• Journal of Korea Water Resources Association
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• v.31 no.2
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• pp.123-132
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• 1998

Monitoring solute transport has been known to be difficult especially for the unsaturated soil. The object of this study is to investigate the TDR application to monitoring solute concentration in the vadose zone. The TDR calibration test was conducted for soil samples with various water contents and concentrations. The voltage attenuation of electromagnetic wave of TDR was used to estimate the bulk electrical conductivity of a soil. The relationship between the bulk soil electrical conductivity and the solute concentration was assumed to be linear at a constant volumetric soil water content. In this study four proposed relationships were compared using data obtained from KCI solution at three different concentrations. Relationships given by Topp, Daltaon, Yanuka showed the linearity between the bulk soil electrical conductivity and the solute concentration, which were more pronounced than Zegelin's. The three relationships were found to be useful to measure the solute concentration in the vadose zone. In addition, TDR method was proven to be a viable technique in monitoring solute transport through unsaturated soils in transient flow condition.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.7
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• pp.528-534
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• 2011

In this paper, thermal characteristics of cylindrical grooved wick heat pipes with water-based MWCNT nanofluids as working medium are experimentally investigated. Volume fractions of nanoparticles are varied with 0.1% to 0.5%. Transient hot wire method developed in house is used to measure the thermal conductivity of nanofluids. It is enhanced by up to 29% compared to that of DI water. The thermal resistances and temperature distributions at the surface of the heat pipes are measured at the same evaporation temperature. The experimental results show that the thermal resistance of the heat pipes with water-based MWCNT nanofluids as working fluid is reduced up to 35.2% compared with that of heat pipe using DI water. The reduction rate of thermal resistance is greater than the enhancement rate of thermal conductivity. Finally, based on the experimental results, we present the reduction of the thermal resistances of the heat pipes compared with conventional heat pipes cannot be explained by only the thermal conductivity of water-based MWCNT nanofluids.

• Journal of the Korean earth science society
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• v.45 no.4
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• pp.363-376
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• 2024

Alluvial beds are intimately associated with electrical properties related to soil types, including clay mineral content, porosity, and water content. The hydraulic property governs water movement and storage in alluvial beds. This study revealed electrical resistivity and hydraulic properties in space and time in relation to the hydrogeological data, groundwater pumping, and rainfall infiltration into the alluvial bed located in Daesan-myeon, Changwon City. An electrical resistivity survey with electrode spacings of 2 and 4m using a dipole-dipole array indicates that electrical resistivity changes in the alluvial bed depend on groundwater pumping and rainfall events. Additionally, rainfall infiltration varies with hydraulic conductivity in the shallow zone of the alluvial bed. The 2 m electrode spacing survey confirms that electrical resistivity values decrease at shallow depths, corresponding with rainfall and increased water content in the soil, indicating rainfall infiltration approximately 1-2 m below the land surface. The 4m electrode spacing survey reveals that hydraulic conductivity (K) values and electrical resistivity (ρ) values display an inverse relationship from the surface to the water table (approximately 9 m) and at deeper levels than the water table. Notably, ρ values are impacted by pumping around the depth of the water table at 9 m. This study suggests that time-lapsed electrical resistivity surveys in space and time could be effective tools for detecting the impact of rainfall and pumping, as well as hydraulic conductivity in shallow alluvial beds.

• Journal of Soil and Groundwater Environment
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• v.16 no.4
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• pp.1-9
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• 2011

Bentonite has been generally used as vertical cutoff barrier material and reported to have several problems regarding its low workability, drying shrinkage cracking by particle cohesion, and ineffective waterproof ability under sea water condition. In this study, the particle sealant, the furnace slag coated by the mixture of bentonite, sepiolite and guargum, was developed to compensate these weak points and the hydraulic conductivity of the particle sealant was evaluated. Drying shrinkage cracking and swelling index was estimated to find the optimal mixing ratio of bentonite, sepiolite and guargum. The hydraulic conductivity of the particle sealants having different amount of sealant (bentonite-sepioliteguargum mixture) coating the furnace slag was estimated using the rigid wall permeameter and flexible wall permeameter. The results showed that drying shrinkage cracking was not found in the bentonite-sepiolite mixture with 20% sepiolite contents and the results from free swelling tests for the sealant having 1 : 0.025, 1 : 0.05 and 1 : 0.075 of weight ratios of bentonite-sepiolite mixture and guargum under simulated sea water condition were higher than those for the bentonitesepiolite mixture without guargum under tap water condition. These three sealants were coated on the furnace slag with 50% and 60% of sealant in the particle sealant and the hydraulic conductivity was estimated. In the cases of the particle sealants having 20% sepiolite in the bentonite-sepiolite mixture and 1 : 0.075 weight ratio of the bentonite-sepiolite mixture and guargum, the hydraulic conductivity from the rigid wall permeameter was below $1.0{\times}10^{-7}$ cm/sec under simulated sea water condition. The hydraulic conductivity of the particle sealant having $1.0{\times}10^{-6}$~$1.0{\times}10^{-7}$ cm/sec by the rigid wall permeameter was estimated using the flexible wall permeameter and found to be below $1.0{\times}10^{-7}$ cm/sec.

• Journal of Soil and Groundwater Environment
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• v.20 no.1
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• pp.65-75
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• 2015

An artificial recharge test aimed at investigating transport characteristics of the injected water plume in a fractured rock aquifer was conducted. The test used an injection well for injecting tap water whose temperature and electrical conductivity were different from the groundwater. Temporal and depth-wise variation of temperature and electrical conductivity was monitored in both the injection well and a nearby observation well. A highly permeable fracture zone acting as the major pathway of groundwater flow was distinctively revealed in the monitoring data. A finite element subsurface flow and transport simulator (FEFLOW) was used to investigate sensitivity of the transport process to associated aquifer parameters. Simulated results showed that aperture thickness of the fracture and the hydraulic gradient of groundwater highly affected spatio-temporal variation of temperature and electrical conductivity of the injected water plume. The study suggests that artificial recharge of colder water in a fractured rock aquifer could create a thermal plume persistent over a long period of time depending on hydro-thermal properties of the aquifer as well as the amount of injected water.

• Water for future
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• v.27 no.3
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• pp.107-113
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• 1994

The analysis of Richards eq. requires data of the soil water retention function and the unsaturated hydraulic conductivity. The soil water retention function was measured through the use of the developed apparatus and the saturated hydraulic conductivity was measured by the constant head method for each soil sample corresponding to the A, B, C types of SCS. In order to obtain one water retention function and one unsaturated hydraulic conductivity which represent each soil group, van Genuchten's eq. and Mualem's pore-structure model was chosen respectively. Parameters of van Genuchten's eq. are estimated for each soil group using data obtained in the experiments, and estimated values give a basis to analyze the unsaturated flow in the non-measured region efficiently.

• Journal of Electrical Engineering and Technology
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• v.5 no.2
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• pp.329-336
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• 2010

The paper describes the electrical and optical properties of underwater discharges in highly inhomogeneous electric fields caused by 1.2/50 ${\mu}s$ impulse voltages as functions of the polarity and amplitude of the applied voltage, and various water conductivities. The electric fields are formed by a point-to-plane electrode system. The formation of air bubbles is associated with a thermal process of the water located at the tip of the needle electrode, and streamer coronas can be initiated in the air bubbles and propagated through the test gap with stepped leaders. The fastest streamer channel experiences the final jump across the test gap. The negative streamer channels not only have more branches but are also more widely spread out than the positive streamer channels. The propagation velocity of the positive streamer is much faster than that of the negative one and, in fact, both these velocities are independent of the water conductivity; in addition the time-lag to breakdown is insensitive to water conductivity. The higher the water conductivity the larger the pre-breakdown energy, therefore, the ionic currents do not contribute to the initiation and propagation of the underwater discharges in the test conditions considered.

• Journal of the Institute of Convergence Signal Processing
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• v.7 no.3
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• pp.143-148
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• 2006

There are need to manage the water quality to supply an safety to consumer through pipe and reservoir the drinking water that produced in a clean water reservoir. However, a management of water quality and monitoring in reservoir have never been performed. Recently, the government has enforced standards of water quality. However, we have a inferior technology of water quality as compared with one in USA, Japan, Germany, etc. In case of water quality inspection and analysis equipments, sensor technology is very important to improve the water quality inspection and to develop the analysis equipments. In this paper, we analyze a law and a regulation for management of drinking water quality, and propose the measurement standards of drinking water quality in pH, conductivity, residual chloride, turbidity and water temperature. Then, we analyze electrode sensors that interference within pH, conductivity, residual chloride in interference experiment.

• Journal of Korean Society on Water Environment
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• v.26 no.5
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• pp.768-774
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• 2010

This study was conducted to provide a technical solution to treat effectively perchlorate from inorganic wastewater of zinc smelting. Despite an inhibition dissolved inorganic substances in the wastewater discharged from zinc smelting has demonstrated with the activity of microbes, biological treatment technology could reduce perchlorate to a satisfactory level under such stressful conditions. It was found that either conductivity or $SO{_4}^{2-}$ concentration of the wastewater was able to be used as the adequate index and the values were $2,450{\mu}S/cm$ and 1,200 ppm respectively. When $SO{_4}^{2-}$ increased from 0 to 16,000 ppm (conductivity : $428{\rightarrow}24,800{\mu}S/cm$), perchlorate biodegradation rate was reduced due to 1/10 times from 0.0365 to 0.0033/h, however, most of perchlorate was removed under the condition of hydraulic retention time (HRT) at 0.5day and mixed liquor volatile suspended solid (MLVSS) at 2,000 ~ 3,000 ppm.

• Journal of Korea Water Resources Association
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• v.31 no.4
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• pp.363-373
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• 1998

In this study, random flow field in a nonstationary porous formation is characterized through cross covariances of the velocity with the log conductivity and the head. The hydraulic head and the velocity in saturated aquifers are found through stochastic analysis of a steady, two-dimensional flow field without recharge. Expression for these cross covariances are obtained in quasi-analytic forms all in terms of the parameters which characterize the nonstationary conductivity field and the average head gradient. The cross covariances with a Gaussian correlation function for the log conductivity are presented for two particular cases where the trend is either parallel or perpendicular to the mean head gradient and for separation distances along and across the mean flow direction. The results may be of particular importance in transport predictions and conditioning on field measurements when the log conductivity field is suspected to be nonstationary and also serve as a benchmark for testing nonstationary numerical codes. Keywords : cross covariance, nonstationary conductivity field, saturated aquifer, stochastic analysis.