52,059 research outputs found
Adaptive threshold optimisation for colour-based lip segmentation in automatic lip-reading systems
A thesis submitted to the Faculty of Engineering and the Built Environment,
University of the Witwatersrand, Johannesburg, in ful lment of the requirements for
the degree of Doctor of Philosophy.
Johannesburg, September 2016Having survived the ordeal of a laryngectomy, the patient must come to terms with
the resulting loss of speech. With recent advances in portable computing power,
automatic lip-reading (ALR) may become a viable approach to voice restoration. This
thesis addresses the image processing aspect of ALR, and focuses three contributions
to colour-based lip segmentation.
The rst contribution concerns the colour transform to enhance the contrast
between the lips and skin. This thesis presents the most comprehensive study to
date by measuring the overlap between lip and skin histograms for 33 di erent
colour transforms. The hue component of HSV obtains the lowest overlap of 6:15%,
and results show that selecting the correct transform can increase the segmentation
accuracy by up to three times.
The second contribution is the development of a new lip segmentation algorithm
that utilises the best colour transforms from the comparative study. The algorithm
is tested on 895 images and achieves percentage overlap (OL) of 92:23% and segmentation
error (SE) of 7:39 %.
The third contribution focuses on the impact of the histogram threshold on the
segmentation accuracy, and introduces a novel technique called Adaptive Threshold
Optimisation (ATO) to select a better threshold value. The rst stage of ATO
incorporates -SVR to train the lip shape model. ATO then uses feedback of shape
information to validate and optimise the threshold. After applying ATO, the SE
decreases from 7:65% to 6:50%, corresponding to an absolute improvement of 1:15 pp
or relative improvement of 15:1%. While this thesis concerns lip segmentation in
particular, ATO is a threshold selection technique that can be used in various
segmentation applications.MT201
A Boltzmann Equation for the QCD Plasma
We present a derivation of a Boltzmann equation for the QCD plasma, starting
from the quantum field equations. The derivation is based on a gauge covariant
gradient expansion which takes consistently into account all possible
dependences on the gauge coupling assumed to be small. We point out a
limitation of the gradient expansion arising when the range of the interactions
becomes comparable with that of the space-time inhomogeneities of the system.
The method is first applied to the case of scalar electrodynamics, and then to
the description of long wavelength colour fluctuations in the QCD plasma. In
the latter case, we recover B\"odeker's effective theory and its recent
reformulation by Arnold, Son and Yaffe. We discuss interesting cancellations
among various collision terms, which occur in the calculation of most transport
coefficients, but not in that of the quasiparticle lifetime, or in that of the
relaxation time of colour excitations.Comment: 58 pages, 11 figures, LaTeX, some references added, new abstract.
Final version, as published in Nucl.Phys.
Interactions of B = 4 Skyrmions
It is known that the interactions of single Skyrmions are asymptotically
described by a Yukawa dipole potential. Less is known about the interactions of
solutions of the Skyrme model with higher baryon number. In this paper, it is
shown that Yukawa multipole theory can be more generally applied to Skyrmion
interactions, and in particular to the long-range dominant interactions of the
B = 4 solution of the Skyrme model, which models the alpha-particle. A method
that gives the quadrupole nature of the interaction a more intuitive meaning in
the pion field colour picture is demonstrated. Numerical methods are employed
to find the precise strength of quadrupole and octupole interactions. The
results are applied to the B = 8 and B = 12 solutions and to the Skyrme
crystal.Comment: 21 pages, 11 figure
On the origin of families of quarks and leptons - predictions for four families
The approach unifying all the internal degrees of freedom--proposed by one of
us--is offering a new way of understanding families of quarks and leptons: A
part of the starting Lagrange density in d(=1+13), which includes two kinds of
spin connection fields--the gauge fields of two types of Clifford algebra
objects--transforms the right handed quarks and leptons into the left handed
ones manifesting in d=1+3 the Yukawa couplings of the Standard model. We study
the influence of the way of breaking symmetries on the Yukawa couplings and
estimate properties of the fourth family--the quark masses and the mixing
matrix, investigating the possibility that the fourth family of quarks and
leptons appears at low enough energies to be observable with the new generation
of accelerators.Comment: 31 pages,revte
Scale-discretised ridgelet transform on the sphere
We revisit the spherical Radon transform, also called the Funk-Radon
transform, viewing it as an axisymmetric convolution on the sphere. Viewing the
spherical Radon transform in this manner leads to a straightforward derivation
of its spherical harmonic representation, from which we show the spherical
Radon transform can be inverted exactly for signals exhibiting antipodal
symmetry. We then construct a spherical ridgelet transform by composing the
spherical Radon and scale-discretised wavelet transforms on the sphere. The
resulting spherical ridgelet transform also admits exact inversion for
antipodal signals. The restriction to antipodal signals is expected since the
spherical Radon and ridgelet transforms themselves result in signals that
exhibit antipodal symmetry. Our ridgelet transform is defined natively on the
sphere, probes signal content globally along great circles, does not exhibit
blocking artefacts, supports spin signals and exhibits an exact and explicit
inverse transform. No alternative ridgelet construction on the sphere satisfies
all of these properties. Our implementation of the spherical Radon and ridgelet
transforms is made publicly available. Finally, we illustrate the effectiveness
of spherical ridgelets for diffusion magnetic resonance imaging of white matter
fibers in the brain.Comment: 5 pages, 4 figures, matches version accepted by EUSIPCO, code
available at http://www.s2let.or
Soft-gluon resummation for squark and gluino hadroproduction
We consider the resummation of soft gluon emission for squark and gluino
hadroproduction at next-to-leading-logarithmic (NLL) accuracy in the framework
of the minimal supersymmetric standard model. We present analytical results for
squark-squark and squark-gluino production and provide numerical predictions
for all squark and gluino pair-production processes at the Tevatron and at the
LHC. The size of the soft-gluon corrections and the reduction in the scale
uncertainty are most significant for processes involving gluino production. At
the LHC, where the sensitivity to squark and gluino masses ranges up to 3 TeV,
the corrections due to NLL resummation over and above the NLO predictions can
be as high as 35% in the case of gluino-pair production, whereas at the
Tevatron, the NLL corrections are close to 40% for squark-gluino final states
with sparticle masses around 500 GeV.Comment: 31 pages, 7 figure
Resummed event shapes at hadron colliders
We present recently defined jet-observables for hadron-hadron dijet
production, which are designed to reconcile the seemingly conflicting
theoretical requirement of globalness, which makes it possible to resum them
(automatically) at NLL accuracy and the limited experimental reach of
detectors, so that they are measurable at the Tevatron and at the LHC.Comment: 7 pages, Talk given at the XXXIV International Symposium on
Multiparticle Dynamics, Sonoma, July 26 - August 1, 200
A robust adaptive wavelet-based method for classification of meningioma histology images
Intra-class variability in the texture of samples is an important problem in the domain of histological image classification. This issue is inherent to the field due to the high complexity of histology image data. A technique that provides good results in one trial may fail in another when the test and training data are changed and therefore, the technique needs to be adapted for intra-class texture variation. In this paper, we present a novel wavelet based multiresolution analysis approach to meningioma subtype classification in response to the challenge of data variation.We analyze the stability of Adaptive Discriminant Wavelet Packet Transform (ADWPT) and present a solution to the issue of variation in the ADWPT decomposition when texture in data changes. A feature selection approach is proposed that provides high classification accuracy
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