• 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.

• 설비공학논문집
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• 제16권12호
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• pp.1126-1133
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• 2004

This paper presents an experimental measurement of effective thermal conductivity in an adsorbent packed bed with silica gel A type. The effective thermal conductivity was measured under different conditions of the adsorbent bed temperature, pressure, particle size and water content by using the transient hot wire method. The measured effective thermal conductivity showed to become bigger with decreasing particle size or increasing water content, but it was a little affected with increasing bed temperature and pressure. The bed temperature was varied in the range of 1$0^{\circ}C$ (equation omitted) T (equation omitted) 5$0^{\circ}C$ and the pressure in the range of 10 kPa (equation omitted) P (equation omitted) 190 kPa. The results show that 0.10～0.18 W/mㆍK of effective thermal conductivity measured for the zero water content.

• KIEAE Journal
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• 제13권2호
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• pp.107-112
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• 2013

The purpose of this study is to analyze an insulation property and to establish a design standard for the underground space in architecture. Insulation materials for this study are 12 kinds of Insulation which qualified KS standards(3 classes of EPS type 1, 3 classes of EPS type 2(Neopor), 3 classes of XPS and 3 classes of PU Boards). For insulation materials of underground space, insulating and water tightening property are desired. So conductivity for insulating and water absorption for water tightening are measured in this study. Temperature, insulation is exposed to in the underground space, is different from temperature above the ground. Conductivity is measured in a temperature of $17^{\circ}C$, $20^{\circ}C$, $23^{\circ}C$ and $26^{\circ}C$. In KS standards, water absorption are measure after 24 hours, but insulation is exposed to water for a long time in the underground. So after 110 days, water absorption are measured. As time goes by, increasing of water absorption means decreasing of water tightening and insulating. So after water absorption had measured for 110 days, conductivity has measured again. As a result, XPS is selected as optimized insulation for underground. And Conductivity of XPS insulation with water should be added by 20%.

• 한국농공학회논문집
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• 제55권4호
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• pp.1-11
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• 2013

Unsaturated hydraulic conductivity function is one of key parameters to solve the flow phenomena in problems of landslide. Prediction models for hydraulic conductivity function related to soil-water retention curve equations in many geotechnical applications have been still used instead of direct measurement of the hydraulic conductivity function since prediction models from soil-water retention curve equations are attractive for their fast and easy use and low cost. However, many researchers found that prediction models for the hydraulic conductivity function can not predict the hydraulic conductivity exactly in comparison with experimental outputs. This research introduced an inverse analysis to evaluate the hydraulic conductivity function corresponding to experimental output from the flow pump system. Optimisation process was carried out to obtain the hydraulic conductivity function. This research showed that the inverse analysis with flow pump system was suitable to assess the hydraulic conductivity in unsaturated soil, and the prediction models for the hydraulic conductivity were led to the significant discrepancy from actual experimental outputs.

• 한국분무공학회지
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• 제21권2호
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• pp.111-115
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• 2016

This paper experimentally reports the effect of suspension stability on the thermal conductivity of water-based Au nanofluids. For this purpose, the water-based Au nanofluids are prepared by the one-step method called electro-chemical method with volume fraction of 0.0005%. The thermal conductivity of water-based Au nanofluids is measured from $22^{\circ}C$ to $42^{\circ}C$ using the transient hot wire method. To quantify the suspension stability of Au nanofluids, the suspension stability of nanofluids is evaluated using the in-house developed laser scattering system at a fixed wavelength of 632.8nm with the elapsed time. Based on the experimental results, the both thermal conductivity and suspension stability of water-based Au nanofluids are gradually decreased according to the time. These results experimentally show that the suspension stability of water-based Au nanofluids is the one of the important factor of thermal conductivity.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.427-434
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• 2000

Hydraulic conductivity of soil-cement was measured as a function of some selected construction variables that are often encountered in practice. They are initial (or compaction) water content, delayed compaction after mixing, and repeated freezing and thawing. Sandy and clayey soils were used. The hardening agent used was a cement based soil stabilizer consisting of 80% of ordinary Portland cement and 20% of a combination of supplementary materials. Hydraulic conductivity of soil-cement with varying initial water content was, in trend, similar to that of compacted clay. Hydraulic conductivity of soil-cement decreased with increasing initial water content and reached its minimum when compacted wet of optimum water content. Pore size distributions of soil cement at different initial water contents were analyzed using mercury intrusion porosimetry. The analysis showed that dryer condition led to the formation of larger pores with lesser total pore volume; smaller pores with larger total pore volume at wetter condition. Hydraulic conductivity of soil-cement increased by orders in magnitude when specimen underwent delayed compaction of longer than 4 hours after mixing and repeated freezing and thawing.

• 한국환경복원기술학회지
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• 제5권2호
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• pp.17-24
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• 2002

This research was conducted to investigate the influences caused by solifluction soil on the physicochemistry of stream water quality at the riparian area four points in the northeastern part of the Bughansan National Park from March to May of 2001. The average pH of stream water was higher than those in the caused by solifluction soil. The average electrical conductivity of upstream water was about 0.8~1.7 times lower than those in the caused by solifluction soil, but the average electrical conductivity of downstream water was about 1.6~3.8 times higher than those in the caused by solifluction soil. Therefore, these results showed that the water quality of downstream was worse than that of upstream. Twelve factors including the physicochemistry on the stream water and caused by solifluction soil were analyzed by spss/pc+ for the data collected from during March to May of 2001. pH of stream water was very significantly correlated with pH and electrical conductivity at the caused by solifluction soil. And the electrical conductivity of stream water was very significantly correlated with electrical conductivity and the amount of cation($Na^+$, ${NH_4}^+$, $Mg^{2+}$) at the caused by solifluction soil.

• 한국지반공학회논문집
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• 제20권3호
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• pp.47-51
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• 2004

불포화 투수계수함수는 흙수분 특성곡선과 함께 불포화토를 이해 연구하는데 있어서 없어서는 안 될 중요한 요소이다. 일반적으로 불포화 투수계수함수를 직접 측정하기에는 많은 어려움이 있기에, 흙수분 특성곡선에 근거한 예측함수를 사용하여 불포화 투수계수함수를 구하곤 했다. 본 연구에서는 이러한 예측함수를 사용하지 않고, 피스톤 펌프기법과 역해석 기법을 이용한 불포화 투수계수함수를 구하는 방법을 제시한다. 이렇게 구해진 불포화 투수계수함수는 예측함수를 사용하지 많았기 때문에, 흙수분 특성곡선으로부터 독립적이며 예측함수를 사용한 경우보다 보다 정확한 불포화토의 특성을 보여준다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3142-3147
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• 2008

A simple transient simulation of ground source heat pump system was carried out to investigate the effects of ground thermal conductivity on its performance. The TRNSYS code with a simple water to water heat pump model was used to compare the COP variation of the system. A new ground heat exchanger called by semi-closed loop was proposed and constructed in the real site. The effective thermal conductivity was measured using the test equipment developed by according to the line source model. The simulation results showed that highly efficient thermal conductivity of the grout material could increase the performance of the heat pump system very well. And the new ground heat exchanger showed the increased effective thermal conductivity as the penetration water flow rate(PWFR) was increased. Therefore, the performance improvement of the heat pump system using the proposed ground heat exchanger can be expected.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3371-3376
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• 2007

The design of a ground-source heat pump system includes specifications for a ground loop heat exchanger where the heat transfer rate depends on the thermal conductivity of the ground. To evaluate this heat transfer property, in-situ thermal response tests on four vertical test boreholes with different grouting materials were conducted by adding a monitored amount of heat to water over various test lengths. By measuring the water temperatures entering and exiting the loop, water flow rate, and heat load, effective thermal conductivity values of the ground were determined. The effect of increasing thermal conductivity of grouting materials from 0.82 to 1.05 W/m$^{\circ}C$ resulted in overall increases in effective ground thermal conductivity by 25.8% to 69.5%.