• Journal of the Korean GEO-environmental Society
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• v.14 no.8
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• pp.11-21
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• 2013

In-situ test to find the change of $Fe^{2+}$ and $Mn^{2+}$ concentrations and ion contents in groundwater was conducted during two pumping tests at the riverbank filtration site, where is the riverine area of the Nakdong River in Changnyeong-Gun. Groundwater was sampled at one pumping well and 10 monitoring wells during a 5 steps drawdown pumping test with the rates from $500m^3/day$ to $900m^3/day$ and a constant pumping test with $800m^3/day$. The change in ion concentration of groundwater was more remarkable during a step drawdown pumping test than a constant pumping test. Especially, the decrease in $Fe^{2+}$ and $Mn^{2+}$ concentrations was distinct in a step drawdown pumping test and it happens predominantly along the direction that the radius of pumping influence was small due to a good aquifer connectivity to a pumping position. The precipitation and the oxidation of iron and manganese were caused by an air inflow and a disturbance in groundwater flow due to an abrupt change in pumping rate. The pumping rate and spatial distribution of an aquifer around a pumping well need to be considered as an important factor for the development of in-situ iron and manganese treatment technology.

• Journal of Korea Water Resources Association
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• v.45 no.12
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• pp.1243-1258
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• 2012

The objective of this study is to develop the relational formula to estimate the streamflow depletion due to groundwater pumping near stream, which has been statistically derived by using the simulated data. The integrated surface water and groundwater model, SWAT-MODFLOW was applied to the Sinduncheon and Juksancheon watersheds to obtain the streamflow depletion data under various pumping conditions. Through the multiple regression analyses for the simulated streamflow depletion data, the relational formula between the streamflow depletion rate and various factors such as pumping rate, distance between well and stream, hydraulic properties in/near stream, amount of rainfall was obtained. The derived relational formula is easy to apply for assessing the effects of groundwater pumping on near stream, and is expected to be a tool for estimate the streamflow contribution to the pumped water.

• Journal of Soil and Groundwater Environment
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• v.19 no.3
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• pp.66-81
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• 2014

A Fortran program was developed to determine the optimal locations of an artificial recharge well. Three objective functions were considered: (1) maximizing the recovery rates, (2) maximizing the injection rates, and (3) minimizing the coefficient of variation of the increased pumping rates. We also suggested a new aggregate objective function which combined the first and the third objective functions. The model results showed that locating the injection well inside the cluster of pumping wells was desirable if either the recovery or the injection rate was taken into account. However, the injection well located outside the cluster evenly increased the pumping rates in existing pumping wells. Therefore, for clustered pumping wells, installing an injection well at the center or the upstream of the pumping wells seems beneficial. For linear arrangement of pumping wells parallel to the constant head boundary, locating the injection well in the upstream was recommended. On the contrary, in case of the linear arrangement perpendicular to the constant head boundary, the injection well installed on both sides of the central part of the pumping wells was preferable.

• Journal of the Korean Vacuum Society
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• v.8 no.4B
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• pp.548-555
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• 1999

The NBI (Neutral BGeam Injection) System for the Korea Superconducting Tokamak Advanced Research (KSTAR) is composed of ion sources, neutralizers, bending magnets, ion dumps, and calorimeter. The vacuum chamber, in which all of the beam line components are enclosed, is composed of differential pumping system for the effective transfer of the neutral beams. The needed pumping speeds of each of the divided vacuum chamber and the optimized gas flow rate ot the neutralizer were calculated with the help of the particle balance equations. The minimum gas flow rate to the ion sources for producing needed beam current (120kV, 65A, 78MW), the pressure distributions in the vacuum chamber for minimizing re-ionization loss, and the beam loss rate on the beam line components were used as the input in the calculation. Also the scenario for short pulse operation was determined by analysing the time dependent equations. It showed that beam extraction during less than 0.5 sec could be made only with TMP.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2374-2376
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• 2005

본 연구에서 제안한 microfluidic system은 열공압 방식으로 구동되고 indium tin oxide (ITO) 및 polydimethylsiloxane(PDMS)로 제작하여 공정이 간단하고 비용이 저렴하여 일회용으로 사용이 가능하며 투명한 장점을 갖는다. 또한 마이크로 펌프는 인-채널 구조의 마이크로 밸브와 동일한 공정으로 제작하였다. 제안된 마이크로 펌프는 인-채널 구조의 마이크로 밸브와 같은 기판 위에 쉽게 집적하여 제작할 수 있다. 마이크로 펌프의 pumping rate는 인가 펄스 전압의 주파수와 duty비를 변화시켜 최적화하였다. Duty 비가 1%이고 주파수가 2 Hz일 때 최대 pumping rate를 보였으며 이때 pumping rate는 26.18nl/min이였다. 마이크로 밸브는 ITO 히터에 전력을 인가함으로서 유량의 on/off 제어가 잘 됨을 확인할 수 있었고 유체를 closing하기 위해 필요한 전력은 100mW이다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.4
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• pp.617-625
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• 2016

The objective of this study was to evaluate the groundwater drawdown and streamflow depletion due to each groundwater pumping from 110 wells located near stream using the Hunt's analytical solution (1999). The calculated results revealed that the streamflow depletion rate divided by the pumping rate for each well location mostly exceeded about 80% of pumping rate on average for 5 years. The results also showed that the stream boundary condition has made the influence distance shorter and the drawdown distribution skewed except for the streambed hydraulic conductivity and the stream bed factor (SBF) lower than $1.0{\times}10^{-9}m/s$ and 1.0, respectively. It was found that the groundwater pumping has significant impacts on the stream depletion showing above 80 % of stream depletion rate when the streambed hydraulic conductivity is higher than $1.0{\times}10^{-7}m/s$ and the stream depletion factor(SDF) is lower than 100. However, for other conditions, the SDF is not sufficient to be used as a criterion for determining whether the pumping has great impacts on stream depletion or not. Furthermore, the variation of the streambed hydraulic conductance has little change in stream depletion rate for the condition that the stream width is greater than 400 m.

• The Journal of Engineering Geology
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• v.22 no.2
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• pp.195-205
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• 2012

We evaluated the results of pumping tests, the amount of groundwater used by Protected Cultivation with Water Curtain (PCWC), and monthly depth to water table (DTW) at the Wangjeon-ri area, Nonsan City, to elucidate the cause of a decrease in pumping rate during the winter PCWC season. The transmissivity and storage coefficient at eight sites where the major aquifer is alluvium, vary from 119.9 to $388.1m^2/d$ and $1.5{\times}10^{-4}$ to $5.5{\times}10^{-4}$, respectively. The pumping rate for PCWC during three months (Dec. to Feb.) averaged about $8,100m^3/d$ and the maximum water level in the area varied by about 10 m. Groundwater levels had fully recovered by August-five months after pumping for PCWC had ceased. These observations indicate that the pumping rate during the winter PCWC season was excessive compared with groundwater productivity in the area. Groundwater level in the central PCWC area varied from -3.0 to 4.38 m, exceeding the water level of the Nosung Stream for only three months (Aug. to Oct.). This result indicates that Nosung Stream recharges the area during the period from November to July. To solve the problem of reduced pumping rate during the winter PCWC season, it would be necessary to reduce the amount of groundwater used for PCWC or to develop an artificial recharge system using recycled groundwater.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.111-120
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• 1999

Leachate flow behavior due to intermediate cover soil of low hydraulic conductivity and the applicability of pumping method for reducing the leachate level in the landfill are analyzed with the numerical flow model, MODFLOW. Using the hydraulic conductivity and storativity data obtained from the field pumping and slug tests(Jang and Cho, 1999), the hydraulic condition within the landfill is validated. The optimum rate of pumping, the radius of influence, and the efficiency of horizontal drain are analyzed for reducing the leachate level in the landfill. From the results of the analyses, the barrier effect that the buried cover soil of low hydraulic conductivity prevents the vertical movement of leachate flow through the cover soil, which is found from the in-situ geotechnical studies(Jang and Cho, 1999), is identified again. Also, the installation of horizontal drains to the pumping well can increase the pumping rate from 120 ton/day per a well to 300 ton/day. The length of horizontal drain did not influence significantly on the drawdown-time curve of leachate in the landfill.

• Current Optics and Photonics
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• v.5 no.2
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• pp.180-185
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• 2021

A femtosecond-laser inscribed Yb:YAG surface channel waveguide (WG) laser with single-walled carbon nanotubes deposited on the top surface of the WG was passively Q-switched by evanescent field interaction. Q-switched operation of the 14-mm-long compact Yb:YAG WG laser was achieved near 1031 nm with two different pumping schemes (single- and double-pass pumping) with an output coupling transmission of 91%. The Q-switched pulse characteristics depending on the absorbed pump power were investigated for both pumping geometries and analyzed in detail based on theoretical modeling. The best performances (energy/pulse duration) for each configuration were 204.4 nJ/75 ns at a repetition rate of 1.87 MHz, and 201.1 nJ/81 ns at 1.75 MHz for single- and double-pass pumping, respectively.

• Journal of the Korean Vacuum Society
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• v.10 no.1
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• pp.1-9
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• 2001

Pumping characteristics of a turbomolecular pump are influenced by interrelations of the down-stream and upstream pumping speeds (transmission probabilityxaperture conductance), and of gas flow rates (pumping speedxentrance pressure) in two directions. The pumping speed, one of the most important items characterized the performance of a pump, is given by dividing the net flow rate, that is, the difference between the counter flow rates by the pressure at the pumping port. The maximum compression ratio is defined as the ratio of the downstream pumping speed to the upstream one. Because these directional characteristics affect each other and are functions of the pressures of both sides, it is difficult to distinguish the relevant factors. However, quasi-quantitative analyses on them can be done if considering carefully the results of measuring the pumping speed and the maximum compression ratio.