• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.9
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• pp.41-45
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• 2014

In this paper, a high-efficiency power amplifier is implemented by using a drain bias control circuit operated at low input power for WPT(Wireless Power Transfer). Adaptive bias control circuit was added to high-efficiency class-E amplifier. It was possible to obtain the overall improvement in efficiency by adjusting the drain bias at low input power. The proposed adaptive class-E amplifier is implemented by using the input and output matching network and serial resonant circuit for improvement in efficiency. Drain bias control circuit consists of a directional coupler, power detector, and operational amplifier for adjusting the drain bias according to the input power. The measured results show that output powers of 41.83 dBm were obtained at 13.56 MHz. At this frequency, we have obtained the power added efficiency(PAE) of 85.67 %. It was confirmed increase of PAE of an average of 8 % than the fixed bias from the low input power level of 0 dBm ~ 6 dBm.

• Journal of the Korea Fashion and Costume Design Association
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• v.17 no.1
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• pp.13-24
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• 2015

The purpose of this study is to examine the influences of learners' self-efficacy on class satisfaction in learning practical basic sewing. Questionnaires were distributed to 181 college women students living in the areas of Deagu Metropolitan City and Gyeongbuk Province. The data obtained were analyzed by using various statistical tools: frequency, factor analysis, reliability analysis, correlation analysis, and multiple regression. The self efficacy of learners of practical basic sewing were made up of five factors: ability to manage interpersonal relationships, ability to deal with assigned tasks, anxiety, challenging spirit, and fear. Class satisfaction was composed of the following factors such as interest in class, professors' ability, achievement of class objectives, connectivity, preparation for class, preference for practices, and perfectibility. This study indicated the correlations between sub-variables of learners' self efficacy and class satisfaction. In other words, the higher were the levels of ability to manage interpersonal relationships, and ability to deal with assigned tasks in self efficacy, the higher were the levels of interest in class, professors' ability, achievement of class objectives, preference for practices, and perfectibility in class satisfaction. The factors of ability to deal with assigned tasks, anxiety, and challenging spirit, in learners' self efficacy were found to have statistically significant effects on the achievement of class objectives. The factor of ability to deal with assigned tasks in self efficacy had a statistically significant influence on professors' ability. The factors of ability to deal with assigned tasks, anxiety, challenging spirit and fear were found to have statistically significant effects on all the factors of class satisfaction.

• Journal of Korean Elementary Science Education
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• v.33 no.1
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• pp.129-139
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• 2014

This study was conducted to examine the effect of elementary science class using name card method on scientific learning motivation and academic achievement of elementary students. Two sixth grade classes were divided into experimental group and comparison group to treat the experimental group with elementary science class using name card method. General class according to teacher manual was implemented for the comparison group. Elementary science class applying name card method was conducted for 10 sessions throughout the experimental period of 8 weeks. The results of this study were as follows. First, elementary science class with name card method was effective in improving scientific learning motivation. Second, elementary science class with name card method had significant effect on improvement of scientific learning academic achievement. The study results showed that elementary science class with name card method was effective for scientific learning motivation and academic achievement of elementary students.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.5
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• pp.71-78
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• 2011

In this paper, we describe the design and implementation of a high efficiency and broad-band Class-J mode power amplifier using gallium nitride(GaN) high-electron mobility transistor(HEMT). The matching circuit of proposed class-J mode power amplifier for 2nd harmonic impedance designed to provide pure reactance alone. The measurement results show that output power of $40{\pm}1$ dBm, power-added efficiency of 50%, and drain efficiency of 60% for a continuous wave signal at 1.4 to 2.6 GHz.

• Journal of Korean Elementary Science Education
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• v.36 no.2
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• pp.143-154
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• 2017

The purpose of this study is to examine the educational effects of STEAM class by focusing on $21^{st}$ century learner competencies based on burning and extinguishing unit. Two 6th grade classes were divided into experimental group and comparison group to treat the experimental group with elementary science class using STEAM class. General class according to teacher manual was implemented for the comparison group. Elementary science class applying STEAM class was conducted for 9 lessons throughout the experimental period. The result of this study are as follows. Elementary science class with STEAM class had significant effect on 21st century learner competencies compared to traditional instructor-led classroom. Looking specifically, it was a significant difference in the three domains of the seven domains (problem solving, collaboration, flexibility). The study results indicated that STEAM class was effective in improving learners'recognition of 21st century learner competencies.

• Kyungpook Mathematical Journal
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• v.59 no.3
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• pp.415-431
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• 2019

In this paper we introduce a new class of operators which will be called the class of k-quasi-class A(s, t) operators. An operator $T{\in}B(H)$ is said to be k-quasi-class A(s, t) if $$T^{*k}(({\mid}T^*{\mid}^t{\mid}T{\mid}^{2s}{\mid}T^*{\mid}^t)^{\frac{1}{t+s}}-{\mid}T^*{\mid}^{2t})T^k{\geq}0$$, where s > 0, t > 0 and k is a natural number. We show that an algebraically k-quasi-class A(s, t) operator T is polaroid, has Bishop's property ${\beta}$ and we prove that Weyl type theorems for k-quasi-class A(s, t) operators. In particular, we prove that if $T^*$ is algebraically k-quasi-class A(s, t), then the generalized a-Weyl's theorem holds for T. Using these results we show that $T^*$ satisfies generalized the Weyl's theorem if and only if T satisfies the generalized Weyl's theorem if and only if T satisfies Weyl's theorem. We also examine the hyperinvariant subspace problem for k-quasi-class A(s, t) operators.

• Journal of Periodontal and Implant Science
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• v.46 no.2
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• pp.96-106
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• 2016

Purpose: Stress distribution and mandible distortion during lateral movements are known to be closely linked to bruxism, dental implant placement, and temporomandibular joint disorder. The present study was performed to determine stress distribution and distortion patterns of the mandible during lateral movements in Class I, II, and III relationships. Methods: Five Korean volunteers (one normal, two Class II, and two Class III occlusion cases) were selected. Finite element (FE) modeling was performed using information from cone-beam computed tomographic (CBCT) scans of the subjects' skulls, scanned images of dental casts, and incisor movement captured by an optical motion-capture system. Results: In the Class I and II cases, maximum stress load occurred at the condyle of the balancing side, but, in the Class III cases, the maximum stress was loaded on the condyle of the working side. Maximum distortion was observed on the menton at the midline in every case, regardless of loading force. The distortion was greatest in Class III cases and smallest in Class II cases. Conclusions: The stress distribution along and accompanying distortion of a mandible seems to be affected by the anteroposterior position of the mandible. Additionally, 3-D modeling of the craniofacial skeleton using CBCT and an optical laser scanner and reproduction of mandibular movement by way of the optical motion-capture technique used in this study are reliable techniques for investigating the masticatory system.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.8 no.3
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• pp.357-365
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• 2001

Purpose: The purpose of this study was to identify the death orientation of college student nurses and to evaluate the effectiveness in death orientation of a class on 'hospice care'. this was done by investigating the difference between the death orientation before and after the class. Method: The instrument used in this Investigation was the death orientation scale developed by Thorson and Powell (1988). The subjects of the study were the 47 college student nurses in a 'hospice care' class. The research was carried out between March 2, 2001, when the class began, and June 21, 2001 when the class ended The collected data were examined using arithmetic mean, percentage, t-test, ANOVA. Result: The results of the study are as follows : 1. The average death orientation score of the subjects before the class was 2.80. 2. There were a significant difference in the death orientation scores before and after the class (p<0.001). Before the class, 'hospice care', the students had an average score of 2,80. Their average score decreased to 2.55 after the class. Of 25 death orientation items on the scale, 14 items decreased significantly after the class as compared to before the class. 3. According to personal attributes (religion. the existence of religion, the experience of a death in recently) of subjects, there were no significant statistical differences in death orientation (p>0.05). Conclusion: This study showed that a class on hospice care was effective in changing the death orientation of student nurses.

• Journal of Engineering Education Research
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• v.23 no.1
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• pp.3-9
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• 2020

The purpose of the study was to develop the Arduino based STEAM instruction materials for creative engineering design class. PDIE model was used in this study. We developed a STEAM lesson plan and a STEAM lesson worksheet for a total of six sessions through the steps of preparation, development, implementation and evaluation. The validity of the instruction materials was evaluated by the 10 experts using a survey. The instruction materials were applied to the class (52 students attended) of the creative engineering designs unit in technology and home economics subject. The class satisfaction and the creative solving-problem ability were examined after the calss. The class satafacition was high as the average of 10 item was 4.57 (out of 5). The paired t-test was conducted to compare the means of the creative solving-problem ability. It was observed that 'understanding and mastery of knowledge, thought, function and skills in a specific domain', 'divergent thinking', 'critical and logical thinking' and ' motivational factors' were significantly increased after the class. The instruction materials develped in this study were successfully designed to enhance the creative solving-problem ability by designing creative tasks and to intrique the interest by adding visual and auditory stimuli with the Arduino.

• Journal of The Korean Society of Integrative Medicine
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• v.6 no.4
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• pp.63-73
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• 2018

Purpose : This study aims to verify the effects of flipped learning on self-directed learning and class satisfaction in a class of college physical therapy students. Methods : The subjects were 97 students in College A who had registered for musculoskeletal examination and assessment and practice at the second semester of 2017. All subjects were measured with the self-directed learning questionnaire for college student proposed by Lee et al., and the class satisfaction questionnaire proposed by Lee et al., before and after intervention. The collected data were processed using a computerized statistical program SPSS Win version 21.0. Mean, standard deviation, paired t-test and Cronbach's alpha coefficient were calculated. Results : The results showed significant differences in goal setting, identify resources for learning, effort attributed to results, self-reflection of self-directed learning and problem solving excellence, class methods and contents attention and understanding(p<.05), class interest of class satisfaction(p<.05). Conclusion : These results suggest that flipped learning improves learning motivation and attitudes. Therefore, follow-up study is necessary to investigate further the application of flipped learning in various students and teaching methods.