Cyclic and unstable chaotic dynamics in models of two populations of sturgeon fish

This paper considers nonlinear effects in the dynamics of biological models. We describe two dynamic systems elaborated for simulating populations of Russian sturgeon and stellate sturgeon and based on formalization of the relationship between the spawning stock and recruitment according to the analysis of observational data. For the numerical study of differential equations with a structurally changing right-hand side, we use the method of representing models based on maps of states with conditional transitions. For dynamic systems, the presence of qualitatively different modes of the behavior of trajectories is revealed: stable periodic oscillations (sturgeon model) and unstable chaotic oscillations (stellate model) realized in a limited time interval due to a chaotic subset not being an attractor, which is present in the phase space.     

An analysis of the impact of chaotic dynamics on management information flow models

Defined very broadly, Chaos Theory is the study of the behavior of dynamic, nonlinear, feedback equations which, with certain parameters, produce random-appearing output, although all parts of the equation system are deterministic. In this research we use the insights provided by the study of Chaos Theory to investigate how chaos can impact management dynamics and thus influence managerial decision-making.It is common to use dynamic mathematical models as aids to management. If model formulation is such that the model produces chaotic output under certain circumstances, decisions based on the use of that model are seriously compromised. Further, when several models are used concurrently, the interactions between them may cause output to be chaotic even if no individual model exhibits such behavior. We provide an explanation of the reasons why this may happen, and illustrate the consequences through an example.     

Empirical chaotic dynamics in economics

Barnett and Chen [4–6] have displayed evidence of chaos in certain monetary aggregates, but the tests have unknown statistical sampling properties. Using monthly growth rates in monetary aggregates, we conduct bispectral tests for nonlinearity. Our tests have known sampling properties, and we find deep nonlinearity in some monetary aggregate series.     

Realizing nonholonomic dynamics as limit of friction forces

The classical question whether nonholonomic dynamics is realized as limit of friction forces was first posed by Carathéodory. It is known that, indeed, when friction forces are scaled to infinity, then nonholonomic dynamics is obtained as a singular limit.Our results are twofold. First, we formulate the problem in a differential geometric context. Using modern geometric singular perturbation theory in our proof, we then obtain a sharp statement on the convergence of solutions on infinite time intervals. Secondly, we set up an explicit scheme to approximate systems with large friction by a perturbation of the nonholonomic dynamics. The theory is illustrated in detail by studying analytically and numerically the Chaplygin sleigh as an example. This approximation scheme offers a reduction in dimension and has potential use in applications.     

Endogenous chaotic dynamics in transitional economies

This paper examines a model of labor market dynamics in an economy undergoing transition from command socialism to market capitalism. State sector layoffs are modeled as a function of forecasts made by state planners of private sector wages where the laidoff workers are to be re-employed. The state switches between using a high information cost perfect forecast and a free naive forecast in a system that resembles a cobweb supply-demand model. Under certain specifications and parameter values chaotic dynamics are shown to endogenously emerge along with several other varieties of complex dynamics including strange attractors, coexistence of infinitely many stable cycles, cascades of infinitely many period doubling bifurcations and fractal basin boundaries between coexisting non-chaotic attractors.     

Crisis-limited chaotic dynamics in ecological systems

We review our recent efforts to understand why chaotic dynamics is rarely observed in natural populations. The study of two-model ecosystems considered in this paper suggests that chaos exists in narrow parameter ranges. This dynamical behaviour is caused by the crisis-induced sudden death of chaotic attractors. The computed bifurcation diagrams and basin boundary calculations reinforce our earlier conclusion [Chaos, Solitons & Fractals 8 (12) (1997) 1933; Int J Bifurc Chaos 8 (6) (1998) 1325] that the reason why chaos is rarely observed in natural populations is hidden within the mathematical structure of the ecological interactions and not with the problem associated with the data (insufficient length, precision, noise, etc.) and its analysis. We also argue that crisis-limited chaotic dynamics can be commonly found in model terrestrial ecosystems.     

Kinematics and dynamics of a mechanical system on rollers that provide nonholonomic constraints

We consider the plane motion of a mechanical transport system with shock-absorbing roller supports in the form of a "ball in a split triaxial ellipsoidal socket." Kinematic relationships describing nonsliding conditions are derived and shown to be nonintegrable.Kiev Scientific-Research Institute of Building Construction. Translated from Dinamicheskie Sistemy, No. 10, pp. 42–51, 1992.     

The dynamics of nonholonomic systems consisting of a spherical shell with a moving rigid body inside

In this paper we investigate two systems consisting of a spherical shell rolling without slipping on a plane and a moving rigid body fixed inside the shell by means of two different mechanisms. In the former case the rigid body is attached to the center of the ball on a spherical hinge. We show an isomorphism between the equations of motion for the inner body with those for the ball moving on a smooth plane. In the latter case the rigid body is fixed by means of a nonholonomic hinge. Equations of motion for this system have been obtained and new integrable cases found. A special feature of the set of tensor invariants of this system is that it leads to the Euler — Jacobi — Lie theorem, which is a new integration mechanism in nonholonomic mechanics. We also consider the problem of free motion of a bundle of two bodies connected by means of a nonholonomic hinge. For this system, integrable cases and various tensor invariants are found.     

Simple polynomial classes of chaotic jerky dynamics

Third-order explicit autonomous differential equations, commonly called jerky dynamics, constitute a powerful approach to understand the properties of functionally very simple but nonlinear three-dimensional dynamical systems that can exhibit chaotic long-time behavior. In this paper, we investigate the dynamics that can be generated by the two simplest polynomial jerky dynamics that, up to these days, are known to show chaotic behavior in some parameter range. After deriving several analytical properties of these systems, we systematically determine the dependence of the long-time dynamical behavior on the system parameters by numerical evaluation of Lyapunov spectra. Some features of the systems that are related to the dependence on initial conditions are also addressed. The observed dynamical complexity of the two systems is discussed in connection with the existence of homoclinic orbits.     

Synchronizing chaotic dynamics with uncertainties using a predictable synchronization delay design

This paper deals with synchronization and optimization problems of second-order chaotic oscillators by applying a novel control scheme. The approach developed considers incomplete state measurements and no detailed model of the systems to guarantee robust stability. This approach includes an uncertainty estimator and leads to a robust predictable feedback control scheme. The synchronization of the ⁶-Duffing and ⁶-Van der Pol oscillators was used as an illustrative example. A fairly good agreement is obtained between the analytical and numerical results.     

Conservation laws, hierarchy of dynamics and explicit integration of nonholonomic systems

This paper can be regarded as a continuation of our previous work [1, 2] on the hierarchy of the dynamical behavior of nonholonomic systems. We consider different mechanical systems with nonholonomic constraints; in particular, we examine the existence of tensor invariants (laws of conservation) and their connection with the behavior of a system. Considerable attention is given to the possibility of conformally Hamiltonian representation of the equations of motion, which is mainly used for the integration of the considered systems.      

Complex dynamics of a simple 3D autonomous chaotic system with four-wing

The present paper revisits a three dimensional (3D) autonomous chaotic system with four-wing occurring in the known literature [Nonlinear Dyn (2010) 60(3): 443--457] with the entitle ``A new type of four-wing chaotic attractors in 3-D quadratic autonomous systems'' and is devoted to discussing its complex dynamical behaviors, mainly for its non-isolated equilibria, Hopf bifurcation, heteroclinic orbit and singularly degenerate heteroclinic cycles, etc. Firstly, the detailed distribution of its equilibrium points is formulated. Secondly, the local behaviors of its equilibria, especially the Hopf bifurcation, are studied. Thirdly, its such singular orbits as the heteroclinic orbits and singularly degenerate heteroclinic cycles are exploited. In particular, numerical simulations demonstrate that this system not only has four heteroclinic orbits to the origin and other four symmetry equilibria, but also two different kinds of infinitely many singularly degenerate heteroclinic cycles with the corresponding two-wing and four-wing chaotic attractors nearby.     

Periodic and chaotic dynamics in an asymmetric elastoplastic oscillator

We consider the dynamics of a harmonically forced oscillator with an asymmetric elastic–perfectly plastic stiffness function. The computed bifurcation diagrams for the oscillator show regions of periodic motion, hysteresis and large regions of chaotic motion. These different regions of dynamical behaviour are plotted in a two-dimensional parameter space consisting of forcing amplitude and forcing frequency. Examples of the chaotic motion encountered are shown using a discontinuity crossing map. Comparisons are made with the symmetric oscillator by computing a typical bifurcation diagram and considering previously published results for the symmetric system. From this we conclude that the asymmetric system is dominated by a large region of chaotic motion whereas in the symmetric oscillator period one motion and coexisting period three motion predominates.     

Bifurcation and chaotic dynamics of homoclinic systems in ℝ3

We consider perturbations which may or may not depend explicitly on time for the three-dimensional homoclinic systems. We obtain the existence and bifurcation theorems for transversal homoclinic points and homoclinic orbits, and illustrate our results with two examples.     

On stabilization of a nonholonomic system

In this paper we consider the problem of stabilization of nonholonomic systems in the neighborhood of the set of unstable positions of equilibrium, and construct a stabilizing control analytical in coordinates and velocities.     

Complex dynamics and synchronization in two non-identical chaotic ecological systems

Synchronization is a natural phenomenon in non-linear dynamical systems. The relative importance of various mechanisms of population synchrony has been debated by population ecologists. The debate revolves around the issue whether the regionally extrinsic or locally intrinsic agents are more potent. In the present paper, we have attempted to demonstrate that a local intrinsic mechanism, predation, can be more common cause of population synchrony than is believed. Two chaotic food chains having different kinds of top-predators are synchronized using a recently proposed algorithm by Lu and Cao [Lu J, Cao J. Adaptive complete synchronization of two identical or different chaotic (hyperchaotic) dynamical systems with fully unknown parameters. Chaos 2005;15(043901):1–10]. The idiosyncracy of this approach is that it takes care of the uncertainties involved in the parameter estimation. The complete synchronization achieved is robust to noise present in the system. We suggest that local intrinsic causes of population synchrony should be given more attention.