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Wyświetlanie 1-3 z 3
Tytuł:
Using symbolic computation in the characterization of frictional instabilities involving orthotropic materials
Autorzy:
Agwa, M. A.
Pinto da Costa, A.
Powiązania:
https://bibliotekanauki.pl/articles/330798.pdf
Data publikacji:
2015
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
Coulomb friction
dynamic instabilities
surface solutions
orthotropic material
tarcie Coulomba
niestabilność dynamiczna
roztwór powierzchniowy
materiał ortotropowy
Opis:
The present work addresses the problem of determining under what conditions the impending slip state or the steady sliding of a linear elastic orthotropic layer or half space with respect to a rigid flat obstacle is dynamically unstable. In other words, we search the conditions for the occurrence of smooth exponentially growing dynamic solutions with perturbed initial conditions arbitrarily close to the steady sliding state, taking the system away from the equilibrium state or the steady sliding state. Previously authors have shown that a linear elastic isotropic half space compressed against and sliding with respect to a rigid flat surface may get unstable by flutter when the coefficient of friction μ and Poisson's ratio ν are sufficiently large. In the isotropic case they have been able to derive closed form analytic expressions for the exponentially growing unstable solutions as well as for the borders of the stability regions in the space of parameters, because in the isotropic case there are only two dimensionless parameters (μ and ν). Already for the simplest version of orthotropy (an orthotropic transversally isotropic material) there are seven governing parameters (μ, five independent material constants and the orientation of the principal directions of orthotropy) and the expressions become very lengthy and literally impossible to manipulate manually. The orthotropic case addressed here is impossible to solve with simple closed form expressions, and therefore the use of computer algebra software is required, the main commands being indicated in the text.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2015, 25, 2; 259-267
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A sixth-order finite volume method for the 1D biharmonic operator: Application to intramedullary nail simulation
Autorzy:
Costa, R.
Machado, G. J.
Clain, S.
Powiązania:
https://bibliotekanauki.pl/articles/330268.pdf
Data publikacji:
2015
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
finite volume method
polynomial reconstruction operator
harmonic operator
biharmonic operator
high order method
Opis:
A new very high-order finite volume method to solve problems with harmonic and biharmonic operators for one-dimensional geometries is proposed. The main ingredient is polynomial reconstruction based on local interpolations of mean values providing accurate approximations of the solution up to the sixth-order accuracy. First developed with the harmonic operator, an extension for the biharmonic operator is obtained, which allows designing a very high-order finite volume scheme where the solution is obtained by solving a matrix-free problem. An application in elasticity coupling the two operators is presented. We consider a beam subject to a combination of tensile and bending loads, where the main goal is the stress critical point determination for an intramedullary nail.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2015, 25, 3; 529-537
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An Expert System Coupled With a Hierarchical Structure of Fuzzy Neural Networks for Fault Diagnosis
Autorzy:
Calado, J. M. F.
Costa, I. S.
Powiązania:
https://bibliotekanauki.pl/articles/908283.pdf
Data publikacji:
1999
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
rozpoznanie błędu
wykrywanie błędu
system ekspertowy
sieć neuronowa rozmyta
fault diagnosis
fault detection
fault isolation
shallow knowledge
deep knowledge
expert system
fuzzy neural network
abrupt faults
incipient faults
Opis:
An on-line fault diagnosis system, designed to be robust to the normal transient behaviour of the process, is described. The overall system consists of an expert system cascade with a hierarchical structure of fuzzy neural networks, corresponding to a multi-stage fault detection and isolation system. The fault detection is performed through the expert system by means of fault detection heuristic rules, generated from deep and shallow knowledge of the process under consideration. If a fault is detected, the hierarchical structure of fuzzy neural networks starts and it performs the fault isolation task. The structure of this diagnosis system was designed to allow for the diagnosis of single and multiple simultaneous abrupt and incipient faults from only single abrupt fault symptoms. Also, it combines the advantages of both fuzzy reasoning and neural networks learning capacity. A continuous binary distillation column has been used as a test bed of the current approach. Single, double and triple simultaneous abrupt faults, as well as incipient faults, have been considered. The preliminary results obtained show a good accuracy, even in the case of multiple faults.
Źródło:
International Journal of Applied Mathematics and Computer Science; 1999, 9, 3; 667-687
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-3 z 3

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