1,524 research outputs found
Condition Monitoring and Fault Diagnosis of Roller Element Bearing
Rolling element bearings play a crucial role in determining the overall health condition of a rotating machine. An effective condition-monitoring program on bearing operation can improve a machine’s operation efficiency, reduce the maintenance/replacement cost, and prolong the useful lifespan of a machine. This chapter presents a general overview of various condition-monitoring and fault diagnosis techniques for rolling element bearings in the current practice and discusses the pros and cons of each technique. The techniques introduced in the chapter include data acquisition techniques, major parameters used for bearing condition monitoring, signal analysis techniques, and bearing fault diagnosis techniques using either statistical features or artificial intelligent tools. Several case studies are also presented in the chapter to exemplify the application of these techniques in the data analysis as well as bearing fault diagnosis and pattern recognition
Topology of the landscape and dominant kinetic path for the thermodynamic phase transition of the charged Gauss-Bonnet AdS black holes
We study the generalized free energy of the five dimensional charged
Gauss-Bonnet AdS black holes in the grand canonical ensemble by treating the
black hole radius and the charge as the order parameters. On the two
dimensional free energy landscape, the lowest points in the basins represent
the local stable black holes and the saddle point represents the unstable black
hole. We show that black hole is the topological defect of gradient field of
the landscape. The black hole stability is determined by the topography of the
free energy landscape in terms of the basin depths and the barrier height
between the basins and is not by the topology of the gradient field. In
addition, we study the stochastic dynamics of the black hole phase transition
and obtain the dominant kinetic path for the transition on the free energy
landscape. Unlike the one dimensional landscape, the dominant kinetic path
between the small and the large black hole state does not necessarily pass
through the intermediate black hole state. Furthermore, the inhomogeneity in
diffusions can lead to the switching from the coupled cooperative process of
black hole phase transition to the decoupled sequential process, giving
different kinetic mechanisms
High-fidelity information recovery from radiating black holes through random local projection
The unitary evaporation of black holes enables the potential retrieval of
information from Hawking radiation, leading to the development of explicit
decoding protocols. However, the effective field theory description introduces
redundant degrees of freedom that necessitate deviations from unitarity at late
stages to conserve entropy. Consequently, information recovery becomes
uncertain. The prevailing view is that such effective process can result in
information loss unless the redundant states are annihilated in maximally
entangled pairs, resembling quantum teleportation. In this Letter, we show that
this assumption is unnecessary. We study information recoverability in a
radiating black hole through the non-unitary dynamics that projects the
randomly-selected modes from a scrambling unitary. We show that the model has
the merit of producing the von Neumann entropy of black holes consistent with
the island formula calculation and that information in the black hole interior
can be decoded from the Hawking radiation without loss after the Page time. We
present two decoding strategies along with their quantum circuit realizations.
Experimental verification of the strategies employs 7-qubit IBM quantum
processors, demonstrating the viability of these strategies and the potential
for quantum processors to probe the black hole interior.Comment: 5 pages. arXiv admin note: text overlap with arXiv:2307.0145
Generalized free energy and dynamical state transition of the dyonic AdS black hole in the grand canonical ensemble
We study the generalized free energy of the dyonic AdS black hole in an
ensemble with varying electric charge and fixed magnetic charge .
When we adjust the temperature and the electric potential of the
ensemble, the Ricci scalar curvature and electromagnetic potential
usually diverge at the horizon. We regularize them and incorporate the
off-shell corrections into the Einstein-Hilbert action. Alternatively, we find
that the off-shell corrections can also be obtained by adding a boundary near
the horizon to exclude the singularities. Ultimately, we derive the generalized
free energy which is consistent with the definition of the thermodynamic
relations. Based on the generalized free energy landscape, we can describe the
dynamics of state transition as a stochastic process quantified by the Langevin
equation. The path integral framework can be formulated to derive the
time-dependent trajectory of the order parameter and the time evolution of the
transition probability. By comparing the probability with the result of the
classical master equation, we attribute the contribution to the probability of
one pseudomolecule or antipseudomolecule (the instanton and anti-instanton
pair) to the rate of state transition. These results are consistent with the
qualitative analysis of the free energy landscape
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