• Journal of Wetlands Research
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• v.18 no.4
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• pp.424-431
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• 2016

LID facilities like bio-retention cells is applied to manage stormwater. LID concept becomes an important part in stormwater management, and the clear understanding of hydrologic performance and hydrologic impact on the corresponding catchment has been needed. In this study, the application of flow duration curves as design strategy is investigated. Bio-retention cells like many LID facilities are installed to reproduce natural hydrologic processes. In this study, the attempt to determine the size of a bio-retention cell is carried out to satisfy the flow duration criteria. From the results, it is shown that "5 mm * the area of a target catchment" which is the current facility design capacity is valid for the drainage area with 20-30% impervious rate. In the 100% impervious catchment where LID facilities are typically installed, the design capacity to intercept stormwater of approximately 47 mm depth is required to reproduce natural flow duration curves. This means that about 11% of the target catchment area should be allocated as a bio-retention cell. However, the criteria of the design capacity and facility surface area should be set at the possible implementation conditions in reality, and site-specific hydrologic characteristics of a target catchment should be considered.

• Journal of Environmental Impact Assessment
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• v.19 no.1
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• pp.49-57
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• 2010

The objective of the research is to analyze changing trend of water discharge in precipitation, according to changing land use, through an environment-friendly urban development method called LID. The study chose S1 basin (Separated Sewer districts) in Cheongju region for survey. Among LID methods, relatively more applicable methods of green rooftop space and parking lot with permeable material were selected to construct plausible scenarios. Curve Number (CN) value was calculated due to land use patterns in each scenario, and SWMM model simulation were conducted during 2008 for comparative analysis. For Case 1, only parking lot with permeable material was applied to the scenario. Green rooftop space I and II were applied to Case 2 and 3 respectively. For Case 4 and 5, green rooftop space I and II were applied, in addition to parking lot with permeable material, Calculation of CN value showed that for S1 basin, the value was 88.1 (prior to scenario application), 86.5 (Case 1), 81.9 (Case 2), 68.5 (Case 3), 80.4 (Case 4) and 67.2 (Case 5). Changing pattern of rain water discharge was analyzed for each scenario. For Case 1, the change was not remarkable before and after application of scenario. In Case 2 and 4, the impact of rain water discharge as source of pollutant fell to 20~30%. The rate dropped to 30~50% in Case 3 and 5 respectively. The result demonstrates that the amount of rain water discharge, amount and frequency of sewer overflow, frequency of rain water discharge, and pollution load decreased in accordance with declining CN value in each scenario. In installing green rooftop space, the effect was twice greater when rain water discharge was directly infiltrated into soil.

• Journal of Wetlands Research
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• v.21 no.2
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• pp.181-190
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• 2019

Recently, Low impact development techniques, a form of nature-based solutions (NBS), were seen cost-efficient alternatives that can be utilized as alternatives for conventional stormwater management practices. This study evaluated the effectiveness of an infiltration trench (IT) and a small constructed wetland (SCW) in treating urban stormwater runoff. Long-term monitoring data were observed to assess the seasonal performance and cite the advantages and disadvantages of utilizing the facilities. Analyses revealed that the IT has reduced performance during the summer season due to higher runoff volumes that exceeded the facility's storage volume capacity and caused the facility to overflow. On the other hand, the pollutant removal efficiency of the SCW was impacted by the winter season as a result of dormant biological activities. Sediment data also indicated that fine and medium sand particles mostly constituted the trapped sediments in the pretreatment and media zones. Sediments in SCW exhibited a lower COD and TN load due to the phytoremediation and microbiological degradation capabilities of the system. This study presented brief comparison LID facilities equipped with pre-treatment zones. The identified factors that can potentially affect the performance of the systems were also beneficial in establishing metrics on the utilization of similar types of nature-based stormwater management practices.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.259-266
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• 2001

This paper presents the results of a structural analysis to determine design variables such as the inner basket array type, and thicknesses of the outer shell and the lid and bottom of a spent nuclear fuel disposal canister. The canister construction type introduced here is a solid structure with a cast iron insert and a corrosion resistant overpack, which is designed for the spent nuclear fuel disposal in a deep repository in the crystalline bedrock, entailing an evenly distributed load of hydrostatic pressure from the groundwater and large swelling pressure from the bentonite buffer. Hence, the canister must be designed to withstand these large pressure loads. Many design variables may affect the structural strength of the canister. In this study, among those variables, the array type of inner baskets and thicknesses of outer shell and lid and bottom are attempted to be determined through a linear static structural analysis. Canister types studied here are one for the pressurized water reactor (PWR) fuel and another for the Canadian deuterium and uranium reactor (CANDU) fuel.

• Journal of Wetlands Research
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• v.21 no.2
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• pp.173-180
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• 2019

This study was conducted to understand factors affecting TSS and heavy metals transport on the road, parking lot and roof. During storm events, heavy metals, which were mostly attached to TSS, were also transported when TSS was washed off in the road, parking lot and roof. This finding may be supported by the significant correlations between TSS load and total and soluble heavy metals load including Cr, Fe, Cu, and Pb (Pearson r value: 0.52 to 0.73; probability p value<0.01). Generation and transport of TSS and heavy metals were greater in the road and parking lot compared to the roof due to vehicular activities, slope and greater catchment areas of these sites. It was found that TSS transport during peak flows of storm events ranges from 65% to 75% implying that by controlling peak flows, TSS transportation to nearby water bodies may be decreased. Depending on the target TSS and heavy metal reduction, sizing of low impact development (LID) technologies and green infrastructures (GI) such as infiltration trench, tree box filter, and rain garden may be calculated. Future researchers were recommended to assess the limitations of the systems and determine the design considerations for these types of facilities.

• Journal of the Korean Association of Geographic Information Studies
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• v.24 no.3
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• pp.41-57
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• 2021

This study evaluated the application of water quality management measures using the SWAT model and the effectiveness of the measures using the load duration curve targeting the Seohwacheon watershed located upstream of Daecheongho. As water quality management measures, artificial wetlands, reduction of neglected livestock, reduction of runoff from greenhouses, restoration of ecological rivers, application of LID technology, and management of point sources were applied. The applied technology evaluated the efficiency of water quality improvement measures by using the target water quality excess rate and the degree of load reduction for each sulfur through the load duration curve. The load duration curve was created by creating a long-term flow duration curve using SWAT and multiplying it by the target water quality. For the target water quality, the value corresponding to the 60th percentile was set as the target water quality using the 10-year data from the Okcheoncheon water quality observation point located in the downstream of Seohwacheon. Through this study, it was possible to confirm the applicability of various water quality measures through the SWAT model, and to examine the applicability of each period according to the sulfur through the load retention curve.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.9
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• pp.5813-5819
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• 2014

LID planning and application has been actively developed to reduce the runoff volume at increased impervious areas due to rapid urbanization. In this study, a performance and applicability evaluation was performed in an infiltration trench using the SWMM model, based on the experimental conditions for infiltration trenches. The infiltration trench application area was applied to 5~15% of the drainage area. The SWMM results of discharge and the BOD reduction efficiency were analyzed at a peak discharge of 45.7~61.9%, total discharge of 47.2~62.3%, and BOD load of 52.3~55.3. The discharge and BOD was estimated to be 12~24% higher and 37~38% smaller than the experimental results. This study can help in the application and performance evaluation of infiltration trenches.

• Journal of Mechanical Science and Technology
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• v.15 no.3
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• pp.327-338
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• 2001

This paper presents the results of a structural analysis to determine design variables such as the inner basket array type, and thicknesses of the outer shell, and lid and bottom of a spent nuclear fuel disposal canister. The canister construction type introduced here is a solid structure with a cast iron insert and a corrosion resistant overpack, which is designed for the spent nuclear fuel disposal in a deep repository in the crystalline bedrock, entailing an evenly distributed load of hydrostatic pressure from the groundwater and high swelling pressure from the bentonite buffer. Hence, the canister must be designed to withstand these high pressure loads. Many design variables may affect the structural strength of the canister. In this study, among those variables, the array type of inner baskets and thicknesses of outer shell and lid and bottom are attempted to be determined through a linear structural analysis. Canister types studied hear are one for the pressurized water reactor (PWR) fuel and another for the Canadian deuterium and uranium reactor (CANDU) fuel.

• Journal of the Semiconductor & Display Technology
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• v.21 no.3
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• pp.125-129
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• 2022

The current display technology tends to be highly integrated with high resolution, the element size is gradually downsized, and the structure becomes complicated. Inductively coupled plasma (ICP) dry etcher of various types of etching equipment is a structure that places a large multi-divisional antenna source on the top lid, passes current to the Antenna, and generates plasma using the induced magnetic field generated at this time. However, in the case of a device of a large area size, a support that can withstand a load structurally is necessary, and when these support portions are applied, arrangement of antenna becomes difficult, which causes reduction in uniformity. As described above, the development of antenna source of a large area having a uniform plasma density on the whole surface is difficult to restrict hardware (H/W). As a solution to this problem, we confirmed the change in uniformity of plasma by applying two kinds of specific shape faraday shield(FICP) to the lower part of the large area upper lid antenna of 6 and 8th more than that generation size. In this thesis, we verify the faraday shield effect which can improve plasma uniformity control of ICP dry etcher equipment applied to medium and large displays.

• Geotechnical Engineering
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• v.13 no.5
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• pp.75-88
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• 1997

In this study an iterative procedure for the analysis of drilled shafts was proposed on the basis of the load transfer mechanism. Special attention was given to the estimation of bearing capacity of drilled shafts which was compared with driven piles, and then with the results of pile load test. The load displacement at the pile head was calculated by load than sfer curves (t -z curves, q-z curves) by using Vljayvergiya, Castelli and hi -linear models. Bab ed on the analytical results, it is found that the behavior of drilled shafts is different from that of driven piles the smaller the skin friction mobilized at the pile-boil interface, the smaller the development of the bearing capacity. Hence the greater pile head movement is required to mobilize the same mainitride of bearing capacity. This trend is more noticeable in sand than in clay. It is also found that as the length-todiameter ratios increase, the dirtference of ultimate bearing capacity between drilled shafts and driven piles is becoming lass ger in sand, but it is minor in clay.