• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.29 no.3
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• pp.151-156
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• 2003

This study was performed to develop a useful nerve conduit which provides favorable environment for Schwann cell viability and proliferation. Milipore membrane of $0.45{\mu}m$ pore size was selected because it permits nutritional inflow from the outside of the conduit and prevents from invading the fibrotic tissue into the conduit. The membrane was rolled and sealed to form a conduit of 2mm diameter and 20mm length. To improve the axonal regeneration and to render better environment for endogenous and exogenous Schwann cell behaviour, the microgeometry and surface of conduit was modified by coating with thin film of calcium phosphate. Cellular viability within the conduit and attachment to its wall were assessed with MTT assay and SEM study. Milipore filter conduit showed significantly higher rate of Schwann cell attachment and viability than the culture dish. However, the reverse was true in case of fibroblast. Coating with thin film of low crystalline calcium phosphate made more favorable environment for both cells with minimal change of pore size. These findings means the porous calcium phosphate coated milipore nerve conduit can provide much favorable environment for endogenous Schwann cell proliferation and exogenous ones, which are filled within the conduit for the more advanced strategy of peripheral nerve regeneration, with potential of reducing fibrotic tissue production.

• Journal of the Korea Organic Resources Recycling Association
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• v.22 no.3
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• pp.41-52
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• 2014

In this study, to estimate the biodegradability of sewage discharged intermittently, field scale sampling and analysis was conducted and the results were obtained as follows. According to results of the biodegradability of sewage discharged intermittently, average concentration of TCODcr is 325.5mg/L and ratio of TCOD fraction resulted 100%. Also, average concentration of SCODcr resulted 135.9mg/L and ratio of TCOD fraction resulted 41.8%. Average concentration of Ss showed 74.1mg/L and ratio of TCOD fraction resulted 22.8%. Average concentration of $S_I$ was analyzed to be 61.8mg/L and ratio of TCOD fraction was calculated to 19.0%. Xs which is particulate matter was analyzed to show 27.8mg/L and ratio of TCOD fraction also showed 8.5%. Average concentration of $X_H$ is 103.4mg/L and ratio of TCOD fraction resulted 31.8%. Inert particulate matter showed that average concentration of $X_I$ is 58.5mg/L and ratio of TCOD fraction resulted 18.0%. Accordingly, dissolved biodegradable organic matter showed the ratio of 41.8%, and readily biodegradable matter among this showed 22.8%. Thus intermittent inflow is expected to have less effect with regards equalization by organic loading rate of influent.

• Korean Journal of Environment and Ecology
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• v.20 no.2
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• pp.235-258
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• 2006

The monitoring of vegetation and water quality before(2003), during(2004) and after(2005) the restoration work of Cheonggye Stream indicated that $BOD_5$ concentration before the project averaged 51.1mg/L and that both the inflow of water from Hang River and the funnel of subway station water into the stream lowered the $BOD_5$ to 3.3mg/L, improving its water quality to the third grade. Species of plants slightly increased from 121 to 132 after the restoration. Specifically, perennial plant comprised 35.6%, an increase from 24.8% recorded before the restoration. Phragmites communis and Zoysia japonica communities were observed as the introduction vegetation. However, Humulus japonicus and Erigeron canadensis communities, which were classified into the first grade according to the vegetation conservation classification, were found to be still prevailing though they were dominant community before the restoration, meaning that the ecological condition of plants had not changed very significantly. An the other hand the water quality of the reference reach was classified into the first grade based on $BOD_5$, which implies the water quality of the section was better than the project reaches. Besides the section had more diverse plant species which numbered 154, and furthermore, the rate of immigrated plants comprised 13% which was lower than 28.8% recorded by the project sections. The project reaches are considered to be inferior to the reference section in terms of ecological condition. The effectiveness of the stream restoration cannot be determined only by such short-term investigation as was conducted in this study, and it is considered that the effectiveness of the restoration of Cheonggye Stream can be determined only if investigations in other major factors are conducted over the long-term period.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.2
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• pp.122-130
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• 2016

The past few decades of industrialization enabled human-centered stream developments, which in turn resulted in constructing straight or covered streams, which are used only for sewage disposal purpose. However, these types of streams have become the cause of flood damages such as localized heavy rain. In response, various construction methods have been implemented to prevent stream and embankment damages. However, regulations regarding these measures only lay out minimum standards such as the height of slopes and the minimum angle of inclination. Moreover, examination of tractive force, the most crucial factor in preventing flood damage, is nonexistent. Therefore, this study evaluates various tractive forces by implementing a porous concrete tetrapod at a full scale artificial stream for experiment, controlling the rate of inflow, and measuring the velocity and depth of the stream under different experiment conditions. The test results of the compressive strength, and porosity and density of rock of the porous concrete tetrapod was between 16.6 and 23.2 MPa, and the actual measurement of air void was 10.1%, thus satisfying domestic standard. The result of tractive force experiment showed a limiting tractive force of $47.202N/m^2$, not satisfying the tractive force scope of $67N/m^2$ the stream design working expertise proposes. However, there was neither damage nor loss of blocks and hardpan. Based on previous researches, it can be expected that there will be resistance against a stronger tractive force. Therefore, it is necessary to conduct another experiment on practical limiting tractive force by adjusting some experimental conditions.

• Journal of Korea Water Resources Association
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• v.53 no.8
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• pp.597-604
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• 2020

Muskingum, a hydrologic channel flood routing, is a method of predicting outflow by using the relationship between inflow, outflow, and storage. As many studies for Muskingum model were suggested, parameters were gradually increased and the calculation process was complicated by many parameters. To solve this problem, an optimization algorithm was applied to the parameter estimation of Muskingum model. This study applied the Advanced Nonlinear Muskingum Model considering continuous flow (ANLMM-L) to Wilson flood data and Sutculer flood data and compared results of the Linear Nonsingum Model incorporating Lateral flow (LMM-L), and Kinematic Wave Model (KWM). The Sum of Squares (SSQ) was used as an index for comparing simulated and observed results. Exponential Bandwidth Harmony Search with Centralized Global Search (EBHS-CGS) was applied to the parameter estimation of ANLMM-L. In Wilson flood data, ANLMM-L showed more accurate results than LMM-L. In the Sutculer flood data, ANLMM-L showed better results than KWM, but SSQ was larger than in the case of Wilson flood data because the flow rate of Sutculer flood data is large. EBHS-CGS could be appplied to be appplicable to various water resources engineering problems as well as Muskingum flood routing in this study.

• Economic and Environmental Geology
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• v.38 no.1
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• pp.67-78
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• 2005

Riverbank filtration has been used in advanced countries for 150 years. In Korea, investigations for producing riverbank filtrate started in the Han River, Nakdong River, Geum River, Yeongsan River and Seomjin River basins in the 1990s. The lower part of the Nakdong River has a poorer water quality than the upper part of the river. A water balance analysis and groundwater flow modeling were conducted for the riverbanks of the Nakdong River in Daesan-Myeon, Changwon City. The results of the water balance analysis revealed the groundwater infiltration rate into the aquifer to be 245.26 mm/year (19.68% of the average annual precipitation, 1,251.32 mm). Direct runoff accounts for 153.49 mm/year, evapotranspiration is 723.95 mm/year and baseflow is 127.63 mm/year. According to the groundwater flow modeling, 65% of the total inflow to the pumping wells originates from the Nakdong River, 13% originates from the aquifer in the rectilinear direction, and 22% originates from the aquifer in the parallel direction. The particle tracking model shows that a particle moving from the river toward the pumping wells travels 100 m in 50 days and a particle from the aquifer toward the pumping wells travels 100 m in 100 days.

• Korean Journal of Heritage: History & Science
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• v.45 no.3
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• pp.100-113
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• 2012

In the midst of recent active excavation, lots of Silla(新羅) roof-end tiles are unearthed in Yeongnam area(嶺南地域). These are confirmed the same tile frame as the Silla tiles excavated in Gyeongju(慶州). It is represented by the Silla tiles excavated in Ingaksa Temple(麟角寺) excavation research. Roof-end tile with arabesque design(唐草文平瓦當) etc. including roof-end tile with lotus design(蓮花文圓瓦當) are judged to be the tile frame produced by the same frame of roof-end tile that was excavated in Gyeongju, Wolseong(月城) and Hwangyongsa Temple(皇龍寺址). There are three kinds of cases concerning the transportation of tile manufacture ; the roof-end tile manufactured in Gyeongju directly moved to each region, only tile frame moved to site to be manufactured there, and tile manufacturer moved to site to manufacture there. This article considers the case of the roof-end tile manufactured in Gyeongju that was directly moved to each region. In case of the Silla tiles excavated in region especially Ingaksa Temple, the aspects of tiles in accordance with different era show the repeated coexistence, expansion and maintenance. This situation is significant as a clue to understand the supply from Gyeongju not as temporary, but as continuous. On the other hand, if the Gyeongju tiles flowed directly into each region, and if the road was built of gravels and the means of transportation was cart, the damage from movement must never be prevented. On the contrary, transportation through waterway might be advantageous due to the reduction of labor and damage rate and the easiness of loading. Accordingly, it tells us why the ruins where roof-end tiles were excavated located near big and small rivers or streams. Of course there are some ruins located in a fixed distance, but the distance may be enough to endure the impact put on tiles from the overland movement. Therefore, in case of direct inflow form long distance, transportation must be finished by overland movement after waterway movement.

• Journal of Korean Society on Water Environment
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• v.27 no.1
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• pp.19-29
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• 2011

In order to assess the influences of bottom sediment on water quality, following measurement were made. (1) Estimations of pollutant loads from the bottom sediment based on mass balance concept, (2) measurements of pollutant concentrations in the sediment to assess the pollution level and influence potential, (3) in situ and laboratory measurements of Sediment Oxygen Demants (SOD) and pollutant load (sediment release) from bottom sediment. Analyses of inflow and outflow loadings using simple mass balance show that there are some variations found according to the pollutants. However, there is no consistent evidence that the sediment can be a source of pollutants. Pollutant concentrations in the sediment range 16~724.8 mg/kg (COD), 1.68 ~12.64 mg/kg (T-P), 5.6~76.8 mg/kg (T-N), 0.32~21.6 mg/kg ($NH_3$-N), 0.092~0.544 mg/kg ($NO_2$-N), 4.8~18.4 mg/kg ($NO_3$-N), and 1.59~11.23 mg/kg ($PO_4$-P). Measured SOD ranges $0.190{\sim}0.802g{\cdot}m^{-2}{\cdot}d^{-1}$ and measured release rate ranges $-1618.42{\sim}10mg/m^2{\cdot}d$(COD), $-12{\sim}16mg/m^2{\cdot}d$(T-P), $-197.37{\sim}140mg/m^2{\cdot}d$(T-N), $0.4{\sim}74.32mg/m^2{\cdot}d$($NH_3$-N), $-2.04{\sim}0.8mg/m^2{\cdot}d$ ($NO_2$-N), $-70{\sim}40mg/m^2{\cdot}d$ ($NO_3$-N), and $-26.11{\sim}28.55mg/m^2{\cdot}d$($PO_4$-P). All study results indicate that bottom sediments in the Seoha weir show only limited effects on the water quality. It implies that sediment dredging is not an effective option or management measure to reduce pollutant loading.

• Journal of Korean Society of Disaster and Security
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• v.15 no.2
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• pp.37-44
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• 2022

As the frequency of torrential rains and typhoons increases due to climate change, the frequency of occurrence of debris flow is also increasing. In particular, in the case of Kangwon-do, the occurrence of damage caused by mountain disasters is increasing as it has a topographical characteristic where the mountains and the coast are in contact. In order to analyze the flow characteristics in the sedimentary part of the debris flow, input data were constructed through numerical maps and field data, and a two-dimensional model, FLO-2D, was simulated. The damaged area was divided into the inflow part of the debris flow, the village center, and the vicinity of the port, and the flow center and flow velocity of the debris flow were simulated and compared with field survey data. As a result, the maximum flow depth was found to be 2.4 m at the debris flow inlet, 2.7 m at the center of the village, and 1.4 m at the port adjacent to the port so the results were similar when compared to the field survey. And in the case of the maximum flow velocity, it was calculated as 3.6 m/s at the debris flow inlet, 4.9 m/s in the center of the village and 1.2 m/s in the vicinity of the port, so It was confirmed that the maximum flow center occurred in the section where the maximum flow rate appeared.

• Korean Journal of Environmental Biology
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• v.40 no.1
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• pp.54-69
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• 2022

We conducted a field survey from 2018 to 2020 to analyze the spatial distribution of phytoplankton communities at 13 stations in the East Sea. The diatom Chaetoceros curvisetus appeared as the dominant species in winter, and small flagellates less than 20 ㎛ prevailed in all seasons except winter. The seasonal average range of the micro (>20 ㎛), nano (20 ㎛≥Chl-a>3 ㎛), and picophytoplankton (≤3 ㎛) was 20.6-26.2%, 27.1-35.9%, and 40.8-49.0%, respectively. The composition ratio of nano and picophytoplankton was high at the surface mixed layer from spring to autumn when the water columns were strongly stratified. Especially, the stability of the water mass was increased when the summer surface water temperature was higher than that of the previous year. As a result, the nutrient inflow from the lower layer to the surface was reduced as the ocean stratification layer was strengthened. Therefore, the composition ratio of nano and picophytoplankton was the highest at 77.9% at the surface mixed layer. In conclusion, the structure of the phytoplankton community in the East Sea has been miniaturized, which is expected to form a complex microbial food web structure and lower the carbon transfer rate to the upper consumer stage.