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Wyświetlanie 1-14 z 14
Tytuł:
Non-stationary heat transfer in two-phase hollow cylinder with functionally graded effective material properties with second kind of boundary conditions
Niestacjonarny przepływ ciepła w przewodniku cylindrycznym z warunkami brzegowymi drugiego rodzaju
Autorzy:
Ostrowski, P.
Powiązania:
https://bibliotekanauki.pl/articles/395935.pdf
Data publikacji:
2010
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
przewodnictwo cieplne
niestacjonarny przepływ ciepła
kompozyt
heat conduction
FGM
composite
Opis:
The unidirectional non-stationary heat conduction in two-phase hollow cylinder is considered. The conductor is made of two-phase stratified composites and has a smooth gradation of effective properties in the radial direction. Therefore, we deal here with a special case of functionally graded materials, FGM (cf. [6]). The formulation of mathematical model of the conductor is based on the tolerance averaging approach (TAA), cf. [8]. Considerations in this paper are restricted only to the unidirectional nonstationary heat conduction, where on the boundaries are given [phi]-constant or periodic function of heat fluxes q_o = q_o([phi]t), qk = qk([phi]t) for every time period t, and function of initial temperature [...]. The effect of fibres width on the temperature field will be also examined.
Przedmiotem rozważań niniejszej pracy jest analiza wpływu pewnych parametrów geometrycznych przewodnika na przebieg pola temperatur dla zagadnienia niestacjonarnego przepływu ciepła. Rozpatrywany przewodnik jest dwuskładnikowym kompozytem o deterministycznej mikrostrukturze, który w kierunku kątowym jest .- periodyczny (dla ustalonego promienia .), a w kierunku promieniowym jego efektywne własności zmieniają się w sposób wolnozmienny. Stąd, mamy tutaj do czynienia ze szczególnym przypadkiem materiału o funkcyjnej gradacji własności, FGM (por. Suresh , Mortensen, 1998). Samo zjawisko przewodznia ciepła opisane jest równaniem Fouriera, które zawiera nieciągłe i silnie oscylujące współczynniki. Model matematyczny opisujący zjawisko przewodzenia ciepła w rozpatrywanym kompozycie opierać się będzie na technice tolerancyjnej aproksymacji (por. Woźniak, Wierzbicki, 2000). W pracy ograniczymy się jedynie do przypadku jednowymiarowego przepływu ciepła, w którym na brzegach przewodnika dana jest stała bądź periodyczna funkcja gęstości strumienia ciepła q0 = q0(.,t), qk = qk(.,t) dla dowolnej chwili czasu t, oraz funkcja pola temperatury .0 = .0(.,t) w chwili początkowej t = t0. Rozpatrywano również wpływ szerokości inkluzji na prędkość zmian pola temperatury w obszarze przewodnika.
Źródło:
Civil and Environmental Engineering Reports; 2010, 5; 113-122
2080-5187
2450-8594
Pojawia się w:
Civil and Environmental Engineering Reports
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On Adaptive Control for the Continuous Time-varying JLQG Problem
Autorzy:
Czornik, A.
Świerniak, A.
Powiązania:
https://bibliotekanauki.pl/articles/908494.pdf
Data publikacji:
2005
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
adaptacyjny układ sterowania
układ niestacjonarny
time varying systems
adaptive control
JLQG problem
Opis:
In this paper the adaptive control problem for a continuous infinite time-varying stochastic control system with jumps in parameters and quadratic cost is investigated. It is assumed that the unknown coefficients of the system have limits as time tends to infinity and the boundary system is absolutely observable and stabilizable. Under these assumptions it is shown that the optimal value of the quadratic cost can be reached based only on the values of these limits, which, in turn, can be estimated through strongly consistent estimators.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2005, 15, 1; 53-62
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Unsteady Hartmann two-phase flow: the Riemann-sum approximation approach
Autorzy:
Jha, B. K.
Babila, C. T.
Isa, S.
Powiązania:
https://bibliotekanauki.pl/articles/264967.pdf
Data publikacji:
2016
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
przepływ dwufazowy
przepływ niestacjonarny
magnetohydrodynamika
Riemann-sum approximation
unsteady flow
Hartmann two-phase flow
Opis:
We consider the time dependent Hartmann flow of a conducting fluid in a channel formed by two horizontal parallel plates of infinite extent, there being a layer of a non-conducting fluid between the conducting fluid and the upper channel wall. The flow formation of conducting and non-conducting fluids is coupled by equating the velocity and shear stress at the interface. The unsteady flow formation inside the channel is caused by a sudden change in the pressure gradient. The relevant partial differential equations capturing the present physical situation are transformed into ordinary differential equations using the Laplace transform technique. The ordinary differential equations are then solved analytically and the Riemann-sum approximation method is used to invert the Laplace domain into time domain. The solution obtained is validated by comparisons with the closed form solutions obtained for steady states which have been derived separately and also by the implicit finite difference method. The variation of velocity, mass flow rate and skin-friction on both plates for various physical parameters involved in the problem are reported and discussed with the help of line graphs. It was found that the effect of changes of the electric load parameter is to aid or oppose the flow as compared to the short-circuited case.
Źródło:
International Journal of Applied Mechanics and Engineering; 2016, 21, 4; 891-904
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
MHD two-layered unsteady fluid flow and heat transfer through a horizontal channel between
Autorzy:
Linga Raju, T.
Nagavalli, M.
Powiązania:
https://bibliotekanauki.pl/articles/955179.pdf
Data publikacji:
2014
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
magnetohydrodynamika
przepływ niestacjonarny
transfer ciepła
magnetohydrodynamics
immiscible fluids
rotating fluid
unsteady flow
heat transfer
Opis:
An unsteady magnetohydrodynamic (MHD) two-layered fluids flow and heat transfer in a horizontal channel between two parallel plates in the presence of an applied magnetic and electric field is investigated, when the whole system is rotated about an axis perpendicular to the flow. The flow is driven by a constant uniform pressure gradient in the channel bounded by two parallel insulating plates, when both fluids are considered as electrically conducting, incompressible with variable properties, viz. different viscosities, thermal and electrical conductivities. The transport properties of the two fluids are taken to be constant and the bounding plates are maintained at constant and equal temperatures. The governing partial differential equations are then reduced to the ordinary linear differential equations using two-term series. Closed form solutions for primary and secondary velocity, also temperature distributions are obtained in both the fluid regions of the channel. Profiles of these solutions are plotted to discuss the effects of the flow and heat transfer characteristics, and their dependence on the governing parameters involved, such as the Hartmann number, rotation parameter, ratios of the viscosities, heights, electrical and thermal conductivities.
Źródło:
International Journal of Applied Mechanics and Engineering; 2014, 19, 1; 97-121
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An extension of the Cayley-Hamilton theorem for nonlinear time-varying systems
Autorzy:
Kaczorek, T.
Powiązania:
https://bibliotekanauki.pl/articles/908465.pdf
Data publikacji:
2006
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
wydłużenie
twierdzenie Cayleya-Hamiltona
nieliniowość
układ niestacjonarny
extension
Cayley-Hamilton theorem
nonlinear
time-varying system
Opis:
The classical Cayley-Hamilton theorem is extended to nonlinear time-varying systems with square and rectangular system matrices. It is shown that in both cases system matrices satisfy many equations with coefficients being the coefficients of characteristic polynomials of suitable square matrices. The proposed theorems are illustrated with numerical examples.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2006, 16, 1; 141-145
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Supervisory fault tolerant control of the GTM UAV using LPV methods
Autorzy:
Péni, T.
Vanek, B.
Szabó, Z.
Bokor, J.
Powiązania:
https://bibliotekanauki.pl/articles/330070.pdf
Data publikacji:
2015
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
fault tolerant control
linear parameter varying systems
supervisory architecture
flight control
sterowanie tolerujące uszkodzenia
układ liniowy niestacjonarny
sterowanie lotem
Opis:
A multi-level reconfiguration framework is proposed for fault tolerant control of over-actuated aerial vehicles, where the levels indicate how much authority is given to the reconfiguration task. On the lowest, first level the fault is accommodated by modifying only the actuator/sensor configuration, so the fault remains hidden from the baseline controller. A dynamic reallocation scheme is applied on this level. The allocation mechanism exploits the actuator/sensor redundancy available on the aircraft. When the fault cannot be managed at the actuator/sensor level, the reconfiguration process has access to the baseline controller. Based on the LPV control framework, this is done by introducing fault-specific scheduling parameters. The baseline controller is designed to provide an acceptable performance level along all fault scenarios coded in these scheduling variables. The decision on which reconfiguration level has to be initiated in response to a fault is determined by a supervisor unit. The method is demonstrated on a full six-degrees-of-freedom nonlinear simulation model of the GTM UAV.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2015, 25, 1; 117-131
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Classification in the Gabor time-frequency domain of non-stationary signals embedded in heavy noise with unknown statistical distribution
Autorzy:
Świercz, E.
Powiązania:
https://bibliotekanauki.pl/articles/907771.pdf
Data publikacji:
2010
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
sygnał niestacjonarny
klasyfikacja sygnału
rozpoznawanie obrazów
transformator czas-częstotliwość
non-stationary signals
signal classification
pattern recognition
time-frequency transforms
Opis:
A new supervised classification algorithm of a heavily distorted pattern (shape) obtained from noisy observations of nonstationary signals is proposed in the paper. Based on the Gabor transform of 1-D non-stationary signals, 2-D shapes of signals are formulated and the classification formula is developed using the pattern matching idea, which is the simplest case of a pattern recognition task. In the pattern matching problem, where a set of known patterns creates predefined classes, classification relies on assigning the examined pattern to one of the classes. Classical formulation of a Bayes decision rule requires a priori knowledge about statistical features characterising each class, which are rarely known in practice. In the proposed algorithm, the necessity of the statistical approach is avoided, especially since the probability distribution of noise is unknown. In the algorithm, the concept of discriminant functions, represented by Frobenius inner products, is used. The classification rule relies on the choice of the class corresponding to the max discriminant function. Computer simulation results are given to demonstrate the effectiveness of the new classification algorithm. It is shown that the proposed approach is able to correctly classify signals which are embedded in noise with a very low SNR ratio. One of the goals here is to develop a pattern recognition algorithm as the best possible way to automatically make decisions. All simulations have been performed in Matlab. The proposed algorithm can be applied to non-stationary frequency modulated signal classification and non-stationary signal recognition.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2010, 20, 1; 135-147
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
LMI-based robust control of uncertain nonlinear systems via polytopes of polynomials
Autorzy:
Sánchez, Marcelino
Bernal, Miguel
Powiązania:
https://bibliotekanauki.pl/articles/330548.pdf
Data publikacji:
2019
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
robust control
uncertain system
nonlinear system
linear parameter-varying systems
LMIs
sterowanie odporne
układ niepewny
układ nieliniowy
układ liniowy niestacjonarny
Opis:
This investigation is concerned with robust analysis and control of uncertain nonlinear systems with parametric uncertainties. In contrast to the methodologies from the field of linear parameter varying systems, which employ convex structures of the state space representation in order to perform analysis and design, the proposed approach makes use of a polytopic form of a generalisation of the characteristic polynomial, which proves to outperform former results on the subject. Moreover, the derived conditions have the advantage of being cast as linear matrix inequalities under mild assumptions.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2019, 29, 2; 275-283
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fault-tolerant control strategy for actuator faults using LPV techniques: application to a two degree of freedom helicopter
Autorzy:
Montes de Oca, S.
Puig, V.
Witczak, M.
Dziekan, Ł.
Powiązania:
https://bibliotekanauki.pl/articles/331468.pdf
Data publikacji:
2012
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
sterowanie tolerujące uszkodzenia
układ liniowy niestacjonarny
liniowa nierówność macierzowa
fault tolerant control
linear parameter varying
virtual actuator
linear matrix inequality
Opis:
In this paper, a Fault Tolerant Control (FTC) strategy for Linear Parameter Varying (LPV) systems that can be used in the case of actuator faults is proposed. The idea of this FTC method is to adapt the faulty plant instead of adapting the controller to the faulty plant. This approach can be seen as a kind of virtual actuator. An integrated FTC design procedure for the fault identification and fault-tolerant control schemes using LPV techniques is provided as well. Fault identification is based on the use of an Unknown Input Observer (UIO). The FTC controller is implemented as a state feedback controller and designed using polytopic LPV techniques and Linear Matrix Inequality (LMI) regions in such a way as to guarantee the closed-loop behavior in terms of several LMI constraints. To assess the performance of the proposed approach, a two degree of freedom helicopter is used.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2012, 22, 1; 161-171
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Convective heat transfer in a micropolar fluid over an unsteady stretching surface
Autorzy:
Prasad, K. V.
Vaidya, H.
Vajravelu, K.
Powiązania:
https://bibliotekanauki.pl/articles/266164.pdf
Data publikacji:
2016
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
przepływ niestacjonarny
wymiana ciepła
tarcie
metoda Keller-box
unsteady flow
microrotation
heat transfer
skin friction
Nusselt number
Keller-box method
Opis:
An unsteady boundary layer free convective flow and heat transfer of a viscous incompressible, microploar fluid over a vertical stretching sheet is investigated. The stretching velocity is assumed to vary linearly with the distance along the sheet. Two equal and opposite forces are impulsively applied along the x-axis so that the sheet is stretched, keeping the origin fixed in the micropolar fluid. The transformed highly non-linear boundary layer equations are solved numerically by an implicit finite difference scheme for the transient, state from the initial to the final steady-state. To validate the numerical method, comparisons are made with the available results in the literature for some special cases and the results are found to be in good agreement. The obtained numerical results are analyzed graphically for the velocity, the microrotation, and the temperature distribution; whereas the skin friction, the couple stress coefficient and the Nusselt number are tabulated for different values of the pertinent parameters. Results exhibit a drag reduction and an increase in the surface heat transfer rate in the micropolar fluid flow compared to the Newtonian fluid flow.
Źródło:
International Journal of Applied Mechanics and Engineering; 2016, 21, 2; 407-422
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An LMI-based heuristic algorithm for vertex reduction in LPV systems
Autorzy:
Sanjuan, Adrián
Rotondo, Damiano
Nejjari, Fatiha
Sarrate, Ramon
Powiązania:
https://bibliotekanauki.pl/articles/331436.pdf
Data publikacji:
2019
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
linear parameter varying
linear matrix inequality
Gershgorin circles
gain scheduling
controller design
układ liniowy niestacjonarny
liniowa nierówność macierzowa
twierdzenie Gerszgorina
harmonogramowanie wzmocnienia
Opis:
The linear parameter varying (LPV) approach has proved to be suitable for controlling many non-linear systems. However, for those which are highly non-linear and complex, the number of scheduling variables increases rapidly. This fact makes the LPV controller implementation not feasible for many real systems due to memory constraints and computational burden. This paper considers the problem of reducing the total number of LPV controller gains by determining a heuristic methodology that combines two vertices of a polytopic LPV model such that the same gain can be used in both vertices. The proposed algorithm, based on the use of the Gershgorin circles, provides a combinability ranking for the different vertex pairs, which helps in solving the reduction problem in fewer attempts. Simulation examples are provided in order to illustrate the main characteristics of the proposed approach.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2019, 29, 4; 725-737
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Robust quasi-LPV model reference FTC of a quadrotor UAV subject to actuator faults
Autorzy:
Rotondo, D.
Nejjari, F.
Puig, V.
Powiązania:
https://bibliotekanauki.pl/articles/331147.pdf
Data publikacji:
2015
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
linear parameter varying systems
fault tolerant control
quadrotor
model reference based control
linear matrix inequalities
układ liniowy niestacjonarny
sterowanie tolerujące uszkodzenia
liniowe nierówności macierzowe
Opis:
A solution for fault tolerant control (FTC) of a quadrotor unmanned aerial vehicle (UAV) is proposed. It relies on model reference-based control, where a reference model generates the desired trajectory. Depending on the type of reference model used for generating the reference trajectory, and on the assumptions about the availability and uncertainty of fault estimation, different error models are obtained. These error models are suitable for passive FTC, active FTC and hybrid FTC, the latter being able to merge the benefits of active and passive FTC while reducing their respective drawbacks. The controller is generated using results from the robust linear parameter varying (LPV) polytopic framework, where the vector of varying parameters is used to schedule between uncertain linear time invariant (LTI) systems. The design procedure relies on solving a set of linear matrix inequalities (LMIs) in order to achieve regional pole placement and H∞ norm bounding constraints. Simulation results are used to compare the different FTC strategies.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2015, 25, 1; 7-22
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Unsteady two-layered fluid flow and heat transfer of conducting fluids in a channel between parallel porous plates under transverse magnetic field
Autorzy:
Linga Raju, T.
Nagavalli, M.
Powiązania:
https://bibliotekanauki.pl/articles/264466.pdf
Data publikacji:
2013
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
magnetohydrodynamika
mieszanie płynów
przepływ niestacjonarny
ruch oscylacyjny
przenikanie ciepła
magnetohydrodynamics
two-layered fluid flow/immiscible fluids
unsteady flow
oscillatory motion
heat transfer
porous plate
Opis:
The unsteady magnetohydrodynamic flow of two immiscible fluids in a horizontal channel bounded by two parallel porous isothermal plates in the presence of an applied magnetic and electric field is investigated. The flow is driven by a constant uniform pressure gradient in the channel bounded by two parallel insulating plates, one being stationary and the other oscillating, when both fluids are considered as electrically conducting. Also, both fluids are assumed to be incompressible with variable properties, viz. different viscosities, thermal and electrical conductivities. The transport properties of the two fluids are taken to be constant and the bounding plates are maintained at constant and equal temperatures. The governing equations are partial in nature, which are then reduced to the ordinary linear differential equations using two-term series. Closed form solutions for velocity and temperature distributions are obtained in both fluid regions of the channel. Profiles of these solutions are plotted to discuss the effect on the flow and heat transfer characteristics, and their dependence on the governing parameters involved, such as the Hartmann number, porous parameter, ratios of the viscosities, heights, electrical and thermal conductivities.
Źródło:
International Journal of Applied Mechanics and Engineering; 2013, 18, 3; 699-726
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An LPV pole-placement approach to friction compensation as an FTC problem
Autorzy:
Patton, R. J.
Chen, L.
Klinkhieo, S.
Powiązania:
https://bibliotekanauki.pl/articles/331466.pdf
Data publikacji:
2012
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
układ liniowy niestacjonarny
detekcja uszkodzeń
diagnostyka uszkodzeń
liniowa nierówność macierzowa
lokowanie biegunów
friction
linear parameter varying
fault detection
fault diagnosis
linear matrix inequality
pole placement
Opis:
The concept of combining robust fault estimation within a controller system to achieve active Fault Tolerant Control (FTC) has been the subject of considerable interest in the recent literature. The current study is motivated by the need to develop model-based FTC schemes for systems that have no unique equilibria and are therefore difficult to linearise. Linear Parameter Varying (LPV) strategies are well suited to model-based control and fault estimation for such systems. This contribution involves pole-placement within suitable LMI regions, guaranteeing both stability and performance of a multi-fault LPV estimator employed within an FTC structure. The proposed design strategy is illustrated using a nonlinear two-link manipulator system with friction forces acting simultaneously at each joint. The friction forces, regarded as a special case of actuator faults, are estimated and their effect is compensated within a polytope controller system, yielding a robust form of active FTC that is easy to apply to real robot systems.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2012, 22, 1; 149-160
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
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