• 제목/요약/키워드: Regularization

검색결과 480건 처리시간 0.034초

격자 정방형화 방법을 이용한 박판 성형해석의 효율개선 (Efficiency Enhancement in Sheet Metal Forming Analysis with a Mesh Regularization Method)

  • 윤종헌;허훈
    • 소성∙가공
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    • 제12권4호
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    • pp.401-407
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    • 2003
  • This paper newly proposes a mesh regularization method for the enhancement of the efficiency in sheet metal forming analysis. The regularization method searches for distorted elements with appropriate searching criteria and constructs patches including the elements to be modified. Each patch is then extended to a three-dimensional surface in order to obtain the information of the continuous coordinates. In constructing the surface enclosing each patch, NURBS(Non-Uniform Rational B-Spline) surface is employed to describe a three-dimensional free surface. On the basis of the constructed surface, each node is properly arranged to form unit elements as close as to a square. The state variables calculated from its original mesh geometry are mapped into the new mesh geometry for the next stage or incremental step of a forming analysis. The analysis results with the proposed method are compared to the results from the direct forming analysis without mesh regularization in order to confirm the validity of the method.

THE METHOD OF REGULARIZATION RATIOS APPLIED TO RECONSTRUCTIONS OF ELASTIC RIGID OBSTACLES VIA THE FACTORIZATION METHOD

  • Kim, K.;Leem, K.H.;Pelekanos, G.
    • East Asian mathematical journal
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    • 제32권1호
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    • pp.129-138
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    • 2016
  • In this paper, we propose an efficient regularization technique (The Method of Regularized Ratios) for the reconstruction of the shape of a rigid elastic scatterer from far field measurements. The approach used is based on the factorization method and creates via Picard's condition ratios, baptized Regularized Ratios, that serve to effectively remove unwanted singular values that may lead to poor reconstructions. This is achieved through the use of a sophisticated algorithm that progressively adjusts an initially set moderate tolerance. In comparison with the well established Tikhonov-Morozov regularization techniques our new algorithm appears to be more computationally efficient as it doesn't require computation of the regularization parameter for each point in the grid.

Prediction of propagated wave profiles based on point measurement

  • Lee, Sang-Beom;Choi, Young-Myoung;Do, Jitae;Kwon, Sun-Hong
    • International Journal of Naval Architecture and Ocean Engineering
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    • 제6권1호
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    • pp.175-185
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    • 2014
  • This study presents the prediction of propagated wave profiles using the wave information at a fixed point. The fixed points can be fixed in either space or time. Wave information based on the linear wave theory can be expressed by Fredholm integral equation of the first kinds. The discretized matrix equation is usually an ill-conditioned system. Tikhonov regularization was applied to the ill-conditioned system to overcome instability of the system. The regularization parameter is calculated by using the L-curve method. The numerical results are compared with the experimental results. The analysis of the numerical computation shows that the Tikhonov regularization method is useful.

A Regularization-direct Method to Numerically Solve First Kind Fredholm Integral Equation

  • Masouri, Zahra;Hatamzadeh, Saeed
    • Kyungpook Mathematical Journal
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    • 제60권4호
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    • pp.869-881
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    • 2020
  • Most first kind integral equations are ill-posed, and obtaining their numerical solution often requires solving a linear system of algebraic equations of large condition number, which may be difficult or impossible. This article proposes a regularization-direct method to numerically solve first kind Fredholm integral equations. The vector forms of block-pulse functions and related properties are applied to formulate the direct method and reduce the integral equation to a linear system of algebraic equations. We include a regularization scheme to overcome the ill-posedness of integral equation and obtain a stable numerical solution. Some test problems are solved using the proposed regularization-direct method to illustrate its efficiency for solving first kind Fredholm integral equations.

Effective Determination of Optimal Regularization Parameter in Rational Polynomial Coefficients Derivation

  • Youn, Junhee;Hong, Changhee;Kim, TaeHoon;Kim, Gihong
    • 한국측량학회지
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    • 제31권6_2호
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    • pp.577-583
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    • 2013
  • Recently, massive archives of ground information imagery from new sensors have become available. To establish a functional relationship between the image and the ground space, sensor models are required. The rational functional model (RFM), which is used as an alternative to the rigorous sensor model, is an attractive option owing to its generality and simplicity. To determine the rational polynomial coefficients (RPC) in RFM, however, we encounter the problem of obtaining a stable solution. The design matrix for solutions is usually ill-conditioned in the experiments. To solve this unstable solution problem, regularization techniques are generally used. In this paper, we describe the effective determination of the optimal regularization parameter in the regularization technique during RPC derivation. A brief mathematical background of RFM is presented, followed by numerical approaches for effective determination of the optimal regularization parameter using the Euler Method. Experiments are performed assuming that a tilted aerial image is taken with a known rigorous sensor. To show the effectiveness, calculation time and RMSE between L-curve method and proposed method is compared.

볼록 규준화 RLS의 규준화 상수를 정하기 위한 두 가지 방법과 희소성 음향 통신 채널 추정 성능 비교 (Two regularization constant selection methods for recursive least squares algorithm with convex regularization and their performance comparison in the sparse acoustic communication channel estimation)

  • 임준석;홍우영
    • 한국음향학회지
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    • 제35권5호
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    • pp.383-388
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    • 2016
  • 본 논문은 볼록 규준화 RLS(Recursive Least Squares)에 쓰이는 규준화를 위한 상수를 정하는 법을 제안한다. Eksioglu와 Tanc는 희소성 음향 채널 추정을 위해서 볼록 규준화 RLS 알고리즘을 구현하였다. 그러나 이 알고리즘은 더 좋은 추정 성능을 위해서 채널의 참 임펄스 응답 정보가 사용된다. 본 논문에서는 이 같은 참 임펄스 응답 정보가 필요 없는 규준화 상수를 위한 두 가지 선정법을 제안한다. 그리고 제안한 방법을 사용했을 때 Eksioglu와 Tanc의 방법에 필적한 추정 성능을 유지함을 보인다.

Regularization Parameter Selection for Total Variation Model Based on Local Spectral Response

  • Zheng, Yuhui;Ma, Kai;Yu, Qiqiong;Zhang, Jianwei;Wang, Jin
    • Journal of Information Processing Systems
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    • 제13권5호
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    • pp.1168-1182
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    • 2017
  • In the past decades, various image regularization methods have been introduced. Among them, total variation model has drawn much attention for the reason of its low computational complexity and well-understood mathematical behavior. However, regularization parameter estimation of total variation model is still an open problem. To deal with this problem, a novel adaptive regularization parameter selection scheme is proposed in this paper, by means of using the local spectral response, which has the capability of locally selecting the regularization parameters in a content-aware way and therefore adaptively adjusting the weights between the two terms of the total variation model. Experiment results on simulated and real noisy image show the good performance of our proposed method, in visual improvement and peak signal to noise ratio value.

식생여과대 유사 저감 효율 산정을 위한 정규화 방안 (A Study on Regularization Methods to Evaluate the Sediment Trapping Efficiency of Vegetative Filter Strips)

  • 배주현;한정호;양재의;김종건;임경재;장원석
    • 한국농공학회논문집
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    • 제61권6호
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    • pp.9-19
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    • 2019
  • Vegetative Filter Strip (VFS) is the best management practice which has been widely used to mitigate water pollutants from agricultural fields by alleviating runoff and sediment. This study was conducted to improve an equation for estimating sediment trapping efficiency of VFS using several different regularization methods (i.e., ordinary least squares analysis, LASSO, ridge regression analysis and elastic net). The four different regularization methods were employed to develop the sediment trapping efficiency equation of VFS. Each regularization method indicated high accuracy in estimating the sediment trapping efficiency of VFS. Among the four regularization methods, the ridge method showed the most accurate results according to $R^2$, RMSE and MAPE which were 0.94, 7.31% and 14.63%, respectively. The equation developed in this study can be applied in watershed-scale hydrological models in order to estimate the sediment trapping efficiency of VFS in agricultural fields for an effective watershed management in Korea.

Impact Force Reconstruction of Composite materials based on Improved Regularization Technology

  • Sun, Yajie;Yin, Tao;Yang, Jian;Cai, Zhiyu;Wu, Shaoen
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • 제15권8호
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    • pp.2718-2731
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    • 2021
  • In the structural health monitoring of composite materials, in order to solve the ill-posed problem of impact force reconstruction, regularization techniques are often used to deal with it. Due to the poor convergence of the traditional Tikhonov regularization method, in order to accurately reconstruct the time history of the impact force, this paper improves Tikhonov regularization method and constructs homotopy function with strong convergence. Since the optimal regularization parameters need to be found in the homotopy function, the Newton downhill method is used to find the optimal parameters and the homotopy function can be calculated, which can accurately reconstruct the time history of the impact force. In order to verify the universality of the method in this paper, impact hammers of different materials were used in the experiment in this paper to study and compare the reconstruction effect of impact time history of different impact hammers.

Double 𝑙1 regularization for moving force identification using response spectrum-based weighted dictionary

  • Yuandong Lei;Bohao Xu;Ling Yu
    • Structural Engineering and Mechanics
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    • 제91권2호
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    • pp.227-238
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    • 2024
  • Sparse regularization methods have proven effective in addressing the ill-posed equations encountered in moving force identification (MFI). However, the complexity of vehicle loads is often ignored in existing studies aiming at enhancing MFI accuracy. To tackle this issue, a double 𝑙1 regularization method is proposed for MFI based on a response spectrum-based weighted dictionary in this study. Firstly, the relationship between vehicle-induced responses and moving vehicle loads (MVL) is established. The structural responses are then expanded in the frequency domain to obtain the prior knowledge related to MVL and to further construct a response spectrum-based weighted dictionary for MFI with a higher accuracy. Secondly, with the utilization of this weighted dictionary, a double 𝑙1 regularization framework is presented for identifying the static and dynamic components of MVL by the alternating direction method of multipliers (ADMM) method successively. To assess the performance of the proposed method, two different types of MVL, such as composed of trigonometric functions and driven from a 1/4 bridge-vehicle model, are adopted to conduct numerical simulations. Furthermore, a series of MFI experimental verifications are carried out in laboratory. The results shows that the proposed method's higher accuracy and strong robustness to noises compared with other traditional regularization methods.