• 제목/요약/키워드: Step Size

검색결과 1,945건 처리시간 0.028초

EFDC 모형을 이용한 댐 붕괴류 수치모의 및 매개변수 민감도 분석 (Numerical Simulation of Dam Break Flow using EFDC Model and Parameter Sensitivity Analysis)

  • 장철;송창근
    • 한국안전학회지
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    • 제31권4호
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    • pp.143-149
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    • 2016
  • In this study, a series of numerical simulation of dam break flow was conducted using EFDC model, and input conditions including cell size, time step, and turbulent eddy viscosity were considered to analyze parameter sensitivity. In case of coarse mesh layout, the propagated length of the shock wave front was ${\Delta}_x$ longer than that of other mesh layouts, and the velocity results showed jagged edge, which can be cured by applying fine grid mesh. Turbulent eddy viscosity influenced magnitude of the maximum velocity passing through gate up to 20% and the cell Peclet number less than 2.0 ensured no numerical oscillations.

인버터를 이용한 전기분해전원 설계에 과한 연구 (A Study on the Design of Electrolysis Power Using Inverter)

  • 이정민;목형수;최규하;최동규
    • 전력전자학회:학술대회논문집
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    • 전력전자학회 1998년도 연구회 합동 학술발표회 논문집
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    • pp.55-59
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    • 1998
  • By this time, Diode Rectifier or SCR has been used to gain DC Voltage for Electrolysis Power. Generally DC Voltage is produced from rectifier shall be transformed before rectifier using step-down transformer to obtain adaptable DC Voltage, rectifier output. In the same way, rectifier using SCR shall obtain output voltage after step-down voltage through transformer and control of the SCR firing angle. Transformer shall be used for this two methods to adjust the voltage. But the size and weight of the transformer are increased in accordance with the increase of capacity, and the hardships are accompanied in workspace or transportation. Besides, only the value of input voltage is possible to be regulated, and the expectation of current control is almost impossible during Electrolysis. This study has conducted Design and Simulation to reduce the size and weight of transformer and to be enable voltage and current control of Electrolysis power through high-speed switching using Inverter, Electronics device.

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3차 볼테라 필터링과 VSSGS-PAP 알고리즘을 이용한 배경잡음 변화에 강인한 비선형 능동소음제어 시스템 (Nonlinear ANC system robust to background noise variation by using 3rd-order Volterra filtering with a VSSGS-PAP algorithm)

  • 서재범;김경재;남상원
    • 대한전자공학회:학술대회논문집
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    • 대한전자공학회 2009년도 정보 및 제어 심포지움 논문집
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    • pp.70-72
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    • 2009
  • In this paper, nonlinear active noise control(ANC) of a 3rd-order Volterra system, which is robust to background noise variation, is proposed along with a variable step-size Gauss-Seidel pseudo affine projection(VSSGS-PAP) algorithm. Simulation results demonstrate that the proposed approach yields better nonlinear ANC performance in a background noise variation environment, compared with the conventional methods for the nonlinear ANC.

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새로운 성능지수 함수에 대한 직강하 적응필터 (Novel steepest descent adaptive filters derived from new performance function)

  • 전병을;박동조
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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    • pp.823-828
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    • 1992
  • A novel steepest descent adaptive filter algorithm, which uses the instantaneous stochastic gradient for the steepest descent direction, is derived from a newly devised performance index function. The performance function for the new algorithm is improved from that for the LMS in consideration that the stochastic steepest descent method is utilized to minimize the performance index iterativly. Through mathematical analysis and computer simulations, it is verified that there are substantial improvements in convergence and misadjustments even though the computational simplicity and the robustness of the LMS algorithm are hardly sacrificed. On the other hand, the new algorithm can be interpreted as a variable step size adaptive filter, and in this respect a heuristic method is proposed in order to reduce the noise caused by the step size fluctuation.

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자연 연소중인 궐련내에서 일어나는 물리화학적 현상의 시뮬레이션 (Simulation of Physical Chemistry Phenomena Inside a Naturally Smoldering Cigarette)

  • 오인혁;김기환;정경락
    • 한국연초학회지
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    • 제20권1호
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    • pp.87-94
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    • 1998
  • After we made the computer source code with mathematical model of Muramatsu et al. that was expressed by the set of simultaneous first-order ordinary differential equations in evaporation-pyrolysis zone of cigarette, we simulated the distribution profiles of temperature and density of flue-cured tobacco. Those equations were solved numerically with the Runge-Kutta-Gill algorithm assuming step size of 0.025mm by Muramatsu at at,, but in this study the advanced algorithm of Runge-Kutta 4th Order assuming step size of 0.0005mm. The initial conditions and physical parameters of Muramatsu et at. were used for solving them. The calculated values corresponded well with results of Muramatsu et al., especially the gradient of the temperature profile increased with smoldering speed and the thickness of the evaporation-pyrolysis zone decreased with increasing of smoldering speed. On the other hand, the temperature gradient decreased with increasing of the effective thermal-conductivity value and the thickness of the evaporation-pyrolysis zone increased with the effective thermal-conductivity value.

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적응잡음제거기의 정상상태 성능 및 수렴율 향상에 관한 연구 (A study on improvement of steady-state peformance and convergence rate in an adaptive noise canceller)

  • 배종갑;김창기;박장식;손경식
    • 전자공학회논문지S
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    • 제34S권4호
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    • pp.42-49
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    • 1997
  • A conventional adaptive noise canceller (ANC) using LMS algorithm suffers from the misadjustment of adaptive filter weights due to the gradient-estimate noise by input speech signal at steady state. In this paper, an ANC is proposed which uses the combination of VSLMS (variable step size LMS) and SA (sign algorithm) to improve steady state performance and convergence rate. SA algorithm is applied in speech region to prevent the weights from perturbing by output speech of ANC and VSLMS algorithm is applied to improve convergence rate and channel tracking ability in silence region and adaptive transient region. In compute rsimulation, the performance of the proposed VSLMS-SA combination algorithm is much better than LMS algorithm and the algorithm, recently proposed by greenberg, with adaptation step-size parameter determine dby sum method in convergence rate, channel tracking and steady state performance.

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반향환경에서의 가변 적응 상수를 이용한 FDICA와 여러 BSS 알고리즘과의 비교 (Comparison for the variable step-size FDICA with BSS algorithm in reverberant condition)

  • 박근수;박장식;손경식
    • 한국콘텐츠학회:학술대회논문집
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    • 한국콘텐츠학회 2005년도 춘계 종합학술대회 논문집
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    • pp.369-373
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    • 2005
  • 본 논문은 기존의 주파수 영역 독립 성분 분석(FDICA : frequency domain independent component analysis) 방법에 가변 적응 상수를 이용한 알고리즘을 제안한다. 여러 반향 환경에 대한 모의실험으로 기존의 temporal structure(TA)알고리즘, FDICA알고리즘과 비교하여 그 분리 성능을 평가하고 비교한다. 실제 녹음한 혼합 음원에 대한 분리정도를 비교 분석한다.

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태양광 발전시스템을 위한 새로운 가변폭 변조방식의 최대전력점 추종기법 (A New MPPT Scheme Based on Variable Step Size Incremental Conductance Method for PV Distributed Generation)

  • 고은기;김진호;박준열;이동명
    • 전력전자학회:학술대회논문집
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    • 전력전자학회 2010년도 하계학술대회 논문집
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    • pp.565-567
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    • 2010
  • This paper proposes a new Maximum Power Point Tracking (MPPT) control algorithm for PV-Cell (Photo voltaic) based on Incremental Conductance MPPT algorithm. The ICN (Incremental Conductance method) algorithm is widely used due to the high tracking accuracy and adaptability to the rapidly changing isolation condition. In this paper, a modified ICN MPPT algorithm is proposed. This method adjusts automatically the step-size of reference to track the PV-Cell maximum power point, thus it improves the maximum power point tracking speed and accuracy.

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One Chip 반향 제거기를 위한 알고리즘 개발에 관한 연구

  • 강정신;백인천;박상봉;박노경;차균현
    • 한국통신학회논문지
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    • 제15권8호
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    • pp.689-697
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    • 1990
  • 본 논문에서는 기존의 이중 케이블에서 전 이중방식 디지털 데이터 전송을 위한 적응 스토캐스틱 반복 알고리즘(Adaptive Stochasti Iteration Algorithm)을 제안하였다. 이 알고리즘을 이용한 반향제저기의 Step size는 반향의 크기에 따라서 변하므로 기존의 알고리즘에 의한 것 보다 10 배 이상의 높은 수렴율을 보였다. 그리고 이것은 기존의 반향 제거기 회로를 단순화 시키는 시퀸스 형태의 적응 디지털 필터와 결합하여 구현되며 LSI 수준으로 구현하기에 적합하다. 두 알고리즘에 대한 이론적인 분석을 제시하고 시뮬레이션 프로그램을 개발하였다.

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MOTION IN PARABOLIC CYLINDRICAL COORDINATES: APPLICATION TO J2 GRAVITY PERTURBED TRAJECTORIES

  • Sharaf, M.A.;Selim, H.H.;Saad, A.S.
    • 천문학회지
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    • 제39권4호
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    • pp.147-150
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    • 2006
  • In this paper, initial value problem for dynamical astronomy will be established using parabolic cylindrical coordinates. Computation algorithm is developed for the initial value problem of gravity perturbed trajectories. Applications of the algorithm for the problem of final state predication are illustrated by numerical examples of seven test orbits of different eccentricities. The numerical results are extremely accurate and efficient in predicating final state for gravity perturbed trajectories which is of extreme importance for scientific researches as well as for military purposes. Moreover, an additional efficiency of the algorithm is that, for each of the test orbits, the step size used for solving the differential equations of motion is larger than 70% of the step size used for obtaining its reference final state solution.