34,150 research outputs found
Asymptotic enumeration of incidence matrices
We discuss the problem of counting {\em incidence matrices}, i.e. zero-one
matrices with no zero rows or columns. Using different approaches we give three
different proofs for the leading asymptotics for the number of matrices with
ones as . We also give refined results for the asymptotic
number of incidence matrices with ones.Comment: jpconf style files. Presented at the conference "Counting Complexity:
An international workshop on statistical mechanics and combinatorics." In
celebration of Prof. Tony Guttmann's 60th birthda
A graph partition problem
Given a graph on vertices, for which is it possible to partition
the edge set of the -fold complete graph into copies of ? We show
that there is an integer , which we call the \emph{partition modulus of
}, such that the set of values of for which such a partition
exists consists of all but finitely many multiples of . Trivial
divisibility conditions derived from give an integer which divides
; we call the quotient the \emph{partition index of }. It
seems that most graphs have partition index equal to , but we give two
infinite families of graphs for which this is not true. We also compute
for various graphs, and outline some connections between our problem and the
existence of designs of various types
Communicating research with the public : evaluation of an invasive earthworm education program
Ecologists are increasingly encouraged by funding agencies and professional societies to communicate their research with the public. However, most receive relatively little training in how to do this effectively. Furthermore, evaluation of whether such an investment by ecologists actually achieves conservation objectives is rare. We created an education program, involving print, television, radio, and internet media, to increase awareness about earthworm invasions and to discourage anglers from dumping earthworm bait. Using pre- and post-surveys, we evaluated our program’s success in reaching its target audience and in changing knowledge and behavior. Few participants (4.1%) recalled seeing the program material and knowledge of the fact that earthworms are non-native in Alberta remained low (15.8% before, 15.1% after). Further, after being told about the negative effects of earthworms in forests, 46.7% of the anglers surveyed stated they would not change their bait disposal behavior in the future, with many commenting that they did not believe earthworms could be harmful. These results highlight the importance of evaluating education programs, rather than assuming they are successful. Given many participants' doubts that earthworms have negative effects, both regulations and education may be needed to reduce earthworm introductions
The instability of stellar structures intermediate between white dwarfs and neutron stars
Instability of stellar structures intermediate between dwarfs and neutron star
Surface flux transport modeling for solar cycles 15--21: effects of cycle-dependent tilt angles of sunspot groups
We model the surface magnetic field and open flux of the Sun from 1913 to
1986 using a surface flux transport model, which includes the observed
cycle-to-cycle variation of sunspot group tilts. The model reproduces the
empirically derived time evolution of the solar open magnetic flux, and the
reversal times of the polar fields. We find that both the polar field and the
axial dipole moment resulting from this model around cycle minimum correlate
with the strength of the following cycle.Comment: Accepted for publication by Ap
Penetration and spreading of transverse jets of hydrogen in a Mach 2.72 airstream
Schlieren photography of flow distribution for transverse hydrogen jets from flat plate into Mach 2.72 airstrea
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