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입력전류 제어형 고효율 인버터아크용접시스템의 입력 및 출력 특성연구
최규하 전력전자학회 2000 전력전자학회 논문지 Vol.5 No.4
얇은 판형 용접에 광범위하게 사용되는 피복아크 용접기는 용접전원으로 변압기를 사용하는 AC 아크용접기외 인버터를 사용하는 인버터 아크 용접기로 구분된다. AC아크용접기는 변압기를 사용하므로 전체시스템의 부피 및 무게가 커지며 변압기 탭조정으로 인한 최적 출력전압이 설정되지 않아 용접성는이 저하되는 단침이 있다. 이러한 단점올 개선히고 용접성능을 향상시키기 위하여 고속반도체 소자를 이용한 인버터 아크용접기가 많이 연구되고 있다. 인버터 피복아크 용집기시스템은 다이오드 정류기, 인버터, 고주파 변압기, 출력측 정류기 및 리엑터로 구성되어져 있는데, 입력전원측에 다아오두 정류기를 사용함으로서 고조파 다량 힘유 및 입력역률 저하등을 가져오며, 일정 듀티를 갖는 정전압제어방식을 이용하고 아크용접시스템 고유의 정전류특성은 변압기의 누설구조애 의해 실현하고 았다. 따라서 본 논문에서든 이상의 단점을 해결하기 위하여 PWM 컨버터를 적용하여 입력측의 고조파를 제거하고 입력역률 99% 유지할 수 있었으며, 또한 새로운 혼형제어기법을 적용하여 순시적인 용접 출력전압과 전류를 제어하여 용접 출럭전압과 전류를 일정하게 유지시킴으로서 AC아크용접기와 비교하여 스패터룹 70%감소시켰으며 무부하시 10%의 효율 상승을 가져왔다. Shielded metal arc welding machines with AC transformer have been widely used for thin-plate welding applications. Because of being bulky, heavy and of tap-changing property, so the SMAW's are changing to new power electronic circuits such as inverter circuit in order to reduce the system size and also to improve the welding performances at input output sides. The PWM inverter arc welding machine with diode rectifier has better output welding performances but it is has the plentiful harmonics and the lower input power factor. To solve these problems, input current-controlled scheme is considered for PWM inverter arc welding system, and then total input power factor is maintained to be more than 99%. Also a new combined control is proposed which can control both instantaeous welding output voltage and current under constant power condition, and as a result the variations of instantaneous current and voltage can be reduced to very narrow range in the V-I curve relationship, and hence the variance of welding current and voltage become so reduced. In addition the spatter generated during welding process is greatly reduced up to 70%. And the overall effiency can be improved up to 10%, which becomes higher when the load is lower.
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교육대학생들이 인식하는 좋은 컴퓨터 수업에 대한 개념도 연구
최규하,이재무 한국지식정보기술학회 2021 한국지식정보기술학회 논문지 Vol.16 No.6
This study explores the perception of quality computer classes in which pre-service teachers think of using a concept mapping. The research was conducted according to the concept mapping process of Mary Kane and William M. K. Trochim. For similarity matrix, 11 students of computer education courses were required to calculate similarity data evaluation for 50 statements. As for the group similarity matrix, the similarity matrixes which participants prepared individually were integrated. To create concept maps, multidimensional scale analysis and hierarchical cluster analysis were performed using SPSS 24.0 for group similarity matrix. As a result of multidimensional scale analysis, two dimensions were found as ‘instructor competency-learner change' and ‘learning content-learning process'. In addition, reading the dendrogram, it was divided into three upper and seven lower categories. The upper categories were named as ‘learning goals', ‘instructional methods', and ‘learner-centered'. The upper category of ‘learning goals' included three subcategories: ‘class for affective change', 'class for cognitive achievement', and ‘faithful class to the basic content'. The upper category of ‘instructional methods' included subcategories of ‘classes with appropriate instructional strategies' and ‘learner-focused classes‘. In addition, the upper category ‘learner-centered' included the lower categories of ‘learner participation-centered classes' and ‘classes with proper learning environments'. Among the statements, 'In a quality computer class, it is more important for learners to practice by themselves.' was considered the most important statement.
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Advances towards Controlling Meiotic Recombination for Plant Breeding
최규하 한국분자세포생물학회 2017 Molecules and cells Vol.40 No.11
Meiotic homologous recombination generates new combinations of preexisting genetic variation and is a crucial process in plant breeding. Within the last decade, our under-standing of plant meiotic recombination and genome diversity has advanced considerably. Innovation in DNA sequencing technology has led to the exploration of high-resolution genetic and epigenetic information in plant genomes, which has helped to accelerate plant breeding practices via high-throughput genotyping, and linkage and association mapping. In addition, great advances toward understanding the genetic and epigenetic control mechanisms of meiotic recombination have enabled the expansion of breeding programs and the unlock-ing of genetic diversity that can be used for crop improvement. This review highlights the recent literature on plant meiotic recombination and discusses the translation of this knowledge to the manipulation of meiotic recombination frequency and location with regards to crop plant breeding.
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사회불안과 주관적 안녕감의 관계에서 유능성 욕구 충족의 조절효과
최규하,강병은,최주영 한국청소년학회 2016 청소년학연구 Vol.23 No.4
The purpose of this study was to test moderating effect of the competence need satisfaction on the relation between social anxiety and subjective well-being. A self-report questionnaire was administered to 235 college students. Data were analyzed by the structural equational modeling (SEM). The results are summarized as follows. First, the moderating effect of the need for competence on the relation between social anxiety and subjective well-being was significant. That is, in the low need for competence group, the higher the level of social anxiety the lower level of subjective well-being. In contrast, in the high need for competence group, the relation between social anxiety and subjective well-being was not significant. These results imply that the need for competence may serve as a buffer against the negative effects of the social anxiety on subjective well-being. Finally, limitations of this study and suggestions for further research were discussed. 본 연구는 사회불안과 주관적 안녕감의 관계에서 유능성 욕구 충족의 조절효과를 검증하는데 그 목적이 있다. 이를 위해 대학생 235명에게 자기보고식 설문을 실시하여 자료를 수집하였다. 구조방정식모형 분석을 실시한 결과는 다음과 같다. 첫째, 사회불안과 주관적 안녕감의 관계에서 유능성 욕구 충족의 조절효과가 유의하였다. 둘째, 유능성 욕구 충족 수준에 따른 사회불안과 주관적 안녕감 간 단순회귀선의 기울기를 검증한 결과, 유능성 욕구 충족의 수준이 낮은 집단에서는 사회불안 수준이 높을수록 주관적 안녕감 수준이 유의하게 낮았지만, 유능성 욕구 충족의 수준이 높은 집단에서는 사회불안과 주관적 안녕감의 관계가 유의하지 않았다. 이는 유능성 욕구 충족은 사회불안이 주관적 안녕감에 미치는 부정적인 영향을 완충하는 요인으로 작용함을 시사한다. 마지막으로, 이 연구의 제한점과 후속연구를 위한 제언을 논의하였다.
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