Vanishing components in autonomous competitive Lotka-Volterra systems

Sufficient conditions are found for an n-dimensional autonomous competitive Lotka-Volterra system to have a component vanishing in an exponential rate as t→∞. These conditions incorporate a typical known result in the literature as a particular case. Moreover, if the n-dimensional system degenerates asymptotically to an m-dimensional subsystem as t→∞, then, under these conditions on the subsystem, the property that the ith component of every solution of the subsystem vanishes in an exponential rate is also preserved for the n-dimensional system.     

Buffer overflow calculations using an infinite-capacity model

Sufficient conditions are established for approximation of the overflow probability in a stochastic service system with capacity C by the probability that the related infinite-capacity system has C customers. These conditions are that (a) the infinite-capacity system has negligible probability of C or more customers; (b) the probabilities of states with exactly C customers for the infinite-capacity system are nearly proportional to the same probabilities for the finite- capacity system. Condition (b) is controlling if the probabilities for the infinite-capacity system are rescaled so that the probability of at most C customers is unity. For systems with precisely one state with C customers, such as birth-and-death processes, the latter approximation is exact even when condition (a) does not hold.     

Exponential stability of nonlinear state-dependent delayed impulsive systems with applications

The exponential stability problem for impulsive systems subject to double state-dependent delays is studied in this paper, where state-dependent delay (SDD) is involved in both continuous dynamics and discrete dynamics and the boundedness of it with respect to states is prior unknown. According to impulsive control theory, we present some Lyapunov-based sufficient conditions for the exponential stability of the concerned system. It is shown that the stabilizing effect of SDD impulses on an unstable SDD system changes the stability and achieves desired performance. In addition, the destabilizing effect of SDD impulses is also fully considered and the corresponding sufficient conditions are derived, which reveals the fact that a stable SDD system can maintain its performance when it is subject to SDD impulsive disturbance. As an application, the proposed result can be employed to the stability analysis of impulsive genetic regulatory networks (GRNs) with SDD and the corresponding sufficient conditions are proposed in terms of the model transformation technique and the linear matrix inequalities (LMIs) technique. In order to demonstrate the effectiveness and applicability of the derived results, we give two examples including impulsive GRNs with SDD and the impulsive controller design for the nonlinear system with SDD.     

Riccati equations for abnormal time scale quadratic functionals

This paper focuses on developing new Riccati type conditions for an abnormal time scale symplectic system (S). These conditions provide characterizations of the nonnegativity (with and without a certain “image condition”) and positivity of the quadratic functionals associated with such a system. The novelty of these conditions rely on the natural conjoined basis (Xa,Ua) of (S) in which Xa(t) is not necessarily invertible, and thus the system (S) could be abnormal. These results are new even in the special case of continuous time, as are some of them in the discrete time setting.     

Stability by the linear approximation for discrete equations

This paper is concerned with exponential stability of solutions of perturbed discrete equations. For a given m>1 we will provide necessary and sufficient conditions for exponential stability of all perturbed systems with perturbation of order m under the assumption that the unperturbed linear system is exponentially stable. Basing on this result we obtained necessary and sufficient conditions for exponential stability of the perturbed system for all perturbations of order m>1 for regular systems. Our results are expressed in terms of regular coefficients of the unperturbed system.     

Positive periodic solutions for a system of anisotropic parabolic equations

We consider a system of two degenerate parabolic equations with nonlocal terms and Dirichlet boundary conditions. More precisely, the degeneracy in each equation of the system is of the type r(x)-Laplacian where r(x) is a function depending on x∈Ω, where Ω is a bounded smooth domain of Rn. The system models the diffusion and the interaction between two different biological species sharing the same territory Ω. The paper provides conditions on the parameters of the problem that guarantee the coexistence of a T-periodic non-negative solution (u,v) with both non-trivial u,v.     

Permanence of a discrete nonlinear N-species cooperation system with time delays and feedback controls

A discrete nonlinear N-species cooperation system with time delays and feedback controls is considered in this paper. Sufficient conditions which ensure the permanence of the system are obtained. It is shown that these conditions are weaker than those of Chen [F.D. Chen, Permanence of a discrete N-species cooperation system with time delays and feedback controls, Appl. Math. Comput. 186(2007) 23-29], that is, our investigation shows that the additional condition in Chen’s paper is not necessary.     

Average conditions for permanence and extinction in nonautonomous Lotka-Volterra system

An n species nonautonomous competitive Lotka-Volterra system is considered in this paper. The average conditions on the coefficients are given to guarantee that all but one of the species are driven to extinction. The generalization for the result is presented, that is, for each r?n the average conditions on the coefficients are provided to guarantee that r of the species in the system are permanent while the remaining n−r are driven to extinction. It is shown that these average conditions are improvement of those of Ahmad and Montes de Oca [Appl. Math. Comput. 90 (1998) 155-166] and Montes de Oca and Zeeman [Proc. Amer. Math. Soc. 124 (1996) 3677-3687] and [J. Math. Anal. Appl. 192 (1995) 360-370].     

Multipoint approach to the two-point boundary value problem

This paper treats nonlinear, two-point boundary value problems of the form $\text{x}\text{?}\text{? ?(x, t) = 0}$, in which the Jacobian matrix ?_x(x, t) is characterized by large positive eigenvalues. The resulting numerical difficulties are reduced by treating the two-point boundary value problem as a multipoint boundary value problem. A totally finite-difference approach is employed, thus bypassing the integration of the nonlinear equations, which characterizes shooting methods.The approach employed consists of extending to multipoint boundary value problems the modified-quasilinearization method developed by Miele and lyer for two-point boundary value problems. Basic to the method is the consideration of the performance index P, which measures the cumulative error in the differential equations, the boundary conditions, and the interface conditions.A modified-quasilinearization algorithm is generated by requiring the first variation of the performance index δP to be negative. This algorithm differs from the ordinary-quasilinearization algorithm because of the inclusion of the scaling factor or stepsize α in the system of variations. The main property of the modified-quasilinearization algorithm is the descent property: if the stepsize α is sufficiently small, the reduction in P is guaranteed. Convergence to the desired solution is achieved when the inequality P ? ? is met, where ? is a small, preselected number.The variations per unit stepsize $\text{Δx(t)}\text{α}\text{= A(t)}$ are governed by a system of mn nonhomogeneous, linear differential equations subjected to p initial conditions, q final conditions, and (m ? 1)n interface conditions, with p + q = n, where n is the dimension of the vector x and m is the number of subintervals. Therefore, the total number of boundary conditions and interface conditions is mn. The above system is solved employing the method of particular solutions: m(n + 1) particular solutions are combined linearly, and the coefficients of the combination are determined so that the linear system is satisfied.Two numerical examples are presented, one dealing with a linear system and one dealing with a nonlinear system. The examples illustrate the effectiveness as well as the rapidity of convergence of the present method.     

A numerical study of the formation of spatial patterns in twospotted spider mites

The aim of this paper is to study the formation of spatial patterns in a predator–prey system with Tetranychus urticae as prey and Phytoseiulus persimilis as predator. Logistic Lotka–Volterra predator–prey equations are solved numerically with two different response functions, two initial conditions and one data set. The spatial patterns are generated by introducing diffusion-driven instability in the predator–prey system. Among all parameters involved in predator–prey equations, only the predator interference parameter is varied to generate diffusion-driven instability leading to spatial patterns of population density. Spatial patterns are further generated with the inclusion of prey-taxis in the predator–prey system. Routh–Hurwitz’s conditions for stability are used to create instability with prey-taxis in the system. It is shown that it is possible to generate spatial patterns with zero flux boundary conditions even in a smaller domain with a suitable value of the predator interference parameter or prey-taxis.     

Cauchy matrix for linear almost periodic systems and some consequences

A novel method to construct the fundamental matrix for a linear almost periodic system is proposed, provided that the diagonal terms satisfy an average separation condition and the off-diagonal coefficients are L^∞-small. The idea is to transform the system in a set of Riccati type equations and use exponential dichotomy and its consequences. It is shown that the method yields easy computation procedures with simple and direct conditions depending on the coefficients. Finally, our result enables us to obtain: (i) explicit almost periodic matrices Q(t), Q⁻¹(t) and Q^′(t), which diagonalize the original system and (ii) sufficient conditions for the stability. Two illustrative examples are shown.     

Stability of stationary solutions of a semilinear parabolic partial differential equation

We consider a parabolic partial differential equation u_t = u_xx + f(u) on a compact interval of spatial variable x with Dirichlet boundary conditions. The stability of stationary solutions of this system is studied by the use of Liapunov's second method. We obtain necessary and sufficient conditions for the stability, asymptotic stability, neutral stability, instability, and conditional stability. These conditions are closely connected with the conditions for the existence of the stationary solutions.     

Integrals,Solutions, and Existence Problems for Laplace Transformations of Linear Hyperbolic Systems

We generalize the notions of Laplace transformations and Laplace invariants for systems of hyperbolic equations and study conditions for their existence. We prove that a hyperbolic system admits the Laplace transformation if and only if there exists a matrix of rank k mapping any vector whose components are functions of one of the independent variables into a solution of this system, where k is the defect of the corresponding Laplace invariant. We show that a chain of Laplace invariants exists only if the hyperbolic system has a entire collection of integrals and the dual system has a entire collection of solutions depending on arbitrary functions. An example is given showing that these conditions are not sufficient for the existence of a Laplace transformation.     

Nilpotent bases for distributions and control systems

Let V(M) be the Lie algebra (infinite dimensional) of real analytic vector fields on the n-dimensional manifold M. Necessary conditions that a real analytic k-dimensional distibution on M have a local basis which generates a nilpotent subalgebra of V(M) are derived. Two methods for sufficient conditions are given, the first depending on the existence of a solution to a system of partial differential equations, the second using Darboux's theorem to give a computable test for an (n ? 1)-dimensional distribution. A nonlinear control system in which the control variables appear linearly can be transformed into an orbit equivalent system whose describing vector fields generate a nilpotent algebra if the distribution generated by the original describing vector fields admits a nilpotent basis. When this is the case, local analysis of the control system is greatly simplified.     

On some properties of systems of Volterra integral equations of the fourth kind with kernel of convolution type

We consider the system of integral equations of the form Ax +V x = Ψ, where V is the Volterra operator with kernel of convolution type and A is a constant matrix, det A = 0. We prove an existence theorem and establish necessary and sufficient conditions for the kernel of the operator of the system to be trivial.     

M-matrix asymptotics for Sturm–Liouville problems on graphs

We consider a system formulation for Sturm–Liouville operators with formally self-adjoint boundary conditions on a graph. An M-matrix associated with the boundary value problem is defined and related to the matrix Prüfer angle associated with the system boundary value problem, and consequently with the boundary value problem on the graph. Asymptotics for the M-matrix are obtained as the eigenparameter tends to negative infinity. We show that the boundary conditions may be recovered, up to a unitary equivalence, from the M-matrix and that the M-matrix is a Herglotz function. This is the first in a series of papers devoted to the reconstruction of the Sturm–Liouville problem on a graph from its M-matrix.     

Mean convergence of Fourier-Dunkl series

In the context of the Dunkl transform a complete orthogonal system arises in a very natural way. This paper studies the weighted norm convergence of the Fourier series expansion associated to this system. We establish conditions on the weights, in terms of the Ap classes of Muckenhoupt, which ensure the convergence. Necessary conditions are also proved, which for a wide class of weights coincide with the sufficient conditions.     

Combined m-consecutive and k-out-of-n sliding window systems

This paper proposes a new model that generalizes the linear multi-state sliding window system. In this model the system consists of n linearly ordered multi-state elements. Each element can have different states: from complete failure up to perfect functioning. A performance rate is associated with each state. The system fails if at least one of the following two conditions is met: (1) there exist at least m consecutive overlapping groups of r adjacent elements having the cumulative performance lower than V; (2) there exist at least k arbitrarily located groups of r adjacent elements having the cumulative performance lower than W. An algorithm for system reliability evaluation is suggested which is based on an extended universal moment generating function. Examples of evaluating system reliability and elements’ reliability importance indices are presented. Optimal sequencing of system elements is demonstrated.     

A comparison result for perturbed radial p-Laplacians

Consider the radially symmetric p-Laplacian for p?2 under zero Dirichlet boundary conditions. The main result of the present paper is that under appropriate conditions a solution of a perturbed (radially symmetric) p-Laplacian can be compared with the solution of the unperturbed one. As a consequence one obtains a sign preserving result for a system of p-Laplacians which are coupled in a nonquasimonotone way.     

Exact null controllability of non-autonomous functional evolution systems with nonlocal conditions

In this article, by using theory of linear evolution system and Schauder fixed point theorem, we establish a sufficient result of exact null controllability for a non-autonomous functional evolution system with nonlocal conditions. In particular, the compactness condition or Lipschitz condition for the function g in the nonlocal conditions appearing in various literatures is not required here. An example is also provided to show an application of the obtained result.