• 한국전기전자재료학회논문지
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• 제14권6호
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• pp.466-469
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• 2001

In this paper, we evaluated the dielectric properties of XLPE sheet of 22kV power cable, XLPE/semiconductor and XLPE/water/semiconductor depended on electric field and temperature respectively. Dielectric properties and temperature dependency of XLPE sheet of 22kV power cable increase greatly with as temperature increase and have no effect on applied voltage. And we confirmed that tan$\delta$ values in the samples with semiconductor or water layers were higher than those in the samples without them.

• 한국수소및신에너지학회논문집
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• 제34권6호
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• pp.741-747
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• 2023

In this study, the heat transfer characteristics were numerically analyzed to investigate the possibility of utilizing cooling water using liquid nitrogen. From the study, as the mass flow rate of the hot fluid increased, the heat transfer rate increased by 8.9-81.7%. And lowering the inlet temperature of the hot fluid resulted in increase in the heat transfer rate by 33.8-71.5%. As for the filling level of liquid nitrogen, as higher filling level led to a decrease in the outlet temperature and an increase in the overall heat transfer coefficient.

• 한국수자원학회논문집
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• 제57권6호
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• pp.409-419
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• 2024

기후변화는 이미 지속 가능한 수자원 관리에 영향을 미치고 있다. 기후변화가 댐 저수지의 물 공급에 미치는 영향은 일반적으로 지구 기후 모델 결과 기반으로 생성된 기후변화 시나리오를 사용하여 수행되고 있다. 그러나 기후변화를 추정하기 때문에 시나리오는 미래에 발생할 수도 있는 상황을 가정하는 한계로 인하여 본질적으로 불확실성을 내포하고 있다. 이러한 문제에 대한 대책으로 의사결정 스케일링 접근법을 본 연구에 적용하였다. 연구대상지는 충주, 용담, 합천, 섬진강 댐이다. 강우 유출 모형(IHACRES)과 HEC-ResSim기반 댐 운영 모형을 결합하여 댐 이수 안전도를 분석하였다. 이 수안전도 분석은 안정적인 댐 운영에 목적을 두고 그 결과에 따라 구조적 또는 비구조적 이수공급 계획을 수립하는데 활용하고 있다. 따라서 본 연구에서는 이수안전도 분석으로 댐이 안전하게 운영될 수 있는지를 평가하고 장래 댐 운영 중 발생할 수 있는 잠재적인 위험을 식별하기 위함이다. 1995년 부터 2014년까지 관측된 강수량과 온도를 기준으로 49개의 기후스트레스 시나리오(분위 수 기준 7개의 강수 시나리오와 0℃부터 6℃도까지 1℃ 간격의 7개의 온도 시나리오)를 적용하였다. 그 결과 홍수기 강우 변동이 비홍수기의 강우 증가보다 수위 상승에 더 큰 변화를 가져왔다. 따라서 이수 안전도는 1분위 강우 의존성이 매우 높은 것으로 평가되었다. 또한 강수 및 온도를 결합한 시나리오에서 댐 용수 공급 신뢰도는 개별 강수 및 온도 시나리오 신뢰도 변화의 합계보다 더 큰 변화가 모의되었다. 이러한 차이는 강수량의 감소와 증가가 각각 물과 에너지가 제한된 증발량의 발생으로 초래하는 것으로 나타났다. 본 연구에서 수행한 의사결정 스케일링을 통한 이수안전도 평가는 댐 운영의 효율성 향상을 도모할 것으로 평가된다.

• 한국조경학회지
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• 제26권2호
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• pp.259-268
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• 1998

This study was carried out to evaluate the effect of open space on temperature chang. In open space, lower temperature zones were formed, while high temperature zones were developed around urban areas. In forests and on water within open space, marked temperature reduction was recorded. The 10 % increase of the ratio of green space within fifty meters around the observation point decreased 0.33~0.43$^{\circ}C$ from the maximum temperature and 0.20~0.$25^{\circ}C$ from the minimum temperature. The increase of ten trees in the area decreased 0.33~0.49$^{\circ}C$ from the maximum temperature and 0.20~0.23$^{\circ}C$ from the minimum temperature.

• 한국염색가공학회지
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• 제15권4호
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• pp.8-16
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• 2003

Poly(trimethylene terephthalate)(PTT) fiber was pretreated with organic solvent/water solution of various compositions. The organic solvents used in this experiment were benzyl alcohol, n-buthanol, and N,N-dimethylformamide(DMF). Density of the fibers were investigated as a measure of crystallite region. The dye uptake increased in the order of pretreatment with hot water < untreated < 5% benzyl alcohol < 100% benzyl alcohol < 90% benzyl alcohol; hot water < untreated $\risingdotseq$ 5% butanol < 100% beutanol < 90% butanol; hot water $\risingdotseq$ 5% DMF < untreated < 90% DMF < 100% DMF. The dye uptake increases with increase of crystallinity. It seems likely that the recrystallization process during the pretreatment with organic solvent/water solutions leads to an increase in the microvoid and then a large increase in the dye uptake. Also the dyeing rate increased and the dyeing transition temperature decreased with the pretreatments. The results obtained are corresponds with the plasticization of the fiber structure formed during the pretreatrnent.

• 한국안전학회지
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• 제19권2호
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• pp.61-68
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• 2004

The evaporation phenomena of waterr droplet which has sodium acetate trihydrate($CH_3COONa{\cdot}3H_2O$) as a fire suppression additive were studied. Solutions of sodium salt up to 50% and heated stainless-steel surface were used in the experiment. The evaporation process was recorded using a charge-coupled-device camera at 120 frames per second. The average evaporation rate of the sodium acetate trihydrate soluation was lower than that of pure water at a given surface temperature and decreased with the concentration increase due to the precipitation of salt in the liquid film and change of surface tension. The variation of liquied film diameter was measured by time and it was increased by the hot surface temperature increase.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.13-16
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• 2006

Electro-electrodialysis (EED) experiments were carried out for the HI concentration from HIx $(HI-H_2O-I_2)$ solution to improve the Hl decomposition reaction in the thermochemical water-splitting is (iodine-Sulfur) process. EED cell is composed of the collector electrode and electrolyte. Nafion 117 which was cation exchange membrane used as an electrolyte, and the activated carbon cloth used as an electrode. The HI concentration experiment was carried out using the HIx solution and molar ratio of the $I_2$ were varied from 1 to 3 mole. The cell voltages were decreased as temperature increase. And, membrane properties such as transport number of proton and electro-osmosis coefficient were decreased as temperature increase

• 한국물환경학회지
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• 제35권6호
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• pp.580-588
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• 2019

The flow of the middle and downstream of the Yeongsan River is stagnant by two weirs of Seungchon and Juksan and the estuary dam and maintained in freshwater. In this study, the Environmental Fluid Dynamics Code-National Institute of Environment Research(EFDC-NIER) model was applied to the Yeongsan River to simulate water flow, temperature, and salinity stratification. The EFDC-NIER model is an improved model which can simulate multi-functional weirs operation, multiple algal species, and the vertical movement mechanism of algal based on the EFDC model. The simulation results for the water level, water temperature, velocity, and salinity reproduced the observed values well. The mean absolute error(MAE) of the model calibration in the annual variations of the water level was 0.1-0.3 m, water temperature was 0.8-1.7 ℃, velocity was 4.5-7.1 cm/sec, and salinity was 1.5 psu, respectively. In the case of scenario simulation for the full opening of the estuary dam, the water level of the estuary dam was directly impacted by the tide so it was predicted to rise - 1.35 m to 0.2 m on average sea level. The velocity was also predicted to increase from 2.7 cm/sec to 50.8 cm/sec, and the flow rate to increase from 53 ㎥/sec to 5,322 ㎥/sec.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.395-395
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• 2008

Water-assisted synthesis of carbon nanotubes (CNTs) has been intensively studied in recent years, reporting that water vapor enhances the activity and lifetime of metal catalyst for the CNT growth. While most of these studies has been focused on the supergrowth of CNTs at high temperature, rarely has the similar approach been made for the CNT synthesis at low temperature. Since the metal catalyst are much less active at lower temperature, we expect that the addition of water vapor may increase the activity of catalyst more largely at lower temperature. We synthesized multi-walled CNTs at temperature as low as $360^{\circ}C$ by introducing water vapor during growth. The water addition caused CNTs to grow ~3 times faster. Moreover, the water-assisted growth prolonged the termination of CNT growth, implying the enhancement of catalyst lifetime. In general, a thinner catalyst layer is likely to produce smaller-diameter, longer CNTs. In a similar manner, the water vapor had a greater effect on the growth of CNTs for a smaller thickness of catalyst in this study. To figure out the role of process gases, CNTs were grown in the first stage and then exposed to each of process gases in the second stage. It was shown that water vapor and hydrogen did not etch CNTs while acetylene led to the additional growth of CNTs even faster in the second stage. As-grown CNTs were characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), and Raman spectroscopy.

• 한국수소및신에너지학회논문집
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• 제18권4호
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• pp.413-421
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• 2007

In this paper, the performance characteristics of heat pump system using a new refrigerant subcooling system designed for the study, are introduced. The new heat pump system have the ice storage tank at the outlet of condenser. The experimental apparatus is a well-instrumented water/water heat pump which consisted of working fluid loop, coolant loop, and ice storage tank. The experiment parameters of subcooling ranged as the evaporating temperature from $-5^{\circ}C$ to $8^{\circ}C$, the condensing temperature from $30^{\circ}C$ to $35^{\circ}C$. The test of the ice storage was carried out at evaporating temperature of $-10^{\circ}C$ and the ice storage mode is Ice-On-Coil type. The working fluid was R-22 and the storage materials were city-water. The test results obtained were as follows; The refrigerant mass flow rate and compressor shaft power were unchanged by the degrees of subcooling, that is, they were independent of degrees of subcooling. The cooling capacity of the new heat pump system increase as the evaporating temperature and subcooling degrees increase and is higher by $25{\sim}30%$, compared to the normal heat pump system. The COP of the new heat pump system increases as the degrees of subcooling and evaporating temperature increase and is higher by 28% than that of the normal heat pump system.