20,793 research outputs found
Foldable beam
A foldable beam possessing superior qualities of light weight, compactness for transportation, quick deployment with minimum use of force, and high strength is described. These qualities are achieved through the use of a series of longitudinally rigid segments, hinged along one side and threaded by one or two cables along the opposite side. Tightening the cables holds the beam extended. Loosening the cables permits the segments to fold away from the threaded side. In one embodiment the segments are connected by canted hinges with the result that the beam may be folded in a helix-like configuration around a cylinder. In another embodiment the segments themselves may be hinged to fold flat laterally as the beam is folded, resulting in a configuration that may be helixed around a shorter cylinder
Full-coverage film cooling on flat, isothermal surfaces: Data and predictions
The heat transfer and fluid mechanics characteristics of full-coverage film cooling were investigated. The results for flat, isothermal plates for three injection geometries (normal, slant, and compound angle) are summarized and data concerning the spanwise distribution of the heat transfer coefficient within the blowing region are presented. Data are also presented for two different numbers of rows of holes (6 and 11). The experimental results summarized can be predicted with a two dimensional boundary layer code, STANCOOL, by providing descriptors of the injection parameters as inputs
Implications of recruitment, distribution and availability of stocks for management of South Africa's Western Cape purse-seine fishery
Bibliography: pages 281-290.South Africa's Western Cape purse-seine fishery is situated off the country's western seaboard in the highly productive waters of the southern Benguela Current system (Cushing 1969). Management of the multi-species resource is the responsibility of the government's Department of Industries and since 1950 a large volume of data relating to performances of contributing species has been collected. Recent analyses have indicated an oversubscription of effort, a sequential depletion of the more valuable stocks and, consequently, a present reliance upon less favourable species (Newman and Crawford 1979, Crawford et al. in press). These adverse trends have been precipitated, in part at least, by ineffective legislation, which has resulted from a past failure to appreciate that exceptionally good year classes occur infrequently (Newman and Crawford in- press). Optimal ways of harvesting strong cohorts, or of avoiding overexploitation in the event of recruitment failure, remain to be explored
Radio-continuum study of Large Magellanic Cloud Supernova Remnant J0509-6731
We present a detailed study of Australia Telescope Compact Array (ATCA)
observations ( = 20, 13, 6 & 3~cm) of supernova remnant (SNR)
J0509--6731 in the Large Magellanic Cloud (LMC). The remnant has a ring
morphology with brightened regions towards the south-western limb. We also find
a second brightened inner ring which is only seen in the radio-continuum. The
SNR is almost circular, with a diameter ranging from 7 to 8~pc, and a steep
radio spectral index between 36 and 3~cm of , which is
characteristic of younger SNRs. We also report detection of radially orientated
polarisation across the remnant at 6~cm, with a mean fractional polarisation
level of ~(26~~13)%. We find the magnetic field (168~G)
and ( ~W
m~Hz~sr , 7.35~pc) to be consistent with other young
remnants
Nonlinear saturation of electrostatic waves: mobile ions modify trapping scaling
The amplitude equation for an unstable electrostatic wave in a multi-species
Vlasov plasma has been derived. The dynamics of the mode amplitude is
studied using an expansion in ; in particular, in the limit
, the singularities in the expansion coefficients are
analyzed to predict the asymptotic dependence of the electric field on the
linear growth rate . Generically , as
, but in the limit of infinite ion mass or for
instabilities in reflection-symmetric systems due to real eigenvalues the more
familiar trapping scaling is predicted.Comment: 13 pages (Latex/RevTex), 4 postscript encapsulated figures which are
included using the utility "uufiles". They should be automatically included
with the text when it is downloaded. Figures also available in hard copy from
the authors ([email protected]
Full-coverage film cooling heat transfer study: Summary of data for normal-hole injection and 30 deg slant-hole injection
Heat transfer to a full coverage film cooled turbulent boundary layer over a flat surface was studied. The surface consisted of a discrete hole test section containing 11 rows of holes spaced 5 diameters apart in a staggered array and an instrumented recovery region. Ten diameter spacing was also studied by plugging appropriate holes. Two test sections were used, one having holes normal to the surface and the other having holes angled 30 deg to the surface in the downstream direction. Stanton number data were obtained both in the full coverage region and in the downstream recovery region for a range of blowing ratios, or mass flux ratios, from 0 to 1.3. Initial conditions at the upstream edge of the blowing region were varied from 500 to 5000 for momentum thickness Reynolds number and from 100 to 1800 for enthalpy thickness Reynolds number. The range of Reynolds numbers based on hole diameter and mainstream velocity was 6000 to 22000. Initial boundary layer thicknesses range from 0.5 to 2.0 hole diameters. Air was used as the working fluid. The data were taken for the secondary injection temperature equal to the wall temperature and also equal to the mainstream temperature. Superposition was then used to obtain Stanton number as a continuous function of the injectant temperature. The heat transfer coefficient was defined on the basis of a mainstream-to-wall temperature difference. This definition permits direct comparison of performance between film cooling and transpiration cooling
A bright millisecond radio burst of extragalactic origin
Pulsar surveys offer one of the few opportunities to monitor even a small
fraction (~0.00001) of the radio sky for impulsive burst-like events with
millisecond durations. In analysis of archival survey data, we have discovered
a 30-Jy dispersed burst of duration <5 ms located three degrees from the Small
Magellanic Cloud. The burst properties argue against a physical association
with our Galaxy or the Small Magellanic Cloud. Current models for the free
electron content in the Universe imply a distance to the burst of <1 Gpc No
further bursts are seen in 90-hr of additional observations, implying that it
was a singular event such as a supernova or coalescence of relativistic
objects. Hundreds of similar events could occur every day and act as insightful
cosmological probes.Comment: 18 pages, 4 figures. Accepted by Science. Published electronically
via Science Express on September 27, 200
Heat sterilizable and impact resistant Ni-Cd battery development Quarterly report, 1 Apr. - 30 Jun. 1969
Electrochemistry, battery engineering, and impact tests of heat sterilizable nickel cadmium cell
Scaling and singularities in the entrainment of globally-coupled oscillators
The onset of collective behavior in a population of globally coupled
oscillators with randomly distributed frequencies is studied for phase
dynamical models with arbitrary coupling. The population is described by a
Fokker-Planck equation for the distribution of phases which includes the
diffusive effect of noise in the oscillator frequencies. The bifurcation from
the phase-incoherent state is analyzed using amplitude equations for the
unstable modes with particular attention to the dependence of the nonlinearly
saturated mode on the linear growth rate . In general
we find where is the
diffusion coefficient and is the mode number of the unstable mode. The
unusual factor arises from a singularity in the cubic term of
the amplitude equation.Comment: 11 pages (Revtex); paper submitted to Phys. Rev. Let
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