21,660 research outputs found

    Re-Scaling of Energy in the Stringy Charged Black Hole Solutions using Approximate Symmetries

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    This paper is devoted to study the energy problem in general relativity using approximate Lie symmetry methods for differential equations. We evaluate second-order approximate symmetries of the geodesic equations for the stringy charged black hole solutions. It is concluded that energy must be re-scaled by some factor in the second-order approximation.Comment: 18 pages, accepted for publication in Canadian J. Physic

    Water for rural development: Background paper on water for rural development prepared for the World Bank

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    Water management / Irrigation management / Rural development / Water resources development / Small scale systems / Land management / Groundwater / Environment / Health / Water policy / Institutions / Food consumption / Water supply / Water demand / Water allocation / Crop yield / Cereals / Water scarcity / Food production / Food security / Crop production / Population growth

    Productivity and performance of irrigated wheat farms across canal commands in the Lower Indus Basin

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    Irrigated farmingWheatProductivityPerformance evaluationWater managementCropping systemsWater supplySoil propertiesModels

    A Framework for analyzing socioeconomic, health and environmental impacts of wastewater use in agriculture in developing countries

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    Waste water management / Environmental degradation / Waterborne diseases / Water quality / Irrigation practices / Aquaculture / Economic analysis / Social aspects / Health / Environmental aspects / Agriculture / Developing countries / Policy

    The Coronal Structure of AB Doradus

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    We perform a numerical simulation of the corona of the young, rapidly rotating K0 dwarf AB Doradus using a global MHD model. The model is driven by a surface map of the radial magnetic field constructed using Zeeman-Doppler Imaging. We find that the global structure of the stellar corona is dominated by strong azimuthal tangling of the magnetic field due to the rapid rotation. The MHD solution enables us to calculate realistic Alfv\'en surfaces and we can therefore estimate the stellar mass loss rate and angular momentum loss rate without making undue theoretical simplifications. We consider three cases, parametrized by the base density of the corona, that span the range of possible solutions for the system. We find that overall, the mass and angular-momentum loss rates are higher than in the solar case; the mass loss rates are 10 to 500 times higher, and the angular momentum loss rate can be up to 3×1043\times{10}^4 higher than present day solar values. Our simulations show that this model can be use to constrain the wide parameter space of stellar systems. It also shows that an MHD approach can provide more information about the physical system over the commonly used potential field extrapolation.Comment: 13 pages, 7 figure
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