53,500 research outputs found
A study of the high frequency limitations of series resonant converters
A transformer induced oscillation in series resonant (SR) converters is studied. It may occur in the discontinuous current mode. The source of the oscillation is an unexpected resonant circuit formed by normal resonance components in series with the magnetizing inductance of the output transformers. The methods for achieving cyclic stability are: to use a half bridge SR converter where q0.5. Q should be as close to 1.0 as possible. If 0.5q1.0, the instability will be avoided if psi2/3q-1/3. The second objective was to investigate a power field effect transistor (FET) version of the SR converter capable of operating at frequencies above 100 KHz, to study component stress and losses at various frequencies
Self-reported âcommunication technologyâ usage in patients attending a cardiology outpatient clinic in a remote regional hospital
Peer reviewedPublisher PD
On the Superradiance of Spin-1 Waves in an Equatorial Wedge around a Kerr Hole
Recently Van Putten has suggested that superradiance of magnetosonic waves in
a toroidal magnetosphere around a Kerr black hole may play a role in the
central engine of gamma-ray bursts. In this context, he computed (in the WKB
approximation) the superradiant amplification of scalar waves confined to a
thin equatorial wedge around a Kerr hole and found that the superradiance is
higher than for radiation incident over all angles. This paper presents
calculations of both spin-0 (scalar) superradiance (integrating the radial
equation rather than using the WKB method) and and spin-1
(electromagnetic/magnetosonic) superradiance, in Van Putten's wedge geometry.
In contrast to the scalar case, spin-1 superradiance decreases in the wedge
geometry, decreasing the likelihood of its astrophysical importance.Comment: Submitted to The Astrophysical Journal Letter
Investigating intra-host and intra-herd sequence diversity of foot-and-mouth disease virus
Due to the poor-fidelity of the enzymes involved in RNA genome replication, foot-and-mouth disease (FMD) virus samples comprise of unique polymorphic populations. In this study, deep sequencing was utilised to characterise the diversity of FMD virus (FMDV) populations in 6 infected cattle present on a single farm during the series of outbreaks in the UK in 2007. A novel RTâPCR method was developed to amplify a 7.6 kb nucleotide fragment encompassing the polyprotein coding region of the FMDV genome. Illumina sequencing of each sample identified the fine polymorphic structures at each nucleotide position, from consensus level changes to variants present at a 0.24% frequency. These data were used to investigate population dynamics of FMDV at both herd and host levels, evaluate the impact of host on the viral swarm structure and to identify transmission links with viruses recovered from other farms in the same series of outbreaks. In 7 samples, from 6 different animals, a total of 5 consensus level variants were identified, in addition to 104 sub-consensus variants of which 22 were shared between 2 or more animals. Further analysis revealed differences in swarm structures from samples derived from the same animal suggesting the presence of distinct viral populations evolving independently at different lesion sites within the same infected animal
Origin of the X-ray Quasi-Periodic Oscillations and Identification of a Transient Ultraluminous X-Ray Source in M82
The starburst galaxy M82 contains two ultraluminous X-ray sources (ULXs),
CXOM82 J095550.2+694047 (=X41.4+60) and CXOM82 J095551.1+694045 (=X42.3+59),
which are unresolved by XMM-Newton. We revisited the two XMM-Newton
observations of M82 and analyzed the surface brightness profiles using the
known Chandra source positions. We show that the quasi-periodic oscillations
(QPOs) detected with XMM-Newton originate from X41.4+60, the brightest X-ray
source in M82. Correcting for the contributions of the unresolved sources, the
QPO at a frequency of 55.8+/-1.3 mHz on 2001 May 06 had a fractional rms
amplitude of 32%, and the QPO at 112.9+/-1.3 mHz on 2004 April 21 had an
amplitude of 21%. The QPO frequency may possibly be correlated with the source
flux, similar to the type C QPOs in XTE 1550-564 and GRS 1915+105, but at
luminosities two orders of magnitude higher. X42.3+59, the second brightest
source in M82, displayed a strikingly high flux of 1.4E-11 ergs/cm^2/s in the
2-10 keV band on 2001 May 6. A seven-year light curve of X42.3+59 shows extreme
variability over a factor of 1000; the source is not detected in several
Chandra observations. This transient behavior suggests accretion from an
unstable disk. If the companion star is massive, as might be expected in the
young stellar environment, then the compact object would likely be an IMBH.Comment: 9 pages, 6 figures, submitted to ApJ on May 08, 200
Development of a mechatronic sorting system for removing contaminants from wool
Automated visual inspection (AVI) systems have been
extended to many fields, such as agriculture and the food, plastic
and textile industries. Generally, most visual systems only inspect
product defects, and then analyze and grade them due to the lack
of any sorting function. This main reason rests with the difficulty of
using the image data in real time. However, it is increasingly important
to either sort good products from bad or grade products into
separate groups usingAVI systems. This article describes the development
of a mechatronic sorting system and its integration with a
vision system for automatically removing contaminants from wool
in real time. The integration is implemented by a personal computer,
which continuously processes live images under the Windows
2000 operating system. The developed real-time sorting approach
is also applicable to many other AVI systems
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