별로 일정한 범위내의 값을 갖는 것으로 조사되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 C
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• pp.528-530
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• 2000

In this paper, electric field distribution of GIS by changing conductivity of spacer is analysed by the use of 3 dimensional Surface Charge Method. We find electric field distribution inside GIS was much influenced when volume resistance are lower than $10^7[\Omega-cm]$.

• 동력기계공학회지
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• 제15권2호
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• pp.55-60
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• 2011

The popularity of diesel engines is derived primarily from their higher thermal efficiency resulting from higher compression ratio. NOx removal from the diesel emissions is very important to meet stringent emission regulations. NOx emission from diesel engines is removed by an urea-SCR or an LNT system. The urea-SCR system needs the urea-solution supply system with concentration and level sensor. This study was carried out to develop a sensor for the measurement of urea-solution concentration by an electric conductivity method. Considering experimental parameters were the material of electrode, two kinds of electric power(AC or DC), the distance between two electrodes, and the length of electrode. It was found that the AC electric power was more useful to measure the urea-solution concentration compared to DC, because it prevented an ionization of the urea-solution. The silver rod coated with Pt is the most useful electrode, tendency of which is similar to Pt rod, and the cost is more economic. We could also find out the optimum distance between two electrodes and the length of electrode was 10mm and 3mm, respectively.