• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.8 s.227
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• pp.1190-1195
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• 2004

A novel manipulation of microfluid width in a microchannel was presented by controlling inflation of a gas boundary. The gas boundary was formed by heating water with a microheater in a semicircular shape from a chamber which was connected symmetrically to the microchannel. The formed gas boundary inflated perpendicularly to the flow direction and, consequently, the microfluid width was narrowed. The inflation and contraction were flexibly like a virtual wall and dependent on two factors: one is the flow velocity of the microfluid and the other is the pressure inside the gas boundary. Dimensions of the chamber and the microchannel width were determined empirically as same of $300\;{\mu}m$ for stable operation. The width of microfluid was manipulated manually with the microheater and could be maintained as up to $22\;{\mu}m$. The stable focusing began to be distorted when the flow velocity exceeded 17.8 mm/s.

• Journal of The Korean Society of Agricultural Engineers
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• v.66 no.3
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• pp.39-51
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• 2024

To effectively implement the integrated water management policy outlined in the National Water Management Act, it is essential to analyze agricultural water supply and demand at both basin and water district levels. Currently, agricultural water is primarily distributed through open canal systems and controlled by floodgates, yet the utilization-to-supply ratio remains at a mere 48%. In the case of agricultural water, when analyzing water balance through existing national basin water resource models (K-WEAP, K-MODISM), distortion of supply and regression occurs due to calculation of regression rate based on the concept of net water consumption. In addition, by simplifying the complex and diverse agricultural water supply system within the basin into a single virtual reservoir, it is difficult to analyze the surplus or shortage of agricultural water for each field within the basin. There are limitations in reflecting the characteristics and actual sites of rural water areas, such as inconsistencies with river and reservoir supply priority sites. This study focuses on the development of a model aimed at improving the deficiencies of current water balance analysis methods. The developed model aims to provide standardized water balance analysis nationwide, with initial application to the Anseo standard watershed. Utilizing data from 32 facilities within the standard watershed, the study conducted water balance analysis through watershed linkage, highlighting differences and improvements compared to existing methods.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.5
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• pp.1061-1071
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• 2015

In the present study, the Navier-Stokes (N-S) equations delineating water flows inside porous media were derived applying Reynolds transport theorem in order to provide a basis for analyzing water wave problems inside the porous media. Then, the derived N-S equations were compared with the same species of equations in existing researches. Based on the N-S equations, a set of Boussinesq equations was then derived in such a form that the dispersiveness and nonlinearity of water waves inside the porous media can be properly reproduced. Finally, numerical analyses were carried out to demonstrate the validity of the equations. The reflection and transmission coefficients of porous breakwaters were calculated and compared with the results of existing hydraulic experiments. The numerical results showed a rather sensitive dependency on the virtual mass coefficient of grains constituting the porous media. The selection of the coefficient with zero turned out to give nice agreements with numerical and experimental results.

• The Journal of the Korea Contents Association
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• v.16 no.3
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• pp.116-124
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• 2016

In this paper, we propose digital exhibition contents for the aquarium, especially 'Gyeongpo Lagoon Ecological Museum'. We try to plan appropriate media contents that can be mixed with the aquarium storytelling. The aquarium must have special spaces that are not related with an exhibition directly but are necessary for survival of fishes such as a water circulation room. We design the special spaces using media contents and let visitors feel that the whole aquarium is in the ocean. First of all, we investigate the aquarium currently under construction. And then, we propose the appreciate media platforms and plan individual content. We suggest 3 types of media platforms, 3D water projection, interactive games utilizing Kinect, and a fog screen. Moreover, we produce 2D drawing concepts, 3D modeling images, and virtual exhibitions in virtual reality for the representation of the location in which those platforms are installed and the media contents we plan. The pre-visualization is helpful for the media platform construction and is used as a rough sketch to producing an animation shown in the exhibition.

• Journal of the Korean Society of Safety
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• v.18 no.1
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• pp.19-27
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• 2003

This paper presented an experimental modal analysis of clamped perforated rectangular plates submerged in water. The penetration of holes in the plates had a triangular pattern with P/D (pitch to diameter) 1.750, 2.125, 2.500, 3.000 and 3.750. The natural frequencies of the perforated plates in air were obtained by the Rayleigh-Ritz method and compared with the experimental results. Good agreement was obtained between the analytical solution and experimental result. The experimental results in water showed that the mode shapes are not sensitive to the depth of submergence. The natural frequencies were shown to decrease drastically once the perforated plates come in contact with water. However, the natural frequencies decrease with the depth of submergence until a certain depth is reached, and become the asymptotic values beyond this depth of submergence. The depth of submergence did not affect the damping ratio greatly.

• Journal of Korean Society on Water Environment
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• v.28 no.5
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• pp.686-692
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• 2012

This study illustrates how to design and evaluate a non-point sources management detention pond using SWMM. In particular, special attention is given to the orifice design. In SWMM, orifice properties that need to be defined include its height above the bottom of the storage unit, its type, its geometry and its hydraulic properties. Among the various characteristics of orifice, the orifice hole size which is closely related to hydraulic retention time is focused in this study. Sensitivity analysis of orifice size in annual non-point sources reduction efficiency is carried out. In addition, a methodology which can be used to design a virtual junction in SWMM has been proposed to quantify water quality improvement triggered by the detention pond installation. As a result, it is recommended that a detention outlet should be designed to be about 2 to 3 days of hydraulic retention time.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.5
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• pp.705-712
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• 2012

Selecting Daechung Dam as a sample study site, this study simulates virtual water quality incident which can be occurred using EFDC maintained by USEPA. In order to predict the behavior and diffusion of leaked conservative pollutant within dam under the worst condition, the hydrological data and information from 2008 were used. EFDC was successfully calibrated for observed water level obtained from the above sources. From the results of simulations, even though the concentrations (500 ppm, 1,000 ppm and 10,000 ppm) of leaked pollutant were different with each other at the same sources, the travel time of each peak concentration appeared similar. Also, changing the leak source point from dam gate(0 km) to 7 km, it was found that as leak source point was nearer to the dam gate, the travel time of each peak concentration showed up sooner. It was simulated to take 1 day to 15 days for initial appearance of the leaked pollutant according to the leaked points, and 3 days to 25 days for the reach of the peak concentration, respectively.

• Journal of the Korean Solar Energy Society
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• v.29 no.2
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• pp.31-38
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• 2009

This study was conducted to forecast inner water temperature strata change by extracting deep water from a dam. For the methodology, the scope wherein the balance between the volume of low-temperature water intake through the virtual water intake opening as installed within the stored water area and the volume of water intake from the surrounding area is not destroyed was calculated through the CFD simulation technique using the computational fluid dynamics(CFD) interpretation method. This study suggested a supplementary method(diffuser) to avoid destroying the water temperature strata, and the effect was reviewed. In case of intake of the same volume, when the velocity of flow of water intake is reduced by increasing the pipe diameter, the destruction of water temperature strata can be minimized. When the area(height) where the intake of water is possible is low, a diffuser for interrupting the vertical direction inflow should be installed to secure favorable water intake conditions in case of water intake on the upper part. This study showed that there was no problem if the intake-enabled, low-temperature area was secured approximately 10m from the bottom when the scope that does not destroy the water temperature strata in case of water intake was forecast using the regression formula.

• Journal of Korea Water Resources Association
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• v.46 no.10
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• pp.969-976
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• 2013

Leakage in water distribution system causes social and economic losses by direct water loss into the ground, and additional energy demand for water supply. This research suggests a leak detection model of using adaptive Kalman filtering on real-time data of pipe flow. The proposed model takes into account hourly and daily variations of water demand. In addition, the model's prediction accuracy is improved by automatically calibrating the covariance of noise through innovation sequence. The adaptive Kalman filtering shows more accurate result than the existing Kalman method for virtual sine flow data. Then, the model is applied to data from two real district metered area in JE city. It is expected that the proposed model can be an effective tool for operating water supply system through detecting burst leakage and abnormal water usage.

• Journal of Digital Convergence
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• v.19 no.3
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• pp.437-444
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• 2021

The purpose of this study is to investigate the relationship between consciousness of marine safety, re-participation behavior of marine safety virtual reality experience education. For the study, participants in marine safety virtual reality experience education were surveyed from July to August 2020. Specifically, all participants were NakDanbo Water leisure center and Song-do Marine leisure center. A total of 300 participants were sampled using convenience sampling method, but 253 were finally used in the data analysis excepting incomplete or faithless questionnaires. the data analysis was conducted through frequency analysis, Cronbach's alpha, Exploratory Factor Analysis (EFA), correlation analysis, simple and Multiple regression analysis using SPSS 20.0. The results are as follows. Firstly, participants in marine safety virtual reality experience education positive impact on had a significant effect on consciousness of marine safety. Secondly, participants in marine safety virtual reality experience education positive impact on had a significant effect on re-participation behavior intention. Lastly, consciousness of marine safety had positive effects on re-participation behavior intention.