• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.6
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• pp.1001-1008
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• 2017

This study was to evaluate the stream depletion rate from groundwater pumping with varying stream-well distance, aquifer transmissivity, storage coefficient, leakage coefficient, streambed hydraulic conductance using the Zlotnik and Tartakovsky analytical solution which considers a two-layer leaky aquifer-stream-well system. For the hydraulic conditions applied in this study, the streambed hydraulic conductance and the aquitard leakage coefficient were assessed to have a dominant influence on the stream depletion rate. In order to evaluate the applicability of Zlotnik and Tartakovsky analytical solution ignoring the change in the drawdown in the lower aquifer and applying the fixed head boundary condition, the solution was compared with Hunt analytical solution derived from the more practical conditions simultaneously taking into account the drawdown changes in the upper and lower aquifers. As a result, the Zlotnik and Tartakovsky analytical solution is suitable for predicting short-term effects of less than one year in the pumping period, and when the stream depletion factor (SDF) is greater than 2,500 days, or when the product of the leakage coefficient and the stream-well distance is less than 10 cm/s.

• Pediatric Infection and Vaccine
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• v.19 no.3
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• pp.141-148
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• 2012

Purpose : Ventriculoperitoneal (VP) shunt insertion is an important treatment modality in children with hydrocephalus. VP shunt infection is a major complication and an important factor that determines the surgery outcome. This 15-year study was performed to evaluate the epidemiology of VP shunt infections in pediatric patients treated at our center. Methods : A retrospective review of medical records was performed in patients 18 years old or younger who underwent VP shunt insertion surgery from April 1995 to June 2010. Results : Three hundred twenty-seven VP shunt surgeries were performed in a total of 190 pediatric patients (83 females, 107 males). The median age of the patients was 2.4 years (range, 0.02-17.9 years). Having a malignant brain tumor was the most frequent cause for VP shunt insertion. The shunt infection rate was 6.7% (22/327) per 100 operations and 9.5% (18/190) per 100 patients, and the incidence rate was 0.45 infection cases per 100 shunt operations-year. The most common pathogen was coagulase-negative staphylococcus (n=7) followed by methicillin resistant Staphylococcus aureus (n=1). Ten cases were treated with vancomycin and beta-lactam antibiotic (cephalosporin or carbapenem) combination therapy and 7 cases were treated with vancomycin monotherapy. The median duration of antibiotic treatment was 26 days (range, 7 to 58 days). Surgical intervention was performed in 18 cases (18/22, 81.8%). Conclusion : Epidemiologic information regarding VP shunt infections in pediatric patients is valuable that will help guide proper antibiotic management. Additional studies on the risk factors for developing VP shunt infections are also warranted.

• Journal of Soil and Groundwater Environment
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• v.12 no.2
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• pp.1-8
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• 2007

A series of batch and column experiments were conducted for the development of biobarrier technology which can be applied to containment and reduction of contaminants in soil and ground waters. The growth kinetic constants of Pseudomonas fluorescens on glucose or molasses were determined using batch experiments. The maximum specific growth rate (Vmax) of P. fluorescens at $23^{\circ}C$ on glucose or molasses were $0.246\;hr^{-1}$ and $0.073\;hr^{-1}$, respectively. However, molasses was selected as carbon source due largely to the absence of lag phase of P. fluorescens growth on molasses and economic reason. In constant head column experiments, the hydraulic conductivity of the column soil reduced by $6.8{\times}10^{-3}$ times from $4.1{\times}10^{-2}cm/sec$ to $2.8{\times}10^{-4}cm/sec$ after the inoculation of P. fluorescens and administration of carbon source and nutrients. The biomass concentration was observed highest in the column inlet. Measurements of carbon source and electron accepter (dissolved oxygen) concentration showed that the growth of P. fluorescence, which is the main reason for hydraulic conductivity reduction, was limited not by the concentration of carbon source but by the concentration of electron acceptor.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.3
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• pp.91-100
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• 1988

Assuming that tidal level is constantly changed with an amplitude of 10 meters and a cycle of 12 hours, the slope stability for a typical dyke is analysed. The variation of pore water pressure within the dyke during the tidal change is obtained using a computer program, FLUMP, which is incorporated with saturated-unsaturated and transient flow. The results show that the variation of free water surface and distribution of pore water pressure within the dyke during the tidal fluctuations can be clearly predicted with the computer program. When a tide is lowered to the minimum level, the predicted pressure head is higher than the level of the free water surface in some parts of the dyke; that is, excess pore water pressure is generated in a zone affected by the tidal change. Also an unsaturated zone which shows negative pore water pressure is temporally created when a tide is lowered. The shear strength of the zone can be predicted based on the proposal suggested by Fredlund et al. It is emphasized that the excess pore water pressure generated during tidal fluctuations and strength parameters for the unsaturated zone should be considered in analyzing the slope stability of dykes. When those are considered, the critical slip surface seems to be located below the free water surface obtained when a tide is at the lowest.

• The Journal of Engineering Geology
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• v.25 no.3
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• pp.413-420
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• 2015

Streambed hydraulic conductivity along the upper reaches of the Gongdo stage of Anseong Stream was estimated through measurements of stream-aquifer exchange rates (using a seepage meter) and vertical hydraulic gradients (using a manually driven piezometer). From the measured data, it was found out that the stream-aquifer exchange rates varied from -1.55 × 10^-6 to 1.77 × 10^-5 m/s, the corresponding vertical hydraulic gradient varied from -0.122 to 0.030, and the values of the streambed vertical hydraulic conductivity were estimated from 1.77 × 10^-5 to 1.97 × 10^-3 m/s, with variations representing local differences. The results are within the general range of streambed hydraulic conductivity values suggested by Calver (2001) and are slightly higher than values previously measured at other stream sites in Korea. The combined use of a drive-point piezometer and seepage meter (both constructed of high-strength stainless steel) is expected to be of practical use in the estimation of streambed hydraulic conductance, given the durability and portability of the instruments.

• Journal of Korea Water Resources Association
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• v.47 no.11
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• pp.1007-1015
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• 2014

This study investigates the discharge coefficient of Improved-Pneumatic-Movable (IPM) weir through the weir, a kind of movable weirs, to estimate much more accurate rating curves using laboratory flume experiments. The discharge coefficient ($C_d$) is from 0.613 to 0.634 by the stand-up angle of the weir. The upstream Froude Number ($F_{r1}$), relative crest length(${\xi}$), Headwater Ratio ($H_1/W$), the Overflow depth ratio of weir crest ($y_c/y_1$) was changed by the upstream. And the downstream Froude number ($F_{r2}$), the Overflow depth ratio of weir crest and Downstream Water depth ($y_c/y_2$) was changed by the downstream. The ratio of Downstream and Up and Downstream water Depth (${\Delta}y/y_2$) was found to be changed by both of the up and downstream flow. They considered the major influence variables and derived the Discharge coefficient Formula at this study. The Discharge coefficient of the Improved-Pneumatic-Movable (IPM) weir was settled by the height of the Movable weir, that is to say, it was settled by the flow conditions of upstream approach flow head and physical data according to the standing angle.

• Journal of the Korean Geotechnical Society
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• v.24 no.8
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• pp.5-12
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• 2008

Biot proposed the frequency dependent formulation for the propagation of elastic waves in saturated media based on the coupled theory mixtures. Based on Biot theory, a special frequency called 'the characteristic frequency' contains unique information of the permeability of soils. The characteristic frequency is measured from I/Q (inverse quality factor) versus frequency curve by an acoustic sweep test, and the permeability of soils is computed from Biot equation. In this paper, laboratory tests are performed at The University of Mississippi using a large test box. The measured characteristic frequency is consistently obtained at 3500 Hz for mortar sands. The computed permeability of mortar sands based on Biot equation turned out 2.01 $10^{-4}m/sec$, while the permeability from the laboratory constant head test turned out 1.49 $10^{-4}m/sec$. This paper addresses the theoretical background and experimental procedure of this technique.