245 research outputs found
On the Value of Online Learning for Radar Waveform Selection
This paper attempts to characterize the kinds of physical scenarios in which
an online learning-based cognitive radar is expected to reliably outperform a
fixed rule-based waveform selection strategy, as well as the converse. We seek
general insights through an examination of two decision-making scenarios,
namely dynamic spectrum access and multiple-target tracking. The radar scene is
characterized by inducing a state-space model and examining the structure of
its underlying Markov state transition matrix, in terms of entropy rate and
diagonality. It is found that entropy rate is a strong predictor of online
learning-based waveform selection, while diagonality is a better predictor of
fixed rule-based waveform selection. We show that these measures can be used to
predict first and second-order stochastic dominance relationships, which can
allow system designers to make use of simple decision rules instead of more
cumbersome learning approaches under certain conditions. We validate our
findings through numerical results for each application and provide guidelines
for future implementations.Comment: 15 pages, 15 figures. Final version to appear in IEEE Transaction on
Radar Systems. arXiv admin note: substantial text overlap with
arXiv:2212.0059
Timely Target Tracking in Cognitive Radar Networks
We consider a scenario where a fusion center must decide which updates to
receive during each update period in a communication-limited cognitive radar
network. When each radar node in the network only is able to obtain noisy state
measurements for a subset of the targets, the fusion center may not receive
updates on every target during each update period. The solution for the
selection problem at the fusion center is not well suited for sequential
learning frameworks. We derive an Age of Information-inspired track sensitive
metric to inform node selection in such a network and compare it against
less-informed techniques.Comment: 6 pages, 6 figure
Experimental Analysis of Reinforcement Learning Techniques for Spectrum Sharing Radar
In this work, we first describe a framework for the application of
Reinforcement Learning (RL) control to a radar system that operates in a
congested spectral setting. We then compare the utility of several RL
algorithms through a discussion of experiments performed on Commercial
off-the-shelf (COTS) hardware. Each RL technique is evaluated in terms of
convergence, radar detection performance achieved in a congested spectral
environment, and the ability to share 100MHz spectrum with an uncooperative
communications system. We examine policy iteration, which solves an environment
posed as a Markov Decision Process (MDP) by directly solving for a stochastic
mapping between environmental states and radar waveforms, as well as Deep RL
techniques, which utilize a form of Q-Learning to approximate a parameterized
function that is used by the radar to select optimal actions. We show that RL
techniques are beneficial over a Sense-and-Avoid (SAA) scheme and discuss the
conditions under which each approach is most effective.Comment: Accepted for publication at IEEE Intl. Radar Conference, Washington
DC, Apr. 2020. This is the author's version of the wor
Comparison of pretreatment characteristics and treatment outcomes for alcohol-, cocaine-, and multisubstance-dependent patients.
We investigated whether pretreatment characteristics and measures of outcome differed for alcohol-, cocaine-, and multisubstance-dependent patients receiving outpatient substance abuse treatment. One hundred and forty substance dependent individuals (32 alcohol, 76 cocaine, and 32 multisubstance) enrolled in a 12-week outpatient treatment program were compared across measures of addiction severity, personality, and treatment-readiness at admission. In-treatment, end-of-treatment and 9-month follow-up assessments of treatment outcome were then compared across the three groups. Outcome measures included reduction in problem severity, abstinence, retention, number of sessions attended, dropout, and counselor and patient ratings of treatment benefit. At admission, the multisubstance group had a higher proportion of positive urines, reported more severe drug, alcohol and psychiatric problems, and displayed higher impulsivity and anxiety scores than one or both of the other groups. However, multisubstance patients were more treatment ready in terms of adopting a total abstinence orientation than alcohol or cocaine patients. While a significant reduction in symptoms occurred for the total sample during treatment as well as at follow-up, comparisons of outcomes did not consistently favor any particular group. The three groups had equivalent improvements in eleven of fourteen during-treatment and five of seven follow-up measures. Despite pretreatment differences, in severity and treatment-readiness, outcomes were more similar than different for alcohol-, cocaine-, and multisubstance-dependent patients. Clinicians should be cautious about forecasting treatment-outcomes for addicted patients based on their primary substances of abuse
The Atacama Cosmology Telescope: Two-Season ACTPol Spectra and Parameters
We present the temperature and polarization angular power spectra measured by
the Atacama Cosmology Telescope Polarimeter (ACTPol). We analyze night-time
data collected during 2013-14 using two detector arrays at 149 GHz, from 548
deg of sky on the celestial equator. We use these spectra, and the spectra
measured with the MBAC camera on ACT from 2008-10, in combination with Planck
and WMAP data to estimate cosmological parameters from the temperature,
polarization, and temperature-polarization cross-correlations. We find the new
ACTPol data to be consistent with the LCDM model. The ACTPol
temperature-polarization cross-spectrum now provides stronger constraints on
multiple parameters than the ACTPol temperature spectrum, including the baryon
density, the acoustic peak angular scale, and the derived Hubble constant.
Adding the new data to planck temperature data tightens the limits on damping
tail parameters, for example reducing the joint uncertainty on the number of
neutrino species and the primordial helium fraction by 20%.Comment: 23 pages, 25 figure
LSST: from Science Drivers to Reference Design and Anticipated Data Products
(Abridged) We describe here the most ambitious survey currently planned in
the optical, the Large Synoptic Survey Telescope (LSST). A vast array of
science will be enabled by a single wide-deep-fast sky survey, and LSST will
have unique survey capability in the faint time domain. The LSST design is
driven by four main science themes: probing dark energy and dark matter, taking
an inventory of the Solar System, exploring the transient optical sky, and
mapping the Milky Way. LSST will be a wide-field ground-based system sited at
Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m
effective) primary mirror, a 9.6 deg field of view, and a 3.2 Gigapixel
camera. The standard observing sequence will consist of pairs of 15-second
exposures in a given field, with two such visits in each pointing in a given
night. With these repeats, the LSST system is capable of imaging about 10,000
square degrees of sky in a single filter in three nights. The typical 5
point-source depth in a single visit in will be (AB). The
project is in the construction phase and will begin regular survey operations
by 2022. The survey area will be contained within 30,000 deg with
, and will be imaged multiple times in six bands, ,
covering the wavelength range 320--1050 nm. About 90\% of the observing time
will be devoted to a deep-wide-fast survey mode which will uniformly observe a
18,000 deg region about 800 times (summed over all six bands) during the
anticipated 10 years of operations, and yield a coadded map to . The
remaining 10\% of the observing time will be allocated to projects such as a
Very Deep and Fast time domain survey. The goal is to make LSST data products,
including a relational database of about 32 trillion observations of 40 billion
objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures
available from https://www.lsst.org/overvie
Evidence of lensing of the cosmic microwave background by dark matter halos
We present evidence of the gravitational lensing of the cosmic microwave background by 1013 solar
mass dark matter halos. Lensing convergence maps from the Atacama Cosmology Telescope Polarimeter
(ACTPol) are stacked at the positions of around 12 000 optically selected CMASS galaxies from the
SDSS-III/BOSS survey. The mean lensing signal is consistent with simulated dark matter halo profiles and
is favored over a null signal at 3.2Ï significance. This result demonstrates the potential of microwave
background lensing to probe the dark matter distribution in galaxy group and galaxy cluster halos
Yoga jam: remixing Kirtan in the Art of Living
Yoga Jam are a group of musicians in the United Kingdom who are active members of the Art of Living, a transnational Hindu-derived meditation group. Yoga Jam organize eventsâalso referred to as yoga raves and yoga remixesâthat combine Hindu devotional songs (bhajans) and chants (mantras) with modern Western popular musical genres, such as soul, rock, and particularly electronic dance music. This hybrid music is often played in a clublike setting, and dancing is interspersed with yoga and meditation. Yoga jams are creative fusions of what at first sight seem to be two incompatible phenomenaâmodern electronic dance music culture and ancient yogic traditions. However, yoga jams make sense if the Durkheimian distinction between the sacred and the profane is challenged, and if tradition and modernity are not understood as existing in a sort of inverse relationship. This paper argues that yoga raves are authenticated through the somatic experience of the modern popular cultural phenomenon of clubbing combined with therapeutic yoga practices and validated by identifying this experience with a reimagined Vedic tradition
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