35,400 research outputs found

    Mains power quality improvement using active filters

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    World city network research at a theoretical impasse::On the need to re-establish qualitative approaches to understanding agency in world city networks

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    From the late 1990s, the establishment of a new relational ‘turn’ in the study of world city connectedness in globalization has run parallel to the wider relational turn occurring in economic geography. Early work, built firmly upon a qualitative approach to the collection and analyses of new inter-city datasets, considered cities as being constituted by their relations with other cities. Subsequent research, however, would take a strong quantitative turn, best demonstrated through the articulation of the inter-locking world city network (ILWCN) ‘model’ for measuring relations between cities. In this paper, we develop a critique of research based around the ILWCN model, arguing that this ‘top down’ quantitative approach has now reached a theoretical impasse. To address this impasse, we argue for a move away from Structural approaches in which the firm is the main unit of analysis, towards qualitative approaches in which individual agency and practice are afforded greater importance

    Rurality and Minimal Architecture: An Inquiry into the Genealogy of Tate Modern’s Bankside Gallery Spaces

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    When the Tate institution first announced its plans to build a ‘Tate Modern’ gallery on London’s Bankside it stated its preferences for a ‘rural’ and ‘minimal’ architecture. These are contested terms whose significance for the resultant contemporary art space is by no means apparent. Focusing on the suites of gallery-rooms built on levels 2, 3 & 4, as part of the initial power station transformation, which opened to the public in 2000, this paper will examine the notions of rurality and minimal architecture that underpin the contemporary art space. It will weave their genealogy out of three themes: First, the Tate’s stated interest in the Louisiana Museum of Modern Art in HumlebĂŠk as a potential model for the new gallery. Second, the influence of the artist RĂ©my Zaugg, who had worked with Tate’s architects for the project, Herzog and de Meuron, on a number of studio-gallery projects prior to the Tate commission. Third, the modernist tradition of the ‘white cube’ and its post-modern critique dating from the mid 1970s

    Roche tomography of the secondary stars in CVs

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    The secondary stars in cataclysmic variables (CVs) are key to our understanding of the origin, evolution and behaviour of this class of interacting binary. In seeking a fuller understanding of these objects, the challenge for observers is to obtain images of the secondary star. This goal can be achieved through Roche tomography, an indirect imaging technique that can be used to map the Roche-lobe-filling secondary. The review begins with a description of the basic principles that underpin Roche tomography, including methods for determining the system parameters. Finally, we conclude with a look at the main scientific highlights to date, including the first unambiguous detection of starspots on AE Aqr B, and consider the future prospects of this technique.Comment: 4 pages, 4 figures. Accepted for publication in A

    A general theory for preferential sampling in environmental networks

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    This paper presents a general model framework for detecting the preferential sampling of environmental monitors recording an environmental process across space and/or time. This is achieved by considering the joint distribution of an environmental process with a site--selection process that considers where and when sites are placed to measure the process. The environmental process may be spatial, temporal or spatio--temporal in nature. By sharing random effects between the two processes, the joint model is able to establish whether site placement was stochastically dependent of the environmental process under study. The embedding into a spatio--temporal framework also allows for the modelling of the dynamic site---selection process itself. Real--world factors affecting both the size and location of the network can be easily modelled and quantified. Depending upon the choice of population of locations to consider for selection across space and time under the site--selection process, different insights about the precise nature of preferential sampling can be obtained. The general framework developed in the paper is designed to be easily and quickly fit using the R-INLA package. We apply this framework to a case study involving particulate air pollution over the UK where a major reduction in the size of a monitoring network through time occurred. It is demonstrated that a significant response--biased reduction in the air quality monitoring network occurred. We also show that the network was consistently unrepresentative of the levels of particulate matter seen across much of GB throughout the operating life of the network. Finally we show that this may have led to a severe over-reporting of the population--average exposure levels experienced across GB. This could have great impacts on estimates of the health effects of black smoke levels.Comment: 33 pages of main text, 48 including the supplementary materia

    Encouraging the perceptual underdog: positive affective priming of nonpreferred local–global processes

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    Two experiments examined affective priming of global and local perception. Participants attempted to detect a target that might be present as either a global or a local shape. Verbal primes were used in 1 experiment, and pictorial primes were used in the other. In both experiments, positive primes led to improved performance on the nonpreferred dimension. For participants exhibiting global precedence, detection of local targets was significantly improved, whereas for participants exhibiting local precedence, detection of global targets was significantly improved. The results provide support for an interpretation of the effects of positive affective priming in terms of increased perceptual flexibility

    Inversion of stellar fundamental parameters from Espadons and Narval high-resolution spectra

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    The general context of this study is the inversion of stellar fundamental parameters from high-resolution Echelle spectra. We aim indeed at developing a fast and reliable tool for the post-processing of spectra produced by Espadons and Narval spectropolarimeters. Our inversion tool relies on principal component analysis. It allows reduction of dimensionality and the definition of a specific metric for the search of nearest neighbours between an observed spectrum and a set of observed spectra taken from the Elodie stellar library. Effective temperature, surface gravity, total metallicity and projected rotational velocity are derived. Various tests presented in this study, and done from the sole information coming from a spectral band centered around the Mg I b-triplet and with spectra from FGK stars are very promising.Comment: 13 pages, 8 figures (accepted A&A). arXiv admin note: text overlap with arXiv:1401.108

    Nitrogen transfer between clover and wheat in an intercropping experiment

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    A novel approach to the problem of improving nitrogen supply in organic farming is to use intercropping of cereals with a legume to provide nitrogen transfer within a season and/or to following crops. The affects of intercropping were studied in a column experiment using mixtures of winter wheat (Triticum aestivum cv. Claire), with white clover (w.c.) (Trifolium repens cv. Barblanca) and with red clover (r.c.) (Trifolium pratense cv. Britta). The effects of cutting and removal above ground clover material with and without additional soil disturbance were compared to leaving clover plants in situ and intercropped with wheat in a split root design. Wheat and clover plants, as monocultures, were used for the controls. 15N ammonium nitrate solution was applied. The wheat seeds were sown into the column without nitrogen. We found that the cutting treatment produced the highest yield of wheat. Available ammonium-N in the soil was greatest in the clover control treatment for the column with only red clover roots and in the cutting+soil disturbance treatment for the column with only white clover roots. Available nitrate-N was greatest in the soil disturbance treatment in the column with clover and wheat roots for both red and white clover. The cutting treatment produced the highest yield of wheat
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