• Geomechanics and Engineering
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• v.33 no.1
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• pp.101-112
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• 2023

When a submerged floating tunnel is connected to the ground, there is a risk of stress concentration at the shore connection owing to the displacement imbalance caused by low confinement pressures in water and high confinement pressures in the ground. Here, the effects of the boundary condition and stiffness of the joints installed at the shore connection on the behaviors of a submerged floating tunnel and its shore connection were analyzed using a numerical method. The analysis results obtained with fixed and ground boundaries were similar due to the high stiffness of the ground boundary. However, the stability of the shore connection was found to be improved with the ground boundary as a small displacement was allowed at the boundary. The effect of the joint stiffness was evaluated by investigating the dynamic behavior of the submerged floating tunnel, the magnitude of the load acting on the bored tunnel, and the stress distribution at the shore connection. A lower joint stiffness was found to correspond to more effective relief of the stress concentration at the shore connection. However, it was confirmed that joints with low stiffness also increase the submerged floating tunnel displacement and decrease the frequency of the dynamic behavior, causing a risk of increased resonance when wave loads with low frequency are applied. Therefore, it is necessary to derive the optimal joint stiffness that can achieve both stress concentration relief and resonance prevention during the design of shore connections to secure their dynamic stability.

• Korean Journal of Materials Research
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• v.33 no.8
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• pp.344-351
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• 2023

Cesium lead iodide (CsPbI₃) with a bandgap of ~1.7 eV is an attractive material for use as a wide-gap perovskite in tandem perovskite solar cells due to its single halide component, which is capable of inhibiting halide segregation. However, phase transition into a photo inactive δ-CsPbI₃ at room temperature significantly hinders performance and stability. Thus, maintaining the photo-active phase is a key challenge because it determines the reliability of the tandem device. The dimethylammonium (DMA)-facilitated CsPbI₃, widely used to fabricate CsPbI₃, exhibits different phase transition behaviors than pure CsPbI₃. Here, we experimentally investigated the phase behavior of DMA-facilitated CsPbI₃ when exposed to external factors, such as heat and moisture. In DMA-facilitated CsPbI₃ films, the phase transition involving degradation was observed to begin at a temperature of 150 ℃ and a relative humidity of 65 %, which is presumed to be related to the sublimation of DMA. Forming a closed system to inhibit the sublimation of DMA significantly improved the phase transition under the same conditions. These results indicate that management of DMA is a crucial factor in maintaining the photo-active phase and implies that when employing DMA designs are necessary to ensure phase stability in DMA-facilitated CsPbI₃ devices.

• Journal of the Korean Society of Food Culture
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• v.38 no.4
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• pp.217-223
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• 2023

There has been an increase in the viewing of YouTube content among children and adolescents. This, coupled with the popularity of live-streamed video content such as mukbang, where viewers watch the host eat, has raised concerns about media addiction and the indiscriminate imitation of eating behavior. Therefore, there is a need for guidance on the appropriate behavior for viewing YouTube food content to promote healthy eating habits among children. In this study, we aimed to compare the patterns of the main caregivers and their children while viewing media and investigate the impact of viewing YouTube food content on the physical and mental health of the children. The findings suggest that active YouTube food content viewing by the main caregivers may reduce imitative behaviors due to passive media consumption by their children. This study provides valuable insights by comparing and analyzing the YouTube content viewing of the main caregivers and their children. The results can be used as a basis for the development of lifestyle-centered guidelines for children. However, it is important to note that this study was conducted during the coronavirus disease (COVID-19) pandemic when there was a significant increase in the use of media, which is limitation of the study.

• Geomechanics and Engineering
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• v.33 no.2
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• pp.133-140
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• 2023

Soil erosion can cause scouring and failures of underwater structures, therefore, various soil improvement techniques are used to increase the soil erosion resistance. The microbially induced calcium carbonate precipitation (MICP) method is proposed to increase the erosion resistance, however, there are only limited experimental and numerical studies on the use of MICP treatment for improvement of surface erosion resistance. Therefore, this study investigates the improvement in surface erosion resistance of sands by MICP through laboratory experiments and numerical modeling. The surface erosion behaviors of coarse sands with various calcium carbonate contents were first investigated via the erosion function apparatus (EFA). The test results showed that MICP treatment increased the overall erosion resistance, and the contribution of the precipitated calcium carbonate to the erosion resistance and critical shear stress was quantified in relation to the calcium carbonate contents. Further, these surface erosion processes occurring in the EFA test were simulated through the coupled computational fluid dynamics (CFD) and discrete element method (DEM) with the cohesion bonding model to reflect the mineral precipitation effect. The simulation results were compared with the experimental results, and the developed CFD-DEM model with the cohesion bonding model well predicted the critical shear stress of MICP-treated sand. This work demonstrates that the MICP treatment is effective in improving soil erosion resistance, and the coupled CFD-DEM with a bonding model is a useful and promising tool to analyze the soil erosion behavior for MICP-treated sand at a particle scale.

• Computers and Concrete
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• v.31 no.4
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• pp.349-358
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• 2023

This paper describes an in-depth analysis on flexural strength of a girder-deck system experiencing a strand debonding damage with various strengthening systems, based on finite element software ABAQUS. A detailed finite element analysis (FEA) model was developed and verified against the relevant experimental data performed by other researchers. The proposed analytical model showed a good agreement with experimental data. Based on the verified FE model, over a hundred girder-deck systems were investigated with the consideration of following variables: 1) debonding level, 2) span-to-depth ratio (L/d), 3) strengthening type, 4) strengthening material thickness. Based on the data above, a new detailed analytical model was developed and proposed for estimating residual flexural strength of the strand-debonding damaged girder-deck system with strengthening systems. It was demonstrated that both finite element model and analysis model could be used to predict flexural behaviors for debonding damaged prestressed girder-deck systems. Since the strands are debonding from surrounding concrete over a certain zone over the length of the beam, the increase of strain in strands can be linked with a ratio ψ, which is L_p/c. The analytical model was proposed and developed regarding the ratio ψ. By conducting procedure of calculating ψ, the ψ value varies from 9.3 to 70.1. Multiple nonlinear regression analysis was performed in Software IBM SPSS Statistics 27.0.1 to derive equation of ψ. ψ equation was curved to be an exponential function, and the independent variable (X) is a linear function in terms of three variables of debonding level (λ), span length (L), and amount of strengthening material (A_s). The coefficient of determinate (R²) for curve fitting in nonlinear regression analysis is 0.8768. The developed analytical model was compared to the ultimate capacities computed by FEA model.

• Korean Journal of Community Nutrition
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• v.28 no.2
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• pp.141-159
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• 2023

Objectives: This study aimed to determine whether a mobile health (mhealth) intervention is effective in reducing weight and changing dietary behavior among employees with overweight and obesity. The study also investigated whether engagement with the intervention affected its effectiveness. Methods: The intervention involved the use of a dietary coaching app, a wearable device for monitoring physical activity and body composition, and a messenger app for communicating with participants and an intervention manager. A total of 235 employees were recruited for a 12-week intervention from eight workplaces in Korea. Questionnaire surveys, anthropometric measurements, and 24-h dietary recalls were conducted at baseline and after the intervention. Results: After the intervention, significant decreases in the mean body weight, body mass index, body fat percentage, and waist circumference were observed. Furthermore, the consumption frequencies of multigrain rice and legumes significantly increased, whereas those of pork belly, instant noodles, processed meat, carbonated beverages, and fast food significantly decreased compared with those at baseline. The mean dietary intake of energy and most nutrients also decreased after the intervention. When the participants were categorized into three groups according to their engagement level, significant differences in anthropometric data, dietary behaviors, and energy intake were observed following the intervention, although there were no differences at baseline, indicating that higher engagement level led to greater improvements in weight loss and dietary behavior. Conclusions: The intervention had positive effects on weight loss and dietary behavior changes, particularly among employees with higher engagement levels. These results indicate the importance of increasing the level of engagement in the intervention to enhance its effectiveness. The mhealth intervention is a promising model for health promotion for busy workers with limited time.

• Women's Health Nursing
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• v.28 no.1
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• pp.65-73
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• 2022

Purpose: This study investigated Korean healthcare providers' attitudes toward sexual and gender minority (SGM) persons and their knowledge and behavior concerning the collection of data on sexual orientation and gender identity (SO/GI). Methods: In this cross-sectional, descriptive study, 137 Korean healthcare providers were recruited through convenience sampling from internet communities for medical professionals. A structured questionnaire was created using Google Surveys. The Mann-Whitney U-test, Kruskal-Wallis test, and Spearman correlation analysis were performed. Results: The sample was mostly women (80.3%) and nurses (83.9%), who had overall negative attitudes toward SGM persons and low levels of knowledge and behavior with regard to the collection of patients' SO/GI data. Participants in their 20s, who were religious, and had clinical experiences in treating or providing nursing care for SGM persons had higher levels of knowledge about the collection of SO/GI data. The level of engagement in collecting SO/GI data was higher among women and in their 20s and 30s, unreligious participants, nurses, and those with less than 10 years of clinical experience. Positive attitudes toward SGM persons were associated with higher levels of knowledge, but lower levels of behavior, regarding the collection of SO/GI data. Conclusion: It is important to recognize the diversity of patients' SO/GI and to collect the corresponding information. To this end, it is necessary to develop and use a standardized SO/GI form. Healthcare providers should also receive education and training related to the health of SGM persons to resolve health problems that disproportionately affect SGM persons and related health disparities.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.8 no.1
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• pp.867-874
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• 2018

This study aims to develop a sort of expert system to simulate Internet of Things (IoT) service in architectural design alternatives and enhance the simulation performance using building information. The proposed protype system, named iotBIM, visualizes human behaviors and IoT services in a virtual place that is automatically generated from among design alternatives. We use commercial building information modeling (BIM) authoring tool for the development of iotBIM. The decision to develop iotBIM on the BIM platform was made because BIM tools already generate precise 3D models of design alternatives; iotBIM is plugged into the BIM tool as a simulation module. In the midst of the design process, architectural designers can activate iotBIM to investigate and establish IoT services that accord visually with design alternatives. The purpose of this study is to provide a theoretical and technological basis for the ultimate goal of this study.

• Journal of the Korean Society for information Management
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• v.40 no.2
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• pp.33-57
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• 2023

This study aims to analyze students' information needs and information-seeking behavior at science schools for gifted through in-depth interviews. The research design was conducted based on previous studies. Through in-depth interviews, this study examined ten students from six out of eight science schools for the gifted in Korea for information needs and overall information-seeking behavior. The results showed the information needs of students at science schools for gifted in the areas of curricular and extracurricular activities as well as the information-seeking behavior in teaching, learning, and research activities, which were the main topics of interest to students based on the ISP model. Based on these results, we identified the preferred information sources in the information-seeking process and discussed the peculiarities and implications of students' information-seeking behavior. The research is meaningful as it can be used as a basis for further research on the science school for gifted library and as a resource for providing services for students with deep interests and talents in science subject areas.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2B
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• pp.155-162
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• 2009

Univariate frequency analyses are widely used in practical hydrologic design. However, a storm event is usually characterized by amount, intensity, and duration of the storm. To fully understand these characteristics and to use them appropriately in hydrologic design, a multivariate statistical approach is necessary. This study applied a Gumbel mixed model to a bivariate storm frequency analysis using hourly rainfall data collected for 46 years at the Seoul rainfall gauge station in Korea. This study estimated bivariate return periods of a storm such as joint return periods and conditional return periods based on the estimation of joint cumulative distribution functions of storm characteristics. These information on statistical behaviors of a storm can be of great usefulness in the analysis and assessment of the risk associated with hydrologic design problems.