33,711 research outputs found
Surface temperature distribution along a thin liquid layer due to thermocapillary convection
The surface temperature distributions due to thermocapillary convections in a thin liquid layer with heat fluxes imposed on the free surface were investigated. The nondimensional analysis predicts that, when convection is important, the characteristics length scale in the flow direction L, and the characteristic temperature difference delta T sub o can be represented by L and delta T sub o approx. (A2Ma)/1/4 delta T sub R, respectively, where L sub R and delta sub R are the reference scales used in the conduction dominant situations with A denoting the aspect ratio and Ma the Marangoni number. Having L and delta sub o defined, the global surface temperature gradient delta sub o/L, the global thermocapillary driving force, and other interesting features can be determined. Numerical calculations involving a Gaussian heat flux distribution are presented to justify these two relations
Melt conveying in counter-rotating twin-screw extruders
Imperial Users onl
Analyzing powers in inclusive pion production at high energy and the nucleon spin structure
Analyzing powers in inclusive pion production in high energy transversely
polarized proton-proton collisions are studied theoretically in the framework
of the quark recombination model. Calculations by assuming the SU(6)
spin-flavor symmetry for the nucleon structure disagree with the experiments.
We solve this difficulty by taking into account the %We overcome this
difficulty by taking into account the realistic spin distribution functions of
the nucleon, which differs from the SU(6) expectation at large , %but
coincides with a perturbative QCD constraint on the ratio of the unpolarized
valence distributions, as . We also discuss the kaon spin
asymmetry and find in the polarized proton-proton
collisions at large .Comment: 13 pages, 4 figures, late
Black Hole Production by Cosmic Rays
Ultra-high energy cosmic rays create black holes in scenarios with extra
dimensions and TeV-scale gravity. In particular, cosmic neutrinos will produce
black holes deep in the atmosphere, initiating quasi-horizontal showers far
above the standard model rate. At the Auger Observatory, hundreds of black hole
events may be observed, providing evidence for extra dimensions and the first
opportunity for experimental study of microscopic black holes. If no black
holes are found, the fundamental Planck scale must be above 2 TeV for any
number of extra dimensions.Comment: 4 pages, 4 figures, PRL versio
Binary-Induced Gravitational Collapse: A Trivial Example
We present a simple model illustrating how a highly relativistic, compact
object which is stable in isolation can be driven dynamically unstable by the
tidal field of a binary companion. Our compact object consists of a
test-particle in a relativistic orbit about a black hole; the binary companion
is a distant point mass. Our example is presented in light of mounting
theoretical opposition to the possibility that sufficiently massive, binary
neutron stars inspiraling from large distance can collapse to form black holes
prior to merger. Our strong-field model suggests that first order
post-Newtonian treatments of binaries, and stability analyses of binary
equilibria based on orbit-averaged, mean gravitational fields, may not be
adequate to rule out this possibility.Comment: 7 pages, 5 figures, RevTeX, to appear in Phys. Rev. D, Jan 15 199
Eta-nucleon coupling constant in QCD with SU(3) symmetry breaking
We study the NN coupling constant using the method of QCD sum rules
starting from the vacuum-to-eta correlation function of the interpolating
fields of two nucleons. The matrix element of this correlation has been taken
with respect to nucleon spinors to avoid unwanted pole contribution. The
SU(3)-flavor symmetry breaking effects have been accounted for via the
-mass, s-quark mass and eta decay constant to leading order. Out of the
four sum rules obtained by taking the ratios of the two sum rules in
conjunction with the two sum rules in nucleon mass, three are found to give
mutually consistent results. We find the SU(3) breaking effects significant, as
large as 50% of the SU(3) symmetric part.Comment: 13 pages, 12 figure
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