2,667 research outputs found
GMRT Radio Halo Survey in galaxy clusters at z = 0.2 -- 0.4. II.The eBCS clusters and analysis of the complete sample
We present the results of the GMRT cluster radio halo survey. The main
purposes of our observational project are to measure which fraction of massive
galaxy clusters in the redshift range z=0.2--0.4 hosts a radio halo, and to
constrain the expectations of the particle re--acceleration model for the
origin of the non--thermal radio emission. We selected a complete sample of 50
clusters in the X-ray band from the REFLEX (27) and the eBCS (23) catalogues.
In this paper we present Giant Metrewave Radio Telescope (GMRT) observations at
610 MHz for all clusters still lacking high sensitivity radio information, i.e.
16 eBCS and 7 REFLEX clusters, thus completing the radio information for the
whole sample. The typical sensitivity in our images is in the range 1Jy b. We found a radio halo in A697, a diffuse
peripheral source of unclear nature in A781, a core--halo source in Z7160, a
candidate radio halo in A1682 and ``suspect'' central emission in Z2661.
Including the literature information, a total of 10 clusters in the sample host
a radio halo. A very important result of our work is that 25 out of the 34
clusters observed with the GMRT do not host extended central emission at the
sensitivity level of our observations, and for 20 of them firm upper limits to
the radio power of a giant radio halo were derived. The GMRT Radio Halo Survey
shows that radio halos are not common, and our findings on the fraction of
giant radio halos in massive clusters are consistent with the statistical
expectations based on the re--acceleration model. Our results favour primary to
secondary electron models.Comment: A&A in press, 17 pages, 12 figures, 4 tables Version with high
quality figures available on web at
http://www.ira.inaf.it/~tventuri/pap/Venturi_web.pd
Gearbox Health Condition Monitoring: A brief exposition
Gearbox is a mechanical power transmission device, most commonly used to get the mechanical benefits
in terms of speed and torque. The gearbox is made up of different types of gears assembled in a cascading order to
perform the intended task. Failure of any rotating component inside the gearbox will terminate the working condition
of the mechanical system associated with it. This causes interrupted services to the industries, which lead to expensive compensation. Especially, in an aircraft engine, it is used as an accessory drive, which provides power for hydraulic,pneumatic and electrical systems. This motivated to monitor the gearbox health condition. This paper presents a brief review of GHCM (gearbox health condition monitoring), gearbox faults, overview of time-domain features, frequency-domain features, time-frequency domain; feature extraction techniques, and fault classification techniques.The outcome of this study is to provide brief information regarding gearbox health condition monitoring
Some non-linear function theoretic properties of Riemannian manifolds
We study the appropriate versions of parabolicity stochastic completeness and related Liouville properties for a general class of operators which include the -Laplace operator, and the non linear singular operators in non-diagonal form considered by J. Serrin and collaborators
A finiteness theorem for the space of Lp harmonic sections
In this paper we give a unified and improved treatment to finite dimensionality results for subspaces of Lp harmonic sections of Riemannian or Hermitian vector bundles over complete manifolds. The geometric conditions on the manifold are subsumed by the assumption that the Morse index of a related Schro \u308dinger operator is finite. Applications of the finiteness theorem to concrete geometric situations are also presented
Improving PA efficiency by chaos-based spreading in multicarrier DS-CDMA systems
In this paper, we investigate the effect of spreading sequences on the peak-to-average power ratio (PAPR) in order to improve the power amplifier efficiency of multicarrier direct-sequence code-division multiple access systems. Baseband shaping has been identified to have a key role in reducing PAPR by spreading and we have found that chaos-based spreading sequences give good results as compared with Gold and i.i.d. sequences behaving differently depending on the number of subcarriers
First-principles investigation of electronic, elastic, optical and thermoelectric properties of strontium-based anti-perovskite Sr3MN (M= P and As) for potential applications in optoelectronic and thermoelectric devices
This work aims to study the electronic, elastic, optical and thermoelectric properties of the cubic Sr3MN (M=P and As) anti-perovskites. The properties of the cubic Sr3PN are investigated for the first time in this work while those of the Sr3AsN are compared with other theoretical results in the literature. The Density Functional Theory (DFT) implemented in the Quantum Espresso (QE) package with the GGA-PBE functional was used throughout this study. Sr3PN and Sr3AsN were found to be chemically and mechanically stable with optimized lattice parameters of 5.07 Å and 5.11 Å, respectively. Results also showed that the two compounds are p-type semiconductors with direct band gaps of 0.56 eV and 0.45 eV for the respective compounds. The materials are also predicted to have exceptional optical properties including high absorption in the order of cm-1 in the visible and ultraviolet region and hence are promising optoelectronic materials. Moreover, the calculated thermoelectric properties of the two materials strongly suggest that the two materials are potential for thermoelectric application
Resonate and fire dynamics in Complex Oscillation Based Test of analog filters
Recently, proposals have been made for enhancing the Oscillation Based Test (OBT) methodology by using non-plain oscillation regimes, leading to so called Complex Oscillation Based Test (COBT). Here we focus on a recently illustrated strategy for the testing of analog 2nd order filters, showing that the COBT dynamics is quite similar to that expressed by Resonate & Fire (R+F) neuron models. In this interpretation, the testing approach can be related to firing-rate measures. A brief description is given of the mathematical models necessary to achieve a precise characterization of firing times, showing how it can be used for testing purposes. A practical example with simulation data is also provided. © 2011 IEEE
The number of stimulus-onset asynchronies affects the perception of the sound-induced flash illusion in young and older adults
The sound-induced flash illusion is a multisensory illusion occurring when one flash is presented with two beeps and perceived as two flashes. Younger individuals are largely susceptible to the illusion when the stimulus onset asynchrony between the first and the second beep falls within the temporal window of integration, but the susceptibility falls dramatically outside of this short temporal range. Older individuals, in particular older adults prone to falling and/or mild cognitive impairment, show an extended susceptibility to the illusion. This suggests that they have inefficient multisensory integration, particularly in the temporal domain. In the present study, we investigated the reliability of the illusion across younger and older people, guided by the hypothesis that the experimental context, i.e., exposure to a wider or smaller number of stimulus onset asynchronies, would modify the intra-personal susceptibility to the illusion at shorter asynchronies vs. longer asynchronies, likely due to the gathering of model evidence based on Bayesian inference. We tested 22 young adults and 29 older adults and verified these hypotheses. Both groups showed higher susceptibility to the illusion when exposed to a smaller range of asynchronies, but only for longer ones, not within the 100 ms window. We discuss the theoretical implications in terms of online perceptual learning and practical implications in terms of standardisation of the experimental context when attempting to find normative values
Food waste as a (negative) measure of social capital. A study across Italian Provinces
Household food waste is a crucial problem in developed countries. Food waste behaviour is the result of complex interactions among economic factors, deeply rooted habits, and social norms. It can thus be considered a measure of the social capital characterizing a community. We test this hypothesis using a national-level dataset on household food-related behaviours and opinions in Italy gathered in 2016. This country is an ideal test bed for a comparative analysis on social capital. We find household food waste measures to be negatively related with the local level of social capital. This relationship is mediated by family income, as it becomes weaker for better-off families. Furthermore, we find that behaviours and opinions eliciting status concerns with respect to food, as well as lack of organisational abilities, generate increased food waste. In turn, these behaviours and opinions are more prevalent in areas with low social capital. Our results, captured by a simple model where food waste decisions are considered in the context of a modified public good game, allow to derive several policy implications for the reduction of food waste
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