4,944 research outputs found
Ultrafast Interference Imaging of Air in Splashing Dynamics
A drop impacting a solid surface with sufficient velocity will emit many
small droplets creating a splash. However, splashing is completely suppressed
if the surrounding gas pressure is lowered. The mechanism by which the gas
affects splashing remains unknown. We use high-speed interference imaging to
measure the air beneath all regions of a spreading viscous drop as well as
optical absorption to measure the drop thickness. Although an initial air
bubble is created on impact, no significant air layer persists until the time a
splash is created. This suggests that splashing in our experimentally
accessible range of viscosities is initiated at the edge of the drop as it
encroaches into the surrounding gas
Fabrication of Pd-Cr wire
Fabrication of Pd-13 percent Cr alloy wires is described. Melting, casting, swaging and annealing processes are discussed. Drawing to reach two diameters (0.003 inch and 0.00176 inch) of wire is described. Representative micrographs of the Pd-Cr alloy at selected stages during wire fabrication are included. The resistance of the wire was somewhat lower, by about 15 to 20 percent, than comparable wire of other alloys used for strain gages
The Stellar Mass Spectrum in the Young Populous Cluster NGC 1866
The young populous cluster NGC 1866 in the Large Magellanic Cloud LMC), which
is probably one of the most massive object formed in the LMC during the last ~
3 Gyr, appears to have an unexpectedly high mass-to-light ratio. From its
velocity dispersion Fischer et al. (1992) find its mass to be (1.35 " 0.25) x
105 Mu. The luminosity of this cluster is MV = -8.93 " 0.13, corresponding to
LV = (3.2 " 0.4) x 105 LV (u). This yields M/LV = 0.42 " 0.09 in solar units.
For a cluster of age 0.1 Gyr such a relatively high mass-to-light ratio
requires a mass spectrum with an exponent x = 1.72 " 0.09; or x = 1.75 " 0.09
if mass loss by evolving stars is taken into account.Comment: To be published in the October 1999 issue of the Publications of the
Astronomical Society of the Pacifi
A Baseline Model of Industry Evolution
The paper analyses some general dynamic properties of industries characterized by heterogeneous firms and continuing stochastic entry. After a brief critical assessment of some significant drawbacks of recent contributions to modeling of stochastic industrial dynamics, we propose a novel analytical apparatus able to derive some generic properties of the underlying competition process combining persistent technological heterogeneity, differential growth of individual firms and turnover. The basic model, we suggest, is indeed applicable with proper modifications to a large class of evolutionary processes, well beyond industrial dynamics.Evolution, Competition, Stochastic entry, Industrial dynamics, Evolutionary games
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