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    Wyświetlanie 1-15 z 15
    Tytuł:
    Gradient Observability for Diffusion Systems
    Autorzy:
    Zerrik, E. H.
    Bourray, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/908195.pdf
    Data publikacji:
    2003
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    informatyka
    diffusion system
    observability
    regional gradient observability
    gradient strategic sensor
    gradient reconstruction
    Opis:
    The aim of this paper is to study regional gradient observability for a diffusion system and the reconstruction of the state gradient without the knowledge of the state. First, we give definitions and characterizations of these new concepts and establish necessary conditions for the sensor structure in order to obtain regional gradient observability. We also explore an approach which allows for a regional gradient reconstruction. The developed method is original and leads to a numerical algorithm illustrated by simulations.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2003, 13, 2; 139-150
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Operator-splitting and Lagrange multiplier domain decomposition methods for numerical simulation of two coupled Navier-Stokes fluids
    Autorzy:
    Bresch, D.
    Koko, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/908383.pdf
    Data publikacji:
    2006
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    dwoistość
    gradient sprzężony
    przepływ Naviera-Stokesa
    domain decomposition
    duality
    conjugate gradient
    Navier-Stokes flows
    Opis:
    We present a numerical simulation of two coupled Navier-Stokes flows, using operator-splitting and optimization-based nonoverlapping domain decomposition methods. The model problem consists of two Navier-Stokes fluids coupled, through a common interface, by a nonlinear transmission condition. Numerical experiments are carried out with two coupled fluids; one with an initial linear profile and the other in rest. As expected, the transmission condition generates a recirculation within the fluid in rest.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2006, 16, 4; 419-429
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A proximal-based algorithm for piecewise sparse approximation with application to scattered data fitting
    Autorzy:
    Zhong, Yijun
    Li, Chongjun
    Li, Zhong
    Duan, Xiaojuan
    Powiązania:
    https://bibliotekanauki.pl/articles/2172132.pdf
    Data publikacji:
    2022
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    piecewise sparse approximation
    proximal gradient
    scattered data fitting
    aproksymacja rzadka
    gradient proksymalny
    dopasowanie danych
    Opis:
    In some applications, there are signals with a piecewise structure to be recovered. In this paper, we propose a piecewise sparse approximation model and a piecewise proximal gradient method (JPGA) which aim to approximate piecewise signals. We also make an analysis of the JPGA based on differential equations, which provides another perspective on the convergence rate of the JPGA. In addition, we show that the problem of sparse representation of the fitting surface to the given scattered data can be considered as a piecewise sparse approximation. Numerical experimental results show that the JPGA can not only effectively fit the surface, but also protect the piecewise sparsity of the representation coefficient.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2022, 32, 4; 671--682
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Regional Gradient Controllability of Parabolic Systems
    Autorzy:
    Zerrik, E.
    Boutoulout, A.
    Kamal, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/908270.pdf
    Data publikacji:
    1999
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    układ paraboliczny
    sterowność
    parabolic systems
    regional gradient controllability
    G-strategic actuator
    Opis:
    The purpose of this paper is to show for parabolic systems how one can achieve a final gradient in a subregion w of the system domain W. First, we give a definition and delineate some properties of this new concept, and then we introduce the concept of regionally gradient strategic actuators. The importance of the spatial structure and location of the actuators in achieving regional gradient controllability is emphasized. Consequently, we concentrate on the determination of a control which would realize a given final gradient on w with minimum energy. The developed approach is original and leads to numerical algorithms for constructing optimal controls. This approach is also illustrated by an example.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 1999, 9, 4; 767-787
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Accurate gradient computations at interfaces using finite element methods
    Autorzy:
    Qin, F.
    Wang, Z.
    Ma, Z.
    Li, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/330659.pdf
    Data publikacji:
    2017
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    elliptic interface problem
    gradient flux computation
    IFEM
    mixed FE formulation
    computational tube
    Opis:
    New finite element methods are proposed for elliptic interface problems in one and two dimensions. The main motivation is to get not only an accurate solution, but also an accurate first order derivative at the interface (from each side). The key in 1D is to use the idea of Wheeler (1974). For 2D interface problems, the point is to introduce a small tube near the interface and propose the gradient as part of unknowns, which is similar to a mixed finite element method, but only at the interface. Thus the computational cost is just slightly higher than in the standard finite element method. We present a rigorous one dimensional analysis, which shows a second order convergence order for both the solution and the gradient in 1D. For two dimensional problems, we present numerical results and observe second order convergence for the solution, and super-convergence for the gradient at the interface.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2017, 27, 3; 527-537
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Two implementations of the preconditioned conjugate gradient method on heterogeneous computing grids
    Autorzy:
    Collignon, T. P.
    Van Gijzen, M. B.
    Powiązania:
    https://bibliotekanauki.pl/articles/907778.pdf
    Data publikacji:
    2010
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    przetwarzanie siatkowe
    system liniowy
    metoda iteracyjna
    gradient sprzężony
    przepływ pęcherzykowy
    grid computing
    large sparse linear systems
    iterative methods
    conjugate gradient method
    Chronopoulos/Gear CG
    GridSolve middleware
    bubbly flows
    Opis:
    Efficient iterative solution of large linear systems on grid computers is a complex problem. The induced heterogeneity and volatile nature of the aggregated computational resources present numerous algorithmic challenges. This paper describes a case study regarding iterative solution of large sparse linear systems on grid computers within the software constraints of the grid middleware GridSolve and within the algorithmic constraints of preconditioned Conjugate Gradient (CG) type methods. We identify the various bottlenecks induced by the middleware and the iterative algorithm. We consider the standard CG algorithm of Hestenes and Stiefel, and as an alternative the Chronopoulos/Gear variant, a formulation that is potentially better suited for grid computing since it requires only one synchronisation point per iteration, instead of two for standard CG. In addition, we improve the computation-to-communication ratio by maximising the work in the preconditioner. In addition to these algorithmic improvements, we also try to minimise the communication overhead within the communication model currently used by the GridSolve middleware. We present numerical experiments on 3D bubbly flow problems using heterogeneous computing hardware that show lower computing times and better speed-up for the Chronopoulos/Gear variant of conjugate gradients. Finally, we suggest extensions to both the iterative algorithm and the middleware for improving granularity.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2010, 20, 1; 109-121
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Gradient flow optimization for reducing blocking effects of transform coding
    Autorzy:
    Gao, F.
    Li, X.
    Wang, X.
    Wee, W. G.
    Powiązania:
    https://bibliotekanauki.pl/articles/907251.pdf
    Data publikacji:
    2004
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    przepływ gradientu
    efekt blokowania
    kodowanie transformatowe
    gradient flow
    blocking effects
    optimization
    transform coding
    Opis:
    This paper addresses the problem of reducing blocking effects in transform coding. A novel optimization approach using the gradient flow is proposed. Using some properties of the gradient flow on a manifold, an optimized filter design method for reducing the blocking effects is presented. Based on this method, an image reconstruction algorithm is derived. The algorithm maintains the fidelity of images while reducing the blocking effects. Experimental tests demonstrate that the presented algorithm is effective.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2004, 14, 1; 105-111
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Convergence Analysis for Principal Component Flows
    Autorzy:
    Yoshizawa, S.
    Helmke, U.
    Starkov, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/908317.pdf
    Data publikacji:
    2001
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    badanie zbieżności
    sieć neuronowa
    principal component analysis
    neural networks
    gradient flows
    phase portrait
    Hessians
    Opis:
    A common framework for analyzing the global convergence of several flows for principal component analysis is developed. It is shown that flows proposed by Brockett, Oja, Xu and others are all gradient flows and the global convergence of these flows to single equilibrium points is established. The signature of the Hessian at each critical point is determined.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2001, 11, 1; 223-236
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Newtons iteration with a conjugate gradient based decomposition method for an elliptic PDE with a nonlinear boundary condition
    Autorzy:
    Koko, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/907312.pdf
    Data publikacji:
    2004
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    metoda Newtona
    metoda gradientu sprzężonego
    warunek brzegowy nieliniowy
    Newton's method
    conjugate gradient method
    nonlinear PDE
    Opis:
    Newton's iteration is studied for the numerical solution of an elliptic PDE with nonlinear boundary conditions. At each iteration of Newton's method, a conjugate gradient based decomposition method is applied to the matrix of the linearized system. The decomposition is such that all the remaining linear systems have the same constant matrix. Numerical results confirm the savings with respect to the computational cost, compared with the classical Newton method with factorization at each step.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2004, 14, 1; 13-18
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On the Choice of Subspace for Iterative Methods for Linear Discrete Ill-Posed Problems
    Autorzy:
    Calvetti, D.
    Lewis, B.
    Reichel, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/908057.pdf
    Data publikacji:
    2001
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    metoda sprzężonych gradientów
    problem niewłaściwie postawiony
    minimal residual method
    conjugate gradient method
    ill-posed problems
    Opis:
    Many iterative methods for the solution of linear discrete ill-posed problems with a large matrix require the computed approximate solutions to be orthogonal to the null space of the matrix. We show that when the desired solution is not smooth, it may be possible to determine meaningful approximate solutions with less computational work by not imposing this orthogonality condition.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2001, 11, 5; 1069-1092
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Random perturbation of the variable metric method for unconstrained nonsmooth nonconvex optimization
    Autorzy:
    El Mouatasim, A.
    Ellaia, R.
    Souza de Cursi, J. E.
    Powiązania:
    https://bibliotekanauki.pl/articles/908374.pdf
    Data publikacji:
    2006
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    optymalizacja
    zaburzenie stochastyczne
    zaburzenie losowe
    nonconvex optimization
    stochastic perturbation
    variable metric method
    nonsmooth optimization
    generalized gradient
    Opis:
    We consider the global optimization of a nonsmooth (nondifferentiable) nonconvex real function. We introduce a variable metric descent method adapted to nonsmooth situations, which is modified by the incorporation of suitable random perturbations. Convergence to a global minimum is established and a simple method for the generation of suitable perturbations is introduced. An algorithm is proposed and numerical results are presented, showing that the method is computationally effective and stable.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2006, 16, 4; 463-474
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Infrared small-target detection under a complex background based on a local gradient contrast method
    Autorzy:
    Yang, Linna
    Xie, Tao
    Liu, Mingxing
    Zhang, Mingjiang
    Qi, Shuaihui
    Yang, Jungang
    Powiązania:
    https://bibliotekanauki.pl/articles/2201024.pdf
    Data publikacji:
    2023
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    small target detection
    local gradient contrast
    visual saliency
    infrared image processing
    kontrast lokalny
    wyróżnienie wizualne
    obrazowanie w podczerwieni
    Opis:
    Small target detection under a complex background has always been a hot and difficult problem in the field of image processing. Due to the factors such as a complex background and a low signal-to-noise ratio, the existing methods cannot robustly detect targets submerged in strong clutter and noise. In this paper, a local gradient contrast method (LGCM) is proposed. Firstly, the optimal scale for each pixel is obtained by calculating a multiscale salient map. Then, a subblockbased local gradient measure is designed; it can suppress strong clutter interference and pixel-sized noise simultaneously. Thirdly, the subblock-based local gradient measure and the salient map are utilized to construct the LGCM. Finally, an adaptive threshold is employed to extract the final detection result. Experimental results on six datasets demonstrate that the proposed method can discard clutters and yield superior results compared with state-of-the-art methods.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2023, 33, 1; 33--43
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An automated driving strategy generating method based on WGAIL–DDPG
    Autorzy:
    Zhang, Mingheng
    Wan, Xing
    Gang, Longhui
    Lv, Xinfei
    Wu, Zengwen
    Liu, Zhaoyang
    Powiązania:
    https://bibliotekanauki.pl/articles/2055167.pdf
    Data publikacji:
    2021
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    automated driving system
    deep learning
    deep reinforcement learning
    imitation learning
    deep deterministic policy gradient
    system jezdny
    uczenie głębokie
    uczenie przez naśladowanie
    Opis:
    Reliability, efficiency and generalization are basic evaluation criteria for a vehicle automated driving system. This paper proposes an automated driving decision-making method based on the Wasserstein generative adversarial imitation learning–deep deterministic policy gradient (WGAIL–DDPG(λ)). Here the exact reward function is designed based on the requirements of a vehicle’s driving performance, i.e., safety, dynamic and ride comfort performance. The model’s training efficiency is improved through the proposed imitation learning strategy, and a gain regulator is designed to smooth the transition from imitation to reinforcement phases. Test results show that the proposed decision-making model can generate actions quickly and accurately according to the surrounding environment. Meanwhile, the imitation learning strategy based on expert experience and the gain regulator can effectively improve the training efficiency for the reinforcement learning model. Additionally, an extended test also proves its good adaptability for different driving conditions.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2021, 31, 3; 461--470
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Robust extremum seeking for a second order uncertain plant using a sliding mode controller
    Autorzy:
    Solis, Cesar
    Clempner, Julio
    Poznyak, Alexander
    Powiązania:
    https://bibliotekanauki.pl/articles/330477.pdf
    Data publikacji:
    2019
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    convex optimization
    extremum seeking
    continuous time gradient algorithm
    dynamical constrained optimization
    unknown function
    optymalizacja wypukła
    poszukiwanie ekstremum
    algorytm gradientowy
    optymalizacja ograniczona
    Opis:
    This paper suggests a novel continuous-time robust extremum seeking algorithm for an unknown convex function constrained by a dynamical plant with uncertainties. The main idea of the proposed method is to develop a robust closed-loop controller based on sliding modes where the sliding surface takes the trajectory around a zone of the optimal point. We assume that the output of the plant is given by the states and a measure of the function. We show the stability and zone-convergence of the proposed algorithm. In order to validate the proposed method, we present a numerical example.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2019, 29, 4; 703-712
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A complete gradient clustering algorithm formed with kernel estimators
    Autorzy:
    Kulczycki, P.
    Charytanowicz, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/907781.pdf
    Data publikacji:
    2010
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    analiza danych
    eksploracja danych
    grupowanie
    metoda statystyczna
    estymacja jądrowa
    obliczenia numeryczne
    data analysis
    data mining
    clustering
    gradient procedures
    nonparametric statistical methods
    kernel estimators
    numerical calculations
    Opis:
    The aim of this paper is to provide a gradient clustering algorithm in its complete form, suitable for direct use without requiring a deeper statistical knowledge. The values of all parameters are effectively calculated using optimizing procedures. Moreover, an illustrative analysis of the meaning of particular parameters is shown, followed by the effects resulting from possible modifications with respect to their primarily assigned optimal values. The proposed algorithm does not demand strict assumptions regarding the desired number of clusters, which allows the obtained number to be better suited to a real data structure. Moreover, a feature specific to it is the possibility to influence the proportion between the number of clusters in areas where data elements are dense as opposed to their sparse regions. Finally, the algorithm-by the detection of one-element clusters-allows identifying atypical elements, which enables their elimination or possible designation to bigger clusters, thus increasing the homogeneity of the data set.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2010, 20, 1; 123-134
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-15 z 15

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