7,032 research outputs found
The Evolution of the Government of Canada's Debt Distribution Framework
This overview includes a brief history highlighting the government's use of the primary and secondary markets to develop a framework for distributing its debt securities to financial market intermediaries and end investors. The framework is also intended to meet the government's debt-strategy objectives of raising stable, low-cost funding and maintaining a well-functioning debt market. Pellerin reviews the government's adoption of a new framework in 1998 as well as the 2005 modifications aimed at attracting continued broad and competitive participation in government auctions.
Coupled Ensembles of Neural Networks
We investigate in this paper the architecture of deep convolutional networks.
Building on existing state of the art models, we propose a reconfiguration of
the model parameters into several parallel branches at the global network
level, with each branch being a standalone CNN. We show that this arrangement
is an efficient way to significantly reduce the number of parameters without
losing performance or to significantly improve the performance with the same
level of performance. The use of branches brings an additional form of
regularization. In addition to the split into parallel branches, we propose a
tighter coupling of these branches by placing the "fuse (averaging) layer"
before the Log-Likelihood and SoftMax layers during training. This gives
another significant performance improvement, the tighter coupling favouring the
learning of better representations, even at the level of the individual
branches. We refer to this branched architecture as "coupled ensembles". The
approach is very generic and can be applied with almost any DCNN architecture.
With coupled ensembles of DenseNet-BC and parameter budget of 25M, we obtain
error rates of 2.92%, 15.68% and 1.50% respectively on CIFAR-10, CIFAR-100 and
SVHN tasks. For the same budget, DenseNet-BC has error rate of 3.46%, 17.18%,
and 1.8% respectively. With ensembles of coupled ensembles, of DenseNet-BC
networks, with 50M total parameters, we obtain error rates of 2.72%, 15.13% and
1.42% respectively on these tasks
Two-axis flux gate magnetometer
Magnetometer uses single sensing head to measure magnetic flux density along two axes simultaneously. The sensor head consists of permalloy core and four windings. Two windings perform a multivibrator function, the two remaining windings sense magnetic fields. The smaller magnetometer performs same functions as more complex devices
One machine, one minute, three billion tetrahedra
This paper presents a new scalable parallelization scheme to generate the 3D
Delaunay triangulation of a given set of points. Our first contribution is an
efficient serial implementation of the incremental Delaunay insertion
algorithm. A simple dedicated data structure, an efficient sorting of the
points and the optimization of the insertion algorithm have permitted to
accelerate reference implementations by a factor three. Our second contribution
is a multi-threaded version of the Delaunay kernel that is able to concurrently
insert vertices. Moore curve coordinates are used to partition the point set,
avoiding heavy synchronization overheads. Conflicts are managed by modifying
the partitions with a simple rescaling of the space-filling curve. The
performances of our implementation have been measured on three different
processors, an Intel core-i7, an Intel Xeon Phi and an AMD EPYC, on which we
have been able to compute 3 billion tetrahedra in 53 seconds. This corresponds
to a generation rate of over 55 million tetrahedra per second. We finally show
how this very efficient parallel Delaunay triangulation can be integrated in a
Delaunay refinement mesh generator which takes as input the triangulated
surface boundary of the volume to mesh
There are 174 Subdivisions of the Hexahedron into Tetrahedra
This article answers an important theoretical question: How many different
subdivisions of the hexahedron into tetrahedra are there? It is well known that
the cube has five subdivisions into 6 tetrahedra and one subdivision into 5
tetrahedra. However, all hexahedra are not cubes and moving the vertex
positions increases the number of subdivisions. Recent hexahedral dominant
meshing methods try to take these configurations into account for combining
tetrahedra into hexahedra, but fail to enumerate them all: they use only a set
of 10 subdivisions among the 174 we found in this article.
The enumeration of these 174 subdivisions of the hexahedron into tetrahedra
is our combinatorial result. Each of the 174 subdivisions has between 5 and 15
tetrahedra and is actually a class of 2 to 48 equivalent instances which are
identical up to vertex relabeling. We further show that exactly 171 of these
subdivisions have a geometrical realization, i.e. there exist coordinates of
the eight hexahedron vertices in a three-dimensional space such that the
geometrical tetrahedral mesh is valid. We exhibit the tetrahedral meshes for
these configurations and show in particular subdivisions of hexahedra with 15
tetrahedra that have a strictly positive Jacobian
Finding Hexahedrizations for Small Quadrangulations of the Sphere
This paper tackles the challenging problem of constrained hexahedral meshing.
An algorithm is introduced to build combinatorial hexahedral meshes whose
boundary facets exactly match a given quadrangulation of the topological
sphere. This algorithm is the first practical solution to the problem. It is
able to compute small hexahedral meshes of quadrangulations for which the
previously known best solutions could only be built by hand or contained
thousands of hexahedra. These challenging quadrangulations include the
boundaries of transition templates that are critical for the success of general
hexahedral meshing algorithms.
The algorithm proposed in this paper is dedicated to building combinatorial
hexahedral meshes of small quadrangulations and ignores the geometrical
problem. The key idea of the method is to exploit the equivalence between quad
flips in the boundary and the insertion of hexahedra glued to this boundary.
The tree of all sequences of flipping operations is explored, searching for a
path that transforms the input quadrangulation Q into a new quadrangulation for
which a hexahedral mesh is known. When a small hexahedral mesh exists, a
sequence transforming Q into the boundary of a cube is found; otherwise, a set
of pre-computed hexahedral meshes is used.
A novel approach to deal with the large number of problem symmetries is
proposed. Combined with an efficient backtracking search, it allows small
shellable hexahedral meshes to be found for all even quadrangulations with up
to 20 quadrangles. All 54,943 such quadrangulations were meshed using no more
than 72 hexahedra. This algorithm is also used to find a construction to fill
arbitrary domains, thereby proving that any ball-shaped domain bounded by n
quadrangles can be meshed with no more than 78 n hexahedra. This very
significantly lowers the previous upper bound of 5396 n.Comment: Accepted for SIGGRAPH 201
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