7,617 research outputs found
Multi-user lattice coding for the multiple-access relay channel
This paper considers the multi-antenna multiple access relay channel (MARC),
in which multiple users transmit messages to a common destination with the
assistance of a relay. In a variety of MARC settings, the dynamic decode and
forward (DDF) protocol is very useful due to its outstanding rate performance.
However, the lack of good structured codebooks so far hinders practical
applications of DDF for MARC. In this work, two classes of structured MARC
codes are proposed: 1) one-to-one relay-mapper aided multiuser lattice coding
(O-MLC), and 2) modulo-sum relay-mapper aided multiuser lattice coding
(MS-MLC). The former enjoys better rate performance, while the latter provides
more flexibility to tradeoff between the complexity of the relay mapper and the
rate performance. It is shown that, in order to approach the rate performance
achievable by an unstructured codebook with maximum-likelihood decoding, it is
crucial to use a new K-stage coset decoder for structured O-MLC, instead of the
one-stage decoder proposed in previous works. However, if O-MLC is decoded with
the one-stage decoder only, it can still achieve the optimal DDF
diversity-multiplexing gain tradeoff in the high signal-to-noise ratio regime.
As for MS-MLC, its rate performance can approach that of the O-MLC by
increasing the complexity of the modulo-sum relay-mapper. Finally, for
practical implementations of both O-MLC and MS-MLC, practical short length
lattice codes with linear mappers are designed, which facilitate efficient
lattice decoding. Simulation results show that the proposed coding schemes
outperform existing schemes in terms of outage probabilities in a variety of
channel settings.Comment: 32 pages, 5 figure
VConv-DAE: Deep Volumetric Shape Learning Without Object Labels
With the advent of affordable depth sensors, 3D capture becomes more and more
ubiquitous and already has made its way into commercial products. Yet,
capturing the geometry or complete shapes of everyday objects using scanning
devices (e.g. Kinect) still comes with several challenges that result in noise
or even incomplete shapes. Recent success in deep learning has shown how to
learn complex shape distributions in a data-driven way from large scale 3D CAD
Model collections and to utilize them for 3D processing on volumetric
representations and thereby circumventing problems of topology and
tessellation. Prior work has shown encouraging results on problems ranging from
shape completion to recognition. We provide an analysis of such approaches and
discover that training as well as the resulting representation are strongly and
unnecessarily tied to the notion of object labels. Thus, we propose a full
convolutional volumetric auto encoder that learns volumetric representation
from noisy data by estimating the voxel occupancy grids. The proposed method
outperforms prior work on challenging tasks like denoising and shape
completion. We also show that the obtained deep embedding gives competitive
performance when used for classification and promising results for shape
interpolation
Energy-based temporal neural networks for imputing missing values
Imputing missing values in high dimensional time series is a difficult problem. There have been some approaches to the problem [11,8] where neural architectures were trained as probabilistic models of the data. However, we argue that this approach is not optimal. We propose to view temporal neural networks with latent variables as energy-based models and train them for missing value recovery directly. In this paper we introduce two energy-based models. The first model is based on a one dimensional convolution and the second model utilizes a recurrent neural network. We demonstrate how ideas from the energy-based learning framework can be used to train these models to recover missing values. The models are evaluated on a motion capture dataset
Cost-effectiveness of eplerenone in patients with systolic heart failure and mild symptoms
Aim In the Eplerenone in Mild Patients Hospitalization and Survival Study in Heart Failure (EMPHASIS-HF), aldosterone blockade with eplerenone decreased mortality and hospitalisation in patients with mild symptoms (New York Heart Association class II) and chronic systolic heart failure (HF). The present study evaluated the cost-effectiveness of eplerenone in the treatment of these patients in the UK and Spain.<p></p>
Methods and results Results from the EMPHASIS-HF trial were used to develop a discrete-event simulation model estimating lifetime direct costs and effects (life years and quality-adjusted life years (QALYs) gained) of the addition of eplerenone to standard care among patients with chronic systolic HF and mild symptoms. Eplerenone plus standard care compared with standard care alone increased lifetime direct costs per patient by £4284 for the UK and €7358 for Spain, with additional quality-adjusted life expectancy of 1.22 QALYs for the UK and 1.33 QALYs for Spain. Mean lifetime costs were £3520 per QALY in the UK and €5532 per QALY in Spain. Probabilistic sensitivity analysis suggested a 100% likelihood of eplerenone being regarded as cost-effective at a willingness-to-pay threshold of £20 000 per QALY (UK) or €30 000 per QALY (Spain).<p></p>
Conclusions By currently accepted standards of value for money, the addition of eplerenone to optimal medical therapy for patients with chronic systolic HF and mild symptoms is likely to be cost-effective.<p></p>
Astrophysical Observations of a Dark Matter-Baryon Fifth Force
We consider the effects of an attractive, long-range Yukawa interaction
between baryons and dark matter (DM), focusing in particular on temperature and
pulsar timing observations of neutron stars (NSs). We show that such a fifth
force, with strength modestly stronger than gravity at ranges greater than tens
of kilometers (corresponding to mediator masses less than ), can dramatically enhance dark matter kinetic heating, capture, and
pulsar timing Doppler shifts relative to gravity plus short range interactions
alone. Using the coldest observed NS and pulsar timing array (PTA) data, we
derive limits on fifth force strength over a DM mass range spanning light dark
matter up to order solar mass composite DM objects. We also consider an
indirect limit by combining bullet cluster limits on the DM self-interaction
with weak equivalence principle test limits on baryonic self-interactions. We
find the combined indirect limits are moderately stronger than kinetic heating
and PTA limits, except when considering a DM subcomponent.Comment: 40 pages, 6 figures, v2: updated with analysis using another PTA
dataset, figures updated, conclusions unchange
Macroscopic Dark Matter Detection with Gravitational Wave Experiments
We study signatures of macroscopic dark matter (DM) in current and future
gravitational wave (GW) experiments. Transiting DM with a mass of
kg that saturates the local DM density can be potentially
detectable by GW detectors, depending on the baseline of the detector and the
strength of the force mediating the interaction. In the context of laser
interferometers, we derive the gauge invariant observable due to a transiting
DM, including the Shapiro effect, and adequately account for the finite photon
travel time within an interferometer arm. In particular, we find that the
Shapiro effect can be dominant for short-baseline interferometers such as
Holometer and GQuEST. We also find that proposed experiments such as Cosmic
Explorer and Einstein Telescope can constrain a fifth force between DM and
baryons, at the level of strength times stronger than gravity for,
e.g., kg mass DM with a fifth-force range of m.Comment: 40 pages, 6 figure
Interferometer Response to Geontropic Fluctuations
We model vacuum fluctuations in quantum gravity with a scalar field,
characterized by a high occupation number, coupled to the metric. The
occupation number of the scalar is given by a thermal density matrix, whose
form is motivated by fluctuations in the vacuum energy, which have been shown
to be conformal near a light-sheet horizon. For the experimental measurement of
interest in an interferometer, the size of the energy fluctuations is fixed by
the area of a surface bounding the volume of spacetime being interrogated by an
interferometer. We compute the interferometer response to these "geontropic"
scalar-metric fluctuations, and apply our results to current and future
interferometer measurements, such as LIGO and the proposed GQuEST experiment.Comment: 17 pages, 6 figure
Astroclimatic Characterization of Vallecitos: A candidate site for the Cherenkov Telescope Array at San Pedro Martir
We conducted an 18 month long study of the weather conditions of the
Vallecitos, a proposed site in Mexico to harbor the northern array of the
Cherenkov Telescope Array (CTA). It is located in Sierra de San Pedro Martir
(SPM) a few kilometers away from Observatorio Astron\'omico Nacional. The study
is based on data collected by the ATMOSCOPE, a multi-sensor instrument
measuring the weather and sky conditions, which was commissioned and built by
the CTA Consortium. Additionally, we compare the weather conditions of the
optical observatory at SPM to the Vallecitos regarding temperature, humidity,
and wind distributions. It appears that the excellent conditions at the optical
observatory benefit from the presence of microclimate established in the
Vallecitos.Comment: 16 pages, 16 figures, Publication of the Astronomical Society of the
Pacific, accepte
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