• Journal of electromagnetic engineering and science
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• v.16 no.3
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• pp.143-149
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• 2016

This work presents a method used for designing a broadband class-E power amplifier that combines the two techniques of a nonlinear shunt capacitance and a low quality factor of a series resonator. The nonlinear shunt capacitance theory accurately extracts the value of class-E components. In addition, the quality factor of the series resonator was considered to obtain a wide bandwidth for the power amplifiers. The purpose of using this method was to produce a simple topology and a high efficiency, which are two outstanding features of a class-E power amplifier. The experimental results show that a design was created using from a 130 to 180 MHz frequency with a bandwidth of 32% and a peak measured power added efficiency of 84.8%. This prototype uses an MRF282SR1 MOSFET transistor at a 3-W output power level. Furthermore, a summary of the experimental results compared with other high-efficiency articles is provided to validate the advantages of this method.

• Korean Journal of Childcare and Education
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• v.13 no.1
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• pp.19-41
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• 2017

Objective: This study aimed to provide policy implications by studying the class size of early childhood education institutes. Methods: By looking through researches, the educational influence of class size was examined. By using the latest statistical data, class size standard and status were compared. After class size perception in the field was considered and the main results of advanced researches were summarized and analyzed, the actual condition of class size was diagnosed. Furthermore, the national research trend was analyzed. Results: First, class size was an influencing factor on young children and teachers and its importance was reconfirmed. Second, as for standard in relation to class size in Korea, the maximum class size and teacher-child ratio were not presented together. In respect of overseas standards, infancy has similar standards, but early childhood has a little higher ratio. In the educational fields, there was growing awareness that class size should be modified. Third, there were not enough domestic researches on class size and they tended to be biased in terms of the method, targets, and contents. Conclusion/Implications: It is suggested that it is necessary to establish a class size policy for future early childhood education institutes, to implement a system, and to perform follow-up studies.

• Journal of the Korea Convergence Society
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• v.8 no.4
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• pp.255-264
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• 2017

The study is aimed to investigate the relationship between physical competence and physical education class satisfaction. For this purpose, 556 questionnaires were used for the final analysis by using convenience extraction method for middle and high school students. For statistical analysis, descriptive statistics for each factor were presented using PASW ver. 18.0 program, and exploratory factor analysis and reliability analysis were conducted for factor extraction and item internal consistency confirmation. Furthermore, a multiple regression analysis was conducted to clarify the relation between physical competence and satisfaction of class, and the results were as follows: First, feedback factors influenced the relationship between physical competence and teaching behavior. Second, athletic performance, victory, peer comparison factor, etc. influenced the relationship between physical competence and satisfaction of class. Third, the feedbacks and the experience factors influenced the relationship between the physical competence and the physical environment. Fourth, feedback factors also influenced the relationship between physical competence and athletic ability.

• Journal of Korea Multimedia Society
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• v.9 no.6
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• pp.693-699
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• 2006

Object-oriented databases (OODBs) have been adopted for managing non-standard applications such as computer-aided design (CAD), office document management and many multimedia applications. One of the major characteristics of OODBs is class hierarchy where a subclass is allowed to inherit the definitions defined on its superclasses. In this paper, I present the evaluation metrics for class hierarchy quality in OODBs. These metrics are developed to determine if a concurrency control scheme can achieve good performance or not on a given class hierarchy. I first discuss the existing concurrency control schemes for OODBs. Then I provide evaluation metrics based on structural information and access frequency information in class hierarchies. In order to discuss significance of the proposed performance metrics, an analytical model is developed. Analysis results show that the performance metrics are important factor in concurrency control performance. I consider both single inheritance and multiple inheritance. The proposed metrics can be used to provide guidelines on how to design class hierarchy of an OODB for maximizing the performance of concurrency control technique.

• Journal of Engineering Education Research
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• v.25 no.6
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• pp.69-80
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• 2022

In this study, the application of flipped learning methodology to thermodynamics in mechanical engineering was examined, and how university students view flipped learning and the effects of flipped learning were analyzed. To analyze the effects of flipped learning, pre-class survey, assessment on learning in pre-class, team activities during class, and post-class survey were conducted. The analysis was also conducted on 33 students who took the thermodynamics course in mechanical engineering, and the PARTNER flipped learning model was applied to the class. The results of this study are as follows; In the preliminary survey, the students expected that the flip-learning class with team activities and teaching between team members would be helpful in improving their learning. In addition, students recognized that cooperative learning through a team was helpful for learning. The case reflecting the result of pre-learning evaluation to the subject grades showed higher pre-learning evaluation results than the case not reflecting the result of the pre-learning evaluation to the subject grades, and it was found that the pre-learning evaluation was acting as a factor to promote learning in pre-class. In post-class survey, the satisfaction with the flipped learning class was high, indicating that the effectiveness of the flipped learning class applied to the thermodynamics class was excellent.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.13 no.5
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• pp.59-80
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• 2010

This research This research aims at developing systemic evaluation model in terms of biotope preservation through reports, literatures, and expert survey analysis by implementing biotope structure analysis in area level with selecting Hyunpoong and Yuga-myeon, Dalseong county, Daegu metropolitan city as a site. First of all, as a result of biotope type classification of research site, biotope type groups are classified into total 13, and its biotope types are divided into total 61. Also, as a result of literature analysis, total 18 items are drawn such as diversity of biotope typical species as a index item to assess the preservation value of biotope, and the first evaluation index are divided into 10 and the second ones are divided into 8 according to characteristic of index items. As a result of expert survey analysis, All 10 index items, first evaluation index, show high importance average (above 4.7). As a result of implementation of main cause for categorizing evaluation index by characteristic, there are 3 factors such as 'obstructive factor.' Based on above survey analysis result, as a result of estimating the weight of each item, 'restoration factor' showed the highest, 3.4541, but 'factor of habitat stability' showed 3.1468, which is the lowest The systemic value evaluation was set by comprehensively analyzing these results. As a result of biotope preservation value evaluation through applying research site, total 19 types which are abundant in vegetation are classified into I class, 12 types in II class, 5 types in III class, 10 types in IV class, and 15 types in V class respectively. Lastly, as a result of second evaluation, it is analyzed that there are 17 special meaningful space to preserve species and biotope(1a, 1b) and 61 meaningful space to preserve species (2a, 2b, 2c).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.3
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• pp.638-644
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• 2008

It is required small size electronic ballast to fullfill the design philosophy of miniaturizing in the application of slim lamps. However, the traditional magnetic ballasts operated at 50-60Hz have been suffered from noticeable flicker, high loss, large crest factor and heavy weight. In this study, in order to solve these problems, It was proposed for driving 35W Class fluorescent lamp in the new type of electronic ballast, which is composed of rectifier, active power factor corrector, series resonant half bridge inverter and piezoelectric transformer. A 35W class(T5 class) fluorescent lamp is driven to successful by the fabricated ballast with piezoelectric transformer. Experimental results, It is proposed to driving the lamp using a electronic ballast at operating frequency of $75{\sim}79kHz$ approximatively. It is operated after for 25 min that were obtained good results of the input power factor of 0.95 and efficiency of 86%, respectively.

• Journal of Digital Convergence
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• v.12 no.6
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• pp.645-653
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• 2014

Purpose of this study was to reveal the relationship between Cultural physical Education's Enjoyment Factor and Happiness, social physique anxiety via structural equation model. For the research object of this study 380 students, taking a cultural physical education class in Kyungki-Incheon district, have been selected. Statistics processing was carried out through PASW 18.0 and AMOS 18.0. The following results were obtained by analysis of frequency, confirmatory factor analysis, correlation analysis, structural equation model analysis to serve it's purpose. First, perceived enjoyment factor of cultural physical education student had positive(+) correlation with happiness. Sencond, perceived happiness of cultural physical education student had negative(-) correlation with social physique anxiety. Third, cultural physical education student's happiness has mediating effects as a buffer between class enjoyment factor and social physique anxiety.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1193-1195
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• 2002

This paper presents Active-clamp Class-E high frequency resonant inverter with single-stage. The proposed circuit is integrated Active-c class-E circuit to boost converter with the funct power factor correction. Boost converter is opera positive and negative half cycle respectively at frequency(60Hz), operating in Discontinuous Con Mode(DCM) of boost converter performs high p factor. By adding active-clamp circuit in Cl inverter, main switch of inverter part is operat only ZVS(Zero Voltage Switch), but also reduce switching voltage stress of main switch. Simulation result using Psim4.1 show that the p prove the validity of theoretical analysis. This proposed inverter will be able to be pract used as a power supply in various fields are ind heating applications, DC-DC converter etc.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2002.11a
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• pp.287-291
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• 2002

This paper presents active-clamp class-E high frequency resonant inverter with single-stage. The proposed circuit is integrated active-clamp class-E circuit to boost converter with the function of power factor correction. Boost converter is operated in positive and negative half cycle respectively at line frequency(60Hz), Such a operating in discontinuous conduction mode(DCM) of boost converter performs high power factor. By adding active-clamp circuit in class-E inverter, main switch of inverter part is operated not only ZVS(Zero Voltage Switch) but also reduced the switching voltage stress of main switch. This paper shows that simulation result using Psim 4.1 prove the validity of theoretical analysis. This proposed inverter will be able to be practically used as a power supply in various fields as induction heating applications, DC-DC converter etc.