• Title/Summary/Keyword: approximate model

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Cavitating Flow Simulation Using Two-Fluid Two-Phase Flow Model and HLL Scheme (이유체 이상유동 모델과 HLL 스킴을 이용한 캐비테이션 유동 해석)

  • Yeom Geum-Su;Chang Keun-Shik
    • 한국전산유체공학회:학술대회논문집
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    • 2005.04a
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    • pp.219-222
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    • 2005
  • A compressible two-fluid two-phase flow computation model using the stiffened-gas equation of state is formulated. Since the conservation equation system is of mixed type, it gives complex eigenvalues. The sonic speeds obtained from the individual single phase have been simply used in the literature for the fastest wave speeds necessary in the HLL scheme. This method has worked fine but proved to be quite diffusive according to our test. To improve the accuracy, we here propose to utilize the analytic eigenvalues evaluated from an approximate Jacobian matrix lot the fastest wave speeds. The interfacial transfer terms were dropped in constituting the Jacobian matrix for this purpose. The present scheme proved efficient, robust and accurate in comparison with other existing methods. We solved the cavitating flow problem using the present scheme. The result shows more detailed wave structure in the cavitating process caused by the strong expansion waves.

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Near Time Maximum Disturbance Design for Second Order Oscillator with Model Uncertainty (모델 불확실성을 갖는 이차 오실레이터에 대한 근사화된 최대 시간 교란 신호 설계)

  • You Kwan-Ho
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.52 no.4
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    • pp.205-211
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    • 2003
  • In this paper we propose a disturbance design method to test a system's stability. It is shown that the time maximum disturbance is represented in bang-bang and state feedback form. To maximize the time severity index, the value of disturbance is determined by the associated switch curve. The original switch curve is vulnerable to model uncertainties and takes much calculation time. We propose an improved method to approximate the original switch curve. This reduces the computational time and implements sufficiently to test the stable system. Simulation results show how the approximate switch curve can be used to stress a system by driving it to oscillation along the maximum limit cycle.

PROCESS RESEARCH FOR DEVELOPMENT OF STRUCTURAL COST ESTIMATING MODEL BASED QUANTITY - FOCUSED ON PUBLIC OFFICE BUILDING PROJECT -

  • Soo-Min Kim;Jung-Kyu Seo;Sung-Uk Kim;Chang-Hyun Shin;Yung-Jin Kim;Jae-Youl Chun
    • International conference on construction engineering and project management
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    • 2009.05a
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    • pp.1170-1175
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    • 2009
  • When managers estimate exact construction cost at early stage and design phase, they can reduce construction cost in a more efficient way than to predict at construction stage. But, the current of public construction cost estimation and management is concentrated almost after detailed design phase. Therefore, construction cost management in design development phase to generally use approximate estimating is not correct. Also, the existing construction cost used the method that estimated by gross floor area-based cost estimates at design development phase. So, it is difficult to show the specific amount of materials and basis about the estimated cost of the construction. This study derived problems and limits of construction management at design development phase in case of public office building project through review of literature and current survey, and suggested estimating process model process of structural construction cost go improve these matters.

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A Parabolic Model to the Modified Mild Slope Equation (수정 완경사 파랑식에 대한 포물형 근사식 모형)

  • Seo, Seung-Nam;Lee, Jong-Chan
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.18 no.4
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    • pp.360-371
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    • 2006
  • In order to calculate waves propagating into the shallow water region, a generalized parabolic approximate model is presented. The model is derived from the modified mild slope equation and includes all the existing parabolic models presented in the paper. Numerical results are presented in comparison to laboratory data of Berkhoff et al.(1982). The existing parabolic model shows almost same accuracy against the modified parabolic model and both results of models stand in closer agreement to the laboratory data. Therefore the existing parabolic model based on mild slope equation is a useful tool to compute shallow water waves which turns out to be more fast and stable in computational aspect.

Significance of rigorous fluid-foundation interaction in dynamic analysis of concrete gravity dams

  • Lotfi, Vahid
    • Structural Engineering and Mechanics
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    • v.21 no.2
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    • pp.137-150
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    • 2005
  • Dynamic analysis of dam-reservoir-foundation system is usually carried out by employing a simplified and approximate one-dimensional model to account for fluid-foundation interaction. The approximation introduced on this basis is examined thoroughly in this paper by comparing the method with the rigorous approach. It is concluded that the errors due to approximate method could be very significant both for horizontal and vertical ground motions.

An Approximate Description of Strain-Voltage Relationships for SWNTs/Conducting Polymer Composite Actuator (카본나노튜뷰/전도성 폴리머 복합재 엑츄에이터의 전압-변형률 관계식)

  • Liu Xinyun;Kim Cheol
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2004.10a
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    • pp.9-14
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    • 2004
  • An approximate relationship of the strain and applied potential was derived for SWNTs and conductive polymer composite actuator. During the deriving process, we used an electrochemical system to model the electromechanical actuation of the composite film. This relationship can give us a direct understanding to the actuation of a nanoactuator

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Censored Kernel Ridge Regression

  • Shim, Joo-Yong
    • Journal of the Korean Data and Information Science Society
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    • v.16 no.4
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    • pp.1045-1052
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    • 2005
  • This paper deals with the estimations of kernel ridge regression when the responses are subject to randomly right censoring. The weighted data are formed by redistributing the weights of the censored data to the uncensored data. Then kernel ridge regression can be taken up with the weighted data. The hyperparameters of model which affect the performance of the proposed procedure are selected by a generalized approximate cross validation(GACV) function. Experimental results are then presented which indicate the performance of the proposed procedure.

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Analysis of the Effects of Scaling Factors of Fuzzy Controller (퍼지 제어기의 Scaling Factor의 영향 분석)

  • Lee, Chul-Heui;Seo, Seon-Hak
    • Journal of Industrial Technology
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    • v.15
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    • pp.195-202
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    • 1995
  • In this paper, we analyze the effects of scaling factors on the performance of a fuzzy controller. The quantitative relation between input and output variables of a fuzzy controller is obtained by using a quasi-linear fuzzy model. And an approximate transfer function of a fuzzy controller is derived from the comparison of fuzzy controller with the conventional PID controller. Then we analyze the effects of scaling factor using this approximate transfer function and root locus method.

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NUMERICAL METHODS FOR A STIFF PROBLEM ARISING FROM POPULATION DYNAMICS

  • Kim, Mi-Young
    • Korean Journal of Mathematics
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    • v.13 no.2
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    • pp.161-176
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    • 2005
  • We consider a model of population dynamics whose mortality function is unbounded. We note that the regularity of the solution depends on the growth rate of the mortality near the maximum age. We propose Gauss-Legendre methods along the characteristics to approximate the solution when the solution is smooth enough. It is proven that the scheme is convergent at fourth-order rate in the maximum norm. We also propose discontinuous Galerkin finite element methods to approximate the solution which is not smooth enough. The stability of the method is discussed. Several numerical examples are presented.

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Approximation of the State Variables of the Original System from the Balanced Reduced Model (발란싱축소화로 구한 축소모델로부터 원 시스템 상태변수를 구하는 방법)

  • 정광영
    • 제어로봇시스템학회:학술대회논문집
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    • 2000.10a
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    • pp.333-333
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    • 2000
  • When the generalized singular perturbation method is used for model reduction, the state variables of the original system is reconstructed from the reduced order model. The state reduction error is defined, which shows how well the reconstructed state variables approximate the state variables of the original system equation.

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