2,512 research outputs found
Viscoelastic propellant effects on Space Shuttle Dynamics
The program of solid propellant research performed in support of the space shuttle dynamics modeling effort is described. Stiffness, damping, and compressibility of the propellant and the effects of many variables on these properties are discussed. The relationship between the propellant and solid rocket booster dynamics during liftoff and boost flight conditions and the effects of booster vibration and propellant stiffness on free free solid rocket booster modes are described. Coupled modes of the shuttle system and the effect of propellant stiffness on the interfaces of the booster and the external tank are described. A finite shell model of the solid rocket booster was developed
Effect of wall roughness on liquid oscillations damping in rectangular tanks
Tests were conducted in two rectangular glass tanks using silicon carbide grit bonded to walls to determine effect of wall roughness for damping liquid oscillations. Tests included effects of roughness height, roughness location, roughness at various values, amplitude decay, Reynolds number, and boundary layer thickness
Solid rocket booster water impact test
Water impact drop tests were performed on the space shuttle solid rocket boosters (SRB). Peak water impact pressures and pressure/time traces were measured for various impact velocities using a two-dimensional, full-scale SRB aft skirt internal ring model. Passive burst disc-type pressure transducers were calibrated for use on flight SRB's. The effects on impact pressure of small ring configuration changes and application of thermal protection system cork layers were found to be negligible
Experimental determination of liquid oscillation frequency in an inclined right circular cylinder
Liquid oscillation frequency measurement in inclined right circular cylinde
Understanding I=2 pi-pi Interaction
A correct understanding and description of the I=2 pi-pi S-wave interaction
is important for the extraction of the I=0 pi-pi S-wave interaction from
experimental data and for understanding the I=0 pi-pi S-wave interaction
theoretically. With t-channel rho, f2(1270) exchange and the pi pi -> rho rho
-> pi pi box diagram contribution, we reproduce the pi-pi isotensor S-wave and
D-wave scattering phase shifts and inelasticities up to 2.2 GeV quite well in a
K-matrix formalism.Comment: Talk given at Hadron 03: 10th International Conference on Hadron
Spectroscopy, Aschaffenburg, Germany, 31 Aug - 6 Sep 200
Is it time to ban oxytocin for poor labour progress?
Oxytocin causes myometrial contractions and prostaglandin release. It is commonly used as an intervention for women in established labour with slow progress. However recent large randomised trials of oxytocin for this indication have shown no difference in caesarean section rates associated with its use. This may be due to inadequate doses of oxytocin and small randomised studies have suggested high dose oxytocin may indeed reduce caesarean delivery. The results of a high quality large randomised trial of high versus low dose oxytocin for women with slow progress are keenly awaited. There is no evidence to support the concept of turning the oxytocin off once contractions have been established, although this certainly merits further investigation. Recent evidence of contemporary labour patterns indicate that our whole concept of slow progress in labour is fundamentally flawed
Torsional vibration analysis of Saturn vehicles
Torsional vibration analysis of Saturn vehicle
The nature of , , and
Masses and widths of the four light scalar mesons , ,
(980) and (980) may be reproduced in a model where mesons scatter via
a loop. A transition potential is used to couple mesons to
at a radius of fm. Inside this radius, there is an
infinite bare spectrum of confined states, for which a harmonic
oscillator is chosen here. The coupled-channel system approximately reproduces
the features of both light and heavy meson spectroscopy. The generation of
, , and is a balance between attraction
due to the loop and suppression of the amplitudes at the Adler zeros.
Phase shifts increase more rapidly as the coupling constant to the mesons
increases. This leads to resonant widths which decrease with increasing
coupling constant - a characteristically non-perturbative effect.Comment: Plain LaTeX, 10 pages, 3 EPS figures; v2: 11 pages, better-quality
figures, extra references, version accepted for publication in Phys. Lett.
Nature of the f_0(600) from its N_c dependence at two loops in unitarized Chiral Perturbation Theory
By using unitarized two-loop Chiral Perturbation Theory partial waves to
describe pion-pion scattering we find that the dominant component of the
lightest scalar meson does not follow the q-qbar dependence on the number of
colors that, in contrast, is obeyed by the lightest vectors. The method
suggests that a subdominant q-qbar component of the f_0(600) possibly
originates around 1 GeV.Comment: 4 pages, 1 Figure. To appear in Phys. Rev. Let
Initial experience with Vanguard(R) total knee arthroplasty
Introduction Biomet Vanguard(R) Complete Knee System is a total knee replacement system, introduced into the market in 2003: thissystem boasts a designed kneecap track or groove which allows for greater mobility and decreased loss of healthy bone during the replacement process. Clinical and radiographic results in Varese Orthopaedics Unit initial experience are reported. Materials and methods Clinical and radiographic parameters are evaluated in 29 patients who underwent TKA (Vanguard(R) Complete Knee System- Biomet Inc.) for primary gonarthrosis during the last 2 years at Orthopaedics and Traumatology Unit of Ospedale di Circolo\u2014Fondazione Macchi in Varese. ROM, type of anaesthesia, patellar pain, clinical and functional Knee Score (pre-operative), size of implant, ROM, blooding, patellar pain, VAS, clinical and func-
tional Knee Score (post-operative) are analyzed. Radiographic follow-up is made at 6 and 12 months. Results Clinical and Functional Knee Score respectively improve from 47 to 88 pts and from 51 to 88 pts in pre- and post-operative period (p\0.001). Post-operatively no patellar pain, 2 pts VAS and 1215 cc blooding are reported. ROM doesn\u2019t significantly improve from pre- to post-operative. No relevant complications are reported.
Due to the short follow-up, radiographic evaluation does not allow to demonstrate polyethylene liner wear. Conclusions Vanguard(R) Knee Replacement significantly shows a clinical and functional improvement in patients affected by primary gonarthrosis. Moreover, post-operative pain decrease allows early mobilization and rehabilitation
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