• 제목/요약/키워드: maximum density

검색결과 3,088건 처리시간 0.035초

고밀도 광기록 채널에서의 NPML 검출 성능 한계 분석 (Performance Limit of NPML Detection on High Density Optical Recording Channels)

  • 윤민영;이재진;홍유표
    • 한국통신학회논문지
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    • 제33권8C호
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    • pp.569-574
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    • 2008
  • 잡음예측 최대유사도(NPML, Noise Predictive Maximum Likelihood) 검출기는 잡음 예측/백색화 과정을 비터비 검출기의 가지 메트릭 계산 과정에 삽입하여 데이터 검출의 신뢰성을 높인다. 본 논문에서는 고밀도 광기록 채널에서 밀도가 높아짐에 따라 고차 전달함수 다항식으로 요구되는 성능을 달성할 수 있음을 보인다. 모의실험을 통해 밀도마다 가장 적합한 PR 타겟값을 찾고, NPML 다항식 차수를 올려가며 BER을 측정하였다. 결과로 각 밀도에 따른 적절한 차수가 필요함을 보였다.

켄치 상태에서 고온 초전도 한류기의 전자기적 거동 (Electromagnetic Behavior of High-Tc Superconducting Fault Current Limiters under the Quench State)

  • Hyo-Sang Choi
    • 대한전기학회논문지:전력기술부문A
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    • 제53권1호
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    • pp.38-42
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    • 2004
  • In this paper we analyzed the electromagnetic behavior of a superconducting fault current limiter (SFCL) under the quench state using FEM. The analysis model used in this work is 5.5 KVA meander-line type SFCLs which are currently developed by Superconductor Power System Lab in Korea Electric Power Research Institute. Meshes of 3,650 triangular elements were used in the analysis of this SFCL. Analysis results showed that the distribution of current density was concentrated to inner curved line in meander-line type SFCL and the maximum current density was 14.61 A/$m^2$ and also the maximum Joule heat was 2,030 W/$m^2$ in this region. We think that the new and the modified structure must be considered for an uniform distribution of the electromagnetic field.

Nb 변화에 따른 KNN 세라믹스의 압전 및 전기적 특성 (Piezoelectric and Electrical properties of KNN ceramics as a function of the Variation of Nb)

  • 이갑수;류주현;김인성;송재성
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2010년도 하계학술대회 논문집
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    • pp.302-302
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    • 2010
  • The lead-free piezoelectric ceramics must have high piezoelectric properties and electrical properties for the applications of piezoelectric devices. Therefore, KNN ceramics were investigated as a function of the variation of Nb. The density was increased with the increase of Nb. The density was saturated above 0.8895 mol Nb. The maximum value of electromechanical coupling coefficient(kp) was obtained 0.428 at 0.8895mol Nb. This result can be attributed to the well sintered of specimens. Also, The maximum value of mechanical quality factor(Qm) showed 1554 at 0.8895mol Nb. Therefore, this composition can be used for application of piezoelectric device such as piezoelectric transformer and piezoelectric actuator.

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아트리아 안정화 지르토니아 소결체의 특성에 $SiO_2$$Al_2O_3$ 가 미치는 영향 (Effect of $SiO_2$ and $Al_2O_3$ on Characteristics of Yttria-Stabilized Zirconia Ceramics)

  • 손정덕;최시영;조상희
    • 대한전자공학회논문지
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    • 제27권6호
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    • pp.886-894
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    • 1990
  • Sinterbility, microstructure, mechenical and electrical properties of yttriastabilized zirkconiz (92 mole % ZrO2 + 8 mole % Y2O3) doped with 0.5 mole % SiO2 and 0-2.O mole% Al2O3 were studied as a functin of Al2O3 addition. Sintered density increased with increasing Al2O3 addition up to o.5 mole%but decreased up to 1.0mole% Al2O3. Vickers hardness is proportional to sintered density. The specimen added 0.5mole% Al2O3 and 0.5mole% SiO2 exhibited a maximum conductivity. And the specimen added 0.5 mole % Al2O3 and 0.5 mole% SiO2 was measured a maximum electromotive force for a characteristics of oxyzen partial pressure.

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로버스트추정에 의한 지구물리자료의 역산 (Inversion of Geophysical Data with Robust Estimation)

  • 김희준
    • 자원환경지질
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    • 제28권4호
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    • pp.433-438
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    • 1995
  • The most popular minimization method is based on the least-squares criterion, which uses the $L_2$ norm to quantify the misfit between observed and synthetic data. The solution of the least-squares problem is the maximum likelihood point of a probability density containing data with Gaussian uncertainties. The distribution of errors in the geophysical data is, however, seldom Gaussian. Using the $L_2$ norm, large and sparsely distributed errors adversely affect the solution, and the estimated model parameters may even be completely unphysical. On the other hand, the least-absolute-deviation optimization, which is based on the $L_1$ norm, has much more robust statistical properties in the presence of noise. The solution of the $L_1$ problem is the maximum likelihood point of a probability density containing data with longer-tailed errors than the Gaussian distribution. Thus, the $L_1$ norm gives more reliable estimates when a small number of large errors contaminate the data. The effect of outliers is further reduced by M-fitting method with Cauchy error criterion, which can be performed by iteratively reweighted least-squares method.

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Compact ECR plasma장치의 제작 및 특성 연구 (Study on the Fabrication and Characterization of Compact ECR Plasma System)

  • 윤민기;박원일;남기석;이기방
    • 전자공학회논문지A
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    • 제31A권4호
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    • pp.84-91
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    • 1994
  • A compact electron cyclotron resonance(ECR) plasma system composed of a microwave generator and a magnet coil was fabricated. A Langmuir single probe was used to investigate the plasma characteristics of the system through I-V measurements. The performance of the compact ECR plasma system was tested for the case of silicon etching reaction with $CF_{4}/O_{2}$(30%) mixed gas. Electron density and etch rate increased to maximum values and then decreased with increasing argon gas pressure, but electron temperature changed in the opposite way. The electron density and the electron temperature of argon gas plasma were 0.85${\times}~5.5{\times}10^{10}cm^{-3}$ and 4.5~6.0 eV, respectively, in the pressure range from $3{\times}10^{4}$ to 0.05Torr. The etch rate reached a maximum value at the position of 2.5cm from the bottom of plasma cavity. Etch rate uniformity was $\pm$6% across 6cm wafer. Anisotropic index was 0.75 at 1.5${\times}10^{-4}$Torr.

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PEA법에 의한 캐패시터내 전하분포 측정 (Charge Distribution in a capacitor observed by PEA Method)

  • ;한덕우;곽동주;성열문
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2008년도 제39회 하계학술대회
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    • pp.1156-1157
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    • 2008
  • The use of the pulsed electro acoustic (PEA) method allowed us to perform the direct observations of spatio-temporal charge distributions in Electric double layer capacitors (EDLCs) based on polarizable nanoporous carbonaceous electrode. The negative charge density became the maximum, about 205 $C/m^3$ at the region where was near to collector layer in EDLCs for case $V_{DC}$ = 2.5 V, while the positively charged density became the maximum, about 61.1 $C/m^3$ at the region where it was located around the cathode layer. The PEA measurement used here is a very useful method to quantitively investigates the spatio-temporal charge distribution in EDLCs.

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NATURAL CONVECTION OF WATER IN AN INCLINED CAVITY WITH HEAT GENERATION

  • Sundaravadivelu, K.;Kandaswamy, P.
    • Journal of applied mathematics & informatics
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    • 제12권1_2호
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    • pp.281-289
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    • 2003
  • The convection of water is investigated in the vicinity of its density maximum temperature (277 K) in an inclined square cavity in the presence of heat sources. Numerical investigations are carried out by maintaining one of the vertical walls uniformly at 273 K and varying the other wall between temperatures 275 K and 285 K at different inclinations angles. The isotherms, streamlines and velocity profiles reveal the possible existence of multicellular fluid motions, and bidirectional velocity distributions. These fluid flow and heat transfer characteristics are significantly modified by the cavity inclination in the presence of heat sources.

Electromagnetic Behavior of High -$T_c$ Superconductors underthequenchstate -

  • 정동철;최효상;황종선;윤기웅;한병성
    • Progress in Superconductivity
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    • 제3권2호
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    • pp.183-187
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    • 2002
  • In this paper we analyzed the electromagnetic behavior of high $-T_{c}$ superconductor under the quench state using finite element method. Poisson equation was used in finite element analysis as a governing equation and was solved using algebra equation using Gallerkin method. We first investigate d the electromagnetic behavior of U-type superconductor. Finally we applied our analysis techniques to 5.5 kVA meander-line superconducting fault current limiters (SFCL) which are currently developed by many power-system researcher in the world. Meshes of 14,600 elements were used in analysis of this SFCL. Analysis results show that the distribution of current density was concentrated to inner curvature in meander-line type-superconductors and maximum current density 14.61 $A/\m^2$ and also maximum Joule heat was 6,420 W/㎥. We concluded that this meander line-type SFCL was not pertinet fur uniform electromagnetic field distribution.n.

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Tape Casting법을 이용한 W-Cu, Mo-Cu 박판소재 제조 (Manufacturing of W-Cu and Mo-Cu Sheet by Tape Casting Method)

  • 박치완;장건익;김태형;우용원
    • 열처리공학회지
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    • 제17권5호
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    • pp.293-298
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    • 2004
  • For the application of heat sink device, the green sheets of powder of W-XCu and Mo-XCu composites were fabricated by tape casting technique. The mixing ratio of powder and binder was 6:4. The green sheet was shrinked up to 10~20% after sintering and the maximum relative density was above 95%. Thermal conductivity and Thermal expansion systematically increased with increasing Cu contents. The maximum thermal conductivity of W-20wt.%Cu was about 206[W/mK].