20,708 research outputs found
Applications of Evolutionary Economic Geography
This paper is written as the first chapter of an edited volume on evolutionary economics and economic geography (Frenken, K., editor, Applied Evolutionary Economics and Economic Geography, Cheltenham: Edward Elgar, expected publication date February 2007). The paper reviews empirical applications of evolutionary economics in the field of economic geography. The review is divided in four parts: the micro-level of the firm, the meso-levels of industry and network, and the macro-level of spatial system. Some remarks on evolutionary policy in regional development are added as well as a short discussion of empirical problems that remain.
Great cities look small
Great cities connect people; failed cities isolate people. Despite the
fundamental importance of physical, face-to-face social-ties in the functioning
of cities, these connectivity networks are not explicitly observed in their
entirety. Attempts at estimating them often rely on unrealistic
over-simplifications such as the assumption of spatial homogeneity. Here we
propose a mathematical model of human interactions in terms of a local strategy
of maximising the number of beneficial connections attainable under the
constraint of limited individual travelling-time budgets. By incorporating
census and openly-available online multi-modal transport data, we are able to
characterise the connectivity of geometrically and topologically complex
cities. Beyond providing a candidate measure of greatness, this model allows
one to quantify and assess the impact of transport developments, population
growth, and other infrastructure and demographic changes on a city. Supported
by validations of GDP and HIV infection rates across United States metropolitan
areas, we illustrate the effect of changes in local and city-wide
connectivities by considering the economic impact of two contemporary inter-
and intra-city transport developments in the United Kingdom: High Speed Rail 2
and London Crossrail. This derivation of the model suggests that the scaling of
different urban indicators with population size has an explicitly mechanistic
origin.Comment: 19 pages, 8 figure
The Extent and spatial scale of connectivity among reef fish populations: implications for marine protected areas designated for fisheries enhancement
Enthusiasm for the use of no-take marine protected areas (MPAs) as management tools for the protection and enhancement of coral reef fishes is widespread. However, evidence that such marine reserves actually enhance fishery yields is limited, primarily because of difficulties in quantifying the exchange of individuals—especially larvae—between local populations within and outside the protected area. Knowledge of the extent and spatial scale of this connectivity is of vital importance for the effective design and implementation of marine reserves intended as fishery management tools. We review our current understanding of connectivity among coral reef populations, including the role of important determining factors such as pelagic larval duration, larval behavior, and hydrodynamics. We also discuss artificial and natural tagging methods that potentially can be used to track movements of larvae between marine reserves and surrounding waters. To illustrate the application of such methods, we discuss ECONAR (Ecological CONnections Among Reefs), a new, regional-scale research project designed to measure the extent of connectivity among populations of coral reef fishes in the Mesoamerican Barrier Reef System
Synchronization in complex networks
Synchronization processes in populations of locally interacting elements are
in the focus of intense research in physical, biological, chemical,
technological and social systems. The many efforts devoted to understand
synchronization phenomena in natural systems take now advantage of the recent
theory of complex networks. In this review, we report the advances in the
comprehension of synchronization phenomena when oscillating elements are
constrained to interact in a complex network topology. We also overview the new
emergent features coming out from the interplay between the structure and the
function of the underlying pattern of connections. Extensive numerical work as
well as analytical approaches to the problem are presented. Finally, we review
several applications of synchronization in complex networks to different
disciplines: biological systems and neuroscience, engineering and computer
science, and economy and social sciences.Comment: Final version published in Physics Reports. More information
available at http://synchronets.googlepages.com
Digital Ecosystems: Ecosystem-Oriented Architectures
We view Digital Ecosystems to be the digital counterparts of biological
ecosystems. Here, we are concerned with the creation of these Digital
Ecosystems, exploiting the self-organising properties of biological ecosystems
to evolve high-level software applications. Therefore, we created the Digital
Ecosystem, a novel optimisation technique inspired by biological ecosystems,
where the optimisation works at two levels: a first optimisation, migration of
agents which are distributed in a decentralised peer-to-peer network, operating
continuously in time; this process feeds a second optimisation based on
evolutionary computing that operates locally on single peers and is aimed at
finding solutions to satisfy locally relevant constraints. The Digital
Ecosystem was then measured experimentally through simulations, with measures
originating from theoretical ecology, evaluating its likeness to biological
ecosystems. This included its responsiveness to requests for applications from
the user base, as a measure of the ecological succession (ecosystem maturity).
Overall, we have advanced the understanding of Digital Ecosystems, creating
Ecosystem-Oriented Architectures where the word ecosystem is more than just a
metaphor.Comment: 39 pages, 26 figures, journa
The Global City as a Space for Transnational Identity Politics
Global Cities are key nodes in circuits of transnational political activity. As dense spaces of political interaction, cities provide bundles of material, political and ideational resources that allow for the generation of new identities and frames of meaning, shifts in tactical and strategic alliances, and network brokerage activities. The key function of cities in facilitating transnationalism has not been adequately explored in the existing International Relations literature on transnationalism. In this paper, we use the case of London as a Global City to examine how its features as a dense institutional context; a node in multiple global networks; and as a resource-rich environment creates a creative space for innovations in transnational politics. We focus on the strategies employed by identity-based transnational political entrepreneurs and discuss four mechanisms of mobilization: brokerage (the linking of disparate networks), strategic framing (the use of symbolic politics), coalition-building (the forging of alliances between organizations) and social learning or mediated diffusion (the adoption of new ideas and practices). Our analysis challenges both standard state-centric and single-case study accounts of transnational activity, suggesting a novel site of investigation for IR scholars
Griffiths phases and localization in hierarchical modular networks
We study variants of hierarchical modular network models suggested by Kaiser
and Hilgetag [Frontiers in Neuroinformatics, 4 (2010) 8] to model functional
brain connectivity, using extensive simulations and quenched mean-field theory
(QMF), focusing on structures with a connection probability that decays
exponentially with the level index. Such networks can be embedded in
two-dimensional Euclidean space. We explore the dynamic behavior of the contact
process (CP) and threshold models on networks of this kind, including
hierarchical trees. While in the small-world networks originally proposed to
model brain connectivity, the topological heterogeneities are not strong enough
to induce deviations from mean-field behavior, we show that a Griffiths phase
can emerge under reduced connection probabilities, approaching the percolation
threshold. In this case the topological dimension of the networks is finite,
and extended regions of bursty, power-law dynamics are observed. Localization
in the steady state is also shown via QMF. We investigate the effects of link
asymmetry and coupling disorder, and show that localization can occur even in
small-world networks with high connectivity in case of link disorder.Comment: 18 pages, 20 figures, accepted version in Scientific Report
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