3,305 research outputs found
Work-rate of substitutes in elite soccer: A preliminary study
The aim of this study was to investigate the work-rate of substitutes in professional soccer. A computerised player tracking system was used to assess the work-rates of second-half substitutes (11 midfielders and 14 forwards) in a French Ligue 1 club. Total distance, distance covered in five categories of movement intensity and recovery time between high-intensity efforts were evaluated. First- and second-half work-rates of the replaced players were compared. The performance of substitutes was compared to that of the players they replaced, to team-mates in the same position who remained on the pitch after the substitution and in relation to their habitual performances when starting games. No differences in work-rate between first- and second-halves were observed in all players who were substituted. In the second-half, a non-significant trend was observed in midfield substitutes who covered greater distances than the player they replaced whereas no differences were observed in forwards. Midfield substitutes covered a greater overall distance and distance at high-intensities (p<0.01) and had a lower recovery time between high-intensity efforts (p<0.01) compared to other midfield team-mates who remained on the pitch. Forwards covered less distance (p<0.01) in their first 10-minutes as a substitute compared to their habitual work-rate profile in the opening 10-minutes when starting matches while this finding was not observed in midfielders. These findings suggest that compared to midfield substitutes, forward substitutes did not utilise their full physical potential. Further investigation is warranted into the reasons behind this finding in order to optimise the work-rate contributions of forward substitutes
Effective Lagrangians in bound state calculations
In order to investigate specific aspects of bound state calculations in a
non-relativistic framework, we consider the energy-levels of a massive scalar
particle, which moves in an external field and interacts in addition with a
massless scalar particle. The discussion includes the following topics:
dimensionally regularized bound-state calculations, ultraviolet finiteness of
bound-state observables and their independence of the off-mass-shell behavior
of Green functions, non-renormalizable interactions, structure of the
non-relativistic two-point function, power counting and matching.Comment: 45 pages, 8 postscript figures, RevTeX styl
Human Pose Estimation using Deep Consensus Voting
In this paper we consider the problem of human pose estimation from a single
still image. We propose a novel approach where each location in the image votes
for the position of each keypoint using a convolutional neural net. The voting
scheme allows us to utilize information from the whole image, rather than rely
on a sparse set of keypoint locations. Using dense, multi-target votes, not
only produces good keypoint predictions, but also enables us to compute
image-dependent joint keypoint probabilities by looking at consensus voting.
This differs from most previous methods where joint probabilities are learned
from relative keypoint locations and are independent of the image. We finally
combine the keypoints votes and joint probabilities in order to identify the
optimal pose configuration. We show our competitive performance on the MPII
Human Pose and Leeds Sports Pose datasets
A specialized isotope mass spectrometer for noninvasive diagnostics of Helicobacter pylori infection in human beings
A specialized isotope mass spectrometer for noninvasive diagnostics of Helicobacter pylori infection in human beings based on the carbon-13 isotope breath test has been designed and constructed. Important stages of the work included (i) calculating a low-aberration mass analyzer, (ii) manufacturing and testing special gas inlet system, and (iii) creating a small-size collector of ions. The proposed instrument ensures 13C/12C isotopic ratio measurement to within 1.7‰ (pro mille) accuracy, which corresponds to requirements for a diagnostic tool. Preliminary medical testing showed that the mass spectrometer is applicable to practical diagnostics. The instrument is also capable of measuring isotopic ratios of other light elements, including N, O, B (for BF2+ ions), Ar, Cl, and
Quantum Algorithms for Matrix Products over Semirings
In this paper we construct quantum algorithms for matrix products over
several algebraic structures called semirings, including the (max,min)-matrix
product, the distance matrix product and the Boolean matrix product. In
particular, we obtain the following results.
We construct a quantum algorithm computing the product of two n x n matrices
over the (max,min) semiring with time complexity O(n^{2.473}). In comparison,
the best known classical algorithm for the same problem, by Duan and Pettie,
has complexity O(n^{2.687}). As an application, we obtain a O(n^{2.473})-time
quantum algorithm for computing the all-pairs bottleneck paths of a graph with
n vertices, while classically the best upper bound for this task is
O(n^{2.687}), again by Duan and Pettie.
We construct a quantum algorithm computing the L most significant bits of
each entry of the distance product of two n x n matrices in time O(2^{0.64L}
n^{2.46}). In comparison, prior to the present work, the best known classical
algorithm for the same problem, by Vassilevska and Williams and Yuster, had
complexity O(2^{L}n^{2.69}). Our techniques lead to further improvements for
classical algorithms as well, reducing the classical complexity to
O(2^{0.96L}n^{2.69}), which gives a sublinear dependency on 2^L.
The above two algorithms are the first quantum algorithms that perform better
than the -time straightforward quantum algorithm based on
quantum search for matrix multiplication over these semirings. We also consider
the Boolean semiring, and construct a quantum algorithm computing the product
of two n x n Boolean matrices that outperforms the best known classical
algorithms for sparse matrices. For instance, if the input matrices have
O(n^{1.686...}) non-zero entries, then our algorithm has time complexity
O(n^{2.277}), while the best classical algorithm has complexity O(n^{2.373}).Comment: 19 page
Skew-Unfolding the Skorokhod Reflection of a Continuous Semimartingale
The Skorokhod reflection of a continuous semimartingale is unfolded, in a
possibly skewed manner, into another continuous semimartingale on an enlarged
probability space according to the excursion-theoretic methodology of Prokaj
(2009). This is done in terms of a skew version of the Tanaka equation, whose
properties are studied in some detail. The result is used to construct a system
of two diffusive particles with rank-based characteristics and skew-elastic
collisions. Unfoldings of conventional reflections are also discussed, as are
examples involving skew Brownian Motions and skew Bessel processes.Comment: 20 pages. typos corrected, added a remark after Proposition 2.3,
simplified the last part of Example 2.
Electronic viscosity and energy relaxation in neutral graphene
We explore hydrodynamics of Dirac fermions in neutral graphene in the Corbino geometry. In the absence of magnetic field, the bulk Ohmic charge flow and the hydrodynamic energy flow are decoupled. However, the energy flow does affect the overall resistance of the system through viscous dissipation and energy relaxation that has to be compensated by the work done by the current source. Solving the hydrodynamic equations, we find that local temperature and electric potential are discontinuous at the interfaces with the leads as well as the device resistance and argue that this makes Corbino geometry a feasible choice for an experimental observation of the Dirac fluid
Corbino magnetoresistance in neutral graphene
We explore the magnetohydrodynamics of Dirac fermions in neutral graphene in
the Corbino geometry. Based on the fully consistent hydrodynamic description
derived from a microscopic framework and taking into account all peculiarities
of graphene-specific hydrodynamics, we report the results of a comprehensive
study of the interplay of viscosity, disorder-induced scattering,
recombination, energy relaxation, and interface-induced dissipation. In the
clean limit, magnetoresistance of a Corbino sample is determined by viscosity.
Hence the Corbino geometry could be used to measure the viscosity coefficient
in neutral graphene.Comment: 13 pages, 11 figure
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