• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1556-1570
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• 2016

In the process of virtual inertia control (VIC), the frequency regulation capability of the directly-driven wind turbine with permanent-magnet synchronous generator (D-PMSG) on wind farm is related to its rotor kinetic energy and capacity margin. This paper proposes the method for assessing the D-PMSG frequency regulation capability and defining its coefficient according to the operating state of wind power generators. In addition, the calculating method of parameters in VIC is also discussed according to the principles of primary frequency regulation and inertia response of synchronous generators. Then, by introducing the capability coefficient into the proportion-differential virtual inertia control (PD-VIC) for power coordination, a coordinated virtual inertia control (C-VIC) strategy is developed, with the consideration of the difference in frequency regulation capability between wind power generators. The proposed control method can not only give full play to the frequency regulation capability of wind power generators, decrease the movements of the pitch angle control system but also bring some self-coordination capability to different wind power generators thus to avoid a secondary drop in system frequency. The simulations and experiments prove the proposed method to be effective and practicable.

• Hwankyungkyoyuk
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• v.19 no.2 s.30
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• pp.1-11
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• 2006

In Korea nearly all the subjects teach environmental education in the secondary school. In addition we have a separate environmental education subject (environmental subject). This could be a very strong point in the Korean environmental education. The environmental subject and the other subjects, however, overlap in teaching materials and methods in almost all aspects. Because of this, the environmental subject has not done its job effectively, and is sometimes considered as an unnecessary surplus. To effectively play its own role in environmental education, the subject should focus on environmental issues rather than on contamination, which it is focusing on now. The contamination-focused environmental subject simply teaches nearly the same contents that the other subjects teach. In addition, it makes students visit actual sites related to pollution in order to encourage them to be aware of the severity of pollution. However, it has difficulty in teaching how environmental problems occur in a society and how the social decisions are made to resolve the problems. To overcome this difficulty the environmental subject should employ discussion classes more substantially, which let students investigate social aspects as well as scientific aspects of environmental problems and make integrated decisions through interdisciplinary approaches, to make students understand social mechanisms of environmental problems. The subject should focus on teaching what factors influence producers' and consumers' behavior and what factors they should consider when they have to make decisions on environmental issues. It should leave teaching technical knowledge and skill to the other subjects, and train students by the integrated approach which makes them see technology through a sociologist's eye. Although such integrated approach is emphasized in the environmental subject, environmental teachers should be trained to understand technological knowledge and skill in profound depth.

• Journal of the Korean earth science society
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• v.32 no.3
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• pp.324-333
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• 2011

The opinion, that the history of science should be introduced to science lesson, has been continuously emphasized by a group of people who supported the needs of science and scientific process, nature of science, and the interaction between science and society. When the importance of the integrated science education is emphasized, the history of science is suggested as an effective curriculum for it. To respond to this identified interest, we developed a lesson of the history of science by selecting the contents of the history of science as subject topics of the integrated science and by utilizing the findings of previous studies related to the history of science in science educations. To develop the history of science class as a subject of integrated science, we chose 'the age of the earth' as a unit. After the pilot test of the unit in secondary school students, the possibility of offering the lesson as a regular course was examined with analysis of the students' reactions showing its effectiveness.

• Communications of Mathematical Education
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• v.31 no.4
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• pp.389-407
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• 2017

Many researches related to STEAM education have been actively conducted for developing elementary and secondary school students' comprehensive and logical thinking ability in relation to creativity education in Korea. Each sub factor of STEAM education requires creative thinking with the ability to be merged together to solve problems as integrated or combined forms in the fields of Science, Technology, Engineering, Arts, and Mathematics. Also, these STEAM activities and experiences should be carried out at various places outside the classroom in school. Although various educational programs to enhance mathematical creativity have been emphasized for elementary and secondary school students, recent tendency to focus on classroom learning in the school makes it difficult to develop creative thinking ability of students. This research is mainly based on the result of the project "Development and Administration of STEAM Outreach Program in 2016" supported by KOFAC(Korea Foundation for the Achievement of Science & Creativity). The purpose of this research is to develop a STEAM outreach program including students' activity books, teachers' manuals and administration manual that can maximize STEAM-related interest of students, and to provide a chance for elementary and secondary school students to experience creative thinking based on sub factors of STEAM. The STEAM competency total score and the perception of convergence education were significantly increased for all students participating this program, but some sub factors showed different result by school levels. The STEAM outreach program developed by this study is designed to emphasize STEAM education especially 'based on' mathematics in order to provide students with the opportunity to experience more interest in the field of mathematics and will be able to provide an interesting creative STEAM outreach program that utilizes a variety of activities which, we expect, would help students to consider their career in the future.

• Korean Journal of Health Education and Promotion
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• v.33 no.1
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• pp.71-85
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• 2016

Objectives: The aim of this study is to verify relationship between suicidal ideation and associated socio-demographic, psychological and behavioral, violence, protective factors among in poor urban area adolescents in Peru. Methods: A cross-sectional survey was conducted in a sample of 981 secondary school adolescents in 2014 collaborating with Korea International Cooperation Agencies (KOICA) Peru office. For statistical analysis, Chi-square test, logistic regression analysis methods were used. Results: 14.0% of male and 37.1% of female were reported having suicidal ideation during the past 12 months. Suicidal ideation experience of male is affected by mother's education level, depression, life satisfaction, sexual intercourse experience, fight experience, insulted experience. Female is affected by depression, life satisfaction, sexual intercourse experience, insulted experience and physical abuse experience. Conclusions: Suicidal ideation experience in poor urban area of Peru is affected by socio-demographic, psychological and behavioral, violence factors. To solve and prevent suicide of adolescents in this kind of area, it is necessary to apply an integrated development program for parents and teachers to participate. For the sustainable preventive program, there is a need to introduce a counseling program, such as psychological counseling to adolescents suicide prevention programs.

• Journal of Educational Research in Mathematics
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• v.24 no.4
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• pp.645-668
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• 2014

This study was designed to gain insights into contemporary secondary mathematics curriculum revision in Korea. The two secondary mathematics curriculum reports submitted in the 1920s, the Kilpatrick Reports and 1923 Reports were compared and contrasted as the origin of recent math wars, and their backgrounds, committee members, viewpoints of math and math education and contents were analyzed to understand the perspectives of the two extreeme parts. Kilpatrick Reports was selected at that time, but nevertheless 1923 Report had taken a role of guiding secondary mathematics in US until the New Math era. The direction and process of mathematics curriculum revision were suggested based on the analysis of reports' short- and long-term influences. A close examination of the curriculum revision process in US and in Korea and the implications from the results are also included in the suggestion.

• Journal of Mechanical Science and Technology
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• v.17 no.5
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• pp.726-739
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• 2003

A multi-dimensioanl model is being increasingly used to predict the thermo-flow field in the gas turbine combustor. This article addresses an integrated survey of modeling of the liquid spray formation and fuel distribution in gas turbine with high-shear nozzle/swirler assembly. The processes of concern include breakup of a liquid jet injected through a hole type orifice into air stream, spray-wall interaction and spray-film interaction, breakup of liquid sheet into ligaments and droplet,5, and secondary droplet breakup. Atomization of liquid through hole nozzle is described using a liquid blobs model and hybrid model of Kelvin-Helmholtz wave and Rayleigh-Taylor wave. The high-speed viscous liquid sheet atomization on the pre-filmer is modeled by a linear stability analysis. Spray-wall interaction model and liquid film model over the wall surface are also considered.

• Nuclear Engineering and Technology
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• v.54 no.6
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• pp.2055-2061
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• 2022

In the event of a short-circuit accident on a 4.16 kV non-safety bus, the voltage is temporarily lowered as backflow occurs on the safety bus. In such cases, the undervoltage relay of the safety bus shall not pick up the undervoltage so as not to interfere with the operation of the safety motors. The aim of this study is to develop an adaptive undervoltage protection scheme for the 4.16 kV safety bus considering the faults on the 13.8 kV and 4.16 kV non-safety buses connected to secondary windings of the three winding transformers, UAT and SAT. The result of this study will be the adaptive undervoltage protection scheme for the safety bus of nuclear power plants satisfying functional requirements of the safety related medium voltage motors. The adaptive undervoltage protection scheme can be implemented into an integrated digital protective relay to make user friendly and reliable protection scheme.

• International Journal of Computer Science & Network Security
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• v.23 no.4
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• pp.55-68
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• 2023

In recent years, the Television White Space (TVWS) has attracted the interest of many researchers due to its propagation characteristics obtainable between 470MHz and 790MHz spectrum bands. The plenty of unused channels in the TV spectrum allows the secondary users (SUs) to use the channels for broadband services especially in rural areas. However, when the number of SUs increases in the TVWS wireless network the aggregate interference also increases. Aggregate interferences are the combined harmful interferences that can include both co-channel and adjacent interferences. The aggregate interference on the side of Primary Users (PUs) has been extensively scrutinized. Therefore, resource allocation (power and spectrum) is crucial when designing the TVWS network to avoid interferences from Secondary Users (SUs) to PUs and among SUs themselves. This paper proposes a model to improve the resource allocation for reducing the aggregate interface among SUs for broadband services in rural areas. The proposed model uses joint power and spectrum hybrid Firefly algorithm (FA), Genetic algorithm (GA), and Particle Swarm Optimization algorithm (PSO) which is considered the Co-channel interference (CCI) and Adjacent Channel Interference (ACI). The algorithm is integrated with the admission control algorithm so that; there is a possibility to remove some of the SUs in the TVWS network whenever the SINR threshold for SUs and PU are not met. We considered the infeasible system whereby all SUs and PU may not be supported simultaneously. Therefore, we proposed a joint spectrum and power allocation with an admission control algorithm whose better complexity and performance than the ones which have been proposed in the existing algorithms in the literature. The performance of the proposed algorithm is compared using the metrics such as sum throughput, PU SINR, algorithm running time and SU SINR less than threshold and the results show that the PSOFAGA with ELGR admission control algorithm has best performance compared to GA, PSO, FA, and FAGAPSO algorithms.

• Journal of The Korean Association For Science Education
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• v.19 no.2
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• pp.315-328
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• 1999

The purpose of this study was to investigate the effects of psychological learning environment generated by science teachers upon students' affective perceptions and cognitive learning. The subjects of the study were consist of 2.693 students from secondary school. The students' perception were examined by the tools of PLEIS(Psychological Learning Environment Instrument by Science teacher). SAMS(Science Anxiety Measurement Scale). HARS(High schools' s Attitude Related Science). and ALWSS(Attitude toward Laboratory Work Scale in Secondary school). and cognitive learning outcomes assessed to TIPS II (Test of Integrated Process Skills II ) and science test score. The results of this study suggest that positive psychological learning environment by science teacher should be offered to students for the improvement of science achievement. and learning environment will be used as an instrument of self assessment for improving science teaching strategy. Understanding of relationship among psychological learning environment, affective perception and cognitive learning will be helpful to the design of science teaching and learning process.