• Journal of Christian Education in Korea
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• v.64
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• pp.203-235
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• 2020

The purpose of this study is to identify the degree of social presence perceived by students and to explore the factors that have affected it after practicing Christian Education classes as synchronous distance course due to Covid-19. It is also to suggest effective ways in the aspects of the design and operation to improve social presence. In order to measure social presence and derive influencing factors, research related to synchronous distance class and social presence is summarized through literature review. The researchers also surveyed 58 students in three courses of Christian education major at a University in Gyeonggi-do and conducted in-depth interviews with 6 students. The main findings are as follows: First, the sense of social presence was moderate, the emotional bond was the lowest by sub-factor, the open communication, the sense of community was moderate, and the mutual support and concentration were the highest. Second, factors that had a positive impact on the sense of social reality were group activities, selfintroduction activities, active participation in classes, mutual communication such as Q & A or response to peer learners' opinions during lectures by professors, questions, feedback, etc, and having a smaller number of students. Factors that had a negative impact on the perception of social presence were lack of private conversations, poor participation in classes, lack of communication with each other, and difficulty concentrating. The causes of these negative factors were technical problems and limitations arising from zoom, inconvenience and distracting surroundings, lack of time, and psychological awkwardness. Reflecting the results of the study, orientation to effective synchronous distance course, guidance on smooth communication methods, strengthening the role of professors to promote learning, strengthening group activities and learner-centered activities, and proposing a smaller scale of students were ways that are offered to improve the sense of social presence in synchronous distance courses.

• Toxicological Research
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• v.17
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• pp.47-57
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• 2001

Alzheimer's disease (AD) is the most common cause of dementia in the elderly, and its pathology is characterized by the presence of numerous numbers of senile plaques and neurofibrillary tangles. Several genetic and transgenic studies have indicated that excess amount of $\beta$-amyloid protein (A$\beta$) is produced by mutations of $\beta$TEX>$\beta$-amyloid precursor protein and causes learning impairment. Moreover, $A\beta$ has a toxic effect on cultured nerve cells. To prepare AD model animals, we have examined continuous (2 weeks) infusion of $A\beta$ into the cerebral ventricle of rats. Continuous infusion of $A\beta$ induces learning impairment in water maze and passive avoidance tasks, and decreases choline acetyltransferase activity in the frontal cortex and hippocampus. Immunohistochemical analysis revealed diffuse depositions of $A\beta$ in the cerebral cortex and hippocampus around the ventricle. Furthermore, the nicotine-evoked release of acetylcholine and dopamine in the frontal cortex/hippocampus and striatum, respectively, is decreased in the $A\beta$-infused group. Perfusion of nicotine (50 $\mu\textrm{M}$) reduced the amplitude of electrically evoked population spikes in the CA1 pyramidal cells of the control group, but not in those of the $A\beta$-infused group, suggesting the impairment of nicotinic signaling in the $A\beta$-infused group. In fact, Kd, but not Bmax, values for ［$^3H$］ cytisine binding in the hippocampus significantly increased in the $A\beta$-infused rats. suggesting the decrease in affinity of nicotinic acetylcholine receptors. Long-term potentiation (LTP) induced by tetanic stimulations in CA1 pyramidal cells, which is thought to be an essential mechanism underlying learning and memory, was readily observed in the control group, whereas it was impaired in the $A\beta$-infused group. Taken together, these results suggest that $A\beta$ infusion impairs the signal transduction mechanisms via nicotinic acetylcholine receptors. This dysfunction may be responsible, at least in part, for the impairment of LTP induction and may lead to learning and memory impairment. We also found the reduction of glutathione- and Mn-superoxide dismutase-like immunoreactivity in the brains of $A\beta$-infused rats. Administration of antioxidants or nootropics alleviated learning and memory impairment induced by $A\beta$ infusion. We believe that investigation of currently available transgenic and non-transgenic animal models for AD will help to clarify the pathogenic mechanisms and allow assessment of new therapeutic strategies.

• Journal of the Korea Computer Graphics Society
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• v.25 no.3
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• pp.11-20
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• 2019

In this study, a novel virtual reality (VR) experience environment is proposed for enabling walking adaptation of visually impaired people. The core of proposed VR environment is based on immersive walking interactions and deep learning based braille blocks recognition. To provide a realistic walking experience from the perspective of visually impaired people, a tracker-based walking process is designed for determining the walking state by detecting marching in place, and a controller-based VR white cane is developed that serves as the walking assistance tool for visually impaired people. Additionally, a learning model is developed for conducting comprehensive decision-making by recognizing and responding to braille blocks situated on roads that are followed during the course of directions provided by the VR white cane. Based on the same, a VR application comprising an outdoor urban environment is designed for analyzing the VR walking environment experience. An experimental survey and performance analysis were also conducted for the participants. Obtained results corroborate that the proposed VR walking environment provides a presence of high-level walking experience from the perspective of visually impaired people. Furthermore, the results verify that the proposed learning algorithm and process can recognize braille blocks situated on sidewalks and roadways with high accuracy.

• KIPS Transactions on Software and Data Engineering
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• v.12 no.2
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• pp.99-110
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• 2023

This study proposed a classification of malicious network traffic using the cyber threat framework(Mitre ATT&CK) and machine learning to solve the real-time traffic detection problems faced by current security monitoring systems. We applied a network traffic dataset called UNSW-NB15 to the Mitre ATT&CK framework to transform the label and generate the final dataset through rare class processing. After learning several boosting-based ensemble models using the generated final dataset, we demonstrated how these ensemble models classify network traffic using various performance metrics. Based on the F-1 score, we showed that XGBoost with no rare class processing is the best in the multi-class traffic environment. We recognized that machine learning ensemble models through Mitre ATT&CK label conversion and oversampling processing have differences over existing studies, but have limitations due to (1) the inability to match perfectly when converting between existing datasets and Mitre ATT&CK labels and (2) the presence of excessive sparse classes. Nevertheless, Catboost with B-SMOTE achieved the classification accuracy of 0.9526, which is expected to be able to automatically detect normal/abnormal network traffic.

• Journal of the Society of Disaster Information
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• v.19 no.3
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• pp.498-509
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• 2023

Purpose: This paper proposes a method detecting the falling of a maintenance worker in the underground utility tunnel, by applying deep learning techniques using CCTV video, and evaluates the applicability of the proposed method to the worker monitoring of the utility tunnel. Method: Each rule was designed to detect the falling of a maintenance worker by using the inference results from pre-trained YOLOv5 and OpenPose models, respectively. The rules were then integrally applied to detect worker falls within the utility tunnel. Result: Although the worker presence and falling were detected by the proposed model, the inference results were dependent on both the distance between the worker and CCTV and the falling direction of the worker. Additionally, the falling detection system using YOLOv5 shows superior performance, due to its lower dependence on distance and fall direction, compared to the OpenPose-based. Consequently, results from the fall detection using the integrated dual deep learning model were dependent on the YOLOv5 detection performance. Conclusion: The proposed hybrid model shows detecting an abnormal worker in the utility tunnel but the improvement of the model was meaningless compared to the single model based YOLOv5 due to severe differences in detection performance between each deep learning model

• Journal of The Korean Association For Science Education
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• v.43 no.2
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• pp.59-72
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• 2023

This study analyzed a group interview with six earth science teachers and eight middle school students to find out the evaluations and criteria they use to evaluate VR/AR contents (two virtual reality content and two augmented reality contents) in middle school science digital textbook. The study found the VR/AR contents were evaluated on four criteria as follows: VR/AR media characteristics; technical operation; user interface; and teaching-learning design. The evaluations can be summarized by each criterion. First, regarding VR/AR media characteristics, interesting features of VR/AR contents were considered relatively advantageous compared to other media like videos. However, its shortage of visual presence and inconvenience of using markers were mentioned as shortcomings. Second, in the technical operation criteria, teachers and students found the following conditions as technically challenging: failing to properly operate on a particular OS; huge volumes of contents in the application; and frequent freezing when using the application. Third, poor intuitiveness and lack of flexibility were found as negative aspects in user interface. Fourth, regarding teaching-learning design, the teachers evaluated whether the VR/AR contents delivered scientifically accurate information; whether they incorporated class goals set by teachers; and whether they can help students' inquiry. It turned out teachers gave negative feedbacks on VR/AR contents. The students evaluated VR/AR contents by assessing whether they help them with learning science but concluded they did not regard them necessary in science learning at school. Based on the findings, this study discusses which development direction VR/AR contents should take to be useful in teaching and learning science.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.18 no.2
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• pp.53-66
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• 2023

Role models are also known to influence an individual's job or career choice. The positive effect of role models on entrepreneurship has already been revealed through many precious researches. It is said that people choose not only family members who are related by blood, such as parents, siblings, and relatives, but also acquaintances whom they have met through social relationships as role models. In this study, we divided into entrepreneurs with no role models other than themselves and entrepreneurs with role models. In addition, we classified parental siblings and relative role models as role models with strong ties, and acquaintance role models as role models with weak ties. We analyzed the differences in personal attributes, entrepreneurial orientation factors, and learning orientation between the entrepreneurs with role models and those without role models. Also, the differences in personal attributes, innovativeness, proactiveness, risk-taking propensity, and learning orientation between the entrepreneurs with strong ties role models and those with weak ties role models were examined. The empirical analysis results are as follows. First, it was found that the proportion of women entrepreneurs without role models is higher. Second, the entrepreneurs with role models with weak ties tend to run larger scale start-ups. Third, it was found that the entrepreneurs with role models of weak ties tend to have higher learning orientation. Fourth, gender shows the greatest influence on th absence or presence of role models. Fifth, it was found that learning orientation and startup size have the greatest influence on the decision of the role model with weak ties or that with strong ties.

• Korean Journal of Radiology
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• v.21 no.10
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• pp.1165-1177
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• 2020

Objective: To assess the feasibility of applying a deep learning-based denoising technique to coronary CT angiography (CCTA) along with iterative reconstruction for additional noise reduction. Materials and Methods: We retrospectively enrolled 82 consecutive patients (male:female = 60:22; mean age, 67.0 ± 10.8 years) who had undergone both CCTA and invasive coronary artery angiography from March 2017 to June 2018. All included patients underwent CCTA with iterative reconstruction (ADMIRE level 3, Siemens Healthineers). We developed a deep learning based denoising technique (ClariCT.AI, ClariPI), which was based on a modified U-net type convolutional neural net model designed to predict the possible occurrence of low-dose noise in the originals. Denoised images were obtained by subtracting the predicted noise from the originals. Image noise, CT attenuation, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were objectively calculated. The edge rise distance (ERD) was measured as an indicator of image sharpness. Two blinded readers subjectively graded the image quality using a 5-point scale. Diagnostic performance of the CCTA was evaluated based on the presence or absence of significant stenosis (≥ 50% lumen reduction). Results: Objective image qualities (original vs. denoised: image noise, 67.22 ± 25.74 vs. 52.64 ± 27.40; SNR [left main], 21.91 ± 6.38 vs. 30.35 ± 10.46; CNR [left main], 23.24 ± 6.52 vs. 31.93 ± 10.72; all p < 0.001) and subjective image quality (2.45 ± 0.62 vs. 3.65 ± 0.60, p < 0.001) improved significantly in the denoised images. The average ERDs of the denoised images were significantly smaller than those of originals (0.98 ± 0.08 vs. 0.09 ± 0.08, p < 0.001). With regard to diagnostic accuracy, no significant differences were observed among paired comparisons. Conclusion: Application of the deep learning technique along with iterative reconstruction can enhance the noise reduction performance with a significant improvement in objective and subjective image qualities of CCTA images.

• Korean Journal of Child Studies
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• v.33 no.4
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• pp.1-17
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• 2012

This study examined the developmental trajectories of perceived level of stress and depression in Korean youth using longitudinal data from the Korean Youth Panel Study (KYPS) of 2,844youth (1,524 boys) across $4^{th}$ grade through $8^{th}$ grade. Latent growth modeling indicated the presence of age-related, significant increases in stress and depression for both boys and girls. Girls experienced greater in stress and depression than did boys. Multiple group analysis indicated that there was no significant sex difference in effects of stress on depression. Overall, increases in stress were associated with increases in depression levels for both boys and girls. Conceptual and clinical implications of the findings were discussed.

• Korean Journal of Mathematics
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• v.18 no.4
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• pp.409-424
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• 2010

We observed the symptoms that occur to students who dislike mathematics when they study mathematics and the data that mathematics is related to foreign language. This study investigated the relation between mathematics and foreign language. Continuous immersion aids not only in acquiring language but also in learning mathematics. For continuous immersion, it is essential to organize small class. We organized small class and compared large class with small class about how the relation between mathematics and language appears in achievement, rate of presence, rate of submission of report, and attitude and enthusiasm. Based on the result, we try to find out the way to increase understanding mathematics and level up the achievements.