• Nuclear Engineering and Technology
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• v.53 no.7
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• pp.2207-2220
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• 2021

Lead alloy is used as coolant in Lead-based cooled Fast Reactor (LFR). The natural characteristics of lead alloy are combined with the simple structural design of LFR. This constitutes the inherent safety characteristics of LFR. The main work of this paper is to take the main coolant pump (MCP) in the lead-cooled fast reactor (LFR) as the research object, and to study the flow pattern distribution of the internal flow field under the reverse rotation pump condition, the reverse rotation positive-flow braking condition and the reverse rotation negative-flow braking condition. In this paper, the double-outlet volute type and the space guide vane are selected as the potential designs of the CLEAR-I MCP. In this paper, the CFD method is used to study the potential reverse accident of the MCP. It is found that the highest flow velocity in the impeller appears at the impeller outlet, and the Q-H curves of the two design programs basically coincide. The space guide vane type MCP has better hydraulic performance under the reverse rotation positive-flow condition, the Q-H curves of the two designs gradually separate with increasing flow rate, and the maximum flow velocity inside the space guide vane type MCP is obviously lower than that of the double-outlet volute type. For the reverse rotation test of MCP, only the condition of the forward rotating pump of the main coolant pump is tested and verified. For the simulation of the MCP in LBE medium, it proved that the turbulence model and basic settings selected in the simulation are reliable.

• Journal of the Society of Disaster Information
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• v.15 no.1
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• pp.84-97
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• 2019

Purpose: The consolidation settlement of soft ground is dependent on the distribution of pore water pressure which is also affected by hydraulic conductivities (boundary condition) of layers, thickness of clayey soil layer and surcharge. Results: However, the current consolidation analyses are mostly based on Terzaghi's consolidation theory that assumes the initial pore water pressure ratio with depth to be constant. In this study, numerical analysis are carried out to investigate the variation of pore water pressure dissipation with depth and thickness of clayey soil layer, time, surcharge as well as drainage conditions. Conclusion: Comparative study with Terzaghi's consolidation theory is also conducted. The result shows that Terzaghi's consolidation theory should be used with caution unless it is ideally corresponded to the isochrone.

• Korean Journal of Agricultural Science
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• v.48 no.1
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• pp.141-149
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• 2021

The cultivation area for domestic cabbage increased by 26.3% from 10,968 ha in 2019 to 13,854 ha in 2020, and among leafy vegetables, the cabbage cultivation area was 62%, and production was 78.9%. Demand for field crop production of cabbage, which has a relatively high-income level compared to rice farming, is increasing, and mechanization of the field operation is urgently needed due to the insufficient development of related farming machinery. In this study, a prototype fabrication and performance test of a tractor-attached cabbage collector was carried out. The transport section was divided into two parts, one for the feeding and transportation and the other for the screening and packaging to selectively collect cabbages in bulk bags or boxes. The length of the primary collecting conveyor was designed to meet the field conditions of the Korean cabbage cultivation standards so that six cultivation rows could be worked simultaneously. Power was controlled by a hydraulic transmission line of the tractor and was easily mounted onto the 3-point hitch links behind the tractor. When the performance was evaluated, the transfer rate, loss rate, damage rate, and work performance were 100, 0, 1.2%, and 1.9 h·10 a^-1. Final improvement and commercialization of the prototype would considerably contribute to the mechanization of harvesting cabbage, the main ingredient of Kimchi.

• Journal of the Korean GEO-environmental Society
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• v.12 no.12
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• pp.13-20
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• 2011

The main objective of this paper is finding the influence factors and their degree of importance to steel liner's safety by investigating and evaluating the buckling incidents of steel tunnel liner under external water pressure. The study was based on the detailed investigation to the design conditions and incident shapes at 2m diameter waterway tunnel with a partially buckled internal steel liner and concrete backfilled lining as the raw water transmission pipe line of regional water supply project. Appropriate buckling theory capable of applying this incident points was selected by referring the existing literature and compared with the results of investigation. Also, hydrogeological characteristics of this site on buckling pressure was evaluated. The result of this study was shown that both the hydrogeological characteristics of upper geologic layers and proper tunnel construction are important factors on buckling at steel liner, and hydraulic gradient level should be decided according to the hydrogeological characteristics. This incident case analysis on steel liner of pressurized waterway tunnel was expected to provide more information for realizing the problems and improvements at each design, construction and maintenance stages.

• Advances in environmental research
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• v.10 no.1
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• pp.87-103
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• 2021

Anaerobic digestion (AD) refers to the biological process which can convert organic substrates to biogas in the absence of oxygen. The aim of this study was to determine the capability of feedstock to produce biogas and to quantify the biogas yield from different feedstocks. A co-digestion approach was carried out in a continuous stirred tank reactor operated under mesophilic conditions and at a constant organic loading rate of 0.0756 g COD/ L.day, with a hydraulic retention time of 25 days. For comparison, mono-digestion was also included in the experimental work. 2 L working volumes were used throughout the experimental work. The seed culture was obtained from composting as substrate digestion. When the feedstock was added to seeding, the biogas started to emit after three days of retention time. The highest volume of biogas was observed when the seeding volume used for 1000mL. However, the lowest volume of biogas yield was obtained from both co-digestion reactors, with a value of 340 mL. For methane yield, the highest methane production rate was 0.16 L CH4/mg. The COD with yield was at 8.6% and the lowest was at 0.5%. The highest quantity of methane was obtained from a reactor of Euphorbiaceae peel with added seeding, while the lowest methane yield came from a reactor of Euphorbiaceae stems with added seeding. In this study, sodium bicarbonate (NaHCO3) was used as a buffering solution to correct the pH in the reactor if the reactor condition was found to be in a souring or acidic condition.

• Geomechanics and Engineering
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• v.24 no.5
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• pp.407-418
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• 2021

Due to the complexity of the causes of the sliding mass instabilities, landslide susceptibility and hazard evaluation are difficult, but they can be more carefully considered and regionally evaluated by using new programming technologies to minimize the hazard. This study aims to evaluate the landslide hazard zonation in the Tabriz region, Iran. A fuzzy logic-based multi-criteria decision-making method was proposed for susceptibility analysis and preparing the hazard zonation maps implemented in MATLAB programming language and Geographic Information System (GIS) environment. In this study, five main factors have been identified as triggering including climate (i.e., precipitation, temperature), geomorphology (i.e., slope gradient, slope aspect, land cover), tectonic and seismic parameters (i.e., tectonic lineament congestion, distribution of earthquakes, the unsafe radius of main faults, seismicity), geological and hydrological conditions (i.e., drainage patterns, hydraulic gradient, groundwater table depth, weathered geo-materials), and human activities (i.e., distance to roads, distance to the municipal areas) in the study area. The results of analyses are presented as a landslide hazard map which is classified into 5 different sensitive categories (i.e., insignificant to very high potential). Then, landslide susceptibility maps were prepared for the Tabriz region, which is categorized in a high-sensitive area located in the northern parts of the area. Based on these maps, the Bozgoosh-Sahand mountainous belt, Misho-Miro Mountains and western highlands of Jolfa have been delineated as risk-able zones.

• Journal of The Korean Society of Agricultural Engineers
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• v.64 no.1
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• pp.27-37
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• 2022

This study established a water supply network based on the operation case of Mandae Reservoir in Yanggu-gun, Gangwon-do, to analyze the efficient distribution and management of agricultural water supplied from the reservoir to irrigation areas using the hydraulic analysis model SWMM. In order to construct a model to analyze the water canal network, network conditions needs to be simplified, and in particular, excessive detail or simplification of the irrigation area can lead to errors in the analysis results. Therefore, the effect of the water canal network model was analyzed by simulating the appropriate simplification process step by step. The results of simplifying the actual block shape of the analysis target area using SWMM showed that there was no significant difference in the results even if 7 lots were simplified to 2. Also, it was found that the construction and analysis of a simplified network model were reliable when the excess quantity was 2% or more compared to the required quantity for each case of analysis of the paddy field.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.2
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• pp.27-36
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• 2022

The large uprush could be occurred when the waves hit the coastal structure and this uprush by wave could make the overtopping. The downfall of the wave overtopping water over the structure brought about the vertical impact loads. The vertical impact loads should be evaluated in order to design the pavement behind the crown wall however these loads were still unclear. In this study, the hydraulic model tests for the downfall impact loads by wave overtopping were performed and the various conditions were applied to the tests. The effect of the incident wave condition, the freeboard, the armour crest height and the height of the parapet were investigated. The test results showed that the parapet on the crown wall could reduce the wave overtopping however the inclusion of parapet could lead to the increased downfall wave pressures behind the crown wall. The empirical formulae were proposed for evaluating the maximum downfall pressures behind the crown wall of rubble mound structure.

• Journal of Drive and Control
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• v.19 no.4
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• pp.46-53
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• 2022

RIn this study, a test tractor that could measure various types of agricultural operational loads was developed, and its performance was verified. This tractor could be used to measure the load generated during agricultural work and convert the related data into a database. A test tractor was developed using an 80-kW-rated load tractor, and it could measure various types of field test data, such as engine torque and rpm, wheel torque, PTO(power take-off) torque, hexometer, IMU/INS sensor, steering angle sensor, hydraulic pressure, and flow sensor data. To verify the developed test tractor, a verification test using an agriculture rotavator was performed. The test conditions were L1, L2, and L3 based on the tractor's main and sub-transmission stages, and stages 1 and 2 were selected as the PTO. In a comparison of the analyzed test data, similar tendencies in the test results of this research and other research (Kim's research) were seen. Through this, the developed test tractor was verified. In the future, we plan to conduct research on the tractor developed in this study using various attached working machines.

• Coupled systems mechanics
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• v.11 no.4
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• pp.315-333
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• 2022

Fluid-Structure Interaction (FSI) modeling is highly effective to reveal deformations, fatigue failures, and stresses on a solid domain caused by the fluid flow. Mechanical properties of the solid structures and the thermophysical properties of fluids can change under different operating conditions. In this study, we investigated the interaction of [45/-45]₂ wounded composite tubes with the fluid flows suddenly pressurized to 5 Bar, 10 Bar, and 15 Bar at the ambient temperatures of 24℃, 66℃, and 82℃, respectively. Numerical analyzes were performed under each temperature and pressure condition and the results were compared depending on the time in a period and along the length of the tube. The main purpose of this study is to present the effects of the variations in fluid characteristics by temperature and pressure on the structural response. The variation of the thermophysical properties of the fluid directly affects the deformation and stress in the material due to the Wall Shear Stress (WSS) generated by the fluid flow. The increase or decrease in WSS directly affected the deformations. Results show that the increase in deformation is more than 50% between 5 Bar and 10 Bar for the same operating condition and it is more than 100% between 5 Bar and 15 Bar by the increase in pressure, as expected in terms of the solid mechanics. In the case of the increase in the temperature of fluid and ambient, the WSS and Von Mises stress decrease while the slight increases of deformations take place on the tube. On the other hand, two-way FSI modeling is needed to observe the effects of hydraulic shock and developing flow on the structural response of composite tubes.