• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.2
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• pp.168-174
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• 2016

In this paper, current control using PI controller in the synchronous reference frame is analyzed through the relationship among bandwidth, resonance frequency, and sampling frequency in the grid-connected inverter with LCL filter. Stability is investigated by using bode plot in frequency domain and root locus in discrete domain. The feedback variable is the grid current, which is regulated by the PI controller in the synchronous reference frame. System delay is modeled as 1.5Ts, which contains computational and PWM modulator delay. Two resonance frequencies are given at 815 Hz and 3.16 kHz from LCL filter parameters. Sufficient phase and gain margins can be obtained to guarantee stable current control, in case that resonance frequency is above one-sixth of the sampling frequency. Unstable current control is performed when resonance frequency is below one-sixth of the sampling frequency. Analysis results of stability from frequency response and discrete response is the same regardless of resonance frequency. Finally, stability of current control based on theoretical analysis is clearly verified through simulation and experiment in grid-connected inverters with LCL filter.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.5
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• pp.1395-1406
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• 2016

The purpose of this study was to examine the effects of interaction based mother-child art therapy on the change of child and mother's interactions in a child who was in trouble due to attachment problems. The subject in this study was a six-year-old child who faced difficulties in peer relationship building and who were maladjusted to kindergarten because of unstable attachment and negative feedback from his parents. Also, he showed serious problem behaviors at home. The ABA design was adopted among single-subject research designs, and the Target child was observed in the sessions in terms of the subfactors of Marschak's Behavioral Rating Scale to gather data related to the changes of child and mother's interactions. As a result of analyzing the collected data, there were positive changes in all the subfactors that were the child's verbal/nonverbal interactions, the mother's verbal/nonverbal interactions and mother-child interactions. Therefore the interaction based mother-child art therapy that was designed to boost child and mother's interactions was effective at furthering the mother-child interactions of the child with attachment problems.

• Journal of the Korea Society of Computer and Information
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• v.23 no.2
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• pp.117-123
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• 2018

This article is to investigate the possibility that project-based classes introducing mobile phones can replace the monotony of traditional classes led by teachers as well as they can encourage students to take active part in the classes to some extent. The students in groups choose a genre for their own video projects (e.g., movie, drama, news, documentary, and commercial) and produce the video contents using a mobile phone for presentation made at the end of a semester. In the sense that the students are allowed to do video-based mobile phone projects, they can work independently outside of class, where time and space are more flexible and students are free from the anxiety of speaking or acting in front of an audience. A mobile phone project consists of around five stages done both in and outside of the classroom. All of these stages can be graded independently, including genre selection, drafting of scripts, peer review and revision, rehearsals, and presentation of the video. Feedback is given to students. After the presentation, students filled out a survey questionnaire sheet devised to analyze students' responses toward preferences and level of difficulty of the project activity. Finally, proposals are made for introduction of a better mobile phone-based project classes.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.896-904
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• 2017

Lean premixed combustion was successful in meeting current NOx emission regulations. However, these often leads to combustion instability. This phenomena results from the feedback relationship between heat release perturbations and acoustic pressure oscillations in the combustor. Researches on the combustion instability in an annular combustor have recently received great attention due to the enhanced NOx requirement in aero-engines. In this study, the thermoacoustic network model has been developed in order to calculate the acoustics for longitudinal as well as circumferential modes in the annular combustor. The combustion model in the network model is calculated by flame transfer function(FTF). Numerical and analytical results are compared to an measurement data.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.1
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• pp.123-128
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• 2010

To increase the chance of the success of project, it is necessary to identify the important factors influencing the performance of project. Cognitive map has been used for analysing by investigating causal links among relevant factors. A fuzzy cognitive map (FCM) is an extension of a cognitive map with the additional capability of representing feedback through weighted causal links. Project performance is influenced by several factors such as input resources, possibility of achievement, concern of others and so on. The object of this paper is to develop the project success model of enterprise using a fuzzy cognitive map approach to investigate the degree of causal relationship between project performance and these factors.

• The Korean Journal of Physiology and Pharmacology
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• v.8 no.1
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• pp.33-41
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• 2004

We developed a cardiac cell model to explain the phenomenon of mechano-electric feedback (MEF), based on the experimental data with rat atrial myocytes. It incorporated the activity of ion channels, pumps, exchangers, and changes of intracellular ion concentration. Changes in membrane excitability and $Ca^{2+}$ transients could then be calculated. In the model, the major ion channels responsible for the stretch-induced changes in electrical activity were the stretch-activated channels (SACs). The relationship between the extent of stretch and activation of SACs was formulated based on the experimental findings. Then, the effects of mechanical stretch on the electrical activity were reproduced. The shape of the action potential (AP) was significantly changed by stretch in the model simulation. The duration was decreased at initial fast phase of repolarization (AP duration at 20% repolarization level from 3.7 to 2.5 ms) and increased at late slow phase of repolarization (AP duration at 90% repolarization level from 62 to 178 ms). The resting potential was depolarized from -75 to -61 mV. This mathematical model of SACs may quantitatively predict changes in cardiomyocytes by mechanical stretch.

• Journal of the Korea Safety Management & Science
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• v.19 no.4
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• pp.169-182
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• 2017

Predicting a box office gross in the film industry is an important goal. Many works have analyzed the elements of a film making. Previous studies have suggested several methods for predicting box office such as a model for distinguishing people's reactions by using a sentiment analysis, a study on the period of influence of word-of-mouth effect through SNS. These works discover that a word of mouth (WOM) effect through SNS influences customers' choice of movies. Therefore, this study analyzes correlations between a box office gross and a ratio of people reaction to a certain movie by extracting their feedback on the film from before and after of the film opening. In this work, people's reactions to the movie are categorized into positive, neutral, and negative opinions by employing sentiment analysis. In order to proceed the research analyses in this work, North American tweets are collected between March 2011 and August 2012. There is no correlation for each analysis that has been conducted in this work, hereby rate of tweets before and after opening of movies does not have relationship between a box office gross.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.10
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• pp.19-28
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• 2021

The present study aims to evolve the value cycle of e-business through value co-creation during the Coronavirus pandemic. The population of the study is experts consisting of university professors in the fields of marketing management, e-commerce, and managers of organizations and companies in Iran. Using the snowball sampling method, 50 of them were selected as the sample. This study employs the factor analysis method and structural equation modeling (SEM) approach for identification of the factors. The findings of this study reveal that 10 factors affect the evolution of the value chain into the value cycle, including customer relationship management, e-literacy, value co-creation, e-readiness, and integrated value creation, the logic of service dominance, shared value creation, virtual culture, e-trust, and network economics. Despite the difficulties that COVID-19 has created for businesses worldwide, the evolution of the e-business value cycle through value co-creation in the Coronavirus pandemic can be considered as a positive aspect of the pandemic. In fact, with more pandemics and more customers turning to e-businesses due to the co-creation of customer value, e-businesses can cover their weaknesses and improve their strengths by engaging customers and receiving their feedback, thus transforming their value chain into the value cycle.

• The Journal of Economics, Marketing and Management
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• v.12 no.3
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• pp.35-42
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• 2024

Purpose This study aims to investigate the correlation of social skills and metacognition among university students participating in service-learning programs. Also by evaluating the satisfaction of college students participating in service learning, this research seeks to understand the impact of this program on learning experiences. Research design, data and methodology: The research period spans two semesters, each comprising 15 weeks, from March 2, 2023, to December 20, 2023. Detailed procedures, including planning, preparation, data collection, analysis, and organization, cover activities conducted over the course of 30 weeks. These activities encompass various stages, from initial classroom planning with designated English storybooks to reflection and feedback sessions aimed at continuous development. Data collection methods include surveys, interviews, and observations, allowing for a comprehensive examination of social skills and metacognition among participating students. Results: The results show significant correlations between social skills and metacognition, such as the correlation between knowledge and statistics (r = 0.759, p < .01), the moderate correlation between cooperation and knowledge (r = 0.532, p < .01), the moderate correlation between statistics and cooperation (r = 0.539, p < .01), and the correlation between self-regulation and assertion (r = 0.278, p < .001). The average score of the satisfaction of college students participating in service learning was 4.8 out of 5. Conclusions: This study highlights the significant role of service-learning in boosting social skills and metacognition among university students. This study enhances the academic understanding of the relationships between social skills, metacognition, and service-learning programs, contributing to the expansion of both theoretical and practical knowledge in the field.

• Herbal Formula Science
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• v.32 no.1
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• pp.91-98
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• 2024

Objective : This study aimed to investigate Korean medical students' satisfaction with Korean medicine education and their trust in Korean medicine. It also explored the factors affecting satisfaction with Korean medicine education and trust in Korean medicine. Methods : Based on a total of 381 survey responses, the satisfaction with Korean medicine education, reflection of educational needs, trust in Korean medicine, reasons for maladjustment to education, and suggestions for improving education were analyzed. Results : Satisfaction with Korean medicine education and trust in Korean medicine were generally above average. However, reflection of educational needs was below average. It was found that the curriculum should be rearranged according to the needs of premedical students and medical students. The factors affecting satisfaction with Korean medicine education were gender, academic year, dropout experience, trust in Korean medicine, and reflection of educational needs. Factors affecting trust in Korean medicine were gender, academic year, and satisfaction with Korean medicine education. Conclusion : This study found that satisfaction with Korean medicine education and trust in Korean medicine have a reciprocal relationship. To improve students' satisfaction and adjustment to Korean medicine education, it is necessary to implement strategies to increase students' trust in Korean medicine. In addition, it is important for students and instructors to collaborate on curriculum design by establishing a feedback system that reflects students' needs.