• 제목/요약/키워드: least-squares problems

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최소 제곱 무요소법을 이용한 적응 기법에 관한 연구 (A Study on the Adaptive Scheme Using Least-Squares Meshfree Method)

  • 박상훈;권기찬;윤성기
    • 대한기계학회논문집A
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    • 제26권9호
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    • pp.1849-1858
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    • 2002
  • An h-adaptive scheme of first-order least-squares meshfree method is presented. A posteriori error estimates, which can be readily computed from the residual, are also presented. For elliptic problem the error indicators are further improved by applying the Aubin-Nitsche method. In the proposed refinement scheme, Voronoi cells are utilized to insert nodes at appropriate positions. Through numerical examples, it is demonstrated that the error indicators reveal good correlations with the actual errors and the adaptive first-order least-squares meshfree method is effectively applied to the localized problems such as the shock formation in fluid dynamics.

ANALYSIS OF FIRST-ORDER SYSTEM LEAST-SQUARES FOR THE OPTIMAL CONTROL PROBLEMS FOR THE NAVIER-STOKES EQUATIONS

  • Choi, Young-Mi;Kim, Sang-Dong;Lee, Hyung-Chun;Shin, Byeong-Chun
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • 제11권4호
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    • pp.55-68
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    • 2007
  • First-order least-squares method of a distributed optimal control problem for the incompressible Navier-Stokes equations is considered. An optimality system for the optimal solution are reformulated to the equivalent first-order system by introducing velocity-flux variables and then the least-squares functional corresponding to the system is defined in terms of the sum of the squared $L^2$ norm of the residual equations of the system. The optimal error estimates for least-squares finite element approximations are obtained.

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ANALYSIS AND COMPUTATIONS OF LEAST-SQUARES METHOD FOR OPTIMAL CONTROL PROBLEMS FOR THE STOKES EQUATIONS

  • Choi, Young-Mi;Kim, Sang-Dong;Lee, Hyung-Chun
    • 대한수학회지
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    • 제46권5호
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    • pp.1007-1025
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    • 2009
  • First-order least-squares method of a distributed optimal control problem for the incompressible Stokes equations is considered. An optimality system for the optimal solution are reformulated to the equivalent first-order system by introducing the vorticity and then the least-squares functional corresponding to the system is defined in terms of the sum of the squared $H^{-1}$ and $L^2$ norms of the residual equations of the system. Finite element approximations are studied and optimal error estimates are obtained. Resulting linear system of the optimality system is symmetric and positive definite. The V-cycle multigrid method is applied to the system to test computational efficiency.

견인한 완전최소자승법과 시스템 식별에의 적용 (Robust Total Least Squares Method and its Applications to System Identifications)

  • 김진영;최승호
    • 한국음향학회지
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    • 제15권4호
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    • pp.93-97
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    • 1996
  • 완전최소자승법(total least squares method, TLS) Ax${\simeq}$b와 같은 형태의 시스템 식을 푸는데 있어 데이터 행렬 A와 b에 잡음비 섞인 경우에 편이 되지 않은 해를 구하기 위하여 널리 이용된다. 그러나 임펄수성의 잡음과 같은 heavy tailed 확률분포를 갖는 잡음이 존재할 때 완전 최소자승법은 unbiased estimator이지만 최소자승법(least squares, LS)과 마찬가지로 경인하지 못한 성능을 보인다. 본 논문에서는 TLS 방법의 견인성에 대하여 논하고 완전최소자승법의 해의 특성을 기반으로 하여 견인한 완전최소자승법(robust TLS, ROTLS)을 제안한다. 또한 ROTLS 방법을 시스템식별문제에 적용하여 그 성능을 평가한다.

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Diagnostic Study of Problems under Asymptotically Generalized Least Squares Estimation of Physical Health Model

  • Kim, Jung-Hee
    • 대한간호학회지
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    • 제29권5호
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    • pp.1030-1041
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    • 1999
  • This study examined those problems noticed under the Asymptotically Generalized Least Squares estimator in evaluating a structural model of physical health. The problems were highly correlated parameter estimates and high standard errors of some parameter estimates. Separate analyses of the endogenous part of the model and of the metric of a latent factor revealed a highly skewed and kurtotic measurement indicator as the focal point of the manifested problems. Since the sample sizes are far below that needed to produce adequate AGLS estimates in the given modeling conditions, the adequacy of the Maximum Likelihood estimator is further examined with the robust statistics and the bootstrap method. These methods demonstrated that the ML methods were unbiased and statistical decisions based upon the ML standard errors remained almost the same. Suggestions are made for future studies adopting structural equation modeling technique in terms of selecting of a reference indicator and adopting those statistics corrected for nonormality.

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상관관계가 강한 독립변수들을 포함한 데이터 시스템 분석을 위한 편차 - 복구 알고리듬 (Biased-Recovering Algorithm to Solve a Highly Correlated Data System)

  • 이미영
    • 한국경영과학회지
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    • 제28권3호
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    • pp.61-66
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    • 2003
  • In many multiple regression analyses, the “multi-collinearity” problem arises since some independent variables are highly correlated with each other. Practically, the Ridge regression method is often adopted to deal with the problems resulting from multi-collinearity. We propose a better alternative method using iteration to obtain an exact least squares estimator. We prove the solvability of the proposed algorithm mathematically and then compare our method with the traditional one.

데이터베이스 기반 유전 알고리즘을 이용한 효율적인 에어포일 형상 최적화에 대한 연구 (Study on the Airfoil Shape Design Optimization Using Database based Genetic Algorithms)

  • 권장혁;김진;김수환
    • Journal of Advanced Marine Engineering and Technology
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    • 제31권1호
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    • pp.58-66
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    • 2007
  • Genetic Algorithms (GA) have some difficulties in practical applications because of too many function evaluations. To overcome these limitations, an approximated modeling method such as Response Surface Modeling(RSM) is coupled to GAs. Original RSM method predicts linear or convex problems well but it is not good for highly nonlinear problems cause of the average effect of the least square method(LSM). So the locally approximated methods. so called as moving least squares method(MLSM) have been used to reduce the error of LSM. In this study, the efficient evolutionary GAs tightly coupled with RSM with MLSM are constructed and then a 2-dimensional inviscid airfoil shape optimization is performed to show its efficiency.

Motion analysis within non-rigid body objects in satellite images using least squares matching

  • Hasanlou M.;Saradjian M.R.
    • 대한원격탐사학회:학술대회논문집
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    • 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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    • pp.47-51
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    • 2005
  • Using satellite images, an optimal solution to water motion has been presented in this study. Since temperature patterns are suitable tracers in water motion, Sea Surface Temperature (SST) images of Caspian Sea taken by MODIS sensor on board Terra satellite have been used in this study. Two daily SST images with 24 hours time interval are used as input data. Computation of templates correspondence between pairs of images is crucial within motion algorithms using non-rigid body objects. Image matching methods have been applied to estimate water body motion within the two SST images. The least squares matching technique, as a flexible technique for most data matching problems, offers an optimal spatial solution for the motion estimation. The algorithm allows for simultaneous local radiometric correction and local geometrical image orientation estimation. Actually, the correspondence between the two image templates is modeled both geometrically and radiometrically. Geometric component of the model includes six geometric transformation parameters and radiometric component of the model includes two radiometric transformation parameters. Using the algorithm, the parameters are automatically corrected, optimized and assessed iteratively by the least squares algorithm. The method used in this study, has presented more efficient and robust solution compared to the traditional motion estimation schemes.

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Influencing factors and prediction of carbon dioxide emissions using factor analysis and optimized least squares support vector machine

  • Wei, Siwei;Wang, Ting;Li, Yanbin
    • Environmental Engineering Research
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    • 제22권2호
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    • pp.175-185
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    • 2017
  • As the energy and environmental problems are increasingly severe, researches about carbon dioxide emissions has aroused widespread concern. The accurate prediction of carbon dioxide emissions is essential for carbon emissions controlling. In this paper, we analyze the relationship between carbon dioxide emissions and influencing factors in a comprehensive way through correlation analysis and regression analysis, achieving the effective screening of key factors from 16 preliminary selected factors including GDP, total population, total energy consumption, power generation, steel production coal consumption, private owned automobile quantity, etc. Then fruit fly algorithm is used to optimize the parameters of least squares support vector machine. And the optimized model is used for prediction, overcoming the blindness of parameter selection in least squares support vector machine and maximizing the training speed and global searching ability accordingly. The results show that the prediction accuracy of carbon dioxide emissions is improved effectively. Besides, we conclude economic and environmental policy implications on the basis of analysis and calculation.

FINITE ELEMENT APPROXIMATION OF THE DISCRETE FIRST-ORDER SYSTEM LEAST SQUARES FOR ELLIPTIC PROBLEMS

  • SHIN, Byeong-Chun
    • 대한수학회논문집
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    • 제20권3호
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    • pp.563-578
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    • 2005
  • In [Z. Cai and B. C. Shin, SIAM J. Numer. Anal. 40 (2002), 307-318], we developed the discrete first-order system least squares method for the second-order elliptic boundary value problem by directly approximating $H(div){\cap}H(curl)-type$ space based on the Helmholtz decomposition. Under general assumptions, error estimates were established in the $L^2\;and\;H^1$ norms for the vector and scalar variables, respectively. Such error estimates are optimal with respect to the required regularity of the solution. In this paper, we study solution methods for solving the system of linear equations arising from the discretization of variational formulation which possesses discrete biharmonic term and focus on numerical results including the performances of multigrid preconditioners and the finite element accuracy.