• Journal of Korea Water Resources Association
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• v.57 no.8
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• pp.493-507
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• 2024

RANS-based CFD analysis is widely applied in various engineering fields, including practical hydraulic engineering, due to its high computational efficiency. However, problems of non-physical behavior in the analysis of two phase flow, such as free surfaces, have long been raised. The two-equation turbulence models used in general RANS-based analysis were developed for single phase flow and simulate unrealistically high turbulence energy at the interface where there are abrupt changes in fluid density. To solve this issue, one of the methods recently developed is the buoyancy-modified turbulence model, which has been partially validated in coastal engineering, but has not been applied to open channel flows. In this study, the applicability of the buoyancy-modified turbulence model is evaluated using the VOF method in the open-source program OpenFoam. The results of the uniform flow showed that both the buoyancy-modified k-𝜖 model and the buoyancy-modified k-ω SST model effectively simulated the reduction of turbulence energy near the free surface. Specifically, the buoyancy-modified k-ω SST model accurately simulated the vertical velocity distribution. Additionally, the model is applied to dam-break flows to examine cases with significant surface variation and cavity formation. The simulation results show that the buoyancy-modified turbulence models produce varying results depending on the VOF method and shows non-physical behavior different from experimental results. While the buoyancy-modified turbulence model is applicable in cases with stable surface shapes, it still has limitations in general application when there are rapid changes in the free surface. It is concluded that appropriate adjustments to the turbulence model are necessary for flows with rapid surface changes or cavity formation.

• Economic and Environmental Geology
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• v.57 no.4
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• pp.387-396
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• 2024

The geological disposal of high-level radioactive waste (HLW) involves permanently isolating the wastes in stable geological formations deep underground. Mudstone (siltstone and claystone) containing abundant clay minerals is proposed as a host rock for geological disposal of HLW because clay minerals have low permeability and high ion sorption/exchange capacity. Despite the widespread occurrence of sedimentary basins in Korea, there is a lack of evaluation of mudstone as host rocks for geological disposal. In this study, we utilized the JBH-1 borehole (7-754 m) obtained from the Jinju Formation to investigate the distribution trend and mineral compositions of mudstone. Additionally, we conducted comparative analyses with the Opalinus Clay in Switzerland considered as host rock of geological disposal of HLW. Claystone containing more than 40% clay minerals exhibit thick layers primarily in the upper section (7-350 m) of the JBH-1 borehole. While the clay minerals content of claystone does not show significant variation with depth, there are differences in the characteristics of feldspar and carbonate minerals. These mineralogical variations can led change in pore water chemistry and rock mechanical properties. The clay minerals content of claystone in the Jinju Formation is similar to that of the Opalinus Clay. However, there are notable differences in clay minerals composition. While the Opalinus Clay contains smectite-illite mixed-layer minerals, the Jinju Formation are dominated by illite indicating higher burial temperatures. This information will be useful for studying the host rock of HLW geological disposal site in Korea.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.36 no.4
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• pp.129-137
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• 2024

An analytic solution for the interaction between an array of circular piles made by joining trapezoid steel pipes (TSP) and waves was obtained using an eigenfunction expansion method. First, an analytic model for the wave scattering of multiple piles fixed at arbitrary positions was derived, and then a simplified model was obtained assuming that an infinite array of identical piles were deployed perpendicular to the propagating direc- tion of incident waves. A regular wave experiment was conducted using an experimental model with a scale ratio of 1/100 in a two-dimensional wave tank to verify the analytic solutions. The analytic results and experimental results were qualitatively consistent with each other. Using a developed analytic model, we examined the wave force on the multiple piles and the wave deformation in front of the arrayed piles. The period for the installation is greatly reduced as the TSP pile can be prefabricated in a factory. In particular, it is possible to install at the soft seabed. A seawall structure using arrayed TSP piles will be an ideal complement for a concrete seawall in future.

• Journal of Korean Society of Forest Science
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• v.113 no.3
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• pp.308-318
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• 2024

Forest fuel management plays a crucial role in the proper management of frequent and large-scale forest fires worldwide. This study evaluated the impact of fuel management on reducing forest fire risk by through surface fire behavior through laboratory experiments and simulations using the Wildland Fire Dynamics Simulator. For Pinus densiflora litter, fuel conditions were established based on field surveys in Goseong-gun, Gangwon-do, focusing on control, 20% thinning, and 40% thinning sites. Results indicated that visible flame height, vertical temperature distribution, and maximum heat release rate tended to decrease with higher thinning intensity, implying a lower forest fire risk. Overall, the WFDS simulations produced higher values compared to the laboratory experiments, but the trends were similar. The results of this study can serve as fundamental data for evaluating forest fire risk based on thinning intensity and establishing a research foundation for fire prevention.

• Korean Chemical Engineering Research
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• v.62 no.4
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• pp.355-363
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• 2024

Although copolymer aramid is a fiber with excellent flexural performance, there is no test method to evaluate flexural fatigue performance. Various studies are currently being conducted in korea to develop copolymer aramid, and in order to develop the reliability of aramid fibers to a global level, it is necessary to develop a test method to evaluate the flexural fatigue performance of aramid fibers. In this study, we developed an test equipment and test method that can evaluate the flexural fatigue performance of copolymer aramid and analyzed the flexural fatigue performance of aramid fiber. Flexing rollers are made of ceramic materials and rotating shapes to minimize friction. The diameter of the roller was set to 10 mm by calculating the minimum allowable curvature. The B₁₀ life was calculated through a flexural fatigue test, and the para-aramid was 125,770 cycles, the copolymer aramid was 598,150 cycles, and the aramid nano fiber(ANF) coated copolymer aramid was 589,073 cycles. Through the S-N diagram, the fatigue life relationship according to the load change was confirmed. copolymer aramid fibers exhibit better flexural fatigue performance than para-aramid fibers at high loads. The ANF coated copolymer aramid also exhibits excellent flexural fatigue performance.

• Research in Plant Disease
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• v.30 no.3
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• pp.256-267
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• 2024

We have developed FBcastS (Fire Blight Forecasting System), a cloud-based information system that leverages the K-Maryblyt forecasting model. The FBcastS provides an optimal timing for spraying antibiotics to prevent flower infection caused by Erwinia amylovora and forecasts the onset of disease symptoms to assist in scheduling field scouting activities. FBcastS comprises four discrete subsystems tailored to specific functionalities: meteorological data acquisition and processing, execution of the K-Maryblyt model, distribution of web-based information, and dissemination of spray timing notifications. The meteorological data acquisition subsystem gathers both observed and forecasted weather data from 1,583 sites across South Korea, including 761 apple or pear orchards where automated weather stations are installed for fire blight forecast. This subsystem also performs post-processing tasks such as quality control and data conversion. The model execution subsystem operates the K-Maryblyt model and stores its results in a database. The web-based service subsystem offers an array of internet-based services, including weather monitoring, mobile services for forecasting fire blight infection and symptoms, and nationwide fire blight monitoring. The final subsystem issues timely notifications of fire blight spray timing alert to growers based on forecasts from the K-Maryblyt model, blossom status, pesticide types, and field conditions, following guidelines set by the Rural Development Administration. FBcastS epitomizes a smart agriculture internet of things (IoT) by utilizing densely collected data with a spatial resolution of approximately 4.25 km to improve the accuracy of fire blight forecasts. The system's internet-based services ensure high accessibility and utility, making it a vital tool in data-driven smart agricultural practices.

• Microbiology and Biotechnology Letters
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• v.52 no.3
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• pp.304-313
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• 2024

In this study, the microbial distribution and diversity of kimchi manufactured in the same method as salted cabbage manufactured from Pyeongchang, Andong, and Haenam cabbage according to the storage period were compared. Among Pyeongchang, Andong, and Haenam salted cabbages, the Haenam salted cabbage microbial community showed the highest diversity on the 1st day of storage. As the storage period of salted cabbage increased, the alpha diversity value increased, the proportion of cyanobacteria decreased, and bacteria derived from sea salt and water increased. Principal coordinates analysis(PCoA) and unweighted pair group method with arithmetic mean(UPGMA) trees showed that Andong salted cabbage on the 5th day of storage had a microbial community close to salted cabbage on the 10th day of storage. At the species level, Sinocapsa zengkensis was 78.65%, 90.64%, and 63.44%, respectively, in Pyeongchang, Andong, and Haenam salted cabbages on the 1st day of storage. Marinomonas primoryensis was showed in Pyeongchang, Andong, and Haenam salted cabbage on the 5th day of storage at 24.39%, 26.60%, and 21.75%, respectively, and at 42.17%, 31.43%, and 45.21%, respectively, on the 10th day of storage. Kimchi made from Pyeongchang, Andong, and Haenam salted cabbages showed Janthinobacterium lividum at 30.47%, 29.60%, and 25.97%, respectively. In addition, Leuconostoc spp. involved in fermentation were showed from the 5th day of storage, but Andong salted cabbage on the 10th day of storage was not showed. These results show to be due to differences in soil, climate, and cultivation methods of cabbage.

• Journal of Practical Agriculture & Fisheries Research
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• v.26 no.3
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• pp.64-71
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• 2024

This study investigated the electrical conductivity, pH, and diastase activity characteristics of 31 types of domestic and imported honey, which are not currently used in the Korean honey grading system, to determine the feasibility of introducing these indicators into the honey grading system. The results showed that the moisture content of domestic and imported honey is around 20%, indicating that domestic quality standards are relatively well controlled, and the pH values are distributed in the range of pH 3.91 to 6.31. The electrical conductivity of domestic and imported honey ranged from 0.09-1.51mS/cm, which showed a large difference between the samples. Although there was a large difference of electrical conductivity from the honey types, further research is needed to determine whether it is applicable to Korean honey. Finally, in the case of diastase activity, Korean honey showed relatively high DN values compared to imported honey from Vietnam, New Zealand, the United States, and China. Therefore, diastase activity is an important indicator for evaluating the quality of honey, and further research is needed to confirm its feasibility as an additional indicator for the domestic honey grading system in Korea. This study evaluated the physical properties and enzyme activity characteristics of domestic and imported honey, and is expected to provide basic information for the establishment of a honey grading system, thereby improving consumer trust in the honey grading system and enhancing the development of honey distribution in Korea.

• Applied Chemistry for Engineering
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• v.35 no.5
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• pp.468-472
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• 2024

This study experimentally examined the separation performance of indole (IN) contained in crude methyl naphthalene oil (CMNO) by methanol extraction and then compared these results with formamide extraction. CMNO containing about 4.36% IN, which is attracting attention as an intermediate raw material such as medicine, essential amino acids, and perfumes, was used as a raw material, and methanol aqueous solution was used as a solvent, respectively. The increase in the initial volume fraction of water in the solvent (y_w,0) sharply decreased the distribution coefficient (m_IN) and yield (Y_IN) of IN, but conversely increased the selectivity of IN in reference to 2-methylnaphthalene (2MNA). An increase in the initial volume ratio of solvent to feed (E₀/R₀) increased m_IN, Y_IN, and 𝛽_IN,2MNA. In the range of 0.1 ≤ y_w,0 ≤ 0.3, m_IN and Y_IN of methanol extraction were approximately 1.9~5.9 times and 1.8~3.6 times greater than those of formamide extraction, respectively, whereas 𝛽_IN,2MNA of formamide extraction were 4.6~8.2 times greater than those of methanol extraction.

• Journal of the Korean Geotechnical Society
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• v.40 no.5
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• pp.93-101
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• 2024

Numerical analysis methods are widely used to assess the safety of hydrogen storage facilities; however, obtaining data under various conditions poses significant challenges. This study aims to expand the dataset using oversampling algorithms and utilize these enhanced datasets as diverse input parameters for numerical analysis. The oversampling techniques applied include SMOTE, Borderline-SMOTE, ADASYN, and CTGAN, with data amplified by factors of 2, 5, and 100 relative to the original dataset. This approach increases data volume based on the characteristics of the existing data, which may consequently introduce outliers. To address this, statistical methods such as the 3-sigma rule and the confidence level method are employed to identify and remove outliers beyond the normal distribution range. The reliability of the conditions generated through data amplification and outlier analysis is evaluated by comparing them with trends observed in the original dataset. Additionally, the SHAP algorithm is utilized to analyze changes in the importance values of each parameter. The SHAP values derived from the original dataset and those processed through AI techniques and outlier analysis exhibit similar trends, validating the proposed methodologies. The methods proposed in this paper are applicable not only to hydrogen storage facilities but also to the systematic construction of data for assessing the stability of various geotechnical structures.