• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.5
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• pp.343-354
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• 2009

In this paper, a magnetic-less dc-dc switching converter realizing an integrable power conversion system is described. Instead of magnetic devices, the inductive impedance range of piezoelectric transducers is utilized to store and resonate the energy for soft-switching. Piezoelectric devices have no windings and deliver the power by the electrodes, which lead to mass product through semiconductor-manufacturing process. This paper presents a resonant-type step-up dc-dc power converter employing a disk-type piezoelectric transducer, analyzing the operation principles and the frequency control characteristics. Also, a topology extension of the single stage converter into cascaded multi-stage is presented and analyzed with the operation principles and control characteristics. For verification of the analysis, a 10W output dc-dc power converter hardware was implemented. The hardware experiments shows a good frequency control and power efficiency greater than 96% in the single stage. A hardware prototype of the extended multi-stage one was also realized and tested. The results shows that the converter has the same frequency control performance and high efficiency such as 93%.

• Journal of the Korean association of regional geographers
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• v.19 no.1
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• pp.162-180
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• 2013

This paper is to explore the relationship between global citizenship education needed to be taught recently and geography. First, the paper examines the concept, as well as the reason why it became important concept in dimension of education in terms of progress of globalization. Second, the paper examines justification of global citizenship education through geography subject through discussion of place, space, scale and interdependence as geographical key concepts. Then, it establishes the category of sub-area of global citizenship education to grasp structurally. This is to reestablish in terms of knowledge and understanding, skill, value and attitude through the inductive examination of existing system of classification. Third, for geography instruction as practical dimension for fostering global citizenship, the paper discusses things to consider previously to design it in terms of aims, contents and methods, and examined instruction strategies in terms of issues-based approach and geographies of resistance. The last, the paper should things to pay attention to be cautious in global citizenship education through geography.

• Journal of Convergence for Information Technology
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• v.9 no.10
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• pp.163-169
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• 2019

The purpose of this study is to examine about PBL implementation strategies employed by faculty members who have successfully managed PBL class. By adopting the inductive content analysis, this study has analyzed the contents related with the strategies about PBL implementation in the course result reports and best practice presentation materials made by 6 professors selected as a PBL best practicer of B university from the 2017 to the 2018. After the analysis, it is revealed that PBL best practicers have used 13 strategies in domain of classroom culture, learning facilitation, and assessment. The following further studies and supports have been suggest: First, a study on PBL best practice faculty member's implementation strategies should be further expanded. Second, a comparative study on the PBL implementation strategies between PBL best practice faculty members and general faculty members should be launched. Third, an organizational system to share PBL best practice faculty member's implementation strategies should be supported.

• Journal of the Korean earth science society
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• v.42 no.3
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• pp.325-343
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• 2021

This study aims to develop two science education programs using Angbuilgu and ancient astronomical data, are Korean astronomical heritage, and explore its educational possibility through the pilot application. Considering the TSK compositional characteristics of Angbuilgu and ancient astronomical data, linkage with science curriculum, and linkage with NOS, Angbuilgu was developed as a hands-on activity for elementary school students and ancient astronomical data as a science inquiry activity for middle and high school students. The educational availability of the developed program was confirmed by pilot application to elementary and high school groups. Through the Angbuilgu activity, the students refined their conceptual knowledge by correcting misconceptions about the solar motion by season and then confirmed the possibility of connection with the concept of the celestial coordinate system. Students recognized the scientific value of Angbuilgu and understood the nature of interactions STS. In the ancient astronomical data activity, students experienced inductive and deductive inquiry methods and utilized various information and strategies. Through the activities, students improved their scientific understanding and attitude towards TSK.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.6
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• pp.437-445
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• 2021

This paper proposes an operating frequency design method that limits the voltage applied to aload-side converter during the initial operation of a loosely coupled resonant dual-active bridge (LCR-DAB) converter and an initial operating strategy that applies it. The LCR-DAB converter uses two wireless power transfer coils instead of the high-frequency transformer of the general DAB converter. The wireless power coil has a physical distance of several tens of millimeter or more between the two coils; thus, the LCR-DAB converter is a bidirectional isolated power conversion system that can easily achieve high insulation performance. However, for the initial operation of the LCR-DAB, if the power-side converter is operated at the resonance frequency while the load-side converter is not operating, then a very high voltage due to resonance is applied to the load-side converter, thereby causing damage to the converter. Therefore, a method that can stably charge the DC link voltage of the secondary-side converter during the initial operation is needed. This paper proposes a method to initially charge the secondary-side DC link by operating the primary-side converter at a frequency with limited voltage gain rather than at a steady-state operating frequency. The validity of the proposed frequency design method and initial operating sequence is verified through simulation and experimentation of the 1 KW LCR-DAB converter.

• Journal of Industrial Convergence
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• v.21 no.1
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• pp.55-65
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• 2023

The purpose of this study is to explore the teaching experience of first-time youth soccer leaders. To this end, four leaders registered in the U-12 team were selected from those with more than 10 years of player experience, less than 5 years of coaching experience, and a level C or higher of the Korea Football Association leader's license. Accordingly, the analysis categories and analysis units were categorized according to the research problem, and data analysis was conducted through an inductive method. As a result of the study, youth soccer leaders were starting their coaching with the mindset of "I shouldn't" and "I can do it" based on their past experiences. They who concerned their uncertainty about the future in the teaching field were struggling with how to communicate with student and were less professional in teaching and learning ability. but they were trying to gain expertise while feeling rewarded in teaching. Accordingly, it was discussed to improve the treatment of youth soccer leaders and improve the program that is the leader training system.

• Journal of Microbiology and Biotechnology
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• v.33 no.6
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• pp.707-714
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• 2023

Plant-derived insecticide-neonicotinoid insecticides (NIs) played a crucial role in the development of agriculture and food industry in recent years. Nevertheless, synthesis of these nitrogen-containing heterocyclic compounds with an effective and greener routing remains challenging especially to the notion raise of "green chemistry" and "atom economy". While bio-catalyzed methods mediated by nicotinate dehydrogenase (NDHase) then provide an alternative. The current review mainly focuses on the introduction of sources, components, structure, catalytic mechanism and applications of NDHase. Specifically, NDHase is known as nicotinic acid hydroxylase and the sources principally derived from phylum Proteobacteria. In addition, NDHase requires the participation of the electron respiratory chain system on the cell membrane. And the most important components of the electron respiratory chain are hydrogen carrier, which is mainly composed of iron-sulfur proteins (Fe-S), flavin dehydrogenase (FAD), molybdenum binding protein and cytochromes. Heterologous expression studies were hampered by the plasmid and host with high efficiency and currently only Pseudomonas entomophila L48 as well as Comamonas testosterone was successfully utilized for the expression of NDHase. Furthermore, it is speculated that the conjugate and inductive effects of the substituent group at position 3 of the substrate pyridine ring exerts a critical role in the hydroxylation reactions at position 6 concerning about the substrate molecular recognition mechanism. Finally, applications of NDHase are addressed in terms of pesticide industry and wastewater treatment. On conclusion, this critical review would not only deepen our understanding of the theory about NDHase, but also provides the guideline for future investigation of NDHase.

• Journal of Industrial Convergence
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• v.21 no.10
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• pp.47-56
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• 2023

The purpose of this study was to explore educational awareness and meaning by applying an role-playing game (RPG) type class based on constructivism in physical education class in middle school. Regarding the research method, data collection was conducted through in-depth interviews, observations, and related documents, and data analysis was performed using case record analysis, inductive category analysis method, and case extraction process. Results of the study First, in terms of teachers' perceptions, there are both positive and negative aspects of teachers' perceptions of middle school physical education classes using the role-playing game (RPG) format. Second, in terms of educational meaning, the educational meaning of middle school physical education classes using the role-playing game (RPG) format emphasizes the need for a systematic lesson plan and sufficient support system. In conclusion, positive attitudes toward physical education as well as educational implications can be formed, and the basic foundation of the constructivist physical education class method and its preparation are thought to be of greater significance than anything else.

• Journal of Industrial Convergence
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• v.22 no.8
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• pp.37-50
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• 2024

The elderly customized care service, which began in 2020, aims to improve professionalism and service quality by introducing dedicated social workers for responsible management of living area performing institutions. Through inductive content analysis, this study attempted to examine the work adaptation process of dedicated social workers who are human resources performing the elderly customized care service system. As a result, 9 upper categories, 25 lower categories, and 56 conceptualizations were derived. This study attempted to provide basic policy data on the adaptation of dedicated social workers by exploring new policies and special work systems from the perspective of practitioners.

• Journal of Digital Convergence
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• v.12 no.11
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• pp.289-298
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• 2014

Recently, the traditional paradigm in railroad technology is changing as more efficient and cost-effective electric vehicle (EV) technologies have emerged. The original concept of PRT (Personal Rapid Transit) proposed in the past has come to be regarded as unrealistic, but its feasibility is improving through the utilization of an EV platform. In particular, battery-powered vehicles pose difficult technical challenges in attempts to achieve reliable and efficient operation. However, based on the inductive power transfer (IPT) technology, the fast charging of supercapacitors with high energy density can contribute to overcoming this technical challenge and promote the transition to electric-powered ground transportation by improving the appearance of cities. This study discusses the development process of a power supply system for PRT, including concept design, numerical analysis, and device manufacturing, along with performance predictions and evaluations. In terms of results, the system was found to meet the performance requirements for power supply modules on a test-bed.