• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.173-176
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• 1999

The production of fine metal oxide particles in supercritical water has been studied. Cobalt nitrate solution and manganese nitrate solution have been selected as model solutions for metal salt aqueous solution and the particles of cobalt oxide and manganese oxide have been produced. It was observed that the production of fine metal oxide particles in supercritical water was feasible and the dehydration rate was remarkably high in supercritical water. In spite of a short residence time (3~100 seconds), fine particles ($0.5{\sim}2{\mu}m$) have been produced. In the supercritical water process, the temperature of mixer had a significant effect on particle size and size distribution. It was observed that a change in reaction temperature resulted in the control of particle size.

• Journal of Korean Society of Water and Wastewater
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• v.10 no.1
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• pp.121-130
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• 1996

Adsorption isotherms of three trihalomethanes(THMs: $CHCl_3$, $CHBrCl_2$ and $CHBr_2Cl$) and the other organics(p-chlorophenol and sucrose)on activated carbon fibers(ACFs) were measured. Adsorption capacities of the ACFs for these THMs were found to be comparable with or slightly larger than those of granular activated car bons(GACs) which have been widely used for trihalomethanes control in drinking water. Also, the breakthrough curve prediction was successfully carried out using a mathematical model on basis of the assumption that the adsorption equilibrium is instantaneously established when a THM solution contacts the ACF. In practice, THM removal from drinking water was investigated at water works using benchscale ACF adsorptJOn columns. The volume of water treated at a space velocity(SV) of about $100h^{-1}$ was approximately 40 l/g-ACF. The practical adsorption capacities of PCP and sucrose in column adsorption were in good agreement with those of theoretically calculated results using the batch adsorption measurments. And the saturation time model of these substrates in the columns was also agreed succesfully with practical measurments.

• Journal of Environmental Science International
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• v.25 no.7
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• pp.937-950
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• 2016

Algal blooming in 4 major rivers introduces substantial impacts to water front activity. Concentrations of algae are increasing at major points along the Geum River. Ecosystem food webs can be affected by algal blooming because blue-green algae release toxic materials. Even though there have been many studies on blue-green algae, its causality to environmental factors has not been completely determined yet. This study analyzed the exclusive correlation between various hydrometeorological, water quality, and hydrologic variables and the cell number of cyanobacteria to understand causality of blue-green algae in the Geum River. A prewhitening process was introduced to remove the autocorrelation structure and periodicity, which is useful to evaluate the effective relationship between two time series.

• Microbiology and Biotechnology Letters
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• v.47 no.4
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• pp.473-486
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• 2019

In the aquatic environment, microorganisms are predominantly organized as biofilms. Biofilms are formed by the aggregation of microbial cells and are surrounded by a matrix of extracellular polymeric substances (EPS) secreted by the microbial cells. Biofilms are attached to various surfaces, such as the living tissues, indwelling medical devices, and piping of the industrial potable water system. Biofilms formed from a single species has been extensively studied. However, there is an increased research focus on multispecies biofilms in recent years. It is important to assess the microbial mechanisms underlying the regulation of multispecies biofilm formation to determine the drinking water microbial composition. These mechanisms contribute to the predominance of the best-adapted species in an aquatic environment. This review focuses on the interactions in the multispecies biofilms, such as coaggregation, co-metabolism, cross-species protection, jamming of quorum sensing, lateral gene transfer, synergism, and antagonism. Further, this review explores the dynamics and the factors favoring biofilm formation and pathogen transmission within the drinking water distribution systems. The understanding of the physiology and biodiversity of microbial species in the biofilm may aid in the development of novel biofilm control and drinking water disinfection processes.

• Journal of the Korean Applied Science and Technology
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• v.29 no.3
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• pp.412-420
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• 2012

This study was carried out to investigate the antidiabetic effect of Lonicerae japonica Thunb(LJ) in the streptozotocin(STZ)-induced diabetic rats. The effective fractions were prepared as a form of organic solvents of hexane, chloroform, ethylacetate, butanol, water fractions prepared from the ethanol extract of LJ. The content of serum glucose and the activities of glucose-6-phosphatase(G-6-Pase) in the hexane and water fractions treated rats were significantly decreased compared to those of the STZ control group. Whereas the activity of hepatic glucose-6-phosphate dehydrogenase(G-6-PDH) was significantly increased in the hexane and water fractions treated rats. In conclusion, these results indicated that the hexane and water fractions of LJ were effective for the antidiabetes in the STZ-induced diabetic rats.

• Journal of ILASS-Korea
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• v.18 no.3
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• pp.126-131
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• 2013

This paper describes the effect of ultrasonic frequency(f) on the atomization and deformation characteristics of single water droplet in an acoustic levitation field. To achieve this, the ultrasonic levitator that can control sound pressure and velocity amplitude by changing frequency was installed, and visualization of single water droplet was conducted with high resolution ICCD and CCD camera. At the same time, atomization and deformation characteristics of single water droplet was studied in terms of normalized droplet diameter($d/d_0$), droplet diameter(d) variation and droplet volume(V) variation under different ultrasonic frequency(f) conditions. It was revealed that increase of ultrasonic frequency reduces the droplet diameter. Therefore, it is able to levitate with low sound pressure level. It also induces the wide oscillation range, large diameter and volume variation of water droplet. In conclusion, the increase of ultrasonic frequency(f) can enhance the atomization performance of single water droplet.

• Ocean Systems Engineering
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• v.4 no.1
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• pp.1-19
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• 2014

Hydrodynamic coefficients strongly affect the dynamic performance of autonomous underwater vehicles (AUVs). A novel kind of underwater vehicle (Heavier-than-water AUV) with higher density than water is presented, which is different from conventional ones. RANS method and overlapping grids are used to simulate the flow field around the vehicle. Lifts, drags and moments of different attack and drift angles in steady state are calculated. The hydrodynamic performances and how the forces change with the attitude are analyzed according to the flow field structure. The steady-state results using overlapping grid method are compared with those of software FLUENT and wind tunnel tests. The calculation results show that the overlapping grid method can well simulate the viscous flow field around the underwater vehicle. Overlapping grid skills have also been used to figure out the planar-motion-mechanism (PMM) problem of Heavier-than-water AUV and forecast its hydrodynamic performance, verifying its effectiveness in dealing with the dynamic problems, which would be quite helpful for design and control of Heavier-than-water AUV and other underwater vehicles.

• Journal of Forest and Environmental Science
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• v.30 no.1
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• pp.76-84
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• 2014

This study was performed to monitor the effects of water level change on changes of landscape, vegetation community, and species diversity of riparian forest. Hantan river dam, study area, has been constructed in the area of Chansoo-myeon, Pocheon-si and Yeoncheon-eup, Yeoncheon-gun, Gyeonggi-do, which is a dam for flood control only in flooding season. Landscape changes were notable after the construction of coffer dam, and the changes were caused by water level increase in areas of riparian forests which consisted of mainly withered willow as a dominant species in the flooding season. It changed vegetation communities of riparian forest from Phragmites japonica and Salix koreensis to Phragmites japonica. Species diversity index was lowest in 2010 when the coffer dam was constructed and showed an increasing trend later. Thus, this study is well in agreement with a previous report that plants of the genus Salix wither by muddy water during flooding and also suggests, controlling water level of river and prediction of water level change's effects should be considered when any facilities are planned.

• Journal of the East Asian Society of Dietary Life
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• v.16 no.3
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• pp.357-363
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• 2006

This study examined the effect of medicinal herbs on the growth of 3 strains of lactic starter cultures in a MRS broth by adding a 0, 1, 3, 5, and 10% water extract. The pH, titratable acidity and OD of lactic acid bacteria were investigated in order to obtain fundamental knowledge for the development a new product, box thorn yogurt. In the case of adding the Acanthopanax sessiliflorum Seeman water extract, Streptococcus thermophilus was largely activated by the addition of the 5% extract. The growth of Lactobacillus acidophilus was activated by the extracts but it was depressed by the addition of the 3% Acanthopanax sessiliflorum Seeman water extract. Compared with the control, the growth of Bifidobacterium longum was largely activated by the addition of the 10% extract but it was depressed by the addition of the 5% Acanthopanax sessiliflorum Seeman water extract.

• Journal of Korean Society on Water Environment
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• v.32 no.6
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• pp.582-588
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• 2016

The hydrological simulation program FORTRAN (HSPF) is a comprehensive watershed model that employs the hydraulic function table (FTABLE) (depth-area-volume-flow relationship) to represent the geometric and hydraulic properties of water bodies. The hydraulic representation of the HSPF model mainly depends on the accuracy of the FTABLES. These hydraulic representations determine the response time of water quality state variables and also control the scour, deposition, and transport of sediments in the water body. In general, FTABLES are automatically generated based on reach information such as mean depth, mean width, length, and slope along with a set of standard assumptions about the geometry and hydraulics of the channel, so these FTABLES are unable to accurately describe the geometry and hydraulic behavior of rivers and reservoirs. In order to compensate the weakness of HSPF for hydraulic modeling, we generated alternate method to improve the accuracy of FTABLES for rivers, using the surveyed cross sections and rating curves. The alternative method is based on the hydraulics simulated by HEC-RAS using the surveyed cross sections and rating curves, and it could significantly improve the accuracy of FTABLES. Although the alternate FTABLE greatly improved the hydraulic accuracy of the HSPF model, it had little effect on the hydrological simulation.