• Journal of Korea Foundry Society
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• v.41 no.5
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• pp.434-444
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• 2021

This study investigated the overall dependence of the tensile properties of Al-Si alloys on the distribution aspect of a eutectic Si particle in terms of defect susceptibility to the effective void area fraction, referring to the sum of pre-existing microvoids and the damage evolution of the Si particle. The network morphology of as-cast Al-xSi (x=2,5,8,11) alloys was modified to a granular type via a T4 treatment, after which a computational topography (CT) analysis and scanning electron microscope (SEM) observations were utilized to evaluate the size and distribution of the microvoids. The CT and SEM analyses indicated that the main cracks grow along local regions that possess the highest porosity level. The local plastic deformation around the microvoids and the distribution aspect of the microvoids induced a practical difference between the iso-volumetric CT measurement and the SEM fractography outcomes. The results demonstrated that the overall dependence of the ultimate tensile strength (UTS) and elongation on the effective void area fraction is more sensitive to the variation of the area fraction of the Si particle in the network morphology than in the granular type; this is due to the sequential damage evolution of the neighboring Si particles in the eutectic Si colony.

• Journal of Dairy Science and Biotechnology
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• v.37 no.1
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• pp.1-14
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• 2019

In general, milk is a nutritious food and is very helpful in improving and maintaining a person's health. However, over the past 30 years, a number of studies have reported the presence of Aflatoxin M1 in milk and milk products worldwide. The contamination with Aflatoxin M1 in milk and dairy products has become an important issue all over the world. The presence of the mycotoxin in these products was a major concern particularly among children and infants, who are more sensitive than adults. This study reviewed recent data to summarize the current status of Aflatoxin M1 in milk and dairy products produced in various regions around the world, related regulations, reduction strategies, detection methods, and future research tasks. Strict regulation and superior milk-handling techniques are essential to minimize Aflatoxin M1 contamination in milk and dairy products using ever-evolving analytical techniques. Furthermore, education should be imparted to ensure that Aflatoxin M1 that may exist in milk and dairy products and its effects on human health are made aware of.

• Korean Journal of Environmental Biology
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• v.37 no.1
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• pp.8-18
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• 2019

The objectives of this study were to analyze the influence of chemical water quality on fish guilds, pollution tolerance and the multi-metric ecological health, based on the Fish Assessment Index (FAI) in the main stream of Mangyeong River between 2009-2016. The quality of water with specific conductivity, TP, and $NH_4-N$ got worse dramatically in the down region. During the study, a total of 50 species were collected and the most dominant species was Zacco platypus. Also known as tolerant species, accounted 22.9% of the total abundances, thus indicating a trophic degradation. The downstream region (S5) had the highest number of fish external abnormalities, indicating a degradation of ecological health, based on the fish assemblages. Pearson correlation analysis indicated that relative abundance of tolerant fish species and omnivore fish species had a significant positive correlation(r>0.30, p<0.05) with values of BOD, conductivity and $NH_4-N$. Whereas, the relative abundance of the sensitive species and insectivore species had a significant negative relations (r<-0.30, p<0.001) with the parameters. The mean obtained from the multi-metric fish model, based on the FAI of all sites was 47 (n=40). This indicated a "fair condition" in the ecological health, and the downstream regions (S3-S5) were judged as "bad condition", indicating an influence of the chemical degradation on the ecological health.

• Journal of the Korean Association of Geographic Information Studies
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• v.23 no.4
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• pp.52-67
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• 2020

Recently, the Arctic has been exposed to snow-covered land due to melting permafrost every year, and the Korea Geographic Information Institute(NGII) provides polar spatial information service by establishing spatial information of the polar region. However, there is a lack of spatial information on vegetation sensitive to climate change. This research used a multi-temporal Sentinel-2 image to perform land cover classification of the Ny-Ålesund in Arctic Svalbard. In the pre-processing step, 10 bands and 6 vegetation spectral index were generated from multi-temporal Sentinel-2 images. In image-classification step is consisted of extracting the vegetation area through 8-class land cover classification and performing the vegetation species classification. The image classification algorithm used Random Forest to evaluate the accuracy and calculate feature importance through Out-Of-Bag(OOB). To identify the advantages of multi- temporary Sentinel-2 for vegetation classification, the overall accuracy was compared according to the number of images stacked and vegetation spectral index. Overall accuracy was 77% when using single-time Sentinel-2 images, but improved to 81% when using multi-time Sentinel-2 images. In addition, the overall accuracy improved to about 83% in learning when the vegetation index was used additionally. The most important spectral variables to distinguish between vegetation classes are located in the Red, Green, and short wave infrared-1(SWIR1). This research can be used as a basic study that optimizes input characteristics in performing the classification of vegetation in the polar regions.

• Journal of the Korean Association of Geographic Information Studies
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• v.24 no.1
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• pp.92-111
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• 2021

As fine dust negatively affects disease, industry and economy, the people are sensitive to fine dust. Therefore, if the occurrence of fine dust can be predicted, countermeasures can be prepared in advance, which can be helpful for life and economy. Fine dust is affected by the weather and the degree of concentration of fine dust emission sources. The industrial sector has the largest amount of fine dust emissions, and in industrial complexes, factories emit a lot of fine dust as fine dust emission sources. This study targets regions with old industrial complexes in local cities. The purpose of this study is to explore the factors that cause fine dust and develop a predictive model that can predict the occurrence of fine dust. weather data and fine dust data were used, and variables that influence the generation of fine dust were extracted through multiple regression analysis. Based on the results of multiple regression analysis, a model with high predictive power was extracted by learning with a machine learning regression learner model. The performance of the model was confirmed using test data. As a result, the models with high predictive power were linear regression model, Gaussian process regression model, and support vector machine. The proportion of training data and predictive power were not proportional. In addition, the average value of the difference between the predicted value and the measured value was not large, but when the measured value was high, the predictive power was decreased. The results of this study can be developed as a more systematic and precise fine dust prediction service by combining meteorological data and urban big data through local government data hubs. Lastly, it will be an opportunity to promote the development of smart industrial complexes.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.103-110
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• 2020

In the recent seismic design code KDS 41 17 00, selection and modification procedures of ground motions which are used for nonlinear dynamic analyses were adopted. However, its practical applications are still limited due to the lack of literatures. This paper introduces case studies which used site-response analyses to select and modify ground motions for nonlinear dynamic analyses. Based on the case studies, design criterion for site-response analyses were reviewed thoroughly in the viewpoint of practical applications. It was found that design requirements related with bedrock motions are too conservative that ground motions are selected and modified in the excessive manner. It is especially true for low-rise building structures with period ranges including acceleration-sensitive regions. Even though surface motions have shown appropriate responses, such building structures have to re-select and re-modify ground motions based on pre-analysis procedures rather than post-ones according to the current seismic design code. Also, it was observed that building structures with soft soils under strong ground motions need more comprehensive investigations on soil properties and efficient analysis methods in order to perform site-response analyses. This is due to the fact that lack of reliabilities on soil properties and analysis methods could result in unstable site-responses.

• Journal of Ecology and Environment
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• v.48 no.1
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• pp.17-23
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• 2024

Background: Honey bees play a crucial role in pollination and ecological balance. Apis mellifera L. colonies, especially those located in specific geographic regions, such as the palm garden in Eastern Thailand, are susceptible to potential threats from microbial contaminants. Understanding and detecting microbial organisms in these beehives is essential for the preservation of bee health, honey production, and the broader ecosystem. However, the problem of microbial infection and antibiotic-resistant bacteria is more severe and continuously increasing, resulting in a health, economic, and social crisis. The purpose of this study is to determine the prevalence of microorganisms in A. mellifera beehives in palm gardens in Rayong province, Eastern Thailand. Results: Ten swabs in transport media were swabbed and obtained from different parts of each beehive (1 swab per beehive), for a total of 10 hives. Traditional microbial culture-based methods, biochemical tests, and antimicrobial susceptibility (disc-diffusion) tests were used to detect microbial organisms and antibiotic resistance in bacteria. The swab tests from nine beehives resulted in the detection of Gram-positive bacteria (63.64%), Gram-negative bacteria (27.27%), and fungi/yeast (9.09%). These microorganisms are classified as a group of coagulase-negative Staphylococcus spp. and made up 40.91% of the bacteria discovered. Other bacteria found were Coryneform bacteria (13.64%), Pantoea spp. (13.64%), Bacillus spp. (9.09%), yeast (9.09%), glucose non-fermentative Gram-negative bacilli (9.09%), and Pseudomonas spp. (4.55%). However, due to the traditional culture-based and 0biochemical tests usually used to identify the microbial organisms in clinical specimens and the limitation of identifying some environmental microbial species, the results of the antimicrobial susceptibility test cannot reveal if the organism is resistant or susceptible to the drug. Nevertheless, drug-sensitive inhibition zones were formed with each antibiotic agent. Conclusions: Overall, the study supports prevention, healthcare, and public health systems. The contamination of microorganisms in the beehives may affect the quality of honey and other bee products or even the health of the beekeeper. To avoid this kind of contamination, it is therefore necessary to wear personal protective equipment while harvesting honey and other bee products.

• Childhood Kidney Diseases
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• v.14 no.2
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• pp.174-183
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• 2010

Purpose : The organisms causing peritonitis and their antibiotic sensitivities vary in different regions and centers, and these data are necessary to establish regional treatment guidelines. The aim of this study was to investigate the changes in incidence and characteristics of the organisms that cause peritonitis in children undergoing peritoneal dialysis (PD) during recent 10 years. Methods : We retrospectively collected and analyzed the data from medical records of 110 children on PD during the period from 2000 to 2010. Results : One hundred and forty episodes of peritonitis have occurred in 57 patients. The overall incidence of peritonitis was 0.43 episodes/patient year, and similar incidence have been maintained since 2003. Sixty percent of the patients experienced peritonitis within 1 year of PD, and all patients commencing PD in infancy experienced peritonitis. Gram positive (G (+)), gram negative (G (-)) organisms and fungi were cultured in 58%, 38%, and 4.1% respectively and cultures were negative in 13.6%. Staphylococcus was the most common G (+) organism, and Pseudomonas and Acinetobacter were 2 most frequent G (-) organisms isolated. Fifty-six percent of the G (+) organisms were sensitive to first generation cephalosporin and 91% of G (-) pathogens were sensitive to ceftazidime. Methicillin-resistance rate was not higher in children less than 2 years of age than in those more than 2 years. Conclusion : An additional breakthrough has to be made to further reduce the incidence of peritonitis. Treatment guideline customized for peritonitis in Korean children on PD need to be established through a nationwide co-work.

• Journal of Wetlands Research
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• v.22 no.1
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• pp.8-14
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• 2020

This study was carried out to compare the Snout-vent length (SVL) and the biomass for the endangered species II, narrow-mouthed toad (Kaloula borealis), at the three different latitude sites (Seoul, Nonsan, Busan) in Korea. For the narrow-mouthed toad study, pitfall traps and inducement traps were used to catch the species, and environmental factors (temperature, precipitation, humidity) were compared by region. As a result of this study, each of the male narrow-mouthed toads' SVL and biomass in Busan was 41.6±0.39mm, and 11.3±0.17g, which showed that it was the biggest and heaviest among the three regions. For Seoul and Nonsan, each of the SVL of the female narrow-mouthed toad was 36.6±2.03mm, 36.6±1.76mm, and the biomass was 8.1±0.55g, 8.2±0.91g, which showed that there was no significant difference between Seoul and Nonsan. Each of the female narrow-mouthed frogs' SVL and biomass in Busan was 44.7±0.35mm, 13.1±0.18g, which was also biggest but showed no significant difference in biomass by region. Concluding, this showed that the female narrow-mouthed toad in Busan is larger and heavier than those of other regions. We hope this study will be a standard for the future amphibian research with comparing the SVL and biomass for the endangered species II, narrow-mouthed toad. It is expected that if this kind of study keeps for long, it will be a basis for understanding changes in biomass of amphibian species due to climate change.

• Journal of Environmental Impact Assessment
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• v.26 no.1
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• pp.27-43
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• 2017

The objectives of the study were to evaluate fish compositions, endangered species, community structure, physical habitat, and general water quality for a preliminary environmental impact assessment of Jeokbyeok River on the road construction between two regions. Total number of species and total number of individuals, based on CPUE, were 23 and 1186, respectively. The endangered species (I, II) as the legal protection species were Pseudopungtungia nigra (79 samples) Gobiobotia brevibarba) (5) Gobiobotia macrocephala (2), indicating a requiring of endangered species conservation. In the meantime, exotic species and ecological disturbing species such as Micropterus salmoides and Lepomis macrochirus, were not present, indicating a well conserved area. According to fish community analysis, values of species diversity index were high (range: 0.788 - 1.030), and the dominance index were low (range: 0.097 - 0.183), indicating that the fish community in this area was maintained well without high dominacne by specific species. Also, fish analysis on tolerance guilds and trophic guilds showed that the proportions of sensitive species were largely exceeded the proportions of the tolerant species, while the proportions of insectivore species were largely exceeded the proportions of the omnivore species. This outcome suggests that the ecosystem was well maintained in terms of tolerance and trophic compositions (food chain). Ecological health, based on the multi-metric fish model of Fish Assessment Integrity (FAI), reflected those fish conditions. In other words, values of FAI model averaged 82.4, which means a "good condition" in the criteria of ecological health by the Minstry of Environment, Korea. In addition, general water quality and physical habitat analyses showed that the system was in good condition. Under these conditions, if the road constructions between the two regions happen in the future, inorganic suspended solids may increase in the waterbody, and this may result in indirect or direct influences on the physical habitats and food chain as well as fish compositions, so the ecological protections and prevention strategy from the soil erosion are required in the system.