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Browsing by Author "Mann, D. G."

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  • Diatom classification in ecological applications
    Publication . Loke, R. E.; du Buf, J. M. H.; Bayer, M. M.; Mann, D. G.
    We apply new contour features: (1) Point features by computing the convexity and curvature in small Contour neighborhoods. (2) Segment features by segmenting the contour into convex, concave and straight segments, and computing length and curvature measures for each segment. (3) Global features by computing the mean, maximum and minimum of all point and segment features. Features can be extracted from noisy contours with convex, concave and straight parts, but also from completely convex ones, for the purpose of shape analysis or identification (ID) tasks. Using only four global features, a nearest-mean classifier yielded a perfect ID rate of 100% on diatoms with minute differences in shape, which are difficult to identify, even for diatomists. (C) 2003 Pattern Recognition Society. Published by Elsevier Ltd. All rights reserved.
    2004Journal article Restricted access Show more
  • Diatom recognition by convex and concave contour curvature
    Publication . Loke, R. E.; Bayer, M. M.; Mann, D. G.; du Buf, J. M. H.
    In this paper we describe a new contour feature set. A contour is segmented into convex, concave and straight segments, after which length and curvature features are computed. A symmetry analysis allows the detection of the number of elementary segments. Results on two contour test sets were obtained: Using only four features, a simple nearest-mean classifier yielded a perfect identification (ID) rate of 100% on a small set consisting of shapes with minute differences, which are difficult to identify even for human experts. Using 10 features, it yielded 83.5% on a large set with very diverse shapes.
    2002Conference object Restricted access Show more
  • The Sellaphora pupula species complex (Bacillariophyceae): morphometric analysis, ultrastructure and mating data provide evidence for five new species
    Publication . Mann, D. G.; McDonald, S.M.; Bayer, M. M.; Droop, S. J. M.; Chepurnov, V. A.; Loke, R. E.; Ciobanu, A.; du Buf, J. M. H.
    Morphometric shape analysis and ultrastructural data are provided for six genodemes of the Sellaphora pupula species complex that have been studied during the last 20 years from Blackford Pond, Edinburgh, UK. The demes have previously been shown to be separated by prezygotic reproductive barriers: cells of different demes do not pair, though they may show residual interactions when sexualized. A new morphometric method, contour segment analysis, which was recently developed for diatoms in relation to automated identification, gives a clear separation of all six genodemes and indicates no heterogeneity within each. Legendre shape analysis gives less separation in this instance. All other available data, including molecular sequence data, also support separation of the six demes at species level. Five new species are therefore described: S. auldreekie, S. blackfordensis, S. capitata, S. lanceolata and S. obesa. The identity of S. pupula sensu stricto is clarified through designation of epitypes.
    2004Journal article Restricted access Show more