共查询到20条相似文献,搜索用时 15 毫秒
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The number of states in a deterministic finite automaton (DFA) recognizing the language , where is regular language recognized by an -state DFA, and is a constant, is shown to be at most and at least in the worst case, for every and for every alphabet of at least six letters. Thus, the state complexity of is . In the case the corresponding state complexity function for is determined as with the lower bound witnessed by automata over a four-letter alphabet. The nondeterministic state complexity of is demonstrated to be . This bound is shown to be tight over a two-letter alphabet. 相似文献
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Wenqiang Zhao 《Computers & Mathematics with Applications》2018,75(10):3801-3824
In this article, we use the so-called difference estimate method to investigate the continuity and random dynamics of the non-autonomous stochastic FitzHugh–Nagumo system with a general nonlinearity. Firstly, under weak assumptions on the noise coefficient, we prove the existence of a pullback attractor in by using the tail estimate method and a certain compact embedding on bounded domains. Secondly, although the difference of the first component of solutions possesses at most -times integrability where is the growth exponent of the nonlinearity, we overcome the absence of higher-order integrability and establish the continuity of solutions in with respect to the initial values belonging to . As an application of the result on the continuity, the existence of a pullback attractor in is proved for arbitrary and . 相似文献
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In this paper, four alternating direction implicit (ADI) schemes are presented for solving two-dimensional cubic nonlinear Schrödinger equations. Firstly, we give a Crank–Nicolson ADI scheme and a linearized ADI scheme both with accuracy , with the same method, use fourth-order Padé compact difference approximation for the spatial discretization; two HOC-ADI schemes with accuracy are given. The two linearized ADI schemes apply extrapolation technique to the real coefficient of the nonlinear term to avoid iterating to solve. Unconditionally stable character is verified by linear Fourier analysis. The solution procedure consists of a number of tridiagonal matrix equations which make the computation cost effective. Numerical experiments are conducted to demonstrate the efficiency and accuracy, and linearized ADI schemes show less computational cost. All schemes given in this paper also can be used for two-dimensional linear Schrödinger equations. 相似文献
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In this article, we propose a second-order uniformly convergent numerical method for a singularly perturbed 2D parabolic convection–diffusion initial–boundary-value problem. First, we use a fractional-step method to discretize the time derivative of the continuous problem on uniform mesh in the temporal direction, which gives a set of two 1D problems. Then, we use the classical finite difference scheme to discretize those 1D problems on a special mesh, which results almost first-order convergence, i.e., . To enhance the order of convergence to , we use the Richardson extrapolation technique. In support of the theoretical results, numerical experiments are performed by employing the proposed technique. 相似文献
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Ke Wu 《Computers & Mathematics with Applications》2018,75(3):755-763
We consider the existence of ground state solutions for the Kirchhoff type problem where , and . Here we are interested in the case that since the existence of ground state for is easily obtained by a standard variational argument. Our method is based on a Pohoaev type identity. 相似文献
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Michael Thomas 《Information Processing Letters》2012,112(10):386-391
For decision problems defined over Boolean circuits using gates from a restricted set B only, we have for all finite sets B and of gates such that all gates from B can be computed by circuits over gates from . In this note, we show that a weaker version of this statement holds for decision problems defined over Boolean formulae, namely that and for all finite sets B and of Boolean functions such that all can be defined in . 相似文献
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Eigenvalues of a real supersymmetric tensor 总被引:3,自引:0,他引:3
In this paper, we define the symmetric hyperdeterminant, eigenvalues and E-eigenvalues of a real supersymmetric tensor. We show that eigenvalues are roots of a one-dimensional polynomial, and when the order of the tensor is even, E-eigenvalues are roots of another one-dimensional polynomial. These two one-dimensional polynomials are associated with the symmetric hyperdeterminant. We call them the characteristic polynomial and the E-characteristic polynomial of that supersymmetric tensor. Real eigenvalues (E-eigenvalues) with real eigenvectors (E-eigenvectors) are called H-eigenvalues (Z-eigenvalues). When the order of the supersymmetric tensor is even, H-eigenvalues (Z-eigenvalues) exist and the supersymmetric tensor is positive definite if and only if all of its H-eigenvalues (Z-eigenvalues) are positive. An -order -dimensional supersymmetric tensor where is even has exactly eigenvalues, and the number of its E-eigenvalues is strictly less than when . We show that the product of all the eigenvalues is equal to the value of the symmetric hyperdeterminant, while the sum of all the eigenvalues is equal to the sum of the diagonal elements of that supersymmetric tensor, multiplied by . The eigenvalues are distributed in disks in . The centers and radii of these disks are the diagonal elements, and the sums of the absolute values of the corresponding off-diagonal elements, of that supersymmetric tensor. On the other hand, E-eigenvalues are invariant under orthogonal transformations. 相似文献
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A. Mardani M.R. Hooshmandasl M.H. Heydari C. Cattani 《Computers & Mathematics with Applications》2018,75(1):122-133
In this paper, an efficient and accurate meshless method is proposed for solving the time fractional advection–diffusion equation with variable coefficients which is based on the moving least square (MLS) approximation. In the proposed method, firstly the time fractional derivative is approximated by a finite difference scheme of order and then the MLS approach is employed to approximate the spatial derivative where time fractional derivative is expressed in the Caputo sense. Also, the validity of the proposed method is investigated in error analysis discussion. The main aim is to show that the meshless method based on the MLS shape functions is highly appropriate for solving fractional partial differential equations (FPDEs) with variable coefficients. The efficiency and accuracy of the proposed method are verified by solving several examples. 相似文献