2,863 research outputs found
Modelling and filtering almost periodic signals by time-varying fourier series with application to near-infrared spectroscopy
We propose a new approach to modelling almost periodic signals and to model-based estimation of such signals from noisy observations. The signal model is based on Fourier series where both the coefficients and the fundamental frequency can continuously change over time. This signal model can be represented by a factor graph which we use to derive message passing algorithms to estimate the time-dependent model parameters from the observed samples
Behaviour of factors II, VII, IX and X in bleeding complications during long-term treatment with Coumarin
In 20 patients suffering from bleeding complications during long-term treatment with phenprocoumon, the depression of the activity of Factors II, VII, IX and X, on the average, was found to be stronger than in so-called adequately treated patients, whereas no statistically significant differences could be demonstrated between the average activity of the 4 factors. The individual variations between the 4 factors were higher than those found in normal individuals and adequately treated patients. Thrombotest activity appeared to be considerably lower than the average factor activity. This discrepancy is mainly caused by the action of the recently discovered circulating anticoagulant occurring in coumarin-treated or vitamin K-deficient patients
Loop series for discrete statistical models on graphs
In this paper we present derivation details, logic, and motivation for the
loop calculus introduced in \cite{06CCa}. Generating functions for three
inter-related discrete statistical models are each expressed in terms of a
finite series. The first term in the series corresponds to the Bethe-Peierls
(Belief Propagation)-BP contribution, the other terms are labeled by loops on
the factor graph. All loop contributions are simple rational functions of spin
correlation functions calculated within the BP approach. We discuss two
alternative derivations of the loop series. One approach implements a set of
local auxiliary integrations over continuous fields with the BP contribution
corresponding to an integrand saddle-point value. The integrals are replaced by
sums in the complimentary approach, briefly explained in \cite{06CCa}. A local
gauge symmetry transformation that clarifies an important invariant feature of
the BP solution, is revealed in both approaches. The partition function remains
invariant while individual terms change under the gauge transformation. The
requirement for all individual terms to be non-zero only for closed loops in
the factor graph (as opposed to paths with loose ends) is equivalent to fixing
the first term in the series to be exactly equal to the BP contribution.
Further applications of the loop calculus to problems in statistical physics,
computer and information sciences are discussed.Comment: 20 pages, 3 figure
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