• Journal of electromagnetic engineering and science
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• 제16권3호
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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.

• 한국보육지원학회지
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• 제13권1호
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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.

• 한국융합학회논문지
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• 제8권4호
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• pp.255-264
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• 2017

본 연구의 목적은 신체적 유능감과 체육수업 만족도의 관계를 규명하는데 있다. 이를 위해 중 고교학생을 대상으로 편의추출방법을 사용하여 556부의 설문지를 최종 분석에 사용하였다. 분석을 위해 통계프로그램은 PASW ver. 18.0 프로그램을 이용하여 각 요인에 대한 기술통계를 제시하였으며, 요인추출 및 문항의 내적 일관성 확인을 위해 탐색적 요인분석과 신뢰도분석을 실시하였다. 또한, 신체적 유능감과 수업만족도와의 관계에 대한 규명을 위해 다중회귀분석을 실시하였으며, 그 결과는 다음과 같다. 첫째, 신체적 유능감과 교수행동의 관계에 있어 피드백 요인이 영향을 주는 것으로 나타났다. 둘째, 신체적 유능감과 체육성적의 관계에 있어 승리, 동료비교 요인 등이 영향을 주는 것으로 나타났다. 셋째, 신체적 유능감과 체육환경의 관계에 있어 피드백, 대리경험 요인 등이 영향을 주는 것으로 나타났다. 넷째, 신체적 유능감과 운동능력의 관계에 있어 피드백 요인이 영향을 주는 것으로 나타났다.

• 한국멀티미디어학회논문지
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• 제9권6호
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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.

• 공학교육연구
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• 제25권6호
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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.

• 한국환경복원기술학회지
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• 제13권5호
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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).

• 한국산학기술학회논문지
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• 제9권3호
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• pp.638-644
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• 2008

슬립램프의 응용은 소형으로 디자인되는 원리를 이행하므로 작은 사이즈의 전자식 안정기가 요구된다 하지만 기존의 $50{\sim}60Hz$에서 동작되는 자기석 안정기들은 현저한 플리커(깜빡거림) 현상, 높은 손실, 큰 파고율 그리고 무거운 단점을 가지고 있다. 본 연구에서는 이러한 문제들을 해결하기 위해서 35W급(T5급) 형광등을 동작시키기 위한 제안된 새로운 타입으로 구성된 전자식 안정기로 정류기, 역률개선, 직렬 공진 하프 브리지 인버터 그리고 압전 변압기를 구성한 시스템을 제안하였다. 이 같은 압전 변압기를 이용한 전자식 안정기 구성으로 35급(T5급) 형광등을 성공적으로 동작시킬 수 있었다. 제안된 전자식 안정기를 약 $75{\sim}79kHz$의 주파수로 구동 시켜서 실험한 결과 25분 구동 후에 형광램프는 시스템 전체 안정기의 역률과 효율은 각각 0.95, 0.86%의 양호한 결과를 얻을 수 있었다.

• 디지털융복합연구
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• 제12권6호
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• pp.645-653
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• 2014

이 연구는 교양체육 수강생의 수업에 대한 재미요인과 행복감 및 사회적 체형불안이 어떠한 관계를 형성하고 있는지를 구조방정식모형을 통해 실증적으로 검증하는데 목적이 있다. 연구대상은 2013년도 경인지역에 소재한 대학에서 교양체육 수업을 수강하고 있는 학생 380명을 선정하였다. 자료처리는 PASW 18.0과 AMOS18.0프로그램을 활용하였으며, 연구의 목적에 맞도록 빈도분석, 확인적요인분석, 상관분석, 구조방정식모형분석을 실시하여 다음과 같은 연구결과를 얻었다. 첫째, 교양체육 수강생이 인지하는 수업 재미요인은 행복감에 정(+)적인 영향을 미치는 것으로 나타났다. 둘째, 교양체육 수강생이 인지하는 행복감은 사회적 체형불안에 부(-)적인 영향을 미치는 것으로 나타났다. 셋째, 교양체육 수강생이 인지하는 행복감은 수업 재미요인과 사회적 체형불안 사이에 완충역할을 하는 매개효과가 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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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.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2002년도 학술대회논문집
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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.