• 제목/요약/키워드: the n-value

검색결과 7,089건 처리시간 0.038초

SF6및 SF6-N2 가스 중에서 직류전동에 \ulcorner나 스페이서 연면간락에 관한 연구 (A Study on the Flashover along the Spacer Surface SF6-N2 Gas Mixtures Stressed by D.C)

  • 김정달;정재길;이동인
    • 대한전기학회논문지
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    • 제36권11호
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    • pp.796-805
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    • 1987
  • The flashover voltages have been investigated for spacer and unbridged-gap in SF6-N2 gas mixtures up to the value of 760(torr. cm), The gap was stressed by DC source The results obtained are as follows` 1) The flashover voltages for an unbridged gap and for a spacer in SF6, N2 and SF6-N2 gas mixtures follow the Paschen's curve. 2) The polarity effects was not observed in both unbridged gap and a spacer which had per ect contact with an electrode. The flashover voltages for negative polatity are lower than those for positive polarity in case of imperfect contact. 3) 3%flashover voltage is decreased by putting a spacer which had perfect contact with an electrode. The spacer which has a gap void shows the lowest flashover voltage. 4) The lowest spacer efficiency was obtained with higher gas pressure & large amount of N2 content. The flashover voltages depend on the gas pressure rather than the spacer efficienty at low value of pd. 5) The flashover voltages of gas mixtures of N2 with SF6 are relatively high, even though the amount of SF6 gas content is small.

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준설매립지반의 액상화 간편예측 개선에 관한 연구 (Improvement Scheme of Simplified Liquefaction Potential Evaluation for a Dredged and Reclaimed Ground)

  • 정민형;김주현;정상국;이송
    • 한국지반공학회논문집
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    • 제23권8호
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    • pp.47-57
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    • 2007
  • 본 연구는 사질토로 준설매립된 지반의 액상화 평가를 위해 반드시 요구되는 초기 밀도특성을 분석하였고, 국내 내진 설계기준에서 제시한 SPT-N을 이용한 액상화 간편예측 방법의 문제점을 분석하여 개선방안을 제시하였다. 기존 시공사례를 토대로 매립 직후 준설매립지반의 밀도특성을 분석한 결과, 상대밀도와 초기 N값은 대체로 각각 $40{\sim}50%,\;5{\sim}8$의 범위에 분포하였다. 액상화 간편예측에 있어서 유효상재압 보정의 Liao & whitman식은 항상 지진에 취약한 상부층이 하부층보다 액상화 저항응력이 크게 산정되어 Skempton식의 적용이 추천된다. 또한, 설계단계에서 준설매립 지반의 심도별 N값을 산정할 경우에는, 유효응력에 따른 N값의 변화를 나타내는 누승함수 $N=1.35{\sigma}^{'0.75}$를 이용하여 액상화 간편예측을 실시할 것을 추천한다.

GaN FET 기반 동기정류기를 적용한 저전압-대전류 DC-DC Converter 효율예측 (A Study on the Efficiency Prediction of Low-Voltage and High-Current dc-dc Converters Using GaN FET-based Synchronous Rectifier)

  • 정재웅;김현빈;김종수;김남준
    • 전력전자학회논문지
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    • 제22권4호
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    • pp.297-304
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    • 2017
  • The purpose of this paper is to analyze losses because of switching devices and the secondary side circuit diodes of 500 W full bridge dc-dc converter by applying gallium nitride (GaN) field-effect transistor (FET), which is one of the wide band gap devices. For the detailed device analysis, we translate the specific resistance relation caused by the GaN FET material property into algebraic expression, and investigate the influence of the GaN FET structure and characteristic on efficiency and system specifications. In addition, we mathematically compare the diode rectifier circuit loss, which is a full bridge dc-dc converter secondary side circuit, with the synchronous rectifier circuit loss using silicon metal-oxide semiconductor (Si MOSFET) or GaN FET, which produce the full bridge dc-dc converter analytical value validity to derive the final efficiency and loss. We also design the heat sink based on the mathematically derived loss value, and suggest the heat sink size by purpose and the heat divergence degree through simulation.

MULTIPLE SOLUTIONS OF IMPULSIVE BOUNDARY VALUE PROBLEMS ON THE HALF-LINE

  • Liu, Xiyu;Yan, Baoqiang
    • Journal of applied mathematics & informatics
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    • 제5권1호
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    • pp.111-124
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    • 1998
  • Existence results of multiple solutions are obtained un-der suitable conditions for impulsive integrodifferential boundary value problems on the half-line which may be singular at the boundary.

CFUBMS을 이용한 TiZrAlN 나노복합 박막의 미세 구조와 기계적 특성 (Microstructural and Mechanical Characteristics of TiZrAlN Nanocomposite Thin Films by CFUBMS)

  • 김연준;이호영;김용모;김갑석;한전건
    • 한국표면공학회지
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    • 제40권1호
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    • pp.1-5
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    • 2007
  • Quaternary TiZrAlN nanocomposite thin films were synthesized by Closed-Field Unbalanced Magnetron Sputtering (CFUBMS), and their microstructure and mechanical characteristics were examined. The grain refinement of the TiZrAlN nanocomposite thin films was controlled by adjusting the $N_2$ partial pressure. The hardness of the film varied with the $N_2$ partial pressure and the maximum value was obtained approximately 47 GPa. It was also confirmed that there is a critical value of the grain size($d_c$) to need maximum hardness.

최적 설계를 위한 3점 탐색 알고리즘의 제안 (A Proposal of 3 Point Search Algorithm for Optimal Design)

  • 김주홍;공휘식
    • 한국통신학회논문지
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    • 제16권7호
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    • pp.640-650
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    • 1991
  • 最適 設計를 위한 최적치 탐색 알고리즘으로 직접 탐색법의 일종인 3점 탐색 알고리즘을 제안하였다. 본 알고리즘은 N차원 탐색 범위 내에 있는 수공간의 3N 점에서 함수의 최소차를 탐색하고 점차로 탐색 범위를 축소하여 동일한 타색과정을 반복수행하는 방법이다. 그러므로, 1회 탐색시에 성능 지표의 계산횟수는 3N이다. 도한 3N점 탐색법을 대산히나 3N점에 대한 탐색법으로 단순 3N탐색법을 기술하였으나, 이것은 서로 다른 매개 변수가 乘서항을 갖는 성능지표의 경우에는 불확실함이 발견되었다. 제안된 알고리즘은 2차 형식이나 선형함수로 구성되는 성능 지표에 적용이 가능하며, 안정하고 신회도가 높은 특성을 갖고 있음이 확인되었다.

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Mg도핑된 GaN 반도체 박막의 전자스핀공명 (Electron Spin Resonance from Mg-doped GaN Semiconductor Thin Films)

  • 박효열
    • 반도체디스플레이기술학회지
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    • 제4권2호
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    • pp.1-5
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    • 2005
  • Electon spin resonance measurements have been performed on the Mg-doped wurtzite GaN thin films grown on sapphire substrates by low-pressure metal-organic chemical vapor deposition. The sample set included films as-grown with the regular Mg doped and Mg delta doped samples and the corresponding annealed ones. The resonance signal has been observed from the annealed Mg delta-doped sample with the Lande g value of 2.029. This indicates that the singlet resonance signal originates from the neutral Mg acceptor located at 0.24 eV above the valence band edge and 0.13 eV above the Fermi level because of the nuclear hyperfine spin 1=0 of Mg and the larger value than the free electron g=2.0023.

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경산시 지하수의 수질특성에 관한 연구 (A Study on the Characteristics of Groundwaters in Gyeongsan City)

  • 송성숙;박병윤;이부용
    • 한국환경과학회지
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    • 제16권6호
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    • pp.677-682
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    • 2007
  • This study was performed to provide the basic information on characteristics of groundwater pollution in Gyeongsan city. Forty two groundwater samples were collected, and pH, DO, COD, $NH_3-N,\;NO_3^--N$, T-N, $PO_4^{3-}-P$, Cl, Ca, Mg, hardness, evaporate residues and others were investigated. And, ANOVA analyses were carried out to reveal the differences in water pollution indicator values of by industry, commerce/residence and agriculture areas. The results were as follows. 1. The mean values of pH, DO, COD, $NH_3-N,\;NO_3^--N$, T-N, $PO_4^{3-}-P$, Cl, evaporate residues, Ca and hardness were 6.9, $7.9mg/\ell,\;0.4mg/\ell,\;2.44mg/\ell,\;2.73mg/\ell,\;6.06mg/\ell,\;0.82mg/\ell,\;32.72mg/\ell,\;381.67mg/\ell,\;41.53mg/\ell,\;177.17mg/\ell$, respectively. 2. As groundwater became deeper, the values of Cl, Ca, Mg, Na, hardness and evaporate residues remarkably increased, but those of COD, $NH_3^--N,\;NO_3^--N,\;NO_2^-N$, T-N decreased. 3. The values of COD, Cl, Ca, Mg, Na, hardness and evaporate residues were very high in industrial area, and those of $NH_3-N,\;NO_2^--N$, T-N were very high in commercial/residential area, and those of $NO_3^--N$ were a little high in agricultural area. 4. The correlations between depth and each value of Mg, Na, Fe, hardness and evaporate residues were highly positive, and those between DO and each value of Mg, Cu, Fe, hardness and evaporate residues were highly negative. 5. According to ANOVA analyses, the differences in three area groups (industry, commerce/residence and agriculture) on the values of $NH_3-N$, T-N, evaporate residues, hardness, Ca, Mg, K and Fe were significant at 1% level.

A Comparative Study of Controllers for CSI Fed Induction Motor

  • Kumar, Piush;Agarwal, Vineeta
    • Journal of Power Electronics
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    • 제10권2호
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    • pp.165-170
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    • 2010
  • This paper presents a comparative study of P and PI controllers for a current source inverter (CSI) fed induction motor drive system. A dq model has been used which incorporates the induction motor and the inverter power supply with current feedback. The model is used first to generate the steady state curves to determine the operating point through computer simulations using the software package MATLAB. Then a transient analysis has been carried out for different values of the speed and current controller parameters. The controller value is adjusted by the Ziegler-Nichols method. It has been observed that the transient time to reach the steady state value is larger with the PI controller than with the P controller.

nML 프로그래밍 환경에서 SOAP 클라이언트 구현 (Implementation of SOAP Client in U Programming Environment)

  • 권오경;한태숙
    • 한국정보과학회논문지:소프트웨어및응용
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    • 제30권1_2호
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    • pp.164-172
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    • 2003
  • 웹 서비스에 대한 구현이 많이 늘고 있다. 웹 서비스는 각 프로그래밍 언어에서 XML를 이용해서 원격 호출을 한다. 이때 사용하는 대표적인 프로토콜이 SOAP으로써 본 논문에서는 nML 프로그래밍 환경에서 SOAP 클라이언트 구현을 제시한다. nML은 한국과학기술원 ROPAS에서 만든 SML과 OCaml의 한국형 함수형 언어이다. nML에서의 soaptype 타입으로 SOAP 값을 정의한다. SOAP은 XML Schema에 의해서 객체에 대한 인코딩이 정의된다. 즉 XML Schema가 SOAP 값의 유효성을 판단한다. 본 논문은 XML Schema의 엘리먼트와 타입에 대한 정의로써 element와 typeinfo 타입을 정의한다. 그리고 상호호환성 테스트를 통하여 안전하게 다른 언어와 대응됨을 보인다.