5,512 research outputs found
Particle Filtering and Smoothing Using Windowed Rejection Sampling
"Particle methods" are sequential Monte Carlo algorithms, typically involving
importance sampling, that are used to estimate and sample from joint and
marginal densities from a collection of a, presumably increasing, number of
random variables. In particular, a particle filter aims to estimate the current
state of a stochastic system that is not directly observable by
estimating a posterior distribution
where the are observations related to the through some
measurement model . A particle smoother aims to estimate a
marginal distribution for . Particle methods are used extensively for hidden Markov models where
is a Markov chain as well as for more general state space models.
Existing particle filtering algorithms are extremely fast and easy to
implement. Although they suffer from issues of degeneracy and "sample
impoverishment", steps can be taken to minimize these problems and overall they
are excellent tools for inference. However, if one wishes to sample from a
posterior distribution of interest, a particle filter is only able to produce
dependent draws. Particle smoothing algorithms are complicated and far less
robust, often requiring cumbersome post-processing, "forward-backward"
recursions, and multiple passes through subroutines. In this paper we introduce
an alternative algorithm for both filtering and smoothing that is based on
rejection sampling "in windows" . We compare both speed and accuracy of the
traditional particle filter and this "windowed rejection sampler" (WRS) for
several examples and show that good estimates for smoothing distributions are
obtained at no extra cost
The prognostic value of eighth grade records with respect to pupils' achievement in the high school sciences.
Thesis (Ed.M.)--Boston Universit
Alien Registration- Corcoran, Horace D. (Baldwin, Cumberland County)
https://digitalmaine.com/alien_docs/33003/thumbnail.jp
CP violation and rare Bs decays at the Tevatron
This note gives updates on three results from the Fermilab Tevatron p¯p collider operating at √s = 1.96TeV. The results presented include: the D0 dimuon charge asymmetry; the measurement of the CP-violating phase φs in the decay Bs → J/ψφ from both CDF and D0; and the most recent results from both CDF and D0 on the search for the ultra-rare decay Bs → μ+μ−
Laser Guide Star Adaptive Optics Integral Field Spectroscopy of a Tightly Collimated Bipolar Jet from the Herbig Ae star LkHa 233
We have used the integral field spectrograph OSIRIS and laser guide star
adaptive optics at Keck Observatory to obtain high angular resolution (0.06"),
moderate spectral resolution (R ~ 3800) images of the bipolar jet from the
Herbig Ae star LkHa 233, seen in near-IR [Fe II] emission at 1.600 & 1.644
microns. This jet is narrow and tightly collimated, with an opening angle of
only 9 degrees, and has an average radial velocity of ~ 100 km/s. The jet and
counterjet are asymmetric, with the red-shifted jet much clumpier than its
counterpart at the angular resolution of our observations. The observed
properties are in general similar to jets seen around T Tauri stars, though it
has a relatively large mass flux of (1.2e-7 +- 0.3e-7) M_sun/year, near the
high end of the observed mass flux range around T Tauri stars. We also
spatially resolve an inclined circumstellar disk around LkHa 233, which
obscures the star from direct view. By comparison with numerical radiative
transfer disk models, we estimate the disk midplane to be inclined i = 65 +- 5
degrees relative to the plane of the sky. Since the star is seen only in
scattered light at near-infrared wavelengths, we detect only a small fraction
of its intrinsic flux. Because previous estimates of its stellar properties did
not account for this, either LkHa 233 must be located closer than the
previously believed, or its true luminosity must be greater than previously
supposed, consistent with its being a ~4 M_sun star near the stellar birthline.Comment: Accepted for publication in the Ap
Motor-starting characteristics of two inductor alternators
Motor starting characteristics of two inductor alternator
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Evaluating the use of rate-based monitoring for improved fatigue remnant life predictions
Supercritical multicomponent solvent coal extraction
The yield of organic extract from the supercritical extraction of coal with larger diameter organic solvents such as toluene is increased by use of a minor amount of from 0.1 to 10% by weight of a second solvent such as methanol having a molecular diameter significantly smaller than the average pore diameter of the coal
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