• The Journal of the Acoustical Society of Korea
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• v.28 no.6
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• pp.491-498
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• 2009

This paper presents the design method of an impedance matching network using an isolation transformer and the Chebyshev filter function for the high efficiency and the flat power driving of an underwater acoustic piezoelectric transducer. The proposed impedance matching network is designed for minimizing the reactance component of transducer and having the flat power response in the wide frequency range. We design a low pass filter with ladder-type circuit using the Chebyshev function as standard prototype filter function. In addition, we design the impedance matching network which is suitable for the equivalent circuit of transducer and the turn ratio of transformer through the bandpass frequency transformation. The proposed method is applied to the simulated dummy load of the tonpilz-type transducer operating in the middle frequency range. The simulation results are compared with the measured characteristics and the validity of the proposed method is verified.

• Journal of Industrial Convergence
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• v.22 no.5
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• pp.39-48
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• 2024

Due to COVID-19, much research has been conducted on learning loss and educational gaps due to the postponement of the start of school and prolonged online distance learning, and most of the research has focused on the phenomenon of educational gaps. If a pandemic situation like this occurs in the future, fundamental policies are needed to resolve the educational gap. A fundamental solution requires not only an understanding of the educational gap phenomenon, but also the structure behind the phenomenon. Therefore, from a structuralist perspective, this study sought to model the educational gap caused by COVID-19 as a prototype of systems thinking and identify its structure. In addition, we looked at the unintended consequences resulting from policies aimed at resolving existing educational gaps. In order to respond to similar disaster situations in the future, policies for resolving the digital gap, support for basic academic skills, quality improvement for distance learning, and self-directed learning were discussed based on the structure of this study.

• Science of Emotion and Sensibility
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• v.26 no.4
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• pp.29-40
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• 2023

Anxiety is known to upset the balance of the attentional system and prioritize the stimulus-driven system over the goal-directed system; however, self-instruction induces goal-directed behavior with the self-regulation effect. This study verified the effects of meteorological and self-instruction conditions on pilot anxiety and flight task performance for in-service pilots in a virtual reality environment. The meteorological conditions were divided into visual meteorological and very low visibility conditions, and the flight tasks were conducted by varying whether or not self-instruction was performed. The experiment results reveal that anxiety and heart rate were higher, and the performance of the flight task was lower in the very low visibility condition. However, anxiety and heart rate were lower, and the performance of the flight task was higher in the self-instruction condition. This result suggests that accidents due to difficulty in flight may increase because of anxiety, but such accidents may decrease because of flight performance improvement by self-instruction.

• Journal of the Korean Society of Clothing and Textiles
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• v.48 no.2
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• pp.193-210
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• 2024

The portrait featuring Jo Ban(1341-1401), a scholar-official from the late Goryeo and early Joseon period, and his wife is the oldest surviving couple portrait in Korea. It is of great value in uncovering the clothing culture of the period given the limited number of historical artifacts and records. This study examines the historical clothing and textile patterns of Jo Ban's wife and reproduces them using 3D fashion design software program CLO. She wears jokduri, chima, and baeja over layers of jeogori, a mixture of traditional Korean and Chinese styles. Her clothing illustrates eight patterns-one flower, five geometric, and two cloud. Records and relics of similar periods show that flower and geometric patterns in her clothing follow the prevailing styles of Goryeo, while the cloud patterns are representative of early Joseon. These details are used to reproduce six different styles of Jo Ban's wife with CLO tools. Various visualizations of textile patterns are applied to materials, generating a more realistic look than her existing 3D character created with the portrait. Results of this study are expected to help promote the use of Goryeo clothing and patterns in numerous designs and enhance intuitive understanding of Goryeo clothing based on 3D visualization.

• Journal of the Korean Society of Radiology
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• v.18 no.2
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• pp.179-185
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• 2024

By applying the various energy spectrum imaging functions of DECT, To quantitatively distinguish between contrast agent and calcification, changes in image quality are analyzed by comparing CNR and SNR. We investigated the level of dose reduction during two scans and one VNC scan. As a result, contrast agent and calcification were best distinguished in the 70 keV area, CNR and SNR were excellent, and scan dose was reduced by about 26.5%. Therefore, by applying DECT, meaningful results were obtained that could visually and quantitatively distinguish between the intravascular contrast agent and the shade of calcification. If clinical research is conducted in the future considering the patient's age, gender, and body type, quantitative analysis of calcification will be possible even with intravascular contrast agent flowing in, which will have a significant effect in reducing the patient's scan dose and the burden of multiple scans.

• Information Systems Review
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• v.22 no.3
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• pp.15-30
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• 2020

In the real estate industry, the latest changes in the Fourth Industrial Revolution, such as big data analytics, machine learning, and VR (virtual reality), combine to bring about industry change. Proptech is a new term combining properties and technology. This study aims to derive and analyze from a comprehensive perspective the quality factors (systems, services, interfaces, information) for mobile real estate brokerage services that are well known and used in the domestic market. The surveys in this study were conducted online and offline and a total of 161 samples were used for statistical analysis. As a result, all hypotheses were approved to except system quality and service quality. The results show that the domestic proptech companies who are mostly focused on real estate brokerage services, peer-to-peer lending, advertising platforms and apartments need to grow in various fields of proptech business of other countries including Europe, USA and China.

• Journal of Technologic Dentistry
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• v.46 no.2
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• pp.36-41
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• 2024

Purpose: This study aimed to generate virtual mandibular left first molar teeth using deep convolutional generative adversarial networks (DCGANs) and analyze their matching accuracy with actual tooth morphology to propose a new paradigm for using medical data. Methods: Occlusal surface images of the mandibular left first molar scanned using a dental model scanner were analyzed using DCGANs. Overall, 100 training sets comprising 50 original and 50 background-removed images were created, thus generating 1,000 virtual teeth. These virtual teeth were classified based on the number of cusps and occlusal surface ratio, and subsequently, were analyzed for consistency by expert dental technicians over three rounds of examination. Statistical analysis was conducted using IBM SPSS Statistics ver. 23.0 (IBM), including intraclass correlation coefficient for intrarater reliability, one-way ANOVA, and Tukey's post-hoc analysis. Results: Virtual mandibular left first molars exhibited high consistency in the occlusal surface ratio but varied in other criteria. Moreover, consistency was the highest in the occlusal buccal lingual criteria at 91.9%, whereas discrepancies were observed most in the occusal buccal cusp criteria at 85.5%. Significant differences were observed among all groups (p<0.05). Conclusion: Based on the classification of the virtually generated left mandibular first molar according to several criteria, DCGANs can generate virtual data highly similar to real data. Thus, subsequent research in the dental field, including the development of improved neural network structures, is necessary.

• Journal of Korean society of Dental Hygiene
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• v.24 no.3
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• pp.197-208
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• 2024

Objectives: Extended reality technology offers an innovative opportunity to enhance self-directed learning through interactive processes in healthcare education. This study aims to analyze research trends in the application of extended reality technology-based educational content in the field of healthcare. Methods: Through literature search, selection, and exclusion processes based on predefined criteria, we conducted an analysis of domestic healthcare studies employing extended reality technology, ultimately selecting and examining 39 relevant publications. Results: The analysis reveals diverse applications of extended reality across various fields such as medicine, dentistry, and nursing. Positive effects, including increased academic satisfaction, immersion, and interest, are observed, alongside challenges like media usage difficulties and cybersickness. Conclusions: Future research should focus on the development and application of extended reality-based educational content in diverse healthcare curricula, emphasizing both educational approaches and continuous technological advancements.

• Journal of the Korea Society of Computer and Information
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• v.29 no.7
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• pp.99-107
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• 2024

In an environment where computer-related technologies are rapidly changing, cyber threats continue to emerge as they are advanced and diversified along with new technologies. Therefore, in this study, we would like to collect security-related news articles, conduct LDA topic modeling, and examine trends. To that end, news articles from January 2020 to August 2023 were collected and major topics were derived through LDA analysis. After that, the flow by topic was grasped and the main origin was analyzed. The analysis results show that ransomware attacks in 2021 and hacking of virtual asset exchanges in 2023 are major issues in the recent security sector. This allows you to check trends in security issues and see what research should be focused on in the future. It is also expected to be able to recognize the latest threats and support appropriate response strategies, contributing to the development of effective security measures.

• Smart Media Journal
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• v.12 no.11
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• pp.67-76
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• 2023

We propose a visualization method to respond to civil complaints through an analysis of the impact of blasting. In order to analyze the impact of blasting on tunnel excavation, we propose a simulation visualization method considering the mutual influence of the construction infrastructure by linking measurement data and 3D BIM model. First, the level of BIM modeling required for simulation was defined. In addition, vibration measurement data were collected for the GTX-A construction site, terrain and structure BIM were created, and a method for visualizing measurement data using blast vibration estimation was developed. Next, a spherical blasting influence source library was developed for visualization of the blasting influence source, and a specification table that could be linked with Revit Dynamo automation logic was constructed. Using this result, a method for easily visualizing the impact analysis of blasting vibration in 3D was proposed.