10,130 research outputs found
The animal quarantine service
Exotic diseases are a constant threat to Australia\u27s animal industry and there are many reasons for the uncompromising ban on the import of certain animals from overseas.
Such diseases as foot and mouth and blue tongue would cost Australia a tremendous amount of money if they became established here.
Just how Australia protects itself against the introduction of exotic diseases is described by Veterinary Surgeon, R. K. Kent, M.R.C.V.S., in this article
A Fast and Efficient Algorithm for Slater Determinant Updates in Quantum Monte Carlo Simulations
We present an efficient low-rank updating algorithm for updating the trial
wavefunctions used in Quantum Monte Carlo (QMC) simulations. The algorithm is
based on low-rank updating of the Slater determinants. In particular, the
computational complexity of the algorithm is O(kN) during the k-th step
compared with traditional algorithms that require O(N^2) computations, where N
is the system size. For single determinant trial wavefunctions the new
algorithm is faster than the traditional O(N^2) Sherman-Morrison algorithm for
up to O(N) updates. For multideterminant configuration-interaction type trial
wavefunctions of M+1 determinants, the new algorithm is significantly more
efficient, saving both O(MN^2) work and O(MN^2) storage. The algorithm enables
more accurate and significantly more efficient QMC calculations using
configuration interaction type wavefunctions
First record of Pholcus opilionoides (Schrank) (Araneae: Pholcidae) in Canada, with notes on its biology
None
An analysis of mixed integer linear sets based on lattice point free convex sets
Split cuts are cutting planes for mixed integer programs whose validity is
derived from maximal lattice point free polyhedra of the form called split sets. The set obtained by adding all
split cuts is called the split closure, and the split closure is known to be a
polyhedron. A split set has max-facet-width equal to one in the sense that
. In this paper
we consider using general lattice point free rational polyhedra to derive valid
cuts for mixed integer linear sets. We say that lattice point free polyhedra
with max-facet-width equal to have width size . A split cut of width
size is then a valid inequality whose validity follows from a lattice point
free rational polyhedron of width size . The -th split closure is the set
obtained by adding all valid inequalities of width size at most . Our main
result is a sufficient condition for the addition of a family of rational
inequalities to result in a polyhedral relaxation. We then show that a
corollary is that the -th split closure is a polyhedron. Given this result,
a natural question is which width size is required to design a finite
cutting plane proof for the validity of an inequality. Specifically, for this
value , a finite cutting plane proof exists that uses lattice point free
rational polyhedra of width size at most , but no finite cutting plane
proof that only uses lattice point free rational polyhedra of width size
smaller than . We characterize based on the faces of the linear
relaxation
Monte Carlo energy and variance minimization techniques for optimizing many-body wave functions
We investigate Monte Carlo energy and variance minimization techniques for
optimizing many-body wave functions. Several variants of the basic techniques
are studied, including limiting the variations in the weighting factors which
arise in correlated sampling estimations of the energy and its variance. We
investigate the numerical stability of the techniques and identify two reasons
why variance minimization exhibits superior numerical stability to energy
minimization. The characteristics of each method are studied using a
non-interacting 64-electron model of crystalline silicon. While our main
interest is in solid state systems, the issues investigated are relevant to
Monte Carlo studies of atoms, molecules and solids. We identify a robust and
efficient variance minimization scheme for optimizing wave functions for large
systems.Comment: 14 pages, including 7 figures. To appear in Phys. Rev. B. For related
publications see http://www.tcm.phy.cam.ac.uk/Publications/many_body.htm
Redescription of the spider Robertus arcticus (Chamberlin & Ivie) (Araneae: Theridiidae), with the first description of the female
The original description of Robertus arcticus (Chamberlin and Ivie, 1947) (Araneae: Theridiidae) was based on a single male collected in Alaska, United States of America. The female has remained undescribed, although specimens of both sexes have been collected over the intervening decades. The species occurs in boreal Alaska, and records from Cold Lake, Alberta, Canada and James Bay, Ontario, Canada suggest that it is probably widely distributed in the Canadian boreal. Here we redescribe the male and describe the female for the first time. Most specimens examined in our study were collected from the ground of boreal forest peatlands in northeastern Alberta
Evaluation on Cruise CD 62A of a Magnavox MX 4200 GPS receiver and KVH fluxgate compass to provide ship speed and heading
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