• 한국환경과학회지
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• 제24권8호
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• pp.1075-1084
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• 2015

This study was conducted to investigated the changes in the nutrient components ($NO_3{^-}-N$, $NH_4{^+}-N$, $PO_4{^{3-}}P$, $K^+$, $Ca^{2+}$, and $Mg^{2+}$) and environmental parameters (electrical conductivity, total dissolved solids and pH) on the leaf lettuce (Lactuca sativa L.) grown with hydroponics. Recirculating hydroponic cultivation system was consisted of planting port, LED lamp, water tank, and circulating pump for hydroponic. Nutrient solution was used in the standard solution for Japan vegetables experimental station and commercial hydroponic. The result showed that electrical conductivity (EC), total dissolved solids (TDS) and pH, depending on the growth of lettuce decreased continuously. With the growth of the lettuce, nitrate nitrogen, ammonia nitrogen, phosphate phosphorus were required for periodic replacement. The number of pH compensation due to the growth of lettuce are the most high. The concentration of $Ca^{2+}$ and $Mg^{2+}$ during the lettuce growth showed no significant change. However, $K^+$ concentration increased due to the replacement with nitrogen and phosphorus. Electric conductivity and total dissolved solids with total nutrient concentration showed the linear relationship and the correlation coefficient $R^2$ were 0.8601 and the 0.827, respectively.

• 한국재료학회지
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• 제25권3호
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• pp.119-124
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• 2015

This paper investigates the change of the percolation threshold in the carbon powder-filled polystyrene matrix composites based on the experimental results of changes in the resistivity and relative permittivity of the carbon powder filling, the electric field dependence of the current, and the critical exponent of conductivity. In this research, the percolation behavior, the critical exponent of resistivity, and electrical conduction mechanism of the carbon powder-filled polystyrene matrix composites are discussed based on a study of the overall change in the resistivity. It was found that the formation of infinite clusters is interrupted by a tunneling gap in the volume fraction of the carbon powder filling, where the change in the resistivity is extremely large. In addition, it was found that the critical exponent of conductivity for the universal law of conductivity is satisfied if the percolation threshold is estimated at the volume fraction of carbon powder where non-ohmic current behavior becomes ohmic. It was considered that the mechanism for changing the gaps between the carbon powder aggregates into ohmic contacts is identical to that of the connecting conducting phases above the percolation threshold in a random resister network system. The electric field dependence is discussed with a tunneling mechanism. It is concluded that the percolation threshold should be defined at this volume fraction (the second transition of resistivity for the carbon powder-filled polystyrene matrix composites) of carbon powder.

• E2M - 전기 전자와 첨단 소재
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• 제10권7호
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• pp.719-726
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• 1997

This research was conducted to analyze the change of surface tension, viscosity, streaming current and conductivity of transformer oil when it were injected with the interface active substances.(anionic:S-111, cationic:S-121, amphoteric:S-131) The changes properties of the surface tension and viscosity of the oil which were injected with the interface active substances were divided into the changes area and the minimum reduction area. The surface tension and viscosity of the oil which were injected with three different kinds of interface active substances showed remarkable change at the point where the concentration of the substance in anionic, in cationic and in amphoteric were 100[ppm], 10[ppm] and 1[ppm] respectively. The streaming current and conductivity of the same sample oil were also changed at the same densities of the surface tension and viscosity. For this factor, it was possibile for us to interpret the mechanism of the streaming current and conductivity. Therefore the interface active substances of the three kinds were injected into the oil within the limit of optimal volume, prevention effects of electrification were showed more excellence than unmixed insulating oil.

• 한국재료학회지
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• 제9권6호
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• pp.569-576
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• 1999

In this study, the effect of the microstructural evolution on the electrical of Cu-Ag microcomposite was investigated. The nature of interfaces between silver filaments and Cu matrix may have pronounced effects on the physical properties of Cu-Ag filamentary microcomposites, little is known about these interfaces. In heavily drawn Cu-Ag filamentary microcomposities, the microstructure is too fine and the interfacial area is too large to maintsin a stable internal dislocation structure because of closely spaced filaments. Rather, most dislocations are thought to be gradually absorbed at the interfaces as the draw ratio increases. The mechanical and electrical properties of Cu-Ag filamentary microcomposites wires were also examined and correlated with the microstructural change caused by thermomechanical treatments. The study on the electrical conductivity combined to resistivity in Cu-Ag filamentary microcomposites and the rapid increase of the electrical conductivity at high annealing temperatures is mainly caused by the dissolution and coarsening of silver filaments. The relatively low ratio of the resistivities is mainly caused by the dissolution and coarsening of silver filaments. The relatively low ratio of the resistivities at 295K($\rho$\ulcorner/$\rho$\ulcorner) in as-drawn Cu-Ag microcomposites can also be explained by the contribution of the interface scattering.

• 조명전기설비학회논문지
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• 제18권2호
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• pp.44-48
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• 2004

수표면을 전극으로 사용한 무성방전형 오존발생기를 제안하고 수중의 전도도 변화가 수표면 방전에 미치는 영향을 실험적으로 조사하였다. 수표면 방전에 중요한 영향을 줄 수 있는 요소로 방전공간내의 이온과 수중의 이온 및 극성분자등이 있다. 본 연구에서는 전도도를 변화시켜 수중에 존재하는 이온의 수를 조절함으로써 방전특성을 변화시키고자 하였다. 이를 위해 증류수내에 각각 다른양의 NaCl을 투입함으로써 전도도를 변화시켰고 이때의 전류-전압특성과 오존발생특성을 비교 조사하였다. 결과적으로 순수한 증류수를 사용한 경우보다 NaCl을 투입한 경우 안정된 방전을 발생시킬 수 있었고 투입하는 NaCl의 양을 늘여감에 따라 방전개시전압을 낮출 수 있었다.

• 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.

• Bulletin of the Korean Chemical Society
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• 제31권11호
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• pp.3225-3227
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• 2010

The thermal conductivity of layered metal chalcogenides such as $MT_2$ (M = Mo, W; T = S, Se) shows a marked decrease after exfoliation and subsequent restacking process. Random stacking of two-dimensional crystalline sheets circumvents thermal conduction pathways along a longitudinal direction, which results in a reduction in thermal conductivity. $WS_2$ and $WSe_2$ compounds retain p-type conducting behavior after exfoliation and restacking with decreased electrical conductivity due to the change in carrier concentration. $MoSe_2$ compound exhibits metallic behavior < $130^{\circ}C$ with a small Seebeck coefficient, which results from metastable 1T-$MoSe_2$ structure of the restacked phase.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.505-508
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• 1999

In this study, weight loss, ESDD, surface conductivity and leakage current were measured at the different saline solutions by salt fog method. The magnitude of leakage current was higher at higher conductivity of 2 S/m saline water, but weight loss ESDD and surface conductivity which are indices of degradation were lower. This is considered that the current includes mainly ohmic component which doesn\`t contribute to surface degradation. In addition, it is shown that FFT could be useful in measuring initial transition from hydrophobic to hydrophilic surface.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.112-115
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• 2003

There is a growing need for a nonvolatile memory technology with faster speed than existing nonvolatile memories. $T_c$(crystallization temperature) is confirmed by measuring the conductivity with the varying temperature. The sample is heated on the hotplate and slow down to the room-temperature. We prepared Te based alloy bulk. The materials can be used for nonvolatile random access memory.

• Composites Research
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• 제34권6호
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• pp.412-420
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• 2021

본 연구에서는 탄소 단섬유를 천연고무 기지에 혼합한 탄소섬유/고무 시편과 그에 니켈입자를 추가한 탄소섬유-니켈입자/고무 시편의 초기 전기전도도를 측정하고, 그 시편에 압축스트레인을 가하면서 변화하는 전기전도도를 측정하였다. 실험을 통해 탄소섬유의 체적분율 및 추가된 니켈입자, 외부스트레인 등이 전기전도도에 미치는 영향을 관찰하였다. 탄소섬유 체적분율은 작은 차이로도 시편의 전기전도도의 변화에 매우 큰 역할을 하였고, 외부스트레인에 따른 탄소섬유 재배열에 의해 압저항이 증가하는 것을 알 수 있었다. 또한, 니켈입자의 추가는 탄소섬유가 임계체적분율 이상인 시편에서 전기전도도를 개선하는데 기여하는 것을 볼 수 있었는데, 이로부터 외부변형에 따른 탄소섬유의 재배열에 의해 압저항이 증가하는 현상을 상쇄하는 효과가 있음을 확인하였다.