5,088 research outputs found
Characterizing Intermittency of 4-Hz Quasi-periodic Oscillation in XTE J1550-564 using Hilbert-Huang Transform
We present the time-frequency analysis results based on the Hilbert-Huang
transform (HHT) for the evolution of a 4-Hz low-frequency quasi-periodic
oscillation (LFQPO) around the black hole X-ray binary XTE J1550-564. The
origin of LFQPOs is still debated. To understand the cause of the peak
broadening, we utilized a recently developed time-frequency analysis, HHT, for
tracking the evolution of the 4-Hz LFQPO from XTE J1550 564. By adaptively
decomposing the ~4-Hz oscillatory component from the light curve and acquiring
its instantaneous frequency, the Hilbert spectrum illustrates that the LFQPO is
composed of a series of intermittent oscillations appearing occasionally
between 3 Hz and 5 Hz. We further characterized this intermittency by computing
the confidence limits of the instantaneous amplitudes of the intermittent
oscillations, and constructed both the distributions of the QPO's high and low
amplitude durations, which are the time intervals with and without significant
~4-Hz oscillations, respectively. The mean high amplitude duration is 1.45 s
and 90% of the oscillation segments have lifetimes below 3.1 s. The mean low
amplitude duration is 0.42 s and 90% of these segments are shorter than 0.73 s.
In addition, these intermittent oscillations exhibit a correlation between the
oscillation's rms amplitude and mean count rate. This correlation could be
analogous to the linear rms-flux relation found in the 4-Hz LFQPO through
Fourier analysis. We conclude that the LFQPO peak in the power spectrum is
broadened owing to intermittent oscillations with varying frequencies, which
could be explained by using the Lense-Thirring precession model.Comment: 27 pages, 9 figures, accepted for publication in The Astrophysical
Journa
Quantum heat valve and entanglement in superconducting resonators
Quantum superconducting circuit with flexible coupler has been a powerful
platform for designing quantum thermal machines. In this letter, we employ the
tunable coupling of two superconducting resonators to realize a heat valve by
modulating magnetic flux using a superconducting quantum interference device
(SQUID). It is shown that a heat valve can be realized in a wide parameter
range. We find a consistent relation between the heat current and quantum
entanglement, which indicates the dominant role of entanglement on the heat
valve. It provides an insightful understanding of quantum features in quantum
heat machines.Comment: 9 figures, 4 figure
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Stretching Micro Metal Particles into Uniformly Dispersed and Sized Nanoparticles in Polymer.
There is a longstanding challenge to disperse metal nanoparticles uniformly in bulk polymers for widespread applications. Conventional scale-down techniques often are only able to shrink larger elements (such as microparticles and microfibers) into micro/nano-elements (i.e. nanoparticles and nanofibers) without much altering their relative spatial and size distributions. Here we show an unusual phenomenon that tin (Sn) microparticles with both poor size distribution and spatial dispersion were stretched into uniformly dispersed and sized Sn nanoparticles in polyethersulfone (PES) through a stack and draw technique in thermal drawing. It is believed that the capillary instability plays a crucial role during thermal drawing. This novel, inexpensive, and scalable method overcomes the longstanding challenge to produce bulk polymer-metal nanocomposites (PMNCs) with a uniform dispersion of metallic nano-elements
Set voltage distribution stabilized by constructing an oxygen reservoir in resistive random access memory
In this letter, the instability mechanism of RRAM was investigated, and a technique was developed to stabilize the distribution of high resistance state (HRS) and better concentrate the SET voltage. In previous research, we found that an interface-type switching characteristic was observed on the I-V curve beneath the filament-type switching behavior, owing to the oxygen accumulation effect. In this letter, this interface-type switching characteristic is used to fit the natural distribution of HRS for an analysis of the instability mechanism. According to the results, the reason for the HRS distribution is the accumulation of extra oxygen ions which are left over from a lower degree of oxygen and oxygen vacancy recombination during the reset process. We propose a solution which creates an extra oxygen reservoir by changing the surface topography of the electrode to store the surplus oxygen ions from the reset process, eliminating the accumulation effect, and indeed improving stability.
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Feature knowledge based fault detection of induction motors through the analysis of stator current data
Participatory Agricultural Humanities for the new Ruralism Tea-Community Revitalization In Taiwan
This paper examines the most effective ways of engaging urban citizens to appreciate rural villages and agriculture traditions. Pondering on experiences of rural revitalization experiments in Asian societies, this paper proposes the concept of “participatory agricultural humanities.” Participatory agricultural humanities are tools and processes engaging citizens into eco-friendly farming and land related works or events. Based on action research and qualitative research methods, we have been working with peri-urban and rural communities in Taiwan since 2009. Only embracing agricultural humanities as our values, we could re-establish eco-friendly rural developments with biodiversity and cultural diversity as a whole.© 2016. The Authors. Published for AMER ABRA by e-International Publishing House, Ltd., UK. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Peer–review under responsibility of AMER (Association of Malaysian Environment-Behaviour Researchers), ABRA (Association of Behavioural Researchers on Asians) and cE-Bs (Centre for Environment-Behaviour Studies), Faculty of Architecture, Planning & Surveying, Universiti Teknologi MARA, Malaysia.Keywords: agricultural humanities, rural revitalization, participation, new ruralis
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