• Economic and Environmental Geology
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• v.27 no.1
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• pp.101-113
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• 1994

Geochemical investigations based on measurements of water parameters and sampling of stream sediments have been carried out, in the Okdongcheon stream and its tributaries in the Sangdong area of South Korea. There are two main problems occurring in the Okdongcheon stream: an acid mine drainage in the upper reaches and toxic trace metal contamination of the stream sediments mainly in the lower reaches. Acid mine water originating from coal mining was neutralized at the confluence of the Cheonpyongcheon stream whilst suspended solids due to flocculation of iron in water caused turbidity which was undesirable. Sediments in the Okdongcheon stream have been contaminated by mining activites. Iron was heavily concentrated in sediments in the upper Okdongcheon whilst toxic trace metals including Pb, Cu, Zn, Co, Cd, As and Bi were accumulated in sediments at stations draining metallic mining areas and near the tailings dam. There is now a requrement to neutralise the acid mine drainage and to use site-specific analysis of biological communities to ensure the conservation and preservation of aquatic organisms.

• Journal of the Society of Disaster Information
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• v.16 no.3
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• pp.550-557
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• 2020

Purpose: Greenhouse gases are one of the major causes of global warming, a global disaster. In this study, the priority that affects when calculating the GHG emissions in the road sector is accurately calculated based on the speed of individual vehicles from the existing section average speed. I have the purpose of finding a possible factor. Method: A comparative analysis is conducted between the conventional method of the general passage section, the rest area section, the entrance section, and the confluence section of the highway and the speed-based emission calculation method of individual vehicles. Result: As a result of analyzing a total of 6 sections of the Gyeongbu Expressway, it was found that the standard deviation of the speed and the congestion of the sections had a great influence. Conclusion: When comparing the existing GHG emission calculation method with the speed-based emission calculation method of individual vehicles, it is clear that the speed-based method of individual vehicles is more precise. However, since it is difficult to apply it all over the country, this study compares the existing method with the speed-based method of individual vehicles and presents factors that have a significant difference.

• The Journal of the Korea Contents Association
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• v.11 no.6
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• pp.486-494
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• 2011

River bed change due to various factors in watershed and/or river environment would one of the most important issues in river management. To judge whether the river bed was aggrading or degrading, normally we use the change in thalweg or average bed, calculated using the design flood of the river. The present study is to figure out the problems of the existing methods and to propose a new concept of average river bed using annual maximum flood. To evaluate the new method, it was applied to the Nakdong River. We use the river bed data surveyed in 1983, 1993, and 2005. The results showed that there were no significant river bed change during 1983 and 1993, while the river bed was degraded significantly during 1993 and 2005. In the latter period, the river had severe degradations, 2~3 m in average sense and 5 m for the maximum in the middle reach(120~200 km from river mouth), and 1~2 m in average in the upper reach(200~240 km from river mouth). For the upstream reach of the confluence of the Naesung River(about 240 km from river mouth), most of the river bed change seemed to be only local phenomena. The main cause of the river bed change in the Nakdong River seems to be massive gravel mining in the middle reach of the river.

• Journal of Chest Surgery
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• v.29 no.1
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• pp.7-13
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• 1996

The conventional glutaraldehyde (GA) fixation method of tissue valves is considered to be responsible for accelerated valve degeneration. The release of toxic GA from the valve tissue is believed to limit endothelial cell (EC) ingrowth. Removal of toxic GA by reaction with L-glutamic acid and storage in a Paraben solution may offer good EC growth. To investigate the conditions for endothelialization of tissue valves, the growth properties of ECs on the conventionally and alternatively treated pericardial tissue were compared. Conventional preparation included zero-pressure fixation for 72 hours in phosphated-buffered saline (PBS) solution containing 0.5% GA at 4$^{\circ}C$ and storage into PBS containing 0.2% GA(group I). Alternatively treated pericardial tissues were divided into three postfixation treatment groups : (1) storage in PBS solution containing Paraben(group II), (2) treatment with PBS containing 8$^{\circ}C$ L-glutamic acid(PH 7.35) and storage in PBS solution containing Paraben (g oup III), (3) treatment with L-glutamic acid dissolved in distilled water (PH 3.5) (group IV). Pericardial tissue were transferred into the 24-well plate after storage for 4 weeks. ECs were harvested enzymatically from the bovine pulmonary artery and grown to confluence on culture flask surfaces. Detached ECs by trypsin were incubated into the each well of the 24-well plate including test pericardial tissues. Cells were detached by trypsin, 1, 2, 3, 5, 7 days after incubation and counted on the hemacytometer. Cell viability test was performed by frypan-blue exclusion method. Acute cell death in the group I were found even after prolonged washing. The group II showed prolonged cell survival compared with the group I. Both group III and group IV showed better cell growth than group II. There was no statistically significant difference between group III and group IV method in terms of EC growth. This results suggest that treatment by L-glutamic ac id and storage in a Paraben solution be a promising approach for improvement of durability of GA-treated tissue valves.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.1
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• pp.1-8
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• 2010

To investigate the effects of sediments on the water quality of an estuary reservoir, Asan reservoir, we analyzed physical and chemical characteristics of the sediments and estimated nutrients release rate from the sediments. The sediments characterized as sandy loam are mainly composed of Nonapatite-P(64.7%) which has strong influence on the eutrophication of the reservoir by releasing from the sediments under the condition of increasing pH and anaerobic environment. High nutrient release rates was observed in April. Negative release rates in June show that there is no significant nutrient release from the sediments. The nutrient release was active at the Site B around the confluence of tributary compared to the Site A near the embankment. Based on the information of nutrient release rates and sediments surface area, daily average nutrient release rates of Asan reservoir are estimated; TN 6,609 kg/d, TP 3,877 kg/d. Since the amount of N and P released from the sediments corresponds to the 7.06% of N and 22.04% of P incoming from the watershed, it can be concluded that there is little influence of sediments on the water quality of Asan reservoir.

• Journal of Korea Water Resources Association
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• v.53 no.2
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• pp.141-154
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• 2020

The accidents of toxic chemical spill into rivers are increasing in recent years due to expansion of heavy industries in Korea. In order to respond to the chemical spills, accident response systems have been established for both main rivers and tributary rivers. However, since these accident response system adopted the water quality models imported from the foreign countries, it is difficult to acquire the model parameters and to calibrate and validate the water quality models. Therefore, this study developed a depth-averaged two-dimensional river water quality model to analyze the behavior of hazardous chemicals in rivers and proposed an efficient simulation execution framework by identifying the significant reaction mechanisms considering the characteristics of the toxic chemicals. The depth-averaged two-dimensional river water quality model CTM-2D was upgraded by adding reaction terms representing mechanisms of the adsorption, desorption, and volatilization of toxic chemicals. In order to verify the model, the analytical solution was compared with the numerical solution, and results showed that the error was less than 0.1%. In addition, the model was applied to a virtual scenario which is a water pollution accident at the confluence of the Nakdong River - Kumho River, and model results showed that an efficient simulation could be carried out by activating only significant reactions which were assessed by the sensitivity analysis.

• Journal of the Korean Geographical Society
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• v.51 no.1
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• pp.23-40
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• 2016

In this study, long-term changes in means and extreme events of precipitation during summer rainy period called Changma (late June~early September) are examined based on rainfall data observed by Chukwooki during Joseon Dynasty (1777~1907) and by modern rain-gauge onward (1908~2015) in Seoul, Korea. Also, characterizations of the relevant changes in synoptic climate fields in East Asia are made by the examination of the NCEP-NCAR reanalysis I data. Analyses of 239-year time series of precipitation data demonstrate that the total precipitation as well as their inter-annual variability during the entire Changma period (late June~early September) has increased in the late 20th century and onward. Notably, since the early 1990s the means and extreme events during the summer Changma period (late June~mid-July) and Changma break period (late July~early August) has significantly increased, resulting in less clear demarcations of sub-Changma periods. In this regard, comparisons of synoptic climate fields before and after the early 1990s reveal that in recent decades the subtropical high pressure has expanded in the warmer Pacific as the advection of high-latitude air masses toward East Asia was enhanced due to more active northerly wind vector around the high pressure departure core over Mongolia. Consequently, it is suggested that the enhancement of rising motions due to more active confluence of the two different air masses along the northwestern borders of the Pacific might lead to the increases of the means and extreme events of Changma precipitation in Seoul in recent decades.

• Journal of Periodontal and Implant Science
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• v.25 no.3
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• pp.694-702
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• 1995

Using the Korean red ginseng saponin, which is known to world-wide and thd effects of it have been investigated by many reserachers for years. Ginseng saponin, one of the major components of Korea ginseng root, has many various biologic effects, such as cytotoxic effect, tumorcidal activity, protein biosynthesis and membrane modifying effect. The purpose of this study was to evaluate effects of ginseng saponin on the alkaline phosphatase activity of ROS cells in culture. After ROS cells were seeded into a 96-well plate, 96-well plate cultured until confluence was obtained. To evaluate cytotoxic effect of total saponin in cultured ROS cells, the plates were added to each total saponin concentration (0-1mg/ml). After 48hr., cells were counted by stain with 0.2% trypan blue at randomly selected field microscopically. Also, to evaluate alkaline phosphatase(ALP) activity of total saponin in cultured ROS cell, the plate was added to each total saponin concentration (0-1mg/ml) and ALP activity was assayed. To evaluate time-course of ALP activity, $31.25{\mu}g/ml$ of saponin added to 96-well plate. After culture of 6, 12, 24 and 48hr., ALP activity test was performed. To evaluate effect of cycloheximide in ALP activity, 96-well plate was added to saponin and cycloheximide. In control group, the plate was added saponin only. The results were as follows. 1. After the various concentration of total saponin was added in the medium, 500 and $1000{\mu}g/ml$ of total saponin showed cytotoxic effect of ROS(P<0.005). 2. In contrast to control group, 7.6, 15.6, 31.25, 62.5 and $250{\mu}g/ml$ of total saponin increased ALP activity significantly. 3. Otherwise, 500 and $1000{\mu}g/ml$ of total saponin decreased ALP activity significantly(P<0.005). 4. As the time span increases, $31.25{\mu}g/ml$ of total saponin increased ALP activity. 5. Cycloheximide decreased saponin-indueced ALP actitity in ROS(P<0.005). These results suggest that Ginseng total saponin stimulates the ALP activity of rat osteoblastic cells.

• Journal of the korean academy of Pediatric Dentistry
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• v.44 no.3
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• pp.350-357
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• 2017

The purpose of this study was to evaluate the difference of differentiation potential in each passage of dental pulp stem cells from supernumerary tooth (sDPSCs). The sDPSCs were obtained from a healthy 6-year-old male patient under the guidelines and got the informed consent. Cells were cultured until passage number 16 and divided into two groups; 1 - 8 passages as a young group and 9 - 16 passages as an old group. It was taken $2.25{\pm}0.46days$ in a young group and $3.25{\pm}0.46days$ in an old group to propagate cells of each passage until confluence and there were statistically significant differences between two groups (p < 0.05). In every passage, cell morphology was observed with microscope and evaluated the capacity to form high levels of minerals by alizarin red solution staining after treating differentiation medium. Fibroblast-like, spindle shaped, elongated cells and a few nodules were found in uninduced cultures of passage number 1, 8 and 9. But at 16 passage culture, cell size became larger and broader and observed with more nodules. After inducing differentiation, mineralized nodules were detected at the first passage of 7th day culture whereas at the 8 passage culture, nodules were seen clearly at 14th day culture. In addition, the amount of mineralized nodules were remarkably decreased after passage 9. From the data presented in this study, it is recommended to use sDPSCs of passage number within 8 for utilizing as stem cells.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.450-457
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• 2019

Sedimentation is a common problem for river ports. But its intensity depends on the rate of sedimentation, channel shape and size, hydrodynamic behavior of the river and the importance of the port. High sedimentation rate in Yangon River has become one major issue for Myanmar as her largest port is located on the Yangon riverbank. As a result of the high sedimentation rate, shallow water area near the confluence of Yangon River, Pazundaung Creek, and Bago River keeps blocking the navigation channel to the Yangon Port, which also limits the size of vessel calling to Yangon Port. Therefore, studies to understand sediment transport process in Yangon River are required because the economic development of Myanmar highly relies on the Yangon Port. This paper aims to calculate the sediment transport and to predict the riverbed elevation changes in Yangon River by using Bagnold (1966) theory. Calculation result shows that huge difference can be found in the bed load transport between the rainy season and dry season in Yangon River, and thus the sedimentation problem would become more severe in the dry season when the transported sediments are reduced. The estimated sedimentation rate in dry season indicates that the rate of riverbed level rise near the Yangon Port area is about 0.063 m per year, which would lead to approximately 3.15 m rise in the riverbed level in next 50 yrs, considering the same workload of dredging to maintain the navigation channel.