989 research outputs found

    Visualising Time

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    This study investigates the visualisation of temporal relationships between objects. A popular method employed for such information visualisations is the time line consisting of a single horizontal axis along which temporal events or objects are depicted at specific points or intervals. The orientation of the temporal progression along the axis line will generally coincide with the orientation of the literary writing progression of the culture and language. For example a time line visualised in a Western culture with English as its literary base will exhibit a temporal progression orientation of early/left, later/right whereas Arabian culture with an Arabic literary base will exhibit the reverse temporal progression orientation. In both cultures and languages temporal metaphor use spatial concepts to describe temporal relationships with no discourse to transversal orientation. This is reflected by never hearing the phrase “the months to the right” but rather “the months ahead”. In science, Einstein showed via his special and general theories of relativity that time and space are interlinked. The scientific rationalisation of time and space along with the use of spatial concepts as temporal metaphor implies that the underlying perception of time is spatial. Information visualisations are the externalisations of our perceptions. Therefore temporal information visualisations should employ spatial visualisation techniques. This study evaluated spatial visualisation techniques for temporal information visualisations via a web survey. The spatial temporal information visualisations used in the survey employed no temporal cues such as time or date stamps but conferred all temporal progression via spatial cues. The findings from the analysis of the participant responses to the survey showed that spatial cues do impart temporal cues for temporal relationships

    The Ends of the Earth: Defining an Australian Sense of an Ending

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    Both Patrick White and D. H. Lawrence are writers obsessed with the of an ending. Critics have already begup to explore the primary function of apocalypse in much of their respective work; thematically and structurally, it is not hard to see that both authors were haunted (or hounded) by Christian eschatology, and that the apocalyptic types are major sources for interpreting their works

    Field Results from Three Campaigns to Validate the Performance of the Miniaturized Laser Heterodyne Radiometer (MiniLHR) for Measuring Carbon Dioxide and Methane in the Atmospheric Column

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    In a collaboration between NASA GSFC and GWU, a low-cost, surface instrument is being developed that can continuously monitor key carbon cycle gases in the atmospheric column: carbon dioxide (CO2) and methane (CH4). The instrument is based on a miniaturized, laser heterodyne radiometer (LHR) using near infrared (NIR) telecom lasers. Despite relatively weak absorption line strengths in this spectral region, spectrallyresolved atmospheric column absorptions for these two molecules fall in the range of 60-80% and thus sensitive and precise measurements of column concentrations are possible. In the last year, the instrument was deployed for field measurements at Park Falls, Wisconsin; Castle Airport near Atwater, California; and at the NOAA Mauna Loa Observatory in Hawaii. For each subsequent campaign, improvement in the figures of merit for the instrument has been observed. In the latest work the absorbance noise is approaching 0.002 optical density (OD) noise on a 1.8 OD signal. An overview of the measurement campaigns and the data retrieval algorithm for the calculation of column concentrations will be presented. For light transmission through the atmosphere, it is necessary to account for variation of pressure, temperature, composition, and refractive index through the atmosphere that are all functions of latitude, longitude, time of day, altitude, etc. For temperature, pressure, and humidity profiles with altitude we use the Modern-Era Retrospective Analysis for Research and Applications (MERRA) data. Spectral simulation is accomplished by integrating short-path segments along the trajectory using the SpecSyn spectral simulation suite developed at GW. Column concentrations are extracted by minimizing residuals between observed and modeled spectrum using the Nelder-Mead simplex algorithm. We will also present an assessment of uncertainty in the reported concentrations from assumptions made in the meteorological data, LHR instrument and tracker noise, and radio frequency bandwidth and describe additional future goals in instrument development and deployment targe

    The crime drop and the security hypothesis

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    Major crime drops were experienced in the United States and most other industrialised countries for a decade from the early to mid-1990s. Yet there is little agreement over explanation or lessons for policy. Here it is proposed that change in the quantity and quality of security was a key driver of the crime drop. From evidence relating to vehicle theft in two countries it is concluded that electronic immobilisers and central locking were particularly effective. It is suggested that reduced car theft may have induced drops in other crime including violence. From this platform a broader security hypothesis, linked to routine activity and opportunity theory, is outlined

    Are the Faraday Rotating Magnetic Fields Local to Intracluster Radio Galaxies?

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    We investigate the origin of the high Faraday rotation measures (RMs) found for polarized radio galaxies in clusters. The two most likely origins are, magnetic fields local to the source, or magnetic fields located in the foreground intra-cluster medium (ICM). The latter is identified as the null hypothesis. Rudnick & Blundell (2003) have recently suggested that the presence of magnetic fields local to the source may be revealed in correlations of the position angles (PAs) of the source intrinsic linear polarization and the RMs. We investigate the claim of Rudnick & Blundell to have found a relationship between the intrinsic PA0 of the radio source PKS 1246-410 and its RM, by testing the clustering strength of the PA0-RM scatter plot. We show that the claimed relationship is an artifact of an improperly performed null-experiment. We describe a gradient alignment statistic aimed at finding correlations between PA0 and RM maps. This statistic does not require any null-experiment since it gives a unique (zero) result in the case of uncorrelated maps. We apply it to a number of extended radio sources in galaxy clusters (PKS 1246-410, Cygnus A, Hydra A, and 3C465). In no case is a significant large-scale alignment of PA0 and RM maps detected. We find significant small-scale co-alignment in all cases, but we are able to fully identify this with map making artifacts through a suitable statistical test. We conclude that there is presently no existing evidence for Faraday rotation local to radio lobes. Given the existing independent pieces of evidence, we favor the null hypothesis that the observed Faraday screens are produced by intracluster magnetic fields.Comment: accepted by ApJ, 8 pages, 1 figure, minor style improvement
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