• Journal of Power Electronics
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• v.17 no.1
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• pp.200-211
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• 2017

Conventional boost-full-bridge and boost-hybrid-bridge two-stage inverters are widely applied in order to adapt to the wide dc input voltage range of photovoltaic arrays. However, the efficiency of the conventional topology is not fully optimized because additional switching losses are generated in the voltage conversion so that the input voltage rises and then falls. Moreover, the electrolytic capacitors in a dc-link lead to a larger volume combined with increases in both weight and cost. This paper proposes a higher efficiency inverter with time-sharing synchronous modulation. The energy transmission paths, wheeling branches and switching losses for the high-frequency switches are optimized so that the overall efficiency is greatly improved. In this paper, a contrastive analysis of the component losses for the conventional and proposed inverter topologies is carried out in MATLAB. Finally, the high-efficiency under different switching frequencies and different input voltages is verified by a 3 kW prototype.

• The Journal of Korean Association of Computer Education
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• v.14 no.5
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• pp.1-8
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• 2011

The purpose of this study is to explore vocational high school students' understanding levels and misconceptions regarding the time-efficiency of algorithms. In this study, a questionnaire with nine questions was developed. The questionnaire is base on three misconceptions about the time-efficiency of algorithms that are examined through prior studies. The questionnaire was applied to 51 students who completed a programming course. The result shows that the students didn't sufficiently understand the concept of time-efficiency of algorithms and several common misconceptions appeared repeatedly. Finally, teaching strategies using simulation and assesment framework for algorithm's time-efficiency were presented and some recommendations were suggested for refining the curriculum relating computer programming and algorithms.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.977-986
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• 2021

This study was processed to improve educational efficiency of the specialized fishing education program, which is conducted for safety of fishermen and protection of marine resources by analyzing the problems. The research method was carried out as a case study, which is one of the qualitative research methods. Participants selected recipient and related experts for the education. As a result three problems and six improvement plans are deduced; renewal of educational system, improvement upon quality of education, and systemization of training expert instructor were the problems, followed by improvements which are increase in instruction time, expansion of budget, diversification of education program, enlargement on practical training, systemized instructor training, and specialized education according to region. These results will play a key role in enhancing the educational efficiency of specialized fishing education and suppressing social problems caused by the expansion of the fishing industry.

• Journal of the Korean School Mathematics Society
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• v.6 no.1
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• pp.87-100
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• 2003

In this paper we have studied the efficiency of GSP which is widely used in the school. In order to study the efficiency of the computer aided education we divided the students into two groups in the Namwon Middle School : One group called "A" is the classes using GSP, the other called "B" is the classes not using GSP. In the three times examination group A got good marks better than group B. In the questionnaires about the interest in geometry group A is higher than group B. By the results of this study the effort on education with using various multi media can come into the utmost educational effect. Therefore it is necessary for the teachers at school to have self training continuously in order to carry a higher educational quality.

• Korean Journal of Health Education and Promotion
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• v.24 no.4
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• pp.219-230
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• 2007

The purpose of this study was to identify the current problems of school health education policies and practices in Korea, and to establish the strategies to improve the effectiveness and efficiency of school health education program. The severity of adolescents's health problems including obesity, smoking, drug abuse, teen pregnancy, etc has been increased recently and coping strategies to deal with these problems became urgent. The role of school as a key setting for health education should be empathized. However, there were limitations for the effectiveness of school health education in Korea because of the lack of recognition about the importance, guiding principles of the school health education by the school health related law, life skill-focused curriculum, capacity of teachers for health education, and linkage between school and community. In order to improve the effectiveness of school health education, establishment of infrastructure, national and local health education standard, and operating principles for the school health education program should be provided. Life skill-focused health education curriculum should be developed for the effective health education. Teacher training and education also should be the essential component of school health education program. For the improvement of efficiency in school health education practices, cooperation with family and community support system would be necessary.

• Korean Journal of Health Education and Promotion
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• v.29 no.2
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• pp.71-81
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• 2012

Objectives: Effective and efficient response for public health crisis necessitate planning how to respond and mobilize the resources in schools. We preformed this study to develop the strategies to improve efficiency of school health education in an outbreak of pandemic disease. Methods: We tried to review the policies, regulations and response systems of all related sectors, and advanced cases associated with pandemic disease control measures by searching databases and on-line networks connected with the Korean Ministry of Education, Science and Technology. Results: It was important to implement a consistent and systematic approach for educational offices and schools to prevent confusion resulted from the inaccurate information. First, the systems and action plans for school health should be established to prepare and respond to an outbreak of pandemic disease. Secondly, the strategies to improve the efficiency of school health education in public health crisis should be in place. Finally, the personnel pool would be needed to provide the crisis management programs. Conclusion: In order for staffs and students to have abilities to respond in an outbreak of pandemic disease, comprehensive school health approaches and efficient educational efforts should be prepared in collaboration with related sectors.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.6
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• pp.1629-1639
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• 2016

This study is to estimate the production efficiency of abalone aquaculture and to find its determinants utilizing the survey data of operating expenses in 2015. The first part of the analysis applied both DEA and Super-DEA for the estimation of efficiency of each aquaculture household as DMU. We used wages, feeding costs and area as inputs and annual profits and sales as outputs of the model. The second part of the study applied both Tobit and OLS for the identification of determinants of the efficiency. We investigated cost-ratio, depreciation costs, careers, value of living seeds, cleaning costs of farming ground and a ratio of 1 and 2 year-old abalone at shipment as potential determinants. The estimation results show us that the average technical efficiency, pure technical efficiency, and scale efficiency score turn out to be 72%, 81% and 85% respectively. The Super-BCC and Super-CCR models reveal their average efficiency scores as 81% and 80%. All of the variables used to identify the determinants of the efficiency. The study results suggests that the production efficiency can be improved by cleaning farming ground and hence lowering the death rate of seeds.

• Journal of the Korean Home Economics Association
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• v.26 no.1
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• pp.123-136
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• 1988

This study attempts to shed some lights on an effect of consumer education by using the formal education as a proxy variable and measuring the effect of the formal education on consumer behavior. This study utilizes economic theories and develops a theory to analyze the effect. Within the conceptual framework employed in this study, it is hypothesized that education raises productivity in the nonmarket sector and thereby affects consumer behavior in the same manner as money income affects behavior. the data are taken from the self-administered questionnaires among 553 housewives in July 1987. the procedure used is to fit separate engel curves for the expenditures on various goods by the weighted regression technique. The empirical results support the hpothesis. Therefore, this study shows positive effects of education on the productivity of household production functions. This result implies that consumer education would enhance efficiency in consumer behavior significantly.

• Smart Structures and Systems
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• v.26 no.6
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• pp.693-701
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• 2020

The conventional Kalman Filter (KF) provides a promising way for structural state estimation. However, the physical parameters of structural systems or models should be available for the estimation. Moreover, it is not applicable when the loadings applied to the structures are unknown. To circumvent the aforementioned limitations, a two-stage KF with unknown input approach is proposed for the simultaneous identification of structural parameters and unknown loadings. In stage 1, a modified observation equation is employed. The structural state vector is estimated by KF on the basis of structural parameters identified at the previous time-step. Then, the unknown input is identified by Least Squares Estimation (LSE). In stage 2, based on the concept of sensitivity matrix, the structural parameters are updated at the current time-step by using the estimated structural states obtained from stage 1. The effectiveness of the proposed approach is numerically validated via a five-story shearing model under random and earthquake excitations. Shaking table tests on a five-story structure are also employed to demonstrate the performance of the proposed approach. It is demonstrated from numerical and experimental results that the proposed approach can be used for the identification of parameters of structure and the external force applied to it with acceptable accuracy.

• Smart Structures and Systems
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• v.31 no.2
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• pp.131-140
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• 2023

As well-known, the extended Kalman filter (EKF) is a powerful tool for parameter identification with limited measurements. However, traditional EKF is not applicable when the external excitation is unknown. By using least-squares estimation (LSE) for force identification, an EKF with unknown input (EKF-UI) approach was recently proposed by the authors. In this approach, to ensure the influence matrix be of full column rank, the sensors have to be deployed at all the degrees-of-freedom (DOFs) corresponding to the unknown excitation, saying collocated measurements are required. However, it is not easy to guarantee that the sensors can be installed at all these locations. To circumvent this limitation, based on the idea of first-order-holder discretization (FOHD), an improved EKF with unknown input (IEKF-UI) approach is proposed in this study for the simultaneous identification of structural parameters and unknown excitation. By using projection matrix, an improved observation equation is obtained. Few displacement measurements are fused into the observation equation to avoid the so-called low-frequency drift. To avoid the ill-conditioning problem for force identification without collocated measurements, the idea of FOHD is employed. The recursive solution of the structural states and unknown loads is then analytically derived. The effectiveness of the proposed approach is validated via several numerical examples. Results show that the proposed approach is capable of satisfactorily identifying the parameters of linear and nonlinear structures and the unknown excitation applied to them.