3,307 research outputs found
20 cm VLA Radio-Continuum Study of M31 - Images and Point Source Catalogues DR2: Extraction of a supernova remnant sample
We present Data Release 2 of the Point Source Catalogue created from a series
of previously constructed radio-continuum images of M31 at lambda=20 cm (nu=1.4
GHz) from archived VLA observations. In total, we identify a collection of 916
unique discrete radio sources across the field of M31. Comparing these detected
sources to those listed by Gelfand et al. (2004) at lambda=92 cm, the spectral
index of 98 sources has been derived. The majority (73%) of these sources
exhibit a spectral index of alpha <-0.6, indicating that their emission is
predominantly non-thermal in nature, which is typical for background objects
and Supernova Remnants (SNRs). Additionally, we investigate the presence of
radio counterparts for some 156 SNRs and SNR candidates, finding a total of
only 13 of these object in our images within a 5 arcsec search area. Auxiliary
optical, radio and X-ray catalogs were cross referenced highlighting a small
population of SNR and SNR candidates common to multi-frequency domains
The number of independent sets in a graph with small maximum degree
Let be the number of independent sets in a graph . We show
that if has maximum degree at most then
(where is vertex degree, is the number of isolated
vertices in and is the complete bipartite graph with vertices
in one partition class and in the other), with equality if and only if each
connected component of is either a complete bipartite graph or a single
vertex. This bound (for all ) was conjectured by Kahn.
A corollary of our result is that if is -regular with then with
equality if and only if is a disjoint union of copies of
. This bound (for all ) was conjectured by Alon and Kahn and
recently proved for all by the second author, without the characterization
of the extreme cases.
Our proof involves a reduction to a finite search. For graphs with maximum
degree at most the search could be done by hand, but for the case of
maximum degree or , a computer is needed.Comment: Article will appear in {\em Graphs and Combinatorics
Wage theft is widespread, but politics and policies can play a powerful role in reducing it.
Wage theft is pervasive in America; in a new study of low-wage workers across the US, Daniel J. Galvin finds that 16 percent were paid less than their state’s minimum wage. He also finds that workers in those states which had greater employment law protections tended to have a lower chance of experiencing wage theft, and that those protections tended to be in states with unified Democratic governments. With Donald Trump’s Labor Department unlikely to do much to address the problem, he writes that workers’ advocates will need to build coalitions and work with Democrats at the state and city level in order to ensure workers are protected from wage theft
Mandarin speech perception in combined electric and acoustic stimulation.
For deaf individuals with residual low-frequency acoustic hearing, combined use of a cochlear implant (CI) and hearing aid (HA) typically provides better speech understanding than with either device alone. Because of coarse spectral resolution, CIs do not provide fundamental frequency (F0) information that contributes to understanding of tonal languages such as Mandarin Chinese. The HA can provide good representation of F0 and, depending on the range of aided acoustic hearing, first and second formant (F1 and F2) information. In this study, Mandarin tone, vowel, and consonant recognition in quiet and noise was measured in 12 adult Mandarin-speaking bimodal listeners with the CI-only and with the CI+HA. Tone recognition was significantly better with the CI+HA in noise, but not in quiet. Vowel recognition was significantly better with the CI+HA in quiet, but not in noise. There was no significant difference in consonant recognition between the CI-only and the CI+HA in quiet or in noise. There was a wide range in bimodal benefit, with improvements often greater than 20 percentage points in some tests and conditions. The bimodal benefit was compared to CI subjects' HA-aided pure-tone average (PTA) thresholds between 250 and 2000 Hz; subjects were divided into two groups: "better" PTA (<50 dB HL) or "poorer" PTA (>50 dB HL). The bimodal benefit differed significantly between groups only for consonant recognition. The bimodal benefit for tone recognition in quiet was significantly correlated with CI experience, suggesting that bimodal CI users learn to better combine low-frequency spectro-temporal information from acoustic hearing with temporal envelope information from electric hearing. Given the small number of subjects in this study (n = 12), further research with Chinese bimodal listeners may provide more information regarding the contribution of acoustic and electric hearing to tonal language perception
The radio continuum emission of star forming galaxies at low to high redshift
In this thesis, the radio-continuum emission of starburst galaxies is explored to understand the physical processes that trace star formation. Separating and constraining these processes require a broad, densely sampled spectral energy distribution that can be used to apply and constrain various radiative transfer models. Existing tracers of star formation include a suite of multi-wavelength diagnostics, including UV, optical, infrared, nebular transitions, and radio continuum. At present, optical and near infrared observations have been the most successful at probing the high redshift volume and constraining the star formation at the earliest epochs of the Universe. However, such approaches are critically awed in that they are subject to the effects of dust obscuration, requiring sophisticated methods to recover the intrinsic luminosities of the optical tracers of star formation. In the high redshift Universe, these corrections are increasingly compromised and uncertain. Radio-continuum measurements of star formation have the potential to be the most reliable in this high redshift regime because they are not affected by the presence of dust, allowing observers to acquire uncompromised measures of star formation. At frequencies below _ 2 GHz, the radio continuum is made up overwhelmingly by non-thermal synchrotron emission, produced by near light speed cosmic rays interacting with the large-scale magnetic structure of a galaxy. Although this type of emission is not a direct product of stars, it has been reasonably well calibrated to exploit the far-infrared to radio correlation to obtain a measure of star formation. Our current understanding of the far-infrared to radio correlation suggests that there should be an evolution as a function of redshifts; however, observationally evidence both confirms and rejects this evolution hypothesis. As the far-infrared to radio correlation is the foundation of star formation rate indicators based on the radio continuum for frequencies where synchrotron emission is a significant component of the observed spectrum, there is a requirement to investigate, and if necessary repair, radio-based star formation rate measures in preparation for radio telescopes like the Square Kilometre Array. Throughout my candidature, I have studied the spectral energy distribution of 30 local galaxies that were selected based on their high star formation rates, as indicated by their radio and infrared emission data collected from existing surveys. Across a broad frequency range spanning 80MHz to 50 GHz, the underlying physical processes driving the radio continuum have been disentangled. By comparing these products to other multi-wavelength indicators of star formation, we can begin to understand the radio-based tracers for faint star forming galaxies at high redshift that the next generation of radio telescopes will reveal
State of the Art of Virtual Reality Simulation Technology and Its Applications in 2005
The School of Mining Engineering at the University of New South Wales (UNSW) has been developing immersive, interactive computer-based training simulators for a number of years with research funding provided by Coal Services (CS), the Australian Coal Association Research Program (ACARP) and the Australian Research Council (ARC). The virtual reality(VR) simulators are being developed to improve the effectiveness of training in the Australian coal mining industry with a view to enhancing health and safety. VR theatres have been established at UNSW and at the Newcastle Mines Rescue Station (NMRS).A range of experienced and inexperienced mining personnel has already had the opportunity to train in them. A capability in immersive, interactive virtual reality training has been established and the reaction to the new technology has been positive and confirmed the benefits to be gained in going to the next stage in developing this capability. Given the significant advances in computer technology that have occurred since this research was initiated at UNSW, it was considered wise to undertake a study of the ‘State of the Art of Virtual Reality Simulation Technology and Its Application in 2005’. This should enable nformed decisions to be made on technologies and techniques that could further enhance the simulators and give insight into how the existing VR capability at UNSW can be placed on a sustainable foundation. This Research Overview summarises the findings of the study. It recommends the continued development and testing of the simulators towards a system that presents the users with hi-fidelity imagery and function that is based on 3D models, developed using real mine plans, safety data and manufacturer’s drawings. The simulators should remain modular in design, such that equipment can be updated and added easily over time. Different mine training scenarios and models based on sound educational principles should be developed with major input from experienced mining industry personnel. The simulations that have been developed, that is, Self-Escape, Rib Stability and Sprains and Strains should also continue to be developed and refined. The study has confirmed that such simulations are a powerful visualisation and training tool for enhancing the understanding of mine safety procedures and operations in the coal mining industry. This Scoping Study was undertaken with funding provided from the JCB Health and Safety Trust administered by Coal Services Pty Limited. The support of the Trust and trustees is gratefully acknowledged. The contributors of information are also gratefully acknowledged
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