1,971 research outputs found
A biologically inspired computational vision front-end based on a self-organised pseudo-randomly tessellated artificial retina
This paper considers the construction of a biologically inspired front-end for computer vision based on an artificial retina pyramid with a self-organised pseudo-randomly tessellated receptive field tessellation. The organisation of photoreceptors and receptive fields in biological retinae locally resembles a hexagonal mosaic, whereas globally these are organised with a very densely tessellated central foveal region which seamlessly merges into an increasingly sparsely tessellated periphery. In contrast, conventional computer vision approaches use a rectilinear sampling tessellation which samples the whole field of view with uniform density. Scale-space interest points which are suitable for higher level attention and reasoning tasks are efficiently extracted by our vision front-end by performing hierarchical feature extraction on the pseudo-randomly spaced visual information. All operations were conducted on a geometrically irregular foveated representation (data structure for visual information) which is radically different to the uniform rectilinear arrays used in conventional computer vision
Menelaus' theorem, Clifford configurations and inversive geometry of the Schwarzian KP hierarchy
It is shown that the integrable discrete Schwarzian KP (dSKP) equation which
constitutes an algebraic superposition formula associated with, for instance,
the Schwarzian KP hierarchy, the classical Darboux transformation and
quasi-conformal mappings encapsulates nothing but a fundamental theorem of
ancient Greek geometry. Thus, it is demonstrated that the connection with
Menelaus' theorem and, more generally, Clifford configurations renders the dSKP
equation a natural object of inversive geometry on the plane. The geometric and
algebraic integrability of dSKP lattices and their reductions to lattices of
Menelaus-Darboux, Schwarzian KdV, Schwarzian Boussinesq and Schramm type is
discussed. The dSKP and discrete Schwarzian Boussinesq equations are shown to
represent discretizations of families of quasi-conformal mappings.Comment: 26 pages, 9 figure
Polycrystalline graphene and other two-dimensional materials
Graphene, a single atomic layer of graphitic carbon, has attracted intense
attention due to its extraordinary properties that make it a suitable material
for a wide range of technological applications. Large-area graphene films,
which are necessary for industrial applications, are typically polycrystalline,
that is, composed of single-crystalline grains of varying orientation joined by
grain boundaries. Here, we present a review of the large body of research
reported in the past few years on polycrystalline graphene. We discuss its
growth and formation, the microscopic structure of grain boundaries and their
relations to other types of topological defects such as dislocations. The
review further covers electronic transport, optical and mechanical properties
pertaining to the characterizations of grain boundaries, and applications of
polycrystalline graphene. We also discuss research, still in its infancy,
performed on other 2D materials such as transition metal dichalcogenides, and
offer perspectives for future directions of research.Comment: review article; part of focus issue "Graphene applications
Adaptive Digital Scan Variable Pixels
The square and rectangular shape of the pixels in the digital images for
sensing and display purposes introduces several inaccuracies in the
representation of digital images. The major disadvantage of square pixel shapes
is the inability to accurately capture and display the details in the objects
having variable orientations to edges, shapes and regions. This effect can be
observed by the inaccurate representation of diagonal edges in low resolution
square pixel images. This paper explores a less investigated idea of using
variable shaped pixels for improving visual quality of image scans without
increasing the square pixel resolution. The proposed adaptive filtering
technique reports an improvement in image PSNR.Comment: 4th International Conference on Advances in Computing, Communications
and Informatics, August, 201
Geometric auxetics
We formulate a mathematical theory of auxetic behavior based on one-parameter
deformations of periodic frameworks. Our approach is purely geometric, relies
on the evolution of the periodicity lattice and works in any dimension. We
demonstrate its usefulness by predicting or recognizing, without experiment,
computer simulations or numerical approximations, the auxetic capabilities of
several well-known structures available in the literature. We propose new
principles of auxetic design and rely on the stronger notion of expansive
behavior to provide an infinite supply of planar auxetic mechanisms and several
new three-dimensional structures
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