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Blind Separation of Filtered Sources Using State-Space Approach

Neural Information Processing Systems

In this paper we present a novel approach to multichannel blind that both mixingseparation/generalized deconvolution, assuming and demixing models are described by stable linear state-space systems. Based on the minimization of Kullback-Leibler Divergence, we develop a novel learning algorithm to train the matrices in the output equation. To estimate the state of the demixing model, we introduce a new concept, called to numerically implement the Kalman filter.hidden Referany priori knowledge of to review papers [lJ and [5J for the current state of theory and methods in the field. There are several reasons why as blind deconvolution models.


Discovering Hidden Features with Gaussian Processes Regression

Neural Information Processing Systems

W is often taken to be diagonal, but if we allow W to be a general positive definite matrix which can be tuned on the basis of training data, then an eigen-analysis of W shows that we are effectively creating hidden features, where the dimensionality of the hidden-feature space is determined by the data. We demonstrate the superiority of predictions usi ng the general matrix over those based on a diagonal matrix on two test problems.


General Bounds on Bayes Errors for Regression with Gaussian Processes

Neural Information Processing Systems

Based on a simple convexity lemma, we develop bounds for different typesof Bayesian prediction errors for regression with Gaussian processes. The basic bounds are formulated for a fixed training set. Simpler expressions are obtained for sampling from an input distribution whichequals the weight function of the covariance kernel, yielding asymptotically tight results. The results are compared with numerical experiments.


Replicator Equations, Maximal Cliques, and Graph Isomorphism

Neural Information Processing Systems

We present a new energy-minimization framework for the graph isomorphism problem which is based on an equivalent maximum clique formulation. The approach is centered around a fundamental result proved by Motzkin and Straus in the mid-1960s, and recently expanded in various ways, which allows us to formulate the maximum cliqueproblem in terms of a standard quadratic program. To solve the program we use "replicator" equations, a class of simple continuous-and discrete-time dynamical systems developed in various branchesof theoretical biology. We show how, despite their inability to escape from local solutions, they nevertheless provide experimental results which are competitive with those obtained using moreelaborate mean-field annealing heuristics. 1 INTRODUCTION The graph isomorphism problem is one of those few combinatorial optimization problems which still resist any computational complexity characterization [6]. Despite decadesof active research, no polynomial-time algorithm for it has yet been found.



Exploratory Data Analysis Using Radial Basis Function Latent Variable Models

Neural Information Processing Systems

Two developments of nonlinear latent variable models based on radial basis functions are discussed: in the first, the use of priors or constraints on allowable models is considered as a means of preserving data structure in low-dimensional representations for visualisation purposes. Also, a resampling approach is introduced which makes more effective use of the latent samples in evaluating the likelihood.


Maximum-Likelihood Continuity Mapping (MALCOM): An Alternative to HMMs

Neural Information Processing Systems

We describe Maximum-Likelihood Continuity Mapping (MALCOM), an alternative to hidden Markov models (HMMs) for processing sequence data such as speech. While HMMs have a discrete "hidden" space constrained bya fixed finite-automaton architecture, MALCOM has a continuous hidden space-a continuity map-that is constrained only by a smoothness requirement on paths through the space. MALCOM fits into the same probabilistic framework for speech recognition as HMMs, but it represents a more realistic model of the speech production process. To evaluate the extent to which MALCOM captures speech production information, we generated continuous speech continuity maps for three speakers and used the paths through them to predict measured speech articulator data. The median correlation between the MALCOM paths obtained from only the speech acoustics and articulator measurements was 0.77 on an independent test set not used to train MALCOM or the predictor.


Regularizing AdaBoost

Neural Information Processing Systems

We will also introduce a regularization strategy(analogous to weight decay) into boosting. This strategy uses slack variables to achieve a soft margin (section 4). Numerical experiments show the validity of our regularization approach in section 5 and finally a brief conclusion is given. 2 AdaBoost Algorithm Let {ht(x): t 1, ...,T} be an ensemble of T hypotheses defined on input vector x and e


Tractable Variational Structures for Approximating Graphical Models

Neural Information Processing Systems

Graphical models provide a broad probabilistic framework with applications inspeech recognition (Hidden Markov Models), medical diagnosis (Belief networks) and artificial intelligence (Boltzmann Machines). However, the computing time is typically exponential in the number of nodes in the graph. Within the variational framework forapproximating these models, we present two classes of distributions, decimatableBoltzmann Machines and Tractable Belief Networks that go beyond the standard factorized approach. We give generalised mean-field equations for both these directed and undirected approximations. Simulation results on a small benchmark problemsuggest using these richer approximations compares favorably against others previously reported in the literature. 1 Introduction Graphical models provide a powerful framework for probabilistic inference[l] but suffer intractability when applied to large scale problems.