3,026 research outputs found
An expert system to analyze high frequency dependent data for the space shuttle main engine turbopumps
The prototype expert system ADDAMX identifies selected sinusoid frequencies from spectral data graphs as speed frequencies and harmonics from each turbopump, frequency feed through from one turbopump to another, frequencies generated by turbopump bearings, pseudo 3N for the phase 2 high pressure fuel turbopump, and electrical noise. ADDAMX does the analysis in an interactive or batch mode and the results can be displayed on the screen or hardcopy
Continuous-variable quantum key distribution protocols over noisy channels
A continuous-variable quantum key distribution protocol based on squeezed
states and heterodyne detection is introduced and shown to attain higher secret
key rates over a noisy line than any other one-way Gaussian protocol. This
increased resistance to channel noise can be understood as resulting from
purposely adding noise to the signal that is converted into the secret key.
This notion of noise-enhanced tolerance to noise also provides a better
physical insight into the poorly understood discrepancies between the
previously defined families of Gaussian protocols.Comment: Minor modifications to match published manuscrip
Unconditional optimality of Gaussian attacks against continuous-variable QKD
A fully general approach to the security analysis of continuous-variable
quantum key distribution (CV-QKD) is presented. Provided that the quantum
channel is estimated via the covariance matrix of the quadratures, Gaussian
attacks are shown to be optimal against all eavesdropping strategies, including
collective and coherent attacks. The proof is made strikingly simple by
combining a physical model of measurement, an entanglement-based description of
CV-QKD, and a recent powerful result on the extremality of Gaussian states
[Phys. Rev. Lett. 96, 080502 (2006)].Comment: 4 pages, 4 figure
Qualitative properties and existence of sign changing solutions with compact support for an equation with a p-Laplace operator
We consider radial solutions of an elliptic equation involving the p-Laplace
operator and prove by a shooting method the existence of compactly supported
solutions with any prescribed number of nodes. The method is based on a change
of variables in the phase plane corresponding to an asymptotic Hamiltonian
system and provides qualitative properties of the solutions
The noisy Hegselmann-Krause model for opinion dynamics
In the model for continuous opinion dynamics introduced by Hegselmann and
Krause, each individual moves to the average opinion of all individuals within
an area of confidence. In this work we study the effects of noise in this
system. With certain probability, individuals are given the opportunity to
change spontaneously their opinion to another one selected randomly inside the
opinion space with different rules. If the random jump does not occur,
individuals interact through the Hegselmann-Krause's rule. We analyze two
cases, one where individuals can carry out opinion random jumps inside the
whole opinion space, and other where they are allowed to perform jumps just
inside a small interval centered around the current opinion. We found that
these opinion random jumps change the model behavior inducing interesting
phenomena. Using pattern formation techniques, we obtain approximate analytical
results for critical conditions of opinion cluster formation. Finally, we
compare the results of this work with the noisy version of the Deffuant et al.
model for continuous-opinion dynamics
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