• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.65-67
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• 2018

최근 무선전력분야에서도 고전력 시스템에 대한 적용 연구가 활발해지고 있다. 이러한 시스템 설계는 시뮬레이션 소프트웨어 프로그램으로 설계를 할 수는 있지만, 실험 검증을 위해서는 고전력 수전 설비 및 고가의 측정 설비가 필요하고, 하드웨어를 제작하려면 많은 시간과 비용이 필요하다. 본 논문은 척도변환을 이용하여 코일 형상을 포함한 하드웨어 구조는 최대한 유지하고 소자정격과 입력 전력을 축소하여 시스템 성능을 사전 평가하는 방법을 제안한다. 도출된 이론을 바탕으로 150W급 무선전력 전송 시스템을 대상으로 15W급으로 10 : 1 비로 축소 적용 가능함을 시뮬레이션 실험으로 검증한다.

• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.77-79
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• 2018

본 논문에서는 inductive power transfer (IPT) 시스템 2차측 semi-bridgeless 정류기에 pulse density modulation (PDM) 제어를 적용하였을 때 1차측에 나타나는 영향을 최소화하기 위한 공진 네트워크 설계 방안을 제안한다. PDM 제어를 적용하였을 때 2차측 전류 리플이 증가하는 문제를 해결하기 위해 2차측 수신 인덕턴스를 증가시킴으로써 전류 리플을 저감하여 1차측 영향을 최소화한다. 이를 위해 적절한 설계 조건을 구하는 방안에 대하여 제시하고, 방안의 적용에 따른 1차측 영향을 시뮬레이션을 통해 분석한다.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.190-192
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• 2020

본 논문은 LCC-S 보상회로를 적용한 무선충전시스템의 출력전압 크기에 따른 송신부와 수신부 시스템의 손실을 비교하여 출력전압 설계 기준을 제시한다. 출력전압에 따라 풀 브리지 인버터와 송수신 PAD 및 보상회로, 정류기의 손실을 분석한다. 출력전압에 따른 송수신 시스템의 손실을 비교하여 LCC-S 공진 방식을 적용한 무선충전 시스템의 출력전압을 설계하는 기준을 제시한다. 출력전압에 따른 3.3kW 급 프로토타입을 제작하여 실험을 통해 제안된 분석의 타당성을 검증한다.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.181-183
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• 2020

본 논문에서는 DQ 변환을 적용한 직렬-병렬 공진형 무선전력 전송 시스템의 동기 좌표계 모델과 이를 이용한 전류제어기 시스템을 제안한다. 무선 전력 전송 시스템은 일반적으로 급전 측과 집전 측에 단상 전류가 흐르기 때문에 제어에 어려움이 있다. 따라서 정상 상태의 전압 및 전류의 수식을 이용하여 부하에 전달되는 전압 및 전류의 크기를 제어하는 경우가 많다. 따라서 과도 상태의 전압 및 전류의 동특성이 원하는 특성과 다르게 나타날 수 있다. 본 논문에서는 직렬-병렬 공진형 무선전력 전송 시스템의 단상 전압 및 전류를 DQ 변환하여 과도 상태 및 정상 상태의 전압 및 전류의 동특성을 해석할 수 있는 등가 회로 모델을 제시하고 이를 이용하여 과도 상태 제어를 위한 고성능 전류 제어기를 제안한다.

• Educational Technology International
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• v.24 no.2
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• pp.295-329
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• 2023

The recent development of metaverse-related technology has led to efforts to overcome the limitations of time and space in education by creating a virtual educational environment. To make use of this platform efficiently, applying learning analytics has been proposed as an optimal instructional and learning decision support approach to address these issues by identifying specific rules and patterns generated from learning data, and providing a systematic framework as a guideline to instructors. To achieve this, we employed an inductive, bottom-up approach for framework modeling. During the modeling process, based on the activity system model, we specifically derived the fundamental components of the learning analytics framework centered on learning activities and their contexts. We developed a prototype of the framework through deduplication, categorization, and proceduralization from the components, and refined the learning analytics framework into a 7-stage framework suitable for application in the metaverse through 3 steps of Delphi surveys. Lastly, through a framework model evaluation consisting of seven items, we validated the metaverse learning analytics framework, ensuring its validity.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.1
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• pp.148-156
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• 2007

This paper explains stocker system that is operated in the long distance and linear area. The power system of stocker system uses Contactless Power Supply(CPS) to reduce problems of particle generation. The circuit configuration of CPS is simplified than the conventional ones, and the prototype is designed for commercial product. To transfer output data(information) from crane(secondary vehicle system) of the CPS to Primary system optical modem and TMS320F243(DSP, TI) are used between primary and secondary. power system are used, and the output voltage is controlled by operating frequency modulation. This paper is applied to stocker system controlled as one to one communication between the moving part(secondary system) and fixed part(primary system) of crane using optical modem. The study makes one to multi communication between fixed part and moving part for the purpose of multi crane operation of stocker system and must be done in the future.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.12
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• pp.1958-1964
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• 2016

AC railway feeding system use single phase to supply power to the railway vehicles. And the system use the rail track as a return current path, so that current flows in the rail. In this situation inductive interference on communication system and unsafe environment can appear on railway system. Therefore knowing the current distribution of catenary system and analysing the return current is required. In this study detail return current distribution was analyzed by modeling the catenary system as 4-conductors group. The distribution characteristics and trends of return current were studied by using the PSCAD/EMTDC and FDTD method that based on Maxwell equation was used to calculate the induced voltage. Simulation code was made by MATLAB. Using this study result data, we can suggest the proper installation location of digital device and these data can be used for additional studies related to return current or induced voltage as a base data.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1778-1780
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• 2004

Microwave heating system of KSTAR consists of ECH and LHCD. ECH and LHCD offer the reliability of operation in the beginning of plasma formation and non-inductive current drive for long time steady state operation with maintaining MHD stability, respectively. LHCD demands 5 GHz of frequency and consists of c-band waveguide, 4-port circuitor, dry dummy load, dual directional coupler, E-bend, arc detector. Our system is a lineup type pulse modulator that has 45 kV of output pulse voltage, 90 A of pulse current, 4 us of pulse width. 1:4 step-up pulse transformer, 7 stages of PFN and thyratron tube (E2V, CX1191D) are used in this modulator. The purpose of this paper is to show the modulator design and experimental result.

• The Transactions of the Korea Information Processing Society
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• v.4 no.9
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• pp.2299-2308
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• 1997

While most machine learning research has been primarily concerned with the development of systems that implement one type of learning strategy, we use a multistrategy approach which integrates rule induction learning and instance-based learning, and show how this marriage allows for overall better performance. In the rule induction learning phase, we derive an entropy function, based on Hellinger divergence, which can measure the amount of information each inductive rule contains, and show how well the Hellinger divergence measures the importance of each rule. We also propose some heuristics to reduce the computational complexity by analyzing the characteristics of the Hellinger measure. In the instance-based learning phase, we improve the current instance-based learning method in a number of ways. The system has been implemented and tested on a number of well-known machine learning data sets. The performance of the system has been compared with that of other classification learning technique.

• The Mathematical Education
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• v.26 no.1
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• pp.11-19
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• 1987

The purpose of this research is to investigate the strategies for problem solving used by teachers and students and obtain some information which would be useful to enhance the ability of problem solving of the students. For this purpose we apply the thinking aloud method to study 6 graders and 6 teachers who were asked to solve 5 word problems. And we create a coding system to analyze those strategies. Using this coding system, we code the examinees and problems. we come up with the following facts from our study. (1) The number of strategies used by teachers is less than that used by students. (2) The characteristic of the strategies used by students is to set up an equation. (3) There is deep relationship between understanding the question and choosing the successful strategies for problem solving. (4) The students use the inductive argument more often than the teachers in the case of nonroutine mathematical problem. (5) The student of high success rate have fewer strategies than the others. From the above facts. it proposes the following conclusion for the enhancement of the ability of problem solving: So far the teachers usually use a few typical strategies for problem solving. But they need to create various strategies for pqoblem solving. It makes it possible for the students to choose proper strategies according to their ability. The students need to be given nicely constructed problem with enough time.