• 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.

• 한국전자파학회논문지
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• 제26권6호
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• pp.593-596
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• 2015

본 논문은 무선전력전송 시스템에 활용할 수 있도록 낮은 드레인 전압에서 높은 효율을 가지는 class E 전력증폭기를 설계하였다. 붕괴전압이 40 V인 Si MOSFET을 이용하여 드레인 바이어스 전압이 12.5 V인 13.56 MHz 전력증폭기를 설계하였다. 출력 전력 및 효율을 개선하기 위하여 품질계수가 우수한 솔레노이드 인덕터를 제작하여 출력 정합회로에 사용하였다. 발진 방지와 간단한 회로 구성을 위하여 인덕터와 저항으로 입력 정합회로를 구성하였다. 측정 결과, 제작된 전력증폭기는 13.56 MHz에서 38.6 dBm의 출력전력과 16.6 dB의 전력이득, 그리고 89.3 %의 높은 전력부가효율을 보였다.

• Journal of electromagnetic engineering and science
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• 제2권1호
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• pp.5-10
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• 2002

We have analized the inverse class-F and class-F amplifiers using their waveforms. From the analytic equations derived from the analysis, we have calculated tole efficiencies, output powers, DC power dissipations, and optimum fundamental load impedances of the inverse class-F and class-F amplifiers. We also have compared them for various operation conditions, which include the same peak current, saute DC power dissipation, same fundamental RF output power, and same fundamental load impedance with different Ron(on-resistance). These analyses have clearly shown the performance limitations, advantages, and guide to the optimized design of the inverse class-F amplifiers.

• 한국과학교육학회지
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• 제29권7호
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• pp.767-782
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• 2009

The researchers who are studying biology and teachers who are teaching biology think that the genetics-related concepts are highly significant than other concepts in biology. With such background, researches on the identification of major concepts have been under way to guide in biology class. Minimal research has been carried out, however, on what concepts should be taught to achieve the specific objectives of the class in relation to the unit of genetics in middle and high school. Accordingly this study was designed to determine the concepts of genetics that should be taught to achieve the objectives of the genetics unit in secondary school. For this purpose 5 instructional objectives of the genetics unit on the 9th grade and 4 instructional objectives of Biology I were selected and the concepts that were taught to achieve class objectives. The survey was conducted among 114 science teachers from middle schools and 85 biology teachers from high schools. The results indicated that 9.1 and 10.2 concepts on average were taught in the 9th grade and in Biology I respectively. Moreover statistical difference in the number of concepts that were taught according to the teachers' teaching experiences appeared among the middle school teachers (p<.05). But such statistical difference did not appear among the high school teachers (p>.05). Furthermore the concepts for the 9th grade consist of the basic genetics concepts although Biology I concepts were integrated and advanced contents for same concepts. Thus this finding suggests that concepts of genetics units to be taught in middle and high school were in linkage.

• Human Ecology Research
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• 제54권4호
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• pp.351-363
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• 2016

This study examined in depth what teachers experience in a practical problem-based home economics class. This study established the research question, "What do teachers experience in the practical problem-based home economics class?" and selected three teacher participants who had steadily performed a practical problem-based home economics class to directly observe classes and conducted intensive interviews with the class performing teachers. The three research participants performed the practical problem-based class as a method of practicing their educational beliefs and based on a problem consciousness that textbook centered classes focusing on concepts cannot manage. They also tried to make efforts to reconstruct the textbook centered with practical problems to promote the critical thinking abilities of students. In practicing the practical problem-based class, the research participants recognized that it was important to show the present problems in reality to the students, teach broad value concepts, and establish rapport with students. They tried to make class content correspond to class evaluation. They felt awarded in how they influenced the development of students and the perception of home economics subjects in a positive way as well as experienced various actual difficulties in performing the practical problem-based class. The three research participants examined themselves through the agony and reflection of the class, and integrated the class with daily activities by applying problem solving methods of practical problem-based classes to their lives.

• 복식
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• 제31권
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• pp.165-188
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• 1997

This study aims at 1) examining the perceived importance of clothing norms 2) examining relationship between perceptions of clothing norms clothing behavior and psycho-logical variables-ego identity(uniqueness and self acceptance) and sex role identity and 3) ascertaining any significant differences in the level of the perceived importance of clothing norms among variables-sex role identity and the uniqueness in psychological variables-and which variables are influencingon perception of clothing norms. The perception of cloth in norms inventory clothing norms inventory clothin behavior inventory ego identity in-ventory and the Bem Sex Role Inventory were administered to 620 college students. Sex role identity was classified into androgynous mas-culine feminine and undifferentiated type. Subjects were asked to rate each statement on the clothing norms under two kinds of instructions: their attitudes(TATT) and their beliefs about the expectations of others toward clothing norms(TBEO). 1) The scores of 3 TBEO of the students were higher than the scores of TATT. But the scores of TBEO concerning modesty of students were lower than the scores of TATT. Discrepancy scores of TATT and TBEO of the students were revealed significances differently according to clothing norms. males lower and higher class students had more free attitudes to the norms concerning genaral clothing attitudes. Females and higher class students had less free attitudes to the clothing norms concerning modesty. Females and lower and higher class students had more free attitudes to the norms concening sex-role related clothing attitudes but male students had less free to the sex-role related clothing norms. 2) Significant negative correlations between each variable of clothing norms and conform-ity-individuality were found. But negative correlations between those variables of the males and lower class students were higher than the correlations of the female and higher class students and the former had more posi-tive relationships with clothing norms and con-formity as compared with the latter. And sig-nificant positive correlations between each variable of clothing norms and modesty were found. But positive correlations between those variables of the males females and higher class students were higher than the correlations of the lower class students and the latter had less positive relationship with clothing norms and modesty as compared with the former. 3) Significant negative correlations between clothing norms and uniqueness were found in the subjects groups. The females and lower class students had more negative relationships with clothing norms and uniqueness as compared with the male and higher class students. Significant positive correlations be-tween uniqueness and conformity-individuality were found in all subjects groups, Therefore the higher uniqueness the student have the less they perceive theimportance of clothing norms and the more they have individuality. Significant positive correlations between sex-role related(higher class) general(female) clothing norms and self acceptance were found. but significant negative correlations be-tween campus style(higher class) general(female) clothing norms and self acceptance were found. But significant negative correlations be-tween campus style(males lower class, higher class) clothing norms and self acceptance were found. Clothing norms therfore related posi-tively or negatively with self acceptance ac-cording to the subjects groups. And significant negative correlations between conformity in-dividuality and self acceptance was found in higher class students. 4) The female masculine groups and the masculine groups of lower class revealed high scores than the scores of andrgynous group and undifferentiated group in clothing norms concerning modesty. And the feminine group revealed high scores in conformity-individu-ality than the scores of the masculine group. Male masculine and feminine group revealed high scores in clothing norms concerning cam-pus style than the scores of the androgynous group. The masculine group and feminine group of the lower classes revealed high scores in general clothing norms than the scores of the androgynous group. 5) The most influencing variables on the clothing norms were sex conformity-individu-altiy and masculine-feminine variables in the right order. The general clothing norms and clothing norms concerning modesty were influened by the sex role identity but the sex role related clothing norms and clothing norms concerning campus style were influenced by the ego identity. 6) Based on the sum scores of the uniqueness each group of the subjects was separately segmened into "high medium and low" groups. By the analysis of variances sig-nificant differences in discrepancy scores of TBEO and TATT among 3 uniqueness level groups were found on all clothing norms variables in all students three clothing norms variables in male and female students and one clothing norms variable in lower and higher students and in each clothing norms variable the mean discrepancy scores of the high uniqueness group were higher than those of the other groups. The findings indicated that the differences in the discrepancy score mainly contributed to the results of correla-tions described above.bed above.

• 한국과학교육학회지
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• 제36권1호
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• pp.159-166
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• 2016

과학수업에서의 거꾸로 수업에 대한 이해와 경험을 바탕으로 거꾸로 수업을 적용하는데 겪는 어려움을 면담조사방법을 활용하여 분석하였다. 면담자는 서울, 경기에 근무하고 있는 교사 중 거꾸로 수업 경력을 기준으로 과학 교과에 2년 이상 거꾸로 수업을 운영한 경험을 가진 교사와 올해 처음 거꾸로 수업을 운영하기 시작한 교사를 초 중 고 학교급별로 각 1명 씩 총 6명을 선정하였다. 참여한 교사들에게 3단계 면담 조사를 실시한 결과, 초중고 과학 수업에서 거꾸로 수업 수행에 매우 높은 만족감을 나타내었다. 특히 탐구활동에 거꾸로 수업이 많은 도움이 된다고 하였다. 그러나 교사들은 수업 준비에 부담감을 가지고 있었으며 수업 구성에 대한 어려움을 겪고 있었다. 거꾸로 수업의 어려움 해결 방안에 대한 탐색으로서 교과서 체제에 대한 논의를 통해 현재의 수업을 개선하는데 다양한 시사점을 도출할 수 있었다.

• 한국산학기술학회논문지
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• 제19권4호
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• pp.383-394
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• 2018

현대 청소년은 스마트폰의 기능과 다양한 앱의 내용을 이해하는 수용력, 분석하고 평가할 수 있는 비판력, 창조적으로 다양한 정보를 이용해 소통할 수 있는 능력을 키워나가야 한다. 하지만 많은 청소년이 스마트폰을 제대로 활용하지 못하고 있다. 본 연구는 종단분석을 사용하여 청소년 스마트폰 의존의 양태에 따라 분류된 하위집단의 잠재프로파일별로 스마트폰의존에 방임과 자기결정성이 미치는 효과를 검증하였다. 분석자료는 한국아동 청소년패널조사 초4패널을 활용하였으며, 분석방법은 청소년 스마트폰의존의 변화양태에 따라 분류된 잠재프로파일별로 스마트폰의존에 부모의 방임과 자기결정성이 미치는 효과를 검증하기 위해 잠재프로파일성장분석을 적용하였다. 본 연구의 결과는 다음과 같다. 첫째, 스마트폰의존 변화양상에 따른 잠재계층이 시간의 흐름에 따라 스마트폰의존 정도가 감소되는 유형과 스마트폰의존 정도가 증가되는 유형의 2가지로 분류되었다. 둘째, 스마트폰의존 감소집단은 부학력이 높고, 초기 자아존중감이 높으며, 초기 또래애착이 낮았다. 셋째, 방임의 변화양상은 스마트폰의존 감소집단이 방임이 더 증가하였다. 넷째, 스마트폰의존 감소집단에서는 방임과 스마트폰의존 사이에서 자기결정성이 완전매개효과로 분석되었지만, 스마트폰의존 증가집단에서는 자기결정성이 부분매개효과를 가지는 것으로 분석되었다.

• 한국의상디자인학회지
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• 제23권3호
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• pp.73-85
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• 2021

The purpose of this study is to understand the influence of the professor's image making (internal, external, social image) perceived by college students on instructional outcomes. The influence of the professor's image making on class satisfaction and class commitment was analyzed, and the mediating effect of class satisfaction and the relationship between class satisfaction and class commitment in the relationship between image making and class commitment was considered. First, it was found that the external image and social image of the professor had a significant effect on class satisfaction. The level of interpersonal relations, such as communication, manners, manners, and intimacy as well as the management of external expressions, clothing style, makeup, hair, gestures, postures, attitudes, voices, speech, and speech speed brings satisfaction to the class. Second, it was found that the professor's inner image, outer image, and social image had a significant effect on class commitment. In order to satisfy the students' immersion in class, professors are required to manage internal, external, and social images. Third, it was found that class satisfaction had a significant effect on class commitment. If the class satisfaction is high, it means that class immersion also increases. Fourth, as for the social image of a professor, it was found that class satisfaction had a completely mediating effect in the relationship between class commitment, and the external image of a professor was found to have a partial mediating effect in class satisfaction in the relationship between class commitment. It was found that the social image of professors perceived by college students improve class satisfaction, and this improves class satisfaction further enhances class immersion.

• Nutritional Sciences
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• 제7권2호
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• pp.107-112
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• 2004

This study investigated the interactions of bone health with several variables such as outdoor activity hours, nutritional status including habitual intake of calcium andvitamin D status in 72 high school girls aged 16-17 yearsattending day classes or night classes. The subjects consisted of 39 day-class students and 33 night-class students. Dietaty nutrient intakes were estimated using the 24-hour recall method. The daily activities of each subject were assessed using an activity questionnaire. Urinary calcium and creatinine excretion were assayed from subjects' 24-hoururine, while 25-OH-vitamin D[25-(OH)-D] and osteocalcin were measured from the subjects' fasting blood. Intake of energy, iron, vitamin A and vitamin C were worse in the night-class students. There was no significant difference in dietary calcium between the subjects in the different class types. Time spent on outdoor activities was significantly less in subjects attending night classes. Urinary calcium excretion of the night-class subjects was significantly higher than that of the day-class subjects (p<0.05). There was no significant difference in serum 25-(OH)-D level according to class type. Serum osteocalcin for night-class subjects was significantly higher than that for day-class subjects (p<0.01). It appeared that the night-class students had poorer dietary habits as well as fewer outdoor activities. Even though the estimated bone health of both groups of subjects appeared to be normal, the overall nutritional intake and duration of outdoor activities appeared to be important for maintaining bone health and lowering the future risk of osteoporosis.