1,859,817 research outputs found

    Conceptualising Cluster Evolution: Beyond the Life-Cycle Model?

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    Although the literature on the evolution of industrial clusters is not vast, a preferred approach has already become evident, based around the idea of a cluster 'life-cycle'. This approach has several limitations. In this paper we explore a different conception of cluster evolution drawing on the 'adaptive cycle' model that has been developed in evolutionary ecology. Using this model, cluster evolution is viewed as an adaptive process with different possible outcomes based on episodic interactions of nested systems. Though not without limitations, this approach offers greater scope as a framework for shaping the research agenda into the evolution of clusters.Clusters, Evolution, Life-cycle model, Complex systems, Adaptive cycle model

    Damage spreading and dynamic stability of kinetic Ising models

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    We investigate how the time evolution of different kinetic Ising models depends on the initial conditions of the dynamics. To this end we consider the simultaneous evolution of two identical systems subjected to the same thermal noise. We derive a master equation for the time evolution of a joint probability distribution of the two systems. This equation is then solved within an effective-field approach. By analyzing the fixed points of the master equation and their stability we identify regular and chaotic phases.Comment: 4 pages RevTeX, 2 Postscript figure

    Managing evolution and change in web-based teaching and learning environments

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    The state of the art in information technology and educational technologies is evolving constantly. Courses taught are subject to constant change from organisational and subject-specific reasons. Evolution and change affect educators and developers of computer-based teaching and learning environments alike – both often being unprepared to respond effectively. A large number of educational systems are designed and developed without change and evolution in mind. We will present our approach to the design and maintenance of these systems in rapidly evolving environments and illustrate the consequences of evolution and change for these systems and for the educators and developers responsible for their implementation and deployment. We discuss various factors of change, illustrated by a Web-based virtual course, with the objective of raising an awareness of this issue of evolution and change in computer-supported teaching and learning environments. This discussion leads towards the establishment of a development and management framework for teaching and learning systems

    Self-similar approach to market analysis

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    A novel approach to analyzing time series generated by complex systems, such as markets, is presented. The basic idea of the approach is the {\it Law of Self-Similar Evolution}, according to which any complex system develops self-similarly. There always exist some internal laws governing the evolution of a system, say of a market, so that each of such systems possesses its own character regulating its behaviour. The problem is how to discover these hidden internal laws defining the system character. This problem can be solved by employing the {\it Self-Similar Approximation Theory}, which supplies the mathematical foundation for the Law of Self-Similar Evolution. In this report, the theoretical basis of the new approach to analyzing time series is formulated, with an accurate explanation of its principal points.Comment: Latex file, 17 pages, no figure

    Algebraic Structure of Discrete Zero Curvature Equations and Master Symmetries of Discrete Evolution Equations

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    An algebraic structure related to discrete zero curvature equations is established. It is used to give an approach for generating master symmetries of first degree for systems of discrete evolution equations and an answer to why there exist such master symmetries. The key of the theory is to generate nonisospectral flows (λt=λl,l≄0)(\lambda_t=\lambda ^l, l\ge0) from the discrete spectral problem associated with a given system of discrete evolution equations. Three examples are given.Comment: 24 pages, LaTex, revise

    An Emergent Economics of Ecosystem Management

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    Economics is an evolving and emerging field of study, so is the management of ecosystems. As such, this paper delineates the co-evolution of economic evaluation that reflects the various recognized ecosystem management approaches of anticipative, adaptive and capacitive ecosystem management. Each management approach is critiqued and from this theoretical analysis an emergent approach for the management of ecosystem is put forward, which accordingly suggests an alternative methodological approach for economic evaluations.Complexity, creativity, economic evaluation, ecosystem management, evolution, open systems, rationality, Resource /Energy Economics and Policy,

    Stability radius and internal versus external stability in Banach spaces: an evolution semigroup approach

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    In this paper the theory of evolution semigroups is developed and used to provide a framework to study the stability of general linear control systems. These include time-varying systems modeled with unbounded state-space operators acting on Banach spaces. This approach allows one to apply the classical theory of strongly continuous semigroups to time-varying systems. In particular, the complex stability radius may be expressed explicitly in terms of the generator of a (evolution) semigroup. Examples are given to show that classical formulas for the stability radius of an autonomous Hilbert-space system fail in more general settings. Upper and lower bounds on the stability radius are provided for these general systems. In addition, it is shown that the theory of evolution semigroups allows for a straightforward operator-theoretic analysis of internal stability as determined by classical frequency-domain and input-output operators, even for nonautonomous Banach-space systemsComment: Also at http://www.math.missouri.edu/~stephen/preprint
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