• 한국과학교육학회지
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• 제22권4호
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• pp.862-871
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• 2002

본 연구에서는 사전개념 검사 문제를 분석하여 간단한 전기회로 개념에 관한 초등학생들의 오개념 유형을 알아보고, 인지갈등 검사문항으로 자신의 생각과 불일치한 동료 한명과 자유롭게 토론을 한 후의 인지갈등정도와 토론에서 사용한 같은 인지갈등 검사 문항으로 체험을 한 후의 인지갈등정도를 비교하였다. 대도시에 위치한 K초등학교 6학년 7개 학급 264명을 대상으로 학생들의 간단한 전기회로 개념에 관한 오개념 유형을 조사한 결과, 많은 학생들이 전구가 2개의 전기적 단자를 갖고 있음을 모르고 있었으며, 전구의 꼭지를 강조하거나 전지의 +극을 강조하는 경우가 있었고 단일극 모형을 가진 경우도 상당수 나타났다. 전지의 +극에 전구가 옆으로 뉘어져 있고 전선이 꼭지쇠와 전지 -극에 연결된 문항을 인지갈등 검사문항으로 선정하였다. 선정된 인지갈등 검사문항으로 미리 구성한 토론 조에게 동료의 생각을 듣고 학습지에 적도록 한 다음에 자유롭게 토론을 하게 하였으며, 토론을 마친 후에 인지갈등검사를 하였다. 토론 내용을 알아보기 위해서 몇 쌍은 녹음, 녹화하여 프로토콜을 전시하여 학생들의 생각을 알아보았다. 체험은 토론을 하지 않은 같은 학교 6학년 학생으로 짝과 함께 2인 1조로 직접 실험을 하여 인지갈등 정도를 측정하였다. 토론과 체험을 통한 인지갈등 요소별 응답 점수를 비교해 본 결과는 다음과 같다. 토론은 인지적 재평가, 불안, 인식, 흥미 순으로 인지갈등이 높게 나타났고 그 중에서 인지적 재평가가 높게 나타났다. 체험은 인식, 인지적 재평가, 흥미, 불안 순으로 인지갈등이 높게 나타났고 불안의 반응치가 현저하게 낮게 나타났다. 인지갈등 요소별 인지갈등 점수를 살펴보면 흥미, 불안, 인지적 재평가에서는 토론이 체험보다 점수가 높게 나타났다. 특히 불안 요소와 인지적 재평가 요소에서는 토론이 체험보다 점수가 높고 유의미한 차이를 보였다. 그 까닭은 직접 실험으로 확인하지 못하고 토론만 하였기 때문으로 생각된다. 토론집단의 남녀 차이에 따른 인지갈등 요소별 응답 점수를 분석한 결과 남자는 인지갈등 요소별 점수가 인지적 재평가, 인식, 불안, 흥미 순으로 높게 나타났다. 그 중에서 인식의 반응치가 높게 나타난 반면에 흥미 점수가 낮게 나타났다. 여자는 인지적 재평가, 불안, 흥미, 인식 순으로 높게 나타났고 인지적 재평가의 반응치가 그 중에서 높게 나타난 반면에 인식 점수가 낮게 나타났다. 토론으로 인지갈등을 유발했을 때 갈등 요소 중 인지적 재평가에서는 여자가 남자보다 점수가 높고 유의미한 차이를 보였고, 인식에서는 남자가 여자보다 점수가 높고 유의미한 차이를 보였다. 체험집단의 남녀 차이에 따른 인지갈등 요소별 응답 점수를 분석한 결과 체험으로 인지갈등을 일으켰을 때 인식요소를 제외한 흥미, 불안, 인지적 재평가 요소에서 남자가 여자보다 인지갈등 점수가 높게 나왔고, 특히 인지적 재평가 요소에서는 유의미한 차이를 보였다. 그 까닭은 남학생이 여학생보다 직접 실험하고 조작해 보는 경험을 많이 가졌기 때문이라고 생각된다.

• 전기학회논문지P
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• 제59권4호
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• pp.434-439
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• 2010

This study fabricated a simulation facility which reduced the structure of a current distribution line to 50:1 in order to analyze the induced lightning shielding effect of a 22.9kV-Y distribution line according to ground resistance capacity, grounding locations, etc. When installing an overhead ground wire, the standard for grounding a distribution line with a current of 22.9kV-Y requires that ground resistance in common use with the neutral line be maintained less than $50\Omega$every 200m span. The reduced line for simulation had 7 electric poles and induced lightning was applied to the ground plane 2m apart from the line in a direction perpendicular to it using an impulse generator. If induced voltage occurred in the line and induced current flowed through the line due to the applied current, the induced voltage and current of the 'A' phase were measured respectively using an oscilloscope. When all 7 electric poles were grounded with a ground resistance of less than $50\Omega$ respectively, the combined resistance of the line was $7.4\Omega$. When an average current of 230A was applied, the average induced voltage and current measured were 1,052V and 13.8A, respectively. Under the same conditions, when the number of grounding locations was reduced, the combined resistance as well as induced voltage and current showed a tendency to increase. When all 7 electric poles were grounded with a ground resistance of less than $100\Omega$, the combined resistance of the line was $14.9\Omega$. When an average current of 236A was applied, the average induced voltage and current of the 'A' phase calculated were 1,068V and 15.6A, respectively. That is, in this case, only the combined resistance was greater than when all 7 electrical poles were grounded, and the induced voltage and current were reduced. Therefore, it is thought that even though ground resistance is slightly higher under a construction environment with the same conditions, it is advantageous to ground all electric poles to ensure system safety.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.1497-1502
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• 2011

Increasing tensions of contact wire and messenger wire are essential to construct a test-bed for catenary system in the 400km/h speed on Honam high-speed railway. Because heavy load is applied to a mast due to the increased the tensions of both wires it is required to investigate the strength of the foundation. Therefore, in this study the maximum moment of an electric pole under the worst condition was calculated to investigate the strength of the pole foundation on the bridges. The maximum moment database table used in the construction of Kyungbu high-speed railway was referenced to derive the worst conditions and to review the composition of catenary system in the test-bed section. From the results of this study regarding assumptions and calculation process it will be possible to estimate the optimized strength of the pole foundations on the bridges which will be constructed in the future.

• 전기학회논문지
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• 제62권4호
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• pp.573-576
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• 2013

In this paper, analysis method for current collection performance based on real-time current of catenary system is proposed. An innovative method based on track-side of railway system is used for measurement of currents for overhead contact line during the collection with pantograph. The evaluation of a qualitative ratio for current collection performance were conducted using proposed algorithm under various conditions such as laboratory and track-side. To check the validity of our approach, we compared between calculation results from current of contact wire and measurement results from arcing of pantograph using simulator in laboratory conditions. The results show that the behavior of current collection performance were analysis from currents of overhead contact line in AC electric railway system.

• 전기학회논문지P
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• 제66권4호
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• pp.200-205
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• 2017

In this paper, we propose a technique to determine the normal and arc of an alternating current using a mixed filter composed of an average filter and a band-pass filter and a frequency analysis. The proposed method uses the moving average filter of the FIR filter structure for noise removal and the band-pass filter of the IIR filter structure for detecting only specific frequency components after normalizing the measured current signal based on the maximum value. After performing Fast Fourier Transform (FFT) using the band-pass filtered signal, the total energy is calculated using the magnitude component of the frequency, and the arc is detected using the magnitude of the calculated energy. In order to show the validity of the proposed method, we experimented with various data and found that arc and steady state can be easily discriminated by calculating spectral energy. Therefore, it is considered that the proposed method can be applied to arc diagnosis of low voltage electric wire.

• 조명전기설비학회논문지
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• 제21권9호
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• pp.57-63
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• 2007

The occurrence of a corona is that electrical discharge due to the heterogeneity that occurs when an electrical field is concentrated in an electrode due to a cusp formed on said electrode. Wire treatment at the end of a 154[kV] dead end clamp for end users accelerates the occurrence of corona, which in turn leads to power loss and noise. In this study, the characteristics of the corona which occurs between porcelain insulators and support clamps of overhead lines used in 154[kV] power receiving facilities for end users were investigated. The corona, which cannot be identified by one common method, was measured utilizing a UV image camera. A risk assessment for fire damage and its status was suggested. The stress distribution of the electrical field by length of bare wire was suggested by means of the finite element method(FEMLAB). As a result, it was found to affect a porcelain insulators. These results can be utilized for the enhancement of clamp installation and safety in power facilities.

• Structural Engineering and Mechanics
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• 제17권3_4호
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• pp.331-346
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• 2004

A new sensor system is proposed for measuring damage indexes. The damage index is a physical value that is well correlated to a critical damage in a device or a structure. The mechanism proposed here utilizes elastic buckling of a thin wire and does not require any external power supply for memorizing the index. The mechanisms to detect peak strain, peak displacement, peak acceleration and cumulative deformation as examples of damage indexes are presented. Furthermore, passive and active wireless data retrieval mechanisms using electromagnetic induction are proposed. The passive wireless system is achieved by forming a closed LC circuit to oscillate at its natural frequency. The active wireless sensor can transmit the data much further than the passive system at the sacrifice of slightly complicated electric circuit for the sensor. For wireless data retrieval, no wire is needed for the sensor to supply electrical power. For the active system, electrical power is supplied to the sensor by radio waves emitted from the retrieval system. Thus, external power supply is only needed for the retrieval system when the retrieval becomes necessary. Theoretical and experimental studies to show excellent performance of the proposed sensor are presented. Finally, a prototype damage index sensor installed into a 7 storey base-isolated building is explained.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 춘계학술대회 논문집 전기설비전문위원
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• pp.10-12
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• 2009

Electromagnetic Interference(EMI) in electric railway operation has become increasingly important. The components within very high power electronic, and the circuits for treating low-level signals, comprise complex system that must coexist and be highly reliable. To study it, It were included how much the HEMU-400X generates EMI and it has an effect on the power conversion units which resulted from Power Line Disturbance (PLD) phenomenon by contact loss during its running. In this study, the dynamic characteristic of a contact wire and pantograph suppling electrical power to high-speed trains are investigated. The analysis of the loss of contact based on Power Simulator program software is performed to develop power line disturbance model suitable for high speed operation. It is confirmed that a contact wire and pantograph model are necessary for studying the dynamic behavior of the pantograph system.

• Progress in Superconductivity
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• 제5권2호
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• pp.149-152
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• 2004

The design and the fabrication of a 1 MVA single-phase HTS transformer are presented in this paper, The rated voltages are 22.9 ㎸ for primary and 6.6 ㎸ for secondary, and the rated currents are 44 A and 152 A respectively. The transformer has HTS double pancake type windings. This type of winding has many advantages such as ease of fabrication and maintenance, good distribution of surge voltage and insulation of windings. Single HTS wire was used for primary winding and four HTS parallel wires were used for secondary winding. These windings are arranged reciprocally with the shell type iron core. An FRP cryostat with room temperature bore was fabricated to isolate the iron core from the coolant. The winding will be cooled down to 65 K with sub-cooled liquid nitrogen using a GM-cryocooler. The sub-cooled liquid nitrogen has advantages of good insulation because of no bubbles as well as increased current capacity of HTS wire.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.251-254
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• 2001

In this paper, we analyzed the properties change of electric wire when the thermal stress was applied to NFR-8 and FR-PVC 600[V] wire. Messurement is made of the attenuation of a light beam by smoke accumulating with in a closed chamber due to nonflaming pyrolytic decomposition and flaming combustion. Results are expressed in terms of specific optical density which is derived from a geometrical factor and the measured optical density a measurement characteristic of the concentration of smoke. Referenced documents were ASTM E662 standard test method for specific Ds genalated by solid materials. The furnace control system shall maintain the required irradiance level under steady-state condition with the chamber door closed of $2.5{\pm}0.04[w/cm^{2}]$ for 20 min. According to the results of the smoke density analysis of NFR-8 and FR-PVC the highest decomposition flaming smoke density range of NFR-8 and FR-PVC were 25.2 to 37.5 and 51.1 respectively. Nonflaming smoke density range of NFR-8 and FR-PVC were 100.4 to 112.2 and 126.5 to 398.8. The amount of carbon monoxide generated was found to be much higher in FR-PVC decomposition than in NFR-8 due to incomplete combustion of FR-PVC which has high content of carbon in compound.