배전계통의 중성선에 흐르는 영상분 고조파의 저감장치에 대한 효용성 검토

노경수,김지만 동국대학교 산업기술연구원 2008 산업기술논문집 Vol.18 No.1

3상 4선식 배전계통에서 중성선에 흐르는 영상분 고조파 성분의 대부분은 단상교류 부하와 밀접한 관계가 있다. 이는 각상에 연결된 다수의 단상 정류회로에서 발생된 영상분 고조파가 중성선에서 각각의 합이 되어 선로보다 중성선에 더 많은 전류가 흐를 수 있다. 이 경우 중성선의 과부하나 배선용차단기 (MCCB)의 오동작을 유발할 수 있다. 그 대책으로 중성선에 영상분 고조파 저감장치(NCE)를 설치하는 것을 제시하고 있다. 본 논문에서는 영상분 고조파 저감장치 설치에 따른 중성선의 영상분 고조파 저감효과를 분석하여 전력계통 운용에 도움이 되고자 한다. Overcurrent at a neutral line in a three-phase four-wire distribution power system involves zero-sequence harmonic current which is deeply related to the single-phase loads. The zero-sequence harmonic currents caused by a number of single phase circuits are summed up at the neutral line and can be larger than the sum of each phase current. This causes the disturbances, such as the overheat of neutral and misleading Molded Case Circuit Breaker (MCCB). So, we propose a NCE(neutral current eliminator) at the neutral line to remove the disturbances. And this paper discusses that the proposed NCE effectively decreases the zero-sequence harmonic current, so it would help the power system operation.

空氣流動中의 噴射가스 燃料의 擴散에 關한 實驗的 硏究 (Ⅰ)

朴涇錫,金錫魯 慶熙大學校 1989 論文集 Vol.18 No.-

The mixture formation process has a great, influence on the performance and exhaust gas characteristics in the direct injection engines, such as Hydrogen engines and Diesel engines. This paper presents a fundamental study on the mixing process of compound jets. In this experimental study, the tracers used are CO_2, H_2 and He. The average-velocity of the air injected is 3m/sec, 5m/sec, 8m/sec, and 10m/sec. To observe spreading behavior of gas fuel, the Schlieren apparatus was used to take a picture of the fluid density. Then the values of the potential core length(Z_P), the potential core length and the transient length (Z_t), and the visual extension angle (φ) were obtained by visualized photo-analysed. The visual extension angle is decreased irrelatively for variety of injected gas, and is increased with constant grade in the area transient jet is occured. Experimental parameters are the average injection velocity of the tracer and the average injection velocity of the air.

초등학교 고학년 학생의 과학 탐구능력 측정을 위한 평가 도구 개발

송경혜,이항로,임청환 한국과학교육학회 2004 한국과학교육학회지 Vol.24 No.6

본 연구에서는 평가도구의 구비조건을 갖춘 초등학교 고학년 학생의 과학탐구능력을 측정할 수 있는 과학탐구 능력 평가도구를 개발하고자 하였다. 평가도구를 구성하는 문항은 R&D 방법에 의해 개발되었으며, 2차례에 걸친 과학교육 전문가의 점검과 2번의 현장 검증을 통해 문항을 수정ㆍ보완하였다. 각 평가 문항은 교과 내용에 대한 지식이 없어도 해결할 수 있는 범교과적인 문항으로 제작하여 과학탐구능력의 하위 요소들을 측정하고자 하였다. SAPA 교육과정과 제7차 과학과 교육과정에서 제시한 과학탐구과정 요소를 근간으로 관찰, 분류, 측정, 예상, 추리, 문제인식, 변인통제, 자료해석, 결론도출, 실험설계의 10가지 하위 요소들을 선정하고 각 요소에 대한 조작적 정의와 평가 목표를 설정하였다. 물질과 에너지, 생명과 환경, 지구와 순환의 3가지 내용 영역의 소재를 중심으로 총 30문항을 개발하였다. 개발된 문항을 과학교육 전문가에게 2회 의뢰하여 타당도, 객관도, 문항의 명료성을 점검 받았으며 2번의 현장 검증을 통해 신뢰도, 변별도, 난이도를 검증하였다. 그 결과 타당도 91.6%, 신뢰도 지수 Cronbach α값 0.79, 객관도 93.3%, 변별도 지수 0.30, 난이도 지수 66.1%로 나타났다. 위와 같은 값들은 평가도구가 갖추어야 할 구비조건의 허용 범위내에 있는 것으로 보아 본 연구에서 개발한 과학탐구능력 평가도구는 양호한 것으로 볼 수 있다. 따라서 본 연구에서 개발한 과학탐구능력 평가도구는 초등학생들의 과학탐구능력 성취 수준의 진단, 과학과 교육과정과 교수?학습 자료 및 과학과 교수ㆍ학습 방법의 과학탐구능력 반영 수준을 평가하는 도구로도 이용될 수도 있을 것이다. The purpose of this study is to develop a valid and reliable evaluating instrument for elementary school fifth and sixth graders. The instrument is developed through R&D procedure, which includes two checks of science specialist and two field trials of the instrument. Evaluating items are content-free for each science inquiry skill. Each science inquiry element is based on SAPA and the 7th curriculum. This study has selected 10 science inquiry skills(observing, classifying, measuring, predicting, inferring, recognizing of a problem, controlling variables, interpreting data, drawing a conclusion, designing an experiment), formulated a clear definition of the elements of science inquiry skills, and established the objectives of evaluation. The content areas are divided into three categories, material and energy, life and environment, and the earth and circulation. Each category contains 10 items. So the instrument consists of 30 items. The content validity of items, objectivity of the scoring keys, and clarity of the items has been checked twice by specialists in science education. At the same time, two field trials were performed to produce the reliability of the instruments, discrimination index, and item difficulty index. The instrument has the content validity is 91.6%, reliability 0.79, objectivity 93.3%, discrimination index 0.30, and item difficulty index 66.1%.

Polystyrene 이장재가 아말감 변연부 미세누출에 미치는 영향

윤태철,노병덕,이경선 大韓齒科保存學會 1998 Restorative Dentistry & Endodontics Vol.23 No.2

전력산업 구조개편 후 주택용 부하의 전기요금 불균형에 대한 고찰

박왕규,노경수 동국대학교 산업기술연구원 1999 산업기술논문집 Vol.14 No.-

21세기를 향하는 시점에서 세계 여러 나라들은 전력산업의 규제와 독점의 시대에서 벗어나 효율성 증진을 위해 경쟁체제 도입을 추진하고 있으며 국내 전력산업 또한 구조개편을 통하여 새로운 시대로의 도약을 준비하고 있다. 전력산업 구조개편 후 전력회사들간의 경쟁으로 인하여 전기요금의 변화는 불가피하다고 여겨진다. 본 논문에서는 이러한 변화 후 주택용 부하에 대한 전기요금 부과에서 나타날 수 있는 전기요금 불균형에 대해서 살펴보고자 한다. 임의의 주택용 부하곡선 샘플에 대하여 실례를 적용하여 설명하고자 하며 이에 대한 대책을 아울러 제시하고자 한다. Traditional power industries have been characterized by government's regulation and monopoly within their operating territories. This trend recently has been changed into competition in order to improve overall system efficiency for electricity generation. Our country is also preparing to step on that vehicle under the 'IMF era' began in the end of 1997. Competition among electric power utilities inevitably brings about electricity price change. The paper reviews our country's progress process for power utility deregulation and indicates a possibility of unfair electricity pricing method for residential loads. Case study is carried out for sample residential load curves and thus some price adjusting methods for power distributing utilities are proposed.

연속파형 Nd:YAG 레이저를 이용한 SM45C 용접특성

유영태,노경보,오용석 朝鮮大學校 機械技術硏究所 2002 機械技術硏究 Vol.5 No.2

The Nd:YAG laser in combination with the optical fiber increase the automation and the flexibility of a whole industry. The Nd:YAG laser welding process in one of the most advanced manufacturing technologies owing to its high speed and penetration. This paper describes the weldability of SM45C carbon steel for machine structural use by Nd:YAG laser. Major process parameters were position of focus, travel speed and laser power. The results showed that peneration depth of the weld was increased with increasing applied laser power. Microstructural examinations and calculations and indicated that the microstructure of the laser weld, which experienced very high heating and cooling cycle during welding process. The results of this study provide application possibility of Nd:YAG laser welding for SM45C carbon steel

동일한 시료에 대한 국내 기관간의 STR 분석결과 비교 : STR 유전자좌 분석법의 표준화 설정을 위하여

박종태,신경진,양윤석,우광만,이숭덕,이승환,이정빈,정연보,조승희,한길로,한면수,홍승범 大韓法醫學會 2001 대한법의학회지 Vol.25 No.1

This paper described a collaborative exercise intended to see what kinds of short tandem repeat (STR) loci are used in different DNA typing laboratories in Korea and to compare their results for the demonstration whether uniformity of DNA profiling results from different laboratory could be achieved in Korea Laboratories were asked to test five tissue DNAs using methods routinely used in each laboratory and to report the results to the coordinating laboratory. The exercise demonstrated that each laboratory was using different STR loci for the typing with different STR numbers,2 VNTRS,36 STRs and amelogenin in total, and the direct comparison of the results from all the laboratory for the 18 loci could not be done as only one laboratory submitted typing results. Among 21 loci for which several laboratories submitted typing results, results for 14 loci were the same and results for the other 7 loci were different depending on the participating laboratory. D1S80, F13A01, D16S539, D21S11, D18S51, D3S1744 were the loci with different typing results. Even in the cases where commercial kits were used, the results were not the same depending on the machines used, that is the capillary electrophoresis or the gel based electrophoresis. The reason for the different results, points about the standardization of the methods arid the profiling data were described.

연속파형 Nd:YAG SM45C 레이저 용접의 결함 감소연구

유영태,오용석,노경보,신호준 朝鮮大學校 機械技術硏究所 2003 機械技術硏究 Vol.6 No.1

본 연구에서는 Nd:YAG 연속파형 레이저를 이용하여 레이저 용접시 레이저빔의 출력에 대한 레이저범의 이송속도를 변화시켜 심입용접을 실시했다. 열처리를 하지 않고 용접을 실시했을 경우 매우 조대한 기공이 많이 발생하였지만 열처리 후 용접을 실시했을 때는 몇몇 미세한 기공만 발생하였다. Present investigation reports on the effect of incorporating pre-heating on the mechanical properties of laser weldi'ng joints. The Nd:YAG laser in combination with the optical fiber increase the automation and the flexibility of a whole industry. The Nd:YAG laser welding process is one of the most advenced menufacturing technologies owing to its high sped and penetration. This paper describes the weldability of Sh4456 carbon steel fox machine structural use by Nd:YAG laser. Optical microscopy SEM were performed to observe the micro structures and to determine the structures of welded zone. In addtion, mechanical propreties, were measured by tensile test to evaluate the formablity of the welded specimen. The results show that proper selection of the control parameters for per-heating technique can result the porosity and cracking of the welding significantly, and improve the welded joints mechanical properties, such as higher tensile strength and better durability.

오스테나이트계 304 스테인레스강과 Nd-YAG 레이저빔과의 상호작용

유영태,오용석,노경보,임인호 조선대학교 에너지.자원신기술연구소 2002 에너지·자원신기술연구소 논문지 Vol.24 No.1

Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and penetration. The thermal cycles associated with laser welding are generally much faster than those involved in conventional arc welding processes, leading to a rather small weld zone. The experiments are performed for 304 stainless steel plate applying variation of : laser power(600~2000W), welding speed (3~10m/min), shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between the similar and dissimilar and plates, etc. The variation of brightness temperature versus modification of operational parameters is found, certain typical welding defects can be detected.

플륨 모니터링에 의한 SM45C 레이저 용접특성 평가

유영태,김재열,노경보,양동조,오용석,임기건,김지환 한국공작기계학회 2003 한국생산제조학회지 Vol.12 No.6

With the increased use of lasers in industrial welding applications, techniques for monitoring and controlling these processes become increasingly important. It is very important that we understand the dynamic behaviors of the laser induced plume in welding because the laser induced plume has considerable effects on welding efficiency and the quality of materials. As the plume fluctuation was associated with keyhole instability, unstable vapor plume indicated the process was unstable and would result in poor welds. An Infrared Themal-vision Camera can be utilized compensate for incurracies encountered in real-time monitoring during laser welding. We have results that instabilities of plume are closely dated with hot cracking and defect of laser welding.