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.
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.
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.
Exploiting the Herschel Astrophysical Terahertz Large Area Survey Science Demonstration Phase survey data, we have determined the luminosity functions (LFs) at rest-frame wavelengths of 100 and 250 ...Delta *mm and at several redshifts z 1, for bright submillimeter galaxies with star formation rates (SFRs) 100 M yr--1. We find that the evolution of the comoving LF is strong up to z 2.5, and slows down at higher redshifts. From the LFs and the information on halo masses inferred from clustering analysis, we derived an average relation between SFR and halo mass (and its scatter). We also infer that the timescale of the main episode of dust-enshrouded star formation in massive halos (M H 3 X 1012 M ) amounts to ~7 X 108 yr. Given the SFRs, which are in the range of 102-103 M yr--1, this timescale implies final stellar masses of the order of 1011-1012 M . The corresponding stellar mass function matches the observed mass function of passively evolving galaxies at z 1. The comparison of the statistics for submillimeter and UV-selected galaxies suggests that the dust-free, UV bright phase is 102 times shorter than the submillimeter bright phase, implying that the dust must form soon after the onset of star formation. Using a single reference spectral energy distribution (SED; the one of the z 2.3 galaxy SMM J2135-0102), our simple physical model is able to reproduce not only the LFs at different redshifts >1 but also the counts at wavelengths ranging from 250 Delta *mm to 1 mm. Owing to the steepness of the counts and their relatively broad frequency range, this result suggests that the dispersion of submillimeter SEDs of z > 1 galaxies around the reference one is rather small.