10,964 research outputs found
Comparison of vibrations of a combination of solid-rocket launch vehicle and payload during a ground firing and launching
The results of a study into the environmental vibrations of a payload mounted on the Nike rocket launch vehicle were presented. Data were obtained during the flight acceptance test of the payload, the firing of the total vehicle in a special test stand, and the powered and unpowered flights of the vehicle. The vibrational response of the structure was measured. Data were also obtained on the fluctuating pressure on the outside surface of the vehicle and inside the forward and after ends of the rocket chamber. A comparison of the data from the three test conditions indicated that external pressure fluctuations were the major source of vibrations in the payload area, and pressure fluctuations within the rocket motor were the major source of vibrations contiguous to the payload area
Two phase detonation studies
An experimental study of the passage of a shock wave over a burning fuel drop is described. This includes high speed framing photographs of the interaction taken at 500,000 frames per second. A theoretical prediction of the ignition of a fuel drop by a shock wave is presented and the results compared with earlier experimental work. Experimental attempts to generate a detonation in a liquid fuel drop (kerosene)-liquid oxidizer drop (hydrogen peroxide)-inert gas-environment are described. An appendix is included which gives the analytical prediction of power requirements for the drop generator to produce certain size drops at a certain mass rate. A bibliography is also included which lists all of the publications resulting from this research grant
The influence of composition, annealing treatment, and texture on the fracture toughness of Ti-5Al-2.5Sn plate at cryogenic temperatures
The plane strain fracture toughness K sub Ic and conventional tensile properties of two commercially produced one-inch thick Ti-5Al-2.5Sn plates were determined at cryogenic temperatures. One plate was extra-low interstitial (ELI) grade, the other normal interstitial. Portions of each plate were mill annealed at 1088 K (1500 F) followed by either air cooling or furnace cooling. The tensile properties, flow curves, and K sub Ic of these plates were determined at 295 K (room temperature), 77 K (liquid nitrogen temperature), and 20 K (liquid hydrogen temperature)
Preliminary evaluation of radar imagery of Yellowstone Park, Wyoming
Evaluation of radar imagery of Yellowstone Park, Wyomin
Is the PAMELA Positron Excess Winos?
Recently the PAMELA satellite-based experiment reported an excess of galactic
positrons that could be a signal of annihilating dark matter. The PAMELA data
may admit an interpretation as a signal from a wino-like LSP of mass about 200
GeV, normalized to the local relic density, and annihilating mainly into
W-bosons. This possibility requires the current conventional estimate for the
energy loss rate of positrons be too large by roughly a factor of five. Data
from anti-protons and gamma rays also provide tension with this interpretation,
but there are significant astrophysical uncertainties associated with their
propagation. It is not unreasonable to take this well-motivated candidate
seriously, at present, in part because it can be tested in several ways soon.
The forthcoming PAMELA data on higher energy positrons and the FGST (formerly
GLAST) data, should provide important clues as to whether this scenario is
correct. If correct, the wino interpretation implies a cosmological history in
which the dark matter does not originate in thermal equilibrium.Comment: 7 pages, 4 figue
Navigation/traffic control satellite mission study. Volume 3 - System concepts
Satellite network for air traffic control, solar flare warning, and collision avoidanc
Pregnancy-Related Lumbopelvic Pain: Listening to Australian Women
To investigate the prevalence and nature of lumbo-pelvic pain (LPP), that is experienced by women in the lumbar and/or sacro-iliac area and/or symphysis pubis during pregnancy. Cross-sectional, descriptive study. An Australian public hospital antenatal clinic. Women in their third trimester of pregnancy. Method. Women were recruited to the study as they presented for their antenatal appointment. A survey collected demographic data and was used to self report LPP. A pain diagram differentiated low back, pelvic girdle or combined pain. Closed and open ended questions explored the experiences of the women.Main OutcomeMeasures. The Visual Analogue Scale and the Oswestry Disability Index (Version 2.1a). Results. There was a high prevalence of self reported LPP during the pregnancy (71%). An association was found between the reporting of LPP, multiparity, and a previous history of LPP. The mean intensity score for usual pain was 6/10 and four out of five women reported disability associated with the condition.Most women (71%) had reported their symptoms to their maternity carer however only a small proportion of these women received intervention. Conclusion. LPP is a potentially significant health issue during pregnancy
Multi-transmission-line-beam interactive system
We construct here a Lagrangian field formulation for a system consisting of
an electron beam interacting with a slow-wave structure modeled by a possibly
non-uniform multiple transmission line (MTL). In the case of a single line we
recover the linear model of a traveling wave tube (TWT) due to J.R. Pierce.
Since a properly chosen MTL can approximate a real waveguide structure with any
desired accuracy, the proposed model can be used in particular for design
optimization. Furthermore, the Lagrangian formulation provides for: (i) a clear
identification of the mathematical source of amplification, (ii) exact
expressions for the conserved energy and its flux distributions obtained from
the Noether theorem. In the case of uniform MTLs we carry out an exhaustive
analysis of eigenmodes and find sharp conditions on the parameters of the
system to provide for amplifying regimes
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