• Journal of Hydrogen and New Energy
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• v.31 no.3
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• pp.314-321
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• 2020

In this work, a preliminary design of an inlet guide vane and runner for developing a 2.5 kW hydraulic turbine was conducted by using computational fluid dynamic analysis. Three-dimensional Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model were used to analyze the fluid flow in the hydraulic turbine. The hexahedral grid system was used to construct computational domain, and the grid dependency test was performed to obtain the optimal grid system. Velocity triangle diagram considering the flow angles of the inlet guide vane and runner was analyzed to obtain a basic geometry of the inlet guide vane and runner. Through modification of the preliminary design, the hydraulic performances of the turbine have improved under overall drop conditions. Especially, the efficiency and power of the turbine increased by 0.95% and 1.45%, respectively, compared to those of the reference model.

• Journal of Soil and Groundwater Environment
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• v.8 no.3
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• pp.1-7
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• 2003

A modified model was developed for solute transport in porous media that can consider the movement of an LNAPL above the water table. From the results of sensitivity analyses with and without considering LNAPL movement, there are some differences according to the hydraulic gradient, the quantity of oil leakage and dispersivity. The mean deviation between the model in this study and a conventional model without LNAPL movement increases as the hydraulic gradient decreases and the quantity of oil leakage increases. Variation of dispersivity has no influence on the magnitude of the mean deviation. However, the spatial distribution of the deviation between the two models is wider as dispersivity increases. Furthermore, groundwater is at high risk of contamination in the vertical direction in the case that transverse dispersion value is large. A conventional model underestimates the concentration of solute in an aquifer where the movement of an LNAPL cannot be negligible: Based on the study results, it is important to understand how fast the LNAPL moves on the water table for realistic prediction of solute transport in an aquifer with the movable LNAPL on the water table.

• Proceedings of the Korean Society for Cognitive Science Conference
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• 2002.05a
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• pp.125-130
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• 2002

우리의 언어생활을 비추어 볼 때 한자어 정보처리는 많은 연구가 이루어야 함에도 불구하고 고유어 언구에 비해 소흘해 다루어져 왔다. 본 연구는 단일 한자어를 구성하는 각 음절이 단어의 재인에 어떤 영향을 미치는지 점화과제를 통하여 알아보았다. 본 실험은 기존의 한자어 연구에 빈도특성과 고유어와 외래어의 글자특성까지 고려하여 종합적으로 살펴보았다. 먼저 실험1의 어휘판단관제에서는 고유어와 한자어의 양상이 비슷하며 외래어는 다른 처리를 하는 것으로 드러났다. 고유어와 한자어는 빈도에 따라 영향을 받지만 외래어는 빈도의 영향에 변함없이 일정하게 나타났다. 이런 결과는 한국인은 고유어와 한자어를 동일한 양상으로 처리하며 이런 이유는 외래어의 한국어와는 다른 음운규칙이나 음절규칙의 영향으로 해석할 수 있겠다. 실험 2에서는 한자어 형태소와 의미적으로 유사한 조건(강도-강력)과 철자적 유사 조건(강도-강변), 고유어 유사 조건(강도-강정)조건을 점화과제를 이용하여 어휘판단을 하게 하였다. 실험 결과 모든 조건이 통제조건에 비하여 빠르게 나왔다. 그리고 의미적 유사 조건이 촉진적 점화효과를 일으키고, 철자적 유사조건은 억제 효과를 일으켰으며 고유어는 특이하게도 판단시간이 빠르게 나와 한자어와는 다른 처리과정이 있음을 보여주고 있다. 이런 결과는 지연조건에서도 동일하게 일어나고 있다. 이런 결과는 한자어는 어휘접근 이후에도 실험의 과제 특성상 한자어 형태소는 단어 수준 아래 위치하기는 힘든 반면, 고유어는 단어 수준 아래에 존재한다고 할 수 있다. 결국 한자어와 고유어는 기본적으로 외래어와 다른 처리를 보이면 한자어와 고유어 내에서도 한자어는 단어접근 전에 의미접근의 단계를 거쳐야 하지만 고유어는 각 음절이 형태소가 아니기 때문에 바로 어휘에 접근하는 것이라고 할 수 있겠다.ulic geometry and sediment transport has been applied to: (1) gravel-bed transport measurements in a cobble-bed stream at Little Granite Creek, Wyoming; (2) sand and gravel transport by size fraction in the sharp meander bends of Fall River, Colorado; (3) changes in sand dune geometry and resistance to flow during major floods of the Rhine River in the Netherlands; (4) changes in hydraulic geometry of the Rio Grande downstream of Cochiti Dam, New Mexico; and (5) analysis of the influence of water temperature and the Coriolis force on flow velocity and sediment transport of the Lower Mississippi River in Louisiana. Recent developments also include two textbooks on "Erosion and Sedimentation" and "River Mechanics" by the author and state-of-the-art papers in the ASCE Journal of Hydraulic Engineering.rk on is diversified, the importance of skills are diversified in each field of jobs.

• Journal of the Korean GEO-environmental Society
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• v.15 no.4
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• pp.13-27
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• 2014

Catchments soil erosion, one of the most serious problems in the mountainous environment of the world, consists of a complex phenomenon involving the detachment of individual soil particles from the soil mass and their transport, storage and overland flow of rainfall, and infiltration. Sediment size distribution during erosion processes appear to depend on many factors such as rainfall characteristics, vegetation cover, hydraulic flow, soil properties and slope. This study involved laboratory flume experiments carried out under simulated rainfall in a 3.0 m long ${\times}$ 0.8 m wide ${\times}$ 0.7 m deep flume, set at $17^{\circ}$ slope. Five experimental cases, consisting of twelve experiments using three different sediments with two different rainfall conditions, are reported. The experiments consisted of detailed observations of particle size distribution of the out-flow sediment. Sediment water mixture out-flow hydrograph and sediment mass out-flow rate over time, moisture profiles at different points within the soil domain, and seepage outflow were also reported. Moisture profiles, seepage outflow, and movement of overland flow were clearly found to be controlled by water retention function and hydraulic function of the soil. The difference of grain size distribution of original soil bed and the out-flow sediment was found to be insignificant in the cases of uniform sediment used experiments. However, in the cases of non-uniform sediment used experiments the outflow sediment was found to be coarser than the original soil domain. The results indicated that the sediment transport mechanism is the combination of particle segregation, suspension/saltation and rolling along the travel distance.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.202-210
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• 2005

In this study, the fly ash was employed as a possible alternative to the bentonite for its high sorption capacity against cationic heavy metal. To consider the constituents of barrier possibly used, the specimens were mixed with different material contents (fly ash : weathered soil : bentonite), then sorption test was performed. Also the specimens were molded on the wet side of optimum moisture contents like mixing ratio of sorption test and their hydraulic conductivities were measured in flexible-wall permeameters. And to confirm the effect of dissolved cations, the hydraulic conductivity tests were repeated by converting the permeant liquids from water to $Cd^{2+}$ solution. Finally, the Cd-concentration at the effluent was analyzed for 500hrs to compare the effectiveness of each specimen in contaminant retardation. Test results showed that the more the ratio of fly ash increase, the more Kd value increase, and the hydraulic conductivity of weathered soil/bentonite (95:5) mixture was the lowest $(2.9*10^{-8}cm/sec)$, and specimens made of fly ash and fly ash/weathered soil mixtures showed similar hydraulic conductivity. Although the permeant liquid was changed from water to $Cd^{2+}$ solution, the hydraulic conductivity of all specimens except for weathered soil maintained similarly like before. Consequently, the initial breakthrough point of Cd in weathered soil specimen was observed at about 5hrs after the test started while that of fly ash specimens was not observed during the whole test period of 500hrs. The results implied that fly ash had a sufficient retardation capacity against contaminant transport possibly by its high sorption capacity although it showed little effect on the reduction of hydraulic conductivity. Based on the test results, it could be concluded that the fly ash can be possibly used as a suitable barrier material in containment system to attenuate the contaminant transport for its high retardation capacity and for the low cost.

• The KSFM Journal of Fluid Machinery
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• v.15 no.4
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• pp.19-26
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• 2012

In this paper, a parametric study on ribs which are installed in an equilateral triangular internal cooling channel is presented. The numerical analysis of the flow structure and heat transfer characteristics is performed using three-dimensional Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model. The numerical results are obtained at Reynolds number, 20,000. The parametric study is performed for the parameters, the angle of a rib, rib pitch-to-hydraulic diameter ratio, rib width-to-hydraulic diameter ratio, and rib height-to-hydraulic diameter ratio. The computational results are validated with the experimental data for area-averaged Nusselt number.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.237-238
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• 2005

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.410-411
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• 2005

• Nuclear Engineering and Technology
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• v.42 no.1
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• pp.9-16
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• 2010

Experimental examinations for evaluating fracutres were conducted by using transparent replicas of a single fracture in order to obtain the fracture data to contribute to the methodlogy on how to improve the definitaion of representative parameter values used for a parallel plate fracture model. Quantitative aperture distribution and quantitative tracer concentration data at each point in time were obtained by measuring the attenuation of transmitted light through the fracture in high spatial resolution. the representative aperture values evaluated from the multiple different measurement methods, such as arithmetic mean of aperture distribution measured by the optical method, transport aperture evaluated from the tracer test, and average aperture evaluated from the fracture void volume measurement converged to a unique value that indicates the accuracy of this experimental study. The aperture data was employed for verifying the numerical simulation under the assuption of Local Cubic Law and showed that the calculated flow rate through the fracture is 10%-100% larger than hydraulic test results. The quantitative tracer concentration data is also very valuable for validating existing numerical code for advection dispersion transport in-plane heterogeneous fractures.

• Journal of Radiation Industry
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• v.4 no.1
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• pp.79-83
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• 2010

The pollutants in subsurface soil are advected by groundwater flow and transported by the hydrodynamic dispersion. In this study, laboratory-scale experiments by using a radioisotope were conducted to evaluate the characteristics of the transport and dispersion of pollutants in the soil. The hydraulic model of the laboratory-scale was manufactured based upon its geometric similarity. Tc-99m having a short half-life was used with a tracer and it was injected instantaneously into the soil. Tc-99m milked from a $^{99}Mo/^{99m}Tc$ portable generator fabricated for medical purposes had 0.141 MeV of gamma radiation. The experiments are performed by the different conditions like the variations of groundwater velocity and the results are analyzed by the measured CPS of Tc-99m.