• Journal of Power Electronics
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• 제12권3호
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• pp.429-438
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• 2012

This paper presents the use of a novel, single-stage high-power-factor electronic ballast with a symmetrical class-DE low-$d{\upsilon}$/$dt$ resonant rectifier as a power-factor corrector for fluorescent lamps. The power-factor correction is achieved by using a bridge rectifier to utilize the function of a symmetrical class-DE resonant rectifier. By employing this topology, the peak and ripple values of the input current are reduced, allowing for a reduced filter inductor volume of the EMI filter. Since the conduction angle of the bridge rectifier diode current was increased, a low-line current harmonic and a power factor near unity can be obtained. A prototype ballast, operating at an 84-kHz fixed frequency and a 220-$V_{rms}$, 50-Hz line input voltage, was utilized to drive a T8-36W fluorescent lamp. Experimental results are presented which verify the theoretical analysis.

• 한국과학교육학회지
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• 제5권1호
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• pp.19-34
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• 1985

Teaching inquiry process is one of the most important objectives in science education. To promote students scientific process skills, a science teacher should encourage the students do something by themselves. One method for that purpose which has been used in many schools would be group experiment. The researcher has been experienced a lot of difficulties in controlling or guiding every group to finish the assigned experiment within the given class hour. Therefore, the researcher decided to select several leaders from students and trained them in advance of the given class hour. This leaders are expected to guide the remaining students in the class. As the result of this study, the classroom with and without student leaders showed very significant difference(P>0.001) in their achievement of scientific process skills. The experimental group also showed more positive attitude toward science. The researcher concluded that the use of student leaders is very effective in promoting scientific process skills. This method is also regarded very effective in a large class sized like Korean Schools.

• Journal of Power Electronics
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• 제3권3호
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• pp.175-184
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• 2003

In this paper, a new control scheme of Class-E inverter for reducing the crest factor of electronic ballasts for fluorescent lamps using Pulse-Frequency-Modulation (PFM) is Introduced The lifetime of the lamps is guaranteed by decreasing the lamp crest factor and also voltage stress of the switch is significantly decreased by a new scheme although conventional Class-E Inverter is used In this paper. The proposed PFM control scheme didn't use any auxiliary circuit. The proposed control strategy is executed by feeding back the Input voltage, and the zero-voltage-switching (ZVS) is ensured by maintaining constant turn-off time of the switch Therefore, the control principles of proposed method are explained in detail and its validity is verified through several simulations and experimental results.

• 한국학교수학회논문집
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• 제4권2호
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• pp.103-113
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• 2001

The teaching-learning method utilizing Web makes it possible for the students take the initiative in any field and offers the teaching strategy, methodology and teaching-learning materials suitable for students' ability and standard. The purpose of this study is to investigate the characteristics of WBI in mathematics class for the effective teaching and learning focusing on the unit 'Function' in the 1st grade of middle school and verify its effectiveness by developing the WBI programs which can progress learning achievement and applying them to math class. Two hypotheses were established for this study. Hypothesis 1 : There will be meaningful difference between the group that studies under WBI and the one that doesn't, Hypothesis 2 : There will be meaningful difference in the attitude and interest toward learning between the group that studies under WBI and the one that doesn't. In order to find out the result, I have made a comparative analysis through t-verification on the object of two classes of the 1st grade in P middle school that I have been working for. The result shows that the class utilizing WBI is more effective than the traditional lecture-oriented class since there is a meaningful difference between the control group and experimental one and also that the class based on WEB has a great influence on students' interest and positive attitude toward math class.

• 대한간호학회지
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• 제36권2호
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• pp.286-298
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• 2006

Purpose: This study was to develop an online 'alternative therapy and health promotion' class for university students and to evaluate its changes. Method: The online class was developed based on the Instructional Systems Development(ISD) model and model of Web-Based Instruction(WBI) developmental process. This was a quasi-experimental, one group pretest-posttest design. The subjects of this study were 130 students in 3 universities, and they were provided the cyber class for 16 weeks. Data was analyzed by descriptive and plural answer statistics, and paired t-test. Results: The cyber class was developed in five steps : analysis, design, data collection and reconstruction, programing and publishing, and evaluation. The results of program evaluation were positive, which included learning 3.47. system 3.57, and learning satisfaction 3.64 on the scale of 5. The posttest scores of cognition and reliability of alternative therapy were higher than pretest scores. The posttest score of health promoting lifestyle(t=-5.051, p=.000) and perceived health status(t=2.979, p=.003) were significantly higher than those of the pretest. Conclusion: These results suggest that the cyber class is a positive method in increasing a cognition, reliability of alternative therapy, and is effective to improve a health promotion lifestyle and perceived health status for the university students.

• 한국멀티미디어학회논문지
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• 제24권7호
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• pp.880-889
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• 2021

In everyday life, recognizing people's emotions from their frames is essential and is a popular research domain in the area of computer vision. Visual emotion has a severe class imbalance in which most of the data are distributed in specific categories. The existing methods do not consider class imbalance and used accuracy as the performance metric, which is not suitable for evaluating the performance of the imbalanced dataset. Therefore, we proposed a method for recognizing visual emotion using balanced data augmentation to address the class imbalance. The proposed method generates a balanced dataset by adopting the random over-sampling and image transformation methods. Also, the proposed method uses the Focal loss as a loss function, which can mitigate the class imbalance by down weighting the well-classified samples. EfficientNet, which is the state-of-the-art method for image classification is used to recognize visual emotion. We compare the performance of the proposed method with that of conventional methods by using a public dataset. The experimental results show that the proposed method increases the F1 score by 40% compared with the method without data augmentation, mitigating class imbalance without loss of classification accuracy.

• 한국멀티미디어학회논문지
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• 제25권6호
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• pp.886-893
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• 2022

Outlier detection refers to the task of detecting data that deviate significantly from the normal data distribution. Most outlier detection methods compute an outlier score which indicates the degree to which a data sample deviates from normal. However, setting a threshold for an outlier score to determine if a data sample is outlier or normal is not trivial. In this paper, we propose a binary prediction method for outlier detection based on spectral clustering and one-class SVM ensemble. Given training data consisting of normal data samples, a clustering method is performed to find clusters in the training data, and the ensemble of one-class SVM models trained on each cluster finds the boundaries of the normal data. We show how to obtain a threshold for transforming outlier scores computed from the ensemble of one-class SVM models into binary predictive values. Experimental results with high dimensional text data show that the proposed method can be effectively applied to high dimensional data, especially when the normal training data consists of different shapes and densities of clusters.

• Korean Journal of Acupuncture
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• 제24권4호
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• pp.85-98
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• 2007

Objectives : Standardization and clear description of locating acupuncture points guarantees reproducibility and credibility of the results in animal studies of acupuncture points and meridians. In this study, we aimed at analyzing the acupoint description of the previous experimental studies and suggesting guidelines for related journals. Methods : We searched animal studies where acupuncture points were used in Journal of Korean Acupuncture & Moxibustion Society and Journal of Meridian & Acupoint with a limitation of period, from 2002 to 2006. Data on experimental animals, acupuncture points and their descriptions were extracted and put in a predefined form. They were classified as one of the 4 classes; A) descriptions of the acupuncture points present, B) no description of the acupuncture points and only reference provided, C) neither description of the acupuncture points nor reference provided, or D) acupuncture point detector used. Two authors independently extracted and classified the data and the disagreements were resolved by discussion. Experts were invited to rate acupuncture point description validity on a numeric rating scale in the 11-item questionnaire. Results : Two hundred and five studies were identified and classified as follows; A) 32.2% (n=66), B) 7.8% (n=16), C) 51.2% (n=105), and D) 8.8% (n=18). Experts ratings were significantly lower for class C (mean${\pm}$SD, 2.14${\pm}$1.35, 95% CI [1.90, 2.39], P = 0.004 compared with class B, P ${\leq}$ 0.001 compared with class A or C) and no difference was found between classes A, B, and D. Conclusions : Reporting of acupuncture points in experimental animals is poor and validity and reliability of the result from such reporting is hampered. We suggest that journal editors and experts provide guidelines for reporting animal acupuncture points and adopt them into guide for authors for related journals.

• 대한치과교정학회지
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• 제28권5호
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• pp.751-761
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• 1998

악교정 수술이 꼭 필요한 골격성 제 III급 부정교합환자의 측모두부방사선 사진상의 특징을 알아보기 위하여, 골격성 제III급 부정교합으로 진단받고 수술예정이거나 수술을 시행한 7-17세의 남녀 37명을 실험군으로 하고, 정상교합을 가진 8-13세의 남녀 56명을 정상군으로 하여, 두 군을 비교분석한 바, 다음과 같은 결론을 얻었다. 1. Prepubertal Group내에서의 실험군과 정상군의 비교에서 ANS-U1/Me-L1, Mx. Length/Mn. Length, S-N/Go-Me, Wits, ANB, SN-Pog, IMPA, Facial Convexity, APDI 항목에서 유의차가 있었다. 2. Pubertal Group 내에서의 실험군과 정상군의 비교에서 ANS-U1/Me-L1, S-Go/N-Me, Mx. Lenth/Mn. Length, S-N/Go-Me, Wits, Saddle Angle, SNB, ANB, SN-Pog, IMPA, Interincisal Angle, Facial Convexity, APDI 항목에서 유의차가 있었다. 3. 골격성 제 III급 부정교합의 특성을 나타내는 항목들 중 Prepubertal Group과 Pubertal Group간에는 95% 유의수준에서 Mx. Length/Mn. Length, APDI 외에 다른 항목에서는 유의한 차이가 없었다. 4. 실험군에서 골격성 제 III급 부정교합의 특성을 나타내는 항목들 중 Saddle Angle과 SNB, SN-Pog와 SNB, ANB와 Facial Convexity항목 사이의 상관관계가 가장 높게 나타났다.

• 과학교육연구지
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• 제37권3호
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• pp.562-572
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• 2013

이 연구는 초등학교 과학교과 수업에서 융합인재 교육을 위한 프로젝트 학습 프로그램을 개발하여 학생들의 창의적 문제 해결력, 학업 성취도 및 수업에 대한 만족도에 미치는 영향에 대하여 알아보고자 하였다. 이를 위해 인천광역시에 있는 S초등학교 5학년을 대상으로 각각 1학급씩 실험반(28명)과 비교반(27명)을 선정하여 실험반에는 개발한 융합인재교육 프로젝트 학습 프로그램을 투입하였다. 이에 대한 결과를 정리하면 다음과 같다. 첫째, 융합인재교육 프로젝트 학습은 학생들의 창의적 문제해결력 향상에 긍정적인 영향을 주었음을 알 수 있다. 둘째, 실험반 학생들의 학업 성취도가 비교반 학생들에 비하여 향상되었다. 그러므로 융합인재교육 프로젝트 학습은 학생들의 학업성취도 향상에 긍정적 영향을 준다는 것을 알 수 있다. 셋째, 수업에 대한 학생들의 만족도도 보통이라는 의견 31.1%를 제외하고 59.36%가 만족하고 있었다. 위와 같은 결과로 볼 때 이 연구에서 투여한 융합인재교육 프로젝트 학습은 학생들에게 창의적 문제해결력과 학업성취도 향상에 효과적임을 알 수 있다.