• Journal of Power Electronics
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• v.19 no.5
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• pp.1099-1107
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• 2019

A soft switching converter with wide voltage range operation is investigated in this paper. A series resonant converter is implemented to achieve a high circuit efficiency with soft switching characteristics on power switches and rectifier diodes. To improve the weakness of the narrow voltage range in LLC converters, an alternating current (ac) power switch is used on the primary side to select a half-bridge or full-bridge resonant circuit to implement 4:1 voltage range operation. On the secondary-side, another ac power switch is adopted to select a full-wave rectifier or voltage-doubler rectifier to achiever an additional 2:1 output voltage range. Therefore, the proposed resonant converter has the capacity for 8:1 (320V~40V) wide output voltage operation. A single-stage hybrid resonant converter is employed in the study circuit instead of a two-stage dc converter to achiever wide voltage range operation. As a result, the study converter has better converter efficiency. The theoretical analysis and circuit characteristics are verified by experiments with a prototype circuit.

• Research in Mathematical Education
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• v.8 no.3
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• pp.115-121
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• 2004

This article describes the first results gained from a problem solving test that was administered to grade 4 students in the Netherlands. The students involved are all high achievers in mathematics. The analysis of the student responses gives cause for concern. The often-heard belief that teachers do not need to worry about the better students is clearly in need of revision. It turned out that when high achievers in mathematics are challenged to take on non-typical problems, their abilities are more limited than expected. The study revealed that the students wrote down hardly anything on their scrap paper to solve certain problems. Also it was found that they were not very persistent in their looking for a solution. In this paper we illustrate these first findings by discussing the results of one of the test problems.

• Korean Journal of Child Studies
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• v.26 no.4
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• pp.293-302
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• 2005

This study investigated behavior characteristics for the gifted(N=210) and the high achievers(N=1l5). The participations in this study were 200 teachers who rated their 325 students' behavior characteristics in 25 public elementary schools in U.S.A rating of behavior characteristics in learning style, motivation, creativity, and leaderships by teachers indicated differences in keen observation, rapid insight into cause-effect relationship, a large storehouse of information, language fluency, absorption/task persistent, preference for own learning activities, concerns for moral/ethical issues, and a diversity of interests between groups. No differences in understanding of underlying principles, organization, curiosity, creativeness, motivation, initiating activities in areas of personal interest, directing group activities, and intellectual playfulness/imagination were found in addition to some differences between two groups.

• The Journal of the Korea Contents Association
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• v.20 no.1
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• pp.581-592
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• 2020

This research aims to explore the effect of participation in 'peer tutoring(learning tutoring)' program designed for low achiever students, and to provide an explanation for the improvement of related extracurricular activity. For this, firstly, the study analyzed differences between goal attainment group and non-attainment group in self-directed learning readiness, learning presence and learning transfer. Secondly, the relationships between three variables were analyzed. Based on an online survey of 154 low achievers participating in learning tutoring, two research questions were examined using t-test, correlation and hierarchical multiple regression analyses. Our findings show that firstly, the academic achievement after participating in tutoring improved more than before. Secondly, there were differences in three variables by gender and grades. Also, there were differences in three variables between two groups. Finally, there was a high positive correlation between three variables, and 71% of learning transfer was explained by self-directed learning readiness and learning presence. Based on these findings, the practical implications are discussed regarding the improvement of tutoring program.

• The Journal of the Korea Contents Association
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• v.18 no.11
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• pp.250-257
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• 2018

The program for low-achievers, named 'Running high' is to provide college students whose GPA was lower than 2.5 with 1:1 learning consultation and special lectures of high achievers. Especially, it supports scholarship only for students who attain the target record of a certain course which they choose. The purpose of this study was to examine whether or not academic achievement, grit, ego-resilience of participants in 'Running high' would be more advanced than before. This study also compared academic achievement, grit, ego-resilience between participants who attain the goal of the program and participants who can not attain it. 110 college students joining in 'Running high' responded pre and post surveys of grit and ego-resilience. Their data of academic achievement also were gathered. The result of this study showed that the academic achievement and grit of participants in 'Running high' were advanced more than before, but not ego-resilience. The differences of academic achievement and grit between participants who attained the goal of the program and participants who could not attain it were significant, but not ego-resilience.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.421-424
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• 2004

As the deep sub-micron devices are recently integrated high package density, novel process method for sub $0.1{\mu}m$ devices is required to get the superior thin gate oxide characteristics and reliability. However, few have reported on the electrical quality and reliability on the thin gate oxide. In this paper I will recommand a novel shallow trench isolation structure for thin gate oxide $30{\AA}$ of deep sub-micron devices. Different from using normal LOCOS technology, novel shallow trench isolation have a unique 'inverse narrow channel effects' when the channel width of the devices is scaled down shallow trench isolation has less encroachment into the active device area. Based on the research, I could confirm the successful fabrication of shallow trench isolation(STI) structure by the SEM, in addition to thermally stable silicide process was achiever. I also obtained the decrease threshold voltage value of the channel edge and the contact resistance of $13.2[\Omega/cont.]$ at $0.3{\times}0.3{\mu}m^2$. The reliability was measured from dielectric breakdown time, shallow trench isolation structure had tile stable value of $25[%]{\sim}90[%]$ more than 55[sec].

• Journal of The Korean Association For Science Education
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• v.21 no.4
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• pp.677-688
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• 2001

The purposes of this study are to investigate the school science high achievers' achievements in enrichment physics, logical thinking level, and to analyze the relationship between logical thinking level and the achievement in enrichment physics of high achievers in science. The subjects were 357th and 8th graders who achieved highly in school science. To assess their achievements in enrichment physics, we developed a new test consisting of descriptive problems which were based on middle school curriculum. Those problems require one or two steps of thinking process, not simple knowledge of science. To assess logical thinking level, we used the instrument called GALT(Group Assessment of Logical Thinking) developed by Roadranka et al. The results showed that the school science high achievers' average achievement in enrichment physics was low, 56.3 out of 150, which indicated that they had not done much of enrichment learning beyond middle school science curriculum. Just only 54% of the school science high achievers are in formal logical thinking level. From the analysis of relationship between their logical thinking level and the achievement in enrichment physics, the value of the correlation coefficient was 0.174, which means that they are not almost correlated. Therefore, it is not desirable to judge science gifted children just from achievement in school science or enrichment physics, so both(logical thinking and the achievement in enrichment physics) tests should be taken for selecting gifted student.

• Journal of Gifted/Talented Education
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• v.20 no.2
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• pp.527-546
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• 2010

As research results, male schoolchildren were found to solve problems more easily in the area of basic process skills while female schoolchildren were found to solve problems in the area of integrated process skills. Schoolboys showed the high tendency to solve problems in a planning pattern by memory, or solving pattern in which they are fully aware of the contents of both questions and choices in answer sheets, or the pattern which they are fully aware of distracters in answer sheets; in contrast, schoolgirls showed a high tendency to get a good result by analyzing both questions & choices in answer sheets or analyzing a chart, graph and illustration, which explains that female schoolchildren tend to solve problems in more diverse ways than male schoolchildren. In case of a poor achiever, male schoolchildren tend to make a failure while trying to find answers in an inadequately understood state or trying to solve on mistaken memories while doing questions immediately while female schoolchildren showed a lot of solving patterns based on mistaken memories or wrong analyses of a chart, illustration, or graph. Such results are believed to offer the implications on the understanding of male/female schoolchildren in their problem-solving pattern of their exploratory ability in elementary science and on its subsequent program development.