8,194 research outputs found
Euler analysis of a swirl recovery vane design for use with an advanced single-rotation propfan
Recent work has demonstrated the propulsive efficiency improvement available from single- and counter-rotation propfans as compared with current technology high bypass ratio turbofans. The concept known as swirl recovery vanes (SRV) is examined through the use of a 3-D Euler code. At high speed cruise conditions, the SRV can improve the efficiency level of a single-rotation propfan, but a concern is to have adequate hub choke margin. The SRV was designed with 2-D methods and was predicted to have hub choking at Mach 0.8 cruise. The 3-D Euler analysis properly accounts for sweep effects and 3-D relief, and predicts that at cruise the SRV will recover roughly 5 percent of the 10 percent efficiency loss due to swirl and have a good hub choke margin
A systematic review and meta-analysis of Macroplastique for treating female stress urinary incontinence.
Introduction and hypothesisMacroplastique® (polydimethylsiloxane injection) is a minimally invasive urethral bulking agent with global clinical literature describing its use over 20 years. This study critically assessed the safety and effectiveness outcomes for adult women treated with Macroplastique for stress urinary incontinence (SUI) through a systematic review and meta-analysis.MethodsA systematic review of the scientific literature from 1990 to 2010 was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement to quantitatively summarize the safety and effectiveness of Macroplastique for female SUI. A total of 958 patients from 23 cohorts were eligible for inclusion and were analyzed. Random-effects models were used to estimate the improvement and cure rates following treatment at three time periods: short-term (<6 months), mid-term (6-18 months), and long-term (>18 months). Expanded models assessed the effect of reinjection rate on successful treatment outcomes. Adverse event rates were aggregated and reported.ResultsImprovement rates were 75 % [95 % confidence interval (CI), 69-81] in the short-term, 73 % (95 % CI, 62-83) in the mid-term, and 64 % (95 % CI, 57-71) long-term. Cure/dry rates were 43 % (95 % CI, 33-54), 37 % (95 % CI, 28-46), and 36 % (95 % CI, 27-46) over the same respective follow-up periods. Higher study reinjection rates were associated with improved long-term SUI outcomes. No serious adverse events were reported.ConclusionsThis quantitative review supports Macroplastique as an effective, durable, and safe treatment option for female SUI. Meta-analytic evidence suggests that long-term therapeutic benefit is frequently maintained, with some patients requiring reinjection
Euler analysis comparison with LDV data for an advanced counter-rotation propfan at cruise
A fine mesh Euler solution of the F4/A4 unducted fan (UDF) model flowfield is compared with laser Doppler velocimeter (LDV) data taken in the NASA Lewis 8- by 6-Foot Supersonic Wind Tunnel. The comparison is made primarily at one axial plane downstream of the front rotor where the LDV particle lag errors are reduced. The agreement between measured and predicted velocities in this axial plane is good. The results show that a dense mesh is needed in the centerbody stagnation region to minimize entropy generation that weakens the aft row passage shock. The predicted radial location of the tip vortex downstream of the front rotor agrees well with the experimental results but the strength is overpredicted. With 40 points per chord line, the integrated performance quantities are nearly converged, but more points are needed to resolve passage shocks and flow field details
Nonextremal black holes are BPS
Extremal charged black holes are BPS solutions. It is commonly thought that
their nonextremal counterparts are not. Further, experience with BPS solutions
in flat spacetime suggests that all BPS solutions are supersymmetric; i.e. that
they are invariant under some supersymmetry charges of either the original
field theory or an appropriately extended version thereof. Using nonextremal
Reissner-Nordstr\"om black holes as counterexamples, we show that neither of
these expectations is universally valid. These black holes correspond to a
one-parameter family of BPS solutions. By showing that, subject to one very
plausible assumption, no generalized Killing spinor can be constructed for
these, we show that there is no supergravity theory for which these BPS
solutions preserve a fraction of the supersymmetry, nor is there an associated
Witten-Nester positive energy bound.Comment: LaTeX, 15 pages. v2 Discussion in sec 2.3 amended, small corrections,
reference added. v3 (PRD version) Clarifications, corrections and references
added. Section 3.2 partly rewritten and expanded, and assumption clarifie
The Interplay of Cluster and Galaxy Evolution
We review here the interplay of cluster and galaxy evolution. As a case
study, we consider the Butcher-Oemler effect and propose that it is the result
of the changing rate of cluster merger events in a hierarchical universe. This
case study highlights the need for new catalogs of clusters and groups that
possess quantified morphologies. We present such a sample here, namely the
Sloan Digital Sky Survey (SDSS) C4 Catalog, which has been objectively-selected
from the SDSS spectroscopic galaxy sample. We outline here the C4 algorithm and
present first results based on the SDSS Early Data Release, including an X-ray
luminosity-velocity dispersion (L_x-sigma) scaling relationship (as a function
of cluster morphology), and the density-SFR relation of galaxies within C4
clusters (Gomez et al. 2003). We also discuss the merger of Coma and the
NGC4839 group, and its effect on the galaxy populations in these systems. We
finish with a brief discussion of a new sample of Hdelta-selected galaxies
(i.e., k+a, post--starburst galaxies) obtained from the SDSS spectroscopic
survey.Comment: Invited review at the JENAM 2002 Workshop on "Galaxy Evolution in
Groups and Clusters", Porto, Sep 5-7 2002, eds. Lobo, Serote-Roos and
Biviano, Kluwer in pres
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