2,852 research outputs found
Safe and sustainable lithium-ion batteries
The transition to clean energy and electric mobility is driving unprecedented demand for lithium-ion batteries (LIBs). This paper investigates the safety and sustainability of LIBs, exploring ways of reducing their impact on the environment and ensuring they do not pose a danger to health of workers or users
Exploring and developing a shared understanding of the issues surrounding engineering mathematics
Abstract: - Although Mathematics is a pillar which many of the subjects of any Engineering degree are based on, and in spite of being used as a tool in almost all of such subjects, it is sometimes difficult for students to assimilate the mathematical concepts. Since this relationship between Engineering and Mathematics is unavoidable, a consortium of universities from different countries is working on a project, EngiMath, to, on the one hand, make
it easier for teachers to teach Mathematics in the first years of Engineering degrees; and, on the other hand, to
promote study from a “student-centric” point of view. As a previous step to the development of educational
material that fulfills these purposes, a study of the students' feelings about Mathematics and their experience in
studying them has been carried out.info:eu-repo/semantics/publishedVersio
Nebular Spectroscopy of Kepler's Brightest Supernova
We present late-time (∼240–260 days after peak brightness) optical photometry and nebular (+236 and
+264 days) spectroscopy of SN 2018oh, the brightest supernova (SN) Ia observed by the Kepler telescope. The
Kepler/K2 30 minute cadence observations started days before explosion and continued past peak brightness. For
several days after explosion, SN 2018oh had blue “excess” flux in addition to a normal SN rise. The flux excess
can be explained by the interaction between the SN and a Roche-lobe filling non-degenerate companion star. Such
a scenario should also strip material from the companion star that would emit once the SN ejecta become optically
thin, imprinting relatively narrow emission features in its nebular spectrum. We search our nebular spectra for signs
of this interaction, including close examination of wavelengths of hydrogen and helium transitions, finding no
significant narrow emission. We place upper limits on the luminosity of these features of 2.6, 2.9 and
2.1 × 1037 erg s−1 for Hα, He I λ5875, and He I λ6678, respectively. Assuming a simple model for the amount of
swept-up material, we estimate upper mass limits for hydrogen of 5.4 × 10−4 Me and helium of 4.7 × 10−4 Me.
Such stringent limits are unexpected for the companion-interaction scenario consistent with the early data. No
known model can explain the excess flux, its blue color, and the lack of late-time narrow emission features.The UCSC team is supported in part by NASA grants 14-
WPS14-0048, NNG16PJ34G, and NNG17PX03C; NSF grants
AST-1518052 and AST-1815935; the Gordon & Betty Moore
Foundation; the Heising-Simons Foundation; and by a fellowship from the David and Lucile Packard Foundation to R.J.
Chemical composition of A--F type post-AGB candidates
An abundance analysis has been conducted for a sample of nine post-AGB
candidate stars; eight of them have not been explored before. We find four very
promising objects like HD 105262, HD 53300 and CpD among them. We
find strong evidence of dust-gas separation through selective depletion of
refractive elements in HD 105262. The same effect is also observed in HD 53300,
CpD and HD 114855 although abundance peculiarities are relatively
smaller for the last two stars. We find strong enrichment of nitrogen for HD
725, HD 842, HD 1457, HD 9233 and HD 61227 but no further evidence to support
their post-AGB nature. We have compared the observed [N/C] ratios of these
stars with the predictions of evolutionary models which include the rotation
induced mixing.Comment: Accepted in MNRAS, 18 pages, 12 figure
Highlights from the Pierre Auger Observatory
The Pierre Auger Observatory is the world's largest cosmic ray observatory.
Our current exposure reaches nearly 40,000 km str and provides us with an
unprecedented quality data set. The performance and stability of the detectors
and their enhancements are described. Data analyses have led to a number of
major breakthroughs. Among these we discuss the energy spectrum and the
searches for large-scale anisotropies. We present analyses of our X
data and show how it can be interpreted in terms of mass composition. We also
describe some new analyses that extract mass sensitive parameters from the 100%
duty cycle SD data. A coherent interpretation of all these recent results opens
new directions. The consequences regarding the cosmic ray composition and the
properties of UHECR sources are briefly discussed.Comment: 9 pages, 12 figures, talk given at the 33rd International Cosmic Ray
Conference, Rio de Janeiro 201
A search for point sources of EeV photons
Measurements of air showers made using the hybrid technique developed with
the fluorescence and surface detectors of the Pierre Auger Observatory allow a
sensitive search for point sources of EeV photons anywhere in the exposed sky.
A multivariate analysis reduces the background of hadronic cosmic rays. The
search is sensitive to a declination band from -85{\deg} to +20{\deg}, in an
energy range from 10^17.3 eV to 10^18.5 eV. No photon point source has been
detected. An upper limit on the photon flux has been derived for every
direction. The mean value of the energy flux limit that results from this,
assuming a photon spectral index of -2, is 0.06 eV cm^-2 s^-1, and no celestial
direction exceeds 0.25 eV cm^-2 s^-1. These upper limits constrain scenarios in
which EeV cosmic ray protons are emitted by non-transient sources in the
Galaxy.Comment: 28 pages, 10 figures, accepted for publication in The Astrophysical
Journa
Reconstruction of inclined air showers detected with the Pierre Auger Observatory
We describe the method devised to reconstruct inclined cosmic-ray air showers
with zenith angles greater than detected with the surface array of
the Pierre Auger Observatory. The measured signals at the ground level are
fitted to muon density distributions predicted with atmospheric cascade models
to obtain the relative shower size as an overall normalization parameter. The
method is evaluated using simulated showers to test its performance. The energy
of the cosmic rays is calibrated using a sub-sample of events reconstructed
with both the fluorescence and surface array techniques. The reconstruction
method described here provides the basis of complementary analyses including an
independent measurement of the energy spectrum of ultra-high energy cosmic rays
using very inclined events collected by the Pierre Auger Observatory.Comment: 27 pages, 19 figures, accepted for publication in Journal of
Cosmology and Astroparticle Physics (JCAP
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