8,961 research outputs found
Blind Normalization of Speech From Different Channels
We show how to construct a channel-independent representation of speech that
has propagated through a noisy reverberant channel. This is done by blindly
rescaling the cepstral time series by a non-linear function, with the form of
this scale function being determined by previously encountered cepstra from
that channel. The rescaled form of the time series is an invariant property of
it in the following sense: it is unaffected if the time series is transformed
by any time-independent invertible distortion. Because a linear channel with
stationary noise and impulse response transforms cepstra in this way, the new
technique can be used to remove the channel dependence of a cepstral time
series. In experiments, the method achieved greater channel-independence than
cepstral mean normalization, and it was comparable to the combination of
cepstral mean normalization and spectral subtraction, despite the fact that no
measurements of channel noise or reverberations were required (unlike spectral
subtraction).Comment: 25 pages, 7 figure
Using state space differential geometry for nonlinear blind source separation
Given a time series of multicomponent measurements of an evolving stimulus,
nonlinear blind source separation (BSS) seeks to find a "source" time series,
comprised of statistically independent combinations of the measured components.
In this paper, we seek a source time series with local velocity cross
correlations that vanish everywhere in stimulus state space. However, in an
earlier paper the local velocity correlation matrix was shown to constitute a
metric on state space. Therefore, nonlinear BSS maps onto a problem of
differential geometry: given the metric observed in the measurement coordinate
system, find another coordinate system in which the metric is diagonal
everywhere. We show how to determine if the observed data are separable in this
way, and, if they are, we show how to construct the required transformation to
the source coordinate system, which is essentially unique except for an unknown
rotation that can be found by applying the methods of linear BSS. Thus, the
proposed technique solves nonlinear BSS in many situations or, at least,
reduces it to linear BSS, without the use of probabilistic, parametric, or
iterative procedures. This paper also describes a generalization of this
methodology that performs nonlinear independent subspace separation. In every
case, the resulting decomposition of the observed data is an intrinsic property
of the stimulus' evolution in the sense that it does not depend on the way the
observer chooses to view it (e.g., the choice of the observing machine's
sensors). In other words, the decomposition is a property of the evolution of
the "real" stimulus that is "out there" broadcasting energy to the observer.
The technique is illustrated with analytic and numerical examples.Comment: Contains 14 pages and 3 figures. For related papers, see
http://www.geocities.com/dlevin2001/ . New version is identical to original
version except for URL in the bylin
The Importance of Religion for Parents Coping with a Chronically Ill Child
This study examines differences in the stability and consequences of religious coping among parents (N = 102) of chronically ill children. Analyses revealed that changes in religious patterns due to a child\u27s illness were reflected in changes in other, non-religious coping resources. Specifically, parents whose pre-illness religious patterns were satisfactory did not alter their use of other coping resources, whereas parents who reported changes in their religious patterns also made changes in their use of familial financial and social support systems
Lignin biosynthesis in wheat (Triticum aestivum L.): its response to waterlogging and association with hormonal levels
Phylogenetic relationships of wheat C3H and CCoAOMT genes with the homologs from other species. Phylogenetic trees of C3H (A) and CCoAOMT (B) were generated based on nucleic acid sequence similarity of wheat genes with 15 C3H and 19 CCoAOMT genes, respectively, of other monocot and dicot species identified from the NCBI nucleotide database [39] using MEGA program [41], and the trees were inferred using Maximum Likelihood method based on the Tamura-nei model. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test of 500 replicates is shown next to the branches. â, wheat candidate gene; â˛, genes from dicot species other than Arabidopsis; *, wheat sequence used for the analysis. (PDF 175 kb
Global changes in the proteome of Cupriavidus necator H16 during poly-(3-hydroxybutyrate) synthesis from various biodiesel by-product substrates
Additional file 1: Table S1. P-scores of proteomic runs of C. necator H16 grown with different substrates
Dynamical evolution of the young stars in the Galactic center: N-body simulations of the S-stars
We use N-body simulations to study the evolution of the orbital
eccentricities of stars deposited near (<0.05 pc) the Milky Way massive black
hole (MBH), starting from initial conditions motivated by two competing models
for their origin: formation in a disk followed by inward migration; and
exchange interactions involving a binary star. The first model predicts modest
eccentricities, lower than those observed in the S-star cluster, while the
second model predicts higher eccentricities than observed. The N-body
simulations include a dense cluster of 10 M_sun stellar black holes (SBHs),
expected to accumulate near the MBH by mass segregation. Perturbations from the
SBHs tend to randomize the stellar orbits, partially erasing the dynamical
signatures of their origin. The eccentricities of the initially highly
eccentric stars evolve, in 20 Myr (the S-star lifespan), to a distribution that
is consistent at the ~95 % level with the observed eccentricity distribution.
In contrast, the eccentricities of the initially more circular orbits fail to
evolve to the observed values in 20 Myr, arguing against the disk migration
scenario. We find that 20 % - 30 % of the S-stars are tidally disrupted by the
MBH over their lifetimes, and that the S-stars are not likely to be ejected as
hypervelocity stars outside the central 0.05 pc by close encounters with
stellar black holes.Comment: 6 pages, 2 figures. Minor corrections, Sumitted to Ap
Brain Model State Space Reconstruction Using an LSTM Neural Network
Objective
Kalman filtering has previously been applied to track neural model states and
parameters, particularly at the scale relevant to EEG. However, this approach
lacks a reliable method to determine the initial filter conditions and assumes
that the distribution of states remains Gaussian. This study presents an
alternative, data-driven method to track the states and parameters of neural
mass models (NMMs) from EEG recordings using deep learning techniques,
specifically an LSTM neural network.
Approach
An LSTM filter was trained on simulated EEG data generated by a neural mass
model using a wide range of parameters. With an appropriately customised loss
function, the LSTM filter can learn the behaviour of NMMs. As a result, it can
output the state vector and parameters of NMMs given observation data as the
input.
Main Results
Test results using simulated data yielded correlations with R squared of
around 0.99 and verified that the method is robust to noise and can be more
accurate than a nonlinear Kalman filter when the initial conditions of the
Kalman filter are not accurate. As an example of real-world application, the
LSTM filter was also applied to real EEG data that included epileptic seizures,
and revealed changes in connectivity strength parameters at the beginnings of
seizures.
Significance
Tracking the state vector and parameters of mathematical brain models is of
great importance in the area of brain modelling, monitoring, imaging and
control. This approach has no need to specify the initial state vector and
parameters, which is very difficult to do in practice because many of the
variables being estimated cannot be measured directly in physiological
experiments. This method may be applied using any neural mass model and,
therefore, provides a general, novel, efficient approach to estimate brain
model variables that are often difficult to measure
Coulomb Gap and Correlated Vortex Pinning in Superconductors
The positions of columnar pins and magnetic flux lines determined from a
decoration experiment on BSCCO were used to calculate the single--particle
density of states at low temperatures in the Bose glass phase. A wide Coulomb
gap is found, with gap exponent , as a result of the long--range
interaction between the vortices. As a consequence, the variable--range hopping
transport of flux lines is considerably reduced with respect to the
non--interacting case, the effective Mott exponent being enhanced from to for this specific experiment.Comment: 10 pages, Revtex, 4 figures appended as uu-encoded postscript files,
also available as hardcopies from [email protected]
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