An easy treatment based in carbon layer deposition into aluminium alloys is presented to enhance the performance of Al-air primary batteries with neutral pH electrolyte. The jellification of ...aluminate in the anode surface is described and avoided by the carbon covering. Treated commercial Al alloys namely Al1085 and Al7475 are tested as anodes achieving specific capacities above 1.2 Ah g−1vs 0.5 Ah g−1 without carbon covering. The influence of the binder proportion in the treatment as well as different carbonaceous materials, Carbon Black, Graphene and Pyrolytic Graphite are evaluated as candidates for the covering. Current densities of 1–10 mA cm−2 are measured and the influence of the alloy explored. A final battery design of 4 cells in series is presented for discharges with a voltage plateau of 2 V and 1 Wh g−1 energy density.
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•Carbon treated commercial Al alloy anodes achieve discharges up to 3 times longer.•Al1085 alloy performs better at low current rates, while Al7475 at high rates.•Carbon Black achieves best behaviour/price ratio vs Pyrolytic Graphite and Graphene.•Specific capacities of 1200 mAh g−1 are achieved, and 2 V plateaus in 4s1p battery.
The current generation of ground-based imaging atmospheric Cherenkov telescopes (IACTs) operate in the very-high-energy (VHE) domain from ~100 GeV to ~100 TeV. They use electronic digital trigger ...systems to discern the Cherenkov light flashes emitted by extensive air showers (EASs), from the overwhelming light of the night sky (LoNS) background. Near the telescope energy threshold, the number of emitted Cherenkov photons by gamma-ray-induced EASs is comparable to the fluctuations of the LoNS and the photon distribution at the Cherenkov-imaging camera plane becomes patchy. This results in a severe loss of effectiveness of the digital triggers based on combinatorial logic of thresholded signals. A stereoscopic analog trigger system has been developed for improving the detection capabilities of the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes at the lowest energies. It is based on the analog sum of the photosensor electrical signals. In this article, the architectural design, technical performances, and configuration of this stereoscopic analog trigger, dubbed " Sum-Trigger-II ," are described.
Abstract
Although interesting in themselves, extragalactic sources emitting in the microwave range (mainly radio-loud active galactic nuclei and dusty galaxies) are also considered a contaminant from ...the point of view of Cosmic Microwave Background (CMB) experiments. These sources appear as unresolved point-like objects in CMB measurements because of the limited resolution of CMB experiments. Amongst other issues, point-like sources are known to obstruct the reconstruction of the lensing potential, and can hinder the detection of the Primordial Gravitational Wave Background for low values of r. Therefore, extragalactic point-source detection and subtraction is a fundamental part of the component separation process necessary to achieve some of the science goals set for the next generation of CMB experiments. As a previous step to their removal, in this work we present a new filter based on steerable wavelets that allows the characterization of the emission of these extragalactic sources. Instead of the usual approach of working in polarization maps of the Stokes' Q and U parameters, the proposed filter operates on E- and B-mode polarization maps. In this way, it benefits from the lower intensity that, both, the CMB, and the galactic foreground emission, present in B-modes to improve its performance. To demonstrate its potential, we have applied the filter to simulations of the future PICO satellite, and we predict that, for the regions of fainter galactic foreground emission in the 30 GHz and 155 GHz bands of PICO, our filter will be able to characterize sources down to a minimum polarization intensity of, respectively, 125 pK and 14 pK. Adopting a Π=0.02 polarization degree, these values correspond to 169 mJy and 288 mJy intensities.
A series of poly(vinyl alcohol)-blend-poly(benzimidazole) (PVA:PBI) membranes are synthesized with different ratios of PVA and PBI (2:1, 4:1, 6:1 and 8:1) using the casting method. These materials ...are doped in KOH 6 M solution in order to study their suitability for fuel cell applications. The Infra-red (IR) and Raman spectra confirm the successful doping of the membranes and the dimensional changes due to water and KOH uptakes during the doping are similar to other PBI-based membranes. XPS measurements are performed to evaluate the characteristics of these materials after the doping process. The thermal stability of the membranes is excellent in the range of desired temperatures (below 100 °C) and the conductivity values found are between 10−2 and 10−1 S cm−1. These results are optimal to consider these membranes as candidates for anion exchange membranes (AEMs) and they are tested in a single cell with ethanol as fuel. The PVA:PBI 4:1 membrane have the best behaviour in fuel cell, reaching a power density of 76 mW cm−2, approximately 50% better than the doped PBI in the same conditions. These important results can be considered highly promising for the future application of these membranes in alkaline polymer electrolyte membrane fuel cells (APEMFC).
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•PVA:PBI (KOH doped) anion exchange membranes are prepared.•Hydrogen bridge between PVA and PBI is identified by 1H NMR spectroscopy.•Ionic conductivity of 70 mS cm−1 at 90 °C is attained with PVA:PBI 4:1 wt ratio.•The maximum power density in the single cell is 76 mW cm−2.•Single cell performance of PVA:PBI 4:1 is 43% better than that of pure PBI.
The shallow, all-sky
Planck
surveys at sub-millimetre wavelengths have detected the brightest strongly gravitationally lensed dusty galaxies in the sky. The combination of their extreme gravitational ...flux-boosting and image-stretching offers the unique possibility of measuring in extraordinary detail the galaxy structure and kinematics in early evolutionary phases through high-resolution imaging and spectroscopic follow-up. This enables us to gain otherwise unaccessible direct information on physical processes in action. However, the extraction of candidate strongly lensed galaxies from
Planck
catalogues is hindered by the fact that they are generally detected with a poor signal-to-noise ratio, except for the few brightest galaxies. Their photometric properties are therefore strongly blurred, which makes them very difficult to single out. We have devised a method capable of increasing the number of identified
Planck
-detected strongly lensed galaxies by a factor of about three to four, although with an unavoidably limited efficiency. Our approach exploits the fact that the sub-millimetre colours of strongly lensed galaxies are definitely colder than those of nearby dusty galaxies, which constitute the overwhelming majority of extragalactic sources detected by
Planck
. The sub-millimetre colours of the 47 confirmed or very likely
Planck
-detected strongly lensed galaxies have been used to estimate the colour range spanned by objects of this type. Moreover, most nearby galaxies and radio sources can be confirmed by cross-matching with the IRAS and PCNT catalogues, respectively. We present samples of lensed candidates selected at 545, 857, and 353 GHz, comprising 177, 97, and 104 sources, respectively. The efficiency of our approach, tested by exploiting data from the SPT survey covering ≃2500 deg
2
, is estimated to be in the range 30%−40%. We also discuss stricter selection criteria to increase the estimated efficiency to ≃50%, at the cost of a somewhat lower completeness. Our analysis of SPT data has identified a dozen galaxies that can reliably be considered previously unrecognized
Planck
-detected strongly lensed galaxies. Extrapolating the number of
Planck
-detected confirmed or very likely strongly lensed galaxies found within the SPT and H-ATLAS survey areas, we expect ≃150 to ≃190 such sources over the full |
b
|> 20° sky.
ABSTRACT
We present QUIJOTE intensity and polarization maps in four frequency bands centred around 11, 13, 17, and 19 GHz, and covering approximately 29 000 deg2, including most of the northern sky ...region. These maps result from 9000 h of observations taken between May 2013 and June 2018 with the first QUIJOTE multifrequency instrument (MFI), and have angular resolutions of around 1°, and sensitivities in polarization within the range 35–40 µK per 1° beam, being a factor ∼2–4 worse in intensity. We discuss the data processing pipeline employed, and the basic characteristics of the maps in terms of real space statistics and angular power spectra. A number of validation tests have been applied to characterize the accuracy of the calibration and the residual level of systematic effects, finding a conservative overall calibration uncertainty of 5 per cent. We also discuss flux densities for four bright celestial sources (Tau A, Cas A, Cyg A, and 3C274), which are often used as calibrators at microwave frequencies. The polarization signal in our maps is dominated by synchrotron emission. The distribution of spectral index values between the 11 GHz and WMAP 23 GHz map peaks at β = −3.09 with a standard deviation of 0.14. The measured BB/EE ratio at scales of ℓ = 80 is 0.26 ± 0.07 for a Galactic cut |b| > 10°. We find a positive TE correlation for 11 GHz at large angular scales (ℓ ≲ 50), while the EB and TB signals are consistent with zero in the multipole range 30 ≲ ℓ ≲ 150. The maps discussed in this paper are publicly available.
ALMA photometry of extragalactic radio sources Bonato, M; Liuzzo, E; Herranz, D ...
Monthly Notices of the Royal Astronomical Society,
05/2019, Letnik:
485, Številka:
1
Journal Article
ABSTRACT
Anomalous Microwave Emission (AME) is a significant component of Galactic diffuse emission in the frequency range 10–$60\, \mathrm{GHz}$ and a new window into the properties of ...sub-nanometre-sized grains in the interstellar medium. We investigate the morphology of AME in the ≈10○ diameter λ Orionis ring by combining intensity data from the QUIJOTE experiment at 11, 13, 17, and $19\, \mathrm{GHz}$ and the C-Band All Sky Survey (C-BASS) at $4.76\, \mathrm{GHz}$, together with 19 ancillary data sets between 1.42 and $3000\, \mathrm{GHz}$. Maps of physical parameters at 1○ resolution are produced through Markov chain Monte Carlo (MCMC) fits of spectral energy distributions (SEDs), approximating the AME component with a lognormal distribution. AME is detected in excess of $20\, \sigma$ at degree-scales around the entirety of the ring along photodissociation regions (PDRs), with three primary bright regions containing dark clouds. A radial decrease is observed in the AME peak frequency from $\approx 35\, \mathrm{GHz}$ near the free–free region to $\approx 21\, \mathrm{GHz}$ in the outer regions of the ring, which is the first detection of AME spectral variations across a single region. A strong correlation between AME peak frequency, emission measure and dust temperature is an indication for the dependence of the AME peak frequency on the local radiation field. The AME amplitude normalized by the optical depth is also strongly correlated with the radiation field, giving an overall picture consistent with spinning dust where the local radiation field plays a key role.
Abstract
We present ECLIPSE (Efficient Cmb poLarization and Intensity Power Spectra Estimator), an optimized implementation of the Quadratic Maximum Likelihood (QML) method for the estimation of the ...power spectra of the Cosmic Microwave Background (CMB). This approach allows one to reduce significantly the computational costs associated to this technique, allowing to estimate the power spectra up to higher multipoles than previous implementations. In particular, for a resolution of
N
side
= 64, ℓ
max
= 192 and a typical Galactic mask, the number of operations can be reduced by approximately a factor of 1000 in a full analysis including intensity and polarization with respect to an efficient direct implementation of the method. In addition, if one is interested in studying only polarization, it is possible to obtain the power spectra of the E and B modes with a further reduction of computational resources without degrading the results. We also show that for experiments observing a small fraction of the sky, the Fisher matrix becomes singular and, in this case, the standard QML can not be applied. To solve this problem, we have developed a binned version of the method that is unbiased and of minimum variance. We also test the robustness of the QML estimator when the assumed fiducial model differs from that of the sky and show the performance of an iterative approach. Finally, we present a comparison of the results obtained by QML and a pseudo-
C
ℓ
estimator (NaMaster) for a next-generation satellite, showing that, as expected, QML produces significantly smaller errors at low multipoles. The ECLIPSE fast QML code developed in this work will be made publicly available.
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