6,518 research outputs found

    Design rules for technical-biological bank protection on non-tidal, navigable waterways

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    Good Governance of land and natural resources : Balancing local and global interests

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    This report presents the results of a seminar on ‘good governance of land and natural resources; balancing local and global interests’. Three case studies were presented on large-scale land acquisitions, biofuels – fuelling development in Brazil and governance of the mineral sector in Eastern DRC. Participants identified 6 important challenges for improving land and natural resource governance and concluded that: more research and information sharing is needed; collaborative voluntary and legally binding initiatives are needed at international level to balance local and global interests; accountability arrangements need to be set up that enable stakeholders to hold each other accountable; capacity building of all actors is needed and that each actor has its own contributions to make to good governance

    Unstable vortices do not confine

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    Recently, a geometric model for the confinement of magnetic charges in the context of type II string compactifications was constructed by Greene, Morrison and Vafa. This model assumes the existence of stable magnetic vortices with quantized flux in the low energy theory. However, quantization of flux alone does not imply that the vortex is stable, since the flux may not be confined to a tube of definite size. We show that in the field theoretical model which underlies the geometric model of confinement, static, cylindrically symmetric magnetic vortices do not exist. While our results do not preclude the existence of confinement in a different low-energy regime of string theory, they show that confinement is not a universal outcome of the string picture, and its origin in the low energy theory remains to be understood.Comment: Latex, 8 page

    The role, opportunities and challenges of 3D and geo-ICT in archaeology

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    Archaeology joins in the trend of three-dimensional (3D) data and geospatial information technology (geo-ICT). Currently, the spatial archaeological data acquired is 3D and mostly used to create realistic visualizations. Geographical information systems (GIS) are used for decades in archaeology. However, the integration of geo-ICT with 3D data still poses some problems. Therefore, this paper clarifies the current role of 3D, and the opportunities and challenges for 3D and geo-ICT in the domain of archaeology. The paper is concluded with a proposal to integrate both trends and tackle the outlined challenges. To provide a clear illustration of the current practices and the advantages and difficulties of 3D and geo-ICT in the specific case of archaeology, a limited case study is presented of two structures in the Altay Mountains

    Realisations of W3W_3 Symmetry

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    We perform a systematic investigation of free-scalar realisations of the Za\-mo\-lod\-chi\-kov W3W_3 algebra in which the operator product of two spin-three generators contains a non-zero operator of spin four which has vanishing norm. This generalises earlier work where such an operator was required to be absent. By allowing this spin-four null operator we obtain several realisations of the W3W_3 algebra both in terms of two scalars as well as in terms of an arbitrary number nn of free scalars. Our analysis is complete for the case of two-scalar realisations.Comment: 14 pages, LATEX, UG-6/9
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