7,515 research outputs found

    Mainstreaming Gender Into Project Cycle Management in the Fisheries Sector

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    This manual has been prepared to facilitate gender analysis and project planning in fisheries development projects. It is intended to be a toolkit to help project managers and implementing counterparts (such as extensionists, government and non-government field workers, and private- and public-sector development consultants, community organizers and leaders of local groups), to facilitate the integration of gender issues into the project cycle

    Modeling Structure and Resilience of the Dark Network

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    While the statistical and resilience properties of the Internet are no more changing significantly across time, the Darknet, a network devoted to keep anonymous its traffic, still experiences rapid changes to improve the security of its users. Here, we study the structure of the Darknet and we find that its topology is rather peculiar, being characterized by non-homogenous distribution of connections -- typical of scale-free networks --, very short path lengths and high clustering -- typical of small-world networks -- and lack of a core of highly connected nodes. We propose a model to reproduce such features, demonstrating that the mechanisms used to improve cyber-security are responsible for the observed topology. Unexpectedly, we reveal that its peculiar structure makes the Darknet much more resilient than the Internet -- used as a benchmark for comparison at a descriptive level -- to random failures, targeted attacks and cascade failures, as a result of adaptive changes in response to the attempts of dismantling the network across time.Comment: 8 pages, 5 figure

    Dynamical properties of model communication networks

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    We study the dynamical properties of a collection of models for communication processes, characterized by a single parameter ξ\xi representing the relation between information load of the nodes and its ability to deliver this information. The critical transition to congestion reported so far occurs only for ξ=1\xi=1. This case is well analyzed for different network topologies. We focus of the properties of the order parameter, the susceptibility and the time correlations when approaching the critical point. For ξ<1\xi<1 no transition to congestion is observed but it remains a cross-over from a low-density to a high-density state. For ξ>1\xi>1 the transition to congestion is discontinuous and congestion nuclei arise.Comment: 8 pages, 8 figure

    Communication and optimal hierarchical networks

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    We study a general and simple model for communication processes. In the model, agents in a network (in particular, an organization) interchange information packets following simple rules that take into account the limited capability of the agents to deal with packets and the cost associated to the existence of open communication channels. Due to the limitation in the capability, the network collapses under certain conditions. We focus on when the collapse occurs for hierarchical networks and also on the influence of the flatness or steepness of the structure. We find that the need for hierarchy is related to the existence of costly connections.Comment: 7 pages, 2 figures. NATO ARW on Econophysic

    On Self-Organized Criticality and Synchronization in Lattice Models of Coupled Dynamical Systems

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    Lattice models of coupled dynamical systems lead to a variety of complex behaviors. Between the individual motion of independent units and the collective behavior of members of a population evolving synchronously, there exist more complicated attractors. In some cases, these states are identified with self-organized critical phenomena. In other situations, with clusterization or phase-locking. The conditions leading to such different behaviors in models of integrate-and-fire oscillators and stick-slip processes are reviewed.Comment: 41 pages. Plain LaTeX. Style included in main file. To appear as an invited review in Int. J. Modern Physics B. Needs eps

    Adaptive Mixture Methods Based on Bregman Divergences

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    We investigate adaptive mixture methods that linearly combine outputs of mm constituent filters running in parallel to model a desired signal. We use "Bregman divergences" and obtain certain multiplicative updates to train the linear combination weights under an affine constraint or without any constraints. We use unnormalized relative entropy and relative entropy to define two different Bregman divergences that produce an unnormalized exponentiated gradient update and a normalized exponentiated gradient update on the mixture weights, respectively. We then carry out the mean and the mean-square transient analysis of these adaptive algorithms when they are used to combine outputs of mm constituent filters. We illustrate the accuracy of our results and demonstrate the effectiveness of these updates for sparse mixture systems.Comment: Submitted to Digital Signal Processing, Elsevier; IEEE.or
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