13,016 research outputs found
3D Electromagnetic Diffusion Models for Reverberant Environments
Diffusion equation based modeling has been proposed for mapping the reverberant component of the electromagnetic field in enclosures at high frequencies. Preliminary evaluation of the electromagnetic diffusion model using a dimensional reduction approach showed promising results compared to measurements. Here we develop a full three-dimensional diffusion model of the experimental canonical test cases considered in the preliminary evaluation and obtain finite element method solutions. The results are compared to those of the two-dimensional models. We find that the two- and three-dimensional models are generally in excellent agreement for the pseudo two-dimensional test-cases considered. Some deviations between the two- and three-dimensional models are observed due to the fact the point source must be effectively represented by a line source in the reduced model. The three-dimensional model is still highly efficient compared to other applicable techniques, offering the prospect of a radical reduction in the resources required for simulating reverberant fields in electrically large structures
What's the evidence that NICE guidance has been implemented? Results from a national evaluation using time series analysis, audit of patients' notes, and interviews
OBJECTIVES: To assess the extent and pattern of implementation of guidance issued by the National Institute for Clinical Excellence (NICE). DESIGN: Interrupted time series analysis, review of case notes, survey, and interviews. SETTING: Acute and primary care trusts in England and Wales. PARTICIPANTS: All primary care prescribing, hospital pharmacies; a random sample of 20 acute trusts, 17 mental health trusts, and 21 primary care trusts; and senior clinicians and managers from five acute trusts. MAIN OUTCOME MEASURES: Rates of prescribing and use of procedures and medical devices relative to evidence based guidance. RESULTS: 6308 usable patient audit forms were returned. Implementation of NICE guidance varied by trust and by topic. Prescribing of some taxanes for cancer (P <0.002) and orlistat for obesity (P <0.001) significantly increased in line with guidance. Prescribing of drugs for Alzheimer’s disease and prophylactic extraction of wisdom teeth showed trends consistent with, but not obviously a consequence of, the guidance. Prescribing practice often did not accord with the details of the guidance. No change was apparent in the use of hearing aids, hip prostheses, implantable cardioverter defibrillators, laparoscopic hernia repair, and laparoscopic colorectal cancer surgery after NICE guidance had been issued. CONCLUSIONS: Implementation of NICE guidance has been variable. Guidance seems more likely to be adopted when there is strong professional support, a stable and convincing evidence base, and no increased or unfunded costs, in organisations that have established good systems for tracking guidance implementation and where the professionals involved are not isolated. Guidance needs to be clear and reflect the clinical context
Fluctuation limits of strongly degenerate branching systems
Functional limit theorems for scaled fluctuations of occupation time
processes of a sequence of critical branching particle systems in with
anisotropic space motions and strongly degenerated splitting abilities are
proved in the cases of critical and intermediate dimensions. The results show
that the limit processes are constant measure-valued Wienner processes with
degenerated temporal and simple spatial structures.Comment: 15 page
The Extended Baryon Oscillation Spectroscopic Survey: Variability Selection and Quasar Luminosity Function
The SDSS-IV/eBOSS has an extensive quasar program that combines several
selection methods. Among these, the photometric variability technique provides
highly uniform samples, unaffected by the redshift bias of traditional
optical-color selections, when quasars cross the stellar locus
or when host galaxy light affects quasar colors at . Here, we present
the variability selection of quasars in eBOSS, focusing on a specific program
that led to a sample of 13,876 quasars to over a 94.5
deg region in Stripe 82, an areal density 1.5 times higher than over the
rest of the eBOSS footprint. We use these variability-selected data to provide
a new measurement of the quasar luminosity function (QLF) in the redshift range
. Our sample is denser, reaches deeper than those used in previous
studies of the QLF, and is among the largest ones. At the faint end, our QLF
extends to at low redshift and to
at . We fit the QLF using two independent double-power-law models with
ten free parameters each. The first model is a pure luminosity-function
evolution (PLE) with bright-end and faint-end slopes allowed to be different on
either side of . The other is a simple PLE at , combined with a
model that comprises both luminosity and density evolution (LEDE) at .
Both models are constrained to be continuous at . They present a
flattening of the bright-end slope at large redshift. The LEDE model indicates
a reduction of the break density with increasing redshift, but the evolution of
the break magnitude depends on the parameterization. The models are in
excellent accord, predicting quasar counts that agree within 0.3\% (resp.,
1.1\%) to (resp., ). The models are also in good agreement over
the entire redshift range with models from previous studies.Comment: 15 pages, 12 figures, accepted for publication in A&
Effect of Loading on Field Uniformity : Energy Diffusion in Reverberant Environments
In reverberant electromagnetic environments such as reverberation chambers, shielding enclosures, vehicles and buildings, the electromagnetic energy density is often assumed to be uniform and the direction of arrival of electromagnetic waves (Poynting vector) and their polarisation is assumed uniformly distributed. This is the basis of the power balance method for electromagnetic coupling analysis and much of the theory of reverberation chambers. However significant field inhomogeneity is often encountered in practice when significant losses are present. In this paper we show why this must be so when an energy flow exists from the source of energy to absorptive elements, and how the non-uniformity can be determined using a diffusion based solution. The diffusion based solution, though not as computationally efficient as the power balance method, is still much more efficient than a full-wave approach
Electronic structure of the muonium center as a shallow donor in ZnO
The electronic structure and the location of muonium centers (Mu) in
single-crystalline ZnO were determined for the first time. Two species of Mu
centers with extremely small hyperfine parameters have been observed below 40
K. Both Mu centers have an axial-symmetric hyperfine structure along with a
[0001] axis, indicating that they are located at the AB_{O,//} and BC_{//}
sites. It is inferred from their small ionization energy (~6 meV and 50 meV)
and hyperfine parameters (~10^{-4} times the vacuum value) that these centers
behave as shallow donors, strongly suggesting that hydrogen is one of the
primary origins of n type conductivity in as-grown ZnO.Comment: 4 pages, 4 figures, submitted to PR
Higgs boson production with one bottom quark jet at hadron colliders
We present total rates and kinematic distributions for the associated
production of a single bottom quark and a Higgs boson at the Tevatron and the
LHC. We include next-to-leading order QCD corrections and compare the results
obtained in the four and five flavor number schemes for parton distribution
functions.Comment: 4 pages, 8 figures, RevTeX
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