• Title/Summary/Keyword: direct limit

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New Fault Location Algorithms by Direct Analysis of Three-Phase Circuit Using Matrix Inverse Lemma for Unbalanced Distribution Power Systems

  • Park, Myeon-Song;Lee, Seung-Jae
    • KIEE International Transactions on Power Engineering
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    • v.3A no.2
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    • pp.79-84
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    • 2003
  • Unbalanced systems, such as distribution systems, have difficulties in fault locations due to single-phase laterals and loads. This paper proposes new fault locations developed by the direct three-phase circuit analysis algorithms using matrix inverse lemma for the line-to-ground fault case and the line-to-line fault case in unbalanced systems. The fault location for balanced systems has been studied using the current distribution factor, by a conventional symmetrical transformation, but that for unbalanced systems has not been investigated due to their high complexity. The proposed algorithms overcome the limit of the conventional algorithm using the conventional symmetrical transformation, which requires the balanced system and are applicable to any power system but are particularly useful for unbalanced distribution systems. Their effectiveness has been proven through many EMTP simulations.

The Derivation and Application of Energy Function Reflecting the Governor Cut-off Property (조속기의 CUT-OFF 특성을 반영한 에너지 함수 유도 및 응용)

  • Moon, Young-Hyun;Kim, Hyung-Jun;Ryu, Hun-Su;Cho, Byung-Hoon;Kim, Se-Ho
    • Proceedings of the KIEE Conference
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    • 1996.11a
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    • pp.84-87
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    • 1996
  • This paper presents a energy function to reflect the control effect of speed governor which has a cut-off property which means position and rate limit The proposed energy function satisfies the semi-negativeness of its time derivative and well reflects the parameters of speed governor to the energy function. The transient stability analysis by the direct method for the single machine infinite bus system has been conducted with the use of the proposed energy function, which shows that the results by the direct method well agree with that by the conventional time simulation method. This thesis shows a possibility of more accurate stability analysis by taking into account the cut-off property of speed governor's output.

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The Effect of Compression Ratio on Combustion and Performance Characteristics of Direct Injection Spark Ignition Hydrogen Fueled Engine. (직접분사식 스파크점화 수소기관의 연소 및 성능특성에 미치는 압축비의 영향)

  • 권병준;이종윤;이종태;이성열
    • Transactions of the Korean Society of Automotive Engineers
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    • v.1 no.2
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    • pp.17-26
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    • 1993
  • As fundamental step to find the suitable compression ratio of hydrogen fueled engine, performance and combustion characteristics of that engine were analyzed. Qualitative characteristics of the hydrogen fueled engine were similar to that of the gasoline engine, and it was also found that knock limit compression ratio of the hydrogen fueled engine was higher than that of the gasoline engine.

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Robust Digital Nonlinear Friction Compensation - Theory (견실한 비선형 마찰보상 이산제어 - 이론)

  • 강민식;김창제
    • Journal of the Korean Society for Precision Engineering
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    • v.14 no.4
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    • pp.88-96
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    • 1997
  • This paper suggests a new non-linear friction compensation for digital control systems. This control adopts a hysteresis nonlinear element which can introduce the phase lead of the control system to compensate the phase delay comes from the inherent time delay of a digital control. A proper Lyapunov function is selected and the Lyapunov direct method is used to prove the asymptotic stability of the suggested control.

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Real-Time Voltammetric Assay of Lead Ion in Biological Cell Systems

  • Ly, Suw-Young
    • Toxicological Research
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    • v.25 no.4
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    • pp.231-235
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    • 2009
  • Trace lead detection for cyclic voltammetry (CV) and square-wave (SW) stripping voltammetry was performed using mercury immobilized onto a carbon nanotube electrode (HNPE). Using the characteristics of mercury and the catalytic carbon nanotube structure, a modified technique, the $0.45{\mu}g/l$ detection limit of lead ion was attained. The developed method can be applied to pond water, fish tissue, plant tissue, and in vivo direct assay.

FPF(Fibrillated Polypropylene Fiber) Reinforcement Method for Slope Repair (사면보수보강을 위한 FPF 보강공법개발)

  • 김낙경;박동원
    • Proceedings of the Korean Geotechical Society Conference
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    • 2001.03a
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    • pp.257-264
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    • 2001
  • This study presents the slope stability analysis results for the model slope test. The model slope was made of the soil reinforced by FPF(Fibrillated Polyprophylene Fiber). The shear strength properties of the soil reinforced by FPF fibers were evaluated through the direct shear tests. The model slope 1:1 and 1:1.5 were made and the load tests were performed. Back analysis using limit equilibrium method was carried out to evaluate the shear strength increase on the FPF reinforced slope. The factor of safety of the FPF reinforce slope increased about 23% over unreinforced slope.

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Robust Digital Nonlinear Friction Compensation (견실한 비선형 마찰보상 이산제어)

  • 강민식;송원길;김창재
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1996.11a
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    • pp.987-993
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    • 1996
  • This report suggests a new non-linear friction compensation for digital control systems. This control adopts a hysteric nonlinear clement which can introduce the phase lead of the control system to compensate the phase delay comes from the inherent time delay of a digital control. The Lyapunov direct method is used to prove the asymtotic stability of the suggested control, and the stability and the effectiveness are verified analytically and experimentally on a single axis servo driving system.

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Interfacing of A.C. System with HVDC Schemes : A Comparison of Filter Types (HVDC 구성을 갖는 A.C. System의 필터 유형 비교에 관한 연구)

  • Kim, Chan-Ki;Choy, Young-Do
    • Proceedings of the KIPE Conference
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    • 2005.07a
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    • pp.373-375
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    • 2005
  • AC harmonic filters connected to the terminals of HVDC schemes fulfill two primary functions: to compensate for part or all of the reactive power absorbed by the converter, and to limit to an acceptable level the voltage distortion caused by the converter harmonics. this paper makes a direct comparison between tuned filters and damped filters, each designed for a long HVDC transmission scheme. It Is hoped that by comparing the two approaches a syudy to determine the suitability of filter types to AC systems can be promoted.

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First Derivative Spectrophotometric and Gas-Liquid Chromatographic Determination of Caffeine in Foods and Pharmaceuticals III. Simultaneous assay of caffeine and some antihistaminics

  • Abdel-Moety, Ezzat M.;El-Tarras, Mohamed F.;El-Zeany, Badr-Eldin A.;Kelani, Khadiga O.
    • Archives of Pharmacal Research
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    • v.13 no.3
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    • pp.215-220
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    • 1990
  • Two different, derivative spectrophotometric and gas-liquid chromatographic, procedures for direct quantitation of caffeine and some commonly dispensed antihistaminics in bulk forms, in their laboratory prepared mmixtures and in dosage formulations, have been investigated. The limit, sensitivity reproducibility and accuracy of each method were studied for each individual drug substance and in some usual pharmaceutical formulations.

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Shear Behavior of Precast Prestressed Inverted-Tee Concrete Beams with Dapped Ends (프리캐스트 프리스트레스트 콘크리트 역티형보의 댑단부 전단거동)

  • 유승룡
    • Journal of the Korea Concrete Institute
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    • v.13 no.1
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    • pp.46-53
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    • 2001
  • Two full scale precast pretensioned dapped ended rectangular beams designed by PCI design handbook for a major domestic live load of market and parking building - 500kgf/㎡ and 1,200kgf/㎡ were investigated experimentally. The bottom length of beams was 60cm which was same to the length of rectangular column in the base of five-story market or parking buildings. The height of dap was web hight plus half of the flange height within the allowable limit of PCI method. Shear tests were performed on four beam ends. Followings were obtained from the experimental study. All of the specimens were fully complied with the PCI design handbook. Two of four specimens which were designed for live load of 1,200kgf/㎡ showed crackings at the re-entrant corner of dap before the full service loadings, and failed by direct shear at the load level much less than their calculated nominal strength. The specimens designed for live load of 1,200kgf/㎡ failed at 772 tonf and 78.36tonf by direct shear crackings. This strength was less than PCI limit of 81.9 tonf and higher than ACI limit of 65.62tonf. Thus, the limit suggested by ACI seems more reasonable in regard of safety in view of this test results. According to load-strain curves, the strain of hanger reinforcement reached almost yield strain. It is recommended to use more inclined hanger reinforcement of improve the strength and serviceability.