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1.
New results in the on-line identification of time-varying dynamicprocesses are presented. The performance of the weighted least-squaresidentification algorithm, for different values of signal-to-noiseratio (SNR), is investigated with reference to artificial recordsfrom Monte Carlo tests. It is obvious that a higher SNR willresult in a good estimated model. This paper discusses whetherit stays as easy at low SNR to find the model structure accuratelyas it is at high SNR.  相似文献
2.
This paper presents a combined genetic algorithm-fuzzy logic controller (GA–FLC) technique for constrained nonlinear programming problems. In the standard Genetic algorithms, the upper and lower limits of the search regions should be given by the decision maker in advance to the optimization process. In general a needlessly large search region is used in fear of missing the global optimum outside the search region. Therefore, if the search region is able to adapt toward a promising area during the optimization process, the performance of GA will be enhanced greatly. Thus in this work we tried to investigate the influence of the bounding intervals on the final result. The proposed algorithm is made of classical GA coupled with FLC. This controller monitors the variation of the decision variables during process of the algorithm and modifies the boundary intervals to restart the next round of the algorithm. These characteristics make this approach well suited for finding optimal solutions to the highly NLP problems. Compared to previous works on NLP, our method proved to be more efficient in computation time and accuracy of the final solution.  相似文献
3.
An Eulerian fixed mesh finite element technique applicable to metal-forming processes operating under steady-state condition is presented. Different specific features are demonstrated by solving plane-strain rolling problem. The advantage of the Eulerian fixed mesh technique over the updated Lagrangian one in modelling the elastic flattening of rolls is demonstrated. The obtained pressure distribution and the stress field are compared with other numerical and/or experimental results available in the literature with which good agreement is found. It is found that the consideration of the elastic flattening of rolls decreases the difference between the measured and the computed results.  相似文献
4.
In this paper, we study oscillation and nonoscillation behaviour of the second order nonlinear difference equations of the form $$\Delta (r_n \psi (x_n )\Delta x_n ) + q_{n + 1} f(x_{n + 1} ) = 0, n \in N(n_o ),$$ and $$\Delta (r_n \psi (x_n )\Delta x_n ) + q_n f(n,x_n ) = 0, n \in N(n_o ),$$ whereN(n o ) =n o ,n o + 1, …, (n o is a fixed nonnegative integer number), Δxn =x n +1−x n is the forward difference operator,x :N(n o ) → ℝ,r :N(n o ) → (0, ∞), Ψ : ℝ → (0, ∞),f is a real valued continuous function, andq n is a sequence of real valued.  相似文献
5.
The purpose of this paper is to study a class of delay differential equations with two delays. first, we consider the existence of periodic solutions for some delay differential equations. Second, we investigate the local stability of the zero solution of the equation by analyzing the correlocal stability of the zero solution of the equation by analyzing the corresponding characteristic equation of the linearized equation. The exponential stability of a perturbed delay differential system with a bounded lag is studied. Finally, by choosing one of the delays as a bifurcation parameter, we show that the equation exhibits Hopf and saddle-node bifurcations.  相似文献
6.
Lipschitz stability and Lipschitzϕ - equistability of the functional differential equation $x' = B(x)f(t,x,x_t ), x_{t_ \circ = \theta _ \circ } $ are discussed. Sufficient conditions are given using the comparison with the corresponding scalar equation.  相似文献
7.
This paper is concerned with iterative solution to general Sylvester-conjugate matrix equation of the form $\sum_{i = 1}^{s} A_{i}V + \sum_{j = 1}^{t} B_{j}W = \sum_{l = 1}^{m} E_{l}\overline{V}F_{l} + C$ . An iterative algorithm is established to solve this matrix equation. When this matrix equation is consistent, for any initial matrices, the solutions can be obtained within finite iterative steps in the absence of round off errors. Some lemmas and theorems are stated and proved where the iterative solutions are obtained. Finally, a numerical example is given to verify the effectiveness of the proposed algorithm.  相似文献
8.
In this paper, we introduced an accurate computational matrix method for solving systems of high order fractional differential equations. The proposed method is based on the derived relation between the Chebyshev coefficient matrix A of the truncated Chebyshev solution u(t)u(t) and the Chebyshev coefficient matrix A(ν)A(ν) of the fractional derivative u(ν)u(ν). The fractional derivatives are presented in terms of Caputo sense. The matrix method for the approximate solution for the systems of high order fractional differential equations (FDEs) in terms of Chebyshev collocation points is presented. The systems of FDEs and their conditions (initial or boundary) are transformed to matrix equations, which corresponds to system of algebraic equations with unknown Chebyshev coefficients. The remaining set of algebraic equations is solved numerically to yield the Chebyshev coefficients. Several numerical examples for real problems are provided to confirm the accuracy and effectiveness of the present method.  相似文献
9.
In this paper, the problem of buoyancy driven micropolar fluid flow within an annulus formed between two circular concentric/eccentric tubes has been numerically investigated using Fourier spectral method. The annulus inner wall is uniformly heated and maintained at constant heat flux while the outer wall is cooled and kept at constant temperature. The full governing equations of linear momentum, angular momentum and energy have been solved to give the details of flow and thermal fields. The heat convection process in the annulus is mainly controlled by modified Rayleigh number Ra, Prandtl number Pr, radius ratio Rr, eccentricity, e and material parameters of Micropolar fluid. The material parameters are dimensionless spin gradient viscosity λ, dimensionless micro-inertia density B and dimensionless vortex viscosity D. The study considered a range of modified Ra up to 105 and is carried out at three values of Pr, namely Pr = 0.1, 1.0 and 7.0, and at three values of parameter D, namely, D = 2, 4, 8 while the eccentricity is varied between −0.65 and +0.65. The radius ratio is fixed at 2.6 while the material parameters B and λ are assigned the value of 1. The effect of the controlling parameters on flow and thermal fields has been investigated with emphasis on the effect of these parameters on local and mean inner wall temperatures. The study has shown that for certain controlling parameters the steady mean temperature of inner wall of the annulus is maximum at a certain eccentricity. The study has also shown that as the parameter D increases the steady mean inner wall temperature increases. Moreover, the study has shown that as the Pr increases the mean inner wall temperature decreases.  相似文献
10.
It has been shown by (R.O. Al-Seedy, A.A. El-Sherbiny, S.A. El-Shehawy, S.I. Ammar, Transient solution of the M/M/c queue with balking and reneging, Comput. Math. Appl. 57 (2009) 1280–1285) that a generating function technique can be successfully applied to derive the transient solution for an M/M/c queueing system. In this paper, we further illustrate how this technique can be used to obtain the busy period density function of an M/M/1 queue with balking and reneging. Finally, numerical calculations are presented.  相似文献
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