• Journal of Korean Society of Environmental Engineers
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• v.36 no.9
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• pp.648-658
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• 2014

We examined the effects of pollutants into sub-basin on the water quality and loading based on data surveyed during January-December 2013 from 13 sites of 5 streams in the Jinwi watershed. We used the contour plot and Kruskal-Wallis rank sum test to analyze seasonal variation of water quality and loading and Pearson correlation analysis to assess the relationships between pollutants and loadings. The significantly higher seasonal variation were SS, TN and TOC as compared to other water quality constituents (P < 0.001). A significant interaction existed between the effects of human population and the effects of discharge of Sewage Treatment Plant (STP) on water quality and loading, especially for the spring and winter seasons. It is necessary to control discharge water of sewage and wastewater from industrial facilities and to make full use of the watershed management system such as TMDLs in operation since 2012 for improvement in stream water quality.

• Ocean and Polar Research
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• v.25 no.4
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• pp.459-468
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• 2003

Annual variation of water qualities in the Shihwa Lake were observed 18 times from June 1996 to October 2001. We studied at the station of the upper streams and near the water gate of lake. After the flow of the outer seawater through the water gate, the surface salinity in Shihwa Lake increased to the range of 25-30 psu in both stations after October 1998. Due to the declination of the salinity differences between the surface and the bottom water, the pycnocline in which had existed until 1997 has weakened, and made the water column mix vertically. This led to the improvement of anoxic/hypoxic environment at bottom waters after April 1998. However, despite the continuous flow of the outer seawater, the concentrations of chlorophyll-a at surface layer were varied from $2{\mu}g/l\;to\;60{\mu}g/l$, and these values indicated the eutrophication. The following organic matter load was greatly influencing the surface layer's COD concentration. During the rainy season, the salinity at the surface layer to the below 15 psu resulting in stratification between the surface and bottom layer. Organic matters that were provided from the surface layer to the bottom layer due to active primary production in the year exhausted dissolved oxygen at the bottom layer, and the bulks of organic matters at bottom gave rise to hypoxic or anoxic environment. It was observed that the enrichment of ammonia and phosphate were main factors to worsen the water quality of the Shihwa Lake. The results of examining the annual variations in Shiwha Lake through principal component analysis shown that water characteristics in the rainy season were similar with those before input of outer sea water.

• Journal of the Korean Ceramic Society
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• v.13 no.3
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• pp.37-42
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• 1976

Although the water mixed into the concrete plays the role of hydration and acquiring the necessary workability, the more portion of water acts to obtain the substantial workability rather than to complete the hydration. However, the excess amount of water causes the poor quality of concrete, therefore it is useful to add the minimum amount of water as required as to acquire the proper workability. There have been the considerable numbers of investigations in which the dispersion phenomena of strong eletrolytic high polymer compounds such as lignosulfate and some of surface activation agents were studied to utilize as the dispersion agent of concrete. In the present study, Na-lignate, dispersion properties of which has not been studied yet, were investigated with the purpose of utilizing as a dispersion agent of concrete. The microscopic observations showed a great improvement in the dispersion of cement particles, also the fluidity and compressive strength of concrete were remarkably increased with the addition of Na-lignate: The addition of Na-lignate by 0.02% showed the increase of 1.76 times and 1.27 times of slump value and flow value respectively, and the compressive strength was increased by 1.07 times.

• Journal of Forest and Environmental Science
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• v.29 no.2
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• pp.109-115
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• 2013

Fast-grown wood generally contains a high proportion of juvenile wood that results in inferior dimensional stability and durability against biological deteriorations. In the present research, the Acacia mangium wood from plantation forests in Vietnam was treated with high temperature in air. The effects of heat treatment on physical properties of Acacia mangium wood, including mass loss (ML), water absorption (WA), water-repellent effectiveness (WRE) and anti-swelling efficiency (ASE) were examined. The results showed that the dimensional stability and the water-repellent effectiveness are increased by about 15-46% and 8-18%, respectively. However, the mass and dimension of wood are decreased. The results also indicated that both treatment temperature and treatment duration significantly affect the wood properties of Acacia mangium. It is thus concluded that heat treatment demonstrates an interesting potential to improve the wood quality of Acacia mangium for solid timber products. This technology provides an environmentally safe method of protecting sustainable common woods to give a new generation of value-added biomaterials with increased stability without the use of toxic chemicals.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.6
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• pp.627-632
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• 2008

It is necessary to investigate methods for improvement by diagnosing sludge settling characteristics on inflow of slurry to thickener. The results of the settling tests are correlated to determine zone settling velocities at the various sludge solids concentrations. Conditioning of WTP residuals is generally done by either chemical or physical treatment. The settling test was conducted with 1m columns dosing polymer to WTP residuals at various solids concentration. The estimated results for dosing to WTP residuals for a sludge of 2,100 ~ 16,012 mg/L solids concentration were the zone settling velocities of 48.38 ~ 6.8 m/day, supernatant solid concentration of 3.2 ~ 19 mg/L and solid flux of $101.6{\sim}317.61kg/m^3{\cdot}day$. The values for non-polymer treatment were the zone settling velocities of 28.37 ~ 0.12 m/day, supernatent solid concentration of 8.5 ~ 108 mg/L and solid flux of $59.58{\sim}1.92kg/m^2{\cdot}day$. The limiting solid flux value by Yoshioka methods was $4.0kg\;TS/m^3{\cdot}day$ for Non-polymer and $228.0kg\;TS/m^3{\cdot}day$ for dosing polymer. These results are to indicate a possibility of improvement on the thickening characteristics and the quality of supernatant as increasing the settling velocities by dosing polymer to WTP residuals.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2369-2374
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• 2008

In the precision hot plate for wafer processing, the temperature uniformity of upper plate surface is one of the key factors affecting the quality of wafers. Precision hot plates require temperature variations less than ${\pm}1.5%$ during heating to $120^{\circ}C$. In this study, we have manufactured the flat plate heat pipe hot chuck of circle type(300mm) and investigated the operating characteristics of flat plate heat pipe hot chuck experimentally. Various liquids(aceton, FC-40, water) were used as the working fluid and charging ratio was changed($14{\sim}36\;vol.%$). Several cases were tested to improve temperature uniformity. Major working fluid to be investigated was water. Using water, various parameters such as charging ratio, wafer operation on-off time, different working fluids. In case of water, the temperature uniformity was ${\pm}1.5%$, response time of wafer were investigated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.3
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• pp.771-778
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• 2008

Effects of establishments of more sewer systems on water quality in Nam River, Deokchun River, and Jinyang Lake were analyzed for various scenarios using QUAL2E, WASP 7 water quality model. Three different scenarios were tested: 1) 20.8% of sewer diffusion rate which is same to the existing condition. 2) Expansion of sewer system to 65.2% which would emit less pollutants, BOD 2350.5 kg/d, TN 216.0 kg/d, TP 44.0kg/d. 3) Pollutants emission to maintain first grade water quality in Nam River, Jinyang Lake, BOD and TN in the case 2 were 7.69%, 2.10% lower than those in the case 1 in the Nam River. And in the Jinyang Lake, BOD, TN, and TP in the case 2 were 10.25%, 1.37%, 2.94% lower than those in the case 1. However the simulations showed that water quality could not hold down first grade water quality standard level with the establishments of more sewer systems. To satisfy the criteria in the Nam River and Jinyang Lake, BOD emission must be reduced 27.2%, 37.05% compared to those in the case 1.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.615-618
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• 2003

A prototype of 76 ha Shi-hwa constructed wetland was constructed for the first time in Korea to purify severely polluted stream water. Hydrology, vegetation(macrophyte) and water quality for Banwol and Donghwa wetland built in Shi-hwa tidal reclaimed area were monitored to evaluate the performance of the wetlands. The overall efficiency for the treatment of polluted stream water using the wetlands showed no significant improvement. The monthly average removal rates on SS, BOD, TN and TP for Banwol and Donghwa wetlands showed 66.5% and 62.8%, 14.8 and 34.3%, 33.9 and 47.1% and 20.8 and 51.6%, respectively. It is considered that three major factors, ie. wide fluctuations in inflow rate, short hydraulic retention time and small open area compared with vegetated area could have a great influence on low system efficiency.

• Ecology and Resilient Infrastructure
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• v.6 no.4
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• pp.208-216
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• 2019

This study investigated design factors and removal efficiencies of a sheet flow channel as natural type water improvement techniques in the stream. The channel was designed considering the design factors, then constructed and monitored in the test bed of the Osan stream's floodplain. Water lever, velocity, discharge, T-P, T-N, and NO₃-N were monitored and the removal efficiencies and design formula were suggested. Overall efficiencies of T-P, T-N, and NO₃-N range 10 - 20%, and they show consistent relations with residence times. Minimum velocity requirement is also suggested from the relation of algae conditions and velocities. Relation formula of residence time and removal efficiency will be applicable in the design and operation process of a sheet flow channel.

• Proceedings of KOSOMES biannual meeting
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• 2017.11a
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• pp.98-99
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• 2017

With special condition in the geography, maritime industry is improvement rapidly in the planet, which is covered by approximately $360,000,000km^2$ of Saline water. Together with the development of this field, freight transportation industry becomes one of the most important service in the world as well as in Hai Phong. Meanwhile the number of company and quality of service increased due to the demanding of citizen, the price for this activities also raised.