1,721,212 research outputs found
Cortical dynamics of lateral inhibition: Visual persistence and ISI.
No full textBurr (1980) observed that moving stimuli were not as blurred as would be expected. Studies of visual persistence show that stimuli persist for hundreds of milliseconds (e.g., While the idea of persistence as a fading trace is intuitively appealing, the mechanisms underlying the trace and their interaction with mechanisms of lateral inhibition appear to be more complicated than the Farrell et al. (1990) description. Di Lollo and Other theories emphasize the influence of lateral inhibition rather than the properties of a fading trace. Di Francis, Grossberg, and Mingolla (1994) took a different approach by showing that the mechanisms of a neural network theory of visual perception account for some properties of visual persistence. They showed that 1103 Copyright 1996 Psychonomic Society, Inc. Correspondence should be addressed to the author at Department of Psychological Sciences, 1364 Psychological Science Building, Purdue University, West Layfayette, IN 47907-1364 (e-mail: gfrancis@psych. purdue.edu). Cortical dynamics of lateral inhibition: Visual persistence and ISI GREGORY FRANCIS Purdue University, West Lafayette, Indiana Psychophysical studies show that increasing the interstimulus interval (ISI) between two stimuli decreases persistence of the first stimulus. While some researchers account for these results with interactions of transient and sustained inhibition, this paper describes an alternative explanation. In a neural-network model of boundary detection called the boundary contour system, persistence is the result of feedback-generated reverberations. Mechanisms to control these reverberations include lateral inhibition, which computer simulations show allows persistence in the network to qualitatively match the psychophysical data. Additional simulations predict that increasing the duration of the second stimulus should cause persistence to increase with ISI. The model links psychophysical data on visual persistence with computational requirements of spatial vision and properties of cells in visual cortex
Western Australia, exploration of the Murchison & Gascoyne Rivers [cartographic material] /
No full textMap showing F.T. Gregory's tracks of his explorations of the Murchison and Gascoyne Rivers in Western Australia from April 1858 to May 1858. Relief shown by hachures and spot heights.; In lower right margin: Revised original by A. Hillman 1st Asst. Surveyor Augst 185[9].; Also available in an electronic version via the Internet at: http://nla.gov.au/nla.map-rm1205; Library copy signed (Correct copy) J.S. Roe Surveyor General Perth 30 August 1859".Exploration of the Murchison and Gascoyne River
Explorations in North-Western Australia [cartographic material] : by an expedition sent by the British and local governments under the command of F.T. Gregory, F.R.G.S., April to November 1861.
No full textMap showing the time-dated exploration route of Gregory's 1861 expedition over the Pilbara between Ashburton River, Dampier Archipelago and the De Grey River. Francis Thomas Gregory on the ship 'Dolphin' arrived at Nickol Bay in May 1861, and then proceeded to take an expedition through the Pilbara region as far south as the Ashburton River. Landmarks he identified and named include Hearson's Cove, the Maitland and Fortescue rivers, the Hamersley Ranges, Mt Samson and Mt Bruce. His favorable report of the expedition's findings opened up this area to pastoral development. Relief is shown by hachures.; Prime meridian: Greenwich.; Also available in an electronic version via the Internet at: http://nla.gov.au/nla.map-rm1190; Library's copy at RM 1190 is missing a significant section of the map in the top right corner
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Diffraction Tomographic Imaging of Shallowly Buried Targets using Ground Penetrating Radar
No full textThe problem of subsurface imaging with Ground Penetrating Radar (GPR) is a challenging one. Due to the low-pass nature of soil sensors must utilise wave-lengths that are of the same order of magnitude as the object being imaged. This makes imaging difficult as straight ray approximations commonly used in higher frequency applications cannot be used. The problem becomes even more challenging when the target is shallowly buried as in this case the ground surface reflection and the near-field parameters of the radar need to be considered. This thesis has investigated the problem of imaging shallowly buried targets with GPR. Two distinct problems exist in this field radar design and the design of inverse scattering techniques. This thesis focuses on the design of inverse scattering techniques capable of taking the electric field measurements from the receiver and providing accurate images of the scatterer in real time.\ud
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The thesis commences with a brief introduction to GPR theory. It then provides an extensive review of linear inverse scattering techniques applied to raw GPR data. As a result of this review the thesis draws the conclusion that, due to its strong foundations in Maxwell's equations, diffraction tomography is the most appropriate approach for imaging shallowly buried targets with GPR. A three-dimensional diffraction tomographic technique is then developed. This algorithm forms the primary contribution of the thesis.\ud
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The novel diffraction tomography technique improves on its predecessors by catering for shallowly buried targets, significant antenna heights and evanescent waves. This is also the first diffraction tomography technique to be derived for a range of antenna structures. The advantages of the novel technique are demonstrated first mathematically then on synthetic and finally practical data. The algorithm is shown to be of high practical value by producing accurate images of buried targets in real time
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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