• 제목/요약/키워드: positive element

검색결과 635건 처리시간 0.028초

정상 성분 변화량을 이용한 송전선로 보호용 방향 계전 알고리즘 (A Directional Relay Algorithm Using Positive-Sequence Superimposed Quantity for Transmission Line Protection)

  • 이명수;유석구
    • 대한전기학회논문지:전력기술부문A
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    • 제52권4호
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    • pp.226-233
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    • 2003
  • Directional elements are fundamental to protection scheme security and selectivity, performing such critical tasks as supervising distance elements and controlling overcurrent elements. But, conventional operating principles for directional detection based on negative or zero sequence quantify do not satisfy the requirements for improved sensitivity and fast operation under any fault conditions. In this paper, new algorithm for directional elements is proposed. The proposed algorithm use the positive-sequence superimposed voltages and currents in order to be used in all fault conditions. Also, because this algorithm uses a voltage compensation method. it can be well operated under strong source conditions.

AN ASYMPTOTIC FINITE ELEMENT METHOD FOR SINGULARLY PERTURBED HIGHER ORDER ORDINARY DIFFERENTIAL EQUATIONS OF CONVECTION-DIFFUSION TYPE WITH DISCONTINUOUS SOURCE TERM

  • Babu, A. Ramesh;Ramanujam, N.
    • Journal of applied mathematics & informatics
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    • 제26권5_6호
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    • pp.1057-1069
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    • 2008
  • We consider singularly perturbed Boundary Value Problems (BVPs) for third and fourth order Ordinary Differential Equations(ODEs) of convection-diffusion type with discontinuous source term and a small positive parameter multiplying the highest derivative. Because of the type of Boundary Conditions(BCs) imposed on these equations these problems can be transformed into weakly coupled systems. In this system, the first equation does not have the small parameter but the second contains it. In this paper a computational method named as 'An asymptotic finite element method' for solving these systems is presented. In this method we first find an zero order asymptotic approximation to the solution and then the system is decoupled by replacing the first component of the solution by this approximation in the second equation. Then the second equation is independently solved by a fitted mesh Finite Element Method (FEM). Numerical experiments support our theoritical results.

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Differential Expression of Cyclic AMP-Response Element Binding Protein Zhangfei (CREBZF) in the Mouse Testis during Postnatal Development

  • Jang, Hoon
    • 한국발생생물학회지:발생과생식
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    • 제22권1호
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    • pp.65-72
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    • 2018
  • Cyclic AMP-response element binding protein zhangfei (CREBZF), a member of ATF/CREB (activating transcription factor/ cAMP response element binding protein) family, regulates numerous cellular functions and development of cells by interacting transcription factors. This study discovered the expression pattern of CREBZF in seminiferous tubule of testes during the postnatal development of mice. In testis, CREBZF mRNA expression was the highest among other organs. Immunofluorescence analyses showed that the CREBZF was specifically expressed on spermatocyte but not in spermatogonia and Sertoli cells in seminiferous epithelium of mouse testis. Semi-quantitative polymerase chain reaction (PCR) analysis showed that CREBZF transcript level was significantly elevated during postnatal development of mouse testis. Confocal imaging analysis indicated that the protein expression of CREBZF in seminiferous tubule remained low until postnatal day (PD) 14, and was dramatically increased in PD 21. Interestingly, only one type of the spermatocyte expressed CREBZF specifically among SCP3-positive spermatocytes. Taken together, these results suggest that CREBZF may be novel putative marker of the spermatocyte and regulate meiosis during postnatal development of mice.

가평 사문암 지역의 토양 별 식물체내 희토류 원소 함량 차이: 억세, 쑥, 산딸기를 근거로 (Differences of Rare Earth Element Concentrations of Plants in Top Soils of Gapyeong Serpentine Area: Based on the M. sinensis, A. vulgaris and R. crataegitolius)

  • 송석환;신병철
    • 한국환경과학회지
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    • 제18권6호
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    • pp.621-632
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    • 2009
  • Rare earth contents(REE) were analysed for the plants, M. sinensis. A. vulgaris and R. crataegitolius, from two different soils serpentine area consisting of serpentinite(SP) and non-serpentine area, containing amphibole schist(AS) of Gapyeong area, and were compared with soils and host rocks. The AS were high with the differences of several times in the top soils, and with the differences of several to ten times in the host rocks relative to the SP. In the same area, the SP were high in the soil, but the rocks for the AS. In the plants, the A. vulgaris were high, but low in the R. crataegitolius. Root parts were higher than the upper parts. Differences between the upper and root parts were big in the SP rather than the AS, and were big in the R. crataegitolius, but small in the M. sinensis. Among the parts of the plants, high elements were shown in the R. crataegitolius of the SP, and the A. vulgaris and M. sinensis of the AS. In the correlation coefficients, most of the REE showed positive relationships among the element pairs, especially high positive correlation coefficients in the upper parts of the SP.Differences of the soils and plants(average) were smalle in the M. sinensis and big in the R. crataegitolius. In the upper parts. contents of the A. vulgaris were close to the soils while the R. crataegitolius showed large discrepancies with the soils. In the root parts, contents of the A. vulgaris showed discrepancies with the soils regardless of soil types, but close in the R. crataegitolius of the SP and M. sinensis of the AS.

입도분포에 따른 하상퇴적물의 지구화학적 분산 및 부화 (Geochemical Dispersion and Enrichment of Fluvial Sediments Depending on the Particla Size Distribution)

  • 이현구
    • 자원환경지질
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    • 제32권3호
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    • pp.247-260
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    • 1999
  • Geochermical characteristics of the fluvial sediments deprnding on particle size distribution size were investigated in the respect of majir, minor and rare eath element chemisitry. Ratios of $Al_{2}O_{3}/Na_{2}O$ and $K_{2}O/Na_{2}O$ of the sediments show the homogeneous valus, and partly positive correlation with $SiO_{2}/Al_{2}O_{3}$, respecively. Characteristics of minor element ratios (V/Ni, Cr/V, Ni/Co and Zr/Hf)are within the lower and narrow range. Thesesuggested that sediment sources may be acidic to intermediate granitic rock, and may be explained by simple weathering and sedimentation. With increasing SiO2 contents, concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, CaO and MgO decreased, but those of $K_{2}O$ and $Na_{2}O$ increased, Concentrations of Ba, Be, Cs, Cu, Li, Ni, Sr, V and Zr show comparatively normal negative and some positive trends. Compared with the mean composition of granite, concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, MnO, CaO and MgO in the sediments of the study area were highly enriced. Among some minor and rare earth elements, concentrations of As, Cd, Cu, and V were enriched, but those of Be, Ce, Rb, Sc, Sr and Zn were depleted when compared with average composition of granite. By decreasing of particle size fractions, SiO2, Rb and Sr conterts decreased, but concentrations of $Al_{2}O_{3}$, $Fe_{2}O_{3}$, CaO, MgO, $TiO_{2}$, MgO, $P_{2}O_{5}$, Be, Cu, Hf, Pb, V and Zr increased. From the correlations between particle size fractions and element concenreations, some elements of $Fe_{2}O_{3}$, CaO, MgO, $P_{2}O_{5}$, Cu, Ni, Zn and Zr showed typical trends in the secondary contramination sediments. These trends are typically shown under 100 mesh fractions. It indicates that the fraction of minus 100 mesh is the optimum size fraction for geochemical and environmental survey.

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디젤 차량의 보조 난방을 위한 PTC 히터 개발 (Development of a PTC Heater for Supplementary Heating in a Diesel Vehicle)

  • 신윤혁;김성철
    • 한국산학기술학회논문지
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    • 제15권2호
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    • pp.666-671
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    • 2014
  • 최근 디젤 차량과 같은 내연기관의 고효율화에 따라, 보조난방 열원으로서 PTC 히터의 사용이 증가하는 추세이다. 디젤 차량의 시동 초기에는 냉각수의 온도가 난방으로 직접 사용하기에 충분히 높지 않으므로, 동절기 난방을 위해 보조난방 열원은 필수적이다. 본 연구에서는 스크린 인쇄 전극공정을 바탕으로 한 PTC 소자를 제작하였고, 이를 활용한 PTC 소자 모듈 및 히터를 설계 및 제작하였다. PTC 소자 모듈의 방열핀 접촉형상 및 전열소자의 크기 변경에 따른 난방성능 변화를 열유동 해석을 통해 분석하였고, 난방성능 실험을 수행하여 PTC 히터의 난방성능 및 효율 특성을 살펴보았다. PTC 히터 시작품의 경우, 기존 PTC 히터와 동등한 수준 이상의 난방성능 및 효율을 나타내었으며, 향후 이를 바탕으로 PTC 소자와 히터에 대한 공정개선 및 성능증대 연구를 수행할 계획이다.

소비자혁신성에 따른 이용동기와 이용의도와의 관계 연구 - 디지털사진 인화서비스를 중심으로 - (A Study on Relationship between Usage Motivation and Usage Intentions according to Consumer Innovativeness - Focusing on Digital Photo Printing Service -)

  • 정찬구;정진도
    • 한국산학기술학회논문지
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    • 제9권1호
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    • pp.202-213
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    • 2008
  • 본 연구에서는 디지털사진의 등장과 더불어 변화하는 시장 환경에 대응하기 위한 새로운 비즈니스 모델 구축을 위해 이용충족이론과 기술수용모델을 적용하여 소비자혁신성에 따른 디지털사진 이용동기와 디지털사진 인화서비스의 이용의도와의 관계모형과 가설을 설정하였다. 이에 대한 연구결과는 첫째, 혁신성과 이용동기와의 관계모형에서는 혁신성이 오락성, 사회성, 경제성에 정적인 영향력을 미치는 것으로 나타났다. 둘째, 혁신성과 이용의도와의 관계모형에서는 혁신성이 이용의도에 정적인 영향력을 미치는 것으로 나타났다. 셋째, 이용동기와 이용의도와의 관계모형에서는 편리성, 오락성, 경제성, 사회성이 이용의도에 정적인 영향력을 미치는 것으로 나타났다.

콘크리트 충전 강관을 갖는 프리스트레스트 합성거더의 정모멘트 구간 거동 (Flexural Behaviors of PSC Composite Girders in Positive Moment Regions)

  • 강병수;성원진;장영길;이용학
    • 콘크리트학회논문집
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    • 제18권3호
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    • pp.313-320
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    • 2006
  • 콘크리트 충전 강관을 갖는 프리스트레스트 합성거더(PSC-CFT girder)는 PSC 합성거더와 콘크리트 충전 강관의 이중합성작용으로 인하여 구조물의 저항능력을 증대시킨 새로운 개념의 교량형식이다. 정모멘트 구간에서 콘크리트 충전 강관을 갖는 합성거더의 휨 거동은 지간장 4.4m인 2개의 실험체를 제작하여 수행한 실험결과로부터 분석하였다. 보요소를 사용한 비선형 유한요소해석, 3차원 비선형 유한요소해석 및 단면해석법에 의해 예측된 수치해석결과와 실험결과의 비교를 통해 PSC 합성거더와 콘크리트 충전 강관의 합성작용에 대한 역학적 및 구조적 역할과 파괴메커니즘을 비교하였다.

교수-학습(PBL)과 실무능력의 융합 및 적용 효과 탐색 (Teaching and learning(PBL) and explore the convergence of the Effects of the practical skills)

  • 김수연
    • 한국융합학회논문지
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    • 제7권2호
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    • pp.109-118
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    • 2016
  • 본 연구는 예비스포츠지도자들에게 문제 중심학습을 통한 교육요소를 적용하고 학습과 실무를 융합하여 현장에서의 다양하고 복잡한 문제를 해결 할 수 있는 실무능력을 기르는데 목적이 있다. 이를 위해 S대학교 스포츠과학과 3학년 학생 28명을 연구 참여자로 선정하고 집단면담, 참여관찰, 개방형질문지등의 질적 사례연구 방법을 통하여 다음과 같은 결과를 도출 하였다. 첫째, 수업에 대한 만족도가 높았으며, 생각을 많이 하게 되는 수업으로 평가하였다. 둘째, 다양한 학습 자료를 취합하고 이해, 해석하여 자신의 지식구조를 능동적으로 재구성하는 과정에서 실제적인 문제 해결 능력이 향상되었다고 하였다. 또한 자율성에 증진으로 창의적, 확산적 사고를 촉진하는데 긍정적인 영향을 주었다고 한다. 셋째, 팀워크에 대한 의견으로 동료들과 의견을 나누며 다른 사람의 입장에서 생각해 볼 수 있다는 점이 긍정적 효과로 평가 되었다.

The Spatially Closed Universe

  • Park, Chan-Gyung
    • 한국지구과학회지
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    • 제40권4호
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    • pp.353-381
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    • 2019
  • The general world model for homogeneous and isotropic universe has been proposed. For this purpose, we introduce a global and fiducial system of reference (world reference frame) constructed on a (4+1)-dimensional space-time, and assume that the universe is spatially a 3-dimensional hypersurface embedded in the 4-dimensional space. The simultaneity for the entire universe has been specified by the global time coordinate. We define the line element as the separation between two neighboring events on the expanding universe that are distinct in space and time, as viewed in the world reference frame. The information that determines the kinematics of the geometry of the universe such as size and expansion rate has been included in the new metric. The Einstein's field equations with the new metric imply that closed, flat, and open universes are filled with positive, zero, and negative energy, respectively. The curvature of the universe is determined by the sign of mean energy density. We have demonstrated that the flat universe is empty and stationary, equivalent to the Minkowski space-time, and that the universe with positive energy density is always spatially closed and finite. In the closed universe, the proper time of a comoving observer does not elapse uniformly as judged in the world reference frame, in which both cosmic expansion and time-varying light speeds cannot exceed the limiting speed of the special relativity. We have also reconstructed cosmic evolution histories of the closed world models that are consistent with recent astronomical observations, and derived useful formulas such as energy-momentum relation of particles, redshift, total energy in the universe, cosmic distance and time scales, and so forth. The notable feature of the spatially closed universe is that the universe started from a non-singular point in the sense that physical quantities have finite values at the initial time as judged in the world reference frame. It has also been shown that the inflation with positive acceleration at the earliest epoch is improbable.