BazTech - Yadda

1

Analyzing the Impact of Population Size in AI-Based Reconstruction of the Thermal Parameter in Heat Conduction Modeling

Gawrońska Elżbieta, Zych Maria, Dyja Robert, Kowalkowski Michał

Advances in Science and Technology. Research Journal

|

2024

|

Vol. 18, no 2

349--364

EN

The research shows how to use swarming algorithms to rebuild the heat transfer coefficient, especially in regard to the continuous border condition. The authors utilized their application software to do numerical computations, employing classical variants of swarm algorithms. The numerical calculations employed a functional determining error to assess the accuracy of the estimated result. The functional minimization was conducted with the swarm algorithms (especially ABC and ACO). The geometry analyzed in this study consisted of a square shape referred to as the cast, enclosed within another square shape known as the casting mold. These two squares were separated by a layer facilitating heat conduction, characterized by the coefficient κ. The coefficient of the thermally conductive layer was recalibrated utilizing swarm methods within the range of 900 - 1500 [W/m^2K] and subsequently compared to a predetermined reference value. A finite element mesh consisting of 576 nodes was used for the calculations. The study involved simulations with populations of 5, 10, 15, and 20 individuals. Furthermore, each scenario also took into account noise of 0%, 2%, and 5% of the reference values. Results make evident the reconstructed value of the κ coefficient, cooling curves, and temperatures for the ABC and ACO algorithms are physically correct. The consequences indicate a notable level of satisfaction and strong concurrence with the anticipated of the κ parameter values. The results from the numerical simulations demonstrate considerable promise for applying artificial intelligence algorithms in optimizing production processes, analyzing data, and facilitating data-driven decision-making.

2

Scattering by circular voids with rigid boundary: direct and inverse problems for open and close domains

Rymarczyk Tomasz, Sikora Jan

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

|

2022

|

T. 12, nr 4

4--10

EN

Problems with the accuracy of calculations by the Boundary Element Method of acoustic and ultrasonic problems formulated in the frequency domain were presented in this paper. The inverse problem was formulated to identify the position and dimensions of the scattering object. A seriesof numerical experiments carried out with the help of the Boundary Elements Method proved the algorithm's robustness to noiseand high precisionin a wide frequency spectrum.

PL

W pracy przedstawiono problemy z dokładnością obliczeń Metodą Elementów Brzegowych zagadnień akustycznych i ultradźwiękowych sformułowanych w dziedzinie częstotliwości. Sformułowano zagadnienie odwrotne dla identyfikacji położenia i wymiarów obiektu rozpraszającego. Seria eksperymentów numerycznych przeprowadzonych z pomocą Metody Elementów Brzegowych udowodniła odporność algorytmu na szum oraz wysoką precyzję w szerokim spektrum częstotliwości.

3

On the robustness of the topological derivative for Helmholtz problems and applications

Leugering Günter, Novotny Antonio André, Sokolowski Jan

Control and Cybernetics

|

2022

|

Vol. 51, No. 2

227--248

EN

We consider Helmholtz problems in two and three dimensions. The topological sensitivity of a given cost function J(uɛ) with respect to a small hole Bɛ around a given point x0ɛ ∈ Bɛ ⊂ Ω depends on various parameters, like the frequency k chosen or certain material parameters or even the shape parameters of the hole Bɛ. These parameters are either deliberately chosen in a certain range, as, e.g., the frequencies, or are known only up to some bounds. The problem arises as to whether one can obtain a uniform design using the topological gradient. We show that for 2-d and 3-d Helmholtz problems such a robust design is achievable.

4

Performance of artificial neural networks in an inverse problem of laser beam diagnostics

Pietrak Karol, Muszyński Radosław, Marek Adam, Łapka Piotr

Bulletin of the Polish Academy of Sciences. Technical Sciences

|

2022

|

Vol. 70, nr 1

art. no. e140100

EN

The presented results are for the numerical verification of a method devised to identify an unknown spatio-temporal distribution of heat flux that occurs at the surface of a thin aluminum plate, as a result of pulsed laser beam excitation. The presented identification of boundary heat flux function is a part of the newly proposed laser beam profiling method and utilizes artificial neural networks trained on temperature distributions generated with the ANSYS Fluent solver. The paper focuses on the selection of the most effective neural network hyperparameters and compares the results of neural network identification with the Levenberg–Marquardt method used earlier and discussed in previous articles. For the levels of noise measured in physical experiments (0.25–0.5 K), the accuracy of the current parameter estimation method is between 5 and 10%. Design changes that may increase its accuracy are thoroughly discussed.

5

Machine learning based prediction of regularization parameters for seismic inverse problems

Liu Shihuan, Zhang Jiashu

Acta Geophysica

|

2021

|

Vol. 69, no. 3

809--820

EN

Regularization parameter selection (RPS) is one of the most important tasks in solving inverse problems. The most common approaches seek the optimal regularization parameter (ORP) from a sequence of candidate values. However, these methods are often time-consuming because they need to conduct the estimation process on all candidate values, and they are always restricted to solve certain problem types. In this paper, we propose a novel machine learning-based prediction framework (MLBP) for the RPS problem. The MLBP frst generates a large number of synthetic data by varying the inputs with diferent noise conditions. Then, MLBP extracts some pre-defned features to represent the input data and computes the ORP of each synthetic example by using true models. The pairs of ORP and extracted features construct a training set, which is used to train a regression model to describe the relationship between the ORP and input data. Therefore, for newly practical inverse problems, MLBP can predict their ORPs directly with the pre-trained regression model, avoiding wasting computational resources on improper regularization parameters. The numerical results also show that MLBP requires signifcantly less computing time and provides more accurate solutions for diferent tasks than traditional methods. Especially, even though the MLBP trains the regression model on synthetic data, it can also achieve satisfying performance when directly applied to feld data.

6

A note on confidence intervals for deblurred images

Biel Michał, Szkutnik Zbigniew

Opuscula Mathematica

|

2020

|

Vol. 40, no. 3

361-–373

EN

We consider pointwise asymptotic confidence intervals for images that are blurred and observed in additive white noise. This amounts to solving a stochastic inverse problem with a convolution operator. Under suitably modified assumptions, we fill some apparent gaps in the proofs published in [N. Bissantz, M. Birke, Asymptotic normality and confidence intervals for inverse regression models with convolution-type operators, J. Multivariate Anal. 100 (2009), 2364-2375]. In particular, this leads to modified bootstrap confidence intervals with much better finite-sample behaviour than the original ones, the validity of which is, in our opinion, questionable. Some simulation results that support our claims and illustrate the behaviour of the confidence intervals are also presented.

7

Application of the Monte Carlo method with meshless random walk procedure to selected scalar elliptic problems

Milewski S.

Archives of Mechanics

|

2019

|

Vol. 71, nr 4-5

337–-375

EN

The combined stochastic-deterministic approach, which may be applied to the numerical analysis of a wide range of scalar elliptic problems of civil engineering, is presented in this paper. It is based on the well-known Monte Carlo concept with a random walk procedure, in which series of random paths are constructed. Additionally, it incorporates selected features of the meshless finite difference method, especially star selection criteria and a local weighted function approximation. The approach leads to the explicit stochastic formula relating one unknown function value with all a-priori known data parameters. Therefore, it allows for a fast and effective estimation of the solution value at the selected point(s), without the necessity of generation of large systems of equations, combining all unknown values. In such a manner, the proposed approach develops and extends the original standard Monte Carlo one toward analysis of boundary value problems with more complex shape geometry, natural boundary conditions, non-homogeneous right-hand sides as well as anisotropic and non-linear material models. The paper is illustrated with numerical results of selected elliptic problems, including a torsion problem of a prismatic bar, a stationary heat flow analysis with anisotropic and non-linear material functions, as well as an inverse heat problem. Moreover, the appropriate coupling with other deterministic methods (e.g., the finite element method) is considered.

8

The chances of precision enhance for ultrasonic imaging

Rymarczyk T., Sikora J., Adamkiewicz P., Bożek P., Gołąbek M.

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

|

2018

|

T. 8, nr 3

19--24

EN

The results of ultrasonic imaging with the aid of an algorithm with the virtual rays is presented in this paper. The signal associated with the virtual rays is calculated as an arithmetical mean value of the signals of the rays surrounding the virtual one. Developed algorithm was tested on synthetic free noise data then polluted synthetic data in order to move for the real measurements. Conclusions about the imaging with new algorithm are not obvious. In same cases the significant improvement was achieved but in some not.

PL

W pracy przedstawiono rezultaty działania algorytmu obrazowania ultradźwiękowego z dodatkowymi wirtualnymi promieniami. Sygnał odpowiadający wirtualnym promieniom jest wyliczany jako średnia arytmetyczna rzeczywistych sygnałów pomiarowych odpowiadających promieniom otaczającym dany promień wirtualny. Zaproponowany algorytm najpierw przetestowano na danych syntetycznych niezaszumionych, następnie na danych zaszumionych aby następnie przejść do danych pomiarowych. Wnioski na temat tego czy promienie wirtualne mają szanse podnieść jakość obrazowania nie są jednoznaczne. W niektórych przypadkach jakość jest znacznie lepsza a w innych nie.

9

Uniqueness of solutions to inverse parabolic semilinear problems under nonlocal conditions with integrals

Byszewski L., Wacławski T.

Technical Transactions

|

2017

|

Vol. 8(114)

165--175

EN

The uniqueness of classical solutions to inverse parabolic semilinear problems together with nonlocal initial conditions with integrals, for the operator [mathematical formula], in the cylindrical domain D:=D0×(t0,t0+T)[subset of]Rn+1, where t0[element of]R, 0

PL

W artykule studiowana jest jednoznaczność klasycznych rozwiązań odwrotnych parabolicznych semiliniowych zagadnień z nielokalnymi początkowymi warunkami z całkami dla operatora [wzór matematyczny], w walcowym obszarze D:=D0×(t0,t0+T)[podzbiór]Rn+1, gdzie t0[należy do]R, 0

10

Compressive optical image encryption using phase-shifting interferometry on a joint transform correlator

Li J., Jia B., Dai X., Lei M., Yang C., Li J., Li H., Li R.

Optica Applicata

|

2017

|

Vol. 47, nr 2

245--256

EN

A compressive optical image encryption method, which combines compressive sensing with phase-shifting interferometry on a joint transform correlator, is proposed in the fully optical domain. The object image is first permutated using a binary scrambling method. Next, the permutated object field is encrypted and registered as the holograms by phase-shifting interferometry on the joint transform correlator setup. Then, the encrypted images and the key are compressed to the compressed data using single-pixel compressive imaging. The original image can be reconstructed and decrypted using the specified algorithm. The simulations demonstrate that the method is effective and suitable for image security transmission.

11

Advanced Inversion Techniques for Ground Penetrating Radar

Fedeli A., Pastorino M., Randazzo A.

Journal of Telecommunications and Information Technology

|

2017

|

nr 3

37--42

EN

Ground Penetrating Radar (GPR) systems arenowadays standard inspection tools in several application areas, such as subsurface prospecting, civil engineering and cultural heritage monitoring. Usually, the raw output of GPR isprovided as a B-scan, which has to be further processed inorder to extract the needed information about the inspectedscene. In this framework, inversescattering-based approachesare gaining an ever-increasing interest, thanks to their capabilities of directly providing images of the physical and dielectricproperties of the investigated areas. In this paper, some advances in the development of such inversion techniques in theGPR field are revised and discussed.

12

Self-sensing teleoperation system based on 1-dof pneumatic manipulator

Saków M., Miądlicki K., Parus A.

Journal of Automation Mobile Robotics and Intelligent Systems

|

2017

|

Vol. 11, No. 1

64--76

EN

Paper presents a novel approach to a control design of bilateral teleoperation systems with force-feedback. The problem statement, analysis of research achievements to date, and the scope of the study are presented. The new design of a control unit for a master-slave system with force-feedback is presented on a simple and ideal 1-DOF bilateral teleoperation system. System control unit was based on an inverse model. The model was used to reduce value of force in the force-feedback communication channel, that the system might generate in freemotion. A substantial part of the paper is focused on the development of a mathematical model covering phenomena occurring in the investigated control scheme. The new approach was validated on a test-stand of a rotating non-linear pneumatic manipulator arm. Two linear pneumatic actuators were used in the drive system. The paper presents the modeling procedure of the experimental setup and the model used in the study. Three experiments are described to demonstrate the new control approach to master-slave objects with force-feedback. The paper contains conclusions regarding the control system and the experimental setup.

13

Topological derivative method for electrical impedance tomography problems

Ferreira A. D., Novotny A. A., Sokołowski J.

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

|

2016

|

nr 2

4--8

EN

In the field of shape and topology optimization the new concept is the topological derivative of a given shape functional. The asymptotic analysis is applied in order to determine the topological derivative of shape functionals for elliptic problems. The topological derivative (TD) is a tool to measure the influence on the specific shape functional of insertion of small defect into a geometrical domain for the elliptic boundary value problem (BVP) under considerations. The domain with the small defect stands for perturbed domain by topological variations. This means that given the topological derivative, we have in hand the first order approximation with respect to the small parameter which governs the volume of the defect for the shape functional evaluated in the perturbed domain. TD is a function defined in the original (unperturbed) domain which can be evaluated from the knowledge of solutions to BVP in such a domain. This means that we can evaluate TD by solving only the BVP in the intact domain. One can consider the first and the second order topological derivatives as well, which furnish the approximation of the shape functional with better precision compared to the first order TD expansion in perturbed domain. In this work the topological derivative is applied in the context of Electrical Impedance Tomography (EIT). In particular, we are interested in reconstructing a number of anomalies embedded within a medium subject to a set of current fluxes, from measurements of the corresponding electrical potentials on its boundary. The basic idea consists in minimize a functional measuring the misfit between the boundary measurements and the electrical potentials obtained from the model with respect to a set of ball-shaped anomalies. The first and second order topological derivatives are used, leading to a non-iterative second order reconstruction algorithm. Finally, a numerical experiment is presented, showing that the resulting reconstruction algorithm is very robust with respect to noisy data.

PL

W dziedzinie optymalizacji kształtu i topologii zaproponowano nową koncepcję pochodnej topologicznej danego funkcjonału kształtu. Zastosowano asymptotyczną analizę w celu określenia pochodnej topologicznej funkcjonału kształtu dla zagadnień eliptycznych. Pochodna Topologiczna – PT (ang. the topological derivative – TD) jest miarą wpływu wtrącenia w postaci małego defektu na funkcjonał kształtu w badanym obszarze dla eliptycznego zagadnienia brzegowego. Obszar z małym defektem traktowany jest jako obszar zaburzony przez zmiany topologii. Oznacza to, że dana pochodna topologiczna stanowi aproksymację pierwszego rzędu ze względu na mały parametr, który określa objętość defektu dla obliczanego funkcjonału kształtu w zaburzonym obszarze. PT jest funkcją zdefiniowaną w obszarze niezaburzonym, który może być wyznaczony na podstawie znajomości rozwiązania zagadnienia brzegowego w tym (niezaburzonym) obszarze. Oznacza to że PT może być wyznaczona poprzez rozwiązanie zagadnienia brzegowego w obszarze niezaburzonym. Można rozważyć pierwszego jak również drugiego rzędu pochodną topologiczną, zapewniającą aproksymację funkcjonału kształtu ze znacznie lepszą precyzją w porównaniu do PT pierwszego rzędu rozwinięcia w obszarze zaburzonym. W niniejszej pracy PT jest zastosowana w kontek- ście Elektrycznej Tomografii Impedancyjnej (ETI). W szczególności jesteśmy zainteresowani w rekonstrukcji pewnej liczby anomalii wewnątrz obszaru, na podstawie pomiarów potencjału na brzegu rozpatrywanego obszaru. Podstawowa idea zawarta jest w minimalizacji funkcjonału, będącego miarą niedopasowania między pomiarami potencjału na brzegu obszaru a potencjałem elektrycznym uzyskanym na podstawie modelu matematycznego uwzględniającego zbiór anomalii o kształcie kuli. Zastosowanie pierwszego i drugiego rzędu pochodnej topologicznej prowadzi do nieiteracyjnego algorytmu rekonstrukcyjnego drugiego rzędu. W zakończeniu artykułu przedstawiono eksperyment numeryczny, wykazujący, że zaproponowany algorytm obrazowania jest bardzo odporny na zaszumione dane pomiarowe.

14

Estimation of Cast Iron Substitute Thermal Capacity Using the Experimental Data

Majchrzak E., Mendakiewicz J., Mochnacki B.

Archives of Metallurgy and Materials

|

2016

|

Vol. 61, iss. 1

307--314

EN

In the paper the problem of the cast iron substitute thermal capacity estimation is discussed. This parameter appears when the macroscopic mathematical model of alloys solidification bases on the one domain method (fixed domain approach). In the case of cast iron the form of function describing the course of temperature-dependent thermal capacity is quite complex. Using the experimental data, in particular the measured cooling, heating curves at the set of points selected in the casting – mould domain the identification problem has been solved using the gradient methods. The results presented concern the gray iron 3.21% C and 1.9% Si.

15

Stretching the Least Squares to Embed Loss Function Tables

Yoneda K., Moretti A. C., Poker J. Jr.

Decision Making in Manufacturing and Services

|

2015

|

Vol. 9, no. 2

105--116

EN

The method of least squares is extended to accommodate a class of loss functions specified in the form of function tables. The function tables are embedded into the standard quadratic loss function so that nonlinear least squares algorithms can be adopted for loss minimization. This is an alternative to a more straightforward approach which interpolates the function tables and minimizes the resulting loss function by some generic optimization algorithm. The alternative approach has advantages over the straightforward, such as the wider availability of the least squares programs compared to the generic optimization programs and reduction in computational complexity. Examples are given for its application to multiplicative utility function maximization problems.

16

Inverse heat transfer problems: an application to bioheat transfer

Rojczyk M., Orlande H. R. B., Colaço M. J., Szczygieł I., Nowak A. J., Białecki R. A., Ostrowski Z.

Computer Assisted Methods in Engineering and Science

|

2015

|

Vol. 22, no. 4

365--383

EN

In this work, we applied the Markov chain Monte Carlo (MCMC) method for the estimation of parameters appearing in the Pennes’ formulation of the bioheat transfer equation. The inverse problem of parameter estimation was solved with the simulated transient temperature measurements. A one-dimensional (1D) test case was used to explore the capabilities of using the MCMC method in bioheat transfer problems, specifically for the detection of skin tumors by using surface temperature measurements. The analysis of the sensitivity coefficients was performed in order to examine linear dependence and low sensitivity of the model parameters. The solution of the direct problem was verified with a commercial code. The results obtained in this work show the ability of using inverse heat transfer analysis for the detection of skin tumors.

17

Chlorophyll profile estimation in ocean waters by a set of artificial neural networks

Cortivo F. D., Chalhoub E. S., Campos Velho H. F., Kampel M.

Computer Assisted Methods in Engineering and Science

|

2015

|

Vol. 22, no. 1

63--88

EN

In this work, we propose a methodology to estimate the profile of chlorophyll concentration from the upwelling radiation at the ocean surface, using a system of artificial neural networks (ANNs). The input patterns to train the networks are obtained from the resolution of the radiative transfer equation, where the absorption and scattering coefficients are represented by bio-optical models, with the profile of chlorophyll concentrations based on a shifted-Gaussian model. In the performed analysis, we used 14 720 profiles of chlorophyll that were generated by attributing two values to the biomass quantity, and by considering two sets of wavelengths and three sets containing the directions in which the radiation emitted at the surface is measured. To be able to recover the chlorophyll profile, we need to use a system of networks that works in a “cascade mode”. The first one performs an analysis on the features of the chlorophyll profile from the upwelling radiation and determines which profiles can be recovered. The second and third ANNs act only on those profiles that can be recovered. The second ANN performs estimation of the standard deviation from the upwelling radiation and the chlorophyll concentration at the surface. Finally, the third ANN performs an estimation of the peak depth from the upwelling radiation, the chlorophyll concentration at the surface and the standard deviation estimated by second network. The stopping criteria we adopted was the cross-validation process. The obtained results show that the proposed methodology is quite promising.

18

Optymalizacja kształtu oraz rozmieszczenia kanałów chłodzących w łopatkach turbin gazowych

Wróblewska A.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

|

2014

|

z. 86 [290], nr 1

123--134

PL

W pracy przedstawiono wyniki obliczeń dotyczących problemu chłodzenia łopatek turbin gazowych. Sformułowane zostało zagadnienie odwrotne dotyczące rozmieszczenia kanałów chłodzących w istniejącej konstrukcji łopatki z punktu widzenia kryterium optymalizacyjnego. Jako kryterium optymalizacji przyjęta została stała temperatura na brzegu zewnętrznym łopatki równa 600K i 650K. Obliczenia wykonane zostały dla łopatki Mark2 przy założeniu, że znany jest rozkład współczynnika przejmowania ciepła na brzegu zewnętrznym łopatki. Wyniki obliczeń pokazują, że rozmieszczenie kanałów chłodzących w tej łopatce nie jest prawidłowe z punktu widzenia rozpatrywanego kryterium optymalizacyjnego.

EN

In this paper, the results of calculations concerning the problem of cooling the gas turbine blades were presented. The inverse problem from the optimization criterion point of view for the arrangement of cooling channels in already-existing blade construction was formulated. Constant temperature on the outer edge of the blade equals to 600K and 650K was assumed as the optimization criterion. Calculations were made for the Mark2 blade, assuming that the distribution of the heat transfer coefficient on the outer edge of the blade was known.Results of calculation show that the arrangement of cooling channels in this blade is not correct from the optimization criterion point of view.

19

On reconstructing an unknown coordinate of a nonlinear system of differential equations

Blizorukowa M., Kuklin A., Maksimov V

Opuscula Mathematica

|

2014

|

Vol. 34, no. 2

257--269

EN

The paper discusses a method of auxiliary controlled models and the application of this method to solving problems of dynamical reconstruction of an unknown coordinate in a nonlinear system of differential equations. The solving algorithm, which is stable with respect to informational noises and computational errors, is presented.

20

Maximization of an Asymmetric Utility Function by the Least Squares

Yoneda K., Moretti A. C.

Decision Making in Manufacturing and Services

|

2014

|

Vol. 8, no. 1-2

5--12

EN

This note points out that a utility maximization procedure proposed in an earlier paper may be reduced to the least squares. The utility function is asymmetric in the sense that for each cue its ideal value and the permissible range are assigned in such a way that the ideal is not necessarily at the center of the range, like "a beer of 350 ml would be ideal, but acceptable if within [100, 500]". A practical consequence of the observation is that very little programming will be needed to deploy the utility maximization since software for the least squares is widely available.