10,099 research outputs found
On the Equivalence Between Deep NADE and Generative Stochastic Networks
Neural Autoregressive Distribution Estimators (NADEs) have recently been
shown as successful alternatives for modeling high dimensional multimodal
distributions. One issue associated with NADEs is that they rely on a
particular order of factorization for . This issue has been
recently addressed by a variant of NADE called Orderless NADEs and its deeper
version, Deep Orderless NADE. Orderless NADEs are trained based on a criterion
that stochastically maximizes with all possible orders of
factorizations. Unfortunately, ancestral sampling from deep NADE is very
expensive, corresponding to running through a neural net separately predicting
each of the visible variables given some others. This work makes a connection
between this criterion and the training criterion for Generative Stochastic
Networks (GSNs). It shows that training NADEs in this way also trains a GSN,
which defines a Markov chain associated with the NADE model. Based on this
connection, we show an alternative way to sample from a trained Orderless NADE
that allows to trade-off computing time and quality of the samples: a 3 to
10-fold speedup (taking into account the waste due to correlations between
consecutive samples of the chain) can be obtained without noticeably reducing
the quality of the samples. This is achieved using a novel sampling procedure
for GSNs called annealed GSN sampling, similar to tempering methods that
combines fast mixing (obtained thanks to steps at high noise levels) with
accurate samples (obtained thanks to steps at low noise levels).Comment: ECML/PKDD 201
Efficient Bayesian inference for stochastic volatility models with ensemble MCMC methods
In this paper, we introduce efficient ensemble Markov Chain Monte Carlo
(MCMC) sampling methods for Bayesian computations in the univariate stochastic
volatility model. We compare the performance of our ensemble MCMC methods with
an improved version of a recent sampler of Kastner and Fruwirth-Schnatter
(2014). We show that ensemble samplers are more efficient than this state of
the art sampler by a factor of about 3.1, on a data set simulated from the
stochastic volatility model. This performance gain is achieved without the
ensemble MCMC sampler relying on the assumption that the latent process is
linear and Gaussian, unlike the sampler of Kastner and Fruwirth-Schnatter
X-Ray Ionization of Planet-Opened Gaps in Protostellar Disks
Young planets with masses approaching Jupiter's have tides strong enough to
clear gaps around their orbits in the protostellar disk. Gas flow through the
gaps regulates the planets' further growth and governs the disks' evolution.
Magnetic forces may drive that flow if the gas is sufficiently ionized to
couple to the fields. We compute the ionizing effects of the X-rays from the
central young star, using Monte Carlo radiative transfer calculations to find
the spectrum of Compton-scattered photons reaching the planet's vicinity. The
scattered X-rays ionize the gas at rates similar to or greater than the
interstellar cosmic ray rate near planets the mass of Saturn and of Jupiter,
located at 5 au and at 10 au, in disks with the interstellar mass fraction of
sub-micron dust and with the dust depleted a factor 100. Solving a gas-grain
recombination reaction network yields charged particle populations whose
ability to carry currents is sufficient to partly couple the magnetic fields to
the gas around the planet. Most cases can undergo Hall shear instability, and
some can launch magnetocentrifugal winds. However the material on the planet's
orbit has diffusivities so large in all the cases we examine, that
magneto-rotational turbulence is prevented and the non-ideal terms govern the
magnetic field's evolution. Thus the flow of gas in the gaps opened by the
young giant planets depends crucially on the finite conductivity.Comment: 24 pages, 6 figures. Gap depths are now chosen to match recent
hydrodynamical results. Accepted for publication in Ap
Context-aware Mission Control for Astronaut-Robot Collaboration
Space robot assistants are envisaged as semi-autonomous co-workers deployed to lighten the workload of astronauts in cumbersome and dangerous situations. In view of this, this work considers the prospects on the technology requirements for future space robot operations, by presenting a novel mission control concept for close astronaut-robot collaboration. A decentralized approach is proposed, in which an astronaut is put in charge of commanding the robot, and a mission control center on Earth maintains a list of authorized robot actions by applying symbolic, geometric, and context-specific filters. The concept is applied to actual space robot operations within the METERON SUPVIS Justin experiment. In particular, it is shown how the concept is utilized to guide an astronaut aboard the ISS in its mission to survey and maintain a solar panel farm in a simulated Mars environment
Star Formation and AGN in the Core of the Shapley Supercluster: A VLA Survey of A3556, A3558, SC1327-312, SC1329-313, and A3562
The core of the Shapley supercluster (A3556, A3558, SC1327-312, SC1329-313,
and A3562) is an ideal region in which to study the effects of cluster mergers
on the activity of individual galaxies. This paper presents the most
comprehensive radio continuum investigation of the region, relying on a
63-pointing mosaic obtained with the Very Large Array yielding an areal
coverage of nearly 7 square degrees. The mosaic provides a typical sensitivity
of about 80 uJy at a resolution of 16", enabling detection of galaxies with
star formation rates as low as 1 solar mass per year. The radio data are
complemented by optical imaging in B and R, producing a catalog of 210
radio-detected galaxies with m_R <= 17.36 (M_R <= -19). At least 104 of these
radio-detected galaxies are members of the supercluster on the basis of public
velocity measurements. Across the entire core of the supercluster, there
appears to be a significant deficit of radio galaxies at intermediate optical
magnitudes (M_R between -21 and -22). This deficit is offset somewhat by an
increase in the frequency with which brighter galaxies (M_R less than -22) host
radio sources. More dramatic is the highly significant increase in the
probability for fainter galaxies (M_R between -20 and -21) in the vicinity of
A3562 and SC1329-313 to be associated with radio emission. The radio and
optical data for these sources strongly suggest that these active galaxies are
powered by star formation. In conjunction with recent X-ray analysis, this is
interpreted as young starbursts related to the recent merger of SC1329-313 with
A3562 and the rest of the supercluster.Comment: Accepted by AJ; 50 pages, including 16 figures (for full resolution
PDF, see http://mywebpages.comcast.net/nealamiller2/Shapley_pp.pdf
Adverse Childhood Experiences Screening Among Adults in an Inpatient Behavioral Health Unit
Adverse childhood experiences (ACEs) are common amongst people of all ages, races, and socio-economic statuses. The consequence of ACEs impact ones mental and physical health and life span. High ACE scores lead to increased risk of suicide, depression, anxiety, and substance abuse. The purpose of this project was to screen adults admitted to an inpatient psychiatric hospital for ACEs. This project sought to determine if there is a relationship between overall ACEs score and impact on health versus length of stay. Ultimately, the aim is to reduce negative health outcome for patients as measured by length of stay. The results indicated that overall ACEs score and the impact on health results did not impact length of stay. However, the results were significant in confirming that higher ACE scores are correlated with more significant impact on health
Derivation of Apollo 14 High-Al Basalts from Distinct Source Regions at Discrete Times: New Constraints
Apollo 14 basalts occur predominantly as clasts in breccias, but represent the oldest volcanic products that were returned from the Moon [1]. These basalts are relatively enriched in Al2O3 (11-16 wt%) compared to other mare basalts (7-11 wt%) and were originally classified into 5 compositional groups [2,3]. Neal et al. [4] proposed that a continuum of compositions existed. These were related through assimilation (of KREEP) and fractional crystallization (AFC). Age data, however, show that at least three volcanic episodes are recorded in the sample collection [1,5,6]. Recent work has demonstrated that there are three, possibly four groups of basalts in the Apollo 14 sample collection that were erupted from different source regions at different times [7]. This conclusion was based upon incompatible trace element (ITE) ratios of elements that should not be fractionated from one another during partial melting (Fig. 1). These groups are defined as Group A (Groups 4 & 5 of [3]), Group B (Groups 1 & 2 of [3]), and Group C (Group 3 of [3]). Basalt 14072 is distinct from Groups A-C
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