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Wyświetlanie 1-15 z 21
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:
Rough sets based on Galois connections
Autorzy:
Madrid, Nicolás
Medina, Jesús
Ramírez-Poussa, Eloísa
Powiązania:
https://bibliotekanauki.pl/articles/330499.pdf
Data publikacji:
2020
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
rough sets
Galois connection
approximation operator
zbiór przybliżony
połączenie Galois
operator aproksymacji
Opis:
Rough set theory is an important tool to extract knowledge from relational databases. The original definitions of approximation operators are based on an indiscernibility relation, which is an equivalence one. Lately, different papers have motivated the possibility of considering arbitrary relations. Nevertheless, when those are taken into account, the original definitions given by Pawlak may lose fundamental properties. This paper proposes a possible solution to the arising problems by presenting an alternative definition of approximation operators based on the closure and interior operators obtained from an isotone Galois connection. We prove that the proposed definition satisfies interesting properties and that it also improves object classification tasks.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2020, 30, 2; 299-313
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Hermite-type adaptive semi-Lagrangian scheme
Autorzy:
Mehrenberger, M.
Violard, E.
Powiązania:
https://bibliotekanauki.pl/articles/929682.pdf
Data publikacji:
2007
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
metoda adaptacyjna
równanie Vlasova
symulacja numeryczna
operator hermitowski
adaptive method
Vlasov equation
numerical simulation
Hermite operator
Opis:
We study a new Hermite-type interpolating operator arising in a semi-Lagrangian scheme for solving the Vlasov equation in the 2D phase space. Numerical results on uniform and adaptive grids are shown and compared with the biquadratic Lagrange interpolation introduced in (Campos Pinto and Mehrenberger, 2004) in the case of a rotating Gaussian.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2007, 17, 3; 329-334
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A robust computational technique for a system of singularly perturbed reaction–diffusion equations
Autorzy:
Kumar, V.
Bawa, R. K.
Lal, A. K.
Powiązania:
https://bibliotekanauki.pl/articles/330202.pdf
Data publikacji:
2014
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
asymptotic expansion approximation
backward difference operator
trapezoidal method
piecewise uniform Shishkin mesh
rozwinięcie asymptotyczne
operator różnicowy
metoda trapezowa
Opis:
In this paper, a singularly perturbed system of reaction–diffusion Boundary Value Problems (BVPs) is examined. To solve such a type of problems, a Modified Initial Value Technique (MIVT) is proposed on an appropriate piecewise uniform Shishkin mesh. The MIVT is shown to be of second order convergent (up to a logarithmic factor). Numerical results are presented which are in agreement with the theoretical results.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2014, 24, 2; 387-395
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A sign preserving mixed finite element approximation for contact problems
Autorzy:
Hild, P.
Powiązania:
https://bibliotekanauki.pl/articles/907565.pdf
Data publikacji:
2011
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
nierówność wariacyjna
zagadnienie kontaktowe
metoda elementów skończonych
variational inequality
positive operator
averaging operator
contact problem
Signorini problem
mixed finite element method
Opis:
This paper is concerned with the frictionless unilateral contact problem (i.e., a Signorini problem with the elasticity operator). We consider a mixed finite element method in which the unknowns are the displacement field and the contact pressure. The particularity of the method is that it furnishes a normal displacement field and a contact pressure satisfying the sign conditions of the continuous problem. The a priori error analysis of the method is closely linked with the study of a specific positivity preserving operator of averaging type which differs from the one of Chen and Nochetto. We show that this method is convergent and satisfies the same a priori error estimates as the standard approach in which the approximated contact pressure satisfies only a weak sign condition. Finally we perform some computations to illustrate and compare the sign preserving method with the standard approach.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2011, 21, 3; 487-498
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Iterative Model Reduction of Large State-Space Systems
Autorzy:
Huhtanen, M.
Powiązania:
https://bibliotekanauki.pl/articles/908302.pdf
Data publikacji:
1999
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
redukcja modeli
metoda iteracyjna
równanie macierzowe Lyapunova
kondycjonowanie
operator Hankela
model reduction
iterative methods
Lyapunov matrix equations
Hankel operator
preconditioning
Hankel singular values
Opis:
There exist criteria for reducing the order of a large state-space model based on the accuracy of the approximate solutions to the Lyapunov matrix equations and the Hankel operator. Iterative solution techniques for the Lyapunov equations with the Arnoldi method have been proposed in a number of papers. In this paper we derive error bounds for approximations to the solutions to the Lyapunov equations as well as for the Hankel operator that indicate how to precondition while solving these equations iteratively.These bounds show that the error depends on three terms: First, on the amount of invariance of the constructed subspace for A, second, on the eigenvalues of A at least in proportion to 1/|Re l|, and third, under a certain condition on projectors P_l=W_lW_l* ,on the factor min_{X in C^{l x p}}|| B-( l I-A)W_lX|| for l on a path G surrounding the spectrum of A. Consequently, in order to compensate for those parts of the spectrum where 1/|Re l| is not small, preconditioning or an inverse iteration is needed to keep the sizes of the matrices used in construction of a reduced-order model moderate.
Źródło:
International Journal of Applied Mathematics and Computer Science; 1999, 9, 2; 245-263
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On hyper-regularity and unimodularity of Ore polynomial matrices
Autorzy:
Fritzsche, K.
Röbenack, K.
Powiązania:
https://bibliotekanauki.pl/articles/331500.pdf
Data publikacji:
2018
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
Ore polynomial matrice
hyper regularity
unimodularity
meromorphic function
differential operator
noncommutativity
hyper regular inverse
macierz wielomianowa
macierz unimodularna
funkcja meromorficzna
operator różniczkowy
Opis:
We investigate Ore polynomial matrices, i. e., matrices with polynomial entries in d/dt whose coefficients are meromorphic functions in t and as such constitute a non-commutative ring. In particular, we study the properties of hyper-regularity and unimodularity of such matrices and derive conditions which make it possible to efficiently check for these characteristics. In addition, this approach enables computation of hyper-regular left and right and unimodular inverses.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2018, 28, 3; 583-594
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An n-ary λ-averaging based similarity classifier
Autorzy:
Kurama, O.
Luukka, P.
Collan, M.
Powiązania:
https://bibliotekanauki.pl/articles/330385.pdf
Data publikacji:
2016
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
similarity classifier
λ-averaging
n-ary λ-averaging operator
n-ary t-norm
n-ary t-conorm
classification
klasyfikator podobieństwa
operator uśredniony
sortowanie
Opis:
We introduce a new n-ary λ similarity classifier that is based on a new n-ary λ-averaging operator in the aggregation of similarities. This work is a natural extension of earlier research on similarity based classification in which aggregation is commonly performed by using the OWA-operator. So far λ -averaging has been used only in binary aggregation. Here the λ-averaging operator is extended to the n-ary aggregation case by using t-norms and t-conorms. We examine four different n-ary norms and test the new similarity classifier with five medical data sets. The new method seems to perform well when compared with the similarity classifier
Źródło:
International Journal of Applied Mathematics and Computer Science; 2016, 26, 2; 407-421
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mittag-Leffler stability for a Timoshenko problem
Autorzy:
Tatar, Nasser-eddine
Powiązania:
https://bibliotekanauki.pl/articles/1838213.pdf
Data publikacji:
2021
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
Caputo fractional derivative
Mittag-Leffler stability
multiplier technique
resolvent operator
Opis:
A Timoshenko system of a fractional order between zero and one is investigated here. Using a fractional version of resolvents, we establish an existence and uniqueness theorem in an appropriate space. Moreover, it is proved that lower order fractional terms (in the rotation component) are capable of stabilizing the system in a Mittag-Leffler fashion. Therefore, they deserve to be called damping terms. This is shown through the introduction of some new functionals and some fractional inequalities, and the establishment of some properties, involving fractional derivatives. In the case of different wave speeds of propagation we obtain convergence to zero.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2021, 31, 2; 219-232
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The geometry of Darlington synthesis
Autorzy:
Dewilde, P.
Powiązania:
https://bibliotekanauki.pl/articles/908125.pdf
Data publikacji:
2001
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
Darlington synthesis
Hankel operator
time varying systems
contractive operators
coprime factorization
Opis:
We revisit the classical problem of `Darlington synthesis', or Darlington embedding. Although traditionally it is solved using analytic means, a more natural way to approach it is to use the geometric properties of a well-chosen Hankel map. The method yields surprising results. In the first place, it allows us to formulate necessary and sufficient conditions for the existence of the embedding in terms of systems properties of the transfer operation to be embedded. In addition, the approach allows us to extend the solution to situations where no analytical transform is available. The paper has a high review content, as all the results presented have been obtained during the last twenty years and have been published. However, we make a systematic attempt at formulating them in a geometric way, independent of an accidental parametrization. The benefit is clarity and generality.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2001, 11, 6; 1379-1386
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Argument Increment Stability Criterion for Linear Delta Models
Autorzy:
Hofreiter, M.
Zitek, P.
Powiązania:
https://bibliotekanauki.pl/articles/908101.pdf
Data publikacji:
2003
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
automatyka
delta model
stability criterion
conformal mapping
delta operator
argument increment rule
Opis:
Currently used stability criteria for linear sampled-data systems refer to the standard linear difference equation form of the system model. This paper presents a stability criterion based on the argument increment rule modified for the delta operator form of the sampled-data model. For the asymptotic stability of this system form it is necessary and sufficient that the roots of the appropriate characteristic equation lie inside a circle in the left half of the complex plane, the radius of which is inversely proportional to the sampling period. Therefore the argument increment of the system characteristic polynomial of an asymptotically stable delta model has to increase by 2pi n if this circle has been run around in the counter-clockwise direction. The criterion developed based on this principle permits not only the proof of the system stability itself, but also the approximation of the dominant roots of its characteristic equation.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2003, 13, 4; 485-491
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Koiter shell governed by strongly monotone constitutive equations
Autorzy:
Kalita, P.
Powiązania:
https://bibliotekanauki.pl/articles/907364.pdf
Data publikacji:
2004
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
teoria Koitera
nieliniowość fizyczna
operator monotoniczny
Koiter shell
physical nonlinearity
strongly monotone operators
Opis:
In this paper we use the theory of monotone operators to generalize the linear shell model presented in (Blouza and Le Dret, 1999) to a class of physically nonlinear models. We present a family of nonlinear constitutive equations, for which we prove the existence and uniqueness of the solution of the presented nonlinear model, as well as the convergence of the Galerkin method. We also present the physical discussion of the model.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2004, 14, 2; 127-137
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Exact Observability of Diagonal Systems With a One-Dimensional Output Operator
Autorzy:
Jacob, B.
Zwart, H.
Powiązania:
https://bibliotekanauki.pl/articles/908120.pdf
Data publikacji:
2001
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
obserwator
równanie Lyapunova
infinite-dimensional systems
unbounded observation operator
exact observability
Hautus test
Lyapunov equations
Opis:
In this paper equivalent conditions for exact observability of diagonal systems with a one-dimensional output operator are given. One of these equivalent conditions is the conjecture of Russell and Weiss (1994). The other conditions are given in terms of the eigenvalues and the Fourier coefficients of the system data.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2001, 11, 6; 1277-1283
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The steady-state impedance operator of a linear periodically time-varying one-port network and its determination
Autorzy:
Kłosiński, R.
Powiązania:
https://bibliotekanauki.pl/articles/930020.pdf
Data publikacji:
2009
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
układ liniowy
parametr okresowo zmienny
operator cykloparametryczny
identyfikacja
impedancja okresowo zmienna
okresowy stan ustalony
generowanie harmonicznych
periodically time-varying impedance
periodic steady state
linear periodically time-varying system
circular parametric operator
harmonics aliasing
identification
Opis:
The main subject of the paper is the description and determination of the impedance operator of a linear periodically time-varying (LPTV) one-port network in the steady-state. If the one-port network parameters and the supply vary periodically with the same period, the network reaches a periodic steady state. However, the sinusoidal supply may induce a nonsinusoidal voltage or current. It is impossible to describe such a phenomenon by means of one complex number. A periodically time-varying one-port network working in a steady-state regime can be described with a circular parametric operator. Within the domain of discrete time, such an operator takes the form of a matrix with real-valued entries. The circular parametric operator can be transformed into the frequency domain using a two-dimensional DFT. This description makes it possible to quantitatively assess LPTV system input and output harmonics aliasing. The paper also presents the derivation and the proof of convergence of an iteration scheme for the identification of circular parametric operators. The scheme may be used to determine the impedance of an LPTV one-port network. Some results of computer simulations are shown.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2009, 19, 4; 661-673
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The phase-space approach to time evolution of quantum states in confined systems: The spectral split-operator method
Autorzy:
Kołaczek, Damian
Spisak, Bartłomiej J.
Wołoszyn, Maciej
Powiązania:
https://bibliotekanauki.pl/articles/330780.pdf
Data publikacji:
2019
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
Wigner distribution function
Moyal dynamics
spectral split operator method
funkcja dystrybucji Wignera
dynamika Moyal
metoda podziału operatora
Opis:
Using the phase space approach, we consider the quantum dynamics of a wave packet in an isolated confined system with three different potential energy profiles. We solve the Moyal equation of motion for the Wigner function with the highly efficient spectral split-operator method. The main aim of this study is to compare the accuracy of the employed algorithm through analysis of the total energy expectation value, in terms of deviation from its exact value. This comparison is performed for the second and fourth order factorizations of the time evolution operator.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2019, 29, 3; 439-451
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 21

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