11,517 research outputs found
Results of expert judgments on the faults and risks with Autosub3 and an analysis of its campaign to Pine Island Bay, Antarctica, 2009
Probabilistic risk assessment is a methodology that can be systematically applied to estimate the risk associated with the design and operation of complex systems. The National Oceanography Centre, Southampton, UK has developed a risk management process tailored to the operation of autonomous underwater vehicles. Central to the application of the risk management process is a probabilistic risk assessment. The risk management process was applied to estimate the risk associated with an Autosub3 science campaign in the Pine Island Glacier, Antarctica, and to support decision making. The campaign was successful. In this paper we present the Autosub3 risk model and we show how this model was used to assess the campaign risk
Orbit based procedure for doublets of scalar fields and the emergence of triple kinks and other defects
In this work we offer an approach to enlarge the number of exactly solvable
models with two real scalar fields in (1+1)D. We build some new two-field
models, and obtain their exact orbits and exact or numerical field
configurations. It is noteworthy that a model presenting triple-kinks and
double-flat-top lumps is among those new models
Efficient evaluation of decoherence rates in complex Josephson circuits
A complete analysis of the decoherence properties of a Josephson junction
qubit is presented. The qubit is of the flux type and consists of two large
loops forming a gradiometer and one small loop, and three Josephson junctions.
The contributions to relaxation (T_1) and dephasing (T_\phi) arising from two
different control circuits, one coupled to the small loop and one coupled to a
large loop, is computed. We use a complete, quantitative description of the
inductances and capacitances of the circuit. Including two stray capacitances
makes the quantum mechanical modeling of the system five dimensional. We
develop a general Born-Oppenheimer approximation to reduce the effective
dimensionality in the calculation to one. We explore T_1 and T_\phi along an
optimal line in the space of applied fluxes; along this "S line" we see
significant and rapidly varying contributions to the decoherence parameters,
primarily from the circuit coupling to the large loop.Comment: 16 pages, 20 figures; v2: minor revisio
New Green-Kubo formulas for transport coefficients in hard sphere-, Langevin fluids and the likes
We present generalized Green-Kubo expressions for thermal transport
coefficients in non-conservative fluid-type systems, of the generic form,
+\int^\infty_0 dt V^{-1} \av{I_\epsilon \exp(t {\cal L})
I}_0 where is a pseudo-streaming operator. It consists of a
sum of an instantaneous transport coefficient , and a time integral
over a time correlation function in a state of thermal equilibrium between a
current and its conjugate current . This formula with
and covers vastly different systems,
such as strongly repulsive elastic interactions in hard sphere fluids, weakly
interacting Langevin fluids with dissipative and stochastic interactions
satisfying detailed balance conditions, and "the likes", defined in the text.
For conservative systems the results reduce to the standard formulas.Comment: 7 pages, no figures. Version 2: changes in the text and references
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Effective models of quantum gravity induced by Planck scale modifications in the covariant quantum algebra
In this paper we introduce a modified covariant quantum algebra based in the
so-called Quesne-Tkachuk algebra. By means of a deformation procedure we arrive
at a class of higher derivative models of gravity. The study of the particle
spectra of these models reveals an equivalence with the physical content of the
well-known renormalizable and super-renormalizable higher derivative gravities.
The particle spectrum exhibits the presence of spurious complex ghosts and, in
light of this problem, we suggest an interesting interpretation in the context
of minimal length theories. Also, a discussion regarding the non-relativistic
potential energy is proposed.Comment: Small corrections were made; improved figures; results unchanged;
published versio
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