1,560 research outputs found
Sodium-ion battery cathodes Na2FeP<sub>2</sub>O<sub>7</sub> and Na2MnP<sub>2</sub>O<sub>7</sub>:Diffusion behaviour for high rate performance
Na-ion batteries are currently the focus of significant research interest due to the relative abundance of sodium and its consequent cost advantages.</p
Observability and nonlinear filtering
This paper develops a connection between the asymptotic stability of
nonlinear filters and a notion of observability. We consider a general class of
hidden Markov models in continuous time with compact signal state space, and
call such a model observable if no two initial measures of the signal process
give rise to the same law of the observation process. We demonstrate that
observability implies stability of the filter, i.e., the filtered estimates
become insensitive to the initial measure at large times. For the special case
where the signal is a finite-state Markov process and the observations are of
the white noise type, a complete (necessary and sufficient) characterization of
filter stability is obtained in terms of a slightly weaker detectability
condition. In addition to observability, the role of controllability in filter
stability is explored. Finally, the results are partially extended to
non-compact signal state spaces
Nonlinear Realization of N=2 Superconformal Symmetry and Brane Effective Actions
Due to the incompatibility of the nonlinear realization of superconformal
symmetry and dilatation symmetry with the dilaton as the compensator field, in
the present paper it shows an alternative mechanism of spontaneous breaking the
N=2 superconformal symmetry to the N=0 case. By using the approach of nonlinear
transformations it is found that it leads to a space-filling brane theory with
Weyl scale W(1,3) symmetry. The dynamics of the resulting Weyl scale invariant
brane, along with that of other Nambu-Goldstone fields, is derived in terms of
the building blocks of the vierbein and the covariant derivative from the
Maurer-Cartan oneforms. A general coupling of the matter fields localized on
the brane world volume to these NG fields is also constructed.Comment: 22 pages, more references and comments are adde
Optimizing the fast Rydberg quantum gate
The fast phase gate scheme, in which the qubits are atoms confined in sites
of an optical lattice, and gate operations are mediated by excitation of
Rydberg states, was proposed by Jaksch et al. Phys. Rev. Lett. 85, 2208 (2000).
A potential source of decoherence in this system derives from motional heating,
which occurs if the ground and Rydberg states of the atom move in different
optical lattice potentials. We propose to minimize this effect by choosing the
lattice photon frequency \omega so that the ground and Rydberg states have the
same frequency-dependent polarizability \alpha(omega). The results are
presented for the case of Rb.Comment: 5 pages, submitted to PR
Probing Heavy Higgs Boson Models with a TeV Linear Collider
The last years have seen a great development in our understanding of particle
physics at the weak scale. Precision electroweak observables have played a key
role in this process and their values are consistent, within the Standard Model
interpretation, with a light Higgs boson with mass lower than about 200 GeV. If
new physics were responsible for the mechanism of electroweak symmetry
breaking, there would, quite generally, be modifications to this prediction
induced by the non-standard contributions to the precision electroweak
observables. In this article, we analyze the experimental signatures of a heavy
Higgs boson at linear colliders. We show that a linear collider, with center of
mass energy \sqrt{s} <= 1 TeV, would be very useful to probe the basic
ingredients of well motivated heavy Higgs boson models: a relatively heavy
SM-like Higgs, together with either extra scalar or fermionic degrees of
freedom, or with the mixing of the third generation quarks with non-standard
heavy quark modes.Comment: 21 page
Two-band second moment model and an interatomic potential for caesium
A semi-empirical formalism is presented for deriving interatomic potentials
for materials such as caesium or cerium which exhibit volume collapse phase
transitions. It is based on the Finnis-Sinclair second moment tight binding
approach, but incorporates two independent bands on each atom. The potential is
cast in a form suitable for large-scale molecular dynamics, the computational
cost being the evaluation of short ranged pair potentials. Parameters for a
model potential for caesium are derived and tested
Preanalytical, Analytical, and Computational Factors Affect Homeostasis Model Assessment Estimates
OBJECTIVE—We investigated how β-cell function and insulin sensitivity or resistance are affected by the type of blood sample collected or choice of insulin assay and homeostatis model assessment (HOMA) calculator (http://www.dtu.ox.ac.uk)
Fermiology and superconductivity of topological surface states in PdTe2
We gratefully acknowledge support from the Leverhulme Trust, the Engineering and Physical Sciences Research Council, UK (Grant Nos. EP/M023427/1 and EP/I031014/1), the Royal Society. JC, MJN, LB, VS, and JMR acknowledge EPSRC for PhD studentship support through grant Nos. EP/K503162/1, EP/G03673X/1, EP/L505079/1, and EP/L015110/1.We study the low-energy surface electronic structure of the transition-metal dichalcogenide superconductor PdTe2 by spin- and angle-resolved photoemission, scanning tunneling microscopy, and density-functional theory-based supercell calculations. Comparing PdTe2 with its sister compound PtSe2, we demonstrate how enhanced interlayer hopping in the Te-based material drives a band inversion within the antibonding p -orbital manifold well above the Fermi level. We show how this mediates spin-polarized topological surface states which form rich multivalley Fermi surfaces with complex spin textures. Scanning tunneling spectroscopy reveals type-II superconductivity at the surface, and moreover shows no evidence for an unconventional component of its superconducting order parameter, despite the presence of topological surface states.PostprintPeer reviewe
Detailed study of null and time-like geodesics in the Alcubierre Warp spacetime
The Alcubierre warp spacetime yields a fascinating chance for comfortable
interstellar travel between arbitrary distant places without the time dilation
effect as in special relativistic flights. Even though the warp spacetime needs
exotic matter for its construction and is thus far from being physically
feasible, it offers a rich playground for studying geodesics in the general
theory of relativity. This paper is addressed to graduate students who have
finished a first course in general relativity to give them a deeper inside in
the calculation of non-affinely parametrized null and time-like geodesics and a
straightforward approach to determine the gravitational lensing effect due to
curved spacetime by means of the Jacobi equation. Both topics are necessary for
a thorough discussion of the visual effects as observed by a traveller inside
the warp bubble or a person looking from outside. The visual effects of the
traveller can be reproduced with an interactive Java application
Learning Objects, Learning Objectives and Learning Design.
Educational research and development into e-learning mainly focuses on the inclusion of new technological features without taking into account psycho-pedagogical concerns that are likely to improve a learner's cognitive process in this new educational category. This paper presents an instructional model that combines objectivist and constructivist learning theories. The model is based on the concept of a learning objective which is composed of a set of learning objects. A software tool, called the Instruction Aid System (IAS), has been developed to guide instructors through the development of learning objectives and the execution of the analysis and design phases of the proposed instructional model. Additionally, a blended approach to the learning process in Web-based distance education is also presented. This approach combines various event-based activities: self-paced learning, live e-learning and the use of face-to-face contact in classrooms
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