• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.1
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• pp.26-35
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• 2012

Until now, study on the hydraulic resistance characteristics of the ground at the river and the ocean current has been focused on the behavior under uni-directional flow without the direction change of flow. However, recent research result shows that scour rate which were measured under the bi-directional flow was much higher than those measured under uni-directional flow for both fine grained and coarse soil. Since the direction of inflow and return flow at the shore, where the structure will be constructed, is not always $180^{\circ}$, effect of the incidence angle on the hydraulic resistance capacity of the ground should be examined. Using the improved EFA which can consider the direction change of flow, hydraulic resistance capacities of the artificially composed clayey fine grained soil and clayey sandy soil under $0^{\circ}$, $90^{\circ}$, $135^{\circ}$, $180^{\circ}$ flow angle of incidence were assessed. Test result shows that hydraulic resistance capacity decreases and scour rate increase with the increase of the incidence angle between inflow and return flow. For the low consolidation pressure condition, hydraulic resistance capacity of the fine grained soil decreases rapidly. While the hydraulic resistance capacity of the coarse grained soil decreases more rapidly than fine grained soil under high consolidation pressure. Eventually since the larger the incidence angle between inflow and return flow, the larger the scour rate. Hydraulic resistance capacity under bi-directional flow($0^{\circ}{\longleftrightarrow}180^{\circ}$) should be examined for the design purpose.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.1
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• pp.1-8
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• 2015

Recently, constructions of coastal structure including wind turbine structure have increased at southwest shore of Korea. There is a big difference of tide which rage from 3.0 m to 8.0 m at south and wet shore of Korea, respectively. In such ocean circumstance, large scour may occur due to multi-directional tidal current and transverse stress of the wind. therefore scour surrounding wind turbine structure can make system unsafe due to unexpected system vibration. In this study, hydraulic resistance capacity, i.e., critical velocity and critical shear stress, was evaluated by RCT. Uni-directional and bi-directional hydraulic resistance capacities of the samples which were consolidated by different preconsolidation pressures were correlated with soil resistivities of same samples. According to the correlation, it is possible to estimate hydraulic resistance capacity from electrical resistivity of soil. Through the updating the correlation for various soil types, it is expected that the hydraulic resistance capacity of whole construction site will be simply determined from the electrical resistivity.

• Journal of the Korean GEO-environmental Society
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• v.16 no.5
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• pp.55-66
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• 2015

Big tidal differences, which range from 3.0 m to 8.0 m, exist with regional locations at south and west shores of Korea. Under this ocean circumstance, since a large scour may occur due to multi-directional tidal current and transverse stress of the wind, the scour surrounding the wind turbine structure can make instability of the system due to unexpected system vibration. The hydraulic resistance capacity of soils consolidated under different pressures are evaluated by Erosion Function Apparatus (EFA) under unidirectional and bi-directional flows in this study. It was found that the flow direction change affects significantly on the sour rate and critical shear stress, regardless of soil types while the consolidation pressure affects mainly cohesive soil. Among geotechnical parameters, the undrained shear strength can be well-correlated with the hydraulic resistance capacity, regardless soil type while the shear wave velocity shows the proportional relationships with the hydraulic resistance capacities of fine grained soil and coarse grained soil, respectively.

• Nuclear Engineering and Technology
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• v.52 no.12
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• pp.2789-2802
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• 2020

Small Modular Reactors (SMRs) are attracting wide attention due to their outstanding performance, extensive studies have been carried out for lead-based fast reactors (LFRs) that cooled with Lead or Lead-bismuth (LBE), and small modular natural circulation LFR is one of the promising candidates for SMRs and LFRs development. One of the challenges for the design small modular natural circulation LFR is to master the natural circulation thermal-hydraulic performance in the reactor primary circuit, while the natural circulation characteristics is a coupled thermal-hydraulic problem of the core thermal power, the primary loop layout and the operating state of secondary cooling system etc. Thus, accurate predicting the natural circulation LFRs thermal-hydraulic features are highly required for conducting reactor operating condition evaluate and Thermal hydraulic design optimization. In this study, a thermal-hydraulic analysis code is developed for small modular natural circulation LFRs, which is based on several mathematical models for natural circulation originally. A small modular natural circulation LBE cooled fast reactor named URANUS developed by Korea is chosen to assess the code's capability. Comparisons are performed to demonstrate the accuracy of the code by the calculation results of MARS, and the key thermal-hydraulic parameters agree fairly well with the MARS ones. As a typical application case, steady-state analyses were conducted to have an assessment of thermal-hydraulic behavior under nominal condition, and several parameters affecting natural circulation were evaluated. What's more, two characteristics parameters that used to analyze natural circulation LFRs natural circulation capacity were established. The analyses show that the core thermal power, thermal center difference and flow resistance is the main factors affecting the reactor natural circulation. Improving the core thermal power, increasing the thermal center difference and decreasing the flow resistance can significantly increase the reactor mass flow rate. Characteristics parameters can be used to quickly evaluate the natural circulation capacity of natural circulation LFR under normal operating conditions.

• Journal of Environmental Impact Assessment
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• v.20 no.1
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• pp.37-48
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• 2011

Recently, the social and environmental functions of nature river are important due to the increase of expectation for river restoration. So it should be considered the effect of vegetation affecting the conveyance capacity and hydraulic resistance. However, it has not yet proposed a objective standard and modeling method to estimate the effect of conveyance capacity according to vegetaion distribution in the watercourse such as water level or velocity. Therefore, this study simulates the variations of water level and velocity using 3-dimensional hydrodynamic model, EFDC, to consider a conveyance capacity in downstream of the Soyang Reservoir. The simulation results were validated using statistical index such as F-test and T-test. As results, the water level rises about 0.01 to 0.47m and velocity difference are about -0.95m/s to 0.23m/s.

• Journal of the Korean Geotechnical Society
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• v.32 no.7
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• pp.25-34
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• 2016

Recently, in Korea, problems related with unstability of slope or sinkhole in urban area due to erosion of compacted granite soil which was used as a backfill or embankment material have been treated as important issues. Small hole might develop inside of backfill area due to erosion of not only weathered granite soil but also clay, silt, fine sand size particles when underground water flows. Once erosion starts in a soil mass, erosion rate increases gradually to cause rapid destruction. In this study, a rotating cylinder test (RCT) was performed to evaluate the hydraulic resistance characteristics of compacted weathered granite soil under various relative densities and preconsolidation pressures. Meanwhile, an image analysis method was introduced to analyze radius of irregularly eroded sample. It was found that image analysis is an effective means of minimizing the error in calculating a critical shear stress and threshold shear stress on the irregularly eroded sample. Furthermore, in general, hydraulic resistance capacity increases with the increase of relative density and preconsolidation pressure.

• Nuclear Engineering and Technology
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• v.52 no.5
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• pp.1093-1097
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• 2020

A composite iodine sorbent was obtained in the form of porous polymer matrix with activated carbon particles impregnated with triethylenediamine deposited on its surface. A comparative assessment of the radioactive methyliodide capturing efficiency by the composite sorbent and a sample of industrial charcoal sorbent was conducted. It was shown that under the selected testing conditions, the hydraulic resistance of the composite sorbent is lower, and the sorption capacity is higher than that of the industrial charcoal sorbent. A method for comparing the effectiveness of iodine sorbents, based on the calculation of the ratio of the sorption capacity index to the minimum capacity index, needed for the required purification degree was proposed.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.545-553
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• 2009

A lot of long-span marine bridge, which connects land to island or island to island, are being designed and constructed lately in south-west coast in South Korea. In the past, caisson foundations in marine were mainly adopted in construction and stability aspect, however, nowadays with development of pile construction technology, drilled shaft foundations are mainly adopted. As the long span cable stayed bridge and suspension bridge applied with lots of loads are being designed, the scale of pile foundations are getting larger. As the construction cost of substructure including foundation in marine bridges is too high, the appropriate evaluation of the axial bearing capacity of pile becomes a core factor to decide the construction cost of foundation if the drilled shaft is adopted as foundation type of bridge. The evaluation values of skin friction and end bearing capacity of drilled shaft in weathered rock suggested in south Korea are only to introduce the foreign specifications, and most of them are designed in a kind of hard soil layer. Also the allowable load of pile section is less than the expected bearing capacity of pile in the soil condition since the allowable capacity of pile is undervalued. Recently in order to improve this factor the bi-axial hydraulic load test of pile was taken, the data of load transfer analysis of pile, unit of skin friction and end bearing capacity are accumulated. In our country, the design of piles are made with ASD, however, LRFD considering service, strength and extreme state was adopted in Incheon Grand Bridge implemented with BTL, and the research to systematize the resistance coefficient appropriate at home country are being progressed.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.447-454
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• 2000

This paper presents fundamental characteristics of a copper slag when used geotechnical materials. For this study, it was conducted laboratory tests such as compaction, large direct shear, hydraulic conductivity, leaching, TDR, frost heave test and so on. The results of laboratory tests shown gradually increase in draining capacity and shearing resistance more slag mixing. The unfrozen water in temperature changes and frost heave amounts in condition of -17 $^{\circ}C$ appeared to decrease. Also, toxicity tests based on the domestic solid waste regulations were satisfied with nonhazardous. By this research results, a copper slag mixed with granite soil may been used as granular base and embankment materials, fill etc.

• Steel and Composite Structures
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• v.37 no.3
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• pp.273-289
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• 2020

Due to the unique construction method of modular steel buildings (MSBs) with units prefabricated fully off the site and assembled quickly on the site, the inter-module connection for easy operation and overall performance of the system were key issues. However, it was a lack of relevant research on the system-level performance of MSBs. This study investigated the seismic performance of two-storey modular steel structure with a proposed vertical rotary inter-module connection. Three full-scale quasi-static tests, with and without corrugated steel plate and its combination, were carried out to evaluate and compare their seismic behaviour. The hysteretic performance, skeleton curves, ductile performance, stiffness degradation, energy dissipation capacity, and deformation pattern were clarified. The results showed that good ductility and plastic deformation ability of such modular steel structures. Two lateral-force resistance mechanisms with different layout combinations were also discussed in detail. The corrugated steel plate could significantly improve the lateral stiffness and bearing capacity of the modular steel structure. The cooperative working mechanism of modules and inter-module connections was further analyzed. When the lateral stiffness of upper and lower modular structures was close, limited bending moment transfer may be considered for the inter-module connection. While a large lateral stiffness difference existed initially between the upper and lower structures, an obvious gap occurred at the inter-module connection, and this gap may significantly influence the bending moments transferred by the inter-module connections. Meanwhile, several design recommendations of inter-module connections were also given for the application of MSBs.