• 한국초전도ㆍ저온공학회논문지
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• 제22권2호
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• pp.1-6
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• 2020

Large-scale civil engineering works discharge a large amount of soil suspension contaminated with natural heavy metals. Most of the heavy metal ions due to industrial activities and minings are accumulated in the soils and the sediments of lakes and inner bays through the rivers. It is necessary to remove heavy metals from the soils and the sediments, because some of these heavy metals, such as arsenic and cadmium, have significant biological effects even in small amounts. This study proposes a new volume reduction method of the contaminated soils and sediments by superconducting magnetic separation. Our process can remove the specific minute minerals selectively, which adsorbs heavy metals depending on pH. As a fundamental study, the adsorption behaviors of arsenic and cadmium on minute minerals as a function of pH were investigated, and the adsorption mechanism was discussed based on the crystal structure and pH dependence of surface potential in each minute minerals.

• Ocean and Polar Research
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• 제27권1호
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• pp.45-58
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• 2005

Temperature, salinity, dissolved oxygen, COD, dissolved inorganic nitrogen(DIN), dissolved inorganic phosphorus (DIP), and chlorophyll were measured in the surface and bottom waters of Cheonsu Bay in April, August, December 2003, and Hay 2004. DIN showed a large seasonal variation, with higher values in summer and lower in spring. The significant decrease in DIN concentration was observed from April to May, which may imply the occurrence of spring phytoplankton bloom sometime in these periods. In contrast, DIP did not show distinct seasonal variation, with relatively low values compared with other coastal regions. The low DIP concentration in Cheonsu Bay is ascribed to a limited phosphorus input around Cheonsu Bay. The Nf ratios of Cheonsu Bay much higher than the Redfield ratio(16) in all season indicate that phytoplankton growth is limited by phosphorus. Based on low chlorophyll concentrations and eutrophication index, Cheonsu Bay has not been in eutrophic condition during our observation periods. In the artificial lakes located around Cheonsu Bay, however, chlorophyll concentrations were very high, mostly over $10{\mu}g\;l^{-1}$, indicating that they are now in severe eutrophic condition.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2002년도 추계학술대회 논문집
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• pp.163-170
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• 2002

Terrain surfaces have to be modeled in very detail and wheel-surface contacting geometry must be well defined in order to obtain proper ground-reaction and friction forces for realistic simulation of off-road vehicles. Delaunay triangulation is one of the most widely used methods in modeling 3-dimensional terrain surfaces, and T-search is a relevant algorithm for searching resulting triangular polygons. The T-search method searches polygons in successive order and may not allow real-time computation of off-road vehicle dynamics if the terrain is modeled with many polygons, depending on the computer performance used in the simulation. In order to accelerate the searching speed of T-search, a terrain database of triangular polygons is modeled in multi-levels by adopting the LOD (Level of Detail) method used in realtime computer graphics. Simulation results show that the new LOD search is effective in shortening the required computing time. The LOD search can be even further accelerated by introducing an NN (Neural Network) algorithm, in the cases where a appropriate range of moving paths can be predicted by cultual information of the simulated terrain, such as lakes, houses, etc.. Numerical tests show that LOD-NN search almost double the speed of the original T-search.

• 환경생물
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• 제22권1호
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• pp.184-191
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• 2004

To investigate bacteria with algalytic activities against Anabaena cylindrica when water blooming occurs and to study enzyme profiles associated with alga-lytic activity, various bacterial strains were isolated from surface waters and sediments in eutrophic lakes or reservoirs in Korea. Among 178 isolates, only nine isolates exhibited lytic abilities against A cylindrica on the agar plates, and then the isolate AK-13 was selected as the strongest in lysing the cyanobacterium A. cytindrica. The strain AK-13 was characterized and identified as Sinorhizobium sp. based on fatty acid methyl ether profiles and 16S rDNA sequence. According to the results of the enzyme assays, in the strain An-13 of Sinorhizobium sp., alginase, amylase, proteinase (caseinase and gelatinase), carboxymethyl-cellulase (CMCase), laminarinase, and lipase was produced, namely CMCase, laminarinase and protease were highly active. None of glycosidase was produced. Therefore, enzyme systems of Sinorhizobium sp. AK-13 were very complex to degrade cell walls of A. cylindrica. The peptidoglycans of A. cylindrica mat be hydrolyzed and metabolized to a range of easily utilizable monosaccharides or other low molecular weight organic substances by Sinorhizobium sp. AK-13.

• 한국해양학회지
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• 제25권3호
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• pp.145-150
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• 1990

용존 유기물 풀(pool)의 구성 성분과 그것들이 인 순환에 미치는 영향을 조사하기 위해 용존 유기인의 구성 성분과 용존 유기인에 대해 수집된 자료를 분석하였다. 용존 핵산은 대양수의 영양단계가 높아짐에 따라 그 중요성이 증가하는 것으로 보였 다. 흥미로운 것은 전체 5'뉴클레오티드와 용존 핵산의 합이 용존 유기인 풀을 우점하 는 것으로 보인다는 것이다. 따라서 용존 핵산의 광물화는 대양 표층수에서 용존 핵산 과 용존 유기인이 생성되는 기작으로서 미생물의 사망에 관련된 프로세스들이 중요하 며 특히 용존 핵산의 생성에 있어던 포식자에 의한 먹이의 불완전 소화가 중요한 기작 으로 사료된다.

• 한국물환경학회지
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• 제30권6호
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• pp.596-604
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• 2014

This research has studied the physicochemical environmental factors and communities of epilithic diatom and phytoplanktons at Hongcheon river from December 2011 to September 2012. In case of TN, the result was hypertrophic, and for TP, it ranged from mesotrophic to eutrophic. As for BOD, Hongcheon river was rated level II or better, according to the water quality level; values were found to be below 3mg/L at most sites. Total of 83 and 114 taxa of epilithic diatom and phytoplanktons respectively, were found during the research. When assessed using the TSI, it ranged from oligomesotrophic to eutrophic. In case of DAIpo, it ranged from 64.1 to 99.5, and TDI ranged from 51.5 to74.0. These results signify good water quality, level B or better, for Hongcheon river. P-IBI was rated moderate to low, which showed higher pollution than other indices. Among the biological water quality measures analyzed in the Hongcheon river study, DAIpo best matches TDI and BOD, while TDI showed greater pollution. Therefore, P-IBI appears to be inappropriate when assessing the domestic small rivers and lakes.

• 환경위생공학
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• 제7권2호
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• pp.37-52
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• 1992

Since the first sewage treatment plant was constructed in 1976, the sewerage systems of Korea have been rapidly expanded. As of the end of 1991, 22 sewage treatment plants with total capacity of 5.4 million tons/day are in operation which is equivalent of 3395 total daily sewage generation. Total extension of sewer 39.534 km in 1990 which is 55% of the target extension for the year 2001. However, the most sewage treatment plants employ activated sludge process which may not be suitable for medium and/or small scale plants. The poor existing sewer systems do not effectively collect and transport sewage to adversely affect the function of sewage treatment plant. To select the appropriate treatment system, the cities are classified into 3 categories such as large and medium size inland cities, small size cities and coastal cities. Considering the criteria suggested during this study, appropriate treatment processes were selected for each category. Conventional activated sludge process and step aeration process were found to be the most appropriate for big inland cities while biological nutrient removal processes should be considered for the cities discharge the effluent to lakes or reservoirs. RBC or Oxidation Ditch process might be appropriate for the medium size cities while several processes which do not require skilled operation and maintenance were suggested for the small cities. Ocean discharge after primary treatment can be considered for some east coast cities, Appropriate methodology to rehabilitate the existing sewers and strategy to convert combined sewer system to separate sewer system were proposed. This paper also include the appropriate management system for industrial wastewater, sludge and nightsoil.

• 환경위생공학
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• 제19권2호
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• pp.23-29
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• 2004

An algicidal effect of endemic algicidal bacterium (Pseudomonas putida) and rotifer zooplankton (Brachionus calyciflorus) on diatom Stephanodiscus hantzschii were examined in the filtered water, and were compared with those of bacterium plus ciliate. Bacteria removed as 80% of the diatom within 3.5 days, while ciliate and zooplankton suppressed 57% and 40% of diatom during the same period, respectively. Mixed treatment of bacteria plus ciliate removed as 54% of diatoms, while that of bacteria plus zooplankton decreased as 85%. Although single bacteria and mixed treatment of bacteria plus zooplankton quickly decreased the diatom in the initial of experiment, bacteria plus ciliate perfectly removed the diatom in culture flask within 5.5 days of the study. On the other hand, other single and mixed treatments did not clear the diatom during the same period, and over 10% of them still remain in culture flask. Predator biomass in the presence of algicidal bacteria showed the growth patterns; zooplankton gradually decreased, and ciliate sustained over 0.5 cells/ml. These results indicated that the addition of ciliate to the algicidal bacterium in controlling the diatom Stephanodiscus hantzschii is more effective than that of zooplankton. Therefore, this synergistic interaction relationship between the bacterium and ciliate play an important role in the bio-manipulation using bio-agents to control the diatomal bloom in freshwater lakes and streams.

• 산업기술연구
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• 제26권A호
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• pp.119-127
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• 2006

The purpose of this study is to present quantitatively the influence of variables that had the largest effect on the changes in suspended solids(SS), which would cause turbid water phenomenon, among water quality factors of the non-point pollution source, and then to develop a multiple regression equation of SS and predict the water quality of ungaged watersheds so as to provide basic data to establish efficient management plans for SS which flow in rivers and lakes. To identify the correlation of SS with the amount of rainfall and the state of land use, a simple correlation analysis and a simple regression analysis were conducted respectively. Finally, a multiple regression analysis was conducted to provide that SS were set as dependent variables while the amount of rainfall, paddy fields and dry fields were set as independent variables. As a result, the amount of rainfall had the most significant influence on changes in SS, followed by dry fields and paddy fields. In addition, the multiple regression equation was developed to predict SS in unmeasurable watersheds.

• 한국환경과학회지
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• 제4권5호
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• pp.75-75
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• 1995

In order to provide for the guidance on groundwater quality monitoring network design and also, to suggest the index to the solution of the contaminated groundwater remediation problems in the lake watershed, it is necessary to analyze the contaminant transport in the groundwater. The solute transport was analyzed in the lake watershed to investigate the behavior of the injected contaminant sources depend on the relationships between the point of contaminant sources and position of the lake. Three hypothetical groundwater flow systems, which is composed of a flow-through lake and two solute sources, were considered. The lakes located in the upper, middle, and lower portions of a watershed respectively. The transported contaminant was numerically simulated for five years by using MT3D contaminant transport model under the three-dimentional steady state conditions. From the above simulations, it can be concluded that the contaminant concentration was high as the contaminant source located at the upper position of a watershed, and the influence of the contaminant injection was large as the solute source located at the lower position. When the injection of contaminant was continued for one year without regard to the position of contaminant source and the lake, the influence of contaminant source was reached to bedrock.