195,333 research outputs found

    Spectrum Trading: An Abstracted Bibliography

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    This document contains a bibliographic list of major papers on spectrum trading and their abstracts. The aim of the list is to offer researchers entering this field a fast panorama of the current literature. The list is continually updated on the webpage \url{http://www.disp.uniroma2.it/users/naldi/Ricspt.html}. Omissions and papers suggested for inclusion may be pointed out to the authors through e-mail (\textit{[email protected]})

    Satellite downlink scheduling problem: A case study

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    The synthetic aperture radar (SAR) technology enables satellites to efficiently acquire high quality images of the Earth surface. This generates significant communication traffic from the satellite to the ground stations, and, thus, image downlinking often becomes the bottleneck in the efficiency of the whole system. In this paper we address the downlink scheduling problem for Canada's Earth observing SAR satellite, RADARSAT-2. Being an applied problem, downlink scheduling is characterised with a number of constraints that make it difficult not only to optimise the schedule but even to produce a feasible solution. We propose a fast schedule generation procedure that abstracts the problem specific constraints and provides a simple interface to optimisation algorithms. By comparing empirically several standard meta-heuristics applied to the problem, we select the most suitable one and show that it is clearly superior to the approach currently in use.Comment: 23 page

    Combustion chemistry of solid propellants

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    Several studies are described of the chemistry of solid propellant combustion which employed a fast-scanning optical spectrometer. Expanded abstracts are presented for four of the studies which were previously reported. One study of the ignition of composite propellants yielded data which suggested early ammonium perchlorate decomposition and reaction. The results of a study of the spatial distribution of molecular species in flames from uncatalyzed and copper or lead catalyzed double-based propellants support previously published conclusions concerning the site of action of these metal catalysts. A study of the ammonium-perchlorate-polymeric-fuel-binder reaction in thin films, made by use of infrared absorption spectrometry, yielded a characterization of a rapid condensed-phase reaction which is likely important during the ignition transient and the burning process

    Using high resolution displays for high resolution cardiac data

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    The ability to perform fast, accurate, high resolution visualization is fundamental to improving our understanding of anatomical data. As the volumes of data increase from improvements in scanning technology, the methods applied to rendering and visualization must evolve. In this paper we address the interactive display of data from high resolution MRI scanning of a rabbit heart and subsequent histological imaging. We describe a visualization environment involving a tiled LCD panel display wall and associated software which provide an interactive and intuitive user interface. The oView software is an OpenGL application which is written for the VRJuggler environment. This environment abstracts displays and devices away from the application itself, aiding portability between different systems, from desktop PCs to multi-tiled display walls. Portability between display walls has been demonstrated through its use on walls at both Leeds and Oxford Universities. We discuss important factors to be considered for interactive 2D display of large 3D datasets, including the use of intuitive input devices and level of detail aspects

    Does fast Growth in India and China harm U.S. Workers? Insights from Simulation Evidence

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    A major political and policy issue today is whether globalisation and rapid economic growth in India and China would have an adverse affect on labour markets in the U.S. and other advanced countries. Some leading economists have argued that even though the recent integration of India and China with the liberalised global economy has not so far had a serious negative impact on wages and employment in advanced countries, it is most likely to do so in the future in view of the growing technological and scientific capabilities in the two developing countries. This is also because it is suggested that this integration represents a sudden doubling of the world labour force without a concomitant increase in capital. The present paper argues against this plausible thesis, essentially on two grounds: (a) it does not take into account the demand side effects of fast growth in India and China; and (b) it abstracts from the dynamism of the U.S. real economy and its innovative large corporations. However, simulations of different scenarios on the CAM world econometric model indicate that at a disaggregated level there are severe supply side constraints on energy, raw materials and food which thwart the expansionary demand side effects of fast growth in India and China.Globalisation; China and India; Simulation; U.S. Workers; Economic integration
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