• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.2
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• pp.203-212
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• 2019

Disposal nonconformity of radioactive wastes refers to radioactive wastes that need to be treated, solidified and packaged during operation or decommissioning of NPPs, and are typically exemplified by particulate radioactive wastes with dispersion characteristics. These wastes include the dried powders of concentrated wastes generated in the process of operating NPPs, slurry and sludge, various powdered wastes generated in the decommissioning process (crushed concrete, decontamination sludge, etc.), and fine radioactive soil, which is not easy to decontaminate. As these particulate wastes must be packaged so that they become non-dispersive, they are solidified with solidification agents such as cement and polymer. If they are treated using existing solidification methods, however, the volume of the final wastes will increase. This drawback may increase the disposal cost and reduce the acceptability of disposal sites. Accordingly, to solve these problems, this study investigates the pelletization of particulate radioactive wastes in order to reduce final waste volume.

• Journal of the Korean Society of Mineral and Energy Resources Engineers
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• v.55 no.6
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• pp.546-552
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• 2018

Although there are differences in the history of mining development by country, geographical conditions, and economic status, there are various problems such as water pollution caused by acid mine drainage from past mine development, soil and water pollution caused by mine tailing, and landslides caused by slope failure. Thus, human life is threatened by ground subsidence caused by collapses. Some countries have technology and legal systems that are different from those of others. In countries where mine reclamation is underway, or has to begin, there is a need for institutional arrangements and technical support. Countries trying to start mine reclamation require help from the international community. Technically and institutionally advanced nations need to recover from mine reclamation through cooperation with countries that are beginning to undertake reclamation.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.22 no.1
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• pp.61-72
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• 2019

With the diversification of research using UAV(Unmanned Aerial Vehicle)s, the possibility of remote sensing research for urban green spaces is increasing. UAVs can be used as an investigation method to monitor the successful construction of the park and the planting of vegetation since its creation. This study was carried out to investigate UAVs utilization of urban green space monitoring in Dosol Square. It was photographed three times on May 21, July 13, and September 16, 2018 using DJI Phantom3 pro, Inspire2, and Parrot Sequoia multispectral camera. Orthographic images were overlaid on the planting plan of the site and the construction results were checked, the change of vitality of the plantation area was analyzed by NDVI(Normalized Difference Vegetation Index) and SAVI(Soil Adjusted Vegetation Index). As a result, it was confirmed that the UAVs are very effective for surveying the view of the urban green space after the construction and recording the results, which can be grasped quantitatively by overlaying the planting plan map. UAVs are more likely to be used in terms of monitoring vegetation vitality. It is interpreted that SAVI is better than NDVI in the green space just after composition. Chionanthus retusus and Pinus strobus were analyzed for their low level of vitality, and partially damaged and their vitality was lowered. In addition, there was difficulty in grass planting area and flower garden due to drainage and summer drought problems. In the future, it is expected that orthoimage and multispectral data using UAVs will be useful in the early vegetation monitoring and management field of urban green spaces.

• Korean Journal of Agricultural Science
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• v.47 no.4
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• pp.1039-1048
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• 2020

Food waste causes various economic losses and environmental pollution problems such as soil pollution and groundwater pollution. Food waste has been used as a resource in various forms and has been used mostly for feed and composting. This study compared microalgal nutrient medium (BG-11) with food waste compost to determine the possibility of using it as a culture medium. Scenedesmus quadricauda was isolated and cultured in an eutrophic reservoir and incubated for 3 days in distilled water before laboratory use. Food waste compost was produced in two food waste processing facilities, and hot water was extracted in the laboratory to be used for microalgae cultivation. The growth curve of the microalgae was analyzed based on the Chl-a concentration measured during the experiment, and the growth rate of the microalgae grown in the food waste compost was compared with the growth rate of those grown in the nutrient medium. Food waste compost showed a similar growth rate to that of the nutrient medium, and there was a difference depending on the manufacturing facility. The growth of microalgae in such food waste was further amplified when trace elements were added and showed better growth than that of the nutrient media. Particularly, when trace elements were added, the growth rate increased, and the growth period was further extended. Therefore, food waste compost can be sufficiently utilized as a microalgal culture medium, and if trace elements are added, it is considered that microalgae can be more effectively cultured compared to the existing nutrient medium.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.2
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• pp.309-315
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• 2021

Risks and uncertainty are unavoidable problems in management of projects. Therefore, project managers should not only prevent risks, but also have to respond and manage them. Risk management has become a critical interest subject in the construction industry for both practitioners and researchers. This paper presents critical risk factors of office building projects in the construction phase in Ho Chi Minh City, Vietnam. Data was collected through a questionnaire survey based on the likelihood and consequence level of risk factors. These factors fell into five groups: (i) financial risk factors; (ii) management risk factors; (iii) schedule risk factors; (iv) construction risk factors; and (v) environment risk factors. The research results showed that critical factors affecting office building projects are natural (i.e., prolonged rain, storms, climate effects) and human-made issues (i.e., soil instability, safety behaviors, owner's design change) and the schedule-related risk factors contributed to the most significant risks for office buildings projects in the construction phase in Ho Chi Minh City. They give construction management and project management practitioners a new perspective on risks and risk management of office buildings projects in Ho Chi Minh City and are proactive in the awareness, response, and management of risk factors comprehensively.

• Geomechanics and Engineering
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• v.24 no.2
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• pp.129-141
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• 2021

The vacuum preloading method has been used in many countries for soil improvement and land reclamation. However, the treatment time is long and the improvement effect is poor for the straight-line vacuum preloading method. To alleviate such problems, a novel combined air booster and straight-line vacuum preloading method for shallow ground treatment is proposed in this study. Two types of traditional vacuum preloading and combined air booster and straight-line vacuum preloading tests were conducted and monitored in the field. In both tests, the depth of prefabricated vertical drains (PVDs) is 4.5m, the distance between PVDs is 0.8m, and the vacuum preloading time is 60 days. The prominent difference between the two methods is when the preloading time is 45 days, the injection pressure of 250 kPa is adopted for combined air booster and straight-line vacuum preloading test to inject air into the ground. Based on the monitoring data, this paper systematically studied the mechanical parameters, hydraulic conductivity, pore water pressure, settlement and subsoil bearing capacity, as determined by the vane shear strength, to demonstrate that the air-pressurizing system can improve the consolidation. The consolidation time decreased by 15 days, the pore water pressure decreased to 60.49%, and the settlement and vane shear strengths increased by 45.31% and 6.29%, respectively, at the surface. These results demonstrate the validity of the combined air booster and straight-line vacuum preloading method. Compared with the traditional vacuum preloading, the combined air booster and straight-line vacuum preloading method has better reinforcement effect. In addition, an estimation method for evaluating the average degree of consolidation and an empirical formula for evaluating the subsoil bearing capacity are proposed to assist in engineering decision making.

• Journal of the Korean GEO-environmental Society
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• v.12 no.9
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• pp.5-11
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• 2011

Recently, large and deep excavations are increasing. The damage of adjacent structures due to excavation has steadily increased with increasing construction demand. Especially in urban development and poor conditions, the excavation adjacent to the subway structures has caused a lot of problems. This paper was reviewed that the underground excavation and reinforcement of the status process through a case study on the field. And stability analysis through the case study evaluates applicability for reasonable reinforcement method by numerical analysis. As a result, the strata distribution condition of all 16 sites consisted of landfill from the top and distributed in the order of deposits, weathered soils, weak rock from the bottom. Also, when proceeding the excavation adjacent to structures, the location of site and layer conditions have highly effect on the results of the construction. Therefore, this study was applied reinforcement method to protect damage by excavation. Displacement and settlement were within allowable criterion and hence, stability of structure was analyzed as safe.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.27-36
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• 2020

The purpose of this paper is to study on the applicability of the standard design response spectrum from the response spectrum analysis method, mainly applied to pile mooring facilities. To this end, after performing the ProShake 1-dimensional site response considering various geological conditions, the current standard design response spectrum was compared, and the ground-pile model in time history and two-dimensional site response analysis using Abaqus were performed to analyze the dynamic behavior of the ground-pile and to examine the selection method of the reference surface of the response spectrum on the installed slope, respectively. As a result, it was confirmed that no problems were found in the applicability of the current standard design response spectrum and no improvements are needed as well when considering the characteristics of the ground-pile dynamic behavior and the slope of the pile mooring facility.

• Journal of the Korean Geotechnical Society
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• v.37 no.1
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• pp.5-15
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• 2021

The areas consisting of frost susceptible soils in cold regions, such as the Arctic area, have problems of frost heave and thaw settlement due to the seasonal air temperature changes and internal temperature of installed structures. Ground stabilization methods for preventing frost heave and thaw settlement of frost susceptible soils include trenching, backfilling and thermo-syphon. The thermo-syphon is the method in which refrigerant can control the ground temperature by transferring the ground temperature to atmosphere in the from of two-phase flow through the heat circulation of the internal refrigerant. This numerical study applied the function of these thermo-syphon as the boundary condition through user-subroutine coding inside ABAQUS and compared and analyzed the temperature results of laboratory experiments.

• Journal of the Korean Geotechnical Society
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• v.37 no.12
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• pp.25-31
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• 2021

Boundary conditions for thermal-hydraulic problems of soils play an essential role in the numerical accuracy. This study presents a boundary condition considering the thermo-hydraulic interaction between the ground and the atmosphere. Ground surface energy balance consists of solar radiation, ground radiation, wind convection, latent heat from water evaporation, and heat conduction to the ground. Equations for each heat flux are presented, and numerical analyses are performed in conjunction with the FEM program for the thermal-hydraulic phenomenon of unsaturated soils. Numerical results using the weather data at the Ulsan Meteorological Observatory are similar to the measured surface temperature. Latent heat caused by water evaporation during the daytime lowers the surface temperature of the bare soil, and a thermal equilibrium is reached at nighttime when the effect of the ground condition is significantly reduced. The temperature change of the surface ground is diminished at the deeper ground due to its thermal diffusion. Numerical analysis where the surface ground temperature is the primary concern requires considering the thermo-hydraulic interaction between the ground and the atmosphere.