92,868 research outputs found
A critical review of experimental accomplishments in the field of filament-reinforced metal matrix composites Bimonthly progress report
Critical review of experimental accomplishments in filament reinforced metal-matrix composite
An asymptotic formula for the number of non-negative integer matrices with prescribed row and column sums
We count mxn non-negative integer matrices (contingency tables) with
prescribed row and column sums (margins). For a wide class of smooth margins we
establish a computationally efficient asymptotic formula approximating the
number of matrices within a relative error which approaches 0 as m and n grow.Comment: 57 pages, results strengthened, proofs simplified somewha
The number of graphs and a random graph with a given degree sequence
We consider the set of all graphs on n labeled vertices with prescribed
degrees D=(d_1, ..., d_n). For a wide class of tame degree sequences D we prove
a computationally efficient asymptotic formula approximating the number of
graphs within a relative error which approaches 0 as n grows. As a corollary,
we prove that the structure of a random graph with a given tame degree sequence
D is well described by a certain maximum entropy matrix computed from D. We
also establish an asymptotic formula for the number of bipartite graphs with
prescribed degrees of vertices, or, equivalently, for the number of 0-1
matrices with prescribed row and column sums.Comment: 52 pages, minor improvement
Kinematics of the Broad Line Region in M81
A new model is presented which explains the origin of the broad emission
lines observed in the LINER/Seyfert nucleus of M81 in terms of a steady state
spherically symmetric inflow, amounting to 1 x 10^-5 Msun/yr, which is
sufficient to explain the luminosity of the AGN. The emitting volume has an
outer radius of ~1 pc, making it the largest broad line region yet to be
measured, and it contains a total mass of ~ 5 x 10^-2 Msun of dense, ~ 10^8
cm^-3, ionized gas, leading to a very low filling factor of ~ 5 x 10^-9. The
fact that the BLR in M81 is so large may explain why the AGN is unable to
sustain the ionization seen there. Thus, the AGN in M81 is not simply a scaled
down quasar.Comment: Accepted for Publication in ApJ 7/21/0
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