• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.2
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• pp.271-287
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• 2013

We propose a new multipath-based reliable routing protocol on MANETs, Multipath-based Reliable routing protocol with Fast-Recovery of failures (MRFR). For reliable message transmission, MRFR tries to find the most reliable path between a source and a destination considering the end-to-end packet reception reliability of the routes. The established path consists of a primary path that is used to transmit messages, and the secondary paths that are used to recover the path when detecting failures on the primary path. After establishing the path, the source transmits messages through the primary path. If a node detects a link failure during message transmission, it can recover the path locally by switching from the primary to the secondary path. By allowing the intermediate nodes to locally recover the route failure, the proposed protocol can handle the dynamic topological change of the MANETs efficiently. The simulation result using the QualNet simulator shows that the MRFR protocol performs better than other protocols in terms of the end-to-end message delivery ratio and fault-tolerance capability.

• English Language & Literature Teaching
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• v.16 no.3
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• pp.317-337
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• 2010

The present study has a dual purpose to investigate the current state of school English library and needs required for its effective use, and to propose a reading program at the school library. The literature on school library was reviewed. A questionnaire survey was done to find out the current situation of English library at the secondary school. The analysis of 26 secondary English teachers' responses reveals that there was the absence of librarians or reading specialists at the school English library. It was also found that the uses of the English library were limited due to the absence of the specialists, no guidelines, and no link between the curriculum and the library use. A case study on a 2-week special reading program at the school English library was conducted and 15 middle school students took part in the project. The participants took pre- and post-tests to identify their reading level using a software and did a variety of reading activities using the books selected according to their level. The comparison of the tests shows that most of the students' reading level improved after the reading program. The analysis of their views on the program and its effects reveals that they gained confidence in reading and their vocabulary understanding was improved. Some suggestions are made for the effective management of the school English library.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.12
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• pp.3081-3099
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• 2012

We propose a new multipath-based reliable routing protocol on MANETs, Multipath-based Reliable routing protocol with Fast-Recovery of failures (MRFR). For reliable message transmission, MRFR tries to find the most reliable path between a source and a destination considering the end-to-end packet reception reliability of the routes. The established path consists of a primary path that is used to transmit messages, and the secondary paths that are used to recover the path when detecting failures on the primary path. After establishing the path, the source transmits messages through the primary path. If a node detects a link failure during message transmission, it can recover the path locally by switching from the primary to the secondary path. By allowing the intermediate nodes to locally recover the route failure, the proposed protocol can handle the dynamic topological change of the MANETs efficiently. The simulation result using the QualNet simulator shows that the MRFR protocol performs better than other protocols in terms of the end-to-end message delivery ratio and fault-tolerance capability.

• Journal of Engineering Education Research
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• v.26 no.5
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• pp.29-41
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• 2023

Using text network analysis, this research aimed to identify significant keywords associated with each period of the revised High School Engineering curriculum from 2009-2022 and to examine their interrelationships in order to analyse the observed changes. The results of this study can be summarised as follows. Firstly, a significant increase in the number of words was observed throughout the curriculum revisions, with prominent occurrences of terms such as 'engineering', 'understanding', 'problem', 'solution', 'learning', 'evaluation' and 'diversity'. Secondly, network analysis and examination of connection centrality for each subject revealed the connection relationship that represented distinct subject characteristics. Thirdly, the study of the engineering curriculum revealed shifts in emphasised content with each revision. Based on these findings, recommendations were formulated. Firstly, given the growing importance of engineering, it is imperative to conduct systematic research on engineering education in primary and secondary school contexts. Secondly, efforts should be made to strengthen the link between Engineering and Technogy･Home-economics subjects in secondary schools. Finally, high school engineering subjects should be used not only to explore engineering careers, but also to cultivate talents with interdisciplinary expertise.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.5
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• pp.424-431
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• 2007

This thesis proposed H-Bridge Multi-Level Inverter for Fluidized Bed Combustion Boiler Secondary Air Fan in 200MW thermal power plant. The adjustable speed drive systems improve the efficiency in lightly load condition and extend the life span of motor by limiting the over current at starting. H-Bridge Multi-level Inverter is composed of the several series low voltage power cell inverters, which have the independent isolated do link, in each phase. KEPRI(Korea Electric Power Research Institute) has successfully completed to develop, install, and commission H-Bridge Multi-level Inverter(6.6kV, 1MVA). This thesis gives a full detail about H-Bridge Multi-level Inverter, proposed boiler DCS(Distributed Control System) logic, and commissioning test result.

• Journal of Korean Classical Literature and Education
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• no.32
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• pp.119-158
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• 2016

In this thesis we set forth the reasons for teaching classical river novels in secondary education, and investigated the guiding principles for content design of high school literature textbooks. Although classical river novels have great significance in cultural and narrative histories, they were previously consistently disregarded in secondary education. First, we looked at the need for including classical river novels in the secondary school curriculum to create a well-balanced education of classical novels, to link this with modern river novels, to teach the narrative styles and esthetics of river novels, and to let students understand the various cultures of the late Joseon Dynasty. Second, we examined two ways of educating students about classical river novels. For exclusively teaching classical river novels, we recommended the means of teaching and provided detailed guidelines by which they can be taught, as well as provided complete information about the family tree, the story unit, and the scene deployment. To establish the link between classic river novels and their modern counterparts, we recommended the process of teaching accession and transition of tradition by introducing the commonalities and the differences across three generations stories, besides discussing the viewpoints of female writers. When classical river novels are introduced in literary textbooks, students will realize the existence of such novels though they may not understand all aspects of the novels. We suggest that teaching and introduction of classical river novels in secondary education as soon as possible.

• Journal of Korean Society of Transportation
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• v.10 no.2
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• pp.25-42
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• 1992

The purpose of this paper is to construct a model to compute a progression adjustment factor on a signalized network. In a way to construct the model, a simulation method is introduced and the TRAF-NETSIM is used as a tool of simulation. The structure of the network chooses an urban arterial network so as to measure the effect of progression and compute average stopped delay on each link. A regression model is constructed by using the results of the simulation. The stepwise variable selection in the regression model in used. The findings of this paper are as follows: i)The secondary queue and platoon ratio are sensitive to the values of the progression adjustment factor ii) The continuous model can practically reflect on various situations in the real world. The platoon adjustment factor can be computed by this model and the data required for this model can be easily obtained in the field.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.479-483
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• 2004

Fuel Cell (FC) has slow response characteristic for load variation. During a load step, the inverter cannot pull more power from the fuel cell than is currently available so supplemental power must be provide by some sort of energy storage elements. In this paper, hi-directional do-dc converter for FC generation system is proposed to improve load response characteristic. The hi-directional converter interfaces the low voltage battery to the inverter dc link of FC generation system. The converter is based on a active full bridge in the primary side and on a half bridge in the secondary of a high frequency isolation transformer. The complete operating principles and simulation results in presented.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2795-2797
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• 1999

Several power factor correction(PFC) circuits are presented to achieve high PF electronic ballast for both voltage-fed and current-fed electronic ballast. The proposed PFC circuits use valley-fill(VF) type DC-link stages modified from the conventional VF circuit to adopt the charge pumping method for PFC operations during the valley intervals. In voltage-fed ballast, charge pump capacitors are connected with the resonant capacitors. In current-fed type, the charge pump capacitors are connected with the additional secondary-side of the power transformer. The measured PF and THD are higher than 0.99 and 15% for all proposed PFC circuits. The lamp current CF is also acceptable in the proposed circuits. The proposed circuit is suitable for implementing cost-effective electronic ballast.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.986-987
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• 2015

본 논문은 이차전지 에너지저장장치(ESS)을 위한 충 방전용 5kW급 계통 연계형 PCS(Power Conditioning System) 구성 및 실험에 대하여 서술하였다. 양방향 계통 연계형 PCS는 4Phase 인터리브드 DC/DC컨버터, 단상 계통 연계형 인버터로 구성된다. 4Phase 인터리브드 DC/DC컨버터를 통해 배터리 리플전류를 감소시켰으며, 계통에 의해 DC_Link에 발생하는 리플전류를 저감할 수 있는 L-C공진회로를 설계하고 실험하였다.