• Journal of Radiation Industry
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• v.18 no.3
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• pp.183-193
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• 2024

As part of the social response to the radon bed incident in 2018, the Nuclear Safety and Security Commission took measures to collect and dispose of all radon beds. The Waste Management Act provides landfill disposal as one of the disposal methods for natural radioactive product waste, which is one of the NORM wastes. When NORM wastes are landfilled, workers and the public at the landfill site are exposed to radiation through various pathways, such as leaching of radionuclides through soil and groundwater, and multiple exposure factors are involved simultaneously. In order to improve the reliability of radiological impact assessment, the values of main exposure factors should be selected more accurately. Therefore, before developing the main exposure factors for site characteristics, it is necessary to prioritize main exposure factors reflecting domestic characteristics of NORM waste landfills. Therefore, in this study, the main exposure factors for NORM waste landfill were derived using NDD analysis. To derive the main exposure factors, the analysis tool was first selected as RESRAD-ONSITE computer code, and the exposure scenarios were mainly selected as a resident farmer and suburban resident scenario, recreation scenario, and industrial worker scenario. Then, the priority 1 and 2 factors were selected for sensitivity analysis, and a Korean standard model was established to reflect Korean characteristics. Finally, the sensitivity analysis was conducted through NDD, and the main exposure factors were derived based on this. In the resident farmer scenario, the contaminated zone distribution coefficients of ²²⁶Ra, ²¹⁰Pb, ²³²Th, ²²⁸Ra, ²³⁴U, and ²³⁸U, as well as precipitation and evapotranspiration factors, were derived as the main exposure factors. In the suburban resident scenario, the contaminated zone distribution coefficients of ²²⁶Ra, ²¹⁰Pb, ²³²Th, ²²⁸Ra, ²³⁴U, and ²³⁸U, as well as precipitation and evapotranspiration coefficients, were derived as the main exposure factors. In the recreation scenario, the contaminated zone distribution coefficient of ²³²Th was derived as the main exposure factor. For the industrial worker scenario, the erosion rate was derived as the main exposure factor. The main exposure factors for each scenario were analyzed to be different depending on the scenario characteristics. The results of this study can be utilized as a basis for radiological environmental impact assessment of NORM waste landfill in Korea.

• The Mathematical Education
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• v.63 no.3
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• pp.437-450
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• 2024

Self-directed learning in mathematics education is crucial because it enables students to think creatively and critically while continuously improving. The purpose of this study was to examine the mediating effects of class attitude and class satisfaction in mathematics on the relationship between mathematics teacher characteristics and self-directed learning. Furthermore, the study aimed to determine whether these structural relationships differ between male and female student groups. To achieve this, the theoretical model was tested using the 9th-year data (high school 3rd grade) of the Seoul Education Longitudinal Study (SELS) 2010, comprising 2,325 students (1,187 males and 1,138 females). The results revealed that the mediating effects of mathematics class attitude and class satisfaction on the relationship between teacher characteristics in mathematics and high school students' self-directed learning were significant. At this time, the direct effect of mathematics teacher characteristics on selfdirected learning was not significant, indicating that mathematics class attitude and class satisfaction had full mediating effects. Multi-group analysis results showed no significant differences in path coefficients between male and female student groups. Based on the research findings, implications for teacher education were presented to improve high school students' self-directed learning abilities in mathematics education, focusing on the mediating effects of affective factors in the classroom.

• Economic and Environmental Geology
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• v.57 no.4
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• pp.353-362
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• 2024

This study examined the spectral characteristics of sediments according to moisture content using an unmanned aerial vehicle (UAV)-based hyperspectral sensor and evaluated the efficiency of moisture content detection at different flight altitudes. For this purpose, hyperspectral images in the 400-1000nm wavelength range were acquired and analyzed at altitudes of 40m and 80m for sediment samples with various moisture contents. The reflectance of the sediments generally showed a decreasing trend as the moisture content increased. Correlation analysis between moisture content and reflectance showed a strong negative correlation (r < -0.8) across the entire 400-900nm range. The moisture content detection model constructed using the Random Forest technique showed detection accuracies of RMSE 2.6%, R² 0.92 at 40m altitude and RMSE 2.2%, R² 0.95 at 80m altitude, confirming that the difference in accuracy between altitudes was minimal. Variable importance analysis revealed that the 600-700nm band played a crucial role in moisture content detection. This study is expected to be utilized in efficient sediment moisture management and natural disaster prediction in the field of environmental monitoring in the future.

• Journal of Bio-Environment Control
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• v.33 no.3
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• pp.172-177
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• 2024

Many studies have reported that mealworms can ingest plastic during their larval stage. The purpose of this study was to investigate the effects of expanded polystyrene consumption on the growth and development of mealworms during their larval stage. We found that the growth rate is significantly different between mealworms consumed wheat bran and mealworms consumed expanded polystyrene (p < 0.001). The transformation into pupa occurred faster among the mealworms consumed expanded polystyrene than those consumed wheat bran (p < 0.001). However, the survival rate was not significantly different between the two groups of mealworms (p = 0.786). Based on the data, we conclude that mealworms consuming expanded polystyrene have a slower weight gain and a shorter development period than mealworms consuming wheat bran, but the expanded polystyrene does not affect the survival rate before the transformation into pupa. Practically, we anticipate that mealworms can be a resource for the sustainable and eco-friendly removal of expanded polystyrene waste.

• Nuclear Engineering and Technology
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• v.56 no.8
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• pp.3307-3314
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• 2024

For traditional spent fuel shielding materials, due to physical and chemical defects and cost constraints, they have been unable to meet the needs. Therefore, this paper carries out the first discussion on the application and performance of bismuth in neutron shielding by establishing Monte Carlo simulation on the neutron flux model of shielded spent fuel. Firstly, functional fillers such as bismuth oxide, lead oxide, boron oxide, gadolinium oxide and tungsten oxide are added to the matrices to compare the shielding rates of aluminum alloy matrix and silicone rubber matrix. The shielding rate of silicone rubber mixture is higher than aluminum alloy mixture, reaching more than 56%. The optimal addition proportion of bismuth oxide and lead oxide is 30%, and the neutron radiation protection efficiency reaches 60%. Then, the mass attenuation coefficients of bismuth oxide, lead oxide, boron oxide, gadolinium oxide and tungsten oxide in silicone rubber matrix are simulated with the change of functional fillers proportion and neutron energy. This simulation result shows that the mixture with functional fillers has good shielding performance for low energy neutrons, but poor shielding effect for high energy neutrons. Finally, in order to further evaluate the possibility of replacing lead oxide with bismuth oxide as shielding material, the half-value layers and various properties of bismuth oxide and lead oxide are compared. The results show that the shielding properties of bismuth oxide and lead oxide are basically the same, and the mechanical properties, heat resistance, radiation resistance and environmental protection of bismuth oxide are better than that of lead oxide. Therefore, in the case of neutron source strengths in the range of 0.01-6 MeV and secondary gamma rays produced below 2.5 MeV, bismuth can replace lead in neutron shielding applications.

• Journal of the Korean Regional Science Association
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• v.40 no.3
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• pp.75-93
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• 2024

This study examines the impact of moving to an opportunity-rich area on an individual's wage income to identify the relationship between regional disparities in opportunities throughout a person's life cycle and life outcomes. Based on the Graduate Occupational Mobility Survey (GOMS) provided by the Korea Employment Information Service, individuals with similar life experience prior to regional mobility were selected and analyzed using the Propensity Score Matching (PSM) method. Specifically, the life cycle was classified into stages such as pre-high school, university entrance period, and employment period. Then, a path model was established to analyze regional mobility, education, employment, and wage income by life cycle stage. The analysis results indicate that the life cycle stage where regional mobility had the greatest impact on an individual's economic performance, that is, the stage where the impact of opportunity disparities was most unequal, was the university entrance period. Additionally, moving to an opportunity-rich area was a critical factor that cumulatively affected subsequent life. Hence, pre-high school mobility was also noteworthy as it induced life in the central area later on. Lastly, while parental income itself was influential, but when combined with regional mobility, it could act as a means of transferring wealth to the next generation. These results suggest that the state should strive to alleviate the regional imbalance around universities by fostering universities outside the capital region and reduce the possibility of the influence of parents' socio-economic background on regional mobility.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.17 no.5
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• pp.339-350
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• 2024

In construction sites, the engine of heavy machinery is tested by practitioners who manually adjust engine settings and directly measure the output. This process has consistently raised concerns regarding time costs and the risk of incidents. To address these issues, simulations of heavy equipment are conducted using Speedgoat and the Simulink API. However, due to the varying compatibility of different versions of Speedgoat hardware and Simulink API, engineers need to have a comprehensive understanding of various Simulink APIs. It is practically challenging for engineers, who must have a deep understanding of heavy equipment structures, to also possess programming skills including API usage. Thus, this paper proposes a tool that allows inputting configuration values for heavy equipment simulation and visually outputs and logs the simulation results. The proposed tool provides functionalities to deliver configuration values, such as engine settings of heavy equipment, to the simulator model and to monitor and log the resulting simulation outputs. These functionalities have been validated through scenarios. By using the developed tool, engineers are expected to reduce the burden of learning Simulink API and focus more on understanding the structure of heavy equipment. Additionally, it is anticipated that this tool will provide a more efficient and safer working environment for heavy equipment testing on construction sites.

• Journal of the Korea Society of Computer and Information
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• v.29 no.10
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• pp.69-75
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• 2024

Noise caused by adverse weather conditions in data collected during autonomous driving can lead to object recognition errors, potentially resulting in critical accidents. While this risk is widely acknowledged, there is a lack of research that quantitatively and systematically analyzes it. Therefore, this study aims to examine and quantify the extent to which noise affects object detection in autonomous driving environments. To this end, we utilized the YOLO v5 model trained on unprocessed datasets. The test data were divided into noise ratios of 0% (Original), 20%, 40%, 60%, and 80%, and the detection results were evaluated by constructing a Confusion Matrix. Experimental results show that as the noise ratio increases, the True Positive (TP) rate decreases, and the F1-score also significantly drops across all noise levels, specifically from 0.69 to 0.47, 0.29, 0.18, and 0.14. These findings are expected to contribute to enhancing the stability of autonomous driving technology. Future research will focus on collecting real datasets that include naturally occurring noise and developing more effective noise removal techniques.

• 산업혁신연구
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• v.36 no.1
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• pp.133-163
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• 2020

This study is designed to see whether overpriced IPO is caused from firm's earnings management, and how effects this to IPO firm's long-term performance. To examine addressed above, we take a look into how firm's earning quality listing on Korea Exchange in 2007 through 2016 is related with long-term stock performance post IPO. Especially, we measure how associated the disparate ratio between offer price and fair price with earnings quality and long-term performance. To examine these three factors, 'three-step mediated regression analysis method' is used. Earnings quality's calculated by discretionary accruals. Disparate ratio is calculated with offer price and estimating share price's rate measured by applying relative valuation model. To sum up, it is as follows. At first, as earnings quality gets high, the disparate ratio between offer price and fair price gets reduced. Secondly, as earnings quality gets high, firm's long term stock performance follows high. At last, as the disparate ratio between offer price and fair price gets increased, firm's long-term stock performance gets decreased. Moreover, mediation effect of the disparate ratio between offer price and fair price is partially found. Thus, it addresses that raised earnings revision before listing is resulted in overpricing of the IPO, and it also leads to poor long term stock performance. This study contributes that empirical analysis is applied to examine long-term under performance using disparate ratio between offer price and fair price. Moreover, this is useful not only to alert investors to risky investing pattern, but to provide informative reference to financial institutions in making policies or decisions about IPO.

• Journal of the Korean Applied Science and Technology
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• v.41 no.4
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• pp.1020-1030
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• 2024

The purpose of this study was to examine the relationship between academic stress, drinking related knowledge, and drinking refusal self-efficacy among nursing students, and to identify the influencing factors nursing students' drinking refusal self-efficacy. Data were collected from September 10, 2023 to October 10, 2023 after receiving informed consent from 187 nursing students enrolled in J University in C Province. The collected data were analyzed using descriptive statistics, ANOVA, t-test, Pearson's correlation analysis, and multiple regression analysis according to the characteristics of variables using the SPSS/WIN 28.0 program. The results of the study showed that nursing students' drinking refusal self-efficacy was positively correlated with drinking-related knowledge (r=.21, p=.004) and negatively correlated with academic stress (r=-.21, p=.005). The factors affecting the drinking refusal self-efficacy of nursing students were identified as academic stress (𝛽=-.17, p=.016), drinking related knowledge (𝛽=.21, p=.003), and smoking status (𝛽=.19, p=.008), and the regression model was statistically significant (F=8.30, p<.001), with an explanatory power of 11.0%. Based on the above results, it is necessary to prepare a program to reduce academic stress and increase drinking-related knowledge in order to improve the drinking refusal self-efficacy of nursing students. In addition, including smoking cessation strategies for college students in the program can help increase their drinking refusal self-efficacy.