4,752 research outputs found
Parameter identification in a semilinear hyperbolic system
We consider the identification of a nonlinear friction law in a
one-dimensional damped wave equation from additional boundary measurements.
Well-posedness of the governing semilinear hyperbolic system is established via
semigroup theory and contraction arguments. We then investigte the inverse
problem of recovering the unknown nonlinear damping law from additional
boundary measurements of the pressure drop along the pipe. This coefficient
inverse problem is shown to be ill-posed and a variational regularization
method is considered for its stable solution. We prove existence of minimizers
for the Tikhonov functional and discuss the convergence of the regularized
solutions under an approximate source condition. The meaning of this condition
and some arguments for its validity are discussed in detail and numerical
results are presented for illustration of the theoretical findings
Giant shot noise from Majorana zero modes in topological trijunctions
The clear-cut experimental identification of Majorana bound states in
transport measurements still poses experimental challenges. We here show that
the zero-energy Majorana state formed at a junction of three topological
superconductor wires is directly responsible for giant shot noise amplitudes,
in particular at low voltages and for small contact transparency. The only
intrinsic noise limitation comes from the current-induced dephasing rate due to
multiple Andreev reflection processes
Superconducting transport through a vibrating molecule
Nonequilibrium electronic transport through a molecular level weakly coupled
to a single coherent phonon/vibration mode has been studied for superconducting
leads. The Keldysh Green function formalism is used to compute the current for
the entire bias voltage range. In the subgap regime, Multiple Andreev
Reflection (MAR) processes accompanied by phonon emission cause rich structure
near the onset of MAR channels, including an even-odd parity effect that can be
interpreted in terms of an inelastic MAR ladder picture. Thereby we establish a
connection between the Keldysh formalism and the Landauer scattering approach
for inelastic MAR.Comment: 5 pages, 5 figures, version contains now more details, accepted by
PR
Doping- and size-dependent suppression of tunneling in carbon nanotubes
We study the effect of doping in the suppression of tunneling observed in
multi-walled nanotubes, incorporating as well the influence of the finite
dimensions of the system. A scaling approach allows us to encompass the
different values of the critical exponent measured for the tunneling
density of states in carbon nanotubes. We predict that further reduction of
should be observed in multi-walled nanotubes with a sizeable amount
of doping. In the case of nanotubes with a very large radius, we find a
pronounced crossover between a high-energy regime with persistent
quasiparticles and a low-energy regime with the properties of a one-dimensional
conductor.Comment: 4 pages, 2 figures, LaTeX file, pacs: 71.10.Pm, 71.20.Tx, 72.80.R
Adopting augmented reality in the age of industrial digitalisation
Industrial augmented reality (IAR) is one of the key pillars of the industrial digitalisation concepts, which connects workers with the physical world through overlaying digital information. Augmented reality (AR) market is increasing but still its adoption levels are low in industry. While companies strive to learn and adopt AR, there are chances that they fail in such endeavours due to lack of understanding key challenges and success factors in this space. This study identifies critical success factors and challenges for IAR implementation projects based on field experiments. The broadly used technology, organisation, environment (TOE) framework was used as a theoretical basis for the study, while 22 experiments were conducted for validation. It is found that, while technological aspects are of importance, organisational issues are more relevant for industry, which has not been reflected to the same extent in the literature.No funding source.
22 experiments were conducted with in-kind support (employee time and company access) from Beckhoff Automation, Herman Miller and fluiconnecto as well as University of Cambridge students (see Table 1)
Engineering adiabaticity at an avoided crossing with optimal control
We investigate ways to optimize adiabaticity and diabaticity in the
Landau-Zener model with non-uniform sweeps. We show how diabaticity can be
engineered with a pulse consisting of a linear sweep augmented by an
oscillating term. We show that the oscillation leads to jumps in populations
whose value can be accurately modeled using a model of multiple,
photon-assisted Landau-Zener transitions, which generalizes work by Wubs et al.
[New J. Phys. 7, 218 (2005)]. We extend the study on diabaticity using methods
derived from optimal control. We also show how to preserve adiabaticity with
optimal pulses at limited time, finding a non-uniform quantum speed limit
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