1,724 research outputs found
Data-driven nonparametric Li-ion battery ageing model aiming at learningfrom real operation data – Part A: Storage operation
Conventional Li-ion battery ageing models, such as electrochemical, semi-empirical and empirical models, require a significant amount of time and experimental resources to provide accurate predictions under realistic operating conditions. At the same time, there is significant interest from industry in the introduction of new data collection telemetry technology. This implies the forthcoming availability of a significant amount of real-world battery operation data. In this context, the development of ageing models able to learn from in-field battery operation data is an interesting solution to mitigate the need for exhaustive laboratory testing.
In a series of two papers, a data-driven ageing model is developed for Li-ion batteries under the Gaussian Process framework. A special emphasis is placed on illustrating the ability of the Gaussian Process model to learn from new data observations, providing more accurate and confident predictions, and extending the operating window of the model.
This first paper focusses on the systematic modelling and experimental verification of cell degradation through calendar ageing. A specific covariance function is composed, tailored for use in a battery ageing application. Over an extensive dataset involving 32 cells tested during more than three years, different training possibilities are contemplated in order to quantify the minimal number of laboratory tests required for the design of an accurate ageing model. A model trained with only 18 tested cells achieves an overall mean-absolute-error of 0.53% in the capacity curves prediction, after being validated under a broad window of both dynamic and static temperature and SOC storage conditions.This investigation work was financially supported by ELKARTEK (CICe2018 -Desarrollo de actividades de investigacion fundamental estrategica en almacenamiento de energia electroquimica y termica para sistemas de almacenamiento hibridos, KK-2018/00098) and EMAITEK Strategic Programs of the Basque Government. In addition, the research was undertaken as a part of ELEVATE project (EP/M009394/1) funded by the Engineering and Physical Sciences Research Council (EPSRC) and partnership with the WMG High Value Manufacturing (HVM) Catapult.
Authors would like to thank the FP7 European project Batteries 2020 consortium (grant agreement No. 608936) for the valuable battery ageing data provided during the course of the project
Generation and Evolution of Spin Entanglement in NRQED
A complete analysis on the generation of spin entanglement from NRQED is
presented. The results of entanglement are obtained with relativistic
correction to the leading order of (v/c)^2. It is shown that to this order the
degree of entanglement of a singlet state does not change under time evolution
whereas the triplet state can change.Comment: 8 pages, 1 figure, to appear in Phys. Rev.
Nucleon-nucleon momentum correlation function for light nuclei
Nucleon-nucleon momentum correlation function have been presented for nuclear
reactions with neutron-rich or proton-rich projectiles using a nuclear
transport theory, namely Isospin-Dependent Quantum Molecular Dynamics model.
The relationship between the binding energy of projectiles and the strength of
proton-neutron correlation function at small relative momentum has been
explored, while proton-proton correlation function shows its sensitivity to the
proton density distribution. Those results show that nucleon-nucleon
correlation function is useful to reflect some features of the neutron- or
proton-halo nuclei and therefore provide a potential tool for the studies of
radioactive beam physics.Comment: Talk given at the 18th International IUPAP Conference on Few-Body
Problems in Physics (FB18), Santos, Brasil, August 21-26, 2006. To appear in
Nucl. Phys.
New bounds for the free energy of directed polymers in dimension 1+1 and 1+2
We study the free energy of the directed polymer in random environment in
dimension 1+1 and 1+2. For dimension 1, we improve the statement of Comets and
Vargas concerning very strong disorder by giving sharp estimates on the free
energy at high temperature. In dimension 2, we prove that very strong disorder
holds at all temperatures, thus solving a long standing conjecture in the
field.Comment: 31 pages, 4 figures, final version, accepted for publication in
Communications in Mathematical Physic
Neutron/proton ratio of nucleon emissions as a probe of neutron skin
The dependence between neutron-to-proton yield ratio () and neutron
skin thickness () in neutron-rich projectile induced reactions is
investigated within the framework of the Isospin-Dependent Quantum Molecular
Dynamics (IQMD) model. The density distribution of the Droplet model is
embedded in the initialization of the neutron and proton densities in the
present IQMD model. By adjusting the diffuseness parameter of neutron density
in the Droplet model for the projectile, the relationship between the neutron
skin thickness and the corresponding in the collisions is obtained.
The results show strong linear correlation between and
for neutron-rich Ca and Ni isotopes. It is suggested that may be used
as an experimental observable to extract for neutron-rich nuclei,
which is very significant to the study of the nuclear structure of exotic
nuclei and the equation of state (EOS) of asymmetric nuclear matter.Comment: 7 pages, 5 figures; accepted by Phys. Lett.
Comparison of manual, machine learning, and hybrid methods for video annotation to extract parental care data
Measuring parental care behaviour in the wild is central to the study of animal ecology and evolution, but it is often labour- and time-intensive. Efficient open-source tools have recently emerged that allow animal behaviour to be quantified from videos using machine learning and computer vision techniques, but there is limited appraisal of how these tools perform compared to traditional methods. To gain insight into how different methods perform in extracting data from videos taken in the field, we compared estimates of the parental provisioning rate of wild house sparrows Passer domesticus from video recordings. We compared four methods: manual annotation by experts, crowd-sourcing, automatic detection based on the open-source software DeepMeerkat, and a hybrid annotation method. We found that the data collected by the automatic method correlated with expert annotation (r = 0.62) and further show that these data are biologically meaningful as they predict brood survival. However, the automatic method produced largely biased estimates due to the detection of non-visitation events, while the crowd-sourcing and hybrid annotation produced estimates that are equivalent to expert annotation. The hybrid annotation method takes approximately 20% of annotation time compared to manual annotation, making it a more cost-effective way to collect data from videos. We provide a successful case study of how different approaches can be adopted and evaluated with a pre-existing dataset, to make informed decisions on the best way to process video datasets. If pre-existing frameworks produce biased estimates, we encourage researchers to adopt a hybrid approach of first using machine learning frameworks to preprocess videos, and then to do manual annotation to save annotation time. As open-source machine learning tools are becoming more accessible, we encourage biologists to make use of these tools to cut annotation time but still get equally accurate results without the need to develop novel algorithms from scratch
On Vanishing Theorems For Vector Bundle Valued p-Forms And Their Applications
Let be a strictly increasing function
with . We unify the concepts of -harmonic maps, minimal
hypersurfaces, maximal spacelike hypersurfaces, and Yang-Mills Fields, and
introduce -Yang-Mills fields, -degree, -lower degree, and generalized
Yang-Mills-Born-Infeld fields (with the plus sign or with the minus sign) on
manifolds. When and
the -Yang-Mills field becomes an ordinary Yang-Mills field,
-Yang-Mills field, a generalized Yang-Mills-Born-Infeld field with the plus
sign, and a generalized Yang-Mills-Born-Infeld field with the minus sign on a
manifold respectively. We also introduce the energy functional (resp.
-Yang-Mills functional) and derive the first variational formula of the
energy functional (resp. -Yang-Mills functional) with
applications. In a more general frame, we use a unified method to study the
stress-energy tensors that arise from calculating the rate of change of various
functionals when the metric of the domain or base manifold is changed. These
stress-energy tensors, linked to -conservation laws yield monotonicity
formulae. A "macroscopic" version of these monotonicity inequalities enables us
to derive some Liouville type results and vanishing theorems for forms with
values in vector bundles, and to investigate constant Dirichlet boundary value
problems for 1-forms. In particular, we obtain Liouville theorems for
harmonic maps (e.g. -harmonic maps), and Yang-Mills fields (e.g.
generalized Yang-Mills-Born-Infeld fields on manifolds). We also obtain
generalized Chern type results for constant mean curvature type equations for
forms on and on manifolds with the global doubling property
by a different approach. The case and is due to Chern.Comment: 1. This is a revised version with several new sections and an
appendix that will appear in Communications in Mathematical Physics. 2. A
"microscopic" approach to some of these monotonicity formulae leads to
celebrated blow-up techniques and regularity theory in geometric measure
theory. 3. Our unique solution of the Dirichlet problems generalizes the work
of Karcher and Wood on harmonic map
Reduced Dwell-Fatigue Resistance in a Ni-Base Superalloy After Short-Term Thermal Exposure
The effect of short-term thermal exposure on microstructure and dwell-fatigue resistance of Ni-base superalloy 718Plus was investigated. Contrary to previous studies performed after long-term exposure, an increase in the dwell-fatigue crack growth rate was observed, which was connected to a small increase in the size of the hardening precipitates. The proposed controlling mechanism was the stress relaxation rate at the crack tip, and based on this a schematic model for the development of the properties during exposure is presented
A spatio-temporal description of the abrupt changes in the photospheric magnetic and Lorentz-force vectors during the 2011 February 15 X2.2 flare
The active region NOAA 11158 produced the first X-class flare of Solar Cycle
24, an X2.2 flare at 01:44 UT on 2011 February 15. Here we analyze SDO/HMI
magnetograms covering a 12-hour interval centered at the time of this flare. We
describe the spatial distributions of the photospheric magnetic changes
associated with this flare, including the abrupt changes in the field vector,
vertical electric current and Lorentz force vector. We also trace these
parameters' temporal evolution. The abrupt magnetic changes were concentrated
near the neutral line and in two neighboring sunspots. Near the neutral line,
the field vectors became stronger and more horizontal during the flare and the
shear increased. This was due to an increase in strength of the horizontal
field components near the neutral line, most significant in the horizontal
component parallel to the neutral line but the perpendicular component also
increased in strength. The vertical component did not show a significant,
permanent overall change at the neutral line. The increase in total flux at the
neutral line was accompanied by a compensating flux decrease in the surrounding
volume. In the two sunspots near the neutral line the azimuthal flux abruptly
decreased during the flare but this change was permanent in only one of the
spots. There was a large, abrupt, downward vertical Lorentz force change during
the flare, consistent with results of past analyses and recent theoretical
work. The horizontal Lorentz force acted in opposite directions along each side
of neutral line, with the two sunspots at each end subject to abrupt torsional
forces. The shearing forces were consistent with field contraction and decrease
of shear near the neutral line, whereas the field itself became more sheared as
a result of the flux collapsing towards the neutral line from the surrounding
volume.Comment: DOI 10.1007/s11207-012-0071-0. Accepted for publication in Solar
Physics SDO3 Topical Issue. Some graphics missing due to 15MB limi
Double quantum dot turnstile as an electron spin entangler
We study the conditions for a double quantum dot system to work as a reliable
electron spin entangler, and the efficiency of a beam splitter as a detector
for the resulting entangled electron pairs. In particular, we focus on the
relative strengths of the tunneling matrix elements, the applied bias and gate
voltage, the necessity of time-dependent input/output barriers, and the
consequence of considering wavepacket states for the electrons as they leave
the double dot to enter the beam splitter. We show that a double quantum dot
turnstile is, in principle, an efficient electron spin entangler or
entanglement filter because of the exchange coupling between the dots and the
tunable input/output potential barriers, provided certain conditions are
satisfied in the experimental set-up.Comment: published version; minor error correcte
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