• Journal of Korean Society on Water Environment
• /
• v.27 no.4
• /
• pp.467-474
• /
• 2011

In an effort to investigate water pollution characteristics of Juam lake, water samples were collected from three sites (Sites A, B, and C) of Oenam stream which is a typical tributary of rural watershed in the lake and analyzed for N concentration and the corresponding isotope ratio (${\delta}^{15}N$) of ${NO_3}^-$. Concentrations of ${NO_3}^-$ were not dramatically different among the sites; $0.8{\pm}0.2mgNL^{-1}$ (range: $0.0{\sim}4.3mgNL^{-1}$) for Site A, $1.1{\pm}0.2mgNL^{-1}$ ($0.0{\sim}4.3mgNL^{-1}$) for Site B, and $1.1{\pm}0.1mgNL^{-1}$ ($0.1{\sim}2.6mgNL^{-1}$) for Site C. Meanwhile, ${\delta}^{15}N$ tended to decrease with river flow; it was highest for Site A ($45.5{\pm}5.3$‰) followed by Site B ($19.7{\pm}2.0$‰) and Site C ($8.7{\pm}1.5$‰). Such high ${\delta}^{15}N$ values of ${NO_3}^-$ in Site A suggested that ${NO_3}^-$ derived from livestock feedlot (specifically livestock excrete of which ${\delta}^{15}N$ is higher than 10‰) is the predominant pollution sources despite mountainous area occupied the most of land-use in the watershed. Using the two-sources isotope mixing model, it was estimated that the contribution of cropping activities (i.e. fertilization) became greater in down-stream area (Sites B and C) due to the higher agricultural land-use than the up-stream area (Site A). Particularly, during the active cropping season, the low contribution of organic pollution sources indicated that domestic sewage was not the predominant pollution source. Therefore, it was suggested that agricultural sources such as livestock farming and cropping rather than mountainous and residential are the dominant sources of water pollution in the study area. These results could be effectively utilized in elucidating water pollution sources in rural areas and selecting water management practices.

• Journal of the Korean GEO-environmental Society
• /
• v.22 no.3
• /
• pp.5-13
• /
• 2021

Due to population growth and industrial development, the amount of industrial waste is increasing every year. In particular, in a thermal power plant using finely divided coal, a large amount of coal ash is generated after combustion of the coal. Among them, fly ash is recycled as a raw material for cement production and concrete admixture, but about 20% is not utilized and is landfilled. Due to the continuous reclamation of such a large amount of coal ash, it is required to find a correct treatment and recycling plan for the coal ash due to problems of saturation of the landfill site and environmental damage such as soil and water pollution. In recent years, the use of a fluid embankment material that can exhibit an appropriate strength without requiring a compaction operation is increasing. The fluid embankment material is a stable treated soil formed by mixing solidifying materials such as water and cement with soil, which is the main material, and has high fluidity before hardening, so compaction work is not required. In addition, after hardening, it is used for backfilling or filling in places where compaction is difficult because higher strength and earth pressure reduction effect can be obtained compared to general soil. In this study, the possibility of use of fluidized soil using high water content cohesive soil and coal ash is considered. And it is intended to examine the flow characteristics, strength, and bearing capacity characteristics of the material, and to investigate the effect of reducing the earth pressure when applied to an underground burial.

• Analytical Science and Technology
• /
• v.33 no.6
• /
• pp.274-284
• /
• 2020

This study described the analytical method for simultaneous determination of 89Sr and 90Sr in liquid sample using automated separation system. Radiostrontium in 0.5 kg of liquid sample was concentrated as SrCO3 to reduce the volume of sample, and purified from the sample using Sr-resin 2 mL (BV, Bed volume). The behavior of Sr and interferences such as Ba, Ca and Y were estimated with various flow rate ranging from 1 to 4 mL min-1. The detailed procedure for the purification of Sr on Sr-resin was presented. The purified radiostronitum was measured in Cerenkov mode and then measured in Scintillation mode by mixing scintillation cocktail. The measured value in both modes were used to calculate the activity of 89Sr and 90Sr. The performance tests were carried out the lab-control-sample having various activity ratio of between 89Sr and 90Sr. The recovery of Sr was ranged from 68 to 94 %. The relative bias of 89Sr activity was ranged from -5 to 20 %, and it was ranged from -10 to 10 % for 90Sr.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.6
• /
• pp.50-58
• /
• 2020

When the concrete surface layer is damaged, The method of impregnating the concrete surface with a water repellent cannot secure the expected durability. Recently, various waterproofing and water-repellent materials were mixed into concrete or mortar to secure water repellency even inside cracks, but compressive strength was greatly reduced. In order to overcome the decrease in compressive strength, there has not yet been a study using the merits of organic and inorganic materials at the same time, so in this study, the physical properties and water repellency performance were evaluated by mixing an organic/inorganic composite water repellent appropriately mixed with an organic and inorganic material into the mortar. When mixed with organic/inorganic water repellent, the flow and air content were reduced by about 10% and 50% compared to the Liquid specimen. In the case of the P6L1 specimen, it was confirmed that the compressive strength decreased by about 3.5% compared to the non-mixed mortar at 39.5 MPa, the same as the existing water repellent, Powder. Water-repellent performance The organic-inorganic composite water repellent mixture specimen confirmed higher water repellency than the existing water repellent mixture powder, and the chloride penetration resistance evaluation result showed that the organic-inorganic composite water repellent mixture specimen reduced the passing charge by about 45% compared to the non-mixed mortar. In summary, it is judged that the P5L1 organic/inorganic composite water repellent mixed with a powder water repellent and a liquid water repellent in a ratio of 5:1 is the most reasonable to prevent the decrease in compressive strength and secure water repellency.

• Journal of the Korea Institute of Building Construction
• /
• v.21 no.1
• /
• pp.31-39
• /
• 2021

The aim of this paper is to improve durability of cement paste by imparting hydrophobicity to the surface and sphere of cement-based materials. A cement paste mixed with a silane/siloxane-based water repellent, and the initial hydration performance, flow performance, and age-specific compressive strength were measured. In addition, the water contact angle, SEM, and XRD before and after surface polishing were measured. When 0.5% of the silane/siloxane-based water repellent was mixed into the cement paste, the compressive strength increased, but the compressive strength decreased as the mixing amount increased by 1.5% and 3.0%. When a silane/siloxane water repellent was incorporated into the cement paste, the hydrophilicity was improved and the contact angle was increased due to hydrophobicity. In addition, the contact angle after surface polishing was found to be larger than the contact angle before surface polishing.

• Journal of Korea Water Resources Association
• /
• v.54 no.8
• /
• pp.553-566
• /
• 2021

River confluence is often characterized by shear layer and the associated strong mixing. In natural rivers, the main channel and its tributary can be separated by the shear layer using contrasting colors. The shear layer can be easily observed using aerial images from satellite or unmanned aerial vehicles. This study proposes a low-cost identification method extracting geographic features of the shear layer using RGB aerial image. The method consists of three stages. At first, in order to identify the shear layer, it performs image segmentation using a Gaussian mixture model and extracts the water bodies of the main channel and tributary. Next, the self-organizing map simplifies the flow line of the water bodies into the 1-dimensional curve grid. After that, the curvilinear coordinate transformation is performed using the water body pixels and the curve grid. As a result, the shear layer identification method was successfully applied to the confluence between Nakdong River and Nam River to extract geometric shear layer features (confluence angle, upstream- and downstream- channel widths, shear layer length, maximum shear layer thickness).

• Economic and Environmental Geology
• /
• v.54 no.6
• /
• pp.699-707
• /
• 2021

Hwajinpo Lagoon, located on the eastern coast of Korea, is a unique environment where freshwater and saltwater are mixed. Systematic management of the lagoon is required because it is a biodiversity-rich and area of high conservation value. The existing environment of the lagoon was evaluated by identifying the distribution of the groundwater level and groundwater flow characteristics. In addition, hydrogeochemical fluctuations were analyzed to determine the effect of seawater intrusion into the aquifer. The results demonstrate that the freshwater-saltwater interface is distributed throughout the aquifer and rises when water of the lagoon evaporates due to prolonged periods of low rainfall and high temperature, thereby increasing the possibility of seawater inflow through groundwater. As for the ionic delta properties (difference between the measured and theoretical concentration of mixed waters), it was estimated that the cation-exchange and precipitation reactions occurred in the aquifer due to seawater intrusion. The ratio of seawater mixed at each point was calculated, using oxygen isotopes and chloride as tracers, resulting in an average of 0.3 and a maximum of 0.87. The overall seawater mixing ratio appears to be distributed according to the distance from the coast. However, some of the results were deviated from the theoretical expectations and reflected the characteristics of the nearby aquifers. Further research on seasonal changes and simulation of seawater intrusion mechanisms is required for specific analysis.

• Journal of Biomedical Engineering Research
• /
• v.43 no.3
• /
• pp.136-146
• /
• 2022

In this study, it is intended to provide basic data that can help develop a cardiovascular simulator for performance evaluation of pulse wave detectors by identifying the development status of domestic and overseas cardiovascular simulators. A total of 119 papers were selected by excluding duplicate literature, gray literature, and literature not related to a cardiovascular simulator. Based on the selected literature, the research trend of cardiovascular simulators was analyzed. As a result of analyzing the purpose of the study, most of the simulators were developed to evaluate the hemodynamic properties of artificial hearts and valves. In addition, it was used for simulation evaluation or hemodynamic studies such as pulse wave studies. As a result of analyzing configurations of the simulators, a heart most often consisted of only one left ventricle. For blood vessels, the Windkessel model was most often constructed using chambers and valves. In most studies, blood was reproduced by mixing glycerin and water to reproduce both density and viscosity. In addition, as a result of analysis from the perspective of medical device performance evaluation, simulators for evaluating artificial heart and artificial valves have been studied a lot, whereas simulators for blood pressure, pulse wave, and blood flow devices have been relatively insignificant. Based on the review results, we suggested considerations when developing a simulator for performance evaluations of a pulse wave detector.

• Journal of the Korean GEO-environmental Society
• /
• v.24 no.1
• /
• pp.15-23
• /
• 2023

The grouting method is a method of construction for the purpose of waterproofing and reinforcing soft ground. When grout is injected into the ground, there are various types of penetration and diffusion of grout depending on the shape of the ground, the size of soil, the porosity, and the presence or absence of groundwater. the current situation. Therefore, in this study, to investigate the penetration performance of the grouting to conductive material, laboratory tests were performed on the addition of the conductive material. In the injection test, 0%, 3%, and 5% of the mixed water were added as conductive materials to the grout, and the original ground condition was composed of various types of ground composed of gravel and silica sand. Conductive grout is injected by pressure into the model ground using a dedicated injection device, and the injection time (t), pressure (p), flow rate (v) and injection amount (q) are measured, and the hardened body injected in the model ground is collected. Penetration performance was evaluated. In the results of the grout injection experiment, the amount of conductive material used and the grout injection rate showed an inverse relationship, and it was confirmed that the penetration pattern was changed according to the size of the soil particles in the model ground. The grout containing the conductive material has relatively good penetration into the ground and excellent strength and durability of the hardened body, so it was judged that it could be used as an additive for measuring the penetration range of the grout.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.11 no.3
• /
• pp.161-168
• /
• 2023

Converter slag is a by-product generated by refining the pig iron produced into molten steel in the blast furnace, occupying about 15 % of the weight of steel production. It has a high free-CaO content that can generate expansion cracks when used for concrete aggregate. This is the main reason to make it difficult to recycle. To solve this problem, government guideline requires that converter slag has to be aged in an open yard for 90 days. However, aging can not be perfectly performed because it entails time and cost. In this study, we tried to investigate the applicability of converter slag as a cementitious material rather than an aggregate by mixing converter slag with mortar formulations. According to the EDS results of the converter slag in the experiment, we found that screening in the aggregate phase was more effective than that in the powder phase. When the particles separated by a magnet in the aggregate state were pulverized and used for concrete up to a 15 % replacement ratio, various engineering characteristics, such as flow, length change, and compressive strength, showed engineering characteristics similar to those of the control mix.