• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.7 s.361
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• pp.12-16
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• 2007

In this paper, The 3rd-IMD of class-F power amplifier is improved using CMRC structure in order to remove the parasitic End harmonic at the output load of class-F power amplifier. The total size is very small more than class-F power amplifier using PBG. (Photonicband Gap) structure during improved 3rd-IMD characteristic performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.3
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• pp.629-642
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• 1996

ATM switch handles the traffic for a wide range of appliations with different QOS(Quality-of-Service) requirements. In ATM switch, the priority control mechanism is needed to improve effectively the required QOS requirements. In this paper, we propose a priority control mechanism using the cell transfer ratio type and discard threshold in order to archive the cell loss probability requirement and the delay requirement of each service class. The service classes of our concern are the service class with high time priority(class 1) and the service class with high loss priority control mechanism, cells for two kind of service classes are stored and processed within one buffer. In case cells are stored in the buffer, cells for class 2 are allocated in the stored and processed within one buffer. In case cells are stored in the buffer, cells for class 2 are allocated in the shole range of the buffer and cells for class 1 are allocated up to discard threshold of the buffer. In case cells in the buffer are transmitted, one cell for class 1 is transmitted whenever the maximum K cells for class 2 are transmitted consecutively. We analyze the time delay and the loss probability for each class of traffic using Markov chain. The results show that the characteristics of the mean cell delay about cells for class 1 becomes better and that of the cell loss probability about cells for class 2 becomes better by selecting properly discard threshold of the buffer and the cell transfer ratio according to the condition of input traffic.

• Journal of the Korean Society of Earth Science Education
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• v.12 no.3
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• pp.174-183
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• 2019

The purpose of this study was to investigate the effects of situation-based class using digital storytelling on elementary school students' science class motivation and scientific attitude for 50 fifth graders in B elementary school in P metropolitan city. In order to conduct this study, 25 students in 5th grade were selected as research group and 25 students in another class as comparative group, and the research group conducted situation-based classes using 8-hour digital storytelling. The comparative group received 8 classes of general science classes by curriculum. The results of this study are as follows. First, the situation-based class using digital-storytelling has a statistically significant effect on elementary school students' science learning motivation. Second, situation-based class using digital-storytelling has a statistically significant effect on the scientific attitudes of elementary school students. It is thought that the situation-based class through digital-storytelling has a positive effect on the exploration of science principles through students' daily experiences.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.87-90
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• 2005

High-efficiency switched-mode circuits such as the class-E amplifier are well-known in the MHz frequency range. The class-E amplifier is a type of switching mode amplifier offering very high efficiency approaching 100%. In this paper of the class-E amplifier by using pHEMT device, the design has been done theoretically and experimentally, with simulation by using the harmonic balance method using circuit simulator. The amplifier using microstrip circuit and the pHEMT demonstrate 66% power-added- efficiency (PAE) at 2.4GHz with 17.6dBm of output power.

• Journal of Korean Institute of Industrial Engineers
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• v.41 no.5
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• pp.439-446
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• 2015

Recently, the importance of one-class classification problem is more increasing. However, most of existing algorithms have the limitation on providing the information that effects on the prediction of the target value. Motivated by this remark, in this paper, we suggest an efficient one-class classifier using hyper-rectangles (H-RTGLs) that can be produced from intervals including observations. Specifically, we generate intervals for each feature and integrate them. For generating intervals, we consider two approaches : (i) interval merging and (ii) clustering. We evaluate the performance of the suggested methods by computing classification accuracy using area under the roc curve and compare them with other one-class classification algorithms using four datasets from UCI repository. Since H-RTGLs constructed for a given data set enable classification factors to be visible, we can discern which features effect on the classification result and extract patterns that a data set originally has.

• 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 Korean Elementary Science Education
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• v.36 no.4
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• pp.303-315
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• 2017

The purpose of this study is to analyze elementary teachers' science class objectively and quantitatively using Mobile Eye Tracker. The mobile eye tracker is easy to wear in eyeglasses form. And experiments are collected in video form, so it is very useful for realizing objective data of teacher's class situation in real time. Participants in the study were 2 elementary teachers, and they are teaching sixth grade science in Seoul. Participants took a 40-minute class wearing a mobile eye tracker. Eye movements of participants were collected at 60 Hz, and the collected eye movement data were analyzed using SMI BeGaze 3.7. In this study, the area related to the class was set as the area of interest, we analyzed the visual occupancy of teachers. In addition, we analyzed the linguistic interaction between teacher and students. The results of the study are as follows. First, we analyze the visual occupancy of meaningful areas in teaching-learning activities by class stage. Second, the analysis of eye movements when teachers interacted with students showed that teacher A had a high percentage of students' faces, while teacher B had a high visual occupation in areas not related to classes. Third, the linguistic interaction of the participants were analyzed. Analysis areas include questions, attention-focused language, elementary science teaching terminology, daily interaction, humor, and unnecessary words. This study shows that it is possible to analyze elementary science class objectively and quantitatively through analysis of visual occupancy using mobile eye tracking. In addition, it is expected that teachers' visual attention in teaching activities can be used as an index to analyze the form of language interaction.

• Journal of Educational Research in Mathematics
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• v.10 no.2
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• pp.229-246
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• 2000

The purpose of this paper is to compare and analyze the two different teaching methods of elementary mathematics in the traditional method and in the constructive view. To do so, the actual class in the constructive view has been made for about four months using a class of 45 students in the second grade of an elementary school. After the class was finished, we collected diverse data from the class, such as the responses from the children(self-evaluation, mathematics diary, observation by the investigator, daily report), class evaluation report by other teacher and so on. The results of this research are as follows: First, the traditional class reaches at the goal of learning in a unit time because the class is guided by the teacher but the class in the constructive view is a little flexible because it is contextual. Second, in the constructive process of mathematical knowledge we knew that small group activities or discussion without intervention of teacher was often ended in exhaustive argument without arriving at valid social consensus. Third, the attitude in mathematics was changed from the passive one to the self-regulated ones. Fourth, the class in the constructive view could extend not only the ability of mathematical communication but also the ability of self-directed learning of children. Fifth, it was a considerable change the role of teacher, that is, guide of instruction instead of unique specialist in the classroom. Sixth, finally, the evaluation was made after finishing a unit class in the traditional instruction but it was integrated in a class in a constructive view.

• Journal of the Korean Society for Library and Information Science
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• v.22
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• pp.143-177
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• 1992

The main purpose of the school library is to present the various kinds of instructional media for an effective instruction including not only books, but also audiovisual materials and equipments. But unfortunately our school libraries have only books for the students and faculties at this time. But hereafter school library should house the various kinds of audiovisual media as well as printed media for the promotion of scholarstic achivemint. With a view to promoting the teaching method, and at the same time improving the scholarstic achivement of the students, instructional media were used in the class. To verify the efficiency of the instructional media, transparencies were used in the social science class of the 1st grade in the middle school and the natural science class of the 1st grade in the high school. In consequence, the academic achievement of the experimental class in which instructional media were used is superior to that of controlled class in which the textbook was only used. In < Social Science I >, the mean difference between the experimental class and the controlled class is 4.199 marks. And the difference, 0.032 is verified as a significant value in concordance to the t-test. In < Natural Science I >, the mean difference of the experimental class over the controlled class is 6.333. And the difference, 0.034 is verified as a significant value in concordance to the t-test. As shown in the above experimental research, using various kinds of the instructional media is more efficient than using textbook only. As a result of the questionaire on using the instructional media, most of the students desire to use of them continually because the use of the instructional media induce the interest, promote the comprehension, and entice the development of better memories.

• Journal of Nutrition and Health
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• v.37 no.3
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• pp.236-250
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• 2004

The objective of this study was to investigate difference in the diet by the kind of meal and the economic status. Nutrient contents at each meals were compared and differences in food intake at different meal were analyzed by economic status. Data from the 1998 Korean National Health Examination Nutrition Survey were used. Using the poverty line based on the 1998 Korean minimum cost of living, the subjects (n = 10400) were classified into high class (36.1％), middle class (40.7％) and low class (23.1 ％). Most nutrient intakes were obtained for main meals regardless of economic status. For high class, breakfast, lunch, dinner and snacks bring about 21, 29, 30 and 19 ％ of total energy intake, for middle class 22, 29, 30 and 19％ and for low class 24, 30, 30 and 16％, respectively. The high-middle class people tend to get more food intakes and nutrients at dinner and snacks, while the low class at main meals. This result was associated with the consumption of a smaller number of meals and a greater number of snacks daily as the economic level was going up (p 〈 0.05). Meals contributed to energy, protein and fat intake, and snacks to water, retinol and vitamin C. The food intakes by food group were different at meals by economic class. Seaweed product were popular breakfast foods in both middle and low groups. Thus three meals such as breakfast, lunch and dinner still delivered most of the energy and most of the macro-nutrients regardless of economic status.