1,725 research outputs found
The switch operators and push-the-button games: a sequential compound over rulesets
We study operators that combine combinatorial games. This field was initiated
by Sprague-Grundy (1930s), Milnor (1950s) and Berlekamp-Conway-Guy (1970-80s)
via the now classical disjunctive sum operator on (abstract) games. The new
class consists in operators for rulesets, dubbed the switch-operators. The
ordered pair of rulesets (R 1 , R 2) is compatible if, given any position in R
1 , there is a description of how to move in R 2. Given compatible (R 1 , R 2),
we build the push-the-button game R 1 R 2 , where players start by playing
according to the rules R 1 , but at some point during play, one of the players
must switch the rules to R 2 , by pushing the button ". Thus, the game ends
according to the terminal condition of ruleset R 2. We study the pairwise
combinations of the classical rulesets Nim, Wythoff and Euclid. In addition, we
prove that standard periodicity results for Subtraction games transfer to this
setting, and we give partial results for a variation of Domineering, where R 1
is the game where the players put the domino tiles horizontally and R 2 the
game where they play vertically (thus generalizing the octal game 0.07).Comment: Journal of Theoretical Computer Science (TCS), Elsevier, A
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Shear thickening of highly viscous granular suspensions
We experimentally investigate shear thickening in dense granular suspensions
under oscillatory shear. Directly imaging the suspension-air interface, we
observe dilation beyond a critical strain and the end of shear
thickening as the maximum confining stress is reached and the contact line
moves. Analyzing the shear profile, we extract the viscosity contributions due
to hydrodynamics , dilation and sedimentation .
While governs the shear thinning regime, and
together determine the shear thickening behavior. As the suspending liquid's
viscosity varies from 10 to 1000 cst, is found to compete with
and soften the discontinuous nature of shear thickening
SplineCNN: Fast Geometric Deep Learning with Continuous B-Spline Kernels
We present Spline-based Convolutional Neural Networks (SplineCNNs), a variant
of deep neural networks for irregular structured and geometric input, e.g.,
graphs or meshes. Our main contribution is a novel convolution operator based
on B-splines, that makes the computation time independent from the kernel size
due to the local support property of the B-spline basis functions. As a result,
we obtain a generalization of the traditional CNN convolution operator by using
continuous kernel functions parametrized by a fixed number of trainable
weights. In contrast to related approaches that filter in the spectral domain,
the proposed method aggregates features purely in the spatial domain. In
addition, SplineCNN allows entire end-to-end training of deep architectures,
using only the geometric structure as input, instead of handcrafted feature
descriptors. For validation, we apply our method on tasks from the fields of
image graph classification, shape correspondence and graph node classification,
and show that it outperforms or pars state-of-the-art approaches while being
significantly faster and having favorable properties like domain-independence.Comment: Presented at CVPR 201
Access to Effective Teaching for Disadvantaged Students
Recent federal initiatives in education, such as Race to the Top, the Teacher Incentive Fund, and the flexibility policy for the Elementary and Secondary Education Act are designed in part to ensure that disadvantaged students have equal access to effective teaching. The initiatives respond to the concern that disadvantaged students may be taught by less effective teachers and that this could contribute to the achievement gap between disadvantaged students and other students. To address the need for evidence on this issue, the Institute of Education Sciences at the U.S. Department of Education initiated a study to examine access to effective teaching for disadvantaged students in 29 diverse school districts. Mathematica Policy Research and its partner, the American Institutes for Research, conducted the study, which focused on English/ language arts (ELA) and math teachers in grades 4 through 8 from the 2008 -- 2009 to the 2010 -- 2011 school year
Strain-stiffening in random packings of entangled granular chains
Random packings of granular chains are presented as a model polymer system to
investigate the contribution of entanglements to strain-stiffening in the
absence of Brownian motion. The chain packings are sheared in triaxial
compression experiments. For short chain lengths, these packings yield when the
shear stress exceeds a the scale of the confining pressure, similar to packings
of spherical particles. In contrast, packings of chains which are long enough
to form loops exhibit strain-stiffening, in which the effective stiffness of
the material increases with strain, similar to many polymer materials. The
latter packings can sustain stresses orders-of-magnitude greater than the
confining pressure, and do not yield until the chain links break. X-ray
tomography measurements reveal that the strain-stiffening packings contain
system-spanning clusters of entangled chains.Comment: 4 pages, 4 figures. submitted to Physical Review Letter
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