11,590 research outputs found
Gridding of near vertical unrectified space photographs
Gridding of near vertical unrectified space photograph
Selecting a Small Set of Optimal Gestures from an Extensive Lexicon
Finding the best set of gestures to use for a given computer recognition
problem is an essential part of optimizing the recognition performance while
being mindful to those who may articulate the gestures. An objective function,
called the ellipsoidal distance ratio metric (EDRM), for determining the best
gestures from a larger lexicon library is presented, along with a numerical
method for incorporating subjective preferences. In particular, we demonstrate
an efficient algorithm that chooses the best gestures from a lexicon of
gestures where typically using a weighting of both subjective and
objective measures.Comment: 27 pages, 7 figure
Improved Algorithms for Radar-based Reconstruction of Asteroid Shapes
We describe our implementation of a global-parameter optimizer and Square
Root Information Filter (SRIF) into the asteroid-modelling software SHAPE. We
compare the performance of our new optimizer with that of the existing
sequential optimizer when operating on various forms of simulated data and
actual asteroid radar data. In all cases, the new implementation performs
substantially better than its predecessor: it converges faster, produces shape
models that are more accurate, and solves for spin axis orientations more
reliably. We discuss potential future changes to improve SHAPE's fitting speed
and accuracy.Comment: 12 pages, 9 figure
Oriented tensor reconstruction: tracing neural pathways from diffusion tensor MRI
In this paper we develop a new technique for tracing anatomical fibers from 3D tensor fields. The technique extracts salient tensor features using a local regularization technique that allows the algorithm to cross noisy regions and bridge gaps in the data. We applied the method to human brain DT-MRI data and recovered identifiable anatomical structures that correspond to the white matter brain-fiber pathways. The images in this paper are derived from a dataset having 121x88x60 resolution. We were able to recover fibers with less than the voxel size resolution by applying the regularization technique, i.e., using a priori assumptions about fiber smoothness. The regularization procedure is done through a moving least squares filter directly incorporated in the tracing algorithm
Detailed Decomposition of Galaxy Images. II. Beyond Axisymmetric Models
We present a two-dimensional (2-D) fitting algorithm (GALFIT, Version 3) with
new capabilities to study the structural components of galaxies and other
astronomical objects in digital images. Our technique improves on previous 2-D
fitting algorithms by allowing for irregular, curved, logarithmic and power-law
spirals, ring and truncated shapes in otherwise traditional parametric
functions like the Sersic, Moffat, King, Ferrer, etc., profiles. One can mix
and match these new shape features freely, with or without constraints, apply
them to an arbitrary number of model components and of numerous profile types,
so as to produce realistic-looking galaxy model images. Yet, despite the
potential for extreme complexity, the meaning of the key parameters like the
Sersic index, effective radius or luminosity remain intuitive and essentially
unchanged. The new features have an interesting potential for use to quantify
the degree of asymmetry of galaxies, to quantify low surface brightness tidal
features beneath and beyond luminous galaxies, to allow more realistic
decompositions of galaxy subcomponents in the presence of strong rings and
spiral arms, and to enable ways to gauge the uncertainties when decomposing
galaxy subcomponents. We illustrate these new features by way of several case
studies that display various levels of complexity.Comment: 41 pages, 22 figures, AJ accepted. Minor changes. Full resolution
version of this paper is available at:
http://users.obs.carnegiescience.edu/peng/work/galfit/galfit3.pd
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