2,279 research outputs found
Identifying cross country skiing techniques using power meters in ski poles
Power meters are becoming a widely used tool for measuring training and
racing effort in cycling, and are now spreading also to other sports. This
means that increasing volumes of data can be collected from athletes, with the
aim of helping coaches and athletes analyse and understanding training load,
racing efforts, technique etc. In this project, we have collaborated with
Skisens AB, a company producing handles for cross country ski poles equipped
with power meters. We have conducted a pilot study in the use of machine
learning techniques on data from Skisens poles to identify which "gear" a skier
is using (double poling or gears 2-4 in skating), based only on the sensor data
from the ski poles. The dataset for this pilot study contained labelled
time-series data from three individual skiers using four different gears
recorded in varied locations and varied terrain. We systematically evaluated a
number of machine learning techniques based on neural networks with best
results obtained by a LSTM network (accuracy of 95% correctly classified
strokes), when a subset of data from all three skiers was used for training. As
expected, accuracy dropped to 78% when the model was trained on data from only
two skiers and tested on the third. To achieve better generalisation to
individuals not appearing in the training set more data is required, which is
ongoing work.Comment: Presented at the Norwegian Artificial Intelligence Symposium 201
Effect of periodic parametric excitation on an ensemble of force-coupled self-oscillators
We report the synchronization behavior in a one-dimensional chain of
identical limit cycle oscillators coupled to a mass-spring load via a force
relation. We consider the effect of periodic parametric modulation on the final
synchronization states of the system. Two types of external parametric
excitations are investigated numerically: periodic modulation of the stiffness
of the inertial oscillator and periodic excitation of the frequency of the
self-oscillatory element. We show that the synchronization scenarios are ruled
not only by the choice of parameters of the excitation force but depend on the
initial collective state in the ensemble. We give detailed analysis of
entrainment behavior for initially homogeneous and inhomogeneous states. Among
other results, we describe a regime of partial synchronization. This regime is
characterized by the frequency of collective oscillation being entrained to the
stimulation frequency but different from the average individual oscillators
frequency.Comment: Comments and suggestions are welcom
Observatory/data centre partnerships and the VO-centric archive: The JCMT Science Archive experience
We present, as a case study, a description of the partnership between an
observatory (JCMT) and a data centre (CADC) that led to the development of the
JCMT Science Archive (JSA). The JSA is a successful example of a service
designed to use Virtual Observatory (VO) technologies from the start. We
describe the motivation, process and lessons learned from this approach.Comment: Accepted for publication in the second Astronomy & Computing Special
Issue on the Virtual Observatory; 10 pages, 5 figure
Sawtooth period pacing and locking by EC power control on TCV
Abstract #TP9.127 submitted for the DPP11 Meeting of The American Physical Society
The Psychological Foundations of The Mediating Learning Support Assistant (MeLSA) Training Programme
It is estimated that a quarter of the mainstream school workforce in the UK are learning support staff. This is a substantial number of adults who have the potential to foster learning. This paper provides a brief summary regarding the impact of support staff on children and young people’s learning. It describes how the Mediating Learning Support Assistant (MeLSA) training programme was developed to meet a training gap identified in the literature. This paper also details the psychological theories and research evidence which provide the foundations for MeLSA and describes the format of the training programme, which consists of six days (mediating learning and mindset, thinking about thinking, memory and recall, mathematics, literacy, and implementation) followed by ongoing supervision. The aim of MeLSA is to ensure that learning support staff have the psychological and evidence-informed expertise to enable those with whom they are working to become competent and independent learners
Statistical features of edge turbulence in RFX-mod from Gas Puffing Imaging
Plasma density fluctuations in the edge plasma of the RFX-mod device are
measured through the Gas Puffing Imaging Diagnostics. Statistical features of
the signal are quantified in terms of the Probability Distribution Function
(PDF), and computed for several kinds of discharges. The PDFs from discharges
without particular control methods are found to be adequately described by a
Gamma function, consistently with the recent results by Graves et al [J.P.
Graves, et al, Plasma Phys. Control. Fusion 47, L1 (2005)]. On the other hand,
pulses with external methods for plasma control feature modified PDFs. A first
empirical analysis suggests that they may be interpolated through a linear
combination of simple functions. An inspection of the literature shows that
this kind of PDFs is common to other devices as well, and has been suggested to
be due to the simultaneous presence of different mechanisms driving
respectively coherent bursts and gaussian background turbulence. An attempt is
made to relate differences in the PDFs to plasma conditions such as the local
shift of the plasma column. A simple phenomenological model to interpret the
nature of the PDF and assign a meaning to its parameters is also developed.Comment: 27 pages. Published in PPC
Some peculiarities of motion of neutral and charged test particles in the field of a spherically symmetric charged object in General Relativity
We propose the method of investigation of radial motions for charged and
neutral test particles in the Reissner-Nordstr\"{o}m field by means of mass
potential. In this context we analyze special features of interaction of
charges and their motions in General Relativity and construct the radial motion
classification. For test particles and a central source with charges and
, respectively, the conditions of attraction (when ) and repulsion
(when ) are obtained. The conditions of motionless test particle states
with respect to the central source are investigated and, in addition, stability
conditions for such static equilibrium states are found. It is shown that
stable states are possible only for the bound states of weakly charged
particles in the field of a naked singularity. Frequencies of small
oscillations of test particles near their equilibrium positions are also found.Comment: 15 pages, 9 figure
Classical model of elementary particle with Bertotti-Robinson core and extremal black holes
We discuss the question, whether the Reissner-Nordstr\"{o}m RN) metric can be
glued to another solutions of Einstein-Maxwell equations in such a way that (i)
the singularity at r=0 typical of the RN metric is removed (ii), matching is
smooth. Such a construction could be viewed as a classical model of an
elementary particle balanced by its own forces without support by an external
agent. One choice is the Minkowski interior that goes back to the old Vilenkin
and Fomin's idea who claimed that in this case the bare delta-like stresses at
the horizon vanish if the RN metric is extremal. However, the relevant entity
here is the integral of these stresses over the proper distance which is
infinite in the extremal case. As a result of the competition of these two
factors, the Lanczos tensor does not vanish and the extremal RN cannot be glued
to the Minkowski metric smoothly, so the elementary-particle model as a ball
empty inside fails. We examine the alternative possibility for the extremal RN
metric - gluing to the Bertotti-Robinson (BR) metric. For a surface placed
outside the horizon there always exist bare stresses but their amplitude goes
to zero as the radius of the shell approaches that of the horizon. This limit
realizes the Wheeler idea of "mass without mass" and "charge without charge".
We generalize the model to the extremal Kerr-Newman metric glued to the
rotating analog of the BR metric.Comment: 23 pages. Misprints correcte
Quaternion-Octonion Unitary Symmetries and Analogous Casimir Operators
An attempt has been made to investigate the global SU(2) and SU(3) unitary
flavor symmetries systematically in terms of quaternion and octonion
respectively. It is shown that these symmetries are suitably handled with
quaternions and octonions in order to obtain their generators, commutation
rules and symmetry properties. Accordingly, Casimir operators for SU(2)and
SU(3) flavor symmetries are also constructed for the proper testing of these
symmetries in terms of quaternions and octonions
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