• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.8
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• pp.2968-2974
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• 2010

Nowadays, the PV systems have been focused on the grid connection between the power source and the grid. The PV inverter can be considered as the core of the whole system because of an important role in the grid-interfacing operation. An important issue in the inverter control is the load current regulation. In the literature, Proportional Integral (PI) controller, which is normally used in the current-controlled Voltage Source Inverter (VSI), cannot be a satisfactory controller for an AC system because of the steady-sate error and the poor disturbance rejection, especially in high-frequency range. Compared with conventional PI controller, Proportional Resonant (PR) controller can introduce an infinite gain at the fundamental frequency of the AC source; hence it can achieve the zero steady-state error without requiring the complex transformation and the de-coupling technique. Theoretical analyses of both PI and PR controller are presented and verified by simulation and experiment. Both controller are implemented in a 32-bit fixed-point TMS320F2812 DSP processor and evaluated on a 3kW experimental prototype PV Power Conditioning System (PCS). Simulation and experimental results are shown to verify the controller performances.

• Journal of Distribution Science
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• v.18 no.5
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• pp.99-109
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• 2020

Purpose: This study aims to develop and empirically analyze a research model in order to comprehend the relationship among the service quality of market-wholesaler system, re-transaction intention, and recommendation intention of forwarder. Further, we suggest new six factors reflecting the service quality of market-wholesaler system and highlight market expansion of forwarder as a mechanism in the relationship. Research design, data and methodology: The authors developed the new scales measuring the service quality of market-wholesaler system (i.e. trade price, price fluctuation, payment receipt, settlement period, trade information, and customer service) and conducted a cross-sectional survey for 439 forwarders in a wholesale market. And then we performed a series of path analyses to test hypotheses. The hypotheses are as follows. [H1] The service quality of market-wholesaler system will positively affect forwarders' market expansion, [H2] Forwarders' market expansion will positively affect their re-transaction intention, [H3] Forwarders' market expansion will positively affect their recommendation intention, [H4] Forwarders' re-transaction intention will positively affect their recommendation intention. Results: The results showed that all the six factors for the service quality of market-wholesaler system were positively related to market expansion of forwarders. There was a differential effectiveness in the six factors of the service quality. More specifically, the positive effect of customer service factor was the strongest on market expansion of forwarders. And the respective effects of trade price, price fluctuation, settlement period, trade information factors were followed in order. The positive effect of payment receipt factor was the weakest on market expansion of forwarders. Also, market expansion of forwarders was positively related to their re-transaction intention and recommendation intention. Furthermore, market expansion of forwarders was indirectly related to recommendation intention through re-transaction intention as well. Conclusions: The research findings provide important theoretical and practical implications. This study is the first to attempt to test the perception of forwarders for the service quality of market-wholesaler system by developing and using the new scales. Also, there has been a sharp controversy about the effectiveness of market-wholesaler system. The findings support that market-wholesaler system would be activated by empirically verifying the effectiveness of the service quality on the various outcomes.

• Journal of the Korean Society for information Management
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• v.37 no.1
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• pp.51-78
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• 2020

Recently, the emphasis on self-directed learning and lifelong education is increasing the importance of school libraries in the curriculum. Accordingly, various studies have been conducted mainly from a structural, institutional and operational point of view. However, more research is necessary on the micro topics such as school library users' autonomous intrinsic motivations in the sense that school libraries play key roles in autonomy-based self-directed education. This study aims at finding out what types of school library use motivations are more important and the degree to which the use motivations affect the school library service quality based on the self-determination theory. In addition, this study examines how the use motivations and the perceived service quality vary depending on the school grade of the library users. Based on a focus-group-interview pilot study, a questionnaire survey was administered on the effects of school library motivations on perceived library service quality to 588 students from 5 high schools and 2 middle schools in Seoul. When the service quality and its components, service affect, information control, and library as place were set as dependent variables, in all these four cases, intrinsic motivations were more significant than extrinsic motivations. In addition, when middle school students and high school students were selected as separate analysis target groups, the results of both analyses show that the higher the intrinsic motivations were, the higher the perceived service quality was. The contribution of this study is that it applies the self-determination theory to school library service, measures the influence of motivation type based on the theoretical basis, and focuses on micro aspects to improve school library services.

• Korean Security Journal
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• no.44
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• pp.225-250
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• 2015

The purpose of this study is to explore the relative influences of juvenile delinquency using variables from Hirschi's social bonding theory, Agnew's general strain theory, Gottfredson and Hirschi's self-control theory, and Akers' social learning theory. The data derived from a sample of 2,018 high school students taken from National Youth Policy Institute in 2013. Multiple OLS regression analysis indicated that social learning theory has the greatest impact on dependent variables than other theories. The results of regression analyses also explore the notion that without the social bond, general strain, and self-control variables, there is very little loss of explained variance when these variables are removed from the full equation. However, when the social learning factors are eliminated from the full equation, the change in $R^2$ is dramatic. This result supported the idea that social learning variables had the strongest effect on the juvenile delinquency of Korean adolescents. The most important implication of this study is that it is the first study to test four major theoretical models for juvenile delinquency in Korea. It also makes a number of important contributions toward the further utilization of social learning in investigating juvenile delinquency for Korean high school students.

• The Journal of Society for e-Business Studies
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• v.22 no.1
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• pp.15-35
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• 2017

The method of weighted sum of evaluation using AHP is widely used in feasibility analysis and alternative selection. Final scores are given in forms of weighted sums and the alternative with largest score is selected. With two alternatives, as in feasibility analysis, the final score greater than 0.5 gives the selection but there remains a question that how large is large enough. KDI suggested a concept of 'grey area' where scores are between 0.45 and 0.55 in which decisions are to be made with caution, but it lacks theoretical background. Statistical testing was introduced to answer the question in some studies. It was assumed some kinds of probability distribution, but did not give the validity on them. We examine the various cases of weighted sum of evaluation score and show why the statistical testing has to be introduced. We suggest a non-parametric testing procedure which does not assume a specific distribution. A case study is conducted to analyze the validity of our suggested testing procedure. We conclude our study with remarks on the implication of analysis and the future way of research development.

• Journal of The Korean Association For Science Education
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• v.30 no.5
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• pp.557-575
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• 2010

The purpose of the study was to suggest the characteristics and goals of the science teaching model for use as criteria in selecting the appropriate teaching model for science in secondary schools. These characteristics and the goals have been organized based on the analyses of the literature on the teaching and/or instructional model. The teaching models have been classified into four areas, and the characteristics and goals of each area have been summarized as follows: $\cdot$ Traditional models: teaching of scientific knowledge through lectures, acquisition of scientific knowledge through discovery, acquisition of inquiry process skills through inquiry-based teaching/learning $\cdot$ Transitional models: demonstration and discovery as teaching strategies, acquisition of inquiry process skills through inquiry approach, acquisition and change of scientific knowledge $\cdot$ Modernistic model - conceptual change models: differentiation of scientific knowledge, exchange of misconceptions for scientific concepts - learning cycle models: conceptual differentiation, exchange of misconceptions, acquisition of science process skills Also described in this paper are the model's characteristics and goals that can be used as the criteria for selecting the appropriate teaching model for the subject that will be taught.

• International Commerce and Information Review
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• v.19 no.4
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• pp.53-74
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• 2017

There have been growing concerns that Korea's products keep losing their international competitiveness. It is necessary to restore strong muscles of manufacturing sectors. Together, efforts must be made to strengthen the competitiveness of service sector. While wide consensus has been reached on the necessity that Korea's service sector needs overhaul for stronger global competitiveness, it is rather difficult to witness any remarkable improvements. Insufficient performances might result from the protection of the captive markets by the interested parties. The research starts from the proposition that the introduction of MDP will bring down the barriers between the segmented services and promote competition. We provide theoretical analyses and report better performances of major countries which introduced MDP in their soils. Considering the reality, we propose that in the foreseeable future, a MDP in the areas of tax, law and accounting be introduced in Korea because these areas seem to create least conflicts of disciplinary duties due to public purposes. Broader MDPs in other areas may take some more time. There exist, however, some limitations. As MDP has not been officially introduced in Korea, it is almost impossible to directly compare the performances between the pre- and post-MDP in Korea. Data scarcity of business performances of companies also limits the study.

• Journal of Animal Environmental Science
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• v.9 no.2
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• pp.69-78
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• 2003

In this study, the energy conversion equipment from the radiation energy to mechanical energy by using n­pentane as the operating fluid was constructed and the performance to pump the water was tested for the utilization of solar powered water pump. The equipment was designed optimally, after the theoretical analyses of the water pumping head and water quantity per cycle were done. The pentane vapour temperature in the condenser and the temperature of the outlet water from the condenser became lowered and the heat transfer rate became higher with decreasing the water inlet level to the condenser. The temperature difference between the condenser and the water tank was significant. Therefore, the distance between the water tank and condenser was recommended to be shorten and the diameter of their connecting pipe was recommended to be narrow in order to reduce the resistance of the fluid passage and improve the heat transfer rate. The amount of water pumped was 1.6­2.4 liters. Mass flow rate of the cooling water became lowered when the cooling water pipe was prolonged from the condenser to improve the heat transfer rate.

• Journal of Gifted/Talented Education
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• v.24 no.1
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• pp.1-16
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• 2014

This study was to examine whether high school students' academic motivation and learning strategies influence their competence. Of the 600 high school students surveyed from 3 high schools in two metropolitan cities, Korea, 489 completed and returned the questionnaires yielding a total response rate of 81.50%. The final sample consisted of 399 males (81.6%) and 82 females (16.8%). Among the final sample, 113 students were gifted, and 376 students were non-gifted. Their average age was 17.20 years. Measures of students' competence (i.e., cognitive competence, and social competence), academic motivation (i.e., intrinsic motivation to know, toward accomplishment, and to experience stimulation, and extrinsic motivation identified, introjected, and external regulation, and amotivation), and learning strategies (i.e., metacognition, self-monitoring, strategy formation) Spearman's rho(${\rho}$) indicated that students' competence was positively associated with intrinsic (i.e., to know, toward accomplishment, to experience stimulation) and extrinsic (i.e., identified, introjected) motivation, and learning strategies. However, students' competence was negatively associated with amotivation. Hierarchical multiple regression analyses showed that intrinsic motivation (i.e., to experience stimulation), extrinsic motivation(i.e., external regulation), and learning strategies (i.e., strategy formation) were the crucial contributors for enhancing students' competence. Results are discussed in relation to theoretical implications and school settings.

• Journal of Gifted/Talented Education
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• v.25 no.4
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• pp.607-628
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• 2015

The purpose of this study was to compare gifted and non-gifted high school students on their perceptions of success, grit, aspirations, and achievement goal orientation. Of the 550 high school students surveyed from 4 high schools (i.e., two schools for gifted, two school for non-gifted) in three metropolitan cities, Korea, 496 (i.e., 153 gifted and 343 non-gifted) completed and returned the questionnaire yielding a total response rate of 90.18%. Measures of students' grit (i.e., consistency of interest, and perseverance of effort), aspirations (i.e., intrinsic aspirations - physical fitness, self-growth, affiliation, community contribution, and extrinsic aspirations - financial success, image, fame), achievement goal orientation (i.e., mastery, performance approach and performance avoidance), and perceptions of success (i.e., Success in life is pretty much determined by forces outside our control.) were administered. It was found that the majority of gifted students and non-gifted students perceived that "success is outside our control.", and chose 'hard-working' as the most influential factor on their success. 60.4% of non-gifted students chose 'wealthy family background' as the other most influential factor, whereas only 48.2% of gifted did. Gifted students had higher 'consistency of interest' and 'mastery goals' than non-gifted students. Hierarchical multiple regression analyses showed that grit (i.e., perseverance of effort) was the crucial contributors for enhancing both gifted and non-gifted students' mastery goals and performance approach goals. Results are discussed in relation to theoretical implications and school settings.