10,342 research outputs found
Experimental aerodynamic heating to simulated shuttle tiles
The heat transfer to simulated shuttle thermal protection system tiles was investigated experimentally using a highly instrumented metallic thin wall tile arranged with other metal tiles in a staggered tile array. Cold-wall heating rate data for laminar and turbulent flow were obtained in the Langley 8-foot high temperature tunnel at a nominal Mach number of 7, a nominal total temperature of 3300 R, free-stream unit Reynolds number from 3.4 x 10 to the 5th power to 2.2 x 10 to the 6th power per foot, and free-stream dynamic pressure of 1.8 psia to 9.1 psia. Experimental data are presented to illustrate the effects of flow angularity and gap width on both local peak heating and overall heating loads
Closed-circuit television welding- electrode guidance system
Closed-circuit TV camera is mounted parallel to electrode and moves along with it. Camera is scanned along seam so seam is viewed parallel with scan lines on TV monitor. Two fiber optics illuminators are attached to guidance system; they illuminate seam for TV camera
Decay
Motivated by the experimental measurement of the decay rate, , and
the longitudinal polarization, , in the Cabibbo favored decay , we have studied theoretical prediction within the context of
factorization approximation invoking several form factors models. We were able
to obtain agreement with experiment for both and by using
experimentally measured values of the form factors ,
and in the semi-leptonic decay . We have also included in our calculation the effect of the
final state interaction () by working with the partial waves amplitudes
, and . Numerical calculation shows that the decay amplitude is
dominated by wave, and that the polarization is sensitive to the
interference between and waves. The range of the phase difference
accommodated by experimental error in
is large.Comment: 7 pages, LaTe
Virtual Data in CMS Analysis
The use of virtual data for enhancing the collaboration between large groups
of scientists is explored in several ways:
- by defining ``virtual'' parameter spaces which can be searched and shared
in an organized way by a collaboration of scientists in the course of their
analysis;
- by providing a mechanism to log the provenance of results and the ability
to trace them back to the various stages in the analysis of real or simulated
data;
- by creating ``check points'' in the course of an analysis to permit
collaborators to explore their own analysis branches by refining selections,
improving the signal to background ratio, varying the estimation of parameters,
etc.;
- by facilitating the audit of an analysis and the reproduction of its
results by a different group, or in a peer review context.
We describe a prototype for the analysis of data from the CMS experiment
based on the virtual data system Chimera and the object-oriented data analysis
framework ROOT. The Chimera system is used to chain together several steps in
the analysis process including the Monte Carlo generation of data, the
simulation of detector response, the reconstruction of physics objects and
their subsequent analysis, histogramming and visualization using the ROOT
framework.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 9 pages, LaTeX, 7 eps figures. PSN
TUAT010. V2 - references adde
Quantum Fluctuations and Excitations in Antiferromagnetic Quasicrystals
We study the effects of quantum fluctuations and the excitation spectrum for
the antiferromagnetic Heisenberg model on a two-dimensional quasicrystal, by
numerically solving linear spin-wave theory on finite approximants of the
octagonal tiling. Previous quantum Monte Carlo results for the distribution of
local staggered magnetic moments and the static spin structure factor are
reproduced well within this approximate scheme. Furthermore, the magnetic
excitation spectrum consists of magnon-like low-energy modes, as well as
dispersionless high-energy states of multifractal nature. The dynamical spin
structure factor, accessible to inelastic neutron scattering, exhibits
linear-soft modes at low energies, self-similar structures with bifurcations
emerging at intermediate energies, and flat bands in high-energy regions. We
find that the distribution of local staggered moments stemming from the
inhomogeneity of the quasiperiodic structure leads to a characteristic energy
spread in the local dynamical spin susceptibility, implying distinct nuclear
magnetic resonance spectra, specific for different local environments.Comment: RevTex, 12 pages with 15 figure
Forest Analysis of the Gordon Natural Area Focusing on Carbon Stock, Forest Structure, and Forest Composition
Bounding effective parameters in the chiral Lagrangian for excited heavy mesons
We use recent experimental data on charmed mesons to constrain three coupling
constants in the effective lagrangian describing the interactions of excited
heavy-light mesons with light pseudoscalar mesons at order .
Predictions in the beauty sector are also derived.Comment: LaTex, 11 pages, 1 eps figur
Feature Selection of Post-Graduation Income of College Students in the United States
This study investigated the most important attributes of the 6-year
post-graduation income of college graduates who used financial aid during their
time at college in the United States. The latest data released by the United
States Department of Education was used. Specifically, 1,429 cohorts of
graduates from three years (2001, 2003, and 2005) were included in the data
analysis. Three attribute selection methods, including filter methods, forward
selection, and Genetic Algorithm, were applied to the attribute selection from
30 relevant attributes. Five groups of machine learning algorithms were applied
to the dataset for classification using the best selected attribute subsets.
Based on our findings, we discuss the role of neighborhood professional degree
attainment, parental income, SAT scores, and family college education in
post-graduation incomes and the implications for social stratification.Comment: 14 pages, 6 tables, 3 figure
Whole blood transfusion versus component therapy in adult trauma patients with acute major haemorrhage
âThis article has been accepted for publication in Emergency Medicine Journal, 2020 following peer review, and the Version of Record can be accessed online at http://dx.doi.org/10.1136/emermed-2019-209040.âObjective: In the era of damage control resuscitation of trauma patients with acute major haemorrhage, transfusion practice has evolved to blood component (component therapy) administered in a ratio that closely approximates whole blood (WB). However, there is a paucity of evidence supporting the optimal transfusion strategy in these patients. The primary objective was therefore to establish if there is an improvement in survival at 30âdays with the use of WB transfusion compared with blood component therapy in adult trauma patients with acute major haemorrhage.
Methodology. A systematic literature search was performed on 15 December 2019 to identify studies comparing WB transfusion with component therapy in adult trauma patients and mortality at 30 days. Studies which did not report mortality were excluded. Methodological quality of included studies was interpreted using the Cochrane risk of bias tool, and rated using the Grading of Recommendations Assessment, Development and Evaluation approach.
Results.
Search of the databases identified 1885 records, and six studies met the inclusion criteria involving 3255 patients. Of the three studies reporting 30-day mortality (one randomised controlled trial (moderate evidence) and two retrospective (low and very low evidence, respectively)), only one study demonstrated a statistically significant difference between WB and component therapy, and two found no statistical difference. Two retrospective studies reporting in-hospital mortality found no statistical difference in unadjusted mortality, but both reported statistically significant logistic regression analyses demonstrating that those with a WB transfusion strategy were less likely to die.
Conclusion. Recognising the limitations of this systematic review relating to the poor-quality evidence and limited number of included trials, it does not provide evidence to support or reject use of WB transfusion compared with component therapy for adult trauma patients with acute major haemorrhage.
PROSPERO registration number: CRD42019131406
Intertwining Relations for the Deformed D1D5 CFT
The Higgs branch of the D1D5 system flows in the infrared to a
two-dimensional N=(4,4) SCFT. This system is believed to have an "orbifold
point" in its moduli space where the SCFT is a free sigma model with target
space the symmetric product of copies of four-tori; however, at the orbifold
point gravity is strongly coupled and to reach the supergravity point one needs
to turn on the four exactly marginal deformations corresponding to the blow-up
modes of the orbifold SCFT. Recently, technology has been developed for
studying these deformations and perturbing the D1D5 CFT off its orbifold point.
We present a new method for computing the general effect of a single
application of the deformation operators. The method takes the form of
intertwining relations that map operators in the untwisted sector before
application of the deformation operator to operators in the 2-twisted sector
after the application of the deformation operator. This method is
computationally more direct, and may be of theoretical interest. This line of
inquiry should ultimately have relevance for black hole physics.Comment: latex, 23 pages, 3 figure
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