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이현동,김충년,박광서,이광식,이동인,Lee, Hyun-Dong,Kim, Chung-Nyun,Park, Kwang-Seo,Lee, Kwang-Sik,Lee, Dong-In 대한전기학회 2000 전기학회논문지C Vol.55 No.12
This paper deals with the multiresolution analysis of wavelet transform for partial discharge(PD). Test arrangement is based on the needle-plane electrode system and applied AC high voltage. The measured PD signal was decomposed into "approximations" and "details". The approximation are the high scale, low-frequency components of the PD signal. The details are the low-scale, high frequency components. The decomposition process are iterated to 3 level, with successive approximation being decomposed in turn, so that PD signal is broken down into many lower-resolution components. Through the procedure of signal wavelet transform, signal noise extraction and signal reconstruction, the signal is analyzed to determine the magnitude of PD.
산화철-탄소나노튜브 나노복합체의 암모니아 가스센서 응용
이현동,김다혜,고다애,김도진,김효진,Lee, Hyundong,Kim, Dahye,Ko, DaAe,Kim, Dojin,Kim, Hyojin 한국재료학회 2016 한국재료학회지 Vol.26 No.4
Fabrication of iron oxide/carbon nanotube composite structures for detection of ammonia gas at room temperature is reported. The iron oxide/carbon nanotube composite structures are fabricated by in situ co-arc-discharge method using a graphite source with varying numbers of iron wires inserted. The composite structures reveal higher response signals at room temperature than at high temperatures. As the number of iron wires inserted increased, the volume of carbon nanotubes and iron nanoparticles produced increased. The oxidation condition of the composite structures varied the carbon nanotube/iron oxide ratio in the structure and, consequently, the resistance of the structures and, finally, the ammonia gas sensing performance. The highest sensor performance was realized with $500^{\circ}C/2h$ oxidation heat-treatment condition, in which most of the carbon nanotubes were removed from the composite and iron oxide played the main role of ammonia sensing. The response signal level was 62% at room temperature. We also found that UV irradiation enhances the sensing response with reduced recovery time.
이현동,정원식,지재성 ( Hyun Dong Lee,Won Sik Chung,Chai Sung Gee ) 한국물환경학회 1998 한국물환경학회지 Vol.14 No.1
Water quality in water distribution system is changed biological, physicochemical and organoleptic qualities, and then it has been more worse. Chlorine residual was used to as indicator for prediction of water quality behavior, characteristics and ensurement of regulatory requirment. Therefore, M&O of chlorine residual is to be important for water quality management in water distribution system. This study was performed to study the relationship for water quality changes and characteristic of chlorine residual decay according to pipe type and diameter, hydraulic effect, and water quality parameter. Results of this study indicated decay coefficient of chlorine residual was to characterized with pipe type and diameter. Also it was to different hydraulic effect and initial chlorine residual concentration and water quality parameter as temperature, TOC, etc.
Iceberg(IB) 모델을 적용한 고등학생의 시스템 사고 분석 및 효과
이현동,이효녕,Lee, Hyundong,Lee, Hyonyong 한국과학교육학회 2017 한국과학교육학회지 Vol.37 No.4
이 연구의 목적은 고등학생들의 시스템 사고를 측정하는 분석하는 도구로 Iceberg(IB) 모델을 적용하고, 시스템 사고 평가를 위한 루브릭을 활용한 IB 모델 활동 결과 분석 방법을 제시하며 그 효과를 검증하는 것이다. 문헌 분석을 통해 IB 모델과 시스템 사고 평가를 위한 루브릭의 활용에 대한 이론적 근거를 조사하였다. 그리고 6명의 고등학교 학생에게 극지방 기후 변화와 관련된 주제에 대하여 IB 모델 활동을 실시하였으며 활동 과정 중 비구조화된 면담을 통해 학생들의 시스템 사고를 조사하였다. 또한 IB 모델을 활용한 시스템 사고 분석 결과에 대한 효과를 검증하기 위하여 시스템 사고 측정 도구를 활용한 정량적 검사도 실시하였다. IB 모델의 분석은 Hung(2008)에 의해 개발된 시스템 사고 평가를 위한 루브릭을 활용하여 분석하였으며 분석한 결과는 지구과학교육 전문가 2인에게 검토를 받아 타당도와 신뢰도를 확인하였다. 그리고 루브릭 결과와 시스템 사고 측정 도구 검사 결과에 대한 상관관계 분석을 통해 타당도를 재확인하였다. 연구 결과 6명의 학생은 IB 모델을 활용하여 자신들이 가지고 있는 사고를 구체적으로 잘 표현하였으며 루브릭을 활용한 시스템 사고 분석 결과 학생들은 17~35점까지의 분포를 보여주었다. 또한 시스템 사고 측정 도구 결과와 상관관계를 분석한 결과 Pearson 상관계수가 유의수준 .05에서 .856으로 매우 높은 상관을 보여주었다. 이 연구에서 제시한 IB 모델을 적용하면 학생 스스로 시스템 사고를 잘 표현할 수 있으며, 루브릭을 활용한 시스템 사고 분석 결과는 타당도와 신뢰도를 가지는 것으로 판단된다. 이러한 연구 결과를 바탕으로 앞으로의 과학 교육에서 시사점과 시스템 사고 연구의 방향을 제안하였다. The purposes of this study are to explore Iceberg(IB) model as a systems thinking analysis tool for high school students, suggest a systems thinking analysis method using rubrics and verify its validity and reliability. For this study, the theoretical basis was examined through literature analysis about IB model and rubrics of evaluating the systems thinking. And 6 high school students participated in IB model activity and were interviewed about polar climate change. In addition, quantitative tests using systems thinking scale were also conducted to support the results of the IB model activity analysis. Data obtained from IB model activity was analyzed by using the rubrics of evaluating system thinking developed by Hung (2008). The analysis results were reviewed by two professors to confirm the validity and reliability. In order to confirm the validity, correlation analysis were performed between the rubrics and the quantitative test results. Finding are as follows: Six students used the IB model to express their systems thinking in detail and the results of the systems thinking analysis of students using rubrics showed a distribution of 17~35 points. Furthermore, the results of correlation analysis between rubrics and systems thinking scale was highly correlated (Pearson product-moment is .856) on significance level from .05. Using the IB model introduced in this study, students express their systems thinking effectively and the results of the systems thinking analysis using IB model is considered to analyze validity and reliability. Based on the results of this study, implication suggests how to study the systems thinking in science education.