| 1. |
- Thomas, HS, et al.
(author)
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- 2019
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swepub:Mat__t
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| 2. |
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| 3. |
- Vincentelli, Federico M., et al.
(author)
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A shared accretion instability for black holes and neutron stars
- 2023
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 615:7950, s. 45-49
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Journal article (peer-reviewed)abstract
- Accretion disks around compact objects are expected to enter an unstable phase at high luminosity1. One instability may occur when the radiation pressure generated by accretion modifies the disk viscosity, resulting in the cyclic depletion and refilling of the inner disk on short timescales2. Such a scenario, however, has only been quantitatively verified for a single stellar-mass black hole3-5. Although there are hints of these cycles in a few isolated cases6-10, their apparent absence in the variable emission of most bright accreting neutron stars and black holes has been a continuing puzzle11. Here we report the presence of the same multiwavelength instability around an accreting neutron star. Moreover, we show that the variability across the electromagnetic spectrum-from radio to X-ray-of both black holes and neutron stars at high accretion rates can be explained consistently if the accretion disks are unstable, producing relativistic ejections during transitions that deplete or refill the inner disk. Such a new association allows us to identify the main physical components responsible for the fast multiwavelength variability of highly accreting compact objects.
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| 4. |
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| 5. |
- Krupko, Yu., et al.
(author)
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Kerr nonlinearity in a superconducting Josephson metamaterial
- 2018
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In: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 98:9
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Journal article (peer-reviewed)abstract
- We present a detailed experimental and theoretical analysis of the dispersion and nonlinear Kerr frequency shifts of plasma modes in a one-dimensional Josephson junction chain containing 500 superconducting quantum interfence devices in the regime of weak nonlinearity. The measured low-power dispersion curve agrees perfectly with the theoretical model if we take into account the Kerr renormalization of the bare frequencies and the long-range nature of the island charge screening by a remote ground plane. We measured the self- and cross-Kerr shifts for the frequencies of the eight lowest modes in the chain. We compare the measured Kerr coefficients with theory and find good agreement.
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| 6. |
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| 7. |
- Beccuti, A. G., et al.
(author)
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Hybrid control techniques for switched-mode DC-DC converters part II : The step-up topology
- 2007
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In: 2007 American Control Conference, Vols 1-13. - 1424409888 - 9781424409884 ; , s. 5464-5471
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Conference paper (peer-reviewed)abstract
- Several recent techniques from hybrid and optimal control are evaluated on a power electronics benchmark problem. The benchmark involves a number of practically interesting operating scenarios for a fixed-frequency step-up dc-dc converter. The specifications are defined such that good performance can only be obtained if the switched and nonlinear nature of the problem is respected during the design phase.
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