12,929 research outputs found
Probabilistic Methodology and Techniques for Artefact Conception and Development
The purpose of this paper is to make a state of the art on probabilistic methodology and techniques for artefact conception and development. It is the 8th deliverable of the BIBA (Bayesian Inspired Brain and Artefacts) project. We first present the incompletness problem as the central difficulty that both living creatures and artefacts have to face: how can they perceive, infer, decide and act efficiently with incomplete and uncertain knowledge?. We then introduce a generic probabilistic formalism called Bayesian Programming. This formalism is then used to review the main probabilistic methodology
and techniques. This review is organized in 3 parts: first the probabilistic models from Bayesian networks to Kalman filters and from sensor fusion to CAD systems, second the inference techniques and finally the learning and model acquisition and comparison methodologies. We conclude with the perspectives of the BIBA project as they rise from this state of the art
A silent speech system based on permanent magnet articulography and direct synthesis
In this paper we present a silent speech interface (SSI) system aimed at restoring speech communication for individuals who have lost their voice due to laryngectomy or diseases affecting the vocal folds. In the proposed system, articulatory data captured from the lips and tongue using permanent magnet articulography (PMA) are converted into audible speech using a speaker-dependent transformation learned from simultaneous recordings of PMA and audio signals acquired before laryngectomy. The transformation is represented using a mixture of factor analysers, which is a generative model that allows us to efficiently model non-linear behaviour and perform dimensionality reduction at the same time. The learned transformation is then deployed during normal usage of the SSI to restore the acoustic speech signal associated with the captured PMA data. The proposed system is evaluated using objective quality measures and listening tests on two databases containing PMA and audio recordings for normal speakers. Results show that it is possible to reconstruct speech from articulator movements captured by an unobtrusive technique without an intermediate recognition step. The SSI is capable of producing speech of sufficient intelligibility and naturalness that the speaker is clearly identifiable, but problems remain in scaling up the process to function consistently for phonetically rich vocabularies
Colloid-Induced Polymer Compression
We consider a model mixture of hard colloidal spheres and non-adsorbing
polymer chains in a theta solvent. The polymer component is modelled as a
polydisperse mixture of effective spheres, mutually noninteracting but excluded
from the colloids, with radii that are free to adjust to allow for
colloid-induced compression. We investigate the bulk fluid demixing behaviour
of this model system using a geometry-based density-functional theory that
includes the polymer size polydispersity and configurational free energy,
obtained from the exact radius-of-gyration distribution for an ideal
(random-walk) chain. Free energies are computed by minimizing the free energy
functional with respect to the polymer size distribution. With increasing
colloid concentration and polymer-to-colloid size ratio, colloidal confinement
is found to increasingly compress the polymers. Correspondingly, the demixing
fluid binodal shifts, compared to the incompressible-polymer binodal, to higher
polymer densities on the colloid-rich branch, stabilizing the mixed phase.Comment: 14 pages, 4 figure
Dangling and hydrolyzed ligand arms in [Mn3] and [Mn6] coordination assemblies: synthesis, characterization, and functional activity
Two flexible, branched, and sterically constrained di- and tripodal side arms around a phenol backbone were utilized in ligands H3L1 and H5L2 to isolate {Mn6} and {Mn3} coordination aggregates. 2,6-Bis{(1-hydroxy-2-methylpropan-2-ylimino)methyl}-4-methylphenol (H3L1) gave trinuclear complex [Mn3(μ-H2L1)2(μ1,3-O2CCH3)4(CH3OH)2](ClO4)2·4CH3OH (1), whereas 2,6-bis[{1-hydroxy-2-(hydroxymethyl)butan-2-ylimino}methyl]-4-methylphenol (H5L2) provided hexanuclear complex [Mn6(μ4-H2L2)2(μ-HL3)2(μ3-OH)2(μ1,3-O2CC2H5)4](ClO4)2·2H2O (2). Binding of acetates and coordination of {H2L1}− provided a linear MnIIIMnIIMnIII arrangement in 1. A MnIII6 fused diadamantane-type assembly was obtained in 2 from propionate bridges, coordination of {H2L2}3–, and in situ generated {HL3}2–. The magnetic characterization of 1 and 2 revealed the properties dominated by intramolecular anti-ferromagnetic exchange interactions, and this was confirmed using density functional theory calculations. Complex 1 exhibited field-induced slow magnetic relaxation at 2 K due to the axial anisotropy of MnIII centers. Both the complexes show effective solvent-dependent catechol oxidation toward 3,5-di-tert-butylcatechol in air. The catechol oxidation abilities are comparable from two complexes of different nuclearity and structure
Quantifying non-Gaussianity for quantum information
We address the quantification of non-Gaussianity of states and operations in
continuous-variable systems and its use in quantum information. We start by
illustrating in details the properties and the relationships of two recently
proposed measures of non-Gaussianity based on the Hilbert-Schmidt (HS) distance
and the quantum relative entropy (QRE) between the state under examination and
a reference Gaussian state. We then evaluate the non-Gaussianities of several
families of non-Gaussian quantum states and show that the two measures have the
same basic properties and also share the same qualitative behaviour on most of
the examples taken into account. However, we also show that they introduce a
different relation of order, i.e. they are not strictly monotone each other. We
exploit the non-Gaussianity measures for states in order to introduce a measure
of non-Gaussianity for quantum operations, to assess Gaussification and
de-Gaussification protocols, and to investigate in details the role played by
non-Gaussianity in entanglement distillation protocols. Besides, we exploit the
QRE-based non-Gaussianity measure to provide new insight on the extremality of
Gaussian states for some entropic quantities such as conditional entropy,
mutual information and the Holevo bound. We also deal with parameter estimation
and present a theorem connecting the QRE nonG to the quantum Fisher
information. Finally, since evaluation of the QRE nonG measure requires the
knowledge of the full density matrix, we derive some {\em experimentally
friendly} lower bounds to nonG for some class of states and by considering the
possibility to perform on the states only certain efficient or inefficient
measurements.Comment: 22 pages, 13 figures, comments welcome. v2: typos corrected and
references added. v3: minor corrections (more similar to published version
Ab Initio Study of Phase Stability in Doped TiO2
Ab-initio density functional theory (DFT) calculations of the relative
stability of anatase and rutile polymorphs of TiO2 were carried using
all-electron atomic orbitals methods with local density approximation (LDA).
The rutile phase exhibited a moderate margin of stability of ~ 3 meV relative
to the anatase phase in pristine material. From computational analysis of the
formation energies of Si, Al, Fe and F dopants of various charge states across
different Fermi level energies in anatase and in rutile, it was found that the
cationic dopants are most stable in Ti substitutional lattice positions while
formation energy is minimised for F- doping in interstitial positions. All
dopants were found to considerably stabilise anatase relative to the rutile
phase, suggesting the anatase to rutile phase transformation is inhibited in
such systems with the dopants ranked F>Si>Fe>Al in order of anatase
stabilisation strength. Al and Fe dopants were found to act as shallow
acceptors with charge compensation achieved through the formation of mobile
carriers rather than the formation of anion vacancies
Efficient Multiband Algorithms for Blind Source Separation
The problem of blind separation refers to recovering original signals, called source signals, from the mixed signals, called observation signals, in a reverberant environment. The mixture is a function of a sequence of original speech signals mixed in a reverberant room. The objective is to separate mixed signals to obtain the original signals without degradation and without prior information of the features of the sources. The strategy used to achieve this objective is to use multiple bands that work at a lower rate, have less computational cost and a quicker convergence than the conventional scheme. Our motivation is the competitive results of unequal-passbands scheme applications, in terms of the convergence speed. The objective of this research is to improve unequal-passbands schemes by improving the speed of convergence and reducing the computational cost. The first proposed work is a novel maximally decimated unequal-passbands scheme.This scheme uses multiple bands that make it work at a reduced sampling rate, and low computational cost. An adaptation approach is derived with an adaptation step that improved the convergence speed. The performance of the proposed scheme was measured in different ways. First, the mean square errors of various bands are measured and the results are compared to a maximally decimated equal-passbands scheme, which is currently the best performing method. The results show that the proposed scheme has a faster convergence rate than the maximally decimated equal-passbands scheme. Second, when the scheme is tested for white and coloured inputs using a low number of bands, it does not yield good results; but when the number of bands is increased, the speed of convergence is enhanced. Third, the scheme is tested for quick changes. It is shown that the performance of the proposed scheme is similar to that of the equal-passbands scheme. Fourth, the scheme is also tested in a stationary state. The experimental results confirm the theoretical work. For more challenging scenarios, an unequal-passbands scheme with over-sampled decimation is proposed; the greater number of bands, the more efficient the separation. The results are compared to the currently best performing method. Second, an experimental comparison is made between the proposed multiband scheme and the conventional scheme. The results show that the convergence speed and the signal-to-interference ratio of the proposed scheme are higher than that of the conventional scheme, and the computation cost is lower than that of the conventional scheme
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