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Wyświetlanie 1-15 z 293
Tytuł:
Shape sensitivity of optimal control for the Stokes problem
Autorzy:
Abdelbari, Merwan
Nachi, Khadra
Sokolowski, Jan
Szulc, Katarzyna
Powiązania:
https://bibliotekanauki.pl/articles/2049935.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
Stokes equations
optimal control problem
coupled partial differential equations
shape optimization
shape gradient
Opis:
In this article, we study the shape sensitivity of optimal control for the steady Stokes problem. The main goal is to obtain a robust representation for the derivatives of optimal solution with respect to smooth deformation of the flow domain. We introduce in this paper a rigorous proof of existence of the material derivative in the sense of Piola, as well as the shape derivative for the solution of the optimality system. We apply these results to derive the formulae for the shape gradient of the cost functional; under some regularity conditions the shape gradient is given according to the structure theorem by a function supported on the moving boundary, then the numerical methods for shape optimization can be applied in order to solve the associated optimization problems.
Źródło:
Control and Cybernetics; 2020, 49, 1; 11-40
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Enhancing the performance of deep learning technique by combining with gradient boosting in rainfall-runoff simulation
Autorzy:
Abdullaeva, Barno S.
Powiązania:
https://bibliotekanauki.pl/articles/28411647.pdf
Data publikacji:
2023
Wydawca:
Instytut Technologiczno-Przyrodniczy
Tematy:
deep learning
gradient boosting
hybrid model
multi-step ahead forecasting
rainfall-runoff simulation
Opis:
Artificial neural networks are widely employed as data mining methods by researchers across various fields, including rainfall-runoff (R-R) statistical modelling. To enhance the performance of these networks, deep learning (DL) neural networks have been developed to improve modelling accuracy. The present study aims to improve the effectiveness of DL networks in enhancing the performance of artificial neural networks via merging with the gradient boosting (GB) technique for daily runoff data forecasting in the river Amu Darya, Uzbekistan. The obtained results showed that the new hybrid proposed model performed exceptionally well, achieving a 16.67% improvement in determination coefficient (R2) and a 23.18% reduction in root mean square error (RMSE) during the training phase compared to the single DL model. Moreover, during the verification phase, the hybrid model displayed remarkable performance, demonstrating a 66.67% increase in R2 and a 50% reduction in RMSE. Furthermore, the hybrid model outperformed the single GB model by a significant margin. During the training phase, the new model showed an 18.18% increase in R2 and a 25% reduction in RMSE. In the verification phase, it improved by an impressive 75% in R2 and a 33.33% reduction in RMSE compared to the single GB model. These findings highlight the potential of the hybrid DL-GB model in improving daily runoff data forecasting in the challenging hydrological context of the Amu Darya River basin in Uzbekistan.
Źródło:
Journal of Water and Land Development; 2023, 59; 216--223
1429-7426
2083-4535
Pojawia się w:
Journal of Water and Land Development
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Design of a linear quadratic regulator based on genetic model reference adaptive control
Autorzy:
Abdullah, Abdullah I.
Mahmood, Ali.
Thanoon, Mohammad A.
Powiązania:
https://bibliotekanauki.pl/articles/27314263.pdf
Data publikacji:
2022
Wydawca:
Sieć Badawcza Łukasiewicz - Przemysłowy Instytut Automatyki i Pomiarów
Tematy:
model reference adaptive control
gradient approach
Linear Quadratic Regulator
genetic algorithm
Opis:
The conventional control system is a controller that controls or regulates the dynamics of any other process. From time to time, a conventional control system may not behave appropriately online; this is because of many factors like a variation in the dynamics of the process itself, unexpected changes in the environment, or even undefined parameters of the system model. To overcome this problem, we have designed and implemented an adaptive controller. This paper discusses the design of a controller for a ball and beam system with Genetic Model Reference Adaptive Control (GMRAC) for an adaptive mechanism with the MIT rule. Parameter adjustment (selection) should occur using optimization methods to obtain an optimal performance, so the genetic algorithm (GA) will be used as an optimization method to obtain the optimum values for these parameters. The Linear Quadratic Regulator (LQR) controller will be used as it is one of the most popular controllers. The performance of the proposed controller with the ball and beam system will be carried out with MATLAB Simulink in order to evaluate its effectiveness. The results show satisfactory performance where the position of the ball tracks the desired model reference.
Źródło:
Journal of Automation Mobile Robotics and Intelligent Systems; 2022, 16, 3; 75--81
1897-8649
2080-2145
Pojawia się w:
Journal of Automation Mobile Robotics and Intelligent Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Structural optimization using topological and shape sensitivity via a level set method
Autorzy:
Allaire, G.
Gournay, F. de
Jouve, F.
Toader, A.-M.
Powiązania:
https://bibliotekanauki.pl/articles/970155.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
optymalizacja kształtu i topologiczna
gradient topologiczny
shape and topology optimization
level set method
topological gradient
Opis:
A numerical coupling of two recent methods in shape and topology optimization of structures is proposed. On the one hand, the level set method, based on the classical shape derivative, is known to easily handle boundary propagation with topological changes. However, in practice it does not allow for the nucleation of new holes (at least in 2-d). On the other hand, the bubble or topological gradient method is precisely designed for introducing new holes in the optimization process. Therefore, the coupling of these two method yields an efficient, algorithm which can escape from local minima in a given topological class of shapes. Both methods rely on the notion of gradient computed through an adjoint analysis, and have a low CPU cost since they capture a shape on a fixed Eulerian mesh. The main advantage of our coupled algorithm is to make the resulting optimal design largely independent of the initial guess.
Źródło:
Control and Cybernetics; 2005, 34, 1; 59-80
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An assessment of machine learning and data balancing techniques for evaluating downgrade truck crash severity prediction in Wyoming
Autorzy:
Ampadu, Vincent-Michael Kwesi
Haq, Muhammad Tahmidul
Ksaibati, Khaled
Powiązania:
https://bibliotekanauki.pl/articles/2176018.pdf
Data publikacji:
2022
Wydawca:
Fundacja Centrum Badań Socjologicznych
Tematy:
crash severity
performance
extreme gradient boosting tree
adaptive boosting tree
random forest
gradient boost decision tree
adaptive synthetic algorithm
Opis:
This study involved the investigation of various machine learning methods, including four classification tree-based ML models, namely the Adaptive Boosting tree, Random Forest, Gradient Boost Decision Tree, Extreme Gradient Boosting tree, and three non-tree-based ML models, namely Support Vector Machines, Multi-layer Perceptron and k-Nearest Neighbors for predicting the level of severity of large truck crashes on Wyoming road networks. The accuracy of these seven methods was then compared. The Final ROC AUC score for the optimized random forest model is 95.296 %. The next highest performing model was the k-NN with 92.780 %, M.L.P. with 87.817 %, XGBoost with 86.542 %, Gradboost with 74.824 %, SVM with 72.648 % and AdaBoost with 67.232 %. Based on the analysis, the top 10 predictors of severity were obtained from the feature importance plot. These may be classified into whether safety equipment was used, whether airbags were deployed, the gender of the driver and whether alcohol was involved.
Źródło:
Journal of Sustainable Development of Transport and Logistics; 2022, 7, 2; 6--24
2520-2979
Pojawia się w:
Journal of Sustainable Development of Transport and Logistics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Crack detection by the topological gradient method
Autorzy:
Amstutz, S.
Horchani, I.
Masmoudi, M.
Powiązania:
https://bibliotekanauki.pl/articles/970147.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
wykrywanie pęknięć
wrażliwość topologiczna
gradient topologiczny
równanie Poissona
crack detection
topological sensitivity
topological gradient
Poisson equation
Opis:
The topological sensitivity analysis consists in studying the behavior of a shape functional when modifying the topology of the domain. In general, the perturbation under consideration is the creation of a small hole. In this paper, the topological asymptotic expansion is obtained for the Laplace equation with respect to the insertion of a short crack inside a plane domain. This result is illustrated by some numerical experiments in the context of crack detection.
Źródło:
Control and Cybernetics; 2005, 34, 1; 81-101
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Forced nonlinear vibrations in a smart magneto-viscoelastic multiscale composite nanobeam in a humid thermal environment
Autorzy:
Anitha, Lakshmanan
Rajalakshmi, Loganathan
Selvamani, Rajendran
Ebrahimi, Farzad
Powiązania:
https://bibliotekanauki.pl/articles/38911353.pdf
Data publikacji:
2023
Wydawca:
Instytut Podstawowych Problemów Techniki PAN
Tematy:
piezoelectric nanobeam
vibration analysis
viscoelastic damping
nonlocal strain gradient
magneto-electro-viscoelastic
Opis:
In this paper, we study forced harmonic waves in a magneto-electro-viscoelastic (MEV) nanobeam embedded in a viscoelastic foundation using nonlocal strain gradient elasticity theory. The viscoelastic foundation is modeled as a Winkler-Pasternak layer. The governing equations of the nonlocal strain gradient viscoelastic nanobeam are derived using Hamilton’s principle and solved analytically. A parametric study is presented to examine the effects of physical variables on the field. It is found that the effect of strain gradient and nonlocal parameter on dimensionless amplitude and phase angle is quite important. The findings from this study highlight the significance of identifying magneto-piezoelectricity in predicting the vibration characteristics of intelligent nanostructures and elucidating the impact of humid thermal effects on nanomaterials.
Źródło:
Engineering Transactions; 2023, 71, 4; 617-644
0867-888X
Pojawia się w:
Engineering Transactions
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A sufficient condition for optimality in nondifferentiable invex programming
Autorzy:
Antczak, T.
Powiązania:
https://bibliotekanauki.pl/articles/205838.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
funkcja półwypukła
uogólniony gradient Clarka
Clarke's generalized gradient
invex function
locally Lipschitz function
semiconvex function
Opis:
In this paper sufficient optimality condition are established for a nonlinear programming problem without differentiability assumption on the data wherein Clarke's generalized gradient is used to define invexity.
Źródło:
Control and Cybernetics; 2001, 30, 4; 431-437
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Adaptation of engineering FEA-based algorithms to LCF failure and material data prediction in offshore design
Autorzy:
Augustyniak, M.
Gajewski, P.
Świątek, K.
Powiązania:
https://bibliotekanauki.pl/articles/279187.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
low-cycle fatigue
finite element method
high-strength steel
stress gradient influence
Opis:
There is an ever growing industrial demand for quantitative assessment of fatigue endurance of critical structural details. Although FEA-based calculations have become a standard in engineering design, problems involving the Low-To-Medium cycle range (101 -104 ) remain challenging. This paper presents an attempt to optimally choose material data, meshing density and other algorithm settings in the context of recent design of the large offshore windfarm installation vessel, VIDAR. In this study, an attempt is made to assess default FEA-based procedures in RADIOSS software by comparing an experimental test against numerical analyses. Standard slender cylindrical (“I”) samples as well as originally designed “Z”-shaped samples made of A90 (S690)-grade steel have been loaded at various nominal stress ranges with or without local yielding. A good correlation has been found between FEA results and experimental cycles-to-failure in I-shaped samples, provided the software material data generator is avoided and Smith-Watson-Topper mean stress correction is used. In the case of Z-shaped samples, the calculated cycles-to-initiation of macro-crack is significantly lower (factor of 3) from the experiment. The observed discrepancy is argued to be due to stress gradient influence.
Źródło:
Journal of Theoretical and Applied Mechanics; 2016, 54, 4; 1345-1356
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mathematical Model of Oxygen Transport in Cornea
Autorzy:
Avtar, Ram
Seth, Deepti
Kumar, Aadesh
Powiązania:
https://bibliotekanauki.pl/articles/1159714.pdf
Data publikacji:
2018
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Crank-Nicoloson method
Michaelis-Menten kinetics
Oxygentransport
Thomas algorithm
finite difference
metabolism
oxygen consumption
pressure gradient
Opis:
The aim of present work is the development of a quasi-steady state model for the time course concentration profile describing the oxygen diffusion and consumption in a multilayered corneal tissue and investigation of the effect of various model parameters on the oxygen concentration for open and closed eyes. A simple mathematical model for the oxygen transport in multilayered corneal tissue was developed using Fick’s law of diffusion, Michaelis-Menten kinetics of metabolism. A Crank-Nicolson finite difference scheme of the equation describing the oxygen diffusion and consumption was written, in which spatial diffusive terms of the equation were approximated by central differences while the temporal terms were approximated by average of forward and backward time differences. A system of linear equations obtained from the Crank-Nicholson finite differences schemes was solved by the Thomas Algorithm in which successive improve approximate results are obtained.
Źródło:
World Scientific News; 2018, 113; 169-184
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Effect of Pallet Component Geometry on Temperature Gradient During Cooling
Autorzy:
Bajwoluk, A.
Gutowski, P.
Powiązania:
https://bibliotekanauki.pl/articles/379657.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
information technology
foundry industry
foundry pallet
temperature gradient
technologia informatyczna
przemysł odlewniczy
paleta
gradient temperatury
Opis:
The paper discusses the impact of the geometry of foundry pallet components on the value of temperature gradient on the wall crosssection during heat treatment. The gradient is one of the most important factors determining the distribution of thermal stresses in these items. Analysis of quantitative simulation was carried out to detect possible effect of the type of connection between pallet walls and thickness of these walls (ribs) on the interior temperature distribution during rapid cooling. The analysis was performed for five basic designs of wall connections used in pallets. Basing on the results obtained, the conclusions were drawn on the best connection between the ribs in foundry pallets.
Źródło:
Archives of Foundry Engineering; 2015, 15, 1; 5-8
1897-3310
2299-2944
Pojawia się w:
Archives of Foundry Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the blowing up solutions of the 4-d general q-Kuramoto-Sivashinsky equation with exponentially “dominated” nonlinearity and singular weight
Autorzy:
Baraket, Sami
Mahdaoui, Safia
Ouni, Taieb
Powiązania:
https://bibliotekanauki.pl/articles/29519212.pdf
Data publikacji:
2023
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
singular limits
Green’s function
nonlinearity
gradient
nonlinear domain decomposition method
Opis:
Let Ω be a bounded domain in $ \mathbb{R}^4 $ with smooth boundary and let $ x^1, x^2, . . . , x^m $ be m-points in Ω. We are concerned with the problem $ \Delta^2 u - H(x, u, D^k u)=\rho^4 \prod_{i=1}^n | x - p_i |^{4 \alpha_i } f(x)g(u), $ where the principal term is the bi-Laplacian operator, $ H(x, u, D^k u)$ is a functional which grows with respect to $ Du $ at most like $ |Du|^q, 1 ≤ q ≤ 4, f : Ω → [0,+∞[ $ is a smooth function satisfying f(pi) > 0 for any i = 1, . . . , n, $ α_i $ are positives numbers and $ g : \mathbb{R} → [0,+∞[ $ satisfy $ |g(u)| ≤ ce^u $. In this paper, we give sufficient conditions for existence of a family of positive weak solutions $ (u_ρ)_{ρ>0} $ in Ω under Navier boundary conditions u = Δu = 0 on ∂Ω. The solutions we constructed are singular as the parameters ρ tends to 0, when the set of concentration $ S = {x^1, . . . , x^m} ⊂ Ω $ and the set $ Λ := {p_1, . . . , p_n} ⊂ Ω $ are not necessarily disjoint. The proof is mainly based on nonlinear domain decomposition method.
Źródło:
Opuscula Mathematica; 2023, 43, 1; 5-18
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mapping of the topography of abrasive tool cutting surfaces, with use of analyses of cast shadow distributions
Odwzorowywanie topografii powierzchni czynnych narzędzi ściernych z wykorzystaniem analiz rozkładu cieni rzutowanych
Autorzy:
Bernat, A.
Powiązania:
https://bibliotekanauki.pl/articles/151785.pdf
Data publikacji:
2012
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
metoda fotostereoskopii
wektorowe pole gradientu
rekonstrukcja 3D z cieni
powierzchnia czynna narzędzi ściernych
Photometric Stereo
vector gradient fields
3D reconstruction from shadows
cutting surface of abrasive tools
Opis:
In this paper a method based on analyses of distributions of cast and attached shadows is presented. It is an alternative to the previously adopted Photometric Stereo method for superior task of mapping the topography of cutting surfaces of abrasives. In this method of geometric approach to the 3D reconstruction within regions of occurrence of the shadows, one spans descending height ramps with their inclinations and tilt angles in accordance to light rays,which are cast onto surface visually inspected.
W artykule przedstawiono metodę rekonstrukcji powierzchni czynnej narzędzi ściernych. Wykorzystuje się w niej analizy rozkładu cieni na obrazach 2D intensywności. Opisano nowatorskie podejście do zagadnienia interpretacji rozkładu cieni rzutowanych, oraz częściowo cieni dołączanych, zawartych w obrazach 2D powierzchni. Obrazy 2D otrzymano w wyniku akwizycji danych, w etapie inspekcji wizualnej, dla ukośnie rzutowanych promieni światła. W metodzie tej, w miejscach występowania cieni generowane są zstępujące rampy wysokościowe, zgodne z kierunkiem promieni rzutowanego światła. Dane wysokościowe rozpinanych ramp miały na celu obrazować występowanie w topografii odwzorowywanej powierzchni zarówno uskoków wysokościowych, jak i zboczy nierówności, o dość znacznym nachyleniu. W pracy najpierw omówiono wady i zalety podejścia radiometrycznego i geometrycznego w odwzorowywaniu powierzchni narzędzi ściernych. W rozdziale drugim, przedstawiono sposób przetwarzania danych w podejściu geometrycznym, uwzględniającym zawartość wektorowych pól gradientu.. W rozdziale trzecim, omówiono sposób reprezentacji danych tych szczytów nierówności, które są permanentnie nieprzesłonięte. W rozdziale czwartym przedstawiono przykładowe wyniki rekonstrukcji 3D dla wybranego zbioru próbek narzędzi ściernych i powierzchni syntetycznych. W podsumowaniu określono możliwe kierunki rozwoju omawianej metody rekonstrukcji 3D.
Źródło:
Pomiary Automatyka Kontrola; 2012, R. 58, nr 5, 5; 448-451
0032-4140
Pojawia się w:
Pomiary Automatyka Kontrola
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The buffered optimization methods for online transfer function identification employed on DEAP actuator
Autorzy:
Bernat, Jakub
Kołota, Jakub
Powiązania:
https://bibliotekanauki.pl/articles/27322621.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
Stochastic Gradient Descent
ADAM
AMSGrad
DEAP
system identification
Opis:
Identification plays an important role in relation to control objects and processes as it enables the control system to be properly tuned. The identification methods described in this paper use the Stochastic Gradient Descent algorithms, which have so far been successfully presented in machine learning. The article presents the results of the Adam and AMSGrad algorithms for online estimation of the Dielectric Electroactive Polymer actuator (DEAP) parameters. This work also aims to validate the learning by batch methodology, which allows to obtain faster convergence and more reliable parameter estimation. This approach is innovative in the field of identification of control systems. The researchwas supplemented with the analysis of the variable amplitude of the input signal. The dynamics of the DEAP parameter convergence depending on the normalization process was presented. Our research has shown how to effectively identify parameters with the use of innovative optimization methods. The results presented graphically confirm that this approach can be successfully applied in the field of control systems.
Źródło:
Archives of Control Sciences; 2023, 33, 3; 565--587
1230-2384
Pojawia się w:
Archives of Control Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mathematical model of architecture and learning processes of artificial neural networks
Autorzy:
Bielecki, A.
Powiązania:
https://bibliotekanauki.pl/articles/1931575.pdf
Data publikacji:
2003
Wydawca:
Politechnika Gdańska
Tematy:
artificial neural networks
neuron
learning process
topological conjugacy
gradient dynamical system
Euler method
Opis:
A mathematical model of architecture and learning processes of multilayer artificial neural netwoks is discussed in the paper. Dynamical systems theory is used to describe the learning precess of networks consisting of linear, weakly nonlinear and nonlinear neurons. Conjugacy between a gradient dynamical system with a constant time step and a cascade generated by its Euler method theorem is applied as well.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2003, 7, 1; 93-114
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 293

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