• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.310-315
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• 2008

Authors design a rotary-type small-scaled linear induction motor(LIM) and a performance test machine before manufacturing a real-scaled LIM for a railway transit. The designed LIM is a single-sided, short primary type and its primary has 4 poles. The rated power is 10(kW). In order to analyze characteristics of the LIM, authors use a mixed 2D-3D FEM analysis. 3-D FEM analysis is used for calculating a distribution of eddy-current on the semi-caped AL-sheet of the secondary reaction. Authors calculate a correction factor of conductivity and an equivalent conductivity on the secondary AL-sheet using a normalized eddy-current. The equivalent conductivity which is calculated in this way includes a transverse edge-effect of the LIM. Authors apply the equivalent conductivity on the secondary AL-sheet of 2D-FEM model and get performance characteristics of the LIM. Basic characteristics such as thrust and normal force, input current, efficiency and power factor of the LIM have been analyzed with the variation of frequency and speed. In order to apply an air-gap control system, the variation of the basic characteristics have been analyzed with the air-gap length variation of the LIM. Finally, authors introduce an operation mode using the air-gap control system and conduct a research on feasibility of the system.

• Current Optics and Photonics
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• 제6권1호
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• pp.69-78
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• 2022

A high-resolution camera is a precise optical system. Its vibrations during transportation and launch, together with changes in temperature and gravity field in orbit, lead to different degrees of defocus of the camera. Thermal refocusing is one of the solutions to the problems related to in-orbit defocusing, but there are few relevant thermal refocusing mathematical models for systematic analysis and research. Therefore, to further research thermal refocusing systems by using the development of a high-resolution micro-nano satellite (CX6-02) super-resolution camera as an example, we established a thermal refocusing mathematical model based on the thermal elasticity theory on the basis of the secondary mirror position. The detailed design of the thermal refocusing system was carried out under the guidance of the mathematical model. Through optical-mechanical-thermal integration analysis and Zernike polynomial calculation, we found that the data error obtained was about 1%, and deformation in the secondary mirror surface conformed to the optical index, indicating the accuracy and reliability of the thermal refocusing mathematical model. In the final ground test, the thermal vacuum experimental verification data and in-orbit imaging results showed that the thermal refocusing system is consistent with the experimental data, and the performance is stable, which provides theoretical and technical support for the future development of a thermal refocusing space camera.

• 한국안전학회지
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• 제38권2호
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• pp.36-43
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• 2023

In this study, a four-point bending test was conducted to assess and detect the damage to reinforced concrete structures using the acoustic emission (AE) technique. Based on the crack investigation results, flexural failure was classified into four stages and compared with the characteristic analysis results of AE parameters. The parametric characterization indicated that the activity of the primary AE signal was high in the early stage, and that of the second signal increased after the flexural cracks stabilized. Because the secondary AE signal included noise generated by friction, parameter-based analysis for damage assessment was performed using the primary signal; the secondary signal was used as complement. The activity analyses of the primary and secondary signals effectively classified crack propagation; however, determining the macrocracks and yielding of reinforcing bars had certain limitations. Nevertheless, applying the damage index with cumulative AE energy is a complementary technique for detecting and assessing structure damage that well detects the occurrence of macrocracks.

• 한국전기전자재료학회논문지
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• 제36권6호
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• pp.614-619
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• 2023

The fault current limiting characteristics of three-phase transformer type superconducting fault current limiter (SFCL), which consisted of three-phase primary and secondary windings wound on E-I iron core, one high-TC superconducting (HTSC) element connected with the secondary winding of one phase and another HTSC element connected in parallel with other two secondary windings of two phases, were analyzed. Unlike other three-phase transformer type SFCLs with three HTSC elements, three-phase transformer type SFCL using double quench has the merit to perform fault current limiting operation for three-phase ground faults with two HTSC elements. To verify its proper three-phase ground fault current limiting operation, three-phase ground faults such as single-line ground, double-line ground and triple-line ground faults were generated in three-phase simulated power system installed with three-phase transformer type SFCL using double quench. From analysis of its fault current limiting characteristics based on tested results, three-phase transformer type SFCL using double quench was shown to be effectively operated for all three-phase ground faults.

• 산업융합연구
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• 제21권8호
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• pp.87-96
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• 2023

본 연구는 중등 예비체육교사들이 배움중심수업에 대해 어떠한 의미를 부여하는지 메타포 분석을 통해 알아보고, 체육수업 중 배움중심수업의 적용에 대하여 인식을 점검하고자 하는 데 그 목적이 있다. 연구 목적을 달성하고자 배움중심수업에 대한 인식을 메타포로 표현하는 설문 조사로 실시하였다. 자료 분석은 메타포 분석방벙론에 따라 코딩, 메타포 분류, 분석 단위 결정, 표본의 범주화 등의 과정을 통해 처리되었다. 그 결과 교육의 필요성, 교육의 목표 및 내용, 교수·학습 방법 및 평가, 교사 교육 및 역할이라는 4개의 대분류와 자아실현을 위한 수업, 미래 사회 준비를 위한 수업, 창의성을 기르는 수업, 개방적이고 다양한 수업, 호기심 자극 및 흥미 유발 수업, 개인의 발달 및 특성에 적합한 수업, 실천하기 부담스러운 수업, 교사의 창의성과 독창성이 필요한 수업의 8개 내용유형으로 도출되었다. 본 연구의 결과를 통해 배움중심수업의 필요성 및 방향에 대해 그 시사점을 확인할 수 있었다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제7권3호
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• pp.138-149
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• 2002

Plant cell culture provides a viable alternative over whole plant cultivation for the production of secondary metabolites. In order to successfully cultivate the plant cells at large scale, several engineering parameters such as, cell aggregation, mixing, aeration, and shear sensitivity are taken into account for selection of a suitable bioreactor. The media ingredients, their concentrations and the environmental factors are optimized for maximal synthesis of a desired metabolite. Increased productivity in a bioreactor can be achieved by selection of a proper cultivation strategy (batch, fed-batch, two-stage etc.), feeding of metabolic precursors and extraction of intracellular metabolites. Proper understanding and rigorous analysis of these parameters would pave the way towards the successful commercialization of plant cell bioprocesses.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.703-706
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• 2011

Contactless systems use electromagnetic fields to transport power from railway substation to the traction system. In Korea Railroad Research Institute, KRRI, the RIPS (Railway Inductive Power Supply), has been developed. The RIPS is based on a contactless transformer with a fixed coreless primary and a moving core, compared with E shape and U shape, in the secondary. The primary coil is supply with 20 kHz current which produces a magnetic flux in the secondary core. Further this flux induces a current in the secondary coil.

• 한국수학교육학회지시리즈D:수학교육연구
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• 제17권2호
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• pp.119-131
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• 2013

It is the first time that there is a subject, advanced mathematics in the 2009 revised high school curriculum. Therefore it is posing a challenge to the teachers who are teaching it. At the advanced level, it is important for learners to reflect on their mental mathematical activities. This research analysed pre-service secondary teachers' reflective thinking in solving the tasks specific for the teaching and learning of polar coordinates. We report how and through what process mathematical tasks that can create disequilibrium for pre-service secondary teachers enable reflective thinking and expand preservice secondary teachers' thoughts and recognition of defining reflective thinking in looking back on one's problem solving and thinking processes.

• 영어어문교육
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• 제11권4호
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• pp.237-259
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• 2005

Secondary English Education in Korea is implemented according to the 7th National Curriculum. The 7th National English Curriculum pursues to achieve communicative competence considering individual differences. According to the research, using various multimedia in English education enhances English proficiency and allows effective individual-based learning. The purpose of this study is to investigate the implementation of applying multimedia in English education within the framework of the 7th National Curriculum. For this purpose, a questionnaire-based survey was conducted in 2005 with 145 secondary English teachers in Kyunggy Province. The results showed that multimedia was not integrated in English education effectively, and individual based-learning was not implemented effectively, either.

• Corrosion Science and Technology
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• 제15권3호
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• pp.135-140
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• 2016

Piping and equipment are degraded by flow-accelerated corrosion (FAC) in nuclear power plants. FAC causes numerous problems and nuclear utilities maintain programs to control FAC. The key parameters influencing FAC are hydrodynamic conditions, water chemistry, and effect of materials. Recently, a nuclear utility has planned slight power uprates in Korea. Operating conditions need to be changed in the secondary system according to power uprates. This study analyzed the effect of wall-thinning caused by power uprates. The change of operation data in the secondary cycle is reviewed, and wall-thinning rates are analyzed in the main lines. As a result, two phase (mixture of water and steam) lines have a greater impact than a water line under power uprate conditions. Also, the quality of steam is the most important factor for FAC in two phase lines.