459,009 research outputs found
Fully Adaptive Gaussian Mixture Metropolis-Hastings Algorithm
Markov Chain Monte Carlo methods are widely used in signal processing and
communications for statistical inference and stochastic optimization. In this
work, we introduce an efficient adaptive Metropolis-Hastings algorithm to draw
samples from generic multi-modal and multi-dimensional target distributions.
The proposal density is a mixture of Gaussian densities with all parameters
(weights, mean vectors and covariance matrices) updated using all the
previously generated samples applying simple recursive rules. Numerical results
for the one and two-dimensional cases are provided
EAGLE multi-object AO concept study for the E-ELT
EAGLE is the multi-object, spatially-resolved, near-IR spectrograph
instrument concept for the E-ELT, relying on a distributed Adaptive Optics,
so-called Multi Object Adaptive Optics. This paper presents the results of a
phase A study. Using 84x84 actuator deformable mirrors, the performed analysis
demonstrates that 6 laser guide stars and up to 5 natural guide stars of
magnitude R<17, picked-up in a 7.3' diameter patrol field of view, allow us to
obtain an overall performance in terms of Ensquared Energy of 35% in a 75x75
mas^2 spaxel at H band, whatever the target direction in the centred 5' science
field for median seeing conditions. The computed sky coverage at galactic
latitudes |b|~60 is close to 90%.Comment: 6 pages, to appear in the proceedings of the AO4ELT conference, held
in Paris, 22-26 June 200
Resource-Constrained Adaptive Search and Tracking for Sparse Dynamic Targets
This paper considers the problem of resource-constrained and noise-limited
localization and estimation of dynamic targets that are sparsely distributed
over a large area. We generalize an existing framework [Bashan et al, 2008] for
adaptive allocation of sensing resources to the dynamic case, accounting for
time-varying target behavior such as transitions to neighboring cells and
varying amplitudes over a potentially long time horizon. The proposed adaptive
sensing policy is driven by minimization of a modified version of the
previously introduced ARAP objective function, which is a surrogate function
for mean squared error within locations containing targets. We provide
theoretical upper bounds on the performance of adaptive sensing policies by
analyzing solutions with oracle knowledge of target locations, gaining insight
into the effect of target motion and amplitude variation as well as sparsity.
Exact minimization of the multi-stage objective function is infeasible, but
myopic optimization yields a closed-form solution. We propose a simple
non-myopic extension, the Dynamic Adaptive Resource Allocation Policy (D-ARAP),
that allocates a fraction of resources for exploring all locations rather than
solely exploiting the current belief state. Our numerical studies indicate that
D-ARAP has the following advantages: (a) it is more robust than the myopic
policy to noise, missing data, and model mismatch; (b) it performs comparably
to well-known approximate dynamic programming solutions but at significantly
lower computational complexity; and (c) it improves greatly upon non-adaptive
uniform resource allocation in terms of estimation error and probability of
detection.Comment: 49 pages, 1 table, 11 figure
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