405 research outputs found
Links between N-modular redundancy and the theory of error-correcting codes
N-Modular Redundancy (NMR) is one of the best known fault tolerance techniques. Replication of a module to achieve fault tolerance is in some ways analogous to the use of a repetition code where an information symbol is replicated as parity symbols in a codeword. Linear Error-Correcting Codes (ECC) use linear combinations of information symbols as parity symbols which are used to generate syndromes for error patterns. These observations indicate links between the theory of ECC and the use of hardware redundancy for fault tolerance. In this paper, we explore some of these links and show examples of NMR systems where identification of good and failed elements is accomplished in a manner similar to error correction using linear ECC's
Human Cognition and Emotion using Physio Psychological Approach : A Survey
A soldier’s responsibility in the military includes his physical and mental attitudes which makes him to support the army in a full-fledged manner. This type of human dimension recognizes Soldier readiness from training proficiency to motivation for the Army’s future success. It introduces the concept of holistic fitness, a comprehensive combination of the whole person, including all components of the human dimension as a triad of moral, cognitive and physical components. The human dimension concept is directly related to the human mind and memory system. In this research, a system which will be capable of recognizing human emotions based on physiological parameters of a human body is discussed. The data from the system is fed to a computer where it is stored. Stored information regarding human parameters is retrieved and classified using support vector machine to generate a data set about the various emotions the human poses at a specific situation. The emotion, thus calculated is grouped to generate a grade for his present status. This grade is used to recommend the suitable working environment for the person
Scintillating double beta decay bolometers
We present the results obtained in the development of scintillating Double
Beta Decay bolometers. Several Mo and Cd based crystals were tested with the
bolometric technique. The scintillation light was measured through a second
independent bolometer. A 140 g CdWO_4 crystal was run in a 417 h live time
measurement. Thanks to the scintillation light, the alpha background is easily
discriminated resulting in zero counts above the 2615 keV gamma line of
Thallium 208. These results, combined with an extremely easy light detector
operation, represent the first tangible proof demonstrating the feasibility of
this kind of technique.Comment: 15 pages, 8 figure
A Comparison of Algorithms for the Construction of SZ Cluster Catalogues
We evaluate the construction methodology of an all-sky catalogue of galaxy
clusters detected through the Sunyaev-Zel'dovich (SZ) effect. We perform an
extensive comparison of twelve algorithms applied to the same detailed
simulations of the millimeter and submillimeter sky based on a Planck-like
case. We present the results of this "SZ Challenge" in terms of catalogue
completeness, purity, astrometric and photometric reconstruction. Our results
provide a comparison of a representative sample of SZ detection algorithms and
highlight important issues in their application. In our study case, we show
that the exact expected number of clusters remains uncertain (about a thousand
cluster candidates at |b|> 20 deg with 90% purity) and that it depends on the
SZ model and on the detailed sky simulations, and on algorithmic implementation
of the detection methods. We also estimate the astrometric precision of the
cluster candidates which is found of the order of ~2 arcmins on average, and
the photometric uncertainty of order ~30%, depending on flux.Comment: Accepted for publication in A&A: 14 pages, 7 figures. Detailed
figures added in Appendi
Compressed sensing imaging techniques for radio interferometry
Radio interferometry probes astrophysical signals through incomplete and
noisy Fourier measurements. The theory of compressed sensing demonstrates that
such measurements may actually suffice for accurate reconstruction of sparse or
compressible signals. We propose new generic imaging techniques based on convex
optimization for global minimization problems defined in this context. The
versatility of the framework notably allows introduction of specific prior
information on the signals, which offers the possibility of significant
improvements of reconstruction relative to the standard local matching pursuit
algorithm CLEAN used in radio astronomy. We illustrate the potential of the
approach by studying reconstruction performances on simulations of two
different kinds of signals observed with very generic interferometric
configurations. The first kind is an intensity field of compact astrophysical
objects. The second kind is the imprint of cosmic strings in the temperature
field of the cosmic microwave background radiation, of particular interest for
cosmology.Comment: 10 pages, 1 figure. Version 2 matches version accepted for
publication in MNRAS. Changes includes: writing corrections, clarifications
of arguments, figure update, and a new subsection 4.1 commenting on the exact
compliance of radio interferometric measurements with compressed sensin
Component separation methods for the Planck mission
The Planck satellite will map the full sky at nine frequencies from 30 to 857
GHz. The CMB intensity and polarization that are its prime targets are
contaminated by foreground emission. The goal of this paper is to compare
proposed methods for separating CMB from foregrounds based on their different
spectral and spatial characteristics, and to separate the foregrounds into
components of different physical origin. A component separation challenge has
been organized, based on a set of realistically complex simulations of sky
emission. Several methods including those based on internal template
subtraction, maximum entropy method, parametric method, spatial and harmonic
cross correlation methods, and independent component analysis have been tested.
Different methods proved to be effective in cleaning the CMB maps from
foreground contamination, in reconstructing maps of diffuse Galactic emissions,
and in detecting point sources and thermal Sunyaev-Zeldovich signals. The power
spectrum of the residuals is, on the largest scales, four orders of magnitude
lower than that of the input Galaxy power spectrum at the foreground minimum.
The CMB power spectrum was accurately recovered up to the sixth acoustic peak.
The point source detection limit reaches 100 mJy, and about 2300 clusters are
detected via the thermal SZ effect on two thirds of the sky. We have found that
no single method performs best for all scientific objectives. We foresee that
the final component separation pipeline for Planck will involve a combination
of methods and iterations between processing steps targeted at different
objectives such as diffuse component separation, spectral estimation and
compact source extraction.Comment: Matches version accepted by A&A. A version with high resolution
figures is available at http://people.sissa.it/~leach/compsepcomp.pd
Relationships between consecutive long-term and mid-term mobility decisions over the life course: a bayesian network approach
Long-term and mid-term mobility decision processes in different life trajectories generate complex dynamics, in which consecutive life events are interrelated and time dependent. This study uses the Bayesian network approach to study the dynamic relationships among residential events, household structure events, employment/education events, and car ownership events. Using retrospective data obtained from a web-based survey in Beijing, China, first structure learning is used to discover the direct and indirect relationships between these mobility decisions. Parameter learning is then applied to describe the conditional probabilities and predict the direct and indirect effects of actions and policies in the resulting network. The results confirm the interdependencies between these long-term and mid-term mobility decisions, and evidence the reactive and proactive behavior of individuals and households in the context of various life events over the course of their lives. In this regard, it is important to note that an increase in household size has a contemporaneous effect on car acquisition in the future; while residential events have a synergic relationship with employment/education events. Moreover, if people’s residential location or workplace/study location will move from an urban district to a suburban or outer suburban district, it has both lagged and concurrent effects on car acquisition
MILCA, a Modified Internal Linear Combination Algorithm to extract astrophysical emissions from multi-frequency sky maps
The analysis of current Cosmic Microwave Background (CMB) experiments is
based on the interpretation of multi-frequency sky maps in terms of different
astrophysical components and it requires specifically tailored component
separation algorithms. In this context, Internal Linear Combination (ILC)
methods have been extensively used to extract the CMB emission from the WMAP
multi-frequency data. We present here a Modified Internal Linear Component
Algorithm (MILCA) that generalizes the ILC approach to the case of multiple
astrophysical components for which the electromagnetic spectrum is known. In
addition MILCA corrects for the intrinsic noise bias in the standard ILC
approach and extends it to an hybrid space-frequency representation of the
data. It also allows us to use external templates to minimize the contribution
of extra components but still using only a linear combination of the input
data. We apply MILCA to simulations of the Planck satellite data at the HFI
frequency bands. We explore the possibility of reconstructing the Galactic
molecular CO emission on the Planck maps as well as the thermal
Sunyaev-Zeldovich effect. We conclude that MILCA is able to accurately estimate
those emissions and it has been successfully used for this purpose within the
Planck collaboration.Comment: 13 page
CHEX-MATE: A non-parametric deep learning technique to deproject and deconvolve galaxy cluster X-ray temperature profiles
Temperature profiles of the hot galaxy cluster intracluster medium (ICM) have
a complex non-linear structure that traditional parametric modelling may fail
to fully approximate. For this study, we made use of neural networks, for the
first time, to construct a data-driven non-parametric model of ICM temperature
profiles. A new deconvolution algorithm was then introduced to uncover the true
(3D) temperature profiles from the observed projected (2D) temperature
profiles. An auto-encoder-inspired neural network was first trained by learning
a non-linear interpolatory scheme to build the underlying model of 3D
temperature profiles in the radial range of [0.02-2] R, using a sparse
set of hydrodynamical simulations from the THREE HUNDRED PROJECT. A
deconvolution algorithm using a learning-based regularisation scheme was then
developed. The model was tested using high and low resolution input temperature
profiles, such as those expected from simulations and observations,
respectively. We find that the proposed deconvolution and deprojection
algorithm is robust with respect to the quality of the data, the morphology of
the cluster, and the deprojection scheme used. The algorithm can recover
unbiased 3D radial temperature profiles with a precision of around 5\% over
most of the fitting range. We apply the method to the first sample of
temperature profiles obtained with XMM{\it -Newton} for the CHEX-MATE project
and compared it to parametric deprojection and deconvolution techniques. Our
work sets the stage for future studies that focus on the deconvolution of the
thermal profiles (temperature, density, pressure) of the ICM and the dark
matter profiles in galaxy clusters, using deep learning techniques in
conjunction with X-ray, Sunyaev Zel'Dovich (SZ) and optical datasets.Comment: 32 pages, 30 figures, 6 tables, Accepted in A&
Polarization leakage in epoch of reionization windows – I. Low Frequency Array observations of the 3C196 field
Detection of the 21-cm signal coming from the epoch of reionization (EoR) is challenging especially because, even after removing the foregrounds, the residual Stokes I maps contain leakage from polarized emission that can mimic the signal. Here, we discuss the instrumental polarization of LOFAR and present realistic simulations of the leakages between Stokes parameters. From the LOFAR observations of polarized emission in the 3C196 field, we have quantified the level of polarization leakage caused by the nominal model beam of LOFAR, and compared it with the EoR signal using power spectrum analysis. We found that at 134– 166 MHz, within the central 4◦ of the field the (Q,U)→I leakage power is lower than the EoR signal at k<0.3 Mpc−¹. The leakage was found to be localized around a Faraday depth of 0, and the rms of the leakage as a fraction of the rms of the polarized emission was shown to vary between 0.2–0.3%, both of which could be utilized in the removal of leakage. Moreover, we could define an ‘EoR window’ in terms of the polarization leakage in the cylindrical power spectrum above the PSF-induced wedge and below k∥∼0.5 Mpc−¹, and the window extended up to k∥∼1 Mpc−¹ at all k⊥ when 70% of the leakage had been removed. These LOFAR results show that even a modest polarimetric calibration over a field of view of ≲4∘ in the future arrays like SKA will ensure that the polarization leakage remains well below the expected EoR signal at the scales of 0.02–1 Mpc−¹
- …